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Contaminated Sediments Research
Milestones
Capping Technology
Bauxite Capping Studies: Bauxite has been found to be capable of sequestering a broad variety of heavy metals, including Hg, As, Cr, Cd, Pb, Zn, and Ni. Due to its unique surface properties, bauxite is able to sequester both cationic and oxy-anionic forms of the metals through a combination of adsorption, absorption, ion exchange, and precipitation. Bauxite can be installed as a much thinner cap over the contaminated sediments, a critical parameter for remedy selection in navigable waters.
Monitored Natural Remediation: Field evaluations of the performance of monitored natural remediation (MNR) and both sand and innovative caps will continue, with the aim of quantifying contaminant transport mechanisms to facilitate the prediction of remedy performance. Innovation in capping, both amendments and construction techniques (e.g., mats), will continue to be investigated.
Sand Capping Studies: Boston Harbor/Eagle Harbor/Wyckoff Superfund Site. ORD is investigating the migration of contaminants through a sand cap and resuspension during cap placement to identify potential field methods for minimizing sediment resuspension during cap placement. The research indicated that resuspension can be minimized by using improved release techniques that result in fewer disturbances of the contaminated sediment.
Active Caps: The results of the Anacostia River demonstration in Washington, DC, completed in September 2007, indicate that an "active" cap can be adequately placed over a contaminated sediment area, remain physically stable over time; effect ground water movement; and have limited impact on the re-establishment of flora and fauna. This information is useful to EPA's Superfund program since effectively capping a contaminated site is less expensive than dredging and off-site treatment, with less environmental disturbances. The demonstration also indicated that re-contamination of the cap surface will occur if the contamination sources are not controlled.
Sediment Methods Development
Ashtabula River Dredging Residuals Study: The development of a method for estimating the volume and contaminant concentration of post-dredging residuals is a high research priority for EPA's Superfund Program. In 2007, EPA's Office of Research and Development (ORD) conducted an extensive study on the Ashtabula River in Ohio to evaluate dredging residuals resulting from a dredging operation conducted by Great Lakes National Program Office (GLNPO) and funded through the Great Lakes Legacy Act. Data collection is nearly complete and analysis continues. Dredging is frequently part of sediment risk management remedies and an effective method for estimating residuals will be a valuable tool for the Superfund Program.
Electrochemical Dechlorination: ORD researchers are pursuing the development of pilot-scale in-situ and ex-situ (within confined disposal facility) applications of an electrochemical dechlorination process to remediate PCB-contaminated sediments in Waukegan Harbor, IL (Region 5). Both EPA's Region 5 Office and GLNPO are very interested in technology.
Arsenic Fate and Transport Study - Fort Devens Superfund Site: ORD researchers are providing a detailed assessment of arsenic transport in ground water and impact of contaminated groundwater discharge on sediments and surface water in the most highly impacted portion of the surface water body ("Red Cove") in Massachusetts. Results will be used to scope an ecological risk assessment in Red Cove, scheduled for spring 2008, and will provide the foundation for planned Remedial Investigation and Remedy Selection. ORD efforts have provided the impetus for stakeholders to initiate risk evaluation and remedial alternatives for contaminated sediments. The technical expertise provided by researchers is respected and valued by EPA's Region 1 Office, Massachusetts Department of Environmental Protection, and U.S. Army.
Development and Evaluation of Passive Sampling Devices: Passive samplers are being developed and evaluated as alternatives to biotic sampling methods for assessing contaminant exposure. Studies have been conducted at Lake Hartwell in South Carolina (monitored natural recovery), Anacostia River in Washington, DC (innovative capping), and Ashtabula River in Ohio (dredging effectiveness). A new study has been initiated at New Bedford Harbor, an urban tidal estuary in Massachusetts, to evaluate different types of passive samplers in parallel. Results indicate that passive samplers are very effective at rapidly assessing the availability of contaminants and are a reasonable alternative to deploying fish and other biotic samplers. Research continues to more fully explore the behavior of passive samplers and calibrate them with biotic receptors.
Ecological Effects Research
PCB residue-effects database: The Land Research Program completed an important database in 2007 that provides new tools for assessing the risks of PCBs in soil or water. The purpose of the PCB Residue Effects (PCBRes) Database is to develop PCB critical residue values for fish, mammals, and birds, especially as these relate to aquatic and aquatic-dependent species. This database also includes expression of critical residue values based upon PCB Aroclors and total PCB-based congener specific methods because PCBs occur as complex mixtures.
The PCB Residue Effects (PCBRes) Database assists scientists and risk assessors in understanding the toxic effects of PCBs and dioxin-like compounds to fish and aquatic wildlife. The database is being used to improve risk assessments to fish and wildlife when PCB has contaminated soil or water. This database will benefit public, private sector, and EPA risk assessors by providing a more efficient, transparent, and consistent risk assessment practices.
Biota-Sediment Accumulation Factor (BSAF) Dataset: The Land Research Program completed a second important database in 2007 that provides new tools for determining accumulation factors in biota from contaminants in sediments. The BSAF dataset was assembled from data provided from 19 Superfund sites. Users also can import their own site data and calculate site-specific BSAFs. It assists risk assessors to determine if BSAFs for their site are reasonable, the dataset can provide a screening assessment for sites with limited and/or no field data. The biota-sediment accumulation factors (BSAFs) data set provides accumulation factors for risk assessors.
ECOTOX Website: The ECOTOX knowledgebase provides a means of locating high quality ecological effects data for a wide-range of terrestrial and aquatic receptors from 23,000 publications.
Cutting Edge Methods to Improve Ecological Risk Assessments: Combined use of field data and bioaccumulation models was demonstrated in a hybrid approach to extrapolate accumulation of persistent contaminants found in sediments. These findings improve ecological risk assessment of contaminated sediments.
Sediment Contaminant Fate and Transport Modeling
Researchers in EPA's Office of Research and Development (ORD) provide consultative assistance to major contaminated sediment sites. Their role has been to work with the site manager to improve the quality of current models used at a site, serve as the EPA expert in peer review of models considered for application at a site, provide modeling tools to site managers, and provide expert advice to senior regional managers. Recent examples are provided below:
EPA Region 1 Office: Technical Advisor to the Region 1 Remedial Project Manager on the Housatonic River Superfund Site in Massachusetts (1999 - 2006). ORD advised the manager on the hydrodynamic, sediment transport, and PCB transport and fate modeling in the Housatonic River. Also, at the request of the R1 Office of Site Remediation and Restoration Director, ORD performed sediment and PCB transport and fate modeling of a 19-mile downstream reach and a 2-mile upstream reach of the Housatonic River.
EPA Region 2 Office: Technical Advisor to the Region 2 Remedial Project Manager on the Passaic River Superfund Site in New Jersey (2005 - 2007). The Region 2 Division Director of Emergency and Remedial Response requested ORD to assist in the development of a numerical model for the Lower Passaic River and Newark Bay Superfund Sites.
EPA Region 3 Office: Technical Advisor to the Region 3 Remedial Project Manager on sediment and contaminant transport and fate issues at the Saltville Waste Disposal Ponds Superfund Site in Virginia and Tennessee (2005 - 2007). ORD provided expert review of several contractor reports and plans.
EPA Region 5 Office: Technical Advisor to the Region 5 Remedial Project Manager on sediment and contaminant transport and fate related issues (including modeling initiated by the Region's modeling contractor) at the Kalamazoo River Superfund Site in Michigan.
EPA Region 9 Office: Technical Advisor to the Region 9 Remedial Project Manager on hydrodynamic, sediment, and contaminant transport related issues at the Palos Verdes Shelf Superfund Site in California (2002 - 2005).
EPA Region 10 Office: Technical Advisor to the Region 10 Remedial Project Manager on hydrodynamic, sediment and contaminant transport related issues at the Portland Harbor Superfund Site and Lower Duwamish Superfund Site in Washington (Dec 2002 - 2007). ORD serves as a member of the Sediment Transport Modeling Advisory Team.