UPDATE: The Marin Municipal Water District has just announced a significant investment of $387,685 to investigate urgent flooding concerns in Nicasio. This decision follows a series of resident protests against a now-canceled plan to increase capacity at the Nicasio Reservoir, amid fears that sediment buildup has worsened flooding along local creeks.
Residents have voiced their frustrations, citing damage to roads, yards, and even the community school due to rising water levels. They argue that expanding the reservoir would only exacerbate these flooding issues. In response, the district has convened a group to address these serious concerns.
During a meeting on November 18, 2025, the district board approved a contract with Environmental Science Associates to conduct a comprehensive study on the flooding situation. General Manager Ben Horenstein stressed the district’s responsibility, stating, “Without question, there’s district responsibility. We feel that there are some opportunities and needs for us to address the streams and the property.”
Board Chair Matt Samson acknowledged the cost of the study, calling it “a very expensive study, but I think it’s warranted.” He emphasized the importance of understanding the flooding impacts to manage the reservoir system effectively.
The halted Nicasio Reservoir expansion was intended to enhance the county’s water supply as part of drought defense strategies. The proposal included modifications at Seeger Dam, which would have involved installing a new inflatable rubber gate to increase storage capacity by approximately 3,700 acre-feet. However, after cost projections soared from $10 million to $15 million to an estimated $37 million to $54 million, the project was scrapped in August.
Residents celebrated the decision but insisted that the district must now focus on mitigating flooding. The newly approved study aims to identify factors contributing to reduced creek flow and to explore long-term management actions. Spokesperson Adriane Mertens clarified, “The study is not tied to pursuing spillway modifications; it is focused on meeting our commitment to gather objective, science-based information about current creek conditions.”
Community members, such as Martha Davis from the Nicasio Landowners Association, expressed appreciation for the district’s responsiveness. Davis emphasized the importance of continuous monitoring, stating, “This is a living ecosystem… You’re going to need to understand how the system is responding to any of the changes that you’re making within it.”
Concerns also extend to the district’s proposed atmospheric river capture project, which involves a new 13-mile pipeline to transport water from the Russian River to the Nicasio Reservoir. Residents worry about the reservoir’s capacity to handle additional water, particularly during drought conditions, as emphasized by district Water Resources Director Paul Sellier.
Additionally, the district is pursuing emergency permits from the San Francisco Bay Regional Water Quality Board to remove accumulated debris from Nicasio Creek, a move prompted by resident concerns over flooding risks. If approved, this debris removal would take approximately two to three weeks, allowing water to flow more freely towards the reservoir.
As this situation develops, the Marin Municipal Water District is committed to addressing the flooding crisis while maintaining open communication with the Nicasio community. Residents remain hopeful that these efforts will lead to effective flood management solutions that safeguard their homes and infrastructure.
