The proposed work consists of dredging approximately 75,000 cubic yards (cy) of material from the Major Canal on a 5-to-7 year maintenance cycle. Approximately 25,000 cy of material will be dredged during one (1) dredging event, for a total of 75,000 cy of material over the course of three (3) dredging events. The dredging area encompasses approximately 20 acres within the existing Major Canal. Dredged material will be removed by hydraulic dredge and pumped to the Horry County-owned confined disposal facility (CDF 320, Tidewater Disposal Basin) near Tidewater Plantation adjacent to the Atlantic Intracoastal Waterway (AIWW). The proposed width of the dredge path in Major Canal will range from approximately 85 feet to 185 feet. The proposed minimum required dredge depth is -5.0 feet mean low water (MLW); for a maximum total proposed depth of up to -6.0 MLW. Dredge side slopes will be 4(h) :1(v).
The proposed dredging will be accomplished with a small (8" -to- I4") hydraulic basket cutterhead, swinging ladder, self-propelled dredge. Dredges of this type generally have three spuds, one of which is used to push the dredge forward to advance into the project cut. The dredge will operate within the footprint of the project. The dredge pipeline, which will consist of high-density polyethylene (HDPE), will either be rafted to the site in 500-foot lengths or may be trucked to the Tidewater Confined Disposal Facility (CDF) in approximately 40-foot lengths and fused into 400-to-500-foot-long sections. A flange will be fused to each end. At high tide, sections will be floated into position and the flanges bolted together to form a continuous pipeline from Major Canal in the vicinity of Cherry Grove to the Tidewater CDF. Weights and anchors and/or temporary pilings will be required to secure the pipeline along the banks of Major Canal and along the dredge pipeline route in House Creek en route to the transition from the water to the upland pipeline route. It is approximately 18,300 feet distance from the farthest end of Major Canal to the discharge location at the Tidewater CDF. It is anticipated that one or two booster pumps may be required to pump the material to the Tidewater CDF. Prior to commencement of dredging, old boards, trash, etc. will be removed from the spillway structure and riser boards reinstalled to provide 2-to-3 feet of ponding at the outlet structure. Once dredging operations commence, the solids will settle out and be retained in the CDF. Excess water will be controlled to ensure that only clean, clear water is released through the spillway outlet structure. Once dredging operations have been completed, an aggressive program will be pursued to dewater and dry the material and prepare it for removal from the CDF. Final removal and relocation of the material will be completed in accordance with the Department of the Army Dredging Permit, and the Horry County Consent Agreements. Once the Tidewater CDF is restored to pre-disposal conditions, a survey will be conducted and submitted to the Corps and Horry County with a request for final inspection and release of Major Canal Dredging (for City of North Myrtle Beach) from the Consent Agreements.