Cascade Canyon Has Half Its Bridges, and the Missing Half Is Closest to the Gate

On October 12, Marin County Parks posted a short update to its Cascade Trail Bridges project page. It said work on the upper Cascade Canyon bridge, which the County calls bridge 2, "and adjacent project elements has been successfully completed." Nearly thirteen years after the first neighborhood meeting on site, there is a permanent way over San Anselmo Creek above the Fairfax end of the canyon. The other bridge, the one planned near the Cascade Fire Road entrance, isn't scheduled to be built until August through October 2027.

That order of construction shapes this winter. The finished span sits farther up the canyon. The crossing you reach first from the gate at the end of Cascade Drive keeps its old arrangement for one more rainy season.

Two crossings, one finished

Marin County Open Space District's approved design, laid out in its 2021 environmental study, describes the two bridges this way:

Both bridges were designed as six-foot-wide prefabricated weathered-steel truss spans with reclaimed redwood decks. They're built offsite in sections and assembled at the creek on concrete footings set back from the channel bank. The design also calls for approach ramps at a grade under 8.3 percent, which fits the district's Inclusive Access Plan. All of these specs come from the approved plan. The County's completion notice doesn't list as-built measurements.

The full project, with both bridges, is expected to be finished by October 2027. So the canyon has one complete season between bridges, and it starts now.

The fords stay, and the old winter detour is off the map

Cascade Fire Road runs from the end of Cascade Drive up the canyon floor and crosses San Anselmo Creek four times on rock fords. The County's environmental study says those fords "are impassable during periods of high storm runoff."

For years, the High Water Trail handled those days. It's a narrow path that climbs about 1,200 feet up the north bank of the creek. The same study describes portions of it as eroding, with steep slopes and active erosion into the creek. It says the trail "is no longer a designated trail within the MCOSD trail system and is not shown on the trail map." The project plan decommissions and restores both the High Water Trail and the Canyon Trail spur that connects to Cascade Fire Road. The October 12 notice doesn't say whether that restoration was part of the phase that just wrapped.

The rock fords themselves aren't going anywhere. Under the approved design they stay in place for district maintenance and emergency vehicles. Split-rail fencing and signage go up along the old approaches to steer walkers and riders toward the bridges, with detachable rails so trucks can still get through.

On a wet weekend this winter, that adds up to a canyon with a new dry crossing upstream, a lower crossing that works the way it always has, and a former high-water bypass the district no longer counts as a trail. The upper bridge changes the walk past the 1,000-foot mark. The first stretch from the gate stays the same until the lower bridge is built.

Why a creek crossing took nearly thirteen years

The County's project timeline shows how much process a short stretch of trail in Fairfax goes through:

1. 2013. Engineering geologist Timothy C. Best prepares a preliminary trail report that includes the bridges, and County representatives meet neighbors on site that December.
2. 2015. The project goes through the Region 2 trail designation process, with a public workshop on October 3 and a designation meeting on November 30.
3. April 14, 2016. Friends of Corte Madera Creek Watershed and the Marin County Bicycle Coalition formally propose the project to the district.
4. September 8, 2016. A public meeting at the Fairfax Women's Club, where Daniel Logan, a fishery biologist with the National Marine Fisheries Service, talks about San Anselmo Creek fish populations.
5. May 23, 2017. The Town of Fairfax and the district sign a Memorandum of Understanding.
6. February 16 to March 19, 2021. The environmental review's public comment period draws 190 comments.
7. 2022. A traffic study, drawing on visitor-use cameras installed in August and September 2019 and again in March and April 2021.
8. October 2023. Responses to comments are published and the Open Space board certifies the review and approves the project.

The Town has a seat at this table for a specific reason. Most of the project sits inside the Elliott Nature Preserve, which Fairfax transferred to the Open Space District in 1987. Through a deed restriction, the Town kept approval authority over any improvements there. That's why the Fairfax Town Council had to vote in December 2016 before the bridges could move forward.

The biology in the creek explains why the project kept going through all that. San Anselmo Creek supports federally listed steelhead and foothill yellow-legged frogs. Foot, bike and horse traffic through the fords can stir up fine sediment that harms the fish downstream and can physically affect the frogs. According to the County, the frog survives in Marin only in a few creeks in isolated watersheds, and Cascade Canyon is one of them. One Tam has more on the species. Seen that way, the bridges are as much about keeping boots and tires out of a rare frog's creek as about keeping hikers dry.

What the steel cost, and what that number leaves out

On April 7, 2026, the Marin County Board of Supervisors approved up to $65,000 to buy the steel bridge frame from Ahlborn Structural Steel Inc. of Santa Rosa. The staff report charges the purchase to the Open Space District's Fund 2540 budget and says there's no impact on the County General Fund.

That figure covers fabricating the frame only. It doesn't include trail work, footings, the riprap along the south bank, or a total project budget. The approved design calls for about 40 cubic yards of new rock at each bridge site to protect the abutments. The Marin County Bicycle Coalition's project page lists Marin County Parks as the funder.

Construction ran on a tight seasonal window. The Town of Fairfax announced that main construction would start August 3. In its August 4 notice, the Town said Cascade Fire Road would be closed Monday through Friday, 8 a.m. to 4 p.m., through October 2026, while Cascade Falls Trail, Middle Fire Road, Carey Camp Trail and Canyon Trail stayed open. Ten weeks later, the County reported the upper bridge finished. The lower bridge gets the same dry-season window in 2027, when the design calls for heavy equipment to ford the creek in low water to reach the site.

Who the bridges open the canyon to

The project changes who can use part of the trail along with where people cross. Canyon Trail runs about 1,600 feet along the south side of San Anselmo Creek, on a flat terrace with a wooden footbridge at Carey Camp Creek. The design study lists it as a hiker and equestrian trail. The County's plan realigns trails to "allow multiuse access" and adds bicycle speed control features and a bike rack. The design describes this as a change in use on one segment of Canyon Trail. Cascade Canyon is a corridor between Fairfax neighborhoods and Camp Tamarancho, used by people on foot, on bikes and on horseback, so the bridges serve all three.

That shift was at the center of the debate. When supervisors advanced the project in late 2023, the Marin Independent Journal reported that some neighbors worried the bridges and bike access could bring more visitors, more trail conflicts with cyclists and more pressure on parking. Supporters and conservation advocates made the case for the project in the same story.

Before you park on Cascade Drive

Access hasn't changed. The canyon is reached from Cascade Drive off Bolinas Road, and the environmental study notes "very limited roadside parking along Cascade Drive but no dedicated visitor parking" inside the preserve. On its Cascade Canyon preserve page, Marin County Parks says parking is limited to residential street parking on Cascade Drive and Canyon Road. It asks visitors to respect residents and points anyone who can't find a spot on Cascade Drive to the Canyon Road trailhead.

A few practical points for the months ahead:

• The upper bridge is the new piece. Expect fencing and signs at the old ford approaches directing you to it.
• The lower crossing near the entrance stays a rock ford until the 2027 bridge is built. On high-water days, the fords are the part of the route the County calls impassable.
• The High Water Trail is no longer a designated trail, so it isn't an official winter backup.
• If Cascade Drive is full, the County directs visitors to the Canyon Road trailhead.

For a few more weeks, the County's project page will have the most recent status for both crossings, and it's the place to watch for the 2027 construction schedule as next summer gets closer.

If you live near the canyon and are curious how a project like this plays into the streets around it, Zamira Knows Marin follows changes to Ross Valley's trails and town life closely, and we're always glad to talk through what's changing near your corner of Fairfax.