Feasibility of Modeling Remedial Measures for Microbiological Pollution of the St. Clair River at Sarnia Bay

A regular grid finite difference hydrodynamic model, which includes the advective acceleration and eddy viscosity terms, was used to predict the circulation in the nearshore areas around Sarnia Bay. Coupled with the hydrodynamic model, a two-dimensional pollutant transport and fate model, which included the advection, diffusion, and decay terms, was used to predict the spatial and temporal distributions of indicator bacteria. This modeling system allowed time dependent inflow/outflow discharges and bacteria fluxes from storm sewers, combined sewer overflows, and tributaries. Cases of dry weather loading, storm loading, and post recovery (i.e., after a rain event) were simulated for a number of hypothetical remedial options including the relocation of storm sewer outfalls and placement of a deflector barrier at the mouth of Sarnia Bay. The planning-level modeling system, which was partially calibrated and verified for the existing conditions in Sarnia Bay, was found to be an effective tool for screening remedial options for mitigation of bacteriological pollution in Sarnia Bay.