Updated May 15, 2025

Pursuant to the California Environmental Quality Act, Marin Water is initiating the environmental review of the Nicasio Spillway Modification Project. Modifying Nicasio Reservoir’s spillway is one of the near-term storage enlargement projects identified through development of the District's Water Supply Roadmap.  

The reservoir's current storage capacity is 22,340 acre-feet. This project would install a 280-foot-long, 4.4-foot-high inflatable rubber gate spanning the width of the existing spillway crest of Seeger Dam. The modification to the existing spillway would provide approximately 3,700 acre-feet of additional temporary water storage capacity. The Project would increase locally stored water supplies in the near-term to reduce adverse effects on Marin Water customers caused by water shortages from droughts and other emergencies. 

The review process begins with a comment period for agencies and the public to comment on the scope of the environmental review, including the project description, environmental issues to be analyzed and potential alternatives. These issues are described in a Notice of Preparation. 

Comment Period

The public comment period will be open from April 30, 2025 to 5 p.m. August 4, 2025. Comments must be submitted before the deadline and may be provided in one of the following ways:

• By email to: 
  Elysha Irish
  eirish@marinwater.org 
  Subject: Nicasio Spillway Modification Project public comment
   
• By U.S. postal mail to:
  Marin Water
  Attention: Elysha Irish
  220 Nellen Ave.
  Corte Madera, CA 94925

Scoping Meetings

As part of the environmental review process, Marin Water is holding two public scoping meetings. These meetings are an opportunity for interested parties to learn more about the project and provide comments. The information presented will be the same for both meetings.