Coastal Circulation and Effluent Transport Modeling at Cherry Point, Washington

A 3-D hydrodynamic circulation and effluent transport model was developed using a combination of the far field model (EFDC) and near-field plume models for the 9 miles of Cherry Point coastline from Point Whitehorne to Sandy Point in the Strait of Georgia, Washington. This study was initiated by the Cherry Point Industries to specifically evaluate the potential for cumulative effects from multiple sources of industrial effluent in the study area. The EFDC model was setup and calibrated using oceanographic data that was collected specifically for the model development. Sensitivity analysis was conducted to evaluate the importance of baroclinic forcing in comparison to barotropic motion. The near-field dilution and far-field effluent plume transport components were calibrated using historical dye study data from the site. The study showed conclusively that accumulation of effluent does not occur. Effluent concentrations reach a dynamic steady state within a few days from the start of the discharge. The distribution patterns for all constituents consistently indicate that water quality standards will not be exceeded in the study area due to the Cherry Point discharges.