MS4 Stormwater Program

What is Stormwater Pollution?

As stormwater streams over streets, driveways, lawns, and other surfaces, the flow picks up chemicals, dirt, debris, and other pollutants. Polluted stormwater can then flow into a storm sewer and be discharged untreated into a waterbody; or it can flow directly into a stream, lake, river, wetland, or coastal water.

This can have many adverse effects on plants and animals, and is becoming the nation's biggest threat to clean water. Unlike polluted discharges from industry or sewage treatment facilities (forms of point source pollution), polluted runoff (a form of nonpoint source pollution) is generated by all of us.

Stormwater pollution starts with everyday activities, like washing our car, fertilizing our lawn, walking our dog, and disposing of motor oil. While most of our individual actions have only a small impact on water quality, the US Environmental Protection Agency (EPA) cautions that "the cumulative impact of how we choose to interact with our land and water is huge."

What is MS4 Stormwater Management?

The federal Environmental Protection Agency (EPA) mandates that the Borough of Downingtown has a comprehensive storm water management program which is monitored by the Pennsylvania Department of Environmental Protection (PADEP). The program is designed to literally “manage” stormwater, both by protecting water quality and by preventing high volumes of runoff from causing flooding in developed areas. Any municipality with a population of at least 5,000 must comply with the program.

As part of the MS4 program, the Borough of Downingtown holds a permit to discharge stormwater into local waterways. This permit requires the Borough to design a stormwater management program that reduces the discharge of pollutants to the maximum extent possible. Ordinance 2013-09, Stormwater Management was adopted and enacted by Borough Council on Dec. 4, 2013.

This requires the Borough to implement and enforce a storm water management program which encompasses six minimum control measures, or best management practices (BMPs):

Public Education - BMPs for MS4s to inform individuals and households about ways to reduce stormwater pollution.

Public Involvement - BMPs for MS4s to involve the public in the development, implementation, and review of an MS4's stormwater management program.

Illicit Discharge Detection & Elimination - BMPs for identifying and eliminating illicit discharges and spills to storm drain systems.

Construction Site Runoff Control - BMPs for MS4s and construction site operators to address stormwater runoff from active construction sites.

Post-construction Runoff Control - BMPs for MS4s, developers, and property owners to address stormwater runoff after construction activities have completed.

Pollution Prevention/Good Housekeeping - BMPs for MS4s to address stormwater runoff from their own facilities and activities.