Rock scaling work precedes Twin Tunnel blasting

April 15, 2014 - Metro Denver Colorado/CDOT Region 1 - Crews work to create safe work area for rock face blasting .

DENVER/MOUNTAIN CORRIDOR – Before rock blasting work begins along the mountainside walls above the westbound Twin Tunnels bore, construction crews need to first create flat bench areas in the rock face to position the heavy equipment and materials needed to conduct these blasts. To do so, workers are climbing the hillsides above the tunnel to manually break up large rocks and push them down the slope – a process known as rock scaling.

“The rock scaling work being done this year is a lot different for the westbound project than the work we performed  last year to widen the eastbound tunnel,” said Colorado Department of Transportation Project Manager Benjamin Acimovic. Because the westbound lanes of I-70 are directly adjacent to the mountainside, as the tunnel is widened to accommodate a future third lane, there needs to be a corresponding widening of the rock walls above the tunnel to help keep motorists safe when the highway is eventually expanded in this area.

As rocks are pushed down the slope toward the highway, I-70 traffic is being stopped in both directions for up to 30 minutes. Motorists should plan on longer delays, however, because it will take several minutes to clear the queue. Crews are working off of a 30 minute stop, 45 minute release schedule. This gives workers only 30 minutes to perform this dangerous and necessary work as traffic is stopped for the safety of the traveling public and also for the safety our crews. After thirty minutes, traffic in the queue is being released. Motorists should anticipate delays in this area when traveling the mountain corridor. This work will continue through September.

Tunnel blasting is likely to being later this week. Once that work begins to blast material from the rock face walls outside the tunnel, rock scaling work to remove loosened materials will require ongoing traffic stops. More than half of nearly 60 rock face blasts to be done will occur on the east side of the tunnel, and crews plan to conduct one or two rock face blasts a week to finish the project by the end of this year. The blasting and scaling operations will be coordinated to use the same closure windows. Once tunnel blasting begins, crews will begin having 4 to 5 tunnel blasts per week that will require full closures of I-70 in both directions for short periods of time. Crews anticipate 4 blasts per week outside of the tunnel, two on each end of the tunnel. Each time a blast occurs outside the tunnel, this will be followed by 1 to 2 days of rock scaling in that area. That rock scaling will be done on the same 30 minute stop, 45 minute release schedule that is ongoing now.

Unlike tunnel blasting, rock face blasting work has to be done during daylight hours to comply with federal safety regulations. Blasting above the west end of the tunnel should be complete in July while blasting above the east side of the tunnel will last through the summer.

To see videos of the rock scaling work, visit

The Westbound I-70 Twin Tunnels project is part of a package of improvements designed to ease congestion on the I-70 mountain corridor. This $55 million project will widen the westbound tunnel bore in Idaho Springs to accommodate a future third westbound lane, but will not add a third highway lane at this time. With resources still in place from the 2013 project that widened the eastbound tunnel, it is estimated that doing this work now will save $5 million to $7 million. The new tunnel is scheduled to open to traffic by the end of this year and project completion is scheduled for the summer of 2015 when restoration work is finished on County Road 314.  For more information, call 303-327-4034 or visit For current road and weather conditions you can also text CDOT to 25827 or download the CDOT mobile application to your smartphone.