Supplemental Notice of Preparation of Environmental Impact Report for Atmospheric River Capture Project

Graphic shows various stages of water delivery and treatment.

Pursuant to the California Environmental Quality Act (CEQA), Marin Water initiated environmental review for the proposed Atmospheric River Capture (ARC) Project in March 2026. This process began with an initial comment period for agencies and the public to provide input on the scope of environmental issues to be addressed in the Project’s Environmental Impact Report (EIR). The District previously published a Notice of Preparation (NOP) for the EIR on March 13, 2026. The initial public comment period, regarding the scope and content of the EIR, closed at noon on April 13, 2026.

Since publication of the March 2026 NOP, the District has been in the process of developing a long-term management plan to address sediment and vegetation buildup in Upper Nicasio Creek, which is being added to the Proposed Project. The District has published a Supplemental NOP, which includes a description of the changes to the Proposed Project. The scope is described in the following Supplemental NOP document:

COMMENT PERIOD FOR THE SUPPLEMENTAL NOP

The Supplemental NOP public comment period, regarding the scope and content of the EIR and Project alternatives to consider, will be open until noon on Monday, October 19, 2026. If you submitted comments on the NOP published for the Proposed Project in March 2026 and have no additional comments related to the new project components, your comments are being considered in the EIR and you do not need to resubmit your comments. Comments may be provided in one of the following ways:

  • By mail:
    Marin Municipal Water District, c/o Lucy Croy
    220 Nellen Avenue
    Corte Madera, CA 94925
    Letter subject heading: “RE: Atmospheric River Capture Project Supplemental Public Comment”

No new scoping meetings are being held for this Supplemental NOP. The District held two public scoping meetings for the original NOP on March 25 and March 26, 2026, and will not be holding an additional meeting.

WHAT’S NEW: UPPER NICASIO CREEK LONG-TERM MANAGEMENT PLAN

Since publication of the March 2026 NOP, the District has been developing a long-term management plan to address sediment and vegetation buildup in Upper Nicasio Creek, which is now being added to the Project. The new components include:

  • Vegetation and sediment removal, approximately 50,000 cubic yards, over at least two construction seasons, along approximately 3,150 linear feet of Upper Nicasio Creek and 1,200 linear feet of Halleck Creek;
  • Lowering the existing delta sediment deposits in Nicasio Reservoir by approximately 4 feet to create a lowered bench approximately 100 feet wide along 2,000 linear feet of the right bank of Upper Nicasio Creek;
  • Maintenance activities on an as needed basis, estimated to include removal of up to 10,000 cubic yards of sediment and vegetation thinning about once every 5–10 years;
  • Staging in designated areas; and
  • Off-hauling of vegetation and excavated sediment to an off-site location for disposal or reuse

More information on the Project can be found on Marin Water’s Atmospheric River Capture Project webpage.

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