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Project: Dominguez Gap Wetlands
Jurisdiction: Los Angeles County
Agency: Flood Control District
Vendor: Denver-based CH2M HILL
Date completed: May 2008
Cost: $7 million
Historically, the Los Angeles River, a 51-mile concrete flood control channel that directs water to the Pacific Ocean, has been impaired by runoff that collects on city streets within the Los Angeles River Watershed. Last May, the county completed one project to reduce the amount of pollution that reaches the ocean: the Dominguez Gap Wetlands in Long Beach. The $7 million treatment wetlands and spreading grounds project was implemented by the Los Angeles County Flood Control District, and is one of the top five demonstration projects of the Los Angeles River Revitalization Master Plan.
The project maintains the integrity of flood protection along the urban lower reaches of the river, while introducing new water quality elements, improving groundwater recharge, restoring native habitat and providing opportunities for environmental education. The project renovated two existing spreading grounds, East Basin and West Basin, located along the Los Angeles River in Long Beach.
Enhancements to the 37-acre East Basin included one mile of constructed treatment wetlands, pedestrian and equestrian trails, two bird observation decks, woodland and riparian habitats, and a bike trail rest station. The wetlands will treat 1.3 to 3.2 million gallons a day of stormwater and urban runoff, significantly reducing fecal coliform, nutrients, heavy metals, organic carbons, and oil and greases. Trash booms collect floatable trash before it can foul the wetlands. Once treated, the runoff flows under the Los Angeles River to the West Basin for groundwater recharge.
Funding was provided by the Los Angeles County Flood Control District, State Water Resources Control Board, California Coastal Conservancy, and Rivers and Mountains Conservancy. The locally based Community Conservancy International named the project a Green Solution Project of the Year for 2009. “The Dominguez Gap Wetlands project will have a measurable impact on water quality and return enough water to the groundwater system to meet the supply demands for 900 families of four for one year,” says Diego Cadena, deputy director of the County Department of Public Works.