One City's Strategy to Meet their Phosphorus TMDL
Tetra Tech, in partnership with the City of Virginia Beach, is undertaking a project to address water quality impairments in the North Landing Watershed. The project aims to achieve a phosphorus reduction target of 775 pounds per year as part of the City's effort to meet Total Maximum Daily Load (TMDL) requirements under the MS4 permit. This involves a comprehensive assessment of potential stormwater management facilities (SWMFs) designed to mitigate phosphorus pollution through structural and non-structural practices. The first phase focused on identifying and prioritizing suitable sites within the watershed for SWMF implementation. Using geographic information system (GIS) tools, a systematic site selection process evaluating potential locations across the entire watershed simultaneously. GIS metrics include, for example, land ownership, slope, proximity to water, and impervious surface coverage. The goal is to select locations that offer the highest potential for cost-effective phosphorus removal while ensuring compatibility with surrounding infrastructure and land use. Tetra Tech engineers have produced conceptual designs for prioritized sites, incorporating a variety of SWMF types, with a focus on retrofitting existing features by transforming level 1 wet ponds to level 2 wet ponds, and finding strategic locations for hydrodynamic separator installation. The completed conceptual designs, prioritization details, and cost estimates can guide future planning for the City's Upper North Landing River TP TMDL Implementation Plan. This project demonstrates a data-driven approach to stormwater management that addresses regulatory requirements and enhances the community’s environmental resilience.
Author Bio
Hillary Yonce is a Professional Hydrologist and Project Manager at Tetra Tech. She leads the Environmental Assessment service line, focusing on answering complex water quality questions which are related to assimilative capacity evaluations for wastewater treatment applications, and siting and development for strategic stormwater management facilities. She holds a BS in Environmental Science from the University of North Carolina, and an MS in Hydrology from the University of Arizona. With over 12 years of experience in environmental consulting at Tetra Tech in the “Water” Operating Unit, and has been working with the City of Virginia Beach on stormwater management projects for 6 years.
