Los Angeles County Supervisor Don Knabe joined other local elected officials this week 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. At peak capacity, the new wetlands will naturally remove pollutants and other harmful chemicals from over one million gallons of storm water every day, before that water reaches the ocean or returns to the ground water supply.
The wetlands project is the first of its kind in Los Angeles County. It maintains the integrity of flood protection along the urban lower reaches of the Los Angeles River, while introducing new water quality elements, groundwater recharge, restoration of native habitat, pedestrian and equestrian trails, environmental education, and river bike trail enhancements.
The project encompassed extensive renovation of two preexisting Flood Control District spreading grounds, located along both the east and west sides of the Los Angeles River between Del Amo Blvd. and the 405 Freeway.
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 are designed to naturally treat from 2-3 cubic feet per second (1.3 to 3.2 million gallons a day) of storm water and urban runoff, the rough equivalent of five Olympic-size swimming pools. The result will be a significant reduction in the amount of pollution, heavy metals, organic carbons, and oil and greases found in runoff 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 moved underneath the Los Angeles River by a pump system to the project’s West Basin for groundwater recharge.
The 15-acre West Basin remains a functional spreading ground 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, one acre-foot of water is approximately the volume of a football field filled one foot deep with water. Both the East and West basin areas are lush with a plant palette of shrubs, trees, brush and wildflowers native to the lower Los Angeles River, selected especially for this project by the County’s project consultant, CH2M Hill.
Historically, the Los Angeles River has been impaired by pollutants from local and regional storm drains that carry storm water and urban runoff away from city streets and communities within the Los Angeles River Watershed. Polluted runoff is the result of harmful human activities like littering, illegally dumping lawn clippings and automobile fluids 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.
This is a great day for Los Angeles County and for its water quality partners, said Supervisor Don Knabe. 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.