MS4 - Municipal Separate Storm Systems

In accordance with the Pennsylvania Department of Environmental Protection’s (DEP) National Pollutant Discharge Elimination System (NPDES) General Permit regulations, Easttown Township is required to develop and implement a stormwater management program. The program is based on the federal Municipal Separate Storm Sewer System (MS4 protocol (developed by DEP).

The Township is subject to the provisions of NPDES Permit No. PAI130509.  To obtain a copy of the 2022-2023 MS4 Annual Report from DEP, please contact the Township.

The DEP’s Protocols provide our township with suitable guidelines to design a local program that addresses the DEP’s six Best Management Practices (or BMPs), which are also known as “control measures.” These six BMP’s are designed to reduce the discharge of pollutants from MS4s, to the maximum extent practicable, to protect water quality, and to satisfy the appropriate requirements of the Federal Clean Water Act. The six BMP categories are:


The federal regulations provide flexibility within these six categories of BMPs.

Township residents can learn more about these regulations and the need to improve stormwater quality by visiting the Pennsylvania Department of Environmental Protection’s (DEP) stormwater website by clicking here, or reviewing the following information.  Additional information can also be found by visiting the websites of the Chester-Ridley-Crum Watersheds Association, the Darby Creek Valley Association or by clicking the links below.