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Seeking to squeeze more value out of wastewater, the Palo Alto City Council approved on May 13 the construction of a $63-million salt-removing plant in the Baylands.
Known as the Local Advanced Water Purification System, the plant will go up at the periphery of the Regional Water Quality Control Plant, the industrial facility at 2501 Embarcadero Way that serves Palo Alto, Mountain View, Los Altos, Los Altos Hills, Stanford University and the East Palo Alto Sanitary District. It will consist of three structures: a 30-foot-tall storage tank, an open-air building and a prefabricated building. They would go up at the northwest side of the regional plant, next to Embarcadero Road.
Unlike other advanced purification systems, the new Palo Alto plant will not make wastewater safe for drinking. It will, however, make more wastewater suitable for irrigation and industrial uses an allow the city to expand the “purple pipe” network that currently brings recycled water to Greer Park, to the Bay Links Golf Course and to dozens of commercial customers in Mountain View.
“That higher-quality recycled water decreases potable water demand for irrigation uses,” project planner Claire Raybould said during the May 13 hearing on the project.
The additional recycled water would mostly flow to Mountain View, which will be charged with repaying the state loan that is enabling the construction. In Palo Alto, there is currently no demand for higher-quality recycled water, according to a report from the Department of Planning and Development Services.
Plans for the salt-removal plant have been in the works for well over a decade. In 2010, the City Council adopted a policy to reduce the level of total dissolved solids of recycled water to 600 parts per million, safe enough to make it palatable to redwood trees and other salt-sensitive species. The project received a boost in 2019, when Palo Alto reached a 76-page agreement with the Santa Clara Valley Water District that obliged the water district to pay $16 million for the new plant, which at the time had an estimated cost of $20 million.
Though the costs have more than tripled since then, the partner agencies have been able to tap into new funding sources, including a $12.9 million grant from the U.S. Bureau of Reclamation and a state loan of $34.7 million, which will be covered by Mountain View.
On May 13, the project received its final green light when the council swiftly and unanimously approved the site and design application that was required to advance the project, which will rely on an industrial process known as reverse osmosis to filter salt out of wastewater. The storage tank will be able to hold 350,000 gallons of wastewater.
If things go as planned, construction would begin early next year and conclude in the summer of 2027, Raybould said.
For the design team, a key challenge has been making sure that the new treatment plant will be compatible with the Baylands habitat. Over the course of the review process, plans had been revised to integrate more native plants into the design and to make sure that the lighting is soft enough to not disrupt birds and other Baylands denizens.
Shani Kleinhaus, an environmental advocate with the Santa Clara Valley Audubon Society, pushed the city to lower the color temperature of the lighting at the plant to 3,000 kelvins, well below the level of the 5,000 threshold that was initially proposed.
“Lights with lower color temperature, typically below 3,000 kelvins, have warmer color and have been shown to be less impactful and harmful to the environment, less impactful on natural behavior and activity of nocturnal animals and also less harmful to the health of night workers – people who work the night shift,” Kleinhaus told the council.
The city’s Architectural Review Board ultimately accepted that suggestion, despite concerns from staff and some board members that the lower color temperature could compromise worker safety. The design team rejected this recommendation but agreed to lower the temperature to 4,000 kelvins, which corresponds to a mostly white light with a slight yellow tint.
Diego Martinez-Garcia, an engineer with the Public Works Department, noted that all the LED lighting at the new plant will be focused on the work area.
“As part of the planning process we performed a lighting study that showed how the spillover from light really doesn’t go out beyond where it needs to be underneath the canopy,” Martinez-Garcia said.
The council broadly supported the staff recommendation for the new plant, which is one of two water-purification facilities that are slated for construction in the coming years. As part of the 2019 agreement, Valley Water is also pursuing a water-treatment plant at 1237 San Antonio Road, next to the city’s soon-to-be-constructed transitional housing project. Unlike the Embarcadero Way plant, the one on San Antonio will purify water to potable levels.
Council member Pat Burt lauded the design team and the city’s various review boards for refining the design of the Embarcadero plant and integrating native species into the landscaping plan. Vice Mayor Ed Lauing called the project a great example of teamwork among the city’s different departments and review bodies.
“To me this is a good case study,” Lauing said. “You don’t go out and solve every problem but it’s a really good effort.”
What type of irrigation system is used near the lawn and plants? Subsurface drip irrigation or classic surface sprinklers? Asking as I’m not if it’s a good idea to breath the fine mist from higher-quality recycled sewer water.