Project Type(s): Sediment budgeting / Historical dredged material placement
Project Description: Thin layer placement of dredged material was planned for multiple placement areas that are historical open-water disposal areas used prior 1986. Thin layer placement benefits channel dredging operations, keeps sediment in the system, provides faster recovery for bay-bottom benthic communities, and has negligible impact on benthic ecology. Emergency in-bay thin layer placement was approved in 2012. Approximately 9 MCY dredged material were placed in a thin layer (thickness smaller than 12 in.) using a hydraulic cutterhead. A monitoring and modeling program were established to evaluate short and long term fate and transport of in-bay thin layer placement. The results of this program indicated that thin layer placement of dredged material in the bay will have negligible impact, hence a long-term in-bay thin layer placement program was approved in 2014. In 2014, 1MCY of dredged material was placed in a thin layer in-bay using a spill barge with a system of winches and a continuous GPS tracking system. Both of these thin layer placement efforts resulted in significant savings in dredging costs, less erodible material in the sediment surface, and a quick recovery of the benthic community.