Fairfax Trails This Winter: Cascade Canyon's New Bridge

About 1,000 feet up San Anselmo Creek from the Cascade Drive gate, there is a new 60-foot weathered-steel truss with a reclaimed-redwood deck. It sits above the creek's 100-year flood elevation, right beside the rock ford where people used to cross. Marin County Parks finished it on October 12, 2026. The timing means the upper crossing gets its first rainy season with dry footing.

Go over the ridge onto the Mt. Tam watershed and the calendar runs the other way. Marin Water's tank construction keeps part of Concrete Pipe Road closed during working hours until January 31, 2027. So for the next few months, the hills behind Fairfax work on two clocks. One project's construction season is over. The other has three months left. From February through July, neither project has construction scheduled.

The bridge that went in this fall

Cascade Canyon Open Space Preserve is the trail corridor between the residential streets of Fairfax and Camp Tamarancho. Until this fall, getting into the preserve meant using one of four low-water rock fords across San Anselmo Creek. The county's own project summary says those fords put visitors at risk of injury when the creek runs high in the rainy season. Foot, bike and horse traffic through the fords also stirs up fine sediment, which can harm the federally listed steelhead downstream and the young fish moving upstream to summer rearing habitat.

Construction began the first week of August. The Town of Fairfax's notice said Cascade Fire Road would be closed for the length of the work, Monday through Friday, 8 a.m. to 4 p.m. That closure covered the busy dry-season weeks. Now the weather is turning, and the payoff is arriving just as the creek starts to rise.

The new bridge is 6 feet wide, built in two prefabricated sections and assembled on site. The approaches were designed at a grade under 8.3 percent, and the realigned trail was designed to the Marin County Open Space District's Inclusive Access Plan. The new trail on each side curves on purpose. The project plan calls for about 180 feet of new tread on the north side and about 50 feet on the south, laid out to slow people down and lead them away from the old ford.

Cascade Falls is the reason the timing matters

Late fall through winter is when this canyon is worth the walk. Cascade Falls is a 20-foot waterfall inside the preserve, and Marin County Parks recommends visiting during the rainy season when it is running strong. The county lists the gate at the end of Cascade Drive as the main entry and the end of Canyon Road as an alternate trailhead.

Cascade Falls Trail stayed open through the whole bridge project, along with Middle Fire Road, Carey Camp Trail and Canyon Trail. The waterfall route never closed, and the canyon's interior now has a crossing that high water can't take away.

The lower crossing waits until 2027

The bridge that opened is the upper one. Bridge 1 will be the longer of the two at 90 feet. It goes near the entrance to Cascade Canyon Fire Road, 140 feet downstream of the first of the four fords. Marin County Parks has it scheduled for August through October 2027, with the whole project expected to wrap up by October 2027. The approved design also lets heavy equipment drive through San Anselmo Creek during the dry season to reach the bridge sites. That explains the late-summer work windows in both years.

Some of the trail changes in the plan only take effect once that second bridge is built.

Piece of the plan	Where it stands this winter
Upper bridge, 60 feet	Finished October 12, 2026
Lower bridge, 90 feet, near the Cascade Drive gate	Scheduled for August through October 2027
Canyon Trail changes from hikers and horses only to multiuse with bikes	Part of the plan, with speed-control chicanes on the south side of the lower bridge
Highwater Trail and the Canyon Trail spur to Cascade Fire Road	Slated to be closed and restored
Bike rack at the preserve entrance	Part of the plan

The design ties the Canyon Trail chicanes to the lower bridge, so riders should check the posted trail-use signs before assuming bikes are allowed. The old fords stay in place for district and emergency vehicles. Under the design, split-rail fencing and signs on the approaches will steer visitors to the bridges, and detachable rails will let service vehicles through.

Over the ridge, the calendar is set by owls

The Sky Oaks entrance into the Mt. Tam watershed has its own construction clock, and it runs later in the year. Marin Water is building a pair of seismically resilient, 2-million-gallon concrete storage tanks near Concrete Pipe and Sky Oaks roads. They will be called the Gibson Tanks, after former Marin Water board member Jack Gibson. They replace the Pine Mountain Tunnel, which was built in 1919 to carry water from Alpine Reservoir to Fairfax and San Rafael and has served as water storage since 1971. Marin Water says the new tanks will raise water system capacity in Ross Valley by about 30 percent. The posted funding is $23,188,370, all from the district's Capital Maintenance Fund.

Marin Water's October 2026 update calls this the fourth straight year of construction and the second year of Phase Two. The underground piping is done, and crews are pouring the tank foundations through January 31, 2027. Until then, Concrete Pipe Road between Bolinas Road and Taylor Trail is closed during normal working hours. Bon Tempe and Bullfrog roads also close at times while crews haul material. The current update doesn't spell out the daily hours. When this closure first started in 2023, Marin Water listed it as Monday through Friday, 8 a.m. to 5 p.m.

The end date follows a rule. The construction window usually runs from August 1 to January 31 to protect the Northern Spotted Owl, and the full project is planned to last until winter 2029. That makes the Concrete Pipe Road closure a pattern that repeats every year. It runs on workdays from August through January, then lifts for the six months from February through July.

The winter, month by month

Put the two projects side by side and you get this calendar for the hills behind Fairfax:

Late October through January: Cascade Canyon's upper crossing has its bridge, and Cascade Falls is coming into season. On the watershed, Concrete Pipe Road between Bolinas Road and Taylor Trail stays closed during work hours, with occasional closures on Bon Tempe and Bullfrog roads.
January 31, 2027: This year's tank foundation work is scheduled to end, along with the owl-season construction window.
February through July 2027: Neither project's seasonal construction window is open, so these are the months to plan the longer Sky Oaks loops.
August 2027: Tank work can start again under the owl window, and the lower Cascade Canyon bridge is scheduled to begin.
By October 2027: Marin County Parks expects the Cascade bridges project to be finished.

Weekends are the simpler choice on the watershed until the end of January. The Mt. Tam watershed is open daily from 7 a.m. to sunset, and the Sky Oaks day-use fee is $8 per passenger vehicle, $15 with a trailer and $30 for a bus. Vehicles with a disability placard get in free.

Before any outing, check the live alert pages. As of its September 28 update, Marin County Parks also lists a temporary closure of the Mount Baldy Trail at Bald Hill for improvements. Marin County Parks and Marin Water both keep their alerts current, and those pages are where a reopening or a new closure will show up first.

The longer view on the watershed

The tanks aren't the only planning work on the mountain. In August 2026, Marin Water started environmental review on an update to its Mount Tamalpais Watershed Roads and Trails Management Plan, which would look at possible changes to access. The comment period for that review closed on September 28, and the draft plan's release date is listed as to be determined. No new access rules have been adopted, so the roads and trails you know on the Sky Oaks side work the same way they did last winter. The exception is the construction gate on Concrete Pipe Road.

Back in Cascade Canyon, the next milestone comes in late summer 2027, when the lower bridge goes in near the Cascade Drive gate. When it's finished, both of the project's planned bridges over San Anselmo Creek will be in place.

Questions about the trails come up whenever we talk with clients about life in Ross Valley, and the new bridge is the best update we've had in a while. If you live near Cascade Drive or Sky Oaks and want to know how your home fits into today's market, Suzie Koide is happy to put together a complimentary home valuation and plan, with no pressure and no rush.