Marin Municipal Water District announced Friday that it has found a potential vendor for temporary desalination plants and four Central Valley water suppliers that could transfer water to the county through a pipeline across the Richmond-San Rafael Bridge.
The emergency water projects are being explored based on forecasts that the majority of Marin residents could run out of water by July 2022 if the upcoming winter is as dry as last year’s. The district serves about two-thirds of the county including 191,000 residents in central and southern Marin.
The price tag to build one of these projects is estimated to range from $30 million to $90 million depending on the option, staff said in a presentation to the district’s Board of Directors on Friday.
District Operations Manager Paul Sellier said each option comes with its own costs and benefits and would require aggressive effort to have in place before next summer. Designs for the pipeline, for example, could come to the board in September for approval.
“This is not one of these things where we can continue to scratch our bellies,” district board member Larry Russell said during the meeting. “We’re going to have to make some decisions. I hope, frankly, that it rains like it’s never rained before in the fall and that this money goes down the drain literally, that we never have to use it. But that’s not a wise business approach here. We need the backup of having an alternative.”
Two land-based, prepackaged desalination plants by the Australian company Osmoflo are available to be leased and could provide about 3,600 acre-feet of water per year, Sellier said. This amount equates to about one-third to one-fifth of the district’s annual indoor drinking water demand.
Constructing and permitting the plant would cost between $30 million to $37 million, Sellier said. Part of that cost includes additional energy infrastructure to run the plants, chemical treatment and facilities to carry the brine to the Central Marin Sanitation Agency facility to be mixed with wastewater before being pumped out into the bay.
Purchasing the desalination plants could add another $2 million to $4 million to the price, not including yearly operating costs, Sellier said, though this is not being recommended.
A 6-mile pipeline across the Richmond-San Rafael Bridge could provide between 10,000 and 15,000 acre-feet of water per year, which would cover all essential indoor uses, Sellier said. The cost to build the pipeline and buy the water could range from $60 million to $88 million, Sellier said. The water would come from existing water rights holders in the Central Valley such as agricultural producers that would sell their water and fallow their fields.
Sellier said four water districts in the valley have expressed potential interest in transferring this water to Marin: Glenn-Colusa Irrigation District, Placer County Water Agency, San Juan Water District and Yuba County Water Agency. The Glenn-Colusa Irrigation, the largest irrigation district in the Sacramento Valley, is being eyed as a favorable candidate given its history of water transfers, including transferring 45 acre-feet of water this year to other areas, Sellier said.
Russell expressed concern that Marin may be “slow at the draw” based on the severe drought experienced by other water suppliers in the state.
“We can’t be the only ones looking for water,” Russell said.
Any purchased water would travel more than 100 miles from the Sacramento Valley to Marin through a complex system of rivers, aqueducts, reservoirs and water stations depending on the supplier. Marin would also require the aid of the East Bay Municipal Water District and potentially Contra Costa Water District to convey the water to Marin.
Any purchased water would start out in the Sacramento River but could take various routes from there, Sellier said.
One scenario is the water would be diverted from the river at the East Bay Municipal Utility District’s Freeport Intake station south of Sacramento and fed into its Mokelumne Aqueduct.
From there it would be gravity fed to the Lafayette Aqueduct and end up in the East Bay Municipal Utilities District’s San Pablo Reservoir just south of El Sobrante. The water would then be treated by the district and transferred to newly built pumping stations on the eastern side of the bridge. Once across the bridge, pumping stations on the western end of the bridge would carry it to Marin Municipal Water District’s system.
Alternative routes for the water are available depending on the source of the water, Sellier said. For example, the water could instead flow into the Sacramento-San Joaquin Delta and then into the Los Vaqueros Reservoir owned by the Contra Costa Water District. The water would then be fed from the reservoir into the Mokelumne Aqueduct and eventually arrive in the East Bay treatment system.
Buying and transferring the water could cost between $10 million to $18 million, according to the district. Building the pumping station, pipeline and other required facilities could cost $50 million to $70 million.
It’s also unclear where the pipeline would be located. Caltrans is studying various options including a permanent pipeline installed on the underside of one of the two bridge decks or the potential to place it on the top deck where the bicycle and pedestrian path now exists, Sellier said.
An additional benefit of the pipeline is that it could potentially connect Marin to a $110 million brackish desalination plant approved by the city of Antioch last year to treat San Joaquin River water, according to district General Manager Ben Horenstein.
At the same time, the district is also set to meet with Sonoma Water agency officials next week to discuss other supply options, according to Horenstein. Sonoma Water provides about 25% of the district’s annual water supply.
Sonoma Water is facing its own supply issues, but Marin water officials said it may be worth paying a little extra to secure water from an established partner rather than invest in significant undertakings such as temporary desalination or building a bridge pipeline.
“From my point of view paying a premium to get drought supply is a good investment for both sides of the agreement,” said district board member Larry Bragman.
In the meantime, district staff is urging ratepayers to meet the 40% water conservation mandate to buy them more time. So far, residents have conserved by 23%.
Should this winter be as dry as last year’s, the 40% conservation would give the district until September 2022 rather than July 2022 to have these projects in place before depleting its reservoir supplies. While the difference is slight, Sellier said it would be “providing us valuable time to help deliver the extremely challenging water supply projects.”
More information about water conservation rules and tips can be found at marinwater.org/conserve.
