by Thomas K. Pendergast
To decrease San Francisco’s dependency on the Hetch Hetchy water system, which delivers water from the Sierra Nevada Mountains, the SF Public Utilities Commission (SFPUC) and the SF Recreation and Park Department are in the process of switching to “recycled” water for irrigating Golden Gate and Lincoln parks and the Presidio.
The water will be used strictly for watering lawns and bushes, filling lakes and the like, but will not be for the public to drink.
Currently, the department uses a combination of drinking water and ground water for irrigation, but the ground water is increasingly being used to supplement the drinking water supply.
The $214 million project includes construction of a new recycled water treatment facility, which will be located within the boundaries of the commission’s Oceanside Wastewater Treat ment Plant, which sits just south of the San Francisco Zoo, and the construction of almost eight miles of new pipelines under city streets to convey the recycled water to irrigated areas.
The project also includes the construction of an 840,000 gallon underground reservoir, and an above ground recycled water pump station in Golden Gate Park.
The pump station will also transport recycled water to Lincoln Park and the Presidio.Construction began in early 2017 and recycled water deliveries are scheduled to begin in early 2021.
The funding is coming from bond money, including the $4.6 billion Water System Improve ment Program and Water Enterprise Bonds.
The plan was first introduced in 2010, except back then it was with the water treatment plant located near the western end of Golden Gate Park. This raised a host of concerns among local activists and neighbors, who pointed out that the SF Recreation and Park Department was attempting to evict the Haight Ashbury Neighborhood Council (HANC) recycling center out of the park because, so the argument went, the park’s Master Plan expressly forbids construction of facilities for “industrial use.”
So, rather than keep the recycling center in the park, city planners decided to look for an alternative location for the water treatment plant. Suzanne Gautier, a representative of the SF Water Department, said opposition to the Golden Gate Park site motivated the SFPUC to move it.
“We went back and revisited all of the potential sites that had been explored during the initial process, and there were several options explored and … the determination was made that the Oceanside Plant provided unique opportunities, one of which is it’s within the footprint of the property so there would be no impact to a neighborhood because of the building of a recycled water facility,” Gautier said. “It’s right there inside the footprint.”
The plant now treats residential wastewater from the west side of San Francisco, which goes through several treatment processes to produce “secondary effluent,” which is then discharged into the Pacific Ocean.
The new recycled water treatment facility will take a portion of this secondary effluent flow prior to its discharge into the ocean and treat it further with membrane filtration and reverse osmosis. The recycled water will then be disinfected with ultraviolet light prior to being delivered for irrigating the Golden Gate Park and the Lincoln Park and Presidio golf courses.
The water produced by the state-of-the-art treatment technologies is known as “advanced” treated recycled water, according to the SFPUC. Reverse osmosis removes salt, nutrients and ammonia from water. The treatment technology was selected for the Westside Enhanced Water Recycling Project because the primary uses of recycled water will be for irrigation and filling lakes at Golden Gate Park.
According to the SFPUC, using the higher level of treatment will minimize the potential impacts of salts (sodium, chloride) on park vegetation, and of nutrients (nitrogen, phosphorus) and ammonia on park lakes.
The goal is to save potable water currently used for irrigation and other non-potable applications. The commission says this will make the drinking water supply less vulnerable to risks, like earthquakes and droughts, while helping meet the City’s long-term needs.
Barbara Palacios, an engineer and project manager with the SFPUC, said project overseers are aware of the concerns about cross-contamination with the water used in drinking fountains throughout the park and have a plan to deal with it.
“Part of the changes would be to disconnect those areas from the potable system, so once they are connected to the recycled water system they will be disconnected from the potable system and we would undergo an extensive series of testing to make sure that the two systems aren’t what we call ‘cross connected,’”
Palacios said. “There’s a cross-connection test that we have to perform that will be overseen by our own internal folks as well as regulators, to demonstrate that they are completely separate.”
Categories: Recycled Water