9876401 Hayes The objective of this project is to study the water quality impacts associated with removing contaminated sediments using a conventional hydraulic cutterhead dredge through extensive field data collection in conjunction with the ALCOA Point Comfort/Lavaca Bay Superfund Treatability Study. Specific objectives of the research are to: (1) gather water quality data from near the dredgehead and in the water column (25m to 500m) during conventional hydraulic cutterhead dredging operations under conditions representative of other remedial sites, (2) gather these same data under a range of dredge operating conditions, (3) evaluate the range of water quality impacts associated with this type of dredging operation, (4) use the near-field data to verify and refine the model proposed by Hayes (1998) that relates the rate of sediment resuspension to the dredge characteristics and operating parameters, (5) conduct column settling tests on the sediments and attempt to verify the far-field suspended sediment transport model proposed by Je (1998) and (6) evaluate the potential for recontamination by calculating the amount of sediment and mercury transported away from the site based upon the water quality data collected during the dredging operation and compare that to measured sediment deposition and mercury concentrations at specified locations. The National Research Council estimates that 14 to 28 million cubic yards of contaminated sediments are dredged annually from U.S. ports, harbors and waterways to maintain established navigation depths. Larger volumes of contaminated sediments are known to exist in non-navigable areas and designated superfund sites. While many of these sediments can remain in place, remedial actions are necessary where contaminants are finding their way into the food chain. However, concern over excessive water quality impacts during removal hampers cleanup actions. The results of this study will provide additional knowledge of the effects of contaminated sediments removal operations on the quality of the surrounding and downstream aquatic environments.
