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CDOT Commences Westbound I-70 Twin Tunnels Expansion

The Twin Tunnels, Colorado Department of Transportation The Twin Tunnels, Colorado Department of Transportation

In January, the Colorado Department of Transportation (CDOT) announced that it had allocated $55 million in funding for widening the westbound Twin Tunnel on Interstate 70 in Idaho Springs from two to three lanes. Beginning this week, eastbound traffic will return to the detour route on Clear Creek County Road 314 and westbound traffic will be realigned to run through the newly expanded eastbound tunnel.

Project Benefits

Moving forward with this project now will save approximately $6 million because equipment and resources are already in place.

Additional benefits:

-Eliminates the reduced visibility black hole effect of the old portal that slowed approaching traffic

-New portal design provides added rockfall protection

-Driver safety improved with the added rockfall protection and addition of shoulders in tunnel

-Project enables future low cost, high benefit operational improvements such as peak period shoulder lane

Construction Update

CDOT anticipates tunnel blasting at least once per day, except Sundays and holidays, for about five months. During blasting, traffic in both directions will be stopped in both directions for up to 20 minutes. However, depending on traffic volume the delays from these temporary closures could be considerably longer than 20 minutes. Westbound I70 traffic will be stopped slightly longer while the eastbound tunnel is checked before traffic is allowed to continue.

Westbound I70 traffic will be stopped slightly longer while the eastbound
tunnel is checked before traffic is allowed to continue.

Blasting work on the two rock face walls will have a greater impact on I-70 travelers because this work has to be done during daylight hours for safety reasons. Crews anticipate doing one or two rock face blasts each week. Following each rock face blast, crews will begin removing large rocks and dislodged materials that could pose a threat to I70 traffic traveling below. This process, known as rock scaling, will require stopping highway traffic below to maintain public safety.Motorists can expect traffic stops at various times throughout the day and should plan for extended delays.

Whenever possible, crews will coordinate blasting work to conduct two blasts under one traffic stop (i.e. a tunnel blast and either an east or west rock face blast). This will help minimize the overall impact on travelers.

Stay Informed

If you travel the I70 mountain corridor, you are going to want to stay updated on construction activities that may affect your travel plans:

-Text/Email alerts: To receive text or email alerts with updates on construction activities and traffic impacts, visit and click on the icon at the top of the page for email and wireless alerts.

-I70 mobile application: To download this App to your smartphone, text CDOT to 25827 or search CDOT Mobile in your App store.

-Information hotline: Call the project hotline at 3033274034 to listen to recorded construction schedule and lane closure information.

-Variable message signs: Electronic boards all along the I70 corridor provide information on traffic stops and changing traffic conditions.

-Social media: Before hitting the road, visit CDOTs Facebook page at or follow their @coloradodot Twitter feed using the hashtag #TwinTunnels for the latest construction information.

-Visit the project website at This site includes construction schedule information and a link to listen to the audio recording from the March 13 telephone town hall call hosted by CDOT. As project photos and blasting videos become available they will be posted here as well.