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Pine Mountain Tunnel Tanks Replacement

Project Schedule, Traffic Impacts, Watershed Visitor Access Interruptions

  • Motorist, cyclist and pedestrian access will be restricted on Concrete Pipe Road.
  • Parking will be prohibited along Bolinas Road and Sky Oaks Road (the Sky Oaks Parking lot will remain open). 
  • Heavy truck traffic is expected through the duration of the project, which may cause traffic impacts in area of Bolinas Road and Sky Oaks Road.

Project Update (Aug. 4, 2022)

Marin Water is now pursuing a federal competitive grant funding opportunity for this project that will delay implementation of Phase 1 construction activities. The potential grant funding could significantly lower local costs while helping to ensure important seismic retrofitting can be included in the project. The delay in beginning the project ensures Marin Water is pursuing every opportunity to maximize our leverage of local ratepayer dollars while also protecting critical water system infrastructure from future seismic activity.

Contact Information

Marin Water Construction Management team, 415-945-1560

Maintaining Infrastructure is Top Priority

The Pine Mountain Tunnel was constructed in 1919 to convey water from Alpine Reservoir to Fairfax and San Rafael and was converted to a water storage facility in 1971 and remains in that use today. The storage replacement project will enhance water system resiliency and replaces aging infrastructure on the District’s watershed. A pair of 2-million gallon pre-stressed concrete storage tanks will replace the existing Pine Mountain Tunnel with a modernized design that provides seismic stability, water quality improvements, and low maintenance.  This project also increases water system capacity in Ross Valley by approximately 30%.


Project Pine Mountain Tunnel Tanks Replacement 
Program A1A11 Replacements - Storage Tanks 
Project Number D21043
Contact Jake Miller |  / Alex Anaya | 
Map of two purple circles between Concrete Pipe Rd and Sky Oaks Rd
Trees shading a hillside

Project Description 

This project will cease use and replace the Pine Mountain Tunnel with two 2-million gallon pre-stressed concrete tanks located on Concrete Pipe Road at culvert marker CP-5. 


The benefit of this project is to cease use of Pine Mountain Tunnel for storage, improving water quality, and increase the reliability of storage within Ross Valley, providing emergency storage on the watershed to aid in firefighting capabilities and allow for the future replacement of Ross Reservoir. 

Schedule and Status

Planning: Winter 2020/21 - Spring 2021

Design: Spring 2021 - Spring 2022

Construction: Spring 2022 - Winter 2027/28

*Construction window from August 1 - January 31 to protect Northern Spotted Owl

Expenditure Schedule

Actuals Through
FY 21
FY 22
FY 23
FY 24
FY 25
FY 26
FY 27
FY 28

Funding Sources 

WIFIA Loan (not yet approved)
HMP Grant (not yet awarded)
State Appropriation