Guidance for in situ subaqueous capping of contaminated sediments

In-Situ Capping is defined as the placement of a subaqueous covering or cap of clean isolating material over an in-situ deposit of contaminated sediment. ISC is a potentially economical and effective approach for remediation of contaminated sediment. A number of sites have been remediated by in-situ capping operations worldwide. This document provides technical guidance for subaqueous, in-situ capping as a remediation technique for contaminated sediments. The document was prepared as a part of the studies conducted for the U.S. Environmental Protection Agency (USEPA) under the Assessment and Remediation of Contaminated Sediments (ARCS) Program, administered by USEPA's Great Lakes National Program Office (GLNPO), in Chicago, Illinois. Caps for in-situ sediment remediation may be constructed of clean sediments, sand, gravel, or may involve a more complex design with geotextiles, liners and multiple layers. In-situ capping can provide several primary functions: physical isolation of the contaminated sediment from the benthic environment; stabilization of contaminated sediments, preventing resuspension and transport to other sites; and, reduction of the flux of dissolved contaminants into the water column. To achieve these results, an in-situ capping project must be treated as an engineered project with carefully considered design, construction, and monitoring. The basic criterion for a successful capping project is simply that the cap required to perform some or all of these functions be successfully designed, placed, and maintained. This document provides descriptions of the processes involved with in-situ capping, identification of the design requirements of an in-situ capping project, and a recommended sequence for design. Detailed guidance is provided on site and sediment characterization, cap design, equipment and placement techniques, and monitoring and management considerations. This report should be cited as follows: Palermo, M., Maynord, S., Miller, J., and Reible, D. 1998. "Guidance for In-Situ Subaqueous Capping of Contaminated Sediments," EPA 905-896-004. Great Lakes National Program Office, Chicago, IL.

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