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Scope/Content: Abstract: This Explanation of Significant Differences (ESD) has been prepared to document a significant change to the June 1994 Final Record ofDecision (ROD) for Operable Unit Two (OU2) of the Sangamo Weston, Inc.lTwelve Mile Creek/Lake Hartwell PCB Contamination Superfund Site ("the Site") located in Pickens, Pickens County, South Carolina. Among other components, the OU2 ROD required regular flushing of sediments trapped behind three impoundments on Twelve Mile Creek (12MC) to facilitate burial of contaminated sediments further downstream while mitigating adverse impacts to Lake Hartwell water quality. In May 2006, State and Federal Natural Resource Trustees (NRTs) reached a natural resource damage settlement agreement with Schlumberger Technology Corporation (Schlumberger) via a Consent Decree (Natural Resource Damages Settlement CD) entered in Federal Court. The settlement requires restoration and compensation for alleged injuries to natural resources due to PCB exposure and for alleged lost recreational fishing use due to fish consumption advisories. Ecological restoration projects include removal ofthe lower two hydroelectric impoundments on l2MC known as Woodside 1 (WS 1) and Woodside 2 (WS2) and stream corridor restoration. The removal of the WS 1 and WS2 dams and the associated stream restoration activities are expected to provide significant ecological benefits for the lower reach of 12MC. Moreover, removal ofthe two dams is expected to complement the Remedial Action for OU2 because removal of the dams will allow unimpeded flow of sediments from the Easley-Central water supply reservoir to the l2MC Arm ofLake Hartwell, thus facilitating the natural capping of contaminated sediments downstream. Pursuant to the Natural Resource Damage Settlement CD, engineering design reports have been submitted by Schlumberger to the NRTs for review and approval. These reports have also been submitted to the United States Environmental Protection Agency (EPA). Mobilization for the initial phase ofWSl and WS2 dam removal is anticipated by the 4th Quarter of2009. This ESD is written to incorporate into the selected remedy all activities necessary to facilitate WS 1/WS2 dam removal and regular flushing of sediments from the Easley-Central dam into the l2MC Arm of Lake Hartwell, thereby enhancing the performance of the remedy for Sangamo OU2. As the lead regulatory agency ofthis Superfund Site, the Region 4 EPA is issuing this ESD pursuant to public participation requirements specified in Section l17(c) ofthe Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and Section 300.435(c)(2)(i) of the National Contingency Plan (NCP). The South Carolina Department of Health and Environmental Control (SCDHEC) is the support agency ofthis Site. This ESD will become part ofthe Administrative Record for the site pursuant to NCP Section 300.825(a)(2). The Administrative Record for this Site is available for public review at the locations listed below. Site information can also be found at www.epa.gov/region4/waste/npllnplsc/sangamsc -', - EPA Region 4 Records Center, Sam Nunn Atlanta Federal Center; - Pickens County Library; Easley, South Carolina; - Hart County Library; Hartwell, Georgia; and - Clemson University R.M. Cooper Library; Clemson, South Carolina. Scope/Content: Date removed: 2011.
Pre- and post-project monitoring Dams Dam retirement