Beargrass Creek Water Quality Model

Until 2001, MSD developed projects for the control and mitigation of CSOs, SSOs and storm water within the requirements of the individual regulatory programs. Success was measured on the basis of cost per unit reduction in average annual overflow volume (AAOV) or number of best management practices (BMPs) implemented. However, MSD did not have the tools to quantify the reduction in pollutant loadings or reductions in water quality violations resulting from this approach, or to evaluate if alternative approaches would result in overall greater environmental benefit. Hence, MSD is developing a water quality-based evaluation tool.

Restoring urbanized streams is difficult because of the complex nature of impacts, the cost associated with many of the solutions, and the difficulty predicting the environmental benefit of various solutions. Intensive monitoring and modeling to delineate impacts and evaluate environmental cost/benefit of alternatives is essential. Having a predictive tool that links management strategies with water quality standards, biocriteria, and habitat quality supports the framework for making management decisions. This approach, using a water quality based evaluation tool, will allow more effective management of resources, resulting in enhanced environmental benefit.

The "Water Quality Tool" links a continuous simulation watershed model (HSPF) and a continuous simulation sewer model (XP-SWMM) to predict the water quality benefits of different management scenarios. This two-year effort included intensive sampling and monitoring. Additional modeling refinements are planned and will include integration of biological and habitat data.

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