Creating a Water Quality Credit Generating Facility and Accounting Program for MS4 Permit Compliance Flexibility: Results of a Case Study Analysis in Orange County, CA
Phase I MS4 permits regulating land development in portions of San Diego, Riverside, San Bernardino, and Orange Counties contain stormwater runoff retention requirements. Permits require that all new and re-development which exceed a Priority Development Project (PDP) size threshold install structural treatment control Best Management Practices (BMPs), with emphasis on using Low Impact Development (LID) BMPs. On-site compliance using retention-type BMPs is favored if technically feasible. However, if on-site retention using LID BMPs is infeasible or if a regional/sub-regional retention facility is located within the same watershed and is operating and preferable from a water quality improvement standpoint (defined in a watershed management plan, for example), then PDPs may optionally comply through participation in a LID BMP alternative compliance program.
Central to developing a LID alternative compliance program is creating a water quality credit generating facility and establishing a use, accounting, and verification program which meets MS4 permit conditions. This presentation highlights case study results from Orange County which detail the engineering and hydraulic basis for creating the accounting and reporting procedures at a water quality credit generating facility, and using credits produced for eligible PDPs, either by a municipality for its own public works projects, or a municipality which may allow private sector participation.
The presentation identifies how appropriate types and sizes of BMPs were selected which would generate water quality credits at 23-acre development project site, and proposes a model accounting program including procedures for generating, using, and tracking credits, as well as verifying BMP operation and maintenance. Fundamental in generating water quality credits is the project’s installation of underground retention BMPs (infiltrate stormwater runoff into the ground), which are sized for and accept stormwater runoff from a 23-acre project footprint and from an adjacent, hydraulically connected 241-acre tributary area. In addition, the presentation identifies the costs to install and operate configurations of underground retention BMPs sized for the water quality treatment control design capture volume from the project and tributary drainage area.
It is thought that if alternative compliance programs are available to stormwater dischargers, then greater overall water quality benefits and outcomes (versus on-site compliance) may be realized. Greater water quality benefit would arise because credit generating facilities may be sited in strategic areas, such as within an area hydraulically connected to a TMDL impaired water body, or within an existing urban area where stormwater runoff is untreated. Finally, such alternative compliance programs may also offer a way to engage multiple public agencies and the private sector, building bridges and forming partnerships to address water quality pollution problems. In this instance, collaboration among Orange County Public Works, Orange County cities, a municipal water agency, and the private sector will be described.
Mark Grey is the Director of Environmental Affairs for the Building Industry Association of Southern California (BIA/SC) and the Technical Director for the Construction Industry Coalition on Water Quality (CICWQ). In these roles, Dr. Grey directs education, research and advocacy programs on behalf of the building industry in California, primarily focusing on water quality issues.
Dr. Grey has worked in the fields of water and air quality research and regulatory affairs for the past 30 years in the Pacific Northwest and California. Before joining BIA/SC and directing CICWQ, Dr. Grey operated his own consulting practice and was the Director of Technical Services for Synagro Technologies, Inc., the nation’s largest organic waste recycler.
Dr. Grey holds a Ph.D. in Soil Chemistry and M.S. in Forest Ecosystem Analysis from the University of Washington in Seattle, WA and a B.A. in English from Eastern Washington University in Cheney, WA.