Taking trash out of runoff
Deep beneath a parking lot at Los Angeles’ Mar Vista Park, a new stormwater treatment facility is removing chemicals, debris, oil, grease and heavy metals from urban stormwater runoff before it flows into a nearby creek and eventually into Santa Monica Bay. Completed in September 2006, the Westside Water Quality Improvement Project required the cooperation of several local and state government agencies and paved the way for similar joint projects in the future.
The runoff comes from the Sawtelle Channel stormwater conveyance system, which is owned and operated by the Los Angeles County Flood Control District. Water quality from the system was extremely poor, carrying contaminants into Santa Monica Bay and often prompting beach closures. Unable to find an adequate site for a stormwater treatment facility within city limits, Santa Monica officials expanded their search downstream into Los Angeles and found Mar Vista Park, which met the facility’s hydraulic performance criteria.
To allow Santa Monica to legally build, operate and maintain an urban runoff treatment facility within Los Angeles, Santa Monica and the Los Angeles Department of Recreation and Parks negotiated a unique intergovernmental agreement. Facility construction began in October 2005 and had to be coordinated with an ongoing park improvement project. Except for the construction site, the park remained open to accommodate a heavy schedule of soccer matches and water safety classes. “This multi-agency project had to balance jurisdictional needs, competing site uses, construction scheduling and community activities over two years and rainy seasons,” says Santa Monica Environmental Analyst Neal Shapiro.
The facility uses direct filtration to treat dry-weather flow, and screening and sedimentation to treat wet-weather runoff. Upstream and downstream isolation gate valves can be closed to protect the system from overload during infrequent heavy storms. The facility, which operates by gravity flow alone, was designed without moving parts (except for the manual isolation gate valves and access hatches), chemical additives or electrically powered treatment systems.
State grants and matching resources from Santa Monica funded the project. Kansas City, Mo.-based Black & Veatch provided design and construction-support services from its Los Angeles office, and Oxnard, Calif.-based Blois Construction installed the treatment system. In the November 2006 general election, Santa Monica residents voted to establish a special urban runoff tax that will generate about $2 million in annual revenue to pay for future urban runoff water quality improvement projects.
Westside Water Quality Improvement Project
Santa Monica, Calif.
Santa Monica Bay Restoration Commission; Los Angeles Department of Recreation and Parks, Bureau of Sanitation, Regional Water Quality Control Board; Los Angeles County Department of Public Works
Black & Veatch, Blois Construction, Ecology Construction, Contech Stormwater Solutions, Suntree Technologies, and Golden Harvest