The plan to cure sickly Lake Merced: Here’s how it works

Projects underway to raise water levels with treated stormwater

Mondy Lariz spent his boyhood years learning how to fish at Lake Merced through a program sponsored by the San Francisco Police Department. It was a way to connect with the natural world, he said, and it kept him out of trouble.

“I never forgot (how) that sort of helped me stay away from gang problems,” he said. “It was really formative.”

But as the greens of surrounding golf courses and cemeteries were irrigated from deep wells, and urbanization crept into the area, water levels dropped dramatically. By the 1990s, many declared the lake dead.

Conditions have since improved, thanks in part to advocates like Lariz who pushed The City and golf courses to irrigate with recycled water and conserve the lake’s natural habitat.

But to many, Lake Merced remains a greener, murkier, sicklier version of itself.

“I would never swim in that,” said Ameen Kunbargi, who leads Friends of Lake Merced, noting that water quality also has degraded over time as urban runoff seeped into the lake, affecting dissolved oxygen and pH levels.

Recently, the lake has also been impacted by drought. “If we don’t get rain, there is really no significant recharge for the lake,” said Obiajulu Nzewi, a regulatory specialist at San Francisco’s Public Utilities Commission (SFPUC), who said that shallower waters warm more quickly. “Then the algae start doing their thing,” he said.

But this could be changing soon. A project spearheaded by the Daly City Department of Water and Wastewater Resources and SFPUC is underway to redirect and filter stormwater, returning some to Lake Merced.

The Vista Grande Drainage Basin Improvement Project, which has been in the works for years, is slated to accomplish two goals. The first would relieve the heavy flooding that accumulates in Daly City’s Vista Grande Basin — a roughly 2.5-square-mile area encompassing about one-third of The City. The second would replenish the waning water supply of Lake Merced, a natural lake, dependent upon precipitation and groundwater.

Part of the project’s goal is to restore the area’s historic watershed. The Vista Grande Basin “used to drain to Lake Merced back before we built everything,” said Nzewi, “so part of this is also returning, or trying to return at least some function of the historical watershed to how it used to work before.”

Still, the future of Lake Merced remains unclear. As climate change prolongs drought periods and brings about more extreme storms, the freshwater lake that was once used as a source for The City’s drinking water will continue to be vulnerable to such fluctuations.

In an environmental impact report from 2017, the Olympic Club, which owns and operates one of The City’s most exclusive golf courses in the area, raised concerns about the project’s scope, saying it did not take into account the changing climate.

“Olympic is quite concerned about what will happen in a more severe storm, particularly in light of what Olympic understands to be the current scientific consensus about the types, magnitudes, and frequency of recurrence of storms that might be predicted as a result of climate change,” the report said.

But Daly City claims it’s taking the latest projections into account. “We’ve been looking at all, as best we can, up-to-date data on climate change and what that means to the project,” said Joshua Cosgrove, the assistant director of Water and Wastewater Resources.

The design of the project is now complete, said Cosgrove, but Daly City continues to work with agencies like the California Coastal Commission and the U.S. Army Corps of Engineers to finalize the permitting and financing processes before construction can begin.

“Obviously, it is a very complex project with multiple agencies and permitting,” said Paula Kehoe, director of water resources at SFPUC.

Despite its complexity, the project has garnered support from environmental organizations including Cal Trout, which once hosted an annual fishing event called Trout Days at Lake Merced. (That program was discontinued due to water quality issues and because the California Department of Fish & Wildlife did not want to introduce fish to an environment where they were unlikely to survive.)

Patrick Samuel, regional director with Cal Trout, said of the project: “It can be a huge boost if done well. I think with anything like this, the devil’s in the details.”

Others remain concerned about redirecting stormwater, which picks up oils and pollution as it flows from city streets, into the lake. “If you’ve ever seen stormwater — it is putrid,” said Kunbargi. “If you’re paddling your boat and you get a splash of water on your lip, you’re exposing yourself to all those pathogens.”

According to SFPUC, water from an initial rainstorm would drain directly to the ocean through Fort Funston to eliminate the first flush of pollutants into the watershed. Subsequent stormwater would then be filtered for litter, such as cigarette butts, and sent through two constructed wetlands, further filtering the water before it would enter the lake.

SFPUC is also in the early stages of evaluating the feasibility of using excess supply from the soon-to-be-completed Westside Enhanced Recycled Water Plant, which would provide an additional water supply to manage lake levels.

“The advantage of this, if feasible, is that the supply would be independent of rainfall or precipitation,” said Will Reisman, spokesperson for the SFPUC.

With continued restoration efforts on the horizon, environmental groups like Cal Trout remain hopeful that there might be more Trout Days in the lake’s future. “I think our message is sort of one of optimism,” said Samuel. “There’s been problems out there for a long time, but we’re looking forward to the changes that we think will improve things.”

jwolfrom@sfexaminer.com

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