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Watershed Projects

Mt. Tamalpais Watershed wooden sign

Multi-benefit forestry projects continue in several key areas across Mount Tamalpais Watershed lands as guided by Marin Water’s Biodiversity, Fire, and Fuels Integrated Plan. The projects are meant to:

Restore forest health

Through selective thinning of small diameter conifer trees, which would otherwise be naturally removed by wildfire in this fire-adapted landscape, and through the protection of oak woodlands from the spread of sudden oak death by reducing the volume of infected biomass

Conserve valuable native habitat 

Through removal of non-native invasive species such as French broom, which includes extensive early detection surveys for new weeds before they become established

Improve wildfire resilience 

To protect critical water storage and delivery infrastructure such as reservoirs, treatment facilities, pipelines, and dams, which are essential to providing clean water for more than 191,000 of our water customers

Increase understanding of forest ecosystems 

Through extensive pre-project surveys for nesting birds, sensitive wetland communities, bat roosts, woodrat nests, rare plants, snags, and other valuable habitat, which also ensures that work will not inadvertently harm natural resources

In May of 2019, Marin Water adopted an Amendment to the Mt. Tamalpais Watershed Road and Trail Management Plan (RTMP) for the Restoration of Azalea Hill (Project). This watershed project will:

  • Remove approximately 4.4-miles of non-system roads and trails and restore those routes to natural conditions to improve habitat and water quality.
  • Adopt and improve a 1.9-mile Class IV road comprised of the existing Liberty Gulch Road (1.2 miles) and convert an existing non-system trail (0.7 miles) to the wider, small vehicle route.
  • Improve the hiking and equestrian route over Azalea Hill by correcting erosion and drainage problems along approximately 1.1 miles of existing Class VI trail, rerouting the trail around sensitive plants and adopting 250 feet of an existing non-system trail.
  • Treat the Azalea Hill parking lot to correct its erosion problems and improve the visitor amenities. Upon its completion, the project would prevent up to an estimated 219 cubic yards of sediment from entering Azalea Hill’s creeks and Alpine Lake annually, and would restore approximately one acre of habitat. 

The Project consolidates use on the two existing routes proposed for upgrades and provides a much-needed connection and safety improvement between the “Lakes” and “Pine Mountain” areas. The district will continue to apply for grants to support the major trail segments as funding solicitations become available. 

If your local organization and community group is interested in funding portions of this project, contributions for the project can be made to the Mt. Tamalpais Watershed Fund. Future volunteer opportunities will be available in coordination with major construction phases.

Marin Water, working in collaboration with the U.S Forest Service, Cal Poly, and UC Davis developed the Resilient Forest Study in 2015, which established forestry treatments for sudden oak death (SOD) impacted forests. 

In 2020 the water district began increasing the implementation of forestry restoration projects on its watershed lands based on the treatments designed as part of the Resilient Forest Study and the management actions outlined in the Biodiversity, Fire, and Fuels Integrated Plan (BFFIP). Forestry treatments were designed to break up the vertical and horizontal continuity of vegetation and fuels with an emphasis on treating the diseased and dying tan oak trees and small diameter Douglas fir trees. Selective removal of Douglas fir is undertaken to reduce encroachment into sensitive habitats such as Oak Woodlands and meadows.

The removal of diseased tan oak aims to disrupt the disease cycle within SOD impacted forests and promote establishment of other native trees and vegetation. Follow-up maintenance in the form of removal of Douglas fir saplings, and cutting tan oak re-sprouts will be completed in subsequent years to maintain the desired stand structure. For additional information about the Resilient Forest Project, or for background data, please contact Natural Resources Program Manager Carl Sanders, or 415.945.1189.


Marin Water manages about 22,000 acres of land surrounding seven water supply reservoirs in western Marin County. When combined with easements on other public and privately held lands, the water district is responsible for managing and maintaining over 700 stream crossings which include bridges, culverts, and rock fjords (crossings). The Culvert Maintenance and Replacement Project is being implemented according to our Mount Tamalpais Watershed Road and Trail Management Plan and the associated Programmatic Environmental Impact Report (PEIR). 

The main purpose of the project is to improve water quality and strictly minimize sediment input into creeks and reservoirs fed by the district’s watershed lands. This improves fisheries habitat, prolongs the life of our reservoirs and facilitates the water treatment process, among other benefits. These projects are also designed to reduce environmental impacts of the road and trail network on the flora and fauna of the district’s watershed lands and ensure safe access for recreational visitors and maintain access to water resource infrastructure.

The project is necessary to enhance the resiliency of the watershed and “storm-proof” specific road and trail segments. Marin Water completed a road and trail related erosion site study performed on the entire watershed that looked at more than 1,200 possible erosion sites.  In 2018, the district completed a stream crossing condition assessment of 724 culverts as part of a new asset management program looking to prioritize the expenditure of limited capital resources to maximize system resiliency. During this assessment, 37 crossings were identified that required near-term repairs because they posed an immediate risk to ongoing district operations and another 60 that would require future repairs. The district’s staff completed the necessary hydrological analysis, and biological surveys to inform the environmental permitting process and resource agency review for Phase I in early 2019.