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DATE: |
September 30, 2025 |
15 |
SUBJECT
Title
DEMANDING A COMPREHENSIVE CONTAMINATION ANALYSIS OF THE TIJUANA RIVER (DISTRICTS: ALL)
Body
OVERVIEW
For nearly eighty years, the Tijuana River Valley has absorbed raw sewage, industrial waste, pesticides, heavy metals, and hazardous chemicals carried across the border. These pollutants have settled into the soil, wetlands, and estuary, creating a toxic legacy that endangers public health, fragile ecosystems, and the regional economy.
The Urgent Need for a Comprehensive Contamination Analysis
San Diego cannot secure Superfund designation for the Tijuana River Valley without a robust, up-to-date contamination record. In 2024, regional leaders petitioned the U.S. Environmental Protection Agency (EPA) to take that step, a move that could unlock billions in federal dollars for cleanup. Instead of acting, the EPA relied on a cursory “desk review” of decades-old data and declined to conduct new sampling. That decision left the region without the scientific evidence EPA itself requires to justify designation.
Prior studies over the last twenty years have detected dangerous toxins in the Tijuana River Valley, but they were piecemeal, dated, and never designed to provide the comprehensive picture needed for cleanup. Every day, more than 50 million gallons of contaminated wastewater surge across the border, carrying banned pesticides like DDT, carcinogens such as PCBs and PAHs, and heavy metals including lead and arsenic. Yet no agency has ever undertaken a full analysis of what is embedded in the water, soil, and sediment.
Without that baseline, San Diego is locked out of the very federal tools meant for crises of this magnitude. A comprehensive contamination analysis is not optional, it is the linchpin to proving the case, securing Superfund designation, and beginning the long-delayed cleanup our communities deserve.
The Missing Piece: Direct Analysis of Soil, Water, and Sediment
Recent studies have focused on the human and economic toll of the sewage crisis. These efforts are important, but they do not answer the core question that determines whether EPA will act: what exactly is embedded in the soil, water, and sediment.
• On September 9, 2025 (Item 17), the County advanced a new epidemiological study on long-term public health impacts, alongside a new regional economic impact analysis.
• A CDC Assessment of Chemical Exposure (ACE) study of 2,100 residents found that 64% reported new or worsening physical symptoms consistent with hydrogen sulfide exposure, while two-thirds reported sewage-related mental health impacts.
• A separate CDC Community Assessment for Public Health Emergency Response (CASPER) study of 41,000 households showed nearly half experienced health symptoms they believed were tied to the pollution, and 70% reported major disruptions to daily life. Hydrogen sulfide has been detected miles from the river in neighborhoods like Imperial Beach, Nestor, and San Ysidro, where residents describe daily headaches, nausea, and persistent coughs.
These studies document the scale of harm, but none provide the hard evidence EPA requires to act. A comprehensive contamination analysis will show what is in the ground and water, the essential proof needed for Superfund designation.
This item seeks to fill that void. Working with the San Diego Regional Water Board, the County will advocate to the State Water Board to fund the first comprehensive contamination study of the Tijuana River Valley. Using Sediment Quality Objective Triad Analysis, the study will integrate chemistry, toxicity, and ecological assessments. It will test for heavy metals, pesticides, PCBs, PFAS, hydrocarbons, pharmaceuticals, and other contaminants of concern. Sampling in both wet and dry seasons will provide a complete picture of pollutants across the Tijuana River Valley. This study is the critical missing piece to build an irrefutable scientific record and compel EPA to take our Superfund petition seriously.
Today’s action directs the County to advocate to the State Water Resources Control Board to secure $1.4 million for our San Diego Regional Water Quality Control Board to conduct the comprehensive contamination study and to press the federal EPA to provide support and coordination, including identifying specific chemical thresholds relevant to Superfund designation. This funding could come from the State Water Board’s Clean-Up and Abatement Funds separate and apart from the Prop 4 funds, previously supported by the Board on Sep 9, 2025 (Item 18).
San Diego cannot be left in the dark any longer. Public health studies show the human toll; this analysis will establish the contamination record needed for federal action. By securing funding, coordinating with EPA, and generating the evidence ourselves, we will build the case for Superfund designation, unlocking billions in federal dollars for cleanup and long-term remediation. Families deserve clean air, children deserve safe places to play, and our region deserves its fair share of federal cleanup resources.
RECOMMENDATION(S)
CHAIR TERRA LAWSON-REMER AND CHAIR PRO-TEM PALOMA AGUIRRE
1. Direct the Chief Administrative Officer to advocate for a $1.4 million allocation from the State Water Resources Control Board to support a San Diego Regional Water Quality Control Board two-year comprehensive sediment study of the Tijuana River Valley and Estuary. Advocacy should include, but not be limited to:
a. A formal letter of support sent to the Chair of the State Water Board with copies sent to the Executive Officer and the San Diego State Legislative Delegation.
b. Coordination with the County’s contracted lobbyist to advocate to the State Water Board leadership to prioritize the funding request.
c. A public communications strategy highlighting the importance of the study, it’s relation to potential federal Superfund resource, as well as resources for community health protection.
2. Direct the Chief Administrative Officer to send a letter to the EPA Administrator requesting active coordination from the EPA to identify toxic chemicals and thresholds relevant to Superfund designation.
EQUITY IMPACT STATEMENT
People living near the Tijuana River Valley face ongoing exposure to polluted air and environmental hazards. These impacts fall most heavily on communities of color and neighborhoods with fewer economic resources compared to other parts of the region. This item directs the County to continue advocacy and leadership that will help collect the data to press forward on long-term clean-up solutions. By focusing attention where health risks are greatest, the County affirms its responsibility to protect public health equitably and to guarantee that all communities, regardless of income or demographics, have access to clean air and water.
SUSTAINABILITY IMPACT STATEMENT
This board letter aligns with the County’s sustainability goals to protect the environment and promote our natural resources, diverse habitats, and cultivate a natural environment for residents, visitors, and future generations to enjoy. It also aligns with County Sustainability goals, including: (3): Protect and promote our natural and agricultural resources, diverse habitats and sensitive species. Cultivate a natural environment for residents, visitors and future generations to enjoy, and (4) Ensure the capability to respond and recover to immediate needs for individuals, families, and the region.
FISCAL IMPACT
Funds for the actions requested are included in the Fiscal Year 2025-26 Operational Plan based on existing staff time in the County Communications Office funded by existing General Purpose Revenue. There will be no change in net General Fund cost and no additional staff years. There may be fiscal impacts associated with future related recommendations which staff would return to the Board for consideration and approval.
BUSINESS IMPACT STATEMENT
The impact of beach closures has a devastating impact on coastal communities through decreased visitors and street traffic. The long-term health impact of chronic exposure to transboundary pollutants and chemicals may also impact economic growth and flourishing of communities across San Diego County.
Details
ADVISORY BOARD STATEMENT
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BACKGROUND
For decades, the Tijuana River Valley has absorbed a toxic mix of untreated sewage, industrial discharges, pesticides, heavy metals, and hazardous chemicals. While recent binational infrastructure investments are critical, they cannot undo the long-term accumulation of pollutants already embedded in the Tijuana River Valley’s soil and sediment. The absence of a comprehensive scientific analysis of these contaminants is the single greatest barrier to securing federal Superfund designation - and the billions in cleanup resources that San Diego communities deserve.
When regional leaders petitioned the U.S. Environmental Protection Agency (EPA) in 2024 to designate the Tijuana River Valley as a Superfund site, EPA declined to conduct field sampling and relied instead on decades-old data. That refusal underscored a glaring problem: without updated scientific evidence, federal regulators will continue to deny Superfund designation, leaving communities exposed and cleanup resources out of reach. In the meantime, conditions have deteriorated dramatically - since mid-2023, more than 47 billion gallons of raw sewage have flowed into the Tijuana River Valley, carrying with it banned pesticides such as Dichlorodiphenyltrichloroethane (DDT), carcinogens like polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons PAHs, and heavy metals including lead, arsenic, and hexavalent chromium.
The San Diego Regional Water Quality Control Board has now developed a scope of work to close this gap. The proposed two-year study would apply California’s Sediment Quality Objective Triad Analysis, a gold-standard scientific method that integrates three lines of evidence: (1) sediment chemistry, (2) toxicity, and (3) benthic community condition. This approach will allow regulators to not only identify specific contaminants but also measure their toxicity and document their ecological impacts.
Sampling is planned for 11 sites across the Tijuana River Valley and Estuary, with comparator samples from Los Peñasquitos Lagoon and Fomosa Slough to establish baseline conditions. Analyses will test a wide spectrum of pollutants: heavy metals, pesticides, PCBs, PAHs, per- and polyfluoroalkyl substances (PFAS), pharmaceuticals, hydrocarbons, and other chemicals of concern. Toxicity testing will measure acute and chronic effects on aquatic species, while benthic analysis will document how deeply pollutants have altered the river’s ecological systems. The work will provide the first scientifically rigorous accounting of what decades of transboundary pollution have left behind.
The estimated cost of the two-year study is $1.4 million from the State Water Resources Control Board. Without it, the study cannot proceed, and San Diego will remain without the data needed to compel EPA action. By advocating to the State Water Board to fund this study, pushing for EPA’s participation in establishing thresholds relevant to Superfund designation, and working with regional partners to ensure sampling moves forward, the County will generate the evidence necessary to unlock billions in federal cleanup resources.
San Diego cannot afford further delay. Our communities, our estuary, and our economy have lived under the weight of toxic pollution for too long. This study is not an academic exercise, it is the linchpin for holding polluters accountable, securing federal investment, and ensuring that residents are no longer left to live, work, and raise families in the shadow of one of America’s most contaminated waterways.
LINKAGE TO THE COUNTY OF SAN DIEGO STRATEGIC PLAN
Today’s proposed actions support Sustainability and Equity initiatives in the County’s 2025-30 Strategic Plan by combatting environmental justice, health, and economic issues resulting from the long-standing transboundary pollution.
Respectfully submitted,
TERRA LAWSON-REMER PALOMA AGUIRRE
Supervisor, Third District Supervisor, First District
ATTACHMENT(S)
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