Small municipal separate stormwater sewer systems (MS4s) that are located within the boundaries of an urbanized area, as defined by the US Census Bureau, are regulated under the US Environmental Protection Agency's (USEPA) Phase II Stormwater Rule. The Phase II Stormwater Rule requires MS4 Operators to develop a stormwater management program (SWMP) which includes six minimum control measures (MCMs) that, when implemented together, are expected to reduce the discharge of pollutants to the maximum extent practicable. The goal of the program is to improve water quality and recreational use of waterways.
Stormwater discharges from MS4s in urbanized or additionally designated areas must be authorized in accordance with the permit for stormwater discharges from MS4s. This page contains the General Permit for Stormwater Discharges from Municipal Separate Storm Sewer Systems (MS4 GP) and the forms necessary to obtain coverage under that permit.
General Permit for Stormwater Discharges from Municipal Separate Storm Sewer Systems Permit, GP-0-24-001 (PDF). This permit was issued on December 13, 2023 and will become effective on January 3, 2024.