MS4 System

The Municipal Separate Storm Sewer System

Penn Township’s Municipal Separate Storm Sewer System (commonly referred to as the MS4) is a network of inlets, pipes, swales, outlets, and other features; all designed to control runoff from public streets, sidewalks, and other impervious areas. The storm sewer system plays an important role in keeping roads free of flowing or ponding water and ice, making it a key piece of public infrastructure like roads and public water or sewer.

The series of three maps to the right gives you an idea where the storm sewer system is located in Penn Township. Pipes, inlets, and other drainage facilities shown in red are owned and maintained by the Township. Private and PennDOT-owned facilities are in grey and black, respectively. You can see that more densely-developed areas typically have more storm pipes than rural areas, which are predominantly served by roadside ditches and periodic cross-pipes under the roads.

Our MS4 and the NPDES Program

In the storm sewer system maps on the right, there are points that indicate the location of “Regulated Outfalls”. These represent the ends of pipes or swales that convey stormwater into streams, watercourses, or other areas of interest within the Regulated MS4, The Regulated MS4 area is shown by the light green shading, and corresponds to the 2000 U.S. Census’ designation of urbanized areas. The storm pipes and outfalls in the shaded parts of Penn Township are those subject to a National Pollutant Discharge Elimination System (NPDES) permit issued through the PaDEP & US EPA.

In 2023, Penn Township received a PA DEP grant to address the Township’s requirements for pounds of sediment reduced into the Chesapeake Bay, as well as % decreases in chemicals such as nitrogen and phosphorus. The basin in Cedar Hollow, (10k lb. sediment/year), another basin at White Oak Road, with the school district (15k lb. sediment/year), and a swale (part of the Stehman Land Development) along West End Drive which will remove about 63k lb. sediment/year. Watch a video of work on these projects.

Our Obligations Under the Permit

As part of the township’s authorization to discharge waters from the storm sewer system into streams and waterways, there is a series of six Minimum Control Measures (MCMs) that we must demonstrate progress toward meeting. Under each MCM is a simplified, primary method or guide that we use to achieve these goals. These MCMs are part of the Penn Township Stormwater Management Program, which was created to oversee the township’s efforts towards achieving compliance with the NPDES permit requirements.

The 6 MCMs and Our Plans to Achieve Them

  • MCM #1 – Public Education and Outreach
  • MCM #2 – Public Participation and Involvement
  • MCM #3 – Illicit Discharge Detection and Elimination
  • MCM #4 – Construction Site Runoff Control (administered by the Lancaster County Conservation District)
  • MCM #5 – Post-Construction Storm Water Management in New Development and Redevelopment
  • MCM #6 – Pollution Prevention and Good Housekeeping for Municipal Operations and Maintenance