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The door is open for public comments on a plan to expand bicycle access and habitat restoration in the Mount Tamalpais watershed as an environmental analysis gets underway.

The Marin Municipal Water District, which owns the property, is proposing to update its road and trail management plan, which hasn’t been revamped since its adoption in 2005.

Major proposed updates include the designation of a 2,500-acre conservation area and 68 miles of restoration. The proposal also would establish 27 miles of hiking and biking trails and 15 miles of mixed-use trails for hikers, mountain bikers and equestrians. The plan would create more than 4 miles of trails accessible for people with disabilities.

The state requires an environmental impact report, or EIR, assessing how these changes affect the watershed, and how to mitigate unwanted consequences.

The initial public comment period, which helps shape the content of the report, is open through noon Sept. 28. An event for residents to learn about the proposal and submit comments is scheduled for 4 p.m. Thursday at the Sky Oaks Watershed Headquarters at 49 Sky Oaks Road in Fairfax.

“The EIR will evaluate potential impacts on biological resources, water quality, air quality, transportation and other factors,” said Jessie Underhill, a water district official. “The district welcomes all comments on any potential environmental impacts that should be considered in the EIR, and alternative suggestions or mitigation approaches that may help to minimize environmental impacts.”

Comments will be compiled in the draft environmental impact report, which will be released for another public review and comment period.

Bicycle access in the Mount Tamalpais watershed has been a polarizing issue for decades, with critics citing environmental issues and safety as their main concerns.

Members of an environmental group sued the water district in 2024 to stop a pilot program to allow bikes on trails. Part of the complaint said the water district hadn’t performed an environmental impact report, evaluating how introducing bikes in new areas would alter the watershed.

After a settlement was reached, the district authorized a modified e-bike pilot program so class 1 pedal-assisted electric bikes could be permitted for the first time on the fire roads where traditional bikes are allowed. The modified pilot program began last summer.

The district decided in October to take another look at expanded bicycle access through an update of its road and trail management plan, including an environmental impact report. After more than six months of planning, the board approved sending the proposal to environmental review in June.

Plaintiffs in the 2024 lawsuit said they still have concerns. Barbara Salzman, president of the Marin Audubon Society, said her group will be submitting more thorough comments.

“We’re looking forward to the draft EIR providing a thorough review of the existing conditions and potential impacts of the project on the sensitive natural resources of Mount Tam,” Salzman said. “The health of the ecosystem is at stake.”‘

The Marin Conservation League, also a plaintiff, has an adopted road and trail policy that establishes natural resource protection, sustainable trail management and visitor safety as primary goals, said Larry Minikes, a board member of the nonprofit. The policy calls for management that ensures “the natural environment and the wildlife it sustains will persist into the future,” while assuring users of their safety, he said.

“The EIR offers the opportunity to apply those principles as Marin Water considers restoration, trail classifications, permitted uses and changes in recreational access,” he said. “The completed plan can translate those principles into a clear, measurable and adequately funded framework that protects the watershed, guides appropriate public access and carries its commitments forward.”

Members of the Marin Horse Council have expressed concerns as well.

In an email on behalf of the organization, Linda Novy said introducing bikes, specifically pedal-assisted e-bikes, will change the experience on the mountain, creating avoidable safety and maintenance problems for hikers, equestrians and the trails.

The group says its concern is not opposition to bikes or the cyclists, but whether the trail is suitable for the type of use.

Narrow, winding single-track trails were often designed around slower, predictable travel by hikers and horses, the email says. Introducing bicycles, particularly pedal-assisted e-bikes, changes the speed, acceleration and frequency of encounters on those routes, it says.

“Marin’s trails are a shared public resource, but ‘shared’ should not mean that the quietest and most vulnerable users bear the cost of accommodating faster travel,” the email says. “Hikers and equestrians deserve to feel safe, and the watershed deserves protection from unnecessary erosion and overuse. Until the district can demonstrate that expanded bike access will not compromise those interests, it should preserve the existing limitations and proceed cautiously rather than turning every suitable-looking trail into a multi-use experiment.”

Supporters of the proposal say it is an environmentally-minded way to open new access opportunities.

“Mount Tamalpais is a treasured watershed and one of Marin’s most incredible places for people to connect with nature,” said Krista Hoff of the Marin County Bicycle Coalition.

“MCBC appreciates Marin Water’s thoughtful, thorough and inclusive approach to how its road and trail network can best serve both watershed health and responsible recreation,” she said. “This process represents an important opportunity to simultaneously restore habitat and improve the sustainability of the trail system while providing hikers, equestrians and cyclists with meaningful, safe and well-designed opportunities to experience Mount Tam.”

Bob Mittelstaedt, one of the co-founders of the E-Bike Access advocacy group, had similar thoughts, noting that Mount Tamalpais is the birthplace of mountain biking.

“This next step in updating the recreation management plan will give everyone a chance to be heard,” he said. “I trust that everyone will participate in good faith and accept the results — without litigation this time — even if it means that the imbalance between hiking and cycling trails is somewhat alleviated.”

The Marin Municipal Water District, which owns the property, is proposing to update its road and trail management plan, which hasn’t been revamped since its adoption in 2005.

Major proposed updates include the designation of a 2,500-acre conservation area and 68 miles of restoration. The proposal also would establish 27 miles of hiking and biking trails and 15 miles of mixed-use trails for hikers, mountain bikers and equestrians. The plan would create more than 4 miles of trails accessible for people with disabilities.