BENEFICIAL USE OF DREDGED MATERIALS AT LOUISIANA SHORELINE NEAR SABINE PASS

摘要

Cheniere Sabine Pass Liquefied Natural Gas (SPLNG) Terminal is located 12 miles west of Johnson Bayou, Louisiana, on the Louisiana side of the Sabine Pass Channel. The construction of the Terminal will require the removal of approximately ±4.5 million cubic yards (CY) of mostly virgin soil from the proposed marine berth. The removal of the soil was conducted via a 36-inch hydraulic dredger. Due to the quantity of the dredged material, it is required under Louisiana regulations to utilize the dredged material for beneficial uses, and a decision was made to use the materials for beach nourishment along the shoreline east of Sabine Pass Jetty. The plan included pumping the dredged material south via dredge piping to Louisiana Point and then discharging the material into offshore waters about 2,200-feet (ft) from the Louisiana shoreline in depths ranging from 5 to 8 ft deep. The discharged material is expected to provide wave buffers, increased wildlife and aquatic habitat and act as a barrier to protect the existing shoreline from continued erosion. A two-dimensional hydrodynamic (RMA2) and sediment transport (SED2D) modeling effort was conducted to investigate the transport of the discharged material and its potential effects on the environment. Significant data collection effort, including bathymetric survey, geotechnical studies, current measurements, wind and tide data collection, and water quality sampling, was conducted to support the modeling effort. The bathymetric survey included a 3-mi by 2-mi (6-sq-mi) area surrounding the proposed beneficial use site and the East Jetty Boat Cut area to verify the relative elevation differences between the Boat Cut and the surrounding area. Available navigational charts were used to expand the RMA2 and SED2D models significantly beyond the field survey boundary to allow for sediment transport simulations of a larger area. The data were then used to develop a 2D mesh for RMA2 and SED2D models. The finished mesh has a total of 16,970 nodes and 5,559 elements. The modeling results were presented to federal and state agencies to support the application of necessary permits for the project. As a result, the project has been permitted and construction is ongoing. This paper provides a summary of the modeling effort and the status of the dredged materials placement effort.