Calif. Flood District Opens Dominguez Gap Wetlands

The Los Angeles County Flood District on May 8 opened the $7 million treatment wetlands and spreading grounds project in Long Beach. The project 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.

Officials expect the project will help mitigate stormwater and urban runoff into the Los Angeles River. By 2016, cities and county areas within the Los Angeles River Watershed must effectively have zero trash going into the Los Angeles River.

"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 pre-existing spreading grounds, located along both sides of the Los Angeles River:

• Enhancements to the 37-acre East Basin include 1 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. 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.

• 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.

"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. The firm served as the county's project consultant.

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

Featured Webinar