PB98-964507
                             EPA 541-R98-041
                             March 1999
EPA Superfund
      Record of Decision:
      Andersen Air Force Base OU 3
      (Marbo Annex)
      Yigo, Guam
      6/16/1998

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    THE UNITED STATES AIR FORCE
INSTALLATION RESTORATION PROGRAM
               FINAL

     MARBO ANNEX OPERABLE UNIT
         RECORD OF DECISION
                 for

       Andersen Air Force Base, Guam
               May 1998

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                           TABLE OF CONTENTS

Section                                                            Page

1.0   DECLARATION	  1-1
      1.1    SITE NAME AND LOCATION	  1-1
      1.2    STATEMENT OF BASIS AND PURPOSE	  1-1
      1.3    ASSESSMENT OFTHESITE	  1-1
      1.4    DESCRIPTION OF THE SELECTED REMEDY	  1-2
            1.4.1    Soil	  1-2
            1.4.2    Groundwater	:	  1-4
      1.5    STATUTORY DETERMINATIONS	  1-5
      1.6    SIGNATURES	  1-6

2.0   DECISION SUMMARY FOR SOIL	  2-1
      2.1    SITE NAME, LOCATION, AND DESCRIPTION	  2-1
            2.1.1    Site 20 (Waste Pile 7)	  2-2
            2.1.2    Site 22 (Waste Pile 6)	  2-3
            2.1.3    Site 23 (Waste Pile 5)	  2-3
            2.1.4    Site 24 (Landfill 29)	  2-4
            2.1.5    Site 37 (War Dog Borrow Pit)	  2-5
            2.1.6    Site 38 (MARBO Laundry)	  2-5
      2.2    REGIONAL PHYSIOGRAPHY	  2-6
            2.2.1    Geology	  2-6
            2.2.2    Hydrogeology of Northern Guam	  2-7
            2.2.3    Water Use	2-11
            2.2.4    Andersen AFB Soils	2-12
            2.2.5    Climatology and Meteorology	2-13
            2.2.6    Biology and Ecology	2-14
            2.2.7    Demographics	2-18
      2.3    SITE HISTORY AND ENFORCEMENT ACTIVITIES	2-21
      2.4    HIGHLIGHTS OF COMMUNITY PARTICIPATION	2-24
            2.4.1    Community Relations Activities	2-25
      2.5    SCOPE AND ROLE OF OPERABLE UNIT WITHIN THE SITE
            STRATEGY	2-26
      2.6    SUMMARY OF SITE CHARACTERISTICS	2-27
            2.6.1    Contaminant Screening Process	2-27
            2.6.2    Potential Routes of Exposure	2-37
      2.7    SUMMARY OF SITE RISKS	2-38
      2.8    DESCRIPTION OF ALTERNATIVES	2-43
            2.8.1    No Action (Alternative OU3-A)	2-44
            2.8.2    Institutional Control (Alternative OU3-B)	2-44
            2.8.3    Soil Cover (Alternative OU3-C)	2-45
            2.8.4    Soil Removal (Alternative OU3-D)	2-46
      2.9    SUMMARY OF COMPARATIVE ANALYSIS ALTERNATIVES	2-48
            2.9.1    Overall Protection of Human Health and the Environment	2-49
Andersen AFB MARBO Annex               i                             4/1/98
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                            TABLE OF CONTENTS
                                  (Continued)
Section
            2.9.2    Compliance with ARARs	2-51
                    2.9.2.1   Chemical-Specific ARARs	2-53
                    2.9.2.2   Location-Specific ARARs	2-54
                    2.9.2.3   Action-Specific ARARs	2-54
            2.9.3    Short-Term Effectiveness	2-55
            2.9.4    Long-Term Effectiveness and Permanence	2-56
            2.9.5    Reduction of Toxicity, Mobility, or Volume
                    Through Treatment	2-57
            2.9.6    Implementability	2-57
            2.9.7    Cost	2-59
            2.9.8    Federal and Territory Regulatory Acceptance	2-59
            2.9.9    Community Acceptance	2-59
      2.10  THE SELECTED REMEDY	!	2-60
            2.10.1   Site 20 (Waste Pile 7)	2-60
            2.10.2   Site 22 (Waste Pile 6)	2-64
            2.10.3   Site 24 (Landfill 29)	2-66
            2.10.4   Site 38 (MARBO Laundry)	2-68
      2.11  STATUTORY DETERMINATIONS	2-69
            2.11.1   Protection of Human Health and the Environment	2-70
            2.11.2   Compliance with ARARs	2-70
            2.11.3   Cost Effectiveness	2-70
            2.11.4   Utilization of Permanent Solution and Alternative Treatment
                    (or Resource Recovery) Technologies to the Maximum
                    Extent Possible	2-70
            2.11.5   Preference for Treatment as a Principle Element	2-71
      2.12  DOCUMENTATION OF SIGNIFICANT CHANGES	2-71

3.0   DECISION SUMMARY FOR GROUNDWATER	 3-1
      3.1    SITE HISTORY AND ENFORCEMENT ACTIVITIES	 3-1
      3.2    SUMMARY OF SITE CHARACTERISTICS	 3-5
            3.2.1    Nature and Extent of TCE and PCE	 3-5
            3.2.2    Fate and Transport of TCE and PCE	3-11
            3.2.3    TCE and PCE Trends in Groundwater	3-13
            3.2.4    Potential Routes of Exposure	3-14
      3.3    SUMMARY OF SITE RISKS	3-14
            3.3.1    Human Health Risk	3-14
            3.3.2    Ecological Risk	3-17
      3.4    DESCRIPTION OF ALTERNATIVES	3-18
            3.4.1    No Action (Alternative G-l)	3-18
            3.4.2    Natural Attenuation with Wellhead Treatment
                    (Alternative G-2)	3-18
Andersen AFB MARBO Annex                ii                               4/1/98
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                            TABLE OF CONTENTS
                                 (Continued)
Section
            3.4.3   Ex-Situ Groundwater Treatment (Alternative G-3)	3-21
      3.5    COMPARATIVE ANALYSIS OF ALTERNATIVES SUMMARY	3-23
            3.5.1   Overall Protection of Human Health and the Environment	3-25
            3.5.2   Compliance with ARARs	3-26
            3.5.3   Short-Term Effectiveness	3-30
            3.5.4   Long-Term Effectiveness and Permanence	3-31
            3.5.5   Reduction of Toxicity, Mobility, or Volume
                   Through Treatment	3-32
            3.5.6   Implementability	3-32
            3.5.7   Cost	3-33
            3.5.8   State/Territory Acceptance	3-34
            3.5.9   Community Acceptance	3-34
      3.6    THE SELECTED REMEDY	3-35
      3.7    STATUTORY DETERMINATIONS	3-36
            3.7.1   Protection of Human Health and the Environment	3-37
            3.7.2   Compliance with ARARs	3-37
            3.7.3   Cost Effectiveness	,	3-37
            3.7.4   Utilization of Permanent Solution and Alternative Treatment
                   (or Resource Recovery) Technologies to the Maximum
                   Extent Possible	3-37
            3.7.5   Preference for Treatment as a Principle Element	3-38
      3.8    DOCUMENTATION OF SIGNIFICANT CHANGES	3-38

4.0   RESPONSIVENESS SUMMARY	  4-1
      4.1    OVERVIEW	  4-1
      4.2    BACKGROUND ON COMMUNITY INVOLVEMENT	  4-1
      4.3    SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC
            COMMENT PERIOD	  4-2

REFERENCES

APPENDICES

A - Region IX Preliminary Remediation Goals (PRGs) Second Half 1995
B - Residual Risk Calculations
    Risk Assumptions and Uncertainties
C - Regulatory Comments and Responses
Andersen AFB MARBO Annex                iii                              4/1/98
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                               LIST OF FIGURES

                                                                         Follows
                                                                           Page

        Base Layout	   2-1
        MARBO Annex Layout with Production and Monitoring Well Location	   2-1
        Disposal/Spill Area Locations, Site 20 (Waste Pile 7)	   2-2
        Disposal/Spill Area Locations, Site 22 (Waste Pile 6)	   2-3
        Disposal/Spill Area Locations, Site 24 (Landfill 29)	   2-4
        Disposal/Spill Area Locations, Site 38 (MARBO Laundry)	   2-5
        Structure Contour and Subbasin Map, Northern Guam	   2-6

 3-1     PCE and TCE Concentrations, October-November 1995	   3-5
 3-2     PCE and TCE Concentrations, February-March 1996	   3-5
 3-3     PCE and TCE Concentrations, October-November 1996	   3-5
 3-4     PCE and TCE Concentrations, April-May 1997	   3-5
 3-5     Maximum Historical Concentrations of PCE and TCE	   3-5
 3-6     February 1996 Groundwater Contours for MARBO Annex	   3-5
                                LIST OF TABLES
 2-1     Soil Analysis Range of Detections	  2-29
 2-2     Site Constituent Screening	  2-32
 2-3     Site-Specific Constituents of Concern and Estimated Risk	  2-40
 2-4     Comparison of Soil Alternatives	  2-50
 2-5     Summary of ARARs and TBCs	  2-52
 2-6     Summary of Remedial Alternative Costs and ARARs	  2-63

 3-1     Historical Monitoring and Production Well Sampling	   3-2
 3-2     TCE Concentration Ranges at MARBO Annex Production Wells and
        Monitoring Wells	   3-6
 3-3     PCE Concentration Ranges at MARBO Annex Production Wells and
        Monitoring Wells	   3-8
 3-4     Estimated Human Health Risk	  3-16
 3-5     Summary of TCE/PCE Concentration Changes	  3-19
 3-6     Comparison of Groundwater Alternatives	  3-24
 3-7     Chemical-Specific ARARs and TBCs	  3-27
 3-8     Action-Specific ARARs and TBCs	  3-28
 3-9     Location-Specific ARARs and TBCs	  3-29
Andersen AFB MARBO Annex                 iv                               4/1/98
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                   LIST OF ACRONYMS AND ABBREVIATIONS
AAFB
AFB
ARAR
bgs
CAA
CERCLA
CFR
COC
COPC
CRP
cy
DCE
DDE
DEQPPM
DOD
DTSC
EPC
ESA
ESE
FFA
FIFRA
FS
ft/day
GCA
GEPA
GPA
gpm
GWA
HARM
HI
HSWA
IRP
MARBO
MCL
MEK
mgd
mg/L
MIBK
mph
msl
NCP
NGL
Andersen Air Force Base
Air Force Base
Applicable or Relevant and Appropriate Requirements
Below Ground Surface
Clean Air Act
Comprehensive Environmental Response, Compensation And Liability Act
Code of Federal Regulations
Constituent of Concern
Constituent of Potential Concern
Community Relations Plan
cubic yard
1,1-dichloroethene; 1,2-dichloroethene (also known as vinylidene chloride)
Dichlorodiphenyldichloroethylene
Defense Environmental Quality Program Policy Memorandum
Department of Defense
Department of Toxic Substances Control
Exposure Point Concentration
Endangered Species Act
Environmental Science and Engineering, Inc.
Federal Facility Agreement
Federal Insecticide, Fungicide, and Rodenticide Act
Feasibility Study
feet per day
Guam Code Annotated
Guam Environmental Protection Agency
Guam Power Authority
gallons per minute
Guam Waterworks Authority
Hazard Assessment Rating Methodology
Hazard Index
Hazardous and Solid Waste Act
Installation Restoration Program
Marianas/Bonins Command
Maximum Contaminant Level
Methylethylketone
million gallons per day
micrograms per liter
milligrams per liter
Methyl isobutyl ketone
miles per hour
mean sea level
National Oil And Hazardous Substances Pollution Contingency Plan
Northern Guam Lens
Andersen AFB MARBO Annex
Record of Decision
                                                          4/1/98

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NGLS
NPL
NWS
O&M
OU
PAH
PCB
PCE
P.L.
POL
PRO
PUAG
RAB
RCRA
RI
RI/FS
RME
ROD
RPM
RWQCB
SAP
SARA
SDWA
SVOC
SWMU
TAG
TBC
TCE
TCLP
TMV
TRC
TSCA
UCL
USAFOEHL
USAF
USEPA
USFWS
USGS
USN
VOC
  LIST OF ACRONYMS AND ABBREVIATIONS
                  (Continued)

Northern Guam Lens Study
National Priorities List
National Weather Service
Operations and Maintenance
Operable Unit
Polycyclic Aromatic Hydrocarbon
Polychlorinated Biphenyl
Tetrachloroethylene
Public Law
Petroleum, Oil, and Lubricants
Preliminary Remediation Goal
Public Utility Agency of Guam
Restoration Advisory Board
Resource Conservation and Recovery Act
Remedial Investigation
Remedial Investigation/Feasibility Study
Reasonable Maximum Exposure Scenario
Record of Decision
Remedial Project Manager
Regional Water Quality Control Board
Sampling and Analysis Plan
Superfund Amendments and Reauthorization Act of 1986
Safe Drinking Water Act
Sernivolatile Organic Compound
Solid Waste Management Unit
Technical Assistance Grant
To Be Considered
Trichloroethylene
Toxicity Characteristic Leachate Procedure
Toxicity, Mobility and Volume
Technical Review  Committee
Toxic Substances Control Act
Upper Confidence Limit
USAF Occupational and Health Environmental Laboratory
U.S. Air Force
United States Environmental Protection Agency
U.S. Fish and Wildlife Service
United States Geological Survey
U.S. Navy
Volatile Organic Compound
Andersen AFB MARBO Annex
Record of Decision
                         VI
4/1/98

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                               1.0 DECLARATION

1.1          SITE NAME AND LOCATION

Andersen Air Force Base
MARBO Annex Operable Unit
Guam, USA

1.2          STATEMENT OF BASIS AND PURPOSE

This decision document, a Record of Decision (ROD), presents the selected remedial actions for
soil and groundwater at the Marianis/Bonins Command (MARBO) Annex Operable Unit (OU) at
Andersen Air Force Base (AFB), Guam.  The selected remedial alternatives were 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).  The MARBO Annex OU includes six sites within the
property line of the MARBO Annex, and groundwater underlying the Annex.  This decision is
based on the Administrative Record for this site and complies  with  40 Code of Federal
Regulations (CFR),  Pan 300. The purpose of this ROD is to set forth the remedial action to
remediate soil and groundwater that has been impacted by past activities at Andersen AFB.

The U.S. Air Force  (USAF), U.S. Environmental Protection Agency (USEPA) Region IX, and
the Guam Environmental Protection Agency (GEPA) concur with the selected remedy.

13          ASSESSMENT OF THE SITE

Risks to human health and the environment were evaluated for groundwater underlying MARBO
and at six surface sites within MARBO.  No risk was found at Waste Pile 5 and the War Dog
Borrow Pit, so no further action is planned for these two sites. Current risks associated with soil
Andersen AFB MARBO Annex                    1-1                                4/1/98
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exceed acceptable risk levels at Waste Pile 6, Waste  Pile 7, Landfill 29, and the MARBO
Laundry, thus remedial alternatives were evaluated for these four sites (ICF, 1996). Current risks
associated with contaminants in groundwater at the MARBO Annex are within the acceptable
risk   management   range   utilized  by   the   USEPA.    Trichloroethylene   (TCE)   and
tetrachloroethylene (PCE) concentrations in groundwater still exceed the Safe Drinking Water
Act (SDWA) Maximum Contaminant Levels (MCLs) in two locations, thus requiring an analysis
of remedial alternatives.

Actual or threatened releases of hazardous substances from the four soil sites, if not addressed by
implementing the remedial actions presented in this ROD, may present a risk to public health,
welfare, or the environment.

1.4          DESCRIPTION OF THE SELECTED REMEDY

This ROD addresses the selected remedy for soil at the four sites, as well as groundwater
underlying the  MARBO Annex  OU.  The MARBO Annex OU is the first of four OU's at
Andersen AFB to complete the CERCLA regulatory process, which includes site investigation
and the recommendation of remedial alternatives for soil  and groundwater, if necessary.

1.4.1        Soil

Based on alternatives evaluated in the OU 3 Focused FS (ICF,  1997a) the US Air Force, the
USEPA, and Guam have selected Soil Removal (Alternative OU3-D) as the remedy for three of
the sites, and Soil Cover (Alternative OU3-C) for one of the sites.  The alternatives are described
briefly below:

Soil Removal is the selected alternative  for Sites 22 (Waste Pile 6), 24 (Landfill 29) and 38
(MARBO Laundry).   The Constituents of Concern  (COCs)  at  the  four  sites include
polychlorinated biphenyl (PCB) Aroclor 1254;  metals lead, antimony, cadmium, chromium and
arsenic; and polycyclic  aromatic hydrocarbons  (PAH's)  benzo(a)anthrocene, benzo(a)pyrene,
Andereen AFB MARBO Annex                     1 -2                                4/1 /98
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benzo(b)fluoranthene and indeno (1,2,3 cd) pyrene.  The soil removal alternative consists of the

following:
       •      Site preparation for soil removal  and preparation  of appropriate construction
              support plans (e.g., Health and Safety Plan, Quality  Assurance Project Plan, and
              Environmental Response Plan);

       •      Excavation of soil with contaminant concentrations exceeding cleanup screening
              criteria.  Backfill and compaction of the excavations with clean soil will be
              performed.  Confirmatory sampling  will be performed after an  excavation to
              verify that soil exceeding the screening criteria is removed;

       •      Soil and  debris disposal.  Impacted soil and debris which are considered non-
              hazardous will be excavated  and disposed of as solid waste in the Andersen AFB
              solid waste landfill.  If the soil and debris  are considered hazardous (based on a
              Toxicity  Characteristic Leachate Procedure  [TCLP] - analysis), then  it will be
              consolidated for off-island disposal at a licensed hazardous waste facility;

       •      Public meetings to  inform  Andersen AFB personnel and local residents of
              potential  risks during and after soil removal.  Risks may include the exposure risk
              during soil  removal and/or residual  risk after soil  removal (residual  risk  is
              expected  to be within USEPA's risk  management  range).  This  effort will be
              completed as part  of the existing  community relations program  established  at
              Andersen AFB.


Soil Cover is the selected alternative for Site 20 (Waste Pile 7). The COCs for Site 20 include

pesticides 4,4'-DDE, 4,4'-DDT, Dieldrin, alpha-chlordane and  gamma-chlordane; PCB Aroclor

1260; and the metal lead. The soil cover alternative consists of the following:
              Site  preparation for soil-fill  stockpile areas,  and preparation  of appropriate
              construction support plans (e.g., a Health and Safety  Plan, Quality Assurance
              Project Plan, and Environmental Response Plan);

              Soil  cover construction over  1.8 acres of Site 20.  Fill consisting of locally
              available crushed coral will be used to establish a subgrade layer up to 6 inches in
              depth that will be followed with a 12-inch soil layer  consisting of clayey  silt
              obtained from borrow sources on the island.  In addition, a final 6-inch soil layer,
              obtained locally, will be used to accommodate the root system of the vegetation
              established over the covered area;
Andersen AFB MARBO Annex                       1-3                                   4/1/98
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       •     A fence will be constructed around the site to prevent access during revegetation.
             Signs will be posted to restrict access to the site, and deed restrictions to place
             legal constraints on any future use of the site;

       •     Public education to inform Andersen AFB personnel and  local residents  of
             potential risks during soil cover construction and after completion of the soil
             cover. Risk education will address exposure risk during soil  cover construction
             and residual risk after installation of the soil cover (residual risk is expected to  be
             within USEPA's risk management range).  This will also include public meetings
             and presentations, press releases, and posting of signs where appropriate.  Similar
             to the Soil Removal  Alternative, this effort will  be completed as part  of the
             existing community relations program established at Andersen AFB.

       •     A review of site conditions every 5 years.  Periodic reviews will include  an
             evaluation of existing and new information along with an assessment of the future
             use of the site.


1.4.2         Groundwater


Based on alternatives evaluated in the OU 2 Focused FS (EA and Montgomery Watson, 1997)
the USAF, the USEPA, and the Guam EPA have selected Natural Attenuation with Wellhead
Treatment (Alternative G-2) as the remedy for the TCE and PCE contaminated groundwater
beneath the  MARBO  Annex.   The  remedy  addresses  the  principal threat of elevated
concentrations of TCE and/or PCE in the drinking water through monitoring existing wellhead
treatment and institutional controls. The potential threat of further migration of TCE and/or PCE
is addressed via long-term monitoring. The selected remedy consists of:
             Natural attenuation of TCE and PCE in the aquifer. TCE and PCE concentrations
             in groundwater indicate an overall decreasing trend, and are expected to decrease
             to concentrations below federal MCLs;

             Continued wellhead treatment at those wells which are presently undergoing Air
             Stripping. The treatment of these wells will continue until influent TCE and PCE
             concentrations are consistently below federal MCLs;

             Long-term sampling and monitoring of select production and monitoring wells in
             the MARBO Annex, and  adjacent to the MARBO Annex.  The frequency and
             number  of  wells to  be  monitored will  be  addressed  every two  years, in
             conjunction with the Basewide Groundwater Monitoring Plan.
Andersen AFB MARBO Annex                     1-4                                  4/1/98
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             Institutional controls  to  monitor groundwater  development  in  those areas
             impacted by  TCE and PCE.   This will  be done primarily  through Guam's
             Groundwater Protection Zone Policies.
1.5          STATUTORY DETERMINATIONS

The selected remedies are protective of human health and the environment, comply with Federal
and Territory requirements that are legally applicable or relevant and appropriate to the remedial
action, and are cost-effective.  These remedies utilize permanent solutions to the maximum
extent practicable. The benefit resulting from treatment of the soil and groundwater would result
in substantial and disproportionate effort and cost, thus the soil and groundwater remedies do not
satisfy the statutory preference for treatment as a principal element of the remedy.  The depth to
groundwater in a highly conducive aquifer precludes a remedy where groundwater could be
treated effectively. The small volume of soil and distribution of contaminants at Waste Pile 7
similarly precludes a treatment alternative. Because the remedy for Waste Pile 7 will result in
hazardous substances remaining on-site above health based levels, a review will be conducted
within five years after the commencement of the remedial action to  ensure that the remedy
continues to provide adequate protection of human health and the environment.  A review of the
selected groundwater alternative will occur every five years as part of the ROD process, and
every two  years  to evaluate the  frequency and number  of wells which require long-term
monitoring as part of the Andersen AFB Long-Term Monitoring Plan.

1.6          SIGNATURES

The following  pages  are  signature pages for the Air Force, United  States Environmental
Protection Agency, Region 9 and the Guam Environmental Protection Agency.
Andersen AFB MARBO Annex                    1 -5                                 4/1/98
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Euge£b D. Ssmardli                                   Date
Lieutenant Genoa], USAF
Vice ComznandeT, Pacific Air Forces (PACAF)
 AndmcnAFBMARBO Annex                    1-6                               4/1/98
 Record of Decision

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          UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
DarHJpalski
Chief Federal Facilities Cleanup Branch
U.S. Environmental Protection Agency Region IX
          Date
Andersen AFB MARBO Annex
Record of Decision
1-7
4/1/98

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TERRITORY OF GUAM ENVIRONMENTAL PROTECTION AGENCY
Jesus Salas
Administrator
Guam Environmental Protection Agency
                                          Date
Andersen AFB MARBO Annex
Record of Decision
                                       1-8
                                                               4/1/98

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                        2.0 DECISION SUMMARY FOR SOIL

This decision summary provides a description of the MARBO Annex and the six Installation
Restoration Program (IRP) sites, including the  regional setting, physiography, meteorology,
demography and land use, hydrology, hydrogeology, and  water use.   This  section  also
summarizes legal and public involvement issues, site risks, remedial alternatives,  the rationale
for the  selection, and how the  selected remedy satisfies statutory  requirements.   The site
investigation and risk assessment is included in the OU 3 Remedial Investigation (RI) report,
conducted and  written by  ICF Technology, Incorporated (ICF,  1996).   The evaluation  of
remedial alternatives  was also  performed by ICF, and  is included in  the OU 3 Focused
Feasibility Study (FFS) report (ICF, 1997a).

2.1          SITE NAME, LOCATION, AND DESCRIPTION

Andersen AFB is located on the northern half of the island of Guam.  The largest island in the
Mariana Islands, Guam is located in the western Pacific region, approximately halfway between
Japan and New Guinea, between latitudes 13° 15° N. and 13° 39° N. and longitudes 144° 37° E.
and 144° 57° E.  The island covers an area of nearly 209 square miles, and is approximately  30
miles long and from 4 to 8  miles wide (Figure 2-1).  Andersen AFB is located on the northern
half of the island which is a broad undulating limestone plateau overlying a volcanic core.

Andersen AFB consists of several parcels of land located in the northern portion of the island,
comprising North and Northwest Fields, and is 8 miles wide, between 2 and 4 miles  long, and
covers approximately 24.S square miles. It is bounded on the east, north and west by cliffs rising
about 500 feet above the ocean.  The active base  operations are located on the Main Base.
Northwest Field has been  generally  inactive since the mid  1950s.   Several non-contiguous
properties are also part of Andersen AFB. The Harmon Annex contains a 2.8-square-mile area
along the west side of the island, 4 miles south of Northwest Field, and is sparsely populated.
The MARBO Annex, which contains the six sites addressed in this section, lies 4 miles south of
North and Northwest Fields, and covers a 3.8-square-mile area (Figure 2-2).
Andersen AFB MARBO Annex                     2-1                                  4/1/98
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                                                                          PLOT SCALE:  1=1


                                                                          REVISED:  04/15/98
             LEGEND:
                    ANDERSEN AFB PROPERTY



               •    TOWN SITE
                                                                     ANDERSEN
                                                                   AIR FORCE BASE
                                                       BARRIGADA
                                                      COMMUNICATION
                                                         ANNEX
                                                                       SCALE


                                                                   01234 MILES
     SOURCE: ESE. 1985
                                                                  FIGURE  2-1
MARBO ANNEX  - RECORD OF  DECISION
  ANDERSEN  AIR FORCE  BASE, GUAM
                                                               BASE LAYOUT
                                                   DATE:   9/29/97
                                                                  SCALE:  AS NOTED

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                                                                                                                  ^ J^      ^  (     "1  msimc si«uci
                                                                                                                           \ IHWn * 'AM IMC

                                                                                                                           /         CUSIINC
I>1.0I SOU: I-1100
                                                                                  MARBO ANNEX - RECORD OF  DECISION
                                                                                    ANDERSEN  AIR FORCE BASE. GUAM
 MARBO  ANNEX LAYOUT WITH
PRODUCTION  AND MONI10RING
      WELL LOCAlIONS
                                                                                                                     DAU:   9/29/97   I SCALE: AS NOTED

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2.1.1         Site 20 (Waste Pile 7)

Waste Pile 7 is located in the south-central portion of the MARBO Annex (Figure 2-2).  Waste
Pile 7 is an abandoned  quarry that is partially filled with waste, and covered with soil and
vegetation.  The "Buried Waste Area," which was the focus  of the investigation,  covers
approximately 1.84 acres in size and has an average depth to the bottom of the fill layer of
10.8 feet.

Based on information from previous IRP studies and site visits conducted in 1992, Waste Pile 7
was thought to consist of two separate disposal areas (Figure 2-3).  Area A was considered to be
a former quarry that was partially filled with waste, and covered with soil and vegetation. Area
B adjoins  the Area A quarry, and based on site inspections performed in the summer of 1992,
was suspected to contain numerous mounds of soil-covered construction debris.  Following a
review  of historical  records, a  topographic  survey,  a detailed  site  inventory, exploratory
excavations, and geophysical and soil gas surveys, Area A was found to be a former quarry
partially filled with waste and soil, and covered with vegetation  (ICF,  1996).  The mounds in
Area B  were found to consist of mostly soil with very limited scattered debris.  These mounds
may have  been created by the removal of soil from the Area A quarry at the initiation of quarry
operations.

As a result of these findings, the boundary of Waste Pile 7 was redefined to include only the
portion  of the Area  A  quarry that contained buried waste.  Additional sampling was also
conducted at a soil mound in Area B and at an Empty Drum Area southwest of the Buried Waste
Area.  For reference, the original site reconnaissance boundary, and other boundaries discussed
here are shown on Figure 2-3.  Based on a risk evaluation of soil analytical data, a health risk
was identified for this  site.  The  COCs identified at Site  20  include pesticides 4,4'-DDE,
4,4-DDT,  Dieldrin, alpha chlordane  and gamma chlordane; the PCB Aroclor 1260; and the metal
lead.
Andersen AFB MARBO Annex                     2-2                                  4/1/98
Record of Decision

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directory  ifo-cod'ondersen/rod-rot   file  2.3wp7.dgn
       GRAPHIC  SCALE
      e       IN      T
          (  IN FEET (
                                                                            GRID ESTABLISHED
                                                                               DURING THE
                                                                  WMS7F     199«-»95 OU 3 Rl
                                                                flfi£
SOIL MOUND (GLASS
AND  METAL DEBRIS)
                                           MONITORING
                                           WELL IRP 10
                                CORAL BASED
                                   ROAD
                                  10 EMPTY DRUMS /
                                  DRUM  REMNANTS
                                 fMPTY MUM AKCA
                                                                                                               APPROXIMATE
                                                                                                            BOUNDARY BETWEEN
                                                                                                           AREA A AND AREA B
                                            V   v-
                                                                                                                         NOTE:
                                                                                                                         1.  SAt*>U  LOCATIONS AND CONSTITUENT
                                                                                                                            CONCENTRATIONS ARE IN SECTION 3
                                                                                                                            OF THE  OU 3 Rl REPORT IICF.  1996)
                                                                   ORIGINAL SITE
                                                                 RECONNAISSANCE
                                                                    BOUNDARY
FIGURE 2-3
MARBO ANNEX
ANDERSEN A
- RECORD OF DECISION
IR FORCE BASE. GUAM
DISPOSAL/SPILL AREA LOCATIONS
SITE 20 (WASTE PILE 7)
MARBO ANNEX
DATE: 9/29/97 SCALE : AS NOTED

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2.1.2         Site 22 (Waste Pile 6)

Waste Pile 6 is a small site located centrally within the MARBO Annex as shown in Figure 2-2.
Based on information from previous IRP studies and site visits, the boundary of Waste Pile 6 was
thought to encompass a large area] expanse (Figure 2-4). As with Waste Pile 7, however, the
original boundaries of Waste Pile 6  were re-established after completion of a more  thorough
review of historical records, a topographic survey, a detailed site inventory, geophysical surveys,
exploratory excavations, and soil gas sampling (ICF, 1996).

This characterization identified several discrete disposal/spill areas  throughout  the  area and
vicinity of Waste Pile  6, shown and described on Figure 2-4.  The depth of contamination in
these areas ranges from surface debris to approximately  8.5 feet bgs.  Soil analytical  data
indicated  seven disposal/spill areas which represent  a health  risk, including:   l)an  area
containing six  car battery casings ("Car Battery  Area"); 2) an area  containing nine apparent
alkaline radio batteries ("Radio Battery Area"); 3) an area containing  three "possible" batteries
("Unknown Battery Area");  4) a pile of roofing material ("Roofing Material Pile"); 5) an area
containing subsurface metal debris ("Metal Debris Pile"); and 6) an  area where  empty drums
were detected in the shallow subsurface ("Empty Drum Pile").  The seventh area is a drum pile
containing about 108 deteriorated drums of paving grade asphalt, conservatively estimated to be
approximately 2,900 gallons in volume ("Asphalt Drum Pile"). Most of the drums were stacked
together in rows, and several had leaked onto the ground.   Based on a risk evaluation  of soil
analytical data, a health risk was identified for this site.  The COCs identified at Site  6 include
the metals antimony, arsenic, cadmium and lead; and PAHs benzo(a)anthracene, benzo(a)pyrene.
benzo(b)fluoranthene and indeno (1,2,3 cd)pyrene.

2.13         Site 23 (Waste Pile 5)

Waste Pile 5 is located in the south-southwest section of the MARBO Annex, approximately
1,500 feet west of Waste Pile 6 (Figure 2-2). The site investigation focused on a 2.17-acre trench
landfill that consisted of eight large trench-like waste disposal cells containing mostly municipal
Andersen AFB MARBO Annex                      2-3                                  4/1/98
Record of Decision

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directory  ifo.cod/ondersen/rod.rpt  file 2_4wo6.dqn
                                  ORIGINAL SITE
                                 RECONNAISSANCE
                                   BOUNDARY
           S-FOOT DEEP TRENCH
                                                                    5 DRUMS / DRUM REMNANTS
                                                                     (3-HOCKS / SOIL. 2-EMPTY)
                                                   DRUM
                                              <<5 GAL. OILY WATER)
B EMPTY DRUMS /
DRUM  REMNANTS
                                                     /  6 BATTERY CASINGS
                                                 I   /  "CM BATTERY AREA"
                3 POSSIBLE BATTERIES
              "UNKNOWN BATTERY AREA
                                   GRID ESTABLISHED DURING
                                     THE 1994-1995 OU3 Rl
      GRAPHIC  SCALE

              70   3
        i IN FEET >
                                                                                                      7 EMPTY DRUMS /DRUM REMNANTS
                                                                                                          (4-ROCKS /SOIL. 3-EMPTY)
                                                                                                                  SOIL MOUND
                                                                                                                (6 EMPTY DRUMS)

                                                                                                                  SOIL MOUND
                                                                                                                IB EMPTY DRUMS)
                                                                                                               13 EMPY DRUMS /
                                                                                                               DRUM  REMNANTS
                                                                                                             S DRUMS /DRUM REMNANTS
                                                                                                            (4-ROCKS /SOIL /METAL /GLASS.
                                                                                                                    1-EMPTY)

                                                                                                             9 ALKALINE  RADIO BATTERIES
                                                                                                               "RADIO BATTERY AREA"

                                                                                                           "ROOFING MATERIAL PILE"
                                                                                                           11 DRUMS /DRUM  REMNANTS
                                                                                                             (3-ROCKS /SOIL. 8-EMPTY)

                                                                                                         108 DRUMS OF ASPHALT
                                                                                                         "ASPHALT DRUM PILE"
     SHALLOW TEST PIT
     16 EMPTY DRUMS
    "EMPTY DRUM PILE'
                                                 CORAL ROAD
                                                                        TEST PIT-
                                                                  SUBSURFACE METAL DEBRIS
                                                                    "METAL DEBRIS PILE"
     NOTE:
     I. SAMPLE LOCATIONS AND CONS1I1UCNT
       CONCENTRATIONS ARE  IN SECTION )
       OF THE OU J Rl REPORT IICf. 19961
                        MARBO  ANNEX  -  RECORD  OF  DECISION
                           ANDERSEN  AIR FORCE  BASE,  GUAM
                                                                                                                     FIGURE  2-
DISPOSAL/SPILL  AREA  LOCATIONS
      SITE  22  (WASTEPILE 6)
             MARBO  ANNEX
                                                                                          DATE:    9/29/97
                                                                                                     SCALE:  AS  NOTED

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trash such  as bottles, cans,  cardboard  paper, kitchen ware;  and construction debris, including
concrete, pipe fragments, and corrugated metal.   A total  of 25 drum/drum fragments  were
observed on the surface in 16 locations. Sixteen of the drums were empty and the rest contained
soil, rocks and concrete.  The  lengths  of  the trenches ranged  from 150  feet to 650  feet.
Measurements taken during excavations showed the average thickness of the fill layer was 7.5
feet (range 1.5 to 14.5 feet), and the average depth  to the bottom of the fill layer was 10.8 feet
(range  6 to 17 feet) below ground surface (bgs). The surface of this landfill did not contain a
uniform cap or cover, but was vegetated and covered with  soil and debris.  Some trenches
contained several feet of debris-free soil above the fill material, whereas other trenches contained
debris throughout.  No health risk was identified at Waste Pile 5.

2.1.4         Site 24 (Landfill 29)

Site 24 is located in the southwest portion of the MARBO Annex, as shown on Figure 2-2. As
with Waste Piles 6 and 7, a more thorough field investigation indicated that the original Site 24
boundary did not outline a true disposal  site  (i.e., a landfill or consolidated  waste dump), but
instead was an abandoned quarry containing scattered debris such as drum remnants and metal
(Figure 2-5). The focus of the investigation was on three primary areas, including: 1) a 2.44-acre
landfill located south-southwest of the original location, 2) an area west of the original location
containing soil-filled drums ("Surface Drum Area"), and 3) a small area which identified shallow
subsurface metal debris ("Subsurface Metal Area").

The 2.44-acre area landfill contained mostly municipal waste (i.e., bottles, cans, etc.), as well as
other types of wastes such as ferrous and copper metal debris, and crushed empty deteriorated
drums.  Measurements taken during excavations showed the average thickness of the fill  layer
was 4.2 feet (range 3 to 6.5 feet), and the average depth to the bottom of the fill layer was 6.2 feet
(range  5 to 8.5 feet) bgs.  The waste material was covered with a relatively uniform 2-foot  layer
of recemented limestone  and several inches of soil.  The surface of the landfill was vegetated.
The Surface Drum Area contains an estimated 86 empty or soil-filled drums/drum remnants, and
the Subsurface Metal Area contains subsurface metal debris.  Both of these areas are shown on
Andersen AFB MARBO Annex                      2-4                                  4/1/98
Record of Decision

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UECEND:
      DISPOSAL/SPILL ARE* LESS
      THAN 100 SQUARE FEET
 NOTE:
 1. SAMPLE LOCATIONS AND CONSTITltNT
   CONCENTRATIONS ARE IN SECTION J
   OF THE OU 3 Rl REPORT IICF. 19961
                                               ORIGINAL SITE
                                              RECONNAISSANCE
                                                BOUNDARY
 GRID ESTABLISHED
DURING THE 1994-1995
     OU 3 Rl
                                                                 /DRUM
                                                                 NTS
                                                                . 7-EMPTY)
                                    2 DRUMS /DRUM
                                      REMNANTS
                                    0-TRASH. VEMPTY)
  APPROXIMATE
  BOUNDARY OF
 AREA CONTAINING
 ABOUT 86 EMPTY
  OR SOIL-FILLED
    DRUMS
'SURFACE DRUM
    AREA"
                                                              SHALLOW  SUBSURFACE
                                                                 METAL DEBRIS
                                                           SUBSURFACE METAL
                                                                  APPROXIMATE
                                                                  BOUNDARY OF
                                                                    2.44-ACRE
                                                                    LANDFILL
   GRAPHIC SCALE

  •     IM     MB
                                                                         FIGURE  2-5
                                                     DISPOSAL/SPILL  AREA  LOCATIONS
                                                          SITE  24  (LANDFILL  29)
                                                                 MARBO  ANNEX
MARBO  ANNEX - RECORD OF  DECISION
  ANDERSEN  AIR  FORCE  BASE.  GUAM
                                                                          SCALE: AS  NOTED

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Figure 2-5.  The COCs identified at Site 24 include the metals antimony and lead.  Based on a
risk evaluation of soil analytical data, a health risk was identified for this site.

2.1.5        Site 37 (War Dog Borrow Pit)

The  War Dog Borrow Pit is an abandoned quarry in the  northernmost portion of the MARBO
Annex, located adjacent to Route No.  1, near the former location of the War Dog Cemetery
(Figure 2-2). The  site investigation focused on a 1.82-acre area landfill within the quarry that
contained scrap automobile parts. Measurements taken during excavations showed the average
thickness of the fill layer was 4.8 feet (range 2.5 to 8.5 feet), and the average depth to the bottom
of the fill layer was 6.8 feet (range 4.5 to 8.5 feet) bgs. The  fill layer was covered with about
2 feet of recemented limestone.  The limestone cover was exposed in some areas, whereas other
areas contained surface soil and  vegetation. Miscellaneous trash was widely distributed on the
ground surface, and several soil mounds of various sizes were  located across the site. No health
risk was identified at the War Dog Borrow Pit.

2.1.6        Site 38 (MARBO Laundry)

The  MARBO Laundry  is located  in  the eastern half of the MARBO Annex,  as shown on
Figure 2-2.  The MARBO Laundry was a military laundry  facility operated in Building 01125
between 1948 and  1973 (Figure 2-6). The laundry was modified in 1970 with the addition of a
dry cleaning facility.  This facility may have discharged solvents to the base sanitary sewer via a
floor drain in the dry  cleaning room. Building 01125 has since been utilized as a storage facility
for furniture, among other uses. The building was renovated immediately before and during the
OU 3 sampling. The renovation included scraping old paint from the outside walls which caused
paint chips to be deposited on the  ground surface (grass or soil) outside the  building  where
surface soil samples were collected. The COCs identified at the MARBO Laundry include the
PCB Aroclor 1254, and the metal  lead. Based on a risk evaluation of soil analytical data, a
health  risk was identified for soil surrounding the facility as well as for the north and south
transformers, as shown on Figure 2-6.
Andersen AFB MARBO Annex                      2-5                                  4/1/98
Record of Decision

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                                            GRID ESTABLISHED OVER
                                           AREA INVESTIGATED DURING
                                             THE 1994-1995 OU 3 Rl
                                               DRY CLEANING
                                              EQUIPMENT ROOM
          NOTE:
          1. SAMPLE LOCATIONS AND CONSTITUENT
            CONCENTRATIONS ARE IN SECTION 3
            Of THE OU J Rl REPORT (ICf. 1996)
                GRAPHIC SCALE
                  < IN FEET I
                                                                 FIGURE 2-6
MARBO  ANNEX  -  RECORD  OF  DECISION
  ANDERSEN  AIR FORCE  BASE,  GUAM
DISPOSAL/SPILL  AREA  LOCATIONS
    SITE  38 (MARBO LAUNDRY)
           MARBO  ANNEX
                                           DATE:   9/29/97
                   SCALE: AS NOTED

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2.2          REGIONAL PHYSIOGRAPHY

Andersen  AFB  is  located in the  Northern  Physiographic Province  of Guam, which is
characterized by a broad undulating limestone reef plateau. Numerous sinkholes are present on
the northern plateau. The sinkholes and the very porous limestone bedrock provide rapid surface
water infiltration with ultimate percolation to the underlying fresh water aquifer.  The surface of
the limestone plateau is interrupted by two volcanic peaks, Mount Santa Rosa and Mataguac Hill
located northeast and north of the MARBO Annex, at elevations of 828 and 630 feet above mean
sea level (msl), respectively (Figure 2-7).  Surface elevations of the limestone plateau range from
300 to over 500  feet msl in the MARBO Annex area. The northern limestone plateau (where
AAFB is located) is bounded by the Pacific Ocean to the east side and the Philippine Sea to the
west.  Several beach terraces formed by eustatic sea level fluctuation, exist between the edge of
the sea and the foot of the cliff forming narrow coastal lowland areas.

2.2.1         Geology

The geology underlying the MARBO Annex consists of limestone reef  deposits underlain by
volcanic rocks. The volcanically derived Alutom formation consists of thick  sequences of water-
laid  tuffaceous  shales  containing  pyroclastic  deposits   of  ash,  dust,  sandstones,  and
conglomerates.  Interlaycred within this formation are lava flows, breccia, and fragments of reef
limestones.  The Alutom formation is the oldest  rock unit on Guam with deposition occurring
during the Eocene (57 to 36 million  years before present) and Miocene (24 to 5 million years
before present) epochs. This formation outcrops in northern Guam at Mount Santa Rosa and
Mataguac Hill, and underlies the limestone plateaus beneath the MARBO Annex.

The MARBO Annex is underlain by the Barrigada  and  Mariana limestone formations (2 to 5
million  years before present)  which is underlain by the Alutom formation. The Barrigada
formation is generally a deep water deposit of fine grained  texture, composed of foramanifera
tests.  The Barrigada limestone was deposited on the  volcanically derived Alutom formation and
Andersen AFB MARBO Annex                      2-6                                 4/1/98
Record of Decision

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                                                               ELEVATION CONTOUR - TOP
                                                               Or ALUTOM FORMATION
                                                               (FEET ABOVE M.S.I
                                                               CROUNDWATER SUBBASIN
                                                               BOUNDARY
                                                               ANDERSEN AIR FORCE BASE
                                                               PROPERTY BOUNDARY
                         ANDERSEN AIR FORCE BASE
                                                            Source: 1CF. 1997
                                         AFGAGUMAS
                                          SUBBASIN
                                                                 ANDERSEN
                                                                  SUBBASIN
               FINEGAYAN
                SUBBASIN
                                                               Mount Santa Rota
                       Y1GO
                        BASIN
                       MANGILAO
                        SUBBASIN
  AGANA
\SUBBASIN
                                                                  GRAPHIC SCOlE
                                                                 FIGURE 2-7
                                                  STRUCTURE CONTOUR AND
                                              SUBBASIN MAP  -  NORTHERN GUAM :
                                              (TOP OF  THE ALUTOM FORMATION)
MARBO  ANNEX -  RECORD  OF  DECISION
  ANDERSEN AIR FORCE  BASE.  GUAM
                                           DATE:    10/6/97
                                                                SCALE: AS  NOTED

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forms an outcropped semi-circle around the edges of the MARBO Annex.  Maximum thickness
of this  formation exceeds 540 feet (Tracey et  al., 1964).  The younger Mariana limestone
includes approximately 80 percent of the exposed reef-associated limestones of Guam.  This
formation onlaps the Barrigada limestone as a vertical and transgressional fades change from a
deep to a shallow water depositional environment.

2.2.2         Hydrogeology of Northern Guam

Throughout most  of northern Guam, fresh groundwater floats on seawater in an approximate
buoyant equilibrium, described by the Ghyben-Herzberg model, which, when combined with the
effect of dynamics of flow of the freshwater, results in a lens-shaped body of freshwater (Ward et
al., 1965). Groundwater resources are primarily found in the northern half of the island in porous
limestone deposits of the Barrigada and Mariana formations. The groundwater is encountered
approximately 300-500 feet bgs. The groundwater surface generally coincides with sea level and
the depth to water depends on surface elevation. The thickness of the lens is generally around 90
to 120 feet.  Freshwater is drawn from this aquifer, which is known as the Northern Guam Lens
(NGL).  The NGL and its subsurface groundwater subbasin divides are discussed below and are
shown on Figure 2-7.

The NGL is a dynamic system; water is in constant motion from areas of recharge to areas of
discharge.  The  energy involved in this movement affects the  shape of the lens and the depth of
the freshwater.  The important factors governing the amount  of freshwater in the lens are:  the
effects of mixing freshwater and marine water, the permeability of the limestone formations, and
the rate of recharge (discussed below) (Ward et  al., 1965).   Regionally, the groundwater flow
direction in the NGL is from the limestone/volcanic  contacts toward the sea.  Flow  can be
affected by faults, fractures, brecciated zones, joints, vertical and horizontal solution channels or
cavities, lithology, and by pumping wells.

Mink (1976), identified the NGL as consisting of two pans: the basal and parabasal groundwater.
The basal lens is that portion of the freshwater described by the Ghyben-Herzberg model. The
Andersen AFB MARBO Annex                     2-7                                 4/1/98
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lower boundary of the freshwater lens in the basal portion consists of the transition zone and
seawater.  Moving inland away from the coast, the base of the lens is intercepted by the rising
surface of the volcanic Alutorn formation.  It is at this point that the Ghyben-Herzberg model
ceases to be  the controlling factor in the definition of the base of the freshwater  lens.  The
volcanic  surface becomes the lower boundary condition and water resting on the relatively
impermeable  volcanic unit is referred to as parabasal groundwater.

The NGL study (NGLS-CDM, 1982) divided the  aquifer under the Northern Plateau (i.e., the
NGL) into six hydrogeologic subbasins (Figure 2-7).  Subbasin boundaries were drawn along
sub-topographic divides on the top of the Alutom Formation depicted from geophysical methods.
Five of the  subbasins (Andersen, Agafa Gumas, Finegayan, Mangilao, and Yigo) underlie
Andersen AFB properties. The MARBO Annex lies within the Yigo and Mangilao subbasins,
however  the  Mangilao subbasin was not included as part of the MARBO Annex remedial
investigation  (RI) because there are no remedial investigation/feasibility study (RI/FS) sites in
the subbasin.

The following subsections briefly  discuss a compilation of studies  performed by  the  United
States Geological Survey (USGS), the Water and Energy Research Institute and the Groundwater
Resources of  Guam on the hydraulic properties and subdivisions of the aquifer.

Porosity.  Spatial variation in porosity of the Barrigada and Mariana limestone formations varies
considerably  depending on the depositional settings  in  the vicinity  of the Northern Plateau.
Openings can range in size from microscopic to large, well-developed cavern systems, but are
generally about 1/8 to 1/4 inches in diameter and are the result of dissolution of the limestone.

Hydraulic Conductivity.  Estimates of hydraulic conductivity within the NGL range over three
orders of magnitude. Local hydraulic conductivity varies considerably because of the limestone
matrix.  Transmissivity,  which is the  product of hydraulic conductivity and thickness (and
represents an  aquifer's ability to transmit water), exhibits a 17-fold difference between lowest and
highest values (Mink, 1976). The results of the NGLS (CDM, 1982) gave estimates of hydraulic
Andersen AFB MARBO Annex                      2-8                                  4/1/98
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conductivities ranging from 2 to 20,670 feet per day (ft/day); these estimates were derived from
various indirect methods, including head-gradient relationships, tidal attenuation, recovery tests,
intrusion analyses, and numerical modeling  techniques.  The hydraulic conductivities and, as
previously  noted, the porosity of the limestone vary considerably both regionally and locally
depending on the depositional setting.

Recharge.   The MARBO Annex is underlain by highly permeable limestone.  No perennial
streams exist on the northern half of the island.  During heavy rainfall, the surface water runoff
may flow in short channels in the  limestone, but  it  eventually disappears  into the  numerous
dolines, fissures and other secondary porosity openings. The only runoff of consequence in the
area occurs on  the steep volcanic slopes  of  Mataguac Hill and  Mt. Santa Rosa;  however, the
water  eventually disappears  into the  limestone  bedrock surrounding the hills (Ward  and
Brockhart,  1962). Once surface water seeps into the limestone bedrock surrounding the hills, it
flows along the surface of the volcanic rock or as discrete  recharge through caverns until it
reaches the water table and becomes pan of the parabasal lens.

Data obtained from the National Climatic Data Center covering  the period  1957 to 1991  show
that Guam rainfall averages almost 102  inches per year and is divided between  two distinct
seasons,  rainy  and  dry.  The rainy season begins in July  and extends through November.
Roughly 65 percent of the annual precipitation falls during these five  months. The dry season
extends from January through May  and during this period water shortages are not uncommon.
Both June  and December are considered transitional months.  The  total  annual recharge is
essentially the amount determined by the annual precipitation minus evapotranspiration.

No data are available on the amount of rainfall  returned to the  atmosphere by vegetation
transpiration. As a first approximation, studies to date have used a value for evapotranspiration
equal to the pan evaporation rate reported by the National Weather Service (NWS) Station of the
U.S. Weather Bureau at Finegayan, located just north of the Andersen  AFB Harmon Annex, for
the period 1974 through 1981. The reported average pan evaporation  rate is about 7 inches per
month during the dry season and about 6  inches per month during the  wet season.  The average
Andersen AFB MARBO Annex                      2-9                                  4/1/98
Record of Decision

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monthly  pan evaporation  is 6.85 inches  and the  annual  average  is about 82  inches.  This
compares favorably with calculated evapotranspiration rates, which range from approximately 40
to 80 inches per year (CDM, 1982).

Average  recharge rates range from approximately  25 to 35 inches per  year depending on the
method used (CDM, 1982; Mink, 1976).   Mink computed the recharge to Andersen AFB  at
27.69 inches. Recharge to the NGL was estimated  to be approximately 165 million gallons per
day (mgd) (CDM, 1982).

Storativity. Storativity for an unconfined aquifer is essentially equal to the specific yield and is
defined as the volume of water that an aquifer releases from storage per unit surface area of an
aquifer per unit decline in hydraulic head.  In the NGL, Storativity is approximately equal to the
porosity (i.e., between 0.1 and 0.2, dimensionless) (CDM, 1982).

Sustainable Yield. The estimated sustainable yield of the aquifer is reported to be 59 mgd, and
an estimated 37 mgd is considered available for future development.  Sustainable yield is defined
as the  maximum amount of water that can be continuously withdrawn from an aquifer (i.e., the
NGL) without impairing the integrity of the lens and the water quality due to saltwater intrusion.
Sustainable yield is not equal to recharge, for if all water contributed by recharge were extracted,
the lens would slowly dissipate because of continued leakage along the coastline. The amount of
freshwater  loss to the ocean is estimated at 143 mgd, averaged annually  (CDM, 1982).  Typical
production well yields are approximately 200 gallons per minute (gpm).

Groundwater Geochemistry.  Water  quality of  the NGL was evaluated during the NGLS
(CDM,  1982)  and  discussed  in the Guam  Water Facilities  Master Plan  Update  (Barrett
Consulting Group, 1992).  The chemical characteristics that have been evaluated include those
regulated under both the Safe Drinking Water Act and the Clean Water Act.

The  general groundwater chemistry of the NGL indicates that the main chemical constituents are
calcium,  chloride, silica, nitrate,  and  magnesium.  Chloride  is a critical constituent because it
Andersen AFB MARBO Annex                    2-10                                 4/1/98
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provides a measure of seawater intrusion, while calcium and magnesium concentrations allow for
the computation of total hardness. Silica provides an index of the lithology in which the water
moves.  Nitrate can be useful as an indicator of surface infiltration.

The water quality indicator parameters suggest the groundwater is hard, based on an average
hardness of 270 milligrams per liter (mg/L) measured as calcium carbonate (CaCO3).  Levels as
high as 400 mg/L of CaCO, were measured during the evaluation, with the high hardness a result
of the limestone bedrock. Other characteristics of the lens include nitrates ranging from 2 to  10
mg/L (as  NO3);  specific conductance ranging from 300  to  1,300 micromhos;  and chloride
ranging from less than 30 mg/L in the parabasal lens to between 70 and 280 mg/L in the basal
lens.

As noted in the OU-2  RI, pumping wells generally have  an increased chloride concentration
when compared to the monitoring wells,  likely  due to overpumping of the freshwater lens.
Additional water quality parameters are discussed in Section 4.0 of the OU-2 RI.

2.2.3        Water Use

According  to  the  Revised  Guam Water Quality  Standards  adopted January  2,  1992, all
groundwater in northern Guam, whether fresh or saline, is categorized as G-l Resource Zone
water.   The primary use of groundwater  within this zone is for human consumption.  This
category includes virtually all water in the saturated zone of Guam.  Specifically, it includes all
water occurring in the saturated zone below the groundwater table, all vadose water occurring in
an unsaturated zone interval extending 100 feet above any water table, or to within 20 feet of the
ground surface of all fresh groundwater bodies, all water of the  basal and parabasal freshwater
bodies, and all water of and below the freshwater/seawater transition zone beneath the basal
water body.  Because any water discharges within this zone will (by definition) be tributary to
groundwater bodies which are  actual  or potential sources of fresh, potable water supply, no
pollutant discharges to the groundwater within this zone are allowed.
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Freshwater in the NGL is the principal source of potable water for Guam and represents almost
the entire freshwater resource available for  future development.  The Yigo subbasin alone
provides 100 percent of the drinking water for Andersen AFB as well as a significant portion of
the civilian supply. Guam drinking water comes from groundwater production wells installed in
the upper portion of the  aquifer.  According to the Guam Water Facilities Master Plan Update
(Barren, 1992), there are 117 production wells on Guam with a total average withdrawal rate of
28 mgd.  The water  from these wells is mixed and  treated  in distribution tanks  prior to
distribution throughout the northern part of Guam.  Water from the wells in the MARBO Annex
area is distributed, along with water produced in other locations, to Dededo, Yigo, Barrigada,
Mangilao,  and Andersen AFB,  where  the  total  civilian  water usage was reported  to  be
approximately 17 mgd.  Andersen AFB reportedly produces 5.19 mgd, 0.38 mgd of which is
supplied to the Public Utility Agency of Guam (PUAG) distribution system (Barrett,  1992).
There are currently eight Air Force production wells located on the MARBO Annex (MW-series
wells).

2.2.4         Andersen AFB Soils

The primary geographic area in which all the investigated OU 3 sites are located is the limestone
uplands. The MARBO  Annex area has one mapped soil type:  the Guam series. The  Guam
series consists of a shallow, well-drained, moderate to highly permeable soil that is found on
uplifted plateaus. This soil formed in sediment overlying porous coralline limestone, with slopes
of 0 to 15%.  This soil is characteristically a dark reddish brown, cobbly clay loam; moderate to
very fine granular structure; friable; slightly sticky, and slightly plastic with about 10% pebbles
and 10% cobbles in the upper 2 inches. From 2-8 inches, soil is a gravely clay loam, moderate to
fine  granular structure; very friable; slightly sticky, and slightly plastic; and increasing amounts
of pebbles. Below 8 inches, porous limestone is generally encountered
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2.2.5         Climatology and Meteorology

This section presents data describing the climatic conditions,  seasonal changes, temperatures,
rainfall and evaporation rates, and ambient air quality for the island of Guam.

Precipitation. Guam has distinct dry and rainy seasons.  The rainy season typically begins in
July and extends through November.  Roughly 65% of the annual precipitation falls during these
5 months. Tropical storms are frequent during the rainy season, and occasionally they increase
in intensity to become typhoons. The dry season extends from January through May, and during
this period, water  shortages are not  uncommon.  Both  June  and  December  are  considered
transitional.  The average annual rainfall ranges from approximately 72 inches to approximately
112 inches.  As noted earlier, the  average annual rainfall measured at Andersen AFB on the
Northern Plateau is approximately 100 inches.

Temperature. Guam lies about 13° (900 miles) north of the equator, which creates a year-round
warm climate.  Temperatures accompanied by high humidity range  from the  low 70s to the
middle 80s.  The average annual temperature is 79.6°F.  The mean monthly temperatures range
from 80°F (26.76C) during January  to 82°F (27.8°C) in June.  Rarely does the  temperature
exceed 90°F (32.2°C) during the daytime hours or fall below 70°F (21.1°C) at  night.  The
humidity ranges from 65 to 80% in the late afternoon and 85 to 100% at night  with a monthly
average of at least 66%.

Wind.  The dominant winds are  the trade winds,  blowing from the east or northeast with
velocities between 4 and 12 miles per hour (mph) throughout the year. These winds are strongest
during the dry season, averaging 15 to 25 mph and calms are rare.  During the  wet season, the
trade winds are  still dominant, but not constant.  The winds can blow from any direction with
windspeeds generally less than 15 miles per hour, interspersed with frequent calms. Storms may
occur at  any time  during the year, but are most common during the wet season.  Although
typhoons can occur at anytime, their likelihood is greatest from July through September.
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Evaporation and Evapotranspiration. The average pan evaporation is reported to be about
7 inches per month during the dry season and about 6 inches per month in the wet season. The
average monthly pan evaporation is 6.85 inches and the annual average is about 82 inches.

Evapotranspiration is the combined total of evaporation and  plant transpiration  which occurs if
the vegetation has a continuous supply of water. To estimate recharge of the fresh water lens, the
rate of evapotranspiration is required.  Evapotranspiration rates for various types of vegetation
have not been measured on Guam, but are considered roughly equivalent to tropical vegetation.

Air Quality. The ambient air of Guam remains relatively clean at all times, because prevailing
winds carry clean air from the ocean across the island. Air pollution sources on Guam include:
exhaust from automobiles; smoke and fumes from the burning of solid wastes; paniculate dust
from construction projects,  parking  lots,  and roadsides; and emissions from power plants.
Asbestos, another potential pollutant, is present in a few old buildings.

2.2.6         Biology and Ecology

Biology and ecology are  important considerations in the Andersen AFB RI/FS activities. Most
of the native terrestrial birds and mammals on Guam are considered threatened or endangered
(DAWR, 1988), and  parts of Andersen AFB provide critical habitats for several of these species.
Also, many natural  habitats  and communities on  Guam have been destabilized  by  the
introduction of non-native species.  The following section summarizes the considerations relating
to threatened and endangered species, non-threatened or non-endangered wildlife, and other
information on terrestrial ecological communities  that occur on  the island of  Guam and may
occur on parts of Andersen  AFB.  Because MARBO Annex is inland from the ocean, marine
habitats and species are not considered.

Threatened or Endangered Species.  Most of the native or endemic  species of non-marine or
non-migratory birds on Guam are listed as endangered either by the Government of Guam or by
the U.S. Fish and Wildlife Service. All except four of these  15 species are either thought to be
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extinct, extirpated from the island of Guam, or occur only as  captive breeding populations.
Small populations of the remaining species of native birds occur in much reduced ranges relative
to those they once occupied.  The ranges of three of these species do not presently include
Andersen AFB.  Mariana common moorhens are restricted to wetlands in central and southern
Guam.  Micronesian starlings are found primarily on Cocos Island, as well  as a resident
population on the developed part of the Anderson Main Base.  Vanikoro swiftlets are known to
occupy two caves in southern Guam. The currently known range of the Mariana crow is centered
on Northwest Field of Andersen AFB and extends along the cliff-line adjacent to North Field
(USAF, 1994).  However, MARBO Annex is inland and disjunct from North and Northwest
Fields, and is not within the current range of the Mariana crow.

The only native mammals on Guam are bats, and all of these species are listed as endangered by
either the Government of Guam or by the U.S.  Fish and Wildlife Service (USFWS) (DAWR,
1988).  However, the records documenting the occurrence of a Emballonura sp. on Guam are
based only on historical visual observations (Perez, 1972), and the endemic little Mariana fruit
bat is believed to be extinct. The population of Mariana fruit bat on Guam was estimated to be
295-370 individuals in 1992 (DAWR, 1992b), and most of these bats are found among several
roosts along the cliff-line in the vicinity of Pati Point, along the northeast shoreline of the North
Field.  However, MARBO Annex is inland and disjunct from North Field, and is not within the
current range of the Mariana fruit bat.

One  species of tree, the hayan lagu or Serianthes nelsonii, has  been listed as an endangered
species by the U.S. Fish and  Wildlife Service.   In addition, a second tree, ufa-halomtano or
Heritiera longipetiolata, is listed by the Government of Guam as endangered (DAWR, 1988).
The known distribution of both hayan lagu and ufa-halomtano is  along the cliff-line adjacent to
North and Northwest Fields of Andersen AFB. However, MARBO Annex is inland and disjunct
from North and Northwest Fields, and is not within the current range of these two trees.

Critical Habitat for Threatened or Endangered Species.  In 1991, the U.S. Fish and Wildlife
Service proposed the designation of critical habitat on Guam for the little Mariana fruit  bat,
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Mariana fruit bat, Guam broadbill, Mariana crow, Guam  Micronesian kingfisher,  and Guam
bridled white-eye (Federal Register,  1991).  In northern Guam, this area includes the Anao
Conservation Reserve along the coast east of Mt. Santa Rosa and much of the North Field and
Northwest Field areas of Andersen AFB.

In 1992, the U.S. Fish  and Wildlife Service proposed the establishment of a national wildlife
refuge that would overlay most of the North Field and Northwest Field areas of Andersen AFB,
excluding  operational areas, the  former U.S. Naval  Facility  at  Ritidian Point,  and certain
Government of Guam lands (USFWS, 1993).

The MARBO Annex area of Andersen AFB is outside of both the proposed critical habitat area
and the proposed national wildlife refuge.  In addition, these sites are inland and disjunct from
the currently known distributions of the Mariana crow, Mariana fruit bat, hayan lagu, and ufa-
halomtano along the northern cliff-line of the island adjacent to North and Northwest  Fields.  No
observations (i.e., direct or sign) of these species were made during the ecological habitat surveys
of the sites (USAF, 1994), and these sites generally lack trees of the correct species and size that
are used for roosting, nesting, or foraging by the Mariana crow and Mariana fruit bat. Therefore,
it  is  unlikely that any threatened  or endangered species would be associated with any of  the
MARBO Annex sites.

Other Vertebrate Terrestrial Wildlife.  Only one species of non-marine or non-migratory bird
on Guam is not considered endangered on Guam:  the yellow bittern (Ixobrychus sinensis). This
species is still counted regularly during roadside bird counts (DAWR, 1992a), and is considered
common throughout  the island. They are most  abundant in the southern portion of the island
where freshwater habitats are present.
                                                            4
All other non-marine or non-migratory birds commonly observed on Guam have been introduced
by man.   These birds include the black francolin, blue-breasted quail,  rock dove, Philippine
turtle-dove, black drongo, Eurasian tree sparrow ,  and chestnut mannikin. The black francolin,
blue-breasted quail, and Philippine turtle-dove were apparently introduced to Guam as potential
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game-species.  The rock dove, Eurasian tree sparrow, chestnut mannikin, and black drongo are
all introduced species that are generally most abundant in disturbed or urban habitats.

All species of mammals on Guam, excluding the bats, are introduced.  Two species, the Guam
(Sambar) deer (Cervus unicolor mariannus) and the wild (feral) pig (Sus scrofa) are generally
free-ranging and are hunted on the island. Several species of rodents and a shrew have been
introduced to the island (DAWR,  1988), but are generally  associated  with residential or urban
areas.  Other species of feral or semi-feral domestic animals may be  common (i.e., feral dog,
feral cat) or uncommon (i.e., domestic horse, domestic  cow, Asiatic water buffalo, domestic
goat), but are usually associated with human residences.  While the deer and pigs are hunted as
game-species, these two species are poorly controlled by hunting, and foraging by these species
have caused damage to sensitive habitats  on Andersen AFB and contribute to the rarity of the
endangered plant species (Conry, 1989).

Seventeen  species of terrestrial reptiles have  been identified on the  island of Guam.  These
species include five native and one introduced species of geckos, one introduced chameleon, six
native and  one introduced species of skinks, the introduced monitor lizard, and two species of
introduced  snakes. The historical introduction of at least six species, particularly the brown tree
snake, and the  continuing human development of natural habitats  have apparently destabilized
the resident herpetological communities.  Rodda et al. (1991) report six species of skinks or
geckos that have exhibited significant recent population decreases  and range reductions island-
wide on Guam.

The drastic decline of native forest  birds species  on Guam, particularly since  1960, has been
largely attributed to predation by the introduced brown tree snake (Boiga irregular is) (Savidge,
1987; Conry, 1988a). This nocturnal, arboreal and terrestrial predator was apparently introduced
to Guam from the Admiralty Islands, north of New Guinea.  The snake is an effective nest
predator, and the population declines in most forest birds paralleled the population increases in
the brown tree snake.
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Amphibians do not tolerate exposure to salt water and are not normally native to oceanic islands.
However, two species have been introduced to Guam: the marine toad and the dwarf tree frog.

Terrestrial Ecological  Habitats.   A  number of terrestrial ecological  habitat  types  were
previously identified on Andersen AFB in the environmental impact statement for the proposed
Guam National Wildlife Refuge (USFWS, 1993).  The following terrestrial habitat  types were
observed on or adjacent to the MARBO Annex:

       •      Second-growth Limestone Forest
       •      Leucaena (Tangantangan) Forest
       •      Former Coconut Plantation
       •      Active Base Aiea

Three additional ecological habitat types were identified during the ecological habitat surveys of
the sites  (USAF,  1994).  These three habitats are described as "weed communities"  that are
characteristic of areas where there has been physical disturbance of the original vegetation:

       •      Mixed Shrub Forest
       •      Mixed Herbaceous Vegetation
       •      Pennisetum purpureum (Elephant Grass) Grassland

Each of the sites that were investigated as part of OU 3 were mosaics of the above terrestrial
habitats, that seem to vary in relation to the extent and severity of past physical disturbance to the
vegetation and soils.

2.2.7         Demographics

Population Density. Prior to the Spanish-American War in 1898, Spanish soldiers forced all of
the natives of the neighboring islands to resettle on Guam. After WWII the population soared
with the influx of American military personnel.  The military  presence still  influences the
demographics of the island with military populations dominating the native Guam population in
both the 0-5 and  20-34 age groups (Guam Annual  Economic Review, 1987). The population of
Guam was 133,159 in 1990 (1990 Census).  The geographic distribution of Guam's population
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has shifted from the central to the northern region over the last 20 years. Approximately 47% of
the total population resides in cities in northern Guam.  The cities and their populations are as
follows:   Dededo  (29,480), Tamuning (16,932), and  Yigo  (12,916) (1990  Census).   The
population on  Andersen AFB currently includes approximately 2,900 military personnel and
1,100 civilians.

Age Distribution.  The median age of residents on  Guam is 25.0 years (1990 Census).  Age
distribution is as follows: 35.2%- 0-18 years, 60.9%- 18-64 years, and 3.9% are 65 years and
older (1990 Census).

Household Income.  The median household income for Guam in 1990  was $31,178 (1990
Census).  The income for the northern and central regions of Guam was slightly higher than the
overall median.  Sixteen percent of Guam's population was below the poverty level.

Education Level. In 1990, approximately 73.3% of the  population were high school graduates,
and 17.5% were college graduates.  The proportion of persons completing fewer than 8 years of
elementary education was 13.9% (1990 Census).

Socioeconomics.  The standard of living on Guam  has improved  since WW  II.  One of the
factors responsible  for this improvement has been the strengthening of Guam's economy.   In
1989, 68% of the employed persons on the island were working in the private sector, 32% were
employed in public positions,  and only 2.1% were unemployed (Department of Commerce,
1989).  Guam  is in the midst of an economic  boom.   Strong  and steady growth  in  the
construction/development and  tourism industries  has fueled this sudden prosperity.   Over
1 million tourists visited Guam in 1995 with most  tourists coming  from Japan.  Tourism is
expected to grow by at least 10% over the next few years.

Land Use.  Most of the land in the northern portion of Guam is used by the  Air Force and Naval
operations on their respective installations.  Private, nonmilitary residences are  usually situated
in areas that are accessible to  Marine  Drive, which loops through the central portion of the
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region.  Andersen AFB occupies the northern tip of Guam, with  numerous annexes located
throughout the northern half of the island.  Small-scale agricultural crops produced on the island
include  pineapples,  bananas., papayas, mangos, limes,  avocados, and melons  as well as
cucumbers, green beans, pepj>ers, squash, and eggplant.

Three principal areas account for most of the land on Guam under the control of the Andersen
AFB Wing Commander.  These are Andersen AFB, which includes the North Field, extending
northeastward to Pati Point, and  the Northwest Field, extending northward to Ritidian Point; the
MARBO Annex, located 3.7 miles south-southwest of the Andersen AFB main gate; and the
Harmon Annex, located on the west side of the island about 4 miles south of the Main Base. The
Northern and Northwestern Field include approximately 24.5 square miles at the northern end of
Guam, while the MARBO Annex (including the Andersen South housing area) occupies an area
of 3.8 square miles on the southern slopes of the Yigo-Mofog Valley.  The Harmon Annex,
which has been included  in  Public Law  (P.L.) 103-339 for transfer from  the USAF to the
Government of Guam, includes an area of approximately 2.5 square miles (1,601 acres).

The  USAF controls  other  properties  located on  Guam,  including Camp Edusa, Harmon
Petroleum, Oil, and Lubricants (POL) Annex, Harmon Radio Beacon Annex, Tumon Tank Farm,
Potts  Junction  Tank  Farm,  Mt.  Santa Rosa  Communications Station,  and  Barrigada
Communications Station.  The Camp Edusa,  Harmon Radio Beacon Annex,  and Harmon POL
Annex have been included in PL 103-339 for transfer from the USAF to the Government of
Guam. Other properties such as portions of the MARBO Annex are under consideration by the
USAF to determine whether they are excess to the mission on Guam.

Two conservation reserves are situated in northern Guam; the Anao Conservation  Reserve and
Y-Piga Conservation Reserve. These areas are reserved for the preservation of natural habitats.
The Anao Conservation Reserve, which is south of Anao Point on the east coast, occupies a strip
of land approximately 1 mile long and O.S miles wide along the shoreline immediately east of
Mount Santa Rosa.  Y-Piga Conservation Reserve is located 0.5 miles due  west  of Andersen
AFB's main gate and 0.75 miles southwest of Marine Drive on the southwest border of the Base.
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The  Y-Piga Conservation  Reserve is  approximately 0.25 miles wide  and 1.0 mile long.
Andersen AFB operations do not have any impact on these conservation areas.

23          SITE HISTORY AND ENFORCEMENT ACTIVITIES

In February  1992, the USEPA proposed to list Andersen AFB on the National Priorities List
(NPL).  Following the addition of Andersen AFB to the  NPL on October  14,  1992, USAF
entered into a Federal Facility Agreement (FFA) with USEPA and GEPA.  The FFA establishes
the process for involving Federal  and  Territorial  regulatory  agencies  and the public in the
Andersen  AFB remedial response process.   It also provides a procedural framework for
developing, implementing, and monitoring response actions at Andersen AFB in accordance with
CERCLA, SARA, the NCP, pertinent provisions of the Resource Conservation and Recovery
Act of 1976 (RCRA), Hazardous and Solid Waste Act of  1982 (HSWA), and other applicable
laws. A history of activities at each site that have led to the current status is included in
Section 2.1

The DOD began the IRP in 1976 to identify, investigate, and mitigate environmental hazardous
waste contamination that may be present at DOD facilities.  Under Executive Order  12316, dated
August 14, 1981, the military branches were directed to design their own program to remedy
uncontrolled hazardous waste disposal sites in a manner consistent with the NCP and  as
established by CERCLA. In response to the Order, the DOD  directed its branches to identify
hazardous waste disposal sites to which  they  were  contributors, and to comply  with the
environmental regulations at the installation level when implementing clean-up activities.  The
IRP was used as a model for the USAF IRP. The authority and objectives of the USAF programs
were set forth in the Defense Environmental Quality Program Policy Memorandum (DEQPPM)
81-5, dated December 11,  1981, which was implemented by the Air  Force  Headquarters in
January 1982.

In response to changes in the NCP brought about by SARA,  the USAF IRP was modified in
November 1986 to improve continuity in the site investigation and remedial planning process for
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USAF installations. In July 1987, Executive Order 12580 was signed, and the responsibility to

conduct  site  investigations  and remedial  actions at Federal  facilities  was delegated to the

Secretaries of Defense and Energy.


Prior to 1988, the basic USAF IRP consisted of the following four phases:
       •      Phase I - Initial Assessment/Records Search. This phase identified past disposal
              sites that might pose a hazard to public health or the environment and, therefore,
              required  further  action,  such as a  confirmation of an  environmental hazard
              (Phase II).  If a site required an immediate remedial action, the  program could
              proceed directly to Phase IV.

       •      Phase II  -  Confirmation/Quantification Study.   This phase was designated to
              define and  quantify the extent  of contamination, waste characteristics (when
              required by a regulatory agency), and sites or  locations that required remedial
              actions.   Stage 1 of Phase n was an initial assessment that  was conducted to
              determine whether contamination was present at a  site.   Sites found  to be
              contaminated may have required  further investigation during  subsequent stages of
              Phase II to  assess the extent and significance of contamination.   However, sites
              warranting  immediate remedial  action could be transferred to Phase IV.   The
              research requirements identified during Phase II were included in Phase III.

       •      Phase III - Technology Base Development. This phase consisted of research and
              development to create new technologies for treating pollutants that  otherwise were
              not  technically or economically  feasible to  test.   All of the research  and
              development requirements, which could be identified at any time during the
              program, were addressed during Phase III.

       •      Phase  IV  - Remedial  Action.   This  phase involved the preparation  and
              implementation of the remedial action plan.


In 1988,  the  phased  approach of the  IRP was superseded by a  method  that more closely

approximates  the RI/FS guidelines in use by the USEPA.  The new IRP format combines the

Phase II - Confirmation/Quantification Study and the Phase IV - Remedial  Action, and more

closely parallels the CERCLA RI/FS process.  This program modification provided the USAF

the means to arrive at appropriate remedial actions in a timely and effective manner.
Phase I of the Andersen AFB IRP was completed in March 1985, and Phase II, Stage 1, was

completed in January 1989. IRP Phase n, Stage 2 was completed in December 1991.

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The FFA identified 39 sites to be investigated during the Andersen AFB RI/FS.  Six of these
sites are located on the MARBO Annex, and were investigated during the OU 3 RI. Although
Landfill 29 was recommended for no further action at the conclusion of the IRP Phase II, Stage 1
investigation, it was investigated during the RI/FS because the recommendation for no  further
action was not approved by the regulatory agencies.

Phase I:  During the Phase I records search, Waste Pile 7 was the only OU  3 site that was
identified, and determined to be a potential source or migration pathway  for contamination.
Waste Pile 7 was among the 20 sites that were ranked using the USAF's Hazard Assessment
Ranking Method (HARM) and was assigned a priority score of 86 (a score of 100 indicated the
highest priority for future investigation), using the rating procedure described in the Installation
Restoration Program Phase I: Records Search. Andersen AFB. Guam (ESE, 1985). Waste Pile 7
was recommended for field investigation in IRP Phase II. The other five OU 3 sites were added
to the IRP during subsequent IRP investigation activities at Andersen AFB.

Phase II. Stage 1:  In addition to Waste Pile 7, three additional OU 3 sites were discovered and
investigated during Phase n, Stage 1:  Waste Pile 6, Waste Pile 5 and Landfill 29.

The IRP Phase II, Stage 1 investigation included the following field activities:

      •      Aerial infrared photographs of the MARBO Annex were taken and anomalies
             were investigated;
      •      Shallow geophysical  investigations (Electromagnetic Induction  [EM]  Surveys)
             were conducted at Waste Piles 5, 6, and 7, and Landfill 29 to verify anomalies
             identified  in aerial photographs;
      •      Records review and identification of two additional sites.

The results of that investigation are presented in the IRP Phase n, Stage  1 Final Report (Battelle,
1989).  Further investigation was recommended for Waste Piles 5, 6, and 7. In addition, the War
Dog Borrow  Pit and MARBO Laundry were added to the IRP  during that stage.  Additional
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information regarding Phase n, Stage 1 activities is available in the report entitled "Installation
Restoration Program Phase II Stage 1 - Confirmation/Quantification  for Andersen  Air Force
Base. Guam" (Battelle, 1989).

Phase II. Stage 2: Waste Piles 5,6, and 7, the War Dog Borrow Pit, and MARBO Laundry were
investigated during Phase n, Stage 2.  Landfill 29 was previously  recommended for no further
action and was not investigated during Stage 2. The IRP Phase n, Stage 2 investigation included
shallow soil sampling at Waste Piles 5, 6, and 7, the War Dog Borrow Pit, and MARBO Laundry
and some subsurface soil sampling at Waste Pile 7. The preliminary information obtained during
the Phase n, Stage 2 work is presented in the report entitled "Remedial Investigation/Feasibility
Study. Phase II Stage 2. RI/FS Andersen Air Force Base. Guam" (SAJC, 1991).

Phase n. Stage 3:  Waste Piles 5, 6, and 7, the War Dog Borrow Pit, Landfill  29 and MARBO
Laundry were investigated during this phase.  The investigation included a topographic survey,
site  reconnaissance, electromagnetic  survey, test excavations, soil gas sampling and soil
sampling.  Results of the investigation indicated that sufficient information had been collected to
assess whether a health or ecological risk existed at any of the sites, and that no further sampling
or field investigation was necessary. The results of the investigation are presented in the report
entitled "Andersen Air Force Base Guam: Operable Unit 3 Remedial Investigation Report (OU 3
RI) (ICF. 1996)."  Remedial alternatives for soil impacted by Air Force Activities are presented
in the  report entitled "Andersen Air Force Base Guam: Operable Unit 3 Focused  Feasibility
Study Report: (OU 3 FFS) fICF. 1997a)"

2.4          HIGHLIGHTS OF COMMUNITY PARTICIPATION

Regulations under CERCLA require several community relations activities to occur before and at
the completion of the ROD.  These  requirements are summarized  in "Community Relations in
Superfund:  A Handbook" (USEPA,  1992).  The  required activities include:  community
interviews, a Community Relations  Plan (CRP),  an information repository and administrative
record. Technical Assistance Grant (TAG) notification, public notice of the availability of the
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Proposed Plan and RI/FS reports, public comment period and public meeting for the Proposed
Plan, responsiveness summary to the Proposed Plan, pre-ROD significant changes, and public
notice of selection of remedy. A summary of community activities to date is discussed below.
2.4.1
Community Relations Activities
Andersen AFB conducted interviews with 67 community members in 1992.  On the basis of
these interviews, it completed a CRP in 1993. The CRP was continually updated as the program
evolved.  In 1994, Anderson AFB established a Technical Review Committee (TRC) with
representatives   from:    Government  of  Guam  agencies,  U.S.   Congressional Delegate
Underwood's office, the  Guam  Legislature, Mayor's offices, Guam  Chamber of Commerce,
USEPA, and the Water and Energy Research Institute at  the University of Guam. In  1995,
Andersen AFB converted  the  TRC  to a Restoration Advisory  Board  (RAB)  by adding
representatives  from the local community.  The RAB meets quarterly and meetings are open to
the public. The RAB serves as a focal point for environmental exchange between Andersen AFB
and the local community. Andersen AFB has informed RAB members and the public of their
option to apply  for a TAG.

Andersen AFB published a  notice of the availability of the  RI report, FS report,  and Proposed
Plan for the MARBO Annex in the Pacific Daily News from October 8 through October  10,
1997. The  notice announced the 30-day public comment period from Saturday, October 10 to
Tuesday, November 10, 1997.  A press release was also distributed to newspaper, radio, and
television companies announcing the public meeting and public comment period. Andersen AFB
made these reports, the Proposed Plan, and all IRP  documents available  at the Information
Repositories and Administrative Record files shown below.
       Installation Restoration Program
       36 CES/CEVR
       Unit 14007
       Andersen AFB, Guam
       APO AP 96543-4007
       Telephone: (671) 366-5080
       Contact: Marriane Miclat
Andersen AFB MARBO Annex
Record of Decision
                                   Nieves M. Flores Memorial Library
                                   254 Martyr Street
                                   Agana,Guam 96910
                                   Telephone:  (671) 475-4751,4752,
                                   4753, or 4754
                                   Contact: Christine Scott-Smith
                              2-25
4/1/98

-------
      University of Guam
      Federal Documents Department
      RFK Library, UOG Station
      Mangilao, Guam 96923
      Telephone: (671)735-2321
      Contact:  KenCarriveau

Andersen AFB distributed  the Proposed Plan to all parties identified in the CRP including
government officials, elected officials, media, private organizations, and interested community
members.  Andersen AFB presented a summary of proposed remedial alternatives and solicited
comments on  the Proposed  Plan at  a public meeting on Friday, October 24, 1997 at the Guam
Hilton. Representatives from Andersen AFB, GEPA, and USEPA were present at the meeting to
answer questions, and a transcript of this meeting was made available to the public.  An official
transcript of the meeting minutes is available in the Administrative Record.

Significant comments, criticisms, and modifications are included in the responsiveness summary
of this document. A notice of this document's availability in the Administrative Record File will
be published in the Pacific Daily News after it is signed.

2.5           SCOPE  AND  ROLE OF  OPERABLE  UNIT  WITHIN  THE  SITE
             STRATEGY

Andersen AFB elected to use an Operable Unit or "OU" approach to manage the investigation
and remediation of environmental conditions at the facility. The OUs described in the 1993 FFA
were selected to:

      •      Expedite the completion of investigation activities;
      •      Evaluate sites with similar locations and potentially similar requirements as a
             group;
      •      Complete remedial design investigations at sites where closure decisions had been
             previously reached with the Government of Guam; and
Andersen AFB MARBO Annex                    2-26                                 4/1/98
Record of Decision

-------
       •      Provide a screening mechanism for evaluating newly or tentatively identified sites
             for inclusion in the RI/FS.

The site investigations and studies at the MARBO Annex were conducted under the designation
of OU 2 and OU 3.  OU 3 consists of all of the sites located on the MARBO Annex. This OU
addresses soil and wastes associated with past activities. OU 2 consists of the groundwater in
four subbasins (Yigo, Andersen, Agafa Gumas, and Finegayan) located under Andersen AFB
properties (i.e., the North and Northwest Fields, MARBO Annex, and Harmon Annex). Most of
the MARBO Annex is underlain by the Yigo subbasin (Figure 2-7).  In 1996 (while the OU 2
RI/FS and OU 3 RI/FS were in progress at the MARBO Annex), the GEPA, USEPA Region IX,
and Andersen AFB Remedial Project Managers (RPMs) reorganized the Andersen AFB OUs.
As a  result,  the MARBO  Annex soils and groundwater are now evaluated  together as the
MARBO Annex OU.

The MARBO Annex OU is one of four OUs at Andersen AFB, and  the most advanced in the
CERCLA regulatory process. Andersen AFB has selected a soil removal remedy for three sites
at the MARBO Annex, thus addressing the principal threat of exposure to soils through removal.
Andersen AFB  has  selected a soil cover for the fourth site (Waste Pile  7), addressing the
principal threat of exposure  to soils by mitigating exposure to soils which exceed health-based
levels.

2.6          SUMMARY OF SITE CHARACTERISTICS

This section presents a summary of the contaminant screening process, with an overview of site
contamination and potential routes of exposure.

2.6.1         Contaminant Screening Process

As described in the OU 3 RI (ICF, 1996), soil analytical data obtained from each disposal/spill
area was compared to several screening criteria in order to determine whether or not detected
compound(s) in a particular  area warranted consideration for potential health or ecological risk.

Andersen AFB MARBO Annex                     2-27                                4/1/98
Record of Decision

-------
The screening criteria are human health-risk based formulations which have been approved by
Region  DC USEPA and the GEPA; the application  of these criteria to human health risk  is
addressed in Section 2.7.   The cleanup performance standards are Region  DC Residential
Preliminary  Remediation Goals (PRGs).  For some  inorganic compounds  (i.e., metals) at the
MARBO  Annex, the background  concentrations  exceed  the  PRGs,  in which case  the  soil
analytical data are  then compared to background metals' concentrations.  The background
metals'  concentrations at Andersen AFB and the MARBO Annex are  based  on a statistical
analysis of samples obtained during the OU 3 RI investigation. The comparison to background
concentrations assesses whether the metals which were detected are naturally occurring in soil, or
are potentially a byproduct  of human activities. Lead concentrations in soil were compared to
the USEPA's screening residential concentration of 400 mg/kg.

The first step in the screening process was a comparison of the maximum concentration of each
detected constituent to the  appropriate screening criteria.  If the maximum concentration  of a
constituent exceeded the screening criteria, then the constituent was considered a Constituent of
Potential Concern (COPC).  The second step in the screening process was to  assess the frequency
of distribution of the  COPC(s)  at the site and/or disposal area.   Potential exposure  to site
contaminants  is  a function of the  frequency  and distribution of the  constituents in  the  soil,
referred to as Exposure Point  Concentrations (EPC).  The EPC is calculated  to quantify the
Reasonable  Maximum  Exposure (RME) scenario,  defined by  the  USEPA  as the  "highest
exposure that is  reasonably expected to occur at the site."  The EPC was the lesser of the 95%
Upper Confidence Limit (UCL) of the mean and the maximum concentration. In the case where
there were only one, two or three samples obtained, the maximum concentration was utilized as
the EPC.  The third step was to compare the EPC to the screening criteria.  If the EPC exceeded
the screening criteria, the  constituent was retained  as a Constituent  of Concern (COC), and
carried  in to  the risk evaluation stage.  In some cases,  where a metal's EPC only slightly
exceeded the screening criteria, the metal was not retained as a COC (ICF, 1996).

The following subsections summarize the constituents that were detected at each site, and those
that were identified  as  COPCs and further screened to COCs.  The maximum and minimum
concentration of detected constituents at each site are shown on Table 2-1;  the resulting COPCs
Andersen AFB MARBO Annex                     2-28                                 4/1/98
Record of Decision

-------
if
                                                                   TABLE 2-1

                                                       SOIL ANALYSIS RANGE OF DETECTIONS
                                                                 MARBOANNEX
                                                                   (Page 1 of 2)
Parameter
Units
Residential
Soil PRO
Background
Cone.
Site 20-
Waste Pile 7
Range of Detection
Site 22 -
Waste Pile 6
Range of Detection
Site 23 -
Waste Pile 5
Range of Detection
Site 24 .
Landfill 29
Range of Detection
Site 37 -
War Dog Borrow Pit
Range of Detection
Site 38 •
MARBO Laundry
Range of Detection
Semlvolatlle Organic Compounds
Acenaphthylene
Anthracene
Benzo(a)anthracene
Benzo(b)fluoranthene
Benzo(g.h,i)perylene
Benzo(a)pyrene
bis(2-Ethylhexyl)- phthalate
Butyl benzyl phthalale
Carbazolc
Chrysene
Di-n-butyl phthalale
Fluoranthene
lndeno( 1 ,2.3-cd)pyrene
Phenanthrene
Pyrene
Pesticides and PCBs
beta-BHC
alpha-Chlordane
gamma-Chlordane
4.4--DDC
4.4'-DDE
4,4'-DD1
Dieldrin
Endosulfan 1
Endrin
Heptachlor epoxide
Aroclor 1254
Aroclor 1260
Inorganics and Moisture
Cyanide. Total
Percent Water
Aluminum
Antimony
Barium
Beryllium
Cadmium
Calcium
^romium, f
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg

Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg

mg/kg
%
mg/kg
mg/kg
mg/kg
mp/kg
mg/kg
mg/kg
mg/kg
None
19.000
610
610
None
61
32,000
13.000.000
22.000
24.000
6.500.000
2.600.000
610
None
2.000.000

250
340
340
1,900
1,300
1.300
28
None
20,000
49
66
66

1.300
None
77.000
31
5.3(10
014
38
None
210
-
••
-•
•-
-
--
--
-
-
-
--
-
-
--
-

•-
--
--
•-
-
«
--
•-
-
--
--
••

1.47
--
173.500
63
335
3.34
6.5
-
1.080
ND
ND
ND
ND
ND
ND
ND-4.000
ND
ND
ND
ND
ND
ND
ND
ND

ND
ND-440
ND-380
ND- 1,900
170-26,000
42-13,000
ND-120
ND
ND
ND
ND
ND-4.400

ND-383
2.7-41.6
15.600-605.000
ND-91.3
19.2-1.020
ND-3.63
ND-37
ND- 395.000
30-1.030
ND-580
ND-760
ND- 1.900
ND-32.000
ND-5.300
ND- 15.000
ND-400
ND-4.800
ND-610
ND-4.800
ND
ND-53,000
ND-5,600
ND- 52.000
ND-380

ND-0.89
ND
ND
ND-4.4
ND-110
ND-5.6
ND
ND
ND-0.52
ND
ND
ND

ND-0.543
11-316
4.32-158.000
ND-823
ND-3 II
ND-3.9
ND-183
123-383.000
— 0.736-1.430
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND-280
ND
ND
ND
ND

NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA

ND-I.4I
7.6-61.5
1.950-201.000
ND 115
14.5-628
0.156-3.43
ND-6.43
2.630-314,000
87.6-1.760
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND

ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND

ND-0.573
12.6-31.6
2.730-172,000
ND-224
3.89-56
ND-3.29
ND-II.3
25,300-367.000
34.7-865
ND
ND
ND
ND
ND
ND
ND-38
ND-320
ND
ND
ND
ND
ND
ND
ND

ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND

ND-0.477
7.3-26.4
194-105.000
ND-24.7
0.46-33.2
ND-2.91
ND-5.86
50,900-410,000
8.83-671
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND

ND
ND-330
ND-690
ND-9.6
ND-290
ND-7.7
ND-6.7
ND-0.96
ND-390
ND-12
21-26,000
ND

ND-0845
12.6-34.2
11.900-175.000
ND-15
7.51-55.4
0.189-4.21
ND-28.4
20.900-303.000
^^-1.270

-------

£
00
                                                                                    TABLE 2-1

                                                                     SOIL ANALYSIS RANGE OF DETECTIONS
                                                                                 MARBO ANNEX
                                                                                   (Page 2 of 2)
!2. »
§ 1
S Parameter
o
> Cobalt
§ Copper
JJ Iron
Magnesium
Manganese
Nickel
PC'SSSiUili
Silver
Sodium
Vanadium
Zinc
Mercury
Thallium
Arsenic
to Lead
Unit*

mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
Residential
SollPRG

4.600
2.800
None
None
380
1.500
None
380
None
540
23.000
23
6.13
0.38
400
Background
Cone.

29
72.2
-
--
3.150
242.5
--
14.9
•-
206
III
0.28
1.42
62
166
Site 20 -
Waste Pile 7
Range of Detection

ND-26.5
26.2-15.200
3.200-158.000
159-3.610
60.1-1.970
ND-250
ND-393
ND-10.5
48.6-469
17.9-181
37.5-9,280
ND-21 9
ND-I.I3
ND-435
56.5-18.500
Site 22 -
Waste Pile 6
Range of Detection

ND-29.5
ND-2.500
71.2-498.000
10.5-3.630
4.67-3.650
ND-2&9
ND-488
ND-386
ND-860
ND-281
2.64-3.120
ND-4.23
ND-1.84
ND-93.3
4.1 1-5.910
Site 23 -
Waste Pile 3
Range of Detection

ND-33.8
13.5-132
15.900-330.000
70.1-2,930
133-3,750
23.8-292
ND-416
ND-4.39
42.3-351
2.91-203
20.4-1.330
ND-5.14
ND-1.85
4.14-138
9.28-38.800
Site 24 . Site 37 • Site 38 •
Landfill 29 War Dog Borrow Pit MARBO Laundry
Range of Detection Range of Detection Range of Detection

ND-36
3.13-1.880
1.800-129.000
938-3.460
37.1-5.040
ND-249
ND-605
ND-167
ND-256
4.29-207
13.7-3,450
ND-1.74
ND-1.53
0.378-71.3
7.86-18,700

ND-18 4
ND-35.6
195-69.500
841-3.040
5.49-2,550
ND-143
ND-146
ND-3.81
182-121
ND-III
ND-402
ND-0.139
ND-1.73
ND-35.6
0.607-833

ND-21. 2
8.42-52.6
8.550-122.000
1.330-2,600
266-2.&6C
13-192
ND-263
ND
72.9-158
15.1-198
33-188
0.0606-0.818
ND-1.74
5.45-60.20
50.80-4.210
Volatile Organic Compounds
Acetone
Benzene
2-Butanone (MEK)
Carbon disulfide
Chloro benzene
Ethylbenzene
2-Hexanone
4-Methyl-2-penlanone (MIBK
Tetrachloroethene
Toluene
Xylenes (total)
NUTRIENTS
Organic Carbon. Total
Organic Carbon. Total (%)
Nitrogen. Tola)  Kjetdahl
Phosphorus. Total  as P
pH (s.u.)

Total Petroleum Hydrocarbons
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
M*/kg
Mg/kg
Mg/kg
Mg/kg
Mg/kg
mg/kg
%
mg/kg
mg/kg
s.u.
2.000.000
1.400
8.700.000
16.000
160.000
690.000
None
5,200.000
7.000
1.900.000
990.000
None
None
None
None
None
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND-5.7
ND
ND- 26.300
0.8-2.4
1.570
747
7.70
ND-130
ND
ND-92
ND
ND-0.82
ND-1.7
ND
ND
ND
ND-21
ND-4.6
NA
0.73-4
5.170
956
7.4
ND-440
ND-7.1
ND-230
ND-17
ND
ND-220
ND-840
ND-35
ND-130
ND-220
ND- 1.300
NA
0.26-37.7
4,930
2.400
7.20
ND-18
ND
ND-II
ND
ND
ND
ND-9.1
ND-IO
ND
ND-2.2
ND
NA
0.27-12.2
8.810
2.200
7.1
                                                                                                                                                   ND-9.2
                                                                                                                                                    ND
                                                                                                                                                   ND-9.5
                                                                                                                                                    ND
                                                                                                                                                    ND
                                                                                                                                                    ND
                                                                                                                                                    ND
                                                                                                                                                    ND
                                                                                                                                                    ND
                                                                                                                                                   ND-3.7
                                                                                                                                                    ND

                                                                                                                                                    NA
                                                                                                                                                   ND-5.4
                                                                                                                                                   1.160
                                                                                                                                                    167
                                                                                                                                                   7.50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA

NA
NA
NA
NA
NA
Diesel
Gasoline
JP4
PC/kg None
|it/lp Nimr
fffAf NlHlf
22.000-53.000
ND
27,000-54.000
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
             ND - Not Detected Above Rrnnntnp I imtt
             NA - Not Analyzed
                                                         PRO • Preliminary Remediation Goal
                                                         -- • Background value not calculated for organics and nutrient metals

-------
and COCs for each site are shown on Table 2-2.  Some of the sites have been subdivided into
discrete spill/disposal areas.  Only those spill/disposal areas  where COCs have been identified
are summarized in Table 2-2.

Site 20 (Waste Pile 7)

Waste Pile  7  is  an  abandoned quarry  that  is  partially  filled  with  waste (primarily
construction/metal debris), and is covered with soil,  vegetation, and scattered surficial debris.
Several organic compounds were detected in the surface and subsurface  samples. The detected
organic compounds  included  pesticides  (alpha-chlordane,  gamma-chlordane,   4,4'-DDE,
4,4'-DDT, and dieldrin), Aroclor 1260, toluene, and  bis(2-ethylhexyl)phthalate.  The pesticide
concentrations and frequency of detections indicated that these compounds are likely related to
past site activities.  Aroclor 1260 was found in only two samples but these concentrations are
also likely related to past site activities because waste electrical components were observed at the
site.   Because toluene was not detected during the active soil  gas surveys,  and was detected
infrequently and  at very low levels, the presence of this volatile organic compound (VOC) in two
subsurface soils  is not believed to be significant.  Bis(2-ethylhexyl)phthalate was detected in
several samples,  but these concentrations were qualified because the compound was also detected
in blank samples, therefore the bis(2-ethylhexy])phthalate detections are not believed  to  be
significant.  Inorganic analytes were detected in the surface and subsurface soils, however, based
on the frequency and magnitude of detections these analytes (except lead), were considered to be
representative of background conditions. A range of organic and inorganic  detections for  all
samples is presented in Table 2-1.

Based on maximum concentrations, the COPCs at Site 7 were identified as 4-4'-DDE, 4-4'-DDT,
Aroclor 1260, Dieldrin,  alpha-chlordane,  gamma-chlordane, aluminum, antimony,  arsenic,
copper, lead and  beryllium. Based on the frequency and distribution of these constituents at Site
7, the COCs were identified as 4-4'-DDE, 4-4'-DDT, Aroclor 1260, Dieldrin, alpha-chlordane,
gamma-chlordane and lead, estimated over an area of approximately two acres by 11-feet deep.
A summary of COPCs, the calculated EPCs, and COCs are shown on Table 2-2.
Andersen AFB MARBO Annex                     2-31                                  4/1/98
Record of Decision

-------
                                       TABLE 2-2

                             SITE CONSTITUENT SCREENING
                                       (Page 1 of 2)
Screening Criteria (rag/kg)
Site Name
Site 20
(Wasie Pile 7)










Site 22
(Waste Pile 6)






















Site 23
(Waste Pile 5)





Area












Car Battery
Area
Radio Battery
Area


Unknown
Battery Area
Asphalt Drum
Pile





Roofing
Material Pile



Metal Debris
Pile
Empty Drum
Pile







COPC*
4-4'-DDE
4-4--DDT
Aroclor 1260
Dieldrin
Alpha-chlordane
Gamma-chlordane
Aluminum
Antimony
Arsenic
Copper
Lead
Beryllium
Antimony
Lead
Antimony
Cadmium
Lead
Manganese
Lead

Benzo(a)anthracene
Benzo(a)pyrene
Benzo(k)nuoranthene
Arsenic
Beryllium
Chromium
l*ad
Benzo(a)pyrene
BenzcKa) fluoranthene
Indeno< 1 ,2.3-cd)pyrene
Arsenic
Chromium
Cadmium
Silver
Beryllium
Chromium
Aluminum
Antimony
Ajsenic
Beryllium
Chromium
Lead
Manganese
Background
NA
NA
NA
NA
NA
NA
173.500
63
62
72
166
3.34
63
166
63
6.5
166
3,150
166

NA
NA
NA
62
3.34
1,080
166
NA
NA
NA
62
1.080
6.5
15
3.34
1,080
173.500
63
62
3.34
1.080
166
3.150
PRG
1.3
1.3
0.066
0.028
0.34
0.34
77,000
31
0.38
2,800
400
0.14
31
400
31
38
400
380
400

0.61
0.061
0.61
0.38
0.14
210
400
0.061
0.61
0.61
0.38
210
38
380
0.14
210
77,000
31
0.38
0.14
210
400
380
Lead
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
400
NA
NA
400
NA
NA
400
NA
400

NA
NA
NA
NA
NA
NA
400
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
400
NA
EPC'
6.7
6.2
4.4
0.12
0.44
0.38
57,700
43.9
27.5
365
3,604
3.63
823
5,910
71
41.9
1.560
3.190
3,410

1.9
1.5
7.6
73.8
3.5
1.270
903
15
32
5.6
65.8
1.120
183
386
3.66
1,290
152,000
16.25
37.6
2.62
720
79.7
1.715
coc"
4-4'-DDE
4-4'.DDT
Aroclor 1260
Dieldrin
Alpha-chlordane
Gamma-chlordane
Lead





Antimony
Lead
Antimony
Cadmium
Lead

Lead

Benzo(a)anthracene
B«nzo(a)pyrene
Benzo(a)fluoranthene
Arsenic
Chromium
Lead

Benxo(a)pyrene
Benzo(a)fluoranthene
Indeno< 1 ,23-cd )py rene


Cadmium

Chromium

No COCs*






Andersen AFB MARBO Annex
Record of Decision
2-32
4/1/98

-------
Notes:
                                                    TABLE 2-2

                                        SITE CONSTITUENT SCREENING
                                                    (Page 2 of 2)
Screening Criteria (mg/kg)
Site Name
Site 24
(Landfill 29)



Site 37
(War Dog
Borrow Pit)
Site 38
(MARBO
Laundry)







Area
Surface Drum
Area

Subsurface
Metal Area



Building
Surroundings



South
Transformer

North
Transformer
COPC*
Antimony
Arsenic
Lead
Antimony
Lead
Lead


Aroclor 1254
Gamma-chlordane
Aluminum
Beryllium
Chromium
Aroclor 1254
Gamma-chlordane
Lead
Aroclor 1254
Lead
Background
63
662
166
63
166
166


NA
NA
173.500
3.34
1,080
NA
NA
166
NA
166
PRG
313
0.38
400
31
400
400


0.066
0.34
77,000
0.14
210
0.066
0.34
400
0.066
400
Lead
NA
NA
400
NA
400
400


NA
NA
NA
NA
NA
NA
NA
400
NA
400
EPC'
224
67.3
18,700
123
1.120
833


1.9
0.46
117,011
2.7
845
26
0.69
4,210
1.5
3,080
coc"
Antimony
Lead

Antimony
Lead
Lead'


Aroclor 1254




Aroclor 1254
Lead

Aroclor 1254
Lead
   COPC is Constituent of Potential Concern if maximum concentration exceeds screening criteria.
   Screening criteria based on health-risk based PRGs unless background metals' concentrations are higher. Lead screening criteria is 400
   mg/kg per Region VI USEPA Lead Model.
   EPC is Exposure Point Concentration which is based on the 95% Upper Confidence Limit. This is considered a Reasonable Maximum
   Exposure Scenario based on the statistical concentration and distribution of contaminants throughout the disposal area.
   COC is Constituent of Concern if EPC exceeds screening criteria.
   EPC concentrations at Site 23 were below the screening criteria, thus no COCs were identified.
   Lead was detected above screening criteria in only one isolated sample at a depth of 11 -feet below gound surface in a test pit. Due to
   the isolated nature of the  sample, this was not considered a health risk.
   Andersen AFB MARBO Annex
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Site 22 (Waste Pile 6)

The investigation of Waste Pile 6  identified surface debris  but  no buried wastes.   Several
pesticides were detected in the surface and  subsurface soil samples collected from the three
battery  areas,  including  4,4'-DDD,  4,4'-DDE,  4,4'-DDT,  endrin,  and  beta-BHC.   The
concentrations were  relatively low  and likely the result of  routine pest control  operations.
Acetone, methyl ethyl ketone (MEK), and bis(2-ethylhexyl)phthalate were detected at low levels,
and were believed to be insignificant.  Organic compounds were also detected at the remaining
four discrete/disposal  areas.   Site-related polycyclic  aromatic hydrocarbons  (PAHs) were
detected under and around the Asphalt Drum Pile and Roofing Material Pile, as well as other
VOCs (acetone,  chlorobenzene,  ethylbenzene,  toluene,  and  total  xylenes).    The  VOC
concentrations were  low and  believed to be insignificant.   Project inorganic  analytes were
detected  in the  surface and subsurface  soils at each of  the  discrete/disposal areas.   The
concentrations of many of these analytes were considered to  be representative of background
conditions, however some of the  inorganic  detections were believed to  be caused by  the
associated debris.  A range of organic and inorganic  detections for all samples is presented in
Table 2-1.

Based on maximum concentrations, COPCs were identified at each discrete  disposal area,
including  benzo(a)anthracene, benzo(a)pyrene,  benzo(k)fluoranthene,  indeno(l,2,3)pyrene,
antimony, cadmium, arsenic, chromium, silver, beryllium, manganese and lead.   Based on the
frequency and distribution of these constituents within each disposal area, the COCs were
identified as benzo(a)anthracene,  benzo(b)pyrcne,  benzo(a)fluoranthene,  indeno(l,2,3)pyrene,
antimony, cadmium, arsenic, chromium, and lead, estimated at a total volume of approximately
130 cubic yards. A summary of COPCs for each disposal area at Site 6, the calculated EPCs, and
COCs for each disposal area are shown on Table 2-2.
Andersen AFB MARBO Annex                     2-34                                  4/1/98
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Site 23 (Waste Pile 5)

Waste Pile 5 is a trench-style landfill that consists of several large trench-like waste disposal
cells containing mostly municipal waste. Several organic compounds were detected in some of
the surface and subsurface samples.  Acetone and toluene were detected in several subsurface
soil samples at low levels. It is unlikely that these two VOCs are site-related, and the low-level
presence of these VOCs is not believed to be significant.  Other VOCs (benzene, MEK, methyl
isobutyl ketone (MIBK), PCE, ethylbenzene, 2-hexanone, and carbon disulfide) were detected in
two subsurface samples that contained organic wastes such as paint from a paint can and/or
decomposing cardboard observed in a test pit. These detections are likely related to the debris,
but the low concentrations and the minimal amount of organic waste suggests that the presence
of these VOCs is  not significant.  The SVOC, di-n-butylphthalate was detected  in one surface
sample,  and is not believed to be significant. Project inorganic  analytes were detected in the
surface and subsurface soils.  Based  on the frequency and magnitude of inorganic compound
detections at Waste Pile 5, they were  considered to be representative of background conditions.
A range of organic and inorganic detections is presented in Table 2-1.

Based on maximum concentrations, the COPCs at Site  23 were identified  as  aluminum,
antimony, arsenic, chromium, beryllium,  manganese  and lead.  Based on the frequency and
distribution of these constituents within each disposal area, there were no COCs identified at Site
23. A summary of COPCs for Site 23, and the calculated EPCs, are shown on Table 2-2.

Site 24 (Landfill 29)

Soil samples collected from the Surface Drum Area and  Metal Debris Area in Landfill 29
contained  several  organic compounds (acetone,  toluene, MEK, MIBK, and  2-hexanone).
Because these VOCs were not detected during the active soil gas surveys, and were detected at
very low levels, their presence in the  subsurface soils is not believed to be significant.  Project
inorganic  analytes detected in the surface and subsurface samples from these two areas were
considered to be  representative  of background conditions.  However, some of  the inorganic
Andersen AFB MARBO Annex                     2-35                                  4/1/98
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detections were believed to be caused by the associated debris.  Samples were also collected
from the area outside of the Surface Drum Area and Metal Debris Area.  Organic compounds
were not detected in  these soil samples. Project inorganic analytes were detected in the soil
samples, but all detections were less than screening levels. A range of organic and  inorganic
detections for all samples is presented in Table 2-1.

Based  on maximum  concentrations, the COPCs at  the two disposal areas at Site 24  were
identified as antimony, arsenic, and lead.  Based on the  frequency and distribution of  these
constituents within each disposal area, COCs were identified as antimony and lead, estimated at a
total volume of approximately 35 cubic yards. A summary of COPCs for each disposal area at
Site 24, the calculated EPCs, and COCs for each disposal area are shown on Table 2-2.

Site 37 (War Dog Borrow Pilt)

The War Dog Borrow Pit is an area landfill that contains waste automobile parts.   Organic
compounds were detected  in some of the subsurface samples.  Acetone, toluene  and MEK were
detected in subsurface soil samples at low levels. It is unlikely that these VOCs  are site-related,
and the   low-level   presence  of  these   VOCs  is  not  believed   to  be  significant.
Bis(2-ethylhexyl)phthalate was detected in one subsurface soil sample and butyl benzyl phthalate
was detected in two subsurface soil samples. However, these low level concentrations were not
believed to be significant. Project inorganic analytes were detected  in the surface and surface
soils,  however, the  concentrations of these analytes  (except  lead) were  considered to  be
representative  of background conditions.  A range  of organic and inorganic detections is
presented in Table 2-1.

Based  on maximum concentrations, the only  COPC  identified at Site 37 was lead.   Lead was
retained as a COC but not considered a health risk due to  the isolation of the sample.  This is
shown on Table 2-2.  Of the 14 soil samples obtained at Site 37, lead was detected above the 400
mg/kg screening criteria only once (at 833 mg/kg). This was obtained from a depth of 11 feet
bgs, from the bottom of a test pit.
Andersen AFB MARBO Annex                     2-36                                 4/1/98
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Site 38 (MARBO Laundry)

The MARBO Laundry was a military laundry facility that was modified with the addition of a
dry cleaning facility in 1970.  Since  1974, the building has had other uses such as a storage
facility for  furniture. The building was renovated immediately before and during the  OU 3
sampling.   There  were no  SVOCs  detected in the surface  soil samples obtained from the
MARBO  Laundry.  Pesticides and PCBs  were detected in  some of  the samples, including
alpha-chJordane, gamma chlordane,  4-4' DDE, Dieldrin,  Endrin and  Aroclor 1254.  These
compounds  are considered representative of past activities.  Project inorganic analytes were also
detected and were considered representative of background conditions, with the exception of
lead.  A range of organic and inorganic detections is presented in Table 2-1.

Based on maximum concentrations, the COPCs at the Site 38 were identified as Aroclor 1254,
gamma-chlordane, beryllium,  chromium, lead and aluminum.   Based on the frequency  and
distribution  of these constituents, COCs were identified as Aroclor 1254 and lead, estimated at a
total volume of approximately 135 cubic yards. A summary of COPCs for each disposal area at
Site 38, the calculated EPCs, and COCs are shown on Table 2-2.

2.6.2         Potential Routes of Exposure

Practices  at all  sites have potentially affected  surface and  subsurface soil.  Under present
conditions,  potential current receptors include a maintenance worker  and trespasser.  Under
future conditions, potential residential receptors include a maintenance worker and trespasser, as
well as a resident and construction worker.  Present and future potential receptors are the same
for all of the sites  because current and future land use and accessibility are similar.  Therefore,
under current conditions, the most likely receptors at these sites are a maintenance worker and a
trespasser. Each of these receptors would be exposed to surface soils.  Under future conditions,
potential exposure to site constituents is evaluated for a hypothetical construction  worker.  This
receptor may be involved in the construction of a residential development, and  could contact
Andersen AFB MARBO Annex                     2-37                                  4/1/98
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subsurface soil via digging activities. Similarly, a hypothetical future resident may be exposed to
subsurface soil that mixed with surface soil during digging activities.

Potential routes of exposure for all receptors include incidental ingestion and dermal contact of
soils. Inhalation of soil particles is not considered to be a significant pathway for surface soils
due to the nature of the constituents of concern. Under current conditions, wind-generation of
particles is likely to be insignificant because all of the MARBO sites are extensively vegetated,
or in the case of MARBO Laundry, paved. Airborne panicles could be generated during digging
activities, so inhalation of paiticulates may be a potential route of exposure for the construction
worker  for subsurface soils.  This pathway would not be complete for  a residential receptor
because the ground in residential areas would be assumed to be covered by buildings, pavement,
and vegetation. With regard to inhalation of volatiles at each site, active soil gas sampling failed
to detect volatile constituents. In addition, detections of VOCs in subsurface soil  samples at the
sites were all below screening values. For these reasons,  inhalation of VOCs was not evaluated
as an exposure pathway.

2.7           SUMMARY OF SITE RISKS

Health Risk.  The human health risk assessment was based  on the  guidance. Region  IX
Preliminary Remediation Goals (PRGs) Second Half 1995 (USEPA,  1995), per the request of
Region IX USEPA. The PRG's were selected as cleanup performance standards. Based on this
approach, exposure point concentrations (EPCs) for site COCs were compared directly to Region
IX PRGs for cancer or non-cancer effects.  The exposure assumptions and toxicity assessment
information,  including cancer potency factors and non-cancer reference doses,  used in the
development of Region IX PRGs, are documented in the PRO guidance (USEPA,  1995).  A copy
of the this guidance is included in this ROD as Appendix A.

As noted in  Section  2.6, background concentrations  for  inorganic chemicals  and  a lead
concentration of 400 mg/kg were also utilized as screening criteria. After a COC was identified,
following the screening process outlined in Section 2.6.1, the constituent was utilized for the
Andersen AFB MARBO Annex                     2-38                                  4/1/98
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quantification  or  risk within each  site and/or discrete source area.   For COCs that  exert
carcinogenic effects, the chemical-specific EPC was divided by the cancer PRO. The resultant
EPC/PRG ratio was then multiplied by 1 x 106 to derive a chemical-specific cancer risk.  For
chemicals that exert non-carcinogenic effects, the EPC was divided by the non-cancer PRO.  The
resultant EPC/PRG ratio is  equal to the chemical-specific hazard index.  Chemical-specific
cancer risks and hazard indices were summed across all COCs to derive a total cumulative cancer
risk and hazard index for each site and/or discrete source area.

The USEPA considers a risk of less than IxKX6 (one in one million) to be protective of human
health, and uses this  value  as the point of departure.  The  USEPA  has developed the risk
management range of  1x10* to IxlO"4 (one in  ten thousand), as the  target  for managing cancer
risk.  The hazard index calculates potential  non-cancer  risks (e.g.,  skin lesions,  decreased
fertility, organ damage) that may be caused by  exposure to a compound or group of compounds.
For non cancer risk, the EPA has recommended a hazard  index equal to or less than one.  A
hazard index number below one indicates that non-cancer health effects are not expected.

Based on  this  assessment, a  human health  risk was identified  at one or more discrete disposal
areas within Sites 20, 22, 24 and 38.  There were no COCs identified at  Site 23, and the isolated
lead sample obtained from the bottom of a test  pit at Site 37 was not considered a health risk.  A
summary of the estimated health risk for potential future residents at each site is shown below
and on Table 2-3.
             A potential cancer risk of 2x10'' and potential HI of 4 was identified at the 1.84-
             acre area of Site  20 (Waste Pile 7), based on elevated concentrations of PCBs,
             pesticides and lead;
             A potential cancer risk range of 2x10l2 to 5x10" and HI range of 0.01 to 27 was
             identified at the six disposal areas at Site 22 (Waste Pile 6), based on elevated
             concentrations of  metals and PAHs;
             A potential  cancer risk of 4x10" to  2x10", and an HI  range  of 4 to  10 was
             identified at the two disposal areas at Site 24 (Landfill 29), based on elevated
             metals concentrations;
Andersen AFB MARBO Annex                     2-39                                  4/1/98
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                                                  TABLE 2-3

                   SITE-SPECIFIC CONSTITUENTS OF CONCERN AND ESTIMATED RISK


Site
Site Name
20 Waste Pile 7






22 Waste Pile 6

Waste Pile 6


Waste Pile 6

Waste Pile 6





Waste Pile 6


Waste Pile 6

Waste Pile 6

24 Landfill 29

Landfill 29

38 MARBO
Laundry
MARBO
Laundry
MARBO
Laundry
Notes:


Area
Description
Buried Waste Area






Car Battery Area

Radio Battery Area


Unknown Battery
Area
Asphalt Drum Pile





Roofing Material Pile


Metal Debris Pile

Empty Drum Pile

Surface Drum Area

Subsurface Metal
Area
Building Surrounding

South Transformer

North Transformer


Impacted
An* (ft1) and
Volume
(cubic yds)
Impacted area of
1.84 acres x 10.8'
deep




7ft1
(0.2 cy)
800ft'
(30 cy)

7ft1
(0.2 cy)
1.300 ft'
(49 cy)




50ft1
(3.5 cy)

78ft'
(25 cy)
70ft'
(12 cy)
175ft1
(3lcy)C
52ft1
(4cy)
3.625 ft1
(134 cy)
9ft1
(0.3 cy)
9ft1
(0.3 cy)

*
Constituents
of Concern
(COC)
4.4--DDE
4.4--DDT
Aroclor 1260
Dieldrin
alpha-Chlordane
gamma -ChJordane
Lead
Antimony
Lead
Antimony
Cadmium
Lead
Lead

Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)fluoren!hene
Arsenic
Chromium
Lead
Benzo(a)pyrene
Benzo(b)fluoranthenc
lndeno(123cd)pyrene
Cadmium

Chromium

Antimony
Lead
Antimony
Lead
Aroclor 1254

Aroclor 1254
Lead
Aroclor 1254
Lead



COC
Concentration
6.7
6.2
4.4
0.12
0.44
0.38
3.604
823
5.910
71
41.9
1.560
3.410

1.9
1.5
7.6
73.8
1.270
903
15
32
5.6
183

1290

224
18.700
123
1.120
1.9

26
4.210
1.5
3.080


Potential
PRGor k Hazard Cancer
Background Index Risk
1.3 4 2x10"
1.3
0.066
0.028
0.34
0.34
400
63 27 2x10"
400
63 12 3xlOJ
38
400
400

0.61 3 3x10"
0.061
0.61
62.0
1080
400
0.061 3 5x10"
0.61
0.61
38 6 IxlO'

1080 0.01 3x10'

63 10 2x10"
400
63 4 4x10"
400
0.066 3 5x10'

0.066 19 4x10"
400
0.066 1 2x10'
400



Lead
Risk
Yes






Yes

Yes


Yes

Yes





..


..

Yes

Yes

Yes

..

Yes

Yes


COC concentration is calculated as an Exposure Point Concentration (EPC) based on the distribution of contaminants throughout the site. The EPC is
t then used to calculate health risk. Concentrations are in nig/kg.
   antimony), or the residential screening criteria for lead. Concentrations are in mg/kg.
   Includes volume of the drums, which may contain soil.
cy - cubic yards
(--) - Not Applicable either because COCs were not identified, or lead was not detected above screening levels.
    Andersen AFB MARBO Annex
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       •      A potential cancer risk range of 5xl05 to 4x10"* and HI range of  1 to 19 was
             identified at the three disposal areas  at Site  38 (MARBO Laundry), based on
             elevated concentrations of PCBs and metals.

The OU3 RI Report (ICF, 1996) identified uncertainties in the human health risk assessments for
the above  sites.   The presence of uncertainty  is  inherent in  the risk assessment process.
Generally,  uncertainties in risk assessment typically result from limitations in the available
methods, information, and data used in the hazard identification, exposure assessment, toxicity
assessment, and risk characterization steps.  For many  of the discrete source areas that were
evaluated in the OU3 RI, the nature and extent of contamination was characterized by only one
sample, collected in order to locate the highest concentrations of constituents. The maximum
detected concentration, or 95 percent upper confidence limit (UCL), was assumed to represent
the concentration (i.e., EPC) to which most people are exposed all of the time.  Additionally, the
calculated  EPCs  for  several inorganic chemicals (e.g.,  aluminum, arsenic, beryllium, and
chromium) were less  than their respective background  threshold levels.  Furthermore, cancer
risks and non-cancer His were calculated based on the use of integrated PRGs which assume that
ingestion, dermal, and inhalation routes of exposure are complete; the only receptor identified in
the conceptual site model with inhalation as  a complete exposure pathway was a construction
worker.  The conclusions of the OU3 RI Report (ICF,  1996) indicate  that most sources  of
uncertainty in the human health risk assessment erred on the protective side, and that the cancer
risks  and  non-cancer His reported  for Sites  20, 22,  24,  and  38 most likely represent
overestimates.  Site-specific, tabulated summaries of the significant sources of uncertainty in the
human health risk assessment are included in Appendix B of this ROD.

Based on the potential risks associated with Sites 20,22, 24, and 38, actual or threatened releases
of hazardous substances from these sites, if not addressed by implementing the response actions
selected in this  ROD, may present an imminent  and  substantial endangerment to public health,
welfare, or the environment.
Andersen AFB MARBO Annex                     2-41                                 4/1/98
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Ecological Risk.   The ecological  risk assessments for the OU  3 sites were  conducted in
accordance with USEPA  guidance (USEPA,  1989b).   The objectives of the ecological  risk
assessments were to (ICF,  1996):

       •       Qualitatively  characterize the potential  ecological  receptors that  have been
              observed or could be present in terrestrial habitats on or adjacent to  each of the
              sites;
       •       Qualitatively and quantitatively characterize the potential effects of the identified
              chemicals of potential concern in soils at each of the sites to potential ecological
              receptors;
       •       Assess potential exposures of ecological receptors to chemicals  of concern in soils
              at each of the sites; and
       •       Characterize the risks associated with exposures of ecological receptors to the
              chemicals of potential  concern in soils at  each of  the  sites under  current
              conditions.
                                         •
The framework is conceptually similar to the approach used for the human health risk assessment
but distinctive in  its emphasis in three  primary areas:   l)The ecological risk  assessment
considers effects beyond those on individuals of a single species and may examine effects on
populations, communities, or ecosystems; 2) While there are general classes of ecological values
that can be defined and should be considered in any ecological risk assessment, there is no single
specific set of ecological resources to be protected that  can be generally applied to every  site,
because of differences  in the specific receptor habitats and their biological communities;  3) If
needed, the ecological risk assessment can consider non-chemical as well as chemical stressors.
However, no  site-specific, non-chemical stressors were identified in association with these sites,
therefore, only chemical  stressors  were evaluated.  In accordance with  this framework, an
ecological risk assessment was conducted at five of the sites;  (an ecological risk assessment  was
not conducted at the MARBO Laundry because the site is a building surrounded by maintained
lawn and there are no ecological receptors).

Three receptors were evaluated based on species with the greatest exposure to COCs and their
relevance to  the  overall ecosystems.   These  species were  the  blue-tailed  skink  (Emoia
Andersen AFB MARBO Annex                      2-42                                 4/1/98
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caeruleocanda), terrestrial plants growing at the  sites, and soil invertebrates (earthworms).
Because there is little chemical toxicity data on reptiles, ecological risks to the blue-tailed skink
were not quantified.  Instead, qualitative observations were made of skinks during the ecological
habitat survey for OU 3.  Biologists counted the number of skinks observed while walking along
paths cut at 50-foot intervals across each site. Populations of blue-tailed skinks were comparable
between the  sites under investigation and off-site locations with similar habitat.   Risks to
terrestrial plants were also evaluated based on the habitat survey.  Vegetation was generally lush,
and there were no significant observations of stressed vegetation.

Potential effects on  earthworms were evaluated quantitatively,  where COPCs were identified
based on those chemicals that exceeded background threshold values in more than one or two
samples, that had a  frequency of detection  greater than  5%,  and that were  not considered
essential nutrients (e.g., calcium, iron, magnesium, potassium, and sodium).

Based on this assessment the ecological risk assessment did not identify any sites with a potential
for adverse ecological effects based on the mean concentrations of the COPCs. Details of the
ecological risk assessment are included in the OU 3 RI (ICF, 1996).

2.8           DESCRIPTION OF ALTERNATIVES

The remedial objective at each site is to reduce cancer risk to within or less than the target risk
range of 1x10* to 1x10"*, and non cancer risks to a Hazard Index less than  1. The remedial action
objective for lead contaminated soils is to reduce lead in the soil to concentrations less than 400
mg/kg.  Four remedial alternatives were evaluated for the soil sites at the MARBO Annex.  One
of the four alternatives was then selected for each site after an analysis of site specific conditions.
The four alternatives which were evaluated to address estimated health risk at each site are:
       •      No Action;
       •      Institutional Control;
              Soil Cover; and
              Soil Removal.
Andersen AFB MARBO Annex                      2-43                                   4/1/98
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2.8.1          No Action (Alternative OU3-A)

The NCP and CERCLA, as amended, require the evaluation of a No Action alternative as a
baseline for comparison with other remedial technologies. No Action represents a pure no action
scenario. Under this alternative, no control or active treatment of the site soils or waste materials
is performed. Potentially impacted media, therefore, remain at the site. The no action alternative
does not decrease human health risks associated with exposure pathways at impacted sites.

2.8.2          Institutional Control (Alternative OU3-B)

Institutional Control utilizes specific controls to reduce the probability of exposure to impacted
media at disposal/spill areas at a site, but no action with respect to site soils or waste  materials is
performed  to  remediate  the constituents of  concern.   Institutional Control consists of the
following components:

       •       Site Controls;
       •       Public Education; and
       •       Periodic Site Review.

Site Controls.  Fencing would be constructed and signs would be used to restrict access to the
site.   To ensure  that  human health and the environment are protected in the future,  deed
restrictions will be implemented to place legal constraints on the future use of sites not used by
the military.

Public Education. Public education programs would be developed to inform Andersen  AFB
personnel and local  residents  of potential risks.   The  public  education  effort  under the
Institutional Control alternative would include public meetings and presentations, press releases,
and posting of signs where appropriate. This effort would be completed as part  of the existing
community relations program established at Andersen AFB, whose elements include  a RAB.
The RAB is comprised of members from  the  public who have  the opportunity to read and
Andersen AFB MARBO Annex                     2-44                                  4/1/98
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comment on IRP documents and provide input on project issues, and the maintenance of an
Administrative Record.

Periodic Site Review.  A review of site conditions would be conducted every 5 years. Periodic
reviews include an evaluation of existing and new information along with an assessment of the
future use of the site. The need for additional remedial measures would also be evaluated during
the review.

2.8.3         Soil Cover (Alternative OU3-C)

The Soil Cover alternative consists of constructing  a  soil cover over  impacted soils.   By
implementing this alternative, reductions in constituent  toxicity, mobility, or volume are not
achieved, but routes of exposure may be eliminated or reduced.  The Soil Cover alternative
consists  of the  following  components,  which include  two  actions  coupled  together:
1) constructing a soil cover over the impacted area; and 2) implementing the  same components
associated with the Institutional Control alternative (OU3-B):

       •     Site Controls;
       •     Public Education;
       •     Periodic Site Review;
       •     Site Preparation; and
       •     Soil Cover Construction.

Under this alternative, the site controls, public education, and periodic site reviews are the same
as those described for Institutional Control.

Site Preparation.  Prior to constructing  the soil cover, soil stockpile areas for fill material will
be designated, and appropriate construction support plans developed (e.g., a Health and Safety
Plan, Quality Assurance Project Plan,  and Environmental Response Plan).  Air monitoring
equipment will be set up around the excavation perimeter to monitor fugitive dust emissions. An
equipment decontamination area will be constructed.
Andersen AFB MARBO Annex                     2-45                                  4/1/98
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Soil Cover Construction. The purpose of the soil cover is to reduce exposure to contaminants.
Grading of soils will utilize appropriate  heavy construction equipment.  Fill material will be
stockpiled in designated areas prior to utilizing it as subgrade material. Random fill consisting of
locally available crushed coral:  will be used to establish a subgrade layer up to 6 inches in depth
that will be followed with a 12-inch soil layer consisting of clayey silt, obtained from borrow
sources on the island. In addition, a final  6-inch soil layer will be used to accommodate the root
system of the vegetation established over the covered area. A fence would be constructed around
the site to prevent  access during  revegetation, and  removed  when revegetation is complete.
Upon completion of site preparation and soil cover construction activities, the heavy equipment
will be decontaminated and demobilized.

Approximately two  acres of land will utilize the soil  cover as the selected remedial alternative.
Costs are discussed in Section 2.10.

2.8.4          Soil Removal (Alternative OU3-D)

The Soil Removal alternative consists of the excavation and disposal of impacted soil and has the
following components:

       •       Public Meetings;
       •       Site Preparation;
       •       Soil and Debris  Removal; and
       •       Disposal.

Under this alternative, the public  meeting portion of the public education  component of the
Institutional Control alternative will be implemented. The site preparation activities  identified
for the Soil Cover  alternative (OU3-C) are applicable.   Soil/debris removal and disposal are
discussed below.

Debris/Soil Removal. Debris from impacted disposal/spill  areas will be removed.  Soil with
contaminant concentrations exceeding the screening  criteria (either PRG's, background values
for metals, or 400  mg/kg for  lead) will  be excavated from each impacted  disposal/spill area
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where a health risk has been identified. Utilizing the sample data and results from the OU 3 RI
Report, an excavation plan will be developed to identify the soil/debris to be initially excavated
and removed.

Excavated soil will be  stockpiled within  the site from which it was removed,  for analytical
testing to determine disposal location.  Clean soils will be used as backfill, if needed, and the
backfilled areas compacted and revegetated.

Confirmatory  sampling will  be performed after excavation to verify that  soil exceeding the
screening criteria is removed.  Samples will be collected from the excavation area and analyzed
for site constituents of concern.  If analytical  results demonstrate that the  remaining soil  still
exceeds the criteria, additional soil removal and confirmatory sampling will be repeated until the
appropriate levels are achieved or until the RPM's indicate that the soil removal activities should
stop.   A formally approved sampling  and analysis  plan (SAP) will be  followed  during
performance of confirmatory sampling.

Disposal. Impacted soil and  debris exceeding PRGs or background will be excavated, analyzed
for COCs, and characterized as RCRA hazardous or non-hazardous wastes. The characterization
includes  assessing the two major categories which classify  a soil waste  as either hazardous or
non-hazardous - listed and characteristic  waste.  Listed  wastes include solid wastes that are
generated by industry and assigned a specific work number, including: non-specific source "F"
wastes (40CFR261.31); specific source "K" wastes (40 CFR 261.32) and commercial chemical
"P" and "U" wastes (40 CFR 261.33). The soil and debris proposed for disposal at  AAFB does
not conform to either of these definitions.  A characteristic waste is defined as a waste that is
either ignitable (40 CFR 261.21), corrosive (40 CFR 261.22), reactive (40 CFR 261.23) or toxic
(40 CFR 261.24).  The  determination of whether a solid  waste is considered characteristically
hazardous is made by analyzing the soil via the TCLP analysis.  The TCLP analysis is designed
to conservatively estimate the amount of contaminant that may leach out of the soil if the soil
were exposed to environmental conditions where water (i.e., rainfall) could potentially percolate
through the soil. If the results of the TCLP analysis indicate that either of the four characteristics
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exceed acceptable  levels (40CFR261, App. n),  then  the material  is considered hazardous.
Otherwise, the soil and debris is non-hazardous RCRA waste, and, equivalently, non-hazardous
CERCLA waste (40 CRF 302..3).

Soil from each removal area exceeding industrial PRGs will be analyzed by TCLP analysis to
determine if the soil will be regulated as RCRA hazardous or non-hazardous waste. If the soil is
non-hazardous (i.e., below the TCLP criteria), it will be disposed of on site as solid waste at the
Main Base landfill. If the soil is considered hazardous, based on the TCLP analysis, then it will
be consolidated for off-island disposal. Other non-hazardous excavated debris (not specifically
mentioned above)  will also  be  disposed of in the Main Base landfill.    As Land  Disposal
Restrictions are potentially applicable, this may affect the off-island disposition of some of the
soil and debris that is characterized as RCRA hazardous waste.

Plastic battery casings, batteries, and asphalt debris will be properly disposed  of or recycled
according to applicable regulations.  It is anticipated that asphalt debris will be recycled.  That
which is not recycled and is removed from impacted disposal/spill  areas will be considered non-
hazardous and disposed of or recycled as applicable.  Batteries will be considered hazardous
waste and disposed of accordingly.

Approximately 290 cubic yards will be removed as part of the Soil Removal Alternative. Costs
are discussed in Section 2.10.

2.9          SUMMARY OF COMPARATIVE ANALYSIS ALTERNATIVES

The remedial alternatives developed were analyzed in detail using the nine evaluation  criteria
required  by  the NCP.  These criteria are classified as threshold criteria, primary balancing
criteria, and modifying criteria. Threshold criteria are:
       1.     Overall protection of human health and the environment
       2.     Compliance with Applicable Relevant and Appropriate Requirements (ARARs)
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Primary balancing criteria are:
       3.     Long-term effectiveness and permanence
       4.     Reduction of toxicity, mobility, or volume through treatment
       5.     Short-term effectiveness
       6.     Implementability
       7.     Cost

Modifying criteria are:
       8.     State/support agency acceptance
       9.     Community acceptance

The resulting strengths and weaknesses of the alternatives were then weighed to identify the
alternative providing the best balance among the nine criteria.  Because each of the  sites  is
similar in nature with respect to contaminants, site layout, vegetation, and associated remedial
alternatives, the comparison of the nine CERCLA criteria are applicable to each site. Table 2-4
summarizes this comparison.  The cost of each alternative is site specific, which is discussed
separately.

2.9.1         Overall Protection of Human Health and the Environment

This criterion is an overall assessment of whether each alternative provides adequate protection
of human health and the environment. The evaluation focuses on a determination of the degree
to which a specific alternative achieves adequate protection and describes the manner in which
site risks are eliminated, reduced, or controlled through •treatment, engineering, or institutional
measures.

Institutional Control, Soil Cover, and Soil Disposal are expected to provide adequate protection
of human health from soils presenting unacceptable risks.  In  addition, the site controls to be
implemented with Institutional  Control, Soil Cover, and Soil  Disposal also provide adequate
protection of human health for anticipated future land uses. Soil Disposal will reduce risks by
excavating, removing, and properly disposing of the impacted material. Soil Cover will  reduce
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2,3
   to
                                                                                       TABLE 2-4

                                                                        COMPARISON OF SOIL ALTERNATIVES
\FB MARBO Annex
Alternative
No Action
institutional
Control
Compliance with
ARARs'
Does not comply
Exposure io soils
exceeding chemical
ARAR screening
criteria is reduced.
Protection of
Human Health and
the Environment
Potential for future
exposure remains.
Potential for future
exposure slightly
reduced.
Short-Term
Effectiveness
Not Effective
Effective
Long-Term
Effectiveness
Not Effective
Marginally
effective.
Reduction
ofTMV*
No reduction
inTMV
No reduction
inTMV
ImplemenUbility
No Technical
Limitations
Easy
Implementation
Territorial
Cost* Acceptance
Site Specific Not Acceptable*
Site Specific Not Acceptable"
Community
Acceptance
Not Acceptable"
Not Acceptable*
Soil Cover      Exposure to soils    Potential for future    Effective       Effective      No reduction         Easy
              exceeding chemical   exposure reduced.                                  inTMV      Implementation
               ARAR screening
              criteria is eliminated
                  or reduced.

Soil Removal    Soils exceeding    Potential for future    Effective       Effective      No reduction         Easy
               chemical ARAR        exposure                                      in TMV      Implementation
               screening criteria   significantly reduced.
                 excavated and
                   removed.
                                                                                                                                Site Specific     Acceptable      Acceptable
                                                                                                                                Site Specific     Acceptable      Acceptable
            Notes:
            '   Action and Location specific ARARs are met for each alternative, where applicable. Site specific ARARs are further discussed separately for each site.
            "   TMV - Toxicity, mobility, and volume.
            '   Cost is discussed separately for each site.
            '   Not acceptable for the four sites above acceptable health risk (Waste Pile 5 and (he War Dog Borrow Pit were within acceptable health risk range, therefore no further action was
                necessary).
            '   Not acceptable as a stand-alone alternative.

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risks associated with impacted disposal/spill areas by covering the soils and implementing site
controls to prevent exposure to the identified constituents of concern.  Institutional Control will
limit  exposure pathways and  may also reduce risks by  controlling  access  to impacted
disposal/spill areas, but there is more uncertainty in the protectiveness that this alternative will
provide than there is for the Soil Cover and Soil Disposal alternatives. The No Further Action
alternative does not provide adequate protection of human health at impacted disposal/spill areas
where risks have been identified.

2.9.2          Compliance with ARARs

This threshold factor evaluates a remedial alternative's  compliance with Federal and Territorial
(Guam) ARARs as defined in CERCLA Section 121. Because ARARs vary with each  site, the
applicability  of ARARs  to the  individual sites at  the MARBO  Annex  is  discussed  in
Section 2.10.  The  list of soil  ARARs and To Be  Considered criteria (TBCs) is shown on
Table 2-5. Pursuant to Section 121 (d) CERCLA, as amended, the remedial actions must attain a
degree of cleanup which assures protection of human health  and the environment.  In  addition
CERCLA requires that remedial actions meet standards, requirements, limitations, or criteria that
are applicable or relevant and appropriate requirements (ARARs).  ARARs are of three types:
chemical-, action-, and location-specific.  Identification and consideration of potential  ARARs
associated with a  site  and its  remedial action   is   an ongoing  process  throughout  site
characterization and remediation.

An ARAR may be either "applicable" or "relevant and appropriate," but not  both.  The NCP
defines "applicable" and "relevant and appropriate requirements" as follows:
       Applicable requirements means those cleanup standards, standards of control, and other
       substantive requirements, 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 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 requirements, may be applicable.
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                                                          TABLE 2-5

                                              SUMMARY OF ARARs AND TBCs
Actor
Authority
Issues and Requirements
Citation
Status
Rationale for Inclusion
as ARAR or TBC
Affected
Alternative
Federal Chemical-Specific ARARs
USEPA Region   Health-based concentration
IX Preliminary   goals for chemicals in
Remediation     environmental media: air, soil
Goals (PRGs)    and water.
Federal
Insecticide,
Fungicide and
Rodeniicide Act
(F1FRA)
Regulates the disposal and
storage of pesticides and
pesticide containers.
Toxic Substances  Regulates wastes containing
Control Act       PCB constituents.
(TSCA)
                                N/A
60 FR 32094;
   6/19/95
                             40CFR76I
                 To Be     PRGs to be used as preliminary cleanup
               Considered  criteria for constituents of concern at sites
                 (TBC)     with identified risks (if the PRG exceeds
                                        background).
 Applicable
(Site 20 only)
                Applicable
               (Sites 20 and
                 38 only)
Federal Location-Specific ARARs
Endangered       Promotes actions to conserve    16 USC I S31:    Applicable
Species Act       endangered species or habitat.  SO CFR 200,402
  ederal Action-Specific ARARs
    in Air Act     National Ambient Air Quality    40 CFR 50

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       Relevant and appropriate requirements means those cleanup standards,  standards of
       control,  and other substantive requirements, 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.

In other words, a requirement is "applicable" when the remedial action or the circumstances at
the site  satisfy  all of  the jurisdictional prerequisites  of  that requirement.  Relevant  and
appropriate requirements must be complied with to the same degree as if they were applicable,
but there is more discretion in this determination and it is  possible for only part of a requirement
to be considered relevant and appropriate in a given case.

Where no  promulgated standards exist for  a given chemical  or situation,  nonpromulgated
advisories  and  guidance ("to-be-considered"  materials  [TBCs])  issued  by federal  or state
government may be used in determining the necessary level of cleanup for protection of human
health  or the environment.   TBCs do  not  have the status  of ARARs; however, in many
circumstances they will be considered along with ARARs as part of the site risk assessment and
may be used in determining the necessary level of cleanup.

Identification of ARARs and TBCs must be done on a site-specific basis. Neither CERCLA nor
the NCP provide across-the-board standards for determining whether a particular remedy will
effect an adequate cleanup at a particular site. Rather, the process recognizes that each site will
have unique characteristics that must be evaluated and compared to those requirements that apply
under the given circumstances.

2.9.2.1       Chemical-Specific  ARARs.     Chemical-specific  ARARs  include  those
environmental laws and regulations that regulate  the release to the environment of materials
possessing certain  chemical or physical characteristics  or containing specified  chemical
compounds.  These requirements generally set health-  or  risk-based concentration limits or
discharge limits for specific hazardous substances (USEPA, 1989).

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Chemical-specific ARARs an: determined by identifying federal and state environmental statutes
that are potentially applicable or relevant and appropriate to chemicals found at a particular site.
Both ARARs and TBCs are subject to a site-specific risk assessment to ensure exposure levels
are within acceptable  limits for the protection  of human  health and  other environmental
receptors. In some cases, such as multiple exposure pathways or multiple contaminants, a risk
assessment may indicate that an ARAR alone is not sufficiently protective and TBCs, including
risk-based limits,  will  be used  to establish  more  stringent  clean-up  requirements.   The
applicability of chemical-specific ARARs relative to specific site  conditions is discussed in
Section 2.10.

2.9.2.2       Location-Specific ARARs. As defined in the USEPA draft guidance (USEPA,
1988):

       "Location-specific  ARARs  are  restrictions  placed   on  the concentration of
       hazardous substances or the conduct of activities solely because  they are in
       specific  locations.  Some  examples of special locations  include  floodplains,
       wetlands, historic places, and sensitive ecosystems or habitats."

Endangered  species and their habitats are protected by the Endangered Species  Act  (ESA)
(16 USC Sections 1531-1543).  The proposed remedial actions could affect some species or their
critical habitat during invasive installation. The mitigation efforts that would be performed prior
to construction  of any  remedial alternative would entail inspection of the site for  endangered
species by qualified personnel, and selection of an alternative to eliminate or minimize impacts
to these  species if their presence  is detected.  The  applicability of location-specific ARARs
relative to specific site conditions is discussed in Section 2.10.

2.9.2J       Action-Specific ARARs.  Action-specific  ARARs are  restrictions  that  define
acceptable treatment and disposal procedures for hazardous substances.  These ARARs generally
set performance,  design, or other  similar action-specific controls or restrictions on particular
kinds of activities related to management of hazardous substances or pollutants, such as RCRA
regulations for waste treatment, storage, and disposal. These requirements are triggered by the
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particular remedial activities that are selected to accomplish a remedy. The type and nature of
these requirements is dependent upon the particular remedial or removal  action taken at a site.
Therefore, different actions or technologies are often subject to different action-specific ARARs.
The applicability of  action-specific ARARs relative to specific site conditions is discussed in
Section 2.10.

2.93         Short-Term Effectiveness

Alternatives are evaluated with respect to their effects on human health and the environment
during implementation of the remedial action.  This evaluation  addresses protection of site
workers and the community during remedial actions, potential environmental impacts, and the
time until remedial action objectives are achieved.

Because direct remedial actions will  not be implemented as part of the Institutional Control
alternative, increased short-term risks to workers, the community, and the environment during
construction are expected to be minimal. Site controls would be implemented in approximately
one month.

Increased short-term risks  to  workers,  the community,  and the  environment during  the
implementation of the Soil Cover and Soil Removal alternatives are also expected to be minimal.
A health and safety  plan will be developed to mitigate risks from performing excavation, soil
cover construction, and disposal activities. The health and safety plan will address items such as
the use of personal protective equipment and the proper handling of impacted media.  An air
monitoring plan will  be established to monitor the potential for off-site emissions of dusts. Dust
control measures will be implemented as necessary. Site controls, construction activities, and the
soil cover installation for the Soil Cover are expected to be completed in approximately 4 to 6
weeks.
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2.9.4          Long-Term Effectiveness and Permanence

The purpose of this criterion is to assess the residual risk and the adequacy and reliability of
controls  associated with a particular alternative.   The magnitude of risk resulting from the
presence of untreated waste or treatment residuals is assessed with respect  to the volume or
concentration of residual contaminants.

The second component, adequacy and reliability of controls, assesses the containment  systems
and institutional controls in place to determine  if they are sufficient to ensure that both human
and environmental exposure is within protective levels. The long-term reliability of management
controls to provide continued protection from residuals is also addressed with regard to (1) the
potential need to replace technical components of the alternative, and (2) the potential exposure
pathway and resulting risks should the remedial action need replacement.

Soil Removal will reduce risks  associated with impacted disposal/spill areas to acceptable target
risk levels (i.e., less than a cancer risk  of 1.0x10^ and noncancer  hazard  index of 1.0)  by
excavating and removing impacted material.

Soil Cover will reduce risks associated with disposal/spill  areas by covering the soils to prevent
exposure to the identified constituents of concern.  By limiting the potential contact with  elevated
concentrations  of constituents of concern in soils, the risks will be lowered to acceptable target
risk levels (i.e., less than a cancer risk of  l.OxlO"6 and noncancer hazard index of 1.0).  Soil
covers may have a long life if properly installed.  The soil cover alternative restricts future use of
the site to non-intrusive activities, thus reducing the potential economic value when compared to
soil removal.

The use of Institutional Control will limit exposure pathways and, therefore, reduce risks to
acceptable target risk levels by controlling access to impacted disposal/spill areas at OU 3 sites.
Because impacted soils are left in place under this  alternative, periodic site reviews will occur.
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The long-term management activity associated with this alternative includes the performance of a
pehodic review.

2.9.5         Reduction of Toxicity, Mobility, or Volume Through Treatment

Alternatives are assessed to determine the extent to which  they permanently reduce toxicity,
mobility, and  volume (TMV) of the contaminants posing the principal threats at a  site.  The
specific factors considered in this assessment include:

       •      treatment  or  recycling process(es) of associated  target contaminants and the
              amount of contaminants to be destroyed or treated;
       •      degree of expected reduction in the TMV and the degree to which treatment or
              recycling will be irreversible;
       •      type and quantity of treatment residuals expected to remain following  treatment;
              and
       •      whether or not the alternative satisfies the statutory preference for treatment as a
              principal element.

None of the alternatives satisfy the statutory preference for using treatment to reduce toxicity,
mobility, or volume of contaminants.  However, each alternative will limit or eliminate the
exposure pathways to the contaminants.  Institutional Control will  limit exposure through
administrative and site controls, Soil Cover through the covering of impacted areas, and Soil
Removal through the removal of impacted soil volume at identified disposal/spill areas at the soil
sites.

2.9.6         Implementability

This criterion has three components:  (1) technical feasibility, (2) administrative feasibility, and
(3) availability  of services and materials.  Each alternative is assessed on  the basis  of  factors
within these three categories.
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The assessment of the administrative feasibility of a particular remedial alternative is based on
the number and complexity of activities needed to coordinate with other offices and regulatory
agencies during preparation and implementation of the alternative.  Factors that are considered in
the assessment of technical feasibility include:

       •      potential for  problems  associated with construction and operation  of an
              alternative;
       •      reliability of an alternative and its components;
       •      ease of undertaking additional remedial action, if needed; and
                                    n
       •      ability to monitor the effectiveness of the  remedy and evaluate the risks  of
              exposure should monitoring be insufficient to detect a failure.

The availability of services and materials is to be considered. This includes such items as off-site
treatment, storage or disposal capacity, equipment, and specialists.

Institutional Control is technically simple to implement. The establishment of deed restrictions
would be implemented as a component for future nonmilitary land use where a restriction on the
property title would be added during a land transfer.  Installation  of the temporary site fencing
uses standard construction practices.  The ability to keep potential squatters from locating to
impacted sites involves periodic inspections. Fencing with the posting of signs will be a suitable
deterrent while the site is being revegetated.

For the Soil  Cover Alternative, the subgrade  is established by using standard excavation and
backfilling techniques, and is not expected to present technical implementability concerns.  All
components of this alternative use relatively common, uncomplicated construction procedures.
The construction materials needed for the soil cover are available on Guam.

Soil  Removal and  light grading  or backfilling  are not  expected  to present  technical
implementability  concerns for Soil  Removal.  The impacted site soils  and  debris are generally
located near the ground surface.  Special care will be necessary for the MARBO Laundry, where
piping and other underground features may exist.
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2.9.7        Cost

Both capital costs and operation and maintenance costs are considered for each alternative, with a
target accuracy of -30 to +50 percent.  Capital  costs include both direct (e.g., equipment) and
indirect (e.g., contingency allowances) costs.  Costs are presented on a present-worth basis over a
period of 30 years, with a discount rate of five percent.  Detailed cost analysis is presented in the
Focused FS (ICF, 1997a), and discussed on a site-specific basis in Section 2.10 of this document.

2.9.8        Federal and Territory Regulatory Acceptance

This assessment considers the technical and administrative issues and concerns the USEPA and
Territory of Guam may have regarding each of the alternatives. The USEPA and Guam EPA
both submitted comments to the  draft version of this  document prior to its going final.  The
comments ranged from editorial suggestions to comments concerning the implementation of the
selected alternatives, particularly at Waste Pile 7. After addressing comments and concerns, the
USEPA and Guam EPA are in concurrence and agreement with the selected soil alternatives.
Their comments, and  Andersen AFB's  responses  to those comments,  are  included as
Appendix C.

2.9.9        Community Acceptance

This assessment evaluates  the issues and  concerns  of the public regarding  the proposed
alternatives. A Proposed Plan and Community Relations Plan (CRP) was prepared to address
community concerns and provide a forum for the exchange of information on the MARBO sites.
As  part of this  plan, public participation is encouraged throughout all phases of design and
remediation. After release of the Proposed Plan, which presented  the same preferred remedies
identified in the  ROD,  the community did not  express significant objection during the  public
meeting or public comment period.  Senator Brown noted concern pertaining to the connection
between soil contamination at Waste Pile 7 and the groundwater. She also noted a concern over
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land use restrictions on Waste Pile 7 after transfer to the Government of Guam. Responses to
Senator Brown's concerns, and public comments, are included in Section 4.0.

2.10         THE SELECTED REMEDY

This section provides a description of the preferred alternative for addressing soil contamination
at the MARBO Annex based on the detailed evaluation of alternatives presented in the Focused
FS (ICF, 1997a). This section includes the basis for selection of a selected remedy, a description
of the selected remedy, discussion of ARARs compliance,  a discussion of the residual risk
remaining after implementation of the selected remedy, and a cost analysis.  The four remedial
alternatives were evaluated for each site, and are summarized below.  When compared to site-
specific conditions, the selected  remedy for each site balanced most effectively with the nine
CERCLA criteria.

2.10.1       Site 20 (Waste Pile 7)

No Action, Institutional  Control, and Soil Cover were evaluated for the Buried Waste Area at
Waste Pile 7.  Soil removal was  considered impracticable at Waste Pile 7 as the level of effort
and cost associated with soil removal outweighed the benefit of risk reduction, when compared
to a soil cover.

Soil Cover is the Air Force selected remedy. Soil cover eliminates potential future health risk by
cutting off direct exposure to the COCs through site controls and covering of the buried waste.
Soil removal at Site 7 is impracticable where  reduced risk of exposure can be attained via soil
cover. Crushed coral will be used to establish a subgrade layer up to 6 inches in depth that will
be followed with a 12-inch soil layer consisting of clayey silt. A final 6-inch soil layer will be
used to accommodate the  root system of the vegetation established over  the covered area. A
fence will be constructed around the site to prevent access during revegetation.
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The cover will meet the objective of minimizing the potential for disturbing the wastes in the
future and the potential for direct exposure. The cover will also minimize the potential future
migration of contaminants to groundwater. To ensure that human health and the environment are
protected in the future, land use at Waste Pile 7 is restricted to activities that cannot disrupt the
physical or structural integrity of the cover.  Restricted activities include trenching, excavation,
or any other activity that could breach the cap.  This restriction does not apply to maintenance
activities conducted within the top 12 inches of the soil cap, to preserve or restore the physical or
structural integrity of the cap. The Air Force shall place warning notices around the periphery of
Waste Pile 7 stating that activities in the area are restricted.

The written concurrence of the FFA signatories is required before the Air Force takes any action
at Waste Pile  7 that could disrupt the physical or structural nature of the cover.  If any such
action is proposed, the Air Force must provide FFA signatories with written notification of such
proposed action.  The notice shall  include (i) an evaluation of the risk to human health and the
environment, (ii) an evaluation of the need for any additional remedial action  as a result of the
proposed action, and (iii) a description of the changes necessary to the selected remedy for Waste
Pile 7.  The FFA signatories must provide written concurrence with the Air Force's evaluation of
risk and proposal regarding any necessary changes in the remedial action, if required, before the
Air Force can commence any action.

The Air Force shall notify the FFA signatories of any plan to lease or transfer Waste Pile 7 to a
non-federal or federal entity, notify the transferee or  leasee of the restrictions on  activities at
Waste Pile 7, and include the restriction in the transfer or lease.  The Air Force shall comply with
CERCLA 120(h)(3) in any such transfers.

The Andersen AFB Master Plan will be amended to incorporate the above-mentioned restrictions
on activities at Waste  Pile 7. The Master Plan amendments will  also include language that
describes the risk to human health and the environment that exists at Waste Pile 7, with reference
to the OU 2 and OU 3 RI/FS and the MARBO Annex ROD; and will provide a legal description
(metes and bounds) of the boundaries of Waste Pile 7.  The language in the Master Plan will also
include the title and dates of  the above-listed documents and their storage location.  The Air
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Force will  provide  the FFA signatories with a copy of the amendments to the Master Plan
reflecting the restrictions on Waste Pile 7.

The  ARARs and TBCs determined to  be pertinent to the remedial alternatives identified for
Waste Pile 7 are shown on Table 2-6, along with estimated cost.  The Federal Endangered
Species Act was determined to be not relevant because no endangered species have been found at
Waste Pile 7. However, the Act is retained as an ARAR which would be applicable if conditions
at Waste Pile 7 are found to have changed during remediation activities.  The Toxic Substances
Control Act (TSCA) is not relevant to Waste Pile 7 because the alternatives considered do not
involve the transportation, storage  or  disposal of PCBs (i.e., the activities regulated  under
TSCA).  The Federal Insecticide, Fungicide and Rodenticide Act  (FIFRA) regulates the sale,
distribution and use of pesticides.  As the remedy of Waste Pile 7 does not include any of these
activities, and as  there were no containers or drums of pesticides discovered at Waste  Pile 7,
FIFRA  is not applicable.  RCRA, the Hazardous Materials Transportation Act, and the  Guam
Code Annotated (GCA) regulating solid waste management are  also not relevant because the
alternatives evaluated for this site do not involve the transportation, storage, or disposal of solid
or hazardous waste.

A qualitative evaluation of residual risk was performed, based on the selected remedy (i.e., soil
cover).  Under the selected remedy, impacted soils at Waste Pile 7 will be covered with 18  inches
of clean fill  soils and 6 inches  of topsoil.  The soil cover will  effectively eliminate  future
exposures to site contaminants, by serving as a barrier to exposure pathways. Future exposures
to site COCs will be eliminated, as long as the soil cover remains intact.  As a result  of the
elimination of exposure pathways, there are no residual risks associated with the COCs that are
being left in place. Therefore, the residual risks associated with this site are anticipated to be less
than the cancer risk criterion of 1.0 x 10"* and non-cancer HI of 1.0, as long as the soil cover
remains intact.

Total 30-year present worth cost is  estimated to be $629,800 in  capital costs and $260,800 in
O&M costs.
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                                                  TABLE 2-6

                       SUMMARY OF REMEDIAL ALTERNATIVE COSTS AND ARARs

Site
Name
Site 20 -
Waste Pile 7



Site 22 -
Waste Pile 6
(Battery Areas)


Evaluated
Alternative
No Action
Institutional Control
Soil Cover

Soil Removal
No Action
Institutional Control
Soil Cover
Soil Removal

Pertinent ARARs and Performance
Standards Compliance
PRGs— Not met.
PRGs — Soil exposure reduced.
PRGs — Soil exposure eliminated.
Clean Air Act— Will be met.
b
PRGs— Not met.
«
—
PRGs— Will be met.
Total Cost
(30-yr; 5% Discount
Present Worth)'
No Action: $0
Inst. Control: $222.900
Soil Cover: $890.600

Soil Removal:
No Action: $0
Inst. Control:
Soil Cover:
Soil Removal: $30,600

Preferred
Alternative
Soil Cover




Soil Removal



Site 22 -
Waste Pile 6
(Asphalt And
Metal Pile Areas)
    No Action
Institutional Control
    Soil Cover
  Soil Removal
Site 24 -
Landfill 29
    No Action
Institutional Control
    Soil Cover
   Soil Removal
Site 38 -
MARBO Laundry
    No Action
Institutional Control
    Soil Cover
   Soil Removal
RCRA 40 CFR 261. 262.263, and 268
Will be met. if necessary.
Clean Air Act—Will be met.
DOT 49 CFR—Will be met.
Guam 10 CCA 51—Will be met.

PRGs—Not met.
PRGi—Will be met.
RCRA 40 CFR 261. 262.263, and 268
Will be met. if necessary.
Clean Air Act—Will be met.
DOT 49 CFR—Will be met.
Guam 10 CCA 51—Will be met.

PRGs—Not met.
PRGs—Will be met.
RCRA 40 CFR 261.262, 263, and 268
Will be met, if necessary.
Clean Air Act—Will be met.
DOT 49 CFR—Will be met.
Guam 10GCA 51—Will be met.

PRGs—Not met.
                                     PRGs—Will be met.
                                     RCRA 40 CFR 261,262,263, and 268
                                     Will be met. if necessary.
                                     Clean Air Act—Will be met.
                                     DOT 49 CFR—Will be met.
                                     Guam 10 GCA 51—Will be met.
                                     TSCA 40 CFR 761—Will be met.
No Action:
Inst. Control:
Soil Cover:
Soil Removal:
    $0
$42.600
Soil Removal
No Action:
Insl. Control:
Soil Cover:
Soil Removal:
     $0
                                                                                        $22,500
Soil Removal
No Action:
Inst. Control:
Soil Cover:
Soil Removal:
     $0
                                                   $29.900
Soil Removal
Notes:
    Costs are based on ICFTechnology Incorporated (ICROperable Unit 3 Focused Feasibility Study Report (OU 3 FFS). These criteria do
    not include costs for the disposal of soil which may be handled as hazardous waste.
    (--) Alternative not Evaluated.
     Andersen AFB MARBO Annex
     Record of Decision
                                        2-63
                                                                      4/1/98

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2.10.2        Site 22 (Waste Pile 6)

Battery Areas. No Action and Soil Removal were evaluated for the three battery areas ("Car
Battery  Area," "Radio  Battery Area,"  and "Unknown  Battery  Area") at  Waste  Pile  6.
Institutional Control and Soil Cover are not applicable because these alternatives would restrict
the future land use, whereas the removal of the small quantity of waste along with any impacted
soil would allow unrestricted land use. Soil removal includes battery and soil removal.

Soil Removal  is  the Air Force selected remedy for the Battery Areas at Waste Pile  6.  Soil
removal can be readily implemented and will reduce health risk associated with soil exposure by
removing the batteries and the soil which exceed  residential PRGs/background.

The battery casings and batteries will be removed from each area.  This includes approximately 6
plastic  battery casings and 12 batteries.  Soil exceeding residential PRGs/background will be
excavated from each area. This includes an estimated 30 cubic yards (cy) of soil.  The total
impacted ground surface area was estimated at approximately 814 square feet, with an estimated
depth of 1 foot.  Soil  and debris removal and confirmatory sampling will be  performed after
removal at Waste Pile 6.  Pending TCLP analyses, impacted soil will either be disposed of as
hazardous waste, off island, or as solid waste, at  the Main Base landfill.  It is anticipated that the
batteries will be handled and disposed of as hazardous waste or recycled.

The ARARs and  TBCs determined to be  relevant to the remedial alternatives identified for the
former Waste Pile 6 are shown on Table 2-6, along with estimated cost. The Federal Endangered
Species Act was deemed not relevant for the same reasons described for Waste Pile 7.  FIFRA
and TSCA are not relevant because no pesticides or PCBs exceeding preliminary cleanup criteria
were detected at this site.  An  evaluation of residual risk was performed for Waste Pile 6.
Because this residual risk evaluation was performed  for the entire site, the results are presented at
the end of this section. Total present worth cost is estimated to be $30,600 in capital costs. This
estimate is based  on the assumptions presented in the OU 3 FFS (ICF, 1997), which assume that
Andersen AFB MARBO Annex                     2-64                                 4/1/98
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all soil and debris would be disposed on site. Costs would be expected to increase should off-site
disposal be required.

Asphalt and Metal Pile Areas. Similar to the battery areas, No Action and Soil Removal were
evaluated for the remaining four disposal areas (the "Asphalt Drum Pile," "Roofing Material
Pile," "Metal Debris Pile," and "Empty Drum Pile") at Waste Pile 6.

Soil Removal is the Air Force selected remedy for the Asphalt, Roofing, Empty Drum, and Metal
Piles at Waste Pile 6.  This alternative removes asphalt and  contaminated soil  which poses a
potential  health risk, and can be readily implemented. Soil removal includes the removal of 108
asphalt drums, the roofing material, the 16 empty drums and the other metal debris located in the
shallow subsurface soil, as well as impacted soil exceeding the screening values.  Based on the
information presented in the OU 3 RI Report,  the total impacted volume is estimated to  be
approximately 90 cubic yards of soil.  Soil  and  debris removal  and confirmatory  sampling
activities  will be performed after removal.   Asphalt  in the drums will be recycled.   It is
anticipated that  the asphalt in the 108 drums will be recycled  to the  extent possible and
remaining debris will be disposed of as solid waste at the Andersen AFB landfill. Pending TCLP
analyses, impacted soil will either be disposed  of as hazardous  waste, off island, or as solid
waste, at  the Main Base landfill.

The ARARs and TBCs determined to be pertinent  to the remedial alternatives identified for the
former Waste Pile 6 are shown on Table 2-6, along with estimated cost. The Federal Endangered
Species Act was deemed not pertinent for the same reasons described for Waste Pile 7. PTFRA
and TSCA are not pertinent because no pesticides or PCBs exceeding  preliminary cleanup
criteria were detected at this site.

A quantitative evaluation of residual risk was performed for Waste Pile 6, based on the selected
remedy (i.e., soil removal). Supporting data and the residual risk calculations for the evaluation
are presented in Appendix B. Waste Pile 6 currently contains seven discrete areas of impacted
soil, as previously described.  Under the selected  remedy, impacted  soils exceeding screening
Andersen AFB MARBO Annex                     2-65                                 4/1/98
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criteria (i.e., residential PRGs) will be excavated and removed from all seven areas of Waste
Pile 6. Areas of the site containing COCs at concentrations less than the screening criteria will
remain in place.  As  part of the residual risk evaluation,  the analytical data (i.e.,  soil boring
results) associated with the areas remaining in place were evaluated, and the residual COCs and
their maximum concentrations were identified. The maximum concentrations of residual COCs
were  included  in calculations of residual risk for  potential  future residential and industrial
receptors. For the potential future residential receptor, the presence of residual COCs in site soils
is associated with a cancer risk of 1.0 x 10"7 and a non-cancer HI of 0.20.  For the potential future
industrial receptor, the presence of residual COCs in  site soils is associated with a cancer risk of
3.0x10* and a non-cancer HI of 0.01. Therefore, residual risk for Waste Pile 6 has been reduced
to an acceptable cancer risk criterion of 1.0x10* and non-cancer HI of 1.0.

Total present worth cost is estimated to be $42,600 (all capital costs).  Costs would be expected
to increase should off-site disposal be required.

2.10.3        Site 24 (Landfill 29)

No Action and Soil Removal were evaluated  for the Surface Drum Area and Subsurface Metal
Area  at  Landfill  29.   Institutional  Control and Soil  Cover are not applicable because these
alternatives would restrict the future land use of Landfill 29, whereas the removal of the small
quantity  of waste along with any impacted soil would allow unrestricted land use. Soil removal
includes  the removal of drums, metal debris, and soil.

Soil Removal  is the Air Force selected remedy for the surface drum area and the subsurface
debris area at Landfill 29.  The soil removal alternative removes contaminated soil which poses a
potential health risk, and can be readily implemented. The 86 drums scattered across the surface
of the "Surface Drum Area" and the metal debris  in the "Subsurface Metal Area" will  be
removed, in addition to the soil exceeding screening criteria. Based on the information presented
in the OU 3  RI Report, these removal activities include approximately 35 cubic yards of material
(inclusive of 25 cubic  yards of drums partially filled with soil, and 10 cubic  yards of impacted
Andersen AFB MARBO Annex                      2-66                                  4/1/98
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soil). The estimated soil depth in the surface drum area is I foot, and 2 feet in the subsurface
debris area.  Soil removal and confirmatory sampling activities will be performed after removal.
Pending TCLP analyses, impacted soil will either be disposed of as hazardous waste, off island,
or as solid waste, at the Main Base landfill.  It is anticipated that remaining debris will be
disposed of as solid waste at the Andersen AFB landfill.

The ARARs and TBCs determined to be pertinent to the remedial alternatives identified for the
Landfill 29 are shown on Table 2-6, along with estimated cost.  The Federal Endangered Species
Act was deemed not relevant for the same reasons described for Waste Pile 7.  FIFRA and TSCA
are not  relevant because no pesticides or PCBs exceeding preliminary cleanup criteria  were
detected at this site.

A quantitative evaluation of residual risk was performed, based on the selected remedy (i.e., soil
removal).  Supporting data  and the residual risk calculations for the evaluation are presented in
Appendix B.   Landfill 29 currently contains  two discrete areas of impacted soil, as previously
described.  Under the selected remedy, impacted soils exceeding screening  criteria will be
excavated and removed from both  areas of Landfill 29.  Areas of the site containing COCs at
concentrations less than the screening criteria will remain in place. The analytical data (i.e., soil
boring results) associated with  the areas remaining in  place were evaluated, and the residual
COCs and their maximum concentrations were  identified. The maximum concentrations of
residual COCs were included in calculations of the residual HI for potential future residential and
industrial receptors; residual cancer risks were not calculated because no carcinogenic COCs will
remain post-remediation. For the potential future residential receptor, the presence of residual
COCs in site  soils is associated with a non-cancer HI of 0.00001.  For the  potential future
industrial receptor, the presence of residual COCs in site soils is associated with a non-cancer HI
of 0.000003.  Therefore, residual risks for Landfill 29 are anticipated to be less than the cancer
risk criterion of 1.0x10"*, and residual hazards are less than the target  non-cancer HI of 1.0.
                                                                         >
Total present worth cost is estimated to be $22,500 (all capital costs). This estimate is based on
the assumptions presented in the OU 3 FFS (ICF, 1997), which assumes that all soil and debris
Andersen AFB MARBO Annex                     2-67                                  4/1/98
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would be disposed on site.  Costs would be expected to increase should off-site disposal be
required.

2.10.4        Site 38 (MARBO Laundry)

No Action and Soil  Removd were evaluated for the MARBO Laundry.  Soil  Cover would
restrict the future land use of MARBO Laundry, whereas the removal of the small quantity of
impacted soil would allow unrestricted land use at MARBO Laundry.

Soil Removal is  the  Air Force selected remedy at the MARBO Laundry.  This alternative
removes contaminated soil which poses a potential health risk, and can be readily  implemented.
Affected soil exceeding screening criteria will be excavated and removed from each area.  The
OU 3 RI samples were located about 2-3 feet from the  edge of the building and the east parking
area. Analysis of soil samples showed the  presence of PCBs at the two former transformer
locations, and near the edge of the building, but not in other samples taken further away from the
building.  Therefore,  soils containing elevated levels of Aroclor  1254 are assumed to extend
laterally about 5 feet out from the north and south side  of the building and at a location near the
east side of the east  parking area.  The total impacted ground surface area is estimated to be
approximately 3,600  square feet, with an estimated depth  of  1 foot.  Total impacted soil is
estimated to be approximately 135 cubic yards.  Confirmatory sampling will be performed after
removal.  Pending TCLP analyses, impacted soil will either be disposed of as hazardous waste,
off island, or as solid waste, at the Andersen AFB active landfill.

The ARARs and  TBCs determined to be pertinent to the remedial alternatives identified for the
former Waste Pile 6 are shown on Table 2-6, along with estimated cost.  As shown in Table 2-6,
TSCA  may be a pertinent ARAR if PCB concentrations exceed  50 ppm. .Transportation and
disposal of the soil  and debris will conform with appropriate TSCA  regulations under this
scenario, however PCB concentrations at the MARBO Laundry have been well below 50 ppm.
The Federal Endangered Species Act was deemed not relevant for the same reasons described for
Andersen AFB MARBO Annex                    2-68                                 4/1/98
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Waste Pile  7.   FEFRA is not relevant because there are no pesticides which  exceed the
preliminary cleanup criteria.

A qualitative evaluation of residual risk was performed, based on the selected remedy (i.e., soil
removal).  Under the selected remedy, all areas of MARBO Laundry containing impacted soils
exceeding screening criteria will be excavated and removed from the site. Since all areas of the
site containing impacted soils exceeding screening criteria will be excavated and removed, it is
anticipated that residual risks will be less than the cancer risk criterion of l.OxlO4 and non-cancer
HI of 1.0.

Total present worth cost is estimated to be $29,900 (all capital costs). This estimate is based on
the assumptions presented in the OU 3 FFS (ICF, 1997), which assumes that all soil and debris
would be  disposed on  site.  Costs would be expected to increase should off-site disposal be
required.

2.11         STATUTORY DETERMINATIONS

The  selected remedy for soils  satisfies most of the statutory requirements of Section  121  of
CERCLA, as amended by SARA, per the following mandates:
             The selected remedies are protective of human health and the environment, will
             decrease site risks, and  will not create short-term  risk nor have cross-media
             consequences;
             The selected remedies comply  with  federal and state requirements that  are
             applicable or relevant and appropriate to the remedial action such as chemical-
             specific  ARARs,  chemical-specific  clean-up   standards,  and  action-specific
             ARARs;
             The selected  remedies  are  cost-effective,  and address the  nine  CERCLA
             evaluation criteria through remediation of the contaminated soil in a reasonable
             period of time.
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2.11.1        Protection of Human Health and the Environment

Soil removal will eliminate site COCs and the soil cover will eliminate and/or reduce exposure to
site COCs. The implementation of these remedies will not create any short-term risk nor any
negative cross-media aspects.  The residual risk remaining at each site after implementation of
the selected remedy is discussed in Section 2.10.

2.11.2        Compliance with ARARs

All ARARs will be met by the selected remedies.  The remedies will achieve compliance with
chemical-specific clean-up standards. Action-specific ARARs will be met during soil removal
and construction of the cover.  None of the anticipated actions or construction is expected to have
a detrimental impact on endangered species.

2.113        Cost Effectiveness

The USEPA, the USAF, and the Territory of Guam believe that the selected remedies address the
nine criteria of the NCP and provide overall effectiveness in relation to their cost.

2.11.4        Utilization of Permanent Solution and Alternative Treatment (or Resource
             Recovery) Technologies to the Maximum Extent Possible

The selected remedy uses a permanent solution  and treatment technology to the maximum extent
practicable. Due to the small  amount of impacted soil, and the cost and effort associated with a
permanent solution or an alternative treatment technology, permanent solutions and treatment
technologies were deemed impracticable. Thus, the selected remedies do not meet the statutory
requirements to utilize permanent solutions and treatment  technologies. The selected remedies
were made public in the Proposal  Plan (October  1997) and presented at a  public meeting
(October 1997), with no significant objections from either the public or the Territory of Guam.
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2.11.5        Preference for Treatment as a Principle Element

As noted above, due to the small amount of impacted soil, a treatment technology is considered
impracticable.

2.12         DOCUMENTATION OF SIGNIFICANT CHANGES

There are no significant changes in this ROD from the Proposed Plan. The Proposed Plan and
ROD vary from the OU 3 FFS with regard to soil and debris disposal, however.  The OU 3 FFS
proposed disposal of soil and most of the  debris from  Waste Pile 6, Landfill 29 and MARBO
Laundry to Waste Pile 7, where the accumulated soil and debris would be placed under the Waste
Pile 7 soil cover.  Current remedial alternatives recommend conducting a TCLP leachate analysis
on soils where COC concentrations  exceed industrial  PRGs to determine whether the  soil is
hazardous.  If the soil is considered hazardous, then it will be consolidated and disposed  of off-
island in a licensed hazardous waste facility.  If the soil  is considered non-hazardous, then it will
be disposed of on-site in the Main Base landfill.  Though the removal/disposal technology does
not change for Waste Pile 6, Landfill  29 and the MARBO Laundry, the cost will increase  should
off site disposal be necessary.
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                 3.0 DECISION SUMMARY FOR GROUNDWATER

This decision summary provides a description of groundwater conditions at the MARBO Annex,
including legal and public involvement issues, site risks, remedial alternatives and the rationale
for selection, and how the selected remedy satisfies statutory requirements.  The more general
issues that were discussed in Section 2.0 will not be repeated here, such as site description,
regional  setting,   physiography,  meteorology,  demography  and  land  use,   hydrology,
hydrogeology, and water use.

3.1          SITE HISTORY AND ENFORCEMENT ACTIVITIES

Groundwater related field activities followed the same phased approach as described in Section
2.2, beginning with Phase II.

Phase n. Stage 1  was  completed in  1989.   This included groundwater monitoring  well
installation, groundwater elevation monitoring, and sampling and analysis.  A total of five IRP
monitoring wells were installed and sampled during this phase, including: IRP-1, IRP-2, IRP-8,
IRP-10 and IRP-12. Each of the wells were installed in the upper portion of the freshwater lens
(i.e., shallow wells), in the Mariana/Barrigada limestone formations.  The wells were sampled in
May, August, and October 1987.  Three discrete rounds of water level measurements were made;
one in June and two in October 1987. Groundwater samples were also collected from four off-
site production  wells (M-6, D-l, D-4 and D-5) and eight on-site Air Force production wells
(MW-1  through MW-3 and  MW-5  through  MW-9).   The results of this investigation  are
presented in the IRP Phase II, Stage 1 Final  Report (Battelle, 1989).  The  wells which were
sampled are  summarized on Table 3-1.

Phase n, Stage 2 was completed in December 1991. Three additional IRP monitoring wells were
installed and sampled during this stage of work, including IRP-14, IRP-15 and IRP-16. IRP-14
was installed to monitor the groundwater in the  vicinity of the MARBO Laundry, and IRP-15
and 16 were installed to monitor groundwater in  the vicinity of Site 20. Groundwater sampling
Andersen AFB MARBO Annex                     3-1                                 4/1/98
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                                    TABLE 3-1

             HISTORICAL MONITORING AND PRODUCTION WELL SAMPLING
                                  MARBO ANNEX
                                    (Page 1 of 2)
Well ID
IRP Wells 1
2
8
10
12
14
15
16
23
24(dccp)
25
26
27
28
29«Jeep)
30
31(dcep)
32B
33(deep)
34
35(deep)
Production Wells MW-1
MW-2
MW-3
MW-5
MW-6
MW-7
MW-8
MW-9
D-l
D-2
D-3
D-4
D-5
D-14
Y-2
Y-4
Y-5
Y-6
M-5
M-6
M-7
M-15
Phase n
Stage 1
Rounds 1,2, and 3
X
X
X
X
X






1









X
X
X
X
X
X
X
X
X


X
X






X


Phase II
Stage 2
Rounds 1 and 2
X
X
X
X
X
X
X
X













X
X
X
X
X
X
X
X
X


X
X

X







Phase II
Stage 3
Rounds 1 and 2
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X


X
X

X







Phase DI
Stage 3
Rounds 1 and 2
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
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                                          3-2
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                                          TABLE 3-1

               HISTORICAL MONITORING AND PRODUCTION WELL SAMPLING
                                       MARBO ANNEX
                                          (Page 2 of 2)



Monitoring Wells



Well ID
GPA-l(deep)
GPA-2(deep)
Phase II
Stage 1
Rounds 1,2, ud 3


Phase D
Stage 2
Rounds 1 and 2


Phase II
SUge3
Rounds 1 and 2
xa
xa
Phase ID
Stage 3
Rounds 1 and 2
X
X
   Wells sampled during Phase H, Stage 3. Round 2 (February 19%) only.

Phase II, Stage 1: Three monitoring rounds, completed in 1989
Phase II. Stage 2: Two monitoring rounds, completed in 1991
Phase II, Stage 3: Four monitoring rounds - Round 1 - Oct/Nov 1995
                                 Round 2 -Feb/Mar 1996
                                 Round 3 -Oct/Nov 1996
                                 Round 4 - Apr/May 1997
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and measurements were conducted on the same wells as Stage 1, with the addition of IRP-14, 15
and 16 and Y-2. Production well M-6 was not sampled during this stage of work. Groundwater
samples and depth-to-water measurements were conducted twice during this stage, from April
through August 1989. The results of this investigation are presented in the IRP Phase II, Stage 2
Final Report (SAIC, 1991).  The wells which were sampled are summarized on Table 3-1.

Phase n, Stage 3 (Groundwater Monitoring Rounds 1 and 2) took place at the MARBO Annex
from November 1995 to February  1996, including: borehole drilling, lithologic well logging,
borehole condition logging and downhole geophysics, and monitoring well installation.  The
groundwater investigation consisted of water level measurements and groundwater sampling. A
total of thirteen monitoring wells were installed, IRP-23 through IRP-35.  Monitoring wells
IRP-24, 29, 31, 33 and 35 were installed approximately 90 feet below the top of the groundwater
surface (deep wells) in order to monitor water quality at the base of the freshwater lens.  The
remaining  IRP wells  were installed at the top of the  freshwater lens  (shallow  wells).
Groundwater sampling and  measurements were conducted during October-November 1995 and
February-March 1996. A total  of 21 IRP wells, twelve production wells, and two monitoring
wells  (GPA-1  and GPA-2  [both sampled February 1996 only]) were sampled, as shown  on
Table 3-1.   Continuous groundwater level measurements were also conducted on some of the
IRP wells  and production wells from December 1994 through October 1995.  The results and
assessment of the  groundwater sampling (through  Phase  n, Stage 3, Rounds 1  and 2) are
presented in ICF's March 1997 final report entitled "Andersen Air Force Base Guam; Operable
Unit 2 MARBO Annex Remedial Investigation Report" (OU 2 RI) (ICF, 1997b). The wells
which were sampled are summarized on Table 3-1.

Phase II,  Stage 3 (Groundwater Monitoring Rounds 3  and 4)  encompasses the remaining
groundwater sampling and measurement activities that are included in this document.   Two
additional  rounds  of groundwater sampling were conducted in October-November 1996 and
April-May 1997, and utilized in the OU 2 FFS in order to assess longer-term trends. A total of
21 IRP wells (same as Stage 3), 22 production wells and two monitoring wells (GPA-1 and
GPA-2) were  sampled,  as shown on Table 3-1.   Groundwater sampling  and analysis will
continue at the MARBO Annex until at least four complete rounds of sampling have  been
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conducted. Any additional sampling at the MARBO Annex would be conducted in order to meet
long-term sampling requirements which are proposed as part of the OU 2 FFS (discussed in
Sections 3.4 and 3.5 of this document). Remedial alternatives for groundwater impacted by Air
Force Activities are presented in the "Andersen Air Force Base Guam; MARBO Annex Operable
Unit 2 Focused Feasibility Study Report" (OU 2 FFS) (EA and Montgomery Watson, 1997). The
results of the October-November 1996 and April-May 1997 sampling (for TCE and PCE only)
are included in the OU 2 FFS.

BioEnvironmental Engineering Groundwater Monitoring. The Air Force production wells have
been monitored since  1978 under the Safe Drinking Water Act for PCE and TCE, along with
other required analytes under this Act.

3.2         SUMMARY OF SITE CHARACTERISTICS

This section presents an overview of site contamination and potential routes of exposure posed
by conditions at the site.

3.2.1         Nature and Extent of TCE and PCE

Two COCs were identified in the OU 2 RI, trichloroethylene (TCE) and tetrachloroethylene
(PCE), based primarily on their frequency of detection above Federal Maximum Contaminant
Levels  (MCLs).  The Federal MCL for both TCE and PCE is 5 micrograms per liter (ug/L).
Analytical results for the four most recent sampling events are shown on Figures 3-1  through 3-4.
Figure  3-5  shows the maximum TCE and PCE  concentrations historically detected at the
MARBO Annex, and Figure 3-6 shows representative groundwater contours for the MARBO
Annex. Tables showing historical maximum, minimum and recent TCE and PCE concentrations
are also included as Tables 3-2 and 3-3, respectively.

A total of 29 wells which are presently installed within the property boundary of the MARBO
Annex  were monitored for TCE and PCE (as well as other constituents required  either under
Andersen AFB MARBO Annex                    3-5                                4/1/98
Record of Decision

-------
                                                             J  \_r—SITE  J7
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                                                                                                                                                                                                GRAPHIC SCALE
                                                                                                                      MARBO  ANNEX  - RECORD  OF  DECISION
                                                                                                                         ANDERSEN  AIR FORCE  BASE.  GUAM
PLOT SC*IE:I-UOO
                                                                                                                                                                                                 | FIGURE  3-1
PCE  AND TCE CONCENTRATIONS
  OCTOBER  -  NOVEMBER 1995
          MARBO ANNEX
                                                                                                                                                                        DATE:    9/29/97
                 | SCALE: AS NOTED

-------
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PCE AND  TCE CONCENTRATIONS
   FEBRUARY  -  MARCH  1996
        MARBO  ANNEX
MARBO ANNEX  - RECORD  OF  DECISION
  ANDERSEN AIR FORCE  BASE.  GUAM
              |SCALE: AS NOTED

-------
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                                                                                                                                 PC£  AND  TCt. CONCtNfRATlONS
                                                                                                                                  OCTOBER -  NOVEMBER  1996
                                                                                                                                        MfiRBU ANN£X
                                                                                                                                     (PRELIMINAHY QAIA
                                                                    MARBO ANNEX  - RECORD OF  DLCISJON
                                                                      ANDERSEN AIR  FORCE  BASE.  GUAM

-------
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                                                                                                    MARBO  ANNEX  - RECORD  OF  DECISION
                                                                                                      ANDERSEN  AIR FORCE  BASE.  GUAM

-------
                                                             APPBOXIMATE LOCATION
                                                               OF MAXMUM TCS
                                                                CONCENTRATION
                                                                                                 J^i _
                                                                                                 E  o.e  io/c
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                                                                                                                                                            MAXIMUM HISTORICAL  CONCtNIRAT IONS

                                                                                                                                                                       OF  PCE  AND TCE
                                                                                                                                                                         MARBO ANNEX
OMMR TO 6C CONSISTENT «ITH EAItL If

CONSISTENT «|TH 0IOENV
                                                                                      MARBO  ANNEX  -  RECORD  OF  DECISION
                                                                                        ANDERSEN  AIR  FORCE  BASE.  GUAM

-------
FEB. 1996 CROUNDWAUR CONTOURS
       FOR MARBO ANNEX
MARBO  ANNEX  - RECORD  OF  DECISION
  ANDERSEN AIR FORCE BASE. GUAM
 :   9/29/97   TSCALl:  AS NOUO

-------
                                     TABLE 3-2

               TCE CONCENTRATION RANGES AT MARBO ANNEX PRODUCTION
                           WELLS AND MONITORING WELLS
                                     (Page 1 of 2)
Well
ID
MW-lb
MW-2"
MW-3b
MW-5"
MW-6b
MW-7b
MW-8"
MW-9b
D-lb
D-2b
D-3b
D-4b
D-5b
D-14"
M-5b
M-6b
M-7b
M-15b
Y-2b
Y^»Ab
Y-5b
Y-6b
IRP-1
IRP-2
ERP-8
IRP-10
IRP-1 2
IRP-14
IRP-15
IRP-1 6
IRP-23
IRP-24(deep)11
ERP-25
ERP-26
ERP-27
IRP-28
IRP-29(deep)
IRP-30
IRP-31(deep)
ERP-32
Sampling
Date Range*
78 to '97
78 to '97
78 to '97
78 to '97
78 to '97
78 to '97
78 to '97
78 to '97
'78 to '97
10/96 to 4/97
10/96 to 4/97
'87 to '97
'87 to '97
10/96 to 4/97
10/96 to 4/97
'89,10/96-4/97
10/96 to 4/97
10/96 to 4/97
'89 to -97
10/96 to 4/97
10/96 to 4/97
10/96 to 4/97
•87 to "97
'87 to "97
'87 to "97
'87 to -97
•87to-97
'89 to '97
'89 to '97
'89 to '97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
Maximum
Detection
8.5
39
4.1
0.5
0.8
0.5
0.5
83
ND
ND
ND
1.7
4.0
OJ
ND
ND
ND
ND
ND
ND
ND
ND
ND
3.8
ND
10.0
ND
4.2
0.6
ND
ND
ND
2.1
0.9
ND
ND
0.6
0.2
210
ND
Date of Max.
Detection
4/85
3/78
4/85
2/83
12/83
2/83
2/83
7/85
.,
	
__
10/87
9/89
10/96
..
..
„
..
—
_
_
—
—
10/87
~
9/87
—
10/87
3/96
..
—
-
10/95
5/97
—
—
3/96
4/97
5/97
~
Minimum
Detection
0.3
4.0
NDC
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
0.3
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
1.4
ND
ND
ND
ND
ND
110
ND
DateofMin.
Detection
5/97
5/97
5/97
5/97
5/97
5/97
5/97
5/97
„
..
._
4/97
10/87
4/97
..
..
	
_
—
..
..
..
~
4/97
—
4/97
—
4/97
4/97
..
—
—
3/96
10/96
—
—
11/96
10/96
11/96
—
April/May '97
Results
0.3
4.0
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
1.0
0.3
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
2.0
0.9
ND
ND
0.4
0.2
210
ND
Andersen AFB MARBO Annex
Record of Decision
3-6
4/1/98

-------
                                                 TABLE 3-2

                   TCE CONCENTRATION RANGES AT MARBO ANNEX PRODUCTION
                                    WELLS AND MONITORING WELLS
                                                 (Page 2 of 2)
Well
n>
IRP-33(deep)
IRP-34
IRP-35(deep)
GPA-le
GPA-2'
Sampling
Date Range*
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
2/96 to 4/97
2/96 to 4/97
Maximum
Detection
ND
ND
0.8
10.0
3.1
Date of Max.
Detection

—
10/96
10/96
2/96
Minimum
Detection
ND
ND
0.5
1.0
0.8
Date of Min.
Detection
„
—
5/97
4/97
10/96
April/May 497
Results
ND
ND
0.5
9.0
1.0
Notes:
   Contractor results and BioEnvironmental results used for MW-wclls.
   Production well - installed in the shallow portion of the freshwater lens.
   ND - Nondetectable concentrations.
   Deep monitoring well at the base of the freshwater lens (all other monitoring wells at top of lens).
   GPA-1 and GPA-2 are screened and sampled at variable depths. Max and min concentrations for entire well shown here. Highest
   concentration for April/May  1997 is shown in the last column.
Andersen AFB MARBO Annex
Record of Decision
3-7
4/1/98

-------
                                  TABLE 3-3

       PCE CONCENTRATION RANGES AT MARBO ANNEX PRODUCTION WELLS AND
                              MONITORING WELLS
                                  (Page 1 of 2)
Well
ID
MW-l"
MW-2*
MW-3"
MW-5*
MW-6b
MW-?"
MW-8"
MW-9b
D-lb
D-2b
D-3"
D-4"
D-5b
D-14b
M-5"
M-6"
M-7b
M-15"
Y-2"
Y-4Ab
Y-5b
Y-6b
IRP-1
IRP-2
1RP-8
IRP-10
1RP-12
IRP-1 4
IRP-1 5
IRP-1 6
IRP-23
IRP-24(deep)e
IRP-25
IRP-26
IRP-27
IRP-28
IRP-29(deep)
Sampling
Date Range*
•87 10 '97
*7 to '97
•87 to '97
•87 to '97
•87 to '97
•87 to '97
37 to '97
«7 to '97
'87 to '97
10/96to4/97
10/96 to 4/97
'87 to '97
'87 to '97
10/96 to 4/97
10/96 to 4/97
•89. 10/96-4/97
10/96 to 4/97
10/96 to 4/97
'89 to '97
10/96 to 4/97
10/96 to 4/97
10/96 to 4/97
'87 to '97
'87 to '97
'87 to '97
'87 to '97
'87 to '97
*89to '97
'89 to '97
'89 to '97
10/95 to 4/97
10/95to4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
Maximum
Detection
25
0.1
2.0
OJ
ND
0.8
ND
22J?fND
ND
ND
ND
ND
0.2
ND
0.6
ND
OJ
ND
0.6
ND
ND
ND
ND
ND
3.0
0.8
1.0
26
U
ND
ND
0.5
OJ
0.6
1.1
ND
14
Date of Max.
Detection
9/87
2/96
9/89
11/95
..
10/87
„
3/97
„
..
..
„
3/96
„
10/96
..
10/96
„
9/89
_
„
..
-
-
9/89
jo/87
9/89
9/89
11/95
-
'--
4/97
10/96
9/96
3/96
--
5/97
Minimum
Detection
ND0)
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
OJ
ND
5.7
DateofMin.
Detection
5/97
5/97
5/97
5/97
„
5/97
..
5/97
..
..
..
..
4/97
..
4/97
..
4/97
„
4/97
..
__
._
-
—
4/97
4/97
4/97
10/87
4/97
-
-
3/96
3/96
3/96
10/95
--
3/96
April/May '97
Results
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
11
ND
ND
ND
0.5
0.2
OJ
1.0
ND
14
Andersen AFB MARBO Annex
Record of Decision
3-8
4/1/98

-------
                                             TABLE 3-3
         PCE CONCENTRATION RANGES AT MARBO ANNEX PRODUCTION WELLS AND
                                       MONITORING WELLS
                                             (Page 2 of 2)
Well
n>
IRP-30
IRP-31(deep)
IRP-32B
IRP-33(deep)
IRP-34
IRP-35(decp)
GPA-l'
GPA-2'
Sampling
Date Range*
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
10/95 to 4/97
2/96io4/97
2/96 to 4/97
Maximum
Detection
0.2
2.0
ND
ND
ND
0.4
0.4
0.1
Date of Max.
Detection
10/96
5/97
—
5/97
10/96
2/96
Minimum
Detection
ND
ND
ND
ND
ND
ND
ND
ND
DateofMin.
Detection
,4/97
10/95
—
10/96
4/97
10/96
April/May '97
Results
ND
2.0
ND
ND
ND
0.4
OJ
ND
Notes:
   Contractor results and BioEnvironmental results used for MW-wells.
   Production well - installed in the shallow portion of the freshwater lens.
   ND - Non Detectable concentrations.
4
   MW-9 was re-sampled. Subsequent result was ND. Historically, PCE has not been detected in MW-9.
   Deep monitoring well at the base of the freshwater lens (all other monitoring wells at top of lens).
   GPA-l and GPA-2 are screened and sampled at variable depths. Max and nun concentrations for entire well shown here.
   Highest concentration for April/May 1997 is shown in the last column.
Andersen AFB MARBO Annex
Record of Decision
3-9
4/1/98

-------
CERCLA or the SDWA). Of the 29 wells, 21 of them are monitoring wells which were installed
                                                                                    o
as part of the CERCLA process (IRP-wells) and eight of them are Air Force production wells
(MW-wells).  As discussed in Section 3.1, production wells from outside the MARBO Annex
were also  monitored  with varying frequency, including: production  wells from  the adjacent
Dededo production  well field  (D-wells), the  nearby Yigo  wellfield (Y-wells), the  nearby
Mangilao wellfield (M-wells),  and two monitoring wells near the  Guam Power Authority
Dededo Power Plant (GPA-wells). Of the 21 IRP wells in the MARBO Annex, five of them are
"deep" monitoring wells which were installed at the base of the freshwater lens  (IRP-24, 29, 31,
33, and 35).  The deep monitoring wells are generally screened approximately 90 to 100-feet
below the production wells and shallow monitoring wells in order to monitor water quality near
the freshwater/saltwater interface. The remaining IRP monitoring wells are installed in the upper
portion of the  freshwater lens, at approximately the same depth as production wells.  The number
of samples collected from each well varies considerably, based on when the well was installed,
and/or when sampling commenced.  For example, the Air Force production wells have samples
dating back as far as  1978, whereas the more recently installed IRP-wells were installed in
phases between 1987 and 1996, thereby having fewer overall samples.

Based on historical and recent  sampling, TCE and PCE concentrations were detected above
Federal MCLs at two locations inside the MARBO Annex.  One location is southwest of Site 37
(directly south of the GPA Power Plant), where TCE was most recently detected at a maximum
concentration  of 210 ug/L in the deep monitoring well IRP-31.  The other location is adjacent to
the MARBO Laundry, where PCE was detected in two monitoring wells which are installed next
to each other (monitoring wells IRP-14 and  IRP-29), ranging from 11  to 14 pg/L.  These
locations are shown on Figure 3-5. The April/May 1997 sampling also indicated TCE exceeding
MCLs in monitoring well GPA-1.  A TCE source was not identified during either the OU 2 or
OU 3 RIs.  A  definitive source for PCE near the MARBO Laundry was not identified during the
OU 3 RI, but appears to be in the vicinity of the MARBO Laundry.  The former  dry cleaning
facility at the  MARBO Laundry may have discharged PCE to the base sanitary sewer via floor
drains.
Andersen AFB MARBO Annex                    3-10                                 4/1/98
Record of Decision

-------
3.2.2         Fate and Transport of TCE and PCE

Complex structural features, lithologic features, and secondary porosity control groundwater
flow and, therefore, complicate the migration of TCE and PCE. Groundwater flow within the
MARBO Annex may  be controlled by complex faulting near the center of the Annex,  as
described in the OU 2 RI report (ICF, 1997b). Groundwater flow to the southwest and northwest
is  additionally  influenced by the numerous  pumping  wells  which capture some of  the
groundwater flow.  Groundwater flow at the south end of the MARBO Annex appears  to be
influenced by a groundwater mound just west of MARBO Laundry. To the south of this mound
groundwater flow is southerly and may  also be affected by a fault along the southern boundary of
the MARBO Annex. It is uncertain if groundwater flows along this fault zone or passes through
and continues south. Figure 3-6 shows groundwater elevation contours for February 1996. The
contours are consistent  with historical contours drawn at the MARBO Annex.

Groundwater flow  from the MARBO Laundry area  is believed to be primarily south and
southwest based on groundwater contours and historically low-level concentrations (below
MCLs)  of PCE found in monitoring  wells IRP-10  and IRP-15.  Historical TCE and PCE
concentrations can be seen o:n Figures 3-1  through 3-5.  Low level  detections of PCE were also
detected in IRP-08, 26  and 27, which are to the north and west of IRP Site 38 (former MARBO
laundry), possibly due  to vadose zone dissolution channel flow and/or subsurface PCE residual
outside the vicinity of the MARBO laundry.

Groundwater flow from the IRP-31 area appears to flow primarily into a groundwater trough
where movement is westward.  Some of the groundwater in this vicinity may also be influenced
by flow gradients induced by on-site and off-site production wells.  Due to the ubiquitous nature
and persistence of chlorinated hydrocarbons, concentrations of TCE and PCE are detected at low
levels at some of the monitoring wells at the MARBO Annex, generally at 1 ug/L or less. The
highest  concentrations  detected in IRP-31 and IRP-14/29 may represent  the  locations where
residual TCE/PCE is present as a continuing, but decreasing secondary source.
Andersen AFB MARBO Annex                    3-11                                 4/1/98
Record of Decision

-------
Cross-sectional  information  and  a  block  diagram  showing  potential  groundwater and
contaminant migration pathways in the vadose zone and aquifer are included in the OU 2 RI
report (ICF, 1997b). A description of the potential pathways and flow regime for groundwater
and TCE/PCE was also discussed in the OU 2 RI and is summarized here for consistency.  In the
limestone karst  environment, precipitation percolates rapidly into  the  soils and  limestone
bedrock. The upper portion of the epikarst zone limestone is capable of storing large volumes of
water due to dissolution porosity  that has  developed with time.   Dissolution decreases with
depth, decreasing the storage capacity. Epikarst water is gradually released to the underlying
vadose zone and to the aquifer as  diffuse recharge.  Discrete/concentrated runoff occurs only
where there are enlarged joints, faults, brecciated zones, and surface depressions that concentrate
runoff to a discrete subsurface inlet.   The  vertical migration of groundwater is altered due to
interconnecting fractures, solution cavities, or lithologic changes. Vertical flow and flow along
the hydraulic gradient occurs where vadose zone groundwater contacts the water table. The rate
and direction of flow is further altered by encountering other preferential pathways.  The flow
regime in the vadose zone ranges from  diffuse/slow flow, similar to a macro-porous media
aquifer, to preferential/channeled fracture flow.  Flow in the  phreatic zone mimics the slow
flow/diffuse flow (slow for a karst aquifer  is approximately 20-30 ft/day) but is influenced by
preferential pathways (ICF, 1997b).

Contaminant transformations can occur through degradation of the constituent, however this has
been only minimally observed at the MARBO  Annex, as evidenced by the lack of a significant
occurrence of typical  degradation by  products such  as cis-l,2-DCE  and  vinyl chloride.
Groundwater velocities (20-36 ft/day) were derived from the dye trace investigation performed at
the Main Base and Northwest Field Area (ICF,  1995). This estimate appears to be representative
of the MARBO Annex based on the hydraulic gradient and lithology, and is consistent with other
investigations indicating the age of the freshwater lens may be less than 5 years (Mink and Low,
1977).  The OU  2 RI has  assumed that if  it  takes 10 aquifer volumes to remediate  the
groundwater  system, the  aquifer  will be  cleansed naturally  within  SO years,  assuming no
additional contamination is stored in the vadose zone. However, because of potential movement
of contaminants from the vadose to the phreatic zone, contaminant persistence may continue for
an unknown period of time, but should diminish, assuming the primary source is gone.
Andersen AFB MARBO Annex                     3-12                                 4/1/98
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3.23         TCE and PCE Trends in Groundwater

In addition to the four sampling events from October 1995 to May 1997, some of the monitoring
wells and production wells have been monitored for TCE and PCE prior to 1995.  The range of
sampling dates for each of these wells, as well as the historical maximum, minimum and most
recent TCE and PCE concentrations, are shown on Tables 3-2 and 3-3.  Based on some of the
longer-term monitoring that has occurred at the MARBO Annex,  it is possible to observe
decreasing trends, or natural attenuation, of TCE and PCE.  This is most evident in Air Force
production wells MW-1 and MW-2, where TCE and/or PCE has been detected, and long term
monitoring has occurred. Trends are expected to become more apparent in some of the recently
installed monitoring wells, after additional  sampling has been conducted.

As seen on Tables 3-2 and 3-3 the wells which have been monitored for 8 to 10 years or more
show decreasing concentrations of TCE and PCE. The concentrations of TCE in MW-2 ranged
from a high of 39 ug/L in 1978, to 4 ug/L in April 1997.  TCE concentrations in MW-1 ranged
from a high of 8.5 ug/L in  1985 to less  than 0.3 ug/L in  April 1997. Based on 8 years of
sampling in the vicinity of trie MARBO Laundry, PCE concentrations in monitoring well IRP-14
ranged from 26 ug/L in September 1989 to 11 ug/L in April 1996.  Other IRP wells, although
representing short-term data, also indicate  a decrease in TCE and PCE concentrations. Though
the newly installed monitoring wells have  been monitored for only 1 to 2 years, the majority of
these wells  also indicate decreasing concentrations of TCE and PCE.  Two of the monitoring
wells, deep monitoring wells IRP-29 and  IRP-31, indicate either steady, or slightly increasing
concentrations  of PCE and TCE, however this is over a period of only 2 years.  Additional
sampling of these wells, over a longer period of time,  will provide sufficient information to
indicate whether these wells will conform to the trends of the decreasing levels of TCE and PCE
concentrations  that have been observed in the other production and monitoring wells.

Historic data for the production wells and monitoring wells at the MARBO Annex has been
compiled and graphed. Appendix A of the OU 2 FFS  (EA and Montgomery Watson,  1997)
illustrates TCE and PCE trends on graphs which plot TCE/PCE concentrations over time.
Andersen AFB MARBO Annex                     3-13                                 4/1/98
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3.2.4         Potential Routes of Exposure

Human Health Risk. Exposure assumptions used for the human health risk assessment include
potential  ingestion  and/or dermal  exposure of  groundwater,  and  inhalation  of  volatile
constituents released from bathing and showering.  Though production wells offer the only
realistic exposure to groundwater, potential risk was also evaluated for monitoring wells. This
scenario is considered unlikely, especially where some of the wells are installed at the base of the
freshwater lens, in higher saline water.

Ecological Risk. An ecological risk assessment was performed in accordance with USEPA
guidelines outlined in the OU 2 RI,  presuming exposure to marine life through  groundwater.
There were no exposure pathways identified for terrestrial receptors.

33          SUMMARY OF SITE RISKS

3.3.1         Human Health Risk

The human health risk assessment for groundwater  was also based on  USEPA Region IX
Preliminary Remediation Goal  (PRG) guidance (USEPA, 1995).  Groundwater analytical data
obtained from each monitoring well and production well was compared to Region DC PRGs for
tap water.   Constituents with maximum concentrations exceeding  the tap water PRGs were
identified as constituents of concern (COCs).  After separating out COCs as to their carcinogenic
and non-carcinogenic potential, a cancer risk was calculated  for COCs with  carcinogenic
potential, and an estimated hazard index was calculated for non-carcinogenic endpoints.  Rather
than calculate the Exposure Point Concentration for each compound, which was done for soil, the
maximum concentration for each constituent was utilized.  Individual constituent risk and HI
were then  summed to obtain total risk and HI for each production well and monitoring well.

As with soil, the USEPA considers a risk of less than 1x10"* (one in one million) to be protective
of human  health, and uses this value  as the point  of departure. The USEPA has developed the
Andersen AFB MARBO Annex                    3-14                                 4/1/98
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risk management  range of IxlO"6 to IxlO"4 (one in ten thousand), as the target for managing
cancer risk. The hazard index calculates potential non-cancer risks (e.g., skin lesions, decreased
fertility, organ damage) that may be caused by exposure to a compound or group of compounds.
For non cancer risk, the USEPA has recommended a hazard index equal to or less than one.  A
hazard index number below one indicates that non-cancer health effects are not expected.

For those production wells where COCs were detected, the health risk findings are shown in
Table 3-4. The groundwater risk  assessment utilized conservative assumptions, resulting in
estimated risks that are likely higher than actual risks. As seen on Table 3-4, the potential risk
for production wells where COCs were detected is within the risk management range of 1x10* to
1x10"*. Production wells MW-1, MW-2, and MW-3 are additionally treated with Air Stripping to
remove  low level concentrations of TCE and PCE, though  MW-2 is the only production well
where concentrations have recently exceeded MCLs1.  Because risk is within an acceptable range
for production wells at the MARBO Annex, groundwater quality goals at the MARBO Annex
are primarily determined by  federally allowable concentrations  of TCE  or  PCE  in  the
groundwater  (i.e., MCLs).  Remedial alternatives were evaluated to  assess the feasibility of
achieving concentrations of TCE and  PCE in the aquifer to  below the Federal MCL of 5 ug/L.
Federal  MCL's will also continue to be met at the Air Force supply wells presently being treated
by Air Stripping.  These public water supplies will be maintained as part of the Andersen AFB
Long Term Monitoring Plan. Monitoring wells where COCs were detected are generally within
EPA's risk management range of IxlO'* to 1x10"* and below a Hazard Index of 1, with the
exception of IRP-31. Monitoring well IRP-31 exceeds the Hazard Index of 1, however this is a
deep well with high chloride content and not meant for consumption.  In addition, land use
restrictions will be implemented to regulate the installation of new wells, and  groundwater
monitoring is included  as  a  component to overall  protection  of  human health  and  the
environment.
1 TCE concentrations have been below Federal MCLs since 1989 in MW-1, and have never exceeded MCLs in
MW-3.  PCE has never been detected above MCLs in either MW-1,2, or 3. Groundwater from the off-site Tumon-
Maui well is also treated by the same air strippers due to low levels of PCE detected in 1995.
Andersen AFB MARBO Annex                     3-15                                 4/1/98
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                                            TABLE 3-4

                               ESTIMATED HUMAN HEALTH RISK
Well
ro1
D-5C
MW-101
MW-2"
MW-5C
GPA-1-420'"
GPA- 1-480'"
GPA-2 - 423>U
GPA-2-483>tJ
IRP-14'
IRP-15'
IRP-25'
IRP-27'
IRP-29 (D)'
IRP-31 (D)'
Hazard
Index
0.044
0.033
0.181
0.004
0.075
0.182
0.085
0.063
0.180
0.130
0.057
0.018
0.224
4.34
Potential
Health Risk"
1x10*
3x10*
4x10*
2xl07
2x10*
4x10*
2x10*
2x10*
IxlO5
6x10*
1x10*
1x10*
9x10*
IxlO4
Estimated
Current Risk
1x10*

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The OU2 RI Report (ICF, 1997) identified uncertainties in the human health risk assessment for
groundwater. As previously described (Section 2.7), the presence of uncertainty is inherent in
the risk assessment process. Potential sources of uncertainty in the OU2 RI human health risk
assessment include, but are not limited to, the type of groundwater data evaluated, the EPCs used
to estimate exposures, and the assumptions used in the exposure assessment. Groundwater data
derived from IRP wells, production wells, and monitoring  wells were used in the derivation of
EPCs for  groundwater constituents; some of these wells  were screened at depths which are
unlikely to serve as drinking water sources.  Additionally, the maximum detected concentration
was assumed as the EPC for each groundwater constituent.  Furthermore, it was  assumed that
groundwater concentrations remain constant over a residential receptor's entire 30-year exposure
duration; recent groundwater monitoring events indicate that natural  attenuation of groundwater
constituents is occurring. The conclusions of the OU2 RI Report (ICF, 1997) indicate that most
sources of uncertainty  in the human  health risk assessment  for  groundwater  erred on  the
protective side, and that the cancer  risks  and non-cancer His  reported most  likely represent
overestimates.  A more detailed, tabulated summary of the sources of uncertainty  in the human
health risk assessment for groundwater are included in Appendix B of this ROD.

Based on  the results of the human health risk assessment for groundwater, actual or threatened
releases of hazardous  substances from the  site, if not addressed by  implementing the response
actions selected in this ROD, may present an imminent and substantial  endangerment to public
health, welfare, or the environment.

3.3.2        Ecological Risk

Based on a screening comparison to Ambient Water Quality Criteria that are  protective of
freshwater and  saltwater organisms, there were no COCs identified,  and therefore no ecological
risk identified.
Andersen AFB MARBO Annex                     3-17                                 4/1/98
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3.4          DESCRIPTION OF ALTERNATIVES

Three remedial alternatives were developed, as presented below.

3.4.1         No Action (Alternative G-l)

As required by the NCP, a no action alternative is developed and used as a baseline case for
evaluating risk and for evaluating other alternatives.  Under existing conditions at the MARBO
Annex, human health risk is acceptable, falling within the USEPA cancer risk guidelines of 10*
to 10"4.  No Action does not actively address TCE/PCE in the groundwater at  the MARBO
Annex.   There are no  institutional controls implemented, no considerations  are  made for
protection of human health and the environment, and no process options are considered.

3.4.2         Natural Attenuation with Wellhead Treatment (Alternative G-2)

This alternative  utilizes  Natural  Attenuation of TCE/PCE  in  the  aquifer to achieve  the
remediation goal of decreasing TCE/PCE concentrations in the aquifer to concentrations below
MCLs.  Supplemental to this remedy are three institutional controls, including: l)Land Use
Restrictions (to monitor  and restrict groundwater access  in  areas impacted by TCE/PCE);
2) Groundwater Monitoring (to monitor  the decrease of TCE/PCE and confirm the stability of
TCE/PCE plumes in the MARBO Annex); and 3) Existing Wellhead Treatment (to ensure public
health risk is within acceptable range at existing Air Force production wells).

Natural Attenuation. As noted in the previous  section, the decreasing trends of TCE and PCE
in the groundwater at the MARBO Annex would be due to the physical processes of dispersion
and dilution, which are largely dependent on the volume and rate of water traveling through the
vadose zone and aquifer.  The conditions at the MARBO Annex favor both of these factors.
Average precipitation on the island of Guam is in the range of 100 inches per year. Over the 3.8
square mile area of the MARBO Annex, and  assuming a 50% evapotranspiration rate, this
equates to a recharge rate in the range of 3.3 billion gallons per year, or nine million gallons per
Andersen AFB MARBO Annex                     3-18                                 4/1/98
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day. The combination of these high recharge rates in a transmissive limestone aquifer provide a
supportive environment for accelerated physical natural attenuation of TCE and PCE.  The
natural attenuation  would  occur by "flushing" out any residual TCE/PCE remaining in the
vadose zone and/or aquifer.

As illustrated earlier, there is good evidence that natural attenuation has occurred, and continues
to occur, at the MARBO Annex. All of the production wells which have had either TCE or PCE
detected in them show a decrease, and all of the monitoring wells which have had TCE or PCE
detected in them, which have been monitored for greater than two years, also show a decrease.
This is summarized on the table below:

                                    TABLE 3-5
              SUMMARY OF TCE/PCE CONCENTRATION CHANGES
                          Number of Wells Indicating Changes in
                                TCE/PCE Concentrations
      Well Type
Decrease
Increase
No Change
Total Wells
Production wells
(8+ yrs of monitoring)
IRP wells
(>2 yrs of monitoring)
IRP wells
(2 yrs of monitoring)
GPA monitoring wells
(1+ yrs of monitoring)
TOTAL:
   10
   19
   0        3 (All non detect)
   0        2 (All non detect)
   3         9 (5 non detect)
   0               0
   3	14 (10 non detect)
                      13
                      8
                      13
                      2
                      36
Thus, all of the production wells, and all of the IRP monitoring wells that have been monitored
for greater than 2 years, which have had concentrations of TCE or PCE detected in the past,
indicate decreasing TCE and/or PCE concentrations.  The monitoring wells which indicate an
increase in TCE/PCE concentrations have been monitored for only 2 years. These monitoring
wells are expected to follow the same decreasing  trend as the other wells which have been
monitored over a longer time period.
Andersen AFB MARBO Annex
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                   3-19
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A degradation rate was estimated in order to estimate potential times for TCE and PCE to

attenuate below MCLs.  The range of degradation rates is considered roughly representative of

how TCE and/or PCE reacts in the aquifer. The primary limitation to these estimates include the

uncertainty of total TCE/PCE mass that may exist in the subsurface, which likely varies between

the locations where wells presently exceed MCLs. Thus estimated cleanup times should take this

in to consideration, with the understanding that actual cleanup times may exceed the high end of

the range.


There are presently two locations (three monitoring wells) that exceed MCLs: IRP-31 exceeds

the MCL for TCE, and IRP-14 and IRP-29 (located adjacent to each other) exceed the MCL for
PCE.  The estimated time to achieve the TCE MCL in IRP-31 may range from approximately 10

to 40 years.   The  estimated time  to  achieve the PCE  MCL in IRP-14 may  range  from

approximately 1 to 10 years.  The estimated time to achieve the PCE MCL in IRP-29 may range

from 2 to 10 years. Again, these are estimates which have limitations that should be considered.


Institutional Controls. As noted earlier, there are three institutional control mechanisms which

are included with the Natural Attenuation remedy, as shown below:
             Land  Use Restrictions involve placing restrictions on the property deeds
             pertaining to the installation of water supply wells on properties affected by PCE
             and TCE-impacted groundwater.  The intent of land use restrictions is to reduce
             potential exposure to contaminants by  legally restricting future groundwater
             development  from  those  areas that  are  known  to   be   impacted.    The
             implementation mechanism  for  this component  would be  through GEPA's
             Wellhead Protection Program and Well Installation licensing and permitting.  As
             part of the Wellhead Protection program, GEPA has developed a Groundwater
             Protection Zone Map which identifies those areas where surface activities above
             the resource or recharge zone have the ability to impact the water quality.  The
             metes and bounds descriptions  of the land are designated on this map along with
             other pertinent information (GEPA, 1993). GEPA reviews groundwater data from
             the Andersen AFB CERCLA process, and all  well installation applications are
             reviewed by GEPA first prior to installation.   Also, as  part of the Wellhead
             Protection Program, well installation within 1,000 feet of an existing production
             well is prohibited.  As GEPA has been involved with the development of this
             ROD,  this would  easily facilitate the necessary transfer of  information from
Andersen AFB MARBO Annex                     3-20                                  4/1/98
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             Andersen AFB to GEPA, for implementation of the above-mentioned institutional
             controls.

      •      Existing Wellhead Treatment is in place for three of the production wells on the
             MARBO  Annex (MW-1,   MW-2  and  MW-3)  until  TCE  and/or  PCE
             concentrations are consistently below MCLs.  Two of these wells (MW-1 and
             MW-2) have slightly exceeded the MCL for TCE in the past.  Groundwater at
             MW-1, 2 and 3  is presently  routed through dual-packed,  once-through, counter-
             current air stripping  system with a hydraulic capacity of 725 gallons per minute
             (gpm). The endorsement and recommendation of continued wellhead treatment in
             these production wells would provide additional health risk benefit to those wells
             which exceed MCLs for TCE and/or PCE.  Treatment status would be evaluated
             every  two years  in conjunction with the Andersen AFB Long-Term Groundwater
             Monitoring Plan;

      •      Long-Term Groundwater Monitoring involves the sampling and monitoring of
             the groundwater  at the MARBO Annex through  existing monitoring wells and
             production wells.  The groundwater would be analyzed for TCE, PCE and other
             constituents  which  would be deemed  pertinent  for monitoring.   Long-term
             monitoring is consistent  with existing plans for monitoring under the IRP (EA
             Engineering and Montgomery Watson, 1995), and would  monitor constituents in
             select IRP wells as well as production wells in and around the MARBO Annex.
             Monitoring would continue  until TCE and PCE concentrations are consistently
             below MCLs.


3.4.3         Ex-Situ Groundwater Treatment (Alternative G-3)


This alternative was  evaluated in order to assess the feasibility and level of effort that would be
necessary to address  groundwater restoration, where TCE/PCE exceeds MCLs in the aquifer. An

effective evaluation of equipment,  labor and cost is conducted here to assess the magnitude of
effort necessary to address TCE and  PCE in the groundwater.   Should  this alternative  be

evaluated  for detailed  consideration, a more  comprehensive groundwater model would  be

necessary to optimize and calibrate the extraction system. Assuming these parameters could be

met, and  performance  is  measurable and accurate,  the  primary  marginal benefit of  this

Alternative, when compared to the  Natural Attenuation Alternative (Alternative G-2), would be

that the TCE/PCE in the aquifer may be removed at a slightly accelerated rate.
Andersen AFB MARBO Annex                     3-21                                4/1/98
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The groundwater extraction scenario addresses TCE in the vicinity of IRP-31 and PCE in the

vicinity of the former MARBO laundry.  This alternative assumes two extraction wells at each

location,  pumping  at 500  gpm each, with aboveground treatment via dual packed tower air

strippers and discharge to separate, one acre percolation ponds at each location. A summary of

the assumptions, conceptual layout and design is presented below; calculations are included in

Appendix E of the OU 2 FFS.
             Assumes  institutional  controls similar to  that for the  Natural  Attenuation
             alternative, including land use restrictions, long-term groundwater monitoring and
             continued wellhead treatment;

             Assumes  two  areas of concern within the MARBO Annex  - the groundwater
             which is impacted by TCE in the vicinity of IRP-31, and the groundwater which is
             impacted by PCE in the vicinity of the former MARBO laundry;

             A radius of influence of 300 feet was estimated at each well (500 to 600 feet at
             each location), based on the site's physical  information presented in the OU 2 RI.
             This is  the equivalent of 1.5 mgd at each location,  or 3 mgd combined.  Each
             location is treated separately due to the distance (approximately 1 mile) between
             them;

             Assumes the upper end hydraulic conductivity value of 20,000 ft/day presented in
             the OU  2  RI (which equates to a transmissivity of 200,000 ftVday assuming  100-
             foot-thick fresh water lens);

             In order to maximize drawdown and account for potential pump downtime, two
             downhole pumps at each location are assumed to be pumping at 500 gpm each
             (four pumps total). A 100-HP pump in each of the four drawdown wells would be
             necessary in order to pump this volume of groundwater from the required depths;

             The pumps would discharge to a dual packed counter-current air stripping system
             at each  location, similar to the one in place now;

             An average concentration of TCE of 80 ug/L was assumed at IRP-31,  which is
             one half of the  November 1995 and March 1996 concentrations.   This  value
             assumes dilution from the upper portion  of the aquifer, where TCE was  not
             detected, as well as groundwater flux toward the drawdown well from the outer
             edge of the TCE plume and surrounding volumes of the aquifer where TCE was
             not detected;
Andersen AFB MARBO Annex                    3-22                                 4/1/98
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       •      An average concentration of 10 ug/L of total VOCs (PCE plus TCE) was assumed
             at the MARBO laundry area, where VOCs were detected throughout the length of
             the water column and in downgradient wells;

       •      Based on the average VOC concentrations at both locations, and the assumptions
             presented above, VOC off-gas is calculated to be approximately 0.06 tons/year for
             the IRP-31  area,, and 0.02 tons/year for the MARBO laundry area.  This is within
             the limits of 100 tons/year  for a minor source, therefore off-gas  treatment would
             not be necessary'.


In summary, three alternatives were retained for evaluation, ranging from no-action to potential

groundwater  restoration.   The  No-Action alternative  includes  only the  efforts and  costs

associated with a 5-year review, as required by  CERCLA. Natural Attenuation is augmented

with a  combination of land  use restrictions and  groundwater monitoring, and continued

commitment  to  wellhead treatment at  the MARBO  Annex.   Ex-Situ Treatment  utilizes

artificial/technical means  to potentially accelerate the attenuation of TCE/PCE in  the  aquifer,

with continued commitment to wellhead treatment.


3.5          COMPARATIVE ANALYSIS OF ALTERNATIVES SUMMARY


The remedial alternatives developed were analyzed in detail using the nine evaluation criteria
required by the NCP, as discussed in Section  2.8. These criteria are again shown below, and

discussed relative to the groundwater remedial alternatives:


       •     Overall protection of human health and the environment
       •     Compliance with ARARs
       •     Reduction of toxicity, mobility, or volume through treatment
       •     Short-term effectiveness
       •     Implementability
             Cost
       •     State/support agency acceptance
       •     Community acceptance


The resulting strengths and weaknesses of the alternatives were then weighed to identify the

alternative providing the best balance among the nine  criteria.  Table  3-6  summarizes this
comparison.
Andersen AFB MARBO Annex                    3-23                                 4/1/98
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                                                               TABLE 3-6

                                            COMPARISON OF GROUND WATER ALTERNATIVES
2,3
o Q3
5 ^
o g
£
O Alternative

§

N>


Compliance
With
ARARs


Does not comply

Compliance
achievable


Compliance
achievable




Protection of
Human Health
and the Short-Term
Environment Effectiveness


Potential for future Not Effective
exposure
Exposure potential Effective
reduced through
natural attenuation
ofTCEandPCE
Exposure potential Effective
reduced through
engineered removal
ofTCEandPCE




Long-Term
Effectiveness


Not Effective

Effective



Potentially
effective, with
likely adverse
effect of saline
intrusion



Reduction
of TMV* Implemcntability


No reduction No Technical
in TMV. Limitations
Some reduction Easy
in TMV.


Some reduction Difficult
in TMV.






Cost * Territorial
$1,000 Acceptance


$77 Not Acceptable

$3,649 Acceptable



$18,447 Not Acceptable







Community
Acceptance


Not Acceptable

Acceptable



Not Acceptable




Notes:
    Includes Short Term Effectiveness and Long Term Effectiveness and Permanence.
    TMV - Toxicily, Mobility and Volume of contaminant.

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3.5.1   Overall Protection of Human Health and the Environment

The Natural Attenuation alternative addresses TCE and PCE in groundwater via the natural
attenuation of these constituents, as shown through historical monitoring.  Natural Attenuation
would ensure overall protection  of  human  health  and the  environment through  natural
remediation of the TCE and PCE in the aquifer. The risk pathway  at the MARBO Annex is
through drinking water, which is presently treated and monitored. Therefore the implementation
of institutional controls augment the natural attenuation remedy in order to protect human health
and the environment.  Land use restrictions would be implemented to  regulate the installation of
new production wells.  Wellhead treatment would continue at production wells MW-1, MW-2
and MW-3 until TCE and/or PCE concentrations consistently fall below MCLs (this will be
evaluated every  two years).  As human health risk is presently within acceptable limits, the
institutional controls would maintain and monitor this as a component to overall protection of
human health  and the environment.  This alternative  provides both short-term and  long-term
effectiveness.

The Ex-Situ Treatment  alternative provides  the same degree of overall protection  of human
health and  the  environment as  the  Natural  Attenuation alternative,  and the  same  set of
institutional controls would be incorporated. It is possible that the TCE/PCE may be remediated
at a slightly accelerated rate, however, the marginal benefit to the protection of human health and
the environment would  remain the  same  as  the Natural Attenuation alternative.   Overall
protection of human health and the environment may be adversely affected by pumping at depth
at high rates in the vicinity of IRP-31.  The  high pump rate required for this alternative may
induce upconing of the deeper TCE,  which would  increase risk by introducing TCE in to the
upper portion of the aquifer, where production wells draw from. For this reason, groundwater
treatment (Alternative G-3) iin lieu of natural attenuation (Alternative G-2) will likely not provide
additional marginal benefit to protection of human health and the environment.

The No Action alternative is currently protective of human health and the environment, based on
the fact that existing hypothetical cancer risk from production wells is within the EPA range of
Andersen AFB MARBO Annex                     3-25                                  4/1/98
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10" to 10"*.  However, this alternative does not provide additional protection or assurance that
potential exposure pathways may  not exist  in the future from either additional migration of
TCE/PCE or the installation of new production wells.

3.5.2         Compliance with ARARs
                                     L

The primary chemical-specific ARARs/TBCs which are considered applicable to the MARBO
Annex are federal and local MCLs for TCE and PCE; Guam's Water Pollution Control Act (10
GCA  47); and Guam's Revised Water Quality Standards (GEPA, 1992).  The primary action
specific ARAR is Guam's Wellhead Protection Program (GEPA,  1993) and Guam's Water
Resource  and  Development Operating Regulations (GEPA,  1990),  which  monitors the
installation of extraction/pumping  wells in or adjacent  to  wellfields,  and reviews existing
hydrologic and land-use data prior to approving the installation of new production wells.  Prior to
the installation of a new production well, applicants must submit the location of the proposed
well to GEPA, who then reviews existing land use  and  hydrologic  information in that area.
Bused on this information, GEPA has the authority to deny  well installation in  compromised
portions of the aquifer. Andersen AFB will continue to work closely with GEPA in supplying all
groundwater quality data collected as part of the IRP program, so that GEPA can maintain an
adequate database for their Wellhead Protection Program.

Ex-situ treatment has been considered with the intent of meeting and/or accelerating the rate to
achieve chemical-specific ARARs  through  engineered means.  Whether artificial restoration
would result in the achievement of ARARs in a more expeditious time frame is uncertain.  By
attempting to meet the ARAR for MCLs, other ARARs would likely be compromised, especially
the drinking water standard for chlorides, due to chloride upconing and subsequent discharge to
the percolation ponds. The pump rate required for a sufficient capture zone is high, and certain
to result in significant upconing and degradation of the aquifer.  Chloride upconing will affect the
potable, upper portion of the freshwater lens, where production wells draw from.  The upper limit
chloride concentration for drinking water is 250 mg/L (GEPA, 1992). Chloride concentrations in
the deeper monitoring wells are presently around 170 mg/L. Action and location specific
 Andersen AFB MARBO Annex                     3-26                                4/1/98
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                                                                                   TABLE 3-7

                                                                    CHEMICAL-SPECIFIC ARARs AND TBCs
                                                                                        ARAR Status
                Potential ARAR
                                   touts and Requirements
   Applicable
Relevant and
Appropriate
Applicability to FS Alternatives
to
-J
                                                                           FEDERAL REQUIREMENTS
           Drinking Water
           SDWA Maximum
           Contaminant Levels 40
           CFK 141.11 to 141.16
           Surface Water
           CWA. National Pollutant
           Discharge Elimination
           System (NPDES) 40 CFR
           122 and 125
           Other
           EPA Carcinogen
           Assessments Group
           Potency Factors

           NIOSH  OSHA
                        Enforceable standards for public water systems.        Yes
                        Regulates the discharge of water to surface water       Yes
                        bodies.
                        Most up-to-date information on cancer risks           Yes
                        derived from EPA's Cancer Assessment Group
                        (CAG).

                        Standards for worker exposure to specific chemical     Yes
                        compounds.
                      Yes
                      Yes
                      Yes
                     Yes
Drinking Water
Guam SDWA. 10 CCA.
Chapter S3

Groundwater
Revised Guam Water
Quality Standards.
Adopted 7/18/87 and 1/2/92

Water Pollution Control
Act 10 CCA, Chapter 47
                                   Establishes primary and secondary standards and
                                   MCL.
GUAM REQUIREMENTS

      Yes            Yes
                                   Restricts, controls, and permits pollutant              Yes
                                   discharges, and defines water quality criteria.
                                   Determines ways and means of eliminating and/or      TBC
                                   preventing pollution to surface waters and
                                   groundwaters.
           Others
           Air Pollution Control Act,
           10 CCA, Chapter 49
                        Establishes air quality criteria; sampling, testing.       Yes
                        monitoring, record keeping requirements, source
                        permitting system; and specific control requests.	
                     Yes
                     TBC
                     Yes
               G-1:  Meets MCL at point of use but not aquifer.
               G-2:  Meets MCL at point of use but not aquifer.
               G-3:  Meets MCL at point of use and possibly aquifer.

               G-l:  Not applicable.
               G-2:  Not applicable.
               G-3:  Meets discharge requirements.
               Utilized for Risk assessment at MARBO complex.
               G-l: Not applicable.
               G-2: Monitoring and sampling under existing HASP.
               G-3: Covered under future HASP and O&M manual.
               G-1:  Meets MCL at point of use but not aquifer.
               G-2:  Meets MCL at point of use but not aquifer.
               G-3:  Meets MCL at point of use and possibly aquifer.

               G-l:  Not applicable.
               G-2:  Not applicable.
               G-3:  Meets discharge requirements.

               G-1:  Does not address future conditions.
               G-2:  Monitors long term conditions with institutional controls.
               G-3:  Monitors long term conditions with marginal aquifer
                    restoration.

               G-l:  Not applicable.
               G-2:  Not applicable.
               C-3:  VOC off-gas discharge within acceptable regulatory limits.
           ARARs   Applicable and Relevant and Appropriate Requirements.          CWA
           RI/FS    Remedial Investigalion/Feasihiliiy Study.                      POTW
           RCRA    Resource Conservation and Recovery Act.                     MCL
           SDWA   Safe Drinking Water Act                                    TBC
           tiPA     Environmental Protection Agency                            CCA
                                                                          Clean Water Act                       MOU
                                                                          Publicly Owned Treatment Works.        GEPA
                                                                          Maximum Contaminant Level.           ROD
                                                                          To Be Considered.                     HASP
                                                                          Guam Code Annotated.
                                                     Memorandum of Understanding.
                                                     Guam Environmental Protection Agency.
                                                     Record of Decision.
                                                     Health and Safely Plan.

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                                                                                             TABLE 3-8
                                                                             ACTION-SPECIFIC ARARs AND TBCs
                                                                                                              ARAR Stain*
                   Potential ARAR
                                             Israes and Requirements
Applicable
Relevant and
Appropriate
Applicability to FS Alternatives
U)
to
00
                                                                                      FEDERAL REQUIREMENTS
            Safe Drinking Water Act (SDWA)
            40 CFR 144 Underground        bract: T1»e control program restricts the underground injection         Yes
            Injection Control Program        of wattes and treated waslewater.

                                          Requirement!: The underground injection of fluids must meet
                                          the established standards and procedures.
                                                                                                              Yes
            Occupational Safely and Health Act (OSHA)
            29 CFR 1910 120 Regulations    Issue*: These requirements must be implemented during
                                                                                            Yes
            for Workers Involved in
            Hazardous Waste Operations
                   Potentially
            29 CFR 1900 Standard for
            Worker Protection
            Clean Air Art (CAA)
            CAA Section 109 and
            40 CFR 50
                             hazardous waste operations.

                             Requirements: The OSHA standards for hazardous waste
                             operations include regulations for training, protective
                             equipment, proper handling of wastes, monitoring of employee
                             health, site information, and emergency procedures for workers
                             at hazardous waste operations.

                             Issues: These standards were developed to ensure a safe
                             workplace.

                             Requirements: In general, the OSHA standards have been
                             promulgated to provide a workplace free of harm.
                             Issues:  Determine whether the air strippers would be considered
                             a major source or minor source.

                             Requirements: Permits and regulates air emissions if considered
                             a major source.
                                                                                                         Yes
                                                                                                                           Yes
                                                                                            Yes
                                                                                                              Yes
                                                                                                                          G-l: Not Applicable.
                                                                                                                          G-2: Not Applicable.
                                                                                                                          G-3: Infiltration pond meets established standards.
                C-l: Not applicable.
                G-2: Monitoring and sampling under existing HASP.
                G-3: Covered under future HASP and OAM manual.
                     Employees may need Health and Safely 40-hour course
                     and annually updated 8-hour refresher course.
                                 G-l: Not applicable.
                                 G-2: Monitoring and sampling under existing HASP.
                                 G-3: Covered under future HASP and OiM manual
                                 G-l
                                 G2
                                 G-3
                    Not applicable.
                    Not applicable
                    Not considered a major source, therefore off gas
                    treatment not required.
            Guam Wellhead Protection      Protects groundwater in wells/wellfields that supply drinking
            Program Adopted March 4, 1993 water.  Regulates permitting of production and monitoring wells,
            and Guam's Water Resource and and contractor licensing.
            Development Operating
            Regulations
                                                                           GUAM REQUIREMENTS

                                                                                            Yes
            Water Resources Conservation
            Act IOGCA. Chapter 48


            UIC Regulations
                             Restricts development of groundwater through licensing and
                             permit issuance for well drilling and operation, and sets
                             construction standards.

                             Restricts subsurface injection to prevent contamination and/or
                             deterioration of groundwaier resource
   Yes
   Yes
                     Yes        G-l: Not applicable.
                                 G-2: Not applicable.
                              "   G-3: May affect installation of extraction well so close to
                                      existing production well field
    Yes         G-l. Not applicable.
                G-2: Not applicable.
                G-3: Will address during permitting.

    Yes         G-l: Not applicable.
                G-2: Not applicable.
                G-3: Groundwaier treated to within standards  Possible
   	exceedance of chloride due to upconing.
ARARs
RI/FS
EPA
                         Applicable and Relevant and Appropriate Requirements
                         Remedial Investigation/Feasibility Study
                         Environmental Protection Agency
                         Comprehensive Environmental Response. Compensation, and Liability Act.
     POTW    Publicly Owned Treatment Works
     IX)T     Department of Transportation
     NEPA    National Environmental Policy Act.
     TBC     To Be Considered.

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                                                                        TABLE 3-9

                                                        LOCATION-SPECIFIC ARAte AND TBCs
                                                                                          ARAR Status
            Potential ARAR
         Issues and Reqirirtmcnts
                 Applicable
Relevant and
Appropriate
Applicability to FS Alternatives
                                                               FEDERAL REQUIREMENTS
 Habitat/Wildlife
 Endangered Species Act of 1973 (16 USC    Action to conserve endangered species or           Yes
 I S31), SO CFR 200,402; Fish and Wildlife   threatened species if action may be critical or
 Coordination Act (16 USC 661): 33 CFR     threatens the habitat upon which species
 320 to 330                              depend.
 History
 National Historic Preservation Act (16 USC  Action to recover and preserve artifacts if in an
 Section 469). 36 CFR 65.40 CFR 6.301 (b)   area where action may cause irreparable harm,
                                        loss, or destruction of significant artifacts.
                                             Yes
                                                              Yes        G-l:  Not Applicable.
                                                                         G-2:  Not Appiicabie.
                                                                         G-3:  Will consult with Fish and Wildlife.
                                  Potentially      G-l:  Not Applicable.
                                                G-2:  Not Applicable.
                                                G-3:  Will consult with Guam and National
                                                     Register of Historic Places if necessary.
 5 GCA, Chapter 63
Lists endangered and threatened species;
regulates wild game and fish.
GUAM REQUIREMENTS

                    Yes
    Yes        G-l: Not Applicable.
               G-2: Not Applicable.
               G-3: Will consult with Fish and Wildlife.
ARARs   Applicable or Relevant and Appropriate Requirements.
RI/FS     Remedial Investigation/Feasibility Study.
CWA     Clean Water Act.
F&W     Fish and Wildlife Service.
GCA     Guam Code Annotated.
TBC      To Be Considered

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ARARs would also factor into the location of the extraction wells, limiting the effectiveness of
Ex-Situ treatment, as they are required to be no  closer than  1,000  feet from  an existing
production well  (GEPA, 1993).  Remaining ARARs/TBCs  and their applicability to each
alternative are summarized in Tables 3-7 through 3-9.

The  Natural  Attenuation alternative  meets  chemical-specific  ARARs (i.e., MCLs) through
natural  attenuation.   There  are no  action  or location-specific ARARs  associated  with this
alternative. Long-term monitoring data  indicates that groundwater restoration through natural
attenuation has occurred and is still occurring.  Assuming no additional contaminant sources, the
remaining two areas exceeding MCLs (the vicinity of IRP-31 vicinity of the MARBO Laundry)
would be expected to follow the same decreasing trend.  As these areas have been monitored for
only 2 years (except for IRP-14), this would be confirmed through longer-term monitoring.

Though MCLs are a  Safe Drinking Water Act promulgation, which requires compliance at the
point of use, CERCLA proposes the point of compliance  in the aquifer.  The No Action
alternative does not provide a monitoring network or remedy to address ARARs.

3.5.3        Short-Term Effectiveness

AH three alternatives are expected to be effective  in the short term, as  risk is currently within
acceptable  limits. The  Ex-Situ alternative will be protective of workers during construction, as
necessitated through the site work  plan and health and safety plan. TCE/PCE concentrations are
low enough that the public will not be endangered during the construction phase.  Environmental
impacts from construction of the  air  stripping system and percolation pond will be  addressed
through consultation  with the USEPA, GEPA and the U.S. Fish and Wildlife Service. Impacts
would include clearing approximately two acres for the infiltration ponds.
Andersen AFB MARBO Annex                     3-30                                  4/1/98
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3.5.4         Long-Term Effectiveness and Permanence

The  Natural  Attenuation  alternative provides  long-term  effectiveness  through  the natural
attenuation of TCE and PCE:.  Long-term monitoring and continued wellhead treatment at
production wells which  are impacted  by  TCE/PCE will  continue.   Future groundwater
development  in  impacted areas will  be precluded through the establishment of land use
restrictions and the wellhead protection  regulations.  This alternative is  suited for long term
effectiveness, as  long term effectiveness of naturally decreasing TCE/PCE to below MCLs has
been shown at other wells on the MARBO Annex which have exceeded MCLs in the past.  The
high precipitation flux through the vadose zone, and rapid groundwater movement through the
aquifer effectively flushes potentially remaining TCE/PCE from  the vadose zone and/or aquifer.
This alternative  does not have  significant overhead and maintenance concerns beyond those
which are required under the existing program to monitor existing wells.

The  long-term effectiveness of the Ex-Situ treatment alternative is based  on the efficacy of
capture of the TCE/PCE impacted groundwater. Though all hydrogeologic  environments have
inherent complexities, limestone environments, such as that beneath the MARBO Annex, have
added uncertainties due to potential secondary solution channeling and fracturing. Additionally,
the depth to groundwater at the  MARBO Annex is high, especially in monitoring wells IRP-31
and  IRP-29,  where TCE and PCE, respectively, presently exceed  MCLs  at the base of the
freshwater lens.,  The effectiveness of a groundwater extraction  system is largely dependent on
the efficiency of groundwater and contaminant removal, and the ability to monitor removal.
These complexities, and  the  uncertainty associated with the distribution of TCE/PCE in the
groundwater, add an uncertainty  to the monitoring and measurement of TCE/PCE removal.
Where the Natural Attenuation alternative does not attempt  artificial TCE  or PCE removal from
the aquifer, this level of design and monitoring  is  not a concern.   The Ex-Situ  treatment
alternative is also disadvantageous due to high electricity requirements, an  issue which the island
of Guam  is presently dealing with.  The electricity demands must be considered and balanced
with  the  marginal  benefits  of  groundwater  treatment and  risks   of  saline  upconing.
Approximately 50 percent of the present worth cost is due to electricity.  High  groundwater
 Andersen AFB MARBO Annex                     3-31                                 4/1/98
 Record of Decision

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extraction rates would also tap in to the effective yield of the NGL as a drinking water source,
thus reducing the overall available capacity of the lens.  The marginal benefit  for long-term
effectiveness of Alternative G-3 would not exceed that of Alternative G-2.

The No Action  alternative does  not address PCE/TCE impacted groundwater and long-term
effectiveness is not monitored.

3.5.5         Reduction of Toxicity, Mobility, or Volume Through Treatment

The Ex-Situ Treatment alternative  slightly reduces the  toxicity, mobility  and volume of
contaminants through groundwater extraction and treatment.  Presuming an effective  capture
zone, this alternative would provide  additional  marginal  reduction of toxicity, mobility and
volume of contaminants, over the Natural Attenuation alternative.

The Natural Attenuation alternative slightly reduces the mobility and volume of contaminants in
the aquifer through continued pumping of production wells, and eliminates the toxicity  through
wellhead treatment, on  an as-needed basis.  Thus, the Natural Attenuation alternative provides
some toxicity reduction through wellhead treatment.   Due to the  high  dissolved  oxygen
concentrations, anaerobic reductive dehalogenization of TCE and PCE to potentially more toxic
byproducts does not appear to be of concern at the site. This is evidenced primarily by a lack of
degradation byproducts  in the groundwater,  supported by  the high dissolved oxygen.

The No Action alternative does not reduce the toxicity, mobility or volume of contaminants.

3.5.6         Implementability

There are no implementability concerns for the No Action alternative since it is a no action
alternative.
Andersen AFB MARBO Annex                     3-32                                  4/1/98
Record of Decision

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The Natural Attenuation alternative consists of very little implementation, as natural attenuation
is occurring and  will continue to occur.  Groundwater monitoring procedures are already in
place. Land use restrictions would need to be implemented and O&M considerations for the
existing air strippers would need to be implemented for the long term. Equipment issues with
this alternative may include the periodic replacement of monitoring well piston pumps and O&M
associated with the existing air strippers.

The  Ex-Situ Treatment alternative implements well installation, air stripping and percolation
ponds, which all have predictable operating parameters, and are available for competitive bid to
many vendors.  Construction considerations include extraction well modeling and design, well
and pump installation, construction of the air strippers and  concrete  pad, and excavation and
construction of a percolation pond.  O&M considerations include  possible replacement of the
extraction pumps< maintenance of the well screens, maintenance of the air strippers and packing
material, maintenance of the distribution system to and  from the air strippers, and maintenance of
the percolation ponds.

Though groundwater extraction is a conventional and proven technology, the implementation of
extraction in a  deep aquifer with heterogeneous limestone conditions would be  difficult.   Air
stripping is a proven technology and would be easily implemented.   As noted earlier, electricity
consumption and the impact on future sustainable yield  from a sole source aquifer are  also
implementability concerns.

3.5.7         Cost

This assessment evaluates the costs of the remedial actions on the basis of present worth. Present
worth analysis allows remedial actions to be compared on the basis  of a single cost representing
an amount that, if invested in the base year at an assumed interest (discount) rate and disbursed
over the study  period as  needed, is sufficient to cover all costs associated with the remedial
action over its planned life. This study  assumes a 30-year duration and 5 percent discount rate.
CERCLA guidance suggests a cost accuracy to within -30 percent to +50 percent.  Detailed costs
Andersen AFB MARBO Annex                     3-33                                  4/1/98
Record of Decision

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are included  in the OU  2 FFS  (EA  and Montgomery Watson,  1997) and, based on these
assumptions, are presented below.

No Action. The estimated present worth cost for this alternative is $77,000.  This includes a
5-year site review over the 30-year duration.

Natural  Attenuation  with Wellhead  Treatment. The estimated present worth  cost  for  this
alternative is  $3,649,000,  including $12,000  in capital costs and $3,637,000 in  present worth
O&M costs.

Ex-Situ  Treatment. The  estimated present  worth  cost for  this  alternative  is $18,447,000,
including $2,488,000 in capital costs and $15,959,000 in present worth O&M costs.

3.5.8        State/Territory Acceptance

This  assessment evaluates the technical  and administrative  issues  and concerns  that the
State/Territory may have  regarding each of the remedial actions. The USEPA and Guam EPA
commented on the  draft version of this document.  As with the soil alternatives, the comments
were both editorial and technical in nature,  including  the implementation mechanism for the
selected groundwater alternative.  After  addressing comments  and concerns,  the USEPA and
Guam EPA are in concurrence and agreement with the selected alternatives.  Their comments,
and Andersen AFB's responses to those comments, are included in Appendix C.

3.5.9        Community Acceptance

This  assessment evaluates the  issues of concerns of  the  public  regarding  the proposed
alternatives.  After release of the Proposed Plan,  which presented Natural Attenuation  with
                                                                    i
Wellhead Treatment as the preferred remedy, the community did not express objection during the
public meeting or public comment period.  Senator Brown noted concern pertaining to the
Andersen AFB MARBO Annex                     3-34                                  4/1/98
Record of Decision

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connection between soil contamination at Waste Pile 7 and the groundwater. Senator Brown's

comments, and other public comments, are addressed in Section 4.0 of this document.


3.6          THE SELECTED REMEDY


Natural Attenuation with Wellhead Treatment provides the most effective balance of trade-

offs with respect to  the nine criteria, and is the preferred alternative.  This alternative would

protect human health and the environment, is effective in the short and long term,  is easy to

implement, and is cost effective.  The  remedy would continue until long term groundwater
quality monitoring indicates that TCE and PCE concentrations are consistently below MCLs.
Each five year review would:  1) determine if the remedy is still effective, and 2) determine if

the remedy has achieved its goals, and thus can be discontinued.  Additionally, the Andersen

AFB  Long Term Monitoring Plan will be reviewed every two years,  which includes  the

groundwater monitoring wells at the MARBO Annex and immediate vicinity. A brief summary
and comparative benefit of this alternative is presented below:
             TCE and PCE concentrations are decreasing and/or consistently at low levels, as
             seen where long term monitoring has occurred  at Air Force production wells.
             TCE and PCE concentrations are also decreasing in the majority of monitoring
             wells within the MARBO Annex. Based on historical groundwater data collected
             from the MARBO Annex, TCE/PCE concentrations are expected to drop  over
             time due to naturally high flushing rates in the vadose zone and aquifer, assuming
             there is no continuing source.  Thus Natural Attenuation has shown to be an
             effective alternative  in  reducing  TCE  and  PCE  concentrations.   Natural
             Attenuation would be monitored for  effectiveness and applicability in  recently
             installed monitoring wells to confirm decreasing concentrations.

             The higher concentrations of TCE and PCE are focused  in two distinct areas
             within  the MARBO Annex, and do not appear to be migrating. The two areas are
             southwest of  Site 37  (primarily TCE  in IRP-31), and  area in the vicinity of the
             MARBO Laundry  (primarily PCE in  IRP-14 and 29). The low  levels  detected
             outside of these two areas are presently below MCLs, with the exception of
             GPA-1. Additionally, the TCE detected southwest of Site 37 is in the deep zone,
             which  precludes the installation of production wells.  Natural Attenuation would
             provide continued monitoring and confirmation of the stability of these two areas,
             as well as provide monitoring for overall decreasing trends.
 Andersen AFB MARBO Annex                    3-35                                 4/1/98
 Record of Decision

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       •      Existing risk at the MARBO Annex is presently within the USEPA's acceptable
             health  risk range for the  production wells.   This  would be maintained with
             continued wellhead treatment  of MW-1, MW-2 and MW-3 (until TCE/PCE
             concentrations are consistently below MCLs), the incorporation  of a long term
             monitoring plan, and by regulating the installation of potentially new production
             wells in areas that are impacted with TCE/PCE.

       •      Natural Attenuation with Wellhead Treatment  has high implementability, and can
             be incorporated into  existing Air Force plans to monitor groundwater over the
             short and long term.

       •      Natural Attenuation with Wellhead Treatment does  not potentially compromise
             aquifer groundwater quality to conditions which may deteriorate due to excess
             pumping.  The excessive high pump  rates required for Ex-Situ Treatment would
             likely result in saline upconing.

       •      From a cost perspective, Natural Attenuation with Wellhead Treatment can be
             implemented at a minimal cost and provide maximum benefit, compared to the
             other two alternatives.  Though more expensive than the No Action alternative,
             the benefits of Natural Attenuation with Wellhead Treatment outweigh  its added
             cost.  Conversely, the benefits associated with the additional costs for Ex-Situ
             Groundwater Treatment are marginal, uncertain and potentially detrimental to the
             aquifer.


3.7          STATUTORY DETERMINATIONS
The selected remedy satisfies the statutory requirements of Section 121 of CERCLA, as amended

by SARA, in that the following mandates are attained:
             The selected remedy is protective of human health and the environment, will
             decrease site risks, and will not create short-term  risk nor have cross-media
             consequences;

             The selected remedy complies  with federal  and  state requirements that are
             applicable or relevant and appropriate to the remedial action such as chemical-
             specific  ARARs,  chemical-specific clean-up  standards,  and  action-specific
             ARARs;

             The selected remedy  is cost-effective in its fulfillment of the nine CERCLA
             evaluation  criteria through remediation of the contaminated groundwater in a
             reasonable period of time.
Andersen AFB MARBO Annex                     3-36                                4/1/98
Record of Decision

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3.7.1         Protection of Human Health and the Environment

Through  long-term monitoring, institutional control  and continued wellhead treatment, the
Natural Attenuation with  Wellhead Treatment  alternative will monitor  and confirm  that
groundwater will not exceed drinking water standards.  The  Natural Attenuation alternative
utilizes natural flushing of a highly  transmissive aquifer to remove contaminated groundwater
from the aquifer. The implementation of this remedy will  not create any short-term risk nor any
negative cross-media aspects.

3.7.2         Compliance with ARARs

All ARARs will be met by  the selected  remedy.  The remedy will achieve compliance  of
chemical-specific clean-up standards. None of the anticipated actions for the Natural Attenuation
alternative is expected to have a detrimental impact on endangered species.

3.7.3         Cost Effectiveness

The USEPA, the USAF, and the Territory of Guam believe that the selected remedy fulfills the
nine criteria of the NCP and provides overall effectiveness in relation to its cost.  The Natural
Attenuation alternative has a total capital  cost of approximately $12,000 and  an  approximate
annual O&M present worth cost of $3,637,000. The total  net present worth is $3,649,000 based
on a 30-year estimate.

3.7.4        Utilization of Permanent Solution and Alternative Treatment (or Resource
             Recovery) Technologies to the Maximum Extent Possible

The selected remedy represents, to the reasonable extent possible, a cost-effective manner for
remediating groundwater at the MARBO Annex. The remedy selected provides the best balance
of long-term effectiveness and permanence, marginal reduction of TMV  through  wellhead
treatment, short-term effectiveness, implementability and cost-effectiveness.
 Andersen AFB MARBO Annex                     3-37                                 4/1/98
 Record of Decision

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3.7.5         Preference for Treatment as a Principle Element

Contaminants of concern in the groundwater will be removed through natural attenuation of the
aquifer.  Remediation of the groundwater will occur naturally, without the use of a treatment
technology.  The balance of natural means versus artificial means favors utilizing natural means
to remediate the aquifer when compared to the overall effectiveness, cost, and implementation of
an engineered alternative.

3.8           DOCUMENTATION OF SIGNIFICANT CHANGES

The Focused FS and Proposed Plan for the MARBO Annex based the overall cost of the Natural
Attenuation  remedy on a long term monitoring plan of 40 wells (including  some production
wells). As noted in the Proposed Plan and Focused FS, the actual  number of  wells to  be
monitored will be re-evaluated every two years, as longer term data becomes available.  This
does not impact the remedy, but will impact (decrease) cost in the long term.  Per the October 22,
1997 Remedial Project Manager's (RPM) meeting, Andersen AFB and the  USEPA and GEPA
agreed to an initial reduction of wells for monitoring at the MARBO Annex, for  a total of 26
wells.  This  decision was made after two years of sampling at the MARBO Annex, where the
reduction of wells was based on either consistent non-detectable concentrations of TCE and PCE,
or concentrations consistently below MCLs.  A summary of this data is included in the OU 2
FFS (EA and Montgomery Watson, 1997) and the Andersen AFB Groundwater Summary Report
(EA and  Montgomery Watson, 1997).  The reduction in the number of wells would reduce the
estimated 30-year  present  worth cost of this remedy  to approximately  $2,364,000:.   Re-
evaluation of the long term  monitoring program at the MARBO Annex will occur every two
years in accordance with the Final Groundwater Monitoring Plan (EA and Montgomery Watson,
1995).
2 This includes the following monitoring and production wells for monitoring:
       Production wells D-2, D-5, D-14, M-6, and M-7.
       Monitoring wells IRP-1. 2, 8, 10, 12, 14, 15, 16. 23.24, 25, 26, 27, 29. 30, 31. 33. 34, and 35 and GPA-1
       and GPA-2.
Andersen AFB MARBO Annex                     3-38                                 4/1/98
Record of Decision

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                        4.0  RESPONSIVENESS SUMMARY

4.1           OVERVIEW

The public comment period for the Proposed Plan began on October 10,  1997 and ended on
November 10, 1997. A public notice summarizing the Proposed Plan, and announcing the public
comment period and public meeting was printed in the Pacific Daily News from October 8
through October 10.

At the public meeting, which was held on October 24, 1997, questions and comments were
received from the audience related to the Proposed Plan.  A transcript  of the public  meeting
minutes has been included in the Administrative Record. Judging from the comments received,
the  community  accepts  the USAFs preferred remedial alternatives  for addressing soil and
groundwater contamination at the MARBO Annex.  There were no written comments received
during the 30-day public review period.

4.2           BACKGROUND ON COMMUNITY INVOLVEMENT

In an effort to involve the community, Anderson AFB established the Restoration Advisory
Board (RAB), which includes representatives from the local community.  The RAB replaced the
Technical Review Committee, which consisted primarily of elected officials and Government of
Guam Agency Representatives.  Since its establishment in 1995 the  RAB has regularly held
quarterly meetings, which are open to the public.  The RAB serves as  a focal point for
environmental exchange between  Andersen  AFB and the local  community.   In addition to the
announcement of the Proposed Plan in the Pacific Daily News from October 8 through October
10,  1997, a press release was also distributed to radio and television companies.

Andersen AFB presented a summary of proposed remedial alternatives and solicited comments
on the Proposed Plan at a public meeting on Friday, October 24,  1997 at  the Guam Hilton.
Andersen AFB MARBO Annex                     4-1                                4/1/98
Record of Decision

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Representatives from Andersen AFB, GEPA, and USEPA were present at the meeting to answer
questions; a transcript of this meeting is available for the public in the administrative record.

4.3          SUMMARY OF  COMMENTS  RECEIVED  DURING  THE  PUBLIC
             COMMENT PERIOD

Comments received during the Andersen AFB MARBO Annex public comment period on the
final OU 2 and OU 3 FS, and the Proposed Plan are summarized below.  The comment period
was held from October 10, 1997 to November 10,  1997.  The comments are presented in the
order in which they were received.

Public Meeting Comments Summary

Senator Joanne Brown,  member  of the 24th Guam  Legislature and co-chair of the AAFB
Restoration Advisory Board (RAB): Senator Brown followed up on the comments she made at
last week's RAB meeting. Her comment addressed the issue of how sites are treated, particularly
Waste Pile 7. The risk assessment process evaluates sites  by assessing the threat they pose to
contaminating groundwater (drinking water).    However,  from  a public  policy-making
perspective, the condition of the land when it is returned to the people of Guam is also a concern.
Public  policy-makers must ensure that  the lands  that  are returned to the people of Guam are
useable.  Risk assessments do not take  into account this concern.  Other environmental policy
issues, such as  the  how useable the land  is when it is returned, should also be considered.
Southern High School is an example of how past waste disposal interfered with the  construction
of the school. In the future, the technology may be available to clean up these sites.  On going
monitoring is also critical particularly with regard to constituents that may be contained in Waste
Pile 7.

The Proposed Plan recommends that AAFB will leave the constituents in  place at this two-acre
property and return it to the people of Guam with restrictions on how the  property can be used.
Our ultimate objective is to see that as much of this property is as usable as possible in the future.
This will be a concern with  other sites as we move along  in the process.  Funding  and
Andersen AFB MARBO Annex                     4-2                                 4/1/98
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environmental cleanup decisions are looked at in terms of the threat posed to groundwater, but
this should not be the only issue.  Returning this property to the people of Guam in its original
condition so that it can be used by the people of Guam is an important issue.  Future land use
considerations should be part of the decision-making process  in addition to the threats posed to
groundwater.

The metallic waste in Waste Pile 7 may not pose a major threat to the groundwater, but it will
limit the use of this property in the future. It needs to be made very clear to the people of Guam
that this property is going to have restrictions on future  development. The average person on the
street is not going to understand the concept of risk assessment and setting priorities on the basis
of the risk assessment.  What they will understand is  whether or not the land is usable. The
current proposal is going  to  limit their use of this property  in the future.   Under the current
process, we are going to take a map and begin to draw little circles around areas that are going to
have restrictions even if the land is returned to the people of Guam. This is a legitimate concern
because ultimately the desire is to see that when the property is returned it is returned in a usable
form.  Otherwise we are going to have  chunks  of Guam that are not  usable.  This will be the
reality if we continue to deal with the concept of only  dealing with these sites in terms of their
threat to groundwater. If we continue  to leave constituents in the ground,  then we  will have
more and more unusable property in the future.

AAFB Response: Dr. Mark Rodriguez of the Waste Policy Institute reported that the MARBO
Proposed Plan used Preliminary Remedial Goals (PRGs) to assess the risks to human and health
posed by the sites. He said that PRGs are concentrations that are protective of human health. He
stated that the key point to understand is that by using a soil cover at Waste Pile 7, the exposure
pathway is limited. The soil cover will prevent health problems from occurring. As far as future
use of the property, he noted that deed restrictions will determine how the land will be used.

Additionally, Site 20 lies within an abandoned quarry,  with an average depth to the base of the
fill of 10.8 feet bgs, and as such it has limited future land use regardless of whether the waste pile
was removed. The restrictions on Waste Pile 7  would  limit the use of the property to activities
which are non-intrusive in nature, and would be included in the deed drilling transfer. Intrusive
Andersen AFB MARBO Annex                      4-3                                  4/1/98
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activities would open an exposure pathway and defeat the purpose of the soil cover. Some ideas
of non-intrusive activities use may include a maintenance yard or storage area.

Fred Castro. AAFB RAB member:  Has the  Proposed Plan been reviewed by the regulators?
Were there any outstanding issues?

AAFB Response:  The Proposed Plan was reviewed by Guam Environmental Protection Agency
and U.S. Environmental Protection  Agency.   Mark  Ripperda from the U.S. Environmental
Protection Agency said that he approved the Proposed Plan and that  he had no outstanding
issues.  Victor  Wuerch from the  Guam Environmental  Protection Agency said that he also
approved the Plan.  He noted  that his major concern is to protect groundwater and that the
Proposed Plan recommends long-term groundwater monitoring at MARBO Annex.

Fred Castro: What is the estimated cost for the cleanup and monitoring and what is the status of
the funding?  If there is a change in the constituents in the groundwater, how will the necessary
money be obtained to cleanup the site? On average, how much funding (total capital outlay) is
available each year.

AAFB Response:   The estimated costs are in the Proposed Plan.  AAFB has FY97 funds to
cleanup the  sites  at MARBO based on the recommended alternatives in the Proposed Plan.
AAFB expects  to receive funds for  continued groundwater monitoring.  AAFB will have to
request for funds for monitoring on a yearly basis.  If there are major changes to the  Proposed
Plan, AAFB will have to submit other requests for funds.  AAFB averages approximately $10
million per year for the IRP.

Ernie Wusstig. Board of Directors for the Guam Soil and Water Conservation District:  What
kind of damage has occurred to our aquifer from all of the pollution, that is all of the chemical
waste from military activities. I was bom and raised in Yigo and I have seen all kinds of military
activities. Now, thirty years later, why has it taken so long to address these issues? What has the
military done to damage our aquifer?
Andersen AFB MARBO Annex                     4-4                                  4/1/98
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AAFB Response: Extensive groundwater studies have been conducted in this area.  AAFB has
installed monitoring wells and it samples these wells and the production wells. The chemicals
that have been detected are volatile organic compounds including tetrachloroethylene (PCE) and
trichloroethylene (TCE). These chemicals are addressed in the Proposed Plan.  The Proposed
Plan recommends wellhead treatment and natural attenuation to remove the PCE and TCE from
the aquifer.

There are two areas of concern in the groundwater underlying the  MARBO Annex, where
concentrations of TCE and/or PCE exceed Federal allowable levels. One is beneath the former
MARBO Laundry, where PCE slightly exceeds Federal levels, and the other is across from the
Yigo Power Plant, where TCE exceeds Federal levels.  Though the PCE underlying the MARBO
Laundry  is likely a result of military activities, it is unclear where the source of the TCE
originated.  After approximately 10 years of monitoring these areas, the TCE and PCE do not
appear to be migrating.  Thus, the overall impact on the aquifer is isolated to two small areas
representing a very small portion of the groundwater underlying the MARBO Annex.

On a broader, national level, impacts to soil and groundwater from industrial activities were not
known to be an issue until the early 1970s. The military has been consistent and pro-active with
investigative and remedial activities occurring nationally.  Should there have been a situation
where an imminent health risk existed, immediate measures would have been taken.

Ernie Wusstig: Where was all of the used oil from the vehicles dumped over the years?  Do you
have any data that  shows where the used oil was disposed?   Is there any  evidence of
contamination at MARBO?
                                                                                    *
AAFB response: AAFB analyzes its samples for petroleum products, but it has not detected any
petroleum products in the  groundwater samples.  It also has not found large quantities of
petroleum products in the six Installation Restoration Program (IRP) sites.
Andersen AFB MARBO Annex                     4-5                                  4/1/98
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Rudy Wusstig:  Where has the wastewater from MARBO Annex been going for the past 30
years? We used to farm in the MARBO cave area and we used to see wastewater disposed there.

AAFB Response:  The  sewage outfall was part of another investigation.   It is in the area
designated as excess land in Public Law 103-339. AAFB collected samples in the sewage outfall
area near MARBO cave and nothing over acceptable levels was detected.

Rudy Wusstig:  There are a lot of people from Guam that are so heavy in lead poisoning.  My
mother had high levels of lead in her blood. Where is this lead coming from and is it coming
from our water?

AAFB Response:  Island-wide, Guam has noticeable background concentration levels of lead
associated with the groundwater.  AAFB has not been able to attribute the lead to any of the IRP
sites at MARBO.  These levels are also found in places around the island far away from Air
Force property such  as central Guam, Pago Pago, and Ordot.  These concentration levels are not
above the levels that may pose a risk to human health. It is hard to determine if the prevalence of
lead poisoning in many of the people  is attributable to water  or to another source. Another
source of lead could be attributed to the lead solder in copper pipes in older water distribution
systems.  It could also come from lead-based paint.

Rudy Wusstig:  There are also high incidents of degenerative  diseases on Guam like diabetes in
Guam. There is three percent hereditary diabetes nation wide, but I saw a study that said Guam
had a 33 percent rate of diabetes.

AAFB Response:  Not a question, but a statement. No response necessary.

Rudy Wusstig:  Why did the Air Force have the sewage outfall at the MARBO cave for years
and years?
Andersen AFB MARBO Annex                      4-6                                  4/1/98
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AAFB Response: It was the acceptable practice at that time.

Rudy Wusstig:  Why was this an acceptable practice in Guam when at the time it was not an
acceptable practice in California or other parts of the mainland?

AAFB Response: This practice was acceptable at that time, both on Guam and many places on
the mainland.

Jesus Torres: Nice program.  What are the schedule dates?  Will these studies go on  forever?
Have you any idea when some of these studies will be completed? Please advise.

AAFB response: The MARBO Annex sites are  expected to be closed out by December 1998.
The studies for the MARBO Annex Operable Unit are completed.
Andersen AFB MARBO Annex                     4-7                                 4/1/98
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                                  REFERENCES

Barrett Consulting Group.  1992, Water Facilities Master Plan Update. Prepared for the Public
       Utility Agency of Guam and Government of Guam, February, 308 p. + Appendices.

Batelle Columbus Division (Batelle).  1989.  Installation Restoration Program Phase n Stage 1 -
       Confirmation/Quantification Andersen AFB. Guam: Prepared for the Department of the
       Air Force, Occupational and Environmental Health Laboratory Technical Services, Final
       Main Report, January 1989,247 pp. + Appendices.

Camp, Dresser & McKee, Inc. and Barret, Harris & Associates.  1982.  Northern Guam Lens
       Study Aquifer Yield  Report. Guam  Environmental Protection Agency, Government of
       Guam, December 1982,68 pp. + Appendices.

Conry, P.J.  1988a. High nesi predation by brown tree snakes on Guam. Condor 90: 478-482.

Conry, P.J.  1989.  Ecology of wild (feral) pig (Sus scrofa) on Guam.  Technical Report #7.
       Division of Aquatic Wildlife  Resources, Department of Agriculture, Mangilao, Guam.
       60pp.

Department  of Aquatic and Wildlife Resources (DAWR).   1988.   Checklist of terrestrial
       vertebrates and selected terrestrial invertebrates of Guam.  Division  of Aquatic and
       Wildlife Resources, Department of Agriculture, Agana, Guam.

DAWR, Government of Guam. 1992a. Job progress report, survey and inventory of non-game
       birds. October 1, 1991 to September 30,1992.

DAWR, Government of Guam. 1992b. Job progress report. Natural history, biology, and habitat
       protection for Mariana fruit bats. October 1,1991 to September 30,1992.

EA Engineering  Science  and Technology  (EA) and Montgomery Watson.   1997a.  Final
       MARBO Annex Operable Unit 2 Focused Feasibility Study Report (FFS).  October.
       1997.

EA Engineering Science and Technology (EA) and Montgomery Watson, 1997b. Groundwater
       Summary Report. October, 1997.

EA and Montgomery Watson.  1995.  Final Groundwater Monitoring Plan for Andersen AFB.
       Guam. October, 1995.

Environmental Science and Engineering,  Inc.  (ESE).  1985. Installation Restoration Program
       Phase I:  Records Search.  Andersen Air Force Base. Guam: Prepared for the U.S. Air
       Force HQ SAC/DEPV by  Contract personnel of Reynolds, Smith and Hills, Inc., March
       1985,139 pp. + Appendices.
Andersen AFB MARBO Annex                    R-1                                4/1/98
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Federal Register. 1991. Endangered and threatened wildlife and plants:Designation  of critical
       habitat for the little Mariana fruit bat. Mariana fruit bat. Guam broadbill. Mariana crow.
       Guam Micronesian kingfisher, and Guam bridled white-eye.  50 CFR Part 17.  Federal
       Register 56(115):  27485-27493.

Government of Guam, Bureau of Labor Statistics. 1989.  Current Employment Survey.

Government of Guam, Bureau of Labor Statistics. 1990.  Current Labor Force Survey.

Guam Annual Economic Review. 1987.

Guam Code Annotated (GCA), Chapter 47, Title 10. The Water Pollution Control Act.

Guam EPA.  1990. Water Resource Development and Operating Regulations.  August 2,1990.

Guam EPA.  1992. Revised Guam Water Quality Standards. January, 1992.

Guam EPA.  1993. Guam's Wellhead Protection Program. March, 1993.

ICF Technology Incorporated (ICF).  1995. Groundwater Dye Trace Program and Well Cluster
       Proposal for the Landfill Area. Andersen Air Force Base. Guam. Final. February, 1995.

ICF. 1996.  United States Air Force IRP Operable Unit 3 Remedial Investigation for Andersen
       AFBGuam (OU3 RI). Final.  December  1996.

ICF.  1997a. Operable Unit 3 Focused Feasibility Study Report (OU3 FFS). Final.  January
       1997.

ICF. 1997b. Operable Unit 2 MARBO Annex Remedial Investigation Report (OU2 RI). March
       1997.

Mink, J.F., and S.L.  Low (Mink & Low).  1977. Groundwater Analysis by Tritium Technique:
       A Preliminary Evaluation. University of Guam Technical Report 2, 25 pp.

Mink, J.F.  1976.  Groundwater Resources of Guam:  Occurrence and Development.  Technical
       Report No. 1, Water Resources Research Center, University of Guam, September 1976,
       275 pp.

Perez, G.S.A. 1972.  Observations of Guam bats. Micronesica8(l-2):  141-149.

Rodda, G.H., T.H. Fritts, and J.D. Reichel.  1991.  The distributional patterns of reptiles and
       amphibians in the Mariana Islands.  Micronesia 24: 195-210.

Savidge, J.A. 1987.  Extinction of an island forest avifauna by an introduced snake.  Ecology
       68(3): 660-668.
Andersen AFB MARBO Annex                    R-2                                4/1/98
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Science Applications International Corporation (SAIC). 1991. Installation Restoration Program
       Phase  II Stage 2 - Remedial Investigation/Feasibility Study Andersen  AFB. Guam:
       Prepared for United States Air Force Human System Division. Final Report. November
       1991.

Tracey, J.I., S.O. Schlanger, J.T. Start, D.B. Doan, and H.G. May.  1964.  General Geology of
       Guam: U.S.G.S. Professional Paper 403-A.

United States Air Force (USAF).   1994.  United States Air  Force Installation Restoration
       Program. Informal Technical Information Report. Ecological Habitat Survey of Operable
       Unit 3. Andersen Air Force Base. Guam. October 1994.

U.S. Bureau of the Census, Census of Population:   1990 Volume I.  U.S. Department of
       Commerce.

U.S. Department of Commerce, Economic Research Center.  1989. Annual Economic Review
       and Statistical Abstract.

U.S. Environmental Protection Agency (USEPA).  1988.  Superfund Exposure Assessment
       Manual.  Office of Emergency and Remedial Response. EPA/540/1-88/001.

USEPA.   1989a.   Risk Assessment Guidance for  Superfund. Volume I.   Human Health
       Evaluation  Manual  (Part A).  EPA/540/1-89/002.   U.S. Environmental Protection
       Agency, Office of Emergency and Remedial Response, Washington, DC.

USEPA.  1989b.  Statistical Analysis  of Groundwater Monitoring Data at RCRA Facilities.
       EPA/530-SW-89-026.  U.S. Environmental Protection Agency, Office of Solid Waste,
       Washington, D.C.

USEPA.  1992. Community Relations in Superfund: A Handbook.

USEPA.    1995.     Region  DC  Preliminary  Remediation Goals (PRGs)  Second  Half.
       September 1995.

U.S. Fish and Wildlife Service (USFWS).  1993.  Final Environmental Assessment. Proposed
       Guam  National Wildlife Refuge. Territory of Guam.  Department of Interior, Fish and
       Wildlife Service, Portlamd, OR.

Ward, P.E., and J.W. Brockhart.  1962. Military Geology of Guam, Mariana Islands:  Water
       Resources Supplement, prepared by Intelligence and Mapping Division,  Office of the
       Engineer Headquarters United States Army Pacific in cooperation with the U.S. Geology
       Survey, Department of the Interior, 35 pp. + Appendices and 1 plate.

Ward, P.E., S.H. Hatford, and D.A. Davis.  1965. Geology  and Hydrology of Guam, Mariana
       Islands U.S.G.S. Professional Paper 403-H, 29 p.
Andersen AFB MARBO Annex                    R-3                                 4/1/98
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                        APPENDIX A




REGION IX PRELIMINARY REMEDIATION GOALS (PRGs) SECOND HALF 1995

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                                     September 1,1995

Subject:       Beaton IX Preliminary Remediation Goals fPRQsl Second Half 1995

From:         Stanford J. Smuoker, Ph.D.
              Regional Toxfcotogist (H-9-3)
              Technical Support Section

To:           PRO Table Mailing List

Please find the update to the Region DC PRQ table. The table has been revised to reflect the most
current EPA lexicological and risk assessment information. Updates to EPA toxicity values were
obtained from IRIS through July 1995 and HEAST through November 1994.

Although Region 9 risk-based PRQs are 'evergreen* and will change as new methodologies and
parameters are developed, they have matured and are changing less than in the past  Meanwhile,
the mailing list has increased exponentially and updating and distributing the table by mail has
become a considerable burden.  Upon reflection, we've decided to change from a semi-annual to •
annual distribution beginning in 1996.  We think this change wOl allow us to keep publishing the PRQ
table, while having Uttle effect on the table's usefulness.

If you are not currently on the PRQ mailing list, but would like to be, please make the request through
EPA's project manager working on your site.  Or, for faster service, simply download the file
(PRG2ND95J3P) from California Regional Water Board's BBS  [(510) 286-0404].  Abo, in the not-too-
distant future, we anticipate that the PRQ table will be available via internet access. To determine
whether the file is available through  this delivery system, direct gopher client to •gopher.epa.gov' and
select the following menus:  EPA Offices and Regions; Region 9; Superfund Program.

Before relying heavily on any number in the table, It is recommended that the user verify the numbers
with a toxicologist or Regional risk assessor because the toxfcity / exposure information in the table
may contain errors or default assumptions that need to be refined based on further evaluation. If you
find an error please send me a note via fax at (415) 744-1916.

This version of the table contains new toxidty values for arsenic, benzene, l-chkyo-1,1-dffluoroethane
(HCFC-142b), cobalt, danftol, hydrogen chloride, hydrogen sulfide, methyl mercury, and phosphine.
The updated values are indicated in boldface print in the table.

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DISCLAIMER

Preliminary remediation goals (PRQa) focus on common exposure pathways and may not
consider all exposure pathways encountered at CERCLA / RCRA sites (Exhibit 1-1).  PRGs do not
consider Impact to groundwater or address ecological concerns. PRGs are specifically not
Intended as a (1) stand-alone decision-making tool, (2) ss a substitute for EPA guidance for
preparing baseline risk assessments, or (3) a rule to determine If a waste Is hazardous under
RCRA.

The guidance set out In this document is not final Agency action.  It Is not Intended,  nor can It be
relied upon to create any rights enforceable by any party In litigation with the United States.  EPA
officials may decide to follow the guidance provided herein, or act at variance with the guidance,
based on an analysis of specific circumstances. The Agency also reserves the right to change
this guidance at any time without public notice.
                                   1.0 INTRODUCTION

The Region DC PRO tabto combines current EPA toodcfty values with "standard* exposure factors to
estimate concentrations in environmental media (sofl, air, and water) that are protective of humans,
including sensitive groups, over a Rfetime.  Concentrations above these levels would not automatically
designate a site as 'dirty* or trigger a response action.  However, exceeding a PRG suggests that
further evaluation of the potential risks that may be posed by site contaminants is appropriate.
Further evaluation may include additional sampling, consideration of ambient levels in the
environment, or a reassessment of the assumptions contained in these screening-level estimates (e.g.
appropriateness of route-to-route extrapolations).

PRG concentrations presented in the table can be used to screen pollutants in environmental media,
trigger further investigation, and provide an initial cleanup goal If applicable. When considering PRGs
as preliminary goals, residential concentrations should  be used for maximum beneficial uses of a
property.  Industrial ounuttiuratiom are Included hi the table as an alternative cleanup goal for soils,
but It is not recommended that industrial concentrations be used for screening sites.

Before applying PRGs as screening tools or initial goals, the user of the table should consider whether
the exposure pathways and exposure scenarios at the  site are fully accounted for in the PRG
calculation. Region IX PRG concentrations are based on exposure pathways for which generally
accepted methods, models, and assumptions have been developed  (i.e. ingestion, dermal contact,
and inhalation) for specific land-use conditions and do not consider impact to groundwater or
ecological receptors (see Developing a Conceptual Site Model below).

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                                    EXHIBIT 1-1
                     TYPICAL EXPOSURE PATHWAYS BY MEDIUM
                   FOR RESIDENTIAL AND INDUSTRIAL LAND USES*
IEXPOSURE PATHWAYS, ASSUMING:
MEDIUM
Ground Water
Surface Water

.


Soil






RESIDENTIAL LAND USE
ifnpcction from drinking
inhalation of volatile
Dermal absorption from bathing
Jngection from drinking
Inhalation of votetf/m
Dermal absorption from bathing
Ingestion during swimming
Ingestion of contaminated fish
Ingottlon
Inhalation of partteufate*
Inhalation of votetf/M
Exposure to indoor air from sol
gas
Exposure to ground water
contaminated by soil teachate
Ingestion via plant, meat or
dairy products
Danrtal absorption
INDUSTRIAL LAND USE
Ingestion from drinking
Inhalation of voJatites
Dermal absorption
Ingestion from drinking
Inhalation of volatiles
Dermal absorption


Ingattion
Inhalation of particulata*
Inhalation of volatile
Exposure to indoor air from
son gas
Exposure to ground water
contaminated by soil teachate
Inhalation of particulates from
trucks and heavy equipment
Derma/ absorption
Footnote:
•Exposure pathways considered in the PRG calculations are indicated in boldface italics.

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                               2.0 READING THE PRG TABLE

2.1    General Considerations:

With the exceptions described below, PRGs are  risk-based concentrations that correspond to either a
one-in-one million (10"*) cancer risk or a noncarcinogenic hazard quotient of one, whichever is lower.
In most cases, where a substance causes both cancer and noncancer or systemic effects,  the 10"6
cancer risk will result in a more stringent criteria and consequently this value is presented in the table.
PRG concentrations based on cancer risk are indicated by *ca*. PRG concentrations based on
noncarcinogenic health threats are indicated by •nc*.

If the risk-based concentrations are to be used to screen sites, It is recommended that both cancer
and noncancer-based PRGs be obtained even though the printed fist wfll contain only the more
conservative of the two values.  To obtain additional values (e.g. noncancer PRGs for a carcinogenic
substance), the user has two options.  The simplest option Is to obtain the complete set of PRGs by
downloading the file (PRG2ND95.ZIP) from California Regional Water Board's Bulletin Board System at
((510)286-0404)]. Or, if no modem is available, one could use the equations provided  below to
calculate additional PRGs.

It has come to my attention that some users have been multiplying the cancer PRG concentrations by
10 or 100 to set 'action levels' for triggering remediation or to set less stringent cleanup levels for a
specific site after considering non-risk-based factors such as (ambient levels, detection limits, or
technological feasibility).  This practice recognizes that there may be a range of values that may be
•acceptable* for carcinogenic risk (EPA's cancer risk range is from 10"6 to 10*4).  However, this
practice could lead one to overlook serious noncancer health threats and it is strongly recommended
that the user consult with a toxicologist or Regional risk assesssor before doing this. For carcinogens,
I have indicated by asterisk pea**) in the PRG table where the noncancer PRGs would be exceeded if
the cancer value that is listed is multiplied by 100. Two stars (•«•••) indicate that the  noncancer
values would be exceeded tf the cancer PRG were multiplied by 10.  There is no range of •acceptable*
noncarcinogenic •risk* so that under no circumstances should noncancer PRGs be multiplied by 10 or
100, when setting final cleanup criteria

In addition to federal PRGs, the PRG table also includes California EPA PRGs (*CAL-Modified PRGs*)
for specific chemicals where CAL-EPA values may be more restrictive than the federal values. These
differences typically reflect  differences in toxidty values and not exposure assumptions. Where CAL-
Modified values are presented, they should be used for screening purposes within the State of
California

In general, PRG concentrations in the table are risk-based but for soil there are two important
exceptions: 1) for several volatile chemicals PRGs are based on soil saturation equation (*sar) (see
below), and 2)  for relatively less toxic inorganic and semivolatile contaminants, a non-risk based
•ceiling limit* concentration is given as 10+8mg/kg  Tnax*. PRG concentrations that are not risk-
based (le. either *sat* or •max') should be segregated before screening multiple pollutant risks.

2J    Toxlclty Value*:

EPA toxidty values, known as noncarcinogenic reference doses (RfD) and carcinogenic slope factors
(SF) were obtained from IRIS through July 1995, HEAST through November 1994, and ECAO-
Cincinnati. The priority among sources of toxfcotogicaJ constants used are as follows: (1) IRIS
(indicated by T). (2) HEAST Ch*). (3) ECAO (V). and (4) withdrawn from IRIS or HEAST and under
review (Y).

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Route-to-route extrapolations (V) were frequently used when there were no toxicity values available for
a given route of exposure. Oral cancer slope factors fSFo") and reference doses CRfDo1) were used
for both oral and inhaled exposures for organic compounds lacking inhalation values. Also, inhalation
slope factors CSFP) and inhalation reference doses f RfDF) were frequently used for both inhaled and
oral exposures for organic compounds lacking oral values.  An additional route extrapolation is the
use of oral tcoddty values for evaluating dermal exposures.  Although route-to-route methods are a
useful screening procedure, the appropriateness of these default assumptions for specific
contaminants should be verifttd by a toxlcologlst

This update contains new toxicity values for arsenic, benzene, 1-ch(oro-1,1-difluoroethane (HCFC-
142b), cobalt, danitol, hydrogen chloride, hydrogen sutftde, methyl mercury, and phosphine. The
updated values are indicated in boldface print In the table.

2.3    Soil Factors:

Chemical-specific information for soils, volatilization factors ("VF,*) and skin absorption factors CABS'),
are listed  in the table to provide additional assumptions used to calculate soil PRQs. For volatile
chemicals, the "VF,* term was incorporated into the PRQ equations to address long-term inhalation
exposures. Volatile organic chemicals (VOCs) are indicated by M* in the VOC column of the Table
and are defined as those chemicals having a Henry's Law constant greater than 10"* (atm-m3/moQ
and a molecular weight less than 200 g/mote).

Chemical-specific soil 'ABS* virtues are provided for arsenic, cadmium, pentachlorophenol, PCBs, and
dioodn as recommended by EPA's Office of Research and Development (1994) for the evaluation of
contaminant absorption through the skin Otherwise, default skin absorption fractions are assumed to
be 0.01 and 0.10, for inorganics and organics, respectively. Although It is debatable whether a
default of 0.10 skin absorption is appropriate for volatile contaminants hi soils, k should be noted that
in practical terms, this assumption makes little difference in the soil PRG because the risk driver for
volatiles is generally based on the soiUo-air pathway and not ingestton or skin contact

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                                 3.0 USING THE PRO TABLE

The decision to use PRQs at a site will be driven by the potential benefits of having generic risk-based
concentrations in the absence of site-specific risk assessments. The original intended use of PRGs
was to provide initial cleanup goals for individual chemicals given specific medium and land-use
combinations (see RAGS Part B, 1991), however risk-based PRQs actually have several uses in
addition to providing initial goals.  These include:

       •      Screening sites to determine further evaluation
       •      Prioritizing areas of concern at megasites (e.g. federal facilities)
       •      Calculating risks associated with multiple contaminants

A few basic procedures are recommended for using PRQs properly. These are briefly described
below. Potential problems with the use of PRQs are also identified.

3.1    Developing a Conceptual Site Model

The primary conditRr for use of PRQs is that exposure pathways of concern and conditions at the site
match those taken ir  o account by the PRQ framework.  Thus, it is always necessary to develop a
conceptual site model (CSM) to identify Bkety contaminant source areas, exposure pathways, and
potential receptors. This information can be used to determine the applicability of PRQs at the site
and the need for additional information. For those pathways not covered by  PRQs, a risk assessment
specific to these additional pathways may be necessary. Nonetheless, the PRQ lookup values will still
be useful in such situations for focusing further investigative efforts on the exposure pathways not
addressed.

To develop a  site-specific CSM, perform an extensive records search and compile existing data  (e.g.
available site sampling data, historical records, aerial photographs, and hydrogeologic information).
Once this  information is obtained, CSM worksheets such as those provided in ASTM's Guide for Risk-
Based Corrective Action Applied at Petroleum Release Sites (1994) can be used to tailor the generic
worksheet model to a site-specific CSM.  The final CSM diagram represents linkages among
contaminant sources, release mechanisms, exposure pathways and routes and receptors. It
summarizes our understanding of the contamination problem.

As a final check, the CSM should answer the following questions:

•      Are there potential ecological concerns?

•      Is  there potential for land use other than those covered by the PRQs (that is, residential  and
       industrial)?

•      Are there other Dkety human exposure pathways that were not considered in development of  .
       the PRQs (e.g. impact to groundwater, local fish consumption; raising beef, dairy, or other
       livestock)?

•      Are there unusual site conditions (e.g. large areas of contamination, high fugitive dust levels,
       potential for indoor air contamination)?

tf any of these four conditions exist, the PRQ may need to be modified to reflect this new information.
Suggested references for evaluating pathways not currently evaluated by Region IX PRG's are
presented in Exhibit 3-1.
                                        EXHIBIT 3-1

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              SUGGESTED READINGS FOR EVALUATING SOIL CONTAMINANT
              PATHWAYS NOT CURRENTLY ADDRESSED BY REGION DC PRO*
EXPOSURE PATHWAY
Migration of contaminants to an underlying
potable aquifer
Ingestion via plant uptake
Ingestion via meat or dairy products
Inhalation of volatiles that have migrated Into
basements
Terrestrial environmental pathways
REFERENCE
Technical Background Document for Soil
Screening Guidance - Review Draft
(USEPA 1994C)
Technical Support Document for Land
Application of Sewage Sludge (USEPA 1992a)

Estimating Exposure to Dioxin-Like Compounds
-Review Draft (1994d)
Technical Background Document for Soil
Screening Guidance - Review Draft
(USEPA 1994C)
Role of the Ecological Risk Assessment in the
Baseline Risk Assessment (USEPA 1994e)
3.2    Background Level* Evaluation

A necessary step in determining the usefulness of Region IX PRGs is the consideration of background
contaminant concentrations.  EPA may be concerned with two types of background at sites: naturally
occurring and anthropogenic. Natural background is usually limited to metals whereas anthropogenic
(i.e. human-made) background includes both organic and inorganic contaminants. Before embarking
on an extensive sampling and analysis program to determine local background concentrations in the
area, one should first compile laxteting data on the subject Far too often there is pertinent information
in the literature that gets ignored, resulting in needless expenditures of time and money.

Generally EPA does not dean up below natural background.  If natural background concentrations are
higher than the PRGs, the generic PRGs may not be the best tool for site dedsionmaking. Or, an
adjustment of the PRG may be needed.  For example, naturally occurring arsenic frequently is higher
than the soil PRG set equal to a one-in-one-million cancer risk (the point of departure), thus an
alternative PRG for arsenic is provided hi the  lookup tables based on non-cancer endpoints that is still
protective of cancer risks as wefl (Le. falls within EPA's •acceptable* risk range). Because of the
problems associated with adjusting PRGs to an alternate risk level, this procedure is not
recommended without first consulting a staff toxfcotogist at state and / or federal regulatory agencies.

Where anthropogenic background levels exceed PRGs and EPA has determined that a response
action is necessary and feasible, EPA's goal win be to develop a comprehensive response to the
widespread contamination. This will often require coordination with different authorities that have
jurisdiction over the sources of contamination in the area

3.3    Rtok Screening

A suggested stepwise approach for screening sites with PRGs is as follows:

       •      Perform an extensive records search and compile existing data

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              Identify site contaminants in the PRQ Table. Record the PRO concentrations for
              various media and note whether PRQ is based on cancer risk (Indicated by 'ca') or
              noncancer hazard (indicated by "nc"). Segregate cancer PRGs from non-cancer PRGs
              and exclude (but don't eliminate) non-risk based PRGs ("sat* or 'max*).

              For cancer risk estimates, take the site-specific concentration (maximum or 95 UCL)
              and divide by the PRQ concentrations that are designated for cancer evaluation Cca").
               Multiply this ratio by Iff* to estimate chemical-specific risk. For multiple pollutants,
              simply add the risk for each chemical :


                                            conc_.    .cone.
       •      For non-cancer hazard estimates. Divide concentration term by its respective non-
              cancer PRQ designated as •nc* and sum the ratios for multiple contaminants. [Note
              that carcinogens may also have an associated non-cancer PRG that is not listed in the
              printed copy of the table and these will also need to be obtained in order to complete
              the non-cancer evaluation.]  The non-cancer ratio represents a hazard index (HI).  A
              hazard index of 1 or less is generally considered safe . A ratio greater than 1
              suggests further evaluation:


                     „     j , j      ,i cone..
                     *«ard index- [(_•)


For more information on screening site risks, the reader should contact EPA Region DCs Technical
Support Section.

3. 4   Potential ProMenw:

As with any risk-based tool, the potential exists for misapplication. In most cases the  root cause will
be a lack of understanding of the intended use of Region DC PRGs.  In order to prevent misuse of
PRQs, the following should be avoided:

       •      Applying PRQs to a site without adequately developing a conceptual  site model that
              identifies relevant exposure pathways and exposure scenarios,

       •      Not considering background concentrations when choosing PRQs as  cleanup goals,

       •      Use of PRQs as cleanup levels without the nine-criteria analysis specified in the
              National Contingency Plan (or, comparable analysis for programs outside of
              Superfund),

       •      Use of PRQs as cleanup levels without verifying numbers with a toodcotogist,

       •      Use of antiquated PRQ tables that have been superseded by more recent
              publications,
       •      Not considering the effects of addKMty when screening multiple chemicals, and

       •      Adjusting PRQs upward by factors of 10 or 100 without consulting a toxicotogist


                                             a

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                        4.0 TECHNICAL SUPPORT DOCUMENTATION

PRQs consider human exposure hazards to chemicals from contact with contaminated soils, air, and
water. The emphasis of the PRG equations and technical discussion are aimed at developing initial
goals for soils, since this is an area where few standards exist For air and water, additional reference
concentrations or standards ate available for many chemicals (e.g. non-zero MCLQs, AWQC, and
NAAQS) and consequently the discussion of these media are brief.

4.1    Inhalation of Volatile* and Fugitive Dusts:

Agency toxicrty criteria indicate that risks from exposure to some chemicals via inhalation far outweigh
the risk via ingestion; therefore soil PRQs have been designed to address this pathway as well.  The
models used to calculate PRGs for Inhalation of votetiles / particulates are updates of risk assessment
methods presented in RAGS Part B (USEPA1991 a) and are consistent with the Technical Background
Document tor Soil Screening Guidance - Review Draft  (USEPA 1994c).

To address the soil-to-air pathways the PRG calculations incorporate volatilization factors (VF,) for
volatile contaminants and paniculate emission factors (PEF) for nonvolatile contaminants. These
factors relate soil contaminant concentrations to air contaminant concentrations that may be inhaled
on-site.  The VF, and PEF equations can be broken into two separate models:  an emission model to
estimate emissions of the contaminant from the soil and a dispersion model to  simulate the dispersion
of the contaminant in the atmosphere.

It should be noted that the box model in RAGS Part B has been replaced with a dispersion term (Q/C)
derived from a modeling exercise using meteorologicaJ data from 29 locations across the United
States because the box model may not be applicable to a broad range of site types and meteorology
and does not utilize state-of-the-art techniques developed for regulatory dispersion modeling.  The
dispersion model for both volatiles and particulates is the AREA-ST, an updated version of the Office
of Air Quality Planning and Standards, Industrial Source Complex Model, ISC2. However, different
O/C terms are used in the VF and PEF equations.  Los Angeles was selected as the 90th percentite
data set for volatiles and Minneapolis was selected as the 90th percentite data set for fugitive dusts
(USEPA 1994c).  A default source size of 0.5 acres was chosen for the PRG calculations. This is
consistent with the default exf>osure area over which Region DC typically averages contaminant
concentrations in soils.  This differs from the default (30 acres) assumed in Technical Background
Document for Soil Screening Guidance • Review Draft  (USEPA 1994c).  However, based on
communications with project managers and technical staff, an assumed contaminant source size of 30
acres was considered inappropriate for most sites.  If unusual site conditions exist such that the area
source is substantially larger than the default source size assumed here, an alternative Q/C could be
applied (see USEPA 1994C).

Volatilization Factor for Softs

Volatile chemicals, defined as those chemicals having a Henry's Law constant greater than 10"5 (atm-
m3/moT) and a molecular weight less than 200 g/mote, were screened for inhalation exposures using a
volatilization factor for soils (VF,).

The emission terms used in the VF, are chemical-specific and were calculated from physical-chemical
information obtained from a number of sources including Superfund Exposure Assessment Manual
(SEAM, EPA 1988), Superfund Public Health Evaluation Manual (EPA 1986), Subsurface Contamination
Reference Guide (EPA 1990a) and fan and Exposure Data  (Howard 1991).  In  those cases where
Diffusivity Coefficients (Di) were not provided in existing literature, Di's were calculated using Fuller's
Method described in SEAM.  A surrogate term was required for some chemicals that lacked physico-

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chemical information. In these cases, a proxy chemical of similar structure was used that may over- or
under-estimate the PRG for soils. Physical-chemical information is available in the electronic version of
the PRO table. To access this information, the user should display the hidden columns in the table.

Equation 4-9 forms the basis for deriving generic soil PRQs for the inhalation pathway. The following
parameters in the standardized equation can be replaced with specific site data to develop a simple
site-specific PRO

       •      Source area
       •      Average soil moisture content
       •      Average fraction organic carbon content
       •      Dry soB bufc density

The basic principle of the VF,  model is applicable only If the son contaminant concentration is at or
below soil saturatioa Above this level the model cannot predict an accurate VF. If the PRG
calculated using VF, was greater than the calculated •saf (Equation 4-10), the PRG was set equa
•sar in accordance with Risk Assessment Guidance for Superfund - Pan B (EPA. 1991).

Volatilization Factor for Tap Water

For tap water, an upperbound volatilization constant (VFJ is used that is based on all uses of
household water (e.g showering, laundering, and dish washing).  Certain assumptions were made.
For example, it is assumed that the volume of water used in a residence for a family of four is 720
tyday, the volume of the dweffing is 150,000 L and the air exchange rate is 0.25 air changes/hour
(Andelman in RAGS Part B). Furthermore, It is assumed that the average transfer efficiency weighted
by water use is 50 percent (Le. half of the concentration of each chemical In water will be transferred
into air by all water uses).  Note: the range of transfer effldendes extends from 30% for toilets to 90%
for dishwashers.

Paniculate Emission Factor for Soils

Inhalation of chemicals adsorbed to respirabie particles (PM10) were assessed using a default PEF
equal to 1.316 x 109 m'/kg that relates the contaminant concentration in soil with the concentration of
respirabie particles in the air due to fugitive dust emissions from contaminated soils. The relationship
is derived by Cowherd (1985)  for a rapid assessment procedure applicable to a typical hazardous
waste site where the surface contamination provides  a relatively continuous and constant potential for
emission over an extended period  of time (e.g. years). This may not be an appropriate assumption
for an sites.

The impact of the PEF on the  resultant PRG concentration (that combines soil exposure pathways for
ingestion, skin contact,  and inhalation) can be assessed by downloading the PRG tables and
displaying the hidden columns.  With the exception of specific heavy metals, the PEF does not appear
to significantly affect most soil PRGs. Equation 4-11  forms the basis for deriving a generic PEF for the
inhalation pathway.  For more details regarding specific parameters used in the PEF model, the reader
is referred to Technical Background Document for Soil Screening Guidance - Review Draft  (December
1994).

Note:  the PEF considers windbome emissions and does not consider dust emissions from traffic
or other forms of mechanical disturbance.

4.2     Dermal Absorption of Contaminants In Soil:


                                             10

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Much uncertainty surrounds the determination of hazards associated with skin contact with soils.
Thus far, chemical-specific absorption values for skin have been recommended for only five chemicals
by EPA's Office of Research and Development   For all other chemicals,  default absorption values for
inorganics and organics are assumed to be 1 and 10 percent, respectively.  An additional uncertainty
is the lack of toxicity values for the dermal route. For screening purposes it is assumed that dermal
toxicrty values can be route-to-route extrapolated from oral values but this may not always be an
appropriate assumption and should be checked.

At 10 % skin absorption, the dermal dose is estimated to equal an ingestion dose for adults, using
the best estimate default values in Dermal Exposure Assessment  Principles end Applications (EPA
1992). At 1 % absorption, the dermal dose is estimated to be 10% of the oral dose (Le. based on an
adult ingestion rate of 100 mg/day). Note:  worker and children intake rates, 50 mg/day and 200
mg/day,
respectively, yield somewhat different results.

                                dermal dose « ingestion dose


                                  x ABS x AF x SA - C^ x IR
                        ABS -	0>10
                               t(0.2jng/cma-day) (5000cm2)]

4.3    Exposure Factors:

Default exposure factors were obtained primarily from RAGS Supplemental Guidance Standard
Default Exposure Factors (OSWER Directive, 9285,6-03) dated March 25,1991 and supplemented with
more recent information from U.S. EPA's Office of SoHd Waste and Emergency Response, U.S. EPA's
Office of Research and Development, and California EPA's Department of Toxic Substances Control
(see Exhibit 4-1).

Because contact rates may bo different for children and adults, carcinogenic risks during the first 30
years of life were calculated using age-adjusted factors Cadf). Use of age-adjusted factors are
especially important for soil ingestion exposures, which are higher during childhood and decrease with
age. However, for purposes of combining exposures across pathways, additional age-adjusted factors
are used for inhalation and dermal exposures. These factors approximate the integrated exposure
from birth until age 30 combining contact rates, body weights, and exposure durations for two age
groups - small children and adults. Age-adjusted factors were obtained from RAGS PART B or
developed by analogy (see derivations next page).

For soils only,  noncardnogenic contaminants are evaluated in children separately from adults. No
age-adjustment factor is used in this case. The focus on children is considered protective of the
higher daily intake rates of soil by children and their lower body weight  For maintaining consistency.
when evaluating soils, dermal and inhalation exposures are also  based on childhood contact rates.
 (1)     Jngestton([mg»yr]/[kg»d]:

                                             11

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                                         IRSe    (EDr - £DC)  X IRS.
                                          —
                              ;       BWe               Bff,


(2)     skin contact([mg»yr]/(kg»d]:

                              EDe X AF X SAe    (JED, - EDe)  X
                          >         BWe


(3)     inhalation ([m3«yr]/Ikg*d]):
4.4    PRO Equations:

The equations used to calculate the PRQs for carcinogenic and noncarcJnogenic contaminants are
presented in Equations 4-1 through 4-8. The PRQ equations update RAQS Part B equations.  Briefly,
PRQs are risk assessments run in reverse.  The methodology backcalculates a soil, air, or water
concentration level from a target risk (for carcinogens) or hazard quotient (for noncarcinogens). For
completeness, the soil equations combine risks from ingestion, skin contact, and inhalation
simultaneously. Note: the electronic version of the table also includes route-specific PRQs that are
similar to OSWER's Soil Screening Levels (EPA 1994c), should the user dedde against combining
specific exposure pathways or wants to identify the relative contribution of each pathway to the
resulting contaminant concentration in soil

To calculate PRQs for vciatite chemicals in soil, a chemteakspedfic volatilization factor is calculated
per Equation 4-9. Because of its reliance on Henry's law, the VF model is applicable only when the
contaminant concentration in soil water is at or below saturation (Le. there is no free-phase
contaminant present). This corresponds to the contaminant concentration in soil at which the
adsorptive limits of the soil particles and the solubility limits of the available soil moisture have been
reached. Above this point, pure liquid-phase contaminant is expected in the soil The updated
equation for deriving (sat) is presented in Equation 4-1 a Note that it supersedes the equation
presented in RAQS Part B.
                                             12

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                                                EXHIBIT 4-1
                                    STANDARD DEFAULT FACTORS
Symbol

CSFo
CSFi
RfDo
RfOi

TR
THQ

BWa
BWc

ATc
ATn

SA«
SAc
AF
ABS
IRA*
tRAc

IRWa
IRWc

IRS*
IRSe
IRSo

EFr
EFo
EDr
EDc
EOo
IFSedJ
SFSadj
InhFadj
IFWadj

VFw
PEF
VFe

Mt
Definition (units)

Cancer slop* factor oral (mg/kg-d)-1
Cancer slop* factor inhaled (mg/kg-d)-1
Reference dose onil (mg/kg-d)
Reference doee inhaled (mo/kg-d)

Target cancer riek
Target hazard quotient

Body weight aduK (kg)
Body weight child (kg)
                       Default
Averaging time <
Averaging time <
carcinogens (days)
noncarclnogene (day*)
25% Surface area, adult (cm2/day)
25% Surface area, child (cm'/day)
Adherence factor (mg/cm*)
Skin absorption  (unMees):
- organic*
-Inorganic*

Inhalation rate • adult (m'/day)
Inhalation rat* • child (m'/day)
10"
1

70
15

25550
ED*365

5000
2000
02

0.1
0.01

20
10
Drinking water ingestion • adult (Uday      2
Drinking water tag«stion • child (Uday)     1

Soil mgestion - adult (mg/day)            100
Soil ingectfon • child (mg/day),            200
Soil ingestion - occupational (mg/day)       50

Exposure frequency - residential (oVy)      350
Exposure frequency • occupational (d/y)    250
Exposure duration - residential (yean)      30*
Exposure duration • child (years)          6
Exposure duration - occupational (years)    25

Age-adjusted factor* for carcinogen*:
IngeeHon factor, eoU* ([n»fl»yr]/Ikg»d])     114
Skin contact factor, soil* flmg«yrj/fkg»d])   503
Inhalation factor flmj»yr]7ltkg»d])          11
Ingeetion factor, water Q>*yr]/Ikg*d])       1.1

Volatilization factor for water (Urn1)        0.5
Paitieulat* emission factor (m'/kg)     See below
Volatilization factor for aoil (m'/kg)     See below
 Soil eaturatie
          i (mg/kg)   See below
            Reference

            IRIS, HEAST, or ECAO
            (RIS. HEAST. or ECAO
            IRIS. HEAST, or ECAO
            rRIS. HEAST, or ECAO
RAOS (Part A),  EPA 1960 (EPA/540/1-88/002)
Expoeur* Factor* , EPA 1991 (OSWER No. 9285.643)

RAQSfPart A), EPA 1969 (EPA/540/149/002)
                                    Dermal Assessment EPA 1992 (EPA/600/8-91/01 IB)
                                    Dermal Assessment EPA 1992 (EPA/ 600/8-9/011B)
                                    Dermal Aa*e**m*nt EPA 1992 (EPA/ 800/8-9/01 IB)

                                    PEA, Ca»-EPA (DTSC. 1994)
                                    PEA. Cal-EPA (DTSC, 1994)

                                    Exposure Factors , EPA 1991 (OSWER No. 9285.6-03)
                                    RAOS (Part A).  EPA 1969 (EPA/540/1 -69/002)

                                    RAQSfPart A). EPA 1989 (EPA/540/1-69/002)
                                    PEA. Cal-EPA (DTSC, 1994)

                                    Exposure Factor* . EPA 1991 (OSWER No. 9285.643)
                                    Expoeur* Factors . EPA 1991 (OSWER No. 9285.643)
                                    Exposure Factors . EPA 1991 (OSWER No. 9285.6-03)

                                    Exposure Factors , EPA 1991 (OSWER No. 9285.6-03)
                                    Exposure Factors . EPA 1991 (OSWER No. 9285.6-03)
                                    Exposure Factors . EPA 1991 (OSWER No. 9285.643)
                                    Exposure Factors . EPA 1991 (OSWER No. 9285.643)
                                    Exposure Factors . EPA 1991 (OSWER No. 9285.6-03)
             RAOS(Part B) . EPA 1991 (OSWER No. 9285.741 B)
             By analogy to RAQS (Part B)
             By analogy to RAQS (Part B)
             By analogy to RAQS (Part B)

             RAQS(Part B). EPA 1991 (OSWER No. 9285.741 B)
             Technical Background Document for Draft SSL (EPA 1994)
             Technical Background Document for Draft SSL (EPA 1994)

             Technical Background Document for Draft SSL (EPA 1994)
Footnote:
"Exposure duration for lifetime resident* i* assumed to be 30 year* total.  For carcinogen*, exposure* are combined for children (6 years)
and adults (24 years).
                                                          13

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                                        PRQ EQUATIONS
       Soil Equations: For soils, equations were based on three exposure routes (ingestion, skin contact,
       and inhalation).
       Equation 4-1: Combined Exposures to Carcinogenic Contaminants In Residential Soil
    /	y i- \                                 TR X AA£

            "  EF  ft1™-* * <**•}  - I SFS^XABSXCSF       InbF^ x CSF,
                 *        '
       Equation 4-2: Combined Exposures to Noncarclnogenlc Contaminants In Residential Soil
                          r,  i        IRSe  %   ,  i      SACXAF X
                EFrxEDe[(—x
       Equation 4-3: Combined Exposures to Carcinogenic Contaminants In Industrial Soil



                                               77? X £Wj X ATe
           .  .
                     ..                             .                         .
                                 10*aig/lcgr              10'mg/kff                VF/

       Equation 4-4: Combined Exposures to Noncarclnogenlc Contaminants In Industrial Soil
               	rap x flya x ATD
   C(mg/kg)  » ~   —--—   -        —   -    -   -         xAFxABS.
                                                      x _t___)  *
Footnote:
*UM VF, for votatflc ctMmio^s (drtmd M having • Hwwy't Lwr ConMuit [«tnMn'/mol] grMtvr «Mn 104 end • metoeuter wright IM« than
200 gnunt/mol) or PEF for nor>voUdil* chemical*.



                                               14

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Tap Water Equations:



Equation 4*5: Ingestlon and Inhalation Exposures to Carcinogenic Contaminants In Water




                 .      	TR x ATe X lOOOuy/mg	
               *    - £f, KIFW^ X CSF0)  *  (VFW X InhFtia X CSFt) ]





Equation 4-6: Ingestlon and Inhalation Exposures to Koncarclnogenlc Contaminants In Water




                                THO X B9fm X ATa X 1000u^/mgr
                 C(ug/L)
                                                  VF_ x IRA..
                                                     ~      '
Air Equations:
Equation 4*7: Inhalation Exposures to Carcinogenic Contaminants In Air
                               ..    TR x ATe x 1000ug/mg

                               l  '  Eft X £*F^ X
Equation 4-8: Inhalation Exposures to Noncarclnogenlc Contaminants In Air
                 -.   ,  M  m THQ x RfDj x Bff, x AT, X IQOOug/my

                    y/                EFt xEDrx IRAt
                                       15

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                            SOIL-TO-AIR VOLATILIZATION FACTOR (VFJ
       Equation 4-9:  Derivation of the Volatilization Factor
where:
                                              (3.14 x a x T)
                                                                1/2
                                                               *«)
                                                                          >-«m2
                                                                 /cm3
Parameter

Q/C

T
Dei

Di
n
w

Pb
P.
H
                                              1 (P.)
Definition funltsl
Volatilization factor (m3/kg)
Inverse of the mean cone, at the center of a
0.5-acre square source (g/rrr^-s per kg/m3)
Exposure interval (s)
Effective diffusivrty (cm2/*)
Air filled soft porosity Q^LMU)
Diffusivrty in air (crrf/s)
Total soH porosity
Default

68.81

7.9x10*
'oc
Average soil moisture content
(0^9rti°rc"'3w*M/9Mii)
Dry soil bulk density (g/cm3)
Soil particle density (g/cm3)
SoO-aJr partition coefficient (g-soil/cm3-air)

Henry's Law constant (atm-m3/mof)
Soil-water partition coefficient (cm'/g)
Soil organic carbon/water partition coefficient (cm3/g)
Fraction organic carbon content of soil (g/g)
0.28 or n-wpb
Chemical-specific
0.43 (loam)
0.1

1.5or(1-n)p.
2.65
(H/Kd)x41
(41 is a conversion factor)
Chemical-specific
                                                                Chemical-specific
                                                                0.02 or site-specific
                                                 16

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                             SOIL SATURATION CONCENTRATION (cat)
       Equation 4-10: Derivation of the Soil Saturation UmH
                                    sat - -f (Kj>b + 8., + H'6.)
Parameter
sat
S
Pb
n
P.
*d
*oc

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                       SOIL-TO-AIR PARTICULATE EMISSION FACTOR (PEF)


       Equation 4-11: Derivation of the Partlculate Emission Factor
                PEF(m>/kg) -  QIC X	3600S/A	
                                         0.036 X (1-V) x (UjUt)* x F(x)
Parameter     Definition (units)                                  Default

PEF           Paniculate emission factor (m3/kg)                  1.316x10°

Q/C    -       Inverse of the mean concentration at the center       90.80
              of a 0.5-acre-square source (g/m2-s per kg/m3)

V             Fraction of vegetative cover (unltless)                0.5

Um           Mean annual windspeed (m/s)                     4.69

U(            Equivalent threshold value of windspeed at 7 m (m/s)  11.32

F(x)           Function dependent on UJU, derived using         0.194
              Cowherd (1985) (unitiess)
REFERENCES


ASTM. 1994. Emergency Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites.
Designation ES 38-94. Philadelphia, Pennsylvania

California EPA. 1994. Preliminary Endangerment Assessment Guidance Manual. Department of Toxic
Substances Control, Sacramento, California

Cowherd, C., Q. Muteski, P. Engelhart, and D. Gillette. 1985. Rapid Assessment of Exposure to Paniculate
Emission from Surface Contamination. EPA/600/8-85/002. Prepared for Office of Health and Environmental
Assessment, U.S. Environmental Protection Agency, Washington, DC. NT1S PB85-192219 7AS.

Howard, P.H. 1990. Handbook of Environmental Fate and Exposure Data for Organic Chemicals.
Lewis Publishers, Chelsea Michigan.

U.S. EPA. 1986. Supertund Public Health Evaluation Manual.  EPA/540/1-86/060.  Office of Emergency and
Remedial Response, Washington, DC.

U.S. EPA. 1988. Superfund Exposure Assessment Manual.  EPA/540/1-88/001. Office of Emergency and

                                               18

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Remedial Response, Washington, DC.

U.S. EPA. 19903. Subsurface Contamination Reference Guide. EPA/540/2-90/011. Office of Emergency and
Remedial Response, Washington, DC.

U.S. EPA 1990b. Exposure Factors Handbook.  EPA/600/8089/043. Office of Health and Environmental
Assessment, Washington, DC.

U.S. EPA,  1991 a Risk Assessment Guidance for Superfund Volume 1:  Human Health Evaluation Manual
(Part B, Development of Risk-Based Prefiminary Remediation Goals).  Publication 9285.7-01 B.  Office of
Emergency and Remedial Response, Washington, DC. NT1S PB92-963333.

U.S. EPA.  1991b. Human Health Evaluation Manual, Supplemental Guidance:  Standard Default Exposure
Factors. Publication 9285.6-03. Office of Emergency and Remedial Response, Washington, DC. NT1S PB91-
921314.

U.S. EPA. 1992a Technical Support Document for Land Application of Sewage Sludge; Volumes I and II. Office
of Water, Washington. DC. B22/R-93-001a,b.

U.S. EPA.  1992b Dermal Exposure Assessment: Principles and Applications. EPA/600/8-91 /011B. Office of
Health and Environmental Assessment, Washington, DC.

U.S. EPA. 1994a. Integrated Risk Information System  (IRIS). Duluth.  MN.

U.S. EPA. 1994b. Health Effects Assessment Summary Tables (HEAST): Annual Update, FY1994.
Environmental Criteria Assessment Office, Office of Health and Environmental Assessment, Office of Research
and Development, Cincinnati, OH.

U.S. EPA. 1994C. Technical Background Document for Soil Screening Guidance.  EPA/540/R-94/106. Office
of Emergency and Remedial Response, Washington, DC. PB95-9633530.

U.S. EPA 1994d. Estimating Exposure to Dtoxin-lflce Compounds. U.S. EPA Office of Research and
Development. EPA/600/6-88/0058.

U.S. EPA 1994e. Role of Ecological Assessment in the Baseline Risk Assessment OSWER Directive No.
9285.7-17.  Office of Solid Waste and Emergency Response, Washington, DC.
                                              19

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 I3C-02I              l3C-02f       0.10            8(02-31-2
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 10C-O3I              10C-03 r       O.IO            OM-BO-0
 3 OE-041              3 OE-04 >       O.IO            08-04-3
 30C-02I   20E-02I    3.OE-O2I       0.10     S OE+04 030-20-0
                                    010     4 9E+04 70-34-9
                                    a 10     1.2E+O4 127-10-4

 30C-02I              lOE-Otl       O.M)            M-00-2
           20E+01r                  a 10            8210-29-1
 3 OE-oa i   24C-oar    a oE-oa i       0.10            OOI-II-B
 B OC-041              O.OC-04r       0.10            3*0*-24-B
 7 OE-OB b                            0.01            IIM-32-B
 • OE-Oa I                            0.01            B03-00-*
 0 OE-Oa I                            0.01            0833-73-0
 O.OE-oai                            0.01            7701-12-0
 • OE-OOI                            0.01            10102-43-1
 o.oE-oa i                            o-ot            tjoao-aa-o
 o.oc-oai                            o.ot            7440-to-o
 I.OE-021              1.0E-OX       0.10            2024O-77-0
 3 oE-oa x              3 oc-oa c       ato            aaoo-24-a
 3 OE-04 h              3 OE-041       O10            M100-10-4
 0OE-021              OOE-O21       010            23804-O9-I
 a oE-oa i              8.oE-oar       010            137-20-0
 O.OE-01 k                            0.01            ft*
 2 OE-OI I              1.1E-OI k       0.10     I.3E+04 IM-O8-3
           &2E+OOr                  0.10            OS-00-7
 OOE-01 k              O.OE-01 f       0 tO            08-70-8
 10E-OI k              KOE-Ot I       0.10            023-40-8
           t.OE-OI I                  atO            108-40-0
           1.1E+OOI                  0.10            OOOt-39-2
 70E-03I              78E-03f       010            OOMt-29-0
 1.36-021              I3E-02I       010            2303-17-8
 I.OE-021              I.OE-02 r       0.10            020*7-90-0
 9OE-03I              8OE-031       010            (18-94-3
 3 OE-OS I               3 OE-001       010            80-30-0
           34E-02I                  0.10           034-03-8
           2.0E-02r                  O.tO           33OH-BO-2
 I.OE-021              a.7E-02k       0.10     t.BE+08120-02-1
 •.OE-02 k              2.0E-OI >       0.10     t.BE+04 71-88-0
4.0E-O3I    8.0E-02I    4.0E-O31       O.IO     I.4E+04 70-00-8
• OE-03 •   0OE-03 •    OOE-03 r       O.IO     7OE+03 70-01-0
30C-OII               20E-Oth       O.tO     2.3E+O17a-0»-4
 1.0E-011               10E-OI r       atO           (8-09-4
           1.1E-02I                  010           00-00-t
 I.OE-021               10E-02 r       0.1O           03-70-0
OOE-031               (OC-Cdr       010           03-72-1
8 OC-031               8OE-03 >       0.10     7 7E+03 800-77-0
• OE-031    70C»OOr    8OE-O3r       OIO     7.7E+O30O-t(-4
80C-03H              8 OE-03 r       0.10     I.2E+04CO-I»-B
                      OOE+OOk       0.10     3.1E+09 70-13-1
                      30C-03f       0.10           B013*-00-2
                      SOE-031       0.10     0.3E+03121-44-0
                      7.8E-03r       010            1902-00-0
           3.7C-02r                  0.10           812-80-1
B OE-001               B OE-OS I       010           M-39-4
 LOC-O2k              I.OE-02 r       0.10           470-49-0
B OE-041    30C-03r    80E-O4I       010           110-00-7
3OE-031                             001           7440-01-1
7 OE-03 k                            001           7440-02-2
• OE-031                             001           1314-02-1
20E-O2k                            0.01           27774-13-0
20E-02h                            001           13701-70-7
 IOE-O3I               I OC-031    0   OIO           IOM-77-7
29C-02I               29E-02r    0   OIO           90471-44-0
 lOE+OOIl              9rE-03l    0   OIO           101-08-4
—         3OE-Olh     .          I   OIO     24E4O2 79-01-4
3 OE+OI I
3.0E-03I
2 OE-01 r
7.8E-03I    77E-03t
                                                                         Stontu*. •**>«•
                                                                         8»ychnln«
                                                               2.3,7.0-TCOO »*M*n)
                                                               T4binMHM
                                                                         T«
                                                                         t**Mi*vn
                                                                         l.2.4.B-T«tacMMDlMn«M
                                                                         1.t.M-T*»MMe«MOiBM
                                                               t.1.2.2-T«*
                                                                                                        (TCMTB)
                                                              2.4.»-Trfc*bronn« _
                                                              2.4.0-TrtckbrewiHn* ny
                                                                         l.1.1-T
                                                                                      (TC6)
                                                                         >.4.0-TitcM>raD«Mnol
                                                                         8.4^-Til
                                                                         2-C2.4£-TrtEMo>qplMne«r) |
                                                                         t,t.2-THcnbcopfoa»n»
                                                                         U,3-Td
                                                                           .
                                                                         t. U-Trtckbn>- 1 .U-
                                                              Trihiram
                                                              TrtHMOtflptKMpni
                                                                         TrtnJkepk
                                                                         2.4,(-Trtn»o«XlMn*
                                                                         UrmnkMi (M>4iM» MJk)
                                                                         VnMdkin)
                                                                         VwMdkim pwitorid*
                                                                         V«»Mn
                                                                         Wictavln
                                                                         VMflcMMUi
O.SE+01 no
4.0E+04 nc
2.0E+Ot nc
2.2E+03MI
1.0£+03nc
3.0E-OOa
4.0E+03nc
l.3E+03nc
0.9E+O2ne
t.OE+OOnc
• BE+01 nc
2 OE+OI nc
4.0E+OOCB
OOE-01 a
7.0E+OOC*

2OE+03nc
2.2E-02a
1.0E+01CB
33E+01 ne
B4E+OOne
OOE+OOnc
tlE+OOnc
OlE+OOnc
•.OE+OOnc
OOE+OOnc
O.IE+OOnc
• SC+Oanc
2 OE+03 no
2.0E+Olnc
B2E+03M
33E+02M
4 OE+04 ne
1OE+O3nc
1.4E-01 a
3 OE+04 no
1.3E+04 nc
23E+OOC*
4 OE-01 a
4 1C 403 nc
0 BE +02 no
09E+O2M
a.3E+O2nc
I.OE+OOne
1.3C+OIC*
t BE +01 a
02E+02nc
3.0E+03at
I4C+OOC*
7.tE+OOa*
7.1E+O2ne
0.9E+03nc
4.0E+01 a
08E+02ne
9.2C+02ne
OtE+Otnc
O.OE-O3 a
7.8E+01 nc
4 IE +03 at
20E+02nc
2.2E+Olne
SOE+Ola**
t.2E+Ola
33E+OOnc
OBE+02nc
I.SE+Ot a**
23C+02nc
B4E+02nc
• OE+Oanc
l9E»03nc
IBE«03nc
• SC40IKC
I«,o3nc
• 5C * 04 ne
82E-O3C*
•.OE+02nc
lOE+OBntti
20E+02nc
22E+03M*
I.TE+OInc
2.4C-oaa
4.0E+04 nc
I.4E+04M
0 OE+03 nc
1.7E+01 nc
OOE+02M
20E+02M
1.2C+01 a
24C+OOa
2.9E+OI a

20E+04nc
• 8C-03a
7.0E+01 a
a.4E«02nc
1.2E+02nc
I.BE+02nc
I4E+02W
1.4E+O2M
I.Se+02nc
t.OE+02nc
l.4E+O2nc
OOE+03nc
2.0E+04 ne
20E+02nc
O.OE+04nc
3.4E+03IK
t.OE+00 MM
2.0E +03 Ml
O.OE-01 a
I.OE+OS MI
LOE+oaMu
I.OE+Ot a
I.TE+OOa
O.IE+O3ne
O.OE+03nc
O.OC+03nc
34C+03 nc
IOC +01 nc
B.OE+OI a
OOE +01 a
B.BC+03HI
3 OE+03 Ml
3.3E+OOa
1.7E+01 a*
2.4E+O3M
• OE+04 nc
l.7E+O2a
OOE+03nc
BSE 403 nc
I.OE+O2nc
LBE-03a
2.0E+O2 nc
4.1E+03al
2.OE«o3nc
OOE+01 nc
29E+02a*
B.2E+01a
34E+01 ne
O.OE+03nc
04E+Ola"
OIE«03nc
l2E«04nc
l.8E«O4nc
34E+04nc
34E+04 nc
• OE«02nc
t 7E404nc
t OC+08 Max
l.lE-02a
37E+OOnc

I.IE+OOnc
t.1E+O3nc
• lE+OInc
49E-OOa
20E+02ne
73E+Olnc
4 7E+OI nc
O.IE-02nc
37E+OOnc
I.IE+OOnc
2.0E-OI a
3 3E-02 a
3.3E+OOa
3.2E-OI
l.lE+02nc
34E-04 a
20E-OI a
t.OE+OOnc







3.7E+Ot nc
t.lE+O2ne
t.tE+oOnc
2.OE+O2nc
I.OE+Ot nc

4.0E*02nc
2 IE-O3c*
2.2E+O3ne
7.3E+02nc
39E-02a
OOE-03 a
2.7C+OI nc
4.7E+OI nc
37E+OI nc
t.OE+OI nc
t.lE-OInc
20E-OI a
23E-01a
2.lE+O2nc
IOE«03nc
1.2E-oia
l.tE+OOa*
7.3E + 02nc
37E+02M
0.2E-01 a
3.7E+01 nc
20E+Otnc
tOE+Otnc
OOE -04 a
t.oE+Oinc
3.IE+04nc
t.lE+Olne
73E+OOM
• 7E-01 c**
1 OE-OI a
1 OE-OI nc
3.7E + OI nc
2.2E-01 ei"





3 7E «00 nc
• IE.OI nc
2 IE f 0?Aec
iX-OJa
37E+Oln4
22E»04nc
LIE +01 nc
I.OE+03M
0.tE+O2nc
4 BE -07 a
2.0E+03HC
73C+02nc
4.7E»02ne
0.1E-01 nc
37E+OI nc
L1E+OI nc
43E-Ola
89E-02a
1 IE «00 a

I.IE+OIne
34E-03 a
20E+OOa
1 OE+OI no
2 OE+OOnc
33E+POM
lOE+OOnc
2.0E+OOnc
3.3E+OOM
33C+OOM
2.0E+OOM
3.7E«02nc
LlE+Oanc
t.lE+Olne
2.OE«03ne
IOE+02nc
2.2E+04 nc
7.2C+O2nc
2lE-02a
22E+04 nc
7.3E+03nc
39E-OI a
OlE-02a
27E+02nc
47E+02nc
37E+02nc
IOE+O2nc
I tE+OOnc
20E+OOa
23E+OOa
10E+02nc
I 36 403 nc
2 OE-OI a
I.OE+OOa*
l.3C«O3nc
3 re 403 nc
0. IE +OO a
37E402M
2 1C 402 nc
30C+Olnc
1 OE-03 a
30C+OIM
90E+04M
1 IE+O2IM
I2E40I nc
07E400a*
IK«OOc«
t«C400nc

22E400a"
1 lE*O2nc
2K402nc
33E»02nc
73E402nc
73E402nc
37E40I nc
• lE«02nc
3rC>04nc
tot -03 if

-------
10E-M I
»OC»OOI
101*001

t.OE«OOI
10E-OII
30E-OII
8.0E-OI I
SOE-Mr
20E-01 *
S.OE-01 •

10E-OK
                     S.OE-OXr
0  0.10
1  0.10
   0.10
   0.10
   0.10
   001
   0.01
                                0  0.10
       01-11-t
4 IE»04 I01-M-3
S.IE»MM-47-«
4.IE404 101-41-3
4.7C«M IMO-H-7
       T440-M-4
       ISI4-M-7
       itia-07-r
•-Kylvw
•-Xytan*
                                                                                                                   roe »oi M
                                                                      tOEMBn*
OOE«C9Ml
ISEtOtiw
2.9E*01M
                                                                      0«E»« Ml
                                                                      o.tc«oa M
                                                                      t.OE»08 Mi
                                                                      •.1E»09ne
                                 l.1C*OOnc
                                 TX4C0M
                                 ?.JE«-O2nc
1 IE«01 nc
14C403M
                                                                                                                                               ME«Mnc
                                                                                                                                               I.IEtOI tic
                                                                                                                                               IJEtUnc

-------
           APPENDIX B

   RESIDUAL RISK CALCULATIONS
RISK ASSUMPTIONS AND UNCERTANTIES

-------
                                                                TABLE B.l-1
                           SUMMARY OF SITE INVESTIGATION, RISK, AND PROPOSED SOIL REMOVAL QUANTITIES
                                                               WASTE PILE 6
Site Am Impacted Ana (ft1)
Site Name Description & Volume (cy) (1)
22 Waste Pile 6 Car Battery
Area
Radio Battery
Area

Unknown Battery
Area
Asphalt Drum
Pile




Roofing Material
Pile

Metal Debris
Pile
Empty Drum
Pile
7ft1
(0.2 cyj
800ft1
(30 cy)

7ft1
(0.2 cy)
1.300ft1
(49 cy)




50ft2
(3.5 cy)

78 ft1
(25 cy)
70ft1
(12 cy)
Constituents of
Concern (COCs) (1)
Antimony
Lead
Antimony
Cadmium
Lead
Lead

B(a)A
B(a)P
B(b)F
Arsenic
Chromium
Lead
B(a)P
B(b)F
l(!23cd)P
Cadmium

Chromium

coc
Concentration (1)
(rag/kE)
823
5,910
71
41.9
1,560
3.410

1.9
1.3
7.6
73.8
1.270
903
15
32
5.6
183

1.290

PRGorBkgnd
Concentration (1) Hazard Cancer Lead Soil
(mx/kt) Indei(l) Rlsk(l) Rlsk(l) Sample No (1)
63
400
63
38
400
400

0.61
0.061
0.61
62
1.080
400
0.061
0.61
0.61
38

1.080

27 2.0E-I2 Yes S010

12 3.0E-08 Yes SOI 2


nc nc Yes S015

3 3.0E-04 Yes SI45
SI46
S147
SI65
SI66
SI67/SI68
3 5.0E-04 No SI 48


6 I.OE-07 No SI63

0.01 3.0E-05 Yes S164

Soil
Removal
Quantity (2)
7ft1
(0.2 cy)
800ft1
(30 cy)

7ft1
(0.2 cy)
1.300ft1
(49 cy)




50ft1
(3.5 cy)

78ft1
(25 cy)
70ft1
(12 cy)
(I) Source: Operable Unit 3 Remedial Investigation Report - Final (December 19%).
(2) Source: Operable Unit 3 Focused Feasibility Study Report (January 1997).

-------
                                                                         TABLE B.l-2
                                   DATA SUMMARY AND SCREENING FOR MAXIMUM RESIDUAL CONCENTRATIONS (1)
                                                                        WASTE PILE 6

SMI*
Nmfetr /
$009
son
SOI)
SOI4
SOI6
SOI 7
SOI 8
SOI9
5020
S02I
son
soy
S024
S025
S033
sow
S0.1)
Muhnum
Background
Bkgnd Exceeded
Avence

milnim
ND
ND
2.43
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
14.3
ND
ND
14.3
63
No


r AIMS*
31.1
50.3
J 17.1
28.8
21
2.M
0.39) 1
16.3
12.1
11.9
18.9
21
19.)
21.2
J 44.)
32.1
30.1
50.3
62
No


Cilia •>••
6.13
4.61
4.39
ND
2.)9
ND
ND
3.))
).62
I.B9
6.03
654
6.54
4.86
6
741
).)
7.61
6.S
Yet
3.2

CkrwBtai
367
IIM
966
663
759
117
21
492
70S
341
994
1070
885
894
947
1020
709
1100
1080
No
721.2

» Lewi
162
(2) 70.1
84
72.7
241
8.94
1 4.11
32.2
45.6
51
108
126
59.2
127
73.1
64.6
41
248 J
166
(3) Ye«
82.2

A 1-1134
NA
NA
NA
NA
NA
NA
NA
ND
ND
ND
ND
ND
ND
ND
NA
NA
NA
0




AMMO
NA
NA
NA
NA
NA
NA
NA
ND
ND
ND
ND
ND
ND
ND
NA
NA
NA
0




alph*
CMordmw
NA
NA
NA
NA
NA
NA
NA
ND
ND
ND
ND
ND
ND
ND
NA
NA
NA
0



o
gwnma-
CMontem
NA
NA
NA
NA
NA
NA
NA
ND
ND
ND
ND
ND
ND
ND
NA
NA
NA
0



MtCCtttrBflOtl (l
• 4.4-DDD
NA
NA
NA
NA
NA
NA
NA
ND
ND
ND
ND
ND
ND
0.6044 1
NA
NA
NA
0.0044



nt/kf)
4v4-DOB
NA
NA
NA
NA
NA
NA
NA
0.0027 J
ND
0.00083 1
ND
ND
0.01) J
0.11 1
NA
NA
NA
0.11




4,4-DDT
NA
NA
NA
NA
NA
NA
NA
0.003 J
ND
0.0031 I
ND
ND
00013 I
&OOM J
NA
NA
NA
0.0056




k-BHC
NA
NA
NA
NA
NA
NA
NA
ND
ND
ND
ND
ND
UOM9 1
ND
NA
NA
NA
0.00089




Xi)A
NA
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
0




BMP
NA
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
0




Bf»)F
NA
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
0




KI23cd)l
NA
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
0




• DEHP
NA
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
6.4
0.3 J
0.4




DMdrta
NA
NA
NA
NA
NA
NA
NA
ND
ND
ND
ND
ND
ND
ND
NA
NA
NA
0




Ewtrte
NA
NA
NA
NA .
NA
NA
NA
ND
ND
OJ0052 j
ND
ND
ND
ND
NA
NA
NA
0.00052



(I) Source of data: Operable Unit 3 Remedltl Investigation Report - Hnal (December 1996)
(2) Bold indicates the maximum detected value for I given chemical.
(3) Concentration it not significantly greater than background, baaed on the conclusions of the Rl Report.

-------
                                                             TABLE B.l-3

                                        RESmENTIAL RESIDUAL HEALTH RISK EVALUATION
                                                            WASTE PILE 6
Residential Exposure
Region IX PRG (mg/kx) (1) Point Concentration (2) EPC/PRG Ratio
Constituent
Cadmium
Lead
4,4-DDD
4,4-DDE
4.4-DDT
beta-BHC
DEHP
Endrin

Cancer
1400
na
1.9
1.3
1.3
0.25
32
na

Noncancer
38
na
na
na
33
na
1300
20

(me/kg)
7.61
248
0.0044
0.11
0.0056
0.0009
0.4
0.0005

Cancer
0.0054
nc
0.0023
0.0846
0.0043
0.0036
0.0125
nc

Noncancer
0.20
nc
nc
nc
0.00017
nc
0.00031
0.00003
Total:
Residual
ELCR (3)
5.E-09
nc
2.E-09
8.E-OS
4.E-09
4.E-09
l.E-08
nc
l.E-07
Residual
HI (4)
0.20
' nc
nc
nc
0.00017
nc
0.00031
0.00003
0.20
Notes:
(I) Source: Region DC Preliminary Remediation Goals (PRGs) Second Half 1995; refer to 'Appendix A'.
(2) The maximum'concentration remaining over the entire area of Waste Pile 6 post-remediation was assumed as the exposure point concentration.
(3) Excludes risks associated with beryllium and chromium, which were determined in the RI Report to be representative of background.
(4) Excludes hazards associated with beryllium and manganese, which were determined in the RI Report to be representative of background.

ELCR - Excess lifetime cancer risk.
EPC - Exposure point concentration.
HI - Hazard Index.
na - Not available.
nc • Not calculated.
PRG - Region IX Preliminary Remediation Goal.

-------
                                                             TABLE B.I-4

                                        INDUSTRIAL RESIDUAL HEALTH RISK EVALUATION
                                                            WASTE PILE 6
Residential Exposure
Rerion IX PRG (m*/k*) (1) Point Concentration (2) EPC/PRG Ratio
Constituent
Cadmium
Lead
4,4-DDD
4.4-DDE
4,4-DDT
beta-BHC
DEHP
Endrin

Cancer
3000
na
7.9
5.6
5.6
1.1
140
na

Noncancer
850
na
na
na
340
na
14000
200

(mg/kg)
7.61
248
0.0044
0.11
0.0056
0.0009
0.4
0.0005

Cancer
0.0025
nc
0.0006
0.01%
0.0010
0.0008
0.0029
nc

Noncancer
0.01
nc
nc
nc
0.00002
nc
0.00003
0.00000
Total:
Residual
ELCR (3)
3.E-09
nc
6.E-IO
2.E-08
l.E-09
8.E-IO
3.E-09
nc
3.E-08
Residual
HI (4)
0.01
nc
nc
nc
0.00002 _
nc
0.00003
0.00000
0.01
Notes:
(I)  Source: Region IX Preliminary Remediation Goals (PRGs) Second Half 1995; refer to 'Appendix A'.
(2) The maximum concentration remaining over the entire area of Waste Pile 6 post-remediation was assumed as the exposure point concentration.
(3)  Excludes risks associated with beryllium and chromium, which were determined in the RI Report to be representative of background.
(4)  Excludes hazards associated with beryllium and manganese, which were determined in the RI Report to be representative of background.
ELCR - Excess lifetime cancer risk.
EPC - Exposure point concentration.
HI • Hazard Index.
na - Not available.
nc - Not calculated.
PRG - Region IX Preliminary Remediation Goal.

-------
                                                               TABLE B.l-5
                           SUMMARY OF SITE INVESTIGATION, RISK, AND PROPOSED SOIL REMOVAL QUANTITIES
                                                               LANDFILL 29
Site Area Impacted Area (ft1)
Site Name Description ft Volume (cy) (1)
24 Landfill 29 Surface
Dram Area
Subsurface
Metal Area
175ft2
(3! cy)
52M2
(4cy)
Constituents of
Concern (COCs)(l)
Antimony
Lead
Antimony
Lead
COC
Concentration (1)
(rag/kg)
224
18.700
123
1,120
PRGorBkgnd
Concentration (1) Hazard Cancer Lead Soil
(mc/kR) Index (1) Rlsk(l) RJsk(l) Sample No (1)
63 10 2.0E-04 Yes S149
400 SI50
SISI
63 4 4.0B-I3 Yes SI62
400
Soil
Removal
Quantity (2)
I75R2
(31 cy)
S2R2
(4cy)
(I) Source: Operable Unit 3 Remedial Investigation Report - Final (December 19%).
(2) Source: Operable Unit 3 Focused Feasibility Study Report (January 1997).

-------
                                                             TABLE B.I-6
                          DATA SUMMARY AND SCREENING FOR MAXIMUM RESIDUAL CONCENTRATIONS (1)
                                                            LANDFILL 29
Sample
Number
SOOI
S002
S003
S004
S005
S006
S007
S138
SI39
SI40
SI41
SI42
SI43
SI52
S153
S154
SI55
SI56
S157
SI58
SI59
SI61
Maximum
Background
Bkgnd Exceeded
Average
Concentration (m£/kg)
Antimony
ND
ND
ND
ND
ND
18.2 J
ND
ND
ND
6.12 J
ND
ND
ND
31.4
11.2 J
16.6 J
8.98 J
ND
15 J
56.2
26.3 J
14.2 J
56.2
63
No

Arsenic
0.378 J
18.6
5
14.5
12.3
17.3
0.504 J
26.6
5.53
40.2
9.2
9.15
2.72
12.1
58.9
61.5
44.9
56
35.7
2.51
71.3
50.2
71.3
62
No (3)
25
Manganese
43.4
1610
229
267
462
1020
37.1 J
985
270
386
280
241
226
787
3010
4700
5040
1830
1720
103
2380
4890
5040
3150
No (3)
1387
Lead
7.86 J
31.7 J
321 J (2)
26.1 J
43.2 J
122 J
12 J
36.6
41.6
85
18.9
18.2
54.5
266
37.7
34.8
33.3
44.1
44.7
30.3
41.9
34.8
321 J
166
Yes
63
Acetone
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
0.018 J
0.018 J
0.0095 J
ND
0.0
ND
0.0099 J
0.013
0.018 J



MEK
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA*
NA
NA
ND
ND
ND
ND
ND
ND
ND
0.011
0.011



2-Hexanone
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
0.0052 J
NA
ND
0.0047 J
ND
ND
ND
J 0.0091 J
J 0.0091 J



MIBK
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
0.0047 J
ND
ND
0.0055 J
ND
ND
ND
0.010 J
0.010 J



Toluene
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
0.0013
ND
ND
ND
0.0022
ND
ND
ND
0.0022


















J



J



J



(1) Source of data: Operable Unit 3 Remedial Investigation Report - Final (December 1996).
(2) Bold indicates the maximum detected value for a given chemical.
(3) Concentration is not significantly greater than background, based on the conclusions of the RI Report.

MEK - Methyl ethyl ketone (2-Butanone)
MIBK • Methyl isobutyl ketone (4-Me(hyl-2-pcntanone)

-------
                                                             TABLE B.l-7

                                        RESIDENTIAL RESIDUAL HEALTH RISK EVALUATION
                                                            LANDFILL 29
Residential Exposure
Reckm IX PRG (mc/kc) (1) Point Concentration (2) EPC/PRG Ratio
Constituent
Lead
Acetone
MEK
2-Hexanone
MIBK
Toluene

Cancer
na
na
na
na
na
na

Noncancer
na
2000
8700
na
5200
1900

(me/kg)
321 (5)
0.018
0.011
0.0091
0.010
0.0022

Cancer
nc
nc
nc
nc
nc
nc

Noncancer
nc
0.00001
0.000001
nc
0.000002
0.000001
Total:
Residual
ELCR (3)
nc
nc
nc
nc
nc
nc
nc
Residual
HI (4)
nc
0.00001
0.000001
nc
0.000002
0.000001
0.00001
Notes:
(I)  Source: Region IX Preliminary Remediation Goals (HRGs) Second Half 1995; refer to 'Appendix A'.
(2) The maximum concentration remaining over the entire area of Landfill 29 post-remediation is assumed to be the exposure point concentration.
(3)  No carcinogenic chemicals at concentrations above background remain at Landfill 29 post-remediation; therefore, a residual ELCR was not calculated.
(4)  Excludes hazards associated with arsenic and manganese, which were determined in the RI Report to be representative of background.
(5)  The exposure point concentration for lead is below the residential screening criterion of 400 mg/kg.

ELCR - Excess lifetime cancer risk.
EPC - Exposure point concentration.
HI - Hazard Index.
MEK -  Methyl ethyl ketone (2-Butanone)
MIBK - Methyl isobutyl ketone (4-Methyl-2-pentanonc)
na - Not available.
nc - Not calculated.
PRG - Region IX Preliminary Remediation Goal.

-------
                                                              TABLE B.I-8

                                         INDUSTRIAL RESIDUAL HEALTH RISK EVALUATION
                                                             LANDFILL 29
Residential Exposure
Region IX PRG (me/kg) (1) Point Concentration (2) EPC/PRG Ratio
Constituent
Lead
Acetone
MEK
2-Hexanone
MIBK
Toluene

Cancer
na
na
na
na
na
na

Noncancer
na
8434
33619
na
54487
2800

(niK/kR)
321 (5)
0.018
0.01 1
0.0091
0.010
0.0022

Cancer
nc
nc
nc
nc
nc
nc

Noncancer
nc
0.000002
0.0000003
nc
0.0000002
0.000001
Total:
Residual
ELCR (3)
nc
nc
nc
nc
nc
nc
nc
Residual
HI (4)
nc
0.000002
0.0000003
nc
0.0000002
0.000001
0.000003
Notes:
(1)  Source: Region IX Preliminary Remediation Goals (FRGs) Second Half 1995; refer to 'Appendix A'.
(2) The maximum concentration remaining over the entire area of Landfill 29 post-remediation is assumed to be the exposure point concentration.
(3)  No carcinogenic chemicals at concentrations above background remain at Landfill 29 post-remediation; therefore, a residual ELCR was not calculated.
(4)  Excludes hazards associated with arsenic and manganese, which were determined in the RI Report to be representative of background.
(5)  The exposure point concentration for lead is below the residential screening criterion of 400 mg/kg.

ELCR - Excess lifetime cancer risk.
EPC - Exposure point concentration.
HI - Hazard Index.
MEK -  Methyl ethyl ketone (2-Butanonc)
MIBK - Methyl isobutyl ketone (4-Methyl-2-pentanone)
na - Not available.
nc - Not calculated.
PRG - Region IX Preliminary Remediation Goal.

-------
                                                                        TABLE B.l-9

                               SUMMARY OF SITE INVESTIGATION, RISK, AND PROPOSED SOIL REMOVAL QUANTITIES
                                                                    MARBO LAUNDRY
COC PRG or Bkgnd
Site Area Impacted Area (n1) Constituents of Concentration (1) Concentration (1) Hazard Cancer Lead Soil
Site Name Description & Volume (cy) (1) Concern (COCs) (1) (mg/Vg) (mg/kg) Index (1) Risk(l) Rlsk(l) Sample No (1)
38 MARBO Building 3,625ft2 Aroclor 1254 1.9 0.066 3 5.0E-05 No SI 20
Laundry Surrounding (I34cy) SI 21
Si22
SI 23
SI24
SI 25
SI26
SI36
SI37
South 9ft' Aroclor 1254 26 0.066 19 4.00E-04 Yes SI28
Transformer Area (0.3 cy) Lead 4,210 400 SI 29
SI30
North 9ft2 Aroclor 1254 1.5 0.066 1 2.0E-05 Yes SI 31
Transformer Area (0.3 cy) Lead 3,080 400 SI 32
SI33
Soil
Removal
Quantity (2)
3,625ft1
(134 cy)







9ft2
(0.3 cy)

9ft2
(0.3 cy)

(I) Source: Operable Unit 3 Remedial Investigation Report - Final (December 19%).
(2) Source: Operable Unit 3 Focused Feasibility Study Report (January 1997).
Note:  Under the selected remeby. all areas of MARBO Laundry containing impacted soils exceeding screening criteria will be excavated and removed from the site. Since all impacted soils
      exceeding screening criteria will be removed, it is anticipated that residual risks will be less than the cancer risk criterion of I.OxlO"* and non-cancer HI of 1.0.

-------
                         TABLE B.M
ASSUMPTIONS AND UNCERTAINTIES: THEIR POSSIBLE EFFECTS ON RISKS
                     SITE 20- WASTE PILE 7
                         (Page 1 of 2)
Assumption/Uncertainty
May
Over-Estimate
Risk
May
Under-Estimate
Risk
May
Over- or Under-
Estimate Risk
HAZARD IDENTIFICATION
Some discrete source areas at this site (the surface drum area and the soil/trash mound) are represented
by only one sample, which was collected in order to locate highest concentrations of constituents.

EXPOSURE ASSESSMENT
USEPA Region IX (1995) PRGs assume that the following soil pathways are complete: ingestion,
dermal contact, and inhalation. The only receptor identified in the conceptual site model with inhalation
as a complete pathway is a construction worker.
In addition to surface soil samples, subsurface samples were evaluated in the industrial scenario. The
only non-residential receptor identified in the conceptual site model with potential to contact subsurface
soil is a construction worker.
Summary statistics calculated for constituents of potential concern assume 1/2 the limit of detection
(LOD) for non-detects. Non-detects are within the range of 0 - LOD.
The 95% upper confidence limit (UCL) or maximum detection is assumed to represent the concentration
to which most people may be exposed.
Media intake is assumed to be constant over time and representative of the exposed population; however,
all exposure factors tend to be upper-bound estimates.
The assessment assumed 100% bioavailability of all constituents for the oral route of exposure.
The noncancer-based residential PRGs for soil are calculated using the exposure factors for a child. This
would overestimate risks for an older receptor.
/


/
/
/
/

/









/
/




TOXIC1TY ASSESSMENT
USEPA Region IX (1995) PRGs incorporate toxicity criteria obtained from IRIS through July 1995 and
from HEAST through November 1994; therefore, toxicity criteria used in this assessment may not be
current.
Both cancer and noncancer endpoinls are calculated for all constituents using the integrated PRG values
(USEPA Region IX, 1995).

/


/


-------
                         TABLE B.2-1
ASSUMPTIONS AND UNCERTAINTIES: THEIR POSSIBLE EFFECTS ON RISKS
                     SITE 20 - WASTE PILE 7
                          (Page 2 of 2)
Assumption/Uncertainty
Not all cancer slope factors (CSFs) or reference doses (RfDs) represent the same degree of certainty.
Toxicity criteria are not available for the dermal route of exposure. Dermal toxicity values are route-to-
route extrapolated from oral values.
The oral CSF for Aroclor 1 260 incorporated into this assessment is 7.7 mg/kg/day ' . This value has
recently been revised to 2.0 mg/kg/day '.
The oral CSF for beryllium is based on a study (Schroeder and Mitchener, I97S) in which the lowest
dose did not have a statistically different tumor incidence than the control.
The critical study for deriving the inhalation unit risk of beryllium did not account for smoking (Wagoner
etal., 1980).
The oral RfD for beryllium is based on a no observed adverse effect level (NOAEL) that is the highest
experimental dose. The NOAEL could be significantly higher.
May
Over-Estimate
Rbk


/
/
/
/
RISK CHARACTERIZATION
The calculated exposure point concentrations for aluminum, antimony, and arsenic were less than the
background values. Inclusion of these constituents in the assessment overestimates risk associated with
past waste disposal practices.
Cancer risks and hazard indices associated with multiple constituent exposure is assumed to be additive.
Risks and hazards may, in fact, be antagonistic (less than additive) or synergistic (more than additive)
with other constituents.
All constituent-specific hazard quotients are summed regardless of target organ.
Risks and hazards associated with multiple exposure pathways are combined.
/

/
/
May
Under-Estimate
Risk






May
Over- or Under*
Estimate Risk
/
; '










/



-------
                         TABLE B.2-2
ASSUMPTIONS AND UNCERTAINTIES: THEIR POSSIBLE EFFECTS ON RISKS
                     SITE 22 - WASTE PILE 6
                         (Page 1 of 2)
Assumption/Uncertainty
May
Over-Esdmate
Risk
May
Under-Estimate
Risk
May
Over- or Under-
Estimate Risk
HAZARD IDENTIFICATION
Most of the discrete source areas at this site (with the exception of the two trenches) are represented by
only one sample, which was collected in order to locate highest concentrations of constituents.
EXPOSURE ASSESSMENT
USEPA Region IX (1995) PRGs assume that the following soil pathways are complete: ingestion,
dermal contact, and inhalation. The only receptor identified in the conceptual site model with inhalation
as a complete pathway is a construction worker.
In addition to surface soil samples, subsurface samples were evaluated in the industrial scenario. The
only non-residential receptor identified in the conceptual site model with potential to contact subsurface
soil is a construction worker.
Summary statistics calculated for constituents of potential concern assume 1/2 the limit of detection
(LOD) for non-detects. Non-detects are within the range of 0 - LOD.
The 95% upper confidence limit (UCL) or maximum detection is assumed to represent the concentration
to which most people may be exposed.
Media intake is assumed to be constant over time and representative of the exposed population; however,
all exposure factors tend to be upper-bound estimates.
The assessment assumed 100% bioavailability of all constituents for the oral route of exposure.
The noncancer-based residential PRGs for soil are calculated using the exposure factors for a child. This
would overestimate risks for an older receptor.



/


/
/
/
/







TOXICITY ASSESSMENT
USEPA Region IX (1995) PRGs incorporate toxicity criteria obtained from IRIS through July 1995 and
from HEAST through November 1994; therefore, toxicity criteria used in this assessment 'may not be
current.


^


/
/





/

-------
                         TABLE B.2-2
ASSUMPTIONS AND UNCERTAINTIES: THEIR POSSIBLE EFFECTS ON RISKS
                     SITE 22 - WASTE PILE 6
                          (Page 2 of 2)
Assumption/Uncertainty
Both cancer and noncancer cndpoints are calculated for all constituents using the integrated PRO values
(USEPA Region IX. 1995).
Not all cancer slope factors (CSFs) or reference doses (RfDs) represent the same degree of certainty.
Toxicity criteria are not available for the dermal route of exposure. Dermal toxicity values are route-to-
route extrapolated from oral values.
The oral CSF for beryllium is based on a study (Schroeder and Mitchener. 1975) in which the lowest
dose did not have a statistically different tumor incidence than the control.
The critical study for deriving the inhalation unit risk of beryllium did not account for smoking (Wagoner
et al., 1980).
The oral RfD for beryllium is based on a no observed adverse effect level (NOAEL) that is the highest
experimental dose. The NOAEL could be significantly higher.
May
Over-Estimate
Risk
/


/
/
/
May
Undcr-EstJmate
Risk






May
Over- or Under-
Estimate Risk

/
/



RISK CHARACTERIZATION
Cancer risks and hazard indices associated with multiple constituent exposure is assumed to be additive.
Risks and hazards may, in fact, be antagonistic (less than additive) or synergistic (more than additive)
with other constituents.
All constituent-specific hazard quotients are summed regardless of target organ.
Risks and hazards associated with multiple exposure pathways are combined.

/
/



/



-------
                         TABLE B.2-3
ASSUMPTIONS AND UNCERTAINTIES: THEIR POSSIBLE EFFECTS ON RISKS
                     SITE 24 - LANDFILL 29
                         (Page 1 of 2)
Assumption/Uncertainty
May
Over-Estimate
Risk
May
Undcr-Estimate
Risk
May
Over, or Under*
Estimate Risk
HAZARD IDENTIFICATION
The metal debris area is represented by only one sample, which was collected in order to locate the
highest concentrations of constituents.
EXPOSURE ASSESSMENT
USEPA Region IX (1995) PRGs assume that the following soil pathways are complete: ingestion,
dermal contact, and inhalation. The only receptor identified in the conceptual site model with inhalation
as a complete pathway is a construction worker.
In addition to surface soil samples, subsurface samples were evaluated in the industrial scenario. The
only non-residential receptor identified in the conceptual site model with potential to contact subsurface
soil is a construction worker.
Summary statistics calculated for constituents of potential concern assume 1/2 the limit of detection
(LOD) for non-detects. Non-detecls are within the range of 0 - LOD.
The 95% upper confidence limit (UCL) or maximum detection is assumed to represent the concentration
to which most people may be exposed.
Media intake is assumed to be constant over time and representative of the exposed population; however,
all exposure factors tend to be upper-bound estimates.
The assessment assumed 100% bioavailability of all constituents for the oral route of exposure.
The noncancer-based residential PRGs for soil are calculated using the exposure factors for a child. This
would overestimate risks for an older receptor.


/

/


/
/
/
/








/
/




TOXICITY ASSESSMENT
USEPA Region IX (1995) PRGs incorporate toxicity criteria obtained from IRIS through July 1995 and
from HEAST through November 1994; therefore, toxicily criteria used in this assessment may not be
current.


/

-------
                         TABLE B.2-3
ASSUMPTIONS AND UNCERTAINTIES: THEIR POSSIBLE EFFECTS ON RISKS
                     SITE 24 - LANDFILL 29
                          (Page 2 of 2)
Assumption/Uncertainty
Both cancer and noncancer endpoints are calculated Tor all constituents using the integrated PRO values
(USEPA Region IX. 1995).
Not all cancer slope factors (CSFs) or reference doses (RfDs) represent the same degree of certainty.
Toxicily criteria are not available for the dermal route of exposure. Dermal toxicity values are route-to-
route extrapolated from oral values.
May
Over-Estimate
Risk
/


May
Under-Estiinate
Risk



May
Over* or Under-
Estimate Risk

/
/
RISK CHARACTERIZATION
The calculated exposure point concentration for arsenic in the landfill area was less than the background
value. Inclusion of this constituent in the assessment overestimates risk associated with past waste
disposal practices.
Cancer risks and hazard indices associated with multiple constituent exposure is assumed to be additive.
Risks and hazards may. in fact, be antagonistic (less than additive) or synergistic (more than additive)
with other constituents.
All constituent-specific hazard quotients are summed regardless of target organ.
Risks and hazards associated with multiple exposure pathways are combined.
/

/
/





/



-------
                        TABLE B.2-4
ASSUMPTIONS AND UNCERTAINTIES: THEIR POSSIBLE EFFECTS ON RISKS
                      MARBO LAUNDRY
                         (Page 1 of 2)
Assumption/Uncertainty
May
Over-Estimate
Risk
May
Under-Estimate
Risk
HAZARD IDENTIFICATION
Both transformer areas at this site are represented by only three samples, which were collected in an
attempt to locate the highest concentrations of constituents.


May
Over- or Under-
Estimate Risk

/
EXPOSURE ASSESSMENT
USEPA Region IX (1995) PRGs assume that the following soil pathways are complete: ingestion.
dermal contact, and inhalation. The only receptor identified in the conceptual site model with inhalation
as a complete pathway is a construction worker.
Summary statistics calculated for constituents of potential concern assume 1/2 the limit of detection
(LOD) for non-detects. Non-detects are within the range of 0 - LOD.
The 95% upper confidence limit (UCL) or maximum detection is assumed to represent the concentration
to which most people may be exposed.
Media intake is assumed to be constant over time and representative of the exposed population; however,
all exposure factors tend to be upper-bound estimates.
The assessment assumed 100% bioavailability of all constituents for the oral route of exposure.
The noncancer-based residential PRGs for soil are calculated using the exposure factors for a child. This
would overestimate risks for an older receptor.
/

/
/
/
/







^




TOXICITY ASSESSMENT
USEPA Region IX (1995) PRGs incorporate toxicity criteria obtained from IRIS through July 1995 and
from HEAST through November 1994; therefore, toxicity criteria used in this assessment may not be
current.
Both cancer and noncancer endpoints are calculated for all constituents using the integrated PRG values
(USEPA Region IX. 1995).
Not all cancer slope factors (CSFs) or reference doses (RfDs) represent the same degree of certainly.

/




/

/

-------
                         TABLE B.2-4
ASSUMPTIONS AND UNCERTAINTIES: THEIR POSSIBLE EFFECTS ON RISKS
                      MARBO LAUNDRY
                         (Page 2 of 2)
Assumption/Uncertainty
Toxicity criteria are not available for the dermal route of exposure. Dermal toxicity values are route-to-
route extrapolated from oral values.
The oral RfD for Aroclor 1254 is based on non-critical health effects such as eye inflammation and nail
growth and on immunologies! changes that are not directly quantifiable to adverse health effects.
The oral CSF for Aroclor 1 254 incorporated into this assessment is 7.7 mg/kg/day '. This value has
recently been revised to 2.0 mg/kg/day '.
The oral CSF for beryllium is based on a study (Schroeder and Mitchener. 1975) in which the lowest
dose did not have a statistically different tumor incidence than the control.
The critical study for deriving the inhalation unit risk of beryllium did not account for smoking (Wagoner
etal., 1980).
The oral RfD for beryllium is based on a no observed adverse effect level (NOAEL) that is the highest
experimental dose. The NOAEL could be significantly higher.
May
Over-Estimate
Risk

/
/
/
/
/
May
Under-Estimate
Risk






May
Over- or Under*
Estimate Risk
/





RISK CHARACTERIZATION
The calculated exposure point concentrations for aluminum, beryllium, and chromium were less than the
background values. Inclusion of these constituents in the assessment overestimates risk associated with
past waste disposal practices.
Cancer risks and hazard indices associated with multiple constituent exposure is assumed to be additive.
Risks and hazards may, in fact, be antagonistic (less than additive) or synergistic (more than additive)
with other constituents.
All constituent-specific hazard quotients are summed regardless of target organ.
Risks and hazards associated with multiple exposure pathways are combined.
/

/
/





/



-------
                             TABLE B.2-5
ASSUMPTIONS AND UNCERTAINTIES: THEIR POSSIBLE EFFECTS ON RISK ESTIMATES
                         OU2 (GROUNDWATER)
                             (Page 1 of 2)
Assumption/Uncertainty
May
Over-Estimate
Risk
May
Under-Estimate
Risk
May
Over- or Undcr-
Estimate Risk
HAZARD IDENTIFICATION
Eliminating constituents whose maxima are within an order of magnitude of their PRGs may miss additive
risks or hazards over 10* or one. respectively.

S
•
EXPOSURE ASSESSMENT
Exposure to constituent concentrations from deep in the aquifer is highly unlikely.
The maximum is assumed to represent the concentration to which most people may be exposed.
Concentration of constituents of potential concern in groundwater is assumed to remain constant over
residential receptors' entire 30-year exposure duration.
Use of production well data rather than tap water for exposure point concentrations of VOCs.
Estimated data are included in quantitative risk assessment.
Dermal exposure pathway is excluded from PRG calculations for tap water.
Media intake is assumed to be constant over time and representative of the exposed population.
Assumed standard assumption for body weight, exposure period and frequency, and life expectancy.
Conservative model used to evaluate volatile emissions to air.
•S
S
S
S


S

S





S







S


S

TOXICITY ASSESSMENT
Carcinogenicity of tetrachloroethene and trichlorcethene in humans is uncertain. Only provisional CSFs are
available for these constituents.
Toxicity criteria were derived from animal studies.
The cancer potencies used are 95% UCLs derived from the linearized multistage model.
Not all carcinogenic potencies or reference doses represent the same degree of certainly.
S
S
•/








S

-------
                             TABLE B.2-5
ASSUMPTIONS AND UNCERTAINTIES: THEIR POSSIBLE EFFECTS ON RISK ESTIMATES
                         OU2 (GROUNDWATER)
                             (Page 2 of 2)
Assumption/Uncertainty
May
Over-Estimate
Risk
May
Under-Estimate
Risk
May
Over- or Under-
Estimate Risk
RISK CHARACTERIZATION
Risk and hazards associated with multiple chemical exposure were assumed to be additive. Risks and
hazards may. in Tact, be antagonistic (less than additive) or synergistic (more than additive) with other
chemicals.
Risks and hazards associated with multiple exposure pathways combined.

•


; •


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            APPENDIX C




REGUIATORY COMMENTS AND RESPONSES

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                RESPONSES TO USEPA REGION IX COMMENTS
                          DATED FEBRUARY 11,1998
        MARBO ANNEX OPERABLE UNIT RECORD OF DECISION (R.O.D.)
                       DRAFT FINAL, DECEMBER 1997
GENERAL COMMENTS

The two references cited throughout these comments are the Interim Final Guidance on Preparing
Superfund Decision Documents (EPA, 1989) and EPA's Record of Decision Checklist for Final
Source Actions (ROD Checklist).

Comment No. 1:          Soil Disposal

                        Under CERCLA, disposal of any soil or debris contaminated
                        with  any  hazardous  substance,  pollutant or  contaminant
                        off-site will be subject to the Off-Site Disposal Rule (40 CFR
                        200.440).  EPA Region 9 has taken the position that on-site is
                        the area designated in the NPL listing and thus the Off-Site
                        Rule  does not apply to the disposal of contaminated soil from
                        one part of Andersen  to another  area within  Andersen.
                        However, such disposal may trigger RCRA as an ARAR.
                        Disposal  of  soil  not  contaminated  with  any  hazardous
                        (substance, pollutant or contaminant may trigger the RCRA
                        Bolid  waste disposal requirements as ARARs.  The ARARs
                        discussion should  more  fully discuss  the  applicability  to
                        inapplicability of the solid waste disposal requirements to the
                        tielected remedy  and, to the extent relevant, explain why the
                        (hazardous waste is not RCRA hazardous waste.

                        The ROD should also clarify whether the "non-hazardous" soil
                        that will be disposed of on-site is merely non-RCRA-hazardous
                        waste or also non-CERCLA-hazardous waste.  The modifier
                        "non-hazardous" should not be used lightly.

Response:                The soil and debris  which is proposed for  disposal at the  AAFB
                        landfill is material which will not exhibit RCRA hazardous waste
                        characteristics under 40 CFR 261.20 through 261.24 and is not
                        listed RCRA hazardous waste under 40  CFR 261.30 through
                        261.33. CERCLA 40 CFR 302.3 defers to RCRA for hazardous
                        waste classification, thus the waste would also not be considered
                        hazardous  under CERCLA  (as  defined  by  RCRA). The
                        classification  of  soil and debris as RCRA hazardous or non-
1 April. 1998® 11:54 AM

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Comment No. 2:



Response:

Comment No. 3:
Response:
hazardous is discussed in the text of the R.O.D. and presently
included as an ARAR in the R.O.D.

The soil and debris which is proposed for disposal at the AAFB
Main  Base landfill is  not a RCRA hazardous waste, but will be
solid  waste.  The Andersen AFB landfill meets the Guam EPA
solid  waste disposal  requirements.  Additionally, construction
activities are in progress at the landfill to meet RCRA Subtitle D
requirements.

For clarification and public record, it is assumed that the Off-Site
rule referenced as 40 CFR 200.440 is 40 CFR 300.440.

The discussion concerning  public meetings to inform the
community of "potential risks" should be expanded to identify
briefly the potential risks.

This is discussed more fully in Section 1.4.

Deed  Restrictions

The ROD needs to identify exactly what deed restrictions will
be placed on the site(s) and explain how and when such deed
restrictions will be executed.

At  page 3-10,  what  will trigger the  land use  restrictions
pertaining  to future  locations  of water wells?  The  ROD
says"~.restrictions  on  the  property   deeds  (if  necessary)
pertaining to.-" If this is a contingency measure, what is the
trigger? Why is this contingent?

Deed  restrictions apply  to Waste Pile  7 as one  of the soil
alternatives, as well as to the selected groundwater alternative. The
intent of the soil cover at Waste Pile 7 is to eliminate or mitigate
the exposure pathway to soils, which slightly exceed the risk
management range of  1x10"* to IxlO"4 under a residential scenario.
The deed restrictions will restrict the future use of Waste Pile 7 to
activities which are non-intrusive to the soil cover, as noted in the
OU 3 Focused Feasibility Study. This does not preclude activities
which  are   non-intrusive;  some examples  may   include   a
maintenance yard or storage area. The deed restrictions will apply
during transfer of ownership, and will apply and be included in the
deed as a land use limitation.
1 April. 1998 @ 11:54 AM

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Comment No. 4:
Response:

Comment No. 5:
Response:


Comment No. 6:
                         Due to the nature  of Guam's aquifer as a sole source  aquifer,
                         production well installation is closely monitored by the Guam EPA
                         through Guam's Groundwater Protection Zone program and strict
                         permitting  requirements.     Guam EPA's "Guam  Wellhead
                         Protection Program" (GWP) (GEPA: March 4,  1993) outlines the
                         requirements and permitting necessary prior to the installation of
                         new wells (Chp VITB), as well as the institutional mechanisms for
                         implementation (Chp mA).  As  GEPA is part of this CERCLA
                         process, and is also the implementor of the GWP program, transfer
                         of groundwater quality information to GEPA's GWP Zone  map
                         will be easily facilitated to safeguard future use of the aquifer.

                         Presuming the cited page is 3-19, the "if necessary" refers to those
                         properties affected by  TCE/PCE where restrictions  would be
                         necessary.  Many  of the  detections at the MARBO Annex are
                         below MCLs and below 1 |ig/l, thus property restrictions may not
                         apply. This has been removed from the text.
In  Section  1.4,  DESCRIPTION  OF
REMEDY, page 1-2:
THE  SELECTED
This section does not seem to include an explanation of how
tltiis response action (remedy) fits into the overall site cleanup
strategy  (EPA, 1989).  It is suggested that an introductory
explanation be included to put the proposed remedies for soil
and groundwater at the MARBO Annex into context with the
overall plan for cleanup at the Andersen AFB NPL site.

An introductory explanation has been added to Section 1.4.

In Section 1.4.4, Groundwater, page 1-4:

This section does not include a statement as to how the selected
response action does or does not address the principal threat(s)
posted by the site (EPA, 1989, page 6-7). It is suggested that a
statement  be  included  to address this requirement at the
beginning of this section.

Presuming the cited section is actually 1.4.2, a statement pertaining
the principal threats has been added to Section 1.4.2.

In Section LS, STATUTORY DETERMINATIONS page 1-4:

This section should  include a statement explaining why the
statutory preference for treatment (TMV  reduction) was not
1 April, 1998 @ 11:54 AM

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Response:


Comment No. 7:
Response:

Comment No. 8:
                         employed (EPA, 1989, pages 6-7 and 6-8; e.g., substantial and
                         disproportionate benefit analysis) in selecting the remedies for
                         soil and groundwater at the MARBO Annex site. Additionally,
                         per the EPA "ROD  Checklist", the text should include the
                         following standard language for  the  selected soil remedies:
                         "However, because treatment of the principle threats of the site
                         was found to be practicable, this remedy does not  satisfy the
                         statutory preference  for treatment as a principle element*'
                         Since Hazardous substances will remain on-site above health-
                         risk levels, per the EPA "ROD Checklist", the ROD should
                         include  the  following  standard   language,  "Because  the
                         remedies will result hi hazardous substances remaining on-site
                         above health-based levels, a review will be conducted within
                         five years after commencement of the remedial action to ensure
                         that the remedy continues  to provide adequate protection of
                         human health and  the environment.**

                         Per the EPA ROD  checklist,  these  suggestions  have  been
                         incorporated in to Section 1.5.

                         In Section  2.3,   SITE  HISTORY AND ENFORCEMENT
                         ACTIVITIES, page 2-21 through 2-24:

                         This section did not contain a "-history of activities at the site
                         that have led to the current problems...'* (EPA, 1989, page 6-
                         11), though  this  information was presented in Section 2.1.
                         Please add a sentence in Section 23 that refers the reader to
                         Section 2.1 for a history of each of the sites.

                         A reference sentence has been added to Section 2.3.

                         In Section 2.5, SCOPE AND ROLE OF OPERABLE  UNIT
                         WITHIN THE SITE STRATEGY, page 2-26:

                         This section did not seem to "...focus on how the response
                         actions fit into the  overall strategy for addressing the principal
                         threat(s) posed by conditions at the site** (EPA, 1989, page 6-
                         13). Perhaps a description could be added as a paragraph at
                         the end of this section.  Additionally,  per the EPA "ROD
                         Checklist**, the text should more explicitly "describe  whether
                         or not the action will address any of the principle or low level
                         threats posed by conditions at the site.*'
1 April, 1998 @ 11:54 AM

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Response:


Comment No. 9:
Response:
Comment No. 10:
Response:
A paragraph on  how the response actions  address the principal
threat(s) has been added to Section 2.5.

In Section 2.6, SUMMARY OF SITE CHARCTERISTICS, page
2-27:

Per the EPA "ROD Checklist", for each site description, please
include estimated volumes of contaminated  soil.  It may be
more appropriate to include this information in Section 2.1.

Estimated volumes have been included at  the end of each site
description in Section 2.6.

In Section 2.7, SUMMARY OF SITE RISKS, page 2-38, and
Section 3.3 SUMMARY OF SITE RISK, page 4-14:

These sections do not seem to contain a  summary of toxicity
assessment  information such  as exposure  frequency  and
duration assumptions, cancer potency factors for contaminants
of concern that are carcinogens, and reference doses for the
contaminants  of concern that  have  noncarcinogenic effects
(EPA, 1989, pages 6-16 through 6-18). It  is suggested that this
information from the baseline risk assessment be summarized
here.  Also, per  the EPA "ROD Checklist", please indicate the
source of toxicity information used  to  calculate risks  (e.g.,
cancer potency factor, reference dose) and the risk model from
which  the risk  value:   were  derived (e.g., IRIS, HEAST,
ECAO-Cincinnati).   Additionally,  per  the  EPA  "ROD"
Checklist", a description of significant sources of uncertainty
uii the risk assessment should be summarized.  Finally,  these
sections should  include the following standard language per
the EPA "ROD" Checklist".  "Actual or threatened releases of
hazardous substances  from  this site, if not addressed by
implementing the response actions selected in this ROD, may
pinesent an imminent and substantial endangerment to public
health, welfare, or,  the environment" an imminent  and
substantial  endangerment  to public health, welfare,  or, the
environment"

Site risks were  calculated using the screening risk assessment
approach outlined in USEPA's Region IX Preliminary Remediation
Goals (PRGs) Second Half 1995 (USEPA,  1995).  Based on this
approach, site-specific exposure  point concentrations (EPCs) are
compared directly to Region DC PRGs. The exposure assumptions
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Comment No. 11:
Response:


Comment No. 12:
and  toxicity assessment information,  including  cancer potency
factors and non-cancer reference doses, used in the development of
Region   IX  PRGs   are  documented  in   USEPA   (1995).
Commensurate with the OU  3 FFS, a copy of the Region IX
Preliminary  Remediation  Goals  (PRGs) Second  Half  1995
(USEPA, 1995) will be included in the ROD as Appendix A.

General discussions of the uncertainties in the human health risk
assessments for soil and groundwater will  be included in Section
2.7 and Section  3.3, respectively.   In addition, more detailed,
tabulated summaries of site-specific sources  of uncertainty  will
included in Appendix B.

The  following statement will be included in  Section 2.7 of the
ROD, "Based on the potential risks associated with Sites 20, 22,
24, and 38, actual or threatened releases of hazardous substances
from these sites,  if not addressed by implementing the response
actions  selected  in this ROD, may present an imminent  and
substantial  endangerment  to  public  health, welfare,  or  the
environment."   In addition,  the  following  statement  will be
included in Section 3.3 of the ROD, "Based on the results of the
human health risk assessment for groundwater,  actual or threatened
releases of hazardous substances from the site, if not addressed by
implementing the response actions  selected in this ROD,  may
present an imminent and substantial endangerment to public health,
welfare, or the environment."

In Section 2.8,  DESCRIPTION  OF ALTERNATIVES,  page
2-42:

Please identify the quantity of waste to be covered or excavated
in this section, per the EPA "ROD Checklist" This section
should also refer to Section 2.9 for a description of estimated
present worth, capital, and O&M costs.

Volumes and area applicability have been added to Section 2.8 and
costs have been referenced to Section 2.10.

In Section 2.9,  SUMMARY OF COMPARATIVE  ANALYSIS
ALTERNATIVES, page 2-46 and Section 3.5, COMPARATIVE
ANALYSIS OF ALTERNATIVES SUMMARY, page 3-22:

EPA guidance (EPA, 1989, page 6-25) suggests that "-.under
each criterion, the  alternative that  performs best in   that
1 April, 1998 @ 11:54 AM

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Response:


Comment No. 13:
Response:
Comment No. 14:
Response:

Comment No. 15:
Response:

Comment No. 16:
category is discussed first, with the other options discussed in
{sequence from most to least advantageous."

The  modification of discussing the  best to worst performing
alternative has been made in each criteria section.

In Section 2.9.4, Long-Term  Effectiveness  and Permanence,
page 2-53:

Per the EPA "ROD Checklist", please address the residual risk
of each alternative, assuming the alternative is implemented.
At a minimum indicate if the remaining risk  would be less than
1 x 10-6, between 1 x 10-6 and 1  x  10-4, or  greater than 10-4.
Please also address the hazard index.

General descriptions of the residual risk (i.e., cancer risk and non-
cancer hazard index) associated with each potential alternative will
be  included  in  Section 2.9.4.     Additionally,  site-specific
descriptions of  the residual  cancer risk  and  non-cancer  hazard
index associated with  the selected remedial alternative (i.e., soil
cover or soil removal) will be incorporated into Section 2.10 (refer
to the Response to General Comment No. 16).

In Section 2.9.7, Cost, page 2-56:

Per the EPA "ROD Checklist", please include the capital and
O&M costs for each alternative evaluated.  Table 2-6 only
provides present worth costs.

Costs have been broken down in to capital and O&M.

In Section 2.9.8, State/Territory Acceptance, page 2-57:

Per the EPA "ROD Checklist", since the Air Force is the lead
agency, this section  should  address EPA's  acceptance  of the
sellected remedy.

EPA's acceptance of the selected remedy has been added.

In Section 2.10, THE SELECTED REMEDY, page 2-57 to 2-63:

This  section  incorrectly  refers to the selected remedy  as the
preferred alternative.  For example, on page 2-58, the text
states ''Soil  Cover  is the  preferred alternative."   Similar
I April, 1998 @ 11:54 AM

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                           language exists for other soil sites. Please change "preferred
                           alternative'* to "selected remedy."  Also, per the  EPA "ROD
                           Checklist", please provide capital and present worth costs for
                           the selected remedy.  Additionally, although contaminated soil
                           will not be treated, this section should indicate, for each site,
                           the remaining risk levels corresponding to the selected remedy.
                           See  EPA "ROD Checklist", and similar comment above on
                           Section 2.9.4.  Finally, to address "point of compliance" and
                           "residual contamination" in the  EPA "ROD Checklist", the
                           selected remedy should explain why  long term groundwater
                           compliance monitoring at each site is not a component of the
                           selected remedies.

Response:                  The term "preferred  alternative" has been changed  to "selected
                           remedy" and costs have been broken down in to capital and O&M.

                           For each site, a description of the residual cancer risk and non-
                           cancer  hazard  index  associated  with the  selected  remedial
                           alternative (i.e.,  soil cover or soil removal) will be  incorporated
                           into Section 2.10.  For Site 20 (Waste  Pile 7), a  qualitative
                           evaluation  of residual  risk will be presented since  the  selected
                           remedy (i.e., soil cover) will result  in the elimination of exposure
                           pathways, as long as the soil cover remains intact.  A qualitative
                           evaluation  of residual  risk will also be presented  for Site 38
                           (MARBO Laundry) since all known contamination associated with
                           the site  will be  removed under the selected  remedy (i.e., soil
                           removal).  For Site 22 (Waste Pile 6) and Site 24 (Landfill 29),
                           where residual contaminants will be left in place under the selected
                           remedy (i.e., soil removal), quantitative evaluations of residual risk
                           will be presented. (Calculations indicate that residual risk is less
                           than 1 x 10"6 for each of the selected remedies.)

                           Long term  groundwater compliance monitoring is  part of the
                           overall  AAFB groundwater  monitoring program, including the
                           MARBO Annex. For Waste Pile 7, where soil removal is not  a
                           selected alternative, site specific  groundwater monitoring wells
                           (IRP-10,  -15,  and  -16)  will  continue  to  be  monitored for
                           contaminants detected at Waste Pile 7.  For those sites where soil
                           removal is the  selected alternative,  any potential  impact on
                           groundwater via precipitation  leachate from the surface has been
                           removed. In both cases, the monitoring wells closest to each site
                           are being monitored as part of the Long Term Monitoring Plan.
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Comment No. 17:
Response:
Comment No. 18:
Response:


Comment No. 19:
Response:
In Section 2.11.4, Utilization  of Permanent Solution..., page
2-64:

Per the EPA "ROD Checklist", please describe the role of the
State and community acceptance considerations and provide a
statement that the selected remedies do not meet the statutory
requirements to utilize  permanent solutions  and  treatment
technologies because treatment if impractical.

The State (Territory) and community acceptance considerations
have been added, as well as discussion on permanent solutions and
treatment technologies.

In Section 3.4,  THE  DESCRIPTION OF ALTERNATIVES,
page 3-17 to 3-21:

Section 3.4.2 (Natural Attenuation), first sentence states, 'This
alternative utilizes Natural  Attenuation  of TCE/PCE in the
aquifer to achieve remediation goals." It would be useful in
this section,  and hi other appropriate sections, to explicitly
define "remediation  goals" (e.g., to reduce TCE  and PCE
concentrations in groundwater to below MCLs).

TCE and PCE remediation goals have been added in the necessary
sections.

In Section 3.6, THE SELECTED REMEDY, page 2-33 to 3-34:

The description of the selected remedy,  Natural Attenuation
and Wellhead Treatment, does not define an end point or
"point of compliance."  For example, the text could indicate
tiuit this remedy will continue until long  term  groundwater
monitoring indicates  that TCE and PCE  concentrations are
consistency below MCLs. Additionally, the text could indicate
that each five year review would:  1) determine if the remedy is
still effective, 2) determine if the remedy has achieved its goals,
and thus, can be discontinued.

A paragraph has been added  indicating that  the remedy  will
continue until long term monitoring indicates that TCE and PCE
concentrations are consistently below MCLs,  as well  as the
suggested five year criteria.  Additionally,  AAFB will conduct a
review of it's long term groundwater monitoring plan every two
years.
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SPECIFIC COMMENTS
Comment No. 1:
Response:

Comment No. 2:
Response:

Comment No. 3:
Response:

Comment No. 4:
In  TABLE OF  CONTENTS, LIST OF ACRONYMS  AND
ABBREVIATIONS, pages v and vi:

The definitions should have the same capitalizations as they
would when they appear in the text (e.g., below ground surface,
polycyclic aromatic hydrocarbon, volatile organic compound,
etc.)

This has been corrected.
In Section 1.3'.

The  language  is rather cumbersome and vague.
something like the following would be more clear:
                                                                        Perhaps
"Risks to human health and the environment were evaluated
for groundwater near MARBO and at six surface sites within
MARBO. No risk was found at Waste Pile 5 and the War Dog
Borrow Pit, so no further action is planned for these two sites.
Current risks associated with soil exceed acceptable risk levels
at Waste Pile 6, Waste Pile 7, Landfill 29, and the MARBO
Laundry, thus remedial alternatives were evaluated for  these
four sites.*'

"Current risk associated with contaminants in groundwater...*'
The rest of this section is O.K.

This language has been added.

In Section 1.4.1, Sot/, page 1-2:

It is suggested that the contaminants of concern for which the
remedy is to be implemented be mentioned so  the reader
understands what in the soil is of concern.

The contaminants of concern have been added.

In Section 1.4.1, Soil, page 1-3, first bullet:

For completeness, backfilling and compacting the excavations
with clean fill should be mentioned as part of the soil remedial
action.
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Response:


Comment No. 5:
Response:


Comment No. 6:
Response:

Comment No. 7:
Response:

Comment No. 8:


Response:

Comment No. 9:
Backfilling and compacting is part of the remedy and has been
mentioned.

In Section 1.5, STATUTORY DETERMINATIONS, page 1-4,
sixth line:

Please include an explanation of why the statutory preference
for remedies that employs treatment as a principal element was
not met

As noted in general comment #6, this discussion has been added to
the text.

In Section 2.1, SITE NAME, LOCATION, AND DESCRPT1ON,
page 2-1, first paragraph, lines 3 and 4:

Please include the ""  symbol in the latitude and longitude
citations.

The degree symbol has been added.

In the same section and page, second paragraph, last line:

Because the North  and Northwest Fields are mentioned in the
text as points of reference, it would be helpful to show their
locations in Figure 2-1.

These locations have been added.

In Section 2.1.2, Site 22 (Waste Pile 6), please identify  the
vertical extent of contamination.

The vertical extent of contamination has been added.

In Sections 2.1.4 and 2.1.5, please change the phrase ''Based on
a risk evaluation of soil analytical data,  a health risk was not
identified..." to "No health risk was identified at Waste Pile 5
(or War Dog Borrow Pit), based on  a risk evaluation of soil
analytical data.**

It is suggested that the contaminants  of concern for which the
remedy  is  to be implemented be mentioned so the  reader
understands what in the soil is of concern.
1 April, 1998 @ 11:54 AM
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Response:



Comment No. 10:



Response:

Comment No. 11:



Response:
Comment No. 12:



Response:

Comment No. 13:
Response:

Comment No. 14:
Response:
The  health  risk evaluation  terminology has  been  added as
suggested.   As  also noted in General Comment Number 3,
contaminants of concern are mentioned.

On the top of page 2-5, please delete "in addition to the 2.44
acre landfill," and begin that sentence  with 'The Surface
Drum Area~."

This modification has been made.

In Section 2.1.5, Site 37 (War Dog Borrow Pit), please include a
detailed  size  map to  be  consistent  with  the other  site
descriptions.

Figures for the ROD were obtained from the OU 3  FFS.  The
decision was made not to include figures for the War Dog Borrow
Pit and Waste Pile 5 primarily because of a lack of detail pertinent
to the ROD, and because both of these sites are no further action.

In Section 23.1, Geology, first paragraph,  second  line:  Is
"tests" the correct word  in the phrase*  .  . . composed of
formanifers tests."

Yes, tests is the correct term.

In 2.3, SITE HISTORY AND ENFORCEMENT ACTIONS,
page 2-24, second paragraph, fifth line:

We suggest that "either" be changed to "any."

This modification has been made.

In Section 2.6.1, Contaminant Screening Process, page 2-27,
sixth line:

Spell out Preliminary Remediation Goals (PRGs) (in first use).

This modification has been made.
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Comment No. 15:
Response:

Comment No. 16:
Response:

Comment No. 17:
Response:
Comment No. 18:
Response:
lln Section 2.8.4, Soil Removal (Alternative OU3-D), page 2-45,
last paragraph:

As  Land Disposal Restrictions are  potentially  applicable,  it
might helpful to  mention that this ARAR  could affect the
disposition of some of the soil and debris removed.

This addition has been made.

In Section 2.9.4,  Long-Term Effectiveness and Permanence,
page 2-54, third paragraph:

Under "Soil Cover/' it should be noted that this alternative
restricts future uses of the applicable sites in that soil intrusive
activities are not  to be permitted (Institutional Control)  and
hence economic values of such restricted sites may be lessened
compared to a "Soil Removal" alternative.

This addition has been made.

b» Section 2.10.1, Site 20 (Waste Pile 7), page 2-57, second line:

Please clarify the  reason  "Soil  removal  was  not deemed
applicable . .. "; e.gM cost (versus soil cover) exceeds benefit
(reduced risk of exposure).

The level  of effort and  cost  associated  with  soil removal
outweighed the benefit of risk  reduction at Waste Pile 7. This has
been added to the text.

On page 2-58: TSCA regulates PCBs at concentrations of [>]
50 ppm.  Did Andersen look at the PCB Spill Policy and the
EPA Guidance on Remedial Action  for Superfund Sites  with
PCB Contamination?  Is leaving PCB contamination on/in the
ground a "PCB spill" or "PCB disposal."

The document "A  Guide on Remedial Actions at Superfund Sites
With PCB Contamination" (EPA, August 1990) was  referenced
for this comment.  Based on a  review of this document, the R.O.D.
appears to be consistent with this guidance.  By definition, the
PCB  spill policy  40CFR  761.120 addresses PCB  spills which
occurred after May  4, 1987.   The two  sites where PCBs were
detected in the soil became inactive prior to 1987.  Additionally,
40CFR  761.3 defines a "disposal" as "...spills, leaks  and other
 1 April. 1998 @ 11:54 AM
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Comment No. 19:
Response:
Comment No. 20:
Response:

Comment No. 21:
uncontrolled discharges of PCBs...". Given these criteria, the PCB
contamination detected at Waste Pile  7 and the former MARBO
Laundry appears to be a disposal.

Page 2-28 and page 2-58:  Are the pesticides in the soil at
Waste Pile 7 from normal application. Is leaving the pesticides
in the ground "disposal" under FIFRA?  Please discuss the
ARAR implications a little more fully on page 2-58.

The  highest concentrations of pesticides were detected in surface
soil samples from Waste Pile 7, indicating that this may have been
due  to surface  application.   However,  there were pesticides
detected in subsurface soil samples as well.  Also, the OU 3 RI
indicates that debris and disposal material at Waste Pile 7 came
from a variety of sources. Thus, it is possible that some of the
pesticides are from normal application and some are from disposal,
but this is speculative.

Based  on a review of the pesticide  regulations,  EPA regulates
pesticides under FIFRA, which regulates the sale, distribution and
use of pesticides, and the Federal Food, Drug and Cosmetic Act
(FFDCA) which regulates, among other things, pesticide residues
in food and feed.  As FIFRA is a licensing statute, there were no
references found which addressed whether leaving pesticides in the
ground is considered "disposal".   Additionally,  there were no
pesticide containers or product containers discovered at Waste Pile
7, which'would have otherwise triggered FIFRA as a potential
ARAR.

These points have been added to Section 2.10.1.

In Table 2-6, page 2-59:

Footnote  "b"  should be added to  the Pertinent  ARARs
Compliance  column  for  the  Institutional  Control and  Soil
Cover Alternatives for Site 22, Site 24, and Site 38.  Under Site
22, Total Cost column, "$0,600: should be "$30,600."

These corrections have been made to Table 2-6.

In Section 2.10.4, Site 38 (MARBO Laundry), page 2-63, second
paragraph, third sentence:

This sentence conflicts with the PCB information presented in
Tables 2-2,2-3, and 2-5 (ARARs). The means of disposal (and
1 April, 1998 @ 11:54 AM
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Response:
Comment No. 22:
Response:

Comment No. 23:
Response:
Comment No. 24:
costs) of PCB-containing soil is not discussed.  Please discuss
the TSCA regulations governing PCB cleanup and disposal
and  evaluate whether they  are  ARARs at  the MARBO
laundry.

This sentence does indeed  conflict with  analytical data and
previous tables.  The paragraph was intended to discuss TSCA as
an ARAR, consistent with previous tables.  This correction has
been made and TSCA is  discussed as a pertinent ARAR for
transportation and disposal of the soil  and debris contaminated
with PCBs.

In Figure 3-2:

The locations of wells M-6 and D-2 are slightly different than
in the other figures in this sections.

This correction has been made.

In Section 3.3.1, Human Health Risk, pages 3-14 and 3-15.

The significance of the 434 (Table 3-4) Hazard Index for well
IRP-31 (D) was not addressed.

The  following statement  will be  included in  Section  3.3.1:
"Monitoring wells where COCs were detected are generally  within
EPA's risk management range of 1 x 10* to 1 x  10** and below an
HI of 1.0, with the exception of IRP-31. Monitoring well IRP-31
exceeds an HI of 1.0, however this is  a deep  well with a high
chloride content and not meant for consumption. In addition, land
use restrictions will be implemented to regulate  the installation of
new wells,  and  groundwater  monitoring is  included   as  a
component to overall protection  of  human  health and the
environment."

In Section 3.5.5, Reduction of Toxicity,. Mobility, or  Volume
Through Treatment, page 3-30:

No discussion is included on  the potential for  an increase in
toxicity through  natural  biodegration of TCE and PCE to
more toxic COCs such as 1,2-DCE and vinyl chloride (through
this is apparently not occurring at any measurable rate).
1 April, 1998 @ 11:54 AM
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Response:
Comment No. 25:
Response:
Comment No. 26:
Response:
This was not mentioned as it was not considered to be of concern.
It has been added, however, under the "Natural Attenuation"
scenario for completeness.

On Page 4-3:

The AAFB response to the comments by Senator Brown could
be more expansive, i.e^ responsive. In particular, the response
might attempt to address the issue of the capacity for future
use or development at the site, what exactly deed restrictions
will mean, and what type of use will be safe with the cap.

The response has been modified by removing the  last sentence of
AAFB's original response and adding the following text:

"Site 20 lies within an abandoned quarry, with an average depth to
the base of fill of 10.8 feet bgs, and as  such it has limited future
land use regardless of whether the waste pile were removed.  The
restrictions on Waste Pile 7 would additionally limit the use of the
property to activities which are non-intrusive in nature, and would
be included in the deed during transfer.  Intrusive  activities would
open an exposure pathway and defeat the purpose of the soil cover.
Some ideas of non-intrusive activities may include a maintenance
yard or storage area."

On page 4-4:

The response to Ernie Wusstig could also be more expansive.

The following is a response to Mr. Wusstig's first question, to be
appended to AAFB's original response.

"There are two areas of concern in the groundwater underlying the
MARBO Annex, where concentrations of TCE and/or PCE exceed
Federal allowable levels.   One is beneath the former MARBO
Laundry,  where PCE slightly exceeds Federal levels, and the other
is across from the Yigo Power Plant, where TCE exceeds Federal
levels. Though the PCE underlying the MARBO Laundry is likely
a result of military activities, it is unclear where the source of the
TCE originated.  After approximately ten years of monitoring these
areas, the TCE and PCE do not appear to be migrating. Thus, the
overall impact on the aquifer is isolated  to two  small  areas
representing a very small portion of the groundwater underlying
the MARBO Annex.
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                           On a broader, national level, impacts to soil and groundwater from
                           industrial activities were not known to be an issue until the early
                           1970's.  The military has  been consistent and pro-active with
                           investigative and remedial activities occurring nationally.   Should
                           there have been  a situation where an imminent health risk existed,
                           immediate measures would have been taken."
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                    RESPONSES TO GUAM EPA COMMENTS
                           DATED FEBRUARY 20,1998
        MARBO ANNEX OPERABLE UNIT RECORD OF DECISION (R.O.D.)
                        DRAFT FINAL, DECEMBER 1997
SPECIFIC COMMENTS
Comment No. 1:
Response:
Comment No. 2:
Response:
Comment No. 3:


Response:

Comment No. 4:
Page 2-11, First Paragraph.  Groundwater in the NGL ranges
from a calcium - bicarbonate type, through a calcium • sodium -
bicarbonate - chloride type, water as the effects of salt water
intrusion become more significant The relative concentrations
of magnesium, silica, and nitrate are low in comparison to the
major cations and anions hi the NGL, and their occurrence and
significance should be discussed separately.

A statement has been added to this section regarding the effect that
oveipumping would have on elevated chloride concentrations. The
relative concentrations of the naturally occurring ions  is important
and discussed fully in the RI. A sentence has been added referring
the reader to Section 4.0 of the OU 2 RI for detailed information
pertaining to inorganic water quality conditions.

Page 2-11, Second  Paragraph. Concentrations of chloride in
basal sections of the NGL have been reported much  higher than
the 150 mg/L concentration presented hi this paragraph.

Concentrations up to 280 mg/1  were detected in IRP-40 during the
IRP investigation, and up to 1,100 in IRP-41 (though IRP-41 was
due to excessive pumping in an attempt to lower pH). This has been
modified in the text.

Page 2-45, Fourth Paragraph. The reference to "RPM" should
be"RPMs"

This correction has been made.

Page 2-57, Section 2.9.9. This section is misleading.  Although
public participation was extremely low in terms of numbers of
people who expressed concerns regarding the Proposed Plan, the
comments which were expressed were very significant in terms
of their impact on the island.
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Response:
Comment No. 5:
Response:
In particular, comments were made by Senator Joanne Brown
during the RAB prior to the public hearing on the Proposed
Plan and during the public hearing itself regarding Waste Pile 7,
the connection between soil contamination and groundwater
contamination and land use restrictions  on federal properties
after lease or transfer to GovGuam.  The Senator's concerns are
significant and most likely represent concerns shared by other
community  members  who  may  not  be  as educated  in the
CERCLA process as the Senator, who is the Co-Chair  of the
RAB. The Senator's concerns are presented hi Section 4-2 of the
Draft ROD and should be referenced hi all other sections of this
document  which refer to  "Public  Comment",  or "Public
Acceptance", including Section 2.9.9.

The following statement has been added to Section 2.9.9 and 3.5.9 of
the main body of the text:

"Senator Brown noted concern pertaining  to the connection between
soil contamination at Waste Pile 7 and the groundwater, as well  as
the land use restrictions that will be applied to Waste Pile 7  after
transfer to Gov Guam. The land use restrictions preclude the use of
activities that would disrupt the integrity of the soil cover."

Similar to  U.S.E.P.A.  comment #25, the Andersen Air Force
response to Senator Brown's comment has been  supplemented  to
address her primary concern's, including a discussion on the land use
restrictions1 applicability, and potential future  uses of the site.  The
following text has been added to Section 4.3:

"Site 20 lies within an abandoned quarry, with an average depth to
the base of fill of 10.8 feet bgs, and as such it has limited future land
use regardless of whether the waste pile were removed.   The
restrictions on Waste Pile 7 would additionally limit the use of the
property to activities which are non-intrusive in nature and would be
included in the deed during transfer.  Intrusive activities would  open
an exposure pathway and defeat the purpose of the soil cover. Some
ideas of non-intrusive activities may include a maintenance yard or
storage area."

Page 2-57, Section 2.10.1, First Paragraph.  The last sentence in
this  paragraph  is confusing to the reader and needs to  be
expanded and more fully explained.

This sentence has been modified to read more clearly.
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Comment No. 6:
Response:
Comment No. 7:
Response:
Page 3-19, Section 3.4.2, First Paragraph.  Chemical analysis of
groundwater samples collected from the MARBO OU indicate
that daughter  products of PCE  and  TCE degradation  are
generally  absent   This  does not  suggest  effective natural
attenuation.  Documenting the efficiency of natural attenuation
of (chlorinated solvents requires an understanding of the ambient
redox conditions in the aquifer, the tracking of the presence and
disappearance  of  electron acceptors, the appearance of end
products, and other appropriate stoichiometric conditions of the
degradation reactions. Please provide evidence which supports
the process  of  TCE  and  PCE degradation  in  MARBO
groundwater, rather than the dilution process, which may in fact
be the controlling process in the documented decreases in the
concentration of the contaminants.

It is stated throughout the OU 2 FFS, Proposed Plan and R.O.D. that
the controlling mechanism of attenuation is based on the high rate of
groundwater  flux  through the aquifer.   There  have  been  no
significant detections of dehalogenated byproducts such as DCE or
Vinyl  Chloride.  This is further supported by  the high dissolved
oxygen  concentrations in the  aquifer,  whereas dehalogenated
byproducts are manifestations of less aerobic, reductive conditions.

Page  3-19,  Section  3.4.2, Institutional Controls,  Land  Use
Restrictions.  This section should include a provision by which
any  land  leased or transferred  to  GovGuam   on which
production wells are installed and become contaminated because
of Air Force activities are  included in the  existing wellhead
treatment program. This would apply to properties under which
groundwater contamination  has  not  been  documented,  but
becomes contaminated at some time in the future as a result of
migration or continued leaching of soil contaminants.

Evidence suggests that TCE and PCE concentrations in groundwater
are decreasing, and that the two areas of concern in the  MARBO
Annex are isolated and not migrating. Thus a scenario where other
wells are potentially impacted by existing groundwater conditions is
unlikely.  As part of the CERCLA process, the groundwater
alternative is evaluated every five years, in part to address situations
such as this which may arise.

Soil is not considered a future threat to groundwater.  Soil will be
removed from three of the  four sites which pose a potential health
risk, thus  removing  any potential  threat to  groundwater.   The
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Response:
Comment No. 8:
contaminants in the soil at the fourth site, Waste Pile 7, are primarily
lead and pesticides, which are highly immobile in soil  and water.
There have been no pesticides or lead detected in the groundwater
monitoring wells closest to Waste Pile 7.  Based on this, and the fact
that these contaminants are immobile, they are not expected to pose a
threat to groundwater in the future.  As with the soil alternatives
however, the CERCLA process requires that the soil alternatives also
be  re-evaluated for effectiveness  every five years.  This  will be
conducted in conjunction with groundwater monitoring results from
the Andersen AFB  Long Term Groundwater Monitoring  Plan every
two years.

In  addition, any  property  which is transferred to GovGuam
must be remediated to the level which would allow the specified
reuse of the property without exposing people involved in the
reuse scenario to unacceptable health risks.   This  especially
applies to the reuse of Waste Pile 7 if the property is ever reused
for purposes which would require  intrusive activities exposing
people to the contaminants which are proposed to be covered at
the site.

The selected alternative for Waste Pile 7 includes deed restrictions
which preclude future use  involving  intrusive activities.  Intrusive
activities would re-open an exposure pathway and defeat the purpose
of the soil cap. This is consistent with the OU 3 FFS, which had the
concurrence of all of the RPM's and was finalized in January 1997.
Some possible  re-use scenarios  may include a  storage  area or
maintenance yard. In addition it will be noted that Site 20 is situated
within an abandoned quarry with an average depth to the  base of fill
of 10.8 feet bgs.  As such the land has limited future use regardless
of whether the waste pile were removed.

Page 3-19,  Long-Term Monitoring.  Appropriate monitoring
wells should be monitored  for contaminants which have been
detected in soil contamination sites at MARBO OU, but which
contaminated soils have not been removed from the site. Also, if
contaminants associated with Air Force activities in the MARBO
OU become detected hi GovGuam Production wells through the
Safe Drinking Water sampling requirements, the Air  Force
should implement a sampling program for those affected wells
and assess possible remediation strategies through discussions by
the RPMs. These details should be presented in the ROD.
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Response:
Response:
The groundwater alternative will be evaluated every five years as
part of the CERCLA process.  This includes all RPMs and interested
parties. As part of the IRP the present long-term monitoring plan
includes monitoring of the full suite of analytes for the wells in the
vicinity of Site 20 (IRP-10, -15 and -16).  The IRP will re-evaluate
the long-term groundwater monitoring program every  two years, also
inclusive of RPMs.

Long-term monitoring requirements need to specifically address
the cleanup goals of the selected  remedy, and  duration.  Goals
need to be defined in terms of contaminants levels and frequency
of occurrence, as well as the efficiency of the natural attenuation
process (please refer to Comment Number 6, above).

The   long  term  monitoring  will  continue  until   TCE/PCE
concentrations are consistently below MCLs. This has been added to
thetextoftheR.O.D.
Response:
Comment No. 9:
Natural attenuation is also a process which occurs in the soil. At
Waste Pile 7, organic contaminants which are proposed to be left
in place at the site will experience a reduction in concentration
over tune due to natural degradation.  The ROD should contain
a description of the methodology to be used to document the
natural attenuation process at Waste Pile 7.

The  intent of the cover is to reduce or mitigate exposure to the
contaminants at Waste  Pile 7 to within  an acceptable health risk
range, without the benefit of reduced soil concentrations.   It is
unlikely that natural attenuation will play a significant role  in
reducing the concentrations of the types of contaminants detected at
Waste Pile 7. The contaminants of concern at  Waste Pile 7 are
pesticides  and  lead, both  persistent,  recalcitrant and  relatively
immobile.

Page 3-33, Section 3.6.  Please refer to the appropriate comments
above.
Response:
Modifications have been made to Section 3.6 which include the five
year CERCLA review, the two year Long Term Monitoring review,
and  & discussion on  the parameters which will  be assessed  to
determine the effectiveness of natural attenuation and the necessary
length for long term monitoring (i.e., until TCE/PCE concentrations
are consistently below MCLs).
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