Stormwater Management – MS4

What is MS4?

Municipal Separate Storm Sewer System (MS4) is a system of conveyances including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains. As stormwater runs over driveways, lawns, and sidewalks it picks up debris, chemicals, dirt, and other pollutants.

Polluted stormwater runoff is often conveyed to MS4s and ultimately discharged into local rivers and streams without treatment. Anything that enters a storm sewer system is discharged into the water bodies we use for recreation and providing drinking water. Polluted runoff is the nation’s greatest threat to clean water.

public street drains demonstrating navigation to fresh natural water ways

How Can Your Household Help?


By practicing healthy household habits, homeowners can keep common pollutants like pesticides, pet waste, grass clippings, and automotive fluids off the ground and out of stormwater. For more information, please see the “Homeowners Guide to Stormwater” located in our links section of this page.

Illicit Discharges


An illicit discharge is defined as any unauthorized discharge other than clean stormwater released into the Municipal Separate Storm Sewer System (MS4). Illicit connections may be intentional or may be the result of connections made years ago when water quality issues were not a concern.

The types of illicit discharges vary widely with some examples being:

• Waste oil, antifreeze, paint, trash or other household chemicals

• Car wash, laundry, and  industrial wastewaters

 • Pool water discharge (chlorinated and dechlorinated)

 • Spills on roadways and other accidents

• Failing septic systems and illegal dumping practices

• Improper disposal of sewage from recreational practices such as boating or camping

Common indicators of illicit discharges include abnormal odors, strange colors, or oil sheen present around or inside storm inlets or pipes. Keeping harmful substances out of our water benefits everyone; environmentally and economically.


illicit stormwater discharge into public water ways.
illicit stormwater discharge into public water ways.

For questions regarding the MS4 Stormwater Program:

Stormwater Program Manager / Environmental Planner

100 Gettysburg Pike

Mechanicsburg, PA 17055

  • Telephone: Office: 717-766-0756

  • Mail: 

If you witness or become aware of an illicit discharge or illegal dumping, please contact:

Collin Barge, MS4 Coordinator

100 Gettysburg Pike

Mechanicsburg, PA 17055

  • Telephone: Office: 717-766-0756

  • Cell: 717-756-9169

  • Mail:

What Is An MS4 Program


Listed below are the six minimum control measures that the Township must incorporate into the stormwater management program.  These measures are expected to result in significant reductions of pollutants discharged into receiving waterbodies.


1. Public Education and Outreach – An informed and knowledgeable community is crucial to the success of a stormwater management program since it helps to ensure greater support and program compliance as the public becomes aware of individual actions they can take to protect or improve the quality of area waters.

2. Public Participation/Involvement – An active and involved community allows for broader public support, a broader base of expertise and a connection to other local environmental programs.

3. Illicit Discharge Detection and Elimination – Illicit discharges are untreated discharges that could contribute high levels of pollutants, including heavy metals, toxins, oil and grease, solvents, nutrients, viruses and bacteria to receiving water bodies. The Township is required to develop, implement and enforce an illicit discharge detection and elimination program.

4. Construction Site Runoff Control – Stormwater runoff from construction activities can have a significant impact on water quality. As stormwater flows over a construction site, it can pick up pollutants like sediment, debris, and chemicals and transport these to a nearby storm sewer system or directly to a river, lake or stream.

5. Post-Construction Runoff Control – Increased impervious surfaces, like parking lots, driveways, and rooftops, interrupt the natural cycle of gradual percolation of water through vegetation and soil. Instead, water is collected from surfaces such as asphalt and concrete and routed to drainage systems where large volumes of runoff quickly flow to the nearest receiving water. The effects of this process can include stream bank scouring and downstream flooding, which often lead to a loss of aquatic life and damage to property. Ordinances and other regulations are required to determine the appropriate best management practices and to ensure adequate long-term operation and maintenance of stormwater controls.

6. Pollution Prevention/Good Housekeeping – This measure involves recognizing the benefits of pollution prevention practices and includes the development and implementation of an operation and maintenance program. Reducing pollutant runoff from municipal operations into the storm sewer system can include employee training on how to incorporate pollution prevention/good housekeeping techniques into municipal operations.

Tips For Homeowners

A screenshot of a cell phone screen with text

Volunteer Spotlight

stormwater management cub scout volunteers
stormwater management cub scout volunteers

Links And Additional Information