Maine Stormwater-Municipalities regulations & environmental compliance analysis

Maine Stormwater-Municipalities: What you need to know

Governing Law and Regulations

National Pollutant Discharge Elimination System (NPDES) permitting for stormwater discharges: Code of Maine Rules (CMR) 06-096 500 and CMR 06-096 502

Regulatory Agency
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Maine Department of Environmental Protection (DEP)Bureau of Land and Water Quality

See ADDRESSES & CONTACTS for addresses and telephone numbers.

Comparison: State vs. Federal

·Rules. Maine is authorized by the U.S. Environmental Protection Agency (EPA) to administer the federal National Pollutant Discharge Elimination System (NPDES) permit program for wastewater discharges, including permitting authority for stormwater discharges associated with municipal separate storm sewer systems (MS4s). See the national section STORMWATER—MUNICIPALITIES for more information on the federal MS4 permitting program.

· Administration and enforcement. In Maine, the DEC’s DEP is responsible for administering the stormwater MS4 permitting program.

State Requirements


Under the NPDES stormwater program, operators of large, medium, and regulated small MS4s require authorization to discharge pollutants under an NPDES permit. Regulated small MS4s are defined as all small MS4s located in "urbanized areas" (UAs) as defined by the Bureau of the Census, and those small MS4s located outside of a UA that are designated by NPDES permitting authorities.

Maine issues three MS4 general permits:

  • General Permit for the Discharge of Stormwater from Small MS4s;
  • General Permit for the Discharge of Stormwater from the Maine Department of Transportation and Maine Turnpike Authority MS4 Facilities; and
  • General Permit for the Discharge of Stormwater from State or Federally Owned MS4 Facilities.

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