IDAHO SPRINGS, Colo. (CBS4)– It’s one of the biggest bottlenecks on the drive to and from the mountains– the Twin Tunnels east of Idaho Springs.

The Colorado Department of Transportation is already working on a third eastbound lane through the tunnel in what is one of the worst traffic tie-ups along Interstate 70.

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Until the new lane opens there will be a big detour around the massive rock that the tunnel was built through. In order for the tunnel to be expanded the rock needs to come out.

A majority of that work will start in 40 days. CDOT crews started blasting some of that rock on Tuesday.

“The contractor will go in there and remove the concrete liner and do a lot of blasting, rock bolting, it is all rock,” said CDOT Project Engineer Bob Smith.

Although crews have been working on that area for about a year, Tuesday was a major step forward for the first rock blasting near the east portal.

“We stopped traffic 1,000 feet on each side of the blast, we hold them, we make sure everything is clear, we release them. It’s about a 10 or 15 minute process this morning,” said Smith.

In the coming weeks crews are going to blast all the rock that is in one section so they can remove it and make room for the third lane of I-70.

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There will be similar traffic stops on both directions of I-70 about 20 times through April 1. That is when the tunnel will be closed to traffic.

“We are on track with decent weather we’re making a big push coming up right now. We’re working 24 hours a day, you’re going to see a lot of activity out here,” said Smith.

A retaining wall is being built that will not only provide a lane for the detour but also the outside lane when the work is complete.

“Traffic will actually stay in the two lanes and they’ll turn right before the tunnel. The tunnel will be closed, they’ll stay in the two lanes and the two lanes will continue until right before the Hidden Valley interchange and come right back on to I-70,” said Smith.

Speeds on the detour will drop to 35 miles per our. Crews believe it will be worth the wait.

“We’ll pour a new concrete liner, pour a new road and you’ll have three full lanes and shoulders going through there,” said Smith.

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CDOT said the project will be complete before ski traffic builds at the end of the year.