The National Academies of Sciences, Engineering and Medicine
Office of Congressional and government Affairs
At A Glance
: Strategies to Address Contaminated Sediments
: 07/19/2001
Session: 107th Congress (First Session)
: John W. Farrington,Danny D. Reible

John W. Farrington, Associate Director for Education/Dean and Senior Scientist, Woods Hole Oceanographic Institution, Woods Hole, MA and Chair, Committee on Remediation of PCB-Contaminated Sediments, Board on Environmental Studies and Toxicology, National Research Council

Danny D. Reible, Chevron Professor of Chemical Engineering and Director, Hazardous Substance Research Center, Louisiana State University, Baton Rouge, and Member, Committee on Remediation of PCB-Contaminated Sediments, Board on Environmental Studies and Toxicology, National Research Council

: House
: Committee on Transportation and Infrastructure

(PLEASE NOTE: Dr. Reible’s testimony follows Dr. Farrington’s)

Testimony of

John W. Farrington, Ph.D.,
Associate Director for Education/Dean and Senior Scientist,
Woods Hole Oceanographic Institution
Committee on Remediation of PCB-Contaminated Sediments
Board on Environmental Studies and Toxicology
National Research Council

before the

Subcommittee on Water Resources and Environment,
Committee on Transportation and Infrastructure
U.S. House of Representatives

July 19, 2001

Mr. Chairman:

Thank you for your invitation to testify before the Subcommittee on Water Resources and Environment. I appear here in my private capacity as a scientist who has studied and been involved for the past thirty years with issues associated with contaminated sediments, particularly the aspects of biogeochemistry of organic chemical contaminants -- inputs, movement through aquatic ecosystems, biological availability, and fate. While I am not a representative of any specific organization, I will be summarizing the findings and recommendations of the report from the National Research Council Committee I chaired, "A Risk-Management Strategy for PCB Contaminated Sediments," issued a few months ago by the National Academies Press. My colleague and a member of that committee, Professor Danny Reible, will be amplifying on some aspects of the Committee’s report in his testimony today. A copy of the Executive Summary of the Report is attached to this written testimony, and copies of the entire report have been made available to the Subcommittee by the Board of Environmental Studies and Toxicology of the National Research Council.

My presentation will consist of a brief introductory overview, description of the main conclusions and recommendations of the National Research Council Report, and concluding personal observations.


There has been substantial progress in research concerned with toxic chemicals in the environment in general and specifically for the topic of your committee’s deliberations - the aquatic environment. Knowledge gained has been converted to useful information. Public policy and management/regulatory actions have addressed the major acute toxicity concerns.

It was natural and necessary for society to focus on cleanup of contaminated sediments once many of the major problems with cleaning up effluents had been addressed during the 1960s through the 1980s. There is substantive evidence that these chemically contaminated sediments are a continuing source of contaminants to the overlying water and contiguous ecosystems. Of course, for several chemicals of environmental concern, diffuse source inputs via land runoff and atmospheric processes continue to be of significant concern.

Simply stated, in many areas of contaminated sediments such as urban harbors or bodies of water having received inputs from industrial effluents, there has been a transition from "Top Down" - effluent and atmospheric dominated inputs, to "Bottom Up" - sediment release dominated inputs.

Often, the sediments of concern are contaminated with multiple chemicals. This can lead to the need for assessment of human health and ecological risks for various risk management remedial technologies and approaches for multiple chemicals. The time frames of consideration are usually at least several decades. Given these parameters, achieving efficacious risk management is a formidable task.

There has been near-gridlock in identifying and implementing remediation management strategies at several contaminated sediment sites, despite the dedicated hard work and professionalism of employees, members and the leadership of federal, state and local regulatory agencies, industry, consulting companies, citizens groups, non-governmental organizations, and the academic sector

Why? I believe that it is due mainly to the following five factors:

NRC Committee Report's
(This section of Testimony taken largely verbatim from the NRC Report)


In an effort to address these complexities and to understand the risks associated with the management of PCB-contaminated sediments, Congress directed the EPA to "enter into an arrangement with the National Academy of Sciences to conduct a review which evaluates the availability, effectiveness, costs, and effects of technologies for the remediation of sediments contaminated with polychlorinated biphenyls, including dredging and disposal." In order to address this Congressional request, the National Research Council (NRC) convened the Committee on Remediation of PCB-Contaminated Sediments, which prepared this report. The committee was charged to address the following tasks:

• Select, refine, and apply a scientific, risk-based framework for assessing the remediation alternatives for exposure of humans and other biota to PCBs in contaminated sediments.

• Evaluate the likelihood that the specified remediation technologies will achieve their remedial objectives, by considering different site-specific conditions such as water and sediment dynamics.

• For a few selected sites and using the framework, estimate human and ecological risks associated with each of the specified remediation approaches for contaminated sediments containing PCBs in light of the availability, costs, and effectiveness of the various approaches.

• Where applicable, recommend areas for future research.


During its deliberations, the NRC committee held three public sessions (Washington, DC; Green Bay, Wisconsin; and Albany, New York) to gather information from a broad audience with interest in the remediation of PCB-contaminated sediments. Two of these meetings were held in areas with known PCB contamination (i.e., Fox River in Wisconsin and the upper Hudson River in New York) so that the committee could hear from affected parties about their understanding of the risks posed by the sediments and of possible management options. Numerous affected parties attended the meeting and/or submitted written materials to the committee. The committee considered these materials in the preparation of this report.

In the full report, the committee presents its conclusions regarding the need for a framework to evaluate the overall risks associated with the management of PCB-contaminated sediments. The committee also uses selected real sites to illustrate key aspects of the framework. The committee highlights the broad conclusions that apply to all contaminated sites and makes recommendations for further scientific and engineering research. Because the committee found that risks beyond those of traditional human health and ecological risk assessment should be considered in any risk management, the committee realized that any attempt to address these risks in a comprehensive manner without the participation of those affected by such a decision would have been inconsistent with the framework the committee recommends. Furthermore, to have conducted a traditional quantitative human health or ecological risk assessment for a variety of remediation technologies at a site without full consideration of these additional risks would not demonstrate the utility of the framework, and the risk values may be misconstrued.


Below are the committee’s major conclusions and recommendations concerning the risks posed by PCB-contaminated sediments and the options that may be used to manage them.

(1) The committee’s review of recent scientific information supports the conclusions that exposure to PCBs may also result in chronic effects (e.g., cancer, immunological, developmental, reproductive, neurological) in humans and/or wildlife. Therefore, the committee considers the presence of PCBs in sediments may pose long-term public health and ecosystems risks.

(2) The paramount consideration for PCB contaminated sediment sites should be to manage overall risks to humans and the environment, rather than the selection of a remediation technology (e.g., dredging, capping or natural attenuation).

(3) Risk management of PCB contaminated sediment sites should comprehensively evaluate the broad range of risks posed by PCB contaminated sediments and associated remedial actions. These risks should include societal, cultural, and economic impacts as well as human health and ecological risks.

(4) Risk management of PCB contaminated sediments sites should include early, active and continuous involvement of all affected parties and communities as partners. Although the need for involvement of the affected communities has often been recognized, it has not been implemented on a consistent basis.

(5) All decisions regarding the management of PCB contaminated sediments should be made within a risk-based framework. The framework developed by the Presidential/Congressional Commission on Risk Assessment and Risk Management provides a good foundation and should be used to assess the broad range of risks associated with PCB-contaminated sediments and the various management options for a site.

(6) Risk assessments and risk management decisions should be performed on a site-specific basis and should incorporate all available scientific information.

(7) Identification and adequate control of sources of PCB releases to sediments should be an essential early step in site risk management.

(8) There should be no presumption of a preferred or default risk management option that is applicable to all PCB contaminated sediment sites. A combination of technical and non-technical options will likely be necessary at any given site.

(9) Current management options can reduce risks, but cannot completely eliminate PCBs and PCB exposure from contaminated sediment sites. Because all options will leave some residual PCBs, the short - and long-term risks they pose should be considered when evaluating management strategies.

(10) Long-term monitoring and evaluation of PCB-contaminated sediment sites should be conducted to evaluate the effectiveness of the management approach and to ensure adequate, continuous protection of humans and the environment.

(11) Further research is recommended in several areas of investigation. These research areas concern:

• A better assessment of human health and ecological risks associated with mixtures of individual chlorobiphenyls present in specific environmental compartments.

• The impact of co-contaminants (e.g. polycyclic aromatic hydrocarbons and metals) on PCB risk assessments and risk-management strategies.

• Processes governing the fate of PCBs in sediments, including erosion, suspension, transport of fine cohesive sediments, pore water diffusion, biodegradation, and bioavailability.

• Improvement of ex situ and in situ technologies associated with removal or containment of PCB-contaminated sediments, treatment of PCB-contaminated material, and disposal of such sediments.

• Pilot scale testing of innovative technologies, such as biodegradation and in situ active treatment caps, to assess their effectiveness and applicability to various sites.

• The impact of continuing PCB releases and global environmental cycling on site-specific risk assessments.


My concluding remarks are my personal thoughts and not part of the NRC report. During the years over the past decade leading up to the NRC report and having read reports and listened to comments from various stakeholders in preparation of the report, I have become concerned about a phenomena, now minor - but subtle and seductive - that seems to be growing in our nation. The best way I can think of illustrating my concern is to quote from history and use an analogy, however imperfect the analogy.

Forty years ago last January 17th, General Dwight D. Eisenhower presented his farewell address to the nation as President of the United States. In this address, speaking in the midst of a growing cold war, he noted among other salient points:

"Crises there will continue to be. In meeting them, whether foreign or domestic, great or small, there is a recurring temptation to feel that some spectacular and costly action could become the miraculous solution to all current difficulties . . .

This conjunction of an immense military establishment and a large arms industry is new in the American experience. The total influence -- economic, political, even spiritual -- is felt in every city, every statehouse, every office of the Federal government. We recognize the imperative need for this development. Yet we must not fail to comprehend its grave implications. Our toil, resources and livelihood are all involved; so is the very structure of our society . . .

Only an alert and knowledgeable citizenry can compel the proper meshing of the huge industrial and military machinery of defense with our peaceful methods and goals so that security and liberty may prosper together."

While the analogy with the military and industrial complex does not hold in the strictest sense, there are some parallels between the military-industrial complex in the 1960s and the environmental "industry" of consulting companies, non-governmental organizations, governmental environmental agencies, and associated academic researchers and consultants. I believe that there are many highly qualified, thoughtful, well meaning people in those groups, who are responding to legitimate societal needs in the environmental quality arena. However, I am concerned with an emerging trend that some people in various sectors noted above are confusing perpetuation of their business, agency position, organization, or research goals with legitimate needs of the greater public. The intentions of all should be to serve the greater public good.

Mr. Chairman, that concludes my testimony. Thank you and the members of your committee for the opportunity to participate in this hearing.


Statement of

Danny D. Reible, Ph.D., P.E.
Director, Hazardous Substance Research Center/South and Southwest
Chevron Professor of Chemical Engineering
Louisiana State University

Before the

Subcommittee on Water Resources and Environment
Committee on Transportation and Infrastructure
U.S. House of Representatives

July 19, 2001

Good morning, Mr. Chairman and members of the Committee. My name is Danny Reible. I am a Professor of Chemical Engineering at Louisiana State University and Director of the Hazardous Substance Research Center/South and Southwest (HSRC/S&SW), an EPA-funded, University-based program for basic and applied research, technology transfer, and training that is a cooperative effort between Louisiana State University, Georgia Tech, and Rice University. The Center is focused on developing, and communicating to users, improved approaches for the management of hazardous substances in sediments, and it is the cumulative experiences in working with industry, regulatory bodies and the public on various contaminated sediment sites that I bring to this hearing.

Contaminated sediments represent some of the most difficult hazardous substance problems that we face today. The average land-based Superfund site for which removal and treatment has been attempted contains less than 30,000 yd3 of contaminated soil. Many contaminated sediment sites, however, may involve >1 million yd3 of solids and are accompanied by at least an equal amount of water generated during its removal. Add to this the dynamic, highly variable setting of sediments, which complicates both in situ and removal options, and it is easy to understand the difficulties of finding effective, low-cost solutions to managing contaminated sediments.

Sediment contaminants tend to partition strongly to solids and are persistent and slow-moving in the environment, except when storms or other events mobilize the solids with which they are associated. Especially important sediment contaminants are polychlorinated biphenyls, PCBs, once heavily-used industrial chemicals that persist in sediments throughout the US and the world. Management of PCB contaminated sediments mirror the difficulties in managing contaminated sediments of all types.

John Farrington spoke to you about the key conclusions of the Committee on Remediation of PCB Contaminated Sediments convened by the National Research Council, the operating arm of the National Academy of Sciences and the National Academy of Engineering, to help identify appropriate approaches to the management of PCB contaminated sediments. I was honored to be a part of the Committee and I concur wholeheartedly with its conclusions.

Of all the conclusions of the Committee, I believe that there are four that are of overriding importance:

1. Risks are not limited to quantifiable risks to human and ecological health but also include economic, social and cultural risks that may not be easily defined or evaluated. These risks may be important during application of a management approach or afterward as a result of the residual contamination that is always present.

2. Early, active and continuous involvement of all affected by the contaminated sediment site is required to help identify these risks and to identify the best possible means of reducing or eliminating them. I think broad participation is especially important when the overall goals of managing a site are identified, that is, defining the resource at risk and what constitutes recovery. Participation and the resulting "buy-in" of all involved is also critically important when technical evaluation suggests that certain management approaches are inappropriate or infeasible.

3. There are no easy, default management approaches that are generally applicable and effective. Every management approach or technology has advantages has advantages and disadvantages, and contaminant and environmental settings in which they may be most appropriate. Site-specific analysis of conditions and the effectiveness of potentially applicable technologies and approaches is the key to successful management of contaminated sediment sites.

4. Any management approach must be monitored to evaluate its effectiveness, both to determine if alternative approaches should be applied and to provide information that can be used to assist in the evaluation of the approach at other locations.

Decision making about managing contaminated sediments has often been reduced to the question of "to dredge or not to dredge?" but this is clearly an example of putting the "cart before the horse." Before we can hope to focus on identifying an appropriate remedial technology, we must reach agreement as to the nature of the resource we are trying to protect and how contaminated sediments place that resource at risk. The resources that may be valued by the various stakeholders can vary widely. Are the sediments of intrinsic value, or is the primary concern a navigable waterway and port, a fishery, a drinking water supply, or a bird and large animal habitat that may be degraded by contaminated sediments? I would suggest that the most effective management options might be much different for these different objectives. The recovery of the resource of concern may be difficult to measure or may require a long time such that interim measures may be employed to evaluate the success of any management or remedial approach. I feel strongly, however, that such interim measures should never replace attempts to measure success by direct observation of the recovery or protection of the resource or resources of concern. If the primary concern is recovery of a fishery, then the removal of contaminant mass from sediments, for example by dredging, is, ultimately, only important to the extent that the contaminant mass may contribute to degradation of the fishery. Depending upon site-specific conditions, contaminant mass that is deeply buried by clean sediment may or may not contribute to the degradation of the fishery. Measurement of the contamination removed by dredging, the so-called "mass removal objective," may thus be a poor measure of the recovery of the resource at risk.

As indicated by this example, the relationship between contaminated sediment levels and risk to a resource can be much different at different sites due to natural environmental processes and conditions. In a stable sediment environment in which the sediment does not migrate significantly, contaminant levels in the water column and in fish are most likely related to the average concentrations in just the upper few inches of the sediment. In an active sediment environment in which storm or other high flow events may regularly scour sediment, contaminant levels in the water column and fish may be related to the sediment concentrations averaged over the entire depth subject to this scour. In some cases, however, contaminants in fish and in water column may not be related to the sediments at all, but instead to continuing uncontrolled sources, such as watershed runoff or industrial or municipal effluents. In many cases, continuing contaminant sources have been controlled but it remains necessary to assess their importance before embarking upon a management option focused solely on the sediments. Simply stated, it is impossible to effectively mange or remediate contaminated sediments if you don't understand the site-specific causes of exposure and risk, and how a remedial approach will interact with the important site processes to achieve the desired goals.

For many complicated sediment sites, no individual technology can achieve the desired objective of recovery of the resource at risk. Often, when one talks about remediating contaminated sediment the actual goal is to speed recovery of the resource, not directly provide that recovery. As pointed out by the NAS Committee, natural attenuation processes are a component of all management approaches to contaminated sediments since no technology is 100% efficient or capable of completely remediating a complex contaminated sediment site. Thus any management approach must be consistent with the natural attenuation processes that are ultimately expected to provide the complete recovery of the resource at risk.

The three basic approaches to remediating contaminated sediments are:

1. monitored natural recovery,

2. in situ treatment or containment and,

3. removal followed by ex situ treatment or containment.

These options are listed in order of increasing complexity and cost and, at least in principle, the speed with which full recovery can be obtained. As indicated above, effective management of any sediment site may involve several or all of these approaches. Even removal followed by ex situ treatment or containment, however, often requires either capping with clean sediments (an example of in situ containment) or monitored natural recovery to ultimately achieve recovery goals.

The natural setting and contaminant sources, fate, and transport processes are critical to defining which (or which combination) of these options may be appropriate in particular portions of a site. Dredging may be preferred in locations where the contamination is found in relatively small, well-defined zones near the surface with little adjacent debris, and when options for effective management of the dredged material and produced water are available. Recognize that often the most difficult issues surrounding dredging are not associated with removal but how to manage the residuals: residual contamination in the sediments, residual dredged material solids, and residual water produced with the dredged material. In situ approaches such as capping with clean sediments are often effective where these questions cannot be satisfactorily answered or where the contamination of concern is spread over large areas and difficult to remove. An important concern for a clean sediment cap is permanence and the cap may be armored and/or monitored to ensure long-term stability. Finally, monitored natural attenuation may be most effective in situations where water flows and sediments are relatively stable and where clean sediments are slowly burying the contaminants. Since many contaminated sediment problems are historical, that is, associated with industrial or municipal effluents that have since been largely controlled, contaminated sediments are often currently found in stable, depositional areas. If such areas can be expected to remain stable, then monitored natural attenuation may be the least disruptive means of effectively managing the contaminated sediments.

This emphasis on the need for understanding your particular system is not to encourage that all sites become as well-studied as the Fox or Hudson Rivers. For simple sites, it is possible to frame appropriate objectives and an adequate conceptual model of the site on the basis of little information. For complicated sites, however, the site-specific nature of the potential effectiveness of any management approaches must be recognized and detailed study is needed. This study often requires the development of sophisticated mathematical models that can project forward in time so that a variety of "what if?" questions can be answered. For such sites, no default or preferred remedy is appropriate and only site-specific analysis involving all stakeholders can provide the information needed to define appropriate goals and approaches to achieve those goals.

Whatever the approach ultimately employed to manage a contaminated sediment site, a stronger focus on monitoring the effectiveness of that approach is needed. The purpose of this monitoring is to evaluate the effectiveness of the remedy and to develop the information needed to evaluate the appropriateness of the approach at other sites. Despite incredible technological improvements in many areas of human endeavor, we continue to manage sediments with tools that have been available for many years. There have been significant improvements in our understanding of the natural processes that influence contaminants and create risk, but the technologies applied to manage and remediate sites are generally quite conventional. Part of this is due to the large volumes and complexities of contaminated sediment sites and it is doubtful that we could ever afford "NASA-like" solutions to the mud in our rivers. Part of this is due, however, to our limited ability to learn form our own mistakes. There are many disincentives to long term monitoring of contaminated sediment sites after remediation, not the least of which is concern about finding out that one did not make the best decision. Such knowledge is critical, however, to avoid the same mistakes in the future and I encourage finding the time and the funds to critically evaluate our efforts long past the time that we are supposedly "done."

I think it would be useful to demonstrate in the field many of the technologies that have been developed in the laboratory and may have the potential for cost-effectively managing contaminated sediments. Another part of the reason that our sediment management tools are so conventional is that we do not have field information on how effective and practical innovative tools may be. The Assessment and Remediation of Contaminated Sediments (ARCS) program in the Great Lakes demonstrated many technologies but more remains to be done. For several years, I have encouraged a side-by-side field demonstration of a variety of innovative sediment capping technologies. Others are currently working on demonstrating innovative dredging technologies and dredged material treatment technologies. As long as these demonstrations collect the long-term monitoring information necessary to truly judge success, perhaps we will soon have a broader range of tools that can be applied to managing contaminated sediments.

Finally, I would like to recognize that the level of interest in contaminated sediments has grown dramatically since our HSRC/S&SW was founded in 1992. The growth in interest has generated a great deal of recent information on the effectiveness and practicality of certain sediment management technologies. Much of this came too late for the NAS Committee to fully evaluate but it is now being distributed to the sediments community. As a result of the heavy focus in recent years on contaminated sediments, I think that many people have come to the same conclusions as the NAS Committee. They recognize the need for site-specific evaluation of processes and technologies, the need for inclusiveness in this evaluation as well as in the setting of goals, and the need to monitor whatever is done to insure that it meets those goals. I cannot help but feel that wider recognition of these principles will improve our ability to effectively manage contaminated sediments in the future.

Thank you Mr. Chairman. That concludes my testimony. Thank you for the opportunity to participate in the hearing. I would be happy to try and answer any questions that you may have.

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