The Marin Municipal Water District has launched an effort to explore new sources of water and study how it might help the county weather future droughts.
The study comes after the district and the 191,000 residents in central and southern Marin it serves faced potentially depleted reservoirs following two years of drought.
To prevent running out of water, the district scrambled to plan a $100 million emergency pipeline across the Richmond-San Rafael Bridge to pump in water purchased from the Sacramento Valley before mid-2022.
But heavy rains in late 2021 worked to nearly refill the district’s reservoirs, allowing the district to take a step back from the emergency and take a more in-depth look at new supply options, Paul Sellier, a district official, said during a public workshop this month.
“We have a little bit more time with the water supply that we now have, and that’s going to allow us to take this strategic water supply assessment,” Sellier said. “The result of the assessment will be a road map toward water supply resiliency.”
A variety of options is on the table for the assessment, including the bridge pipeline, also called intertie; a desalination plant; raising dams at reservoirs; expanding the recycled water system; and groundwater banking in partnership with the Sonoma Water agency.
The assessment will be performed by the Texas-based Jacobs Engineering Group. The company’s project manager, Armin Munevar, said the study will have two main phases.
The first is to study how the district’s two-year water supply could be affected by future changes such as increased demand, a variety of drought scenarios and climate projections. The group will also run these same stress tests against scenarios where the district has more water supplies to see how they compare.
“What we’re attempting to do is explore different futures, droughts, demands, policies, et cetera, and ensure that the system is resilient given those plausible futures,” Munevar said. “We’re not trying to predict one particular outcome.”
The study will then look at a variety of new water sources and evaluate their costs, their resiliency in future droughts, environmental impacts and social factors.
“What we may find is some of the alternatives work best in combination with other alternatives,” Munevar said. “So there is likely a process where we’ll develop portfolios of a combination of alternatives.”
A second public workshop set to take place in May or June will provide an update on some of these efforts. In June and July, the study will review the water sources and prepare a final report. A third public workshop will be held in July or August.
Ratepayers who attended the March 9 workshop had questions and comments ranging from desalination options to the role of conservation to housing development impacts.
“Could our potential intertie be able to connect us to a future desalination plant in the San Pablo Bay so we can draw from that source rather than needing our own desal system?” Beryn Hammill asked district staff.
Steve Isaacs asked the board whether it has given Jacobs Engineering Group a set water supply target it wants to achieve.
“A two-year water supply for Marin has been an acceptable strategy for the MMWD board, and that has been a disaster,” Isaacs said.
Ben Horenstein, the district’s general manager, said the first part of the study will be exploring the amount of water the utility might want to obtain rather than setting a specific target now.
“I’m really not seeing the disaster,” Horenstein said. “What I’m seeing is a district responding to the external change of climate change in a similar fashion as we did in the late 70s and early 80s when we had the record drought back then.”
Sellier said the district can’t arbitrarily select a number for storage.
“It needs to have some basis, and that’s what we’re trying to do with this water supply assessment,” Sellier said.
