Testing the CORMIX model using thermal plume data from four Maryland power plants

Historical thermal plume studies from four Maryland power plants (Calvert Cliffs, Chalk Point, Dickerson, and Wagner) were used to test the realism of the CORnell MIXing Zone Expert System (cormix). Test data were from a wide range of challenging discharge environments, including a large freshwater river (Potomac), a narrow tidal estuary (Patuxent), a wide tidal estuary (Chesapeake Bay), and a wind-driven tidal estuary (Baltimore Harbor). Historical case studies were simulated, and results were compared qualitatively and quantitatively with historical measurements. Qualitative results show that the model performed optimally for simple discharges into large basins such as Chesapeake Bay. For complex discharges and complex ambient environments, the model often mixed plumes too rapidly, resulting in smaller modeled plumes that were cooler than the measured plumes. The mixing model also could not account for the re-entrainment of effluent from previous tidal cycles. Sensitivity results show that sensitivity is often dependent on model run time and discontinuities in the cormix flow classification scheme. Users of the cormix model need to be aware of these limitations in applying the model to complex situations. cormix results should be used with caution in evaluating the effects of a discharge and only in conjunction with information from the field.