The Stormwater Program in the
Los Angeles Region

Stormwater is defined by US EPA as the runoff generated when precipitation from rain and snowmelt events flows over land or impervious surfaces without percolating into the ground. As it flows, stormwater runoff collects and transports pollutants to surface waters. Some of these pollutants are visible such as sediment, motor oil and trash, as well as pollutants that are not easily visible such as dissolved metals, nutrients, oxygen demanding substances, and organic chemicals.

Although the amount of pollutants from a single residential, commercial, industrial or construction site may seem unimportant, the combined concentrations of contaminants threaten our lakes, rivers, wetlands and other water bodies. Pollution conveyed by stormwater degrades the quality of drinking water, damages fisheries and habitat of plants and animals that depend on clean water for survival. Pollutants carried by stormwater can also affect recreational uses of water bodies by making them unsafe for wading, swimming, boating and fishing. In most cases, stormwater flows directly to water bodies through separate storm sewer systems, contributing a major source of pollution to rivers, lakes, and the ocean.

Stormwater discharges in California are regulated through National Pollutant Discharge Elimination System (NPDES) permits. However, stormwater may also act as a resource and recharge groundwater when properly managed. The Water Boards are actively involved in initiatives to improve the management of stormwater as a resource.

In the Los Angeles region, the stormwater program is a comprehensive program to manage the quality of discharges from the municipal separate storm sewer system in the incorporated and unincorporated areas in Los Angeles, and Ventura counties, the discharges from the 10 categories of industries listed in the Federal Regulations (40 CFR 122.26), and the discharges from construction sites with land disturbance of 1 acre or more.