Marin County’s major water providers are looking for new ways to expand their supply amid increasingly intense and unpredictable droughts. At a board meeting late last month, Marin Water directors discussed a wide range of options to make the utility more resilient, including reuse, desalination and closer ties with Sonoma County.
Many of the methods to improve the reliability of Marin’s water supply could take years to realize, but consultants said they could happen much faster if drought conditions get significantly worse. “I think a number of them are really long-range projects but, given the right political will, they might become mid-term projects,” said Armin Munevar, a water engineering consultant from the firm Jacobs.
With Marin Water’s reservoirs at over 90 percent capacity, above average for May, the district’s supply is safe for the immediate future. But long-term rain prospects are marked by extreme uncertainty. Northern California rains usually come in the form of atmospheric rivers, ribbons of concentrated atmospheric moisture that are likely to both intensify and shrink in duration just as overall conditions become drier and hotter. Marin Water’s engineering consultants said their recommendations, based on an ongoing water supply enhancement study, would help the district adapt to long droughts punctuated by quick drenchings.
The same evening Marin Water’s board met, North Marin Water District officials heard a similar presentation from water engineering consultants. Though North Marin serves 1,800 people in Point Reyes Station, Olema and Inverness Park, the new supplies it hopes to tap would only affect Novato customers who depend in part on Stafford Lake for water.
Resiliency for both of Marin’s major water suppliers will depend on closer ties with Sonoma County, consultants found. Surplus water from the Russian River, collected during the winter rains, provides 25 percent of Marin Water’s potable supply and about three quarters of Novato’s water. The Sonoma Aqueduct pipes the water through Petaluma, where the recently rehabilitated Kastania Pump Station will soon be able to deliver an additional 5,000 acre-feet to Marin annually. Sonoma water flows into the two districts’ distribution systems, and can be pulled into Stafford Lake. Marin Water is considering building new pipelines to store that water in Nicasio and Soulajule Reservoirs.
Last year, Marin Water was ready to begin the emergency construction of a pipeline across the Richmond-San Rafael Bridge. But in January, the district announced that the project would be held up by the usual regulatory hurdles after generous rains caused it to lose its emergency exemption. When the project is complete, it will give Marin Water the infrastructure to purchase water from the Yuba County Water Agency in the Sierra foothills, and independent districts like Inverness could get a sliver of the supply under that agreement.
In last month’s presentation, Mr. Munevar said his firm would study the costs of other large-scale intertie agreements, including lengthening the Richmond Bridge pipeline to connect directly with Contra Costa Water District, building a new pipeline to connect Novato with the North Bay Aqueduct that ends in Vallejo and even creating an intertie agreement with San Francisco.
Recycled water could make up a much bigger part of Marin’s supply in the future. The two districts’ applications of recycled water are currently limited: Around 300 commercial and residential customers in Terra Linda get treated wastewater for uses like irrigation and toilet flushes, and 90 Novato hookups use it for landscaping and car washes. Marin Water is looking to expand those applications, including by irrigating Peacock Gap golf course in San Rafael with non-potable water, and its consultants suggested two concepts for reusing treated water in their study.
Through indirect potable reuse, the wastewater from Las Gallinas, Central Marin and Southern Marin Sanitary Districts would be treated and then pumped into Kent Lake. A so-called direct potable reuse system would divert and purify up to 4 million gallons of Central Marin wastewater per day, piping it straight back into the distribution system. Alternatively, the consultants found, the district could use treated wastewater in lieu of reservoir water for water releases into Lagunitas Creek mandated by environmental regulations. Although the cost of the advanced treatment required for recycling could be high, and treated wastewater tends to run warmer than regular reservoir water, several directors expressed a commitment to exploring how these ideas could be implemented in the next decade.
“We want to be moving from that 20th-century way of thinking about these resources as waste and more about thinking of them as assets,” director Cynthia Koehler said.
Desalination using a bayside plant to render seawater drinkable took a back seat to the Richmond Bridge pipeline project as an emergency solution to Marin’s water stresses last year. North Marin’s customer base is too small to make a desalination facility feasible, but in the long term, the prospect will remain on the table. Marin Water could eventually use the Richmond Bridge pipeline to participate in a regional collaboration with five other Bay Area water agencies, tapping into seawater desalinated at a plant in the East Bay or on the ocean in San Francisco.
Both Marin Water and N.M.W.D. are also examining the potential to expand their own reservoirs. Mr. Munevar suggested dredging to expand the capacity of reservoirs like Soulajule and Nicasio, but North Marin’s consultants focused on how an adjustable spillway gate could be added to Stafford Lake, allowing the reservoir to fill to the brim. Marin Water board member Larry Bragman suggested this solution could be cheaper and more sensible for his district’s seven reservoirs. “The financial feasibility is orders of magnitude less than excavation, and the technical requirements seem quite conventional,” Mr. Bragman said.
Late-season rain has helped ease the sense of urgency that animated northern California water providers to tighten restrictions last year. Last week, Marin Water announced it was lifting temporary emergency water restrictions in response to recovered reservoir levels. Customers can once again wash their cars at home, fill swimming pools and irrigate golf courses. But the district also hardened its long-term, year-round rules: Outdoor watering using overhead spray systems is now limited to two days per week and swimming pools must be covered to cut down on evaporation.
Small, self-reliant districts like the Inverness Public Utility District have fewer opportunities to expand supply than Marin Water and N.M.W.D., even during drought emergencies. With scarce opportunities for new wells and treatment plants, IPUD and the Bolinas Community Public Utility District are often the first to enforce conservation measures when droughts become severe. “It’s the way it’s always been,” IPUD customer services manager Wade Holland said. “In tight times, we tighten our belts.”
This article was corrected on May 18 to reflect the fact that North Marin Water District already has the ability to bring water from the Russian River into its Stafford Lake reservoir; it is Marin Water that is considering building infrastructure to store that water in its reservoirs.