Stormwater Management Program - MS4 Permit

The Municipal Separate Storm Sewer System (MS4) General Permit is issued every five years by the Maine Department of Environmental Protection (MEDEP) on a state-wide basis to all communities designated as small MS4s. The MS4 designation is based on the decennial U.S. census data for "Urbanized Areas," which are generally defined as densely developed census tracts or blocks with populations of at least 50,000. (Certain non-residential urban land uses with lower populations that are linked to more densely developed cores are also listed as Urbanized Areas).

The current General Permit identifies 30 MS4 communities in Maine and requires all of them to implement Minimum Control Measures (MCMs) to reduce pollution from stormwater runoff. South Portland's Urbanized Area encompasses nearly all of the land in the City except for the area west of the Maine Mall (which is regulated under a separate permitting system).


Stormwater Program Coordinator Presentation to Council on MS4 Permit


Minimum Control Measures

State and federal regulations require more urbanized communities like South Portland to implement the following six Minimum Control Measures (MCMs) to significantly reduce the discharge of pollutants into local waterways. The City is required to develop a detailed Stormwater Program Management Plan that describes how each of the MCMs will be implemented over the five year permit period. Each of these MCMs is targeted towards specific audiences and activities as briefly described below.

MCM1. Public Education and Outreach: distribute educational materials and conduct public outreach to inform citizens about the impacts polluted stormwater on receiving water quality.

MCM2. Public Participation and Involvement: provide opportunities for citizens to participate in stormwater management program development and implementation.

MCM3. Illicit Discharge Detection and Elimination (IDDE): develop and implement an enforceable ordinance that prohibits non-stormwater discharges into the City's MS4 system and implement a plan to conduct routine inspections of stormwater systems to eliminate illicit pollutant discharges to receiving waters. The City's Illicit Discharge Detection & Elimination Plan establishes methodologies for identifying and addressing non-stormwater discharges to the public stormwater system.

In 2023, the Interlocal Stormwater Working Group (ISWG) worked with South Portland's Community Television staff to develop this IDDE training video for use by MS4 communities throughout the State.

MCM4. Construction Site Runoff Control: develop and implement an enforceable plan to minimize sediment transport to receiving waters from construction activities disturbing more than 1 acre of land. The City has a robust program to address erosion & sediment control for construction projects.

MCM5. Post-Construction Runoff Control: develop and implement an enforceable program to minimize polluted stormwater runoff to receiving waters from new development or redevelopment projects. The City's Stormwater Performance Standards were established in 2009 to comply with this requirement. These standards require annual inspections to certify the proper functioning of certain stormwater treatment systems by qualified 3rd party inspectors, including those owned and maintained by the City.

MCM6. Pollution Prevention and Good Housekeeping: develop and implement a training program to minimize stormwater pollution from municipal activities. The City provides annual training on the use of "Best Management Practices" to minimize the potential for operations & maintenance staff to generate stormwater pollution.

In compliance with the Maine MS4 General Permit, we have also developed Stormwater Pollution Prevention Plans (SWPPPs) for our Municipal Services Facility, Transfer Station and School Bus Maintenance Facility. In compliance the U.S. Environmental Protection Agency's oil pollution prevention regulations, we have developed Spill Prevention Control & Countermeasure (SPCC) plans for the Municipal Services Facility and Front Street Wastewater Pump Station.