Washtenaw County's Stormwater Discharge Permit

Water Quality

Water quality is paramount in Washtenaw County. The county is situated within six different watersheds. We are largely located within the Huron River Watershed, but portions of the county are within the Rouge River, Raisin River, North Branch Swan Creek, Stony Creek, and Grand River watersheds.

As stormwater flows over lawns, driveways, parking lots, and construction sites it is picking up pollutants such as fertilizers, oil, yard waste, litter, animal waste, and anything else along the way. The storm drain system then transports these pollutants into the nearest lake, stream or river. These pollutants may cause algae blooms, increased temperature, or contribute to the degradation of lakes, streams, and rivers.


What is Stormwater?

Stormwater is the result of rainfall or snowmelt that flows over our lawns, streets, parking lots, and buildings. This water runs into storm drains and ditches and then directly into lakes, streams, and rivers, carrying the pollutants it picks up along the way.

Phase II Storm Water Regulations

In 1999, the Environmental Protection Agency (EPA) established the Phase II regulations to reduce the impact of pollution that was being created by increased development. The permit was created to preserve, and protect our water resources from polluted stormwater runoff.  Regulations require stormwater discharges from Municipal Separate Storm Sewer Systems (MS4) within the designated urbanized area, (which are areas with populations greater than 10,000), to obtain a permit from the Michigan Department of Environmental Quality. View a map of the designated urbanized areas in Washtenaw County (PDF). The Washtenaw County Water Resources Commissioner’s Office administers the National Pollution Discharge Elimination System (NPDES) MS4 permit on behalf of Washtenaw County.  

Per federal and state regulations, the MS4 permit requires urban communities to address both the amount of runoff and the pollution carried by that runoff that is deposited, untreated, into surface waters. Under this permit, the County must comply with several requirements, which, if implemented, should result in a significant reduction in pollutants discharged to receiving waters. The required components of the permit include a watershed management plan and stormwater management plan.

Washtenaw County is one of several Huron River Partners working collaboratively on implementing several of the permit requirements. The collaborative approach is designed to accomplish stormwater quality improvements and provide an added benefit of cost sharing for some stormwater controls. The partners include the City of Ann Arbor, City of Ypsilanti, Eastern Michigan University, Pittsfield Charter Township, City of Dexter, Ypsilanti Charter Township, Village of Barton Hills, Ann Arbor Public Schools and the Washtenaw County Road Commission.

Stormwater Permit for Washtenaw County (pdf)

Watershed Management Plan

The Middle Huron River Watershed Management Plan (PDF) was originally developed in 1994 and was updated in 2000, 2008, 2011 and has been broken up into 3 sections for updates in 2020+. The Middle Huron River Watershed Management Plan, Section 2 (2020) includes the Huron River from Barton Pond to the Confluence of Fleming Creek,  Associated Tributaries, Fleming Creekshed, Allens Creekshed, Malletts Creekshed, Millers Creekshed, Swift Run Creekshed, Traver Creekshed.  The plan outlines strategies to protect sensitive natural areas, mitigate impacts of existing point and non-point source pollution, and restore degraded areas in the Middle Huron Watershed.  Visit the Huron River Watershed Council's webpage for plan updates here.

Stormwater Management Plan (SWMP)

The Stormwater Management Plan details the specific actions watershed partners will implement to meet the permit requirements. The SWMP has seven main pieces.

  1. Public Education Program (PEP): Municipalities must develop a program to promote, publicize, and facilitate educational materials and activities on stormwater and pollution prevention. This plan was developed and will be implemented in partnership with other permitted communities in the watershed.
  2. Public Participation Program (PPP): Municipalities must have a program to facilitate the involvement of the Municipalities in the watershed and the general public in the revision of SWMPs.
  3. Illicit Discharge Elimination Program (IDEP): Municipalities must develop a plan with mechanisms designed to locate and eliminate discharges into storm sewer from sources other than stormwater.
  4. Post-Construction Stormwater Management (PCSW): Municipalities must have a program requiring new and redevelopment projects to implement on-site controls that will reduce pollutant loads in stormwater runoff.
  5. Construction Stormwater Controls (CSW): Municipalities must have a regulatory mechanism in place for erosion and sediment control, as well as best management practices (BMPs) for preventing or reducing other pollutants associated with construction activity.
  6. Pollution Prevention and Good Housekeeping Practices for Municipal Operations (P2GH): Municipalities must have an operation and maintenance program to prevent or reduce pollutant runoff from municipal operations.
  7. Total Maximum Daily Load (TMDL): Municipalities must identify and prioritize actions to reduce pollutants in stormwater discharges to make progress toward meeting water quality standards.

To submit comments to WCWRC regarding the Stormwater Management Planplease send an email to Heather Rice,  

Stormwater Permit Reports

Educational Materials

MI Environment, Great Lakes, & Energy

MiEnviro Portal

Visit the portal and use the Site Map Explorer to view issued permits, including Washtenaw Co MS4 - stormwater permit, stormwater management plan, reports and more.