BMP Prioritization for TP Reduction in Virginia Beach
Municipalities subject to total maximum daily load (TMDL) requirements often seek more sophisticated methods for compliance. The City of Virginia Beach is subject to TMDL compliance across its jurisdiction with required total phosphorus (TP) reductions. Most of the Virginia Beach MS4 coverage area is located within the North Landing and Chesapeake Bay watersheds with specific TMDL requirements, for which the City developed a best management practice (BMP) prioritization methodology that incorporates their large quantity of high-quality geospatial data to optimize plans for retrofits, providing opportunities for the largest TP reductions for the lowest cost.
Tetra Tech assisted the City of Virginia Beach in developing a GIS-based feasibility analysis and prioritization matrix of potential sites. Key metrics included for prioritization ranking are land use, easement presence, imperviousness, available space, and proximity to features like floodplains, waterbodies, tidal areas, and existing stormwater features. The City explored options for retrofits on existing public and private lands without BMPs, as well as opportunities to modify existing BMP features to provide improved TP reductions. High priority locations were modeled to determine potential pollutant reductions and conceptual designs for top sites were developed to represent a range of BMP opportunities.
This approach evaluates and ranks every property in the City based on relative likelihood for potential suitability to plan a water quality improvement project. The City then uses all available information from the metrics and prioritization scheme to further evaluate high ranking sites for BMP types, refined feasibility, and cost/benefit analyses.