St. Mary’s Regional Water Quality & Nutrient Removal Project

St. Mary’s County Government, as a requirement for satisfying their Watershed Implementation Plan (WIP), a component of the Chesapeake Bay TMDL, and their NPDES MS4 permit, enlisted Soltesz, with a collaborative effort with the Center for Watershed Protection (CWP), with developing a program to reduce stormwater pollutant loading of nitrogen (1,300 lbs. annually) to meet their Phase 2 WIP target goal of 60% by 2017, while simultaneously gaining a head start on addressing their NPDES MS4 target goal of treating 20% of the County’s unmanaged impervious surface area. The County had identified existing 139 candidate stormwater management dry pond facilities for retrofitting to address their WIP and NPDES MS4 target goals.

Soltesz was tasked with developing the Program Development Phase of the project. The Program Development Phase included:

• Evaluating the feasibility that the County can reasonably achieve the 60% (2017) and 100% (2025) WIP target goals for pollutant reduction of nitrogen and providing water quality treatment of 20% of existing contributing impervious surface to satisfy the pending NPDES MS4 permit.
• Performing desktop evaluations of BMPs utilizing GIS, aerial photography, construction drawings, as-built drawings to assess preliminary design efforts.
• Performing site reconnaissance of each of the 139 stormwater management facilities, conducting field sketches, and developing concept designs to address County goals in the most efficient and cost-effective manner.
• Identifying environmental constraints for each candidate SWM site and performing environmental permitting (wetlands, wetland buffers, and streams) where deemed necessary to ensure the retrofit design.
• Providing a Measure of Effectiveness (MOE) matrix of all 139 BMPs with conceptual designs and cost estimates to rank sites which offer the most cost effective means to reduce stormwater pollution (WIP) while still meeting NPDES MS4 requirements. Soltesz identified the best locations for retrofitting to meet County target goals.
• Preparing a final report of analysis, findings, and recommendations to demonstrate the County’s ability to meet both the WIP and the NPDES MS4 requirements.

The Soltesz team effectively demonstrated that the County could address both the TMDL and their pending NPDES MS4 permit with a very minimal number of proposed BMP retrofits, saving St. Mary’s County valuable CIP funding moving forward with their implementation phase.