URGENT UPDATE: The Marin Municipal Water District has just announced a groundbreaking investment of $387,685 to investigate escalating flood concerns in Nicasio. This decision comes on the heels of significant resident protests against a now-canceled plan to expand the Nicasio Reservoir, which locals feared would worsen flooding along Nicasio Creek and Halleck Creek.
Residents have reported increasing damage to roads, yards, and even the community school due to frequent flooding, leading to heightened tensions and calls for action. The district’s board met on November 18, 2025, where they officially approved a contract with Environmental Science Associates to conduct this critical study.
Ben Horenstein, general manager of the district, stated, “What we found is, without question, there’s district responsibility.” He emphasized the need to address the streams and the property to mitigate flooding risks. Board chair Matt Samson acknowledged the cost of the study but insisted it is warranted: “I appreciate the fact that we’re moving forward with it and better understanding not only the impacts of what’s going on out there, but it’s going to help us manage our reservoir system all together.”
The proposed expansion of the Nicasio Reservoir was initially seen as a low-cost solution to bolster the county’s water supply and enhance drought resilience. Modifications to the spillway gates at Seeger Dam were intended to increase capacity by about 3,700 acre-feet of water. However, after estimates ballooned from $10 million to $15 million to an astonishing $37 million to $54 million, the project was scrapped in August, much to the relief of local residents.
With the study now underway, the focus will shift to identifying what factors are contributing to reduced creek flow and assessing long-term management actions to alleviate flooding, according to spokesperson Adriane Mertens. “The study is focused on gathering objective, science-based information about current creek conditions,” Mertens added.
Community leaders are hopeful about the district’s responsiveness. Martha Davis from the Nicasio Landowners Association emphasized the importance of continuous monitoring, stating, “This is not a one-and-done. This is a living ecosystem.” There’s also a call for ongoing dialogue about the district’s proposed “atmospheric river capture” project, which aims to transport water from the Russian River into Marin.
Residents have expressed concerns over whether the existing infrastructure can handle the intended volume of water for the reservoir. However, district officials, including water resources director Paul Sellier, reassured the community that the new pipeline will be operational during drought conditions when reservoir levels are low.
In addition to the study, the district is pursuing emergency permits from the San Francisco Bay Regional Water Quality Board to remove accumulated woody debris from Nicasio Creek. This action, requested by residents due to flood risks, aims to enhance water flow into the reservoir. If approved, this debris removal could take just two to three weeks.
As this situation continues to evolve, the community is watching closely for updates on both the study and the anticipated debris removal efforts. Stay tuned for further developments as the Marin Municipal Water District takes significant steps to address pressing flooding issues in Nicasio.
