Monday morning, the Dry Creek Trailhead gate swings shut, and it won't open again until October. Boulder County needs to replace a bridge on Baseline Road, and the trailhead sits in the way. If that's been your starting point for a morning walk or ride, you'll need a new one as of August 24.
That single closure would be a minor inconvenience on its own. It isn't on its own. Right now, four separate infrastructure projects are running at the same time across Boulder's trail and path network, and the timeline for each one is telling a different story about how this city decides what gets fixed fast and what waits.
Four Projects, One Six-Week Window
Here's what's actually blocked as of this week, and for how long.
| Location | Closed Since | Expected Reopening | What's Happening |
|---|---|---|---|
| Dry Creek Trailhead | Aug. 24, 2026 | October 2026 | Boulder County is replacing a bridge on Baseline Road |
| 1st/2nd Flatiron Trail (bridge to New Saddle Rock junction) | June 15, 2026 | Fall 2026 | Closed Mon-Thu, 8am-4:30pm, for stone infrastructure rebuilding |
| Arapahoe Avenue Pedestrian and Bike Bridge over South Boulder Creek | Aug. 11, 2026 | Roughly early October 2026 | Full bridge replacement, about two months of work |
| Fourmile Canyon Creek path (47th Street to Foothills Parkway) | June 25, 2026 | Several months out | Bikeway connections tied to the CO 119/Diagonal Highway project |
Layer the Diagonal Highway work on top of that. A lane closure that started August 10 sits on southbound 63rd Street in the median between the north and southbound lanes of CO 119, expected to last about a month, and the RTD bus stop at CO 119 and 47th closed as of August 17 for roughly four months, which means the BOLT route between Boulder and Longmont is running a modified stop pattern through the fall.
Look at where the detours actually land and the map splits into two clusters. Down in south Boulder, the Arapahoe bridge work pushes cyclists onto Cherryvale Road, a project with nothing to do with anything happening north of town. Up along the Diagonal corridor, the Fourmile Canyon Creek closure reroutes riders onto Independence Road and 47th Street, the same stretch where CDOT is simultaneously narrowing lanes and closing a bus stop for its own bikeway project. None of these four closures caused each other, but two of them are now asking the same few blocks of north Boulder to absorb rerouted bike traffic and reduced car capacity at the same time.
The Twenty-Day Fix
Compare that to what happened in March.
A section of the Boulder Canyon Trail closed after a hole opened up under a bridge abutment about a quarter mile downhill from Fourmile Canyon Drive. No detour existed. Cyclists who needed to get past the closure had one option: ride on Boulder Canyon Drive itself, a stretch of Highway 119 with no shoulder and speeds that don't slow down for bikes.
That stretch of road already had a body count. The original trail bridge was built after a cyclist was killed there in 1991, and the advocacy group Community Cycles didn't let the county forget it. Within days of the March closure, Community Cycles sent a formal letter to Boulder County commissioners demanding a structural assessment and a safe interim route. The Boulder Mountainbike Alliance backed the request. County commissioners Stolzmann and Levy responded, and Boulder County Parks and Open Space completed a temporary repair and reopened the bridge on April 3, roughly three weeks after the hole was first discovered on March 12.
Three weeks, start to finish, for a structural repair that involved a creek crossing, a highway shoulder, and underground water infrastructure.
The Multi-Year Wait
Boulder Falls is still closed, and it has been for close to two years.
A rockslide in November 2024 damaged the trail infrastructure that kept loose stone off the path, and the city shut the area down. It drew roughly 261,000 visits in 2023, one of the most-visited spots in Boulder's entire open space system, and it has sat behind a fence ever since. City staff spent 2025 weighing whether to reopen it at all. By January 2026 they'd settled on a plan: build a new viewing platform farther from the rockfall zone instead of repairing the original trail. A feasibility study running through 2026 will determine what that actually costs and how long it takes to build.
There's no date attached to any of it. The fix under consideration involves mesh netting and long steel bolts drilled into the hillside, work that requires helicopter support because of the terrain. That's not a bridge patch. It's a different category of engineering problem, and it's being treated like one.
What Actually Explains the Gap
Two things separate the twenty-day fix from the multi-year one, and neither of them is how much anyone cared.
The first is who showed up. The Canyon Trail bridge had an organized user base with a specific ask and a direct line to the commissioners who could act on it. Boulder Falls draws hikers, families, and tourists on a single afternoon visit, a crowd with no standing advocacy group and no formal channel for collective pressure the way commuting cyclists have.
The second is what the fix actually requires. A bridge patch is a known problem with a known solution. A hillside that just proved it can drop boulders 17 feet into the air and across a creek needs geotechnical review before anyone commits public money to a design, because the wrong fix doesn't just fail, it fails on top of people.
Both of those forces are doing something to the four closures on this week's map too. The Arapahoe bridge and the Dry Creek trailhead are straightforward infrastructure replacements with fixed timelines because the engineering problem is well understood. The Fourmile Canyon Creek path closure is tied to a larger CDOT bikeway project with its own multi-year build schedule, which is why "several months" is the best estimate anyone can currently give.
How to Get Real-Time Updates Instead of Guessing
The city and county post updates faster than any single article can track, so build the habit now rather than after you've hit a barricade.
- Text "OSMP" to 888-777 for updates on trail closures, muddy conditions, and prescribed burns directly from Boulder's Open Space and Mountain Parks department.
- Check the Cone Zones map before a bike commute that touches downtown or the Diagonal corridor. It tracks active construction citywide, updated as projects change.
- Bookmark the OSMP closures page itself. It's the single source the city updates first when a trailhead status changes.
- Follow Community Cycles and the Boulder Mountainbike Alliance if you ride regularly. Both organizations track closures the moment they happen and have a track record of pushing the county for faster fixes and safer detours.
The Short Version
If you're planning a ride or a hike over the next six weeks, expect Dry Creek Trailhead to be gone until October, the Flatiron approach to be off-limits on weekday afternoons through the fall, and the Fourmile Canyon Creek connector to stay fenced off longer than that. The Arapahoe Avenue bridge should be back by early October if the two-month estimate holds. Boulder Falls isn't on anyone's near-term calendar, and probably shouldn't be.
What's worth carrying forward isn't just the map. It's the read on how Boulder actually fixes things: fast when the fix is simple and someone organized is pushing for it, slow when the ground itself hasn't decided it's safe yet.
Boulder's trail network is one of the things that makes living here different from living almost anywhere else, and knowing how it actually works, closures and all, is part of knowing the town. If you're weighing a move into a specific pocket of Boulder and want someone who can tell you not just what a listing looks like but what your actual commute, dog walk, or ride to the trailhead will be like once the cones come down, The Bernardi Group knows this ground the way only people who ride it every week can.
