CO 119 Boulder Canyon Improvements

Colorado Highway 119 Traffic Alert

CO 119 Boulder Canyon opens with one lane following safety assessment

Road will close at regular 10 a.m. time for continued cleanup

Colorado Highway 119 in Boulder Canyon was opened with one lane of alternating traffic around 4 a.m. this morning after geotech experts determined the slope was stable and additional blasting was not needed on part of the rockface.

This assessment allowed crews to move safely and clear the one lane area. Included in that clearing was the need to blast several large boulders, estimated to be the size of a bus, into smaller pieces that could be hauled away. That additional blasting took place before dark which then gave time for crews to haul away and clear the one lane. 

The road will close again at 10 a.m. -- which is the normal closure time -- to allow crews to continue the cleanup and it will reopen with at least one lane again at 2 p.m.

“We thank everyone for their continued patience as we work through a technically complex effort,”said Colorado Department of Transportation Executive Director Shoshana Lew. “This work is important for keeping people safe when driving in mountain areas, but it’s difficult work and we know that it causes inconvenience for the traveling public during construction.” 

After the rockfall from blasting on Wednesday sent 8,000 cubic yards of rock to the road, it was initially determined that another area of rock would need to be blasted which is why the Colorado Department of Transportation said the road would be closed for two to three days. 

After given the all-clear by the experts, crews worked through the night to clear about 4,000 cubic yards of rock to make room for the one lane. 

No closures are expected for Friday or over the weekend. Regular blasting closure will start at 10 a.m. Monday.


During the 10 a.m. to 2 p.m. closure, travelers are urged to avoid the Boulder Canyon route if possible. Local detours are available. From Boulder, a northern alternate route can be taken via CO 7, US 36 and CO 72. A southern alternate route is available via CO 93 and CO 72. Please note, motorists taking the southern alternate route should be aware of a current project on CO 72 in Coal Creek Canyon, between Plainview Road (mile point 12.3) and Pinecliffe (MP 24.6). Expect lane shifts and short delays at this work zone. 

Anyone wanting to receive text alerts about this project and the closure can text CO119 to 21000.

Work this Week
September 8-14

Sunday, September 8 through Saturday, September 14, Colorado Highway 119 - Boulder Canyon will have single and full lane closures. During working hours, there will be up to five areas impacted concurrently.
Full Highway Closures 

Monday through Thursday (Sept. 9 - Sept. 12 ) rock blasting activities will result in a full closure of Colorado Highway 119 from MP 39-40 between the hours of 10 a.m. to 2 p.m. Motorists entering the canyon from Nederland will be stopped at 9:45 a.m.  

In order to prevent extended closures this week, crews will implement 10 minute stops near the blasting zone at MP 39-40 between the hours of 7 a.m. - 10a.m., and 2 p.m. - 6 p.m Monday, Sept. 9 - Thursday, Sept. 12.
24/7 Ongoing Impacts
Culvert installation will impact MP 36, and rock hauling will impact MP 40. Shouldering continues between MP 34 - 38, west of Magnolia and Sugarloaf roads.

Motorists will be guided around the single lane closures with traffic control flaggers.
Three traffic signal zones will remain in place near MP 32, MP 38 and near MP 39, 24-hours a day, 7 days a week, to preserve the work areas.  
Up to 40-minute delays are expected through the canyon during work hours. Speed limits are reduced to 25 miles per hour in the construction zones. The work is weather-dependent, and the schedule may change. 
Please plan additional time to travel through the construction zones or to use the alternate routes of Colorado Highway 72 or Lefthand Canyon Drive during the full road closure. 
Trail Closure
The Boulder Canyon Trail, from the canyon mouth in Boulder to the Fourmile Canyon trailhead, will be closed, Monday – Thursday, 7 a.m. to 2 p.m. 

On Monday, Sept. 9, the Boulder Canyon Trail will be closed at MP 40 where it crosses under CO 119, preventing through access from Boulder to the Four Mile trailhead from 7 a.m. - noon while crews prepare for the upcoming rock protection work.

Beginning as soon as Sept. 13, the Boulder Canyon Trail will be closed at MP 40 where it crosses under CO 119, preventing through access from Boulder to the Four Mile trailhead, while crews install rock protection around the highway structure. This closure will be in place through the end of the year. Eastbound cyclists will need to use CO 119 during this time. Westbound cycling will be closed. 

Creek Closure
The Boulder Canyon Creek will be closed for use from the canyon mouth in Boulder to the Fourmile Canyon trailhead, Monday - Thursday, 10 a.m. – 2 p.m.

ALERT: Four Mile Resident Permits  

Residential permits remain available for residents who live on Four Mile Road, to maintain access to their homes from Nederland while the full closures are in place. If you live on Four Mile, and still need a permit, please call the project hotline. 

Unfortunately, Sugarloaf and Magnolia residents do not qualify for these permits. Local emergency service groups, in partnership with CDOT, cannot allow detour traffic over Fourmile/Poorman due to fears of construction congestion preventing emergency access.

When will the full closures for blasting end? 

Although we know that the blasting will be completed this fall, we currently do not have an exact end date, due to design changes. In order to make sure the final product is secure but still achieves the ultimate goal of protecting the roadway from future floods, the designers are adjusting the plans. As soon as an end date is determined, a public announcement will be made.

What construction will take place following the blasting? 
Following the blasting, work crews will begin the widening of the existing pedestrian underpass for the new Boulder trail, new guardrail and barrier throughout the canyon, retaining walls, six areas of rip-rap installation (rock used to protect the roadway from flooding), two bridge rehabilitations, and a new roadway through the blasting area at MP 39-40.  Many of these operations, including the bridge rehabs and rip-rap installation, can only be performed during the winter when there is low flow in the creek. 

How long will there be single lane closures with traffic signals in the canyon?
Single lane closures controlled by either flaggers or signals will be used until all work is completed in early spring 2021.

How will you maintain the road this winter? 
CDOT Maintenance will plow CO 119 in Boulder Canyon this winter. Zak Dirt will maintain the construction work areas.

When will the bike path be completed? 

The bike path extension will be completed late fall 2020. 

How far does the new bike path extend? 
The project, in partnership with Boulder County, will extend and reinforce sections of the Boulder Canyon Trail. The 10-foot-wide, multi-use trail will be extended from Four Mile Canyon to Chapman Drive, adding two new bike-friendly tunnels under the highway and approximately 3500 feet of length to the trail.

Project Facts

  • Cost: $31 Million
  • Contractor: Zak Dirt
  • Timeline: Winter 2019 - Summer 2020
  • Location: CO 119 between Boulder and Nederland
  • Alternate Route During Construction: CO 72 is a recommended detour. Learn more about the CO 72 Coal Creek Canyon project.

In March 2019, crews began repairing a 15-mile stretch of Colorado Highway 119, between Boulder and Nederland, which was damaged during flooding in 2013.

Work includes:

  • resurfacing 13 miles of highway, and entirely replacing two miles of highway;
  • building concrete islands to improve the roundabout in Nederland;
  • installing new highway directional and safety signage;
  • replacing multiple pipes conveying stormwater drainage under the highway;
  • scaling rock in selected areas to reduce rockfalls on the highway;
  • repairing soft shoulder areas immediately adjacent the highway;
  • replacing 29,000 linear feet of concrete or metal guardrail;
  • removing and replacing materials placed during emergency repairs;
  • excavating areas where the slope had failed in the storm;
  • redesigning and widening specific sections of the roadway;
  • reconstructing embankments; and
  • re-establishing native grass seed and erosion control to slopes that were disturbed during emergency recovery work.

Boulder County Trail Improvements

The project, in partnership with Boulder County, will extend and reinforce sections of the Boulder Canyon Trail. The 10-foot-wide, multi-use trail will be extended from Four Mile Canyon to Chapman Drive—adding two new bike-friendly tunnels under the highway and approximately 3500 feet of length to the trail.

Project Work Hours:

  • 7 a.m. - 7 p.m., Monday - Friday
  • Rock-blasting work hours: 10 a.m. - 2 p.m., Monday – Thursday 
  • No night or weekend work is planned. However, some work zones will remain closed to preserve the work area.

Travel Impacts & Delays

Various delays from single lane & full road closures are expected throughout the project.  Motorist are strongly encouraging everyone to plan ahead to give yourselves enough time to reach your destination.

  • Expect full highway closures for rock blasting and excavation, with four-hour complete closures.
  • Expect various long-term single-lane closures managed by temporary traffic signals, and various short-term single-lane closures managed by flagging.
  • Full Canyon Closures Monday through Thursday and 40-Minute Delays.
  • Speed limits will be reduced to 25 mph in the work zones. Expect several stops through the corridor.  
  • A permit-load restriction will be in effect.

Boulder Canyon Trail Impacts

  • April – August 2019
    • Crews will close the trail and parking areas adjacent to the trail (near mile point 40) when rock blasting is needed.
    • The trail could be impacted four times a week for nine hours at a time to allow for safe rock-blasting activities.
    • No weekend or holiday work is planned.
  • August - December 2019
    • The trail will be closed below the Boulder Canyon Trailhead at all times, including weekends and holidays.
    • Crews will place signage along the trail, at the opening of the canyon near Boulder City limits.

Updated Cycling Closures

To help keep everyone safe, the project team is continually monitoring the movement of vehicles and cyclists through the canyon and making adjustments as necessary. Starting Wednesday, July 3, cyclists will be allowed to travel in both directions of CO119 west of Fourmile Canyon Road. Project crews will be updating signage in the coming days. 

Between Fourmile Canyon Road and Arapahoe Avenue, all westbound cycling is restricted and eastbound travel is restricted between the hours of 9:45 a.m. and 2 p.m. Monday through Thursday. In this area all westbound cyclists and eastbound cyclists traveling between the hours of 9:45 a.m. and 2 p.m. on these days must use the Boulder Canyon Trail at all times. This is a safety measure to help keep the public safe in the busiest work area.

The Boulder Canyon Creek bike path is closed in both directions in the canyon from 6:45 a.m. to 2 p.m. Monday through Thursday. Due to the path's proximity to the blast area, this is a safety measure to make sure no pedestrians or cyclists are inside the blast zone during the day. 

If cyclists ride on Chapman Drive to CO119, they can now travel eastbound or westbound. Please note that anyone traveling eastbound on CO119 between 9:45 a.m. and 2 p.m. Monday through Thursday will be turned around at Fourmile Canyon Road. Additionally, the signalized closure for the barrier replacement work that’s occuring just east of Chapman Road is long and steep. This area could be difficult for less experienced cyclists. Cycling access remains open but is not advised in this area. 

There are no closures on the Betasso Canyon Link Trail. Cyclists can access this area from CO119, however, riders traveling from Boulder Monday through Thursday must be west of Fourmile Canyon Road by 6:45 a.m. to avoid the closure between Fourmile and Arapahoe Avenue.  

Boulder County is currently making improvements along Fourmile Canyon. At this time, all non-residential cycling is closed through the canyon. Please contact Boulder County for more information.

Contact Us

[email protected]
Text CO119 to 21000 to receive project text alerts.


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