Municipal Stormwater Program Audits in California: Findings and Lessons Learned

EPA, with the assistance of Tetra Tech and the California Regional Water Quality Control Boards, has conducted 122 on-site audits of municipal stormwater programs over past six years to assess NPDES permit compliance and program effectiveness. Evaluations consisted of a programmatic review of individual MS4s and an in-field verification of these program elements. The project goals of the MS4 evaluations include obtaining an overall picture of MS4 compliance, documenting effective elements of existing MS4 programs, identifying methods to improve MS4 program reporting, and developing a guidance document to assist State and/or EPA inspectors in conducting future MS4 evaluations. Although the programs varied considerably in terms of organizational structure, geography, local water quality resources and challenges, many common elements were found both in terms of deficiencies and well-run programs.