How does beach bacteria get so high?

Among the 10 beaches on the nonprofit’s statewide “Beach Bummer” list were Lakeshore Park in San Mateo’s Marina Lagoon, Linda Mar Beach in Pacifica and Half Moon Bay’s Roosevelt Beach and Surfers Beach. Though the three coastside beaches were new on the list, the enclosed beach at Lakeshore Park has drawn concern from the nonprofit for years, making it onto the list five times in the last decade, according to the report.

With pump stations, a goose management program and chemical applications to manage the growth of algae and weeds in place at Marina Lagoon, San Mateo city officials have been using a multi-pronged approach to counteract the weak circulation allowing bacteria growth near the beach at Lakeshore Park, said Deputy Public Works Director Gary DeJesus.

“This is not a new problem,” he said. “It’s been an ongoing problem, and it’s a natural problem due to drainage into the lagoon.”

Positioned along a series of the lagoon’s inlets, the enclosed beach at Lakeshore Park is subject to the weak circulation and shallow depths allowing algae and other vegetation to grow in the lagoon, explained DeJesus. He said nutrients created when vegetation growth and algae decay can invite other aquatic life and plants to grow in and near the water.

Through periodic monitoring of water quality at the lagoon over the years, DeJesus said animal waste — specifically that left by geese — has been pegged as a major factor in the fluctuations of bacteria levels logged at the park. As part of a geese management program the city has developed over the years, DeJesus said officials have hired a team with a dog trained to chase geese away from the area and picked up droppings.

DeJesus said the lagoon’s natural position combined with its role as a place where storm runoff and water from lawn sprinklers collects also make it susceptible to higher bacteria levels. He said city officials test water at the beaches weekly and advised residents to heed signs advising visitors not to swim in the water that officials post when levels rise.

“Just actually going to the beach and picnicking is not a problem [when bacteria levels are high], it’s water contact that creates the problem,” he said.

Though the city’s goose management and vegetation control programs are currently underway, DeJesus looked to longer term projects to help mitigate the problem. Those include capital improvements to the city’s sanitary sewer system to take shape in the next year, an effort to explore deepening the lagoon by dredging sediment out of it and installing updated stormwater infrastructure able to filter water.

Those who come in contact with high bacteria levels in water run the risk of ear and upper respiratory infections and even stomach flu, in some cases, said Karen Vu, beach water quality analyst at Heal the Bay. To avoid the negative health effects of beaches with advisories, Vu said visitors should avoid the water — especially putting one’s head under the surface — and to wash off afterwards if one does have contact with it. She noted enclosed beaches like Lakeshore Park are typically popular with families with kids to keep them away from bigger waves found at coastside beaches.

“Unfortunately, these enclosed beaches are really popular with families with young children because there are fewer waves,” she said.

Though residents may seek Pacific-facing beaches with access to creeks because they may seem safer, creeks and storm drains near the three coastside beaches on the nonprofit’s list may be behind their elevated bacteria levels, said Greg Smith, supervisor of water protection and land use programs at the county. Smith said some of the water quality changes recorded as county officials monitor some 20 Pacific-side beaches, 13 corresponding creek mouths and six Bayside swimming beach locations may be attributed to fecal loads building up over the course of the drought that have been washing into creeks and stormwater flows with the rain that came this past winter.

Smith said county officials prioritize outreach to residents when water quality at county beaches shift through signs at beaches, email notifications and a telephone hotline, among other efforts. But he said they’ve also been spreading the word to residents about ways they might be contributing to the water quality at beaches, noting droppings from pets and other wildlife can contain bacteria and become washed into stormwater flow.

“One of the hardest jobs officials have is making the public aware of how they contribute to the poor water quality at our beaches,” he said in an email.

Visit smchealth.org/beaches for water quality updates at county beaches and to sign up for weekly beach and creek sample results. Visit healthebay.org/beach-report-card-2018 to read Heal the Bay’s full report.

anna@smdailyjournal.com

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