NPDES MS4 Permit
According to 40 Code of Federal Regulations (CFR) §122.26, owners of storm sewer systems serving populations greater than 100,000 were required to apply for Phase I NPDES MS4 permit coverage. The County permit has been renewed 3 times, in 1999, 2004 and 2014. The latest permit renewal outlined more stringent requirements than those imposed in previous permit renewals.
Previous permit conditions mandated the County to:
- Develop geographic information system mapping on a watershed basis.
- Develop management programs to address runoff from new and significant redevelopment, construction site discharges, illegal storm drain system connections, and road maintenance operations.
- Maintain legal authority to control storm drain system pollution.
- Provide education and outreach regarding stormwater pollution.
- Use a combination of chemical, physical and biological monitoring to characterize urban stormwater.
The new permit increased the impervious area treatment goals from 10% to 20% of the total impervious area that the County is regulating. Additionally, the 2014 permit augmented the permit conditions to include:
- Litter and trash reduction strategies.
- Implementation of environmental site design (ESD) technologies for new and redevelopment projects to the maximum extent practicable (MEP).
- Development of watershed restoration plans to address stormwater waste load allocations (WLA) established under the EPA approved total maximum daily loads (TMDL) estimates.
The overall goals of the County's five-year NPDES municipal stormwater permit program are to control stormwater pollutant discharges by implementing Best Management Practices (BMP) and programs, show a reduction of pollutants pursuant to EPA approved TMDLs and improve water quality. The County evaluates and documents progress toward improving water quality within its jurisdiction on an annual basis and submits a report to MDE. To view this report as well as other reports the County has developed, see the links provided below.
Select the following links to access the latest NPDES MS4 annual report documentation submitted to MDE.
- 2018 NPDES MS4 Annual Report
- 2018 NPDES MS4 Supplemental Report
- NPDES Annual Report Phase 1
- NPDES Annual Report Phase 2