A new study by San Diego State University scientists finds that bacterial outbreaks in the San Diego River that often close local beaches are caused primarily by leaks in aging sewer pipes, not homeless encampments or faulty septic tanks.
Environmentalists are calling the study a warning to local sewer agencies and political leaders, arguing that quick and large financial investments are needed to upgrade many local sewer lines that are more than 50 years old.
The cost of replacing the pipes, which could run into the billions of dollars, would be passed on to sewer and water ratepayers by the sewer agencies that fund the upgrades.
Fecal bacteria in the San Diego River is a big problem because the river empties into the ocean, potentially polluting the water and closing beaches that attract tourists and are often used by many local residents for swimming, surfing and other activities.
Recent beach closures in Coronado and Imperial Beach are unrelated to the bacteria outbreaks in the San Diego River. These dams are the result of sewage being released south of the international border.
The study came about two years before a more comprehensive analysis of the sources of bacteria in the river was due to be completed.
The San Diego Regional Water Quality Control Board ordered this analysis in 2019 when it found the river had persistently high levels of bacteria, so it ordered the study to be completed by sewer agencies in San Diego, El Cajon, La Mesa, Santee and nearby areas in the lower part of the river basin.
“I guess the SDSU study is a precursor to what the larger study will show,” said Matt O’Malley, executive director of San Diego Coastkeeper. “This study confirms a lot of what we thought. All signs point to aging and leaking wastewater infrastructure across the region.”
The SDSU study attempted to pinpoint the source of fecal matter in the river by testing for the presence of two substances used only by humans—caffeine and an artificial sweetener—as well as a virus and bacteria commonly found in human feces.
“We were interested in where it came from,” said SDSU environmental engineering professor Natalie Mladenov, lead author of the study.
Local officials have already said the most likely sources of fecal material in the river are leaking sewer pipes, illegal dumps, broken septic systems and homeless encampments where there are no toilets.
The two-year study analyzed how long caffeine, the artificial sweetener sucralose, the bacteria HF183 and the RNA virus PMMoV were present in the river water – and at what concentrations.
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For example, caffeine leaves wastewater faster than most other chemicals, so it is not expected to be in high concentrations in the river for long. Since the study showed that caffeine is in high concentration in the river, the caffeine must come from a relatively fresh source.
Based on this, the researchers conclude that homeless encampments and septic tanks, where caffeine is expected to dissipate fairly quickly by the time the pollution enters the river, are not likely sources of fecal material in the river.
And as a result, the study concludes that the most likely sources of fecal matter are leaky sewer pipes.
The study analyzed the locations of 13 homeless camps along the river. There are also approximately 17,000 septic tanks in the river basin.
One thing the SDSU study didn’t analyze was whether the leaks were coming from municipal sewer lines or “private laterals” — privately owned pipes that connect homes to municipal sewers.
O’Malley said this will be a key decision going forward. If the problem is mostly utility lines, sewer agencies must replace the leaking pipes. If the problem is mostly private pipes connecting homes to the system, agencies may need to encourage property owners to upgrade those pipes.
A relatively new idea is that leaking pipes may be to blame for beach closures.
For years, local swimmers were told to stay off the beaches for 72 hours after rain because polluted city runoff washes into rivers and then into the ocean.
Conventional wisdom has been that heavy rains make ocean water dangerous because the rain picks up chemicals and bacteria as the water washes over concrete, sidewalks and other hard surfaces. But that could turn out to be misleading if leaking sewer pipes become the main source of bacteria during storms.
Some scientists believe that untreated sewage, which slowly flows out of pipes, mostly stays put when it doesn’t rain. But in a rainstorm, these leaked sewage quickly wash into local waterways in large quantities.
San Diego officials, including Mayor Todd Gloria, often acknowledge that the city’s aging infrastructure — including its sewer lines — is in dire need of major upgrades and repairs.
In February, the city’s infrastructure backlog topped $4 billion for the first time.
“There were so many more assets built in the 1950s and 1960s than before that period, and those assets are now maturing — they’re reaching the end of their useful life,” said James Nagelvoort, the city’s longtime chief public works official. “So we should anticipate a greater volume of things to address as we look to the future.”
A city spokesman did not comment directly on the SDSU study Friday, but said the city’s sewage spill rate is 0.04 spills per 100 miles of pipeline. This rate does not take into account any additional leakage in the pipelines.
Spokesman Arian Collins also said the city has identified several pipe segments as potential candidates to understand if the sewer leak is affecting the river.
Mladenov, lead author of the SDSU study, said she hopes the research will spur action. The study will be published in ES&T Water, a journal of the American Chemical Society.
“We want it to be relevant, not just on the shelf,” said Mladenov, who came to the university eight years ago from Colorado.
La Jolla Beach One of San Diego’s best beach destinations for families, La Jolla offers the gentlest waves along its mile-long coastline. On this beach, you can join a diving course and watch sea lions and seals lounging in the bays.
Which beach has the clearest water in California?
If you want to experience the cleanest water in California where you can snorkel, kayak, swim and have a crystal clear view of the marine life in the water, then you will fall in love with La Jolla Cove Beach, the cleanest beach in California.
Does California have any white sand beaches? Carmel City Beach is a long, wide white sand beach that’s hard to beat anywhere on California’s Central Coast.
What is the best beach to swim in California?
Here are our top 10 swimming beaches in California:
- Santa Monica Beach.
- Venice Beach.
- Coronado Island.
- Manhattan Beach.
- Hermosa Beach.
- Huntington Beach.
- Catalina Island.
- Moonlight State Beach.
What is the warmest beach to swim in California?
The Balboa Peninsula provides shelter from the open Pacific, making Newport Beach’s waters the warmest in California year-round.
Are California beaches swimmable?
California in the USA is an ideal destination for surfing, swimming and lying on the beach. Laguna Beach, Venice Beach and Newport Beach are the trademarks of the California coastline and attract millions of water users each year.
Can you see Mexico from Coronado?
Coronado Island Tour The views by car from the graceful blue arch of the iconic San Diego-Coronado Bridge are second to none! You can see all the way to Mexico and the ‘lil Islas Coronadas (Crowned Islands) off the coast.
How far is coronado from the mexico border? The largest and closest island, South Coronado, is located approximately 13 km (8 mi) from the Mexican mainland and 12 km (7 mi) south of the sea border with the United States.
What islands are visible from San Diego?
If you’ve ever looked out into the ocean from San Diego toward Mexico, especially on a clear day, you’ve probably seen the Coronado Islands just off the coast. This group of four islands is located about 15 miles south of San Diego and 8 miles off the coast of Mexico.
What are the islands off Point Loma?
The Coronado Islands (Islas Coronado or Islas Coronados; English: Islands of the Coronation(s); Kumeyaay: Mat hasil ewik kakap) are a group of islands located 13 km (8 mi) off the northwest coast of the Mexican state of Baja California. .
What islands are off the California coast?
Known as the Galapagos of California, these five islands cover approximately 250,000 hectares of land and are known for their stunning scenery and biodiversity… Here are the five islands:
- Anacapa Island.
- Santa Cruz Island.
- Santa Rosa Island.
- Santa Barbara Island.
- San Miguel Island.
How far offshore is Coronado Island?
The Coronado Islands are a group of 4 islands off the coast of Rosarito, MX that are about 7 miles offshore (but still visible as you drive along scenic Highway 1 down Baja). They are about 15 miles south of San Diego proper and a short boat ride away.
Are the Coronado Islands in Mexican waters?
The Coronado Islands (Islas Coronado or Islas Coronados; English: Islands of the Coronation(s); Kumeyaay: Mat hasil ewik kakap) are a group of islands located 13 km (8 mi) off the northwest coast of the Mexican state of Baja California. .
How many miles long is Coronado Island?
Coronado Island is about 1 mile long and wide and extends another 8 miles along the Silver Strand/Highway 75 to the Loews Coronado Bay Resort in the Coronado Cays.
What is the best beach for swimming in San Diego?
12 Best Swimming Beaches in San Diego
- Aerial view of La Jolla Bay. …
- A beautiful sandcastle in front of Hotel Del Coronado. …
- Surfer at Del Mar City Beach. …
- A beautiful sea beach. …
- Nice open beach at Fletcher Cove Beach. …
- Aerial shot of Mission Beach with South Mission in the distance.
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