Title: Introduction (1 of 3) Text: Several established techniques exist for sediment remediation of harbors, rivers, and lakes. This tool will examine three sediment remedies: (1) environmental dredging, (2) in-situ capping, and (3) monitored natural recovery (MNR). The map to the left illustrates locations where these technologies have been applied. Applicable contaminants include a range of metals and organics.

Title: Navy Policy and Guidance (2 of 3) Text: The Navy Policy on Sediment Investigations and Response Actions specifies that: 1. Contaminant sources must be identified 2. Investigations shall be linked primarily to a specific Navy IR/BRAC site 3. Sources must be controlled before cleanup 4. Cleanup must be risk-based 5. Sediment cleanup goals must be site-specific 6. Monitoring criteria must be established before the first sample is collected.

Title: Site Assessment Considerations (3 of 3) Text: Before a sediment remediation strategy may be selected and applied to a contaminated site, site characterization and risk assessment need to be conducted as outlined in previous ERT2 tool Sediment Guide Data Sheet. Site characterization should allow the project manager to accomplish the following: Identify, locate, and quantify contaminants Identify ongoing sources Understand the hydrology and geomorphology of site Understand chemical and biological processes that affect the fate of contaminants Collect data to compare potential effectiveness of various strategies Provide baseline data for monitoring From the site characterization data, a conceptual site model should be developed and human health and/or ecological risk assessments should be performed. Additionally there are a number of issues unique to sediment sites. Project managers should understand the role of the contaminated water body (i.e., habitat or flood control functions), the presence of non-site-related contaminant sources in the watershed, and current and future uses of the water body and surrounding land. More information on remedial investigations is available in EPA Contaminated Sediment Remediation Guidance for Hazardous Waste Sites.

Title: Conceptual Site Model Text: A conceptual site model (CSM) generally is a representation of the environmental system and the physical, chemical, and biological processes that determine the transport of contaminants from sources to receptors.

Title: Environmental Dredging Text: The objective of environmental dredging is to remove contaminants from the waterway and reduce the risk to environmental resources and human health. Environmental dredging is applicable when: Achieving a navigable depth is desirable Soil stability is uncertain High environmental concern exists Evaluating environmental dredging as a remedial alternative differs from evaluating a navigational dredging project because the drivers are different and environmental concerns are high. For example, the objective of environmental dredging is to precisely remove contaminated sediment without spreading the contamination to the surrounding environment, rather than to simply remove the greatest volume of sediment possible.

Title: Conditions Conducive for Environmental Dredging Text:

Title: Pros and Cons of Environmental Dredging Text: Environmental dredging is advantageous as it restores water depth and removes contamination through the mass removal of sediments. If the site reaches the cleanup goals, this cleanup method offers the least uncertainty about long-term effectiveness (e.g., future exposure to contaminated sediment). Dredging may offer the most flexibility for the future use of the water body whereas remediation methods like capping and monitored natural recovery (MNR) often require institutional controls (ICs). However, dredging effectiveness is reduced by resuspension, release, and residuals. Additionally, the treatment and/or disposal of contaminated sediments is costly. Finally, dredging or excavation includes at least a temporary destruction of the aquatic community and habitat within the remediation area.

Title: Resuspension Text: Resuspension is the loss of sediment particles to the water column during dredging. Resuspension is related to the sediment type.

Title: Release Text: Release is the contaminant mobilization associated with in-situ sediment disturbance during dredging. Contaminants are released through the desorption from particles, liberation of pore water, and surface volatilization.

Title: Residual Text: Residual occurs when contaminated sediments remain post-dredging due to insufficient site characterization, ineffective dredging, or settling of resuspended sediments.

Title: Design Considerations (1 of 3): Dredging Equipment Text: Dredging equipment options include: Mechanical dredges--advantages include higher solids content, which minimizes waste disposal, and high positioning precision; limitations include lower production than hydraulic dredge, applicability only to shallow water depths, and potentially higher rates of resuspension Hydraulic dredges--advantages include potential high production and functionality in deep waters; limitations include low precision and high water content with increased treatment/disposal costs Pneumatic dredge--advantages include applications within deep water; limitations include low production and air entrainment Diver assisted--high precision; low production, potential residuals Specialty dredges for cleanup available Equipment selection must be based on site-specific factors, including the applicability of equipment modifications to reduce contaminant resuspension and the associated impact on production rates.

Title: Production Text: Production is the rate of removal of sediment measured in volume per unit time (e.g., cy/hr).

Title: Design Considerations (2 of 3): Transport Text: Transport distance, availability of transport equipment, and optimal water content for the process train are factors to consider when determining the transport method for the treatment and disposal of removed material. Typically, hydraulic dredging loads are transported via pipeline and mechanical dredging loads are transported by mechanical (see photo) or hydraulic offloading.

Title: Design Considerations (3 of 3): Containment Text: Various disposal and containment options are available for the waste removed by environmental dredging. Because hazardous waste disposal is much more costly than solid waste disposal, options should be considered for minimizing hazardous volume. Some of the facilities available [and the regulations governing them] include: landfills [Subtitle D], hazardous waste disposal facilities [Subtitle C], confined disposal facilities (CDF), and contained aquatic disposal (CAD).

Title: Contained Aquatic Disposal Text: Contained Aquatic Disposal (CAD) facilities are newly constructed or existing pits used to laterally confine contaminated sediments. The depth of the pits range from a few to forty feet, and the width usually ranges from 1,500-5,000 feet. Larger CAD sites are filled incrementally. Once filled, the pits are capped to contain the contaminated sediments.

Title: Mixing Text: When contaminated sediments are capped, some contaminants may be resuspended into the water column or mixed with the capping material. The most significant releases occur during the application of the first layers of capping material. Equipment and placement rates should be selected to minimize mixing.

Title: Effectiveness of Environmental Dredging Text: All dredges resuspend some sediment, release some contaminants, and leave some residuals. Resuspension accounts for <1% of mass removed, and in some cases, specialized methods of operation or equipment may be needed to minimize resuspension of sediment and transport of contaminants. Residuals account for about 2% to 9% of the last pass dredge volume. Where residuals are a concern, thin layer placement/ backfilling, MNR, or capping may also be needed. Controls may be added at an additional cost, but may have limited effectiveness. For example, caps can be used as a management option. However, according to a 2007 National Research Council report only 25% of the 20 Superfund Megasites evaluated met remedial goals.

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Title: Fox River Cleanup (1 of 5) Text: Fox River is an U.S. Environmental Protection Agency (EPA) Cleanup site in Green Bay, Wisconsin. From 1954 to 1971, 690,000 pounds of polychlorinated biphenyls (PCBs) were released into the river. In addition to environmental dredging, several remedial alternatives were considered including: capping, dredging and landfilling, and vitrification.

Title: Fox River Cleanup (2 of 5) Text: From May-December 2000, 50,000 cubic yards (cy) of sediment were removed by hydraulic dredging from the Sediment Management Unit (SMU) 56/57. After dewatering, the sediments were transported to the Fort James Green Bay Landfill Cell 12A (TSCA permitted), and the water was treated. Project cost was $8.18M. However, the actual cost was estimated at $14.9M due to a discounted disposal cost ($21/ton versus $141/ton) and in-kind services (staging area lease, internal project team) that were not included in the project cost.

Title: Fox River Cleanup (3 of 5) Text: The performance specifications for the 2000 SMU 56/57 demonstration were: 1) Residual surficial sediment concentrations of: <1 ppm PCBs, or <10 ppm PCBs plus 6 in. sand cap, or 90% of subunits <10 ppm (not-to-exceed 25 ppm in any subunit), with overall average <=10 ppm, plus 6-in. sand cap for subunits >1 ppm 2) All side slopes capped with 6 in. sand

Title: Fox River Cleanup (4 of 5) Text: Target production for SMU 56/57 was 833 cy/day. Maximum production reached 1,599 cy/day with 8.4% solids content. Of the volume removed, 51,613 tons were disposed of in the Fort James Green Bay Landfill in Cell 12A and 66.33M gallons of water were treated.

Title: Fox River Cleanup (5 of 5) Text: As seen in the table to the left, dredging significantly reduced the concentration of PCBs in three areas of the Fox River Megasite. Despite these reductions, these concentrations were still greater than the site's goal for average surface concentrations of 1 ppm or less. According to a report published by the National Research Council's Committee on Sediment Dredging at Superfund Megasites, only 25% of the 20 sites evaluated met remedial goals. About half of the sites either did not meet remediation goals or monitoring was insufficient to assess dredging performance. Insufficient time had elapsed to determine whether goals were met at the remaining 25% of the sites.

Title: Vitrification Text: A high temperature process, which uses an electrical current to heat (melt) and vitrify the soil in place. This process can destroy organic contaminants and incorporate metals into a glassy matrix.

Title: Environmental Dredging Cost Text: Because reported costs for environmental dredging projects vary widely and are site-specific, a project database was created. The Major Contaminated Sediment Sites Database (Release 3.0) offers literature and statistics on approximately 66 dredging case studies implemented from 1990 to 2006. Project volumes range from 2,500 cy - 2.8M cy. Unit costs (adjusted to an August 2006 cost basis) and trend analyses allow improved project planning.

Title: Capping Text: In-situ capping is applicable where dredging is infeasible, where the risk of removal is greater than the risk of leaving contaminants in place, or where effective isolation is possible. Capping can also be used to isolate dredging residuals or in conjunction with dredging to maintain or increase existing water depth. Further information on determining when capping is appropriate is provided in the reference section including EPA Contaminated Sediment Remediation Guidance for Hazardous Waste Sites.

Title: Conditions Conducive for Capping Text:

Title: Pros and Cons of Capping Text: Capping may be a favorable remediation alternative because the contaminant is contained in place, and capping may be more implementable and cost effective than dredging. However, capping is an emerging technology. With capping, contaminated sediments remain in the aquatic environment, water depth is reduced, and long-term monitoring and maintenance are required. In some situations a preferred habitat may not be provided by the surficial cap materials. Additionally, the cap is subject to episodic storms and floods, which may compromise its integrity.

Title: Design Considerations for Capping (1 of 4) Text: Design Objectives: The objectives of cap design are to construct and maintain a cap which is physically stable, protective against boat and ice scour, effectively isolates contaminants, is compatible with bioturbation, and provides enhancements to the aquatic habitat.

Title: Bioturbation Text: Bioturbation is the alteration (mixing and turning of sediments) by living organisms, especially by burrowing or boring. Bioturbation generally occurs within the top 1 to 2 feet of sediment where benthic organisms tend to thrive.

Title: Design Considerations for Capping (2 of 4) Text: Materials include: Granular materials--sediments, soils, quarry run materials Amendments--adsorbents, reactants Fabrics and membranes Armor stone Sand is often used as a primary capping material. Sand caps provide a physical barrier and are easy to place, non-reactive, and stable.

Title: Design Considerations for Capping (3 of 4) Text: Placement methods include: Barge (see illustration)--high velocity dump, significant mixing, limited spread or thickness control Hopper Dredge--similar issues to barge placement, slightly lower velocity dump, can fluidize to minimize mixing Pipeline--most precise placement, greatest velocity control, least mixing Direct mechanical placement-- shallow water, limited thickness control

Title: Design Considerations for Capping (4 of 4) Text: Cap placement issues include: Mixing Achieving uniform cap thicknesses Placement on soft sediments Slope stability Monitoring cap placement The following models are available from the U.S. Army Corps of Engineers (USACE) to model cap placement: STFATE, MDFATE, LTFATE, CDFATE, SSFATE, and DREDGE.

Title: Variations: Active Cap Amendments Text: Active caps contain amendments which reduce bioavailability and encourage the sorption or degradation of contaminants, minimize recontamination, and offset cap loss. Nevertheless, active caps are generally more expensive than sand caps and may require special placement/armoring considerations.

Title: Bioavailability Text: Bioavailability is the extent or degree to which a substance (contaminant) is absorbed or made available to a living organism.

Title: Effectiveness Text: Cap effectiveness is a function of its placement and integrity. Waves, currents, and boat and ice scour can erode the cap. Also, advective transport processes (groundwater discharge, gas production, bioadvection, and pore water release) can cause contaminant releases. These factors affecting cap integrity should be evaluated carefully, and the decision to install a cap should only be made if it is determined that these factors are not likely to cause cap failure. Long-term physical, chemical, and/or biological monitoring should be done post-placement, both at predicted intervals and following extreme events.

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Title: Anacostia River Capping (1 of 3) Text: The Anacostia River is located in Maryland and the District of Columbia. Sediments in the river contain significant concentrations of heavy metals, PCBs, hydrocarbons, and chlordane. Likely sources of these contaminants are long-term military and industrial activity in the Anacostia River. This case study focuses on an EPA project on an area of the Anacostia River adjacent to the Navy Yard in the District of Columbia where a series of active cap materials were placed in March and April 2004.

Title: Anacostia River Capping (2 of 3) Text: Three active cap materials (AquaBlok™(TM), coke breeze, and apatite) were selected for this demonstration project for the purpose of evaluating subaqueous active capping technologies. Post-cap physical, chemical, and biological monitoring has followed construction to verify the integrity and performance of the caps and to evaluate their long-term biological impact. The capping demonstration evaluated the effectiveness of the AquaBlok(TM) technology as a potential sediment remedy based on measures of physical stability, ability to prevent hydraulic seepage, and influence on flora/fauna. However, overall risk reduction was not specifically evaluated in this demonstration.

Title: Anacostia River Capping (3 of 3) Text: Through 30 months of monitoring, cap thickness was found to be consistent with the physical design objectives set forth for the project. Chemical concentrations in the caps indicate contaminants of interest are not migrating into the cap layers. While a number of worms were observed during biological monitoring of the caps, they do not pose a threat to cap integrity.

Title: Cost of Active Capping at Anacostia 10-Acre Site Text: As an emerging technology, there are fewer sites where caps have been installed and therefore limited data on typical costs are available. The table to the left lists a cost breakdown developed for the Anacostia capping demonstration project for placement of the AquaBlok™(TM) active cap with a sand cover on 10 acres. Costs assumed 4,900 tons of AquaBlok™(TM) and 6,000 tons of sand to create target thicknesses of 4" and 6", respectively.

Title: Monitored Natural Recovery Text: MNR is a remedy that typically uses known, ongoing, naturally occurring processes to contain, destroy, or otherwise reduce the bioavailability or toxicity of contaminants in sediment. Isolation and mixing of contaminants through natural sedimentation is the process most frequently relied upon for contaminated sediment. MNR is applicable where natural recovery processes show significant rate of recovery by reduction in surficial contaminant concentration or by reduction in the bioavailability or toxicity of contaminants. With MNR, actions are generally limited to monitoring and ICs. MNR can be used as a stand alone technology following source control or in conjunction with active sediment remediation.

Title: Conditions Conducive for MNR Text:

Title: Pros and Cons of MNR Text: Pros: No disruption to waterbody or to aquatic communities Solution has relatively low cost of implementation Cons: Contaminants remain in the aquatic environment Processes act slowly Subject to episodic storms, floods, etc. Long-term monitoring/ICs required Public acceptance difficult to gain

Title: Variations: Engineered MNR Text: Engineered MNR, also referred to as "Enhanced Natural Recovery," is a permutation of capping where a thin layer of clean sediment or media (e.g., 4-6 in. sand) is placed above the contaminated sediment. This thin layer of media is not designed to provide long-term isolation of contaminants from benthic organisms, but to jump-start the remediation of contaminated sediments through several processes, including increased dilution through bioturbation of clean sediment mixed with underlying contaminants. Other engineered alternatives include addition of flow control structures to enhance deposition in certain areas of a site, or addition of an additive to accelerate contaminant degradation.

Title: Case Study: Fox River Text: Fox River sites OU2 and OU5 were selected for MNR in 2003. Design plans began in March 2004, and monitoring at the sites will continue to measure the progress towards the achievement of remedial action objectives. Institutional controls placed on OU2 and OU5 include land or water access and domestic water restrictions, dredging moratoriums, and fish consumption advisories.

Title: Selection Criteria Text: Risk-based evaluations are essential for sediment remediation projects. Solutions need to be project specific, site specific, and material specific. Costs constraints should be balanced with the degree of environmental protection, permanence, and the ability to achieve site closure. The proper balance between short- and long-term environmental effects should be evaluated carefully. A Net Environmental Benefits Analysis (NEBA) can be a useful tool for assessing and documenting these effects. As selection of a single technique requires tradeoffs, combinations of the techniques may be most acceptable to all parties. A combined approach for large sites may provide a balance of effectiveness and cost, and offset the disadvantages of respective single-option plans. An example combined approach could be: Dredging of hotspots followed by thin capping of residuals Capping of nearby mid-level contamination MNR for larger adjacent areas of low-level contamination Lastly, project monitoring is essential to document project success. Clear data quality objectives and an exit strategy are key to identifying when remedial action objectives are achieved and whether site closure may be obtained.

Title: References Text: Sediment Remediation NAVFAC, 2005. Implementation Guide for Assessing and Managing Contaminated Sediment at Navy Facilities. January. USEPA, 2005. Contaminated Sediment Remediation Guidance for Hazardous Waste Sites. December. USEPA, 1994. Assessment and Remediation of Contaminated Sediments (ARCS) Remediation Guidance Document. EPA-905-B94-003. Environmental Dredging USACE and USEPA, 2004. Evaluating Environmental Effects of Dredged Material Management Alternatives: A Technical Framework. May. USACE and USEPA, 1995. Evaluation of Dredged Material Proposed for Discharge in Waters of the US Testing Manual. March. USACE and USEPA, 1991. Evaluation of Dredged Material Proposed for Ocean Disposal Testing Manual. February. Capping USACE, 1998. Guidance for Subaqueous Dredged Material Capping. June. USEPA, 1998. ARCS Program: Guidance for In-Situ Subaqueous Capping of Contaminated Sediments. September.

Title: Contact Text: For more information, please contact: NFESC Sediment Remedy POC (805) 982-4890 NFESC POC (805) 982-1656 PRTH_NFESCT2@navy.mil