• Brownfield Redevelopment
     • Green Building Standards
     • Accessory Dwelling Units

     • Historic Preservation
     • Main Street Program

     • Alt. Energy Ordinances
     • Stormwater Management

     • Smart Growth Code Fixes
     • Form-Based Codes
     • LEED-ND
     • Transit Oriented Dev.
     • Zoning Ordinances
     • Scenario Planning

     • Agricultural Security Areas
     • Clustered Subdivisions
     • Official Map Ordinance

     • Access Management
     • Complete Streets Policy
     • Impact Fees
     • Traffic Calming
     • Walkability

Stormwater Management

Photo of rain barrel under a home's downspout

Stormwater begins as rain or snow, but conventional development patterns and engineering practices typically make it difficult for stormwater to soak into the ground naturally. Instead, it flows into a man-made system where it eventually is released as surface water.  Stormwater is an important issue because it can carry pollutants, cause significant erosion and contribute to flood events. As fresh water sources become even more burdened, the collection of stormwater could become a crucial future resource.

Engineers and planners have developed several Best Management Practices (BMPs) concerning stormwater management.

They include retention ponds, rain gardens, rain barrels, pervious pavement and filtration systems. Most municipal regulations require the use of stormwater management BMPs in their Subdivision and Land Development Ordinances. This encourages smart development that focuses on the amount of runoff caused by new development.

The US Environmental Protection Agency (EPA) has developed programs to help states and municipalities enforce stormwater management policies.  National Pollution Discharge Elimination System (NPDES) permits are issued nationwide to help monitor the number of point source pollution systems.  Additionally, small and large municipal separate sewer systems (MS4) require permits. Municipalities that fall under these regulations needed to acquire new permits in 2012.

In the Tri-County Region, the following are MS4 municipalities: Camp Hill, Carlisle, Conewago, Dauphin, Derry, East Hanover, East Pennsboro, Hampden, Harrisburg, Highspire, Hummelstown, Lemoyne, Londonderry, Lower Allen, Lower Paxton, Lower Swatara, Marysville, Mechanicsburg, Middle Paxton, Middletown, Monroe, New Cumberland, Paxtang, Penbrook, Royalton, Rye, Shiremanstown, Silver Spring, South Hanover, Steelton, Susquehanna, Swatara, Upper Allen, West Hanover, Wormleysburg.

In order to meet the requirements of MS4 permits, the operator must develop a Storm Water Management Program (SWMP) consisting of BMPs that reduce the pollutants from the discharge.

Cartoon illustration of a storm cloud with rain droplets

The PA Department of Environmental Protection (DEP) has developed a draft model stormwater management ordinance for municipalities to adopt.  Originally developed in 2009, the model ordinance is currently under revision. This model will provide a template for municipalities to be included in the watershed management plans. For urban MS4 municipalities the model can be used to enact or amend current regulations. The draft model ordinance will also establish municipal authority to regulate stormwater runoff and proper stormwater BMPs.


  • Protects community from downstream flooding, stream bank erosion, combined sewer overflow, infrastructure damage and stream pollution
  • The reduction of impervious surfaces and implementation of a stormwater management plan can help to improve surface water quality
  • Implementing stormwater management BMPs during development can reduce future costs to the municipality and homeowners


  • Installation and maintenance expenses of BMPs on private property
  • Site specific characteristics can complicate BMP installation

Practical Tips

  • Using the model ordinance, adopt a stand-alone or integrate an ordinance into a Subdivision and Land Development Plan
  • Contact the County Conservation District or Planning Commission for additional MS4 information