Introduction and Methods for this Study

The purpose of this investigation was to validate the mixing zone model CORMIX (CORnell MIXing Zone Expert System) using measured thermal plume data from four Maryland power plants (Calvert Cliffs, Chalk Point, Dickerson, and Wagner).  These facilities were chosen to represent a range of discharge environments used by power plants in the state, such as:

• Large freshwater rivers  (Dickerson on the Potomac River)
  
• Narrow tidal estuaries (Chalk Point on the Patuxent River)
  
• Large and wide tidal estuaries (Calvert Cliffs on the Chesapeake Bay)
  
• Complex and unsteady tidal environments (H.A. Wagner on Baltimore's Outer Harbor)

A brief review of existing discharge studies suggested that these sites offered more historical data than others.  Data sources included original blue-prints of the discharge configuration, personal correspondence from power plant operators, public information on weather and tidal predictions for local areas, and historical field surveys of thermal plumes.

For each site, a 'base case' was constructed which represented historic parameters for the dates that plume mapping took place.  This method varies slightly from typical scenarios in which 'worst-case' and 'average-case' parameter values are used in mixing zone analyses.  The goal of the study was not to calibrate the model or analyse the mixing zone but to run the model using the assumptions of a user who would not have access to detailed survey data.

Once the base case was established, the CORMIX predictions were mapped and laid over the measured contours from historic studies.

Next, sensitivity runs were conducted to compare the model's response to variations in parameters.  Each parameter was ranked according to its sensitivity.  The results are available as a Maryland Power Plant Research Program (PPRP) report.