work underway on a water-discharge structure we designed for poor soil conditions
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thermal-discharge-study plan for environmental compliance

thermal-discharge-study plan for environmental compliance
client
Xcel Energy
location
Minnesota

After converting two of its coal-fired units to natural gas, Xcel Energy’s Black Dog generating plant in Burnsville, Minnesota, needed to demonstrate compliance with portions of the Clean Water Act—including item 316a—required for an NPDES permit. Barr prepared a plan for a thermal monitoring and mixing study of the facility's discharge water that would meet the Minnesota Pollution Control Agency’s requirements while minimizing costly and time-consuming collection of field data.

We used a combination of field measurements and calibrated model simulations to characterize the discharge-water plume. We measured river temperatures for 10 events over a range of outfall and environmental conditions to develop, calibrate, and validate a thermal discharge model. Once the model was validated, we used it to investigate plume characteristics under a range of plant and environmental conditions of special concern to Xcel Energy or the regulators. Based on the results, we recommended modifications to the monitoring criteria the power plant uses to determine when it needs to restrict discharge from the cooling ponds to avoid a temperature exceedance.