GAO

United States General Accounting Office

Report to Congressional Requesters

September 2000 SUPERFUND

Information Regarding 

EPA’s Cleanup 

Decision Process on 

the Hudson River Site

GAO/RCED-00-193

Page 1 GAO/RCED-00-193 Hudson River Superfund Site

Contents

Letter 3

Appendixes Appendix I: Chronology of Major Events Relating to the Hudson

River Superfund Site 20

Appendix II: Overview of EPA’s Computer Model for the Hudson 

River Superfund Site 24

Appendix III: The Peer Review Process at the Hudson River Superfund 

Site 28

Appendix IV: Comments From the Environmental Protection Agency 32

Figures Figure 1: Upper and Lower Hudson River 8

Figure 2: Upper Hudson River and Thompson Island Pool 9
Contents

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Abbreviations

BMR Baseline Modeling Report 

RBMR Revised Baseline Modeling Report

CERCLA Comprehensive Environmental Response, Compensation, and 

Liability Act of 1980

CIP Community Interaction Program

CWA Clean Water Act

DEIR Data Evaluation and Interpretation Report

DOSM Depth of Scour Model

EPA Environmental Protection Agency

ERA Ecological Risk Assessment

GE General Electric Company

HHRA Human Health Risk Assessment

HUDTOX Hudson River Toxic Chemicals Model

LRC Low Resolution Sediment Coring Report

NAS National Academy of Sciences

NOAA National Oceanic and Atmospheric Administration

NYSDEC New York State Department of Environmental Conservation

NYSDOT New York State Department of Transportation

PCBs polychlorinated biphenyls 

PMCR Preliminary Model Calibration Report

RI/FS remedial investigation/feasability study 

ROD record of decision

SAB Science Advisory Board

TIP Thompson Island Pool
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United States General Accounting Office

Washington, D.C. 20548

Resources, Community, and

Economic Development Division

B-285646 Letr

September 28, 2000

The Honorable Thomas Bliley

The Honorable John E. Sweeney

House of Representatives

Approximately 1.1 million pounds of polychlorinated biphenyls (PCB) were 

discharged into the Hudson River in upstate New York from two General 

Electric Company (GE) manufacturing plants during a 30-year period 

ending in 1977, according to the Environmental Protection Agency (EPA). 

This substance, long suspected and subsequently classified by EPA in 1996 

as a probable human carcinogen, has also been linked to a number of 

serious noncancerous health and environmental effects. Sediments 

containing PCBs ultimately contaminated a 200-mile stretch of the Hudson 

River, making it one of the largest sites in Superfund, EPA’s program to 

clean up the nation’s worst hazardous waste sites. Beginning in 1977, New 

York State required GE’s plants to take a number of actions, such as 

treating their wastewater and removing some contaminated sediment, to 

stem the flow of PCBs from them. In 1984, EPA issued an interim decision 

not to implement a long-term cleanup action at the Hudson River 

Superfund site because a technically feasible, cost-effective alternative was 

not available. In response to a request from New York State, in 1989, EPA 

decided to reexamine its earlier decision. It subsequently embarked upon 

an assessment, now in its tenth year, to determine whether health or 

ecological risks exist that are sufficient to warrant cleanup action. EPA 

plans to use this assessment to support its new cleanup decision, which is 

scheduled to be proposed for public comment in December 2000. 

Meanwhile, GE, which EPA considers to be the primary party potentially 

responsible for the contamination, is conducting its own studies because of 

its concern regarding the potential choice of a cleanup action for the site. 

EPA and GE are using complex computer models, developed and operated 

by contractors, to predict future PCB levels in the Hudson River under a 

variety of scenarios. EPA will use its model as one source of information 

for assessing cleanup alternatives, along with geochemical work, data 

analyses, and risk assessments. 

Because of significant public concerns about EPA’s cleanup decision and its 

potential major impact on communities along the upper Hudson River, you 

asked us a number of questions that we addressed by providing 

information on (1) the computer models EPA and GE are using in their 
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assessments and related scientific and technical issues and (2) the 

processes EPA is using to obtain and respond to scientific and technical 

comments on its modeling and other assessment studies. 

We discussed the assessment of the Hudson River site with both EPA and 

GE officials, as well as peer reviewers who evaluated EPA’s modeling 

efforts. To obtain information about EPA’s and GE’s computer models, we 

reviewed supporting documentation and discussed the models and their 

differences with EPA and GE contractors involved in designing and running 

them. However, we did not independently assess the models or any 

differences identified. We also contacted the peer reviewers of one of the 

five peer review panels, the one charged with reviewing EPA’s final 

modeling efforts. For information on EPA’s processes for obtaining and 

responding to scientific and technical comments on its work, we also 

obtained the views of individuals and community groups that have 

consistently provided technical comments on EPA’s assessment, as well as 

their views on EPA’s public participation process. While we recognize that 

other constituencies, such as the downriver communities, environmental 

groups, and commercial fisherman, have an interest in the outcome of 

EPA’s reassessment, the individuals and groups that consistently provided 

technical comments were generally located in upper Hudson River 

communities, which would be the most affected by dredging the site. 

Results in Brief The computer models that EPA and GE have developed to predict PCB 

levels in the Hudson River are generally similar in structure and have 

produced generally comparable outcomes. For example, both models 

indicate that PCB levels in the Hudson River will eventually decline if no 

cleanup action is taken. However, the models differ in certain technical 

respects, particularly concerning the level of complexity and detail used to 

describe how PCBs behave in the environment. As a result, since the 

models are not interchangeable, they could lead to different conclusions 

regarding the extent to which PCBs pose an unacceptable level of risk to 

human health and the environment, currently and in the future. In addition 

to the modeling differences, EPA and GE disagree on related scientific and 

technical issues, for example, whether PCBs in a certain area of the river 

are a continuing source of contamination for the entire river. 

EPA obtained public and external scientific and technical comments on its 

assessment model and studies from several sources. First, EPA, through a 

contractor, established five independent peer review panels comprised of 

29 experts to review its major scientific and technical work products. 
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These panels received public comments during peer review meetings, a 

step not normally taken. Second, EPA used an extensive public outreach 

process as part of its assessment of the Hudson River. This process 

involved several working groups established by EPA to help ensure that its 

public outreach process was inclusive. Finally, EPA consulted with 

interested federal and state agencies and GE to obtain scientific and 

technical information and suggestions on its approach. EPA expects to 

propose its decision for public comment by December 2000. In reaching its 

decision, EPA plans to incorporate comments received from a number of 

sources, including GE. 

In reviewing a draft of this report, EPA raised four issues that it believed 

warranted clarification. These issues involved the role of its computer 

model in its decision-making process, the differences between EPA’s and 

GE’s computer models, the portions of the Hudson River addressed by the 

computer models, and, regarding the cleanup decision, the views of 

constituencies other than those directly affected by dredging. We clarified 

the report and incorporated additional information to address EPA’s 

comments and made technical changes as appropriate. We also provided 

relevant portions of the draft report to GE for its review and comment. GE 

provided technical clarifications to the draft report, which we incorporated 

as appropriate. 

Background In 1980, the Congress passed the Comprehensive Environmental Response, 

Compensation, and Liability Act (CERCLA), thereby establishing the 

Superfund program to clean up highly contaminated hazardous waste sites. 

To determine the best way to clean up a Superfund site, EPA, or the 

potentially responsible party with EPA’s oversight, generally conducts two 

studies that are part of a site’s assessment process—an extensive 

investigation of a site’s contamination and the risks it poses and an 

evaluation of alternative remedies to address these risks. 

According to EPA officials, the agency decided to conduct these studies for 

the Hudson River Superfund site because it was uncertain whether GE 

could be objective.1

 If a cleanup action were ultimately selected, GE would 

be potentially responsible for the cleanup, which could cost hundreds of 

millions of dollars if the cleanup action involved dredging. GE, therefore, is 

1

EPA refers to the site as the “Hudson River PCBs Site.”
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conducting its own parallel study because of its concern regarding the 

choice of the cleanup action. At the end of the assessment process, EPA is 

required to solicit and respond to public comments on its overall 

assessment and proposed remedy. For the Hudson River site, EPA has also 

issued 13 interim assessment studies for public comment. In addition, it has 

convened five peer review panels to address the scientific merits of the 

most important of these studies, which include descriptions and results of 

EPA’s data analyses, its computer model to predict how PCBs behave in the 

environment, and risk assessments. According to the results of this work, 

EPA plans to propose one or more cleanup actions, called remedies, or 

propose that no action is necessary. For a chronology of major events 

related to the assessment of the Hudson River Superfund site, see appendix 

I.

The computer model developed by EPA, along with geochemical work, 

data analyses, and risk assessments, will be used in selecting a cleanup 

remedy for the Hudson River. The model’s results are used to assess the 

ecological and human health risks posed by PCBs in the river and, 

ultimately, as tools to assess alternatives to address contamination in the 

river, if that is determined to be necessary. Both GE and EPA have 

concluded that the PCBs in the river will continue to diminish, but they 

disagree on such other issues as the risks to human health and the 

environment in the interim. A fundamental area of disagreement is that GE 

believes, on the basis of its analysis, that the PCBs in a certain area of the 

river are buried in deep sediments, while EPA believes that the PCBs in this 

area are a continuing source of contamination for the entire river. 

There are also differences of opinion between GE and EPA regarding the 

effectiveness and the environmental impacts of dredging sediment 

containing PCBs. GE has stated that dredging has not been effective at 

other sites and poses environmental risks; EPA has stated that dredging has 

been effective at other sites without risk. Some communities along the 

Hudson River, particularly those in the upper Hudson River, oppose 

dredging because they fear the establishment of any nearby landfills and 

the significant negative impacts of dredging on their local economies. A 

study of potential landfill sites that EPA initiated in February 1996 

provoked significant concern among the upper Hudson River communities. 

Other Hudson River communities support dredging because of public 

health concerns, including cancer risks and noncancerous health hazards 

from the consumption of contaminated fish, the loss of recreational and 

commercial fishing, and the environmental consequences of PCB pollution 

in the river. Similar questions and issues have arisen at other sites 
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contaminated with PCBs, such as the Fox River site in northeastern 

Wisconsin, where approximately 19,000 pounds of PCBs have been 

identified in Green Bay sediments. EPA stated that it has not yet taken a 

position as to whether dredging is needed and will await the conclusion of 

its assessment process to present its proposed cleanup strategy for public 

comment. 

On the basis of laboratory studies, EPA has classified PCBs as probable 

carcinogens that are also linked to noncancerous health effects, such as a 

reduced ability to fight infections, low birth weights, and learning 

problems. When PCBs are released into the environment, they pass 

throughout the aquatic food chain at increasing levels, a process referred to 

as “bioaccumulation.” The greatest human risk from exposure to the 

Hudson River’s PCBs is through the consumption of contaminated fish. As 

a result, there currently are restrictions on the consumption of fish in parts 

of the Hudson River. Using the river for other activities, such as swimming 

or boating, or as a source of drinking water, does not pose a health risk. 

PCBs also present a threat to wildlife and the environment. 

EPA’s modeling effort is designed to answer the following three questions: 

(1) If no cleanup action is taken at the site, when will PCB levels in the fish 

population recover to acceptable levels for human health and the 

environment? (2) Can cleanup actions significantly shorten the time 

required to achieve acceptable risk levels? (3) What is the risk that, 

following a major flood, PCBs that have been buried by new, cleaner 

sediments would be released into the environment?

The Hudson River Superfund site in New York State extends almost 200 

river miles, from the town of Hudson Falls to New York Harbor. Because of 

different physical and hydrologic characteristics, approximately 40 miles of 

the upper Hudson River, from Hudson Falls to the town of Troy, is 

distinguished from the lower Hudson River below Troy. Of special concern 

to EPA is part of the river, referred to as the Thompson Island Pool (TIP), a 

6-mile area that, according to EPA, contains nearly a quarter of the 

estimated 154,000 pounds of PCBs in the upper Hudson River. EPA does 

not have specific information on the amount of PCBs in the lower Hudson 

River, but they estimate it to be greater than 154,000 pounds. Figure 1 

shows the upper and lower Hudson River, and figure 2 shows details of the 

upper Hudson River and the TIP. 
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Figure 1: Upper and Lower Hudson River

Source: GAO’s presentation of information from an EPA assessment document. 

0 20 mi

Upper

Hudson

Lower

Hudson

Mohawk Riv er

Legend

und So and sl g I Lon

Hudson

River

0

200

150

100

50

0 200

Glens Falls

Hudson Falls

Troy

Albany

Kingston

Newburgh

Poughkeepsie

New York City River miles

Cities

Dams

Vermont

Massachusetts

Connecticut

New York

Pennsylvania

New Jersey

Federal dam
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Figure 2: Upper Hudson River and Thompson Island Pool

Source: GAO’s presentation of information from an EPA assessment document. 

Legend

2000 River miles

Cities

Dams

0 5 mi

Washington County

Warren County

Saratoga County

Rensselaer County

Albany County

Schenectady County

Fish Cr eek

S nook Kill

210 200

220

190

Hoosic River

Hudson River

Moose Kill

180

170

160

Battan Kill

Federal dam

Thompson Island Dam

Fort Miller Dam

Troy

Stillwater

Hadley Glens Falls

Schuylerville

Waterford

Hudson Falls

Fort Edward

Mohawk

River

Thompson 

Island Pool
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EPA is conducting its assessment in four major steps: analysis of the 

existing site data, computer modeling to predict future PCB levels, 

assessment of related risks to human health and the environment, and 

evaluation of alternative ways to address the Hudson River’s PCBs. EPA 

has completed the majority of its assessment work and published 

numerous studies describing its work and results. The agency’s intention in 

publishing these studies was to help ensure that interested parties were 

made aware of its progress. EPA is currently in the process of finalizing its 

cleanup options, including taking no action, and expects to issue a 

proposed cleanup plan by December 2000. After a public comment period 

of at least 60 days on its proposal, EPA will prepare a Responsiveness 

Summary addressing public comments on its proposal and develop a 

Record of Decision, which it expects to issue by June 2001. In addition to 

EPA’s assessment, in 1997, the House Committee on Appropriations 

directed the National Academy of Sciences to conduct a study assessing 

dredging methodologies. The results of this study are expected in 

November 2000. 

EPA’s and GE’s Models 

Are Similar in 

Structure But Differ on 

Some Details 

The computer models that EPA and GE have developed to predict PCB 

levels in the Hudson River’s sediments, water, and fish are generally similar 

in structure and have produced comparable outcomes. For example, both 

models indicate that PCB levels in the Hudson River will eventually 

decline, although at different rates, if no cleanup action is taken. However, 

the models differ in certain technical respects, particularly concerning the 

level of complexity and detail used to describe how PCBs behave in the 

environment. As a result, because the models are not interchangeable, they 

could lead to different conclusions regarding the extent to which PCBs 

present an unacceptable level of risk to human health and the environment, 

both currently and in the future. In addition to the modeling differences, 

EPA and GE disagree on related scientific and technical issues, such as the 

extent to which PCBs are buried by new, cleaner sediments. 

Comparison of EPA’s and 

GE’s Models

Both EPA and GE have developed structurally similar computer models to 

describe the physical and chemical processes that affect PCB levels and to 

predict future PCB levels in the sediment, the water, and the fish in the 

upper Hudson River. Specifically, both models consist of four linked 

components: a hydrodynamic model framework to estimate sediment 

erosion, a sediment transport model to describe the movement of 

contaminated PCB sediments in the river, a PCB fate and transport model 

to predict PCB levels in sediment and water, and a bioaccumulation model 
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to predict PCB levels in fish. In addition, both models use a “mass-balance” 

approach to help ensure that the mass (i.e., the sediment, the water, and the 

PCBs) entering a specified area of the river equals the mass that leaves the 

area. The two models are generally based on the same data. The overall 

results of both models show that under a “no action” scenario PCB levels in 

the Hudson River would decline over time but at different rates and that a 

major flood would probably not significantly release PCBs that have been 

buried in the sediment. For more detailed information on EPA’s model, see 

appendix II. 

However, EPA’s and GE’s models differ in some respects. For example, for 

the hydrodynamic model, EPA modeled 6 miles of the Hudson River, while 

GE modeled the entire 40-mile upper Hudson River. In addition, EPA 

assumed that particles suspended in the water settle down to the surface 

sediment at a constant rate, while GE assumed that the impact of water 

flow and particle size affect the settling rate. Because of these differences, 

the models could lead to different conclusions regarding the extent to 

which PCBs pose an unacceptable level of risk to human health and the 

environment, both currently and in the future.

EPA modelers agree that GE’s model might be more complex and detailed 

than the agency’s in some areas. For example, in estimating erosion rates, 

GE’s model is generally structured to account for the impacts of both shortterm and long-term events. However, EPA’s assessment objectives are to 

describe the long-term impacts of river dynamics. Therefore, in EPA’s 

opinion, GE’s detailed approach is not necessary and might not be always 

supported by the available data. For example, in commenting on GE’s 

model, EPA stated that GE found that some of the predicted PCB 

concentrations in fish computed by the GE model needed to be divided by 

two to fit the observed data. EPA modelers believe their model has 

performed well in capturing historical site data and that peer review 

comments on their model have been generally positive. They further 

believe that the agency’s model is a very good tool for describing and 

predicting PCBs’ behavior in the Hudson River. EPA modelers also said that 

differences between the two models are generally a matter of professional 

judgment and do not reflect “flaws” in either approach. Officials in EPA’s 

Region II office, which covers the Hudson River area, stated that any 

differences between GE’s and EPA’s models are not significant in the 

overall assessment process, that their models were found adequate by peer 

review panels, and that the differences do not have to be further addressed 

by EPA or a peer review panel. According to the GE official responsible for 

the Hudson River site, although GE’s model had not been peer-reviewed in 
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a public forum as EPA’s model had been, it had undergone review by 

experts from specific scientific and technical fields as part of the 

company’s policy for its science and product development. The official also 

stated that a major component of GE’s model was recently accepted for 

publication in the scientific journal, Environmental Science and 

Technology, after undergoing the journal’s independent peer review 

process. 

GE modelers, however, believe that the differences between the two 

models could affect EPA’s evaluation of a cleanup alternative, such as 

dredging. For example, they stated that because of the food web structure 

(i.e., the pathway by which PCBs are transferred from water and sediment 

to fish) EPA modelers selected, the agency’s model overly emphasizes the 

importance of water as a source of PCBs to fish. Consequently, they believe 

that EPA would be likely to attach greater importance to cleanup actions 

that lower PCB levels in the water. GE modelers believe that fish are 

getting more PCBs from local sediment, an assertion that they state is 

consistent with the data. 

EPA’s and GE’s Views on 

Related Scientific and 

Technical Issues 

EPA and GE also differ on related scientific and technical issues, such as 

the major sources of PCBs in the river and on the extent of PCB burial by 

new, cleaner sediments. Regarding the sources of PCBs, EPA has 

concluded that while upstream sources significantly contribute to them, 

the sediments in the TIP are the major source of PCBs in the river. EPA has 

primarily supported this position with the results of earlier data analyses, 

published in 1997, which used sediment and water samples to identify the 

sources of PCBs in the river. In contrast, GE believes that the area 

upstream from the TIP, and not the TIP, is the major source of PCBs. 

EPA also concluded that the burial of PCBs by cleaner sediments does not 

prevent them from being released again into the water. EPA bases this 

position primarily on results of its 1998 data analysis involving 60 samples 

of fine sediments taken from the TIP. PCBs are more likely to be deposited 

in these sediments. EPA found that, from 1984 through 1994, from 4 to 59 

percent of the PCBs in these samples were not buried but rather released 

into the water. At a June 1999 public meeting, EPA modelers presented 

additional information on PCB burial rates, which showed that, from 1984 

through 1997, 32 percent of the PCBs in fine sediments in the TIP were 

released into the water and 68 percent were buried. GE modelers, using 

EPA’s model, calculated that only 3 percent of the PCBs in these sediments 
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entered the water. Because of the differences in results, GE believed that 

EPA should have done further modeling. 

Other interested parties, including the Saratoga County Environmental 

Management Council, which is located along the upper Hudson River, 

shared GE’s view on the issues of the major sources of PCBs and the extent 

of their burial. They believe that EPA should have presented more 

modeling results to support its conclusions on these two issues. EPA 

officials stated that they did not conduct additional modeling on this issue 

for two reasons: First, they felt that the monitoring data were sufficiently 

reliable. (Peer review of EPA’s 1997 and 1998 data analyses, conducted in 

March 1999, showed the analyses were acceptable with minor revisions.) 

Second, the differences between the results from EPA’s model and its data 

analyses were presented as a question in the peer review of EPA’s Revised 

Baseline Modeling Report, and the reviewers found no conflicts between 

the results of the agency’s model and data analyses.

EPA Used Three 

Principal Processes to 

Obtain Comments on 

Its Site Assessment 

Studies

EPA has received comments on its Hudson River site assessment studies 

from peer reviews conducted on the agency’s major work products, an 

extensive public participation process, and consultations with interested 

federal and state agencies and with GE. EPA convened five independent 

peer review panels during four peer review sessions to review six major 

assessment studies, including its model. These panels were to determine if 

the agency’s science was credible and valid and to provide it with 

suggestions for improvement. EPA also included the opportunity for public 

comment during the peer review meetings, which is not advised by its 

guidance and not normally done. Furthermore, EPA organized a 

Community Interaction Program (CIP) to ensure public participation in its 

assessment process. As part of this program, the public, including GE, was 

encouraged to review EPA’s assessment work and provide written 

comments, which included suggestions and observations on EPA’s 

scientific and technical analyses. Finally, during its assessment, EPA 

consulted with other interested federal and state agencies and with GE to 

obtain scientific information, suggestions, and data. EPA expects to 

propose its preferred remedy for public comment by December 2000. In 

reaching its final decision, which is currently planned for June 2001, EPA 

plans to consider comments received from a number of sources, including 

GE.
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EPA’s Peer Review Process 

Provided Useful Scientific 

Comments 

EPA obtained scientific comments from peer reviews of all its major 

Hudson River site assessment products, which are largely descriptions of 

its data analyses, computer models, and risk assessments. The goal of peer 

review is to enhance the quality and the credibility of EPA’s decisions by 

ensuring that the underlying scientific and technical studies receive a 

documented, independent, critical review by scientific and technical 

experts. EPA also provided the public with the opportunity to make some 

comments during peer review meetings, which is generally not done. 

EPA’s peer review policy and guidance is presented in its Peer Review 

Handbook, which explains the scientific and technical work products that 

are needed to support rulemaking actions and agency decisions. The 

handbook, prepared by members of the Peer Review Advisory Group (a 

group within EPA’s Science Policy Council), describes the basic peer 

review requirements (including the need for peer review), planning and 

conducting a peer review (such as the selection of peer reviewers), the 

charge questions reviewers are expected to address and their materials, 

and other administrative tasks. The handbook does not provide specific 

guidance on managing peer review meetings and dealing with controversial 

issues, and it provides EPA officials with a significant amount of discretion 

in conducting peer reviews. Furthermore, EPA’s guidance states that public 

comment should be separate from the peer review process, which is 

limited to the consideration of technical issues. However, EPA chose to 

allow public comment during its peer review meetings on the Hudson River 

site. A November 1999 Science Advisory Board (SAB) report on EPA’s peer 

review process favored incorporating public comments in the peer review 

process and stated that EPA’s guidance to avoid public comments and 

controversy was too conservative. Furthermore, the report stated that such 

consideration of diverse views might be helpful to determine needed 

changes to studies, such as those peer-reviewed for EPA’s Hudson River site 

assessment. 

As of June 2000, EPA had conducted five peer review panels that addressed 

six assessment studies of the Hudson River site. Overall, four peer review 

panels found EPA’s work to be acceptable with some revisions. The fifth 

panel generally rejected EPA’s approach to assessing ecological risk, and 

EPA is in the process of responding to the reviewers’ concerns. The five 

panels used a total of 29 experts. EPA has obtained technical comments 

from the panels and has used their comments to change its models and 

studies. For example, in response to comments by the first panel, EPA 

revised its scientific approach to evaluate the PCB levels in fish. In 
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response to comments by the second panel, it adopted a suggestion to 

better quantify the amount of PCBs lost from sediments into the water. 

EPA has also made adjustments to improve its peer review process. For 

example, at the end of panel deliberations for the first peer review, EPA 

allowed members of the public to each make 5-minute presentations to the 

panelists, a time period considered usual by EPA’s contractor. After these 

presentations, however, several members of the public felt that this period 

was not long enough to provide their comments and make their points. In 

response, for the subsequent four panels, EPA provided additional 5-minute 

comment periods before the meetings’ deliberations. Similarly, EPA added 

more formal orientation sessions for subsequent peer review panels in 

response to suggestions received from panelists in the first peer review. 

Despite these changes, some of the peer reviewers we interviewed felt that 

there was insufficient time to review all of the background documents 

provided by EPA, that some of the charge questions did not specifically 

highlight controversial issues, and that they would have liked additional 

background documents to provide a better understanding of certain issues. 

In addition, several of the reviewers felt that, since the public was invited to 

raise controversies at the peer review meetings, it would have been more 

effective to do so at the start of a panel’s review than at the end of the 

review process, thereby giving the panelists more time to consider the 

public’s comments. EPA responded that its goal was to focus the peer 

reviewers on their particular areas of expertise, without overburdening 

them with materials being peer-reviewed by other scientific experts. 

Furthermore, according to EPA, its charge questions to the panelists 

identified the areas of controversy that the panelists had also received 

information on from GE and the Saratoga County Environmental 

Management Council before the meetings. Moreover, GE’s own consultants 

had highlighted controversial issues to the peer reviewers in both the preobserver comment session and again at the final observer comment 

session. Nonetheless, EPA provided more background information, such as 

responsiveness summaries and GE’s reports, to peer review panels. For a 

description of how these peer reviews were conducted, see appendix III.

EPA Provided Opportunities 

for Other Public Comment 

To respond to regulatory requirements and address the unique conditions 

at the Hudson River site, in 1990, EPA established the CIP—a public 

participation program that has allowed the public, including GE, to review 

the agency’s work and provide written comments throughout the 

assessment. Under EPA’s regulations, before the agency adopts a cleanup 
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plan, it must give the public an opportunity to comment on the proposed 

plan and prepare a written summary of significant comments, criticisms, 

and new relevant information submitted during the public comment period 

and of its response to each issue. This responsiveness summary must be 

included with the agency’s final cleanup decision. The regulations do not 

require EPA to prepare or release responsiveness summaries prior to the 

final cleanup decision. In reaching its cleanup decision, EPA plans to 

incorporate comments received from a number of sources, including GE.

Because of the complexity and time taken for the Hudson River 

assessment, EPA decided to make several important work plans and 

certain assessment documents available for public review and comment 

throughout its process. Specifically, the CIP was set up to elicit ongoing 

public feedback through regular meetings and discussions and to facilitate 

review of and comment on work plans and reports prepared during all 

phases of the assessment. The CIP involves several interested parties—

individual citizens; various environmental and community groups; 

scientific and technical experts; GE; and officials from federal, state, 

county, and local governments. The CIP also includes a Scientific and 

Technical Committee that provides technical input during the assessment 

by evaluating scientific data and other information, such as modeling 

approaches. 

One of the CIP’s objectives is to give interested parties the opportunity to 

comment on EPA’s work throughout the course of the assessment and for 

EPA to provide timely and accurate responses to their comments. The CIP 

consists of several volunteer committees and liaison groups and has 

generated extensive public comments on EPA’s assessment. To date, EPA 

has received formal written comments on 12 assessment studies and has 

issued responsiveness summaries for all required products. However, the 

reactions to these summaries have differed: Some parties—specifically, 

GE, the Saratoga County Environmental Management Council, located in 

the upper Hudson River, which would be the most affected by dredging, 

and some of the CIP’s participants—believed that EPA’s responsiveness 

summaries often did not adequately respond to their comments. Other 

parties, such as the New York State Department of Environmental 

Conservation (NYSDEC) and the National Oceanic and Atmospheric 

Administration (NOAA), believed EPA responded adequately to their 

comments. To provide the public with access to significant amounts of 

information regarding its assessment, EPA also maintains 16 information 

repositories at various locations along the Hudson River site. 
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Page 17 GAO/RCED-00-193 Hudson River Superfund Site

EPA’s Contacts With 

Government Agencies and 

GE Yielded Additional 

Technical Comments

In addition to the formal public participation process, EPA has obtained 

input on the Hudson River site assessment, such as additional scientific 

information, suggestions, and data, from interested federal and state 

agencies and GE. For example, EPA has obtained informal comments from 

NYSDEC through almost daily informal contact. As part of its more formal 

interagency review process, EPA sent draft reports to NYSDEC and NOAA 

for their review, prior to making them officially available for public 

comment. 

To a varying degree over the course of the assessment, EPA also exchanged 

information with GE and its technical advisers through such formal and 

informal communications as teleconferences, meetings, and computer 

messages. For example, from October 1996 (following the release of EPA’s 

preliminary report on its model) through October 1998, EPA actively 

worked with GE and its modelers in developing modeling approaches to 

predict PCB levels. 

Agency Comments and 

Our Evaluation

We provided a copy of this draft report to EPA for its review and comment. 

EPA’s comments are presented in appendix IV. EPA raised four issues that it 

believed warranted clarification. First, EPA stated that our draft report 

focused on the role of its computer model in the decision-making process, 

but there is other information it will also use in the process. We agree that 

other information will be used, and this is acknowledged in our report. 

Second, EPA stated that while there are similarities between EPA’s and 

GE’s models in predicting the decline of PCB levels in the Hudson River, 

because these rates of decline differ, the conclusions differ. We revised our 

report to indicate that the rates of decline differ. Third, EPA stated that our 

discussion of the portion of the river addressed by its model applies only to 

two specific components of the model rather than all of EPA’s modeling 

efforts. We revised our report to reflect this distinction. Lastly, EPA stated 

that while the communities along the upper Hudson River would be the 

most physically affected by dredging, there are other constituencies with 

an interest in its final cleanup decision. While we agree that other 

constituencies would be affected by the decision, our review’s objective 

focused on scientific and technical comments, which were provided 

principally by the upper Hudson River community. EPA provided other 

technical clarifications, which we incorporated as appropriate. 
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Page 18 GAO/RCED-00-193 Hudson River Superfund Site

We also provided relevant portions of the draft report to GE for its review 

and comment. GE provided technical clarifications, which we incorporated 

as appropriate. 

Scope and 

Methodology

We reviewed and analyzed various studies from EPA and GE and 

supporting documents that provide information on their modeling 

approaches and overall assessment work to identify the main differences 

between EPA’s and GE’s models and related scientific concerns. These 

studies involved estimating the contamination of PCBs in the Hudson River 

and the environmental and human risks of this contamination. We 

interviewed EPA Region II officials, EPA’s contractor and two 

subcontractors, GE representatives, and GE’s contractors about 

differences and similarities between EPA’s and GE’s assessment models 

and their results. We discussed related scientific concerns with EPA and 

GE officials, relevant federal and state agencies, participants in EPA’s CIP, 

and members of the public and other interested groups. We also reviewed 

documentation on both EPA’s and GE’s models, including the peer review 

comments on EPA’s models.

To describe the processes EPA used to obtain and respond to external 

scientific and technical comments on its assessment studies, we reviewed 

documents and interviewed agency officials involved in the public 

comment process for EPA’s assessment studies, EPA’s informal 

coordination with various governmental organizations and GE, and the 

peer review process. We also reviewed EPA’s and the Science Advisory 

Board’s documents regarding peer review criteria. We observed the 

deliberations of EPA’s third peer review panel and interviewed six of its 

seven panelists. We also interviewed participants in EPA’s CIP and other 

groups interested in the Hudson River site assessment that had consistently 

provided technical comments to EPA’s work products, such as the Saratoga 

County Environmental Management Council, which is located along the 

upper Hudson River, an area that would be most affected by dredging. We 

obtained documents describing EPA’s CIP, attended selected program 

meetings, and discussed the program with its participants. We also 

reviewed the scientific and the technical comments on EPA’s assessment 

studies from GE and the public and EPA’s responsiveness summaries. 

As arranged with your offices, unless you publicly announce its contents 

earlier, we plan no further distribution of this report until 30 days after the 

date of this letter. At that time, we will send copies of this report to 
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Page 19 GAO/RCED-00-193 Hudson River Superfund Site

appropriate congressional committees; interested Members of Congress; 

the Honorable Carol M. Browner, Administrator, Environmental Protection 

Agency; and other interested parties. We will make copies available to 

others on request.

If you or your staff have any questions about this report, please call me at 

(202) 512-6111. Key contributors to this report were Pauline Lichtenfeld, 

James Musial, and John Wanska.

Peter F. Guerrero

Director, Environmental Protection Issues
Page 20 GAO/RCED-00-193 Hudson River Superfund Site

Appendix I

Chronology of Major Events Relating to the Apendxies

Hudson River Superfund Site ApendxiI

Year Event

1957-75 According to the Environmental Protection Agency (EPA), the General Electric Company (GE) discharged an 

estimated 209,000 to 1,300,000 pounds of polychlorinated biphenyls (PCB) into the upper Hudson River from 

factories in Fort Edward and Hudson Falls, New York. Before 1973, the majority of the PCBs were trapped in the 

river bottom’s sediments behind the Fort Edward dam. 

1973 Because of its deteriorating condition, the Fort Edward dam, owned by Niagara Mohawk Corporation, was removed. 

During subsequent spring floods, PCB-contaminated sediments, previously trapped behind the dam, moved 

downstream. PCB contamination now exists in all 200 miles of river sediment downstream of Fort Edward, and, 

according to EPA, an estimated 500,000 to 700,000 pounds of PCBs still remain in the river’s sediments. The 

exposed sediments remaining upstream of the site of the former Fort Edward dam, after the dam’s removal and 

subsequent floods, are referred to as “remnant deposits.” 

1976-77 The New York State Department of Environmental Conservation (NYSDEC) brought suit against GE. As a result, GE 

terminated its use and discharges of PCBs by 1977 and collected and treated storm water and industrial 

wastewater. In addition, the settlement provided for a $7 million program to investigate PCBs and develop methods 

to reduce or remove the threat of PCB contamination. NYSDEC also imposed a ban on fishing in the upper Hudson 

River due to the potential risk posed by the consumption of PCB-contaminated fish.

1976-78 NYSDEC conducted extensive sampling and data analyses of PCBs. This work revealed that the most extensive 

contamination was confined to 40 “hot spots” (areas with PCB concentrations of 50 parts per million) located along 

the 40-mile stretch of the river between Fort Edward and Albany and in five exposed remnant deposits located north 

of the former site of the Fort Edward dam. Twenty of the hot spots were in the Thompson Island Pool (TIP).

1977 The manufacture and sale of all PCBs within the United States was stopped under provisions of the Toxic 

Substances and Control Act.

1977-78 NYSDEC began studies on reducing PCB contamination in the Hudson River. It also removed 14,000 cubic yards of 

highly contaminated material from one of the remnant deposits and performed some containment and bank 

stabilization in the area. 

1980 Section 115 of the Clean Water Act (CWA) was passed, which authorized up to $20 million for the Hudson River 

PCB Reclamation Demonstration Project. The project was intended to determine (1) the feasibility of storing 

dredged toxic materials in secure landfills and (2) the improvement that dredging could make in the rate of recovery 

of a contaminated national waterway. Subsequent lawsuits prevented NYSDEC from undertaking this project.

1983 On October 7, the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) draft 

remedial investigation/feasibility study (RI/FS) for the site was released for public comment. In this document, EPA 

made a preliminary decision to take no action on in-river sediments. However, the remnant deposits were to be 

remediated by in-place containment (i.e., covering them with an impermeable cap and stabilizing the shoreline). 

On October 27, EPA issued a notice to GE that it was a responsible and liable party under CERCLA and that EPA 

would conduct a study and implement any selected remedial alternatives unless GE agreed to do so.

1984 During this year, EPA notified Niagara Mohawk Corporation, owner of the old Fort Edward Dam, that it was a 

potentially responsible party for the site.

In April, EPA issued the final RI/FS on the CERCLA cleanup action for the site.

On September 21, the Hudson River PCB site was placed on the National Priorities List.

On September 25, EPA formally selected the remedial alternative preferred in the final RI/FS. EPA said that in-place 

containment of the remnant deposits was cost-effective but that a technically feasible, or reliable, cost-effective 

cleanup action for the river’s contaminated sediment was not available. EPA also recognized that PCB levels in fish 

and water had been decreasing. However, EPA provided for a future assessment of the no-action alternative for the 

river’s sediment.

1985 NYSDEC continued monitoring PCB contamination in the Hudson River, including sediment sampling programs. 

The New York State courts struck down the state’s approval of a landfill site for PCBs because it violated a local 

zoning ordinance. 
Appendix I

Chronology of Major Events Relating to the 

Hudson River Superfund Site

Page 21 GAO/RCED-00-193 Hudson River Superfund Site

Year Event

1986-88 NYSDEC studied the environmental impacts of dredging at a limited number of highly contaminated sites and 

considered different locations for siting a facility to hold the dredged material. However, NYSDEC was unable to 

obtain approvals for a landfill site.

1989 On July 28, NYSDEC requested that EPA reexamine its no-action decision for sediments in the river presented in the 

CERCLA Record of Decision (ROD).

After several months of negotiation and discussion, on September 27, EPA issued an administrative order to GE to 

design and install the access roads needed to cover the remnant deposits.

On October 13, GE notified EPA of its intention to comply with the administrative order to construct access roads to 

the remnant deposits; surveying and clearing for the roads were initiated.

On December 19, the EPA Regional Administrator sent a letter to the NYSDEC Deputy Commissioner, agreeing to 

reconsider the no-action decision for the river’s sediments and stressing the need for interim remediation of the 

remnant deposits.

On December 20, EPA announced its intention to reassess its original 1984 ROD to address the PCB-contaminated 

river sediments.

1990 On March 7, EPA sent a proposed consent decree to GE that called for it to implement EPA’s approved cleanup 

action for the remnant deposits (i.e., impermeable cap and shoreline protection).

On March 12, EPA and NYSDEC met with GE to discuss the scope of the RI/FS and the possibility of GE’s 

conducting the study. GE made a presentation on the research it planned to conduct with respect to the biological 

degradation of PCBs in the sediments.

On April 6, the Regional Administrator approved the consent decree, which GE had signed on April 2, for 

remediating the remnant deposits. The Department of Justice signed the consent decree on May 11.

On June 4, EPA notified GE that it intended to conduct the RI/FS.

On September 28, EPA gave final approval to GE for cleanup activities at the remnant deposits.

1991 During this year, GE completed “in-place” containment of the remnant deposits in accordance with EPA’s 1984 

decision and a 1990 consent decree between the federal government and GE. GE conducted maintenance and 

postconstruction monitoring associated with the remnant containment on an on-going basis. In addition, in an effort 

to understand the sources and movement of PCBs in the river, GE began a data collection program to fully 

characterize PCB levels in the sediments and the water.

On May 14, EPA granted approval to GE to conduct research and development on biological degradation of PCBs in 

Hudson River sediments.

On August 23, EPA released its Interim Characterization and Evaluation Report on the first phase of its RI/FS.

In September, GE detected a large increase in PCB levels in the river at Fort Edward. The source of this increase 

was attributed to PCB releases associated with the collapse of a wooden gate structure within Allen Mill, an 

abandoned mill located adjacent to the Hudson Falls capacitor plant. PCB concentrations in the river remained 

elevated until 1993, after which remediation efforts controlled releases. 

1992 In July, EPA released the Responsiveness Summary to its Interim Characterization (Phase 1) report.

In September, EPA released its Final Phase 2 Work Plan and Sampling Plan.

1992-93 Under EPA order, the New York State Department of Transportation capped two dredge spoils sites.

1993 During this year, studies identified “seeps” (i.e., pockets of extremely contaminated groundwater) that were oozing 

an oily substance ranging from hundreds of parts per million to 90 percent pure PCBs near an old discharge pipe 

and tons of heavily contaminated sediments in the raceways of the old mill building. 

In April, GE and the NYSDEC shut off the water flow through abandoned Allen Mill (adjacent to the Hudson Falls 

plant site). Bedrock seeps within the mill and raceways were no longer in contact with Hudson River.

During the fall, GE and NYSDEC, operating under an order of consent, removed contaminated sediment in the 

upper raceway of Allen Mill, and a seep collection system was installed.

1994-95 GE removed an estimated 45 tons of PCBs contained in the 3,420 tons of sediment from the Allen Mill.

(Continued From Previous Page)
Appendix I

Chronology of Major Events Relating to the 

Hudson River Superfund Site

Page 22 GAO/RCED-00-193 Hudson River Superfund Site

Year Event

1994 During this year, under a voluntary agreement, GE began funding the annual NYSDEC fish collection and 

monitoring program for the Hudson River.

In June, GE found more seeps of highly concentrated PCB oil in the river bottom at Bakers Falls, adjacent to the 

Hudson Falls plant site.

In September, GE undertook pressure grouting of fractured bedrock in the upper raceway.

1995 During this year, GE constructed a new water treatment plant at the Hudson Falls plant site for seep collections and 

recovery wells to try to reduce PCB levels originating at that site in the Hudson River. 

In August, the upper Hudson River was re-opened to catch and release fishing with a no consumption advisory 

remaining in effect.

In November, EPA released its database report.

1995-97 Recovery wells on the Hudson Falls plant site and a tailrace tunnel were installed.

1996 During this year, sediment from the lower raceway and tailrace tunnel was removed. 

In February, EPA provided a draft statement of work to its contractor to study alternatives for a landfill or treatment 

facility should a dredging remedy be selected for the Hudson River Superfund site. 

In September, another seep at the base of Bakers Falls was discovered, which was releasing approximately 0.5 lbs. 

per day of PCBs. To arrest the flow of PCBs into the river from this source, GE installed a subaquatic collection 

system.

In October, EPA released the Preliminary Model Calibration Report (PMCR).

1997 During this year, EPA classified PCBs as a probable human carcinogen.

In January, EPA installed a groundwater collection well on shore and an upgradient in an effort to hydraulically 

control PCB discharges from the recently discovered seep at Bakers Falls. Significant quantities of PCBs were 

recovered from this well, which appears to have controlled discharges from the seep. Since then, levels in the 

Hudson River originating from this site declined but now remain at approximately 0.2 lbs. per day. 

In February, EPA released the Data Evaluation and Interpretation Report (DEIR).

In July, a House Appropriations Committee report directed EPA to enter into an agreement with the National 

Academy of Sciences (NAS) to evaluate technologies, including dredging, for cleaning up PCB-contaminated 

sediments. In subsequent years, relevant appropriations committee reports have directed EPA not to implement 

dredging as a cleanup remedy until the NAS study is completed. NAS expects to release the study in November 

2000. 

In December, EPA released its Landfill/Treatment Facility Siting Survey Report. The report presented the findings of 

the screening level effort to determine whether there are viable alternatives to agricultural land for a landfill or 

treatment facility should a dredging remedy be selected for the Hudson River Superfund site.

11/97-present Contaminated sediment above Bakers Falls dam was removed to investigate bedrock seeps.

1998 In July, EPA released the Low Resolution Sediment Coring Report (LRC) and the Human Health Risk Assessment 

Scope of Work.

In July, EPA reissued the CD-ROM database.

In July, peer review on the PMCR began.

On July 23, EPA issued a statement regarding the conclusions of the LRC, indicating that EPA would consider taking 

early action on the Hudson River Superfund site to mitigate any further migration of PCBs throughout the river.

In August, GE undertook a sediment sampling program to see what had happened since its last sampling program 

in 1991.

In September, the peer review meeting on the PMCR took place.

In September, EPA released the Ecological Risk Assessment Scope of Work.

In December, EPA released its responsiveness summary for the Database Modeling Report, the PMCR, and the 

DEIR.

On December 17, EPA issued a press release stating that EPA was not able to identify a feasible and appropriate 

interim action and that it would continue to focus its attention and resources on completing the ongoing Hudson 

River site assessment.

(Continued From Previous Page)
Appendix I

Chronology of Major Events Relating to the 

Hudson River Superfund Site

Page 23 GAO/RCED-00-193 Hudson River Superfund Site

Year Event

1999 In January, the peer review on the DEIR and the LRC report began.

In February, EPA released the responsiveness summary on the LRC report.

In March, the peer review meeting for the DEIR and the LRC report took place.

In March, EPA released its Evaluation of Removal Action Alternatives: Thompson Island Pool Early Action

Assessment. The report evaluated removal action alternatives (e.g., dredging and capping) to address PCB 

releases from the sediment as reported in the LRC. In response to the report, EPA announced in December 1998 

that it was not able to identify a feasible and appropriate interim action and that it would focus on completing the 

assessment study.

In April, EPA released responsiveness summaries for the Scope of Work reports for its human health and ecological 

risk assessment reports.

In April, GE released its Modeling Report.

In May, EPA released its Baseline Modeling Report (BMR).

In June, the fish consumption advisory for the Hudson River from the Federal Dam at Troy to Catskill was modified to 

advise eating no more than one meal per month of alewife, blueback herring, rock bass, and yellow perch. For this 

stretch of the river, the advisory to eat no more than one meal per week of American shad and to “eat none” for all 

other species remained in effect. Between Dobbs Ferry and Greystone, a stricter advisory for American eel was 

issued to recommend no consumption. The commercial fishing ban for striped bass in the lower Hudson River was 

being reconsidered.

In August, EPA released its Human Health Risk Assessment-Upper Hudson River and Ecological Risk Assessment 

reports.

On November 15, New York’s Attorney General filed a suit in state court seeking, among other things, to force GE to 

carry out or fund the navigational dredging of the upper Hudson River and claiming that the contamination had 

caused a public nuisance by preventing the state from dredging areas of the river for navigational purposes. 

On December 29, EPA released the Baseline Ecological Risk Assessment for Future Risks in the Lower Hudson 

River report.

On December 29, EPA released the Baseline Human Health Risk Assessment for the Mid-Hudson River report.

2000 On January 12 and 13, the peer review of EPA’s revised BMR began.

On January 25, EPA issued the revised BMR, an update to its May 1999 BMR. 

On February 22, EPA released the BMR Responsiveness Summary.

In February, EPA released its response to peer review comments on its Preliminary Model Calibration Report.

On March 28, the peer review of the revised BMR was completed.

On May 31, the peer review of the Baseline Human Health Risk Assessment—Upper Hudson River report was 

completed.

On June 2, the peer review of the Baseline Ecological Risk Assessment was completed.

(Continued From Previous Page)
Page 24 GAO/RCED-00-193 Hudson River Superfund Site

Appendix II

Overview of EPA’s Computer Model for the 

Hudson River Superfund Site ApendxiI

EPA has developed four integrated models to help it assess the potential 

cleanup actions for the Hudson River Superfund site. The four models are 

the hydrodynamic model, the Depth of Scour Model (DOSM), the upper 

Hudson River Toxic Chemical Model (HUDTOX), and the bioaccumulation 

model referred to as FISHRAND. EPA incorporated a large body of 

information from site-specific data, laboratory experiments, and scientific 

literature in these models. In addition, the four modeling components were 

“linked”—results from one modeling component were integrated into the 

next.

Hydrodynamic Model 

Description and 

Results

EPA’s modeling approach starts with the hydrodynamic model, which 

provides velocity information for the 6-mile Thompson Island Pool (TIP) 

area only. Major factors to this model include data on incoming water flow 

at Fort Edward and data describing the river “bathymetry”—information on 

the river’s water depths. Another important input parameter to the 

hydrodynamic model is the river’s resistance to flow, or friction due to the 

roughness of the river bottom. This value cannot typically be determined 

accurately from physical river measurements, and as a result, it is usually 

calibrated. EPA calibrated this parameter based on two related published 

studies. EPA then ran the hydrodynamic model for eight different flows at 

Fort Edward. 

The major results of the hydrodynamic model were the following. First, the 

model computed velocities for the eight selected flows, which EPA then 

used to calculate friction, an input to the next modeling component, the 

DOSM. Second, the model established routing information on water 

flowing from the TIP, an input to the third modeling component, HUDTOX. 

EPA then conducted calibration and validation testing and sensitivity 

analyses and concluded that the hydrodynamic model is a good 

representation of the TIP’s hydraulics for various flows. 

Depth of Scour Model 

Description and 

Results

EPA’s modeling approach followed the hydrodynamic model with the 

DOSM, which focuses on the depth of sediment erosion as it applies to the 

TIP. The DOSM was developed as a stand-alone tool specifically to 

determine whether contaminated sediments now buried, are likely to 

become released following a major flood, possibly resulting in an increase 

in PCB levels in fish. Using resistance to flow or shear stress information, 

DOSM calculates scour or erosion for fine and coarse sediments in the TIP. 

For fine sediments, it uses site-specific data provided by GE. In contrast, 
Appendix II

Overview of EPA’s Computer Model for the 

Hudson River Superfund Site

Page 25 GAO/RCED-00-193 Hudson River Superfund Site

site specific data for coarse sediments was incomplete, so EPA based its 

computed coarse sediment erosion on a combination of the limited sitespecific data available and formulations available in the scientific literature 

that describe a relationship between erosion depth and shear stress. 

DOSM results showed that the expected impact of a major flood on surface 

sediment PCB levels in the TIP is small because it will not result in a 

significant release of buried PCBs in fine TIP sediments. In addition, DOSM 

formulations for resuspension in fine sediments in the TIP were used as an 

input to the HUDTOX model.

Upper Hudson River 

Toxic Chemical Model 

Description and 

Results

The third and most important modeling component is HUDTOX, the PCB 

fate and transport model used to forecast PCB concentrations in the upper 

Hudson River water and sediment. These calculations are sensitive to 

changes in hydrology, movement of solids, sediment particle mixing depth, 

and initial sediment conditions. HUDTOX is applied to the entire 40-mile 

upper Hudson River from Fort Edward to Troy. HUDTOX represents three 

different mass balances: (1) a water balance, (2) a solids balance, and (3) 

PCB mass balance.1

 A water balance is necessary because PCB dynamics 

are influenced by river flows. A solids balance is necessary because PCB 

dynamics are influenced by the tendency of PCBs to attach to solids in the 

river. Finally, a PCB mass balance is necessary to account for all sources, 

losses, and internal transformations in the river. HUDTOX represents PCBs 

in both the water and the sediments. The principal application of HUDTOX 

was a long-term calibration for a 21-year period from 1977 to 1997 for 

PCBs. After calibration, HUDTOX was used to conduct forecast 

simulations for a 70-year period beginning in 1998. These forecast 

simulations were intended to estimate long-term system responses to 

continued “no action” and impacts due to a major flood. 

The key HUDTOX model results include the following: 

• The river is generally “net depositional,” which means that new 

sediments tend to accumulate over existing surface sediments, adding 

more layers.

1

A mass balance approach ensures that within the model, all mass (i.e., sediment, water, and 

PCBs) entering a specified area of the river equals the mass that leaves the area.
Appendix II

Overview of EPA’s Computer Model for the 

Hudson River Superfund Site

Page 26 GAO/RCED-00-193 Hudson River Superfund Site

• PCB loads to the water column are primarily the result of the transfer of 

PCBs from sediment to the water column, under flows that are too low 

to cause sediment erosion.

• PCB concentrations in the water column and surface sediment gradually 

decline because of reduced input loads from upstream sources and 

natural attenuation.2

• PCB concentrations in the surface sediment will decline at annual rates 

of approximately 7 to 9 percent over the next two decades, consistent 

with long-term historical trends.

• Upstream sources of PCB loads at Fort Edward control the long-term 

PCB concentrations in the water column and surface sediments, and 

accordingly, PCB levels in fish.

• In several localized areas in the Stillwater reach and the TIP, PCB 

concentrations in the surface sediment will increase after 40 to 50 years, 

despite exponential-type decreases up to that time. These computed 

increases are due to relatively small annual erosion rates that eventually, 

over an extended length of time, expose PCB concentrations that were 

previously buried. The relative magnitude of these computed increases 

is small within the context of long-term trends in historical 

concentrations. In addition, their occurrence, magnitude, and timing are 

dependent on forecast assumptions.

• A major flood would result in only a small additional increase in 

sediment erosion beyond what might be expected for a reasonable 

range of annual peak flows. 

Results from 70-year forecast simulations contain inherent uncertainty due 

to estimating future flow and solids movement. Furthermore, various 

assumptions about inputs to the model, while less influential in 21-year 

simulations, can become more important in 70-year forecast simulations. 

EPA assessed and accounted for these uncertainties by evaluating 

predictions across a range of alternate scenarios for these inputs.

FISHRAND Model 

Description and 

Results

The fourth modeling component is FISHRAND, a framework that relates 

PCB concentrations in fish to exposure concentrations in the Hudson 

River’s water and sediments. The model then predicts future PCB 

concentrations in fish tissue, which is used in EPA’s evaluation of human 

health and ecological risks. EPA based its selection of fish species to be 

2

Natural attenuation makes use of natural processes, including burial and dilution by clean 

solids, to reduce the concentration of pollutants at contaminated sites.
Appendix II

Overview of EPA’s Computer Model for the 

Hudson River Superfund Site

Page 27 GAO/RCED-00-193 Hudson River Superfund Site

“modeled” in FISHRAND on several criteria, including (1) the importance 

to fishing, (2) abundance, (3) the importance in diet of other fish, (4) 

whether the selected species is representative of particular habitats or 

trophic levels, and (5) whether the selected species is representative of 

other fish species. FISHRAND provided results for spottail shiner, 

pumpkinseed, brown bullhead, yellow perch, largemouth bass, and white 

perch. Overall, FISHRAND showed that PCB concentrations in fish decline 

over the 70-year forecast. These concentrations are species-specific, 

depending on the relative influence of sediment versus water sources, and 

depend on the assumption used for PCB levels coming from upstream 

sources. 
Page 28 GAO/RCED-00-193 Hudson River Superfund Site

Appendix III

The Peer Review Process at the Hudson River 

Superfund Site ApendxiI

EPA conducted five peer reviews of its assessment work at the Hudson 

River Superfund site. The first, September 1998, covered EPA’s Preliminary 

Modeling and Calibration Report; the second, March 1999, reviewed its 

Data Evaluation and Interpretation, and Low Resolution Sediment Coring 

Reports; the third, March 2000, evaluated its revised Baseline Modeling 

Report; and the fourth and fifth, May and June 2000, covered its Human 

Health Risk Assessment Report and Ecological Risk Assessment Report.

EPA’s Peer Review 

Process

Peer review is a documented critical review of EPA’s products to help 

ensure activities are technically adequate, competently performed and 

properly documented, and satisfy established quality requirements. Peer 

review is intended to uncover technical problems or unresolved issues in a 

preliminary, or draft, product through the use of independent experts. This 

feedback is then used to revise that draft product so the final product will 

reflect sound technical information and analyses. 

Through an EPA headquarters contract, the agency secured the services of 

the Eastern Research Group (ERG) to manage and operate the peer review 

process for the Hudson River site. ERG developed peer review work plans; 

selected expert independent peer review participants; and scheduled, 

managed, and facilitated the required peer review meetings. For each peer 

review, EPA developed a “charge” that identified issues and invited 

comments or assistance from the public. The charge focuses the peer 

review by presenting specific questions and concerns that EPA expects the 

peer reviewers to address and invites general comments on the entire work 

product under review. EPA developed a total of 66 charge questions for the 

five peer reviews—9 for the first, 16 for the second, 21 for the third, and 20 

for the fourth and fifth. EPA also assembled background materials for the 

peer reviewers, including a current copy of the work product under review, 

the charge, related documents, and responsiveness summaries and reports. 

The background materials also contained a schedule of the process, 

including the due date for reviewers’ comments, the format for the 

responses, and a point of contact for any questions. ERG distributed the 

charge and background materials to the peer reviewers.

For the five peer reviews, peer reviewers were allowed 30 to 60 days to 

conduct their individual reviews of the work product, depending on the 

volume and the complexity of the product. The reviewers were then 

required to submit their individual premeeting comments to ERG, which 

consolidated the comments into a package for distribution to all of the peer 

reviewers prior to a peer review meeting. The meetings provided the peer 
Appendix III

The Peer Review Process at the Hudson River 

Superfund Site

Page 29 GAO/RCED-00-193 Hudson River Superfund Site

reviewers with the opportunity to discuss their colleagues’ views of the 

product before formulating their individual conclusions. Peer review is not 

intended to achieve a consensus but to obtain the views and suggestions 

from each of the participants. ERG facilitated the meetings, which followed 

an agenda based on the charge questions requiring comment. The meetings 

were open to the public to observe and were attended by EPA and its 

contractors, who could be called upon to clarify the work product by the 

peer reviewers. The meeting summary reports that ERG prepared from 

audio tape recordings of the proceedings were reviewed by the panel’s 

chair and served as ERG’s final product for that peer review. EPA, with its 

contractors, prepared “responsiveness summaries” to document the 

agency’s responses to the peer reviewers’ comments.

The first peer review comments on EPA’s Preliminary Model Calibration 

Report were received in September 1998, and EPA issued a response to 

them 17 months later in February 2000. EPA officials explained that their 

response was delayed because agency resources were needed to complete 

other reports, specifically, the May 1999 Baseline Modeling Report (BMR) 

and its January 2000 revision and the Responsiveness Summary for the 

BMR, released in February 2000. Nevertheless, EPA stated the first set of 

peer review comments were considered and incorporated, as appropriate, 

in the 1999 BMR and its 2000 revision. In its February 2000 response to the 

first peer review comments, EPA explained how the subsequent products 

reflected the panel’s suggestions. As of June 2000, EPA has not yet issued 

its responses to the four other peer reviews completed for the Hudson 

River site. 

Summary of Five Peer 

Reviews Conducted for 

the Hudson River Site 

EPA’s first Hudson River peer review evaluated EPA’s Preliminary Model 

Calibration Report (PMCR), released in September 1998. Seven peer 

reviewers addressed two general questions on the appropriateness of EPA’s 

models, data sets, and assumptions to answer the following three principle 

charge questions: (1) When will PCB levels in the fish population recover to 

levels meeting human health and ecological risk criteria under a “no action” 

decision? (2) Can remedies other than “no action” significantly shorten the 

time required to achieve acceptable risk levels? (3) Are there contaminated 

sediments now buried and effectively sequestered from the food chain that 

are likely to become “reactivated” following a major flood, resulting in an 

increase in contamination of the fish population? In addition, the reviewers 

addressed seven specific questions covering the adequacy, the 

reasonableness, and the support for certain scientific aspects of the report. 
Appendix III

The Peer Review Process at the Hudson River 

Superfund Site

Page 30 GAO/RCED-00-193 Hudson River Superfund Site

The seven reviewers unanimously agreed that the modeling approach 

described in the PMCR was “acceptable with major revision.”

In March 1999, the second peer review evaluated EPA’s Data Evaluation and 

Interpretation Report (DEIR) and Low Resolution Sediment Coring Report 

(LRC). Six reviewers addressed seven specific questions related to the 

consistency, the appropriateness, and the reasonableness of scientific 

aspects of the DEIR; seven specific questions covering the consistency, the 

appropriateness, and the support for aspects of the LRC; two general 

questions regarding the reports’ sufficiency to understanding the behavior 

of PCBs in the upper Hudson River, and the question of whether additional 

verification analyses were needed. Four of the six reviewers found the 

reports “acceptable with minor revisions;” the other two reviewers found 

the reports acceptable but were unsure if their recommended revisions 

were “minor” or “major.”

In March 2000, the third peer review evaluated EPA’s revised Baseline 

Modeling Report (BMR). Seven reviewers addressed twelve questions 

dealing with the appropriateness, the reasonableness, and the sufficiency 

of aspects of the science employed in the Fate and Transport Model; five 

questions covering the science of the Bioaccumulation Model; and four 

general questions regarding the accuracy, the appropriateness, and the 

coverage provided by these two models. Six reviewers found EPA’s Fate 

and Transport Model acceptable with minor revisions, and one reviewer 

found it acceptable but did not classify the necessary revisions as “minor” 

or “major.” Four reviewers found EPA’s Bioaccumulation Model acceptable 

with minor revisions; one reviewer found it acceptable with major 

revisions; and two reviewers who were experts, primarily with water 

quality and sediment transport modeling, did not offer recommendations 

on the Bioaccumulation Model.

In May 2000, the fourth peer review evaluated EPA’s Human Health Risk 

Assessment (HHRA). Six reviewers addressed seven specific questions 

related to the reasonableness, the adequacy, and the appropriateness of 

scientific aspects employed in this assessment and two general questions 

regarding their measurements. Two reviewers found the assessment 

acceptable with minor revisions, two reviewers found it acceptable with 

major revisions, and two reviewers were undecided as to whether the 

revisions were “major” or “minor.” 

In June 2000, the fifth peer review evaluated EPA’s Ecological Risk 

Assessment (ERA). Seven reviewers addressed nine specific questions 
Appendix III

The Peer Review Process at the Hudson River 

Superfund Site

Page 31 GAO/RCED-00-193 Hudson River Superfund Site

covering the sufficiency, the adequacy, and the appropriateness of 

information and techniques used in the ERA and two general questions 

covering their measurements. The ERA was generally rejected with four 

reviewers suggesting major revisions and two rendering unacceptable 

opinions.1

1

The peer reviews of the HHRA and ERA were conducted and completed after the 

completion of GAO’s field work. 
Page 32 GAO/RCED-00-193 Hudson River Superfund Site

Appendix IV

Comments From the Environmental 

Protection Agency ApendxiIV
Appendix IV

Comments From the Environmental 

Protection Agency

(160503) Letr Page 33 GAO/RCED-00-193 Hudson River Superfund Site
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