Water Quality Equivalency Guidance Document

About the Program

Category: County Administration and Management (Best in Category)

Year: 2016

In May 2013, the San Diego California Regional Water Quality Control Board Region 9 (RWQCB) issued a new Regional Municipal Stormwater (or “MS4”) Permit which placed more stringent stormwater management requirements on development projects. This Permit includes an optional element termed “Offsite Alternative Compliance” which introduces greater flexibility in the water quality performance standards that development projects must satisfy onsite provided that they are supplemented with another offsite project elsewhere in the same watershed and provide a greater overall water quality benefit. Recognizing the potential for such a program to accelerate water quality improvements, while also allowing greater flexibility to the development community, the County elected to pursue an Offsite Alternative Compliance Program. To address the question of what constitutes a greater water quality benefit, the County and other RWQCB Copermittees developed a Water Quality Equivalency (WQE) Guidance Document. This 18-month intensive effort was guided by a Technical Advisory Committee of local Copermittees, representatives of Orange and Riverside counties, consultants, the Southern California Coastal Waters Research Project, environmental non-governmental organizations, and RWQCB staff. It resulted in the development of the first of its kind WQE Guidance Document that provides tools and methodologies for calculating water quality equivalency for offsite alternative compliance projects.