Nicasio Reservoir project prompts flooding concerns

Nicasio residents are urging the Marin Municipal Water District to reconsider a proposal to add storage to the nearby reservoir.

Over the past two weeks, residents have told district officials that they fear the project could exacerbate flooding along Nicasio and Halleck creeks, and that the community would see no benefit from the added storage at Nicasio Reservoir. The community uses well water and is not served by the reservoir or the district’s supply.

Residents said increased flooding would threaten their properties, the roads, the school and their well water and septic systems.

“In light of the drawbacks, I urge the board to seek alternatives to your proposal to raise the level of Nicasio Reservoir,” resident Tom Wood said at a project meeting on May 22.

The proposal calls for modifying the spillway gates at Seeger Dam, which was constructed on Nicasio Creek in 1960 to create the reservoir. The reservoir has a storage capacity of 22,340 acre-feet of water.

The district’s seven reservoirs comprise about 75% of its water supply, holding up to 80,000 acre-feet of water, equal to about a two-year supply. An acre-foot is about 326,000 gallons.

The project would install a 280-foot-long, 4.4-foot-high inflatable rubber gate spanning the spillway crest to increase capacity by about 3,700 acre-feet. The project was selected from several proposals as a short-term and efficient way to increase supply.

The district recently started the process for an environmental review of the project, which involved “scoping meetings” held on May 22 and on Tuesday.

Wood said the reservoir’s creation in the 1960s put six ranches out of business and left others struggling.

“Trees and vegetation were scraped off the fertile land and houses and barns were bulldozed and burned,” he said. “MMWD’s hardball negotiations to acquire the property alienated many people, and the loss of ranches bred ill feeling and sorrow that still lingers in the Nicasio community today.”

Nicasio residents said flood maps that show current conditions do not match what they experience during heavy rains. Residents complained that the water district has neglected to dredge the creek, and they believe a buildup of sediment has led to more frequent flooding.

“If the dam were to be raised, our yard and buildings could be flooded, which could result in us losing our property insurance,” said Dorene Schiro, who has lived near the creek with her husband Bob for about 30 years. “All over Marin, homeowners are losing their insurance for fire concerns. We would have the additional risk of flood concerns.”

Leanne Wolfson, a board member of the Nicasio Valley Ranch Mutual Water Co., said flooding could contaminate wells and aquifers, as well as clog septic system leach fields, making them unable to filter waste water properly.

“While I understand that Marin Water is trying to increase water supply for its users, you must also ensure that this project does not harm our Nicasio community,” Wolfson said. She also suggested the district consider a way to add Nicasio to its service area.

Barbara Snekkevik, superintendent and principal of the Nicasio School District, said the school playground floods regularly, causing erosion of the creek bank, creating gaps under the schoolyard fence and “posing a significant danger to our students.”

Under drinking water regulations, the district has to shut off its well, its sole source for the campus, during flooding.

“Clearly this is of great concern to the district,” she said. “We are requesting that the MMWD’s proposed mitigation measures thoroughly address our concerns and that alternative sites within Marin County be given serious consideration.”

Residents suggested that the district pursue an expansion of Kent Lake instead, because the district owns the surrounding land and it wouldn’t have the same negative community impacts. Such an expansion has been estimated to cost more than $500 million, whereas the plan at Nicasio Reservoir is closer to $15 million.

Initially, staff proposed to have the Nicasio project ready for construction in 2027. Because of the public response, the project schedule is now going to be driven by several investigations that are part of the environmental review.

Ben Horenstein, general manager of the water district, said at a planning committee meeting Tuesday that staff are looking into why the district stopped dredging the creek. Staff are also studying creek conditions and behavior, as well as species and habitat in the area, to provide a fuller picture.

“There is a lack of understanding generally … of what really is causing these flooding issues that appear to have gotten worse over the years,” Horenstein said. “We’re looking at this as a partnership with the community, full transparency, as we go through this to collectively understand and kind of make collective decisions on how we proceed.”

Board member Ranjiv Khush said he’s glad these studies are happening because staff could determine the costs required to mitigate impacts might not justify the project going forward.

“Having the best data to understand that cost-benefit analysis is going to be critical, because we know that the decisions have to be defensible,” Khush said.

Board member Larry Russell said the community has “got the ear of the board and the staff.”

“We hear you, and we’re going to do our best to solve all the issues,” he said.

The public comment period has been extended to 5 p.m. Aug. 4. A third scoping meeting is scheduled for 1 p.m. July 15. More information is at marinwater.org.