PB96-964412
EPA/ROD/R08-96/128
April 1997
EPA Superfund
Record of Decision:
Rocky Mountain Arsenal,
(Offpost Site) Adams County, CO
12/19/1995
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MATERIEL COMMAND
~~ COMMITTED To PROTECTION OF THE ENVIRONMENT —
Rocky Mountain Arsenal
Offpost Operable Unit
Final Record of Decision
Rocky Mountain Arsenal
Commerce City, Colorado
Harding Lawson Associates
REQUESTS FOR COPIES OF THIS DOCUMENT
SHOULD BE REFERRED TO THE PROGRAM MANAGER
FOR ROCKY MOUNTAIN ARSENAL
AMXRM-PM, COMMERCE CITY, COLORADO 80022
This document complies with the
National Environmental Policy Act of 1969.
ROCKY MOUNTAIN ARSENAL • COMMERCE CITY, COLORADO • 80022-2180
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Rocky Mountain Arsenal
Off post Operable Unit
Final Record of Decision
Rocky Mountain Arsenal
Commerce City, Colorado
Prepared for
Program Manager for Rocky Mountain Arsenal
Building 111, Rocky Mountain Arsenal
Commerce City, Colorado 80022-2180
HLA Project No. 21905 402010
Contract No. DAAA05-92-D-0003
Delivery Order No. 0005
THIS DOCUMENT IS INTENDED TO COMPLY WITH THE NATIONAL
ENVIRONMENTAL POLICY ACT OF 1969.
THE INFORMATION AND CONCLUSIONS PRESENTED IN THIS REPORT REPRE-
SENT THE OFFICIAL POSITION OF THE DEPARTMENT OF THE ARMY UNLESS
EXPRESSLY MODIFIED BY A SUBSEQUENT DOCUMENT. THIS REPORT CONSTI-
TUTES THE RELEVANT PORTION OF THE ADMINISTRATIVE RECORD FOR THIS
CERCLA OPERABLE UNIT.
December 19, 1995
Harding Lawson Associates
Engineering and Environmental Services
707 Seventeenth Street, Suite 2400
Denver, CO 80202 - (303) 292-5365
Recycled Paper
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CONTENTS
DECLARATION STATEMENT DS-1
1.0 SITE NAME, LOCATION, AND DESCRIPTION 1-1
1.1 Environmental Setting 1-2
1.2 Geology 1-2
1.3 Hydrogeology 1-3
2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES 2-1
2.1 Operational History 2-1
2.2 Previous Investigations 2-2
2.2.1 U.S. Environmental Protection Agency Study Area 2-2
2.2.2 U.S. Department of the Army Investigation 2-3
2.3 Boundary Containment Systems 2-4
2.3.1 - North Boundary Containment System 2-5
2.3.2 Northwest Boundary Containment System 2-6
2.3.3 Irondale Containment System 2-6
2.4 Interim Response Actions 2-7
2.4.1 Offpost Interim Response Action 2-7
2.5 History of CERCLA Enforcement Activities 2-8
3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION 3-1
4.0 SCOPE AND ROLE OF THE OFFPOST OPERABLE UNIT 4-1
5.0 SUMMARY OF SITE CHARACTERISTICS 5-1
5.1 Sources of Contamination 5-1
5.2 Nature of Contamination 5-1-
5.3 Contamination Migration Pathways 5-2
5.4 Extent of Contamination 5-3
5.4.1 Groundwater 5-3
5.4.2 Surface Water 5-4
5.4.3 Stream-bottom Sediments 5-5
5.4.4 Surface and Subsurface Soil 5-5
5.4.5 Biota 5-6
5.5 Potential Routes of Human and Environmental Exposure 5-7
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6.0 SUMMARY OF SITE RISKS 6-1
6.1 Human Health Risks 6-2
6.1.1 Identification of Chemicals of Concern 6-2
6.1.2 Exposure Assessment 6-3
6.1.2.1 Offpost Study Area Exposure Assessment Zones 6-3
6.1.2.2 Offpost Study Area Potential Exposure Points 6-5
6.1.2.3 Potential Exposure Pathways and Routes 6-6
6.1.2.4 Estimation of Chemical Intake 6-8
6.1.3 Toxicity Assessment 6-8
6.1.4 Risk Characterization 6-9
6.1.4.1 Carcinogenic Risks 6-9
6.1.4.2 NoncarcinogenicEffects 6-10
6.2 Estimation of Potential Ecological Effects 6-11
6.2.1 Method 6-11
6.2.2 Results 6-13
6.3 Conclusion 6-14
7.0 DESCRIPTION OF GROUNDWATER REMEDIATION ALTERNATIVES 7-1
7.1 Common Elements of Alternatives 7-4
7.2 Identification of Groundwater Alternatives: North Plume Group 7-6
7.2.1 Alternative N-l: No Action 7-6
7.2.2 Alternative N-2: Continued Operation of the North
Boundary Containment System With Improvements as Necessary 7-6
7.2.3 Alternative N-4: Offpost Groundwater Intercept and Treatment System . . 7-7
7.2.4 Alternative N-5: Expansion of the Offpost Groundwater
Intercept and Treatment System 7-10
7.3 Identification of Groundwater Alternatives: Northwest Plume Group 7-12
7.3.1 Alternative N-l: No Action 7-12
7.3.2 Alternative NW-2: Continued Operation of the Northwest
Boundary Containment System With Improvements as Necessary 7-13
8.0 COMPARATIVE ANALYSIS OF ALTERNATIVES 8-1
8.1 Comparative Analysis of Remedial Alternatives 8-2
8.1.1 Overall Protection of Human Health and the Environment. . . • 8-3
8.1.2 Compliance With Applicable or Relevant and Appropriate Requirements . 8-4
8.1.3 Long-term Effectiveness and Permanence 8-5
8.1.4 Reduction in Toxicity, Mobility, or Volume . 8-6
8.1.5 Short-term Effectiveness 8-6
8.1.6 Implementability 8-7
8.1.7 Cost 8-9
8.1.8 State Acceptance 8-10
8.1.9 Community Acceptance 8-11
8.2 Conclusions of the Comparative Analysis of Alternatives 8-11
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9.0 IDENTIFICATION OF THE SELECTED REMEDY 9-1
9.1 Alternative N-4: Offpost Groundwater Intercept and Treatment System 9-1
9.2 Alternative NW-2: Continued Operation of the Northwest Boundary
Containment System with Improvements as Necessary 9-3
9.3 Additional Components of the Selected Remedy 9-5
9.4 Cost of Selected Remedy 9-6
9.5 Limitations 9-6
9.6 Criteria for Shutting Down Boundary and Offpost Containment Groundwater
Systems 9-7
10.0 STATUTORY DETERMINATIONS 10-1
10.1 Consistency with the Statutory Requirements of CERCLA in Section 121 10-1
10.1.1 Protection of Human Health and the Environment 10-1
10.1.2 Compliance With Applicable or Relevant and Appropriate Requirements 10-2
10.1.3 Cost Effectiveness 10-3
10.1.4 Utilization of Permanent Solutions to the Maximum Extent Practicable . 10-4
10.2 Consistency with the National Contingency Plan 10-4
10.3 Summary 10-5
11.0 DOCUMENTATION OF SIGNIFICANT CHANGES 11-1
12.0 GLOSSARY 12-1
13.0 BIBLIOGRAPHY 13-1
TABLES
6.1 Offpost Operable Unit Groundwater Chemicals of Concern
6.2 Offpost Operable Unit Surface-Water Chemicals of Concern
6.3 Offpost Operable Unit Sediment Chemicals of Concern in First Creek
6.4 Offpost Operable Unit Soil Chemicals of Concern
6.5 Summary of Land-Use Scenarios and Exposure Routes by Zone
6.6 Reference Doses and Slope Factors for Chemicals of Concern
6.7 Summary of Reasonable Maximum Exposure Carcinogenic Risks by Zone and Exposure Route
6.8 Summary of Adult Reasonable Maximum Exposure Noncarcinogenic Hazard Indices by Target
Organ and Exposure Assessment Zone
7.1 Containment System Remediation Goals for the Offpost Groundwater Intercept and Treatment
System
7.2 Containment System Remediation Goals for the North Boundary Containment System
7.3 Containment System Remediation Goals for the Northwest Boundary Containment System
7.4 Groundwater Alternatives for the North and Northwest Plume Groups
8.1 Summary of the Detailed Analysis and Ranking of Groundwater Alternatives for the North
Plume Group
8.2 Summary of the Detailed Analysis and Ranking of Groundwater Alternatives for the
Northwest Plume Group
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9.1 Estimated Costs of the Offpost Operable Unit Selected Remedy
10.1 Summary Evaluation of Chemical-specific and Other Applicable or Relevant and Appropriate
Requirements for the Offpost Operable Unit
10.2 Summary Evaluation of Action-specific Applicable or Relevant and Appropriate Requirements
for the Offpost Operable Unit
10.3 Summary Evaluation of Location-specific Applicable or Relevant and Appropriate
Requirements for the Offpost Operable Unit
FIGURES
1.1 Rocky Mountain Arsenal Operable Units and Offpost Study Area
2.1 Locations of Contaminant Source Areas
5.1 Contaminant Migration Pathways
6.1 Offpost Study Area Exposure Assessment Zones
6.2 Site Conceptual Model for the Offpost Study Area
6.3 Ecological Site Conceptual Model for the Offpost Study Area
7.1 Alternative N-4 Remedial System Components
7.2 Alternative N-5 Remedial System Components
9.1 Offpost Area of Revegetation
APPENDIXES
A RESPONSIVENESS SUMMARY
B INSTITUTIONAL CONTROLS
C WELL CLOSURE CRITERIA
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DECLARATION STATEMENT
Rocky Mountain Arsenal
Offfpost Operable Unit
Commerce City, Colorado
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DECLARATION FOR THE RECORD OF DECISION
SITE NAME AND LOCATION
Rocky Mountain Arsenal
Offpost Operable Unit
Commerce City, Adams County, Colorado
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for the Rocky Mountain Arsenal (RMA)
Offpost Operable Unit (OU) in southern Adams County, east of Commerce City, Colorado, chosen in
accordance with the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA) of 1980, as amended by the Superfund Amendments and Reauthorization Act (SARA) of
1986, and the National Environmental Policy Act (NEPA), and, to the extent practicable, the National
Oil and Hazardous Substances Pollution Contingency Plan (NCP). This decision is based on the
administrative record file for the Offpost OU, and this document explains the basis and purpose of
the selected remedy for the Offpost OU.
ASSESSMENT OF THE SITE
The Offpost Study Area risk assessment showed that even without remedial action, the baseline
cumulative cancer risks from contamination in surface water, soil, sediment, air, and groundwater are
within the acceptable cancer risk range established by the U.S. Environmental Protection Agency
(EPA). However, several site-specific factors suggest that remedial alternatives for groundwater
should be developed. These site-specific factors are: (1) groundwater contributes a maximum of
2 x 10"4, or approximately 75 percent of the total carcinogenic risk, (2) maximum contaminant levels
(MCLs), maximum contaminant level goals (MCLGs), and Colorado Basic Standards for Groundwater
(CBSGs) are exceeded for some groundwater contaminants, and (3) hazard indices (His) for children
exceed 1.0 in Zones 2, 3, and 4. Although the hazard indices exceed 1.0 in Zones 2, 3, and 4, the
bulk of the HI value is contributed through an assumed domestic use of alluvial groundwater, which
is not presently occurring and under this remedy is not intended to occur in the future. The elevated
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Declaration for the Record of Decision
His occur only when considering the contribution of groundwater. Therefore, groundwater contami-
nation is the focus of this decision document.
Actual or threatened releases of hazardous substances from this site, if not addressed by imple-
menting the response action selected in this ROD, may present a potential threat to public health,
welfare, or the environment.
DESCRIPTION OF THE REMEDY
The Offpost OU is one of two OUs at RMA. The Onpost OU addresses the contamination within the
27 square miles of RMA. The Offpost OU addresses groundwater contamination north of RMA that
migrated (1) before the RMA boundary groundwater extraction and treatment systems were installed,
and (2) around the boundary systems prior to recent improvements. The selected remedy described
in this Record of Decision (ROD) will permanently address contaminants at the site through
treatment to reduce the toxicity, mobility, or volume of contaminants. Groundwater containment
system remediation goals are based on the risk assessment and on federal Safe Drinking Water Act
MCLs, proposed MCLs, nonzero MCLGs, and CBSGs. Action levels also meet those state drinking
water standards found to be applicable or relevant and appropriate requirements (ARARs).
The major components of the selected remedy are as follows:
• Operation of the Offpost Groundwater Intercept and Treatment System
Removal of contaminated groundwater from the alluvial and the weathered upper
portion of the Denver Formation (hereafter called the unconfined flow system [UFS])
north of the RMA boundary in the First Creek and northern paleochannels using
groundwater extraction wells
Treatment of the organic chemicals of concern (COCs) present in the groundwater
using carbon adsorption
Recharge of treated groundwater to the UFS using wells and trenches
• Natural attenuation of inorganic chloride and sulfate concentrations to meet applicable
standards for groundwater in a manner consistent with the Onpost remedial action
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Declaration for the Record of Decision
Continued operation of the North Boundary Containment System (NBCS) and the Northwest
Boundary Containment System (NWBCS) - In addition, the Irondale Contaminant System
(ICS) will continue to operate, as required, for onpost contaminants consistent with the
Irondale Interim Response Action (IRA). These containment systems will be operated to the
requirements of Section 2.7 of the FFA, the Agreement for a Conceptual Remedy for the
Cleanup of the Rocky Mountain Arsenal (Conceptual Remedy Agreement), and the onpost
ROD, when it is signed. Cessation may occur as provided in Sections 35.3 and 35.4 of the
FFA and paragraph 20 of the Conceptual Remedy Agreement.
Improvements to the NBCS, NWBCS, ICS, and the Offpost Groundwater Intercept and
Treatment System as necessary
Long-term groundwater monitoring (including monitoring after groundwater treatment has
ceased to assure continued compliance with the groundwater containment system remedia-
tion goals)
Five-year site reviews
Exposure control/provision of alternate water supply as follows:
As of the date of the Onpost ROD, and based on a .392 parts per billion (ppb) detec-
tion limit, the U.S. Army will use the last available quarterly monitoring results to
determine the DIMP plume footprint.
As part of the Onpost ROD, the U.S. Army and Shell Oil company will pay for the
extension of, and hook-up to, the current distribution system for all existing well
owners within the DIMP plume footprint referenced above.
Existing domestic well owners outside of the DIMP plume footprint as of the date of
the Onpost ROD where it is later determined that levels of DIMP are eight ppb or
greater (or other relevant CBSG at the time) will be hooked up at the U.S. Army and
Shell Oil Company's expense to the SACWSD distribution system or provided a deep
well or other permanent solution.
For new domestic wells with DIMP levels of eight ppb or greater (or other relevant
CBSG at the time), the Offpost ROD institutional controls will provide that the U.S.
Army and Shell Oil Company will pay for hook-up to the distribution system or
provided a deep well or other permanent solution.
Any user of a domestic well within the Offpost Operable Unit that contains ground-
water contaminants derived from RMA at concentrations that exceed the greater of
the remediation goals in Tables 7.1 through 7.3 or the ARARs in Table 10.1 will be
provided an alternative water supply. Bottled water will be provided for cooking and
drinking until a permanent alternative water supply is provided. Permanent alter-
native water supplies could include installation of a deep uncontaminated well or
connection to a municipal potable water-supply system. This commitment applies to
both users of existing domestic wells and users of wells that are lawfully drilled in
the future.
Institutional controls to prevent the use of groundwater exceeding remediation goals.
Closure of poorly constructed wells within the Offpost Study Area that could be acting as
migration pathways for contaminants found in the Arapahoe Aquifer.
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• The U.S. Army and Shell Oil Company agree to continue monitoring and to complete an
assessment of the MDMA plume by June 13,1996, using a 20 ppt method detection limit.
• The U.S. Army and Shell Oil Company agree to prepare a feasibility study of potential
actions, both onpost and at the boundary, or adjacent to the boundary in order to achieve
MDMA remediation goals at the RMA boundary and to use 7.0 ppt PRG or a certified
analytical detection level readily available at a certified commercial laboratory (currently
33 ppt).
• The U.S. Army and Shell Oil Company agree to revegetate approximately 160 acres located in
the southeast portion of Section 14 and the southwest portion of Section 13 as depicted in
Figure 9.1. Revegetation will involve tilling and seeding. No sampling will be conducted
before or after revegetation. Existing soil risks in the are to be revegetated fall within EPA;s
establish acceptable risk range and revegetation is not necessary. However, the U.S. Army
and Shell Oil Company agree to the revegetation program as part of the offpost settlement.
• The Army will treat any contaminated extracted groundwater prior to discharge or reinsertion
so that it meets the current water quality standards established in the Colorado Basic
Standards for Groundwater and the Colorado Basic Standards and Methodologies for Surface
Water.
• As part of the Onpost remedy, the U.S. Army and Shell Oil Company will pay for and
provide, or arrange for the provision, of 4000 acre-feet of water to SACWSD.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment, complies with federal and
state requirements that are legally applicable or relevant and appropriate to the remedial action, and
is cost-effective. The remedy uses permanent solutions and alternative treatment technologies to the
maximum extent practicable. The remedy satisfies the statutory preference for remedies that employ
treatment that reduces toxicity, mobility, or volume as a principal element.
Because this remedy may result in hazardous substances remaining in the groundwater of the Offpost
OU for more than five years, a review will be conducted within five years after commencement of
remedial action to ensure that the remedy continues to adequately protect human health and the
environment.
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Declaration for the Record of Decision
SIGNATURE PAGE
(7
iam P. Yellowtail
ional Administrator, Region VIII
ited States Environmental Protection Agency
Raymokd)Fatz t/
Acting Deputy Assistant Secretary of the Army
(Environment, Safety and Occupational Health)
STATE OF COLORADO CONCURRENCE
Tom Looby X'/
Director, Office of Environmefar
Colorado Department of Public Health and Environment
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DECISION SUMMARY FOR THE RECORD OF DECISION
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1.0 SITE NAME, LOCATION, AND DESCRIPTION
The Rocky Mountain Arsenal (RMA) National Priorities List (NPL) site is comprised of two Operable
Units (OUs): Onpost and Offpost. As shown in Figure 1.1, the Offpost Study Area occupies approxi-
mately 27 square miles in southern Adams County, Colorado, and lies north of the Denver metropo-
litan area and east of Commerce City, Colorado. The Offpost Study Area is defined as the area
southeast of the South Platte River, north of 80th Avenue, southwest of Second Creek, and north of
the north and northwest boundaries of RMA. Additionally, the Offpost Study Area includes the
surface waters of O'Brian Canal and Burlington Ditch as they extend northeast from Second Creek to
Barr Lake and the surface waters of First Creek and Barr Lake. The Offpost OU (also shown in
Figure 1.1) is defined by the RMA Federal Facility Agreement (FFA) as that portion of the Offpost
Study Area where hazardous substances, pollutants, or contaminants from RMA are found and are
subject to remediation. The Offpost OU encompasses rural residential, agricultural, and commercial
and industrial areas located north and northwest of RMA.
Areas within the Offpost OU are used for rangeland, dryland farming, and irrigated farming with
some rural residential areas and scattered areas of intensive agricultural use. Parts of the Offpost OU
are currently zoned and developed for commercial/industrial activities. Commerce City, located west
of RMA, is the only urban area in the immediate vicinity of the Offpost OU and has recently annexed
lands within the Offpost OU.
On the basis of an evaluation of planning information provided by the Adams County Planning
Commission, it is projected that areas of commercial, industrial, and urban residential land use will
increase in the Offpost OU (Adams County Planning Commission, 1987). Rural residential (including
agricultural) land use is expected to decrease in the Offpost OU because anticipated increases in
property values are expected to preclude increased traditional crop and livestock production land
use, including hobby farming as discussed in the Airport Environs Plan (Adams County, City of
Aurora, City of Brighton, City of Commerce City, 1990).
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Site Name, Location, and Description
1.1 Environmental Setting
The topography of the Offpost Study Area consists of stream-valley lowlands separated by gently
rolling uplands. The maximum local topographic relief in the Offpost Study Area is approximately
100 feet. The elevation above mean sea level ranges from approximately 5140 feet at the northern
and northwestern boundary of RMA to approximately 5030 feet at the South Platte River.
Cropland and rangeland provide habitat for numerous animal species. Lake and wetland areas at
Barr Lake provide feeding, breeding, and roosting areas for waterfowl and endangered species,
including the bald eagle. The climate of the Offpost Study Area is characterized by sunny, semiarid
conditions.
The regional surface drainage is to the northwest toward the South Platte River. Surface water
originating south of RMA, on RMA, or in the Offpost Study Area flows toward the South Platte River.
Two major canals, O'Brian Canal and Burlington Ditch, and several smaller ditches flow from
southwest to northeast between RMA and the South Platte River. O'Brian Canal receives some
drainage from the Offpost Study Area and RMA where the canal intercepts First Creek. Burlington
Ditch may receive surface water infrequently from First Creek.
1.2 Geology
Sediment at the land surface in the Offpost Study Area consists of unconsolidated alluvial and eolian
deposits. The composition of the unconsolidated sediment varies from clays to coarse gravels, and
the thickness varies from less than 10 feet to approximately 100 feet. The thickest deposits of
unconsolidated sediment occur in paleochannels eroded into the underlying Denver Formation.
The Denver Formation consists of 250 to 300 feet of interbedded shale, claystone, siltstone, and
sandstone, with a regional dip of 1/2 to 1 degree to the southeast. The presence of paleochannels in
the Denver Formation surface impacts groundwater flow in the unconsolidated sediment and the
upper weathered portion of the Denver Formation. Three such paleochannels, the First Creek,
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Site Name, Location, and Description
northern, and northwestern paleochannels, are present in the Offpost Study Area. Coarse, unconsoli-
dated materials commonly found within these paleochannels provide preferential pathways for
groundwater movement. Groundwater contaminant plumes that have historically migrated across the
RMA boundaries to the Offpost OU contain the highest concentrations of contaminants in and near
these paleochannels. The Arapahoe Formation lies beneath the Denver Formation at depths of 230 to
300 feet at the RMA north boundary and has a regional dip of 1/2 to \ degree to the southeast. The
formation consists of 400 to 700 feet of interbedded conglomerate, sandstone, siltstone, and shale.
The upper portion of the Arapahoe Formation consists predominantly of 200 to 300 feet of blue to
gray shale with some conglomerate and sandstone beds. The lower portion consists largely of
sandstone and conglomerate with less prevalent beds of shale. The lower portion is a source zone for
many water-supply wells in the area. A thick, impermeable claystone unit is variously assigned to
the lower Denver formation and the upper Arapahoe Formation. The claystone unit is called the
"Buffer Zone" and is approximately 50-ft. thick. This unit further isolates the underlying Arapahoe
aquifer from any localized contamination in the Denver confined flow system. The Arapahoe
Formation is the oldest geologic unit present beneath the Offpost Study Area that was investigated
during the Offpost Remedial Investigation program.
Alluvial and eolian deposits form the ground surface in the Offpost Study Area. The Denver
Formation and Arapahoe Formation are not present at the ground surface anywhere in the Offpost
Study Area.
1.3 Hydrogeology
The two principal water-bearing units in the Offpost Study Area that have been impacted by
contaminants originating from RMA are the unconsolidated alluvial deposits and the underlying
Denver Formation. The hydraulic properties of these two units, including hydraulic conductivity,
porosity, and associated groundwater flow velocities, are distinctly different. The low permeability of
the Denver Formation and upper Arapahoe Formation limit contaminant transport into the lower
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Site Name, Location, and Description
Arapahoe Formation. Hydraulically, the two units generally behave as two distinct hydrostrati-
graphic units: the unconfined flow system (UFS) and the confined flow system (CFS).
The UFS includes groundwater present in the unconsolidated materials overlying the Denver
Formation, the weathered upper portion of the Denver Formation, and, where the Denver Formation
is missing near the South Platte River, the weathered upper portion of the Arapahoe Formation. The
CFS includes the deeper portions of the Denver Formation and the underlying Arapahoe Formation.
On the basis of an evaluation of the distribution of contaminant plumes in the Offpost Study Area,
the UFS is considered the principal migration route for groundwater contaminants from RMA to the
Offpost Study Area, although some contaminants are present in the CFS. Although low-level
contamination may be present in isolated portions of the Denver Formation CFS, this formation has
low productivity as a groundwater resource.
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2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES
2.1 Operational History
Congress established RMA in 1942. The United States acquired land included within the boundaries
of the Arsenal for chemical weapons manufacturing, constructed a base, and commenced Army
weapons production and ancillary activities in 1943. From 1945 to 1950, RMA distilled available
stocks of mustard, demilitarized several million rounds of mustard-filled shells and incendiary
munitions, and test-fired mortar rounds filled with smoke and high explosives. Also, many different
types of obsolete World War II ordnance were destroyed by detonation or burning.
After the conclusion of World War II, selected surplus facilities were leased to nongovernment
entities as warehouses and for the manufacture of agricultural chemicals. Colorado Fuel and Iron
(CF&I) leased facilities at RMA in 1946. Julius Hyman & Company (Hyman) first leased facilities in
1947 and succeeded to the CF&I leasehold interest, with some modifications and additions in 1949.
Shell Oil Company (Shell) acquired a majority interest in Hyman in 1952 and operated the plant as
the Julius Hyman Company until 1954, when the operation became the Shell Chemical Company -
Denver Plant.
RMA was selected as the site for construction of a facility to produce Sarin, a nerve agent. The
facility was completed in 1953, with the manufacturing operation continuing until 1957 and the
munitions-filling operations continuing until late 1969. From 1970 until 1984, the primary operation
at RMA was the disposal of chemical warfare material. Disposal practices included incinerating TX
anticrop agent and mustard agent explosive components and destroying Sarin and related munitions
casings by caustic neutralization.
Chemicals were introduced to the RMA environment primarily by the burial or surface disposal of
solid wastes, discharge of wastewater to basins, and leakage of wastewater and industrial fluid from
chemical and sanitary sewer systems. Munitions were destroyed and disposed in trenches.
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Site History and Enforcement Activities
Wastewater generated by the U.S. Department of the Army (Army) and private industry in the South
Plants and North Plants areas was discharged to a series of unlined evaporation and holding basins
(Basins A, B, C, D, and E) and to asphalt-lined Basin F at various times throughout the history of
RMA operations. The locations of these source areas are shown in Figure 2.1.
The primary areas that have contributed to groundwater contamination at RMA include (I) former
manufacturing facilities, (2) former waste storage basins, (3) solid waste disposal areas, (4) the
chemical sewer system, (5) locations within, the rail classification yard, and (6) the motor pool area.
2.2 Previous Investigations
From 1975 to the present, numerous groundwater monitoring programs have been conducted at RMA,
both onpost and offpost, by the Army. The U.S. Environmental Protection Agency (EPA) has also
conducted several offpost investigations. The Army designed and implemented monitoring programs
to monitor regional groundwater and surface-water quality. The Army also designed and
implemented the boundary system monitoring program to support the operation of the boundary
groundwater containment systems.
2.2.1 U.S. Environmental Protection Agency Study Area
Several organic chemicals were detected in South Adams County Water and Sanitation District
(SACWSD) wells in 1981, as part of a random national survey of drinking water systems conducted
by EPA. Additional sampling in 1982 and 1985 confirmed these initial findings. As a result, EPA
began a remedial investigation/feasibility study (RVFS) of an area west of RMA and south of the
Offpost Study Area (Figure 1.1).
RMA was suspected as one of the possible sources of contaminants in the EPA study area because of
RMA's historical waste disposal practices. To mitigate the groundwater contamination problem, the
Army and EPA built a water-supply system for SACWSD. Further investigation by EPA's Field
Investigation Team indicated that source areas in addition to RMA contributed to groundwater
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Site History and Enforcement Activities
contamination detected within the EPA study area. Groundwater monitoring wells installed on the
Chemical Sales Company (CSC) property have since identified CSC as a significant source of
groundwater contamination in the EPA study area. Recent investigations by EPA and the Army have
detected the presence of a trichloroethene plume entering RMA at Section 9, Township 3S,
Range 67W along the southern boundary of RMA, as described in the Western Tier Report, the
Stapleton Airport Environmental Assessment (Camp Dresser & McKee, Inc., 1993), and the CSC ROD
(EPA, 1991a, 1991b, 1992). (Ebasco Services, Inc., 1988),
2.2.2 U.S. Department of the Army Investigation
Because chemicals were detected in the Offpost Study Area, the Army initiated a regional hydro-
geologic surveillance program requiring the quarterly collection and analysis of samples from more
than 100 onpost and offpost wells and surface-water stations. The program was carried out under
the direction of the RMA Contamination Control Program, established in 1974 to ensure compliance
with federal and state environmental laws. The objectives of the program were to (1) evaluate the
nature and extent of contamination and (2) develop response actions to control contaminant
migration. Potential and actual contaminant sources were assessed, and contaminant migration
pathways were evaluated.
From 1975 to the present, numerous groundwater monitoring programs have been conducted at RMA.
The Army designed and implemented the 360 Degree Monitoring Program to monitor regional
groundwater and surface water. The Army designed and implemented a boundary system monitoring
program to support the operation of the boundary groundwater containment systems. Studies
conducted at RMA to assess groundwater and surface-water conditions are discussed below.
The RMA Offpost Contamination Assessment Report (CAR) (Environmental Science and Engineering,
Inc. [ESE], 1987a) incorporated data from several studies to define the concentrations and distri-
bution of offpost contamination north and northwest of RMA. The scope of the CAR investigation
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was intended to address critical data gaps required to evaluate a comprehensive set of multimedia
exposure pathways.
The potential for contamination of private wells was investigated in the mid-1980s during the Con-
sumptive Use (CU) Studies, Phases I, n, and III. The CU Phases I and II studies addressed the
Offpost Study Area. In the CU Phase HI study, the Army conducted an inventory of privately-owned
drinking water wells in an area bound by East 80th Avenue on the south, East 96th Avenue on the
north, the South Platte River on the west, and RMA on the east. The objectives of the CU Phase III
study were as follows:
• Locate all shallow domestic wells (less than 100 feet) in the Offpost Study Area.
• Sample a representative number of the located wells.
• Assess the groundwater quality of the shallow alluvial aquifer.
The Army developed the Comprehensive Monitoring Program (CMP), a long-term multimedia
monitoring program designed to provide data to facilitate evaluation of response actions, in the mid-
1980s. Sample collection under the CMP commenced in 1987 and is continuing as the Groundwater
Monitoring Program (GMP).
An RI was initiated in 1985 by the Army in the Offpost Study Area. The primary objectives of the
Offpost RI were as follows:
• Collect additional data to refine the current understanding of groundwater flow and surface-
water patterns and the nature and extent of contaminants offpost of RMA.
• Evaluate the potential for chemical migration to the Offpost Study Area in various environ-
mental media, such as groundwater, surface water, sediment, air, and biota.
Following completion of the RI, it was apparent that additional data were needed before evaluation
and selection of a remedial alternative could occur. Therefore, a second RI was initiated in 1988 to
collect additional data for groundwater, surface water, soil, sediment, and biota (plants and animals).
The results of the second RI are reported in the Offpost Operable Unit Remedial Investigation, Final
Addendum (HLA, 1992b).
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2.3 Boundary Containment Systems
Concurrent with and as a result of the EPA and Army investigations, the Army constructed three
boundary containment systems (the North Boundary Containment System [NBCS], the Northwest
Boundary Containment System [NWBCS], and the Irondale Containment System [ICS] at the north,
northwestern, and western boundaries of RMA, respectively) to minimize offpost discharge of RMA
chemicals via groundwater. The locations of these containment systems are shown in Figure 1.1. All
three systems currently intercept and treat contaminated groundwater and recharge treated water to
the UFS.
2.3.1 North Boundary Containment System
The NBCS is just south of the RMA north boundary in Sections 23 and 24. The NBCS consists of
(I) a system of extraction wells that remove contaminated groundwater from the UFS, (2) a soil-
bentonite barrier that impedes migration of contaminated groundwater to the Offpost Study Area,
(3) a carbon-adsorption treatment system that removes organic contaminants from extracted
groundwater, and (4) a system of recharge wells and trenches that return treated groundwater to the
UFS.
The NBCS pilot system became operational in 1978. The pilot system was expanded approximately
1400 feet to the west and 3840 feet to the east in 1981 during the second phase of construction.
Several improvements have been made to the NBCS since 1981: ten recharge trenches were added to
the west end of the system and became operational in December 1988, and five additional recharge
trenches were added to the east end of the system in 1990. Currently, the soil-bentonite barrier is
6740 feet long, approximately 3 feet wide, and varies in depth from 20 feet at the western end to
more than 40 feet along the eastern extension. The barrier is anchored in the Denver Formation.
Review of groundwater contaminant distribution patterns indicates that the NBCS is having a
significant effect on the distribution of organic compounds in the Offpost Study Area. Monitoring
program data indicate that contaminant concentrations downgradient of the NBCS are decreasing.
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Activated carbon is being used to effectively remove the organic contaminants from the extracted
groundwater to meet containment system remediation goals. Organic contaminant concentrations are
generally below certified reporting limits (CRLs) in system effluent.
2.3.2 Northwest Boundary Containment System
The NWBCS is along the northwest boundary of RMA in the southeast quarter of Section 22.
Constructon of the NWBCS began in 1983, and the system became operational in 1984. The NWBCS
originally consisted of (1) 15 extraction wells, (2) a soil-bentonite-barrier approximately 1600 feet in
length, (3) a carbon adsorption treatment system, and (4) a system of 21 downgradient recharge wells.
The carbon adsorption system was designed to intercept and remove dibromochloropropane and
other organic compounds from a plume of contaminated groundwater originating onpost.
Contaminant bypass was observed at the southwest and northeast ends of the NWBCS in 1988. An
interim resonse action (IRA) to improve the NWBCS was initiated in 1989. In April 1990, the
NWBCS Improvements IRA was divided into two phases: NWBCS Short-term Improvements IRA and
NWBCS Long-term Improvements IRA. Under the NWBCS Short-term Improvements IRA, which was
completed in 1991, the existing slurry wall was extended 665 feet to the northeast to prevent
contaminant bypass, and two additional extraction wells were added at the northeast end of the
extraction well alignment. Three additional extraction wells and four additional recharge wells were
installed in Section 27, southwest of the NWBCS in August 1991. The NWBCS Long-term Improve-
ments BRA is being used to assess the NWBCS and its short-term improvements by reviewing
groundwater monitoring data.
2.3.3 Irondale Containment System
The ICS, which became operational in 1981, is at the southern end of the RMA northwest boundary
within Section 33 and consists of (1) a hydraulic control system of extraction and recharge wells, and
(2) a carbon adsorption treatment system. The ICS was originally developed to intercept the
migration of dibromochloropropane (DBCP) at the RMA boundary. There have been no downgradient
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Site History and Enforcement Activities
detections of DBCP after the first two years of operation. The majority of the area downgradient of
the ICS is contained within the EPA study area, although portions of the downgradient area are
within the confines of the Offpost Study Area. Therefore, the design and operation of the ICS was
not included in the evaluation of alternatives; however, the continued operation of the ICS, as
required, for onpost contaminants consistent with the Irondale ERA remains an integral part of the
Army's offpost contaminant reduction program to meet onpost cleanup goals defined in the Irondale
IRA. Cessation of operation of the ICS will be in accordance with paragraphs 35.2 and 35.4 of the
FFA and paragraph 20 of the Conceptual Remedy Agreement.
2.4 Interim Response Actions
As part of the Army's compliance with the requirements of the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA), and as described in the FFA, the Army has
instituted several IRAs that have been performed concurrently with the ongoing onpost and offpost
RI programs. IRAs, which are designed to be compatible with the final remedy, are actions taken
before the signing of the Record of Decision (ROD) and are expedited remedial measures to contain,
remove, or treat wastes before the final remedy is selected. Numerous IRAs have been implemented
to mitigate contamination both onpost and offpost. As indicated in the previous sections, some
portions of the boundary containment systems have been constructed as IRAs. The Offpost IRA is
discussed in the following section.
2.4.1 Offpost Interim Response Action
The Offpost IRA addresses groundwater contaminant migration north of RMA and downgradient of
the NBCS along two primary contaminant pathways, defined by the First Creek and northern
paleochannels.
Evaluation and selection of the collection and treatment system components that comprise IRA A,
referred to as the Offpost Groundwater Intercept and Treatment System, began in 1988. The Offpost
Groundwater Intercept and Treatment System Decision Document (HLA, 1989) presents the basis for
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Site History and Enforcement Activities
system placement to address remediation of contamination in alluvial groundwater in the First Creek
and northern paleochannels. The system was designed to intercept and extract contaminated
groundwater from the UFS, treat the groundwater for organics, and recharge treated water to the UFS.
Construction of the Offpost Groundwater Intercept and Treatment System began in November 1991
and was completed in June 1993. Groundwater extraction is accomplished through a network of
extraction wells. The organic contaminants in extracted groundwater are treated using activated
carbon adsorption, and the treated water is then recharged to the UFS using a combination of
recharge wells and trenches.
The Offpost Groundwater Intercept and Treatment System was designed to be flexible and to be
compatible with the final remedy, consistent with EPA guidance and the FFA.
2.5 History of CERCLA Enforcement Activities
Most of RMA was added to the National Priorities List (NPL) in 1987; Basin F was added in 1989. As
such, RMA is subject to compliance with CERCLA (also known as Superfund). A facility is subject to
compliance with CERCLA when a release or a threat of a release of hazardous substances from the
facility has occurred and when response costs have been incurred. In some cases, the potentially
responsible parties (PRPs) either cannot respond or cannot be found, so funding for the response
comes from the government fund called Superfund. At RMA, the Army and Shell were identified as
PRPs and are funding the cleanup.
On February 1,1988, a proposed Consent Decree was filed in the case of U.S. v. Shell Oil Company
with the U.S. District Court in Denver, Colorado. A modified version of the Consent Decree was filed
on June 7,1988. The Consent Decree was entered by the U.S. District Court on February 12,1993.
On February 17,1989, an FFA was executed by the Army, Shell, EPA, the U.S. Department of the
Interior (DOI), the U.S. Department of Justice (DOJ), and the U.S. Agency for Toxic Substances and
Disease Registry (ATSDR). The FFA sets forth the procedures to be followed by the Organizations
(i.e., signatories to the FFA) to cooperate in the assessment, selection, and implementation of
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response actions resulting from the release or threat of release of contaminants from RMA. The FFA
designates the Army as the lead agency.
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3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION
Community participation opportunities were provided during the remedy selection process to fulfill
the requirements of CERCLA Sections 113(k)(2)(B)(i-v) and 117.
The RI, RI Addendum, Endangerment Assessment/Feasibility Study (EA/FS), and Proposed Plan for
the Offpost OU were released to the public on March 21, 1993. The documents were made available
to the public in the Administrative Record (located at the Joint Administrative Record Document
Facility at the west entrance to RMA at 72nd Avenue and Quebec Street), in an information
repository maintained at the EPA Docket Room in Region Vffl, and at the Adams County, Aurora,
Commerce City, Denver, Lakewood, Montbello, and Thornton Public Libraries. The notice of
availability for these four documents was published in the Denver Post and Rocky Mountain News
newspapers.
An expanded Community Relations outreach was implemented to ensure community members had
the opportunity to comment on the Proposed Plan for the Offpost OU. Community outreach started
in January 1993 with the announcement that all documents supporting an impending Proposed Plan
were available for review in local libraries. A direct mailing to more than 1200 local citizens was
made.
In March 1993, a press release was made and a legal notice was published announcing that a public
meeting was scheduled for April 28, 1993, at Dupont Elementary School, Commerce City, Colorado,
to address the Proposed Plan. A separate letter was sent to citizens informing them of the documents
availability in the libraries. The letter also included a brief fact sheet summarizing the Proposed
Plan. Originally, the public meeting was scheduled for April 21,1993, at RMA. The Army received
requests to hold the meeting on a different day and offpost. Because of these factors and Earth Day
events in Denver for April 21, the meeting was moved to April 28, 1993.
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Highlights of Community Participation
A Media Day was held the day of the public meeting to provide local media information on the
Army's proposal. Both print and video media representatives attended.
Knowing the importance of the public meeting, the announcement was expanded to include display
advertising in 12 local and weekly newspapers in the Denver metropolitan area. This was in
addition to the normal press release and Media Day event.
As a result of comments received at the public meeting concerning the official comment period, the
Army published a legal notice and sent letters to citizens announcing that the comment period was
extended to June 21,1993.
At the April 28, 1993, public meeting, representatives from the Army, EPA, and the State of Colorado
answered questions regarding issues at the site and the remedial alternatives under consideration.
Responses to comments received during the public comment period are included in the Responsive-
ness Summary, which is part of this ROD (Appendix A). This decision document presents the
selected remedial action for the RMA Offpost OU in Adams County, Colorado, chosen in accordance
with CERCLA, as amended by the Superfund Amendments and Reauthorization Act (SARA), and
with the NEPA, and, to the extent practicable, with the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP). The decision for this site is based on the Administrative Record
for the Offpost OU.
Additionally, settlement discussions involving municipalities, local health departments, special
districts, and citizen groups were held from late 1994 until April 1,1995, to discuss the final
remedies for both Onpost and Offpost OUs. The Draft Final ROD (December 7, 1993) was revised
taking into account comments presented by the public, local communities, and the Parties.
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4.0 SCOPE AND ROLE OF THE OFFPOST OPERABLE UNIT
Three RMA boundary containment systems currently intercept, treat, and recharge groundwater at
the RMA north, northwest, and west boundaries. These boundary systems, along with the physical
boundaries of RMA, provide a logical delineation between OUs. Therefore, the FFA divided the work
into the following two OUs:
• Onpost OU: Media requiring remediation within the Onpost Study Area (within RMA
boundaries)
• Offpost OU: Media requiring remediation within the Offpost Study Area (outside RMA
boundaries)
The Offpost OU addresses contamination in the groundwater north and northwest of RMA. As
discussed in Section 6.0 of this ROD, groundwater contamination in the UFS poses the principal
potential threat to human health because of the risks from possible exposure to groundwater.
Although health risks are possible, the estimated risk levels are within the acceptable risk range
established by EPA. The purpose of the remedy is to (1) reduce groundwater contaminant concen-
trations, (2) reduce risk to human health and the environment, and (3) reduce the potential human
exposure to contaminated UFS groundwater.
The potential risks to ecological receptors were also evaluated. Wildlife are not exposed to contami-
nated groundwater; therefore, there are no risks to wildlife from the groundwater exposure. Wildlife
exposures to soil and surface water and potential livestock exposure to contaminated groundwater
were evaluated. However, the potential risks associated with these exposures were shown to be
negligible. Therefore, the selected remedy for the Offpost OU addresses the reduction of potential
human exposure to contaminated UFS groundwater.
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5.0 SUMMARY OF SITE CHARACTERISTICS
Six media were evaluated in the RI for the Offpost Study Area: groundwater, soil, surface water,
sediment, air, and biota. Each medium was evaluated in the Offpost EA with respect to (1) the
nature and extent of contamination and (2) potential exposure pathways and associated risk to
humans and the environment. A map delineating the boundaries of the Offpost Study Area is
included as Figure 1.1. The site characteristics are more fully described in the Offpost Operable Unit
Remedial Investigation Report (ESE, 1988a) and the Offpost Operable Unit Remedial Investigation,
Final Addendum (HLA, 1992b).
5.1 Sources of Contamination
As described in Section 2.1, chemicals were introduced to the RMA environment primarily by the
burial or surface disposal of solid wastes, discharge of wastewater to basins, and leakage of waste-
water and industrial fluid from chemical and sanitary sewer systems. Chemicals migrated to the
Offpost Study Area primarily by shallow (i.e., shallow or unconfined) groundwater and airborne
pathways. Contaminant transport in the shallow or unconfined groundwater has been controlled by
construction of the boundary containment systems and improvements to these systems (completed as
IRAs). Offpost Study Area surface water was contaminated primarily by the natural interaction with
offpost groundwater. Offpost Study Area surface soil was contaminated by the deposition of airborne
contaminants, non-RMA-related agricultural application of pesticides, and irrigation practices.
Agricultural sources of pesticides are discussed in the Final Offpost RI Addendum (HLA, 1992b). Air
monitoring data indicate that the air pathway does not contribute to human exposure.
5.2 Nature of Contamination
Several chemicals of concern (COCs) are present in offpost groundwater, surface water, sediment, and
soil (see Tables 6.1 through 6.4). COCs include organochlorine pesticides (OCPs), halogenated
aliphatics, aromatic hydrocarbons, diisopropylmethyl phosphonate (DIMP), sulfur-containing organic
chemicals, arsenic, and dissolved salts.
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Summary of Site Characteristics
The COCs exhibit great variability in their mobility and persistence in environmental media. OCPs
are less mobile than the other COCs and more persistent, tending to associate with soil and sediment
and to biomagnify in the food chain. Most of the remaining COCs are mobile in groundwater, and
the aromatics and aliphatics are volatile in surface water. The fate properties of the COCs tend to
determine their distribution in the Offpost Study Area. All COCs were detected in groundwater, but
the more mobile chemicals are more widely distributed. The OCPs are virtually the only COCs
detected at concentrations above background levels in soil and sediment. The volatile compounds
were not significantly elevated above background levels in surface water and, in fact, were rarely
detected.
5.3 Contamination Migration Pathways
The RI programs have shown that there are three groundwater migration pathways in the Offpost
Study Area. These migration pathways (shown in Figure 5.1) are referred to as the northern
paleochannel, due north of the RMA north boundary; the First Creek paleochannel, paralleling First
Creek to the northwest from the RMA north boundary; and the northwest paleochannel, northwest of
the RMA northwest boundary. The northern and First Creek paleochannels compose the North
Plume Group, and the northwest paleochannel composes the Northwest Plume Group. These two
plume groups encompass an area of approximately 590 acres in the Offpost Study Area. The alluvial
flow system transports most of the contamination in paleochannels characterized by coarser
sediment. Some of the groundwater traveling through the First Creek paleochannel discharges to
First Creek, probably seasonally, resulting in transfer of contaminants to First Creek.
Figure 5.1 also presents the offpost surface-water features. The primary surface-water pathway is
First Creek, which flows northwest from the northern RMA boundary. First Creek empties into
O'Brian Canal, which flows northeast and empties into Barr Lake. Burlington Ditch, which parallels
O'Brian Canal, also flows into Barr Lake. The majority of the surface-water contamination is located
in First Creek, with some contamination in O'Brian Canal downstream of the confluence with First
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Summary of Site Characteristics
Creek and Burlington Ditch. Barr Lake has not been shown to be contaminated with RMA-related
chemicals greater than naturally occurring background levels.
In addition to the contaminant migration pathways of groundwater and surface water, prevailing
winds transport onpost surface soil to offpost locations, and sediment provides a potential contami-
nant source for aquatic species.
5.4 Extent of Contamination
Varying levels of contamination exist in the following five media in the Offpost OU: groundwater,
surface water, stream-bottom sediment, surface and subsurface soil, and biota. More detailed
discussions of the offpost contaminant concentrations, along with figures showing concentration
distributions are found in Sections 3.0, 4.0, 5.0, and 6.0 of the Final Offpost RI Addendum (HLA,
1992bj.
5.4.1 Groundwater
Table 6.1 presents the groundwater COCs and the exposure point concentrations used in the
Endangerment Assessment. The most widespread RMA-related groundwater COG in the Offpost
Study Area is DIMP, which is present in the UFS at varying concentrations in a band from the west
end of the NWBCS to the east end of the NBCS, and from the RMA north and northwest boundaries
to. the South Platte River. The other primary contaminants present in the offpost UFS are chloro-
form, chlorobenzene,trichloroethene, tetrachloroethene, dibromochloropropane (DBCP), dieldrin,
endrin, dicycloj>entadiene (DCPD), arsenic, chloride, fluoride and sulfate.
The highest concentrations of DIMP observed in the past three years are in the First Creek paleo-
channel. Concentrations of DIMP are lower in the northern paleochannel and lower still in the
northwestern paleochannel. The maximum concentrations of DIMP in the Offpost Study Area have
decreased by approximately 50 percent over the past 10 years. The NBCS is currently operating and
has been operated in the past to remove multiple contaminants. DIMP concentrations are being
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Summary of Site Characteristics
reduced to less than 8 ppb. Cut-off of groundwater contaminants at the NBCS and recharge of the
treated groundwater has resulted in the observed decrease in DIMP concentrations specifically, as
well as the other contaminants found offpost.
The highest contaminant levels downgradient from the NBCS occur upgradient of the O'Brian Canal.
Certain volatile compounds such as chlorobenzene, chloroform, trichloroethene, and DBCP have been
detected at low concentrations downgradient from the canals, but well-defined plumes do not exist in
this area and these detections may be anomalous. Semivolatile organic compounds such as dieldrin
and other OCPs are present almost exclusively upgradient of the canals. Maximum concentrations of
the OCPs (i.e., aldrin, isodrin, chlordane, 2,2-bis[p-chlorophenyl]-l,l-dichloroethene[DDE], and
2,2-bis[p-chlorophenyl]-l,l,l-trichloroethane[DDT]) generally occur in the First Creek paleochannel
within 500 to 1000 feet of the NBCS. Only sporadic and isolated occurrences of OCPs are observed
northwest of the RMA northwestern boundary.
Contaminants found downgradient from the NWBCS are primarily chlorobenzene, chloroform, DIMP,
and dieldrin. The highest concentrations of chloroform occur downgradient of the RMA boundary.
Detections of chlorobenzene near the NWBCS may be anomalous. In 1989, semivolatile compounds
such as dieldrin and possibly DIMP appeared to have bypassed the NWBCS at the northeast and
southwest ends. Subsequently, the NWBCS IRA was initiated that included improvements and
operational changes to correct the bypass. Recent modifications to the NBCS and NWBCS, in
addition to the remedial action selected in this ROD, are expected to further reduce contaminant
levels downgradient of the RMA boundaries.
5.4.2 Surface Water
Table 6.2 presents the surface water COCs and the exposure point concentrations used in the
Endangerment Assessment. The principal organic compounds identified in Offpost Study Area
surface-water samples are DIMP and dieldrin. In general, the highest concentrations of the organic
and inorganic analytes were detected in First Creek. DIMP concentrations in First Creek were highest
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Summary of Site Characteristics
in the area 100 to 200 feet upstream of O'Brian Canal where groundwater discharges to First Creek.
DIMP was not detected in Burlington Ditch or O'Brian Canal upstream of the confluence with First
Creek. DIMP was detected in Barr Lake in only one of 20 samples collected from 1985 to 1990 and
was not detected in the duplicate sample collected at the same time. This one detection is anoma-
lous and not considered representative of conditions at Barr Lake.
The highest concentrations of arsenic were detected in First Creek near the northern RMA boundary.
These detections are likely associated with discharge from the onpost sewage treatment plant.
Mercury and arsenic were detected in surface water in O'Brian Canal upstream of the confluence
with First Creek, suggesting that sources of these contaminants other than RMA probably exist.
Some contaminants identified in O'Brian Canal and Burlington Ditch may originate from the
diversion of treated sewage effluent from Denver.
5.4.3 Stream-bottom Sediments
Table 6.3 presents the sediment COCs and the exposure point concentrations used in the Endanger-
ment Assessment. The most commonly detected contaminants in stream-bottom sediment in the
Offpost Study Are'a were dieldrin, arsenic, and mercury. The highest concentration of dieldrin was
found in First Creek immediately north of the northern RMA boundary. Additional contaminants
were detected in O'Brian Canal and Burlington Ditch upstream of the confluence with First Creek,
suggesting that sources of these contaminants other than RMA probably exist such as diversion of
treated sewage effluent from Denver.
5.4.4 Surface and Subsurface Soil
Table 6.4 presents the soil COCs and the exposure point concentrations used in the Endangerment
Assessment. Approximately 100 soil samples were collected as part of the RI Addendum investi-
gation and were analyzed for OCPs, arsenic, and mercury. Dieldrin was the most frequently detected
OCP (in approximately 90 percent of the samples) with a maximum concentration located approxi-
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Summary ol Site Characteristics
mately 100 to 200 feet north of the northern RMA boundary. DDT, DDE, aldrin, endrin, and
chlordane were detected less frequently.
The distribution of OCPs in Offpost Study Area soil appears to correlate with the dominant wind
patterns at RMA. The greatest number and highest contaminant concentrations are observed in
samples collected immediately north of the northern RMA boundary, consistent with the prevalent
wind direction of south to north. Isolated elevated concentrations of OCPs observed between the
northern RMA boundary and O'Brian Canal may be the result of local residential and/or commercial
use of pesticides and not related to migration from RMA. Anomalously high concentrations of
dieldrin, DDE, and DDT were also detected approximately 1.5 miles northwest of RMA. These
detections are considered to be agricultural-related and not RMA-related because the area is currently
and has historically been a farming community.
The uneven distribution of arsenic and mercury in Offpost Study Area surface soil suggests that the
occurrence of these inorganic contaminants is not related to RMA activities.
5.4.5 Biota
The RI Addendum biota monitoring program provided additional data to assess the potential impacts
on plants and animals in the Offpost Study Area. During the RI Addendum study, biota samples
were analyzed for aldrin, dieldrin, endrin, DDE, DDT, DBCP, arsenic, and mercury. Dieldrin, the
contaminant most often found in Offpost Study Area biota (36 percent of samples), was detected in
cattle, chicken, fish, earthworm, deer mouse, prairie dog, and pheasant samples. Arsenic and
mercury were detected less frequently (19 and 14 percent, respectively). DDE was detected only
once, and aldrin, endrin, DDT, and DBCP were not detected in any biota samples from the Offpost
Study Area. Contaminants identified in the Offpost Study Area biota survey are similar to those
found onpost, although the concentrations detected in the Offpost Study Area biota are considerably
lower than concentrations detected in the onpost biota.
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The Offpost Study Area is known to contain suitable habitat for endangered species such as the bald
eagle. A nesting pair of eagles was identified during offpost assessment activities. Contaminants
(mercury, dieldrin, and DDE) were detected in a bald eagle egg collected in 1988 from a nest at Ban-
Lake. According to the U.S. Fish and Wildlife Service, the concentrations of these contaminants
were typical of bald eagle egg contamination throughout the United States.
5.5 Potential Routes of Human and Environmental Exposure
Based on the current land uses in the Offpost Study Area, a review of local city and county planning
and zoning ordinances, and consultation with local planning authorities, three primary land uses
were considered in estimating the risks to human health. These land uses are urban residential, rural
residential, and commercial and industrial. The exposure routes and pathways considered for the
Offpost Study Area include the following:
• Ingestion of groundwater
• Ingestion of soil
• Ingestion of sediment
• Ingestion of vegetables
• Ingestion of dairy products
• Ingestion of eggs
• Ingestion of meat
• Ingestion of surface water
• Inhalation of volatile chemicals in groundwater
• Inhalation of dust
• Dermal contact with soil
• Dermal contact with sediment
• Dermal contact with surface water
• Dermal contact with groundwater
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6.0 SUMMARY OF SITE RISKS
The risks estimated in the EA and summarized in this section are baseline risks corresponding to
current conditions and are, therefore, pre-remediation risk estimates. Implementation of the selected
remedy presented (Section 9.0) will lower the potential risks. The estimated maximum cumulative
potential cancer risk to humans in the Offpost Study Area is 3 x 10"4 (or 3 in 10,000 people) on the
basis of the reasonable maximum exposure (RME) risks presented in the Final EA (Volume HI,
Section 4.0, and Volume IV, Appendix G). This estimated potential risk level is within the accept-
able risk range established by EPA (1 x 10"6 to 5 x 10"4; letter from EPA to Army dated February 21,
1992). A cancer risk estimate of 3 in 10,000 indicates an upperbound estimate of risk. Actual cancer
risks are likely to be below this level and may be as low as zero. These carcinogenic risks are
usually termed "excess lifetime cancer risks," which means there is an increased chance of an
individual developing cancer over 70 years of exposure to the carcinogenic chemicals in excess of the
normal cancer rate. The background cancer rate determined by the American Cancer Society is
about 1 in 3.
Because the Offpost Study Area cumulative risk is less than the upper risk level established by EPA,
remedial action in the Offpost Study Area is not required. The Army, nevertheless, recognizes that
several site-specific factors suggest that remediation of the groundwater is preferable to no action in
the Offpost OU. These site-specific factors are: (1) groundwater contributes a maximum risk of
2 x W4, or approximately 75 percent of the total carcinogenic risk, (2) maximum contaminant levels
(MCLs), maximum contaminant level goals (MCLGs), and Colorado Basic Standards for Groundwater
(CBSGs) are exceeded for some groundwater contaminants, and (3) hazard indices (His) for children
exceed 1.0 in Zones 2, 3, and 4. Although the estimated child hazard indices exceed 1.0 in Zones 2,
3, and 4, the bulk of the HI value is contributed through an assumed domestic use of alluvial
groundwater, which is not presently occurring in the Offpost OU. Treatment of groundwater to the
containment system remediation goals will reduce (1) the total estimate risk to less than 1x10"* and
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toward 1 x 10"6 and (2) the His to less than 1.0 in Zones 2, 3, and 4. Soil, surface water, and
sediment do not require remediation because of the low risk attributable to these media. Air was not
identified as a medium of concern on the basis of air monitoring data and initial risk screening.
Protection of biota was evaluated through development of ecological exposure criteria for the
protection of species potentially at risk. The ecological assessment indicated that the potential for
adverse ecological effects is minimal.
6.1 Human Health Risks
Human health risks in the Offpost Study Area were calculated in four steps: identification of COCs,
exposure assessment, toxicity assessment, and risk characterization. It should be noted that many of
the exposures evaluated do not currently exist and therefore do not represent existing exposures.
6.1.1 Identification of Chemicals of Concern
A data set consisting of groundwater, surface water, sediment, soil, air, and biota data collected
between 1985 and 1991 was used to evaluate which chemicals were of concern to human health and
the environment. A trend of declining contaminant concentrations in groundwater since 1985 was
noted in portions of the Offpost Study Area, particularly near the north boundary of RMA and
downgradient of the NBCS. This trend is due to the operation and improvement of the boundary
systems and natural attenuation processes. Considering this trend, only the most recent groundwater
data (i.e., from 1989 through 1991) were used to estimate groundwater exposure point concentrations.
Data for the other media were also considered, and only the data resulting from analytical methods
sensitive enough to detect low concentrations were used. Data were also compared statistically with
background concentrations consistent with EPA guidance presented in Risk Assessment Guidance for
Superfund (EPA, 1989a). Statistical procedures included the Wilcoxonrank sum test and the Method
of Proportions. These procedures are discussed in Section 1.2 of the Final Offpost EA/FS (HLA,
1992a).
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The primary criterion for identifying COCs was that the chemical concentrations at locations of
expected maximum concentration (i.e., near the RMA borders) must be significantly greater than
concentrations found at background locations (i.e., no RMA-related contamination present). By
applying statistical methods, Offpost Study Area contaminant concentrations were compared to
background concentrations at reference locations. If statistical analysis indicated that Offpost Study
Area concentrations were significantly higher than the background concentrations, the presence of
the chemical in the Offpost Study Area was considered to be RMA-related and the chemical was
designated as a COG. This procedure was followed for each environmental medium. Tables 6.1
through 6.4 list the GOCs for groundwater, surface water, sediment, and soil, respectively. The
exposure point concentration associated with each COC is also shown in the tables.
To select COCs for biota (plants and animals), analytical data obtained from the onpost biota RI were
compared to background chemical concentrations available in the scientific literature. This
procedure was less precise but nonetheless indicated that two chemicals (dieldrin and arsenic) may
be elevated, although in low concentrations, in the tissues of animals located in the Offpost OU.
6.1.2 Exposure Assessment
6.1.2.1 Offpost Study Area Exposure Assessment Zones
The Offpost Study Area is a large, heterogeneous area with a variety of characteristics that can affect
exposure levels. Specifically, distinct zones of the Offpost Study Area exhibit different exposure
concentrations of COCs in groundwater, surface water, and surface soil, including hot spots where
contaminant levels are higher than the average for the entire Offpost Study Area. In addition,
population density, land use, and water use varies throughout the Offpost Study Area. Therefore, to
avoid diluting or averaging contaminant concentrations over the entire Offpost Study Area, the
Offpost Study Area was subdivided into six zones (Figure 6.1) with different exposure conditions.
The primary factor used to define the exposure zones was the pattern of COC concentrations in
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groundwater. The six zones, and the land use and populations evaluated within each zone, are
described below.
Zone 1 is an area with relatively low levels of COCs in groundwater and surface soil. Rural
residential land use, which includes consumption of homegrown vegetables, milk, meat, and eggs, is
the current and potential future population characteristic.
Zone 2 is an area of relatively high levels of COCs in groundwater, low levels of COCs in surface soil,
and no permanent surface-water features. A rural residential land-use scenario, identical to Zone 1,
was evaluated.
Zones 3 and 4 are similar. Zone 3 is an area of relatively high levels of pesticide COCs in ground-
water, surface water, and surface soil. Zone 4 is an area of relatively high levels of COCs in
groundwater and surface water, but relatively low levels of COCs in surface soil. Both Zones 3 and 4
have recently been purchased by Shell Oil Company and are expected to be unoccupied at least until
completion of offpost remediation. Plans for improvement of 96th Avenue as an access road for the
new Denver International Airport may result in predominantly commercial and industrial land use in
these zones. An urban residential land use for Zones 3 and 4 is considered possible and was
selected for evaluation because this land use would result in higher exposures than the current land
use. Urban land use assumes that exposure to meat, dairy, and eggs would not occur, but that local
planting and consumption of vegetables are possible.
Zone 5 is an area with moderate levels of COCs in groundwater and relatively low levels of COCs in
surface soil. A commercial and industrial land use for Zone 5 was evaluated. Zone 5 is zoned for
industrial use over the majority of its area, is currently developed for industrial use, and is projected
as industrial land use for the future.
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Zone 6 is an area with moderate levels of COCs in groundwater and relatively low levels of COCs in
surface soil. Because farm residences currently exist in Zone 6, a rural residential land use was
evaluated that is identical to the land use (rural residential) in Zones 1 and 2.
6.1.2.2 Offpost Study Area Potential Exposure Points
There are several potential exposure points in the Offpost Study Area. The most significant routes of
exposure have already been mitigated by exposure controls in areas with the highest groundwater
COG concentrations (e.g., the UFS is no longer used in Zones 3 and 4). Exposure to COCs in surface
soil has also been mitigated by relocating residents from the area near the intersection of
96th Avenue and Peoria Street where soil contaminant concentrations are highest. Additionally, the
Army and Shell Oil Company have agreed to till and revegetate approximately 160 acres located in
the southeast portion of Section 14 and the southwest portion of Section 13 in accordance with
Paragraph 22 of the Conceptual Remedy Agreement (see Figure 9.1). Shell Oil Company and the U.S.
Army believe that existing soil risk in the revegetated area falls within EPA's established acceptable
risk range and that remediation is not necessary. However, Shell Oil company and the U.S. Army
agree to the revegetation program as part of the remedy.
Concentrations of surface-water contaminants were higher in First Creek than other surface-water
bodies during 1986 through 1990, creating a potential exposure point for nonhuman receptors and a
direct-contact human pathway associated with wading. First Creek does not support a recreational
fishery; Barr Lake is the most likely point of human exposure to bioaccumulatedresidues in fish
tissue. Because COCs are not elevated in Barr Lake, with the exception of a single DIMP detection
that was not verified in duplicate or later sampling events, consumption of contaminated fish was not
evaluated.
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6.1.2.3 Potential Exposure Pathways and Routes
An exposure pathway consists of four elements: (1) a source and mechanism of release, (2) a
transport medium, (3) a point of potential contact with the contaminated medium, and (4) an
exposure route, such as ingestion, at the contact point.
The Site Conceptual Model (Figure 6.2) presents the potential exposure pathways identified in the
Offpost Study Area. The Site Conceptual Model also indicates which exposure routes were
quantitatively evaluated for risk. Because of the variations in land use and the presence or absence
of surface water in the six zones, not all exposure routes are applicable to all zones. Table 6.5
summarizes the exposure zones by land-use category and identifies the exposure routes quantified in
each zone.
Inhalation Route
On the basis of risk screening evaluations conducted according to EPA guidance, the release of
volatile chemicals from groundwater used in the home for all purposes (e.g., showering, dishwashing,
laundry, toilets) was determined to result in potentially significant exposures by the inhalation route.
Therefore, inhalation of volatile chemicals resulting from domestic use was quantified. Other
potential sources of exposure, such as the inhalation of contaminated dust particles, and inhalation
of vapors resulting from volatilization from underlying groundwater, were found to be very minor
contributors to the overall exposure potential.
Dermal Route
Dermal contact with surface soil is likely and was quantified for all potential land uses. Dermal
contact with sediment in First Creek was quantified. Dermal contact with sediment of Barr Lake is
not feasible, considering the depth of the water and the prohibition of swimming.
Dermal contact with surface water in First Creek was quantified. However, dermal contact with
canal water is expected to be unlikely and, in the worst case, infrequent; therefore, dermal contact
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was not quantified for the canals. Direct contact recreation is prohibited in Barr Lake; therefore, the
dermal contact pathway was not quantified for Barr Lake.
Dermal contact with groundwater used domestically is likely. However, dermal intake during
showering is approximately 0.15 percent of the intake resulting from ingestion of groundwater.
Potential exposures from direct ingestion and inhalation will be much higher than from dermal
contact. Therefore, the dermal intake resulting from domestic use was not quantified. EPA guidance
(EPA, 1989a) allows for certain pathways to be eliminated from evaluation if other pathways have
much higher exposure.
Ingestion Route
Incidental ingestion of surface soil is likely under all potential land uses; therefore, this pathway was
quantified. Incidental ingestion of First Creek sediment is possible in association with wading or
recreational activities; therefore, this pathway was also quantified.
Cattle and other livestock raised for human consumption may bioaccumulate COCs from (1) surface
water or groundwater used for watering livestock, (2) forage grown in contaminated surface soil or
irrigated by contaminated surface water or groundwater, and (3) direct ingestion of soil while grazing.
This pathway was quantified, using cattle as the representative species for development of a
bioaccumulation model. Additionally, bioaccumulation resulting in dieldrin contamination of
chicken eggs was quantified in the EA.
Vegetable crops grown for human consumption may contain COCs because of uptake of COCs from
contaminated surface soil and surface water or groundwater for irrigation. Ingestion of vegetable
crops was quantified.
Although ingestion of the shallow groundwater is unlikely, this exposure pathway was quantified. It
has been conservatively assumed that ingestion of untreated alluvial groundwater might occur even
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though there is insufficient water in portions of the UFS contaminated above groundwater contain-
ment system remediation goals to supply a municipal water system.
6.1.2.4 Estimation of Chemical Intake
Analytical data from each media within each of the six exposure assessment zones (Section 6.1.2.1)
was identified. Exposure point concentrations were selected such that they represent an RME
concentration. The RME exposure point concentrations were calculated as the upper 95 percent
confidence limit on the arithmetic mean of the data. The RME values for the COCs in each media
are presented in Tables 6.1 through 6.4. Exposure point concentrations were combined with
standard EPA intake assumptions and variables to estimate the intake of each COG by each exposure
route.
To estimate the exposure point concentration for food products (e.g., meat, eggs, vegetables), several
models were used to estimate the plant and animal uptake of a chemical from soil or water and the
resultant concentration in the edible portion of the plant or animal. All of the uptake and parti-
tioning coefficients were selected so that the resultant COG concentration in the food would also
represent an RME value. A complete discussion of the plant and animal chemical uptake models is
provided in the Offpost EA/FS.
6.1.3 Toxicity Assessment
The toxicity of chemicals is evaluated in terms of carcinogenic and noncarcinogenic effects. Cancer
slope factors and reference doses are used to evaluate potential risks posed by the exposure to
carcinogenic and noncarcinogenic chemicals, respectively.
EPA-established slope factors for inhalation and ingestion exposures to COCs are presented in
Table 6.6. The slope factor for a given compound is multiplied by the estimated intake to obtain the
carcinogenic risk estimate. The individual risks from each compound in a particular exposure
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pathway are then summed to obtain an estimate of the overall carcinogenic risk for each pathway
and for all pathways combined.
The reference doses (RfDs) used in the EA for inhalation and ingestion exposures are presented in
Table 6.6. The estimated intake is divided by the RfD for a given compound to obtain its hazard
quotient (HQ). For each exposure pathway, chemicals were segregated by their target organ. For
each target organ group, the HQs for each chemical were then summed to obtain a hazard index (HI)
for each pathway and for all pathways combined. When the HQ and/or the HI exceed 1.0, there may
be concern for potential noncarcinogenic health effects.
6.1.4 Risk Characterization
Following the estimation of exposure point concentrations and chemical intakes, the slope factors
and RfDs are used to estimate carcinogenic risks and the potential for noncarcinogenic effects. The
following sections discuss the results of this procedure.
6.1.4.1 Carcinogenic Risks
Table 6.7 summarizes the estimated current carcinogenic risks corresponding to existing exposures
by exposure assessment zone and exposure route. The total carcinogenic risks range from 1 x 10"4 to
3 x 10"4 (1 to 3 in 10,000) in Zones 1 through 4, 3 x 10'5 (3 in 100,000) in Zone 5, and 7 x 10'5 (7 in
100,000) in Zone 6. The total carcinogenic risks for each of the six exposure assessment zones are
within the acceptable risk range established by EPA. The hypothetical risks in Zones 3 and 4 are
highly conservative in that they are based on an urban residential land-use scenario and there are no
humans currently living in Zones 3 and 4. Additionally, the risks estimated for a portion of Zone 1
and Zone 2 are not current risks, because residents in these areas do not use UFS groundwater for
domestic use. Because there are no current residents in Zones 3 and 4, and the current residents in
Zone 5 have water supplies other than shallow wells, the estimated risks from residential use in
these zones are conservative because they do not represent existing exposures.
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Groundwater usage (either domestic and/or agricultural) is the primary contributor to carcinogenic
risk, accounting for 45 to 99 percent of the total risk estimated for each zone. This indicates the
major role of the groundwater-related exposure pathways. Risks related to chemicals in soil are less
than 1 in 10,000 (1 x 10"4), and the risks resulting from the surface-water and sediment exposure
pathways are less than 1 in 100,000 (1 x 10"5). Because of the importance of the groundwater
pathway, the remediation of groundwater will have the greatest effect in reducing potential offpost
risks.
Dieldrin contributes the most to the total carcinogenic risk, followed by arsenic, chloroform, and
atrazine. All of the estimated risks from dieldrin are conservative in that the dieldrin concentrations
were considered to be constant throughout the exposure period (30 years). The natural reduction in
dieldrin concentrations over time was not considered. Additionally, not all of the total carcinogenic
risks for each zone are attributable to RMA activities. Background concentrations of dieldrin in soil
attributable to agricultural practices may contribute up to 50 percent of the total carcinogenic risk in
some zones based on a background concentration for dieldrin of approximately 8 nag/kg. Naturally
occurring arsenic in groundwater may be responsible for a risk of approximately 4 in 100,000
(4 x 10"5), based on a background concentration of arsenic in groundwater of approximately 3 jjg/l.
6.1.4.2 Noncarcinogenic Effects
As presented in Section 6.1.3, His are derived by comparing the estimated daily chemical intake to
the estimated acceptable intake. Acute, or short-term, effects were evaluated for children because
children would have the highest chemical intake per body weight and would be expected to be the
most sensitive to the chemical. The EA concluded that there is a low potential for adverse health .
effects in children from hypothetical short-term exposures to dieldrin in groundwater in Zones 2, 3,
and 4. The HI exceeds 1 in Zones 2, 3, and 4, with a maximum HI of 4 in Zone 3. Dieldrin is the
primary contributor to the HI.
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His were also estimated for long-term exposures for both children and adults. The risk characteri-
zation presented in the EA found that, with the exception of ingestion of DIMP in groundwater in
Zone 4, no single chemical or exposure pathway resulted in an HI greater than 1. His were also
calculated on the basis of target organ effects and the mechanism of toxic action. For children, both
liver and central nervous system (CNS) toxicants were found to exceed an HI of 1. For liver
toxicants, the HI exceeds 1 in Zones 2, 3, and 4, with a maximum HI of 2 in Zone 2, predominately
attributable to inhalation and ingestion of chloroform. The HI for CNS effects exceeds 1 in Zones 2
and 4, with a maximum HI of 3.7 in Zone 4. The primary contributors to the estimation of CNS
effects are DIMP and manganese. Direct ingestion of groundwater and ingestion of vegetable crops
irrigated with groundwater are the two primary exposure pathways for DIMP and manganese.
Adult future His are all less than the child His. Table 6.8 summarizes the adult His segregated by
target organ. When segregated for liver toxicants, the highest HI is 1.3 in Zone 3. The HI for CNS
effects also exceeds 1.0, where DIMP is the major contributor to an HI of 2.4 in Zone 4.
6.2 Estimation of Potential Ecological Effects
6.2.1 Method
An Offpost Study Area ecological risk assessment was performed to evaluate potential adverse effects
to the environment and nonhuman receptors as a result of potential exposure to chemicals migrating
from onpost sources. The two natural ecosystems occurring in the Offpost OU are terrestrial and
aquatic. Figure 6.3 presents the ecological site conceptual model and presents the potential exposure
pathways quantified. The chemicals selected for evaluation of potential effects on the terrestrial and
aquatic receptors were limited to RMA-related chemicals found in surface water, surface soil, and
sediment. Chemicals identified in groundwater were used to evaluate agricultural receptors (e.g.,
crops, livestock) because of the potential for exposure through irrigation and livestock watering. The
chemicals evaluated for potential ecological effects were aldrin, arsenic, dieldrin, endrin, DDE, DDT,
and mercury.
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Two methods of exposure were evaluated: direct exposure and biomagnification. Direct exposure is
a result of contact with the original source of the chemical (e.g., ingestion of surface water or soil,
ingestion of groundwater, or fish swimming in contaminated surface water). Biomagnification occurs
when the tissue concentrations of a chemical increase with progression up the food chain. Over
time, the concentrations of chemicals in tissues may reach a level detrimental to the organism's
health.
The evaluation of ecological effects via direct exposure is analogous to the evaluation of human
effects. Direct toxicity was evaluated by comparing the estimated daily intake of a receptor to the
estimated toxicity reference value for a receptor. The toxicity reference values are similar to human
RfDs in their derivation and use. These toxicity reference values were animal- and chemical-specific
values, or, in the case of aquatic life, federal Ambient Water Quality Criteria values established to
protect aquatic life.
To evaluate the potential effects of biomagnification, the estimated tissue concentrations resulting
from biomagnification were compared to residue concentrations known to be without deleterious
effects. Only the top indicator species were selected to evaluate the effects of biomagnification.
These species were the bald eagle, great blue heron, and mallard duck.
In coordination with the U,S, Fish and Wildlife Service, it was agreed that screening levels,
developed to ensure compliance with enforceable remediation levels, would meet the requirements of
the federal Endangered Species Act, the Migratory Bird Treaty Act, and the Bald and Golden Eagle
Protection Act. These screening levels were not exceeded in the Offpost OU. These levels are
presented in the Final Offpost Operable Unit Endangerment Assessment/Feasibility Study in
Table 3.3.3-1 (Toxicity Reference Values for Avian and Terrestrial Vertebrate Species of Concern
Identified at Rocky Mountain Arsenal) of Volume II and Table H5-1 (Maximum Allowable Tissue
Concentration [MATC] Values for the Offpost EA Ecological Assessment) of Appendix H in
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Volume IV. If the screening levels are exceeded or effects are observed in the future, enforceable
remediation levels will be developed consistent with CERCLA, the Endangered Species Act, the
Migratory Bird Treaty Act, and the Bald and Golden Eagle Protection Act.
Potential effects on wetlands and critical habitats were also evaluated. This assessment is presented
in Appendix B of the Final Offpost EA/FS (HLA, 1992a). The U.S. Fish and Wildlife Service
(USFWS) National Wetlands Office identified approximately 300 acres of wetlands along First Creek
from the north boundary of RMA to O'Brian Canal. Potential effects of construction of the Offpost
Groundwater Intercept and Treatment System included temporary dewatering during excavation of
recharge trenches and pipelines near First Creek.
6.2.2 Results
Underwater aquatic life was evaluated on the basis of direct toxicity by comparing water concen-
trations to aquatic reference concentrations. Chlordane, dieldrin, fluoride, and DDT appeared to
present a potential for an adverse effect to aquatic life in First Creek. However, because First Creek
is dry much of the year and does not support a stable and ongoing fish population, adverse effects to
aquatic life are expected to be minimal. Because of interaction between groundwater and First Creek,
remedial actions taken to reduce the concentration of COCs north of the NBCS will also reduce
concentrations of COCs in First Creek.
Agricultural life was evaluated in Zones 1,2, and 6 (rural residential). The results of the direct
toxicity evaluation indicated no potential adverse impacts to poultry from soil contaminants or to
cattle from ingestion of contaminated soil and groundwater.
The ecological risk assessment concluded that for animals in the terrestrial and aquatic food webs,
there is minimal potential for adverse effects. However, the Army and Shell Oil Company have
agreed to till and revegetate approximately 160 acres located in the southeast portion of Section 14
and the southwest portion of Section 13 (see Figure 9.1). Shell Oil Company and the U.S. Army
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believe that existing soil risk in the revegetated area falls within EPA's established acceptable risk
range and that remediation is not necessary. However, Shell Oil Company and the U.S. Army agree
to the revegetation program as part of the remedy.
Construction of the Offpost Groundwater Intercept and Treatment System was coordinated with
USFWS to minimize the potential impacts on wetlands and habitat. Although the wetlands area has
been slightly altered because of construction of roads in the area, the wetlands still exist, dewatering
is no longer occurring, and the amount of recharged groundwater is equal to the amount of extracted
groundwater, thereby maintaining the stability of the wetlands area.
6.3 Conclusion
Actual or threatened releases of hazardous substances from this site, if not addressed by imple-
menting the response action selected in this ROD, may present a potential threat to public health,
welfare, or the environment.
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7.0 DESCRIPTION OF GROUNDWATER REMEDIATION ALTERNATIVES
An FS was conducted to develop and evaluate remedial alternatives for the Offpost OU. The first
task performed during the FS was to identify media that require remedial action and correspondingly
require development and evaluation of remedial alternatives. Risks calculated in the EA were
compared to acceptable risk levels established by EPA in the NCP and other guidance. The Army
has closely followed EPA guidance and the National Contingency Plan (NCPj regarding the use of the
10"4 risk threshold to assess whether remediation is necessary. Guidance states that if the cumulative
cancer risk to an individual is less than 10"4, remedial action may not be warranted unless certain
site-specific conditions exist. If remedial action is warranted, then the 10"4 to 10"6 risk range must be
achieved, with an initial preference for the 10"6 end. EPA guidance further states that the upper
boundary of the risk range is not an absolute at 1 x 10"4, but rather, the acceptable risk range can
extend to 5 x W4. The cumulative offpost cancer risk is a maximum of 3 x 10"4, which is within the
acceptable risk range.
In explaining the use of the point of departure, the EPA, in the preamble to the NCP, states
• The use of 10"6 expresses EPA's preference for remedial actions that result in risks at the more
protective end of the risk range, but does not reflect a presumption that the final remedial
action should attain such a risk level (55 FR 8718).
The operation of the Offpost Groundwater Intercept and Treatment System reflects the Army's goal of
further reducing the potential risks toward the 10"6 level. Using conservative assumptions, including
several exposure pathways that do not currently exist, the maximum cumulative cancer risk in the
Offpost OU was estimated to be 3 in 10,000, which is within the acceptable risk range established by
EPA.
Although the maximum offpost cumulative carcinogenic risk is below the acceptable risk level,
remediation of groundwater is preferable to no action for the following reasons:
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• Groundwater concentrations exceed National Primary Drinking Water Standards maximum
contaminant levels (MCLs) and CBSGs in some areas of the Offpost OU.
• Groundwater is the greatest contributor to cancer risk and contributes a maximum risk of 2 in
10,000 (or approximately 75 percent) to the cumulative risk in zones 1, 3, and 4.
• Evaluation of potential noncarcinogenic health effects indicate that His calculated for ground-
water contaminant concentrations in zones 2, 3, and 4 are slightly greater than 1.0.
Soil, surface water, sediment, and air contribute maximum cancer risks less than 1 in 10,000 in
zones 1 through 6. Soil, surface water, sediment, and air do not require remediation because of the
low risks contributed by these media to the total risk. Remedial alternatives were developed and
evaluated to address contaminated groundwater in the Offpost OU North and Northwest Plume
Groups. Additionally, as part of the Conceptual Remedy Agreement, the Army and Shell Oil
Company have agreed to till and revegetate approximately 160 acres located in the southeast portion
of Section 14 and southwest portion of Section 13.
Remedial alternatives for groundwater were developed by (1) establishing groundwater containment
system remediation goals , (2) identifying the areas of groundwater exceedances of containment
system remediation goals , and (3) assembling combinations of remedial process options into
remedial alternatives.
Containment system remediation goals (Table 7.1., 7.2, and 7.3 were established on the basis of
chemical-specific applicable or relevant and appropriate requirements (ARARs), health-based criteria
(HBC), exposure factors, and the statutory requirements stated in Section 121 of CERCLA. ARARs
were used as groundwater containment system remediation goals for contaminants with promulgated
standards, and HBC based on a risk of 1 x 10"8 calculated using RME assumptions were used for
carcinogens without ARARs. A risk level of 1 x 10"6 was selected to correspond to the point of
departure as defined in the NCP. The promulgated standards adopted as containment system
remediation goals for Offpost OU groundwater include MCLs and CBSGs. In addition, containment
system remediation goals for several contaminants with promulgated standards were adjusted
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downward to reduce risk corresponding to the containment system remediation goals. For some
analytes, the certified reporting limit (CRL) or the practical quantitation limit (PQL) are higher than
the containment system remediation goal. The CRL and PQL represent the lower practical limit for
quantitation.
Attainment of the groundwater containment system remediation goals developed for the site will
reduce the estimated total hypothetical cancer risks to less than 1 x 10~* toward the 1 x 10"6 level.
Because the total cancer risk assumes that all chemicals are present in groundwater at all locations,
and since groundwater contamination is variable throughout the OU, the estimated risk reduction
may be greater. Attainment of the groundwater containment system remediation goals developed for
the site will also reduce His discussed in Section 6.1.4.2 to below 1.0 for all target organ groups and
receptors. Again, variability in contaminants present in groundwater may increase the estimated risk
reduction from that estimated by extrapolating directly from the risk assessment.
Groundwater requiring remediation in the Offpost Study Area was identified by comparing ground-
water containment system remediation goals to the areal extent of groundwater contamination.
Groundwater containment system remediation goals are exceeded for the carcinogens arsenic, chloro-
form, DBCP, tetrachloroethylene,trichloroethylene, and dieldrin. Groundwater containment system
remediation goals are also exceeded for the noncarcinogens chlorobenzene, dicyclopentadiene, and
DIMP. The area of groundwater exceeding containment system remediation goals (and thus the
Offpost OU) t-ncompasses approximately 590 acres of the Offpost Study Area.
Groundwater alternatives were developed and evaluated using two groundwater models. The models
simulated groundwater flow and contaminant transport for the North and Northwest Plume Groups.
Groundwater modeling was used for the following purposes: developing conceptual designs for
sizing and locating groundwater extraction, recharge, and treatment systems; estimating future
contaminant transport; evaluating the relative merits of remediation alternatives; and estimating the
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time required to clean up the contaminated groundwater. Because of the approximate nature and
inherent uncertainties of the models, none of the model results should be interpreted as an accurate
prediction of future conditions. The predicted remediation time frames are estimates. Accordingly,
estimated remediation time frames were only used to assess the relative effectiveness of the ground-
water alternatives.
Remedial alternatives were initially screened on the basis of effectiveness, implementability, cost,
and attainment of ARARs. The alternatives passing the initial screening were then evaluated on the
basis of nine criteria required by the NCP. In addition to remedial alternatives, the NCP requires that
a No Action alternative be considered at every site. The No Action alternative serves primarily as a
point of comparison for other alternatives.
A total of six alternatives for the North Plume Group and four remedial alternatives for the Northwest
Plume Group were developed for analysis. Following the initial screening analysis in the FS,
four remedial alternatives for the North Plume Group (N-l, N-2, N-4, and N-5) and two remedial
alternatives for the Northwest Plume Group (NW-1 and NW-2) remained for evaluation during the
detailed analysis of alternatives. These alternatives are described below with the original alternative
numbering sequence from the FS report.
7.1 Common Elements of Alternatives
All of the alternatives developed included the following elements:
• Groundwater and surface-water monitoring: Samples will be collected periodically from
groundwater monitoring wells and surface-water locations throughout the Offpost Study Area
and analyzed to assess changes in groundwater and surface-water quality during and after
remediation.
• Site review: In accordance with CERCLA, a site review will be conducted at least every five
years until groundwater containment system remediation goals are achieved to assure that
human health and the environment are protected during and after remediation. The site
review will use monitoring program data to assess whether additional remedial action would
be warranted.
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Except for the No Action alternative, each alternative also includes the following activities:
• Exposure control/provision of alternate water supply as described below:
As of the date of the Onpost ROD, and based on a .392 parts per billion (ppb)
detection limit, the U.S. Army will use the last available quarterly monitoring results
to determine the DIMP plume footprint.
As part of the Onpost ROD, the U.S. Army and Shell Oil Company will pay for the
extension of, and hook-up to, the current distribution system for all existing well
owners within the DIMP plume footprint referenced above.
Existing domestic well owners outside of the DIMP plume footprint as of the date of
the On-post ROD where it is later determined that levels of DIMP are eight ppb or
greater (or other relevant CBSG at the time) will be hooked up at the U.S. Army and
Shell Oil Company's expense to the SACWSD distribution system or provided a deep
well or other permanent solution.
For new domestic wells with levels of eight ppb or greater (or other relevant CBSG at
the time), the Offpost ROD institutional controls will provide that the U.S. Army and
Shell Oil Company will pay for hook-up to the distribution system or provided a deep
well or other permanent solution.
Any user of a domestic well within the Offpost Operable Unit that contains ground-
water contaminants derived from RMA at concentrations that exceed the greater of
the remediation goals in Tables 7.1 through 7.3 or the ARARs in Table 10.1 will be
provided an alternative water supply. Bottled water will be provided for cooking and
drinking until a permanent alternative water supply is provided. Permanent alter-
native water supplies could include installation of a deep uncontaminated well or
connection to a municipal potable water-supply system. This commitment applies to
both users of existing domestic wells and users of wells that are lawfully drilled in
the future.
As part of the Onpost ROD, the U.S. Army and Shell Oil Company agree to pay for,
and provide or arrange for the provision of 4,000 acre feet of water, the details of
which will be worked out between the U.S. Army, Shell Oil Company, and SACWSD.
If such water is not available, the U.S. Army and Shell Oil Company will provide
payment of an agreed upon amount of money in lieu of water.
• Use of institutional controls to prevent the future use of groundwater exceeding remediation
goals. Institutional controls are reflected in Appendix B.
• Continued operation of the existing boundary containment systems - The NBCS and NWBCS
will continue to operate and improvements will be made, as necessary, to assure that offpost
groundwater containment system remediation goals are not exceeded. In addition, the ICS
will continue to operate, as required, for onpost contaminants consistent with the Irondale
IRA. These containment systems will be operated to the requirements of Section 2.7 of the
FFA, the Conceptual Remedy Agreement, and the Onpost ROD, when it is signed. Cessation
may occur as provided in Sections 35.3 and 35.4 of the FFA and paragraph 20 of the
Conceptual Remedy Agreement. Currently, approximately 125 million gallons per year are
treated at the NBCS, 450 million gallons per year are treated at the NWBCS, and 45 million
gallons per year are treated at the ICS.
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Description of Groundwater Remediation Alternatives
Closure of poorly constructed wells within the Offpost Study Area - Wells that could be
acting as migration pathways for contaminants in the Arapahoe Aquifer will be closed using
approved methods. The pertinent criteria are presented in Appendix C - Well Closure
Criteria.
7.2 Identification of Groundwater Alternatives: North Plume Group
Alternatives developed for remediation of groundwater in the North Plume Group are described
below. Table 7.4 presents the alternatives corresponding to the North Plume Group and identifies
process options, numbers of wells and trenches, flow rates, estimated remediation time frames,
treatment facility location, and process residuals generated.
7.2.1 Alternative N-1: No Action
Under Alternative N-1, the operation of the NBCS would be discontinued. Alternative N-1 would
therefore not provide for active remediation of affected groundwater within the North Plume Group.
Ceasing operation of the NBCS would likely cause an increase in contaminant concentrations within
the North Plume Group. Natural fate processes, including degradation and attenuation, would be the
only mechanisms that would reduce contaminant concentrations in groundwater within the North
Plume Group. The major components of Alternative N-1 include the following:
• Long-term groundwater and surface-water monitoring
• Site reviews
A long-term groundwater and surface-water monitoring program would be implemented. The
purpose of the monitoring program is to assess changing UFS and CFS aquifer and surface-water
conditions during and after remedial action. As part of Alternative N-1, a site review would be
conducted at least every five years until containment system remediation goals are achieved.
The total present worth cost estimate for Alternative N-1 ranges from $4,061,000 to $6,102,000. This
includes long-term operation and maintenance costs for performing site reviews, groundwater and
surface-water monitoring, and regulatory oversite activities.
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7.2.2 Alternative N-2: Continued Operation of the North Boundary
Containment System With Improvements as Necessary
Alternative N-2 would provide for active remediation of affected groundwater approaching the north
boundary of RMA through continued remediation of groundwater at the NBCS. The major compo-
nents of Alternative N-2 are as follows:
• Continued operation of the NBCS
• Improvements to the NBCS as necessary
• Long-term groundwater and surface-water monitoring
• Site reviews
• Exposure control/provision of alternate water supply as described in Section 7.1
• Well closure in conformance with criteria listed in Appendix C, pages C-l and C-2
• Institutional controls as described in Appendix B
Under Alternative N-2, the NBCS would continue to contain, extract, treat, and recharge approxi-
mately 125 million gallons of groundwater per year. Improvements would be made to the NBCS if it
was determined that the system was allowing groundwater containing COCs at concentrations
exceeding offpost groundwater containment system remediation goals to migrate from RMA to the
North Plume Group.
As part of Alternative N-2, an alternative water supply would be provided to any user of a domestic
well in accordance with the provisions described in Section 7.1. The long-term groundwater and
surface-water monitoring and site review remedial components under Alternative N-2 would be
identical to those proposed under Alternative N-l.
The total present worth cost estimate for Alternative N-2 ranges from $30,600,000 to $32,500,000.
This incudes long-term operation and maintenance costs for the NBCS and the cost of long-term
groundwater monitoring and site review components included under Alternative N-l.
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7.2.3 Alternative N-4: Offpost Groundwater Intercept and Treatment System
Under Alternative N-4, the NBCS would continue to operate, and the Offpost Groundwater Intercept
and Treatment System would be constructed and operated to contain, remove, treat, and recharge
groundwater exceeding containment system remediation goals in the First Creek and northern
paleochannels downgradient of the NBCS. Detailed information concerning the Offpost Groundwater
Intercept and Treatment System is presented in the Final Implementation Document for the
Groundwater Intercept and Treatment System North of Rocky Mountain Arsenal (HLA, 1991). The
Offpost Groundwater Intercept and Treatment System has been in operation since early 1993. The
major components of Alternative N-4 are as follows: •
• Removal of contaminated UFS groundwater north of the RMA boundary in the First Creek
and northern paleochannels using Offpost Groundwater Intercept and Treatment System
groundwater extraction wells
• Treatment of organic contaminants in extracted groundwater using carbon adsorption
• Recharge of treated groundwater to the UFS using Offpost Groundwater Intercept and
Treatment System recharge wells and trenches
• Continued operation of the NBCS
• Improvements to the NBCS and Offpost Groundwater Intercept and Treatment System as
necessary
• Long-term groundwater and surface-water monitoring
• Site reviews
• Exposure control/provision of alternate water supply as described in Section 7.1
• Well closure in conformance with criteria listed in Appendix C, pages C-l and C-2
• Institutional controls as described in Appendix B
Alternative N-4 would remediate UFS groundwater in the First Creek and northern paleochannels
that is contaminated with organic COCs at concentrations exceeding groundwater containment
system remediation goals.
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Extraction wells would be used in the Offpost Groundwater Intercept and Treatment System to
remove contaminated groundwater. Extracted groundwater would be conveyed to the treatment
facility via double-contained polyvinyl chloride (PVC) pipelines.
Based on the results of the groundwater modeling, the configuration of five extraction wells and six
recharge trenches shown in Figure 7.1 would capture and remove contaminants axially in the First
Creek paleochannel. The recharge trenches would be placed both downgradient of the extraction
wells and along the outer boundaries of the First Creek paleochannel. In this manner, the recharge
trenches would provide both lateral hydraulic containment of the First Creek paleochannel and water
flushing for enhancing the removal of contaminants. Capture would be attained using a transverse
system of 12 extraction and 24 recharge wells directly downgradient of the extraction wells in the
northern paleochannel system. The Offpost Groundwater Intercept and Treatment System would
contain, extract, treat, and recharge approximately 480 gallons per minute (gpm). Construction of
this system began in November 1991 and was completed in June 1993.
Extracted groundwater from both the First Creek and northern paleochannels would be conveyed by
pipeline to a central carbon adsorption treatment facility on land in the Offpost Study Area that was
previously purchased by Shell. Activated carbon adsorption is a well-developed technology that is
widely used in removing organic contaminants from liquid hazardous waste streams and offgas
airstreams. The waste stream comes in contact with granular activated carbon (GAG) by flowing
through one or more packed-bed reactors. Organic chemicals and, to some degree, inorganic
chemicals, are adsorbed onto the internal pores of the carbon granules by surface-attractive
phenomena. Activated carbon removes many nondegradable organic compounds and is most
effective for nonpolar, slightly soluble compounds.
Carbon adsorption is readily implementable. Carbon adsorption is a demonstrated, proven techno-
logy documented to be effective at the NWBCS, NBCS, and ICS. Activated carbon treatment would
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achieve groundwater containment system remediation goals for organic contaminants before
discharge via the recharge systems.
An intensive short-term monitoring component would be included in Alternative N-4 as part of the
long-term monitoring program. The intensive short-term program would consist of monitoring
approximately 60 wells in a network that would be finalized through implementation of the altern-
ative. Two years of data would be collected during the period commencing with Offpost Ground-
water Intercept and Treatment System operations start-up. Such a program is necessary to evaluate
the performance of the NBCS and the Offpost Groundwater Intercept and Treatment System and
would provide an increased understanding of contaminant transport, an estimated time to achieve
groundwater containment system remediation goals, and to determine whether improvements to the
Offpost Groundwater Intercept and Treatment System are warranted.
The total present worth cost estimate for Alternative N-4 ranges from $56,500,000 to $63,100,000.
This includes the capital and long-term operation and maintenance cost for construction, operation,
and performance monitoring of the Offpost Groundwater Intercept and Treatment System. This cost
estimate also includes the continued operation of the NBCS, long-term groundwater monitoring, site
review, and exposure control components of Alternative N-2.
7.2.4 Alternative N-5: Expansion of the Offpost Groundwater Intercept and
Treatment System
Similar to Alternative N-4, this alternative would remediate the First Creek paleochannel and
northern paleochannel groundwater downgradient of the NBCS. Based on the results of the
groundwater modeling, the configuration of extraction wells and recharge systems proposed under
Alternative N-5 would place additional extraction wells in locations where the limiting hydrogeologic
and contaminant characteristics are controlling remediation time frames. Two additional extraction
wells and four recharge trenches would be installed in the area of relatively slower groundwater
velocity and high dieldrin concentrations in the First Creek paleochannel. One additional extraction
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well and two recharge trenches would be installed in an area of low hydraulic conductivity in the
northern paleochannel. The major components of Alternative N-5 are as follows:
• Removal of contaminated UFS groundwater north of the RMA boundary in the First Creek
and northern paleochannels, using Offpost Groundwater Intercept and Treatment System
groundwater extraction wells
• Expansion of the Offpost Groundwater Intercept and Treatment System extraction and
recharge systems
• Treatment of extracted groundwater using carbon adsorption
• Recharge of treated groundwater to the UFS, using recharge wells and trenches
• Continued operation of the NBCS
• Improvements to the NBCS as necessary
• Long-term groundwater and surface-water monitoring
• Site reviews
• Exposure control/provision of alternate water supply as described in Section 7.1
• Well closure in conformance with criteria listed in Appendix C, pages C-l and C-2
• Institutional controls as described in Appendix B
The expansion of the Offpost Groundwater Intercept and Treatment System is shown in Figure 7.2.
The three additional extraction wells would each pump 30 gpm (90 gpm additional), and the
additional trenches would recharge the same volume. Thus, Alternative N-5 would extract and treat
a total of 570 gpm compared to 480 gpm for Alternative N-4. Other remedial components under
Alternative N-5 would be identical to those proposed under Alternative N-4.
The total present worth cost estimate for Alternative N-5 ranges from $56,200,000 to $63,000,000.
This includes the capital and operation and maintenance costs of the expansion systems to the
Offpost Groundwater Intercept and Treatment System and the cost components of Alternative N-4.
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7.3 Identification of Groundwater Alternatives: Northwest Plume Group
The following subsections identify the alternatives developed for the Northwest Plume Group.
Table 7.4 presents the alternatives corresponding to the Northwest Plume Group and identifies
process options, numbers of wells and trenches, flow rate, estimated remediation time frames,
treatment facility location, and process residuals generated.
7.3.1 Alternative N-1: No Action
Under Alternative NW-1, the operation of the NWBCS would be discontinued. Alternative NW-1
would not provide for active remediation of affected groundwater within the Northwest Plume Group.
Ceasing operation of the NWBCS would likely cause an increase in contaminant concentrations
within the Northwest Plume Group. Natural fate processes, including degradation and attenuation,
would be the only mechanisms that would reduce contaminant concentrations in groundwater within
the Northwest Plume Group. The major components of Alternative NW-1 are as follows:
• Long-term groundwater monitoring
• Site reviews
A long-term groundwater monitoring program would be implemented. The purpose of the monitor-
ing program would be to assess changing UFS and CFS aquifer conditions during and after remedial
action. As part of Alternative NW-1, a site review would be conducted at least every five years until
containment system remediation goals are achieved.
The total present worth cost estimate for Alternative NW-1 ranges from $608,000 to $1,260,000. This
includes long-term operation and maintenance costs for performing site reviews, groundwater
monitoring, and regulatory oversite activities.
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7.3.2 Alternative NW-2: Continued Operation of the Northwest Boundary
Containment System With Improvements as Necessary
Alternative NW-2 would provide for active remediation of affected groundwater approaching the
northwest boundary of RMA through continued remediation of groundwater at the NWBCS. The
major components of Alternative NW-2 are as follows:
• Continued operation of the NWBCS
• Improvements to the NWBCS as necessary
• Long-term groundwater monitoring
• Site reviews
• Exposure control/provision of alternate water supply as described in Section 7.1
• Well closure in conformance with criteria listed in Appendix C, pages C-l and C-2
• Institutional controls as described in Appendix B
Under Alternative NW-2, the NWBCS would continue to contain, extract, treat, and recharge
approximately 450 million gallons of groundwater per year. Improvements would be made to the
NWBCS if it was determined that the system was allowing groundwater containing COCs at
concentrations exceeding offpost groundwater containment system remediation goals to migrate from
RMA to the Northwest Plume Group.
As part of Alternative NW-2, an alternative water supply would be provided to any user of a
domestic well that contains groundwater contaminants at concentrations exceeding containment
system remediation goals . Other remedial components under Alternative NW-2 would be identical to
those proposed under Alternative NW-1.
The total present worth cost estimate for Alternative NW-2 ranges from $12,400,000 to $13,100,000.
This includes long-term operation and maintenance costs for the NWBCS and the long-term
groundwater monitoring, site reviews, and exposure control components of Alternative NW-1.
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8.O COMPARATIVE ANALYSIS OF ALTERNATIVES
The remedial alternatives were evaluated with respect to nine threshold, primary balancing, and
modifying criteria as required by the NCP. The criteria are as follows:
Threshold Criteria
• Overall protection of human health and the environment
• Compliance with ARARs
Primary Balancing Criteria
• Long-term effectiveness and permanence
• Reduction of toxicity, mobility, or volume
• Short-term effectiveness
• Implementability
• Cost
Modifying Criteria
• State acceptance
• Community acceptance
Threshold criteria must be satisfied by the selected alterative. Primary balancing criteria are used to
weigh trade-offs among alternatives. Modifying criteria may be used to alter a proposed remedial
alternative. Brief descriptions of the evaluation criteria and the items considered when assessing
alternatives with respect to each criterion are presented in the summary of the comparative analysis
of alternatives.
The models simulating UFS groundwater flow and dissolved chemical transport were prepared for
the analysis of alternatives and are approximate in nature. Because detailed models were not needed
to compare the benefits of each remedial alternative, attempts were made to produce models that
incorporate general features of groundwater flow and associated transport phenomena in the Offpost
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Study Area. Nonetheless, the resulting models predicted flow and chemical transport phenomena
that agree with historical and current hydrogeologic data and observed contaminant distributions.
Because of the approximate nature of the models and the considerable uncertainty in the conceptual
model and hydrogeologic parameters, none of the modeling results should be construed as accurate
predictions of future contaminant distribution. Rather, the models and modeling results should be
viewed as tools for assessing the relative merits of remedial alternatives. Although there are inherent
uncertainties in the groundwater model, it is the tool being used to evaluate the alternatives, and
predicted differences in remediation time frames are considered with respect to evaluating alternative
effectiveness.
For the North Model, the following remedial action scenarios were simulated: (1) continued
operation of the NBCS with improvements as necessary (Alternative N-2), (2) Offpost Groundwater
Intercept and Treatment System (Alternative N-4), and (3) expansion of the Offpost Groundwater
Intercept and Treatment System (Alternative N-5). The results of these simulations were evaluated
on the basis of estimated remediation times measured on maximum concentrations versus time
graphs. The range of estimated remediation times was based on attainment of the groundwater
cleanup standards for DIMP, chloroform, and dieldrin, using a range of retardation factors. Although
some remediation goals have changed since modelling was performed, these changes do not affect the
assessment of the relative merits of the remedial alternatives.
For the Northwest Model, the remedial action scenario for continued operation of the NWBCS with
improvements as necessary (Alternative NW-2) was simulated.
8.1 Comparative Analysis of Remedial Alternatives
The purpose of the comparative analysis is to identify the advantages and disadvantages of each
alternative relative to the others. Critical tradeoffs were identified and used to assist in selection of
the preferred remedy. Summaries of the detailed analysis of the North Plume Group and Northwest
Plume Group alternatives are presented in Tables 8.1 and 8.2, respectively. A brief description of the
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evaluation criteria and a comparison of each alternative with respect to the evaluation criteria is
presented below. Components common to all of the alternatives were not evaluated in the
comparative analysis.
8.1.1 Overall Protection of Human Health and the Environment
The criterion of overall protection of human health and the environment serves as a final check in
assessing whether each alternative provides adequate protection of human health and the environ-
ment. This criterion was also used to evaluate how risks would be eliminated, reduced, or controlled
through treatment, engineering, institutional controls, or other remedial activities.
North Plume Group Alternatives
Overall protection of human health and the environment would be provided by all alternatives with
the exception of Alternative N-l. Alternatives N-4 and N-5 would provide greater protection than
Alternative N-2 because extraction, treatment, and recharge systems within the North Plume Group
would decrease organic contaminant concentrations and reduce potential risks within a shorter time
period. Although groundwater modeling estimates that Alternative N-5 would achieve containment
system remediation goals in a shorter time period than Alternative N-4 (10-20 years for Alternatives
N-5 versus 15-30 years for Alternative N-4), the two alternatives are essentially equivalent with
respect to providing protection of human health and the environment for the following reasons:
• Alternatives N-4 and N-5 both provide for active remediation of the First Creek and Northern
paleochannel groundwater in approximately the same time period through removal of
contaminated UFS groundwater, treatment of the organics in the contaminated groundwater
using carbon absorption, and recharge of the treated groundwater using recharge wells and
trenches.
• Both alternatives also provide a significant reduction in potential risk in approximately the
same time period through organic contaminant removal and treatment by the Offpost Ground-
water Intercept and Treatment System.
Northwest Plume Group Alternatives
Alternative NW-1 would not be protective of human health and the environment because the NWBCS
would cease operation. Overall protection of human health and the environment would be provided
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by Alternative NW-2. Alternative NW-2 would decrease contaminant concentrations and reduce
potential risks associated with groundwater entering the Offpost Study Area north of the NWBCS.
Recharge of groundwater treated at the NWBCS would reduce contaminant concentrations in the
Northwest Plume Group through flushing with treated groundwater. Groundwater modeling
estimates that Alternative NW-2 would achieve groundwater containment system remediation goals
in approximately three to eight years. Alternative NW-1 would not likely achieve groundwater
containment system remediation goals because operation of the NWBCS would cease.
8.1.2 Compliance With Applicable or Relevant and Appropriate Requirements
The criterion of compliance with ARARs is used to assess whether each alternative will attain
ARARs. The comparative analysis describes how each alternative exceeds, attains, or does not attain
these requirements. Other information such as advisories, criteria, or guidance documents have been
considered where appropriate during the ARARs analysis (see Section 10.0).
North Plume Group Alternatives
Compliance with chemical-specific ARARs would be achieved by all alternatives with the exception
of Alternative N-l. Cleanup standards for Offpost OU groundwater include Safe Drinking Water Act
MCLs and CBSGs. Groundwater modeling estimates that chemical-specific ARARs would be
achieved in the shortest time by Alternative N-5, foil owed by Alternative N-4, folio wed by
Alternative N-2.
Compliance with location-specific and action-specific ARARs will be achieved by all treatment
alternatives. Because no remediation would take place under Alternative N-l, there would be no
federal and state location- or action-specific ARARs. Inorganic standards for chloride and sulfate will
be met by natural attenuation consistent with the onpost remedial action.
Northwest Plume Group Alternatives
Compliance with chemical-specific ARARs would be achieved only by Alternative NW-2. Ground-
water modeling indicates that Alternative NW-2 would achieve chemical-specific ARARs in approxi-
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mately three to eight years. Alternative NW-2 would comply with location- and action-specific
ARARs.
8.1.3 Long-term Effectiveness and Permanence
The long-term effectiveness and permanence criterion addresses the risk remaining at the site after
response objectives have been met. Components of the criterion that were addressed for each
alternative are as follows:
• Magnitude of residual risk at the end of remedial activities
• Adequacy and reliability of controls that are used to manage either treatment residuals or
untreated materials that remain at the site
North Plume Group Alternatives
Comparison of North Plume Group alternatives with respect to long-term effectiveness and perma-
nence indicates that each alternative, except Alternative N-l, provides a high degree of effectiveness
and permanence. However, Alternative N-4 is superior to Alternative N-5 because using full-scale
operating data as the basis for identifying the need for placing additional wells and trenches and
identifying the optimum locations will enhance long-term system performance. All of the alterna-
tives with the exception of the No Action alternative would reduce potential risk and address
exposure pathways by reducing COC concentrations in the North Plume Group. Under the No
Action alternative, potential risks would likely increase after ceasing operation of the NBCS.
Northwest Plume Group Alternatives
Comparison of the Northwest Plume Group alternatives with respect to long-term effectiveness and
permanence indicates that Alternative NW-2 reduces potential risk and addresses exposure pathways
by reducing COC concentrations in the Northwest Plume Group. Under the No Action alternative,
potential risks would likely increase after ceasing operation of the NWBCS.
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8.1.4 Reduction in Toxicity, Mobility, or Volume
The reduction of toxicity, mobility, or volume criterion addresses the statutory preference for
selecting remedial actions that permanently and significantly reduce toxicity, mobility, or volume of
hazardous materials at the site. This preference is satisfied when treatment is used to reduce
principal risks through destruction or irreversible reductions of toxicity, mobility, and/or volume.
North Plume Group Alternatives
All North Plume Group alternatives with the exception of the No Action alternative would reduce the
toxicity, mobility, and volume of contaminated groundwater entering the Offpost OU north of the
NBCS. Groundwater contaminant concentrations under the No Action alternative would likely
increase. Alternatives N-4 and N-5 would provide the greatest reduction in toxicity, mobility, and
volume of contaminated groundwater, through extraction, treatment, and recharge within the North
Plume Group. As stated previously, the uncertainty associated with the remediation time frames
estimated by the groundwater modeling suggests that, in practical terms, the estimated time frames
for both Alternatives N-4 and N-5 are essentially equivalent. Further, the intensive short-term
groundwater monitoring component of Alternative N-4 would allow for full-scale performance data
regarding the reduction of contaminant concentrations. Such data would be necessary to assess the
need for and optimum location of any modifications to Alternative N-4.
Northwest Plume Group Alternatives
Alternative NW-2 would reduce the toxicity, mobility, and volume of contaminated groundwater
entering the Offpost OU northwest of the NWBCS through extraction, treatment, and recharge.
Groundwater contaminant concentrations under the No Action alternative would likely increase; thus
toxicity, mobility, or volume would not be reduced.
8.1.5 Short-term Effectiveness
The short-term effectiveness criterion addresses the protection of human health and the environment
during the construction and implementation phase. The following factors were addressed during the
evaluation process:
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• Protection of the community during remedial actions - This factor addresses any risk that
results from implementation of the proposed remedial alternative, such as dust from
excavation or transportation of hazardous material.
• Protection of the workers during remedial actions - This factor assesses threats that may be
posed to workers and the effectiveness and reliability of measures to be taken.
• Environmental impacts of the remedial action - This factor addresses the potential adverse
environmental impacts that may result from construction and implementation of a remedial
alternative and evaluates the reliability of mitigation measures, if necessary, to prevent or
reduce potential impacts.
• Time lapse before achievement of response objectives - This factor includes an estimate of
the time required to achieve protection for the site.
North Plume Group Alternatives
Assessment of the North Plume Group alternatives with respect to protection of the community and
workers, short-term adverse environmental impacts, and implementation period indicates that the No
Action alternative and Alternative N-2 are slightly better than the alternatives with active remediation
components. However, during the implementation period, Alternatives N-4 and N-5 would be able to
minimize adverse short-term impacts through standard engineering controls and adherence to
standard health and safety practices.
Northwest Plume Group Alternatives
The assessment of the two Northwest Plume Group alternatives with respect to protection of the
community and workers, short-term adverse environmental impacts, and implementation period
shows that the No Action alternative and Alternative NW-2 are essentially equivalent except that the
discontinued operation of the NWBCS, as part of the No Action alternative, has an adverse environ-
mental impact. Neither alternative, with the exception noted above, has significant short-term
effectiveness issues.
8.1.6 Implementability
The implementability criterion evaluates the technical and administrative feasibility of implementing
each alternative, and it addresses the availability of required services and materials during
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implementation of the alternative. The following factors were addressed during the evaluation
process:
• Construction and operation - This factor considers the technical difficulties and the
unknowns associated with the technology.
• Reliability of the technology - This factor considers the likelihood that problems associated
with implementation may result in schedule delays.
• Implementing additional remedial action - This factor is not applicable to the alternatives
developed because the alternatives considered are not interim measures.
• Monitoring the effectiveness of the remedy - This factor addresses the ability to evaluate the
effectiveness of the remedy and includes an evaluation of the risks of exposure should
monitoring be insufficient to detect a system failure.
• Coordination with other offices and agencies needed to implement remedial alternatives (e.g.,
obtaining necessary permits for offsite activities)
• Availability of necessary equipment, specialists, services and materials, and adequate offsite
treatment, storage, and disposal services
North Plume Group Alternatives
All North Plume Group alternatives evaluated would be technically feasible to implement. The No
Action alternative and Alternative N-2 would be the easiest to implement with respect to technical
feasibility because the monitoring wells have already been installed and the NBCS system is
currently operational. Alternative N-4 is constructed and is fully operational. However, Alterna-
tive N-5 would require additional design and construction. All treatment alternatives would use
carbon adsorption treatment, which has been demonstrated at the boundary containment systems to
be a reliable groundwater treatment process option. Groundwater monitoring is a component of all
four alternatives and would provide information regarding the effectiveness of each alternative.
All alternatives with the exception of the No Action alternative would be administratively feasible. It
is unlikely that the regulatory agencies or the public would accept shutdown of the NBCS as
proposed under the No Action alternative. Additionally, the Army will not cease operating the NBCS
until cleanup certification. Each of the three treatment alternatives would meet federal and state
substantive requirements for recharging the treated groundwater to the UFS.
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The No Action alternative and Alternative N-2 would not require additional equipment and services.
The implementation of Alternative N-5 would not be limited with respect to availability of services
and materials. Contractors with the equipment and knowledge to construct and implement this
alternative are readily available. The remedial systems of Alternative N-4 were completed in June
1993.
Northwest Plume Group Alternatives
Both Northwest Plume Group alternatives evaluated would be technically feasible to implement. The
No Action alternative and Alternative NW-2 would be implementable with respect to technical
feasibility because the monitoring wells have already been installed and the NWBCS is currently
operational. Alternative NW-2 would use carbon adsorption treatment, which has been demonstrated
at the boundary containment systems to be a reliable groundwater treatment process option.
Groundwater monitoring is a component of both alternatives and would provide information regard-
ing the effectiveness of each alternative.
The No Action alternative would not be administratively feasible. It is unlikely that the regulatory
agencies or the public would accept shutdown of the NWBCS as proposed under the No Action
alternative. Additionally, the Army does not intend to cease operating the NWBCS.
Alternative NW-2 would meet federal and state substantive requirements for recharging the treated
groundwater to the UFS. Neither alternative would require additional equipment and services.
8.1.7 Cost
The cost criterion evaluates both capital costs and any long-term costs required to operate and
maintain an alternative. Cost estimates for each alternative were based on vendor information, cost
estimating guides, review of published cost data at previous sites, and operation and maintenance
costs at the boundary containment systems.
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North Plume Group Alternatives
The total present worth costs range from $4.1 to $6.0 million for Alternative N-l to $56.5 to
$63.1 million for Alternative N-4. The present worth costs are nearly identical for Alternatives N-4
and N-5 because the additional capital expenditures required for Alternative N-5 are balanced by the
additional operation and maintenance (O&M) costs incurred through the estimated 10-year
differences in remediation timeframe for Alternative N-4.
The additional capital expenditure of approximately $2.7 million for Alternative N-5 as compared to
Alternative N-4 points out the importance of collecting additional full-scale operating data to aid in
decision-making regarding any necessary expansion of the Offpost Groundwater Intercept and
Treatment System. Collection of full-scale data on contaminant transport and actual plume
remediation time frames through the intensive short-term monitoring program is currently being
conducted. This monitoring program will provide data for use in any system expansion decision-
making regarding the potential need for and placement of improvements to Alternative N-4 to reduce
the remediation timeframe and/or efficiency.
Northwest Plume Group Alternatives
The total present worth costs range from $0.6 to $1.3 million for Alternative NW-1 to $12.4 to $13.1
million for Alternative NW-2.
8.1.8 State Acceptance
State acceptance evaluates technical and administrative concerns the State may communicate in its
comments concerning each alternative. The State has been actively involved throughout the RI/FS
and remedy selection process for the Offpost OU. The State was provided the opportunity to
comment on the RI/FS document and proposed plan, and took part in the public meeting held to
inform the public on the proposed plan. Written comments from the state received during the public
comment period indicate that the State prefers Alternative N-5 or a slightly modified version of
Alternative N-5 over Alternative N-4 because of the addition of several wells and trenches for
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Comparative Analysis of Alternatives
enhanced contaminant removal. Responses to the State's concerns on this and other issues are
provided in Appendix A - Responsiveness Summary.
Additional discussions were held between the U.S. Army, Shell Oil Company, the State of Colorado,
the U.S. EPA, and the U.S. Fish and Wildlife Service following the issuance of the Offpost proposed
plan regarding the remedy for both the Offpost and Onpost OUs. As a result of these discussions, the
State of Colorado and the other parties have agreed to the remedy as described in Agreement for a
Conceptual Remedy for the Cleanup of the Rocky Mountain Arsenal (Conceptual Remedy Agreement).
Each party has agreed to support the conceptual remedy as the preferred remedial alternative and to
support the proposed plan based on the elements of the conceptual remedy.
8.1.9 Community Acceptance
The preferred alternative for the Offpost OU was presented to the public in a Proposed Plan, which
provides a brief summary of all of the alternatives evaluated during the detailed analysis of alterna-
tives in the FS. In accordance with the NCP, the public had an opportunity to review and comment
on the selected remedial alternatives presented in the Proposed Plan. The concerns expressed
included (1) soil remediation issues, (2) DIMP groundwater cleanup standard, (3) why expansion of
the Offpost Groundwater Intercept and Treatment System was not selected, (4) the presence of DIMP
immediately downgradient of the Offpost Groundwater Intercept and Treatment System in the First
Creek area, and (5) the classification of potential future land use. The public's comments are
addressed in the attached responsiveness summary (Appendix A). Community participation was also
included during the Conceptual Remedy Agreement negotiations.
8.2 Conclusions of the Comparative Analysis of Alternatives
The conclusions of the comparative analysis of groundwater alternatives for the North and Northwest
Plume Groups are summarized below.
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Comparative Analysis of Alternatives
In terms of overall protection of human health and the environment, compliance with ARARs,
effectiveness, and reduction of toxicity, mobility, or volume, Alternatives N-4 and N-5 are superior to
\
Alternatives N-l and N-2. Alternative N-4 is equal to Alternative N-2 in implementability.
Alternative N-4 is more readily implementable than Alternatives N-l and N-5 because Alterna-
tive N-l would not be administratively feasible, and Alterative N-5 would require a second design
and construction phase. Alternatives N-4 and N-5 are approximately equal in cost when compared to
each other and higher in cost when compared to Alternatives N-l and N-2. Therefore, Alternatives
N-4 and N-5 were identified as being superior to Alternatives N-l and N-2. Alternatives N-4 and N-5
are essentially equivalent with respect to evaluation of compliance with ARARs, short-term effective-
ness, and reduction in toxicity, mobility, or volume.
Alternative N-4 was demonstrated to be superior to Alternative N-5 with respect to the detailed
analysis criteria for the following reasons:
• The remedial system in Alternative N-4 is designed to effectively address groundwater
contamination within the North Plume Group on the basis of all available data. The Offpost
Groundwater Intercept and Treatment System is designed similar to the existing boundary
containment systems in that monitoring data is being evaluated to assess whether any
improvements are necessary. The intensive short-term groundwater monitoring program
included under Alternative N-4 adds flexibility through providing information that will be
used to identify any necessary or beneficial improvements to the Offpost Groundwater
Intercept and Treatment System and provides information about the optimal location of
additional wells or trenches. Because the estimates of remediation time frames developed for
the groundwater alternatives are uncertain, additional capital expenditures are not justified
until actual full-scale data is available.
• Alternative N-4 is superior to Alternative N-5 with respect to long-term effectiveness and
permanence. The combination of full-scale operational data from the Offpost Groundwater
Intercept and Treatment System and future possible system modifications will result in an
optimized treatment system. Immediate placement of additional wells and trenches in
Alternative N-5, based on groundwater modeling results, would not be based on the more
accurate empirical data.
• Alternative N-4 is more readily implementable than Alternative N-5 because implementation
of Alternative N-5 would require additional remedial design and construction. Operation of
Alternative N-4 would start immediately.
Alternative NW-2 ranks above Alternative NW-1 in all criteria except cost; however, the additional
costs are not prohibitive in light of the reduction in time for remediation.
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9.0 IDENTIFICATION OF THE SELECTED REMEDY
The selected remedy for the Offpost OU consists of implementing Alternative N-4 for remediation of
groundwater in the North Plume Group, Alternative NW-2 for remediation of groundwater in the
Northwest Plume Group, and continued operation of the Irondale Containment System consistent
with the Irondale ERA. The selected alternatives are described in detail in Section 7 and the
Declaration to the ROD.
9.1 Alternative N-4: Offpost Groundwater Intercept and Treatment System
Construction of the Offpost Groundwater Intercept and Treatment System began in November 1991
and full-scale system operation began in June 1993. Additional detail concerning design specifics is
contained in the Final Implementation Document for the Groundwater Intercept and Treatment
System North of RMA (HLA, 1991). The major components of this alternative are as follows:
• Operation of the Offpost Groundwater Intercept and Treatment System
Removal of contaminated UFS groundwater north of the RMA boundary in the First
Creek and northern paleochannels, using Offpost Groundwater Intercept and Treat-
ment System groundwater extraction wells
Treatment of the extracted groundwater, using carbon adsorption
Recharge of treated groundwater to the UFS, using Offpost Groundwater Intercept and
Treatment System recharge wells and trenches
Natural attenuation of inorganic chloride and sulfate concentrations to meet
applicable standards for groundwater in a manner consistent with the on-Post
remedial action
• Continued operation of the NBCS
• Improvements to Offpost Groundwater Intercept and Treatment System and the NBCS, as
necessary
• Long-term groundwater and surface-water monitoring
• Site reviews
• Exposure control/provision of alternate water supply as described in Section 7.1
• Well closure in confonnance with criteria listed in Appendix C, pages C-l and C-2
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identification of the Selected Remedy
• Institutional controls for the selected remedy are reflected in Appendix B. These institutional
controls are intended to prevent the future use of groundwater exceeding remediation goals.
The Offpost Groundwater Intercept and Treatment System is an array of extraction wells and
recharge trenches in the northern and First Creek paleochannels. The system is configured to extract
and treat UFS groundwater that exceeds containment system remediation goals and to recharge the
treated groundwater. Figure 7.1 presents the placement of extraction wells and recharge wells in the
northern paleochannel and the placement of extraction wells and recharge trenches in the First Creek
paleochannel. The location of the treatment facility is also shown in Figure 7.1. The northern paleo-
channel collection system consists of 12 extraction wells spaced approximately 200 feet apart across
the paleochannel, perpendicular to the direction of groundwater flow. The recharge system in the
northern paleochannel consists of 24 recharge wells spaced 100 feet apart and placed parallel to and
approximately 300 feet downgradient of the collection system. The First Creek paleochannel
collection system consists of 5 extraction wells spaced 200 to 500 feet apart along the axis of the
paleochannel. Recharge trenches are placed such that four of the six trenches are parallel to the flow
axis and located on the margins of the paleochannel, with the remaining two trenches located
downgradient of the extraction well system and oriented perpendicular to the flow axis.
The system is designed to extract and treat an average flow of 300 gpm from the northern paleochan-
nel, an average flow of 180 gpm from the First Creek paleochannel, and a peak flow of 1.5 times the
average flow. The treatment facility basic process flow includes influent storage, pumping, bag
filtration for particulate removal, carbon adsorption, multimedia filtration, treated water storage,
treated water pumping, and final bag filtration.
A total of approximately 250 million gallons per year would be treated by the Offpost Groundwater
Intercept and Treatment System at the average flows. In addition, operation of the NBCS component
of this alternative will treat approximately 125 million gallons per year. Thus, a total of approxi-
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Identification of the Selected Remedy
mately 375 million gallons of UFS groundwater will be treated annually to attain Offpost OU
containment system remediation goals (Tables 7.1, 7.2, and 7.3) under this alternative.
An intensive short-term monitoring component will be included in Alternative N-4 as part of the
long-term monitoring program. For costing purposes, it is assumed that this program will consist of a
network of approximately 60 wells to be sampled semiannually for two to three years, beginning with
the Offpost Groundwater Intercept and Treatment System start-up. The intensive monitoring
program will allow the collection and subsequent interpretation of performance data for the full-scale
operation of both the Offpost Groundwater Intercept and Treatment System and the NBCS. The data
will also be used to assess the need for any improvements to the systems. The acquisition of such
data will allow for increased accuracy in assessing the response of the UFS groundwater to the NBCS
and Offpost Groundwater Intercept and Treatment System remediation systems.
In addition, the preferred alternative includes long-term monitoring of offpost groundwater and
surface water to assess contaminant concentration reduction and remedy performance. Groundwater
monitoring will continue utilizing both monitoring wells and private drinking water wells. Selected
surface-water monitoring locations will be included to evaluate the effect of groundwater treatment
on surface water quality. Monitoring will continue after system shut-off to assure continued
compliance with containment system remediation goals. The Army will present the scope of these
ongoing monitoring programs in an Implementation Plan to be submitted within 90 days following
issuance of the ROD. A schedule for compliance with the containment system remediation goals will
be included in the Implementation Plan.
9.2 Alternative NW-2: Continued Operation of the Northwest Boundary
Containment System with Improvements as Necessary
This section summarizes Alternative NW-2, the continued operation of the NWBCS with improve-
ments as necessary. For additional details of the extraction/recharge systems, the recent upgrades to
the system, and the treatment facility at the NWBCS, the reader is referred to the following reports:
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Final Implementation Document for NWBCS Short-term Improvements IRA. (Morrison-Knudsen
Environmental Services [MKES], 1990a); NWBCS Long-term Improvements IRA B(ii) Final Assess-
ment Document (Woodward-Clyde [WWC], 1991a); Proposed Decision Document NWBCS RMA Long-
term Improvements ERA (WWC, 199lb); Report of Field Investigations, Assessment, and Final
Decision Document for the NWBCS Short-term Improvements BRA (MKES, 1990b); Implementation
Document for the Northwest Boundary System long-term Improvements IRA Final Report (MKES,
1992); and Northwest Boundary Containment System Long-term Improvements IRA One-year
Evaluation Report (MKES, 1993). The major components of this alternative are as follows:
• Continued operation of the NWBCS
• Improvements to the NWBCS as necessary
• Long-term groundwater monitoring
• Site reviews
• Exposure control/provision of alternate water supply as described in Section 7.1
• Well closure in conformancewith criteria listed in Appendix C, pages C-l, and C-2
• Institutional controls as described in Appendix B
In addition, the preferred alternative includes long-term monitoring to assess contaminant concentra-
tion reduction and remedy performance. After attainment of groundwater containment system
remediation goals and system shut-off, groundwater monitoring will continue to assure continued
compliance with containment system remediation goals. The Army will present the scope of these
monitoring programs in implementation plans to be submitted following issuance of the ROD.
The NWBCS began operation in 1984. The NWBCS collection system consists of 20 extraction wells
and a soil bentonite barrier approximately 2300 feet in length. The recharge system consists of 25
downgradient recharge wells.
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Identification of the Selected Remedy
9.3 Additional Components of the Selected Remedy
In accordance with the NCP, the public had an opportunity to review and comment on the selected
remedial alternatives presented in the Proposed Plan. In response, the Parties held additional
discussions to determine how best to address these comments. These discussions resulted in
clarifications and minor technical changes that do not significantly alter the overall scope, perfor-
mance, or cost of the Offpost preferred alternative.
Because the main focus of the Offpost preferred alternative is unchanged, and the additional actions
only clarify and enhance the preferred alternative, the changes were not considered to be significant.
The discussions also involved broader issues which were resolved in a document entitled "Agreement
for a Conceptual Remedy for the Cleanup of the Rocky Mountain Arsenal," dated June 13, 1995.
With regard to the Offpost area, the Parties agreed to several additional components which are an
integral part of the overall remedy but are proposed for inclusion in the Onpost ROD. Many of these
components are in the Onpost Proposed Plan, which is available for public comment from
October 16, 1995, through January 19,1995.
The additional components added in response to public comment and as part of the Conceptual
Remedy Agreement discussions include:
• The U.S. Army and Shell Oil Company agree to continue monitoring and to complete an
assessment of the MDMA plume by June 13,1996, using a 20 ppt method detection limit.
• The U.S. Army and Shell Oil Company agree to prepare a feasibility study of potential
actions, both onpost and at the boundary, or adjacent to the boundary in order to achieve
NDMA remediation goals at the RMA boundary and to use 7.0 ppt PRG or a certified analyti-
cal detection level readily available at a certified commercial laboratory (currently 33 ppt).
• The U.S. Army and Shell Oil Company agree to revegetate approximately 160 acres located in
the southeast portion of Section 14 and the southwest portion of Section 13 as depicted in
Figure 9.1. Revegetation will involve tilling and seeding. No sampling will be conducted
before or after revegetation. Existing soil risks in the area to be revegetated fall within EPA's
established acceptable risk range and revegetation is not necessary. However, the U.S. Army
and Shell Oil Company agree to the revegetation program as part of the Offpost settlement.
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identification of the Selected Remedy
• The Army will treat any contaminated extracted groundwater prior to discharge or reinjection
so that it meets the current water quality standards established in the Colorado Basic
Standards for Groundwater and the Colorado Basic Standards and Methodologies for Surface
Water.
• As of the date of the Onpost ROD, and based on a 0.392 parts per billion (ppb) detection
limit, the U.S. Army will use the last available quarterly monitoring results to determine the
DIMP plume footprint.
• The Army and Shell Oil Company will pay for the extension of, and hook-up to, the current
water distribution system for all existing well owners within the DIMP plume footprint
referenced above.
• Existing domestic well owners outside of the DIMP plume footprint as of the date of the
Onpost ROD where it is later determined that levels of DIMP are eight ppb or greater (or
other relevant CBSG at the time) will be hooked up at the U.S. Army and Shell Oil Com-
pany's expense to the SACWSD distribution system or provided a deep well or other
permanent solution.
• For new domestic wells with levels of eight ppb or greater (or other relevant CBSG at the
time), the Offpost ROD institutional controls will provide that the U.S. Army and Shell Oil
Company will pay for hook-up to the distribution system or provided a deep well or other
permanent solution.
• The parties to the Conceptual Remedy Agreement commit to good faith best efforts to
establish a trust fund for the operations and maintenance of the remedy, including habitat
and surficial soil. The parties recognize, however, that establishment of such a trust fund
requires special legislation and there are restrictions on the actions federal agencies can take
with respect to proposing legislation and supporting proposed legislation.
• As part of the Onpost remedy, the U.S. Army and Shell Oil Company will pay for and
provide, or arrange for the provision, of 4000 acre-feet of water to SACWSD.
9.4 Cost of Selected Remedy
A detailed cost summary for the selected remedy is presented in Table 9.1. The total estimated cost
ranges from approximately $69 to $76 million. This cost does not include implementation of the
additional components discussed in Section 9.3. However, these additional components would be
included in all the alternatives evaluated (except the No Action alternative); therefore, the relative
relationship of the cost of the various alternatives will not change.
9.5 Limitations
It should be recognized that U.S. Environmental Protection Agency (EPA) studies (EPA, 1988b) have
indicated that it may not always be possible to reach MCLs or proposed MCLs through currently
available technology. If it becomes apparent during implementation or operation of the selected
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Identification of the Selected Remedy
remedy that contaminant levels are remaining constant for a significant amount of time at levels
higher than the groundwater containment system remediation goals delineated in the ROD, the
containment system remediation goals and the remedy will be reevaluated. Further, the NCP
requires a formal review of the effectiveness of the selected remedy at least every five years. As
needed, the operational design of the selected remedy will be reviewed to achieve the groundwater
containment system remediation goals .
9.6 Criteria for Shutting Down Boundary and Offpost Containment
Groundwater Systems
Existing wells within the boundary and offpost containment systems can be removed from produc-
tion when concentrations of constituents detected in the well are less than applicable or relevant and
appropriate requirements (ARARs) established in the ROD and/or it can be demonstrated that
discontinuing operation of a well will not jeopardize the containment objective of the systems. Wells
removed from production, and monitoring wells upgradient and downgradient of the boundary and
offpost containment systems, will be monitored quarterly for a period of five years to determine if
contaminants reappear. Wells turned off for hydraulic purposes will not be subject to the quarterly
monitoring requirements. Boundary and offpost containment system extraction wells removed from
production for water quality reasons will be placed back into production if contaminant concentra-
tions exceed the ARARs established in the ROD. Wells with concentrations less than ARARs
established in the ROD can remain in production if additional hydraulic control is required.
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10.0 STATUTORY DETERMINATIONS
A description of how the selected remedy meets statutory requirements, compliance with the
requirements of CERCLA, and consistency with the NCP is presented in this section.
10.1 Consistency with the Statutory Requirements of CERCLA in Section 121
The statutory requirements of CERCLA Section 121, as described below, and the statutory preference
for treatment are met through implementation of the selected remedy.
10.1.1 Protection of Human Health and the Environment
The selected remedy will result in the remediation of the Offpost OU groundwater consistent with
remedial action objectives and containment system remediation goals established for the site.
Contaminated groundwater in the North and Northwest Plume Groups will be addressed by
implementing the selected remedy through groundwater extraction, treatment, and recharge.
The groundwater remedial actions proposed under Alternatives N-4 and NW-2 will permanently
address the primary threat to human health and the environment for the Offpost Study Area through
carbon adsorption treatment to reduce the toxicity, mobility, and volume of contaminated ground-
water. Contaminant levels in Offpost Study Area groundwater will be reduced to or below ground-
water containment system remediation goals following treatment. Reduction of groundwater
contaminant concentrations to these goals will further reduce the groundwater cumulative excess
cancer risk toward 10"6. Following groundwater remedial action, the HI for noncarcinogens will be
less than 1.
It should be recognized, however, that studies conducted at other sites (by EPA and others) have
indicated that it may not always be possible to reach groundwater containment system remediation
goals because of the limitations of the technology used to assess groundwater hydrogeological
properties, the technology used to estimate aquifer remediation time frames, and the technology used
to extract and recharge groundwater. If it becomes apparent during operation of the groundwater
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Statutory Determinations
treatment systems that groundwater contaminant levels are remaining constant at levels higher than
the Offpost OU groundwater containment system remediation goals , the selected remedy provides for
improvements to the proposed remedial systems as necessary. An alternative water supply will be
provided to any user of a domestic well in accordance with the provisions in Section 7.1. Institu-
tional controls that are part of this remedy are intended to prevent the future domestic use of
groundwater exceeding the containment system remediation goals.
Of the alternatives evaluated for cleaning up the groundwater, the selected remedy provides the
highest degree of protection of human health without adverse impact to the environment. No
unacceptable short-term risks will be caused by implementing this remedy.
Potential ecological impacts during remediation will be continually evaluated. Maintenance of
existing habitats and ecosystems are important. Although the Federal Endangered Species Act, the
Migratory Bird Treaty Act, and the Bald Eagle Protection Act were not considered as ARARs, the FFA
requires their application. Remediation goals consistent with the substantive requirements of these
Acts are being met and will be assured through close interaction with the U.S. Fish and Wildlife
Service. In coordination with the U.S. Fish and Wildlife Service, it was agreed that screening levels,
developed to ensure compliance with enforceable remediation levels, meet the requirements of the
federal Endangered Species Act, the Migratory Bird Treaty Act, and the Bald and Golden Eagle
Protection Act. These screening levels were not exceeded in the Offpost OU. These levels are
presented in the Final Offpost Operable Unit Endangerment Assessment/Feasibility Study in
Table 3.3.3-1 (Toxicity Reference Values for Avian and Terrestrial Vertebrate Species of Concern
Identified at Rocky Mountain Arsenal) of Volume II and Table H5-1 (Maximum Allowable Tissue
Concentration [MATC] Values for the Offpost EA Ecological Assessment) of Appendix H in
Volume IV. If the screening levels are exceeded or effects are observed in the future, enforceable
remediation levels will be developed consistent with CERCLA, the Endangered Species Act, the
Migratory Bird Treaty Act, and the Bald and Golden Eagle Protection Act.
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Statutory Determinations
10.1.2 Compliance With Applicable or Relevant and Appropriate Requirements
Under Section 121(d)(l) of CERCLA, remedial actions must attain standards, requirements, limita-
tions, or criteria that are applicable or relevant and appropriate under the circumstances of the
release at a site. ARARs would be met or exceeded upon completion of the selected remedy at the
Offpost OU.
Chemical-specific ARARs
Groundwater containment system remediation goals are based on chemical-specific ARARs for those
chemicals having promulgated standards and on HBC for those chemicals without ARARs
(Tables 7.1, 7.2, and 7.3). The preferred sitewide alternative is expected to attain or exceed
chemical-specific ARARs. A summary of the chemical-specific and other ARARs that have been
assessed to be applicable or relevant and appropriate is presented in Table 10.1.
Action-specific ARARs
The selected remedy will comply with action-specific ARARs. A summary of the action-specific
ARARs that have been assessed to be applicable or relevant and appropriate is presented in
Table 10.2.
Location-specific ARARS
The selected remedy will comply with location-specific ARARs. A summary of the location-specific
ARARs that have been assessed to be applicable or relevant and appropriate is presented in
Table 10.3.
10.1.3 Cost Effectiveness
The selected remedy is cost-effective in mitigating the risks posed at the site by contaminated
groundwater. Cost-effectiveness is determined by evaluating three of the five balancing criteria to
determine overall effectiveness: long-term effectiveness and permanence; reduction of toxicity,
mobility, or volume through treatment; and short-term effectiveness. Overall effectiveness is then
compared to cost to ensure that the remedy is cost-effective.
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Statutory Determinations
The selected remedy for groundwater provides the best overall effectiveness of all alternatives
considered proportional to its cost. The selected remedy will greatly reduce the toxicity, mobility,
and volume of groundwater exceeding containment system remediation goals. Also the implementa-
tion of this remedy will result in long-term effectiveness by reducing residual carcinogenic risks
through permanent treatment.
Through the groundwater monitoring program, the Army can more accurately assess the contaminant
removal rates as a function of time, using the full-scale data available during operation of the Offpost
Groundwater Intercept and Treatment System, the NBCS, and the NWBCS. The analysis of this data
will allow for cost-effective decisions regarding any future improvements that may be required for the
remedial systems.
10.1.4 Utilization of Permanent Solutions to the Maximum Extent Practicable
The selected remedy for the Offpost OU represents the maximum extent to which permanent
solutions and treatment technologies can be used in a cost-effective manner to remediate ground-
water at the site. Of those alternatives that are protective of human health and the environment and
comply with ARARs, the selected remedy (Alternatives N-4 and NW-2) will provide the best balance
of trade-offs in terms of long-term effectiveness and permanence; reduction of toxicity, mobility, or
volume through treatment; short-term effectiveness; implementability; cost; the statutory preference
for treatment as a principal element; and state and community acceptance.
10.2 Consistency with the National Contingency Plan
The NCP requires that the following two features be present in the remedy selection process:
• The nine criteria used to evaluate alternatives in the detailed analysis are used to select a
remedy.
• Selected Superfund remedies must employ the nine criteria to make the following four
determinations:
Each remedial action selected shall be protective of human health and the environ-
ment.
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Statutory Determinations
Onsite remedial actions selected in a ROD must attain ARARs or provide grounds for
invoking a waiver.
Each remedial action selected shall be cost effective, provided that it first satisfies the
threshold criteria (defined in Section 8.0).
Each remedial action shall use permanent solutions to the maximum extent
practicable.
The preferred sitewide alternative is fully consistent with the NCP, as is the selection process used to
arrive at the preferred alternative. Alternatives were developed and screened, and the detailed
analysis of alternatives was performed in a manner consistent with the NCP.
1O.3 Summary
The preferred sitewide alternative for remediation of the Offpost OU is the combination of Alterna-
tives N-4 and NW-2. The preferred alternative was selected in accordance with the requirements of
CERCLA and the NCP. The remedial actions that compose the sitewide preferred alternative will
permanently address the principal threats through groundwater extraction and treatment to reduce
the toxicity, mobility, or volume of contaminants for protection of human health and the environ-
ment.
Although the requirements for provision of an alternate water supply and hookup to the SACWSD
are part of the Onpost remedy, these actions will also significantly reduce the potential for exposure
to offpost groundwater.
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11.0 DOCUMENTATION OF SIGNIFICANT CHANGES
The Proposed Plan for the Rocky Mountain Arsenal Offpost Operable Unit was released for public
comment in March 1993. The Proposed Plan identified Alternative N-4 (Offpost Groundwater
Intercept and Treatment System) as the preferred alternative for groundwater in the North Plume
Group and Alternative NW-2 (Continued Operation of the Northwest Boundary Containment System
With Improvements as Necessary) as the preferred alternative for groundwater in the Northwest
Plume Group. The Army received written comments from the U.S. Environmental Protection
Agency, the State of Colorado, the Tri-County Health Department, city and county governments,
environmental action groups, and citizens. After review of these comments, it was determined that
no significant changes to the preferred alternative, as it was originally identified in the Proposed
Plan, were necessary.
As indicated earlier in Section 8.1.8, following the issuance of the Offpost Proposed Plan, additional
discussions were held between the Parties regarding the implementation of the preferred alternative
for the Offpost OU and the remedies for the Onpost OU. The main components of the preferred
alternative for the Offpost OU remain intact. These components are:
• Operation (and improvement, if necessary) of the Offpost Groundwater Intercept and
Treatment System
• Continued operation (and improvement, if necessary) of the NBCS and NWBCS
• Long-term groundwater and surface-water monitoring
• Five-year site review
• Well closure
• Provision of alternate water supplies and implementation of institutional controls intended to
prevent future use of contaminated groundwater.
The Conceptual Remedy Agreement provides more specific criteria for the provision of alternate
water supplies to current and future well owners, specific criteria for continued operation of and
requirements for shutdown of the groundwater treatment systems, and additional requirements for
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Documentation of Significant Changes
the Army and Shell Oil Company such as tilling and revegetationof surface soil and additional study
requirements. Because the main focus of the preferred alternative is unchanged by the Conceptual
Remedy Agreement, and the additional actions specified in the Conceptual Remedy Agreement only
clarify and enhance the preferred alternative, the Conceptual Remedy Agreement was not considered
to be a significant change. Therefore, the preferred alternative as presented in the Proposed Plan,
and additional actions to enhance the preferred alternative as outlined in the Conceptual Remedy
Agreement, is the selected remedy.
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12.0 GLOSSARY
ARAR
Army
ATSDR
CAR
CBSG
CBSM
CERCLA
CF&I
CFS
CMP
CNS
COG
CRL
CSC
CU
DBCP
DCPD
DDE
DDT
DIMP
DOI
DOJ
EA/FS
EPA
ESE
FFA
Applicable or relevant and appropriate requirement
U.S. Department of the Army
U.S. Agency for Toxic Substances and Disease Registry
Contamination Assessment Report
Colorado Basic Standards for Groundwater
Colorado Basic Standards and Methodologies for Surface Water
Comprehensive Environmental Response, Compensation, and Liability Act
Colorado Fuel and Iron
Confined flow system
Comprehensive Monitoring Program
Central nervous system
Chemicals of concern
Certified reporting limit
Chemical Sales Company
Consumptive use
Dibromochloropropane
Dicyclopentadiene
2,2-bis(p-Chlorophenyl)-l,l-dichloroethene
2,2-bis(p-Chlorophenyl)-l,l,l-trichloroethane
Diisopropylmethyl phosphonate
U.S. Department of Interior
U.S. Department of Justice
Endangerment assessment/feasibility study
U.S. Environmental Protection Agency
Environmental Science and Engineering, Inc.
Federal Facility Agreement
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Glossary
GMP
gpm
HBC
HI
HQ
Hyman
ICS
IRA
MCL
MCLG
MKES
NBCS
NDMA
NCP
NEPA
NPL
NWBCS
O&M
OCP
OU
PRP
PVC
RfD
RI/FS
RMA
RME
ROD
Groundwater Monitoring Program
Gallons per minute
Health-based criteria
Hazard index
Hazard quotient
Julius Hyman & Company
Irondale Containment System
Interim response action
Maximum contaminant level
Maximum contaminant level goal
Morrison-Knudsen Environmental Services
North Boundary Containment System
N-nitrosodimethylamine
National Oil and Hazardous Substances Pollution Contingency Plan
National Environmental Policy Act
National Priorities List
Northwest Boundary Containment System
Operation and maintenance
Organochlorine pesticide
Operable unit
Potentially responsible party
Polyvinyl chloride
Reference dose
Remedial investigation/feasibility study
Rocky Mountain Arsenal
Reasonable maximum exposure
Record of Decision
12-2
Harding Lawson Associates
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Glossary
SACWSD
SARA
Shell
UFS
wwc
//g/1
//8/kg
South Adams County Water and Sanitation District
Superfund Amendments and Reauthorization Act
Shell Oil Company
Unconfined flow system
Woodward-Clyde
Micrograms per h'ter
Micrograms per kilogram
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13.0 BIBLIOGRAPHY
Adams County, City of Aurora, City of Brighton, City of Commerce City. 1990. Airport Environs
Concept Plan, Brighton, Colorado.
Adams County Planning Commission. 1987. Adams County Future Land Use Plan, Brighton, CO.
Camp Dresser & McKee, Inc. 1993. Stapleton International Airport Environmental Assessment,
Northern Zone. Prepared for Stapleton International Airport, City and County of Denver. June 15.
Ebasco Services, Inc. 1988. Western Tier TCE Soil Gas Investigation, Final Summary Report.
January.
Ebasco Services, Inc. 1989. Technical Support for Rocky Mountain Arsenal Draft Final Water
Remedial Investigation Report. Contract Nos. DAAK11-84-D0016 and DAAA15-88-D0024.
Denver, CO.
Environmental Science and Engineering, Inc. 1985. Rocky Mountain Arsenal Offpost Assessment:
Ground Water Quality Report (Consumptive Use - Phase I) for Sampling Period December 1984
through January 1985. Prepared for U.S. Army Toxic and Hazardous Materials Agency. Denver, CO.
Environmental Science and Engineering, Inc. 1986. Rocky Mountain Arsenal Offpost Assessment:
Ground Water Quality Report (Consumptive Use - Phase II) for Sampling Period September through
October 1985. Contract No. DAAK-ll-D-007, Task Order 0006. Denver, CO.
Environmental Science and Engineering, Inc. 1987a. Rocky Mountain Arsenal Offpost Assessment,
Contamination Assessment Report: Draft Final, Denver prepared for the Office of the Program
Manager, Rocky Mountain Arsenal.
Environmental Science and Engineering, Inc. 1987b. Rocky Mountain Arsenal Offpost Assess-ment:
Ground Water Quality Report (Domestic Use - Phase IE) for Sampling Period September through
October 1986 and February 1987. Contract No. DAAK-11-83-D-007, Task Order 0006.
Environmental Science and Engineering, Lie. 1988a. Offpost Operable Unit Remedial Investigation
and Chemical Specific Applicable or Relevant and Appropriate Requirements, Final Report. Prepared
by Environmental Science and Engineering, Inc., Harding Lawson Associates; and Applied Environ-
mental, Inc., Rocky Mountain Arsenal, Commerce City, CO. 3 volumes.
Environmental Science and Engineering, Inc. 1988b. Air Remedial Investigation Report, Final.
Prepared for Office of the Program Manager. Denver, CO.
Environmental Science and Engineering, Inc. 1989. Draft Final Endangerment Assessment/
Feasibility Study and Applicable or Relevant and Appropriate Requirements. Prepared for Office of
the Program Manager. Denver, CO.
Federal Facility Agreement. 1989. Pursuant to CERCLA Section 120, Docket No. CERCLA VHI-89-13,
signed by U.S. Department of the Army, U.S. Environmental Protection Agency, U.S. Environmental
Protection Agency Region Vm, U.S. Department of Interior, U.S. Fish and Wildlife Service, Agency
for Toxic Substances and Disease Registry, U.S. Department of Justice, and Shell Oil Company.
Harding Lawson Associates 1989. Final Decision Document for the Groundwater Intercept and
Treatment System North of Rocky Mountain Arsenal, Interim Response Action.
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Bibliography
Harding Lawson Associates. 1991. Final Implementation Document for the Ground-water Intercept
and Treatment System North of Rocky Mountain Arsenal, Interim Response Action.
Harding Lawson Associates. 1992a. Offpost Operable Unit, Endangerment Assessment/Feasibility
Study, Final Report, 8 volumes.
Harding Lawson Associates. 1992b. Offpost Operable Unit Remedial Investigation, Final Addendum,
2 volumes.
Morrison-Knudsen Environmental Services. 1990a. Implementation Document for Northwest
Boundary System Short-term Improvements IRA. June.
Morrison-Knudsen Environmental Services. 1990b. Report of Field Investigations, Assessment, and
Final Decision Document for the Northwest Boundary System Short-term Improvements Interim
Response Action, RMA. June.
Morrison-Knudsen Environmental Services. 1992. Implementation Document for the Northwest
Boundary System Long-term Improvements IRA Final Report. January
Morrison-Knudsen Environmental Services. 1993. Northwest Boundary Containment System Long-
term Improvements IRA One-year Evaluation Report. July.
Mullins, D.E., Johnsen, R.E., and Starr, R.I. 1971. Persistence of Organoclorine Insecticide Residues
in Agricultural Soils of Colorado. Pest. Monit. J. 5: 268-275.
R.L. Stollar & Associates, Inc. 1990. Comprehensive Monitoring Program; Air Quality Data Assess-
ment Report for 1989. Contract Number DAAA15-87-0095. Prepared for U.S. Army Program
Manager for Rocky Mountain Arsenal. Commerce City, CO.
U.S. Environmental Protection Agency. 1988a. CERCLA Compliance with Other Laws Manual Draft,
OSWER Directive 9234.1-01, August.
U.S. Environmental Protection Agency. 1988b. Guidance on Remedial Actions for Contaminated
Groundwater at Superfund Sites, OSWER Directive 9283.1-2, August.
U.S. Environmental Protection Agency. 1988c, Guidance for Conducting Remedial Investigations and
Feasibility Studies Under CERCLA, Interim Final, EPA/540/G-89004, October.
U.S. Environmental Protection Agency. 1989a. Risk Assessment Guidance for Superfund, Volume 1,
Human Health Evaluation Manual (Part A), Interim Final, EPA/540/1-89/002.
U.S. Environmental Protection Agency. 1989b. Exposure Factors Handbook, Final Report, Office of
Health and Environmental Assessment, EPA/600/8-89/043.
U.S. Environmental Protection Agency. 1991a. Record of Decision for Chemical Sales Company,
Operable Unit 2, June 27, 1991.
U.S. Environmental Protection Agency. 199lb. Record of Decision for Chemical Sales Company,
Operable Unit 3, June 27,1991.
U.S. Environmental Protection Agency. 1992. Record of Decision for Chemical Sales Company,
Operable Unit 2, December 29, 1992.
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Bibliography
Woodward-Clyde. 1991a. Northwest Boundary System Long-term Improvements Interim Response
Action B(ii) Final Assessment Document. June.
Woodward-Clyde. 199lb. Proposed Decision Document Northwest Boundary System Rocky
Mountain Arsenal Long-term Improvements Interim Response Action. June.
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Table 6.1: Offpost Operable Unit Groundwater Chemicals of Concern
Exposure Point Concentration
Chemicals of Concern Zone 1
Aldrin 0.029*
Arsenic 2.15
Atrazine 2.87
Benzene 0.61
Carbon tetrachloride
Chlordane
Chloride 120,000
Chlorobenzene 1.02
Chloroform 0.68
CPMSO
CPMS02
Dibromochloropropane
1 ,2-Dichloroethane
Dicyclopentadiene
DDE 0.029
DDT 0.037
Dichlorobenzene
DIMP 63.3*
Dieldrin 0.034*
Dithiane
Endrin 0.033
Ethylbenzene
Fluoride 1830
Hexachlorocyclopentadiene 0.029
Isodrin 0.028
Malathion
Manganese
Oxathiane
Sulfate 340,000*
Tetrachloroethene 0.70
Toluene
Trichloroethene
Xylene 0.75
Zone 2
0.045*
1.63
5.31*
0.64
0.76*
0.18*
205,000
1.78
67.5*
14.5
4.35
0.44*
0.77*
3.64
0.029
0.033
5.1
713*
0.035*
—
0.037
—
2210*
0.033
0.035
0.26
1580
—
636,000*
10.1*
—
0.64
ZoneS
0.050*
-
12.9*
0.75
—
0.19*
487,000*
1.77
5.01
10.4
6.63
0.14
0.92*
163*
0.22*
0.11*
—
590*
0.21*
1.97
0.73*
—
3510*
0.044
0.047
0.38
—
1.32
909,000*
20.7*
1.28
0.51
Zone 4
0.12*
2.78*
7.36*
0.93
—
0.54*
660,000*
4.51
1.51
7.68
5.09
0.15
7.32*
66.6*
0.085
0.10
2.9
4950*
0.055*
4.22
0.058
0.57
3290*
0.043
0.057
0.32
1250
2.21
1,118,000*
6.09*
1.18
2.70
1.11
(z/fi/11* .
Zone 5
0.039*
2.68*
—
—
—
—
262,000*
1.09
12.0*
—
—
0.10
—
—
—
—
—
7.68
0.071*
—
—
—
1810
0.035
—
—
670
—
148,000
0.75
—
—
Zone 6
0.030*
—
4.48*
—
...
—
191,000
1.27
3.33
—
—
—
—
—
—
—
—
4.67
0.039*
—
—
—
2230*
—
0.040
—
—
—
213,000
1.67
—
4.04*
Not a chemical of concern in this zone
CPMSO 4-chlorophenylmethyl sulfoxide
CPMS02 4-chlorophenyhnethyl sulfone
DDE 2,2-bis(p-chlorophenyl)-l,l-dichloroethene
DDT 2,2-bis(p-chlorophenyl)-l,l,l-trichloroethane
DIMP Diisopropylmethyl phosphonate
/yg/1 Micrograms per liter
* Exceeds groundwater containment system remediation goal listed in Tables 7.1, 7.2, and 7.3.
* All exposure point concentrations represent the upper 95 percent confidence limit on the arithmetic mean of
measured concentrations in monitoring and private wells.
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Table 6.2: Offpost Operable Unit Surface-Water Chemicals of Concern
Exposure Point Concentration
Chemicals of Concern First Creek Irrigation Canals
Arsenic
Chlordane
Chloride
Dicyclopentadiene
DDE
DDT
Dieldrin
DMP
Fluoride
Sulfate
18
0.18
206,000
10
0.089
0.046
2.6
230
2550
438,000
NE
NE
NE
NE
NE
NE
NE
20
970
NE
DDE 2,2-bis(p-chlorophenyl)-l,l-dichloroethene
DDT 2,2-bis(p-chlorophenyl)-l,l,l-trichloroethane
DIMP Diisopropylmethyl phosphonate
NE Chemical not significantly elevated above background levels in the irrigation canals
fjg/1 Micrograms per liter
* All exposure point concentrations represent the upper 95 percent confidence limit on the
arithmetic mean of measured concentrations in unfiltered surface-water samples.
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Table 6.3: Offpost Operable Unit Sediment Chemicals of Concern in First Creek
Exposure Point
Chemicals of Concern Concentration (mg/kg)a
Aldrin 0.011
Dibromochloropropane 0.099
Dieldrin 0.134
Endrin 0.0038
DDE 0.0005
DDT 0.0084
DDE 2,2-bis(p-chlorophenyl)-l,l-dichloroethene
DDT 2,2-bis(p-chlorophenyl)-l,l,l-trichloroethane
mg/kg Milligrams per kilogram
* All exposure point concentrations represent the upper 95 percent confidence limit on the
arithmetic mean of measured concentrations in sediment.
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Table 6.4: Offpost Operable Unit Soil Chemicals of Concern
Exposure Point Concentration fmg/kgl*
Chemicals of Concern Zone 3 Outside Zone 3
Aldrin 0.014 0.0021
Chlordane 0.049 MD
Dieldrin 0.112 0.018
Endrin 0.032 0.0042
DDE 0.024 0.015
DDT 0.063 0.030
DDE 2,2-bis(p-chlorophenyl)-l ,1-dichloroethene
DDT 2,2-bis(p-chlorophenyl)-l,l,l-trichloroethane
mg/kg Milligrams per kilogram
ND Chlordane not detected in soil outside zone 3
* All exposure point concentrations represent the upper 95 percent confidence limit on the
arithmetic mean of measured concentrations in soil.
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Table 6.5: Summary of Land-Use Scenarios and Exposure Routes by Zone
Scenario
Zone
Exposure Routes Quantified
Rural residential
1,2,6
Urban residential
3,4
Commercial and industrial
Dermal, soil
Inhalation, groundwater
Oral, dairy
Oral, eggs
Oral, groundwater
Oral, meat
Oral, soil
Oral, vegetables
Dermal, soil
Dermal, sediment
Dermal, surface water
Inhalation, groundwater
Oral, groundwater
Oral, sediment
Oral, soil
Oral, vegetables
Dermal, soil
Inhalation, groundwater
Oral, groundwater
Oral, soil
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Table 6.6: Reference Doses and Slope Factors for Chemicals off Concern
Noncarcinogenic
Chronic RfD
fmg/ks/dav)
Chemicals
of Concern
Aldrin
Arsenic
Atrazine
Benzene
Carbon tetrachloride
Chlordane
Chloride
Chlorobenzene
Chloroform
CPMSO
CPMSO2
Dibromochloropropane
Dichlorobenzenes (as 1,2-)
DDE
DDT
1,2-Dichloroethane
Dicyclopentadiene
Dieldrin
DMP
1,4-Dithiane
Endrin
Ethylbenzene
Fluoride
Hexachlorocyclopentadiene
Isodrin
Malathion
Manganese
1,4-Oxathiane
Sulfate
Tetrachloroethene
Toluene
Trichloroethene
Xylene
Oral
3E-5
3E-4
5E-3
2E-2
7E-4
6E-5
7.1
2E-2
1E-2
2E-2a-b
2E-2a'b
5E-3
9E-2
5E-4
5E-4
7E-2
3E-2
5E-5
8E-2C
3E-la
3E-4
1E-1
6E-2
7E-3
7E-5"
2E-2
1E-1
3E-1"
1.1E+1
1E-2
2E-1
4E-1"
2
Carcinogenic
Slope Factor
fma/ks/davV1
Inhalation Oral
NE
NE
NE
NE
NE
NE
NE
5E-3
NE
NE.
NE
5.7E-5
4E-2
NE
NE
NE
6E-5
NE
NE
NE
NE
3E-1
NE
NE
NE
NE
1.1E-4
NE
NE
1E-2
1.1E-1
4E-1
8.6E-2
1.7E+1
1.75
2.2E-1
2.9E-2
1.3E-1
1.3
NA
NA
6.1E-3
NA
NA
1.4
2.4E-2
3.4E-1
3.4E-1
9.1E-2
NA
1.6E+1
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
5.1E-2
NA
1.1E-2
NA
Carcinogenic
Inhalation Weight-of-Evidence
1.7E+1
5.0E+1
NE
2.9E-2
5.3E-2
1.3
NA
NA
8.1E-2
NA
NA
2.4E-3
NE
3.4E-1
3.4E-1
9.1E-2
NA
1.6E+1
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
1.8E-3
NA
1.7E-2
NA
B2
A
C
A
B2
B2
NA
NA
B2
NA
NA
B2
C
B2
B2
B2
NA
B2
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
B2
NA
B2
NA
Weight of Evidence Classification
A = Human carcinogen
Bl or B2 = Probable human carcinogen. Bl indicates that limited human data are available. B2
indicates sufficient evidence in animals and inadequate or no evidence in humans.
C = Possible human carcinogen
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Table 6.6 (continued)
CPMSO 4-chlorophenylmethyl sulfoxide
CPMS02 4-chlorophenyhnethyl sulfone
DDE 2,2-bis(p-chlorophenyl)-l,l-dichloroethene
DDT 2,2-bis(p-chlorophenyl)-l,l,l-trichloroethane
DIMP Diisopropylmethyl phosphonate
mg/kg/day Milligrams per kilogram per day
NA Not applicable
NE Not established
RfD Reference dose
a. Derived from scientific literature or obtained from agencies other than EPA.
b. Subsequent to this assessment, a Region Vm Health Advisory was issued (see letter dated
January 27,1994). This Health Advisory has not been reviewed by the other parties. The other
parties may provide comments to this Health Advisory in the future. Reference to these values
from EPA Region VIU's Health Advisory in this document does not constitute agreement by other
parties. The Region VIII Health Advisory values are as follows:
10-Day Longer-term
Child 0.2 mg/1 0.02 mg/1
Adult 0.6 mg/1 0.06 mg/1
c. This RFD is taken from the 1989 EPA Health Advisory for DIMP.
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Table 6.7: Summary of Reasonable Maximum Exposure Carcinogenic Risks
by Zone and Exposure Route
Exposure
Assessment
Zone
1A*
IB*
1C*
2
3
4
5
6
Exposure Route
Ingestion
1.1E-4
1.3E-4
1.1E-4
1.6E-4
2.5E-4
2.1E-4
2.4E-5
6.9E-5
Inhalation
8.7E-7
8.7E-7
8.7E-7
6.6E-5
6.5E-6
l.OE-5
3.4E-6
4.0E-6
Dermal
l.OE-7
l.OE-7
l.OE-7
l.OE-7
1.3E-6
7.3E-7
6.7E-8
l.OE-7
Total
1.1E-4
1.3E-4
1.1E-4
2.3E-4
2.6E-4
2.2E-4
2.7E-5
7.3E-5
Zone 1 is subdivided on the basis of the presence of surface water and whether the ditch water
used for irrigation is collected upstream or downstream of the mouth of First Creek.
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Table 6.8: Summary of Adult Reasonable Maximum Exposure Noncarcinogenic
Hazard Indices by Target Organ and Exposure Assessment Zone
Exposure Assessment Zone
Target
Organ
Blood
Cardiovascular
CNS
Gastrointestinal
Hepatic
Ocular
Renal
Respiratory
Skin
1A
1.7E-3
1.6E-2
2.4E-2
1.5E-4
1.8E-1
7.0E-3
2.4E-4
2.0E-1
IB
1.8E-3
2.0E-2
2.6E-2
3.1E-4
2.1E-1
7.4E-3
2.4E-4
2.3E-1
1C
1.7E-3
1.6E-2
2.3E-2
1.5E-4
1.8E-1
7.0E-3
2.4E-4
2.0E-1
2
1.9E-3
3.8E-2
8.4E-1
3.5E-4
1.1E+0
2.3E-1
2.3E-4
1.7E-1
3
2.4E-3
9.0E-2
2.4E-1
4.3E-4
1.3E+0
3.1E-4
8.1E-2
5.8E-4
2.3E-2
4
2.9E-3
5.4E-2
2.4E+0
4.2E-4
9.0E-1
2.8E-4
1.1E-1
2.8E-3
3.1E-1
5
—
6.6E-2
4.9E-5
7.2E-2
2.0E-2
8.7E-2
6
2.5E-2
1.6E-3
—
2.0E-1
8.8E-1
—
Chemicals for this target organ not detected in this zone
CNS Central nervous system
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Table 7.1: Containment System Remediation Goals for the
Offpost Groundwater Intercept and Treatment System
Analyte
1 ,2-Dichloroethane
1,3-Dichlorobenzene
1,4-Oxathiane
Aldrin
Atrazine
Benzene
Carbon tetrachloride
Chlordane
Chlorobenzene
Chloroform
CPMS
CPMSO
CPMS02
DBCP
DCPD
DDE
DDT
Dieldrin
DIMP
Dithiane
Endrin
Ethylbenzene
Hexachlorocyclopentadiene
Isodrin
Malathion
NDMA
Tetrachloroethylene
Toluene
Trichloroethylene
Xylenes
Arsenic
Chloride
Fluoride
Sulfate
CSRG
U/S/1)
0.4
6.5
160
0.002
3
3
0.3
0.03
25
6
30
36
36
0.2
46
0.1
0.1
0.002
8
18
0.2
200
0.23
0.06
100
0.007
5
1,000
3
1,000
2.35
250,000f
2,000
250,000*
Source
CBSG
HBC
HBC
CBSG
MCL, CBSG
HBC
CBSG
CBSG
HBC
CBSG
HBC
HBC
HBC
MCL, CBSG
HBC
CBSG
CBSG
CBSG
CBSG
HBC
CBSG
HBC
HBC
HBC
HBC
(e)
MCL, CBSG
MCL, CBSG
HBC
HBC
HBC
CBSG
CBSG
CBSG
Rural
Residential
Hypothetical
PQL" Cancer Riskb
1.0° 9.1 x 10'7
NA
NA
0.05d 4.0 x 10'7
NA
2.0 x 10"6
0.99d 7.9 x 10'7
0.095d 5.7 x 10'7
NA
6.4 x 10'6
NA
NA
NA
3.8 xlO"6
NA
8.5 x 10'7
4.1 x 10'7
0.05d 1.2 x 1Q-6
NA
NA
NA
NA
NA
NA
NA
0.033 1.0 x 10'5
4.0 x 10"6
NA
9.9 x 10'7
NA
5.6 x 1Q-5
NA
NA
NA
Total11 8.8 x ID'5
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Table 7.1 (continued)
The following chemical have ARARs that were adjusted downward to reduce overall risk: arsenic
benzene, chlorobenzene,l,3-dichlorobenzene,trichloroethylene,and xylene.
CBSG Colorado Basic Standards for Groundwater
CPMS 4-chlorophemylmethylsulfide
CPMSO 4-chlorophenyhnethyl sulfoxide
CPMSO2 4-chlorophenyhnethyl sulf one
CSRG Containment system remediation goal
DBCP Dibromochloropropane
DCPD Dicyclopentadiene
DDE 2 ,2-bis(p-chlorophenyl)-l ,1-dichloroethene
DDT 2 ,2-bis(p-chlorophenyl)-l ,1 ,1-trichloroethane
DIMP Diisopropylmethyl phosphonate
HBC Health-based criteria
MCL Maximum containment level
NA Not applicable
NDMA N-nitrosodimethylamine
PQL Practical quantitation limit
Micrograms per liter
Practical quantitation limit; presented only when the PQL is greater than the CSRG.
Based on the CSRG.
PQL listed in the CBSG standards
PQL attainable by the U.S. Army
The remediation goal for NDMA was established at 0.007 parts per trillion (ppt) in the
Conceptual Remedy Agreement. The current PQL readily available is 0.033 ppt. The estimated
risk associated with NDMA is based on a 70-year residential exposure duration.
Inorganic standard for chloride will be met by natural attenuation consistent with the onpost
remedial action.
Inorganic standard for sulfate may be the natural background concentration, which will be
established and met by natural attenuation consistent with onpost remedial action.
Because of the variability in contaminant distribution and concentration, the maximum risk
associated unth the groundwater cleanup concentrations is not expected to occur at any one
location.
a.
b.
c.
d.
e.
g.
h. .
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Table 7.2: Containment System Remediation Goals for the
North Boundary Containment System
Analyte
1 ,2-Dichloroethane
1 ,2-Dichloroethylene
1,4-Oxathiane
Aldrin
Atrazine
Benzene
Carbon tetrachloride
Chloroform
CPUS
CPMSO
CPMS02
DBCP
DCPD
Dieldrin
DEMP
Dithiane
Endrin
Isodrin
Malathion
Methylene chloride
MDMA
Tetrachloroethylene
Toluene
Trichloroethylene
Xylenes
Arsenic
Chloride
Fluoride
Sulfate
CSRG
(A/S/1)
0.4
70
160
0.002
3
3
0.3
6
30
36
36
0.2
46
0.002
8
18
0.2
0.06
100
5.0
0.007
5
1,000
3
1,000
2.35
250,000f
2,000
250,000*
Source
CBSG
CBSG
HBC
CBSG
MCL, CBSG
HBC
CBSG
CBSG
HBC
HBC
HBC
MCL, CBSG
HBC
CBSG
CBSG
HBC
CBSG
HBC
HBC
MCL, CBSG
(e)
MCL, CBSG
MCL, CBSG
HBC
HBC
HBC
CBSG
CBSG
CBSG
Rural
Residential
Hypothetical
PQL" Cancer Riskb
1.0C 9.1 x 10'7
NA
NA
0.05d 4.0 x 10'7
NA
2.0 x 1Q-6
0.99d 7.9 x 10'7
6.4 xlO"6
NA
NA
NA
3.8 x 10'6
NA
0.05d 1.2 x 10-6
NA
NA
NA
NA
NA
NA
0.033 1.0 x 10'5
4.0 x 10-6
NA
9.9 x 10'7
NA
5.6 x 10'5
NA
NA
NA
Totalh 8.0 x 10'5
Methylene chloride is a common laboratory contaminant and analytical anomalies are anticipated
during compliance monitoring.
The following chemical have ARARs that were adjusted downward to reduce overall risk: arsenic
benzene, chlorobenzene.trichloroethylene.and xylene.
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Table 7.2 (continued)
CBSG Colorado Basic Standards for Groundwater
CPMS 4-chlorophenylmethylsulfide
CPMSO 4-chlorophenylmethylsulfoxide
CPMSO2 4-chlorophenylmethylsulfone
CSRG Containment system, remediation goal
DBCP Dibromochloropropane
DCPD Dicyclopentadiene
DIMP Diisopropylmethyl phosphonate
HBC Health-based criteria
MCL Maximum containment level
NA Not applicable
MDMA N-nitrosodimethylamine
PQL Practical quantitation limit
//g/1 Micrograms per liter
a. Practical quantitation limit; presented only when the PQL is greater than the CSRG.
b. Based on the CSRG
c. PQL listed in the CBSG standards
d. PQL attainable by the U.S. Army
e. The remediation goal for NDMA was established at 0.007 parts per trillion (ppt) in the
Conceptual Remedy Agreement. The current PQL readily available is 0.033 ppt. The estimated
risk associated with NDMA is based on a 70-year residential exposure duration.
f. Inorganic standard for chloride will be met by natural attenuation consistent with the onpost
remedial action.
g. Inorganic standard for sulfate may be the natural background concentration, which will be
established and met by natural attenuation consistent with onpost remedial action.
h. Because of the variability in contaminant distribution and concentration, the maximum risk
associated with the groundwater cleanup concentrations is not expected to occur at any one
location.
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Table 7.3: Containment System Remediation Goals for the
Northwest Boundary Containment System
Rural
Residential
Analyte
Chloroform
DMP
Dieldrin
Endrin
Isodrin
NDMA
Trichloroethylene
Arsenic
Chloride
Fluoride
Sulfate
CSRG
(A/g/1)
6
8
0.002
0.2
0.06
0.007
3
2.35
250,000e
2,000
250,000f
Hypothetical
Source
CBSG
CBSG
CBSG
CBSG
HBC
(d)
HBC
HBC
CBSG
CBSG
CBSG
PQL" Cancer
6.4 x 10'6
NA
0.05C 1.2 x ID"6
NA
NA
0.033 l.OxlO'5
9.9 x 10'7
5.6 x 1Q-5
NA
NA
NA
Riskb
Total8 7.5 x 1Q-5
The following chemical have ARARs that were adjusted downward to reduce overall risk: arsenic
and trichloroethene.
CBSG Colorado Basic Standards for Groundwater
DIMP Diisopropylmethyl phosphonate
HBC Health-based criteria
MCL Maximum containment level
NA Not'applicable
NDMA N-nitrosodimethylamine
PQL Practical quantitation limit
//g/1 ' Micrograms per liter
Practical quantitation limit; presented only when the PQL is greater than the CSRG.
Based on the CSRG
PQL attainable by the U.S. Army
The remediation goal for NDMA was established at 0.007 parts per trillion (ppt) in the
Conceptual Remedy Agreement. The current PQL readily available is 0.033 ppt. The estimated
risk associated with NDMA is based on a 70-year residential exposure duration.
Inorganic standard for chloride will be met by natural attenuation consistent with the onpost
remedial action.
Inorganic standard for sulfate may be the natural background concentration, which will be
established and met by natural attenuation consistent with onpost remedial action.
Because of the variability in contaminant distribution and concentration, the maximum risk
associated with the groundwater cleanup concentrations is not expected to occur at any one
location.
a.
b.
c
d.
e.
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Table 7.4: Groundwater Alternatives for the Korth and Northwest Plume Groups
Alternative*
Recharge
Extractions Wells/Trenches
Wells (total number/ Flow Rate
Process Options Paleochannel (total number) total length) (8Pm)
Remediation Treatment
Tiniofrnme Facility Residuals
(years) Location Generated
North Plume Group
N-l No action
Monitoring site FC, N
reviews
N-2 Continued operation of the NBCS NBCS operation FC, N
with improvements as necessary {soil-bentonite
harrier, carbon
adsorption)
N-4 Offpost Intercept and Treatment Carbon adsorption FC
System NBCS operation N
N-5 Expansion of the Offpost Intercept Carbon adsorption FC
and Treatment System NBCS operation
N
Northwest Plume Group
NW-1 No action
Monitoring site
reviews
NW
NW-2 Continued operation of the NWBCS NWBCS operation NW
with improvements as necessary
FC First Creek
gpm Gallons per minute
N/A Not applicable
N Northern
NBCS North Boundary Containment System
NW Northwest
NWBCS Northwest Boundary Containment System
* All alternatives include groundwater monitoring and site reviews.
None None N/A
No additional No additional 240
5
12
13
None
6 trenches/1500 feet 180
300
10 trenches/ 240
2700 feet
2 trenches/600 feet 330
None
No additional No additional
N/A
850
Unknown N/A
15 to 30+ NBCS
3 to 8
None
No additional
15 to 30 T2S, R67W, Spent carbon
Sec. 14,
NE 1/4 Sec.
10 to 20 T2S, R67W, Spent carbon
Sec. 14,
NE 1/4 Sec.
Unknown N/A
None
NWBCS No additional
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Tabla 8.1: Summary of the Detailed Analysis and Ranking of Groundwater Alternatives for the North Plume Group
Criteria
Alternative N-l
No Action
Alternative N-2
Continued Operation
of the North Boundary
Containment System With
Improvements as Necessary
Alternative N-4
Oflposl Intercept and
Treatment System
Alternative N-5
Expansion 1 to Interim
Response Action A
Overall protection of
human health and
the environment
Compliance with
ARARs
Long-term effective-
ness and permanence
Reduction of mobil-
ity, toxicity, or
volume
This alternative would not
provide protection of human
health and the environment.
This alternative is not
expected to achieve
chemical-specific ARARs.
This alternative would not
reduce the residual risk
associated with groundwater
exposure pathways.
This alternative would not
employ any treatment
process options and would
not reduce toxicity, mobility,
or volume of groundwater
within the North Plume
Group or groundwater
migrating from RMA to the
Offpost Study Area.
This alternative provides limited overall protec-
tion of human health and the environment by
preventing migration of contaminants from
RMA to the Offpost Study Area north of the
NBCS. Potential risk associated with
groundwater in the North Plume Group would
decrease over time.
Chemical-specific ARARs would be attained in
approximately 15 to 30-plus years, as estimated
by groundwater modeling.
This alternative would reduce residual risk
associated with North Plume Group
groundwater by preventing contaminant
migration at the NBCS and continuing recharge
of treated groundwater to flush contaminants
in the North Plume Group.
This alternative would reduce toxicity,
mobility, and volume of groundwater migrating
from RMA to the Offpost Study Area.
This alternative reduces potential risk
and provides protection of both human
health and the environment by remedia-
ting North Plume Group groundwater
and groundwater migrating from RMA to
the Offpost Study Area.
Chemical-specific ARARs would be at-
tained in approximately 15 to 30 years,
as estimated by groundwater modeling.
This alternative would reduce residual
risk associated with North Plume Group
groundwater, through operation of the
NBCS and the Offpost Intercept and
Treatment System and improvements to
both systems as necessary.
Through treatment, this alternative
would reduce toxicity, mobility, and
volume of groundwater within the North
Plume Group and groundwater migrating
from RMA to the Offpost Study Area.
This alternative reduces potential risk
and provides protection of both human
health and the environment by
remediating North Plume Group
groundwater and groundwater
migrating from RMA to the Offpost
Study Area.
Chemical-specific ARARs would be
attained in approximately 10 to 20 ye-
ars, as estimated by groundwater
modeling.
Through treatment, this alternative
would reduce residual risk associated
with North Plume Group groundwater
through operation of the NBCS, the
Offpost Intercept and Treatment
System, and the Expansion 1 system.
Through treatment, this alternative
would reduce the toxicity, mobility,
and volume of groundwater within the
North Plume Group and groundwater
migrating from RMA to the Offp-
ost Study Area.
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Table 8.1 (continued)
Criteria
Alternative N-l
No Action
Alternative N-2
Continued Operation
of the North Boundary
Containment System With
Improvements as Necessary
Alternative N-4
Offpost Intercept and
Treatment System
Alternative N-5
Expansion 1 to Interim
Response Action A
Short-term effective-
ness
Implementability
Estimated cost
Because no remedial action
would he performed, there
would be no short-term
impacts. There would be no
implementation period.
Technical feasibility would
be high. The administrative
feasibility would be low.
There would be no short-term impacts because
the NBCS is already operating. There would
be no implementation period.
This alternative is readily iinplementable.
Technical and administrative feasibility would
be high.
Total Capital Cost = $ -0- Total Capital Cost = $ -0-
Total Long-term O&M
Cost = $4.1 to 6.0 million
Total Present Worth
Cost = $4.1 to 6.0 million
Total Long-term O&M Cost = $30.6 to 32.5
million
Total Present Worth
Cost = $30.6 to 32.5 million
Community and workers were protected
by adhering to standard health and
safety practices. The implementation
period is complete and the system is
fully operational.
This alternative is readily
implementable. Technical and
administrative feasibility would be high.
Total Capital Cost = $16.7 million
Total Long-term O&M Cost = $39.8 to
46.4 million
Total Present Worth
Cost = $56.5 to 63.1 million
Community and workers would be pro-
tected during construction through
adhering to standard health and safety
practices. The implementation period •
would be approximately 14 months.
This alternative is readily
implementable. However, the
construction would be conducted in
two time periods due to the design
phase for the expansion. Technical and
administrative feasibility would be
high.
Total Capital Cost = $19.4 million
Total Long-term O&M Cost =
$36.9 to 43.6 million
Total Present Worth
Cost = $56.2 to 63 million
ARAR Applicable or relevant and appropriate requirement
NBCS North Boundary Containment System
O&M Operation and maintenance
RMA Rocky Mountain Arsenal
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Table 8.2: Summary off the Detailed Analysis and Ranking of Groundwater Alternatives for the Northwest Plume Group
Criteria
Alternative NW-1
No Action
Alternative NW-2
Continued Operation of the Northwest
Boundary Containment System With
Improvements as Necessary
Overall Protection of Human Health
and the Environment
Compliance With ARARs
Long-term Effectiveness and Perma-
nence
Reduction of Toxicity, Mobility, or
Volume
Short-term Effectiveness
Implementahility
Estimated cost
This alternative would not provide protection of
human health and the environment.
This alternative is not expected to achieve
chemical-specific ARARs.
This alternative would not reduce the residual
risk associated with potential groundwater expo-
sure pathways.
This alternative would not employ any treatment
process options and would not reduce the
toxicity, mobility, or volume of groundwater
within the Northwest Plume Group or ground-
water migrating from RMA to the Offpost Study
Area.
Because no remedial action would be performed,
there would be no short-term impacts. There
would be no implementation period.
The technical feasibility would be high. The
administrative feasibility would be low.
Total Capital Cost = $ -0-
Total Long-term O&M Cost = $0.6 to 1.3 million
Total Present Worth Cost = $0.6 to 1.3 million
This alternative would provide protection of human health and the envi-
ronment by preventing migration of contaminants from RMA to the Offpost
Study Area north of the NWBCS. Potential risks associated with the North-
west Plume Group groundwater would be substantially reduced through
continued operation of the NWBCS and improvements as necessary.
This alternative is expected to meet or exceed chemical-specific ARARs in
approximately three to eight years, as estimated by groundwater modeling.
This alternative would reduce residual risk associated with groundwater
within the Northwest Plume Group through preventing contaminant migration
at the NWBCS and recharging treated groundwater to flush contaminants in
the Northwest Plume Group.
This alternative would reduce toxicity, mobility, and volume of groundwater
migrating from RMA to the Offpost Study Area. Groundwater contaminant
concentrations would be reduced within the Northwest Plume Group by
flushing provided by recharge of treated water at the NWBCS.
There would be no short-term impacts. There would be no implementation
period.
This alternative is readily implementable. Technical and administrative
feasibility would be high.
Total Capital Cost = $ -0-
Total Long-term O&M Cost = $12.4 to 13.1 million
Total Present Worth Cost = $12.4 to 13.1 million
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Table 8.2 (continued)
ARAR Applicable or relevant and appropriate requirement
NWBCS Northwest Boundary Containment System
O&M Operation and maintenance
RMA Rocky Mountain Arsenal
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Table 9.1: Estimated Costs of the Offpost Operable Unit Selected Remedy
Cost Component
Alternative N-4
Alternative NW-2a
Capital Costs
Monitoring well system
Offpost Intercept and Treatment
System extraction/recharge system
Treatment facility
Startup costs
Indirect costs
Total estimated capital costs
Annual Operation and Maintenance Costs
Groundwater monitoring
Site reviews
North and northwest boundary system
operations
Offpost Intercept and Treatment
System facility O&M
Offpost Intercept and Treatment
System carbon replacement11
0 to 3/5 years
3/5 years to system shutdown
Total estimated Annual O&M Costs
0 to 3/5 years
3/5 years to system shutdown
$ 908,000
4,593,000
4,106,000
341,000
6,715,000
$16,663,000
352,000
150,000
,724,000
522,000
817,000
227,000
$
$
4,618,000
4,028,000
Nonconservative':
Total remedy costs
$68,911,000
NA
NA
NA
NA
NA
$0
$ 134,000
150,000
769,000
NA
NA
NA
$ 1,053,000
Conservative0
$76,143,000
DIMP Diisopropylmethyl phosphonate
NA Not applicable
O&M Operation and maintenance
a. There are no capital costs for Alternative NW-2 because the remedial systems are currently
operational.
b. The carbon usage rate is assumed to decrease over time as a result of expected decreases in
influent DIMP concentration. The duration of time before a decrease in carbon usage rate is
expected to occur within three to five years.
c. A range of total costs has been estimated on the basis of the range of expected remediation
timeframes as estimated by the groundwater model results.
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Table 10.1: Summary Evaluation of Chemical-specific and Other Applicable or Relevant and
Appropriate Requirements for the Offpost Operable Unit
Standard, Reqiiireniout
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Requirement
Comment
Chemical-specific
ARARs
Safe Drinking Water Act 40 CFR
Part 141
Establishes primary MCLs for public water-
supply systems.
40 CFR
Sections 141.50
and 141.51
Other ARARs
Colorado Basic Standards 5 CCR 1002-8
for Groundwater; Section 3.11.0 et seq.;
Colorado Basic Standards Section 3.1.0 et seq.
and Methodologies for
Surface Water
Establishes MCLGs (nonenforceable health goals)
for public water systems.
Establishes statewide standards for waters of the
state.
No/Yes Groundwater in the vicinity of the site
is being used or may be used as a
source of water for public water system
or private supply wells. Therefore,
those primary MCLs that are more
stringent than the Colorado Primary
Drinking Water Regulations (because
Colorado has primary enforcement
authority) are relevant and appropriate.
No/Yes Groundwater in the vicinity of the site
is being used or may be used as a
source of water for a public water
system or private supply wells. There-
fore, in accordance with the NCP,
nonzero MCLGs are considered to be
relevant and appropriate.
Yes/No State standards that are more stringent
than federal standards are considered
applicable.
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Table 10.2: Summary Evaluation of Action-specific Applicable or Relevant and Appropriate Requirements
for the Offpost Operable Unit
Standard, Requirement
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Action-specific
Requirement
Comment
Federal ARARs
Safe Drinking Water Act 42 USC Sections 300h to
300H-7
- Underground Injection 40 CFR Parts 144 to 147
Control Regulations
Establishes standards for construction and
operation of injection wells/trenches
Colorado Air Quality
Standards
- Odor Emission
Regulations
CRS Sections 25-7-101 to
25-7-806
Colorado Air Quality
Control Regulation No. 2
Sets limits on emission of odorous air
contaminants
Yes/No Applicable if reinjection wells/trenches are
used for discharge of treated water;
relevant and appropriate if some other
method of reinjection is used.
Under the provisions of 40 CFR 144.13(L),
EPA has determined that the reinjection
wells/trenches used in conjunction with the
barrier treatment system do not endanger
underground sources of drinking water. The
level of treatment prior to reinjection, offpost
alternative water supplies, and other remedies
are sufficient to meet the requirements of the
UIC program.
Yes/No Applicable to remedial action for the Offpost
OU.
ARAR
CFR
CRS
OU
EPA
UIC
USC
VOC
Applicable or relevant and appropriate requirement
Code of Federal Regulations
Colorado Revised Statues
Operable unit
U.S. Environmental Protection Agency
United States Code
Volatile organic compound
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Table 10.3: Summary Evaluation of Location-specific Applicable or Relevant and Appropriate
Requirements for the Offpost Operable Unit
Standard, Roquirnmonl
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Location-specific
Requirements
Comment
Federal ARARs
Executive Order 11988 -
Flood Plain Management
Executive Order 11990
40 CFR Part 6,
Appendix A
40 CFR
Part 6, Appendix A
Directs federal agencies to avoid long- or short- Yes/No
term impacts associated with occupancy and
modification of a floodplain.
Minimizes the destruction, loss, or degradation of Yes/No
wetlands.
Requires a 500-year floodplain to he identified
and considered in scoping any remedial
actions.
Requirements associated with this order
would he applicable to any remedial actions
that could affect the existing wetlands.
ARAR Applicable or relevant and appropriate requirement
CFR Code of Federal Regulations
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Explanation
Offpost Study Area
Offpost Operable Unit
North Boundary
Containment System
Northwest Bound
Containment System
Onpost i
Operable I
I Itii* I
Containment System
EPA
Study
Area
Rocky Mountain
Arsenal
RMA Boundary
Stapleton International Airport
Figure 1.1
Rocky Mountain Arsenal Operable Units and Offpost Study Area
-------
North Boundary Containment System
/
Northwest Boundary ' / 22
Containment System /
Irondale Containment
System .
'
Explanation
Major potential contaminant source area
Sanitary sewer system
Chemical sewer system
0 0.5 1.0
Scale in miles
Figure 2.1
Locations of Contaminant Source Areas
-------
Off post
Study
Area
0 1 2
SSB^
Scale in milM
First Creek
Paleochannel
Northern
Paleochannel
North Boundary
Containment System
Northwest Bounda
Containment System
Onpost
Study
Area
Containment System
Explanation
Groundwater flow direction
Northwest plume group
North plume group
Figure 5.1
Contaminant Migration Pathways
-------
Northwest
Boundary
Containment
System
Explanation
Zone 1 Rural residential land use
Zone 2 Rural residential land use
Zones Urban residential land use
Zone 4 Urban residential land use
Zone 5 Commercial and industrial land use
Zone 6 Rural residential land use
• • • mam Offpost study area boundary
Figure 6.1
Offpost Study Area Exposure Assessment Zones
-------
Primary Primary Primary Secondary Secondary Secondary Medium
Sources Release Transport Sources Release Transport
Mechanism Processes Mechanism Processes
RMA
sou
Lagoona
(Baalna)
RMA
SurfactWaltr
•nd Sadlmnl
EXPL/
Q Quantilie
NQ Notquar
Air
ParlleulaUa Dloptrtlon
^ and/or -^
*" Vapora "" Dagradatlon
>|k A
w Wlpo.1
^ Raauapanalon — 9 Otpotlllon f g^
T
«.
EmlMlon — ) '
/
\
Inlllltlllon * ltila*ll«ii
Oroundwatar
[ Diaparawn Ground- ,
Degradation ww*r
D*potlllon Surlac*
Sorpllon/OMorpllon Stdlnwnl
> f Dapotlllon
Digradallon
^
f
' cvnlrallon
Dlaparalon
' Dagradallon
^ lo Surlaca • ^ son
Wal« Dtgra
Runoll R«»u»f
* Sorpllon/ '
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Secondary
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Figure 6.3
Ecological Site Conceptual Model
for the Offpost Study Area
-------
Explanation
A Offpost Intercept and Treatment System extraction well
• Offpost Intercept and Treatment System recharge well
x Offpost Intercept and Treatment System recharge trench
Pipeline
Unsaturated alluvium
Rgure 7.1
Alternative N-4 Remedial System Components
-------
jlFirst Creek
Paleochannel
Explanation
Additional extraction well under Alternative N-5
Additonal recharge trench under Alternative N-5
Offpost Intercept and Treatment System extraction well
Offpost Intercept and Treatment System recharge well
Offpost Intercept and Treatment System recharge trench
Pipeline
Unsaturated alluvium
0 750 1500
Scale in Iml
Figure 7.2
Alternative N-5 Remedial System Components
-------
I
I
2182600
200000
197500
-------
2185000
Figure 9.1
Offpost Area of Revegetation
SHELL OFFPOST PROPERTIES
VEGETATION
CLASSIFICATION
with
1995 ESTIMATED SURFACE SOIL
DffiLDRIN DISTRIBUTION
Arsenal Boundary
Native Perennial Grassland
Wetland
Tree Grove
Seeded Area
Homestead Site
Seeded Barrow Area
Seeded Fill Area
Unclassified
Shell Properties
Dieldrin >= .04 ug/g (1995)
Acreage Breakdown
Area of OSpoet Plume 193.87 Acres
(On Shell Property)
AreaofOffcostPtame 21.24 Acres
(Not on Shell Property)
PLOWABLE AREA 167.69 ACRES
(On Shell Property)
Includes:
Seeded Ana 110.04
Seeded Barrow Area 5.98
Seeded Fill Area 2.24
Native Perennial Onosbnd 49.43
Other Areas:
Tree Groves 4.76
Wetlands 16.07
Homestead Site 1.25
Treatment Plant 4.10
From: "Dieldrin in Swficial Soib'.DPA, May 30,1995.
RMA EoviiDnmental Database, Dieldan comoor
data ftom Foster Wheeler &DPA (1995).
MORRISON KNODSEN CORPORAHON
Environmental Services Division
SCALE 1 : 7,000
500 1000
II - II - II - II
FEET
December 01,1995
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Appendix A
RESPONSIVENESS SUMMARY
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Appendix A
PREFACE
This appendix contains the Army's responses to comments and new relevant information submitted in
regard to the Proposed Plan, the Remedial Investigation, the Endangerment Assessment/Feasibility Study,
and the selected remedy for the Offpost Operable Unit at Rocky Mountain Arsenal. Comments were
received from the State of Colorado, U.S. Environmental Protection Agency Region Vm, city and county
governments, environmental action groups, and private citizens.
A glossary of acronyms used in Appendix A is provided at the end of the Appendix A Introduction.
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Appendix A
RESPONSIVENESS SUMMARY FOR THE ROCKY MOUNTAIN ARSENAL
Offpost Operable Unit
The Program Manager for Rocjcy Mountain Arsenal (PMRMA) solicited comments regarding the
U.S. Department of the Army's (Army's) findings in the Offpost Operable Unit Proposed Plan and the
Endangerment Assessment/Feasibility Study (EA/FS) during a public comment period from March 21,
1993 through June 21,1993. Both the Proposed Plan and the EA/FS were made available to the public
for the entirety of the public comment period. These documents were available at various city and
county libraries in the area as well as at the U.S. Environmental Protection Agency (EPA) Region VHI
library. These documents, as well as the complete administrative record, were also available at the RMA
Joint Administrative Record Document Facility. A public meeting was held in Commerce City, Colorado,
on April 28, 1993, to present and discuss the Proposed Plan and the EA/FS report with citizens and
public officials. This Responsiveness Summary has been prepared to respond to written questions or
concerns received by the Army during the public comment period.
The public meeting was held at the Dupont Elementary school in Commerce City, Colorado, on April 28,
1993 from 7:00 p.m. to approximately 11:00 p.m. Those in attendance included representatives from the
Army, the Army's contractor (Harding Lawson Associates), EPA, State of Colorado (State), Tri-County
Health Department, city and county officials, public interest groups, and citizens. Also, a Court Reporter
and Notary Public reported the proceedings of the meeting in a stenographic transcript, available for
review in the site administrative record. An agenda was prepared for the meeting and provided to
attendees along with a copy of the Proposed Plan. A copy of the State's concerns regarding the Proposed
Plan was also made available to attendees. The Army presented a review of the Superfund process, a
video of the existing Offpost Groundwater Intercept and Treatment System, a brief review of the history
of the Offpost Study Area, a review of the endangerment assessment results, a description of the alterna-
tives evaluation process, information on the remedy selection process, and a presentation of the preferred
alternative.
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Appendix A
History of Community Relations Activities
The Remedial Investigation (RI), RI Addendum, EA/FS, and Proposed Plan for the Offpost OU were made
available to the public in the Administrative Record (located at the Joint Administrative Record
Document Facility at the west entrance to RMA at 72nd Avenue and Quebec Street), in an information
repository maintained at the EPA Docket Room in Region VHI, and at the Adams County, Aurora,
Commerce City, Denver, Lakewood, Montbello, and Thornton Public Libraries. The notice of availability
for these four documents was published in the Denver Post and Rocky Mountain News newspapers.
An expanded Community Relations outreach was implemented to ensure community members had
opportunity to comment on the Proposed Plan for the Offpost OU. Community outreach started in
January 1993 with the announcement that all documents supporting an impending Proposed Plan were
available for review in local libraries. PMRMA sent a direct mailing of the announcement to more than
1200 local citizens.
In March 1993, a press release was made and a legal notice was published announcing that a public
meeting was scheduled for April 28,1993, at Dupont Elementary School, Commerce City, Colorado, to
address the Proposed Plan. A separate letter was sent to citizens informing them of the documents
availability in the libraries. The letter also included a brief fact sheet summarizing the Proposed Plan.
Originally, tho public meeting was scheduled for April 21,1993, at RMA. The Army received requests to
hold the meeting on a different day and offpost. Because of these factors and Earth Day events in Denver
for April 21. the meeting was moved to April 28, 1993.
A Media Day was held the day of the public meeting to provide information on the Army's proposal to a
local media. Both print and video media representatives attended.
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Appendix A
Recognizing the importance of the public meeting, PMRMA expanded the meeting announcement to
include display advertising in 12 local and weekly newspapers in the Denver metropolitan area in
addition to the normal press release and Media Day event.
The remainder of this Responsiveness Summary will consist of Army responses to written questions and
comments received during the public comment period. Specific questions, comments, and replies
received during the public meeting may be reviewed in the meeting transcript.
Since 1989, all remedial investigation activities at the RMA have been performed in accordance with a
Federal Facility Agreement (FFA) signed by the Army, EPA, Shell Oil Company, U.S. Department of the
Interior, U.S. Department of Justice, and the U.S. Agency for Toxic Substances and Disease Registry. By
signing the FFA, these parties were made part of all decision processes at the Rocky Mountain Arsenal.
It is significant to note that the State elected not to sign the FFA, thereby declining involvement in the
Offpost Operable Unit decision-making processes. However, during the development of the Offpost
EA/FS, the State has been involved in the entire process and provided comments on the RI, EA/FS, and
Proposed Plan to the Army. Accordingly, the Army has provided responses to these comments as they
have been received (e.g., Volume VQI of the Final Offpost Operable Unit EA/FS).
Responses to comments are presented in the following order, based on the originator of comment: the
State of Colorado, Region VIII EPA, city and county governments, the Farmers Reservoir and Irrigation
Company, environmental action groups, and citizen comments. Three sets of comments from the State
are addressed in this Responsiveness Summary. The first two sets were received by the Army prior to
the official comment period on the Proposed Plan, and the third was received during the public comment
period.
In the following comments and responses, text printed in italics is verbatim text of comments received
regarding the Proposed Plan and EA/FS as received from the commentor. The response from the Army
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Appendix A
follows each comment. This format is followed for the State of Colorado, Region VIE EPA, and the
Farmers Reservoir and Irrigation Company.
For responses to comments received from city and county governments, and from environmental action
groups, a copy of the comments as received by the Army is provided followed by a response to each
issue raised, numbered as appropriate.
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Appendix A
This Appendix is organized as follows:
Section Topic
A-l Responses to State of Colorado Comments dated February 19, 1993
A-2 Responses to State of Colorado Comments dated March 16,1993
A-3 Responses to State of Colorado Comments dated June 21,1993
A-4 Responses to Region VHI U.S. EPA Comments
A-5 Responses to City and County Government Comments
• Tri-County Health Department
• Commerce City
• City of Brighton
• City of Thornton
• City and County of Denver
• Adams County
• City of Aurora
A-6 Responses to Farmers Reservoir and Irrigation Company Comments
A-7 Responses to Environmental Action Group Comments
• Sierra Club
• Citizens Against Contamination
• Arsenal Action Alliance
• Colorado Pesticide Network
• Environmental Information Network
• Denver Audubon Society
• We the People
• League of Women Voters
• Denver Region Greens
A-8 Responses to Citizen Comments
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Appendix A
GLOSSARY
*
ADI Acceptable daily intake
ARAR Applicable or relevant and appropriate requirement
Army U.S. Department of Army
ATSDR Agency for Toxic Substances and Disease Registry
AWQC Ambient water quality criteria
BDL Below detection limit
CBSG Colorado Basic Standards for Ground Water
CBSM Colorado Basic Standards and Methodologies for Surface Water
CCR Code of Colorado Regulations
CDH Colorado Health Department
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act of 1980
CFR Code of Federal Regulations
COC Chemical of concern
CRL Certified reporting limit
CRS Colorado Revised Statutes
DIMP Diisopropyl methylphosphonate
EA/FS Endangerment Assessment/Feasibility Study
EA Dndangerment assessment
EPA U.S. Environmental Protection Agency
BSD Explanation of Significant Difference
PEL Frank effect level
FFA Federal Facility Agreement
FR Federal Register
FRICO Farmers Reservoir and Irrigation Company
FS Feasibility study
FtA Health advisory
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Appendix A
BBCS Irondale Boundary Containment System
IMPA Isopropyl methylphosphonic acid
IRA Interim response action
IRIS Integrated Risk Information System
kg Kilogram
I/day Liters per day
LOAEL Lowest observed adverse effect level
MATC Maximum allowable tissue concentration
MCL Maximum contaminant level
mg/kg/day Milligrams per kilogram per day
mg/1 Milligrams per liter
NCP National Oil and Hazardous Substances Pollution Contingency Plan
NOAEL No observed adverse effect level
OSWER Office of Solid Waste and Emergency Response
OU Operable unit
PMRMA Program Manager for Rocky Mountain Arsenal
ppb Parts per billion
ppm Parts per million
PQL Practical quantitation limit
PRG Preliminary remediation goal
RA Risk assessment
RAGS Risk Assessment Guidance for Superfund
RCRA Resource Conservation and Recovery Act
RfD Reference dose
RI Remedial investigation
RMA Rocky Mountain Arsenal
RME Reasonable maximum exposure
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Appendix A
ROD Record of Decision
SQI Submerged quench incinerator
TBC To be considered
TCE Trichloroethene
TCHD Tri-County Health Department
TRV Toxicity reference value
UF Uncertainty factor
USATHAMA United States Army Toxic and Hazardous Materials Agency
USC United States Code
USFWS U.S. Fish and Wildlife Service
//g/1 Micrograms per liter
UST Underground storage tank
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Appendix A-1
RESPONSES TO STATE OF COLORADO COMMENTS
DATED FEBRUARY 19,1993
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO STATE OF COLORADO COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
FEBRUARY 19, 1993
GENERAL COMMENTS
Comment No. 1. PIMP Contamination in Groundwaten
The State continues to disagree with the Army's use of 600 parts per billion (ppb) as a safe level of
DIMP in groundwater.
The Army plans on remediating only areas of groundwater with concentrations of DIMP in excess
of 600 ppb. The State believes that DIMP at much lower concentrations may pose a threat to human
health. For that reason, the State, since 1990, has been providing free bottled water for
approximately 600 residents with DIMP in their wells. The State is concerned, furthermore, that a
portion of a plume of DIMP may have already passed the off post intercept system constructed by
the Army, leaving high concentrations of this chemical, possibly greater than 600 ppb,
unremediated.
Response
The U.S. Environmental Protection Agency (EPA) developed the Health Advisory for diisopropyl
methylphosphonate (DIMP) in 1989 on the basis of an extensive review of more than 30 existing
toxicology studies involving a variety of animal species. EPA's Office of Drinking Water re-
reviewed the Health Advisory, in light of the State's concern, and concluded on March 28, 1990,
that "the existing Health Advisory values and the basis for the values represent the best scientific
position for the protection of human health."
In accordance with EPA's Risk Assessment Guidance for Superfund (RAGS), the Army used
EPA's Health Advisory and information contained in the Integrated Risk Information System
(IRIS) to evaluate risk to human health.
The Offpost Groundwater Intercept and Treatment System is located in areas of highest contam-
inant concentrations. The Army is aware that concentrations of DIMP greater than 600 parts per
billion (ppb) have been reported north of the Offpost Groundwater Intercept and Treatment
System. In that regard, the offpost remedial action groundwater monitoring program will be
coordinated with the three existing groundwater monitoring programs active in the Offpost Study
Area. These three programs are (1) the Groundwater Monitoring Program, (2) the Interim
Response Action A monitoring program, and (3) the private well monitoring program. Addition-
ally, in the area north of the Offpost Groundwater Intercept and Treatment System where DIMP
has been reported to exceed 600 ppb, three monitoring wells will be replaced and three new
monitoring wells will be installed. Replacement wells are being installed for three wells originally
in the monitoring network that were found to be damaged or destroyed. Two new monitoring
wells will be installed downgradient of the First Creek Pathway, and one new monitoring well will
be installed downgradient of the northern Pathway. The purpose of the three new monitoring
wells is to aid in assessing the extent of contamination downgradient of the Offpost Groundwater
Intercept and Treatment System. Data collected from these wells and existing wells will be used to
further define the extent of contamination greater than the remediation goals in this area and
assist in determining whether modifications to the design of the Offpost Groundwater Intercept
and Treatment System are necessary.
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Comment No. 2. IMPA Contamination in Groundwater:
The State continues to be concerned with the Army's use of 700 parts per billion (ppb) as a safe
level of IMPA in ground-water.
The State is concerned that the Army has not adequately characterized IMPA contamination in the
offpost groundwater. An understanding of where IMPA exists in groundwater, both onpost and
off post, has been hindered because of a lack of an acceptable Army analytical methodology. In
addition, the State believes that IMPA at a much lower concentration than 700 ppb, the acceptable
level recommended by EPA, may pose a threat to human health.
Response
On the basis of toxicity information summarized in EPA's isopropyl methylphosphonic acid
(IMPA) Health Advisory and the IRIS database, there is no information to indicate that IMPA
concentrations lower than 700 ppb may pose a threat to human health.
It is highly unlikely that lexicologically significant concentrations of IMPA will occur in ground-
water because the abiotic formation of IMPA from DIMP occurs under alkaline conditions in the
presence of heat. IMPA is primarily formed as a biological metabolite of DIMP and excreted in
the urine. The toxicological data on the metabolism of DIMP indicates that the formation of
IMPA is part of the metabolic elimination process and not a bioactivation reaction. IMPA is a
very polar metabolite that is most likely readily eliminated in the urine rather than reabsorbed by
the kidneys and redistributed throughout the body.
The EPA reference dose for IMPA was based on a simple IMPA subchrpnic study; however, EPA
indicates in IRIS that the DIMP database can be used to support the toxicological conclusions
regarding IMPA because more than 90 percent of the ingested DIMP is rapidly (within 24 hours)
converted to IMPA. EPA states that the DIMP studies showed that DIMP was relatively nontoxic
to all species. Additionally, because DIMP is rapidly and mostly metabolized to IMPA, it is
reasonable to conclude that the DIMP administered to mammals in the studies was metabolized to
IMPA; therefore, the absence of effects from DIMP also may be considered to indicate an absence
of effects from IMPA.
Analytical data collected to date in the Offpost Study Area for IMPA has not indicated that IMPA
is present at or above the certified reporting limit (CRL) in groundwater or tap water samples.
The Army's current CRL for IMPA is 25 ppb. From 1989 through 1992, the IMPA analytical
method used by the Army for analysis of groundwater and tap water had a CRL of 100 ppb. In
1993, following additional method development, the CRL was reduced to 25 ppb. The 1993
reporting limit of 25 ppb is 28 times less than the EPA health advisory concentration of 700 ppb.
For this reason, the Army believes it has adequately characterized the extent of IMPA in the
Offpost Study Area in a manner sufficient to conclude that potential health effects from IMPA
are minimal.
The Army has vigorously pursued the development of more sensitive methods for the identifica-
tion of IMPA in RMA groundwater. The Army is currently unaware of a standard EPA method
capable of attaining a reliable reporting limit near 6 ppb, the concentration proposed by the State.
The Army has reviewed the State's evaluation of IMPA toxicity and will be providing additional
comments.
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Comment No. 3. More Aggressive Treatment of Groundwaten
The State believes that the cleanup of groundwater to the north of the Arsenal can be achieved in a
more timely manner without a significant increase in costs.
The Army evaluated six different alternatives for the northern plume group, and four different
alternatives for the northwest plume group. For the northern plume group, the Army estimates that
it will take 15 to 30 years to clean up the groundwater. The State believes that the Army signifi-
cantly underestimated the actual time necessary to clean the groundwater in this area to a safe level.
In addition, the Army screened out an alternative that, according to the Army's groundwater model,
would have lessened their estimated remediation time to 10 to 20 years, because it would have
required an additional year to implement. This alternative, called N-5 in the Proposed Plan, would
actually cost less than the Army's selected alternative, N-4 since it would not have to be operated as
long.
The State contends that a more aggressive alternative is preferable because it would take a shorter
time period to remediate the groundwater plume, and is therefore more cost effective. The State is
waiting for additional information from the Army prior to making a proposal as to how a more
aggressive remediation of groundwater could be achieved.
Response
The Army selected Alternative N-4 instead of Alternative N-5 primarily because Alternative N-4
includes potential future modifications, only if such modifications are found to be necessary based
on actual operating data, to the Offpost Groundwater Intercept and Treatment System. Selection
of Alternative N-5 instead of Alternative N-4 will not necessarily provide a more cost effective
alternative because of a slightly shorter estimated remediation timeframe. The Army based its
assessment of the relative differences between the groundwater alternatives and estimates of
remediation timeframes on groundwater models that are very general in nature; thus, the
estimated remediation timeframes should not be construed as precise predictions. Use of actual
full-scale operating data is preferable to selecting additional components for the Offpost
Groundwater Intercept and Treatment System using the more speculative modeling data (i.e.,
Alternative N-5).
The Army is committed to efficient operation of the Offpost Groundwater Intercept and
Treatment System and will evaluate operating data to assess the need for system modification.
Similar to the onpost boundary treatment systems, it is difficult to assess whether the installation
of additional wells will provide more efficient operation without collecting full-scale operating
data for the Offpost Groundwater Intercept and Treatment System. The Army has included an
intensive monitoring component as part of the preferred alternative, Alternative N-4, in the
Proposed Plan. This intensive monitoring program will allow the collection and subsequent
interpretation of performance data for the full-scale operation of both the Offpost Groundwater
Intercept and Treatment System and the onpost boundary systems. The data will be used to assess
the need for any improvement to the systems and will provide increased accuracy in assessing
contaminant cleanup. Acquisition of this operational data is preferable to adding extraction wells
and recharge trenches without the benefit of operational data, because additional data are required
to assess the necessity and placement of any additional extraction wells or trenches. If operational
data supports the conclusion that the cleanup timeframe can be shortened without a significant
increase in long-term costs, modifications to Alternative N-4 will be implemented. By taking this
approach, improvements to the system will be more effective than improvements made based on
computer modeling data.
The State's contention that a more aggressive alternative is preferable because it would shorten
remediation timeframes and thus would result in a more cost-affective alternative relies on the use
of modeling data to make the assessment. The Army proposes to use actual operations data from
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Alternative N-4 to make the same assessment. Modification of the Offpost Groundwater
Intercept and Treatment System, if necessary, would be based on field operations and monitoring
data.
Comment No. 4. Selection of the Appropriate Risk Level:
The State is concerned that the Army's selected risk level for excess cancer incidence in the off post
is not protective and is contrary to federal law. In addition, the Proposed Plan does not state what
level of health protection will be achieved.
The regulations that implement the Super fund law, the National Contingency Plan (NCP), state that
a remediation plan should be designed to prevent excess risk to human health greater than
approximately one in a million (1x10-6). This number, or cancer risk level, is called the point of
departure. EPA, because risk levels are sometimes difficult to predict, and because remediation is
sometimes impractical, has allowed the risk level to be approximately one in ten thousand (1x10-4)
in certain instances. At the Rocky Mountain Arsenal, the Army is assuming that a risk level of 5 in
ten thousand (5x10-4), or one in two thousand is acceptable, even though it has made no showing
that the NCP's point of departure could not be achieved. Because the risk level is higher than the
acceptable risk level provided for in the NCP, the Army has been able to avoid cleanup soils in parts
of the off post operable unit.
Response
The Army has closely followed EPA guidance and the NCP regarding the use of the 10"4 risk
threshold to assess whether remediation is necessary. Guidance states that if the cumulative
cancer risk to an individual is less than 10"*, remedial action may not be warranted unless certain
site-specific conditions exist. If remedial action is warranted, the 10"1 to 10"6 risk range must be
achieved, with an initial preference for the 10"6 end. EPA guidance further states that the upper
boundary of the risk range is not an absolute at 1 x 10"*, but rather, the acceptable risk range can
extend to 5 x 10"4. The cumulative off post cancer risk is a maximum of 3 x 10"*, which is within
the acceptable risk range. The Army's goal, through operation of the Offpost Groundwater
Intercept and Treatment System, is to further reduce off post risk toward the 10"6 level.
Potential risk attributable to soil is a maximum of 8 x 10"*. This risk would only be realized for a
population exposed at reasonable maximum exposure (RME) levels for all pathways. Because this
scenario is unlikely and because maximum cancer risks are within the EPA risk range, offpost soil
does not require remediation.
Comment No. S. Acknowledging the State Groundwater Regulations as Legal Standards:
The state disagrees with the Army's decisions to omit State environmental regulations when defining
cleanup levels.
Under CERCLA, State environmental laws and regulations which set standards for cleanup, fulfill
certain statutory criteria, and are more stringent than the comparable federal standards, must be
used as the appropriate cleanup standards at Super fund sites. The Colorado Basic Standards for
Groundwater have been acknowledged as the appropriate cleanup standard at other Super fund sites
in Colorado. In fact, the Army itself has recognized these regulations as the governing standards
for Interim Response Actions at the Rocky Mountain Arsenal. For the Offpost Operable Unit,
however, the Army has refused to use the Colorado regulations as a remedial standard. It is
important to the State of Colorado that our laws and regulations be obeyed. The State therefore
maintains that Colorado law must be recognized as providing appropriate cleanup standards for the
Offpost Operable Unit at the Rocky Mountain Arsenal.
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Response
The Army has recognized all state laws and regulations that meet the applicable or relevant and
appropriate requirements (ARARs) criteria under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) and the NCP. After extensive discussion with all the
parties, the Army has concluded that the Colorado Basic Standards for Groundwater (CBSGs) do
not meet the ARARs criteria because of inconsistent application and ambiguous language.
ARARs for the Offpost Operable Unit are based on federal drinking water standards and are
protective of human health. In most cases, the treatment goals for the offpost and boundary
treatment systems exceed the drinking water standards.
CERCLA expressly provides that state standards can be ARARs at a site. However, only those
standards that are more stringent than federal requirements may be considered. In addition, the
state standards must be promulgated (i.e., the requirement must be of general applicability and
legally enforceable). Finally, the requirements must be identified in a timely manner by the
particular state (40 Code of Federal Regulations [CFR] Section 300.400[g][4]).
Regulations promulgated pursuant to the Colorado Water Quality Control Act, Colorado Revised
Statutes (CRS) Sections 25-8-101, et seq., establish standards for groundwater (5 Code of Colorado
Regulations [CCR] 1002-8, Section 3.11.0). A key aspect of the regulation is that Tables 1
through 4 standards are not automatically applicable to groundwater (Section 3.11.7[A]), but apply
only if the aquifer has been classified in accordance with Section 3.11.4.
Most aquifers in the state are unclassified. Consequently, the Water Quality Control Commission
(Commission) promulgated the interim narrative standard (Section 3.12.5) for five specified
aquifer systems to avoid degradation of water quality prior to aquifer classification. Each of the
five identified aquifers must meet the standards in Tables 1 through 4 or the ambient quality as of
October 30, 1991, if it was less restrictive, until the aquifers are classified and numerical standards
are adopted.
The Commission promulgated a second group of groundwater standards that are applied different-
ly than the standards in Tables 1 through 4. These statewide standards (Section 3.11.5[C]) include
water quality standards for radioactive materials and interim standards for organic pollutants
(Table A), including chloroform. Table A standards differ from the standards in Tables 1 through
4 in an important way: Table A standards are automatically applicable to all state groundwater
(Section 3.11.7[A]). The Commission recognized that the automatic application of Table A
standards can lead to unnecessarily overprotective and technically impracticable results at
contaminated sites and added exceptions to the regulation for remediation activities at CERCLA
sites, Resource Conservation and Recovery Act (RCRA) sites, and underground storage tank
(UST) sites. The CERCLA exception, Section 3.11.5(C)(5)(a), states the following:
Nothing in this regulation shall be interpreted to preclude...[a]n agency
responsible for implementation of the Comprehensive Environmental Response,
Compensation and Liability Act (CERCLA), 42 U.S.C. 9601, et seq., as amended,
from selecting a remedial action and a point of compliance that are more or less
stringent than would be achieved by compliance with the statewide numerical
standards established in this subsection, or alternative site specific standards
adopted by the Commission, when a determination is made that such a variation is
authorized pursuant to the applicable provisions of CERCLA.
Sections 3.11.5(C)(5)(b) and (c) provide similar exceptions for corrective actions under RCRA
Subtitle C (hazardous waste treatment, storage, and disposal facilities) and Subtitle I (UST sites),
respectively.
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Section 3.11.5(C)(5) is internally consistent only if the Commission intended not to impose the
interim organic standards in Table A as cleanup standards. According to the regulations, the
interim organic standards automatically apply on a statewide basis, except at CERCLA, RCRA,
and UST sites where "certain federal regulatory determinations regarding groundwater quality
would not be superseded by the Commission's standards" (Section 3.11.10[B]). In promulgating the
Table A exceptions, the Commission recognized that implementing agencies are more familiar
with site-specific conditions and are in a better position to determine the appropriate cleanup
standards. By not imposing unnecessarily stringent application of the Table A standards, the
Commission sought to show "explicit deference to certain federal regulatory programs, which may
apply different standards" (Section 3.11.10[H]).
The Army concludes that the CBSG interim organic standards are not ARARs for several reasons.
The CERCLA exception in Section 3.11.5(C)(5)(a) applies to remedial actions authorized under
CERCLA that are more or less stringent than would be achieved by compliance with the statewide
standards. As a result, the overall effect of the statewide standard and accompanying exceptions
is a state regulation that is only sometimes more stringent than a federal requirement. CERCLA
only considers state standards that are stricter at all times as potential ARARs. Therefore, by
definition, the interim organic standards are not ARARs at Superfund sites.
Second, the CBSG interim organic standards cannot be ARARs because they are not generally
applicable or legally enforceable. A requirement in CERCLA for state requirements to be
ARARs is that they must be promulgated standards, which means they must be generally
applicable and legally enforceable. Clearly, the interim organic standards do not meet this test
when applied at CERCLA sites. By definition, the interim organic standards are applicable
throughout the state, except at CERCLA, RCRA, and UST sites. In those instances, the relevance
of the standards is determined by the remedial sites. It is hard to understand how the standard
could be legally enforceable when the Commission added language specifically ensuring that the
standards may or may not be met at CERCLA sites.
Comment No. 6. Future Land Use:
The State believes that the Army failed to consider all reasonable land uses, and therefore exposure
pathways, when it defined risks to human health.
The NCP requires the Army to consider current and reasonable potential land use in evaluating the
risk to human health and the environment posed by contamination. The Army has decided that
zones 3 and 4 of the operable unit should be analyzed assuming an urban residential scenario. The
land in question is currently unoccupied because it is owned by Shell Oil Company. It was being
used a rural residential property before Shell bought it, and is presently zoned for rural residential
use. The Army justifies its classification of this property by relying on future land use projections
which have been made by Adams County. The State contends that the rural residential scenarios
should be used since it is currently permitted and there is no assurance that the land will not be
used in this manner in the future. This is important because using the urban residential scenario
results in elimination of exposure pathways of consumption of homegrown meat, milk, and eggs in
estimating risk, thereby allowing the Army to leave higher levels of contamination in the soils.
Response
The land use designations and plans were established by the appropriate jurisdictional agencies,
not by EPA or the Army, and were used to establish land use scenarios for use in the risk
assessment within each risk assessment zone. Evaluation of current zoning regulations, discussions
with local planning officials, examination of future land use master plans for the city and county,
and visual surveys were used to establish land use scenarios. These designations are supported by
established zoning, planning maps, and planning documents. The future land use scenarios used
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by the Army in the risk assessment are highly conservative. For example, the rural residential
scenario used in zones 1, 2, and 6 includes all pathways contributing substantially to potential risk,
even though most of the total population is not exposed to the agricultural exposure pathways
described in the risk assessment. Shell Oil Company purchased the land in zones 3 and 4 for
Army use in constructing the Offpost Groundwater Intercept and Treatment System. It is not
presently occupied; therefore, the current zoning designation as rural residential is not applicable.
Given the probability of the realignment and widening of 96th Avenue, future development along
96th Avenue will likely be commercial/industrial or urban residential. The Army selected an
urban residential land use for the risk evaluation as this would result in more conservative (e.g.,
higher) estimated risks than the likely commercial/industrial land use.
Comment No. 7. Institutional Controls:
The State is concerned that people unaware of the contamination problems may purchase property
and be exposed to unacceptable risks.
The Proposed Plan does not include active remediation of soils or groundwater in Zones 2, 3, or 4.
Groundwater contamination in these areas exceeds state and federal cleanup level. Shell Oil
Company owns portions of these areas, the rest is privately owned. The State is concerned that
there is nothing to prevent people from developing land in these areas, and sinking domestic wells,
which would contain contaminated groundwater. The State, although preferring active remediation
in these areas, maintains that institutional controls such as deed and well restrictions must be
imposed to ensure that people will not be exposed to unacceptable risk in the future.
Response
Institutional controls have been added as a component of the selected remedy. Appendix B of the
Record of Decison (ROD) provides an evaluation of the institutional controls available and their
applicability. See the response to State Comment No. 4 regarding remediation of soil in the
Offpost Study Area.
Comment No. 8. Human Health Risk Characterization:
The State has several concerns with how the Army defined potential risks to human health.
The State has several concerns with the method the Army has used to evaluate risk to human health
in the off post. Several pathways, which the State considers important, were not considered in
evaluating risk; for example, dermal absorption of contaminated groundwater during bathing or
showering, inhalation of dust, incidental ingestion of surface water during wading, and ingestion of
fruits grown in contaminated soil or irrigated with contaminated groundwater. The State also has
concerns with the fact that the Army concluded that only dieldrin posed a risk to people eating eggs
from chickens raised in the off post operable unit. This conclusions was based on the sampling of
only one egg. The State believes that these are insufficient data from which to draw such a
conclusion. And perhaps most importantly, that Army ignored data presented to it by the State
regarding soil ingestion rates and pica behavior (children who eat dirt), which that this behavior
should be evaluated in assessing risk caused by contaminants in soil.
Response
The Army considered all of the exposure pathways listed by the State and, on the basis of EPA
guidance presented in RAGS, the pathways were eliminated from further evaluation in the risk
assessment. The Army presented the human health risk assessment pathways to EPA, the U.S.
Fish and Wildlife Service (USFWS), Shell Oil Company, and the State for discussion. After
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identifying all potential complete exposure pathways, the Army followed EPA guidance in RAGS
(page 6-17) to select those pathways to be evaluated further in the exposure assessment. Guidance
allows for the elimination of some complete pathways if there is sound justification, such as:
1. The exposure resulting from the pathway is much less than that from another pathway
involving the same medium at the same exposure point.
2. The potential magnitude of the exposure from the pathway is low.
3. The probability of the exposure occurring is very low, and the risks associated with the
occurrence are not high.
The Army did consider dermal absorption of contaminated groundwater during bathing or
showering (see page II-2-61, Volume II of the Endangerment Assessment [EA]); however, this
pathway's contribution to the overall intake and risk was considered to be very small when
compared to the intake of groundwater contaminants via ingestion and inhalation. The inhalation
of dust is addressed on pages II-2-59 and II-2-60, Volume II and Appendix B, Volume IV of the
EA. The conservative screening level model of exposure to dust presented in Appendix B
indicated that the contact rate via this route is very small compared to incidental direct soil
ingestion. The incidental ingestion of surface water was considered (see page II-2-63 of the EA).
However, it is highly unlikely that this route for exposure would be a significant contributor to
the overall risk because of the low frequency of occurrence, ingestion rate, and concentration of
contaminants in surface water. The ingestion of homegrown fruit was considered (see
page 11-2-62 of the EA); however, for the purpose of the offpost risk assessment, tomatoes were
considered as a vegetable. Fruit production is such a minor contributor to the agricultural
economy of the area that fruit production statistics are not kept by local agricultural economists.
Therefore, fruit ingestion was not evaluated. Intake via the consumption of eggs was only
evaluated for dieldrin because dieldrin was the only contaminant detected in the egg sample.
The Army has previously responded to the State's request that soil ingestion rates related to pica
behavior be considered. The Army followed EPA's guidance in RAGS to evaluate the soil
ingestion pathway and the soil ingestion rate. The rate used accounts for both outdoor soil and
indoor dust ingestion by children and is considered by EPA to represent an upperbound value (a
conservative value that is highly unlikely to result in an underestimation of risk). EPA is aware of
the information presented by the State. EPA guidance specific to CERCLA risk assessments is the
most reliable and authoritative source for the soil ingestion exposure parameter.
Comment No. 9. Ecological Risk Characterization:
The State does not agree with how the Army defined potential risks to vegetation and wildlife
offpost of the Arsenal.
The State continues to have significant concerns with the methodology used by the Army in defining
ecologically based cleanup levels. The State contends that the Army has made assumptions based
on insufficient data and that the Ecological Risk Assessment will likely allow levels of contamina-
tion to remain in the offpost that may not be protective of biota.
Response
The State has not presented any evidence to support its contention that assumptions made for the
ecological risk assessment (RA) will result in levels of contamination remaining in the Offpost
Study Area that may not be protective of biota. The Army presented the ecological RA assump-
tions and approaches to the USFWS, EPA, Shell Oil Company, and the State at meetings through-
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out the ecological RA study period. The Army considered these meetings and subsequent
feedback critical because of the lack of formalized EPA guidance on conducting a dose-based
ecological assessment. The Army believes that the findings of the ecological RA are protective of
wildlife because many aspects of the approaches used to estimate potential effects are more
conservative than other hazard assessment methodologies currently followed by EPA and other
agencies. Because the approaches to conducting an ecological RA are continually being devel-
oped, the assumptions and parameters used by the Army for the final ecological RA were
thoroughly discussed with the parties and modified throughout the ecological RA process, and the
best available methodology and professional judgement were used. The USFWS participated in
the ecological RA process and supported the final methodologies used to evaluate the potential
ecological hazards.
Comment No. 10. Hot Soots in Soils:
The State is concerned that the Army has not met the burden of proof that contaminated soils off
the Arsenal are not RMA related.
The soil sampling program identified several spots in zones 3 and 4, and along Buckley road,
where concentrations of dieldrin, a pesticide, exceeded the Army's proposed cleanup goals. These
"hot spots" were eliminated from remediation based on the Army's assumption that these
concentrations were due to agricultural practices, and it was therefore not responsible. There are no
data indicating the source of these contaminants in the EA/FS. The State requests additional
sampling in the area, so that is can better determine if the Army's assumptions are correct.
Response
The Army did not base conclusions regarding the assessment of soil contamination on the potential
for contamination attributable to agricultural practices in certain offpost areas.
The Army used a large amount of onpost and offpost surface soil data to interpret Rocky
Mountain Arsenal (RMA)-related soil contamination. The combination of onpost and offpost data
demonstrates that detected concentrations of contaminants offpost are attributable to windblown
transport from RMA and to offpost activities, including agricultural application of pesticides.
Further, risks corresponding to offpost soil concentrations are within EPA's acceptable risk range.
As discussed in response to the State's Comment No. 4, remediation of offpost soil is not required.
Comment No. 11. Contamination of Barr Lake:
The State is concerned that the Proposed Plan does not include remediation of surface water and
sediments.
The Army has decided not to actively remediate surface water in the offpost operable unit. First
Creek, which flows from the Rocky Mountain Arsenal to O'Brian Canal and ultimately into Barr
Lake, is contaminated with RMA-related chemicals. The Army's position is that First Creek will be
cleaned over time, as uncontaminated groundwater flows into it, and flushes out the contamination.
This could take several decades. During this period of time, small quantities of contamination will
continue to flow into Barr Lake. The State believes that the First Creek water should be
remediated, so that no further degradation of Barr Lake occurs.
Response
Remediation of offpost groundwater will reduce contaminant concentrations in First Creek.
Surface-water monitoring will continue as part of the offpost monitoring plan. A surface-water
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monitoring program has been included as a component of the selected remedy. An offpost
implementation document will be prepared following approval of the ROD.
Comment No. 12. Closing Poorly Constructed Domestic Wells:
The State remains concerned with the continued migration of contaminated ground-water into the
deeper aquifer.
The State has identified approximately 20 domestic wells that are either in poor condition, or are
screened through more than one aquifer. These wells are responsible for allowing RMA
contamination to migrate to the Arapahoe Formation, a deeper aquifer. The Proposed Plan does not
address these wells. The State has repeatedly requested that the Army close these wells to prevent
further degradation of the deeper aquifers.
Response
The Army has incorporated well closure as a component of the selected remedy. The criteria for
well closure are presented in Appendix C of the ROD.
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Appendix A-2
RESPONSES TO STATE OF COLORADO COMMENTS
DATED MARCH 16,1993
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO THE STATE OF COLORADO COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
MARCH 16, 1993
SPECIFIC COMMENTS
Comment No. 1. page 2. 2nd paragraph. 1st sentence
The State does not agree that the Proposed Plan is consistent with CERCLA § 121 and the National
Contingency Plan (NCP). Among other issues, the Plan does not conform to ARARS, is not
sufficiently protective of human health and the environment, and does not follow NCP guidance
relating to institutional controls.
Response
Section 121 of the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA) pertains to cleanup standards, specifically (1) selection of remedial actions, (2) general
rules for selection of remedial actions, (3) five-year review, (4) degree of cleanup, (5) permits and
enforcement, and (6) state involvement.
The Offpost Proposed Plan is fully consistent with the above-referenced CERCLA Section 121.
Selection of the remedial actions described in the Proposed Plan's preferred alternative is
necessary in accordance with CERCLA Section 121, is consistent with the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP), and provides for a cost-effective
response, per the requirements of item 1 above. Consistent with item 2 above, the Proposed Plan's
preferred alternative is protective of human health and the environment, is cost- effective, and
uses permanent solutions and alternative treatment technologies to the maximum extent practica-
ble. Provisions for a periodic review of site conditions are specifically incorporated into the
Proposed Plan's preferred alternative per item 3 above. The Proposed Plan's preferred alternative
incorporates those standards, requirements, criteria, or limitations resulting from a complete
analysis of applicable or relevant and appropriate requirements (ARARs) per item 4 above. The
U.S. Department of the Army (Army) has recognized all state and federal laws and regulations
that meet the ARARs criteria under CERCLA. Item 5 above is met by the preferred alternative
through substantive compliance with federal, state, and local permitting requirements in the
implementation of remedial components. Item 6 above requires involvement of the state in
decisions regarding initiation, development, and selection of remedial actions to be undertaken
and, specifically, provides the opportunity for the State of Colorado (State) to review and
comment on the remedial investigation (RI) and feasibility study (FS), the planned remedial action
identified in the RI/FS, the engineering design, and other technical data and reports relating to
implementation of the remedy. The State has had opportunity to comment on the RI/FS, technical
data, and other offpost reports. In addition, item 6 above requires that the State have the
opportunity to comment on the Proposed Plan for remedial action and that responses to the State's
comments are provided. The State has also commented on the Proposed Plan, and the Army has
provided responses. All comments and repsonses are part of the offpost administrative record.
The preferred alternative presented in the Proposed Plan is fully protective of human health and
the environment. The components of the preferred alternative provide for reduced potential risk
and protection of human health and the environment through remediation of offpost groundwater
that exceeds cleanup standards. Cumulative potential risks in the Offpost Study Area are within
health standards established by the U.S. Environmental Protection Agency (EPA) and will be
reduced further through remediation associated with the preferred alternative.
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Institutional controls have been added as a component of the preferred alternative. Appendix B
of the Record of Decision (ROD) provides a discussion of institutional controls that may be
implemented for the Offpost Study Area.
Comment No. 2. page 2. Figure 1
This figure is misleading. It implies that the only areas of contamination in the operable unit are
the groundwater plumes. There is soil and groundwater contamination in the area between the
plumes, as well as east, west, northwest and north of the plumes depicted on the map. The State is
also concerned about concentrations of trichloroethylene in wells north of 88th Avenue, and west of
Quebec Street. Although the Army may not be solely responsible for that contamination, and some
of the contamination may be from other super fund sites within the EPA study area, there are no
data in the EA/FS analyzing this contamination. The Army, as part of the off post study, should
have investigated this contamination, and the possibility that it is a result of either bypasses of the
Irondale Boundary Control System, or from other sources on RMA.
Response
Figure 1 of the Proposed Plan delineates the boundaries of the Offpost Operable Unit according to
the definitions provided by the Federal Facility Agreement (FFA). The FFA defines the Operable
Unit as that portion of the Offpost Study Area where hazardous substances are subject to
remediation. On the basis of the risk assessment, contamination present in media (e.g., groundwa-
ter, soil, surface water, sediment, air) outside the operable unit boundaries was shown to result in
risk levels that meet EPA's health guidelines and within the acceptable risk range specified in the
NCP.
The Army evaluated the risks associated with trichloroethene (TCE) in groundwater within the
boundaries of the designated study zones. Zone 6, which is north of 88th Avenue and east of
Quebec Street, had the highest exposure point concentration for TCE. However, this value, which
is 4 micrograms per liter (/xg/1), is below the Safe Drinking Water Act maximum contaminant level
(MCL) of 5 W5/1 and near the 1 x 10"6 cancer risk level of 3 j*g/l (based on a residential exposure
scenario).
Comment No. 3. page 3. 1st paragraph. 6th sentence
This sentence is incorrect. This sentence should be revised to read, "...most of RMA was added to
the National Priorities List in 1987." As the Army is well aware. Basin F was listed in 1989.
Response
The Record of Decision (ROD) has been revised accordingly.
Comment No. 4. paee 3. 5th paragraph. 2nd sentence
The State disagrees with the statement that the areas east of the RMA are not contaminated by
RMA-related chemicals. Concentrations of dieldrin as high as 99 ppb have been detected. The
State has requested additional onpost and off post soil sampling to determine if contamination was
transported from the Arsenal. Additionally, although it is probably correct that RMA has not
significantly contaminated the areas to the south, the statement in the Proposed Plan is misleading
because it implies that sampling was conducted to support that conclusion. It would be more
appropriate to state that, because of the north and northwest direction of the prevailing winds and
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the low concentrations along the southern tier, there is no reason to believe that areas south of RMA
have been significantly affected by contamination at the Arsenal.
Response
Because of the extensive agricultural activities that have occurred in areas north and east of the
Rocky Mountain Arsenal (RMA) boundaries and the application of registered pesticides that are a
consequence of agricultural activities, it is not unusual to find dieldrin residues in soil. Examina-
tion of organochlorine pesticide data obtained from onpost surface soil samples does not support
RMA as being the source for organochlorine pesticide transport east of RMA. In addition,
five samples collected east of RMA have dieldrin concentrations ranging from nondetectable to
approximately 25 parts per billion (ppb). On this basis, it is the Army's position that the one
sample with dieldrin detected at 99 ppb east of RMA is not related to onsite activities. Soil
samples collected at the southern boundary of RMA did not contain concentrations of contami-
nants above levels that pose a health risk.
Comment No. 5. page 4. Figure 2
This map is misleading. The Army should make it clear that the plumes shown are of
contamination in excess of federal ARARS, but that other areas are contaminated as well.
Response
As stated in the Proposed Plan, Figure 2 shows plume groups corresponding to locations in the
Offpost Study Area where shallow groundwater contaminant concentrations exceed cleanup goals
presented in the Feasibility Study (FS). The Endangerment Assessment/Feasibility Study (EA/FS)
provides additional discussion regarding contaminant concentrations in the areas outside the
Operable Unit.
Comment No. 6. page 5. 6th paragraph. 7th sentence
The text states that soil, surface water, and sediment are within the acceptable risk range. The
risks should be specifically stated for each medium in addition to the cumulative risk for all
exposures.
Response
The purpose of the Proposed Plan is to briefly summarize the risk assessment findings and to
present, in some detail, the remediation alternatives to clean up the site. The inclusion of all
media-specific risks and cumulative risks for all exposure pathways is beyond the recommen-
dations set forth by EPA guidance and would result in a more complicated document. Interested
individuals are referred to the EA/FS for a complete discussion of the media-specific and
pathway-specific risks.
Comment No. 7. page 6. 2nd bullet. Site Review
The text should be clarified that the five year review is required under CERCLA §121(c), because
hazardous substances, pollutants, or contaminants will be left in place. The public should be
informed that the purpose of this review is to ensure that the remedy remains sufficiently protective
of human health and the environment. In addition, the remedy may be amended at that time, if
EPA decides that the remedy is not sufficiently protective.
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Response
The State's comment that contaminants will be left in place is misleading in that active remedial
measures that result in contaminant removal and treatment are the primary components of the
preferred alternative. As stated in the reference section of the Proposed Plan, a site review will
be performed to ensure that human health and the environment are protected during and after the
remediation.
Comment No. 8. page 6. 4th bullet. Continued Operation
This bullet implies that the remedy selected is an off post remedy. In fact, this is the onpost
remedy.
Response
The continued operation of the onpost boundary systems to meet the offpost cleanup standards is
an integral component of the offpost preferred alternative.
Comment No. 9. page 6. Alternative N-1
The State disagrees with the presentation of the "no-action" alternative described by the Army. "No
action" as defined by NEPA and incorporated in CERCLA, means maintenance of the status quo.
40 CFR 300.430(a)(6) states that, among other alternatives, the lead agency must develop "ft}he
no-action alternative, which may be no further action if some removal or remedial action has
already occurred at the site." (55 Fed. Reg. 8849, March 8, 1990; emphasis added.) This
alternative is not, as the Army states, a shutdown and dismantling of preexisting remedial
measures. A true "no action alternative," as envisioned by the NCP, would include continued
operation of the boundary control systems without modifications or additions. See State's
comments on EA/FS, December 13, 1991 at pages 4-5.
Response
The Army has included in its evaluation of offpost alternatives both a no-action alternative
(NW-1 and N-l) and a no further action alternative (NW-2 and N-2), as defined by the State.
The no further action alternative presented in the EA/FS meets the NCP requirement specified at
40 Code of Federal Regulations 430(e)(6).
Comment No. 10. page 8. Definitions of Criteria
The State disagrees with the statements regarding State Acceptance. The Army is disingenuous
when it implies that the State's positions on the proposed remedy are unknown. The State's views on
the selected remedy and other issues have been conveyed in extensive comments on prior drafts of
the EA/FS. The NCP provides, moreover, that as part of the Proposed Plan the lead agency shall
assess "(I) The state's position and key concerns related to the preferred alternative and other
alternatives; and (2) State comments on ARARs or the proposed use of waivers" NCP
§ 300.430(a)(iii)(9)(H). In addition, the Proposed Plan shall "provide a summary of any
comments received from the support agency." NCP § 300.430(f)(2)(iii); emphasis added. The
Army has failed to include these matters in the Proposed Plan.
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Response
The NCP, Section 430(e)(9)(iii)(H), states:
State Acceptance. Assessment of state concerns may not be completed until comments on
the RI/FS are received but may be discussed, to the extent possible, in the proposed plan
issued for public comment, (emphasis added).
Because many of the issues regarding the EA/FS and the preferred alternative were still being
discussed between the Army, EPA, and the State at the time the Proposed Plan was issued, the
Army believed that these issues should be resolved before making a definitive statement regarding
State acceptance. A handout detailing the State's concerns was provided at the public meeting,
and the State was provided time to present its concerns orally at the public meeting.
Comment No. 11. Tables 2 and 3
The State requests that all of the action alternatives be contained within these summaries.
Response
Consistent with EPA guidance, the Army has included those alternatives passing initial screening
of alternatives conducted in the FS. Alternatives that did not pass initial screening are presented
in the EA/FS.
Comment No. 12. Glossary
The following term should be redefined:
a. Federal Facility Agreement: The definition was corrected in the body of the text, but
remains incorrect in the Glossary. The FFA formalizes the parties' responsibilities for
cleanup at RMA. The framework is set by CERCLA and the NCP.
Response
The definition of the FFA has been corrected in the ROD.
Comment No. 13. Glossary:
The following word should be defined:
a. Contamination: The Army appears to use the word solely to mean levels of contamination
above federal ARARs. The dictionary defines contamination as "the state of being impure
or corrupt." The Army is therefore implying to the public that the "uncontaminated" areas
are clean. In fact, the "uncontaminated" areas are not pristine, but are not sufficiently
contaminated, according to the Army, to warrant remediation.
Response
Most of the contaminants found in the Offpost Study Area are not unique to RMA. Many of
these substances have been used in crop and livestock production, including areas north and east
of RMA, and others are naturally occurring. The Army frequently qualifies its use of the word
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"contamination" as being above or below levels that would pose a threat to human health or the
environment. On this basis, no further definition is necessary.
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Appendix A-3
RESPONSES TO STATE OF COLORADO COMMENTS
DATED JUNE 21,1993
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO STATE OF COLORADO COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JUNE 21, 1993
GENERAL COMMENTS
Comment No. 1 - Risk Assessment
a. Point of Departure
The Proposed Plan states that the cumulative potential cancer risks range from 1 X 10~* in
Zone 1 to 3 X W* in Zone 3. In the Final EA/FS, the Army cites an OSWER directive, dated
April 22, 1991, which it claims authorizes no action at sites that do not exceed a 10~* risk
level. The NCP, however, clearly states that EPA's preference is for remediation goals at the
more protective end of the range, that is 10*. The Army is clearly disregarding the express
language of the NCP which sets the Point of Departure at 10"6. See. 40 C.F.R.
§300.430(e)(2)(i)(A)(2) (1991).
This issue was specifically addressed in a letter from EPA to the Army, dated February 21,
1992. In that letter, in which the State did not concur, EPA Region VIII set down the criteria
that it would consider in allowing the Army to deviate from the NCP's point of departure of
W6. Specifically, EPA stated: "We agree that the Army would not have to develop PRGs for
those media where the cumulative risk was not greater than 10"4, if_, for those cases, the Army
could adequately document that the 10"4 PRGs were appropriate." (Emphasis added). The
Army has not been able to demonstrate that a point of departure of W4 is appropriate for the
off post operable unit. Among other requirements, the Army was required to show:
a) That all of the media had been evaluated so as to demonstrate "that the total additive risk
does not exceed the 1Q~* risk level or a hazard index of one."
b) That sample sizes for all media were sufficiently large to statistically represent the
site/receptor conditions.
c) That all potential exposure routes were evaluated.
d) That sensitive subpopulations, especially pica children, had been evaluated to ensure that
the risks to these groups do not exceed 10"*.
e) That all contaminants of concern (COCs) tentatively identified compounds and unknowns
are evaluated and do not contribute to risk or hazard.
The Army has failed to comply with the requirements contained in EPA's letter. For example,
the hazard index exceeds one in three of the six zones and part of Zone I. In Zone 4, the
long term exposure HI is 4, four times the EPA accepted limit. Potential exposure routes were
not fully evaluated; for example, all COCs except dieldrin were eliminated from consider-
ation in the soil/egg pathway because dieldrin was the only COC found in the one egg that
the Army sampled. Other pathways were excluded entirely, including dermal absorption due
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to direct contact with groundwater, inhalation of dust, incidental ingestion of surface water
during wading, and consumption of fruits grown in contaminated soil or irrigated with
contaminated groundwater or surface water. The State also believes that the Army's data with
respect to pica children, a sensitive subpopulation, is inadequate. See, state comments on the
EA/FS, April 6, 1992 at pages 2-3. The EA has also not sufficiently considered other
sensitive subpopulations such as people who might reside in the off post area for 30 years or
longer; sufferers of diabetes who are known to consume up to 8 liters a day of water; or
people of predisposed sensitivity such as victims of multiple chemical sensitivity syndrome.
See, state comments on the EA/FS, January 27,1992, Comments Related to the Human
Health Endaneerment Assessment, at pages 2-3.
In its letter, EPA specifically noted that a number of uncertainties were not sufficiently
addressed in the Risk Assessment, and that lO"6 was the required point of departure if these
issues were not addressed. These concerns include lack of toxicity estimates for develop-
mental toxicants, no consideration of synergism/'antagonism of contaminants, the fact that
the monitoring data may not represent actual site conditions, and lack of consideration of the
soil type and climate present off post relative to soil ingestion rates. The State contends that
these uncertainties have not been adequately addressed in the EA, and therefore use of 10* as
the target risk level for cleanup is not appropriate.
For some zones, according to the Army, the risk is as high 3 X 10"4 not including several of
the important pathways described above. This relatively high risk is not justified on the basis
of technical impracticability or any other rationale. It is therefore unacceptable to the State.
The State urges the Army to comply with the NCP, which sets the Point of Departure at W6
risk level. 40 C.F.R. §300.430(e)(2)(i)(A)(2) (1991). Only if achievement of this level is
impracticable, may the Army adopt a less protective cleanup level.
Response
The Army has closely followed U.S. Environmental Protection Agency (EPA) guidance and the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP) regarding the use of the
10"1 risk threshold to assess whether remediation is necessary. Guidance states that if the
cumulative cancer risk to an individual is less than 10"*, remedial action may not be warranted
unless certain site-specific conditions exist. If remedial action is warranted, the 10"* to 10"* risk
range must be achieved, with an initial preference for the 10"6 end. EPA guidance further states
that the upper boundary of the risk range is not an absolute at 1 x 10"*, but rather, the acceptable
risk range can extend to 5 x 10"*. The cumulative off post cancer risk is a maximum of 3 x 10"4,
which is within the acceptable risk range.
In explaining the use of the point of departure, the EPA, in the preamble to the NCP, states
The use of 10"6 expresses EPA's preference for remedial actions that result in risks
at the more protective end of the risk range, but does not reflect a presumption
that the final remedial action should attain such a risk level (55 Federal Register
8718).
The operation of the Offpost Groundwater Intercept and Treatment System reflects the Army's
goal of further reducing the potential risk toward the 10"6 level.
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In addition to the pathways retained in the risk assessment, the Army considered all of the
exposure pathways listed by the State and, on the basis of EPA guidance presented in Risk
Assessment Guidance for Superfund (RAGS), the latter pathways were eliminated from further
evaluation in the risk assessment. The Army presented the human health risk assessment pathways
to EPA, the U.S. Fish and Wildlife Service (USFWS), Shell Oil Company, and the State for
discussion. After identifying all potential complete exposure pathways, the Army followed EPA
guidance in RAGS (page 6-16) to select those pathways to be evaluated further in the exposure
assessment. Guidance allows for the elimination of some complete pathways if there is sound
justification, such as:
1. The exposure resulting from the pathway is much less than that from another pathway
involving the same medium at the same exposure point.
2. The potential magnitude of the exposure from the pathway is low.
3. The probability of the exposure occurring is very low, and the risks associated with the
occurrence are not high.
The Army did consider dermal absorption of contaminated groundwater during bathing or
showering (see page II-2-61, Volume II of the Endangerment Assessment [EA]); however, this
pathway's contribution to the overall intake and risk was considered to be very small when
compared to the intake of groundwater contaminants via ingestion and inhalation. The inhalation
of dust is addressed on pages II-2-59 and n-2-60, Volume II and Appendix B, Volume IV of the
EA. The conservative screening level model of exposure to dust presented in Appendix B
indicated that the contact rate via this route is very small compared to incidental direct soil
ingestion. The incidental ingestion of surface water was considered (see page n-2-63 of the EA).
However, it is highly unlikely that this route for exposure would be a significant contributor to
the overall risk because of the low frequency of occurrence, ingestion rate, and concentration of
contaminants in surface water. The ingestion of homegrown fruit was considered (see
page H-2-62 of the EA); however, for the purpose of the offpost risk assessment, tomatoes were
considered as a vegetable. Fruit production is such a minor contributor to the agricultural
economy of the area that fruit production statistics are not kept by local agricultural economists.
Therefore, fruit ingestion was not evaluated. Intake via the consumption of eggs was only
evaluated for dieldrin because dieldrin was the only contaminant detected in the egg sample.
The Army has previously responded to the State's request that soil ingestion rates related to pica
behavior be considered. The Army followed EPA's guidance in RAGS to evaluate the soil
ingestion pathway and the soil ingestion rate. The rate used accounts for both outdoor soil and
indoor dust ingestion by children and is considered by EPA to represent an upperbound value (a
conservative value that is highly unlikely to result in an underestimation of risk). EPA is aware of
the information presented by the State. EPA guidance specific to CERCLA risk assessments is the
most reliable and authoritative source for the soil ingestion exposure parameter.
The use of a water consumption rate of 8 liters per day (I/day) would not be representative of the
majority of individuals in the area. The EPA does not consider worst case risk assessments to be
beneficial in evaluating the overall potential risk at a site. A water ingestion rate of 2 I/day was
used as the adult water ingestion rate in accordance with EPA guidance. While multiple chemical
sensitivities may exist for some individuals, the evaluation of this potential effect is difficult
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because of the lack of comprehensive scientific information. The Army believes that the
conservative uncertainties in the risk assessment more than likely account for this possible effect.
When evaluating the potential noncarcinogenic effects of chemicals of concern (COCs), the Army
followed EPA guidance in identifying and segregating constituents according to their lexicological
endpoints, including mechanisms of action. This categorization was done on the basis of
toxicological information provided in the toxicology databases available at the time the risk
assessment was conducted (e.g., EPA's Integrated Risk Information System [IRIS] and the Health
Effects Assessment Summary Tables). Table 4.0-1 in the EA lists the target organ or system
categories identified for the COCs evaluated. Information was unavailable from these databases
on the developmental effects of these COCs. If chemical-specific information was available from
these sources, it would have been used to evaluate the potential concern for developmental effects.
It is possible that some information is available in the open scientific literature describing
potential developmental effects; however, this information apparently has not been peer-reviewed
by EPA toxicologists for inclusion in the recommended risk assessment databases. EPA specifi-
cally recommends a hierarchy of toxicological information sources to be consulted when perform-
ing a baseline risk assessment, and nonpeer-reviewed scientific sources of information are the
least preferred.
The Army followed accepted practice and EPA guidance when evaluating the potential synergistic
and antagonistic interactions of the COCs. Because of the infinite number of possible toxicologi-
cal outcomes, most of them unknown, resulting from chemical interactions, EPA guidance
recommends a cautious assumption of dose additivity for both carcinogenic and noncarcinogenic
health effects. The Army applied this widely accepted practice as specified in EPA's RAGS and
Guidelines for Health Risk Assessment of Chemical Mixtures. The application of dose additivity
is prudent because of the lack of information on chemical mixtures in general and on the mix of
chemicals present in the Offpost Operable Unit specifically.
The Army disagrees with the State's assertion that "the monitoring data may not represent actual
site conditions." The State has provided no supportive evidence that the measured soil, ground-
water, surface water, sediment, or air concentrations are not indeed representative of actual site
conditions. Over the last decade, tens of thousands of analytical data points have been obtained
from the Offpost Study Area. The Army is continuing to refine and enhance its monitoring
programs to provide the most representative data for all areas under investigation. The Army is
confident that it has adequately monitored and will continue to adequately monitor environmental
conditions in the Offpost Study Area.
b. Hazard Index
The Final Endangerment Assessment/Feasibility Study indicates that for both chronic and
acute residential child non-cancer risks, the Hazard Index exceeds 1 in Zones 2, 3, and 4; the
Hazard Index for Zone 4 is four times the acceptable limit. In Zone IB, the child acute
Hazard Index exceeds 1. In other words, children exposed to existing contamination in the
manner described in the EA would be expected to suffer adverse effects. (See Tables 4.1.1-2,
-3). This is contrary to the NCP. See NCP, 40 C.F.R. §300.430(e)(2)(i)(A)(l) (1991). See
also: EPA guidance. Risk Assessment Guidance for Super fund fRAGs). Volume I. Part A
which states that the Hazard Indices may not exceed I and still be considered consistent with
the remedial goals of the NCP.
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Response
The Army disagrees with the assertion that "children exposed to existing contamination in the
manner described in the EA would be expected to suffer adverse effects," and that a Hazard Index
of 1 represents the "acceptable limit." According to the Risk Assessment Guidance for Superfund
(RAGS), exceedance of a hazard index of 1 is neither an absolute indicator of adverse effects nor
an indication of probability of adverse effects. A hazard index greater than 1 does not indicate
that anyone is expected to suffer adverse effects. RAGS (page 8-13) states "[w]hen the hazard
index exceeds unity, there mav be concern for potential health effects" (emphasis added).
Similarly, the Guidelines for the Health Risk Assessment of Chemical Mixtures (51 FR 34019,
September 24, 1986) state that "(t)he hazard index provides a rough measure of likely toxicity and
requires cautious interpretation." The degree of concern when the hazard index exceeds 1 depends
on several issues including the conservativeness of the assumptions used in the risk assessment, the
likelihood of exposure occurring, and the contributions to the hazard index from specific
environmental media.
The hazard index is calculated by dividing the estimated daily chemical intake by the reference
dose (RfD). The hazard index is thus subject to uncertainties from the derivation of both the
estimated intake and the reference dose. Therefore, it is important to understand the basis and
interpretation of both the reference dose and hazard index. As defined by the EPA in the
Integrated Risk Information System, Supportive Documentation, March 1987, the reference dose
is:
An estimate (with uncertainty spanning perhaps an order of magnitude) of the
daily exposure to the human population (including sensitive subgroups) that is
likely to be without appreciable risk of deleterious effect during a lifetime.
The reference dose (from which the hazard indices are calculated) is similar in concept to the
acceptable daily intake (ADI), the term previously used. The term ADI was changed because of
the connotation that any dose above the ADI was "unacceptable." The general interpretation of
the ADI, at the time of its use, was:
A "ballpark figure" which represents a level of exposure which is not likely to
result in adverse effects in humans. It is viewed as a soft estimate in that
exposures somewhat higher than the ADI are generally not expected to result in
adverse effects; only if the ADI is significantly exceeded would one expect such
negative consequences (50 FR 46936, November 13, 1985).
The IRIS Supportive Documentation further states "(i)t is generally useful to the risk manager to
have information regarding the contribution to the RfD from various environmental media." In
this context, it is important to recognize two issues. First, the hazard indices summarized in the
EA tables are representative of the reasonable maximum exposure (RME). As presented in the
uncertainty analysis discussion in the EA, the estimated RME exposure concentrations and
resultant hazard indices may be overestimated by a factor as high as 5. Secondly, although
domestic use of alluvial groundwater is not a complete exposure pathway, its inclusion in the risk
assessment contributes significantly to the estimated risks. For example, this pathway contributes
to 56 percent of the child chronic hepatic hazard index even though it is not a current exposure
pathway. Therefore, it is likely that the estimated hazard indices presented in the EA are
conservative and overestimated.
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The cited section of the NCP states:
For systemic toxicants, acceptable exposure levels shall represent concentration
levels to which the human population, including sensitive subgroups, may be
exposed without adverse effect during a lifetime or part of a lifetime, incor-
porating an adequate margin of safety.
The methodology for the derivation of the reference dose itself contains several safety factors,
and, as indicated, is associated with an uncertainty of an order of magnitude. The hazard index
value of 4 is within an order of magnitude of a hazard index value of 1 and therefore should not
be viewed as connoting unacceptability. Because the EPA has stated that there is uncertainty
associated with the hazard index values, it is inappropriate to use a hazard index value of 1 as a
definitive cutoff value.
The Army believes that the uncertainties and safety factors inherent in the derivation of the
reference dose, the statements by EPA regarding the interpretation of the hazard index, the
probable overestimation of the hazard index by the EA methodology, and recognition that several
exposure pathways associated with the alluvial groundwater do not currently exist, indicate that
the hazard index of 4 should not be viewed as absolute indicator of unacceptability. In fact,
because of the conservative nature of the risk assessment, a hazard index of 4 should be viewed as
supporting a conclusion of minimal risk.
RAGS, Volume 1, Part A does not state that hazard indices greater than 1 are unacceptable.
Rather, page 8-16 of RAGS states that "(w)hen the total hazard index for an exposed individual or
group exceeds unity, there mav be concern for potential noncancer health effects" (emphasis
added). On page 8-25 of RAGS, the guidance on summarizing the risk characterization efforts
states that the summary should include, among other things, the magnitude of the cancer risks and
noncancer hazard indices relative to the Superfund site remediation goals in the NCP.
The attainment of the hazard index goal of 1.0, like the cancer risk remediation goal of 10"*, needs
to be tempered with the purpose of the goal and the site-specific and risk-assessment-specific
issues reflected in the final risk estimates. In the areas where hazard index exceeds 1.0, contami-
nants in groundwater contribute the majority of the hazard index. Operation of the Offpost
Groundwater Intercept and Treatment System will result in a reduction in the estimated hazard
indices.
c. Endangerment Assessment
The State remains concerned with the methods used by the Army in defining cleanup levels
that are protective of biota. We believe that levels of contamination remaining in the off post
may pose potential health threats to wildlife. The State was not allowed to participate in
several dispute resolution meetings where issues such as defining maximum allowable tissue
concentrations (MATCs) were discussed and formalized. In addition, on 4/19/93, the State
provided the Parties with a report, "State of Colorado Proposal on How to Conduct a Site
Specific Ecological Risk Assessment at the Rocky Mountain Arsenal." While the timing of
this report made it difficult to incorporate into the off post EA, a majority of the concerns and
ERC methodologies identified in the report were provided to the Army orally through EA
subcommittee meetings and by written comments prior to finalization of the off post EA/FS
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report. To date, we have yet to receive any comments from the Army on our report. We
believe this approach to defining cleanup levels protective of biota is well-justified and
should be used for both the on and off post Endangerment Assessments.
Response
The State has not presented any evidence to support its contention that assumptions made for the
ecological risk assessment (RA) will result in levels of contamination remaining in the Offpost
Study Area that may not be protective of biota. The Army presented the ecological RA assump-
tions and approaches to the U.S. Fish and Wildlife Service (USFWS), EPA, Shell Oil Company, and
the State at meetings throughout the ecological RA study period. The Army considered these
meetings and subsequent feedback critical because of the lack of formalized EPA guidance on
conducting a dose-based ecological assessment. The Army believes that the findings of the
ecological RA are protective of wildlife because many aspects of the approaches used to estimate
potential effects are more conservative than other hazard assessment methodologies currently
followed by EPA and other agencies. Because the approaches to conducting an ecological RA are
continually being developed, the assumptions and parameters used by the Army for the final
ecological RA were thoroughly discussed with the parties and modified throughout the ecological
RA process, and the best available methodology and informed professional judgement were used.
The USFWS participated in the ecological RA process and supported the final methodologies used
to evaluate the potential ecological hazards.
Dispute resolution meetings were open for attendance by all signatories to the Federal Facility
Agreement. As indicated in the introduction to the Response to Comments, the State of Colorado
declined to sign the FFA and become an official party to all proceedings and issue resolution
meetings pertaining to RMA activities. The Army is aware of the States's comments (both verbal
and written) regarding the methodologies used to conduct the ecological risk assessment. These
issues were discussed at the dispute resolution meetings and agreement was reached by the
involved parties. The Army believes that the final maximum allowable tissue concentrations
(MATCs) agreed to by the EPA, USFWS, and Shell Oil Company are sufficient to define the
cleanup levels protective of offpost biota.
Comment No. 2 - State Groundwater Concerns
a. Selected Groundwater Cleanup Alternative
The Army has chosen Alternative No. N-4, essentially continuation of an already implemented
interim response action, as its preferred alternative for the offpost. The State believes that
this remedy is not sufficiently justified in accordance with the selection criteria in the NCP
and CERCLA and that a more aggressive groundwater cleanup alternative is appropriate.
hems 1 through 3 below explain why the State does not agree with the Army's selection of
Alternative N-4. The State has obtained and reviewed the groundwater model created and
used by the Army to evaluate groundwater cleanup alternatives for the north and northwest
plume groups, and has concluded that a more efficient alternative could be selected for the
north plume group based on this analysis (see item 4).
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1. Cost Considerations
Alternatives N-5 and N-6 were eliminated based mostly on the fact that they would require
greater initial capital outlay than the selected alternative. This decision failed to consider
the fact that the rejected alternatives would be more protective of the environment and
provide a shorter remediation time frame. N-5 was eliminated even though it is more cost
effective than N-4, given that its total present worth costs are actually less than N-4, since
N-5 has a shorter predicted remedial time frame.
Response
The State has incorrectly stated the Army's rationale for elimination of Alternatives N-5 and N-6.
As presented in the Final Offpost EA/FS report Volume VI, Section 4.2.1, Screening of Alterna-
tives - North Plume Group, effectiveness, implementability, and cost criteria were explicitly
evaluated consistent with the requirements of the NCP. In this section of the EA/FS, it was
concluded that Alternatives N-4, N-5, and N-6 afford the best reduction in toxicity, mobility,
and volume, the best long-term protection, and the best compliance with remediation goals.
Alternative N-6 was screened out at this point on the basis of similar performance in comparison
with Alternative N-5 with respect to reduction in toxicity, mobility, and volume, yet it afforded
no benefit in terms of remediation timeframe (10 to 20 years) and at higher cost.
The Army selected Alternative N-4 instead of Alternative N-5 primarily because Alternative N-4
includes potential future modifications, only if such modifications are found to be necessary based
on actual operating data, to the Offpost Groundwater Intercept and Treatment System. Selection
of Alternative N-5 instead of Alternative N-4 will not necessarily provide a more cost effective
alternative because of a slightly shorter estimated remediation timeframe. The Army based its
assessment of the relative differences between the groundwater alternatives and estimates of
remediation timeframes on groundwater models that are very general in nature; thus, the
estimated remediation timeframes should not be construed as precise predictions. Use of actual
full-scale operating data is preferable to selecting additional components for the Offpost
Groundwater Intercept and Treatment System using the more speculative modeling data (i.e.,
Alternative N-5).
The Army is committed to efficient operation of the Offpost Groundwater Intercept and
Treatment System and will evaluate operating data to assess the need for system modification.
Similar to the onpost boundary treatment systems, it is difficult to assess whether the installation
of additional wells will provide more efficient operation without collecting full-scale operating
data for the Offpost Groundwater Intercept and Treatment System. The Army has included an
intensive monitoring component as part of the preferred alternative, Alternative N-4, in the
Proposed Plan. This intensive monitoring program will allow the collection and subsequent
interpretation of performance data for the full-scale operation of both the Offpost Groundwater
Intercept and Treatment System and the onpost boundary systems. The data will be used to assess
the need for any improvement to the systems and will provide increased accuracy in assessing
contaminant cleanup. Acquisition of this operational data is preferable to adding extraction wells
and recharge trenches without the benefit of operational data, because additional data are required
to assess the necessity and placement of any additional extraction wells or trenches. If operational
data supports the conclusion that the cleanup timeframe can be shortened without a significant
increase in long-term costs, modifications to Alternative N-4 will be implemented. By taking this
approach, improvements to the system will be more effective than improvements made based on
computer modeling data.
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2. Cleanup Time Frames
Alternative N-4 was selected over N-5 even though the Army's own projected cleanup time
frames show N-5 requiring one-third less time for groundwater remediation. The Army
has cautioned that its time frames are only estimates and should be viewed as a tool for
comparison between alternatives. Apparently, the Army has not used its model for the
purpose for which it was designed. Estimates provided by the Army are 15-30 years for
N-4 and 10-20 years for N-5. This is a substantial reduction. Based on our understanding
of groundwater flow, and the contaminants of concern in the off post, the State believes that
the actual remedial time frames will be significantly longer than Army estimates, and in
that case, a one-third reduction in cleanup time would be even more important in terms of
protection for human health arid the environment, as well as reduced cleanup costs.
Response
The Army's basis for selection of Alternative N-4 over N-5 is based on use of actual field
operating data from both the North Boundary Containment System (NBCS) and the Offpost
Groundwater Intercept and Treatment System in combination with an integrated set of offpost
groundwater monitoring programs (as in Alternative N-4) to make decisions about the need for
an Offpost Groundwater Intercept and Treatment System upgrades. This approach is fundamen-
tally superior to the methodology structured in Alternative N-5, which would proceed with
modifications to the Offpost Groundwater Intercept and Treatment System, based on groundwater
modeling results alone.
The State claims that the Army should have relied on the model simulations that predict a slightly
shorter cleanup time for Alternative N-5 as compared to N-4 to select an approach that would
install additional wells and trenches based on modeling. The Army, however, has selected
Alternative N-4 because actual field operating data can be better used to optimize any required
system modifications.
3. Short-term Monitoring
The Army has stated that N-4 is superior to N-5 because N-4's short-term intensive
monitoring will ".. identify any necessary improvements to the system..." First of all,
short-term performance monitoring should logically be a part of any remedy to determine
whether the system is functioning as planned. Second, it appears from the detailed
analysis of alternatives that N-5 does include a similar monitoring scenario. In the
Feasibility Study, the Army describes how performance would be monitored for both
alternatives (Offpost EA/FS, Final Report, pgs. V 1-5-14 and VI-5-21). Since both plans
contain provisions for short term intensive monitoring, this is not a proper basis for
selection of N-4 over N-5.
Response
The Army has not relied on the short-term intensive monitoring program component of Alterna-
tive N-4 in selecting Alternative N-4 over N-5. The rationale and basis for this selection is
presented in responses to parts 1 and 2 of State Comment No. 2.
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In addition, the State has incorrectly stated that the referenced sections of the Final Offpost
EA/FS report describe the same short-term intensive monitoring program. In fact, the State's
citation, Offpost EA/FS report Vol. VI pg. 5 - 14 is in Section 5.4.1, which evaluates the remedial
alternatives with respect to the criterion of overall protection of human health and the environ-
ment. The intensive short-term monitoring component of Alternative N-4 is explicitly referenced
in this section, while it is not referenced for Alternative N-5. The State's second citation (Final
Offpost EA/FS report Vol. VI pg. 5-21 in Section 5.4.3) contains a general reference to monitor-
ing for both Alternatives N-4 and N-5 in the context of evaluating both alternatives and
permanence. There is no reference to the short-term monitoring component for either Alternative
N-4 or N-5.
4. Optimizing Selected Groundwater Remedial Alternative - Alternatives N-5A and N-5B
Though the Army states that Alternatives N-4 and N-5 are essentially equivalent, they
select Alternative N-4 because: a) it is claimed to be more readily implementable, b)
system modification is based on operation data, rather than modeled data, and therefore, is
considered more effective, and c) the additional capital expenditures of N-5 are not
justified until performance monitoring data are available. The Army's justification is
based on the premise that Alternative N-5 is an enhancement to Alternative N-4. This, in
part, is a fault of the range of alternatives considered by the Army during the Feasibility
Study.
Using the Army's model, the State has been able to improve on N-5. Two modifications to
Alternative N-5 are presented. The first modification will be referred to as Alternative N-
5A. The main improvement comes by relocating extraction wells closer to the center of
mass of the dieldrin plume. The dieldrin plumes are located further upgradient, due to this
contaminant's lower relative mobility. The simulated cleanup times indicate that dieldrin is
the limiting constituent (i.e. the one taking the most amount of time to reach the cleanup
goals). Therefore, the first modification focusses on this contaminant to decrease the
overall remedial duration.
Alternative N-5 consists of an expansion to Alternative N-4 (IRA A). In the North
Paleochannel, however, the expansion well is located very near the IRA and results in only
a 15% reduction of the cleanup time for dieldrin compared to N-4. Alternative N-5A
consists of modifying Alternative N-5 by relocating the extraction wells and reinjection
trenches to reduce the cleanup time of the dieldrin plume by containing it within its current
boundaries thereby preventing further degradation of the aquifer. Alternative N-5A uses
the same number of pumping wells pumping at the same rate (30 gallons per minute).
However, the number of recharge trenches is reduced from the six used for N-5 to three
used for N-5A thus reducing capital costs.
Simulating Alternative N-5 A with the Army's model, the State was able to decrease the time
estimated to achieve ARARs for dieldrin by approximately 30% compared to the time
estimated for Alternative N-5. The cleanup time for chloroform increases by about 15%.
However, due to chloroform's greater mobility compared to dieldrin, the cleanup time for
chloroform is still less than that of dieldrin. This decrease in the operational period,
combined with lower capital costs than N-5, results in a present worth cost of alternative
N-5 A of $53.5 to 59.5 million compared to the present worth cost of Alternative N-4 ($56.5
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to 63.1 million) and N-5 ($56.2 to 63 million). The improvement in total cost combined
with the decrease in the time of the remediation shows the benefit of Alternative N-5 A.
The second modification to Alternative N-5 is referred to as N-5B. Though simulation
revealed that Alternative N-5A was superior to Alternative N-5 (and N-4) since it
decreased the cleanup time for dieldrin, it also resulted in a slight increase in the cleanup
time for the rest of the plume, in particular, chloroform as compared to N-5. Alternative
N-5B builds on N-5A by placing an additional extraction well and recharge trench near the
center of mass of the limiting compound for the rest of the plume, chloroform. All wells
pump at 30 gpm; each injection well-pair constitutes a recharge trench and receives the
water from one pumping well. The addition of the extraction well and trench near the
chloroform center of mass results in a decrease in the cleanup time for chloroform
(approximately 8% faster than N-5). The simulated cleanup times for dieldrin are
approximately the same as cleanup times for Alternative N-5 A. Based on the predicted
cleanup time frames for chloroform and dieldrin in Alternative N-5B, it's possible that the
downgradient portion of the Alternative (the N-5 wells and the additional N-5B well-pair)
could be turned off when the chloroform plume is remediated while the upgradient portion
would continue to operate.
The present worth cost of Alternative N-5B would be S53.9 to 60.0 million. The reduction
in total cost compared with N-4 coupled with an even further decrease in remediation time
for the chloroform plume over N-5A shows this alternative to be superior. The State will
provide the Army with a more detailed description of this analysis within the next 10 days.
Response
The Army's offpost groundwater modeling study used in evaluating remedial alternatives in the
Offpost EA/FS report was based on hydraulic and contaminant distribution data from the
1989/1990 time period. Since that time, significant changes in contaminant distribution have
occurred, apparently resulting from recent improvements with the NBCS and the continuation of
reduced contaminant concentration trends from past NBCS improvements. In addition, approxi-
mately 85 new monitoring wells have been installed offpost in the past two years. Geologic and
hydraulic data from these new wells have greatly improved the Army's hydrogeologic conceptual
model offpost. Baseline groundwater sampling episodes of new and existing wells offpost prior to
operating the Offpost Groundwater Intercept and Treatment System indicated smaller contaminant
plumes than were present in 1989/1990. The new wells have resulted in more precise definition
of the plumes. With the wealth of new information resulting from the implementation and
monitoring of the Offpost Groundwater Intercept and Treatment System, it is illogical and
inappropriate to base potential expansion of the Offpost Groundwater Intercept and Treatment
System on data that does not include full-scale operation.
Selection of Alternative N-4 over N-5, N-5A, and N-5B is based only in part on modeling
results. The State has failed to consider other factors in the selection process and the dynamic
nature of the contaminant distribution offpost due to the continuing effects on contaminant
distribution and concentration in the offpost from NBCS modifications. The State has also placed
too much emphasis on the modeling results alone for recommending either Alternative N-5A or
N-5B over Alternative N-4 . Given the fact that the Offpost Groundwater Intercept and
Treatment System has been fully operational since June 1993 and a wealth of new information is
becoming available for evaluating the Offpost Study Area, it makes little sense to rely heavily
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upon the FS modeling results for selection of the preferred alternative and ignore full-scale data.
It is the Army's goal to select the most technically sound alternative. Alternative N-4 fits this goal
by considering the most current information on plume distribution as a basis for potential system
expansion.
b. Dieldrin Certified Reporting Limit
The Army's characterization of the dieldrin groundwater plumes is limited by its certified
reporting limit (CRL) of 0.05 pg/l. This is unacceptable because it is above the state's
health-based ARAR of 0.002 ftg/l. Since 1987, the State has repeatedly objected to the
Army's use of its CRL methodology because it results in detection limits that are higher than
EPA method detection limits and, in some instances, exceed health-based levels. This issue
was again raised in the state comments on the RI/EA/FS Workplan, 1/26/90. The Army
promised to get its CRLs down in the Final Decision Document Groundwater Intercept and
Treatment System North of RMA, July, 1989, pp. 37-38.
Response
First, as discussed in the response to State Comment No. 4 in this section, the Army does not
consider the Colorado Basic standards for Groundwater to be chemical-specific ARARs.
Secondly, Table A, Section 3.11.5(C) of the Basic Standards for Groundwater (5 CCR 1002-8),
lists the standard for dieldrin as 0.002 ug/l, with a practical quantitation limit (PQL) of 0.1 jtg/1.
Furthermore, Section 3.11.5(C)(4) states:
Whenever the current detection level (PQL) for a pollutant is higher (less strin-
gent) than a standard listed in Subsection 2 or 3 above, the detection level shall be
used as the performance standard in regulating specific activities. The detection
levels (PQL's) identified in Table A shall apply, unless and until they are mod-
ified as the result of a subsequent rulemaking hearing, (emphasis added)
Thus, the State's enforceable numerical performance standard for dieldrin in groundwater is 0.1
/ig/1 because the detection limit is higher than the health-based standard.
The most recent proposed update of EPA's pesticide method 8081 (in Proposed Update II to SW-
846, 3rd edition, Revision 0, November, 1992) lists a method detection limit of 0.044 pg/1.
Because the Army's CRL of 0.05 jig/1 is less than the Table A PQL (0.1 /ig/1) obtainable by the
Colorado Department of Health, and almost identical to the proposed EPA method detection limit
of 0.044 /ig/l,the Army believes its current CRL is adequate to characterize the dieldrin plume.
c. Northwest Plume
The Army has proposed no active remediation of groundwater downgradient of the northwest
boundary system. Instead it is relying on flushing and dilution of the contaminants by
reinjecting treated water on the downgradient (northwest) side of the boundary system. Its
modeling results predict that PRGs (chloroform: 15 ftg/l, dieldrin: 0.05 pg/l) will be
achieved in approximately 3 to 8 years by this method. This is unacceptable because it does
not consider remediation of the aquifer to state ARARs (chloroform: 6 ftg/l, dieldrin: 0.002
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ug./l). Moreover, water treated at the boundary is being reinjected to the aquifer at concen-
trations above the state ARARs. Therefore, the Army must first improve the boundary
treatment process whereby the effluent concentrations are lowered to levels below the state
ARARs. Additional data should be obtained to determine the leading edge of the dieldrin
plume based on detection limits at or approaching the state's health-based standard of .002
fig/I. Once the plume has been adequately evaluated, the Army should evaluate containment
of the dieldrin plume.
Response
As described in response to State Comment No. 4, Colorado Basic Standards for Groundwater
were not found to be chemical-specific ARARs.
Treated water from the Northwest Boundary Containment System (NWBCS) being recharged
meets the remediation goals set forth in the ROD.
The dieldrin plume downgradient of the NWBCS has been adequately characterized by the Army.
Response to State Comment No. 2b addresses the dieldrin detection limit.
d. State DIMP Standard and the Provision of Bottled Water
The report entitled "Human Effects Assessment of Diisopropyl Methylphosphonate (DIMP)"
by Edward J. Calabrese (1990 Report) has been in the possession of the Army and EPA for
several years and is hereby incorporated into these comments by reference. As more fully
explained in that report and as stated previously, the State cannot accept the EPA DIMP
Health Advisory of 600 ug/l as being protective of human health. Therefore, we believe that
the Army's remedy, which does not attempt to prevent exposures to DIMP below that level,
violates section 121(b) of CERCLA and section 300.430(e)(9)(iii)(a) of the NCP which
establish protectiveness as a threshold criterion for all CERCLA remedies.
To briefly summarize Dr. Calabrese's report, the State believes that the EPA DIMP Health
Advisory is unsupportable because it incorrectly disregards the 1979 Aulerich reproductive
study on mink in which the authors noted treatment-related deaths. EPA rejected the Aulerich
study for two reasons: (1) the extrapolative relevance of mink to human toxicity estimates was
unknown; and (2) the background mortality of mink confounded any findings of adverse
effects in the treated groups. Both of these concerns have been thoroughly explored by Dr.
Calabrese's research which has been communicated to the EPA and the Army and is reflected
in the 1990 Report at pages 8-51.
Because mink have been demonstrated to be an appropriate animal model; because the control
in the Aulerich study was demonstrated to have behaved consistently with the historical control
constructed from relevant studies conducted at Michigan State University, and therefore
should be used; and because the mink demonstrated a clear, statistically significant dose-
response relationship to DIMP, it must be adopted as the critical study from which to derive
an acceptable drinking water standard. Such an approach is consistent with the rules
established by EPA and set forth in its Integrated Risk Information System (IRIS) which
establishes the general methodology to be used to establish reference doses or "acceptable
daily intake" values and, ultimately, water quality standards. A copy of that methodology is
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attached. IRIS mandates that health-based standards be based on the most sensitive species
investigated. Since no statistically significant adverse effects were noted in EPA's selected
critical study using beagles and since mink experienced death in response to exposure to
DIMP, the mink study is clearly the appropriate study upon which to base a standard.
Rejection of the mink study in the face of Dr. Calabrese's compelling documentation is
arbitrary and capricious.
To further explain the application of the generally accepted methodology of IRIS to the
Aulerich study:
I. Identify the Lowest Observed Adverse Effect Level (LOAEL) in the appropriate animal
study
LOAELs are based upon two considerations, biological and statistical significance. As
demonstrated in Dr. Calabrese's report the lowest does, 11 mg/kg/day, is the LOAEL
based upon regression analysis of the data. The State agrees with Dr. Calabrese that the
more appropriate statistical analysis to apply in this instance is regression, or trend
analysis rather than pair-wise comparison between each dose group and the control. This
is because pair-wise comparisons can mask treatment-related effects as a result of
insufficient statistical power due to relatively small sample size.
2. Apply appropriate uncertainty factors (UFs)
IRIS recognized four fundamental areas of uncertainty:
a. LOAEL to NOAEL (no observed adverse effect level)
b. interspecies extrapolation
c. intraspecies variation
d. less than lifetime study duration
The scope of these factors is described in Dr. Calabrese's 1990 Report at pages 66-69.
Each of the factors is given a default value of 10, and all of them must be applied to the
LOAEL identified in the Aulerich study.
In addition, IRIS recognizes that problems with available data may indicate a need for
further reduction of a dose in certain instances. Dr. Calabrese believes that because death
is a frank effect level (PEL), not a LOAEL, the factor of 10 for LOAEL to NOAEL
extrapolation is insufficiently protective, and therefore recommends an additional modify-
ing factor of 5. The State has elected not to adopt this recommendation because, although
toxicologists may legitimately disagree, it is the professional judgement of CDH that
application of the other four uncertainty factors In this instance results in a sufficiently
conservative exposure level.
3. Calculation of Drinking Water Equivalent Level
Once an adjusted "NOAEL" is established it remains necessary to calculate an appropriate
drinking water concentration which would ensure that exposure over a 70 year life-span
would not result in an exceedance of that NOAEL. This is done based upon certain
exposure assumptions adopted by EPA and explained in the 1990 Report. Dr. Calabrese
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has deviated from standard IRIS methodology in two respects: (1) he recommends that
65 kg, the average body weight of women, be used instead of 70 kg. which is the average of
male and female body weights; (2) he recommends that surface area scaling be employed
to adjust the mink dose to a human dose. Although these recommendations have merit,
CDH is not adopting them at this time because they have not yet been incorporated into
state and federal regulatory programs. Accordingly, based on the above descriptions, an
appropriate calculation of a drinking water level for DIMP would be:
(1) 11 me/kf/dav (LOAEL) = 0.0011 mg/kg/day
10,000
(2) 0.0011 me/ke/dav x 70 ke x 0.2 = 0.0077 mg/l = 7.7 pg/l
2 liters/day = 8.0 pg/l
(0.2 is the source contribution from groundwater)
In conclusion, selection of the Aulerich mink study as the critical study, and application of standard
IRIS methodology to that study results in a drinking water equivalent level of 8 tig/I. This level
should be incorporated as a remediation goal by the Army into its Proposed Plan. The treatment
facility should be operated to achieve a level of no more than 8 ng/l in its effluent, and the Army
should evaluate the feasibility of containing the DIMP plume where concentrations exceed 8 pg/l.
Where active remediation is impracticable, the Army could ensure the protection of public health by
providing an alternative water supply, and institutional controls to prevent unknowing use of the
water in contaminated areas.
Response
The U.S. Environmental Protection Agency (EPA) developed the Health Advisory for diisopropyl
methylphosphonate (DIMP) in 1989 on the basis of an extensive review of more than 30 existing
toxicology studies involving a variety of animal species. EPA's Office of Drinking Water re-
reviewed the Health Advisory, in light of the State's concern, and concluded on March 28, 1990,
that "the existing Health Advisory values and the basis for the values represent the best scientific
position for the protection of human health." The Army is not in violation of Section 121(b) of
CERCLA and Section 300.430 (e)(9)(iii)(a) of the NCP because the DIMP standard proposed by
the State has not been promulgated.
The Army contends that the EPA acted appropriately when rejecting the Aulerich mink study as
the critical study on which to establish a human health drinking water advisory on the basis of
extrapolative relevance to humans and the confounding influences of background mortality in
mink. The Army disagrees with the State's statement that IRIS mandates that health-based
standards be based on the most sensitive species tested. IRIS describes through a "concept paper"
(IRIS Background Document 1A - Reference Dose (RfD): Description and Use in Health Risk
Assessment) the recommended approach to select the most appropriate critical study and implies
the use of informed professional judgment when making that selection, particularly when
identifying the animal model that is most relevant to humans. EPA uses a panel of high-level
peer scientists to make the critical study selection rather than relying on the opinions of a single
individual.
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The CDH apparently recognizes some of the additional flaws in the health-based DIMP standard
proposed by Dr. Calabrese. The State is correct that Dr. Calabrese's application of an additional
modifying factor of 5 to overall uncertainty is inappropriate as well as the use of some exposure
parameters. In fact, the approach as described by Dr. Calabrese illustrates how unrealistic health-
based standards are derived when guidelines recommended by EPA are followed as an arbitrary
"yes or no" paradigm, ignoring informed professional judgment (peer review) on biological and
lexicological relevance.
In accordance with EPA's Risk Assessment Guidance for Superfund (RAGS), the Army used
EPA's Health Advisory and information contained in the IRIS database to evaluate risk to human
health.
e. DIMP Exceedances Past the First Creek Intercept System
The State is concerned that a portion of the concentrated DIMP plume has already passed the
off post intercept system, leaving concentrations of the chemical, greater than 600 ppb,
unremediated. This concern is compounded by the fact that the Army is unaware of the extent
of this plume. Additional characterization of the groundwater downgradient of the intercept
system is necessary. Additional alternatives should then be evaluated to attempt to capture
this plume before this high concentration of DIMP contamination affects a larger number of
domestic wells.
Response
The Offpost Groundwater Intercept and Treatment System is located in areas of highest contam-
inant concentrations. The Army is aware that concentrations of DIMP greater than 600 parts per
billion (ppb) have been reported north of the Offpost Groundwater Intercept and Treatment
System. In that regard, the offpost remedial action groundwater monitoring program will be
coordinated with the three existing groundwater monitoring programs active in the Offpost Study
Area. These three programs are (1) the Groundwater Monitoring Program, (2) the Interim
Response Action A monitoring program, and (3) the private well monitoring program. Addition-
ally, in the area north of the Offpost Groundwater Intercept and Treatment System where DIMP
has been reported to exceed 600 ppb, three monitoring wells will be replaced and three new
monitoring wells will be installed. Replacement wells are being installed for three wells originally
in the monitoring network that were found to be damaged or destroyed. Two new monitoring
wells will be installed downgradient of the First Creek Pathway, and one new monitoring well will
be installed downgradient of the northern Pathway. The purpose of the three new monitoring
wells is to aid in assessing the extent of contamination downgradient of the Offpost Groundwater
Intercept and Treatment System. Data collected from these wells and existing wells will be used to
further define the extent of contamination greater than the remediation goals in this area and
assist in determining whether modifications to the design of the Offpost Groundwater Intercept
and Treatment System are necessary.
f. The Army's Definition of the DIMP Plume
According to the Proposed Plan, "The Offpost Study Area was defined to assess potential
effects of RMA-related contamination beyond the RMA boundary. On the basis of north and
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northwesterly flow directions of groundwater and surface water, the boundary of the Offpost
Study Area was defined to include the area bounded by 80th Avenue, the South Platte River,
Second Creek and the north and northwest boundaries of RMA." The State believes the
Army's definition of the Offpost Study Area is insufficient for two reasons:
First, the Army has defined the Offpost Study Area based largely on its own definition of the
areal extent of the DIMP plume in the alluvial aquifer. These data include only Army
monitoring well data and does not take into consideration numerous domestic alluvial and
Arapahoe wells that have consistently contained levels of DIMP, according to CDH data.
Second, the Offpost Study Area was geographically limited in part by the South Platte River
on the west and Second Creek on the east. Historically, the South Platte River has been
regarded as a hydrologic barrier which prevented contaminant plumes from migrating to the
west side of the river. More recent Army data reveals DIMP contamination on the west side
of the Platte present since 1989. This was confirmed in April of 1993 by two CDH samples
taken west of the Platte River, near the Army monitoring well. In addition, detections of
DIMP in both the alluvial and Arapahoe aquifer adjacent to Second Creek fall well outside
the Army's plume interpretation, suggesting that the DIMP "plume" is not restricted by the
definition of the "study area".
The State believes that the Study Area be expanded to include a larger geographic area that
includes all domestic-use and monitoring wells that contain concentrations of DIMP.
Response
The delineation of the Offpost Study Area in the Federal Facility Agreement (FFA) was agreed to
by EPA, Army, Shell, U.S. Department of the Interior, U.S. Department of Justice, and the
Agency for Toxic Substances Disease Registry (the signatories to the FFA). Groundwater cleanup
standards are not exceeded in the areas outside the Offpost Study Area; therefore, an expansion of
the study area is unnecessary.
The Army has used and continues to include data from the various Army-sponsored offpost
monitoring programs and the private well monitoring programs to evaluate which areas are
impacted by RMA contamination. All available data is used in developing the plume maps.
The Army will continue to use all available domestic use and monitoring well data and to include,
as appropriate, locations outside of the Offpost Study Area in future monitoring events.
g. Degradation of the Arapahoe Aquifer
The Army does not address the continued degradation of the deeper Arapahoe Aquifer. Since
1990, testing by the Army and the Colorado Department of Health has revealed widespread
contamination of this aquifer. Of the 70 wells so far tested for DIMP in this aquifer, 42 were
below detection levels (BDL), 8 samples contained Trace amounts (defined as <0.5 ppb), and
20 had measurable amounts ranging from 0.5 to 39.7 ppb. This is of concern to the State
because there are a large number of domestic Arapahoe wells in the Offpost area, most of
which have not yet been sampled for DIMP.
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On several occasions, CDH has presented to the Army evidence of wells known to be conduits
of contamination from the alluvial aquifer to the Arapahoe aquifer and consequently into
neighboring Arapahoe wells. For example, at a December 11,1991 meeting, the State pointed
out that well #985 (TCHD ID) was known to be completed over more than one water bearing
zone consistent with completion practices of the time of its construction. Based on testing of
several downgradient Arapahoe wells and their geographical location with respect to the
DIMP plume in the alluvial aquifer, it was determined that well #985 was acting as a conduit
for inter aquifer communication.
The State believes that the Proposed Plan must protect the integrity of the Arapahoe Aquifer.
To this end, the State believes that it is essential to close, as they are identified, all wells
which are known to be pathways of contamination to the deeper aquifers by evaluating each
domestic well on a case by case basis, taking into account the completion history, geographic
location and geology of each candidate.
The State is concerned that further degradation of the Arapahoe Aquifer violates the Colorado
Basic Standards for groundwater, 5 CCR 1002-8, §3.12.5(2)(a). This interim narrative
standard specifically applies to RMA, which lies within the Denver Basin Aquifer system and
provides that groundwater quality shall be maintained at either the ambient quality as of
October 31, 1991, or the Table Value Standards, whichever is less restrictive. Since there is no
table value standard applicable to DIMP, and the Army has maintained that the Arapahoe
Aquifer is clean, no degradation of the aquifer is permissible under this section. In addition,
further degradation must be prevented to comply with the CBSG 5 CCR 1002-8
§ 3.11.5(c)(l)(b). This section requires that organic pollutants must be "maintained at the
lowest practicable level."
Response
The Army has incorporated well closure as a component of the offpost selected remedy. The
criteria for well closure are presented in Appendix C of the ROD.
h. Isopropylmethyl Phosphonic Acid (IMPA) in Groundwater and Surface Water
In 1990 the EPA completed a health advisory (HA) for the compound Isopropylmethyl
phosphonic acid (IMPA). The EPA's HA concluded that a concentration of 700 ppb is an
allowable lifetime exposure level. The Colorado Department of Health (CDH) recently
finalized its review of EPA's HA to ensure that it is protective of human health. This review
identified several areas of concern with the EPA's report and recommends a lifetime HA for
IMPA of 6.0 ppb. CDH's review will be distributed to the Parties in the near future.
The State is concerned that based on EPA's HA of 700 ppb, the Proposed Plan may not be
protective of human health and the environment. The State is primarily concerned that the
Army has not adequately characterized IMPA contamination in the Offpost Study Area. The
chemical characteristics of IMPA indicate that the likelihood of IMPA contamination in
offpost soils is small. However, IMPA contamination in the groundwater and surface water
may be inevitable due to the compound's long half-life, its low partition coefficient, and the
high concentrations of IMPA detected in groundwater onpost. Moreover, it is likely, due to its
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similar chemical characteristics, the compound may have developed a groundwater plume
typical of DIMP.
The Army has been unable to properly characterize the IMP A groundwater plume and the
levels of IMP A in surface water due to its analytical detection limit. The Army's current
detection limit of 150 ppb is more than 20 times the state's HA number of 6 ppb.
The State urges the Army to certify an analytical methodology that provides adequate IMP A
characterization to ensure that residents in the Off post Study Area are not exposed to
unacceptable risks, If USATHAMA certification cannot be achieved in a timely manner, the
Army should resort to using EPA analytical methodology in its characterization of IMP A
contamination. Once the characterization of IMP A in the off post study area has been
completed, the endangerment assessment and feasibility study may need to be modified to
include these data.
Response
On the basis of toxicity information summarized in EPA's isopropyl methylphosphonic acid
(IMPA) Health Advisory and the Integrated Risk Information System (IRIS) database, there is no
information to indicate that IMPA concentrations lower than 700 ppb may pose a threat to human
health.
It is highly unlikely that lexicologically significant concentrations of IMPA will occur in ground-
water because the abiotic formation of IMPA from diisopropyl methylphosphonate (DIMP) occurs
under alkaline conditions in the presence of heat. IMPA is primarily formed as a biological
metabolite of DIMP and excreted in the urine. The toxicological data on the metabolism of DIMP
indicates that the formation of IMPA is part of the metabolic elimination process and not a
bioactivation reaction. IMPA is a very polar metabolite that is most likely readily eliminated in
the urine rather than reabsorbed by the kidneys and redistributed throughout the body.
The EPA reference dose for IMPA was based on a simple IMPA subchronic study; however, EPA
indicates in IRIS that the DIMP database can be used to support the toxicological conclusions
regarding IMPA because more than 90 percent of the ingested DIMP is rapidly (within 24 hours)
converted to IMPA. EPA states that the DIMP studies showed that DIMP was relatively nontoxic
to all species. Additionally, because DIMP is rapidly and mostly metabolized to IMPA, it is
reasonable to conclude that the DIMP administered to mammals in the studies was metabolized to
IMPA; therefore, the absence of effects from DIMP also may be considered to indicate an absence
of effects from IMPA.
Analytical data collected to date in the Offpost Study Area for IMPA has not indicated that IMPA
is present at or above the certified reporting limit (CRL) in groundwater or tap water samples.
The Army's current CRL for IMPA is 25 ppb, not 150 ppb. From 1989 through 1992, the IMPA
analytical method used by the Army for analysis of groundwater and tap water had a CRL of
100 ppb. In 1993, following additional method development, the CRL was reduced to 25 ppb.
The 1993 reporting limit of 25 ppb is 28 times less than the EPA health advisory concentration of
700 ppb. For this reason, the Army believes it has adequately characterized the extent of IMPA in
the Offpost Study Area in a manner sufficient to conclude that potential health effects from
IMPA are minimal.
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The Army has vigorously pursued the development of more sensitive methods for the identifica-
tion of IMPA in RMA groundwater. The Army is currently unaware of a standard EPA method
capable of attaining a reliable reporting limit near 6 ppb.
The Army has received the State's evaluation of IMPA toxicity and will be providing additional
comments.
i. Point of Compliance
The Proposed Plan relies on intercept systems located immediately upgradient of O'Brian
Canal and some distance from the RMA boundary as the remedy. The Preamble to the
Proposed NCP provides that "EPA's policy is to attain ARARs and TBCs pertaining to
contaminant levels...so as to ensure protection at all points of potential exposure. 53 Fed.
Reg. 51440 (Emphasis added). The NCP, furthermore, clearly states that "remediation levels
should generally be attained throughout the contaminated plume." EPA acknowledges,
however, that an alternative point of compliance may also be protective in some circumstances.
See NCP C.F.R. §300.430(f)(5)(iii)(A) (1991). The Army has not demonstrated that it will
achieve protectiveness and ARAR compliance throughout the plume, nor has it made the
requisite findings to support an alternative point of compliance. Therefore, the Proposed Plan
is in violation of the groundwater policy set forth in the preamble to the NCP. The State
contends that ARARs must be met throughout the plume unless the Army can demonstrate
technical impracticability or justify an alternative point of compliance.
Response
The Army intends to achieve the remediation goals at all points within the contaminated plume,
consistent with the NCP. The groundwater modeling conducted by the Army in support of the
remedial alternatives evaluation in the Offpost EA/FS report used attainment of remediation goals
as a primary criterion in assessing time to cleanup for the various remedial alternatives. This
information is presented in summary form in the Proposed Plan and Volume VI, Section 3.2 of the
EA/FS and in detail in Volume VII, Appendix E of the EA/FS. The area of concern to the State
appears to be the portion of the plume that lies between the North Boundary Containment System
"(NBCS) and the Offpost Groundwater Intercept and Treatment System. The NBCS has been
demonstrated to be effective in reducing the contaminant concentrations at the RMA boundary to
meet remediation goals. The purpose of the Offpost Groundwater Intercept and Treatment
System is to extract and treat that portion of the plume that has migrated past the RMA boundary
and that contains contaminants exceeding the remediation goals. The groundwater monitoring
program implemented as part of the selected remedy will provide the data necessary to evaluate
attainment of treatment goals within the plume and to assess and design modifications to the
treatment system, if necessary.
Comment No. 3 - Land Use
a. Classification of Land Use
Zones 3 and 4 are currently zoned as agricultural/rural residential. This was the predom-
inant use until Shell Oil Company purchased the land in 1991. The Army, however, has
designated the land use for these zones as urban residential. The Army justifies this
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classification on two grounds. According to Adams County planning documents, the expected
future use is presumed to be urban. The other basis, according to the Army, is the fact that the
majority of this land is presently owned by Shell Oil Company which allegedly will not sell
that land except for commercial use. By assuming that the future use is urban residential, the
Army has eliminated the consumption of homegrown meats, milk, and eggs from the baseline
risk assessment, thereby reducing the calculated risk and avoiding remediation. The NCP
provides that both current and reasonable potential exposures must be considered in the
baseline risk assessment. 40 C.F.R. §300.430(d)(4) (1991). The Army has eliminated the
current land use, agricultural, in its evaluation.
Land use controls should be considered as an interim response measure, or final response
action where a more aggressive remedy is impracticable, but should not be considered in
conducting a cumulative site baseline risk assessment. OSWER Directive 9355.0-30, dated
April 22, 1991 at page 4. The Proposed Plan does not comply with this guidance or NCP
preamble language to the same effect; furthermore, it contains no provisions to ensure that
agricultural/rural residential uses are not allowed to occur in the future. The State therefore
maintains that the risk assessment should include the rural residential scenario, which more
accurately reflects current land use.
Response
The future land use scenarios used by the Army in the risk assessment are highly conservative.
For example, the rural residential scenario used in zones 1, 2, and 6 includes all pathways
contributing substantially to potential risk, even though most of the total population is not exposed
to the agricultural exposure pathways described in the risk assessment. Shell Oil Company
purchased the land in zones 3 and 4 for Army use in constructing the Offpost Groundwater
Intercept and Treatment System. It is not presently occupied; therefore, the current zoning
designation as rural residential is not applicable. Given the probability of the realignment and
widening of 96th Avenue, future development along 96th Avenue will likely be commercial/
industrial or urban residential. Based on local agency planning documents, the Army selected an
urban residential land use for the risk evaluation as this would result in more conservative (e.g.,
higher) estimated risks than the likely commercial/industrial land use.
The Army disagrees with the interpretation of land use designations as a type of "land use
controls." The referenced OSWER Directive, on page 4 states:
(t)he cumulative site baseline risk assessment should include all media that the
reasonable maximum exposure scenario indicates are appropriate to combine and
should not assume that institutional controls or fences will account for risk
reduction.
The future land use designation of urban residential was not presented as, nor was it intended to
be interpreted as, an institutional control. Following the purchase of these properties by Shell Oil
Company, the current land use is vacant, not rural residential, as no individuals currently reside in
these zones. The land use designation is made only to assess the types of potential exposure
pathways. These designations are made in accordance with the National Contingency Plan, which
states that the baseline risk assessment must look at a reasonable future land use. The Army
believes that urban residential is a reasonable future land use designation. In accordance with
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Risk Assessment Guidance for Superfund, one of the key factors in determining potential future
land use is an evaluation of planning and zoning documents. The land use designations and plans
were established by the appropriate jurisdictional agencies, not by EPA or the Army. Evaluation
of current zoning regulations, discussions with local planning officials, examination of future land
use master plans for the city and county, and visual surveys were used to establish land use
scenarios. These designations are supported by established zoning, planning maps, and planning
documents.
b. Institutional Controls
Zones 2, 3. and 4 are the most contaminated zones in the Off post study area. Because risks
from soil and groundwater contamination exceed acceptable levels in these zones, either
remediation or institutional controls are necessary in order to comply with CERCLA's
prescription that remedies be protective. A mere promise by a responsible party not to sell the
property until the remedy is complete would not be enforceable and therefore does not ensure
protectiveness. Institutional controls could be used to prevent exposure during the remediation
period. For example, restrictions may need to be imposed to prevent the construction of any
wells for the purpose of supplying drinking water from contaminated aquifers. The State
Engineer, for instance, has the authority to deny well permits located "closer than 100 feet
from the source of contaminants..." 2 CCR -2, Rule 10.2.1 (1988).
The NCP specifically encourages the use of institutional controls and deed restrictions as a
supplement to "engineering controls as appropriate for short-and long-term management to
prevent or limit exposure to hazardous substances, pollutants, or contaminants." 40 C.F.R.
§300.430 (a)(l)(iii)(D). This section emphasizes, however, that institutional controls are not
appropriate as a substitute for active response measures such as treatment and/or containment
of source material, and remediation of groundwaters. Id.
Thus, the State continues to urge that aggressive cleanup be undertaken to comply with the
prescriptions of section 121 of CERCLA, as well as the NCP. To the extent that such
remedies are impracticable or do not ensure protection of human health in the interim,
however, institutional controls must be adopted to supplement the selected remedy. Otherwise,
the Proposed Plan will not meet the NCP's threshold criterion of protectiveness.
Response
Institutional controls have been added as a component of the selected remedy. Appendix B of the
ROD provides an evaluation of the institutional controls available and their applicability.
Comment No. 4 - Applicable. Relevant and Appropriate Requirements (ARARS)
The State of Colorado has consistently identified the Colorado Basic Standards for Groundwater
(CBSG), 5 C.C.R. 1002-8, Section 3.11.0 et sea., and the Colorado Basic Standards and Methodol-
ogies for Surface Water, (CBSM), 5 C.C.R. 3.1.0 e± secj. as ARARs. These standards were
identified in a timely manner, as is required by the NCP. Although the Army has previously
recognized the CBSG as ARARs at interim response actions at the Rocky Mountain Arsenal (RMA),
(See footnote 2, infra.) the Army has failed to acknowledge the CBSG or the CBSM as ARARs for
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the off post operable unit at RMA according to the off post Endangerment Assessment/Feasibility
Study (EA/FS).1
The NCP provides that in order to be recognized as ARARs, state standards must fulfill several
requirements: they must be promulgated; they must be more stringent than the comparable federal
standards; and they must be either 'applicable" or "relevant and appropriate". NCP, 40 C.FJ?.
§300.400(g)(4) (1991). Applying these criteria to the CBSG and the CBSM, it is clear that these
standards are ARARs, and that unless they are explicitly waived according to the six criteria set
forth in §121(d)(4) of CERCLA, these regulations should form the basis for the cleanup of the
off post operable unit at the Rocky Mountain Arsenal.
Response
The Army has recognized all state laws and regulations that meet the applicable or relevant and
appropriate requirement (ARAR) criteria under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) and the NCP. After extensive discussion with all the
parties, the Army has concluded that the Colorado Basic Standards for Groundwater (CBSGs) do
not meet the ARARs criteria because of inconsistent application and ambiguous language.
ARARs for the Off post Operable Unit are based on federal drinking water standards and are
protective of human health. In most cases, the treatment goals for the offpost and boundary
treatment systems exceed the drinking water standards.
CERCLA expressly provides that state standards can be ARARs at a site. However, only those
standards that are more stringent than federal requirements may be considered. In addition, the
state standards must be promulgated (i.e., the requirement must be of general applicability and
legally enforceable). Finally, the requirements must be identified in a timely manner by the
particular state (40 Code of Federal Regulations [CFR] Section 300.400[g][4]).
Regulations promulgated pursuant to the Colorado Water Quality Control Act, Colorado Revised
Statutes (CRS) Sections 25-8-101, et seq., establish standards for groundwater (5 Code of Colorado
Regulations [CCR] 1002-8, Section 3.11.0). A key aspect of the regulation is that Tables 1
through 4 standards are not automatically applicable to groundwater (Section 3.11.7[A]), but apply
only if the aquifer has been classified in accordance with Section 3.11.4.
1 The Army states in the EA/FS that the CBSG are not ARARs because the water near the Arsenal
has not been classified. The Army ignores the fact that the Table Value Standards apply to the
aquifer near the Arsenal pursuant to an interim rule which applies the Table Value Standards to all
unclassified aquifers. See. CBSG, 5 C.C.R. 1002-8, §3.12.5 (1). The Army dismisses the statewide
interim organic standards by stating, without further explanation, that they are not ARARs because
they are ambiguous and inconsistently applied. The Army has not indicated to the State how these
standards are ambiguous, or given examples of inconsistent application. The Army also states that
the CBSM are not ARARs because the remedy does not discharge to surface water. This analysis
fails to recognize that the CBSM are chemical-specific ARARs as well as action-specific ARARs;
they are therefore used to determine whether remedial actions are necessary to protect human health
and the environment from unacceptable risks due to exposures to concentrations exceeding State
standards. Such an evaluation should be conducted for offpost surface water bodies.
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Most aquifers in the state are unclassified. Consequently, the Water Quality Control Commission
(Commission) promulgated the interim narrative standard (Section 3.12.5) for five specified
aquifer systems to avoid degradation of water quality prior to aquifer classification. Each of the
five identified aquifers must meet the standards in Tables 1 through 4 or the ambient quality as of
October 30, 1991, if it was less restrictive, until the aquifers are classified and numerical standards
are adopted.
The Commission promulgated a second group of groundw'ater standards that are applied different-
ly than the standards in Tables 1 through 4. These statewide standards (Section 3.11.5[C]) include
water quality standards for radioactive materials and interim standards for organic pollutants
(Table A), including chloroform. Table A standards differ from the standards in Tables 1 through
4 in an important way: Table A standards are automatically applicable to all state groundwater
(Section 3.11.7[A]). The Commission recognized that the automatic application of Table A
standards can lead to unnecessarily overprotective and technically impracticable results at
contaminated sites and added exceptions to the regulation for remediation activities at CERCLA
sites, Resource Conservation and Recovery Act (RCRA) sites, and underground storage tank
(UST) sites. The CERCLA exception, Section 3.11.5(CX5)(a), states the following:
Nothing in this regulation shall be interpreted to preclude...[a]n agency respon-
sible for implementation of the Comprehensive Environmental Response, Com-
pensation and Liability Act (CERCLA), 42 U.S.C. 9601, et seq., as amended,
from selecting a remedial action and a point of compliance that are more or less
stringent than would be achieved by compliance with the statewide numerical
standards established in this subsection, or alternative site specific standards
adopted by the Commission, when a determination is made that such a variation is
authorized pursuant to the applicable provisions of CERCLA.
Sections 3.11.5(C)(5)(b) and (c) provide similar exceptions for corrective actions under RCRA
Subtitle C (hazardous waste treatment, storage, and disposal facilities) and Subtitle I (UST sites),
respectively.
Section 3.11.5(C)(5) is internally consistent only if the Commission intended not to impose the
interim organic standards in Table A as cleanup standards. According to the regulations, the
interim organic standards automatically apply on a statewide basis, except at CERCLA, RCRA,
and UST sites where "certain federal regulatory determinations regarding groundwater quality
would not be superseded by the Commission's standards" (Section 3.11.10[B]). In promulgating the
Table A exceptions, the Commission recognized that implementing agencies are more familiar
with site-specific conditions and are in a better position to determine the appropriate cleanup
standards. By not imposing unnecessarily stringent application of the Table A standards, the
Commission sought to show "explicit deference to certain federal regulatory programs, which may
apply different standards" (Section 3.11.10[H]).
The Army concludes that the CBSG interim organic standards are not ARARs for two reasons.
First, the CERCLA exception in Section 3.11.5(CX5)(a) applies to remedial actions authorized
under CERCLA that are more or less stringent than would be achieved by compliance with the
statewide standards. As a result, the overall effect of the statewide standard and accompanying
exceptions is a state regulation that is only sometimes more stringent than a federal requirement.
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CERCLA only considers state standards that are stricter at all times as potential ARARs.
Therefore, by definition, the interim organic standards are not ARARs at Superfund sites.
Second, the CBSG interim organic standards cannot be ARARs because they are not generally
applicable or legally enforceable. A requirement in CERCLA for state requirements to be
ARARs is that they must be promulgated standards, which means they must be generally applica-
ble and legally enforceable. Clearly, the interim organic standards do not meet this test when
applied at CERCLA sites. By definition, the interim organic standards are applicable throughout
the state, except at CERCLA, RCRA, and UST sites. In those instances, the relevance of the
standards is determined by the remedial sites. It is hard to understand how the standard could be
legally enforceable when the Commission added language specifically ensuring that the standards
may or may not be met at CERCLA sites.
a. Promulgated
"Promulgated" state requirements include those which are enacted by State legislative bodies
or adopted as regulations by State agencies pursuant to formal rulemaking proceedings, as is
the case with the CBSM and the CBSG. According to the NCP, the standards must also be
generally applicable, and legally enforceable. 40 C.F.R. § 300.400(g)(4) (1991).
1. Legally Enforceable:
State standards are "legally enforceable", according to the preamble to the proposed NCP
if they "contain either specific enforcement provisions, or are otherwise enforceable under
state law." 53 Fed. Reg. 51437-38. They must also be issued in accordance with proce-
dural rules. 40 C.F.R. §§300.400(g)(4) and (5) (1991).
The enabling statute for the Water Quality Control Commission makes it clear that the
regulations promulgated by the Commission, including the CBSG and the CBSM, are
enforceable standards to be applied throughout the State of Colorado. See 25-8-102,25-8-
204(4) C.R.S., (1989 Repl. Vol.). The regulations promulgated by the Commission are
used not only by the Division of Water Quality Control, but also by the other "implementing
agencies" such as the Office of Mined Land Reclamation, the State Engineer, the Oil and
Gas Conservation Commission, agencies responsible for RCRA enforcement, as well as by
other state agencies. 25-8-202, C.R.S., (1992 Supp.).
These regulations are formally promulgated pursuant to an "on the record" administrative
rulemaking proceeding, which includes notice and comment, according to the provisions of
the rules of the Water Quality Control Commission and the Colorado Administrative
Procedure Act. 24-4-101 et. sea.. C.R.S.,(1988 Repl. Vol., and 1992 Supp.). See
generally. CERCLA Compliance with other Laws Manual. Part II. pages 7-2 through 7-4.
Response
See response to Comment No. 4, part 1, given above.
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2. Generally Applicable:
The preamble to the proposed NCP explains that the term "generally applicable" means
that potential state ARARs must be applicable to all remedial situations described in the
requirement, not just CERCLA sites. 53 Fed. Reg. 51437-38. The CBSM and the CBSG
are used as the appropriate cleanup standards in state cleanup and enforcement actions, as
well as at other CERCLA sites within the State of Colorado. The regulations therefore
fulfill the "general applicability" requirement set out in the NCP.2
Response
The state claims in its November 20, 1992, letter that the U.S. District Court for Colorado held
that the CBSG are applicable requirements under CERCLA (Colorado v. Idarado Mining Co..
707 F. Supp. 1227 [D. Colo. 1989]). In its proper context, the case does not hold that the interim
organic standards are ARARs. First, the case merely points out that the State of Colorado
identified the CBSG as an ARAR in its Record of Decision (ROD). Second, the case did not
address the Table A interim organic standards or the CERCLA exception in Section 3.11.5(C)(5)
because those provisions were promulgated after the case was decided. Therefore, the Idarado
case has very little relevance to the application of the Table A standards to the Offpost OU.
b. More Stringent
A comparison of the numeric chemical-specific standards contained in the CBSG and the
CBSM, as well as the narrative standards in both regulations, reveals that in many instances
the Colorado Basic Standards are more stringent than the comparable federal standards. The
State has timely identified the more stringent state standards applicable to specific contam-
inants at the Rocky Mountain Arsenal that are to be recognized and applied as ARARS.3
Response
The Army disagrees with the State's contention that CBSG standards are more stringent for many
of the chemicals listed by the State. These include aldrin, carbon tetrachloride, chloroform, 1,2-
2 There are numerous state compliance actions as well as CERCLA sites in which the CBSG have
been used as a cleanup standard. See, letter from Paul R. Towangeau (AGO), to Elizabeth T. Wald
(EPA), dated November 20,1992, for some of these examples. This letter is hereby incorporated
into these comments by reference. EPA recently affirmed that the CBSG are ARARs at the
CERCLA Wastewater Interim Response Action at the Arsenal. See. Comments on Shell's Request to
Modify CERCLA Wastewater IRA ARARs, attached to letter from Connolly Mears (EPA) to
Charles F. Scharmann (Army), also incorporated by reference. The State does not understand how
EPA can ignore the ARARs for the off post operable unit while simultaneously recognizing these
standards as ARARs at another action at the same site.
3 The chemicals for which the State standards are more stringent include: aldrin, carbon tetra-
chloride, chloroform, 1,2-Dichloroethane, dieldrin and manganese.
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dichloroethane, and dieldrin. For these compounds, the Army's cleanup standards are the
respective certified reporting limits (CRLs).
c. Applicable Requirements
According to the NCP, "Applicable Requirements"
means those cleanup standards, standards of control, or other substantive environ-
mental protection requirements, criteria or limitations promulgated under federal
environmental or state environmental or facility siting law (sic) that specifically
address a hazardous substance, pollutant, contaminant, remedial action, location, or
other circumstance at a CERCLA site.
40 C.F.R. §300.5 and 300.400(g)(l)(1991).
In determining if a requirement is applicable, the Proposed NCP offers some further
guidance. Several jurisdictional prerequisites must be considered:
a. Who, as specified by the statute or regulation, is subject to its authority;
b. The activities the statute or regulation requires, directs or prohibits;
c. The substances or places within the authority of the requirement; and
d. The time period for which the statute is in effect.
53 Fed. Reg. 51436
The CBSG and CBSM are state standards which specifically address the majority of
chemicals of concern at the Rocky Mountain Arsenal. The regulations set standards for those
chemicals in groundwater and surface water, the former being the primary medium of concern
in the off post operable unit. These standards have been applied as both cleanup and anti-
degradation standards, and must be complied with by any person exercising control over the
relevant type of water. The regulations are currently in effect. The CBSG and CBSM are
therefore applicable to the Arsenal, and must be adopted as the appropriate standards for the
remedial action.
The preamble to the Proposed NCP also makes it clear that there is no discretion in the
selection of ARARS when a standard is applicable. "Applicable requirements are identified
by a largely objective comparison to the circumstances at the site; if there is a one-to-one
correspondence between the requirement and the circumstances at the site, then the requirement
is applicable." 53 Fed. Reg. 51436-37.
Response
The Army has reviewed the regulatory language of the CERCLA exception in Section
3.11.5(C)(5)(a) and the accompanying Basis and Purpose, published by the Commission. A careful
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reading of both sources indicates that the Commission did not promulgate the CBSG interim
organic standards as mandatory cleanup standards, but rather as levels to be utilized by remedial
authorities when appropriate.
The regulation states that it does not preclude an implementing agency (e.g., the Army) from
selecting a remedial action (e.g., the selected remedy for the Offpost OU) that is less stringent
than would be achieved by the interim organic standard. Further, a determination must be made
that the selected remedial action is authorized by CERCLA. Several important points can be
drawn from the regulation.
First, the remedial site exceptions in Section 3.11.5(C)(5) are more than merely preemption
statements. In its November 20, 1992, letter, the State suggests that the provision states the
obvious, that the CBSG does not preempt CERCLA. The Army agrees with the State that the
Commission did not intend for the CBSG to preempt CERCLA. But that is only the starting point
for interpreting the regulation. The state appears to have ignored the remainder of the regulatory
language in Section 3.11.5(C)(5)(a).
Second, compliance with the CBSG interim organic standards is not required at remedial sites.
The regulation does not state that the implementing agency must use the statewide standards.
Instead, the regulation is written not to preclude an implementing agency from choosing to use the
statewide standards. This is a critical distinction not addressed by the State. The Commission is
emphasizing that the interim organic standards are not mandatory at certain remedial sites, but
can be used if the implementing agency elects to use them. The logical conclusion is that the
interim organic standards do not apply automatically to CERCLA, RCRA, and UST sites, where
their use is ultimately determined by the remedial authority at the site.
Third, the CERCLA waiver provision is not the sole mechanism for not implementing the CBSG
interim organic standards. The regulation explicitly states that the remedial action, not a
chemical-specific standard, selected by the implementing agency can be more or less stringent
than a remedial action that achieves the CBSG interim organic standard. By referring to the
authority of the implementing agency to select the remedy, the Commission is obviously giving
the exception a broader application than just the statutory waivers in CERCLA. Rather, the
Commission is leaving the decision to apply the Table A standards to the agency authorized under
CERCLA to select the remedial action. This logically leads to the conclusion that the interim
organic standards are not cleanup standards, but merely guidance levels that may or may not be
met at CERCLA, RCRA, and UST sites where statutory standards protective of the environment
are already incorporated into the remedial process.
Section 3.11.5(C)(5) is internally consistent only if the Commission intended not to impose the
interim organic standards in Table A as cleanup standards. According to the regulations, the
interim organic standards automatically apply on a statewide basis, except at CERCLA, RCRA,
and UST sites where "certain federal regulatory determinations regarding groundwater quality
would not be superseded by the Commissions's standards" (Section 3.11.10[B]). In promulgating
the Table A exceptions, the Commission recognized that implementing agencies are more familiar
with site-specific conditions and are in a better position to determine the appropriate cleanup
standards. By not imposing unnecessarily stringent application of the Table A standards, the
Commission sought to show "explicit deference to certain federal regulatory programs, which may
apply different standards" (Section 3.11.10[H]).
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The Army concludes that the CBSG interim organic standards are not ARARs for two reasons.
First, the CERCLA exception in Section 3.11.5(C)(5)(a) applies to remedial actions authorized
under CERCLA that are more or less stringent than would be achieved by compliance with the
statewide standards. As a result, the overall effect of the statewide standard and accompanying
exceptions is a state regulation that is only sometimes more stringent than a federal requirement.
CERCLA only considers state standards that are stricter at all times as potential ARARs.
Therefore, by definition, the interim organic standards are not ARARs at Superfund sites.
Second, the CBSG interim organic standards cannot be ARARs because they are not generally
applicable or legally enforceable. A requirement in CERCLA for state requirements to be
ARARs is that they must be promulgated standards, which means they must be generally applica-
ble and legally enforceable. Clearly, the interim organic standards do not meet this test when
applied at CERCLA sites. By definition, the interim organic standards are applicable throughout
the state, except at CERCLA, RCRA, and UST sites. In those instances, the relevance of the
standards is determined by the remedial sites. It is hard to understand how the standard could be
legally enforceable, when the Commission added language specifically ensuring that the standards
may or may not be met at CERCLA sites.
d. Relevant and Appropriate
The State contends that the CBSG and the CBSM are applicable to the Rocky Mountain
Arsenal offpost operable unit. Regardless, they are, at a minimum, "relevant and appropri-
ate." The NCP defines "relevant and appropriate" as
those cleanup standards, standards of control, and other substantive requirements,
criteria, or limitations promulgated under federal environmental or state environ-
mental 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 encoun-
tered at the CERCLA site that their use is well suited to the particular site.
40 C.F.R. §300.5(1991).
It has been suggested that the CBSG and the CBSM are not ARARs because they do not
specifically state that they are cleanup standards. These standards are being used by the
Water Quality Control Division, as well as by the other implementing agencies as cleanup
standards, thereby leading to the conclusion that the regulations are "relevant and appropri-
ate".4
4 // has also been suggested that the regulations are "merely" anti-degradation standards. This
label, however, does not mean that the regulations are not ARARs. Both the NCP and EPA guidance
make it very clear that anti-degradation statutes ace frequently ARARs. See. Preamble, 55 Fed.
Reg. 8746, and CERCLA Compliance with Other Laws Manual: Part II. pages 7-28, and 7-30.
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The NCP includes eight factors to be considered in determining relevance and appropriate-
ness:
i. The purpose of the requirement and the purpose of the CERCLA action;
ii. The medium regulated or affected by the requirement and the medium contaminated or
affected at the CERCLA site;
Hi. The substances regulated by the requirement and the remedial action contemplated at the
CERCLA site;
iv. The actions or activities regulated by the requirement and the remedial action contem-
plated by the CERCLA action:
v. Any variances, waivers, or exemption of the requirement and their availability at the
CERCLA site;
vi. The type of place regulated and the type of place affected by the release or CERCLA
action;
vii. The type and size of structure or facility regulated and the type and size of structure or
facility affected by the release or contemplated by the CERCLA action;
viii. Any consideration of use or potential use of affected resources in the requirement and the
use or potential use of the affected resource at the CERCLA site.
40 C.F.R. §300.400(g) (2) (1991).
An examination of these eight factors leads to the conclusion that the CBSG and the CBSM
are relevant and appropriate. The media, the substances, the actions, the type of place, the use
and potential use of the affected resources which are covered by the CBSG and the CBSM are
identical to those at the Rocky Mountain Arsenal. These regulations are therefore "relevant
and appropriate."
Thus, the CBSG and the CBSM fulfill all the prerequisites to be ARARs under the NCP. They
are promulgated state standards, both generally applicable and legally enforceable; they are
more stringent than the relevant federal standards; and they are applicable or relevant and
appropriate. It is therefore contrary to CERCLA and the NCP to fail to identify them as
ARARs and to apply the less stringent federal standards as the basis for cleanup at RMA's
off post operable unit.1
s The Army has previously raised the question of whether 5 C.C.R.1002-8, §3.11.5 (C)(5)(a),
constitutes a "CERCLA exemption" from the provisions of the CBSG. That section of the CBSG
merely states the obvious, that when CERCLA dictates a standard other than that prescribed in the
regulations, CERCLA is not preempted by the CBSG. See. Letter from Paul R. Tourangeau (AGO),
to Elizabeth T. Wald (EPA), dated November 20, 1992, responding to a request for clarification of
the general applicability and legal enforceability of the CBSG.
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Response
See response to comment to Comment No. 4 Part c given above.
e. Secondary Maximum Contaminant Levels
The Army in its Proposed Plan has failed to acknowledge secondary MCLs as ARARs. The
secondary MCLs, promulgated pursuant to the Safe Drinking Water Act, 42 U.S.C.300g-l(c)
(1992), address a contaminant "(A) which adversely affect the odor or appearance of such
water and consequently may cause a substantial number of the persons served by the public
water supply to discontinue its use, or (B) which may otherwise adversely affect the public
welfare." 42 U.S.C. 300(f)(2) (1992). The secondary MCLs, while not federally enforce-
able, are nevertheless relevant and appropriate as "guidelines for the States." 40 C.F.R. 143.3
(1992). The State of Colorado, moreover, has promulgated secondary drinking water
standards, and incorporated those standards in the Colorado Basic Standards for Ground-
water. 5 C.C.R. 1002-8, Table 2. The numeric standards contained in Colorado's regulations
are the same as in the federal regulations. The State maintains that these standards are
ARARs, and must be addressed by the Army in the Proposed Plan. Specifically, chloride
samples since June 1992 show exceedances of the secondary standard of 250 ppm during the
3rd and 4th quarters of 1992. Likewise, fluoride and manganese data illustrate a history of
exceedances of their secondary MCLs of 2 and 500 ppm, respectively.
Response
Regulations promulgated pursuant to the Colorado Water Quality Control Act, Colorado Revised
Statutes (CRS) Sections 25-8-101, et seq., establish standards for groundwater (5 Code of Colorado
Regulations [CCR] 1002-8, Section 3.11.0). These regulations create a system for classifying
groundwater and adopting water quality standards to protect existing and potential beneficial uses
(Tables 1 through 4). Groundwater is categorized into five classifications on the basis of use
(Section 3.11.4[A]). Standards specified in the regulation are then applied to the classified aquifer
(Tables 1 through 4; e.g., human health standards, secondary drinking water standards, agricul-
tural standards, and total dissolved solids [TDS] water quality standards). A key aspect of the
regulation is that Tables 1 through 4 standards are not automatically applicable to groundwater
(Section 3.11.7[A]), but apply only if the aquifer has been classified in accordance with
Section 3.11.4. Since the off post aquifers have not been classified by the State, Tables 1 through 4
are not automatically applicable.
The Water Quality Control Commission (Commission) also promulgated the interim narrative
standard (Section 3.12.5) for five specified aquifer systems in order to avoid degradation of water
quality prior to aquifer classification. Each of the five identified aquifers must meet the Tables 1
through 4 standards or the ambient quality as of October 30, 1991, if it was less restrictive, until
the aquifers are classified and numerical standards are adopted. However, the Offpost Study Area
does not fall within any of the five specified aquifer systems; consequently, Tables 1 through 4
(including the secondary drinking water standards in Table 2) do not apply.
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Comment No. 5 - Surface Water
The Army's Off post Proposed Plan indicates that no active remediation is planned for surface
water off post; the Army maintains that surface water will be cleaned up as a result of ground-water
remediation. The Army has not provided any estimation of how long this will take: nor is any
future sampling planned to verify this expected improvement of surface water quality.
According to the surface water data available for First Creek, contaminants of concern such as
chlordane, dieldrin, endrin and DDT exceed the state aquatic life chronic standards. As the Army
readily admits in the Off post Endangerment Assessment/Feasibility Study Final Report, page III-
5-30, "chlordane, dieldrin, fluoride and DDT appear to present a potential for an adverse effect to
aquatic life in First Creek, based on a comparison of exposure point concentrations in surface water
to TRV's (chronic AWQC values) for aquatic life" The State believes that these contaminants
should be addressed in the Off post Proposed Plan.
The State agrees with the position that EPA took on this issue a year ago. "The Army has not
provided an objective evaluation of possible alternatives for the remediation of the contaminated
surface water other than concluding that the remediation of the groundwater would remediate the
surface water. The time frame and costs for remediation of surface water are not identified, even
within the context of the remediation of the groundwater, since a portion of these elements reside in
the remediation costs and time frame for the Onpost OU, for which the FS has not yet been
prepared." (See, letter from Connolly Mears, EPA, to Kevin Blose, U.S. Army, dated May 6, 1992).
The Army has justified its failure to examine alternatives for surface water cleanup off post mainly
by stating that because First Creek is a gaining stream in the off post area, the Creek will be
eventually cleaned up as the groundwater is flushed by the North Boundary Containment System.
In the Army's response to a state comment (Offpost Endangerment Assessment/Feasibility Study,
Proposed Final Report, Vol. 8, pg.78) the Army states: "Groundwater interaction with First Creek
surface water is known to occur in First Creek between the northern RMA boundary and the
confluence of First Creek with O'Brian Canal. This interaction of off post groundwater with First
Creek surface water is quite complex. Seasonal fluctuations in the water table and seasonal
fluctuations in First Creek flow rate result in gaining and losing stretches of First Creek, that vary
temporally. Further, slight variations in the water table elevation and in the First Creek stream
elevation along the length of First Creek result in spacial variations in stretches identified as
gaining or losing independent of the season.'' The Army also states on pg. 76 of the same volume:
"The secondary source of surface water in First Creek off post is watershed runoff." The State
agrees that remediation of groundwater should have a positive net effect on surface water quality
off post. Given the complexity of groundwater/surface water interaction off post and the potential
contribution of contamination resulting from overland flow during storm events, however, the State
remains concerned with the lack of consideration given to the surface water medium by the Army.
The State believes the Army should evaluate remedial alternatives in order to meet state surface
water quality standards in First Creek. In addition, we urge the Army to commit to future sampling
to ensure these standards are achieved.
Response
Given that the following three factors point to continuing beneficial impacts to offpost water
quality, the Army is committing to an ongoing surface-water monitoring program to track the
cleanup of offpost surface water (1) remediation of groundwater should have a beneficial effect
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on offpost surface-water quality, (2) contaminant concentrations are lower during storm event
runoff periods (Surface Water Comprehensive Monitoring Program Annual Report for 1989 [R.L.
Stellar & Associates, and others, 1990]), and (3) the Army has committed to closing the onpost
sewage treatment plant, thus eliminating a possible source of contaminants in the First Creek
surface water drainage.
The components of the offpost surface-water monitoring program will be contained in a report to
be completed following completion of the ROD. The ROD contains the Army commitment to
both surface-water and groundwater monitoring programs in the offpost area as a component of
the selected remedy.
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Appendix A-4
RESPONSES TO REGION VIII
U.S. ENVIRONMENTAL PROTECTION AGENCY COMMENTS
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO REGION VIII U.S. ENVIRONMENTAL PROTECTION AGENCY
COMMENTS REGARDING THE ROCKY MOUNTAIN ARSENAL
OFFPOST PROPOSED PLAN
JUNE 17, 1993
GENERAL COMMENTS
Comment No. 1 - Irondale Boundary Control System (IBCS)
Along with the north and northwest boundary control system, the IBCS must also be committed by
the Off post Record of Decision (ROD) to continue to operate as required in the Federal Facilities
Agreement (FFA). We understand this omission from the Proposed Plan to be unintentional.
Response
Continued operation of the Irondale Boundary Containment System has been included as a
component of the selected remedy in the Offpost Record of Decision (ROD).
Comment No. 2 - Continued Operation of Three Boundary Systems
The Offpost ROD will have to select the Federal Facilities Agreement requirement at Section 2.7
(regarding ground water quality flowing off post). The three boundary systems must be required to
continue operation, as necessary to accomplish that obligation.
Response
Continued operation of the three boundary containment systems is required as part of the selected
remedy in the Offpost ROD.
Comment No. 3 - Acknowledging the State Ground Water Regulations as Legal Standards:
EPA considers the Colorado Basic Standards for Ground Water (CBSGs) to be Action Specific
ARARs (and has adopted them on other Superfund sites, as well as for RMA IRAs). EPA's use of
this regulation as an Action Specific ARAR is to require that cleanup activities do not degrade the
quality of existing ground water during response activities. This is consistent with such ARARs as
Section 7020 of RCRA, which are established to improve ground water quality without setting
specific standards. EPA also believes that the CBSGs should be used to establish chemical specific
remediation levels. The clear language of the regulation allows for the establishment, for
CERCLA, RCRA, and UST sites, of cleanup levels which differ from the standards set forth in the
Tables, therefore, those tables do not provide a chemical specific numerical standard for CERCLA
actions. Nevertheless, chemical specific cleanup levels should be derived using the site specific
exemption language and the procedure provided by the CBSGs to set protective levels for cleanup.
Response
The Army has recognized all state laws and regulations that meet the applicable or relevant and
appropriate requirement (ARAR) criteria under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) and the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP). After extensive discussion with all the parties, the Army has
concluded that the Colorado Basic Standards for Groundwater (CBSGs) do not meet the ARARs
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criteria because of inconsistent application and ambiguous language. ARARs for the Offpost
Operable Unit are based on federal drinking water standards and are protective of human health.
In most cases, the treatment goals for the off post and boundary containment systems are more
protective than the drinking water standards.
CERCLA expressly provides that state standards can be ARARs at a site. However, only those
standards that are more stringent than federal requirements may be considered. In addition, the
state standards must be promulgated (i.e., the requirement must be of general applicability and
legally enforceable). Finally, the requirements must be identified in a timely manner by the
particular state (40 Code of Federal Regulations [CFR] Section 300.400[g][4]).
Regulations promulgated pursuant to the Colorado Water Quality Control Act, Colorado Revised
Statutes (CRS) Sections 25-8-101, et seq., establish standards for groundwater (5 Code of Colorado
Regulations [CCR] 1002-8, Section 3.11.0). A key aspect of the regulation is that Tables 1
through 4 standards are not automatically applicable to groundwater (Section 3.11.7[A]), but apply
only if the aquifer has been classified in accordance with Section 3.11.4.
Most aquifers in the state are unclassified. Consequently, the Water Quality Control Commission
(Commission) promulgated the interim narrative standard (Section 3.12.5) for five specified
aquifer systems to avoid degradation of water quality prior to aquifer classification. Each of the
five identified aquifers must meet the standards in Tables 1 through 4 or the ambient quality as of
October 30, 1991, if it was less restrictive, until the aquifers are classified and numerical standards
are adopted.
The Commission promulgated a second group of groundwater standards that are applied different-
ly than the standards in Tables 1 through 4. These statewide standards (Section 3.11.5[C]) include
water quality standards for radioactive materials and interim standards for organic pollutants
(Table A), including chloroform. Table A standards differ from the standards in Tables 1 through
4 in an important way: Table A standards are automatically applicable to all state groundwater
(Section 3.11.7[A]). The Commission recognized that the automatic application of Table A
standards can lead to unnecessarily overprotective and technically impracticable results at
contaminated sites and added exceptions to the regulation for remediation activities at CERCLA
sites, Resource Conservation and Recovery Act (RCRA) sites, and underground storage tank
(UST) sites. The CERCLA exception, Section 3.11.5(C)(5)(a), states the following:
Nothing in this regulation shall be interpreted to preclude...[a]n
agency responsible for implementation of the Comprehensive
Environmental Response, Compensation and Liability Act
(CERCLA), 42 U.S.C. 9601, et seq., as amended, from selecting a
remedial action and a point of compliance that are more or less
stringent than would be achieved by compliance with the statewide
numerical standards established in this subsection, or alternative site
specific standards adopted by the Commission, when a determina-
tion is made that such a variation is authorized pursuant to the
applicable provisions of CERCLA.
Sections 3.11.5(C)(5)(b) and (c) provide similar exceptions for corrective actions under RCRA
Subtitle C (hazardous waste treatment, storage, and disposal facilities) and Subtitle I (UST sites),
respectively.
Section 3.11.5(C)(5) is internally consistent only if the Commission intended not to impose the
interim organic standards in Table A as cleanup standards. According to the regulations, the
interim organic standards automatically apply on a statewide basis, except at CERCLA, RCRA,
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and UST sites where "certain federal regulatory determinations regarding groundwater quality
would not be superseded by the Commission's standards" (Section 3.11.10[B]). In promulgating the
Table A exceptions, the Commission recognized that implementing agencies are more familiar
with site-specific conditions and are in a better position to determine the appropriate cleanup
standards. By not imposing unnecessarily stringent application of the Table A standards, the
Commission sought to show "explicit deference to certain federal regulatory programs, which may
apply different standards" (Section 3.11.10[H]).
The Army concludes that the CBSG interim organic standards are not ARARs for several reasons.
The CERCLA exception in Section 3.11.5(C)(5)(a) applies to remedial actions authorized under
CERCLA that are more or less stringent than would be achieved by compliance with the statewide
standards. As a result, the overall effect of the statewide standard and accompanying exceptions
is a state regulation that is only sometimes more stringent than a federal requirement. CERCLA
only considers state standards that are stricter at all times as potential ARARs. Therefore, by
definition, the interim organic standards are not ARARs at Superfund sites.
Second, the CBSG interim organic standards cannot be ARARs because they are not generally
applicable or legally enforceable. A requirement in CERCLA for state requirements to be
ARARs is that they must be promulgated standards, which means they must be generally applica-
ble and legally enforceable. Clearly, the interim organic standards do not meet this test when
applied at CERCLA sites. By definition, the interim organic standards are applicable throughout
the state, except at CERCLA, RCRA, and UST sites. In those instances, the relevance of the
standards is determined by the remedial sites. It is hard to understand how the standard could be
legally enforceable, when the Commission added language specifically ensuring that the standards
may or may not be met at CERCLA sites.
Comment No. 4 - Institutional Controls
Use of Institutional Controls presently exists in the Off post in the form of permitting and
development laws, etc. This concept is not limited to deed restrictions or prohibitions on use of
property. The Proposed Plan could have acknowledged that Institutional Controls will be consi-
dered; however, the ROD should select them, as necessary, to ensure protection of human health and
the environment. They can be refined in the design and remedial activity phases, or anytime on
data review, via an appropriate process (e.g., a ROD Amendment or Explanation of Significant
Difference (BSD)).
Response
Institutional controls have been included as a component of the selected remedy in the Offpost
ROD.
Comment No. 5 - Contamination in the Deeper Aquifer
The Abandoned Well Closure IRA was expanded to address off post wells, and such activities must
be required in the Offpost ROD. The parties need to discuss the criteria that will be used to trigger
such activities.
However, the Army's draft response to the State's concern does not specifically address the issue.
Given that some twenty wells are currently identified and information exists on them, a more
detailed response should be given. The Army acknowledges its current well closure plan but does
not describe it; therefore, there is no information on closure to apply to the specific conditions of
the wells. Since such information exists, it should be provided in that response.
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Response
Well closure activities have been included as a component of the selected remedy. Appendix C of
the ROD provides the criteria for closure of abandoned wells.
Comment No. 6 - Flexible Implementation of the Remedy
EPA's final concern is to ensure expeditious implementation of the flexibility for change in the
Army's preferred alternative, in light of recent information received indicating that DIMP exists
above health based levels north of (i.e. beyond) the Off post IRA Intercept and Treatment System
for the ground water plumes. Discussions have begun on the first step, which is to obtain additional
sampling data to better characterize the area beyond the current intercept location. EPA expects
that, to the maximum extent possible, such information will be used to evaluate potential modifica-
tion of the current system, prior to the Off post ROD. EPA, at this time, concurs with the Army's
preferred remedy (pending evaluation of State and public concerns), due to its inherent flexibility.
If information cannot be timely developed before the ROD, the option will still be available to later
select and implement change, via an appropriate process (e.g., ROD amendment or ESD). The
parties need to discuss this matter further.
Response
In the area north of the Offpost Groundwater Intercept and Treatment System, the Army intends
to replace three groundwater monitoring wells and install three new groundwater monitoring
wells. The Army has provided this information to the Organizations and State in a letter report
with accompanying map showing proposed monitoring well locations. The purpose of the three
new monitoring wells is to aid in assessing the extent of contamination downgradient of the
Offpost Groundwater Intercept and Treatment System. Data collected from these wells and
existing wells will be used to further define the extent of contamination greater than the
remediation goals in this area and to evaluate whether modifications to the Offpost Groundwater
Intercept and Treatment System are necessary.
Comment No. 7 - Exposure Pathway of Dermal Contact with Ground water
On page 5, Column I, of the Proposed Plan, when discussing Exposure Pathways, the word "Ground
water" was omitted from the first bullet of the "Dermal" section. The omission of the word ground
water is not consistent with the Dispute Resolution Agreements of May 5, 1992, which exclude only
Zones 3 & 4 from using ground water for domestic purposes.
Response
The omission of "groundwater" was inadvertent. Dermal contact with groundwater was evaluated
in the Endangerment Assessment.
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Appendix A-5
RESPONSES TO CITY AND COUNTY GOVERNMENT COMMENTS
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RESPONSES TO TRI-COUNTY HEALTH DEPARTMENT COMMENTS
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO TRI-COUNTY HEALTH DEPARTMENT COMMENTS
REGARDING THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JUNE 21, 1993
Comment 1 - Preferred Alternative
We concur that Alternative N-4, Offpost Intercept and Treatment Systems, presents an
appropriate treatment system to reduce shallow alluvial unconfined aquifer contamination. Since
much of the excess risk in the offpost area is from the groundwater, limiting this exposure
pathway is of primary importance. Along with the operation of this system an aggressive tap and
monitoring well surveillance program should be maintained to evaluate success of this treatment
system and to identify any other areas of concern.
Enhancement of N-4, such as is proposed in N-5 to provide more aggressive treatment within the
same cost parameters should be evaluated with implementation reconsidered, if determined to be
feasible and effective. We are concerned, however that more aggressive treatment within the same
cost parameters should be evaluated with implementation reconsidered, if determined to be
feasible and effective. We are concerned, however that more aggressive treatment may alter the
groundwater flow such that it will be more difficult to predict the effectiveness of the remedy
and the time required for completion. If such alternatives are reconsidered the Army should
verify the reliability of the assumptions used in the model from which the cleanup time is
calculated. Based on continued monitoring of domestic water supplies and assurance that exposure
pathways for consumption of contaminated groundwater are not complete, the time required to
implement the alternative becomes less critical particularly if it increases the complexity and
uncertainty associated with implementation.
Tri-county also endorses the continued operation and expansion, as necessary, of the North
Boundary, Northwest Boundary and the Irondale Groundwater intercept and treatment systems to
prevent further offpost migration of the contaminated unconfined/alluvial groundwater.
Response 1
The Army agrees that an evaluation of the potential need to enhance Alternative N-4 is appropri-
ate. Collection and evaluation of site-specific operational data during the initial phases of
operation of the Offpost Groundwater Intercept and Treatment System will be the basis for
assessing the need for design modifications. Continued operation of the three existing boundary
containment systems is a part of the selected alternative. A tap water and groundwater monitoring
program is included as a component of the preferred alternative.
Comment 2 - PIMP
We are concerned about the repeated detection of high concentrations of DIMP in the well
identified as TCHD Well 1178B, downgradient of the proposed intercept system described in N-4.
Although there is historical evidence of a high concentration of DIMP in this well, this anomaly
has not been adequately explained. We are particularly interested in whether further
characterization of the problem with that well will impact the anticipated effectiveness of
Alternative N-4 and what additional action will be taken to remediate the shallow alluvial
unconfined aquifer in that area.
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Response 2
The Offpost Groundwater Intercept and Treatment System is located in areas of highest contami-
nant concentrations. The Army is aware that concentrations of diisopropyl methylphosphonate
(DIMP) greater than 600 parts per billion (ppb) have been reported north of the Offpost Intercept
and Treatment System. In that regard, the offpost remedial action groundwater monitoring
program will be coordinated with the three existing groundwater monitoring programs active in
the Offpost Study Area. These three programs are (1) the Groundwater Monitoring Program, (2)
the Interim Response Action A Monitoring Program, and (3) the private well monitoring program.
Additionally, in the area north of the Offpost Groundwater Intercept and Treatment System
where DIMP has been reported to exceed 600 ppb, three monitoring wells will be replaced and
three new monitoring wells will be installed. Replacement wells are being installed for wells
originally in the monitoring network that were found to be damaged or destroyed. Two new
monitoring wells will be installed downgradient of the First Creek Pathway and one new
monitoring well will be installed downgradient of the Northern Pathway. The Army has provided
information regarding the additional monitoring wells to the Organizations, State, and Tri-County
Health Department in a letter report and accompanying map showing the locations of the proposed
monitoring well locations. The purpose of the three new monitoring wells is to aid in assessing the
extent of contamination downgradient of the Offpost Groundwater Intercept and Treatment
System. Data collected from these wells and existing wells will be used to further define the
extent of contamination greater than the remediation goals in this area and assist in determining
whether modifications to the Offpost Groundwater Intercept and Treatment System are necessary.
Comment 3 - Risk Levels Used To Initiate Cleanup
We are aware of some discussion concerning the risk level that should initiate the need for cleanup
action. If 1 x 10-4 were used to trigger cleanup what additional offpost areas would require
attention? It is our opinion that the National Contingency Plan guidelines should be followed. We
also understand that there may be different interpretations of NCP guidance. The overriding
issue to Tri-County is what is the likelihood o guidance. The overriding issue to Tri-county is
what is the likelihood of exposure to Arsenal contaminants and the risk associated with that
exposure. Based on our analysis of the available information we see no need, at this time, to
consider a change in the proposed plan based on the risk level trigger utilized. We would request
further discussion concerning this issue which may result in additional comment.
Response 3
The Army has closely followed U.S. Environmental Protection Agency (EPA) guidance and the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP) regarding the use of the
10"4 risk threshold to assess whether remediation is necessary. Guidance states that if the
cumulative cancer risk to an individual is less than 10"*, remedial action may not be warranted
unless certain site-specific conditions exist. If remedial action is warranted, the 10"4 to 10"6 risk
range must be achieved, with an initial preference for the 10"* end. EPA guidance further states
that the upper boundary of the risk range is not an absolute at 1 x 10"4, but rather, the acceptable
risk range can extend to 5 x 10"4. The cumulative offpost cancer risk is a maximum of 3 x 10"4,
which is within the acceptable risk range. The Army's goal, through operation of the Offpost
Groundwater Intercept and Treatment System, is to further reduce offpost risk toward the 10"6
level.
The Offpost Study Area risk assessment showed that, even without remedial action, the baseline
cumulative risks from contamination in surface water, soil, sediment, air, and groundwater are
within the acceptable risk range established by the EPA. However, several site-specific factors
930423A.enc 2
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suggest that remedial alternatives for groundwater should be considered. These site-specific
factors consider (1) that groundwater contributes approximately 73 percent of the total baseline
risk, (2) maximum contaminant levels (MCLs) and maximum contaminant level goals (MCLGs)
are exceeded for some groundwater contaminants, and (3) hazard indices (His) for children
slightly exceed 1.0 in zones 2, 3, and 4. Through operation of the Off post Groundwater Intercept
and Treatment System and attainment of the cleanup standards specified in the Record of
Decision (ROD), the Army intends to further reduce risks toward the 10"6 level.
Comment 4 - Inter-aquifer Migration
To prevent contamination of the Arapahoe aquifer from the migration of shallow groundwater
containing Arsenal contaminants and to assure the long term quality and safety of the Arapahoe
aquifer as a drinking water source we urge the Army to close/seal all wells that penetrate more
than one aquifer and are poorly constructed or otherwise damaged or abandoned. This action
should be taken in accordance with Rule 11 -Abandonment Standard of the State of Colorado,
Office of the Engineer. A list of the known wells that present a threat, as described, is available
as a result of our ongoing Offpost Private Well Inventory. The prevention of interaquifer
migration should be identified as a high priority by the Army in order to avoid degradation of the
Arapahoe aquifer.
Response 4
Well closure has been added as a component of the selected remedy. Appendix C of the ROD
describes criteria for well closure. Table C.I in Appendix C presents the wells identified by the
Colorado Department of Health (CDH) and the Tri-County Health Department (TCHD) as
candidate wells for closure. The Army will review the information available for the candidate
wells for closure and present recommendations for closure to CDH, TCHD, and EPA. Several of
these wells have been identified as no longer in use. As noted in the comment, Rule 11.1.1 of the
Abandonment Standards states that it is the responsibility of the well owner to plug and abandon
unused wells properly.
Comment 5 - Control of New Well Construction
We recommend the use of institutional controls to prevent the construction of wells allowing use
of the unconfined alluvial groundwater that may contain Arsenal contaminants. It is our
understanding that the State Engineer's office is responsible for issuing well permits and has, to
date, not established a policy preventing, or at least controlling, the construction of new wells in
the offpost area. The Army, EPA, the Colorado Department of Health and Tri-County Health
Department should meet with the State Engineer and insist that action be taken to assure that
future exposure to Arsenal contaminants cannot take place through consumption of water from
new wells that are constructed.
Further, those agencies should work with the State Engineer to assure adequate
oversight of the construction of all new water wells in the offpost areas to control the potential for
future aquifer contamination.
Response 5
Institutional controls have been added as a component of the selected remedy. Appendix B of the
ROD provides an evaluation of the institutional controls available and their applicability. These
controls include prohibitions on well construction in areas where groundwater contaminant
concentrations exceed cleanup standards and potential well bans in larger areas.
930423A.enc 3
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Comment 6
The Army should commit to review of the Proposed Plan in view of future changes in zoning and
land use that are proposed for offpost areas 3 and 4. The Army should work with Adams County
and/or Commerce City to ensure that any proposed change in land use designation for the offpost
areas 3 and 4 will require consideration, with opportunity for public input, of the potential for an
increase or decrease in risk to health associated with exposure to Arsenal contaminants. Further
clean-up may then be required based on the risk that is calculated and the land use designation
proposed. Changes by County or City in land use designation should not result in increased risk to
the public. Although all feasible land uses should be considered in the Endangerment Assessment
it is Tri-county's opinion that the remedy should also be based on a realistic scenario with a clear
commitment to re-evaluate, as necessary, not one that is unduly speculative.
Response 6
The Army is committed to working with Adams County and/or Commerce City to assure that
human health is protected in the event that offpost zoning and/or land use changes in the future.
The land use scenarios studied in the final Offpost Endangerment Assessment are extremely
conservative and provide protectiveness for a range of future land uses. Given the probability of
the realignment and widening of 96th Avenue, future development along 96th Avenue will likely
be commercial/industrial or urban residential. Based on local agency planning documents the
Army has selected an urban residential land use for the risk evaluation as this would result in
more conservative (e.g., higher) estimated risks than the likely commercial/industrial land use. In
addition, the institutional controls described in Appendix B of the ROD provide additional
protection of the public in the event of future land use changes.
Comment 7 - Colorado Standards As ARAR's
We request that the Army provide an explanation of what Colorado standards were not designated
as ARAR's and why. Based on this response we may have further questions or comments on the
subject of ARAR's.
Response 7
The Army has recognized all state laws and regulations that meet the applicable or relevant and
appropriate requirement (ARAR) criteria under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) and the NCP. After extensive discussion with the
Organizations and State the Army has concluded that the Colorado Basic Standards for Ground-
water (CBSGs) do not meet the ARARs criteria because of inconsistent application and ambiguous
language. ARARs for the Offpost Operable Unit are based on federal drinking water standards
and are protective of human health. In most cases, the treatment goals for the offpost and
boundary treatment systems exceed the drinking water standards.
CERCLA expressly provides that state standards can be ARARs at a site. However, only those
standards that are more stringent than federal requirements may be considered. In addition, the
state standards must be promulgated (i.e., the requirement must be of general applicability and
legally enforceable). Finally, the requirements must be identified in a timely manner by the
particular state (40 Code of Federal Regulations [CFR] Section 300.400[g][4]).
The Army concludes that the CBSG interim organic standards are not ARARs for two reasons.
First, the CERCLA exception in Section 3.11.5(CX5)(a) applies to remedial actions authorized
under CERCLA and allows the selection of a remedy that is more or less stringent than would be
930423A.enc 4
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achieved by compliance with the statewide standards. As a result, the overall effect of the
statewide standard and accompanying exceptions is a state regulation that is only sometimes more
stringent than a federal requirement. CERCLA only considers state standards that are stricter at
all times as potential ARARs. Therefore, by definition, the interim organic standards are not
ARARs at Superfund sites.
Second, the CBSG interim organic standards cannot be ARARs because they are not generally
applicable or legally enforceable. A requirement in CERCLA for state requirements to be
ARARs is that they must be promulgated standards, which means they must be generally
applicable and legally enforceable. Clearly, the interim organic standards do not meet this test
when applied at CERCLA sites. By definition, the interim organic standards are applicable
throughout the state, except at CERCLA, RCRA, and UST sites. In those instances, the relevance
of the standards is determined by the remedial sites. It is hard to understand how the standard
could be legally enforceable when the Commission added language specifically ensuring that the
standards may or may not be met at CERCLA sites.
For additional discussion, see response to State comment No. 4 in Appendix A-3 of the ROD.
Comment 8 - Soil Contamination In Zones 3 and 4
There was a wide range of results from surficial soil sampling for pesticides in Zones 3 & 4. The
risk for each area was calculated based on an average of all samples in that area. We are
concerned that the risk for selected areas, in which the highest concentrations of dieldrin were
found, may be understated through the averaging process. Has the Army evaluated what risk is
associated with each "hot spot?" What is the potential for completing the pathway for exposure of
current or future residents or others to that increased risk? We are concerned that there has not
been adequate characterization of the risk in those Zones, both of the concentration and source of
dieldrin contamination.
Response 8
The Army used a large amount of onpost and offpost surface soil data to interpret Rocky
Mountain Arsenal (RMA)-related soil contamination. The combination of onpost and offpost data
demonstrates that detected concentrations of contaminants offpost are attributable to windblown
transport from RMA and to offpost activities, including agricultural application of pesticides.
Localized areas of high dieldrin concentrations are unlikely to result from windblown contami-
nants. Windblown contamination would more likely result in a uniform deposition.
Because of the extensive agricultural activities that have occurred in areas north and east of the
RMA boundaries and the application of registered pesticides that are a consequence of agricul-
tural activities, it is not unusual to find dieldrin residues in soil. Examination of organochlorine
pesticide data obtained from onpost surface soil samples does not support RMA as being the
source for organochlorine pesticide transport east of RMA. In addition, five samples collected
east of RMA have dieldrin concentrations ranging from nondetectable to approximately 25 ppb.
On this basis, it is the Army's position that the dieldrin detected at 99 ppb east of RMA is not
related to onsite activities. This value is at the lower end of EPA's acceptable risk range as
specified in the NCP. Therefore, the incorporation of this single value would not have affected
the final results of the risk assessment.
930423A.enc
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Comment 9 - Public Water Supply
Arsenal contaminants, regardless of concentration, have impacted the quality of alluvial ground
water, in the offpost area, which is used for domestic purposes. There are also other potential
sources of such contamination within the same aquifer for which the Army is not responsible.
Whereas there may not be a violation of existing drinking water standards or health advisories
and, therefore, no imminent public health hazard, the Army should work with other agencies,
residents and elected officials that are considering alternative strategies to secure a higher quality
and possibly safer domestic water supply for residents in the area.
Response 9
The Army has committed, as part of the Preferred Alternative, that anyone who is drinking water
with Arsenal related contaminants above applicable, relevant, and appropriate drinking water
standards will be provided an alternative water supply. At this time, the Army is not planning to
provide a public water supply to residents offpost and cannot unless drinking water standards are
being exceeded over a large area.
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Office of the Program Manager
Mr. Chris Wiant, M.A., M.P.H.
Director of Environmental Health Services
Tri-County Health Department
4301 East 72nd Avenue
Commerce City, Colorado 80022-1488
Dear Mr. Wiant:
Enclosed are responses to your comments on the Offpost Proposed Plan for
the Rocky Mountain Arsenal. The Army appreciates the large number of comments
submitted on the Offpost Proposed Plan. I hope these responses increase your
understanding of the offpost cleanup.
If you have any further questions please contact Mr. Tim Kilgannon of my
staff at (303) 289-0201.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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RESPONSES TO CITY OF COMMERCE CITY COMMENTS
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO CITY OF COMMERCE CITY COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JUNE 21, 1993
The City of Commerce City (City) submitted comments dated June 21, 1993, on the Off post
Proposed Plan. Attached to the City's comments were two sets of comments from the State of
Colorado: The first set of comments was a copy of the State of Colorado's draft formal comments
dated May 4, 1993. The State's comments were later submitted, in a slightly reorganized format
but essentially verbatim from the draft, as official comments on June 21, 1993. The Army's
responses to the State's official comments are provided in Appendix A-3. The second set of State
comments attached to the City's comments is identical to the State's comments on the Proposed
Plan dated February 19, 1993. The Army's responses to the State's February 19, 1993, comments
are provided in Appendix A-l.
The City expressed agreement with the State's comments and offered additional comments on
particular issues. The Army's responses are provided below.
Comment 1 - Applicable. Relevant and Appropriate Requirements
(ARARS) CERCLA Section 121(d)(2)(A) (ii) which specifically states, "Any promulgated
standard, requirement criteria or limitation under a State environmental or facility siting law that
is more stringent than Federal standard, requirement, criteria or limitation, including each such
State standard, requirement, criteria or limitation contained in a program approved, authorized or
delegated by the Administration under a statute cited in sub-paragraph (A), and that has been
identified to the president by the State in a timely manner..." is an 'Applicable, Relevant and
Appropriate Requirement,' i.e., (ARAR).
It's believed that this section clearly demonstrates that Congress intended for the states to be pro-
active participants in CERCLA actions and allows for stricter state environmental control
standards. The city holds that the Army and the U.S. Environmental Protection Agency (EPA)
have failed to demonstrate any formal evidences to waive the applicability of the Colorado Basic
Standards for Ground Water or the Methodologies of Surface Waters, as is required under Section
121(d)(4) of CERCLA. Furthermore, one of the Army's arguments to dismiss these as ARARs
centers on the State purportedly failing to consistently apply these standards. Now where can one
discern any examples offered by the Army or the EPA to substantiate this conclusion. The City
finds it paradoxical that the Army would recognize some of these stricter State requirements as
ARARs for the remediation of uninhabited Arsenal land and deny their applicability for
residential and commercially inhabited off-post areas. Ironically, if the State allows the presently
planned remediation to proceed, it would establish the very precedent the Army is attempting to
use in foregoing these State standards.
Response 1 - Applicable. Relevant and Appropriate Requirements
The Army has recognized all state laws and regulations that meet the applicable or relevant and
appropriate requirement (ARAR) criteria under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) and the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP). After extensive discussion with all the parties, the Army has
concluded that the Colorado Basic Standards for Groundwater (CBSGs) do not meet the ARARs
criteria because of inconsistent application and ambiguous language. ARARs for the Offpost
Operable Unit are based on federal drinking water standards and are protective of human health.
930423B.ene 1
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In most cases, the treatment goals for the offpost and boundary treatment systems exceed the
drinking water standards.
The Army concludes that the CBSG interim organic standards are not ARARs for two reasons.
First, the CERCLA exception in Section 3.11.5(C)(5)(a) applies to remedial actions authorized
under CERCLA and allows for a remedy that is more or less stringent than would be achieved by
compliance with the statewide standards. As a result, the overall effect of the statewide standard
and accompanying exceptions is a state regulation that is only sometimes more stringent than a
federal requirement. CERCLA only considers state standards that are stricter at all times as
potential ARARs. Therefore, by definition, the interim organic standards are not ARARs at
Superfund sites.
Second, the CBSG interim organic standards cannot be ARARs because they are not generally
applicable or legally enforceable. A requirement in CERCLA for state requirements to be
ARARs is that they must be promulgated standards, which means they must be generally
applicable and legally enforceable. Clearly, the interim organic standards do not meet this test
when applied at CERCLA sites. By definition, the interim organic standards are applicable
throughout the state, except at CERCLA, RCRA, and Underground Storage Tank sites. In those
instances, the relevance of the standards is determined by the remedial sites. It is hard to
understand how the standard could be legally enforceable when the Commission added language
specifically ensuring that the standards may or may not be met at CERCLA sites.
For additional discussion, see response to State comment No. 4 in Appendix A-3 of the ROD.
Comment 2 - Risk Assessment
It perceives the risk assessment as inadequate and not in compliance with the spirit and the intent
of the National Contingency Plan (NCP). It is clear that the Army's Risk Assessment is lacking in
the following required assessment parameters.
a. Thorough understanding of all possible hazardous constituents (especially DIMP &
IMPA) their basic toxicology, routes of exposure, synergistic and antagonistic
effects.
b. Thorough delineation of both the vertical and horizontal migration of the contami-
nants.
c. Failure to address the levels and effects the contaminants would have on receptors
who are predisposed to health problems.
d. Failure to adequately address why the Army departed from the NCP's acceptable
basic cancer risk level of one in a million.
Response 2a - Risk Assessment - DIMP and IMPA
The U.S. Environmental Protection Agency (EPA) developed the Health Advisory for diisopropyl
methylphosphonate (DIMP) in 1989 on the basis of an extensive review of more than 30 existing
toxicology studies involving a variety of animal species. EPA's Office of Drinking Water re-
reviewed the Health Advisory, in light of the State's concern, and concluded on March 28, 1990,
that "the existing Health Advisory values and the basis for the values represent the best scientific
position for the protection of human health." On the basis of toxicity information summarized in
EPA's isopropyl methylphosphonic acid (IMPA) Health Advisory and the Integrated Risk
930423B.enc
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Information System database, there is no information to indicate that IMPA concentrations lower
than 700 ppb may pose a threat to human health.
In accordance with EPA's Risk Assessment Guidance for Superfund (RAGS), the Army used
EPA's Health Advisory and information contained in the IRIS database to evaluate risk to human
health.
For additional discussion of DIMP and IMPA, see response to State comment Nos. 2d and 2h in
Appendix A-3 of the ROD.
Response 2b - Risk Assessment - Vertical and Horizontal Extent of Contamination
The Army believes that it has adequately defined the vertical and horizontal extent of contamina-
tion in a manner sufficient to allow definition of those areas requiring remediation. However,
additional monitoring wells are being installed to enhance the assessment of the locations and
concentrations of contaminants in the Offpost Study Area. The performance of the Offpost
Groundwater Intercept and Treatment System will be evaluated based on the results of the
monitoring program and the system will be modified, if necessary.
Response 2c - Risk Assessment - Individuals Predisposed to Health Problems
The purpose of the baseline risk assessment is to provide estimated risks on the basis of exposures
to a normal population. Many of the safety factors built into the assessment of noncarcinogenic
and carcinogenic risks are intended to result in the protection of sensitive individuals. While
individuals may have specific sensitivities, an assessment of these individuals, as well as the
particular type of sensitivity or predisposition, is beyond the scope of CERCLA and NCP
requirements for a baseline risk assessment.
Response 2d - Risk Assessment - Departure from one in a million risk level
The Army has closely followed EPA guidance and the NCP regarding the use of the 10"4 risk
threshold to assess whether remediation is necessary. Guidance states that if the cumulative
cancer risk to an individual is less than 10"*, remedial action may not be warranted unless certain
site-specific conditions exist. If remedial action is warranted, the 10"* to 10"6 risk range must be
achieved, with an initial preference for the 10"6 end. EPA guidance further states that the upper
boundary of the risk range is not an absolute at 1 x 10"*, but rather, the acceptable risk range can
extend to 5 x 10~V The cumulative off post cancer risk is a maximum of 3 x 10"4, which is within
the acceptable risk range.
In explaining the use of the point of departure, the EPA, in the preamble to the NCP, states
The use of 10"6 expresses EPA's preference for remedial actions that
result in risks at the more protective end of the risk range, but does
not reflect a presumption that the final remedial action should
attain such a risk level (55 Federal Register 8718).
The operation of the Offpost Groundwater Intercept and Treatment System reflects the Army's
goal of further reducing the potential risks toward the 10"6 level.
930423B.enc
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Comment 3 - Point of Compliance
The NCP is clear on the issue of ensuring that all points of exposure to a contaminant be
addressed in the risk assessment and any resulting remediation. Essentially, this alternative creates
a no-man's land that is unavailable for development and/or other uses.
Response 3 - Point of Compliance
The results of the risk assessment do not preclude development or other land uses. The Army
intends to achieve the remediation goals at all points within the contaminated plume, consistent
with the NCP. The groundwater modeling conducted by the Army in support of the remedial
alternatives evaluation in the Offpost Endangerment Assessment/Feasibility Study (EA/FS) report
used attainment of remediation goals as a primary criterion in assessing time to cleanup for the
various remedial alternatives. This information is presented in summary form in the Proposed Plan
and Volume VI, Section 3.2 of the EA/FS and in detail in Volume VII, Appendix E of the EA/FS.
The area of concern to the State appears to be the portion of the plume that lies between the
North Boundary Containment System (NBCS) and the Offpost Groundwater Intercept and
Treatment System. The NBCS has been demonstrated to be effective in reducing the contaminant
concentrations at the RMA boundary to meet remediation goals. The purpose of the Offpost
Groundwater Intercept and Treatment System is to extract and treat that portion of the plume that
had migrated past the RMA boundary (prior to installation of the North Boundary System) and
contains contaminants exceeding the remediation goals. The groundwater monitoring program
implemented as part of the selected remedy will provide the data necessary to evaluate attainment
of treatment goals within the plume and provide data necessary for assessment of modifications to
the treatment system, if necessary.
Comment 4 - Land Use
a. Classification of Land Use
The assessment process fails to use proper and correct demographics, zoning and land use data.
The City is of the opinion that the Army failed to consider that the City has and is currently in
the process of annexing properties to the north and west of the Arsenal. It appears that the
current remediation plan was based solely upon land use information provided by Adams county,
and thereby neglects the future land use plans of Commerce City.
b. Institutional Controls
The use of institutional controls are only useful temporary procedures and by themselves offer a
loop hole to responsible parties to negate CERCLA's main purpose: the thorough restoration of
contaminated environments. The Army should seek whatever institutional controls are necessary
to prevent any possible adverse health effects to residents and businesses in the affected area. The
City also believes that it is the responsibility of the Army to provide water taps as emergency
institutional controls to negate any possible adverse health effects to the areas citizens during
remediation of the ground water.
Response 4a - Classification of Land Use
The future land use scenarios used by the Army in the risk assessment are highly conservative.
For example, the rural residential scenario used in zones 1, 2, and 6 includes all pathways
contributing substantially to potential risk, even though most of the total population is not exposed
to the agricultural exposure pathways described in the risk assessment. Shell Oil Company
930423B.enc 4
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purchased the land in zones 3 and 4 for Army use in constructing the Offpost Groundwater
Intercept and Treatment System. It is not presently occupied; therefore, the current zoning
designation as rural residential is not applicable. Given the probability of the realignment and
widening of 96th Avenue, future development along 96th Avenue will likely be commercial/
industrial or urban residential. Based on local agency planning documents, the Army selected an
urban residential land use for the risk evaluation as this would result in more conservative (e.g.,
higher) estimated risks than the likely commercial/industrial land use.
The Army did not neglect land use plans of Commerce City. Section 2.2.2, Volume II, of the
Endangerment Assessment (EA) discusses the master plans, zoning, and planning documents from
Commerce City that were utilized. Figure 2.2.2.1.2-2 of the EA presents those areas immediately
north and west of RMA that have been zoned by Commerce City.
For additional discussion, see response to State comment No. 3a in Appendix A-3 of the ROD.
Response 4b - Institutional Controls
Institutional controls have been added as a component of the selected remedy. Appendix B of the
ROD provides an evaluation of the institutional controls available and their applicability.
Comment 1 and 2 - PIMP and IMPA Contamination in GroundWater.
This appears to be another instance where the Army and EPA are ignoring CERCLA's Section
121(d)2(A) mandating the use of State environmental standards and/or criteria as legal ARARs.
Both the Army and the EPA have failed to produce any convincing scientific evidence to make
use of the waiver from these under Section 121(d)(4). While the Army, EPA and the State Health
Department disagree over what levels of these substances may be safe, the City is of the opinion
that additional toxicological information is needed before proceeding with any remediation choice.
Therefore, the City feels it is incumbent upon the Army to provide funding for an independent
toxicological study to ascertain the actual hazards of these two substances.
Response 1 and 2 - PIMP and IMPA Contamination in Groundwater
See response to State comment Nos. 2d and 2h in Appendix A-3 of the ROD.
In accordance with EPA guidance on conducting risk assessments, the Army has used the EPA's
Health Advisory levels for both DIMP and IMPA. The Army believes that the State has not
provided sufficient or scientifically defensible evidence that the EPA's Health Advisory levels are
not sufficiently protective of human health. The EPA and the Army believe that there is
sufficient toxicological information available to support the Health Advisory levels. The Army is
currently evaluating the applicability of the 8 parts per billion level for DIMP that the Water
Quality Control Commission may promulgate in a few months.
The Offpost Groundwater Intercept and Treatment System is located in areas of highest contam-
inant concentrations. The Army is aware that concentrations of DIMP greater than 600 parts per
billion (ppb) have been reported north of the Offpost Groundwater Intercept and Treatment
System. In that regard, the offpost remedial action groundwater monitoring program will be
coordinated with the three existing groundwater monitoring programs active in the Offpost Study
Area. These three programs are (1) the Groundwater Monitoring Program, (2) the Offpost
Groundwater Intercept and Treatment System monitoring program, and (3) the private well
monitoring program. Additionally, in the area north of the Intercept and Treatment System where
DIMP has been reported to exceed 600 ppb, three monitoring wells will be replaced and three new
930423B.enc 5
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monitoring wells will be installed. Replacement wells are being installed for three wells originally
in the monitoring network that were found to be damaged or destroyed. Two new monitoring
wells will be installed downgradient of the First Creek Pathway, and one new monitoring well will
be installed downgradient of the northern Pathway. The purpose of the three new monitoring
wells is to aid 'in assessing the extent of contamination downgradient of the Of fpost Groundwater
Intercept and Treatment System. Data collected from these wells and existing wells will be used to
further define the extent of contamination greater than the remediation goals in this area and
assist in determining whether modifications to the design of the Offpost Groundwater Intercept
and Treatment System are necessary.
Comment 3 - More Aggressive Treatment of Ground water
If the final remediation includes a "pump and Treat System." At the present, the City holds that
the selection of the current preferred remediation plan was based upon inconclusive scientific
studies and unfounded assumptions. In view of these inadequacies, and the lack of local public
support, it is hoped that the Army and EPA will re-examine its reasons for selecting this
alternative, with a focus on a more realistic remediation time frame.
Although the City has no problem with the pump and treat technology for some remediation
objectives, it is now of the opinion that the Army and EPA appear determined to foist what was
once originally intended to be an interim remedial measure as a permanent solution. Although the
City supported the interim use of the proposed alternative action, it did so with the understanding
that it was an auxiliary plan to prevent future migration of the contaminants. Now that it appears
that the Army is relying upon this supposed interim action as a permanent solution, the City must
now question the wisdom of commenting favorably upon this as well as other interim Arsenal
actions.
Response 3 - More Aggressive Treatment of Groundwater
The Army selected Alternative N-4 instead of Alternative N-5 primarily because Alternative N-4
includes potential future modifications, only if such modifications are found to be necessary based
on actual operating data, to the Offpost Groundwater Intercept and Treatment System. Selection
of Alternative N-5 instead of Alternative N-4 will not necessarily provide a more cost effective
alternative because of a slightly shorter estimated remediation timeframe. The Army based its
assessment of the relative differences between the groundwater alternatives and estimates of
remediation timeframes on groundwater models that are very general in nature; thus, the
estimated remediation timeframes should not be construed as precise predictions. Use of actual
full-scale operating data is preferable to selecting additional components for the Offpost
Groundwater Intercept and Treatment System using the more speculative modeling data (i.e.,
Alternative N-5). The Offpost Proposed Plan culminates approximately 10 years of study. The
Army believes that the alternative chosen combines exceptional protection of human health and
the environment with the common sense approach of improving the groundwater systems if post-
ROD monitoring results determine it necessary.
For additional discussion, see response to State comment No. 2a in Appendix A-3 of the ROD.
Comment 8 - Human Health Risk characterization. 9 - Ecological Risk Characterization. 10 - Hot
Spots in Soils, and 11 - Contamination of Barr Lake
Because of the lack of toxicological and assessment sampling data, it appears that the Army (with
the approval of the EPA) has selected a premature remedial action plan that fails to sufficiently
930423B.ene 6
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address all contaminated environs. Further, there is still the unresolved question of what
particular ARARs apply. It's hoped that the Army and EPA broaden the scope of the remediation
study to cover all the off-post contamination areas and contaminates.
Response 8 - Human Health Risk Characterization
The Army considered all of the exposure pathways listed by the State and, on the basis of EPA
guidance presented in Risk Assessment Guidance for Superfund (RAGS), the pathways were
eliminated from further evaluation in the risk assessment. The Army presented the human health
risk assessment pathways to EPA, the U.S. Fish and Wildlife Service (USFWS), Shell Oil Company,
and the State for discussion. After identifying all potential complete exposure pathways, the
Army followed EPA guidance in RAGS (page 6-16) to select those pathways to be evaluated
further in the exposure assessment. Guidance allows for the elimination of some complete
pathways if there is sound justification, such as:
1. The exposure resulting from the pathway is much less than that from another pathway
involving the same medium at the same exposure point.
2. The potential magnitude of the exposure from the pathway is low.
3. The probability of the exposure occurring is very low, and the risks associated with the
occurrence are not high.
For additional discussion, see response to State comment No. 8 in Appendix A-l of the ROD.
Response 9 - Ecological Risk Assessment
The State has not presented any evidence to support its contention that assumptions made for the
ecological risk assessment (RA) will result in levels of contamination remaining in the Offpost
Study Area that may not be protective of biota. The Army presented the ecological RA assump-
tions and approaches to the USFWS, EPA, Shell Oil Company, and the State at meetings through-
out the ecological RA study period. The Army considered these meetings and subsequent
feedback critical because of the lack of formalized EPA guidance on conducting a dose-based
ecological assessment. The Army believes that the findings of the ecological RA are protective of
wildlife because many aspects of the approaches used to estimate potential effects are more
conservative than other hazard assessment methodologies currently followed by EPA and other
agencies. Because the approaches to conducting an ecological RA are continually being devel-
oped, the assumptions and parameters used by the Army for the final ecological RA were
thoroughly discussed with the parties and modified throughout the ecological RA process, and the
best available methodology and professional judgement were used. The USFWS participated in
the ecological RA process and supported the final methodologies used to evaluate the potential
ecological hazards.
Response 10 - Hot Spots in Soil
Background sampling indicated that pesticides are present throughout the Offpost Study Area.
Agricultural application of pesticides is a contributing source. Agricultural application of a
registered pesticide is exempt from CERCLA. However, the risk associated with the dieldrin
concentrations in these hot spots do not exceed a lifetime caner risk of 5 x 10"6, which is at the
lower end of the acceptable risk range defined by the U.S. Environmental Protection Agency
(EPA). Therefore, specific cleanup of these soil areas is not required. Cleanup of offpost
groundwater will provide the greatest benefit of risk reduction.
930423B.enc 7
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Response 11 - Contamination of Barr Lake
Remediation of offpost groundwater well reduce contaminant concentrations on First Creek.
Surface-water monitoring will continue as part of the offpost monitoring program. A surface-
water monitoring program has been included as a component of the selected remedy. An offpost
implementation document will be prepared following the approval of the Record of Decision,
which will include a monitoring program for surface water and groundwater.
Comment 12 - Closing Poorly Constructed Domestic Wells
The City strongly agrees with the State on this issue. It is incumbent upon the Army to stop the
migration of the contaminants to the deeper Arapahoe Formation aquifer, and at the same time
provide fresh water to affected area residents and businesses. CERCLA and the NCP both
emphasize the importance of preventing the spread of contamination during emergency and long-
term removal and remediation actions. Given the lack of thorough understanding of al possible
contamination, routes of exposure, toxicological effects, and ARA applicability, the Army should
take the prudent move to close these wells regardless of what particular remediation plan is
instituted.
Response 12 - Closing of Poorly Constructed Domestic Wells
The Army has incorporated well closure as a component of the selected remedy. The criteria for
well closure are presented in Appendix C of the Record of Decision.
930423B.enc
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Office of the Program Manager
Mr. Steven S. Crowell, Sr.
City Manager of Commerce City
5291 East 60th Avenue
P.O. Box 40
Commerce City, Colorado 80037
Dear Mr. Crowell:
Enclosed are responses to your comments on the Offpost Proposed Plan for
the Rocky Mountain Arsenal. The Army appreciates the large number of comments
submitted on the Offpost Proposed Plan. I hope these responses increase your
understanding of the offpost cleanup.
If you have any further questions please contact Mr. Tim Kilgannon of my
staff at (303) 289-0201.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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RESPONSES TO CITY OF BRIGHTON COMMENTS
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A
CITY OF
BRIGHTON
v
June 17, 1993
Colonel Eugene H. Bishop
Program Manager for the Rocky Mountain Arsenal
United States Army
Attn. AMXRM-PM
Bldg. Ill RMA
Commerce City, Colorado 80022-2180
Dear Colonel Bishop:
The City of Brighton wishes to comment on the off post plan
proposed by the U.S. Army for the Rocky Mountain Arsenal.
The City has been harmed by the presence of DIMP and possibly
other Arsenal contaminants in our growth area. We feel that this
limits our ability to access new water supplies locally for
future growth and poses a threat to our existing wells since DIMP
has been found as close to Brighton as 136th Avenue. ,
JjOur Southern growth area is located in the Northern reaches of
the DIMP influence area,/} Because of this the City feels that we
should be guaranteed an uncontaminated water supply for the
present and future.
Installing a municipal supply to the DIMP areas should not be the
only answer. We must insure that the contamination from the past
does not come back to haunt the future residents of this area.
If many years down the road we find that there is a very serious
problem with DIMP or any other Arsenal contaminants then it would
cause an even more monumental problem than what we have now.
The U.S. Army should meet the primary drinking water standards
for groundwater within a ten year program.
Sincerely,
James Ed Burke
Dir. of Utilities Operations
cc: Hank Brown, U.S. Senator
Mayor Hamstra and City Council Members
Ted Anderson, City Manager . $Vvwl
South K»th Avenue - Brighton, Colorado 80801 - [3O3] BBS-4QSO
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO CITY OF BRIGHTON COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JUNE 17, 1993
GENERAL COMMENTS
Comment 1. Contamination Problems in the Future
The Army does not anticipate that increased concentrations of contaminants will occur in the
future. The purpose of the long-term monitoring program to be implemented as part of the
selected remedy is to assess the performance of both the existing boundary containment systems
and the Offpost Groundwater Intercept and Treatment System. If monitoring data indicate that
these systems can be improved with little or no change in long-term cost and thus result in a
quicker remediation of offpost groundwater, modifications to the system will be made. The Army
remains committed to long-term monitoring of Rocky Mountain Arsenal (RMA)-related contami-
nants.
21905 301020 - CR-04
0808120193
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RESPONSES TO CITY OF THORNTON COMMENTS
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CMeCwnar
City of
Thornton
9500 Civic Center Drive
P.O. Box 291220
Thornton. Colorado 80229-1220
April 19, 1993
Program Manager for Rocky/Mountain Arsenal
Attru AMXRM-PM/Col. Ettgene H. Bishop
Building 111-RMA
Commerce City, CO 800^2-2180
Dear Col. Bishop:
On behalf of the Thornton City Council and the residents of Thornton, I would like
to express our concerns about the Rocky Mountain Arsenal Offpost Proposed Plan.
Based on staffs review of the Proposed Plan and comments we have received from
the Colorado Department of Health, we feel the Colorado Department of Health has
expressed legitimate concerns with which we concur. For example, regulations that
implement Superfund law state that a remediation plan should be designed to prevent
excess risk to human health greater than one in one million (carcinogen risk). The
Army proposes a carcinogen exposure level as high as three in 10,000 (Area I, Zone
3). We oppose special standards for the Army.
The City would like to see the Army work cooperatively with the Colorado
Department of Health to determine an acceptable level of DIMP (a byproduct of
nerve gas) in the groundwater and/or an alternative to providing bottled water to
over 600 residents. Finally, we feel that state standards for groundwater cleanup
should be used for offpost cleanup. It is important that the Army comply with
Superfund cleanup regulations for offpost areas as well as within the gates.
To summarize, we feel it is important that the Army adhere to regulations established
by Superfund regulations. The Army is not above the law and should ensure that
State and Superfund regulations are being met in order to provide safe drinking
water to the residents of Colorado.
Thank you for your time and consideration. If you have any questions or comments,
please contact Doug Lewis at 538-7692.
Sincerely,
CC: Hank Brown, United States Senate
Ben Nighthorse Campbell, United States Senate
David Skaggs, United States House of Representatives . /'/r/i/Y
Wayne Allard, United States House of Representatives ''
"The City of Planned Progress"
*'-
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO THE CITY OF THORNTON COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
APRIL 19, 1993
GENERAL COMMENTS
Comment 1. Acceptable Risk Level and Departure from One in a Million
The Army has closely followed U.S. Environmental Protection Agency (EPA) guidance and the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP) regarding the use of the
10"4 risk threshold to assess whether remediation is necessary. Guidance states that if the
cumulative cancer risk to an individual is less than 10"4, remedial action may not be warranted
unless certain site-specific conditions exist. If remedial action is warranted, the 10"1 to 10"6 risk
range must be achieved, with an initial preference for the 10"6 end. EPA guidance further states
that the upper boundary of the risk range is not an absolute at 1 x 10"1, but rather, the acceptable
risk range can extend to 5 x 10"4. The cumulative off post cancer risk is a maximum of 3 x 10"*,
which is within the acceptable risk range.
In explaining the use of the point of departure, the EPA, in the preamble to the NCP, states
The use of 10"6 expresses EPA's preference for remedial actions that result in risks
at the more protective end of the risk range, but does not reflect a presumption
that the final remedial action should attain such a risk level (55 Federal Register
8718).
The operation of the Off post Ground water Intercept and Treatment System reflects the Army's
goal of further reducing the potential risks toward the 10"6 level.
Comment 2. Acceptable Level of PIMP
The U.S. Environmental Protection Agency (EPA) developed the Health Advisory for diisopropyl
methylphosphonate (DIMP) in 1989 on the basis of an extensive review of more than 30 existing
toxicology studies involving a variety of animal species. EPA's Office of Drinking Water re-
reviewed the Health Advisory, in light of the State's concern, and concluded on March 28, 1990,
that "the existing Health Advisory values and the basis for the values represent the best scientific
position for the protection of human health."
In accordance with EPA's Risk Assessment Guidance for Superfund, the Army used EPA's Health
Advisory and information contained in the IRIS database to evaluate risk to human health.
For additional discussion of DIMP, see response to State comment No. 2d in Appendix A-3 of this
ROD.
21905 301020 - CR-04
0808120193
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Comment 3. Alternatives to Bottled Water
The Army will continue to work with EPA, the Colorado Department of Health (CDH), and the
Tri-County Health Department (TCHD) in evaluating the performance of the Offpost Ground-
water Intercept and Treatment System. Although drinking water standards are not exceeded for
private residences, CDH is providing bottled to many residents.
Comment 4. Use of State Standards for Cleanup Goals
The Army has recognized all state laws and regulations that meet the applicable or relevant and
appropriate requirement (ARAR) criteria under the CERCLA and the NCP. After extensive
discussion with all the parties, the Army has concluded that the Colorado Basic Standards for
Groundwater (CBSGs) do not meet the ARARs criteria because of inconsistent application and
ambiguous language. ARARs for the Offpost Operable Unit are based on federal drinking water
standards and are protective of human health. In most cases, the treatment goals for the offpost .
and boundary treatment systems exceed the drinking water standards.
CERCLA expressly provides that state standards can be ARARs at a site. However, only those
standards that are more stringent than federal requirements may be considered. In addition, the
state standards must be promulgated (i.e., the requirement must be of general applicability and
legally enforceable). Finally, the requirements must be identified in a timely manner by the
particular state (40 Code of Federal Regulations [CFR] Section 300.400[g][4]).
The Army concludes that the CBSG interim organic standards are not ARARs for two reasons.
First, the CERCLA exception in Section 3.11.5(C)(5)(a) applies to remedial actions authorized
under CERCLA that are more or less stringent than would be achieved by compliance with the
statewide standards. As a result, the overall effect of the statewide standard and accompanying
exceptions is a state regulation that is only sometimes more stringent than a federal requirement.
CERCLA only considers state standards that are stricter at all times as potential ARARs.
Therefore, by definition, the interim organic standards are not ARARs at Superfund sites.
Second, the CBSG interim organic standards cannot be ARARs because they are not generally
applicable or legally enforceable. A requirement in CERCLA for state requirements to be
ARARs is that they must be promulgated standards, which means they must be generally
applicable and legally enforceable. Clearly, the interim organic standards do not meet this test
when applied at CERCLA sites. By definition, the interim organic standards are applicable
throughout the state, except at CERCLA, RCRA, and UST sites. In those instances, the relevance
of the standards is determined by the remedial sites. It is hard to understand how the standard
could be legally enforceable when the Commission added language specifically ensuring that the
standards may or may not be met at CERCLA sites.
For additional discussion, see response to State comment No. 4 in Appendix A-3 of this ROD.
Comment 5. Compliance with Superfund Regulations
The Army is meeting all applicable Superfund regulations.
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0808120193
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RESPONSES TO CITY AND COUNTY OF DENVER COMMENTS
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CITY AND COUNTY OF DENVER
DEPARTMENT OF HEALTH AND HOSPITALS
WELLINGTON E WEBB ENVIRONMENTAL HEALTH
605 BANNOCK STREET
DENVER, COLORADO 80204-4507
(8M) 8087003 PHONE: (303) 436-7300
FAX: (303) 436-5074
June 21, 1993
Offpost Proposed Plan Comments
Program Manager for
Rocky Mountain Arsenal
Attn: AMXRM-PM/Col. Eugene H. Bisnop
Building 111-RMA
Commerce City, Colo. 80022-2180
R£: City and County of Denver Comments on The Proposed Plan
For The Rocky Mountain Arsenal Offpost Study Area
On behalf of the city and County of Denver the proposed plan
has been reviewed by this office. We appreciate this
opportunity to provide comments.
We are concerned that the Offpost Plan may be construed as
the final resolution necessary to address all offpost
contamination. We question the decision that no offpost ,
response is necessary for soils to the west, east, and south
of the Arsenal in the absence of sufficient (or, in some
areas, any) offpost soil sample data. We think that a
thorough investigation of soil, surface and ground water in
all areas adjacent to the Arsenal is essential. The offpost
study area should either be expanded to include these areas,
or a second offpost study for these areas should be
undertaken.
We hope that our input vill assist in ensuring a remedy
protective of human health and the environment.
Sincerely.,
Thomas L Stauch, Chief
Environmental Protection Division
cc: Franklyn Judaon, Director, Denver Public Health
Theresa Donahue, Deputy Chief of Staff, Mayor's Oftice
/
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO THE CITY AND COUNTY OF DENVER COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JUNE 21, 1993
GENERAL COMMENTS
Comment 1. Additional Off post Remedial Actions may be Necessary
The preferred alternative identified in the Record of Decision (ROD) is "final" in the context that
it is based on currently available information. Because of the flexibility in implementation, if
additional concerns are identified in the Offpost Study Area, an amendment to the ROD may be
issued to address additional remediation actions. Although the Offpost Groundwater Intercept
and Treatment System was originally developed as an Interim Response Action (IRA), the
evaluation of alternatives for the Offpost Operable Unit (OU) indicated that this IRA is the most
effective alternative studied in the Feasibility Study and, thus, is the selected remedy for the
Offpost OU. The Army has adequately evaluated the soils to the west, east, and south of the
Arsenal and determined that either 1) contaminant concentrations identified are typical of
background or 2) the risks associated with the contamination are within the acceptable risk range
defined by the U.S. Environmental Protection Agency. Based on these factors, remediation of soil
is not necessary.
21905 301020 - CR-04
0808120193
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RESPONSES TO ADAMS COUNTY COMMENTS
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TO COMM CITY PflGE.082
ADAMS COUN
COLORADO
4SOSOUIM4TH AVENUE
003XS9-Z120
ADMINISTRATION BOOOM6
FAX: 0031459-0577
May 19. 1993
Colonel Eugene EL Bishop
Program Manager for Rocky Mountain Arsenal
Building 111-RMA
Commerce City. CO 80022-2180
Dear Colonel Bishop:
Adams County has reviewed the Proposed Plan for the Rocky Mountain
Arsenal Oflpost Study Area (the Plan). That review has generated the
following comments made on behalf of the County:
1. The Flan fhfTa to address the potential of surface water runon/zunoff in the.
Irondale Gulch and First Creek drainageways. These drainageways. traverse
the Arsenal property in a northwestexiy direction and drain into the South
Plattc River. Development in the Denver Gateway planning area and Aurora
to the southeast of the Arsenal will add significant amounts of impervious
surfaces within these drainageways. The Plan should address the potential
for carrying pollutants off the Arsenal properly through surface water
intrusion and necessary mitigation of ftmt potential.
2. The options analyzed appear somewhat Hunted, particularly as they relate
to the northwest plume group. For remediation of that Itftn ' a n^gnon plume.
there are two alternatives advanced: do nothing or continue operation of the
containment system. Are there no other options feasible to analyze
pertaining to remediation of this plume?
3. There fs an area Just north of the Arsenal boundary in the vicinity of
Peoria Street which is contaminated with pesticides suspected to havp been
wind-deposited. The Plan does not address itself to remediation of this
problem area. The County considers this oversight to be a flaw in the Flan
which the Department of the Army should address.
10601
Although not a consideration made by the Department of the Army in the
Plan, the County strongly urges the Federal Government to adopt the State of
Colorado standard for DIMP when thai standard is adopted by the State.'
Considerable analysis has been undertaken by the Colorado Department of
Health in order to adopt a reasonable standard for H"tr»ar> exosure to this
compound. Although, not yet formally adopted by the State, the County ***&*
its acceptance and adoption by the Federal Government after adoption by the
State.
BOARD OF COim
COMMBSONSS:
gJUNEt-VJUlNIE
DISTRICT 1
SWUSMOAWHOTESA
OCTRICT2 •
HAJtOUPE-PlE
osnacT3
PEOPLE. PJBOE AND fHOORESS
-------
Thank you for the opportunity to comment on the Proposed Plan for the
Rocky Mountain Arsenal Ofipost Study Area. The County looks forward to the
continued remediation of fo*g facility and elimination of its endangerment to
off-post properties and the citizens of Adams County.
Sincerely,
Harold E. ^t*. Chairman
• Board of County Commissioners
copies: The Honorable David RD. Busby. Mayor of Commerce City
Ms. Marlon Qatar.* CDOH
** TOTflL PflGE.e03
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO ADAMS COUNTY COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL PROPOSED PLAN
MAY 19, 1993
Response 1. Surface Water Runon/runoff
An evaluation of additional surface-water flow through and beyond Rocky Mountain Arsenal
(RMA) as a result of increased development southeast of RMA is beyond the scope of the
Endangerment Assessment/Feasibility Study (EA/FS). The surface-water monitoring program, a
component of the selected remedy in the Record of Decision (ROD) that will be developed after
finalizing the ROD, will aid in assessing the potential impacts from any additional surface water
runon and runoff.
Response 2. Remedial Alternatives for the Northwest Plume Group
The groundwater northwest of RMA contains concentrations of contaminants slightly exceeding
the remediation goals. Evaluation of remedial alternatives in the EA/FS showed that alternatives
consisting of extraction wells in this dilute plume did not appreciably accelerate clean up
imeframes as compared to continued operation of the Northwest Boundary Containment System
(NWBCS). Continued operation of the NWBCS will further reduce the concentrations of
contaminants in the Offpost Study Area north and northwest of the boundary system. Approxi-
mately three to eight years would be required to achieve remediation goals in this area.
Response 3. Pesticide-Contaminated Soil near Peoria Street
The estimated risks associated with the measured concentrations of pesticides in soil in this area
are within the acceptable risk range established by the EPA and therefore clean up of these soils is
not required.
Response 4. PIMP Standard
The U.S. Environmental Protection Agency (EPA) developed the Health Advisory for diisopropyl
methylphosphonate (DIMP) in 1989 on the basis of an extensive review of more than 30 existing
toxicology studies involving a variety of animal species. EPA's Office of Drinking Water re-
reviewed the Health Advisory, in light of the State's concern, and concluded on March 28, 1990,
that "the existing Health Advisory values and the basis for the values represent the best scientific
position for the protection of human health."
The EPA acted appropriately when rejecting the Aulerich mink study as the critical study on
which to establish a human health drinking water advisory on the basis of extrapolative relevance
to humans and the confounding influences of background mortality in mink. The Army disagrees
with the State's statement that the Integrated Risk Information System (IRIS) mandates that
health-based standards be based on the most sensitive species tested. IRIS describes through a
"concept paper" (IRIS Background Document IA - Reference Dose (RfD): Description and Use in
Health Risk Assessment) the recommended approach to select the most appropriate critical study
and implies the use of informed professional judgment when making that selection, particularly
when identifying the animal model that is most relevant to humans. The EPA uses a panel of
high-level scientists to make the critical study selection rather than relying on the opinions of a
single individual.
930423F.enc 1
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In accordance with EPA's Risk Assessment Guidance for Superfund, the Army used EPA's Health
Advisory and information contained in the IRIS database to evaluate risk to human health.
The Water Quality Control Commission may adopt an 8 parts per billion (ppb) level in a few
months. The Army is currently evaluating the applicability of the 8 ppb level for DIMP to the
Off post area.
For additional discussion regarding DIMP, see response to State comment No. 2d in Appendix A-3
of this ROD.
930423F.ene
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Office of the Program Manager
Mr. Harold E. Kite
Chairman, Board of Adams County Commissioners
450 South 4th Avenue
Brighton, Colorado 80601
Dear Mr. Kite:
Enclosed are responses to your comments on the Offpost Proposed Plan for
the Rocky Mountain Arsenal. The Army appreciates the large number of comments
submitted on the Offpost Proposed Plan. I hope these responses increase your
understanding of the Offpost cleanup.
If you have any further questions please contact Mr. Tim Kilgannon of my
staff at (303) 289-0201.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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RESPONSES TO THE CITY OF AURORA COMMENTS
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WWLE.TAUER
Mayor
1470 South Havana Street
Aurora, Colorado 60012
303495-7015
July 19. 1993
Offpost Proposed Plan Comments
Program Manager for Rocky Mountain Arsenal
Attn: AMXRM-PM/Col. Eugene H. Bishop
Building 111-RMA
Commerce City, Colorado 80022-2180
Dear Colonel Bishop,
While we are aware that the public comment period for the Offpost Proposed Ran has closed,
the City of Aurora still wishes to express some concerns relative to the various positions
assumed by the Colorado Department of Health and the Army on proposed clean-up activities.
In particular, the City concurs with two of the State's concerns: 1) State environmental laws
and regulations should be observed as appropriate clean-up standards for local Superfund
sites, such as the Colorado Basic Standards for Groundwater; and 2) assumptions of
appropriate risk levels for cancer (1 x 10"") under National Contingency Plan provisions should
apply, unless deviation from this "point of departure* can be demonstrated. It doesn't appear
that the State's objections with regard to these issues have been adequately addressed by the
Army.
In addition to our continuing participation on the Technical Review Committee, we appreciate
the opportunity to comment on this and other upcoming remediation programs of interest at
the Arsenal.
Sincerely,
Paul E. Tauer
Mayor
t
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO CITY OF AURORA COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JULY 19, 1993
GENERAL COMMENTS
Response to Comment No. 1
The Army has recognized all state laws and regulations that meet the applicable or relevant and
appropriate requirement (ARAR) criteria under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) and the NCP. After extensive discussion with the
Organizations and State the Army has concluded that the Colorado Basic Standards for Ground-
water (CBSGs) do not meet the ARARs criteria because of inconsistent application and ambiguous
language. ARARs for the Offpost Operable Unit are based on federal drinking water standards
and are protective of human health. In most cases, the treatment goals for the offpost and
boundary treatment systems exceed the drinking water standards.
CERCLA expressly provides that state standards can be ARARs at a site. However, only those
standards that are more stringent than federal requirements may be considered. In addition, the
state standards must be promulgated (i.e., the requirement must be of general applicability and
legally enforceable). Finally, the requirements must be identified in a timely manner by the
particular state (40 Code of Federal Regulations [CFR] Section 300.400[g][4]).
The Army concludes that the CBSG interim organic standards are not ARARs for two reasons.
First, the CERCLA exception in Section 3.11.5(C)(5)(a) applies to remedial actions authorized
under CERCLA that are more or less stringent than would be achieved by compliance with the
statewide standards. As a result, the overall effect of the statewide standard and accompanying
exceptions is a state regulation that is only sometimes more stringent than a federal requirement.
CERCLA only considers state standards that are stricter at all times as potential ARARs.
Therefore, by definition, the interim organic standards are not ARARs at Superfund sites.
Second, the CBSG interim organic standards cannot be ARARs because they are not generally
applicable or legally enforceable. A requirement in CERCLA for state requirements to be
ARARs is that they must be promulgated standards, which means they must be generally
applicable and legally enforceable. Clearly, the interim organic standards do not meet this test
when applied at CERCLA sites. By definition, the interim organic standards are applicable
throughout the state, except at CERCLA, RCRA, and UST sites. In those instances, the relevance
of the standards is determined by the remedial sites. It is hard to understand how the standard
could be legally enforceable when the Commission added language specifically ensuring that the
standards mav or mav not be met at CERCLA sites.
Response to Comment No. 2
The Army has closely followed U.S. Environmental protection Agency (EPA) guidance and the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP) regarding the use of the
10'4 risk threshold to assess whether remediation is necessary. Guidance states that if the
21905 301020 - CR-04
0808120193
-------
cumulative cancer risk to an individual is less than 10"*, remedial action may not be warranted
unless certain site-specific conditions exist. If remedial action is warranted, the 10"* to 10"6 risk
range must be achieved, with an initial preference for the 10"6 end. EPA guidance further states
that the upper boundary of the risk range is not an absolute at 1 x 10"*, but rather, the acceptable
risk range can extend to 5 x 10"*. The cumulative offpost cancer risk is a maximum of 3 x 10"4,
which is within the acceptable risk range. The Army's goal, through operation of the Offpost
Groundwater Intercept and Treatment System, is to further reduce offpost risk toward the 10"6
level.
The Offpost Study Area risk assessment showed that, even without remedial action, the baseline
cumulative risks from contamination in surface water, soil, sediment, air, and groundwater are
within the acceptable risk range established by the EPA. However, several site-specific factors
suggest that remedial alternatives for groundwater should be considered. These site-specific
factors consider (1) that groundwater contributes approximately 73 percent of the total baseline
risk, (2) maximum contaminant levels (MCLs) and maximum contaminant level goals (MCLGs)
are exceeded for some groundwater contaminants, and (3) hazard indices (His) for children
slightly exceed 1.0 in zones 2, 3, and 4. Through operation of the Offpost Groundwater Intercept
and Treatment System attainment of the cleanup standards specified in the Record of Decision
(ROD), the Army intends to further reduce potential carcinogenic risks toward the 10"6 level and
reduce His to less than 1.0.
21905 301020 - CR-04
0808120193
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Appendix A-6
RESPONSES TO FARMERS RESERVOIR AND IRRIGATION COMPANY COMMENTS
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO THE FARMERS RESERVOIR AND IRRIGATION COMPANY
COMMENTS REGARDING THE ROCKY MOUNTAIN ARSENAL OFFPOST
PROPOSED PLAN
APRIL 20, 1993
GENERAL COMMENT
Comment No. 1
The companies divert water from First Creek on their decrees into either the Burlington-O'brian
canal which continues to Barr Lake or to the "Little Burlington" canal which delivers water
directly to the shareholder's lands without entering Barr Lake.
The offpost study area delineated in the Citizen's Summary refers only to consideration of the
surface waters of Barr Lake and the Burlington-O'Brian canal. It does not appear as if the area
served directly by the Little Burlington canal as been specifically identified as a study area.
During the irrigation season, First Creek is diverted into the Little Burlington Canal. In relation
to the amount of water diverted through the main Burlington Canal, flows in the Little Burlington
canal are very small. The amount of dilution of First Creek flows in the Little Burlington Canal is
quite small. At times, the only flow in the canal will be First Creek water—undiluted by any
other flows. The Little Burlington canal provides irrigation water for a significant amount
(approximately 10,000 total acres) of vegetables and other crops in the Burlington area.
It does not appear whether this direct and undiluted use of First Creek water for vegetable
irrigation has been adequately considered. From the exposure zone mapping and exposure
pathway analysis presented in the plan synopsis, it does not appear that interception and transport
by the Little Burlington canal system has been adequately assessed.
Response
Although Little Burlington Canal was not specifically evaluated for the Endangerment Assess-
ment/Feasibility Study (EA/FS), the U.S. Department of the Army (Army) believes that all
potential impacts that may result from the direct and undiluted use of First Creek water in Little
Burlington Canal, especially for irrigation purposes, are addressed by the EA. Generally, the
concentrations of constituents detected in First Creek surface water are lower than the concentra-
tions detected in groundwater. (Arsenic is an exception; however, the arsenic levels may be
attributed to naturally occurring sources.) Also, samples taken from the Little Burlington Canal
indicate that RMA contaminants, when detected, are at lower concentrations than those found in
First Creek. Therefore, the potential risks resulting from use of surface water are less than the
potential risks resulting from use of groundwater. The EA quantitatively evaluated the uptake of
constituents by vegetables irrigated with groundwater and/or surface water. For study zones 1A,
1C, and 6, the EA assumed irrigation water was primarily surface water (more than 92 percent).
For zones IB, 2, 3, 4, and 5, the EA assumed shallow groundwater provided more than 90 percent
of the irrigation water. On the basis of the irrigation/plant uptake modeling effort, the lowest
estimated concentrations of constituents in vegetables occurred in the zones irrigated primarily
with surface water. The plant uptake model and exposure equations used very conservative or
cautious assumptions; therefore, it is highly unlikely that the potential plant concentrations and
associated risks were underestimated. The Army believes, on the basis of the findings of the EA,
that any Rocky Mountain Arsenal (RMA)-related constituents that may be transported to Little
Burlington Canal via First Creek do not pose a health threat to humans and the environment.
Comment No. 2
Water from Barr Lake presently forms a portion of the physical municipal supply for the City of
Brighton. Use of Barr Lake for potable municipal water purposes is anticipated to significantly
increase in response to the new airport and related urbanization. The Barr Lake "plan" to integrate
930424A.enc 1
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Barr Lake into a metropolitan water use system has gained recognition from the State of Colorado
as one of the primary municipal water supply plans which can provide for increasing demands
into the next century.
Any discharge into First Creek or any groundwater which is otherwise intercepted by the
Burlington ditch system must take into account the existing and proposed future domestic water
uses.
It is not apparent whether the domestic water quality requirements have been adequately
considered in the remediation plan.
Response
Based on existing monitoring data, the concentrations of constituents (RMA or from other
sources) in Barr Lake are not statistically elevated above background. The low concentration of
constituents indicates that any potential health risk from the surface water pathway would be very
small compared to other possible pathways of exposure (e.g., domestic use of groundwater). EPA
risk assessment guidance allows for the elimination of pathways of exposure for quantitative risk
evaluation if the potential risks associated with the pathway are likely to be very small. Addition-
ally, it is anticipated that any contribution of contaminants to First Creek and ultimately to Ban-
Lake from RMA-related sources will be decreased because of the operation of the groundwater
intercept and treatment systems.
Comment No. 3
Reference is made to identification of various constituents in soils and groundwater. The offpost
study area identification referred only to surface waters in Barr Lake (in which some RMA
substances were found). Sediment accumulation in the Burlington Canal and Barr Lake does not
appear to have been sufficiently considered.
No quantification of the metals (arsenic and manganese) appears in the Citizen's Summary. The
experience of the company in one of its other lakes (Standley lake) with regard to these metals
may be applicable to Barr.
In Standley lake, seasonal variations in the dissolved oxygen levels of the lake has resulted in re-
solution of metals from the bottom sediments by a factor of more than 10 to 1. The impact of
metals transported to the lake sediment may thus vary with time, season and eutrophic conditions.
no consideration of these conditions appears in the plan.
Response
Because of the historic input of constituents from other sources (e.g., Denver sewage effluent and
agricultural runoff) into Barr Lake and ultimately into the lake sediment, it is nearly impossible to
differentiate the percent contribution from RMA. Inorganic constituents, such as arsenic and
manganese, complicate the issue further because these constituents also occur naturally; the levels
found in Barr Lake may be unrelated to RMA activities.
The Army agrees that physical, chemical, and biological conditions present at any given moment
may influence the distribution of metals in sediments and in surface water. However, the EA
evaluated constituent concentrations on the basis of available sediment and surface-water
analytical data and showed that the concentrations of constituents in Barr Lake were not signifi-
cantly elevated above background concentrations.
Comment No. 4
Various of the substances identified appear to be persistent or are bio-accumulated. There does
not appear to have been any consideration of these issues as applied to the Barr Lake sediments in
the offpost study plan.
930424A.enc
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Response
The concentrations of the persistent and bioaccumulative constituents found in the sediment of
Barr Lake are below background concentrations. The EA evaluated the potential impact of
constituents found in First Creek sediment (elevated above background) on human health and the
environment. The findings of the EA indicated that even under this "worst case scenario" in First
Creek (as compared to the potential risk posed by lower level constituents in Barr Lake), the
contribution from the sediment to overall risk was very small, even for ecological receptors.
Conclusion
These comments have been submitted to insure that the present and future uses of Barr Lake, the
Burlington Canal and waters transported through the system have been adequately considered.
Various of these uses do not appear to have been considered in the existing plan.
The companies do not have the technical or financial resources to adequately assess the past and
future impact of contamination into and through the companies' systems.
The companies' irrigation system is the recipient of all First Creek flows, as well as groundwater
migration to the creeks and the canals themselves. As such the companies believe that at a
minimum an ongoing water and sediment monitoring program is required to adequately assess past
contamination and the efficacy of the proposed remediation.
Until continued assessment of present conditions, taking into account all existing and proposed
uses of the waters in the companies' system, has been undertaken delineation of the companies
specific concerns cannot be made.
Response
The Army is committed to an ongoing surface-water and groundwater monitoring program to
ensure that the preferred alternative continues to meet the remedial action goals and to ensure the
protection of human health and the environment. The Army would be glad to discuss the
monitoring program with the Farmers Reservoir and irrigation Company (FRICO) in the future.
930424A.ene
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Office of the Program Manager
Mr. Albert F. Sack
President
Farmers Reservoir and Irrigation Company
80 South 27th Avenue
Brighton, Colorado 80229-1220
Dear Mr. Sack:
Enclosed are responses to your comments on the Offpost Proposed Plan for
the Rocky Mountain Arsenal. The Army appreciates the large number of comments
submitted on the Offpost Proposed Plan. I hope these responses increase your
understanding of the Offpost cleanup.
Also enclosed is information your group requested at a meeting held with the
Army on May 18, 1993.
If you have any further questions please contact Mr. Tim Kilgannon of my
staff at 289-0201.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
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Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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Appendix A-7
RESPONSES TO ENVIRONMENTAL ACTION GROUP COMMENTS
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RESPONSES TO SIERRA CLUB COMMENTS
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO SIERRA CLUB COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
RECEIVED JUNE 21, 1993
Comment A - Air quality:
1. Why wasn't air quality addressed more specifically? We are particularly concerned
about the reference to the widening of 96th Ave. which would increase traffic,
air current flow from the location of the SQI on the Arsenal, and increased airport
activity following the opening of the new airport. The only reference we have
seen in the study to air is the inhalation of particulates from soil and dust.
2. Ref. Vol.1, ES-3: How can it be stated that air exposure to chemicals of concern
does not contribute to human exposure to these chemicals? Even if the
concentrations are very low, it is not accurate to say that exposure does not
contribute even slightly to increasing the total doses of chemicals to which
residents of the offpost area are exposed.
3. When considering total solid Particulates (TSP) in air, the Plan states that
concentrations at the RMA boundaries are lower that those found in metro
Denver's air, and that metals are proportional to the same. Again, we are
concerned that the activation of the SQI and the possibility of the widening of the
road along the northern border of RMA will increase the TSP above the levels in
metro Denver.
Response Al:
Air emissions from the submerged quench incinerator (SQI) have been addressed as part of the
SQI risk assessment and were determined to be within federal and state health guidelines.
Potential air emissions resulting from widening 96th Avenue will be addressed by the appropriate
regulatory agencies when that construction activity occurs.
Response A2:
The Rocky Mountain Arsenal (RMA) Comprehensive Air Quality Data Assessment Report by
R.L. Stollar and others, 1990, presented data that indicated air quality within the Offpost
Operable Unit (OU) was not impacted by contaminants related to RMA. Additional information
is presented in the "Nature and Extent" subsection of Volume I of the Final Offpost Endangerment
Assessment/Feasibility Study report. The evaluation of exposure to dusts presented in Appendix
B of the Endangerment Assessment (EA) indicates that the potential exposures through inhalation
of chemicals in dust are much less than exposures that could be received through other routes.
The Risk Assessment Guidance for Superfund allows for the elimination of a route of exposure if
the contribution to exposure from that route is small compared to other routes.
Response A3:
See Response Al above.
93042SA.enc
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Comment B - Chemicals of Concern:
1. We question the validity of 4 of the twelve background sites used in the study as
being agricultural areas. Although these sites would have increased levels of
pesticides present from crop applications, how does this site relate to what a
residential area concentration of Dieldrin should be, for example? We feel that
these sites may be biasing the background reference data to appear higher in
chemical concentrations, than would normally be present without agricultural
practices.
2. When analyzing the degradation charts for Dieldrin and Aldrin in zones 3 and 4, it
is evident that these COC's will not be down to "background" levels within their
boundaries for 25 and 15 years respectively. We would like to see a moratorium on
development in these zones for the amount of time it would take to achieve the
background levels for these COC's.
3. Ref. Vol. 2053: It was stated here that the COC's are diluted 130:1 after O'Brian
Canal, this would seem to indicate that the authors feel the "solution to pollution is
dilution." We are supposed to be cleaning things up here, not dilution the problem.
The COC's are still present in relative quantities, particularly in the sediments.
Response Bl:
Generally, the concentration of dieldrin would be lower in residential areas compared to agricul-
tural areas; however, it is impossible to make a definitive statement without knowing anything
about the residential area and whether historical domestic applications of dieldrin occurred. The
soil samples collected from the background sites in the predominately agricultural area did not
bias the pesticide reference data. Table 1.3.3-1 (Volume II, Section 1.0 of the EA) shows that soil
samples collected within the designated locations where the highest concentrations of RMA-
related chemicals occur, or are expected to occur, had pesticide detections that were significantly
elevated above the background soil samples, except for isodrin. All of the pesticides were
evaluated in the risk assessment, including isodrin. Additionally, the risk assessment estimated
risk on the basis of total risk rather than incremental risk (i.e., the Army did not subtract
background residue contributions from the computation of exposure concentrations).
Response B2
The estimated potential risks associated with the soil in zones 3 and 4 are presented in the Final
Offpost EA report and are within the acceptable risk range as defined by U.S. Environmental
Protection Agency (EPA). Based on this evaluation, potential risks due to contamination should
not limit rural residents or commercial/industrial development in these areas, although the Army
is not aware of any plans for such development at this time.
Response B3
The reference to dilution of contaminants in surface water flowing from First Creek into O'Brian
Canal is not made in the context of remediation. It is simply a statement of fact. The Army
evaluated the potential risks associated with the contaminant concentrations in First Creek without
regard to potential dilution for both human and animal receptors and showed the overall risks to
be very small.
93042SA.ene
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Comment C - Water
1. Since the proposed clean-up for the Off-Post area is currently planned for
groundwater only at the plume peripheries, but since readings for certain COCs
have been found beyond where the original plume borders had been determined,
we cannot support option N-4 of the Plan. We would prefer to see option N-5
enacted.
2. Ref. Vol 2-1 -6: It states in reference to groundwater contamination that "inorganic
chemical background concentrations are substantially different (and generally
higher) in the Arapaho Formation when compared to the alluvium and upper
Denver." We are concerned that this matter is not being addressed.
In addition we have been made aware that some wells on the other side of the
Platte have yielded traces of certain COCs, and that the South Platte may not be
acting as the hydrological barrier that it once was thought to be. Has this been
considered in the clean-up effort and how will it be addressed?
3. Ref. Vol. 2, Table 1.3.2-7" In analyzing the sediment samples from Barr Lake,
only 5 samples were used. We do not consider this to be a representative sample
for the lake. Perhaps more sampling is necessary to adequately evaluate lake
contamination.
4. Ref. Vol. 2, 1-19: Sediments form First Creek were poorly studied. Only 2
samples were listed for the reference data, while 11 samples were collected for
RMA-tainted samples. According to proper risk assessment protocol, an n=3 is the
minimum number acceptable for samples. An n=2 is not valid for accurate
statistical analysis.
Because one of the two reference samples had high levels of several COC's, the
background level is high, therefore leading RMA samples to appear statistically
insignificant from controls. There was reference to "other data" which was used in
evaluating the samples, but no mention was made as to what it was. Consequently,
we believe more sediment samples are required from First Creek to obtain an
adequate reference database.
Also, an assumption has been made that metals are not COC's in First Creek based
on the background data. We think that this assumption was inappropriate since the
reference sampling was not complete.
5. Ref. Vol. 2-2-53: In reference to gfoundwater contamination by chemicals, the
study states that "hydrophobic chemicals are absorbed by aquifer materials". Please
clarify which materials COC's are absorbed by and where they deposit to?
Can you also clarify the following statements:
"aliphatic COC's undergo dechlorination under anaerobic
conditions"
What anaerobic conditions?
What is the relevance of this statement?
930425A.enc
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"aromatic COC's (i.e. benzene, etc.) are readily biodegraded under
aerobic conditions". However, for aliphatic chemicals an anaerobic
degradation was stated.
Which condition prevails?
What are the degradative products which are referred
to...phenols, quinones, etc.?
Which may be potentially more toxic?
6. We would like to see a surface water monitoring program established in the Off-
Post area including:
- South Platte River
- O'Brian Canal
- Burlington Canal
- Barr Lake
- First Creek
- Second Creek
- Fulton Ditch.
Response Cl
The Commenter has incorrectly stated the Army's rationale for elimination of Alternatives N-5
and N-6. As presented in the Final Off post EA/FS report Volume VI, Section 4.2.1, Screening of
Alternatives - North Plume Group, effectiveness, implementability, and cost criteria were
explicitly evaluated consistent with the requirements of the National Oil and Hazardous Sub-
stances Pollution Contingency (NCP). In this section of the EA/FS, it was concluded that
Alternatives N-4, N-5, and N-6 afford the best reduction in toxicity, mobility, and volume, the
best long-term protection, and the best compliance with remediation goals. Alternative N-6 was
screened out at this point on the basis of similar performance in comparison with Alternative N-5
with respect to reduction in toxicity, mobility, and volume, yet it afforded no benefit in terms of
remediation timeframe (10 to 20 years) and at higher cost.
The Army selected Alternative N-4 instead of Alternative N-5 primarily because Alternative N-4
uses actual operating data as a basis for system modifications, if necessary. This is considered to
be more effective than expanding the system based on more speculative modeling data.
The Army is committed to efficient operation of the Offpost Groundwater Intercept and
Treatment System and will evaluate operating data to assess the need for system modification.
Similar to the onpost boundary treatment systems, it is difficult to assess whether the installation
of additional wells will provide more efficient operation without collecting full-scale operating
data for the Offpost Groundwater Intercept and Treatment System. The Army has included an
intensive monitoring component as part of the preferred alternative, Alternative N-4, in the
Proposed Plan. This intensive monitoring program will allow the collection and subsequent
interpretation of performance data for the full-scale operation of both the Offpost Groundwater
Intercept and Treatment System and the onpost boundary systems. The data will be used to assess
the need for any improvement to the systems and will provide increased accuracy in assessing
contaminant cleanup. Acquisition of this operational data is preferable to adding extraction wells
and recharge trenches without the benefit of operational data, because additional data are required
to assess the necessity and placement of any additional extraction wells or trenches. If operational
data supports the conclusion that the cleanup timeframe can be shortened without a significant
increase in long-term costs, modifications to Alternative N-4 will be implemented. By taking this
930425A.enc
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approach, improvements to the system will be more effective than improvements made based on
computer modeling data.
The selected remedy does not address groundwater only at the periphery of the plume. The
Offpost Groundwater Intercept and Treatment System is located in the middle of the North Plume
Group in the area of highest concentration.
For additional discussion, see response to State comment No. 2a in Appendix A-3 of the ROD.
Response C2
The background concentrations of certain inorganic compounds in the Arapahoe Formation are
naturally occurring and are not addressed by the offpost clean up.
As defined by the Federal Facility Agreement (FFA), the areas requiring remediation are those
areas where concentrations of contaminants exceed the remediation goals. These remediation
goals were developed to be protective to both human and ecological receptors and are within the
acceptable risk range defined by EPA. The diisopropyl methylphosphonate (DIMP) detections
west of the South Platte River are approximately 100 times less than the concentration recom-
mended by EPA to be protective of human health. Continued groundwater monitoring will ensure
that all areas will not exceed the remediation goals established to be protective of human health.
Response C3
Chemicals of concern in the canals were not present above background concentrations in the
sediments of Barr Lake. Additionally, the absence of elevated concentrations in Barr Lake surface
water indicate that sediments are unlikely to be contaminated. Sampling locations for Barr Lake
sediments included locations near the inlet to Barr Lake, expected to have the highest sediment
concentrations.
The Army acknowledged that intensive statistical analysis of the sediment at Barr Lake was
hampered by the small sample size; however, on the basis on the sampling locations, the Army
contends that the samples are representative of sediment at Barr Lake. Additional sampling is not
warranted.
Response C4
The Army indicated that the reference data set was not sufficient to adequately address whether
First Creek sediment was elevated for chlorinated hydrocarbon pesticides; therefore, as indicated,
other criteria were used. These "other criteria" are specified in the EA and included the detection
frequency of the constituent in First Creek sediment, status of the constituent as a surface-water
chemical of concern (COC), and the organic partition coefficient for the constituent. The
assumption was made that if a constituent concentration was elevated in the surface water, it
would also be elevated in the sediment. Although a statistical comparison of the chlorinated
hydrocarbon pesticides in First Creek sediment compared to background was not possible, all
detected pesticides in the sediment were evaluated in the risk assessment (see Table 2.4.2.6-9 in
the Final Offpost EA).
Although the background (reference) data set is small, the concentrations of metals present in the
First Creek sediment samples (n=l 1) are low by any standard and are unlikely to pose an adverse
effect to human and ecological receptors.
930425A.enc
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Response C5
The hydrophobia COCs, such as the chlorinated hydrocarbon pesticides, may be adsorbed to clay
particles and organic matter present in the aquifer. These particles are not likely to be mobile;
thus significant desorption is unlikely to occur.
Anaerobic conditions indicate a lack of oxygen. Such conditions may be present in portions of the
saturated areas of an aquifer and may be ideal conditions for the biological transformation
(i.e., biodegradation) of some chlorinated hydrocarbon pesticides by anaerobic microorganisms.
Aerobic conditions may be present in the unsaturated zones of an aquifer. Either aerobic or
anaerobic conditions may be present at any given time. The type of biotransformation (aerobic or
anaerobic) depends on the type of microbial population present in the aquifer as well as the nature
of the chemical substrate (aliphatic or aromatic) and the presence of any microbial nutrients.
Although some degradation products may be more toxic than the parent compound, the usual
condition is to produce less toxic and more soluble products. Most of the products (toxic and
nontoxic), if present above detection levels are measured using standard analytical methods and
would have been included in the risk assessment.
Response C6
A surface-water monitoring program is a component of the selected remedy in the Record of
Decision (ROD). The specifics of the program will be developed after the ROD is finalized.
Comment D - Soil:
1. Ref. Vol. 2-1-21: Regarding surficial soil, comparison was made between RMA-
tainted samples and regional reference data instead of reference data obtained at
the Off-Post sites. We cannot understand how rules can be changed in the middle
of the game. As such, we believe that comparisons should be made between all
RMA-tainted samples and reference data from the Off-Post sites. A comparison
of RMA-tainted data for copper, lead and zinc would have been statistically
elevated compared to the reference data. This is not acceptable, and we would like
the surficial soil data re-evaluated.
2. Ref. Vol. 2-2-49 and 2-2-74: Why haven't the vegetables been analyzed for
COC's? Because the produce is grown in soil on the Off-Post area and irrigated
with groundwater contaminated with COC's, it would seem logical to sample the
vegetables grown there. They are a relevant source of exposure for humans
inhabiting the Off-Post area as well as for local residents purchasing the goods.
3. We are concerned about localized soil contamination hot spots in the Off-Post area
which we don't see being addressed by any of the clean-up proposals. We would
like these areas identified to the local residents and the contamination addressed.
Response Dl
The extension of the background data set to include regional data is appropriate and allows for a
more realistic analysis of the significance of site-related metal concentrations. There can be
tremendous variability in metal concentration as a result of natural geologic phenomena at a site,
particularly a site the size of the Offpost Study Area. Thus, it is important to evaluate site data
with all available appropriate information. The "rules" did not change. Reference to Shacklette
9S0425A.enc
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and Boerngen's soil data, as well as other soil databases, is common accepted practice in risk
assessment.
Response D2
The Army recognizes the value of actual site-specific data when performing a risk assessment.
Vegetables were not analyzed because no clear guidance exists on which kinds of plants are the
most appropriate and because of seasonal availability during the scheduled soil sampling events.
The Army's modeling approach uses conservative input parameters to predict potential plant tissue
concentrations; thus, it is highly likely that potential risks associated with vegetable ingestion by
local residents have been overestimated.
Response D3
The estimated risks associated with the areas of elevated pesticide concentrations in soil are within
the acceptable risk range as established by the EPA. However, particularly with regard to the
distribution of pesticides, it is apparent that localized areas of higher concentrations may not be
attributable to simple windblown erosion from onpost soil. Because of the widespread use of
pesticides in agricultural practices, pesticide residues are widespread and are found in nearly all
soil samples in the offpost area. The general nature of windblown soil indicates that localized
offpost areas of high soil pesticide concentrations are unlikely. Intentional pesticide application is
believed to be at least partly responsible for the high concentrations of pesticides in certain soil
areas.
However, the estimated risks (approximately 5 x 10"6) associated with these higher concentrations
of pesticides found offpost are well within the EPA health guidelines.
Comment E - Land Usage:
1. Have the Army and Shell been communicating with Commerce City and the Adams
County Board of Commissioners with regards to master plans and future zoning
requirements for the Off-Post area? We are particularly concerned about zones 2,
3, and 4.
Response El
As discussed in Volume II, Section 2.2.2 of the EA, master plans, future use forecasts, and zoning
information from both Commerce City and Adams County were utilized in establishing the
reasonable future land use for the Offpost Study Area.
Comment F - Testing Procedures:
1. Ref. Vol. 2-2-74: Why are samples form agricultural products considered
insufficient for exposure determinations of eggs, meat and milk? When evaluation
sediment samples in /first Creek, an n=2 for control samples was considered
adequate.
2. Ref. Vol. 2-2-76: Why was modeling conducted for vegetable exposure?
Wouldn't it have been much more relevant to sample actual produce? We don't
understand why so much time and money was wasted modeling egg, meat and
vegetable contamination when samples were readily available and would have been
930425A.enc 7
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more reliable. Vol. 2-2-85 indicated the limited monitoring data showed higher
Dieldrin levels than the model's predicted value for meat and eggs.
3. Ref. Vol. 2-2-90: Why is age 0-30 considered a lifetime risk? We realize that 30
.years is considered average for the U.S. due to population movement statistics.
However, much of the Adams County area in question has a very stable population
which often resides on a site for a lifetime. Many residents have already lived
with high exposure rates for over 40 years and may live in this area for another 30
years. We feel that the risk values would change if residency were considered for a
longer time.
4. Ref. Vol. 2-2-90: Please justify how and increased length of lifetime exposure
would result in a reduced estimate of COC intake. How is it presumed that soil
exposure and dairy product consumption would be lower for an adolescent than an
adult? Anyone who has observed, or been, a teenager can attest to the fact that
they play a variety of sports in the dirt, and will drink quantities of milk.
5. Relating to the risk management decision by the Army to use 1 in 2000 as the
acceptable cancer risk, the Sierra Club feels that this is unacceptable. We feel that
the clean-up should be to 1 in 1,000,000 as set by the EPA.
Response Fl
There is a greater potential for sample variability to occur when evaluating biological samples
from a population rather than abiotic samples, such as sediment, from a limited area; therefore, a
larger sample size is critical for meaningful interpretation of results. Each animal may have
unique individual biological characteristics that are not readily apparent but that can influence
chemical residue and toxicity evaluations. It is difficult to address the influence of individual
variability when an evaluation is limited to a very small data set.
Response F2
See Response D2 above.
Response F3
A time span of thirty years is used as the estimated reasonable maximum lifetime exposure in
accordance with risk assessment guidance documents from EPA. The basis of this value is that 90
out of 100 people will live 30 years or less at one residence. Hence, 30 years is the expected
duration of potential exposure to contaminants. Although some people will exceed 30 years at one
residence, the intent of this value is not to represent the absolute maximum number of years that
would be represented by a very limited number of people, but rather a value that encompasses the
majority of people. EPA does not advocate utilizing absolute "worst^case" values in risk assess-
ments. Use of the standard EPA default factors provides for more consistent risk assessments. A
statistical evaluation of the Army's risk assessment exposure parameters actually indicated that the
reasonable maximum exposure intake used by the Army approaches the 99th percentile, meeting
and exceeding the definition for a reasonable maximum exposure (RME) estimate.
930425A.ene
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Response F4
The basis of the comment, the reference to page II-2-90 of Volume II, is unclear. The risk
assessment estimated potential risk on the basis of a reasonable maximum exposure as defined in
the response to comment F3 for all populations evaluated.
As shown in Tables 2.4.3.2-1 and 2.4.3.2-la of the Final Offpost EA report, the intake rates for
soil and water used in the risk assessment are greater for an adolescent/child than for an adult.
Response F5
The Army has closely followed EPA guidance and the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP) regarding the use of the 10"1 risk threshold to assess whether
remediation is necessary. Guidance states that if the cumulative cancer risk to an individual is less
than 10"*, remedial action may not be warranted unless certain site-specific conditions exist. If
remedial action is warranted, the 10"1 to 10"6 risk range must be achieved, with an initial prefer-
ence for the 10"8 end. EPA guidance further states that the upper boundary of the risk range is
not an absolute at 1 x 10"1, but rather, the acceptable risk range can extend to 5 x 10"4. The
cumulative off post cancer risk is a maximum of 3 x 10"*, which is within the acceptable risk range.
The risk was calculated without operations of the Offpost Groundwater Intercept and Treatment
System being considered.
In explaining the use of the point of departure, the EPA, in the preamble to the NCP, states
The use of 10"6 expresses EPA's preference for remedial actions that result in risks at the
more protective end of the risk range, but does not reflect a presumption that the final
remedial action should attain such a risk level (55 Federal Register 8717).
The operation of the Offpost Groundwater Intercept and Treatment System reflects the Army's
goal of further reducing the potential risk toward the 10"6 level.
Also, refer to the NCP and EPA risk assessment guidance documents, including Office of Solid
Waste and Emergency Response Directive 9355.0-30 (Role of the Baseline Risk Assessment in
Superfund Remedy Selection Decisions, April 22, 1991), for clarification of this issue.
Comment G - Legal Requirements:
1. Ref. Vol. 7-A-6: This ARAR analysis section states that the Federal Endangered
Species Act, Migratory Bird Treaty Act, and Bald Eagle Protection Act apply to
RMA. This section further states that remediation goals have been established for
Off-Post contamination in conformity with the requirements of these three
statutes. It further states that these remediation goals will be included as
enforceable remediation levels in the proposed plan and record of decision.
However, on page A-7, it is specifically stated that these three statutes are not
ARAR's, but that they will be complied with for purposes of implementing an
alternative remedy.
The Sierra Club is concerned that as the requirements of these three statutes
regarding wildlife protection are not ARAR's, there may be some conflict between
complying with these statutes and meeting the remediation goals for the Off-Post
OU. Specifically, how will conflicts between the requirements of these three
statutes and established ARAR's be resolved in the Off-Post remediation?
930425A.enc 9
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Additionally, how can it be anticipated that remediation goals for the Off-Post OU
can be achieved along with the requirements of those statutes for protection of
wildlife?
The Sierra Club has concerns that there will be conflicts due to the presence of
bald eagles in and around the Arsenal. To the greatest extent possible, the
proposed plan and record of decision for the Off-Post OU should set forth how
any potential conflicts are to be resolved to assure that remediation goals will be
met, while at the same time protecting the wildlife included under the three
statutes.
2. Ref. Vol. 7-A-20: Section 4.9 raises the question of protection of the wetlands in
the remediation process. This section specifically states the requirements of
Executive Order 11990 for protection of wetlands. This executive order directs
federal agencies to take action to minimize the destruction, loss, or degradation of
wetlands. The EA/FS states that because wetlands have been identified at the
Arsenal, the requirements of this executive order may be potential location specific
ARAR's
We are also concerned that there may be conflicts between wetlands protection and
meeting required remediation levels. To the greatest extent possible, existing
wetlands at the Arsenal should be protected in the Off-Post remediation process.
Moreover, any contamination of wetlands areas should be remedied to a 1x10 -6
localized risk of cancer.
3. Ref. Vol. 7-A-22: Section 4.12 deals with the Colorado Non-Game Endangered or
Threatened Species Conservation Act. This section states that because remedial
alternatives anticipated for the Off-Post OU are primarily sub-surface, and do not
detail harassing, taking or possession of non-game species, these regulations are not
applicable or relevant to the Off-Post OU.
While remedial alternatives may be primarily sub-surface in nature, they may
never-the-less involve some harassment or destruction of non-game, endangered or
threatened species. For this reason, the Colorado Non-Game Endangered or
Threatened Species Conservation Act should apply in evaluating alternatives for
the Off-Post OU.
Response Gl
The EA/FS (vol. 7, pg. A-6) does state that these three statutes apply to RMA and are applicable
to the offpost remedy. In itself, the FFA requirement is not an ARAR because it is not a
promulgated standard. However, the FFA requirement is legally binding on RMA activities.
Language has been added to the ROD indicating that all appropriate actions will be taken during
the operation of the preferred alternative to ensure compliance with these statutes.
Response G2
Protection of wetlands will be an integral part of the operation of the preferred alternative.
Presently, the Army does not anticipate any conflict between operation of the Offpost Ground-
water Intercept and Treatment System and protection of wetlands. If modifications to the Offpost
Groundwater Intercept and Treatment System are necessary, protection of wetlands will be one of
the issues evaluated.
930425A.enc 10
-------
Response G3
Colorado non-game endangered or threatened species will be protected during the operation and
modification (if necessary) of the Offpost Groundwater Intercept and Treatment System.
Comment H
Our last question does not fall under a particular heading, but we would like you to answer it
Why can't the Army and Shell take the lead in developing new techniques for
chemical clean-up using both the Off-Post area and RMA to do this? This would
be an excellent money-making opportunity for Shell. It would also give both the
Army and Shell Oil Company a more positive image in the eyes of the community
and ultimately the nation.
Response H
The Army and Shell Oil Company have evaluated a number of new and emerging technologies for
use at RMA. Both bench- and pilot-scale tests of several technologies have been or will be
conducted. The biggest problem, when evaluating new technologies, is their application to large
scale clean up activities. If data becomes available indicating potential applications of new
technology at RMA, the Army and Shell will evaluate and apply these technologies to the cleanup
program at RMA.
930425A.enc 11
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Office of the Program Manager
Ms. Sandra A. Horrocks
Subcommittee Chairperson
Rocky Mountain Chapter, Sierra Club
1452 East Northcrest Drive
Highlands Ranch, Colorado 80126
Dear Ms. Horrocks:
Thank you for providing comments on the Offpost Proposed Plan for Rocky
Mountain Arsenal. The Army appreciates the large number of comments submitted
on the Offpost Proposed Plan. I hope the enclosed responses increase your
understanding of the offpost cleanup. Also included are the comments you
submitted on the Offpost Proposed Plan for easier reference to the response.
If you have any further questions please contact Mr. Tim Kilgannon of my
staff at (303) 289-0201.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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RESPONSES TO CITIZENS AGAINST CONTAMINATION COMMENTS
-------
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CITIZENS AGAINST CONTAMINATION
6821WE.61STPLACE
COMMERCE CITY. COLORADO 80022
892-1158
I
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MAY I7OB
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-""T*^»*»lte^->-Af3»»Jr>t-,-1fr1^M>|M^j^
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FAX 893-8562 """" '
StMring CommtttM:
BethGallegoe
JlmHaulg
Sandy JaquHh
Jean Martinez
TomMcCormte
Deny) Thomas
Rita Thomas
Monica Zubla
May 13, 1993
Offpost Proposed Plan Comments
Program Manager for the Rocky Mountain Arsenal
Attn: AMXRM-PM/ Col. Eugene H. Bishop
Bldg. Ill - RMA
Commerce City, CO 80022-2180
Dear Col. Bishop;
Please accept this correspondence as our comments regarding
the Offpost Proposed Plan by the Army:
o cancer risks - the excess cancer risks of approximately
3 in 10,000 or potential risks as high as 1 in 2,000'
are unacceptable. 1 in 1,000,000 is a number we can
accept.
o we would like to see some soil cleanup planned in zone 2
and an articulated plan dealing with prevention of exposure
to ground water in zones 2,3, and 4.
o we would like to see the residents who are exposed to DIMP
in their wells hooked up to S. Adams County Water District
and paid for by the Army and Shell.
o we would like the Army to comply with State regulations for
surface water.
Thank you for this opportunity to comment on this plan.
Very truly yours,
CITIZENS AGAINST CONTAMINATION
Beth Gallegos
cc:
CDH
EPA
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO CITIZENS AGAINST CONTAMINATION COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
MAY 13, 1993
GENERAL COMMENTS
First bullet
The Army has closely followed U.S. Environmental Protection Agency (EPA) guidance and the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP) regarding the use of the
10'4 risk threshold to assess whether remediation is necessary. Guidance states that if the
cumulative cancer risk to an individual is less than 10"1, remedial action may not be warranted
unless certain site-specific conditions exist. If remedial action is warranted, the 10"1 to 10"6 risk
range must be achieved, with an initial preference for the 10"6 end. EPA guidance further states
that the upper boundary of the risk range is not an absolute at 1 x 10"1, but rather, the acceptable
risk range can extend to 5 x 10"1. The cumulative offpost cancer risk is a maximum of 3 x 10"*,
which is within the acceptable risk range.
In explaining the use of the point of departure, the EPA, in the preamble to the NCP, states
The use of 10"6 expresses EPA's preference for remedial actions that result in risks
at the more protective end of the risk range, but does not reflect a presumption
that the final remedial action should attain such a risk level (55 Federal Register
8718).
The operation of the Offpost Groundwater Intercept and Treatment System reflects the Army's
goal of further reducing the potential risk toward the 10"6 level.
Second bullet
The Army used a large amount of onpost and offpost surface soil data to interpret Rocky
Mountain Arsenal (RMA)-related soil contamination. The combination of onpost and offpost data
demonstrates that detected concentrations of contaminants offpost are attributable to windblown
transport from RMA and to offpost activities, including agricultural application of pesticides.
Further, risks corresponding to offpost soil concentrations are within EPA's acceptable risk range.
Therefore, remediation of offpost soil is not required.
For additional discussion, see response to State comment No. 4 in Appendix A-l of this ROD.
Third bullet
The Army will continue to work with EPA, the Colorado Department of Health, and the Tri-
County health Department in assessing the effectiveness of one Offpost Groundwater Intercept
and Treatment System in evaluating the need for alternative water supplies where remediation
goals are exceeded.
21905,301020 - CR-08
0817120193
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Fourth bullet
The Army has recognized all state laws and regulations that meet the applicable or relevant and
appropriate requirement (ARAR) criteria under CERCLA and the NCP. After extensive
discussion with all the parties, the Army has concluded that the Colorado Basic Standards for
Groundwater (CBSGs) do not meet the ARARs criteria because of inconsistent application and
ambiguous language. ARARs for the Offpost Operable Unit are based on federal drinking water
standards and are protective of human health. In most cases, the treatment goals for the offpost
and boundary treatment systems exceed the drinking water standards.
CERCLA expressly provides that state standards can be ARARs at a site. However, only those
standards that are more stringent than federal requirements may be considered. In addition, the
state standards must be promulgated (i.e., the requirement must be of general applicability and
legally enforceable). Finally, the requirements must be identified in a timely manner by the
particular state (40 Code of Federal Regulations [CFR] Section 300.400[g][4]).
The Army concludes that the CBSG interim organic standards are not ARARs for two reasons.
First, the CERCLA exception in Section 3.11.5(C)(5)(a) applies to remedial actions authorized
under CERCLA that are more or less stringent than would be achieved by compliance with the
statewide standards. As a result, the overall effect of the statewide standard and accompanying
exceptions is a state regulation that is only sometimes more stringent than a federal requirement.
CERCLA only considers state standards that are stricter at all times as potential ARARs.
Therefore, by definition, the interim organic standards are not ARARs at Superfund sites.
Second, the CBSG interim organic standards cannot be ARARs because they are not generally
applicable or legally enforceable. A requirement in CERCLA for state requirements to be
ARARs is that they must be promulgated standards, which means they must be generally
applicable and legally enforceable. Clearly, the interim organic standards do not meet this test
when applied at CERCLA sites. By definition, the interim organic standards are applicable
throughout the state, except at CERCLA, RCRA, and UST sites. In those instances, the relevance
of the standards is determined by the remedial sites. It is hard to understand how the standard
could be legally enforceable when the Commission added language specifically ensuring that the
standards may or may not be met at CERCLA sites.
For additional discussion, see response to State comment No. 4 in Appendix A-3 of this ROD.
21905,301020 - CR-08
0817093093
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RESPONSES TO ARSENAL ACTION ALLIANCE COMMENTS
-------
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO ARSENAL ACTION ALLIANCE COMMENTS
REGARDING THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JUNE 21, 1993
GENERAL COMMENTS
Comment 1
The proposed plan for groundwater clean-up is completely inadequate.
The Army fails to propose a plan for the clean-up and/or replacement of domestic
water supplies that are currently contaminated with by-products of chemical
warfare agents, solvents and other Arsenal-related compounds which have been
identified in over a hundred wells spanning miles at varying levels.
The boundary system plan in its current form will do nothing to suck up or treat
the contaminant plume that has already spread for miles past the interceptor points.
Response 1
The proposed plan includes a requirement for providing alternate domestic water supplies at
locations where domestic water currently contains contaminants above applicable relevant and
appropriate drinking water standards. These standards have been established to be protective of
human health. The Army will continue to monitor groundwater contaminant concentrations
during cleanup activities and will provide an alternate domestic water supply for any locations
identified in the future where RMA contaminants exceed groundwater cleanup standards.
As indicated in the proposed plan, the North Boundary Contaminant System is not designed to
capture contamination that has migrated past the RMA north boundary. Capture and treatment of
groundwater downgradient of the North Boundary Contaminant System is the basis for the
construction and operation of the Offpost Groundwater Intercept and Treatment System.
Additional monitoring wells have been installed in this area to help define the extent of
contamination and to aid in monitoring the effectiveness of the treatment system. The Offpost
Groundwater Intercept and Treatment System is designed to extract and treat groundwater in
order to attain groundwater cleanup standards.
Comment 2
The proposed plan fails altogether to address soil contamination in the offpost area, with no plan
to remove toxins in yards where children and pets play, and track contaminants to indoor living
areas.
Response 2
Remediation of soil is not necessary because the estimated risk from exposure pathways relating to
soil is within EPA health guidelines. Extraction and treatment of offpost groundwater will reduce
the total potential risk through all pathways toward the IxlO"6 level.
Comment 3
The plan fails to base its assessment of human health risks on actual conditions and the history of
prior Arsenal-related exposures.
930435.enc 1
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While the Army is aware that elevated rates of at least one cancer type were
demonstrated in the population for a period of time studied, the Army and EPA
have based the "risk assessment" on projections that falsely assume a previously
healthy population.
The Army ignores the fact that a significant number of offpost residents,
especially in the Irondale area, were literally "gassed" by seven months of virtually
uncontrolled toxic fumes including high levels of deadly Shell pesticides and other
toxic Arsenal compounds during the Basin F excavation in 1988 and '89, causing
significantly high levels of risk for cancers and other diseases, according to some
independent medical experts.
The Army ignores the fact that human beings in some sectors of the offpost area
already have elevated risk from Arsenal poisons, having consumed levels of TCE
and other toxins exceeding federal health guidelines in their drinking water
through South Adams County's Water system for years prior to charcoal filtration,
and even at times since.
Response 3
The Army followed EPA guidance in the conduct of the risk assessment for the Offpost Study
Area. These guidelines do not account for existing health conditions, which may or may not be
present in a population. However, the EPA risk assessment procedures include sufficient safety
factors to be protective for sensitive populations.
The risk assessment conducted for the Offpost Study Area does not, by definition, assess whether
adverse health effects have occurred or will occur and cannot identify particular individuals likely
to suffer health problems because of contamination at a site. The Agency for Toxic Substances
and Disease Registry (ATSDR), in cooperation with the Colorado Department of Health, have
ongoing epidemiological studies near RMA to address the occurrence of health effects and assess
whether these effects may be attributable to exposure to contaminants from a hazardous waste
site. To date, the health study completed by the Colorado Department of Health and ATSDR has
given no proof of a cause-effect relationship between Arsenal contamination and health problems
in the offpost area.
Questions regarding violation of federal drinking water standards by the South Adams County
Water and Sanitation District (SACWSD) should be addressed directly to SACWSD. The Army is
not involved in the operation or maintenance of that facility.
CITIZEN RECOMMENDATIONS FOR THE U.S. ARMY AND SHELL
Recommendation 1
All domestic wells currently contaminated by DIMP, IMPA and/or any other Arsenal-
related toxins, found at any level should immediately be replaced with an alternative
source of water, to eliminate all current routes of toxics exposure, including dermal
exposure and steam inhalation while bathing and showering.
93043S.enc
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Response to Recommendation 1
The Army will continue to work with the U.S. Environmental Protection Agency (EPA), the
Colorado Department of Health, and the Tri-County Health Department in assessing the effec-
tiveness of the. Off post Groundwater Intercept and Treatment System and in evaluating the need
for alternative water supplies where cleanup standards are exceeded.
Recommendation 2
Cap all shallow groundwater wells, to prevent continuing migration of Arsenal poisons to
the deeper aquifer, as was recommended by the U.S. Public Health Service in 1959. over
30 years ago.
Response to Recommendation 2
Well closure of offpost wells has been included as a component of the selected remedy. See
Appendix C of the Record of Decision (ROD). Specifics, relating to the criteria for individual
well closures, are being discussed with the EPA, Colorado Department of Health and Tri-county
Health Department.
Recommendation 3
Install groundwater interceptor systems along the leading edge of the plume, to the west of
the South Platte River, to the north near or above Brighton, and east where the plume has
not been adequately characterized, to date.
Response to Recommendation 3
The Offpost Groundwater Intercept and Treatment System is located such that the groundwater
will be treated to meet or exceed the remediation goals established to be protective of human
health. Diisopropyl methylphosphonate (DIMP) concentrations at the leading edge are approxi-
mately 100 times less than the concentration established by the EPA to be protective of human
health. The National Oil and Hazardous Substance Pollution Contingency Plan (NCP) does not
require cleanup to a concentration of zero.
Recommendation 4
Develop a comprehensive contaminated soil removal and clean-up plan for any and all
offpost areas (including areas to the east and elsewhere, not currently included in the
"offpost study area") where RMA chemicals — including Shell's dieldren, aldrin, endrin
and other poisons — have been identified.
Response to Recommendation 4
Background sampling indicated that pesticides are present throughout the Offpost Study Area.
Agricultural application of pesticides is a contributing source. Agricultural application of a
registered pesticide is exempt from CERCLA. However, the risk associated with the dieldrin
concentration in these hot spots do not exceed a lifetime cancer risk of 5 x 10"6, which is at the
lower end of the acceptable risk range defined by the U.S. Environmental Protection Agency
(EPA). Therefore, specific cleanup of these soil areas is not required. Cleanup of offpost
groundwater will provide the greatest benefit of risk reduction.
930435.enc
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Recommendation 5
Develop a plan that includes analysis for compounds in offpost soil and surface waters
associated with the RMA's onsite hazardous waste incineration and mechanisms for clean-
up of heavy metals, dioxins and other toxins released to offpost area yards, farms and/or
businesses in conjunction with the Army's two-year incineration activities.
Response to Recommendation 5
Monitoring plans will be developed following completion of the ROD. See Response to Comment
4, regarding the Submerged Quench Incinerator, following the Offpost Proposed Plan Responses.
Recommendation 6
Postpone the "Record of Decision" on the offpost clean-up until the State of Colorado
enacts groundwater standards for currently unregulated, Arsenal-related toxic compounds,
based on independent medical opinion without conflicts of interest with the Army or its
agents. Once those standards are adopted, set clean-up levels that meet — or preferably
exceed -- the standard.
Response to Recommendation 6
The Army is not required to postpone the ROD in order to wait until a standard is promulgated.
Flexibility is inherent in the Army's selected alternative, and if a standard changes and subse-
quently applies to the offpost program, the selected alternative will be modified.
Health advisories developed for DIMP and isopropyl methylphosphonic acid (IMPA) by the EPA
and its Office of Drinking Water represent an evaluation by independent organizations that have
no conflict of interest with the Army.
Recommendation 7
Abandon risk assessment for the offpost based on "zones," and clean up all contaminated
soil and water areas to the maximum extent considered safe for residential use, since there
are no mechanisms in place whereby land uses are to be restricted on private property, and
cannot be projected in perpetuity.
Response to Recommendation 7
The NCP does not assume that unrestricted residential use will be the overriding consideration in
cleanup efforts. In fact, the NCP states that the assumption of residential use is not a
requirement, only that future land use be evaluated. Section 104(i) of Comprehensive Environ-
mental Response, Compensation, and Liability Act (CERCLA) states that health risk assessments
should evaluate the potential risk to human health posed by "individual sites," based on such site-
specific factors as the "nature and extent of contamination" and the "existence of potential
pathways of human exposure." Clearly, this language indicates that the EPA recognizes that all
areas of a site are not equal in terms of potential risk. Because the guidelines for determining
which areas require remediation are risk-based, it is important and essential to establish exposure
areas (e.g., zones) with differing chemical concentrations and potential exposure patterns. This
allows identification of those areas that pose the greatest concern (by virtue of higher risk) and
that will require remediation. In addition, Institutional Controls have been added to the ROD to
further protect the public from potentially contaminated areas.
930435.enc 4
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Recommendation 8
Amend the plan to reflect clean up standards that meet — or preferably exceed — the
EPA's National Contingency Plan level of "acceptable" risks, which clearly states no more
that 1 excess cancer per million is considered safe. The Army's plan to allow a level of 1
excess cancer per 10,000 is outrageous, inconsistent with Superfund clean-up levels at
other sites around the country, and which we believe to be overt environmental
discrimination, whereby the U.S. Army would intentionally subject citizens in
predominantly low-income communities to dramatically higher risks of death from its
cleanup actions alone, on top of already elevated risks due to previous water, air and soil
contamination from the Arsenal.
Response to Recommendation 8
The Army has closely followed EPA guidance and the NCP regarding the use of the 10"* risk
threshold to assess whether remediation is necessary. Guidance states that if the cumulative
cancer risk to an individual is less than 10"*, remedial action may not be warranted unless certain
site-specific conditions exist. If remedial action is warranted, the 10"4 to 10* risk range must be
achieved, with an initial preference for the 10"6 end. EPA guidance further states that the upper
boundary of the risk range is not an absolute at 1x10"*, but rather, the acceptable risk range can
extend to 5 x 10"4. The cumulative offpost cancer risk is a maximum of 3 x 10"*, which is within
the acceptable risk range. This risk was calculated without considering operations of the Offpost
Groundwater Intercept and Treatment System.
In explaining the use of the point of departure, the EPA, in the preamble to the NCP, states
The use of 10"6 expresses EPA's preference for remedial actions that
result in risks at the more protective end of the risk range, but does
not reflect a presumption that the final remedial action should
attain such a risk level (55 Federal Register 8718).
The operation of the Offpost Groundwater Intercept and Treatment System reflects the Army's
goal of further reducing the potential risk toward the 10"6 level.
Additionally, the Army is following EPA regulations and does not practice environmental
discrimination, as implied in the comment.
Recommendation 9
Abandon so-called "clean-up" plans that allow people to be exposed to known dangerous
toxic compounds, in addition to an array of unknown hazards from the negligent actions at
the Rocky Mountain Arsenal over the last half century, which continue to sacrifice public
health, homeowners' investments, the environment, and the viability of whole
communities.
Response to Recommendation 9
The Army will not abandon the cleanup plan identified in the Proposed Plan. The selected
alternative for offpost cleanup will not be determined until the Final ROD is accepted by the U.S.
EPA and issued (now scheduled for early 1994). The Army believes its preferred alternative will
protect human health and the environment and benefit property values offpost.
930435.enc 5
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Office of the Program Manager
Ms. Adrienne Anderson
P.O. Box 512
1200 Madison Street
Denver, CO 80206
Mrs. Bennie Muniz
P.O. Box 261
Henderson, CO 80640
Mrs. Mary Daigle
8810 E. 88th Ave. #40
Henderson, CO 80640
Dear Madams:
Thank you for providing comments on the Offpost Proposed Plan for Rocky
Mountain Arsenal. The Army appreciates the large number of comments submitted
on the Offpost Proposed Plan. Also included are responses to comments you
submitted on the Submerged Quench Incinerator (SQI). I hope these responses
increase your understanding of the SQI and offpost cleanup.
Please Contact Mr. Bill Thomas, Public Affairs Office, at (303) 289-0136 if you
have any questions regarding the SQI and Mr. Tim Kilgannon at (303) 289-0201, if
you have any questions regarding the Offpost Proposed Plan.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
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Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-EDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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RESPONSES TO COLORADO PESTICIDE NETWORK COMMENTS
-------
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p»i Tup
We support the N-5 cleanup alternative because it will give a more
? ~ s ? ^ v ?**'t'3tv.'s t " t *"! • c '??**" 7 ? * * *". * ? s " s 3 . E '' p e c t e "1 pressures f ;•• r
developing the area because of the new Denver International Airport
necessitate giving attention to the cleanup.
We would like the dieldrin hot spots and other contaminated areas t
be remediated. CERCLA established a strict joint and several liability
Scheme. If other parties also contributed to the contamination, the cleanu
remedy is a contribution suit. We have not seen any evidence which would
prove that the arsenal did not at least contribute to the excess dieldrin
contami nati on.
DIMP should be cleared from ground and surface water to at least 8
•jpt. T*~? CDS SV?TSct?d cleanup |c\/el -<•* *00 r " * '? ipn^h tOO Hf Qh bfC3US£'
different criteria are used to determine nutrient needs in human and te
anima Is;
the average American diet CUSDA 1977) does not even supply the
recommended daily doses for nutrients;
test animals were given extra supplements to meet their nutrient needs
off cost dwellers may not take any supplements.
The 1990 mink study only solicits further questions about the impacts
DIMP and sudden deaths of mink related to DIMP. The former mink study show
S'jdden death should be given top consideration in considering DIMP toxicity
Submitted by,
• igela Medbery -cr
Colorado Pesticide Network
c/o 2205 Meade Street
Denver, CO 80211
1\
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO COLORADO PESTICIDE NETWORK COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JUNE 21, 1993
Response to Comment No. 1 - Preference for Alternative N-5.
The Army selected Alternative N-4 rather than N-5 on the basis of the evaluation criteria
specified by the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) as
described in the Record of Decision (ROD). The slightly shorter time frame for cleanup
estimated for Alternative N-5 was not the overriding issue in the selection process. The Army
believes that the immediate operation of the existing Offpost Groundwater Intercept and
Treatment System with later evaluation (Alternative N-5) is preferable to incurring increased
construction costs for Alternative N-5 based on results of computer modeling. After review of
actual operational data (which includes an evaluation of the change in chemical concentrations in
groundwater), if improvements or modifications to the existing system are necessary, they can be
implemented more effectively. These improvements would be based on actual data and would
therefore be more effective than Alternative N-5 based on computer modeling results.
For additional discussion, see response to State comment No. 2a in Appendix A-3 of the ROD.
Response to Comment No. 2 - Dieldrin Hot Spots.
Based on our evaluation, isolated areas of increased dieldrin concentration (i.e., hot spots) in
offpost soil are not a result of transport from Rocky Mountain Arsenal. Windblown soil would be
deposited in a more uniform pattern and would not result in a deposition of high concentrations of
dieldrin in one area. Additionally, background sampling indicated that pesticides are present
throughout the Offpost Study Area. Agricultural application of pesticides is a contributing
source. Agricultural application of a registered pesticide is exempt from CERCLA. However, the
risks associated with the dieldrin concentrations in these hot spots do not exceed a lifetime cancer
risk of 5 x 10"6, which is at the lower end of the acceptable risk range defined by the U.S.
Environmental Protection Agency (EPA). Therefore, specific cleanup of these soil areas is not
required. Cleanup of offpost groundwater will provide the greatest benefit of risk reduction.
Response to Comment No. 3 - PIMP Cleanup Standard and Studies
The Army is using the EPA's Health Advisory value for diisopropyl methylphosphonate (DIMP)
of 600 parts per billion (ppb) to determine which areas of DIMP-contaminated groundwater
require remediation. This value represents a determination concurred by many EPA scientists and
toxicologists. As stated in the Operation and Maintenance Manual for the Offpost Groundwater
Intercept and Treatment System, the treatment system is designed such that the treated water
contains no more than 10 ppb of DIMP. Because the treatment system is located in the area of
highest groundwater contamination, treatment of the groundwater to a level of 10 ppb DIMP
should have a significant impact on the regional DIMP concentrations.
Because humans and animals are different, their nutrient needs are also different. All EPA
animal testing guidelines indicate that animals should be properly fed with a diet that includes the
appropriate nutrients. Although the average human diet may be lacking in some nutrients, there
are no procedures currently being used by EPA or state agencies to specifically account for this.
There are, however, a number of safety factors built into the determination of the health advisory
that the EPA believes are sufficient to account for potential variation among human sensitivities.
930425C.enc 1
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The EPA has recommended that the mink DIMP study not be used for human health effect studies
because of the high natural annual mortality in mink, the general lack of information on the mink,
and uncertainties concerning the relevance of mink to human health assessment.
For additional discussion of the DIMP standard, see response to State comment No. 2d in
Appendix A-3 of the ROD.
930425C.ene
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Office of the Program Manager
Ms. Angela Medbery
Colorado Pesticide Network
2205 Meade Street
Denver, Colorado 80211
Dear Ms. Medbery:
Thank you for your comments on the Offpost Proposed Plan for Rocky
Mountain Arsenal. The Army appreciates the large number of comments submitted
on the Offpost Proposed Plan. I hope the enclosed responses increase your
understanding of the Offpost cleanup. Also included are the comments you
submitted for easier reference to the Army's response.
If you have any further questions please contact Mr. Tim Kilgannon of my
staff at (303) 289-0201.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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RESPONSES TO ENVIRONMENTAL INFORMATION NETWORK COMMENTS
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO ENVIRONMENTAL INFORMATION NETWORK COMMENTS
REGARDING THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
Comment 1:
The preferred option cites Barr Lake and Burlington Ditch as offpost study areas, yet it appears
that a comprehensive characterization has not occurred as yet. Are there current plans for
extensive sediments and sediment core samples to be done throughout these areas?
Response 1:
The Army believes that the sampling activities conducted at Barr Lake and Burlington Ditch have
been sufficient to adequately characterize these areas and to evaluate the need for remediation. In
addition, a surface-water monitoring program will be implemented as a component of the
preferred alternative.
Comment 2:
Have sufficient 3-dimensional plume maps been generated to answer the following questions:
have the plume heads been defined in such a manner that the locations are identified? Have the
plume heads reached and dispersed in the local tributaries, canals, and lakes?
Response 2:
Through the combination of data collected from an extensive system of offpost and onpost
monitoring wells and use of groundwater modeling techniques, the areal extent of Rocky
Mountain Arsenal (RMA)-related contaminants is well-defined. As discussed in the Final
Remedial Investigation report, contaminant detections in local tributaries, canals, and lakes are
generally not above background levels.
Comment 3:
The Groundwater monitoring alternative cited states the samples will be collected periodically.
Will these be grab or composite samples? What exactly will be monitored? What are the target
analytes? How long will it take to get results from this testing? How frequently will the samples
be taken, and at what locations?
Response 3:
Specifics of the groundwater monitoring program to be implemented as part of the offpost
selected remedy have not yet been developed. The Record of Decision (ROD) states that the
monitoring plan will be developed following finalization of the ROD.
Comment 4:
A site review will be conducted at least every five years according to the U.S. Army brochures. A
site of this complexity and severe nature of contamination dictates a much more aggressive review
time line. Every 5 years therefore is not acceptable. This should be brought forward for further
public discussion. Please explain why the Army feels that a 5 year parameter is sufficient.
930376.enc
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Response 4:
As stated in the Proposed Plan and the ROD, Section 121(c) of the Comprehensive Environmental
Response, Liability, and Compensation Act (CERCLA) mandates that a formal site review be
conducted at least every five years to assure that human health and the environment are protected
during and after remediation. However, informal reviews of the efficiency, effectiveness, and
environmental impacts of the treatment systems will be a continuous process. A large part of these
informal reviews will be an assessment of the groundwater and surface-water monitoring data
collected as part of the long-term monitoring program. These informal reviews will be performed
as often as long-term monitoring is performed. Based on the information obtained during
operation of the treatment systems, a formal review may be conducted sooner than five years
following implementation of the remedy, but no later.
Comment 5:
Alternate Water Supply is cited as being provided if domestic wells are identified as containing
concentrations that exceed remediation goals. Please specify exactly what those concentrations
consist of, and whether they are protective of chronic exposures and synergistic accumulative
uptake in small children, and pregnant women.
Response 5:
Remediation goals (i.e., cleanup standards) are listed in Table 7.1 of the ROD. Based on U.S.
Environmental Protection Agency (EPA) guidance on risk assessment methodology, these
concentrations are expected to be protective of adverse health effects for sensitive individuals and
for chronic exposures.
Comment 6:
The RMA boundary containment systems may not be adequate systems for ground water recharge
pump-and-treat containment if they are relying solely on carbon adsorption units for removal of
organics only. Other contaminants at the RMA include metals, which are not affected by carbon
adsorption units. Other processes such as precipitation may be required to address this.
Response 6:
Concentrations of metals and other inorganics approaching the RMA boundaries were determined
to meet all applicable groundwater standards. If ongoing groundwater monitoring results show
that other chemicals are approaching the RMA boundaries above standards, the Army will revise
the treatment systems as necessary.
930376.enc
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Office of the Program Manager
Ms. Paula Elofson-Gardine
Executive Director
Environmental Information Network (EIN), Inc.
P.O. Box 280087
Lakewood, CO 80228
Dear Ms. Elofson-Gardine:
Thank you for providing comments on the Offpost Proposed Plan for Rocky
Mountain Arsenal. The Army appreciates the large number of comments submitted
on the Offpost Proposed Plan. Also included are responses to comments you
submitted on the Submerged Quench Incinerator (SQI). I hope these responses
increase your understanding of the SQI and offpost cleanup.
Please contact Mr. Bill Thomas, Public Affairs Office, at (303) 289-0136 if you
have any questions regarding the SQI, and Mr. Tim Kilgannon at (303) 289-0201, if
you have any questions regarding the Offpost Proposed Plan.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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RESPONSES TO DENVER AUDUBON SOCIETY COMMENTS
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DENVER
AUDUBON
SOCIETY
OH 24 03
8751 £. Hampden Am., Suite A-l • Denver, CO 80231 • (303) 696-0877
21 June, 1993
Offpost Proposed Plan Comments
Program Manager for Rocky Mountain Arsenal
Attn: AMXRM-PM/
Col. Eugene H. Bishop
Building 111-RMA
Commerce City, CO 80022-2180
Dear Sir:
We would like to endorse the recommendation from CDH that option N-5 be
selected in preference to N-4, because it provides a more aggressive
treatment . The tradeoff, by which both plans are estimated to cost
the same, is for N-5 more immediate expenses for construction of wells
and trenches, in place of more expense for intensive monitoring over two
years indicated for N-4. The additional monitoring would provide data
for improved modeling of groundwater movements. It would not of itself
provide improvement in protection of the environment. On the other
hand, N-5 would provide a more rapid reduction in concentrations of
groundwater contaminants, which in our view would be a reassurance for
environmental protection.
In support of this view, we would direct attention to the large
uncertainties in any risk assessment. This is not to fault the
methods used by the Army in its decision making. Nor are we taking
issue with the reasoning for rejecting some insights on the possiblfe
impact of contaminants which are not at present fully supported by
experimental data. But in this instance we have a tradeoff which
involves no change in estimated cost. This seems to be the logical time
to give the benefit of the doubt to impacts of contaminants, which,
while not "proven", at least are considered believable by many qualified
observers.
In rejecting CDH arguments concerning ecological risk characterization
which might involve multiple chemical interactions as documented in a
monograph by Calabrese, the Army said (VIII- p.60) "...because of its
early investigational stages and lack of scientific concensus,
acceptable guidelines for use in ecological assessment are lacking."
This no doubt is a compelling argument for the practice of risk
assessment, but it does nothing to quiet the uneasiness of observers who
find evidence of adverse impacts on biota, necessarily without being
able to pinpoint the agents responsible. Again, we do not dispute the
risk assessment, but accept it as a necessary though imperfect tool.
Our argument in this instance is that with costs being equal, the more
aggressive clean-up is more desirable.
The same considerations apply to surface runoff in First Creek. No
attempt is being made to intercept and filter this water, because th'e
concentrations are low, and the water is hydrologically interrelated
with the ground water. However, higher concentrations are episodic,
and it would again seem desirable to favor a more aggressive- cleanup
option.
I PONTEDOH
1 RECYCLED fArea
I
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In justifying the selection of N-4 as the favored option, the Army
observes (5.4.1.4) that "the potential for exposure in the timeframe is
reduced by the Army committment to provide alternative water to any
future identified ground water users." While this seems prudent, we
are concerned that the uncertainties in ecological risk might be
ignored.
The Army has emphasized that the 2-year intensive monitoring proposed
under option N-4 is needed for decision-making regarding potential
improvements to the treatment installations. They have not made
clear the compelling need. On the other hand there seems to be clear
justification for expecting more rapid cleanup for the treatment plans
under N-5. The real tradeoff seems to be more accurate modeling for
risk assessment as opposed to more aggressive removal of groundwater
contaminants, which might not be optimal, but is sure to work.
Sincerely yours,
Frank Clough
Pesticide Representative for
Denver Audubon Conservation Committee
c: Polly Reetz
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO DENVER AUDUBON SOCIETY COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JUNE 21, 1993
GENERAL COMMENTS
Comment 1: Selection of N-4 instead of N-S
As presented in the Final Off post EA/FS report Volume VI, Section 4.2.1, Screening of Alterna-
tives - North Plume Group, effectiveness, implementability, and cost criteria were explicitly
evaluated consistent with the requirements of the NCP. In this section of the EA/FS, it was
concluded that Alternatives N-4, N-5, and N-6 afford the best reduction in toxicity, mobility,
and volume, the best long-term protection, and the best compliance with remediation goals.
Alternative N-6 was screened out at this point on the basis of similar performance in comparison
with Alternative N-5 with respect to reduction in toxicity, mobility, and volume, yet it afforded
no benefit in terms of remediation timeframe (10 to 20 years) and at higher cost.
The Army selected Alternative N-4 instead of Alternative N-5 primarily because Alternative N-4
includes potential future modifications, if such modifications are found to be necessary based on
actual operating data, to the Offpost Groundwater Intercept and Treatment System and because
use of actual full-scale operating data is preferable to selecting additional components for the
Offpost Intercept and Treatment System using the more speculative modeling data (i.e., Alterna-
tive N-5).
The Army is committed to efficient operation of the Offpost Groundwater Intercept and
Treatment System and will evaluate operating data to assess the need for system modification.
Similar to the onpost boundary treatment systems, it is difficult to assess whether the installation
of additional wells will provide more efficient operation without collecting full-scale operating
data for the Offpost Groundwater Intercept and Treatment System. The Army has included an
intensive monitoring component as part of the preferred alternative, Alternative N-4, in the
Proposed Plan. This intensive monitoring program will allow the collection and subsequent
interpretation of performance data for the full-scale operation of both the Offpost Groundwater
Intercept and Treatment System and the onpost boundary systems. The data will be used to assess
the need for any improvement to the systems and will provide increased accuracy in assessing
contaminant cleanup. Acquisition of this operational data is preferable to adding extraction wells
and recharge trenches without the benefit of operational data, because additional data are required
to assess the necessity and placement of any additional extraction wells or trenches. If operational
data supports the conclusion that the cleanup timeframe can be shortened without a significant
increase in long-term costs, modifications to Alternative N-4 will be implemented. By taking this
approach, improvements to the system will be more effective than improvements made based on
computer modeling data.
For additional discussion, see response to State comment No. 2a in Appendix A-3 of this ROD.
21905,301020 - CR-08
0817120193
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Comment 2: Cleanup of Surface Water
Given that the following three factors point to continuing beneficial impacts to offpost water
quality, the Army is committing to an ongoing surface water monitoring program to track the
cleanup of offpost surface water: (1) remediation of groundwater should have a beneficial effect
on offpost surface water quality, (2) contaminant concentrations are lower during storm event
runoff periods (Surface Water Comprehensive Monitoring Program Annual Report for 1989 [R.L.
Stollar & Associates, and others, 1990]), and (3) the Army has committed to closing the onpost
sewage treatment plant, thus eliminating a possible source of contaminants in the First Creek
surface water drainage.
The components of the offpost surface water monitoring program will be contained in a report to
be completed following completion of the ROD. The ROD contains the Army commitment to
both surface water and groundwater monitoring programs in the offpost area as a component of
the selected remedy.
21905,301020 - CR-08
0817120193
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RESPONSES TO WE THE PEOPLE COMMENTS
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO WE THE PEOPLE COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
GENERAL COMMENTS
Comment 1:
The plan and its alternatives are based on suspect or manipulated data. This was evidenced at the
April 28, 1993 public meeting by comments regarding DIMP levels in wells showing levels
exceeding what is often broadly and publicly reported.
Response 1:
The Army has not based the selection of the preferred alternative on suspect DIMP data, nor has
the Army engaged in manipulating DIMP data. If the commentor is referring to the State of
Colorado's statement regarding levels of DIMP exceeding 600 ppb north (downgradient) of the
Offpost Groundwater Intercept and Treatment System, the Army is aware of these data. A
component of the preferred alterative involves installation of three new monitoring wells. Two
new monitoring wells will be installed downgradient of the First Creek Pathway and one new
monitoring well will be installed downgradient of the Northern Pathway. The purpose of the
three new monitoring wells is to aid in assessing the extent of contamination downgradient of the
Offpost Groundwater Intercept and Treatment System. Data collected from these wells and
existing wells will be used to further define the extent of contamination greater than the cleanup
goals in this area and assist in determining whether modifications to the Offpost Groundwater
Intercept and Treatment System are necessary.
Comment 3:
The offpost plan and its alternatives are so inadequate in their remediation and ongoing
monitoring of; water, soils, the air basin, existing and ongoing harm to the public health, offpost
wild and domestic animal life; plus the very limited scope of the offpost area itself, that the only
possibility is to start over.
Response 3:
The selection of the preferred alternative in the Record of Decision was based on the evaluation
criteria established in the National Oil and Hazardous Substances Pollution Contingency Plan
(NCP). The results of the EA/FS indicated that groundwater is the major contributor to potential
risks. Treatment of groundwater with the Offpost Groundwater Intercept and Treatment System
will reduce the estimated risk toward the level of one excess cancer per one million people
(IxlO"6).
Part of the preferred alternative involves extensive monitoring of offpost groundwater conditions
throughout the operation of the Offpost Groundwater Intercept and Treatment System. Results of
the Comprehensive Air Monitoring Program for RMA indicated that the air quality is not a health
concern in the offpost area. The results of the risk assessment conducted for the Offpost Study
Area indicated that potential harm to wildlife is minimal, and that potential harm to domestic
animals is nonexistent. However, the Army will continue to monitor offpost groundwater surface
water, and soil as needed as part of the preferred alternative. The Agency for Toxic Substances
and Disease Registry (ATSDR) and the Colorado Department of Health (CDH) have ongoing
930377.enc 1
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epidemiological studies near RMA to evaluate the occurrence of health effects. The Army
believes that the Offpost Study Area and the investigations conducted to date are not of "limited
scope." The studies conducted for the offpost area have been done with the approval of the U.S.
Environmental Protection Agency (EPA) and with review and comment by CDH. The Army does
not intend to start over; rather, the Army intends to proceed with implementation of the preferred
alternative so that potential offpost risks will be reduced.
SPECIFIC COMMENTS
Comment 1:
The offpost study area is too limited in scope to be meaningful. The following scope areas and
the way they are addressed are inadequate in the proposed plan and its alternatives:
Comment Ib: Soil monitoring and remediation is inadequate. The idea that other sources are
responsible for the contamination of soils in the surrounding area is an
unacceptable premise to make from any organizations that have openly, blatantly,
willfully, and; who without any regard whatsoever for environmental, health, and
social harms, freely polluted surrounding communities for 40 years. A soils
remediation plan needs to be developed, and in such a way as to not create
additional risk exposure to the environment and the public.
Response Ib:
The Army has adequately characterized the extent of contamination in the offpost soil. The Army
has not stated that other sources are entirely responsible for the offpost soil contamination.
However, particularly with regard to the distribution of pesticides, it is apparent that localized
areas of higher concentrations may not be attributable to simple windblown erosion from onpost
soil. Because of the widespread use of pesticides in agricultural practices, pesticide residues are
widespread and are found in nearly all soil samples in the offpost area. The general nature of
windblown soil indicates that localized offpost areas of high soil pesticide concentrations are
unlikely. Intentional pesticide application is believed to be at least partly responsible for the high
concentrations of pesticides in certain soil areas.
However, the estimated risks (approximately 5 x 10"6)associated with these higher concentrations
of pesticides found offpost are well within the EPA health guidelines.
Comment Ic: The lack of establishing a thorough baseline health study of the affected areas and
the deviation or lack of deviation from the health of unaffected areas. This must
include the evaluation of human, wildlife, and domestic animal populations.
Response Ic:
The baseline risk assessment performed for the Offpost study area is not based on knowledge or
information regarding the current health status of potentially exposed individuals. The risk
assessment is based on estimating the current and potential future exposures. A comprehensive
epidemiological study is not required by either CERCLA or the NCP. While this information may
be useful, the EPA does not require it as part of the risk assessment process or as a factor in the
selection of the remedy. Rather, the EPA has consistently used the results of the site-specific risk
930377.enc
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assessment as a basis for determination of the need for cleanup.
A risk assessment, like the one performed for the Offpost Operable Unit, is a scientific evaluation
of the probability that adverse effects will occur if people, wildlife, or domestic animals are
exposed to contaminants present at the site. The risk assessment considers the ways humans and
animals may be exposed (pathways of exposure), the likelihood of adverse health effects, the
expected types of health effects, and the toxicity of individual chemicals. A risk assessment does
not, by definition, determine whether adverse health effects have occurred or will occur and
cannot identify particular individuals likely to suffer health problems because of contamination at
a site.
However, separate from the risk assessment process, the ATSDR in cooperation with CDH may
conduct a health assessment and, on the basis of their findings, institute a full-scale epidemio-
logical study to address the actual occurrence of health effects and determine if these effects may
be attributable to exposure to contaminants from a hazardous waste site. The ATSDR and CDH
have ongoing epidemiological studies near RMA.
Comment Id: The lack of ongoing monitoring of health harms; and provisions for harm(s) done
or yet to be done to the health of human, wildlife and domestic (including pets,
farm, and ranch) populations.
Response Id:
See response to comment Ic above.
Comment If: In an information meeting at the Montbello library it was revealed that water
coming back to the RMA from the Montbello area was contaminated. The
assumption stated was, that this contamination was generated by industrial sources
within the Montbello community. Once again, the idea that other sources are
responsible for the contamination of water or soils in the surrounding area is an
unacceptable premise to make from any organizations that have openly, blatantly,
willfully, and; who without any regard whatsoever for environmental, health, and
social harms, freely polluted surrounding communities for 40 years. An in-depth
determination must be made to determine that this contamination is not from prior
exposure to pollutants from RMA ground and air pathways to Montbello soils and
water, and further if other Pollution generators are discovered that they and the
appropriate community authorities and governmental regulators be notified.
Further, if the contaminants were possible products from RMA activities, with no
present day generators then remediation and ongoing monitoring plans should be
established.
Response If:
The commentor has misinterpreted the statement made at the informational meeting. Water does
not "come back" to RMA from the Montbello area. Groundwater flow direction is from the south
to the north. Groundwater contaminants present beneath RMA would therefore be transported to
the north. If contaminated groundwater is identified at the southern boundary of RMA, the
source of this contamination is most likely located south of RMA, perhaps within the Montbello
area. The Army has not stated that other sources are responsible for the contamination. The
Army is stating that in some areas, it is apparent that some contamination appears to have
originated from sources other than RMA activities. The Army is in full agreement with the
statement that if the contaminants are possible products from RMA activities, remediation and
930377.enc 3
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ongoing monitoring plans should be established. This is the purpose of the Remedial Investiga-
tion, Endangerment Assessment/Feasibility Study (EA/FS), the Proposed Plan, and selection of
the preferred alternative in the Record of Decision.
Comment 2:
The offpost study area is too limited in size to be meaningful. The following areas need to be
added to the study area along with the pertinent scope that including them would necessitate:
Comment 2ai The entire western boundary of the RMA needs to be part of the plan even if
there is another superfund site along part of it. Pollution was done to the whole,
the plan needs to address in detail the whole.
Response 2a:
The entire western boundary of RMA was included initially in the evaluation of the offpost area.
Soil and groundwater samples were collected and analyzed from the area included in the EPA
Study Area. Concentrations of contaminants in this area do not exceed offpost cleanup goals. As
defined in the Federal Facility Agreement, the offpost areas requiring cleanup are those areas
where RMA-related chemical concentrations exceed EPA standards or cleanup goals. Conse-
quently, this area was not included in further offpost studies. Additionally, the groundwater
migration direction indicates that sources other than RMA are responsible for the contamination
in this area. Because it is part of another study area, other parties are responsible for the cleanup.
Comment 2c: Include the communities of Montbello and Green Valley Ranch. They are
downwind of RMA and therefore were exposed to definite pollution via air
pathways. They may have also been exposed via heavy rains and blowing snow.
Response 2c:
The claim of "definite pollution via air pathways" cannot be substantiated. Results of the
Comprehensive Air Monitoring Program (CAMP) for RMA indicate that potential exposures at
the boundaries of RMA through the air pathway are negligible, if not unmeasurable. However,
the CAMP will monitor air quality at the RMA boundaries as long as cleanup continues onpost.
Response 2d: Expand the northern boundaries to include leaching areas on both sides of the
shown waterways and the area to and including the perimeter of Barr lake.
Additionally, add the Brighton area water supply area for ongoing monitoring and
a remediation contingency plan if plumes of pollution continue their creep
towards their water supply.
Response 2d:
The boundaries of the Offpost Study Area were defined to include those areas of groundwater
known to contain RMA-related chemicals and surface water bodies that may be affected. The
land adjacent to the streams was not shown to contain elevated concentrations of contaminants.
Similarly, the land surrounding Barr Lake would not be expected to contain chemicals in
concentrations exceeding other land areas included in the Offpost Study Area. Therefore, the
land adjacent to the waterways and Barr Lake were not included as part of the Offpost Study
Area.
930S77.enc
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The Army has many groundwater monitoring wells downgradient of the Offpost Groundwater
Intercept and Treatment System, including wells upgradient of the Brighton area water supply
wells. The monitoring program implemented as part of the preferred alternative will adequately
identify potential plume migration before reaching the Brighton water supply wells. If such
migration is identified and is a threat to the safety of the drinking water, the Army will modify
the offpost cleanup plan to protect the Brighton water supply wells.
Comment 2e: A minimum of 5 kilometers in all directions from each stack of the north plant and
south plant.
Response 2g:
Neither the North Plants or the South Plants are currently operating or involved in any manufact-
uring processes. There are no emissions from the stacks at either location. RMA-related
contamination has not been detected at locations other than north of the RMA boundary (the
Offpost Study Area). Therefore, it is not appropriate to include a 5 kilometer 360-degree radius
around the RMA onpost area as the Offpost Study area.
Comment 3:
We would request that the Army respect the Colorado Department of Health's recommended
Standard for DIMP in ground water at 8 ppb. Further the Army, Shell, its agents Holme Roberts
and Owen, and the EPA should not further interfere with or lobby the Colorado Water Quality
Commission (WQCC) to set a higher standard in order to benefit the RMA parties at the risk of
Public Health and the ENVIRONMENT. We feel these activities undermine Public confidence in
the WQCC and will dilute the sovereignty of the State of Colorado.
Response 3:
The Army did not interfere with or lobby the Colorado Water Quality Commission to set a higher
standard for DIMP in groundwater. The Army has presented its position to the Commission as
part of the public hearing process. The Army stated that in was in agreement with the EPA's
position which has the support of many top-level scientists, both from within the EPA and other
national organizations. The Army believes it is inappropriate to set a standard based on the
opinions of one scientist when that opinion is not shared by the scientific peer group.
The Colorado Water Quality Control Commission recently set an 8 parts per billion standard for
DIMP in groundwater. The Army is currently evaluating the applicability of this standard to the
preferred alternative.
Comment 4:
In reviewing the various DIMP data and after talking with personnel from EPA and the State of
Colorado we find it incomprehensible for the EPA to have not considered the Mink study with a
great deal more importance than they did. Their assumptions on the controls seem to be greatly
flawed and suspect. We feel there exists a significant difference of opinion between the State and
the EPA. Therefore:
Comment 4a: DIMP only affected the area around the RMA. It does not exist anywhere else in
the country, nor does it affect any other ongoing production activity. Since it is
only a product of SERAN production which is not now or will be manufactured,
no ongoing industry will be affected.
930377.enc 5
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Response 4a:
No specific comment or recommendation made.
Comment 4b: Humans using DIMP contaminated water wells are being exposed daily via direct
and indirect Pathways and are therefore exposed to significant health risk.
Response 4b:
Based on the EPA health advisory for DIMP, which has been peer-reviewed by many nongovern-
mental scientists, the results of the endangerment assessment indicate that the concentrations of
DIMP in groundwater do not correspond to a significant health risk. However, treatment
efficiency data for the Offpost Groundwater Intercept and Treatment System indicate that
concentrations of DIMP in the treated groundwater are reduced to less than 10 to 15 parts per
billion on average, thereby reducing the potential risks from DIMP to an insignificant level.
Comment 4c: Further study and manipulation of the regulatory process should be no longer
considered. Reasonable responsibility for providing a alternatives for water in the
DIMP affected area should be undertaken by the Army as soon as possible.
Response 4c:
The Army has not manipulated the regulatory process. All investigative and interpretive efforts
have been conducted in accordance with the NCP and with the cooperation and approval of the
EPA. The Army has provided an alternative water supply to all residents where private well
water exceeds the cleanup goals established in the Record of Decision. See response to
Comment 3.
Comment 4d: Further the parties should step up to their responsibility to monitor and provide
for health contingencies of affected people who have had Prolonged exposure to
DIMP.
Response 4d:
The Army is not in the position to monitor the health of all people in the Offpost Study Area.
The Army is committed to operation of the Offpost Groundwater Intercept and Treatment System
to reduce the concentrations of groundwater contaminants to meet or exceed the cleanup goals.
As indicated in the response to comment Ic above, the ATSDR is currently conducting an
epidemiological study of the health status of offpost residents.
Response 4e: No offpost plan or alternative is acceptable without providing for alternative water
for DIMP affected wells.
Response 4e:
The Army continues to support and provide alternative water supplies to individuals where
private drinking water wells contain concentrations of RMA-related contaminants above the EPA
health guidelines. See response to Comment 3.
930S77.ene
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Comment 5:
Rationalizing which ARARs the Federal Government agencies and Shell are willing to live with is
unacceptable. Standards set by the State of Colorado should unconditionally be followed (i.e.
Chloroform). Also in that same spirit, the parties should conform to Colorado's Sunshine act and
open up all proceedings without exception.
Response 5:
The Army has followed all applicable federal regulatory guidance for Superfund in determining
which standards apply to the offpost cleanup effort. Neither CERCLA nor the NPL require that
meetings between the Army, Shell, CDH, EPA, and contractors be open to the public. CERCLA,
however, does provide for specific public involvement opportunities as part of the overall
Superfund process. The Army has provided these opportunities to the public. Additionally, all
documents relating to the offpost program are available for your review at the Joint Administra-
tive Records Facility at the Security building at the west gate of RMA. Also, RMA's Technical
Review Committee meeting monthly and is open to the public. You are welcome to call the RMA
Public Affairs Office at 289-0136 for more information.
Comment 6:
Further planning and alternatives should be based on human health and animal health studies in
place of risk assessments. Moreover the actual baseline health of the area should be established
prior to determining possible risk exposure. Conventional risk assessments are not respected or
believed by the public and, as we have found, most non-governmental professionals. These
health studies must account for all health and reproductive risks, not just carcinogenic. We
recognize that hazard quotient and hazard index were used, but this we view as risk art and
definitely no risk science. Based on information that we believe, risk assessments have a very
high degree of fallibility and are not in the least reassuring. We have often heard and seen it
written that risk assessments can be made to say almost anything.
Response 6:
See response to comment Ic regarding the establishment of baseline health. Many of the risk
assessment procedures and methodologies recommended by the EPA were originally developed by
nongovernmental professionals. The Army is legally bound to use EPA-approved procedures and
to follow the requirements listed in the NCP. The risk assessment procedures used by the EPA
have been developed to be conservative, and final risk estimates are interpreted to be a worst case
estimate of risk, meaning that the true risk is likely to be much less.
Comment 7:
Various financial trusts should be established for the care of harms due to exposure of health risks
caused by activities connected to past, present and future activities at the RMA. In connection to
these trusts, ongoing human and animal health monitoring must be established. This may need to
last several generations due to the hormonal nature of some toxics and the saturation levels in the
environment.
Response 7:
The EPA, CERCLA, and NCP do not require the establishment of financial trusts specific for
potential health effects caused by exposure, nor is the establishment of such a trust appropriate
9S0377.enc 7
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for RMA. No offpost health effects have ever been documented from RMA activities. The Army
is committed to providing adequate funding for both the present and future operation of the
Offpost Groundwater Intercept and Treatment Facility until the cleanup goals established in the
ROD are achieved. With regard to ongoing human and animal health monitoring, see response to
comment Ic above.
Comment 8:
By its very nature clean-up says something is wrong. Even in terms of the proposed plan offpost
cleanup could take 15 to 30 years. This and of course prior activities has a very depressing effect
on the value of all property in the surrounding area. Therefore a plan needs to be established as
part of the offpost proposal for the immediate and ongoing rehabilitation of property values and
the real value of the affected communities. None of the alternatives address this.
Response 8:
Implementation of the preferred alternative will further reduce contamination in the offpost area.
Contamination has already been reduced offpost through the operation of the boundary treatment
systems. By implementing the preferred alternative, the offpost area will experience quicker
reduction of contamination, which should protect property values offpost.
Comment 9:
We have heard many anecdotal stories of the stress and strain experienced on a day to day basis by
residents of these communities who worry about their health, the affect on their communities, the
affect on their property values, and the RMA unknowns. As part of the proposed plan,
psychotherapy alternatives should be established and funded to clean-up this most insidious kind
of offense against the people.
Response 9:
The Army does not intend to establish a regional outpatient psychotherapy center. The Army has
based its offpost cleanup program on the most current and peer-reviewed information regarding
chemical toxicity. The Army believes that the procedures followed by the Army, and instituted at
other Superfund cleanup sites, are protective of human and ecological health.
Comment 10:
All areas need to be remediated to the highest standards. It is unacceptable for the artificial
manipulation of standards by predetermining use, particularly zones 3 and 4 whose designation as
urban residential appears to be completely arbitrary since it is zoned rural. Moreover, the
established designations don't reflect the value that the community applies to these areas. This is
procedurally and bureaucratically tyrannical.
Response 10:
The Army has not predetermined use for zones 3 and 4. The selection of an urban residential land
use was made in accordance with local governmental planning documents from Commerce City
and Adams County. Based on these planning documents, the likely future use along 96th Avenue
is either commercial/industrial or urban residential. Selection of an urban residential scenario is
930377.enc
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more conservative (e.g., results in higher estimated risks) than selection of a commercial/industrial
scenario.
Comment 11:
The EPA, USFWS and Shell invoked dispute resolution concerning the MATC values used in the
ecological risk assessment. Initially, the value of the MATC for both aldrin and dieldrin in birds
of prey was set at 1.6 ppm. The EPA pointed out that 1.6 ppm was the average concentration in
the carcasses of 101 bald eagles found dead between 1971 and 1974 (p. VIII-13), and thus could
hardly be considered a "protective" level. Furthermore, the EPA wrote that a carcass
concentration as low as 0.66 has been associated with deaths from dieldrin poisoning. How is the
MATC of 1.1 established by the dispute resolution process protective of the birds' health? The
MATC for Endrin; for the Great Horned Owl and for the American Kestrel = 4 (p. II-5-27); can
we expect some birds to die as a result of endrin poisoning? How were the synergistic effects of
contaminants taken into account? How do you understand the fact that "only a fraction of the
eagles who visited the RMA roosting sites during the 1988-1989 season (possibly 100) only 7
returned form the previous year?" (p. HI-5-33).
Response 11:
As discussed in Volume VIII of the EA/FS, the Army does not agree with the conclusions drawn
by the EPA regarding the literature studies reviewed for dieldrin toxicity. The Army believes
that the literature cited by the EPA does not support their contention that dieldrin concentrations
of 0.66 ppm were associated with death. These concentrations were present in dead animals but,
according to the research authors, were not responsible for the animals' death. As part of the
dispute resolution process, several articles published on dieldrin toxicity were reviewed by the
dispute resolution parties. Following review and discussion, including inptlt from the scientist
whose study was cited by EPA, a dieldrin concentration of 1.1 ppm was agreed to by the Army,
EPA, U.S. Fish and Wildlife Service, and Shell.
The Army does not expect birds to die from endrin poisoning. While the ratio value of 4 does
exceed 1 for the great horned owl and the american kestrel, this is only an indication of potential
concern and not an absolute indication of the severity of a potential effect. The maximum
allowable tissue concentration (MATC) does not represent a lethal concentration. The interpreta-
tion of the MATC is that this concentration is expected to be protective against health effects
much less severe than death. Similar to the application of a reference dose in humans, exceedance
of the MATC does not indicate unacceptability, only that an increased potential for adverse health
effects (not including death) may occur. Additionally, measured tissue concentrations in wildlife
were less than those predicted by the food web model, indicating that the modeled tissue
concentrations may be overly conservative.
Synergistic effects in wildlife were not evaluated because adequate scientific literature is not
available for reference, and EPA has not developed specific guidance on appropriate methods to
use in evaluating these effects in wildlife and ecosystems.
With respect to the comment on the number of eagles returning from the previous year, the
commentor has apparently misinterpreted the information presented in the EA/FS, which is itself
slightly misleading. The EA/FS (vol III, page 5-33) states "The (U.S. Fish and Wildlife) report
states that possibly 100 or more eagles visited the RMA roost during the 1988-1989 wintering
season and that casual observation of the eagles in early November suggests that up to seven of the
eagles may have returned from the previous year." Eagle populations at RMA do not peak until
early January. In early November, it is likely that there were only seven eagles at the roosting
930377.enc 9
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area at that time. The population continues to increase until January. Over the years, the number
of eagles using the RMA roosting sites has increased. It is important to understand that although
as many as 100 eagles may use the roosting site during any given season, the number of eagles
present on any given day may only be 30 to 40. Eagles do not use the same roost continuously but
instead migrate to different areas (sometimes on a daily basis) depending on where the food
supply is located. Banding, capture, and observation efforts by the USFWS in recent years have
demonstrated that the number of eagles using and returning to the RMA roost sites is at least
stable and possibly increasing.
Comment 12:
What is the "hot spot of surficial soil contamination" (p. II-2-56) located within 1/2 mile of the
intersection of 96th and Peoria street? Is it located on the property Shell recently purchased? To
what extent does it contribute to the high cancer and liver toxicity risks associated with zone 3
and 4? To what extent does it contribute to the contamination of First Creek? What assurances
do we have that no homes will be built on top of this "Hot Spot?" Are there any plans to remediate
the soil contamination here? If not, please explain.
Response 12:
The NCP requires an evaluation of future land use that is both reasonable, from land use develop-
ment patterns, and may be associated with the highest (most significant) risk. The Army believes
that designation of these zones as rural residential is inappropriate for 1) current use, because
these zones are not currently used as such, or 2) future use, because of the probability of develop-
ment along 96th Avenue.
The hot spot of surficial contamination near 96th and Peoria Street is an area of localized higher
pesticide concentrations. Concentrations of these pesticides contribute approximately 50 percent
of the carcinogenic risks and 25 percent of the noncarcinogenic hazard indices in zones 2 and 3.
This area of surficial contamination is not expected to have a significant effect on the pesticide
concentrations identified in First Creek. At the present time, there are no cleanup plans for the
soil in this area. Estimated risks associated with this soil are within EPA's health guidelines. If it
becomes apparent that future land use in this area will be different from the land use evaluated in
the EA, the Army will reevaluate the risks in this area and coordinate discussions with the EPA
and CDH regarding land use.
930377.ene 10
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Office of the Program Manager
Mr. Dan Mulqueen
Project Leader RMA
We The People
661 Pennsylvania Street
Denver, CO 80203
Dear Mr. Mulqueen:
Thank you for providing comments on the Offpost Proposed Plan for Rocky
Mountain Arsenal. The Army appreciates the large number of comments submitted
on the Offpost Proposed Plan. Also included are responses to comments you
submitted on the Submerged Quench Incinerator (SQI). I hope these responses
increase your understanding of both the SQI and the offpost cleanup.
Please contact Mr. Bill Thomas, Public Affairs Office, at (303) 289-0136 if you
have any questions regarding the SQI, and Mr. Tim Kilgannon at (303) 289-0201, if
you have any questions regarding the Offpost Proposed Plan.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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RESPONSES TO LEAGUE OF WOMEN VOTERS COMMENTS
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THE LEAGUE
OF WOMEN VOTERS
OF COLORADO
1410 Grant. B-204
Denver. Colorado 80203
303«863«0437
June 21, 1993
Offpost Proposed Plan Comments
Program Manager for Rocky Mountain Arsenal
Attn: AMXRM-PM\Col. Eugene H. Bishop
Building 111-RMA
Commerce City, CO 80022-2180
The League of Women Voters of Colorado commends you for your
efforts at citizen involvement in the Offpost Proposed Plan. The
"Citizens' Summary" was one of the most useful such documents we
have encounteredi He are, however, not completely satisfied with
the PROCESS. He believe that the intent of CERCLA was to involve
citizens in all stages of the decision-making process. He believe
that a CITIZEN ADVISORY COMMITTEE or possibly a SITE SPECIFIC
ADVISORY BOARD should be in place before any more decisions are
made, including the Offpost Plan.
He feel comfortable with the current off-post operations as an
INTERIM measure, but request that ALL LONG TERM DECISIONS BE
POSTPONED UNTIL THERE IS ADEQUATE CITIZEN INVOLVEMENT and
evaluation of cumulative effects.
Since the Cleanup of Rocky Mountain Arsenal is, in a sense,
serving as a pilot for the cleanup of many Federal Facilities,
there is increased scrutiny of the process. Last year there was
speculation that the SQI project was in jeopard because of
neighborhood perceptions. He submit that the root cause was a
failure to involve that group of stakeholders in the decision-
making process.
At the public meeting on the Offpost Propose Plan it was
announced that no public hearing was to be held. The role of a
public hearing is to include all concerns in the official record
and thus require an official response. Public Hearings are, in
effect, an insurance policy that you did, indeed, listen to the
concerns of stakeholders. Public Perception is an important
element in the success or failure of any cleanup project. •
Some issues which still must be addressed in the public realm
are:
*Levels of dieldrin, DIMP, and chloroform in the groundwater
as well as locations. •
*Lab results from samples taken in November, 1992. -
* Future Land Use, including possible restrictions on use.
*A satisfactory substitute for the failed mink studies
Justification for decision making before the F.inal Record of
Decision
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The League of Women Voters of Colorado continues to request
that an ADVISORY COMMITTEE, with attendance open to the public, be
created, at least for the Final Record of Decision. The stakes are
high and the Army's continual refusal to have an Advisory Committee
is seen as an effort to hold back information. We are not
advocating replacing the Technical Review Committee. That body can
continue to serve by reviewing information being prepared for
public distribution and be a first line conduit for dissemination
of information between their various constitutiencies and the
decision-makers .
We would suggest that a process be put in place which would
include workshops, public meetings and public hearings leading up
to the Final Record of Decision (ROD) . The work already done on
the Proposed Offpost Plan is the kind of work we would support for
each of the components of the Final Plan, and we commend you for
making studies available as they are produced, but we would
recommend that NO FURTHER DECISIONS be made until the Final Record
of Decision.
There are those who feel that the Interim Response Action
process has been abused in order to bypass public involvement and
the creation of an adequate database. Many studies which have been
suggested in the past have not been completed. It is time to stop,
look at the total pro j ect , bring in an advisory committee and
proceed with the caution needed to guarantee that the Cleanup of
Rocky Mountain Arsenal will, indeed, be a model to be emulated at
other Federal Facilities. *
Sincerely,
Betsy McBride, President
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO LEAGUE OF WOMEN VOTERS COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JUNE 21, 1993
Response to General Comment Regarding Citizen Involvement
The Army has provided for appropriate citizen involvement in the selection of the remedy as
required by the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) and the
Comprehensive Environmental Response, Liability, and Compensation Act (CERCLA). The
design and conduct of offpost investigative activities have been carried out with input and
cooperation of the Colorado Department of Health, the U.S. Environmental Protection Agency,
and the U.S. Fish and Wildlife Service. All documents relating to the offpost program are
available for your review at the Joint Administrative Records Facility (JARDF) at the Security
building at the west gate of RMA and local libraries. You are welcome to call the RMA Public
Affairs Office at 289-0136 for more information.
A public hearing was not held. However, all comments made at the public meeting are part of the
official record and a transcript is part of the Administrative Record. In addition, all public
comments sent to the Army were responded to personally and are included as an appendix to the
Record of Decision.
The Army has implemented an Interim Response Action (operation of the Offpost Groundwater
Intercept and Treatment System) to begin cleanup of groundwater offpost. The Army will
conduct groundwater and surface-water monitoring during operation of the treatment system to
ensure compliance with the groundwater cleanup standards. If monitoring data suggest that the
system is not performing as expected, the Army will modify the treatment system to achieve the
cleanup standards.
The Department of Defense is currently evaluating its role in the Site Specific Advisory Board
(SSAB) concept at cleanup sites. The RMA has not created an overall plan for participating in a
SSAB, should one be established, and cannot until the Department of Defense and the Department
of the Army complete their evaluations. The Army is, as you know, expanding the role of the
Technical Review Committee to implement some of the SSAB philosophies. As always we
encourage any ideas or comments you may have on the Technical Review Committee.
ISSUES RAISED IN LETTER
1) The Dieldrin, DIMP, and Chloroform concentrations in groundwater are well defined. An
extensive monitoring effort continues in the offpost area to track these and other compounds.
The locations of highest concentrations can be found in the Remedial Investigation Addendum for
the Offpost Study Area. This document can be found at the JARDF as mentioned in the above
comment.
2) All Lab results taken in November, 1992 were sent to the owners offpost. The Army has
taken steps to correct the poor turnaround time, the time from when the wells are sampled to
when results are available, it had experienced in the past.
3) Future land use is summarized in the Final Endangerment Assessment/Feasibility Study
based on planning information from Adams County and Commerce City. Institutional Controls
930425E.enc
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have been added to the Record of Decision (ROD) to further preclude the possibility of shallow
drinking water wells being drilled in areas of higher contaminant concentrations.
4) The Army completed a 90 day mink study with DIMP that concluded that the 600 parts
per billion Health Advisory set by the EPA is protective of Human Health and the Environment.
The Army is currently evaluating the applicability of the 8 parts per billion level that the Water
Quality Control Commission is expected to promulgate in a few months.
5) The Final Decision for cleanup of the Offpost Operable Unit will not be made until the
Final ROD is released in early 1994. No final cleanup decisions have been made Offpost, to date.
930425E.ene
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Office of the Program Manager
Ms. Betsy McBride
President, League of Women Voters
1410 Grant, B-204
Denver, CO 80203
Dear Ms. McBride:
Thank you for providing comments on the Offpost Proposed Plan for Rocky
Mountain Arsenal. The Army appreciates the large number of comments submitted
on the Offpost Proposed Plan. I hope the enclosed responses increase your
understanding of the offpost cleanup. Also included are the comments you
submitted on the Offpost Proposed Plan for easier reference to the response.
If you have any further questions please contact Mr. Tim Kilgannon of my
staff at (303) 289-0201.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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RESPONSES TO DENVER REGION GREENS COMMENTS
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U.S. DEPARTMENT OF THE ARMY
RESPONSES TO DENVER REGION GREENS COMMENTS REGARDING
THE ROCKY MOUNTAIN ARSENAL OFFPOST PROPOSED PLAN
JUNE 21, 1993
Comment 1:
The OSA is not large enough. The limiting of the offpost plan to just the area north of 80th Ave.
between the South Platte River and Second Creek, with Barr Lake included, does not make sense,
since the Colorado Department of Health (CDH) has found diisopropyl methyl phosphonate
(DIMP) west of the South Platte, and has stated it has not conducted adequate testing northeast of
Second Creek. We question the criteria used to determine what constitutes "acceptable" and
"unacceptable" risk (see comment #5 below) used to rule out inclusion of the other offpost areas
east, south, and west of the RMA in the OSA.
Response 1:
The Offpost Study Area was defined as those areas where RMA-related contaminants could be
identified in soil, surface water, groundwater, or sediments. The general areas east, west, and
south of RMA were not found to contain contaminants that could be directly attributable to RMA
activities. The major factor in this finding is the direction of groundwater flow, which is toward
the northwest. The Army is cooperating with the Colorado Department of Health with regard to
additional sampling in certain areas. If the results from these sampling activities indicate that
conclusions of the Endangerment Assessment/Feasibility Study are no longer correct, the Army
will evaluate the need to expand the area encompassed by the selected remedy.
Comment 2:
The OSA plan does not address remediation of ground water contamination that has already
occurred beyond the current and proposed contaminated ground water intercept and treatment
systems. At a minimum, residents who might be exposed to contamination from non-intercepted
contamination plumes should be provided with a safe, non-contaminated alternative water supply,
not just bottled drinking water.
Response 2:
The Army is aware that contamination exists downgradient of the Offpost Groundwater Intercept
and Treatment System. Two new monitoring wells will be installed downgradient of the First
Creek Pathway and one new monitoring well will be installed downgradient of the Northern
Pathway. The purpose of the three new monitoring wells is to aid in assessing the extent of
contamination downgradient of the Offpost Groundwater Intercept and Treatment System. Data
collected from these and existing wells will be used to further define the extent of contamination
greater than the remediation goals in this area and assist in determining whether modifications to
the design of the Offpost Groundwater Intercept and Treatment System are necessary.
The Army is committed to providing alternative water supplies to residents whose drinking water
exceeds groundwater cleanup standards as defined in the Record of Decision.
930425F.enc
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Comment 3:
The OSA plan does not deal with other forms of offpost contamination such as air, surface water,
and soil contamination by RMA sources. Assessment of air contamination to offpost areas was
made before the Submerged Quench Incinerator (SQI) went into operation; the same for surface
water and soil contamination. Again, we also question the criteria used to determine what
constitutes "acceptable" health and environmental risk (see #5 below).
Response 3:
The three media mentioned (air, surface water, and soil) were addressed in the Endangerment
Assessment/Feasibility Study. The air pathway was determined to be a negligible contributor to
potential risks in the Offpost area. Potential health hazards associated with soil contamination are
within the acceptable range as defined by the U.S. Environmental Protection Agency. Following
implementation of the selected remedy, the water quality of First Creek will improve. The Army
will implement a long-term surface water monitoring program to ensure the effectiveness of the
remedy on surface water quality. The Army has also committed to closing the onpost sewage
treatment plant, thus eliminating a possible source of contaminants in the First Creek surface
water drainage.
Comment 4:
The OSA plan does not deal with compensation of residents living near the RMA for
a) negative health effects due to current and past exposures to RMA offpost
contaminants;
b) continuing expenses to near-by residents for past, present and future health care and
health monitoring costs due to exposure to RMA offpost contamination;
c) losses in property values to near-by residents due to contamination of air, soil, and
water by the RMA.
Any plan to deal with RMA offpost contamination needs to address these very critical
compensation and continuing health care issues.
Response 4:
The risk assessment conducted for the Offpost Study Area does not, by definition, determine
whether adverse health effects have occurred or will occur and cannot identify particular
individuals likely to suffer health problems because of contamination at a site. The Agency for
Toxic Substances and Disease Control, in cooperation with the Colorado Department of Health,
have ongoing epidemiological studies near RMA to address the occurrence of health effects and
determine if these effects may be attributable to exposure to contaminants from a hazardous waste
site. To date, no adverse health effects have been attributed to RMA.
The Army continues to conduct comprehensive monitoring programs in the Offpost area. If data
is obtained indicating that chemical concentrations exceed (1) the cleanup standards established
for the Offpost OU, or (2) other EPA health standards, the Army will institute appropriate action
to reduce the health threat.
930425F.ene
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Comment 5:
The levels of "acceptable" health risks in offpost areas, as high as five (5) excess cancers per ten
thousand (10,000) people, using an Environmental Protection Agency (EPA) suggested level, is
obscenely high, and should be raised to at least only one excess cancer per one million (1,000,000)
people, and we strongly urge a human health risk factor of no more than one excess cancer per ten
million (10,000,000) people. We hold that no one should involuntarily be subjected to health risks
on the order of 5 excess cancers per 2,000 people. People living in such conditions are living in
environmentally toxic circumstances which should be viewed as repugnant by the EPA or any
other regulatory or responsible agency or entity (business, federal facility, etc.). We also point out
that there exist different opinions between the CDH and the EPA on what levels of exposure to
certain chemicals are "acceptable" or not, e.g., DIMP standards. We support the most protective
standards.
Response 5:
Operation of the Offpost Groundwater Intercept and Treatment System will reduce the estimated
risks toward 1 x 10"6, the lower end of the acceptable risk range defined by the EPA. It is
important to realize that the estimated risks presented in the EA/FS are most likely overestimated,
in that several exposure pathways considered do not now occur and may not occur in the future.
The army is aware of the recent Water Quality Control Commission standard of 8 ppb DIMP in
groundwater. The Army is evaluating the applicability of this standard to the offpost remedial
actions.
Comment 6:
There has been no epidemiological study of the residents living near-by the RMA for a range of
possible health problems that could reasonably be expected from exposure to RMA contaminants.
A limited study by the CDH found elevated levels of certain cancers in some near-by RMA
residents. A comprehensive epidemiological study, including former residents who have since
moved, should be conducted as part of the OSA plan to assess the possible extent of negative
health effects due to RMA contamination, and as a basis for compensation issues.
Response 6:
The Cancer Incidence Study completed by CDH found no conclusive evidence that cancer rates in
nearby residences were increased due to RMA contamination. For additional information see
Response No. 4.
Comment 7:
The Record of Decision (ROD) regarding the OSA plan should be delayed until the State of
Colorado has determined the State standards for RMA water and air contaminants, e.g., a DIMP
groundwater standard.
Comment 8:
The ROD should be delayed until the legal status of the recent 10th Circuit Court of Appeals
ruling given the State of Colorado increased standards setting and other authority over RMA clean
up activities has been clarified.
930425F.enc
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Comment 9:
The ROD should be delayed until any legal and implementation questions regarding the
applicability of the 1992 Federal Facilities Compliance Act to the RMA have been clarified.
Provisions of this ACT bear directly on actions the State of Colorado can take regarding RMA
clean up.
Response 7. 8. and 9:
The Army is not required to delay the issuance of the ROD pending State promulgation of
standards or court interpretations on various issues. The Army intends to proceed with imple-
mentation of the selected remedy to begin Offpost cleanup as soon as possible.
Comment 10:
The ROD regarding the OSA should be delayed until the other outstanding issues mentioned in
comments #1 through #6 above have been resolved through a process of negotiation which
includes all interested and affected parties, a process which has not been developed at this time.
Such a process would include representatives of citizens' groups, environmental and public interest
groups, neighborhood associations, city and county and state governments, special district boards,
unions, and any other organizations that have an interest in such a decision, e.g., public health
associations, etc.
Response 10:
The Army has provided for public involvement opportunities for the public as required by the
National Contingency Plan and the Comprehensive Environmental Responsibility, Compensation,
and Liability Act. All documents relating to the offpost program are available for your review at
the Joint Administrative Record and Document Facility at the Security building at the west gate
of RMA. You are welcome to call the RMA Public Affairs Office at 289-0136 for more
information.
930425F.enc
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Office of the Program Manager
Mr. T. Philip Hufford
Denver Region Greens
1071 Madison Street
Denver, CO 80206
Dear Mr. Hufford:
Thank you for providing comments on the Offpost Proposed Plan for Rocky
Mountain Arsenal. The Army appreciates the large number of comments submitted
on the Offpost Proposed Plan. I hope the enclosed responses increase your
understanding of the offpost cleanup. Also included are the comments you
submitted on the Offpost Proposed Plan for easier reference to the response.
If you have any further questions please contact Mr. Tim Kilgannoh of my
staff at (303) 289-0201.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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Appendix A-8
RESPONSES TO CITIZEN COMMENTS
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PUBLIC COMMENT
U.S. Army's "Proposed Plan for the Offpost Study Area"
Colonel Eugene H. Bishop, RMA Bldg. 111, Cormerce City, Colorado 80022-2180
I an a resident of the "Offpost Study Area" and am directly affected by contamination from
the Rocky Mountain Arsenal. I join with others in my community in opposing the Army's
proposed plan. We urge that it be amended to address broad comunity concerns with a
comprehensive solution to widespread contamination problems that the Army and Shell Chemical
Company have failed to address, to date, and which currently poison domestic water supplies
and private property for miles to the north and northwest of the Rocky Mountain Arsenal.
Contaminants include deadly pesticides that were banned by the EPA years ago, by-products of
chemical warfare agents, and other toxic substances.
I demand that the U.S. Army and Shell Chemical Company develop and implement a plan to: 1)
eliminate ajj current sources of toxic exposure to citizens affected by off-site poisons from
the Rocky Mountain Arsenal; 2) provide a permanent, alternative, uncontaminated source of
water to residents with any level of RMA toxins in their water; 3) conduct a comprehensive
offpost soil and water clean-up that meets all applicable federal and state guidelines,
including RCRA; 4) that no final "Record of Decision" be issued until the Colorado Water
Quality Control Commission adopts standards for unique, unregulated, Arsenal-related poisons,
such as "DIMP"; and 5) that the Army will meet or exceed those standard(s) in all grgajndwater
clean-up actions on and offpost.
My additional Garments about the Army's inadequate clean-up plan are these:
(see reverse side for continued Garments)
Please send written
nts in response to the urgent concerns raised in my Garments before
a "pSpord of Decision" is issued regarding offpost Rocky Mountain Arsenal poisons.
/} n * ^j4 .
NAM (Signature)
NAME (Printed!
ADDRESS
TOWN
ZIP
PHONE
cc: Les Aspin, Secretary of Defense, Vice President Al Gore, Carol Browner, U.S. EPA,
Colorado Congressional delegation, chairs of key Congressional oversight comvittees; Colorado
Governor Roy Romer, Attorney General Gale Norton, CDH Director Patricia Nolan; public media
-------
DEPARTMENT OF THE ARMY
PROGRAM MANAGER FOR ROCKY MOUNTAIN ARSENAL
COMMERCE CITY. COLORADO 80022-1748
December 9, 1993
REPLY TO
ATTOfflON OF:
Office of the Program Manager
Mr. and Mrs. Owen Bakes
11460 Peoria Street
Henderson, Colorado 80640
Dear Mr. and Mrs. Bakes:
Thank you for your comments. The Army appreciates the many comments received on
the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public input is a key part of
the cleanup process at RMA.
The preferred alternative for the Offpost Operable Unit will clean up contamination that
came from RMA. The Army has spent nine years studying the best possible way to eliminate
potential health threats offpost. We believe the Offpost Preferred Alternative goes beyond what
is required by the U.S. Environmental Protection Agency (EPA). In addition, the Army cannot
legally provide offpost residents with a new water supply because legal
chemical health guidelines are not being exceeded. The Army will, as it has in the past, provide
offpost residents an alternative water supply if applicable EPA health guidelines are not being
met in their private well water. Finally, the Army believes that all applicable federal and
state guidelines are being met for soil and water offpost.
One of the major concerns to offpost residents is the DIMP contamination in groundwater
offpost. Since my tenure began at RMA, I wanted to make sure the Army would further study
the DIMP tests to evaluate whether the EPA DIMP Health Advisory of 600 parts per billion is
safe. Overall, the Army has conducted more than 30 separate animal studies with DIMP,
including one study with humans. The EPA and the National Academy of Sciences evaluated
all health studies and concluded that the EPA's 600 parts per billion Health Advisory is
protective of human health and the environment. In addition, the Army evaluated all possible
ways DIMP and other chemicals could enter the human body. These tests again showed that the
water offpost is protective of human health and the environment. As an additional protective
measure, the Offpost Treatment System and the North Boundary System will treat the
groundwater to less than 10 parts per billion. The Army is currently evaluating the applicability
of the 8 parts per billion level that the Colorado Water Quality Control Commission is expected
to promulgate in the next several months.
Readiness is our Profession
-------
I hope this information has helped to alleviate your concerns. Any other questions
regarding the Offpost Proposed Plan may be directed to Mr. Tim Kilgannon of this office at
289-0201. Thank you again for your comments.
Sincerely,
agene/H. Bishop
Colonel', U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
-------
Jack E. Clancy
12220 Peoria
Henderson, Co. 80601
Col. Eugene H. Bishop
United States Army/
Building 111-RMX
Commerce City/Co. 80022
Dear Col. Bishop:
As owner- of property north of the Rocky Mountain Arsenal that has
a DIMP contaminated well on it, I urge the Army to take action
above and beyond what it is now doing to remedy the ground water
contamination problem faced by me and my 600 neighbors.
We use the bottled water for drinking and cooking, but we still
bathe in DIMP water every day, we water our vegetable garden with
DIMP water, we give our livestock DIMP water and we still don't
know what the eventual effect on our health will be.
From a risk management viewpoint, it would be wise for the Army to
spend the $7 million now to provide a clean water system to the area
and protect the health of residents rather than to wait 10 to 20 year's
and face the possibility of numerous lawsuits or a class action suit if
it is proved that DIMP has. damaged the health of residents.
We cannot wait the 10 to 20 years that it will take to clean up the
ground water using the current methods. WE NEED AND ARE
ENTITLED TO HAVE CLEAN WATER. WE NEED IT NOW AND WE WILL
NOT SETTLE FOR ANYTHING LESS!
Sincerely,
Jack E. Clancy
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Office of the Program Manager
Mr. Jack E. Clancy
12220 Peoria
Henderson, Colorado 80601
Dear Mr. Clancy:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for the Rocky Mountain Arsenal (RMA).
Public feedback is a key part of the cleanup process at RMA. I will respond to your
comments in the order we received them.
One of the major concerns to offpost residents is the DIMP contamination in
groundwater offpost. Since my tenure began at RMA, I have ensured that the Army
would further study the DIMP tests to evaluate whether the U.S. Environmental
Protection Agency (EPA) DIMP Health Advisory of 600 parts per billion is safe.
Overall, the Army has conducted more than 30 separate animal studies with DIMP,
including one study with humans. The EPA and the National Academy of Sciences
evaluated all health studies and concluded that the EPA's 600 parts per billion
Health Advisory is protective of human health and the environment. In addition,
the Army evaluated all possible ways DIMP and other chemicals could enter the
human body. These tests again showed that the water offpost is safe for
consumption and for the environment. As an additional protective measure, the
Offpost Treatment System and the North Boundary System treats the groundwater to
less than 10 parts per billion. The Army is currently evaluating the applicability of
the 8 parts per billion level that the Colorado Water Quality Control Commission is
expected to promulgate in the next several months.
Based on our current data, all residents in the offpost study area are drinking
water that meets all applicable or relevant and appropriate federal and state
regulations. Army continues to extensively monitor drinking water wells in the
offpost area. If levels of Arsenal-Related chemicals were to rise above health
guidelines in the drinking water for any resident, the Army will provide an alternate
water supply to that resident.
-------
Any other questions regarding the Offpost Proposed Plan may be directed to
Mr. Tim Kilgannon of this office at 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
-------
PUBLIC COMMENT
U.S. Army's "Proposed Plan for the Offpost Study Area
Colonel Eugene H. Bishop, RMA Bldg. 111, Connerce City, Colorado 80022-2180
I am a resident of the "Offpost Study Area" and am directly affected by contamination from
the Rocky Mountain Arsenal. I join with others in my ccmnunity in opposing the Army's
proposed plan. We urge that it be amended to address broad coimunity concerns with a
comprehensive solution to widespread contamination problems that the Army and Shell Chemical
Company have failed to address, to date, and which currently poison domestic water supplies
and private property for miles to the north and northwest of the Rocky Mountain Arsenal.
Contaminants include deadly pesticides that were banned by the EPA years ago, by-products of
chemical warfare agents, and other toxic substances.
I demand that the U.S. Army and Shell Chemical Company develop and implement a plan to: 1)
eliminate alj. current sources of toxic exposure to citizens affected by off-site poisons frcm
the Rocky Mountain Arsenal; 2) provide a permanent, alternative, uncontaminated source of
water to residents with any level of RMA toxins in their water; 3) conduct a comprehensive
offpost soil and water clean-up that meets all applicable federal and state guidelines,
including RCRA; 4) that no final "Record of Decision" be issued until the Colorado Water
Quality Control Commission adopts standards for unique, unregulated, Arsenal-related poisons,
such as "DIMP"; and 5) that the Army will meet or exceed those standard(s) in all gcoundwater
clean-up actions on and offpost.
My additional comnents about the Army's inadequate clean-up plan are these:
Please send written
a /Record of-Decision"/
(see reverse side for continued comnents)
its in response to the urgent concerns raised in my
nts before
issued regarding offpost Rocky Mountain Arsenal poisons.
NAME (Printed)
ADDR
TOWN
ZIP
PHONE
cc: Les Aspin, Secretary of Defense, Vice President Al Gore, Carol Browner, U.S. EPA,
Colorado Congressional delegation, chairs of key Congressional oversight committees; Colorado.
Governor Roy Rcmar, Attorney General Gale Norton, CDH Director Patricia Nolan; public media
-------
Office of the Program Manager
Mr. and Mrs. Steve Evanoff
11890 Peoria Street
Henderson, Colorado 80640
Dear Mr. and Mrs. Evanoff:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public
input is a key part of the cleanup process at RMA.
The preferred alternative for the Offpost Operable Unit will clean up
contamination that came from RMA. The Army has spent nine years studying the best
possible way to eliminate potential health threats offpost. We believe the Offpost
Preferred Alternative goes beyond what is required by the U.S. Environmental
Protection Agency (EPA). In addition, the Army cannot legally provide offpost residents
with a new water supply because legal
chemical health guidelines are not being exceeded. The Army will, as it has in the
past, provide offpost residents an alternative water supply if applicable EPA health
guidelines are not being met in their private well water. Finally, the Army believes that
all applicable federal and state guidelines are being met for soil and water offpost
One of the major concerns to offpost residents is the DIMP contamination in
groundwater offpost. Since my tenure began at RMA, I wanted to make sure the Army
would further study the DIMP tests to evaluate whether the EPA DIMP Health Advisory
of 600 parts per billion is safe. Overall, the Army has conducted more than 30 separate
animal studies with DIMP, including one study with humans. The EPA and the
National Academy of Sciences evaluated all health studies and concluded that the
EPA's 600 parts per billion Health Advisory is protective of human health and the
environment. In addition, the Army evaluated all possible ways DIMP and other
chemicals could enter the human body. These tests again showed that the water
offpost is protective of human health and the environment. As an additional protective
measure, the Offpost Treatment System and the North Boundary System will treat the
groundwater to less than 10 parts per billion. The Army is currently evaluating the
applicability of the 8 parts per billion level that the Colorado Water Quality Control
Commission is expected to promulgate in the next several months.
-------
I hope this information has helped to alleviate your concerns. Any other
questions regarding the Offpost Proposed Plan may be directed to Mr. Tim Kilgannon
of this office at 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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Offpost Proposed Plan Comments
Program Manager for Rocky Mountain Arsenal
Attn: AMXRM-PM\Col. Eugene H. Bishop
Building 111-RMA
Commerce City/ CO 80222-2180
Colonel Bishop,
I feel there are still some unresolved issues related to the
Offpost Proposed Plan. First, however, is the issue of the
appropriateness of the Plan at this time. I submit that the intent
of the FINAL RECORD OF DECISION is to include all long-term
decisions under one process. I would, therefore, request that no
further action be taken on the Offpost Plan. Continue operation of
the offpost water treatment facility and use the next year or so to
gather data as to what contaminants are still getting past it,
where else contaminants are showing up, and how best to handle the
land use issues.
Here is a list of the issues I feel should be addressed before
a final decision is made:
1. CITIZEN INVOLVEMENT: There is a significant difference
between a Technical Review Committee and an Advisory Committee or
Board, both in function and in makeup. I would like to see bothl
The information I have seen so far about Site Specific Advisory
Boards leads me to suggest you explore that type of approach £or
the final ROD.
2. CUMULATIVE EFFECTS: By looking at each action as a
separate unit, there is a good chance that the cumulative effect of
all actions will be much more detrimental to human health and the
environment than is being suggested by the current approach. I'll
be more comfortable with the Final Decision after I've seen some
more data on long-term, cumulative effects of such things as DIMP,
dieldrin and chloroform. Bow much of each is added to the life-
time exposure for people by the combination of all actions at Rocky
Mountain Arsenal and what are the risks?
3. DATABASE: Until all of the data is in about the health
effects of some of the chemicals of note, it is premature to decide
on the final level of cleanup. My reading of the preferred
alternative for the Off Post Plan is that further monitoring and
upgrades would be expected, just as they have been for the NK
Boundary System. Since mink studies did not work out, there must
be some way to test for harm. Without proof that there is no harm,
I would recommend total cleanup. My guess is that it would be less
expensive to conduct further studies than to remove all
contaminants. Even one person able to win a suit that he or she
has been harmed by the DIMP (for instance) would hurt the Army's
credibility at all of its cleanup sites! Better safe than sorry.
-------
Before a final decision is made/ I would recommend retesting
all of the wells in and near the study area to verify that the
current system is working as designed. Public availability of the
data would add to the credibility of the Army and Shell. Also,
the levels and types of contaminants on the soil could be verified
on a smaller scale, perhaps even lot by lot, before final land use
restrictions and decisions are agreed to by Adams County, Commerce
City and any other land use decisionmakers.
4. ARARs: Given the historical propensity to sue, someone is
bound to push for State standards and/or guidelines, especially
when they are more stringent than those of EPA. It seems to me to
be a better use of taxpayer money to try to meet the most stringent
levels as a part of the Final Plan, rather than to spend years
defending the decision in court.
5. LAND USE: There seem to be legitimate concerns for the
future land use of the area. By postponing the final decision on
the Off post area, you will have more time to work with the
appropriate land use decisionmaking bodies in order to guarantee
safe use of the land and/or adequate cleanup for the allowed land
use.
You have done a good job 'so far and the cleanup is at a
critical point. People are not nearly as easy to predict as
chemical compounds, but it is a safe bet that support is more
likely when stakeholders have "bought into the decisions." ,
Hone of these comments should come as a great surprise to you,
but I want them in the official record, in part because my
experiences with both public participation and the planning process
lead me to hope that you will do everything possible to prevent
embarrassing problems later. I have been a member of the Technical
Review Committee since 1988 and, honestly, want to be proud of what
is accomplished at Rocky Mountain Arsenal.
Sincerely
0^^
Clara Lou Humphrey
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Office of the Program Manager
Ms. Clara Lou Humphrey
9390 W. 1st Avenue
Lakewood, Colorado 80226
Dear Ms. Humphrey:
Thank you for your comments. The Army appreciates the many comments received
on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public input is an
integral part of the cleanup process at Rocky Mountain Arsenal. I will respond to your
comments in the order we received them.
I appreciate your request to delay the Offpost Final Record of Decision until
monitoring of the Offpost Treatment System has been completed for one year. The Army
will be constantly reevaluating the Offpost Treatment System through our ongoing monitoring
program to examine whether modifications are necessary. The Final Record of Decision does
not include the details of the monitoring programs and modifications to the Offpost
Groundwater Treatment System. The Final Record of Decision states the selected alternative
for cleanup of the Offpost Operable Unit. This selected alternative is based on nine years of
study. Subsequent documents, including an implementation plan, will be completed detailing
the offpost monitoring to be conducted and any changes to the selected alternative that are
based on monitoring data. Listed below are responses to your numbered comments:
1. The Department of Defense is currently evaluating its role in the Site Specific Advisory
Board (SSAB) concept at cleanup sites. The RMA has not created an overall plan for
participating in a SSAB, should one be established, and cannot until the Department of
Defense and the Department of the Army complete their evaluations. The Army is, as you
know, expanding the role of the Technical Review Committee to implement some of the
SSAB philosophies. As always we encourage any ideas or comments you may have on the
Technical Review Committee.
2. The Army evaluated the long-term and cumulative health effects of the chemicals offpost.
These effects were analyzed in the Offpost Risk Assessment. In fact, the Offpost Risk
Assessment evaluated the cumulative risks of contamination offpost over a 70- year period,
which is stipulated by U.S. Environmental Protection Agency (EPA) guidance. The risks
presented in the Offpost Proposed Plan are the long-term risks of the contamination offpost
without considering the benefit of Offpost Treatment System operations.
3. One of the major concerns to offpost residents is the DIMP contamination in groundwater
offpost. Since my tenure began at RMA, I have ensured that the Army complete additional
DIMP tests to evaluate whether the U.S. Environmental Protection Agency (EPA) DIMP
Health Advisory of 600 parts per billion is safe. Overall, the Army has conducted more than
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30 separate animal studies with DIMP, including one study with humans. The EPA and the
National Academy of Sciences evaluated all health studies and concluded that the EPA's 600
parts per billion Health Advisory is protective of human health and the environment. In
addition, the Army evaluated 'all possible ways DIMP and other chemicals could enter the
human body. These tests again showed that the water offpost is protective of human health
and the environment. As an additional protective measure, the Offpost Treatment System and
the North Boundary System will treat the groundwater to less than 10 parts per billion. The
Army is currently evaluating the applicability of the 8 parts per billion level that the Colorado
Water Quality Control Commission is expected to promulgate in the next several months.
The land use projections were used for the Offpost Risk Assessment. The Offpost
Risk Assessment analyzes potential risks from chemicals to the human body. These land use
projections in no way mean that the offpost area has been or will be zoned in a particular
fashion. The land use projections we established for the Offpost Risk Assessment are the
most conservative for the zone studied in the Proposed Plan. Conservative land use
projections are the human health problems that could possibly develop and pose the highest
potential risk. Say, for instance, that in zones 3 and 4 the Army projected urban residential
land use. According to Adams County and Commerce City projections, the land in these two
zones will most likely be industrial/commercial in the future, but the actual land use won't be
decided until the land is developed. The Army decided that by using urban residential land
use for the Offpost Risk Assessment, we were examining the worst-case risk assessment and
thus providing the best cleanup alternative.
Soil contamination was evaluated in the Remedial Investigation and subsequently in
the Offpost Risk Assessment. After evaluating wind patterns at the Arsenal and
concentrations of contaminants as they travel from onpost to offpost, the Army concluded that
offpost soils are well within EPA's health guidelines. Over 70 percent of the risk calculated
offpost (prior to construction of the Offpost Treatment System) was due to groundwater
contamination; thus surface water, soil, and sediment are minor contributors to the overall
risk. Institutional controls have been incorporated into the Offpost Preferred Alternative based
on State, EPA, and public comments. These institutional controls will prevent offpost
residents from drilling new drinking water wells in groundwater that does not meet applicable
federal and state standards.
4. First, human health and the environment are not impacted by the fact that the Army has
not adopted state standards as Army standards. Second, the Army does not believe that the
state standards are drinking water standards. Even though the Army does not believe the state
standards are drinking water standards, the differences between federal and state standards are
described below.
For the chemicals of concern for the Offpost Study Area, only two chemical standards
within the state standards are more stringent than the federal standards. Dieldrin, a pesticide,
has both federal and state standards that are below the chemical detection limit, which means,
with current technology, the Army cannot measure to the federal or state standard. When a
chemical standard is below the detection limit, treatment must be made to that detection limit.
-------
The other chemical where the state regulations differ is chloroform. The Colorado
standard for chloroform is 6 parts per billion. The Army treats chloroform in the
Groundwater Treatment Systems to approximately 12 parts per billion. Municipal water
supplies for drinking water in the Denver Metro Area typically have chloroform
concentrations of 10-50 parts per billion as a result of the chlorination process, which kills
bacteria living in the water supplies.
Again, the Army believes that the federal drinking water standards are protective of
human health.
5. See response to comment number 3.
I hope this information helps to alleviate your concerns. I appreciate your continued
support of the RMA program and the input you give the Army with the Technical Review
Committee. Any other questions regarding the Offpost Proposed Plan may be directed to Mr.
Tim Kilgannon of this office at 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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Protecting This Con|gmity and Your Future?
Please take the time to complete the following information to help us compile a community
comment that we can submit to the US Army.
Name:
Address:
Phone:
fiGoez. ci+ ST.
239- 49/D
Are there any unusual health conditions being experienced by anyone in your home? What?
What do you want the Army to do for the area that is contaminated?.
Concerns and or Comments
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RESIDENT
11690 PEORIA ST
HENDERSON, CO 80640
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Office of the Program Manager
Mr. and Mrs. John Humphreys
11690 Peoria Street
Henderson, Colorado 80640
Dear Mr. and Mrs. Humphreys:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for the Rocky Mountain Arsenal (RMA).
Public input is a key part of the cleanup process at RMA.
The Army, as stated in the Proposed Plan, will spend more than 70 million
dollars cleaning up the groundwater (water beneath the ground surface) at the north
and northwest boundaries of RMA and offpost during the next 15 to 30 years. The
Army has already spent over 15 million dollars to treat the groundwater offpost
Groundwater offpost, even though within the U.S. Environmental Protection Agency
health guidelines, contributes approximately 70 percent of the health risk offpost
For this reason, the Army decided to clean up the groundwater to further reduce the
possible risk.
The Army, in cooperation with Tri-County Health Department, samples
private wells offpost on a quarterly basis. The Army will notify Tri-County Health
Department about your well so that it can be sampled as soon as possible.
If you have any questions regarding the sampling procedures of your private
well(s), please contact Tri-County Health Department at (303) 288-6816. Questions
regarding the Offpost Proposed Plan may be directed to Mr. Tim Kilgannon of this
office at (303) 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
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Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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PUBLIC COM1ENT
U.S. Army's "Proposed Plan for the Off post Study Area"
Colonel Eugene H. Bishop, RMA Bldg. 111, Carmerce City, Colorado 80022-2180
I am a resident of the "Offpost Study Area" and am directly affected by contamination frcm
the Rocky Mountain Arsenal. I join with others in my ccrmunity in opposing the Army's
proposed plan. We urge that it be amended to address broad comunity concerns with a
ccrrorehensive solution to widespread contamination problems that the Army and Shell Chemical
Company have failed to address, to date, and which currently poison domestic water supplies
and private property for miles to the north and northwest of the Rocky Mountain Arsenal.
Contaminants include deadly pesticides that were banned by the EPA years ago, by-products of
chemical warfare agents, and other toxic substances.
I demand that the U.S. Army and Shell Chemical Company develop and implement a plan to: 1)
eliminate all current sources of toxic exposure to citizens affected by off-site poisons from
the Rocky Mountain Arsenal; 2) provide a permanent, alternative, unoontaminated source of
water to residents with any level of RMA toxins in their water; 3) conduct a comprehensive
offpost soil and water clean-up that meets all applicable federal and state guidelines,
including RCRA; 4) that no final "Record of Decision" be issued until the Colorado Water
Quality Control Ccrmrission adopts standards for unique, unregulated, Arsenal-related poisons,
such as "OIMP"; and 5) that the Army will meet or exceed those standard(s) in all groundwater
clean-up actions on and offpost.
My additional ccmnents about the Army's inadequate clean-up plan are these:
(see reverse side for continued ccmnents)
Please send written ccmnents in response to the urgent concerns raised in my ccmnents before
a "Record of Decision" is issued regarding offpost Rocky Mountain Arsenal poisons.
ADDRESS TOWN ZIP . PHONE
cc: Les Aspin, Secretary of Defense, Vice President Al Gore, Carol Browner, U.S. EPA,
Colorado Congressional delegation, chairs of key Congressional oversight ccmnittees; Colorado
Governor Roy Romer, Attorney General Gale Norton, CDH Director Patricia Nolan; public media
-------
Office of the Program Manager
Mr. J.H. Irthum
11230 Peoria Street
Henderson, Colorado 80640
Dear Mr. Irthum:
Thank you for your comments. The Army appreciates the many comments received on
the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public input is a key part of the
cleanup process at RMA.
The preferred alternative for the Offpost Operable Unit will clean up contamination that
came from RMA. The Army has spent nine years studying the best possible way to eliminate
potential health threats offpost. We believe the Offpost Preferred Alternative goes beyond what
is required by the U.S. Environmental Protection Agency (EPA). In addition, the Army cannot
legally provide offpost residents with a new water supply because legal chemical health guidelines
are not being exceeded. The Army will, as it has in the past, provide offpost residents an
alternative water supply if applicable EPA health guidelines are not being met in their private
well water. Finally, the Army believes that all applicable federal and state guidelines are being
met for soil and water offpost.
One of the major concerns to offpost residents is the DIMP contamination in groundwater
offpost. Since my tenure began at RMA, I wanted to make sure the Army would further study
the DIMP tests to evaluate whether the EPA DIMP Health Advisory of 600 parts per billion is
safe. Overall, the Army has conducted more than 30 separate animal studies with DIMP,
including one study with humans. The EPA and the National Academy of Sciences evaluated
all health studies and concluded that the EPA's 600 parts per billion Health Advisory is protective
of human health and the environment. In addition, the Army evaluated all possible ways DIMP
and other chemicals could enter the human body. These tests again showed that the water offpost
is protective of human health and the environment. As an additional protective measure, the
Offpost Treatment System and the North Boundary System will treat the groundwater to less than
10 parts per billion. The Army is currently evaluating the applicability of the 8 parts per billion
level that the Colorado Water Quality Control Commission is expected to promulgate in the next
several months.
-------
I hope this information has helped to alleviate your concerns. Any other questions
regarding the Offpost Proposed Plan may be directed to Mr. Tim Kilgannon of this office at 289-
0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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STEVEN L. JANSSEN, P.C.
Counsellor & Attorney at Lnr
745 Walnut Street
Boulder, CO 80302
telephone: (303) 443-4337
facsimile: (303)443-1897
June 18, 1993
Off-Post Proposed Comments
Program Manager for Rocky
Mountain Arsenal
ATTN - Colonel Eugene H. Bishop
Building 111
Rocky Mountain Arsenal
Commerce City, CO 80022-2180
Dear Colonel Bishop:
This office represents the Henrylyn Irrigation District, comprising approximately 33,000
acres of irrigated farm land in southern Weld County, Colorado. *
Our District derives the majority of water from the South Platte River through the
Burlington Ditch.
My client has reviewed the proposed plan for the Rocky Mountain Arsenal Off-Post Study
Area and is principally concerned that the proposed plan for study does not address the
possibility of, and regular scientific investigation for, contamination to my client's numerous
and various water rights which pass through the Burlington Ditch. My client's users utilize
said water for many purposes, including the irrigation of crops and the watering of livestock.
Our review of the previous scientific investigation shows that there has been a detection of
DIMP at Barr Lake. My client also owns a significant portion of the water stored in Ban-
Lake. Because DIMP has travelled to Barr Lake, it is entirely possible that it will travel to
other reservoirs in my client's system.
Therefore, my client requests that you consider a revision to this proposed plan for study,
incorporating a periodic (suggested one year intervals) scientific study (suggested to be
completed by experts selected by my client but paid for by the Dept. of the Army) to
determine whether contamination has migrated to my cb'ent's facilities or is present in my
client's water supply.
Please Recycle
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Off-Post Proposed Comments
Program Manager for Rocky
Mountain Arsenal
ATTN - Colonel Eugene H. Bishop
June 18, 1993
Page 2
We would request that this additional investigation be maintained for the 30 year life
expectancy of the plan. It is our understanding that the Dept. of the Army has cooperated
with other entities on similar matters in the past My client believes the additional cost of
this requested monitoring will be minimal as compared to the increase in safety of the
people utilizing my client's water storage facilities and irrigation water rights.
Of course, if you have any questions in this matter, or wish to discuss this further, do not
hesitate to contact me.
Very Truly Yours,
STEVE&is-JANSSEN, P.C
SLJ/mtm
cc Board
enrylyn Irrigation District
PleaceRecyde
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Office of the Program Manager
Mr. Steven L. Janssen, P.C.
745 Walnut Street
Boulder, Colorado 80302
Dear Mr. Janssen:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public
input is a key part of the cleanup process at RMA. I will respond to your comments
in the order we received them.
The Offpost Proposed Plan outlines a preferred alternative that is based on
nine years of study. Following selection of a final alternative, the Army will
produce an Implementation Plan that will address the monitoring of offpost
groundwater and surface water. This document will be available for review in the
Joint Administrative Record and Document Facility.
Over the years the Army has documented a decrease of contaminants offpost,
primarily due to the Boundary Groundwater Treatment Systems. With the addition
of the Offpost Treatment System, which was fully operational in June 1993,
contaminant concentrations will be reduced even further. The Treatment Systems
are also important in improving the quality of water in First Creek as groundwater
discharges into First Creek in some areas, including just north of the RMA
boundary.
The DIMP contamination you are referring to in Barr Lake was detected only
once, approximately 100 times below the U.S. Environmental Protection Agency's
(EPA's) Health Advisory level. No detections of DIMP were found in the many other
water and sediment samples taken in Barr Lake. In addition, samples taken in the
canals and creeks that eventually discharge to Barr Lake have shown only sporadic
detections of DIMP at very low concentrations (more than 100 times below EPA's
Health Advisory level).
Because chemical standards are being met in the canals and Barr Lake, the
Army cannot provide funds to your client. As mentioned above, the Army will
produce monitoring plans and will make these available for public review. The
Army looks forward to working with you in the future.
-------
I hope this information helps to alleviate your concerns. Any other questions
regarding the Offpost Proposed Plan may be directed to Mr. Tim Kilgannon of this
office at 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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First Christian Assembly of God.
12505 Elmendorf Place
Pastor Madlyn Tombs
Denver, Colorado 80239
(303) 373-5200
JUN 2 2 1993
June 21. 1993
Program Manager RMA
AMCRM - PM/Colonel Eugene H. Bishop
Building 111
Commerce City, Colorado (30022-2180
Dear Colonel Bishop-
I am writing in regards to the off post clean-up plan of the
Rocky Mountain Arsenal. I am an Associate Minister of First
Christian Assembly of God Montfaello a representative of the
Montbello Cooperative Ministries and a member of the Far
Northeast Neighbors. *
I am part of the. process to keep each one of these organiza-
tions informed of the various aspects of clean-up on the RMA
itself.' I would like to also be a part of the off post site
clean-up in regards to meetings and information. There are
many concerns that need to be addressed in regards to the
Montbello Community and the contamination it has recieved
from the RMA.
> cna be reached at (303)-(373-5200) , from 8:30 AM to 5:00 PM
ON Monday thru Friday.
Thank You,
Jeffery D. Kanost
cc/pf
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Office of the Program Manager
Mr. Jeffery D. Kanost
12505 Elmendorf Place
Denver, Colorado 80239
Dear Mr. Kanost:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public
input is a key part of the cleanup process at RMA.
The Army will continue to keep you informed about RMA activities and
meetings. If you wish to discuss your concerns in more detail, please contact Mr.
Tim Kilgannon at the number listed below.
The Offpost Proposed Plan identified only two areas to the north and
northwest of the Arsenal boundary that require cleanup. In these north and
northwest areas, only groundwater, which is water beneath the ground surface,
requires cleanup. Montbello is not affected by RMA groundwater because
groundwater travels to the north and northwest from the Arsenal and not south
toward Montbello.
Any other questions regarding the Offpost Proposed Plan may be directed to
Mr. Tim Kilgannon of this office at 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
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Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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May 19, 1993
Col. Eugene H. Bishop
Program Manager -for the
Rocky Mountain Arsenal
Building 111-RMA
Commerce City, Colo 80022-2130
Dear Col. Bi shop
Concerning the of-fpost proposal plan for groundwater
clean-up of the north boundary containment system. NBCS.
I have reviewed the proposed plan and understand that
the army plans to treat the groundwater thru extraction
weils. Using plan N-4; Offpost Intercept and treatment
Systems. I believe that there is four major problems with
this plan.
First the length of time to perform the ciean-up . In
N-4 the time frame is 15 to 30 years. Yet in your proposal N-
5 : Expansion of offpost Intercept and Treatment System plans
only 10 to 20 years. After reading both proposals they
basically are the same , with N-5 has an increase of
groundwater being cleaned-up at a rate of 90 gpm more. Thank
to the increase of extraction wells and additional recharge
trenches. It is my belief that the groundwater may be
cleaned up by use of N-5 with additional potential future
modification as needed to insure a complete clean-up . There
is no reason that the Army can't clean-up the groundwater off
the Rocky Mountain Arsenal.
Second is the Army's position that 600 ppb of DIMP is
the only guidelines needed. I have a personnel believe that
6OO ppb of DIMP is not adequate number. This number is
inadequate do to the increase on cancer and kidney problems
of residents within the boundaries of the off.post study
areas's. Being a firefighter within the area known as the
offpost study area, I have witnessed an increase of cancer,
kidney or liver problems within this area. Personally my
family has been subjected to the Army's contamination ,
either by air containments, or by our water supply for over
37 years . I watched my Father having to have a kidney
removed and obtain leukemia cancer and die. My belief is
that the standards for DIMP and the other chemicals listed in
your information sheet < Table 1 ) is set to high. If DIMP
was the only problem I would still be opposed to the 600 ppb
rating. However by the Army's own determination there are 34
chemicals that have contaminated the land /air/ water leaving
the Rocky Mountain Arsenal . EF'A's figures are inadequate !
i
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Third is the Army's commitment to continued monitoring
program for private wells. I asked both Tri-County and the
Army why analytical reports from November 92 we not released.
Mr. Charlie Scharmann stated that it takes months to obtain
analytical reports. I find this unacceptable. I know that
analytical become unstable if not properly Cc^red for and most
have a period of time when the material being analyzed become
unusable. Most analytical laboratories are able to complete
results within in a period of ten days to two (2) month . Why
does it takes the Army over eight (8) months to obtain a
report, this is beyond me.
Forth is my belief that the Army and Shell Oil should
provide adequate water supply to ail of the residents who
have had their water contaminated . This does not mean just
bottled water , but water service from a South Adams Water
District. The Army has created a monster for families ,
there property values have become on nonexistence. Their
lives have been changed for the worst . And the Army and
Shell Oil has not offered to assist the residents who they
have effected.
As a final statement and questions to the Army / Shell
Oil Co. I would like to know why the Army chose N-4, a system
that cost more (by their own determination), takes more time
to complete and jeopardizes the residents of Adams County .
My second question is why does the Army believe that it is
above legal regulations . If the company I work for
contaminated groundwater, it would be sued for the clean-up
and any hardship that the residents may have endured and pay
fines and penalties . The last question is what does the
Army / Shell Oil Co. plan to due for the residents who's
ground water they have effected. I believe that the Army
must start the clean-up , But using only N-4 plan is only
half a plan. Since N-5 follows the same guidelines as N-4 .
The Army should add additional systems listed in N-5 to
remediate the problem of groundwater .
I-f there is any addition communication, feel free to
call me at the phone number list below or write to the
address listed below.
Sincerely ;
Carl P. Kern
10O20 Havana
Henderson. Colorado 80640-8439
303-2S8-0656
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Office of the Program Manager
Mr. Carl P. Kern
10020 Havana
Henderson, Colorado 80640-8439
Dear Mr. Kern:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public
input is a key part of the cleanup process at RMA. I will respond to your comments
in the order we received them.
Alternative N-4 was chosen as the Army's preferred alternative over
Alternative N-5, an expansion to the Offpost Treatment System, for two major
reasons. The Offpost Treatment System, a major component of Alternative N-4,is
already in operation has been for five months. Secondly, the most important
component of the preferred alternative, N-4, is the flexibility of improving the
Offpost Treatment System as the Army evaluates its. performance. For these reasons,
the Army selected the use of operational data as a basis for any future expansion of
the Offpost Treatment System (Alternate N-4) instead of using a computer model as
a basis for any expansion as called for in alternative N-5. With the flexibility of N-4,
water monitoring results will show the Army how best to shorten and improve the
cleanup time frame in the offpost area, which may include the addition of more
extraction and recharge wells or trenches. Finally, the Offpost Treatment System
was designed with extra capacity so that additional wells can be connected if
determined necessary.
One of the major concerns to offpost residents is the DIMP contamination in
offpost groundwater. Since my tenure began at RMA, I have made sure that the
Army conducted further assessment of the DIMP tests to evaluate whether the U.S.
Environmental Protection Agency (EPA) DIMP Health Advisory of 600 parts per
billion is safe. Overall, Army has conducted more than 30 separate animal studies
with DIMP, including one study with humans. The EPA and the National Academy
of Sciences evaluated air health studies and concluded that the EPA's 600 parts per
billion Health Advisory is protective of human health and the environment In
addition, the Army evaluated all possible ways DIMP and other chemicals could
enter the human body. These tests again showed that the water offpost is protective
of human health and the environment. As an additional protective measure, the
-------
Offpost Treatment System and the North Boundary System will treat the
groundwater to less than 10 parts per billion.
The Army is currently evaluating the applicability of the 8 parts per billion level
that the Colorado Water Quality Control Commission is expected to promulgate in
the next several months.
The EPA conducts extensive analyses before setting safe chemical standards.
The Army, like other Superfund cleanup sites, must follow the guidance and
regulations the EPA has selected. If you have further questions regarding EPA's
standard-setting criteria, I suggest calling the Denver Office (EPA, Region VET) at
(303) 294-7559 for information.
I apologize for the poor turnaround time on the private well results. Since
the beginning of this year, the Army has refined the sampling and analysis process
so that well results can be given to each homeowner more quickly. The turnaround
time from well sampling to well results will still take approximately three months to
complete because of the laboratory quality control and quality assurance that is done
for each chemical sample. The laboratory quality control and quality assurance
ensures that the chemical results are correct The turnaround time, from well
sampling to chemical results, will be much improved than it has in the past.
The Army has committed to treating groundwater offpost with Alternative N-
4, with improvements as necessary. This alternative will achieve clean up levels
that are more strict than EPA's own health guidelines, based on the Offpost Risk
Assessment The Army believes that this will benefit offpost residents for many
years to come. As the groundwater aquifer becomes cleaner, everyone offpost will
benefit. The Offpost Risk Assessment evaluated all ways of exposure through water,
soil, sediment, and air, and showed that residents offpost are living well within
EPA's safe health guidelines.
Finally, the Army is required to follow all applicable federal and State of
Colorado regulations, as any other Superfund site must do. Any other questions
regarding the Offpost Proposed Plan may be directed to Mr. Tim Kilgannon of this
office at 289-0201. Thank you again for your comments.
Sincerely,
-------
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
-------
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-------
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10730 Brighton Rd
Henderson. CO 80640
1
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-------
Office of the Program Manager
Mr. Jess Masunaga
10730 Brighton Road
Henderson, Colorado 80640
Dear Mr. Masunaga:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public
input is a key part of the cleanup process at RMA. I will respond to your comments
in the order we received them.
One of the major concerns to offpost residents is the DIMP contamination in
groundwater. Since my tenure began at RMA, I have ensured that the Army would
further study the DIMP tests to evaluate whether the U.S. Environmental Protection
Agency (EPA) DIMP Health Advisory of 600 parts per billion is safe. Overall, the
Army has conducted more than 30 separate animal studies with DIMP, including
one study with humans. The EPA and the National Academy of Sciences evaluated
all health studies and concluded that the EPA's 600 parts per billion Health
Advisory is protective of human health and the environment. In addition, the Army
evaluated all possible ways DIMP and other chemicals could enter the human body.
These tests again showed that the water offpost is safe for consumption and for the
environment. As an additional protective measure, the Offpost Treatment System
and the North Boundary System will treat the groundwater to less than 10 parts per
billion. The Army is currently evaluating the applicability of the 8 parts per billion
level that the Colorado Water Quality Control Commission is expected to promulgate
in the next several months.
Based on our current data, all residents in the offpost study area are drinking
water that meets all applicable or relevant and appropriate federal and state
regulations. The Army continues to extensively monitor drinking water wells in the
offpost area. If levels of Arsenal-related chemicals were to rise above health
guidelines in the drinking water for any resident, the Army will provide an
alternative water supply to that resident.
-------
Any other questions regarding the Offpost Proposed Plan may be directed to
Mr. Tim Kilgannon of this office at 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridge-water, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
-------
PUBLIC COMMENT
U.S. Army's "Proposed Plan for the Offpost Study Area"
Colonel Eugene H. Bishop, RMA Bldg. 111, Ocmnerce City, Colorado 80022-2180
I am a resident of the "Offpost Study Area" and am directly affected by contamination from
the Rocky Mountain Arsenal. I join with others in my ccrmunity in opposing the Army's
proposed plan. We urge that it be amended to address broad comunity concerns with a
comprehensive solution to widespread contamination problems that the Army and Shel 1 Chemical
Company have failed to address, to date, and which currently poison domestic water supplies
and private property for miles to the north and northwest of the Rocky Mountain Arsenal.
Contaminants include deadly pesticides that were banned by the EPA years ago, by-products of
chemical warfare agents, and other toxic substances.
I demand that the U.S. Army and Shell Chemical Company develop and implement a plan to: 1)
eliminate aJJ current sources of toxic exposure to citizens affected by off-site poisons from
the Rocky Mountain Arsenal; 2) provide a permanent, alternative, uncontaminated source of
water to residents with any level of RMA toxins in their water; 3) conduct a comprehensive
offpost soil and water clean-up that meets all applicable federal and state guidelines,
including RCRA; 4) that no final "Record of Decision" be issued until the Colorado Water
Quality Control Ccrmvission adopts standards for unique, unregulated, Arsenal -related poisons,
such as "OIMP"; and 5) that the Army will meet or exceed those standard(s) in all groundwater
clean-up actions on and offpost. *
My additional Garments about the Army's inadequate clean-up plan are these:
<-•>
(see reverse side for continued ccrrments)
-4%t_
-------
11/14/95 11:34 fj303 288 0485 PMRKA/EED
DEPARTMENT OF THE ARMY
PROGRAM MANAGER FOR ROCKY MOUNTAIN ARSENAL
RCE CITY, COLORADO tUO2AW
December 9, 1993
unriD
Office of die Program Manager
Mr. Beanie Muniz
P.O. Box 261
Henderson, Colorado 80640
Dear Mr. Muitir
Thank you for your comments. The Army appreciates die many comments received
on die Ofrpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public input is a key
part of die cleanup process at RMA.
The preferred alternative for die Ofrpost Operable Unit win clean up contamination
that came from RMA. The Army has spent nine years studying die best possible way to
eliminate potential health threats ofrpost. We believe die Ofrpost Preferred Alternative goes
beyond what is required by die U.S. Environmental Protection Agency (EPA). In addition,
die Army cannot legally provide ofrpost residents widi a new water supply because legal
chemical healdi guidelines are not being exceeded. The Army will, as it has in die past,
provide residents oftpost an alternative water supply, if applicable EPA healdi guidelines are
, not being met in their private well water. Finally, die Army believes that all applicable
federal and state guidelines are being met for soil and water oftpost.
One of die major concerns to ofrpost residents is die DIMP contamination in
groundwater oftpost. Since my tenure began at RMA, I wanted to make sure die Army
would further study the DIMP tests to evaluate whedier die EPA DIMP Healdi Advisory of
600 parts per billion is safe. Overall, die Army has conducted more than 30 separate animal
studies widi DIMP, including one study widi humans. The EPA and die National Academy
of Sciences evaluated all health studies and concluded that die EPA's 600 parts per billion
Healdi Advisory is protective of human healdi and die environ In addition, die Army
evaluated all possible ways DIMP and odier chemicals could enter die human body. These
tests again showed that the water ofrpost is protective of human healdi and die environment.
As an additional protective measure, die Oftpost Treatment System and die North Boundary
System will treat die groundwater to less than 10 parts per billion. The Army is currently
evaluating die applicability of the 8 parts per billion level that die Colorado Water Quality
Control Commission is expected to promulgate in the next several months.
7,
Readiness is our Profession
-------
11/14/95 11:35 ©303 289 0485 PMRMA-'EED
I hope this information has helped to alleviate your concerns. Any other questions
regarding the Offpost Proposed Han may be directed to Mr. Tim Eilgannon of this office at
2894)239. Thank you agam for your comments.
Sincerely,
l, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite SOI, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building HI, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
-------
Do You Want to be Involved
in
Protecting This Community and Your Future?
Please take the time to complete the following information to help us compile a community
comment that we can submit to the US Army.
Name:
Address: ///?/^7
Phone:
^
^A^A ST"
A To
Are there any unusual health conditions being experienced by anyone in your home? What?
What do you want the Army to do for the area that is contaminated? o»..- ^ *
.. />\ gc »vt u. n i'<^. / wJiv I If.* O ?>v^7^ei^i Tin l"k .fc-
f-\ 1A
Concerns and or Comments.
«*~
__ i ^j
/
1P"^,ffSS:
-------
Office of the Program Manager
Mr. Glen Murray
11010 Havana Street
Brighton, Colorado 80601
Dear Mr. Murray:
Thank you for your comments. The Army appreciates the many comments received on
the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public input is a key part of the
cleanup process at RMA.
The preferred alternative for the Offpost Operable Unit will clean up contamination that
came from RMA. The Army has spent nine years studying the best possible way to eliminate
potential health threats offpost. We believe the Offpost Preferred Alternative goes beyond what
is required by the U.S. Environmental Protection Agency (EPA). In addition, the Army cannot
legally provide offpost residents with a new water supply because legal chemical health guidelines
are not being exceeded. The Army will, as it has in the past, provide offpost residents an
alternative water supply if applicable EPA health guidelines are not being met in their private
well water. Finally, the Army believes that all applicable federal and state guidelines are being
met for soil and water offpost.
One of the major concerns to offpost residents is the DIMP contamination in groundwater
offpost. Since my tenure began at RMA, I wanted to make sure the Army would further study
the DEVEP tests to evaluate whether the EPA DIMP Health Advisory of 600 parts per billion is
safe. Overall, the Army has conducted more than 30 separate animal studies with DIMP,
including one study with humans. The EPA and the National Academy of Sciences evaluated
all health studies and concluded that the EPA's 600 parts per billion Health Advisory is protective
of human health and the environment. In addition, the Army evaluated all possible ways DIMP
and other chemicals could enter the human body. These tests again showed that the water offpost
is protective of human health and the environment. As an additional protective measure, the
Offpost Treatment System and the North Boundary System will treat the groundwater to less than
10 parts per billion. The Army is currently evaluating the applicability of the 8 parts per billion
level that the Colorado Water Quality Control Commission is expected to promulgate in the next
several months.
-------
I hope this information has helped to alleviate your concerns. Any other questions
regarding the Offpost Proposed Plan may be directed to Mr. Tim Kilgannon of this office at 289-
0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
-------
Do You Want to be Involved
In
Protecting This Community and Your Future
Please take the time to complete the following information to help us o
comment that we can submit to the US Army.
Name:
, Afe) M Sift
Address:
Phone:
Are there any unusual health conditions being experienced by anyone in your home? What?
E-k.. tb/u> f>£/£*
What do you want the Army to do for the area that is contaminated? (B/£^/u uP //?£
fj H
s
Concerns and or Comments fffa-ffl Sr}£.//. "ffizts &
*77i£
NELSON, JAMES
11810E124THAVE
HENDERSON, CO 80640
-------
Office of the Program Manager
Mr. James E. Nelson
11810 East 124th Avenue
Henderson, Colorado 80640
Dear Mr. Nelson:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public
input is a key part of the cleanup process at RMA.
The preferred alternative for the Offpost Operable Unit will clean up
contamination that came from on-post contaminants, including the pesticides you
reference in your letter. The Army has spent nine years studying the best possible
way to eliminate potential health threats offpost. We believe the Offpost Preferred
Alternative goes beyond what is required by the U.S. Environmental Protection
Agency (EPA). In addition, the Army cannot legally provide residents offpost with a
new water supply because health guidelines are not being exceeded. The Army
will, as it has in the past, provide offpost residents an alternative water supply if
applicable health guidelines are not being met in their private well water. Finally,
the Army believes that all applicable or relevant and appropriate requirements
federal and state are being met for soil and water offpost.
One of the major concerns to offpost residents is the DIMP contamination in
groundwater offpost. Since my tenure began at RMA, I wanted to make sure the
Army would further study the DIMP tests to evaluate whether the EPA DIMP Health
Advisory of 600 parts per billion is safe. Overall, the Army has conducted more
than 30 separate animal studies with DIMP, including one study with humans. The
EPA and the National Academy of Sciences evaluated all health studies and
concluded that the EPA's 600 parts per billion Health Advisory is protective of
human health and the environment. In addition, the Army evaluated all possible
ways DIMP and other chemicals could enter the human body. These tests again
showed that the water offpost is protective of human health and the environment
As an additional protective measure, the Offpost Treatment System and the North
Boundary System will treat the groundwater to less than 10 parts per billion. The
Army is currently evaluating the applicability of the 8 parts per billion level that the
Colorado Water Quality Control Commission is expected to promulgate in the next
several months.
-------
I hope this information has helped to alleviate your concerns. Any other
questions regarding the Offpost Proposed Plan may be directed to Mr. Tim
Kilgannon of this office at 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
-------
MAY24I993
May 20, 1993
Col. Eugene H. Bishop
Program Manager
Rocky Mountain Arsenal
Building 1 1 1 -RMA
Commerce City, Colo
80022-2180
Attention: Col. Eugene H. Bishop
AMXRM-PM
Reference: Proposed Plan For The Rocky Mountain Arsenal
Off Post Study Area
Citizen Comment
The Army has presented a proposed plan on the Offpost in
great detail with studies to support their position.
The following are areas of comment, question, and concern.
The Army has proposed land uses .
The Army has proposed land use for development in the future,
defining future as now and development as residential and or
industrial.
"The "Shell" Property on the north side of 96th along
Peoria Street and properties at approximately 100th
Avenue . "
Rezoned to 1-2. May 1992
This land was rezoned without public notice as required by
zoning practices.
Why is this land already rezoned when this proposal is still
in the proposed stage? Please explain.
The defined zones along E. 96th Avenue to Peoria are already
zoned industrial as above thus making the evaluations of land
use within these zones incorrect.
Industrial zoned land on the north side of the Arsenal places
people working in an environment between two treatment plant
systems and in some instances less than one mile from the
Submerged Quench Incinerator.
We are unable to find documentation of industrial development
of Army Bases. Please explain why the Army has choseri to
develope landVon this particular base.
Please outline the plan and time frame for development of land
north of the Arsenal on E. 96th Avenue from Peoria Street to
Hi9hway2' ' -
-------
We are unable to find any information explaining how contaminated
land is rendered ready for development. In the off post
study area the only visible changes we have been able to observe
is the demolition of homes/buildings and in some areas the
planting of anti-contaminate grass.
Please explain and clarify.
Housing foundations and sidewalks were left in place on properties
north of the Arsenal along E. 96th Avenue between Highway 2 and
Peoria Street.
Please explain and clarify.
The Army has proposed health risks and assessment.
. The Army has identified chemicals of concern in this offpost
area. We think based on our own knowledge and exposure that
these chemicals are only the tip of the iceberg of in this
case' the tip of the plume.' As advanced as the testing methods
are we think that more research and accurate technology is
needed in this area.
We now know that we have been exposed to numerous known and
unknown chemicals, metals, pesticides, and by products of
over a twenty year period.
We do not wish at this time to speculate as to which statistic
we may be classified as.
»
The Army has proposed remedial alternatives.
We feel that measures should be taken to clean up contaminants
identified in the ground water.
Summary
We" feel that the Army has devoted a great deal of time, manpower,
and money in preparing this proposal and in creating an illusion
of well-being.
Albert H. Ohle/Barbara Ohle
P.O.Box 129
Oupont,Colo
80024/0129
333-4510
-------
Office of the Program Manager
Albert H. and Barbara Ohle
P.O. Box 129
Dupont, Colorado 80024-0129
Dear Mr. and Mrs. Ohle:
Thank you for your comments. The Army appreciates the many number of
comments received on the Offpost Proposed Plan for Rocky Mountain Arsenal.
Public input is an integral part of the cleanup process at Rocky Mountain Arsenal. I
will respond to your comments in the order we received them.
I hope my responses to your comments will relieve some of the concerns you
both have regarding the Army's Proposed Plan for the Offpost Study Area and
treatment of groundwater offpost.
Your first comments are in regard to the land use the Army projected for the
future in the offpost area. The Army did not rezone areas offpost The land use
projections were used in the Human Health Risk Assessment only. The Human
Health Risk Assessment analyzes potential risks from chemicals to the human body.
These land use projections in no way mean that the offpost area has been or will be
zoned in a particular fashion. The land use projections we established for the
Human Health Risk Assessment are the most conservative for every zone we studied
in the Proposed Plan. Conservative land use projections are the human health
scenarios that could conceivably develop in a certain zone and that could pose the
highest risk. Say, for instance, that in zones 3 and 4, where you use to live, the
Army projected urban residential land use. According to Adams County and
Commerce City projections, the land in these two zones will most likely be
industrial/commercial in the future, but the actual land use won't be decided until
the land is developed. The Army decided that by using urban residential land use
for the Human Health Risk Assessment, we were examining the worst-case risk
assessment and thus providing the best cleanup alternative.
The Army and the U.S. Fish and Wildlife Service are working cooperatively to
cleanup the Arsenal so that it can become a wildlife refuge. No industrial
development of the Arsenal will occur. Also, only Commerce City and/or Adams
County can outline a timeframe for development of land offpost.
-------
The Army, through its Preferred Alternative, is cleaning up the offpost area.
During the cleanup timeframe, development of land by Commerce City or Adams
County may occur as long as complete safety of human health and the environment
is ensured. The Army studies supported by the Environmental Protection Agency,
show that people residing offpost will be safe.
Demolition of homes was completed to install the Offpost Treatment System.
The Army is not aware of an anti-contaminate grass. The Army did plant native
grass seed offpost, once the demolition of buildings and the offpost groundwater
treatment system were completed. This planting was done in order to restore the
areas damaged by construction activities.
Once residents vacated the premises, the above-ground structures were
demolished to avoid potential safety hazards with the abandoned buildings. Since
the sidewalks and foundations pose no safety hazard, they were left in place.
The health risks presented in the Offpost Proposed Plan are present-day risks-
in the offpost area without accounting for cleanup that is being accomplished by the
Offpost Treatment System. The Army has committed to the Offpost Groundwater
Treatment System, any necessary modifications to the system, and continued
monitoring offpost as part of the Preferred Alternative. As the groundwater
treatment systems continue to operate, risks to human health and the environment
will further decrease. The Army believes that evaluation of the contaminants and
associated human and environmental risks was very detailed.
I hope this information has helped to alleviate your concerns. Any other
questions regarding the Offpost Proposed Plan may be directed to Mr. Tim
Kilgannon of this office at 289-0239. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
-------
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
-------
-------
Office of the Program Manager
Ms. Annie R. Redmond
5331 Troy Street
Denver, Colorado 80239
Dear Ms. Redmond:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public
input is a key part of the cleanup process at RMA.
The Offpost Proposed Plan identified only two areas to the north and
northwest of the Arsenal boundary that require cleanup. In these areas, only
groundwater, which is water beneath the surface, requires cleanup. Montbello is not
affected by RMA groundwater because groundwater from RMA travels north and
northwest and not south toward Montbello.
In addition, the Offpost Proposed Plan summarizes the Offpost Health Risk
Assessment that was completed. The Offpost Health Risk Assessment showed that
Montbello residents are not affected by offpost contamination. Also, an Onpost
Health Risk Assessment will be completed before cleanup begins on RMA. The
Onpost Health Risk Assessment will evaluate the health risks to the onpost and
offpost plants, animals, and humans before cleanup begins. The Army will not
begin cleanup unless it determines that the public's health is protected.
Any other questions regarding the Offpost Proposed Plan may be directed to
Mr. Tim Kilgannon of this office at 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
-------
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
-------
may 8, 1993
Offpo*t Proposed Comments
Program Manager for Rocky Mountain arsenal
Attention: Colonel Eugene H. Bisnoo
Building 111
Rocky Mountain Arsenal
Commerce City, Colorado 80022-2188
Dear Colonel Bishop, «
You have asked me to write a letter exDressing my concern
about your water cleanup policies. I greatly admire your oesire
and efforts to clean up the Arsenal problem, however in the
process, you have practically destroyed an excellent, small,
minority owned business.
I represent The Fountain of Health. I have been selling
natural artesian water now for 13 years. I sell it for £5 cents
per gallon. I have followed all of the rules of the Colorado
Department of Health. Because of the ourity, the State Department
has issued a special waiver saying I DO NOT HAVE TO CHLORINATE.
FILTER OR TREAT THE WATER.
I was never contacted when you started the program to
deliver free water to my customers. The reouirement that this
water be delivered to peoole's homes, should not have been
considered one of the reauirements of the program. The only
consideration to deliver it to people's home would be, if they
are elderly, disabled and cannot drive. The rest of the
people should be issued food stamps or some kind of couoon
redeemable anywhere. This would save the tax oayers, literally
millions and millions of wasted dollars.
Why should the customers drive here and pay *0.£5, when
they can have it delivered to their door for nothing. This
policy has had a devastaing affect on my business. in tne
winter time I have driven around and taken pictures of piles
and piles of frozen and busted deeprock bottles. I have seen
many bottles in pig pens and horse corrals. This does not seem
like a sensible way to handle the problem. ,
I am a 65 year old American Indian woman. I am too old to
start over. I was enjoying my retirement years until you started
this program. Now I am devastated. I cannot wait another 38
years for you to clean up your mess.
Brace Russetl
Fountain of Health
13185 Brighton Road
Brighton, CO. 80631
659-0800
/
-------
Office of the Program Manager
Ms. Grace Russell
13185 Brighton Road
Brighton, Colorado 80601
Dear Ms. Russell:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public
input is a key part of the cleanup process at RMA.
The Army was not responsible for providing residents with bottled water
offpost. The State of Colorado provided bottled water to offpost residents, even
though all drinking water from private wells meets existing drinking water
regulations.
Any other questions regarding the Offpost Proposed Plan may be directed to
Mr. Tim Kilgannon of this office at 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
-------
rss"
PUBLIC COMMENT
U.S. Army's "Proposed Plan for the Offpost Study Area
Colonel Eugene H. Bishop, RMA Bldg. 111, Comnerce City, Colorado 80022-2180
it
I am a resident of the "Offpost Study Area" and am directly affected by contamination fron
the Rocky Mountain Arsenal. I join with others in my ccmrunity in opposing the Army's
proposed plan. We urge that it be amended to address broad comunity concerns with a
comprehensive solution to widespread contamination problems that the Army and She! 1 Chemical
Company have failed to address, to date, and which currently poison domestic water supplies
and private property for miles to the north and northwest of the Rocky Mountain Arsenal.
Contaminants include deadly pesticides that were banned by the EPA years ago, by-products of
chemical warfare agents, and other toxic substances.
I demand that the U.S. Army and Shell Chemical Company develop and implement a plan to: 1)
eliminate an current sources of toxic exposure to citizens affected by off-site poisons frcm
the Rocky Mountain Arsenal ; 2) provide a permanent, alternative, uncontaminated source of
water to residents with any level of RMA toxins in their water; 3) conduct a comprehensive
offpost soil and water clean-up that meets all applicable federal and state guidelines,
including RCRA; 4) that no final "Record of Decision" be issued until the Colorado Water
Quality Control Ccmnission adopts standards for unique, unregulated, Arsenal -related poisons,
such as "D1MP"; and 5) that the Army will meet or exceed those standard(s) in al 1 grcjindwatar
clean-up actions on and offpost.
My additional Garments about the Army's inadequate clean-up plan are these:
S£22
ADDRESS
TOWN
ZIP
PHONE
cc: Les Aspin, Secretary of Defense, Vice President Al Qore, Carol Browner, U.S. EPA,
Colorado Congressional delegation, chairs of key Congressional oversight ccmnittees; Colorado
Governor Roy Rcmer, Attorney General Gale Norton, CDH Director Patricia Nolan; public media
-------
^^/_.-ft A ^/ ^_
"
1
1
1
-------
I
DEPARTMENT OF THE ARMY
PROGRAM MANAGER FOR ROCKY MOUNTAIN ARSENAL
COMMERCE CTTf, COLORADO 8002M 748
December 9, 1993
ATTENTION OF:
Office of the Program Manager
Mr. and Mrs. Roger Sable
12270 Brighton Rd. P.O. Box 161
Henderson, Colorado 80640
Dear Ms. Sable:
Thank you for your comments. The Army appreciates the many comments received
on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public input is a key
part of the cleanup process at RMA. I will respond to your comments in the order we
received them.
One of the major concerns to offpost residents is the DIMP contamination in groundwater
offpost. Since my tenure began at RMA, I wanted to make sure the Army would further
study the DIMP tests to evaluate whether the U.S. Environmental Protection Agency (EPA)
DIMP Health Advisory of 600 parts per billion is safe. Overall, Army has conducted more
than 30 separate animal studies with DIMP, including one study with humans. The EPA and
the National Academy of Sciences evaluated all health studies and concluded that the EPA's
600 parts per billion Health Advisory is protective of human health and the environment. In
addition, the Army evaluated all possible ways DIMP and other chemicals could enter the
human body. These tests again showed that the water offpost is protective of human health
and the environment. As an additional protective measure, the Offpost Treatment System
and the North Boundary System will treat the groundwater to less than 10 parts per billion.
The Army is currently evaluating the applicability of the 8 parts per billion level that the
Colorado Water Quality Control Commission is expected to promulgate in the next several
months.
Based on current data, all residents in the offpost study area are drinking water that
meets all applicable or relevant and appropriate federal and state requirements. The Army
continues to extensively monitor drinking water wells in the offpost area. If levels of
Arsenal-related chemicals were to rise above health guidelines in the drinking water for any
resident, the Army will provide an alternate water supply to that resident.
Readiness is OUT Profession
-------
Any other questions regarding the Ofrpost Proposed Plan may be directed to Mr. Tim
Kilgannon of this office at 289-0201. Mr. Kilgannon and Mr. Charles Scharmann both
spoke at the Public Meeting. They can both be reached at the number listed above. Thank
you again for your comments.
Sincerely,
Eugene M. Bishop
Colonel/U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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June 21,1993
Leif R. Southwell
11355 N Racine CT
Henderson Co, 80640
Offpost Proposed Plan Comments
Program Manager For Rocky Mountain Arsenal
Attn: AMXRM/ Col. Eugene Bishop
Building 111-RMA
Commerce City, Co 80022-2180
Dear Sir, Re: Comments
BACKGROUND
The Army is authorized by Congress and therefore the American people
to develop weapons for the defense of our nation. None of the above
authorizes the Army to pollute our nation.
The Army has pursued a cocaine like addiction for weapons which has
resulted in a blatant disregard for the environment. In the case of
RMA the Army casually and haphazardly dumped the by-products of
chemical warfare into evaporation pond(s) where the contents were
allowed to leak directly into the water table.
Since the Arsenal was in full operation from the 1940's to the mid 1980'
the Army's only act of remediation was to pump 110 million gallons
of the weapons by-product 5 miles deep into the earth's crust
causing the first and only known man-made earthquake.
The Army has never had a viable plan either to protect the environment
or the surrounding residents until it was discovered by an outside.
entity that drinking water was contaminated.
FINDINGS
The Army and the EPA refer to scientific levels of parts per
billion when testing for some 34 chemicals which have contaminated
residents drinking water but these standards are guesses only, as:
A. There are no long term health studies on the effects of
chemicals such as DIMP.
B. There have been no studies done on the effect on humans of
the combination of these chemical.
Scientific data is constantly changing as an example during the
testing of Atomic the bomb the military told residents "down wind" in
Utah that the bomb would not harm them. This was totally false
as the military admitted this was inaccurate some 40 years later.
Advertisments on TV during the 1950's advocated school children
to hide under their desks in the event of an Atomic Bomb attack.
Another totally false assumption.
-------
Once again many of these chemicals are unique to the RMA and projections
from recent labratory tests on rats are not acceptable.
CONCLUSION
The Army's and EPA have somehow decided that current unsubstantiated
levels of pollution are acceptable for offsite remediation efforts.
This is not comprehensible considering the Army has not been
subject to any rules or laws during the last 51 years at the RMA.
Why -are guidelines suddenly being invoked now?
Short term health studies on chemicals leaked from the RMA
which only exist at this site cannot possibly be accurately
determined.
The Army has an obligation to the citizens of the impacted area
to make the drinking water as it was before the pollutants were
allowed to leak from the RMA and to infiltrate the ground water
and aquifers. Since the goal of safe drinking water cannot be
safely achieved even for deep wells the only alternative remaining
would be a municipal type water supply. This alternative is never
considered in the proposed plan since the Army and the EPA have
seriously erred in their methodology by accepting "guesses" as
scientific fact.
Leif R. Southwell
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DEPARTMENT OF THE ARMY
PROGRAM MANAGER FOR ROCKY MOUNTAIN ARSENAL
COMMERCE CITY, COLORADO 80022-1748
December 9, 1993
REPLY TO
ATTENTION OF:
Office of the Program Manager
Mr. Leif R. Southwell
11355 North Racine Court
Henderson, Colorado 80640
Dear Mr. Southwell:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public
input is a key part of the cleanup process at RMA. I will respond to your comments in
the order we received them.
The Army evaluated the long-term and cumulative health effects of the chemicals
offpost. These effects were analyzed in the Offpost Risk Assessment. In fact, the
Offpost Risk Assessment evaluated the cumulative risks of contamination offpost to
humans over a 70-year period. The risks presented in the Offpost Proposed Plan are the
long-term risks of the chemicals offpost without considering the benefits of operating the
Offpost Treatment System.
One of the major concerns expressed by offpost residents is the DIMP
contamination in groundwater offpost. Since my tenure began at RMA, I wanted to
make sure the Army would further study the DIMP tests to evaluate whether the U.S.
Environmental Protection Agency (EPA) DIMP Health Advisory of 600 parts per billion
is safe. Overall, the Army has conducted more than 30 separate animal studies with
DIMP, including one study with humans. The EPA and the National Academy of
Sciences evaluated all health studies and concluded that the EPA's 600 parts per billion
Health Advisory is protective of human health and the environment. In addition, the
Army evaluated all possible ways DIMP and other chemicals could enter the human
body. These tests again showed that the water offpost is protective of human health and
the environment. As an additional protective measure, the Offpost Treatment System
and the North Boundary System will treat the groundwater to less than 10 parts per
billion. The Army is currently evaluating the applicability of the 8 parts per billion level
that the Colorado Water Quality Control Commission is expected to promulgate in the
next several months.
Readiness is our Profession
-------
I hope this information alleviates your concerns. Any other questions regarding the
Offpost Proposed Plan may be directed to Mr. Tim Kilgannon of this office at
(303) 289-0201. Thank you again for your comments.
Sincerely,
< --- O
Eugene [H. Bishop
Colonel, U.S. Army
Program Manager
Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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MAY 20
May 14, 1993
Offpost Proposed Plan Comments
Program Manager for Rocky Mountain Arsenal
Attn: AMXRM-PM/Col. Eugene H. Bishop
Building 111-RMA
Commerce City, Colorado 80022-2180
Dear Sirs:
I am submitting these comments on behalf of my mother, Irma L.
Temmer, who resides at and owns the property at 16250 E. 104th
Avenue, Commerce City, Colorado 80022. *
I have enclosed a copy of a document entitled "State concerns"
prepared by the Colorado-Department of Health, dated April 1993.
We agree with the concerns stated in this document and adopt it as
part of our comments.
In addition we believe the Army should be responsible for all clean
up, even if poor well construction or maintenance may have
contributed. The pollution would not have occurred if the
chemicals would not have been allowed to migrate off the Arsenal.
The state tests show that this has happened, so the Army should
clean it up.
Robert E
For:
Temmer
Irma L. Temmer
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Jtate Concerns
On the Rocky Mountain Arsenal
Offpost Proposed Plan
Colorado
Department
of Health
April 1993
L What is the Offpost Proposed Plan?
the cleanup method selected. Federal Superfund law
The plan was created by the U.S. Army to describe requires the Army to provide this plan to the public so
nsks associated with contamination to the north and that you have a chance to give your opinion You
northwest of the Rocky Mountain Arsenal, explain the may have recently received a fact sheet from the Army
cleanup alternatives that were considered, and identify which is a summary of the Proposed Plan. To review
a copy of the entire 12-page
Proposed Plan, contact the
Army, the Colorado Depart-
ment of Health, EPA, or
local libraries. If you would
like your own copy of the
plan, please call the Colo-
rado Department df Health
(CDH) at 692-3410 and
leave a message. We will
send you a copy.
2. What area does the
Offpost Proposed Plan
cover?
The figure below shows the
area covered. This area was
defined in 1989 based on
known areas of contamina-
tion and the predominant
ground water and surface
water flow patterns. No
additional offpost investiga-
tion related to the Arsenal is
expected.
3. Does the state sup-
port the plan? Why or
why not/
The state has many con-
cerns. Below are the most
significant:
Protectiveness of the
Proposed Remedy
According to federal law,
appropriate clean-up levels
Rocky Mountain Arsenal ,n]d Offpost Study Areas
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jn existing state and federal environmental
jS, if they exist. In addition, risk assessments
.1 estimate cancer and non-cancer risks are used
jetermine clean-up levels when environmental laws
Cither do not exist or are not considered to be protec-
tive at a particular site. A risk assessment compares
the levels of contamination to EPA-established num-
bers to determine hazard indices for non-cancer risk.
Cancer risk is established through excess cancer risk
predictions. An "excess" cancer means a cancer in
addition to the predicted cancer risk. According to
the American Cancer Society, one in three of us will
develop a cancer sometime in our lives. The state has
concerns with what the Army considers acceptable
risk. These concerns are explained below:
Cancer Risk
Zones 2, 3 and 4, as depicted on the illustra-
tion, are the most highly contaminated areas of the
offpost study area. Contamination has been found in
ground water, soil, and surface water. At current
concentrations such contamination, according to the
Army's studies, could pose excess cancer risks of
approximately 3 in 10,000. The Army states that
potential risks as high as 1 in 2,000 are acceptable.
However, the state believes that federal law requires
Superfund cleanups to aim for an excess cancer risk of
not more than 1 in 1,000,000, unless that number
cannot be achieved.
Non-Cancer Risk
Federal law states that hazard indices reflecting
non-cancer risk should not exceed one. The Proposed
Plan indicates that the hazard index exceeds one in
Zones 2, 3 and 4 and a portion of Zone 1. This means
that people exposed to existing contamination in those
areas could suffer adverse health effects other than
cancer, ranging from short-term effects such as eye
and skin irritation to long-term effects such as asthma,
liver or kidney damage. The state believes that the
risk should be reduced at least to the hazard index of
one.
Access and Use
Zones 3 and 4 are owned by Shell OH Com-
pany; Zone 2 is mostly privately owned. The Pro-
posed Plan does not include active cleanup of soil in
these three zones. In addition, ground water contami-
nation will likely remain there for decades while it is
gradually flushed by water treated at the North
Boundary System. The Proposed Plan does not
provide any mechanism for preventing people from
drinking ground water while it is being cleaned up.
Nor is there a commitment to provide access and use
controls (like deed and well restrictions) to prevent
exposure to water or soils. Therefore, the state would
like the Army to evaluate active remediation of the
soil and at the very least initiate measures which
would prevent exposures to ground water until it is
cleaned up.
DIMP in Ground Water
In 1990 the state requested that the Water
Quality Control Commission set a ground water
standard for DIMP (diisopropylmethylphosphonate), a
byproduct of nerve gas production at Rocky Mountain
Arsenal. A current EPA Health Advisory Level of
600 ppb has been used by the Army to determine what
areas of ground water should be cleaned up. The
Army will consider cleanup only in those areas where
DIMP levels are greater than the EPA Advisory Level.
The state believes that a more conservative figure
should be used.
The Army has asserted that the part of the
ground water plume with DIMP concentrations above
600 ppb has not moved past their Offpost Intercept
and Treatment System. The most recent testing done
by CDH has found 800 ppb DIMP in a private well at
least 1/2 mile past the proposed intercept system,
indicating that DIMP well above EPA's Health Advi-
sory Level is already in private drinking water sup-
plies. The well owner was already receiving bottled
water from the state. The state believes the Army
should address the significantly elevated level of
DIMP contamination which has moved beyond the
offpost intercept and treatment system.
• Bottled water has been provided since July
1990 to more than 600 residents with DIMP in their
well water. This water has been paid for by the state
of Colorado, with costs shared the first year with
EPA. Due to the widespread nature of DIMP con-
tamination in the offpost, the state believes that the
Army should provide all residents in the study area a
permanent, municipal water supply.
Contamination of the Deeper Aquifer
Since 1990, testing by the state has revealed
that DIMP is present in the deeper Arapahoe aquifer
at depths greater than 100 feet. The levels found
range from a trace to 39.7 ppb. The state has identi-
fied approximately 20 domestic use wells that should
be closed because they may be allowing contamination
to move down to the deeper aquifer. The Army has
not closed any of these wells, and the Proposed Plan
does not address this problem. The Army has argued
that contamination of the deep aquifer is a localized
occurrence, that it is due to poor private well con-
struction and is therefore not its responsibility. The
Army believes that only wells with more than 600 ppb
should be closed, while DIMP in lesser, but signifi-
cant, quantities continues to move into the Arapahoe
aquifer. The state would like the Army to close
Page 2
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ells to protect the Arapahoe aquifer from
.itamination.
Ground Water Cleanup Action
The Proposed Plan states that it will take
^roximately 15 to 30 years to cleanup the ground
/ater in the northern plume. However, the Army's
supporting documents state that it is not actually
known how long it will take; the time estimates are
only for comparing relative timeframes between
alternatives. The state believes that the Army has
significantly underestimated the actual time that will
be required. Also, the Army eliminated a cleanup
alternative (Alternative N-5 in their Proposed Plan)
that it estimated would reduce the cleanup time to 10
to 20 years, a one-third reduction. This was based on
the fact that this alternative would require one more
, year to put into place. In addition, the Army states it
prefers Alternative N-4 because it allows the Army to
1 make improvements to the ground water cleanup
system as needed; but according to the Army's Feasi-
bility study, so does Alternative N-5. Alternative N-5
1 would actually cost less because it would clean up the
ground water more quickly. The state believes that
the Army should design a more aggressive system that
will clean up the ground water faster.
State Ground Water Standards
Under federal law, state environmental stan-
dards which meet certain criteria must be used at
Superfund sites. The Army does not plan to use state
standards in the offpost cleanup, saying there is
'inconsistent application and ambiguous language".
These standards, however, are enforced at all other
Superfund sites in Colorado, and have been used by
he Army itself for earlier ground water cleanup at the
RMA. The state wants the Army to recognize these
standards for cleanup in the offpost.
Surface Water
The surface water in First Creek currently has
ontamination that exceeds several state surface water
tandards. The Proposed Plan does not address
surface water because the Army maintains that if
round water is cleaned up as it leaves RMA, it will
ventually cleanse First Creek. The state agrees that
this action will have a beneficial effect on First Creek
water quality since ground water seeps into First
'reek during part of the year, but there is no clear
estimate as to how long this cleansing process will
take. In the meantime, the contamination will con-
nue to migrate into O'Brian Canal and ultimately into
i arr Lake. The state wants the Army to commit to
further water sampling and to attempt to meet state
pirface, water standards.
4. What role does the state have in the
Proposed Plan?
The state and the public have a similar role at this
stage of the process. The Army must consider state,
local government and community comments to the
Proposed Plan before the Record of Decision (ROD)
is issued. The state has reviewed and commented on
all the supporting documents which led up to the
Proposed Plan; the Army is therefore very familiar
with the state's concerns. To date, however, the
Army has not changed the Proposed Plan to address
the state's concerns. It is therefore essential for the
public to contribute its views during this review.
5. What happens next?
All comments received will be reviewed by the Army
and EPA. Responses to all comments will appear in a
document called the ROD. The Army plans to release
this document October 30, 1993. This ROD an-
nounces the selection of the final clean-up alternative.
This will be the "final word" on cleanup for the
offpost; no public comment period or public meetings
are required on that document.
6. How can I voice my opinion?
The public comment period on the Proposed Plan is
from March 21,1993 through May 21,1993. Please
mail your comments to: Ofipost Proposed flan Com-
ments, Program Manager for the Rocky Mountain
Arsenal, Attn: AMXRM-PM/ Col. Eugene H. Bishop,
Bldg. 111-RMA, Commerce City, CO 80022-2180.
The state would appreciate copies of written com-
ments submitted on the Proposed Plan which are
submitted to the Army. We urge the public to attend
a meeting on the Proposed Plan to be held April 28.
1993. 7 p.m.. at the Dupont Elementary School. 7970
Kimberly Street. Commerce Citv. This comment
period is your only opportunity to comment on the
Army's proposed plan.
More Information
For a copy of the 12-page Proposed Plan, or to ask
additional questions or express concerns related to the
Proposed Plan, call the CDH RMA Team at 692-3410
and leave a message, and appropriate team member
will respond. Or you can call Marion Galant, Commu-
nity Relations Manager, at 692-3304.
Page 3
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Office of the Program Manager
Mr. and Mrs. Robert E. Temmer
16250 E. 104th Avenue
Commerce City, Colorado 80022
Dear Mr. and Mrs. Temmer:
Thank you for your comments. The Army appreciates the many comments
received on the Offpost Proposed Plan for Rocky Mountain Arsenal (RMA). Public
input is a key part of the cleanup process at RMA. I will respond to your comments
in the order we received them.
Enclosed is a copy of the Army responses to State comments. The State's
comments are also included with the responses for easier reading. The State's
comments include the items listed in their fact sheet titled "State Concerns".
The Army continues to monitor offpost wells and will do so until the
groundwater (water beneath the ground surface) is cleaned to applicable federal and
state regulations. Currently, the Army's criteria for well closure, which was
approved by the U.S. Environmental Protection Agency (EPA), provides for closure
of wells under specific conditions. The first condition requires that a poorly
constructed or damaged well be identified. Second, the upper groundwater aquifer
must be exceeding EPA standards for one or more chemicals. Third, the upper
aquifer must be leaking into the lower aquifer because of the poorly constructed or
damaged well. If all of these conditions are met, the Army will close the offpost
well. Additionally, many wells offpost are no longer being used. The Army is
currently working with the State of Colorado and Tri-Coumy Health Department to
discuss how we will work together to close abandoned wells offpost.
Any other questions regarding the Offpost Proposed Plan may be directed to
Mr. Tim Kilgannon of this office at 289-0201. Thank you again for your comments.
Sincerely,
Eugene H. Bishop
Colonel, U.S. Army
Program Manager
Enclosure
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Copies Furnished:
Captain Jonathan Potter, Litigation Attorney, Rocky Mountain Arsenal
Building 111, Commerce City, Colorado 80022
Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Street,
Suite 501, North Tower, Denver, Colorado 80202
Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky
Mountain Arsenal, Commerce City, Colorado 80022
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Appendix B
INSTITUTIONAL CONTROLS
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1.0 OFFPOST INSTITUTIONAL CONTROLS
This Appendix to the Rocky Mountain Arsenal (RMA) Final Offpost Operable Unit (OU) Record of
Decision (ROD) presents the institutional controls for the Offpost OU selected remedy. The combination
of Alternative N-4 and NW-2 is identified as the selected remedy in the ROD and the Final Offpost
Endangerment Assessment/Feasibility Study (EA/FS) for the RMA Offpost OU and is described fully in
the Section 9.0 of the ROD and in the EA/FS. The ROD identifies the following objective for institutional
controls as a component of remedial action in the Offpost OU: prevention of the use of the ground water
underlying areas of the Offpost OU exceeding groundwater containment system remediation goals .
The State of Colorado and the local governmental agencies that have regulatory authority over certain
activities in the Offpost OU land area have several current regulations that significantly limit or prevent
use of the groundwater from the alluvial aquifer. Attachment 1 (Controls of Alluvial [Unconfined]
Aquifer Use, RMA Offpost Operable Unit) and Attachment 2 (Land and Water Use, Management, and
Approval Processes - Adams County, City of Brighton, Commerce City) provide the current regulations
applicable to groundwater use, well construction, building permits, and zoning requirements. Attach-
ment 1 particularly describes the institutional controls relied upon to meet the objectives for institutional
controls established in the selected remedy.
This appendix identifies the authority for use of institutional controls under the Comprehensive
Environmental Response, Compensation and Liability Act of 1980, as amended (CERCLA), 42 U.S.C.
§9601 et seq. and the National Contingency Plan (NCP), 40 CFR Part 300.
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2.0 THE USE OF INSTITUTIONAL CONTROLS UNDER CERCLA
Section 121 of CERCLA requires that EPA select remedial actions that assure protection of human health
and the environment. 42 U.S.C. § 9621. EPA has recognized that this protection can be achieved
through a variety of methods, including institutional controls (Preamble to the NCP, 55 Fed. Reg. 8666,
8703 [March 8, 1990]; 40 C.F.R. § 300.430[a] [1] [iii] [C]). Institutional controls may be an integral
component of a remedy that is necessary for such remedy to achieve CERCLA's protectiveness mandate.
(See for example, Preamble to the NCP, 55 Fed. Reg. at 8703, 8706, 8711, and 8734). Additionally,
institutional controls may be a component of a completed remedy to protect human health and the
environment from treatment residuals and untreated wastes. (40 C.F.R. § 360.430[a] [1] [Ed] [C]-[D]).
Institutional controls are a necessary supplement when some waste is left in place, as it is in most
response actions (Preamble to the NCP, 55 Fed. Reg. at 8706).
EPA identifies examples of institutional controls in the NCP Preamble, and expressly acknowledges that
institutional controls have a valid role in CERCLA cleanups:
Examples of institutional controls, which generally limit human activities at or near facilities
where hazardous substances, pollutants, or contaminants exist or will remain on-site, include
land and resource (e.g. water) use and deed restrictions, well-drilling prohibitions, building
permits, and well use advisories and deed notices. EPA believes, however, that institutional
controls have a valid role in remediation and are allowed under CERCLA (e.g., 55 Fed. Reg. at
8706, section 121[d][2][B][kk]).
Within ninety days of the issuance of the Offpost ROD, the Army will issue an Implementation Plan
which will contain a schedule for finalization of the Institutional Controls provided for in the ROD, That
plan will provide that all Institutional Controls will be in place not later than September 1, 1996. All
dates contained in that Plan will be enforceable as provided in CERCLA Section 310 and the FFA.
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3.0 SITE DESCRIPTION
A detailed description of the Offpost Study Area is presented in Section 1.0 of the ROD and in the
EA/FS. The Offpost Study Area was defined to include the area bounded by 80th Avenue, the South
Platte River, Second Creek, and the north and northwest boundaries of RMA. The Offpost Study Area
also includes the surface waters of Barr Lake, the O'Brian Canal, and Burlington Ditch from 80th Avenue
to Barr Lake.
The Offpost OU is a portion of the Offpost Study Area north of RMA. The Offpost OU consists of the
area within the Offpost Study Area that requires remediation; specifically, the groundwater containment
system remediation goals exceeding cleanup standards.
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Attachment 1
CONTROLS OF ALLUVIAL (UNCONFINED) AQUIFER USE
RMA OFFPOST OPERABLE UNIT
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Attachment 1
U.S. Department of the Army
Telephone No: (303) 289-0202
1. The Army will provide the Office of the State Engineer, State of Colorado, with a map identifying
those areas in the Offpost Study Area where groundwater could potentially exceed containment
system remediation goals. This map will be updated based on each sampling round.
2. The Army will establish procedures to ensure that the well notification program is operating
effectively. The Army will inspect, or oversee inspection, of all well construction activity to
monitor conformance with the State Board of Examiners well drilling regulations.
3. The Army will fund analytical sampling of any future domestic well constructed in the area of
contamination, if requested.
4. The Army will provide Commerce City, the City of Brighton, and Adams County officials with
the same map (as described in item No. 1) provided to the Office of the State Engineer. The
Army will make arrangements with these governmental agencies to ensure that the map is used
in the most effective manner possible to reduce exposure to potentially contaminated
groundwater.
5. For new domestic wells with DIMP levels of eight ppb or greater (or other relevant CBSG at the
time), the U.S. Army and Shell Oil Company will pay for hook-up to the SACWSD distribution
system or provided deep well or other permanent solution.
6. Additional elements of exposure control and requirements for alternate water supply are
presented in Section 7.1 of the main text.
Shell Oil Company
Telephone No.: (303)860-8621
1. To eliminate potential exposure to contaminated groundwater under the Shell Oil Company
properties, Shell Oil Company will execute and record proper documentation (e.g., covenant/
negative easement) for its properties to: (i) preclude drilling of all groundwater wells into any
alluvial aquifer water under Shell's property for future use until such groundwater no longer
contains contamination in exceedance of groundwater containment system remediation goals
established in the ROD, and (ii) preclude any use of any deeper aquifer water (e.g., Denver Basin)
containing contamination in exceedance of groundwater containment system remediation goals in
the ROD. The recorded documents shall be enforceable by the U.S. EPA, the U.S. Army, and the
State of Colorado, and shall touch upon and run with the land.
2. Deed restrictions on the Shell property shall be in place no later than forty-five days after the
issuance of the ROD.
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Attachment 1
Colorado Department of Natural Resources
Office of the State Engineer - Contact: Steve Lautenschlader
1. Alluvial groundwater in the Operable Unit is part of the South Platte River Flow System (which
is over appropriated). Therefore new large appropriations (uses) will not be approved without
appropriate augmentation plans (replacing the water to be used with water from another aquifer
or another off site source). Augmentation plans are often quite expensive and hard to get
approved due to the associated requirements.
2. On parcels less than 35 acres created prior to June, 1972 - One permit for a well is allowed under
a presumption of no injury to other holders of water rights [CRS 37-92-602(3)(b)(H)(A)]. This
well is allowed for used inside of one dwelling only and may be from any aquifer.
3. On parcels less than 35 acres not created prior to June, 1972 - This land would only come into
existence by being subdivided and would therefore have to go through the County or City
subdivision process and meet applicable regulations (CRS 30-28-101 - a.k.a. SB 35). Prior to
issuance of any permit a water rights and/or an augmentation plan would have to be submitted
and approved by "water court." (CRS 37-90-137(1) et seq. and/or CRS 37-92-302(2), et seq.).
4. On parcels greater than 35 acres - Permits may be issued serve up to 3 homes, irrigation of up to
one acre of home garden and lawn (person use) and watering of domestic animals and/or
livestock. This use is also allowed under a presumption of no injury to other holders of water
rights [CRS 37-92-602(3)(b)(II)(A)].
5. Permits will be issued for replacement (into the same aquifer) of currently permitted or adjudi-
cated wells as requested. (CRS 37-90-137(1), CRS 37-92-602(3).)
6. All wells installation must be done in compliance with State of Colorado, Office of the State
Engineer, State Board of Examiners of Water Well Construction and Pump Installation Contrac-
tors, Revised and Amended Rules & Regulations of the Board or Examiners of Water Well
Construction and Pump Installation Contractors (2 CCR 402-2) (most current version).
7. The Office of the State Engineer will include a distinctive notice on each well permit application
correspondence, each well permit, and each drilling permit. The area included in this require-
ment is any part of the Offpost Study Area where groundwater could potentially exceed ground-
water containment system remediation goals. This notice would require the applicant to contact
the Tri-County Health Department and the EPA for information regarding groundwater quality
and the options provided by the Army to avoid use of potentially contaminated groundwater.
8. The Office of the State Engineer will contact the Tri-County Health Department, EPA, and the
Army regarding any application or permit issued with the notice.
South Adams County Water & Sanitation District (SACWSD)
Water & Wastewater - Contact: Larry Ford
1. Rules & Regulations - South Adams County Water & Sanitation District - New Service Area -
February 1992. Application for Service, as well as, Petition for Inclusion within the Boundaries
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Attachment 1
of the District both require that the Property/Parcel owner convey all rights to groundwater for
each Parcel or Subdivision Parcel to the District upon inclusion [4.0 (4.1.3) & 5.0 (5.1.3)]. The
District may at its sole discretion abandon right conveyed to it and physically abandon the wells
in accordance with the above referenced state Water Well Regulations [5.0 (5.1.4)].
2. Rules & Regulations - South Adams County Water & Sanitation District - Existing Service Area -
January 1992 (Updated February 24,1993). Application for Service, as well as, Petition for Inclu-
sion within the Boundaries of the District both require that the Property/Parcel owner convey all
rights to groundwater for each Parcel or Subdivision Parcel to the District upon inclusion [4.1
(4.1.3) & 5.0 (5.1.3)]. The District may at its sole discretion abandon rights conveyed to it and
physically abandon the wells in accordance with the above referenced State of Colorado Water
Well Regulations [5.1 (5.1.4)].
3. It is the policy of SACWSD not to serve wastewater without providing water service and vice
versa.
Adams County Water Quality Association Management Agency (see attached By-Laws)
(Wastewater (DRCOG) Clean Water Plan Amendment, 1991)
Member Agencies: City of Commerce City, Adams County, City of Brighton, South Adams County
Water & Sanitation District.
Contact: Board President Harry Tate (Commerce City Councilman)
This Agency reviews and may approve or reject all major additions or changes to sewer lines, lift stations
and plant improvements. Essentially any new line is considered a major line. This Agency is intended
to prevent line overlap and encourage intergovernmental cooperation.
Tri-County Health Department
Contact(s): Tom Butts or Warren Brown
Regulation NO. 1-88, Individual Sewage Disposal Systems
Promulgated by the Board of Health of the Tri-County Health Department
Effective Date, February 1,1988
Pursuant to Title 25, Article 10, Paragraph 104, CRS & Guidelines Adopted by the Colorado
Department of Health
The Health Officer may refuse to grant a permit for the construction of an individual sewage disposal
system where a sewage treatment works is available within 400 feet of the nearest property line and
connection can be made thereto. Section 111(3.14) CRS 30-l-1006(l)(a) (Special Districts), 31-35-601
(municipalities), 30-20-416 (counties).
City of Commerce City
Contact: Steve Hause, Community Planning Director
Lands currently within the City of Commerce City
-South of 120th Avenue while west of Highway 2 and then further north to the east.
'21905402010 Harding Lawson Associates • A1-3
1107121495 RO2
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Attachment 1
"Commerce City Code - Article V. Subdivisions". Section 17-105 - Water Facilities (a) General require-
ments. This section essentially defers water service issues to SACWSD for either connection to the
public water supply system immediately or in some cases allows use of individual wells or community
water systems until lines reach the subdivision when connection is then required, (see SACWSD above)
Building Code (UBC & UPC 1991) - Requires proof of water and sewer taps (or well permit & approved
septic system application) prior to issuance of building permit.
City of Brighton
Contact(s): Chief Building Official, City Planner
- Areas north of 120th Avenue including the triangular area between Peoria and State High-
way 51, north of 112th/Highway 2
"Land Use and Development Regulations and Guidelines" (Zoning Regulations)
"Subdivision Regulations" Section V, (B.) The subdivider is required to provide and connect the
following utilities (Water lines and fire hydrants, Sanitary sewer lines,...) to existing public systems.
Building Code (UBC & UPC 1991) - Requires proof of water and sewer taps (or well permit and approved
septic system application prior to issuance of building permit.
Water & Sewer service are provided by Brighton Utilities Department within the City. Connection to the
municipal water system may be recommended for developments within two miles of the current City.
However, staff recommendations may not be included as part of the final approval by the City Council.
Adams County
Contact(s): Planning Dept, Director of Planning and Development, Building Dept.
Remainder of Lands in the Offpost OU not in Brighton or Commerce City
See attached "Development Review Overview"
Adams County Zoning Regulations
Adams County Subdivision Regulations
Building Code (UBC & UPC 1991) - Requires proof of water and sewer taps (or well permit and approved
septic system application) prior to issuance of building permit.
Staff recommends connection to public water and sewer if with a reasonable distance, however, these
recommendations may not be retained by either the Planning Commission or Board of County
Commissioners.
A1-4 Harding Lawson Associates '21905402010
1107121495 RO2
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Attachment 2
LAND AND WATER USE, MANAGEMENT, AND APPROVAL PROCESSES
ADAMS COUNTY, CITY OF BRIGHTON, COMMERCE CITY
-------
-------
Adams County
Land and Water Use, Management and Apprcnral Processes
Is tfaeciutxatv properly zoned faring jp***"fad use?
Y« Almost* No*
(Use by Right) Seek approval for Conditional SeekRezoning
DBSIS toe mtM^Q^q use ^Jsff i FM$ leuuiJTes a> ^fftft* TCview- &
is appropnate bssed on the This requires a sta£Treview,ft Planning Commission hearing
current zoning of the property Planning Conmrisskn hearing and an approval by the Board
and an approval by'die Board
of County Qsmntssioces
Proceed to the Building Department if Approved
* Conditions may be placed or removed as part of the approval of Ihe use at tiw Planning
Commission or Board of County Commissiooers levels.
Commente are soKched from other Ageacifis (local and state)
Building Department
BuDduig permit process (UBC 1991, UPC 1991)
A •water scarce and method of sewage disposal are required
prior to issuance of a Building Permit
Water Sewer
Public Water Supply Public Sewer
Qareariy avahbte on. site Curremry available on SOB
Yes Yes
Brighton or SACWSD Brighton or SAC WSD
No No
Colorado Department of Natural Resources, Septic System (TCHD)
Office of the State Engineer Well permit wffl
be flagged if issued
Community Well System
PrivateWell
-------
City of Brighton
Land and Water Use, Management and Approval Processes
Is the property property zoned for the intended use?
Yes
(Use by Right)
This means the intended use
is appropriate based on the
Q j the
prcp&iry
Maybe*
Seek approval for
Conditional Use
Tins requires a staff review,
a Planning Commission
hearing and an approval by
the Citv Council
No*
SeekRezoning
This requires a staffreview,
a Planning Commission
hearing and an approval by
the City Council
Proceed to the Building Department if Approved
* Conditions may be placed or removed on the property use at the Planning ComnnssioD or
City Council levels.
Comments are solicited firm other Agencies (local and state)
Building Department
Building penna process (UBC 1991, UPC 1991)
A water source and method of sewage disposal are required
prior to issuance of a Building Permit
Sewei*
Water
Public Water Supply
CurrentJy available on site
Yes
Brighton Utilities
No
Brighton Utilities
Extend mams after approval
No
Colorado Department of Natural
Resources,
Office of the State Engineer Well permit
will be flagged if issued
Community Well System or Private Wdl
Public Sewer
Currently available on site
Yes
Brighton Utilities
No
Brighton Utilities
Extend tmitig after approval by the
Adams County Water Quality Association
No
Septic System (TCHD)
-------
Commerce City
Land and Water Use, Management and Approval Processes
Yes
(Use by Right)
Urn means the intended use
is appropriate based on the
cuiTGflt zoninc or the
piuyeiLy
Almost"
Conditional Use Tins requires a staff review,
Tins requir ts a staff review, a Planning Commission
3 Plamrir j Commission hf^nnp and an approval by
* Conditions may be placed or removed ox
City Council levels.
Comnifints ate solicited from other Agenjciea (local and state)
] vy
.*
Wate-
Public Water Supply
Currentiy available on ate
No*
aa approval by
the Qtv Council
.1
the City Council
Proceed to the Building Department if Approved
the property use at th^ Plamnxtfii Commission or
Building permit pro %$s (UBC 1991, UPC 1991)
A water source and meth id of sewage disposal are required
prior to ififtiatiftft of a Building Pennh
SeWer
Public Sewer
Yes
SACW5D
No
SACWSD
Extend mains after approval by SACWSD
No
Colorado Department ofNatural
Resources,
OfSce of the State Engineer Wefi permit
vriD be flagged if issued
Community Well System or Private Wen
until SACWSD is available
Currently available on site
Yes
SACWSD
No
SACWSD
Extend mains after approval by the
Adams County Water Quality Association
No
Septic System (TCHD)
-------
§ 17-104
COMMERCE
drz CODE
proved
1 timing
drainage will be
tsry, to an adeouate
provided,
orainage watercourse or regional fac£uty.
(7) The city rmincH may, when it connidras it
^^trffjrS^_^V fjnf tPff 31&fuXi&B S3££iiY Of ^WG22876
0* vftft DU0jlCv9232CuXCu32£r COntSff^^^ttrTOB OI
water and thfreficct on drainage and sani-
gnhftfgigrrm
any portion -of^rthe properly which lies
within tf*** fl*»**«^f>t«»T*» of any s£
orai^xase coucse»*f^ooo>Dia2n areas
ved Jtoni'iipy and aH destruction
or
01T QJXCDOS^B^^ 0« Cflftn OF OtiufiF
(Ord. No. 1026, § l,.6-21r93)
See. 17-105. Water facilities.
(aJ G&tsroi fsoiufuiii cnti> ,
(1) The
or create & po-
water supply system. «*gpan^ of pro-
Tiding domestic water 42se and fire pro tec-
tion, according to approval by the
fijjrrfppfjg^g firB Q^^fcfjtcfc 3HQ tll& oOTZtn
A ,in». r* in.-j TTffW^jq» •,--j p i *, . m;_••. TV*.
*&u2^BS V/wU^XUJr Tnf^EEE& ^^uu 2^UXL«AHXUU> J^*j^>*
trict.
(2) Where a public, water main is
(ynriTt«Jifiu fire
subject
to the CT"J*'" "r0^1""0 of the South Adams
County Water and Sart'*-gfc"''Ti District *">^
(3) AH water rnnrns shall be a minimum of
d£ut 18) Tp^fo^s ^n ^r^^.^i^^?yi ?m? s&au oe
subject to approval of the South Adams
County Water »™^ Sanitation District smn
the aiiuropnatP Htc oistnct.
(b) Individual wells, central looter systems.
(1) At the discretion of South Adams County
Water a^irf Sanitation District, individual
wells may be used or a central water system
provided in such a rnannef that an ade-
quate supply of potable water-will be avail-
able to every lot in the subdivision. Water
samoies shall be submitted to the Tri-county
Health Deoarrment and the state water con-
servation board as oeemed Tuxmmuify by
such entities to ensure a potable water
(2) Tho appKi-tm* g^aTt agrao, ag a <^ndtti"n pf
approval for an individual well or central
no. thr*^ f* "^Tn^fftirr1 tff p putniff
eventoauy shall be provided.
ayiM
future watur service at the time tiie plat
i revives ^™i approvaL Collateral maybe
(Ord. No. 1026, § 1, 6-21-93)
Sec. 17-106: Sewerage facilities.
(a) General n
(1) The applicant shall ™«ta»n sanitary sewer
^yfr & ZD8Z2Q£7 Tyrp^ffnofifl by tn^*
South Adams Comity Water and Sanita-
tion District coTifttnJrtrton standards and
ATI plans shall be designed
in accordance with the rules and regula-
tions ar"^ ujiinjarfg of tt»> South Adams
the Td-county Health Department. Flans
shall be approved by these agencies prior to
approval of the final plat by the city coundL
(2) The applicant shall extend the sanitary
sewer district systems for the purpose of
rifiitnnfn^ f^jmpppgp facilities to ^^ subdi-
vision, subject to the provisions of para-
graph (b) below.
(b) Connection to Sautk Adams County Water
and Sccnitotiojt District.
(1)
Tf ^nrri-h Atfawse nmrrriy Wnfa»r anri RanTta-
tion District fi"^^*^pg are
ry sewer is placed in a street or ease-
ment abuttmgupon the property, the owner
thereof shall be required to connect to the
sewer for the purpose of disposing of waste,
or occunant to
sewage disposal system.
an individual
(2) Where South Adams County Water and
Sanitation District systems are not reason-
ably accessible, &ot will become available
1178
-------
PLANNING AND DEVELOPMENT
§ 17-ia
>aCT^ system,
nnnro fpg^ fa? he
property bensfxtted. Where pfcmg for
provide for the South Adams
County Water ano Sanitation District
to f»g*oTI riit» imjuiup linoq ffio Ip+ppulg
«f tfo^ dsveloonient shall be
with the plans of the
ready for
in
fo
nrri
tion to the proposed sewer mains of the
district*
b. individual disoosai. syscems, nrovioed
the aT*pfr'rqTt* ghalT ingfcan ^nil^ry
ffp;n.
the dticct ciuu to a. point in the subdi-
reconnee-
tion with the South Adams District
frtira tfagj tnrftt^fng'fyi •»>»» ct T^iot Tfna and
a Qinnertinn shnlT be available in the
scnzccozdo coTTP&ct ij^^^n tft? inonQust
dfsposnl synuaii to the Sooth Adams
County Water *""? Sanitarirm District
system when it becomes available The
sewei ^yH^*"1!0 »tigfl be TS'np0*^ until
ready for use ynn chaii confionn to q^
plBas fat installations of South Adams
County ^^n ^-*p ^71^ ^^*n? t-^t 1^*^ t*islincti
where they erist. and f'n**M be ready
for «^nTio>l1 '"" to the sewer TT>ar*"
(3) Where Sooth Adams County Water and
Sflnitatjnp TrT^rtrTCtr faculties are not reason*
ably afitxunKl*^ *nnn will not become avail-
able within a roggrnafrja oeriod of time the
applicant may, at the discretion of South
Adams Cfflif^y Water a-nrf Sanitation Dis-
trict ay"^ with the approval of Til-County
Health Department, install sewerage sys-
tems as follows:
*4^l (B.-2, B.-3)
tial
areas,
a f**>?'pg^ sewerage sybii*i>i shall be in-
stalled. The JrnnHrqnr g^a?l metatll aJJ
DC
m confbrmance wife plans of the South
Adams County Water
p>»an jjg ready for CTTTP*^
tion to the public sewer main when the
mafu becomes available.
b. For low-density residential (R-l) areas,
systems or central
sewerage systems may be used, subject
to approval of tie South Adams County
Water and ganTtatirm
(4) Where individual disposal systems are pro-
posed, minimum lot areas shall conform to
of the zoning ordinance
and percolation tests and test holes shall be
made as directed by the Tri-Connty Health
T^UJIHI 1.11 »»nt and &u* results submitted to
the department of community development.
The individual disposal system, including
th^ ***** of the septic ta'"^'g sn^ g*?» of the
tile fields or other secondary treatment de-
vice, shaTl be approved by Tri-County
Health Department prior to final approval
of the plat by the city council,
(Ord. No. 1026, § 1, 6-21-93)
Sec. 17-107. Sidewalks and trails.
(a) Reoutrea improvements.
(I) Sidewalks and disabled ramp access shall
be TncniMpti. m 11. HTH *fepA oedicated nonpave-
ment right-of-way of aH roads as described
in rit^gjgT) standards of the city, "T»ipgg
waived by the city g""""^ as not being re-
xare of tnfi T*}f|af)|^i^ta of ^n^ (^i^y.
(2) Concrete curbs and gutters are required for
afl sUcui& where sidewalks are required by
this article or where required at the discre-
tion of the city council for the uublic health,
safety, an^ welfare of the tnfoahitartts of the
city.
(3} In residential subdivisions, a median strip
of gyagsprf of }tmAr)f^ art»ag at least five
(5) feet wide shall separate all sidewalks
by the
city council as not being required for the
public hp?ltb, safety,grtr^ welfare of tfr** in-
habitants of the city.
(b) Pedestrian, access.
(1) In order to facilitate pedestrian access from
the streets to schools, parks, playgrounds
Snpp. No. 10
1177
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-11
:REGULATTON NO. 1-88
INDIVIDUAL SEWAGE DISPOSAL SYSTEMS
Promulgated by the
Board of~HeaIth of the
Tri-County Health Department
Effective Date
February 1,1988
Pursuant to Title 25, Article 10,
Paragraph 104, Colorado Revised Statutes
and Guidelines Adopted by the
Colorado DeDartment of Health
-------
demonstrate that no hazard cr nuisancs exists on the
property.
2.13 Denials of permits shall be made in writing by the Health
Officer stating reasons for the denial and requirements for
reconsideration of the application.
3.14 The Health Officer say refuse to grant a permit for the csn-
struction of an individual sevage disposal system where a
sewage treatment works is available within 400 feet cf* the
nearest property line and connection can be made thereto.
3.15 Any applicant who is denied a construction permit, or any
person who is adversely affected by the denial cr issuance of
a permit, within thirty (30) days following sues-denial, nay
request cJid receive a hearing before the Board of Health.
3.16 The State Administrative Procedure Act (Article 4 cf Title
24, C.R.S.) shall govern any hearings held by the Department
mrigr the "Individual Sewage Disposal systems Act."
3.17 The issuance cf a permit and specifications of terms and
conditions therein shall not constitute assumption cr create
a presumption that the Department or its employees nay be
liable for the failure of any system nor act as a certifica-
tion that the equipment used in the gystgm or any component
thereof used in its operation or that the system for which
the permit was issued insures continuous compliance with the
provision of Title 25, Article 10, C.R.S. 1973, the rules and
regulations adopted thereunder cr any terms and conditions of
a permit.
SECTION IV. APPLICATION SZgTZ3agHTS:
The application shall include such information, data, plans,
-------
County, Colorado
Development Review Overview
A Citizen's Guide to the Process of Reviewing
Applications for Land Development and Land Use
Permitting for Adams County
-------
Summary
This document is designed to provide a brief overview of the process for
making land use decisions in Adams County and who participates in the
process. Its purpose is to give citizens the background they need to
effectively participate in that decision-making process and influence
decisions that affect them. The term "land development" is intended to be
general and includes rezonings. conditional uses, subdivisions and
exemptions from subdividing, variances, special uses and certificates of
designation. Except for differences between which board or commission
makes the ultimate decision, the steps that are tak^n to make the
particular decision are very similar. Adams County has land use
jurisdiction over all public and private property located in the
unincorporated portions of the County. The County does not have land use
jurisdiction over any property located'in a City.
The Process
The steps that are taken when an application for land development is
made are the following:
1. A potential applicant rails or visits the Planning and Development
Department and discusses their land development idea. The staff advises
what action would need to be tak-pn to achieve the end result that is
desired.
2. A "pre-application meeting" 2s scheduled. For simple and straight-
forward applications, the pre-application meeting may take place during
the initial contact by a potential applicant. An example of such an
application could be a variance from the side yard setback to. construct a
garage. More ^QTPpliT'at^l anplications. such as the platting of land for a
new two-hundred acre subdivision, would require research by the staff to
be knowledgeable about a given area or prupeity so that a ynpantngfai pre-
application meeting could be conducted.
Pre-application. meetings have two purposes: a} to advise potential
applicants what they need to submit in order for their application to be
placed on the appropriate agenda, and b) to advise applicants what the
staff reaction to an application is likely to be. given what we know about
the issues that are likely to affect :tfaat application.
3. An application is submitted. The staff reviews it for fnrnpipftn^g and
if it is complete, it is placed on the next available agenda for the
appropriate board or commission which meets the notice and referral
time requirements.
4. Copies of the application materials - are mailed out to a number of
governmental agencies and any citizen!s groups that have expressed a
-------
being appllep^for. asks for comments within a deadline, and provides the*
name of tfaiEStalBf "person who «*an anyu»*f questions about the application:
5. LettersryEer mailed out to property owners near the site of the
application^.~3Bbtne case of Board of Adjustment hearings. abutting property
owners are~mailed letters. In the case of Planning Commission and Board
of County Commissioner hearings, property owners -within at least 500 feet
are mailed letters. These distances may be expanded at the discretion of
fee County
6. The staf&eviews the application and writes a written report with
consideration! being given to the criteria for icview of the particular -
application .and the comments received from citizens and agencies. The
report is sezn^to the appropriate Board or Commission for their review
riOT tO thar
priOT tO
7. The pubHcrnearmg is held and a decision is made on the application^
The Board of£Adjustment mqires a fi"«i decision on variances and special
uses. Th«* -PE&nrring Commission makes a. recommendation to the Board of
Commissioners" who. in turn, mafc-g a final decision .n rszonings.
' subdivisions qncj certificates of dCSiSnati ~rL Except for
minor differences, the Board, of nnmmigginnfrs, tni* Planning Commission
and the Board of Adjustment conduct *b*"*r hearings in a very -similar
manner. First. the staff introduces thp case **"*•*» a brief summary of what
is being applied for and provides the staff recommendation. Next, the
applicant makes a presentation of the application and responds to the
staffs recommendation and any conditions being recommended. After the
applicant "«g made the presentation, the public is invited to be heard.
'
The Chairman will asfr for public comment in favor of tfr'ft application, in
opposition to.jti and any questions that thg public "as foe information only.
Often, questions are asked by those who are speaking in favor or in
opposition orrjust for information.. At the conclusion of thp public input
portion of the* hearing the gp|ii'npriafe persons (usually the applicant but
also staff orra Aboard or commission member) wifl answer t^fif questions
which have been asked. At any time during the hearing, a board or
commission member may be recognized by the nhaii man m order to ask-
questions or get clarification of the information being given. The
application is then discussed by the board or rf>mm
-------
1. To adopt anrf amend, as appropriate, the County Comprehensive Plan.
This Plan is the pffa**aj policy of the County for how the County ghmild
grow and develop (or redevelop) in the future. The Plan provides guidance
for decisions to be made on development applications af<1 public capital
improvement projects. The Flan is not regulatory: it is a statement of
policy. The Planning Commission fanrHnng as a legislative body when they
perform tn*g duty.
2. To review applications 'for land use changes gnd land subdivision and
recommend action on those applications to the Hoard of Commissioners.
In mqfe-ing tb^lT decision, the Planning Commission considers the
consistency between the application and the Comprehensive Plan, the
compatibility between the requested development and existing
development in t"^ area, and the ability of th<* proposed development to
meet the requirements of the Zoning Regulations or Subdivision
Regulations, as appropriate. The Planning Commission fimrHnng as a
quasi-judicial body when they perform thig duty.
3. To recommend adoption of the County Zoning Regulations and
Subdivision Regulations. The Planning Commission may recommend
tO tfoe ?ontpg 'Regulations and Subdivision Rfgiilatjnn.s faut
'
Board nf '(^OTpTn^g-<5rinr"*rs has thi* final fjgC7gtnn,-making aiithrtggioncrs "^fo* the
•final decision on ?n change of nge apptirgfions, gnfryfhrisinrts and regulatory
s- They hold pnh'lffv hgarintrg fn 3, similar mann^ tO tnf>lg** Of
the Pianntng o^i'nntisginn The County Commissioners consider all the
input that tln^ Planning Commission does plus thip> Planning Commission
in Tnatcing tngjf decision PTI an ^nfMJffflt iff H 'Jtfo^r Board Of
County Commissioners functions as a quasi-Judicial body when they hear
change in T»se or subdivision applications an<| as a legislanve body when
they hpar proposed regulatory
The Board of
Board of Adjustment members, like the Planning Commissioners, are
appointed by the Board of County Commissioners. The Board of
Adjustment hears applications for variances, special pses and appeals of
decisions. Unlike the Planning Commission, however, the
decisions of the Board of Adjustment are f»"»? and not appealable to the
Board of County Commissioners. The Board of Adjustment functions as a
quasi-judicial bodv.
4.
-------
aacMjevelopment Pcumiment Staff
The staff members of the Planning ?*id Development Department (staff)
are employeesrof the County. The Director of the Department reports to
the Coiinty-'ASministrator who. in turn, reports to the Board of County
Commissioneisr: Staff administers, the processes for land development
public information. a"d ^natees rppnynTngndaflnns to
approprizcEcboard or commission on the part-Tester applications.
Appeal of «M*^AH-n*fn*g+ra*-ttr» Decision— The Zoning Regulations delegate
authority to^G&unty staff to ra^fo* administrative decisions. These staff
members may^fae the Director of Planning and Development the Chief
Building Official,' or other County staff. An appeal may be made to the
Board of Adjustment fav an applicant concerning an interpretation of the
2/mlng Regulations, denial of a building permit due to a zoning standard,
or some othieasrdecisiori which is not agreed with by the applicant The
Board of Adjustment reviews th^ decision made and rsay uphold it -or*
reverse it irB-wirole or in part For a decision to be reversed, four of the
five Board ofeAdjustment members must vote for the- reversal of the
decision.
Certificate ofSDesignation-A type of use approval that is limited to waste
such as lanijfflTs or waste incinerators. Certificate
of Designation is a State of Colorado review process that requires a
dation of approval by the Colorado Department of Health before
the County-may grant a certificate. The State review involves technical
considerations. concerning whether a proposed operation will be
consistent wf(li tfo«* State's waste Tngmaffl*Tnpnt regulations. The County
review involves land use considerations such as compatibility with a
gxisttrtg uses^ effect on th^ Comprehensive Plan objectives for an area and
traffic impacts.
Compatibility-A condition that exists, or is believed to be possible,
between two or more uses whereby the conduct of one use does not injure
thi» ability to conduct another use. It does not Tnt*an that the uses are the
same or tfvgrr sftplfaf- It does mean that if n$&$ are compatible, property
owners may use thmr properties without being *Tn.T¥»asnT7ahly affpfrted by
the other use(s).
Conditiosal Use—An additional use of land within a given zone district not
otherwise allowed as a use-by-right tfaat may be authorized by the County
and may be restricted by conditions to establish compatibility between the
use and adjacent tsseg. Coixdltiaai?! rases j??§y oj?ry be authorized by the
Board of CnfmfifsrsfaRF'r* sftrr ^F\rff.w ?jy -£m ©taff STirf th*» Planning
Commission iira due process review.
-------
Dae Process— A method of making decisions that is based on following
previously adopted rules of procedure. In the contCTt of land development
review, it Tq*»gpg a process for making those decisions that ensures that an
parties have an opportunity to provide information on an equal basis •which
is intended to influence the outcome of the dgcig*nr|-Trii!>*rir>g process.
Ex Parte Contacts— A legal principle that means contact by a decision-
maker in a 'quasi-judicial decision-making process with a party or parties
to an application outside the public h*»arfng A party1 to an application is
the applicant.' affected citizens, or arty other person who will potentially be
benentted or .Injured by the action tak-^n on the application. Ex Parte
Contacts shmiid be avoided so that all parties to an application may have an
equal opportunity to provide information in the public hearing and
influence the ultimate decision.
Legislative Process— A decision-making process that seeks information
from all fitf^pns on a matter of community-wide interest. Citizens are
encouraged to contact their elected or appointed representatives and
provide then-viewpoint on such matters on a formal or informal basis.
Quasi-Judicial Process— A (j^fisign-Tnairing process tha.t bases a decision on
previously-established criteria for making the decision. Citizen input is
encouraged t**?t provides information concerning how an application does.
or does not. meet those criteria. The input 'is restricted to a public
hearing where the input is made and decisions are reached.
Special Use— Any use of land, not prohibited within the zone district
authorized by the Board of Adjustment after a due process review, for a
period not to exceed five years. .
Subdivision. Regulations— The document approved by the Board of
Commissioners that provides for the standards by which la™* is divided
into smaller parcels or combined into larger parcels and how the
description of these parcels is made a matter of public record. It also
provides standards for the configuration of parcels, access provisions, and
roadway and drainage standards.
Subdivision— A legally recognised parcel of land, or collection of parcels of
lanri that is defined by a narrative and graphic description. The document
that depicts a subdivision is a plat
Temporary- Use— Any use of land, not prohibited within the zone district
authorized by the Director of Planning and Development but for a period
not to exceed ninety days. However, grading and hauling operations may
be authorized under a Temporary Use permit for a period of up to one-
hundred-eighry days on properties of ten acres or less.
Variance— A variance is authorized fay the Board of Adjustment Variances
relate to the physical requirements of the Zoning Regulations only, not to
use of property." In theory, all property in the same zone district is the
6.
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same—in practice, lots are not alike but the standards of a given zone
district apply to afl lots in the zone district. The variance process allows
tne Board of Adjustment to "adjust" the zoning standards to accommodate
tor differences between the physical layout of lots so that all property
owners may by able to enjoy thmr properties in an equitable manner.
Zoning~The practice of establishing districts within a jurisdiction that
allow specific uses to be conducted, under standards, in order to establish
separation between uses which otherwise would conflict.
Zoning Map—The official map of the County that shows the boundaries of
all zone districts. The map is adopted by the Board of Commissioners fay
resolution and each change to the map is also adopted by resolution. Both
tne map (which is really a collection of approximately 80 sheets to cover
Jj16_e?ire County) and the resolution are recorded in the office of the
County Clerk *-nA Recorder.
Zoning Regulations—The document approved by the Board of
Commissioners that defines afl zone districts and the standards expected
of all uses within zone districts. These regulations aisc provide for the
process by which zoning is changed, y-nntng enforcement procedures, and
general standards that apply to any land use in all zone districts.
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BY-LAWS
OF
ADAMS COUHTY HATER QUALITY ASSOCIATION
ARTICLE I
OFFICES
Section 1.
The office of the Adams County Water Quality Association
("Association") shall be at- the office of South Adams County Water
and Sanitation District, 6595 East 70th Avenue, Commerce City,
Colorado- 80037-0597 or such other place the board of directors nay
from timeeto- tine determine.
-—. •»,».• • wj. auwa
from timesto-time determine.
ARTICLE 2
DIRECTORS
Section 1.
The board of directors for the Association shall consist of
one representative elected by each participating entity, consisting
of the Cityjpf Commerce City, Colorado; City of Brighton, Colorado?
County of"'Adams, Colorado; and South Adams county Water and
Sanitation • District.
Section 2.
ARTICLE 3
OFFICERS
Section 1.
Sha11 ^ a preside,
a vice-
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ABTICLE 4
ELECTION OF OFFICERS
Section 1.
Officers shall be elected by a majority vote of the directors
at the organizational meeting held in 1991.
Section 2.
Beginning in 1992, and every year thereafter, election of
officers shall be held at the first annual meeting of the
Association.
Section 3.
There shall be no prohibition against an officer succeeding
him or herself in any of the offices of the Association.
ARTICLE 5
HEETIRGS
Section 1.
Unless otherwise noted, regular quarterly meetings of the
Association shall be held on the second Thursday of January, April,
July and October as set forth in the Memorandum of Understanding
between members of the Association.
Section 2.
In the event there shall be no business to conduct at such
quarterly meeting, the president may cancel such meeting in writing
to all directors setting forth the reason for such cancellation.
ARTICLE 6
SPECIAL MEETINGS
Section 1.
A request for a special meeting of the board of directors may
be requested by a director in writing. to the president of the
Association with copies to all member directors. Such request
shall set forth the purpose of such request for a special meeting.
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Section 2.~ ~
Afterr receipt of a request for a special meeting, the
presiderrtr-shall set a special meeting of the board of directors
within twenty days after "receipt of such request and shall give the
members ofrthe board of directors notice in writing of the date and
time of such-special meeting and the purpose of such meeting. Such
notice shall also include copies of any reports, exhibits, or other
material that may have been submitted to the president by the
requesting: director.
ARTICLE 7
COMMITTEES
Section-1.
The president shall appoint such committees as he or she deems
necessary to: carry out the purposes and the activities of the
Memorandum- of Understand ing between the member entities of the
Association.
ARTICLE 8
RECOMMENDATIONS
Section 1.
All recommendations or decisions of the board of directors on
all Clean Water Flan Amendments, 201 Facility Plans, proposals or
other submittal shall be by majority vote, each director snail have
one vote. In the absence of a director, his or her duly appointed
alternate shall be entitled to vote.
Section 2.
The result of such votes shall be submitted by the president
on all Clean Water Flan Amendments, 201 Facility Flans or such
other plans, studies or reports submitted by the Association or one
of its director entities to Denver Regional council of Government
or to the Colorado Water Quality Control Division or to any other
regulating agency.
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ARTICLE 9
EMPLOYEES OF ASSOCIATION
Section 1.
The Association may appoint a Recording Secretary to take all
of the minutes of the board of directors and to conduct such other
activities deemed necessary by the Association.
Section 2. ~
The Association say employ such other employees it deems
necessary to carry out the purposes and the activities of the
Association.
Section 3.
Compensation for such employees shall be determined and
allocated between the members of the Association in such a manner
as may be determined by the Association.
ARTICLE 10
CONFLICT
Section 1.
In the event a conflict develops between the provisions of the
Memorandum of Understanding entered into between the member
entities and these By-laws, the provisions of the Memorandum of
Understanding will control.
THESE BY-LAWS ADOPTED THIS DAY OF , 1991.
4
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Appendix C
WELL CLOSURE CRITERIA
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Appendix C
In June 1988, the Final Decision Document for the Interim Response Action for the Closure of Aban-
doned Wells at Rocky Mountain Arsenal was issued by the U.S. Department of the Army (Army). This
final document was issued following review and comment by Region VHI U.S. Environmental Protection
Agency (EPA) and the Colorado Department of Health. This Interim Response Action (ERA) included
only onpost wells in its coverage. EPA proposed modification of this IRA to include offpost wells in a
letter to the Army dated March 15,1990. EPA proposed criteria for the selection of wells to be
abandoned and closed in the Offpost Study Area. In a letter dated June 13,1991 (U.S. Army, 1991) to
the Colorado Department of Public Health and Environment (CDPHE), the Army agreed in principle with
the EPA request to modify the Well Closure ERA to include wells meeting the criteria in the Offpost
Study Area.
The following set of criteria were developed to identify wells to be abandoned in the Offpost Study Area.
1. Offpost wells will be abandoned according to the regulations set forth by the Office of the State
Engineer
a. if the well is completed in one or more aquifers below the alluvial aquifer, and
b. if the well is judged to be of improper construction or is in deteriorating condition such
that it is leaking from the alluvial aquifer to lower aquifers as indicated by physical
parameters (such as hardness and conductivity measurements), and
c. if the well contains contaminants which originated from RMA in excess of the remedia-
tion goals.
2. Offpost wells will be monitored a minimum of annually
a. if the well is completed in one or more aquifers below the alluvial aquifer, and
b. if the well is within 500 feet of a groundwater plume which originated from the RMA, or
c. if the well is judged to be of improper construction or is .in deteriorating condition such
that it is leaking from the alluvial aquifer to lower aquifers as indicated by physical
parameters (such as hardness and conductivity measurements), and
d. if the well contains contaminants originating from the RMA at any level.
3. If, based on current water table data, the well is located in an area of dry alluvium, the well will
not be considered a candidate for closure.
4. Wells located on the property currently owned by Shell are included in this well closure plan.
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Appendix C
5. Well closure will be at the expense of the United States.
6. Well closure methods will be identical to those used for the closure of onpost wells.
7. The United States and the Department of the Army are removed from liability for dealing with
unpermitted wells.
8. Following identification of wells meeting all of the criteria listed in item 2 above, the Tri-County
Health Department (TCHD) will notify individual well owners informing them of suspected faulty
construction and request permission to enter the property and abandon the well. THCD will
inform the Army if and when permission has been received from the well owner to close the
well.
9. Well closure expenses will not be borne by the United States in the event that unused wells are
listed for closure and the well owner is known. Pursuant to Rule 11.1.1, Abandonment Stan-
dards (2 Code of Colorado Regulations 402-2), it is the responsibility of the well owner to have an
unused well properly plugged and abandoned.
A list of wells meeting the closure criteria will be compiled at a meeting of the parties' technical staff. A
list of wells to be monitored will also be compiled. A consensus will be reached on guidelines to be
used to evaluate the hardness and conductivity data. At the time of the five year review the monitoring
information will be reviewed and it will be determined by the parties if a continued monitoring of wells
in the deeper aquifers is warranted.
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Appendix C
REFERENCES
Shell Oil Company, 1991, Letter to U.S. Department of the Army, July 3.
U.S. Department of the Army, 1991, Letter to Colorado Department of Health, June 13.
U.S. Environmental Protection Agency, 1991, Letter to U.S. Department of the Army and Shell Oil
Company, January 6.
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