Controlling algae growth and high levels of fecal bacteria in San Mateo’s Marina Lagoon requires consistent maintenance and, while the city will continue with its current vegetation management contractor, it’s still looking for solutions to control the excessive bacteria.
Residents living near the lagoon expressed concern at a March 17 council meeting when the city considered switching providers for the lagoon’s algae management and prompted the council Monday night to extend the contract with its current provider, Aquatic Environments, Inc. through Oct. 31.
However, some are more concerned with high levels of fecal bacteria in the lagoon that can cause illness.
The lagoon, which spans between State Route 92 and east of Highway 101, serves two purposes.
“For summertime, it’s for recreational use and then in the wintertime, it’s for storm control events,” said Interim Public Works Director Ray Towne.
There are two aspects in managing the water quality — algae growth and bacteria levels, Towne said.
Controlling algae is important because it can give off a foul odor and propellers of boats can get stuck, Towne said. The growth is offset by chemically treating it or harvesting it, Towne said.
The city has a clear plan for managing algae growth, however, it has yet to identify the source of excessive bacteria levels and how to control it.
Water samples are taken from the lagoon’s Aquatic and Lakeside parks’ beaches and between 18 to 50 percent of the time there is excessive bacteria, said Jan O’Hara, a water resource control engineer with the Regional Water Quality Control Board.
“It’s not really uncommon to find pathogen exceedances in an urban area. There’s paving areas because that allows things to flow really quickly into a water body and not get trapped into the soil that would get cleaned up naturally. ... Where there’s a high density of pets you will find pathogens in the water,” O’Hara said.
Yet the Marina Lagoon has higher levels of fecal bacteria than many other beaches along the Bay, including Foster City, O’Hara said.
Swimming in water with excess fecal bacteria can cause infections in the eyes, ears, nose and respiratory system that could leave one feeling sick for a few days, O’Hara said.
Planning Commissioner Rick Bonilla has become increasingly concerned by the public’s willingness to expose themselves at the Marina Lagoon. He often sees children swimming in the lagoon and people ignoring signs warning when there are high levels of bacteria, Bonilla said.
High fecal bacteria levels are typically found on the ocean side, but it’s becoming prevalent in the Bay so the State Water Resources Control Board is working on studying the Marina Lagoon, two beaches in Marin County and three locations in San Francisco, O’Hara said.
Before it can recommend an action plan, it must identify the contributing source of the high fecal bacteria levels, O’Hara said.
Depending on what it finds, it may recommend San Mateo evaluate its sewage infrastructure, educate people about their effects on the watershed, reduce the lagoon’s exposure to trash and possibly flush the lagoon to deter stagnant water, O’Hara said.
Conducting the studies, recommending plans and resolving the bacteria problem will likely take at least two years, but San Mateo is on board and dedicated to finding a solution, O’Hara said.
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