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New Construction Project Gets Started At Twin Tunnels

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IDAHO SPRINGS, Colo. (CBS4) – Officials with the Colorado Department of Transportation are warning travelers that they should be prepared for more construction on Interstate 70 at the Twin Tunnels starting this week.

The department is widening the westbound bore of the Twin Tunnels, located near Idaho Springs, after successfully widening the eastbound bore in a project that wrapped up late last year.

For the next few weeks, CDOT will periodically redirect the westbound traffic into the eastbound lanes as they get ready for blasting work. During selected times, there will be lane closures and eastbound and westbound traffic will share the eastbound bore’s new three lanes.

“It’s overnight when the volumes are much less and we do a lot of cautions to make sure people are safe,” said CDOT spokeswoman Amy Ford.

(credit: CBS)

(credit: CBS)

Then in April blasting will start on a routine schedule that will widen the westbound bore. The westbound tunnel blasting and reconstruction will last for the rest of the year.

“So the blasting itself will always take place during the day,” Ford said. “The safety situations there are such that we do not want to do blasting overnight.”

Due to a lack of finances, the westbound tunnel won’t have three lanes like the eastbound one does right away, but CDOT spokeswoman Amy Ford said the ride through should be safer and quicker.

“Because we’ll have wider shoulders it’s a little safer, and with the new type of tunnel you have — that sort of impact of going into a long, dark tunnel which causes people to slow down — that will also be alleviated,” Ford said.

During the blasting portion of the project, eastbound I-70 traffic will be shifted over to the same frontage road that was used last year while work on the eastbound bore was ongoing.

“It worked pretty well in that case and so we’re expecting the same, but obviously out goal is to finish the project as quickly as we can and the goal is to really finish before the ski season really gets going,” Ford said.

Plans call for blasting in April every three days, with traffic stopped for 30 minutes at a time.

More From CDOT

The following information about this project was released by CDOT last Friday.

Before crews can begin the blasting work that will widen the tunnel and remove a portion of the rock face walls above the westbound tunnel, traffic must be rerouted from the westbound bore into the eastbound bore. To accommodate this traffic shift, crews will put down temporary pavement in the center median area on both sides of the tunnel to transition westbound traffic into and out of the eastbound lanes. This center median work will take about a month to complete and requires closing the far left lane of eastbound I-70 during off-peak travel hours.

Along with these off-peak lane closures, preparatory work in the westbound tunnel bore will require putting I-70 traffic in a head-to-head configuration through the eastbound tunnel for overnight work. This will be done several nights throughout March and will involve maintaining two eastbound lanes and one westbound lane.

Other work scheduled to take place in March includes one or two small blasts outside the westbound tunnel to facilitate the extension of a drainage box beneath the highway and two or three days of rock scaling work in late March to prepare for the larger rock face blasts that will begin in April. The blasting operations in March will require stopping traffic in both directions for about 15 minutes while the rock scaling work will require stopping traffic in both directions for up to 30 minutes so crews can safely remove large boulders and rocks from the rock face above the highway.

In April, eastbound traffic will be reduced to two lanes of travel and will move back onto the detour route around the tunnel while westbound traffic slides over into the eastbound tunnel bore. Once traffic is shifted, crews will begin large-scale blasting inside the tunnel as well as rock cut blasting on both ends of the tunnel.

Blasting activities will continue through the end of summer and involve stopping I-70 traffic in both directions. Tunnel blasts require shorter duration stops of about 15 minutes while the rock cut blasts will have a greater impact on I-70 travelers. Following each rock cut blast, crews will need to scale the hillside to remove any loose rocks and debris to keep it from falling on the highway below. This scaling work requires stopping traffic for up to 30 minutes followed by about 45 minutes of free-flowing traffic to clear the queues. This alternating process of stopping and releasing traffic will continue as long as necessary to finish removing blasted materials.

Construction crews anticipate conducting one or two rock face blasts each week and tunnel blasting just about every day of the week through August.

CDOT estimates widening the westbound tunnel now will save $5 million to $7 million because the equipment, resources and detour needed to do the work are already in place. Tunnel widening work is scheduled to be complete by the end of this year and at that time all I-70 traffic will be back in its regular alignment. Project completion is scheduled for summer 2015 when County Road 314 is restored to its original configuration with completed facia walls and an improved recreational trailhead.

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