California's most polluted beaches ranked in Heal the Bay's 2024 report

Heal the Bay has released its annual report ranking the most polluted beaches and best kept oceanwaters along the West Coast.

The report, published Wednesday by the nonprofit, examines bacteria levels and looks at how frequently beaches are monitored in giving them each a grade between A and F. While some of the dirtiest beaches listed are in Los Angeles County, and other parts of Southern California, an estimated 90% of beaches along the West Coast — from Washington state down to the region surrounding the U.S.-Mexico border — had oceanwaters that were safe to swim in during summer of last year, Tracy Quinn, the nonprofit's CEO and president, said Wednesday.

For the first time, San Diego County's Imperial Beach made Heal the Bay's Top 10 Beach Bummers, a list of the most polluted beaches along the West Coast. Imperial Beach has struggled for years with pollution stemming from sewage coming out of the Tijuana River, with nonprofits such as the Surfrider Foundation and even the city of Imperial Beach filing lawsuits over the long-running issue. 

Meanwhile, the beach surrounding Santa Monica Pier nabbed the No. 3 spot for the Top 10 Beach Bummers. Last year, the beach topped the list but Heal the Bay said improvements such as a a stormwater capture system have helped improve conditions.

At the No. 1 spot is the Tijuana River Mouth, struggling with the same sewage-derived pollution issues facing Imperial Beach. Just a little further south, Playa Blanca beach in Baja California comes in at No. 3 with Heal the Bay reporting that the nearby Punta Bandera treatment plant discharges millions of gallons of only partially treated wastewater into the waters there.

Among the other top 10 dirtiest beaches are two in Northern California's San Mateo County and another in LA County. 

Below are the Top 10 Beach Bummers, the most polluted of the West Coast, according to Heal the Bay's report — which gave them each an F grade.

• 1. Tijuana River Mouth in San Diego County
• 2. Playa Blanca in Baja California, Mexico
• 3. Santa Monica Pier in Los Angeles County
• 4. Tijuana Slough in San Diego County
• 5. Linda Mar Beach in San Mateo County
• 6. Lakeshore Park in San Mateo County
• 7. Imperial Beach at Seacoast Drive in San Diego County
• 8. Border Field State Park in San Diego County
• 9. Marina Del Rey Mother's Beach at Lifeguard Tower in Los Angeles County
• 10. El Faro in Baja California, Mexico

Some of the factors contributing to high bacteria levels leading to dirty beaches are fuel emissions, poor air quality in the surrounding areas and aging infrastructure, such as nearly century-old sewer pipes, according to research from Heal the Bay. However, climate change was a notable contributor to the unusually high bacteria levels reported last year, Quinn said, with higher than usual rainfall turning into stormwater runoff polluting waters along the coastline.

Annalisa Moe, a water quality scientist at Heal the Bay, said sewage spills are also a major contributor to poor water quality, with 38 million gallons of sewage dumped in California's coastal waters last year. 

Meanwhile, Heal the Bay's "Honor Roll" list — naming the least polluted beaches which are also the most frequently monitored for water quality — included nine beaches in Orange County, two in San Diego County and one in Ventura County.

Heal the Bay notes that beaches in Northern and Central California are often not eligible for that list since many counties in those parts of the state do not typically monitor water quality levels year-round, which is a requirement to make the list.

The full list of "Honor Roll" beaches and other information on how beaches were ranked can be found in the full annual report.