Modeling the effects of a power plant's thermal discharge on an indigenous fish community

The Quad Cities Nuclear Station (QCNS) on the Mississippi River has been operating on once-through cooling since 1983.  The station discharges heated water to the river via a diffuser which enhances dilution and reduces nearfield effects of the thermal plume. As part of a request for a modification of thermal discharge standards at the facility, the owner contracted HDR to study the effects of the proposed alternate standard on the indigenous fish community.   To perform this analysis, HDR developed an innovative biothermal modeling approach that links biological metrics (growth, avoidance, thermal mortality) to hydrothermal simulations of the plant’s thermal plume under different plant operating scenarios.  Species-specific temperature tolerance polygons that incorporate information on the thermal tolerance regimes for the biological metrics as a function of acclimation temperature were developed for four target species (walleye, channel catfish, spotfin shiner and largemouth bass). Combining this information with hydrothermal modeling results detailing the spatial and temporal characteristics of the QCNS thermal plume, the biothermal model provides an estimate of effects of the thermal discharge in terms of percentage changes in the important biological metrics, thus providing a quantitative evaluation of the effect of a proposed alternate standard on the balanced indigenous fish community.