The last time Marin Water came up with a plan for increasing water resiliency in times of drought, Nicasio residents rose up in protest. Now the water district has a new plan for boosting its water supply, and locals are worried again.
The Atmospheric River Capture, or ARC, project involves constructing a 13-mile-long, 36-inch-wide pipeline that would carry rainwater from the Russian River watershed to the Nicasio Reservoir. The anticipated cost surged from $168 million to $214 million last month, after the district board decided to plan for a second pump station for the project, which originally called for one.
The new pipe would connect to the existing North Marin Aqueduct, which runs along Highway 101. It would follow San Marin Drive to Novato Boulevard, pass Stafford Lake and take a left at the Point Reyes-Petaluma Road before connecting to the reservoir.
Because the Russian River watershed is many times larger than the Lagunitas Creek watershed that feeds Nicasio, it can produce excess flows even in drought years, but much of that water empties into the Pacific Ocean at Jenner.
The ARC pipeline would transport water during winter when three conditions occur at once: the reservoir level is low, Marin is in an extended dry period with little or no rain in the forecast, and storms have saturated the Russian River watershed.
Some residents worry that the plan could exacerbate flooding along Halleck and Nicasio Creeks, where clogged channels force stormwater into roads and yards at homes and the school. Last year, residents had similar concerns about the plan to increase the reservoir’s storage capacity by raising the height of the spillway over the Seeger Dam. The district abandoned that idea after residents raised their voices and dug up historical records that showed a previous effort to raise the spillway had been abandoned.
Martha Davis, a Nicasio resident and retired water policy strategist, said there are many operational questions about the ARC project. What if major storms strike both Napa and Marin at the same time?
“This is a huge operation, and it would put water into Nicasio with a question mark on the other end,” she said. “Can Nicasio take that water? That’s what the community of Nicasio is worried about: Does this add flooding potential to us?”
Although the tiny community is located next to the reservoir, Marin Water doesn’t serve its residents, who rely on well water. The district serves the San Geronimo Valley, but most of its 191,000 customers live in southern Marin.
The district estimates that the ARC project would add about 3,800 acre-feet of water a year to the reservoir, or about 17 percent.
Ms. Davis wonders if Sonoma would produce enough water to help Marin, as both counties are typically dry at the same time. “I’m concerned there’s something fundamentally wrong with the math,” she said.
To address flooding concerns, the district applied for emergency permits late last year to remove woody debris from Nicasio Creek and improve flows to the reservoir. The San Francisco Bay Water Quality Control Board approved the permits but ordered the district to develop a long-term maintenance plan that includes removing sediment from the creek.
“Over the last three decades, huge amounts of sediment have built up—six to eight to 10 feet within the creek itself—plus all of the vegetation that has encroached on it,” Ms. Davis said. “We’re very grateful to the regional board for requiring the plan.”
The comment period for the ARC project ends April 13. More information is at https://tinyurl.com/ARCwaterproject