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Drainage Design

Drainage Design (Discharging Stormwater)

The Michigan Department of Transportation (MDOT) is responsible for regulating the storm water flow rate and velocity from retention/detention systems (basins, infiltration systems, underground storage, etc.) on private property adjacent to State highway Right-of-Way. MDOT also evaluates the potential impacts from the permit applicant’s property on the water quality of MDOT’s storm water conveyance system.

MDOT is not required to receive additional flow. That is why MDOT restricts the allowable flow, via the permit process, to the existing established flow rate.

The following may be permitted:

  • Ditch enclosures
  • Shared Conveyance Systems
  • Commercial Developments Zoned Residential
  • Sewer Taps
  • Longitudinal Sewer Systems 

Applicants must submit an individual permit application package through the Construction Permit System (CPS) with the following:

  • Drainage Agreement, if applicable
  • Drainage Design Checklist for Accessing state Trunklines, (Form 2484), which requires a Registered Professional Engineer’s seal and signature in the space provided
  • Copy of the recorded public easement or a letter from the Drainage Commissioner, if applicable
  • Existing storm water runoff, proposed storm water runoff, and required detention volume
  • Map of the existing and proposed contours for the permit applicant’s property
  • Elevation (head) vs. discharge table or curve for the detention system and hydrologic route
  • Copy of Michigan Department of Environmental Quality (MDEQ) application for a National Pollution Discharge Elimination System (NPDES) Industrial Storm Water permit, if applicable