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Contaminated Sediment Remediation Guidance 

for Hazardous Waste Sites 

Executive Summary 

In 2001, the U.S. Environmental Protection Agency (EPA) released for comment a draft 

report, The Incidence and Severity of Sediment Contamination in Surface Waters of the United 

States, identifying locations in all regions of the country where sediment contamination could be 

associated with probable or possible adverse effects to aquatic life and/or human health (U.S. 

EPA 2001a). In addition, contaminated sediment has significantly impaired the navigational and 

recreational uses of rivers and harbors in the U.S. (NRC 1997 and 2001). As of 2001, EPA had 

decided to take an action under the Comprehensive Environmental Response, Compensation, and 

Liability Act (CERCLA) to clean up sediment at approximately 140 sites (U.S. EPA 2001a) and 

additional sites under the Resource Conservation and Recovery Act (RCRA). The remedies for 

66 sites are large enough that they are being tracked at the national level. Many other sites are 

being cleaned up under state authorities, other federal authorities, or as voluntary actions. 

This document provides technical and policy guidance for project managers and 

management teams making risk management decisions for contaminated sediment sites. It is 

primarily intended for project managers considering actions under CERCLA, although technical 

aspects of the guidance are also intended to assist project managers addressing sediment 

contamination under RCRA. However, many aspects of this guidance will be useful to other 

governmental organizations and potentially responsible parties (PRPs) that may be conducting a 

sediment cleanup. Provided below is a short summary of each of the eight chapters. Sediment 

cleanup is a complex issue, and as new techniques evolve, EPA will issue new or updated 

guidance. 

Chapter 1, Introduction, describes the general backdrop for sediment remediation and 

reiterates EPA’s previously issued OSWER Directive 9285.6-08, Principles for Managing 

Contaminated Sediment Risks at Hazardous Waste Sites (U.S. EPA 2002a). Other issues 

addressed here include the role of the natural resource trustees, states, tribes, and the community 

at sediment sites. Where there are natural resource damages associated with sediment sites, 

coordination between the remedial and trusteeship roles at the federal, state, and tribal levels is 

especially important. In addition to their role as natural resource trustees, certain state cleanup 

agencies and certain Indian tribes or nations have an important role as co-regulators and/or 

affected parties and as sources of essential information. Communities of people who live and 

work adjacent to waterbodies containing contaminated sediment should be given understandable 

information about the safety of their activities, and be provided opportunities for involvement in 

the EPA’s decision-making process for sediment cleanup. Social and cultural practices should 

also be considered in evaluating the impacts associated with contaminated sediment and 

sediment cleanup. 

Chapter 2, Remedy Investigation Considerations, introduces investigation issues unique 

to the sediment environment, including those related to characterizing the site, developing 

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Contaminated Sediment Remediation Guidance 

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conceptual site models, understanding current and future watershed conditions, controlling 

sources, and developing cleanup goals. Especially important at sediment sites is an accurate 

conceptual site model that identifies contaminant sources, transport mechanisms, exposure 

pathways, and receptors at various levels of the food chain. Project managers should consider 

the role of a sediment site in the watershed context, including other potential contaminant 

sources, key issues within the watershed, and current and reasonably anticipated or desired 

future uses of the waterbody and adjacent land. Essential parts of good site characterization and 

remedy selection include the identification and control of continuing sources of contamination 

and an accurate understanding of their contribution to site risk and potential for recontamination. 

It is also very important that remedial action objectives, remediation goals, and cleanup levels 

are based on site-specific data and are clearly defined. At most Superfund sites, chemicalspecific remediation goals should be developed into final sediment cleanup levels by weighing 

the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) balancing and 

modifying criteria and other factors relating to uncertainty, exposure, and technical feasibility. 

Chapter 2 also introduces issues relating to sediment bed stability and modeling at 

sediment sites. An important part of the remedial investigation at many sediment sites is a sitespecific assessment of the extent of sediment disturbance in the past, and a prediction about 

whether there is likely to be significant disturbance in the foreseeable future. An accurate 

assessment of sediment stability (e.g., erosion and deposition rates) can be one of the most 

important factors in identifying areas suitable for monitored natural recovery (MNR), in-situ 

caps or near-water confined disposal facilities. Evaluation of alternatives should include 

consideration of disruption from human and natural causes, including at a minimum, the 100-

year flood and other events with a similar probability of occurrence. Project managers should 

make use of the variety of empirical field methods available for evaluating sediment stability 

and, where appropriate, also use numerical models for evaluating events for which there is no 

field record and for predicting future stability. There is a wide range of empirical models and 

more robust computer models that can be applied to contaminated sediment sites. Models are 

useful tools, but they can be very time consuming and expensive to apply at complex sediment 

sites. Nevertheless, models are helpful in that, when properly applied, they provide a more 

complete understanding of the future transport and fate of contaminants. When using models, 

project managers should be aware of the uncertainties and variability of model predictions and, 

where possible, quantify these using sensitivity analysis or other evaluation methods. Project 

managers should, where possible, use validated and verified models that are in the public domain 

and calibrate them to site-specific conditions. 

Chapter 3, Feasibility Study Considerations, supplements existing EPA guidance by 

offering sediment-specific guidance about developing alternatives, applying the NCP remedy 

selection criteria, identifying applicable or relevant and appropriate requirements (ARARs), 

estimating cost, and using institutional controls. Major cleanup methods include dredging and 

excavation, in-situ capping, and MNR. Innovative pilot and lab testing of in-situ treatment in the 

form of reactive caps or sediment additives are underway and may be useful in the future. Due 

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to the limited number of cleanup methods available for contaminated sediment, generally project 

managers should evaluate both in-situ and ex-situ methods at every site where they may be 

appropriate. At large or complex sites, project managers have found that alternatives that 

combine a variety of cleanup methods are frequently cost effective. All final remedial actions at 

CERCLA sites must be protective of human health and the environment, and must comply with 

ARARs unless a waiver is justified. Developing accurate cost estimates is an essential part of 

evaluating sediment alternatives. Project managers should evaluate capital costs, operation and 

maintenance costs (including long-term monitoring), and net present value. Institutional controls 

are frequently evaluated as part of sediment alternatives to prevent or reduce human exposure to 

contaminants. Common types of institutional controls at sediment sites include fish consumption 

advisories, commercial fishing bans, and waterway use restrictions. In some cases, land use 

restrictions or structure maintenance requirements have also been important elements of an 

alternative. 

Chapter 4, Monitored Natural Recovery, summarizes the natural processes that should be 

considered when evaluating MNR as a cleanup method, and briefly discusses enhanced natural 

recovery through thin-layer placement. The chapter defines MNR as a sediment cleanup method 

that uses known, ongoing, naturally occurring processes to contain, destroy, or otherwise reduce 

the bioavailability or toxicity of contaminants in sediment. Although “natural recovery” may be 

ongoing at many sites, the key factors that distinguish use of MNR as a remedy are the presence 

of unacceptable risk (i.e., the need for action), the ongoing burial or degradation/transformation 

of contaminants, and the establishment of a cleanup level that is expected to be met in a 

particular time frame. Although burial by clean sediment is often the dominant process relied 

upon for natural recovery, multiple physical, biological, and chemical mechanisms frequently act 

together to reduce risk. MNR should be evaluated based on site-specific data collected over a 

number of years, including an assessment of seasonal variation. Project managers should 

evaluate the long-term stability of the sediment bed and the likely ecological and human health 

impacts of sediment movement. Contingency measures should be included as part of a MNR 

remedy when there is significant uncertainty that the remedial action objectives will be achieved 

within the predicted time frame. MNR should generally be used as one component of an overall 

site remedy, and cautiously as the sole cleanup method. 

Chapter 4 also discusses the major advantages and disadvantages of MNR. The major 

advantages of MNR are its relatively low cost and its non-invasive nature which involves 

minimal disruption to the existing biological community. In addition, because no construction or 

infrastructure is needed, it is generally much less disruptive to communities than active cleanup 

methods. Major disadvantages of MNR are that it generally leaves contaminants in place 

without engineered containment; it can be slow to reach cleanup levels in comparison to active 

cleanup methods; its effectiveness may be more uncertain than active cleanup methods; and it 

frequently relies upon institutional controls, such as fish consumption advisories, which may 

have limited effectiveness to control human exposure during the recovery period. 

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Chapter 5, In-Situ Capping, summarizes the major capping technologies and describes 

the site conditions that are critical to understand in evaluating the feasibility and effectiveness of 

in-situ capping. In-situ capping refers to placement of a subaqueous covering or cap of clean 

material over contaminated sediment. A cap reduces risk through three primary functions: 1) 

physical isolation of the contaminated sediment from the aquatic environment; 2) stabilization of 

contaminated sediment, preventing resuspension and transport to other sites; and 3) reduction of 

the movement of dissolved and colloidally transported contaminants. Backfill of clean material 

designed to mix with dredging or excavation residuals or to fill post-dredging depressions, rather 

than act as a engineered cap to isolate buried contaminants, is not considered in-situ capping in 

this guidance. 

Chapter 5 also discusses the major advantages and disadvantages of in-situ capping. The 

major advantage of in-situ capping is that it can quickly reduce exposure to contaminants. 

Compared to dredging and excavation, less infrastructure is needed (e.g., materials handling, 

treatment, disposal), and the potential for contaminant resuspension and the risks associated with 

dispersion of contaminated materials during construction is typically lower. In-situ capping may 

also be less disruptive to communities than dredging or excavation. The major disadvantage of 

in-situ capping is that the contaminated sediment is left in place in the aquatic environment 

where contaminants may be exposed or dispersed if the cap is significantly disturbed or not 

properly maintained. Another potential disadvantage to in-situ capping may be that in some 

situations usable habitat may not be provided by the cap materials. 

Chapter 6, Dredging and Excavation, summarizes excavation (conducted in the dry) and 

dredging (conducted under water) technologies; the components involved in transport, treatment, 

storage, and disposal of dredged or excavated sediment; and describes the importance of 

evaluating site conditions that are critical to the feasibility and effectiveness of dredging and 

excavation. A dredging or excavation alternative should include a thorough evaluation of the 

details concerning all phases of the project, including removal, transport and storage, treatment 

(pretreatment, treatment of decant and/or dewatering effluents and sediment, if necessary), and 

disposal (liquids and solids). When conducted, environmental dredging should use equipment 

and methods of operation which minimize resuspension. In some environments, excavation may 

lead to lower levels of residual contamination than dredging, although site preparation for 

excavation can be more lengthy and costly than for a dredging project due to the need for rerouting or draining the waterbody. Dredging projects should make realistic assumptions 

regarding residual contamination. Where over-dredging is possible, residual contamination is 

generally lower than where this practice is not possible. When predicting the effects on risk 

reduction of a dredging or excavation remedy which includes removal of deeply buried 

contaminants, it is important that project managers recognize that contaminant levels in fish 

tissue or other biota will only respond to removal of contaminants that are bioavailable. 

Chapter 6 also discusses the major advantages and disadvantages of sediment removal by 

dredging and excavation. One of the principal advantages of removing contaminated sediment 

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Contaminated Sediment Remediation Guidance 

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from the aquatic environment is that, if residuals are low, it results in the least uncertainty 

regarding future environmental exposure to contaminants because they are removed from the 

aquatic ecosystem and treated and/or disposed in a controlled environment. Sediment removal is 

currently the only cleanup method that allows for treatment and/or beneficial reuse of previously 

contaminated material. Sediment removal also allows maximum flexibility regarding future use 

of a waterbody. The principal disadvantages of sediment removal are that it is usually more 

complex and costly than in-situ cleanup methods, and that there is frequently significant 

uncertainty concerning the extent of residual contamination. The need for transport, storage, 

treatment (where applicable), and disposal facilities may lead to increased social or risk impacts 

on communities. In particular, disposal capacity may be limited in existing municipal or 

hazardous waste landfills and it may be difficult to site new local disposal facilities. Another 

disadvantage includes the potential for contaminant losses during dredging through 

resuspension, and to a generally lesser extent, through other processes during transport, 

treatment, or disposal. Finally, short-term disruption of the benthic environment is unavoidable 

during sediment removal, as it is for a capping remedy. 

Chapter 7, Remedy Selection Considerations, discusses applying the NCP expectations 

(NCP §300.430(a)(1)(iii)) to CERCLA sediment remedies, considering a no-action alternative, 

choosing among sediment cleanup methods, and considering alternatives that include 

institutional controls. Generally, selecting a “no-action” remedy may be appropriate when: 1) 

the site poses no current or potential threat to human health or the environment; 2) CERCLA or 

RCRA do not provide the authority to take action; or 3) a previous action has eliminated the 

need for further action. Where a remedy is necessary, the best route to overall risk reduction 

depends on a large number of site-specific considerations, some of which may be subject to 

significant uncertainty. Any decision regarding the specific choice of a risk management 

strategy for contaminated sediment should be based on careful consideration of the advantages 

and disadvantages of each available option and a comparison among them. Documenting and 

communicating how and why remedy decisions were made are especially important at complex 

sediment sites. When considering remedies that include institutional controls, project managers 

should determine what entities possess the legal authority, capability and willingness to 

implement, and where applicable, monitor, enforce and report on the status of the control. When 

evaluating cleanup alternatives, project managers should include realistic assumptions 

concerning residuals and contaminant releases from in-situ and ex-situ remedies, the potential 

effects of those residuals and releases, and the length of time over which a risk may persist. In 

addition to considering the impacts of each alternative on human health and ecological systems, 

the social and cultural impacts of each alternative on the community and the opportunities for 

site reuse and redevelopment should be assessed. 

At many sites, but especially at large sites, a combination of sediment cleanup methods 

may be the most appropriate way to manage the risk. The remedy selection process for sediment 

sites should include a clear understanding of the uncertainties involved, including uncertainties 

concerning the predicted effectiveness of various alternatives and the time frames for achieving 

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remedial goals. The uncertainty of factors very important to the remedy decision should be 

quantified, so far as this is possible. Where it is not possible to quantify uncertainty, sensitivity 

analysis may be helpful to determine which apparent differences between alternatives are most 

likely to be significant. 

Chapter 8, Remedial Action and Long-Term Monitoring, provides an approach to 

developing an effective remedial action and long-term monitoring program at contaminated 

sediment sites. It presents the key elements of a contaminated sediment site monitoring 

program, introduces some of the monitoring techniques available for physical, chemical, and 

biological measurements, and summarizes some of the factors to consider when monitoring 

remedies which include natural recovery, in-situ capping, or dredging/excavation. A monitoring 

program is important for all types of sediment remedies, both during the remedial action and 

over the long-term to ensure that sediment risks and exposure pathways at a site have been 

adequately managed and the remedy remains protective. The development of monitoring plans 

should follow a systematic planning process that identifies monitoring objectives, decision 

criteria, endpoints, and data collection and analysis methods. Remedial action monitoring 

includes both construction/operational monitoring and monitoring intended to measure whether 

cleanup levels and remedial action objectives have been met. After completion of the remedial 

action, long-term monitoring is important to assess potential re-contamination, to evaluate 

continued containment of buried or capped contaminants, and to monitor dredging residuals and 

on-site disposal facilities. Additional monitoring data will help not only to answer site-specific 

questions but will also contribute to better understanding of technology performance at the 

national level. 

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