The proposed project submitted to the Corps for permit consideration consists of conducting annual maintenance dredging, the discharge of sediment laden water from an existing Dredged Material Containment Area (DMCA), and the transportation of dredged material from UPT to the Charleston Ocean Dredged Material Disposal Site (ODMDS) for the purpose of ocean disposal. In detail, the applicant has proposed to dredge approximately 100,000 cubic yards of accumulated sediment each year in order to maintain the depth of the existing berth at CST (-44 feet Mean Lower Low Water + 1 foot of allowable overdepth).
The existing DA permit (SAC-2003-13026) authorizes the SCPA to use a hydraulic cutterhead or a mechanical dredge to remove accumulated sediment from the berth at CST. As shown on drawing sheets 2 and 3 of 8, the existing berth is 2,670 feet long and 125 feet wide (7.66 acres), and the total depth is -45 feet Mean Lower Low Water. Depending on the method of dredging, maintenance material is hydraulically pumped to an existing DMCA (e.g., Clouter Island, Daniel Island, and/or Drum Island) or placed in scows before being pumped into one of these existing DMCAs. The existing DA permit is scheduled to expire on March 31, 2024.
The proposed work is consistent with the existing DA permit and would not alter the length, width, or depth of the berth at UPT. In addition, the SCPA has proposed to use the same two dredging methods to remove accumulated sediment, and the dredged material would be hydraulically pumped to an existing DMCA or placed in scows before being pumped into an existing DMCA. The only difference is that the SCPA has also proposed to transport dredged material from UPT to the Charleston ODMDS for the purpose of ocean disposal. The Charleston ODMDS is located approximately 9 nautical miles southeast of Charleston, South Carolina and is identified as “Dump Site (dredged material)” on NOAA Nautical Chart 11521, Charleston Harbor and Approaches.
The Charleston ODMDS was designated by the U.S. Environmental Protection Agency (EPA) for the long-term placement of dredged material associated with the Charleston Harbor Federal navigation channel and other dredging projects near Charleston, South Carolina. Over the past 20 years more than 22 million cubic yards of new work material and approximately 1 million cubic yards per year of maintenance material has been placed within the ODMDS (a total of more than 42 million cubic yards). Since the existing berth at UPT is located immediately adjacent to the Federal navigation channel, the SCPA believes there may be opportunities for contractors to use the same dredging equipment to conduct work associated with both projects.