Large hole that formed under bridge on Boulder Canyon Trail partially reopens

Update: April 3

The bridge section of Boulder Canyon Trail closed late last week is now open after maintenance crews implemented a temporary repair to the hole that had formed under the bridge, according to BCPOS.

The repairs at the bridge had to be narrowed, BCPOS said, to approximately 6 feet from the usual 8-10 feet. A chain fence is in place to block off the damaged area beneath the trail surface.

BCPOS said the repairs are temporary in order for the full length of the trail can safely reopen to pedestrians and cyclists.

Update: April 1

BCPOS said in an email update on April 1 that the large hole forming under a bridge on a section of the Boulder Canyon Trail is approximately 6 feet long, 4-5 feet wide, and 3-4 feet deep.

“The top surface of the trail looks intact because it sits on a thin concrete or rock slab with crusher-fines on top, however, the area beneath that layer has washed away and there is potential it will collapse creating an unsafe sinkhole,” BCPOS said in the email.

At this time, no detour remains unavailable, according to BCPOS.

“The canyon’s geography does not provide a feasible alternative route off of Highway 119,” BCPOS said. “Staff are partnering with the Colorado Department of Transportation (CDOT) to add additional signage on the road to alert drivers of the extra bike traffic present.”

A section of the Boulder Canyon Trail is closed currently because a hole has formed under the abutment of a bridge, according to Boulder County Parks & Open Space (BCPOS).

The closure is at the bridge a quarter-mile east (downhill) of Fourmile Canyon Drive, approximately 3.5 miles west of downtown Boulder, and a detour is NOT available, BCPOS said in a statement March 27. 

According to BCPOS, staff are developing a plan to repair the damage.

“The project is complex due to the proximity along Boulder Creek and Boulder Canyon Drive (Highway 119), the potential permitting needed, and the City of Boulder’s water utility infrastructure that runs under the bridge,” BCPOS said in the statement.

According to BCPOS, the bridge will remain closed while a repair plan is finalized, necessary permits are secured and construction is completed. A timeline is not yet available.

“Addressing this issue is a top priority, and staff are working as quickly as possible,” BCPOS said. “Public safety remains the highest priority, and trail users are asked not to use the closed bridge.”

Boulder Canyon Trail is a highly popular route for both hikers and cyclists, and BCPOS said “staff are working diligently to restore access as soon as it can be done safely.”

Updates will be posted on the Boulder Canyon Trail webpage.