Aquifers – Historical Background

West Coast Basin Barrier Project
West Basin Municipal Water District (West Basin) is a public agency providing wholesale water to local water utility companies and municipal water agencies within its service area. West Basin constructed the Edward C. Little Water Recycling Facility (ECLWRF) in 1994 to treat and supply recycled water for non-potable uses. One of these non-potable uses is the West Coast Basin Barrier Project (WCBBP), a seawater intrusion prevention barrier designed to prevent seawater from further polluting the aquifers that are used as a potable water source. Due to over-pumping in the West Coast basin, sea water from the Pacific Ocean has already begun to infiltrate into significant portions of the West Coast basin.

The WCBBP is operated through a unique partnership between the City of Los Angeles Hyperion Wastewater Treatment Plant (HWWTP), the Los Angeles County Department of Public Works (LADPW), and the Water Replenishment District (WRD) of Southern California1.

Water Source
The source of water for treatment at the ECLWRF is secondary treated water from the HWWTP (West Basin, 2015). Treatment at HWWTP consists of preliminary, primary, and secondary treatments. HWWTP treats sludge and wastewater from industrial, commercial and residential sources from the City of Los Angeles (85%) and adjacent cities and agencies (15%) in compliance with 40 Code of Federal Regulations Part 403 and the National Pollution Discharge Elimination System (NPDES) permits for Hyperion and other publicly owned treatment works (POTWs). The City of Los Angeles Bureau of Sanitation is responsible for collecting all water quality samples of the treated effluent from HWWTP to fulfill the requirements of its NPDES permits issued by the Regional Board2.

Tertiary Treatment
Requirements for the injection of recycled water from ECLWRF at the WCBBP are outlined in California Regional Water Quality Control Board (CARWQCB) Los Angeles Region, Order No. R4-2006-00692. The recycled water from HWWTP must undergo tertiary treatment at ECLWRF before injection at WCBBP. The tertiary treatment process consists of ozone pre-treatment, microfiltration, reverse osmosis, advanced oxidation, decarbonation, pH stabilization, and chlorination1,2.   Continuous monitoring and regular sampling are conducted to ensure that treatment objectives are being achieved.

Re-Injection
Purified recycled water from the ECLWRF is blended with imported potable water and injected at the WCBBP into a series of 153 injection wells located approximately 0.4 to 1.9 miles inland, parallel to the Santa Monica Bay coastline from Los Angeles International Airport to the Palos Verdes Hills (approximately 9 miles long). The injection wells are screened at depths ranging from approximately 280 feet to 700 feet below ground surface to allow water injection into three different aquifers: 200-ft Sand, Silverado, and Low San Pedro Aquifers2. The current permit allows for eventual contribution of 100% recycled water, implemented in a two-step process and beginning with a 75% recycled water blend. Production up to 75% was possible after the facility’s Phase III expansion was completed in 2007. Operational improvements continue at the ECLWRF and the WCBBP distribution system to expand to near 100% recycled water injection1. Approximately 15,000 acre-feet per year (13 MGD) of 75% recycled water blend is injected in the WCBBP3.

 

 
 

1 West Basin Municipal Water District (West Basin), 2015. Groundwater Replenishment – Subsurface Application Compliance Status Report. June.
2 California Regional Water Quality Control Board Los Angeles Region (RWQCB), 2006. Order No. R4-2006-0069 Amending Order No. R4-2006-0009 – Waste Discharge and Water Recycling Requirements for West Coast Basin Barrier Project – Expansion Phase III Project. 14 September.
3 Intera, 2015. West Coast Basin Barrier 2014 Recycled Water Simulations. March 23.