Municipal Separate Storm Sewer (MS4) Program

The federal Clean Water Act (CWA) prohibits the discharge of pollutants into waterways without the appropriate permits. Pennsylvania’s Stormwater Management Act (better known as Act 167), MS4 Program, Chapter 102 (Erosion and Sediment Control Requirements), and NPDES Permit Program for Stormwater Discharges Associated with Construction Activities are amongst the Commonwealth’s methods for meeting the runoff-related requirements of the Clean Water Act.

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MS4-Municipal Separate Storm Sewer System

MS4 is a program written and monitored by Pennsylvania’s Department of Environmental Protection (PA DEP) in conformity with the U.S. EPA’s 1987 Clean Water Act. Its purpose is to ensure that municipalities considered to be in “urbanized areas” are making an effort to control the pollution of local streams and rivers due to contaminated stormwater.

How does Stormwater become contaminated?

Stormwater is rainfall that seeps into the ground, or else flows across ground and pavement to inlets, drains, gullies, etc. Eventually, all of this water flows into the local streams and rivers, carrying whatever it has picked up along the way. Ideally, all rainfall soaks into the ground and is filtered by the soil before flowing underground to the nearest waterway. However, in urbanized areas, much of the ground is covered by asphalt and concrete, which do not drain very well; in order to keep the water from flooding heavily populated areas, water flows from streets and driveways into stormwater sewer inlets that do not filter out all the contaminants. Water then flushes into streams carrying oil, chemicals, dirt, and harmful bacteria that damage stream life.

What’s the Solution?

The MS4 program was written to encourage municipalities to find more ways to prevent pollution from killing stream and river life. Municipalities are required to check all of the outlets of their stormwater drainage system for pollutants every 5 years. For municipalities with impaired streams, a Pollution Reduction Plan (PRP) is developed to reduce the pollutants going into the stream and/or restore the stream by removing pollutants and protecting against erosion.

The Program also maintains a goal to educate the public about pollution and how they can help by doing their part.


When you are conscientious about moving your car out of the way on street-sweeping days, you are helping the local government to keep roads clean, which limits the amount of debris that goes into the stream.

When you are careful not to spill automobile fluids (oil, coolants, grease, etc.) in your driveway, you are also preventing chemicals from being washed into the nearest stream.

When you pick up after your dog on a walk, not only are you being a good neighbor, but you are also preventing harmful bacteria from being washed, untreated, into the nearest waterway.

Illicit Discharge: Smell Something Foul?

The percentage of municipal workers among the population of citizens is less than 1%; you play an important role in identifying illicit discharge from the storm sewers because you live nearer to it. Illicit discharge is flow out of storm sewer pipes that contains pollutants that are harmful and need to be treated; generally they are noticeable as dry weather flows that may appear discolored, oily, and/or give off foul odors.  If you see something that doesn’t look right, report it!

Monaca’s PRP (pollutant reduction program)

A Pollutant Reduction Plan is required for municipalities that host impaired streams; plans reduce pollutants (often sediment) that go into the stream. The Borough has chosen to undertake a stream restoration project in fulfillment of the PRP requirements for this permit cycle. This project will restore 250 feet of Markey’s Run just off Brodhead road.