UPDATE: The Marin Municipal Water District has just announced a significant investment of $387,685 for an urgent study addressing flooding concerns in Nicasio. This decision comes after residents protested a now-canceled plan to increase capacity at the Nicasio Reservoir, fearing that sediment buildup has intensified flooding issues along Nicasio and Halleck Creeks.
Residents have reported damage to roads, yards, and the local school, raising alarm about the impact of reservoir expansion on their community. In response, the district’s board convened a meeting on November 18, 2025, where they approved a contract with Environmental Science Associates to conduct this critical study.
“What we found is, without question, there’s district responsibility,”
said Ben Horenstein, general manager of the district. He emphasized the need to address the streams and surrounding properties effectively.
Matt Samson, chair of the board, acknowledged the high cost of the study but deemed it necessary: “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 initial proposal for the Nicasio Reservoir aimed to bolster the county’s water supply as a drought defense but faced complications when projected costs skyrocketed from $10 million to $15 million to an estimated $37 million to $54 million. Consequently, the district terminated the project, a decision celebrated by residents who urged for immediate action on flooding.
The study aims to identify factors contributing to the reduced creek flow and evaluate longer-term management strategies to mitigate flooding effects. According to Adriane Mertens, a spokesperson for the district, “The study is not tied to pursuing spillway modifications — it is focused on gathering objective, science-based information about current creek conditions.”
Community member Martha Davis from the Nicasio Landowners Association expressed gratitude for the district’s response, emphasizing the importance of continuous monitoring: “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.”
Residents are also concerned about a proposed 13-mile, 36-inch pipeline tapping into an aqueduct system along Highway 101, aimed at transporting water from the Russian River to the Nicasio Reservoir. They worry about the capacity to fill the reservoir adequately with additional water.
Paul Sellier, the district’s water resources director, reassured that the new pipeline will be utilized during drought conditions when reservoir levels are low, addressing community concerns effectively.
The district is also pursuing emergency permits from the San Francisco Bay Regional Water Quality Board to remove accumulated debris from district-owned sections of Nicasio Creek. This initiative, requested by concerned residents, aims to allow water to flow more freely to the reservoir. If approved, this removal process could take about two to three weeks, according to Mertens.
This latest development highlights the Marin Municipal Water District’s commitment to addressing community flooding concerns while ensuring sustainable water management strategies for the future. Stay tuned for more updates as the situation evolves and the study progresses.
