EXPANDING LOCAL WATER SUPPLY

The Brackish Groundwater Reclamation Program (BGRP) seeks to reclaim the historical brackish water plume in the West Coast Groundwater Basin and create a new local drinking water supply. 

The Program will be comprised of multiple capital projects to desalt the brackish water plume. A critical step in achieving the objectives of BGRP is to expand WRD’s Torrance Groundwater Desalter facility. The expanded desalter facility will use new groundwater extraction wells, desalination, and state-of-the-art technology to purify the salty water and use it for distribution through local municipal drinking water systems. The Torrance Groundwater Desalter Expansion Project (TGDE)  will use reverse osmosis to remove the salts from the water and will provide up to 7,100 acre-feet per year of additional high-quality drinking water to local water customers. 

The removal of salty groundwater will in turn create available groundwater storage capacity for excess local freshwater and recycled water. Local water providers will be able to store surplus water for use during dry years—thus creating drought resiliency for generations to come.

THE HISTORY OF BRACKISH WATER IN THE GROUNDWATER BASINS

Groundwater over-pumping in the early 1900s lowered groundwater levels to below sea level along the coast (see the infographic below). This resulted in saltwater flowing into, or “intruding” into the groundwater aquifers. As the seawater mixed with the freshwater aquifers, the groundwater became “brackish,” or too salty for drinking. 

Groundwater production wells in the West Coast Basin and in the southeastern tip of the Central Basin were affected, and water producers had to consider abandoning their wells.

In response, the courts legally limited groundwater extraction for the basins and LA County constructed seawater barrier injection wells starting in the early 1960s. The wells actively pump fresh water into the ground, thereby creating a water pressure “barrier” to keep seawater out of the aquifers. The Seawater Barrier system now consists of over 100 injection wells located along the coast and effectively protects the aquifers from seawater contamination. 

While the Seawater Barrier system was an overall success, saving many wells, it trapped a plume of brackish groundwater inland from the barrier injection wells. This 14-square-mile plume still exists today, rendering groundwater pumping unfeasible in certain West Coast Basin areas.

TRIED AND TESTED

WRD’s experience in brackish groundwater reclamation started with the Robert W. Goldsworthy Desalter, located in the City of Torrance. The Goldsworthy Desalter was commissioned in 2001 and expanded in 2018. The facility now treats 3.6 million gallons per day (mgd) of salty groundwater extracted from the brackish plume in the West Coast Groundwater Basin using reverse osmosis technology. The plant is owned by WRD and operated by the City of Torrance. The treated water produced by this facility is added to the water distribution system for the City of Torrance and meets 25% of the city's water needs. 

WRD, working in partnership with regional stakeholders will take the best practices and expertise from the Goldsworthy Desalter and apply them to the future  Torrance Groundwater Expansion Project.

HOW IS BRACKISH GROUNDWATER TREATED?

Groundwater desalination works primarily through the use of reverse osmosis treatment. Salty brackish groundwater extracted from wells is forced through reverse osmosis membranes to remove the salts in the water. The water is then disinfected and the pH level is adjusted to create fresh, potable water.

Program Next Steps

In 2021, WRD completed a Feasibility Study for the Program. Based on the Feasibility Study findings and stakeholder input, BGRP will include the Torrance Groundwater Desalter Expansion Project and potentially, a new desalter in Manhattan Beach to treat the northern portion of the brackish plume. A copy of the Final Feasibility Study and two follow-up addenda regarding project refinements and a new project site are available for download below.

After the Feasibility Study, Program Phase 1 of BGRP is a water quality testing program to drill and install small production wells and monitoring wells to evaluate aquifer water movement and zonal water quality. In addition, the Phase 1 project includes a treatment system pilot test to prove and select the optimum treatment processes for the TGDE Project. Phase 1 of the BGRP started in 2022 and will go through the end of 2024.

WRD is also in the process of procuring a design-builder for the Torrance Groundwater Desalter Expansion (TGDE) project. Requests for Qualifications were issued in July 2023 and an executed contract for design-build services is expected in early 2024. The TGDE Project will be a progressive design-build project. This project delivery method will expedite the project schedule compared to traditional project delivery methods and will allow WRD to collaborate more closely with design and construction teams.