About Stormwater & Urban Runoff 

Stormwater is precipitation, including rain, hail, and snow. Urban runoff is stormwater that doesn’t seep into the ground but ‘runs off’ through streets, parking lots and other parts of the storm drain system eventually flowing into the nearest stream, creek, river, lake, or ocean. The runoff is not treated in any way. 


Stormwater Pollution 

Stormwater pollution is everything, seen and unseen, mixed with stormwater. As stormwater passes through the network of streets and drains it picks up everything along the way including trash, debris, metals, sediment, and many unseen pollutants. Unlike the sewer system, this polluted stormwater receives no treatment and flows directly into our local streams and rivers. 

Please look at the following web pages for more information on where our stormwater goes and what we do to combat pollution. 


Santa Ana Watershed

A watershed is the area of land where all of the water that is under it or drains off of it goes into the same place.  The City of Riverside is part of the Santa Ana Watershed which catches stormwater from a 2,650 square mile region and channels it into the Pacific Ocean at the City of Huntington Beach. It stretches from the peaks of the San Bernardino and San Gabriel Mountains, through the coastal plains in Orange County all the way to the Pacific Ocean. The Santa Ana River (River), flowing over 100 miles, drains the largest coastal stream system in Southern California including parts of Orange, Riverside and San Bernardino Counties, as well as a sliver of Los Angeles County. The total length of the River and its major tributaries is about 700 miles, one of the largest River systems in California. 


NPDES Program 

In 1972, the United States Congress passed amendments which significantly enhance the federal laws governing water pollution in the United States. These and subsequent amendments comprise the Clean Water Act (CWA) which establishes a framework for regulating municipal and industrial (including construction) storm water discharges under the National Pollutant Discharge Elimination System (NPDES) permit. Section 402(p) of the CWA requires NPDES permits for storm water discharges from municipal separate storm sewer systems (MS4), as well as other designated storm water discharges that are considered significant contributors of pollutants to waters of the United States. 

In accordance with the CWA, the Santa Ana Regional Water Quality Control Board developed the NPDES Permit and Waste Discharge Requirements Order No. R8-2010-0033 (MS4 Permit) for the Riverside County Flood Control District, the County of Riverside, and many incorporated cities of Riverside County within the Santa Ana Region. 

This MS4 Permit requires the City to perform various activities including: 

  • Create and enforce ordinances 

  • Conduct inspections on businesses, construction sites, and other facilities 

  • Ensure new development is built using Low Impact Development (LID) techniques 

  • Educate the Public 

  • Maintain City facilities and more