Last blast to widen Twin Tunnel set for Monday

August 15, 2014 - Metro Denver Colorado/CDOT Region 1 - Blasting work continues on rock face wall above westbound I-70 tunnel

DENVER/MOUNTAIN CORRIDORThe final blast needed to widen the westbound bore of the I-70 Twin Tunnels is scheduled for 6:30 a.m. Monday, Aug. 18. Later in the week there will be one final blast inside the tunnel to remove the structure’s rock base floor. Since the first week of April, crews have conducted 85 blasts to widen the westbound tunnel in Idaho Springs to a width of 53 feet.

“This is a significant milestone for the project, especially considering this tunnel is about 100 feet longer than the eastbound bore that we widened last year,” said Tony DeVito, Region 1 Transportation Director for the Colorado Department of Transportation.

The joint venture contracting team of Edward Kraemer & Sons and the Obayashi Corporation has worked around-the-clock six days a week in removing about 21,500 cubic yards of material from the westbound bore. It took more than 2,100 truck hauls to remove this much material.

With blasting work complete inside the tunnel, tunneling crews can now focus on putting the steel rebar framework in place before moving the tunnel form liner into the tunnel to start the segmental concrete pours. The form liner, which stands about three stories high, is being built on the west side of the tunnel and will be wheeled into the tunnel on a set of rails in the coming weeks so work can start on placing the 40-foot sections of concrete.

Along with these segmental concrete pours, blasting work will continue outside the tunnel through September. Most of the exterior rock yet to be removed is on the rock face wall above the east end of the tunnel. Until this rock face blasting work is done, I-70 mountain corridor drivers can expect periodic traffic stops for these blasts and any subsequent scaling operations that might be necessary.

To view tunnel blast videos, 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.