Gripped by Drought, Marin Considers Desalination, Water Pipeline Over the Richmond Bridge

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Workers with the Marin Municipal Water District (MMWD) fill buckets with drought information and water-saving tools during a "Drought Drive Up" event at the MMWD headquarters on June 12, 2021, in Corte Madera, California.  (Justin Sullivan/Getty Images)

As the drought deepens across the West, coastal cities are considering whether or not to filter ocean water as a solution to their water woes. In the Bay Area, Marin Water is mulling plans to draw its drinking water from the  San Francisco Bay.

Reservoir levels in Marin County are at historic lows this year, and water leaders are calling for a 40% reduction. So far the county has reached a 23% reduction, says Cynthia Koehler, president of the agency’s board of directors.

“We need to do more,” she said. “We're expecting another relatively low rainfall year. So, we're preparing not just for right now, but really for 2022.”

The harrowing prospect of another dry winter has the district toying, once again, with the idea of desalination, a process — removing salt and minerals from the sea for clean drinking water — that is simple in principle, maddeningly complicated in practice.

Here’s how it works: Salty water is pumped in from the ocean, filtered, chemically treated and then forced with high pressure through hole-lined pipes, which are tightly bound by a special polymer membrane — basically a microscopic strainer. Salt, bacteria and viruses can’t get through the membrane. Fresh water escapes, brine remains in the tubes.

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Marin Water looked at desalination twice in three decades. It shelved a desalination project in 2010 after water use declined, following a couple of dry years. One reason the agency ditched the idea? Cost concerns, which — at the time — could have been as much as $173 million.

“The cost was disproportionately high,” Koehler said, who joined the district 15 years ago “It's not a light switch, you can't turn it on or off, you've got to run it all the time. And so it would have been our most expensive source of supply.”

A shoreline project the district is now considering would cost in the ballpark of $37 million, and could clean enough water to fulfill about a third of the county's drinking water needs.  The agency could lease some facilities, keeping the costs down.

Agency staff are considering a floating facility on a barge, too.

They say the boat is likely more expensive and does “not appear feasible for a number of reasons” Koehler said.

The terrestrial plant, while cheaper than the floating barge and “technically feasible” still has “fairly high costs associated with it,” she noted.

A third option — not desalination, a pipeline over the bridge from Richmond to San Rafael to pump water from the East Bay — is likely to win out, Koehler said.

The agency could buy water from farmers in the Central Valley and elsewhere. Koehler said it is still somewhat up in the air about where the water would come from, but staff is meeting with neighbor agencies like the East Bay Municipal Utility District and others much further away in Amador, Placer and Yuba counties.

But if the drought worsens other areas of the state could be more in need and the water may go to them instead. If the 6-mile pipeline is successful it could provide for all essential homes, businesses, and other indoor water use, and it would cost between $66 million and $88 million — which is more expensive than the desalination option, but would cover a large percentage of the county's water needs.

“The preliminary information is that there would be water on the market in California, if we were able to get that infrastructure in place,” she said.

But these options are not quick fixes to the current water shortage and wouldn’t be ready until at least June 2022.

A decision could come by the end of the year, but Koehler says the best current option is water conservation.

“We want a community that is beautiful and that has landscaping, but native landscaping, low-water landscaping, Earthscape, all of these are options that don't require that level of investment,” she said.

Marin isn’t the only Bay Area community considering desalination. The city of Antioch is building a plant to clean brackish water from the San Joaquin River. It’s supposed to be completed in 2023. When the $100 million project is finished it will allow water to be used from the river year-round instead of purchasing costly water from other agencies.

Environmental factors essentially forced the city’s hand, says Peter Fiske, director for the National Alliance for Water Innovation at the Lawrence Berkeley National Laboratory.

“Because of climate change and the drought the salinity of that river is getting worse and worse,” he said “They got to the point where they were like, ‘Oh, my God, I guess we're going to have to desalinate.'”

Desalination doesn’t make sense for every city, because of the high cost and harm it can cause to marine ecosystems. Fiske says other options should be adopted first, like cleaning wastewater.

“Across the Bay Area, we generate a lot of wastewater,” he said. “We are essentially throwing it back into the bay and much of that wastewater could be reprocessed and reused.”

Adrian Covert, senior vice president of public policy at the Bay Area Council, a business and industry group, recently evaluated desalination regionally and found that recycling water could have a large impact. 

“Every year, the Bay Area pumps about 500,000 acre feet of highly treated wastewater into the bay,” he said. “It's more than enough to meet the Bay Area's water demand through 2040. And because wastewater is cleaner than ocean water, treating it to potable standards is also about 20% cheaper than desalinating water.”

Agencies like Santa Clara Valley Water, which provides water to 2 million people in the San Jose area, are planning on doubling recycling water efforts. But that still only equals about 10% of their water supply.

Gregory Pierce agrees that recycling water or fixing infrastructure is a faster solution than constructing a desalination plant. In a 2019 study, he examined the impact desalination could have on low-income or marginalized communities as the co-director of the UCLA Luskin Center for Innovation.

Pierce says people need “an even higher ethic of water conservation” because saving water is about preserving life for all Californians, not just the wealthy, with sprawling green lawns.

“In California, I think desalination can be part of the answer. But it's not the best answer right now or in the near term,” he said.

Pierce says desalination can hurt the environment and water agencies often push the high cost onto ratepayers.  Desalination doesn’t encourage people to use less water and could lead to agencies delaying upgrades to aging, leaky water systems.

As a concept, desalination sounds good, he says, but it's not usually delivered equitably. If water is truly a human right, it should be affordable to everyone.

Andrea León-Grossmann, director of climate action for the ocean conservation group Azul, advocates against desalination because the high costs are shouldered by ratepayers.

“Proponents claim it will be a few dollars a month," she said. "For them, it might be a few dollars a month, but for someone who's struggling to put food on the table that is a struggle."

She says there are better options for dealing with water shortages, like recycling water and fixing leaky pipes that waste water.

“If we were to plug all those pipes and invest in maintaining our infrastructure that could provide a lot more water than building desalination plants,” she said.

Desalination isn’t just expensive, it’s hard on ocean life, says Daniel Ellis, a senior scientist with the state water board.

“You're not just killing the phytoplankton, you're also killing the food source for the broader food web,” he said. “The second part of the environmental impact is you take in ocean water, you take out the freshwater and you're left with a lot of salt.”

Ellis says the brine byproduct can be twice as salty, and when it’s pumped back into the ocean, can be toxic for some aquatic life.

Even though desalination is theoretically becoming more popular — there are, at least, 11 active seawater desalination plants statewide —  he says there are only a few new pending projects in the state, like those in Huntington Beach and Laguna Beach.

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Correction: A previous version of the story mislabeled the San Joaquin River.