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Title: Charleston Harbor Section 204 Beneficial Use of Dredged Material, Charleston, South Carolina : Detailed Project Report
Authors: United States. Army. Corps of Engineers. Charleston District
Keywords: Charleston Harbor (S.C.)
Dredging spoil
Channels (Hydraulic engineering)
Environmental protection
Environmental management
Publisher: United States. Army. Corps of Engineers. Charleston District.
Abstract: This Section 204 Detailed Project Report presents the evaluation of beneficial uses for dredged material resulting from the planned deepening of the federal channel in Charleston Harbor. Through both previous coordination efforts and during the Charleston Harbor, South Carolina Project (Charleston Harbor Post 45 Project), stakeholders have requested that the USACE place dredged material along certain shorelines to reduce the effects of erosion such as on Fort Sumter, Crab Bank, and Shutes Folly Island. The recommended plan would address these concerns by restoring Crab Bank. Normal Operations and Maintenance (O&M) annually removes about 1 million cubic yards of material in the lower reaches of the harbor. A shoaling analysis related to the upcoming deepening of the federal channel indicates an approximate 50% increase in the O&M material that will be dredged. In addition to the increase in O&M material, the deepening will produce a one‐time opportunity to use new work material to the benefit of the harbor. While this study initially evaluated uses for both maintenance material and new work material from the lower reaches of the harbor, it was determined that the O&M material was not suitable for the alternatives that were ultimately formulated. These alternatives involved placing material at Crab Bank and Shutes Folly Island to enlarge both islands, extend their lives in the face of wave erosion and sea level rise, and expand nesting, foraging, and loafing habitat for avian species. The habitat suitability index (HSI) model for the brown pelican was used to derive environmental benefits and served as a proxy for other shorebirds that use Crab Bank. Over thirty different measures were initially screened and eliminated. Twenty five alternatives were evaluated as part of this study. It was ultimately determined that the most cost effective beneficial use of the new material was to use it to enlarge Crab Bank and provide new avian habitat. The estimate of available material resulting from the deepening is approximately 825,000 cubic yards (cy), with approximately 660,000 cy ultimately being used. The restored Crab Bank will have an initial footprint of 79.4 acres at MLLW, with 27.8 acres, available for brown pelican nesting. At the end of the period of analysis, approximately 15.25 acres of Crab Bank will remain, with 1.36 acres of pelican nesting habitat remaining. All analysis was based on best available information at the time which was LiDar data from 2017. The design phase will utilize the most recent data available to develop the final footprint. The fully funded costs for the design and construction of the recommended plan are estimated to be approximately $3.98 million, with the federal share costing approximately $2.59 million.
Description: Definite Project Report
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Environmental Documents

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