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Dominguez Gap Wetlands Project

Los Angeles County Flood Control District Opens Historic LA River Wetlands Project

LONG BEACH , CALIF. (May 8, 2008) – County of Los Angeles Supervisor Don Knabe (4th District) was joined by City of Long Beach Mayor Bob Foster and a host of municipal officials today for the opening of the Dominguez Gap Wetlands in Long Beach. The $7 million treatment wetlands and spreading grounds project is the latest in a series of regional, multi-benefit projects implemented by the Los Angeles County Flood Control District, including the Sun Valley Park and Tuxford Green projects in the Sun Valley Watershed and the Tujunga Wash Greenway and River Restoration project in the San Fernando Valley's Valley Glen community. The wetlands project is one of the top five demonstration projects of the Los Angeles River Master Plan.

“This is a great day for Los Angeles County and for its water quality partners,” Supervisor Knabe said. “The project's open space, water quality improvements, and groundwater recharge make it a cost-effective solution for addressing some of the County's toughest regional issues.”

The wetlands project is the first of its kind in the Los Angeles County region. It maintains the integrity of flood protection along the urban lower reaches of the river, while introducing new water quality elements, groundwater recharge, restoration of native habitat, pedestrian and equestrian trails, environmental education, and river bike trail enhancements.

“We're extremely pleased to see the hard work of our watershed advisory groups bearing fruit within the County's Flood Control District,” said Diego Cadena, Deputy Director of the County of Los Angeles Department of Public Works. “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.”

The project encompassed extensive renovation of two preexisting Flood Control District spreading grounds, located along both sides of the Los Angeles River between Del Amo Blvd. and the 405 Freeway.

  • EAST BASIN : Enhancements to the 37-acre East Basin include one mile of constructed, treatment wetlands, pedestrian and horseback trails, two bird observation decks, woodland and riparian habitat, and a bike trail rest station. The wetlands will naturally treat from 2-3 cubic feet per second (1.3 to 3.2 million gallons a day) of stormwater and urban runoff—enough water to fill five Olympic-size swimming pools. The result will be a significant reduction in the amount of fecal coliform, nutrients, heavy metals, organic carbons, and oil and greases within the runoff that is treated within the system. Trash booms will collect floatable trash, allowing it to be removed before it can foul the wetlands. Once treated, the runoff will be conveyed underneath the Los Angeles River to the project's West Basin for groundwater recharge.
  • WEST BASIN : The 15-acre West Basin remains a functional spreading grounds that, with new project improvements, will allow as much as 450 acre feet a year of water to permeate into the underground aquifer of the West Coast Groundwater Basin . In simplified terms, an acre foot of water is approximately the volume of one football field filled one foot deep and provides enough water for two families of four for one year.

“One of our most challenging restoration efforts ever, the Dominguez Gap Wetlands will return important ecological functions of water quality improvement, wildlife habitat, and aquifer recharge to the urban lower Los Angeles River ,” says CH2M HILL Principal Scientist Jim Bays. “By encompassing the restoration within an attractive community park, the project will be certain to become an exciting destination for birdwatchers, hikers, bicyclists, and the interested public.” 

Funding was provided by the Los Angeles County Flood Control District ($4 million), State Water Resources Control Board ($2.3 million), California Coastal Conservancy ($400,000), and Rivers and Mountains Conservancy ($200,000).

Historically, the Los Angeles River has been impaired by stormwater and urban runoff that collects on city streets and communities within the Los Angeles River Watershed. Polluted runoff is the result of harmful human activities like littering, illegally dumping automobile fluids and other contaminants into catch basins, and over-watering lawns. These activities, among others, have led to stringent federal regulations (known as Total Maximum Daily Load allocations or TMDLs) that restrict the amount of trash and other pollutants that may enter designated receiving waters. By 2016, cities and County areas within the Los Angeles River Watershed must effectively have zero trash going into the Los Angeles River.