You’ve heard the term “MS4 Permit”. But do you know what it means?
Each state within the USA has its own regulations relating to storm water management. California has, for twenty years, regulated the runoff and treatment of stormwater in its industrial and municipal sources. Urban storm water in California is considered to be a primary impairment source for ten percent of all local rivers, lakes and reservoirs, and almost twenty percent of all estuaries (source: 2010 Integrated Report). This is high considering only six percent of all California’s land mass is urbanized.
An MS4 or Municipal Separate Storm Sewer System is a storm water sewer system including roads with drains, streets, catchments, gutters, curbs, ditches, channels, and storm drains.
The term “MS4 permits” refers to the regulations that have been developed to minimize the environmental impact of stormwater discharge as separate from other sewer systems.
In California, the Municipal Storm Water Permitting Program regulates discharge of stormwater runoff from rooftops, streets, highways, parking lots, and any large or impervious surface that increases the volume and flow of stormwater. Storm water is untreated and it can flow in very fast and strong volumes. This can impact negatively on streambeds and natural waterway channels and also damage the natural habitats within these, as well as discharging pollution into the waterways. This is a threat to both aquatic and ultimately public health.
MS4 permitting was issued in two phases:
Phase I was rolled out beginning in 1990 with permits for medium and large (over 100,000 and 250,000 respectively) municipalities. These permits require the holder to develop and implement stormwater management and pollution prevention plans to reduce pollution discharged as much as possible. There must be specification of best management practices as well as illicit discharge detection, public education, and monitoring.
Phase II was adopted in April 2003. It relates to a General Permit for Discharge of Storm Water from Small MS4s. It provides permit coverage for municipalities of fewer than 100,000 people, including public education campuses, government facilities, hospital facilities, prison complexes, and military bases.
MS4 permits do expire and need to be updated periodically for complete compliance.
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