Common Questions
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Municipal Separate Storm Sewer System (MS4)

Overview and Definition of an MS4

Clean water is important to us because it provides us with drinking water, a place for recreation, and supports habitat for wildlife. Harborcreek Township has initiated a public education program on storm water management because of its effect on water quality. According to the United States Environmental Protection Agency, polluted storm water runoff is a leading cause of impairment to the nearly 40 percent of U.S. water bodies which do not meet water quality standards.

Harborcreek Township Pollutant Reduction Plan

NPDES Permits

A National Pollutant Discharge Elimination System (NPDES) permit is required for any point source discharge to waters of the Commonwealth. The Clean Water Program in DEP's regional offices issues the majority of NPDES permits for sewage, industrial waste (IW), IW stormwater, municipal separate storm sewer system (MS4), Concentrated Animal Feeding Operation (CAFO), biosolids and pesticides activities or facilities that are regulated under the NPDES program. The Bureau of Clean Water (BCW) in DEP's Central Office issues statewide General NPDES permits. If applicants qualify, they may be approved for coverage under a General NPDES permit.

For more information visit the NPDES website at:

Storm Water Runoff

When it rains, the draining water is called storm water runoff. Storm water can be a problem when there is a decrease in quality and an increase in quantity. Development can alter the natural pathway that storm water takes to travel over land, and increases the rate at which it travels over the land by changing porous surfaces (soil) to non-porous, or impervious surfaces (pavement). Natural surfaces, such as soil, act as a filter for storm water and clean it as it infiltrates into the ground.

Ways to prevent storm water pollution:
  • Never pour any hazardous substance such as used oil, cleaning supplies and paint down any part of the storm sewer system.
  • Use pesticides and fertilizers sparingly to prevent excess runoff.
  • Never dump automotive fluids into storm drains.
  • Correct motor vehicle leaks (vehicles drip fluids such as oil, grease, gasoline, antifreeze, and brake fluid).
  • When walking your pet, pick up the waste and dispose of it properly. Leaving pet waste on the ground increases public health risks by allowing harmful bacteria to wash into the storm drain and eventually into local water bodies.
  • Sweep up litter and debris from sidewalks, driveways, and parking lots especially around storm drains to avoid having it wash into the storm sewer system.
“When it Rains it Drains” – brochure – This image is decorative
Polluted storm water runoff and its adverse effects:
  • Sediment can cloud the water and make it difficult or impossible for aquatic plants to grow.
  • Bacteria can wash into swimming areas and create health hazards.
  • Plastic bags, six pack rings, bottles, and other debris washed into water bodies can disable aquatic life such as ducks, fish, turtle, and birds.
  • Household hazardous wastes such as insecticides, pesticides, paint solvents, used motor oil, and other auto fluids can poison aquatic life. Land animals and people can become sick or die from eating diseased fish or ingesting polluted water.
  • Polluted stormwater can affect drinking water, which can affect human health and increase drinking water treatment costs.
  • Waste from chemicals and materials used in construction can wash into the storm sewer when it rains.
When left uncontrolled, this can result in the destruction of fish, wildlife, and aquatic life habitats; a loss in aesthetic value; and threats to public health due to contaminated food, drinking water supplies, and recreational waterways.
Accordion Content

PA DEP Car Wash PosterThis image is decorativeThis image is decorative – “When you’re washing your car in the driveway, remember you’re not just washing your car in the driveway.”

This image is decorative


The construction industry has a key role to play in storm water management. As storm water flows over a construction site, it can pick up pollutants such as sediment, debris, and chemicals. Uncontrolled erosion can have a significant financial impact on a construction project. It costs time and money to repair gullies, replace vegetation, clean sediment clogged storm drains, and mitigate damage to other people’s property. At a construction site, it is important to protect the natural features by:

  • Minimizing the amount of exposed soil, because the less soil that is exposed the easier and cheaper it will be to control erosion.
  • Identify and protect areas where existing vegetation such as trees will not be disturbed by construction activity.
  • Protect streams, wild woodlands, wetlands, and other sensitive areas from any disturbance or construction activity by fencing or otherwise clearly marking those areas.

Where ever possible sequence construction activities so that the soil is not exposed for long periods of time. Schedule site stabilization activities such as landscaping to be completed as quickly as possible after the land has been graded to the final contour.

Silt fencing

  • Inspect and maintain silt fences after each rainstorm.
  • Make sure the bottom of the silt fence is buried in the ground.
  • Securely attach the material to the stakes.

Construction entrances

  • Make sure the construction entrance doesn’t become buried in soil.
  • Regular street sweeping at construction entrance will prevent dirt from entering storm drains.

Installing and maintaining pollution prevention techniques on site can reduce the potential for storm water pollution and help protect our nation’s water supply.

PA DEP Construction Industry Storm Water Information – “Don’t Let Storm Water Run Off With Your Time and Money.”


Excess fertilizers and pesticides applied to lawns and gardens wash off and can pollute streams. Use pesticides and fertilizers in accordance with the manufacturer’s recommended amount. Never leave yard waste in the street and don’t sweep it into storm drains or streams.

PA DEP Fertilizer PosterThis image is decorativeThis image is decorative – “When you’re fertilizing the lawn remember, you’re not just fertilizing the lawn.”

This image is decorative

Vehicle Maintenance

Repair motor vehicle leaks and never dump into a drain, or ditch used motor vehicle fluids such as solvents, antifreeze, brake fluid, and motor oil. When it rains or snows, the flowing water can carry oil, antifreeze, and other fluids away ending up in streams, rivers, and lakes killing aquatic life and seriously polluting water bodies where people swim, fish, and boat. If you see a leak from your motor vehicle, contain it with a drip pan or absorbent material and clean up the residue from the ground. When spills and leaks happen, clean up as much fluid as you can as quickly as possible. Don’t mix used oil with solvents, brake cleaner, or antifreeze, because this creates a hazardous waste.

PA DEP Oil Slick PosterThis image is decorativeThis image is decorative – “When your car’s leaking oil on the street, remember it’s not just leaking oil on the street.”

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Pet Waste

Pet waste can be a major source of bacteria and excess nutrients in local waters. When walking your pet, pick up the waste and dispose of it properly. Flushing pet waste in the toilet is the best disposal method. Leaving pet waste on the ground increases public health risks by allowing harmful bacteria and nutrients to wash into the storm drain and eventually into local water bodies.

PA DEP Pet Waste PosterThis image is decorativeThis image is decorative – “When your pet goes on the lawn, remember it doesn’t just go on the lawn.”

This image is decorative
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