EPA Superfund Record of Decision: Lowry Landfill EPA ID: COD980499248 OU 00 Aurora CO

                                     EPA/ROD/R08-94/087
                                     1994
EPA Superfund
     Record of Decision:
     LOWRY LANDFILL
     EPA ID: COD980499248
     OUOO
     AURORA, CO
     03/10/1994

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                       United  States Environmental Protection Agency
                                    Region VIII
                            999 18th Street - Suite 500
                           Denver,  Colorado  80202-2466

                                Record of Decision

                           Lowry Landfill Superfund Site

                             Arapahoe County, Colorado


                                    March 1994

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                                    Contents

List of Acronyms	xvi

Glossary of Terms	xx

1.0   Declaration for the Record of Decision	1-1
      1.1   Site Name and Location	1-1
      1.2   Statement of Basis and Purpose	1-1
      1.3   Assessment of the Site	1-1
      1.4   Description of the Selected Remedy	1-1
      1.5   Statutory Determinations  	  1-3

2.0   Site Summary	2-1
      2.1   Site Name, Location,  and Description	2-1
      2.2   Area and Topography	2-1
      2.3   Natural Resource Use	2-1
            2.3.1   Evaluation of Threatened and Endangered Species 	  2-1
                    2.3.1.1   Ecological Setting  	  2-1
                    2.3.1.2   Endangered Species  	  2-2
            2.3.2   Evaluation of Wetland Areas	2-3
                    2.3.2.1   Ecological Setting  	  2-3
      2.4   Cultural Resources  	  2-3
      2.5   Adjacent Land Use	2-4
      2.6   Distance to Nearby Populations  	  2-4
      2.7   Future Land Use and Populations	2-4
      2.8   Location in a Floodplain	2-5
      2.9   General Surface Water and Ground-Water Resource 	  2-6
            2.9.1   Surface Water Resources 	  2-6
            2.9.2   Ground-Water Resources	2-6
                    2.9.2.1   Residential Wells 	  2-6
                    2.9.2.2   Industrial Wells  	  2-6
                    2.9.2.3   Municipal Wells 	  2-7
      2.10  Surface and Subsurface Features 	  2-7
            2.10.1  Structures  	  2-7
            2.10.2  Roads 	  2-8
            2.10.3  Fencing 	  2-8
            2.10.4  Pipelines and Utility Lines 	  2-8
            2.10.5  Surface Disposal Areas  	  2-8
            2.10.6  Soil Borrow Areas	2-9
            2.10.7  Surface Drainage and Sediments  	  2-9
            2.10.8  Subsurface Features 	  2-9
                    2.10.8.1  Hydrogeologic Conceptual Model	2-10
                    2.10.8.2  OU 1:   Shallow Ground-Water System	2-11
                    2.10.8.3  OU 6:   Deep Ground-Water System	2-11

3.0   Site History and Enforcement Activities	3-1
      3.1   Operational History 	  3-1
      3.2   History of Site Investigations	3-2
            3.2.1   Site Investigation Activities from 1964 to 1984	3-2
            3.2.2   Preliminary Assessment, Hazard Ranking, and NPL
                     Listing	3-2
            3.2.3   Phase I RI:   February 1985 to April 1986	3-3
            3.2.4   ATSDR Determination 	  3-3
            3.2.5   Phase II RI:   January 1987 to October 1989	3-3
      3.3   History of CERCLA Enforcement	3-4
            3.3.1   The 1988 Consent Order for OU 1 RI/FS and the 1989
                     Amended and Restated Consent Order for OU 6 RI/FS  ....  3-4
            3.3.2   The 1990 Administrative Order on Consent for OUs 2&3
                     RI/FS	3-5
            3.3.3   The 1991 Consent Order for OUs 4&5 RI/FS	3-5
            3.3.4   History of the 1984 Barrier Wall Consent Order,  the
                     1986 Barrier Wall Consent Decree, the 1991 Surface
                     Removal Action, and the 1993 Modified Consent Decree .  .  .  3-6
            3.3.5   History of the 1989 Drum Removal Action	3-7
            3.3.6   PRP Search	3-7
            3.3.7   Bankruptcy Settlements  	  3-8

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            3.3.8   De Minimis Settlements
4.0   Highlights of Community Participation 	  4-1
      4.1   Community Relations Plan	4-1
      4.2   Lowry Landfill Monitoring Committee 	  4-1
      4.3   Technical Advisory Group  	  4-1
      4.4   Outreach Program	4-2
      4.5   Technical Assistance Grant  	  4-3
      4.6   Information Repositories  	  4-3

5.0   Scope and Role of Operable Units	5-1

6.0   Summary of Site Characteristics	6-1
      6.1   Extent of Contamination in Affected Media 	  6-1
            6.1.1   OUs 1&6:  Shallow Ground Water and Subsurface Liquids,
                     and Deep Ground Water-Operable Units	6-2
                    6.1.1.1   Sources of Contamination  	  6-2
                    6.1.1.2   Nature and Extent of Contamination  	  6-2
                    6.1.1.3   Concentrations of Contaminants  	  6-4
                    6.1.1.4   Volume Estimates  	  6-4
            6.1.2   OU 2:   Landfill Solids	6-5
                    6.1.2.1   Source of Contamination 	  6-5
                    6.1.2.2   Nature and Extent of Contamination Within the
                               Landfill Mass	6-5
                    6.1.2.3   Concentrations of Contaminants Within the
                               Landfill Mass	6-5
                    6.1.2.4   Nature and Extent of Contamination Within the
                               Former Tire Pile Area	6-6
                    6.1.2.5   Concentrations of Contaminants Within the
                               Former Tire Pile Area	6-7
                    6.1.2.6   Volume Estimates  	  6-7
            6.1.3   OU 3:   Landfill Gas	6-7
                    6.1.3.1   Source of Contamination 	  6-7
                    6.1.3.2   Nature and Extent of Contamination  	  6-7
                    6.1.3.3   Concentrations of Contaminants  	  6-8
                    6.1.3.4   Volume Estimates  	  6-9
            6.1.4   OU 4:   Soil	6-9
                    6.1.4.1   Source of Contamination 	  6-9
                    6.1.4.2   Nature and Extent of Contamination  	  6-9
                    6.1.4.3   Concentrations of Contaminants	6-10
                    6.1.4.4   Volume Estimates	6-12
            6.1.5   OU 5:   Surface Water	6-12
                    6.1.5.1   Past Source of Contamination	6-12
                    6.1.5.2   Nature and Extent of Contamination	6-12
                    6.1.5.3   Concentrations of Contaminants	6-13
                    6.1.5.4   Volume Estimates	6-13
            6.1.6   OU 5:   Sediments	6-13
                    6.1.6.1   Past Source of Contamination	6-13
                    6.1.6.2   Nature and Extent of Contamination	6-14
                    6.1.6.3   Concentrations of Contaminants	6-14
                    6.1.6.4   Volume Estimates	6-15
      6.2   Surface and Subsurface Pathways of Migration	6-15
            6.2.1   Subsurface Liquids to Shallow Ground Water	6-16
            6.2.2   Subsurface Liquids and Shallow Ground Water to Surface
                     Water and Sediments	6-16
            6.2.3   Volatiles from Subsurface Liquids to Landfill Gas	6-17
            6.2.4   Landfill Solids to Landfill Gas to Atmosphere	6-17
            6.2.5   Contaminated Surface Water to Shallow Ground Water  .  .  .  .6-18
            6.2.6   Shallow Ground Water to Deep Ground Water	6-18
7.0   Summary of Site Risks	7-1
      7.1   Human Health Risks  	  7-2
            7.1.1   Chemicals of Concern	7-2
            7.1.2   Summary of Exposure Assessment	7-3
                    7.1.2.1   Current Exposure  	  7-3
                    7.1.2.2   Hypothetical Future Exposure  	  7-3
                    7.1.2.3   Summary of Toxicity Assessment  	  7-7
                    7.1.2.4   Summary of Risk Characterization  	  7-9

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                    7.1.2.5   Uncertainty in the Risk Assessment	7-15
            7.1.3   Summary of Lead Risks	7-15
            7.1.4   Summary of Radiological Risks	7-17
                    7.1.4.1   Contaminated Media and Exposure	7-17
                    7.1.4.2   Summary of Toxicity Assessment	7-18
                    7.1.4.3   Summary of Risk Characterization	7-18
                    7.1.4.4   Uncertainties	7-19
            7.1.5   Summary of Environmental Risks	7-20
                    7.1.5.1   Ecological Setting	7-20
                    7.1.5.2   Ecological Chemicals of Concern	7-21
                    7.1.5.3   Exposure Assessment	7-21
                    7.1.5.4   Ecological Effects Assessment	7-22
                    7.1.5.5   Uncertainties	7-23
      7.2   Baseline Risk Assessment Summary	7-24

8.0   Description of Remedial Alternatives  	  8-1
      8.1   Cost Estimating Procedures	8-2
            8.1.1   Respondents'  Cost Estimates 	  8-3
            8.1.2   EPA's Revised Cost Estimates	8-3
            Features Common to All Remedial Alternatives  	  8-3
            Interim Remedial Measures 	  8-5
            Description of Alternatives 	  8-6
            8.4.1   Description of No Action Alternative for all
                     Operable Units 	  8-6
            8.4.2   OUs l&6-Shallow Ground Water and Subsurface Liguids,
                     and Deep Ground Water	8-6
                    8.4.2.1   Alternative GW-l-No Further Action  	  8-7
                    8.4.2.2   Alternative GW-2-North Boundary (Downgradient)
                               Containment,  Collection,  and Treatment	8-10
                    8.4.2.3   Alternative GW-3-North Boundary and Toe of
                               Landfill Containment,  Collection, and
                               Treatment	8-11
                    8.4.2.4   Alternative GW-4-North Boundary,  Toe of Landfill,
                               and Upgradient Containment,  Collection and
                               Treatment,  Plus Multilayered Cap in Landfill
                               Area	8-12
                    8.4.2.5   Alternative GW-5-North Boundary,  Toe of
                               Landfill and Lateral Containment, Collection
                               and Treatment	8-14
                    8.4.2.6   Alternative GW-6-North Boundary and Toe of
                               Landfall Containment,  Collection and
                               Treatment,  and Waste-Pit  Pumping	8-15
                    8.4.2.7   EPA's Preferred Alternative-Modified Alternative
                               GW-5-North Boundary,  Toe  of Landfill,  and
                               Lateral Containment,  Collection,  and Treatment
                               plus Upgradient Containment,  Collection,  and/or
                               Diversion	8-17
            8.4.3   OUs 2&3-Landfill Solids and Gas	8-18
                    8.4.3.1   Alternative LFS-2-No Further Action	8-19
                    8.4.3.2   Alternative LFS-3-Clay Cap	8-20
                    8.4.3.3   Alternative LFS-4-Drum Removal/Offsite
                               Disposal	8-21
                    8.4.3.4   Alternative LFS-6-Drum Removal/Low
                               Temperature Thermal Desorption/
                               Stabilization/Disposal	8-22
                    8.4.3.5   Alternative LFS-7-Landfill Mass Regrading .  . .  .8-24
                    8.4.3.6   EPA's Preferred Alternative-Modified Alternative
                               LFS-4-Drum Removal/Offsite Disposal/North
                               Face Cover	8-25
                    8.4.3.7   Alternative LFG-2-No Further Action	8-26
                    8.4.3.8   Alternative LFG-3-Gas Collection/Enclosed
                               Flare	8-27
                    8.4.3.9   Alternative LFG-5-Gas Collection with Heat
                               Recovery	8-29
                    8.4.3.10  EPA's Preferred Alternative-Modified Alternative
                               LFG-3-Gas Collection/Enclosed Flare	8-30
            8.4.4   OUs 4&5-Soils, Surface Water,  and Sediments	8-31

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                    8.4.4.1   EPA's Preferred Alternative-Alternative SOIL-1-
                               No Further Action	8-32
                    8.4.4.2   Alternative SOIL-2-Access Restrictions and Dust
                               Control	8-33
                    8.4.4.3   Alternative SOIL-4a Excavation and Landfill
                               (onsite)	8-34
                    8.4.4.4   Alternative SOIL-4b,  Excavation and Landfill
                               (offsite)   	8-37
                    8.4.4.5   EPA's Preferred Alternative-Alternative SW-1-
                               No Further Action	8-38
                    8.4.4.6   EPA's Preferred Alternative-Section 6 Sediments
                               Alternative SED6-1-NO Further Action	8-42
                    8.4.4.7   Section 6 Sediments Alternative SED6-2-Access
                               Restrictions	8-44
                    8.4.4.8   EPA's Preferred Alternative-Section 31 Sediments
                               Alternative SED31-1-NO Further Action	8-45
                    8.4.4.9   Section 31 Sediments Alternative SED31-2-Access
                               Restrictions and Capping	8-46
                    8.4.4.10  Section 31 Sediments Alternative SED31-3-
                               Excavation and Landfill	8-48

9.0   Summary of the Comparative Analysis of Alternatives 	  9-1
      9.1   OU 1:   Shallow Ground Water and Subsurface Liquids and OU 6:
             Deep Ground Water	9-2
            9.1.1   Threshold Criteria  	  9-2
                    9.1.1.1   Overall Protection of Human Health and the
                               Environment	9-2
                    9.1.1.2   Compliance with ARARs	9-5
            9.1.2   Primary Balancing Criteria  	  9-6
                    9.1.2.1   Long-Term Effectiveness and Permanence  	  9-6
                    9.1.2.2   Reduction of Toxicity, Mobility, or Volume
                               Through Treatment  	  9-8
                    9.1.2.3   Short-Term Effectiveness  	  9-8
                    9.1.2.4   Implementability  	  9-9
                    9.1.2.5   Cost	9-10
            9.1.3   Modifying Criteria	9-12
                    9.1.3.1   State/Support Agency Acceptance
                               (August 1993)	9-12
                    9.1.3.2   Community Acceptance	9-12
      9.2   OU 2:   Landfill Solids and OU 3:   Landfill Gas	9-13
            9.2.1 Threshold Criteria	9-13
                    9.2.1.1   Overall Protection of Human Health and the
                               Environment	9-13
                    9.2.1.2   Compliance with ARARs	9-15
            9.2.2   Primary Balancing Criteria	9-15
                    9.2.2.1   Long-Term Effectiveness and Permanence	9-15
                    9.2.2.2   Reduction of Toxicity, Mobility, or Volume
                               Through Treatment	9-16
                    9.2.2.3   Short-Term Effectiveness	9-17
                    9.2.2.4   Implementability	9-17
                    9.2.2.5   Cost	9-18
            9.2.3   Modifying Criteria	9-20
                    9.2.3.1   State/Support Agency Acceptance  	 9-20
                    9.2.3.2   Community Acceptance	9-20
      9.3   OU 4:   Soil and OU 5:   Surface Water and Sediments	9-21
            9.3.1   Threshold Criteria	9-21
                    9.3.1.1   Overall Protection of Human Health and the
                               Environment	9-21
                    9.3.1.2   Compliance with ARARs	9-22
            9.3.2   Primary Balancing Criteria	9-22
                    9.3.2.1   Long-Term Effectiveness and Permanence	9-22
                    9.3.2.2   Reduction of Toxicity, Mobility, or Volume
                               Through Treatment	9-23
                    9.3.2.3   Short-Term Effectiveness	9-24
                    9.3.2.4   Implementability	9-24
                    9.3.2.5   Cost	9-25
                    Modifying Criteria	9-27

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                    9.3.3.1   State/Support Agency Acceptance	9-27
                    9.3.3.2   Community Acceptance	9-27

10.0  Documentation of Significant Changes	10-1

11.0  Selected Sitewide Remedy	11-1
      11.1  General Components of the Selected Sitewide Remedy	11-1
      11.2  Remedy for Shallow Ground Water and Subsurface Liguids and
             Deep Ground Water	11-3
            11.2.1  Containment Components (Barrier Walls and Collection
                     Systems)	11-5
                    11.2.1.1  Performance Standards and Points of
                               Compliance	11-7
                    11.2.1.2  Contingency Measures	11-8
            11 2.2  Treatment Component	11-9
                    11.2.2.1  Performance Standards and Points of
                               Compliance	11-9
                    11.2.2.2  Contingency Measures  	  11-10
      11.3  Remedy for Landfill Solids  	  11-10
            11.3.1  Performance Standards and Points of Compliance  	  11-11
      11.4  Remedy for Landfill Gas	11-12
            11.4.1  Performance Standards and Point of Compliance	11-13
            11.4.2  Contingency Measures	11-14
      11.5  Remedy for Soils and Surface Water and Sediments	11-14
            11.5.1  Performance Standards and Points of Compliance	11-15
            11.5.2  Contingency Measures	11-16
      11.6  Cost of the Selected Sitewide Remedy	11-17

12.0 Statutory Determinations	12-1
      12.1  Protection of Human Health and the Environment	12-1
      12.2  Compliance with ARARs	12-3
      12.3  Cost Effectiveness	12-4
            12.3.1  Shallow Ground Water and Subsurface Liguids (OU 1)  and
                     Deep Ground Water (OU 6)	12-4
            12.3.2  Landfill Solids (OU 2)   	12-4
            12.3.3  Landfill Gas (OU 3)	12-5
            12.3.4  Soil (OU 4)	12-5
            12.3.5  Surface Water (OU 5)   	12-6
            12.3.6  Sediments (OU 5)   	12-6
            12.3.7  Selected Sitewide Remedy	12-6
      12.4  Utilization of Permanent Solutions and Alternative Treatment
             Technologies (or Resource Recovery Technologies)  to the
             Maximum Extent Practicable	12-7
            12.4.1  Long-Term Effectiveness and Permanence  .    	12-7
            12.4.2  Reduction of Toxicity,  Mobility, or Volume Through
                     Treatment	12-9
            12.4.3  Short-Term Effectiveness	12-9
            12.4.4  Implementability  	  12-11
            12.4.5  Cost	12-12
            12.4.6  State Acceptance  	  12-13
            12.4.7  Community Acceptance  	  12-13
      12.5  Preference for Treatment as a Principal Element 	  12-14

13.0  Responsiveness Summary for Operable Units 1&6	13-1
      13.1  Response to Oral Comments on the Proposed Plan for Operable
             Units 1&6 Shallow Ground-Water and Subsurface Liguids and
             Deep Ground-Water Operable Units Lowry Landfill Public Meeting
             December 9, 1992	13-1
      13.2  Response to Written Comments on the Proposed Plan for Operable
             Units 1&6 Shallow Ground-Water and Subsurface Liguids and
             Deep Ground-Water Operable Units August 1993	13-83
            13.2.1  EPA's Response to Comments from Citizens Against Lowry
                     Landfill Richard Schelin, Chairman	13-83
            13.2.2  EPA's Response to Comments from City of Aurora	13-89
            13.2.3  EPA's Response to Comments from Colorado Department
                     of Health	13-96
            13.2.4  EPA's Response to Comments from East Cherry Creek

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                     Valley Water and Sanitation District	13-97
            13.2.5  EPA's Response to Comments from William G.
                     Kennedy 	  13-104
            13.2.6  EPA's Response to Comments from the Lowry
                     Coalition 	  13-110
            13.2.7  EPA's Response to Comments from Robert Velton,
                     Pemex,  Inc  	  13-111
            13.2.8  EPA's Response to Comments from United States
                     Department of Interior,  Fish and Wildlife  Service .  .  .  13-112
            13.2.9  EPA's Response to Comments from Waste Management
                     of Colorado, Inc.,  Chemical Waste Management,  Inc.,
                     and the City and County of Denver	13-113
            13.2.10 EPA Response to comments from Wilbur A. Young  	  13-124

14.0  Responsiveness Summary for OUs 2&3 and 4&5	14-1
      14.1  Response to Oral Comments Proposed Plan Public Meeting
             Lowry Landfill Solids/Gas Operable Units (OUs 2&3)  and
             Soils/Surface Water and Sediments Operable Units (OUs 4&5)
             September 21, 1993	14-1
      14.2  Response to Written Comments Proposed Plan Lowry Landfill
             Solids/Gas Operable Units (OUs 2&3) and Soils/Surface
             Water and Sediments Operable Units (OUs 4&5)   	14-13
            14.2.1  Response to Written Comments
                     Hadden and Bonnie Robinson	14-13
            14.2.2  Response to Written Comments
                     Wilbur Young,  November 1, 1993 Letter	14-15
            14.2.3  Response to Written Comments
                     East Cherry Creek Valley Water and
                     Sanitation District (ECCV)  	14-17
            14.2.4  Response to Written Comments
                     Wilbur Young,  November 5, 1993 Letter	14-22
            14.2.5  Response to Written Comments
                     City of Aurora	14-23
            14.2.6  Response to Written Comments City and County of Denver
                     (Denver),  Waste Management of Colorado,  Inc. (WMC),
                     and Chemical Waste Management, Inc.  (CWM)	14-24

15.0  Bibliography	15-1

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                                     Tables

                                                                                Page

2-1    Wildlife Species Observed Within or Near the Lowry Site	2-21
2-2    Plant Species Noted Within the Vicinity of the Lowry Site	2-22
2-3    Potentially Occurring Threatened and Endangered Species
        Within or Around the Lowry Site	2-24
2-4    Well Inventory Summary	2-25

3-1    De Minimis Settlement,  Consent Order Docket No.  CERCLA VIII-93-04
        Effective August 28, 1992 and De Minimis Settlement Consent Order
        Docket No. CERCLA VIII-93-21 Effective June 2,  1993	3-11

4-1    Lowry Landfill Superfund Site Fact Sheets and Updates  	   4-4

6-1    Summary of Chemical Concentration Data for Waste Pit Liguids Well
        Points and Shallow Ground-Water Monitoring Wells in the Source Area .  .  6-25
6-2    Summary of Chemical Concentration Data for Downgradient Weathered
        Dawson Monitoring Wells Outside of the Source Area  	  6-29
6-3    Summary of Chemical Concentration Data for Downgradient Unweathered
        Dawson Monitoring Wells Outside the Source Area 	  6-32
6-4    Summary of Chemical Concentration Data for Deep Ground-Water
        Monitoring Wells	6-35
6-5    Summary of Chemical Concentration Data for Upgradient Monitoring Wells
        Outside the Source Area	6-37
6-6    Summary of Chemicals Detected in Unsaturated Solids Within the
        Landfill Mass	6-39
6-7    Summary of Chemicals Detected in Unsaturated Solids Within the
        Former Tire Pile Area	6-44
6-8    Methane Concentrations in Perimeter Gas Monitoring Wells 	  6-49
6-9    Landfill Gas Data Summary	6-50
6-10   Sewage Sludge Application/Leachate Injection Area (Group 1)  Soils
        Data Summary	6-51
6-11   Sewage Sludge Application (Group 2)  Soils Data Summary 	  6-53
6-12   Leachate Spraying Area (Group 3)  Soils Data Summary	6-54
6-13   Chemicals Detected in Surface Soil Samples in the Tire Pile Area ....  6-55
6-14   Subsurface Soil Data Summary	6-57
6-15   Surface Water Data Summary	6-58
6-16   Summary of Chemicals Detected in Sediments in Section 6	6-59

7-1    Minimum/Maximum Concentrations of Contaminants of Concern  	  7-26
7-2    Ground-Water Exposure Point Concentrations for the Hypothetical Future
        Onsite Residential Setting  	  7-29
7-3    Subsurface Soil and Landfill Gas Exposure Point Concentrations 	  7-31
7-4    Surface Soil Exposure Point Concentrations for the Hypothetical Future
        Onsite Residential Setting  	  7-33
7-5    Surface Water and Sediment Exposure Point Concentrations for the
        Hypothetical Future Onsite Residential Setting  	  7-35
7-6    RME Exposure Parameters	7-37
7-7    Toxicity Values for Chemicals with Carcinogenic Effects  	  7-39
7-8    Toxicity Values for Chemicals with Noncarcinogenic Effects 	  7-41
7-9    COCs Without Toxicity Values	7-45
7-10   Summary of Quantified Site Risks Based on Hypothetical Future Onsite
        Residential Setting 	  7-46
7-11   Comparison of Subsurface Soil Maximum Detected Concentrations to
        Carcinogenic Risk-Specific Values and Noncarcinogenic Reference
        Concentrations in the Future Onsite Residential Setting 	  7-49
7-12   Comparison of Exposure Point Concentrations of Landfill Gas Within the
        Landfill Mass to Carcinogenic Risk-Specific Values and Noncarcinogenic
        Reference Concentrations in the Future Onsite Residential Setting .  .  .  7-51
7-13   Comparison of Modeled Exposure Point Concentrations Assuming a Cracked
        Slab to Carcinogenic Risk-Specific Values and Noncarcinogenic Reference
        Concentrations in the Future Offsite Residential Setting  	  7-52
7-14   Cumulative Total Risk for the Hypothetical Future Onsite Residential
        Setting	7-53
7-15   Default Parameters Used in Uptake/Biokinetic Model 	  7-54

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7-16   Risk Assessment Radionuclides	7-55
7-17   Summary of Radiological Risk from Ingestion of Ground Water at the RME
        Future Onsite Residential Setting 	  7-56
7-18   Comparison of Maximum Detected Subsurface Soil Concentrations to
        Carcinogenic Risk-Specific Values at the RME for the Future Onsite
        Residential Setting 	  7-57
7-19   Summary of Radiological Risk from Exposure to Surficial  Soil at the RME
        Future Onsite Residential Setting 	  7-58
7-20   Summary of Radiological Risk from Exposure to Sediments  at the RME
        Future Onsite Residential Setting 	  7-59
7-21   Summary of Radiological Risk at the RME Future Onsite Residential
        Setting	7-60
7-22   Potentially Occurring Threatened and Endangered Species  Within or
        Around the Lowry Site	7-61
7-23   Constituents Eliminated on the Basis of Relative Toxicity  	  7-62
7-24   Maximum Detected Concentrations of Ecological Chemicals  of Concern .  .  .7-63

8-1    ARARs for OUs 1&6  	
8-2    ARARs for OUs 2&3  	
8-3    ARARs for OUs 4&5  	
11-1   Selected Sitewide Remedy ARARS	11-22
11-2   Ground-Water Compliance Boundary Performance Standards
        Sitewide Remedy	11-33
11-3   Ground-Water Point of Action Boundary Standards	11-38
11-4   Surface Water Standards	11-41
11-5   Air Quality Performance Standards Sitewide Remedy	11-46
11-6   Landfill Gas Point of Action Boundary Standards	11-49
11-7   Landfill Gas Compliance Boundary Performance Standards
        Sitewide Remedy	11-50
11-8   Cost Estimate Summary Selected Sitewide Remedy	11-51

13-1   Lowry Landfill,  Arapahoe County,  Colorado
        Operable Units  1&6,  Proposed Plan,
        Effect of Discount Rate on Cost Estimates 	  13-121

14-1   Chemical Concentration Data Summary	14-49

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                                     Figures

                                                                                Page

1-1    Lowry Landfill Combined Sitewide Remedy  	   1-5

2-1    The Lowry Site and DADS Facility Location	2-12
2-2    Current Zoning in the Vicinity of the Lowry Site	2-13
2-3    Major Land Uses in the Vicinity of the Lowry Site	2-14
2-4    Expected Future Land Use in the Vicinity of the Lowry Site	2-15
2-5    Ground-Water Supply Wells	2-16
2-6    Cross-Section Through the Denver Basin 	  2-17
2-7    Drinking Water Supply Sources  	  2-18
2-8    Lowry Landfill Site Surface Features 	  2-19
2-9    Schematic of Hydrogeologic Setting 	  2-20

3-1    Approximate Waste Pit, Tires, and Sludge Application Area Locations   .  .  3-10

6-1    Approximate Waste-Pit Locations (1965-1980)  and Well Points  Where
        Non-Agueous Phase Liguids were Observed 	  6-19
6-2    Extent of Contaminated Shallow Ground Water  	  6-20
6-3    Extent of Contaminated Deep Ground Water	6-21
6-4    General Source and Extent of Contamination Within Unsaturated Solids  Within
        the Former Tire Pile Area	6-22
6-5    General Source and Extent of Contamination From Landfill  Gases 	  6-23
6-6    Potential Sources of Soil Contamination  	  6-24

7-1    Selection Criteria for the Chemicals of Potential Concern  	  7-25

11-1   Lowry Landfill Combined Sitewide Remedy	11-19
11-2   Ground-Water Compliance Boundary and Ground-Water Action
        Boundary	11-20
11-3   Landfill Gas Compliance and Point of Action Boundaries	11-21

13-1   Lowry Landfill OUs 2&3 Area	13-106
13-2   Lowry Landfill OUs 4&5 Area	13-107

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                              List of Acronyms

AAL          allowable ambient levels
AOCs         Administrative Orders on Consent
APEN         Air Pollution Emission Notice
ARARs        applicable or relevant and appropriate requirements
ASC          Additional Site Characterization
ATSDR        Agency for Toxic Substances and Disease Registry
Aurora       City of Aurora
AWQC         Ambient Water Quality Criteria
BNA          base-neutral acid
CAA          Clean Air Act
CALL         Citizens Against Lowry Landfill
CCD          City and County of Denver
CDC          Center for Disease Control
CDD/CDF      Chlorinated Dibenzo-p-dioxin and dibenzofurans
CDH          Colorado Department of Health
GDI          Chronic Daily Intake
CDOW         Colorado Division of Wildlife
CPDES        Colorado Pollution Discharge Elimination System
CERCLA       Comprehensive Environmental Response,  Compensation, and Liability Act of 1980
CFR          Code of Federal Regulations
cfs          cubic feet per second
GIN          Citizen's Information Network
CHWA         Colorado Hazardous Waste Act
CLP          Contract Laboratory Program
CNAP         Colorado Natural Areas Program
COG          chemicals of concern
COPC         chemicals of potential concern
COSA         Colorado Occupational Health and Safety
CWA          Clean Water Act
CWM          Chemical Waste Management, Inc.
CWP          Conceptual Work Plan
DADS         Denver Arapahoe Disposal Site
Denver       City and County of Denver
DQOs         data quality objectives
EA           Ecological Assessment
EE/CA        Engineering Evaluation/Cost Analysis
EPA          United States Environmental Protection Agency
°F           degrees Fahrenheit
FEMA         Federal Emergency Management Agency
FIT          Field Investigation Team
FS           feasibility study
ft/day       feet per day
ft3/yr       cubic feet per year
FWPCA        Federal Water Pollution Control Act
GMP          gas monitoring probes
GW           ground water
GWTP         ground-water treatment plant
gpm          gallons per minute
HEAST        Health Effects Assessment Summary Table
HEW          United States Department of Health, Education, and Welfare
HI           Hazard Index
HLA          Harding Lawson Associates
HQ           Hazard Quotient
HRS          Hazard Ranking System
HSWA         Hazardous and Solid Waste Amendments
HVOC         hazardous volatile organic chemicals
IDE          Initial Data Evaluation
IRIS         Integrated Risk Information System
IRM          interim remedial measure
kg           kilograms
1            liter
L/DNAPLs     low/dense non-aqueous phase liquids
LFS          landfill solids
LFG          landfill gas
LLMC         Lowry Landfill Monitoring Committee

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LOAEL        Lowest Observed Adverse Effect Level
Lowry Site   Lowry Landfill Superfund Site
MCLG         maximum contaminant level goal
MCL          maximum contaminant level
jig           microgram
jig/kg        microgram per kilogram
Metro        Metro Wastewater Reclamation District
mg/kg        milligram per kilogram
mph          miles per hour
NAAQS        National Ambient Air Quality Standards
NC           not calculated
NCP          National Contingency Plan for Oil and Hazardous Substances Pollution
ND           not detected
NESHAPs      National Emissions Standards for Hazardous Pollutants
NOAEL        No Observed Adverse Effects Level
NOV          Notice of Violation
NPL          National Priorities List
NRC          Nuclear Regulatory Commission
NRHP         National Register for Historic Places
NSPS         New Source Performance Standards
O&M          operation and maintenance
OSHA         Occupational Safety and Health Administration
OSWER        Office of Solid Waste and Emergency Response
OUs          operable units
OU 1         Shallow Ground Water and Subsurface Liguids Operable Unit
OU 2         Landfill Solids Operable Unit
OU 3         Landfill Gas Operable Unit
OU 4         Soils Operable Unit
OU 5         Surface Water and Sediments Operable Unit
OU 6         Deep Ground Water Operable Unit
PA           Preliminary Assessment
PAG          Policy Advisory Group
PAHs         polynuclear aromatic hydrocarbons
PCBs         polychlorinated biphenyls
pCi/L        picocuries per liter
PEA          Preliminary Endangerment Assessment
POA          Point of Action
POTW         Publicly Owned Treatment Works
ppb          parts per billion
ppm          parts per million
PRPs         potentially responsible parties
QA/QC        guality assurance/guality control
RA           Risk Assessment
RAO          remedial action objectives
RAGS         Risk Assessment Guidance for Superfund
RCRA         Resource Conservation and Recovery Act of 1976
RfD          reference dose
RI           remedial investigation
RI/FS        remedial investigation/feasibility study
RME          reasonable maximum exposure
ROD          Record of Decision
SAPI         Southeast Area Planning Initiative
SARA         Superfund Amendments and Reauthorization Act of 1986
scfm         standard cubic feet per minute
scf/tn/yr    solid waste cubic feet per ton per year
SED          sediment (abbreviation for sediment alternative number)
SF           slope factors
SOW          Statement of Work
SQL          Sample Quantification Limit
SRU          Site Review and Update
STC          Storage Technology Corporation
SVOC         semivolatile organic compounds
SW           surface water
SWA          Solid Waste Act
SWRA         Surface Water Removal Action
TAG          Technical Advisory Group
TAG          Technical Assistance Grant

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TBC          to be considered
TCLP         toxicity characteristic leaching procedure
TEF          Toxicity Equivalent Factors
TEL          threshold effects exposure units
USC          United States Code
UCL          Upper Confidence Limit
USFWS        United States Fish and Wildlife Service
USGS         United States Geological Survey
VOC          volatile organic compounds
WMC          Waste Management of Colorado,  Inc.
WRIS         Wildlife Resource Information System (CDOW)

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Glossary of Terms

Administrative Order: An agreement between EPA and one or more potentially responsible parties whereby the
potentially responsible party or parties agree to perform or pay the cost of site investigations or cleanup.

Administrative Record: A file that is established and maintained by the lead agency and contains all the
documents used by EPA to make a decision on the selection of a remedial action. The administrative record is
available for public review and a copy is established at or near the site, usually at one of the information
repositories.

Alluvium: Sedimentary deposits from streams or rivers.

Applicable Reguirements: Those cleanup standards, standards or control, and other substantive reguirements,
criteria or limitations promulgated under federal environmental or state environmental or facility siting
laws that specifically address a hazardous substance, pollutant, contaminant, remedial action, location, or
other circumstance found at a CERCLA site. Only those state standards that are identified by a state in a
timely manner and that are more stringent than federal reguirements may be applicable.

Aguifer: A geologic formation, group of formations, or part of a formation capable of yielding a significant
amount of ground water to wells or springs.

Baseline Risk Assessment (Baseline RA) : Evaluates the potential risks to human health if nothing is done to
remediate a site or eliminate the risks. The Baseline RA considers current use and hypothetical future use
of the site.

Capital Costs: The costs of items such as buildings, eguipment, engineering, and construction.

CERCLA: The Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended by the
Superfund Amendments and Reauthorization Act of 1986.

Chemicals of Concern: The most prevalent and toxic site-related chemicals.

Co-Disposal: A technigue used at the Lowry Site to dispose of wastes. Liguid industrial wastes were
deposited into unlined trenches or pits, and municipal refuse was added to soak up the liguids.

Compliance Boundary: The boundary at the Lowry Site where chemical-specific remediation levels and
performance standards must be met.

Contingency Plans: Plans that detail the action to be taken in response to a remedy component failure.

Deep Ground Water (Operable Unit 6): All ground water below the shallow ground water (below the separation
layer) to the top of the Pierre Shale, underlying the Laramie-Fox Hills aguifer.

Enclosed Flare: A piece of eguipment (a burner) used to burn landfill gas after collection; the burner and
flame are enclosed.

Excess Lifetime Cancer Risk: The incremental probability of an individual developing cancer over a lifetime
as a result of exposure to a potential carcinogen. A cancer risk of 1 X 10-6 is one additional case of
cancer (over background levels) per million people exposed (a one in a million chance of having cancer). The
NCP specifics that 1 X 10-6 is an acceptable risk level for multiple contaminants (NCP
300.430[e][2][i][A][2]). EPA uses a 1 X 10-4 to 1 X 10-6 risk level as a "target range" within which to
manage risk at Superfund sites.

Exposure: Contact of a chemical with the outer boundary of a human (skin, nose, mouth, skin punctures and
lesions) (EPA 1992, Guidelines for Exposure Assessment; Notice, EPA, Federal Register 57 [104]; 22888-22938,
May 29, 1992).

Exposure Parameter: Factors such as body weight, breathing rate, or time/activity that may be needed to
guantify (calculate) human exposure to a contaminant.

Exposure Pathway: The course a chemical or physical agent takes from a source to a receptor. An exposure
pathway describes a unigue mechanism by which an individual or population is exposed to chemicals or physical
agents at or originating from a site. Exposure pathway includes a source or release from a source, an
exposure point, and an exposure route. If the exposure point differs from the source, the transport/exposure
medium (such as air) or media (in cases of intermedia transport, such as water to air) are also included (EPA
1989, Risk Assessment Guidance for Superfund, Vol I, Human Health Evaluation Manual [Part A], Office of
Emergency and Remedial Response, EPA/540/1-89/002).

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Exposure Point: A geographical location of potential contact between a receptor and a chemical or physical
agent, e.g., a child ingesting soil containing PCBs within the sewage sludge application/leachate injection
area (EPA, 1989, Risk Assessment Guidance for Superfund, Vol I, Human Health Evaluation Manual [Part A],
Office of Emergency and Remedial Response, EPA/540/1-89/002).

Exposure Point Concentration: Concentration at the point where receptors may be exposed.

Exposure Route: The way a chemical or physical agent comes in contact with a receptor, that is, inhalation,
ingestion, dermal contact, e.g., inhalation by a hypothetical future resident of vinyl chloride in landfill
gas contained within a home onsite (EPA, 1989, Risk Assessment Guidance for Superfund, Vol I, Human Health
Evaluation Manual [Part A], Office of Emergency and Remedial Response, EPA/540/1-89/002).

Exposure Setting: A combination of potential land uses and exposure routes that describes the ways by which
a specific type of receptor can contact contaminants, that is, residential setting, occupational setting,
recreational setting.

Feasibility Study (FS): A study undertaken to develop and evaluate options for remedial action. The FS
emphasizes alternative analysis and is generally performed concurrently and in an interactive fashion with
the remedial investigation (RI), using data gathered during the RI. The RI data are used to define the
objectives of the response action, to develop remedial action alternatives, and to undertake an initial
screening and detailed analysis of the alternatives. The term also refers to a report that describes the
results of the study.

Former Tire Pile Area: The approximately 30-acre area in Section 6 of the Lowry Site from which
approximately 8 million old tires were removed.

Fund or Trust Fund: The Hazardous Substance Superfund established by Section 9507 of the Internal Revenue
Code of 1986.

Ground Water: As defined by Section 101(12) of CERCLA, water in a saturated zone or stratum beneath the
surface of land or water.

Hazard Ranking System (HRS): The method used by EPA to evaluate the relative potential of hazardous
substance releases to cause health or safety problems, or ecological or environmental damage.

Hydrogeologic: Relating to the science of hydrogeology, which studies the interactions among ground water
and geologic formations.

Intake: The measure of exposure expressed as the mass of a chemical that crosses an outer boundary of a
human or the chemical per unit body weight per unit time, i.e., milligrams of chemical per kilogram of body
weight per day.

Institutional Controls: Rules, regulations, laws, or covenants that may be necessary to assure the
effectiveness of a cleanup alternative. Examples of institutional controls include, but are not limited to,
deed restrictions, zoning controls, and access restrictions.

Interim Remedial Measures: An early action taken to control a release or threatened release of hazardous
substances.

Landfill Gas (Operable Unit 3): Gas generated at the Lowry Site resulting from degradation of the landfill
solids and chemical constituents volatilized from contaminant sources such as waste pit liguids, leachate,
ground water, surface water (including unnamed creek and Pond 3; Pond 4 will be included if it is in
existence), surface and subsurface soils, and solids (saturated and unsaturated).

Landfill Solids (Operable Unit 2): For the solids media, "unsaturated" is defined as material, excluding
saturated solids within the waste pits, that is above ground water associated with the shallow ground water
at the Lowry Site. The solids media include materials located within the Section 6 area that has received or
will receive solid wastes and the area formerly covered with tires. Leachate is defined as the liguids
generated during consolidation and/or degradation of the landfill solids or through interaction of water that
percolates through the solids media. Leachate within the solids media is included as part of the Landfill
Solids OU media. The solids media also includes:

• Unsaturated municipal solid waste (MSW) (e.g., household refuse).

• Unsaturated industrial waste, including drums and their contents.

• Buried and partially buried tires within the unsaturated zone.

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• Unsaturated solids contaminated by the migration of waste pit fluids or leachate.

• Unsaturated solids located within waste pits.

• Publicly-owned treatment works (POTW) sludge and sludge from industrial treatment plants
disposed of in the landfill within the Unsaturated zone.

• Hospital wastes disposed of in the landfill within the Unsaturated zone.

• Unsaturated subsurface and surface soils within the Landfill Solids OU area.

• Unsaturated low-level radioactive wastes. These wastes were reportedly disposed of in pits
near the southeast corner of Section 6.

• Zones of saturated solids located above the shallow ground water (perched), excluding saturated
solids within the waste pits.

Leachate: Contaminated liguids that result from the degradation of refuse or from water percolating through
refuse.

National Priorities List (NPL): The list, compiled by EPA pursuant to CERCLA Section 105, of uncontrolled
hazardous substance releases in the United States that are priorities for long-term remedial evaluation and
response.

Net Present Worth: An analysis of the current value of all costs. Net present worth is calculated based on
a 30-year time period and a 5% interest rate.

North Face: The north end of the former landfill that is sloped.

Onsite: The areal extent of contamination and all suitable areas in very close proximity to the
contamination necessary for implementation of the response action.

Operable Unit: A term used to describe certain portions of a Superfund site. An operable unit may be
established based on a particular type of contamination, contaminated media (e.g., soils, water), source of
contamination, and/or geographical location.

Operation and Maintenance: Measures reguired to maintain the effectiveness of the selected remedy.

Parts per billion (ppb)/parts per million (ppm): Units commonly used to express low concentrations of
contaminants. For example, 1 ounce of trichlorethylene (TCE) in 1 million ounces of water is 1 ppm; 1 ounce
of TCE in 1 billion ounces of water is 1 ppb.

Point of Action Boundary: The boundary of the Lowry Site where specific performance standards must be
achieved. The purpose of the POA boundary is to trigger early remedial actions, so that contaminants do not
migrate beyond the compliance boundary.

Potentially Responsible Party (PRP): An individual or company (such as owners, operators, transporters, or
generators of hazardous waste) potentially responsible for, or contributing to, the contamination problems at
a Superfund site.

Proposed Plan: A document that summarizes EPA's preferred cleanup strategy, the rationale for the
preference, and alternatives presented in the detailed analysis of the feasibility study. The Proposed Plan
solicits public review and comment on all alternatives under consideration.

Reasonable Maximum Exposure (RME): The RME is the highest exposure that is reasonably expected to occur at a
site. It is the product of a few upper-bound exposure parameters with primarily average or typical exposure
parameters so that the result represents an exposure that is both protective and plausible, exposure point
concentration and exposure freguency and duration, that are a mix of distributions (averages, 95th
percentile, etc.) to reflect a 90th percentile.

Receptor: Any organism (such as humans, terrestrials, wildlife, or aguatic) potentially exposed to chemicals
of concern.

Record of Decision (ROD): A public document that explains the remedial action plan for a Superfund site or
operable unit. A ROD serves three functions:

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       •       It certifies that the remedy selection process was carried out in accordance with CERCLA and,
              to the extent practicable,  with the NCP

       •       It describes the technical  parameters of the remedy,  specifying the treatment,  engineering,  and
              institutional components,  as well as remediation goals

       •       It provides the public with a consolidated source of information about the site and the chosen
              remedy,  including the rationale behind the selection

       •       The ROD also provides the  framework for the transition into the next phase of the remedial
              process,  Remedial Design (RD)

Relevant and Appropriate Reguirements:  Those cleanup standards, standards of control, and other substantive
reguirements, criteria or limitations promulgated under federal environmental or state environmental or
facility siting laws that, while not "applicable" to a hazardous substance, pollutant, contaminant, remedial
action, location, or other circumstance at a CERCLA site, address problems or situations sufficiently similar
to those encountered at the CERCLA site that their use is well suited to the particular site.  Only those
state standards that are identified in a timely manner are more stringent that federal reguirements may be
relevant and appropriate.

Remedial Action  (RA) or Remedy:  Those actions consistent with a permanent remedy taken instead of, or in
addition to, removal action in the event of release or threatened release of a hazardous substance into the
environment, to prevent or minimize the release of hazardous substances so that they do not migrate to cause
substantial danger to present or future public health or welfare or the environment.  The term includes, but
is not limited to, such actions at the location of the release as storage, confinement, perimeter protection
using dikes, trenches,  or ditches, clay cover, neutralization, cleanup of diversion, destruction, segregation
of reactive wastes, dredging or excavations, repair or replacement of leaking containers, collection of
leachate and runoff, onsite treatment or incineration, provision of alternative water supplies, any
monitoring reasonably reguired to assure that such actions protect the public health and welfare and the
environment and, where appropriate, post-removal site control activities.

Remedial Action Objectives  (RAOs):  Objectives developed by EPA at individual Superfund sites that, in
connection with chemical-specific remediation goals and performance standards define acceptable levels of
risk.

Remedial Design  (RD):  The technical analysis and procedures which follow the selection of remedy for a site
and result in a detailed set of plans and specifications for implementation of the remedial action.

Remedial Investigation (RI):  A process undertaken to determine the nature and extent of the problem
presented by the release.  The RI emphasizes data collection and site characterization, and is generally
performed concurrently and in an interactive fashion with the feasibility study.  The RI includes sampling
and monitoring, as necessary, and the gathering of sufficient information to determine the necessity for
remedial action and to support the risk assessment evaluation of remedial alternatives.

Resource Conservation and Recovery Act (RCRA):  A Federal law that reguires safe and secure procedures to be
used in treating, transporting, storing and disposing of hazardous wastes.

Respondent:  Identifies the party entering into an Administrative Order on Consent  (AOC or Consent Order)
with EPA.

Sediments  (Operable Unit 5):  Sediments in Sections 6 and 31 at the Lowry Site are defined as unconsolidated
deposits of particulates that originated from the weathering of rocks and organic matter and were transported
by water and deposited in drainage pathways.  If a particulate is not a sediment or a landfill solid as
defined in OU 2, it is defined as soil.

Settling Defendant:  Identifies the party entering into a Consent Decree with the Department of Justice (DOJ)
and EPA.

Shallow Ground Water and Subsurface Liguids  (Operable Unit 1):

       •       Ground water within the alluvium and weathered bedrock in the upper Dawson formation.
              Weathered bedrock is that  portion of the Dawson Formation,  nearest to the ground surface,  that
              has had an increase  in its  ability to transmit ground water because of the action of the
              physical  and chemical processes.   This portion of the Dawson Formation is more similar to the
              overlying alluvial aguifer  than the underlying unweathered Dawson with respect to its ability
              to transmit ground water.

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• Waste Pit Liquids. Liquids that are within the waste pits.

• Subsurface Leachate and Infiltration. Subsurface leachate is defined to be all liquids that
emanate from the waste pits, waste pit solids, and waste pit refuse that are subsurface.
Infiltration is water that enters into the ground through the soil surface.

• Saturated subsurface solids, including:

Soils that are below the water table
Saturated waste pit solids
Saturated soils adjacent to waste pits
Saturated refuse below the shallow ground-water table

Soils (Operable Unit 4): Soils at the Lowry Site are defined as consolidated and unconsolidated material
consisting essentially of mineral and organic matter above the water table.

Subtitle C: A program under RCRA that regulates the management of hazardous waste from the time it is
generated until its ultimate disposal.

Subtitle D: A program under RCRA that regulates the management of solid waste.

Superfund Amendments and Reauthorization Act of 1986 (SARA): Amendments to CERCLA, enacted on October 17,
1986.

Surface Water (Operable Unit 5): At the Lowry Site, surface water originates from precipitation,
ground-water discharge or leachate seeps and occurs on the surface of the site in drainage subbasins,
including the unnamed creek.

Surface Water Removal Action (SWRA): A system at the Lowry Site that separates normal precipitation in the
unnamed creek from contaminated leachate that previously surfaced in the creek bed. The contaminated
leachate is collected in the system and sent to the onsite treatment facility.

Tire Monofill: An excavation used at the Lowry Site to contain tire shreds.

Toe of the Former Landfill: The northernmost edge of the former landfill.

Vertical Migration: The ability of media such as water, to move vertically upwards or downwards through
various subsurface strata.

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                                       Section 1.0
                         Declaration for the Record of Decision

1.1  Site Name and Location

Lowry Landfill
Arapahoe County, Colorado

1.2  Statement of Basis and Purpose

The decision document presents the selected remedy for the Lowry Landfill Superfund site  (the Lowry Site),  in
Arapahoe County, Colorado, chosen in accordance with the Comprehensive Environmental Response, Compensation,
and Liability Act of 1980  (CERCLA),  as amended by the Superfund Amendments and Reauthorization Act of 1986
(SARA) ,  and, to the extent practicable, the National Oil and Hazardous Substances Pollution Contingency Plan
(NCP).   This decision is based on the administrative record for this Site.

The State of Colorado concurs with the selected remedy.

1.3  Assessment of the Site

Actual or threatened releases of hazardous substances from this site, if not addressed by implementing the
selected remedy in this Record of Decision (ROD),  may present an imminent and substantial endangerment to
public health, welfare, or the environment.

1.4  Description of the Selected Remedy

The selected sitewide remedy is composed of selected alternatives for the six operable units  (OUs) identified
at the Lowry Site.  The sitewide remedy includes operation of elements of the interim remedial measures at
the Lowry Site and the Surface Water Removal Action, which includes the ground-water barrier wall/treatment
facility.  All six of the operable units identified at the Lowry Site (and described in this ROD) are
addressed in the selected sitewide remedy.  The selected sitewide remedy addresses the potential risks
identified at the Site through containment, collection, and treatment.  The primary threats at the Lowry Site
are posed by:  landfill gas; waste-pit liguids; contaminated ground water; and buried drums, drum contents,
and contaminated soils within the former tire pile area.

Contaminated ground water will be addressed by containment, collection,  and treatment, utilizing an onsite
treatment plant.  Landfill gas will be addressed by containment, collection, and treatment using enclosed
flare technology.  Contaminated seepage and surface water are addressed through a drainage and underground
collection system in the unnamed creek area as part of the Surface Water Removal Action.  The response action
identified for the former tire pile area will address principal threats (drums, drum contents, and
contaminated soils) through treatment and offsite disposal to reduce the toxicity, mobility, and volume of
contaminants.  Landfill mass solids and soils are low-level threats at the Lowry Site and are addressed
through containment.

Major components of the remedy (as shown in Figure 1-1) include:

       •      Continued operation of the existing  ground-water barrier wall,  collection system,  and
              ground-water treatment plant (the Surface Water Removal Action [SWRA]).   The existing
              ground-water treatment plant may be  upgraded to increase the capacity of the treatment system
              and to  treat more concentrated  liguids from the toe of the landfill,  or a new ground-water
              treatment plant may be constructed to accomplish the same  objectives.

       •      Installation of a ground-water  extraction system at the toe  of the landfill mass.

       •      Construction and operation of underground barrier walls and  ground-water collection systems on
              the east and west sides of the  Lowry Site.

       •      Implementation of a ground-water monitoring program along  the circumference of the point of
              action  (POA)  boundary  to detect future releases of contaminants to the east, west,  north,  and
              south.

       •      Construction and operation of an approximately 50-foot-deep  upgradient ground-water
              containment,  collection,  and diversion system along the southern perimeter of the  Lowry Site.

       •      Annual  treatment of approximately 6.4 million gallons of contaminated ground water from the new
              barrier wall and collection systems  and the existing barrier wall using either the existing

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ground-water treatment plant, an upgraded treatment plant, or a new ground-water treatment
plant.

• Implementation of a long-term, sitewide ground-water monitoring program to assess remedy
compliance for the shallow ground-water system and potential impacts to deep ground water.

• Monitoring to detect future releases of contaminants to the ground water. Should releases be
detected, corrections to the containment systems would be made with the potential for
additional extraction wells and/or expansion of the barrier system, and/or other technologies
to restrict offsite groundwater migration.

• Excavation, removal, and treatment within the former tire pile area, of surface and subsurface
drums, contaminated soils, and waste pits.

• Landfill gas collection using interior and perimeter collection systems and an enclosed flare
for treatment.

• Installation of a perimeter gas monitoring system to detect potential landfill gas migration.
Should migration be detected, corrections to the system would be made with the potential for
installation of additional extraction wells to restrict offsite landfill gas migration.

• Placement of an additional two (2) feet of cover on the north face of the landfill mass.

• Continued maintenance of the landfill mass cover.

• Construction of wetlands to mitigate loss of wetlands areas from SWRA construction activities
within unnamed creek.

• Surface-water monitoring to allow detection of future releases of contaminants to surface
water.

• Visual monitoring of actual and potential soil erosion.

• Establishment of institutional controls to limit access to the Lowry Site, prohibit such
activities as construction on the Lowry Site, and prohibit the use of water beneath the Lowry
Site or in the immediate vicinity of the Lowry site. Offsite institutional controls shall
serve as an additional measure of protection to enhance the effectiveness of the selected
remedy and to act as preventative measures to preserve the implementability and
effectiveness of any of the selected remedy contingency measures that EPA determines must be
implemented at the Lowry Site.

• A review of the selected remedy at the Lowry Site no less often than each 5 years after the
initiation of the remedial action to assure continued protection of human health and the
environment.

1.5 Statutory Determinations

The selected sitewide remedy is protective of human health and the environment, complies with Federal and
State reguirements that are legally applicable or relevant and appropriate to the remedial action, and is
cost effective. This remedy utilizes permanent solutions and alternative treatment technologies to the
maximum extent practicable. Components of the selected sitewide remedy satisfy the statutory preference for
remedies that employ treatment that reduce toxicity, mobility, or volume as a principle element. The size of
the landfill mass and inaccessibility of the waste pits, located within and underneath the landfill mass
(exclusive of those in the former tire pile area), precludes a remedy in which all contaminants could be
excavated and effectively treated. Therefore, consistent with the NCP and EPA guidance Conducting Remedial
Investigations/Feasibility Studies for CERCLA Municipal Landfill Sites (EPA OSWER Directive 9355.3-11,
February 1991), containment is selected to address the low-level threat from the landfill mass and the
primary threats from the waste pits within the landfill mass area. Because treatment of these threats was not
found to be practicable, this portion of the selected sitewide remedy does not satisfy the statutory
preference for treatment.

Principal threats (drums, drum contents, contaminated soils, and waste pits) in the former tire pile area
will be addressed through excavation, treatment, and disposal. Conseguently, this component of the remedy
satisfies the statutory preference for treatment as a principal element of the remedy.

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Because this remedy will result in hazardous substances remaining on the Lowry Site above health-based
levels, a review will be conducted no less often than each 5 years after the initiation of the remedial
action to assure that the remedy continues to provide adequate protection of human health and the
environment.

William P. Yellowtail, Regional Administrator
U.S. Environmental Protection Agency, Region VIII

Thomas P. Looby, Director, Office of Environment
State of Colorado Department of Health
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Section 2.0
Site Summary

2.1 Site Name, Location, and Description

The Lowry Landfill Superfund Site (the Lowry Site) is located in the western three-quarters of Section 6,
Township 5 South, Range 65 West in unincorporated Arapahoe County, Colorado, approximately 15 miles southeast
of the City and County of Denver and 2 miles east of Aurora, near the intersection of Easy Quincy Avenue and
Gun Club Road; the street address is 3500 South Gun Club Road, Denver, Colorado. The Lowry Site consists of
480 acres, and is a portion of the Denver Arapahoe Disposal Site (DADS), owned by the City and County of
Denver (Denver) and operated by Waste Management of Colorado, Inc. (WMC). DADS consists of Sections 4, 6,
and 9, Township 5 South, Range 65 West and Selections 31 and 32, Township 4 South, Range 65 West (Figure
2-1) .

2.2 Area and Topography

The Lowry Site consists of gentle slopes on the north half of the section and a topographic high on the south
half of the section caused by past landfilling activities (Figure 2-1).

2.3 Natural Resource Use

The Lowry Coalition conducted an evaluation of potentially protected resources as part of the OUs 1&6
Remedial Investigation/Feasibility Study (RI/FS). The area for which the evaluation was conducted includes
the landfill located north of Quincy Avenue and east of Gun Club Road, and all of Section 6, Range 65W,
Township 5S, and the south half of Section 31, Range 65, Township T4S. This area is referred to as the
"project area" in the following text.

2.3.1 Evaluation of Threatened and Endangered Species

2.3.1.1 Ecological Setting

The Lowry Site is located in gently rolling short-grass prairie characteristic of the Great Plains
physiographic province. The land is largely undisturbed native prairie, disturbed weedy prairie, and areas
of unirrigated small grain crops.

Habitats within the Lowry Site boundaries have been disturbed by past and ongoing landfill disposal
activities. Aguatic habitats within the Lowry Site boundaries are limited and lack the capacity to support
fish. Habitats in Section 6, east of the Lowry Site, are primarily native prairie with an intermittent
riparian corridor. Habitats on the south half of Section 31, north of the Lowry Site, include stripped
prairie, the Command Post, fallow fields, native prairie, weeded, disturbed prairie, and a wetland along
Murphy Creek.

2.3.1.2 Endangered Species

Endangered species that may be present in the vicinity of the Lowry Site, specifically the bald eagle,
peregrine falcon, whooping crane, black-footed ferret, and Federal endangered species candidates, are
discussed in the following paragraphs. No specific occurrences of listed candidate species have been
recorded within 1 mile of the Lowry Site.

Tables 2-1, 2-2, and 2-3 list the wildlife, plant, and threatened and endangered species, respectively,
observed or occurring on the Lowry Site or in the vicinity of the Lowry Site.

The United States Fish and Wildlife Service (USFWS) lists the bald eagle (Haliaeetus leucocephalus) as an
endangered species in Colorado. Bald eagles are spring and autumn migrants, but uncommon winter residents in
the vicinity of the Lowry Site. However, they are common winter residents in suitable nearby habitats. The
Lowry Site and adjacent lands are not an important area for bald eagles. Individual eagles have been seen
irregularly in the vicinity of the Lowry Site, but these birds are generally flying through the area. The
USFWS is not aware of any recent bald eagle sightings. However, a golden eagle nest has been identified at
the intersection of Smoky Hill and Gun Club Road.

The peregrine falcon (Falco peregrinus) is a Federal and Colorado endangered species. The gently rolling
prairie, on and around the Lowry Site, is not suitable peregrine falcon habitat. There are no suitable nest
sites closer than downtown Denver. Airspace in the vicinity of the Lowry Site may be used by migrating
peregrines; however, it is more likely that migrants would follow the Front Range (18 miles to the west) for
their spring and autumn migrations. The Lowry Site vicinity does not offer any potentially suitable habitat
for the peregrine falcon.
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Whooping cranes (Grus americana) are one of the rarest of all North American endangered species. Colorado
has historically been outside the normal range of the species, except for stragglers migrating between
breeding grounds in Canada and wintering grounds in Texas. Habitats adjacent to, and in the vicinity of, the
Lowry Site provide a suboptimal crane habitat. There are no large wetlands or water bodies present to
provide the horizontal visibility required for secure roosting.

Black-footed ferrets (Mustela nigripes) have historically been associated with the range of prairie dogs
(Cynomys ludovicianus) throughout the Great Plains, semi-arid grasslands, and mountain basins of North
America. The Lowry Site and adjacent areas occur within the general historic range of the black-footed
ferret; however, no black-footed ferret sightings have been confirmed in Colorado in recent years.

Federal candidate species are sensitive wildlife species currently under consideration by the USFWS for
addition to the threatened and endangered species list.

2.3.2 Evaluation of Wetland Areas

The following evaluation includes a description of the ecological setting, wetland identification and
mapping, and a description of the wetlands on or near the Lowry Site, including a delineation of specific
types of wetland vegetation along Murphy Creek in Section 31 and the unnamed creek drainage in Section 6, and
an estimate of acreages for each wetland vegetation type.

2.3.2.1 Ecological Setting

The study area used for the wetlands evaluation is within the southern half of Section 31, Township 4S, Range
65W, and Section 6, Township 5S, Range 65W. No natural permanent surface-water source exists within the
study area. The land is largely native prairie and areas of dryland crops. Short-grass prairie and dryland
crop-field also characterizes much of the area to the north, south, and east of the Lowry Site.

The Lowry Site is drained by unnamed creek, which is an intermittent stream. Most habitats within the Lowry
Site have been disturbed by past landfilling or ongoing disposal activities. The irregular topography of the
Lowry Site produced by landfill grading activities has created two small basins which collect water from
precipitation events.

Wetlands plant species along the unnamed creek drainage in Section 6 include cattail (Typha latifolia and T.
angustifolia), three-sguare (Scirpus americana), and fox-tail barley (Hordeum jubatum).

During the construction of the SWRA, a total of 0.87 acre of wetlands was disturbed. As part of the sitewide
remedy, an equal amount of wetlands will be created in another location near the Lowry Site.

2.4 Cultural Resources

During August 1989, an intensive survey of approximately 400 acres of the Lowry Site was performed to
identify and evaluate cultural resources for the National Register of Historic Places (NRHP) by the Lowry
Coalition. The work was conducted to comply with requirements and responsibilities under the National
Historic Preservation Act of 1966, as amended, and its implementing regulations (36 CFR Part 800). No
resources were identified for inclusion in the NRHP.

2.5 Adjacent Land Use

Current zoning and land uses by Arapahoe County in the vicinity of the Lowry Site are presented in Figures
2-3 and 2-3. No residences are located onsite.

The areas immediately surrounding the Lowry Site are zoned for agricultural use and mixed use. Much of the
area surrounding the Lowry Site is undeveloped and used primarily for cattle ranching and grazing. Some
sections are used for production of dryland (no irrigation) winter wheat. A few homes are scattered on these
farms and ranches in the areas around the Lowry Site. Two older homes are located roughly one-third and
two-thirds of a mile west of the Lowry Site on East Quincy Road.

2.6 Distance to Nearby Populations

A few subdivisions have been built in unincorporated areas near the Lowry Site. Dove Hill is a small
subdivision approximately 1 mile south of Section 6. The Trail Ridge, Park View, and Parborough subdivisions
are located about 2 miles southwest.

The most intensive nearby urban and residential development is within the corporate limits of the City of
Aurora, approximately 2 miles west and north of the Lowry Site. Gun Club Estates and Thunderbird Estates are
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located 3 and 4 miles north of Section 6, respectively.

A number of schools are located in the general vicinity of the Lowry Site. Eaglecrest High School and
Thunder Ridge Junior High, 2 miles to the southwest, are the closest schools. Sunrise Elementary School is
within approximately 3 miles of the Lowry Site; other elementary schools are located in a 4- to 5-mile
radius.

Overall, based on information provided by the Cherry Creek and the Aurora School Districts, 11 elementary
schools, 4 middle schools, and 2 high schools are located within a 5-mile radius of the Lowry Site. Combined
enrollment in these schools is about 13, 824 students. Over the past 5 years, the net enrollment gain has
been about 8.9 percent, or 1.8 percent per year.

2.7 Future Land Use and Populations

Located in the southeast guadrant of the Denver Metropolitan area, the Lowry Site faces development pressure
influenced by the economic growth of the City of Aurora and surrounding area. The City of Aurora anticipates
mixed land use for the area surrounding the Lowry Site, as depicted in Figure 2-4. Mixed use includes
industrial, commercial, and residential development compatible with anticipated growth in the area.

The area directly south and west of the Lowry Site, as well as a mile to the north and northwest, is zoned
for office and industrial use. Under the terms of an ordinance issued by the City of Aurora, new residences
may be built as close as 0.5 mile to the south and west of the Lowry Site, as shown in Figure 2-4. More
residences may be constructed 1.5 miles directly north and 2 miles northeast. Residences, in addition to
business facilities, could also be developed in the mixed-use corridor along the eastern border.

Land use restrictions were imposed on the Lowry Site by former Denver Mayor Federico Pena in June, 1991.
Executive Order No. 97 restricts use of the land, surface water, and ground water on the Lowry Site.
Specifically, the Executive Order prohibits:

• Direct use or reuse of the surface water or alluvial ground water or ground water in the Dawson
and Denver aguifers on or underlying either Section 6 or Section 31 that could cause exposure
of humans or animals to contaminants, provided that this restriction shall not interfere with
treatment and subseguent use or discharge of any such water.

• Direct use or reuse of ground water in the Arapahoe and Laramie-Fox Hills aguifers underlying
Sections 6 and 31 for domestic, residential, or municipal water supply purposes.

• Water production or dewatering wells constructed on Sections 4, 9, and 32 without the express
written consent of the Denver Mayor or his designee.

• Agricultural development, residential development, commercial development, day-care centers,
preschool, schools, hospitals, nursing homes, community recreational facilities, senior citizen
centers, restaurants, hunting, or fishing on Sections 6 and 31.

• Construction of a building or other structure on those portions of Sections 6 and 31 that have
been used as a landfill.

2.8 Location in a Floodplain

Murphy Creek, an intermittent stream in a plains environment, flows north immediately east of the Lowry Site.
The 100-year floodplain along Murphy Creek has been identified and mapped for the Federal Emergency
Management Agency (FEMA).

2.9 General Surface Water and Ground-Water Resources

2.9.1 Surface Water Resources

The Lowry Site is located within the Murphy Creek drainage system, which covers approximately 7,800 acres.
The unnamed creek and its tributaries in Section 6, and Murphy Creek and its tributaries to the east and
north of Section 6 are included in this system. These streams generally flow north, and flow is ephemeral,
usually in response to storm events or snowmelt.

2.9.2 Ground-Water Resources

Sixty-one ground-water wells located within 2 miles to the west, south, and east of Section 6 and within 3
miles to the north of Section 6 were identified in a ground-water well inventory. Figure 2-5 shows the
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locations of the ground-water supply wells in the vicinity of the Lowry Site. Table 2-4 summarizes the
number and uses of wells within the well survey area, including wells that are no longer in use.

Although the main source of drinking water for the Denver metropolitan area comes as surface water from
mountain areas, a portion of the metropolitan area's drinking water needs are met by ground water. The
Arapahoe Aguifer yields the largest amount of ground water and is a source of drinking water for many
households in the metropolitan area. The upper two aguifers, the Denver and the Dawson, serve residents near
the Lowry Site. The Laramie-Fox Hills aguifer is also used in the Denver area. Figure 2-6 is a
cross-section of the Denver Basin showing the formations or aguifers beneath the Lowry Site.

2.9.2.1 Residential Wells

Generally, residential wells in the area are used for potable water and livestock purposes. Private wells are
located in the northeast corner of Section 11, approximately 2 miles north (downgradient) of the Lowry Site.
Four of the residential wells that are closest to the Lowry Site were sampled by EPA in 1986. No organics
were detected, and all samples were below maximum contaminant levels (MCLs) for inorganics.

2.9.2.2 Industrial Wells

Onsite workers previously used water for industrial and sanitation purposes from a 925-foot deep well located
north of the Lowry Site in Section 31 and screened in the Arapahoe Aguifer. This well was recently abandoned
and is no longer in use. A new well in Section 6 (No. 43 on Figure 2-5) has been drilled and is used for
industrial and sanitation purposes. This new well was screened at a depth of 1,061 to 1,263 feet in the
Arapahoe Aguifer. Although no contaminants have been detected in these wells, commercially bottled drinking
water is supplied to workers.

Onsite workers also used water for industrial and sanitation uses from a well designated by Denver as B-225
and referred to by the United States Geological Survey (USGS) as 6RDC. The water was not used for human
consumption. The well was installed in the southern portion of Section 6 in 1974 and is reportedly 150 feet
deep. The exact location, how long the well was in operation, and when and if it was abandoned are unknown.
This well may serve as a conduit for contaminant migration to the deeper aguifers and is currently buried by
approximately 100 feet of refuse.

It should be noted that in addition to well B-225, seven USGS wells were drilled as part of a study conducted
in mid to late 1970 to monitor for water guality and evaluate local hydrological conditions. These wells
were reportedly abandoned, however it is not possible to confirm the abandonment because several of the wells
have since been buried under approximately 100 feet of municipal refuse.

2.9.2.3 Municipal Wells

The East Cherry Creek Valley Water & Sanitation District (ECCV) owns ground-water rights in the vicinity of
the Lowry Site. The ECCV serves unincorporated areas to the west and southwest of Section 6, using a series
of deep ground-water wells to supply water for domestic uses. The ECCV regularly samples and tests these
wells to measure compliance with reguirements of the Safe Drinking Water Act (SDWA) . Analytes tested under
the SDWA include inorganics, organics, and primary anions and cations. Additionally, the ECCV also tests
these samples for radionuclides.

City of Aurora residents are served by the municipal water system, which diverts water from surface
reservoirs.

Figure 2-7 shows the drinking water supply sources in the vicinity of the Lowry Site, including the
approximate locations of residential homes with private water wells, areas serviced by the ECCV, and
nonresidential structures with private water wells.

2.10 Surface and Subsurface Features

Site surface features identified and described on Figure 2-8 include structures, roads, fence boundaries,
pipelines and utility lines, surface disposal areas, soil borrow areas, and other notable surface features.

2.10.1 Structures

Facilities within the northwest guarter of Section 6 are the WMC entrance road and gate, the WMC scale house,
and the WMC maintenance facility, which surrounded by a maintenance yard adjacent to the entrance road.
Denver's existing ground-water treatment plant and ground-water barrier wall are located approximately 0.5
mile east of Gun Club Road and 300 feet north of Section 6.
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The Command Post is located in the southeast portion of Section 31 in the southeast corner of the section.
The Command Post is the area where drummed wastes from site investigations are stored and managed, and where
trailers are located for the workers. The Command Post contains a fenced drum storage facility, a
decontamination pad, an office trailer, a storage trailer, and a rock (or drill) core storage shed.

2.10.2 Roads

A paved road extends east from the main entrance along the north section line in Section 6 and into Section
31 to Denver's existing ground-water treatment plant.

2.10.3 Fencing

The landfill area within Sections 6 and 31 is enclosed by fences. The north and east boundaries of the
landfill in Section 31 and the east landfill boundary in Section 6 are enclosed by a 4-foot-high barbed-wire
fence. The south and west boundaries of the landfill in Section 6 and the west boundary of Section 31 are
enclosed by a 6-foot-high chain-link fence with a 2-foot-high barbed-wire top.

2.10.4 Pipelines and Utility Lines

Pipelines and utility lines exist primarily around the perimeter of the Lowry Site, as shown on Figure 2-8.
An underground natural gas pipeline and associated surface vents and access roads trend north-south adjacent
to a drainage ditch along the east boundary of the Lowry Site.

2.10.5 Surface Disposal Areas

Currently, active municipal refuse disposal is occurring in the Phase I area of the new landfill in the
southwest portion of Section 31 (shown as current landfilling area). The active landfilling area changes as
operations progress. An asbestos disposal area is currently located in the northwest portion of Section 6,
just southwest of WMC's maintenance facility.

A closed asbestos disposal pit is located in the southeast portion of Section 6. The inactive pit was
excavated in the mid 1980s and was approximately 30 feet deep, 100 feet wide, and 1,000 feet long. Asbestos
was double bagged and containerized in drums that were covered daily with soil. The pit is currently covered
by approximately 60 feet of municipal refuse.

Previous waste disposal practice on the surface of Section 6 consisted of sewage sludge land application and
leachate injection (northern part), leachate spraying (north-central part), sewage sludge land application
(east-central margin), and oil sludge land application (southeast margin).

The tire piles that covered a large area in the center of Section 6 (approximately 45 acres) were shredded by
an onsite tire shredding facility which was operated by WMC. The shredding project began in October 1989 and
was completed by April 1992. The tire shreds have been placed in a monofill located on the east side of the
landfill in east-central Section 6.

2.10.6 Soil Borrow Areas

The soil borrow area currently being used in Section 6 is located south-southeast of WMC's maintenance
facility (Figure 2-8). This area consists of approximately 30 acres. All surficial soils in this area have
been removed to a depth of approximately 15 feet. Analysis of surficial soil samples taken from this area
indicated that levels of contaminants in the soils were comparable to background levels. EPA, in
consultation with CDH, has approved use of the soils as a daily and final cover for the former landfill area.
They are currently being used as daily cover for landfilling operations in Section 31.

2.10.7 Surface Drainage and Sediments

EPA has divided surface drainage within the Lowry Site into six subbasins. The drainage patterns are
described in detail in the OUs 4&5 RI report.

2.10.8 Subsurface Features

The Lowry Site is located in the Denver Basin, a north-south trending structural depression that extends from
Pueblo, Colorado, into Wyoming. The basin is asymmetric with a gently dipping eastern flank bounded by the
Great Plains and a very steep to overturned western flank bounded by the Colorado Front Range. Five major
bedrock formations are regionally important as aguifers in the basin. In descending stratigraphic order,
these formations include the Dawson, Denver, Arapahoe, Laramie, and Fox Hills Formations. Borings and wells
drilled at the Lowry Site penetrate the Dawson, Denver, and Arapahoe Formations.
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A detailed description of the geology/hydrogeology is presented in the Final RI Report for OUs 1&6. The
following are key features of the surficial deposits and Dawson and Denver Formations:

• Surficial sediments that overlie the Dawson Formation. These sediments consist of residual
soil, colluvium, and alluvium. Residual soil is produced by the in-place weathering of bedrock
and colluvium. These sediments are unconsolidated; poorly to moderately well sorted clays,
silts, sands; and some gravels that are Pleistocene to Holocene in age. The alluvial deposits
are estimated to be about 20 feet wide along the unnamed creek and occur at depths of 5 to 18
feet.

• The Dawson Formation unconformably overlies the Denver Formation and is the uppermost bedrock
of the basin. The Dawson Formation generally consists of 800 to 1,000 feet of arkosic
conglomerates and sandstones interbedded with lesser amounts of siltstones, shales, and local
lignitic coal beds. The sandstones are poorly cemented at the Lowry Site. The upper portion
of the Dawson Formation has been eroded, leaving the lower portion of the Dawson exposed.
Approximately 200 to 300 feet of the Lower Dawson is present. The base of the Dawson Formation
is generally considered to be the top of the first thick lignite bed; the formation occurs
approximately 310 feet below ground surface in the southern portion of Section 6, and
approximately 180 feet below ground surface in the central portion of Section 31.

• The Denver Formation is of late Cretaceous and Paleocene age and unconformably underlies the
Dawson Formation. The Denver Formation consists of approximately 600 to 1,500 feet of
interbedded claystones, siltstones, fine-grained sandstones, minor conglomerates, and lignites.
The sandstone units are lenticular and discontinuous. The formation contains an overall
greater proportion of fine-grained sediments than either the Arapahoe or the Dawson Formation.

• The Arapahoe Formation, of late Cretaceous age, is a 400- to 700-foot-thick seguence of
interbedded conglomerates, sandstones, siltstones, and shales that unconformably overlies the
Laramie Formation. The Arapahoe Formation is distinguished from the underlying Laramie
Formation and overlying Denver Formation by (1) the larger proportion of conglomerates and
sandstones with respect to shales, (2) the absence of significant carbonaceous beds, and (3) a
generally lighter color. The Arapahoe Formation contains a greater proportion of
coarser-grained sediments and generally lacks the coals beds found in the overlying Denver
Formation. Coarser sandstones and conglomerates characterize the lower 100 to 200 feet of the
formation, and the upper portion is generally finer grained and darker in color. Limited
information is available on the onsite Arapahoe Formation. Well WW40, recently installed by WMC
as a water supply, provides the only onsite data regarding the Arapahoe Formation. This well
encountered the top of the formation at 1,004 feet below ground surface.

2.10.8.1 Hvdroaeologic Conceptual Model

Available ground-water data from the Lowry Site monitoring programs were reviewed to develop a hydrogeologic
conceptual model that is described in the Final RI Report for OUs 1&6. The hydrogeologic conceptual model
divides the water-bearing units beneath the Lowry Site into a shallow and a deep ground-water system. The
division is based on the presence of a separation layer within the lower part of the Lower Dawson Formation.
The shallow ground-water system (OU 1) includes all ground water contained within the alluvium and within the
Dawson Formation above and including the separation layer. The deep ground-water system (OU 6) consists of
all ground water below the separation layer. Figure 2-10 presents a schematic drawing of the conceptual
model that depicts the Dawson and Denver Aguifers.

2.10.8.2 OU 1: Shallow Ground-Water System

Ground-water flow in the shallow ground-water system occurs within the weathered and unweathered Dawson
Formation, the overlying alluvial deposits, the refuse, and waste-pit solids.

Predominant ground-water flow direction in the unweathered Dawson is toward the north with an estimated mean
velocity of 0.03 ft/year. There are also components of flow to the east and west. Recent compliance
boundary sampling has detected contaminants in Well U-510. This well is located on the southern border of
the Lowry Site and was previously considered to be an upgradient well. Sampling results from this well
confirm that contamination has migrated to the south of the waste pit source area.

Additional monitoring wells were installed in Section 7 to evaluate ground-water contamination and flow.
Preliminary data show an eastern component of ground-water flow in the weathered Dawson. These data will be
incorporated with site data to further refine interpretations of ground-water flow south of the Lowry Site.
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2.10.8.3 OU 6: Deep Ground-Water System

Deep ground water is defined as the water-bearing zones below the Dawson Aguifer. These strata include the
lower portion of the Dawson formation beneath the Lowry Site and the underlying formations extending
vertically through the Arapahoe Aguifer to the base of the Laramie-Fox Hills Aguifer. Ground-water flow
within the deep ground-water system is predominantly lateral and to the north.

The Denver Aguifer extends from the base of the separation layer to the top of the Arapahoe Aguifer. A
laterally continuous lignite bed extends across the Lowry Site and stratigraphically divides the Denver
Aguifer into upper and lower zones.

The Arapahoe Aguifer beneath the Lowry Site extends from the base of the Denver Aguifer to the top of the
Laramie-Fox Hills Aguifer.

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Table 2-1
Wildlife Species Observed Within or Near the Lowry
Mammals
Black-tailed Prairie Dog
(Cynomys ludovicianus)

White-tailed Jackrabbit
(Lepus townsedii)

Coyote (Canis latrans)
Pronghorn
(Antilocapra americana)

Mule Deer (Odocoileus hemionus)

White-tailed Deer
(Odocoileus virginianus)
Birds

Ring-necked Pheasant
(Phasianus colchicus)

Mallard (Anas platyrhynchos)

Green-winged Teal (Anas crecca)

American Wigeon
(Anas Americana)

Red-tailed Hawk (Buteo janaicensis)

Common Snipe (Capella gallinago)

Great Horned Owl (Bubo virgonianus)

Black-billed Magpie
(Eremophila alpestris)

American Robin (Turdus migratorius)

Western Meadowlark
(Sturnella neglecta)

Starling (Sturnus vulgaris)

Vesper Sparrow (Poocetus gramineus)

Mourning Dove (Zenaida macrowa)
Site

Reptiles

Plains Garter Snake
(Thamnophis radix)

Gopher Snake
(Pituophis melanoleucus)

Short-horned lizard
(Phrynosoma douglassi)

Prairie Rattlesnakes
(Crotalus viridis viridis)
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Table 2-2
Plant Species Noted Within the Vicinity of the Lowry Site
Grasses

Needle-and-Thread
(Stipa comata)

Sand Grama
(Sporobolus cryptandrus)

Blue Grama
(Bouteloua gracilis)

Buffalo Grass
(Buchloe dactyloides)

Sagebrush
(Artemisia frigida)

Common Rabbit Brush
(Chysothamnus nauseosus)

Western Wheat Grass
(Agropyron smith!i)

Bromes (Bromus spp.)
Riparian

Plains Cottonwood
(Populus sargentii)

Peachleaf Willow
(Salix amygdaloides)

Skunkbush
(Rhus trilobata)
Wetlands

Sedges (Carex spp.)
American Bulrush
(Scirpus americanus)

Water Speedwell
(Veronica anagallis-aguatica)

Alkal Muhly
(Muhlenbergia asperifolia)

Common Spike-rush
(Eleocharis machrostachya)

Licorice
(Glycrrhiza Lepidota)

Broad-leaved Cattail
(Typha latifolia)

Sandbar Willow
(Salix exigua)
Wet/Meadows

Mallow (Malva sp.)
Western Ragweed
(Ambrosia psilostachya)

Fleabane (Erigeron sp.)
False Gromwell
(Onosmadium molle)

Curly Dock
(Rumex crispus)

Cockel-lour
(Xanthium italicum)

Purple-flowered Ground
Cherry (Physalis lobata)
Three-awn
(Aristida longiseta)

Cushion Coryphanta
(Coryphanta vivipara)

Yucca (Yucca sp.)
Bull-thistle
(Cirsium vulgare)

Red Globe Mallow
(Sphaeralcea coceinea)

Blazing Star
(Liatris punetata)

Prairie Coneflower
(Ratibida colonmifera)

Scurfpea
(Psoralea tenuiflora)
Canadian Thistle
(Cirsium arvense)

Evening Primrose
(Oenothera strigosa)

Horseweed
(Conyza canadensis)

Foxtail Barley
(Hordeum jubatum)
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Table 2-3
Potentially Occurring Threatened and Endangered
Species Within or Around the Lowry Site
Birds
Peregrine falcon
Bald Eagle
Black terna
Mountain plovera
White-faced ibisa
Baird's sparrowa
Western boreal toada
Amphibians
Insects

Regal fritillary butterflya
Mammals
Preble's meadow jumping mouse
Swift foxa
Falco peregrinus
Haliaeetus leucocephalus
Chlidonia niger
Charadrius montanus
Plegadis chihi
Ammodramus bairdii
Bufo boreas boreas
Speyeria idalia
Zapus hudsonius preblei
Vulpes velos
aSpecies that are candidates for official listing as threatened or
endangered species (Federal Register, Vol. 54, No. 4, January 6,
1989; Vol 55, No. 35, February 21, 1990).
-------
Use

Domestic/Livestock
Windmill
Table 2-4
Well Inventory Summary
Well
Numbers

5, 8, 10, 14
15, 16, 18
19, 21, 22
25, 28, 31
44, 45, 49
50, 51, 52
53, 54, 56
57, 58, 59
60, 61

4, 6, 7, 23,
42
Aquifer
Designation

Denver,
Dawson, or
unknown
Denver,
Dawson, or
unknown
Page 1 of 2
Comments

Some wells may be used for
only part of the year. Well
Nos. 22 and 50 are not
currently used but future use
is possible. Use of Well
No. 59 is unknown but is
listed as domestic.
Primarily used for livestock.
Industrial

Industrial
1, 24 Denver Well No. 24 is closed.

43 Arapahoe Well No. 43 replaced Well
No. 24.
Municipal
29, 32, 36 Arapahoe
Owned by East Cherry
Creek Valley Water and
Sanitation District.
Municipal
33, 37
Laramie-Fox
Hills
Owned by East Cherry
Creek Valley Water and
Sanitation District.
Municipal
34
Denver
Owned by East Cherry
Creek Valley Water and
Sanitation District; however,
the well is currently not
used.
Municipal
35
Denver/Dawson
Owned by East Cherry
Creek Valley Water and
Sanitation District; however,
the well is currently not
used.
Unknown
2, 26, 27, 30 Denver,
38, 39, 40 Dawson, or
41, 55, unknown
3 unnumbered
wells
Locations not verified.
-------
Use

Municipal permit
pending
Table 2-4
Well Inventory Summary
Well
Numbers

NA
Aquifer
Designation

Arapahoe
Page 2 of 2
Comments

Permit application by East
Cherry Creek Valley Water
and Sanitation District.
Municipal permit
pending
NA
Laramie-Fox Permit application by East
Hills Cherry Creek Valley Water
and Sanitation District.
Not currently in use 3, 9, 11, 12 Denver
13, 17, 20 Dawson, or
46, 47, 48 Arapahoe
Well Nos. 46 and 47 are
located on property that is in
bankruptcy proceedings.
Well No. 48 is located in a
recreational area that is no
longer used.
Notes: NA = Not applicable.
-------
Section 3.0
Site History and Enforcement Activities
3.1 Operational History
In the late 1930s, Denver purchased land southeast of its corporate limits for the purpose of attracting an
Army Air Corps Technical School to Denver. In December 1937, the Denver City Council conveyed title of the
land, without cost, to the Federal government. From about 1930 to 1962, the U.S. Air Force used the Lowry
Site as a bombing range.

In 1962, Denver became aware that the Bombing Range (with certain exceptions for missile launching complexes)
had been declared a surplus property by the Federal government. In 1964, the United States conveyed all or
portions of the five sections of the Lowry Bombing Range back to Denver by Quitclaim Deed, with the provision
that the land be used for public utility purposes; specifically, a landfill.

In February 1966, Denver began operation of a municipal solid waste landfill. Liguid and solid municipal
refuse and industrial wastes, including sewage sludge, were accepted until 1980. These materials included
hazardous substances, such as volatile organic compounds and heavy metals, listed pursuant to 40 CFR Section
302.4.

From 1966 until 1980, approximately 138 million gallons of waste were disposed of at the Lowry Site,
primarily by using a disposal practice known as "co-disposal." Approximately 75 unlined waste pits or
trenches were excavated to accommodate a mixture of liguids, industrial waste, and municipal waste. In the
southern half of Section 6, the pits were filled about three-guarters full with liguid wastes and topped with
25 to 60 feet of municipal refuse. The waste pits ranged in depth from approximately 15 to 30 feet, length
from 100 to 1,100 feet, and width from 50 to 150 feet. No measures are known to have been implemented to
prevent leachate or liguid waste seepage from the pits. Conseguently, over time, the liguid seeped out of the
pits and mixed with the surrounding refuse and ground water. In the north-central portion of Section 6,
excavated pits were filled with liguid wastes and municipal refuse, then covered with 2 to 5 feet of native
soil and piles of discarded tires. Over time, this liguid seeped out to ground water and to surface water in
unnamed creek. Approximately 8 million tires were stockpiled at the Lowry Site in the 1970s.

In addition, land application of wastewater sludge began at the Lowry Site in 1969 and continued into 1986.
Approximately 160 acres along the northern and eastern boundaries of Section 6 were utilized for land
application of wastewater sludge. The wastewater sludge was applied to the surface and then incorporated
into the native soils. After 1980, leachate collected in onsite surface impoundments was injected in the
same 160-acre area. Figure 3-1 presents the waste pits, tires, and sludge application areas.

The total volume of liguid wastes disposed of at the landfill is estimated to be 138 million gallons. This
estimate was developed from the records kept by the landfill and by the parties disposing of the wastes. The
types of wastes disposed of at the Lowry site until 1980 include acid and alkaline sludges; asbestos; caustic
liguids and solids; brines, including plating wastes and other water-based sludges; laboratory wastes;
organics, including petroleum based oils, grease, chlorinated solvents, and sludges; waste solvents,
chemicals, and oil; biomedical wastes; low-level radioactive medical wastes; pesticides and garden chemicals;
water-soluble oils; sewage sludge; paint and varnish waste, sludge and thinners; photographic chemicals and
industrial solvents; construction waste; municipal refuse; household hazardous waste; appliances; tires;
livestock carcasses; and metallic wastes.

Waste Management of Colorado, Inc. (WMC), operator of the landfill and a subsidiary of Waste Management of
North America, Inc., began landfill operations on July 30, 1980, under a contract with Denver. At that time,
waste disposal in Section 6 was restricted to municipal refuse and at a later time, asbestos waste.

Municipal solid waste (MSW) disposal activities at the Section 6 (Figure 3-1) landfill unit ceased in August
of 1990. A minimum 4-foot thick soil cover (except for the north slope) was completed over the landfill
unit, which is now closed. One area of Section 6 west of the landfill continues to receive asbestos wastes,
which is disposed of in sealed containers. Asbestos disposal is regulated by the Colorado Department of
Health (CDH). In addition, Section 6 also contains 7.5 million shredded tires in a monofill to the north of
the landfill on the east side of the section, and construction wastes from the Surface Water Removal Action
(SWRA) were disposed immediately north of the landfill. Section 31, located north of the Lowry Site, is
currently being used for disposal of MSW.
-------
3.2 History of Site Investigations

3.2.1 Site Investigation Activities from 1964 to 1984

Preliminary site investigations at the Lowry Site began in the mid-1970s. Various parties including United
States Geological Survey (USGS), EPA, CDH, Denver, and WMC performed site studies before 1984 when the Lowry
Site was named a Superfund site through listing on the NPL. These investigations included installation of
ground-water monitoring wells, surface-water and sediment sampling, air studies, soil gas monitoring, and
surface geophysical surveys.

3.2.2 Preliminary Assessment, Hazard Ranking, and NPL Listing

A preliminary assessment (PA) was conducted of the Lowry Site in June 1982 and a site inspection (SI) was
conducted in August 1982. The PA/SI briefly identified contaminant sources, pathways, receptors, and the
existing use of the Lowry Site's surrounding environment. The results of the PA/SI were used to apply the
Hazard Ranking System (HRS) to the Lowry Site. The HRS results in a cumulative score based on ground-water,
surface-water, and air risks. EPA has determined that a score of 28.5 or higher on the HRS is reguired for a
site to be eligible for the NPL. In August 1982, the Lowry Site was given an HRS score of 21. In March
1983, the Lowry Site was reevaluated and assigned a score of 49.35. After a guality analysis (QA) check, the
score was revised to 48.36. The Lowry Site was added to the NPL on September 21, 1984.

3.2.3 Phase I RI: February 1985 to April 1986

The first phase of the RI was conducted by EPA and included data collection and analyses of site conditions
to evaluate onsite and offsite geologic conditions, types and concentrations of contaminants in all media,
locations of buried waste pits, preliminary characterization of site contaminants, and climatological
conditions.

The field investigations conducted include geophysical investigations, soil vapor studies, installation of
monitoring wells, air monitoring and operation of an onsite meteorological stations, and ground-water,
surface-water, soil, sediment, landfill solids, and landfill gas sampling.

The findings of these investigations are described in the Phase I RI report, dated September 1986.

3.2.4 ATSDR Determination

In January 1987, the Agency for Toxic Substances and Disease Registry (ATSDR) conducted an assessment of the
public health threat attributed to ground-water contamination and volatile organic compounds (VOCs) being
released from the soil. The 1987 health assessment concluded that the Lowry Site was a potential public
health hazard.

3.2.5 Phase II RI: January 1987 to October 1989

The second phase of the RI was conducted by EPA and involved remedial planning, preliminary assessment of
data and risks, and an extensive sampling program. The investigations included installation of exploratory
borings, well points, deep and shallow ground-water wells, and refuse leachate wells; ground-water, refuse,
surface-water, waste-pit liguid, soil, and landfill solids sampling; water and liguid level monitoring;
limited air monitoring; and continued collection of meteorological data.

EPA issued a series of technical memoranda that constituted Phase II of the RI.

3.3 History of CERCLA Enforcement

In 1988, EPA divided the Lowry Site into six OUs, or study areas. These were grouped according to the
contaminated media which they address: OUs 1&6 address shallow ground water, subsurface liguids, and deep
ground water; OUs 2&3 address landfill solids and landfill gas; and OUs 4&5 address soils, surface water, and
sediments. A complete description of each operable unit may be found in the Glossary of this ROD.

In accordance with the reguirements of CERCLA, as amended by SARA, EPA provided the potentially responsible
parties (PRPs) with the opportunity to perform the OU RI/FSs at the Lowry Site. Under the terms of
negotiated Administrative Orders on Consent (Consent Orders), groups of PRPs performed the OU-specific
RI/FSs. The elements of each OU RI/FS are described in a Conceptual Work Plan (CWP), which is attached as an
Appendix to each Consent Order.
-------
3.3.1 The 1988 Consent Order for OU 1 RI/FS and the 1989 Amended and Restated Consent Order for OU 6 RI/FS

The purpose of the 1988 Consent Order (Docket No. CERCLA VIII-88-18) for the Shallow Ground Water and
Subsurface Liquids OU (OU 1) was to establish requirements for the OU 1 RI/FS to be performed by the Lowry
Coalition Respondents. The Lowry Coalition Respondents included Adolph Coors Company, AMAX Research &
Development, Inc. (formerly known as AMAX/Extractive Research & Development, Inc.), Asamera Oil (U.S.) Inc.,
Conoco Inc., Gates Rubber Company, Hewlett Packard Company, Honeywell Inc., International Business Machines
(IBM), City of Lakewood, Littleton-Enqlewood Bi-City Wastewater Treatment Plant, Metro Wastewater Reclamation
District (formerly Metropolitan Denver Sewaqe Disposal District No. 1), Sundstrand Corporation, Syntex
Chemicals, Inc., and S.W. Shattuck Chemical Company Inc. The Consent Order was amended in December 1989 to
include the Deep Ground Water OU (OU 6). The amended Consent Order is referred to as the Second Amended and
Restated Consent Order.

The OUs 1&6 RI report was completed in March 1992, and the FS report was completed in October 1992.

In accordance with the terms of the Consent Order, the Respondents aqreed to reimburse the Superfund for all
response costs incurred by EPA not inconsistent with the NCP related to the Consent Order. For OUs 1 and 6,
EPA has billed a total of $2,002,648.05 for cost recovery (includinq interest and stipulated penalties) and
has collected $1,300,189,58 throuqh September 1993.

3.3.2 The 1990 Administrative Order on Consent for OUs 2&3 RI/FS

The purpose of the 1990 Consent Order (Docket No. CERCLA VIII-90-1) for the Landfill Solids (OU 2) and
Landfill Gas (OU 3) OUs was to establish requirements for the OUs 2&3 RI/FS to be performed by Respondents
Chemical Waste Manaqement, Inc. (CWM), Waste Manaqement of Colorado, Inc. (WMC), and Denver. The Consent
Order for these OUs was siqned in January 1990.

The RI report was issued on January 7, 1993, and amended by EPA's comments (May 6, 1993) . The FS report was
issued on April 8, 1993, and amended by EPA's comments dated May 6, 1993.

Under the terms of the Consent Order, the Respondents aqreed to reimburse the United States for all response
costs incurred by the United States that are not inconsistent with the NCP related to the Consent Order.
Because of the special circumstances of the City and County of Denver's municipal financinq restrictions, the
Respondents were qranted the option of partially reimbursinq the United States for each billing until the
final accounting was submitted. Upon receipt of the final accountinq, Respondents are to reimburse the
United States for all response costs, includinq those costs not previously reimbursed and the associated
accrued interest on those costs not previously reimbursed. In accordance with the partial payment provisions,
EPA has billed $1,463,016.09 and collected $249,719.50 throuqh September 1993.

3.3.3 The 1991 Consent Order for OUs 4&5 RI/FS

The purpose of the 1991 Consent Order (Docket No. CERCLA VIII-91-04) for the Soils (OU 4) and Surface Water
and Sediments (OU 5) OUs was to establish requirements for the OUs 4&5 RI/FS to be performed by Respondents
Metro Wastewater Reclamation District (Metro) and Denver. The Consent Order for these OUs was siqned in
March 1991.

The RI report was issued on January 20, 1993, and amended by EPA's comments dated February 17, 1993. The FS
report was issued on April 16, 1993, and amended by EPA's comments dated May 18, 1993.

Under the terms of the Consent Order, the Respondents aqreed to reimburse the United States for all response
costs incurred by the United States not inconsistent with the NCP related to the Consent Order. Because of
the special circumstances of the City and County of Denver's municipal financinq restrictions, the
Respondents were qranted the option of partially reimbursinq the United States for each billing until the
final accounting was submitted. Upon receipt of the final accountinq, Respondents are to reimburse the
United States for all response costs, includinq those costs not previously reimbursed and the associated
accrued interest on those costs not previously reimbursed. In accordance with the partial payment
provisions, EPA has billed $486,331.50 and collected $75,376.63 throuqh September 1993.

3.3.4 History of the 1984 Barrier Wall Consent Order, the 1986 Barrier Wall Consent Decree, the 1991 Surface
Water Removal Action, and the 1993 Modified Consent Decree

In 1984, Respondent Denver entered into a Consent Order with EPA, for the desiqn, construction and operation
of an interim remedial measure (IRM). This IRM consisted of a qround-water control and treatment system,
commonly referred to as the barrier wall and qround-water treatment plant. The qround-water barrier wall was
desiqned to minimize the offsite miqration of contaminated shallow qround water by collectinq the
contaminated qround water at the barrier wall and pumpinq it to the qround-water treatment plant.
-------
In 1985, EPA alleged that Denver failed to fulfill certain conditions of the Consent Order and to resolve
these alleged violations, entered into a Consent Decree with Denver in January 1986. In June 1986, EPA, CDH,
and Denver began discussions regarding implementation of the SWRA. The SWRA would be designed to enhance the
existing measures that prevent offsite migration of contaminants from the Lowry Site. In pursuit of this
goal, EPA issued an Engineering Evaluation/Cost Analysis (EE/CA) on May 19, 1988, which described and
evaluated alternatives for the SWRA.

On October 25, 1990, EPA issued a Responsiveness Summary to provide a written response to the public comments
received on the EE/CA for the SWRA. EPA developed and issued an Action Recommendation on November 13, 1990,
which defines the basis and scope of the SWRA. The reguirements for the SWRA replaced those that had been
identified in the 1984 Consent Order and 1986 Consent Decree. The SWRA Consent Order became effective on
August 15, 1991.

Final design plans for upgrading the ground-water treatment plant and construction of a collection system
within unnamed creek were completed in June of 1992. Construction of both the treatment plant additions and
collection system was completed in November of 1992. The upgraded treatment plant is referred to as the
existing ground-water treatment plant.

Under the terms of the Consent Order, the Respondents agreed to reimburse the United States for all response
costs incurred by the United States not inconsistent with the NCP related to this Consent Order. The Consent
Order for the Surface Water Removal Action was attached to the Modified Consent Decree. By attaching the
SWRA Consent Order to the Modified Consent Decree, updated performance standards and compliance monitoring
reguirements, specified for the SWRA, replaced those identified in the 1984 Consent Order and 1986 Consent
Decree. Although the SWRA Consent Order became effective on August 15, 1991, the Barrier Wall Modified
Consent Decree was not filed with the U.S. District Court until July 13, 1993. On September 29, 1993, the
Barrier Wall Modified Consent Decree was signed and entered by United States District Court Chief Judge
Sherman Finesilver.

Because of the special circumstances of the Denver's municipal financing restrictions, the Respondents were
granted the option of partially reimbursing the United States for each billing until the final accounting was
submitted. Upon receipt of the final accounting, Respondents are to reimburse the United States for all
response costs, including those costs not previously reimbursed and the associated accrued interest on those
costs not previously reimbursed. In accordance with the partial payment provisions, EPA has billed
$443,279.76 and collected $56,924.70 through September 1993.

3.3.5 History of the 1989 Drum Removal Action

During a routine inspection of the drum storage area on February 9, 1989, EPA observed that many of the drums
were damaged. EPA initiated a drum removal action on March 1, 1989, to allow EPA's Emergency Response Branch
to stabilize the drums and control the liguids. In conjunction with this removal action, EPA constructed two
temporary lined storage pads to contain the drums and to manage the liguids.

In 1990, EPA conducted Phase II of the Drum Removal Action in cooperation with Denver. This removal action
involved: bulking the less contaminated wastes and treating them in the ground-water treatment plant;
re-packaging the highly contaminated liguids and solids from the old drums; decontaminating and disposing the
empty drums; and decommissioning the temporary drum storage pad.

3.3.6 PRP Search

In accordance with Section 104 (e) of CERCLA, as amended by SARA, EPA conducted a search for the parties who
generated, treated, stored, or disposed of materials at the Lowry Site (including the owners and operators).
This included obtaining information from the parties pertaining to their ability to pay for or perform the
cleanup of the Lowry Site. In conjunction with the identification of PRPs at the Lowry Site, EPA:

• Issued reguests for information from parties who were known to have involvement with the Lowry
Site.

• Issued General Notice letters in May 1988 to the 195 companies believed to have generated,
treated, stored, or disposed of hazardous waste at the Lowry Site and the owners and operators
of the landfill.

• Developed a Waste-In List to determine the volume and composition of wastes that were generated
or transported to the Lowry Site.

• Issued Special Notices to selected groups of PRPs to perform the OU RI/FSs. EPA issued the
following Special Notice letters to the PRPs at the Lowry Site:
-------
On June 24, 1988, EPA issued a Special Notice to 28 PRPs to perform the OU 1 RI/FS.
The majority of these PRPs joined together to form a group known as the Lowry
Coalition. (This agreement was later amended in December 1989 to include the OU 6
RI/FS.)

On June 30, 1989, EPA issued a Special Notice to Denver, WMC, and CWM to perform the
RI/FS for OUs 2&3.

On October 19, 1990, EPA issued a Special Notice to Denver and Metro to perform the
RI/FS for OUs 4&5.

3.3.7 Bankruptcy Settlements

The United States, on behalf of EPA, entered into bankruptcy settlement with Storage Technology Corporation
(STC) which was consummated in 1993. Under the STC settlement, EPA recovered $3,304,672.89 in past response
costs, and $4,957,009.33 in future response costs incurred at the Lowry Site. In addition, EPA received
payment of $29,133.14 from the bankruptcy trustee for C.W. Silver.

3.3.8 De Minimis Settlements

This subsection discusses the CERCLA Section 122(g) de minimis settlements negotiated with eligible de
minimis parties. To gualify as a de minimis PRP:

• The party's volumetic contribution must be 300,000 gallons of waste or less.

• The party's waste stream must not be significantly more toxic or of greater hazardous effect
than all other waste streams at the Lowry Site.

• The settlor must have certified that the information provided in its CERCLA Section 104(e)
information reguest response was accurate and complete.

• At the time of the settlement, the settlor must not have been a party to any other litigation
pertaining to the Lowry Site against or challenging the EPA.

In March 1993, EPA entered into a Consent Order (Docket No. CERCLA VIII-93-04) with 22 of 144 eligible de
minimis PRPs. Respondents entering into this de minimis settlement are listed in Table 3-1. These settlors
paid a total of $633,789.81 to the Superfund Trust Fund.

In October 1993, EPA entered into a Consent Order (Docket No. CERCLA VIII-93-21) with three Colorado state
agencies and two Colorado state colleges. Respondents entering into this settlement are listed in Table 3-1.
These settlors paid a total of $653,570.97 to the Superfund.

-------
Table 3-1
De Minimis Settlement, Consent Order Docket No. CERCLA VIII-93-04
Effective August 28, 1992
and De Minimis Settlement Consent Order Docket No. CERCLA VIII-93-21
Effective June 2, 1993
Amount
Potentially Responsible Party ($)

Docket No. CERCLA VIII-93-04

Adams Arapahoe Joint District No. 28J $1,085.76
Allied Trades, Inc. (now known as Barnett Lumber Co.) 2,262.00
Asarco Inc. Globe Plant 20,358.00
AT&T Industries, Inc. 5,655.00
Burlington Northern Railroad 2,488.20
Camp Dresser & McKee, Inc. 8,991.45
City of Colorado Springs 1,950.98
Cobe Laboratories, Inc. 79,464.06
Lowenstein Theater/Denver Center for the Performing Arts 28.28
Marathon Oil Company 1,131.00
Martin Marietta Corporation-Denver Aerospace 94,975.73
National Wire and Stamping, Inc. 6,141.33
Pepsi-Cola Bottling Company 15,364.64
Samsonite Corporation 30,508.73
Smith Kline Beecham Corporation 6,220.50
U.S. Geological Survey National Water Quality Laboratory 61,271.93
U.S. Air Force 116,866.23
U.S. Defense Logistics Agency 24,259.95
U.S. EPA Region VIII Lab 1,413.75
U.S. Mint, Treasury Department 42,978.00
U.S. Veterans Administration Medical Center 106,133.04
ValleyLab, Inc. 4,241.25
Subtotal $633,789.81

Docket No. CERCLA VIII-93-21

Colorado Department of Agriculture $7,441.98
Colorado Department of Highways 175,203.21
Colorado School of Mines 46,246.59
Colorado Surplus Agency 369,316.74
Colorado State University (Environmental Health Services) 55,362.45
Subtotal $653,570.97
De Minimis Total $1,287,360.78
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Section 4.0
Highlights of Community Participation

EPA implemented a broad-based, comprehensive community involvement program to keep the community informed
about the Lowry Site, and to provide an opportunity for citizens to participate in the Superfund process.

4.1 Community Relations Plan

A Community Relations Plan for the Lowry Site was first developed in 1984. The Community Relations Plan
provided a basis for EPA' s community involvement program at the Lowry Site by identifying community interests
and concerns, and outlining the community relations activities to be conducted. In December 1987, EPA
conducted interviews with other agencies, community groups, and individuals as a first step in updating the
Community Relations Plan. A draft of the revised Community Relations Plan was issued for public comment in
March 1988. The plan was revised based on the comments received and the Revised Community Relations Plan was
issued in January 1989.

4.2 Lowry Landfill Monitoring Committee

EPA participated in the Lowry Landfill Monitoring Committee (LLMC), which was established by the Governor of
Colorado. This committee met on a guarterly basis for several years. EPA provided information to the
committee and offered to assist in distributing information to the public. The purpose of the committee was
to provide a channel of communication among industry representatives, private citizens, and the State of
Colorado. LLMC meetings were discontinued once all participants were satisfied with the progress at the
Lowry Site.

4.3 Technical Advisory Group

In July 1987, EPA organized the Technical Advisory Group (TAG), which was composed of various regulatory
agencies, local governmental entities, PRPs, and community organizations interested in Lowry Site activities.
The purpose of the TAG was to provide PRPs, municipalities, regulatory agencies, special interest groups, and
individuals with the opportunity to participate in the Superfund process at the Lowry Site. Participants
exchanged ideas and points-of-view, and reviewed planning documents, technical memoranda, data, and other
site-specific information.

TAG meetings were held on a monthly basis through the spring of 1993. TAG members decided to discontinue the
monthly meetings in April of 1993 since major activities at the Lowry Site, including the RI/FSs for OUs 2&3
and OUs 4&5, had been recently completed.

4.4 Outreach Program

In 1987, EPA began issuing periodic updates and fact sheets to the public, other regulatory agencies, local
governmental entities, PRPs, and community groups (see Table 4.1). These updates/fact sheets reported on the
progress of Superfund activities at the Lowry Site. Since that time, 12 updates and numerous fact sheets on
specific topics have been issued. These special topic fact sheets have included summaries of site-specific
baseline risk assessments and proposed plans for remediation of the Lowry Site.

In September 1991, an 18-minute video of the Lowry Site was produced by EPA and was made available for use by
the public. The video's purpose was to explain the basic history of the Lowry Site, the Superfund process,
the status of the studies to date, and to provide a tour of the entire site.

Volume 1 (OUs 1&6) of the Baseline Risk Assessment was issued for public comment in February 1992. EPA
received significant public comment on Volume 1 and amended the document with a Response to Comments, dated
August 20, 1993.

Volumes 2A and 2B (OUs 2&3 and OUs 4&5) of the Baseline Risk Assessment were issued for public comment in
December 1992. The final volume, Volume 2C (sitewide issues, lead, and radionuclides), of the Baseline Risk
Assessment was issued for a public comment in April of 1993. On July 2, 1993, EPA issued a Response to
Comments document for Volumes 2A, 2B, and 2C.

Issuance dates for the RI reports, FS reports, and proposed plans were as follows:

RI Reports FS Reports Proposed Plan

OUs 1&6 March 1992 October 1992 November 1992
OUs 2&3 May 1993 May 1993 September 1993
OUs 4&5 February 1993 May 1993 September 1993
-------
A public comment period for the OUs 1&6 proposed plan was held from November 23, 1992 to March 1, 1993 and a
public meeting was held on December 8, 1992 at Eaglecrest High School. The initial 30-day comment period was
extended twice (30 days each time), in response to reguests from the community.

For the OUs 2&3 and OUs 4&5 proposed plan, a public comment period was held from September 1, 1993 to
November 29, 1993 and a public meeting was held on September 21, 1993 at Eaglecrest High School. The initial
30-day comment period was extended twice (30 days each time), in response to reguests from the community.

Comments which were received by EPA prior to the end of each of the public comment periods, including those
expressed orally at the public meetings, are addressed in the Responsiveness Summary for OUs 1&6, and in the
Responsiveness Summary for Ous 2&3 and 4&5, which are attached to this Record of Decision. This decision
document presents the selected remedial action for the Lowry Landfill Superfund Site in Arapahoe County,
Colorado, chosen in accordance with CERCLA, as amended by SARA and, to the extent practicable, the NCP.

Historically, the following publications have reported on the progress of Superfund-related activities at the
Lowry Site: The Denver Post; the Rocky Mountain News; Up the Creek; Westword; the Denver Business Journal;
Aurora Daily Sentinel; Community Accent; the Wall Street Journal; Colorado Daily; the Financial Times of
Canada; the Littleton Independent; Littleton Report; Englewood Sentinel; the Salt Lake Tribune; Superfund
Week; Colorado Association of Commerce and Industry; the Colorado Statesman; Wastetech News; and the Boulder
Daily Camera.

4.5 Technical Assistance Grant

SARA provides that technical assistance grants may be awarded to groups who may be affected by a Superfund
site. The purpose of these grants is to foster informed public involvement in decisions related to a site by
providing funds for a particular group to hire independent technical advisors.

In September 1989, a Technical Assistance Grant was awarded to the Citizens Against Lowry Landfill (CALL).
This grant was used to fund reviews and analyses by technical experts.

4.6 Information Repositories

Since 1987, Lowry Site documents and reports have been maintained in two information repositories
(libraries). These repositories are accessible to the public and are at the following locations.

EPA Superfund Records Center Aurora Central Public Library
999 18th Street 14949 East Alameda
5th Floor North Terrace Aurora, Colorado 80002
Denver, Colorado 80202 (303) 340-2290
(303) 293-1807

The EPA Superfund Records Center contains the complete Administrative Record. The Aurora Central Public
Library houses pertinent documents that may be of interest to the public.
-------
Table
Lowry Landfill
Fact Sheets
Date

January 1985

June 1987

May 1988
Document
June 1988
Lowry Landfill Fact Sheet

Superfund Program Fact Sheet
Update, Lowry Landfill RI/FS
Phase II

Superfund Program Fact Sheet
Landfill Site, Contaminated
Surface Water
Lowry Landfill Information
Update No. 1
October 1988 EPA Superfund Program, Update
No. 2, Lowry Landfill Superfund
Site
July 27, 1989

January 1990

May 1990

September 1990

January 1991

April 1991

June 1991

September 1991

August 1991

April 1992

June 1992

July 1992
Lowry Landfill Superfund Site,
Preliminary Endangerment
Assessment

Lowry Landfill Information
Update No. 3

Lowry Landfill Information
Update No. 4

Lowry Landfill Information
Update No. 5

Lowry Landfill Information
Update No. 6

Lowry Landfill Information
Update No. 7

Lowry Landfill Information
Update No. 8

Lowry Landfill Information
Update No. 9

Surface Water Removal Action
Fact Sheet

Draft Baseline Risk Assessment
for Shallow Ground Water and
Subsurface Liguids

Lowry Landfill Information
Update No. 10

Surface Water Removal Action
Notice of Public Meeting
4-1
Superfund Site
and Updates Page 1 of 2

Contents

Activities to be carried out during the RI/FS.

Covered results of the Phase I RI/FS and planned
activities for the Phase II RI/FS.
Addressed an Engineering Evaluation/Cost
Analysis (EE/CA) for the Surface Water Removal
Action (SWRA), announced a public comment
period during May and June, and announced a
public meeting on May 26, 1988.

Reviewed the Lowry Site and the six Operable
Units (OUs) that divided the Lowry Site for
Phase II activities.

Reviewed RI/FS activities, the Lowry Coalition,
and radioactivity at the Lowry Site.
Reviewed the results of the PEA.
Reviewed RI/FS activities and presented the
cleanup schedule.

Further reviewed the Lowry Site, the OUs, and
the cleanup schedule.

Revised the cleanup schedule, presented the de
minimis settlement, and reviewed RI/FS activities.

Reviewed RI/FS activities and asbestos disposal.
Continued the review of RI/FS activities.
Continued the review of RI/FS activities.
Announced the video, a risk assessment
workshop, and updated RI/FS activities.

The construction schedule and engineering of the
SWRA were discussed.

Explained the baseline risk assessment process and
the findings for OUs 1/6.
Updated RI/FS activities and revised the cleanup
schedule.

Announced a meeting to discuss final design
plans.
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Table 4-1
Lowry Landfill Superfund Site
Fact Sheets and Updates
Page 2 of 2
Date

November 1992

December 1992

April 1993

August 1993

September 1993
Document

Lowry Landfill Information
Update No. 11
Proposed Plan for Operable Units
1 and 6: Shallow Ground Water
and Subsurface Liguids and Deep
Ground Water

Notice of Public Comment Period
Extension for the Proposed Plan
for Operable Units 1 and 6

Draft Baseline Risk Assessment
for Landfill Solids, Landfill Gas,
Soils, and Surface Water and
Sediment Operable Units

Lowry Landfill Information
Update No. 12

Proposed Plan for OUs 2/3 and
4/5

Notice of Public Comment Period
Extension of the Proposed Plan
for Operable Units 2, 3, 4, and 5
Contents

Reviewed the status of the OUs and featured a
summary of the Draft Phase III FS Report for
OUs 1/6.

Reviewed and analyzed the final remedies
proposed for OUs 1/6.
The public comment period was extended twice; it
ended on March 1, 1993.
Reviewed the findings of the baseline risk
assessment for OUs 2/3 and 4/5.
Updated the cleanup schedule, the status of the
OUs, and other activities.

Reviewed and analyzed the final remedies
proposed for OUs 2, 3, 4, and 5.

The public comment period was extended twice; it
ended on November 29, 1993.
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Section 5.0
Scope and Role of Operable Units

The NCP recommends the use of operable units (OUs) in situations in which early actions are necessary to
achieve quick risk reduction; when phased analysis is necessary for the size or complexity of the site; or to
expedite completion of total site cleanup. An OU may be a discrete action that comprises an incremental step
toward comprehensively addressing site problems.

The Lowry Site was divided into six OUs based on the complexity of the contamination problems and the size of
the site. At the Lowry Site, OUs were established for each of the environmental media as follows: OU
1-Shallow Ground Water and Subsurface Liquids; OU 2-Landfill Solids; OU 3-Landfill Gas; OU 4-Soils; OU
5-Surface Water and Sediments; and OU 6-Deep Ground Water. To facilitate effective implementation of the
RI/FS activities, the OUs were grouped and studied as follows: OUs 1&6, OUs 2&3, and OUs 4&5.

The primary threats to human health and the environment posed by the Lowry Site consist of exposure to and
contamination by landfill gas, waste-pit liquids, drums, ground water, and contaminated seepage in the former
unnamed creek drainage. Other threats arise from contaminated landfill solids, soils, sediments, and ground
water. This ROD summarizes the alternatives considered for all threats and presents the final selected
sitewide remedy to address these threats. The overall cleanup strategy at the Lowry Site is to reduce
current or future exposure to: landfill gas; waste-pit liquids; seepage in the unnamed creek drainage; and
contaminated ground water. Landfill gas, seepage, and ground water will be contained, collected, and
treated. Drums, drum contents, and contaminated soils in the former tire pile area will be excavated,
treated, and disposed of offsite in a permitted disposal facility.

The selected sitewide remedy is an integration of interim remedial measures and remedies for all the OUs and
comprehensively addresses all contaminated media at the Lowry Site. As discussed in the site history section
of this ROD, EPA has previously selected interim remedial measures to address the seepage in the unnamed
creek and the migration of contaminated ground water in the alluvium underlying the unnamed creek drainage.
The migration of contaminated ground water in the alluvium has been addressed through the construction and
operation of the ground-water barrier wall and treatment plant. Primary threats from organic and inorganic
contaminated seepage in unnamed creek have been addressed through implementation of the SWRA, which included
an upgrade of the existing ground-water treatment plant.

The interim remedial measures have been integrated into and are key elements in the selected sitewide remedy.
Other key elements of the selected sitewide remedy include: a gas collection and treatment system to address
the primary threat of landfill gas and gas migration offsite; barrier walls to contain and treat waste-pit
liquids and contaminated ground water; excavation, treatment, and disposal of contaminated solids within the
former tire pile area; containment of landfill solids through maintenance of the existing cover and by the
addition of 2 feet of cover on the north face of the landfill; and containment of soils by maintaining
vegetative covers. this selected sitewide remedy will achieve the sitewide cleanup strategy and partially
satisfies the preference for treatment as a principal element.

Section 6.0
Summary of Site Characteristics

This section provides an overview of the Lowry Site's contamination, including the source, nature and extent,
concentrations, and volume of contamination. In addition, potential surface and subsurface pathways for
contamination migration are summarized. Actual routes of exposure and exposure pathways are discussed in
Section 7.0. A general overview of the Lowry Site is presented in Section 2.0.

6.1 Extent of Contamination in Affected Media

The contaminant source discussions are presented by each OU, unless otherwise noted.

The primary sources of contamination at the Lowry Site have been identified as subsurface liquids, waste
pits, landfill solids, sewage sludge, injected leachate from Pond 3 (eliminated during implementation of the
SWRA), sprayed leachate, and landfill gas.

Between 1964 and 1980, Lowry Landfill accepted solid and liquid municipal and industrial wastes including
hazardous substances. Prior to 1976, trenches would first be filled with liquid waste, and then backfilled
with solid waste. This method was known as co-disposal. Once filled with waste, a trench would then be
covered with soil from the Lowry Site. In approximately 1976, this co-disposal technique was reversed with
solid waste first being placed in the trench. Following compaction of the solid waste, the trench would be
filled with liquid waste. Once the trench was full, it was covered with soils from the Lowry Site. The
reason for the change in method was to promote more immediate absorption of the liquids into the solid waste,
and to minimize potential fire hazards created by the open trenches of liquid. The co-disposal waste pits
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are located in Section 6 within the western two-thirds of the landfilled area and former tire pile area
(Figure 6-1).

In addition to the co-disposal and sanitary landfilling techniques, other waste disposal procedures employed
at the Lowry Site included sewage sludge land application and leachate land application (leachate injection)
on the northern and north-central portions of Section 6, respectively.

Over time, some of the contaminated liguid originally placed into the pits has seeped out of the pits and has
mixed with the surrounding solid wastes, ground water, and surface water.

6.1.1 OUs 1&6: Shallow Ground-Water and Subsurface Liquids, and Deep Ground-Water Operable Units

6.1.1.1 Sources of Contamination

Waste pits and landfill solids within and underneath the landfill mass (source area) are the primary sources
of ground-water contamination at the Lowry Site. Although media interactions among ground water, soils,
surface war, and sediments were studied, the focus of the following discussion is the interaction among
ground water, waste pits, and landfill solids.

6.1.1.2 Nature and Extent of Contamination

The hydrogeologic setting underneath the Lowry Site is described in Section 2.0, and in the RI report. There
are two major ground-water systems: shallow ground water (which includes the subsurface liquids); and deep
ground water. Hydrogeologic studies have shown that the majority of the ground water under the Lowry Site
flows laterally to the north. A less significant vertical gradient is present within and between aquifers;
it predominantly flows in a downward direction. Vertical gradients generally decrease from south to north
and with depth at the Lowry Site.

A variety of contaminants, including organic chemicals and trace metals, have been detected in the shallow
ground water directly beneath the Lowry Site. There are several residential wells approximately 2 miles
downgradient of the Lowry Site that have been investigated for possible contamination from the ground water
at the Lowry Site. To date, there has been no evidence of contamination in these wells.

Data from ground-water monitoring wells and waste-pit liquid well points were grouped together on the basis
of hydrogeology, derived from the Lowry Coalition well groupings, as follows: shallow ground-water
monitoring wells and waste-pit liquid well points in the source area; ground-water monitoring wells completed
in the weathered Dawson Aquifer outside the source area; ground-water monitoring wells completed in the
unweathered Dawson Aquifer outside the source area; deep ground-water monitoring wells; and upgradient
ground-water monitoring wells outside the source area.

The estimated areal extent of contamination is based on data from existing monitoring wells. Certain
portions of the Lowry Site (such as the northwest corner of the Lowry Site, which is outside of the waste
pits source area) lack sufficient numbers of wells for an exact determination of the horizontal and vertical
extent of contamination. The extent of contamination in these areas will be further refined during the
remedial design.

6.1.1.2.1 Waste-Pit Liquid Within the Source Area. The waste pits and associated liquids contain the highest
average concentrations of nonhalogenated VOCs (volatile organic compounds), and SVOCs (semivolatile OCs;
base/neutral and acid), metals, and radionuclides, as compared to other contaminated ground waters at the
Lowry Site.

Toxicity Characteristic Leaching Procedure (TCLP) analyses were performed on waste-pit liquids and waste
solids. The liquid analyses were performed by filtering the liquid samples and analyzing the filtered
materials. Several VOCs, SVOCs, and one pesticide and metal were detected at or above regulatory levels in
the extract from these samples. Based on RCRA toxicity characteristic testing, waste-pit solids and liquids
are hazardous.

Analytical results from waste-pit liquid samples indicate a high degree of spatial variability across the
Lowry Site. On the basis of field observations and liquid-level measurements recorded during sampling,
immiscible phase liquids have been identified in 10 of the approximately 70 waste pits. These phases
included both light nonaqueous phase liquids (LNAPLs) and dense nonaqueous phase liquids (DNAPLs). The
amount and type of nonaqueous phase liquids (NAPLs) present varied considerably between well points, and in
some cases between measurements in the same well point. Figure 6-1 shows the waste-pit well points that
contained either LNAPLs or DNAPLs.
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The mobile-phase NAPL contamination extent appears to coincide with the horizontal extent of the waste pits
(Figure 6-1) and to the vertical extent of the weathered system.

6.1.1.2.2 Saturated Refuse Within the Source Area. Saturated refuse samples were collected from three
borings within the source area. VOCs, semivolatiles, and metals were detected. Compared to the waste-pit
liguid, waste pit solids, and source area shallow ground-water analytical results, the saturated refuse
(saturated solids outside of the waste pits) samples contained similar contaminants at similar or lower
concentrations.

6.1.1.2.3 Shallow Ground Water in the Weathered System within the Source Area. VOCs were the most prevalent
organic compounds present in the ground water in the weathered system. The SVOCs, pesticides/PCBs, and
additional organic compounds were also present in samples from ground water in the weathered system inside
the source area. Results of sample analyses indicated that radionuclides, trace metals, and inorganics were
freguently present in samples collected from monitoring wells at levels that exceeded Lowry Landfill
upgradient values.

In general, similar compounds were detected in samples from waste-pit liguid and ground water in the
weathered system. Concentrations of parameters present in samples from waste-pit liguid generally exceeded
concentrations of the same parameters present in samples from ground water in the weathered system. The
extent of horizontal contamination coincides with the boundaries of the weathered system within the source
area as shown in Figure 6-2. The vertical extent of contamination extends to the base of the weathered
system throughout the source area. The base of the unweathered system is estimated to be 30 to 50 feet below
the ground surface.

6.1.1.2.4 Shallow Ground-Water Upgradient of the Source Area. Parameters detected in samples from the
upgradient ground-water monitoring wells (B519, B520, MW003, MW004, MW005, MW22, U509, and U510) include
organics, trace metals, and radionuclides. The organics present in samples from upgradient monitoring wells
are common laboratory contaminants, and the concentrations are most likely indicative of laboratory
artifacts. However, one perimeter upgradient monitoring well, U-510, has confirmed organic contamination,
indicating contaminant migration toward the southern boundary of the Lowry Site. Recent sampling of Well
U-510 revealed seven organic and eight inorganic compounds. This well is screened from 48 to 58 feet below
ground surface.

6.1.1.2.5 Shallow Ground Water in the Weathered and Unweathered Systems Outside of the Source Area.
Contamination detected in the weathered system outside of the source area and unweathered Dawson include
VOCs, SVOCs, radionuclides, and trace metals. The lateral extent of contamination (Figure 6-2) appears to be
generally confined to three areas. The areas are located near (1) unnamed creek (Well A116A) , (2) the
existing barrier wall (Wells B214, GW1074, A115, GW1144, GW106A, B307, and U701), and (3) east of the Command
Post (Well MW23). Maximum contamination was detected in Well B712, which is located at the toe of the
landfill mass, approximately 100 yards to the east of unnamed creek.

6.1.1.2.6 Deep Ground Water. The deep ground-water system includes the water-bearing zones beneath the
Dawson Aguifer, which includes the upper and lower Denver aguifers. Contaminants within the deep
ground-water monitoring wells include organics, dissolved NAPL compounds, radionuclides, and trace metals.
Several deep monitoring wells were installed at the Lowry Site. Results from these wells indicate that the
extent of impacted deep ground water is limited to Wells B504 and C702Q2, shown in Figure 6-3. These wells
are screened at 105 to 125 feet, and 162 to 172 feet below ground surface, respectively. The average
concentration of organics in deep ground water is substantially lower compared to the average concentrations
of organics in shallow ground water. The presence of contaminants in monitoring well C702Q2 was generally
not confirmed between sampling events.

Computer modeling results indicate that, in the absence of any remedial action, it would take approximately
200 years for contamination from the source area to reach the lignite layer. The areal extent of
contamination in deep ground water is provided in Figure 6-3.

6.1.1.3 Concentrations of Contaminants

Tables 6-1 through 6-5 present the chemical concentration data summary for each hydrogeologic grouping.

6.1.1.4 Volume Estimates

The total volume of potentially contaminated ground water at the Lowry Site was estimated as follows:

6.1.1.4.1 Shallow Ground Water. The volume of potentially contaminated shallow ground water is estimated to
be in the range of 900 million to 2 billion gallons. A broad range is observed because of differing methods
of estimating the volume of contaminated shallow ground water. Twelve million gallons of the ground water
are considered to be in the saturated alluvium.
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6.1.1.4.2 Deep Ground Water. The volume of potentially impacted deep ground water is estimated to be in the
range of 93 million to 1.2 billion gallons.

6.1.1.4.3 Saturated Refuse. The volume of liguid within saturated refuse was estimated to be approximately
14 million gallons.

6.1.1.4.4 Waste-Pit Liquid. The current volume of liguid within the saturated waste pits is estimated to be
approximately 95 million gallons.

6.1.2 OU 2: Landfill Solids

The following includes discussions of landfill solids OU media in both the landfill mass and the former tire
pile area.

6.1.2.1 Source of Contamination

The primary sources of contamination of the landfill solids in both the landfill mass and the former tire
pile area are the waste-pit liguids and the municipal refuse.

6.1.2.2 Nature and Extent of Contamination Within the Landfill Mass

The nature of contamination within the landfill mass includes volatile and semivolatile organics, metals,
pesticides, PCBs, and radionuclides. The extent of landfill solids is shown in Figure 6-4. The former
landfill occupies approximately 195 acres and is estimated to average 80 to 100 feet in thickness. The areal
extent of the landfill is shown in Figure 6-1.

6.1.2.3 Concentrations of Contaminants Within the Landfill Mass

The detection freguencies of the following VOCs exceeded 10 percent: 1,1-dichloroethane;
1,1,1-trichloroethane; 1,2-dichloroethane; 2-butanone; 4-methyl-2-pentanone; acetone; chloroform; methylene
chloride; tetrachloroethylene; and trichloroethylene. The data generally show the highest concentration of
VOCs to be associated with unsaturated solids samples from within or below suspended waste pits, thereby
reflecting the impacts of residual waste-pit liguid contamination. Concentrations of VOCs are usually lowest
in post-1980 samples. No samples exceeded established standards for TCLP VOCs.

Phthalates were the most commonly detected SVOC. There is no apparent areal distribution trend (for example,
similar ranges of concentrations from areas with suspended liguid waste pits as with areas with saturated
waste pits, medical waste, or no waste pits). There is however, a general vertical trend with the highest
phthalate concentrations found in the post-1980 solids. In general, phthalate concentrations decreased with
depth. Phthalates are common plasticizer chemicals and the noted trend may, therefore, reflect the increased
use of plastics and plastic containers over time.

Phenol was detected at the highest freguency. As with the phthalate, there is no apparent areal distribution
trend for phenol; however, there does not appear to be a general decrease in phenol concentrations with
depth. A number of polyaromatic hydrocarbons (PAHs) were also detected.

PCBs and pesticides were also detected in some of the samples. There are no distinct areal or vertical
distribution trends for any of the metals. The concentrations of the more toxic metals (such as arsenic,
cadmium, chromium, and mercury) are generally below 50 mg/kg with the exception of lead, which had a maximum
detection of 1,410 mg/kg. No samples exceeded established standards for TCLP metals. For radionuclides, the
values measured are generally low and within the background concentrations established for soils as part of
the OUs 4&5 RI.

Table 6-6 presents a summary of chemicals detected in unsaturated solids within the landfill mass and their
concentrations.

6.1.2.4 Nature and Extent of Contamination Within the Former Tire Pile Area

The former tire pile area, occupying approximately 54 acres, is located immediately north of the main
landfill mass and is shown in Figure 6-4. The measured depth to ground water in this area generally ranges
from approximately 2 to 11 feet. The tires that were formerly stockpiled in the area have been shredded and
placed into a monofill cell by WMC under contract to Denver. As part of the SWRA effort, an engineered
collection system and cover were placed in the unnamed creek drainage. Waste pit disposal operations
occurred in three general areas within the tire pile area.
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A geophysical investigation consisting of an electromagnetic survey was performed in conjunction with
confirmatory trenching to estimate the number of buried drums in the former tile pile area of the Lowry
Landfill. Nine confirmatory trenches were excavated in areas identified as anomalies by the geophysical
investigation. Twelve corroded drums were encountered in four of the six anomalous areas. Data from the
trenching efforts suggest that there may be as many as 1,350 buried drums. Appendix E of the feasibility
study for OUs 2&3 estimates that approximately 19 percent (257 drums) of the total estimate of buried drums
may contain liguids. Based on treatability study results, the feasibility study also suggested that, on the
average, approximately 5 gallons of liguid may be present in each of the estimated 257 liquid-filled drums;
this provides the basis for an estimated yield of a total liquid volume of no less than 1,300 gallons of
liquid waste.

6.1.2.5 Concentrations of Contaminants Within the Former Tire Pile Area

Organic chemicals including volatile organics, semi-volatile organics, pesticides, PCBs, and inorganics
including metals and cyanide were detected in subsurface solid samples in the former tire pile area. A
summary of these chemicals appears in Table 6-7. The unsaturated solids are a source that contributes to
ground-water contamination.

6.1.2.6 Volume Estimates

Landfill solids volumes were calculated for pre-1980 solids (co-disposal practices were ceased on August 11,
1980), post-1980 solids, and total solids. Both the total saturated solids and total unsaturated solids
volumes were calculated for the landfill mass. Estimated landfill solids volumes are as follows:

Volume of pre-1980 Solids-3.2 X 106 yd3g
Volume of post-1980 Solids-8.9 X 106 yd3
Total Volume of Solids-1.2 X 107 yd3
Volume of Saturated Solids-2.2 X 105 yd3
Volume of Unsaturated Solids-1.2 X 107 yd3

These calculations show that about 74 percent of the total solids at the Lowry Site were disposed of after
1980, and approximately 98 percent of the total solids volume is unsaturated.

6.1.3 OU 3: Landfill Gas

6.1.3.1 Source of Contamination

The primary sources of contaminants in the landfill gas are subsurface liquids, saturated and unsaturated
landfill solids, and leachate.

6.1.3.2 Nature and Extent of Contamination

As with other municipal solid waste landfills, methane gas and other gases are generated at the Lowry Site
from the degradation of solids and chemical constituents present in the landfill mass. RI data were used to
characterize the nature and extent of methane and other gases generated at the Lowry Site. Following the
completion of the low permeability landfill cap in 1992, methane gas excursions outside the landfill
perimeter have been observed on a regular basis at Wells GMP-3, GMP-6A, GMP-7, and GMP-9. Figure 6-5 shows
the general source and extent of contamination.

Ambient air was sampled during the Phase I, Phase II, and ASC monitoring programs. No evidence of
site-related contaminants was found in the ambient air data.

6.1.3.3 Concentrations of Contaminants

Frequently detected chemicals in landfill gas include 1,1,1-trichloroethane, 1,1-dichloroethane, carbon
disulfide, chloroethane, methylene chloride, tetrachloroethylene, trichlorethylene, methane, and vinyl
chloride. These compounds were detected most frequently in both waste-pit gas samples and samples from
refuse located above waste pits. Concentrations of the VOCs generally decreased with distance from the waste
pits. The decrease in concentrations is attributed to the dilution of the volatiles carried within the
methane generated from the refuse. Concentrations of contaminants in samples collected at the refuse
surface, in areas with underlying waste pits, were approximately 1.5 to 10 times lower than concentrations in
samples taken directly above the refuse/waste-pit interface. Concentrations of contaminants in samples
collected at the refuse surface in areas without underlying waste pits were approximately 1 to 8 times lower
than concentrations in samples taken from the same zone in areas with underlying waste pits.
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Gas concentrations detected within the former tire pile area are considerably higher than those detected
outside the landfill mass. For example, benzene was detected at a maximum concentration of 18,000 ]lg/m3
within the former tire pile area and 500 jlg/m3 outside the landfill mass; vinyl chloride was detected at a
maximum concentration of 680,000 jlg/m3 within the former tire pile area, and 7,000 jlg/m3 outside the
landfill mass.

Headspace samples taken with Summa canisters from monitoring wells in the waste pits provide an indication of
the amount of chemicals volatilizing from the ground water. Chemicals detected in greater than 50 percent of
the samples include 1,2-dichloroethylene, benzene, chloroethane, ethylbenzene, toluene, xylene, and vinyl
chloride. These data provide information on the mixture and amount of chemicals emitted from ground water
and those that contribute to landfill gas volumes.

Volatile organics were also collected in gas samples taken outside the landfill mass but within the Lowry
Site boundary. Soil gas samples taken from outside the landfill mass indicate the presence of five
chemicals: 1,1,1-trichloroethane, benzene, ethylbenzene, toluene, and xylene. The compounds detected in
these samples were also detected in gas samples taken from within the landfill mass or from gas probes
adjacent to the landfill. Of the nine locations from which samples were analyzed, three samples showed
consistent and positive detects-two on the north, and one on the southwest side of the landfill. Chloroform
was the most freguently detected chemical (7 out of 10 samples) in the remaining gas monitoring wells. All
other chemicals were detected in two or less samples.

Combustible gas was first detected in perimeter gas monitoring wells in August 1991. Four out of 13 probes
(GMP-3, GMP-6A, GMP-7 and GMP-9) were found to contain measurable levels of combustible gas. Since August
1991, the freguency of monitoring has been increased to a monthly basis and the same four gas wells have
continued to show detectable levels of combustible gas, although the percent of detected methane varies from
month to month. Table 6-8 summarizes the methane data obtained from the perimeter gas monitoring wells.

Table 6-9 presents the summary data for all the landfill gas samples.

6.1.3.4 Volume Estimates

In 1987, WMC conducted a gas recovery study for the Lowry Landfill and estimated gas generation rates were
shown to be approximately 170 standard cubic feet per ton of solid waste per year (scf/tn/yr). The Lowry
Site contains approximately 5 million tons of solids. Therefore, the gas generation rate is estimated to be
1,600 standard cubic feet per minute (scfm) . This generation rate is an "estimated maximum" and is expected
to decrease with time.

6.1.4 OU 4: Soil

6.1.4.1 Source of Contamination

Four distinct areas of the Lowry Site (not including the landfill mass) were used for waste disposal (Figure
6-6) and contribute to surface soil contamination. The areas are distinct either because of the type of
waste disposed or the method of disposal. These areas are identified as: the sewage sludge
application/leachate injection area; the sewage sludge application area; the leachate spraying area; and the
former tire pile area. Figure 6-6 depicts the approximate boundaries of each area.

6.1.4.2 Nature and Extent of Contamination

For the purposes of this discussion, surface soil is defined as zero to 12 inches in depth. Subsurface soil
is defined as soil from a depth of 1 to 10 feet.

6.1.4.2.1 Sewage Sludge Application/Leachate Injection Area. This area is approximately 200 acres in size
and is in the northern portion of Section 6. Of the areas in which surface soils were sampled, this area
exhibited the greatest number of organic chemicals detected. Thirty-eight organic chemicals were detected,
although 68 percent of these were detected only once or twice. PCB-1260 was detected in eight samples within
this area. This is the only area of the soils media in which PCB-1260 was detected in more than one sample.
Although 2,3,7,8-TCDD was not detected in samples from this area, nine other more highly chlorinated dioxins
and furan isomers were detected in one sample out of two analyzed for these compounds.

Eighteen inorganic constituents were detected, with one constituent, selenium, detected only once in 11
samples. The inorganic chemicals that were detected were distributed throughout the area. The highest
concentrations of inorganic constituents were detected in two adjacent sample locations near the unnamed
creek channel. Eighteen samples were analyzed for radionuclides and four naturally-occurring isotopes were
detected in the majority of these samples.
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6.1.4.2.2 Sewage Sludge Application Area. This area is comprised of approximately 40 acres. Nine organic
chemicals were detected in surface soil in this area. Five of these chemicals-benzoic acid, chloroform,
4,4'-DDD, di-n-octylphthalate, and toluene were detected only once with methylene chloride and phenol
detected twice. Only 4-chloroaniline and bis(2-ethylhexyl)phthalate were consistently detected in samples
from this area. Background inorganic constituents, except selenium and thallium (no positive detections),
were detected consistently throughout the area. No samples were analyzed for radionuclides from this area.

6.1.4.2.3 Leachate Spraying Area. The leachate spraying area occupies an area of approximately 4 acres.
Three organic chemicals, benzene, bis(2-ethylhexyl)phthalate, and methylene chloride were each detected once
out of the seven samples in surface soil taken from this area. Chloroform was detected in one of two
samples. Cyanide, selenium, silver, and thallium were not detected above the detection limit, and mercury
was detected once. All other typical inorganic constituents were detected consistently in samples from this
area. Radionuclides were detected in the two samples taken.

6.1.4.2.4 Former Tire Pile Area. The former tire pile area occupies an area of approximately 54 acres.
Thirty-four organic chemicals were positively detected in samples from this area. The following pesticides
were detected in more than one sample: alpha chlordane, DDT, dieldrin, endrin aldehyde, gamma chlordane, and
methoxychlor. Alpha chlordane in more than half of the sample locations and nine PAHs were detected at one
sample location along unnamed creek. Twelve inorganic constituents were detected at sample locations
throughout the former tire pile area. Mercury was detected in two samples, selenium in one sample, and
cadmium, cyanide, silver, and thallium were not detected over the detection limit in this area. Soil samples
were not analyzed for radionuclides.

6.1.4.2.5 Subsurface Soil. Organic chemicals, including VOCs, pesticides and PCBs were detected
infreguently in subsurface soil. The following organic chemicals were detected at a freguency greater than
10 percent: 2-butanone, 4-chloroaniline, acetone, methylene chloride, bis(2-ethylhexyl)phthalate, DDT,
endrin, and PCB-1260. Subsurface samples from the sewage sludge application area, leachate spraying area,
and tire pile area were analyzed for radionuclides. Eight radionuclides, including plutonium-239,
potassium-40, strontium-90, thorium-228, -230, and -232, uranium-234, and uranium-2-38, were detected at a
freguency of 100 percent. Lead-210 was detected at a freguency of 75 percent.

6.1.4.3 Concentrations of Contaminants

The following summaries are based on an evaluation of data collected from the zero to 12-inch soil horizon
and the subsurface soil interval of 1 to 10 feet.

6.1.4.3.1 Sewage Sludge Application/Leachate Injection Area. The minimum and maximum detected and the mean
concentrations of organic chemicals detected in surface soil samples taken from this area are presented in
Table 6-10. The mean was calculated by using one-half the detection limit as a place holder for samples
without a value above the detection limit. Compared to the other areas identified under OU 4, this area
displayed the maximum concentrations of organics. Specifically, the following three chemicals detected at
concentrations exceeding 1,000 jig/kg: 4-chloroaniline, bis(2-ethylhexyl)phthalate, and PCB-1260.

Summary data for inorganic constituents are also presented in Table 6-10. Maximum concentrations of
inorganics for the Lowry Site, excluding manganese and aluminum, were detected within this area.

6.1.4.3.2 Sewage Sludge Application Area. Summary data for organic chemicals in surface soil samples are
presented in Table 6-11. The most freguently detected chemicals, 4-chloroaniline and
bis(2-ethylhexyl)phthalate had maximum concentrations of about 500 jig/kg. Table 6-11 also presents
inorganic summary data. The maximum concentration of manganese for the Lowry Site was detected in this area.

6.1.4.3.3 Leachate Spraying Area. Summary data for organic chemicals in surface soil samples from the
leachate spraying area are presented in Table 6-12. There were four organic chemicals that were each
detected only once. The maximum concentration of these chemicals was less than 25 jig/kg. The exception was
bis(2-ethylhexyl)phthalate, with a maximum concentration of 215 jig/kg. Table 6-12 also presents inorganic
summary data. Concentrations of inorganic constituents are generally lower than those detected in other
areas.

6.1.4.3.4 Former Tire Pile Area. For this area, the minimum, maximum, and the mean concentrations of
detected organic chemicals in surface soil samples are presented in Table 6-13. Although six pesticides were
present in more than one sample, none were detected at concentrations greater than 2 jig/kg. Table 6-13 also
presents inorganic summary data. The maximum concentration of aluminum for the Lowry Site was detected in
the former tire pile area.

6.1.4.3.5 Subsurface Soil. The data summary for subsurface soil, presented in Table 6-14, does not
distinguish between areas. All subsurface soil samples were grouped because of the limited number of samples
and detected constituents. No consistent distribution of organic chemical concentrations could be determined
-------
with available sample data. In general, inorganic constituent concentrations decrease with increasing depth.
In the sewage sludge application area, zinc, lead, cadmium, nickel, and chromium exhibited lower
concentrations in subsurface soil than in the zero to 12-inch horizon. In the leachate spraying area,
concentrations of inorganics remained relatively unchanged throughout the soil profile. The maximum
concentration of arsenic, 18,000 jig/kg, was detected in the leachate spraying area at the 4.5- to 6-foot
interval. Two radionuclides, thorium-228 and potassium-40, were detected in background samples.

Reported onsite concentrations for these radionuclides are comparable to the background concentrations.

6.1.4.4 Volume Estimates

For purposes of estimating the volume of soil in OU 4, an aerial extent of approximately 103 acres (excluding
the former tire pile area) and an average excavation depth of 15 feet was assumed. This depth was based on
the detection of arsenic at 18,000 jig/kg at 6 feet below ground surface and the depth of the current borrow
area. The total volume of soil in OU 4 is estimated as approximately 2.5 million cubic yards.

6.1.5 OU 5: Surface Water

The SWRA, implemented in 1992, eliminated the offsite migration of contaminated seepage from unnamed creek.
The SWRA collects the unnamed creek base flow in a subsurface drain and maintains flows that are in contact
with the ground-water table until the ground water is captured at the barrier wall. At the barrier wall, the
base flows are pumped to the existing ground-water treatment plant. The existing ground-water treatment
plant was recently upgraded to treat larger quantities and a more expansive list of contaminants. A soil cap
was placed within the onsite unnamed creek channel as well.

6.1.5.1 Past Source of Contamination

Seeps have historically been observed in locations along the banks of the unnamed creek near the center of
Section 6. The sources of these seeps are believed to be the waste pits, ground-water discharge, and seepage
from the toe of the landfill. The seeps contributed to perennial contaminated surface water flows in the
unnamed creek. Prior to the SWRA, surface water would flow into the area previously occupied by Pond 3,
which was located along the unnamed creek upstream of the barrier wall. Previously, water that collected in
Pond 3 would infiltrate through the bottom of the pond and into the subsurface (upgradient of the barrier
wall); it was then collected for treatment. During periods of high precipitation, Pond 3 would overflow;
this caused contaminated runoff to flow within the offsite portion of the unnamed creek channel.

6.1.5.2 Nature and Extent of Contamination

Prior to implementation of the SWRA, numerous sampling events detected at least 20 organic chemicals in
surface water in unnamed creek-from the toe of the landfill to the area previously occupied by Pond 3.
Within the unnamed creek drainage, between the area previously occupied by Pond 3 and the confluence of
Murphy Creek, the detection of organic chemicals was infrequent and generally not reproducible because of
dilution and low perennial flow. Inorganic constituents follow the same concentration pattern as organics;
twice the number of inorganic constituents were detected (with a frequency over 50 percent) in Section 6 than
beyond the area previously occupied by Pond 3.

6.1.5.3 Concentrations of Contaminants

The highest concentrations of organic chemicals that were detected in unnamed creek prior to implementation
of the SWRA were found in samples collected in the surface drainage between the toe of the landfill and the
area previously occupied by Pond 3. Significantly lower concentrations were detected in samples downstream of
the area previously occupied by Pond 3. Historical data are summarized in Table 6-15 according to the
geographic location of the samples:

• Toe of the landfill to the area previously occupied by Pond 3 (Group 1);

• Downstream of the area previously occupied by Pond 3 to the confluence of unnamed creek with
Murphy Creek (Group 2); and

• Beyond the confluence with Murphy Creek to Section 30 (Group 3).

Generally, concentrations of inorganic constituents were also highest in unnamed creek between the toe of the
landfill and the area previously occupied by Pond 3. These historical data are also summarized in Table
6-15.
-------
6.1.5.4 Volume Estimates

Through implementation of the SWRA, measurable quantities of surface-water flow within unnamed creek have
been eliminated. The SWRA collection system is designed to collect ground-water flow of up to 13 gallons per
minute (gpm). Although the volume of ground-water flow into the collection system is not known, the
treatment plant has reportedly processed approximately three million gallons in a 9-month period.

6.1.6 OU 5: Sediments

Implementation of the SWRA eliminates the offsite transport of surface water and suspended sediments in
unnamed creek. As part of the SWRA, a soil cap was constructed in the onsite unnamed creek channel (see
Figure 11-2 for approximate location of the collection system soil cap). Contaminated sediments within
unnamed creek are currently covered by the SWRA soil cap.

6.1.6.1 Past Source of Contamination

The potential sources of sediment contamination in the unnamed creek were discussed in Subsection 6.1.5.1.
Sediments within the unnamed creek in Section 6 are now covered by the SWRA soil cap.

6.1.6.2 Nature and Extent of Contamination

Prior to the implementation of the SWRA, at least 15 organic chemicals were detected in sediments within the
onsite unnamed creek channel. Few organic chemicals were detected in sediments downstream of the area
previously occupied by Pond 3.

Inorganic constituents were detected above background levels throughout the creek channel as well as beyond
the confluence of unnamed creek and Murphy Creek.

6.1.6.3 Concentrations of Contaminants

The concentrations of sediment contaminants are discussed separately for Section 6 sediments and Section 31
sediments.

6.1.6.3.1 Section 6. Prior to implementation of the SWRA, elevated concentrations of organic chemicals were
detected in the sediments of unnamed creek. Specifically, these chemicals were found in samples collected
from the portion of the creek channel that is within the former tire pile area. For example,
1,1,1-trichloroethane, toluene, and total xylenes were detected at maximum concentrations greater than 100
mg/kg. Significantly lower organic concentrations were detected upstream of this area, in the general
vicinity of the toe of the landfill. All sediments in Section 6 were covered as part of the SWRA.

Elevated concentrations of barium, chromium, and lead were detected in sediment samples from within the creek
channel in the former tire pile area, in close proximity to the waste pits on the east side of the former
creek. Historical data for sediments in Section 6 are summarized in Table 6-16.

6.1.6.3.2 Section 31. Samples collected downstream of the barrier wall in Section 31 exhibited inconsistent
detections of organic chemicals. The area downstream of Section 31 can be divided into two smaller
geographical segments to more easily discuss contaminants detected:

• From Section 31 to confluence with Murphy Creek; and

• From the confluence with Murphy Creek to Section 31 northern boundary line.

Fifteen organic chemicals were detected in the segment from Section 31 to the confluence with Murphy Creek.
Eleven of these chemicals were detected only once. Of those chemicals detected more than once,
bis(2-ethylhexyl)phthalate had the highest detection frequency at 50 percent. PCBs, toluene, and acetone had
detection frequencies between 30 and 40 percent. With the exception of 2,4-dinitrophenol (detected once out
of 11 samples), which was detected at 2.7 mg/kg, maximum concentrations of these organic compounds were below
one mg/kg.

Five organic compounds were detected in the segment from the confluence with Murphy Creek to the northern
boundary of Section 31. Three of these were detected only once. Bis(ethylhexyl)phthalate and
octochlorodibenzodioxin were detected more than once (three and two detections, respectively). The maximum
concentrations of these organic compounds was 0.3 mg/kg for di-n-butylphthalate which is at the detection
limit. The maximum concentration of octochlorodibenzodioxin was 0.00012 mg/kg.
-------
Seventeen inorganic constituents (out of 19 analyzed for) were detected within the segment from Section 31 to
the confluence with Murphy Creek. Two, cyanide and tin, were detected only once. The remaining fifteen
compounds had detection freguencies greater than 40 percent. Two inorganic chemicals not detected in these
sediment samples were antimony and silver. Average concentrations of most inorganic constituents were
approximately the same as those calculated for Section 6. However, average concentrations of barium,
chromium, mercury, and lead were ^L to an order of magnitude lower than those calculated for Section 6.

Eighteen inorganic constituents (out of 19 analyzed for) were in the segment from the confluence with Murphy
Creek to the northern boundary of Section 31. Four constituents, silver, iron, antimony, and tin were
detected only once. The remaining constituents had detection freguencies between 20 and 88 percent. Cadmium
was not detected in a single sediment sample from within this segment. Average concentrations of most
inorganic constituents were approximately the same as those calculated for Section 6. However, average
concentrations of arsenic, barium, chromium, manganese, mercury, and lead were ^L to an order of magnitude
lower than those concentrations calculated for Section 6.

6.1.6.4 Volume Estimates

According to the OUs 4&5 feasibility study, the SWRA soil cap covers an area of approximately 320,000 sguare
feet in size. This estimate includes the areas previously occupied by Ponds 3 and 4 (Pond 4 was previously
located directly west of the existing treatment plant). The volume of contaminated sediments that were left
in place and covered by SWRA soil cap was not estimated. The volume of sediments in the unnamed creek
segment of Section 31 is estimated to be 23,700 cubic yards.

6.2 Surface and Subsurface Pathways of Migration

Conceptual models were developed for each OU and were designed to detail potential contaminant sources,
potential routes of migration, and contaminant fate and transport. The models focused the RI/FS site
characterization activities and formed the basis of the pathways identified in the baseline risk
assessment(s).

The sources of contamination at the Lowry Site include subsurface liguids, waste pits, landfill solids,
sewage sludge, injected surface water from Ponds 2 and 3, sprayed surface water from Pond 2, and landfill
gas. These sources have released, and will continue to release, contaminants to environmental media. The
environmental media may then act as secondary sources for distributing contamination throughout the
environment and to human and environmental receptors.

Sampling of these media was conducted during the pre-Phase I, the Phase I and Phase II RI, and the OUs 1&6,
2&3, and 4&5 Additional Site Characterization (ASC) efforts to assess media interactions and their potential
as secondary sources of contamination. Interactions were evaluated as part of each OU RI Report. However,
only the significant pathways of migration are discussed here. Significant pathways have been chosen based
on their contribution to site risk.

The significant pathways of migration include subsurface liguids to shallow ground water, subsurface liguids
and shallow ground water to surface water and sediments, volatiles from subsurface liguids to landfill gas,
landfill solids to landfill gas to the atmosphere, leachate from landfill solids to shallow ground water,
contaminated surface water to shallow ground water, and shallow ground water to deep ground water.

6.2.1 Subsurface Liquids to Shallow Ground Water

Contaminants from the waste pits have migrated into both the weathered Dawson shallow ground-water system and
the unweathered Dawson formation. Migration primarily occurs in a horizontal direction. In certain areas of
the Lowry Site, waste pits and shallow ground water have no hydraulic separation. As a result, the waste-pit
liguids and shallow ground water have co-mingled.

Although contaminants in the waste-pit liguids are similar to contaminants in the shallow ground water,
individual comparisons of analytical results between waste pit well points and adjacent shallow ground-water
monitoring wells indicate variable trends. The differences in contaminant occurrence and concentrations
between the well points and adjacent monitoring wells could result from one or more of the following
conditions: variability in geology; lack of contaminant migration, or variability in the rate, volume, and
pattern of contaminant migration from the waste pits; location of a waste pit in relation to the water table;
the influence of other waste pits on the monitoring wells; the presence and possible migration of multiple
liguid phases in the waste pits; or contaminant migration from the waste pit along pathways not encountered
by the adjacent monitoring wells.
-------
6.2.2 Subsurface Liquids and Shallow Ground Water to Surface Water and Sediments

Data collected during Phase I and Phase II investigations confirmed that the shallow ground-water and
subsurface liguids located within or just below the landfill mass flowed to the north and discharged to the
unnamed creek. Available data also support the conclusion that the shallow ground-water and subsurface
liguids in the former tire pile area were discharged to the surface water through seeps located along the
banks of unnamed creek. These ground-water discharges contributed to the base flow within unnamed creek.
For the area north of the former tire piles, available data support the conclusion that the shallow
ground-water system was recharged through surface water infiltration.

Subsurface sand channels have also been identified at the Lowry Site. These sand channels promote enhanced
subsurface fluid flow and provide another mechanism for subsurface liguids to intermingle with shallow ground
water.

The majority of the organic compounds which were detected in the shallow ground water and subsurface liguids
were also detected in surface water, and at a similar freguency of detection. A similar correlation was
observed between OU 1 and sediments, although OU 1 contaminants were typically detected less freguently in
sediments. Concentrations of organics detected in shallow ground water (OU 1) were typically higher than in
either the surface water or the sediments.

Based on the correlation between contaminant levels in sediments and their location with respect to waste
pits, contaminants from the waste pits have migrated through the ground water and discharged via seeps to
surface water in the unnamed creek.

Although analytical results indicate that ground-water discharge to the unnamed creek has historically
impacted surface water and sediments onsite, implementation of the SWRA has isolated these media and prevents
offsite migration of contaminated surface water.

6.2.3 Volatiles from Subsurface Liquids to Landfill Gas

Analyses have shown that both the waste pit and refuse gas samples contained similar organic compounds.
Because these two types of samples were collected at various elevations above the waste pits, the results
indicate that: (1) within the refuse, waste-pit vapors and waste-pit gases are highly mobile and widely
dispersed in the subsurface; and/or (2) that the refuse serves as a source for gas generation.

Similar types of volatile organic compounds are seen in the landfill gas and source area shallow ground
water, and substantiate that there are interactions between the media.

6.2.4 Landfill Solids to Landfill Gas to Atmosphere

Significant pathways of migration between the landfill solids, landfill gas, and the atmosphere are as
follows:

• Gas produced within the landfill mass migrates primarily by advective flow toward the landfill
perimeter and into the atmosphere.

• The highest contaminant concentrations and the greatest number of contaminants at the perimeter
tend to occur closest to the landfill margin.

• The composition and concentrations of VOCs detected in perimeter areas are consistent with gas
compositions within the landfill mass.

• Soil gas VOC concentrations in the former tire pile area are consistent with VOC concentrations
within the waste pits; gas contamination by VOCs in the former tire pile area is characterized
by localized sources.

6.2.5 Contaminated Surface Water to Shallow Ground Water

Seepage within unnamed creek transported contaminants to the sediments and surface water. The potential
contribution of contamination from sediments and surface water to the shallow ground water depends on the
amount of precipitation runoff and recharge that occurred within unnamed creek.

Prior to implementation of the SWRA, surface water was observed to infiltrate into the subsurface through the
bed of unnamed creek. A comparison of surface water data (from the area previously occupied by Pond 3) to
ground-water data (from wells located along the unnamed creek north of the former tire pile area) indicates
recharge from contaminated surface water potentially impacted ground water in the former tire pile area.
-------
Comparisons indicate, however, that other sources, including subsurface liquids, have also had a significant
impact on ground-water quality in this area. Completion of the SWRA eliminated potential recharge to the
shallow ground-water system underlying unnamed creek.

6.2.6 Shallow Ground Water to Deep Ground Water

Hydraulic gradient data indicate that downward vertical gradients exist between the shallow and deep ground
water. Chemical analyses from the deep ground water indicate the presence of low levels of organic
contamination near Wells B504 and C702Q2. A potential exists for contaminated shallow ground water to
migrate to the deep ground water.

-------
Table 6-1
Summary of Chemical Concentration Date for
Waste Pit Liquids Well Points and Shallow Ground-Water
Monitoring Wells in the Source Area
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2,
2-
2-
2-
2-
2-
2-
Chemical Name (a)
1,1-Trichloroethane
1,2,2-Tetrachloroethane
1,2-Trichloroethane
1-Dichloroethane
1-Dichloroethylene
2,3,4,6,7,8-Heptachlordibenzo-p-Dioxin
2,3,4,6,7,8-Heptachlorodibenzofuran
2,3,4,7,8,9-Heptachlorodibenzo-p-Dioxin
2,3,4,7,8,9-Heptachlorodibenzofuran
2,3,4,7,
8-Hexachlorodibenzo-p-Dioxin
2,3,4,7,8-Hexachlorodibenzofuran
2,3,6,7,8-Hexachlorodibenzo-p-Dioxin
2,3,6,7,8-Hexachlorodibenzofuran
2,3,7,8,9-Hexachlorodibenzofuran
2,3,7,8-Pentachlorodibenzo-p-Dioxin
2,3,7,8-Pentachlorodibenzofuran
2,4-Trichlorobenzene
2-Dichlorobenzene
2-Dichloroethane
2-Dichloroethene (Total)
2-Dichloropropane
4-Dichlorobenzene
3,4,6,7,8-Hexachlorodibenzofuran
3,4,7,8-Pentachlorodibenzofuran
3,7,8-Tetrachlorodibenzodioxin
3,7,8-Tetrachlorodibenzofuran
4,5-T
4,5-TP
4,5-Trichlorophenol
4,6-Trichlorophenol
4-D
4-Dichlorophenol
4-Dimethylphenol
4-Dinitrophenol
Butanone (MEK)
Chioronaphthalene
Chiorophenol
Hexanone
•Methylnaphthalene
Methylphenol
Frequency
of
No. of No. of Detects (b)
Analyses Detects (%)
Minimum (c)
Detected
Concentration
Maximum (c)
Detected
Concentration
Average (d)
Detect
Organics (y.g/1)
141
140
141
140
140
39
39
39
39
39
39
39
39
39
39
39
120
120
141
141
141
120
39
39
41
41
25
27
97
99
26
99
98
85
127
116
97
141
125
115
58
1
3
76
49
29
25
19
13
13
22
25
13
3
9
8
5
18
77
51
11
21
12
11
10
29
5
8
1
2
3
8
28
1
47
1
1
4
35
34
41
1
2
54
35
74
64
49
33
33
56
64
33
8
23
21
4
15
55
36
8
18
31
28
24
71
20
30
1
2
12
8
29
1
37
1
1
3
28
30
3.
66.
3.
2.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
8.
4.
3.
1.
1.
2.
0.
0.
0.
0.
2.
1.
18.
13.
46.
22.
9.
500.
17.
11.
8.
48.
3.
14.
000000
000000
000000
000000
800000
000050
000020
000003
000020
000007
000003
000010
000003
000008
000004
000009
500000
000000
000000
000000
000000
000000
000010
000007
000005
000002
300000
000000
000000
000000
000000
000000
000000
000000
000000
000000
000000
900000
000000
000000
2768511.3
66
104.1
1051621.6
140000
0.928
0.142
0.0167
0.0167
0.0082
0.0172
0.0486
0.0048
0.00022
0.0026
0.0013
1663.3
180
1800000
160000
268.2
321.1
0.0034
0.0019
0.0011
0.0014
90
48.5
18
15
2450
164
3900
500
230000
11
8
269.9
43900
7500
101.41
18
16.71
219.44
41.75
0.0013
0.0001
0.000041
0.000032
0.000016
0.000032
0.0001
0.000013
0.000009
0.000010
0.000009
13.13
13.52
221.56
61.10
16.31
15.08
0.000014
0.000011
0.000007
0.000030
2.45
3.36
59
16.50
13.55
21.70
47.11
47
383.85
13
17
25.73
32.44
31.57
-------
Table 6-1
Summary of Chemical Concentration Data for
Waste Pit Liquids Wells Points and Shallow Ground-Water
Monitoring Wells in the Source Area
Chemical Name (a)

4,4'-DDD
4,4'-DDE
4,4'-DDT
4-Methyl-2-Pentanone (MIBK)
4-Methylphenol
Acenaphthene
Acetone (2-Propanone)
Aldicarb
Aldicarb Sulfoxide
Alpha Chlordane
Alpha-BHC
Aniline
Anthracene
Benzene
Benzo(a)Anthracene
Benzoic Acid
Benzyl Alcohol
bis (2-Chloroethyl)Ether
bis(2-Etherlhexyl)Phthalate
Bromodi chloromethane
Bromoform
Butylbenzylphthalate
Carbaryl
Carbazole
Carbofuran
Carbon Disulfide
Carbon Tetrachloride
Chlorobenzene
Chloroethane
Chloroform
Chloromethane
Chrysene
cis-1,3-Dichloropropene
Delta-BHC
Di-N-Butylphthalate
Di-N-Octylphthalate
Dibenzofuran
Dibromochloromethane
Dicamba
Dieldrin
Diethylphthalate

No. of
Analyses
102
102
102
140
119
119
140
22
22
71
102
20
116
140
116
76
96
115
117
141
140
116
23
30
23
141
141
141
139
141
141
116
141
102
116
116
118
141
26
102
101
Frequency
of
No. of Detects (b)
Detects (%)
4
2
3
72
51
3
68
1
1
3
3
3
1
97
1
24
8
1
27
1
1
6
5
2
3
14
6
19
25
20
3
2
1
1
11
4
1
1
6
3
12
4
2
3
51
43
3
49
5
5
4
3
15
1
69
1
32
8
1
23
1
1
5
22
7
13
10
4
13
18
14
2
2
1
1
9
3
1
1
23
3
12
Minimum (c)
Detected
Concentration

0.140000
0.280000
0.080000
4.000000
1.600000
Maximum (c)
Detected
Concentration
Average (d)
Detect
5.900000
4.000000
60.000000
23.000000
0.380000
0.150000
21.000000
3.400000
1.000000
83.800000
15.600000
7.200000
3.000000
1.000000
3.000000
13.000000
18.100000
2.000000
7.000000
6.000000
15.000000
14.600000
2.000000
2.000000
0.600000
2.000000
20.000000
5.000000
0.030000
2.000000
5.700000
4.000000
7.000000
0.800000
0.140000
6.800000
1.06
0.34
0.66
956573.7
200000
120.1
2984870
60
23
1.2
0.71
41
3.4
974172.9
83.8
30200
1930
3
21500
3
13
1010.3
97
12
640
14180.2
26000
5200
257.1
56000
18
72
5
0.03
266.6
1205.8
4
7
250
1.3
340
0.13
0.12
0.12
220.51
66.26
13
1041.47
2.4
2.1
0.19
0.07
57.31
14
131.53
13
315.42
30.40
15
43.17
13
17
16.71
3.34
15.43
3.13
46.66
21.91
18.29
36.54
26.06
20.91
12.76
16
0.060
13.93
14.78
12
16
2.46
0.13
19.06
-------
Table 6-1

Summary of Chemical Concentration Data for
Waste Pit Liquids Well Points and Shallow Ground-Water
Monitoring Wells in the Source Area
Chemical Name (a)

Endosulfan II
Endrin
Endrin Aldehyde
Endrin Ketone
Ethylbenzene
Ethylene Glycol
Ethylenedibromide
Fluoranthene
Fluorene
Gamma Chlordane
Gamma-BHC (Lindane)
Heptachlor
Heptachlor Epoxide
Heptachlorodibenzodioxins
Heptachlorodibenzofurans
Hexachlorodibenzodioxins
Hexachlorodibenzofurans
Isophorone
MCPA
Methoxychlor
Methylene Chloride
N-Nitrosodiphenylamine
Naphthalene
Octachlorodibenzodioxins (Total)
Octachlorodibenzofurans (Total)
PCB-1242 (Aroclor 1242)
PCB-1260 (Aroclor 1260)
Pentachlorodibenzodioxins (Total)
Pentachlorodibenzofurans (Total)
Pentachlorophenol
Phenanthrene
Phenol
Pyrene
Styrene
Tetrachlorodibenzodioxin (Dioxin)
Tetrachlorodibenzofuran (Dioxin)
Tetrachloroethylene
Toluene
Total Heptachlorodibenzo-P-Dioxin
Total Xylenes

No. of
Analyses
102
102
11
101
141
26
24
117
117
71
102
101
102
22
68
78
82
118
24
102
140
117
127
61
61
107
108
75
77
95
117
102
117
140
77
89
141
140
40
141

No. of
Detects
1
3
2
3
71
1
3
3
7
1
4
2
2
3
33
21
23
12
1
2
56
6
53
36
29
1
5
13
24
8
15
38
5
4
17
24
51
97
29
88
Frequency
of
Detects (b)
(%)
1
3
18
3
50
4
13
3
6
1
4
2
2
14
49
27
28
10
4
2
40
5
42
59
48
1
5
17
31
8
13
37
4
3
22
27
36
69
73
62

Minimum (c)
Detected
Concentration
0.640000
0.060000
1.000000
0.760000
3.000000
650000.000000
0.120000
25.900000
2.000000
0.620000
0.025000
0.470000
0.240000
0.090000
0.000061
0.000020
0.000006
3.000000
650.000000
0.120000
3.000000
10.000000
2.000000
0.000021
0.000154
19.350000
15.000000
0.000009
0.000005
4.000000
4.200000
3.000000
36.300000
17.000000
0.000002
0.000008
0.900000
0.900000
0.000050
5.000000

Maximum (c)
Detected
Concentration
0.64
1.1
2.98
1.78
3514995
650000
0.28
200
241.4
0.62
1.02
1.5
0.94
0.23
0.784
0.098
0.195
1376340
650
14
440000
5972
109622
14.93
1.16
19.35
493
0.0301
0.0657
4125
1690
29000
230
28101.4
0.0064
0.0107
341360.5
10938360
1.73
2279915.6

Average (d)
Detect
0.12
0.13
0.17
0.14
107.22
2,000
0.02
13.18
13.14
0.71
0.07
0.07
0.06
0.0023
0.00054
0.00017
0.00016
23.25
400
0.36
107.37
17.84
31.66
0.01
0.00071
1.2
1.39
0.000036
0.000091
81.11
22.26
60.92
14.30
20.10
0.000021
0.000060
84.61
627.65
0.0019
436.11
-------
Table 6-1

Summary of Chemical Concentrations Data for
Waste Pit Liquids Well Points and Shallow Ground-Water
Monitoring Wells in the Source Area
Chemical Name
Trans-1,3-Dichloropropene
Trichloroethylene
Vinyl Chloride
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Chromium (Total)
Cobalt
Copper
Cyanide
Ferrous Iron
Fluoride
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Thallium
Tin
Vanadium
Zinc
(a)

No. of
Analyses
141
141
141

No. of
Detects
2
78
48
Frequency
of
Detects (b)
f o \
\ "° /
1
55
34
113
109
105
114
114
44
114
114
114
113
109
21
50
92
114
114
114
102
107
76
9
114
114
83
10
77
109
12
35
45
52
71
52
26
21
34
45
113
25
85
45
19
16
1
44
79
Inorganics (y.g/1)

73
9
73
96
11
80
39
46
62
46
24
100
68
49
99
22
75
44
18
21
11
39
69
Minimum (c)
Detected
Concentration
2.200000
4.000000
2.600000
3.500000
4.066400
2.200000
13.900000
0.870000
80.702200
2.500000
0.712900
5.400000
4.700000
5.300000
200.000000
160.000000
1.000000
182.000000
0.210000
13.000000
1.800000
0.660000
0.342100
200.000000
1.800000
4.600000
Maximum (c)
Detected
Concentration
3
772347.3
1800
Average (d)
Detect
14.86
110.16
54.23
310000
1170
1550
16600
12
34700
517
1660
328
1550
6910
1720000
1760000
506
69600
3.3
2000
6540
78
763
200
760
28800
3099.21
30.53
68.08
410.70
3.02
1504.12
16.51
24.99
30.40
82.07
37.26
58535.20
3496.15
36.61
2952.23
0.20
161.01
82.88
7.20
29.75
68
74.03
247.26
Actinium-228
Americium-241
Americium-241 (Alpha)
Bismuth-214
Cerium-143
Cesium-136
Cesium-137
Cobalt-57
Cobalt-60
67
39
7
79
6
59
68
59
67
Radionuclides (pCi/1)

2 3
1 3
1 14
41 52
6 100
1 2
3 4
1 2
2 3
5.000000
2.000000
0.100000
1.060000
25.000000
1.500000
1.500000
1.500000
1.500000
80.7
2000000
1500000
200
92
15
19
5
22
11
79
7.9
13.54
43.81
3.7
2.52
2.2
2.49
-------
Table 6-1

Summary of Chemical Concentrations Data for
Waste Pit Liquids Well Points and Shallow Ground-Water
Monitoring Wells in the Source Area
Chemical Name (a)
Iodine-124
Iron-59
Lead-210
Lead-212
Lead-212-Bismuth
Lead-214
Neodynium-147
Plutonium-239
Potassium-40
Radium-226
Sodium-22
Strontium-90
Thallium-208
Thorium-228
Thorium-230
Thorium-232
Tritium
Uranium-234
Uranium-235
Uranium-238
Uranium-Natural
Zirconium-95

No. of
Analyses
59
67
2
20
48
79
59
42
89
12
59
58
67
63
13
51
57
13
38
45
9
60

No. of
Detects
1
1
1
9
10
39
1
19
51
6
1
6
5
10
10
25
45
11
4
32
6
1
Frequency
of
Detects (b)
(%)
2
1
50
45
21
49
2
45
57
50
2
10
7
16
77
49
79
85
11
71
67
2
Minimum (c)
Detected
Concentration
2.000000
2.500000
3.000000
3.250000
2.500000
0.904000
15.000000
0.020000
25.000000
0.350000
1.500000
0.000002
4.500000
1.000000
0.040000
0.035000
25.000000
0.100000
10.000000
0.050000
1.200000
2.500000
Maximum (c)
Detected
Concentration
300
32
11
47
108
202.5
150
25
1930
75.4
4
4.5
650
105
75
146
7500
49
25
426.7
150
8

Average (d)
Detect
12
3.1
5.7
10.55
5.24
16.36
29
0.47
153.49
2.85
1.9
0.44
7.14
4.70
1.99
1.08
601.39
4.02
17.60
2.96
5.68
3.8
Notes:

a. Only chemicals detected at least once in the source area well grouping are presented.
b. Method of calculation: (number of samples with detected concentrations/number of samples within this well grouping)
c. Minimum/Maximum detected concentration values (only two figures are significant).
d. Geometric mean of the median concentrations from all wells in this well grouping including ^> the detection limit for non-detects (only two figures are
Source: Appendix A, Baseline Risk Assessment (EPA, 1992) .
-------
Table 6-2
Summary of Chemical Concentration Data for
Downgradient Weathered Dawson Monitoring Wells
Outside of the Source Area
No. of
Detects
Frequency (b)

Detects
Minimum (c)
Detected
Concentration
Maximum (c)
Detected
Concentration
Average (d)
Detect
1,1,1-Trichloroethane
1,1,2-Trichloroethane
1,1-Dichloroethane
1,1-Dichloroethylene
1,2,3,4,6,7,8-Heptachlordibenzo-p-Dioxin
1,2,3,4,6,7,8-Heptachlorodibenzofuran
1,2,3,4,7,8,9-Heptachlorodibenzo-p-Dioxin
1,2,3,4,7,8,9-Heptachlorodibenzofuran
1,2,3,4,7,8-Hexachlorodibenzo-p-Dioxin
1,2,3,4,7,8-Hexachlorodibenzofuran
1,2,3,6,7,8-Hexachlorodibenzo-p-Dioxin
1,2,4-Trichlorobenzene
1,2-Dichloroethane
1,2-Dichloroethene (Total)
1,2-Dichloropropane
1,4-Dichlorobenzene
2,3,4,6,7,8-Hexachlorodibenzofuran
2,3,7,8-Tetrachlorodibenzofuran
2,4-D
2,4-Dichlorophenol
2,4-Dimethylphenol
2-Butanone (MEK)
2-Hexanone
2-Methylphenol
4-Bromophenyl-Phenylether
4-Methyl-2-Pentanone (MIBK)
4-Methylphenol
4-Nitroaniline
Acenaphthene
Acetone (2-Propanone)
Aldicarb Sulfoxide
Benzene
Benzo(G,H,I)Perylene
Benzole Acid
bis(2-Ethylhexyl)Phthalate
Bromodichloromethane
Bromoform
Carbon Disulfide
Chloroform
Delta-BHC
Di-N-Butylphthalate
Dibromochloromethane
1
1
1
1
1
1
1
10
12

1
2
2
1
1
1
4
1
1
1
1
1
1
1
6
1
4
1
21
4
15
15
9
4
4
15
3
4
4
3
4
4
4
18
9
12
4
16
12
2.80
3.90
2.50
16.00
0.000010
0.000002
0.000030
0.000008
0.000020
0.000001
0.000020
1.30
5.00
5.80
2 .10
10.00
0.000004
0.000004
1.50
5.70
13.00
2 . 30
3.50
8.00
10.00
8.70
13.00
50.00
2.00
9.80
1.00
5.20
10.00
2.00
1.00
3.00
17.00
10.00
2 . 60
0.01
2.00
7.00

o
o
0
0
0
0
0

0
0

5300.00
13.00
770.00
750.00
.000290
.000002
.000030
.000008
.000020
.000001
.000020
1.30
200.00
610.00
75.00
10.00
.000004
.000007
1.50
5.70
13.00
12.00
3.50
8.00
10.00
8.70
13.00
50.00
2.00
180.00
1.00
44 .00
10.00
9.10
5.60
3.00
17.00
12.00
21.00
0.01
2.00
7.00
26.27
3.92
14 .77
13.05
0.0000087
0.0000021
0.0000029
0.0000032
0.0000025
0.0000018
0.0000023
5.5
6.33
10.61
4 .92
6.4
0.000003
0.000002
1.3
5 . 6
6.0
5.57
6. 6
5.8
6.4
7.1
6.0
32
5.7
11.72
0.56
4 .08
6.4
19.60
5.29
3.5
3.9
4 .76
4 .36
0.02
5 . 7
3. 7
-------
Table 6-2

Summary of Chemical Concentration Data for
Downgradient Weathered Dawson Monitoring Wells
Outside of the Source Area
Chemical Name (a)
Diethylphthalate
Dinoseb
Ethylbenzene
Heptachlorodibenzofurans
Hexachlorodibenzodioxins
Hexachlorodibenzofurans
Methylene Chloride
N-Nitroso-Di-N-Propylamine
Octachlorodibenzodioxins (Total)
Octachlorodibenzofurans (Total)
Pentachlorodibenzodioxins (Total)
Pentachlorodibenzofurans (Total)
Phenol
Pyrene
Tetrachlorodibenzodioxin (Dioxin)
Tetrachloroethylene
Toluene
Total Heptachlorodibenzo-P-Dioxin
Total Xylenes
Trichloroethylene
Vinyl Chloride

No. of
Detects
1
1
1
1
3
1
1 2
1
1
1
1
1
2
1
1
14
4
1
3
14
1
Frequency (b)
of
Detects
(%)
4
11
3
8
23
8
36
4
8
8
7
8
8
4
8
42
12
8
9
42
3

Minimum (c)
Detected
Concentration
2.00
0.10
38.00
0.000004
0.00001
0.000003
1.60
0.86
0.00007
0.000004
0.00003
0.000002
2.10
2 .10
0.000006
2.00
1.00
0.0005
14 .00
3.00
6.80

Maximum ( c )
Detected
Concentration
2.00
0.10
38.00
0.000004
0.00019
0.000003
110.00
0.86
0.00007
0.000004
0.00003
0.000002
3.80
2.10
0.000006
790.00
4 .00
0.0005
360.00
400.00
6.80

Average (d)
Detect
5.7
0.82
3.5
0.0000026
0.000006
0.0000023
6 . 29
5.3
0.0000030
0.00000053
0.00000041
0.00000019
5.86
5.7
-
12.15
3.22
0.0000079
6 . 00
10.20
6.2
Inorganics (|Ig/l)
Aluminum
Antimony
Arsenic
Barium
Boron
Chromium (Total)
Cobalt
Copper
Fluoride
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Thallium
Tin
Vanadium
Zinc
11
19
10
12
8
8
1
4
18
2
15
11
1
8
1
2
22
7
0.
3 .
10.
42.
0.
0.
1 .
600.
0 .
8.
0 .
0 .
5 .
0 .
0 .
50.
1.
2.
. 90
.80
.90
.72
. 06
. 25
. 7 6
. 61
.00
.80
.64
.20
. 95
.00
. 90
. 30
.00
.91
.10
507.
1.
55.
236.
661.
19.
78.
42.
600.
8.
23800.
0.
138.
414 .
0.
1 .
50.
24 .
250.
.00
. 60
.20
.00
.00
.07
.00
. 21
.00
.00
.00
.48
.00
.00
.90
.60
.00
.00
.00
57.
9.
5 .
36.
238.
2 .
5 .
5 .
3
2.
72.
0.
11.
10.
2
3 .

8.
20.
51
01
22
68
54
15
19
75
50
41
52
14
16
16
. 6
06
20
16
98
-------
Table 6-2
Summary of Chemical Concentration Data for
Downgradient Weathered Dawson Monitoring Wells
Outside of the Source Area
No. of No. of
Analyses Detects
Radionuclides (pCi/1)
Frequency (b)

Detects
Minimum (c)
Detected
Concentration
Maximum (c)
Detected
Concentration
Average (d)
Detect
Ant imony-125
Antimony-12 6
Bismuth-214
Cerium-139
Chromium-51
Europium-152
Europium-155
Iodine-132
Iodine-133
Iron-59
Lanthanum-14 0
Lead-212-Bismuth
Lead-214
Mercury-203
Neptunium-239
Plutonium-239
Potassium-4 0
Radium-224
Ruthenium-106
Scandium-106
Silver-110
Sodium-22
Strontium-85
Strontium-90
Technetium-96
Thallium-208
Thorium-228
Thorium-230
Thorium-232
Tin-113
Tritium
Uranium-234
Uranium-235
Uranium-238
Xenon-131M
Xenon-133
Zinc-65
Zirconium-95
13
13
13
13
13
13
13
13
6
13
13
13
13
13
12
13
13
13
13
13
13
13
13
13
13
13
13
11
13
13
13
13
13
13
13
13
13
13
1
1
4
1
1
1
1
1
1
1
2
3
3
1
1
1
1
4
1
1
1
2
1
1
2
1
1
2
2
1
4
11
2
8
1
1
2
1
31
15
31
3 .
3 .
3 .
1.
15.
4 .
4 .
10.
10000.
3 .
3 .
3 .
5 .
1 .
150.
0.
25 .
30.
10.
2.
1 .
1 .
1 .
0 .
5 .
5 .
3 .
0.
0.
1 .
20.
0.
10.
0 .
100.
25 .
3 .
3 .
.50
.00
.50
.50
.00
.00
.50
.00
.00
.00
.00
.00
.00
.50
.00
. 03
.00
.00
.00
.00
.50
.50
.50
.10
.00
.00
.00
.04
. 03
.00
.00
.20
.00
.05
.00
.00
.00
.00
10
15
32
5
40
10
10
15000.
1000000.
10.
20.
17.
24 .
4 .
6000000.
0.
100.
100.
40.
6.
6 .
5.
5.
2.
1500.
16.
15.
5.
0.
3 .
350.
21.
40.
17.
1000.
1500.
10.
6 .
.00
.00
.70
.00
.00
.00
.00
00
00
00
00
80
80
00
00
45
00
00
00
00
00
00
00
00
00
80
70
20
15
00
00
00
00
00
00
00
00
00
5.1
4 .9
6.7
2.2
2.4
5.6
6 .8
100
100,000
4 .7
6.05
5.20
10.13
2 .4
3,100
0.15
39
46.69
18
2.9
2 .4
2.13
2 . 6
0.34
41.44
6.4
4 .9
0.12
0.06
1 .7
68.41
2.15
17.43
1.18
260
82
4 .55
4 .3
-------
a. Only chemicals detected at least once in the source area well grouping are presented.
b. Method of calculation: (number of samples with detected concentrations/number of samples within this well grouping)
c. Minimum/Maximum detected concentration values (only two figures are significant).
d. Geometric mean of the median concentrations from all wells in this well grouping including ^ the detection limit for non-detects (only two figures
are significant).
-------
Table 6-3

Summary of Chemical Concentration Data for
Downgradient Unweathered Dawson Monitoring Wells
Outside the Source Area
Frequency (b)
of
No. of Detects
Detects (%)
Minimum (c)
Detected
Concentration
Maximum (c)
Detected
Concentration
Average (d)
Detect
Organics (|Ig/l)
1,1,1-Trichloroethane
1,1-Dichloroethane
1,1-Dichloroethylene
1,2,3,4,6,7, 8-Heptachlordibenzo-p-Dioxin
1,2,3,4,7,8-Hexachlorodibenzofuran
1,2,3,6,7,8-Hexachlorodibenzofuran
1,2,3,7,8,9-Hexachlorodibenzofuran
1,2-Dichloroethane
2,3,4,6,7,8-Hexachlorodibenzofuran
2,3,7,8-Tetrachlorodibenzofuran
2,4,5-T
2-Butanone (MEK)
2-Hexanone
4-Methyl-2-Pentanone (MIBK)
Acetone (2-Propanone)
Benzene
bis(2-Ethylhexyl)Phthalate
Chloroform
Di-N-Butylphthalate
Heptachlorodibenzofurans
Hexachlorodibenzofurans
Methylene Chloride
Pentachlorodibenzofurans (Total)
Phenol
Propoxur
Tetrachlorodibenzofuran (Dioxin)
Tetrachloroethylene
Toluene
Total Heptachlorodibenzo-P-Dioxin
Trichloroethylene
24
1
8
4
3
1
1
13
1
2
1
1
4
14
14
7
8
4
24
1
3.00
2.00
1.00
0.00001
0.000003
0.00001
0.00001
5.00
0.00001
0.00001
0.30
1.10
1.30
1.60
3.00
11.00
1.00
0.30
4 .00
0.00001
0.00001
0 . 90
0.00002
3.40
2.00
0.000004
1.00
1.00
0.0001
8.00
77.00
35.00
5.00
0.00006
0.000003
0.00001
0.00001
459.00
0.00001
0.00001
0 . 30
7 . 90
5.00
2.00
140.00
11.00
33.00
5.00
4 .80
0.00001
0.00001
640.00
0.00002
6 . 00
2.00
0.000004
31.00
3.00
0.0001
8.00
3.30
2.72
2 .45
0.000007
0.0000019
0.0000019
0.000003
3.14
0.000003
0.0000019
0 . 30
4 .85
4 . 65
4 .59
11.31

4 .08
2.31
4 .67
0.0000026
0.0000024
2.72
0.0000034
5.26
0.65
0.0000024
2.78
1 . 96
0.0000074
2.62
Inorganics (|Ig/l)
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Chromium (Total)
11
81
-------
Table 6-3

Summary of Chemical Concentration Data for
Downgradient Unweathered Dawson Monitoring Wells
Outside the Source Area
Cobalt
Copper
Cyanide
Fluoride
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Thallium
Tin
Vanadium
Zinc

No. of
Detect
10
16
5
18
13
85
9
17
13
7
13
1
6
46
Frequency (b)
of
Detects
(%)
11
18
6
58
18
96
10
19
15
8
16
6
7
52

Minimum (c)
Detected
Concentration
0.
1.
10.
140.
0 .
1 .
0 .
1 .
1 .
3 .
0.
102.
1.
3 .

Maximum ( c )
Detected

Concentration
56
40
00
00
88
80
2 6
40
90
40
25
00
41
50
4 .
47.
180.
1750.
12.
603.
2 .
40.
188.
14 .
1.
102.
2 6 .
200.
. 90
.00
.00
.00
.00
.00
.00
.00
.00
.00
. 30
.00
.00
.00

Average (d)
Detect
1.51
6.21
8.80
352.64
1.66
121.99
0.19
6. 97
2.77
2.74
1.18
11
4 .04
15.57
Americium-241 (Alpha)
Ant imony-122
Ant imony-125
Arsenic-7 6
Barium-140
Bismuth-214
Cadmium-109
Cerium-139
Cerium-14 3
Cerium-14 4
Cesium-134
Cesium-137
Chromium-51
Cobalt-57
Cobalt-60
Iodine-124
Iodine-131
Iodine-132
Lanthanum-14 0
Lead-212
Lead-212-Bismuth
Lead-214
Plutonium-239
Potassium-40
Radium-22 6
Radium-228
Rubidium-83
4
1
1
1
11
1
1
3
1
1
1
1
1
2
1
1
1
3
4
1
11
20
14
3
4
3
3
10
57
4
31
21
0 .
0 .
4 .
0 .
3 .
3 .
30 .
1 .
35 .
10.
1.
1.
10.
1 .
1 .
0.
1.
0 .
1.
8.
2 .
5 .
0 .
25 .
0.
5 .
2.
.04
.15
.00
.01
.50
.00
.00
.50
.00
.00
.50
.50
.00
.50
.50
.50
.00
.25
.00
.49
.50
.00
.03
.00
.20
.00
.50
2000000.
800.
10.
8000000.
30.
92 .
150.
5 .
50.
460.
60.
20.
60.
5 .
17.
200.
30.
300.
20.
25 .
15.
89.
45.
163.
30.
25 .
10.
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
. 30
.00
.00
.00
.00
.00
.00
.00
.00
.90
.50
.00
.00
.00
.00
.00
10.1
19
5.1
1,300
8.5
8.4
54
2.3
41.21
27
3 . 7
2 . 8
20
2.3
2.8
2.8
16
15
3.7
14 .38
4 .3
13.07
0.2
54
1.2
10
4 .0
-------
Table 6-3
Summary of Chemical Concentration Data for
Downgradient Unweathered Dawson Monitoring Wells
Outside the Source Area
Ruthenium-106
Scandium-4 6
Silver-110
Strontium-90
Thallium-208
Thorium-228
Thorium-230
Thorium-232
Thorium-234
Tritium
Uranium-234
Uranium-235
Uranium-238
Uranium-Natural
Yttrium-88
Zinc-65

Notes:

a. Only chemical detected at least once in the source area well groupings are presented.

b. Method of calculation: (number of samples with detected concentrations/number of samples within this well grouping)

c. Minimum/Maximum detected concentration values (only two figures are significant).

No. of
Detect
1
1
1
2
1
2
5
12
1
3
15
4
12
4
2
1
Frequency (b)
of
Detects
(%)
3
3
3
7
3
7
31
41
3
10
71
13
36
67
7
3

Minimum (c)
Detected
Concentration
10.
1.
1.
0 .
4 .
2 .
0 .
0 .
25 .
15.
0.
0.
0.
0.
1 .
2.

00
50
50
15
50
50
05
02
00
00
10
10
02
15
50
50

Maximum ( c )
Detected
Concentration
87 .50
7.00
6 . 00
1.90
15.00
10.00
6.30
17.00
100.00
1000.00
3.80
40.00
190.00
2.35
5.00
27.00

Average (d)
Detect
2 3
2 .8
2.5
0.43
7.6
4 .0
0.20
0.30
49
50
0.6
15
0.3
1.00
2.1
5.4
-------
Table 6-4
Summary of Chemical Concentration Data for Deep Ground-Water Monitoring Wells
1,1,1-Trichloroethane
1,1,2-Trichlorethane
1,1-Dichloroethane
1,1-Dichloroethylene
1,2,3,4,6,7,8-Heptachlorodibenzofuran
1,2,3,4,7,8-Hexachlorodibenzofuran
1,2,3,6,7,8-Hezachlorodibenzofuran
1,2-Dichloroethene (Total)
1,2-Dichloropropane
2,3,4,6,7,8-Hexachlorodibenzofuran
4-Methyl-2-Pentanone (MIBK)
Acetone (2-Propanone)
Aluminum
Benzene
bis(2-Ethylhexy)Phthalate
Boron
Carbon Bisulfide
Chloroform
Di-N-Butylphthalate
Di-N-Octylphthalate
Ethylbenzene
Keptachlorodibenzofuran
Hexachlorodibenzodioxins
Hexachlorodibenzofurans
Manganese
Methoxychlor
Methylene Chloride
Naphthalene
Octachlorodibenzodioxins (Total)
Octachlorodibenzofurans (Total)
Pentachlorodibenzofurans (Total)
Phenol
Tetrachlorodibenzofuran (Dioxin)
Tetrachloroethylene
Toluene
Total Heptachlorodibenzo-P-Dioxin
Total Xylenes
Trichloroethylene
45
44
44
44
11
1
10
9
1
1
1
1
1
1
3
11
1
1
3
1
1
1
1
1
29
1
6
1

1
1
1
1
11
12
1
3.00
2.00
86 . 00
54 .00
0.00008
0 .00003
0.00002
7.00
2.00
0.00002
10.00
5.30
7.29
2.00
3.00
39.10
24 .00
2.00
2.40
18.00
22.00
0.000110
0.000005
0 000090
1.80
0.11
2.90
2.80
0.00004
0.00008
0.00003
2 .40
0.00003
2.90
1.80
0.00002
15.00
9.00
23000. 00
2.00
1900.00
560.00
0.00008
0.00003
0.00002
7.00
2.00
0.00002
600.00
1100.00
30100.00
47.00
30 00
602.00
24.00
2.00
6.00
18.00
22.00
0.000110
0.000005
0.000090
9100.00
0.11
13000.00
2.80
0.00010
0.00008
0.00003
2.40
0.00003
5000.00
1200.00
0.00002
750.00
290.00
4.76
2.4
4.43
4.26
0.000011
0.0000061
0.0000049
2 . 8
2 .4
0.0000053
5.51
16.68
116.49
3.48
6. 35
157. 60
3.2
2.4
4.70
6.2
3.2
0.000014
0.0000042
0.0000088
34 .50
0.19
3.53
4 .7
0.00005
0.000035
0.0000048
5.0
0.0000028
5.01
5.17
0.000014
3.94
3. 65
Arsenic
Barium
Beryllium
Inorganics (jJ.g/1)

1
-------
Table 6-4
Summary of Chemical Concentration Data for Deep Ground-Water Monitoring Wells
Chromium (Total)
Cobalt
Copper
Cyanide
Fluoride
Lead
Mercury
Nickel
Selenium
Thallium
Vanadium
Zinc
14
5
11
3
82
19
11
14
59
Minimum (c)
Detected
Concentration
0.48
7.30
7.40
25.70
350.00
1.10
0.13
2.20
1.80
0.33
1.90
3.80
Maximum (c)
Detected
Concentration
60.00
35. 00
72.00
25.70
970.00
26.00
1.70
162.00
2.90
0.91
90.00
275.00
Average (d)
Detect
3.89
7.75
6.36
5 . 8
631.30
1.75
0.20
13.81
1.36
1.38
5.41
17.13
Americium-241
Americium-241 (Alpha)
Arsenic-7 6
Barium-133
Bismuth-214
Cadmium-109
Cerium-14 3
Iron-59
Lead-212
Lead-212-Bismuth
Lead-214
Neodynium-14 7
Plutonium-239
Radium-22 6
Rubidium-83
Thallium-208
Thorium-228
Thorium-230
Thorium-232
Tin-113
Uranium-234
Uranium-235
Uranium-238
Uranium-Natural
Xenon-131M
Zirconium-8 9
0.
0.
4 .
1.
4 .
40.
18.
3 .
3 .
3 .
5.
15.
0 .
0.
3.
4 .
0.
0.
0.
1.
0.
8 .
0.
0.
75.
2.
.31
. 2 1
.50
.50
.50
.00
.00
.00
.25
.50
.00
.00
.03
.60
.00
.85
.25
.04
.03
.50
.10
.30
.03
.10
.00
.00
1500000.
1500000.
3500000.
5 .
141.
430.
51.
26.
31.
6 .
148.
100.
0 .
0.
6.
17.
4 .
16.
1.
3 .
2.
20.
23.
1.
400.
500.
.00
.00
.00
.00
.00
.00
.00
. 75
.00
.00
.00
.00
.60
.80
.00
.00
.50
.00
.70
.00
.20
.00
.50
.50
.00
.00
160.69
140
180
2 . 3
21.74
64 .45
30.30
6.6
11.11
4 .3
28 .13
36
0.1
0.71
4.1
6.6
2.5
0.80
0.22
1.9
0.38
16.30
0.25
0. 7
166.32
17
-------
a. Only chemicals detected at least once in the source area well grouping are presented.

b. Method of calculation: (number of samples with detected concentrations/number of samples within this well grouping)

c. Minimum/Maximum detected concentration values (only two figures are significant).

d. Geometric mean of the median concentrations from all wells in this well grouping including ^ the detection limit for non-detects (only two figures
are significant.)
-------
Table 6-5
Summary of Chemical Concentration Data for Upgradient Monitoring Wells Outside of the Source Area
1,1,1-Trichloroethane
1,1, -Dichloroethylene
2,3,4,6,7,8-Hexachlorodibenzofuran
2-Butanone (MEK)
4-Methyl-2-Pentanone (MIBK)
Acetone (2-Propanone)
Benzole Acid
bis ( 2-Ethylhexyl)Phthalate
Di-N-Butylphthalate
Di-N-Octylphthalate
Hexachlorodibenzofurans
Methylene Chloride
Octachlorodibenzodioxins (Total)
Octachlorodibenzofurans (Total)
Phenol
Tetrachloroethylene
Toluene
Trichloroethylene
4
1
1
1
1
7
1
2
3
1
1
11
1
1
2
5
11
4
4 . 00
1.00
0.000004
7.50
14 .00
1.00
4 . 60
8.00
3.60
8.00
0.000004
1.60
0.00012
0.00002

1.60
1.10
1.00
5.00
1.00
0.000004
7.50
14.00
1.00
4 . 60
8.00
3. 60
8.00
0.000004
1.60
0.00012
0.00002
2.20
1. 60
1.10
1.00
3 . 33
2.10
0.0000045
5.30
5.90
6. 96
21.00
8 . 65
6.70
61.00
0.0000045
7.68
0.000047
0.000013
4 .27
2.98
2.20
2.10
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Chromium (Total)
Cobalt
Copper
Cyanide
Fluoride
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Vanadium
Zinc
19
10
1
1
4
38
4
6
2 5
2
15.
3 .
1 .
8 .
0.
14 .
2.
3 .
2 .
3 .
5 .
670.
4 .
5 .
0 .
20.
1 .
3 .
1 .
3 .
.13
.07
.10
.01
.30
.40
.20
.40
.10
. 90
. 00
. 00
.00
.90
.31
.50
.30
.30
.30
.60
24600.
770.
6 .
188.
1.
210.
3.
210.
27.
90.
5 .
670.
34.
958.
1.
61.
372.
3 .
65 .
655000.
.00
.00
.00
.00
.10
.00
.40
.00
.90
.90
.00
.00
.60
.00
.00
.00
.00
.50
.00
.00
176.
4 .
8 .
2 2 .
0.
107.
2 ,
6.
1.
10.
3 .
230 .
1.
28.
0.
15.
36.
2.
9.
66.
.41
.15
. 64
. 36
.67
.36
.08
.17
.85
.87
.00
.00
.90
.39
. 29
.90
.10
.19
.18
.37
-------
Table 6-5
Summary of Chemical Concentration Data for Upgradient Monitoring Wells Outside of the Source Area
Americium-241 (Alpha) 2 1 50 0.10 1.30
Bismuth-214 15 5 33 3.50 74.00
Lead-212 41 25 2.75 30.00
Lead-214 15 3 20 5.00 55.00
Plutonium-239 41 25 0.05 0.59
Potassium-40 51 20 25.00 200.00
Radium-226 31 33 0.50 50.00
Thorium-232 4 2 50 0.02 12.00
Uranium-234 2 2 100 0.60 2.20
Uranium-235 51 20 12.50 20.00
Uranium-238 42 50 0.04 5.20
Uranium-Natural 2 1 50 1.50 19.00
a. Only chemicals detected at least once in the source area well grouping are presented.

b. Method of calculation: (number of samples with detected concentrations/number of samples within this well grouping)

c. Minimum/Maximum detected concentration values (only two figures are significant).

d. Geometric mean of the median concentrations from all wells in this well grouping including ^ the detection limit for non-detects (only two figures are significant):
-------
Table 6-6
Parameter Name
Summary of Chemicals Detected in Unsaturated Solids Within the Landfill Mass
Frequency of
No. of Analyses No. of Detects Minimum Detect Maximum Detect Average Detect Detects (%)
Organics (]Jg/kg)
1,1-Dichloroethane
1,1,1-Trichloroethane
1,2-Dichlorobenzene
1,2-Dichloroethane
1,2,4-Trichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
2-Butanone (MEK)
2-Hexanone
2-Methylnaphthalene
2-Methylphenol
4-Chloroaniline
4-Methylphenol
4-Methyl-2-pentanone (MIBK)
4,4'-ODD
4,4'-DDE
4,4'-DDT
Acenaphthene
Acetone (2-propanone)
Aldrin
Alpha Chlordane
Alpha-BHC
Benzene
Beta-BHC
Bis(2-ethylhexyl)phthalate
Butylbenzylphthalate
Carbon disulfide
Chlorobenzene
Chloroform
Delta-BHC
Dibenzofuran
Dieldrin
Diethylphthalate
Dimethylphthalate
Di-n-butylphthalate
Di-n-octylphlhalate
Endosulfan sulfate
Endosulfan II
Endosulfan I
Endrin ketone
Endrin
Endrin aldehyde
Ethylbenzene
Fluoranthene
Gamma chlordane
Gamma-BHC (Lindane)
19
19
18
19
18
18
18
18
19
18
18
18
18
19
19
19
19
18
19
19
19
19
19
19
17
18
19
19
19
19
18
19
18
18
18
18
19
19
19
19
19
17
19
18
19
19
1
11
4
6
2
800
3
11,000
1,300
540
6.0
85
290
2,000
680
180
25
1.9
0.52
1.1
220
110
1.1
1.9
1.3
2.0
4 .1
640
190
2.0
2.0
3. 0
0.50
140
0.50
100
510
280
450
0.19
0.25
0 .36
0.90
0.49
0.44
4.0
500
0.57
1.5
950
24,000
800
510
11,000
1,300
1, 900
3,100
85
5, 900
2,000
680
8, 000
330
400
87
1,700
220
8,200
3.2
390
2.0
16
17
52,000
37,000
2 . 0
2.0
300
14
140
21
8,200
510
19,000
9,000
640
790
6.2
95
38
370
5,300
500
18
13
480
12,000
800
220
11,000
1,300
1,300
610
85
2,500
2, 000
680
3,100
120
150
2 2
290
220
1,700
1.7
71
1.7
8.0
9.2
18,100
9, 700
2 . 0
2.0
110
7 .3
1 40
4 .9
2,200
510
4,700
6,100
110
160
2.5
28
9 . 6
52
580
500
-------
Table 6-6
Parameter Name
Summary of Chemicals Detected in Unsaturated Solids Within the Landfill Mass
Frequency of
No. of Analyses No. of Detects Minimum Detect Maximum Detect Average Detect Detects (%)
Organics (|Ig/kg) (Continued)
Heptachlor
Methoxychlor
Methylene chloride
N-nitroso-di-n-propylamine
N-nitrosodiphenylamine
Naphthalene
PCB-1260 (Aroclor 1260)
Pentachlorophenol
Phenanthrene
Phenol
Pyrene
Styreno
Tetrachloroethylene
Toluene
Total xylenes
Trichloroethylene
11
1
14
14
0. 60
0.41
13
3,000
800
7 6
230
480
450
120
560
3 . 0
6.0
5.0
7.0
8.0
13,000
23,000
1,500
3,100
54,000
3,200
1,300
7,000
560
120
4,800
530,000
61,000
3,000
14
1,300
23,000
1,100
1,200
27,000
2,200
910
2,400
560
52
650
43,000
8,500
690
Aluminum
Arsenic
Barium
Beryllium
Cadmium
Chromium (Total)
Cobalt
Copper
Fluorene
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Vanadium
Zinc
17
18
17
18
18
17
18
17
18
17
17
18
18
18
18
17
17
9
3
13
10
14
1
14
14
5
11
1
1
11
14
25,000
7 .3
355
1.1
15.3
46.7
10
2,500
260
1,400
940
0.87
45
1.6
4 .1
65
3,800
Alpha (Gross)
Americium-241 (Alpha)
Beta (Gross)
Bismuth-214
Iodine- 131
Iron-59
Lead-210
Lead-214
13
13
13
13
13
13
13
11
10
10
10
-------
Table 6-6
Parameter Name
Summary of Chemicals Detected in Unsaturated Solids Within the Landfill Mass

No. of Analyses No. of Detects Minimum Detect Maximum Detect Average Detect
Phosphorus-32
Plutonium-239
Potassium-40
Radium-226
Radium-228
Strontium-90
Thorium-228
Thorium-232
Uranium-234
Uranium-235
Uranium-238
13
13
13
13
13
13
13
13
13
13
13
Radionuclides-pCi/g (Continued)
1 5.0
10 0
7 11
10 0.01
10 0
10 0
10 0
10 0
10 0
10 0
10 0
77
77
77
-------
Table 6-7

Summary of Chemicals Detected in Unsaturated Solids
Within the Former Tire Pile Area
Parameter Name
No. of Analyses
Average Detect
1,1-Dichlorethane
1,1,1-Trichlorothane
1,1,2,2-Tetrachlorethane
1,2-Dichlorethane
1,2-Dichlorethene (total)
1,2-Dichloropropane
1,2,3,4,6,7, 8-Heptachlordibenzo-p-dioxin
1,2,3,4,6,7,8-Heptachlordibenzofuran
1,2,3,4,7,8-Hexachlordibenzofuran
1,2,3,4,7,8-Hexachlorodibenzo-p-dioxin
1,2,3,4,7,8,9-Heptachlordibenzo-p-dioxin
1,2,3,4,7,8,9-Heptachlorodibenzofuran
1,2,3,6,7,8-Hexachlorodibenzo-p-dioxin
1,2,3,6,7,8 Hexachlorodibenzofuran
1,2,3,7, 8-Pentachlorodibenzo-p-dioxin
1,2,3,7,8-Pentachiorodibenzofuran
1,2,3,7,8,9-Hexachlorodibenzofuran
2-Butanone (MEK)
2-Hexanone
2-Met hylnapht halene
2,3,4,6,7,8-Hexachlordibenzofuran
2,3,4,7,8-Pentachlorodibenzofuran
2,3,7,8-Tetrachlordibenzofuran
3,3'-Dichlorobenzidine
4-Methyl-2-pentanone (MIBK)
4,4'-DDE
4,4'-DDT
Acetone (2-propanone)
Aldrin
Alpha chlordane
Benzene
Beta-BHC
Bis(2-ethylhexyl)phthalate
Butylbenzylphthalate
Chlorobenzene
Delta-BHC
Di-n-octylphthalate
Dieldrin
Ethylbenzene
Gamma chlordane
Heptachlor
Heptachlorodibenzofurans
Hexachlorodibenzofurans
HXCDD (Dioxin)
15
15
9
15
13
15
3
3
3
3
3
3
3
3
3
3
3
11
15
15
3
3
3
14
15
15
15
15
15
13
15
15
15
14
15
15
14
15
15
13
15
3
3
3
1
2
1
1
2
1
3
3
3
1
2
3
3
3
1
3
1
1
1
2
1
3
3
1
3
3
2
6
2
1
3
1
8
1
2
1
1
1
3
1
1
3
3
3
6.7
13
11
6.7
15
6 . 7
100
100
100
33
67
100
100
100
33
100
33
9.1
6.7
13
33
100
100
7 .1
20
20
13
40
13
7 . 7
20
6 . 7
53
7.1
13
6.7
7.1
6 . 7
20
7 . 7
6 . 7
100
100
100
1,2
3.9
5,0
3, 9
3, 9
11,

2,
6,
11,

420
2
96
30
24
3
0
1
6
49
48
2,800
8
4

90
5
8

00
00
00
000
0.68
0.13
0.0060
0.0080
0.0030
0.0020
0.030
0.0020
0.0050
0.0010
0.040
200
900
000
0.020
0.0040
0. 0080

_ 7

.7
.16
.0
.0

. 0
3
9.5
0
1
3
0.74
0.12
0.08
1,200
1,700
5,000
3, 900
34,000
11,000
1 .3
0.28
0.12
0.0080
0.020
0.28
0.070
0.050
0.0050
0.15
0.040
2,200
6, 900
70,000
0.020
0.060
0.17
420
54,000
25,000
63
360,000
55
0.16
5,500
6.0
35,000
48
16,000
8.0
43
9.5
170,000
51
83
1.3
0.44
0.43
1,200
840
5,000
3, 900
19,000
11,000
1.
0.
0.
0.
0.
0.
0.
0 .
0 .
0 .
0 .
2,200
6, 900
40,000
0.
0.
0.
420
22,000
9,000
47
78,000
29
0 .
2 600
6 .
9, 100
48
9,300
8 .
43
9.
80,000
51
83
0.
0.
0.

. 0
.1
. 0
. 0'
.0
.1
. o.
. 0.
. 0'
.0
. o.

. 0.
. 0
. 0

. 9
. 2

-------
Table 6-7

Summary of Chemicals Detected in Unsaturated Solids
Within the Former Tire Pile Area
Parameter Name
Average Detect
Methoxychlor
Methylene chloride
Naphthalene
Octachlorodibenzodioxins (Total)
Octachlorodibenzofurans (Total)
PCB-1016 (Ardor 1016)
PCB-1254 (Aroclor 1254)
Pentachlorodibenzodioxins (Total)
Pentachlorodibenzofurans (Total)
Phe riant hrene
Phenol
Tetrachlorethylene
Tetrachlorodibenzofuran (dioxin)
Toluene
Total Heptachlorodibenzo-p-dioxin
Total Xylenes
Trichlorethylene
Organics (|lg/kg) (Continued)
15
15
14
3
3
15
15
3
3
15
15
15
3
15
3
15
15
1
2
1
3
3
1
1
2
3
3
1
3
3
3
3
3
2
6 . 7
13
7.1
100
100
6.7
6 . 7
67
100
20
6.7
20
100
13
100
20
13
0 .
7 _
8, 600
5 .
1.
950
1,000
0.
0.
43
47,000
1.
0 .
120,000
1 .
2, 600
11,000
61
0

6
10

0010
010

9
020

0.61
9, 600
8, 600
12
2.1
950
1,000
0.0040
0.83
17, 000
47,000
83,000
1.0
790,000
2 .1
2,500,000
41,000

4,
8,

6
47,
28,

460,

1,000,
26,
0.61
800
000
9.0
1.5
950
,000
0.0030
0 .30
600
000
000
0.38
000
2.0
000
000
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Chromium (Total)
Cobalt
Copper
Cyanide
Lead
Manganese
Mercury
Nickel
Silver
Thallium
Vanadium
Zinc
16
8
13
16
16
9,200
1.0
0.86
24
0. 10
9. 8
0.09
6 . 6
4 .1
13
0 . 94
8.3
120
0.070
9.0
0.253
0.030
12
40
21,000
30
18
1,200
2 . 1
10
3 . 3
240
15
40
1 . 6
250
1,100
20
40
16
0.22
170
110
15,000
16
7.3
270
1.1
7.4
1.4
32
8.7
22
1 .3
35
560
5.0
13
8.1
0.15
44
65
NR
-------
Table 6-7

Summary of Chemicals Detected in Unsaturated Solids
Within the Former Tire Pile Area
Parameter Name
Average Detect
Beta (Gross)
Bismuth-214
Fluorene
Iodine-131
Lead-210
Lead-212-bismuth
Lead-214
Plutonium-239
Potassium-40
Radium-228 (Beta)
Radium-22 6
Radium-228
Strontium-90
Thallium-208
Thorium-228
Thorium-230
Thorium-232
Tritium
Uranium-234
Uranium-235 (Alpha)
Uranium-235
Uranium-238
9
5
1
5
4
1
9
8
9
3
6
9
6
3
9
6
9
1
9
1
6
9
100
56
6.7
63
67
33
100
89
100
100
100
100
67
100
100
100
100
33
100
33
67
100
9 .
0 .
22,000
0
1.
0.
0.
0
4 .
0.
1.
0 .
0
0 .
0 .
1 .
0 .
0 .
0.
0.
0
0.
. 8
. 69

.2
.27
. 33

. 8
. 2 6
.2
.2

.40
. 27
.2
.15
. 27
.12
.05

.07
1.5
22,000
0.20
1.6
0.27
1.4
0.12
2 2
0.92
1.8
1.4
0.030
0.85
1.4
1.6
1.1
0.27
1.1
0.050
0.020
0.89
NR = Not reported.
-------
Table 6-8

Methane Concentrations in Perimeter Gas Monitoring Wells

Methane Concentrations (% by Volume)a
GMP-1 000 0
GMP-2 000 0
GMP-3 0.8 0.8 0.8 0
GMP-4A 000 0
GMP-5A 000 0
GMP-6A 15 30 30 1.8
GMP-7 1.7 20 15 7
GMP-8 000 0
GMP-9 600 0
GMP-10 000 0
GMP-11 000 0
GMP-12 000 0
GMP-13 000 0
GMP-109 000 0
GMP-110 000 0

aReadings taken with a direct reading instrument.

Note:

NR = No reading taken.

- = No data collected.
GMP-1 0 NR 0 0 - 0 0 0.8 0 0 0 0
GMP-2 000 0 - 000 0000
GMP-3 0.6 5 0 0.9 - 1.0 0 6 0.8 1.8 7 2.2
GMP-4A 000 0 - 000 0000
GMP-5A 000 0 - 000 0000
GMP-6A 30 4 0 0 - 1.5 44 50 47 45 36 38
GMP-7 10 16 0.3 10 - 19 7.5 30 16 25 16 13
GMP-8 0 0 0 0 - 0 0 0 0 0 0.40
GMP-9 0.7 30 0 1.6 - 25 0.2 0.2 1.1 0.3 0.2 0.1
GMP-10 000 0 - 000 0000
GMP-11 ONRO 0 - 000 0000
GMP-12 ONRO 0 - 000 0000
GMP-13 ONRO 0 - 000 0000
GMP-109 ONRNR 0 - 000 0000
GMP-110 ONRNR 0 - 000 0000
-------
Table 6-9
Landfill Gas Data Summary
Parameter Name

1,1,1-Trichloroethane
1,1,2-Trichloroethane
1,1-Dichloroethane
1,1-Dichloroethylene
1,2-Dichloroethane
1,2-Dichloroethylene (Total)
1,2-Dichloropropane
2-Butanone
4-Methyl-2-Pentanone
Acetone
Benzene
Bromomethane
Carbon disulfide
Carbon tetrachloride
Chlorobenzene
Chioroethane
Chloroform
Chioromethane
Ethylbenzene
Methylene chloride
Styrene
Tetrachloroethylene
Toluene
Total Xylenes
Trans-1,2-dichloroethylene
Trichloroethylene
Vinyl Acetate
Vinyl Chloride
cis-1,2-Dichloroethylene
Detection
Frequency
Minimum
Detection
(Ug/m3)

38
300
300
170
110
75
1,000
1.0
2,000
43
10
62

86
170
21
19
4,000
30
42
150
14
19
17
71
64
98,000
270,000
300
770,000
18,000
68,000
61,000
12,000
38,000
49,000
85,000
190,000
230
160,000
86
3,000
780,000
4,000
4,000
80,000
840,000
19,000
160,000
1,400,000
120,000
110,000
24,000
98,000
680,000
670,000
-------
Table 6-10

Sewage Sludge Application/Leachate Injection Area (Group 1) Soils Data Summary
Minimum
Detected
(lag/kg)
Calculated
Mean
(lag/kg)
1,1,1-Trichloroethane
2-Butanone
4,4'-DDE
4-Chloroaniline
4-Nitrophenol
Acetone
Benzene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzole acid
beta-BHC
Bezno(g,h,i)perylene
bis(2-ethylhexyl)phthalate
Butylbenzylphthalate
Carbon disfulide
Chloroform
Chrysene
di-n-Butylphthalate
Dieldrin
Fluoranthene
gamma-Chlordane
Heptachlor
Heptachlor epoxide
Heptachlorodibenzodioxins
Heptachlorodibenzofurans (Total)
Hexachlorodibenzodioxins (Total)
Hexachlorodibenzofurans (Total)
Indeno(1,2,3-cd)pyrene
Methylene chloride
Octachlorodibenzodioxins (Total)
Octachlorodibenzofurans (Total)
PCB-1260
Pentachlorodibenzodioxins
Pentachlorophenol
Phenanthrene
Phenol
Pyrene
Toluene
0.5
1.0
0.90
44
530
5.0
0.50
52
33
72
60
0.90
64
35
100
2.5
0.50
110
27
1.6
25
1.6
1.5
1 . 6
0. 020
0.010
0.010
0.010
0.9
1.0
1.2
380
530
30
2.7
52
75
72
68
1.7
64
380
200
5.0
0.80
110
60
2.9
58
Aluminum
Arsenic
Barium
100
100
100
-------
Table 6-10
Sewage Sludge Application/Leachate Injection Area (Group 1) Soils Data Summary
Constituent
Beryllium
Cadmium
Chromium (total)
Cobalt
Copper
Cyanide
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Tin
Vanadium
Zinc
Cesium-137
Radium-226
Uranium-234
Uranium-235
Uranium-238
a. Arithmetic mean using one-half the detection limit for non-detects.

Source: Table A-7, Baseline Risk Assessment (EPA, 1992).

Total
Observation
16
16
16
16
16
16
16
16
16
16
11
12
2
16
16
Detection
Frequency
(%)
75
100
100
100
100
25
100
100
94
100
9.0
92
100
100
100
Minimum
Detected
(lag/ kg)
500
1, 900
19,000
7,300
27,000
300
37,000
420,000
50
17,000
350
750
11,000
25,000
70,000
Maximum
Reported
(lag/ kg)
13,000
13,000
130,000
120,000
150,000
830,000
151,000
830,000
1,000
130,000
1,000
9,800
12,000
140,000
290,000
Calculated
Mean
(lag/ kg)

60
17
81

77
600

5
11
50

(a)

1,700
3, 900
, 000
, 000
,000
900
,000
,000
500
,000
430
,300
,000
,000

-------
Table 6-11
Sewage Sludge Applications Area (Group 2) Soils Data Summary
Minimum
Detected
(lag/kg)
4,4'-DDD
4-Chloroaniline
Benzoic acid
bis(2-ethylhexyl)phthalate
Chloroform
di-n-Octylphthalate
Methylene chloride
Phenol
Toluene
Inorganics
Aluminum
Arsenic
Barium
Beryllium
Cadmium
Chromium (total)
Cobalt
Copper
Cyanide
Lead
Manganese
Mercury
Nickel
Vanadium
Zinc
11,000,000
1,300
140,000
550
1,400
23,000
8, 800
33,000
300
44,000
400,000
50
22,000
31,000
77,000
7,300
240,000
1,500
3,000
62,000
12,000
83,000
1,800
81,000
2, 700,000
500
30,000
39,000
160,000
5,100
210,000
1,100
2,300
45,000
10,000
60,000
650
63,000
830,000
225
26, 000
36,000
120,000
a. Arithmetic mean using one-half the detection limit for non-detects.
-------
Table 6-12
Leachate Spraying Area (Group 3) Soils Data Summary
Minimum
Detected
(1-Lg/kg)
Benzene
bis(2-ethylhexyl)phthalate
Chloroform
Methylene chloride
Aluminum
Arsenic
Barium
Beryllium
Cadmium
Chromium (total)
Cobalt
Copper
Lead
Manganese
Mercury
Nickel
Vanadium
Zinc
6,400
170,000
550
980
13,000
7, 900
17,000
26,000
370,000
50
12,000
25,000
44,000
12,000
260, 000
1,200
1,500
17,000
9,000
21,000
36,000
640,000
200
16,000
34,000
62,000
9,000
230,000
900
1,300
15,000
8,400
19,000
34,000
460,000
80
15,000
30,000
55,000
-------
Table 6-13

Chemical Detected in Surface Soil Samples
in the Tire Pile Area
Detection Frequency
Within the Tire Pile Area
Chemical
Minimum Detected
(Ug/kg)
Calculated Mean
(Ug/kg)
1,1,1,-Trichloroethane
2-Methylnaphthalene
Alpha chlordane
Acenaphthene
Acetone
Aldrin
Anthracene
Benzo(a)anthracene
Benzo(a)pyreno
Benzo(b)fluoranthene
Alpha-BHC
Beta-BHC
Delta-BHC
Gamma-BHC
Benzo(k)fluoranthene
bis(2-Ethylhexyl)phthalate
Chrysene
4,4'-DDE
4,4'-DDT
Dieldrin
Endrin aldehyde
Endosulfan I
Endosulfan II
Fluoranthene
Fluorene
Gamma chlordane
11
11
56
11
11
11
11
11
11
11
11
11
11
11
11
2 2
11
11
22
22
22
11
11
11
11
22
4,600
0.25
770
31
0.75
260
1,100
840
740
0.96
0.58
2
8 .7
740
2,400
2,000
2.1
0.58
0.24
0.54
2.2
0.24
900
930
1.9
4, 600
0.07
770
31
0.75
260
1,100
840
740
0.96
0.58
2
8.7
740
85
2,000
2.1
0.32
0.08
0.41
2.2
0.24
900
930
0.11
-------
Table 6-13
Chemicals Detected in Surface Soil Samples
in the Tire Pile Area
Deletion Frequency
With the Tire Pile Area
Chemical
Minimum Detected
(Ug/kg)
Calculated Mean
(Ug/kg)
Heptachlor
Heptachlor epoxide
Methoxychlor
Naphthalene
Phenanthrene
PCB-1260 (Aroclor 1260)
Tetrachloroethylene
Pyrene
11
11
22
11
11
11
11
11
Aluminum
Arsenic
Barium
Beryllium
Chromium
Cobalt
Copper
Lead
Manganese
Mercury
Nickel
Selenium
Vanadium
Zinc
25,100,000
5,250
331,000
1,300
35,200
11,500
46,700
36,500
1,880,000
130
20,500
1,000
68,300
95,500
7,860,000
1,400
124,000
720
8, 800
5,000
13,400
7,300
206,000
46
7,100
455
19,400
44,500
21,000,000
3, 000
220,000
1,100
19,000
9,000
25,500
19,000
830,000
73
14,000
555
44,000
74,000
-------
Table 6-14
Subsurface Soil Data Summary
Maximum
Reported
(Ug/kg)
1,2-Dichloroethane
1,1,1-Trichloroethane
2-Butanone
4,4'-DDD
4,4'-DDE
4,4'-DDT
4-Chloroaniline
4-Methyl-2-pentanone
Acetone
Aldrin
Benzene
Benzo(b)fluoroanthene
Benzole acid
beta-BHC
bis(2-ethylhexyl)phthalate
Butylbenzyl phthalate
Chloroform
di-n-Butylphthalate
di-n-Octylphthalate
Dieldrin
Endrin
Endrin ketone
Fluoranthene
gamma Chlordane
gamma-BHC (lindane)
Methylene chloride
PCB-1260
Phenanthrene
Phenol
Pyrene
Tetrachloroethene
Toluene
7.0
2.0
12
3.0
2.0
15
13
4 .0
20
8.0
2.0
3.0
7.0
3.0
47
8 . 0
10
5.0
2.0
2.0
12
4 .0
3.0
2.0
4 .0
41
11
3.0
9.0
3.0
4 .0
5.0
42
3 . 9
44
0.26
0.11
0 . 34
53
2.7
15
0.15
1.0
52
81
1.1
41
48
2.0
45
43
9 5
210
6. 0
1,800
170
4.0
110
43
9.5
0.15
0.21
69
0.13
0.11
120
2,100
46
95
75
1.9
4.0
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium (total)
Cobalt
Copper
13
25,000,000
30,000
18,000
1,200,000
21,000
3,900
83,000
17,000
97,000
-------
Table 6-14
Subsurface Soil Data Summary
Maximum
Reported
(Ug/kg)
Cyanide
Lead
Manganese
Mercury
Nickel
Silver
Vanadium
Zinc
Inorganics (cont.^
12
100
100
43
Lead-210 (pCI/g)
Plutonium-239
Potassium-4 0
Strontium-90
Thorium-228
Thorium-230
Thorium-232
Uranium-234
Uranium-238
-------
Table 6-15
Constituent
Total
Observation
Detection
Frequency
Minimum
Detected
(jig/kg)
Surface Water Data Summary

Group 1
Maximum
Reported
(jig/kg)
Calculated
Mean
(Ug/kg)
Maximum
Reported
(Ug/kg)
Calculated
Mean
(lag/kg)
Calculated
Mean
(Ug/kg)
1,2-Dichloroethene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
2-Butanone
Acetone
di-n-Butylphthalate
Methylene chloride
OCDD (total)
PCDD (total)
Pyrene
Styrene
Aluminum
Arsenic
Barium
Boron
Chromium (total)
Copper
Cyanide
Fluoride
Manganese
Mercury
Nickel
Selenium
Vanadium
Zinc
11
11
— = Not analysed for or not reported.
-------
Table 6-16
Summary of Chemicals Detected in Sediments in Section 6
Detection
Frequency
1,1,1-Trichloroethane
1,1,2-Trichloroethane
1,1-Dichloroethane
1,1-Dechloroethylene
1,2-Dichloroethane
1,2-Dichlorobenzene
1,2-Dichloroethlene (Total)
1,2-Dichloropropane
2,4-Dinitrophenol
2,4-Dimthylphenol
2-Butanone
2-Chlorophenol
2-Methylnaphthalene
2-Methylphenol
3,3'-Dichlorobenzidine
4-Methyl-2-pentanone
4-Methylphenol
Acenaphthene
Acetone
Aniline
Anthracene
Benzo(a)anthracene
Benzo(b)fluoranthene
Benzene
Gamma-BHC (Lindane)
Benzo(k)fluoranthene
bis(2-Ethylhexyl)phthalate
Chlorobenzene
Carbon disulfide
Chloroform
Chrysene
Dibenzofuran
Di-n-butylphthalate
2,4-Dichlorophenol
4,4'-DDT
Dieldrin
Di-n-octylphthalate
Ethylbenzene
Fluoranthene
Methylene chloride
Naphthalene
N-Nitrosodiphenylamine
Phenanthrene
15
12
15
15
4
15
10
1
1
15
10
1
14
4
15
15
1
15
15
15
15
15
15
15
14
12
8
15
15
15
15
14
14
15
15
15
14
15
1
15
5
11
6
12
3
10
10
0
0
0
10
4
0
13
2
14
11
0
13
13
14
11
14
14
6
13
11
8
13
14
13
3 .
2.
1.
2 ,
2 ,
100.
3 .
2.
800
69.
33.
50.
54 .
98.
70.
5 .
165.
165.
4 .
330.
59 .
87.
165.
3 .
4 .
165.
120.
2 ,
2 ,
1.
86 .
165.
145.
170.
8 .
8 .
165.
1.
69.
4 .
81.
75.
62 .
.35
.50
.00
.00
.00
.00
.00
.50
no
.00
.00
.00
.00
.00
.00
.00
.00
.00
.05
.00
.00
.00
.00
.35
.00
.00
.00
.50
.50
.50
.00
.00
.00
.00
.00
.00
.00
.00
.00
.95
.00
.00
.00
110,

3,
1,

15,

24,

2,
8 ,

1,
2 ,
3 ,
6 ,

3 ,
95,

3 ,
1,
2,
2,

3,
95,
7,

14,

6,
000.
18 .
400.
800 .
6 .
900.
570.
270.
200.
310.
000.
50.
000.
470.
70.
570.
390.
400.
400.
330 .
200.
400.
400.
100.
300.
400.
000.
710.
9
3 .
200.
400.
700.
700.
280.
280.
750.
000.
700.
710.
000.
75 .
200.
. 00
. 00
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
. 00
. 00
. 00
. 00
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
.10
.50
. 00
. 00
. 00
. 00
.00
.00
.00
.00
.00
.00
.00
.00
.00
-------
Table 6-16
Summary of Chemicals Detected in Sediments in Section 6
Detection
Frequency
PCB-1260 (Aroclor 1260)
Tetrachloroethylene
Phenol
Pyrene
trans-1,2-Dichloroethylene
Trichloroethylene
Toluene
Total Xylenes
Vinyl chloride
Silver
Aluminum
Arsenic
Barium
Beryllium
Cadmium
Cyanide
Cobalt
Chromium (Total)
Copper
Fluorene
Mercury
Manganese
Nickel
Lead
Antimony
Tin
Vanadium
Zinc
11
11
4
12
13
10
14
9
9
14
11
14
14
15
14
9
14
12
1
1
14
14
1
12
7
12
1
3
2
9
12
12
1
5
7
11
10
1
1
12
12
14
105
3
130
50
3
3
3
3
2
800
6,070,000
3,550
147,000
355
650
145
5, 600
3,700
11,
165
50
476,000
9,100
5,500
29,000
13,000
24,500
36,000
.00
.00
.00
.00
.35
.35
.35
.35
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
000
.00
.00
.00
.00
.00
.00
.00
.00
.00
2,
48,

5,
3,
41,
280,
580,

3,
22,300,
21,
859,
1,
2,
1,
18,
420,
159,
1,
1,
1, 860,
22,
2, 950,
29,
13,
71,
535,
400.
000.
130.
500.
100.
000.
000.
000.
57 .
300.
000.
000.
000.
800.
600.
910.
000.
000.
000.
800.
900.
000.
000.
000.
000.
000.
000.
000.
. 00
. 00
. 00
. 00
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no
. 00
. 00
. 00
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
-------
Section 7.0
Summary of Site Risks

Baseline risk assessments (baseline RAs) were conducted for each environmental medium at the Lowry Site to
evaluate the potential for adverse health and environmental effects caused by actual or potential releases of
and exposure to site-related chemicals under current and hypothetical future conditions. A baseline risk
assessment evaluates what types of risks could be present now and in the future if a site is not remediated
or cleaned up. Under the baseline RA scenarios, EPA would not restrict the use of the Lowry Site and its
resources and would take no action to prevent exposure of people or the environment to contaminants (the
No-Action Alternative). This no-action scenario is used to assess the need for remedial action, to provide a
basis for determining cleanup levels, and for comparing potential health effects of various remedial
alternatives.

The baseline risk assessment for the Lowry Site consists of three volumes and will hereafter be referred to
as the Baseline RA. A separate assessment was conducted for each group of OUs and for lead and
radionuclides, as follows:

• Volume 1: OUs 1&6, which include shallow ground water and subsurface liguids and deep ground
water.

• Volumes 2A and 2B3: OUs 2&3, which include landfill solids and landfill gas and OUs 4&5, which
include soils, surface water and sediments.

• Volume 2C: sitewide issues relating to lead and radionuclides, and the relative risk
contribution by media.

The Baseline RA for the Lowry Site assumed the following conditions:

• No further remedial actions would be implemented to address hazardous substances at the site.

• Interim remedial measures would be discontinued. Existing structures, such as fences and the
ground-water barrier wall, would not be maintained and would eventually deteriorate. The
Surface Water Removal Action (SWRA) would also not be maintained and would eventually
deteriorate.

• Existing physical structures would not be maintained and would eventually deteriorate.

• Hypothetical future use of the Lowry Site would not be restricted and any type of land use
could occur, including agricultural, industrial, recreational, or residential.

The results of the Baseline RA will be presented according to each medium and designated OU. The site risks
presented by lead and radionuclides are presented separately. Key terms are defined in the ROD glossary.

7.1 Human Health Risks

A baseline risk assessment provides the basis for taking action and indicates the exposure pathways that need
to be addressed by the remedial action. It serves as the baseline, indicating what risks could exist if no
action were taken. This section of the ROD reports the results of the Baseline RA conducted for the Lowry
Site.

Results are presented for each of the four basic components of the risk assessment: identification of
chemicals of concern; exposure assessment; toxicity assessment; and risk characterization.

7.1.1 Chemicals of Concern

The chemicals of concern (COCs) for each OU were selected from all available Lowry Site data. Three primary
criteria were used to select COCs:

• Comparing the chemical concentration to background levels to determine if the concentration in
each sample was greater than the concentration expected under natural background conditions.

• Determining if the detection freguency of a chemical in a medium was greater than 10 percent.

• Toxicity-concentration screening to identify those chemicals, by media, that may contribute up
to 99 percent of the risk.
-------
Figure 7-1 presents the screening steps and selection criteria.

Table 7-1 presents the COCs selected for each medium and the minimum and maximum detected values for each.
Forty-six chemicals were retained as COCs for the OUs 1&6 baseline risk assessment. Thirteen chemicals were
selected as COCs for OU 3 and all 49 chemicals detected in subsurface soils were retained as COCs for OU 2.
Thirty-six chemicals in surface water, 33 chemicals in sediments, and 23 chemicals in surface soil were
retained as COCs for OUs 4&5. Radionuclides were detected in all media except landfill gas (no analyses were
conducted for radionuclides in landfill gas) but they are not included in the COG counts above. Separate
risk assessments for lead and radionuclides were conducted and are summarized in subseguent subsections
(7.1.3, Summary of Lead Risks; 7.1.4, Summary of Radiological Risks).

7.1.2 Summary of Exposure Assessment

The exposure assessment identifies:

• Receptors (people) who could potentially be exposed to media containing COCs by looking at land
use, both onsite and offsite (media may have migrated from the site) under current and
hypothetical future conditions

• Pathways of exposure (such as ingestion, inhalation, dermal contact)

• Geographic locations where exposure could occur (exposure point)

• How much exposure could occur (exposure point concentrations, freguency, and duration of
exposure, the amount of media contacted)

7.1.2.1 Current Exposure

Currently, the Lowry Site is zoned as agricultural and is only used for asbestos disposal. Figure 2-2 depicts
major current land uses in the vicinity of the Lowry Site.

Currently, employees of WMC are onsite during the work week. There are no onsite residences and offsite
receptors include farm residents near the Lowry Site, agricultural workers, and persons that may use the
surrounding farmlands for recreation.

Under current conditions, no onsite or offsite exposures occur. WMC workers are subject to Federal and State
regulations prescribing worker protection reguirements to control exposure and, therefore, potential exposure
pathways are not complete. Current offsite exposures do not occur because COCs have not been detected in
media beyond the Section 6 boundaries to the south, east, and west, nor beyond Section 31 to the north.

7.1.2.2 Hypothetical Future Exposure

Development pressure for the area around the Lowry Site is influenced by projected population growth within
Arapahoe County, economic growth of the City of Aurora, and the construction of the E-470 Beltway and
interchanges. The U.S. Census Bureau projects a 50 percent increase in the population of Arapahoe County
within the next 20 years. The City of Aurora anticipates mixed use for the area surrounding the Lowry Site,
including industrial, commercial and residential. Following completion of the E-470 Beltway construction, it
is expected that traffic will increase in the area. It may be assumed that increases in traffic may lead to
increases in new businesses and eventually new residential development.

Given the potential for population growth and future land uses, three types of potentially exposed
populations were identified: residential; commercial/industrial; and recreational.

Hypothetical future exposure settings were developed by integrating populations potentially exposed with the
pathways through which exposure could occur. Settings identified include:

• Hypothetical future onsite and offsite residential (adults and children):

Ingestion of ground water

Incidental ingestion of surface soil, subsurface soils brought to the surface from
excavation, sediment, and surface water

Inhalation of volatiles from surface water and sediment

Inhalation of suspended soil and/or dry sediments as particulates
-------
Inhalation of landfill gas emissions

Dermal contact with surface soil, subsurface soil, surface water, sediment, and
landfill gas

Encountering concentrated levels of methane

• Hypothetical future onsite commercial/industrial (worker):
Ingestion of ground water
Incidental ingestion of surface soil and subsurface soil
Inhalation of suspended surface soil as particulates
Inhalation of landfill gas emissions
Dermal contact with surface soil, subsurface soil, and landfill gas
Encountering concentrated levels of methane

• Hypothetical future onsite and offsite recreational:

Incidental ingestion of surface soft, surface water, and sediment
Inhalation of suspended soil and/or dry sediment as particulates
Inhalation of landfill gas emissions
Inhalation of volatiles from surface water and sediment
Dermal contact with surface soil, surface water, sediment, and landfill gas

The baseline risk assessments for the Lowry Site guantified exposure by estimating the highest exposure that
could reasonably occur, the reasonable maximum exposure (RME), and for some media, the typical
exposure-approximating conditions that are most likely to occur to provide a range of potential exposures.
The RME is designed to be a conservative estimate of exposure that is within the range of possible exposures,
but is higher than typical exposures. Exposure point concentrations and exposure parameter values are
selected so the total exposure represents the upper 90th percentile estimate of possible exposures.

Exposure point concentrations were estimated from monitoring data, either directly or indirectly using simple
models. In either case, monitoring data for each medium were summarized. Statistics used for the summary of
each environmental medium vary because of the nature of the sample collection method (random or non-random),
the distribution of the data in each medium, the variation in detection limits between various sampling
events, and the number of values reported at the detection limit. For ground water, to control the bias
introduced by multiple detection levels spanning several orders of magnitude, the median of the positively
detected values (nondetects were ignored) from each well was used to generate a geometric mean and a 95th
percentile upper confidence limit (95th UCL) on the geometric mean of the median for a specific grouping of
wells (for example, waste-pit well points and shallow ground-water wells within the source area). If a well
had no positive detects for a particular contaminant, one-half of the lowest detection limit was used to
represent the median value.

For all other media, the data were log-transformed, and an arithmetic mean and a 95th UCL of the mean were
calculated. A value of one-half the sample guantitation limit was used in the calculations for all
nondetects.

Direct use of monitoring data utilized either the 95th UCL on the appropriate statistical parameter (mean or
median) or the maximum concentration detected if the 95th UCL was greater than the maximum concentration
detected in estimating the exposure point concentration for the RME. When typical exposure conditions were
evaluated, average concentrations were used as the exposure point concentrations. Models used to estimate
the exposure point concentration at a location where monitoring data were not available used the 95th UCL or
maximum value as an input parameter for RME conditions and the average concentrations for typical conditions.
A basic assumption of the risk assessments is that no physical, chemical, or biological processes reduce the
chemical concentration over time, and therefore, exposure point concentrations are constant for the duration
of exposure.

Exposure point concentrations for chemicals in ground water were developed for one onsite and seven offsite
locations for different aguifers using various pumping rates (domestic at 15 gpm and municipal at greater
than 200 gpm). Of these eight locations, the highest concentrations were obtained with the direct use of
monitoring data from shallow ground-water wells in the weathered Dawson aguifer and waste-pit liguid well
points within the source area (the landfill mass). These concentrations, presented in Table 7-2, were used
to evaluate RME conditions for the future onsite residential setting.

The maximum detected concentration of chemicals in subsurface soil (see Table 74) were used as the exposure
point concentrations for the future onsite residential setting and the future onsite worker setting. The
assumption was made that subsurface soils could be excavated to 10 feet, spread over the surface, and
regraded.
-------
Human exposure to landfill gas in a future onsite residence was evaluated at two distinct locations onsite
that corresponded to the origin of the gas: the landfill mass area with exposure to refuse gas; and the tire
pile area with exposure to soil gas.

The assumption was made that subsurface gas would be transported into a home through a combination of
convective and diffusive transport mechanisms. Exposure point concentrations inside an onsite residence were
obtained by direct use of subsurface gas concentrations assuming eguilibrium between the home and the
subsurface gas and through modeling which varied the parameters governing gas migration. The highest
concentrations were obtained with direct use of subsurface refuse gas data. These exposure point
concentrations are reported in Table 7-3 and were used to evaluate RME conditions for the future onsite
residential setting.

Inhalation of landfill gas was evaluated for the future offsite residential setting by estimating exposure
point concentrations along the southwest perimeter of the Lowry Site. This location was selected because gas
migration has occurred about 200 feet beyond the landfill mass in this area. Four different modeling
scenarios were evaluated; the highest concentrations resulted from assuming a residence had a cracked
structural slab. These were used as the exposure point concentrations for RME conditions in the future
offsite residential settings and are reported in Table 7-3.

Exposure point concentrations for chemicals in surface soil were developed for four distinct areas onsite
according to the chemical distribution. The chemical distributions corresponded with past onsite disposal
activities. The four areas consist of:

• The sewage sludge application/leachate injection area (Group 1)
• The sewage sludge application area (Group 2)
• The leachate spraying area (Group 3)
• The tire pile area (Group 4)

It was assumed that future use at the Lowry Site could occur in each of the four areas. Exposure point
concentrations used for RME conditions for the future onsite residential setting are reported in Table 7-4
for each area. The exposure point concentrations for Group 4 include only inorganic constituents. Data on
organic constituents were evaluated separately for the Baseline RA. Exposure point concentrations for dust
arising from these four distinct locations were derived with the use of an analytical mass-load model. Dust
concentrations are also reported in Table 7-4.

Surface water data were grouped according to geographic location and creek flow for the derivation of
exposure point concentrations. Three groups were formed:

• Group 1 included data taken within the unnamed creek, from the toe of the landfill to the area
previously occupied by Pond 3.

• Group 2 included samples taken in Section 31, from the area previously occupied by Pond 3 to
the confluence of unnamed creek and Murphy Creek.

• Group 3 included samples taken in Section 31 and 30, from the confluence of unnamed creek and
Murphy Creek to the southern portion of Section 30.

It was assumed future onsite residents would use the unnamed creek for recreational purposes, from the toe of
the landfill to the area previously occupied by Pond 3 (Group 1). For this group, exposure point
concentrations used for RME conditions and the future onsite residential setting are reported in Table 7-5.
Similar procedures were employed for the sediment data groupings and are reported in Table 7-5.

Exposure parameters used for the future onsite residential RME were obtained from risk assessment guidance
and were not adjusted to account for site-specific conditions.

Typical exposure parameters approximated the 50th percentile of the parameter distribution and were then
adjusted to account for local and regional conditions, such as:

• Number of days children would be expected to play out-of-doors considering school schedules and
weather conditions

• Number of days when soil is expected to be frozen, which would limit ingestion and dust
generation

• Number of days when precipitation exceeds 0.01 inch and dust generation would be suppressed
-------
Table 7-6 presents RME parameter values for pathways quantified for the future residential,
commercial/industrial, and recreational settings. Absorption of chemicals through dermal contact was not
specifically quantified in any exposure setting because of the uncertainties associated with this pathway.

Combining exposure meters for each exposure route for a medium (for example, soil ingestion) with exposure
point concentrations for each chemical in that medium results in the calculation of a chronic daily intake
(GDI) of each chemical for the exposure route for a medium.

7.1.2.3 Summary of Toxicitv Assessment

Chemical contaminants may be divided into two groups according to their effects on human health.
Contaminants may have carcinogenic effects or noncarcinogenic/systemic effects. Exposure to some of the
chemicals detected at the Lowry Site could potentially result in both types of effects.

Carcinogenic effects result in or are suspected to result in, the development of cancer. EPA assumes a
non-threshold mechanism for carcinogens; that is, any amount of exposure to a carcinogenic chemical poses a
potential for generating a carcinogenic response in the exposed organism. EPA has developed a
carcinogen-classification system using weight-of-evidence to classify the likelihood that a chemical is a
human carcinogen. Chemicals are classified by EPA as:

A Human carcinogen

Bl Probable human carcinogen; limited human data are available

B2 Probable human carcinogen; sufficient evidence in animals and inadequate
or no evidence in humans

C Possible human carcinogen

D Not classifiable as to human carcinogenicity

E Evidence of noncarcinogenicity for humans

Noncarcinogenic or systemic effects include a variety of toxicological end points and may include effects on
specific organs or systems, such as the kidney, liver, lungs, etc. EPA believes that thresholds exist for
noncarcinogenic effects.
Slope factors (SFs) have been developed by EPA's Carcinogenic Assessment Group for estimating excess lifetime
cancer risks associated with exposure to potentially carcinogenic COCs. SFs, which are expressed in units of
(mg/kg-day)-1, are multiplied by the estimated intake of a potential carcinogen, in mg/kg-day, to provide an
upper-bound estimate of the excess lifetime cancer risk associated with exposure at the intake level. The
term "upper bound" reflects the conservative estimate of the risks calculated from the SF. Use of this
approach makes underestimation of the actual cancer risk highly unlikely. Slope factors are derived from the
results of human epidemiological studies or chronic animal bioassays to which animal-to-human extrapolation
and uncertainty factors have been applied (for example, to account for the use of animal data to predict
effects on humans).

Reference doses (RfDs) have been developed by EPA for indicating the potential for adverse health effects
from exposure to COCs exhibiting noncarcinogenic effects. RfDs, which are expressed in units of mg/kg-day,
are estimated threshold levels for daily exposure above which exposure is considered unsafe for humans,
including sensitive individuals. Estimated intakes of COCs from environmental media (for example, the amount
of a COG ingested from contaminated drinking water) can be compared to the RfD. RfDs are derived from human
epidemiological studies or animal studies to which uncertainty factors have been applied (for example, to
account for the use of animal data to predict effects on humans).

Toxicity values for COCs are presented in Table 7-7 for carcinogenic effects and in Table 7-8 for
noncarcinogenic effects.

As suggested by the EPA Risk Assessment Forum, the Toxicity Equivalence Factor (TEF) approach was used for
estimating risk from the dioxin-furan congeners without SFs. Currently, a SF is available for only
2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). Where a specific congener was not given in the
analytical data (that is, total hexachlorodibenzo-p-dioxins rather than a specific one such as
2,3,7,8-hexachloro-dibenzo-p-dioxin), the corresponding 2,3,7,8-congener TEF was used.

The chromium toxicity values presented in Tables 7-7 and 7-8 are for hexavalent chromium. In the absence of
species-specific data, all chromium detected was assumed to be hexavalent chromium.
-------
Slope factors and RfDs are specific to the route of exposure, for example, oral SFs are used to evaluate risk
through ingestion of a carcinogenic COG. Oral SFs and RfDs are not available for all COCs identified at the
Lowry Site. Table 7-9 identifies the chemicals, by medium, for which toxicity values were not available.

Lead, listed on Table 7-9, does not have an EPA-developed toxicity value for the ingestion or inhalation
pathways. The toxic effects of lead exposure are correlated with blood lead levels rather than a daily
intake. EPA has developed a model, the Uptake/Biokinetic Model (U/BK, version 0.5), to assess the potential
effects of lead exposure in the most sensitive population, children ages 1 to 6 years. The use of the model
and results are discussed separately in Section 7.1.3, Summary of Lead Risks.

Radionuclides, also listed on Table 7-9, were evaluated separately from other chemical contaminants and are
discussed in Section 7.1.4, Summary of Radiological Risks.

7.1.2.4 Summary of Risk Characterization

For carcinogens, risks are estimated as the incremental probability of an individual developing cancer over a
life-time as a result of exposure to the carcinogen. Excess lifetime cancer risk is calculated from the
following eguation:
Risk = GDI x SF
where:

Risk = A unitless probability of an individual developing cancer (for example,
one chance in 10,000 or 1 x 10-4)

GDI = Chronic daily intake averaged over 70 years (mg/kg-day)

SF = Slope factor (mg/kg-day)-1

Risks are probabilities that are generally expressed in exponential form (1 x 10-4). An excess lifetime
cancer risk of 1 x 10-6 indicates that as a reasonable maximum estimate, an individual has a one-in-1 million
additional chance of developing cancer as a result of site-related exposure to a carcinogen over a 70-year
lifetime under specific exposure conditions at the Lowry Site.

EPA uses the general 1 x 10-4 to 1 x 10-6 risk range as a "target range" within which the EPA strives to
manage risks as part of a Superfund cleanup. Although waste management strategies achieving reductions in
site risks anywhere within the risk range may be deemed acceptable by the EPA risk manager, EPA has expressed
a preference for cleanups achieving the more protective end of the range (for example, 1 x 10-6).
Furthermore, although EPA generally uses 1 x 10-4 in making risk management decisions, the upper boundary of
the risk range is not a discrete line at 1 x 10-4. A specific risk estimate less than 1 X 10-4 may be
considered unacceptable based on site-specific conditions, including any remaining uncertainties about the
nature and extent of contamination and associated risks.

The potential for noncarcinogenic effects is evaluated by comparing an exposure level over a specified time
period (for example, a lifetime) with a reference dose (RID) derived for a similar exposure period. The
ratio of exposure to toxicity is called a hazard guotient (HQ).

The HQ is calculated as follows:

GDI
Noncancer HQ =
RfD

where:

GDI = Chronic daily intake averaged over the exposure period (mg/kg-day)

RfD = Reference dose (mg/kg-day)

The GDI and RfD are expressed in the same units and represent the same exposure period (that is, chronic,
subchronic or short-term).

If the GDI (exposure) is greater than the Rfd, the HQ will be greater than one. An HQ greater than one
indicates the potential for an adverse noncarcinogenic health effect from exposure to the chemical.

A Hazard Index (HI) is generated by adding the HQs for all COCs that affect the same target organ or system
(for example, the liver or respiratory system) within a medium or across all media to which a given
population may reasonably be exposed. If the HI for each toxic end point exceeds one, the potential for an
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adverse noncarcinogenic health effect from exposure to the medium is indicated.

To evaluate the potential for adverse effects from exposure to subsurface soil and landfill gas, the baseline
risk assessment used risk-specific values as a screening tool. A risk-specific value is a concentration that
will result in a 1 x 10-6 excess lifetime cancer risk for carcinogenic effects. A reference concentration is
a concentration that will result in a hazard guotient of one for noncarcinogenic effects. Both risk-specific
values and reference concentrations are calculated with the same media-specific intake parameters developed
for the Lowry Site. Risk-specific values and reference concentrations were then compared to the exposure
point concentrations calculated for subsurface soil and landfill gas.

The following discussion of OU groups presents the risks associated primarily with the onsite exposure
scenario. In general, the onsite exposure scenario results in the greatest or most significant estimates of
risks.

7.1.2.4.10Us 1&6: Shallow Ground Water, Subsurface Liquids, and Deep Ground Water. The highest excess
lifetime cancer risk from ingesting water from a well within the source area, for a future onsite resident
adult using RME conditions, is 1 x 10-2. Three COCs (arsenic at 23 percent; benzo(a)anthracene at 24 percent;
and vinyl chloride at 22 percent) are responsible for about 70 percent of the total risk estimate. With 6
years of exposure, the HI for noncarcinogenic effects through ingestion could be as high as 47 for an adult
and 46 for a child. Five COCs exceed their reference dose and contribute to the total HI. Table 7-10
presents the excess lifetime cancer risk and non-cancer HQ for the COCs with the greatest contribution to
risk in subsurface liguids.

7.1.2.4.2 OU 2: Landfill Solids. (Landfill solids are evaluated as subsurface soil 1 to 10 feet below
ground surface). The potential for adverse effects of landfill solids was evaluated on a screening level
basis only. Concentrations of four chemicals exceed their carcinogenic risk-specific values for the
ingestion or inhalation pathway in a future onsite residential setting. Concentrations of arsenic, beryllium
and PCB-1260, in subsurface soil, exceed their risk-specific values for the ingestion pathway. Concentrations
of arsenic, beryllium, and chromium (hexavalent), in subsurface soil, exceed their risk-specific values for
the inhalation pathway. The chemical concentrations that exceed risk-specific values were detected through
the Lowry Site and at many were co-located. The term co-located is explained as follows. Forty-four
separate samples had concentrations of arsenic that exceeded its risk-specific value for ingestion of soil
and inhalation of dust. Thirty-six separate samples had concentrations of beryllium that exceeded its
risk-specific value for ingestion of soil and inhalation of dust. Concentrations of arsenic and beryllium
were co-located in 30 samples. only one sample location contained concentrations of all four chemicals that
exceeded their risk-specific values. At selected sample locations, exposure to these chemicals in subsurface
soil would result in an excess lifetime cancer risk greater than 1 x 10-5 for each individual chemical.

None of the COCs evaluated in this manner exceed their noncarcinogenic reference concentration for ingestion
or inhalation. Table 7-11 presents the comparison of subsurface soil concentrations to risk-specific values
calculated at a 1 x 10-6 risk and to reference concentrations.

Concentrations of two chemicals exceed their carcinogenic risk-specific values for the ingestion or
inhalation pathway in a future onsite occupational setting. The concentration of PCBs in one sample exceeds
its risk-specific value for the ingestion pathway. The concentration of chromium in 37 samples exceed its
risk-specific value for the inhalation pathway. Concentrations of PCBs and chromium are co-located at one
sample location.

None of the COCs evaluated in this manner exceed their noncarcinogenic reference concentration for ingestion
or inhalation in an occupational setting.

7.1.2.4.3 OU 3: Landfill Gas. The potential for adverse effects of landfill gas was evaluated on a
screening level basis only. For the RME future onsite residential setting, exposure point concentrations of
all carcinogenic VOCs from within the landfill mass exceed their carcinogenic risk-specific values for the
inhalation pathway. Furthermore, exposure to these chemicals through inhalation could result in an excess
lifetime cancer risk of one in one, due to the measured concentrations of vinyl chloride within the landfill
mass. A cancer risk of one in one is exceedingly high. Concentrations of five VOCs with noncarcinogenic
effects from within the landfill mass exceed their noncarcinogenic reference concentrations for inhalation
(the HQ for each chemical is greater than one). Table 7-12 presents the comparison of exposure point
concentrations of refuse gas within the landfill mass to risk-specific values and reference concentrations.

Methane is present within the landfill mass at concentrations above the lower explosive limit. Methane has
been detected above the lower explosive limit outside of the landfill mass, but not offsite. It therefore
presents an explosion hazard under a prescribed set of conditions (i.e., concentrations between 5 and 15
percent by volume and the presence of a spark source).
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Modeled concentrations of 1,1-dichloroethene and vinyl chloride, within a future offsite residence with a
cracked structural slab, exceed their carcinogenic risk-specific values for the inhalation pathway. Exposure
to these chemicals through inhalation would result in an excess lifetime cancer risk greater than 1 x 10-6
for each individual chemical. Modeled concentrations of noncarcinogenic VOCs do not exceed their
noncarcinogenic reference concentrations for inhalation. Table 7-13 presents the comparison of exposure
point concentrations modeled from 95th UCL concentrations to risk-specific values and reference
concentrations.

7.1.2.4.4 OU 4: Soil. The highest excess lifetime cancer risk, 4 x 10-5 (summation of cancer risks from
arsenic, beryllium, 2,3,7,8-TCDD, and PCB-1260), was estimated for a future onsite resident child ingesting
surface soil from the sewage sludge application/leachate injection area (Group 1, see Figure 6-6). Arsenic
contributes 53 percent and beryllium contributes 28 percent to the cancer risk estimate for Group 1,
regardless of the age of the receptor soils. Using the same receptor and exposure settings, all remaining
soil groups (2 through 4) had estimated risks egual to or less than those calculated for Group 1 (Group 2
risk was estimated as 4 x 10-5; Group 3 as 3 x 10-5; and Group 4 as 1 x 10-5; the inclusion of organic data
in risk estimates for Group 4 would increase the risk to 4 x 10-5) . The pathway total HI for a future onsite
resident child ingesting and inhaling soil from Group 2 is slightly higher at 1.2.

The estimated risks for an adult receptor are similar; ingestion of surface soil from Group 1 soil results in
an estimated risk of 2 x 10-5; 2 x 10-5 for Group 2 soil; 1 x 10-5 for Group 3 soil; and 6 x 10-6 for Group 4
soil. The total pathway risk from ingestion of soil over a period of 30 years as an onsite resident (child
and adult) is 6 x 10-5 for Group 1 soil; 6 x 10-5 for Group 2 soil; 4 x 10-5 for Group 3 soil; and 2 x 10-5
for Group 4 soil (without the inclusion of organic data).

The estimated excess lifetime cancer risk from inhalation of dust arising from the soil in Group 1 was 8 x
10-5 for an adult. Estimated cancer risks for a child for all remaining soil groups were less than those
calculated for Group 1. The future onsite resident adult had the highest estimated risks through inhalation
of dust arising from the remaining soil groups (2 through 4), although less than those calculated from Group
1 soil (Group 2 risk was estimated as 8 x 10-6; Group 3 as 3 x 10-6; and Group 4 as 4 x 10-6). The total
pathway risk from inhalation of dust arising from Group 1 soil is 2 x 10-5 (adult of 1 x 10-5 plus the child
of 8 x 10-6, for a total of 1.8 or 2 x 10-5) . Chromium (assumed to be in the carcinogenic hexavalent form),
is the primary contributor to the risk estimate for inhalation of dust. Table 7-10 presents the excess
lifetime cancer risk for the COCs, within soil from the sewage sludge application/leachate injection area
(Group 1), that contribute to the greatest risk estimates for the future onsite residential setting.

For the scenario in which a future onsite resident child ingests surface sod from the Group 1 soil, the
pathway total HI for noncarcinogenic effects eguals 1. The pathway total HI for a future onsite resident
child ingesting and inhaling soil from Group 2 soil is slightly higher at 1.2. Other His for the ingestion
and/or inhalation pathways using different soil groups or children or adult receptors are below one. Table
7-10 presents the noncancer HQs for adults and children using for COCs in Group 1 surface soil that have the
greatest contribution to risk in the future onsite adult residential setting.

7.1.2.4.5 OU 5: Surface Water and Sediments. Using the onsite portion of unnamed creek for recreational
purposes, a child in the future onsite residential setting could experience an excess lifetime cancer risk of
8 x 10-4 from ingestion (at the RME) of vinyl chloride (85 percent contribution) and 1,1-dichloroethene (14
percent contribution) in surface water. An excess lifetime cancer risk of 9 x 10-6 could result from
ingestion of arsenic (77 percent contribution) in sediments from the same section of the creek. Table 7-10
presents the excess lifetime cancer risk for the COCs within the onsite section of the unnamed creek for
surface water and sediment exposure that contribute the most to risk form a recreational use by a child in
the future onsite residential setting.

The HI for noncarcinogenic effects was 2 for the future onsite resident child ingesting acetone and
trans-1,2-dichloroethene (each contributes 30 percent of the total HI) in surface water and 0.4 for ingesting
antimony and arsenic (75 percent contribution) in sediments from recreational use on the onsite section of
the unnamed creek. Table 7-10 also presents the noncancer HQ for each COG guantified in surface water and
sediments for exposure to a child in the future onsite residential setting. Table 7-10 also summarizes the
potential maximum cumulative excess lifetime cancer risk for the future onsite resident.

Exposure to offsite surface water (Group 2 and 3) in a recreational setting resulted in estimated risks less
than 10-6. Exposure to offsite sediments assumed that sediments had spread beyond the creek banks during
periods of high flow. Therefore, sediment data were used in a residential setting. Childhood exposure to
offsite sediments (Group 2) in a residential setting resulted in an estimated risk of 7 x 10-5 from ingestion
of arsenic and dioxins and 4 x 10-6 from inhalation of chromium (IV) and arsenic. Ingestion of arsenic,
manganese, and vanadium by a child in a residential setting resulted in a pathway HI for noncancer effects of
1. However, these chemicals affect different target organs. An HI should be calculated for each target organ
which would result in an HI less than 1 for each target organ.
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Childhood exposure to offsite sediments (Group 3) in a residential setting resulted in an estimated risk of 2
x 10-5 from ingestion of arsenic and beryllium and 6 x 10-6 from inhalation of chromium (IV) and arsenic.
Ingestion of antimony, arsenic, and chromium by a child in a residential setting results in an HI for
noncancer effects of 2. Antimony had an HQ of 1, while the remaining chemicals each had HQ significantly
below 1. Antimony was detected once in one analysis. The uncertainty of the resulting HI from the
contribution of antimony is high.

For Sections 30/31 sediments (offsite), a child could experience an excess cancer risk of 2 x 10-5 from
ingestion (at RME) of sediments primarily from arsenic and beryllium. For noncancer effects, the HI of 2 is
based on the ingestion of antimony and arsenic.

Table 7-14 summarizes the total risk for the future onsite residential setting for all pathways guantified.
Cancer risks from all pathways guantified are added together to obtain a cumulative risk for the exposure
setting. The cancer risks presented represent RME conditions, the full 30-year exposure duration (child and
adult and the highest exposure point concentrations estimated for each onsite media. Noncancer His are added
together to obtain a cumulative risk for each receptor (adult or child) within a pathway. Adult and child
Hi's are not additive. Landfill solids and landfill gas are not included in this summary table because risk
from exposure to these media were evaluated on a screening level basis only and were not guantified.

7.1.2.5 Uncertainty in the Risk Assessment

Several significant sources of uncertainty impacted the baseline risk assessments. These have been described
in detail in the Baseline RA. To summarize, the major sources of uncertainty and their effect on the risk
assessments include:

• Use of data from investigations spanning 8 years. The resulting data base contained a wide
variation in sample guantitation limits (SQLs) and a large number of nondetects. This adds
uncertainty to the selection of COCs and could overestimate or underestimate exposure point
concentrations.

• The prediction of human activities that lead to contact with media and exposure to chemicals is
highly uncertain. Assumptions used to estimate RME conditions may lead to an overestimation of
risk.

• Simplifying assumptions used to estimate exposure point concentrations may result in an
overestimation of exposure. For example, it was assumed that: contaminant concentrations
remain constant over time; all dust originates from soil contaminated at the 95th UCL
concentration; and eguilibration occurs between subsurface refuse gas concentrations and
concentrations inside a home constructed on the landfill.

• Toxicity data and the assumptions made in using toxicity values (for example, all chromium was
assumed to be present in the hexavalent form, and bioavailability was assumed to be 100
percent) could result in an overestimation of risk. On the other hand, the unavailability of
toxicity values for all COCs could result in an underestimation of risk.

• Risk and doses within an exposure route are assumed to be additive when, in fact, synergisms
and antagonisms occur. This could act to overestimate or underestimate risk.

• The prediction of risks associated with the dermal exposure pathway is difficult since
mechanisms to guantify the contribution of dermal absorption are not well established and
considerable uncertainty surround estimates of dermal exposure and risk. As a result, the
uncertainty associated with the dermal route of exposure necessitates excluding the dermal
contribution from the other routes of exposure.

7.1.3 Summary of Lead Risks

Exposure to lead cannot be evaluated through the same methodology used in the baseline risk assessments.
Toxicity values cannot be determined because research has not identified a threshold below which no adverse
health effects occur. Therefore reference doses, for evaluating the potential for noncancer effects, cannot
be developed. Lead is also thought to be carcinogenic through prolonged low dose exposure; however, its
noncarcinogenic effects on infants and children are more serious because they are manifested in a shorter
time period than the onset of cancer.

Toxic effects of lead exposure are correlated with blood lead levels, and therefore, blood lead levels have
been determined to be an appropriate benchmark for exposure. The Uptake/Biokinetic Model (U/BK, version 0.5)
developed by EPA, allows the estimation of blood lead levels in infants and children (zero to 7 years of age)
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from exposure to lead in environmental media. This model was used to evaluate the potential for adverse
health effects in infants and children exposed (current and potential future) to lead in environmental media
at the Lowry Site by estimating the percent of children that would have a blood lead level greater than the
"level of concern" of 10 jlg/dl established by the EPA and Centers for Disease Control (CDC).

Lead was detected in ground water, soil, surface water, and sediments at the Lowry Site. The summary
statistics for lead in each medium have been presented in Tables 7-2 through 7-5. Potential receptors and
exposure pathways and, therefore, possible exposure settings, have also been described in Volume 2C of the
Baseline RA. The most conservative setting involving children to 7 years in age is the future onsite
residential setting. Because the U/BK model is specific to children, only the following pathways were
considered in this evaluation:

• Ingestion of ground water
• Incidental ingestion of surface soil and subsurface soil from an excavation
• Ingestion of indoor dust derived from outdoor soil
• Inhalation of suspended soil as particulates

Incidental ingestion of surface water and sediments from the unnamed creek were not included in this
evaluation because it was assumed that a child under the age of 7 would not leave the house to play in the
creek. Dermal exposure was not evaluated because percutaneous absorption is not considered a significant
route of exposure for inorganic forms of lead.

Exposure point concentrations of each medium were taken from the sitewide Baseline RA. The future onsite
residential setting evaluates ground water using data from shallow ground-water wells in the weathered Dawson
aguifer and waste-pit liguid well points within the source area (Table 7-2) ; soft from the sewage sludge
application/leachate injection area (Table 7-4); and dust derived from soil in this area (also Table 7-4).
The U/BK model default intake parameters reflect the central tendency of each parameter for the exposed
population of zero to 7-year-olds. Table 7-15 presents the default parameters used in this evaluation. The
U/BK model includes ingestion of lead in the diet and in lead-based paint. Lead-based paint was not included
in the evaluation for the Lowry Site because of the assumption of new residential development. New
developments do not contain lead-based paint. The U/BK model can be effectively employed without including
ingestion of paint. Ingestion of lead in the diet was included using default intake and exposure point
concentrations.

The U/BK model results in a freguency distribution that displays the probability density corresponding to the
estimated mean blood lead level concentration for a given exposure setting. For the future onsite
residential setting, 6 percent of the children ages zero to 7 years were estimated to have blood lead levels
above 10 jlg/dl. Uptake of lead from ground water had the greatest contribution to total lead uptake.

7.1.4 Summary of Radiological Risks

A radiological risk assessment was prepared separately from the assessment of chemical risk from the Lowry
Site. Refer to Volume 2C of the Baseline RA for details on the assessment for radionuclides. While much of
the data needed for a radiological risk assessment is similar to that reguired for a chemical risk
assessment, the procedures used to characterize the radionuclide contaminants and estimate exposure are
different.

7.1.4.1 Contaminated Media and Exposure

As previously stated, radionuclides were detected in all media except landfill gas. With the exception of
gross alpha and gross beta, characterization of radionuclides in gas was not conducted. Because specific
isotopes were not identified, exposure to radionuclides in landfill gas was not guantitatively evaluated in
this ROD.

The following steps were used to select the radionuclides in each media to be carried through the risk
assessment: an evaluation of the detection freguency; a comparison to background concentrations; a
determination of parent radionuclides; and an elimination of radionuclides with short half-lives.

Table 7-16 lists the risk assessment radionuclides detected in each medium.

Potential receptors and exposure pathways, and therefore, possible exposure settings were described in the
sitewide Baseline RA for chemical contaminants. Further, it was assumed that all future offsite settings
would result in lower exposures than future onsite exposures. Conseguently, future offsite exposures were
not evaluated for radionuclide exposure.
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Dermal contact with radionuclides was not included as an exposure pathway because percutaneous absorption is
not considered a significant route of exposure for radionuclides. Therefore, dermal exposure was not
evaluated in this Baseline RA.

However, radionuclides, unlike chemicals, can have deleterious effects on humans without being taken into, or
brought in contact with, the body. This is because high energy beta particles and photons from radionuclides
in contaminated air, water, or soil can travel long distances with only minimum attenuation in these media
before depositing their energy in human tissue. Therefore, external radiation exposure was included as an
exposure pathway for evaluation in this Baseline RA.

7.1.4.2 Summary of Toxicitv Assessment

EPA classifies all radionuclides as human carcinogens (Group A) based on their property of emitting ionizing
radiation and the extensive weight of evidence provided by epidemiological studies of radiogenic cancers in
humans. EPA generally evaluates potential human health risks based on radiotoxicity, considering only the
carcinogenic effects of radionuclides. One exception to this is uranium, which is a kidney toxin as well as
a carcinogen. Given that kidney toxicity may occur prior to the onset of cancer from exposure to uranium
concentrations in drinking water, EPA has developed a reference dose for chronic oral exposure to uranium.

7.1.4.3 Summary of Risk Characterization

Residential ingestion of ground water at the RME from a future onsite domestic well within the source area
could result in an excess lifetime cancer risk of 5 x 10-4 from radionuclides. Three radionuclides are
responsible for the majority of the risk: radium-226 contributes a risk of 1.9 x 10-4 (31 percent); lead-210
contributes a risk of 1.5 x 10-4 (25 percent); and potassium-40 contributes a risk of 1.1 x 10-4 (18
percent). Radium-226, lead-210, and potassium-40 are naturally occurring radionuclides and both radium-226
and potassium-40 were detected in upgradient (background) ground-water samples lead-210 data are not
available). Concentrations of the two radionuclides in upgradient wells results in a total risk of 2 x 10-4
with radium-226 contributing a risk of 1.3 x 10-4 (86 percent) and potassium-40 contributing a risk of 2.2 x
10-5 (14 percent).

Risks from ingestion of radionuclides in upgradient ground water (for example, water with background or
naturally-occurring concentrations) are approximately eguivalent to those onsite. Table 7-17 presents a
summary of radiological risks onsite and upgradient (or offsite).

The HQ resulting from ingestion of uranium at the RME, for a future onsite resident child, was estimated as
2.3 and as 1.0 for an adult. These HQ values indicate the potential for an adverse noncarcinogenic health
effect. The HQs for children or adults ingesting uranium in upgradient (or offsite) wells was estimated to
be below 1 (0.4 and 0.2, respectively).

The concentrations of four radionuclides in subsurface soil exceed their carcinogenic risk-specific values
for the ingestion, inhalation, and external exposure pathways in the future onsite residential setting. The
maximum concentrations of potassium-40, lead-210, thorium-228, and uranium-238 in subsurface soil exceed
their risk-specific values, which were derived for soil ingestion, particulate inhalation, and external
exposure assuming subsurface soil was excavated and spread on the surface. Exposure to these radionuclides
in subsurface soil would result in an excess lifetime cancer risk greater than 1 x 10-6 for each individual
radionuclide. Maximum concentrations of potassium-40 and thorium-228 in background subsurface soil also
exceed their respective carcinogenic risk-specific values. Table 7-18 presents the comparison of onsite and
background concentrations to risk-specific values corresponding to a 10-6 cancer risk.

An excess lifetime cancer risk of 4 x 10-7 was estimated for the future onsite residential setting from
ingesting surface soil from the sewage sludge application/leachate injection area (Group 1). Inhalation of
soil suspended as dust from this area resulted in a 7 x 10-7 excess lifetime cancer risk estimate. External
exposure to these soils resulted in an estimated risk of 4 x 10-4 from radium-226 (97 percent of the total
risk estimate). However, since radium-226 is a naturally occurring element, the background risk was also
estimated. The excess lifetime cancer risk from external exposure to background concentrations of radium-226
is 5 x 10-4; and is basically the same risk that was calculated for onsite external exposure. If radium-226
is not considered in estimating the risk from external exposure to surface soil in the sewage sludge
application/leachate injection area, the risk drops to 1 x 10-5. Table 7-19 presents a summary of onsite and
background radiological risk from exposure to surface soil.

Although external exposure from contact with surface water is possible, only incidental ingestion of surface
water was evaluated quantitatively. Two surface water sampling points were available for radionuclide
analysis; one onsite and one offsite. The assumption was made that the concentrations of radionuclides at
the two sampling points were representative of all surface water and, therefore, could be used as exposure
point concentrations for the future onsite residential setting. Ingestion of surface water by a future
onsite resident child (ages 7 to 18 years) using the unnamed creek for recreation could result in an excess
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lifetime cancer risk of 2 x 10-7.

For the future onsite residential setting, the only exposure to sediments for children or adults that results
in an excess lifetime cancer risk greater than 1 x 10-6, is external exposure. Radium-226, potassium-40, and
thorium-228 contribute to 98 percent of the estimated risk of 1 x 10-3. As all three radionuclides are
naturally occurring, the excess lifetime cancer risk of background concentrations was also calculated. The
background risk from external exposure was estimated as 9 x 10-4, indicating that onsite and background risks
are approximately egual. Table 7-20 presents a summary of the onsite and background radiological risk.

Table 7-21 presents a summary of radiological risk from all exposure pathways. Total radiological risk
estimated for background and onsite concentrations is the same, 2 x 10-3. Radionuclides present in media
onsite do not appear to present an increased risk over background, using exposure conditions outlined in this
assessment.

7.1.4.4 Uncertainties

Uncertainties in the data include the lack of a rigorous evaluation of data useability, due to the lack of
laboratory documentation and the limited guantity of radionuclides data available. The representativeness of
the data is guestionable and affects the estimation of external dose and the risk from external exposure.
External exposure assumes a uniform distribution of radionuclides in the environmental medium of interest.
Uniformity in distribution is difficult to determine with limited data.

Shielding was not accounted for in the estimation of external exposure. Shielding can reduce the exposure by
a factor of 0.5, thereby reducing the risk from exposure. The toxicological data base is limited for
low-level environmental exposures; most available data on risk are from high-dose radiation exposures (such
as survivors of the atomic bomb). Extrapolation to low-dose environmental exposures is subject to much
scientific debate. Conseguently, the degree of conservatism introduced into estimates of risk from
incomplete toxicological data cannot be estimated.

7.1.5 Summary of Environmental Risks

The Lowry Site ecological assessment (EA) consisted of:

• An ecological site description

• Identification of ecological chemicals of concern (ECOCs)

• Identification of the actual and potential ecological receptors

• Characterization of ecological exposure pathways

• Identification of ECOC exposure levels considered to have no observable adverse effects from
literature references

• Comparison of potential exposure levels to receptors with exposure levels considered to have no
observable adverse effects

• A gualitative description of uncertainty

The ecological assessment, included in Volume 2B of the Baseline RA, focused on potential effects on
terrestrial wildlife from ingestion of contaminated media.

7.1.5.1 Ecological Setting

The ecological setting of the Lowry Site has been described in other sections of this document. A list of
threatened and endangered species that could be present in the vicinity of the Lowry Site is provided as
Table 7-22. None of these species have been observed at the site and it is unlikely that these species would
be found onsite. However, the area surrounding the Lowry Site could provide a habitat for these species, and
therefore, they were considered potential ecological receptors.

7.1.5.2 Ecological Chemicals of Concern

The EA was based on data collected during the RIs for OUs 2&3 and 4&5. Only data from surface soil (zero to
1 foot), surface water, and sediment were used in the assessment. Landfill gas was not addressed because of
a lack of literature information on the toxicity of gas to ecological receptors. Landfill solids were not
addressed because it was assumed that the most significant exposures for terrestrial organisms would result
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from the upper 1 foot of the soil column. Because of the transient nature of terrestrial receptors, it was
assumed that potential receptors would have access to the entire site. Therefore, data were summarized by
media.

Chemicals detected in surface soil, surface water, and sediments were initially screened on the basis of
comparisons with background concentrations, frequency of detection, and relative toxicity for use in the EA.
The first two screening steps follow the procedure outlined in the Baseline RA. The relative toxicity
screening step eliminates inorganic constituents that are commonly found in the environment, act as
macronutrients to living organisms, and/or are relatively nontoxic to environmental receptors. Table 7-23
lists the constituents eliminated from each medium because of their relative nontoxicity. Table 7-24 lists
the COCs evaluated in each medium and their maximum detected concentration.

7.1.5.3 Exposure Assessment

No aquatic organisms were observed within the limited aquatic habitat onsite, therefore, aquatic organisms
were not considered potential receptors to environmental contamination. Terrestrial wildlife are considered
potential receptors as they can use the Lowry Site as habitat and become exposed to site-related
contamination through daily activities. Other potential receptors include terrestrial and riparian vegetation
growing in contaminated media.

Exposure pathways for terrestrial wildlife may include:

• Foraging and ingestion of vegetation or invertebates contaminated through biomagnification or
bioaccumulation

• Ingestion of vegetation, which may result in the incidental ingestion of surface soil and the
inhalation of surface soil as dust or volatile constituents in surface soil

• Ingestion of surface water and inhalation of volatile constituents volatilizing from surface
water

• Incidental ingestion of sediments while drinking or searching for food in the unnamed creek

• Dermal contact with soil, surface water, and sediment while burrowing or grooming

Terrestrial wildlife currently use the Lowry Site and could continue to use the site in the future,
regardless of planned land use. Therefore, this EA focused on direct exposures (ingestion of media) to
terrestrial wildlife. Because the habitat in the area occupied by the former landfill is highly disturbed
and of relatively poor quality, exposures resulting from biomagnification and bioaccumulation of contaminants
were considered minor and therefore, not addressed. Other exposure routes affecting terrestrial wildlife
including inhalation and dermal contact and effects to vegetation were also not addressed because of the lack
of quantitative literature values for quantifying exposure.

7.1.5.4 Ecological Effects Assessment

The potential for adverse effects to terrestrial wildlife was assessed through comparison of potential intake
through ingestion with an appropriate toxicity value. Toxicity values were obtained from the literature for
all COCs in each media evaluated. The lowest observable adverse effect level (LOAEL), no observable adverse
effect level (NOAEL), and the lethal dose that kills half of the population exposed (LD50) were obtained from
toxicological investigations using laboratory or wild animal species. Data related to chronic oral exposure
studies (garbage, drinking water, or diet) were used preferentially to data derived from intraperitoneal or
intramuscular studies. Inhalation toxicity data were not included. Toxicity data are media- and
species-specific and were not available for all COCs.

LOAELs were used in comparison to doses received from ingestion of soil and sediment for small mammals. Each
constituent-specific LOAEL was divided by an uncertainty factor to adjust the value to account for the
uncertainty involved with data comparisons. Small mammal soil ingestion rates, in mg soil/kg body weight/day,
were available in the literature. Small mammals ingest soil during feeding, grooming, and burrowing
activities whereas no data are available for soil ingestion in larger animals. Species specific (rats, mice,
or rabbits) soil ingestion rates were multiplied by the maximum constituent concentration in surface soil or
sediments. The adjusted LOAEL was then compared to the dose received through ingestion (using the species on
which the LOAEL was developed). If the dose received exceeded the adjusted LOAEL, an adverse effect to
ecological health may exist and further evaluation of ecological exposure would be appropriate.

For surface water, the preferred toxicity value is the NOAEL. If an NOAEL was not available, a LOAEL was
used and then an LD5o. Water criteria were calculated using drinking water ingestion rates for laboratory
animals to represent rates for small mammals in the wild. This will result in conservative criteria because
-------
most small mammals in the wild do not consume water on a regular basis. The NOAEL (or other toxicity value)
was divided by both water intake rate for an appropriate species and an uncertainty factor to estimate a
water concentration (termed water criteria) associated with the no adverse effects. The water criteria were
then compared to the maximum detected concentration of the constituent. If the maximum concentration
detected in surface water exceeded the water criteria, the potential for adverse effects to terrestrial
receptors using surface water within the Lowry Site may be present.

For surface soil, the ingestion of aluminum, barium, cadmium, cobalt, iron, and octochlorodibenzodioxins
exceeded their respective adjusted LOAEL value. In addition, because of the lack of toxicological
information for acetone and ammonia, as they pertain to environmental receptors, these two chemicals could
not be evaluated.

For sediments, ingestion of aluminum, barium, cobalt, iron, lead, and heptachlorodibenzo-p-dioxin exceeded
their respective adjusted LOAEL value. Due to the lack of toxicological information for acetone, ammonia,
aniline, and benzene, these chemicals could not be evaluated for their effects on environmental receptors.

For surface water, maximum concentrations of aluminum, antimony, barium, cobalt, iron, mercury, vanadium,
benzene, 2-butanone, 1,2-dichloroethene (trans and total), 2,4-dichlorophenol, methylene chloride,
2-methylnaphthalene, 2-methyl phenol, 4-methylphenol, 4-methyl-2-pentanone, octochlorodibenzodioxins, phenol,
tetrachloroethene, trichloroethene, toluene, and vinyl chloride exceeded calculated water criteria.

On the basis of comparisons in this assessment, maximum detected concentrations of select inorganic and
organic chemicals in surface soil, surface water, and sediments may result in adverse effects to terrestrial
wildlife.

7.1.5.5 Uncertainties

The EA has a high level of uncertainty as a result of the many assumptions made and issues addressed. The
following assumptions contribute to the uncertainty:

• All soil and sediment consumed was from a contaminated source.
• All water ingested was from onsite contaminated surface water.
• The maximum detected concentration of each constituent in each medium represents the potential
exposure concentration.

These assumptions act to overestimate intake, since terrestrial species are mobile and have access to
multiple sources of food and drinking water. Not all terrestrial species would be contaminated at the
maximum concentration, and not all would ingest food and water from the Lowry Site.

The assumption was made that all chemicals in each media were 100 percent bioavailable, which overestimates
the true dose received. For example, chemicals bound to soil may not be readily digested and may pass
through the gastrointestinal system; or, chemicals ingested may be metabolized and rendered nontoxic.

In addition, chemical interactions were not addressed. The true toxicity of an environmental medium cannot
be known unless synergistic and/or antagonistic effects can be determined. The total hazard of each media
has not been addressed because comparisons made in the EA were on a constituent-by-constituent basis.

Soil and sediment consumption and water ingestion were estimated using laboratory animals to represent small
mammals. This may overestimate intake and the potential hazard since correlations between standard lab
animals and actual receptor species are not known. Uncertainty factors were applied to account for this.
However, there is no means to measure the magnitude of uncertainty involved.

The EA only quantified the ingestion route. Other routes, such as inhalation and dermal contact, may have a
significant impact for small mammals that burrow in the ground. The potential hazard to small mammals may
therefore have been underestimated.

7.2 Baseline Risk Assessment Summary

Actual or threatened releases of hazardous substances from the Lowry Site, if not addressed by implementing
the response action selected in this ROD, may present an imminent and substantial endangerment to public
health, welfare, or the environment. The most significant risks are summarized in Subsection 7.1.2.4.

-------
Minimum/Maximum

OUs 1/6
Table 7-1
Concentrations of Contaminants of Concern

OUs 2/3
Page 1 of 3

OUs 4/5
Chemical
1,1-Dichloroethane
1,1-Dichloroethene
1,2-Dichloroethane
1,2-Dichloroethene
1,4-Dichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
1,2,4-Trichlorobenzene
1,1,2,2-Tetrachloroethane
2,4-Dichlorophenol
2,4-Dimethylphenol
2,4-Dinitrophenol
2,3,7,8-TCDD

2-Butanone (MEK)
2-Chlorophenol
2-Hexanone
2-Methylnaphthalene
2-Methylphenol
4,4'-DDD
4,4'-DDE
4,4'-DDT
4-Chloroaniline
4-Methylphenol
4-Methyl-2-pentanone
Acetone
Aldrin
Aniline
Benzene
Benzo(a)anthracene
Benzo(b)fluoranthene
Benzoic acid
Benzyl alcohol
beta-BHC
bis (2-chloroethyl)ether
bis(2-Ethylhexyl)phthalate
Butylbenzylphthalate
Carbazole
Carbon disulfide
Carbon tetrachloride
Subsurface
Liquids
(Ug/L)
2/1,100,000
0.8/14,000
3/1,800,000
1/160,000
3/100
B.5/1,700
66/66
22/160

500/500
5 x 106/
1.1 x 10-3
17/230,000
8/8
49/270
3/44,000
Subsurface
Soil
(Ug/kg)
4/960,000
4/3,000,000
1/970,000
84/84
7.2/1,900

3/3
1/22,000

7/12

15/26,000
Organics
42,/30
3.9/3.9
44/120
0.26/1.2
0.11/0.11
0.34/30
53/2,500

2.7/170
15/160
0.15/3.7

1/1

52/52
81/210

1.1/6
48/170
Landfill
Gas
(Ug/m2)
300/770,000
170/18,000
110/68,000
38/270,000
Surface
Soil
(jig/kg)
1/38,000
0.02/14a

1/1
10/190,000
Surface
Water
(Ug/L)
1/150,000
6.4/5,000

2/730

4/31,000
26/190
14/920

0.04/0.04a

3.1/51,000

4/7,400
4.7/10
87/4,100
380/6,600
3.7/27,000
3/240,000
1.5/180
Sediment
(jig/kg)
2/1,800

6,110,000

170/2,700

0.1/5.6a

33/15,000

54/24,000
330/330
2/6,100
330/330
22/160,000
46/2,200
9/25
49/95,000
-------
Minimum/Maximum
OUs 1/6
Table 7-1
Concentrations of Contaminants of Concern
OUs 2/3
Page 2 of 3
OUs 4/5
Chemical
Chloroethane
Chloroform
d-n-Butylphthaiate
di-n-Octylphthalate
Dibenzofuran

Dieldrin
Endrin
Endrin ketone
Ethylbenzene
Ethylene dibromide
Fluoranthene
gamma Chlordane
gamma-BHC
Methylene chloride
Naphthalene
PCB-1260
Pentachlorophenol
Phenanthrene
Phenol
Pyrene
Tetrachloroethylene
Toluene
Trans-1,2-Dichloroethene
trans-1,3-Dechloropropane
Trichloroethylene
Vinyl chloride
Xylenes
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium (IV)
Chromium (total)
Cobalt
Copper
Subsurface
Liquids
(Ug/L)
2/260
0.6/56,000

5.7/1,200
2.0xlO-6/
1.4x10-3
0.12/0.28
26/200
3/440,000
2.0/110,000

4/4,100
4.2/1,700
0.9/340,000
0.9/11,000,000

2.2/3.0
4/7,700,000
2.6/1,800
2.2/1,600
0.71/1,700
5.4/330
Subsurface
Soil
(jig/kg)

Organics (continued)
214
45/110
43/43
9.5/9.5
0.11/0.15
0.21/0.21
69/69
0.13/0.13
0.11/0.11
1.2/120

270/2,100

46/46
40/95
75/75
1.9/1.9
1/4
Landfill
Gas
()lg/m2)
Surface
Soil
(jig/kg)
Surface
Water
(Ug/L)
Sediment
(jig/kg)
19/4,000
1/3
42,840,000
200/7,600
19/1,400,000
77/680,000
17/120,000
2/11
Inorganics (Metals)
1.1/340
1/7,700
73/4,100

0.7/2,300
1/28,800
5.7/56,000

0.6/2,500
27/9,600
1.3/9,700
4/95,000

69/7,700

170/2,400

62/6,200
3/48,000
3/280,000
2/57
4/580,000
6,400/2.5x107
30/30,000
0.86/18,000
43/1,200,000
0.78/2,100
0.823/3,900

6.6/83,000
5.81/17,000
13/97,000
7,900/2.8x107

1.4/14,000
120/1,200,000
0.72/13,000
0.98/13,000
8.8/130,000
5/120,000
13/150,000
32/260,000
26/82
4/82
54/1,500

3/200
6.7/210
2.5/660
3.2x107
29/32,000
2/21,000
79/860,000
0.79/2,700
1.5/3,900
2.5/42,000

-------
Table 7-1
Minimum/Maximum Concentrations of Contaminants of Concern
OUs 1/6
OUs 2/3
OUs 4/5
Page 3 of 3
Chemical
Cyanide
Fluoride
Lead
Manganese
Mercury
Nickel
Silver
Thallium
Vanadium
Zinc
Subsurface
Liquids
(Ug/L)

1/510
180/70,000

13/2,000

0.34/760

Subsurface Landfill
Soil Gas
(Ug/kg) (ug/m2)
Inorganics (Metals) (Continued)
0.52/2,400

8.3/100,000
120/1,800,000
0.1/1,100
7.7/29,000
2.3/16,000

20/85,000
43/180,000
Surface
Soil
(jig/kg)

0.914,900

7.3/150,000
200/2,700,000
0.13/1,000
7.1/130,000
3.1/9,800

19/140,000
44/340,000
Surface
Water
(Ug/L)

8/250
0.66/660
5/290
6.9/38,000

1.2/630

Sediment
(jig/kg)

0.29/2,300

6.7/2,950,000
380/1,900,000
0.1/1,900
2.8/42,000

12/71,000
13/540,000
Sm-fam
Water
Sediment
Radionuclides
Radionuclides
NA
NA
NA
NA
NA
-------
Table 7-2
Ground-Water Exposure Point
Concentrations for the
Hypothetical Future
Onsite Residential Setting
Page 1 of 2
Chemical

1,1-Dichloroethane
1,1-Dichloroethene
1,2-Dichloroethane
1,2-Dichloroethane
1,4-Dichlorobenzene
1,1,2-Trichloroethane
1,2,4-Trichlorobenzene
1,1,2,2-Tetrachloroethane
2,4-Dichlorophenol
2,4-Dinitrophenol
2,3,7,8-TCDD
2-Butanone (MEK)
2-Chlorophenol
2-Hexanone
2-Methylnaphthalene
4-Methyl-2-pentanone
Acetone
Benzene
Benzo(a)anthracene
Benzyl alcohol
bis (2-chlorethyl)ether
bis(2-ethylhexyl)phthalate
Carbazole
Carbon tetrachloride
Chloroethane
Chloroform
di-a-Octylphthalate
Dibenzofuran
Ethylene dibromide
Fluoranthene
Methylene chloride
Naphthalene
Onsite-Source Area Wells
95 UCL of Geometric
Mean of the Median

(ug/D

520
83
590
140
21
29
18
31
31
220
0.00053
980
8
45
58
520
2,800
270
17
53
3 m
82
12
40
62
49
22
4
49
18
270
56
-------
Table 7-2

Ground-Water Exposure Point
Concentrations for the
Hypothetical Future
Onsite Residential Setting
Page 2 of 2

Onsite-Source Area Wells
95 UCL of Geometric
Mean of the Median
Chemical (y.g/1)

Organics

Pentachlorophenol 130
Phenanthrene 36
Tetrachloroethylene 190
Toluene 1,600
trans-1,3-Dichloropropene 3 m
Trichloroethylene 250
Vinyl chloride, 99

Inorganic (Metals)

Arsenic 110
Chromium (IV) 40
Cobalt 45
Lead 61
Manganese 4,300
Nickel 230
Thallium 61

Note: An "m" after the value indicates it is the maximum
concentration detected rather than a 95 UCL of the geometric
mean of the median.
-------
Table 7-3
Subsurface Soil and Landfill Gas Exposure Point Concentration
Chemical
1,1-Dichloroethane
1,1-Dichloroethene
1,2-Dichloroethane
1,1,1-Trichloroethane
2-Butanone (MEK)
4,4,'-DDD
4,4'-DDE
4,4'-DDT
4-Chloroaniline
4-Methyl-2-pentanone
Acetone
Aldrin
Benzene
Benzo(b)fluoranthene
Benzole acid
Beta-BHC
bis (2-Exthylhexyl)phthalate
Butylbenzylphthalate
Carbon disulfule
Chloroform
di-n-Butylphthalate
di-n-Octylphthalate
Dieldrin
Endrin
Endrin ketone
Ethylbenzene
Fluoranthene
gamma Chlordane
Subsurface Soil RME
Concentration
(mg/kg)
130 m
3.9 m
120 m
1.2 m
0.11 m
30 m
2,500 m
170 m
160 m
3.7 m
1 m
52 m
210 m
6 m
1,800 m
170 m

4 m
110 m
43 m
9.5 m
0.15 m
0.21 m

690 m
0.13 m
Organics
Landfill Gas Onsite
RME Concentration
()lg/m3)
129,571 m
8,669
1,498 m
37,061
38,282 m
Page 1 of 2

Landfill Gas Offsite
Modeled RME
Concentration
()lg/m3)
1.17

3.65
12,541
22,066
1,217 m
4,133
Note:
UCL.
An "m" after the value indicates it is the maximum concentration detected rather than a 95 percent
-------
Table 7-3
Subsurface Soil and Landfill Gas Exposure Point Concentrations
Chemical
gamma-BHC
Methylene chloride
PCB-1260
Phenanthrene
Phenol
Pyrene
Tetrachloroethylene
Toluene
Vinyl chloride
Xylenes
Subsurface Soil RME
Concentration
(mg/kg)
Landfill Gas Onsite
RME Concentration
(jlg/mS)
Page 2 of 2

Landfill Gas Offsite
Modeled RME
Concentration
(jlg/mS)
Organics (continued)
0.11 m
120 m
2,100 m
46 m
95 m
75 m
1.9 m
4 m
Inorganics (Metal)
441,718 m
90,486
438,037 m
4,997
22.26

0.16
30.71
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium (total)
Cobalt
Copper
Cyanide
Lead
Manganese
Mercury
Nickel
Silver
Vanadium
Zinc
25,000,
30,
18,
1,200,
2,
3,
89,
17,
97,
2,
100,
18,000,
1,
29,
16,
85,
180,
000 m
000 m
000 m
000 m
100 m
900 m
000 m
000 m
000 m
400 m
000 m
000 m
100 m
000 m
000 m
000 m
000 m
Note:
UCL.
An "m" after the value indicates it is the maximum concentration detected rather than a 95 percent
-------
Table 7-4
Surface Soil Exposure Point Concentrations for the
Hypothetical Future Onsite Residential Setting
Page 1 of 2
Group la

Chemical
2,3,7,8-TCDD
2-Butanone
bis (2-ethylhexyi;
Carbon disulfide
Chloroform
PCB-1260
Toluene
Aluminum
Arsenic
Barium
Beryllium
Cadmium
Chromium (total)
Cobalt
Copper
Cyanide
95 UCL
of the Mean
Soil
Concentration
(ilg/kg)
0. 057 e
1 m
Phthalate 586.63
6.53
1.05
633.86
3.84
16,000, 000
9,200
510,000
2,300
5,000
1,600
21,000
110,000
85,000
95 UCL
of the Mean
Modeled Dust
Concentration
(Tlg/m3 )
0.000000009
0. 000000025
0. 000015
0. 00000016
0. 0000000026
0. 000016
0. 000000098
NC
0. 00023
0.013
0.000057
0. 00012
0.0021
NC
NC
0.000039
95 UCL
of the Mean
Soil
Concentration
(Tig/kg)
0. 11 e

424

3 m

3 m
19,000,000
7,300
240,000
1,500
3, 000
62,000
11, 000
83, 000
1, 800
95 UCL 95 UCL
of the Mean of the Mean
Modeled Dust Soil
Concentration Concentration
(Tlg/m3) (Tig/kg)
0.0000000028

0.000011 215 m

0.000000075 2 m

0.000000075
NC 170,000,000
0. 00018 12, 000
0.006 260,000
0.000038 1,200
0.000075 1,500
0. 0016 16, 000
NC 8,900
NC 21,000
0.000045
95 I
of the
Modeled
Concent
(Ug/m:

0.00000=

0. OOOOOOC

NC
0. 0003
0. 0064
0. 00003
0. 000038
0.00041
NC
NC

aGroup 1 consists of data from the sewage sludge application/leachate injection area.
bGroup 2 consists of data from the sewage sludge application area.
cGroup 3 consists of data from the leachate spraying area.
dGroup 4 consists of data from the tire pile area.
e2,3,7,8 TCDD eguivalents.
-------
Table 7-4
Surface Soil Exposure Point Concentrations for the
Hypothetical Future Onsite Residential Setting
Page 2 of 2

6
2
0,000
7,000
880
2,000
9,400
,3000
00,000
0.0024
0.017
0.000022
0.0011
0.00023
0.0016
0.005
80,000
2,300,000
500
29,000
5,000
39,000
160, 000
0. 002
0.057
0. 000013
0.00072
0.00013
0. 00097
0.0039
95 UCL
of the Mean
Modeled Dust
Concentration
(]Jg/m3)
aGroup 1 consists of data from the sewage sludge application/leachate injection area.
bGroup 2 consists of data from the sewage sludge application area.
cGroup 3 consist of data from the leachate spraying area.
dGroup 4 consists of data from the tire pile area.
e2,3,7,8 TCDD eguivalents.
-------
Table 7-5

Surface Water and Sediment Exposure Point
Concentrations for the Hypothetical
Future Onsite Residential Setting
Page 1 of 2
Chemical
1,1-Dichloroethane
1,1-Dichloroethene
1,2-Dichloroethene
1,1,1-Trichloroethane
2,4-Dichlorophenol
2,4-Dimethylphenol
2-Butanone
2-Hexanone
2-Methylnaphthalene
2-Methylphenol
2,3,7,8-TCDDc
4-Methylphenol
4-Methyl-2-pentanone
Acetone
Aniline
Benzene
bis(2-ethylhexyl)phthalate
Ethylbenzene
Fluoranthene
Methylene chloride
PCB-1260
Phenanthrene
Phenol
Tetrachloroethene
Toluene
trans-1,2-Dichloroethene
Trichloroethene
95 UCL of the Mean
Surface Watera
Concentration
(lig/D

Organics

15,000
5,000
730
31,000
170
920
51,000
7,400
9.0
2,700
0.0033
6,600
27,000
240,000

180

340

7,700

0.74
4,100
2,300
28,000
56,000
2,500
95 UCL of the Mean
Sedimentb
Concentration
(jig/kg)
1,800

110,000
710

15,000

2,100
330
4,700
11,000
95,000
940

550
910

48,000
280,000
aSurface water data in unnamed creek from the toe of the landfill to Pond 3 in Section 6.
bSediment data in unnamed creek from the toe of the landfill to Pond 3 in Section 6.
Note: The notation "m" next to the concentration indicates a maximum value used for the RME.
values reported are 95 UCL of the mean.
All other
-------
Chemical
Vinyl chloride
Xylenes
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium (total)
Cobalt
Copper
Cyanide

Fluoride
Lead
Manganese
Mercury
Nickel
Vanadium
Zinc
Table 7-5

Surface Water and Sediment Exposure Point
Concentrations for the Hypothetical
Future Onsite Residential Setting

95 UCL of the Mean
Surface Water
Concentration
(lig/D

Organics (continued)

9,600
9,700

Inorganics (Metals)

110,000
40
24
420
33
51
43
20

660
59
24,000
120
Page 2 of 2
95 UCL of the Mean
Sediment
Concentration
(jig/kg)
19
580,000
15,000,000
29,000
21,000
430,000
980
2,400
59,000
12,000
46,000
650
700,000
1,100,000
1,000
17,000
44,000
130,000
aSurface water data in unnamed creek from the toe of the landfill to Pond 3 in Section 6.
bSediment data in unnamed creek from the toe of the landfill to Pond 3 in Section 6.
Note: The notation "m" next to the concentration indicates a maximum value used for the RME.
values reported are 95 UCL of the mean.
All other
-------
Table 7-6
PME Exposure Parameters
Page 1 of 2
Ground-water irrigation
Surface or subsurface soil
ingestion
C: 1-6
Particulate inhalation (surface A: 19-70
soil)
C: 1-18
Surface water ingestion while C: 7-18
wading
A: 19-70
Intake
Rate
2
1
100
200
20
14
50

100
100
20
14
50
20
20
100
200
20
14

Units
L/day
L/day
ing/ day
ing/ day
m3/day
m3/day
mL/hr

mg/ day
nig/ day
ni3/day
ni3/day
nig/ day
ni3/work day
ni3/work day
nig/ day
ni3/day
ni3/day

mL/hr

Reference
RAGS
OSWER
OSWER
OSWER
OSWERc
IPGDd
RAGS

OSWER
OSWER
OSWERc
IPGDd
OSWER
OSWERc
OSWER
OSWERb
OSWERb,c
IPGDd

RAGSb

Exposure
Freguency
350
350
350
350
350
350
60

350
60
350
350
250
250
250
6 0
60
60
60

Units
days/yr
days/yr
days/yr
days/yr
days/yr
days/yr
days/yr

days/yr
days/yr
days/yr
days/yr
days/yr
days/yr
days/yr
days / vr
days/yr
days/yr
days/yr

days/yr

Comments

4 days/wk at 12 wks/yr (summer) +
2 days/wk at 6 wks/yr (spring/ fall )

2 days/wk at 6 wks/yr (spring/ fall )
4 days/wk at 12 wks/yr (summer) +
2 days/wk at 6 wks/yr (spring/ fall )
4 days/wk at 12 wks/yr (summer) +
2 days/wk at 6 wks/yr (spring/ fall )
4 days/wk at 12 wks/yr (summer) +
2 days/wk at 6 wks/yr (spring/ fall )
4 days/wk at 12 wks/yr (summer) +
2 days/wk at 6 wks/yr (spring/ fall )
Exposure
Reference Duration Units
30 years
6 years
OSWER 24 years
OSWER 6 years
OSWER 30 years
OSWER 15 years
SS 12 years

OSWER 24 years
OSWER 12 years
OSWER 30 years
OSWER 15 years
OSWER 25 years
OSWER 25 years
OSWER 25 years
SS 6 years
SS 30 years
SS 15 years

SS 12 years

Reference
RAGS
OSWER
OSWER
OSWER
RAGS
EPA VIII
EPA VIII

OSWER
EPA VIII
RAGS
EPA VIII
OSWER
OSWER
OSWER
OSWERb
RAGSb
EPA VI lib

EPA VIII

Body
Weight Units
70 kg
15 kg
70 kg
15 kg
70 kg
33 kg
38 kg

70 kg
38 kg
70 kg
33 kg
70 kg
70 kg
70 kg
70 kg
15 kg
70 kg
33 kg

38 kg

Ref erenci
RAGS
OSWER
EPA VII
OSWER
EPA VIII
IPGDd
EPA VIII

OSWER
EPA VII
EPA VII
IPGDd
OSWER
OSWER
OSWER
OSWERb
EPA VIII
IPGD4

EPA VIII

yr (summer) +
kg
-------
Table 7-6
PME Exposure Parameters
Intake
Rate
200
20

Units
mg/day
mg3/day

Reference
OSWERb
OSWERc
Exposure
Frequency
60
60
Comments

4 days/wk at 12 wke/yr (summer) +
2 days/wk at 6 wks/yr (spring/fa11)
4 days/wk at 12 wks/yr (summer) +
2 days/wk at 6 wks/yr (spring/fall)
Exposure
Duration Units
Body
Weight
Reference

OSWERb

EPA VIlib
1-18
14
aA = Adult and C = child.
bThe residential exposure value was considered applicable to the corresponding Recreational or Occupational setting.
cReas onable upperbound value based on "conservative" activity and "average" inhalation rates.
dValues are average of three age groups defined by IPGD as follows:
EPA VHIb
Inhalation Rate (m3/day)
Average Maximum
5 5
10 12
17 26
11 14
Average Body
Weight
(kg)
14
29
57
33
EPA VIII = EPA Region VIII Draft intake Assumptions.
= Clement Associates, Inc. 1988. Multipathway Health Risk Assessment Input Parameters Guidance Document.
= USEPA 1991. Human Health Evaluation Manual, Supplemental Guidance; Standard Default Exposure Factors.
= USEPA 1989. Risk assessment guidance for Super fund, Human health evaluation manual, Part A.
= Exposure values are based on site-specific conditions and professional Judgement. See text for full explanation.
-------
Table 7-7
Toxicity Values for Chemicals with Carcinogenic Effectsa

Oral
Page 1 of 2

Inhalation
1,1-Dichloroethane
1,1-Dichloroethylene
1,2-Dichloroethane
1,1,2-Trichloroethane
1,1,2,2-Tetrachloroethane
2,3,7,8-TCDD

2-Methylphenol
4,4 '-DDD
4,4 '-DDE
4,4 '-DDT
Aldrin
Aniline
Benzene
Benzo(a)anthracene
Benzo(b)fluoranthene
Beta-BHC
bis(2-chloroethyl)ether
bis(2-ethylhexyl)phthalate

Carbon tetrachloride
Chloroform
Dieldrin
Ethylene dibromide
Gamma-BHC
Methylene chloride
PCB-1260
Pentachlorophenol
Tetrachloroethylene
IRIS 12/7/89
IRIS 1/1/91
IRIS 1/1/91
IRIS 1/1/91
IRIS 1/1/91
HEAST 1/91
HEAST 1/92
IRIS 8/1/91
IRIS 1/1/91

IRIS 6/1/89
IRIS 1/1/91
HEAST 1/91
HEAST 1/91
IRIS 5/1/90
IRIS 8/l/91d
IRIS 1/1/91
IRIS 1/1/91
IRIS 9/1/90
IRIS 1/9/90
IRIS 3/1/91
IRIS 6/1/90
HEAST l/91d
IRIS 1/1/91
IRIS 6/1/90
HEAST 1/91
0.34
17. 15
IRIS 1/1/91
IRIS 1/1/91
HEAST 1/92
(oral)
IRIS 1/1/91
HEAST 1/91
aOnly those chemicals classified as A, Bl, B2, or C carcinogen are listed on this table.
bSF = Slope factor.
cRef = Reference, citation and date of toxicity value.
dValue and date used for Oils 2s3 and 4s5 if different than that used for OUs 1&6.
-------
Table 7-7

Toxicity Values for Chemicals with Carcinogenic Effectsa Page 2 of 2

Oral Inhalation

SF
Refc

Inorganic (Metals)

Arsenic A 1.75 IRIS 9/1/91 15.05 IRIS 1/13/8E
Beryllium B2 4.3 IRIS 1/1/91 8.4 IRIS 1/1/91
Cadmium Bl (inhalation) 6.3 IRIS 1/1/91
Chromium (IV) A (inhalation) IRIS 3/1/91 42 IRIS 3/1/91
Lead B2 IRIS 5/1/91

aOnly those chemicals classified as an A, Bl, B2, or C carcinogen are listed on this table.
bSF = Slope factor.
cRef = Reference, citation and date of toxicity value.
dValue and date used for OUs 2s3 and 4s5 if different than that mind for Oils 1&6.
-------
Table 7-8

Toxicity Values for Chemicals with Noncarcinogenic Effectsa

Oral
Page 1 of 4

Inhalation
Confidence/
U/M Factorsb
Health Effects
4,4 '-DDT
4-Chloroaniline
4-Methylphenol

4-Methyl-2-pentanone
—/1001—
M/1000/1
L/1000/1
—lOOOd/—
—/1000/—
M/1000/1
—/1000/—
L/100/1
HEAST 1/92
IRIS 1/1/91
IRIS 1/1/89
HEAST l/92d
HEAST 1/92
IRIS 1/1/91
HEAST 8/1/90
IRIS 8/1/89
IRIS 9130187

HEAST 1/92

HEAST 1/92
Decreased fetal
birth weight
HEAST 1/92
HEAST 1/92
HEAST 1/92
Liver and kidney
effects
aOnly those chemicals with an RfD or a pending Rt-D are listed on this table.
bConfidence is the level of confidence in the RfD and is given as L for low, M for medium, and H for high. U/M is the uncertainty and modifying factors used to derived the RfD,
the uncertainty factor is the middle value and the modifying factor is the last value given.
cRef = Reference, citation and date of toxicity value.
dValue and date used for Oils 2/3 and 4/5 if different than that used for OUs 1/6.
eNo toxicity value was used for OUs 2/3 and 4/5.
fRfD is pending.
-------
Table 7-8

Toxicity Values for Chemicals with Noncarcinogenic Effectsa

Oral
Health Effects Referencec

Organics (continued)

IRIS 12/1/90
Confidence/
U/M Factorsb
Health Effects
Increased liver
IRIS 1/1/91
Aldrin
Aniline
Benzene
Benzole acid
bis (2-ethylhexl)phthalate
Butylbenzyl phthalate
Carbon disulfide

Carbon tetrachloride
Chloroform
Di-n-butylphthalate
Dieldrin
Endrin

Gamma-BHC
Methylene chloride
Naphthalene
Pentachlorophenol
Phenol

aOnly those chemicals with an RfD or a pending Rt-D are listed on this table.
bConfidence is the level of confidence in the RfD and is given as L for low, M for medium, and H for high. U/M is the uncertainty and modifying factors used to derived the RfD,
the uncertainty factor is the middle value and the modifying factor is the last value given.
cRef = Reference, citation and date of toxicity value.
dValue and date used for OUs 2/3 nnd 4/5 if different than that used for Oils I/6.
eNo toxicity value was used for OUs 2/3 and 4/5.
fRfD is pending.
Liver toxicity
-------
Table 7-8
Toxicity Values for Chemicals with Noncarcinogenic Effectsa
Oral
Inhalation
Reference
Dose (R/D)
Chemical (rag/kg/day)
U/M Factorsb Health Effects
Reference (rag/ kg/day) U/M Factorsb
Health Effects Referencec
Toluene

trans-1,2-Dichloroethene
trans-1,3-Dichloropropene
Trichloroethylene
Xylenes
Hepatotoxicity, weight
gain
Changes in liver and
kidney weight
HS peractivity,
decreased body weight
HEAST 1/92
Arsenic

Barium
Decreased longevity,
increased blood
cholesterol
Hyperpigmentation,
vascular complications
Increased blood
pressure
None observed
Proteinuria
None observed

aOnly those chemicals with an RfD or a pending Rt-D are listed on this table.
bConfidence is the level of confidence in the RfD and is given as L for low, M for medium, and H for high. U/M is the uncertainty and modifying factors used to derived the RfD,
the uncertainty factor is the middle value and the modifying factor is the last value given.
cRef = Reference, citation and date of toxicity value.
dValue and date used for OUs 2/3 and 4/5 if different than that used for OUs I/6.
eNo toxicity value was used for OUs 2/3 and 4 /5 .
fRfD is pending.
-------
Table 7-8
Toxicity Values for Chemicals with Noncarcinogenic Effectsa
Inhalation
Page 4 of 4
Manganese
Mercury
Nickel

Silver
Thallium
Vanadium
Zinc
Health Effects Reference

Inorganics (Metals) (continued)

IRIS 3/1/91
HEAST 1/91
HEAST 1/92

IRIS 12/1/91
HEAST 1/91
HEAST 1/92
HEAST 9/30/87
Health Effects
Increased
prevalence of
respiratory
symptoms,
psychomotor
disturbances
Neurotoxicity
aOnly those chemicals with an RfD or a pending Rt-D are listed on this table.
bConfidence is the level of confidence in the RfD and is given as L for low, M for medium, and H for high. IJ/M is the uncertainty and modifying factors used to derived
the uncertainty factor is the middle value and the modifying factor is the last value given.
cRef = Reference, citation and date of toxicity value.
dValue end date used for OUs 2/3 and 4/5 if different than that used for Oils I/6.
eNo toxicity value was used for OUs 2/3 and 4 /5 .
fRfD is pending.
-------
Table 7-9

COCs Without Toxicity Values
OUs 1/6
OUs 2/3
OUs 4/5
Subsurface
Liquidsa

X
X
X
X
X
X
X
X
X

X
Subsurface Landfill
Soil Gas
Organics
X

X
X
Inorganics (Metals)
X
X
X

X
Surface Surface
Soil Water

X
X

X X
X X
X X
X
X X
Chemical
1,1-Dichloroethane
1,4-Dichlorobenzene
2-Hexanone
2-Methylnaphthalene
Benzyl alcohol
Carbazole
Chloroethane
di-n-octylphthalate
Dibenzofuran
Endrin ketone
Phenanthrene
Aluminum
Cobalt
Copper
Fluoride
Lead
aSubsurface liguids consist of shallow ground water, waste-pit liguids, and deep ground water.

Note: An X indicates the medium the chemical was detected in.
Sediment
X
X
X
-------
Table 7-10
Summary of Quantified Site Risks Based on Hypothetical Future Onsite Residential Setting Page 1 of 3

Reasonable Maximum Exposure
Exposure Pathwaysa
Ingestion of subsurface liquids as a drinking water sourceb
Pathway Totald
Surface Soil Ingestione
Chemicals of Concern

Organics

Benzo(a)anthracene
Arsenic
Vinyl chloride
2,3,7,8-TCDDc
1,2-Dichloroethane
1,1-Dichloroethene
bis (2-chloroethyl)ether
Pentachlorophenol
Tetrachloroethene
Thallium
2,4-Dinitrophenol
Carbon tetrachloride
Manganese

Arsenic
Beryllium
Excess Lifetime
Cancer Risk
2 x 10-3
2 x 10-3
2 x 10-3
1 X 10-3
6 x 10-4
6 x 10-4
3 x 10-4
2 x 10-4
1 X 10-4
NC
NC
6 x 10-5
NC
1 x 10-2
8 x 10-6
5 x 10-6
Noncancer Hazard
Quotient
NA
10
NA
NA
NA
0.25
NA
0.12
0.52
24
3.0
1.5
1.2
47
0.04
<0.01
aExposure pathways presented are for adults using reasonable maximum exposures (RMEs).
bSubsurface liquids consist of shallow ground-water, waste-pit liquids, and deep ground water from source area wells.
cDioxin equivalents.
dNot all COCs that contribute to the total risk are listed, therefore, sum of risk (or HQs) for listed chemicals will not equal the total.
eUsing Group 1 exposure point concentrations.
fDust arising form Group 1 surface soil.
gAs hexavalent chromium.

NC = Not carcinogenic through this pathway.
NA = Not applicable.
-------
Table 7-10

Summary of Quantified Site Risks Based on Hypothetical Future Onsite Residential Setting Page 2 of 3

Reasonable Maximum Exposure

Excess Lifetime Noncancer Hazard
Exposure Pathwaysa Chemicals of Concern Cancer Risk Quotient

Organics (continued)

Surface Soil Ingestione 2,3,7,8-TCDD 4 x 10-6 NA
PCB-1260 2 x 10-6 NA
Chromium NC 0.02
Pathway Totald 2 x 10-5 0.1
Particulate Inhalationf Chromiumg 1 x 10-5 NA
Manganese NC 0.04
Barium NC 0.02
Pathway Totald 1 x 10-5 0.06
Surface Water Ingestion as a Child Vinyl chloride 7 x 10-4 NA
1,1-Dichloroethene 1 x 10-4 0.12
2,3,7,8-TCDDc 2 x 10-5 NA
trans-l,2-Dichloroethene NC 0.61
Acetone NC 0.52
4-Methyl-2-pentanone NC 0.12

aExposure pathways presented are for adults using reasonable maximum exposures (RMEs).
bSubsurface liguids consist of shallow ground-water, waste-pit liguids, and deep ground water from source area wells.
cDioxin eguivalents.
dNot all COCs that contribute to the total risk are listed, therefore, sum of risk (or HQs) for listed chemicals will not equal the total.
eUsing Group 1 exposure point concentrations.
fDust arising form Group 1 surface soil.
gAs hexavalent chromium.

NC = Not carcinogenic through this pathway.
NA = Not applicable.
-------
Table 7-10

Summary of Quantified Site Risks Based on Hypothetical Future Onsite Residential Setting Page 3 of 3

Reasonable Maximum Exposure

Excess Lifetime Noncancer Hazard
Exposure Pathwaysa Chemicals of Concern Cancer Risk Quotient

Organics (continued)

Surface Water Ingestion as a Child 1,1,1-trichloroethane NC 0.075
Manganese NC 0.05

Pathway Totald 8 x 10-4 2

Inorganics (Metals)

Sediment Ingestion as a Child Arsenic 7 x 10-6 0.15
Antimony NC 0.16
Chromium NC 0.03
Manganese NC 0.03
Pathway Totald 9 x 10-6 0.4
Maximum Cumulative Total 2 x 10-2 49

NC = Not carcinogenic through this pathway.
NA = Not applicable.
-------
Table 7-11
Comparison of Subsurface Soil Maximum Detected Concentrations
to Carcinogenic Risk-Specific Values and Noncarcinogenic
Reference Concentrations in the Future Onsite Residential Setting

Reasonable Maximum Exposurea
Page 1 of 2
Chemical

1,1,1-Trichloroethane
1,2-Dichloroethane
2-Butanone
4,4'-DDD
4,4'-DDE
4,4'-DDT
4-Chloroaniline
4-Methyl-2-pentanone
Acetone
Aldrin
Aluminum
Antimony
Arsenic
Barium
Benzene
Benzo(b)fluoranthene
Benzoic acid
Beryllium
Beta-BHC
Butylbenzylphthalate
Cadmium
Chloroform
Chromium (Total)
Cobalt
Copper
Cyanide
Di-n-butylphthalate
Di-n-octylphthalate
Dieldrin
Endrin
Endrin Ketone
Maximum
Detected
Concentration
3.9
130
6,700
1.2
0.11
30
2,500
540
15,000
3.7
124,700,000
30,000
18,000
1,190,000
1
52
210
2,100
6
170
3,900
4
83,000
17,000
97,000
2,400
110
62
9.5
0.15
0.21
Risk-Specific
Valueb
(jig/kg)
NA
6,986
NA
2, 654
1,873
1,870
NA
NA
NA
37
NA
NA
358
NA
21,922
87
NA
148
353
NA
53,990
101,899
8,098
NA
NA
NA
NA
NA
40
NA
NA
Exceeds
Risk- specific
Value?
-
No
-
No
No
No
-
-
-
No
-
-
Yes
-
No
No
-
Yes
No
-
No
No
Yes
-
-
-
-
-
No
-
-
Reference
Concentration
(Jig/kg)
7,029,702
NA
31,923,383,879
NA
NA
39,063
312,500
3,900,284
7,821,500
2,344
NA
31,250
23,438
4,073,201
NA
NA
312,500,000
390, 625
NA
15, 625,000
39,063
781,250
390, 625
NA
NA
1,562,500
7,812,500
NA
3,906
23,438
NA
Exceeds
Reference
Concentration
No
-
No
-
-
No
No
No
No
No
-
No
No
No
-
-
No
No
-
No
No
No
No
-
-
No
No
No
No
No
-
aReasonable maximum exposure parameters and maximum detected concentrations.
bRisk-specific values and reference concentrations assume ingestion of soil and inhalation of airborne
contaminants adsorbed to dust.
Note: NA = No toxicity values with which to calculate a value.
= Not applicable.
-------
Table 7-11

Comparison of Subsurface Soil Maximum Detected Concentrations
to Carcinogenic Risk-Specific Values and Noncarcinogenic
Reference Concentration in the Future Onsite Residential Setting

Reasonable Maximum Exposurea
Maximum
Detected
Concentration
69
0.13
0.11
101,000
1,770,000
1,100
120
29,000
2,100
46
95
75
16,000
1.9
4
85,000
179,000
1,800
Risk-Specific
Valueb
(jig/kg)
NA
NA
490
NA
NA
NA
84,891
NA
83
NA
NA
NA
NA
12,488
NA
NA
NA
45,496
Exceeds
Risk-Specific
Value?
_
-
No
-
-
-
No
-
Yes
-
-
-
-
No
-
-
-
No
Reference
Concentrationb
(Jig/kg)
Chemical

Fluoranthene
Gamma chlordane
Gamma-BHC (Lindane)
Lead
Manganese
Mercury
Methylene chloride
Nickel
PCB-1260 (Aroclor 1260)
Phenanthrene
Phenol
Pyrene
Silver
Tetrachloroethene
Toluene
Vanadium
Zinc
bis(2-Ethylhexyl)phthalate

aReasonable maximum exposure parameters and maximum detected concentrations.
bRisk-specific values and reference concentrations assume ingestion of soil and inhalation of airborne
contaminants adsorbed to dust.
Page 2 of 2
Exceeds
Reference
Concentration
3,

4,
1,

46,
2,

15,

15,
1,
125,

23,

847,
23,
687,
562,

875,
343,
390,
781,
605,
546,
625,
562,
000
NA
438
NA
016
380
500
500
NA
NA
000
750
625
250
904
875
000
500
No
-
No
-
No
No
No
No
-
-
No
No
No
No
No
No
No
No
Note: NA = No toxicity values with which to calculate a value.
= Not applicable.
-------
Table 7-12

Comparison of Exposure Point Concentrations of Landfill Gas Within
the Landfill Mass to Carcinogenic Risk-Specific Values and Noncarcinogenic
Reference Concentrations in the Future Onsite Residential Setting

Reasonable Maximum Exposurea

95 UCL Gas Risk-Specific Exceeds Reference
Concentration Value Risk-Specific Concentration Reference
Chemical (]lg/m3) (]lg/m3) Value? (]lg/m3) Concentration?

1,1,1-Trichloroethane 3.7 x 104 NA - 1,043 Yes
1,1-Dichloroethane 1.3 x 105 (M) NA - 521 Yes
1,1-Dichloroethene 8.7 x 103 0.05 Yes NA
1,2-Dichloroethane 1.5 x 103 (M) 0.09 Yes NA
2-Butanone 3.8 x 104 (M) NA - 1,043 Yes
Benzene 1.3 x 104 0.29 Yes NA
Carbon disulfide 2.2 x 104 NA - NA -
Chloroform 1.2 x 103 (M) 0.11 Yes NA
Ethylbenzene 4.1 x 103 NA - 1,043 Yes
Methylene chloride 4.4 x 105 (M) 5.18 Yes NA
Toluene 9.0 x 104 NA - 417 Yes
Xylenes 5.0 x 103 NA - NA -
Vinyl chloride 4.4 x 105 0.03 Yes NA

aRME uses reasonable maximum exposure parameters and 95 UCL concentrations.

Notes: (M) = Maximum concentration used; 95 UCL exceeds maximum concentration.
NA = No inhalation toxicity value with which to calculate a value.
-------
Table 7-13

Comparison of Modeled Exposure Point Concentrations Assuming a Cracked Slab to Carcinogenic
Risk-Specific Values and Noncarcinogenic Reference Concentrations in the Future Offsite
Residential Setting
Reasonable Maximum Exposure
Chemical

1,1,1-Trichloroethane
1,1-Dichloroethene
Vinyl chloride
Modeled Gas
Concentration
()lg/m3)

3.6
1.2
31.0
Risk-Specific
Value
()lg/m3)

NA
0.05
0.03
Exceeds
Risk-Specific
Value?
Yes
Yes
Reference
Concentration
(]lg/m3)

1,043
NA
NA
Exceeds
Reference
Concentration

No
aRME uses reasonable maximum exposure parameters and 95 UCL modeled gas concentrations.

Notes:
NA = No inhalation toxicity values with which to calculate value.
= Not applicable.
-------
Table 7-14

Cumulative Total Risk for the
Hypothetical Future Onsite Residential Setting

Reasonable Maximum Exposure

Exposure Media/Exposure Excess Lifetime
Pathway Cancer Risk Noncancer HI

Ground Water

Ingestion 1 x 10-2 47

Surface Soil

Ingestion 2 x 10-5 0.1

Inhalation 1 X 10-5 0.06

Surface Water

Ingestion 8 x 10-4 2

Sediments

Ingestion 9 X 10-6 0.4

Cumulative Total 2 x 10-2 49
-------
Table 7-15
Default Parameters Used in Uptake/Biokinetic Model

Age Group
(yrs)
0.5-1
1-2
2-3
3-4
4-5
5-6
6-7

Time Spent
Outdoors
(hr/day)
1.0
2.0
3.0
4.0
4.0
4.0
4.0

Verification
Rate
(jig/day)
2.0
3.0
5.0
5.0
5.0
7.0
7.0

Dietary Lead
Uptake
(jig/day)
5.88
5.92
6.79
6.57
6.36
6.75
7.48

Water
Consumption
(L/day)
0.20
0.50
0.52
0.53
0.55
0.58
0.59
Dust/Soil
Ingestion
Rate
(mg/day)
100
100
100
100
100
100
100
Notes: Additional assumptions used for all age groups:

(1) Indoor air concentration of Pb = 30 percent of outdoor air concentration of Pb.
(2) Lung absorption: 32 percent of inhaled Pb is absorbed by respiratory tract.
(3) Nonlineal gastrointestinal tract absorption method was used for all model runs.
(4) Fraction of household dust derived from soil = 0.28 jlgPb/g dust per jlgPb/g soil.
(5) Concentration of Pb in indoor dust derived from air = 100 jlgPb/g dust per jlgPb/g
air.
(6) Pb in indoor dust derived from soil and airborne particulates only.
(7) Percent of soil/dust that is soft = 45 percent.
(8) Mother's blood Pb level at birth of child =7.50 jlg/dL.

% = Percent
hr/day = hour(s) per day
m3/day = cubic meter(s) per day
jlg/dL = microgram(s) per deciliter
L/day = liter (s) per day
Pb = Lead
yr(s) = year(s)
mg/day = milligrams per day
jig/day = microgram(s) per day
-------
Table 7-16
Risk Assessment Radionuclid.es
OUs 1/6
OUs 2/3
OUs 4/5
Radi onuclide
Subsurface
Liquidsa
Americium-241
Cadmium-109
Cesium-137
Europium- 15 9
Lead-210
Plutonium-239
Potassium-40
Radium-226
Strontium-90
Thorium-228
Thorium-230
Thorium-232
Tritium
Uranium-234
Uranium-235
Uranium-238
X

X
X
X
X
X
X
X
X
X
X
X
X
Subsurface
Soil
Landfill
Gas
Surface
Soil
X
X
X

X
X
X
X

X
Surface
Water
Sediment

X
X
X
X
X

X
X

X
X
X
X
X

X
X

X
X
X
-------
Table 7-17

Summary of Radiological Risk from Ingestion of Ground Water at the RME
Future Onsite Residential Setting

95 UCL Concentration Excess Cancer Risk

Onsitea Upgradient
Radionuclide (pCi/L) (pCi/L) Onsite Upgradient

Potassium-40 462 97 1.1 x 10-4 2.2 x 10-5
Lead-210 11 M NA 1.5 x 10-4
Radium-226 75 50 (M) 1.9 x 10-4 1.3 x 10-4
Uranium-234 49 (M) 2.2 (M) 1.6 x 10-5 7.4 x 10-7
Uranium-235 18 (M) 20 (M) 6.0 x 10-6 6.6 x 10-6
Uranium-238 73 (M) 5.2 (M) 4.3 x 10-5 3.1 x 10-6
Total 5 x 10-4 2 x 10-4

aShallow ground-water wells and waste pit liguids well point within the source area.

(M) = Maximum concentration used as 95 UCL exceeds maximum concentrations or insufficient data
to calculate a 95 UCL.

NA = Not available.
-------
Table 7-18
Comparison of Maximum Detected Subsurface Soil Concentrations
to Carcinogenic Risk-Specific Values at the RME for the Future Onsite Residential Setting

Reasonable Maximum Exposure
Radionuclide

Potassium-40
Lead-210
Plutonium-239
Strontium-90
Thorium-230
Thorium-232
Thorium-228
Uranium-234
Uranium-238
Risk-
Specific
Value2
(pCi/g)

0.064
0.79
1.6
14.6
5.6
5.9
0.0062
5.9
0.73
Onsite
Maximum
Detected
Concentration
(pCi/g)
27
L.8
3.4
3.2
2.1
1.7
2.2
2.9
1.5
Exceeds
Risk-
Specific
Value?

Yes
Yes
No
No
No
No
Yes
No
Yes
Background
Maximum
Detected
Concentration
(pCi/g)

21
NA
NA
NA
NA
NA
2.2
NA
NA
Exceeds
Risk-
Specific
Value?

Yes
Yes
2Risk-specific values account for internal (ingestion and inhalation) and external exposure and
correspond to a 10-6 excess cancer risk.
NA = Not available.
-------
Table 7-19
Summary of Radiological Risk from Exposure to Surficial Soil2
at the RME Future Onsite Residential Setting
95 UCL Concentration
Pathway Specific Excess Cancer Risk
Ingestion
Inhalation
External
Onsite
Radionuclide
Cesium-137
Radium-226
Uranium-234
Uranium-235
Uranium-238
(pCi/g)
0,
2,
1.
0,
1.
.17
.3
.6
.25
.6
Background
(pCi/g)
0.23
2.8
1.2
0.3
1.3

Onsite
5
3
3
5
5
.9 x
.4 x
.2 x
.1 x
.6 x
10-9
10-7
10-8
10-9
10-8

Background
8.3 x 10-9
4.2 x 10-7
2.4 x 10-8
6.0 x 10-9
4.6 x 10-8

Onsite
1
3
2
3
4
.7 x
.6 x
.2 x
.3 x
.4 x
10-11
10-8
10-7
10-8
10-7

Background
2.3 X 10-11
4.4 x 10-8
1.6 x 10-7
3.9 x 10-8
3.5 x 10-7

Onsite
9.7 X
3.9 x
1.4 x
1.7 x
1.7 x
10-6
10-4
10-9
10-6
10-6

Background
1.3 x 10-5
4.8 x 10-4
1.0 x 10-9
2.1 x 10-6
1.3 x 10-6
Total 4 x 10-7 5 x 10-7 7 x 10-7 6 x 10-7

2Surface soil from the sewage sludge based application/leachate injection area (Group 1 soils).
4 x 10-4
5 x 10-4
-------
Table 7-20
Summary of Radiological Risk from Exposure to Sedimentsa
at the RME Future Onsite Residential Setting
95 UCL Concentration
Pathway Specific Excess Cancer Risk
Ingestion
Inhalation
External
Radionuclide
Europium- 15 4
Potassium-40
Radium-226
Thorium-232
Thorium-228
Uranium-234
Uranium-235
Uranium-238
Onsite
(pCi/g)
0
.20
23.0
2
1
1
1
0.
1
.7
.3
.6
.5
077
.5
Background
(pCi/g)
NA
19.
2.
,0
,1
NA
1.
1.
0.
1.
,3
,8
,30
,2
7
3
4
2
1
3
1
5
Onsite
.6 x
.2 x
.0 x
.0 x
.1 x
.0 x
.6 x
.3 x
10-10
10-7
10-7
10-8
10-7
10-8
10-9
10-8
Background

2.7
3.2

9.2
3.6
6.0
4.2
—
x
x
—
x
x
x
x

10-7
10-7

10-8
10-8
10-9
10-8
Onsite
1.5
9.3
4.2
2.0
6.6
2.0
1.0
4.1
x
x
X
X
X
X
X
X
10-10
10-10
10-8
10-7
10-7
10-7
10-8
10-7
Background

7.7
3.4

5.4
2.5
3.9
3.3
—
x
x
—
x
X
X
X

10-10
10-8

10-7
10-7
10-8
10-7
Onsite
2.4
3.6
4.6
9.9
2.6
1.3
5.3
1.6
x
x
X
X
X
X
X
X
10-5
10-4
10-4
10-10
10-4
10-9
10-7
10-6
Background

3.0
3.7

2.1
1.6
2.1
1.2
—
x 10-4
x 10-4
—
x 10-4
x 10-9
x 10-6
x 10-6
Total
aSediments from eight sample locations.
9 x 10-7
x 10-7
2 x 10-6
1 x 10-6
1 x 10-3
9 x 10-4
-------
Table 7-21
Summary of Radiological Risk at the RME
Future Onsite Residential Setting

Excess Cancer Risk
Exposure Media Exposure Pathway Onsite Background

Ground Water
Surface Soil
Surface Water
Sediments
Total Exposure 2 x 10-3 2 x 10-3
Ingestion
Ingestion
Inhalation
External
Ingestion
Ingestion
Inhalation
External
5
4
7
4
2
9
2
1
x
x
X
X
X
X
X
X
10-4
10-7
10-7
10-4
10-7
10-7
10-6
10-3
2
5
6
5

8
1
9
x 10-4
x 10-7
x 10-7
x 10-4
NA
x 10-7
x 10-6
x 10-4
-------
Table 7-22
Potentially Occurring Threatened and Endangered
Species Within or Around the Lowry Site
Peregrine falcon
Bald Eagle
Black terna
Mountain plovera
White-faced ibisa
Baird's sparrowa
Whooping crane
Long-billed curlew
Ferruginous hawk
Westerhn boreal toada
Birds
Falco peregrinus
Haliaeetus leucocephalus
Chlidonia niger
Charadrius montanus
Plegadis chihi
Ammodramus bairdii
Grus americana
Numenius americanus
Buteo regalis

Amphibians
Bufo boreas boreas
Regal fritillary butterflya
Preble's meadow jumping mouse
Swift foxa
Black-footed ferret
Diluvium lady's tressesb
Colorado butterfly plantc
Insects
Speyeria idalia

Mammals
Zapus hudsonius preblei
Vulpes velos

Mustela nigripes

Vegetation
Spiranthes diluvialis
Gaura neomexicana ssp, Coloradensis
a Species that are candidates for official listing as threatened or endangered species (Federal Register,
Vol. 54, No. 4, January 6, 1989; Vol 55, No. 35, February 21, 1990).
b Listed by USFWS as Category 2, under review for protective status, Final Remedial Investigation Report for
the Shallow Ground Water and Subsurface Liquids and Deep Groundwater Operable Units, Lowry Landfill, Vol.
VI of VIII. Lowry Coalition, Boulder, CO).
c Listed by USFWS as Category 1, under review for protective status with sufficient information to support
proposing to list the taxa as Threatened and Endangered.
-------
Table 7-23
Constituents Eliminated on the Basis of Relative Toxicity
Constituent
Surface Soil
Bromide
Calcium
Chloride
Magnesium
Nitrate
Nitrite
Nitrogen
Phosphorous
Potassium
Sodium
Sulfate
Sulfur

X
X
X
X

X
X
X
X
X
Surface Water

X
X
X
X
X
X
X
X
X
X
Sediments
X
X
X
X
-------
Table 7-24
Maximum Detected Concentrations of
Ecological Chemicals of Concern
Page 1 of 2
Chemical
Surface Soil
(mg/mg soil)
Surface Water
(lig/D
Sediment
(mg/mg sediment)
Organics
1,1-Dichloroethane
1,1-Dichloroethane
1,2-Dichloroethane (total)
1,1,1-Trichloroethane
2,4-Dichlorophenol
2,4-Dimethylphenol
2-Butanone
2-Hexanone
2-Methylnaphthalene
2-Methylphenol
4-Chloroaniline
4-Methylphenol
4-Methyl-2-pentanone
Acetone
Aniline
Benzene
Benzoic acid
bis(2-ethylhexyl)phthalate
Carbon disulfide
Chloroform
di-n-Butylpthalate
Ethylbenzene
Fluoranthene
Heptachloroodibenzofurans
Heptachlorodibenzo-p-dioxins
Hexachlorodibenzodioxins
Hexachlorodibenzofurans
Methylene chloride
Naphthalene
octochlorodibenzodioxins
Octochlorodibenzofurans
PCB-1260
Pentachlorodibenzodioxins
0.0000000065
0.0000025
0.00000014
0.0000022
0.000000025
0.0000000035
0.0000020
0.00000000030
0.0000000029
0.00000000030
0.00000000010
0.00000015

0.000000014
0.00000000020
0.0000076
0.00000000010
15,000
5,000
730
31,000
400
920
51,000
10,000
400
66,000
27,000
240,000

5,000
6,300
4,000
5,000
77,000
400
0.040
0.0000034

0.00000057
0.00011
0.0000027
0.0000038
0.000015

0.000024
0.0000038
0.0000084
0.00000033
0.00000061

0.000095
0.0000027
0.000095
0.0000077

0.0000000056
0.00000000070
0.000014
0.00000000060

0.0000024
Note: Blanks indicate chemical not of concern in the medium.
-------
Table 7-24
Maximum Detected Concentrations of
Ecological Chemicals of Concern
Page 2 of 2
Chemical
Phenanthrene
Phenol
Pyrene
Toluene
Tetrachloroethene
trans-1,2-Dichloroethene
Trichloroethene
Vinyl chloride
Xylenes

Aluminum
Ammonia
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Chromium (total)
Cobalt
Copper
Cyanide
Iron
Lead
Magnesium
Mercury
Nickel
Silver
Tin
Vanadium
Zinc
Surface Soil
(mg/mg soil)
Surface Water
(lig/D
Organics (continued)
0.000000011
Inorganics
0.027
0.0000032

0.000014
0.0016

240
0.000013
0.00013
0.00012
0.00015
0.0000049
0.039
0.00015

0.0000010
0.00013
0.0000098
0.000014
0.00014
0.35
(Metals)
4,100

28,000
2,300
56,000
5,000
9,600
9,700

260,000
25,000
150
42
1,500
130,000
210
210
660
250
360,000
290
38,000
3.6
250

250
620
1,300
Sediment
(mg/mg sediment)
0.0000062

0.0000055
0.00028
0.000048
0.0000031
0.000041
0.0000012
0.00058

0.032
0.000051
0.000032
0.000021
0.00086
0.0000027

0.0000042
0.00042
0.000018
0.00016
0.0000023
0.042
0.0030
0.0019
0.0000019
0.000042

0.000018
0.000071
0.00054
Note: Blanks indicate chemical not of concern in the medium.
-------
Section 8.0
Description of Remedial Alternatives

Feasibility Studies (FSs) were conducted to develop and evaluate remedial alternatives for ground water,
subsurface liquids, landfill solids and gas, soils, surface water, and sediments at the Lowry Site. Several
alternatives were assembled from the applicable remedial technology process options and were screened for
their effectiveness, implementability and cost. The alternatives passing this screening were then evaluated
in further detail based on the nine criteria required by the NCP. This section provides a description of
each alternative that was retained for the detailed to provide a point of comparison for other alternatives.

The descriptions of alternatives in this section follow the groupings of OUs by media: shallow ground water
and subsurface liquids (OU 1) and deep ground water (OU 6)/landfill solids (OU 2) and landfill gas (OU 3);
and soils (OU 4), surface water, and sediments (OU 5).

The descriptions of alternatives include the following components:

• Treatment components

Treatment technologies that will be used;
Type and volume of waste to be treated;
Process sizing; and
Primary treatment levels.

• Containment or storage components

Type of storage;
Type of closure that will be implemented;
Type and quantity of waste to be stored; and
Quantity of untreated waste and treatment residuals to be disposed offsite or managed
onsite in a containment system and the degree of hazard remaining in such waste.

• General components and cost

Contaminated media addressed (and their physical location at the Lowry Site);
Risk reduction (including initial risk);
Whether treatability testing has been or will be conducted;
Implementation requirements;
Institutional controls;
Residual levels;
Assumptions, limitations, uncertainties;
Estimated implementation time frame; and
Estimated capital, operation and maintenance (O&M), and present worth costs.

• Major ARARs, risk-based levels, and TBCs being met/utilized for the specific components of the
alternatives

How specific components of each alternative will comply with the major ARARs and why
the standard is applicable, or relevant and appropriate.

In addition, for ground-water remedial alternatives, the following ground-water components are addressed, as
appropriate:

• Ground-water classification;
• Performance standards;
• Estimated restoration timeframe; and
• Area of attainment.

8.1 Cost Estimating Procedures

Alternatives were evaluated in terms of capital costs, annual or operation and maintenance (O&M) costs, and
present worth costs. Capital costs include the sum of the direct capital costs (materials, equipment, labor,
land purchases) and indirect capital costs (engineering, licenses, or permits). Annual costs include the
cost for labor, O&M, materials, energy, equipment replacement, disposal, and sampling to operate the
treatment facilities. Present worth costs include capital costs and O&M costs calculated over a 30-year
period.
-------
The present worth analysis is used to evaluate expenditures that would occur over an assumed 30-year
operation period by discounting all future costs to a common base year. This allows the cost of remedial
action alternatives to be compared on the basis of a single figure representing the amount of money that, if
invested in the base year and disbursed as scheduled, would be sufficient to cover the costs associated with
the remedial alternative over its planned life.

Additional assumptions used in cost estimation include: a real discount rate of five percent (the difference
between the nominal discount rate and inflation is five percent); and a constant value based on 1993 rates
for materials, expenses, and services.

The accuracy of costs is subject to substantial variation since details about the specific design of each
alternative (such as design details, the bidding element, changes during construction and operation, interest
rates, labor and eguipment rates, tax effects, and other similar items) will not be known until the time of
actual implementation of the remedies.

Remedial Design efforts may also reveal that it is possible to reduce the original project cost estimates.
Reductions in the estimated costs could be the result of value engineering conducted during Remedial Design.
Through the value engineering process, modifications could be made to the functional specifications of the
remedy to optimize performance and minimize costs. These changes would fall within the definition of "non-
significant modifications," as defined by EPA's guidance for preparing Superfund decision documents. For
example, it may be determined that a reduction in costs could be effected by non-significant changes to type,
guantity, and/or cost of materials, eguipment, facilities, services, and supplies used to implement the
remedy. It should he noted that this type of design variance may have a noticeable impact on the estimated
cost of the remedy, but will not affect the remedy's ability to comply with the performance standards.

8.1.1 Respondent's Cost Estimates

Standard cost data from the following sources were used in the OU RI/FSs prepared by the various Respondents:
EPA guidance, construction industry guidance, remedial action contractors, vendors, and treatability studies.
While the Respondents used these sources to develop their cost data, each group of Respondents used these
sources assumptions in developing the costs. As a result, the cost estimates were not directly comparable
across RI/FSs. EPA has revised the cost estimates as described below.

8.1.2 EPA's Revised Cost Estimates

Present worth cost calculations, as they appear in the ROD, differ slightly from those presented in the
feasibility studies for all OUs. In order to allow for the consistent comparison of costs for the various
alternatives, EPA recalculated the costs using a single set of assumptions. The following factors were
standardized for all alternatives: interest rates and inflation rates.

8.2 Features Common to All Remedial Alternatives

All remedial alternatives, except for the No Action Alternative, have the following common features:

• Institutional Controls-Institutional controls are non-engineering methods by which Federal,
State, local governments, or private parties can prevent or limit access to or use of a site.
Institutional controls for the Lowry Site shall include, but not be limited to, deed notices
and restrictions that run with the land; onsite-access restrictions including, but not limited
to, fencing and warning signs; zoning controls; and well restrictions. Executive Order No. 97,
as issued by City and County of Denver Mayor Federico Pena, currently provides some measure of
control. Institutional controls at the Lowry Site must prohibit all activities and uses that
EPA determines would interfere or be incompatible with, or that would in any way reduce or
impair the effectiveness or protectiveness of, the sitewide remedy. These shall include, but
not be limited to, prohibitions on all ground-water well construction and use not necessary for
implementation and monitoring of the selected remedy; prohibitions on access; and prohibitions
on activities and land use not connected with design, construction, and implementation and
monitoring of the selected sitewide remedy. Offsite institutional controls shall serve as an
additional measure of protection to enhance the effectiveness of the selected remedy and to act
as preventative measures to preserve the implementability and effectiveness of any of the
selected remedy contingency measures. Offsite institutional controls shall include, but not be
limited to, deed notices and restrictions, zoning controls, and well restrictions. These
controls must prohibit all offsite activities in the vicinity of the Lowry Site that would
interfere or be incompatible with, or that would in any way reduce or impair the effectiveness
or protectiveness of, the selected sitewide remedy.
-------
All onsite and offsite institutional controls shall be adequately administered, maintained, and
enforced.

The owner and operator of the Lowry Site shall be responsible for access restrictions, warning
signs, and fences.

• Performance and Compliance Monitoring-To ensure that the performance standards are met for all
components of the selected remedy for as long as contamination remains onsite, a long-term
monitoring program shall be designed and implemented during the RD/RA and shall continue
throughout the implementation of the selected sitewide remedy. The monitoring program shall
assess compliance with the remediation levels in the ground-water system, monitor effluent
chemical concentrations from the treatment plant, evaluate the horizontal and vertical
migration of contamination, monitor the erosion of soils and sediments, and monitor the
migration of landfill gases. Details of the monitoring program shall be determined by EPA, in
consultation with CDH, during the RD. The monitoring program shall include, at a minimum, the
following: analytical parameters and methods; indicator parameters; monitoring locations;
monitoring frequency and duration; sampling methods; well installation, maintenance and
abandonment procedures; statistical methods for evaluating data; reporting methods and
procedures for tracking and maintaining sample records; and QA methods, including data
validation methods. The FSs estimated that approximately 60 to 100 ground-water monitoring
wells will be sampled semi-annually. Landfill gas shall be monitored quarterly, or more
frequently if migration is detected, using approximately 40 to 60 monitoring wells. The
ground-water monitoring component of the selected sitewide remedy includes an early-warning
monitoring component; this will allow for a timely remedial response in the event that EPA
determines that additional remedial actions are necessary. Soil and sediment erosion shall be
monitored on a monthly basis using three surface-water samplers installed in drainages. The
actual details of the monitoring program are subject to revisions and refinement during RD.

Five-Year Review-As specified in Section 121 (c) of CERCLA, as amended by SARA, and Section
300.430(f)(4)(ii) of the NCP, EPA will review the sitewide remedy no less often than each 5
years after the initiation of the remedial action to assure that human health and the
environment are being protected by the implemented remedy (this review will ensure that the
remedy is operating and functioning as designed and that institutional controls are in place
and are protective). An additional purpose for the review is to evaluate whether the
performance standards specified in this ROD remain protective of human health and the
environment. EPA will continue the reviews until no hazardous substances, pollutants, or
contaminants remain at the Lowry Site above levels that allow for unrestricted use and
unlimited exposure.

8.3 Interim Remedial Measures

The following interim remedial measures, as described in Section 3.0 of this ROD, have already been
constructed and are operational at the Lowry Site. These measures shall continue to operate in accordance
with the existing design and operations criteria unless EPA determines that modifications are needed:

• Ground-Water Barrier Wall-The ground-water barrier wall system shall continue to be operated in
accordance with the existing design and operations program. The existing barrier wall consists
of a 30-foot-deep, 1,000-foot-long compacted clay wall with a central collection sump. The
base of the barrier wall is anchored to the top of the unweathered bedrock (Dawson formation).

• Surface Water Removal Action (SWRA)-The Surface Water Removal Action shall be continued and the
collection system along unnamed creek shall be maintained.

• Existing Ground-Water Treatment Plant (GWTP)-The existing groundwater treatment plant shall be
upgraded and maintained on the basis of SWRA design criteria.

8.4 Description of Alternatives

8.4.1 Description of No Action Alternative for all Operable Units

Evaluation of the No Action Alternative is required under CERCLA (as amended by SARA) and is used as a
baseline against which other alternatives are evaluated. Under this alternative, no remedial action would be
undertaken to treat, contain, or remove contaminated media at the Lowry Site. All interim remeaial measures
currently being taken at the Lowry Site would be discontinued. The SWRA collection system, existing GWTP,
and barrier wall would no longer function and would be allowed to deteriorate. The landfill cap and existing
fencing would be allowed to degrade and become nonfunctional. Landfill gas and ground-water monitoring would
-------
also cease and no action would be taken to prevent migration of contaminants offsite. No institutional or
operational controls would be implemented to restrict access to the Lowry Site or to restrict exposure to
contaminants.

There would be no reduction in the volume, toxicity, or mobility of the contaminants. The overall volume of
contaminated water could increase from infiltration. Monitoring would not be a component of this
alternative.

There would be no treatment or containment components associated with this alternative. Under the No Action
Alternative, all waste would be left in place and there would be no reduction in risk. The remedial action
objectives (RAOs) would not be met for this alternative because contaminants would migrate offsite, and
protection of human health and the environment would not be achieved.

Because the interim remedial measures would be discontinued, chemical-, location-, and action-specific would
not be met.

The total 30-year present worth cost of this alternative is $0 with no capital costs and no annual O&M costs.
The No Action Alternative would be immediately implementable.

8.4.2 OUs 1&6-Shallow Ground Water and Subsurface Liquids, and Deep Ground Water

The following remedial alternatives were evaluated in detail during the FS for OUs 1&6:

Alternative GW-l-No Further Action;

• Alternative GW-2-North Boundary (Downgradient) Containment, Collection, and Treatment,

• Alternative GW-3-North Boundary and Toe of landfill Containment, Collection, and Treatment;

• Alternative GW4-North Boundary, Toe of Landfill and Upgradient Containment, Collection, and
Treatment, Plus Multilayered Cap in Landfill Area;

• Alternative GW-5-North Boundary, Toe of landfill and Lateral Containment, Collection, and
Treatment;

• Alternative GW-6-North Boundary and Toe of Landfill Containment.

In addition, EPA added the following alternative to the list of alternatives to be evaluated:

• Modified Alternative GW-5 (North Boundary, Toe of Landfill and Lateral Containment, Collection
and Treatment, and Southern Containment, Collection, and Diversion).

The alternatives for OUs 1&6 are described below. Major ARARs are identified for each alternative.
Additional ARARs for OUs 1&6 alternatives are presented in Table 8-1.

8.4.2.1 Alternative GW-l-No Further Action

The No Further Action Alternative (GW-1) would entail the continued implementation of the existing interim
remedial and monitoring measures at the Lowry Site. Under this alternative, the following activities and
components would be maintained:

• The existing ground-water barrier wall/collection system and treatment facility would remain
intact and functional. The existing ground-water barrier system consists of a 1,000-foot-long
drain backed by a 30-foot-deep compacted clay barrier.

• The SWRA, which includes a collection system and an upgrade to the treatment facility, would
remain intact and functional.

• The landfill cover would be maintained, and landfill gas monitoring would continue.

• Existing ground-water monitoring would continue.

• Surface-water and ground-water restrictions that are currently in place would continue.

• Existing onsite and offsite institutional controls would be enforced.
-------
Treatment components associated with this alternative include removal of contaminants in ground water by air
stripping and carbon adsorption. The existing treatment plant has an optional aerobic biological treatment
unit available if phenols and ketones are detected in the early-warning monitoring well. Spent carbon is
regenerated offsite and treated ground water is injected into the shallow subsurface beyond the barrier wall.
It is estimated that 3.7 million gallons of ground water would be treated annually, resulting in
approximately 60 pounds per year of contaminants being removed. The SWRA performance standards have been
updated in this ROD to comply with current reguirements. Although the existing plant capacity is 30 gpm, the
plant is currently operating at about 15 gpm. The restoration time frame would be more than 30 years and
because wastes would be left in place, treatment would continue in perpetuity.

The barrier wall intercepts the northward migration of contaminants flowing through the alluvium of unnamed
creek as well as the seepage collected in the SWRA collection system. The SWRA collection system keeps the
waste-pit seepage separated from precipitation runoff, thus preventing contaminated water from migrating
offsite during storm events. The landfill cover minimizes production of leachate and limits migration into
the underlying Dawson Aguifer.

The remedy is primarily containment-based; therefore, wastes would be left in place. The Baseline Risk
Assessment for OUs 1&6 indicated that there are no current exposure pathways to ground water. However, if
onsite residents used ground water as a drinking water source in the future, the estimated cancer risk would
be 1x10-2. Onsite risks would remain and would be controlled through the use of institutional controls.
Estimated risk for a residential setting using a hypothetical future offsite drinking water well in the
direction of regional ground-water flow could be 2x10-5 within 30 years. This risk could increase to 1x10-3
after 150 years of contaminant migration. Under the No Further Action alternative, offsite migration of
contaminants toward the north would be prevented. It is assumed that contaminant migration toward the west,
east, and south would be controlled through monitoring and implementation of contingency measures. However,
the exact nature of these measures has not been identified or costed out. In the absence of these
contingency measures, contaminant migration toward the west, east, and south would continue, and offsite
risks would not be eliminated.

Treatability studies were performed during the ground-water treatment plant design, and formed the basis for
the original treatment train. Additional treatability studies were conducted prior to the implementation of
the SWRA. Based on these additional studies, the treatment plant was upgraded to address a wider range of
contaminants. Treatment residuals from this alternative consist of spent carbon (4,000 pounds/month), which
is regenerated offsite approximately every 10 weeks. Other treatment residuals may include solids from bag
filters and, in the future, sludge from the biotreatment unit. The alternative assumes that future treatment
plant upgrades as described and mandated by the SWRA would be adeguate to treat all chemicals that may be
present in the contaminated ground water. The No Further Action Alternative would use current technologies.

The following major ARARs have been identified for this alternative:

Colorado Water Quality Control Act (5 CCR 1002-8), Colorado Basic Standards for Ground Water,
Classifications and Water Quality Standards for Ground Water: These regulations establish
standards for both classified and unclassified ground water. The standards are applicable
because ground water (within confined, unconfined, and alluvial aguifers) near the Lowry Site
and ground water (within unconfined and alluvial aguifers) within the Lowry Site have been
classified for domestic- and agricultural-guality use. Ground water within confined aguifers
of the Lowry Site is not classified. However, regulatory standards that are pertinent to
classified ground water also apply to unclassified ground water for the protection of offsite
beneficial uses of the ground water. Under this alternative, ground water would be treated to
meet these standards and then discharged to the shallow ground-water system. This alternative
would comply with the reguirements specified under these ARARs.

Safe Drinking Water Act, National Primary Drinking Water Regulations (40 CFR Part 141) and the
Colorado Primary Drinking Water Regulations (5 CCR 1003-1) : These regulations establish
health- and treatment-based standards for public drinking water systems. These regulations
would be relevant and appropriate because the shallow and deep ground water in the vicinity of
the Lowry Site is being used or may be used in the future as a source of water for a public
water system or private supply wells. Under this alternative, treated ground water from the
treatment plant Would be injected into the shallow ground-water system. This alternative would
comply with the reguirements specified under these ARARs.

Safe Drinking Water Act, and National Secondary Drinking Water Regulations (40 CFR Part 143):
These regulations establish welfare-based standards for public water supply systems and have
been adopted by the State of Colorado under the basic standards for ground water. The
regulations would be relevant and appropriate because the shallow and deep ground water in the
vicinity of the Lowry Site is being used or may be used in the future as a source of water for
a public water system or private supply wells. Under this alternative, ground water would be
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treated to meet these standards and then discharged to the shallow ground-water system. This
alternative would comply with the requirements identified under these regulations.

Colorado Air Quality Act/Colorado Air Pollution Regulations (5 CCR 1001): These regulations
establish standards for air emissions from stationary sources. These regulations are
applicable because the treatment plant is a source of air emissions. These regulations would
be met for the air stripper/carbon-polishing treatment process.

This alternative includes contingency measures to ensure that RAOs and ARARs would be met at the compliance
boundary.

The total 30-year present worth of this alternative is $31,970,000, with capital costs of $4,300,000, and
annual O&M costs of $1,800,000. The implementation time is immediate.

8.4.2.2 Alternative GW-2-North Boundary (Downgradient) Containment, Collection, and Treatment

Under Alternative GW-2, all existing interim remedial measure identified in the No Further Action Alternative
(GW-1) would continue. Additionally, a 2,200-foot groundwater barrier wall and collection system (referred
to as an extraction trench in the Proposed Plan for OUs 1&6) would be constructed along the northern boundary
of Section 6. The barrier wall would be an extension of the existing barrier wall or a separate barrier wall
adjacent to the existing barrier wall. The effectiveness of the existing barrier wall in capturing the
northward migration of the contaminated ground water would be evaluated to determine the necessary barrier
wall configuration. Contaminated ground water, collected from the new extraction trench and/or the existing
barrier wall, would be treated using the existing ground-water treatment plant.

The barrier wall would be constructed so that it would be anchored into the separation layer, which in this
area averages about 65 feet in depth. Four ground-water collection sumps would be located along the
collection system and connected to a header pipeline to the existing ground-water treatment plant.

Since the barrier wall and collection system would capture additional ground water, approximately 6.3 million
gallons per year of contaminants ground water would be treated, and would result in the removal of
approximately 100 pounds per year of contaminants. The restoration time frame would be more than 30 years,
and since waste would be left in place, treatment would continue in perpetuity.

This alternative is primarily containment-based; therefore, waste would remain in place. Onsite risks would
remain at unacceptable levels and would be controlled through institutional controls. Offsite migration of
contaminants toward the north would be prevented. It is assumed that contaminant migration toward the west,
east, and south would be controlled through monitoring and implementation of contingency measures. However,
the exact nature of these measures has not been identified or costed out. In the absence of these
contingency measures, contaminant migration toward the west, east, and south would continue, and offsite
risks would not be eliminated.

Treatability testing has been performed in conjunction with the design of the existing ground-water treatment
plant and the SWRA. This alternative assumes that the existing ground-water treatment plant would be
adequate to treat all contaminants in ground-water and waste-pit liquids. The alternative is considered
implementable since proven technologies are being proposed.

Major ARARs for this alternative are the same as the ARARs identified for the No Further Action alternative
(GW-1) and would be met by this alternative using similar methods.

This alternative includes contingency measures to ensure that RAOs and ARARs would be met at the compliance
boundary.

The total 30-year present worth cost of this alternative is $39,010,000, with capital cost of $9,800,000, and
annual O&M cost of $1,900,00. The estimated implementation time is 2 years.

8.4.2.3 Alternative GW-3-North Boundary and Toe of Landfill Containment, Collection, and Treatment

Under Alternative GW-3, all existing interim remedial measures identified in the No Further Action
Alternative (GW-1) would continue. The ground-water barrier wall and collection system on the northern
boundary of Section 6, as identified in Alternative GW-2, would also be constructed. In addition, the other
containment components discussed for Alternative GW-2 would apply as well. For Alternative GW-3, an
additional ground-water extraction system, to extract highly contaminated ground water, would be constructed
near the toe of the landfill mass. This system would be approximately 300 feet long and 50 feet deep, and
would be constructed approximately 200 feet north of the downgradient edge of the landfill (termed "toe of
the landfill").
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The extraction system would consist of a subsurface drain, a line of extraction wells, or horizontally
drilled wells. For the comparative analysis of alternatives, it was assumed that the ground-water extraction
system would consist of 15 wells, 50 feet deep, and 20 feet apart. Ground water would be pumped to the
surface and piped to the existing or a new ground-water treatment facility for highly contaminated liguids.

The cost for a new ground-water treatment plant have been incorporated into this alternative. The need for
an additional ground-water treatment plant would be evaluated during Remedial Design. A new ground-water
treatment plant would need to be designed and constructed unless it could be demonstrated through pilot-scale
testing that the existing ground-water plant could effectively treat the more highly contaminated ground
water to the performance standards.

The treatment technologies used for this alternative are part of the conceptual treatment model presented in
the FS for OUs 1&6 and include: gravity phase separation for NAPLs; lime soda softening for metals,
radionuclides, hardness, and solids; biological treatment (PACTTM) to remove organic compounds, BOD, COD,
ammonia, and nitrate; and granular-activated carbon to remove volatile organics in offgas streams.

The extraction system at the toe of the landfill is expected to capture approximately 3.9 million gallons of
contaminated ground water annually. The total annual amount of ground water to be treated from the toe of
the landfill and the northern boundary would be approximately 6.3 million gallons. Approximately 700 pounds
per year of contaminants would be removed and treated. Although the existing ground-water treatment capacity
is 30 gpm, the ground-water treatment plant is currently operating at almost 15 gpm. If an additional
ground-water treatment plant were required, it is expected that it would be sized for 20 gpm. The
restoration time frame would be more than 30 years, and because waste would be left in place, treatment would
continue in perpetuity.

The remedy is containment based; therefore waste would be left in place. Onsite risks would remain, and
would be controlled through institutional controls. Offsite migration of contaminants toward the north would
be prevented. It is assumed that contaminant migration toward the west, east, and south would be controlled
through monitoring and implementation of contingency measures. However, the exact nature of these measures
has not been identified or costed out. In the absence of these contingency measures, contaminant migration
toward the west, east, and south would continue, and offsite risks would not be eliminated.

The treatment technologies, tested during OUs 1&6 treatability study stages 1 through 3, were selected on the
basis of demonstrated effectiveness for removal. Residuals would include spent vapor-phase granular
activated carbon, solids from lime-soda softening, and PACTTM solids. Carbon would be regenerated offsite
and reused. Other solids (550 tons of lime-softening and 430 tons of sludge produced annually from the
biological treatment) would be disposed in accordance with ARARs. The alternative would be implementable
since proven technologies are being proposed.

Major ARARs for this alternative are the same as the ARARs identified for the No Further Action alternative
(GW-1) and would be met by this alternative using similar methods.

This alternative includes contingency measures to ensure that RAOs and ARARs would be met at the compliance
boundary.

The total 30-year present worth cost of this alternative is $61,420,000 with capital costs of $15,300,000,
and annual O&M costs of $3,000,000. The estimated implementation time is 3 years.

8.4.2.4 Alternative GW-4-North Boundary, Toe of Landfill, and Upgradient Containment, Collection and
Treatment, Plus Multilavered Cap in Landfill Area

Under Alternative GW-4, all provisions identified in Alternative GW-3 would be constructed, except the
extraction system at the toe of the landfill would be 100 feet deep rather than 50. All existing remedial
measures identified in the No Further Action alternative (GW-1) would continue. Containment components would
include all those described in Alternatives GW-2 and GW-3.

In addition, a 50-foot-deep containment, collection, and diversion system would be constructed upgradient of
(south of) the landfill mass. This ground-water extraction system (3,600-foot-long) would be located
upgradient of the source area, approximately 50 feet deep (keyed to the unweathered Dawson aquifer).

Also, a multilayer cap would be placed over the existing landfill cover and over the waste pits in the former
tire pile area. The multi-layered RCRA cap would cover 220 acres of the Site, including the landfill and
waste pits, and the northern pits near the former tire pile area. Components of the cap would include a
minimum of three feet compacted native clay soil, flexible membrane cap (60-mil) constructed of high density
polyethylene, filler fabric to protect the drainage layer, and soil cover capable of supporting vegetation.
A RCRA Subtitle C landfill closure would be implemented.
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Treatment components are the same as those described for Alternative GW-3.

Approximately 6.8 million gallons per year of contaminated ground-water would be treated, resulting in
removal of approximately 700 pounds per year of contaminants. The existing treatment plant were reguired, it
is expected that it would be sized at 20 gpm. The upgradient system is expected to intercept 0.5 million
gallons per year of clean water, thereby reducing the volume of clean ground water mixed with contaminated
ground water. The restoration time frame would be 30+ years and because waste would be left in place,
treatment would continue in perpetuity.

The costs for a new treatment plant have been incorporated into this alternative. The need for an additional
treatment plant would be evaluated during Remedial Design. A new treatment plant would need to be designed
and constructed unless it could be demonstrated through pilot-scale testing that the existing plant could
effectively treat the more highly contaminated ground water to the performance standards.

This alternative is containment-based; therefore, waste would remain in place. Onsite risks would remain,
and would be controlled through institutional controls. Offsite migration of contaminants toward the north
and south would be prevented. It is assumed that contaminant migration toward the west and east would be
controlled through monitoring and implementation of contingency measures. However, the exact nature of
these measures has not been identified or costed out. In the absence of these contingency measures,
contaminant migration toward the west and east would continue, and offsite risks would not be eliminated.

The treatment technologies, tested during OUs 1&6 treatability study stages 1 through 3, were selected on the
basis of demonstrated effectiveness for removal. Residuals would include spent vapor-phase granular
activated carbon, solids from lime-soda softening, and PACTTM solids. Spent carbon (approximately 4,000
pounds per month) would be regenerated offsite. Other solids would be disposed in accordance with ARARs.
The alternative would be implementable since proven technologies are being proposed.

Major ARARs for this alternative are the same as the ARARs identified in GW-1 and would be met by this
alternative using similar methods.

This alternative includes contingency measures to ensure that RAOs and ARARs would be met at the compliance
boundary.

The total 30-year present worth cost of this alternative is $113,300,000, with capital costs of $64,100,000
and annual O&M costs of $3,200,000. The estimated implementation time is 3 years.

8.4.2.5 Alternative GW-5-North Boundary, Toe of Landfill, and Lateral Containment, Collection and Treatment

Under Alternative GW-5, all existing interim remedial measures identified in the No Further Action
Alternative (GW-1) would continue. The ground-water collection system would be constructed at the toe of the
former landfill, as with Alternative GW-3. Treatment components are also the same as those described for
Alternative GW-3.

In addition, this alternative would provide for lateral containment of ground water on the eastern and
western boundaries of the Lowry Site through underground barrier walls and collection systems. The lateral
containment would consist of a barrier wall and collection system measuring approximately 2,000 feet in
length along the eastern boundary and 1,000 feet in length along the southwest portion of the compliance
boundary.

Ground water would be intercepted annually in the amount of 6.3 million gallons. Approximately 700 pounds of
contaminants would be removed by the treatment system. Although the existing treatment capacity is 30 gpm, it
is currently operating at almost 15 gpm. If an additional treatment plant were reguired, it is expected that
it would be sized at 20 gpm. The restoration time frame would be 30+ years and because wastes would be left
in place, treatment would continue in perpetuity.

The remedy is containment based; therefore, waste would be left in place. Onsite risks would remain, and
would be controlled through institutional controls. Offsite migration of contaminants toward the north,
west, and east would be prevented. It is assumed that contaminant migration toward the south would be
controlled through monitoring and implementation of contingency measures. However, the exact nature of these
measures has not been identified or costed out. In the absence of these contingency measure, contaminant
migration toward the south would continue, and offsite risks would not be eliminated.
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Treatment technologies, tested during OUs, 1&6 treatability study stages 1 through 3, were selected on the
basis of demonstrated effectiveness for removal. Treatment residuals include spent vapor-phase granular
activated carbon, solids form lime-soda softening, and PACTTM solids. Spent carbon (approximately 4,000
pounds per month) would be regenerated offsite. Other solids would be disposed in accordance with ARARs.
This alternative would be implementable because proven technologies are proposed.

Major ARARs for this alternative are the same as the ARARs identified for GW-1 and would be met by this
alternative using similar methods.

This alternative includes contingency measures to ensure that RAOs and ARARs would be met at the compliance
boundary.

The total 30-year present worth cost of this alternative is $68,820,000 with capital costs of $17,700,000 and
annual O&M cost of $3,000,000. The estimated implementation time is 3 years.

8.4.2.6 Alternative GW-6-North Boundary and Toe of Landfill Containment, Collection and Treatment, and
Waste-Pit Pumping

Under Alternative GW-6, all existing interim remedial measures identified in the No Further Action
Alternative (GW-1) would continue. Ground-water collection systems as described in Alternative GW-3 would be
constructed at the toe of the landfill mass. This alternative includes the same containment components as
identified for Alternatives GW-2 and GW-3. In addition, waste-pit pumping wells would be installed, liguids
would be extracted from waste pits, and the liguids would be treated.

Treatment components are the same as those described for Alternative GW-3. Treatment technologies would
include: gravity-phase separation for NAPLs; lime soda softening for metals, radionuclides, hardness, and
solids; biological treatment (PACTTM) to remove organic compounds, BOD, COD, ammonia, and nitrate; and
granular activated carbon to remove volatile organics in offgas streams. Treatment residuals would be
disposed in accordance with ARARs.

Approximately 52 waste-pit extraction wells (one for each waste pit) would be installed and pumped at 0.04
gpm per well, totaling about two gpm for all wells or 1.1 million gallons per year. A total of 7.4 million
gallons of ground water and waste-pit liguids would be treated. Contaminant removal is estimated to total
about 1,800 pounds per year. Although the existing treatment capacity is 30 gpm, it is currently operating
at almost 15 gpm. If an additional treatment plant were reguired, it is expected that it would be sized at
20 gpm. The restoration time frame would be 30+ years and because wastes would be left in place, treatment
would continue in perpetuity.

The cost for a new treatment plant have been incorporated into this alternative. The need for an additional
treatment plant would be evaluated during Remedial Design. A new treatment plant would need to be designed
and constructed unless it could be demonstrated that the existing plant could effectively treat the more
highly contaminated ground water to the performance standards.

Although the remedy is primarily containment-based and waste would be left in place, waste-pit extraction
wells would remove approximately 1.1 million gallons per year. Onsite risks would remain, and would be
controlled through institutional controls. Offsite migration toward the west, east, and south would be
controlled through monitoring and implementation of contingency measures. However, the exact nature of these
measures has not been identified or costed out. In the absence of these contingency measures, contaminant
migration toward the west, east, and south would continue, and offsite risks would not be eliminated.

Treatment technologies, tested during OUs 1&6 treatability study stages 1 through 3, were selected on the
basis of demonstrated effectiveness for removal. Residuals from gravity-phase separation, lime-soda
softening, and biological treatment would be thickened and dewatered. The dewatered solids are not expected
to demonstrate RCRA-toxicity characteristics and would therefore be disposed in a Subtitle D-eguivalent
landfill. Spent granular activated carbon would be regenerated offsite. Residuals would include spent
vapor-phase granular activated carbon, solids from lime-soda softening, and PACTTM solids. Spent carbon
(approximately 4,000 pounds per month) would be regenerated offsite. Other solids would be disposed in
accordance with ARARs. This alternative assumes sustained pumping from waste pits could be achieved. The
implementability of this alternative could be affected by the technical feasibility of drilling and
installing extraction waste-pit well points.

Major ARARs for this alternative are the same as the ARARs identified for GW-1 and would be met by this
alternative using similar methods.

This alternative includes contingency measures to ensure that RAOs and ARARs would be met at the compliance
boundary.
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The total 30-year present worth cost of this alternative is $72,570,000 with capital costs of $20,300,000 and
annual O&M cost of $3,400,000. The estimated implementation time is 3 years.

8.4.2.7 EPA's Preferred Alternative-Modified Alternative GW-5-North Boundary, Toe of Landfill, and. Lateral
Containment, Collection, and Treatment plus Upgradient Containment, Collection, and/or Diversion

This alternative is similar to Alternative GW-5, but has been modified by the addition of an upgradient
containment/collection and/or diversion system. Modified Alternative GW-5 would use barrier walls as the
type of containment, collection, and diversion system. Due to the presence of subsurface sand lenses at the
Site, barrier walls would be the most effective method to isolate site containments and restrict offsite
migration of contaminated ground water. This alternative would contain and treat onsite shallow ground
water. Modified Alternative GW-5 would include construction of underground barrier walls and collection
systems to the east, west, north and south of the Lowry Site and installation of a ground-water extraction
system at the toe of the landfill.

Collected liquids would be treated in the existing ground-water treatment facility, an upgraded facility, or
a new ground-water treatment facility, if required. Operation of the existing ground-water barrier wall
would continue. This alternative also includes additional measure to address the potential for offsite
migration of contaminated ground water at the northern boundary. These measure include construction of a
separate barrier wall adjacent to the existing barrier wall, or construction of an extension to the existing
barrier wall.

Treatment components would be the same as those described for Alternative GW-3. The following treatment
technologies are part of the conceptual treatment model presented in the FS for OUs 1&6: gravity phase
separation for NAPLs; lime soda softening for metals, radionuclides, hardness, and solids; biological
treatment (PACTTM) to remove organic compounds, BOD, COD, ammonia, and nitrate; and granular activated carbon
to remove volatile organics in offgas streams. Treatment residuals would be disposed in accordance with
ARARs.

Approximately 6.3 million gallons of ground water would be intercepted on an annual basis. Contaminant
removal is estimated to total about 700 pounds per year. Although the existing treatment capacity is 30 gpm,
it is currently at almost 15 gpm. If an additional treatment plant were required, it is expected that it
would be sized at 20 gpm. The restoration time frame would be 30+ years and because waste would be left in
place, treatment would continue in perpetuity.

This alternative would effectively isolate onsite contaminated ground water from the offsite ground-water
systems through containment on the southern, eastern, western, and northern boundaries. In addition,
containment, collection, and treatment at the toe of the landfill mass would extract highly contaminated
liquids closer to the source.

While this alternative does include a limited treatment component, the remedy would be primarily
containment-based; therefore, waste would remain onsite. Because Modified Alternative GW-5 would effectively
restrict offsite migration of contaminated ground water, this alternative would prevent offsite migration of
contaminants and would eliminate offsite risks. Onsite risks would remain, and would be controlled through
institutional controls.

Treatment technologies, tested during the OUs 1&6 treatability study stages 1 through 3, were selected on the
basis of demonstrated effectiveness for removal. Residuals would include spent vapor-phase granular
activated carbon, solids from lime-soda softening, and PACTTM solids. Spent Carbon would be regenerated
offsite and other solids would be disposed in accordance with ARARs. This alternative would use current
technology and therefore would be implementable.

Major ARARs for this alternative are the same as the ARARs identified for GW-1 and would be met by this
alternative using similar methods.

RAOs relating to offsite migration would be met without the use of contingency measures.

The total 30-year present worth cost of this alternative is $65,030,000, with capital costs of $19,000,000
and annual O&M costs of $2,400,000. The estimated implementation time is 3 years.
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8.4.3 OUs 2&3-Landfill Solids and Gas

The following alternatives were evaluated as part of the FS for OUs 2 and 3:

Landfill Solids (OU 2)

Alternative LFS-2 (No Further Action);
Alternative LFS-3 (Clay Cap);
Alternative LFS-4 (Drum Removal and Offsite Disposal);
Alternative LFS-6 (Drum Removal/Low Temperature Thermal
Desorption/Stabilization/Disposal); and
Alternative LFS-7 (Landfill Mass Regarding).

Landfill Gas (OU 3)

Alternative LFG-2 (No Further Action);
Alternative LFG-3 (Gas Collection/Enclosed Flare); and
Alternative LFG-5 (Gas Collection with Heat Recovery).

In addition, EPA added the following two alternatives to the list of alternatives to be evaluated for
consideration:

• Modified Alternative LFS-4 (Drum Removal/Offsite Disposal/North Face Cover); and

Modified Alternative LFG-3 (Gas Collection/Enclosed Flare).

These modified alternatives were discussed in the Proposed Plan for OUs 2&3, 4&5, and the sitewide remedy.

Major ARARs for each alternative are identified below. Additional ARARs for OUs 2&3 alternatives are
presented in Table 8-2.

8.4.3.1 Alternative LFS-2-No Further Action

Under Alternative LFS-2, the No Further Action Alternative for landfill solids, no additional remedial action
would be undertaken to treat, contain, or remove contaminated landfill solids within the landfill mass and
the former tire pile area. Existing sitewide operational measures pertinent to landfill solids such as cover
maintenance, site access restrictions and security, and interim remedial measures would continue to be
operated and maintained. Under these measures:

• The landfill in Section 6 would remain closed and the existing landfill cover would be
maintained;

• The existing soft cover in the former tire pile area would be maintained; and

• Existing institutional controls and onsite access restrictions including fencing and warning
signs, and land use restrictions including well drilling restrictions would be enforced.

There are no treatment components associated with this alternative.

Containment of the landfill mass solids would be achieved by proper maintenance of the existing cover on the
landfill. Approximately 12 million cubic yards of landfill solids would be contained.

Because there are currently no residential or recreational uses at the Lowry Site, there is no current risk
from ingestion, inhalation, or skin adsorption of landfill solids. The Baseline Risk Assessment indicated
that if no remedial actions were taken, and if people lived or worked (without protective regulations) on the
Lowry Site, the excess cancer risk could be 1 x 10-5 from ingestion or inhalation of contaminants.

There would be no reduction of toxicity, mobility or volume under the No Further Action Alternative. By
maintaining the existing landfill cover, risks from exposure to the solids would be minimized.

The following major ARARs have been identified for this alternative:

Criteria for Classification of Solid Waste Disposal Facilities and Practices (40 CFR Part 257):
This reguirement establishes criteria for use in determining which solid waste disposal
facilities and practices pose a reasonable probability of adverse effects on health or the
environment. This reguirement would be relevant and appropriate to maintenance of the landfill
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cover and would be met through proper maintenance of the cap.

• Regulations Concerning Municipal Solid Waste Landfills (40 CFR Part 258): This reguirement
establishes the design and operational criteria for solid waste landfills. The operational
criteria would applicable to closure and would be met through proper maintenance of the cap.

The total 30-year present worth cost of this alternative is $7,260,000, with capital costs of $36,000 and
annual O&M costs of $470,000. The No Further Action Alternative could be implemented immediately.

8.4.3.2 Alternative LFS-3-Clav Cap

Under Alternative LFS-3, all existing interim measures identified in the No Further Action Alternative would
continue. In addition to the existing soil cover for the landfill mass, a clay cap would be placed in the
former tire pile area over areas where drums and waste pits have been identified. This cap would provide an
additional physical barrier that would reduce the potential for contact with contaminated solids and reduce
infiltration, thus reducing additional ground-water contamination. The drums at or near the surface
(approximately 10 drums) would be removed for offsite disposal at a Subtitle C landfill. Additionally,
approximately 600 tires from the unnamed creek area would be removed and placed against the north toe of the
landfill mass area. This alternative would be simple to implement because it involves common earthwork.

There would be no treatment components associated with this alternative.

The containment component of this alternative would be the placement of a 24-inch clay cap in the former tire
pile area (approximately 1.9 acres) where several metal anomalies and drums have been identified. The area
would be revegetated after the cap was placed. Containment of the landfill mass solids would also be achieved
by proper maintenance of the existing cover on the landfill.

Although waste would be left in place (approximately 12 million cubic yards of solids), risks would be
reduced because use the potential for exposure to the contaminated solids in the landfill mass and the former
tire pile area would be decreased due to the cap. No treatability testing was conducted during the RI/FS
that relates specifically to this alternative.

Maintenance of the existing landfill mass cover would be performed in compliance with RCRA Subtitle D
regulations. The former tire pile area clay cap would meet pertinent criteria for RCRA Subtitle D landfills.
The drums at or near the surface would be removed offsite for disposal. These drums would be transported and
disposed of at a RCRA Subtitle C facility which complies with the Superfund Offsite Policy.

The major ARARs for this alternative would be the same as those identified for Alternative LFS-2 and would be
met by this alternative using similar methods.

The total 30-year present worth cost of this alternative is $6,970,000, with capital costs of $670,000 and
annual O&M costs of $410,000. The estimated time to implement Alternative LFS-3 would be 1 year.

8.4.3.3 Alternative LFS-4-Drum Removal/Off site Disposal

Under Alternative LFS-4, all existing interim measures identified in the No Further Action Alternative would
continue. The alternative consists of continued maintenance of the existing cover on the landfill mass;
surface and subsurface drum removal from the former tire pile area (approximately 1,350 drums); offsite
treatment and disposal of drums, drum contents, and contaminated soils from near the drums at an offsite RCRA
Subtitle C facility. The excavated areas would be backed and revegetated.

Liguids in drums (estimated at 1,300 gallons) removed would be transported to an offsite RCRA Subtitle C
facility for incineration and ash stabilization. Treatment by incineration is expected to result in a 99.99
percent reduction in contaminants.

Containment of the landfill mass solids would be achieved by proper maintenance of the existing cover on the
landfill.

This alternative would result in the removal of approximately 1,350 drums and contaminated material
surrounding drums in the former tire pile area. All solids in the landfill mass (approximately 12 million
cubic yards) would be left in place. Risks in the former fire pile area from the unsaturated solids would be
reduced by excavation and offsite treatment and disposal of these materials. Risks posed by the landfill
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mass would be reduced by decreasing the potential for exposure to the solids through maintenance of the
cover.

This remedy would be implementable because it utilizes conventional eguipment, construction technigues, and
established treatment and disposal facilities. Institutional controls such as access controls and land use
restrictions would be reguired to limit access to the Lowry Site.

Because solids in the landfill mass would not be treated or moved, residual levels would be the same as the
initial levels; solids in the former tire pile area would be excavated, treated, and disposed to achieve the
performance standards. This alternative assumes that solids in the former tire pile area would only be
excavated down to the depth of ground water.

The major ARARs for this alternative would be the same as those for Alternative LFS-2 and would be met by
this alternative using similar methods.

The total 30-year present worth cost of this alternative is $8,700,000, with capital costs of $2,400,000 and
annual O&M costs of $410,000. The estimated time to implement Alternative LFS-4 would be 6 months.

8.4.3.4 Alternative LFS-6-Drum Removal/Low Temperature Thermal Desorption/Stabilization/Disposal

Under Alternative LFS-6, all existing interim measures identified in the No Further Action Alternative would
continue. In addition, this alternative would consist of continued maintenance of the existing cover on the
landfill mass area; surface and subsurface drum removal from the former tire pile area (approximately 1,350
drums); offsite treatment and disposal of the drums and drum contents; treatment of approximately 4,200 cubic
yards of contaminated soil through desorption, stabilization, fixation and onsite disposal, and reclamation
of the former tire pile area.

Containment of the landfill mass solids would be achieved by proper maintenance of the existing cover on the
landfill.

All solids in the landfill mass (approximately 12 million cubic yards) would be left in place. Risks posed
by the landfill mass would be reduced by reducing the potential for exposure to the solids through
maintenance of the cover. Risks posed by the former tire pile area would be reduced by removing and treating
the contaminated soil to the performance standards.

Results of treatability tests conduction during the RI/FS indicated that low temperature thermal desorption
would meet cleanup levels. This alternative would be implementable because it would utilize conventional
eguipment and construction technigues, and established treatment and disposal facilities. Institutional
controls such as access restrictions and land use restrictions would be reguired. This alternative might be
difficult to implement if soils were encountered with different contaminants than those encountered for the
treatability study. This alternative assumes that the soils used in the treatability study would be
sufficiently similar to those in the former tire pile area to allow treatment levels to be met.

Because solids in the landfill mass would not be treated or moved, residual levels would be the same as the
initial levels; solids in the former tire pile area would be excavated down to the depth of ground water to
meet the performance standards.

Maintenance of the existing landfill mass cover would be performed in compliance with RCRA Subtitle D
regulations. Overpacked drums and bulk liguids would be transported to an offsite RCRA Subtitle C facility
for incineration and ash stabilization. Approximately 4,200 cubic yards of contaminated sod would be
excavated and treated through low temperature thermal desorption to separate volatile and semivolatile
organic compounds from soils. The treatment would be followed by stabilization of the soils to minimize
leaching of inorganic compounds from the soils. The stabilization would result in an increase in volume to
6,000 cubic yards. The soils would be TCLP-tested and, if they were not found to be RCRA characteristic
wastes, would be disposed in an onsite RCRA Subtitle D disposal cell.

Waste residuals produced by low temperature thermal desorption treatment technologies would include
condensate and treated soils. The condensate would be transported to an offsite RCRA Subtitle C facility for
incineration, and the treated soils would be stabilized ands disposed onsite. Vented gas produced through
the operation of the low temperature thermal system would meet standards outlined in the Clean Air Act, and
the Colorado Air Quality Act/Colorado Air Pollution Regulations.

The thermal desorption unit would be an existing unit on a trailer; retention time in the treatment unit
would be 1 to 5 hours.

The major ARARs identified for Alternative LFS-2 also apply to this alternative and would be met by this
alternative using similar methods. In addition, the following major ARARs have been identified:
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• Standards for Owners and Operators of Hazardous Waste Treatment, Storage, and Disposal
Facilities (40 CFR Part 264 and 6 CCR 1007-3 Part 264): This requirement establishes standards
for the design and operation of hazardous waste facilities and closure and post-closure care.
This requirement would be applicable if solids (including the soils) are identified as a RCRA
hazardous waste and relevant and appropriate if solids are sufficiently similar to RCRA
hazardous waste. In either event, the low temperature thermal desorption unit would be
constructed and operated to comply with these requirements.

Land Disposal Restrictions (40 CFR Part 268 and 6 CCR 1007-3 Part 268): This requirement
establishes prohibitions on land disposal unless treatment standards are met. If soils were
determined to be a hazardous waste, these restrictions would be applicable for disposal of the
soils following treatment. The soils would meet these requirements before disposal.

Colorado Air Quality Act/Colorado Air Pollution Regulations (5 CCR 1001): These regulations
establish standards for air emissions from stationary sources. These regulations are
applicable because the low temperature thermal desorption system is a source of air emissions
and would be met for the low temperature thermal treatment process.

The total 30-year present worth cost of this alternative is $11,500,000 with capital costs of $5,200,000 and
annual O&M costs of $410,000. The estimated time to implement Alternative LFS-6 would be 1 year.

8.4.3.5 Alternative LFS-7-Landfill Mass Regrading

Under Alternative LFS-7, all existing interim measures identified in the No Further action Alternative would
continue. In addition, under this alternative all existing wastepit liquid, gas, and ground-water monitoring
wells would be abandoned. The soft cover in the former tire pile area would be maintained. The top layers
of the existing landfill mass cover would be stripped and the clay stored temporarily. The landfill mass in
Section 6 would be regraded by placing approximately 1.2 million cubic yards of additional municipal solid
waste on top of the existing landfill and then the clay cover would be placed. An additional 2-foot clay
layer would be placed on the north face of the landfill mass to minimize infiltration and erosion.

There are no treatment components associated with this alternative. Containment of the landfill mass solids
would be achieved by proper maintenance of the new cover on the landfill. All waste would be left in place
(approximately 12 million yards).

No treatability testing was conducted during the RI/FS that relates specifically to this alternative. This
alternative is implementable because it would utilize conventional equipment and construction techniques, and
established disposal facilities. Institutional controls such as access restrictions and land use
restrictions would be required. Maintenance of the new landfill cover would continue.

The following major ARARs have been identified for this alternative:

Criteria for Classification of Solid Waste Disposal Facilities and Practices (40 CFR Part 257)
and Regulations Concerning Municipal Solid Waste Landfills (40 CFR Part 258): These
requirements establish design and operational criteria for all new municipal solid waste
landfills. These requirements would be applicable to future land filling actions at the Lowry
Site. As proposed, this alternative would not meet these requirements because it would not
include the necessary liner and leachate collection system.

Colorado Solid Wastes Disposal Sites and Facilities Act (6 CCR 1007-2): This requirement
establishes standards for municipal solid waste disposal facilities. This requirement would be
applicable to future landfilling actions at the Lowry Site. As proposed, this alternative
would not meet this requirement because the regulation requires that new municipal solid waste
disposal facilities be constructed with engineering liners and leachate collection systems on a
stable sub-base. This alternative does not include these components.

The total 30-year present worth cost of this alternative is $5,380,000, with capital costs of $0 and annual
O&M costs of $350,000. The estimated time to implement Alternative LFS-7 would be 9 months.

8.4.3.6 EPA's Preferred Alternative-Modified Alternative LFS-4-Drum Removal/Offsite Disposal/North Face Cover

Under Modified Alternative LFS-4, all existing interim measures identified in the No Further Action
Alternative would continue. Alternative LFS-4 was modified to increase the volume of soils excavated,
treated, and disposed offsite by including excavation of contaminated materials associated with unsaturated
waste pits in the former tire pile area. Excavation would include waste-pit solids and surrounding
contaminated soil and would reduce contamination sources and thus, reduce adverse risks.
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This alternative consists of continued maintenance of the existing soil cover on the landfill mass;
excavation of approximately 10 surface and 1,350 subsurface drums, contaminated soils associated with the
drums to a depth of 15 feet, and excavation of approximately 15,000 cubic yards of contaminated materials
associated with waste pits to a depth of three feet beneath the bottom of each pit within the former tire
pile area; offsite treatment and disposal of drums, drum contents, and contaminated soils; and reclamation of
the former tire pile area.

This alternative also modifies Alternative LFS-4 to include an additional two feet of soil cover on the north
slope of the landfill mass. This additional cover would further reduce risk from landfill solids by
decreasing the potential for contact with contamination from landfill solids and by minimizing infiltration
and erosion.

Liguids in drums removed (estimated at 1,300 gallons) would be transported to an offsite RCRA Subtitle C
facility for incineration and ash stabilization. Treatment would be expected to result in a 99.99 percent
reduction of contaminants.

Containment of the landfill mass solids would be achieved by proper maintenance of the existing cover on the
landfill. Landfill solids in the landfill mass would remain in place. Approximately 15,00 cubic yards of
contaminated material would be removed from the former tire pile area.

Risks would be reduced because of the diminished potential for exposure to contaminated solids. Risks in the
former tire pile area from the unsaturated solids would be eliminated by excavation of these materials.

This alternative is implementable because it would utilize conventional eguipment and construction
technigues, and established treatment and disposal facilities. Institutional controls such as access
restrictions and land use restrictions would be reguired.

Because solids in the landfill mass would not be treated or moved, residual levels would be the same as the
initial levels; solids in the former tire pile area would be excavated to the performance standards and
treated and disposed offsite.

The major ARARs identified for this alternative are the same as those identified for Alternative LFS-2 and
would be met by this alternative using similar methods.

The total 30-year present worth cost of this alternative is $13,460,000 with capital costs of $8,600,000 and
annual O&M costs of $316,000. The estimated time to implement Modified Alternative LFS-4 Alternative would
be 1 year.

8.4.3.7 Alternative LFG-2-No Further Action

Under LFG-2, the No Further Action Alternative for landfill gas, no additional remedial action would be
undertaken to treat, contain, or remove landfill gas. The perimeter gas monitoring program at existing gas
probes would be continued. Existing sitewide operational measures such as cover maintenance, site access
restrictions and security, and interim remedial measures would continue to be maintained.

There are no treatment or containment associated with this alternative. There would be no reduction of
toxicity, mobility, or volume. This alternative would not be protective of human health and the environment
because it would not prevent gas migration from occurring.

The Baseline Risk Assessment indicated that if people lived on the Lowry Site, there would be a probability
that 100% of the population would contract cancer from exposure to vinyl chloride and other contaminants in
landfill gas. In addition, there would be risks of injury due to explosion and adverse health effects to
individuals exposed to landfill gas on or offsite.

The following major ARARs have been identified for this alternative:

Criteria for Classification of Solid Waste Disposal Facilities and Practices (40 CFR Part 257)
and Regulations Concerning Municipal Solid Waste Landfills (40 CFR Part 258): These
reguirements establish design and operational criteria for all new municipal solid waste
landfills. These reguirements are relevant and appropriate because the Lowry Site operated as a
landfill and accepted municipal solid waste. These reguirements might not be met because
landfill gas might migrate offsite above the regulated limits in the future.

Colorado Solid Wastes Disposal Sites and Facilities Act (6 CCR 1007-2): This reguirement
establishes standards for municipal solid waste disposal facilities. This reguirement would be
applicable to the closed landfill at the Lowry Site. The reguirement might not be met because
landfill gas might migrate offsite above the regulated limits in the future.
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The total 30-year present worth cost of this alternative is $943,000, with capital costs of $36,000 and
annual O&M costs of $59,000. The No Further Action Alternative could be implemented immediately.

8.4.3.8 Alternative LFG-3-Gas Collection/Enclosed Flare

Alternative LFG-3 for Landfill Gas involves the placement of gas collection wells in the interior and at the
perimeter of the former landfill area and treatment of the gas by an enclosed flare. It also incorporates
all elements of Alternative LFG-2. The main objective of this gas collection system is to prevent lateral
migration of gas offsite. This alternative would be implemented in stages. The staged approach would be to
add gas collection wells, as necessary, to control gas migration.

• Stage 1 would involve constructing approximately seven perimeter collection wells and two
interior collection wells.

• Stage 2 would be implemented if gas monitoring indicates that gas is migrating beyond the
perimeter of the landfill mass. Stage 2 would add approximately 14 perimeter collection wells.

• Stage 3 would add approximately 26 gas extraction wells in the interior if Stages 1 and 2 did
not prevent gas migration at the perimeter.

To supplement the existing gas monitoring network, additional gas monitoring probes would be installed along
the perimeter of the Lowry Site to improve the gas monitoring system (approximately 26 probes would be added
to the existing 17 probes). The gas monitoring probes would be analyzed for methane and VOCs. The levels of
methane and VOCs would be compared to performance standards to determine if the extraction system was
effective in preventing offsite gas migration and if Stages 2 and 3 were necessary.

All existing gas, waste-pit liguid, and ground-water monitoring wells within the landfill mass would be
abandoned to eliminate the potential for vertical gas migration from the wells.

The collected gas would be treated at approximately 750 standard cubic feet per minute (scfm) per day using
an enclosed flare with an 8-foot-diameter stack approximately 40 feet high. It is estimated that treatment
would result in approximately 98 percent destruction of VOCs. Condensate collected in the gas collection
system would be treated in the existing ground-water treatment system.

Approximately 15 tons per year of VOCs would be treated using Stage 1 only and approximately 40 tons per year
of VOCs would be treated using Stage 2. Treatability testing was conducted as part of the FS. This
alternative would be implementable because the system would use established and reliable technologies.
Institutional controls such as ms restrictions and land use restrictions would be required. Residual levels
would achieve performance standards because extraction would continue until the standards were met. This
alternative assumes that methane would continue to be generated in quantifies sufficient to operate the
flare.

The potential for adverse offsite risk (health and explosion) would be significantly reduced through the
collection and treatment of gas.

The following major ARARs have been identified for this alternative:

Clean Air Act [including NAAQS (40 CFR Part 50), NESHAPS (40 CFR Part 61), and NSPS (40 CFR
Part 60)]: These requirements establish emissions standards for air pollutants. NAAQS would
be applicable, and NESHAPS and NSPS would be relevant and appropriate because gas would be
flared under this alternative. These requirements would be met at the compliance boundary.

Colorado Air Quality Control Act/Colorado Air Pollution Regulations (5 CCR 1001) : These
regulations establish standards for air emissions from stationary sources. These regulations
would be applicable during construction and operations activities, and would be met by this
alternative.

• Regulations Concerning Municipal Solid Waste Landfills (40 CFR Part 258): This requirement
establishes design and operational criteria for all new municipal solid waste landfills. This
requirement would be relevant and appropriate because the Lowry Site operated as a landfill and
accepted municipal solid waste. The regulations include controls for explosive gas. The
requirement would be met because landfill gas would be prevented from migrating offsite.
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• Proposed Standards of Performance for New Stationary Sources and Guidelines for Control of
Existing Sources-Municipal Solid Waste Landfills (40 CFR Part 60, Subpart WWW): This
requirement establishes performance standards for new stationary sources. This requirement
would be a to-be-considered (TBC) regulation because the standards are proposed. Landfill gas
would be collected and flared, and would meet these proposed standards.

The total 30-year present worth cost of Stage 1 of Alternative LFG-3 is $7,970,000, with capital costs of
$3,200,000 and annual O&M costs of $310,000. The estimated time to implement Stage 1 of the LFG-3
Alternative would be 6 months.

The total 30-year present worth cost of Stage 2 Alternative of LFG-3 is $8,830,000, with capital costs of
$3,600,000 and annual O&M costs of $335,000. These costs include the costs for implementation of Stage 1.
The estimated time to implement Stage 2 of the LFG-3 Alternative would be 6 months.

The total 30-year present worth cost of Stage 3 Alternative of LFG-3 is $12,930,000 with capital costs of
$5,200,000 and annual O&M costs of $503,000. These costs include the costs for implementation of Stages 1
and 2. The estimated time to implement Stage 3 of the LFG-3 Alternative would be 6 months.

8.4.3.9 Alternative LFG-5-Gas Collection with Heat Recovery

Alternative LFG-5, for Landfill Gas, includes all of the components of Alternative LFG-3. This alternative
would add a heat recovery system which would utilize heat from the enclosed flare for onsite use. At this
time, a practical and economical use for this heat, such as healing offices or maintenance facilities, has
not been identified. Approximately 15 tons per year of VOCs would be treated using Stage 1 only and
approximately 40 tons per year of VOCs would be treated using Stage 2.

The major ARARs identified for this alternative are the same as those identified for Alternative LFG-3 and
would be met by this alternative using similar methods.

The total 30-year present worth cost of Stage 1 of Alternative LFG-5 is $8,510,000, with capital costs of
$3,700,000 and annual O&M costs of $313,000. The estimated time to implement Stage 1 of the LFG-5
Alternative would be 6 months.

The total 30-year present worth cost of Stage 2 of Alternative LFG-5 is $9,330,000, with capital costs of
$4,100,000 and annual O&M costs of $340,000. These costs include the costs for implementation of Stage 1.
The estimated time to implement Stage 2 of the LFG-5 Alternative would be 6 months.

The total 30-year present worth cost of Stage 3 of Alternative LFG-5 is $13,510,000, with capital costs of
$5,700,000 and annual O&M costs of $508,000. These costs include the costs for implementation of Stages 1
and 2. The estimated time to implement Stage 3 of the LFG-5 Alternative would be 6 months.

8.4.3.10 EPA's Preferred Alternative-Modified Alternative LFG-3-Gas Collection/Enclosed Flare

EPA's preferred alternative, Modified Alternative LFG-3 for Landfill Gas, includes Stages 1 and 2 of
Alternative LFG-3, to be implemented simultaneously. By combining these stages, the potential for gas
migration would be decreased, minimizing exposure and thus reducing risks.

Rather than immediately removing existing wells as in Alternative LFG-3, EPA would evaluate existing gas,
waste-pit liquid, and ground-water monitoring wells within the landfill for future use. Wells that are no
longer effective would be abandoned.

Approximately 21 perimeter collection wells and two interior collection wells would be installed to intercept
migrating gas, and the gas would be treated with an enclosed flare. Approximately 26 additional gas
monitoring wells would be installed along the perimeter of the Lowry Site to improve the perimeter gas
monitoring system (17 gas monitoring wells currently exist onsite). If EPA determines that the combined
Stages 1 and 2 efforts are unsuccessful in preventing migration or meeting performance standards, Stage 3
would be activated and would involve installation of approximately 26 interior collection wells.

Approximately 40 tons per year of VOCs would be treated using Stage 2. The gas would be treated at a rate of
approximately 2,000 scfm per day using an enclosed flare with an 8-foot-diameter stack approximately 40 feet
in height. Condensate collected in the gas collection system would be treated in the existing ground-water
treatment system. It is estimated that treatment would achieve approximately 98 percent destruction of VOCs.

There would be no containment components associated with this alternative.

Treatability testing was performed during the FS and showed that cleanup levels can be met. This alternative
would be implementable because the systems would use established and reliable technologies. Institutional
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controls including access restrictions and land use restrictions would be required. Residual levels would
achieve performance standards because extraction would continue until the standards were met. This
alternative assumes that methane would continue to be generated in quantities sufficient to operate the
flare.

The major ARARs identified for this alternative are the same as those identified for Alternative LFG-3 and
would be met by this alternative using similar methods.

The total 30-year present worth cost of EPA' s preferred alternative, Modified Alternative LFG-3, is
$8,430,000 with capital costs of $3,200,000 and annual O&M costs of $340,000. The estimated time to
implement Modified Alternative LFG-3 would be 6 months. If Stage 3 were required, it is estimated that
capital costs would increase by $1,575,000. O&M costs would require an additional $168,000 per year and the
total present worth would increase by $4,160,000.

8.4.4 OUs 4 &5- Soils, Surface Water, and Sediments

The following alternatives were evaluated in detail during the FS for OUs 4&5, and were described in the
Proposed Plan for OUs 2&3 and 4&5, issued in August 1993:
Soils (OU 4)
Alternative SOIL-1, No Further Action;
Alternative SOIL-2, Access Restrictions and Dust Controls;
Alternative SOIL-4a, Option 1, Excavation (as needed) and Landfill (onsite)
Alternative SOIL-4a, Option 2, Excavation (one time) and Landfill
Alternative SOIL-4b Option 1,
and
Alternative SOIL-4b Option 2,
(onsite);
(offsite),
Excavation (as needed) and Landfill

Excavation (one time) and Landfill (off site)
Surface Water (OU 5)
No Further Action.
Section 6 Sediments (OU 5)
Alternative SED6-1, No Further Action; and
Alternative SED6-2, Access Restrictions.

Section 31 Sediments (OU 5)

Alternative SED31-1, No Further Action;
Alternative SED31-2, Access Restrictions and Capping; and
Alternative SED31-3, Excavation and Landfill.

These alternatives are described in the following paragraphs. Major ARARs are identified for each
alternative. Additional ARARs for OUs 4&5 alternatives are presented in Table 8-3.

8.4.4.1 EPA 's Preferred Alternative-Alternative SOIL-1-No Further Action

Under Alternative SOIL-1, the No Further Action Alternative for soil, no additional remedial action would be
undertaken to treat, contain, or remove contaminated soil. Contaminated soil consists of approximately 2.5
million cubic yards contaminated with low levels of arsenic, beryllium, polychlorinated biphenyls, and
dioxins/furans.

This alternative would include maintenance of the SWRA, including the barrier wall, and existing
institutional controls; performance and compliance monitoring associated with the collection system and
treatment facility; and continued operation of the SWRA. The landfill in Section 6 would remain closed and
the existing landfill mass cover would be maintained. The existing soil cover in the former tire pile area
would be maintained.
Existing Lowry Site access and land use restrictions would continue; fencing and vegetative cover would be
maintained. Visual monitoring of the soil areas would be carried out to identify areas of erosion. Periodic
monitoring of the surface water runoff would be conducted to determined if any contaminated is migrating
offsite. One automated surface water runoff sampler would be installed in the Section 31 drainage to monitor
the runoff.
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There would be no treatment components associated with this alternative. There would be a continuation of
existing institutional controls including site fencing, signage, access and land use restrictions.

All of the soil (approximately 2.5 million cubic yards) would be left untreated on site. Contaminated soil
spans approximately 103 acres in the northern half of Section 6. The area is divided into two portions, one
east of the unnamed creek and the other west of the unnamed creek. Because the soil would not be treated or
removed under this alternative, the residual contaminant levels would be the same as the initial levels.

The Baseline Risk Assessment calculated a combined maximum excess cancer risk of 3 x 10-5 for a future
resident adult and a future resident child from the ingestion and inhalation of soil contaminated with
arsenic, beryllium, polychlorinated biphenyls, and dioxins/furans within the sewage sludge
application/leachate injection area (Group 1). The Baseline Risk Assessment estimated that the cancer risk
posed to human health and the environment by soil at the Lowry Site were within EPA's acceptable risk range.
A noncancer HI greater than 1 was estimated for a future resident child that ingest and inhales soil from the
sewage sludge application/leachate injection area (Group 1) or the sewage sludge application area (Group 2).
Although there would be no reduction in toxicity, mobility or volume through treatment, the No Further Action
Alternative would be protective of human health and the environment because estimated cancer risk is within
the acceptable range and noncancer risk would be controlled by land use restrictions.

No treatability testing was performed during the RI/FS for soil because the alternatives considered are
proven technologies. This alternative would be fully implementable. The automated surface water sampler
would be installed within the first year.

The following major ARARS have been identified for this alternative:

Colorado Air Quality Control Act/Colorado Air Pollution Regulations (5 CCR 1001): These
regulations establish standards for air emissions from stationary sources. These regulations
would be applicable during maintenance activities for the vegetated soft cover and would be met
by this alternative.

The RAOs would be achieved for this alternative through institutional controls which would reduce the
disturbance of and exposure to the soil.

The total 30-year present worth cost of this alternative is $390,000 with capital costs of $22,000 and annual
O&M costs of $24,000. The estimated time to implement the No Further Action alternative would be less than 1
year.

8.4.4.2 Alternative SOIL-2-Access Restrictions and Dust Control

Alternative SOIL-2 would include installation of 13,200 linear feet of 6-foot-high chain link fence topped
with three strands of barbed wire to restrict access to the Site. In addition, the elements of Alternative
SOIL-1, the No Further Action alternative would be included.

As a dust control and prevention measure, approximately 103 acres of the soil would be regraded, covered with
six inches of topsoil, and vegetated with seed and mulch as a dust control and erosion prevention measure.
Additionally, during revegetation and fence installation activities, water spraying would be used to minimize
generation of fugitive dust. Existing site access land use restrictions regarding use of the site surface,
surface water, and ground water would be continued.

Visual monitoring of the soil and vegetative cover would be performed on a monthly basis. Annual monitoring
of the surface water runoff would be carried out to evaluate potential for contaminant migration. One
automated surface water runoff sampler would be installed in the Section 31 drainage to monitor the runoff.

There would be no treatment components associated with this alternative.

This alternative would contain the soil via placement of the topsoil and vegetative cover. The potential for
chemical migration through air-borne particulates and runoff erosion would be reduced because of the topsoil
and vegetative cover over the soil. All of the soil (approximately 2.5 million cubic yards) would be left
untreated onsite; but since the soil would be covered, the risks from inhalation and ingestion of soil would
be eliminated.

The Baseline Risk Assessment estimated that the cancer risks posed to human health and the environment by
soil at the Lowry Site were within EPA's acceptable risk range. The noncancer HI greater than 1 was
estimated for a future resident child that ingests and inhales onsite soil. Under this alternative since the
soil would be covered, the risks from inhalation and ingestion of soil would be eliminated.
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Because the soil would not be treated under this alternative, the residual contaminant levels would be the
same as the initial levels. However, exposure pathways would be incomplete and risk would not be present.

No treatability testing was performed for soil, because the alternatives considered are proven technologies.
This alternative would be implementable because it uses proven methods of remediation. The automated surface
water sampler would be installed within the first year.

The following major ARARs have been identified for this alternative:

Although fence installation, soil grading and vegetation activities might increase the potential for
short-term exposure and habitat disturbance, the RAOs would be achieved for this alternative through a
reduced potential for long-term exposure to the soil. Toxicity, mobility, and volume of the contaminants
would not be reduced by this alternative.

The total 30-year present worth cost of this alternative is $2,080,000 with capital costs of $1,400,000 and
annual O&M costs of $44,000. The estimated time to implement Alternative SOIL-2 would be 1 year.

8.4.4.3 Alternative SOIL-4a Excavation and Landfill (onsite)

Alternative SOIL-4a for soil would include excavation of approximately 2.5 million cubic yards of
contaminated soft to a depth of 15 feet. The excavated soils would then be used as a daily cover in the
onsite landfilling operations. In addition, the elements of the Alternative SOIL-1, No-Further Action, would
be included.

Contaminated soil consists of approximately 2.5 million cubic yards contaminated with low levels of arsenic,
beryllium, polychlorinated biphenyls, and dioxins/furans. The soil spans approximately 103 acres in the
northern half of Section 6. The area is divided into two portions, one east of the unnamed creek and the
other west of the unnamed creek.

There are two options for excavation:

• Option 1-Excavate soft on an as needed basis for daily landfill cover; or

• Option 2-Excavate soft at one time and stockpile material for use as daily cover in landfill.

RCRA Subtitle D landfill cells would be constructed on Section 6 in which the excavated soil would be used as
the daily cover. The new landfill would receive municipal solid waste. Excavation of the soil would be to a
depth of 15 feet. The areal extent of the excavation would be 103 acres. Dust suppression technigues would
be used to minimize fugitive dust.

Land use restrictions that are currently in place regarding use of the site surface, surface water, and
ground water would be continued.

Annual monitoring of the surface water runoff would be carried out to evaluate potential for contaminant
migration. One automated surface water runoff sampler would be installed in the Section 31 drainage to
monitor the runoff. Installation of the sampler would be achieved within the first year.

Construction of additional landfill cells would be in compliance with the RCRA Subtitle D reguirements.
Landfill design would promote surface drainage, minimize erosion of the cover and reduce the potential for
precipitation permeation and leachate generation. Disposal of soil, in the form of daily cover over the
municipal solid waste, would result in the containment of the contaminants in the soil within the landfill.

There are no treatment components associated with this alternative.

All of the soil (approximately 2.5 million cubic yards) would be left untreated onsite. Because the soil
would not be treated or moved offsite under this alternative, the residual contaminant levels would be the
same as the initial levels. However, because the soils would be used as daily cover, exposure pathways would
be incomplete.

The Baseline Risk Assessment estimated that the cancer risks posed to human health and the environment by
soil at the Lowry Site were found to be already within EPA's acceptable risk range. Under this alternative,
the long-term risk from the ingestion and inhalation of soil would be eliminated because of the containment
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of the soil; however, there would be an increased potential for short-tern risk from dust generation during
excavation, stockpiling, and handling of the soil.

No treatability testing was carried out for soil, because the alternatives considered are proven
technologies. Construction of the additional landfill cells and complete utilization of the excavated soil
would be expected to take 10 years. In Option 2, onsite stockpiling would be difficult to implement because
of limited area available in Section 6, as well as the potential interference with the daily landfilling
activities.

Existing institutional controls would continue under this alternative.

The following major ARARs have been identified for this alternative:

• Regulations Concerning Municipal Solid Waste Landfills (40 CFR Part 258): This reguirement
establishes design and operational criteria for all new municipal solid waste landfills and
would be applicable because new landfill cells would be constructed. This standard would be
met through proper design and operation of the landfill cells.

Regulations Pertaining to Solid Waste Disposal Sites and Facilities (6 CCR 1007-2, Section 1):
This reguirement establishes standards for new solid waste disposal facilities. Standards for
design, construction and operation of landfill cells would be applicable because new landfill
cells would be constructed and soils would be land filled. These standards would be met
through proper design of the landfill cells.

Colorado Air Quality Act/Colorado Air Pollution Regulations (5 CCR 1001): These regulations
establish standards for air emissions from stationary sources. These regulations would be
applicable during construction and operations activities, and would be met by this alternative.

Although soil excavation, stockpiling and movement activities would increase the potential for short-term
exposure and habitat disturbance, the RAOs would be achieved for this alternative through a reduced potential
for long-term exposure to the soil. Neither toxicity nor volume of the contaminants would be reduced by this
alternative. Mobility would be significantly reduced because of the use of the soil as a daily cover in a
RCRA Subtitle D landfill.

The total 30-year present worth cost for Option 1 of this alternative is $490,000 with capital costs of
$43,000 and annual O&M costs of $29,000. The estimated time to implement Option 1 of Alternative SOIL4a
would be 10 years, at which point all contaminated soil would have been used as daily cover.

The total 30-year present worth cost for Option 2 of this alternative is $3,280,000 with capital costs of
$2,800,000 and annual O&M costs of $31,000. The estimated time to implement Option 2 of Alternative SOIL4a
would be 10 years, at which point all stockpiled soil would have been used as daily cover.

8.4.4.4 Alternative SOIL-4b, Excavation and Landfill (off site)

Alternative SOIL-4b for soil includes excavation of approximately 2.5 million cubic yards of contaminated
soil to a depth of 15 feet. In addition, all elements of Alternative SOIL-1, No-Further Action would be
included in this alternative. The contaminated soil spans approximately 103 acres in the northern half of
Section 6. The area is divided into two portions, one east of the unnamed creek and the other west of the
unnamed creek. Under this alternative, excavated soil would be transported to the Section 31 RCRA Subtitle D
landfill to be used as daily cover.

There are two options for excavation:

• Option 1-Excavate soil for daily landfill cover on an as needed basis; or

• Option 2-Excavate soil at one time and stockpile material for use in the landfill.

The areal extent of the excavation would be 103 acres. Dust suppression technigues would be used to minimize
fugitive dust. Under Option 2, the soil stockpile would be vegetated to minimize contaminant migration,
since the soil might be stockpiled up to 10 years.

Land use restrictions that are currently in place regarding use of the site surface, surface water, and
ground water would be continued. Annual monitoring of the surface water runoff would be carried out to
evaluate potential for contaminant migration. One automated surface water runoff sampler would be installed
in the Section 31 drainage to monitor the runoff.
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There would be no treatment components associated with this alternative.

Under Option 1, the soil would be used as a daily cover in the offsite landfilling operations in Section 31,
on an as needed basis. Under Option 2, excavated soil would require intermediate stockpiling for the
one-time excavation of all soil and would later be used as daily cover in the offsite landfilling operations
in Section 31. Dust control measures would be applied to the stockpile in the latter case.

All of the soil (approximately 2.5 million cubic yards) would be removed from the Lowry Site and transported
to Section 31 for use as daily cover. The existing contamination would be eliminated because the soil would
be excavated and moved offsite.

The Baseline Risk Assessment estimated that the cancer risks posed to human health and the environment by
soil at the Lowry Site were found to be already within EPA's acceptable risk range. Under this alternative,
the long-term risk from ingestion and inhalation of soil would be eliminated; however, there would be a
potential for short-term risk from dust generation during excavation, stockpiling and additional handling of
the soil. No treatability testing was carried out for soil, because the alternatives considered are proven
technologies.

Construction of the additional landfill cells as well as complete utilization of the excavated soil would be
expected to take 10 years. Installation of the automated surface water sampler would be achieved within the
first year. Existing institutional controls would continue under this alternative.

The following major ARARs have been identified for this alternative:

Colorado Air Quality Act/Colorado Air Pollution Regulations (5 CCR 1001): These regulations
establish standards for air emissions from stationary sources. These regulations would be
applicable during construction and operations activities, and would be met by this alternative.

Although soil excavation and transport to Section 31 would increase the potential for short-term exposure and
habitat disturbance, the RAOs would be achieved for this alternative through a reduced potential for
long-term exposure to the soil.

The total 30-year present worth cost for Option 1 of this alternative is $1,880,000 with capital costs of
$1,200,000 and annual O&M costs of $44,000. The estimated time to implement Option 1 of Alternative SOIL4b
would be 10 years, at which point all contaminated soil would have been used as daily cover.

The total 30-year present worth cost for option 2 of this alternative is $4,800,000 with capital costs of
$4,000,000 and annual O&M costs of $52,000. The estimated time to implement Option 2 of Alternative SOIL-4b
would be 10 years, at which point all excavated soil would have been used as daily cover.

8.4.4.5 EPA's Preferred Alternative- Alternative SW-l-No Further Action

Alternatives for surface water were previously evaluated under the Surface Water Removal Action Engineering
Evaluation and Cost Analysis. During the RI/FS process, the SWRA was evaluated for incorporation into the
overall selected remedy. This evaluation included an assessment of the effectiveness, implementability, and
cost of the SWRA, as well as the statutory considerations in CERCLA Section 121(b)(1). Upon the initial
screening of the alternatives, it was determined that the SWRA met the evaluation criteria and should
therefore be retained for detailed analysis as the No Further Action alternative.

This alternative includes the O&M of the barrier wall; the SWRA, including both the collection system and
upgrades to the GWTP; and the enforcement of the existing institutional controls, such as fencing and
signage, and restrictions on land uses, site access, well drilling, and residential development. Additional
measures would include construction of wetlands in accordance with the SWRA Consent Order and implementation
of a long-term monitoring program.

The ground-water barrier system and GWTP is an interim remedial measure implemented pursuant to Consent
Order, EPA Docket No. CERCLA VIII-83-06 (signed January 10, 1984) and is designed to reduce the northern
offsite migration of contaminated ground water via the unnamed creek alluvium and weathered bedrock. The
barrier wall consists of a 1,000-foot-long drain backed by a 30-foot-deep compacted clay barrier located
immediately north of the Section 6 northern boundary. The drain and barrier function as a subsurface
collection system. Water collected in this system is pumped to the GWTP to treat volatile and semivolatile
organic compounds. The treated effluent is released via an injection trench into the alluvium of unnamed
creek north of the barrier wall. The GWTP was modified as part of the SWRA and may be further upgraded,
based on pilot-scale testing, to remove iron, manganese, vanadium, or other contaminants, if these are
detected above performance standards. These upgrades could include biological treatment or ion exchange.
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The SWRA interim remedial measure includes a seepage collection system in the Section 6 portion of the
unnamed creek drainageway, closure of Ponds 3 and 4, and modification of the existing GWTP. The SWRA was
completed in 1992 and is currently operational.

The SWRA collection system consists of a subsurface drainage system wrapped in geotextile that was
constructed within the unnamed creek channel in Section 6. The collection system is designed to keep the
contaminated alluvial flows separate from the uncontaminated surface water runoff. The system collects the
alluvial flows and directs them toward the barrier wall. The drainage system and the Section 6 sediments
located within unnamed creek have been covered by a compacted, fine-grained soil layer, which has been graded
into a broad, gently sloping drainage swale. This relatively low permeability soil layer keeps the
precipitation primarily as surface runoff and prevents it from contacting the covered sediments or entering
the drainage system. The uncontaminated surface water flows over the collection system and eventually
empties into Murphy Creek via the unnamed creek segment in Section 31.

Placement of a compacted 4-foot soil cover over the landfill mass in Section 6 was initiated in 1987. The
landfill mass cover was completed in 1992, vegetated, and graded to provide control of surface water runoff.
The cover efficiently drains precipitation-derived runoff from the landfill, thereby significantly reducing
the potential for infiltration of the runoff into the landfill mass.

Under the preferred alternative, annual monitoring of the surface water runoff into the unnamed creek
drainage would be conducted to evaluate the potential for contaminant migration, although the exposure
pathway to the Section 6 sediments has been eliminated as a result of the soil cover over the SWRA collection
system. An automated surface water runoff sampler would be installed in the drainage in Section 6 for the
purpose of monitoring offsite contaminant migration.

Before the SWRA was implemented, the natural storm water runoff and any underground seepage in the unnamed
creek basin in Section 6 constituted the contaminated media. The contaminated surface water medium, as it
existed before the construction of the SWRA collection system, has been eliminated. The SWRA collection
system effectively limits the contaminated seepage as an underground flow, and keeps it from mixing with
surface water. The SWRA collection system also isolates the sediments from the surface water and provides a
control on the sediment contamination migration. The SWRA collection system covers an area of approximately
4.8 acres.

The treatment of water in the upgraded treatment plant includes aerobic biodegradation treatment to reduce
the biological oxygen demand (BOD). Although the system is not specifically designed to remove particular
organic compounds, significant degradation of phenols, ketones and other biodegradable organic compounds is
expected in the system. The biodegradation system would be incorporated in the overall treatment train only
if EPA determines that phenols and ketones are anticipated based on the early warning monitoring data from
the access well. If iron, manganese, and vanadium are detected in the early warning monitoring system in
guantities above the performance standards, they would be precipitated from the water by addition of
potassium permanganate. The metals precipitation module has not been incorporated into the GWTP at the
present time.

Next, the water is air-stripped to remove volatile organic compounds. The off-gases from the stripper are
then passed through a vapor-phase activated carbon bed to adsorb stripped organics. Clean off-gas is vented
to the atmosphere.

Stripper bottoms or residuals may contain organics that are not biodegradable or strippable to any
significant extent; therefore, the stripper effluent is passed through a bed of liguid-phase carbon to adsorb
these organics. The effluent from the liguid-phase carbon polishing step must meet the performance standards
for injection downgradient of the barrier wall.

The chemical composition of the influent to the treatment plant is assumed. to be compounds detected in the
seepage water, ground water, and in waste-pit liguids. These chemicals consist of volatile and semivolatile
organics, iron, manganese, and vanadium. Existing data from the treatment plant show removal efficiencies of
95 percent or greater. Based on these measurements, approximately 80 pounds of contaminants would be removed
annually (assuming operation at 13 gpm).

The treatment plant has been designed for a combined seepage/ground water inflow of 30 gallons per minute
(gpm) with flexibility to handle flows from 10 to 50 gpm. The treatment process has been designed with
flexibility to handle a wide range of chemicals and concentrations that might need to be treated in the
future.

The SWRA has been designed and constructed to collect and treat contaminated seepage and ground water for at
least 30 years. It is anticipated that this system will be in operation as long as there is contaminated
seepage and/or ground water. If used, biodegradation and permanganate oxidation treatment would produce
treatment residuals or sludge which would be periodically dewatered, and drummed. The sludge would be tested
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to determine the disposal options. If the sludge tests to be hazardous, it would be disposed of in a RCRA
Subtitle C facility; otherwise, it would be disposed of in the Section 31 landfill.

Based on historic data from surface water in the unnamed creek onsite, risks were estimated as 8 x 10-4 for
ingestion by a child in the future onsite residential setting. The SWRA collection system has eliminated the
initial risk from the surface water because contaminated surface water does not exist anymore. Contaminated
underground seepage is treated in the GWTP to meet the SWRA ARARs. Thus, the risk from surface water has
been eliminated and would continue to be eliminated with this approach.

Treatability testing was performed to aid in the design of the original GWTP, modification to the GWTP for
the SWRA, and to test the compatibility of SWRA collection system materials with the contaminated seepage.

Except for the automated runoff sampler and construction of new wetlands, there are no initial measures to
implement in this alternative because the SWRA has already been implemented and is currently operational.
The sampler would be installed within the first year. A location and schedule for constructing the new
wetlands would be determined by EPA during the design phase.

Land use restrictions regarding use of the site surface, surface water, and ground water would be continued.
The GWTP effluent would meet the ARARs for the SWRA as updated in this ROD; therefore, the residual levels
would comply with performance standards.

The following major ARARs were identified for this alternative:

Safe Drinking Water Act, National Primary Drinking Water Regulations (40 CFR Part 141) and the
Colorado Primary Drinking Water Regulations (5 CCR 1003-1): These regulations would be
relevant and appropriate because the shallow and deep ground water in the vicinity of the Lowry
Site is being used or may be used in the future as a source of water for a public water system
or private supply wells. Under this alternative, treated ground water from the treatment plant
would be injected into the shallow ground-water system in compliance with these reguirements.

Safe Drinking Water Act, National Secondary Drinking Water Regulations (40 CFR Part 143):
These regulations establish welfare-based standards for public water supply systems and have
been adopted by the State of Colorado under the basic standards for ground water. The
regulations would be relevant and appropriate because the shallow and deep ground water in the
vicinity of the Lowry Site is being used or may be used in the future as a source of water for
a public water system or private supply wells. Under this alternative, ground water would be
treated to meet these standards and then discharged to the shallow ground-water system in
compliance with these reguirements.

Colorado Air Quality Act/Colorado Air Pollution Regulations (5 CCR 1001) : These regulations
establish standards for air emissions from stationary sources. These regulations are
applicable for treatment plant operations and would be met by this alternative.

• Executive Order 11990, Protection of Wetlands would be applicable because wetlands have been
identified at the Lowry Site and were destroyed as part of construction of the SWRA. New
wetlands would be constructed under this alternative to mitigate the loss of wetlands, thus
meeting the reguirements of this Executive Order.

Excavated sediments would be transported offsite for disposal in accordance with EPA's Offsite Policy (40 CFR
Section 300.400) .

The total 30-year present worth cost of this alternative is $12,190,000 with capital costs of $41,000 and
annual O&M costs of $790,000. The estimated time to implement the No Further Action alternative is 1 year.

The SWRA, GWTP and landfill cover remedies were developed and implemented earlier, independent of the
alternatives developed for OUs 4&5. Therefore, the capital expenditures associated with these remedies are
not considered part of the surface water alternatives developed in conjunction with the sitewide remedy and
presented here. However, because the upgrade and O&M of these facilities are consistent with the sitewide
remedial strategy, their costs are included in the No Further Action alternative.
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8.4.4.6 EPA's Preferred Alternative-Section 6 Sediments Alternative SED6-1-NO Further Action

The major feature of Alternative SED6-1, the No Further Action alternative for Section 6 sediments, is the
SWRA as described in Alternative SW-1.

Although the exposure pathway to the Section 6 sediments has been eliminated as a result of the soil cover
over the SWRA collection system, annual monitoring of the surface water runoff into the unnamed creek
drainage would be conducted to evaluate the potential for contaminant migration. For the purpose of
monitoring offsite contaminant migration, one automated surface water runoff sampler would be installed in
the drainage in Section 6 to monitor runoff.

Before implementation of the SWRA, sediments in the approximately 2,800-foot-long portion of the unnamed
creek in Section 6 constituted the contaminated media: However, during the construction of the SWRA
collection system, a polypropylene geotextile blanket and a 2-foot-thick low-permeability soil cap were
placed over the sediments. As a result, the sediments are no longer exposed.

There would be no treatment components associated with this alternative.

The containment component for the Section 6 sediments includes a geotextile and a low-permeability soil cap
in order to keep the surface water runoff from contacting the sediments or mixing with the contaminated
leachate from the landfill mass. The type of storage utilized by this alternative is in-place containment
under geotextile and soil cap. The areal extent of the sediments is conservatively estimated at 320,000
sguare feet. The volume of the sediments is unknown.

Based on the historic data on sediments, a maximum excess cancer risk of 9 x 10-6 was calculated for
ingestion of sediments by a child. By covering the sediments with a geotextile and a soil cap, the risk has
been eliminated. Geotechnical properties of the sediments were determined during the design of the SWRA
collection system. No other treatability studies were carried out for the sediments. Existing institutional
controls, including site fencing, signage, site access, and land use restrictions would be continued under
this alternative. Because the sediments would not be treated under this alternative, the residual levels
would be the same as the initial levels. However, exposure pathways would be incomplete.

There are no major action-, location-, or chemical-specific ARARs identified for this alternative.

The RAOs would be achieved for this alternative through elimination of exposure to the sediments. Neither
toxicity nor volume of the contaminants would be reduced by this alternative. The potential for mobilization
of the contaminants would still exist, since the underground seepage would flow through the sediments.
However, the seepage would be treated in the GWTP to meet the performance standards.

The total 30-year present worth cost of this alternative is $250,000 with capital costs of $16,000 and annual
O&M costs of $350,000. Except for the automated runoff sampler, there would be no initial measures to
implement in this alternative. The sampler would be installed within the first year.

8.4.4.7 Section 6 Sediments Alternative SED6-2-Access Restrictions

Alternative SED6-2 for Section 6 sediments would include the installation of 6,145 linear feet of 6-foot-high
chain link fence topped with three strands of barbed wire around the unnamed creek to restrict access to the
SWRA collection system cover over the sediments. The SWRA collection system would also be an integral part
of the alternative as described in Alternative SW-1.

The SWRA cover would be inspected after each significant rainfall or runoff. Surface water runoff would be
monitored annually so that EPA could determine whether contaminants were migrating offsite.

Contaminated media include sediments in the approximately 2,800-foot-long portion of the unnamed creek in
Section 6. During the construction of the SWRA collection system, a polypropylene geotextile blanket and a
2-foot-thick low permeability soil cap were placed over the sediments. As a result, the sediments are no
longer exposed.

There would be no treatment components associated with this alternative.
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The containment component for the Section 6 sediments would include a geotextile and a low permeability soil
cap in order to keep surface water runoff from contacting contaminated sediments or mixing with the
contaminated leachate from the landfill mass. Additionally, the fence around the Section 6 area would further
restrict access and potential exposure to the sediments. The fence would cover an area conservatively
estimated at 320,000 sguare feet. The exact area and volume of the sediments are unknown. The type of
storage utilized by this alternative would be in-place containment under geotextile and soil cap.

Based on the historic data on sediments, a maximum excess cancer risk of 9 x 10-6 was calculated for
ingestion of sediments by a child. By covering the sediments with a geotextile and a soil cap, the risk has
been eliminated. Geotechnical properties of the sediments were determined during the design of the SWRA
collection system to evaluate the use of sediments as a daily cover in the landfill. The sediments were
deemed unsuitable for use as a daily cover. No other treatability studies were carried out for the
sediments. Existing institutional controls including site fencing, signage, site access, and land use
restrictions would be continued under this alternative. The additional fencing of 6,145 feet around the
unnamed creek would further restrict access to the sediment area.

The residual levels would be the same as the initial levels, since the sediments would not be treated under
this alternative. In any event, exposure pathways would be incomplete.

The following major ARARs have been identified for this alternative:

Colorado Air Quality Act/Colorado Air Pollution Regulations (5 CCR 1001): These regulations
establish standards for air emissions from stationary sources. These regulations would be
applicable during construction activities and would be met by this alternative.

The total 30-year present worth of this alternative is $450,000 with capital costs of $93,000 and annual O&M
costs of $23,000. The estimated time to implement Alternative SED6-2 would be 1 year. Except for the
automated runoff sampler and the fence, there are no initial measures to implement in this alternative. The
sampler and the fence would be installed within the first year.

8.4.4.8 EPA's Preferred Alternative-Section 31 Sediments Alternative SED31-1-NO Further Action

Alternative SED31-1, The No Further Action alternative, would include continuation of the existing site
fencing, signage, site access, and land use restrictions. The contaminated media are the sediments in the
approximately 2,660-foot-long portion of the unnamed creek in Section 31, from the southern boundary of
Section 31 up to the confluence with Murphy Creek.

Annual monitoring of the surface water runoff into the unnamed creek drainage would be conducted to evaluate
the potential for contaminant migration. For the purpose of monitoring offsite contaminant migration, one
automated surface water runoff sampler would be installed in the drainage in Section 31.

There would be no treatment or containment components associated with this alternative. Approximately 23,700
cubic yards of the untreated sediments would be left in place under this alternative. The risk would remain
unchanged, since no treatment or containment of the sediments would be involved.

The Baseline Risk Assessment assumed the SWRA was no longer operational and future residences were built in
Section 31. An excess cancer risk of 7 x 10-5 was calculated for ingestion of sediments by a child. The
risk would not be reduced by this alternative. However, the risks associated with potential sediment
contaminant exposures is within the acceptable excess cancer risk range. A noncancer HI greater than 1 was
estimated for a future resident child that ingests and inhales sediments from this portion of Section 31. The
three chemicals that contribute to this HI have different target organs; therefore, the HI would be below 1
if the chemical-specific target organ was considered. In addition, land use restrictions would prevent
residential development on this Section. Thus, the No Further Action alternative for Section 31 would be
protective of human health and the environment.

No treatability testing was conducted during the RI/FS for the sediments, because the alternatives considered
are proven technologies. The residual levels would be the same as the initial levels, because the sediments
would not be treated under this alternative.

There are no action-, location-, or chemical-specific ARARs identified for this alternative.
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The RAOs would be achieved for this alternative through the existing restrictions on access and land uses.
Sediments would remain in place, but would be of concern only for a residential exposure (resident in Section
31). Toxicity, volume and mobility of the contaminants would not be reduced by this alternative.

The total 30-year present worth of this alternative is $300,000 with capital costs of $22,000 and annual O&M
costs of $18,000. The estimated time to implement Alternative SED31-1 would be 1 year.

8.4.4.9 Section 31 Sediments Alternative SED31-2-Access Restrictions and Capping

Alternative SED 31-2 for Section 31 Sediments would include a cap over the sediments, and approximately 5,400
linear feet of fence around the unnamed creek to restrict access to the sediments. Sediments in the
approximately 2,660-foot long portion of the unnamed creek in Section 31, from the southern boundary of
Section 31 up to the confluence of Murphy Creek constitute the contaminated media.

The cap would consist of approximately 10,800 sguare yards of a single layer of synthetic liner (60-mil
high-density polyethylene) over the unnamed creek drainageway in Section 31, overlain with a 6-inch layer of
gravel (approximately 1,700 cubic yards) and a 9-inch layer of riprap (approximately 2,500 cubic yards). A
total of 1.47 acres of the drainageway would be capped. Grading operations before the placement of the liner
would create fugitive dust. The dust would be suppressed with water sprays.

Grading might reguire removal of some sediments. These sediments would be characterized to determine if they
could be disposed of in a RCRA Subtitle D landfill. Capping of the sediments would claim approximately 1.27
acres of wetlands. New wetlands would be created in the Murphy Creek drainage or in an offsite area
appropriate for wetland development. Approximately 5,400 linear feet of 6-foot-high chain link fence topped
with three strands of barbed wire would be installed to restrict access to the sediments along the unnamed
creek segment in Section 31 up to the confluence with Murphy Creek. The alternative would also include
maintenance of the cap, wetlands, new site fencing, signage, site access, and land use restrictions.

Annual monitoring of the surface water runoff into the unnamed creek drainage would be conducted to evaluate
the potential for contaminant migration, although the exposure pathway to the Section 31 sediments would have
been eliminated as a result of the cap over the sediments. For the purpose of monitoring offsite contaminant
migration, one automated surface water runoff sampler would be installed in the drainage in Section 31 to
monitor runoff.

There would be no treatment components associated with this alternative.

The Section 31 sediments would be contained and covered with a liner in order to keep the surface water
runoff from contacting the sediments. Additionally, the fence around the sediment area would restrict access
to the sediments. Approximately 23,700 cubic yards of the untreated sediments would be left in place under
this alternative. The risk prior to and following containment would remain unchanged, since no treatment of
the sediments would be involved. Because the sediments would be covered, the exposure pathway would be
incomplete. The long-term risks would be essentially eliminated due to capping of the sediments and access
restrictions. However, there would be a potential for the short-term risk from fugitive dust generated
during the installation of the fence and the cap. Treatability testing was not conducted during the RI/FS
for the sediments, because the alternatives considered are proven technologies.

The initial measures to implement in this alternative are the new chain link fence, synthetic liner and
gravel and riprap, creation of new wetlands, and the automated runoff sampler.

The following major ARARs have been identified for this alternative:

Colorado Air Quality Act/Colorado Air Pollution Regulations (5 CCR 1001): These regulations
establish standards for air emissions from stationary sources. These regulations would be
applicable during construction activities and would be met by this alternative.

• Executive Order 11990, Protection of Wetlands: This reguirement would be applicable to
protection of designated wetlands. Wetlands have been identified at the Lowry Site and would
be destroyed in capping the sediments. New wetlands would be constructed under this
alternative to mitigate the loss of wetlands. Creation of new wetlands would comply with the
reguirements of this Executive Order.

• Clean Water Act (40 CFR Part 230): This reguirement establishes standards for construction
activities affecting waters of the United States. This Act is applicable because this
alternative would involve disturbance of potential wetlands and placement of a cap in the
unnamed creek. Any substantive permit reguirements would have to be met.
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The RAOs would be achieved for this alternative through a reduced potential for long-term exposure to the
sediments due to the cap over the sediments as well as fencing off of the area.

Grading, potential removal of some sediments, and installation of the new fence would create a potential for
occupational (short-term) exposure and habitat disturbance. Neither toxicity nor volume of the contaminants
would be reduced by this alternative. The potential for mobilization of the contaminants would be greatly
reduced due to the isolation of sediments from the surface water runoff.

The total 30-year present worth of this alternative is $1,215,000 with capital costs of $400,000 and annual
O&M costs of $53,000. The estimated time to implement Alternative SED31-2 would be 1 year.

8.4.4.10 Section 31 Sediments Alternative SED31-3-Excavation and Landfill

Alternative SED31-3 would include excavation and landfilling of 23,700 cubic yards of the Section 31
sediments. The excavation would be carried out in the unnamed creek drainage in Section 31 up to the
confluence with Murphy creek (approximately 2,660 feet) at an average width of 24 feet and down to the depth
of the water table (average 10 feet). The sediments would be landfilled in the existing Section 31 landfill,
which complies with the current RCRA Subtitle D reguirements. An area of approximately 1.47 acres, and a
volume of 23,700 cubic yards are calculated for the sediments.

Disposal in a RCRA Subtitle C landfill is not anticipated based on the available contaminant and
concentration information for the sediments. However, the sediments would be tested for RCRA hazard
characteristics prior to disposal. If determined necessary by EPA, excavated sediments would be transported
offsite for disposal in accordance with EPA's Offsite Policy (40 CFR Section 300.400). Following excavation,
the area would be backfilled with clean soil, compacted, graded and vegetated.

Excavation of the sediments would claim approximately 1.27 acres of wetlands. New wetlands would be created
in the Murphy Creek drainage or in an offsite area appropriate for wetland development.

The existing institutional controls such as fencing, signage, site access and land use restrictions would be
maintained under this alternative.

Annual monitoring of the surface water runoff into Murphy Creek would be conducted to evaluate the potential
for contaminant migration, although the Section 31 sediments would have been excavated and landfilled. For
the purpose of monitoring offsite contaminant migration, one automated surface water runoff sampler would be
installed in the drainage in Section 31.

There would be no treatment components of this alternative.

Excavation and landfilling of the sediments would result in the containment of the contaminants in the RCRA
Subtitle D facility in Section 31. The excavated material would be disposed of as solid waste rather than
being used as a daily cover material because the sediments are not expected to be of a guality appropriate
for use as daily cover.

Approximately 23,700 cubic yards of sediments would be excavated and landfilled in the RCRA Subtitle D
facility in Section 31. No sediments would be left in place; therefore, risk would be eliminated.

The Baseline Risk Assessment estimated a maximum excess cancer risk of 7 x 10-5 from ingestion of sediments
by a child in a residential setting. All long-term risk (cancer and noncancer) would be essentially
eliminated due to excavation and land filling of the sediments. A short-term risk would be created from
fugitive dust generation during the excavation and materials handling activities. Treatability testing was
not conducted during the RI/FS for the sediments because the alternatives considered are proven technologies.
Excavation and landfilling of the sediments would be completed in three to 6 months. Installation of the
automated surface water sampler would be achieved within the first year. There would be no residual levels
remaining from removal of the sediments.

Major ARARs for this alternative are the same as for Alternative SED31-2 and would be met by this alternative
using similar methods.

Although excavation and transport of the sediments to the active landfill area in Section 31 would create a
potential for occupational (short-term) exposure and habitat disturbance, the RAOs would be achieved for this
alternative through elimination of potential for long-term exposure to the sediments. Neither toxicity nor
volume of the contaminants would be reduced by this alternative. The potential for mobilization of the
contaminants would be significantly reduced due to the disposal in a RCRA Subtitle D landfill.

The total 30-year present worth of this alternative is $1,235,000 with capital costs of $620,000 and annual
O&M costs of $40,000. The estimated time to implement Alternative SED31-3 would be 1 year.
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Table 8-1
ARARs for OUs 1&6
Citation
Description
Evaluation
Chemical-Specific ARARs-Federal

Safe Drinking Water Act
40 CFR Part 141
Subpart B
Establishes health-based standards for
public drinking water systems (MCLs).
40 CFR Part 141
Subpart F
Establish drinking water guality goals
set at levels of no known or anticipated
adverse health effects, with an adeguate
margin of safer (MCLGs).
These regulations are relevant and appropriate because the
shallow and deep ground water in the vicinity of the Lowry
Site is being used or may be used in the future as a source
of water for a public water system or private supply wells.
Treated ground water from the treatment plant would be
injected into the shallow ground-water system. The
standards are pertinent to treatment plant effluent at the
point of injection as well as within the ground water at the
compliance boundary.

Non-zero MCLGs are relevant and appropriate since
shallow and deep ground water in the vicinity of the Lowry
Site is being used or may be used as a source of water for a
public water system or private supply wells.
Federal Water Pollution Control Act (amended by the Clean Water Act)
40 CFR Part 129
Toxic Pollution Effluent
Standards
Establishes toxic pollutant effluent
standards for six groups of toxic
pollutants from manufacturers,
formulators, and applicators who
develop or use these compounds and
discharge to navigable waters.
Relevant and appropriate for treatment plant effluent
because compound groups were detected in waste pit liguids
and unnamed creek and Murphy Creek discharges to the
South Platte River, which is a navigable water.
Solid Waste Disposal Act-RCRA Subtitle C
40 CFR Part 264
Subpart F
Sets groundwater protection standards
for land disposal units.
The State of Colorado operates an approved delegated
program for this portion of RCRA. See reguirement under
Colorado Hazardous Waste Act. Relevant and appropriate
because the landfill operates like a hazardous waste
management unit.
Chemical-Specific ARARs-State

Colorado Hazardous Waste Act
6 CCR 1007-3 Part 264.94
Colorado Rules and
Regulations Pertaining to
Hazardous Waste-Ground
Water Protection Standard
Establishes concentration levels for
chemicals in ground water.
14 The concentration limits are relevant and appropriate to
ground water at the compliance boundary for ground water
and treatment plant effluent.
-------
Colorado Water Quality Control Act
5 CCR 1002-3
Regulation on Effluent
Limitation
5 CCR 1003-1
Colorado Primary Drinking
Water Regulations.
5 CCR 1002-8
Section 3.11.0
Colorado Basic Standards
for Ground Water
and Section 3.12.0
Classifications and Water
Quality Standards for
Ground Water

5 CCR 1002-8
Section 3.1.0
basic Standards and

Methodologies for Surface
Water
5 CCR 1002-8
Section 3.2.0
Classifications and Numeric
Standards
Establishes specific limitations on point
source discharges of wastewaters into
state waters and from specified industry
sources, specifies sampling and
analytical reguirements.

Establishes health-based standards for
public water systems.
Relevant and appropriate for discharge from treatment plant.
Establishes a system for classifying
ground water and sets water guality
standards for such classifications.
Establishes basic standards and a
system for classifying surface waters of
the State, assigning standards, and

granting temporary variances for the
standard.
Used in conjunction with Basic
Standards and Methodologies Section
3.1.0. South Platte River Standards
(Section 3.8) establish numeric
standards for the South Platte River
Basin based on use classifications for
stream segments.
These regulations are relevant and appropriate because the
shallow and deep ground water in the vicinity of the Lowry
Site is being used or may be used in the future as a source
of water for a public water system or private supply wells.
Treated ground water from the treatment plant would be
injected into the shallow ground-water system.

These regulations establish standards for both classified and
unclassified ground water. The standards are applicable
because ground water (within non-alluvial and alluvial
aguifers) near the Lowry Site and ground water (within
alluvial aguifers) within the Lowry Site have been classified
for domestic and agricultural use-guality. Ground water
would be treated to meet these standards and then
discharged to the shallow ground-water system.

Murphy Creek and the unnamed creek are classified and
regulated as tributaries of the South Platte River Basin
(Stream Segment 16). Segment 16 is classified as

Recreation Class 2, Warm Water Aguatic Life Class 2, and
statewide interim organic pollutant standards for aguatic life
segments (Section 3.1.11 and Table C) are applicable to the
remedy. If surface-water discharge results from injection of
the treated water, surface water standards will be established
based on the more stringent surface water ARAR.

Murphy Creek and the unnamed creek are classified and
regulated tributaries of the South Platte River Basin
(Stream Segment 16). Segment 16 is classified as
Recreation Class 2, Warm Water Aguatic Life Class 2, and
Agricultural Supply. Based on the regulations, numeric
standards for protection of these three classified uses are
applicable. Chemical-specific standards established for
Stream Segment 16 are applicable to the remedy. If
surface-water discharge results from injection of the treated
water, surface water standards will be established based on
the most stringent surface water ARAR.
-------
Chemical-Specific ARARs-State (continued)
Colorado Air Quality Act/Air Pollution Regulations
5 CCR 1001-3
Regulation No. 1
Establishes standards for emissions of
particulates, smoke, carbon monoxide,
and sulfur oxides.
These regulations are applicable because air emissions will
occur at the ground-water treatment plant and due to
construction activities. These regulations would be met for
the air stripper/carbon polishing treatment process and
during construction. Regulations for opacity and offsite
transport of visible fugitive emissions are applicable and
must be attained during construction activities resulting in
disturbance of 5 acres or more in attainment areas or one
acre in nonattainment areas. The Lowry Site is in an
attainment area for sulfur oxides and lead and in a
nonattainment area for PM 10, ozone, and carbon
monoxide.
5 CCR 1001-4
Regulation No. 2
Sets limits on odorous air contaminants
and particulates.
These regulations are applicable because air emissions will
occur at the site during all activities. Activities regulated
include activities such as soil movement or treatment plant
air emissions. These regulations would be met for all
activities including the air stripper/carbon polishing
treatment process and movement of soil for construction of
barrier walls.
5 CCR 1001-10
Regulation No.
Sets emission control reguirements for
hazardous air pollutants.
5 CCR 1001-14
Ambient Standards
Establishes ambient standards for S02,
TSP, N02, CO, ozone, and PM 10.
These regulations are applicable because air emissions occur
at the treatment plant. These regulations would be met for
the air stripper/carbon polishing treatment process. The
lead standards are applicable because they are ambient
standards that apply to all sources. The beryllium
provisions set out emission limitations for stationary sources
that are applicable for all sources. The hydrogen sulfide
standards are applicable to any actions emitting hydrogen
sulfide. The mercury standards are applicable if wastewater
treatment plant sludge is dried or incinerated.

These regulations are applicable because air emissions occur
at the treatment plant. These regulations would be met
because these parameters are not expected to be present. If
these parameters are detected above the regulated levels,
action will be taken to correct the problem.
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Citation
Table 8-1
ARARs for OUs 1&6
Description

Action-Specific ARARs-Federal

Solid Waste Disposal Act-RCRA Subtitle C Regulations
Evaluation
Massachusetts
Allowable Ambient Levels
(AALs) and Threshold
Effects Exposure Limits
(TELs)

40 CFR Part 260-261
Identification and Listing of
Hazardous Waste
Establishes health-based air standards.
40 CFR Part 262
Standards Applicable to
Generators of Hazardous
Waste
Defines those solid wastes that are
subject to regulation as hazardous
wastes under 40 CFR Parts 262-265
and Parts 124, 270, 271.
Establishes standards for RCRA
generators.
TBCs. These standards were used to design the SWRA
when considering air pollution controls for the water
treatment plant. The plant will continue to meet these
standards.
The State of Colorado has an approved delegated program
for this portion of RCRA. The regulations are applicable
for purposes of determining whether any of the materials
being treated or disposed are hazardous wastes. Materials
may also be compared to the waste listings to determine
whether any of the materials are sufficiently similar such
that RCRA regulations are relevant and appropriate.

construction activities for the barrier walls. Therefore,
waste generated must meet these standards which include
testing per 40 CFR Part 261, temporary tanks or containers,
inspection and leak detection, and accumulation time. The
State of Colorado has an approved, delegated program
under RCRA.
40 CFR Part 264 Subparts
B, C, and D

Standards for Owners and
Operators of Hazardous
Waste Treatment, Storage,
and Disposal Facilities
Establishes minimum standards that
define the acceptable management of

hazardous waste for owners and
operators of facilities which treat,
store, or dispose of hazardous waste.
Because remediation activities constitute treatment and
storage activities (ground-water treatment plant and residuals

management), and because the water to be treated is
sufficiently similar to RCRA hazardous waste such that use
of the reguirement is well suited to the situation, the
reguirement is relevant and appropriate to the ground-water
treatment component of the remedy (including residuals
management). Thus, treatment of the ground water must
meet these standards, which include waste analysis, site
security, emergency control and response eguipment,
personnel training, contingency planning and
implementation.
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Table 8-1
ARARs for OUs 1&6
Citation
40 CFR Part 264
Subpart F
Description
Action-Specific ARARs-Federal (continued)
Evaluation
Sets ground-water protection standards
for land disposal units.
40 CFR Part 264 Subpart G
Closure and post-closure care.
40 CFR Part 264
Subpart I
Sets operating and performance
standards for container storage of
hazardous waste.
The State of Colorado operates an approved delegated
program for this portion of RCRA. See the reguirements
under Part 264.94 of the Colorado Hazardous Waste Act.
Relevant and appropriate to ground water under the site
because the landfill operates like a solid waste management
unit. Therefore, ground-water programs must meet these
standards, which include a monitoring and response
program that includes detection monitoring to identify the
presence of hazardous constituents in ground water;
compliance monitoring to determine whether the agency-
specified ground-water protection standard is being met at
the identified compliance point; and corrective action that
prevents hazardous constituents from exceeding the
established concentration limits beyond the point of
compliance.

Because ground-water treatment constitutes treatment of a

waste that is sufficiently similar to RCRA hazardous waste
such that use of the reguirement is well suited to the
situation, the reguirement is relevant and appropriate to the
ground-water treatment component of the remedy.
Therefore, closure and post-closure care for this treatment
system must meet these standards which include removal of
waste, waste residues, contaminated system components,
and contaminated subsoils; or closure with wastes and/or
contamination in place with containment systems and post-
closure care to include ground-water monitoring and
inspection and maintenance on containments and monitoring
systems.

Because ground-water treatment includes storage in
containers of a waste that is sufficiently similar to RCRA
hazardous waste such that use of the reguirement is well
suited to the situation, the reguirement is relevant and
appropriate to the ground-water treatment component of the
remedy. Therefore, container storage at the ground-water
treatment plant must meet these standards, which include
maintaining wastes in containers that are in good condition
and comparable with the wastes they contain, providing a
containment system, managing ignitable and reactive wastes
away from the property line, keeping incompatible wastes in
separate containers and containment systems, and at closure
removing all wastes and decontaminating structures and
eguipment.
-------
40 CFR Part 264
Subpart J
Sets operating and performance
standards for tank storage of hazardous
waste.
40 CFR 265.17
40 CFR Part 268
Land Disposal Restrictions
Sets standards for mixing and treatment
of soils or the mixing and
treatment of potentially incompatible,
reactive, or ignitable hazardous wastes.
Establishes prohibitions on land
disposal unless treatment standards are
met or a "no migration exemption" is
granted.
Because ground-water treatment includes storage in tanks of
a waste that is sufficiently similar to RCRA hazardous waste
such that use of the reguirement is well suited to the
situation, the reguirement is relevant and appropriate to the
ground-water treatment component of the remedy.
Therefore, tank storage at the ground-water treatment plant
must meet the standards, which include secondary
containment; spill and overflow controls; removal from
service if there is a leak, spill, or the tank is unfit for use;
and at closure have all wastes removed and also remove or
decontaminate waste residues, containment systems, soils,
structures, and eguipment.

Because the ground-water treatment plant will mix and treat
potentially incompatible, reactive, or ignitable wastes which
may be similar to hazardous wastes, the reguirement is
relevant and appropriate to the ground-water treatment
plant. Therefore, the wastes must be analyzed to determine
compatibility, reactivity, and ignitability before treatment
in the treatment plant.

Because residuals from the ground-water barrier walls
construction and residuals from the ground-water treatment
plant operations will be land disposed, the reguirement is
applicable. The materials must be tested to determine if
they are a characteristic hazardous waste (per 40 CFR Part
262) and then must meet treatment reguirements for land
disposal as reguired in the standards if they are hazardous
waste for which a treatment standard has been established.
For land disposal of residuals, other than soils, which are
not characteristic hazardous wastes, these reguirements are
relevant and appropriate because the residuals are
sufficiently similar to listed hazardous waste such that use of
the reguirements is well suited to the situation.
Federal Water Pollution Control Act (amended by the Clean Water Act)
40 CFR Part 122
NPDES Stormwater
Regulations
Establishes reguirements for
stormwater discharges related to
industrial activity. Stormwater runoff,
snow melt runoff, and surface runoff
and drainage associated with industrial
activity from remedial actions which
discharge to surface waters shall be
conducted in compliance with RCRA,
FWQC, CWA technology based stan-
dards, Colorado surface water guality
standards, monitoring reguirements,
and best management practices.
Because stormwater discharges will occur from any
treatment process areas constructed (such as the ground-
water treatment plant), this reguirement is applicable to
stormwater discharges. Therefore, stormwater discharges
must meet these standards which include sampling, analysis
and treatment reguirements. Implementation and
enforcement has been delegated to the State of Colorado,
see the Colorado Water Quality Control Act.
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40 CFR, Part 440
Effluent Guidelines and
Standards for Ore Mining
and Dressing Point Source
Categories
40 CFR 61
National Emission
Standards for Hazardous
Air Pollutants (NESHAPs)
Establishes radionuclide concentration
limits for liguid effluents from facilities
that extract and process uranium,
radium, and vanadium ores.
Clean Air Act

Establishes emission standards for
hazardous air pollutants from specific
sources.
Because the effluent from the ground-water treatment plant
could have radionuclides sufficiently similar to those
regulated such that the reguirement is well suited to the
situation, the reguirement is relevant and appropriate to the
ground-water treatment plant effluent. Therefore,
contingencies have been made for the early detection of
radionuclides and for a treatment process to be added to
treat radionuclides at the ground-water treatment plant.
Because the ground-water treatment plant has an air stripper
that is a source of air emissions, and this source is
sufficiently similar to source types in the regulations such
that use of the reguirement is well suited to the situation,
the reguirement is relevant and appropriate to the ground-
water treatment plant. Therefore, the air stripper must meet
these standards which include treatment levels for arsenic,
beryllium, benzene, vinyl chloride and radionuclide
emissions.
40 CFR Parts 144-147
Underground Injection
Control Regulations
Establishes standards for construction
and operation of injection wells.
Provides for protection of underground
sources of drinking water.
Applicable to injection of water from treatment plant. The
reguirements include constructing, operating, and
maintaining a well in a manner that does not result in
contamination of an underground source of drinking water
at levels that violate MCLs or otherwise affect the health of
persons. These reguirements will be met by ensuring the
effluent from the ground-water treatment plant meets
standards that are protective of human health (based on
MCLs and risk-based concentrations).
Action-Specific ARARs-State

Colorado Hazardous Waste Act
6 CCR 1007-3 Part 260-261
Identification and Listing of
Hazardous Waste
Defines solid wastes subject to
hazardous waste regulations.
The State of Colorado has an approved delegated program
for this portion of RCRA. Applicable to determining
whether substances are hazardous wastes under RCRA.
6 CCR 1007-3 Part 262
Standards Applicable to
Generators of Hazardous
Waste
Establishes standards for RCRA
generators.
Because remediation activities will generate waste that will
be sufficiently similar to RCRA hazardous waste such that
use of this reguirement is well suited to the situation, the
reguirement is relevant and appropriate to the ground-water
treatment plant residuals and waste generated during
construction of the barrier walls. Therefore, waste
generated must meet these standards which include testing
per 40 CFR Part 261, temporary tanks or containers,
inspection and leak detection, offsite shipping procedures,
and accumulation time. The State of Colorado has an
approved, delegated program under RCRA.
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6 CCR 1007-3 Part 264
Subparts B, C, and D
Standards for Owners and
Operators of Hazardous
Waste Treatment, Storage,
and Disposal Facilities
Establishes minimum standards that
define the acceptable management of
hazardous waste for owners and
operators of facilities which treat,
store, or dispose of hazardous waste.
6 CCR 1007-3 Part 264
Subpart F
Sets ground-water protection standards
for land disposal units.
6 CCR 1007-3 Part 264
Subpart G
Closure and post-closure care.
Because remediation activities constitute treatment and
storage activities (ground-water treatment plant and residuals
management), and because the water to be treated is
sufficiently similar to RCRA hazardous waste such that use
of the reguirement is well suited to the situation, the
reguirement is relevant and appropriate to the ground-water
treatment component of the remedy (including residuals
management). Thus, treatment of the ground water must
meet these standards, which include waste analysis, site
security, emergency control and response eguipment,
personnel training, contingency planning and
implementation.

The State of Colorado operates an approved delegated
program for this portion of RCRA. See the reguirements
under Part 264.94 of the Colorado Hazardous Waste Act.
Relevant and appropriate to ground water under the site
because the landfill operates like a solid waste management
unit. Therefore, ground-water programs must meet these
standards, which include a monitoring and response
program that includes detection monitoring to identify the
presence of hazardous constituents in ground water;
compliance monitoring to determine whether the agency-
specified ground-water protection standard is being met at
the identified compliance point; and corrective action that
prevents hazardous constituents from exceeding the
established concentration limits beyond the point of
compliance.

Because ground-water treatment constitutes treatment of
waste that is sufficiently similar to RCRA hazardous waste
such that use of the reguirement is well suited to the
situation, the reguirement is relevant and appropriate to the
ground-water treatment component of the remedy.
Therefore, closure and post-closure care for these treatment
systems must meet these standards which include removal of
waste, waste residues, contaminated system components,
and contaminated subsoils; or closure with wastes and/or
contamination in place with containment systems and post-

closure care to include ground-water monitoring and
inspection and maintenance on containments and monitoring
systems.
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6 CCR 1007-3 Part 264
Subpart I
Sets operating and performance
standards for container storage of
hazardous waste.
6 CCR 1007-3 Part 264
Subpart J
Sets operating and performance
standards for tank storage of hazardous
waste.
use,
6 CCR 1007-3 Part 265.17
6 CCR 1007-3 Part 268
Land Disposal Restrictions
Sets standards for mixing and treatment
of contaminated soils or the mixing and
treatment of potentially incompatible,
reactive, or ignitable hazardous wastes.
Establishes prohibitions on land
disposal unless treatment standards are
met or a "no migration exemption" is
granted.
Because ground-water treatment includes storage in
containers of a waste that is sufficiently similar to RCRA
hazardous waste such that use of the reguirement is well
suited to the situation, the reguirement is relevant and
appropriate to the ground-water treatment component of the
remedy. Therefore, container storage at the ground-water
treatment plant must meet these standards, which include
maintaining wastes in containers that are in good condition
and compatible with the wastes they contain, providing a
containment system, managing ignitable and reactive wastes
away from the property line, keeping incompatible wastes in
separate containers and containment systems, and at closure
removing all wastes and decontaminating structures and
eguipment.

and at closure have all wastes removed and also remove or
decontaminate waste residues, containment system, soils,
structures, and eguipment.

Because the construction residuals from the ground-water
barrier walls will be land disposed, the reguirement is
applicable. The materials must be tested to determine if
they are a characteristic hazardous waste (per 6 CCR 1007-
3 Part 262) and then must meet treatment reguirements for
land disposal as reguired in the standards if they are
hazardous waste for which a treatment standard has been
established. For land disposal of residuals, other than soils
which are not characteristic hazardous wastes, these
reguirements are relevant and appropriate because the
residuals are sufficiently similar to listed hazardous waste
such that use of the reguirements is well suited to the
situation.
-------
Colorado Air Quality Act/Air Pollution Regulations
5 CCR 1001-5
Regulation No. 3
5 CCR 1001-8
Regulation No. 6
5 CCR 1001-9
Section II.C.2, Section V
Regulation No. 7
Requires filing of Air Pollution
Emission Notice (APEN) including
estimation of emission rates.
Establishes standards for new stationary
sources including incinerators. Sets
discharge and performance rates and
opacity requirements.
Establishes standards for disposal or
spillage of VOCs.
These regulations are applicable because air emissions will
occur at the treatment plant. The air stripper/carbon
polishing treatment process must meet any substantive
provisions of these requirements.

These regulations are applicable because air emissions will
occur at the treatment plant. The air stripper/carbon
polishing treatment process must meet these requirements
which include controls representing reasonably available
control technology (RACT).
Colorado Noise Abatement Statute
Colorado Revised Statute
Section 25-12-103
2 CCR 402-4
2 CCR 402-2
State of Colorado Division
of Water Resources, 1988,
as revised-Colorado State
Engineers Office
40 CFR Part 230
Provides limits for noise based on time
periods and zones.
Applicable for all construction activities associated with the
remedy.
Water Well Pump Installation Contractors Act

Establishes standards for installation of Applicable because wells will be installed.
water wells and pumping equipment.

Well Construction/Abandonment Requirements
Well construction/abandonment
requirements
Applicable for new wells and abandonment of existing
wells. Additional requirements may be added to ensure that
a migration pathway is not created.
Location-Specific ARARs-Federal

Federal Water Pollution Control Act (Clean Water Act)
Discharge of dredged or fill material
into wetlands prohibited without a
permit.
For areas of the site that have designated wetlands, a permit
will not be required pursuant to Section 121 (c) of
CERCLA, but the substantive requirements of Part 230 will
be applicable if wetlands that have been identified at the
Lowry Site are dredged or filled during implementation of
the remedial activity.
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Certification of Federal Licenses and Permits

5 CCR 1002-18 Discharge of dredge and fill material For areas of the site that have designated wetlands, a permit
into wetlands prohibited without a State will not be reguired pursuant to Section 121 (c) of
certification. CERCIA, but the substantive reguirements will be
applicable if wetlands that have been identified at the Lowry
Site are dredged or filled during implementation of the
remedial activity.
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Table 8-2
ARARs for OUs 2&3
Citation
Description

Chemical-Specific ARARs-State

Colorado Air Quality Act/Air Pollution Regulations
Evaluation
5 CCR 1001-3
Regulation No. 1
Establishes standards for emissions of
particulates, smoke, carbon monoxide,
and sulfur oxides.
These regulations are applicable because air emissions will
occur at the gas treatment system and due to construction
activities. These regulations would be met for the gas
flaring system and during construction. Regulations for
opacity and offsite transport of visible fugitive emissions are
applicable and must be attained during construction activi-
ties resulting in disturbance of 5 acres or more in attainment
areas or one acre in nonattainment areas. The Lowry Site is
in an attainment area for sulfur oxides and lead and in a
nonattainment area for PM 10, ozone, and carbon
monoxide.
5 CCR 1001-4
Regulation No. 2
Sets limits on odorous air contaminants
and particulates.
5 CCR 1001-10
Regulation No.
Sets emission control reguirements for
hazardous air pollutants.
These regulations are applicable because air emissions will
occur at the site during all activities. Activities regulated
include activities such as soil movement. These regulations
would be met for all activities including the excavation of
soil in the former tire pile area, and movement of soil for
construction of the gas collection and treatment system.

These regulations are applicable because air emissions will
occur at the gas treatment system. These regulations would
be met for the gas flare. The lead standards are applicable
because they are ambient standards that apply to all sources.
The beryllium provisions set out emission limitations for
stationary sources that are applicable for all sources. The
hydrogen sulfide standards are applicable to any actions
emitting hydrogen sulfide. The mercury standards are
applicable if wastewater treatment plant sludge is dried or
incinerated.
Action-Specific ARARs-Federal
Solid Waste Disposal Act-RCRA Subtitle D Reguirements
40 CFR Part 241
Guidelines for the Land
Disposal of Solid Wastes
Establishes minimum levels of perfor-
mance reguired of any solid waste land
disposal site operation.
Part 241.205-2(b) states "decomposi-
tion gases should not be allowed to
concentrate in a manner that will pose
an explosion or toxicity hazard."
Because the Lowry Site is a landfill and because decomposi-
tion gases have been detected, this reguirement is well
suited to the situation and is relevant and appropriate to the
gas collection and treatment system. Therefore, the gas
collection and treatment must meet these standards, which
include maintaining methane below explosive limits.
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40 CFR Part 257
Criteria for Classification of
Solid Waste Disposal Facili-
ties & Practices
40 CFR Part 258
Regulations Concerning
Municipal Solid Waste
Landfills
Establishes criteria for use in determin-
ing which solid waste disposal facilities
and practices pose a reasonable proba-
bility of adverse effects on health or
the environment and thereby constitute
prohibited open dumps.

Establishes design and operational
criteria for all new municipal solid
waste landfills or expansions of exist-
ing facilities. The reguirements vary
depending on the time frame that the
land disposal unit is used. Includes
closure and post closure care.
! If the landfill stopped receiving
waste prior to 10/9/91 it is not
regulated
! If the landfill stopped receiving
waste prior to 10/9/93 the facility
must comply with final cover
reguirements.
! If the landfill receives waste on or
after 10/9/93 the facility must
comply with all reguirements of
40 CFR 258
Applicable for existing MSW landfills. The Section 6
MSW landfill is a closed landfill. Landfill cover
reguirements are relevant and appropriate.
Explosive gas reguirements (Part 258.23) are relevant and
appropriate since waste was not received after October 9,
1993, but the use of the reguirement is well suited to the
situation. Therefore, methane monitoring within onsite
structures and at the facility property boundary is reguired.
Landfill cover reguirements are relevant and appropriate
since waste was not received after October 9, 1991, but the
use of the reguirement is well suited to the situation.
Therefore, landfill cover maintenance is reguired.
Solid Waste Disposal Act-RCRA Subtitle C Regulations
40 CFR Part 260-261
Identification and Listing of
Hazardous Waste
40 CFR Part 262
Standards Applicable to
Generators of Hazardous
Waste
Defines those solid wastes that are
subject to regulation as hazardous
wastes under 40 CFR Parts 262-265
and Parts 124, 270, 271.
Establishes standards for RCRA
generators.
The State of Colorado has an approved delegated program
for this portion of RCRA. The regulations are applicable
for purposes of determining whether any of the materials
being treated or disposed are hazardous wastes. Materials
may also be compared to the waste listings to determine
whether any of the materials are sufficiently similar such
that RCRA regulations are relevant and appropriate.

Because remediation activities will generate waste that will
be sufficiently similar to RCRA hazardous waste such that
use of this reguirement is well suited to the situation, the
reguirement is relevant and appropriate to solids excavated
from the former tire pile area, gas that is collected and
treated, and waste generated during construction activities
for the gas extraction system. Therefore, waste generated
must meet these standards which include testing per 40 CFR
Part 261, temporary tanks or containers, inspection and leak
detection, and accumulation time. The State of Colorado
has an approved, delegated program under RCRA.
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40 CFR Part 264 Subparts
B, C, and D
Standards for Owners and
Operators of Hazardous
Waste Treatment, Storage,
and Disposal Facilities
Establishes minimum standards that
define the acceptable management of
hazardous waste for owners and opera-
tors of facilities which treat, store, or
dispose of hazardous waste.
40 CFR Part 264 Subpart G
Closure and post-closure care.
40 CFR Part 264 Subpart 0
Sets standards for destruction and
removal efficiency, HC1 emissions, and
particulate emissions from incinerators
or thermal treatment.
Because remediation activities constitute treatment and
storage activities (gas treatment and residuals management)
and because the gas to be treated is sufficiently similar to
RCRA hazardous waste such that use of the requirement is
well suited to the situation, the requirement is relevant and
appropriate to the gas treatment component of the remedy
(including residuals management). Thus, flaring of the gas
must meet these standards, which include waste analysis,
site security, emergency control and response equipment,
personnel training, contingency planning and
implementation.

Because gas treatment constitutes treatment of a waste that
is sufficiently similar to RCRA hazardous waste such that
use of the requirement is well suited to the situation, the
requirement is relevant and appropriate to the gas treatment
components of the remedy. Therefore, closure and post-
closure care for this treatment system must meet these
standards which include removal of waste, waste residues,
contaminated system components, and contaminated sub-
soils; or closure with wastes and/or contamination in place
with containment systems and post-closure care to include
ground-water monitoring and inspection and maintenance on
containments and monitoring systems.

Because gas treatment constitutes thermal treatment, and
because the gas to be treated is sufficiently similar to RCRA
hazardous waste such that use of the requirement is well
suited to the situation, the requirement is relevant and
appropriate to the gas flaring component of the remedy.
Thus, flaring of the gas must meet these standards, which
include emissions standards and operating constraints as
needed to ensure emissions standards are met.
40 CFR Part 264
Subpart AA
Sets operation and performance stan-
dards for air emissions from process
vents.
40 CFR 265 Subpart P
Interim Standards for
Owners and Operators
Hazardous Waste
Treatment, Storage, and
Disposal Facilities
Standards for thermal treatment.
Because the gas treatment has process vents from thermal
treatment and because the gas to be treated is sufficiently
similar to RCRA hazardous waste such that the use of the
requirement is well suited to the situation, the requirement
is relevant and appropriate to the gas flaring component of
the remedy. Thus, the gas treatment system must meet
these standards, which include standards for process vents
and test methods and procedures.

Because gas flaring constitutes thermal treatment and
because the gas to be treated is sufficiently similar to RCRA
hazardous waste such that use of the requirement is well
suited to the situation, the requirement is relevant and
appropriate to the gas treatment component of the remedy.
Therefore, the gas treatment system must meet the stan-
dards, which include general operating requirements, waste
analysis, monitoring and inspection, and closure.
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40 CFR Part 265 Subpart
AA
40 CFR Part 268
Land Disposal Restrictions
Sets operating and performance stan-
dards for air emissions from process
vents.
Establishes prohibitions on land dis-
posal unless treatment standards are
met or a "no migration exception" is
granted.
Because the gas treatment has process vents from thermal
treatment and because the gas to be treated is sufficiently
similar to RCRA hazardous waste such that the use of the
reguirement is well suited to the situation, the reguirement
is relevant and appropriate to the gas flaring component of
the remedy. Thus, the gas treatment system must meet
these standards, which include standards for process vents
and test methods and procedures.

Because the solids excavation in the former tire pile area
and residuals from the gas extraction system construction
and residuals from the gas extraction system operations will
be land disposed, the reguirement is applicable. The mate-
rials must be tested to determine if they are a characteristic
hazardous waste (per 40 CFR Part 262) and then must meet
treatment reguirements for land disposal as reguired in the
standards if they are hazardous waste for which a treatment
standard has been established. For land disposal of
residuals, other than soils, which are not characteristic
hazardous wastes, these reguirements are relevant and
appropriate because the residuals are sufficiently similar to
listed hazardous waste such that use of the reguirements is
well suited to the situation.
58 FR 48091 (9/14/93)
40 CFR Part 268
Universal Treatment
Standards
40 CFR Part 122
NPDES Stormwater
Regulations
Establishes a concentration limit for
over 200 regulated constituents in soil
regardless of waste type, which must
be met before land disposal.
TBC for soil and sediments because it is a proposed regula-
tion. Excavated soils from the tire pile area must meet
these reguirements.
Federal Water Pollution Control Act (amended by the Clean Water Act)
Establishes reguirements for storm-
water discharges related to industrial
activity. Stormwater runoff, snow melt
runoff, and surface runoff and drainage
associated with industrial activity from
remedial actions which discharge to
surface waters shall be conducted in
compliance with RCRA, FWQC, CWA
technology-based standards, Colorado
surface water guality standards, moni-
toring reguirements, and best manage-
ment practices.

Clean Air Act
Because Stormwater discharges will occur from the landfill
and from any treatment process areas constructed (such as
the gas treatment system), this reguirement is applicable to
Stormwater discharges. Therefore, Stormwater discharges
must meet these standards which include sampling, analysis,
and treatment reguirements. Implementation and enforce-
ment has been delegated to the State of Colorado, see
Colorado Water Quality Control Act.
40 CFR Part 60
New Source Performance
Standards
Establishes performance standards for
new stationary sources of air pollut-
ants .
Relevant and appropriate for gas treatment. Proposed NSPS
for municipal solid waste facilities (Subpart WWW) is a
TBC (56 FR 24468 [5/30/91]).
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40 CFR Part. 61
National Emission
Standards for Hazardous
Air Pollutants (NESHAPs)
Establishes emission standards for
hazardous air pollution from specific
sources.
Because the gas treatment system will have a flare, this
source is sufficiently similar to source types in the regula-
tions such that use of the reguirement is well suited to the
situation, the reguirement is relevant and appropriate to the
gas treatment system. Therefore, the gas flare must meet
these standards which include treatment levels for arsenic,
beryllium, benzene, vinyl chloride and radionuclide
emissions.
Action-Specific ARARs-State
Colorado Solid Wastes Disposal sites and Facilities Act
6 CCR 1007-2 Section 1
Regulations Pertaining to
Solids Waste Disposal Sites

and Facilities
relevant and
6 CCR 1007-2 Section 2.3
Establishes standards for new solid
waste disposal facilities and defines
those solid wastes.
6 CCR 1007-2 Sections 2.6
and 3.6
Establishes minimum standards for
landfill gas collection and treatment
systems.
Post closure maintenance and care.
Explosive gas reguirements and landfill cover reguirements
are relevant and appropriate because waste was not received
after October 9, 1993, but the use of the reguirement is well

suited to the situation so the reguirement is

appropriate to the existing landfill mass. Therefore, the gas
concentrations need to be maintained below the explosive
limits and maintenance of the landfill cover is reguired.

These reguirements are applicable for the landfill gas col-
lection and treatment system and include monitoring
reguirements in structures and at the landfill boundary,

notification of gas excursions, and remediation activities if
explosive gas limits are exceeded.

Substantive reguirements are applicable to the gas extraction
system and landfill cover. Reguirements include maintain-
ing the cover for 30 years, ground-water monitoring,
describing uses of land during post closure care, and certifi-
cation at the completion of post closure care.
Colorado Hazardous Waste Act
6 CCR 1007-3 Part 260-261
Identification and Listing of
Hazardous Waste
Defines those solid wastes subject to
hazardous waste regulations.
The State of Colorado has an approved delegated program
for this portion of RCRA. Applicable to determining whe-
ther substances are hazardous wastes under RCRA.
6 CCR 1007-3 Part 262
Standards Applicable to
Generators of Hazardous
Waste
Establishes standards for RCRA
generators.
Because remediation activities will generate waste that will
be sufficiently similar to RCRA hazardous waste such that
use of this reguirement is well suited to the situation, the
reguirement is relevant and appropriate to the solids exca-
vated from the former tire pile area, gas that is treated, and
waste generated during construction of the gas extraction
system. Therefore, waste generated must meet these
standards which include testing per 40 CFR Part 261, tem-
porary tanks or containers, inspection and leak detection,
-------
offsite shipping procedures, and accumulation time. The
State of Colorado has an approved, delegated program
under RCRA.
6 CCR 1007-3 Part 264
Subparts B, C, and D
Standards for Owners and
Operators of Hazardous
Waste Treatment, Storage,
and Disposal Facilities
Establishes minimum standards that
define the acceptable management of
hazardous waste for owners and opera-
tors of facilities which treat, store, or
dispose of hazardous waste.
6 CCR 1007-3 Part 264
Subpart G
Closure and post-closure care.
6 CCR 1007-3 Part 264
Subpart 0
Standards for Owners and
Operators of Hazardous
Waste TSD Facilities
Sets standards for destruction and
removal efficiency HC1 emissions and
particulate matter in excess of the
stated standard.
6 CCR 1007-3 Part 264
Subpart AA
Sets operating and performance stan-
dards for air emissions from process
vents.
Because remediation activities constitute treatment and
storage activities (gas treatment and residuals management),
and because the gas to be treated is sufficiently similar to
RCRA hazardous waste such that use of this reguirement is
well suited to the situation, the reguirement is relevant and
appropriate to the gas treatment components of the remedy
(including residuals management). Thus, flaring of the gas
must meet these standards, which include waste analysis,
site security, emergency control and response eguipment,
personnel training, contingency planning and
implementation.

Because gas treatment constitutes treatment of a waste that
is sufficiently similar to RCRA hazardous waste such that
use of the reguirement is well suited to the situation, the
reguirement is relevant and appropriate to the gas treatment
components of the remedy. Therefore, closure and post-
closure care for this treatment system must meet these
standards which include removal of waste, waste residues,
contaminated system components, and contaminated sub-
soils; or closure with wastes and/or contamination in place
with containment systems and post-closure care to include
ground-water monitoring and inspection and maintenance on
containments and monitoring systems.

Because the gas treatment has process vents from thermal
treatment and because the gas to be treated is sufficiently
similar to RCRA hazardous waste such that the use of the
reguirement is well suited to the situation, the reguirement
is relevant and appropriate to the gas flaring component of
the remedy. Thus, the gas treatment system must meet
these standards, which include general operating reguire-
ments, waste analysis, monitoring and inspections, and
closure.
6 CCR 1007-3 Part 265
Subpart P
Standards for thermal treatment.
Because gas flaring constitutes thermal treatment and
because the gas to be treated is sufficiently similar to RCRA
hazardous waste such that use of the reguirement is well
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6 CCR 1007-3 Part 265
Subpart AA
Sets operation and performance stan-
dards for air emissions from process
vents.
suited to the situation, the requirement is relevant and
appropriate to the gas treatment component of the remedy.
Therefore, the gas treatment system must meet these stan-
dards, which include standards for process vents and test
methods and procedures.

Because the gas treatment has process vents from thermal
treatment and because the gas to be treated is sufficiently
similar to RCRA hazardous waste such that the use of the
requirement is well suited to the situation, the requirement
is relevant and appropriate to the gas flaring component of
the remedy. Thus, the gas treatment system must meet
these standards, which include general operating require-
ments, waste analysis, monitoring and inspections, and
closure.
6 CCR 1007-3 Part 268
Land Disposal Restrictions
Establishes prohibitions on land dis-
posal unless treatment standards are
met or a "no migration exemption" is
granted.
Because the solids excavation in the former tire pile area
and construction residuals from the ground-water barrier
walls and gas extraction system will be land disposed, the
requirement is applicable. The materials must be tested to
determine if they are a characteristic hazardous waste (per 6
CCR 1007-3 Part 262) and then must meet treatment
requirements for land disposal as required in the standards if
they are hazardous waste for which treatment standard has
been established. For land disposal of residuals, other than
soils, which are not characteristic hazardous wastes, these
requirements are relevant and appropriate because the
residuals are sufficiently similar to listed hazardous waste
such that use of the requirements is well suited to the
situation.
Colorado Air Quality Act/Air Pollution Regulations
5 CCR 1001-5
Regulation No. 3
5 CCR 1001-8
Regulation No. 6
Requires filing of Air Pollution Emis-
sion Notice (APEN) including estima-
tion of emission rates.

Establishes standards for new stationary
sources including incinerators. Sets
discharge and performance rates and
opacity requirements.
These regulations are applicable because air emissions will
occur at the gas treatment system. The gas flaring process
must meet any substantive provisions of these requirements.

These regulations are applicable because air emissions will
occur at the gas treatment system. The gas flaring process
must meet these requirements which include discharge and
performance rates and opacity requirements.
5 CCR 1001-9
Section II.C.2, Section V
Regulation No. 7
Establishes standards for disposal or
spillage of VOCs.
These regulations are applicable because air emissions will
occur at the gas treatment system. The gas flaring process
must meet the requirements which include controls repre-
senting reasonably available control technology (RACT).
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Colorado Noise Abatement Statute

Colorado Revised Statute Provides limits for noise based on time Applicable for all construction activities associated with the
Section 25-12-103 periods and zones. remedy.

Water Well Pump Installation Contractors Act

2 CCR 402-4 Establishes standards for installation of Applicable because wells will be installed.
water wells and pumping equipment.

Well Construction/Abandonment Requirements

2 CCR 402-2 Well construction/abandonment Applicable for new wells and abandonment of existing
State of Colorado Division requirements wells. Additional requirements may be added to ensure that
of Water Resources, 1988, a migration pathway is not created.
as revised-Colorado State
Engineers Office

Location-Specific ARARs-Federal

Federal Water Pollution Control Act (Clean Water Act)

40 CFR Part 230 Discharge of dredged or fill material For areas of the site that have designated wetlands, a permit
into wetlands prohibited without a will not be required pursuant to Section 121 (c) of
permit. CERCIA, but the substantive requirements of Part 230 will
be applicable if wetlands that have been identified at the
Lowry Site are dredged or filled during implementation of
the remedial activity.

Location-Specific ARARs-State

Certification of Federal Licenses and Permits

5 CCR 1002-18 Discharge of dredged or fill material For areas of the site that have designated wetlands, a permit
into wetlands prohibited without a State will not be required pursuant to Section 121 (c) of
certification. CERCIA, but the substantive requirements of Part 230 will be
applicable if wetlands that have been identified at the Lowry
Site are dredged or filled during implementation of the
remedial activity.
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Table 8-3
ARARs for OUs 4&5
Citation
Description
Evaluation
Chemical-Specific ARARs-Federal

Safe Drinking Water Act
40 CFR Part 141
Subpart B
Establishes health-based standards for
public drinking water systems (MCLs).
40 CFR Part 141
Subpart F
Establishes drinking water guality goals
set at levels of no known or anticipated
adverse health effects, with an adeguate
margin of safety (MCLGs).
These regulations are relevant and appropriate because the
shallow and deep ground water in the vicinity of the Lowry
Site is being used or may be used in the future as a source
of water for a public water system or private supply wells.
Treated ground water from the treatment plant would be
injected into the shallow ground-water system. The
are pertinent to treatment plant effluent at the
point of injection as well as within the ground water at the
compliance boundary.

Non-zero MCLGs are relevant and appropriate since shal-
low and deep ground water in the vicinity of the Lowry Site
is being used or may be used as a source of water for a
public water system or private supply wells.
Federal Water Pollution Control Act (amended by the Clean Water Act)
40 CFR Part 129
Toxic Pollutant Effluent
Standards
6 CCR 1007-3 Part 264.94
Colorado Rules and
Regulations Pertaining to
Hazardous Waste-Ground
Water Protection Standard
Establishes toxic pollutant effluent
standards for six groups of toxic pollut-
ants from manufacturers, formulators,
and applicators who develop or use
these compounds and discharge to
navigable waters.

Chemical-Specific ARARs-State

Colorado Hazardous Waste Act

Establishes concentration levels for 14
chemicals in ground water.
Relevant and appropriate for treatment plant effluent
because compound groups were detected in waste pit liguids
and unnamed creek and Murphy Creek discharges to the
South Platte River, which is a navigable water.
The concentration limits are relevant and appropriate to
treatment plant effluent.
5 CCR 1002-3
Regulation on Effluent
Limitation
Colorado Water Quality Control Act

Relevant and appropriate for discharge from treatment plant.
Establishes specific limit on point
source discharges of wastewaters into
state waters and from specified industry
sources, specifies sampling and analyti-
cal reguirements.
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5 CCR 1003-1
Colorado Primary Drinking
Water Regulation
5 CCR 1002-8
Section 3.11.0
Colorado Basic Standards
for Ground Water
and Section 3.12.0 Classifi-
cations and Water Quality
Standards for Ground Water
5 CCR 1002-8
Section 3.1.0
Basic Standards and
Methodologies for Surface
Water
Establishes health-based standards for
public drinking water systems.
5 CCR 1002-8
Section 3.2.0
Classifications and Numeric
Standards
5 CCR 1001-3
Regulation No. 1
Establishes a system for classifying
ground water and sets water guality
standards for such classifications.
Establishes basic standards and a
system for classifying surface waters of
the State, assigning standards, and
granting temporary variances for the
standard.
Used in conjunction with Basic Stan-
dards and Methodologies Section 3.1.0.
South Platte River Standards (Section
3.8) establish numeric standards for the
South Platte River Basin based on use
classifications for stream segments.
These regulations are relevant and appropriate because the
shallow and deep ground water in the vicinity of the Lowry
Site is being used or may be used in the future as a source
of water for a public water system or private supply wells.
Treated ground water from the treatment plant would be
injected into the shallow ground-water system.

Murphy Creek and the unnamed creek are classified and
regulated as tributaries of the South Platte River Basin
(Stream Segment 16). Segment 16 is classified as Recre-
ation Class 2, Warm Water Aguatic Life Class 2, and Agri-
cultural Supply. Because of this classification, statewide
interim organic pollutant standards for aguatic life segments
(Section 3.1.11 and Table C) are applicable to the remedy.
If surface-water discharge results from injection of the
treated water, surface water standards will be established
based on the most stringent surface water ARAR.

Murphy Creek and the unnamed creek are classified and
regulated as tributaries of the South Platte River Rasin
(Stream Segment 16). Segment 16 is classified as Recre-
ation Class 2, Warm Water Aguatic Life Class 2, and Agri-
cultural Supply. Based on the regulations, numeric stan-
dards for protection of these three classified uses are appli-
cable. Chemical-specific standards established for Stream
Segment 16 are applicable to the remedy. If surface-water
discharge results from injection of the treated water, surface
water standards will be established based on the most strin-
gent surface water ARAR.
Colorado Air Quality Act/Air Pollution Regulations
Establishes standards for emissions of
particulates, smoke, carbon monoxide,
and sulfur oxides.
These regulations are applicable because air emissions will
occur at the ground-water treatment plant. These regula-
tions would be met for the air stripper/carbon polishing
treatment process. Regulations for opacity and offsite trans-
port of visible fugitive emissions are applicable and must be
attained during construction activities resulting in distur-
bance of 5 acres or more in attainment areas or one acre in
nonattainment areas. The Lowry Site is in an attainment
area for sulfur oxides and lead and in a nonattainment area
for PM 10, ozone, and carbon monoxide.
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5 CCR 1001-4
Regulation No. 2
5 CCR 1001-10
Regulation No. 8
Sets limits on odorous air contaminants
and particulates.
Sets emission control reguirements for
hazardous air pollutants.
5 CCR 1001-14
Ambient Standards
Massachusetts
Allowable Ambient Levels
(AALs) and Threshold
Effects Exposure Limits
(TELs)
Establishes ambient standards for S02,
TSP, N02, CO, ozone, and PM 10.
Establishes health-based air standards.
These regulations are applicable because air emissions will
occur at the site during all activities. Activities regulated
include activities such as treatment plant air emissions.
These regulations would be met for all activities including
the air stripper/carbon polishing treatment process.

These regulations are applicable because air emissions occur
at the treatment plant. These regulations would be met for
the air stripper/carbon polishing treatment process. The
lead standards are applicable because they are ambient
standards that apply to all sources. The beryllium provi-
sions set out emission limitations for stationary sources that
are applicable for all sources. The hydrogen sulfide stan-
dards are applicable to any actions emitting hydrogen sul-
fide. The mercury standards are applicable if wastewater
from treatment plant sludge is dried or incinerated.

TBCs. These standards were used to design the SWRA
when considering air pollution controls for the water treat-
ment plant. The plant will continue to meet these standards.
Action-Specific ARARs-Federal
Solid Waste Disposal Act-RCRA Subtitle C Regulations
40 CFR Part 260-261
Identification and Listing of
Hazardous Waste
40 CFR Part 262
Standards Applicable to
Generators of Hazardous
Waste
Defines those solid wastes that are
subject to regulation as hazardous
wastes under 40 CFR Parts 262-265
and Parts 124, 270, 271.
Establishes standards for RCRA
generators.
The State of Colorado has an approved delegated program
for this portion of RCRA. The regulations are applicable
for purposes of determining whether any of the materials
being treated or disposed are hazardous wastes. Materials
may also be compared to the waste listings to determine
whether any of the materials are sufficiently similar such
that RCRA regulations are relevant and appropriate.

Because remediation activities will generate waste that will
be sufficiently similar to RCRA hazardous waste such that
use of this reguirement is well suited to the situation, the
reguirement is relevant and appropriate to the ground-water
treatment plant residuals. Therefore, waste generated must
meet these standards which include testing per 40 CFR Part
261, temporary tanks or containers, inspection and leak
detection, and accumulation time. The State of Colorado
has an approved, delegated program under RCRA.
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40 CFR Part 264 Subparts
B, C, and D
Standards for Owners and
Operators of Hazardous
Waste Treatment, Storage,
and Disposal Facilities
Establishes minimum standards that
define acceptable management of
hazardous waste for owners and opera-
tors of facilities which treat, store, or
dispose of hazardous waste.
40 CFR Part 264 Subpart G
Closure and post-closure care.
40 CFR Part 264
Subpart I
Sets operating and performance stan-
ards for container storage of hazard-
ous waste.
40 CFR Part 264
Subpart J
Sets operating and performance stan-
dards for tank storage of hazardous
waste.
Because remediation activities constitute treatment and
storage activities (ground-water treatment plant and residuals
management), and because the water to be treated is
sufficiently similar to RCRA hazardous waste such that use
of this reguirement is well suited to the situation, the
reguirement is relevant and appropriate to the ground-water
treatment component of the remedy (including residuals
management). Thus, treatment of the groundwater must
meet these standards, which include waste analysis, site
security, emergency control and response eguipment, per-
sonnel training, contingency planning and implementation.

Because ground-water treatment constitutes treatment of a
waste that is sufficiently similar to RCRA hazardous waste
such that use of the reguirement is well suited to the situa-
tion, the reguirement is relevant and appropriate to the
ground-water treatment component of the remedy. There-
fore, closure and post-closure care for this treatment system
must meet these standards which include removal of waste,
waste residues, contaminated system components, and
contaminated subsoils; or closure with wastes and/or con-
tamination in place with containment systems and post-
closure care to include ground-water monitoring and installa-
tion and maintenance on containments and monitoring
systems.

Because ground-water treatment includes storage in contain-
ers of a waste that is sufficiently similar to RCRA hazard-
ous waste such that use of the reguirement is well suited to
the situation, the reguirement is relevant and appropriate to
the ground-water treatment component of the remedy.
Therefore, container storage at the ground-water treatment
plant must meet these standards, which include maintaining
wastes in containers that are in good condition and compati-
ble with the wastes they contain, providing a containment
system, managing ignitable and reactive wastes away from
the property line, keeping incompatible wastes in separate
containers and containment systems, and at closure remov-
ing all wastes and decontaminating structures and
eguipment.

Because ground-water treatment includes storage in tanks of
a waste that is sufficiently similar to RCRA hazardous waste
such that use of the reguirement is well suited to the situa-
tion, the reguirement is relevant and appropriate to the
ground-water treatment component of the remedy. There-
fore, tank storage at the ground-water treatment plant must
meet the standards, which include secondary containment;
spill and overflow controls; removal from service if there is
a leak, spill, or the tank is unfit for use; and at closure have
all wastes removed and also remove or decontaminate waste
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40 CFR 265.17
40 CFR Part 268
Land Disposal Restrictions
Sets standards for mixing and treatment
of contaminated soils or the mixing and
treatment of potentially incompatible,
reactive, or ignitable hazardous wastes.
Establishes prohibitions on land
disposal unless treatment standards are
met or a "no migration exemption" is
granted.
residues, containment systems, soils, structures, and
eguipment.

Because the residuals from the ground-water treatment plant
operations will be land disposed, the reguirement is
applicable. The materials must be tested to determine if
they are a characteristic hazardous waste (per 40 CFR Part
262) and then must meet treatment reguirements for land
disposal as reguired in the standards if they are hazardous
waste for which a treatment standard has been established.
For land disposal of residuals, other than soils, which are
not characteristic hazardous wastes, these reguirements are
relevant and appropriate because the residuals are
sufficiently similar to listed hazardous waste such that use of
the reguirement is well suited to the situation.
40 CFR, Part 230/231
Guidelines for Specification
of Disposal Sites for
Dredged or Fill Materials
Federal Water Pollution Control Act (amended by the Clean Water Act)
The discharge of dredged or fill
material into the waters of the U.S.
prohibited without a permit.
Wetlands were destroyed during construction of the SWRA
and must be mitigated during implementation of the selected
remedy by constructing new wetlands.
40 CFR, Part 440
Effluent Guidelines and
Standards for Ore Mining
and Dressing Point Source
Categories
Establishes radionuclide concentration
limits for liguid effluents from facilities
that extract and process uranium,
radium, and vanadium ores.
Because the effluent from the ground-water treatment plant
could have radionuclides sufficiently similar to those
regulated such that the reguirement is well suited to the
situation, the reguirement is relevant and appropriate to the
ground-water treatment plant effluent. Therefore,
contingencies have been made for the early detection of
radionuclides and for a treatment process to be added to
treat radionuclides at the ground-water treatment plant.
Clean Air Act
40 CFR Part 61
National Emission
Standards for Hazardous
Air Pollutants (NESHAPs)
Establishes emission standards for
hazardous air pollutants from specific
sources.
Because the ground-water treatment plant has an air stripper
that is a source of air emissions, and this source is
sufficiently similar to source types in the regulations such
that use of the reguirement is well suited to the situation,
the reguirement is relevant and appropriate to the ground-
water treatment plant. Therefore, the air stripper must meet
these standards which include treatment levels for arsenic,
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beryllium, benzene, vinyl chloride and radionuclide
emissions.
40 CFR Part 144-147
Underground Injection
Control Regulations
Safe Drinking Water Act

Establishes standards for construction
and operation of injection wells.
Provides for protection of underground
source of drinking water.
Applicable to injection of water from treatment plant. The
reguirements include constructing, operating, and
maintaining a well in a manner that does not result in
contamination of an underground source of drinking water
at levels that violate MCLs or otherwise affect the health of
persons. These reguirements will be met by ensuring the
effluent from the groundwater treatment plant meets
standards that are protective of human health (based on
MCLs and risk-based concentrations).
Action-Specific ARARs-State

Colorado Hazardous Waste Act
6 CCR 1007-3 Part 260-261
Identification and Listing of
Hazardous Waste
Defines those solid wastes subject to
hazardous waste regulations.
The State of Colorado has an approved delegated program
for this portion of RCRA. Applicable to determining
whether substances are hazardous wastes under RCRA.
6 CCR 1007-3 Part 262
Standards Applicable to
Generators of Hazardous
Waste
Establishes standards for RCRA
generators.
6 CCR 1007-3 Part 264
Subparts B, C, and D
Standards for Owners and
Operators of Hazardous
Waste Treatment, Storage,
and Disposal Facilities
Establishes minimum standards that
define the acceptable management of
hazardous waste for owners and
operators of facilities which treat,
store, or dispose of hazardous waste.
6 CCR 1007-3 Part 264
Subpart G
Closure and post-closure care.
Because remediation will generate waste that will
be sufficiently similar to RCRA hazardous waste such that
use of this reguirement is well suited to the situation, the
reguirement is relevant and appropriate to the ground-water
treatment plant residuals. Therefore, waste generated must
meet these standards which include testing per 40 CFR Part
261, temporary tanks or containers, inspection and leak
detection, offsite shipping procedures, and accumulation
time. The State of Colorado has an approved, delegated
program under RCRA.

Because remediation activities constitute treatment and
storage activities (ground-water treatment plant and residuals
management), and because the water to be treated is
sufficiently similar to RCRA hazardous waste such that use
of the reguirement is well suited to the situation, the
reguirement is relevant and appropriate to the ground-water
treatment component of the remedy (including residuals
management). Thus, treatment of the groundwater must
meet these standards, which include waste analysis, site
security, emergency control and response eguipment,
personnel training, contingency planning and
implementation.

Because ground-water treatment constitutes treatment of a
waste that is sufficiently similar to RCRA hazardous waste
such that use of the reguirement is well suited to the
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6 CCR 1007-3 Part 264

Subpart I
Sets operating and performance

standards for container storage of
hazardous wastes.
6 CCR 1007-3 Part 264
Subpart J
Sets operating and performance
standards for tank storage of hazardous
waste.
6 CCR 1007-3 Part 265.17
6 CCR 1007-3 Part 268
Land Disposal Restrictions
Sets standards for mixing and treatment
of contaminated soils or the mixing and
treatment of potentially incompatible,
reactive, or ignitable hazardous wastes.
Establishes prohibitions on land
disposal unless treatment standards are
met or a "no migration exemption" is
situation, the reguirement is relevant and appropriate to the
ground-water treatment component of the remedy.
Therefore, closure and post-closure care for this treatment
system must meet these standards which include removal of
waste, waste residues, contaminated system components,
and contaminated subsoils; or closure with wastes and/or
contamination in place with containment systems and post-
closure care to include ground-water monitoring and
inspection and maintenance on containments and monitoring
systems.

Because ground-water treatment includes storage in

containers of a waste that is sufficiently similar to RCRA
hazardous waste such that use of the reguirement is well
suited to the situation, the reguirement is relevant and
appropriate to the ground-water treatment component of the
remedy. Therefore, container storage at the ground-water
treatment plant must meet these standards, which include
maintaining wastes in containers that are in good condition
and compatible with the wastes they contain, providing a
containment system, managing ignitable and reactive wastes
away from the property line, keeping incompatible wastes in
separate containers and containment systems, and at closure
removing all wastes and decontaminating structures and
eguipment.

Because the residuals from the ground-water treatment plant
will be land disposed, the reguirement is applicable. The
materials must be tested to determine if they are a
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granted.
5 CCR 1001-5
Regulation No. 3
5 CCR 1001-8
Regulation No. 6
5 CCR 1001-9
Section II.C.2, Section V
Regulation No. 7
characteristic hazardous waste (per 6 CCR 1007-3 Part 262)
and then must meet treatment reguirements for land disposal
as reguired in the standards if they are hazardous waste for
which a treatment standard has been established. For land
disposal of residuals, other than soils, which are not
characteristic hazardous wastes, these reguirements are
relevant and appropriate because the residuals are
sufficiently similar to hazardous waste such that use of
the reguirements is well suited to the situation.
Colorado Air Quality Act/Air Pollution Reguirements
Reguires filing of Air Pollution
Emission Notice (APEN) including
estimation of emission rates.
Establishes standards for new stationary
sources including incinerators. Sets
discharge and performance rates and
opacity reguirements.
Established standards for disposal or
spillage of VOCs.
These regulations are applicable because air emissions will
occur at the treatment plant. The air stripper/carbon
polishing treatment process must meet any substantive
provisions of these reguirements.

These regulations are applicable because air emissions will
occur at the treatment plant. The air stripper/carbon
polishing treatment process must meet these reguirements
which include controls representing reasonable available
control technology (RACT).
Colorado Noise Abatement Statute
Colorado Revised Statute
Section 25-12-103
CFR Part 6, Appendix A
Provides limits for noise based on time
periods and zones.
Applicable for all construction activities associated with the
remedy.
Location-Specific ARARs-Federal

Executive Order 11990, Protection of Wetlands
Action to avoid adverse effects,
minimize potential harm, and preserve
and enhance wetlands, to the extent
possible. Reguires action to minimize
the destruction, loss, or degradation of
wetlands.
Applicable because wetlands have been identified and
destroyed at the Lowry Site during the SWRA. New
wetlands will be constructed as part of the remedy.
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Federal Water Pollution Control Act (Clean Water Act)
40 CFR Part 230
Discharge of dredged or fill material
into wetlands prohibited without a
permit.
For areas of the site that have designated wetlands, a permit
will not be reguired pursuant to Section 121 (c) of
CERCLA, but the substantive reguirements of Part 230 will
be applicable if wetlands that have been identified at the

Lowry Site are dredged or filled during implementation of
the remedial activity.
Location-Specific ARARs-State

Certification of Federal Licenses and Permits
5 CCR 1002-18
Discharge of dredge and fill material
into wetlands prohibited without a State
certification.
For areas of the site that have designated wetlands, a permit
will not be reguired pursuant to Section 121 (c) of
CERCLA, but the substantive reguirements will be
applicable if wetlands that have been identified at the Lowry
Site are dredged or filled during implementation of the
remedial activity.
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Section 9.0
Summary of the Comparative Analysis of Alternatives

This section compares the remedial alternatives described in Section 8.0. The comparative analysis provides
the basis for determining which alternative presents the best balance between the EPA' s nine evaluation
criteria listed below. The first two cleanup evaluation criteria are considered threshold criteria that must
be met by the selected remedial action. The five primary balancing criteria are balanced to achieve the best
overall solution. The final two modifying criteria that are considered in remedy selection are State
acceptance and community acceptance.

• Threshold Criteria

1. Overall Protection of Human Health and the Environment addresses whether a remedy
provides adeguate protection and describes how risks posed through each pathway are
eliminated, reduced, or controlled.

2. Compliance with Applicable or Relevant and Appropriate Reguirements addresses
whether a remedy will meet all Federal and State environmental laws and/or provide
grounds for a waiver.

• Primary Balancing Criteria

3. Long-Term Effectiveness and Permanence refers to the ability of a remedy to
provide reliable protection of human health and the environment over time.

4. Reduction of Toxicity, Mobility, or Volume Through Treatment refers to the
preference for a remedy that reduces health hazards of contaminants, the movement
of contaminants, or the guantity of contaminants at the Lowry Site through
treatment.

5. Short-Term Effectiveness addresses the period of time needed to complete the
remedy, and any adverse effects to human health and the environment that may be
caused during the construction and implementation of the remedy.

6. Implementability refers to the technical and administrative feasibility of an
alternative or a remedy. This includes the availability of materials and services
needed to carry out a remedy. It also includes coordination of Federal, State,
and local government efforts.

7. Cost evaluates the estimated capital, operation, and maintenance (O&M) costs of
each alternative in comparison to other egually protective alternatives.

• Modifying Criteria

8. State Acceptance indicates whether the State agrees with, opposes, or has no
comment on the preferred alternative.

9. Community Acceptance includes determining which components of the alternatives
interested persons in the community support, have reservations about, or oppose.

The strengths and weaknesses of the alternatives were weighed to identify the alternative providing the best
balance among the nine evaluation criteria. The comparative analysis of alternatives for OUs 1&6, 2&3, and
4&5 is provided in the following discussion.

9.1 OU 1: Shallow Ground Water and Subsurface Liquids and OU 6: Deep Ground Water

9.1.1 Threshold Criteria

9.1.1.1 Overall Protection of Human Health and the Environment

The NCP reguires that all alternatives be assessed to determine whether they can adeguately protect human
health and the environment, in both the short- and long-term, from unacceptable risks posed by hazardous
substances, pollutants, or contaminants present at the site by eliminating, reducing, or controlling
exposures to such hazardous substances, pollutants, or contaminants. Overall protection of human health and
the environment draws on the assessments of other evaluation criteria, especially long-term effectiveness and
permanence, short-term effectiveness, and compliance with ARARs.
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All of the alternatives would be protective of human health and the environment, with the exception of the No
Action alternative. The No Action alternative would not be protective because contamination above ARARs and
other performance standards would migrate offsite and downward into the major water supply aquifers.
Therefore, the No Action alternative will not be considered further in this evaluation. All other
alternatives would be protective because they would: prevent migration of contaminants above performance
standards beyond the compliance boundary through containment and collection and/or through monitoring and
implementation of contingencies; meet ARARs; prevent exposure to contaminants within the compliance boundary
through the use of institutional controls; monitor for vertical migration of contaminants and implement
contingencies to contain such vertical migration; monitor the effectiveness of remedial measures.

The following analysis is structured such that the alternatives are discussed in order of relative
protectiveness. The comparison of alternatives shows that for overall protectiveness, Modified Alternative
Groundwater No. 5 (GW-5) (the North Boundary, Toe of Landfill and Lateral Barrier Walls Collection and
Treatment System, plus Upgradient Containment Collection and Treatment alternative) is superior to all other
alternatives. This is because it is the only alternative which does not rely on contingencies to prevent
lateral migration of contaminated ground water from the Lowry Site. Instead, Modified Alternative GW-5
includes barrier walls and collection systems on all boundaries of the Lowry Site. All other alternatives
rely to one degree or another on monitoring at the boundaries and would require further action if monitoring
revealed offsite migration of contaminants above performance standards.

This distinction between Modified Alternative GW-5 and the other alternatives is important because
contaminants have been detected at the western and southern portions of the Lowry Site near the compliance
boundary, and ground-water modeling performed for the risk assessment and feasibility studies indicates that
offsite migration will occur. By requiring the immediate design and installation of barrier walls on the
eastern, western and southern boundaries, and upgrading of the existing barrier wall or construction of an
additional barrier wall on the northern boundary of the Lowry Site, Modified Alternative GW-5 provides the
greatest assurance that performance standards will be achieved at the compliance boundary.

Like Modified Alternative GW-5, Alternative GW-5 (the North Boundary, Toe of Landfill plus Lateral
Containment, Collection and Treatment alternative) includes containment systems on the eastern and western
boundaries. However, Alternative GW-5 lacks Modified Alternative GW-5's upgradient containment feature on
the southern boundary of the Lowry Site and would require further action if monitoring revealed migration of
contaminants at the southern boundary.

Modified Alternative GW-5's upgradient system would result in the following benefits to human health and the
environment:

• Prevention of migration of contaminants southward from the landfill mass resulting from
localized ground-water flow to the south. As noted above, contaminants have been detected near
the southern compliance boundary. Local southward flow could be caused by mounding from the
landfill, unidentified sand stringers/sand channels, and other geologic heterogeneities,
chemical diffusion, dispersion, and possible unidentified localized seasonal changes in
ground-water flow direction.

• Reduction of ground-water inflow from the south entering the contaminated Site. This would
reduce the volume of clean water that is mixed with contaminated water and thereby reduce the
ground-water treatment cost.

Like Modified Alternative GW-5, Alternative GW-4 (the North Boundary, Toe of Landfill, Upgradient
Containment, Collection, and Treatment, plus Multilayer Cap alternative) includes installation of the
upgradient ground-water containment, collection, and diversion system. However, Alternative GW-4 lacks the
barrier walls on the eastern and western boundaries and would require further action if monitoring revealed
migration of contaminants at the eastern and western compliance boundaries.

Unlike Modified Alternative GW-5, Alternative GW-4 requires installation of a multilayer cap. However, the
existing clay cap is effective in preventing infiltration from precipitation into the landfill mass and
waste-pit liquids. Modeling results show that placement of the multilayer cap in Alternative GW-4 would not
reduce the infiltration rate any more than the current clay cap. Therefore, the multilayer cap in
Alternative GW-4 would not provide any additional protection of human health and the environment than the
existing clay cap.

Unlike the other alternatives, Alternative GW-6 (the North Boundary and Toe of Landfill Containment,
Collection and Treatment plus Waste-Pit Pumping alternative) includes pumping and treatment of waste pit
liquids. However, only a small portion of the waste pit liquids could be extracted and the waste pit liquids
would continue to act as a source for ground water contamination. Alternative GW-6 does not include
containment systems on the eastern, western, and southern boundaries, and thus, is not considered to be as
protective as the alternatives which include such systems.
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Like Alternatives GW-4, GW-5, GW-6 and Modified Alternative GW-5, Alternative GW-3 (the North Boundary and
Toe of Landfill Containment, Collection, and Treatment alternative) includes a toe of the landfill collection
system. This system provides an additional measure of protectiveness over alternatives which don't include
the system by preventing the most highly contaminated liguids from migrating northward and further degrading
ground water between the landfill mass and the northern compliance boundary. This system is an extra safety
measure which, among other things, would limit the negative impacts if there were ever a breakthrough of
contaminated ground water at the northern barrier wall. Alternative GW-3 does not include containment
systems on the eastern, western, and southern boundaries, and thus, is not considered to be as protective as
the alternatives which include such systems.

Like Modified Alternative GW-5 and some of the other alternatives, Alternative GW-2 (the North Boundary
Containment Collection and Treatment alternative) would extend the existing barrier wall on the northern
boundary or build a new longer barrier wall adjacent to the existing one. This feature would provide an
additional measure of protectiveness over Alternative GW-1 (the No Further Action alternative) by providing
greater assurance that contaminants would be captured at the northern compliance boundary and would not move
around the edges of the barrier wall. Neither Alternative GW-2 nor Alternative GW-1 include containment
systems on the eastern, western, and southern boundaries or toe of the landfill collection. Thus, they are
not considered to be as protective as the alternatives which include such systems.

9.1.1.2 Compliance with ARARs

Applicable reguirements are those cleanup standards, standards of control, and other substantive
reguirements, criteria, or limitations promulgated under Federal or State law that specifically address a
hazardous substance, pollutant, contaminant, remedial action, or location at a CERCLA site. Relevant and
appropriate reguirements are similar reguirements that, while not applicable, clearly address problems or
situations sufficiently similar to those encountered at a CERCLA site such that their use is well suited to
the particular site.

The alternatives were assessed to determine whether they would attain applicable or relevant and appropriate
reguirements under Federal environmental laws and State environmental or facility siting laws or provide
grounds for invoking an ARARs waiver.

The ARARs for OUs 1&6 alternatives are discussed in Section 8.0.

All of the alternatives would meet ARARs. Modified Alternative GW-5 and Alternative GW-5 are the only
alternatives that would include control of lateral migration as a principal component to achieve compliance
with ARARs at the eastern and western compliance boundaries. These alternatives would also be superior in
meeting the intent of the closure provisions for RCRA hazardous waste landfills, which are considered
relevant and appropriate at the Lowry Site.

The conclusion that each alternative can meet the ARARs is based on treatability study results.
Contingencies would be implemented if performance data showed that the selected remedy was not achieving
ARARs. Contingencies would include any or all of the following:

• If, during implementation or operation of the ground-water remedy, it was determined that
contaminant levels exceeded the performance standards at the point of action boundary, the
remedy would be re-evaluated and modifications made to prevent contaminant migration beyond the
compliance boundary. Modifications might include any or all of the following, at EPA's
discretion:

Alternating pumping at wells to eliminate stagnation points

Pulse pumping to allow aguifer eguilibration and to allow adsorbed contaminants
to partition into ground water

Installation of extraction wells to facilitate containment of the contaminant
plume and to address possible vertical migration of contaminants and alternate
pumping at these wells to eliminate ground water stagnation points

To ensure that performance standards would continue to be maintained, the aguifer would be
monitored at appropriate locations and freguencies, as determined by EPA.

• If it were determined by EPA, on the basis of the system performance data, that contaminants
had migrated vertically downward to the lignite layer, contingency measures would be
implemented to ensure that the beneficial use of the underlying aguifer would not be impaired.
The following measures involving long-term management might be reguired, at EPA' s discretion,
for an indefinite period of time, as a modification of the existing system:
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Additional engineering controls such as underground barriers, or long-term
gradient control provided by low level pumping, as containment measures

Continued monitoring of specified wells

Periodic re-evaluation of remedial technologies for ground-water restoration

Additional institutional controls on water extraction and use

• Contingencies for the SWRA, which are relevant to the operation of the GWTP, were developed as
part of the SWRA design and are discussed in Subsection 11.5.2. These contingencies would be
reviewed during the selected remedy design and, if necessary, modified or upgraded.

Contingency plans would be developed in detail during the RD. These plans would address measures to be taken
if ARARs are not met.

9.1.2 Primary Balancing Criteria

9.1.2.1 Long-Term Effectiveness and Permanence

The alternatives were assessed for the long-term effectiveness and permanence they afford, along with the
degree of certainty that the alternative would prove successful. Factors that were considered include the
following:

1. The magnitude of residual risk remaining from untreated waste or treatment residuals remaining
at the conclusion of the remedial activities; and

2. The adeguacy and reliability of controls such as containment systems and institutional controls
that are necessary to manage untreated waste and treatment residuals.

All of the alternatives would offer long-term effectiveness and permanence and address the movement of
contaminants to the north (the primary migration pathway) through treatment of ground water collected at the
existing barrier wall system. However, Modified Alternative GW-5 would best address long-term effectiveness
and permanence through up-front construction of containment and collection systems on all sides of the
Lowry Site.

Modified Alternative GW-5 and Alternative GW-5 are the only alternatives that would immediately prevent
potential offsite migration of contaminants to the east and west. In addition, Modified Alternative GW-5 and
Alternative GW-5 provide additional long-term effectiveness and permanence above Alternatives GW-1, 2, 3, and
4, because they extract waste from the east and west sides of the landfill mass.

Alternative GW-6 would extract more subsurface liguids from the landfill; however, because only a small
fraction of the waste pits would be extracted, the waste pit liguids would still act as a continual source
for ground-water contamination. Therefore, Alternative GW-6, although better at extraction, would not offer
any significant additional long-term effectiveness and permanence over Modified Alternative GW-5 or
Alternative GW-5.

Like Alternatives GW-5 and GW-6 and Modified Alternative GW-5, Alternatives GW-3 and GW-4 would reduce risk
through treatment of the highly contaminated ground water collected at the toe of the landfill. Collection
of the contaminated ground water at the toe of the landfill would capture contamination closer to the source
and avoid further contamination of the aguifer downgradient of the landfill mass.

Alternative GW-4 and Modified Alternative GW-5 offer upgradient containment, collection, and diversion, which
reduces the inflow of clean water mixing with contaminated water and also prevents southern offsite
migration. Alternative GW-4 adds a multilayer cap, but this has not been shown to be any more effective in
inhibiting infiltration of surface water into the Lowry Site than the existing clay cap.

Alternatives GW-1 (the No Further Action alternative) and GW-2 (the North Boundary Containment, Collection,
and Treatment alternative) would be the least effective alternatives because they rely on contingency
measures for eastern, western, and southern compliance boundary exceedances and would not capture and treat
contamination as close to the source area as the remaining alternatives which use toe of the landfill
ground-water extraction and treatment. Modified Alternative GW-5 is the only alternative that fully contains
migration to the north, east, west, and south, as well as effectively reduces the long-term potential for
contaminated ground-water migration.
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9.1.2.2 Reduction of Toxicitv, Mobility, or Volume Through Treatment

The degree to which alternatives employ recycling or treatment to reduce toxicity, mobility, or volume was
assessed, including how treatment would be used to address the principal threats posed by the site. Factors
that were considered include the following:

1. The treatment or recycling processes the alternatives employ and materials they will treat;

2. The amount of hazardous substances, pollutants, or contaminants that will be destroyed,
treated, or recycled;

3. The degree of expected reduction in toxicity, mobility, or volume of the waste from treatment
or recycling and the specification of which reduction(s) axe occurring;

4. The degree to which the treatment is irreversible;

5. The type and quantity of residuals that will remain following treatment, considering the
persistence, toxicity, mobility, and propensity to bioaccumulate of such hazardous substances
and their constituents; and

6. The degree to which treatment reduces the inherent hazards posed by principal threats at the
site.

All of the alternatives would reduce the toxicity, mobility, or volume of contaminated ground water migrating
to the north through extraction and treatment at the existing barrier wall. The alternative that would best
achieve this criterion is Alternative GW-6, because it includes extraction and treatment of waste-pit liquids
and extraction and treatment of highly contaminated ground water in the alluvium at the toe of the landfill.

Alternatives GW-3, GW-4, GW-5, and Modified Alternative GW-5 would be next best at reducing toxicity,
mobility, or volume through treatment, because they would provide for extraction of highly contaminated
ground water in the alluvium at the toe of the landfill. Alternative GW-1 (the No Further Action alternative)
and Alternative GW-2 (the North Boundary Containment, Collection, and Treatment alternative) have the least
reduction of mobility, toxicity, or volume through treatment because contamination is allowed to migrate
beyond the toe of the landfill until it is captured at the northern site boundary.

9.1.2.3 Short-Term Effectiveness

The NCP considers the following four features as components of short-term effectiveness:

• Short-term risks to the community during implementation
• Potential impacts to workers during implementation
• Potential environmental impacts during remediation
• Time until protection is achieved

All of the alternatives would have reasonable short-term effectiveness. Alternative GW-1 (the No Further
Action alternative) and Alternative GW-2 (the North Boundary Containment, Collection, and Treatment
alternative) would have no adverse short-term effects. The remaining Alternatives, GW-3, GW-4, GW-5,
Modified Alternative GW-5, and GW-6, would include a ground-water extraction system at the toe of the
landfill for highly contaminated ground water. During construction of this system, construction workers
would be exposed to higher risks from the potential presence of volatile organic compounds in the soil.
However, these risks are not anticipated to be significant during the 3-year design and construction period.

With the exception of measures that may be required during construction of the trench at the toe of the
landfill, the use of unusual or special construction techniques is not anticipated. It has been demonstrated
that workers at the Lowry Site can be adequately protected during construction through routine application of
accepted Occupational Safety and Health Administration (OSHA) health and safety practices. The majority of
the construction would not require special health protective measures.

None of the alternatives would pose short-term risks to the community during implementation or cause adverse
environmental impacts during remediation.

While potential impacts to workers might be greater with Modified Alternative GW-5 than with Alternatives
GW-1 and GW-2, Modified Alternative GW-5 would achieve overall protection in a shorter time frame than these
alternatives because containment systems would be immediately designed and installed on the eastern, western,
and southern sides of the Lowry Site. Thus, from an overall perspective, Modified Alternative GW-5 is as
effective in the short-term as Alternatives GW-1 and GW-2. Likewise, Alternatives GW-5 and GW-4, which both
include lateral containment on the west and east or the south, offer advantages over Alternatives GW-1 and
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GW-2 in terms of the amount of time required until protection is achieved.

9.1.2.4 Implementabilitv

The ease or difficulty of implementing the alternatives was assessed by considering the following types of
factors:

1. Technical feasibility, including technical difficulties and unknowns associated with the
construction and operation of a technology, the reliability of the technology, ease of
undertaking additional remedial actions, and the ability to monitor the effectiveness of the
remedy.

2. Administrative feasibility, including activities needed to coordinate with other offices and
agencies and the ability and time required to obtain any necessary approvals and permits from
other agencies (for offsite actions);

3. Availability of services and materials, including the availability of adequate off-site
treatment, storage capacity, and disposal capacity and services; the availability of necessary
equipment and specialists, and provisions to ensure any necessary additional resources; the
availability of services and materials; and availability of prospective technologies.

All of the alternatives are considered to be administratively and technically implementable. In addition,
the services and materials required to implement all of the alternatives would be readily available.
Alternative GW-1 (the No Further Action alternative) and Alternative GW-2 (the North Boundary Containment,
Collection, and Treatment alternative) would be the easiest to implement. Alternatives GW-3, GW-5, and
Modified Alternative GW-5 would all use current technology and would be the next easiest to implement.

The construction of containment barrier walls that act to collect or divert are considered routine
construction and can be performed by local contractors. The effectiveness of the ground-water treatment
system is proven by the success of the existing treatment facility located onsite.

Alternative GW-4 (the North Boundary, Toe of Landfill, Upgradient and Multilayer Cap alternative) and
Alternative GW-6 (the North Boundary, Toe of Landfill Containment, and Waste-Pit Pumping alternative) are
considered to be the least implementable alternatives. This is because Alternative GW-4 proposes
100-foot-deep extraction trenches that may be difficult to construct, and Alternative GW-6 includes drilling
52 waste-pit extraction wells that may be difficult to drill through landfill refuse.

9.1.2.5 Cost

The types of costs that were assessed include the following:

1. Capital costs, including both direct and indirect costs;
2. Annual operation and maintenance costs; and
3. Net present value of capital and O&M costs.

A description of cost estimating procedures is provided in Section 8.1.

The No Further Action alternative would be the least costly, while Alternative GW-4 (North Boundary, Toe of
Landfill, Upgradient Containment, Collection and Treatment Plus Multilayer Cap alternative) would be the most
costly. Modified Alternative GW-5 is significantly less expensive than Alternative GW-6 and is more
expensive than Alternative GW-3. Modified Alternative GW-5 is comparable in costs to Alternative GW-5, but
i
includes physical barriers and an additional upgradient ground-water collection, containment, and diversion
system. Modified Alternative GW-5 is more expensive than Alternatives GW-1 and GW-2 because Alternatives
GW-1 and GW-2 do not immediately address offsite contaminant migration to the eastern, western, and southern
site boundaries.

Costs for OUs 1&6 alternatives are ranked below from least to most expensive based on the following present
worth estimates:

Alternative GW-1: No Further Action

Capital Costs: $4,300,000
Annual O&M Costs: $1,800,000
Total (30-year Present Worth): $31,970,000
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• Alternative GW-2: North Boundary (Downgradient) Containment, Collection, and Treatment

Capital Costs: $9,800,000
Annual O&M Costs: $1,900,000
Total (30-year Present Worth): $39,010,000

• Alternative GW-3: North Boundary and Toe of Landfill Containment, Collection, and Treatment

Capital Costs: $15,300,000
Annual O&M Costs: $3,000,000
Total (30-year Present Worth): $61,420,000

• Alternative GW-5: North Boundary, Toe of Landfill, and Lateral Containment, Collection, and
Treatment

Capital Costs: $17,700,000
Annual O&M Costs: $3,000,000
Total (30-year Present Worth): $63,820,000

• Modified Alternative GW-5: North Boundary, Toe of Landfill, and Lateral Containment,
Collection and Treatment plus Upgradient Containment, Collection, and Diversion

Capital Costs: $19,000,000
Annual O&M Costs $2,400,000
Total (30-year Present Worth): $65,030,000

• Alternative GW-6: North Boundary and Toe of Landfill Containment, Collection and Treatment,
and Waste Pit Pumping

Capital Costs: $20,300,000
Annual O&M Costs: $3,400,000
Total (30-year Present Worth): $72,570,000

• Alternative GW-4: North Boundary, Toe of Landfill, and Upgradient Containment, Collection and
Treatment, plus Multilayered Cap in Landfill Area

Capital Costs: $64,100,000
Annual O&M Costs: $3,200,000
Total (30-year Present Worth): $113,300,000

It should be noted that the cost figures for alternatives which rely on contingency measures to address
potential contaminant migration to the east, west, and/or south (all alternatives other than Modified
Alternative GW-5) do not include cost figures for such contingency measures. If such contingency measures
had to be initiated, the costs could increase significantly for those alternatives.

9.1.3 Modifying Criteria

9.1.3.1 State/Support Agency Acceptance (August 1993)

The State of Colorado concurs with the EPA on the selection of Modified Alternative GW-5 for OUs 1&6. The
State of Colorado also concurs with the selected ARARs.

9.1.3.2 Community Acceptance

Community input on the alternatives for remedial action for OUs 1&6 was solicited by EPA and CDH during the
public comment period for the OUs 1&6 Proposed Plan from November 23, 1992 to March 2, 1993. Comments from
the public were supportive of the preferred remedy. Several of the commenters recommended that EPA consider
additional efforts to pump waste pits and several commenters were opposed to any use of offsite institutional
controls as a substitute for cleanup actions or which would prohibit use of the surrounding lands. Responses
to community comments are found in the Responsiveness Summary for OUs 1&6 in Section 13.0 of this ROD. The
PRPs were generally supportive of the selected remedy. One set of PRPs was in favor of the upgradient
containment, collection and diversion system, while the other set of PRPs asked for additional justification
on the upgradient system. Responses to PRP comments are found in the Responsiveness Summary for OUs 1&6 in
Section 13.0 of this ROD.
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9.2 OU 2: Landfill Solids and OU 3: Landfill Gas

9.2.1 Threshold Criteria

9.2.1.1 Overall Protection of Human Health and the Environment

Under the No Action alternative, Landfill Solids Alternative 1 (LFS-1), all of the potential risks to human
health and the environment associated with the landfill solids and gas would remain. These include the
excess risk of getting cancer from exposure to gas migrating offsite, risks associated with the potential
buildup and explosion of methane gas, and risks associated with potential exposure to contaminated drums at
or near the land surface in the former tire pile area.

In addition, the existing clay cap would deteriorate without maintenance, which could lead to infiltration of
surface water into the landfill mass and a resultant increase in the potential for migration of contaminants.
EPA has determined that these risks are unacceptable. Because the No Action alternative is not protective
for either landfill solids or landfill gas, it will not be considered further in this evaluation.

9.2.1.1.1 Landfill Solids (LFS). All of the alternatives would be protective of human health and the
environment because they would prevent exposure to contaminants in landfill solids. This would be
accomplished through the use of various combinations of cover over, and excavation and treatment of, landfill
solids, in conjunction with institutional controls.

Modified Alternative LFS-4 (the Drum Removal/Offsite Disposal/North Face Cover alternative) would be the most
protective of human health and the environment. This is because Modified Alternative LSF-4 reguires the
removal of the greatest volume of contaminated materials in the former tire pile area, thereby providing the
greatest risk reduction and overall protection of human health and the environment. Moreover, Modified
Alternative LSF-4 would provide additional protection by including an additional 2 feet of soil cover on the
north slope of the former landfill. This cover would further reduce potential exposure from landfill solids,
thus reducing risks to human health and the environment.

Alternative LFS-6 (the Drum Removal/Low-Temperature Thermal Desorption/Stabilization and Disposal
alternative) would be the second most protective of human health and the environment because this alternative
reguires the removal and treatment of the second greatest volume of contaminated materials (approximately
1,350 drums and 4,200 cubic yards of contaminated soil) in the former tire pile area. Like Modified
Alternative LFS-4, Alternative LFS-6 would include reclamation of excavated areas and maintenance of soil
cover in the former tire pile area. The existing cap over the landfill mass would be maintained. However,
this alternative does not include the additional 2 feet of soil cover on the north slope of the landfill.

Alternative LFS-4 (the Drum Removal/Offsite Disposal alternative) would be the third most protective of human
health and the environment because this alternative reguires the removal and treatment of the third greatest
volume of contaminated materials (approximately 1,350 drums and contaminated soils adjacent to the drums) in
the former tire pile area. Thus, risks would be reduced in the former tire pile area, but not as much as
Alternative LFS-6 and Modified Alternative LSF-4. Alternative LSF-4 would include the same cover elements as
Alternative LFS-6 in the former tire pile area and the landfill mass.

Alternative LFS-3 (Clay Cap alternative) would be slightly less protective than Alternative LSF-4 because it
would remove a lesser volume of contaminated materials (approximately ten drums) in the former tire pile area
and would not result in treatment of those materials (instead they would be disposed of at an offsite RCRA
Subtitle C facility.) However, Alternative LFS-3 would include a clay cap in the former tire pile area rather
than a soil cover. This would provide a more substantial physical barrier to contaminated landfill solids in
this area and thus reduce the potential for exposure.

The No Further Action (LFS-2) and Landfill Regrading (LFS-7) alternatives are considered to be least
protective of human health and the environment because neither alternative reguires removal or treatment of
contaminated materials. Alternative LFS-7 would include an additional 2 feet of clay on the north face of
the landfill mass after landfilling was completed.

9.2.1.1.2 Landfill Gas (LFG). Alternatives LFG-3, LFG-5, and Modified Alternative LFG-3 would each be
protective of human health and the environment. These alternatives would ensure protectiveness by extracting
gas from the landfill, thereby preventing gas migration beyond the Lowry Site boundaries, and treating the
gas. Potentially dangerous buildups of methane would be prevented and migrating VOCs would be captured and
treated.

Modified Alternative LFG-3 (Gas Collection/Enclosed Flare) is the most protective of human health and the
environment. This is because Modified Alternative LFG-3 provides greater short- and long-term risk reduction
than other alternatives involving gas collection because of the initial installation of a more comprehensive
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extraction system (Stage 1 and Stage 2). Alternatives LFG-3 (Stage 1) and LFG-5 (Stage 1) would provide
initial gas extraction in localized areas in the western and southwestern portions of the landfill mass. If
gas continued to migrate from the landfill mass, Stage 2 of these alternatives would be implemented.

Stage 2 includes the addition of gas extraction wells around the perimeter of the landfill mass. If Stage 2
of Alternative LFG-3 and Stage 2 of Alternative LFG-5 were implemented, Alternatives LFG-3 and LFG-5 would be
as protective of human health and the environment as Modified Alternative LFG-3. The No Further Action
alternative (LFG-2) would not be protective of human health and the environment because it would not prevent
gas migration from occurring.

9.2.1.2 Compliance with ARARs

The ARARs for OUs 2&3 alternatives are discussed in Section 8.0.

9.2.1.2.1 Landfill Solids. All alternatives would meet ARARs except Alternative LFS-7 (Landfill Regrading).
Alternative LFS-7 would not meet RCRA Subtitle D Solid Waste Disposal Regulations (40 CFR Parts 257 and 258)
and Regulations Pertaining to Solid Waste Disposal Sites and Facilities (6CCR 1007-2) because standards for
design and construction would not be met.

9.2.1.2.2 Landfill Gas. All alternatives except the No Further Action alternative would meet ARARs. The No
Further Action alternative would not meet RCRA Solid Waste Disposal Regulations (40 CFR Parts 241) because
gas would migrate offsite above the regulated limits.

9.2.2 Primary Balancing Criteria

9.2.2.1 Long-Term Effectiveness and Permanence

9.2.2.1.1 Landfill Solids. Modified Alternative LFS-4 would provide the greatest long-term effectiveness and
permanence because the former tire pile area would be excavated and the largest volume of contaminated
material would be removed relative to the remaining alternatives. This would permanently remove contaminated
material from the Lowry Site. In addition, Modified Alternative LFS-4 would provide 2 feet of additional
cover on the north face of the landfill mass, thus providing greater containment and long-term effectiveness
and permanence in the landfill area.

Alternatives LFS-3, LFS-4, and LFS-6 would each provide a lesser level of effectiveness in the landfill mass
and the former tire pile area because these alternatives would remove a smaller volume of contaminated
material from the former tire pile area and would not provide 2 feet of additional cover on the north face of
the landfill mass. The alternatives that would least meet this criterion are the No Further Action
alternative (LFS-2) and Alternative LFS-7 (Landfill Regrading) because they would remove no contaminated
material from the former tire pile area. Alternative LFS-7 would provide an additional 2 feet of cover on
the north face of the landfill mass.

9.2.2.1.2 Landfill Gas. Modified Alternative LFG-3 would provide the greatest long-term effectiveness and
permanence because it would provide a more extensive gas extraction system throughout the landfill mass, and
it would be less dependent on gas monitoring activities than other alternatives.

Alternatives LFG-3 and LFG-5 would be as effective in the long-term as Modified Alternative LFG-3 if Stage 2
of Alternative LFG-3 and Stage 2 of Alternative LFG-5 were implemented. The No Further Action alternative
(LFG-2) does not remove and treat gas from the landfill and is therefore considered the least effective
alternative. Over time, gas would migrate offsite and pose a risk to human health and the environment.

9.2.2.2 Reduction of Toxicitv, Mobility, or Volume Through Treatment

9.2.2.2.1 Landfill Solids. Modified Alternative LFS-4 (the Drum Removal/Offsite Disposal/North Face Cover
alternative) would reguire excavation and treatment of the greatest volume of contaminated solid material,
and would thus provide the greatest reduction of toxicity, mobility, and volume of contaminants through
treatment. The toxicity, mobility, and volume of liguids in drums would be reduced through incineration and
the mobility of other excavated materials would be reduced through stabilization.

Alternative LFS-6 (the Drum Removal/Low-Temperature Thermal Desorption/Stabilization/Disposal alternative)
reguires the excavation and treatment of the next greatest volume of contaminated solid material and would
thus provide the next greatest reduction of toxicity, mobility, and volume of contaminants through treatment.
This alternative would incinerate the same volume of liguids from drums as Modified Alternative LFS-4, but
would treat a lesser volume of soils (4,200 cubic yards versus 15,000 cubic yards.) Treatment for the soils
would consist of low temperature thermal desorption.
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Alternative LFS-4 (the Drum Removal/Offsite Disposal/North Face Cover alternative) would provide the next
greatest reduction in toxicity, mobility, and volume through excavation and offsite treatment. The same
volume of liquids in drums would be incinerated, but a lesser volume of soils would be treated than with
either Modified Alternative LFS-4 or Alternative LFS-6.

Alternative LFS-3 (Clay Cap alternative), Alternative LFS-2 (No Further Action alternative), and Alternative
LFS-7 (Landfill Regrading alternative) would provide no reduction of toxicity, mobility, or volume through
treatment.

9.2.2.2.2 Landfill Gas. Modified Alternative LFG-3 would provide a greater reduction of toxicity, mobility,
and volume through treatment than other alternatives by extracting and treating more gas from the eastern,
western, and southern portions of the landfill mass than the remaining alternatives. Alternatives LFG-3
(Stage 1) and LFG-5 (Stage 1) would provide for the next greatest reduction in toxicity, mobility, and volume
through the treatment of landfill gas in the western and southwestern portions of the landfill mass.
Alternatives LFG-3 and LFG-5 would provide the same reductions of toxicity, mobility, or volume through
treatment as Modified Alternative LFG-3 if Stage 2 of Alternative LFG-3 and Stage 2 of Alternative LFG-5 were
implemented. Alternative LFG-2 (No Further Action) would provide no reduction in toxicity, mobility, or
volume through treatment.

9.2.2.3 Short-Term Effectiveness

9.2.2.3.1 Landfill Solids. The No Further Action alternative (LFS-2) would provide the greatest short-term
effectiveness because it poses no adverse short-term effects to workers, the community, or the environment.
Construction and implementation risks associated with placing the additional 2 feet of cover on the north
face in Modified Alternative LFS-4 and regrading in Alternative LFS-7 would be similar to typical landfill
grading activities. These portions of the alternatives are considered to have a high level of short-term
effectiveness because they have very few adverse effects. There would be a limited potential for
construction workers or the community to be exposed to volatile organic compounds through the excavation
activities associated with Alternatives LFS-3, LFS-4, and LFS-6, and for the general public to be exposed
during offsite transport of the excavated materials. Modified Alternative LFS-4 would pose a slightly higher
risk to construction workers because of the more extensive level of excavation and thus is considered to have
slightly less short-term effectiveness.

9.2.2.3.2 Landfill Gas. Modified Alternative LFG-3 and Alternative LFG-3 (Stage 1) would be most effective
in the short-term. These alternatives would achieve protectiveness in a short time frame and would pose
minimal short-term risks to workers, the community, or the environment during construction. Modified
Alternative LFG-5 (Stage 1) would be slightly less effective in the short-term because it would pose slightly
greater risks to workers during the installation and operation of heat recovery equipment. Although the No
Further Action alternative (LFG-2) would pose no adverse short-term risks to workers, the community, or the
environment from construction activities (because there would be none), this alternative would not eliminate
potential short-term risks from gas buildup and migration.

9.2.2.4 Implementabilitv

9.2.2.4.1 Landfill Solids. All of the Landfill Solids alternatives are considered relatively equal in terms
of technical and administrative implementability. This is because all alternatives would use proven
technologies that have been successfully implemented at many other sites. Alternatives LFS-4 and LFS-6 would
include the excavation of drums, drum contents, and contaminated soils using readily available construction
equipment. Modified Alternative LFS-4 would consist of excavation as described in Alternatives LFS-4 and
LFS-6, and would also include excavation of waste pits within the unsaturated zone. This type of excavation
is considered routine construction, could be conducted by local contractors, and has been implemented at
other Superfund sites. Construction of the north face cover in Modified Alternative LFS-4 and regrading in
Alternative LFS-7 would involve routine landfill construction procedures, and cover material is readily
available onsite.

9.2.2.4.2 Landfill Gas. All of the landfill Gas Alternatives would be technically and administratively
implementable. Next to Alternative LFG-2, Modified Alternative LFG-3 is considered to be the most
implementable alternative because this alternative would use proven technology, and the construction of gas
extraction wells would be a routine activity that could be conducted by many local contractors. In addition,
constructing Stages 1 and 2 extraction wells together in Modified Alternative LFG-3 would be easier to
implement than constructing them separately in Alternative LFG-3 (Stage 2) and Alternative LFG-5 (Stage 2)
since there would be only one mobilization expense and less monitoring to determine rates and directions of
gas migration.

Alternative LFG-5, which includes heat recovery, would be the most technically difficult to implement because
heat recovery from an enclosed flare is not commonly practiced.
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9.2.2.5 Cost

9.2.2.5.1 Landfill Solids. Modified Alternative LFS-4 (the Drum Removal/Offsite Disposal alternative) and
Alternative LFS-6 (the Drum Removal/Low-Temperature Thermal Desorption/Stabilization/Disposal alternative)
have the highest present-worth costs. However, Modified Alternative LFS-4 would remove a larger volume of
contaminated material than Alternatives LFS-4 or LFS-6. In addition, Modified Alternative LFS-4 includes the
cover on the northern slope of the landfill mass. Alternative LFS-4 (the Drum Removal/Offsite Disposal
alternative) is the next most costly alternative, followed by Alternative LFS-2 (the No Further Action
alternative), Alternative LFS-3 (the Clay Cap alternative), and Alternative LFS-7 (the Landfill Mass
Regrading alternative). The costs for each of the landfill solids alternatives are listed below:

• Alternative LFS-7: Landfill Mass Regrading

Capital Costs: $0
Annual O&M Costs: $350,000
Total 30-year Present Worth): $5,380,000

Alternative LFS-3: Clay Cap

Capital Costs: $670,000
Annual O&M Costs: $410,000
Total (30-year Present Worth $6,970,000

Alternative LFS-2: No Further Action

Capital Costs: $36,000
Annual O&M Costs: $470,000
Total (30-year Present Worth): $7,260,000

• Alternative LFS-4: Drum Removal/Offsite Disposal

Capital Costs: $2,400,000
Annual O&M Costs: $410,000
Total (30-year Present Worth): $8,700,000

• Alternative LFS-6: Drum Removal/Low Temperature Thermal Desorption/Stabilization/Disposal

Capital Costs: $5,200,000
Annual O&M Costs: $410,000
Total (30-year Present Worth): $11,500,000

• Modified Alternative LFS-4: Drum Removal/Offsite Disposal/North Face Cover

Capital Costs: $8,600,000
Annual O&M Costs: $316,000
Total (30-year Present Worth): $13,460,000

9.2.2.5.2 Landfill Gas. The estimated present-worth costs for Modified Alternative LFG-3 are slightly
greater than present-worth estimates for Alternative LFG-3 (Stage 1). These are the least costly
alternatives that meet the threshold criteria. Alternative LFG-5 would be the next most costly based on
present worth estimates. It is slightly less than Alternative LFG-3 (Stages 1 & 2). The most expensive
alternative is Stage 3 of Alternative LFG-3. The present-worth costs for the OU3 alternatives are ranked
below. These costs also include estimated capital and O&M costs.

Alternative LFG-2: No Further Action

Capital Costs: $36,000
Annual O&M Costs: $59,000
Total (30-year Present Worth): $943,000

Alternative LFG-3: Gas Collection/Enclosed Flare (Stage 1)

Capital Costs: $3,200,000
Annual O&M Costs: $310,000
Total (30-year Present Worth): $7,970,000
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Modified Alternative LFG-3: Gas Collection/Enclosed Flare

Capital Costs: $3,200,000
Annual O&M Costs: $340,000
Total (30-year Present Worth): $8,430,000

• Alternative LFG-5: Gas Collection with Heat Recovery (Stage 1)

Capital Costs: $3,700,000
Annual O&M Costs: $313,000
Total (30-year Present Worth): $8,510,000

Alternative LFG-3: Gas Collection/Enclosed Flare (Stages 1 and 2)

Capital Costs: $3,600,000
Annual O&M Costs: $340,000
Total (30-year Present Worth): $8,830,000

Alternative LFG-3: Gas Collection/Enclosed Flare (Stages 1, 2, and 3)

Capital Costs: $5,200,000
Annual O&M Costs: $503,000
Total (30-year Present Worth): $12,930,000

The above-referenced cost breakdowns suggest that capital costs for Modified Alternative LFG-3 are similar to
capital costs for Alternative LFG-3, Stage 1. Although Modified Alternative LFG-3 involves an additional
stage of well construction (Stage 2) compared to Alternative LFG-3, Stage 1, it does not include costs
associated with a well abandonment program. Estimated capital costs for Stage 2 construction are
approximately egual to estimated costs for the well abandonment program. Conseguently, Modified Alternative
LFG-3 and Alternative LFG-3, Stage 1 have similar capital costs.

9.2.3 Modifying Criteria

9.2.3.1 State/Support Agency Acceptance

The State of Colorado concurs with EPA on the selection of Modified Alternative LFS-4 and Modified
Alternative LFG-3 for OUs 2&3.

9.2.3.2 Community Acceptance

Community input on the alternatives for remedial action for OUs 2&3 were solicited by EPA and CDH during the
public comment period from September 1, 1993 to November 29, 1993. Comments received from the community were
strongly supportive of the excavation and treatment of contaminated solids in the former tire pile area. The
community was also generally supportive of the simultaneous implementation of the Stage 1 and 2 gas
extraction measures as a means of controlling gas migration offsite. However, one commenter encouraged EPA to
consider the focus of the gas extraction to be extraction and removal rather than control of offsite gas
migration. The commenter felt that the additional installation of Stage 3 would yield a significant increase
in the annual volume of contaminants removed for a relatively small incremental increase in the overall cost.
The community was also adamantly opposed to the addition of 1.2 million cubic yards of municipal solid waste
over the former waste pits (Alternative LFS-7, Landfill Regrading). Commentors were very supportive of EPA's
proposal to reject this alternative.

Comments from the PRPs opposed EPA' s preferred alternative and proposed a remedy consisting of land
acguisition and land use restrictions 0.5 mile around the perimeter of the Lowry Site, the enhancement of the
landfill cover through the addition of 1.2 million cubic yards of municipal solid waste, and the installation
of Stage 1 of the gas extraction system. The PRPs comments also focused on the short-term effectiveness of
the excavation in the former tire pile area and the potential exposure to workers during the excavation.

Responses to the community and the PRP comments are found in the Responsiveness Summary for OUs 2&3 in
Section 14.0 of this ROD.
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9.3 OU 4: Soil and OU 5: Surface Water and Sediments

9.3.1 Threshold Criteria

9.3.1.1 Overall Protection of Human Health and the Environment

9.3.1.1.1 OU 4: Soils. All of the alternatives for soils are protective of human health and the
environment. This is because the risks to human health and the environment posed by soil at the Lowry Site
are estimated to be minimal and in the range of background risks. Background risks were found to already be
within EPA's acceptable risk range. The No Further Action alternative (SOIL-1) would be the most protective
because it would not entail any disturbance of soils, thereby minimizing the potential for exposure. The
remaining alternatives (SOIL-2, SOIL-4a, and SOIL-4b) would involve soil disturbance during construction or
excavation which could potentially uncover material of greater risk. Moreover, the disturbance of the soil
would result in an exposure pathway to construction workers.

9.3.1.1.2 OU 5: Surface Water. The No Further Action alternative (SW-1) is protective of human health and
the environment because the Surface Water Removal Action (SWRA) isolates and treats, to protective levels,
contaminated seepage that previously existed as surface water flow in the unnamed creek. No other
alternatives were evaluated for surface water because the SWRA can be fully integrated into the sitewide
remedy.

9.3.1.1.3 OU 5: Sediments. All alternatives considered for sediments in both Sections 6 and 31 would be
protective of human health and the environment.

Sediments in Section 6 have already been covered by a geotextile and low-permeability soft cap as part of the
SWRA. Therefore, there is no exposure to Section 6 sediments and no current or future risk to human health
and the environment. Alternative SED6-2 would be slightly more protective of human health and the
environment because the exposure pathway posed by sediments in Section 6 would be further limited through a
physical barrier (fence).

For Section 31 sediments, the Baseline Risk Assessment found that risks associated with potential sediment
contaminant exposures were within the acceptable excess cancer risk range. Therefore, Alternative SED31-1
(the No Further Action alternative) would be protective of human health and environment. Alternatives
SED31-2 and SED31-3 are considered to be the most protective because they would eliminate exposure, although
there would be an increased potential for short-term exposure to sediments from the disturbance of sediments.

9.3.1.2 Compliance with ARARs

The ARARs for OUs 4&5 alternatives are discussed in Section 8.0.

9.3.1.2.1 OU 4: Soils. All alternatives would meet ARARs. The requirements primarily deal with
landfilling and maintenance actions and would be met by following the requirements of the regulations.

9.3.1.2.2 OU 5: Surface Water. The only alternative evaluated, No Further Action, would meet ARARs.

9.3.1.2.3 OU 5: Sediments. All alternatives for both Section 6 and Section 31 sediments would meet ARARs.
The ARARs primarily deal with construction, excavation, and landfilling actions and would be met by
satisfying the requirements of each regulation.

9.3.2 Primary Balancing Criteria

9.3.2.1 Long-Term Effectiveness and Permanence

9.3.2.1.1 OU 4: Soils. Alternatives SOIL-4a, and SOIL-4b (Excavation and Landfill) would provide the
greatest long-term effectiveness and permanence because these alternatives would require excavation and
landfilling of contaminated materials.

Alternative SOIL-2 (Access Restrictions and Dust Control) would provide the next greatest long-term
effectiveness and permanence because the soil would be covered by vegetation and exposure to the soil would
be further restricted by a fence. The No Further Action alternative would provide the next level of
long-term effectiveness and permanence through institutional controls. The risks associated with the No
Further Action alternative are within EPA's acceptable risk range. Therefore, the No Further Action
alternative would offer acceptable long-term effectiveness and permanence.

9.3.2.1.2 OU 5: Surface Water. The SWRA has been constructed, has operated reliably, and has met
performance standards. The SWRA has been designed for long-term operation and will be monitored and
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maintained such that it continues to achieve performance standards. Thus, the SWRA will provide long-term
effectiveness and permanence.

9.3.2.1.3 OU 5: Sediments. In Section 6, the sediments have already been covered as part of the SWRA.
Alternative SED6-2 (Access Restrictions) would provide the greatest long-term effectiveness and permanence by
fencing the cover over the sediments to restrict access and by maintaining the cover. Alternative SED6-1 (No
Further Action) would provide nearly as great long-term effectiveness and permanence through continued
maintenance of the cover.

Alternative SED31-3 (the Excavation and Landfill alternative) would provide the greatest long-term
effectiveness and permanence through removal and landfilling of the sediments. Alternative SED31-2 (the
Access Restriction/Capping alternative) would provide the next level of long-term effectiveness and
permanence by minimizing the exposure to the sediments through physical barriers (a cap and fence).
Alternative SED31-1 (No Further Action) would provide acceptable long-term effectiveness and permanence
because the risks associated with the sediments are within EPA's acceptable risk range.

9.3.2.2 Reduction of Toxicitv, Mobility, or Volume Through Treatment

9.3.2.2.1 OU 4: Soils. None of the soils alternatives involve treatment. Therefore, these alternatives
would not result in a reduction of toxicity, mobility, or volume through treatment.

9.3.2.2.2 OU 5: Surface Water. Under the No Further Action alternative, the SWRA would reduce the volume
of contaminants through collection and treatment of the alluvial seepage. In the absence of the SWRA, this
seepage would have become contaminated surface water by emerging in the unnamed creek drainage. There would
be no apparent reduction in the toxicity or mobility of the contaminants since the treatment would not induce
any changes in the chemical forms; however, the contaminants would be immobilized/adsorbed using granular
activated carbon during treatment.

9.3.2.2.3 OU 5: Sediments. None of the sediments alternatives for Section 6 or 31 would involve treatment.
Therefore, these alternatives would not result in a reduction of toxicity, mobility, or volume through
treatment. However, the mobility of the contaminants would be reduced in Alternatives SED31-2 and SED31-3
through engineering controls.

9.3.2.3 Short-Term Effectiveness

9.3.2.3.1 OU 4: Soils. The No Further Action alternative (SOIL-1) would not involve soil disturbance and,
therefore, would provide maximum short-term protection to workers and the community. The risk from soils are
already within EPA's acceptable risk range and therefore the time until protection is achieved is immediate.

Alternative SOIL-2 would provide the next greatest short-term protection to workers, the environment, and the
community because it involves only access restrictions and dust control activities.

Alternatives SOIL-4a and SOIL-4b would involve disturbance in the short-term through excavation of soils.
This would result in a potential for exposure to workers and disturbance of existing habitats.

9.3.2.3.2 OU 5: Surface Water. Construction and startup of SWRA facilities have been completed and were
conducted in a manner without accidents or adverse environmental impacts. Therefore, the SWRA satisfies the
short-term effectiveness criterion.

9.3.2.3.3 OU 5: Sediments. Alternatives SED6-1 (No Further Action) and SED31-1 (No Further Action) provide
the greatest short-term effectiveness for workers, the community, and the environment because these
alternatives reguire no disturbance of sediments. Alternative SED6-2 reguires installation of fencing, which
would involve minimal exposure to workers and habitat disturbance. Alternatives SED31-2 and SED31-3 would
involve sediment disturbance through capping and/or excavation activities. Therefore, these alternatives
would be the least effective in providing short-term protection.

9.3.2.4 Implementabilitv

9.3.2.4.1 OU 4: Soils. All alternatives are considered to be technically and administratively
implementable. Alternatives SOIL-2, SOIL-4a (Option 1), SOIL-4b (Option 1), and the No Further Action
alternative would be egually implementable. Option 2 of Alternatives SOIL-4a and SOIL-4b would be harder to
implement because of technical difficulties associated with the one-time excavation of approximately 2.5
million cubic yards of soil, uncertainties about availability of land for stockpiling, and difficulties
associated with maintenance of the stockpile.

9.3.2.4.2 OU 5: Surface Water. The SWRA has been constructed and is operational, and is therefore
implementable.
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9.3.2.4.3 OU 5: Sediments. Implementation of Alternative SED6-1 (No Further Action alternative) and
Alternative SED6-2 (Access Restrictions) would be technically feasible because of the availability of
materials for access control and for fugitive dust and noise control. Except for additional fencing,
Alternative SED6-2 (Access Restrictions) is already an integral part of the SWRA.

Alternative SED31-1 (No Further Action) and Alternative SED31-2 (Access Restrictions and Capping) would both
be technically implementable. Alternative SED31-3 (Excavation and Landfill) would also be implementable;
however, some seasonal delays could be encountered when implementing this alternative because of a potential
need for wetlands construction.

9.3.2.5 Cost

9.3.2.5.1 OU 4: Soils. Excavation alternatives generally have the highest present-worth costs.
Alternative SOIL-4b (Option 2) is the most expensive because of the magnitude of excavation, materials
movement, and offsite stockpiling. The No Further Action alternative and Alternative SOIL-4a (Option 1)
would be the least expensive alternatives. Present-worth costs for OU 4 are ranked below. These costs
include estimated capital and O&M costs.

Alternative SOIL-1: No Further Action

Capital Costs: $22,000
Annual O&M Costs: $24,000
Total (30-year Present Worth): $390,000

• Alternative SOIL-4a, Option 1: Excavation (as-needed) and Landfill (onsite)

Capital Costs: $43,000
Annual O&M Costs: $29,000
Total (30-year Present Worth): $490,000

• Alternative SOIL-4b, Option 1: Excavation (as-needed) and Landfill (offsite)

Capital Costs: $1,200,000
Annual O&M Costs: $44,000
Total (30-year Present Worth): $1,880,000

• Alternative SOIL-2: Access Restrictions and Dust Control

Capital Costs: $1,400,000
Annual O&M Costs: $44,000
Total (30-year Present Worth): $2,080,000

• Alternative SOIL-4a, Option 2: Excavation (one-time) and Landfill (onsite)

Capital Costs: $2,800,000
Annual O&M Costs: $31,000
Total (30-year Present Worth): $3,280,000

• Alternative SOIL-4b, Option 2: Excavation (one-time) and Landfill (offsite)

Capital Costs: $4,000,000
Annual O&M Costs: $52,000
Total (30-year Present Worth): $4,800,000

9.3.2.5.2 OU 5: Surface Water. Capital costs for construction of the SWRA have already been incurred and
are not included in the cost estimate. Other costs associated with the No Further Action alternative (SW-1)
would include O&M for the SWRA and the construction of wetlands. These costs are as follows:

Alternative SW-1, No Further Action

Capital Costs: $41,000
Annual O&M Costs: $790,000
Total (30-year Present Worth): $12,190,000
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9.3.2.5.3 OU 5: Sediments. Access Restrictions/Capping (Alternative SED31-2) and Excavation and Landfill
(Alternative SED31-3) would be the most costly alternatives. The No Further Action alternatives (SED6-1 and
SED31-1) would be the least expensive alternatives. Present-worth costs for sediments alternatives are
ranked below. These costs include estimated capital and O&M costs.

• Section 6 Sediments Alternative SED6-1: No Further Action

Capital Costs: $16,000
Annual O&M Costs: $15,000
Total (30-year Present Worth): $250,000

• Section 6 Sediments Alternative SED6-2: Access Restrictions

Capital Costs: $93,000
Annual O&M Costs: $23,000
Total (30-year Present Worth): $450,000

Section 31 Sediments Alternative SED31-1: No Further Action

Capital Costs: $22,000
Annual O&M Costs: $18,000
Total (30-year Present Worth): $300,000

• Section 31 Sediments Alternative SED31-2: Access Restrictions and Capping

Capital Costs: $400,000
Annual O&M Costs: $53,000
Total (30-year Present Worth): $1,215,000

• Section 31 Sediments Alternative SED31-3: Excavation and Landfill

Capital Costs: $620,000
Annual O&M Costs: $40,000
Total (30-year Present Worth): $1,235,000

9.3.3 Modifying Criteria

9.3.3.1 State/Support Agency Acceptance

The State of Colorado concurs with the EPA on the selection of the No Further Action alternative for OUs 4&5.

9.3.3.2 Community Acceptance

Community input on the alternatives for remedial action for OUs 4&5 was solicited by EPA and CDH during the
public comment period from September 1, 1993, to November 29, 1993. Comments received from the community and
the PRPs indicate no opposition to the preferred alternative for each media under OUs 4&5. Responses to
community comments are found in the Responsiveness Summary in this ROD.
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Section 10.0
Documentation of Significant Changes

Two separate Proposed Plans were published by EPA and released for the Lowry Site. One Proposed Plan was for
the Shallow Ground Water and Subsurface Liquids/Deep Ground Water Operable Units (OUs 1&6), and that document
was released for public comment in November 1992. The second Proposed Plan for the Landfill Solids/Gas
Operable Units and for the Soils/Surface Water and Sediments Operable Units (OUs 2&3 and 4&5) was released
for public comment in August 1993. The second Proposed Plan also included a description of the proposed
sitewide remedy that addressed all six OUs.

The Proposed Plan for OUs 1&6 identified Modified Alternative GW-5 (the North Boundary/Toe of
Landfill/Lateral and Upgradient Containment, Collection, and Treatment alternative) as the preferred
alternative for ground-water and subsurface liquids remediation. EPA reviewed all written and verbal
comments submitted during the public comment period, and issued a preliminary response in August 1993.

The OUs 2&3 and 4&5 Proposed Plan identified Modified Alternative LFS-4 (the Drum Removal/Offsite
Disposal/North Face Cover alternative) as the preferred alternative for landfill solids and Modified
Alternative LFG-3 (the Gas Collection/Enclosed Flare alternative) as the preferred alternative for landfill
gas. For soils, surface water, and sediments, the OUs 2&3 and 4&5 Proposed Plan identified the No Further
Action alternative as the preferred alternative. The OUs 2&3 and 4&5 Proposed Plan also described how all of
the preferred alternatives would be integrated into a sitewide remedy. The sitewide remedy is the
combination of the preferred alternatives for each OU.

There are no significant changes from the proposed plans. However, the present worth cost calculations, as
they appear in the ROD, differ slightly from those presented in the proposed plans. In order to allow for
the consistent comparison of costs for the various alternatives, EPA recalculated the costs using a single
set of assumptions. The following factors were standardized for all components of the selected sitewide
remedy: indirect costs; capital costs contingencies; interest rates; and inflation rates.
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Section 11.0
Selected Sitewide Remedy

After considering CERCLA's statutory requirements, the detailed analysis of the alternatives using the nine
criteria, and public comments, EPA, in consultation with CDH, has determined that the most appropriate
sitewide remedy for the Lowry Site includes the following OU components, described in greater detail in
Subsections 11.2 through 11.5 of this ROD:

• OUs l&6-Shallow Ground Water and Subsurface Liquids and Deep Ground Water-Modified Alternative
GW-5 (the North Boundary, Toe of Landfill, and Lateral [Eastern and Western] Containment,
Collection and Treatment plus Upgradient Containment, Collection and Diversion alternative).

OU 2-Landfill Solids-Modified Alternative LFS4 (the Drum Removal/Offsite Disposal/North Face
Cover alternative).

OU 3-Landfill Gas-Modified Alternative LFG-3 (the Gas Collection/Enclosed Flare alternative).

• OU 4&5-Soils, Surface Water, and Sediments-No Further Action alternative.

The selected sitewide remedy also includes the general components described in Subsection 11.1 of this ROD.
The selected sitewide remedy addresses all contaminated media at the Lowry Site and provides the best balance
of tradeoffs among the nine criteria. EPA has also determined that the selected sitewide remedy is
protective of human health and the environment. Although the selected sitewide remedy includes containment
elements, the selected sitewide remedy also includes significant collection and treatment elements. Figure
11-1 is a graphical representation of the selected sitewide remedy. Table 11-1 presents the ARARs for the
selected sitewide remedy. Additional performance standards for the selected remedy are described in the
following subsections.

11.1 General Components of the Selected Sitewide Remedy

The selected sitewide remedy includes the following general components:

• Institutional Controls-Institutional controls are nonengineering methods by which Federal,
State, local governments, or private parties can prevent or limit access to or use of a site.
Institutional controls for the Lowry Site shall include, but not be limited to, deed notices
and restrictions that run with the land; onsite access restrictions including, but not limited
to, fencing and warning signs; zoning controls; and well restrictions. Executive Order No. 97,
as issued by City and County of Denver Mayor Federico Pena, currently provides some measure of
control. Institutional controls at the Lowry Site must prohibit all activities and uses that
EPA determines would interfere or be incompatible with, or that would in any way reduce or
impair the effectiveness or protectiveness of, the sitewide remedy. These shall include, but
are not limited to, prohibitions on all ground-water well construction and use not necessary
for implementation and monitoring of the selected remedy; prohibitions on access; and
prohibitions on activities and land use not connected with design, construction, and
implementation and monitoring of the selected sitewide remedy.

• Offsite institutional controls shall serve as an additional measure of protection to enhance
the effectiveness of the selected remedy and to act as preventative measures to preserve the
implementability and effectiveness of any of the selected remedy contingency measures. Offsite
institutional controls shall include, but not be limited to, deed notices and restrictions,
zoning controls, and well restrictions. These controls must prohibit all offsite activities in
the vicinity of the Lowry Site that would interfere or be incompatible with, or that would in
any way reduce or impair the effectiveness or protectiveness of, the selected sitewide remedy.

All onsite and offsite institutional controls shall be adequately administered, maintained, and
enforced.

The owner and operator of the Lowry Site shall be responsible for access restrictions, warning
signs, and fences.

• Performance and Compliance Monitoring-To ensure that the performance standards are met for all
components of the selected remedy for as long as contamination remains onsite, a long-term
monitoring program shall be designed and implemented during the RD/RA and shall continue
throughout the implementation of the selected sitewide remedy. The monitoring program shall
assess compliance with the remediation levels in the ground-water system, monitor effluent
chemical concentrations from the treatment plant, evaluate the horizontal and vertical
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migration of contamination, monitor the erosion of soils and sediments, and monitor the
migration of landfill gases. Details of the monitoring program shall be determined by EPA, in
consultation with CDH, during the RD. The monitoring program shall include, at a minimum, the
following: analytical parameters and methods; indicator parameters; monitoring locations;
monitoring freguency and duration; sampling methods; well installation, maintenance and
abandonment procedures; statistical methods for evaluating data; reporting methods and
procedures for tracking and maintaining sample records; and QA methods, including data
validation methods. It is estimated that approximately 60 to 100 ground-water monitoring wells
will be sampled semi-annually. Landfill gas shall be monitored guarterly, or more freguently
if migration is detected, using approximately 40 to 60 monitoring wells. The ground-water
monitoring component of the selected sitewide remedy includes an early-warning monitoring
component; this will allow for a timely remedial response in the event that EPA determines that
additional remedial actions are necessary. Soil and sediment erosion shall be monitored on a
monthly basis using three surface-water samplers installed in drainages. The actual details of
the monitoring program are subject to revisions and refinement during RD.

• Five-Year Review-As specified in Section 121(c) of CERCLA, as amended by SARA, and Section
300.430(f)(4)(ii) of the NCP, EPA will review the sitewide remedy no less often than each 5
years after the initiation of the remedial action to assure that human health and the
environment are being protected by the implemented remedy (this review will ensure that the
remedy is operating and functioning as designed and that institutional controls are in place
and are protective). An additional purpose for the review is to evaluate whether the
performance standards specified this ROD remain protective of human health and the environment.
EPA will continue the reviews until no hazardous substances, pollutants, or contaminants remain
at the Lowry Site above levels that allow for unrestricted use and unlimited exposure.

11.2 Remedy for Shallow Ground Water and Subsurface Liquids and Deep Ground Water

The selected remedy for shallow ground water and subsurface liguids and deep ground water (ground-water
remedy) shall contain, collect, and treat contaminated shallow ground water at the Lowry Site. This shall be
achieved through the construction and operation of barrier walls, collection and diversion systems, and a
treatment system to be upgraded as necessary, and continued operation of the existing barrier wall and
collection system, thereby reducing the mobility of potential contamination from the main source and reducing
the level of toxicity and volume of contamination. Specifically, the groundwater remedy shall include the
following containment and treatment components:

• Evaluation of the effectiveness of, and upgrading as necessary, the barrier wall system at the
northern boundary of the Lowry Site to restrict offsite migration of contaminated ground water.

• Installation and operation of a ground-water extraction system at the toe of the former
landfill. This ground water will be pumped to the ground-water treatment plant. The treatment
plant will be upgraded as necessary to meet performance standards, as described below.

• Construction and operation of underground barrier walls and ground-water collection systems on
the west and east sides of the Lowry Site.

• Construction and operation of an approximately 50-foot-deep upgradient ground-water
containment, collection, and diversion system along the southern perimeter of the Lowry Site.

• Design and construction of a new ground-water treatment plant unless it can be demonstrated
through pilot-scale testing during the RD that the existing ground-water treatment plant can
effectively treat the more highly contaminated ground water to the performance standards.

• Annual interception and treatment of approximately 6.4 million gallons of contaminated ground
water from the barrier walls and collection systems.

• Implementation of a long-term ground-water monitoring program for assessing compliance with
performance standards and protectiveness of the remedy for the shallow ground-water system and
potential impacts on deep ground water.

• Implementation of a contingency measure (see Subsection 11.2.1.2) if contaminant migration
(including NAPLs movement) into deep ground water occurs in the future. EPA's decision
regarding the contingency measure will be based on an evaluation of monitoring data and
comparison with performance standards as described in Table 11-2.
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The ground-water remedy also includes components of the selected remedies for OUS 2&3 and OUS 4&5.
Applicable components include:

• Maintenance of the existing cover on the landfill mass (described in Subsection 11.3).

• As modified by this ROD, continued operation of the Surface Water Removal Action (SWRA) ,
including the upgraded treatment plant and collection system within unnamed creek. The Surface
Water Removal Action also includes continued operation, maintenance, and monitoring of the
existing ground-water barrier wall at the northern boundary of the Lowry Site. Transition from
the SWRA performance standards to the ground-water remedy performance standards is described in
Subsection 11.2.2.1.

The ground-water remedy shall achieve the Remedial Action Objectives (RAOs) for the protection of human
health and the environment. The RAOs for the ground-water remedy are:

• Prevention of exposure to humans and the environment (through ingestion, inhalation, or dermal
absorption) from liguids (either ground water or waste-pit liguids) containing contaminants in
excess of the performance standards

• Prevention of migration of contaminants beyond the compliance boundary in excess of the
performance standards

• Prevention of horizontal migration of dissolved ground-water contaminants offsite and to
surface waters

• Prevention of vertical migration of dissolved ground-water contaminants beyond the lignite
layer

• Prevention of movement of nonagueous phase liguids (NAPLs) beyond the compliance boundary and
minimization of movement of NAPLs

• Minimization of infiltration and leachate production in the waste-pit source

11.2.1 Containment Components (Barrier Walls and Collection Systems)

The containment components of the ground-water remedy shall effectively isolate the contamination at the
Lowry Site from the surrounding areas by controlling horizontal migration of contaminated ground water
through the construction of containment and diversion systems. The construction and operation of these
systems shall comply fully with all ARARs as described in Table 11-1. The reguirements of the Colorado
Hazardous Waste Act and Land Disposal Restrictions of the Solid Waste Act shall be met through testing and
proper disposal if RCRA hazardous waste, hazardous waste sufficiently similar to RCRA hazardous waste, or
solid waste is generated during construction. Air emissions shall be monitored to ensure compliance with the
Colorado Air Quality Act/Air Pollution Regulations. All monitoring wells shall be constructed and abandoned
according to the reguirements of the Well Construction and Abandonment Procedures of the State Engineer's
Office to ensure that a migration pathway is not created.

The following discussion provides a detailed description of each containment component. Figure 11-1
illustrates the approximate locations and relative length of each containment component.

Northern Boundary. Containment shall be accomplished using the existing barrier wall, elongating the
existing barrier wall, or constructing a barrier wall immediately upgradient or downgradient of the existing
barrier wall that may be deeper and longer than the existing barrier wall. The effectiveness of the existing
barrier wall and the need for a modified barrier wall or new barrier wall shall be evaluated during the RD.
EPA shall determine whether a modified or new barrier wall is needed, based on an evaluation of whether the
existing system is able to meet performance standards. The protectiveness of this component of the selected
remedy shall be ensured on the northern boundary by the implementation of monitoring systems at the
compliance boundary and at the Point of Action boundary (installation of an early warning monitoring well
network).

Toe of the Landfill. A ground-water extraction system shall be installed and operated at the toe of the
landfill to capture contaminated shallow ground water migrating from the landfill mass at the Lowry Site and
prevent further contamination of the aguifer downgradient of the landfill mass. The dimensions of the
subsurface drain shall be such that the drain will intercept and collect the contaminated ground water within
the shallow ground-water system at the toe of the landfill mass. Approximate dimensions are 300 feet long
and 50 feet deep, but actual dimensions shall be determined by EPA, in consultation with CDH, during RD.
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Eastern and Western Boundaries. Underground barrier walls and ground-water collection systems shall be
constructed and operated on the east and west sides of the Lowry Site so as to prevent potential offsite
migration of contaminated shallow ground water. The dimensions of the systems shall be such that the
collection systems will intercept and collect the contaminated ground water within the sand channels within
the shallow ground-water aguifer. Approximate dimensions are 2,000 feet long by 50 feet deep on the eastern
boundary and 1,000 feet long by 50 feet deep on the western boundary. Actual dimensions shall be determined
by EPA, in consultation with CDH, during RD. The protectiveness of these components of the selected remedy
shall be ensured on the eastern and western boundaries by the implementation of monitoring systems at the
compliance boundary and at the Point of Action boundary (installation of an early warning monitoring well
network).

Southern Perimeter. An approximately 50-foot-deep upgradient ground-water containment, collection, and
diversion system (barrier wall) shall be constructed and operated along the southern perimeter of the Lowry
Site so as to prevent offsite contaminant migration to the south and recharge of ground water from the south.
The barrier wall shall be installed in the saturated portion of the weathered zone. The approximate
dimensions of the barrier wall are 1,500 feet long, 50 feet deep, and 3 feet wide. Upgradient extraction
wells shall also be installed to collect uncontaminated upgradient ground water for diversion around the
Lowry Site. The actual dimensions of the barrier wall system and configuration of the upgradient extraction
wells shall be determined by EPA, in consultation with CDH, during RD. The protectiveness of this component
of the selected remedy shall be ensured on the southern boundary by the implementation of monitoring systems
at the compliance boundary and at the Point of Action boundary (installation of an early warning monitoring
well network).

11.2.1.1 Performance Standards and Points of Compliance

The containment components of the ground-water remedy shall meet the performance standards, which are
presented in Tables 11-1 and 11-2. Table 11-1 includes all ARARs for the selected remedy, including the
ground-water portion of the remedy. Table 11-2 presents chemical-specific numeric standards for the
ground-water remedy, some of which are based on ARARs. Table 11-2 performance standards shall be met at the
ground-water compliance boundary.

The compliance boundary is depicted in Figure 11-2. The compliance boundary for vertical ground-water
migration is the lignite layer. The ground water within the compliance boundary is not expected to be
restored to meet the performance standards because the sitewide remedy consists of containment and the source
areas will remain in place.

In locating the point of compliance for ground-water performance standards, EPA has determined that
performance standards shall be attained at and beyond the edge of the waste management area when waste is
left in place. At the Lowry Site, the plume of ground-water contamination is caused by releases from several
distinct sources that are in close geographical proximity. In addition to the delineated locations of the
waste pits and landfill mass, historical evidence indicates that the northwestern, northern, northeastern,
and eastern areas of the Lowry Site received waste via sludge application, leachate injection, and leachate
spraying. Conseguently, the most feasible and effective groundwater cleanup strategy is to draw the point of
compliance to encompass the sources of release and thereby address ground-water contamination as a whole. In
establishing the ground-water compliance boundary, EPA considered the proximity of the sources, the technical
practicability of ground-water remediation, the vulnerability of the ground water and its possible uses, and
the likelihood of exposure.

The selected ground-water remedy also includes a Point of Action (POA) boundary (Figure 11-2). Table 11-3
identifies numeric standards for the POA boundary which are based on the Colorado Basic Standards for Ground
Water [5 CCR-1002-8 (3.11.5c)]. The POA boundary encompasses the highly concentrated waste-pit liguids and
ground water within the main source area and unnamed creek. Ground-water monitoring shall be conducted at
the POA boundary and additional measures, as described in the next section, shall be taken if Table 11-3
standards are exceeded at the POA boundary. The POA boundary has been established to provide sufficient
warning such that response actions can be taken to prevent violation of performance standards at the
compliance boundary. The physical/surveyed location of the compliance boundary and the POA boundary shall be
determined by EPA during RD.

To ensure compliance of the ground-water containment components with the RAOs and performance standards, the
barrier walls and collection systems shall be monitored. The monitoring systems shall consist of wells
upgradient, downgradient, and adjacent to the barrier walls. The well placement shall be such that the
hydraulic gradient information from the wells demonstrates the containment systems' effectiveness.
Additionally, contaminant concentrations shall be measured to determine whether the containment systems
capture the ground water and prevent contamination downgradient and adjacent to the systems. Details of the
monitoring program shall be determined by EPA, in consultation with CDH, during the RD.
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11.2.1.2 Contingency Measures

If, during implementation or operation of the ground-water remedy, contaminant levels exceed the performance
standards at the POA or compliance boundaries, appropriate measures shall be taken to prevent and remediate
contaminant migration beyond the compliance boundary. Such measures may include but are not limited to any
or all of the following, subject to approval by EPA:

• Alternating pumping at wells to eliminate stagnation points

• Pulse pumping to allow aguifer eguilibration and to allow adsorbed contaminants to partition
into ground water

• Installation of additional extraction wells to facilitate containment of the contaminant plume,
to address possible vertical migration of contaminants, and if necessary to remediate the
ground water to performance standards.

To ensure that performance standards continue to be met and maintained, the aguifer shall be monitored at
appropriate locations and freguencies, as determined by EPA.

If EPA determines, on the basis of monitoring data, that contaminants have migrated vertically downward to
the lignite layer, contingency measures shall be implemented to ensure that performance standards are
achieved and maintained and to ensure that the beneficial use of the underlying aguifer is not impaired.
Contingency measures may include any or all of the following, at EPA's discretion, for an indefinite period
of time, as a modification of the existing system:

• Additional engineering controls such as underground barriers, or long-term gradient control
provided by low level pumping, as containment measures

• Continued monitoring of specified wells

• Periodic re-evaluation of remedial technologies for ground-water restoration

• Additional institutional controls on water extraction and use

11.2.2 Treatment Component

The ground-water remedy shall treat approximately 6.4 million gallons of contaminated ground water annually,
collected from the new and existing collection systems and barrier walls. A new onsite treatment plant shall
be designed and constructed unless it can be demonstrated through pilot-testing that the existing plant can
be upgraded to effectively treat the more highly contaminated ground water from the toe of the landfill to
performance standards. Based on treatability studies of the influent from the toe of the landfill conducted
during the OUS 1&6 RI, the following treatment technologies have been determined to be effective in treating
highly contaminated ground water and may be used to treat the contaminated ground water collected from the
Lowry Site: gravity-phase separation for nonagueous phase liguids (NAPLs); lime soda softening for metals,
radionuclides, hardness, and solids; and biological treatment (PACT) to remove organic compounds, BOD, COD,
ammonia, and nitrate. Treatment technologies shall be evaluated further during RD; actual selection of
treatment technologies shall be subject to EPA approval, in consultation with CDH.

Air emissions from the treatment plant shall be treated using vapor-phase activated carbon and monitored to
ensure that performance standards, including the Colorado Air Quality Act/Air Pollution Regulations are met.
During construction and operation, noise levels will be monitored to ensure that the Colorado Noise Abatement
Statute will be met.

11.2.2.1 Performance Standards and Points of Compliance

The ground-water treatment plant shall meet water and air guality performance standards presented in Tables
11-2 and 11-5 of this ROD, respectively, no later than 60 days after the startup of a new or upgraded
ground-water treatment plant, or no later than 60 days after a determination by EPA that the existing
treatment plant may be used without an upgrade. These performance standards shall supersede the performance
standards identified in the SWRA Consent Order. However, until that time, the performance standards
identified in the SWRA Consent Order shall remain in effect. The point of compliance for the ground-water
treatment plant effluent shall be existing Port 13 of the treatment plant or its eguivalent in the upgraded
or new treatment plant.

Table 11-4 identifies performance standards for surface water. While a surface water discharge from the
ground-water treatment plant is not anticipated, there is a possibility that the ground-water injection
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trench could malfunction and allow water to surface. Any such surface water discharge shall meet the
performance standards in Table 11-4.

Construction, operation, and maintenance of the ground-water treatment plant shall comply with the
performance standards (ARARs) specified in Table 11-1.

Residuals from the treatment process will include spent vapor-phase granular activated carbon, solids from
lime-soda softening, and PACTTM solids. Spent carbon shall be transported and regenerated offsite in
accordance with the performance standards (ARARs) identified in Table 11-1 and in compliance with EPA's
offsite policy. Other residuals shall be transported and disposed in accordance with the performance
standards (ARARs) identified in Table 11-1 and EPA's offsite policy.

Monitoring pursuant to a plan approved by EPA shall be conducted to ensure that performance standards are
met.

11.2.2.2 Contingency Measures

The treatability studies conducted during the OUS 1&6 RI indicated that there may be difficulty in achieving
the performance standards for certain metals and methylene chloride and other similar organics. If
performance standards for metals cannot be met by the existing ground-water treatment plant, additional metal
treatment processes shall be installed to ensure compliance with the performance standards. Additionally, if
performance standards for any organics, including, but not limited to, methylene chloride, cannot be met by
the treatment plant, additional treatment technologies shall be installed to ensure compliance with the
performance standards.

11.3 Remedy for Landfill Solids

The selected remedy for landfill solids is containment for the landfill mass and removal of accessible in the
former tire pile area and shall be achieved through the following activities:

• Maintenance of the existing cover on the landfill mass

• Placement of an additional 2-foot cover on the north face of the landfill

• Excavation, removal, and treatment, within the former fire pile area, of surface and subsurface
drums, contaminated softs, and waste pits and reclamation of the former tire pile area

The solids remedy shall achieve the following landfill solids RAOs:

• Protection of human health and the environment from direct contact or ingestion of landfill
solids or softs intermingled with landfill solids containing contaminants

• Protection of humans from inhalation of volatilized contaminants from landfill solids or soils
intermingled with landfill solids, and inhalation of contaminated airborne particulate matter
from soils or landfill solids that exceed performance standards

• Minimization of the production and migration of leachate, from landfill solids or soils
intermingled with landfill solids, to the saturated zone and ground water

• Minimization of the migration of soils intermingled with solids, caused by erosion or
entrainment by wind or water

• Prevention of offsite migration of landfill solids and soils intermingled with solids into
other media

• Protection of human health and the environment from direct contact with or ingestion of
leachate that exceeds the performance standards for shallow ground water and subsurface liguids

• Prevention of offsite migration of leachate or infiltration into other media

Maintenance of the existing cover on the landfill mass and the addition of a 2-foot cover on the north face
of the landfill mass shall reduce risk by minimizing (1) the potential for contact with contamination from
landfill solids, and (2) infiltration, thus reducing additional ground-water contamination. Details of
operation and maintenance measures for the existing cover and the new north face cover shall be refined
during RD and shall be subject to EPA approval, in consultation with CDH.
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11.3.1 Performance Standards and Points of Compliance

Excavation activities in the former tire pile area shall remove surface and subsurface drums, associated free
liquids, and other visible contamination to the extent practicable. This shall include excavation of
contaminated materials and softs in waste pits in the former tire pile area. It is estimated there are
approximately 10 surface and 1,350 buried drums containing approximately 1,300 gallons of liquid waste, and
that there are approximately 15,000 cubic yards of contaminated sod and debris in the area. The actual
numbers may be different. "Visible" contamination shall include stained or discolored materials such as
soft, construction debris, woody materials, and refuse; excavation "to the extent practicable" shall include
the removal of visible contamination until undisturbed, competent, native bedrock is encountered. These
terms, as well as the overall areal extent of contamination and approach to excavation within the former tire
pile area, will be further defined by EPA, in consultation with CDH, during RD.

Contaminated materials in the former tire pile area shall be excavated and characterized for offsite
treatment and disposal to meet RCRA Subtitle C and D requirements of the Solid Waste Disposal Act and the
Colorado Hazardous Waste Act. In addition, maintenance of the landfill cap shall comply with the above
ARARs. Liquids shall be treated offsite at a RCRA Subtitle C facility using incineration and ash
stabilization, or other treatment method capable of similar performance approved by EPA, in consultation with
CDH. It is anticipated that solids and soils shall be treated using stabilization before disposal, but
actual treatment methods shall be determined by EPA, in consultation with CDH, during RD.

The excavations shall be backfilled with clean softs. To meet the existing grade, a 2-foot-thick layer of
clay soil shall be placed on top of the excavated areas as a cap. The purpose of the cap shall be to
minimize infiltration. The clay shall be placed in lifts not exceeding 6 inches and compacted to a minimum
of 95 percent relative density according to Standard Proctor (ASTM D698). A minimum 6-inch top soil layer
shall be placed on top of the cap and shall be vegetated with a dryland pasture mix similar to that used on
the main landfill mass to stabilize the cap surface and minimize soil and wind erosion.

The remedy for landfill solids shall comply with all other performance standards (ARARs) identified in Table
11-1.

11.4 Remedy for Landfill Gas

The selected remedy for landfill gas shall contain, collect, and treat landfill gas to prevent offsite
migration of, and explosion due to, landfill gas. Containment, collection, and treatment of landfill gas
shall be achieved through the construction and installation of perimeter and interior gas extraction wells
and treatment of the gas using an enclosed flare. Specifically, the selected remedy shall include the
following components:

• Installation of gas collection and monitoring wells on the western, eastern, and southern
perimeter and in the interior of the former landfill

• Treatment of landfill gas using an enclosed flare

The landfill gas remedy shall achieve the following RAOs for landfill gas:

• Protection of human health from inhalation of landfill gases in excess of the performance
standards

• Protection of human health and the environment from explosion hazards associated with landfill
gases

• Prevention of offsite migration of landfill gas or migration to other media

The installation of gas collection wells on the western, eastern, and southern boundaries, and in the
interior of the former landfill, shall control gas migration. Approximately 21 perimeter collection wells
and two interior collection wells shall be installed to intercept migrating gas. The gas shall be treated at
a rate of approximately 2,000 scfm per day using an enclosed flare with an 8-foot-diameter stack
approximately 40 feet in height. Condensate collected in the gas collection system shall be treated in the
groundwater treatment plant. The actual number and location of wells, rate of treatment, and size of the
enclosed flare, may change as a result of RD, subject to EPA approval, in consultation with CDH.

Approximately 26 gas monitoring probes shall also be installed along the perimeter of the Lowry Site to
improve the perimeter gas monitoring system. The actual number may change as a result of RD, subject to EPA
approval, in consultation with CDH. Samples collected from the gas monitoring probes shall be analyzed for
methane and VOCs, which shall act as indicators for the effectiveness of the collection system. EPA will
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evaluate existing gas, waste-pit liguid, and ground-water monitoring wells within the former landfill for the
potential for vertical migration of gas from these wells. Wells that are likely to cause vertical migration
of gas shall be properly plugged and abandoned. The reguirements of the Well Construction and Abandonment
Procedures of the State Engineer's Office shall be met during any installation or abandonment of wells.

The selected remedy for landfill gas shall comply fully with all pertinent ARARs as described in Table 11-1.
The reguirements of RCRA Subtitles C and D, the Clean Air Act, and the Colorado Air Quality Act/Colorado Air
Pollution Regulations shall be met through the use of an enclosed flare. (The enclosed flare is not
considered a "totally enclosed treatment facility" for purposes of RCRA's use/reuse exemption.) The
reguirements of the Colorado Hazardous Waste Act shall be met through proper disposal if RCRA hazardous
wastes or wastes sufficiently similar to hazardous wastes are generated during the installation of gas
monitoring or extraction wells.

11.4.1 Performance Standards and Point of Compliance

The landfill gas remedy shall meet the performance standards presented in Tables 11-1 and 11-7. Table 11-1
includes all ARARs for the selected remedy, including the landfill gas portion of the remedy. Table 11-7
presents chemical-specific numeric standards for the landfill gas remedy, some of which are based on ARARs.
Table 11-7 performance standards shall be met at the landfill gas compliance boundary, which is depicted in
Figure 11-3.

The landfill gas remedy also includes a Point of Action (POA) boundary (Figure 11-3). The POA boundary for
landfill gas borders the toe of the landfill mass. Table 11-6 identifies numeric standards for the POA
boundary which are based on a concentration which corresponds to a 1 x 10-4 risk level. Monitoring shall be
conducted at the POA boundary to allow landfill gas to be addressed before it reaches the compliance
boundary, thus preventing exceedances of the performance standards at the compliance boundary. If Table 11-6
standards are exceeded at the POA boundary, additional measures shall be reguired as described in the next
section.

Monitoring shall also be conducted at the compliance boundary. If Table 11-7 performance standards are
exceeded at the compliance boundary, contingency measures shall be reguired as described in the next section.

Flare emissions shall be measured at the enclosed flare stack and shall attain Table 11-7 performance
standards. The flare shall meet the New Source Performance Standards (40 CFR Section 60.18); compliance
shall be determined by testing for volatile organic compounds using procedures approved by EPA.

The physical/surveyed location of the POA boundary and compliance boundary is preliminary and shall be
refined during the RD and subj ect to EPA approval.

11.4.2 Contingency Measures

If Table 11-6 standards are exceeded at the POA boundary, or if Table 11-7 performance standards are exceeded
at the compliance boundary, contingency measures shall be implemented which may, at EPA's discretion, include
the implementation of increased extraction rates and/or the installation of approximately 26 additional
extraction wells within the landfill (Stage 3). The additional extraction wells would increase the total
amount of gas extracted, thereby reducing landfill gas pressures. In addition, EPA may, at its discretion,
reguire implementation of other technologies to further control landfill gas migration. Use of these other
treatment technologies and operation and maintenance parameters shall be subject to EPA approval, in
consultation with CDH.

11.5 Remedy for Soils and Surface Water and Sediments

The selected remedy for soils, surface water, and sediments is No Further Action. Specifically, the selected
remedy for soils, surface water, and sediments includes the following components:

• Continued maintenance of the existing cover on the landfill mass

• Continued maintenance of other covered areas, including the unnamed creek drainage, vegetated
areas, and the former tire pile area (after it is reclaimed), including visual monitoring for
soil and sediment erosion

• As modified by this ROD, continued operation and maintenance of the SWRA and all its
components, as set forth in the Consent Order (Docket No. CERCLA VII-91-12) and Modified
Consent Decree (Civil Action 84-F-1507), including the existing ground-water barrier wall

• Mitigation of 0.87 acres of wetlands loss through construction of 0.87 acres of new wetlands
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• Periodic monitoring of surface water runoff

The selected remedy for soils, surface water, and sediments shall achieve the following RAOs for soils,
surface water, and sediments:

• Protection of human health and the environment from direct contact or ingestion of soils,
surface water, and sediments containing contaminants that exceed the performance standards

• Protection of human health from inhalation of volatilized contaminants from the soils, surface
water, or sediments; and inhalation of contaminated airborne particulate matter from soils or
sediments that exceeds performance standards

• Minimization of the production and migration of contaminated surface water to the saturated
zone and ground water

• Minimization of the migration of soils and sediments by erosion or entrainment by wind or water

• Minimization of migration of contaminated surface water offsite and into other media

11.5.1 Performance Standards and Points of Compliance

The selected remedy for soils, surface water, and sediments shall comply fully with the performance standards
(ARARs) described in Table 11-1.

The selected remedy shall include the continued operation and maintenance of the SWRA. The components of the
SWRA include a seepage collection system in the Section 6 segment of unnamed creek, a soil cover over the
seepage collection system, the closure of Ponds 3 and 4, and the upgraded treatment plant. The SWRA is
currently being and maintained in accordance with the reguirements of the Final SWRA Performance and
Compliance Monitoring Plan, dated June 1992. The SWRA shall continue to be operated and maintained in
accordance with such plan unless otherwise reguired by this ROD or by EPA. EPA may reguire modifications to
the plan to ensure that the reguirements of this ROD are met.

The selected remedy for surface water and sediments shall also include the construction of 0.87 acres of
wetlands to replace those destroyed during installation of the SWRA. The composition of the vegetation of the
created wetlands shall be egual to the types and percentages that were destroyed by the SWRA. The mitigation
of wetlands shall fully comply with the Executive Order on Protection of Wetlands.

Mitigation shall consist of in-kind replacement of destroyed wetlands, except for the mud flats, which shall
be replaced by vegetated wetlands. To account for mud flats replacement, the area of each of the three
identified species shall be increased in proportion to the ratio of species extent to total extent of
vegetated wetlands. As such, based on 1:1 replacement, 0.31 acres of Cattail Marsh, 0.01 acres of
Three-Sguare Marsh, and 0.55 acres of Foxtail Barley Meadow shall be created.

The constructed wetlands shall be created in a location unaffected by Section 6 landfill closure, the SWRA,
current Section 31 landfill operations, or future Section 31 landfill operations. Wetlands mitigation may
occur offsite at a location more conducive to habitat enhancement. The final location of created wetlands
shall be specified during the RD and shall be subject to EPA approval, in consultation with CDH.

Wetlands mitigation, which is conducted offsite and in connection with CERCLA activities, shall be regulated
by EPA. EPA shall provide the necessary coordination among pertinent regulatory agencies such as the U.S.
Army Corps of Engineers, U.S. Division of Fish and Wildlife, and Colorado Department of Health.

A 5-year maintenance program shall be started on the date that construction of the created wetlands is
completed. This program shall establish successional trends and overall viability of the created wetlands.
Four aspects shall be monitored: surface water, ground water, soils, and vegetation. The first year of
monitoring shall determine if corrective actions are necessary and the approximate acreage in which the
wetlands community has been established. Monitoring during years 2 through 5 shall document functional
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equivalency.

Annual monitoring of the surface water runoff into the unnamed creek drainage basin shall be conducted to
evaluate the incidence of and potential for contaminant migration. Potential or actual migration shall be
evaluated with the installation of approximately three automated surface water samplers. These samplers
shall be installed on the western edge of the former landfill mass, in the unnamed creek drainage, and near
the confluence of unnamed creek and Murphy Creek in Section 31. The specific parameters for annual
monitoring shall be evaluated during RD and shall be subject to EPA approval.

11.5.2 Contingency Measures

Contingencies for the SWRA were developed as part of the SWRA design effort (the SWRA Contingency Plan dated
May 1992; the Final SWRA Performance and Compliance Monitoring Plan dated June 1992; and the Final O&M Manual
dated June 1993), are included as part of the selected remedy, and shall be implemented if (1) chemicals
incompatible with treatment processes are detected in the treatment plant influent; (2) a collection system,
barrier wall, and/or injection trench malfunctions or is inadequate to meet performance standards; (3)
noncompliance with performance standards occurs; (4) surface ponding of seepage water occurs; or (5) new
seeps develop above the engineered drain system. These contingency measures may be modified by EPA during RD
to ensure the requirements of this ROD are met.

11.6 Cost of the Selected Sitewide Remedy

The selected sitewide remedy was evaluated for cost in terms of capital costs, annual or operation and
maintenance costs (O&M), and present worth cost. Capital costs include the sum of the direct capital costs
(materials, equipment, labor, land purchases) and indirect capital costs (engineering, licenses, or permits).
Annual costs include the cost for labor, operation and maintenance, materials, energy, equipment replacement
and disposal, and sampling to operate the treatment facilities. Present worth costs include capital costs
and O&M costs calculated over a 30-year period. Table 11-8 summarizes the capital, annual operations and
maintenance, and present worth costs for the selected sitewide remedy.

EPA integrated the OUS into a sitewide remedy to eliminate the duplication of costs between different OUS.
In addition, EPA incorporated modifications to the alternatives in the selected sitewide remedy. The direct
capital costs were revised to reflect the integration of the OUS and modifications to the alternatives.

The present worth analysis is used to evaluate expenditures that would occur over an assumed 30-year
operation period by discounting all future costs to a common base year. This allows the cost of remedial
action alternatives to be compared on the basis of a single figure representing the amount of money that, if
invested in the base year and disbursed as scheduled, would be sufficient to cover all costs associated with
the remedial action over its planned life.

Remedial design efforts may reveal that it is possible to reduce the original project cost estimates.
Reductions in the estimated costs could be the result of value engineering conducted during the remedial
design. Through the value engineering process, modifications could be made to functional specifications of
the remedy to optimize performance and minimize costs. These changes would fall within the definition of
"non-significant modifications," as defined by EPA guidance for preparing Superfund decision documents.

For example, it may be determined that a reduction in costs could be effected by non-significant changes to
the type, quantity and/or cost of materials, equipment, facilities, services, or supplies used to implement
the remedy. It should be noted that this type of design variance may have a noticeable impact on the
estimated cost of the remedy, but will not affect the remedy's ability to comply with performance standards.

IMG SRC 94087D
IMG SRC 94087DA
IMG SRC 94087DB
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Table 11-1
Selected Sitewide Remedy ARARs Page 1 of 16

Citation Description Evaluation

Chemical-Specific ARARs-Federal

Safe Drinking Water Act

40 CFR Part 141 Establishes health-based standards for These regulations are relevant and appropriate because the
Subpart B public drinking water systems (MCLs). shallow and deep ground water in the vicinity of the Lowry
Site is being used or may be used in the future as a source
of water for a public water system or private supply wells.
Treated ground water from the treatment plant would be
injected into the shallow ground-water system. The
standards are pertinent to treatment plant effluent at the
point of injection as well as within the ground water at the
compliance boundary.

40 CFR Part 141 Establishes drinking water guality goals Non-zero MCLGs are relevant and appropriate since
set at levels of no known or anticipated shallow and deep ground water in the vicinity of the Lowry
adverse health effects, with an adeguate Site is being used or may be used as a source of water for a
margin of safety (MCLGs). public water system or private supply wells.

Federal Water Pollution Control Act (amended by the Clean Water Act)

40 CFR Part 129 Establishes toxic pollutant effluent Relevant and appropriate for treatment plant effluent
standards for six groups of toxic because compound groups were detected in waste pit liguids
pollutants from manufacturers, and unnamed creek and Murphy Creek discharges to the
formulators, and applicators who South Platte River, which is a navigable water.
develop or use these compounds and
discharge to navigable waters.

Solid Waste Disposal Act-RCRA Subtitle C

40 CFR Part 264 Sets ground water protection standards The State of Colorado operates an approved delegated
Subpart F for land disposal units. program for this portion of RCRA. See reguirements under
Colorado Hazardous Waste Act. Relevant and appropriate
because the landfill operates like a hazardous waste
management unit.

Chemical-Specific ARARs-State

Colorado Hazardous Waste Act

6 CCR 1007-3 Part 264.94 Establishes concentration levels for 14 The concentration limits are relevant and appropriate to
Colorado Rules and chemicals in ground water. ground water at the compliance boundary for ground water
Regulations Pertaining to and treatment plant effluent.
Hazardous Waste-Ground
Water Protection Standard
-------
Citation
5 CCR 1002-3
Regulation on Effluent
Limitation
5 CCR 1003-1
Colorado Primary Drinking
Water Regulations
Table 11-1
Selected Sitewide Remedy ARARs

Description

Chemical-Specific ARARs-State (continued)

Colorado Water Quality Control Act
Page 2 of 16
Evaluation
Establishes specific limitations on point
source discharges of wastewaters into
state waters and from specified industry
sources, specifies sampling and
analytical reguirements.

Establishes health-based standards for
public water systems.
Relevant and appropriate for discharge from treatment plant.
These regulations are relevant and appropriate because the
shallow and deep ground water in the vicinity of the Lowry
Site is being used or may be used in the future as a source
of water for a public water system or private supply wells.
Treated ground water from the treatment plant would be
injected into the shallow ground-water system.
5 CCR 1002-8
Section 3.11.0
Colorado Basic Standards
for Ground Water
and Section 3.12.0
Classifications and Water
Quality Standards for
Ground Water

5 CCR 1002-8
Section 3.1.0
Basic Standards and
Methodologies for Surface
Water
Establishes a system for classifying
ground water and sets water guality
for such classifications.
Establishes basic standards and a
system for classifying surface waters of
the State, assigning standards, and
granting temporary variances for the
standard.
These regulations establish standards for both classified and
unclassified ground water. The standards are applicable
because ground water (with non-alluvial and alluvial
aguifers) near the Lowry Site and ground water (within
alluvial aguifers) within the Lowry Site have been classified
for domestic and agricultural use-guality. Ground water
would be treated to meet these standards and then
discharge to the shallow ground-water system.

Murphy Creek and the unnamed creek are classified and
regulated as tributaries of the South Platte River Basin
(Stream Segment 16). Segment 16 is classified as
Recreation Class 2, Warm Water Aguatic Life Class 2, and
Agricultural Supply. Because of this classification,
statewide interim organic pollutant standards for aguatic life

segments (Section 3.1.11 and Table C) are applicable to the
remedy. If surface-water discharge results from injection of
the treated water, surface water standards will be established
based on the most stringent surface water ARAR.
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Citation
5 CCR 1002-8
Section 3.2.0
Classifications and Numeric
Standards
Table 11-1
Selected Sitewide Remedy ARARs

Description

Chemical-Specific ARARs-State (continued)
Page 3 of 16
Evaluation
Used in conjunction with Basic
Standards and Methodologies Section
3.1.0. South Platte River Standards
(Section 3.8) establish numeric
standards for the South Platte River
Basin based on use classifications for
stream segments.
Murphy Creek and the unnamed creek are classified and
regulated as tributaries of the South Platte River Basin
(Stream Segment 16). Segment is classified as
Recreation Class 2, Warm Water Aquatic Life Class 2, and
Agricultural Supply. Based on the regulations, numeric
standards for protection of these three classified uses are
applicable. Chemical-specific standards established for
Stream Segment 16 are applicable to the remedy. If
surface-water discharge results from injection of the treated
water, surface water standards will be established based on
the most stringent surface water ARAR.
Colorado Air Quality Act/Air Pollution Regulations
5 CCR 1001-3
Regulations No. 1
Establishes standards for emissions of
particulates, smoke, carbon monoxide,
and sulfur oxides.
These regulations are applicable because air emissions will
occur at the ground water treatment plant, the gas treatment
system, and due to construction activities. These
regulations would be met for the air stripper/carbon
polishing treatment process, gas flaring system, and during
construction. Regulations for opacity and offsite transport
of visible fugitive emissions are applicable and must be
attained during construction activities resulting in
disturbance of 5 acres or more in attainment areas or one
acre in nonattainment areas. The Lowry Site is in an
attainment area for sulfur oxides and lead and in a
nonattainment area for PM 10, ozone, and carbon
monoxide.
5 CCR 1001-4
Regulations No. 2
Sets limits on odorous air containments
and particulates.
These regulations are applicable because air emissions will
occur at the site during all activities. Activities regulated
include activities such as soil movement or treatment plant
air emissions. These regulations would be met for all
activities including the air stripper/carbon polishing
treatment process, excavation of soil in the former tire pile
area, and movement of soil for construction of barrier walls
and gas collection and treatment system.
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Citation
Table 11-1
Selected Sitewide Remedy ARARs

Description

Chemical-Specific ARARs-State (continued)
Page 4 of 16
Evaluation
5 CCR 1001-10
Regulation No. 8
Sets emission control reguirements for
hazardous air pollutants.
5 CCR 1001-14
Ambient Standards
Massachusetts
Allowable Ambient Levels
(AALs) and Threshold
Effects Exposure Limits
(TELs)
40 CFR Part 241
Guidelines for the Land
Disposal of Solid Wastes
Establishes ambient standards for S02,
TSP, N02, CO, ozone, and PM 10.
Establishes health-based air standards.
These regulations are applicable because air emissions will
occur at the treatment plant and at the gas treatment system.
These regulations would be met for the air stripper/carbon
polishing treatment process and for the fas flare. The lead
standards are applicable because they are ambient standards
that apply to all sources. The beryllium provisions set out
emission limitations for stationary sources that are
applicable for all sources. The hydrogen sulfide standards
are applicable to any actions emitting hydrogen sulfide.
The mercury standards are applicable if wastewater
treatment plant sludge is dried or incinerated.

TBCs. These standards were used to design the SWRA
when considering air pollution controls for the water
treatment plant. The plant will continue to meet these
standards.
Action-Specific ARARa-Federal
Solid Waste Disposal Act-RCRA Subtitle D Reguirements
Establishes minimum levels of
performance reguired of any solid
waste land disposal site operation.
Part 241.205-2(b) states
"decomposition gases should not be
allowed to concentrate in a manner that
will pose an explosion or toxicity
hazard."
Because the Lowry Site is a landfill and because
decomposition gases have been detected, this reguirement is
well suited to the situation and is relevant and appropriate to
the gas collection and treatment system. Therefore, the gas
collection and treatment must meet these standards, which
include maintaining methane below explosive limits.
40 CFR Part 257 Establishes criteria for use in
Criteria for Classification of determining which solid waste disposal
Solid Waste Disposal facilities and practices pose a
Facilities & Practices reasonable probability of adverse
effects on health or the environment
and thereby constitute prohibited open
dumps.
Applicable for existing MSW landfills. The Section 6
MSW landfill is a closed landfill. Landfill cover
reguirements are relevant and appropriate.
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Table 11-1
Selected Sitewide Remedy ARARs Page 5 of 16

Citation Description Evaluation

Action-Specific ARARs-Federal (continued)

40 CFR Part 258 Establishes design and operational Explosive gas requirements (Part 258.23) are relevant and
Regulations Concerning criteria for all new municipal solid appropriate since waste was not received after October 9,
Municipal Solid Waste landfills or expansions of 1993, but the use of the requirements is well suited to the
Landfills
existing facilities. The requirements
vary depending on the time frame that
the land disposal unit is used. Includes
closure and post closure care.
!If the landfill stopped receiving waste
prior to 10/9/91 it is not regulated
!If the landfill stopped receiving waste
prior to 10/9/93 the facility must
comply with final cover requirements
!If the landfill receives waste on or
after 10/9/93 the facility must comply
with all requirements of 40 CFR 258
Solid Waste Disposal Act-RCRA Subtitle C Regulations
situation. Therefore, methane monitoring within onsite
structures and at the facility property boundary is required.
Landfill cover requirements are relevant and appropriate
since waste was not received after October 9, 1991, but the
use of the requirement is well suited to the situation.
Therefore, landfill cover maintenance is required.
40 CFR Part 260-261
Identification and Listing of
Hazardous Waste
40 CFR Part 262
Standards Applicable to
Generators of Hazardous
Waste
Defines those solid wastes that are
subject to regulation as hazardous
wastes under 40 CFR Parts 262-265
and Parts 124, 270, 271.
Establishes standards for RCRA
generators.
The State of Colorado has an approved delegated program
for this portion of RCRA. The regulations are applicable
for purposes of determining whether any of the materials
being treated or disposed are hazardous wastes. Materials
may also be compared to the waste listings to determine
whether any of the materials are sufficiently similar such
that RCRA regulations are relevant and appropriate.

Because remediation activities will generate waste that will
be sufficiently similar to RCRA hazardous waste such that
use of this requirements is well suited to the situation, the
requirement is relevant and appropriate to the ground water
treatment plant residuals, solids excavated from the former
tire pile area, gas that is collected and treated, and waste
generated during construction activities for the barrier walls
or the gas extraction system. Therefore, waste generated
must meet these standards which include testing per 40 CFR
Part 261, temporary tanks or containers, inspection and leak
detection, and accumulation time. The State of Colorado
has an approved, delegated program under RCRA.
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Citation
40 CFR Part 264 Subparts
B, C, and D
Standards for Owners and
Operators of Hazardous
Waste Treatment, Storage,
and Disposal Facilities
Table 11-1
Selected Sitewide Remedy ARARs

Description

Action-Specific ARARs-Federal (continued)
Page 6 of 16
Evaluation
Establishes minimum standards that
define the acceptable management of
hazardous waste for owners and
operators of facilities which treat,
store, or dispose of hazardous waste.
40 CFR Part 264
Subpart F
Sets ground-water protection standards
for land disposal units.
40 CFR Part 264 Subpart G
Closure and post-closure care.
Because remediation activities constitute treatment and
storage activities (ground water treatment plant, gas
treatment, and residuals management), and because the gas
and water to be treated is sufficiently similar to RCRA
hazardous waste such that use of the reguirements is well
suited to the situation, the reguirement is relevant and
appropriate to the ground water treatment and gas treatment
components of the remedy (including residuals
management). Thus, flaring of the gas and treatment of the
groundwater must meet these standards, which include
waste analysis, site security, emergency control and
response eguipment, personnel training, contingency
planning and implementation.

The State of Colorado operates and approved delegated
program for this portion of RCRA. See the reguirements
under Part 264.94 of the Colorado Hazardous Waste Act.
Relevant and appropriate to ground water under the site
because the landfill operates like a solid waste management
unit. Therefore, ground water programs must meet these
standards, which include a monitoring and response
program that includes detection monitoring to identify the
presence of hazardous constituents in ground water;
compliance monitoring to determine whether the agency-
specified ground water protection standard is being met at
the identified compliance point; and corrective action that
prevents hazardous constituents from exceeding the
established concentration limits beyond the point of
compliance.

Because ground treatment and gas treatment constitute
treatment of a waste that is sufficiently similar to RCRA
hazardous waste such that use of the reguirements is well
suited to the situation, the reguirement is relevant and
appropriate to the ground water treatment and gas treatment
components of the remedy. Therefore, closure post-
closure care for these treatment systems must meet these
standards which include removal of waste, waste residues,
contaminated system components, and contaminated
subsoils; or closure with wastes and/or contamination in
place with containment systems and post-closure care to
include ground water monitoring and inspection and
maintenance on containments and monitoring systems.
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Citation
40 CFR Part 264
Subpart I
Table 11-1
Selected Sitewide Remedy ARARs

Description
Action-Specific ARARs-Federal (continued)
Page 7 of 16
Evaluation
Sets operating and performance
standards for container storage of
hazardous waste.
40 CFR Part 264
Subpart J
Sets operating and performance
standards for tank storage of hazardous
such that use of the reguirement
40 CFR Part 264 Subpart 0
Sets standards for destruction and
removal efficiency, HCI emissions, and
particulate emissions from incinerators
or thermal treatment.
Because ground water treatment includes storage in
containers of a waste that is sufficiently similar to RCRA
hazardous waste such that use of the reguirement is well
suited to the situation, the reguirement is relevant and
appropriate to the ground water treatment component of the
remedy. Therefore, container storage at the ground water
treatment plant must meet these standards, which include
maintaining wastes in containers that are in good condition
and compatible with the wastes they contain, providing a
containment system, managing ignitable and reactive wastes
away from the property line, keeping incompatible wastes in
separate containers and containment systems, and at closure
removing all wastes and decontaminating structures and
eguipment.

Because ground water treatment includes storage in tanks of
a waste that is sufficiently similar to RCRA hazardous waste
well suited to the
situation, the reguirement is relevant and appropriate to the
ground water treatment component of the remedy.
Therefore, tank storage at the ground water treatment plant
must meet these standards, which include secondary
containment; spill and overflow controls; removal from
service if there is a leak, spill, or the tank is unfit for use;
and at closure have all wastes removed and also remove or
decontaminate waste residues, containment system, soils,
structures, and eguipment.

Because gas treatment constitutes thermal treatment, and
because the gas to be treated is sufficiently similar to RCRA
hazardous waste such that use of the reguirement is well
suited to the situation, the reguirement is relevant and
appropriate to the gas flaring component of the remedy.
Thus, flaring of the gas must meet these standards, which
include emissions standards and operating constraints as
needed to ensure emissions standards are met.
40 CFR Part 264
Subpart AA
Sets operation and performance
standards for air emissions from
process vents.
Because the gas treatment has process vents from thermal
treatment and because the gas to be treated is sufficiently
similar to RCRA hazardous waste such that the use of the
reguirement is well suited to situation, the reguirement
is relevant and appropriate to the gas flaring component of
the remedy. Thus, the gas treatment system must meet
these standards, which include standards for process vents
and test methods and procedures.
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Citation
40 CFR 265 Subpart P
Interim Standards
Owners and Operators of
Hazardous Waste
Treatment, Storage, and
Disposal Facilities
40 CFR Part 265 Subpart
AA
Table 11-1
Selected Sitewide Remedy ARARs

Description

Action-Specific ARARs-Federal (continued)
Page 8 of 16
Evaluation
Standards for thermal treatment.
Sets operating and performance
standards for air emissions from
process vents.
40 CFR 265.17
40 CFR Part 268
Land Disposal Restrictions
Sets standards for mixing and treatment
of contaminated soils or the mixing and
treatment of potentially incompatible,
reactive, or ignitable hazardous wastes.
Establishes prohibitions on land
disposal unless treatment standards are
met or a "no migration exemption" is
granted.
Because gas flaring constitutes thermal treatment and
because the gas to be treated is sufficiently similar to RCRA
hazardous waste such that use of the reguirement is well
suited to the situation, the reguirement is relevant and
appropriate to the gas treatment component of the remedy.
Therefore, the gas treatment system must meet these
standards, which include general operating reguirements,
waste analysis, monitoring and inspection, and closure.

Because the ground water treatment plant will mix and treat
potentially incompatible, reactive, or ignitable wastes which
may be similar to hazardous wastes, the reguirement is
relevant and appropriate to the ground water treatment
plant. Therefore, the wastes must be analyzed to determine
compatibility, reactivity, and ignitability before treatment in
the treatment plant.

Because the solids excavation in the former tire pile area
and residuals from the ground water barrier walls and gas
extraction system construction and residuals from the
ground water treatment plant and gas extraction system
operations will be land disposed, the reguirement is
applicable. The materials must be tested to determine if
they are a characteristic hazardous waste (per 4 CFR Part
262) and then must meet treatment reguirements for land
disposal as reguired in the standards if they are hazardous
waste for which a treatment standard has been established.
For land disposal of residuals, other than soils, which are
not characteristic hazardous wastes, these reguirements are
relevant and appropriate because the residuals are
sufficiently similar to listed hazardous waste such that use of
the reguirements is well suited to the situation.
-------
Citation
58 FR 48091 (9/14/93)
40 CFR Part 268
Universal Treatment
Standards
Table 11-1
Selected Sitewide Remedy ARARs

Description

Action-Specific ARARs-Federal (continued)
Page 9 of 16
Evaluation
Establishes a concentration limit for
over 200 regulated constituents in soil,
regardless of waste type, which must
be met before land disposal.
TBC for soil and sediments because it is a proposed
regulation. Excavated soils from the tire pile area must
meet these reguirements.
Federal Water Pollution Control Act (amended by the Clean Water Act)
40 CFR Part 122 Establishes reguirements for
NPDES Stormwater discharges related to and from any treatment
Regulations industrial activity. Stormwater runoff,
snow melt runoff, and surface runoff
and drainage associated with industrial
activity from remedial actions which
discharge to surface waters shall be
conducted in compliance with RCRA,
FWQC, CWA technology-based stan-
dards, Colorado surface water guality
standards, monitoring reguirements,
and best management practices.
40 CFR, Part 230/231
Guidelines for Specification
of Disposal Sites for
Dredged or Fill Materials.

40 CFR, Part 440
Effluent Guidelines and
Standards for Ore Mining
and Dressing Point Source
Categories
The discharge of dredged or fill
material into the waters of the U.S.
prohibited without a permit.
Because Stormwater discharges will occur from the landfill
process areas constructed (such as
the ground water treatment plant and the gas treatment
system), this reguirement is applicable to Stormwater
discharges. Therefore, Stormwater discharges must meet
these standards which include sampling, analysis, and
treatment reguirements. Implementation and enforcement
has been delegated to the State of Colorado, see the
Colorado Water Quality Control Act.
Wetlands were destroyed during construction of the SWRA
and must be mitigated during implementation of the selected
remedy by constructing new wetlands.
Establishes radionuclide concentration Because the effluent from the ground water treatment plant
limits for liguid effluents from facilities could have radionuclides sufficiently similar to those
that extract and process uranium, regulated such that the reguirement is well suited to the
radium, and vanadium ores. situation, the reguirement is relevant and appropriate to the
ground water treatment plant effluent. Therefore,
contingencies have been made for the early detection of
radionuclides and for a treatment process to be added to
treat radionuclides at the ground water treatment plant.

Clean Air Act
40 CFR Part 60
New Source Performance
Standards
Establishes performance standards for
new stationary sources of air
pollutants.
Relevant and appropriate for gas treatment. Proposed NSPS
for municipal solid waste facilities (Subpart WWW) is a
TBC (56 FR 24468 [5/30/91]).
-------
Citation
40 CFR Part 61
National Emission
Standards for Hazardous
Air Pollutants (NESHAPAs)
Table 11-1
Selected Sitewide Remedy ARARs

Description

Action-Specific ARARs-Federal (continued)
Page 10 of 16
Evaluation
Establishes emission standards for
hazardous air pollutants from specific
sources.
Because the ground water treatment plant has an air stripper
that is a source of air emissions and the gas treatment
system will have a flare, these two sources are sufficiently
similar to source types in the regulations such that use of
the reguirement is well suited to the situation, the
reguirement is relevant and appropriate to the ground water
treatment plant and the gas treatment system. Therefore,
the air stripper and gas flare must meet these standards
which include treatment levels for arsenic, beryllium, ben-
zene, vinyl chloride and radionuclide emissions.
Safe Drinking Water Act
40 CFR Part 144-147
Underground Injection
Control Regulations
Establishes standards for construction
and operation of injection wells.
Provides for protection of underground
sources of drinking water.
The
Applicable to injection of water from treatment plant.
reguirements include constructing, operating, and
maintaining a well in a manner that does no result in
contamination of an underground source of drinking water
at levels that violate MCLs or otherwise affect the health of
persons. These reguirements will be met by ensuring the
effluent from the groundwater treatment plant meets
standards that are protective of human health (based on
MCLs and risk-based concentrations).
Action-Specific ARARs-State
Colorado Solid Wastes Disposal Sites and Facilities Act
6 CCR 1007-2 Section 1
Regulations Pertaining to
Solids Waste Disposal Sites
and Facilities
6 CCR 1007-2 Section 2.3
Establishes standards for new solid
waste disposal facilities and defines
those solid wastes.
Establishes minimum standards for
landfill gas collection and treatment
systems.
Explosive gas reguirements and landfill cover reguirements
are relevant and appropriate because waste was not received
after October 9, 1993, but the use of the reguirement is well
suited to the situation so the reguirement is relevant and
appropriate to the existing landfill mass. Therefore, the gas
concentrations need to be maintained below the explosive
limits and maintenance of the landfill cover is reguired.

These reguirements are applicable for the landfill gas
collection and treatment system and include monitoring
reguirements in structures and at the landfill boundary,
notification of gas excursions, and remediation activities if
explosive gas limits are exceeded.
-------
Citation
6 CCR 1007-2 Section 2.6
and 3.6
Table 11-1
Selected Sitewide Remedy ARARs

Description

Action-Specific ARARs-State
Page 11 of 16
Evaluation
Post closure maintenance and care.
Substantive requirements are applicable to the gas extraction
system and landfill cover. Reguirements include
maintaining the cover for 30 years, ground water
monitoring, describing uses of land during post closure
care, and certification at the completion of post closure
care.
Colorado Hazardous Waste Act
6 CCR 1007-3 Part 260-261
Identification and Listing of
Hazardous Waste

6 CCR 1007-3 Part 262
Standards Applicable to
Generators of Hazardous
Waste
Defines those solid wastes subject to
hazardous waste regulations.
Establishes standards for RCRA
generators.
6 CCR 1007-3 Part 264
Subparts B, C, and D
Standards for Owners and
Operators of Hazardous
Waste Treatment, Storage,
and Disposal Facilities
Establishes minimum standards that
define that acceptable management of
hazardous waste for owners and
operators of facilities which treat,
store, or dispose of hazardous waste.
The State Colorado has an approved delegated program
for this portion of RCRA. Applicable to determining
whether substance are hazardous waste under RCRA.

Because remediation activities will generate waste that will
be sufficiently similar to RCRA hazardous waste such that
use of this requirement is well suited to the situation, the
requirement is relevant and appropriate to the ground water
treatment plant residuals, solids excavated from the former
tire pile area, gas that is treated, and waste generated during
construction of the barrier walls or gas extraction system.
Therefore, waste generated must meet these standards which
include testing per 40 CFR Part 261, temporary tanks or
containers, inspection and leak detection, offsite shipping
procedures, and accumulation time. The State of Colorado
has an approved, delegated program under RCRA.

Because remediation activities constitute treatment and
storage activities (ground water treatment plant, gas
treatment, and residuals management), and because the gas
and water to be treated is sufficiently similar to RCRA
hazardous waste such that use of the requirement is well
suited to the situation, the requirement is relevant and
appropriate to the ground water treatment and gas treatment
components of the remedy (including residuals
management). Thus, flaring of the gas and treatment of the
groundwater must meet these standards, which include
waste analysis, site security, emergency control and
response equipment, personnel training, contingency
planning and implementation.
-------
Citation
6 CCR 1007-3 Part 264
Subpart F
Table 11-1
Selected Sitewide Remedy ARARs

Description

Action-Specific ARARs-State (continued)
Page 12 of 16
Evaluation
Sets ground-water protection standards
for land disposal units.
6 CCR 1007-3 Part 264
Subpart G
Closure and post-closure care.
6 CCR 1007-3 Part 264
Subpart I
Sets operating and performance
standards for container storage of
hazardous waste.
The State of Colorado operates an approved delegated
program for this portion of RCRA. See the reguirements
under Part 264.94 of the Colorado Hazardous Waste Act.
Relevant and appropriate to ground water under the site
because the landfill operates like a solid waste management
unit. Therefore, ground water programs must meet these
standards, which include a monitoring a response
program that includes detection monitoring to identify the
presence of hazardous constituents in ground water;
compliance monitoring to determine whether the agency-
specified ground water protection standard is being met at
the identified compliance point; and corrective action that
prevents hazardous constituents from exceeding the
established concentration limits beyond the point of
compliance.

Because ground water treatment and gas treatment constitute
treatment of a waste that is sufficiently similar to RCRA
hazardous waste such that use of the reguirement is well
suited to the situation, the reguirement is relevant and
appropriate to the ground water treatment and gas treatment
compounds of the remedy. Therefore, closure and post-
closure care for these treatment systems must meet these
standards which include removal of waste, waste residues,
contaminated system components, and contaminated
subsoils; or closure with wastes and/or contamination in
place with containment systems and post-closure care to
include ground water monitoring and inspection and
maintenance on containments and monitoring systems.

Because ground water treatment includes storage in
container of a waste that is sufficiently similar to RCRA
hazardous waste such that use of the reguirement is well
suited to the situation, the reguirement is relevant and
appropriate to the ground water treatment component of the
remedy. Therefore, container storage at the ground water
treatment plant must meet these standards, which include
maintaining wastes in containers that are in good condition
and compatible with the wastes they contain, providing a
containment system, managing ignitable and reactive wastes
away from the property line, keeping incompatible wastes in
separate containers and containment systems, and at closure
removing all wastes and decontaminating structures and
eguipment.
-------
Citation
6 CCR 1007-3 Part 264
Subpart J
Table 11-1
Selected Sitewide Remedy ARARs

Description

Action-Specific ARARs-State (continued)
Page 13 of 16
Evaluation
Sets operating and performance
standards for tank storage of hazardous
6 CCR 1007-3 Part 264
Subpart 0
Standards for Owners and
Operators of Hazardous
Waste TSD Facilities
Sets standards for destruction and
removal efficiency, HC1 emissions and
particulate matter in excess of the
stated standard.
6 CCR 1007-3 Part 264
Subpart AA
Sets operating and performance
standards for air emissions from
process vents.
Because ground water treatment includes storage in tanks of
a waste that is sufficiently similar to RCRA hazardous waste
such that use of the reguirement is well suited to the
situation, the reguirement is relevant and appropriate to the
ground water treatment component of the remedy.
Therefore, tank storage at the ground water treatment plant
must meet these standards, which include secondary
containment, spill and overflow controls, removal from
service if there is a leak, spill, or the tank is unit for use,
and at closure have all wastes removed and also remove or
decontaminate waste residues, containment system, soils,
structures, and eguipment.

Because the gas treatment has process vents from thermal
treatment and because the gas to be treated is sufficiently
similar to RCRA hazardous waste such that the use of the
reguirement is well suited to the situation, the reguirement
is relevant and appropriate to the gas flaring component of
the remedy. Thus, the gas treatment system must meet
these standards, which include general operating
reguirements, waste analysis, monitoring and inspections,
and closure.
6 CCR 1007-3 Part 265
Subpart P
Standards for thermal treatment.
Because gas flaring constituents thermal treatment and
because the gas to be treated is sufficiently similar to RCRA
hazardous waste such that use of the reguirement is well
suited to the situation, the reguirement is relevant and
appropriate to the gas treatment component of the remedy.
Therefore, the gas treatment system must meet these
standards, which include standards for process vents and
test methods and procedures.
-------
Citation
6 CCR 1007-3 Part 265
Subpart AA
Table 11-1
Selected Sitewide Remedy ARARs

Description

Action-Specific ARARs-State (continued)
Page 14 of 16
Evaluation
Sets operation and performance
standards for air emissions from
process vents.
Because the gas treatment has process vents from thermal
treatment and because the gas to be treated is sufficiently
similar to RCRA hazardous waste such that the use of the
reguirement is well suited to the situation, the reguirement
is relevant and appropriate to the gas flaring component of
the remedy. Thus, the gas treatment system must meet
these standards, which include general operating
reguirements, waste analysis, monitoring and inspections,
and closure.
6 CCR 1007-3 Part 265.17
6 CCR 1007-3 Part 268
Land Disposal Restrictions
Sets standards for mixing and treatment
of contaminated soils or the mixing and
treatment of potentially incompatible,
reactive, or ignitable hazardous wastes.
Establishes prohibitions on land
disposal unless treatment standards are
met or a "not migration exemption" is
granted.
Because the ground water treatment plant will mix and treat
potentially incompatible, reactive, or ignitable wastes which
may be similar to hazardous wastes, the reguirement is
relevant and appropriate to the ground water treatment
plant. Therefore, the wastes must be analyzed to determine
compatibility, reactivity, and ignitability before treatment in
the treatment plant.

Because the solids excavation in the former tire pile area
and construction residuals from the ground water barrier
walls and gas extraction system will be land disposed, the
reguirements is applicable so the materials must be tested to
determine if they are a characteristic hazardous waste (per 6
CCR 1007-3 Part 262) and then must meet treatment
reguirements for land disposal as reguired in the standards if
they are hazardous waste for which a treatment standard has
been established.
Colorado Air Quality Act/Air Pollution Regulations
5 CCR 1001-5
Regulations No. 3
5 CCR 1001-8
Regulation No. 6
Reguires filing of Air Pollution
Emission Notice (APEN) including
estimation of emission rates.
Establishes standards for new stationary
sources including incinerators. Sets
discharge and performance rates and
opacity reguirements.
These regulations are applicable because air emissions will
occur at the treatment plant and at the gas treatment system.
The air stripper/carbon polishing treatment process and the
gas flaring process must meet any substantive provisions of
these reguirements.

These regulations are applicable because air emissions will
occur at the treatment plant and at the gas treatment system.
The air stripper/carbon polishing treatment process and the
gas flaring process must meet these reguirements which
include discharge and performance rates and opacity
reguirements.
-------
Citation
5 CCR 1001-9
Section II.C.2, Section V
Regulation No. 7
Table 11-1
Selected Sitewide Remedy ARARs

Description

Action-Specific ARARs-State (continued)
Page 15 of 16
Evaluation
Establishes standards for disposal or
spillage of VOCs.
These regulations are applicable because air emissions will
occur at the treatment plant and at the gas treatment system.
The air stripper/carbon polishing treatment process and the
gas flaring process must meet these reguirements which
include controls representing reasonably available control
technology (RACT).
Colorado Noise Abatement Statute
Colorado Revised Statute
Section 25-12-103
2 CCR 402-4
Provides limits for noise based on time Applicable for all construction activities associated with the
periods and zones. remedy.

Water Well Pump Installation Contractors Act

Establishes standards for installation of Applicable because wells will be installed.
water wells and pumping eguipment.

Well Construction/Abandonment Reguirements
2 CCR 402-2
State of Colorado Division
of Water Resources, 1988,
as revised-Colorado State
Engineers Office
40 CFR Part 6, Appendix A
Well construction/abandonment
reguirements
Applicable for new wells and abandonment of existing
wells. Additional reguirements may be added to ensure that
a migration is not created.
Location-Specific ARARs-Federal
Executive Order 11990, Protection of Wetlands
Action to avoid adverse effects,
minimize potential harm, and preserve
and enhance wetlands, to the extent
possible. Reguires action to minimize
the destruction, loss, or degradation of
wetlands.
Applicable because wetlands have been identified and
destroyed at the Lowry Site during the SWRA. New
wetlands will be constructed as part of the remedy.
40 CFR Part 230
Federal Water Pollution Control Act (Clean Water Act)
Discharge of dredged or fill material
into wetlands prohibited without a
permit.
For areas of the site that have designated wetlands, a permit
will not be reguired pursuant to Section 121 (c) of
CERCLA, but the substantive reguirements of Part 230 will
be applicable if wetlands that have been identified at the
Lowry Site are dredged or filled during implementation of
the remedial activity.
-------
Table 11-1
Selected Sitewide Remedy ARARs Page 16 of 16

Citation Description Evaluation

Location-Specific ARARs-State
Certification of Federal Licenses and Permits

5 CCR 1002-18 Discharge of dredged and fill material For areas of the site that have designated wetlands, a permit
into wetlands prohibited without a State will not be reguired pursuant to Section 121(c) of
certification. CERCLA, but the substantive reguirements will be
applicable if wetlands that have been identified at the Lowry
Site are dredged or filled during implementation of the
remedial activity.
-------
Table 11-2
Ground-Water Compliance Boundary Performance Standards
Sitewide Remedy
Page 1 of 5
Chemical
Performance Standard
(lig/D
Basis
Organics
1,1-Dichloroethane
1,1-Dichloroethylene 0.068
1,2-Dichloroethylene(cis) 70
1,2-Dichlorethylene(trans) 100
1,1,1-Trichloroethane 200
1,1,2-Trichloroethane 0.32
1,1,2,2-Tetrachlorethane 0.089
1,2-Dibromo-3-Chloropropane 0.2
1,2-Dichlorobenzene 600
1,2-Dichloroethane 0.2
1,2-Dichloropropane 0.56
1,2-Diphenylhydrazine 0.05
1,2,4-Trichlorobenzene 20
1,2,4,5-Tetrachlorobenzene 2
1,3-Dichlorobenzene 620
1,4-Dichlorobenzene 75
2-Butanone 780
2-Chlorophenol 0.1
2-Hexanone
2-Methylnaphthalene 0.0031
(total PAHs)
2,3,7,8-TCDD (dioxin eguivalence .00000022
2,4-D(dichlorophenoxyacetic acid) 70
2,4-Dichlorophenol 21
2,4-Dinitrophenol 14
2,4,5 TP(trichlorophenoxypropionic acid) 10
2,4,6-Trichlorophenol 2
4-Methyl-2-pentanone 780
Acetone 1,600
Alachlor 2.0
Aldicarb 3.0
Aldicarb Sulfone 2 . 0
Aldicarb Sulfoxide 4.0
Aldrin 0.002
Altrazine 3.0
Benzene 0.62
Benzidine 0.0002
B
D
D
D
B
B
D
D
B
D
D
C
D
D
A
C
A

A
D
A
A
D
D
C
C
D
D
D
D
D
D
B
D
Notes: A = ARAR/TBC.
B = Carcinogenic (1 x 10-6) target risk for adult.
C = Noncarcinogenic target concentration for child.
D = Colorado Basic Standards for Ground Water for chemicals that are not COCs.
-------
Table 11-2
Ground-Water Compliance Boundary Performance Standards
Sitewide Remedy
Chemical

Benzo(a)anthracene
Benzo(a)pyrene (PAH)
Benzyl Alcohol
Bis (2-chloroethyl)ether
Bis(2-ethylhexyl)phthalate
Bromodi chloromethane
Bromoform
Carbazole
Carbofuran
Carbon tetrachloride
Chlordane
Chlorobenzene
Chloroethane
Chloroform
Chlorophenol
Dalapon
DDT Metabolite (DDE)
DDT
Di(2-ethylhexyl)adipate
Di(2-ethylhexyl)phthalate
Di-n-Octylphthalate
Dibenzofuran
Dibromochloromethane
Dichloromethane
Dieldrin
Dinoseb
Diquat
Ethylbenzene
Endothall
Endrin
Endrin Aldehyde
Ethylenedibromide
Fluoranthene
Glyphosate
Heptachlor
Heptachlor Epoxide
Hexachlorobenzene
Hexachlorobutadi ene
Performance Standard
(lig/D

0.0031 (total PAHs)
0.2

0.016
6.1
0.3
4.0

36
0.026
0.004
100

0.19
1
200
0.1
0.1
400
6
14
5
0.002
7
20
680
100
0.2
0.2
0.05
188
700
0.008
0.09
1
1
Page 2 of 5
Basis

A
D

B
B
D
D

D
B
D
D

A
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
A
A
D
D
D
D
D
Notes: A = ARAR/TBC.
B = Carcinogenic (1 x 10-6) target risk for adult.
C = Noncarcinogenic target concentration for child.
D = Colorado Basic Standards for Ground Water for chemicals that are not COCs.
-------
Table 11-2
Ground-Water Compliance Boundary Performance Standards
Statewide Remedy Page 3 of 5

Performance Standard
Chemical (y.g/1) Basis

Hexachlorocyclohexane,Alpha 0.2 D
Hexachlorocyclohexane,Gamma 0.004 D
(Lindane)
Hexachlorocyclopentadiene 50 D
Isophorone 1,050 D
Malathion 2,500 D*
Methoxychlor 40 D
Methylene chloride 0.19 A
Monohydric phenol 1 D
Nephthalene
Nitrobenzene 3.5 D
Oxamyl (vydate) 200 D
PCBs 0.005 D
Pentachlorobenzene 6 D
Pentachlorophenol 0.71 B
Phenanthrene 0.0031 A
(total PAHs)
Phenol 1 D
Picloram 500 D
Simazine 4 D
Styrene 100 D
Tetrachloroethylene 1.5 B
Toluene 1,000 A
Toxaphene 0.03 D
Trans-1,3-dichloropropene 3.0 C
Trichloroethylene 2.6 B
Vinyl chloride 0.037 B
Xylenes (total) 10,000 D

Inorganics and Miscellaneous

Aluminum 5,000 D
Antimony 6 D
Arsenic 0.049 B
Asbestos (fibers/1) 30,000 D
Barium 1,000 D
Beryllium 4 D
Boron 750 D
Cadamium 5 D
Chloride 250,000 D

Notes: A = ARAR/TBC.
B = Carcinogenic (1 x 10-6) target risk for adult.
C = Noncarcinogenic target concentration for child.
D = Colorado Basic Standards for Ground Water for chemicals that are not
COCs.
D* = Must be met at the western compliance boundary, based on
classifications and Water Quality Standards for Ground Water.
- = No information available.
-------
Table 11-2
Ground-Water Compliance Boundary Performance Standards
Sitewide Remedy
Chemical

Cobalt
Coliform (total) per 100 ml
Color, color units
Corrosivity
Copper
Chromium (as Cr[VI])
Chromium (total)
Cyanide
Flouride
Foaming Agents
Iron
Lead
Manganese
Mercury
Nickel
Nirate as N
Nirate and Nitrite as N
Nitrite as N
PH
Selenium
Silver
Sulfate
Thallium
Vanadium
Zinc
Performance Standard
(lig/D

50
<1
15
noncorrosive
200
50
50
200
2,000
500
300
15
50
2
2
10,000
10,000
1,000
6.5 to 8.5
10
50
250,000
1.1
100
2,000
Page 4 of 5
Basis

A
D
D
D
D
A
D
D
D
D
D
A
A
D
A
D
D
D
D
D
D
D
C
D
D
Radionuclides
Americium-241
Beta and photon emitters, mrem/yr
Cesium-134
Gross Alpha
Lead-210
Plutonium-238,-239,and -240
Potassium-40
Radium-226 and -228
Strontium-90
Thorium-228
Thorium-230
Thorium-232
0
1.3 pCi/1
4
80 pCi/1
15 pCi/1
072 pCi/1
15 pCi/1
76 pCi/1
5
1.3 pCi/1
0.87 pCi/1
3.7 pCi/1
12 pCi/1
C
D
D
D
B
A
C
A
B
B
B
C
Notes: A = ARAR/TBC.
B = Carcinogenic (1 x 10-6) target risk for adult.
C = Noncarcinogenic target concentration for child.
D = Colorado Basic Standards for Ground Water for Chemicals that are not
COCs.
- = No information available.
-------
Table 11-2
Ground-Water Compliance Boundary Performance Standards
Sitewide Remedy Page 5 of 5

Performance Standard
Chemical (y.g/1) Basis

Tritium 880 pCi/1 B
Tritium 20,000 pCi/1 D
Uranium-234 3.0 pCi/1 B
Uranium-235 20 pCi/1 C
Uranium-238 5.2 pCi/1 C
Xylenes (total) 10,000 D

Notes: A = ARAR/TBC.
B = Carcinogenic (1 x 10-6) target risk for adult.
C = Noncarcinogenic target concentration for child.
D = Colorado Basic Standards for Ground Water for chemicals that are not
COCs.
- = No information available.
-------
Table 11-3
Ground-Water Point of Action Boundary Standards
Page 1 of 2
Parameter Name

1,1,1-Trichloroethane
1,1,2-Trichloroethane
1,1-Dichloroethylene
1,2,4,5-Tetrachlorobenzene
1,2,4-Trichlorobenzene
1,2-Dibromo-3-chloropane
1,2-Dichlorobenzene
1,2-Dichloroethane
1,2-Dichloroethylene (cis)
1,2-Dichloroethylene (trans)
1,2-Dichloropropane
1,2-Diphenylhydrazine
1,3-Dichlorobenzene
1,4-Dichlorobenzene
2,4,6-Trichlorophenol
2,4-Dichlorophenol
2,4-Dinitrophenol
Alachlor
Aldicarb
Aldicarb sulfone
Aldicarb sulfoxide
Aldrin
Atrazine
Benzene
Benzidine
Benzo(a)pyrene (PAH)
Bis (2-chloroethyl)ether
Bromodichloromethane (HM)
Bromoform (HM)
Carbofuran
Carbon Tetrachloride
Chlorodane
Chlorobenzene
Chloroform (HM)
Basic Standards for
Ground Water
Ug/L

200
3
7
2
70
0.2
600
0.4
70
100
0.56
0.05
620
75
2
21
14
2.0
3.0
2.0
4.0
0.002
3.0
5.0
0.0002
0.2
0.03
0.3
4.0
36
0.3
0.03
100
6.0
-------
Table 11-3
Ground-Water Point of Action Boundary Standards
Page 2 of 2
Parameter Name

Dalapon
DDT
DDT Metabolite (DDE)
Di(2-ethylexyl)adipate
Di (2-ethylhexyl)phthalate
Dibromochloromethane (HM)
Dichloromethane
Dichlorophenoxyacetic Acid (2,4-D)
Dieldrin
Dionseb
Dioxen (2,3,7,8-TCDD)
Diquat
Endothall
Endrin
Endrin Aldehyde
Enthylbenzene
Ethylene Dibromide
Glyphosate
Heptachlor
Heptachlor Epoxide
Hexachlorobenzene
Hexachlorobutadi ene
Hexachloroclohexane, Alpha
Hexachloroclohexane, Gamma (Lindane)
Hexachlorocyclopentadiene
Isophorone
Methoxychlor
Nitrobenzene
Oxamyl (vydate)
PCBs
Pentachlorobenzene
Pentachlorophenol
Picloram
Simazine
Styrene
Tetrachloroethylene
Toluene
Toxaphene
Trichloroethylene
Trichlorophenoxypropionic Acid (2,4,5-TP)
Vinyl Chloride
Xylenes (total)
Basic Standards for
Ground Water
Ug/L

200
0.1
0.1
400
6
14
5
70
0.002
7
2.2x10 -7
20
100
2.0
0.2
680.0
0.05
700
0.008
0.09
1
1.0
0.006
0.2
50
1050
40
3.5
200
0.005
6
1.0
500
4
100
5.0
1000
0.03
5
50
2
10,000
Notes: The Standard is based on Colorado Basic Standards for Ground Water-
Statewide Standards (Table A) .
-------
Table 11-4
Surface Water Standards
Basic Standards and Methodologies for Surface Water
Site-Specific Standards for Use Classification
Recreation Class 2, Aquatic Life Warm Water Class 2, Agricultural
Agricultural
Standard
(Ug/L)
Page 1 of 5
Acenaphthene
Acrolein
Acrylonitrile
Aldicarb
Aldrin
Benzene
Benzidine
Beryllium
BHC Hexachlorocyclohexane
Bromodichlormethane (HM)
Bromoform (HM)
Carbofuran
Carbon Tetrachloride
Chlorobenzene
Chlordane
Chloroethyl Ether (bis-2-)
Chloroform (HM)
Chloro-4 Methyl-3 Phenol
2-Chlorophenol
Chlorhyrifos
DDT
DDT Metabolite (DDE)
DDT Metabolite (ODD)
Demton
Dibromochloromethane (HM)
1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
100 (30 day)
Water Supply
Segments
(Ug/D
Organics
—
—
--
10
0.002
1
0.0002
0.007
—
0.3
4
36
0.3
100
0.03
0.03
6
—
—
—
0.1
0.1
—
—
14
620
620
75

Aguatic Life
(Acute)

1,700
68
7,500
—
1.5
5,300
2,500
—
100
—
—
--
35,200
—
1.2
—
28,900
30
4,380
0.083
0.55
1,050
0.6
—
—
—
—
--

Aguatic Life
(Chronic)

520
21
2, 600
—
—
--
—
—
—
—
—
--
—
—
0.0043
—
1240
—
2000
0.041
0.001
—
—
0.1
—
—
—
--
PQL
(ug/D
10
10
5
10
0.1
1.0
10

0.05
1.0
1.0

1.0
1.0
1.0
10
1.0
50
50
0.1
0.1
0.1
0.1
1.0
1.0
1.0
1.0
1.0
-------
Table 11-4
Surface Water Standards
Basic Standards and Methodologies for Surface Water
Site-Specific Standards for Use Classification
Recreation Class 2, Aquatic Life Warm Water Class 2, Agricultural
Page 2 of 5
1,2-Dichloroethane
1,1-Dichlorethylene
1,2-cis-Dichlorethylene
1,2-trans-Dichlorethylene
2,4-Dichlorophenol
Dichlorophenoxyacetic Acid (2,4-D)
1,4-Dichlorobenzene
1,2-Dichloroethane
1,1-Dichlorethylene
1,2-cis-Dichlorethylene
1,2-trans-Dichlorethylene
2,4-Dichlorophenol
Dichlorophenoxyacetic Acid (2,4-D)
1,2-Dichloropropane
1,3-Dichloropropylene
Dieldrin
2,4-Dimethylphenol
2,4-Dinitrophenol
2,6-Dinitrotoluene
Dioxin (2,3,7,8-TCDD)
1,2-Diphenylhydrazine
Endosulfan
Endrin
Endrin Aldehyde
Ethylbenzene
Fluoranthene (PAH)
Guthion
Heptachlor
Heptachlor Epoxide
Agricultural
Standard
(Ug/L)
—
—
—
—
--
—
—
--
—
—
—
--
—
--
—
—
—
—
—
—
—
—
—
—
--
—
—
—
--
Water Supply
Segments
(Ug/L)
0.4
7
70
100
21
70
75
0.4
7
70
100
21
70
0.56
—
0.002
—
14
—
2.2 x 10-7
0.05
—
0.2
0.2
680
—
—
0.008
0.09

Aguatic Life
(Acute)
118,000
—
—
—
2,020
—
—
118,000
—
—
—
2,020
—
23000
6,060
1.3
2,120
—
330
0.01
270
0.22
0.09
—
32,000
3,980
—
0.26
0.26

Aguatic Life
(Chronic)
20,000
—
—
—
365
—
—
20,000
—
—
—
365
—
5700
244
0.0019
—
—
230
0.00001
—
0.056
0.0023
—
--
—
0.01
0.0038
0.0038

PQL
(Ug/L)
1.0
1.0
1.0
1.0
50
2.02
1.0
1.0
1.0
1.0
1.0
50
2.02
1.0
1.0
0.1
50
50
10
0.02

0.1
0.1
0.1
1.0
10
1.5
0.05
0.05
-------
Table 11-4
Surface Water Standards
Basic Standards and Methodologies for Surface Water
Site-Specific Standards for Use Classification
Recreation Class 2, Aquatic Life Warm Water Class 2, Agricultural
Hexachlorobenzene
Hexachlorobutadi ene
Hexachlorocyclohexane, Alpha
Hexachlorocyclohexane, Gamma (Lindane)
Hexachloroethane
Hexachlorocyclopentadiene
Indeno(l,2,30cd)pyrene (PAH)
Isophorone
Malathion
Methoxychlor
Mi rex
Naphthalene (PAH)
Nitrobenzene
Parathion
PCBs
Pentachlorobenzene
Pentachlorophenol
Phenol
1,2,4,5-Tetrachlorobenzene
1,1,2,2-Tetrachlorethane
Tetrachloroethylene
Toluene
Toxaphene
1,1,1-Trichlorethane
1,1,2-Trichlorethane
Trichlorethylene
2,4,6-Trichlorophenol
Trichlorophenoxypropionic Acid (2,4,5-TP) -
Vinyl Chloride
Page 3 of 5
Agricultural Water Supply
Standard Segments
(ug/L) (ug/L)
6
1.0
0.006
0 — 0.2
—
—
—
1050
—
40
—
--
3.5
--
0.005
6
200
--
2
--
5.0
1000
0.03
200
3
5
2.0
i-TP) - 50
2

Aguatic Life
(Acute)
—
90
0.0039
1.0
980
7
—
117,000
—
—
—
2,300
27,000
0.065
2.0
—
9
10,200
—
--
5,280
17,500
0.73
—
9,400
45,000
—
—
—

Aguatic Life
(Chronic)
—
9.3
—
0.080
540
5
—
--
0.1
0.03
0.001
620
—
0.013
0.014
—
5.7
2,560
—
2,400
840
--
0.0002
—
--
21,900
970
—
—

PQL
(ug/L)
10
10
0.05
0.05
10
10
10
10
0.2
0.5
0.1
10
10

1.0
10
50
50
10
1.0
1.0
1.0
5.0
1.0
1.0
1.0
50
0.5
2
-------
Table 11-4
Surface Water Standards
Basic Standards and Methodologies for Surface Water
Site-Specific Standards for Use Classification
Recreation Class 2, Aquatic Life Warm Water Class 2, Agricultural
Agricultural
Standard
(Ug/L)
Antimony
Aluminum
Ammonia (un-ionized as N)
Arsenic
Asbestos, fibers/1
Barium
Boron
Cadmium
Chloride
Chromium (hexavalent)
Chromium (trivalent)
Copper
Cyanide (free)
Dissolved Oxygen
Fecal Coliform
Flouride
Iron
Lead
Manganese
Mercury
Nickel
Nirate as N
Nitrite as N (N02-N)
PH
Selenium
Silver
Sulfide as H2S
100 (30 day)
750 (30 day)
10 (30 day)

100 (30 day)
100 (30 day)
200 (30 day)
200 (1 day)
3000
Page 4 of 5
100
200
(30 day)
(30 day)
200 (30 day)
100,000
10,000

20 (30 day)
Water Supply
Segments
(Ug/D
Ingorganics
14
—
500
50
30000
1000
10 (1 day)
250,000
50 (1 day)
50 (1 day)
1,000 (30 day)
200 (1 day)
3,000
2,000/lOOml
2,000
300 (30 day) a
50 (1 day)
50 (dis) (30 day)
2.0 (1 day)
—
10,000 (1 day)
1,000 (1 day)
5.0 — 9.0
10 (1 day)
50
50

Aguatic Life
(Acute)

—
750
site specific
360
—
—
hardness dep.
—
16
hardness dep.
hardness dep.
--
—
--
—
—
hardness dep
—
2.4
hardness dep.
—
—
—
135
hardness dep.
—

Aguatic Life
(Chronic)

—
87
60--100
150
—
—
hardness dep.
—
11
hardness dep.
hardness dep.
--
—
--
—
1,000 (tot rec
hardness dep
1,000
0.1
hardness dep.
—
—
—
17
hardness dep.
-
PQL
(ug/L)
-------
Table 11-4
Surface Water Standards
Basic Standards and Methodologies for Surface Water
Site-Specific Standards for Use Classification
Recreation Class 2, Aquatic Life Warm Water Class 2, Agricultural Page 5 of 5

Agricultural Water Supply
Standard Segments Aguatic Life Aguatic Life PQL
(]lg/L) (]lg/L) (Acute) (Chronic) (]lg/L)

Sulfate — 250,000
Thallium — — — 15
Uranium -- -- hardness dep. hardness dep.
Zinc 2,000 (30 day) 5,000 (30 day) hardness dep. hardness dep.

Radionuclides

Cesium 134,pCi/l — 80th
Plutonium 238,239, and 240, pCi/1 -- 15th
Radium 226 and 228, pCi/1 — 5th
Strontium 90, pCi/1 — 8th
Thorium 230 and 232 pCi/1 — 60th
Tritium, pCi/1 -- 20,000th
-------
Table 11-5
Air Quality Performance Standards
Sitewide Remedy
Page 1 of 2
Concentration
(jlg/mS)
Chemical/Element
1,1,1-Trichloroethane
1,1,2-Trichloroethaae
1,1-Dichloroethane
1,1,2,2-Tetrachloroethane
1,2,4 Trichlorobenzene
1,2-Dichloroethylene (total)
1,1-Dichloroethylene
1,2-Dichlorobenzene (ortho)
1,2-Dichloroethane
1,2-Dichloroethylene
1,2-Dichloropropane
1,4-Dichlorobenzene
2,3,7,8-TCDD (dioxin
equivalence)
2,4-Dichlorophenol
2,4-Dimethylphenol
2,4—Dinitrophenol
2-Butanone
2-Chlorophenol
2-Hexanone
2-Methylphenol
2-Methylnaphthalene
4,4-DDT
4-Methylpheaol
4-Methyl-2-pentanone
Acetone
Acrylonitrile
Aniline
Benzene
Benzo(a)anthracene
Benzyl alcohol
Bis (2-chloroethyl)ether
Annual
Average
(AAL)
24-Hour
Average
(TEL)
Organics
1038.37
0.06

0.02

107.81

81.74
0.04
107.81
0.05
0.18
10.88

14.25a
160.54
0.01
0.14
0.12
1038.37
14.84

18.67

215.62

81.74
11.01
215.62
94.23
122.61
10.88

14.25a
160.54
1.18
2.07
1.74
Other
521

0.049
0.0103
Source
Massachusetts Guidance
Massachusetts Guidance
Noncarcinogenic Risk
Massachusetts Guidance
Based on RfC
Massachusetts Guidance
Carcinogenic Risk
Massschusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance

Massachusetts Guidance
Base on Slope factor
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
aValue is for sum of naphthalene and 2-methyl naphthalene.
-------
Table 11-5
Air Quality Performance Standards
Sitewide Remedy

Concentration
(jlg/mS)
Page 2 of 2
Chemical/Element

Bis(2-ethylhexyl)phthalate
Carbazole
Carbon disulfide
Carbon tetrachloride
Chlorobenzene
Chloroethane
Chloroform
Chloromethane (methyl
chloride)
Dibenzofurab
Dieldrin
Di-n-Octylphthalate
Ethylbenzene
Ethylenedibromide
Fluoranthene
Gamma BHC (lindane)
Heptachlor
Methylene chloride
Naphthalene
NDMA
PCBs
Pentachlorophenol
Phenanthrene
Phenol
Styrene
Tetrachloroethylene
Toluene
trans-1,3-Dichloropropene
Trichloroethylene
Vinyl chloride
Xylenes (total)
Ammonia
Arsenic
Barium
Beryllium
Cadmium
Chromium
Lead
Manganese
Mercury
Nickel
Selenium
Vanadium
Annual
Average
(AAL)
0.27
0.07
6.26
358.78
0.04
24-Hour
Average
(TEL)
0.27
85.52
93.88
717.55
132.76
118.04
0.003
0.001
0.24
14.25a

0.0005
0.01

52.33
1.75
0.02
10.24
118.04
0.14
0.14
9.45
14.25a

0.003
0.01

52.33
115.81
922.18
10.24
0.61 36.52

11.8 11.8

Inorganics

4.73 4.73
0.0004
0.001

0.07
0.18
0.54
0.27
0.001
0.003

0.14
0.27
0.54
0.27
Other
0.56
0.000219
0.0001
0.028
0.0007
0.5
0.000085

1
0.3
Source
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Based on Slope Factor
Based on Slope Factor

Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Based on Slope Factor
Massachusetts Guidance
Massachusetts Guidance

Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance

Massachusetts Guidance
Carcinogenic Risk
Massachusetts Guidance
Massachusetts Guidance
Based on Slope Factor
Based on Unit Risk
Massachusetts Guidance
Massachusetts Guidance
Based on Slope Factor
Massachusetts Guidance
Based on RfC
Based on Unit Risk
Massachusetts Guidance
Massachusetts Guidance
Massachusetts Guidance
aValue is for sum of naphthalene and 2-methyl naphthalene.
-------
Table 11-6
Landfill Gas Point of Action Boundary
Standards

Chemical Standards
(jlg/mS)

1,1-Dichloreothylene 4.9
1,2-Dichloroethane 9.4
Benzene 29
Chloroform 11
Methylene chloride 520
Vinyl chloride 2 . 8

aStandard based on 10-4 excess cancer risk.
Table 11-7
Landfill Gas Compliance Boundary Performance Standards
Sitewide Remedy

Chemical Performance Standard Basis
()lg/m3)

1,1,1-Trichloroethane 700 C
1,1-Dichloroethane 400 C
1,1-Dichloroethylene 0.033 B
1,2-Dichloroethane 0.040 A
2-Butanone 700 C
Benzene 0.12 A
Carbon disulfide 0.27 A
Chloroform 0.04 A
Ethylbenzene 118.04 A
Methylene chloride 0.24 A
Methane 5% LEL D
Toluene 10.24 A
Total Xylenes 11.8 A
Vinyl chloride 0.020 B

Notes: A = ARAR/TBC (based on the Massachusetts AALs).
B = Carcinogenic (1 x 10-6) target risk (adult).
C = Noncarcinogenic target calculation (Hazard Index = 1).
D =40 CFR, Part 241.
LEL = Lower Explosive Limit.
-------
Table 11-8
Cost Estimate Summary
Selected Sitewide Remedy
OU
Remedial Actions/Components

(1)

Capital
$1,

5,
11,

8,
18,
543,
226,
054,
736,
247,
806,
16,
41,
16,
16,
71,
160,
841,
261,
100,
357,
966,
60,
508,
278,
97,
700,
375,
434,
977,
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
Annual
O&M
$237,
21,
243,

150,
651,
18,
789,
15,
15,
251,
1,088,
83,
11,

618,
218,
10,
840,
30,

543,
2,353,
(2)
Present Worth O&M
(3) = (1)
Present
(i=5%, n=30 years)
000
000
000
0
000
000
000
000
000
000
000
000
000
000
0
000
000
000
000
000
0
0
0
000
000
$3,

2,
10,

12,

3,
16,
1,

9,
3,

12,

8,
36,
643,
323,
736,

306,
008,
277,
129,
231,
231,
858,
726,
276,
169,

500,
351,
154,
913,
461,

347,
171,
000
000
000
0
000
000
000
000
000
000
000
000
000
000
0
000
000
000
000
000
0
0
0
000
000
$5,

7,
21,

12,

3,
16,
4,

13,
4,

13,

16,
55,
+ (2)
Worth
Total
186,
549,
790,
736,
553,
814,
293,
170,
247,
247,
929,
886,
117,
430,
100,
857,
317,
214,
421,
739,
97,
700,
375,
781,
148,
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
2/3 Gas Collection/Flare
Stage 1 (minus abandonment of wells) (630 scfm)
Stage 2 (630 scfm)
Drum Removal (includes cover maintenance)
North Slope Cover
Indirects @ 80% Capital & 30% O&M
Subtotals

4/5 Section 6 Soil Monitoring
Surface Water Removal Action
Section 6 Sediment Monitoring
Section 31 Sediment Monitoring
Indirects @ 80% Capital & 30% O&M
Subtotals

1/6 Slurry Walls
Extraction Wells and Piezometers
Mobilization
Treatment System (20 gpm)
Onsite Subtitle D Landfill
Reinjection Trench
Long-term GW Monitoring
Infrastracture
Well Abandonment
Command Post Demolition
Decommissioning
Indirects @ 80% Capital & 30% O&M
Subtotals

Totals $31,000,000 $4,100,000 $63,000,000 $94,000,000

Note: Indirects include a 25 percent for contingency on capital costs and a 20 percent for contingency on O&M costs.
-------
Section 12.0
Statutory Determinations

Under CERCLA Section 121, EPA must select remedies at Superfund sites that are protective of human health and
the environment. CERCLA Section 121 specifies that when complete, the selected remedial action for a site
must comply with applicable or relevant and appropriate environmental standards established under federal and
state environmental laws unless a statutory waiver is justified. The selected remedy must also be cost
effective and utilize permanent solutions and alternative treatment technologies or resource recovery
technologies to the maximum extent practicable. Finally, CERCLA Section 121 includes a preference for
remedies that employ treatment that permanently and significantly reduce the volume, toxicity, or mobility of
hazardous wastes as their principal element.

12.1 Protection of Human Health and the Environment

The following discussion describes how the risks posed through each pathway will be eliminated, reduced, or
controlled by the components of the selected sitewide remedy and in doing so protect both human health and
the environment. The selected remedy protects human health and the environment by achieving performance
standards that will reduce the risk levels for individual contaminants at the Lowry Site to 1 x 10-6, and
cumulative risk for all exposures and contaminants to between 1 x 10-6 and 1 x 10-6.

The selected remedy protects human health through: containment of contaminated ground water and collection
and treatment of that ground water in an upgraded or new onsite treatment facility; maintenance of a complete
cover over the landfill mass and the addition of cover material on the north face of the landfill;
containment and collection of landfill gases, treatment and destruction of those gases in an enclosed flare,
and treatment of gas condensate in the onsite treatment facility; excavation, treatment, and offsite disposal
of drums and associated contamination in the former tire pile area; construction and operation of an adeguate
ground water/liguids treatment facility onsite; re-engineering of the drainage in unnamed creek to intercept
and contain contaminated seepage and eliminate the release of contamination into sediments and surface water;
implementation of a comprehensive monitoring program for all media; and, establishment of institutional
controls to limit access, prohibit onsite construction, prohibit use of water beneath the Lowry Site, and
prohibit all incompatible offsite land uses and activities.

The selected remedy is protective of the environment because it addresses all concerns identified by the
ecological risk assessment for surface water, sediments, and surficial soils. Environmental risks posed by
contaminated surface water and sediments in Section 6 are addressed by remedial actions, while surface water
and sediments in Section 31 are addressed through limiting exposure and continued monitoring.

The landfill gas collection and treatment systems will minimize landfill gas migration into the offsite
subsurface environment, thus reducing the mobility and volume of toxic substances through their treatment.
The selected sitewide remedy will also remove contaminants from the gas through operation of an enclosed
flare. The selected remedy eliminates the risk of fire or explosion from the accumulation of methane by
reducing methane concentrations to less than 5 percent of the lower explosive limit at the boundary of the
landfill mass. These reductions will also minimize the potential threat of inhalation of contaminants in
landfill gas by future receptors.

According to the Baseline Risk Assessment, the estimated concentration of each carcinogenic contaminant in
landfill gas within a potential future onsite residence would exceed a 1 x 10-6 cancer risk level for each
carcinogenic contaminant. This also would be true for a hypothetical future offsite (200 feet west)
residence if the structural slab of the residence were cracked and gas diffused in. Installation of the gas
collection and flare systems will reduce the offsite risk of cancer from these pathways. Collection of
landfill gas will also reduce the potential for gas to contaminate ground water.

The ground-water barrier walls and collection systems will minimize the potential for any future offsite
migration of contaminated ground water. The upgradient containment, collection and diversion system will
also inhibit offsite ground water from flowing into the Lowry Site's subsurface environment.

Containment and treatment of contaminated ground water will, over time, reduce the contaminant concentration
in ground water onsite. Shallow ground water beneath the Lowry Site is not currently used. Deep ground
water beneath the Lowry Site is used for industrial supply. Shallow and deep ground water downgradient of
the Lowry Site is of domestic- and agricultural-guality and is used by nearby residents and farmers. The
baseline cancer risk associated with the potential future ingestion of onsite shallow ground water within the
waste-pit source area is estimated as 1 x 10-2 . The baseline noncancer hazard index is estimated as 47 for
this potential future pathway. These risks are expected to decrease over time as existing ground water
within the shallow aguifer is treated and flow through the Lowry Site is reduced. Residual risk after
implementation of the selected remedy cannot be guantitatively estimated.
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Operation of the SWRA will eliminate the potential future threat of exposure from direct contact and
incidental ingestion of contaminated surface water and sediments. The baseline cancer risks associated with
the potential future ingestion of onsite surface water and sediments (as they existed before the SWRA) are
estimated as 8 x 10-4 and 9 x 10-6, respectively. The baseline noncancer hazard index for ingestion of
surface water is estimated as 2, and the baseline noncancer hazard index for the ingestion of sediments is
below 1. Baseline cancer and noncancer risks have been reduced to acceptable levels as a result of the SWRA.
The hydraulic connection between ground water and surface water within the unnamed creek has been eliminated
and thus, surface water is no longer contaminated above performance standards. Sediments within unnamed
creek have been covered as a result of the SWRA, and thus, potential exposure to Section 6 sediments has been
eliminated. These measures will be operated and maintained as part of the selected remedy. Institutional
controls and access restrictions will eliminate the potential for exposure to surface water and contaminated
sediments in Section 31. Monitoring will provide a mechanism to detect contaminant migration.

Excavation of contaminated solids from the former tire pile area will eliminate the potential for future
direct contact, incidental ingestion, and inhalation. The baseline carcinogenic risks estimated for a
hypothetical future onsite resident within the former tire pile area are 2 x 10-5 for ingestion and
inhalation (inorganics and organic chemicals). These risks will be eliminated with excavation of the
contaminated solids. In addition, excavation of contaminated solids will eliminate them as a potential source
of further ground-water contamination.

Cap improvements on the north slope and containment of the landfill mass will eliminate the possible exposure
of rectors to physical and chemical hazards associated with contaminated solids and landfill waste. In
addition, the north slope cover will prevent infiltration of precipitation and thus reduce the potential for
leachate generation.

Institutional controls will prohibit future land uses that are incompatible with or that could inhibit or
impair the effectiveness of the on- and potential future offsite remedial actions.

Monitoring of ground water, gas, the SWRA, soil, sediments, ground-water treatment plant effluent, and
surface water will assure that there is early warning of any failure of the selected sitewide remedy. These
reguirements include, but are not limited to: performance and compliance monitoring of the existing
ground-water barrier wall, injection trench, SWRA collection system, and existing ground-water treatment
facility; soil and sediment erosion monitoring; surface water runoff monitoring; monitoring of gas migration;
and ground-water monitoring for detection of potential vertical and/or horizontal contaminant migration.

There will be no unacceptable short-term risks or cross-media impacts. Short-term effectiveness is discussed
in detail in Section 12.4.3. Cross-media impacts were evaluated in terms of contaminant transfer to air,
soil, ground water, surface water, and gas.

12.2 Compliance with ARARs

Under Section 121(d)(1) of CERCLA, remedial actions must attain standards, reguirements, limitations, or
criteria that are "applicable or relevant and appropriate" under the circumstances of the release at a site.
All ARARs would be met upon completion of the selected sitewide remedy at the Lowry Site.

The selected sitewide remedy of additional capping, excavation of contaminated solids in the former tire pile
area, ground-water containment and treatment, active landfill gas collection and treatment, operation and
maintenance of the SWRA, and institutional controls will comply with all Federal and State applicable or
relevant and appropriate chemical-, action-, and location-specific reguirements (ARARs). Federal and State
statutes and regulations pertinent to the selected remedy are discussed in Section 11.0.

The specific ARARs and TBCs for the selected sitewide remedy are presented in Table 11-1.

12.3 Cost Effectiveness

EPA has determined that the selected sitewide remedy will provide overall effectiveness proportional to its
costs and is, therefore, cost effective. In order to make this determination, EPA compared the costs of
components of the selected remedy to the alternatives evaluated during the FSs, as described below. A
description of cost estimating procedures is provided in Subsection 8.1.

12.3.1 Shallow Ground Water and Subsurface liquids (OU 1) and Deep Ground Water (OU 6)

For ground water alternatives (OUS 1&6), Section 9.0 of this ROD provides the capital costs, annual operation
and maintenance costs, and the present worth of each alternative. The selected ground-water remedy, Modified
Alternative GW-5 (the North Boundary and Toe of Landfill and Lateral Barrier Wall, Collection and Treatment
System, Plus Upgradient Containment, Collection and Treatment alternative), is comparable in cost to
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Alternatives GW-3 (the North Boundary, Toe of Landfill Containment, Collection and Treatment alternative),
GW-5 (The North Boundary, Toe of Landfill, Lateral Containment, Collection and Treatment alternative), and
GW-6 (the North Boundary, Toe of Landfill, and Waste-Pit Pumping alternative), but will be more effective
than these alternatives at preventing offsite migration of contaminants. Unlike these other alternatives,
the selected ground-water remedy includes the immediate design and construction of containment and collection
systems on all sides of the Lowry Site.

Alternative GW-6 results in a slightly greater reduction of volume of contaminants than the selected remedy;
however, this alternative would not eliminate the source and the potential for offsite migration of
contaminants would still exist. Thus, the additional cost of this alternative would not be warranted.

The selected ground-water remedy is more expensive than Alternatives GW-1 (the No Further Action alternative)
and GW-2 (the North Boundary Containment alternative), but it is also more effective at containing and
treating contaminants than these alternatives. Alternative GW-4 (the North Boundary, Upgradient Containment
Plus Multilayered Cap alternative) is more expensive than the selected remedy, but would be less effective
because it would not include lateral containment.

12.3.2 Landfill Solids (OU 2)

Section 9.0 of this ROD provides capital costs, annual operation and maintenance costs, and present worth
costs for Landfill Solids (OU 2). Although the selected landfill solids remedy, Modified LFS-4 (the Drum
Removal/Offsite Disposal/North Face Cover alternative), is the most expensive of the alternatives evaluated,
it offers greater long-term effectiveness and permanence and a significantly greater reduction of toxicity,
mobility, or volume through treatment than any of the other alternatives. This is because the selected
remedy will excavate, treat, and dispose offsite a much larger volume of contaminated solids from the former
tire pile area than any of the other alternatives. The effectiveness of the selected remedy is also greater
because it includes 2 feet of additional cover on the north slope of the landfill mass, which will reduce the
potential for exposure to landfill solids and for infiltration of water into the landfill mass.

12.3.3 Landfill Gas (OU 3)

Section 9.0 of this ROD provides cost information for remedial alternatives evaluated for Landfill Gas (OU
3). The selected landfill gas remedy, Modified LFG-3 (the Gas Collection/Enclosed Flare alternative), is
slightly more expensive than Stage 1 of Alternative LFG-3 (the Gas Collection/Enclosed Flare alternative) and
slightly less expensive than Stage 1 of Alternative LFG-5 (Gas Collection/Enclosed Flare and Heat Recovery),
but includes significantly more extraction wells than either alternative, and thus, will be more effective at
preventing offsite migration of landfill gas and dangerous buildup of gases onsite. The selected remedy will
also result in a greater reduction of toxicity, mobility, and volume of contaminants through treatment.

Stage 2 of Alternative LFG-3 would be as effective and offer the same reduction in toxicity, mobility, and
volume through treatment as the selected remedy, but would be more expensive because it would involve the
immediate abandonment of existing wells and would involve remobilization for Stage 2 construction.

Stage 2 of Alternative LFG-5 would be as effective and offer the same reduction in toxicity, mobility, and
volume through treatment as the selected remedy, but would be more expensive because it would involve:
installation of heat recovery eguipment; the immediate abandonment of existing wells; and would involve
remobilization for Stage 2 construction. Alternative LFG-5 would offer the benefit of heat recovery, but an
economical use for the heat has not been identified.

The selected remedy is more expensive than Alternative LFG-2 (the No Further Action alternative), but
Alternative LFG-2 will not prevent the migration of landfill gas offsite or reduce the toxicity, mobility, or
volume of contaminants through treatment. Alternative LFG-2 is not an effective remedy.

12.3.4 Soil (OU 4)

For soil (OU 4), Section 9.0 of this ROD summarizes cost data for each alternative. The selected remedial
alternative for soil, Alternative SOIL-1 (No Further Action), is the least costly option. The remaining
alternatives are more expensive without providing significant additional short-term or long-term
effectiveness. Contaminant concentrations in soils are already at protective levels, and therefore,
excavation or dust control provide no added benefit. None of the alternatives reduces toxicity, mobility, or
volume through treatment, because no alternative involves treatment.

12.3.5 Surface Water (OU 5)

For surface water (OU 5), the SWRA was evaluated for its effectiveness and integration into the sitewide
remedy. Because the SWRA was deemed effective in eliminating surface water exposures at the Lowry Site and
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could be fully integrated into the sitewide remedy, it was the only alternative retained. The design life of
the SWRA was investigated to ensure full integration with the components of the sitewide remedy. The costs
for the SWRA are provided below:

Alternative SW-1, No Further Action

Capital Costs-$41,000
Annual O&M Costs-$790,000
Present Worth-$12,100,000

12.3.6 Sediments (OU 5)

For sediments that are part of OU 5, the remedial alternatives are discussed by location, in either Section 6
or Section 31. For Section 6 sediments, Section 9.3 of this ROD summarizes costs for each alternative. The
selected remedy, SED6-1 (the No Further Action alternative), is the least expensive alternative, will be
virtually as effective as Alternative SED6-2 in the long term, and will be as or more effective than
Alternative SED6-2 in the short term because no construction is reguired. Neither alternative includes
treatment.

For Section 31 sediments (OU 5), Section 9.3 of this ROD summarizes costs for each alternative. The selected
remedial alternative for Section 31 sediments, Alternative SED31-1 (No Further Action), is the least costly
option. The remaining alternatives are more expensive without providing additional short-term or long-term
effectiveness. Contaminant concentrations in sediments are already at protective levels, and therefore,
capping, excavation, or access restrictions provide no added benefit. None of the alternatives reduces
toxicity, mobility, or volume through treatment, because no alternative involves treatment.

12.3.7 Selected Sitewide Remedy

The net present-worth value for the selected sitewide remedy is $94,000,000 (see Table 11-8 for eguated cost
summaries for the selected sitewide remedy). Because there are no significant cross-media impacts, and since
each of the selected components has been demonstrated to be cost effective, the sum of the components is also
cost effective. Therefore, EPA has determined that the sitewide remedy is cost effective in accordance with
Sections 300.430 (f) (1) (i) (B) and 300.430 (f) (1) (ii) (D) of the NCP.

12.4 Utilization of Permanent Solutions and Alternative Treatment Technologies (or Resource Recovery
Technologies) to the Maximum Extent Practicable

EPA has determined that the selected sitewide remedy utilizes permanent solutions and alternative treatment
technologies, or resource recovery technologies, to the maximum extent practicable because it uses
state-of-the-art treatment technologies for landfill gas and ground water. In addition, the removal,
treatment, and disposal of wastes in the former tire pile area will achieve a permanent solution for those
wastes. Although the selected sitewide remedy is in large part a containment remedy, the remedy offers the
best balance of tradeoffs among the five primary balancing criteria and further use of treatment as evaluated
in the RI/FSs is not practicable. State and community acceptance were also considered in making this
determination.

Since the selected sitewide remedy is in large part a containment-based remedy, it is consistent with
Directive No. 9355.0-49FS Presumptive Remedy for CERCLA Municipal Landfill Sites; however, every effort has
been made to treat the landfill gas and ground water within the containment system. The selected remedy will
ensure the containment of ground water on the northern, eastern, western, and southern boundaries, and will
collect ground water for treatment at each of these locations. In addition, ground water will be collected
for treatment at the toe of the landfill. Gas will be collected at the eastern, western, and southern
boundaries of the landfill mass and within the landfill mass and treated. In addition, the removal and
offsite treatment of accessible waste within the former tire pile area (the principal threat in the former
tire pile area) is consistent with the statutory reguirement.

Of the alternatives that meet EPA' s two threshold criteria of overall protection of human health and the
environment and compliance with ARARs, EPA has determined that the selected sitewide remedy best balances the
tradeoffs of the alternatives as they relate to: long-term effectiveness and permanence; reduction in
toxicity, mobility, or volume achieved through treatment; short-term effectiveness; implementability; and
cost.

The following discussion of tradeoffs among alternatives is based on a comparison to the five primary
balancing criteria listed above, and the two modifying criteria of State and community acceptance.
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12.4.1 Long-Term Effectiveness and Permanence

Ground Water

Of the alternatives evaluated, the selected ground-water remedy would offer the greatest long-term
effectiveness and permanence because it addresses the movement of contaminants from all sides of the Lowry
Site. The selected remedy will immediately prevent potential offsite migration of contaminants to the south,
east, and west, using barrier walls and collection systems. Barrier walls are a permanent form of
containment and have been proven effective over the long term at the Lowry Site. The selected ground-water
remedy also includes treatment of contaminated ground water and is the only alternative that fully contains
and collects contaminants migrating to the north, east, west, and south. In addition, the selected remedy
will provide for collection of contaminated ground water at the toe of the landfill mass. Contamination will
be captured closer to the source, thereby avoiding further contamination of the aguifer downgradient of the
landfill mass. The selected remedy effectively reduces the long-term potential for contaminated ground-water
migration.

Landfill Solids

The selected remedy would provide the greatest long-term effectiveness and permanence because portions of the
former tire pile area will be excavated and the largest volume of contaminated material will be removed
relative to the remaining alternatives. This remedy will permanently remove contaminated material from the
Lowry Site. In addition, the selected remedy will provide 2 feet of additional cover on the north face of
the landfill mass, thus providing greater containment and long-term effectiveness and permanence in the
landfill area than the other alternatives.

Landfill Gas

The selected remedy will provide the greatest long-term effectiveness and permanence because it will provide
a more extensive gas extraction system throughout the landfill mass, and will be less dependent on gas
monitoring activities than other alternatives.

Soils

The selected remedy will provide long-term effectiveness and permanence through institutional controls. The
risks associated with the soils are within EPA's acceptable risk range. Therefore, the selected remedy would
offer acceptable long-term effectiveness and permanence.

Surface Water

The SWRA has been constructed, has operated reliably, and has met performance standards. The SWRA has been
designed for long-term operation and will be monitored and maintained such that it continues to achieve
performance standards. Thus, the SWRA will achieve long-term effectiveness and permanence.

Sediments

In Section 6, the sediments have already been covered as part of the SWRA. The selected remedy will provide
long-term effectiveness and permanence through continued maintenance of the cover. The selected remedy for
Section 31 sediments would provide acceptable long-term effectiveness and permanence because the risks
associated with the sediments are within EPA's acceptable risk range.

12.4.2 Reduction of Toxicity, Mobility, or Volume Through Treatment

Ground Water

The selected remedy will provide substantial reduction of toxicity, mobility, and volume through treatment by
extracting highly contaminated ground water from the alluvium at the toe of the former landfill. In
addition, the selected remedy will provide for extraction and treatment of contaminated ground water from the
northern, eastern, western, and southern boundaries of the Lowry Site. Because it would extract and treat
waste-pit liguids, Alternative GW-6 would be the only alternative which would treat a greater volume of
material than the selected remedy. However, Alternative GW-6 does not compare favorably to the selected
remedy with respect to other criteria.

Landfill Solids

The selected remedy will provide the greatest level of excavation and treatment of contaminated solid
material, thereby providing the most effective reduction of toxicity, mobility, and volume through treatment.
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Landfill Gas

The selected remedy will provide the greatest reduction of toxicity, mobility, and volume by extracting and
treating more gas from the eastern, western, and southern portions of the landfall mass than any of the other
alternatives.

Soils and Sediments

None of the alternatives, including the soils and sediments selected remedies, result in a reduction of
toxicity, mobility, or volume through treatment.

Surface Water

Under the selected remedy, the SWRA would reduce the volume of contaminants through collection and treatment
of contaminated alluvial seepage.

12.4.3 Short-Term Effectiveness

Ground Water

All of the alternatives would have reasonable short-term effectiveness. The selected remedy would include a
ground-water extraction system, at the toe of the landfill, for collection of highly contaminated ground
water. During construction of this system, workers and the community would potentially be exposed to higher
risks from the presence of volatile organic compounds in the soil. However, these risks are not anticipated
to be significant during the 3-year design and construction period. It has also been demonstrated that
workers at the Lowry Site, as well as the community, can be adeguately protected during construction through
the routine application of accepted health and safety practices. The selected remedy will achieve overall
protection in a shorter time frame than any other alternative because containment systems would be
immediately designed and installed on the eastern, western, and southern sides of the Lowry Site.

Landfill Solids

The selected remedy is not the best alternative considered under this criterion. The No Further Action
alternative (LFS-2) would have the greatest short-term effectiveness because it would pose no adverse
short-term effects to workers, the community, or the environment and would take the least amount of time
until protection was achieved. However, potential short-term risks to construction workers associated with
excavation of contaminated materials from the former tire pile area can and will be controlled through the
use of appropriate health and safety measures.

Landfill Gas

The selected remedy poses minimal short-term risks in connection with the required construction activities.
These risks would apply primarily to onsite workers during construction. Protectiveness will be achieved
after construction is complete. Alternative LFG-2 (the No Further Action alternative) would pose no adverse
short-term risks to workers because there would be no construction activities, but this alternative would not
eliminate potential short-term risks from gas buildup and migration, and thus, would not be effective in the
short-term.

Soils

The selected remedy would not involve soil disturbance and, therefore, would provide maximum short-term
protection to workers, the environment, and the community. The risk from soils are already within EPA's
acceptable risk range and therefore the time until protection is achieved is immediate.

Surface Water

Construction and startup of SWRA facilities have been completed and were conducted in a manner without
accidents or adverse environmental impacts. Therefore, the SWRA satisfies the short-term effectiveness
criterion.

Sediments

The selected remedies for sediments in Section 6 and Section 31 provide the greatest short-term effectiveness
for workers, the community, and the environment because these alternatives require no disturbance of
sediments. The risks from sediments in Section 6 have been addressed through construction of the SWRA and
the risks from sediments in Section 31 are within EPA's acceptable risk range. Therefore, the selected
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remedies achieve protection immediately.

12.4.4 Implementability

Ground Water

The selected remedy is considered to be administratively and technically implementable. The services and
materials required to implement this remedy are readily available and use current technologies. Construction
of containment barrier walls is considered routine and can be performed by local contractors. The
effectiveness of the ground-water treatment system has been proven by the success of the existing onsite
treatment facility. Alternatives GW-4 and GW-6 would be more difficult to implement than the selected remedy
because Alternative GW-4 would include 100-foot deep extraction trenches that might be difficult to
construct, and Alternative GW-6 would include drilling 52 waste-pit extraction wells that might be difficult
to drill through landfill refuse.

Landfill Solids

Like the ground-water selected remedy, the landfill solids selected remedy is considered to be
administratively and technically implementable. The services and materials required to implement this remedy
are readily available and use current technologies. The selected remedy will include excavation of drums,
drum contents, and contaminated soils using readily available construction equipment. This type of
excavation is considered routine construction, could be conducted by local contractors, and has been
implemented at other Superfund sites. Construction of the north face cover would involve routine landfill
construction procedures, and cover material is readily available onsite.

Landfill Gas

The selected remedy is technically and administratively implementable. The selected remedy will use current
proven technology, and the construction of gas extraction wells would be a routine activity that could be
conducted by local contractors. In the long term, the selected remedy would be more easily implemented than
Alternatives LFG-3 and LFG-5 because construction activities would be limited to one mobilization event.

Soils and Sediments

All of the alternatives, including the selected remedies for soils and sediments, are considered to be
technically and administratively implementable.

Surface Water

The SWRA has been constructed and is operational, and has therefore been demonstrated to be implementable.

12.4.5 Cost

Ground Water

While the selected remedy is not the least costly of the alternatives considered, it has significant
advantages over less costly alternatives. In particular, unlike those alternatives which are significantly
less expensive (Alternatives GW-1 and GW-2), the selected remedy includes the immediate design and
installation of permanent containment and collection systems on all boundaries of the Lowry Site to prevent
offsite migration of contaminants. It would thus offer greater long-term effectiveness and permanence. The
selected remedy also includes toe of the landfill collection and treatment and will thus provide greater
reduction in toxicity, mobility, and volume through treatment than Alternatives GW-1 or GW-2.

Other alternatives which are only slightly less expensive than the selected remedy (Alternatives GW-3 and
GW-5) would also not include containment and collection systems on all boundaries of the Lowry Site. The
same is true of more expensive alternatives (Alternative GW-4 and GW-6.) The addition of a multilayer cap in

Alternative GW-4 would not provide any significant advantages over the existing cap over the landfill mass.
Alternative GW-6's extraction and treatment of waste-pit liquids would only be able to extract a small
percentage of waste-pit liquids, and thus, the source of ground-water contamination would remain.

Landfill Solids

The selected remedy is the most costly of the alternatives evaluated, but it is considered to offer
significant advantages over the other alternatives with respect to reduction of toxicity, mobility, and
volume through treatment and long-term effectiveness and permanence because it would remove and treat the
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greatest volume of contaminated materials in the former tire pile area, including accessible waste pits which
are considered hot spots, and would place an additional two feet of cover on the north face of the landfill
mass.

Landfill Gas

The selected remedy is more costly than the No Further Action alternative, but the No Further Action
alternative would not be effective in either the long or the short-term and would not achieve a reduction in
toxicity, mobility, or volume through treatment. The selected remedy is only slightly more costly than
Alternative LFG-3, Stage 1, but will include the installation of a more extensive array of extraction wells
around and within the landfill and thus offers significant advantages with respect to long-term effectiveness
and permanence and reduction of toxicity, mobility, or volume through treatment. Other landfill gas
alternatives which are more expensive than the selected remedy offer no advantages over the selected remedy.

Soils and Sediments

The selected remedy for soils and sediments is the least costly of the alternatives considered and will also
be effective in both the short and the long-term. None of the alternatives considered included treatment.

Surface Water

The selected remedy was the only alternative considered.

12.4.6 State Acceptance

The State of Colorado concurs with the selected remedy for the Lowry Site and concurs with the selected
ARARs.

12.4.7 Community Acceptance

Based on comments to the Proposed Plan for OUS 1&6, the community and the PRPs support the selected remedy.
The community has reservations about leaving the bulk of waste-pit liguids in place; however, it is
technically infeasible to remove the waste-pit liguids. Comments received from the community on the Proposed
Plan for OUS 2&3 and 4&5 were strongly supportive of the excavation and treatment of contaminated solids in
the former tire pile area. The community was also generally supportive of the simultaneous implementation of
Stage 1 and Stage 2 gas extraction as a means of controlling offsite landfill gas migration. However, one
commenter encouraged EPA to consider the focus of the gas extraction to be extraction and removal rather than
control of offsite landfill gas migration. The commenter felt that the additional installation of Stage 3
would yield a significant increase in the annual volume of contaminants removed for a relatively small
incremental increase in the overall cost. The community was also adamantly opposed to the addition of 1.2
million cubic yards of municipal solid waste over the former waste pits. Commenters were very supportive of
EPA's decision to reject this alternative.

Comments from the PRPs opposed EPA's preferred alternative for landfill gas and landfill solids and proposed
a remedy consisting of land acguisition and land use restrictions of 0.5 miles around the perimeter of the
Lowry Site, enhancement of the landfill cover through the addition of 1.2 million cubic yards of municipal
solid waste, and the installation of only Stage 1 of the gas extraction system. The PRPs' comments also
focused on the short-term effectiveness of the excavation in the former tire pile area and the potential
exposure to workers during the excavation.

12.5 Preference for Treatment as a Principal Element

The selected sitewide remedy includes: treatment of contaminated ground water collected from the northern,
western, eastern, and southern boundaries of the Lowry Site; treatment of contaminated ground water collected
from the toe of the landfill mass; treatment of landfill gas collected from the perimeter of the landfill
mass; and excavation and offsite treatment of "hot spots" from the former tire pile area. The hot spots in
the former tire pile area constitute a principal threat at the Lowry Site. Also, the SWRA utilizes treatment
to control the principal threat of contaminated seepage. The statutory preference for remedies that employ
treatment as a principal element is thus at least partially satisfied by the selected sitewide remedy.

The statutory preference for treatment will not be met for the landfill mass and associated waste pits.
Treatment is not practicable for the following reasons:

• The large volume of waste within the landfill mass.

• The lack of discrete, accessible hot spots that represent major sources of contamination.
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• The impracticability of excavating and treating the entire volume of waste.

• The prohibitive cost. Preliminary estimates during early FS studies indicated that costs would
be in excess of $4.5 billion.

It should be noted that the selection of a remedy based in large measure on containment for the Lowry Site
with excavation of accessible hot spots is consistent with the NCP and EPA's guidance regarding presumptive
remedies for CERCLA municipal landfill sites. Because this remedy will result in hazardous substances
remaining on the Lowry Site above health-based levels, a review will be conducted at least every 5 years
after commencement of remedial action to ensure that the remedy continues to provide adeguate protection of
human health and the environment.
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Section 13.0
Responsiveness Summary for Operable Units 1 & 6

This section presents the oral and written responses to comments from EPA to individuals, concerned citizen
groups, and public entities who have commented on the Proposed Plan for OUS 1 & 6. Comments are presented in
italics; their responses in plain text. Each individual or public group's comments and responses are
presented as individual subsections.

13.1 Response to Oral Comments on the Proposed Plan for Operable Units 1 & 6 Shallow Ground-Water and
Subsurface Liquids and Deep Ground-Water Operable Units Lowry Landfill Public Meeting December 9, 1992

The following subsection is a legal transcript of the comments and responses recorded during the public
meeting held in December 1992.
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1
2
3
4
5
6
7
8 PUBLIC MEETING
9 LOWRY LANDFILL SUPERFUND SITE
10 Proposed Plan for Operable Unites 1 & 6:
Shallow Groundwater and Subsurface Liquids
11 and Deep Groundwater
12 December 9, 1992
7:15 p.m.
13
Eaglecrest High School
14 5100 S. Picadilly Street
Aurora, Colorado
15
16
17
18
19
20
21
22
23
24
25

PAMELA MEADE COURT REPORTERS
(303) 494-2141
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1 MARC HERMAN: I'd like to welcome everyone
2 to the proposed planning meeting for Lowry shallow
3 groundwater and subsurface liguids and deep groundwater
4 operable units. The purpose of the meeting is to present
5 to you, the public, EPA's preferred alternative for
6 remediating the groundwater operable units at Lowry
7 Landfill.
8 I'd like to start, first of all, by
9 providing some introductions. My name is Marc Herman,
10 and I am a remedial project manager on the Lowry Landfill
11 Superfund Site Project — not a supreme commander of
12 allied forces.
13 We have Robert Duprey, the director of the
14 Hazardous Waste Management Division; Barry Levene, Chief
15 of the North Dakota/Colorado Section of the Superfund
16 Remedial Branch; Gwen Hooten, Remedial Project Manager
17 for the Lowry Landfill Operable Units 1 and 6; Jesse
18 Goldfarb, Assistant Regional Counsel; Rob Henneke,
19 Community Relations Coordinator; and representing in this
20 corner the State of Colorado, Colorado Department of
21 Health, Angus Campbell, State Project Coordinator for
22 Lowry Landfill Superfund Site, Joe Vranka; State Project
23 Officer; Jane Mitchell, Toxicologist, Colorado Department
24 of Health; and Bob True, Community Relations Specialist.
25 We also have some other folks without
PAMELA MEADE COURT REPORTERS
(303) 494-2141
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1 whose participation this would not be possible.
2 Representing EPA's technical contractor CH2M Hill, Phil
3 Burke, and operating the slide projector; and Andrea
4 Garcia, Community Relations Coordinator; and representing
5 the Lowry Condition, Paul Rosasco.
6 I have a few announcements to make before
7 we get into the presentation. The last day for written
8 comments is December 30, 1992. However, we have received
9 a reguest to extend the public comment period and it will
10 be extended to January 30, 1993.
11 Everyone on the mailing list will receive
12 a notice and both major newspapers in the Denver
13 metropolitan area will receive notices that they will
14 publish announcing the extension for the public comment
15 period.
16 I would reguest that you hold all
17 guestions or comments until the end when we have a
18 designated guestion and answer period.
19 Can everyone hear me okay? I would ask
20 that all commentors when you get up to ask a guestion or
21 make a comment, that you identify yourself and also
22 identify your affiliation.
23 I would ask that you please limit your
24 guestions or comments to five minutes, and if you have
25 more than one guestion or comment, perhaps you could make
PAMELA MEADE COURT REPORTERS
(303) 494-2141
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1 the initial one and give someone else a chance and then
2 follow that.
3 I would remind you if you do not want to
4 make verbal comments, you can make the comments in
5 writing, and I would remind everyone that all pertinent
6 documents that were used for making this decision are
7 available for review at the Aurora Public Library and EPA
8 Superfund Records Center.
9 With that, I would like to introduce Angus
10 Campbell who will provide you -- oh, I'll go over the
11 outline first. We've already done the introduction.
12 Angus is going to provide a history of the site. Gwen
13 will handle the summary of site studies, and she will
14 discuss the evaluation of cleanup alternatives, and then
15 we'll talk about public comments and open up the meeting
16 to guestions and answers.
17 Angus, go ahead.
18 ANGUS: CAMPBELL: Good evening. I'm here
19 to talk a little bit about the location and history of
20 the Lowry Landfill and some of the actions that have
21 taken place to date.
22 The landfill is located here (indicating)
23 at the corner of Gun Club Road and Quincy Avenue. It's
24 about 15 miles to the southeast of downtown (Denver). It
25 is about two miles east of the city of Aurora city
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1 limits. It's northwest of the Arapahoe Race Track and
2 northwest of the Aurora Reservoir, which is just off the
3 map here (indicating).
4 Communities in the area, there is Murphy
5 Creek Ranch two miles to the north, and Dove Hill which
6 is two miles to the south. Eaglecrest High School is
7 about 2-1/2 miles to the southwest. The proposed E-470
8 alignment goes, depending on which proposal you look at,
9 either east or west of the site.
10 A little more detail on the site is here,
11 again, Gun Club Road and East Quincy Avenue to the south
12 (indicating). The site consists -- well, the site is
13 actually part of the Denver Arapahoe Disposal Site, which
14 is five sections of land that was deeded to the City and
15 County of Denver for waste disposal practices. I'll go
16 into that a little more later. The Superfund site is on
17 Section 6 area (indicating).
18 Section 31 is the current landfill. If
19 you go down Gun Club Road, that's where you see all the
20 trash. The waste pits are in the south here
21 (indicating). Unnamed Creek is a small stream in the
22 middle of the site. The tire fill area is here
23 (indicating).
24 The command post where a lot of the
25 activities for the Superfund studies are headed out of is
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1 here (indicating), the groundwater barrier wall and the
2 treatment plant (indicating).
3 Here is a slide showing the site prior to
4 landfilling (indicating). This is from 1956. Here we
5 can see a good footprint of the Unnamed Creek drainage
6 system. The actual site, again here is Gun Club Road and
7 Quincy here to the south, and you see the section line
8 here for Section 6. This is Unnamed Creek here
9 (indicating). This is Murphy Creek, which is the major
10 tributary that Unnamed Creek flows into.
11 History of the Site. Again, as I
12 indicated, the landfill area was part of the Lowry
13 bombing range during World War II. In 1964 that land was
14 deeded to the City and County of Denver for waste
15 disposal practices. Those practices went from '66 to
16 1980, and the practices were known as codisposal, which
17 was the acceptable method at the time for disposing
18 liguid industrial waste along with municipal solid waste.
19 EPA has calculated 142 million gallons of
20 liguid waste was disposed of into unlined trenches.
21 We'll have some pictures of those later. Again, this is
22 called codisposal.
23 That practice ended in 1980. Since 1980,
24 the landfill was used for municipal solid waste only.
25 EPA listed the site on the NPL, National Priorities List,
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1 which is a list of the most dangerous hazardous waste
2 sites in the nation, and that's where the Superfund Site
3 funds come from.
4 In 1984 the first work began on site with
5 the negotiations on work for the groundwater barrier wall
6 and groundwater treatment facility. In '84, '85 the EPA
7 began Phase I and II remedial investigations of the
8 site.
9 In 1988 the EPA under SARA divided the
10 site up into six operable units. Those are Operable
11 Units 1 and 6 is what we're here for tonight, the shallow
12 groundwater surface liguids and deep groundwaters. That
13 work was conducted by the Lowry Coalition for the RI/FS
14 process. Operable Units 2 and 3 are being conducted by
15 the City and County of Denver, Waste Management of
16 Colorado and Chemical Waste Management. Operable Units 4
17 and 5, again the work is being conducted for the City and
18 County of Denver and Metro Waste Water Reclamation
19 District.
20 In December 1988 under the new Operable
21 Unit Plan, the EPA and CDH negotiated an agreement for
22 Operable Unit 1. In 1989 -- we'll see later there is a
23 lot of tires disposed of at the site. Denver contracted
24 with Waste Management of Colorado to shred 6 to 7
25 million tires on site.
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1 In September of '89, the negotiations and
2 agreement to perform Operable Units 2 and 3 and also OU
3 NO. 1, and there was an administrative amendment to
4 include OU6 in December of that year.
5 In August of 1990 Section 6, the old
6 landfill, was closed to municipal solid waste land-
7 filling, and the cap was subseguently put on the site.
8 And in March 1991, OUS 4 and 5 were negotiated, and in
9 August of that year, the Surface Water Removal Action was
10 negotiated. In October of that year, the design for the
11 Surface Water Removal Action began.
12 Tire shredding was completed 16 months
13 less than the contracted period, in April of this year,
14 and Surface Water Removal Action construction began in
15 August and, as you can see, was completed in November.
16 As we are here tonight the RI/FS for Operable Units 1 and
17 6 was completed also last month.
18 There is a series of slides showing sort
19 of the progression of the landfill and waste pit
20 construction and filling. This is the site in 1965
21 (indicating). You can see a few waste pits. They're
22 fairly long. Some of these waste pits get rather large,
23 800 feet long and up to 300 feet wide and 30 feet deep in
24 spots.
25 This slide is from August of 1969, and you
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1 can see additional waste pits being constructed. Some
2 are up in the northern part.
3 And in '72, again, you can see some rather
4 large features here, which are all waste disposal pits
5 for codisposal.
6 In 1977 we began to see tires being
7 disposed of here. As you'll see later those are now
8 gone, and still we have the waste pits being constructed
9 and filled into the south into the tire area.
10 This is a picture of what codisposal is
11 and why it is listed as a Superfund site. We have drums
12 of liguid waste disposed of in unlined pits. These drums
13 of liguid waste were disposed of in these unlined pits.
14 Drums prior to 1966 were not punctured according to the
15 State records, and they were just disposed of in the
16 pits. Post-1966 they were punctured and drained.
17 Also they came in tanker trucks and opened
18 up the valves of the tankers and let them go into the
19 ground into these unlined pits. And, again, here we can
20 see the tire piles here (indicating) and all the landfill
21 and waste pit areas here, and this is how it was done.
22 This is a good picture of what codisposal
23 is. Again, we have a pit here, 30 feet deep, fairly
24 large, about two-thirds full of liguid. It was backed up
25 -- trucks and waste haulers backed up and just dumped
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1 their solid wastes into the liquid waste.
2 The theory behind it was that the solid
3 waste would act as an absorbent and sop up -- similar to
4 what a sponge does -- sop up the liquids. Just to qive
5 you an idea, 77 pits have been identified on site, and 53
6 of those pits have known liquid in them.
7 To qive you a scope of what these are,
8 qenerally a Superfund site would be one of these pits,
9 and here we have 50 of them, if it was elsewhere in the
10 nation.
11 Contents of the waste pits, aqain it's 142
12 million qallons, qive or take a few, of industrial and
13 municipal liquid and solid waste, includinq sewaqe
14 sludqe, metal platinq wastes, petroleum derived products
15 and waste products, pesticides, industrial solvents.
16 These unlined pits over time leaked, and
17 to address that shallow contamination, several interim
18 remedial actions were put in place. We have the
19 underqround barrier wall -- I'll show you a slide of that
20 later -- the qroundwater treatment facility, the Surface
21 Water Removal Action, and other actions, the shreddinq of
22 the tires on site that allowed for access to the other
23 RI/FS activities.
24 Here's a cross-section of the existinq
25 qroundwater barrier wall (indicatinq). It was built,
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1 again, in 1984. It's about 960 feet long, 30 feet wide
2 and 35 feet deep, and that's made of compacted clay, and
3 on the upgrading side is a French drain or gravel drain
4 that -- there is a pump in it which collects the
5 contaminated groundwater and pumps it to the treatment
6 plant.
7 Here's a picture of the treatment plant --
8 or what it used to look like (indicating). It's been
9 updated tremendously since then. The process used for
10 treating the contaminated groundwater is essentially
11 filtration, air-stripping -- this is the old airstripper
12 (indicating), a carbon unit, which takes up a lot of the
13 volatile and semivolatile organic compounds, and then
14 that clean water which meets standard is injected
15 downgradient of the barrier wall in what is known as the
16 injection trench. I believe the volume is on the order
17 of 10 gallons a minute on the average.
18 Here's a picture of the Unnamed Creek as
19 it used to look several years ago. Again we have
20 contaminated seepage and groundwater flowing to the
21 north. Here are tire piles. This was the problem that
22 the Surface Water Removal Action was trying to address.
23 What happened is that when it would rain, precipitation
24 would go into this Unnamed Creek and flow offsite, this
25 contaminated surface water.

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1 The Surface Water Removal Action is here
2 in green (indicating) and essentially is a drainage
3 blanket that collects the contaminated seepage and keeps
4 it separate from the rain water and precipitation.
5 Again, we have a cartoon of the waste pits, the old tire
6 pile areas and command post and groundwater treatment
7 facilities here.
8 Tire piles. This is an old slide of what
9 the tire piles used to look like. I believe it was 35
10 acres were shredded over a period of 16 months, I
11 believe, and they are put into -- this is the shredding
12 operation -- put into a monofill of 3 acres. The size of
13 shreds are about 2 inches sguare, thereabouts.
14 This is a lined monofill and contains
15 nothing but tire shreds. These shreds have been used as
16 some of the drainage material for the Surface Water
17 Removal Action. In addition the Colorado Department of
18 Highways has used it as a low density fill over some
19 ironically other landfills they're building a highway
20 over, and in addition about 20 percent of the shreds have
21 ended up as a fuel supplement used in cement kilns.
22 And with that I'll allow Gwen to discuss
23 OUs 1 and 6.
24 GWEN HOOTEN: I'm not as loud as Angus.
25 I'll have to use a microphone. I'd like to extend a

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1 special welcome to our students in the back. We're glad
2 to see you here.
3 As part of the site summary, Angus has
4 discussed with you the first portion. What I'd like to
5 do is place special emphasis on what we're here to
6 discuss tonight which is OUS 1 and 6.
7 About 1989 we looked into -- previous to
8 that we were doing an EPA fund project, which means that
9 we financed the studies. Between 1989 and 1990, we moved
10 into what we refer to as an enforcement, which means that
11 the potentially responsible parties, or otherwise known
12 as the polluters, paid for the expense of the studies.
13 These studies, which we will refer to as
14 additional site characterization, the treatability
15 studies and feasibility studies, were done simultaneously
16 so that the work could be completed expeditiously.
17 We are at the end of the feasibility
18 study, and we're here tonight to discuss the proposed
19 plan. In addition to that, we have other studies going
20 on simultaneously. We have OUS 2 and 3 on which the
21 remedial investigation feasibility studies are being
22 conducted. We expect that to be completed -- well, it
23 was August. It has been accelerated up until April or
24 May of this year.
25 In addition we have OUS 4 and 5. We

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1 expect that to be completed in March of '93. We're
2 looking at proposed plans coming out shortly after those
3 feasibility studies are completed, and then we expect to
4 write a site-wide Record of Decision.
5 As far as the results of the studies, what
6 we found is that the groundwater predominantly flows to
7 the north. However, there is a component to the east and
8 to the west.
9 This right here (indicating) is a
10 cross-section of the site, and what we're showing here is
11 what our definition of shallow groundwater is versus deep
12 groundwater. What we have here is -- this is south and
13 this is north, and this is the groundwater containment
14 system that Angus Campbell talked about, and we have
15 refuse to the south, here we have alluvial soils and more
16 refuse with lesser waste pits to the north.
17 Operable Unit 1, which is shallow
18 groundwater, is defined by the weathered and unweathered
19 Dawson. This right here is termed as the separation
20 layer, and below that is considered the deep
21 groundwater. So the deep groundwater includes the lower
22 Dawson, the Denver and all other aguifers underneath
23 there.
24 For the horizontal extent of
25 contamination, what we found is that the waste pits seep

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1 out into the groundwater surrounding them and the extent
2 of the contamination really flows around where the
3 majority of the waste pits are, and, again, the flow is
4 to the north so we see a migration pathway.
5 For the vertical extent of contamination,
6 primarily that is driven into the deep groundwater by a
7 well that we refer to as B-504. We've also placed C-702
8 in here because we do have one hit of benzene.
9 With this what we wanted to demonstrate to
10 you is what the extent of contamination is thus far.
11 This well is located about 150 feet from surface. This
12 one here is about 170 feet. Again, there is the barrier
13 wall (indicating).
14 What we believe is of most concern to you
15 and to us is the protection of human health and the
16 environment. In order to determine that, we have to
17 determine what the risk is. We believe that this graphic
18 demonstrates that.
19 First of 211, we have to have a
20 contaminant source. By the sampling that we've done, we
21 know we have contaminants out there. Then you have to
22 have a transport, a point of exposure, a way that
23 exposure has a route to a receptor, and then what you are
24 drinking or inhaling or touching has to have a toxicity
25 value.
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1 We have to have all of these components
2 before we can say there is risk. A baseline risk
3 assessment is a study that describes the potential risks
4 posed to human health if nothing is done to remediate the
5 risk.
6 Angus Campbell has talked to you about the
7 interim remedial actions that we've had done in coopera-
8 tion with the PRPs to ensure that the contaminants have
9 not migrated off site.
10 If we were to do a baseline risk
11 assessment, we would allow those to deteriorate. We
12 would essentially walk away from the site. Then we're
13 trying to determine what the risk is to those remaining
14 if we were to walk away from the site.
15 So for the results of our groundwater, we
16 supplied to you an aerial photo of the site. This right
17 here is Section 6 (indicating). As you can see, there is
18 little to no development at this present time around the
19 site. Therefore, we do not believe there is a receptor,
20 so there is no current risk.
21 Right here is one of the nearest
22 developments, as well as Murphy Ranch, and then also Dove
23 Hill.
24 What we're finding is that if you built a
25 residence on the site and you did drink water there, you

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1 would have a 1 in 100 chance of getting cancer above what
2 you are normally exposed to, and this graphic shows that
3 you would then be a receptor.
4 Now, we'll go into the evaluation of the
5 cleanup alternative itself. In order to do this, we
6 ended up having to look at very many technologies that
7 would address the type of contaminants that we found.
8 Since we found volatiles, semi-volatiles, metals,
9 pesticides, we looked at a number of different ways to
10 treat them. We then screened those into treatment
11 options and set up treatment trains to do the complexity
12 of the contaminants that we found.
13 We further honed those down to remedial
14 action alternatives. I should tell you right now at this
15 point in the presentation that the remedial action
16 alternatives that we looked at are primarily containment;
17 that is because the Lowry Landfill is about 400 acres. A
18 large portion of that has been landfilled. We have about
19 70 to 100 foot of depth of refuge.
20 We at one time did consider taking 85
21 percent of the landfill and incinerating it, excavating
22 the refuge and then incinerating. The cost of doing that
23 particular remediation ran to $4.5 billion, and that is
24 the estimate that most of you probably read in the
25 papers. We have discounted that remedy for

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1 practicability.
2 So today what we'll be discussing is all
3 the alternatives as well as the EPA preferred
4 alternative.
5 In order to evaluate these alternatives,
6 we looked at what we refer to as nine criteria. The last
7 two criteria, state acceptance and community acceptance,
8 will not be determined until after the comment period for
9 the proposed plan. Based upon the comments that you
10 supply to us, we will be able to gauge community
11 acceptance of the alternatives.
12 The first two criteria are ones that have
13 to be met for all the alternatives before we are able to
14 select one. These are overall protection of human health
15 and environment in compliance with applicable or relevant
16 and appropriate reguirements.
17 The next five are referred to as balancing
18 criteria. In this we have the short-term effectiveness,
19 which may be the risks that we may expose workers to
20 during the implementation of the remedy; the long-term
21 effectiveness and permanence, the ability we're able to
22 reduce the risk irreversibly; reduction of toxicity
23 mobility and volume through treatment; the
24 implementability; and then finally the cost.
25 Now, again, our baseline risk assessment

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1 is based upon no action, we walk away from the site. If
2 we were to do that, what we found is that there would be
3 contaminants moving off site to the north, and there
4 would be the component to both the east and the west.
5 We also looked at the vertical movement of
6 contaminated groundwater in 200 years. These migration
7 pathways are primarily coming from the feasibility study,
8 a groundwater model that we completed.
9 In this, if the barrier wall was allowed
10 to deteriorate, we would see groundwater migrating to the
11 north. In addition, we would see some migration
12 vertically.
13 In Alternative 1, we had referred to this
14 one as the no further action alternative, meaning that we
15 allow the interim remedial measures we had taken
16 previously to be the remedy. This is the existing
17 groundwater barrier wall and the associated treatment
18 plant, the Surface Water Removal Action.
19 In addition to that, we would incorporate
20 Waste Management's soil cover, which is a 4-foot clay,
21 which is 2 feet above and beyond what the Colorado
22 Department of Health regulations for landfill closures
23 reguires, and then we would monitor to ensure the
24 contaminants did not leave the site.
25 So these are the common features. In

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1 addition to that, there would be a contingency plan for
2 vertical migration. We wouldn't allow the model solely
3 to be our prediction of whether or not contaminants would
4 migrate vertically. We would monitor to ensure that it
5 did not reach the lignite bed.
6 Alternative 2, we have again the common
7 features, the barrier wall, Surface Water Removal Action,
8 the landfill cover, and in addition to that, we would put
9 a 2,200-foot groundwater extraction trench. This would
10 be at a cost of $36 million.
11 Alternative No. 3 would again have the
12 common components, but in addition to this we would put
13 what we refer to as a toe drain, a groundwater extraction
14 system that would be closer to the majority of the waste
15 pits on the south side. With this we are assuming that
16 the groundwater -- and have studies that demonstrate this
17 -- is more contaminated than the groundwater that flows
18 to this wall. So, therefore, we would be constructing a
19 new plant that would take care of the contaminants.
20 Alternative No. 4 has again the common
21 elements with a toe drain and an up-gradient containment
22 collection and/or diversion water that would divert clean
23 water from the south away from the site so it would not
24 mix with the contaminated water. This barrier wall would
25 be at a depth of approximately 100 feet and is included

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1 in this cost.
2 In addition to that we would put a multi-
3 layer cap to increase — decrease the infiltration. This
4 overall cost is $101 million.
5 Alternative 5, we have the common
6 components, a toe drain, again with its associated
7 treatment plant, and we have a barrier wall to take care
S of those components of flow on both the east and the
9 west. This would be at a cost of $59 million.
10 And our final alternative is Alternative
11 6. It has the common components again, a toe drain, and
12 then here we would place extraction wells. The graphic
13 shows it as symmetrical, but we would try to put these
14 extraction wells in the waste pits that we believe were
15 pumpable. This would be done at a cost of $66 million.
16 After looking at these alternatives, the
17 EPA determined that Alternative 5 was one that we wished
18 to modify. Alternative 5 is one of the only alternatives
19 that does take care of the east and west components of
20 groundwater flow.
21 So the way that we modified is that we
22 looked at adding a barrier wall to the south so that we
23 could divert clean groundwater from the south away and
24 thereby reduce the volume that would have to be treated.
25 This is the alternative that we are introducing to you as

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1 our preferred alternative.
2 The reason that we're recommending this is
3 because it meets all of the EPA cleanup criteria. It
4 provides control of off-site migration to both the east
5 and the west. It reduces toxicity, mobility, and volume
6 of the contaminated water through collection, treatment,
7 and diversion. Water is collected at both the north, at
8 the toe of this landfill, and also on the east and west.
9 In addition, it would be diverted from the south, thereby
10 reducing the overall volume.
11 We believe it's more protective of the
12 human health and environment through long-term
13 effectiveness and permanence. Once we do treat it, we

14 believe there is a permanent reduction of risk. In
15 addition to that, we believe we are taking care of the
16 east and west groundwater flow patterns.
17 We know that it's using proven technology
18 that is implementable and that it can be easily
19 constructed. And the cost is relatively similar to or
20 less than other alternatives.
21 In addition to the criteria, we also
22 looked at CERCLA statutory reguirements. We felt that we
23 are meeting our preference for treatment, that
24 we are reducing the volume and the toxicity and the
25 mobility of the constituents. We also believe that we

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1 are treating and that we have not looked at the least
2 favorable alternative, which is to take the contaminants
3 off site.
4 We also believe that we are using a
5 permanent solution on the east and west as opposed to
6 allowing it to migrate there and then doing something.
7 With this, Marc Herman is going to be our
8 moderator for the guestions and answers, and I'm going to
9 go ahead and turn it over to him.
10 MARC HERMAN: After the public comment
11 period and responding to comments to this proposed plan,
12 the EPA, in consultation with the Colorado Department of
13 Health and in cooperation with potential responsible
14 parties, will be conducting remedial investigation
15 studies and will finalize feasibility studies for both
16 the landfill solids and gas operable units and for the
17 soils and surface water and sediment operable units, and
18 we will then issue proposed plans for OU's 2 and 3 and 4
19 and 5, and finally we will issue a site-wide Record of
20 Decision that will take into account all public comments
21 from all the proposed plans.
22 Following a record of decision, remedial
23 design negotiations will begin and hopefully conclude in
24 our lifetimes, and we will hopefully then be able to
25 design -- actually design the final remedies for the site

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1 clean-up and get around to constructing those remedies.
2 For your written comments, you are
3 reguested to send those comments to Gwen at the address
4 on the screen, U.S. Environmental Protection Agency, Mail
5 8 HWM-SR, that stands for Hazardous Waste Management
6 Superfund Remedial, 999 - 18th Street, Suite 2500,
7 Denver, Colorado 80202-2466.
8 Again, I would reguest that when you have
9 a guestion or comment, please identify yourself and your
10 affiliation and to limit your comment or guestion to five
11 minutes, please.
12 SPEAKER: I'm a high school teacher in
13 Littleton. I have students who are kind of interested in

14 this whole public process.
15 You mentioned the possibility of vertical
16 migration further down than might be expected for these
17 barriers. What sort of contingency plans do you have for
18 that vertical migration?
19 MARC HERMAN: The guestion is: What are
20 the contingency plans for potential vertical migration of
21 contaminated groundwater?
22 GWEN HOOTEN: What we have is a
23 groundwater model that was performed, and we looked at
24 periods up to 200 years. And what our groundwater model
25 shows — which we don't consider the groundwater model

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1 the answer but it's a relative answer — it showed that
2 we have vertical migration but it does not reach the
3 lignite bed, which is approximately 350 feet below the
4 surface. So we do have a vertical migration component.
5 We will monitor and assess some actions to
6 be taken should we see vertical migration to that lignite
7 bed, but at this time we feel fairly confident that the
8 migration is fairly slow, and we're hoping that we can
9 take care of contamination while it's in the shallower
10 part of the aguifer.
11 MARC HERMAN: We forgot to point out that
12 along the wall are cartoons of all the alternatives that
13 were evaluated in case you want to take a look at them a
14 little closer.
15 SPEAKER: I'm from Thunderbird Home
16 Association across the street at Gunclub Road and
17 Alameda. We're on wells there.
18 How far north have your test sites gone
19 and how deep? We draw on wells anywhere from 700 to 1000
20 feet in that area.
21 MARC HERMAN: Your guestion is: How far
22 north has the groundwater contamination been identified
23 or how far have our studies gone?
24 SPEAKER: I've seen you test wells around
25 your area. But how far north have the test wells gone?

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1 GWEN HOOTEN: Perhaps we misled you a
2 little bit. Our baseline risk assessment is based upon
3 the interim remedial measures not working. What we found
4 is that we have tested all the wells in the local area,
5 including the area that you're talking about, and we have
6 not found contamination to the north.
7 Phil, did you want to say anything more
8 about that?
9 PHIL BURKE: In 1985 we conducted tests of
10 selected holes in the north area there, and there was no
11 contamination found in any of those wells. To date, no
12 groundwater contamination has migrated past the barrier
13 wall that you saw, the red line.
14 SPEAKER: I realize the groundwater — and
15 we're talking about the aguifer which is, I think, a
16 little faster flowing. I know in '85 one well was
17 tested because his water was getting funny looking and
18 brown. Nobody ever contacted any of the homeowners
19 associations. Has anything been done since '85?
20 PHIL BURKE: Since '85 numerous wells have
21 been sampled on the site to the north. We have been
22 monitoring those wells for almost eight years now, deep
23 wells and shallow wells both, and to date there is no
24 contamination migration on site. Even though your home-
25 owner wells to the north haven't been sampled, plenty of

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1 wells have on site, both shallow and deep.
2 SPEAKER: If you want a sample, you can
3 use mine.
4 SPEAKER: Rick Shalene associated with
5 Lowry Landfill.
6 Gwen, can you give us some detail of what
7 sort of actions you might reguest under this alternative
8 if, in fact, you find some contamination in your
9 monitoring down the road?
10 GWEN HOOTEN: Well, Rick, we're talking
11 horizontal contamination, and we believe Alternative 5,
12 our modified 5, takes care of any migration to both the
13 east and west today if it was implemented.
14 If you're talking about a vertical
15 migration, then we would have to institute some actions,
16 and right now we don't know what those actions will be.
17 But if I was to speculate, I would say that we would
18 probably use extraction of the contaminants, if they
19 started to get down near that lignite bed.
20 SPEAKER: The alternative doesn't go into
21 any of that detail.
22 GWEN HOOTEN: No. We were at one time
23 looking at horizontal wells placed at 100-foot spacings
24 throughout the length of the landfill, and what we're
25 finding on Lowry is that we have what is termed as dense

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1 aqueous phased liquids.
2 We don't believe that we will have much
3 success in pullinq those out, and we also believe that
4 the vertical miqration will be somewhat limited due to
5 the tiqht formation.
6 So with those in mind, we have not come up
7 with a vertical miqration remedy. We would look to try
8 to do as much as we can usinq the horizontal collection
9 of qroundwater and hope that that does it.
10 SPEAKER: Do you have any financial
11 continqency in this plan should you detect contamination
12 in some of the monitorinq wells?
13 GWEN HOOTEN: Althouqh the cost estimates
14 you saw did not have amounts -- and, Paul, I'll need you
15 on this one. The estimates that you saw toniqht do not
16 have a financial amount for the vertical continqency
17 plan. However, we will be writinq it into our Record of
18 Decision, and we will hold the potentially responsible
19 parties responsible for any miqration to that liqnite
20 bed.
21 Is there anythinq you want to add to that,
22 Paul?
23 PAUL ROSASCO: We did a lot of analysis,
24 and because, as Gwen indicated, we have very low
25 permeability, we have very low rates of flow. The

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1 estimate was it was going to take over 300 years for it
2 to get to the first unit that we could pump the water
3 out. That's the lignite bed. Coal type bed about 8 feet
4 thick down about 300, 350 feet.
5 When you look at what it would cost 300
6 years from now to build a system and you bring it back to
7 today's dollars and say, "Okay, let's put some money in
8 for financial insurance," it's a minimal amount of money.
9 It takes very little money to, say, put in 50 extraction
10 wells 350 years from now.
11 So we did analyze that and look at that
12 from a financial impact, but the estimates say it's going
13 to take 300 to 600 years for the groundwater to reach
14 that depth, and that's the first level at which we could
15 pump any of the liguids out.
16 SPEAKER: My name is Bob Falcon. I'm an
17 officer in a recycling company and also I'm an engineer.
18 I'm not sure I like at all any sort of containment, much
19 less the modified containment, because I think all you're
20 going to be doing is delaying the problem, and you're
21 feeding the public possibly being assured that you're
22 going to be properly monitoring for 200 years.
23 I have noticed that the EPA has funded
24 grants and research into soil washing, and it seems to me
25 that at least some portion of the surface, say, 10 feet

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1 to 30 feet, could be soiled washed and at least some of
2 the organics taken out and disposed of properly by the
3 same technology that made them in the first place.
4 And so that's -- my first guestion is:
5 Have you done anything with soil washing, and if so, does
6 it apply to the Lowry site as part of — at least part of
7 the modified plan?
8 Also under your modified plan, what is
9 your intention for the use of the surface for, say, the
10 next 200 years? Would you make it a park or wildlife
11 refuge, or is it just to sit there as a great big
12 containment facility waiting for whatever might or might
13 not happen?
14 Have you considered purchase of the
15 surrounding land to make it part of an overall use, and
16 are the polluters paying for whatever these millions of
17 dollars are? Who pays for these modified plans?
18 MARC HERMAN: Those are all excellent
19 guestions. First of all, let me remind you that this
20 proposed plan is for the shallow groundwater subsurface
21 liguids and deep groundwater operable units. I don't
22 know that specifically soil washing is being investigated
23 under the other operable units, but that -- it is being
24 investigated under the soil surface water and sediment's
25 operable units along with other technologies, and there

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1 are also technologies being looked at, potentially
2 digging up some of the contaminated soil in the landfill
3 solids operable units remedies possibilities.
4 So those are being investigated and a
5 similar sort of meeting will be held to propose to you
6 what we think are reasonable alternatives for those
7 environmental media.
8 SPEAKER: So they could retroactively
9 apply for this plan?
10 MARC HERMAN: There are six environmental
11 media broken up into six operable units, and what we
12 strived to do is to take alternatives from each of the
13 operable units and have them blend together to be one
14 cohesive remedy for the site.
15 So in addition to controlling and treating
16 groundwater, we will be looking at treating or digging up
17 whatever soils and sediments there are, and we will be
18 looking at landfill gas and landfill solids in terms of
19 what technologies are available and meet the nine
20 criteria to clean up the site.
21 You asked about land use, and we could
22 spend an entire evening talking about land use, but I
23 will tell you there is a Southeast Area Planning
24 Initiative going on right now, and that is a group of
25 local governmental entities that have been meeting now

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1 for a while -- about four months. We're talking about
2 the City of Aurora and Arapahoe County and City and
3 County of Denver and many other landowners, large
4 landowners, both state and local within the area.
5 And what they're doing is, they're making
6 a plan for land use for that entire eastern portion of
7 the Denver Metro area, and Lowry Landfill Superfund site
8 is one part of that. So the possible land uses and land
9 use restrictions for the area are being investigated
10 right now. And EPA intends to incorporate the
11 recommendations and decisions of the Southeast Area
12 Planning Initiative group into our final proposed
13 site-wide remedy.
14 And then there was another guestion.
15 SPEAKER: Cost. Who's paying?
16 MARC HERMAN: That's an excellent
17 guestion, and that's what I wanted to emphasize. The
18 remedial investigation and feasibility studies that are
19 going on are being paid by private entities, potentially
20 responsible parties, who have been identified as being
21 responsible for either transporting or generating the
22 waste or operating the site, and they perform the studies
23 under the watchful eye of the EPA and the Colorado
24 Department of Health.
25 SPEAKER: Do those who are paying the cost

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1 weigh into the decision for any one of these plans? Do
2 they have input to say, "Well, we like 31 million better
3 than we like 61 million?
4 MARC HERMAN: In that respect they are the
5 public just like you are. They are allowed to provide
6 their comments to the proposed plans.
7 SPEAKER: So how much comment was in the
8 choice?
9 MARC HERMAN: We'll find out. We're in
10 the public comment period right now.
11 And that will be public information. EPA
12 will collect all the comments, either from a private
13 company or an individual, and we will summarize the
14 comments, respond to them, and provide those to everyone
15 who is interested.
16 SPEAKER: I was just wondering if
17 Alternative 5, how long would it take to complete the
18 whole process?
19 MARC HERMAN: That's a good guestion. The
20 guestion is: How long would it take to implement this
21 proposed remedy?
22 GWEN HOOTEN: We're talking about
23 approximately three years to implement. That includes
24 design time. But let me talk to you a little about the
25 process.

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1 Once the EPA writes a Record of Decision,
2 then we enter into negotiations for the remedial design
3 and the remedial action of that Record of Decision. That
4 normally can take about six months to do that.
5 Then after that the PRPs, or those that
6 signed up to do the remedial design and remedial action,
7 we have an estimate that it will take approximately three
8 years to complete the design and start implementation of
9 the action itself.
10 SPEAKER: I'm from Littleton High School
11 and I was wondering -- you stated that one of the nine
12 criteria was short-term, and I was wondering what that
13 risk would be to the workers in Alternative 5?
14 GWEN HOOTEN: We were cueing our
15 toxicologists down here to see if they wanted to
16 respond.
17 But we believe that OSHA will Protect the
18 workers from any short-term effects. OSHA has
19 regulations that talk about protection levels that the
20 workers must be in -- masks so they don't inhale, suits
21 so they don't have any dermal contact, those kind of
22 things.
23 We believe they can be protected during
24 construction if they comply with the OSHA standards.
25 SPEAKER: Rebecca Wild of Lowry Landfill.

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1 What about the people off site, the people who live and
2 work around the Lowry Landfill during the cleanup
3 proceedings and decontamination?
4 MARC HERMAN: The guestion is: What sort
5 of health risks are posed in the short-term to
6 individuals or the public living off site away from the
7 cleanup activities?
8 GWEN HOOTEN: We, again, believe that the
9 -- any disturbance of the soil, any inhalation factors,
10 the dermal factors will be pretty much confined to the
11 site construction. We're not looking at any kind of
12 alternative or the components of the remedy that we
13 believe would enhance either the inhalation exposure or
14 the dermal exposure for anybody off site.
15 SPEAKER: Mary Lake. You mentioned a
16 4-foot clay cover for the landfill mass. I've been here
17 since '77 and was part of CALL when it began. My
18 guestion is: How much clay was protecting when it broke
19 open one summer where it rained and it was dry and rained
20 and it was dry, and it broke open and it smelled to high
21 heaven all over this area. Was there 4 foot of clay
22 then?
23 ANGUS CAMPBELL: When was it? That was
24 early '80?
25 SPEAKER: I can't tell you the year.

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1 ANGUS CAMPBELL: There was 1-foot cover
2 over the landfill at that time. If it was prior to 1980,
3 they would have daily cover, so it was less than that 1
4 foot. So the answer is no, there was not that 4-foot
5 cover as there is on site now.
6 SPEAKER: You started breaking into this.
7 We get a day like today when we have high pollution and
8 high winds. Who is going to tell the people living in
9 the near subdivisions that what they're breathing is
10 okay? Who's going to monitor that? OSHA is not.
11 ANGUS CAMPBELL: The State Health
12 Department Air Program will be monitoring. They will
13 have to have a monitoring plan that will be part of the

14 remedy to ensure that the standards that are in place for
15 the metro area are met at the site boundary.
16 SPEAKER: Where would those testing
17 stations be?
18 ANGUS CAMPBELL: They will probably be at
19 the corners of the landfill mass and at the construction
20 site too, because they have to have monitoring -- air
21 monitoring on site for health and safety purposes.
22 So there will be probably two stages of
23 monitoring, the worker monitoring and ambient air
24 monitoring.
25 MARC HERMAN: We have some experts in the

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1 crowd who can corroborate. As part of the Surface Water
2 Removal Action, construction of the collection system in
3 Unnamed Creek, the entities, Waste Management of
4 Colorado, who constructed the collection system, took
5 great pains to make sure there was monitoring programs
6 both around the construction and on the boundaries of the
7 landfill site to do what you're asking, to monitor
8 potential impacts-- or a potential impact on air
9 contamination.
10 So that's sort of like a small glimpse of
11 what we may look at down the line in the larger scheme of
12 things.
13 Rick?
14 SPEAKER: What kind of standards are we
15 looking at for that type of monitoring? What are the
16 existing standards that have to be met?
17 ANGUS CAMPBELL: The process will be that
18 we will go through and look at the contaminants of
19 concern that have been identified in the risk assessment
20 and to set standards. They will use the State standards
21 and go through a State standard setting procedure on a
22 site by site basis.
23 This will emulate a state permitting
24 issue. It won't get a State permit just because it's a
25 Superfund site, but it will have to meet all the

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1 requirements. And if I'm in charge, then I will make
2 sure that will happen.
3 MARC HERMAN: You want to know specific
4 air regulations?
5 SPEAKER: Yeah.
6 ANGUS CAMPBELL: It will be Regulation 7
7 and 8 and 3.
8 SPEAKER: The reason I'm asking, it's been
9 some time since I looked, but the last time I looked at
10 the Colorado standards, they were pretty lax and almost
11 nonexistent.
12 ANGUS CAMPBELL: I don't know when the
13 last time was you looked at it, but with the new Clean

14 Air Act that was passed in Congress last fall, I believe,
15 all those will come down to the State as well.
16 The Denver area is fairly stringent in
17 what they allow to be permitted from a stationary source,
18 and that's what the landfill will be.
19 SPEAKER: Well, with regard to
20 particulates. What about volatiles?
21 ANGUS CAMPBELL: The State of
22 Massachusetts has set ambient air limits that will be
23 used for our initial evaluation for safe levels at the
24 site boundary.
25 The nonattainment area has been extended

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1 over the metropolitan area. That means that there is no
2 allowable release of volatile or organic compounds within
3 that nonattainment area.
4 If you care to know more, feel free to
5 give me a call, and I can help you when I have the
6 appropriate documents in front of me, or I can direct you
7 to somebody who has a little more expertise in our air
8 program.
9 SPEAKER: My guestion now is regarding
10 liability. Can you name specifically by name who are the
11 polluters who paid for the studies?
12 MARC HERMAN: Remedial investigation
13 studies?
14 SPEAKER: Yes. In other words, who gave
15 the EPA money? Do they still have the liability when the
16 EPA is done here, or does the Colorado Department of
17 Health have the liability if the monitoring system goes
18 awry? Where is the liability located for 200 years?
19 GWEN HOOTEN: I'm going to ask some of the
20 coalition members to help me out here. But the folks
21 that are paying for the studies for the shallow
22 groundwater and the deep groundwater were at one time 14
23 companies. I'm going to attempt to name the 14
24 companies: Adolph Coors, Conoco, Syntex Chemical, Gates
25 Rubber Company, Littleton/Englewood Bi-City Treatment

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1 Plant, the City of Lakewood, Metro Waste Water
2 Reclamation District, IBM, Shattock, Honeywell and
3 Sunstrand and Hewlett Packard — and we got Amax.
4 Is that 147 And Asamera Oil.
5 Is that 14?
6 SPEAKER: The City and County of Denver
7 escaped?
8 GWEN HOOTEN: No. Let me complete the
9 answer. That was for the study on the shallow
10 groundwater and deep water that you're seeing and we're
11 discussing tonight. In addition to that, we have four
12 other operable units being studied under two different
13 orders.

14 Under the OU's 2 and 3 order, we have City
15 and County of Denver, Waste Management of Colorado, and
16 Chemical Waste Management, and they are paying for that
17 study.
18 Then for the last two operable units,
19 Operable Units 4 and 5, we have again the City and County
20 of Denver and Metro Waste Water Reclamation District
21 financing those studies.
22 Now at the end of this process, we have
23 identified over 275 potentially responsible parties. EPA
24 considers their liability joint and severable, so we
25 could bill any one of those 275 parties for the total

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1 bill. So they're all liable.
2 SPEAKER: If the plan is approved and
3 implemented, they still retain liability?
4 MARC HERMAN: Correct.
5 I was just going to say if anybody was
6 wondering why we call it a toe drain, it's because it's
7 at the base or the foot of the landfill mass, and what do
8 you have at the end of a foot — toes. In this case just
9 one.
10 SPEAKER: Could you explain a little bit
11 more exactly what a toe drain is?
12 MARC HERMAN: It will be a — well, you
13 guys did the work on it. Paul, do you want to explain
14 this one?
15 The guestion is exactly what is a toe
16 drain or what is a groundwater collection drain?
17 PAUL ROSASCO: It will either be a series
18 of extraction wells will be installed at close spacing at
19 the foot of the landfill, at the toe, to collect all of
20 the water that otherwise would flow out into the creek or
21 north through the site, or it might be a trench that is
22 dug and filled with a pipe and gravel and a pump that's
23 put into that to pump the water out of the trench.
24 Either one of the those options were
25 looked at and considered valid for future construction.

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1 SPEAKER: What if it gets clogged up like
2 the barrier wall in the past?
3 PAUL ROSASCO: I'm not aware that the
4 barrier wall got clogged up, but the wall itself. That
5 may have been some issues involving the treatment plant.
6 SPEAKER: But the internal —
7 PAUL ROSASCO: The wells would have to be
8 replaced, and that was included in the cost of the
9 remedy, the cost for either rehabilitating the wells
10 using standard well technigues to remove iron or actually
11 replace the wells. But those costs were included in the
12 remedy. The same with the drain, come in and
13 rehabilitate it, remove iron or replace portions of it.
14 SPEAKER: I'm Ellen Fulton, a senior at
15 Littleton High School. After your plan is implemented,
16 would any of the three of you feel safe buying a home
17 there and raising a family next to the site?
18 MARC HERMAN: Excellent guestion. I'm
19 going to let Gwen answer that.
20 GWEN HOOTEN: I live about two miles to
21 the west of the site, and I do have a family and I'm
22 trying to raise her.
23 SPEAKER: This is for Angus. I'm saying
24 this with a smile on my face, but 10 or 11 years ago
25 Chemical Waste, the County, everybody, called this a

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1 sanitary landfill, harmless. When did it become a
2 codisposal?
3 ANGUS CAMPBELL: I think since it began.
4 A sanitary landfill refers to the covering of trash on a
5 periodic basis. And it may not have been daily, however,
6 it was covered up unlike an open dump. It was prior to a
7 sanitary landfill, you had a dump and you go out there in
8 the back 40.
9 SPEAKER: This was referred to at the
10 Governor's Monitoring Committee meetings, and every
11 meeting I attended it was always the sanitary landfill.
12 I notice in actuality you were calling it --
13 ANGUS CAMPBELL: Codisposal.
14 SPEAKER: It was never called that.
15 ANGUS CAMPBELL: Codisposal was the
16 process employed. It was a process employed at the
17 sanitary landfill. Does that help?
18 SPEAKER: That helps.
19 SPEAKER: I have concerns with the
20 environment. I'm wondering with the environment in 100
21 years who is to say you're going to be around to clean it
22 up again? This project seems to be incomplete, if you
23 have to do more work in 300 years on it. Do you see what
24 I'm saying?
25 MARC HERMAN: Yes, I do. The guestion

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1 is: Are any of us going to be around 300 years or
2 whatever from now to make sure that the remedy is
3 implemented properly?
4 I know I won't be around.
5 GWEN HOOTEN: That is a good guestion, and
6 that's the reason that we think Modified 5 is the best
7 one, because it takes care of the east and west
8 components now even though from a modeling effort we
9 don't believe it's contaminated -- the contaminants have
10 not migrated that far.
11 As far as the vertical contaminants, we
12 have discussed with you the technical and practicability
13 we have today, but the EPA as a general practice will

14 revisit Superfund sites every five years. In that
15 five-year review, we go through all the standards that
16 are looked at, we look for any changes in the state of
17 the art on the sampling technigues, and we look for any
18 changes in the technigues we have available for
19 clean-up.
20 So even though we don't have the
21 technology today, perhaps we will have it in the future.
22 But we don't have the answers today.
23 MARC HERMAN: I want to just point out and
24 remind everybody while the private companies or the
25 municipalities that are involved in this project bear the

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1 burden of liability, as everybody might suspect, it
2 eventually gets passed on to either the consumer or the
3 taxpayer. So we all share in the liability eventually.
4 SPEAKER: You didn't answer my question of
5 the role of the Colorado Department of Health. You
6 monitor every five years, but the Department of Health at
7 least has some control or jurisdiction over that site on
8 a daily basis for the next 300 years, if the State is
9 here.
10 MARC HERMAN: On a daily basis?
11 SPEAKER: Isn't the Colorado Department of
12 Health ultimately responsible for the safety and health
13 of the citizens, and, therefore, ultimately responsible
14 for the control of this site?
15 MARC HERMAN: That's why —
16 SPEAKER: So when you're gone and come
17 back in five years and test, during that time doesn't the
18 Department of Health do something?
19 MARC HERMAN: That's why they're a partner
20 with the EPA on this site, but I'll let Angus answer.
21 SPEAKER: What is their role?
22 ANGUS CAMPBELL: What is our role? In the
23 Superfund we are management assistants. Now, on the site
24 itself it has to comply with State solid waste rules and
25 regulations as well as with the air pollution rules and

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1 regulations as I mentioned earlier.
2 It will be an ongoing process. We have
3 standards that have to be met at the site, and we will
4 ensure that those are met by the owner and operator.
5 PHIL BURKE: It probably should be made
6 clear that the testing isn't every five years. In fact,
7 the testing may be many times in a single year. It's
8 every five years that the EPA comes back and evaluates
9 the site as a whole, but all throughout the remediation
10 the site is tested and monitored.
11 MARC HERMAN: We won't make a decision and
12 walk away and come back in five years.
13 SPEAKER: My guestion is: How much,

14 approximately, of the waste do you plan to treat?
15 GWEN HOOTEN: And we have Paul Rosasco
16 here to answer that guestion.
17 PAUL ROSASCO: Modified Alternative 5
18 treats approximately 7 -- it will take out, our estimate
19 was, 700 pounds of the actual chemicals on an annual
20 basis over the life of the remedy. It takes out a lot of
21 groundwater but the actual concentration in the
22 groundwater is very low. It's on the order of parts per
23 million. So you treat a lot of groundwater to get a
24 pound out, but we will take about 700 pounds of the
25 chemicals out a year.

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1 SPEAKER: What's the rate?
2 PAUL ROSASCO: The flow rates for the
3 system were -- we have approximately 12 gallons a minute
4 currently on the existing groundwater barrier treatment
5 system. There is an additional several gallons a minute
6 from the approximately 10 gallons from the landfill toe
7 drain and approximately there is an adjustment of a few
8 gallons per minute on the east and west, so the total
9 flow estimated is 20 gallons a minute we would be taking
10 out of the site.
11 SPEAKER: What's the total amount that is
12 being taken out, how many gallons?
13 PAUL ROSASCO: It's 20 gallons a minute.
14 SPEAKER: How many in the entire landfill?
15 PAUL ROSASCO: Several hundred million
16 gallons in the landfill.
17 SPEAKER: What is the regional flow across
18 the landfill in terms of gallons?
19 PAUL ROSASCO: The regional flow across the
20 site is approximately — essentially the 20 gallons a
21 minute. We're taking out everything that would flow to
22 the north of the site that would have the contamination,
23 collecting all of that.
2 4 MARC HERMAN: I don't know how many of
25 those 142 million gallons is waste. I understand each

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1 gallon has a different part per million, but the bottom
2 line is how many of the 142 million gallons of waste are
3 actually going to be clean?
4 GWEN HOOTEN: If we're treating 20 gallons
5 a minute on an eight-hour-a-day basis — I'll speculate
6 on eight. Paul is telling me that we want to get into 24
7 hours a day. Okay, let's go with 24 hours.
8 If we're going to treat 20 gallons per
9 minute, 60 minutes in an hour, 24 hours a day, 365 days a
10 year, whatever that number comes out with is the amount
11 of gallons that we're going to treat in a year. We
12 expect to be out there at a minimum of 30 years. Our
13 cost estimates have all the estimates based upon 30

14 years.
15 So I don't have a number for you. We
16 could punch it out real guick and find out what it would
17 be. Does that answer your guestion?
18 SPEAKER: It clarifies it at least.
19 ANGUS CAMPBELL: Your guestion was with
20 regards to the liguids disposed of in the waste pits.
21 Those liguids are in the waste pits and are seeping into
22 the groundwater, so you're having a dramatic increase in
23 the volume of water that's contaminated. Does that help
24 too?
25 And this diluted contaminated groundwater

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1 is what is being collected and treated.
2 SPEAKER: I don't know if this is
3 answered. What is the stuff that's been treated? Where
4 does it go?
5 MARC HERMAN: Good guestion. Right now
6 contaminated groundwater is treated at the City and
7 County of Denver's water treatment plant which is on site
8 and all the contaminants are removed, and the water is
9 discharged back into the ground north of the treatment
10 plant and north of Lowry Landfill.
11 SPEAKER: What will be the stuff that's
12 used to decontaminate? Is that waste too?
13 MARC HERMAN: The carbon absorption units
14 that Angus Campbell talked about collects the
15 contaminants. They can be taken and cleaned. They never
16 go away is the problem. We just move it from one place
17 to another presumably. The carbon units can be thermally
18 regenerated. The contaminants are burned off.
19 SPEAKER: My name is Eric Knight, and I go
20 to Littleton High School. I was wondering why has this
21 been discussed recently rather than years or months ago,
22 if it's such a threat to the community?
23 MARC HERMAN: It has been. There are
24 people here in the crowd who remember back in the late
25 '70s.

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1 SPEAKER: I'd like to tell you that we
2 have a number of people here tonight who have been
3 working on this issue for almost 13 years.
4 MARC HERMAN: It's a great guestion. Let
5 me mention to you that we have copies of proposed plans,
6 and we have copies of progress updates down in the front
7 to keep abreast of what's going on with the progress, and
8 you can get on the mailing list, and we'll mail you all
9 the updates and the proposed plans that we issue so you
10 can keep more informed on this.
11 SPEAKER: Two-part guestion. I'm Terry
12 Horn with the Citizens for the Responsible Development of
13 E-470. Has the E-470 Authority asked for your input
14 environmentally on which would be the better route for
15 the routes they have out there; and No. 2, is the EPA in
16 agreement with the E-470 Authority that there should be
17 no need for an environmental impact statement to be
18 produced along this area, a couple hundred feet of your
19 landfill east or west?
20 MARC HERMAN: Well, first of all, I think
21 that -- Carol, can you help out? Is part of the
22 southeast area issue part of the E-470 been involved?
23 CAROL MCLENNAN: We haven't gotten
24 specific comments from the Authority in response to that
25 guestion. The Authority certainly has access to all the

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1 information, and I'm sure they will be commenting.
2 GWEN HOOTEN: The Environmental Protection
3 Agency does not advise government groups as to their land
4 plan. What we try and do is protect human health and the
5 environment on Superfund sites. So we would not be in
6 the position to instruct the E-470 Authority.
7 However, they have contacted both EPA and
8 the Colorado Department of Health. They have been
9 interested in what is happening on Section 6, the
10 Superfund site.
11 Does that help answer your guestion?
12 SPEAKER: Yes. Thank you.
13 SPEAKER: I was just wondering, on TV you
14 see other states bring in waste to this landfill, or are
15 we the only ones in Colorado. Is this like a major
16 landfill or whatever -- or that's what I heard.
17 MARC HERMAN: This was a regional landfill
18 when it was in operation during the periods '66 to '80.
19 ANGUS CAMPBELL: You may be thinking of
20 the Highway 36 Hazardous Waste Landfill out of Last
21 Chance. That's a regionwide Subtitle C landfill.
22 MARC HERMAN: Under the Resource
23 Conservation Recovery Act, which is a different law that
24 EPA administers, that law applies to active hazardous
25 waste sites. The Comprehensive Environmental Response

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1 Compensation and Liability Act, CERCLA, or Superfund,
2 takes care of abandoned or old hazardous waste sites.
3 SPEAKER: This would be a basic political
4 question. You mentioned all the companies that were
5 paying for some of the studies that were done, and I
6 assume paying the salaries for some of the people who did
7 these studies and came up with this particular plan.
8 It also seemed like in today's paper or
9 the other day's paper there was an article on the total
10 cost and who pays for it, and they had listed again
11 Hewlett Packard, Honeywell, Gates, Adolf Coors,
12 Littleton/Englewood Treatment, et cetera.
13 I guess my question is: If that's the

14 bill, 120 million, they paid their portion, are they then
15 finished with this deal, their responsibility?
16 ANGUS CAMPBELL: I gave that quote to the
17 paper. The reporter asked me what was a ballpark figure.
18 I went through the analysis that the groundwater is
19 probably the most expensive remedy at the site, and I
20 said, "Well, go ahead and just double it. It's probably
21 in the ballpark." That's where that came from.
22 Now, with respect to the rest of that,
23 I'll have to let Gwen answer that.
24 GWEN HOOTEN: We haven't publically
25 released an overall ballpark figure so that's why the

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1 facts are misquoted in the paper as EPA saying that.
2 SPEAKER: It's a headline.
3 GWEN HOOTEN: Yes, I'm aware of that.
4 As far as your question -- and I'm qoinq
5 to repeat it back to you so I heard it riqht. You're
6 sayinq that politically are the potentially responsible
7 parties payinq for both the RI/FS and the remedial desiqn
8 and the remedial action, and did I hear also perhaps our
9 oversite cost — the EPA and the Colorado Department of
10 Health?
11 SPEAKER: Is there a political motivation
12 to choosinq this solution -- perhaps of its cost and ease
13 of implementation? And once it's done, does it qet those
14 orqanizations who are payinq for it off the hook?
15 GWEN HOOTEN: Well, Superfund liability,
16 as many of the PRPs can attest to, it's very difficult to
17 qet off the hook. Even when we implement the remedy of
18 which the PRPs would pay for, our five-year reviews
19 really extend their liability to anythinq that we would
20 find.
21 So their liability is pretty much until
22 the site is delisted or until the site is removed from
23 the National Priorities List and we no lonqer feel that
24 there is a risk.
25 I think the second part of your question

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1 -- was there a second part? The political motivation for
2 picking one alternative over another?
3 SPEAKER: Yes. I'm trying to see if there
4 is a tie-in between the groups who paid for the studies,
5 the groups that will have to pay for the clean-up, and
6 perhaps the people paying the salaries of the people
7 coming for the five-year review?
8 GWEN HOOTEN: We are going to invite our
9 divisional director to answer this guestion.
10 BOB DUPREY: I'm not political. Let me
11 try to answer that. I think it's a good guestion.
12 Because since some of the responsible parties produced
13 the technical work, what I'm hearing is then who

14 influenced us on selecting a particular remedy because we
15 have less trouble with the cost and so on.
16 And the answer is no, in my view, that we
17 were looking for -- and, frankly, I think some of the
18 larger responsible parties are looking for -- as
19 permanent a solution as they can get. Because they don't
20 want to come back and face the continuing liability that
21 remains there if other costs or problems arise in the
22 future. It's like they would like to pay their costs and
23 get out.
24 So in our view we picked the one that was
25 actually towards the higher end of the cost range with

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1 additional measures of protection. Even where it didn't
2 show much migration, we decided to go ahead with some
3 measures to fully contain the site to not allow moisture
4 to get into it as much as we could prevent moisture from
5 getting in and to draw down the water and contamination
6 level as much as we can with the treatment system and the
7 draw-down system that has been proposed.
8 So if we could have done more than that
9 and if people have ideas how to increase the
10 effectiveness of that, we certainly welcome that. We
11 haven't made a final decision. This is a proposed plan,
12 so we want to take more comment where we can be more
13 effective and more permanent on the answer.
14 On the liability guestion, I want to
15 answer that a little bit because there is major
16 litigation currently going on this issue in Federal
17 District Court before Judge Finesilver, and the very
18 issue you've raised is the subject of that lawsuit; that
19 is, who will pay what share of these costs ultimately.
20 I believe that ultimately this will either
21 get decided in the course of that litigation or through
22 settlement talks that are taking place among the
23 different parties.
24 The assurance I can give you is that the
25 Federal Government and the State Government are looking

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1 to have all the costs paid by the responsible parties and
2 all the continuing costs that might occur be paid by the
3 responsible parties.
4 SPEAKER: First of all, who owns this part
5 of the land that we're talking about? Second, the liable
6 companies, what are they doing with their current waste?
7 They must be recycling or putting it into a standard
8 center to have it looked after. And, third, the large
9 companies are playing politics because they have been
10 dumping their stuff all over the United States and half
11 the time around the world. They don't want the other
12 sites found, so they're going to comply to bury this and
13 hide instead of looking into technical recycling to clean
14 the mess up that they caused.
15 MARC HERMAN: To answer your first
16 guestion, ownership of the land, the City and County of
17 Denver owns the land. The answer to your second
18 guestion, where does the hazardous waste that was dumped
19 into Lowry Landfill go or similar sort of waste go now,
20 and they go to authorized hazardous waste disposal sites.
21 SPEAKER: I have just two comments. I'm
22 Chuck Barrett, a private consultant.
23 Number one, a guestion about the
24 liability. If everything that was dumped out at this
25 site was done according to the rules and regulations at

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1 the time, the cost associated with the dumping of the
2 waste at that time, and the Federal Government came back
3 in hindsight and said, "You did something wrong in
4 today's standards from 20 years ago."
5 So I foresee the federal regulations will
6 always say that if they have to come back and clean up
7 the site 20 years from now, the potentially responsible
S parties will be the ones to talk with, but ultimately it
9 will be the taxpayers and consumers that are going to pay
10 for it. If you buy Coors beer, they will roll the cost
11 of that onto it.
12 SPEAKER: Your observation is a lie.
13 SPEAKER: The other issue is that I think
14 there was a guestion whether they were actually cleaning
15 up this 142 million gallons, and my understanding is
16 you're not cleaning up any of the 142 million gallons
17 except that which seeps into the rain water that falls on
18 the site and comes down to the collection basin. And the
19 reason why you'll be there for several hundred years is
20 the fact that the amount that will be dissolved in any
21 given time is a relatively minute amount.
22 So if you take your 20 gallons a minute
23 and multiple it out by the hours per year by the 30 years
24 and you come up with a number in excess of 142 million,
25 but you still have got some of the contamination still

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1 entrenched in the soil.
2 MARC HERMAN: Actually the liquid
3 hazardous waste has commingled with the groundwater on
4 site and that's under the ground, and the purpose of this
5 proposed plan is to collect that contaminated
6 groundwater. There is an action going on right now
7 that's designed to effectively -- while we study the
8 site, to effectively collect the contaminated groundwater
9 and to treat it.
10 And that's also the purpose -- to address
11 your question of rain water, that's the purpose of the
12 landfill cap, to prevent more moisture from entering the
13 site and seeping down and mixing with the hazardous
14 waste.
15 SPEAKER: After your proposed plan, your
16 No. 5 — in 1984 you said we were the most hazardous
17 site. After your plan, where will we be on this
18 scale.
19 MARC HERMAN: We were not the most but
20 one of the many. That's a good question. Is that a
21 political question? Maybe Bob will answer that.
22 BOB DUPREY: Well, it's one of the 1200
23 same -- 1250 or something like that on the National
24 Priorities List sites across the nation. There is some
25 15 of those here in Colorado. We didn't give it a

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1 relative priority, and I can't remember quite where it
2 is. I think somewhere in the middle.
3 Basically we will go through a process
4 after we have done at least one of the five-year reviews
5 to see how effective this remedy is after it's been
6 selected to ultimately delist it from that priorities
7 list if the dangers are adequately taken care of.
8 There is a process that's gone through to
9 actually remove it from the priorities list. That
10 doesn't mean that the work won't continue to go on. All
11 that still will be mandated what we'll put into effect
12 and that will be a court ordered remedy. It's required
13 to be entered before a Federal District Court, and it
14 will be enforceable then and the Federal District Court
15 will have continuing jurisdiction over that.
16 SPEAKER: How does your plan solve your
17 need -- toxic waste?
18 GWEN HOOTEN: Are you talking about the
19 nine criteria? How does our plan solve the environmental
20 issue of cleaning up the site?
21 We believe that our remedy is a
22 containment remedy, but we are also collecting and
23 treating groundwater as both the existing barrier wall,
24 the toe drain, and the east and west components. So we
25 believe that we are treating groundwater and that we are

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1 reducing the overall risk.
2 But we don't have a time frame when there
3 will be no risk. We don't know when that will be. We
4 expect to be out there a long time treating the waste.
5 MARC HERMAN: Do you mean how will that
6 accomplish our goal, the EPA mission, to protect human
7 health and the environment?
8 GWEN HOOTEN: Did we answer your
9 guestion?
10 SPEAKER: I guess.
11 SPEAKER: I'm a student. I was wondering,
12 all this stuff is fine and good, but what are you going
13 to do with the other landfills to keep this problem from

14 happening again? How do we make it so we don't have to
15 clean it up?
16 BOB DUPREY: It covers other programs
17 other than the Superfund programs. That is the most
18 important guestion, I thank, because we don't know how to
19 fully solve this problem. If we knew how to do it in a
20 way in which we could get rid all of what was put in
21 there and the haphazardous way it was done. It's mixed
22 in with soils and garbage. We can't extract effectively
23 all those contaminants in a way that's guick and
24 efficient and cost effective.
25 Back in 1980 Congress authorized what is

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1 called the Resource Conservation and Recovery Act. Rules
2 were put in effect that would not allow practices to take
3 place, and since that date those practices have not taken
4 place.
5 There was an attempt out at this very
6 landfill to put in a hazardous waste site during that
7 period and it was done early without all the safeguards.
8 And, frankly, through the action of Paul, I remember the
9 activity, they had that stopped and we made Chemical
10 Waste Management remove that soil and send all that waste
11 out of this area. It was all sent to approved facilities
12 that met the standards.
13 Those facilities now require, first of
14 all, that the waste be treated to meet certain treatment
15 standards and also requires that no liquid waste be put
16 in the ground. It has to be all solidified. And there
17 are liners required, a double lined system, where you
18 have leach checks which monitor those constantly. If you
19 have a problem, to correct it.
20 So we have in place today, and have for a
21 number of years, requirements that prevent this kind of
22 situation from happening again. If it happens, it
23 happens because it's an illegal practice. We go in and
24 use our enforcement authority to correct it.
25 MARC HERMAN: I just want to mention again

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1 that Gwen and I and Angus are very interested in hearing
2 anybody's concerns and comments, and if you don't get
3 your guestions answered tonight, I want to volunteer our
4 phone numbers. Please feel free to call us and ask us
5 guestions. We can provide you with information.
6 Angus' phone number is 692-2385. Gwen's
7 phone number is 293-1533. And my phone number is
8 293-1625.
9 SPEAKER: I'm wondering about the
10 environment and the animals, like the animals around the
11 landfill. On this paper here there is two landfills
12 probably not three miles apart from each other. Is this
13 pushing the animals away from there?

14 MARC HERMAN: Part of our duty is to
15 protect human health and the environment. Included in
16 the environment are the wildlife. And as part of the
17 feasibility studies and the remedial investigations for
18 Superfund sites, we look not only at the threats to human
19 health, but we also look at the impact to vegetation and
20 also wildlife.
21 So I guess what I'm recommending is that
22 if you would like to, you could probably get more detail
23 on how we address the issues of wildlife or the
24 environment in some of the documents we produced.
25 You can get those, again, at the Aurora

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1 Public Library or the EPA Superfund Center.
2 GWEN HOOTEN: We do have our toxicologist
3 here from CH2M Hill, Beth Hudson, and as part of the
4 studies for the operable units, we have done an
5 ecological study.
6 Beth, if you would come up and discuss a
7 little bit the results of that.
8 BETH HUDSON: As part of the risk
9 assessment for Operable Units 4, 5, and 2 and 3, that's
10 the surface water sediment, surface soils, landfill gas,
11 and landfill solids, EPA looked at the aguatic and
12 terrestial habitat at the facility within Section 6,
13 looked for evidence for the presence of threatened or
14 endangered species, also looked at information about the
15 indigenous wildlife in the area, for example, the
16 prong-horned mule deer, some of the smaller animals,
17 mice. Also it looked at some of the vegetation patterns.
18 The ecological risk assessments are guite
19 a bit different than human health in that it's a new
20 science and that it's very difficult to guantify the
21 impacts in terms of risk to those receptors. The overall
22 ecological assessment indicates that there could be
23 adverse impacts to receptors impacted by surface water
24 sediment and surface soil. But beyond identifying the
25 chemicals that could cause impact, it's difficult to

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1 characterize exactly what those impacts are.
2 I hope that answers your question.
3 SPEAKER: Summarizing all the various
4 alternatives that exist on site land and use restrictions
5 that will continue, can you tell us what those
6 restrictions are and what the EPA and the State foresee
7 happening during the clean-up period and after, off site?
8 GWEN HOOTEN: The existing institutional
9 controls that we are talking about are -- the landfill is
10 an operating landfill, and as such they have restricted
11 access through the use of fences, and they have a gate
12 that is monitored for any access. So that's one form of
13 institutional control.
14 In addition to that, the Mayor of Denver
15 has an Executive Order No. 97 that restricts the land use
16 of Section 6.
17 We will look towards the Southeast Plan
18 Initiative Group to tell us any additional institutional
19 controls that they may institute. But those are the ones
20 we're referring to in our document.
21 SPEAKER: So you don't foresee any active
22 land use, industrial use, or anything like that on that
23 site in the future?
24 GWEN HOOTEN: Not in the near future.
25 When we did our baseline risk assessment, we did assume

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1 that a residence will be built on the site. So we have
2 not defined what future or just how soon that will
3 happen.
4 But our risk assessment is based upon a
5 residence, but we don't expect any residences to be built
6 during the term that it's going to be cleaned up.
7 ANGUS CAMPBELL: I would like to add
8 something just as an example. In any institutional
9 controls measure taken on any Superfund site, permanence
10 is something that we evaluate very strongly -- how that
11 control is in place and how permanent is that control.
12 And when you're talking land use plans, over tile those
13 change.
14 BOB DUPREY: Could I add to also since
15 this was also a garbage landfill, the idea of actually
16 putting residents there or structures is not advisable
17 because the gases will build up from the decomposition of
18 the garbage, and as a general rule there will be
19 permanent restrictions I believe that Aurora, Denver will
20 want to see in terms of actually having structures on a
21 garbage landfill. That's not from the hazardous waste.
22 That's from the ordinary paper and solid wastes in
23 there.
24 So from a practical standpoint, we are
25 going to look and see some very strong restrictions on

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1 development on the site itself, and those will need to be
2 built into the final decision and become enforceable but
3 will be there for the future so people won't -- they
4 won't forget over time this is there and they
5 accidentally build on top, which in the past where people
6 have done it in other places, it has created major
7 problems.
8 SPEAKER: I was wondering after the
9 contaminants are extracted from the groundwater, where
10 will they be disposed of and what provisions will be
11 made?
12 MR. HERMAN: If the contaminants are
13 removed from the groundwater through use of carbon

14 absorption units, the granulated carbon pulls the
15 contaminants out. I indicated earlier that the carbon
16 can be thermally regenerated and burn the contaminants
17 off.
18 In other cases the contaminants, if
19 they're accumulated, will have to be disposed of in
20 compliance with the Resource Conservation and Recovery
21 Act, which is the set of laws and regulations that
22 dictate how hazardous wastes currently can be disposed of
23 properly.
24 BOB DUPREY: I can clear that a little bit
25 more. There are companies in the United States -- there

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1 are several of them, one is Calgon, who have as part of
2 their business the destruction of these chemicals that
3 are collected in their activated carbon cells — just one
4 of the companies.
5 But whoever is selected ultimately to do
6 this work, and that's yet to be done, we will make sure
7 that there is a process to monitor where that collected
8 waste goes, how it's disposed of, and to ensure it's not
9 released at a future date back into the environment.
10 That will be a part of this process.
11 But the best method in my view is
12 activated carbon, because there you're going to get
13 destruction of the chemical, and that carbon can then be
14 brought back to the site and reused over and over again.
15 So that has special advantage. It really
16 depends on the particular technigue. Sometimes you end
17 up with a bunch of sludge so that you have no other
18 choice but to go back to another landfill with that. In
19 that instance it has to be an approved hazardous waste
20 facility that is properly designed and monitored.
21 SPEAKER: In burning those toxics off of
22 the carbon, when you release that into the air, does that
23 impact the environment?
24 BOB DUPREY: That' s not the way it works.
25 It has an extremely high performance efficiency and only

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1 volatiles are collected in an activated carbon system.
2 Those are combustible. It's done at very high
3 temperatures and under strict conditions.
4 The air standards that apply to that are
5 very strict so only a tiny, tiny amount of what was
6 originally in there could possibly be released back into
7 the environment.
8 SPEAKER: If any of the waste was to leak
9 out north of your site, who or what would be effected by
10 it, and what would the effect be?
11 MARC HERMAN: Another great guestion.
12 GWEN HOOTEN: We would place monitoring in
13 strategic places looking for that kind of event. And if
14 that happened, then we would have to take additional
15 actions than what has been discussed tonight. But our
16 monitoring would be set up just for that purpose.
17 SPEAKER: What effects would it have on
18 anyone downstream?
19 GWEN HOOTEN: We believe that it would
20 have the same effect that we described to you. If the
21 contaminants do go beyond that barrier wall, we would
22 have one in one hundred chance, additional chance, of
23 getting cancer beyond what you normally are exposed to.
24 So anybody who would drink that
25 contaminated water coming off the site, we believe that

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1 it would be that additional chance of contracting cancer.
2 MARC HERMAN: The national overall average
3 for anybody to contract cancer is one in four. So Gwen
4 was saying above and beyond the national average.
5 SPEAKER: But to drink it for whatever
6 period -- not just a cup of water.
7 GWEN HOOTEN: This is based upon on a lot
8 of assumptions, the body weight of the person, how much
9 they're drinking a day, how many days in a year they're
10 drinking it, how many years they're drinking it.
11 It's based upon a lot of assumptions, and
12 EPA makes what we determine as a reasonable maximum
13 exposure. So we look at the upper limits of all those to
14 determine what the risk would be. So we feel it's fairly
15 conservative.
16 SPEAKER: What would that risk decrease to
17 after this project is finished? What would be the
18 difference?
19 GWEN HOOTEN: We would try for that risk
20 to go down to zero. Whether or not that's technically
21 practical, we're saying right now that we can't achieve
22 that at this time. That's why it's a containment type
23 remedy.
24 BOB DUPREY: I would like to add one
25 thing. There are three or four guestions that I'm

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1 sensing you're not really getting clear.
2 On the first point, I've been here in the
3 area since 1979, and I've been involved with the site,
4 particularly early on, very extensively with some of the
5 difficult problems. But one of the things that was done
6 guite early was to put in that barrier wall and treatment
7 system on flow to the north. And since that time there
8 has been no detection of any off-site contamination from
9 this site, and we've gone a long tame, approximately a
10 decade, now.
11 And part of the reason it's taken so long
12 to get to this point where we decided some of the
13 ultimate things to do is because we made a commitment to
14 Aurora and a number of people to look at as much
15 treatment as we could do at this site and not simply just
16 putting a cap on. We tried to put in as much as we can.
17 But also because there were a lot of
18 unanswered guestions. There has been an enormous amount
19 of studies and monitoring, and that's taken a lot of
20 time, but what it does give us is a great deal of
21 assurance that there is no off-site movement of
22 contamination, and that under this remedy there will be
23 no off-site movement of contamination.
24 And if we're wrong -- and I think some of
25 the best minds in the state are working on this from the

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1 companies involved as well as from the governmental
2 agencies and the consultants that are here -- we'll have
3 to go back and fix that.
4 And if you have some ideas -- as I say,
5 this meeting in large part is to try and find out if
6 there is something that's been missed. And if there is
7 something we can improve on and how we can do that, what
8 further things could be done?
9 We're very open to changes. This isn't
10 the answer. We are required by law to respond to the
11 public's input and the technical input we receive. So if
12 there are things we can do better, let us know and we'll
13 try to do them.
14 SPEAKER: You indicated the three-year
15 period for implementation of the plan. Is that three
16 years from the beginning of construction or end of
17 construction and actually in operation?
18 MARC HERMAN: That's a great question.
19 PAUL ROSASCO: That was the period for
20 doing all the design and the actual construction of the
21 remedy. So it would be fully operable at that point,
22 including initial testing and shake down and so forth.
23 SPEAKER: Are you saying that the EPA or
24 the hazardous waste technology does not exist to pump one
25 or more of the existing ponds of what's in there now and

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1 take it to a hazardous waste site and have it processed
2 of these 142 million gallons? Does that not exist?
3 GWEN HOOTEN: I'm going to let Paul follow
4 up on my answer.
5 In short, we're not saying that. We're
6 saying that anything is pumpable. I mean if we apply as
7 many dollars as possible, anything is possible for
8 pumpability. But we're not convinced that we'll be able
9 to pull out all the contaminants. The dense aqueous
10 phased liquids we do believe will probably still be
11 confined to that area.
12 We're saying that given the pumping rates
13 that we have experienced at that landfill due to its
14 tight formation, that we will gain as much by having it
15 gradually migrate to these points of collection as we
16 would gain from spending money to pump it.
17 Paul, is there anything you want to add to
18 that?
19 PAUL ROSASCO: Earlier on in the process
20 we looked at alternatives that would try to accomplish
21 exactly what you're asking. One of them looked at an
22 alternative where we had 800 wells out there pumping. It
23 still took 200 years to get even a significant amount of
24 the contamination out of the site, because we put in a
25 number of wells into these pits to try and pump the

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1 liquids, and we only get very, very small amounts.
2 If you think back to the photos that they
3 showed, we had all kinds of materials, a lot of sludges
4 in there with the wells you just can't get a lot of
5 liguid out of there.
6 SPEAKER: The pond and groundwaters down
7 below and the big ion exchange column, once you get all
8 the way down to the bottom, it may be benzene or thiozene
9 or some aromatic, which then you process. But in each
10 strata there may be PCBs or something else that you're
11 just keeping. You're using the ground as just a great
12 big ion exchange.
13 PAUL ROSASCO: We did tests to try and
14 look and see if we could get to different fractions, if
15 there were fractions present. We tried all of those
16 things. We set treatment plants out at the site to do
17 exactly what you're asking. We still cannot get a lot of
18 liguid out of the site. The garbage did absorb a lot.
19 The soils are very tight. And what we get out is not
20 those separate cases. It's mixed with leaching from the
21 refuse and other things, so we have to treat all of
22 that.
23 We looked at biological treatment systems
24 that totally destroy the chemicals, totally break them
25 down, running them on site and still we were looking at

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1 hundreds of years to even make a dent in this.
2 So that's why we made the conclusion to
3 look at these types of remedies.
4 SPEAKER: The 142 million gallons doesn't
5 exist except in a mix, soil mix and garbage?
6 BOB DUPREY: I think some of your
7 guestions are some of the same ones I asked and went to
8 this analysis of all these alternatives. If you look at
9 Alternative 6 over here on the wall, you see all the well
10 points. That's one of the ones that was to do part of
11 what you're talking about, even though there were others
12 that were more extensive.
13 The difference in the amount pulled out

14 was inconseguential in my view. But the other point that
15 was persuasive to me, and it's one if you have some ideas
16 which you think we should sift through, was those well
17 points are all going to create potential vents to the
18 atmosphere. And what was said way back in '79, '80 and
19 '81 when we had some problems with the odorous nature of
20 this material, it's vile, because I smelled it too. I
21 remember it well.
22 We were concerned that this would create a
23 pathway to the air that might create more problems than
24 this small amount of additional treatment that we would
25 get out of it versus the toe system that would be put

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1 in.
2 But it is a complex technical question.
3 We were seeking exactly what you're stating we ought to
4 do, and we just simply felt that remedy was not as good
5 as the other one and would offer some additional risk.
6 SPEAKER: Thank goodness you didn't try
7 pond creek.
8 BOB DUPREY: I'm familiar with that too.
9 SPEAKER: You had mentioned some
10 radioactivity material, right, on the 142 million
11 gallons?
12 GWEN HOOTEN: Yes. We are finding some
13 radionuclides out there. For the most part we believe
14 that they're naturally occurring. We have not looked at
15 the radionuclides specifically because we're looking at
16 all media.
17 We plan to release a risk assessment for
18 the radionuclides' portion.
19 SPEAKER: But that can't be cleaned up by
20 carbon?
21 GWEN HOOTEN: In the treatability studies
22 that were conducted, we didn't really have that many
23 radionuclides. There wasn't that much in the residue.
24 So the treatment studies didn't bear out some of the
25 sampling that we found.

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1 SPEAKER: What will go downstream of the
2 pond could be found anywhere in Colorado or anywhere in
3 the world by parts per million?
4 GWEN HOOTEN: Yes, that' s what we're
5 finding.
6 SPEAKER: On your map you have the
7 groundwater extraction trench. What is that exactly? I
8 know what your toe barrier is because I've seen that.
9 MARC HERMAN: The barrier wall?
10 SPEAKER: Yes. What is that extraction
11 trench?
12 MARC HERMAN: The barrier wall is like an
13 underground dam.
14 SPEAKER: I know what that is. On some of
15 your maps you have the new wall which is guite large.
16 PAUL ROSASCO: If you remember the slide
17 that Angus showed that showed what the groundwater
18 barrier wall looks like. There is a gravel drain on one
19 side and clay. The extraction trench would be either the
20 gravel portion or be a series of wells running along that
21 alignment to collect the liguids.
22 SPEAKER: I thought the concern with
23 putting that along the south end was that by digging the
24 trench you create a pathway for more water to come in
25 really than you would be taking out.

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1 When did the decision -- how did that come
2 about that you decided to add that to Alternative 5?
3 MARC HERMAN: The barrier wall on the
4 south?
5 SPEAKER: Yes.
6 GWEN HOOTEN: Charlie, I'm unaware of what
7 you're talking about.
8 SPEAKER: If you look at 5, you don't have
9 an intercept. I heard where the concern was. If you try
10 to dig down on the south end, because the soil was so
11 tight and there was very little seepage coming in that
12 you could break that up and actually allow additional
13 seepage to come in by putting in that kind of a facility.
14 GWEN HOOTEN: Perhaps you're talking about
15 the toe drain.
16 SPEAKER: That's why it wasn't included in
17 the original 5 I thought.
18 PAUL ROSASCO: Charlie, I think there was
19 a discussion earlier on about the toe drain being a lot
20 deeper and a lot more extensive. And what that was, when
21 we looked at the chemical data, we would be taking a lot
22 of clean water at depth and with this other water than we
23 would be taking out in the process.
24 What we do is make the gradient, that is
25 the pressure that's driving the groundwater, make it

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1 stronger to drive it down deeper.
2 So we decided not to build the deeper
3 drain at the landfill but to build the shallower one so
4 we did not aggravate the problem.
5 BOB DUPREY: One of the concerns I had was
6 to try to prevent as much moisture from getting into the
7 system as possible and then drain it as much as possible
8 over time so you draw down the level and you take away
9 the drainage for any vertical movement.
10 Even though it was a small flow in, we
11 thought with a modified, not the original, plan that
12 would actually create that conduit that we're talking
13 about. We could divert some water, and that any water
14 that could be diverted out of the system would in the
15 long term, over hundreds of years, be a benefit. That
16 was the reason for the addition.
17 If there are other concerns that -- or
18 problems created here where we shouldn't do that,
19 obviously we reduce the cost somewhat, and it would be
20 that much easier to implement. That's something we would
21 want to know from the community.
22 The intent was to create as much as
23 possible the situation where the cell out there would be
24 contained fully on all sides, and that the drainage site
25 would be a full collection treatment.

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1 SPEAKER: What were the comparisons of
2 contaminated radionuclides to uncontaminated ground
3 during construction and the rupturing of any of these
4 wells having more seepage in the water?
5 GWEN HOOTEN: I'm going to answer your
6 second guestion first. There is always the potential for
7 a well to become environmentally unsound for some reason.
8 It could be the seasonal changes or what-not. And we
9 would look during the operation and maintenance to ensure
10 the soundness of all the wells. That is something we
11 would look at.
12 And once we found that a well was possibly
13 environmentally unsound or that it was causing cross
14 contamination, we would abandon the well.
15 With respect to your first guestion which
16 had to do with radionuclides, would you repeat that.
17 SPEAKER: If you were to take a sample of
18 the radionuclides in the contaminated ground and compare
19 that to uncontaminated ground off site, what would the
20 comparison be?
21 GWEN HOOTEN: We're finding that the
22 comparison would be guite similar, that the radionuclides
23 that we're experiencing on site are comparable to the
24 background radionuclides.
25 There was some guestion as to whether or

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1 not we had transuranic radionuclides, which is man-made
2 nuclides, and we're finding for the most part that the
3 data that we've collected is inconclusive, and we really
4 cannot say whether it's there or it's not there.
5 SPEAKER: One of the questions that I do
6 recall coming up when we were discussing the containment
7 system concerns whether or not there was actually space
8 to install without getting into private land.
9 Could you elaborate on the proposed
10 location of the harrier wall.
11 GWEN HOOTEN: The alternatives where there
12 was some practicability problem was Alternative 4. That
13 south barrier wall was at a depth of 100 feet.

14 Alternative 5 the barrier wall is at a depth of 50 feet.
15 We believe it's totally impracticable. We
16 don't believe there is the need to access land that's not
17 presently owned by the City and County of Denver to
18 implement that.

19 MARC HERMAN: Any other questions? This
20 is not the only opportunity. I think I mentioned it
21 before.
22 GWEN HOOTEN: Just a wrap-up. We do have
23 extra copies of the proposed plan. If you wish to be a
24 part of our mailing list, we ask that you come down and
25 sign up with us. We will be issuing in both The Denver

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1 Post and the Rocky Mountain News the notification that
2 the comment period has been extended.
3 If there are no other questions we can
4 answer tonight, then we'll formally close this meeting.
5 Thank you to the teacher at Littleton.
6 Your students had excellent guestions.
7 (The hearing was concluded at the hour of
8 9:30 p.m.)
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13.2 Response to Written Comments on the Proposed Plan for Operable Units 1 & 6 Shallow Ground-Water and
Subsurface Liquids and Deep Ground-Water Operable Units August 1993

13.2.1 EPA's Response to Comments from Citizens Against Lowrv Landfill Richard Schelin, Chairman

Comment

None of the proposed alternatives meets the legal requirements in the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) because the alternatives fail to treat any meaningful percentage of
the 142 million gallons of hazardous waste dumped in Section 6 of the landfill. The alternatives are
indefinite containment strategies, not cleanup strategies.

Response

Section 121(a) of CERCLA mandates that EPA select appropriate remedial actions that are in accordance with
Section 121 and, to the extent practicable, the National Contingency Plan (NCP), and which provide for
cost-effective response. Each of the remedial alternatives described in the Proposed Plan for Operable Units
(OUS) 1 & 6 meets these legal requirements. Consistent with Section 300.430 (a) (iii) (c) of the NCP, in
developing appropriate remedial alternatives for the Site, EPA considered a combination of methods to achieve
protection of human health and the environment. EPA considered the expectation described in the NCP that in
appropriate site situations, treatment of the principal threats posed by a site (with priority placed on
treating waste that is liquid, highly toxic or highly mobile) will be combined with engineering controls and
institutional controls, as appropriate, for treatment residuals and untreated waste. In addition, EPA also
considered the expectation described in the NCP that engineering controls, such as containment, will be used
for waste that poses a relatively low long-term threat or where treatment is impracticable. Containment was
chosen at the Lowry Site because of the low level offsite risks and because it is impracticable to remove the
waste. The NCP recognizes that containment should be used to remediate waste present in low levels, waste
that is technically infeasible to treat, and large volumes of waste.

Treatment of contaminated ground water is a principal component of EPA's selected remedy for OUS 1 & 6.
Treatment of ground water beyond that included in that remedy would be impracticable, given the prohibitively
high costs and adverse short-term effects to onsite workers associated with such treatment.

The selected remedy for OUS 1 & 6 is expected to immediately treat 23,652,000 gallons of water per year
extracted from the Shallow Ground Water and Subsurface Liquids at the Site. The selected remedy components
for OUS 2 & 3 and 4 & 5 include, in part, treatment to address Landfill Solids and Gas, Surface Water and
Sediments at the Site.

Comment

EPA should establish a new-technologies escrow fund of $75 million for ultimate cleanup of the Site. The
interest-bearing escrow fund would be available on a competitive basis to vendors of technologies that
detoxify the hazardous waste in Section 6. Payments would be based on the number of gallons of chemicals of
concern (COG) that are removed.

Potentially responsible parties (PRPs) would be required to place in escrow $75 million in an interest
bearing account. At each 5-year review interval, EPA would issue a Request for Proposals for vendors to
apply new technologies to treat the remaining millions of gallons of hazardous waste at Section 6. Pursuant
to a public process, EPA would review the proposals to identify the proposal(s) that results in the greatest
treatment of hazardous waste at the lowest cost. Any qualifying proposal would have to meet community
protection standards and be subject to bonding to assure performance.

The winning vendor would be paid according to the number of gallons (or pounds) of hazardous waste treated.
EPA's administrative costs would be strictly limited to 5 percent of the amount paid the vendor. Funds not
paid to the vendor would remain in the escrow account to be available at the next review in 5 years. EPA
would have to assure all interested vendors access to the Site and preclude the Site owner/operator from
barring competition, as Waste Management has tried to do during the Remedial Investigation/Feasibility Study
(RI/FS).

Response

CALL'S proposal raises a number of legal and policy concerns, including the fact that it does not specify a
remedy which can be evaluated against the NCP criteria for remedy selection.

EPA has determined that the selected remedy for OUS 1 & 6 will be protective of human health and the
environment, and will use the 5-year review process under Section 121 (c) of CERCLA to ensure that the
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selected remedy remains so protective. If the Agency determines during a 5-year review that the remedy is no
longer protective, it may review new technologies and evaluate whether they are appropriate for
implementation at the Site.

Comment

If EPA abandons the cleanup objective at the Lowry Site, the agency will send a clear signal to all PRPs that
the most effective method of avoiding cleanup of a Superfund site is to make it inaccessible by burying it
under tons of municipal solid waste.

Response

EPA has not abandoned the cleanup objective at the Lowry Site. The primary remedial action objectives for
OUS 1 and 6 are the following:

• Prevent human exposure (through ingestion, inhalation, and dermal absorption) to liguids
containing contaminants in excess of the remediation goal

• Prevent migration of contaminants that would result in ground-water concentrations in excess of
the remediation goal

The selected remedy for OUS 1 & 6 meets these objectives. As discussed above, the NCP recognizes that
containment should be used to remediate waste present in low levels, waste that is technically infeasible to
treat, and large volumes of waste. In addition, EPA guidance on Conducting Remedial
Investigations/Feasibility Studies for CERCLA Municipal Landfill Sites recognizes that "[c]ontainment has
been identified as the most likely response action at these sites because (1) CERCLA municipal landfills are
primarily composed of municipal, and to a lesser extent hazardous wastes; therefore, they often pose a
low-level threat rather than a principal threat; and (2) the volume and heterogeneity of waste within CERCLA
municipal landfills will often make treatment impractical."

Comment

The alternatives give insufficient attention to the maximum extraction and treatment of hazardous
constituents at the landfill because approximately 96 percent of the hazardous material in the waste pits
will remain after 30 years of treatment.

Response

Although EPA does not agree with the specific analysis presented, the Agency does agree that a large portion
of wastes will remain in the waste pits. The FS evaluated waste pit pumping and treatment and found that a
significant reduction in volume cannot be achieved because of residual contamination. Because removal of
wastes from the waste pits is technically infeasible and not cost-effective, EPA did not include waste pit
pumping as a component of the selected sitewide remedy. Excavation and disposal of the contents of the
shallow waste pits in the former tile pile area is, however, part of the selected remedy for OUS 2 & 3.

Comment

In the near term, EPA should assume full development of all lands up to the boundaries of Sections 6 and 31.
In the long term, EPA should assume full development of all lands, including Sections 6 and 31. The buffer
zone ordinance adopted by the City of Aurora was intended to protect citizens from the dangers from the
landfill prior to and during cleanup. In convoluted logic, the PRPs argue, however, that they should not
have to conduct extensive cleanup at the Site because EPA should assume institutional controls to prevent use
of Sections 6 and 31 and adjacent land and related ground water now and in perpetuity.

CALL urges EPA to assume no institutional controls and ultimate full use of Sections 6 and 31 and order a
cleanup accordingly.

Response

The risk assessment was based on ultimate residential use of both Sections 6 and 31. However, the lack of
technologies to detoxify the waste pits has lead EPA to consider containment-based remedial alternatives with
onsite institutional controls. EPA has determined that the selected remedy for OUS 1 & 6 is the most
appropriate and technically feasible remedy to address Shallow Ground Water and Subsurface Liguids at the
Site. During the 5-year review, if EPA finds the remedy is not protective, EPA may review new technologies
and evaluate if they are appropriate for implementation at the Site.
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Offsite institutional controls will serve as an additional measure of protection to enhance the effectiveness
of the selected remedy and to act as preventative measures to preserve the implementability and effectiveness
of any of the selected remedy contingency measures.

Comment

By limiting the remedial alternatives to containment strategies and not advancing options involving
significant cleanup, EPA is rewarding PRPs for systematically making cleanup of a Superfund site more
expensive and difficult. It is unconscionable that PRPs would now be able to claim cleaning up Section 6 is
too costly after one such PRP consciously and systematically piled years worth of trash on the Site after the
Site was placed on the National Priorities List (NPL). This type of chicanery for private profit at the
expense of the public interest cannot be tolerated. EPA's sanctioning of this behavior by PRPs will send a
signal to PRPs at other sites that it is profitable to make cleaning up their Superfund sites as costly as
possible, because EPA will let them off the hook. By sanctioning such behavior, EPA will emasculate the
central feature of CERCLA, which is that the polluter must pay.

Response

EPA does not believe that it is rewarding PRPs, who will ultimately pay the costs of cleanup, for piling
trash on the Site over the years. The Lowry Site was permitted as a landfill for municipal and industrial
disposal prior to becoming a Superfund site. In 1984, when the Site was placed on the NPL, the Site already
had a significant amount of municipal waste as well as industrial waste. The Lowry Landfill was the prime
recipient of municipal waste from the Denver metropolitan area. Rather than close the landfill without a
viable alternative municipal landfill, a decision was made to continue landfilling operations until another
facility could be opened.

Comment

CALL proposes that EPA adopt an innovative strategy for the long-term cleanup of the Lowry Landfill, which
will also send a signal to PRPs that they cannot escape cleanup responsibilities. The strategy involves two
elements:

1. Adopt and implement modified Alternative 5, which will contain the hazardous waste on Section
6, but only treat a small portion of the 142 million gallons of hazardous waste in the ground.

2. Place $75 million in an interest-bearing escrow account for applying new technologies to treat
the millions of gallons of hazardous waste remaining at the Site after implementation of EPA's
preferred alternative.

To meet the reguirements of CERCLA, waste at sites on the NPL is to be treated, not merely contained. All
the alternatives being considered by EPA now amount to containment strategies. None of the strategies treats
a significant amount of the waste at the Site. The PRPs and EPA are apparently convinced that current
technologies are insufficient to meet the treatment reguirements of CERCLA.

Response

EPA acknowledges support of the preferred remedial alternative for OUS 1 & 6 as expressed in the Proposed
Plan. EPA disagrees with the statement that "[t]o meet the reguirements of CERCLA, waste at sites on the NPL
is to be treated, not merely contained." (See response to CALL'S first and second comments.)

Comment

Under CERLA, EPA is reguired to review cleanup sites no less often than every 5 years. However, CALL is
unaware of any circumstances where EPA has conducted the reguired review and taken additional cleanup action
following that review. Failure to take additional action may be for a number of reasons:

• Few sites have reached the 5-year review period
• No new cleanup technologies have become available prior to the review
• It is too difficult to acguire money to institute new cleanup actions
• Bureaucratic inertia, which seeks to close the door on sites that the agency says it has
cleaned up

CALL'S proposal would overcome these problems while instilling competition in a cleanup process characterized
by a lack of competition. Competition will necessitate developing an aggressive program that will implement
new technology and, ultimately, lower costs. The program will be applicable to the Lowry Landfill and similar
sites.
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Response

EPA agrees with the first two bullets, but disagrees with the remaining items. PRPs are liable for the costs
of new cleanup actions. Furthermore, EPA does not "close the door" on any site so long as any wastes remain
there.

13.2.2 EPA's Response to Comments from City of Aurora

Comment

Remove the element of the Plan that suggests that Aurora will maintain indefinitely its current restrictions
on land and water development in the City around the Superfund site. The City Council enacted the ordinances
as temporary protection at a time when it was not known if contamination had migrated off the Site or if the
potential for exposure would be heightened during the Site investigation and stabilization.

Institutional controls should not be used as a substitute for cleanup actions, and site contaminants should
be controlled so as to avoid offsite impacts.

Since the site studies have confirmed that contaminants are currently contained onsite and that it is
technically and economically feasible to prevent migration beyond the compliance boundaries, we do not see
the need for offsite institutional controls as a component of the ground-water remedy.

Response

The Proposed Plan cites Aurora's ordinance as an example of an existing institutional control. The risk
assessment recognizes that existing institutional controls may be withdrawn or repealed. The selected
sitewide remedy is a containment-based remedy. Therefore, permanent, enforceable, onsite institutional
controls are reguired. Offsite institutional controls will serve as an additional measure of protection to
enhance the effectiveness of the selected remedy and to act as preventative measures to preserve the
implementability and effectiveness of any of the selected remedy contingency measures.

Comment

Provide additional information on the efficacy and cost-effectiveness of the upgradient system to control the
flow of ground water into the Site. Would the system reverse the ground-water gradient to the south?

Response

The upgradient system proposed to control the flow of ground water into the Site will intercept clean ground
water flowing from the south into the Site. The purpose of the system is also to prevent contaminant
migration to the south, so that a hydraulic gradient reversal to the south will not occur.

Enhanced isolation of site contaminants.

• Prevention of offsite contamination migration, which may occur through the unidentified sand
stringers/sand channels and other geologic heterogeneities.

• Mitigation of contaminant migration on the south that may result from localized ground-water
flow to the south, chemical diffusion, dispersion, or possible unidentified, localized seasonal
changes in ground-water flow direction.

• Prevention of most clean ground water from entering the contaminated site, thus reducing the
treatment cost.

Comment

The EPA should make a commitment to further evaluate the pumpability of selected waste pits. Specifically,
would it be possible to pump any of the waste pits downgradient of the toe drain or further north where the
pits are relatively close to the surface? Such actions could contribute to overall reduction of toxicity at
the Site and could reduce long-term problems, particularly as they relate to significant vertical contaminant
migration. Aurora reguests this additional assessment in furtherance of Superfund's directive to choose
permanent reduction of volume, toxicity, or mobility of wastes wherever practicable.
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Response

EPA evaluated this option in the FS. EPA also evaluated the option of excavating and removing the shallow
pits downgradient of the toe drain. Excavation and disposal of the contents of shallow waste pits in the
former tire pile area is part of the selected remedy for OUS 2 & 3.

Comment

The following policy guidelines were adopted by Aurora City Council May 18, 1992, to guide EPA and the
parties conducting the site investigation in their development of the following potential remedies:

Development Rights

1. The site remedy shall not preclude either private development or the exercise of water use rights
around the Lowry Superfund site.

2. The Record of Decision (ROD) shall not allow for migration of hazardous wastes beyond the Superfund
site boundaries as defined during the remedial investigation.

Land Use Planning Around the Landfill

1. Remediation options shall not presume that local government institutional controls (e.g., the City of
Aurora's 1-mile perimeter development restriction) will be used in lieu of cleanup actions.

2. Cleanup strategies identified by EPA should conform to duly adopted and approved local land use plans
and programs of the City of Aurora and Arapahoe County.

Cleanup Implementation

1. The site remedy shall meet the CERCLA criteria of reducing contaminant toxicity, mobility, and volume
through treatment; providing effectiveness over the long term; and permanence.

2. Reaching an ROD within the shortest reasonable time should be the priority of all parties with an
interest in the Site. Considerations regarding the apportionment of liability must not be allowed to
interfere with the process of identifying the site remedy. EPA should take whatever action is
necessary to implement the selected remedy once the ROD is issued.

Funding

1. Funds collected through the de minimis settlement process should be immediately and solely dedicated to
Lowry Superfund site cleanup actions. Cleanup actions are those that involve treatment of the
contaminants. They specifically exclude transaction and administrative costs, including EPA oversight
activities.

2. Additional technical resources beyond the Technical Assistance Grant awarded to Citizens Against Lowry
Landfill should be made available to assist the community in understanding and reviewing the cleanup
alternatives being proposed for the Site.

The above guidelines will be used by the Aurora Task Force as community standards against which to evaluate
proposed EPA cleanup alternatives.

Response

EPA acknowledges the policy guidelines adopted by Aurora City Council on May 18, 1992. EPA believes that the
selected remedy for OUS 1 & 6 will meet the guidelines described under Development Rights, Land Use Planning
Around the Landfill, and Item 1 under the Cleanup Implementation criteria. With respect to Item 2 under
Cleanup Implementation, EPA believes that selecting a remedy within the shortest reasonable time is a
priority and will ensure that the selected remedy is implemented as soon as possible after the ROD is issued.
With respect to Item 1 under funding, the funds collected through the De Minimis settlement have been
dedicated to the Fund to reimburse EPA's past costs.

A Technical Assistance Grant (TAG), once issued, can be increased to a cap of $100,000 upon petition to EPA.
In accordance with CERCLA Section 117 (e), only one TAG is issued per site. There are no other existing
funding mechanisms for this type of assistance. However, the current community relations program provides
for two-way communication between EPA and the members of the community. EPA has imparted to the community
considerable information regarding the Superfund process and the Site. To date, EPA has committed funds,
personnel, and other resources to assist the community in understanding the cleanup alternatives for the
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Site.

Comment

We wish to point out two inaccuracies in the FS report and Proposed Plan with respect to Aurora's ordinances
and land use planning efforts.

The first relates to references in both documents that Aurora's ordinances 87-165 and 87-166 currently
prohibit development of structures within 1 mile of the Site and well development within ^L mile of the Site.
This is not true. Aurora's code does not prohibit development within the referenced area because the
property within a mile of the Superfund site is not within Aurora's municipal boundaries. Property within a
1-mile radius of Section 6 is in unincorporated Arapahoe County, which does not expressly prohibit
development in the vicinity.

EPA is aware that the Aurora City Council enacted its two ordinances restricting development with City limits
around the Superfund site because of technical uncertainty about the potential for offsite health risks. The
Council stated that they would reevaluate the restrictions at such time as significant new data became
available. With the near completion of the site investigation and baseline risk assessment, the City Council
has begun to evaluate the continuing need for the ordinances. The Council will assess whether the technical
data support reducing or removing the restrictions.

The second inaccuracy is on page 7-5 of the Final Draft Feasibility Study, which states in a discussion of
the Southeast Area Planning Initiative that the joint planning task force has recommended that a
nonresidential or open space buffer of at least ^L mile remain around the landfill. While the concept of
buffers around the Superfund site has been discussed by the task force, no specific recommendation has been
made by the group, which is strictly advisory to the Aurora City Council and Arapahoe County Board of County
Commissioners.

The Lowry Landfill Environs element of the Southeast Area Planning Initiative was undertaken by Arapahoe
County and Aurora, with participation by the City and County of Denver, to provide EPA a conceptual land use
plan for the Superfund site and immediately surrounding area to facilitate the evaluation of site remedies.
As an invited participant in the planning effort, EPA will receive prompt notice of any land use decisions
that are made by the jurisdictions.

Response

EPA appreciates the information provided. As described in the ROD, offsite institutional controls will serve
as an additional measure of protection to enhance the effectiveness of the selected remedy and to act as
preventative measures to preserve the implementability and effectiveness of any of the selected remedy
contingency measures.

Comment

We believe it is critical that the selected remedy rely first on physical barriers to contain the site
wastes, and that the performance of these physical containment systems be evaluated by a comprehensive and
carefully designed monitoring program.

Because of the potential for contaminants to migrate to the east and west of the source area, the proposed
physical barrier systems along these boundaries should both be installed immediately. The City particularly
urges EPA to resist any efforts to delay the installation of the western boundary system, since development
activity to the west of the site has been steadily increasing.

Response

The selected remedy for OUS 1 & 6 includes lateral containment on the eastern and western portions of the
Site. EPA considers containment to be the key concept that may be implemented by several specific
technologies. EPA has determined that physical barriers (such as installing a barrier wall) are more
protective of human health and the environment because of the existence of sand lenses at the Site.

Comment

To the extent possible, contaminants should be kept from spreading beyond the compliance boundaries, even if
the concentrations of those contaminants would meet current Applicable or Relevant and Appropriate
Reguirements (ARARs). EPA may avoid the need for upgrading the cleanup plan in the future by conservatively
setting remediation goals and remedial action objectives close to background levels now.
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Response

The threshold criteria for selection of a remedy is protection of human health and the environment and
attainment of ARARs. The NCP states that the acceptable site risk range for human health is 10-4 to 10-4 for
Superfund sites. EPA does not agree that cleanup should be to background levels for this Site. Based on the
nine criteria and the risk range specified in the NCP, EPA cannot justify cleaning up to background levels
for all contaminants at Lowry.

Comment

Long-term maintenance of the surface water removal action, the landfill cap, and the existing monitoring
system is essential to a successful remedy. Also, since the majority of the ground-water contaminants will
probably remain untreated in Section 6 indefinitely, the institutional controls outlined in Denver's
Executive Order 97 will need to be enforced to prevent potential exposure on the Site.

Response

EPA agrees with this comment. As to Executive Order 97, EPA agrees that it will need to be enforced and that
additional restrictions on the use of the Site will need to be implemented.

Comment

An effective containment and collection system, as described in Alternative 5, will be used to control
further horizontal migration of contaminants in the shallow ground-water system. However, we strongly concur
with EPA that, in addition, an effective long-term monitoring system must be developed to confirm aguifer
characteristics and ground-water migration over time. References in the FS to uncharacterized
heterogeneities, such as high permeability sands or fractures and uncertainties in site data, underscore the
importance of an adeguate monitoring system, particularly to assess vertical migration. We understand that
the conceptual model will be used only for planning and not for management purposes, and we fully support
this decision.

Response

EPA agrees with this comment.

Comment

If the conceptual site model is accurate, contaminant migration to the compliance boundaries is not expected
to occur until after the 30-year estimated life of the cleanup remedies. At that time, there will likely be
far more development around the Superfund site than there is today. This raises concerns for Aurora, despite
EPA and PRP assurances that because of Superfund-mandated 5-year reviews, remedial activities at the Site
will continue as long as they are necessary. It is critical that EPA accurately estimates cleanup costs and
contingencies and is diligent in efforts to legally secure these resources at the time the remedy is
negotiated. Any number of circumstances at the Site could significantly increase future risks. Unforeseen
operation and maintenance problems, for example, could compromise the effectiveness of the remedy if there is
a funding shortfall at the critical period.

Significant funds have already been paid to both EPA and Waste Management through the settlement process at
the Site. A small portion of these funds dedicated now could grow to a substantial resource to finance
future contingencies. The City reguests that EPA investigate this and other potential options for ensuring
that we are not faced with a shortage of funds to properly manage the Site at a time in the future when it
may be most needed.

Response

EPA agrees that ground-water containment and treatment will continue in perpetuity since wastes will remain
on the Site. EPA will seek to obtain financial assurance from any PRPs performing the remedy to ensure
continued O&M of the remedy.

Section 107 of CERCLA provides EPA with the mechanism to obtain cleanup funding in the event that the PRP
performing the RD/RA is no longer viable.

Comment

South Barrier System-We have some guestions regarding the relative benefit of the proposed barrier and/or
diversion system upgradient of the Site along the southern compliance boundary. Is there any potential for
the barrier to cause a reversal of the ground-water gradient to the south? Could the existence of the
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barrier impede potentially beneficial downgradient flushing of the contaminants? Before endorsing
installation of an upgradient barrier, the City reguests that EPA provide additional information on the
effectiveness of the concept. We raise this guestion particularly in light of the conclusion that migration
of ground water onto the Site from the south is responsible for only a very small portion of the total annual
infiltration.

Response

The relative benefits of the upgradient system were discussed previously (see response to City of Aurora's
second comment). Migration of ground water onto the Site from the south is responsible for only a small
portion of the total annual infiltration and would not result in beneficial flushing. However, intercepting
this flow is one of the secondary benefits of the upgradient system. The primary benefit is isolating and
preventing site contaminant migration to the south, as discussed earlier.

The Activity Report for Oversight of Compliance Boundary Sampling, dated May 1993, shows exceedances of the
Preliminary Remediation Goals (PRGs) to the south or the upgradient portion of the Site. In addition, the
Ground-Water Use Evaluation (Lowry Coalition, Draft Addenda 2 and 3 to the Ground-Water Well Inventory
Technical Memorandum, dated July 24 and October 25, 1991, describes the effects of an operating municipal or
industrial well in Section 7. The modeling results show that a reversal in the gradient flow will be induced
by pumping. The function of the barrier wall will be to prevent contaminants from flowing with the reversed
gradient and migrating offsite.

13.2.3 EPA's Response to Comments from Colorado Department of Health

Comment

The proposed point of compliance does not meet certain ARARs and to be considered (TBC) values. The state
would be willing to consider a waiver of the Resource Conservation and Recovery Act (RCRA) ARAR if sufficient
justification exists, and pursuant to the basic standards for ground-water reguirements, if two points of
compliance are established. The first boundary would be called a Point of Action (POA) and would be set at
the current extent of contamination. The second boundary would be called a Point of Compliance and would be
set at the property boundary as shown in the Proposed Plan.

The purpose of the POA boundary would be to trigger corrective measures to address migrating contamination
beyond the areal extent of the existing plume. This will allow for additional time to correct a problem
before offsite migration. The POA need only be set as a concept at this time, with the actual identification
of the POA boundary to be made when sampling takes place during remedial design of the selected remedy.

Response

EPA has included POA and compliance boundaries in the ROD for the Site. Monitoring at the POA allows
contamination to be addressed (via the planning and implementation of appropriate response actions) before it
reaches the compliance boundary, thus preventing exeeedances of performance standards at the compliance
boundary.

Consistent with the NCP, the compliance boundary has been established at the edge of the waste management
area because the waste has been left in place. In this context, the waste management area encompasses the
following waste management units: waste pits, sewage sludge application areas; leachate injection areas;
command post; subsurface barrier wall and treatment facility; and leachate sprayback areas. In
establishing the compliance boundary, EPA considered the proximity of the sources, the technical
practicability of ground-water remediation, the vulnerability of the ground water and its possible uses, and
the likelihood of exposure. Under this approach, there will be no need to waive the ARARs because ARARs will
be met.

The actual surveyed location of the POA and compliance boundaries will be determined by EPA during RD.

13.2.4 EPA's Response to Comments from East Cherry Creek Valley Water and Sanitation District

Comment

The East Cherry Creek Valley Water and Sanitation District (the District) was established in 1962, before
Denver's acguisition of Section 6 from the Army. The District presently serves over 5,000 accounts including
homes, schools, churches, and commercial properties. Presently comprising a population of over 15,000, the
District is poised to grow within its service area to serve as many as 90,000 people. Ground water in the
Dawson, Denver, Arapahoe, and Laramie-Fox Hills aguifers is the primary source of water for the District and
will continue to be a vital component of the District's water supply as it develops. Through its irrigation
return flow recapture programs, the District is also using water from the shallow alluvial aguifer systems
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within its boundaries. Considering its reliance on ground-water resources, the District cannot tolerate any
migration of hazardous waste off of the Lowry Landfill site. We have reviewed EPA's recommended alternative
for remediation of the ground-water OUS on the basis of this standard.

The District believes very strongly that an immediate and active approach to cleaning up and containing the
wastes is crucial to the protection of its water supplies. It further believes that the remediation program
should include, at a minimum, the construction of the perimeter barriers and collection facilities as
depicted in the recommended alternative. Although it generally supports the concepts outlined in the
recommended alternative, the District remains concerned with the effectiveness of the cleanup and the impact
it may have. Specifically, the District has the following general concerns:

1. It is opposed to using any offsite institutional controls which will in any way reduce, or
restrict our access to ground water within the service area of the District.

2. It believes that it is critically important that the monitoring program developed be designed
and operated in a fashion that will allow for the effective identification of any vertical
migration of the plume, or migration of the contamination off of the Site.

3. There is currently no guantification of the impact the dewatering and cleanup would have on the
District's water supplies. The District reguests that such an analysis be undertaken, and that
a means for replacing water impacted by the cleanup be developed.

4. It is concerned that the cleanup, as presented, may allow contamination to move beyond the
western site boundary and onto the District. It understands the well system will be in place
to help mitigate offsite contamination. However, if these wells are not operated until PRG
(Preliminary Remediation Goals) levels of contamination arrive at the boundary, considerable
contamination may migrate onto the District. It strongly recommends that the "trigger" level
for starring the operation of the westside containment well system be set at some agreed upon
background level rather than the PRGs. The water it currently delivers to customers is well
within mandatory Safe Drinking Water Act (SDWA) standards, and it does not want a portion of
its water supply to deteriorate to a marginal level of acceptance.

5. It reguests that some additional effort be made to reduce toxicity onsite through the pumping
of selected waste pits.

Our detailed comments are incorporated in the following document. Please include this cover letter into the
formal record with, and as part of, our comments.

Response

EPA notes that the cover letter is included as part of the District's comments. All have been placed into
the Administrative Record for the Site. EPA has responded to the five general concerns in the District's
detailed comments below. The selected remedy for OUS 1 & 6 is, in part, a containment remedy that will halt
offsite migration of contamination.

Comment

Institutional Controls-The District is strongly opposed to incorporating any offsite institutional controls
that would in any way restrict its access to, or use of water within its boundaries.

The District does not have surplus water to attribute to a "buffer zone." All water within its boundaries is
committed in the District's water supply planning to meet future demands. It cannot donate water to the
cleanup effort either to provide an additional margin of safety in the event that the ground-water modeling
is inaccurate, or to facilitate the operation of the ground-water collection system. The proposal does not
include any detailed analysis of what impact offsite institutional controls would have on District
adjudicated water rights and/or nondecreed water within its boundaries.

Response

As described in the ROD, offsite institutional controls shall serve as an additional measure of protection to
enhance the effectiveness of the selected remedy and to act as preventative measures to preserve the
implementability and effectiveness of any of the selected remedy contingency measures. Offsite institutional
controls shall include, but not be limited to, deed notices and restrictions, zoning controls, and well
restrictions. These controls must prohibit all offsite activities in the vicinity of the Lowry Site that
would interfere or be incompatible with, or that would in any way reduce or impair the effectiveness or
protectiveness of, the selected sitewide remedy.
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Comment

Ground-Water Modeling-What is the potential for future impacts to the deep aquifers beneath and adjacent to
the Site if this plan is implemented? At the Aurora Ordinance Review Meeting on February 21, 1993,
representatives of t he City of Denver concluded that the deep aquifers, including the Arapahoe Aquifer, may
not be protected and may become contaminated if nearby wells are allowed to pump. This is fully contrary to
our understanding of the conclusions reached by EPA and the Coalition. We request that the modeling be
reviewed and rerun, if appropriate, to resolve these questions.

Response

To address concerns that dissolved contaminants may migrate vertically downward under pumping conditions, EPA
completed several scenario runs for potential receptors in the Denver and Arapahoe Formations using the FS
model. The purpose of the simulations was to evaluate the impact of pumping near the Site on the Denver and
Arapahoe aquifers. The simulations considered municipal wells pumping in a dewatered aquifer that reached
water table conditions because of an assumed high level of ground-water development. These are conservative
conditions because the existing confining conditions within the Denver and Arapahoe aquifers help reduce the
rate of downward migration. Under water table conditions, the hydraulic head in the aquifer is lower than the
head under confined conditions, resulting in an increase in the downward hydraulic gradient, which promotes
downward vertical contaminant migration. This scenario simulates greater pumping than the total consumptive
use currently allowed by the Denver Basin Rules. The results of the simulations indicated that no detectable
dissolved contamination was predicted to reach the Denver or the Arapahoe Formations within the 200-year
simulation period. It should be noted that to date, EPA has no reliable mechanism to predict migration of
dense nonaqueous phase liquids. However, EPA will implement a vertical migration contingency plan to monitor
and remediate, if necessary, migration of dense nonaqueous phase liquids.

Comment

Ground-Water Monitoring-What are the primary components of the monitoring system and how will they be
designed? Since the modeling suggests that there will be little vertical migration of contaminants,
engineered facilities to control vertical flow were abandoned in favor of monitoring of the deep ground-water
system. This places a great deal of importance on the placement and design of the monitoring facilities. It
is particularly important to the District that deep aquifer monitoring facilities be effective, and yet
constructed in a manner to assure that the wells themselves will not, in the future provide a preferential
pathway for contaminant migration vertically downward.

Response

The design and placement of the monitoring well network will occur during RD. However, EPA understands the
District's concern that the monitoring wells should not provide a conduit for vertical migration. Monitoring
wells that must be drilled through waste disposal areas will be installed with appropriate precautions. EPA
would welcome any additional information and/or comments from the District pertaining to well monitoring and
design.

Comment

Is there a vertical compliance boundary? Clearly, if contamination was identified offsite in excess of ARAR
standards, some sort of remedial activity would be dictated. However, it is not clear what actions would be
taken if monitoring confirmed that the plumes were migrating vertically downward into clean ground-water
systems within the area of the compliance boundary.

Response

The top of the lignite layer is selected as a vertical compliance boundary and response action will be taken
if contaminants migrate to this layer. The response action to be taken will be determined by the magnitude
and speed of the migration event, the contaminants involved, contaminant concentration, and other physical
parameters.

Comment

Who will be responsible for the Site in the long term (30+ years); and specifically, where is this
responsibility described?

Response

Pursuant to Section 107 of CERCLA, the PRPs remain liable for all response costs associated with the Site,
regardless of when incurred. Response costs were estimated for the 30-year present worth to provide a basis
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for comparing remedial alternatives. The 30-year period was not intended to signify the length of the
remedial action. Under the selected remedy for OUS 1 & 6, the collection and treatment of contaminated
ground water will continue in perpetuity. EPA, through the 5-year review process, will assure that human
health and the environment are being protected by the remedial action selected for the Site.

Comment

What impact will the perimeter collection systems have on water availability and water rights, and how will
these impacts be mitigated? We have seen no analysis of how the proposed dewatering systems might impact
water beneath adjacent parcels within the District, and how replacement water might be made available to the
District to compensate for any adverse impacts.

Response

The impact that the cleanup would have on the District's water rights is negligible for the following
reasons:

• The remedial activities include extraction of contaminated ground water at the Site,
ground-water treatment, and reinjection of the treated ground water at the Site; therefore,
what is extracted from the ground water will be returned. This results in a net balance of
zero; therefore, the amount of available ground water has not changed.

• The cleanup effort will target the Dawson Formation, which is not a major water producer in the
area.

Comment

Ground-Water Quality-It is not clear exactly where the compliance boundary is currently proposed to lie. We
would like better definition of this boundary.

Response

The proposed compliance boundary as shown in Figure 3 of the Proposed Plan is a conceptual boundary.
Conceptually, the boundary consists of a southern boundary at East Quincy Avenue; a western boundary at Gun
Club Road; an eastern boundary at the current fence running north/south in Section 6; and a northern
boundary that is an extension of East Hampden Avenue with the exception of protrusions into Section 31 to
encompass the barrier wall and command post. The actual surveyed location of the compliance boundary will be
determined by EPA during RD.

Comment

Will the concentration of contaminants within plumes inside the compliance boundary be allowed to increase
from current levels as long as compliance is attained at the boundaries?

Response

The concentration of contaminants could theoretically increase inside the compliance boundary. However,
performance standards, including ARARs, must be met at and beyond the compliance boundary. Monitoring will
be reguired within the plume of contaminated water, but action will not be taken unless contamination above
the standards described in Section 11 of this ROD crosses the POA boundary.

Comment

Will contaminants be allowed to spread beyond the compliance boundary as long as ARARs and PRGs are met? For
example, if the PRG for lead is set at 50 micrograms per liter (Table 2.1 in the FS), and the natural
background lead is less than 5 micrograms per liter, will lead contamination be allowed to spread beyond the
compliance boundary as long as it does not exceed 50 micrograms per liter? Although this is a concern with
regard to all parameters, lead is a particularly good example. While the maximum contaminant level (MCL) for
lead remains at 50 parts per billion (ppb), the new EPA notification and treatment level for lead in drinking
water lies at only 15 ppb. We recommend bringing the PRG for lead into conformance with the new EPA
lead-copper rule.

Response

The threshold criteria for selection of a remedy is protection of human health and the environment and
attainment of ARARs. The NCP states that the acceptable risk range for human health is 10-4 to 10-6 for
Superfund sites. Based on the nine criteria and the risk range specified in the NCP, EPA cannot justify
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cleaning up to background levels for all contaminants at Lowry.

Performance standards listed in the ROD, including ARARs and TBC values, use the most current information
available at the time the ROD is issued.

Comment

Will there be provisions for alteration of the PRGs in the future as SDWA regulations become more
comprehensive and stringent?

Response

CERCLA mandates EPA review of the remedy no less often than every 5 years as long as any wastes remain at the
Site, allowing the remedy to be modified if it is not protective of human health and the environment.

Comment

Will any offsite ground-water degradation be allowed to occur before pumping from the barrier system is
initiated? The EPA monitoring, as well as the District's own monitoring, indicate that the ground water
underlying the District has not yet been impacted by the Lowry facility. The District's wells produce water
containing some natural mineralization, but no organic or other induced contaminants. The District feels
very strongly that the contaminant plume should be contained on Section 6, and should not be allowed to
migrate off the Site onto the District at any levels. The District feels this is particularly important
since the recommended alternative is not an effective cleanup proposal, but is in truth a containment
program. The District recommends that a "trigger" level for starting the operation of the containment well
system on the west boundary be set at some agreed upon background level rather than the PRGs. The water the
District currently delivers to customers is well within mandatory SDWA standards, and the District does not
want a portion of its water supply to deteriorate to a marginal level of acceptance.

Response

Offsite migration of contaminated ground water, as measured by the performance standards, including ARARs,
will not be allowed to occur beyond the compliance boundary. Monitoring at the POA will allow guick response
action to ensure that contaminants above performance standards, including ARARs, are not allowed to migrate
beyond the compliance boundary.

Based on the nine criteria and the risk range specified in the NCP, EPA cannot justify cleaning up to
background levels for all contaminants at Lowry.

Comment

Removal of Waste-Can any of the pits be effectively pumped to help reduce the volume of waste on the Site?
The recommended alternative removes only relatively small amounts of waste from the Site. Instead, it relies
upon containing the Site throughout the foreseeable future. If it appears that the pits as a whole cannot be
effectively pumped, the District would like to know if there are select pits that could be pumped efficiently
to help reduce the overall toxicity of the Site and diminish the long-term threat to the ground water.

Response

EPA evaluated the effectiveness of waste pit pumping and found that only a small portion of wastes can be
removed through pumping. Residual contamination of liguids that are sorbed onto various waste materials will
provide a continuous source of ground-water contamination. Excavation and disposal of the contents of
shallow waste pits in the former tire pile area is part of the selected remedy for OUS 2 & 3.

13.2.5 EPA's Response to Comments from William G. Kennedy

Comment

Page 8, Table 1 of the Proposed Plan for OUS 1 & 6, last column-shows costs of Alternative 5 to be $59
million and Modified Alternative 5 to be $61 million. Page 6 shows costs of Alternative 5 and Modified
Alternative 5 to be $17,680,000 and $21,100,000 respectively. What is the reason for this discrepancy?

Response

The $17,680,000 for Alternative 5 and $21,100,000 for Modified Alternative 5 represent the funds needed to
design and construct the components of the project in a period of 3 years. These costs are referred to as
the capital costs. In addition to the capital costs, EPA has estimated the cost to operate and maintain the
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project, typically referred to as O&M costs. The present worth is the amount of money you would need to have
today, assuming that this money would collect 5 percent interest per year, to construct and operate the
remedy for 30 years. The $59 million for Alternative 5 and $61 million for Modified Alternative represent
the 30-year present worth values for both capital and O&M costs.

Comment

Present worth cost figures are estimated for all alternatives, but no mention is made of the interest rate
used to amortize present worth over 30 years. There is no indication that the cost figures are estimates.

Response

EPA assumed a 5-percent discount rate. The FS report provides detailed information on cost estimates. EPA
agrees that the costs are estimates. The accuracy of the estimate is subject to substantial variation since
very little detail is known about the specific design of each alternative. Typically, the cost estimates are
expected to be no more accurate than -30 percent to +50 percent.

Comment

Figures 1, 2, and 3 indicate a "current landfilling area" in Section 36 to the north, just outside the
compliance boundary of the Proposed Plan. Is this an imminent future Superfund site?

Response

No. Superfund was established to provide funding and enforcement authority for past hazardous waste
activities. The current landfill area in Section 31 deals with solid, not hazardous waste and is permitted
under Colorado Hazardous Waste Management Regulations (CHWMR), which is a "cradle-to-grave" regulatory
program for active landfilling facilities.

Comment

The Proposed Plan mentions OUS 2, 3, 4, and 5, but does not delineate their location on Figures 1, 3, or 4.
Perhaps the above-mentioned "current landfill area" is actually OU 2, 3, 4, or 5. Could the Proposed Plan be
edited to clarify this confusion?

Response

Operable Units (OUS) 2, 3, 4, and 5 refer to media addressed at the Lowry Landfill Superfund Site located in
Section 6. The OUS refer to the following media:

Landfill Solids, OU 2
Landfill Gas, OU 3
Soils, OU 4
• Surface Water and Sediments, OU 5

Their location is shown in the attached figures. The current landfill area is located in Section 31,
immediately north of Section 6.

Comment

The word "Permanence" in conjunction with Long-Term Effectiveness appearing at the top of page 8 is defined
on page 9 as "...the ability of a remedy to provide reliable protection of human health and environment over
time." The phrase "over time" is meaningless. Could the word "permanence" appearing in the Proposed Plan be
guantified in number of years?

Response

The phrase "over time" was used because EPA is reguired to determine the magnitude of residual risk remaining
at the Lowry Landfill site after the remedy is implemented and to determine the adeguacy and reliability of
the remedial measures and onsite institutional controls to manage remaining wastes. In this way, the
long-term effectiveness and permanence of the selected remedy can be demonstrated over time.

The word "permanence" cannot be guantified in years because the selected remedy is a containment type of
remedy. Since wastes will remain on the Site, containment and treatment will continue in perpetuity.

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Comment

Page 10, Short-Term Effectiveness. The text that follows this heading addresses risk to construction
workers, 3-year construction period, and special health protective measures. This text has no bearing on the
word "Effectiveness" and vice versa. This is a nonseguitur. If Short-Term Effectiveness were changed to
"Short-Term Adverse Effects," readers would be less confused. Could either the heading or the text be
changed to make sense (in English)?

Response

The NCP defines short-term effectiveness as the short-term impacts of the alternatives. EPA agrees that the
short-term effectiveness is measured by the magnitude of the short-term adverse effects of implementing a
remedy.

Comment

Short-Term Adverse Effects that may be unavoidable during construction include increased dust, noise,
traffic, and perturbance of toxic leachate. Does EPA intend to address these adverse effects to human health
and environment in the final Proposed Plan?

Response

Dust, noise, and traffic will be addressed in the final design of the remedy. Other short-term adverse
effects will be covered by the Occupational Safety and Health Act, which addresses hazardous exposures in the
work place, and the Emergency Planning and Community Right-to-Know Act, which addresses unanticipated
environmental releases.

Comment

Page 9, Implementability. The Proposed Plan does not acknowledge the differential dumping by the PRPs, that
large companies were the major contributors, and that lawsuits are likely to be the greatest obstruction to
implementability.

Response

The items listed in the comment relate to cost recovery. Selection of the remedy and cost recovery are two
distinct phases of the Superfund process. In general, EPA addresses cost recovery issues after the remedy is
selected.

Comment

Please regard these comments as honest inguiry and not as criticism. Everyone at EPA that 1 talked to on the
telephone, relative to Lowry or any other environmental concerns, have been outstandingly courteous, helpful,
and prompt. Despite comments herein, please count me as one in favor of the Proposed Plan as written.

Response

EPA acknowledges support of the selected remedy for OUS 1 & 6 as expressed in the Proposed Plan.

13.2.6 EPA's Response to Comments from the Lowrv Coalition

Comment

The Lowry Coalition agrees that Alternative 5, as modified, meets the criteria that EPA must consider in
evaluating remedial actions at CERCLA sites, and, in particular, meets ARARs and achieves overall protection
of human health and the environment. The Lowry Coalition supports EPA's Proposed Plan.

Response

EPA acknowledges support of the preferred remedial alternative for OUS 1 & 6 as expressed in the Proposed
Plan.

13.2.7 EPA's Response to Comments from Robert Velton, Pemex, Inc.

Comment

My proposal for a Proposed Plan modification and/or Revision of Closure Plan for the Sussguehanna Hazardous
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Waste Site in Pueblo, Colorado, should be reviewed because it has some different approaches, some technical
data, and some private sector thinking that may interest you at the Lowry site.

Response

The alternative methodology proposed for the Sussguehanna site is recycling. Based on Table 1 of your
proposal, you have concluded that no reasonable alternative to containment exists for the Lowry Landfill
site. Containment is part of the selected remedy for OUS 1 & 6. Your entire proposal is being retained as
part of the Administrative Record for those OUS.

13.2.8 EPA's Response to Comments from United States Department of Interior, Fish and Wildlife Service

Comment

The U.S. Fish and Wildlife Service (USFWS) wishes to convey its concern for potential adverse impacts to
natural resources by encouraging EPA to conduct an ecological risk assessment for OUS 1 & 6 if one has not
already been completed. Decisions for interim actions and final remedy should be based on valid ecological
risk assessments. We also encourage EPA to consider the Endangered Species Act, Fish and Wildlife
Coordination Act, Migratory Bird Treaty Act, and the Bald Eagle Protection Act in planning for interim
actions and final remedies.

Response

EPA prepared an ecological risk assessment as part of the Baseline Risk Assessment for Lowry OUS 2 & 3 and 4
& 5. Other ecological evaluations appear in the Preliminary Endangerment Assessment and the Remedial
Investigation Report for the Shallow Ground-Water and Subsurface Liguids and Deep Ground-Water Operable
Units. The Lowry Coalition conducted an Evaluation of Potentially Protected Resources for the Lowry Landfill
site and adjacent areas. This evaluation included an evaluation of threatened and endangered species. The
Lowry Coalition also conducted an investigation of the distribution of wetlands in the area. This evaluation
includes a description and mapping of wetlands and a gualitative delineation of specific wetlands vegetation.

A list of the potentially endangered and threatened species thought to occur in the area of the Lowry
Landfill site is included in the Baseline Risk Assessment for OUS 2 & 3 and 4 & 5. Among the species listed,
there are several species of raptor and terrestrial carnivore that may be subject to bioaccumulation
processes. These species include the Peregrine Falcon, the Bald Eagle, and the Swift Fox. While none of
these species have been observed at the Lowry Landfill Site, the USFWS considers the area a possible habitat
for these organisms.

The Lowry Coalition identified several endangered species that may be present in the vicinity of the Lowry
Landfill site, including the Bald Eagle, Peregrine Falcon, Whooping Crane, and Black-footed Ferret.
Threatened species that may be present include the Ferruginous Hawk, Mountain Plover, Long-billed Curlew,
Preble's Jumping Mouse, Swift Fox, Colorado Butterfly Plant, and Diluvium Lady's Tresses.

EPA will use information from the ecological risk assessments in making decisions for the final remedy for
the Lowry Landfill site.

13.2.9 EPA's Response to Comments from Waste Management of Colorado, Inc., Chemical Waste Management, Inc.,
and the City and County of Denver

Comment

In general, Waste Management of Colorado, Inc., Chemical Waste Management, Inc., and the City and County of
Denver (WMC/CWM/Denver) agree with the remedial alternative that EPA has selected for the shallow and deep
ground-water and subsurface liguids OUS. The concept of containing and treating ground-water contamination
at Lowry is supported by WMC/CWM/Denver based upon:

1. The significant short-term health risk that would be posed by removing all contaminated
materials at the Site, its technical impracticability, and cost/benefit;

2. The proven inability at the Site to remove all of the contaminated liguids from the landfill
mass and underlying and surrounding subsurface by pumping and treating due to low permeability;
and

3. EPA's Baseline Risk Assessment, which showed that ground water at Lowry poses no current health
risk, and only future risk if a number of very conservative assumptions are made about the
hydrogeology of the area, and future land and water use.
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Response

EPA acknowledges support of the preferred remedial alternative for OUS 1 & 6 as expressed in the Proposed
Plan.

Comment

In describing the practice of co-disposal, EPA states on page 3 of the Proposed Plan that "it was thought
that the municipal refuse would act as an absorbent for the liguid wastes." While not 100 percent effective,
municipal refuse did, in fact, absorb or retain much of the industrial liguid disposed of at the Site. This
is evidenced by the presence of "perched" waste pits in the western portion of the Site, the presence of 95
million gallons of contaminated liguids still within waste pits, 14 million gallons of contaminated liguids
in saturated refuse, and the proven increase in contaminant levels within the unsaturated refuse within the
zone formerly containing waste pits.

Response

EPA discussed the procedure of co-disposal in the Proposed Plan to describe what was an accepted disposal
practice in the past. This practice is no longer acceptable. EPA agrees that the refuse acts as an
absorbent for the liguid industrial waste, but notes that refuse does nothing to address contamination from
that waste. Unfortunately, a large volume of waste pit liguids migrated beyond the boundary of the pits and
as a result, has contaminated every media at the Site.

In addition, it is also the presence of the refuse that makes liguid recovery difficult, if not impossible,
and not cost-effective. EPA disagrees that waste pits in the western portion of the Site are "perched." The
Lowry Coalition for OUS 1 & 6, dated March 1992, concluded that the waste pits are in direct hydraulic
connection with ground water. EPA agrees with this conclusion.

Comment

EPA states on page 4 of the Proposed Plan that "the COCs identified in OUS 1 & 6 are the result of liguids
from the buried waste pits and leachate from the buried refuse." There is absolutely no evidence that refuse
at the Site contributed to contamination of media in OUS 1 & 6, nor is there any evidence that any liguids
were generated or infiltrated through municipal waste at Lowry.

Response

There is evidence that refuse may have contributed and could continue to contribute to contamination of media
in OUS 1 & 6. As stated in the draft RI report for OUS 2 & 3, up to 2,700 cubic feet of water per year could
be percolating through the landfill. On the basis of the results of the column leachate study, the flux from
the landfill mass based on this flow is estimated at 34,980 mg/day of toluene. These estimates are based on
the current condition where the landfill has a clay cap covering it. In the past, before the cap was placed,
even more liguid would have percolated through the landfill.

There is also evidence that liguids were generated, or infiltrated, through municipal waste at the Lowry
Landfill site since small guantities of leachate have been noted to exist within the unsaturated landfill
mass during site investigations.

Comment

In the first bullet in the discussion of the Baseline Risk Assessment, EPA discusses future onsite residents
and future use of onsite ground water. Denver, as owner of the Site, regards future onsite residents or
residential ground-water use as extremely unlikely. In 1991, Denver's mayor issued Executive Order No. 97,
which placed restrictions on the use of land, surface water, and ground water at the Site. These
restrictions included the following:

• No direct use or reuse shall be made of the ground water in the Denver or Dawson aguifers
underlying the Site that could cause exposure of humans or animals to contaminants in said
water.

• No direct use or reuse shall be made of ground water in the Arapahoe and Laramie-Fox Hills
aguifers underlying the Site for domestic, residential, or municipal water supply purposes.

• The Site shall not be used for agriculture, residential development, or commercial development.

Executive Order No. 97 officially states the policy of Denver regarding use of its property. This policy has
been followed since the adoption of the executive order by both the Pena and Webb administrations. In view
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of the identified health risks at the Site and Denver's commitment as a governmental entity to the protection
of human health and the environment, this policy is not expected to change.

To further address concerns over the permanence of these controls, Denver Mayor Webb recently committed to
formalizing these controls such that they were permanently enforceable by a responsible third party. Denver
has recently proposed language to EPA and CDH for a declaration of covenants to run with the land. In the
proposed covenants, EPA and CDH, as well as Denver, have enforcement authority to restrict land and
ground-water use at the Site.

Response

Denver appears to be suggesting that EPA should not have used a residential-use scenario in the Baseline Risk
Assessment because of Executive Order No. 97. It is EPA's policy not to consider institutional controls when
conducting Baseline Risk Assessments. Furthermore, EPA has made a risk management decision to retain the
residential scenario when evaluating remedial alternatives because there is residential development in the
area and the ground water will potentially be used for residential consumption. For this and other reasons,
EPA has determined that it is reasonable to assume that the Site could be used for residential purposes in
the future.

As stated in the risk assessment for OUS 1 & 6, Executive Orders may be overturned by this or any future
administration, and therefore do not gualify as permanent enforceable institutional controls. EPA
acknowledges Denver's recent proposal for covenants to run with the land and agrees that this type of
institutional control may meet some of EPA's concerns about permanent enforceability. As described in the
ROD, offsite institutional controls shall serve as an additional measure of protection to enhance the
effectiveness of the selected remedy and to act as preventative measures to preserve the implementability
and effectiveness of any of the selected remedy contingency measures. Offsite institutional controls shall
include, but not be limited to, deed notices and restrictions, zoning controls, and well restrictions. These
controls must prohibit all offsite activities in the vicinity of the Lowry Site that would interfere or be
incompatible with, or that would in any way reduce or impair the effectiveness or protectiveness of, the
selected sitewide remedy.

Comment

In the second bullet discussing the Baseline Risk Assessment, it should be noted that contaminants in offsite
ground water posing an unacceptable health risk are not anticipated for at least 50 years.

Response

The 50-year estimate is solely an estimate. Given the uncertainty associated with numerical models, EPA
believes is prudent to assume a wide margin of error with respect to numerical predictions.

Comment

EPA, on page 4, states that "Executive Order No. 97, as issued by the City and County of Denver, would be
enforced." Who does EPA anticipate will enforce these land-use restrictions? Have these enforcement costs
been included in the total remedial costs?

Response

Since Executive Order No. 97 was written and signed by the Mayor of Denver, EPA expects that Denver would use
its enforcement authorities to ensure that the components of the Order are followed. Furthermore, the land
is owned by Denver. Enforcement costs for implementing this Executive Order have not been included in the
cost of remedy. EPA does not know if the City of Denver has an enforcement budget to enforce this Executive
Order.

Comment

EPA should explain the discrepancies between its Modified Alternative No. 5 described in the Proposed Plan,
and Alternative No. 5 as described in the OUS 1 & 6 FS.

In the FS, east and west boundary containment is composed of 100-foot-deep wells, while in the Proposed Plan,
east and west containment is composed of 50-foot-deep wells or collection systems. Also, the extent of the
southern portion of the west boundary system is dissimilar.

EPA should clarify if the Lowry Coalition's assumptions about the use of wells is included in Modified
Alternative No. 5. If not, and the lateral control systems consist of barrier walls, collection trenches, or
other engineering control, then the cost guoted for the lateral control systems are not correct. At a
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minimum, if EPA intends to delay the decision about the proper engineering control until remedial design,
then a sensitivity analysis of cost impacts of differing designs would be appropriate.

EPA apparently has used the Lowry Coalition's present value cost estimate for Alternative No. 5 as the basis
for its present cost for Modified Alternative No. 5. It is important to note that Alternative No. 5, as
priced in the OUS 1 & 6 FS, had lateral control systems that solely consisted of wells that are monitored
over time, with no money ever allocated for electricity, well maintenance or replacement, or treatment of the
collected ground water. WMC/CWM/Denver support the idea of monitoring the east and west boundaries for
contamination, without implementing remedial action prior to arrival of contaminants, particularly given the
OUS 1 & 6 ground-water modeling results, showing that contamination is not expected at the east or west
boundary for at least 50 years. Any premature pumping of these systems may exacerbate the potential for
lateral ground-water contamination.

Response

EPA has modified Alternative 5 from the FS and has renamed it Modified Alternative 5. The modifications
consist of an additional upgradient containment/collection and/or diversion system on the southern boundary
of Section 6 of the Lowry Landfill Superfund Site.

In Appendix C of the FS Report dated October 1992, the Lowry Coalition provided cost estimates for depths of
50, 65, and 100 feet for extraction trenches. EPA has determined that 50-foot depths will fulfill the
functions of the barrier wall and/or collection system, in that the weathered Dawson is believed to be the
primary pathway of contaminant migration. The weathered Dawson's depth does not exceed 50 feet.

EPA modified the southern portion of the western boundary to be closer to the source area and thus captures
the migration of contamination closer to the source.

EPA used the assumptions outlined in Table 5.14 in the FS Report dated October 1992. EPA developed a cost
estimate for Modified Alternative 5 based upon a 50-foot depth barrier wall and the same length as shown in
Figure 5.51 in the FS Report. EPA reguires that cost estimates for the final FS should be in the range of
+50 percent/-30 percent range. The Modified Alternative 5 has been completed within this range.

Table 5.14 of the FS Report shows costs for electrical power, well replacement, well maintenance and well
cleaning with acid. Tables C3 and C5 show start-up costs and operation and maintenance costs for the
treatment plant. Based upon the January 1993 Compliance Boundary Sampling event, there is confirmed
contamination in B301A and B216A at the western boundary of the Site. Therefore contaminants have migrated
to the compliance boundary and remediation is reguired. EPA agrees that if extraction wells were used,
pumping could cause lateral contaminant migration. This supports the selection of barrier walls over
extraction wells.

Comment

EPA should explain why the southern boundary in the Proposed Plan is designed to a 50-foot depth, while in
HLA's response to EPA comments on the FS, the southern boundary is designed to a 60-foot depth.

Response

See response to the above comment.

Comment

EPA should explain the technical basis for the upgradient containment, collection, and/or diversion system.
The design and cost for the system described in the Proposed Plan is dissimilar to that contained in the
Responsiveness Summary to EPA comments on the draft FS report.

Response

The upgradient system proposed to control the flow of ground water into the Site is conceptualized to
intercept clean ground water flowing from the south into the Site. It is anticipated that the system will be
composed of a barrier wall and an extraction system. A barrier wall will limit the impact of the extraction
system on the ground-water hydraulic gradients inside the Site.

The additional cost associated with the upgradient system is anticipated to be approximately $2 million.
This cost will be offset by the benefits derived from the upgradient system. The following benefits have
been identified:
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• Enhanced isolation of site contaminants. January 1993 sample results along the southern
boundary confirmed contamination that exceeds the preliminary remediation goals.

• Prevention of offsite contamination migration, which may occur through the unidentified sand
stringers/sand channels and other geologic heterogeneities.

• Mitigation of contaminant migration on the south, resulting from localized ground-water flow to
the south, chemical diffusion, dispersion, or possible unidentified, localized seasonal changes
in ground-water flow direction.

• Prevention of most clean ground water from entering the contaminated site, thus reducing the
treatment cost associated with other onsite collection systems.

Modified Alternative 5 costs are different from those for Alternative 7B in the responsiveness summary
because Modified Alternative 5's cost estimate was developed by EPA.

Comment

EPA should state that the present value costs calculated for the preferred alternative are greatly influenced
by the financial assumptions made. EPA has assumed in its costing, as did the OUS 1 & 6 FS documents upon
which EPA relies, a "real interest rate" of 5 percent over the next 30+ years (real interest meaning the
difference between the discount rate and inflation).

EPA should carefully consider the aggressiveness of its financial estimates. It is unlikely that one could
invest monies today and earn, after taxes, a 5 percent greater return than inflation. This point is readily
apparent today, when inflation is running at approximately 4 percent per annum. EPA's financial assumptions
would mean that one would have to generate a 9 percent return on investment, after taxes. If a PRP were
paying 38 percent taxes, then EPA's financial assumptions would be that a PRP would have to make about a
14.5 percent pretax return on investment. Given that commercial paper in today's market is yielding only
approximately 3.5 percent, EPA's aggressive financial assumptions must be guestioned.

Response

EPA agrees that the present worth analysis is influenced by the assumed discount rate and timing of
expenditures. However, the purpose of the present worth analysis is to compare the alternatives on a
relative basis, not to determine the total PRGs cost of any remedy with a high degree of accuracy. The
accuracy of the estimate for each individual remedy is subject to substantial variation since little detail
is known about the specific design of each alternative. Typically, such "order-of-magnitude" estimates are
expected to be no more accurate than roughly -30 to +50 percent.

In reviewing this comment, EPA performed an approximate check to assess whether or not the chosen present
worth discount rate would affect the relative ranking of the alternatives on a cost basis. The method was
only an approximation and used the following procedure:

1. Capital costs, annual O&M costs, and implementation times were taken from the Proposed Plan.

2. Capital costs were assumed to occur in two or three egual mounts at the end of each of two or
three implementation years as given in the Proposed Plan. For example, for Alternative 2
(capital cost = $9,819,000; time to implement = 2 years), an expenditure of $4,905,500 was
assumed at the end of year 1 and year 2.

3. O&M costs were assumed to occur at the end of each of 30 years succeeding the final year of
implementation. For example, for Alternative 2 an expenditure of $1,816,000 was assumed to
occur for 30 years, beginning at the end of year 3.

4. The present worth of the capital and O&M expenses were calculated at the beginning of year 1,
then summed.

The results are presented in the attached table.

Since the flows for capital costs projected by the PRPs' consultants, HLA, were more detailed than the simple
egual annual amounts used in the above procedure, the calculated present worth for 5-percent discount rates
are not identical. However, they are all within 8 percent, which is well within the expected accuracy of the
estimates.

A comparison of the calculated present worth for each discount rate shows that, in all cases, the relative
ranking of the alternative costs remains the same.
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The selection of a discount rate for present worth analysis is not intended to predict future interest rates,
tax effects, or other financial factors. A present worth analysis is simply a technique to permit relative
comparison of options on a cost basis. The actual cost of the selected remedy may vary depending on many
factors, including design details, bidding climate, changes during construction and operation, interest
rates, labor and equipment rates, inflation, tax effects, and similar items that neither EPA nor the PRPs can
control.

Comment

The OUS 1 & 6 FS cost estimates are only for a duration of 30 years. It is highly unlikely that remedial
action at the Site will terminate in 30 years. As EPA stated in its comments on the OUS 1 & 6 draft FS
report, "the ground-water model indicates that dissolved contaminants will increase risks up to 800 years."
EPA should address the length of the remedial action necessary, and state its long-term impact upon the cost.

Response

The treatment of contaminated ground water is likely to continue in perpetuity. The impact to the cost can
be estimated using the same O&M and discount rate for the length of time desired. The Lowry Coalition has
provided tables in Appendix H of the FS Phase 3 Report that describe how the present worth costs are derived.
The PRP would need to invest less than $5,000 today to be able to fund $107,000 of O&M 63 years from now
using a 5 percent discount rate. The amount needed to be invested today for O&M needed 800 years from today
is negligible.
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Table 13-1
Lowry Landfill, Arapahoe County, CO, Operable Units 1 and 6, Proposed Plan, Effect of Discount Rate on Cost
Estimates

Alternative
No Action
1
2
3
4
5
Modified 5
6
Time to
Implement
(yrs)
0
0
2
3
3
3
3
3
PW in
proposed
Plan
($000)
0
31,000
36,000
56,000
101,000
59,000
61,000
66,000
Present Worth of Capital + O&M Costs ($000)
Discount Rate (percent/annum)

2
0
45,976
49,959
77,916
129,512
80,859
85,074
91,181

4
0
36,706
39,284
60,188
108,969
62,872
66,712
70,988

5
0
33,220
35,314
53,653
101,205
56,232
59,921
63,533

6
0
30,301
32,008
48,237
94, 652
50,725
54,281
57,347

8
0
25,748
26,881
39,898
84,260
42,231
45,562
47,803

10
0
22,423
23,152
33,883
76,420
36,088
39,235
40,898

12
0
19,932
20,357
29,409
70,296
31,505
34,495
35,744

14
0
18,021
18,203
25,984
65,362
27,985
30,840
31,782
PW = Present worth costs
O&M = Operation and maintenance
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Comment

EPA's preferred alternative requires constructing collection systems at the east and west boundaries. The
design life of these collection systems using extraction wells is assumed to be 4 years in the FS. If
contamination requiring remediation is not anticipated at the east and west boundaries for at least 50 years,
the extraction wells will need to be replaced 12.5 times before they are needed. Construction of the
collection systems at this time is certainly not cost-effective.

Response

The FS assumes 25 percent of the wells would be replaced every 4 years, therefore the design life of any one
well could be as little as 4 years and as much as 16 years. Most current wells at the Site are about 10
years old and do not require abandonment and replacement. Based upon the January 1993 Compliance Boundary
Sampling event, there is confirmed contamination in B301A and B216A at the western boundary of the Site.
Therefore containments have migrated to the compliance boundary and remediation is required.

Comment

EPA's preferred alternative shows a new ground-water treatment facility, the purpose of which is to treat
high-concentration fluids extracted from the ground-water collection system at the northern toe of the
existing Section 6 landfill mass. While treatment of fluids from this extraction system will be necessary,
it may be possible to adequately treat these fluids at the existing upgraded treatment plant, or to modify
the plant. EPA should not require a new treatment plant, but rather should allow the need for a new
treatment plant versus the existing plant (or modification thereof) to be fully evaluated during remedial
design.

Response

The selected sitewide remedy must meet the performance standards, including ARARs. Whether this is achievable
via modification of the existing plant, or whether a new plant must be constructed, will be determined by EPA
during RD.

Comment

EPA has chosen modified Alternative No. 5, in part, because of its increased reduction of contaminants over
other alternatives. However, modified Alternative No. 5 represents a doubling of the 30-year present worth
costs over the No Further Action Alternative. The cost/benefit of this doubling should be weighted against
the fact that nearly 80 percent of the contaminants of concern will remain in the subsurface after 30 years
(calculated by multiplying the mean concentration of COG in the weathered system, as reported in the OUS 1 &
6 final RI report, by the volume of contaminated ground water, then dividing by the anticipated rate of COG
removal rate of 700 pounds per year).

Response

EPA's selection of Modified Alternative No. 5 shows EPA's commitment to prevent migration offsite while
simultaneously treating to the maximum extent practicable and still be cost-effective.

Comment

In its Responsiveness Summary on the draft FS report, HLA indicated that the south boundary system will
intercept about 21,000 gallons of ground water per year. HLA also calculated in the RI report that the Site
contains in excess of 900 million gallons of contaminated liquids. Preventing 0.002 percent of the
contaminated ground-water volume to flow into the Site seems insignificant when compared to the total volume
of contaminated ground water at the Site. EPA should provide a cost/benefit analysis of the southern
barrier.

Response

EPA believes that the estimated 21,000 gallons of ground water per year expected to be intercepted by the
south boundary system will constitute substantially more than 0.002 percent of the contaminated water at the
Site since the 900 million gallons of contaminated liquids will not all be extracted within a year. As
discussed earlier, south boundary water interception is one of many benefits of the south boundary system.

The benefits derived from the upgradient system at an additional estimated cost of $2 million are as follows:

• Enhanced isolation of site contaminants. January 1993 sample results along the southern
boundary confirmed contamination that exceeds the preliminary remediation goals.
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• Prevention of offsite contamination migration, which may occur through the unidentified sand
stringers/sand channels and other geologic heterogeneities.

• Prevention of most clean ground water from entering the contaminated site, thus reducing the
treatment cost associated with other onsite collection systems.

13.2.10 EPA Response to Comments from Wilbur A. Young

Comment

The commentor expressed a concern over the PRPs' commitment to protecting the environment.

Response

Many PRPs at the Lowry site have been responsive in answering guestions regarding the types and amount of
waste materials deposited at the Lowry Site in their 104 (e) responses. In addition, certain PRPs have
performed RI/FSs at the Site, and have implemented interim remedial measures such as the installation of the
barrier wall and construction of a ground-water treatment facility to stop northward migration of
contaminants.

Comment

The commentor also expressed a concern over the potential risks to human health and the environment posed by
the Site.

Response

A risk assessment was performed to assess potential human health problems, and an ecological risk assessment
was conducted to assess potential adverse effects on wildlife and plants. The cleanup strategy is protective
of human health and the environment. The remedial investigation describes the fate and transport of chemicals
at the Site, including degradation products. The risk assessment, which is based on results of the Remedial
Investigation, addressed both cancer risks and adverse chronic health effects from chemicals at the Lowry
Site.

Comment

The commentor expressed concern over the PRPs' commitment to environmental regulations and laws.

Response

See response to first comment, above.

Comment

The commentor was concerned about individuals coming forth to provide the government additional information
about dumping at Lowry.

Response

EPA has received information, both official (as in the 104(e) responses) and unofficial (such as anonymous
reports of dumping).

Comment

The commentor stated that Modified Alternative 5 is the best alternative based on cost.

Response

EPA acknowledges support of the preferred remedial alternative for OUS 1 & 6 as expressed in the Proposed
Plan.
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Section 14.0
Responsiveness Summary for Operable Units 2 & 3 and 4 & 5

This section presents the oral and written responses to comments from EPA to individuals, concerned citizen
groups, and public entities who have commented on the Proposed Plan for OUS 2, 3, 4, and 5. Comments are
expressed in italics; their responses in plain text.

14.1 Response to Oral Comments Proposed Plan Public Meeting Lowrv Landfill Solids/Gas Operable Units (OUs
2&3) and Soils/Surface Water and Sediments Operable Units (OUS 4&5) September 21. 1993

The following is a summary of citizens' comments received at the September 21, 1993 Proposed Plan Public
Meeting for OUS 2, 3, 4, and 5. The responses given at the public meeting are also listed, and in some
circumstances have been expanded for a more detailed explanation.

1. Comment

How much of the capital costs for cleanup have already been incurred for such items as the Surface Water
Removal Action?

Response

The costs of the interim measures including the Surface Water Removal Action, the ground-water barrier wall
and treatment facility, and the tire shredding operation, have already been expended and are not included in
the total capital costs for the various remedial alternatives.

The approximate cost of the Surface Water Removal Action was 1.5 million dollars. The approximate cost of
the shredding operation was 2.3 million dollars.

2. Comment

Who is in charge of maintenance for the first 30 years and what happens after 30 years? Does EPA walk away ?

Response

Maintenance of the site for the first thirty years, and thereafter, is the responsibility of the Potentially
Responsible Parties (PRPs) that sign up to implement the remedies under the supervision of EPA and the
Colorado Department of Health. EPA often uses a standard period of 30 years to estimate operation and
maintenance costs, so that comparisons can be made between alternatives and between all Superfund sites. For
Lowry Landfill, the lifespan of the sitewide remedy may very well exceed 30 years.

3. Comment

Why aren't all the responsible parties being held accountable for the cost of paying for cleanup at Lowry?
Who will pay for the cleanup?

Response

Under Section 107 of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as
amended (CERCLA), current owners and operators, past owners or operators, transporters and/or generators are
liable for cleanup costs incurred by the United States or a State at a Superfund site. EPA considers each of
these Potentially Responsible Parties (PRPs) to be jointly and severally liable for the costs of cleanup at
the Lowry Landfill site.

The City and County of Denver (Denver), Waste Management of Colorado, Inc. (WMC), and Chemical Waste
Management, Inc. (CWM) have negotiated private settlement agreements with many of the other PRPs at the site.
Although the terms of those settlements have not yet been made available to EPA, Denver and WMC/CWM have
indicated that they intend to perform the cleanup of the site and use monies collected under the private
settlement agreements to reimburse the United States for past and future response costs incurred at the site.

4. Comment

How much of an excavational alternative was considered? Does the excavation alternative include all six
operable units? The reason it wasn't financially viable in part was because Waste Management put six years of
trash on top of the Superfund site?
-------
Response

Excavation of the Lowry Landfill was evaluated in a Technical Memorandum, Preliminary Identification of
Remedial Alternatives, dated April 15, 1988. At that time, it was determined that it was not financially
viable or practical to excavate the entire site. In addition to ground-water treatment, the excavation
alternative included excavating the entire site, incinerating the solids and soils onsite, and disposing of
the incinerated ash offsite. Estimated total capital and operation and maintenance costs for the excavation
alternative would exceed $4.5 billion. Additionally, the volume of ash would be on the order of 40 percent
of the incinerated material. Disposal of the ash would take over 19 years with a dump truck full of ash
leaving every half hour, every day of the year. Onsite worker exposure to hazardous materials was also
determined to be a high safety risk. The excavation analysis that was performed applies to the entire site,
and therefore to all six operable units in combination.

The proposed excavation for the former tire pile area does not address all six operable units; it only
addresses a portion of operable unit 2 (landfill solids).

The additional trash placed on the landfill from the time that it became a Superfund site (September 1984) to
the last time trash was placed on the site (August 1990) was taken into consideration during EPA's evaluation
of cleanup proposals. EPA does not endorse the proposal to place an additional 1.2 million cubic yards of
municipal solid waste on the Lowry Site, as has been proposed by Waste Management of Colorado, Inc.

5. Comment

How does the ground-water treatment system work?

Response

Contaminated ground water is collected at the barrier wall and pumped to the onsite treatment facility. At
this facility, ground water is first processed through an airstripper. As the contaminated ground water
passes through the airstripper, contaminants volatilize (turn into a gaseous phase) and are removed from the
water. These volatilized contaminants are then collected on granular activated carbon. The liguid that
flows out of the airstripper is sent through a series of granular activated carbon units for additional
treatment. The treated water is injected into the shallow ground-water system downgradient of the barrier
wall.

If the collected ground water is observed to exceed concentrations above federal and state standards, a
contingency plan for ground-water treatment will be implemented. The contingency plan includes a bioreactor
and an ion exchange unit to remove ketones and metals/radionuclides, respectively, from the collected ground
water.

6. Comment

Will new wetlands be constructed?

Response

During the Remedial Investigation for Operable Units 1 and 6, wetlands were identified in the former Unnamed
Creek drainage. As a result of the construction of the Surface Water Removal Action, these wetlands were
eliminated. New wetland habitats (0.87 acres) will be constructed to replace the wetlands that were lost.
The final location of the wetlands will be specified during the Remedial Design phase.

7. Comment

What types of contaminants were found in the water?

Response

For this response, it is assumed that the commentor was referring to ground water at the site. A list of
chemicals found in ground water, and their reported concentrations in the ground water at the site, is
provided in Table 14-1.

8. Comment

Would vitrification be a viable cleanup alternative for the Lowry Site?
-------
Response

No. Vitrification is a process in which electric probes are inserted into contaminated soils. The targeted
material is electrified to the point that it melts and then solidifies as a "glass," rendering the
contaminants immobile. Because of the presence of methane and other gases in the Lowry Landfill, the
electric current used in the vitrification process could result in explosions or fires. Also, the
composition of the landfill mass varies significantly (trash, garbage, liguids, etc.) and makes it unsuitable
for heating, melting, and solidification.

9. Comment

In the cancer risk assessment for sediments, it appears that the risk is higher north in Murphy Creek than in
Section 6. Why?

Response

First, it should be noted that the area identified as "north in Murphy Creek" is in fact within Section 31.
Two factors contribute to the higher future risk estimates identified for the sediments in Section 31.
First, the land use scenarios employed for Section 6 were different than for Section 31. To assess the
potential risks, a combined residential/recreational scenario was used for Section 31, while a recreational
only scenario was used for Section 6. This approach was based on the assumption that there would likely be
restrictions on residential land use for Section 6.

For Section 31 sediments, ingestion and inhalation exposures were calculated for both future offsite
residents (children and adults) and offsite recreational users. Risk assessment calculations for the
sediments in Section 6 were estimated based on ingestion exposures to future onsite recreational users
(children and adults) only. In estimating potential health risks, exposure periods and contact times are
typically higher for residential scenarios than for recreational scenarios. Conseguently, calculated health
risks may be expected to be higher for calculations in which a residential scenario is used.

Second, the contaminants identified in Section 6 sediments differed, in some cases, from those identified in
Section 31 sediments. The contaminants that contributed the highest proportion of the estimated risk (from
ingestion) for Section 6 sediments included arsenic, beryllium, and antimony. For Section 31 sediments, the
contaminants that contributed the greatest proportion of estimated risk (from ingestion and inhalation)
included arsenic, dioxins, chromium, beryllium, manganese, and vanadium. Several of the contaminants in
Section 31 sediments possess relatively greater chronic toxicity characteristics than those contaminants
found in Section 6 sediments. As a result, the calculations resulted in a higher relative risk estimate.
The observed concentrations, and resulting risk calculations, were similar to those for background (naturally
occurring) sample concentrations.

10. Comment

Are any of the pollutants in the landfill recyclable, like the methane ?

Response

Heat recovery from flaring of methane gas in the landfill was analyzed in the Feasibility Study for OUS 2&3.
However, it was determined that since the landfill is physically distanced from any potential heat users, it
would not be financially viable to extract the gas at this time. Additionally, there are individual
contaminants such as vinyl chloride in the methane which would have to be removed before the methane could be
used for beneficial purposes. At this time, no other pollutants in the landfill are believed to be
recyclable.

11. Comment

It seems that a combination of land use restrictions/acguisitions and excavation of the landfill in the areas
where it would be effective, would be the best possible solution.

Response

The comment is noted by EPA. While EPA's preference is to implement a cleanup approach that does not rely on
offsite institutional controls such as land use restrictions, restricting landuse around the site would add
an extra measure of protection to the general public.

12. Comment

What is done with the asbestos?
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Response

Asbestos is disposed of in the asbestos pit, which is located in the northwest portion of Section 6.
Asbestos must enter the landfill in sealed containers or double bags, and is buried and covered on a daily
basis. This asbestos disposal operation is regulated by the Colorado Department of Health.

13. Comment

What are the costs in addition to the $ 97 million?

Response

The Present Worth Cost estimate of $97,510,000 is for design, construction, and implementation of the
Selected Sitewide Remedy. In performing calculations for engineering cost estimates, factors of -30 percent
and +50 percent are typically included to account for unforeseen aspects of a project. Therefore the total
cost of cleanup may range from $68,257,000 to $146,265,000.

The additional costs that have been incurred in connection with the site are approximately $60 to $70 million
(this range represents a further refinement from that which was provided at the public meeting). These costs
include, but are not limited to: EPA past costs (including Phase I & II studies, the Baseline Risk
Assessment, oversight); and costs incurred by potentially responsible parties (PRPs) during implementation of
interim remedial measures and the remedial investigations and feasibility studies. In many cases, because
PRPs were not legally reguired to supply EPA with records of their expenditures, costs incurred by those
parties could only be estimated.

14. Comment

What are the discount rates and inflation rates used to determine the present worth on the cleanup costs?

Response

The real net discount rate used for cost estimating purposes is 5 percent. This rate assumes the difference
between the discount rate and inflation is 5 percent. This is the standard rate recommended by EPA for
estimating present worth remediation costs.

15. Comment

Who was the largest polluter at the Lowry Site ?

Response

The Adolph Coors Company is estimated to have disposed of the largest volume of waste, approximately 32
million gallons. The Lowry Landfill Waste-In List (dated April 17, 1992), which is a listing of generators,
transporters, owners, and operators for the Lowry Landfill Superfund Site, may be obtained from the EPA
Superfund Records Center.

16. Comment

What happens at the 5-year review? Has EPA ever ordered additional remediation at a site as a result of the
5-year review?

Response

CERCLA Section 121(c) mandates that EPA review remedial actions which result in any hazardous substances,
pollutants, or contaminants remaining at a Superfund site, no less often that each five years after the
initiation of the remedial action. This reguirement assures that human health and the environment are being
protected by the remedial action being implemented. EPA will continue the reviews until no hazardous
substances, pollutants, or contaminants remain at the Lowry Site above the remediation levels that allow for
unrestricted use and unlimited exposure. Since protectiveness at the Lowry Site will be assured through
containment and onsite institutional controls, the review will focus on the effectiveness of these measures.
In addition, because the sitewide remedy contains a long-term remedial action, the review will also evaluate
the effectiveness and performance of the technologies used in the remedy. The review will examine
information such as monitoring data, applicable or relevant and appropriate reguirements, remediation levels,
and new information or considerations relevant to an assessment of protectiveness.

To date, there have been two 5-year reviews conducted for sites in EPA Region VIII: Chemical Sales Company
Superfund Site; and Rose Park Sludge Pit Superfund Site. Both of these reviews concluded that human health
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and the environment are being protected by the remedial actions being implemented. However one of the
reviews recommended that additional institutional controls, in the form of deed restrictions, be implemented.

For further information on 5-year reviews conducted in other EPA regions, please contact:

Mr. Hugo Fleischman, 5203-6
U.S. Environmental Protection Agency
Office of Emergency and Remedial Response
Hazardous Site Control Division
401 M Street, SW
Washington, B.C. 20460
(703) 603-8769

Response to Specific Oral Comments from The City and County of Denver (Denver), Waste Management of Colorado,
Inc. (WMC), and Chemical Waste Management, Inc. (CWM)

Landfill Solids

1. Comment

The Feasibility Study (FS) fully evaluated waste pit removal and did not recommend it because of health and
safety concerns. Specifically, this remedy would create potential for high level risk to workers during
excavation and removal of those materials.

Response

The Feasibility Study (FS) for the landfill solids operable unit (OU2) did not identify health and safety
concerns as a major issue for waste pit removal. The FS for OU2 did discuss short-term effectiveness for
worker protection. The FS also presented air modeling results, which were used to guantify worst-case
potential and actual risk scenarios. These scenarios modeled volatile organic compound (VOC) releases
resulting from excavation work in the former tire pile area. Under the assumption that all of the emissions
were pure vinyl chloride and that a worker was exposed continually without protective wear, the lifetime
excess cancer risk was estimated to be 2 x 10-5. This value is within the acceptable cancer risk range
established for Superfund sites.

For further discussion on this issue, the reader is referred to the response to Written Comment 20 from
Denver/WMC/CWM.

2. Comment

The only existing exposure pathways are through direct contact. The direct contact at this time is precluded
because these materials are separated from the surface by an engineered drainage system.

Response

For a discussion on this issue, the reader is referred to the response to Written Comment 23 from
Denver/WMC/CWM.

3. Comment

Any hopes of recovering drums of liguids to be shipped offsite and of finding perched liguids in old waste
pits are probably misplaced.

Response

For a discussion on this issue, the reader is referred to the response to Written Comment 21 from
Denver/WMC/CWM.

4. Comment

A remedy to collect and treat any releases from these drums and waste pits is now in place and has been
operating for the last 10 years.

Response

To the extent that the commentor was referring to the barrier wall and treatment plant, it must first be
noted that these facilities have been in operation for less than ten years. It is true that the these
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facilities, combined with the Surface Water Removal Action collection system, are intended to prevent offsite
migration of contaminated ground water. These systems by themselves do not provide the degree of protection
that is afforded by addressing source areas or that is warranted by the site risks. The intent of the
preferred alternative for OU2 is to eliminate or reduce the source of the contamination by excavating drums,
drum contents, and contaminated soils.

For further discussion on this issue, the reader is referred to the response to Written Comment 22 from
Denver/WMC/CWM.

5. Comment

WMC/Denver are concerned during construction about the potential for a significant ground water recharge
event from ponding that may occur during excavation that would carry any contaminants that might be found
down into ground water.

Response

For a discussion on this issue, the reader is referred to the response to Written Comment 24 from
Denver/WMC/CWM.

6. Comment

WMC/Denver are concerned that this selected remedy does not comply with EPA's Landfill Guidance.

Response

For a discussion on this issue, the reader is referred to the response to Written Comment 25 from
Denver/WMC/CWM

7. Comment

The capping alternative fully complies with all laws and guidance and would create no short-term or long-term
health risk. The FS recommended improving the cover over the landfill by adding more municipal solid waste
(MSW) to increase the slope of the cover. The additional solid waste will add a very small increment of mass
to the waste now in place.

Response

For a discussion on this issue, the refer is referred to the response to Written Comment 33 from
Denver/WMC/CWM.

In addition, the community and local governmental entities oppose Alternative 7 for OU2. Community acceptance
is one of the nine evaluation criteria to be evaluated in the
alternative selection process.

The proposed volume of additional MSW (1.2 million cubic yards) represents approximately 10 percent of the
waste in place. To the extent that the landfill cap reguires repairs, there are a variety of other
engineering options that will be evaluated during RD, for example, to minimize any existing surface drainage
problems.

Landfill Gas

8. Comment

WMC/Denver strongly believe the staged approach is the most protective of human health and the environment.

Response

For a discussion on this issue, the reader is referred to the response to Written Comment 34 from
Denver/WMC/CWM.

9. Comment

Denver/WMC/CWM are concerned about the specificity in the Proposed Plan for OUS 2, 3, 4, and 5 (i.e., number
of wells).

Response
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For a discussion on this issue, the reader is referred to the response to Written Comment 35 from
Denver/WMC/CWM.

10. Comment

WMC/Denver believe that the preferred alternative for OU3 would cause undue delay in the collection and
treatment of gas at the site.

Response

For a discussion on this issue, the reader is referred to the response to Written Comment 34 from
Denver/WMC/CWM.

11. Comment

The Proposed Plan for OUS 2, 3, 4, and 5 unnecessarily modifies Landfill Gas Alternative 3, as presented in
the FS for OU3.

Response

For a discussion on this issue, the reader is referred to the response to Written Comment 34 from
Denver/WMC/CWM.

12. Comment

The Proposed Plan for OUS 2, 3, 4, and 5 unfairly compares the preferred alternative for OU3 to Stage 1 of
the Landfill Gas Alternative 3, as presented in the FS for OU3.

Response

For a discussion on this issue, the reader is referred to the response to Written Comment 34 from
Denver/WMC/CWM.

13. Comment

The landfill Gas Alternative 3 and proposed permanent land use restrictions provide a superior remedy.

Response

For a discussion on this issue, the reader is referred to the response to Written Comment 36 from
Denver/WMC/CWM.

14.2 Response to Written Comments Proposed Plan Lowrv Landfill Solids/Gas Operable Units (OUS 2&3) and
Soils/Surface Water and Sediments Operable Units (OUS 4&5)

The following comments were offered in relation to the Proposed Plan for Operable Units (OUS) 2&3 and 4&5.
EPA has taken into consideration that the comments may pertain egually or in greater degree to the selected
remedy or to the Proposed Plan for OUS 1&6, although the comments were not specifically offered in connection
with the Proposed Plan for OUS 1&6.

14.2.1 Response to Written Comments Hadden and Bonnie Robinson

1. Comment

The commentors expressed concern that the contents of the Lowry Landfill are unknown.

Response

Characterization of the waste types disposed at Lowry Landfill was performed during the remedial
investigations of all six operable units. These investigations included the evaluation of landfill operator
and other waste disposal records, as well as the performance of field studies. Over 2,000 samples of ground
and surface water, soils, air, and gas were collected and analyzed. The lists of the chemicals detected at
the site may be found in the remedial investigation reports for each of the operable units.

In general, the types of wastes disposed of at the Lowry Site prior to 1980 include such materials as acid
and alkaline sludges, caustics, brines, oils, greases, solvents, laboratory wastes, construction debris, and
municipal solid waste. Although it is true that a landfill such as Lowry can contain substances not yet
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identified, the cleanup plan is designed to keep all contaminants onsite.

2. Comment

The commentors would like the Lowry Site to be cleaned up soon.

Response

EPA supports the commmenters' recommendation for expeditious cleanup. EPA has recognized for several years
the slow pace of Superfund cleanups and has taken actions to expedite the process, including early actions to
achieve stabilization of immediate problems.

Initial efforts to clean up the Lowry Site began in 1983 with the construction of the ground-water barrier
wall and treatment plant. These facilities prevent offsite migration of contaminated shallow ground water
within the alluvium of unnamed creek. Most recently, contaminated seeps in unnamed creek were removed
through the construction of the Surface Water Removal Action (SWRA) collection system. The selection of the
cleanup remedy for the Lowry site has now been completed by the issuance of this Record of Decision (ROD).
Following the ROD, Remedial Design (RD) activities for the overall sitewide remedy may proceed. It is
anticipated that design of the cleanup will begin in the summer of 1994 and that construction of the remedy
may commence as early as the fall of 1995.

3. Comment

The commentors would like to see legislation that would prohibit expensive hazards like the Lowry Site from
ever occurring again.

Response

In 1976, Congress enacted the Resource Conservation and Recovery Act (RCRA). This law became effective in
1980 and requires hazardous waste to be treated, stored, and disposed of in such a manner as to minimize the
present and future threat to human health and the environment. Hazardous waste disposal was discontinued at
the Lowry Site in response to this law. RCRA was significantly amended by the Hazardous and Solid Waste
Amendments of 1984 (HSWA). To date, there are over 500,000 companies and individuals that must comply with
RCRA. If the RCRA program is effectively implemented, there should be no new Lowry Landfill-type problems.

14.2.2 Response to Written Comments Wilbur Young, November 1, 1993 Letter

1. Comment

The commentor is concerned that the responsible parties have not been held liable for the cleanup of the
Lowry Site.

Response

The City and County of Denver (Denver), Waste Management of Colorado, Inc. (WMC), and Chemical Waste
Management, Inc. (CWM) have indicated that they intend to perform the cleanup of the site and use monies
collected under private settlement agreements to reimburse the United States for past and future response
costs incurred at the Lowry Site.

2. Comment

The commentor is concerned that too much time has been spent on studies and that action needs to be taken
soon.

Response

EPA acknowledges that the studies have taken a considerable amount of time to complete. Initial site studies
began in the early 1980s and were completed in early 1993. Studies at the Lowry Site have involved the
collection of over 2,000 samples of environmental media. Adequate characterization of the nature and extent
of contamination is an essential step in a process that concludes with selection of the most appropriate
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cleanup approach. Initial actions have been implemented, concurrent with these characterization activities,
to prevent offsite releases.

3. Comment

The commentor expressed the belief that complete excavation and disposal should be considered.

Response

Excavation of the Lowry Site was evaluated in 1988 and it was determined that it was not financially viable
or practical to excavate the entire site. The costs for excavation, incineration, and ash disposal were
estimated to exceed $4.5 billion. Additionally, the volume of ash would be about 40 percent of the
incinerated material. Disposal of the ash would take over 19 years with a dump track full of ash leaving
every half hour, every day of the year (refer to Final Draft Technical Memorandum, Preliminary Identification
of Remedial Alternatives, Lowry Landfill Phase II RI/FS).

4. Comment

The commentor expressed the belief that the problems should first be stopped at the Lowry Site, then studied.

Response

The most immediate threats to human health and the environment at the Lowry Site have already been addressed
through implementation of interim cleanup actions. These interim cleanup actions are described in the
proposed plans and ROD. Such actions allow EPA to address the more immediate dangers that might affect human
health and the environment while studies are being performed.

5. Comment

The commentor would like to see that the best possible plan is achieved for the taxpayers.

Response

To obtain the best possible plan, EPA uses the following nine evaluation criteria: overall protection of
human health and the environment; compliance with applicable or relevant and appropriate reguirements
(ARARs); long-term effectiveness and permanence; reduction of toxicity, mobility, or volume through
treatment; short-term effectiveness; cost; implementability; state acceptance; and community acceptance.

The selected remedy will protect human health and the environment, meet ARARs, and offers the best balance of
tradeoffs among all nine evaluation criteria. This includes the cost-effectiveness criterion because the
selected sitewide remedy provides long-term effectiveness and permanence through: collection/treatment of
landfill gas; removal/treatment of contaminated material from the former tire pile area; and containment,
collection, and treatment of contaminated ground water.

14.2.3 Response to Written Comments East Cherry Creek Valley Water and Sanitation District (ECCV)

1. Comment

The commentor believes that there are interactions between media, and that cleanup actions for the landfill
solids and gas can have a positive impact on ground-water guality. Furthermore, the commentor stated that gas
migration from the Lowry Site has the potential of impacting offsite wells, pipelines, pump stations, and
other infrastructures owned and maintained by the ECCV.

Response

EPA agrees that interactions may occur between different contaminated media at the Lowry Site and that
cleanup actions for one medium may improve the guality of other media. Prevention of offsite gas migration
will eliminate the potential contamination of offsite subsurface soils and may reduce the potential adverse
impacts to ground water. In addition, the removal and treatment of an estimated 80,000 pounds of volatile
organic compounds (VOCs) per year through the gas extraction/treatment system will further benefit the
ground-water system through contaminant source reduction.

The uncontrolled migration of gas has the potential to impact infrastructures in the vicinity of the Lowry
Site. Modified Alternative 3 (Gas Collection/Enclosure Flare) was specifically selected to address this
problem through containment, collection, and treatment. This alternative will prevent the offsite migration
of gas.
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2. Comment

Although the commentor would prefer to see more of the contaminated landfill solids treated and/or removed,
the commentor understands the difficulties in accessing much of this material. The commentor feels that the
removal of the accessible drums and contaminated soils in the tire pile area will significantly assist in
achieving the National Contingency Plan (NCP) cleanup criteria that call for long-term effectiveness of the
measures taken, and for reduction of toxicity and volume of waste. The commentor ardently supports this
component of the proposed plan.

Response

EPA acknowledges ECCVs support for the OU2 (landfill solids) selected remedy. The selected remedy achieves
long-term effectiveness and permanence, as stated. The selected remedy is also consistent with EPA's
Guidance for Conducting Remedial Investigations/Feasibility Studies for CERCLA Municipal Landfill Sites.
This guidance recognizes that containment is generally the most appropriate response action because of the
large volume and heterogeneity of the waste typically found within a landfill mass.

This guidance also supports "hot-spot" removal where wastes are accessible, to achieve a decrease in the risk
posed to human health or the environment.

3. Comment

The commentor is opposed to adding municipal solid waste on top of the former landfill as a means of drainage
control.

Response

EPA and CDH agree that municipal solid waste (MSW) should not be added to the former landfill mass. CDH
considers the former landfill to be closed and adding additional MSW to a closed MSW landfill would not be
consistent with the intent of the new Subtitle D reguirements. In addition, there are other engineering
options that would be egually effective in ensuring acceptable drainage control and that would not also add
additional solid waste mass to the Site.

4. Comment

The commentor noted that Waste Management of Colorado, Inc. (WMC) and the City and County of Denver (Denver)
are currently in the process of optioning, or purchasing, all of the land and water rights within a ^L mile
buffer around the Lowry Site. The commentor asked that EPA conduct an evaluation of the impact of this type
of institutional control (land acguisition) since it may be undertaken as part of a potential cleanup
strategy by WMC and Denver.

Response

At the public meeting on September 21, 1993, and in written comments on the proposed plan for OUS 2, 3, 4,
and 5, Denver and WMC indicated that they are considering the purchase of property surrounding the Lowry
Site. However, EPA has not been included in any negotiations regarding options or purchase of land and water
rights by Denver and WMC. Offsite land use restrictions will provide an additional measure of protection
against exposure of human populations to contamination, would be important in the future if additional
measures are determined to be necessary under a contingency plan, and may be necessary to ensure the
integrity of the remedy.

5. Comment

The commentor believes that no contamination should be allowed to migrate offsite. Furthermore, the commentor
believes that offsite standards should include the non-degradation of the ground water and soil, rather than
allowing contamination to migrate offsite until Applicable or Relevant and Appropriate Reguirements (ARARs)
are reached.

Response

The selected sitewide remedy is designed to prevent the offsite migration of contaminants and thus offsite
aguifer degradation. The selected sitewide remedy must ensure that ARARs and other risk-based cleanup levels
are achieved at the compliance boundaries. CERCLA does not reguire clean up to zero levels or to below
background concentrations where MCLs and other ARARs provide numerical cleanup concentrations that are based
on acceptable risk. However, each component of the selected sitewide remedy includes contingency measures to
address offsite migration of contaminants.
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In selecting a remedy, there are two threshold criteria: protection of human health and the environment;
and attainment of ARARs. EPA has set the acceptable risk range for cancer incidents at Superfund sites at 1
x 10-4 (1 in 10,000) to 1 x 10-6 (1 in 1,000,000).

However, at the Lowry Site, there may be cumulative risks posed by the potential additivity of multiple
contaminants or multiple pathways of exposure. Therefore, circumstances at the Lowry Site reguire that the 1
x 10-6 risk level be applied for evaluating individual contaminants to ensure that the cumulative risk does
not exceed 1 x 10-4, thereby ensuring the protectiveness of the remedy.

6. Comment

The commentor asked what actions will be taken if chemical standards for ground water change at some future
date, and if the contamination spreads beyond the current site boundaries.

Response

Chemical cleanup standards, or ARARs, are "frozen" at the time of the ROD. If new information is obtained or
if a regulation changes such that EPA determines the remedy is no longer protective, the ROD would be amended
to incorporate the new standard.

The performance standards will be re-evaluated at a minimum of every 5 years to ensure that the remedy
remains protective of human health and the environment. However, if at any time contamination is detected
above the ARARs (and other performance standards) selected in the Record of Decision, appropriate action will
be taken to achieve the ARAR and to prevent the spread of contamination.

Appropriate action would include implementation of contingency measures that are included in the selected
sitewide remedy. These contingency measures would not only prevent further contamination from occurring, but
would also treat the contamination until ARARs and risk-based concentration limits are achieved and
maintained at and beyond the Compliance Boundaries.

Offsite institutional controls would further facilitate implementation of additional measures if standards
change in the future or if contingency plans must be implemented.

7. Comment

The commentor believes that the creation of a is-mile buffer will allow the spread of low-level contamination.

Response

EPA agrees that creation of a is-mile "buffer zone", as proposed by Denver and WMC/CWM, without the treatment
and containment components of the selected sitewide remedy, would allow offsite migration of contaminants to
occur prior to initiation of active measures to address the contamination problems.

On the other hand, EPA's selected sitewide remedy is designed to prevent offsite contaminant migration and
will not allow the spread of low-level contamination. The selected remedy does not rely on offsite land
acguisition and does not place primary reliance on other offsite institutional controls to accomplish its
objectives. While the selected remedy is not dependent on offsite institutional controls as a primary
element, offsite land use restrictions will provide an additional measure of protection and would allow for
contingency plans to be implemented should they become necessary. Performance standards will not be exceeded
beyond the ground-water compliance boundary.

See responses to Comments 4, 5, and 6 for additional information. Also see responses to Comments 2 and 5
through 11 under Denver and WMC/CWM.

8. Comment

The commentor believes that the extraction component of the gas extraction system is significant, and that
the focus of OU3 should not be placed strictly on the control of gas but also on the extraction of
contaminants and removal of wastes through the gas extraction system. By adding Stage 3 now, the commentor
feels that for an additional 5 percent increase in the cost of sitewide remedy there would be a significant
increase in the annual volume of contaminants removed at the Lowry Site. The commentor believes this is a
good return on a relatively small increase in cleanup costs.
Response
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For the selected remedy, Stage 3 is considered to be a contingency measure. EPA agrees that Stage 3
(interior well network) gas extraction would remove more volatile organic compounds (VOCs). However, at this
time, it is not considered necessary for achieving the performance standards. Stage 3 will be implemented if
the perimeter gas extraction system (Stage 2) does not meet the performance standards.

EPA's overall objectives for Operable Unit 3 (landfill gas) are to:

• Prevent offsite migration of landfill gas; and

• Protect human health and the environment from inhalation of landfill gas and explosion hazards;

The selected remedy will achieve these objectives because it contains, collects, and treats a significant
amount of landfill gas. Also, the selected sitewide remedy is consistent with EPA's Guidance for Conducting
Remedial Investigations/Feasibility Studies for CERCLA Municipal Landfill Sites.

9. Comment

The commentor supports the implementation of contaminant removal activities through the removal of drums and
contaminated soil in the former tire pile area.

Response

EPA acknowledges the support for the removal, treatment, and disposal of drums, drum contents, and
contaminated soils.

14.2.4 Response to Written Comments Wilbur Young, November 5, 1993 Letter

1. Comment

The commentor asked whether reverse osmosis technology could be used as a treatment technology at the Lowry
Site, and if it might be less expensive.

Response

Reverse osmosis has been used in many applications for removing contaminants from liquids, including ground
water and industrial wastes. In general, reverse osmosis is most effective for removing inorganic materials
including metals, and least effective for removing organic contaminants such as pesticides and industrial
chemicals. In fact, there are some organic chemicals that are capable of destroying reverse osmosis
membranes. It is for this reason that reverse osmosis was not chosen as a possible cleanup alternative for
the Lowry Site. In addition to the incompatibility of organic chemicals with membrane material, reverse
osmosis is subject to two additional disadvantages. First, capital and operating costs are typically higher
for reverse osmosis systems than for other technologies. Second, reverse osmosis produces a leftover or
"dirty water" stream that must be properly disposed of. This stream contains all of the contaminants that do
not pass through the membrane and will be 25 to 50 percent of the original untreated volume. Reverse osmosis
does not result in a resin or other solid waste that may be disposed of or processed for reclaiming.

2. Comment

The commentor believes the general health of society would improve and industry would benefit from cleaning
up waterways.

Response

The selected sitewide remedy, which includes the Surface Water Removal Action, will be protective of human
health and the environment. All aspects of the sitewide remedy will be monitored for effectiveness to ensure
that cleanup standards are met.

14.2.5 Response to Written Comments City of Aurora

1. Comment

The commentor endorses EPA's Proposed Plan for OUS 2, 3, 4, and 5 and accepts the need for a
containment-based remedy. The commentor supports the proposal to concurrently install Stages 1 and 2 of the
gas collection system, and endorses the plan to excavate the buried drums, unsaturated waste pits, and
contaminated soils in the former tire pile area. The commentor feels that these aspects of the sitewide
remedy are a reasonable attempt to address long term risk by reducing the source of contamination. The
commentor is opposed to additional municipal solid waste being placed over the former disposal areas in
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Section 6. Finally, the commentor is in favor of retaining for continued use, any monitoring wells that may
have future utility.

Response

EPA acknowledges the commentor's support of the selected remedies for landfill solids and gas. EPA and CDH
agree that additional municipal solid waste should not be added to the former landfill mass. A more complete
discussion of the proposal by Denver and WMC/CWM and EPA' s analysis may be found in the response to Comments
12 and 33 for Denver and WMC/CWM.

EPA also agrees that many of the monitoring wells may have future utility and may be necessary to monitor the
effectiveness of the sitewide remedy. These wells will not be abandoned without a detailed evaluation of
their potential use.

14.2.6 Response to Written Comments City and County of Denver (Denver) Waste Management of Colorado, Inc.
(WMC) Chemical Waste Management, Inc. (CWM)

The following comments were offered in relation to the Proposed Plan for Operable Units (OUS) 2&3 and 4&5.
EPA has taken into consideration that the comments may pertain egually or in greater degree to the selected
sitewide remedy or to the Proposed Plan for OUS 1&6, although the comments were not specifically offered in
connection with the Proposed Plan for OUS 1&6.

On- and Offsite Land Use and Access Controls

1. Comment

The commentors asserted that the comments represent the collective views of over 140 generator, transporter,
operator, and owner potentially responsible parties (PRPs) at the Lowry Site.

Response

Due to the lack of documentation regarding the private settlements between PRPs, EPA is unable to verify the
accuracy of this statement. Nevertheless, EPA has given the comments due consideration.

2. Comment

The commentors stated that through or on behalf of the Lowry Landfill Superfund Trusts,! the commentors are
prepared to acguire property and water rights surrounding Section 6 of the Lowry Site, to at least ^L mile of
the Lowry Site, and to then place permanent land and ground-water use and access controls on these properties
in order to augment the protectiveness of the remedy. (Also refer to similar comments submitted by
the commentors, as documented in the summary of oral comments submitted by the commentors during a meeting
with EPA, held on October 22, 1993; and oral comments by the same commentors, as presented in the Transcript
of the Public Meeting on OUS 2&3 and 4&5, held on September 21, 1993.)

In the offsite areas, the commentors proposed controls that would restrict ground-water use in the Dawson and
Denver aguifers for remediation purposes only. Residential and municipal uses of ground water from these
aguifers, in these areas, would be prohibited. Additionally, the commentors stated that their proposed
controls would not prohibit ground water use in offsite areas in the Arapahoe and Laramie-Fox Hills aguifers.

Response

First, as the commentors acknowledge, some institutional controls have already been established for Section 6
of the Lowry Site. These include Executive Order No. 97, issued by former Denver Mayor Federico Pena.
Executive Order No. 97 places certain restrictions on development of the property, use of the ground water
and surface water onsite, and excavation or well drilling onsite.
[1] EPA believes that these Trusts are privately established instruments holding funds generated
through settlement of third party contribution suits initiated by Denver and WMC/CWM against other
potentially responsible parties at the Site. The trusts are not controlled by, or connected in any
way with the Federal government, and EPA has no independent knowledge concerning the provision of the
agreements.

The selected sitewide remedy shall include, at a minimum, those controls contained in Executive Order No. 97.
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The selected sitewide remedy includes institutional controls to prohibit future land use developments that
would allow unacceptable human exposure to landfill solids, gas, or ground water. At a minimum, the
institutional controls include a prohibition on land use that would damage the landfill cap and a prohibition
against installation of ground-water supply wells on the Lowry Site or in the immediate vicinity of the Lowry
Site. These institutional controls will be effective indefinitely.

Institutional controls reguired by the selected sitewide remedy are at least as broad and as stringent as
those established by Executive order No. 97. EPA agrees with the commentor that such onsite institutional
controls must be adopted in the form of either restrictive covenants or restrictive easements, which would be
duly recorded instruments attached to or included in the chain of title for the Sections 6 and 31 parcels
presently owned by Denver. These institutional controls would run with the land.

EPA, as evidenced by the selected sitewide remedy, also agrees with the commentors that such restrictive
covenants or easements will be made enforceable by EPA or a neutral party other than EPA. EPA, in
consultation with the Colorado Department of Health (CDH), will make the necessary determinations as to which
land use and access controls are appropriate.

EPA is adopting the commentors' proposal that land use and access control measures be instituted in the areas
immediately surrounding the Lowry Site. EPA agrees that the selected sitewide remedy should contain offsite
institutional controls to enhance the protectiveness of the remedy, to allow expeditious and effective
actions should contingency plans be invoked or risk-based performance standards change, and to ensure
continued effectiveness of onsite controls. The size of the area to be addressed by the offsite controls
should be based on the expected area needed to meet these criteria.

EPA agrees with the commentors that controls on construction of new residences immediately adjacent to the
Lowry Site, restrictions on access to areas adjacent to the Lowry Site, and limitations on ground-water well
construction and operation near the Lowry Site are appropriate types of controls. In addition, it is clear
that the likelihood of such controls being included in the chain of title would be enhanced if the land is
owned by parties, such as Denver and WMC/CWM, willing to impose the suggested restrictions.

3. Comment

The commentors stated that they fully support the preferred alternatives presented in the Proposed Plan for
the soils, surface water, and sediments OUS at the Lowry Site, but indicated that this endorsement was
conditioned on EPA's adoption of the commentors' proposal to institute and rely on on- and offsite land use
and access controls.

Response

EPA acknowledges the conditional support for its preferred alternative(s) for OUS 4&5. As the commentors
point out, the selected remedy includes active response measures to separate clean surface water from
potentially contaminated ground water and to collect and treat contaminated ground water prior to its leaving
the Lowry Site. The selected remedy also includes as a minimal level the onsite institutional (land use and
access) controls described by the commentors, as well as offsite controls.

4. Comment

The commentors indicated they believed that EPA's preferred alternatives for OUS 2&3 ignore the studies and
engineering evaluations done at the Lowry Site during the Remedial Investigation/Feasibility Studies
(RI/FSs). The commentors recommend that EPA re-evaluate its determination of the preferred alternative for
OUS 2&3 and select the remedial actions recommended by Denver and WMC/CWM in the FS for OUS 2&3.

Response

EPA recognizes that, based on the information presented in the RI/FSs for OUS 2&3, Denver and WMC/CWM
recommended different remedial alternatives in the FS than those identified by EPA as the preferred
alternatives in the Proposed Plan. However, EPA carefully evaluated the information in the RI/FSs in
identifying the preferred alternatives for OUS 2&3 and fully evaluated the proposed remedies recommended by
Denver and WMC/CWM in the FS for those OUS. EPA has determined that its selected remedies for these OUS
represent the best balance of the nine evaluation criteria and are more protective, in both the short and
long term, of human health and the environment.

5. Comment

The commentors propose that EPA rely on the land use controls proposed by Denver in the draft Declaratory
Statement of Covenants running with the land submitted with Theresa Donahue's January 21, 1993 letter to Mr.
Robert Duprey. Those proposed controls would apply to Sections 6 (Township 5 South, Range 65 West) and 31
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(Township 4 South, Range 65 West) that are part of the Lowry Site. The commentors proposed that either the
State, EPA, or an independent Colorado non-profit organization be authorized to enforce such covenants.

Response

EPA agrees that controls such as the covenants that run with the land, as proposed in Denver's January 21,
1993 letter, should be adopted for the Lowry Site. The selected sitewide remedy incorporates such controls
as a minimum level of control for land and ground-water use and onsite excavation activities. However, EPA
believes that the draft covenants, as presented in Denver's January 21, 1993, letter, must be more definitive
concerning the restrictions on further landfilling at the Lowry Site. The covenants must be consistent with
the selected sitewide remedy and must not allow additional disposal of solid waste in the former landfill
area, but also in disallowing other incompatible uses or activities.

The covenants must permit additional ground-water well installation and operation, as may be necessary, to
monitor and remediate the aguifers beneath the Lowry Site. However, the covenants must also provide
restrictions on such wells for purposes related to human or other uses. Finally, while EPA has not
determined the appropriate enforcement mechanism for such covenants, the selected sitewide remedy provides
that proper and adeguate enforcement of such covenants must be assured. EPA, in consultation with the State,
will determine whether the instrument, in this instance the covenants that run with the land, effectively
provides for the controls included in the selected sitewide remedy.

6. Comment

The commentors make several arguments in support of their proposal that the sitewide remedy should include
the above-described offsite land use restrictions. First, the commentors assert that "although EPA guidance
uniformly indicates that residential use scenarios are inappropriate," EPA has identified the residential
development scenario as the basis for the primary site risks both on- and offsite. The commentors maintain
that their proposed controls will address that risk by controlling and limiting land development on- and
offsite and by assuring that development inconsistent with the selected sitewide remedy does not occur. The
commentors propose that the land will be maintained as "open space" through the deed restrictions and
covenants that run with the land.

Response

EPA disagrees with the commentors regarding the use of the residential development scenario in assessing risk
at the Lowry Site. The baseline risk assessment is not the proper place to take institutional controls into
account (55 FR 55 8710). EPA guidance entitled Risk Assessment Guidance for Superfund, Volume I Human Health
Evaluation Manual (Part A), Interim Final provides that a residential use scenario be employed in the risk
assessment process when available information suggests that future residential land use seems possible. In
the case of the Lowry Site, ground water in the area is currently used, and is expected to be used in the
future, as a source of drinking water. Furthermore, the Lowry Site is currently located near residential
areas. Conseguently, future residential land use is a reasonable possibility.

Moreover, EPA has identified other risks at the site upon which remedial action is based. Thus, EPA's
selection of remedial action at the Lowry Site is not based solely on the residential use scenario, but on a
variety of risks identified at the Lowry Site.

The commentors proposal runs counter to EPA's procedures for assessing risk at a Superfund site. As provided
in EPA guidance and the NCP (55 FR 8709), one specific objective of the risk assessment is to provide an
analysis of baseline risk (i.e., the risks that exist if no remediation or institutional controls are applied
to a site). In other words, a baseline risk assessment is to be performed as if no institutional controls
exist in the on- or offsite areas. The commentors' proposal would reguire that EPA consider the existence of
institutional controls prior to, and as a presumption for, development of the baseline risk assessment. EPA
has determined that the procedures set forth in the NCP and in EPA guidance produce the most reliable
estimates of baseline risks at a site.

In essence, the commentors' proposal would reguire that EPA base its risk assessment on institutional
measures that are not yet in existence and were not in existence at the time the risk assessment was
performed. The approach suggested reguires that EPA revise its definition of baseline risks which is
intended to represent the risks at a site in the absence of any controls or active remedial measures. Such
an approach does not provide a framework to accurately assess site risks because it reguires that EPA
speculate on the breadth and stringency of the proposed controls and project their effectiveness.

Finally, while the selected sitewide remedy imposes a complete prohibition on residential development at the
Lowry Site, EPA does not believe that its selected sitewide remedy would necessarily reguire the offsite
areas to be used as open space and that it is premature to make such a determination. The remedy reguires
that offsite controls be established to allow the unimpeded implementation of contingency plans should they
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become necessary and to ensure the integrity and effectiveness of engineering controls. Although EPA
considers community acceptance in selecting a remedy, EPA received no other comments urging that the areas
surrounding the Lowry Site be maintained as open space.

7. Comment

The commentors state that the proposed restrictions will control and limit construction and use of
ground-water wells on- and offsite. The commentors also state that the proposed restrictions will allow for
monitoring at offsite locations. The commentors further suggest that the proposed offsite restrictions will
allow, as necessary, the construction of containment measures.

Response

EPA does agree that offsite ground-water well construction and extraction, particularly high capacity wells,
must be prohibited to the extent these wells interfere with or diminish the protectiveness or effectiveness
of the selected sitewide remedy. EPA also agrees that it would be desirable to ensure in perpetuity that no
wells will be constructed, close to the Lowry Site, in aguifers that could potentially affect the movement of
contaminants off site, or adversely affect the engineered components of the selected sitewide remedy.
However, EPA does not agree that institutional controls such as those proposed by the commentors are the only
means to accomplish these goals in offsite areas.

EPA does not believe that direct and blanket prohibitions on offsite ground-water wells must be incorporated
in the selected sitewide remedy at the present time. EPA has not made a determination that all offsite well
construction will necessarily affect the movement of contaminants offsite or adversely affect the engineered
components of the selected sitewide remedy. Based on present information on the potential effects of such
wells, EPA believes that this determination is best made on a case-by-case basis as applications for such
wells are made.

EPA disagrees that there is presently very little evidence that contaminants at the Lowry Site could move
offsite. In fact, recent monitoring data has shown evidence of contaminants in ground-water wells at the
western and southern boundaries of the Lowry Site. EPA expects that such contamination, if confirmed, will
be fully addressed by installation of the barrier wall and collection systems at the western and southern
perimeters of the Lowry Site.

Nevertheless, the presence of detectable contamination in these areas underscores the need for engineered
containment structures and systems in those areas. EPA has included such containment systems in the selected
sitewide remedy. Thus, EPA does not agree that imposing institutional controls that merely prohibit future
ground-water extraction is the most prudent way to address the contamination presently detected at the
landfill perimeter.

The selected sitewide remedy includes monitoring of the containment systems to ensure the sitewide remedy is
effective. EPA agrees with the commentors that monitoring in offsite locations may be necessary in the
future to verify that contaminants are not moving offsite, to ensure the effectiveness of the barrier wall
containment systems, or to monitor actual offsite contaminant migration in case it does occur. However, EPA
disagrees that ownership by Denver and WMC/CWM is necessary to implement monitoring activities.

Finally, EPA agrees that offsite institutional controls are necessary at this time because they would allow
for future construction of additional containment systems. EPA's selected sitewide remedy includes
engineered containment components, such as the barrier walls at the south, west, and north perimeters of the
Lowry Site, the cap, and the ground water pump and treatment system. The selected sitewide remedy also
includes contingency measures that would address the failure of constructed barrier walls and other
containment features and any resulting offsite movement of contamination. Even though such failure is not
expected to occur, EPA would consider the need to locate additional containment structures and systems in
offsite areas. Offsite institutional controls will facilitate and protect these aspects of the selected
remedy. EPA does not favor a remedy that would include the acguisition of land surrounding the Lowry Site
for the purpose of constructing containment structures farther out from the present extent of the Lowry Site.

8. Comment

The commentors state that the proposed restrictions will control and limit access to the Lowry Site and
adjacent areas.

Response

EPA agrees with, and the selected sitewide remedy includes, restrictions on access to onsite areas. The
selected sitewide remedy does not include access restrictions to offsite areas. EPA does not believe
controls on access to offsite areas is necessary at this time to ensure protectiveness of the remedy.
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However, such controls may become necessary if additional containment or monitoring systems are constructed
in offsite areas due to implementation of contingency plans that are part of the selected sitewide remedy, or
in the case of remedy failure.

9. Comment

The commentors state that while appropriate zoning and well construction and land use restrictions are
possible with the cooperation of local governments that have jurisdiction, cooperative efforts have not borne
fruit to date. The commentors recommend that land and water right acguisition are the only reliable means of
ensuring that only compatible uses are made of land adjacent to the Lowry Site.

Response

EPA disagrees that the only reliable means of ensuring compatible offsite land use is through the commentors'
purchase of the land. First, no determination of what uses are compatible has yet been made, nor has the
selected sitewide remedy, including its engineered active components, yet been constructed.

EPA agrees in general that some forms of institutional controls, land ownership and water rights acguisition
can enhance the reliability of institutional controls. However, as discussed above, land ownership is not
essential for adeguate implementation of necessary controls. Further, because of the inherent unreliability
and impermanence of all institutional controls in comparison to engineered and/or active treatment remedial
actions, reliance on offsite institutional controls as a major remedial component is not consistent with
EPA's remedy selection reguirements. EPA disagrees with the commentors that purchase of surrounding land and
imposition of the suggested controls will "eliminate" future risks. EPA's selected sitewide remedy places
more emphasis overall on active remedial measures. EPA believes that this approach is the best means to
manage and eliminate unacceptable risks posed by the Lowry Site. Offsite controls are only necessary to
support the integrity of the remedy by ensuring that onsite engineering controls remain effective; such
controls are also reguired to effectively implement future monitoring systems and to allow the expeditious
implementation of contingency plans.

EPA does not believe that voluntary cooperative efforts to secure desirable land use restrictions have been
exhausted. The efforts of the Joint Southeast Area Planning Initiative are ongoing. It is EPA's
understanding that local governments with jurisdiction over the areas adjacent to the Lowry Site have the
same mandate as does Denver to protect the health and welfare of their citizens. EPA expects that the
presence of a Superfund site, and the inherent risks presented by the contamination at the Lowry Site, as
well as the remedial measures that are and will be implemented, will be considered by such local governments
in future zoning and planning decisions. EPA believes that the local governments share the concern that the
Lowry Site remain safe.

10. Comment

The commentors state that they believe their proposed remedy, including on- and offsite ground-water, land
use, and access controls, combined with the active aspects of the remedial alternatives recommended by Denver
and WMC/CWM in the FS for OUS 2&3, provide a remedy that is a better balance of the nine CERCLA evaluation
criteria, and specifically, is more protective than, the preferred alternatives as presented in the Proposed
Plans for all of the OUS.

Response

EPA disagrees that the suggested onsite and additional offsite land use and access controls in combination
with the response action alternatives recommended by Denver and WMC/CWM in the FS for OUS 2&3 would represent
a better balance of the nine CERCLA remedy selection criteria, or that such a combination would be more
protective than the remedy selected by EPA. The Proposed Plan for OUS 2&3 and 4&5 highlights the comparative
analysis of remedial alternatives presented in the FS for OUS 2&3. The active remedial measures included in
the selected remedy, such as the barrier walls, drums and contaminated soils removal, and gas
collection/treatment make the selected remedy more protective and more able to meet ARARs than the
alternative recommended by Denver and WMC/CWM in the FS.

11. Comment

The commentors propose that offsite land use and access controls be instituted in addition to those presented
by EPA in its preferred alternative for Section 6 at the Lowry Site, and not in lieu of active response
measures.
Response
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EPA agrees that institutional controls should not be selected as a remedial component in lieu of active
response measures (55 FR 8846). In addition however, EPA believes that the commentors' proposed remedy does
in fact significantly reduce the active engineering response measures from those included in EPA's selected
sitewide remedy.

EPA can not determine at this time whether the long-term risks to human health would be reduced to any degree
if the commentors' proposed remedy were implemented and believes that they could actually increase. EPA
believes that the approach suggested by the commentors, that is, reliance on institutional controls and the
existence of a monitoring or buffer zone, could ultimately lead to a situation similar to that existing
presently at the site (with potential residential development immediately adjacent to the Lowry Site), but
with a greatly expanded area of contamination.

Also, the remedy proposed by the commentors has less assurance of meeting ARARs than EPA' s selected sitewide
remedy, in particular for offsite areas. The selected sitewide remedy includes barrier walls constructed at
the waste management area boundary. These barrier walls are designed and intended to prevent any offsite
migration of contaminants. Any "breakthrough" will be immediately addressed by the contingency measures
included in the selected sitewide remedy. ARARs for the surrounding ground water will thus be achieved. In
the commentors' proposed remedy, action to install barrier walls will be delayed until after "breakthrough"
to offsite areas has occurred. If barrier walls are constructed in the surrounding land and not at the waste
management area boundary, ARARs will be exceeded in those areas. ARARs must be met at all areas outside the
waste management area boundary when waste is left in place (55 FR 8753).

Detailed Comments on the Proposed Plan

12. Comment

The commentors stated that Section 6 is not closed to municipal solid waste disposal.

Response

EPA and CDH disagree that the landfill in Section 6 is not closed. In accordance with the Regulations
Pertaining to Solid Waste Disposal Sites and Facilities (6CCR1007-2) and 40 CFR Part 258-Criteria for
Municipal Solid Waste Landfills, the Solid Waste Section of the Hazardous Materials and Waste Management
Division, Colorado Department of Health, considers the former solid waste management unit in Section 6 to
be closed to municipal solid waste disposal.

Furthermore, adding waste to a Superfund site contradicts EPA's preference for a reduction in waste volume.
The addition of a significant guantity of municipal solid waste to the existing landfill mass would also
inhibit implementation of remedial activities that might be deemed necessary in the future.

13. Comment

The commentors stated that the dates of operation, provided in the OUS 2, 3, 4, and 5 Proposed Plan, for the
barrier wall and the Ground Water Treatment Plant are incorrect. The commentors noted that the barrier wall
has been in operation since June 1984 and that the Ground Water Treatment Plant has operated since October
1984.

Response

Information available to EPA suggests that the barrier wall was completed in the summer of 1984. EPA
disagrees that the treatment plant began operations in October 1984. Based on the existing record, it is
EPA's determination that the first interim remedial measure (combined operation of both the barrier wall and
treatment plant) began in 1985.

14. Comment

The commentors stated that to be consistent with the No Further Action alternatives for the soils, surface
water, and sediments operable units (OUS 4&5), the No Action and No Further Action alternatives for landfill
solids and gas, as well as alternatives 3 and 7 for landfill solids, should also have a "high level of
compliance" with the short-term effectiveness criterion.

Response

The commentors are correct in noting that the No Action and No Further Action alternatives for the landfill
solids and gas operable units (OUS 2&3) should be identified as having a high level of compliance with the
short-term effectiveness criterion.
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EPA disagrees that Landfill Solids (OU2) Alternatives 3 and 7 would have a high level of compliance with the
short-term effectiveness criterion. Landfill Solids Alternative 3 (Clay Cap) and Alternative 7 (Landfill
Mass Regrading) would not have a high level of compliance with the short-term effectiveness criterion for the
following reasons. Both alternatives involve disturbance of soils, which could precipitate impacts on
workers or pose risks to the community, during remedial action implementation. For example, Alternative 3
includes placement of a clay cap over portions of the former tire pile area, and Alternative 7 includes
removing the top layers of the existing landfill mass cover and regrading additional municipal solid waste on
top of the landfill mass.

15. Comment

The commentors noted that the description for the preferred alternative for OUS 1&6 should be consistent
throughout the Proposed Plan for OUS 2&3 and 4&5.

Response

EPA agrees that the description of this alternative should be consistent throughout the Proposed Plan for OUS
2&3 and 4&5. The selected sitewide remedy includes underground barrier walls and collection systems, and an
upgradient containment, collection, and diversion system.

16. Comment

The commentors stated that there is no evidence that an upgraded ground-water treatment facility will be
necessary.

Response

EPA does not agree with the commentors' statement. The OUS 1&6 Feasibility Study (FS) concluded that a
second treatment plant or a modification to the existing groundwater treatment plant may be necessary to
treat highly contaminated ground water collected at the base of the northern slope of the landfill mass. The
sitewide remedy must meet all performance standards and ARARs. During remedial design, the existing
treatment plant will be evaluated to determine whether or not it is capable of treating: higher volumes of
contaminated ground water; higher contaminant concentrations in the ground water; contaminants present at the
site but not currently found within the treatment plant influent. If it is determined that the existing
plant is not able to meet performance standards, the plant will be upgraded accordingly.

17. Comment

The commentors asked for an explanation of the difference between the costs in the OUS 1&6 Proposed Plan and
those summarized for OUS 1&6 in the Proposed Plan for OUS 2&3 and 4&5. In addition, the commentors asked EPA
to provide costs for the preferred alternatives to explain the differences between those alternatives and the
recommended FS alternatives.

Response

The costs for the OUS 1&6 alternatives in the OUS 1&6 Proposed Plan included costs that had already been
incurred; specifically the capital costs associated with the SWRA. For the OUS 2&3 and 4&5 Proposed Plan,
EPA chose to exclude the capital costs previously incurred through implementation of the SWRA. Where
components of the different OU alternatives overlapped, EPA removed the duplicated cost estimates. This
included, for example, deletion of the SWRA operating and maintenance (O&M) costs from the cost estimate for
the preferred alternative for OUS 1&6. O&M costs for the SWRA are accounted for in the cost estimate for the
preferred alternative for OUS 4&5. Also, the costs associated with the OUS 1&6 preferred alternative, as
presented in the OUS 2&3 and 4&5 Proposed Plan, include estimates for underground barrier walls and
associated well extraction systems.

The cost estimates for each pair of OUS (1&6, 2&3, and 4&5) were developed using slightly different
cost-estimating methodologies. This is due to the fact that a separate feasibility study was prepared for
each set of OUS. Each study estimated indirect costs by assuming different percentages of direct costs.

Indirect capital costs include items that are incidental to direct capital costs such as engineering and
design, legal fees, permitting reguirements, EPA review and oversight, and a contingency for unexpected
costs. Indirect O&M costs represent the estimated costs for administrating the O&M work and a contingency
for unexpected costs. For the preferred alternatives, indirect capital costs ranged from 70 to 80 percent of
direct capital costs, while O&M indirect costs ranged from 17 to 30 percent of O&M direct costs. To maintain
consistency, EPA used the same percentages (80 percent for capital costs and 30 percent for O&M costs) for
each OU.
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18. Comment

The commentors are concerned that the use of specific numbers in the Proposed Plan will constrain the
Remedial Design effort.

Response

EPA disagrees that the Remedial Design will be constrained. EPA's focus is to ensure that the performance
standards, specified in the selected remedy, are achieved.

The Proposed Plan for OUS 2&3 and 4&5 provides estimates of such guantities as volume of material to be
excavated and number of wells to be installed. Approximation is appropriate at this stage of the process and
is necessary for cost estimating purposes. EPA acknowledges that it may be necessary to review these
estimates during the remedial design. However, both the excavation and well-installation components are
included as key components of the selected remedy and both activities must be implemented such that the
performance standards specified in the selected remedy are achieved and maintained.

19. Comment

The commentors stated that the Proposed Plan fails to incorporate existing remedy elements and those proposed
for OUS 1&6. As an example, the commentors suggested that the existing ground-water treatment plant does not
appear to have been factored into the preferred alternative for landfill solids. The commentors also stated
that the costs of certain IRMs do not appear to be factored into the selected alternatives.

Response

EPA disagrees that the Proposed Plan fails to incorporate existing or proposed remedy elements. The Proposed
Plan for OUS 2&3 and 4&5 incorporates both existing remedial elements and the preferred alternative for OUS
1&6. In fact, the existing interim remedial measures (IRMs) and the preferred alternative for OUS 1&6 are an
integral part of the selected sitewide remedy and are discussed in the Proposed Plan for OUS 2&3 and 4&5.

The benefits and treatment aspects of existing IRMs and the preferred alternative for OUS 1&6 were not
specifically mentioned in the separate analyses of each alternative for each operable unit. However, the
remedial benefits, treatment, and costs of existing IRMs and the preferred alternative for OUS 1&6 were
factored into the sitewide remedy discussion and comparative analysis.

The existing ground-water treatment plant and barrier wall address contaminated ground water that is flowing
from the landfill mass and the former tire pile area. While the treatment plant and barrier wall do not
provide for source reduction, the preferred alternative for landfill solids does. The preference for removal
of accessible hot spots is consistent with EPA's guidance Conducting Remedial Investigations/Feasibility
Studies for CERCLA Municipal Landfill Sites.

20. Comment

The commentors stated that excavation in the former tire pile area could create short-term exposure to
workers as well as become a risk to the public during offsite transportation.

Response

The Proposed Plan for OUS 2&3 and 4&5 acknowledges that excavation in the former tire pile area may create
short-term exposure risks for workers. EPA recognizes that offsite transport of wastes has the potential to
create short-term exposure risks for the general public.

The Feasibility Study (FS) for OUS 2&3 notes that it is anticipated that an increase in organic emissions,
and possibly inorganic emissions, would be incurred as a result of excavation of the buried drums and
contaminated soils. Emissions would be controlled using appropriate dust suppression methods that may
include the use of water, foam, or cover materials such as PVC sheeting. The FS also evaluated the
worst-case potential risks from increases of VOCs, as a result of excavation activities in the former tire
pile area. Modeling results indicated that if a worker were continually exposed without protective
eguipment, the lifetime cancer risk would be 2 x 10-5. This calculation is based on conservative
assumptions. Even with these assumptions, the potential risk is within EPA's acceptable range of 1 x 10-4 to
1 x 10-4. Using more realistic assumptions (such as the use of protective eguipment), the risks would be
much lower than 1x10-4.

In terms of offsite transportation and short-term risks to the general public, EPA believes that current
waste transporting technologies are reliable and have proven to be successful. The loading and transport of
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materials would comply with all applicable regulations and would be performed in accordance with a health and
safety plan, thereby minimizing any adverse short-term impacts.

There are numerous examples of situations in which excavation and offsite disposal have been successfully
implemented with minimal risk to either onsite workers or the general public. At the Denver-Arapahoe
Chemical Waste Processing Facility, located adjacent to the Lowry Site, the following materials were safely
excavated with no adverse health impacts to human health: 34,569 55-gallon drums; 4,300 cubic yards of solid
wastes; and 3,516 gallons of liguids in miscellaneous containers ranging from 1 gallon to 25 gallons in size.
Excavation of drums, drum contents, and contaminated materials in the former tire pile area is believed to be
no more complex.

Given the estimated low-level risks, the safety measures that may be taken, the existing regulations for
waste transport and disposal, and the demonstrated success of a similar excavation adjacent to the Lowry
Site, EPA believes that the short-term risks to workers and the general public are low and may be controlled
through proven health and safety measures. In addition, short-term risks are only a part of one criterion,
short-term effectiveness. The selected remedy provides the best balance of all nine evaluation criteria.

21. Comment

The commentors stated that it is not likely that intact drums will be found in the former tire pile area.

Response

EPA disagrees with the commentors. Subsection 4.3 of Appendix E (Former Tire Pile Area Geophysical
Investigation) of the Feasibility Study, Volume 2, Lowry Landfill: drill Solids and Landfill Gas Operable
Units (OUS 2&3), Remedial Investigation and Feasibility Study, Arapahoe County, Colorado estimates that
approximately 19 percent (257 drums) of the total estimate of buried drums (1,350) may be intact and contain
liguids. Based on treatability study results, the feasibility study further suggests that, on the average,
about five gallons of liguid may be present in each of the estimated 257 liguid-filled drums. This would
yield a total liguid volume of no less than 1,300 gallons of waste. Estimates show that a significant amount
of source material may be removed through limited excavation of the hot spots in the former tire pile area.

The contaminant sources discussed in the Proposed Plan for OUS 2&3 and 4&5 include contaminated solids and
liguid-filled drums that provide a source of contamination to other media such as ground water. The intent
of the preferred alternative for OU2 is to remove higher concentration contaminated solids that are
accessible. The excavation will include not only drums, but also contaminated soils and other material
surrounding the drums.

22. Comment

The commentors stated that liguids leached from the former tire pile area will be captured at the barrier
wall and through the SWRA, indicating that additional measures will not be necessary in the former tire pile
area.

Response

EPA does not agree that additional measures will not be necessary in the former tire pile area. The SWRA
collection system and barrier wall intercept some of the contaminated liguids which have migrated laterally
from waste pits within the former tire pile area. These liguids are treated at the existing ground-water
treatment facility. It is undesirable to allow perpetual seepage out of the waste pits in the former tire
pile area. Elimination of this source of contamination, through excavation, reduces the potential for
additional contamination of ground water. The excavation option has the following advantages:

• It further reduces a principle source of risk to human health and the environment;

• It removes accessible hot spots;

• It complements the source-control component (for the landfill mass) of the preferred
alternative for OU2; and

• It complies with the statutory reguirements of CERCLA.
Comment
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The commentors believe that the risks are minimal in the former tire pile area and claim that the drums,
soils, and waste pits are separated from the surface by an engineered drainage system. The commentors also
stated that land use and access controls would eliminate public exposure to subsurface solids.

Response

Contaminated solids in the former tire pile area, within the SWRA collection system boundary, are separated
from the surface by an engineered drainage system. The remainder of the former tire pile area does not have
an engineered drainage system. Institutional controls such as access and land use restrictions will be
implemented but only to supplement, and not replace, such engineering controls as excavation of the
contaminated solids.

24. Comment

The commentors are concerned that excavation of the former tire pile area will involve the potential for
ground-water recharge in disturbed areas.

Response

EPA believes that ground-water recharge can be prevented or limited through the following means:

• Excavation can be sequenced to minimize the open excavation areas;

• Engineering controls (such as berms) can be used to divert ponded water;

• The time period that the excavation area is kept open can be limited; and

• Storm water that may accumulate in the excavation area can be removed and treated onsite.

25. Comment

It is the commentors' opinion that removal of the drums, soils, and waste pits in the former tire pile area
is not consistent with EPA guidance Presumptive Remedy for CERCLA Municipal Landfill Sites, OSWER Directive
9355.0-49FS, September 1993. The commentors identify four guestions to be answered in evaluating the
reasonableness of excavation as a cleanup alternative. The first guestion is whether or not evidence exists
to indicate the presence and location of waste. The commentors stated that there is no evidence of intact
drums or perched waste.

Response

EPA disagrees that the removal of the drums, soils, and waste pits is not consistent with EPA guidance. The
proposed excavation, removal, treatment, and disposal of drums, drum contents, contaminated soils, and
contaminated debris fully complies with EPA' s guidance entitled Presumptive Remedy for CERCLA Municipal
Landfill Sites [OSWER Directive 9355.0-49FS, September 1993]. This guidance indicates that the primary
response action objectives for municipal landfill sites should include preventing direct contact with
contaminated solids and minimizing contaminant infiltration to ground water. The preferred alternative for
OU2 fulfills this requirement and is based on a determination that: evidence exists to indicate the presence
and approximate location of waste; the hot spot is known to be a principal threat waste; the waste is in a
discrete, accessible area of the site; and the hot spot is known to be large enough that its remediation will
reduce the threat posed by the overall site but small enough that it is reasonable to consider removal.

EPA's fast response addresses the commentors' belief that there is no evidence of intact drums or perched
waste. Sufficient evidence exists to indicate the presence and approximate location of waste in the former
tire pile area. This evidence includes: aerial photographs; results from soil gas surveys, borings, and
waste pit well points; geophysical studies; test pits analyses; and visual Observation of contaminated liguid
seeps in the former unnamed creek. Specifically, the Feasibility Study, Volume 2, Lowry Landfill: Landfill
Solids and Landfill Gas Operable Units (OUS 2&3), Remedial Investigation and Feasibility Study, Arapahoe
County, Colorado estimates that, at a minimum, approximately 257 buffed drums may contain liquids and that
there may be, at a minimum, 1,300 gallons of liquid waste in these drums. Thus, substantial evidence exists
that perched liquids are present in the former tire pile area.

26. Comment

The second question posed by the commentors is whether or not the hot spot is known to be a principal threat
waste. The commentors stated that the wastes are not unique.

Response
-------
The concept of a principal threat waste is to be applied on a site-specific basis when characterizing source
material. A Guide to Principal Threat and Low Level Threat Wastes [OSWER Directive 9380.3-06FS, November
1991] defines source material as material that includes or contains hazardous substances, pollutants or
contaminants that act as a reservoir for migration of contamination to ground water, or acts as a source for
direct exposure. Source materials may include drummed wastes, contaminated soft and debris, or dense
non-agueous phase liguids (DNAPLs).

As established in the NCP [40 CFR 300.430(a) (1) (iii)], EPA expects, at a minimum, to:

1. Use treatment to address the principal threats posed by a site, wherever practicable. The EPA
guidance document entitled A Guide to Principal Threat and Low Level Threat Wastes [OSWER
Directive 9380.3-06FS, November 1991], states that principal threat wastes are those source
materials considered to be highly toxic or highly mobile that cannot be reliably contained or
would present a significant risk to human health or the environment should exposure occur.

2. Use engineering controls, such as containment, for wastes that pose a relatively low long-term
threat or where treatment is impracticable.

3. Use a combination of methods to achieve protection of human health and the environment.
Treatment of principal threats will be combined with engineering controls and institutional
controls for treatment residuals and untreated waste.

The source materials discussed in the Proposed Plan for OUS 2&3 and 4&5 include, at a minimum, contaminated
soft and debris and drummed waste that provide a continuous source of contamination to the ground water.
These source materials would present a significant risk to human health or the environment if exposure were
to occur and comprise the hot spots identified in the former tire pile area at the Lowry Site. The hot spots
are principal threat wastes and are in a discrete, accessible area of the site.

For additional discussion concerning documented evidence of buried liquid-filled drums in the former tire
pile area, please see the response to Comment 21.

27. Comment

The third question posed by the commentors is whether or not the waste is in a discrete accessible part of
the landfill. The commentors stated that the drums are not easily accessible.

Response

EPA disagrees that the wastes are not easily accessible. The hot spots that are targeted for excavation and
treatment are located in an area that is physically separate from the main body of the landfill mass. EPA
guidance does in fact suggest that it would be difficult to excavate and/or treat a landfill mass, but allows
for circumstances in which source materials are located in separate or discrete and accessible areas.

The contaminated material to be excavated and treated is located in a discrete, accessible area, separate
from the landfill mass. The waste is accessible through conventional excavation and construction techniques.
The proposed construction process is provided in detail in Subsection 4.2.1.4 of the OUS 2&3 Feasibility
Study. While many of the drums to be recovered may be deteriorated and construction debris over the waste
pits may add some level of complexity to the excavation, neither of these issues are believed to be
significant, and both can be addressed through proven technology. The commentors may also refer to the
response to Comment 21 for additional discussion of a similar excavation project conducted at the
Denver-Arapahoe Chemical Waste Processing Facility adjacent to the Lowry Site.

28. Comment

The fourth question posed by the commentors is whether or not the hot spot is large enough to reduce risk but
small enough to consider removal. The commentors stated that the area is not large enough to reduce the
threat posed by the overall site.

Response

EPA disagrees that the area(s) to be excavated are not large enough. The preferred alternative for OU2 is a
combination of excavation in the former tire pile area and containment of wastes within the landfill mass.
These components of the sitewide remedy would be implemented simultaneously.

In evaluating overall site risk reduction, EPA believes it is appropriate to separately consider the
containment portion (southern portion of the Lowry Site) and the non-containment portion (northern portion
-------
including the former tire pile area of the Lowry Site). In doing so, risks from principal threats within the
main landfill mass are effectively contained in the southern portion of the Lowry Site. Principal threats in
the former tire pile area would be significantly addressed through excavation. Excavation in the former tire
pile are is large enough to significantly reduce the majority of risk in the former tire pile area and is
small enough that it is reasonable and practical to consider.

29. Comment

The commentors stated that the preferred alternative for landfill solids does not meet the reguirements of
the NCP. The commentors also claimed that the preferred alternative is not cost effective and EPA's Proposed
Plan did not evaluate long-term effectiveness, treatment, and short-term effectiveness. Finally, the
commentors stated that EPA's Proposed Plan focused on offsite treatment, did not consider existing onsite
treatment, and short-term risks to onsite workers were hardly mentioned.

Response

The preferred alternative does meet the reguirements of the NCP. EPA, in consultation with CDH, performed a
detailed analysis of all the alternatives, including Modified Alternative 4 (Drum Removal/Offsite
Disposal/North Face Cover). This analysis consisted of two parts: an assessment of individual alternatives
against each of the nine evaluation criteria; and a comparative analysis that focused upon the relative
performance of each alternative against the nine criteria.

With regard to the preferred alternative and the reguirements of the NCP, the results of EPA's detailed
analysis demonstrate that Modified Alternative 4 (Drum Removal/Offsite Disposal/North Face Cover) offers:
the greatest protection of human health and the environment by removing contamination in the former tire pile
area; the greatest long-term effectiveness and permanence through removal of contaminated material; and the
greatest reduction of toxicity, mobility, and volume of contaminated solids through treatment.

The analysis also affirmed that the preferred alternative: is comprised of proven technologies; is
implementable; complies with applicable or relevant and appropriate reguirements; is fully supported by the
State of Colorado; and has a high degree of acceptability to the community.

The commentors are correct in noting that cost effectiveness is determined by evaluating the following items:
long-term effectiveness and permanence; reduction of toxicity, mobility, or volume through treatment; and
short-term effectiveness. Modified Alternative 4 (Drum Removal/Offsite Disposal/North Face Cover) is cost
effective for the reasons discussed below.

EPA disagrees that it did not consider, or that it gave less than due consideration to, the following
criteria: long-term effectiveness; short-term effectiveness; and onsite treatment. First, EPA considered
that Modified Alternative 4 (Drum Removal/Offsite Disposal/North Face Cover) provides long-term effectiveness
and permanence through removal of contaminated drums, debris, and soils from the former tire pile area.
There is a high degree of certainty that this alternative will prove successful and implementation of this
alternative eliminates the need to consider either the magnitude of residual risk remaining from untreated
waste or the adeguacy and reliability of controls such as containment systems to manage the untreated waste.

Second, EPA considered that Modified Alternative 4 (Drum Removal/Offsite Disposal/North Face Cover) does in
fact address treatment of drum contents and contaminated soils. This alternative provides for a significant
reduction in toxicity, mobility, and volume of drum contents and contaminated soils through excavation and
treatment at an offsite facility. Treatment would include, at a minimum, incineration and ash stabilization.

Third, the following potential short-term impacts of Modified Alternative 4 (Drum Removal/Offsite
Disposal/North Face Cover) were also evaluated: short-term risks that might be posed to the community during
implementation of the alternative; potential impacts on workers during remedial action and the effectiveness
and reliability of protective measures; potential environmental impacts of the remedial action and the
effectiveness and reliability of mitigative measures during implementation; and time until protection is
achieved.

Excavation projects, similar in nature to the preferred alternative, have been successfully and safely
implemented both onsite and offsite with minimal short-term risks. Onsite excavation of soils and
potentially contaminated material was performed as part of the construction of the Surface Water Removal
Action collection system within Unnamed Creek. Drum excavation and removal activities were also successfully
completed in Section 32, in connection with the corrective action at the Denver-Arapahoe Chemical Waste
Processing Facility.

Experience from these projects indicates that implementation of the preferred alternative would pose minimal
short-term risk to the community. Furthermore, the preferred alternative can be implemented using effective
-------
and reliable protective measures for the cleanup workers. Also, mitigative measures employed during the
implementation of the above-referenced excavation projects have proven to be effective in minimizing adverse
impacts to the environment during remedial action.

In responding to the commentors' suggestions that EPA only focused on offsite treatment and that existing
onsite treatment was not considered, the following points can be made. First, of the seven alternatives
evaluated for remediation of the landfill solids, two alternatives involve no excavation, one alternative
involves excavation and disposal either on- or offsite, three alternatives involve excavation and offsite
treatment and disposal, and one alternative includes excavation and both onsite and offsite treatment and
disposal.

Second, regarding the commentors' suggestion that the existing ground-water collection and treatment systems
were not considered during the comparative evaluation of the alternatives for the landfill solids, please see
the responses to Comment 19 and Comment 22.

30. Comment

The commentors are opposed to excavation in the former tire pile area for the following reasons: ground
water treatment is already in place; there is a potential risk to onsite workers; long distance transport of
excavated materials would be necessary; there would be congressional disapproval for offsite transport; and
excavation in the former tire pile area does not meet the short-term effectiveness criteria.

Response

EPA acknowledges that a ground-water collection/treatment system is in place and is designed to capture
dissolved contaminants in the ground water. However, source reduction through excavation in the former tire
pile area will address a principal threat at the Lowry Site (see the response to Comment 22). The potential
risks to onsite workers and associated with offsite disposal are discussed in Comments 19 and 20.

31. Comment

The commentors believe that Modified Alternative 4 (Drum Removal/Offsite Disposal/North Face Cover) is not
cost-effective and is not eligible for selection as the remedy.

Response

Please see the response to Comment 29 and the Record of Decision for a discussion of the cost-effectiveness
of Modified Alternative 4 (Drum Removal/Offsite Disposal/North Face Cover).

32. Comment

The commentors noted that the Feasibility Study for OUS 2&3 contained an alternative that included the
following components: the placement of additional cover materials over those areas of the former tire pile
area that potentially contain drums and waste; and permanent land use and access controls on the property.
The commentors also provided an analysis of this alternative within the context of the nine evaluation
criteria.

Response

In preparing the Proposed Plan for OUS 2&3 and 4&5, EPA evaluated the alternative cited by the commentors.
The results of EPA's comparative analysis indicated that other alternatives more fully complied with the nine
evaluation criteria.

33. Comment

The commentors stated that the existing cap on the former landfill should be enhanced and regraded using
municipal solid waste.

Response

EPA disagrees that the existing cap needs to be enhanced by the means suggested by the commentor. The
commentors' proposed approach is part of landfill Solids Alternative 7, which was evaluated as part of the FS
for OUS 2&3. EPA performed a comparative analysis of this alternative in accordance with the nine evaluation
criteria established in the NCP. Justification for not selecting this alternative may be found in the Record
of Decision. The regulatory history of the Section 6 municipal solid waste (MSW) landfill, and its
relationship to EPA's and CDH's analysis of Landfill Solids Alternative 7, is discussed below.
-------
CWM initially submitted a closure plan to CDH for the Section 6 MSW landfill in November 1980. The Closure
Plan was approved for the complete filling of Section 6 (from Quincy Avenue to Hampden Avenue) to a maximum
final cover altitude of 5,862.5 feet. This plan was modified in 1985 to accommodate Superfund activities;
however, the modification only stopped the northward growth of the MSW landfill while the final altitude
remained the same. On August 3, 1990, WMC ceased MSW landfilling in Section 6 and began to utilize the
engineered MSW landfill that was constructed in Section 31 of the Denver/Arapahoe Disposal Site (DADS)
facility. WMC submitted the Quality Assurance report for the final cover of the Section 6 MSW landfill of
the DADS facility in 1992. The report stated that the final cover installed over the MSW landfill in Section
6 met all minimum engineering reguirements specified in the regulations under which the Section 6 MSW
landfill had operated.

EPA, in consultation with CDH, has determined that ARARs regarding the Landfill Solids Alternative include
the reguirements specified in the State of Colorado's Regulations Pertaining to Solid Waste Disposal Sites
and Facilities (6CCR1007-2) (SWA) and the Federal regulations titled Solid Waste Disposal Facility Criteria
(40CFR Part 258) (Subtitle D).

In addition, RCRA Subtitle D regulations, 40 CFR Part 258.2, define an existing municipal solid waste
landfill (MSWLF) unit to be a MSW landfill that received MSW as of October 9,1993. The Section 6 MSWLF unit
did not receive MSW as of that date. Thus the MSW landfill in Section 6 is not an existing unit. All units
not existing are considered to be closed. Based on this determination, Landfill Solids Alternative 7 could
only attain ARARs if Alternative 7 could meet criteria specified in the SWA. Section 3 of the SWA reguires
that all new MSW units be constructed with engineering liners and leachate collection systems on a stable
sub-base. Conseguently, EPA and CDH do not believe that Alternative 7, as proposed, could meet these
reguirements. This conclusion conflicts with the results of the initial ARARs evaluation, which was
presented in the Proposed Plan for OUS 2&3 and 4&5. As presented in the proposed plan, EPA and CDH initially
concluded that the Landfill Solids Alternative 7 would comply with ARARs. However, based on the additional
analysis presented above, Landfill Solids Alternative 7 would not comply with ARARs.

The commentors assert that the additional cover proposed for installation to the closed MSW landfill in
Section 6 will meet the new Subtitle D reguirements by increasing the slope of the final cover to a steeper
grade. This type of approach to closed MSW landfills is not within the intent of the State and Federal
Subtitle D reguirements.

EPA and CDH consider the solid waste management unit within Section 6 to be closed to additional MSW
disposal.

In addition, the placement of an additional 1.2 million cubic yards of MSW onto the existing landfill mass
would serve to further limit access in the event that, in the future, it was determined that excavation was
necessary.

34. Comment

The commentors disagree with the simultaneous installation of the first two stages of the gas collection
system. The commentors also believe that the Proposed Plan for OUS 2&3 and 4&5 has been manipulated to
improperly compare Modified Alternative 3 (Gas Collection/Enclosed Flare) to Stage 1 of Alternative 3 (Gas
Collection/Enclosed Flare).

Response

EPA disagrees that the simultaneous installation of the first two stages of the gas collection system is
unjustified. The preferred alternative for landfill gas, Modified Alternative 3 (Gas Collection/Enclosed
Flare), includes a phased installation of gas collection wells in the landfill mass. The first phase is a
combined source reduction and perimeter gas collection system (Stages 1 and 2 in the OUS 2&3 Feasibility
Study). Installing the perimeter gas collection component is warranted for the following reasons:

• Shallow subsurface geologic uncertainties at the perimeter of the landfill mass indicate that
targeting the few known areas of gas migration (as is proposed under Stage 1) may not
comprehensively address all pathways for migration (monitoring points at some locations are as
far as a 1/4 mile apart).

• The cost difference in targeting a few areas (Stage l-$8.4 million) versus the entire perimeter
(Stages 1 and 2-$9.2 million) is minimal when compared to the increased level of protection.

• By installing the perimeter gas collection system, there will be less reliance on monitoring
and significant removal and treatment of contaminants.
• The level of protectiveness achieved by combined Stages 1 and 2 is higher than for Stage 1
only.
-------
• Perimeter gas collection systems have proven effective at other landfills in Colorado.

Installing a full-perimeter gas collection system would not delay the start of remedial action as implied by
the commentors.

EPA does not agree that the Proposed Plan for OUS 2&3 and 4&5 improperly manipulated the comparative analysis
of Modified Alternative 3 (Gas Collection/Enclosed Flare) and Stage 1 of Alternative 3 (Gas
Collection/Enclosed Flare). EPA's analysis is justified because the comparison between the two alternatives
was made based on the implementation of engineered technology without contingencies. EPA believes it has
fairly evaluated these two alternatives in the Record of Decision.

35. Comment

The commentors believe that the specificity contained in the Proposed Plan for OUS 2&3 and 4&5 (i.e., the
exact number of collection and monitoring wells) cannot be justified and should be evaluated during the
remedial design phase.

Response

A detailed technical justification for the estimated number of collection and monitoring wells identified in
the alternatives may be found in the Feasibility Study for OUS 2&3. As mentioned in the response to Comment
18, the Proposed Plan for OUS 2&3 and 4&5 must, for conceptual and cost estimating purposes, provide
estimates of such guantities as the number of wells to be installed. EPA acknowledges that it may be
necessary to review and revise these estimates during the remedial design. However, the specific numbers
must be sufficient to fully meet all performance standards identified in the selected sitewide remedy.

Comparison of Remedies in the Proposed Plan
with those in the Feasibility Study in
Combination with Land Use and Access Controls

36. Comment

The commentors summarize the analysis of alternatives, as presented in the Feasibility Study for OUS 2&3
(Denver/WMC/CWM, April 1993), and supplement this analysis with an additional discussion of possible onsite
and offsite institutional controls.

Response

This comment serves as a summary of the set of specific comments received from the commentors. Therefore,
the reader is asked to review the Responsiveness Summary for individual responses.
-------
Table 14-1
Chemical Concentration Data Summary

95th Percentile Upper Confidence Limit on the Geometric Mean of the Median Well Concentrations

(ug/1)
Page 1 of 5
Chemical Name
Shallow Ground-water Monitoring
Wells Completed in Weathered
Dawson and Waste Pit Liguids Well
Points Within the Source Area
Ground-water Monitoring
Wells Completed in
Weathered Dawson Aguifer
Outside of the Source Area
Ground-water Monitoring Deep Ground-
Wells Completed in water
Unweathered Dawson Aguifer Monitoring
Outside of the Source Area Wells
Upgradient Ground-
water Monitoring
Wells Outside the
Source Area
1,1,1-Trichloroethane

1,1,2,2-Tetrachloroethane

1,1,2-Trichloroethane
1,1-Dichloroethane
1,1-Dichloroethylene
1,2,4-Trichlorobenzene
1,2-Dichlorobenzene
1,2-Dichloroethane
1,2-Dichloroethene (total)
1,2-Dichloropropane
cis-1,3-Dichloropropene
trans-1,3-dichloropropene
1,4-Dichlorobenzene
2,3,7,8-TCDD (dioxin)a
2,4,5-T
2,4,5-TP
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
2,4-D
2,4-Dichlorophenol
2,4-Dimethylphenol
2,4-Dinitrophenol
2-Butanone (MEK)
2-Chloronaphthalene
2-Chlorophenol
2-Hexanone
2-Methylnaphthalene
250

29
520
83
18
18
590
140
29
27
26
21
0.00053
3.9
5.3
90
24
23
31
80
220
980
18
25
45
58
120

5.9
47
41
7.3
ND
13
31
8.7
ND
ND
7.9
0.000020
ND
ND
ND
ND
1.4
6.4
7.1
ND
7.1
ND
ND
9.8
ND
4.3

ND
3.2
2.7
ND
ND
4.3
ND
ND
ND
ND
ND
0.000024
0.27
ND
ND
ND
ND
ND
ND
ND
5.5
ND
ND
5.1
ND
15

2.6
13
11
ND
ND
ND
3.5
2.6
ND
ND
ND
0.0002
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
4.3

ND
ND
2.9
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
6.1
ND
ND
ND
ND
-------
Table 14-1
Chemical Concentration Data Summary

95th Percentile Upper Confidence Limit on the Geometric Mean of the Median Well Concentrations
(ug/1)
Chemical Name
Shallow Ground-water Monitoring
Wells Completed in Weathered
Dawson and Waste Pit Liquids Well
Points Within the Source Area
Ground-water Monitoring
Wells Completed in
Weathered Dawson Aquifer
Outside of the Source Area
Ground-water Monitoring Deep Ground-
Wells Completed in water
Unweathered Dawson Aquifer Monitoring
Outside of the Source Area Wells
Page 3 of 5
Upgradient Ground-
water Monitoring
Wells Outside the
Source Area
bis(2-ethylhexyl)phthalate
Boron
Bromodichloromethane
Bromoform
Butylbenzylphthalate
Cadmium
Carbaryl
Carbazole
Carbofuran
Carbon disulfide
Carbon tetrachloride
Chlorobenzene
Chloroethane
Chloroform
Chioromethane
Chromium(total)
Chrysene
Cobalt
Copper
Cyanide
Delta-BHC
Dl-n-butylphthalate
Dl-n-octylphthaiate
Dibenzofuran
Dibromochloromethane
Dicamba
Dieldrin
82
2,700
22
30
25
27
5
20
5
87
40
32
62
49
36
40
17
45
120
75
0
20
22
15
27
4
0.19
7.3
400
5.1
6.1
ND
ND
ND
ND
ND
7.4
ND
ND
ND
6.6
ND
3.5
ND
11
10
ND
0.026
7.3
ND
ND
5.5
ND
ND
5.4
220
ND
ND
ND
2.2
ND
ND
ND
ND
ND
ND
ND
2.7
ND
5.0
ND
2.0
9.5
13
ND
5.7
ND
ND
ND
ND
ND
9.3
310
ND
ND
ND
ND
ND
ND
ND
5.1
ND
ND
ND
2.6
ND
12
ND
20
15
8.7
ND
5.5
8.3
ND
ND
ND
ND
23
130
ND
ND
ND
2.6
ND
ND
ND
ND
ND
ND
ND
ND
ND
13
ND
4.7
20
3.6
ND
10
7.8
ND
ND
ND
ND
-------
Table 14-1
Chemical Concentration Data Summary
Page 5 of 5
95th Percentile Upper Confidence Limit on the Geometric Mean of Median Well Concentrations
(ug/1)
Chemical Name
Shallow Ground-water Monitoring
Wells Completed in Weathered
Dawson and Waste Pit Liguids Well
Points Within the Source Area
Ground-water Monitoring
Wells Completed in
Weathered Dawson Aguifer
Outside of the Source Area
Ground-water Monitoring Deep Ground-
Wells Completed in water
Unweathered Dawson Aguifer Monitoring
Outside of the Source Area Wells
Upgradient Ground-
water Monitoring
Wells Outside the
Source Area
Nickel
PCB-1242(Aroclor 1242)
PCB-1248(Aroclor 1248)
PCB-1260(Aroclor 1260)
Pentachlorophenol
Phenanthrene
Phenol
Propoxur
Pyrene
Selenium
Silver
Styrene
Tetrachloroethylene
Thallium
Tin
Toluene
Total xylenes
Trichloroethylene
Vanadium
Vinyl chloride
Zinc
230
2.03
ND
2.3
130
36
120
ND
20
170
11
38
190
61
480
1, 600
930
250
130
99
410
25
ND
ND
ND
ND
ND
7.3
ND
7.3
29
3.5
ND
37
6.5
40
4.9
15
27
15
8.5
37
9.5
ND
ND
ND
ND
ND
5.7
0.92
ND
5.1
3.8
ND
3.4
1.6
28
2.3
ND
2.9
6.1
ND
24
33
ND
ND
ND
ND
ND
6.2
ND
ND
2.4
ND
ND
18
2.8
ND
13
9.2
7.4
15
ND
40
30
ND
ND
ND
ND
ND
6.9
ND
ND
100
2.8
ND
3.5
ND
ND
2.6
ND
2.9
26
ND
110
Note: ND = Not detected.

a2,3,7,8-Dioxin eguivalent concentration.
-------
Section 15.0
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Personal communication by S. Cross regarding attendance at the Aurora Reservoir. 1992.

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"Mobility and Bioavaibility of Chromium in Soils." Advanced Environmental Science and Technology,
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Draft Phase I Feasibility Study. Lowry Landfill: Soils and Surface Water and Sediments Operable
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Carlson, J. Personal communication regarding electric utility repairs. Public Service Company of Colorado.
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City and County of Denver. Executive Order No. 97. Restrictions on the Use of Land, Surface Water and
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Colorado Climate Center. Pan Evaporation at Cherry Creek Reservoir from 1951 through 1985. 1989.

Colorado Department of Health. Personal Communication between Angus Campbell of CDH regarding status of CWM
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Memorandum from N. Chick to Ron Abel, HMWMD. Subject: PM10 Data for Lowry Landfill. June 17, 1992.

Colorado Division of Wildlife (CDOW) . Latilong Microcomputer Database-Species Lists for Terrestrial
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1992.

Colorado Interstate Gas. Personal communication by M. Price regarding gas utility repairs. 1992.

Colorado State University. Personal Communication by Nolan Deskin of CSU regarding frozen ground and
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Personal communication by Nolan Deskin regarding local weather data for the Lowry Landfill vicinity.
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Denver, CWM, and WMC. Administrative Order on Consent: Docket No. VIII-90-1. Lowry Landfill, Landfill
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Denver, CWM, and WMC. Revised Draft Initial Data Evaluation Report Lowry Landfill: Landfill Solids and
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Denver and Metro. Draft Initial Data Evaluation Report. Lowry Landfill, Soils and Surface Water and
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Phase I RI Lowry Landfill, Arapahoe County, Colorado. Hazardous Site Control Division Contract No.
68-01-7251. CH2M HILL. EPA No. 38-8108.3. September 2, 1986.

Guidelines for Carcinogen Risk Assessment. Federal Register 51: 33992-34003. September 24, 1986.

Data Quality Objectives for Remedial Response Activities. EPA/540/6-87/003 (OSWER directive
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Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA. Interim Final.
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Integrated Risk Information System: Background Information. EPA Integrated Risk Information System
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Phase II RI/FS Overall Site Work Plan, Lowry Landfill, Arapahoe County, Colorado, Hazardous Site
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Endangerment Assessment Design Document. Hazardous Site Control Division, Lowry Landfill, Arapahoe
County, Colorado. Contract No. 68-01-7251, CH2M Hill, September 1988.

Interim Procedures for Estimating Risk Associated With Exposures to Mixtures of Chlorinated
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Phase II RI/FS Data Summary Technical Memorandum No. 11, Meteorological Installation and Monitoring
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Phase II RI/FS Data Summary Technical Memorandum No. 19, Meteorological Installation and Monitoring
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Risk Assessment Guidance for Superfund Volume II: Environmental Evaluation Manual. Interim Final.
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Preliminary Endangerment Assessment, Hazardous Site Control Division, Lowry Landfill, Arapahoe County,
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EPA/540/1-89/002, Office of Emergency and Remedial Response, Washington, B.C. December 1989.

Exhibit A to the Second Amended and Restated Administrative Order on Consent, and Conceptual Work Plan
for the Remedial Investigation/Feasibility Study Shallow Ground-Water and Subsurface Liguids and Deep
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National Oil and Hazardous Substances Pollution Contingency Plan (NCP) 40 CFR Part 300; 53 Federal
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Reducing Risk: Setting Priorities and Strategies for Environmental Protection. Science Advisory Board
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Guidance for Data Usability in Risk Assessment. EPA/540/G-90/008. Office of Emergency and Remedial
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PRPs at Lowry Landfill Waste Summaries. December 1990.

Interim Guidance on Establishing Soil Lead Cleanup Levels at Superfund Sites. Office of Solid Wastes
and Emergency Response. Directive No. 9355.4-02. 1991.

National Primary Drinking Water Regulations: Radionuclides. Proposed Rule, 40 CFR, Parts 141 and
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Summary Report on Issues in Ecological Risk Assessment. Risk Assessment Forum. United States
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Technical Support Document for Lead. Environmental Criteria and Assessment office. 1991.

National Primary Drinking Water Regulations Monitoring for Synthetic Organic Chemicals; MCLGs and MCLs
for Aldicarb, Aldicarb Sulfoxide, Aldicarb Solfone, Pentachlorophenol and Barium, Proposed Rule. 40
CFR Parts 141 and 142. Federal Register 56, No. 20. January 30, 1991.

Conducting Remedial Investigation/Feasibility Studies for CERCLA Municipal Landfill Sites. OSWER
directive 9355.3-11. February 1991.

Human Health Evaluation Manual, Supplemental Guidance: Standard Default Exposure Factors. Office of
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Maximum Contaminant Level Goals and National Primary Drinking Water Regulations for Lead and Copper.
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Chromium (III) Compounds; Toxic Chemical Release Reporting; Community Right-to-Know. Federal
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Framework for Ecological Risk Assessment. United States Environmental Protection Agency. Risk
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Integrated Risk Information System: U.S. EPA Integrated Risk Information System Data Base.
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Peer Review Workshop Report on a Framework for Ecological Risk Assessment. Risk Assessment Forum.
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Remedial Activities as Uncontrolled Hazardous Waste Site in the Zone of Regions VI, VII, and VIII.
Draft Baseline Risk assessment Shallow Ground-Water and Subsurface Liguids and Deep Ground-Water
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Risk Assessment Data Useability Evaluation, Landfill Solids, Landfill Gas, Soils, Surface Water, and
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68-W8-0112. CH2M HILL. 1992.

Health Effects Assessment Summary Tables, FY-92 Annual. Office of Research and Development. OERR
9200.6-303 (92-1). January 1992.
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Baseline Risk Assessment Shallow Ground-Water and Subsurface Liquids and Deep Ground-Water Operable
Units. (OUs 1&6) Volume 1 of 3. Lowry Landfall. Arapahoe County, Colorado. February 1992.

Guidance of Risk Characterization for Risk Managers and Risk Assessors. Office of the Administrator.
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Supplemental Guidance to RAGS: Calculating the Concentration Term. Office of Solid Wastes and
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Final RI Report for the Shallow Ground-Water and Subsurface and Deep Ground-Water Operable Units (OUs
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Shallow Ground-Water and Subsurface Liquids and Deep Ground-Water Operable Units, Lowry Landfill,
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Field Oversight of Camp Dresser & McKee, Inc. Activity Report - May 7, 1992 through May 15, 1992.
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EPA Responses on the February 1992 Draft Baseline Risk Assessment Shallow Ground-Water and Subsurface
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1992.

Proposed Plan for Operable Units 1&6: Shallow Ground Water and Subsurface and Deep Ground Water.
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Baseline Risk Assessment. Landfill Solids and Landfill Gas Operable Units, Soils and Surface Water
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Final Operable Units 4&5 Remedial Investigation. Lowry Landfill: Soils and Surface Water and
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Activity Report for Oversight of Compliance Boundary Sampling. Lowry Landfill, Arapahoe County,
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Feasibility Study for the Landfill Solids and Landfill Gas Operable Units (Ous 2&3), Lowry Landfill,
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Feasibility Study for the Soils, Surface Water, and Sediments Operable Units (Ous 4&5), Lowry
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Final Operable Units 2&3 Remedial Investigation. Lowry Landfill: Landfill Solids and Landfill Gas
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Proposed Plan for Operable Units 2&3 and 4&5. Lowry Landfill, Arapahoe County, Colorado. September
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Lowry Coalition. The Initial Data Evaluation Summary and Conclusions Report for the Shallow Ground-Water and
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Lowry Landfill and Environs. Goals and Objectives-Draft. August 17, 1992.

Simon Hydro-Search. Final Additional Site Characterization and Treatability Study Field Activities, Planning
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Draft Data Summary Report Lowry Landfill: Landfill Solids and Landfill Gas Operable Units Remedial
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U S WEST Communications. Personal communication by T. Bugal regarding telephone utility repairs. 1992.

Waste Management Incorporated. Draft Meteorological Monitoring Technical Memorandum, Volume I of II, Lowry
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