Stormwater Performance Standards BMP Expert Panel Report

Description

All of the Bay states are shifting to a new paradigm for managing urban stormwater runoff from both new development and redevelopment projects. The new paradigm is reflected in new performance standards that require greater levels of stormwater treatment using Low Impact Development (LID) and site design practices to mimic predevelopment hydrologic conditions. 

The Panel noted that this new stormwater paradigm has increased capability to reduce runoff and pollutant loads generated by future development and redevelopment that occurs across the Chesapeake Bay watershed. The Panel also wrestled with the fact that each state has adopted (or will soon adopt) unique regulations, performance standards, compliance models and design criteria to implement the new stormwater paradigm. Given this diversity, the Panel decided that assigning a single universal removal rate for BMPs designed to the new standards was not practical or scientifically defensible. Instead, the Panel elected to develop a protocol whereby the removal rate for each individual development project is determined based on the amount of runoff it treats and the degree of runoff reduction it provides. The Panel conducted an extensive review of recent BMP performance research and developed a series of new BMP adjustor curves to define sediment, nitrogen and phosphorus removal rates. This report outlines the panel's recommendations.