Granular Activated Carbon (GAC) Filtration System

State-of-the-Art Water System Upgrades

As part of the upgraded Cypress Water Production Facility (CWPF), the City invested in a new Granular Activated Carbon (GAC) filtration system. This new technology is part of a larger modernization effort to improve system reliability and support the long-term, cost-effective delivery of safe, dependable drinking water.

This state-of-the-art, $5.5 million treatment system improves water quality by completely removing benzene and treating and removing naturally occurring compounds that can affect taste and odor, such as manganese and iron. The system also removes forever chemicals, like PFOS/PFOAs and other substances, to create high quality water. View water sample results from July 2026 that show the effectiveness of the new GAC filtration system. To view all water quality reports, visit the Water Quality Reports webpage.

To help fund the project, the City secured a $2 million grant from the Water Replenishment District — making the net cost to the City $3.5 million.

Timeline

System Enhancements & Treatment Process

Treat Organic Compounds and Improve Taste & Odor


The City installed the GAC filtration system to enhance drinking water quality. It consists of filtering groundwater through vessels of granular activated carbon (GAC). Organic compounds and other contaminants adsorb or “stick” to the surface of the carbon, removing it from the water. It consists of two parallel trains of the Calgon Carbon Model 10 Adsorption System, each with two vessels in series. The carbon used at the CWPF is Calgon Carbon’s Filtrasorb 400, which is NSF 61-certified for the treatment of potable water.

Enhanced Chemical System Reliability

Throughout the water filtration process, treatment chemicals are used to disinfect and oxidize the water. The existing chemical feeder systems were replaced to improve operational reliability. The improved dosing feeders are larger and allow for increased volume of groundwater to be treated, while still providing precise doses of treatment chemicals.

Improved Blending Pipeline Connection

The City blends purchased Metropolitan Water District (MWD) water to meet water demand to Pressure Zones 1-3.

Well No. 5

Due to aging equipment, the submersible pump for Well No. 5 was replaced with a vertical turbine pump. The new well pump allows for easier maintenance and monitoring of groundwater extraction, which increases the reliability of local water supply. Additionally, the well casing and screens were cleaned and flushed to improve well performance.

Drone shot of the Cypress Water Production Facility
Image of the Cypress Water Production Facility
Image of the Cypress Water Production Facility
Image of blue pipes at the Cypress Water Production Facility
Image of the Cypress Water Production Facility
Image of a blue pipe at the Cypress Water Production Facility

Upgraded Technology and Modernized Control Systems

In addition to the GAC upgrade, Lomita took the opportunity to replace the Well pump to enhance efficiency and increase output, invest in upgraded security and emergency preparedness features and upgrade the CWPF technology with the latest Supervisory Control and Data Acquisition (SCADA) monitoring system. Monitoring and control systems are vital to the function and operation of the CWPF. The controls enable staff to manage all steps of the treatment process and the equipment involved. Modernizing the control system allows staff to accurately monitor water quality at any stage of water production.

High Quality Water

When comparing to other neighboring water systems (both municipal and private), Lomita is better or within a similar range.

  • Primary MCLs (Main Project Objective)
    • Benzene (Not Detected)
    • Taste and Odor (Treated and Removed)
    • Manganese & Iron (Treated and Removed)
  • Secondary MCLs (Aesthetic)
    • Total Dissolved Solids levels are in the same range or better than neighbors
    • Hardness is the same as neighbors

GAC removes benzene, “forever chemicals” (PFOS/PFOAs) and other substances to create higher quality water. This includes substances that can cause smelly water or an earthy taste. Greensand filtration removes iron, manganese and other substances that can cause discolored, dark water.

Frequently Asked Questions

Granular Activated Carbon (GAC) is a highly effective water treatment material made from activated carbon. As water passes through the GAC, it removes benzene and reduces naturally occurring organic compounds by adsorption, which can affect the taste and odor of drinking water. This advanced treatment process helps improve overall water quality while maintaining a safe and reliable water supply.

The City approved the GAC filtration project in 2017 in response to community feedback and a commitment to continuously improve drinking water quality. The project also modernized key components of the City’s water treatment facility to enhance system reliability and support long-term water service.

GAC acts like a filter, attracting and removing certain compounds from the water as it flows through the treatment system.

Well 5 pumps to the CWPF through existing raw water pipelines. The flow will pass through the GAC vessels for benzene removal and sulfide treatment. It will then be dosed with sodium hypochlorite (SHC) to oxidize iron and manganese prior to greensand filtration (GSF). Prior to entering the storage reservoir, a second SHC dosing point will provide chlorine residuals for disinfection, followed by ammonia for chloramination and polyphosphate blend for hardness sequestration. As the treated water is sent to distribution, a final SHC dosing point will provide a disinfection boost to ensure no free ammonia remains after the reservoir and to prevent nitrification in the distribution system.

Yes. Lomita’s drinking water meets all federal and state drinking water standards established by the U.S. Environmental Protection Agency (EPA) and the California State Water Resources Control Board.

A variable mix of Colorado River water, Northern California water via the State Water Project, and local groundwater well.

The total cost for the GAC Project was $5.5 million. The City will receive a $2 million grant from the Water Replenishment District (WRD) toward the total cost of the project, making the net cost to the City $3.5 million.

The project was funded through a combination of City investment and grant funding. The total cost for the GAC Project was $5.5 million. The City will receive a $2 million grant from the Water Replenishment District (WRD) toward the total cost of the project, making the net cost to the City $3.5 million.

The cost for importing 1,900 acre feet (AF) of water from MWD, which is the typical water distribution in Lomita for one year, is $3.96 million at $2,085 per AF. The cost for pumping local groundwater through the CWPF is $862,600 at $454 per AF. That represents a $3 million savings per year if pumping 100% local groundwater.

Upon reactivation, the City plans to distribute a blend of 70% local groundwater and 30% imported MWD water. The cost to the City is broken down as follows:

  •  30% Imported MWD Water ($2,085/AF) = $1,188,450
  •  70% Local groundwater ($454/AF) = $603,820
  •  Total Cost to City per year (70/30 Blend) = $1,792,270

The cost to produce local groundwater with a 70/30 blend saves the City $2,167,730 per year when compared to importing 100% MWD water.

As part of the project, the City also upgraded Well No. 5 to further strengthen the reliability of Lomita’s water system. By completing these improvements during construction of the new GAC treatment facility, the City maximized efficiency while enhancing water production. Well No. 5 can produce up to 1.7 million gallons of water per day, helping ensure a reliable local water supply for the community.

No. The completion of the GAC filtration system does not result in a specific water rate increase associated with this project. Water rates are established through a separate public process based on the City’s overall costs to operate, maintain and improve the water system.

Lomita’s drinking water is tested regularly in accordance with strict federal and state regulations. Water quality is monitored throughout the treatment and distribution process to ensure it continues to meet all drinking water standards.

The new treatment process at CWPF is completely different from the City’s previous system. The State is conducting a comprehensive review of the entire operation at CWPF to ensure the treatment system can be operated, maintained and monitored safely and effectively before the operating permit is issued.

Following extensive operational testing and water sampling, the CWPF underwent inspection by the State Water Resources Control Board Division of Drinking Water for full regulatory compliance. Testing evaluated well pump performance, valve operations and control system trials, while multi-point sampling verified the effectiveness of each filtration process and chemical dosage. Water operators will maintain daily testing protocols to guarantee consistently high water quality.