RVSD Fairfax Capacity and
Creek Crossings Project (#957)
Town Council Informational
Presentation
Town of Fairfax • June 3, 2026
Phil Benedetti, P.E.
Senior Engineer
Ross Valley Sanitary District
[email protected]
Presentation
Overview
• RVSD Introduction
• Existing Sewer System issues
• Sewer Main Construction Methods
• Project Goals and Description
• Project Alternatives Analysis
• Expected Project Impacts
• Planned Construction Schedule
• Pavement Restoration
• Parklets, Parking, Traffic Impacts
• California Environmental Quality Act (CEQA)
• Coordination with Town of Fairfax and MMWD
Ross Valley
Sanitary District
• Established on May 27, 1899 – Ross Valley Sanitary
District is believed to be California’s oldest sanitary district.
• Service Area: ~55,000 Residents Served in Fairfax, San Anselmo, Ross, Larkspur, Bon Air, Sleepy Hollow,
Kentfield, Kent Woodlands, Oak Manor and Greenbrae.
• Service Scope: The District operates and maintains
approximately 200 miles of collection sewer lines and 19 pumping stations which collect, pump, and transport
approximately four million gallons of wastewater per day to Central Marin Sanitation Agency for treatment.
Existing Sewer System Issues
Existing System
Issues: Hydraulic
Deficiencies
• As part of RVSD’s 2021
Infrastructure Asset Management
Plan (IAMP), a hydraulic model
was updated to identify capacity
issues.
• Several portions of the existing
sanitary sewer trunk system on
Spruce Rd, Park Rd, and Dominga
Ave were shown to be
hydraulically deficient.
• The risk of sanitary sewer
overflows on the 18” diameter
trunk within these streets has
been exacerbated by climate
change, with larger peak storm
events that can overwhelm the
system through I&I.
Creek
Crossings
• Creek crossings present
additional risks to creeks and
riparian habitat.
• Suspended pipes are susceptible
to impact damage from floating
debris and scouring from
abrasive creek bed materials.
• Exposed pipes can also trap
debris and impact creek channel
flow.
• RVSD monitors the condition of
all ~300 creek crossings within
the system.
• Substandard pipes are replaced
and are re-aligned where
feasible.
Sewer Main
Construction
Methods:
Open-Trench
• Trench is excavated and pipe bedding is installed
and compacted.
• Pipe is placed at the correct grade and slope.
• Trench is backfilled and compacted to meet
Town/County/DOT standards.
• Pavement is restored in compliance with local
construction standards.
Sewer Main Construction Methods:
Pipe Bursting
• Trenchless method of replacing existing sewer mains.
• New flexible pipe is pulled through existing pipe using a winch, breaking the existing pipe in place.
Sewer Main Construction Methods:
Pilot Tube Guided Boring
• Trenchless method
of installing new
sewer.
• Launching and
receiving pits are
excavated and boring
machine is installed.
• Pilot tube is drilled to
receiving pit at
precise grade.
• Pipe is fed into boring
as it is enlarged by
larger auger.
Sewer Main Construction Methods:
Horizontal Directional Drilling (HDD)
• Trenchless method of installing new sewer mains.
• Drill rig is set up at entry point and uses a guided drill head to achieve a curved alignment.
• Once drilling head reaches exit pit, flexible pipe is attached and pulled back through new boring.
• Excellent installation method for new sewers under creeks or other sensitive areas.
Current Project Goals
• Improve sanitary sewer system function and reduce the risk of overflow.
• Addresses hydraulic deficiencies associated with sewer system in multiple project locations.
• Project is required as part of the Cease-and-Desist Order placed upon RVSD in 2013 by the CA State Water Resources Control Board to address these hydraulic deficiencies.
• Reduce risk associated with 4 creek crossings of Fairfax Creek. • Reduce potential for odor complaints.
• Reduce required maintenance on sewer system.
• Minimize impacts to businesses, residents, traffic, and public facilities during construction.
Project
Alternatives
Analysis
• Alignment of downtown relief sewer was selected as the result of a study and forced ranking of alternatives based upon the following key criteria:
• Public Impact
• Relative Cost
• Operations & Maintenance
• Constructability
• Hydraulic Capacity
• Selected alignment avoids Bolinas Rd and most of Park Rd. • Shortest route to install relief sewer, also reducing construction impacts. • Full technical report can be found at:
https://rvsd.org/DocumentCenter/View/3734/Fairfax-Sewer-Relief-ProjectRouting-Study---April-2024- Current Project
Description
• Rehabilitate and install ~5,659 linear feet of sanitary sewer. • Diameter of pipe ranges from 6-inch to 18-inch.
• ~2,311 feet of open-trench.
• ~2,156 feet of pipe bursting.
• ~212 feet of HDD.
• ~980 feet of guided boring. This method was selected to reduce impacts during construction to downtown business corridor. • Replacement of 4 creek crossings.
• Rehabilitate ~23 sanitary sewer manholes.
• Lower laterals are replaced where main is replaced.
Downtown Sewer Installation Work
Upstream Sewer Replacement
Construction Schedule: Downtown
6/22 – 7/31
TO BE COMPLETED PRIOR
TO 9/1 TO COORDINATE
PAVING W/TOWN PROJECT
ON PARK RD
Construction Schedule: Upstream
ONGOING SUMMER AND FALL 2026
Pavement Restoration • Uniform Construction Standards
(UCS) of all cities/towns and the
County of Marin ensures consistency
for construction and other
improvements in the roadway.
• T-cut prevents differential settlement
of patch and existing road surface.
• Includes a 2” grind and overlay of new
Hot Mix Asphalt (HMA).
• Ensures equal treatment of the public
and Public Agencies.
• Avoids potential “gift of public funds”
concerns.
Parklets, Parking, and
Traffic
• No impacts to existing parklets planned.
• Trenchless method of installation along
majority of Broadway reduces the need to
excavate and displace parklets.
• Impacts to parking and traffic downtown will
be greatly reduced because of trenchless
method specified.
• “No Parking” signs will be posted 72-hours in
advance of construction work.
• Traffic Control Plan and Encroachment Permit
application to be submitted to Department of
Public Works for review.
• Work will proceed in a manner that minimizes
disruption to residents, businesses,
commuters, and schools.
California Environmental Quality Act
• Pursuant to the California Environmental Quality Act (CEQA): All property owners within a 500’ radius of the project area were notified of project details on March 9, 2026, and engaged for public comment.
No public comments were received.
• Subsequently, the District adopted an Initial Study/Mitigated Negative Declaration (IS/MND) that found that there is no substantial evidence that the project, as mitigated, will have a significant impact on the environment.
• Mitigation measures include nesting bird surveys prior to construction and continuous monitoring of biological and cultural resources during construction.
• A complete copy of the IS/MND can be found at RVSD’s website:
https://rvsd.org/DocumentCenter/View/5843/Fairfax-Capacity-- Creek-Crossings-Project-Final-ISMND
Project Coordination
and Outreach
• RVSD is coordinating this project closely with the Town Department of Public Works and MMWD projects.
• Construction along Broadway has been specifically designed to avoid conflict with MMWD construction work on Bolinas Rd. • Sewer installation will be completed prior to final paving on Park Rd, avoiding cutting of new pavement surfaces and reducing impacts during construction.
• Continued coordination of project with Fairfax Chamber of Commerce.
• Project updates can be found on RVSD’s website:
https://rvsd.org/374/Fairfax-Capacity-and-Creek-Crossings-Pro