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      Department of Public Works Bureau of Sanitation

A Low Flow Diversion is a structural device that routes urban runoff from canyons, streets and small watersheds away from the storm drain system or waterway, and redirects it into the sanitary sewer system, where the contaminated runoff then receives treatment and filtration before being discharged into the ocean. As the name suggests, the unit collects street runoff and, through a series of tanks and pumps, diverts the liquid flow into the sanitary sewer system, and is rerouted to the City’s Hyperion Sewage Treatment Plant (HTP).

In diverting the flow to a sanitary sewer, this strategy will protect people from runoff-borne microorganisms that cause illness, and also protect marine organisms from harmful pollutants such as metals and pesticides.

Studies in Santa Monica Bay have demonstrated that swimmers have an increased risk of illness when swimming in water contaminated by storm drain runoff. Likewise, runoff-contaminated water has been shown to be toxic to marine organisms.

Click on the image at left for a demonstration (Flash plug-in required)

For a larger view of image, click here.

An area that is being targeted for an LFD is the Santa Monica Canyon watershed.

Other agencies in Southern California have incorporated low-flow diversions into their overall strategy to control runoff pollution. Examples of these agencies include the Counties of Los Angeles and Orange, and the Cities of Huntington Beach, Laguna Beach, Avalon (Santa Catalina Island) and San Diego.

Locations of LFDs

The proposed projects are part of a wider program undertaken by the communities along Santa Monica Bay to divert storm drains that impose a health concern, to the sewer system. The City of Los Angeles has, or is in the process of diverting 8 storm drains.

Santa Monica Bay Low Flow Diversion Sites at left
(click for larger map)