Industrial Solvents in San Fernando Valley Groundwater: The Four-Decade Cleanup and What LADWP's Annual Data Shows Today

How industrial solvents entered SFV groundwater

The San Fernando Valley hosted large-scale aerospace and defense manufacturing from the 1940s through the 1980s. Facilities in Canoga Park, Chatsworth, Northridge, and Van Nuys used chlorinated solvents, primarily TCE and PCE, as industrial degreasers and cleaning agents. Metal plating shops used similar chemicals. Dry cleaning operations throughout the valley used PCE as a standard cleaning solvent.

During this period, industrial waste disposal practices that are now prohibited were common: solvents were discharged into unlined ponds, poured into drains connected to dry wells, or stored in underground tanks that eventually leaked. Because TCE and PCE are denser than water and chemically stable, they migrated downward through soil into the shallow aquifers that underlie the SFV. Once in an aquifer, these compounds dissolve slowly into groundwater and can persist for decades.

By the late 1970s and early 1980s, LADWP well monitoring was detecting TCE and PCE in groundwater sources in the North Hollywood and Burbank areas. Concentrations in some wells exceeded what were then the emerging federal guideline levels. The EPA formally listed the North Hollywood Operable Unit of the San Fernando Valley Superfund Site (EPA ID CAD980818985) on the National Priorities List in 1984. The contamination was traced to multiple industrial users across the valley.

EPA Superfund response and LADWP treatment infrastructure

The Superfund designation triggered a long-term cleanup process that continues today. Responsible parties were identified and required to fund groundwater extraction and treatment. LADWP developed its own parallel infrastructure: the North Hollywood Groundwater Treatment Facility, which uses granular activated carbon (GAC) and air stripping to remove VOCs from affected wellfield water before it enters the distribution system.

GAC works by adsorbing organic compounds onto the surface of activated carbon media as water passes through it. Air stripping passes contaminated water through a tower where air flow volatilizes dissolved VOCs out of the water column. Both are established, well-documented treatment technologies with removal efficiencies for TCE and PCE that routinely exceed 99 percent when properly maintained (EPA TCE fact sheet).

LADWP also relies on source blending. The Metropolitan Water District of Southern California delivers Colorado River Aqueduct water and State Water Project water to LADWP, which blends these imported surface water supplies with treated local groundwater. Imported surface water does not carry the VOC signature of the SFV aquifers, so blending further dilutes any residual VOC concentrations before water reaches distribution mains.

What the CCR data shows today

LADWP publishes its annual Consumer Confidence Report each year covering the prior calendar year's monitoring data. The 2025 CCR (covering 2024 data) is available at ladwp.com/water-quality. TCE, PCE, benzene, and 1,1-dichloroethane are listed in the VOC section, with results reported as ND: not detected at the distribution tap.

ND does not mean zero. Every analytical method has a minimum detection threshold, called the method detection limit (MDL). EPA-approved methods for TCE and PCE typically have MDLs well below 1 ppb, which is a fraction of the 5 ppb federal MCL. An ND result means the laboratory analysis did not find the compound above that lower threshold. It does not exclude concentrations below the MDL, but it does confirm that the measured level is substantially below the regulatory limit.

LADWP is required to report any detection above the MCL to customers within 30 days and to state regulators, and to take corrective action. The continuous ND results in distributed tap water reflect the effectiveness of the wellhead treatment infrastructure LADWP has operated since the 1980s.

The same CCR covers all regulated contaminants in LADWP distributed water. Other monitored parameters in the SFV include nitrate, arsenic, manganese, radium and gross alpha, disinfection byproducts (TTHM and HAA5), and lead and copper. Our overview of the 2025 LADWP annual water quality report covers the full CCR dataset across all monitored parameters.

What a home filter adds beyond wellhead treatment

LADWP's treatment occurs at the wellhead, before water enters the distribution system. Point-of-use filtration at the tap addresses what happens between the treatment plant and your faucet, including any contributions from aging distribution infrastructure or household plumbing.

For VOC reduction at the tap, two treatment technologies carry independent certification. Reverse osmosis systems certified under NSF/ANSI 58 with a VOC reduction claim have been tested to reduce chlorinated solvents. Activated carbon filters certified under NSF/ANSI 53 for VOC reduction are also independently tested. The certification is contaminant-specific: verify that the specific model's contaminant reduction certificate lists TCE, PCE, or VOCs as a tested reduction claim, not just taste and odor or general carbon filtration.

Noohi installs reverse osmosis systems throughout the San Fernando Valley. For households whose primary concern is drinking and cooking water quality, a certified point-of-use RO system at the kitchen tap provides the most independently verified VOC reduction available for residential use. For an NSF certification comparison across standard types, NSF 42 vs NSF 53 vs NSF 58 explained covers which certification applies to which contaminant class. If your concern extends beyond VOCs to PFAS, lead and copper from household plumbing, or chloramines used in LADWP distribution, verify the specific contaminant reduction claim on the model you are considering. Reverse osmosis versus whole-house filtration compares which system type addresses which contaminant categories.

Sources used in this article: EPA 40 CFR 141.61 (National Primary Drinking Water Regulations for VOCs); EPA Superfund: San Fernando Valley (North Hollywood OU), CAD980818985; LADWP Annual Water Quality Reports (Consumer Confidence Reports); California SWRCB Notification Levels for Drinking Water Contaminants; EPA Technical Fact Sheet: Trichloroethylene (TCE); NSF International: Certified Water Filters.