TECHNICAL SUPPORT FOR ROCKY MOUNTAIN ARSENAL

Offpost Operable Unit

Endangerment Assessment/Feasibility Study

Final Report

Volume VIII of VIII

(Responses to Comments)

November 24, 1992

Contract Number DAAA15-88-0021

Task RIFSI (Delivery Order 0001)

PREPARED BY

Harding Lawson Associates

Environmental Science and Engineering, Inc.

PREPARED FOR

PROGRAM MANAGER FOR ROCKY MOUNTAIN ARSENAL

THIS DOCUMENT IS INTENDED TO COMPLY WITH THE NATIONAL

ENVIRONMENTAL POLICY ACT OF 1969.

THE INFORMATION AND CONCLUSIONS PRESENTED IN THIS REPORT REPRESENT

THE OFFICIAL POSITION OF THE DEPARTMENT OF THE ARMY UNLESS EXPRESSLY

MODIFIED BY A SUBSEQUENT DOCUMENT. THIS REPORT CONSTITUTES THE

RELEVANT PORTION OF THE ADMINISTRATION RECORD FOR THIS CERCLA

OPERABLE UNIT.

M9200041
PREFACE TO VOLUME Vill

This volume presents comments regarding the Offpost OU Endangerment Assessment/

Feasibility Study report and responses prepared by Harding Lawson Associates. Four sets of

comments and responses are presented in this volume in the following order:

Shell Oil Company (Shell)

U.S. Environmental Protection Agency (EPA)

U.S. Department of the Interior Fish and Wildlife Service (USFWS)

Colorado Department of Health (CDH)

Within each set, comments are presented in the same order in which they were received. The

comments have not been edited or revised in any way. A Glossary is provided as a list of

acronyms and abbreviations used in the responses.

20000,317.10 - viii-pref

0312112092 Vill - P- I
SHELL OIL COMPANY COMMENTS REGARDING THE ENDANGERMENT

ASSESSMENT/FEASIBILITY STUDY FOR ROCKY MOUNTAIN ARSENAL

OFFPOST OPERABLE UNIT - DISPUTE ISSUES

GENERAL COMMENTS

Comment No. I - Inat)r)roi)riate Land Use Scenario

This EAIFS uses a rural residential (hypothetical subsistence farmer) scenario in its baseline risk

assessment. This hypothetical population of residents, i.e., subsistence farmer residents, and the

associated land uses do not exist in the RMA Offposl Operable Unit. The rural residential cancer

risk estimates and hazard indices are based upon flawed data and faulty assumptions that do not

consider realistic, reasonable maximum current and future exposures to compounds of concern as

required by the National Contingency Plan (NCP) and EPA guidance. Moreover, due to various

factors it is impossible for this scenario to exist in the RMA Offpost Operable Unit at the present

time because of the high land values and the over appropriation of alluvial groundwater. Furthermore, due to the planned realignment of 961h Avenue, if adjacent lands are developed, commercial

and industrial land use is most likely, as the Army recognizes in the FS.

ResL)onse

As a result of dispute resolution, the Organizations agreed to an urban residential scenario for

zones 3 and 4, commercial -industrial for zone 5, and rural residential for zones 1, 2, and 6.

Attachment A to this set of responses to comments is the dispute resolution agreement letter

signed by all parties to the dispute and dated May 5, 1992. Commercial -industrial land use for

zone 5 was contingent on the South Adams County Water and Sanitation District's (SACWSD's)

certification that it does not plan to use groundwater in this zone during the next 30 years.

Attachment B to this set of responses to comments is a letter from SACWSD to the Army,

providing documentation that SACWSD does not intend to install water-supply wells in the future

in zone 5.

Comment No. 2 - InadeQuate Ecotoxicity Assessment

The food web n7odel presented in this EAIFS estimates excess risk to the biola present in the RMA

Offpost Operable Unit due to flawed methodologies and errors it? logic. The model results are

inconsistent with the observation of a healthy wildlife population. Furthermore, the model employs

unrealistic and phYsically impossible parameter values such as those used for bioaccumulation

factors, bioconcentrati .on factors, the dietary intake of aquatic food items by the great blue heron,

and unrealisticall ' v low ioxicit ' v reference values. In addition, the uncertaintY associated with the

food web model is so large that the results are adequate only for screeni .ng purposes.

Resvonse

As a result of dispute resolution (see Attachment A), the Organizations agreed to use literature

values for bioaccumulation factors (BAFs), bioconcentration factors (BCFs), and home range area.

The Army considered literature BAFs less than optimal but an acceptable alternative to onpost

calibrate BAFs. The Organizations also agreed to use spatial weighting factors determined on the

basis of home range area and to modifications to the toxicity reference value (TRV) derivation

process.

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Comment No. 3 - Incorrect Groundwater ExiDosure Point Concentrations

The methodology used in this EAIFS to generate groundwater exposure point concentrations is

flawed; therefore, the results are incorrect and inconsistent with the observed contaminant distribulions. Furthermore, this EAIFS does not present current and future contaminant exposures for the

groundwater compounds of concern, and is therefore inconsistent with the NCP and EPA guidance.

Based on Shell's evaluation of the available data, the EAIFS overestimates the groundwater

exposure point concentrations several fold in some areas.

Rest)onse

Based on dispute resolution (see Attachment A), the Organizations agreed to limit the groundwater

database to 1989 to 1991 and to delete gas chromatography/mass spectrometry (GC/MS) and field

duplicate data where appropriate (Volume 11, Section 2.0). In addition, a future groundwater

exposure scenario was evaluated, and groundwater concentrations were reduced as a result of

treatment of groundwater by the boundary containment systems over 30 years.

Comment No. 4 - Incomvlete Dieldrin Toxicolojaical Profile

This EAIFS fails to include key toxicological information (identified in our comments on the

draft of this document) regarding human data in the dieldrin toxicological profile; however, this

information was included in the aldrin1dieldrin toxicological profile for the RMA On-Post Final

Human Health Exposure Assessment. Furthermore, the inclusion of additional inforrnaiion is

preferred per the NCP and EPA guidance, and is important for risk management decisions.

Resvonse

Based on dispute resolution (see Attachment A), the Organizations agreed to include the Shell

dieldrin toxicological profile as a separate document in Volume IV, Appendix F of the Endangerment Assessment (EA).

Comment No. 5 - Manganese as a Compound of Concern

Manganese should not be a compound of concern (COC) for the RMA Offpost Operable Unit

because there is no known source at RMA, the assessment of the analytical data is flawed, and

manganese, if a COC, would be a pollutant or a contaminant, not a ýaZardous substance under

CERCLA. Furthermore, manganese is a naturally occurring constituent of the soils and

groundivater.

Resnonse

Based on dispute resolution (see Attachment A), the Organizations retained manganese as a

chemical of concern because groundwater monitoring data indicate manganese is associated with

RMA.

Comment No. 6 - ARARs

A number of aspects of the ARARs anal * ysis in this EAIFS are inconsistent with the selection

criteria of CERCLA or the NCP. Following are some of the more significant matters of concern.

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0504112092 VIII - 2
With respect to the ARARs based on the Colorado Basic Standards for Groundwater and the

Colorado Basic Standards for Surface Water, the EAIFS does not explain why the standards are

applicable or relevant and appropriate. In any event, Shell objects to all state groundwater

standards that are more stringent than MCLs on the grounds that the standards were not

automatically intended to be ARARs by 5 CCR 1002-8.3.1.1](5). We also note that one of the most

important tables, 2.4.3.1-1 of Volume V, is missing from this document.

rhe EAIFS is inconsistent in its treatment of Land Disposal Restrictions (LDRs). It correctly

acknowledges that the reinjection of groundwater does not trigger LDRs because LDRs are

superseded by RCRA Section 3020(a). p. VII-A-9. It also states that LDRs are not ARARs because

there are no iisted wastes from RMA in the Offpost Operable Unit.

p. VII-A-15. Despite these concentrations, the EAIFS then incorrectly states that LDRs have been

identified as action -specific ARARs for all treatment alternatives. See p. VII-A-23.

With respect to stormwater discharge regulations, Shell disagrees with the conclusion that the

stormwater discharge regulations may be relevant and appropriate, because, among other reasons,

the FS alternatives do not involve the discharge of stormwater runoff to surface water.

In certain instances, proposed MCLs have been selected as ARARs rather than rBCs. rhis is

inconsistent with the NCP. Furthermore, additional chemical -specific rBCs which were suggested

by Shell have been rejected.

Resnonse

The ARARs analysis presented in Volume VII Appendix A of the Feasibility Study (FS) has been

revised to include an explanation for the finding that the Colorado Basic Standards for Groundwater (CBSG) are not applicable or relevant and appropriate. The basis for this finding is in

Appendix A and rests primarily on citations from the Statement of Basis and Purpose in the

CBSG. The Statement of Basis and Purpose indicates that CDH did not intend that the Table A

Interim Organic Standards be applied as cleanup standards for CERCLA, RCRA Subtitle C, or

UST actions.

Appendix A of Volume VII has been revised to include the language agreed upon in the May 5,

1992, dispute resolution letter concerning land disposal restrictions under RCRA.

The dispute relative to stormwater discharge regulations was withdrawn.

Appendix A has been revised to include considerations of proposed MCLs as TBCs rather than

ARARs.

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U.S. ENVIRONMENTAL PROTECTION AGENCY COMMENTS REGARDING THE

ENDANGERMENT ASSESSMENT/FEASIBILITY STUDY FOR

ROCKY MOUNTAIN ARSENAL OFFPOST OPERABLE UNIT - DISPUTE ISSUES

ENDANGERMENT ASSESSMENT

GENERAL COMMENTS

Comment No. I - Development of PRGs

EPA would invoke dispute concerning the effects of multiple chemicals within a medium and

effects of COCs in multiple media as presented in the offpost endangerment assessment, and all

calculations that utilized the resulting values, for the reasons detailed below, except for the low risk

involved it? the specific example. In any other instance we would not accept this procedure.

A. Effects of Multiple Chemicals Within A Medium and Effects of COCs in Multiple Media.

Soil HBCIPRGs do not adequately address the cumulative effects of multiple carcinogens in

one medium, nor do they provide protection against cumulative effects of COCs it? multiple

media.

In its response to cover letter comment No. 4 (VIII-4) the Army "agrees that the evaluation of

multiple media should be included in the derivation of HBC." However, the response only

discusses multimedia adjustments for non -carcinogens, which were ultimately ?lot found to be

necessarv, and were therefore not made. The document remains silent on the subject of

multimeýia adjustments for carcinogens. The approaches for carcinogens and noncarcinogens should be consistent. Since the Army proposed to divide PRGs for noncarcillogens by the

number of media in which these COC occur, PRGs for carcinogens should also be divided by

the ?lumber of media in which they occur. Yet, calculated HBC for carcinogens were not

adjusted in this manner.

For example, since several carcinogens occur in groundwater as well as in soil in Zones 3

and 4, and commerciallindustrial workers are exposed to both, soil PRGs for these carcinogens should have beet? divided by 2.

However, no adjustments for multimedia effects for carcinogens were made. VII-C-2

describes the derivation of the residential soil PRG for dieldrin which was calculated to be

0.46 ug/kg at the 10-6 risk level. Instead of dividing the PRG by 2, the Army chose a

concentration associated with a higher risk level (33 ug/kg at the 7 x 10-5 ris'k level) and

presented this approach as the adjustment for additive effects of COCs it? soil and groundwater. It is unclear to the EPA how the acceptance of the higher risk level could possibly

counteract additive effects of COCs in multiple media.

Furthermore, the proportion method does not address the effects of multiple carcinogens

within one medium, and no efforts have been made to adjust for this deficiency. EPA

calculated that 23% of the soil carcinogenic risk to coninierciall industrial workers in Zone 3

is attribulable to COCs other than dieldrin, therefore an adjustment to account for the

additional risks is necessary.

Response

Volume V, Section 2.2 of the FS has been significantly revised to include additional detail

concerning development of PRGs in light of comparison of cumulative Offpost Operable Unit

(OU) hypothetical cancer risks to the NCP acceptable risk range. Additional detail is also

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0504112092 VIII - 4
presented in this section concerning risk associated with individual media in the Offpost OU,

based on the risks presented in Volume III, Section 4.0 of the EA. As discussed in detail in

Volume V, Section 2.2, the cumulative Offpost OU hypothetical cancer risk is a maximum of

3 x 10-4 , based on risks presented in the EA. As discussed extensively in Volume V, Section 2.2,

Offpost OU remedial action is not warranted because the Offpost OU cumulative risk is within

the NCP acceptable risk range. Also as discussed in Volume V, Section 2.2, the Army recognizes

that there are several site-specific factors that, when considered in totality, suggest remediation of

groundwater is preferable to no action in the Offpost OU. The above referenced sections of text

concerning PRG development explicitly state the risks corresponding to the groundwater, soil,

surface water, and sediment media. Also, justification is given for the conclusion that soil,

surface water, and sediment media do not require development of remedial action goals.

Remedial action goals were developed for the groundwater medium as discussed in Volume V,

Section 2.2, consistent with the methodology presented in detail in Volume VII, Appendix C.

Appendix C explicitly describes the development of PRGs, considering the effects of multiple

chemicals within the groundwater medium.

See response to Part I given above.

As described in the response to Part I given above, soil PRGS were not developed.

See response to Part I given above.

The development of PRGs for groundwater medium explicitly accounts for the effects of multiple

carcinogens within groundwater. This information is presented in Volume VII, Appendix C.

B. Derivation of PRGs

Some of the soil HBCs differ from those in the draft final text (as shown in Volume V,

Table 2.4.5-1). It appears a new methodology has been used for deriving the HBCs of

carcinogens (described in Volume II Appendix C). We have difficulty duplicating the new

HBC numbers.

PRGs were adjusted based on observed contaminant distribution and with the intent of

achieving low aggregate risk (as per footnote to Volume V. Table 2.4.5.5-1, that "some

preliminary remediation goals are different than HBC presented in Table 2.4.4-1."). Which

PRGs were adjusted, and why?

The soil HBC for the "Adjusted Residential" RME of Aldrin and Dieldrin are 31 ppb and

.5 ppb respectively (listed in Volume V Table 2.4.5-1). Since these two compounds are very

similar, to make the document more defensible it would help to explain why their HBC differ

by such a large amount (a factor of over 60).

To enable the layman reader to better follow the derivations, we suggest that the Army include

the following in its final version of the EAIFS:

i. A flow chart showing how the PRGs for each medium was determined.

ii. A complete listing of HBCs for the COCs in each medium.

iii. An addendum or appendix in which the actual step-by-step derivation of the HBCs and

PRGs (if different from the HBC) were determined. It should the chemical's slope

factor andlor reference dose. It should reflect adjustment effects for multiple media

exposure and organ toxicity.

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ResL)onse

The response to Part A of this comment states that Volume V, Section 2.2 presents justification

based on comparison of cumulative site risk and individual media site risk to the acceptable risk

range. Development of remedial action objectives and PRGs for soil was warranted.

Selected PRGs differ from HBCs because of the need to consider aggregate risk.

A flow chart showing considerations for selecting PRGs has been included in Section 2.4.5.5 of

Volume Il. Step-by-step derivation of HBCs is in Appendix C of Volume V11. This appendix

accounts for multiple organ toxicity. Slope factors and reference doses are in Tables 3.1-3 and

3.1-4 of Volume II of the EA.

Comment No. 2 - The Use of the 10-4 Cancer Risk as a Point of Denarture for Determination

of HBC

EPA invokes dispute concerning the use of the "10 to the minus four" cancer risk as a point of

departure for determination of HBC as presented in the offpost endangerment assessment, and all

calculations that utilized the resulting values, for the reasons detailed below. In its response to

Cover Letter Comment No. I the Army cites the NCP (55FR 8717) which states "Preliminary

remediation goals for carcinogens are set at a 10-6 point of departure, but may be revised to a

different risk level within the acceptable risk range on the basis of the consideration of appropriate

factors including but not limited to: exposure factors, uncertainty factors, and technical factors..."

The Arm), used several factors in an attempt to justify the selection of PRGs which present

carcinogenic risks exceeding 10-6. For example, the Army discusses only briefly the groundwater

CRLs. There is no explanation of how the soil HBCs were derived or why they do not correspond to

the PRG point of departure risk level. Groundwater CRLs are extraneous to soils PRGs. A

discussion is required to justify the higher risk levels selected for soils in zones 1, 2, 5 and 6.

While EPA agrees that there are many uncertainties in the EA, EPA is not at all convinced that all

of the uncertainties can be interpreted to conclude that the results of the EA present an

overestimation of risks. EPA believes that problems and uncertainties associated with data

representiveness, data quality and the approaches in the EA could also have contributed to an

underestimation of risks in the offpost.

Examples of specific issues that may have caused an underestimation were include the following:

A. A ke ' v pathway (COC intake via eggs) was not addressed except for one chemical (dieldrin).

Had the egg pathwa ' 1, been addressed for all relevant COCs, some HIs would have shown even

greater exceedances than they did.

B. Another source of uncertainty is the fact that some groundwater COCs which are currently

moving toward the offpost have not been addressed in the EA. These COCs include NDMA.

The health risks associated with these chemicals would be additive to those already evaluated

in the EA. (EPA still has substantive reservations concerning this issue, and reserves the right

to invoke dispute at a later time.)

C. The EA (1114-7) states that in Zone ]A 70% of the risks are attributable to COC conlamination of soil. Most of this risk stems from the uptake of COCs into food materials. The

fact that soil concentrations were divided by 5, before COC uptake into vegetables, beef and

dairy via soil was assessed. presents a potential for underestimation of risks.

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0504112092 V111 - 6
The Army did not discuss the determination of background contamination levels and their incorporation into the development of the appropriate PRGs. A section such be included which discusses

the development and incorporation of background values.

Rest)onse

As discussed extensively in Volume V, Section 2.2, development of PRGS for the groundwater

medium was performed consistent with the methodology described in the NCP. Groundwater

HBC were calculated at the 10-6 level for carcinogens when ARARs were not available and at a

HI of less than 1.0 for noncarcinogens without ARARs. These criteria were used as a basis for

developing PRGs for groundwater. The NCP states departure from 10-6 may be appropriate

considering various factors, including but not limited to exposure factors, uncertainty factors, and

technical factors. Exposure factors the Army evaluated in the EA included cumulative effects of

multiple contaminants, multiple pathways, population sensitivities, potential impacts on environmental receptors, and cross-media impacts. Additionally, uncertainty factors that evaluate the

effectiveness of the alternative, the weight of scientific evidence concerning exposures in

cumulative health effects, and the reliability of exposure data were also evaluated by the Army in

the EA/FS. Finally, the Army also evaluated technical factors in the selection of PRGs, consistent

with the NCP, including detection and quantitation limits, technical limits to the remediation, and

the ability to monitor and control movement of the contaminants. In summary, the Army's

approach to groundwater PRG development as described in Volume V, Section 2.5 is fully

consistent with the approach described in the NCP. As described in the response to EPA

Comment No. 1, PRGs were not developed for the soil medium.

A. On the basis of dispute resolution (see Attachment A), EPA agreed that the risk assessment

would evaluate only dieldrin for the egg pathway. As stated in Volume II, Section 2.1.1.1,

dieldrin was the only chemical of concern (COC) detected above the certified reporting limit

(CRL) in an egg sample analyzed from the Offpost OU; therefore, inclusion of other COCs

was not indicated.

B. All the groundwater alternatives include a specific component that calls for improvement or

modification of the boundary containment systems, as necessary, to address future chemical

plume concentrations. This information is in Volume VI, Section 3.0.

C. Without sufficient empirical scientific data, it is difficult to determine whether the division

of COC soil concentrations by five actually resulted in an underestimation of risk. The

surficial soil concentrations were divided by five to estimate a depth-averaged concentration

in the root zone because the soil COCs are strongly adsorbed to soil particles and are unlikely

to be readily leached through the soil column. The division of soil concentration by five is

discussed further in the response to Comment No. 5.

Background concentration levels were not used in the development of groundwater PRGS.

Comment No. 3 - Land Use

EPA invokes dispute concerning the land use scenarios as presented in the offpost FS, and all

sections and calculations that utilized the offpost FS conclusions, for reasons detailed below. The

discussion in Volume H demonstrates that there is uncertainty in regard to the land uses offpost.

Uncertainty, per the NCP, would require a comparison of land uses, such as residential, commet -

cial-industrial and recreational.

Scenarios for residential land use should be evaluated whenever there are homes on or near the site,

or when residential development is reasonably expected in the future. Consideration of historical

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d

land use; suitability for residential development; local zoning; and land use trends should be

undertaken. The farm family scenario should be evaluated if it is known that such families reside

in the area. EPA's concern is that residential uses were not compared in the Feasibility Study

(along with the Commercial- Industrial and Recreational uses). This should be done, given the

present level of discussion and the existing situation in the area. Some examples of uncertainty in

the discussion are:

A. PUD is not defined in Figure 7.2.2.1.2-2. A PUD does not support the elimination of

residential use between RMA and Route 2, without a specific definition which precludes

residential.

B. There was not information on the delineation or uses of the wetland it? zones 3 and 4

sufficient to eliminate residential use.

C. The realignment of 96th Avenue has been presented as speculation. There is no information

on whether there are plans to condemn the property for this route, whether land has been

dedicated for this route, whether it is on any official planning or transportation plan

demonstrating such a project. Further, there is not information sufficient to eliminate

residential use along a realigned corridor.

D. There was no explanation concerning the format issue of the 1990 Census which was

described as helping to define the present use. (P 11-2-40)

E. There was no discussion sufficient to conclude that Offpost Groundwater IRA would render

land CommerciallIndustrial. (P 11-2-44).

Presently, it cannot be demonstrated that the likelihood of residential use is small, given the

discussion of the circumstances in the Offpost OU, zones 3 and 4. These comments are premised

upon page 8710 of the National Contingency Plan (55FR8710, March 8, 1990), Section 6.2.2 of the

Risk Assessment Guidance (OSWER Directive 9285.701a; July, 1989), and Human Health

Evaluation Manual, Supplemental Guidance: "Standard Default Exposure Factors" (OSWER

Directive 9285.6-30, March 25, 1991).

Rest)onse

The topic of this comment was addressed during the dispute resolution process. Refer to

Attachment A for additional information in the dispute resolution letter. On the basis of dispute

resolution, all Organizations agreed to use a single land use scenario for each zone within the

Offpost OU. Zones 1, 2, and 6 were classified as rural residential, zones 3 and 4 as urban

residential, and zone 5 as commercial/ industrial. The land use scenarios and potential exposure

pathways were further defined as a result of agreements reached by the Organizations during the

dispute resolution process, as follows:

A. Rural Residential (EA/FS zones 1, 2, and 6)

meat* (75 percent)

dairy* (75 percent)

egg (only evaluated dieldrin)

vegetable* (40 percent)

groundwater (ingestion)

groundwater (inhalation)

soil (dermal)

soil (ingestion)

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0504112092 VIII - 8
sediments (dermal)

surface water (dermal)

B. Urban Residential (EA/FS zones 3 and 4)

vegetable* (40 percent)

soil (dermal)

soil (ingestion)

sediments (dermal)

surface water (dermal)

groundwater (ingestion)

groundwater (inhalation)

*All percents indicate amount of consumption from local sources.

Risk estimates for Zones 3 and 4 will be presented in two manners:

I . As a baseline risk assessment for all media per EPA guidance. The groundwater

portion of the risk assessment will be based on the calculated risks from 1989 to 1991

groundwater data in those zones.

2. The second risk calculations will be based on the continuing beneficial effect of the

onpost boundary system operations in a 30-year time. The text will state that these are

the expected potential exposures for individuals in those zones and the risks associated

with those exposures.

C. Commercial/ Industrial (EA/FS zone 5)

soil (dermal)

soil (ingestions)

groundwater (ingestions)

groundwater (inhalation)

If SACWSD provides appropriate documentation indicating that SACWSD is not planning

to install future water wells in zone 5 over the next 30 years, the groundwater pathway

will be removed from zone 5. Attachment B to this set of responses to comments is a

letter from SACWSD to the Army, providing documentation that SACWSD does not

intend to install water-supply wells in zone 5 in the future.

Comment No. 4 - Interpretation of Uncertainties Analysis

EPA invokes dispute concerning the interpretation of the uncertainty analysis as presented in the

offpost EAIFS, and all sections and calculations that involve this interpretation, for the reasons

detailed below. The response to comments on the uncertainty analysis is inadequate to address the

agency's concerns, in that it failed to distinguish between propagating variability and critical

knowledge uncertainties. The uncertainty analysis is put together in a fashion that renders it, in

reality, an analysis of uncertainties. Site-specific parameters, such as exposure point concentrations, were found to contribute little to overall variability (i.e. they were "insensitive parameters")

compared to various parameters associated with human behavior (exposure duration, ingestion rates,

etc.). This being the case, it is not possible to determine whether the uncertainty analysis over- or

underestimates actual exposures which might occur on the site. Stated in another way, any

"hypothetical" exposed population in the off-site area may vary considerably from the "typical"

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0504112092 Vill - 9
case. The logical conclusion is that there is no way to determine whether the RME estimate or the

quantitative uncertainty analysis better represents potential upper range exposures.

The Army maintain that they accept this conclusion, but the document suggests the opposite. The

risk assessment concludes that the uncertainty analysis "clearly" shows that the RME overestimates

potential exposures and concludes that the risk assessment may be "excessively" conservative. This

conclusion is then carried into the Feasibility Study to help justify a target risk substantially higher

than I X 10-6 for PRGs for the residential scenario. Such conclusions and interpretations clearly

indicate that the Army accepts the uncertainty analysis as a more "accurate" measure of potential

exposures. In view of the lack of knowledge of site-specific exposure parameters in these

"hypothetical" populations, and the lack of meaningful discussion on them, EPA cannot accept this

interpretation. In fact, the analyses seem to suggest that the appropriate conclusion might be almost

the opposite. Agreement within a factor of 3 or so should be viewed as quite good in the face of the

many uncertainties which go into risk assessment. EPA feels that the appropriate interpretation is

that estimates for maximum exposure are quite reasonable in comparison with those expected in a

11 typical" community, and that no substantial "overconservatism" has been documented.

In addition, the document does not distinguish between a "sensitive subpopulation" and the

"population-at -risk". An example may serve to demonstrate the point. As one moves away from the

Arsenal boundary, concentrations of contaminants in soil generally decrease until some

"background" is reached. If data from samples taken over this entire area are averaged, many

current or future residents on the fringe, or outside of the zone of the higher contamination will be

included in the exposure estimates. Since such individuals are not among the "at-risk" population,

the result will be an underestimate of exposures. The Army has recognized this in dividing the offpost into Zones. However, the document does not recognize that individuals may also be on the

fringe in a temporal as well as spatial fashion. As previously affirmed, many individuals in a

population maY be exposed for such short time periods that they cannot be considered "at-risk."

These individuals can reasonably be excluded from a quantitative uncertainty analysis without

changing the basic intent to examine a potential (perhaps "hypothetical") range of exposures in the

AT-RISK population.

Response

The proposed final EA/FS has been revised in response to this comment. Specifically, the Army

has concurred with and added EPA suggested wording regarding the interpretation of the

uncertainty analysis results, specifically, in Section 2.6 and 4.4. The distinction between propagation of variability and critical knowledge uncertainties was specifically addressed in the previous

draft as well as this draft (see Section 2.4.5.5.3), and the Army fails to appreciate how EPA's

previous comments require further elaboration on that issue. The Army agrees that the uncertainty analysis is an analysis of uncertainties. The Army agrees that the uncertainty analysis is prone

to share certain categories of errors with the reasonable maximum exposure (RME) analysis.

Included among these are:

1. Selection of exposure pathways for quantification: The same pathways are included in both

the RME and the uncertainty analysis. Some of these pathways may be incomplete now or

in the future. Conversely, some pathways that were not quantified may contribute to

exposure and risk, but documentation was provided in Section 2.3.3 (and the response to

comments incorporated in the March 17, 1992, proposed final report), supporting the

conclusion that pathways not quantified contribute negligibly to exposure.

2. Use of national average statistics rather than site-specific data for exposure factors, such as

consumption of homegrown vegetables and duration of residency: Additional discussion has

been added to respond to EPA's comment on this issue in Section 2.4.5.4.

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0504112092 Vill - 10
Considering these limitations, the primary conclusion that can be drawn from the uncertainty

analysis is that consistent selection of upper 90th and 95th percentile values for exposure

concentrations, exposure factors, and equilibrium partition coefficients (the procedure used to

derive RME intake estimates) tends to compound conservatism to such an extent that the RME

intake has a very low probability of exceedance. This finding leads the Army to conclude that

selection of a remedial alternative that produces an RME risk near the upper end of the acceptable

risk range would be protective of human health per the NCP.

The Army disagrees with EPA's interpretation that "agreement" within a factor of 3 is significant

of anything more than careful representation of the distributional inputs to the uncertainty

analysis. The inputs were designed to represent the same distributional information used to define

the point values (90th or 95th percentile) input to the RME calculation, so "agreement" simply

confirms that the distributions were represented in a consistent fashion in both the RME and

uncertainty analyses.

EPA's point regarding the difference between a sensitive subpopulation and the "population at

risk" is well taken. The distinction is a difficult issue throughout this and numerous other site risk

assessments. The sensitive subpopulation upon which the RME is based is assumed to maintain a

backyard garden (and domestic animals in some zones). Although it should be clear that not all,

and perhaps relatively few, residents would actually fit this profile, the Army and EPA seek to

protect such residents' health should they choose to do so. The uncertainty analysis attempts to

represent the population at risk, including these relatively highly exposed few. The Army

believes that representation of all the individuals within the population at risk enhances our ability

to communicate risks to the public in a balanced and meaningful way. Individuals who reside in

the offpost area for only one or two years should not be misinformed that their risk is equal to the

RME. Contrary to EPA's comment, the document does address this issue through the uncertainty

analysis by incorporating a realistic range of exposure durations (all the way from I year to 70),

and this is clearly one of the reasons why the median exposure is much lower than the RME. As

derived from the Exposure Factors Handbook, the median duration of residency at a single

residence (nationwide) is approximately 10 years, much lower than the RME estimate of 30 years.

The distribution used in the uncertainty analysis also reflects the possibility of exposure durations

much greater than 30 years, but the probability of longer exposure durations is very low. The

Army sees no compelling reason to exclude either short-duration or unusually long-duration

residents from the uncertainty analysis.

Comment No. 5 - Division of Soil Concentrations by 5

EPA would invoke dispute concerning the division of soil concentration values by the factor of 5 as

presented in the offpost endangerment and all calculations that used the resulting values, for the

reasons detailed below, except for the low risk involved in the specific example. In any other

instance we would not accept this procedure. In its response to General Comment No. 24 the Army

defends the adequacy of the subsurface soil data set, which was used to assess COC concentrations

in subsurface soil. The Arm), claims that 5 sets of corresponding subsurface and surficial soil data

sample points were used for the comparison. However, subsurface sample HA 1261 SO, which is

mentioned in the Army's response is not included in RI Figure 2.5 which gives locations for

subsurface samples. Furthermore, this sample is neither mentioned in the text, nor are any data

included in the relevant Appendix. Since the sample appears to be not documented, it cannot be

used for the comparison.

This would appear to leave 4 soil samples for the 0.5 foot depth analysis. Dieldrin was detected in

only one of the 4 samples (HA 9085 SO), however, the dieldrin concentration in this sample

(70 jug/kg) was higher than that of other surficial soil samples that were collected relatively nearby

(HA 1235 Wb, 30 ILglkg, HA 1229 JVB, 13 pg1kg, and the "collocated" surficial soil sample HA

11788,903 - CR-03

0504112092 Vill - 11
0996 WB, 55 ug/kg). Even though dieldrin concentrations were below the detection limit in the

3 other subsurface samples, EPA believes that the data are not sufficient to justify dividing soil

concentration by 5 (or by 4).

Furthermore, the text (11-2-77) indicates that most of the surficial soil data are from untilled

areas, and that the subsurface soil samples were collected "nearby." It seems inappropriate to

measure subsurface soil concentrations in areas which have not been used for agricultural purposes,

if these soil concentrations are then used to determine COC uptake into vegetables. It is obvious

that in plowed, filled and irrigated soils COCs would more evenly distributed in the subsurface.

Resr)onse

Results from sample HA 1261 SO were reported in the remedial investigation (RI) addendum.

However, a typographical error in that document resulted in the sample being labelled

"HA 1261 S". The results are also part of the Program Manager for Rocky Mountain Arsenal

(PMRMA) database wh ' ere the sample is labelled HA 1261 SO, and that database is part of the

administrative record.

EPA appears to be confused that division of concentration by a factor of 5 is somehow related to

the fact that five sets of corresponding subsurface and surficial samples were used as supporting

documentation. The factor of 5 is derived from the ratio of the depth of the root zone for row

crops to the depth interval of surficial samples. At the risk of belaboring our arguments already

on the record, we assert that all available evidence supports the conclusion that surficial soil

contamination offpost has resulted from deposition of windblown aerosols from onpost sources,

that the soil COCs are all organochlorine pesticides that are highly immobile within the soil

profile, and consequently that it is likely that untilled soil will contain soil COCs only in the upper

one or two inches of the profile. These hypotheses are supported by the fact that detectable

concentrations have been observed nearly exclusively in surficial (upper I to 2 inches) samples

and that nearby samples of the upper 6 inches have lower or nondetectable concentrations. The

portions of the Offpost OU where the highest surficial soil concentrations have been found have

predominantly not been used for row crop cultivation but rather have been fallow/pastureland.

If, under a potential future land use, they were to be cultivated for vegetables, they would be

tilled, thus mixing the contaminants presently found in the upper I to 2 inches through the root

zone, resulting in an average root zone concentration approximately 115 of the observed surficial

concentrations.

EPA's final paragraph suggesting that samples from untilled land not be considered for the

vegetable pathway analysis contradicts related EPA guidance that potential future land uses that

might result in RME exposures be evaluated. The Army, following EPA guidance, has conservatively assumed that land not currently in cultivation might be cultivated in the future. Areas

currently under cultivation for vegetables have substantially lower concentrations of COCs in soil.

Comment No. 6 - Ecological Risk Assessment

EPA invokes dispute concerning a) the values for bioaccumulation factors (BAF) and biomagnification factors (BMF), and b) the value for dieldrin MATC in top predators (eaglelowllkestrell)

presented in the off post ecological risk assessment, and all calculations that used these factors,

such as ecological PRGs, for the reasons detailed below. (See: Volume III, Section 5.0 et sea.,

Volume IV, Appendix H, and Volume V, Ecological PRGs, Volume VII, Appendix C.)

In addition, EPA still has substantial reservations concerning the methodology used to derive

ecological toxic reference (TRV) values. EPA would invoke dispute on the TRV methodology for

dispute at this time: however, since the TRV values were not used to develop ecological PRGs, we

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0504112092 VIII - 12
will not dispute at this time. EPA reserves the right to invoke dispute on the TRV methodology

should it be used in the onpost ecological assessment.

A. Bioaccumulation factors (BAF) and Biomagnification Factors (BMF)

The values for BAFs and BMFs, and other values calculated from these, cannot be accepted as

presented due to serious concerns about the methodology used to derive those BAFIBMFs.

The off post ecological risk assessment (ERA), as currently presented is a deterministic

version of the on post ecological risk characterization (ERC) model.

The ERC has not previously been reviewed, and thus constitutes entirely new information. A

set of computer disks were provided to EPA on March 19, 1992, containing the postcalibration values for on post biota. No supporting documentation was provided with those

disks.

EPA will submit detailed comments concerning the on post biota model under separate cover.

A careful review of the available data set was undertaken for study area 1, and indicates that

there is no acceptable basis for comparing contaminant concentrations in soil, terrestrial

plants, and prairie dogs. Although the sample sizes were reasonably large, at least for soil

and prairie dogs, the number of co-located samples that could be compared rigorously is

extremel ' 1, small. Thus, these data cannot be used to estimate BAFs or BMFs. The attempt to

do so, based on the entire files of soil and biota data, involves almost exclusively the

comparison of non-comparable data.

Response

A. The Army elected to use calibrated onpost data because it felt that site-specific parameters

were preferable over literature values that were based on controlled experimental studies or

field studies conducted in other geographical regions. The Army felt that BAFs derived

from both controlled laboratory studies or other field studies would not reflect influences

from environmental/ecological conditions within the Offpost OU. Therefore, the Army

concluded the onpost values would be preferable because the offpost is environmentally and

ecologically similar to the onpost.

However, the Army acknowledges that because of different scheduling needs, the onpost

values were not adequately reviewed by the Organizations and State (OAS) before their use

in the draft final ecological assessment. Therefore, the Army has agreed to incorporate the

BAF and BCF values derived during the dispute resolution process. The Army still maintains the literature values are not representative of Offpost OU site-specific conditions.

B. Dieldrin MATC in top predators (eaglelowllkestrel)

The dieldrin MATC value of 1.6 ppm cannot be accepted because it relates to lethality in birds

of prey.

The Army selected an MATC value of 1.6 for both aldrin and dieldrin in birds of prey. The

value of 1.6 ppm is the average concentration in the carcasses of 101 bald eagles found dead

between 1971 and 1974. (K.R. Barbehenn and W.L. Reichel, Organochlorine concentrations in

bald eajzles: brain1bodi, lipid relations and hazard evaluation. Journal of Toxicological

Environmental Health 8:325-330, 1981). The value of 1.6 ppm is neither a safe level nor a

minimum level: it is an average level in a collection of birds grouped together for other

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0504112092 VIII - 13
M

reasons. The paper is about the pharmacology of dieldrin in eagles, not about dose-response

relationships.

The best experimental data on effects of dieldrin on birds of prey are those of Wiemeyer gt

al. (DDE, DDT + Dieldrin: Residues in American Kestrels and Relations to Reproduction,

1986). The mean carcass concentrations in birds that died was 1.7 ppm (range, 0.7 -

4.5 ppm). Thus, a carcass concentration of 0.7 ppm is related to lethality, and cannot be

indicated as "allowable." To apply these data to other birds of prey, including eagles, would

require an additional interspecies uncertainty factor.

Reported cases of dieldrin poisoning in bald eagles from several states (Prouty, R.M. et al,

1977. Residues of oreanochlorine pesticides and polychlorinated biphenyls and autopsy data

for bald eagles. 1973-74.

Pestic. Monitor J. 11:134-137, and Kaiser, T.E. et al, 1980. Organochlorine pesticide, PCB,

and PBB residuesand necropsy data for bald ea--Ies from 29 states -- 1975-77. Pestic.

Monitor. J. 13:145-149) indicate median carcass residues in bald eagles of 0.74, 0.63, 0.60,

0.66, and 0.22 ppm, wet weight. Although it is difficult to use these data to define a

minimum or low effect level, it is clear that a population average level of 0.66 ppm is

associated with deaths from dieldrin poisoning in some individuals. Therefore, EPA cannot

accept the MATC value of 1.6 ppm for dieldrin.

Resvonse

B. The MATC values used in the draft final ecological assessment were obtained from the

Onpost Ecological Risk Characterization (ERC). Although these values were not adequately

reviewed by the OAS before the release of the draft final ecological assessment, the Army

has some serious concerns about the adequacy of the data from the Wiemeyer and others

paper cited by EPA for establishing a dieldrin MATC. The Army's concerns include the

following: use of a chemical mixture with no single dosing with dieldrin, study not designed

to investigate dieldrin toxicity only, the presence of other stressors (e.g., periods of low

ambient temperatures and disease episodes of enteritis), study conducted more than 23 years

ago, insufficient numbers for an adequate statistical comparison, and the presence of

toxicological anomalies. For example, the lowest kestrel carcass concentrations associated

with mortality in the low dose groups is 0.7 ppm as cited above by EPA; however, the brain

concentration in this kestrel is one of the lowest levels reported, 0.09 ppm, and this animal

also has the second highest value reported for carcass lipid percent of dry weight,

36.4 percent. Toxicologically, it is highly unlikely that dieldrin either directly or indirectly

caused this animal's death. Additionally, in their summary of dieldrin- related deaths for all

study groups, the authors indicate dieldrin was not the cause of death for any animal in the

low dosage groups and only contributed to the death of three others. Sixteen birds

comprised the low dosage groups. Therefore, the Army cannot accept 0.7 ppm as a suitable

MATC.

Following a review of several articles published on dieldrin toxicity during the dispute

resolution and a conference call with Dr. Stanley Wiemeyer, the Organizations and Army

agreed upon a dieldrin MATC value of 1.1 ppm.

Comment No. 7 - Accemance of Ecological Hazard Indices that Exceed I

EPA invokes dispute concerning the acceptance of ecological hazard indices that exceed I as

presented it? the offpost risk assessment, and all calculations that utilized the resulting values, for

the reasons detailed below.

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0504112092 VIII - 14
A The Army justifies the acceptance of high HIs for ecological receptors with the argument that

the movement of these receptors to areas outside of Zone 3 will reduce the ecological risk. At

the same time the Army dismisses the additional risks that ecological receptors encounter

when they move onpost. The Army states (response to General Comment No. 6) that "movement of receptors to the onpost increases exposure that is more appropriately evaluated it? the

onpost."

EPA disagrees with this statement. The physical setting of RMA and its surroundings

suggests that ecological receptors are more likely to spend time at RMA than in the more

developed areas outside of RMA. While EPA does not require the Army to quantitatively

address the additional risks that animals residing in the offpost encounter due to movement

into the onpost, EPA believes that the additional exposures are a source of uncertainty in the

ecological risk assessment, which should not be dismissed. The potential for additional and

even greater exposures make the risks associated with Zone 3 very significant, and Hazard

Indices above I cannot be accepted.

While the Army is correct in stating that the home range of mobile ecological receptors may

exceed the size of Zone 3, the Army does not provide any quantitative information on how

much time these receptors spend outside of Zone 3, or what percentage of prey is caught

outside of Zone 3. The HIs calculated in ecological risk assessments are quantitative

estimates based on many considerations and factors. These quantitative data cannot be

dismissed based on a completely unquantified assumption. It should also be noted here, that

even though several of the calculated HIs are high, EPA has many concerns with the input

parameters used to calculate the HIs. If more appropriate parameters were used, resulting

HIs would be even higher.

B. The results of the EA showed that the egg pathway is an important contributor to noncarcinogenic risk. For example, for the child resident in Zone IC the egg pathway contributes an HI

of 3.1 x 10-1 to a total HI of 1.2. The fact that the egg pathway has not bee evaluated for

soil COCs other than dieldrin is especially significant in light of the fact the HIs for

hepatotoxic effects in children exceed I in all zones.

The soil concentrations for endrin, DDTIDDE and chlordane are similar to those of dieldrin

(Table 2.4.2.5-8). Therefore, if the soil to egg partitioning coefficients for these chemicals

are similar to the soillegg partitioning coefficient for dieldrin, chemical concentrations in

eggs would be similar to those of dieldrin, and the egg pathway for other soil COCs would

contribute greatly to the already existing calculated risk. For example, at? estimate shows

that the egg pathway for chemicals other than dieldrin might contribute an HI of approximately 0.65 to hepatoxic effects it? children in Zone 3.

The A rm ' v states that it was unable to quantify the egg pathway for chemicals other than

dieldrin, because no literature value for the soil to egg partitioning coefficient could be found

for these chemicals. EPA suggested (General Comment No. 26) that a default value for K,,,.

similar to that of dieldrin be used to estimate the concentrations of soil chemicals in eggs. lit

the absence of site-specific data andlor literature data for the K.', parameter, the approach

recommended by EPA would have been reasonably conservative. To not address potentially

important pathways because of the lack of data is unacceptable in a human health risk

assessment, when use of parallel information would at least yield qualitative information for

the uncertainty analysis.

Remonse

A. The movement of mobile ecological receptors to onpost areas potentially could result in

additional exposure and increased risks; however, the Army cannot quantitatively determine

11788,903 - CR-03

0504112092 VIII - 15
the additional risk that may occur because the onpost ERC is not yet complete. The HI is

the result of a comparison of an estimate close to a benchmark, in this case, a toxicity

reference value. A numeric result greater than one does not indicate the potential magnitude

or severity of effect, only that the benchmark dose was exceeded. The EPA appears to

accept an HI of one as an absolute reference point and any exceedance above one as totally

unacceptable. This defies biological reality and the uncertainty associated with biological

systems. Compared to the physical sciences, biological outcomes are less predictable, and a

range of acceptability is appropriate. Although sufficient monitoring/analytical data are

lacking, it is highly unlikely that the HIs, as determined for this ecological assessment,

underestimate the potential risk and ecological receptors.

The Army strongly disagrees with the statement, "If more appropriate parameters were used,

resulting HIs would be even higher." In fact, on the basis of dispute resolution, the parameters agreed upon by the Army and Organizations resulted in lower HIs. These parameters

included a spatial adjustment factor to account for the receptor's dietary intake fraction

obtained from zone 3 and/or zone 4 relative to the receptor's home range.

Comment No. 8 - General Comment Concerninp, ARARs Analysis

EPA invokes dispute concerning the adequacy of the ARAR analysis as presented in the offpost

EAIFS, and all calculations and conclusions that utilized the analysis, for the reasons detailed

below. The discussion of ARARs in the EAIFS is inadequate. Compliance with ARARs is a

threshold requirement for comparing and selecting remedial alternatives, yet the ARAR discussion

in Appendix A provides no basis for differentiating alternatives. The ARARs analysis should have

considered the universe of ARARs as they applied to each remedial alternative, providing detailed

discussion with respect to the preferred alternative. EPA's "CERCLA Compliance with Other Laws

Manual," OSIVER Dir. 9234.1-01 (August, 1988), specifies the process for completing an ARAR

determination. (See CERCLA Compliance with Other Laws Manual, pp 1-55 to 1-56). In

addition, Appendix E to EPA's "Guidance for Conducting Remedial Investigations and Feasibilit ' i

Studies Under CERCLA," OSWER Dir. 9355.3-01 (October, 1988), provides a suggested formal

for the summary of ARARs. EPA recommends that this formal be used. Even if this format is not

followed, a substantivel ' 1, equivalent discussion is required. EPA believes that the EAIFS does not

sufficiently address ARARs, and therefore objects to the entire proposed ARAR determination.

It is not sufficient to lump together entire statutes or groups of regulations without analyzing the

portions thereof that may be applicable or relevant and appropriate. For example, on p. VII-A-14,

the Armv's ARAR analysis states: "To the extent that hazardous wastes do exist, 40 CFR Part 264

will be an ARAR." This statement is so vague that it cannot reasonably construed to constitute an

anal ' ysis. In fact, it is clear that some sections of Part 264 may be ARARs, and some may not. As

just one example, 40 CFR Part 264.281 relating to ignitable or reacti .ve wastes is not likely to play

a role in this remedial action, but 40 CFR 264.100, which establishes a ground water monitoring

program, may well be relevant and appropriate.

In light of the lack of adequate identification and discussion of individual ARARs, EPA is unable

to provide a comprehensive list of the deficiencies of Appendix A. Instead, EPA requires that a

thorough ARAR analysis be performed taking into account the universe of Federal and Slate

ARARs.

In addition, EPA has disagreed with particular ARAR conclusions that were reached in the Army's

Response to Comments. These are described in more detail below.

11788,903 - CR-03

0504112092 VIII - 16
Response

Volume VII, Appendix A of the FS, ARARs analysis, has been revised to address EPA's concern

that sufficient detail was not provided. Specifically, additional detail was provided in the section

describing each of the major categories of chemical -specific, action -specific, and locationspecific ARARs. Additionally, as requested by EPA, a table summarizing the ARARs analysis

was added.

Additional text was added to Volume VII, Appendix A, specifically addressing sections within

40 CFR, Part 264, and discussing which sections of Part 264 may be ARARs.

Additional text has been added to Volume V11, Appendix A, including and addressing the

universe of Federal and State ARARs.

A. Specific Inaccuracies in ARARs Analysis

EPA invokes dispute concerning specific inaccuracies in ARAR analysis as presented in the

offposl EAIFS that EPA can now identify, and all calculations and conclusions that utilized

the analysis, for the reasons detailed below.

i. Response to Comments on Volume VII:

The portion of this response that states: "ARARs do not discuss surface water and

sediments because the preferred alternative does not require remedial action for th6se

specific media," is inconsistent with CERCLA and the NCP. CERCLA requires that

remedial action.-

attain a degree of cleanup of hazardous substances, pollutants, and contaminants

released into the environment and of control of further release at a minimum which

assures protection of human health and the environment.

42 U.S.C. s'9621(d).

In order to assure that remedies are protective of human health and the environment,

section 121 of CERCLA requires that the remedy attain ARARs. If there is any

exposure pathway for humans, ARARs must be considered to establish protectiveness. If

site conditions do not meet ARARs, remedial alternatives must be developed. Even if

surface water and sediment are determined to have no exposure pathway for humans, in

light of the Endangered Species Act, the Bald and Golden Eagle Protection Act and the

Migratory Bird Treaty Act, surface water and sediment must be considered as potential

exposure pathways for migratory birds and eagles. If ARARs have not been considered

for surface water and sediment, the selected remedy cannot be shown to be protective

and cannot meet the threshold criteria required for comparison of remedies in the NCP.

See 40 CFR § 300.430.

Resi)onse

With regard to the EPA inquiry on the Endangered Species Act (ESA), the Bald and Golden Eagle

Protection Act (BGEPA), and the Migratory Bird Treaty Act (MBTA), Appendix A in

Volume V11 has been revised to include in totality the language agreed upon in the dispute

resolution process and communicated in a letter from EPA to the other parties, dated September 18, 1992, regarding these three federal acts (see Attachment Q.

11788,903 - CR-03

0504112092 VIII - 17
ii. Response to Comment No. 17:

This response states that reports available at EPA or RMA are "publicly available" and

may be cited without constraint. EPA disagrees. The Army has relied on old reports that

may no longer be available, as well as draft reports that may be subject to privilege.

These and any other reports that may not be publicly available, should be included as

appendices to the EA, or, at the very least, added in full to the Administrative Record.

Resr)onse

The Army stands by its response that reports available at EPA or RMA are "publicly available"

and may be cited without constraint. In appropriate appendixes in the Final EA/FS, the Army has

included information that is not yet available, e.g., some ecological risk assessment parameters that

were obtained from the unfinalized Onpost ERC are in Appendix H.

iii. Response to Comment No. 25:

This response is incorrect insofar as it suggests that the Migratory Bird Treaty Act does

not require protection of individual birds. 16 U.S.C. s' 703 clearly states that it is

unlawful to "kill ... any migratory bird ... or any egg of any such bird..." This statute was

amended in 1974 for the specific purpose of changing a reference to "birds" (plural) to

"bird" (singular). The language of the statute "makes it clear that killing a single bird is

sufficient to create criminal liability..." United States v. Corbin Farm Service, 444 F.

Supp. 510 (E.D. Cal. 1978).

For further discussion of the Migratory Bird Treaty Act as an ARAR, see Response to

Comment No. 216, below.

Resr)onse

Refer to response to Ad. given above, regarding the dispute resolution agreement for the three

Federal Acts.

iv. Response to Comment No. 114:

This response suggests that EPA may not dispute the values for the chemical- specified

absorption factor (ABS) because EPA had previously been informed of these values in a

RMA subcommittee meeting and expressed no opposition at that time. This position is

insupportable. EPA is in no way bound by its silence at a time when the Agency was

under no affirmative duty to raise objections. EPA has not waived its right to pursue

dispute resolution on this issue.

Rest)onse

Comment acknowledged.

v. Response to Comment No. 216:

The response to this comment, which states that the Endangered Species Act, 16 U.S.C. s'

1531, et sea., the Bald and Golden Eagle Protection Act, 16 U.S.C. s' 668, et sea., and the

Migralory Bird Treat), Act, 16 U.S.C. s" 701 et sea., are not ARARs is both incorrect and

11788,903 - CR-03

0504112092 VIII - 18
inadequate. Contrary to assertions made in the Army's response, the Endangered Species

Act, the Migratory Bird Treaty Act and Bald and Golden Eagle Protection Act contain

substantive requirements applicable to circumstances present at this site.

With respect to the Endangered Species Act, we note that 16 U.S.C. s' 1538 (1)(B) states:

[i]l is unlawful for any person subject to the jurisdiction of the United States to take

any such species within the United States...

and "take" is defined at s' 1532(19) as "to harass, harm, pursue, hunt, shoot, wound,

kill, trap, capture, or collect, or to attempt to engage in any such conduct." The Agency

interprets "harm" as any harm resulting from contaminant pollution.

The Migratory Bird Treaty Act slates:

Unless and except as permitted by regulations made as hereinafter provided in this

subchapter, it shall be unlawful at any time, by any means or in any manner, to pursue,

hunt, take, capture, kill ... any migratory bird, any part, nest, or egg of any such bird...

16 U.S.C. s' 703.

The United States Court of Appeals for the Second Circuit has interpreted this statute to apply to a

situation in which migrator ' y birds were killed by the release of chemicals into a pond. United

States v. FMC Corp., 572 F.2d 902 (2d Cir. 1978).

Similarly, the Bald and Golden Eagle Protection Act makes it unlawful to kill bald or golden

eagles by poisoning. See 16 U.S.C. s' 668d: "As used in this subchapter... "take" includes also

pursue, shoot, shoot at, Doison, wound, kill, capture, trap..." (emphasis added).

According to the NCP, ARARs are:

[c]leanup standards, standards of control, and other substantive requirements, criteria,

or limitations promulgated under federal environmental or state environmental or

facility siting laws that specifically address a hazardous substance, pollutant, conlaminani, remedial action, location, or other circumstance found at a CERCLA site.

400 CFR § 300.5 (emphasis added).

The Endangered Species Act, the Bald and Golden Eagle Protection Act and the Migratory Bird

Treaty Act, clearly set up substantive requirements andlor limitations (i.e. protection of certain

species) under circumstances that are present at this site. The statement it? the ARAR analysis

(Appendix A) that "the alternatives will have no adverse impact on any endangered species or

migratory birds" is insufficient. Not only are the Endangered Species Act, Bald and Golden Eagle

Protection Act and Migratory Bird Treaty Act ARARs, but they must also be used to set standards

for remediation that will be protective of endangered species, migratory birds and bald and golden

eagles.

Resvonse

Refer to response to Part I above regarding the dispute resolution agreement with respect to the

three Federal Acts.

11788,903 - CR-03

0504112092 Vill - 19
Pages VIII-20 through Vill-26 are missing from the original.
FEASIBILITY STUDY

GENERAL COMMENT

Comment No. I - Alternative Selection

EPA invokes dispute concerning the groundwater alternative selected in the offposl FS, and all

areas of this document and future documents that are effected by the selection, for the reasons

detailed below. Since all of the alternatives presented for the remediation of the groundwater

(excepting the No-Action alternative) are variations on the configuration of the same technology,

the alternatives are essentially equivalent. All of the alternatives evaluate various arrangements of a

transverse pump-and-treat system. In order to make the FS comprehensive and in compliance with

guidance, axial arrangements should also be evaluated. The Guidance for Conducting Remedial

Investigations and Feasibility Studies Under CERCLA states, "For aquifers currently being used as

a drinking water source, alternatives should be configured that would achieve ARARs or risk-based

levels as rapidly as possible." The Offpost FS has not evaluated configurations that could

potentially achieve a more rapid remediation, such as an axial system.

The Guidance on Remedial Actions for Contaminated Ground Water at Superfund Sites states, "A

LgLýj remedial alternative generally should be developed for ground water that is a current or

potential (emphasis added) source of drinking water. This alternative should achieve the selected

cleanup level throughout the area of attainment within the shortest time technically feasible.

Additional alternatives should be developed to ensure that a wide range of distinctive hazardous

waste management strategies are evaluated at most sites." The FS must be modified to broaden the

range of alternatives to include one which would achieve cleanup in the shortest time possible or

demonstrate that a more rapid cleanup is not technically feasible.

Remonse

The Army strongly disagrees with EPA's contention that an aggressive groundwater alternative

was not evaluated in the Offpost FS. As discussed in Volume VI, Section 3.0, Development of

Remedial Alternatives, and Volume VI, Section 6.0, Detailed Analysis of Remedial Alternatives,

the offpost geology, hydrogeologic systems, contaminant distribution, and contaminant transport

properties were studied extensively both analytically and using a groundwater numeric model.

The modeling effort is described in both Volume VI, Section 3.0 in terms of development of

remedial alternatives and extensively in Appendix E of Volume V11.

The results of this analysis are presented in a lengthy discussion in Volume VI, Section 3.0. The

controlling hydrogeologic and contaminant transport properties of the Offpost OU.1groundwater

system include (1) groundwater seepage velocity of the First Creek pathway relative to the

northern pathway, (2) the distribution of the relatively less mobile compound dieldrin compared

to the distribution of more mobile compounds such as DIMP and chloroform, and (3) the

controlling transport properties of dieldrin as compared to the transport properties of DIMP and

chloroform. As described in Volume V1, Section 3.0, Alternative No. N-4 for the North Plume

Group was developed through a combination of analytical well field simulation, knowledge of

contaminant distribution and contaminant transport properties, and hydrogeology of the North

Plume Group.

A transverse capture system for the northern pathway was chosen to intercept contaminants

moving in the northern pathway. An axial system of collection wells and recharge trenches was

selected in the First Creek pathway. Alternative No. N-4 consists of a total of 17 walls and

6 trenches with a total extraction flow rate of approximately 480 gpm. Alternative No. N-5 has a

total of 20 extraction wells and 12 trenches. Alternative No. N-6 has a total of 4 extraction wells

and 19 trenches. The total linear feet of recharge trenches ranges from 1500 feet in Alternative

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0504112092 V111 - 27
No. N-4 to approximately 4400 feet in Alternative No. N-6. The total extraction flow rate ranges

from 480 gpm in Alternative No. N-4 to a total of 690 gpm in Alternative No. N-6.

The increasing complexity of Alternative Nos. N-5 and N-6 as compared to Alternative No. N-4

was evaluated to assess the impact of adding a number of extraction and recharge trenches in areas

where contaminants were remaining in areas of slower relative groundwater velocity and tighter

aquifer materials, and to address less mobile contaminants.

The level of aggressiveness of Alternative Nos. N-5 and N-6 reached a practical maximum

whereby the maximum practical number of additional extraction wells and recharge trenches was

evaluated for remediation timeframe and aquifer drawdown considerations. Model-estimated

groundwater mounding and drawdown resulting from the recharge trenches and extraction well

arrays reached practical limits in Alternative Nos. N-5 and N-6. The discussion presented in

Volume VI, Section 3.0 gives specific information demonstrating the distinct differences in level

of complexity and aggressiveness of the remedial alternatives studied in the EA/FS.

SPECIFIC COMMENTS

Comment No. 2

Response to Comment 201

See dispute item number 2 (land use) above.

Response

See response to EPA General Comment No. 3 under Endangerment Assessment.

Response to Comment 202

The response to this comment is inadequate, but EPA will not dispute this issue at this time.

However, the document would be more defensible if the following concerns were addressed. The

Army has not adequately addressed the remediation of the contaminated surface water. As

presented, the FS evaluates only one alternative for the remediation of surface water, which is the

remediation of the surface water via source removal, i.e., remediation of the groundwater. The FS

Guidance (OSIVER Directive 9355.3-01, October 1988, p. 1-8) states, "As practicable, a range of

trealment alternatives should be developed, varying primarily in the extent to which they rely on

long-term management of residuals and untreated wastes. The upper bound of the range would be

an alternative that would eliminate, to the extent feasible, the need for any long-term management

(including monitoring) at the site. The lower bound would consist of all alternative that involves

treatment as a principal element (i.e., treatment is used to address the principal threats at the site),

but some long-term management of portions of the site that did not constitute "principal threats"

would be required. Between the upper and lower bounds of the treatment range, alternatives varying

in the type and degrees of treatment and associated containment1disposal requirements should be

included as appropriate. In addition, one or more containment option(s) involving little or no

treatment should be developed as appropriate, and a no-action alternative should always be

developed."

The A rm ' 1, has not provided an objective evaluation of possible alternatives for the remediation of

the contaminated surface water other than concluding that the remediatioll of the groundwater

would remediate the surface water. The timeframe and costs for remediation of surface water are

not identified, even within the context of the remediation of the groundwater, since a portion of

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0504112092 VIII - 28
these elements reside in the remediation costs and timeframe for the Onpost OU, for which the FS

has not yet been prepared.

Even though the surface water contamination may not constitute a "principal threat" in the Offpost

OU, this contaminated media must be evaluated in the FS.

Response

See response to EPA General Comment No. I under Endangerment Assessment. Remedial action

objectives were not developed for the surface-water medium.

Response to Comment 229

See response to specific comment 202 above.

Resvonse

See response to EPA General Comment No. I under Endangerment Assessment.

Response to Comment 230

See response to specific comment 202 above.

Rest)onse

See resp onse to EPA General Comment No. I under Endangerment Assessment.

Response to Comment 231

See responses to specific comments 202 above.

Resnonse

See response to EPA General Comment No. I under Endangerment Assessment.

Response to Comment 242

See responses to specific comments 202 above.

Resr)onse

See response to EPA General Comment No. I under Endangerment Assessment.

Response to Comment 246

See responses to specific comments 202 above.

11788,903 - CR-03

0504112092 VIII - 29
Response

See response to EPA General Comment No. I under Endangerment Assessment.

11788,903 - CR-03

0504112092 VIII - 30
U.S. DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE COMMENTS

REGARDING THE ENDANGERMENT ASSESSMENT/FEASIBILITY STUDY FOR ROCKY

MOUNTAIN ARSENAL OFFPOST OPERABLE UNIT - DISPUTE ISSUES

GENERAL COMMENTS

Comment No. I

The Service is concerned that the Migratory Bird Treaty Act (MBTA) is being treated inconsistently

within the Offpost EAIFS process. In response to our General Comment #2 on the Draft Offpost

EAIFS, the Army has stated that protection under the MBTA has been included into the screening

criteria for biological receptors, however, in the response to Specific Comment #24, the Army states

that "there is no need to attempt to protect individual environmental receptors". Additionally, in

response to EPA General Comment #23, the Army states that "the Migratory Bird Treat Act does not

require protection for individual birds". The Army further states that even humans are not protected

at the individual level. While this may be true for humans, federal law does require protection at

the individual level for migratory birds.

While protective models may profess to safeguard only the majority of individuals within a

population, it is generally recognized that their level of precision may not reflect absolute reality.

Conservatism exercised at various steps within modelling efforts may actually come nearer to

protecting wi entire population than an admission of the imperfection of the process would admit.

The Service hopes that through providing its best professional judgement it will protect the welfare

of its trust species to the greatest extent practicable. Service trust species must be protected andlor

damage assessment for any losses may be initiated.

Resvonse

The Army has derived toxicity factors (TRVs and MATCs) for use in the ecological assessment

that at least provide protection to a population of a species and that are highly likely to beeven

more protective. It is impossible to state with absolute scientific certainty that all individuals

covered by the MBTA will be protected because there is a lack of sufficient chronic toxicity data

for the COCs in wildlife species. The Army has incorporated modeling parameters (e.g., BAFs,

BCFs, and MATCs) that have been derived on the basis of input from the Organizations,

including the professional judgment of the U.S. Fish and Wildlife Service (USFWS). The Army's

professional judgment is that these factors are sufficiently conservative to be protective of healthy

animals, including healthy sensitive subpopulations. The emphasis is on "healthy" because the

Army cannot predict the risk to animals that are affected by environmental stressors beyond the

control of the Army (e.g., climatic changes, bacterial and viral infections).

Comment N . 2

Additionally, the Service strongly objects to introducing new information regarding the Food Web

Model developed in the Onpost EA without a formal review of that information. Specifically,

information is presented in this document regarding the input parameters identified as Maximum

Allowable Tissue Concentrations (MATCs), Bioaccumulation Factors (BAFs), Bioconcentration

Factors (BCFs), etc. which the Service has not yet had an opportunity to review. Introduction of

this material justifies a delay in the finalization of this document until all Food Web Model input

parameters and calibrationlvalidation processes have been adequately reviewed and subsequent

comments have been addressed.

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0504112092 VIII - 31
Response

This comment has been addressed through the dispute resolution process (see Attachment A). The

Army and Organizations have agreed to use the revised food web modeling parameters presented

in the final EA/FS Ecological Assessment (Volume 111, Section 5.0 and Volume IV, Appendix H).

The Army agreed to incorporate the values with the understanding that they represent conservative values based on interpretations of literature data and may not be representative of sitespecific conditions present in the Offpost OU.

Comment No. 3

Furthermore, in reference to Food Web Model input parameters, the Service has serious concerns

regarding the incorporation of some of the proposed MATC and BAF values. In particular, the

dieldrin MATC is too high and some of the BAFs have extremely high standard deviations which

can encompass a wide range of values. Additionally, the appendices provided in the document are

incomplete and therefore the Biornagnification Factors cannot be correctly derived using the

available information. The Service will be providing further comment on these concerns at a later

date after a thorough review of this information has been completed.

Resvonse

Refer to the response for USFWS Comment No. 2

Comment No. 4

Finally, the Service is concerned that sediment contamination will not be adequately addressed in

the Feasibility Study. Specifically, the Service is concerned regarding the high level of dieldrin

(370 mglkg) found at one site along the north boundary of the Arsenal. In response to our

Specific Comment #10, the Army slates that "this sample was collected from a groundwater seep

away from the main channel of First Creek and, as such, is not representative of First Creek

sediment". While this may be true, it does not abrogate the potential need for remediation at this

site, particularly as it can be attributed to Arsenal contaminants. Other issues regarding sediment

which the Service previously commented on in the draft document appear to have been addressed in

the response to our comments.

Response

Section 2.2 in Volume V of the EA/FS describes the PRG development methodology and

compares both cumulative offpost risks and individual media risk to the acceptable risk range.

The risk corresponding to the sediment medium is a maximum of 8 x 10-7 . Remedial action

objectives were therefore not developed for the sediment medium. See response to EPA General

Comment No. I Endangerment Assessment.

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0504112092 VIII - 32
COLORADO DEPARTMENT OF HEALTH COMMENTS REGARDING

THE ENDANGERMENT ASSESSMENT/FEASIBILITY STUDY FOR ROCKY

MOUNTAIN ARSENAL OFFPOST OPERABLE UNIT - DISPUTE ISSUES

GENERAL COMMENTS

Comment No. I - Develot)ment of PRGs

a) Use of Health Based Criteria (HBCs) to develop Preliminary Remediation Goals (PRGs).

The parts of the EAIFS that deal with derivation of PRGs have become even more confusing

than in the previous draft. We request that the relevant sections of this document be rewritten

to permit public understanding and to enable more focused review by the parties. Despite our

basic inability to duplicate or follow the Army's process, the State has managed to glean the

following problems with the approach:

Some (but not all) of the soil HBCs (shown in Volume V, Table 2.4.5-1) are different from

those in the draft final text. The Army has used a different methodology for deriving the

HBCs of carcinogens (described in Volume II Appendix C) and our efforts to reproduce the

ArmY's new HBC numbers have not been successful.

The soil PRGs are even further complicated by the Army's footnote to Volume V

Table 2.4.5.5-1 that "[s]ome preliminary remediation goals are different than HBC presented

in Table 2.4.4-1. PRGs were adjusted based on observed contaminant distribution and with

the intent of achieving low aggregate risk." The meaning and effect of the second part of the

footnote are not clear. Which PRGs received this treatment, how were they adjusted, and why?

The soil HBC listed in Volume V Table 2.4.5-1 for the "Adjusted Residential" RME of

Aldrin and Dieldrin are 31 ppb and .5 ppb respectively. The two compounds have very similar

transport and toxicological properties. We request an explanation of why their HBC differ by

a factor of over 60.

In an effort to make the derivation clearer, we request that the Arm), include the following in

its final version of the EAIFS.

i. A flow chart detailing the hierarchy of choices and standards which were employed in the

derivation of the PRGs for each medium.

ii. A complete set of HBC for the COCs in each medium.

iii. An appendix in which the actual values are written, detailing step-by-step derivation of

the HBC and PRG if different from the HBC. This appendix should start with the

chemical's slope factor andlor reference dose and detail the effects of adjustment for

multiple media exposure, common organ toxicity, etc. If the method of proportions is

used, we request that the details of that step be included, too. We request that this be done

for each of the groundwater COCs that do not have ARARs (11 compounds) or have

PRGs that are different than ARARs, and the soil COCs (5). We also request that this

derivation be detailed for the surface water and sediment PRGs.

Rest)onse

Volume V, Section 2.0 has been significantly revised to include additional detail concerning

development of PRGs in light of comparison of cumulative Offpost OU risks to the NCP

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0504112092 VIII - 33
acceptable risk range. Additional detail is also presented in this section concerning risk associated

with individual media in the Offpost OU, based on the risks presented in Volume 111, Section 4.0

of the EA. As discussed in detail in Volume V, Section 2.2, the cumulative Off post OU hypothetical cancer risk is a maximum of 3 x 10-4 based on risks presented in the EA. As discussed

extensively in Volume V, Section 2.2, Offpost OU remedial action is not warranted because the

offpost OU cumulative risk is within the NCP acceptable risk range. Also as discussed in

Volume V, Section 2.2, the Army recognizes that there are several site-specific factors that, when

considered in totality, suggest remediation of groundwater is preferable to no action in the

Offpost OU. The above- referenced sections of text concerning PRG development explicitly state

the risks corresponding to the groundwater, soil, surface water, and sediment media. Also,

justification is given for the conclusion that soil, surface water, and sediment media do not

require development of remedial action goals. Remedial action goals were developed for the

groundwater medium as discussed in Volume V, Section 2.2, consistent with the methodology

presented in detail in Volume VII, Appendix C. Appendix C explicitly describes the development

of PRGs, considering the effects of multiple chemicals within the groundwater medium.

See response to Part I given above.

As described in the response to Part I given above, soil PRGS were not developed.

See response to Part I given above.

The development of PRGs for groundwater medium explicitly accounts for the effects of multiple

carcinogens within groundwater. This information is presented in Volume VII, Appendix C.

b) Use of a 10-6 point of Deqarture. Despite its assertions to the contrar ' y, the Army appears not

to have followed the express prescription of the NCP, cited both in the revised document itself

and in the Army's responses, that a 10-6 point of departure be used in the development of

PRGs. In response to State comments, the Army claimed that it had used a 10-6 point of

departure, but later arrived at a 10-4 risk level PRG after reviewing a "number of elements

and criteria" related to the selection of health-based criteria and determination of PRGs.

(Arm , 1, response to CDH Cover Letter Comment No. 1; see also Response to CDH Cover Letter

Comment No. 3). Unfortunately, there is not enough information presented in either the

document or the responses to comments to enable a reviewer to reproduce and understand the

Army's analysis and decision making. This omission makes an objective review difficult.

The end result, however, indicates that the prescription of the NCP has not been followed.

The Arm ' v states in Volume V of the revised text that "in accordance with the NCP,

Section 300.430(e)(1), PRGs were developed considering ARARs, HBC, factors related to

technical limitations (e.g. detection limits), background concentrations, land use and ecological criteria." (40 C.F.R. Part 300.430(e)(i)). Absent from? the Army's anal * vsis (with the

exception of the cursory and confusing treatment of arsenic in Appendix C) is any detailed

discussion of the determination of background contamination levels and their incorporation

into the development of the appropriate PRGs. In fact, in response to State comments

objecting to the determination of background levels in soils and groundwater, the Army

specifically assured us that its background estimations would not be used to establish PRGs.

(See CDH FS Specific Comment No. 7 and the Army's response to Cover Letter Comment

No. 8(d)). This, and other statements, therefore, contradict the assertions in the responses to

comments. Please clarify whether the Army's background calculations were used in the

derivation of PRGs. The State has previously objected to the ArmY's locations of background

sample sites. (See State comments offpost R.I. as well as pri .or comments on the proposed

offpost EAIFS).

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0504112092 V111 - 34
Also absent from the EAIFS is an adequate explanation justifying the deviation from the

10-6 point of departure. All that is provided in a cursory discussion of groundwater CRLs.

There is no explanation of how the Army arrived at soil HBCs which do not correspond to the

PRG point of departure risk level. Since groundwater CRLs are irrelevant to soils PRGs,

some explanation is needed to justify the higher risk levels selected for soils in zones 1, 2, 5

and 6.

Response

As discussed extensively in Volume V, Section 2.2, development of PRGs for the groundwater

medium was performed consistent with the methodology described in the NCP. Groundwater

HBC were calculated at the 10-6 level for carcinogens when ARARs were not available and at a

HI of less than 1.0 for noncarcinogens without ARARs. These criteria were used as a basis for

developing PRGs for groundwater. The NCP states departure from 1 0-6 may be appropriate,

considering various factors, including but not limited to exposure factors, uncertainty factors, and

technical factors. Exposure factors evaluated by the Army in the EA included cumulative of

multiple contaminants, multiple pathways, population sensitivities, potential impacts on

environmental receptors, and cross-media impacts. Additionally, uncertainty factors that evaluate

the effectiveness of the alternative, the weight of scientific evidence concerning exposures and

cumulative health effects, and the reliability of exposure data were also evaluated by the Army in

the EA/FS. Finally, the Army also evaluated technical factors in the selection of PRGs, consistent

with the NCP, including detection and quantitation limits, technical limits to the remediation, and

the ability to monitor and control movement of the contaminants. In summary, the Army's

approach to groundwater PRG development, as described in Volume V, Section 2.2, is fully

consistent with the approach described in the NCP.

c) Land Use. It appears that the Army has modified portions of the document addressing the

land use issue for zones 3 and 4 of the offpost operable unit area to clarify that it is not

basing its decision on the assurances offered by Shell Oil Co; rather, it is relying on land use

forecasts contained in the documents cited in response to Stale FS General Comment No. 1,

page 65. The State essentially has two problems with this approach. First, by choosing to

remediate only to levels protective of commerciallindustrial or recreational uses, the Army is

ignoring the fact that current use of the land is, (or would be but for the fact that Shell

acquired the property), rural residential. (See also, Figure 2.4.5.5-1, "Offpost Operable Unit

Current Land Use Aýap, 1991" which clearly indicates that, but for the acquisition of land by

Shell, the zones are currenlly used for "General agriculture", "Exclusive Rural Family" "Rural

Subdivision (10 acres minimum)" and "Irrigated Farming"). Second, projected uses as

forecasted in the cited documents do not define all reasonable potential uses; they merely

identify predicted or desired development.

Regarding the first issue, as previously pointed out, the NCP preamble states that "...the

baseline risk assessment should consider both actual risks due to current conditions and

potential risks assuming no remedial actions" (55 Fed. Reg. 8710). Potential carcinogeni .c

risks to people living and consuming vegetables in zones 3 and 4 would exceed I x 10 6 ,

thereby indicating that soil remediation is appropriate. The Army and Shell, as liable parties,

cannot avoid cleanup by merely restricting access to contaminated media.

Regarding the second issue, we believe the Army has misconstrued the intent and language of

the NCP addressing future land use. Future land use considerations are not intended to

eliminate pathways and reduce exposures, rather, they are mandated so that a remedy

selected today will be protective of people exposed, perhaps to a greater degree, in the future.

The provision is meant to be inclusive, not exclusive.

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0504112092 VIII - 35
Furthermore, the Army does not consider whether rural residential land uses represent "reasonably expected exposures" as required by the NCP, (see 55 Fed. Reg. 8710). Instead, in

the Army's own language, they are determined not to be "a likely probability." (See Response

to State FS General Comment No. 1.) These are very different tests. Thus, the Army has

failed to follow the prescriptions of the NCP regarding utilization of land use forecasts.

Factually, the Army's future land use assumptions ignore several important considerations.

The first and most obvious consideration is that the land use forecasts relied on by the Army

explicitly state that a considerable portion of zones 3 and 4, including section 13, are either

currently zoned for residentiallagricultural use or are forecasted to be. (Volume V,

Figures 2.4.1-2 and 2.4.5.5-1).

The exact basis of the Army's "expectation" that commercial and industrial development will

occur in the proximity of the new Denver Airport is also unclear. Stapleton International

Airport has an extensive residential community bordering the airport and extending well into

the Denver metropolitan area. Roadways leading to and from the airport, through these

residential areas, are often four lane divided highways. The Army's basic assumption that a

widening of 96th Avenue, coupled with expected commercial development, will prevent

residential use in zones 3 and 4 defies simple observation of existing land use conditions

around the existing airport.

The Army's suggestion that in the event of residential development, provision of alternative

drinking water will eliminate any potential exposure, begs the question of whether residential

land use is a reasonable potential use. If so, PRGs must be established accordingly and

alternatives developed to meet these PRGs through remediation to the maximum extent

practicable.

Remonse

The topic of this comment was addressed during the dispute resolution process. Refer to

Attachment A for additional information contained in the dispute resolution letter. On the basis

of dispute resolution, all Organizations agreed to use a single land use scenario for each zone

within the Offpost OU. Zones 1, 2, and 6 were classified as rural residential, zones 3 and 4 as

urban residential, and zone 5 as commercial/ industrial. The land use scenarios and potential

exposure pathways were further defined as follows:

A. Rural Residential (EA/FS zones 1, 2, and 6)

meat* (75 percent)

dairy* (75 percent)

egg (only evaluated dieldrin)

vegetable* (40 percent)

groundwater (ingestion)

groundwater (inhalation)

soil (dermal)

soil (ingestion)

sediments (dermal)

surface water (dermal)

B. Urban Residential (EA/FS zones 3 and 4)

vegetable* (40 percent)

soil (dermal)

soil (ingestion)

sediments (dermal)

11788,903 - CR-03

0504112092 V111 - 36
surface water (dermal)

groundwater (ingestion)

groundwater (inhalation)

*All percents indicate amount of consumption from local sources.

Risk estimates for Zones 3 and 4 will be presented in two manners:

1. As a baseline risk assessment for all media per EPA guidance. The groundwater

portion of the risk assessment will be based on the calculated risks from 1989 to 1991

groundwater data in those zones.

2. The second risk calculations will be based on the continuing beneficial effect of the

onpost boundary system operations in a 30-year timeframe. The text will state that

these are the expected potential exposures for individuals in those zones and the risks

associated with those exposures.

C. Commercial/Industrial (EA/FS zone 5)

soil (dermal)

soil (ingestions)

groundwater (ingestions)

groundwater (inhalation)

If SACWSD provides appropriate documentation indicating that SACWSD is not planning

to install future water wells in zone 5 over the next 30 years, the groundwater pathway

will be removed from zone 5. Attachment A to this set of responses to comments is a

letter from SACWSD to the Army, providing documentation that SACWSD does not

intend to install water-supply wells in the future in zone 5.

d) Groundwater PRGs. The Stale objects to the following PRGs for groundwater.-

Chemical PRG Source CBSG

aldrin .05 CRL .002

carbon tetrachloride .99 CRL .3

chloroform 15 HBC

6

1,2-Dichloroelhane 1.1 CRL .4

dieldrin .05 CRL .002

manganese 200 CBSG (agric) 50 (secondary drinking)

(Table 2.4.4.3-1, Offpost PRGs for Groundwater; all values are in micrograms per liter).

i. Man--anese ARAR. This table lists the groundwater PRG for manganese as 200, according to the Colorado Basic Standards for Ground Water (CBSG). While this number is

correct for agricultural uses, the CBSG secondary drinking water standard for manganese is 50 ppb. The PRG must be adjusted to reflect this lower number. (5 CCR 1002-8,

Part 3.11, Table 2.)

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0504112092 VIII - 37
ii. Chloroform ARAR. The Army has refused to recognize the State chloroform standard of

6 as an ARAR on the grounds that it is not generally applicable throughout the State since

municipalities exceed the standard. The Army is incorrect in its assertion. In promulgating the Basic Standards for Regulation of groundwater, the Water Quality Control

Commission was clear in addressing the general applicability of the standards. The

Commission stated: "...The purpose of the adoption of the statewide standards is L(Z

provide a statewide baseline of protection by establishing standards that will apply

broadly to Colorado ground waters, for certain toxic organic pollutants and radioactive

materials." (Emphasis added).

Under 121(d)(4) ARARs may be waived if they are found to be inconsistently applied.

(See also 40 C.F.R. §300.430 (f)(1)(ii)(C)(5)). However, according to the NCP, a State

standard "is presumed to have been consistently applied unless there is evidence to the

contrary". (55 Fed. Reg. 8749.) It is the burden of the President, and not the State, to

submit substantial evidence that the State standard has been inconsistently applied. The

Army has not'met this evidentiary standard with its cursory response to CDH Feasibility

Study Comment 4(d) and CDH Appendix A Comment No. 16.

iii. The other chemicals have PRGs based oil the Army's detection limits which are higher

than the State's health-based standards. As previously asserted, the State's health-based

standards are applicable to the remedial action and must be achieved or waived pursuant

to CERCLA 121(d)(4).

iv. CRL methodolozv. The State has at least since 1987 consistently objected to the Army's

use of its Certified Reporting Limit (CRL) methodology because it results in detection

limits that are higher than EPA method detection limits (MDLs) and, in some instances,

exceed health-based levels. The State again raised this issue in its comments on the

Offpost Operable Unit RIIEAIFS Workplan, January 26, 1990 in which detection limits

for a number of the above-listed chemicals were identified as exceeding health-based

levels. With the exception of carbon tetrachloride, it appears that the Army has been

unsuccessful at lowering its CRLs. Given the fact that lower detection limits are

practicable, the Army has not justified its deviation from a 10-6 point of departure based

on the limitation of its CRL methodology.

v. Arsenic. Arsenic is a unique problem. Although the Army's CRL of 2.35 ugll does not

exceed the MCL this ARAR, as acknowledged in the Army's response to EPA General

Comment No. 1, falls outside of the risk range provided for in the NCP. See "EPA Risk

Assessment Forum Special Report oil Ingested Inorganic Arsenic: Skin Cancer:

Nutritional Essentiality," EPA, July 1980. As previously pointed out by the State, a

concentration representative of a 10-r' risk level would be .023 ugll (State Comments oil

Draft ARARs for the NWBS Long-Term Improvements IRA, submitted 03106191) which

is two orders of magnitude lower than the CRL. Therefore, for this compound, a lower

detection limit and PRG is appropriate.

Response

Response to Comment d) i. - Secondary drinking water standards are nonenforceable standards

and are not ARARs.

Response to Comment d) ii. - The ARARs analysis presented in Appendix A of Volume V11

describes the ARARs selection process and the treatment of the CBSGs. Based on language

presented in the CBSG Statement of Basis and Purpose and on EPA guidance, the CBSGs are not

ARARs.

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0504112092 VIII - 38
Response to Comment d) iii. - CDH has referred to previous documentation provided by the

Army regarding the Army's CRLs as compared to other detection limits.

Response to Comment d) iv. - See response to Comment d) iii presented above.

Response to Comment d) v. - See response to Comment d) iii presented above.

Comment No. 2 - Use of Groundwater Model

The Army's responses to comments on the development, use, and reporting of the groundwater model

fail to address the State's concerns regarding the absence of calibration of the transport model, the

absence of sensitivity analyses to quantify the model's uncertainties, the omission of the unconfined

portion of the Denver Formation, and the poor presentation of the results (no spatial presentation of

plumes at different points in time, and no analysis of the removal rates of contaminant mass as a

function of each simulated remedy). We, therefore, can have no confidence in the modeled results

or in the Army's interpretation of the results: nor are we assured that the optimal injectionl

extraction well locations were even considered.

The Army's response was, in essence, that the model was only to be used to estimate the relative

effectiveness of the various remedial alternatives and that a rigorous modeling exercise was not

justified at this time. The Army further implied that a rigorous modeling exercise is only

warranted when data are obtained from the performance monitoring of the installed remedy. A

model is useful during performance monitoring to update predictions on the installed remedy's

ability to achieve goals within an acceptable timeframe; however, now is the time for a good, sound

modeling exercise, before spending millions of dollars on an inappropriate remedy, and before

rej .ech .ng more aggressi .ve and effective remedies on the basis of projected initial capital outlay.

Rest)onse

Calibration of the transport models would require a large amount of data that is not available for

the systems studied in the Offpost OU. Specifically, data that would be required include

hydraulic heads near the likely sources of contamination at RMA during and soon after the years

that contamination occurred and historical information regarding plume configuration as a

function of time, covering the period commencing with the years that contamination occurred.

The groundwater flow models have been approximately calibrated to time-averaged conditions

during the 1980s, long after the major hydraulic effects of recharge in Basins A through F had

occurred. This fact is what permits the flow model to be based on hydraulic conditions observed

in recent years. The lack of comprehensive head data before the 1980s severely limits the

possibility of viable transport model calibration. For sensitivity analyses to be performed

effectively, the sensitivities of selected parameters, such as hydraulic heads, to model parameters,

such as hydraulic conductivities, should be calculated directly using the calibrated flow model.

These sensitivities would be optimally determined through simultaneous application of automatic

calibration techniques. As stated in Volume VII, Appendix E, the FS models were intended to be

only approximate and, consequently, were not calibrated with an automatic inverse technique.

The Army reconfirms that the groundwater modeling effort conducted is fully sufficient for

purposes of analyzing the relative differences between competing groundwater alternatives. As

stated in Volume VI, Section 5.2, significant effort has been expended to produce models that

incorporate general features of groundwater flow and associated transport phenomena.

Nonetheless, the models are sufficiently detailed that predicted flow and chemical transport

phenomena in the Offpost OU agree with historical and current hydrogeologic data and observed

contaminant distributions.

11788,903 - CR-03

0504112092 VIII - 39
Maximum concentration versus time plots was used because this approach gives a conservative

estimate of remediation timeframes. The location of selected points used at each time step in the

graph reflects the maximum concentration observed within the entire model area. Selection of the

point with maximum groundwater contamination assures that remediation timeframe estimates are

based on a time when no point within the model area exceeds PRGs. This method is fully capable

of comparing the relative effectiveness of remedial alternatives, which is the intent of the

groundwater modeling.

Comment No. 3 - Use of Cost Analysis to Eliminate Alternatives

The Army's selection of no additional remediation other than the currently planned IRA intercept

system is not sufficiently justified in accordance with the selection criteria in the NCP and

CERCLA. The improper reliance on land use projections, the inappropriate analysis of cost

effectiveness, and the utilization of an inadequate model result in violations of these cleanup

prescriptions. The land, use and model issues have been addressed in comments Ic and 2 above.

The State has several concerns with the Army's elimination of alternatives based on time and cost

considerations. For example, N-6 and N-5 were eliminated because 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, provide for a shorter remedialion

timeframe, and be equally or more cost effective in the long term than the selected alternative.

To emphasize short over long term costs in such a manner is not in accordance with the NCP. In

fact, the EPA specifically eliminated language requiring such an analysis from its proposed rule.

(55 Fed. Reg. 8728-29). In doing so, the EPA found such an analysis "too narrow" and not

reflective of overall effectiveness which "involves a composite of effectiveness factors, i.e. long

term effectiveness and permanence, toxicity, mobility or volume reduction through treatment and

short tern? effect i veness. " Id. Thus, the Army's elimination of alternative N-6 based on increased

capital costs when the total present worth costs are "essentially equivalent" to alternative N-5, and

the elimination of alternative N-5 for which total present worth costs are actually less than the

selected alternative, contravenes the NCP and CERCLA prescriptions to utilize permanent treatment

solutions to the maximum extent possible and be cost effective.

NW-4, an alternative which would provide substantial improvements to the Northwest Boundar , y

Containment System (NWBCS), was also eliminated based on projected remediation timeframes

which, by the Army's own admission, were inherently uncertain. By failing to construct a reasonabl * v

reliable model at this time. the Army is precluding its ability to perform an accurate and objective

cost- effectiveness analYsis in accordance with CERCLA and the NCP.

Response

CDH has misinterpreted the analysis of groundwater alternatives presented in Sections 4.0, 5.0,

and 6.0, in Volume V1. As presented in these sections of the FS, the analysis and comparison of

remedial groundwater alternatives focuses on effectiveness, implementability, remedial timeframes, reduction of toxicity, mobility and volume, compliance with ARARs, overall protection

of human health and the environment, and cost considerations. The alternatives studied present a

wide range of levels of complexity in terms of remedial components, total flow rate from

extraction wells, total numbers of recharge trenches, total linear feet of recharge trenches, and

selected location of remedial components with respect to observed plume distribution.

The Army strongly disagrees with EPA's contention that an aggressive groundwater alternative

was not evaluated in the Offpost FS. As discussed in Volume VI, Section 3.0, Development of

Remedial Alternatives, and Volume VI, Section 6.0, Detailed Analysis of Remedial Alternatives,

11788,903 - CR-03

0504112092 VIII - 40
the offpost geology, hydrogeologic systems, contaminant distribution, and contaminant transport

properties were studied extensively, both analytically and using a groundwater numeric model.

The modeling effort is described in both Volume VI, Section 3.0 in terms of development of

remedial alternatives and extensively in Appendix E of Volume VII.

The results of this analysis are presented in a lengthy discussion in Volume VI, Section 3.0. The

controlling hydrogeologic and contaminant transport properties of the Offpost OU groundwater

system include (1) groundwater seepage velocity of the First Creek pathway relative to the

northern pathway, (2) the distribution of the relatively less mobile compound dieldrin compared

to the distribution of more mobile compounds such as DIMP and chloroform, and (3) the

controlling transport properties of dieldrin as compared to the transport properties of DIMP and

chloroform. As described in Volume VI, Section 3.0, Alternative No. N-4 for the North Plume

Group was developed through a combination of analytical well field simulation, knowledge of

contaminant distribution and contaminant transport properties, and hydrogeology of the North

Plume Group.

A transverse capture system for the northern pathway was chosen to intercept contaminants

moving in the northern pathway. An axial system of collection wells and recharge trenches was

selected in the First Creek pathway. Alternative No. N-4 consists of a total of 17 walls and

6 trenches with a total extraction flow rate of approximately 480 gpm. Alternative No. N-5 has a

total of 20 extraction wells and 12 trenches. Alternative No. N-6 has a total of 4 extraction wells

and 19 trenches. The total linear feet of recharge trenches ranges from 1500 feet in Alternative

No. N-4 to approximately 4400 feet in Alternative No. N-6. The total extraction flow rate ranges

from 480 gpm in Alternative No. N-4 to a total of 690 gpm in Alternative No. N-6.

The increasing complexity of Alternative Nos. N-5 and N-6 as compared to Alternative No. N-4

was evaluated to assess the impact of adding a number of additional extraction and recharge

trenches in areas where contaminants were remaining in areas of slower relative groundwater

velocity and tighter aquifer materials, and to address less mobile contaminants.

The level of aggressiveness of Alternative Nos. N-5 and N-6 reached a practical maximum

whereby the maximum practical number of additional extraction wells and recharge trenches was

evaluated for remediation timeframe and aquifer drawdown considerations. Model-estimated

groundwater mounding and drawdown resulting from the recharge trenches and extraction well

arrays reached practical limits in Alternative Nos. N-5 and N-6. The discussion presented in

Volume VI, Section 3.0 gives specific information demonstrating the distinct differences in level

of complexity and aggressiveness of the remedial alternatives studied in the EA/FS.

The Army has not used short-term cost as a basis for rejection of Alternative Nos. N-5 and N-6.

As discussed in Volume VI, Section 5.0 and 6.0, the primary reasons for selecting Alternative No. N-4 over Alternative Nos. N-5 and N-6 are summarized below. With respect to longterm effectiveness and permanence, these alternatives are essentially equivalent. All the alternatives would reduce hypothetical risk and address exposure pathways through reducing COC

concentrations in the North Plume Group. Due to inherent uncertainties in groundwater

modeling, predicted differences between treatment alternatives in the time to achieve PRGs may

not be significant.

With respect to reduction in toxicity, mobility, and volume, all the alternatives would reduce the

toxicity, mobility, and volume of contaminated groundwater through extraction, treatment, and

recharge in the North Plume Group. As stated previously, the uncertainty associated with the

remediation timeframes estimated by the groundwater modeling suggests that, in practical terms,

the estimated timeframes for the alternatives are equivalent.

11788,903 - CR-03

0504112092 VIII - 41
With respect to overall protection to human health and the environment, all the alternatives would

provide significant protection of human health and the environment by decreasing contaminant

concentrations and reducing hypothetical risks within the same approximate time. These

alternatives are essentially equivalent with respect to providing protection of human health and

the environment because the short-term intensive groundwater monitoring program proposed

under Alternative No. N-4 would provide full-scale system performance information that could

be used to identify any necessary or beneficial improvements to the system and to provide

information on optimal location of these additional systems.

See response to CDH Comment No. 3 Parts I and 2, above for information on evaluation of

alternatives.

Sections 4.0, 5.0, and 6.0 in Volume VI of the FS present information concerning the relative

differences between Alternatives Nos. NW-2 and NW-4. As stated previously, the groundwater

model is fully capable of analyzing relative differences between competing alternatives. See

responses to Parts 1, 2,,and 3 of Comment No. 3, above.

Comment No. 4 - Selection of the N-4 Alternative

The State cannot agree that N-4 is superior to N-5 because N-4's short-term intensive monitoring

will "...identify any necessary improvements to the system..." and because "[u]ncertainties inherent

in the groundwater modeling results make the prediction of remediation times imprecise."

(Section 5.5.1.1). Short-term performance monitoring should logically be a part of any remedy to

accomplish the first goal stated above. The short term monitoring program proposed by the Army

(See Draft Final Monitoring Plan for the Groundwater Intercept and Treatment System North of

the RMA, IRA, February, 1992) should also apply to all of the alternatives selected for evaluation.

The State has submitted comments addressing the proposed monitoring plan and incorporates its

comments by reference (See CDH Letter from Edson to Blose, March 4, 1992).

The Army's second reason (as stated above) for not selecting remedies more aggressive than N-4 is

inconsistent with their response that more aggressive remedies for the DIMP plume along First

Creek and the dieldrin plume along the Northern Pathway are not needed because the model

predicts that PRGs will be achieved it? 5 to 15 years and 30 years, respectively. Either the predicted

remedial timeframes are reliable or they are not. The State agrees with the formula statement that

acknowledges that the actual timeframes for remediation are unknown. Simple logic, however,

suggests that a more aggressive remedy along the plume's axis (N-5 and N-6) will remediate the

plume faster and therefore would be a more desirable alternative.

In addition, although the Army adopts 2.35 ugll as its PRG for arsenic, it is not clear that the

selected remedial alternative will achieve this level. Plume maps indicate detections of arsenic

along the First Creek pathway exceeding the PRG: however, the chosen carbon filtration treatment

technology does not treat arsenic. As arsenic is a major contributor to the carcinogenic risk posed

by exposure to this groundwater, treatment alternatives for arsenic must be added to the design of

the treatment facility.

Resr)onse

See response to CDH Comment No. 3, above.

See response to CDH Comment No. 3, above.

11788,903 - CR-03

0504112092 VIII - 42
Estimation of anticipated influent concentrations of contaminants for the alternatives studied in

the Offpost FS indicate that the PRG for arsenic will not be exceeded in the influent to a

treatment plant.

Comment No. 5 - Preferred Alternative for the Northern Plume

As stated in our previous comments, the preferred alternative for the Northern Plume ignores current

and forecasted land use in an area that will contain contaminated water exceeding ARARs. The

area the plume migrates through is, according to the Army's current and forecasted land use maps,

subject to residential use. (See Volume V, Figures 2.4.5.5-1 "Offpost Operable Unit Current Land

Use Map, 1991": and 2.4.1-2 "Offpost Operable Unit Future Land Use" and the corresponding

residential zoning designations for section 13). rhus, use of the unconfined alluvial aquifer as a

source of domestic water is a reasonable possibility. ro suggest, as the Army has in its response to

the Stale's concern, that rapid restoration is unnecessary because contaminated waler is not now

used as a drinking water source, and because potential future users would be put on alternative

water supplies, ignores the prescription of the NCP which requires the rapid restoration of current

and potential drinking water sources. (55 Fed. Reg. 8732). Alternatives that would address

groundwater remediation within the plume migration area should be considered.

Response

The preferred alternative for the Northern Plume Group is fully consistent with the most likely

future land use scenario presented in the Offpost EA/FS. The most likely future land use scenario

is rural residential for zones 1, 2, and 6; urban residential for zones 3 and 4; and commercial/

industrial in zone 5. As stated previously in Sections 4.0, 5.0, and 6.0 in Volume VII and in

response to Comment Nos. 2 and 3 above, Alternative No. N-4 is demonstrably superior to

Alternative No. N-5.

Comment No. 6 - Ot)erable Unit Areas Not Included in EA/FS Evaluations

rhe Army's response to concerns that a significant portion of the Offpost OU area was not

evaluated in the EAIFS was to state that the remaining areas "were not determined to be affected

by RMA related contamination" despite the fact that the Offpost OU "as described in the Federal

Facility Agreement (FFA), is where hazardous substances, pollutants, or contaminants from RMA

are located" (Arm), responses to CDH Cover Letter Comment No. 3, EPA Cover Letter Comment

No. 7, and EPA General Comment No. 1). rhe Army also pointed out that concent rat ions detected

in these areas were less than one half of the dieldrin PRGs.

No information has been included in the EAIFS (or in the Offpost RI Addendum) discussing or

interpreting the existing data to determine the source of contamination. rhe Army needs to

document why it is excluding from the EAIFS process nearly one half of the Offpost OU area. An

analysis must be supplied for those areas outside of zones I through 6, particularly where the

cumulative risks from RMA contaminants exceed a 10-6 risk level. Such a presentation is necessary

before the State could concur with such conclusions.

The Arrnv's dismissal of dieldrin detections identified by the State oil the grounds that they do not

exceed týe Army's PRG ignores the fact that PRGs are supposed to be developed based oil a 10-6

point of departure. No justification for deviating from the point of departure is offered: therefore,

remedial alternatives must be developed to achieve this risk level in these areas.

11788,903 - CR-03

0504112092 VIII - 43
Resoonse

The Offpost EA/FS divides the OU into six zones. These zones were delineated on the basis of

the known extent of contamination as presented in the Offpost OU RI Addendum report.

Section 2.4.1 in Volume II of the EA describes in detail the rationale and the database evaluated in

delineating the zones to be studied in the Offpost EA/FS. Each of these zones was delineated on

the basis of distinctions in exposure conditions. The primary factor used to define the zones was a

pattern of COC concentrations in groundwater. In addition, the spatial pattern of COCs in

surficial soil was also used to set zone boundaries. A broad area extending from the north and

northwest boundaries of RMA to the South Platte River exhibits varying levels of COCs. The

maximum downgradient extent of this contamination area is defined primarily by low levels of

DIMP (i.e., DIMP in excess of CRLs). The existing contaminate distribution in groundwater,

surface water, and surficial soil, as well as differences in land and water use were considered in

mapping six zones where exposures are expected to be distinct from each other. The outermost

boundary defining the six zones is the extent of known contamination associated with RMA,

which is defined as the,Offpost OU by the Federal Facility Agreement.

In response to CDH's contention that no information has been included in the EA/FS discussing or

interpreting the existing data to determine the source of contamination, CDH is referred to

Section 1.0 of Volume I for an extensive four-page discussion detailing the conceptual site model

that delineates the source of contamination to the Offpost OU in groundwater, surface water, soil,

and air.

With respect to CDH's comment regarding the aldrin detections, CDH is referred to Section 2.2,

which discusses the Offpost OU cumulative risk and risk corresponding to individual media as

compared to the NCP-prescribed acceptable risk range. This section of the text describes in detail

the rationale for elimination of the soil medium as requiring development of remedial action

objectives.

Comment No. 7 - Statistical "Hot Soot" Analysis

In its responses to comments, the Army refers to an "additional analysis" that was performed

regarding localized "hot spots" of carcinogenic risk. A more complete explanation of this analysis

is needed in order to understand the Army's decision-making process with respect to the elimination

of "hot spots". This explanation should include the specifics of those areas which were ranked

according to the highest hot spot potential including well identification, soil boring numbers, the

spatial distances between these sample locations, the maximum concentrations in comparison to the

exposure point concentrations, and a calculation of the upper bound aggregate risk at the subsite.

Because residential exposure can be of long duration over a very localized area, results of an

analysis such as the one performed in response to the EPA comment are important to an understanding of potential exposure. The Army has commented to EPA that "[r]isks at localized 'hot

spots' within zones 2 and 3 are less than 2 x 10-3". The State requests that the information which

has led to this conclusion be included in the document and that the results of this evaluation for all

zones be described in the Final version of the EAIFS.

Rest)onse

The "additional analysis" referred to is summarized in the response to EPA General Comment

No. I (March 27, 1992, Volume VIII). The analysis performed at that time is no longer pertinent

to the offpost exposure assessment, however, because the data set used for the assessment has been

revised to include only groundwater data collected from 1989 to 1991, and the previous analysis

was based on older data (1985 to 1990). Further, it has been discovered that some groundwater

11788,903 - CR-03

0504112092 VIII - 44
REFERENCE PAGE FOR 93012RO3

CDH - PAGES 46 THROUGH 5ZARE

NOT INCLUDED IN THE DOCUMENT.
wells used in that analysis and identified as "hot spots" for zone 3 are actually south of 96th

Avenue and not offpost. Our previous analysis provides general support for the conclusion that

localized hot spots would not result in individual risks exceeding zone-RME estimates by more

than a factor of 2.

As described previously in response to CDH General Comment No. 1, a comparison of cumulative

Offpost OU hypothetical cancer risks with the acceptable risk range is presented in detail in

Volume V, Section 2.2. The cumulative Offpost OU cancer risk is a maximum of 3 x 10-4.

Volume V, Section 2.2 also presents several site-specific factors that suggest remediation of

groundwater is preferable to no action in the Offpost OU even considering that the accumulative

Offpost OU cancer risk is within the acceptable risk range. Additionally, the above -referenced

section of the FS presents information supporting the conclusion that soil, surface water, and

sediment media do not require development of remedial action goals because the risk corresponding to these media is low. Because the analysis and calculation of risk performed in the EA

fully considered localized high concentration (hot spots) of contaminants in soil, any additional

analysis of risk corresponding specifically to hot spots is not necessary.

The dispute resolution process resulted in agreement by the Organizations on the most likely

future land use scenarios to be used in the EA. Because the exposure scenarios evaluated in the

EA are different from the exposure scenarios commented on by CDH, this comment is no longer

relevant.

Comment No. 8 - Environmental Remedial Action Obiectives

The Army still has not identified any remedial action objectives nor developed remedial alternatives that are designed to protect the environment as a receptor in and of itself. In its response to

the State's comment, the Army slates that biota ("all plants and animals potentially exposed to

Offpost OU contaminants") was considered in the development of RAOs and that "environmental

receptors" were also considered in the evaluation of certain pathways. (Army response to CDH

Cover Letter Comment No. 5). This response ignores the substance of the State's comment. To

reiterate, the requirement that remedies protect the environment, as well as human health is made

very clear in CERCLA §121(d)(1) and the NCP (40 C.F.R. §§ 300.430 §§ (a)(]) and

(e)(2)(i)(G)). The plain language of CERCLA §101(8)(B) is equally clear in its definition of the

term "environment" (which includes "surface water, groundwater, drinking water supply, land

surface or subsurface strata or ambient air"). Thus, the EAIFS must include a consideration of

measures which are protective of the environment as defined by CERCLA. These receptors should,

at a rninin7um, include.-

a. The surface water medium. Variations in seasonal surface water flow in the First Creek

drainage indicate that surface water runoff is likely to be contaminated fro"? Onpost and

Offpost contaminants. A remedial alternative should be developed to address this medium

as a receptor of contamination.

b. The groundwater medium. There are still no remedial alternatives that address the existing

or potential cross contamination among the Alluvial, Denver and Arapahoe aquifers.

Although the Army has invited the State to submit a list of wells for closure in the offpost

well closure IRA, it has not been receptive to the State's proposals. (See August 2, 1991

Edson (by O'Grady) to Blose letter, re: Criteria for Offpost Abandonment Wells IRA).

There are also no alternatives which protect the alluvial aquifer north of the North Boundary Containment System (NBCS) through section 13 to O'Brian Canal. This area will

contain groundwater exceeding ARARs migrating north from the NBCS. The State will

submit under separate cover a list of wells that should be closed to protect the lower

aquifers from further degradation.

11788,903 - CR-03

0504112092 V111 - 53
Response

Remedial action objectives developed for the Offpost OU consider both human health and

protection of the environment. As described in the response to CDH general comment No. 1,

remedial action objectives were not developed explicitly for the soil, surface water, and sediment

media. However, as described in Sections 5.1 through 5.4 in Volume II, a rigorous ecological

assessment was performed, including the following components:

I . Exposure assessment for biological receptors and sensitive subpopulations included, a risk

characterization for both terrestrial food web ecological risk and aquatic food web

ecological risk, and an ecological risk assessment uncertainty analysis. The results of this

analysis were used in the derivation of ecological criteria presented in Volume 11,

Appendix C, derivation of Health Based Criteria Ecological Criteria.

Data collected in the RI Addendum to characterize Offpost OU surface water in the First

Creek drainage and surface-water bodies leading to Barr Lake are representative of

seasonal changes to be expected in surface-water flow. As stated in the text of the

EA/FS, no remedial action objectives were developed for surface water medium because

neither the human health risk nor the ecological risk corresponding to this medium

warranted remediation.

Data collected during the Offpost RI Addendum program included groundwater samples

from 14 offpost confined Denver Formation wells in the Offpost OU. Additionally,

information concerning the confined Denver Formation groundwater is presented in

Section 3.3.2 of the Final Offpost RI report. As discussed in Volume I, Introduction to

the EA/FS, subheading Nature and Extent of Confined Denver Formation Contamination,

data were examined from fall 1989 and spring 1991 sampling rounds. Analysis of the data

indicated that the detections were not consistent from one sampling event to the next for

the same well. The observed detections are indicative of sporadic, isolated occurrences of

contaminants in the Offpost OU confined Denver Formation. A similar analysis of

available data was performed for the confined Arapahoe Formation. Approximately 30

Arapahoe Formation wells were sampled by the Army with two isolated detections of

DIMP and chloroform observed. A majority of samples collected from the Arapahoe

Formation did not contain detectable concentrations of contaminant.

Comment No. 9 - Surface Water in First Creek

Several State comments were presented to the Army concerning the exclusion of surface water from

the FS. The Army has not responded to these comments salisfactoril ' y. The selected remedial

alternative depends on the validity of the assumption that PRGs will not be exceeded at the

boundaries of RMA. However, the Army's data call this conclusion into question. The Army

concludes from four sampling events at the north boundary of RMA at site (SW24002) that it is in

compliance with PRGs. However, these samples, which apparently are not representative of storm

events, are totally inadequate for the characterization of a surface water flow which is highly

variable both in quantity and in quality. The State's FS General Comment No. 17 quotes from the

R1 stating that chemical concentrations in First Creek are significantly higher during storm events.

The Army's response to the State's FS General Comment No. 7, similarly states that "[tjhe

secondary source of surface water in First Creek offpost is watershed runoff." These Iwo

statements indicate that contaminated surface water will enter the offpost OU during storm events.

This contamination will not be addressed by upgrading or closing the sewage treatment plant.

Therefore, additional means of verifying that surface water PRGs will be met at the RMA north

boundary must be provided by the Army.

11788,903 - CR-03

0504112092 VIII - 54
Response

Surface water was not identified as a medium requiring development of remedial action objectives

because the risk corresponding to surface water is 5 x 10-7 . Refer to Section 2.2 in Volume V of

the FS and response to CDH general comment No. I for additional information concerning

comparison of Offpost OU cumulative cancer risk to the acceptable risk range and discussion of

individual media risk.

The Army disagrees with CDH's assumption that surface-water data collected is inadequate for

characterization of Offpost OU surface water. Data were collected in the Offpost RI Addendum

program from offpost surface water in 1988, from two periods in 1990, and from the 1988 and

1989 surface-water comprehensive monitoring program annual report. Sufficient data from

Offpost OU surface-water sampling plans was available for characterization of Offpost OU

surface water.

Comment No. 10 - Treatment of Chloroform in the NBCS and NWBCS

The groundwater treatment system at the NBCS appears to effectively remove chloroform from its

influent; however, the treatment system at the NWBCS does not. The State requests that an

evaluation be performed of the two systems to determine what changes are needed to effectively

remove chloroform from the NWBCS's influent, and to ensure that the proposed offpost IRA

treatment facility is operated so as to effectively remove chloroform.

Response

The preferred alternative presented in Section 6.0, Volume V for the North Plume Group and the

Northwest Plume Group has continued operation of the boundary containment system with

modification as necessary to achieve PRGs at the boundary as a major component of the

alternative. Additionally, Alternative No. N-4 contains a provision for modification to be made

to the IRA A system in the future in the event that PRGs are not being met.

Comment No. I I - EA: Human Health Soil Ingestion Data

As previously pointed out in State comments on the onpost soil ingestion parameter values, there is

currently a great deal of scientific discussion regarding the interpretation and useability of existing

soil ingestion data. In recently published articles, Drs. Edward J. Calabrese and Edward Stanek,

through the use of a precision of recovery model developed at the University of Massachusetts,

demonstrated that only titanium and zirconium values from their Amherst study could be considered

reliable. Results from other studies were invalidated by this model. Lately, týe reliability of the

zirconium values have been called into question due to probable loss during chemical analyses. As a

result, new soil ingestion values for children are considered appropriate. Based on the most reliable

data from the use of titanium as a tracer, the median value from the Amherst study would be

55 niglkglday,- the 951h percent value would be approximately 1500 mglkglday. An upper

95th percent value based upon all tracers weighted according to their respective precision of

recovery, (not including zirconium), would be approximately 640 mglkglday. The Slate again

urges the Army to avail itself of the expertise of Dr. Calabrese who is willing to meet with the

parties to discuss appropriate soil ingestion estimates.

Rest)onse

The Army has applied RME soil ingestion rates recommended by EPA for CERCLA baseline risk

assessments. The Army understands that "there is currently a great deal of scientific discussions

11788,903 - CR-03

0504112092 VIII - 55
regarding the interpretation and useability of existing soil ingestion data." It is the Army's

understanding that the thrust of Calabrese's research is that existing studies, including his own

1989 research, have significant design flaws such that the studies do not have sufficient sensitivity

to detect and/or quantify the rate of soil ingestion for most of the study subjects. Based on

Calabrese's concerns, the Army rejected the ingestion rates suggested by CDH because they are

insufficiently supported. Calabrese's research may be able to support the conclusion that soil

ingestion rates are "less than" some value but not to determine the actual ingestion rate. Further,

the published results from all these studies do not provide sufficient detail to define the distribution of ingestion rates and thus, the 90th or 95th percentiles. Calabrese's recent papers focus on

the central tendency of the distribution, such as means or medians, because these statistics are

more reliably estimated from the available studies. Although suffering from the same flaws

identified here, the Army's review of Calabrese and others (1989) and Davis and others (1990)

indicates a 90th percentile of 225 mg/day for children, similar to EPA's recommended RME. The

considerable debate and uncertainty regarding quantification of soil ingestion rates indicate that

EPA guidance specific to CERCLA assessments is the most reliable and authoritative source for

this exposure parameter.

Comment No. 12 - EA: Soil to Epm Partitioning Coefficient

rhe State specifically requested clarification from the Arm ' y regarding derivation of the soil to egg

partitioning coefficient (Human Health Endangerment Assessment general comment number 29,

page 27). While the Army did respond to this comment, it never supplied information detailing how

Kee was derived from the results in the Putnam paper. rhe Army's RME value of .087 would

appear to be about an order of magnitude too low based on the following evaluation.

Putnam added pesticides to soil so that the "Low level soil" of aldrin + dieldrin was 0.068 ppm.

After exposure to these soils, the resulting concentration of dieldrin in bird tissue was 0.037 ppm.

If assumptions derived from Putnam are used (i.e. that aldrin was completely converted to dieldrin,

egg and tissue concentrations are equivalent, and no adjustment for control treatment concentrations

is made), a rough estimate of Kee may be derived as the ratio of soil to bird concentrations,

0.03710.068 = 0.54. rhis i .s approximately an order of magnitude larger than the Army's RME

value for Kee,

rhe State requests that the Army demonstrate how they derived their value and distribution for Kee,

what qualifying assumptions were made, and explain why the number was changed frorn the one

give in earlier EA technical meeting handouts. Absent such information, the Stale cannot assess the

validity of the Army's methodology or have any confidence in the values derived.

Remonse

Terms:

Kee = concentration in epgs

concentration in soil

fps = ration of soil ingestion to feed ingestion

Kpc = concentration in eggs

concentration in feed

if = ingestion of feed

11788,903 - CR-03

0504112092 VIII - 56
19 = ingestion of grain

is - ingestion of soil

Cf = concentration in feed

C9 = concentration in grain

Cs = concentration in soil

Ce = concentration in egg

If = 1 19 + Is (1)

Cf = 19 C9 + Is CS (2)

if if

Cf = 19 C9 + Is Cs (3)

Then

19 + Is

From Putnam, it is calculated that fps Is 3.1% 1.2

Ig

Then Ig >> I. and (3) reduces to

Cf = C9 + Is Cs (4)

19

Then (4) becomes

Cf = 1. C. - fps CS (5)

19

By definition

KpC = Ce/Cf (6)

Substituting for Cf (from [5]) into (6)

KpC Ce (7)

fps Ca

11788,903 - CR-03

0504112092 VIII 57
Thus

Kee ý Ce =fps Kpc (8)

Ce

Kpc is calculated from BAF values

1.13 Cummings and others, 1966

1.5 Kan & Jonker-den Rooyen, 1978a

2.5 Driver and others, 1977

1.67 Graves and others, 1969

1.35 Waldon & Nabor, 1974

1.18 Kan & Jonker-den Rooyen, 1978b

1.67 Kan & Turinstra, 1976

Thus

Kpc = 1.57 + 0.17

Kee = (1.57)(0.031 = Kpc fps

= 0.049

To find RME:

(,I Kee 2 Kpc ) 2 = (,, fps ) 2

Kee Kpc f ps

8Kse 0.049 (0.17 2 + 0.012 2 1/2

1 ý 1 5-7 10.031

0.020

RME = 0.049 = ZOA * 0.02 = 0.049 x 1.96(0.02)

= 0.087

Using this simple ratio of 0.54 for K. from Putnam and others (1974) one is limited to soil

ingestion only when in reality there a;e other pathways of concern. The derivations that follow

lead to an RMA value of 0.087 for Kse5 which accounts for the grain ingestion pathway plus the

incidental soil ingestion pathway.

11788,903 - CR-03

0504112092 Vill - 58
Comment No. 13 - Samr)ling of Deever Aauifers

In the Army's Response to General Comment No. 7, it refers to various sampling programs to assert

that the deeper aquifers have been sufficiently evaluated. The State is aware of the ArmylTriCounty Health Department domestic sampling program initiated last year. While we are pleased

with the Army's decision to monitor domestic use of contaminated ground water, we were never

informed by the Army that the domestic use program would be used to characterize Denverl

Arapahoe aquifer contamination. When the State was asked to comment on the Army's domestic

well sampling plan we were asked to identify residences which appeared to be within contaminant

plumes that had not been sampled previously, not to identify locations where sampling should be

performed to characterize DenverlArapahoe contamination.

In addition, it has always been the contention of the Army that characterization of any ground water

plumes cannot be achieved through sampling of domestic wells. The State's domestic well sampling

program was implemented to identify whether contamination (i.e.; DIMP) exists in the deeper

aquifers. Based upon our results. we had anticipated an Army-initiated monitoring well network to

be installed to better characterize Arapahoe contamination. As was agreed to by all parties years

ago, because of the large screen intervals associated with domestic wells, their use in defining

contamination plumes is inappropriate. The State therefore reiterates its concerns that the deeper

aquifers beneath the offpost operable unit have not ben adequately investigated and inappropriately

omitted from the EAIFS programs.

Response

The Army disagrees with CDH's contentions that deeper aquifers beneath the Offpost OU have

not been adequately investigated. Based on a substantial amount of both confined Denver

Formation and confined Arapahoe Formation well data, the isolated detections observed are

sporadic and not indicative of deep aquifer contamination. Refer to CDH comment No. 8B for

more information on the aquifer characterization.

Comment No. 14 - Surface Water PRG Exceedance

In the response to CDH Cover Leiter Comment No. 1, the Army states that there is no risk attributable to sediment and surface water in zones other than 3 and 4. However, the MaY-June 1990

surface water sampling at Station HAII59SE in Section 12, O'Brian Canal (in zone 2), indicated

exceedances of the commerciall industrial PRGs developed for zones 3 and 4 for DDT and DDE.

The exceedances for these two compounds are not shown on Figure 2.5.3-1 of Volume V (Exceedances of Surface Water PRGs in the Offpost Operable Unit), and are exceedances of surface water

PRGs in the Offpost OU. Please explain this omission and why risks associated with these

exceedances were not considered or mentioned in the text.

Remonse

Refer to CDH comment No. 9. Section 2.2 and Volume V of the FS present risk corresponding to

the soil medium and rationale for concluding that the soil medium does not require development

of remedial action objectives. Refer to response to CDH general comment No. I and Section 2.2

in Volume V for additional information.

Comment No. 15 - Aldrin/Dieldrin Soil HBCs

The Health Based Soil Criteria listed in Table 2.4.5-1 for aldrin and dieldrin under the Rural

Residential Scenario are 31 ppb and 0.5 ppb, respectively. Even if the exposures to these analytes

11788,903 - CR-03

0504112092 VIII - 59
are due to secondary sources, the values should be similar. Given the very similar chemical and

toxicological properties of these two compounds, such divergent criteria (by several order of

magnitude) indicate a flow in the derivation of these values. The State requests that the Army

review its methodology with regard to the soil criteria for these two compounds.

Rewonse

ECOLOGICAL RISK CHARACTERIZATION (ERC) COMMENTS

Comment No. I - Volume VIII. vage 45, Resvonse to ERC General Comment No. 4

The Army asserts that lower trophic level animals will be protected by selected TRVs and by the

revised food web model. We have not yet had an opportunity to complete our review of the new food

web model, as it was only delivered to us on March 18, 1992. The TRVs, however, clearly do not

adequately address the lower trophic levels. Some 87 TRVs have been derived for species that were

selected ýased on the criteria set forth in Vol. II, sec. 3.5.2 (p. 11-3-19). Neither this section nor

Table 3.3.1-1 addresses TRVs for other than avian and mammalian species. No reptilian,

amphibians, nor invertebrate and other lower order species are included. Nor has the Army

considered chemical- specific ecosystem TRVs which would be inclusive of most species in an

ecosystem regardless of whether a species- specific TRV has been derived. The latter approach has

been recommended by van Straalen and Denneman, 1989 and Okkerman et al. 1991, and has

recently been accepted by Germany as the preferred approach to performing ecological risk

assessment.

Rest)onse

The Army has derived TRVs protective of lower trophic organisms as well as nonavian and

nonmarnmalian species. These values are presented in Table 3.3.1 -1 as reference media concentrations for vegetation and aquatic organisms. Species -specific TRVs were not derived for

reptiles, amphibian, or invertebrate species because of the general lack of chronic toxicity data for

these animals. The Army also feels that its chemical/species-specific TRVs provide a more

appropriate measure of potential adverse effects in the ecosystem than chemical -specific

ecosystem TRVs suggested by CDH because of the Army's receptor specificity.

Comment No. 2 - Volume VIII. r)aRe 45. Rest)onse to ERC General Comment No. 5

The Army's assertion that "ecotoxicity values do not permit evaluation of multiple chemical

exposures" is not consistent with a large body of information and recommendations presented by

prestigious national and international organizations, including the National Academy of Sciences

and the World Health Organization, as well as leading texts. Attached to these comments is a

limited discussion and listing of highly relevant documents which demonstrate the insupportability

of the Army's ERC program. The text is taken from Calabrese: Multiple Chemical Interactions

(Lewis; 1991).

Rest)onse

Although Calabrese is to be commended for his efforts to publish one of the first comprehensive

reviews on multiple chemical interactions, the test xeroxed by CDH may not be as applicable to

the offpost ecological assessment as CDH would imply. The method described for aquatic

ecosystems assumes simple toxicity additivity for chemicals unless proven otherwise. Other

11788,903 - CR-03

0504112092 VIII - 60
interactions that are possible include antagonism, synergism, and potentiation. All are very

different from additivity, yet no alternative methodology is presented.

Also, by xeroxing the references from Chapter 23 of Calabrese's book and making the above

comment, CDH implies that there is a tremendous amount of accepted scientific information on

multiple chemical interactions. This is hardly the case, especially for ecological receptors. In fact,

the study of multiple chemical interactions is in its infancy compared to other types of toxicological studies. Calabrese alludes to this in the opening chapters of his book and points out in

Chapter 2 that "over the past two decades, considerable debate has occurred within the biostatistical/epidemiological, pharmacologic, and toxicological communities over the concept of

interaction." Certainly, recommendations have been proposed on multiple chemical interaction

methodology; however, because of its early investigative stages and lack of scientific consensus,

acceptable guidance for use in ecological assessments is lacking.

Comment No. 3 - Volume VIII, t)aRe 45, Response to ERC General Comment No. 6

The Army's argument that the RMA ecosystem is probably in equilibrium, given the length of time

that contaminants have been present at the site, misses the point of the State's comment. The critical

question is not whether the environment as a whole is in steady-state, but rather whether the

individual organisms are in steady-state. This is a function not of how long the contaminant has

been in the ecosystem, but rather how long the organism has been exposed to the contaminant, and

how long it takes for the contaminant to reach steady-state within the organism. This issue must be

addressed.

Resr)onse

The Army understands that an organism can attain steady state if exposure and biological factors

affecting the uptake and loss of a chemical remain constant for a sufficient length of time.

However, the Army does not have sufficient data for an inclusive statement regarding steady-state

conditions in the Offpost OU.

Comment No. 4 - Volume VIII. L)ape 46. Rest)onse to ERC General Comment No. 7

In response to the State's inquiry regarding the intended relationship between the TRVs and the

MATissueCs, the Army has asserted that MATissueCs "are most useful for bioaccumulative

chemicals and for food sink species. TRVs are more useful for nonbioaccumulative chemicals and

for lower trophic level species." Yet, TRVs are proposed for lop level predators for highly

bioaccumulative chemicals such as organchlorine pesticides. Therefore, the Army's response has not

clarified the question, which is how will these values be used in arriving at cleanup levels.

From a toxicological perspective, the MATissueCs and TRVs should be consistent. One should be

derivable from the other given knowledge of appropriate toxicokinetic factors. Prior estimated

MATissueCs were significantly greater than those that would be predicted by converted TRVs. We

have not had an opportunity to interconvert the new TRVs ad MATissueCs. However, any inconsistency between the two values would undercut confidence in the' Army's methodology.

Rest)onse

The Army would be interested in reviewing CDH's methodology for interconverting TRVs and

MATCs. The Army uses both MATCs and TRVs to derive ecological soil criteria (Volume VII,

Appendix C of the FS).

11788,903 - CR-03

0504112092 VIII - 61
Comment No. 5 - Volume Vill. page 46. Response to ERC General Comment No. 8

The food web model has now been calibrated with onpost biola data. The State has formally

objected to the use of the limited RMA data base to deviate from peer-reviewed literature derived

values. Specific comments on the new Ecological Risk Characterization ("ERC") model and

calibrated values could not be compiled in time to meet the Army's April 6, 1992 deadline; however,

preliminary review has indicated that, for a variety of reasons, including internal inconsistency and

the lack of accord with available scientific information, the proposed model and output cannot be

relied upon to predict ecosystem responses to contaminants, and does not appropriately reflect

maximum known exposure within the RMA ecosystem. The State intends to transmit detailed

comments on the ERC model by April 21 in accordance with the Army's request. Since the offpost

values are derived from the ERC model, the State cannot support those values at this time.

Response

Refer to response to USFWS Comments No. I and No. 2.

Comment No. 6 - Volume VIII. vage 46. Rest)onse to ERC MATissueC Comment No. I

The Army, in defending its sink species methodology, has attempted to avoid its own obligation of

proving the protectiveness of its approach, instead challenging the State to prove to the contrary.

Such a shifting of the burden of proof is contrary to the prescriptions of CERCLA and the NCP

which require the President to demonstrate protectiveness of the environment as a threshold criterion

for any remedy selected.

The principal premise of the Army's ecological risk assessment method is that reliance on sink

species via food chain modeling will protect all other species, including those species that may be

inherently more sensitive than the sink species at a similar exposure. This premise assumes that the

enhanced exposure in the sink species will more than compensate for any differential susceptibilily

to the agents of concern.

To determine the validity of this assumption, one must identify the degree of interspecies variation

in susceptibility that one can expect if the intent is to protect all biota within the ecosystem.

Differential susceptibility at the ecosystem level has been inferentially addressed by Slooff ei al.

(1987) in their comparison of 35 species over 11 taxa. Their work involved a large series of binar ' v

comparisons which estimate interspecies differences in susceptibility. The results showed up to

100-fold interspecies variability for 60% of the comparisons, and up to 1000-fold variation for 90%

of the comparisons.

A consideration of predicted tissue concentrations from the calibrated biomagnification values

(BMF) (Vol. IV, Table H3, Page 2 of 2, First Creek) reveal that the range of tissue concentrations

for dieldrin was 6.1-fold (algae to heron), DDT was 6.1-fold for algae to the heron and

427.5-fold for invertebrates to the heron; DDE was 1.8-fold for the algae to bald eagle and

39.7-fold for invertebrate to the bald eagle. In addition, the bald eagle was estimated to

bioaccumulate 39.4-fold more DDE, 29.6-fold more DDT, and 5.6-fold more dieldrin than the

small fish; 22.6-fold more DDE and DDT, and 6.0-fold more dieldrin than the mallard duck;

19.1-fold more DDE, 13.8-fold more DDT, and 3.3-fold more dieldrin for the large fish.

In the terrestrial food web (Table H2, page 2 of 3) the variation in predicted tissue concentrations

of prairie dogs and the great horned owl were 6.2, 4.8, 3.1, and 50.9-fold, for DDE, DDT, dieldrin

and endrin, respectively.

11788,903 - CR-03

0504112092 V111 - 62
Regardless of how one estimates exposure, whether on a mglkgldose-rate basis or tissue

concentration basis, the Army's existing data indicate that the premise of using sink species to

compensate for interspecies variation in response to toxic substances may be seriously flawed.

Rest)onse

The Army stands by its original response and fails to see where CDH was challenged to prove

otherwise. The data presented above simply illustrate the concept of bioaccumulation and

biomagnification, and any other interpretation is conjecture.

Comment No. 7 - Volume V111. pape 47. Resr)onse to ERC MATissueC Comment No, 2

To clarify the Slate's ERC General Comment 2 regarding endpoint selection for biota criteria

derivations, "legislative factors" which must be included in cleanup criteria are, for example, the

requirements of the Endangered Species Act ("ESA"), the Bald Eagle Protection Act ("BEPA"), and

the Migrating Bird Treaty Act ("MBTA"). These Acts, as well as the case law construing them,

variously define and prohibit harm and harassment. The Migratory Bird Treaty Act

(16 U.S.C. § 703) is intended to "aid in the restoration of such birds ... where [they] have become

scarce or extinct." The MBTA, similar to the ESA and BEPA, protects individual birds and their

parts, nests, or eggs, by prohibiting hunting, taking, possession, killing, etc., of protected species,

except as permitted by regulation (=, Cg, 50 C.F.R. pts. 20 & 21).

Further, the purposes of the ESA, as set forth at 16 U.S.C. 1531(b), include providing "a means

whereby the ecosi,stems upon which endangered species and threatened species depend may be

conserved..." (emphasis added). Any manifestation of statutory or judicially defined harm must be

considered when selecting appropriate endpoints from which to derive action levels, so that these

levels are sufficiently protective to prevent such harm to biota.

We are disturbed by the Army's assertion that the Migratory Bird Treaty Act does not require

protection of individual animals. The purpose of that act is to "aid in the restoration of such

birds ... where [they] have became scarce or extinct." Legal interprelation in the courts (=, fg.,

U.S. v. Corbin Farm Service, 444 F. Supp. 510 (1978)) supports protection of individuals within a

species. Selection of action levels that would kill, harm or take individuals (or parts or eggs) of

covered species would clearly contravene the purpose of that Act.

Also, the Army is continuing to ignore the variability in endpoints used to derive MATissueCs. The

Arm), states in volume II, page 3-18, section 3.4, second paragraph, that the MATC values "represent tissue concentrations that correspond to no effect, or minimal effects in a few animals in

a population." The specific endpoints used in the derivation of the MATissueCs are not provided

with the EAIFS document. We request that a description of the endpoints along with citations given

the source literature be included in the final version. The secondary source which is cited by the

Army (Onpost HHRA software, version 1.0, EBASCO 1992) does not contain this information.

The most current list of MATissueC endpoints which the Army has supplied the parties is the

"MATC supplemental Tables" dated December 2, 1991. In these tables, endpoints range from

lethality to no effects. This is an unacceptable range of toxic responses on which the Stale has

commenled previously (State letters of September 23, 1992 and December 10, 1991). The Army

states in section 3.4 that "[w]hen the endpoint was lethality, an appropriate uncertainly factor was

applied." However, the EBASCO 1992 citation does not appear to contain any details of this

uncertainly factor.

In human health risk assessment methodology an uncertainty factor of 10 is used if an adverse

effect ("LOAEL") is observed,- if a frank effect ("FEL") is noted, a modifying factor is available

11788,903 - CR-03

0504112092 V111 - 63
to adjust for the additional uncertainty introduced. An analogous approach must be developed to

protect biota.

Response

Regarding CDH's comment on the ESA, BEPA, and MBTA, Appendix A, Volume VII of the FS

has been revised to include in totality the language agreed upon in the dispute resolution process

and communicated in a letter from EPA to the parties on September 18, 1992.

The MATCs have been revised and are discussed in Volume II, Section 3.0 and Volume IV,

Appendix H of the EA.

Comment No. 8 - Volume VIII. vage 48, Response to ERC MATissueC Comment No. 3,

The Army has failed to address to State's concern that MATissueCs based on sublethal effects may

not even protect populations of exposed biota. The topic of acceptable sublethal effects must be

carefully evaluated in both the MATissueC and TRV approaches. The adverse effects are highly

variable and present different health consequences to both individuals and populations. For

example, if the Army accepts a LOAEL for COC No. I at which 30% of the exposed individuals

experienced life shortening physical deformity, a LOAEL for COC No. 2 at which 45% experienced

behavioral abnormalities that reduce reproductive success, and a LOAEL for COC No. 3 at which

35% experienced increased susceptibility to acute viral disease, population effects are likely to be

observed. Analogous problems could be associated with MATissueCs based on sublethal effects.

What criteria have the Army used to judge if there would be a population effect and have these

criteria been developed and validated for the species of interest? Until a systematic assessment of

the role of sublethal effects (both single and multiple concurrent effects) on the survival and

vitality of the population is completed, the Army's approach cannot be considered protective of

populations.

Resnonse

The MATC values presented in the draft final were obtained from the Onpost ERC. Because the

onpost ERC was not finalized at the time of the draft final, several of the MATC values were an

item of dispute. On the basis of the dispute resolution process, revised MATC values were

derived on a basis of scientific consensus. These revised values are discussed and presented in

Volume 11, Section 3.0 and Volume IV, Appendix H of the EA.

Comment No. 9 - Volume VIII. vage 48, Rest)onse to ERC MATissueC Comment No. 5

The Armv uses a relationship between human brain and whole body mercury to establish a constant

so that whole body values can be estimated when only brain levels are measured in a given species.

The State's previously submitted comments documented that there is considerable interspecies

variability in organ to organ ratios of mercury depending on the animal species. Since this

variabilit ' v can be extreme, it introduces a high degree of uncertainty in this process. The Army

procedure does not recognize this uncertainty; nor does it incorporate a means (L.g, UFs) to

compensate for uncertainty.

The Army has responded in part by asserting that the variability noted in the State's comment is

addressed within the context of the interspecies UF. However, this assertion is obviously erroneous.

First, according to the document, only the TRV methodology includes interspecies UFs, not the

MATissueC approach. Yet,it is the MATissueC approach which requires whole body extrapolations,

not the TRV. Secondly, even if MATissueC interspecies UFs were to be adopted, they would

11788,903 - CR-03

0504112092 VIII -. 64
normally be triggered when MATissueCs were derived from a literature value based on different

species. Since it appears that each MATissueC has been derived from studies oil each target

species, no UF factor would be deemed necessary. However, the source of the toxicity information

is irrelevant to the whole body extrapolation issue because the latter extrapolation is based, not on

the toxicity information, but rather, for example, on the mercury brain to whole body ratio that has

been determined for humans. Accordingly, the State again maintains that this inaccuracy must be

addressed in the MATissueC methodology.

Resi)onse

Refer to response to Comment No. 8.

Comment No. 10 - Volume V111, DaPe 51. Response to Comment No. La

The Army has failed tojustify its selection of phylogenetic related interspecies uncertainty factors.

In the interest of determining the validity of the Army's theory and proposed values, the State has

undertaken an evaluation of existing data pertaining to interspecies susceptibility to chemicals. The

results of this analysis are attached and demonstrate that the Army's values cannot be supported.

Analyses of thousands of phylogenetic toxicological comparisons summarized by Suter and others

indicate that, although the data do generally support the theory of phylogenetic relatedness to a

greater extent than previously noted, they refule the Army's proposed values for interspecies

uncertainty factor values. For example, for species within genera, at the 99% confidence interval,

they observed differential susceptibilities between 6 and 21 fold: for orders within classes, there

were differences between 17 and 17,534 fold. These data demonstrate that the Army's proposed

values of 2 for each level of phylogenetic difference are not adequate to address interspecies

variation in susceptibility to contaminants.

Response

Contrary to CDH's position, the magnitude of the Army's uncertainty factors applied in the

derivation of TRVs is supported by the paper published by Suter and Rosen (1988) as well as

Barnthouse and others (1990) as discussed in Volume II, Section 3.0 of the EA. CDH's reference

to the uncertainty factors associated with the 99 percent confidence interval is not appropriate and

would imply the use of extremely conservative uncertainty factors beyond scientific reason.

Comment No. I I - Volume VIII, page 59. Resnonse to ERC Sr)ecific Comment No. 12

In response to the State's previous comment regarding sensitive populations and subpopulalions, the

Army states that it selected representative receptor species and sensitive subpopulations using EPA

criteria and additional information as listed on page 111-5-7. However, it is still not clear how

such species (i.e., species with lower thresholds to toxic substances) were differently addressed.

Please explaiý-how and which species were identified, and the pollutants to which they had lowered

threshold tolerances, and the magnitude of differential susceptibility. Also, please explain how the

ERC methodology was used to derive TRVs and MATissueCs protective of such species.

In addition, the selection criteria referred to relates only to receptor species: it does not address

sensitive subpopulations within a species. Please explain how considerations of such subpopulations

have been incorporated in the ERC methodology, and provide examples of the incorporation of such

considerations in the derivation of specific TRVs and MATissueCs.

11788,903 - CR-03

0504112092 VIII - 65
Rest)onse

The potential receptors listed in Tables 5.2.1-1 and 5.2.1-2 were qualitatively evaluated against the

criteria presented in Section 5.2.1 of Volume Ill. The selection process was according to the

professional judgment of the evaluators. The pollutants to which the receptors were assumed to

have lowered threshold tolerances were the organochlorine pesticides primarily because of their

bioaccumulative properties. Magnitude of differential susceptibility was based on trophic box

level.

The TRV and MATC methodology, including application to sensitive subpopulations, is presented

in Section 3.0, Section 5.0, and Appendix H of the EA.

Comment No. 12 - Volume VIII. page 63. Response to ERC Svecific Comment No. 28

The Army has failed to,justify its requirement that the HI be exceeded by a factor of 10 before

remedial action is considered. In response to the rationale presented:

(1) The assertion that the use of UFs, LOAELs and NOAELs in deriving MATissueCs and TRVs

is conservative demonstrates a profound lack of understanding of the most fundamental tenets

of risk assessment accepted not only by EPA but by major health organizations throughout the

world. While many debate about the size of UFs, UFs are not inherently conservative but

necessary to make valid extrapolations. In fact, the sparse data base that exists indicates that

values traditionally utilized may not be sufficient to account for variability and other

considerations obsensibly embodied in each UF. In Comment 8 above the State points out that

the use of LOAELs and NOAELs may not be protective, let alone conservative.

(2) The fact that mobile species may have had their exposure overestimated does not eliminate

concern with the organisms of limited mobility. Furthermore, if exposure estimates are

known to be unrealistic, they should be revised. Unquantified overconservation in this

assumption does not support the arbitrary use of, essentially, a 10-fold multiplier of the

acceptable does or tissue concentration value.

(3) The Arm * v has not substantiated its belief that modeling assumptions are consistently

conservative; regardless, this issue is best dealt with via the construction of the model itself,

which should reflect the best estimated exposure.

(4) The assertion that soil intakes are "conservative," especially in light of the high uncertainty in

this area, is totally inappropriate and unverified. It therefore cannot be used to justify the

Army's HI approach.

The use of a HI of 10 is inherently irrational. The denominator of the hazard index is suppose to

be the scientists' best professional estimate of an acceptable dose (or, in the case of RMA, tissue

concentration); therefore, any exceedance of such a level should be a cause of concern. If the

parties do not believe that the TRV or MATissueC is accurate, it should be changed to accord with

the best available scientific information and judgement. To add uncertainty factors on the front

end to account for inadequacies, and then basically subtract them in the final analysis, is nonsensical. Essentially, the Arm), is proposing an UF multiplier of 10 which is without supporting documentalion or rationale, and is dramatically deviant from existing risk assessment knowledge and

methodology throughout the world.

11788,903 - CR-03

0504112092 VIII - 66
Resvonse

1. The Army strongly disagrees with CDH. UFs, for the most part, are inherently

conservative. This conservatism is eloquently presented in the recent publication by Lewis

and others (1990). CDH fails to present evidence from the "sparse database" that traditional

UF values (the Army assumes CDH is referring to 10) may not be sufficient to account for

variabilities encountered during toxicity extrapolation. The traditional values were initially

arbitrarily assigned a value of 10 on the basis of professional judgment. They basically have

been accepted by regulatory agencies and organizations as more a matter of convention than

a scientific absolute. It is likely that the UFs now applied will be reduced as more useful

toxicological data become available. The UF values suggested by EPA for the derivation of

human reference doses are not codified. The use of UFs less than 10 at each step of the

iterative process in deriving a TRV is supported by the recent literature, including papers

cited by CDH. CDH is referred to Volume 11, Section 3.0 of the EA for a further discussion

of UFs and is encouraged to read the references cited by the Army. The draft final

ecological assessment used MATC values derived for the Onpost ERC. On the basis of

dispute resolution, some of these values have changed and are discussed and presented in

Volume II, Section 3.0 and Volume IV, Appendix H.

2. Because the exposure estimates were known to be unrealistic when presented in the draft

final, they have been revised for the final ecological assessment.

3. Again, revisions have been made to estimate more realistic exposures.

4. Refer to 2 and 3 above.

Comment No. 13

The Arm), previously proposed a reduction factor of 5 to account for the unique concern over

protecting Endangered Species. In this draft, the factor has been changed to 2. Neither value has

been supported by literature or rational argument. Much literature exists on interindividual

variation in response to toxic substances. In the case of the highly heterogeneous human population,

interindividual variation exceeding 10-fold is commonly encountered. In the case of the highly

inbred rodents, interindividual variation of 3- 5-fold is often seen. These commonly recognized

occurrences indicate that a 5-fold factor may not effectively protect individual eagles. Since the

federal legislation's intent is to protect all individuals, a factor greater than or equal to 10 is

clearlv warranted.

Rest)onse

The selection of an uncertainty factor of 2 to provide additional protection to the bald eagle

population is supported by the literature. The use of a factor of 2 is identical to that selected in

the ecological risk assessment Standard Evaluation Procedures (SEPs) developed by the Office of

Pesticide Programs in EPA to protect threatened and endangered species.

SPECIFIC COMMENT

Comment No. I

Volume IV, Appendix F, "Toxicity Profiles of Chemicals of Concern" has MATissueC values which

do not match the MATissueC values listed in Appendix H of the same volume. For example, the

Toxicity Profile lists aldrin1dieldrin as having a MATissueC of 10 mglkg. Appendix H lists

11788,903 - CR-03

0504112092 VIII - 67
aldrin1dieldrin as having MATissueC values ranging from 1.6 to 3.75. Please update the Toxicity

Profiles.

Rest)onse

Comment noted. The toxicological profile has been updated.

11788,903 - CR-03

0504112092 VIII - 68
GLOSSARY

ABS absorption factor

ARAR applicable or relevant and appropriate requirement

BAF bioaccumulation factor

BCF bioconcentration factor

BEPA Bald Eagle Protection Act

BGEPA Bald and Golden Eagle Protection Act

BMF biornagnification factor

CBSG Colorado Basic Standards for Groundwater

CCR Colorado Code of Regulations

CDH Colorado Department of Health

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

CFR Code of Federal Regulations

COC chemical of potential concern

CRL certified reporting limit

DDE 2,2-bis (para-chlorophenyl)-I,I-dichloroethene

DDT 2,2-bis (para-chlorophenyl)- 1, 1, 1 -trichloroethane

DIMP diisopropyl methylphosphonate

EA endangerment assessment

Ebasco Ebasco Services, Inc.

EPA U.S. Environmental Protection Agency

ERA Ecological Risk Assessment

ERC Ecological Risk Characterization

ESA Endangered Species Act

FFA Federal Facility Agreement

FS feasibility study

GC/MS gas chromatography/mass spectroscopy

11788,903 - CR-03

1119112092 VIII-G- I
HA health advisory

HBC health-based criteria

IRA Interim Response Action

IRA A Additional Interim Response Action

LDR Land Disposal Restrictions

LOAEL lowest -observed -adverse -effect level

MATC Maximum Allowable Tissue Concentration

MBTA Migratory Bird Treaty Act

MCL Maximum Contaminant Level

mg/day milligrams per day

NCP National Contingency Plan

NOAEL no- observed -adverse -effect level

NWBCS Northwest Boundary Containment System

OAS Organizations and State

OSWER Office of Solid Waste and Emergency Response

OU operable unit

PC permeability coefficient

PCB polychlorinated biphenyl

PMRMA Program Manager for Rocky Mountain Arsenal

ppm parts per million

PRG preliminary remediation goal

RCRA Resource Conservation and Recovery Act

RI remedial investigation

RMA Rocky Mountain Arsenal

RME Reasonable Maximum Exposure

SACWSD South Adams County Water and Sanitation District

SEP Standard Evaluation Procedure

11788,903 - CR-03

1119112092 VIII-G-2
TBC to be considered

TRV toxicity reference value

UF uncertainty factor

USFWS U.S. Fish and Wildlife Service

UST underground storage tank

USC United States Code

11788,903 - CR-03

1119112092 VIII-G-3
ATTACHMENT A
DEPARTMENT OF THE ARMY

PROG&RAM MANAGER FOR ROCKY MOtJWrJUN AMMAL

C0MNM=CrrV.C0L0PAW MUM=

(D,Mnv TO

ATTKNTM On

May 5, IM

Office of the Program Manager

Mr. L4ewis D. Walker Mr. Ray Gerard

Deputy Assistant Secretary of the Army Shell Oil Company

. for Installation, Logistics, and Environment P.O. Box 2463

Pentagon, Room 2ES77 Houston, IX 77252

Washington, DC 20310-0103

Mr. Galen Buterbaugh Mr. Jack McGraw

Regional Director Deputy Regional Administrator

U.S. Fish and Wildlife Service US. Environmental Protection Agency

P.O. Box 25486 Suite 500, South Tower

Denver Federal Center 999-18th Street

Denver, CO 80225 Denver, CO 80202-2405

Dear Sir:

Following several weeks of dispute resolution discussions at the RMA Committee and

Council levels regarding the Of[post Operable Unit (OU) Endangerment

Assessment/Feasibility Study (EA/FS), the Organizations have reached agreement an all

but one issue.

The resolutions to the dispute Issues for the Offpost EA/FS are enclosed. The most

complex of the resolved issues was the issue regarding the Ecological Risk Assessment.

The Army agreed to incorporate the values described in the enclosure with the

understanding that they represent conservative values based on interpretations of the

literature and may not be representative of site-specific conditions present in the Of[post

OU. These values have been accepted by the Army in the spirit of cooperation to

facilitate the completion of the Ecological Risk Assessment.

Ile unresolved issue concerns whether the Endangered Species Act (ESA), Migratory

Bird Treaty Act (MBTA), and Bald and Golden Eagle Protection Act (BGEPA) are

applicable or relevant and appropriate requirements (ARARs) for the Offpost OU, and,

if so, what type of ARAR (e.g., location-, action-, or chemical-specific) they are. EPA

argues that all three acts should be chemical-specific ARARs. The Army and USFWS
contend that the acts are not ARARs but are independently enforceable. Shell!s position

is that the ESA, MBTA. and BQEPA are not chemical-specific ARARs.

The discussion of the ARAR issue is now taking place at the national level between

the Department of Interior and EPA. However, because the parties have agreed to the

ecological parameters for the Offpost OU, the offpost process should go forward while

the isme is being resolved at the national level.

The resolution to the dispute, as descr:lbed, will require an additional six months to

complete. 7be delay in completing the EA/FS win also cause a delay in the'issuance of

the OfEpost Record of Decision of up to six months.

sincerely,

Culgee T-LBisho

Co U.S. A=43y

Chairman, RMA Council

Enclosure

Copies Furnished:

Major John M. Fomous, U.S. Army Environmental Law Division, 901 N. Stuart

Street, Suite 400, Arlington, Virginia 22203-1837

Mr. Bradley Bridgewater, U.S. Department of Justice, 999-18th Streetý

Suite 501, North Tower, Denver, Colorado 8MM

Mr. Thomas Cope, Holme Roberts and Owen, Suite 4100, 1700 Lincoln Street,

Denver, Colorado 80203

Ms. Victoria Peters, Attorney Generars Office, CERCLA Law Division,

One Civic Center Plaza, 1560 Broadway, Suite 250, Denver, Colorado 80202

Mr. David C Shelton, Director, Hazardous Material and Waste Management

Division, Colorado Department of Health, 4210 East 11th Avenue, Denver,

Colorado 80220

Mr. Thomas Looby, Colorado Department of Health, 4210 East 11th Avenue, Denver,

Colorado 8=0

Mr. William Clemmens, U.S. Environmental Protection Agency, Region VIM

One Denver Place, Suite 801, 999-18th Street, Denver, Colorado 80202-2405

Document Tracking Center, AMXRM-IDT, Room 132, Building 111, Rocky

Mountain Arsenal, Commerce City, Colorado 80022^R
Ofipost Operable Unit Dispute Resolution Agreement

17he resolution to the dispute, as described, will require an additional six months to

complete. The delay in completing the EA/FS win also cause a delay in the issuance of

the ofipost record of Decision of up to six monthsApproval:-

tEe!ne=I-=LB op k4beit Dufrey

Army EPA

vinfArn M ohn L Sp

Shell #= AUS46"SFW
omosr ENDANGERMENT ASSESsMENT/1-MAMBUM'y M"UDY

DISPUM RESOLU71ON

It is the intent of the Orpnizations to achieve resolution on language prior to

finallZation of the document on November 13, 1992.

1. Development of Preliminary Remediation, Goals (PRGs)

ISSUE: EPA questioned the methodology (but did not dispute given the magnitude of

the impact under the current factual situation) whether the effects of multiple chemicals

within a medium and whether the effects of chemicals of concern (COCs) in multiple

media were considered when PRGs were developed.

RESOLUTION: Ile Army will modify the text in Volume V, Section 2.4.5, and in

Volume VII, Appendix C. 7te Army modifications will include additional discussion

about how soil PRGs were developed and will Incorporate comments provided by EPA

on April 23, 1992.

2. Use of 10'4 vs. 10 Risk as Point of Departure

ISSUE: EPA invoked dispute concerning whether 10'4 or 10'6 cancer risk was used as

the point of departure for determination7of HBC. T%e Army had added sections in the

Proposed Final EA/FS that were intended to address an EPA comm nt, but EPA found

the changes to be inmfficieut.

RESOLUTION: The Army asked EPA to provide specific comments concerning

sections of the EA/FS that still need to be clarified. The Army will incorporate those

comments (received on April 23, 1992) into the Final EA/FS, specifically Volume H,

Sections 2.4 and 2.5, and Volume V, Section 2.432-

3. Uncertainty Analysis

ISSUE: EPA invoked dispute concerning the presentation of the uncertainty analysis in

the EA/FS, particularly (1) the possibility that risks may be underesd=ted in some

areas but not discussed and (2) the discussion of the uncertainty analysis and its

representation of exposure relative to the reasonable maximum exposure OWE).

RESOLLMON: The Army wiH incorporate EPA comments (received on April 23,

1992) to clarify the uncertainty discussions in the EA/FS.

4. Division of Soil Concentrations by 5

1
ISSUE: EPA questioned the methodology (but did not dispute given the magnitude of

the impact under the current factual situation) of the Army's modification of soil

exposure concentrations for the plant uptake model by a factor of 5.

RESOLLMON: The Army will add discussion of uncertainty to Volume M Section 2.6,

to explain why the factor of 5 was used to account for the lower concentrations of COCs

available to plant roots (Le., because COCs acammlate, in the surface I to 2 inches of

soil).

5. FS Alternative Selected

ISSUE: EPA invoked dispute concerning the groundwater alternative selected in the FS,

contending that all alternatives were variations of the same technology/configuration and

that the alternatives were essentially equivalent. EPA also stated that the FS did not

evaluate configurations that potentially could achieve a more rapid reme4diation.

RESOLU71ON: ne Army will clarify the methodology used and the basis for the

development of remedial alternatives. Specifically, the Army will describe: (1) the

controlling contaminant and bydrogeologic considerations, (2) resultant estimated

remediation time frames, (3) relative positions of remedial components for each

alternative, (4) limitations on additional components, and (5) level of aggressiveness of

the remedial alternatives.

6. Surface Water FS

ISSUE: EPA questioned, but did not dispute, whether surface water alternatives should

be developed in the FS.

RESOLLMON: Following finther discussion on the issue, EPA withdrew its objection.

7. Groundwater Exposure Point Concentrations

ISSUE: Shell invoked dispute concerning the Armys use of the 1985-1990 groundwater

database, use of data with high certified reporting limits (CPU) from gas

chromatograph/mass spectrometer (GC/MS) analysis, and inclusion of duplicate

analyses. Shell contended that this approach is unrepresentative of current conditions.

RESOLUTION: The groundwater exposure point concentrations will be revised and will

be based on 1989-1991 groundwater data excluding nondetections with high CRJs and

duplicate data, as well as on the te staý611ý pr6cedura

2
8. Dieldrin Toxicity Profile

ISSUE: Shell invoked dispute concerning the Army's failure to include Shell's

toxicological profile for dieldrin. in the EA/FS.

RESOLUTION: Shell's dieldrin toxicity profile Will be included in Volume IV,

Appendix F, in addition to the Army's dieldrin toxicity profile already in Appendix F.

Sbelrs profile will be added and referenced in the same manner as in the 1991 Onpost

Human Health Exposure AssessmenL

9. Manganese as a COC

ISSUE: Shell invoked dispute concerning the inclusion of man anese as a COC based

on limited data linkinx manganese to RMA.

RESOLILMON: Shell withdraw the dispute when the Army presented additional onpost

and ofipost groundwater data concerning manganese.

10. Applicable or Relevant and Appropriate Requirements (ARARs)

ISSUE:

A. EPA disputed the overall completeness/format of the ARARS assessment.

B. Shell disputed the inconsistent treatment and use of land disposal restrictions

(LDRs) as ARARs.

C. Shell disputed the use of stormwater discharge regulations as ARARL

D. Shell disputed the use of Colorado groundwater stmdards that are more

stringent than federal standards as ARARs rather than as TBCs (to be

considereds).

E. Shell disputed the selection of some proposed MCLs as ARARs instead of

TBCS.

RESOLUTION:

A. The Army will clarify the presentation/screening of ARARS through

additional discussion.

B. The Army wffl revise Volume VIL Appendix A of the Offpost EA/FS, as

agreed to by the partie& (Attachment A).

3
C. Shell withdrew the dispute.

D. Although there is some question whether the Colorado Basic Standards for

Groundwater are legally enforceable as ARARs, the Army is evaluating whether

those standards are ARARs for the purposes of this document.

E. Ile Army will make appropriate changes to the ARARs listings as part of

Item A.

11. Hazard Index (HI) > 1 for Egg Pathway

ISSUE: EPA disputed the Army's use of only dieldrin to assess the egg pathway for

human exposure.

RESOLUTION: EPA dropped the dispute, agreeing that the risk assessment will

evaluate only dieldrin for this pathway.

1Z Land Use Scenarios

ISSUE: Shell invoked dispute concerning the use of the subsistence farmer (rural

residential) scenario in the EA/FS. EPA invoked dispute concerning the selection of

commercial/indu3trial land use in the FS in zones 3 and 4.

RESOLUTION: All o agreed to use one land use scenario per zone.

Zones 1, Z and 6 will remain rural residential. Zones 3 and 4 will be urban residential

with two presentations of risk estimates in the EA. Zone 5 will be

commercialfindustrial. See Attachment B for details of the pathways to be considered in

each zone.

13. Ecological Risk Assessment

ISSUE.

A. Shell invoked dispute concerning the need for a more quantitative assessment

of the spatial and temporal (seasonal) factors involved in the higher trophic level

organism foraging habits.

B. Shell invoked dispute considering the conservative nature of the toxicity

reference value (TRV) process.

C. EPA invoked dispute concerning the maximum allowable tissue concentration

(MATC) value for dieldrim Sbeli disputed MATC values for aldrin/dieldrin,

DDT/DDE, and endrin; USFWS disputed the dieldrin MATC and had general

concerns about other MATC-values.

4
D. EPA, USFWS, and Shell invoked dispute concerning the use of onpost calibrated

ioacal3amilation factors (BAF) values. Shell requested the use of BAF values as used

in the Draft Funi version of the EA/FS; EPA requested the use of literature BAF

values; USFWS supported literature and/or USFWS BAF valucL

13- Shell and USFWS disputed oconce on factors (BCFs).

RESOLLMON:

A. All Organi agreed to the a of a spatial weighting factor to

adjust the predicted tissue co and hazard indices for the great blue heron,

great homed awl, American kestrel, and bald eagle. The spatial weighting factor will

be based on the ratio of available acreage of appropriate habitat and the acreage of

taxon-specific home range. Shell withdrew the temporal (seasonal) factor portion of

the, dispute.

B. All 0 agreed thai-the TRV proem will follow the approach as

originally presented by the Army with uncertainty factor modifications to derive a no

observed adverse effect level (NOAEL) rather than a no observed effect level

(NOEL) from the critical exposure dose. 7be Organizations have agreed to accept

the aldrin/dieldrin critical exposure dose presented by SheJ1 as the basis for the great

blue heron TRV,- the great blue heron TRV value will be 0.06 mg/kg/day. The Army

agreed to provide documentation supporting the uncertainty factor modifications in

the Final EA/FS.

C The following MATC literature values were agreed to by all Organizations:

Aldrin/Dieldrin

Bald eagle 1.1 PPM

Great blue heron Ll ppm

Great homed owl 1.1 ppm.

American kestrel 1.1 ppm

Water birds 1.1 PPM

Small birds 1.1 PPI]kEndrin

Bald eagle, 0.01 ppm,

Great blue heron 0.1 ppm,

Great homed owl 0.01 ppm

American kestrel 0.01 ppm

Water birds 1.0 ppm,

Small birds 0.045 ppm.

5
DDT/DDE

Bald eagle 2.0 ppm

Great blue heron 2.0 ppm Great homed owl 2.6 ppm,

American kestrel 5.1 ppm

Water birds 0 ppm,

Small birds 1.7 ppm

D. 'ne following BAF Utmtwe values (unitlem) were agreed to bY the, Organizations:

Aldrin/Dieldrin

Small bird 2

Small mammal 3

medium mammal 3

worm 6

Insect 2.4

Plant 0.4

owl 19

Ke=ei 12

Eagle 19

Endrin

Small bird 8

Small Msimmal 8

medium 8

Worm 29

bisect 29

Plant 0.06

owl 8

Kestrel 8

Eagle 8

DDT/DDE

Small bird 2

Small momm"I 6

Medium mammal 6

Worm 3

Insect 32

Plant 1.4

owl 31

Kestrel 31

Eagle 31

6
M An organizations agreed to use USFWS BCFs (unitless) for small (lower) fish

(aldrin/dieldrin, 16,716-, DDE/DDT, 70,094) and use literature values for . . small fish, invertebrates and alpe. USFWS is to supply documentation

suppo their BCFs.

The Organizations also agreed to use geometric mean soil concentrations to

determine predicted time concentrations and/or soil criteria exceedanCOL

Miis resolution is considered applicable only to the Oflpost EA. 7Ue Army will

incorporate the MATC and BAF values as agreed to by the organizations.

7
ATrACHUENT A

Based upon oflpost sampling process imowledge, and EPA guidance concerning the Land

Disposal Restrictions (IDRs) under RCRA, the Army has no reason to believe there is

any listed or characteristic hazardous waste in the Offpost OU, or that construction of

any alternative would involve placement of a listed or characteristic hazardous waste. If

it is determined that a listed or characteristic hazardous waste is present and that

placement of such a waste would occur, LDRs will be ARARs and the Army will act in a

manner consistent with EPA guidance for themsina ement of such wastes in the context

of a CERCLA response action.

8
ATrACHMENT B

A. Rural Residential (EA/FS zones 1. Z and 6)

eme,at (75%)

-dairy (75%)

egg (only mhwed dieldrin)

*vegetable (40%)

groundwater (ingestion)

groundwater (inhalation)

soil (dermal)

soil (ingestion)

sedimuts (dermal)

surhm water (dermal)

B. Xjrban Residential (EA/FS zones 3 and 4)

*vegetable (4096)

soil (dermal

soil (ingestion)

sediments (dermal)

surf= water (dermal)

groundwater (ingestion)

groundwater (inhalation)

All iyo indicate amount of consumption from local SOUrCeL

Risk estbmtes for Zones 3 and 4 Will be presented in two MAnnCrs:

1. As a baseline risk Lumsment for all me" per EPA guidance. IMO

groundwater portion of the risk L&wwment will be based on the calculated risks

from 1989-1991 groundwater data in those zones.

2. The second risk calculations will be based on the continuing beneficial effect

of the onpost boundary system operations in a 30-year tim franic. Tbe text will

state that these are the expected potential exposures for individuals in thaw zones

and the risks associated with those exposures.

C Commercialgndustrial (EA/FS zone 5)

soil (

soil (ingestion)

groundwater (ingestion)

groundwater (inhalation)

9
if South Adams County Water and Sanitation District (SACWSD) provides

appropriate documentation of not planning to install future water wells in Zone 5

over the next 30 years, the groundwater pathway will be removed from Zone 5.

In a meeting on April 24, 1997, SACWSD agreed to document that they had no

intentions of installing water wells in zone 5 over the next 30 years. The

documentation, when received, will remove the groundwater pathway from zone 5.

10
ATTACHMENT B
-ýANITATICJ

6595 EAST 70TH AVENUE

P 0. BOX 597

COMMERCE CITY. COLORADO BM37-0597

TELEPHONE 303 288-2646

May 21, 1992

Mr. Kevin T. Blose

Deputy Program Manager

Remedial Planning Branch

Rocky Mountain Arsenal

Commerce City, CO 80022-2180

Re: Request for confirmation of Districts& Ground Water

Development Plans in Zones 3, 4 and S.

Dear Mr. Blose:

In response to your letter of April 27, 1992, please be

advised that the South Adams County Water and Sanitation District

has no current plans to install municipal water wells in the Army's

Zones 3, 4 and 5. This planning assumption is, of course, based

upon current projections of demand in the immediate vicinity of

these zones and existing ground water quality, and therefore could

be subject to change if these circumstances also change. The

District would certainly make every effort to communicate promptly

with the Army if these circumstances do, in fact, change. Also,

because ground water supply and quality are so variable throughout

the District's existing and potential service areas, please be

advised that other requests of this nature will have to be reviewed

on a case-by-case basis.

Sincerely,

SOUTH ADAMS COUNTY WATER AND

SANITATION D.ISTRICT

By:

Larty-rL,./ Ford

Disi:rict Manager

cc: Col. Eugene H. Bishop

Lt. Col. Jeffrey S. Guilford

Mr. Connally E. Mears

Hon. Hank Brown/Ms. Julie Cella

Lysle R. Dirrim, Esq.

David M. Brown, Esq.

Mr. James 1. Michael

Mr. Lewis D. Walker

Mr. Robert L. Duprey
ATTACHMENT C
UNITED STATES ENVIRONMENTAI. PROTECTION AGENCY

REGION viu

999 18th MF.9r - SUITE 900

VVWZM, COLOIMVO 80202-2466

SEP 18 1992

Mf ]EC FM.ýWM

01.7 . WN

mr. Lewis D. Walker &R WNX&..jl AY-ý

Dftnty AselstaUt Sec=i:9%7 Of the A%M 00W.W2

for Inste.13.etion, Logistics and HnvironM=t Jaw-Ma ON

Pentjigon, Room 23577 FILE

Vashingt=# D.C. 20310-03.03 s ivp 2. Z92

bw. Ray Ge=oxd

i Lt 

Vice d -:j

abell, "01 ly

one Sixell ZL

P.O. Ame 2463

zmwCoiý; Twu.w 77252

iftnanweck

RezLoval Mxtctor

U.S. Fish and Wildlife Service

P.O. Box 29486

Dewmr Fedexal Cente'r

De=er, Colomado 80223

Re: Off-post; ZVFS D:LmYutG

em

G=; M. .

you I ave all av=e, the Steezing and Policy COMMitt"

res. ad a umamimus resoluti= of the Off-PoSt WIFS dinmtG

COUG =a3lg 4be g=Umgared Species Act, Migmtory i3ird Treaty Actand Bald and Golden Zqjle Pzvt6ftiOn Act BLt tba September 15, 1

2.992, meeting. ancMosed is etatamBUt of tkat resolution for IMIr

review and conc=ence.

txf*-yW*adu==Ftbat this otat*MQnt aCcumtel-v Mflscts O=

M ?and

decision ezd the basis for the dec:LG:Lmj,

it- to

-ck*. ting ing Regl=a Administrator

znclosure

Mi. an RwjakdAVW
fMni wjt:h encloisure sent tot

Col.. Eugene 3. Disbops U.S. A=T

W. a. mcxi=ny, shaLl. Oil CO.

Rrynal pinle7, U.S. Vish and Wildlife Service

]&=AIGY Bridgmat9r, U.S. Depart=ant of allstieek
R TM AM

The Endangered SpeCiag Act ('BSA'), Migratory Bird TrP_UtY Act

kN) and Buld and GOldGA Nagle protection Act (IIDMA') apply totb?=RcckY VAountaJA Arsez3al . The AXMY shil-I I 613t*bligh reMOdiatiOn

goals for site Contam4-nants to majAtain and enbance healthy

]POPul,ations of the species subject to the BSA, MM and IJGBPA and

their habitats at tba Arseval.

For the off-post cpe=ble vmit, remediation govas for off-post

contau q YMti. t neat the izvmentz of the M, MBT3L and DGMA

have been isbed in coo= tion with the U.S. Fish and Wildlife

service. 9 will ibe I included as enforceable 1: i 9m adistiOn levels in

the 'Propose P, and the Record of Decision.

3por th onýpcot verable unit, remediation goals for roils and

sediments a Cons:Lstent with the BSA, MM and BGZPA will be

estiblis d usirg a methodology aqTsed to by the A=W, Shell and EPA

in c ion, irith the U.S. Fish and Wildlife Service. The A=y

will also t with the Fish and*wild'14fe Service to detexmins

wbether any A activities or rwadial alte=ativen Might

have a a t impact an a subject species or its Mbitat. If SL

date=inant made th the Axwrlo activi .jJw = remadial .

Xn&tive could impact a subjeci species or its babitatp the A=qY

will ccMuslual th the Fish and Wildlife Service to deteruiine whether

the activ-i 8 proceed and whaty it agy mitigation measures =a

necess 8 1uht of azy long te= bensfitn'to protection of

populations of vubi act species.

The Or ations evressly reserve their rights to assext their

respective x tiono r-ancirAing the MA, mBTA and z=PA as ApunRa in

the future.

3
Offpost Operable Unit Endangerment

Assessment/Feasibility Study, Final Report,

Volume Vill of Vill, Task RIFS1

11/24/92, RIC# 93012RO3, Harding Lawson Associates,

Environmental Science and Engineering, Inc.

Diskette #1, ARES&DOC, ARES&EXE,

CHEMRME2.WK1, MASTRMD2.WK1, README

can be located in the Diskette Archive.
Offpost Operable Unit Endangerment

Assessment/Feasibility Study, Final Report,

Volume Vill of Vill, Task RIFS1

11/24/92, RIC# 93012RO3, Harding Lawson Associates,

Environmental Science and Engineering, Inc.

Diskette #2, ARES&DOC, ARES8MLE.EXE,

CHEMMLE.WK1, MASTMLE.WK1, README

can be located In the Diskette Archive.
Offpost Operable Unit Endangerment

Assessment/Feasibility Study, Final Report,

Volume Vill of Vill, Task RIFS1

11/24/92, RIC# 93012RO3, Harding Lawson Associates,

Environmental Science and Engineering, Inc.

Diskette #3, ARES&EXE, CHEMRME2.WK1, DOCUMENT,

MASTRMD2.WK1, READ.ME

can be located in the Diskette Archive.
Oftpost Operable Unit Endangerment

Assessment/Feasibility Study, Final Report,

Volume Vill of Vill, Task RIFS1

11/24/92, RIC# 93012RO3, Harding Lawson Associates,

Environmental Science and Engineering, Inc.

Diskette #4, ARES8.130C, ARES8MLE.EXE,

CHEMMLE.WK1, MASTMLE.WK1, README

can be located in the Diskette Archive.
Offpost Operable Unit Endangerment

Assessment/Feasibility Study, Final Report,

Volume Vill of Vill, Task RIFS1

11/24/92, RIC# 93012RO3, Harding Lawson Associates,

Environmental Science and Engineering, Inc.

Diskette #5, LASUN.WKI, ADBUN.WKI, CADUN.WK1

CHA2UN.WK1, CHE2UN.WK1, DIMPUN.WK1

can be located In the Diskette Archive.
Offpost Operable Unit Endangerment

Assessment/Feasibility Study, Final Report,

Volume Vill of Vill, Task RIFS1

11/24/92, RIC# 93012RO3, Harding Lawson Associates,

Environmental Science and Engineering, Inc.

Diskette #6, LIMPRECS.DBF, GW1RECS.DBF, GW3RECS.DBF,

GW4RECS.DBF, GW5RECS.DBF, GW6RECS.DBF, GW2RECS.DBF,

LIMPFORM.DOC, HIMPFORM.DOC, GW1FORM.DOC, GW2FORM.DOC,

GW3FORM.DOC, GW4FORM.DOC, GW5FORM.DOC, GW6FORM.DOC,

HIMPRECS.DBF can be located In the Diskette Archive.