Coronado Beach has been affected by an ongoing sewage contamination crisis originating from the Tijuana River, which has resulted in periodic advisories and closures along San Diego’s southern coastline. The contamination is not constant, but it is a recurring problem that has worsened significantly since late 2023. Whether the beach is safe on any given day depends on recent weather, ocean currents, and the latest water quality test results.
Where the Contamination Comes From
The source of the problem is roughly 15 miles south of Coronado. A massive wastewater treatment plant on the Mexican side of the border, serving the growing city of Tijuana, has been poorly maintained for years and has discharged nearly 40 million gallons per day of raw sewage onto a Tijuana beach and into the Pacific Ocean. Ocean currents carry that pollution northward along the coast, reaching Imperial Beach, Silver Strand, and Coronado.
Since October 2023, an estimated 31 billion gallons of raw sewage, polluted stormwater, and trash have flowed down the Tijuana River into the ocean. The crisis intensifies during heavy rainfall. Southern California’s “atmospheric river” storms overwhelm the already broken infrastructure, sending untreated sewage directly into the river and out to sea. But dry weather doesn’t guarantee clean water either, because the underlying infrastructure failures create a constant baseline of pollution.
How Coronado’s Water Gets Tested
San Diego County tests beach water using a DNA-based method called droplet digital PCR, which detects bacterial contamination faster and more accurately than older lab culture techniques. Results come back the same day samples are collected and are posted publicly at sdbeachinfo.com. The county monitors several Coronado locations, including North Beach and multiple points along Silver Strand.
On any given day, some of these sites may carry advisories (elevated bacteria levels) or full closures (bacteria high enough that entering the water poses a clear health risk). As of early 2025, the San Diego coastline regularly shows a mix of active advisories and closures, with beaches closer to the border hit hardest. Coronado sits in a middle zone: not as consistently impacted as Imperial Beach, but far from immune.
Health Risks of Swimming in Contaminated Water
Sewage-contaminated ocean water contains bacteria, viruses, and parasites that can make you sick even if the water looks and smells fine. The most common illnesses from contaminated recreational water are diarrhea, skin rashes, ear infections (swimmer’s ear), and respiratory symptoms resembling the flu. Diarrhea outbreaks are the single most reported swimming-related illness.
One pathogen of particular concern is Cryptosporidium, a parasite that can survive in water for over a week and causes life-threatening symptoms in people with weakened immune systems. Children, older adults, pregnant women, and anyone who is immunocompromised face higher risks from exposure. Swallowing even a small amount of contaminated water is enough to cause infection.
How to Check Before You Go
The most reliable step is checking sdbeachinfo.com on the day of your visit. The site lists current advisories, warnings, and closures for every monitored beach in the county, updated with same-day test results. If Coronado North Beach or any Silver Strand location shows an advisory or closure, stay out of the water.
Beyond the daily postings, San Diego County issues a blanket rain advisory for all coastal waters whenever rainfall exceeds roughly 0.2 inches. Stormwater runoff pushes bacteria levels up dramatically, especially near storm drains, rivers, and lagoon outlets. The county directs beachgoers to avoid contact with ocean water for at least 72 hours after rainfall ends. This rule applies to every beach in the region, including Coronado. Even if you don’t see an active advisory posted, treating the 72-hour window as a firm boundary is the safest approach.
What’s Being Done About It
The South Bay International Wastewater Treatment Plant, operated by the U.S. section of the International Boundary and Water Commission, is the primary facility meant to intercept and treat sewage flowing north from Mexico. A major rehabilitation and expansion project is underway, currently in the pre-design phase. The project has received substantial federal investment: over $300 million was initially secured through the 2020 U.S.-Mexico-Canada trade agreement, and total U.S. investment has grown to roughly $650 million.
In 2025, the U.S. and Mexican sections of the boundary commission signed a new agreement called Minute 333, which commits both countries to a list of infrastructure projects, enhanced monitoring, and long-term planning that accounts for Tijuana’s population growth. The agreement does not obligate additional U.S. taxpayer funding, instead pressing Mexico to invest in repairs on its side of the border. Previous agreements, including Minute 328 signed in 2022, were widely viewed as insufficient.
These are large-scale infrastructure projects with long timelines. Expanded treatment capacity won’t come online overnight, which means Coronado’s water quality will likely remain inconsistent for years. Until the underlying sewage infrastructure on both sides of the border is fully operational, contamination events will continue to follow storms and equipment failures.
Is Coronado Beach Safe Right Now?
Coronado Beach is not permanently contaminated, but it is regularly affected by contamination that fluctuates with weather, currents, and the state of cross-border sewage infrastructure. On many dry-weather days the water tests clean and swimming is fine. On other days, bacterial counts spike high enough to trigger advisories or closures. The sand and the beach itself remain usable year-round for walking, sunbathing, and other dry activities. The risk is specifically about water contact.
Your best tool is the county’s daily testing data. Check sdbeachinfo.com before any visit where you plan to swim or surf, avoid the water for 72 hours after any measurable rain, and pay extra attention during winter and early spring when storms are most frequent. If you’re visiting with young children or anyone with a compromised immune system, treat any advisory as a reason to stay on the sand.