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Pine Mountain Tanks Project

A person in a hard hat monitors a piece of drilling equipment as it drills into a wall.

The Pine Mountain Tanks Project is a two-phase effort, which will span multiple years, and adds a pair of 2-million-gallon concrete water storage tanks near Concrete Pipe and Sky Oaks roads, bolstering water supply resiliency for firefighters, as well as for the town of Ross and other area residents. 

Construction Update (Feb. 1, 2024)

Project reaches scheduled construction pause milestone

The Pine Mountain Tanks project, a multi-year effort to replace the aging Pine Mountain Tunnel’s use as a water storage facility with two, 2-million-gallon concrete tanks, has reached its scheduled, Year 1 pause for weather and environmental factors. 

Since construction began in the summer of 2023, crews have worked to excavate the site and install a retaining wall in preparation for the eventual installation of the pre-stressed concrete tanks. The construction site, located on the Mt. Tam Watershed, has now been winterized and construction is on hold through July 31. Concrete Pipe Road is now open to the public during all normal business hours. 

Contact Information

  • Marin Water Construction Management team:  415-945-1560
  • Maggiora & Ghilotti, Inc., (project contractor):  415-459-8640

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%.


ProjectPine Mountain Tunnel Tanks Replacement 
ProgramA1A11 Replacements - Storage Tanks 
Project NumberD21043
ContactAlex 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 - Summer 2025

Construction: Summer 2024 - Spring 2029

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

Expenditure Schedule

Actuals Through
FY 22 (Rounded)
FY 23
FY 24
FY 25
FY 26
FY 27
FY 28
FY 29

*Pending funding

Funding Sources 

Capital Maintenance Fund
State Appropriation
Other Funding Sources*

*Other funding sources to be determined