U.S. ENVIRONMENTAL PROTECTION AGENCY 

OFFICE OF INSPECTOR GENERAL 

Catalyst for Improving the Environment 

Hotline Report 

Contaminated Soil Waste Repository 

at East Mission Flats, Idaho 

Report No. 09-P-0162 

June 8, 2009 
Report Contributors: Eric Lewis 

Dan Cox 

 Tom Reilly 

 Johnny Ross 

 Kathryn Hess

 Kimberly Crilly 

Abbreviations 

BEIPC Basin Environmental Improvement Project Commission 

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

EMF East Mission Flats 

EPA U.S. Environmental Protection Agency 

IDEQ Idaho Department of Environmental Quality 

OIG Office of Inspector General 

ROD Record of Decision 

SVCRC Silver Valley Community Resource Center 

Cover photo: The planned East Mission Flats contaminated soil waste repository location. 

(Photo taken by OIG staff in May 2008) 
U.S. Environmental Protection Agency 09-P-0162 

June 8, 2009 Office of Inspector General 

At a Glance
 

Catalyst for Improving the Environment 

Why We Did This Review 

We conducted this review to 

determine if the U.S. 

Environmental Protection 

Agency (EPA) allowed 

appropriate community

involvement and provided 

adequate notice when selecting 

the East Mission Flats (EMF), 

Idaho, repository location; and 

included flood controls in 

repository design to minimize 

potential for releasing

contaminants. 

Background 

An environmental organization located in Kellogg, 

Idaho, complained to the 

Office of Inspector General 

(OIG) Hotline that EPA did 

not follow Superfund 

requirements in designing the 

repository. The group alleged 

the public was not notified 

appropriately of repository 

plans and did not have an 

opportunity to provide 

comments. 

For further information, 

contact our Office of 

Congressional, Public Affairs 

and Management at 

(202) 566-2391. 

To view the full report, 

click on the following link: 

www.epa.gov/oig/reports/2009/ 

20090608-09-P-0162.pdf 

Contaminated Soil Waste Repository at 

East Mission Flats, Idaho 

What We Found 

EPA Region 10 and the Idaho Department of Environmental Quality (IDEQ) 

provided opportunities for the community to become involved and notified the 

public when selecting the East Mission Flats repository site location and soliciting 

comments on the proposed plan, location, and designs. 

We found that many physical aspects of flooding have been investigated and 

considered in the design process. However, we also found that the geochemical 

aspects and potential for releasing dissolved contaminants had yet to be 

investigated. The proposed repository site is located in an area that floods 

annually. Region 10 and IDEQ have not sufficiently analyzed the geochemical 

conditions that are expected to form near the repository base, the potential for 

annual flooding to introduce water into the repository, and the possibility that 

dissolved contaminants will migrate away from the repository. In response to our 

concerns, Region 10 and IDEQ prepared a draft scope of work for the needed 

analysis. Much of that work was completed and included in Region 10’s response 

to our draft report. But the work leaves unresolved the amount of water that will 

be introduced into the repository with flooding and rising groundwater levels. 

What We Recommend 

We recommended that EPA Region 10 finish analyzing the geochemical and 

physical conditions that may lead to contaminants dissolving near the repository 

base; then confirm the adequacy of the repository design to prevent dissolved 

contaminants from being released under these conditions. 

Region 10 concurred with the recommendation and prepared a technical analysis. 

We acknowledge that the new work is extensive, especially the unsaturated zone 

modeling. However, the Region’s analysis included assumptions, with consequent 

conclusions, that the OIG believes require technical verification. The Region 

should address these issues in its 90-day response to the final report. The 

recommendation will remain open. 
09-P-0162 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF 

INSPECTOR GENERAL 

June 8, 2009 

MEMORANDUM 

SUBJECT: Contaminated Soil Waste Repository at East Mission Flats, Idaho 

Report No. 09-P-0162 

FROM: Wade T. Najjum

 Assistant Inspector General 

Office of Program Evaluation 

TO:	 Michelle Pirzadeh 

 Acting Regional Administrator 

 Region 10 

This is our final report on the subject review conducted by the Office of Inspector General (OIG) 

of the U.S. Environmental Protection Agency (EPA). This report contains findings that describe 

concerns the OIG has identified and corrective actions the OIG recommends. This report 

represents the opinion of the OIG and the findings contained in this report do not necessarily 

represent the final EPA position. Final determinations on matters in this report will be made by 

EPA managers in accordance with established resolution procedures. 

The estimated cost of this report – calculated by multiplying the project’s staff days by the 

applicable daily full cost billing rates in effect at the time – is $418,288. 

Action Required 

In accordance with EPA Manual 2750, you are required to provide this office with a written 

response within 90 days of the date of this report. You should include a corrective action plan 

for agreed-upon actions, including milestone dates. We have no objections to the further release 

of this report to the public. This report will be available at http://www.epa.gov/oig. 

If you or your staff have any questions regarding this report, please contact Eric Lewis at 

202-566-2664 or lewis.eric@epa.gov, or Tom Reilly at 202-566-2897 or reilly.tom@epa.gov. 
Contaminated Soil Waste Repository at 09-P-0162 

East Mission Flats, Idaho 

Table of Contents 

Purpose ................................................................................................................................ 1 

Background .......................................................................................................................... 1 

Scope and Methodology...................................................................................................... 3 

Results of Review ................................................................................................................ 4 

Notification and Community Involvement................................................................... 4 

Evaluating the Potential for Contaminant Release..................................................... 6 

Recommendation ................................................................................................................ 9 

Agency Comment and OIG Evaluation ............................................................................. 9 

Status of Recommendation and Potential Monetary Benefits ........................................ 10 

Appendices 

A Agency Responses .................................................................................................... 11 

B OIG Comments ........................................................................................................... 21
 

C Distribution ................................................................................................................. 26 
09-P-0162 

Purpose 

The purpose of this review was to determine whether an OIG Hotline complaint that the 

Silver Valley Community Resource Center (SVCRC) submitted to the U.S. 

Environmental Protection Agency (EPA) Office of Inspector General (OIG) had merit. 

In conducting this review, we pursued the following questions: 

1.	 Did EPA Region 10 and the Idaho Department of Environmental Quality 

(IDEQ) allow for appropriate community involvement in selecting the 

repository site location and providing comments on the proposed plan and 

repository designs? 

2.	 Did Region 10 and IDEQ provide adequate public notification regarding 

the waste repository proposed for East Mission Flats (EMF)? 

As a result of the community concerns and our own observations, we pursued an 

additional objective: 

3.	 Did Region 10 and IDEQ incorporate flood controls in the repository 

design to minimize potential for contaminant release? 

Background 

SVCRC, an environmental organization located in Kellogg, Idaho, submitted a complaint 

to the OIG Hotline. SVCRC alleged that EPA did not follow Comprehensive 

Environmental Response, Compensation, and Liability Act (CERCLA) requirements in 

designing the EMF repository. The repository is located close to the Old Mission 

National Historic Landmark and State Park near Cataldo, Idaho, in an area that floods 

every spring. SVCRC alleged the public did not receive appropriate notification of the 

repository plans and did not have sufficient opportunity to provide comments. 

Community members were also concerned that contaminants from the repository might 

migrate from the site during annual flooding. 

The EMF repository site (see Figures 1 and 2) encompasses a 23-acre parcel of land 

about 3⁄4 of a mile west of Cataldo, Idaho. The repository site is 1,500 feet from Old 

Mission State Park and about 3,000 feet from the Coeur d’Alene River. Interstate 90 

separates the site from the park and the river. 

Sediments at the repository site are already contaminated. Contamination within the river 

basin includes source areas of mine and mill sites in the upper South Fork of the Coeur 

d’Alene River valley and deposits of mining waste on the 100-year floodplain in the 

lower river valley, west of Cataldo. 

The repository will hold about 416,000 cubic yards of soils contaminated with lead, 

arsenic, and other metals. Remedial actions in the Bunker Hill Mining and Metallurgical 

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Complex (Bunker Hill) Superfund Site (Operable Unit 3) will generate these soils. In 

response to public comments on the 30% Design Report, EPA Region 10 and IDEQ 

reduced the planned height of the repository from 62 feet to 34 feet to eliminate direct 

sight lines from the park to the top of the repository. 

Figure 1. Aerial photo of repository site location. 

(Source: Mapquest.com website) 

Figure 2. EMF Repository Site – December 2007 

(Source: OIG staff photo) 

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09-P-0162 

When Congress passed CERCLA, also known as Superfund, in 1980, it incorporated 

public involvement into the remediation process. Congress intended to ensure that the 

people whose lives were affected by hazardous wastes and EPA’s actions to clean them 

up would have a say in what happened in their community. 

Since then, Congress further strengthened the role of community members through 

passage of the Superfund Amendments and Reauthorization Act of 1986, and EPA, 

through its administrative reforms. While EPA retains the final responsibility and 

authority to decide what will happen at a Superfund site, the Agency must consider 

community input. 

The goal of EPA’s Superfund Community Involvement Program under CERCLA is to 

advocate and strengthen early and meaningful community participation during site 

cleanups. Superfund community involvement staff strive to keep the community well 

informed of ongoing and planned activities, encourage and enable community members 

to get involved, and listen carefully to what the community is saying. EPA’s community 

involvement efforts, through its Community Involvement Plans for specific Superfund 

sites, fulfill the statutory and regulatory requirements of CERCLA, as well as the intent 

of the law. 

The Community Involvement Plan for Operable Unit 3 of the Bunker Hill Site outlined 

community involvement goals and proposed avenues such as local newspapers, public 

meetings, and fact sheets, to provide information to the public. 

The Record of Decision (ROD) for Operable Unit 3 directs EPA to initiate a public 

outreach effort to give citizens and stakeholders an opportunity to comment on the 

location and design of proposed repositories. This outreach effort was to be concurrent 

with the technical evaluation of potential repository sites. 

Scope and Methodology 

We performed work on this assignment from December 2007 through March 2009. We 

interviewed the complainants, local residents, employees in EPA Region 10 and the 

Idaho Department of Environmental Quality, representatives of the Coeur d’Alene Tribe, 

members of the Basin Environmental Improvement Project Commission, and staff from 

the Center for Justice. We visited the planned repository site in East Mission Flats, 

Idaho, during May 2008 and observed that the site was inundated with several feet of 

water. We attended an “open house” conducted by IDEQ and Region 10 in July 2008 to 

update interested local residents on design plans for the repository. We reviewed site 

administrative files, community relations files, cleanup planning documents, and the 

intermediate design reports, referred to as the 30% and 60% Design Reports. 

We performed this review in accordance with generally accepted government auditing 

standards as issued by the Comptroller General of the United States. We limited our 

review of management controls and compliance to those directly relating to the issues 

identified in the hotline complaint. 

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09-P-0162 

Results of Review 

Notification and Community Involvement 

Region 10 provided adequate opportunities for public comment on the ROD 

Region 10 provided adequate opportunities for the public to comment on the ROD for 

Operable Unit 3 of the Bunker Hill Superfund site which was issued in September 2002. 

EPA received more than 3,300 comments on the proposed Basin Cleanup Plan from 

approximately 1,300 different individuals.1 EPA extended the comment period twice, for 

a total of 120 extra days, in response to public requests. Part 3 of the ROD contains the 

summaries of public comments and the EPA responses. 

The Region published a Community Involvement Plan for the Coeur d’Alene Basin and 

Bunker Hill Superfund site in August 2005. Consistent with the plan, EPA and IDEQ 

provided information on ongoing cleanup efforts in the Bunker Hill complex through the 

Basin Environmental Improvement Project Commission (BEIPC)2

, the Citizens 

Coordinating Council3, town hall meetings, Internet sites, newspapers, and a door-to-door 

campaign informing community members of ongoing cleanup efforts. 

Region 10 and IDEQ met ROD community involvement requirements in 

siting the repository 

During January and February 2005, EPA and IDEQ representatives went door-to-door to 

discuss with seven individuals living near the site the potential for siting a repository at 

East Mission Flats. The IDEQ representative also contacted one individual by phone, left 

handouts at four residences, and mailed certified letters and handouts to two individuals. 

Region 10 and IDEQ also discussed, during a July 2005 town hall meeting which 19 

community members attended, the possibility that a repository could be sited at East 

Mission Flats. At this meeting, the Region and IDEQ indicated that attendees were 

welcome to provide written or verbal comments regarding the siting of the repository. 

During an October 2005 town hall meeting, Region 10 again indicated that there was an 

urgent need to site more repositories in the Coeur d’Alene Basin and asked the Citizens 

Coordinating Council for help in identifying appropriate locations. The Region also 

noted that efforts were ongoing to investigate whether a repository could be sited at 

“Mission Flats.” 

1 Ombudsman Review of Bunker Hill and Coeur d’ Alene Basin Superfund Actions; OIG Report No. 2004­

P-00009, March 24, 2004. 

2

 The Coeur d’Alene Basin Environmental Improvement Project Commission (BEIPC) was established 

when the ROD was issued for Operable Unit 3.

3

 The Citizens Coordinating Council was formed as a sub-group under the BEIPC to provide a mechanism 

for the community and other interested stakeholders to obtain information on site plans and activities and 

express their concerns. 

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In the December 2006 Basin Bulletin, Region 10 published an article indicating that 

IDEQ had purchased property at East Mission Flats in September 2006 and, jointly with 

Region 10, was proceeding to design a new repository at that location. 

Region 10 and IDEQ met ROD community involvement requirements in 

designing the repository 

In designing the repository, Region 10 and IDEQ adequately addressed the ROD’s 

community input/notification requirements. Region 10, IDEQ, and BEIPC conducted 

several public meetings where they provided information on the design of the EMF 

repository. For example, they: 

•	 sponsored a community meeting at the Canyon School in March 2006, 

•	 presented information on the repository at a Citizens Coordinating Council 

meeting in May 2006, 

•	 made update presentations at Citizens Coordinating Council meetings in 

February and May 2007, 

•	 provided a public tour of the EMF site in June 2007, and 

•	 held a discussion on the 30% Design Report at the Canyon School in 

October 2007. 

The public was given the opportunity to submit comments on the 30% Design Report 

between May 16 and July 6, 2007. Among those providing comments on the design were 

the Coeur d’Alene Tribe, Center for Justice, Idaho Conservation League, SVCRC, and 

the Lands Council. In response to the public comments received on the 30% Design 

Report, Region 10 and IDEQ made several changes to the repository design. For 

example, 

•	 The height was reduced from 62 to 34 feet for a maximum top elevation of 

2,165 feet. 

•	 The volume was reduced from about 668,000 to 416,000 cubic yards. 

•	 Perimeter protection will now be installed as soon as the perimeter of the 

repository is built to an elevation of 2,152 feet. This change was expected 

to permanently protect the site from erosion due to flooding. 

•	 Temporary protection steps are to be taken to protect the placed soils from 

eroding while the repository is open. 

•	 The existing gate is to be replaced with a key card for controlled and 

monitored access to control what materials are disposed of at the 

repository. 

IDEQ and Region 10 also held a community “open house” on July 31, 2008, where the 

public was invited to review and give suggestions on the executive summary of the 60% 

Design Report for the EMF repository. The public was given the opportunity to submit 

written comments through September 8, 2008. 

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Evaluating the Potential for Contaminant Release 

The complainant and other local citizens raised concerns regarding potential release of 

contaminants from the repository that might result from flooding. The proposed 

repository will be built on the floodplain of the Coeur d’Alene River. The area is known 

to flood annually, although the magnitude of that flooding varies year to year. At a 

minimum, water is expected to cover over half of the lower perimeter of the repository 

for several weeks during the annual run-off period. When OIG personnel visited in May 

2008, the site was under several feet of water (see Figure 3). We reviewed the 30% and 

60% Design Reports to determine the degree to which the repository has been designed to 

prevent contaminants leaving the repository by being eroded or dissolved by flood waters 

that penetrate the repository and then drain away. 

We found that many of the physical aspects of flooding had been considered in the design 

process. However, we also found that: 

•	 the geochemical and physical conditions that might lead to contaminants 

dissolving near the repository base had yet to be investigated, and 

•	 the adequacy of the repository design to prevent dissolved contaminant release 

had yet to be evaluated. 

.

(Source: OIG staff photo) 

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Potential Erosion of Repository Waste Materials 

The latest repository design included armoring the sides of the repository to protect the 

repository waste materials from being carried away by flood waters. Compacting the 

waste materials as the repository is constructed will also make erosion less likely. The 

design specifications were to prevent erosion of the repository waste materials under the 

maximum velocity and shear stress expected in a flood of a magnitude estimated to occur 

once every 100 years. Estimates of stress were made using a numerical model 

constructed to simulate the hydraulic effects of flooding at the repository site. The 

construction plan for the armoring was modified to include annual construction stages 

with the intent of preventing erosion of repository materials throughout the many years 

that the repository is expected to be open to receive new waste soils. 

We found that the design team had considered the potential for erosion of the repository 

materials, and incorporated into the repository design elements that will lessen the 

likelihood that erosion will occur under the expected conditions. 

Potential Geochemical Mobilization of Contaminants 

IDEQ and Region 10 have not evaluated the physical and geochemical changes that will 

develop within and below the repository because the site floods annually. The 60% 

Design Report and the October 2008 response to comments received on the report 

suggest several issues that we detail below. 

We found that the October 2008 response dismisses concerns regarding the potential for 

metals to leach from the repository into the underlying groundwater. The primary 

argument provided is that the metal concentrations in the underlying groundwater are 

below drinking water standards, even though the top 2 to 4 feet of soils at the repository 

site have been contaminated for decades. However, not far from the repository site, 

where the thickness of contaminated soils is much greater due to historic dredge and 

dump activities, the groundwater concentrations, according to Appendix B of the 60% 

Design Report, were more than twice the ecological standard for zinc. As a result, adding 

over 30 feet of contaminated soils may potentially contaminate the groundwater under 

and beyond the repository if adequate mitigation steps are not incorporated into the 

repository design. We also found the argument given did not consider changes in the 

geochemical conditions that are anticipated to occur within and underneath the 

repository. 

The October 2008 response also reports that the repository cap will practically eliminate 

infiltration from precipitation into the compacted, contaminated materials. However, this 

response does not acknowledge that the infiltration cap does not extend down the sides of 

the repository where the contaminated materials will be capped instead by gravel and 

other armoring materials. Nor does the response consider that a liner will not be placed 

at the repository base, even though the groundwater level is known to rise above land 

surface annually with the flooding. No barriers will be present to prevent flood waters 

from infiltrating into the repository materials from the side and from underneath. 

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The metals in the repository materials will be fairly stable, except under the reduced 

geochemical conditions4

 that are expected to occur near the repository base, according to 

the 60% Design Report. The report suggests that a geochemical model could be 

constructed to include the effects of developing a reducing environment near the 

repository base. This modeling should include adding flood waters into the repository 

annually. 

The 60% Design Report identified that dissolved oxygen concentrations in the 

groundwater underlying the repository site are already fairly low (less than or equal to 1 

milligram per liter). The report does not attempt to explain this condition and does not 

explore the implications of this oxygen-reduced water rising into the repository during 

annual flooding. With oxygen concentrations already low, the groundwater may more 

likely become reduced as it rises into the repository during annual flooding. Reduced 

geochemical conditions would then promote dissolving metal contaminants and increase 

the possibility of contaminants migrating. 

We concluded that EPA Region 10 and IDEQ have not sufficiently analyzed: 

•	 the reduced geochemical conditions that are expected to form at the repository 

base, 

•	 the potential for annual inundation by floodwaters to introduce water into the 

repository that will maintain the reduced conditions, and 

•	 the possibility that dissolved contaminants will migrate away from the repository. 

For example, staff calculating the quantity of water that might infiltrate have assumed 

that inundation by flood waters will be on the order of 5 days, whereas the 60% Design 

Report indicates annual flooding persisting for several weeks. Laboratory experiments 

with contaminated soils have been limited to leaching with water similar to precipitation. 

To understand if contaminants will be mobile under the reduced conditions expected to 

form near the repository base, the experiments should include leaching experiments under 

reduced conditions. Region 10 and IDEQ should conduct the analysis needed to 

understand geochemical conditions that will prevail if the repository base stays saturated. 

Factors to consider include infiltration of water with annual flooding and settlement 

beneath the repository. If reduced conditions are predicted to be maintained near the 

base, Region 10 and IDEQ should modify the repository design to mitigate any 

unacceptable migration of dissolved contaminants that might result. 

In response to OIG concerns, Region 10 and IDEQ prepared a draft scope of work for 

this analysis. On December 2, 2008, we met with Region 10 and IDEQ to discuss the 

scope of work and the need for their planned work and results to be reviewed. The 

reviewer or reviewers should be independent of the design team and qualified to assess 

that the analysis is technically sound and that the repository will protect human health 

and the environment. 

4

 Reduced geochemical conditions form when the available oxygen has been consumed by biological or 

abiotic processes. 

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In its response to our report, dated April 17, 2009, Region 10 described the results of the 

analysis. We acknowledge that the new work is extensive, especially the unsaturated 

zone modeling. 

Region 10 sent an additional response, dated May 15, 2009, that included a technical 

review by an EPA research geochemist. The reviewer did not cover work related to 

physical infiltration of water into the proposed repository. 

We have identified several technical issues with the work the Region and IDEQ have 

conducted that leave unresolved the amount of water that will be introduced into the 

repository with flooding and rising groundwater levels. Region 10’s response 

memoranda are included in Appendix A. Our comments, describing technical issues that 

need to be addressed, are in Appendix B. 

Recommendation 

We recommend that the EPA Regional Administrator, Region 10: 

1.	 Finish analyzing the geochemical and physical conditions that might lead to 

contaminants dissolving near the repository base; then confirm the adequacy of 

the repository design to prevent dissolved contaminants from being released 

under these conditions. 

Agency Comment and OIG Evaluation 

Region 10 concurred with the recommendation and prepared a technical analysis. 

However, the Region’s analysis included assumptions, with consequent conclusions, that 

the OIG believes require technical verification. The Region should address these issues 

in its 90-day response to the final report. The recommendation will remain open. 

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Status of Recommendation and 

Potential Monetary Benefits 

POTENTIAL MONETARY 

RECOMMENDATIONS BENEFITS (in $000s) 

Rec. 

No. 

Page 

No. Subject Status1 Action Official 

Planned 

Completion 

Date 

Claimed 

Amount 

Agreed To 

Amount 

1 9 Finish analyzing the geochemical and physical 

conditions that might lead to contaminants 

dissolving near the repository base; then confirm 

the adequacy of the repository design to prevent 

dissolved contaminants from being released under 

these conditions. 

O Regional Administrator, 

Region 10 

O = recommendation is open with agreed-to corrective actions pending 

C = recommendation is closed with all agreed-to actions completed 

U = recommendation is undecided with resolution efforts in progress 

10
 

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Appendix A 

Agency Responses 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 10 

1200 Sixth Avenue, Suite 900
 

Seattle, WA 98101-3140 

April 17, 2009 

Reply To: Coeur d’Alene Field Office 

MEMORANDUM 

SUBJECT: OIG Draft Hotline Report – Contaminated Soil Waste Repository at East 

Mission Flats, Idaho 

OIG Assignment No. OCPL-FY08-0002 

Dated March 30, 2009 

FROM: Daniel D. Opalski, Director 

Office of Environmental Cleanup 

TO: Eric Lewis, 

Product Line Director, Special Reviews 

Office of Program Evaluation 

This memorandum is in response to your draft hotline report on the Contaminated 

Soil Waste Repository at East Mission Flats, Idaho. Region 10 would like to thank you 

for your thorough review of the concerns raised by the complainant and the work 

performed by EPA and the Idaho Department of Environmental Quality (IDEQ). We feel 

the report fully endorses the extensive public outreach efforts that both agencies have 

conducted for this repository site. 

We also believe the report’s technical recommendation is consistent with our 

remedial design process and the adaptive management approach we are using for this 

project and others throughout the Bunker Hill Superfund Site. Below you will find our 

response to the draft recommendation, a discussion of other technical issues contained 

within your report, and a recommendation from Region 10 on the content of your report. 

Region 10 Response 

Region 10 concurs with the report’s recommendation and believes that the 

analyses recommended by OIG have been completed by the IDEQ and incorporated into 

the East Mission Flats Repository Draft 90% Design Report. As you are aware, the Draft 

90% Design Report was not completed at the time the OIG interviews were conducted. 

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09-P-0162 

The report is still in draft and is undergoing internal agency review. Once the agency 

review is complete, IDEQ will provide the Final 90% Design Report to the public. 

See OIG Comment 1 in Appendix B. 

The Draft 90% Design Report contains two appendices that provide technical 

support for the geotechnical and hydrogeologic aspects of the design. We are enclosing 

copies of Appendix G and Q from the Draft 90% Design Report with this response. 

Appendix G discusses consolidation of the soils within the footprint of the future 

repository and Appendix Q addresses multiple geochemistry evaluations. In the interest 

of brevity, the information contained in this memorandum are summaries of more 

detailed information contained in appendices G and Q. 

The following sections summarize the EPA and IDEQ response to the recommendation in 

the OIG draft Hotline Report, our response to a request noted in the draft report, and a 

suggested edit to the background section to provide more detail on the existing 

environmental conditions at the site. Each issue is identified by the page and paragraph it 

appears in the OIG report. 

Recommendation, Page 9 Paragraph 2 

Finish analyzing the geochemical and physical conditions that might lead 

to contaminants dissolving near the repository base; then confirm the 

adequacy of the repository design to prevent dissolved contaminants from 

being released under these conditions. 

Response: OIG staff reviewed design documents up to and including the 60% 

Design Report. At the 60% design phase geochemical and physical conditions that might 

influence contaminant mobility near the repository base had not been fully addressed. 

Contaminant mobility is dependant on the presence of water within the repository to 

saturate waste material and the geochemical behavior of metals in various geochemical 

regimes. Both aspects of contaminant mobility were evaluated during the 90% Design 

Report effort. The results of this evaluation are summarized in Appendix Q of the Draft 

90% Design Report. 

Three pathways of water influx to the repository were assessed for the 90% 

Design Report: (1) downward vertical migration through the evapotranspiration (ET) 

cover; (2) lateral infiltration due to contact with flood water; and (3) upward vertical 

migration from the first water-bearing zone beneath the site. In addition to the water flux 

modeling, an assessment of the potential for metals leaching from remedial actionderived soil under oxidizing conditions was performed. 

See OIG Comment 2 in Appendix B. 

Results of the water influx assessment indicated infiltration through the top 

surface of the repository will be minimized or eliminated by the construction of an ET 

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cover. Vertical migration of groundwater upward into the base of the repository will not 

occur due to the low hydraulic conductivity of the underlying soils and lack of sustained 

driving hydraulic head. Long-term saturation of the base of the repository due to periodic 

flood events and the development of reducing conditions are not expected. Lateral 

infiltration model results estimate inundation by surface water due to periodic flooding 

will saturate a ring approximately 13 to 16 feet wide and 0.3 to 0.5 feet thick at the 

perimeter of the repository, less than 0.05% of the total repository volume. EPA and 

IDEQ believe these are conservative estimates for the extent of saturation. The 

assumptions used in the lateral infiltration model are listed in Appendix Q. Since 

reducing conditions within the waste soil mass were not anticipated, an evaluation of 

metals mobility under reducing conditions was not conducted. 

See OIG Comment 3 in Appendix B. 

Leachate generated from the small volume of water that may penetrate the yard 

waste soil is not expected to contain elevated levels of metals. The surface water will be 

saturated with oxygen, unlike the sub-oxic water in the first water-bearing zone. Based 

on column tests approximating oxidizing conditions at the proposed repository, arsenic, 

cadmium, and lead will not be mobilized and low levels of antimony and zinc will be 

present. The column tests actually indicate that the existing deposits have the potential to 

generate more metals than yard waste soil, specifically cadmium and zinc. Cadmium, 

leached from the existing native deposits, may be in the range of the primary drinking 

water maximum contaminant level (MCL), and zinc could exceed the secondary drinking 

water MCL. Because the existing soils generate higher levels of metals than the 

proposed yard waste, the reduction in infiltration beneath the repository footprint should 

result in an overall decrease in metals leached to shallow groundwater and an 

improvement in water quality. 

See OIG Comment 4 in Appendix B. 

The repository design is intended to protect human health and the environment 

from releases due to reasonably foreseeable events and we believe it is adequate based on 

the results of the referenced studies. Assessment of the design performance is part of the 

operations and maintenance program established for the site. One goal of the design is to 

protect groundwater quality. To help achieve that goal the groundwater monitoring 

program will continue on a regular basis for as least as long as it takes to fill the 

repository to capacity. Currently that monitoring program is conducted quarterly, but that 

may be revised as appropriate through adaptive management and other means. In 

addition, the site will be maintained in perpetuity by the State of Idaho to minimize the 

potential for release of contaminants from the site to the environment. If the water 

quality data show a trend of increasing dissolved metals concentrations, the first issue 

would be to identify the cause of the increase. Once the cause of the increase is 

identified, an appropriate remedy would be developed and implemented. This 

management approach is based on realistic site characterization assumptions in an effort 

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09-P-0162 

to produce a cost-effective solution to long-term waste soil storage at the East Mission 

Flats Repository Site. 

Third-Party Review Request, Page 9, Paragraph 1 

. . . we met with Region 10 and IDEQ to discuss the scope of work and the 

need for the planned work and results to be reviewed. The reviewer . . . 

should be independent of the design team and qualified to assess that the 

analysis is technically sound and that the repository will protect human 

health and the environment. 

Response: A review by an independent third party will be conducted in spring 

2009. Comments from the third-party reviewer will be incorporated into the Final 90% 

Design Report. 

See OIG Comment 5 in Appendix B. 

Suggested Edit to the Background section 

The selected repository site at EMF is located within the drainage of the South 

Fork and main stem Coeur D’Alene River. The entire river drainage has been impacted 

by mine and smelter wastes, including the EMF site and surrounding area. In order to 

provide a more complete description of the existing environmental conditions at the 

repository site, the background section on Page 1 should include reference to the preexisting widespread distribution of metals in soils and groundwater. 

See OIG Comment 6 in Appendix B. 

Conclusion 

I’d like to close by saying that Region 10 appreciates the work of your staff 

during the review of the East Mission Flats Repository. We’d like to work with you to 

finalize your report as soon as possible. At this time, EPA and IDEQ are planning to 

finalize the repository design in May 2009. Please feel free to contact Bob Phillips if 

you have any questions regarding this response. 

Attachments (2) 

cc: Michelle Pirzadeh, 

Acting Regional Administrator, Region 10, ORA 140 

Dan Opalski, 

Director, Office of Environmental Cleanup, ECL 117 

Cami Grandinetti 

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Manager, Cleanup Unit 4, ECL 111 

Angela Chung 

Team Leader, Coeur d’Alene Basin, ECL 111 

Ed Moreen 

Project Manager, EPA - Coeur d’Alene Field Office 

Bob Phillips 

Audit Coordinator, OMP-145 

Rob Hanson 

Mine Waste Cleanup Program Manager, IDEQ, Boise 

Andy Mork 

Project Manager, IDEQ, Boise 

See OIG Comment 7 in Appendix B. 

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 10 

1200 Sixth Avenue, Suite 900
 

Seattle, WA 98101-3140 

OFFICE OF 

ENVIRONMENTAL CLEANUP 

May 15, 2009 

MEMORANDUM 

SUBJECT: Supplemental Information for March 30, 2009 Office of Inspector General 

Draft Hotline Report – Contaminated Soil Waste Repository at East 

Mission Flats, Idaho 

Office of Inspector General Assignment Number: OCPL-FY08-0002 

FROM: Daniel D. Opalski, Director 

Office of Environmental Cleanup 

TO: Eric Lewis, Product Line Director 

 Special Reviews 

Office of Program Evaluation 

This letter is in follow-up to my response dated April 13, 2009, in which I 

indicated that a third party was going to review the geochemical analysis performed for 

the contaminated soil waste repository at East Mission Flats, Idaho. That review has 

been performed and a copy of the final memorandum is attached for your information. 

With this review, all is in order for completion of the design and the inception of 

the construction at this site. The Idaho Department of Environmental Quality plans to 

begin construction as soon as possible and no later than the end of the month. We would 

appreciate receiving your final report before that time. 

Please feel free to contact Bob Phillips at (206) 553-6367 if you have any 

questions regarding this letter. 

Enclosure 

cc: Ed Moreen, Project Manager 

Environmental Protection Agency - Coeur d’Alene Field Office 

Bob Phillips, Audit Coordinator 

Environmental Protection Agency 

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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

NATIONAL RISK MANAGEMENT RESEARCH LABORATORY 

GROUND WATER AND ECOSYSTEMS RESTORATION DIVISION 

PO BOX 1198 • ADA, OK 74821 

May 12, 2009 

OFFICE OF 

MEMORANDUM RESEARCH AND DEVELOPMENT 

SUBJECT: Review of Appendix Q, East Mission Flats Repository Geochemistry 

Evaluation, East Mission Flats Repository – Bunker Hill Site 

(09-R10-001) 

FROM: Richard Wilkin, Ph.D., Environmental Geochemist 

Subsurface Remediation Branch 

TO: Ed Moreen, Coeur d’Alene Field Office 

U.S. EPA, Region 10 

Per the request for technical assistance, this memo presents a technical review of 

geochemical issues relating to contaminant behavior in the proposed East Mission Flats 

(EMF) repository in Kootenai County, Idaho. In particular, this review focuses on the 

potential for metals contained in waste materials to be leached, mobilized, and to 

potentially degrade the quality of groundwater underlying the site. 

The EMF repository site is located within the Coeur d’Alene River floodplain. 

The repository footprint is planned to be roughly triangular in shape, covering an area of 

about 14 acres. The top of the repository will be limited to a maximum elevation of 2165 

feet and is designed to rise approximately 32 feet above the existing ground surface. A 

total of about 445,000 cubic yards of material (yard waste) will be placed in the EMF 

repository. Wastes will be placed in 6- to 12-inch lifts and compacted to 90% in the 

interior of the repository and 95% at the perimeter of the repository. It is noteworthy that 

historical flood events have deposited metals-impacted silt and clay upon the entire site, 

as the site is covered with a 1 to 4 foot-thick layer of soil that contains elevated 

concentrations of lead, zinc, arsenic, and cadmium. Below this surface horizon, metals 

concentrations drop sharply and reflect un-impacted native soils of the area. 

Several groundwater monitoring wells have been constructed at the site. These 

wells have been sampled on a quarterly basis since December 2007. The wells are 

screened over a depth interval of 10 feet, from 17 to 27 feet below ground surface. Water 

quality data and water level data have been collected from these wells. To date, results of 

the monitoring indicate that groundwater underneath the site meets EPA drinking water 

standards for the suite of metals tested. This is significant given the fact that 

contaminated soils are present at the land surface. 

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The potential for groundwater impacts from the placement of metals-impacted 

soil at the EMF repository has been assessed by evaluating hydrological and geochemical 

data and by conducting column leach tests to simulate site conditions. The leach tests 

focused in particular on arsenic, lead, cadmium, copper, and zinc. Based on the results of 

these tests, the EMF repository is not expected to impact metals concentrations in 

groundwater beneath the site. The underlying soils have high sorptive capacity and are 

predicted to remove any mobile metals from the aqueous phase. Because groundwater 

impacts are unexpected, liners and leachate collection systems are not part of the design. 

With respect to the hydrologic assessment, three different water entry pathways 

were evaluated. These pathways include infiltration of precipitation and snowmelt, 

migration of rising groundwater through the base of the repository, and lateral migration 

along the perimeter of the repository from ponded surface water. Minimization of 

infiltration will rely on surface grading and construction of a cover consisting of clean 

soil and a planted native grass seed mix. Over the period of monitoring, groundwater 

levels within the casing of the monitoring wells were found to rise to within about 0.5 

feet of land surface. Estimates of water level changes suggest that the saturated zone will 

not reach the base of the repository. Lateral ingress of water during seasonal high-water 

events is expected to cause periodic saturation of a very small portion of waste materials 

at the base of the repository. Less than 0.05% of the total repository volume is expected 

to experience a moisture increase from lateral infiltration. Overall, lines of evidence 

suggest that very little water will reach the waste materials and consequently there is an 

expectation that limited opportunities will become available for geochemical processes to 

take place that lead to leaching of metals from soil to the aqueous phase with subsequent 

migration down to the groundwater table. 

Geochemical evaluations involved evaluation of distribution coefficients, 

sequential extraction procedures, synthetic precipitation leach tests, and column testing. 

Site specific sorption coefficients were not determined. Average values for soil were 

taken from the survey document published by EPA (2005). Note the Kd values published 

in this report differ from those published in a more complete 3-volume review published 

by EPA (1999a,b; 2004). The significance of this is in the fact that Kd values vary 

widely and are most appropriately determined on a site-by-site basis. Nevertheless, the 

main conclusion is reasonable that native materials at the EMF site are expected to have a 

high sorption capacity for metals. The sequential extraction data collected on two 

samples are especially important, as they provide some indication of the potential 

mobility of metals under variable geochemical conditions. A significant fraction of the 

arsenic, cadmium, copper, lead, and zinc in the soils are bound in the Fe/Mn oxide-bound 

fraction (0.20 to 0.63). This fraction can potentially be leached under reducing 

conditions. However, it is expected that oxidizing conditions will prevail throughout the 

repository. The water that does infiltrate the repository is expected to be oxygenated 

surface water, without the capacity to drive reductive dissolution. 

The question as to whether the redox status of water will shift from oxidizing 

conditions to more reducing conditions is not specifically evaluated with model or 

laboratory assessments. The issue is of interest because, under iron-reducing conditions, 

metals associated with Fe and Mn oxides/hydroxides could potentially be mobilized. 

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Again, as noted above, the sequential extraction tests suggested a significant fraction of 

metals associated in this bonding environment. It is important to point out that if 

conditions moved beyond iron-reducing to sulfate-reducing (if sulfate-rich groundwater 

migrated into the repository), metals would again be strongly partitioned to the solid 

phase as insoluble metal sulfide clusters and precipitates. Hence there is a narrow 

window of reduction-oxidation conditions that could develop in conjunction with seepage 

of water through the repository mass and vadose zone to threaten the quality of the 

underlying groundwater. 

Development of a geochemical model to examine trends as the system moves 

from oxidizing to reducing would require a significant amount of extra supporting 

information (e.g., mineralogy, organic carbon concentrations and reactivity, etc.) and 

would likely yield equivocal results. Likewise establishing lab experimentation to mimic 

potential changes in reduction-oxidation conditions, would perhaps be more tractable, but 

would present additional challenges and may ultimately miss conditions that end up 

developing in the repository. Unfortunately, there is no well-established test that can be 

performed to evaluate contaminant behavior over variable redox conditions. The primary 

concern here, however, feeds back to whether or not water is expected to reach the waste 

soils, from upward, downward, or lateral migration. The analysis presented in the 

Repository Design documentation suggests that the repository soil mass will not be 

saturated for prolonged periods of time. These conclusions are based upon a reasonable 

set of data and model assumptions. Given these conclusions, concerns about the potential 

for metals mobilization, while not to be discounted, do not warrant additional testing and 

assessment. It is noted that a groundwater monitoring program is in place to track any 

changes in groundwater quality through time. A phase of assessment and evaluation of 

options would be triggered in the event that the monitoring program detected any 

unanticipated changes in groundwater quality. It is recommended that the monitoring 

program also track the moisture content in the repository in order to obtain data that can 

be directly compared with estimates derived during the design phase of the project, and to 

ensure that stored waste materials stay dry as intended in the repository design. 

If you have any questions concerning these comments, please do not hesitate to 

call me at your convenience (Wilkin: 580-436-8874). I look forward to future 

interactions with you concerning this and other sites. 

References 

U.S. EPA (1999a). UNDERSTANDING VARIATION IN PARTITION COEFFICIENT, Kd, VALUES 

Volume I: The Kd Model, Methods of Measurement, and Application of Chemical Reaction Codes. EPA 

402-R-99-004, August 1999. 

U.S. EPA (1999b). UNDERSTANDING VARIATION IN PARTITION COEFFICIENT, Kd, VALUES 

Volume II: Review of Geochemistry and Available Kd Values for Cadmium, Cesium, Chromium, Lead, 

Plutonium, Radon, Strontium, Thorium, Tritium (3H), and Uranium. EPA 402-R-99-004B, August 1999. 

U.S. EPA (2004). UNDERSTANDING VARIATION IN PARTITION COEFFICIENT, Kd, VALUES 

Volume III: Review of Geochemistry and Available Kd Values for Americium, Arsenic, Curium, Iodine, 

Neptunium, Radium, and Technetium. EPA 402-R-04-002C, July 2004. 

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U.S. EPA (2005). PARTITION COEFFICIENTS FOR METALS IN SURFACE WATER, SOIL, AND 

WASTE. EPA/600/R-05/074, July 2005. 

cc: Linda Fiedler (5203P) 

Rene Fuentes, Region 10 

Bernard Zavala, Region 10 

John Barich, Region 10 

Marcia Knadle, Region 10 

Howard Orlean, Region 10 

See OIG Comment 8 in Appendix B. 

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Appendix B 

OIG Comments 

OIG Comment 1 

The OIG has analyzed the new work that Region 10 and IDEQ have conducted and have 

documented in the memorandum of April 17, 2009, and in the two appendices to the Draft 90% 

Design Report (Appendices G and Q) that were attached to the memorandum. These 

appendices to the Draft 90% Design Report are not included in Appendix A due to their length, 

but are available upon request. 

We acknowledge that the new work is extensive, especially the unsaturated zone modeling. 

However, we have found technical issues in the analyses that prevent the work from meeting the 

intent of the recommendation. Detailed information on these issues is outlined in other OIG 

comments that follow. 

OIG Comment 2 

We agree with Region 10’s assessment that water may enter the repository through three 

potential pathways. 

Region 10 notes that contaminant mobility is dependant on “the geochemical behavior of metals 

in various geochemical regimes.” However, the Region only investigated the potential for metal 

leaching under oxidizing conditions. The Region should also conduct analyses of metals leaching 

under anoxic conditions. Full saturation is not required for anoxic conditions to form. And yet the 

Region uses its predictions that most of the repository will be unsaturated as reason for not 

conducting analyses of metals leaching under anoxic conditions. 

Region 10 states that mobility is “dependant on the presence of water within the repository to 

saturate waste sediments.” While we agree that the mobility of dissolved contaminants is 

greatest when sediments are saturated, dissolved contaminants are mobile to some degree 

under unsaturated conditions. 

We do not believe that Region 10 has presented a decisive argument that groundwater and flood 

waters will not enter the repository and dissolve the contaminants. As such, Region 10 needs to 

investigate the possible mobilization of metals under anoxic conditions. (See also OIG 

Comment 3.) 

OIG Comment 3 

Water Infiltration. We take issue with the analyses that form the basis for the Region’s 

conclusion that two pathways for water to infiltrate into the repository—rising groundwater through 

the base of the repository and flood waters flowing laterally into the repository—will introduce 

minimal water. These analyses were presented in the Region’s memorandum and in the 

Appendices to the Draft 90% Design Report (Appendices G and Q). We do agree with the 

Region’s assessment that the evapotranspiration (ET) cap that will cover the top and upper sides 

of the repository will minimize the amount of precipitation (rain and snow melt) that enters through 

the third possible pathway. 

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Effects of Compaction on Groundwater Rise. The Region’s analysis of the potential for 

groundwater to rise into the repository used groundwater data from well MW-B. These data, 

along with water level data from the other monitoring wells, were presented in Table 1 of 

Appendix Q. A vertical seepage velocity consistent with the 8-foot rise in water levels observed 

between February and June 2008 in well MW-B was calculated. However, when applying that 

seepage velocity, the Region introduced the effects of settlement and compaction to predict 

groundwater rise under the repository. The Region concluded that settlement and compaction 

would reduce the predicted increase in the water level to the degree that no water would be 

introduced into the repository from rising groundwater. We agree that compaction of the clay 

materials underlying the repository would cause a decrease in hydraulic conductivity and, 

therefore, could inhibit the rise in groundwater levels. However, we disagree that a 550 percent 

decrease in hydraulic conductivity will occur under the entire repository. 

Variable Settlement Under the Repository. Figure 11 in Appendix G presented graphically the 

variable amount of settlement, and thus, the variable amount of decrease in hydraulic 

conductivity, expected in the clay material underlying the repository. The analysis shows little 

settlement expected under the outer parts of the repository. Therefore, in these areas, the 

hydraulic conductivity will not be significantly decreased and water level rises of the magnitude 

measured in 2008 in wells MW-B and MW-A should be expected to occur with that magnitude of 

flooding. This rise in groundwater levels would introduce water into the base of the repository. 

Clay Layer Under the Repository is Overestimated. We also disagree with the simplified 

hydrogeologic characterization of the subsurface underlying the repository site that was used in 

the analysis. As presented in Appendix G, 10 feet of clay is assumed to underlie the entire site. 

The clay is assumed to be underlaid by 10 feet of gravely sand. This conceptual model is a 

conservative approach for the geotechnical analysis focused on estimating the amount of 

settlement that might occur under the repository. However, for estimating the hydraulic effects of 

the subsurface materials on rising groundwater levels related to annual spring snow melt and 

flooding, this conceptual model is anything but conservative. It overestimates the amount of clay 

recorded in the site’s geologic logs. Although every log shows some amount of clay, the 

thickness of that clay varies greatly. At one location the clay is only 1.5 feet thick. The horizon 

where the clay was logged varies as well. And some logs show more than one interval of clay. 

This distribution of clay in the logs suggests that the clay is in lenses, as opposed to being in a 

single continuous layer. Clay is the subsurface material that will undergo the greatest change in 

its ability to transmit water due to the weight of the repository. The hydraulic transmission 

properties of silt, sand, and gravel will not change appreciably. The Region’s assumptions of a 

thick and continuous clay layer bias the results of its analysis towards the sediments being overly 

resistant to water level rises. 

Compaction Increases the Hydraulic Gradient. Another issue we have with calculating 

groundwater rise is with using the same hydraulic gradient resulting from the data collected in 

well MW-B to calculate seepage velocity through materials compacted by the weight of the 

repository. The overall energy driving the rise in the water level with flooding will be the same. 

Therefore, as the hydraulic conductivity decreases with compaction, the upward vertical hydraulic 

gradient across the sediments that drives the rise in the water level will increase. The hydraulic 

gradient will not stay the same as the Region assumes in its calculations. 

Analysis Needs to Assess Seepage Three-Dimensionally. The seepage velocity calculation 

treats the rising water level measured in well MW-B as a one-dimensional problem. However, the 

water level rises in the floodplain sediments in response to complex, dynamic, three-dimensional 

interactions. New water and energy are added to the subsurface from recharge upgradient, local 

areal recharge from snowmelt, linear recharge along the river, and areal recharge due to surface 

water flooding out of the riverbanks and spreading across the flood plain. If the gravely sand 

deposits being tapped by well MW-B are confined, as claimed in Appendix Q, then the upgradient 

recharge would be the dominant, if not only, source of water coming in and would be responsible 

for the rise in the water level. The seepage analysis needs to be three-dimensional. The level of 

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water rises in well MW-B because of increases in pressures from upgradient, not from below as 

implied in the one-dimensional analysis used in Appendix Q. 

Limited Temporal Data Limits Understanding of the Dynamic System. The Region has little 

temporal data to understand the dynamic groundwater system that is located so near the base of 

the planned repository. Water levels now are being measured quarterly in six monitoring wells. 

But the measurements extend only back to December 2007. In addition, when levels were high 

and the site was flooded, measurements could not be obtained in some of the wells. This means 

that there are even less data to understand the groundwater system when water levels are high. 

Clay Compaction not Sufficient to Prevent Groundwater Rise. We know from measurements 

made in June 2008 in wells MW-A and MW-B that water levels rose 7.5 to 8 feet from when 

previously measured in February 2008. This same rise would have put the water level in wells 

MW-C and MW-D about 1.5 feet above the ground surface. The actual water level could not be 

measured in these wells due to flooding. Having the flooding and highest groundwater levels 

occurring at the same time is consistent with the groundwater and surface waters systems being 

hydraulically connected. This connection means that the energy of the flood waters as they 

cascade out of the steep terrain of the upper river basin has the potential of being transmitted 

through the groundwater system as well as the overbanked river system. The Region’s analysis 

relies on compaction of the clays underlying the repository to provide enough resistance to keep 

the groundwater from rising into the repository. We remain unconvinced by the Region’s 

analyses that groundwater will not rise into the repository during some, if not all, floods. 

Model Needs to Assess Floodwater Retained in Unsaturated Wastes. We conclude from the 

Region’s analysis of lateral infiltration during flooding that substantial floodwater remains in the 

repository wastes months (90 days) after flooding has receded. The Region used a sophisticated 

unsaturated model to estimate the third pathway for water entering the repository—infiltration 

through the sides of the repository during flooded conditions. The Region presents results 

(Figures 2 and 3 in Appendix C attached to Appendix Q of the draft 90% Design Report) at two 

different times in the model run: after 75 days of flooding and then after 90 more days of 

drainage. The Region also presents results from two versions of the model that assume different 

hydraulic properties for the waste materials within the repository. In Appendix Q, the Region 

focuses on the small area that is predicted to become fully saturated. However, the results show 

that the saturation remains above 50 percent throughout the modeled domain. In other words, a 

lot of water is in the unsaturated wastes. The amount of water retained is not presented, 

although the model could be used for this calculation. The modeling results do not support an 

assumption that the repository wastes will eventually dry. 

Model Initial Conditions. Transient models, such as the one presented in Appendix Q, require 

the modeler to assume conditions at the start of the simulation. The modeling results presented 

show artifacts of the initial saturation condition assumed at the start of the modeled period 

(Figures 2 and 3 in Appendix C attached to Appendix Q of the draft 90% Design Report). That 

initial condition is described as 20 percent moisture content by volume. The modeling report 

does not specify the porosity used in the model. But an effective porosity of 0.25 was used in 

calculating the rising groundwater. If we assume a similar porosity was used in the unsaturated 

zone modeling, this means the starting saturation would have been 80 percent. The results show 

that the saturation remains above 50 percent throughout the modeled domain. The effects of the 

initial conditions on the results should be investigated and minimized. 

Model Did Not Assess All Relevant Flooding Scenarios. Only the 12-year-recurrence interval 

flood was simulated in the modeling. Floods of greater frequency, such as the 1-year-recurrence 

interval flood, and of greater magnitude, such as the 100-year-recurrence interval flood against 

which the repository is being armored, also should be simulated to better understand the amount 

of water that will enter the repository over the long run. 

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Model Scenarios Did Not Assess Long-Term Repository Performance. The simulation 

durations were very short: 75 days of flooding were followed by 90 days of drainage. The 

simulation should have lasted at least 1 year to fully model the cyclical nature of the flooding at 

the site. Carrying out a simulation over several flooding cycles would provide insight into the 

long-term performance of the repository. A longer simulation over several flooding cycles would 

help to minimize artifacts introduced by the assumed initial conditions. 

Model Configuration Assumption. The assumption in the model that the base of the repository 

is impermeable is conservative considering the short duration of the model simulations presented. 

However, this assumption would affect model results if multiple flood cycles were simulated. Flux 

out of the model domain through the seepage faces might be predicted because of the 

assumption that the base is impermeable. This might result in the model predicting less retention 

of water within the repository. In addition, flux to the groundwater can never occur with this model 

assumption. 

Model Should Be Used to Fully Assess and Document Repository Performance. In all of 

these simulations, the amount of water entering and leaving the model domain and the change in 

water stored within the domain should be documented. For the modeling that has been done, we 

are presented only a few model results in graphical form. From these graphics, it appears that 

substantial water is retained. However, the Region has not used the computational power of the 

model to quantify the water flux and storage. 

The Region needs to test model assumptions and fully analyze model results to ensure that the 

current repository design, as presented in the Draft 90% Design Report, will minimize the 

floodwaters entering and being retained in the repository wastes. 

OIG Comment 4 

We disagree with Region 10’s conclusion that groundwater will not rise into the repository (see 

OIG Comment 3). As the memorandum of April 17, 2009 states, the groundwater has low levels 

of oxygen. We see the continued need for the Region to evaluate the geochemical potential for 

metals within the repository to be mobilized under anoxic conditions. 

OIG Comment 5 

Region 10 should proceed with having the work technically reviewed, as the OIG analysis was 

limited to information contained in the Region’s response memorandum and the two draft 

appendices. For example, the technical reviewer should have access to the full modeling 

records. Technical review of the hydraulic analyses presented in Appendices G and Q of the 

Draft 90% Design Report should specifically address the issues the OIG raised in these 

comments. 

OIG Comment 6 

Information has been added to the final report describing the extent of contamination in the basin. 

OIG Comment 7 

Region 10 sent the OIG an additional response on May 18, 2009. The memorandum, dated May 

15, 2009, included an independent review of Appendix Q to the 90% Design Report conducted by 

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EPA’s Office of Research and Development, dated May 12, 2009. These two memoranda are 

included in Appendix A. 

OIG Comment 8 

Region 10, in its response of April 17, 2009, agreed to have its analysis reviewed by an 

independent third party. We acknowledge that Dr. Wilkin, in his memorandum of May 12, 2009, 

has thoroughly reviewed many of the geochemical issues related to contaminant behavior in the 

proposed repository. However, Dr. Wilkin’s review did not include hydrologic issues related to 

contaminant mobility in the proposed repository. OIG Comment 3 presents a wide range of 

hydrologic issues that we identified in the attachments to the April 17, 2009, response. As Dr. 

Wilkin stated in his review, “the primary concern here, however, feeds back to whether or not 

water is expected to reach the waste soils, from upward, downward, or lateral migration.” The 

Region’s April 17, 2009, response included assumptions, with consequent conclusions, that OIG 

believes require technical verification. The Region should address these issues in its 90-day 

response to the final report. The recommendation will remain open. 

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Appendix C 

Distribution 

Office of the Administrator 

Acting Regional Administrator, Region 10 

Agency Follow-up Official (the CFO) 

Agency Follow-up Coordinator 

Acting General Counsel 

Director, Office of Environmental Cleanup, Region 10 

Acting Associate Administrator for Congressional and Intergovernmental Relations 

Acting Associate Administrator for Public Affairs 

Audit Follow-up Coordinator, Region 10 

Acting Inspector General 

27