Evaluation of Water Quality Impacts Related to the Construction of a Nearshore Confined Disposal Facility

Evaluation of water quality impacts is a critical component of the federal and state permit applications required for the construction of nearshore confined disposal facilities (CDFs). Effective evaluation must consider both short-term impacts due to dredging and placement of material in the nearshore CDF, and long-term impacts as a result of groundwater movement through the CDF. Physical and chemical characterization of the sediments and characterization of water quality in the dredge and disposal areas are used to conduct qualitative and quantitative assessments of water quality impacts. These assessments involve testing procedures developed by the United States Army Corps of Engineers' (USACE) Waterways Experiment Station (WES) and include the dredging elutriate test (DRET) and the thin-layer column leaching test (TCLT). Using a case study, this paper describes the short-term and long-term water quality impact evaluation process, including key elements of a sediment and water quality sampling and analysis plan, and appropriate test methods and interpretation procedures.