TCE, PCE, and 1,4-Dioxane in San Fernando Valley Groundwater: Inside the $600 Million Cleanup

The San Fernando Valley sits above one of the nation's largest Superfund groundwater sites, contaminated since the 1940s with three volatile organic compounds: trichloroethylene (TCE), tetrachloroethylene (PCE), and 1,4-dioxane. LADWP's $600 million San Fernando Groundwater Remediation project now treats up to 75 million gallons per day from that plume, supplying clean water to 800,000 Angelenos. What the project reveals is a regulatory fault line: TCE and PCE each carry an enforceable MCL of 5 micrograms per liter, but 1,4-dioxane has no MCL in California or at the federal level. LADWP treats it anyway, using advanced UV oxidation. Understanding what that means at the tap, and what remains unregulated, is the focus of this piece.

Where the Contamination Came From

The SFV's groundwater problem is a direct product of the Valley's postwar industrial boom. From the 1940s through the 1980s, aerospace and defense manufacturers including Lockheed, Rocketdyne, Bendix, and dozens of suppliers operated in a corridor running from Burbank through North Hollywood and into the eastern Valley. These facilities used TCE and PCE extensively as metal-degreasing solvents and cleaning agents. Starting in the 1970s, 1,1,1-trichloroethane (TCA) was introduced as a replacement for TCE in some processes. Commercial TCA formulations contained 1,4-dioxane as a stabilizer additive, which meant that wherever TCA was used or spilled, 1,4-dioxane entered the environment alongside it.

Improper storage, surface disposal, and unlined pits allowed these solvents to migrate through the soil over decades and reach the SFV groundwater basin. By the time LADWP detected contamination in SFV production wells in the early 1980s, the plume had spread across a significant portion of the aquifer. The EPA designated the San Fernando Valley Area 1 (Burbank and North Hollywood corridor) and Area 2 (Glendale corridor) as Superfund sites, with Superfund enforcement actions requiring Lockheed Martin Corporation and Honeywell International (successors to the original responsible parties) to fund cleanup work. The contamination footprint spans multiple LADWP well fields, including the North Hollywood and Tujunga well fields that historically supplied a significant share of Valley drinking water.

The Three Contaminants and Their Regulatory Status

The regulatory picture for TCE, PCE, and 1,4-dioxane is not uniform. Two carry enforceable maximum contaminant levels. The third does not, and that asymmetry matters for residents trying to evaluate risk.

Sources: EPA National Primary Drinking Water Regulations; SWRCB Notification and Response Levels; SWRCB 1,4-Dioxane page.

The MCL is the number that matters most for public water systems: when a detected level exceeds the MCL, the utility must notify customers, take corrective action, and report to the California State Water Resources Control Board, Division of Drinking Water. For 1,4-dioxane, there is no MCL trigger. A utility detecting 1,4-dioxane above 1 µg/L notifies the state but is not required to notify customers. Above 35 µg/L, the response level, the SWRCB recommends removing the source from service, but no automatic enforcement action follows. This is a weaker regulatory backstop than the MCL regime governing TCE and PCE.

LADWP's $600 Million Remediation Project

The San Fernando Groundwater Remediation (SFGR) project, designed and built by the Kiewit-Stantec team for LADWP, is one of the largest groundwater remediation efforts in United States history. The project encompasses multiple treatment facilities across the contaminated basin, with the North Hollywood Central Response Action Treatment Facility serving as the anchor site. At full operation, the system treats up to 75 million gallons of contaminated groundwater per day, with the treated water blended into the LADWP distribution system and delivered to roughly 800,000 Angelenos annually. The project's estimated cost is $600 million, with construction substantially complete as of late 2023. Source: SFGR project documentation.

The treatment train at the SFGR facilities uses different technologies for different contaminants. For TCE and PCE (volatile organic compounds that bind to carbon surfaces), packed-tower air stripping forces air through contaminated water, volatilizing the solvents and capturing them in an off-gas treatment system. Granular activated carbon (GAC) provides additional polishing for residual VOC concentrations. The combined process consistently reduces TCE and PCE below the 5 µg/L MCL.

For 1,4-dioxane, the process is fundamentally different. 1,4-Dioxane is highly water-soluble and hydrophilic, with a log octanol-water partition coefficient (log Kow) of approximately negative 0.27. That means it does not bind meaningfully to activated carbon surfaces. Air stripping is also largely ineffective because 1,4-dioxane has a low Henry's Law constant; it stays in solution rather than volatilizing. LADWP's facilities, including the Tujunga Well Field treatment system modified specifically to address 1,4-dioxane, use ultraviolet oxidation (UV/H2O2 advanced oxidation process) as the primary 1,4-dioxane treatment step. UV light at 254 nanometers, combined with hydrogen peroxide, generates hydroxyl radicals that break 1,4-dioxane molecules apart, converting them to carbon dioxide and water at the correct dosage and contact time.

What "Treated to Standard" Means at Your Tap

When LADWP certifies that groundwater leaving the SFGR facilities meets the MCL for TCE and PCE and is below the notification level for 1,4-dioxane, it means the water at the point of entry to the distribution system meets those thresholds. What arrives at a specific kitchen faucet in North Hollywood or Burbank is a blend: some fraction of SFGR-treated SFV groundwater, mixed with imported surface water from the Metropolitan Water District of Southern California (Colorado River and State Water Project supply). LADWP adjusts the blend ratio seasonally based on snowpack, reservoir levels, and import availability, which means the proportion of treated groundwater in your tap water varies month to month.

The tool for verifying what is actually in your water is LADWP's annual Drinking Water Quality Report (Consumer Confidence Report), published each July for the prior calendar year. It lists detected levels of TCE, PCE, and 1,4-dioxane by water source area, alongside applicable MCLs and notification levels. Access LADWP's current CCR at ladwp.com. If your home is served by Burbank Water and Power or Glendale Water and Power, those utilities publish their own CCRs through the SWRCB disclosure system.

The 1,4-Dioxane Regulatory Gap

The absence of an MCL for 1,4-dioxane is not a gap the EPA or California has overlooked. It reflects the regulatory timeline for a contaminant that was not widely detected in public water supplies until monitoring technology improved in the 2000s.

At the federal level, the EPA listed 1,4-dioxane on the Contaminant Candidate List 4 (CCL4) as a priority candidate for potential regulation under the Safe Drinking Water Act. As of mid-2026, it has not progressed to a proposed maximum contaminant level. At the state level, California established its notification level (1 µg/L) and response level (35 µg/L) in 1998 and has not yet adopted a formal MCL. A California State Water Board agenda item from March 2026 identified 1,4-dioxane as a priority candidate for MCL rulemaking, citing expanded occurrence data since the 1998 advisory levels were set. The SWRCB 1,4-dioxane page tracks current rulemaking status.

The practical result for SFV residents: LADWP voluntarily treats 1,4-dioxane below the 1 µg/L notification level as part of the SFGR program, because the project targets all three Superfund VOCs together. That is good practice, but it is not legally required in the same way TCE and PCE treatment is required. For a resident on a private shallow well (used for irrigation in some older parcels) or on a small water system not covered by the SFGR project, the regulatory backstop for 1,4-dioxane is thinner than for TCE and PCE.

Treatment Options at the Home

Homes on LADWP supply benefit from SFGR treatment upstream: VOC levels at the tap are already at or below applicable thresholds. Point-of-use or whole-house treatment at the home adds a second line of defense for health-sensitive households, or for homeowners who want to go below regulatory minimums.

The carbon filtration gap for 1,4-dioxane is worth understanding in plain terms. When we install a whole-house catalytic carbon system in a North Hollywood home, it reliably reduces chloramine, chlorine, TCE, PCE, and most other volatile organics detected in SFV tap water. It does not meaningfully reduce 1,4-dioxane. Families who specifically want to go below whatever level LADWP's UV oxidation leaves in the distribution blend would need a technology that home water treatment equipment does not currently deliver at certified performance levels. The good news is that LADWP's upstream treatment is designed to address 1,4-dioxane before the water reaches anyone's meter. An in-home test will confirm your specific tap's current reading. See our water testing service for what the panel includes.

For VOC reduction at the kitchen and cooking tap, an under-sink NSF/ANSI 58 certified reverse osmosis system is the standard proportionate response for LADWP customers who want a point-of-use treatment step. RO reduces TCE and PCE reliably, and provides some reduction of 1,4-dioxane as a secondary benefit. Our reverse osmosis service page covers the systems we install and the NSF certification designations to look for.

Frequently Asked Questions

Is LADWP tap water safe given the SFV Superfund contamination?

LADWP treats groundwater extracted from the contaminated SFV basin before it reaches distribution, targeting TCE, PCE, and 1,4-dioxane. Consumer Confidence Report data shows detected levels at or below applicable MCLs and notification levels. Tap water on LADWP supply meets California and federal drinking water standards for these VOCs as of the most recent CCR publication date.

What is 1,4-dioxane and why does it appear in SFV groundwater?

1,4-Dioxane is a cyclic ether used as a stabilizer additive in commercial formulations of 1,1,1-trichloroethane (TCA), a solvent widely adopted in the 1970s as a replacement for TCE. Wherever TCA was used or spilled at SFV aerospace and manufacturing facilities, 1,4-dioxane entered the soil alongside it. Because it does not bind readily to soil particles and does not biodegrade quickly, it travels farther in groundwater than most co-contaminants, which is why it shows up in portions of the SFV aquifer beyond the core TCE and PCE plume. The EPA classifies 1,4-dioxane as a likely human carcinogen based on animal studies.

How does LADWP remove 1,4-dioxane from groundwater?

LADWP uses ultraviolet oxidation (UV/H2O2 advanced oxidation process) for 1,4-dioxane treatment at the SFGR facilities. UV light combined with hydrogen peroxide generates hydroxyl radicals that break down 1,4-dioxane molecules. Air stripping and granular activated carbon, which handle TCE and PCE effectively, do not reliably remove 1,4-dioxane due to its high water solubility and low tendency to volatilize or adsorb.

Does whole-house carbon filtration remove TCE and PCE?

Yes. Granular activated carbon is the established treatment for TCE, PCE, and most other volatile organic compounds with established MCLs. A properly sized whole-house GAC system will reduce TCE and PCE to non-detect or near non-detect levels from LADWP supply concentrations. It does not effectively reduce 1,4-dioxane, which requires different treatment chemistry. See our whole-house filtration page for system sizing guidance for SFV homes.

Which SFV neighborhoods are closest to the Superfund contamination zone?

The primary contamination footprint covers the North Hollywood and Burbank groundwater pressure zones, with documented plume extent into Sun Valley, parts of Glendale, and the eastern Valley corridor near former aerospace manufacturing sites. LADWP extracts and treats groundwater from the contaminated zones before blending it into distribution. Neighborhoods that historically drew a higher share of local groundwater relative to imported supply were more likely to have received pre-remediation water from affected wells; those same zones now receive SFGR-treated supply.

Can I look up my tap water's TCE, PCE, or 1,4-dioxane levels?

Yes. LADWP's annual Drinking Water Quality Report, published each July for the prior calendar year, lists detected levels for all three compounds by source area. Access it at ladwp.com. If you are served by Burbank Water and Power (PWSID CA1910009) or Glendale Water and Power (PWSID CA1910029), your utility's CCR is available through the SWRCB Division of Drinking Water disclosure portal.

Last updated: July 28, 2026. Regulatory thresholds are current as of that date. MCLs and notification levels are subject to revision; verify current values at waterboards.ca.gov. LADWP CCR data reflects prior-year monitoring; consult your utility's most recent published report for current detected levels.

Related reading: Chromium-6 in SFV Water · PFAS in SFV and Santa Clarita · Lead in SFV Water · What 2,000 SFV Installs Taught Us · CA Water Quality Rules 2026 · SFV Utility Water Quality Comparison · Chloramine in SFV Water · Reverse Osmosis · Water Testing · Whole-House Filtration · SFV Water Quality Overview · Service Areas · FAQ · Contact