MS4 Stormwater Regulations

There are two different categories of MS4s:

Phase 1 MS4s

Phase 1 MS4 regulation began in 1990 and requires medium and large cities of 100,000 or more residents to obtain a permit for their stormwater discharges. Large municipalities in Utah, including Salt Lake City and Jordan Valley municipalities fall under this designation and have their own MS4 permits.

Phase 2 MS4s

Phase 2 MS4 regulation began in 1999 and requires small MS4s in areas defined as “urbanized” by the US Census Bureau to obtain permits for their stormwater discharges. In addition to small counties, cities, and towns, Phase 2 MS4s includes public universities, hospitals, and other large, state-owned campuses. Most MS4s in Utah fall under this designation and are covered by the General Permit for Discharges for Small MS4s.

MS4 permitees must develop, implement, and enforce Stormwater Management Programs (SWMPs).

Stormwater Management Programs are designed to:

Reduce the discharge of pollutants from MS4s to the maximum extent possible

Protect water quality following the Utah Water Quality Act

Include 6 minimum control measures:

(1) Public education and outreach on stormwater impacts, (2) Public involvement and participation, (3) Illicit discharge detection and elimination, (4) Construction site stormwater runoff control, (5)Long-term stormwater management in new and re-development, (6) Pollution prevention and good housekeeping