News Flash


Posted on: June 6, 2023

Cross Border Water Pollution Background Information

IBWC Logo International Boundary & Water Commission

June 6, 2023

Why are ocean waters in the South Bay being intermittently closed?

Many parts of Tijuana’s wastewater infrastructure are decades old, have inadequate capacity to treat and convey wastewater and suffer from repeated breaks and system failures. During and after significant rain events and wastewater system breaks in Mexico, untreated water can flow northward carrying contaminants into U.S. waters off San Diego.

From late December 2022 through May 2023, unusually heavy and frequent rain events created significant flows down the Tijuana River that propelled much higher-than-normal volumes of contaminants into the ocean environment. This resulted in greater number of ocean closures, warnings and advisories from Imperial Beach to Coronado than is typically experienced this time of year. As of late May 2023, Tijuana River flows have returned to a seasonal normal of zero to low flows. This will allow the reconstruction of pollution-preventing measures such as a sediment berm in the river channel.

In May of 2022, San Diego County also introduced a first-in-the-nation ocean water quality testing protocol which has yielded more closures than under prior testing protocols. On Coronado, water samples are taken daily. When samples approach or exceed the test’s threshold, an ocean advisory, warning or closure is designated, and signs are posted on the beach. San Diego County water quality results are published online as conditions change and are available on the San Diego County Beach & Bay Water Quality website, along with information on the ocean advisory, warning and closure levels.

What is the plan for addressing water pollution coming from Mexico?

The City of Coronado has been tirelessly advocating for wastewater treatment solutions since 2016, along with other regional partners. As a result, in 2022 the federal government allocated $330 million to mitigate the problem, with the Mexican government contributing another $144 million.

The U.S. Environmental Protection Agency (EPA) and the International Boundary and Water Commission (IBWC) have planned several projects in San Diego and Tijuana to address cross border water pollution which include:

1) expanding the capacity of the existing sewage treatment plant on the U.S. side of the border;

2) replacing the San Antonio de las Buenas treatment plant that discharges untreated sewage at Punta Bandera in Mexico;

3) building an additional treatment plant on the US side of the border to treat river flows;

4) installing a trash boom in the river on the US side of the border; and

5) additional repairs to the sewage collection system in Mexico.

These projects will help improve water quality for our local communities but will take time to design and construct.

Timeline for current improvements

With this funding, projects are expected to be completed and operational by the end of 2027 that would result in a 50% reduction in the number of days of transboundary wastewater flow in the Tijuana River and an 80% reduction in the volume of untreated wastewater discharged to the Pacific Ocean six miles south of the border.

• July 2023 – IBWC producing estimates for work and releasing bids, with contracts in place by fall.

• Early 2024 – IBWC designs complete and construction breaks ground on infrastructure improvements.

• Mexico has not yet released timelines for construction using their allocated funding.

For a map of the related infrastructure improvements, please visit the EPA’s website.

What are the next steps to make sure our local waters are open for recreation?

The City of Coronado continues collaboration at the local, state and federal levels to protect our water resources. While much has been done to dedicate necessary resources, ongoing attention and advocacy is needed to ensure these projects advance and complete as quickly as possible. It is estimated that an additional $300 million beyond the currently allocated $470 million is needed to fund all of the infrastructure improvements on both sides of the border.

On April 3, 2023 the Coronado City Council voted to create dedicated Council Subcommittee on Cross Border Water Pollution to continue to the City’s focus on legislative advocacy and aggressively pursuing solutions with regional partners. The City of Coronado encourages you to remain informed and sign up for e-updates online as more information becomes available on funding and the status of projects here

How can I support collaborative efforts to improve water quality in South Bay?

If you would like to get involved, please reach out to the EPA Region 9 Office and your local U.S. Senator and Congressmember to voice your concerns. Encourage your representatives to continue to support additional funding for wastewater treatment facilities along the U.S./Mexico border and to support efforts to expedite the IBWC group of improvement projects that have already been funded and are underway.

Together, we can ensure clean water for all who use South County’s bays and beaches.


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