Richmond-San Rafael Bridge water pipeline, desalination plans are being considered

The Marin Municipal Water District has taken the first steps toward building an emergency water pipeline across the RichmondSan Rafael Bridge for the first time in nearly 50 years to avoid potentially running out of water next summer.

The district said that it has hired a consulting firm, Woodard & Curran, to find potential water rights holders in the Central Valley willing to sell their allotments. This water could be pumped across the bridge via the pipeline and into Marin’s water system should the drought stretch into winter.

“That team is out at the moment searching for a source of water,” Paul Sellier, the district’s operations director, told the board at a meeting Friday.

During the major drought of the late 1970s, the district built a temporary 6-mile pipeline across the bridge because it faced running out of water within 120 days. The pipeline was removed in 1982 after the drought ended and at the urging of Caltrans to restore a blocked traffic lane on the bridge.

Nearly 40 years later, the district and the 191,000 central and southern Marin residents it serves face the prospect of running out of water by next summer should this winter be as dry as the last and conservation efforts do not improve. Ben Horenstein, the district general manager, said it is unlikely a similarly dry winter would occur two years in a row, but the district must be prepared for that worst-case scenario.

Horenstein said the district’s focus remains on conservation being the primary tool to retain local supplies, but it is considering the pipeline and a temporary desalination plant as insurance policies. The district estimates said these options likely would cost tens of millions to hundreds of millions of dollars.

“I also want to assure the board and the public that this work is happening in parallel with all of our conservation work,” Horenstein told the board.

A decision on both the pipeline and desalination plant could come as soon as December.

The district is looking for potential water sellers in the Sacramento River, Mokelumne River and Los Vaqueros watersheds, Sellier said. The district has also made inquiries with Sonoma Water, but they are unlikely to yield any options given the drought situation there, Sellier said.

Any sale would need to obtain approval either from the state or federal government, depending on the source, and would need to be studied for environmental impacts. Also, the district is in early talks with the East Bay Municipal Water District and Caltrans to use its facilities to transfer the water to Marin and build the pipeline across the bridge.

Water sales options could come back to the board for consideration as soon as July, Sellier said. From there, the district would need to secure approvals from various agencies between August and November to not only build the pipeline but also get the water from the Central Valley to the Bay Area. The district board then would decide whether to proceed with the project in December or January.

If it approves the project, the district would work to have the pipeline and supporting facilities such as pumping stations built by June 2022 — a similar construction timeframe to 1977.

The pipeline could pump in about 10,000 to 15,000 acre-feet of water per year to be used only for the bare essentials, Sellier said. For comparison, that amount of water is about half of the potable water demand by district customers in all of 2020.

For a temporary desalination plant, the district has hired a consulting firm to identify potential vendors and consider options for purchasing or lease agreements. A plant and any financing for it would require voter approval under a 2010 ordinance, with staff eyeing November for a potential vote. Board members said a desalination plant would likely result in the district having to consider 20% rate increases for a decade.

“We will be bringing back a lot of details in terms of the costs, more granularity as we understand it of what the projects can look like,” Horenstein told the board.

The drastic options are being considered after the district saw its second-lowest rainfall on record this past winter, about 20 inches. The past 18 months were the driest ever in the district’s 143 years of records.

Projections show the district’s seven reservoirs in the Mount Tamalpais watershed could run out of water from June to early August 2022 assuming next winter is just as dry and residents only maintain 20% conservation. This past week, residents were conserving about 19% more water compared with average use from 2018-2020, well short of the district’s 40% conservation mandate imposed in April and just 1% percent more than the previous week.

The district receives about 25% of its supply from Sonoma Water, which is set to cut imports by 20% beginning in July.

The district staff outlined a conceptual timeline for the bridge pipeline and desalination projects on Friday. Each would require a rapid monthslong turnaround.