The TraPac container ship has been experiencing high rates of shoaling since initial construction in 2008, primarily due to eddy formation. Approximately 468,000 cubic yards of sediment was deposited in the two berths between August 2008 and August 2010. ATM performed a hydrodynamic and sedimentation study to evaluate this problem and identify solutions to reduce the sedimentation rate. Current measurements were made with a towed ADCP and a fixed HADCP was mounted on the bulkhead to obtain continuous data to document eddy formation. Bottom sediments were collected at multiple locations and analyzed for grain size distribution and percent organic material along with water samples at multiple depths to determine TSS and salinity. Utilizing the collected data, ATM set up a 3-D curvilinear orthogonal finite difference grid of this region of the river and adapted it to an existing EFDC model.
ATM used modeling results to develop modifications to the existing entrance channel to reduce sedimentation by a predicted 25%. ATM completed permitting efforts, developed construction drawings and specifications, provided bid support and construction administration for the modified entrance channel. Approximately 220,000 cubic yards of material was removed to complete the berth modifications and sediment reduction has been approaching 30% in the berthing areas since completion of the project.