Seven of the Pacific Coast’s filthiest beaches are along the San Diego and Baja California shoreline that is contaminated by Tijuana sewage, according to a report by Heal the Bay, and Coronado did not make the top 10 list.
Heal the Bay is a Santa Monica based non-profit founded in 1985 that is dedicated to protecting local waterways. For 34 years, they have released a report card issuing A through F grades to beaches along the Pacific Coast based on levels of bacterial pollution in the last year.
Their 2023-2024 report from July lists several San Diego County beaches as the top 10 dirtiest among a total of 700 graded beaches, confirming the poor conditions prompted by transborder sewage flows from Tijuana.
While Imperial Beach is ranked No. 7, Coronado did not receive any grade below a ‘C’.
Those findings are starkly different from what San Diego County’s Health officials have put out. They found the the beaches so contaminated with fecal bacteria that water contact closure signs were placed on beaches.
According to the County, they issued a total of 192 intermittent water contact closure days for Coronado’s Avenida Lunar to North Beach between April 2023 to March of this year due to sewage contamination. For recreational waters along the Silver Strand shoreline, that was 288 days.
In an email to The Coronado News, Tammy Glenn from the county’s communication office listed four ways that the county’s testing protocol is better.
“The ddPCR method is faster than the culture method, and it is also impacted less by environmental factors, allowing it to be more accurate in measuring bacteria and illness risk,” Glenn said.
Phillip Musegaas, executive director at San Diego Coastkeeper, said his organization uses the county’s results to track San Diego County beach advisories and present this information to the public daily online.
The San Diego Coastkeeper team, whose mission is to protect and restore swimmable, drinkable, fishable waters in San Diego County, considers ddPCR more accurate and more protective of public health, he said.
“From Coastkeeper’s perspective, relying on the ddPCR data for Coronado beaches, we would not give them an A during that time period,” wrote Musegaas. “In general, [Heal the Bay’s] report is translating raw data into a grade, so just looking at the direct ddPCR data and observing how frequently the result exceeds the threshold is going to be more accurate.”
Heal the Bay uses data from the traditional culture-based testing method to conduct their analysis, but San Diego County has used the droplet digital polymerase chain reaction (ddPCR) method since 2022, a method which, according to Heal the Bay’s report, has a “heightened sensitivity.”
The Tijuana River Mouth (No. 1), Tijuana Slough (No. 4), Imperial Beach at Seacoast Drive (No. 7) and Border Field State Park (No. 8) are some of the most polluted beaches, earning an ‘F’ grade for summer, or dry weather conditions.
Tijuana’s Playa Blanca (No. 2) and El Faro (No. 10) are also on that list, with the former appearing since 2021.
Meanwhile, other San Diego waters “demonstrated exemplary water quality resilience,” including Point Loma Lighthouse and Moonlight Beach.
“Imperial Beach has never been on our Bummer list before so its inclusion this year likely indicates that the problem/pollution is worsening,” wrote Katherine Pease, Heal the Bay’s director of science and policy, in an email to The Coronado News. “In the past, the pollution was not being detected at Imperial Beach with the culture-based method being used and likely due to mixing of the ocean water.”
“The report reinforces what we already know,” said Coronado Mayor Richard Bailey. “The Tijuana sewage issue disproportionately affects the South Bay region, specifically Imperial Beach beaches.”
Why did Coronado beaches get good grades?
Since 2020, parts of the Tijuana Slough near the Tijuana River mouth in San Diego County have made the Beach Bummers list annually. This year, two of its locations got an ‘F’ year round.
Beaches in Imperial Beach at Seacoast Drive and Carnation Avenue followed suit with the latter beach earning a ‘D’ grade for the winter dry period, between Nov.1 and March 31.
On the contrary, the Coronado and Silver Strand shoreline collectively got ‘A’ grades for the year except one ‘C’ winter dry grade for Silver Strand.
In 2022, the county became the first in the nation to use a new method called ddPCR, which they said tests for fecal indicator bacteria DNA and was to be used daily at beaches impacted by cross border sewage from Mexico and the Tijuana River Valley.
The report’s authors acknowledged this change but continued with a grading system that uses culture-based sampling which requires growing bacterial cultures from water samples in petri dishes.
“Although Heal the Bay supports the adoption of ddPCR for its rapidity and precision, our current Beach Report Card grading system is designed for data from cultured bacteria, posing compatibility issues,” reads the report.
Heal the Bay confirmed they graded beaches in Tijuana, Imperial Beach and Coronado using culture-based testing data obtained from local agencies made available at a database from the California State Water Resources Control Board (SWRCB).
“…Water quality at Coronado beaches was good enough that none of them landed on the Beach Bummer list and some even got A grades,” wrote Pease.
Tania Pineda, a water quality data and policy specialist at Heal the Bay, said ddPCR results differ from those of culture-based methods.
“The county is only using ddPCR to test for enterococcus, instead of all three major fecal indicator bacteria, which other counties test for across the state,” explained Pineda in an email.
County no longer using culture testing
Since implementing the ddPCR method in May of 2022, the county said they no longer use culture testing for its program managing beach water safety.
“Beach water monitoring conducted and reported to the public by the county allows people to make their own informed decisions on water quality conditions and their own health risks,” Glenn said.
The County said Heal the Bay’s “conversion factor” to compare locations in an annual report is very different from years of thorough research and side-by-side testing conducted by federal, state, regional, and local agencies to authorize the County’s use of the ddPCR testing method.
Heal the Bay said they used a recommended conversion factor to see how often the ddPCR results exceeded California’s state approved standards between April 1, 2023 and March 30, 2024.
Their analysis revealed that in 50% to 76% of samples taken, these beaches exceeded standards—a significant increase from the 5% to 10% exceedance rates observed with older culturing methods, reads the report.
“This discrepancy does not necessarily indicate higher pollution levels but rather reflects the heightened sensitivity of ddPCR testing,” the report continues. “Heal the Bay is actively exploring ways to integrate ddPCR data into our Beach Report Card framework. Meanwhile, we recommend that San Diego County continue to use traditional culturing methods alongside ddPCR to ensure consistent water quality assessments until these methodological discrepancies can be fully addressed.”
Amid the scientific and political confusion, meanwhile, Pease said Coronado residents and visitors should educate themselves and take reasonable precautions.
“We recommend that beachgoers arm themselves with as much information as they can, relying on more recent information for real-time decisions,” added Pease. “For instance, children are more susceptible to ingesting water and have less well-developed immune systems so if you’re planning a beach day with young children, we would recommend utilizing the most conservative advisory or closure information.”
