Offsite Alternative Compliance For Priority Development Projects - What Constitutes "Greater" Water Quality Benefit?
The Development Planning provisions of the San Diego Regional Water Quality Control Board’s Regional MS4 Permit allow for forward-thinking, innovative, and creative solutions for achieving tangible improvements to surface and ground water quality. Rather than continuing with rigid requirements to implement structural BMPs on each and every Priority Development Project, the Regional MS4 Permit allows for an Alternative Compliance Program to Onsite Structural BMP Implementation. This program recognizes that improvements to water quality may perform more effectively if analyzed and executed on a watershed scale. In order to participate in this program, a Priority Development Project must demonstrate to the governing Copermittee that the proposed offsite project will provide greater water quality benefit to the watershed than simply complying with the structural BMP requirements onsite.
What constitutes greater water quality benefit? San Diego County embarked on a Water Quality Equivalency study to answer just that. A 2-year intensive effort from Region 9 Copermittees, engineering consultants, the Southern California Coastal Waters Research Project, environmental non-governmental organizations, and the San Diego Water Board staff resulted in the development of a Guidance Document providing tools and methodologies for calculating water quality equivalency for offsite alternative compliance projects. The study included a rigorous assessment of the most appropriate metric for calculating and equating the water quality impacts and benefits for several project types. Ultimately, metrics of pollutant-weighted volume and directly connected impervious area were selected to track the water quality benefits associated with pollutant control and hydromodification flow control respectively.
The types of alternative compliance projects addressed in the draft Guidance Document include regional BMPs, retrofit BMPs, groundwater recharge and water supply augmentation projects, land preservation, land restoration, and stream or riparian area rehabilitation. The Guidance Document steps the reader through a process of calculating water quality debits accrued from not implementing structural BMPs onsite, and water quality credits earned from implementation of an offsite alternative compliance project, which are then used to offset and exceed the debits. This approach is expected to improve overall watershed functions by incentivizing projects that retrofit, rehabilitate, or preserve watershed functions to produce greater water quality benefits than onsite compliance alone. This will provide local jurisdictions the ability to better address stormwater pollution from areas of existing development, and will encourage applicants to propose projects that optimize the critical balance between cost and performance.
The Water Quality Equivalency Draft Guidance Document is scheduled for submission to the San Diego Water Board in September, 2015. The San Diego Water Board’s Executive Officer must approve the Water Quality Equivalency Guidance Document before it can be used by the Copermittees.
Conference presenters will answer questions pertaining to the development of the Draft Guidance Document, both from the technical aspect and the stakeholder process aspect. Presentation emphasis will include a discussion of how this program is expected to provide tangible opportunities in storm water quality improvement. This presentation will move beyond the conference theme of “Are We Making a Difference?” to “We Will Make a Difference.”