Regional: Colorado’s Twin Tunnels nearing next construction milestone with westbound bore
Blasting is complete and construction crews are working frantically in preparation for the next major milestone of the Twin Tunnels project near Idaho Springs.
On Tuesday, Colorado Department of Transportation officials hosted a tour of the westbound bore of the Twin Tunnels, where workers were installing a waterproof liner to the interior walls and pouring concrete for a temporary roadway. Next, workers will lay rails to wheel in two, three-story-tall form liners, which will serve as the tunnel’s new concrete lining.
It took 85 blasts to widen the tunnel enough for the liners to fit inside, according to a CDOT Twin Tunnels fact sheet. CDOT estimates it will take 10,000 to 12,000 yards of concrete to complete installation of the tunnel lining.
Last year, construction was completed to widen the eastbound bore to three lanes. The project was launched in conjunction with several others aimed at improving traffic congestion to Denver along the notoriously frustrating stretch of Interstate 70 between Floyd Hill and Idaho Springs.
Although the westbound bore was expanded to 53 feet, also wide enough to house three lanes of traffic, CDOT officials said Tuesday westbound traffic in that same area will remain in its current two-lane configuration, at least for now. Officials don’t have a timeline yet, but touted the project as a critical first step towards future westbound expansion of the I-70 mountain corridor.
With expansion of westbound I-70 expected to take place sometime in the undetermined future, one might ask why the state decided to undertake the estimated $50 million project — that provides no significant improvements to traffic congestion — a year after spending a whopping $100 million to expand the eastbound bore.
Despite eastbound bore improvements coming in $40 million over budget, CDOT Region 1 design engineer Mike Keleman said cost and convenience played a significant role in getting the go ahead to expand the westbound bore.
“We’re kind of killing two birds with one stone,” Keleman said. “We’re not making nearly the same amount of mistakes we made last year because for the most part this is the same crew that worked on the eastbound tunnel.”
In addition to experience, officials estimate they’ll be able to shave about $5 to $7 million off the final cost of the westbound bore because all of the equipment was stored near the site and the detour was already in place.
Motorist safety also played a pivotal role in tackling the westbound bore project, Keleman said, noting the entrance was a prime location for rock falls. As part of the project, much of the rock face was scaled back and a 50-foot-long tapered wall will be constructed to provide additional protection from falling boulders.
Although cost, safety and convenience were all motivators, officials said they do expect westbound traffic to improve once the wider and brighter tunnel opens to motorists. A major contributor to traffic congestion in the westbound lanes was due to drivers riding their brakes as they entered the narrow and dimly lit tunnel, officials said. LED lighting also will be installed in the tunnel and embedded in the pavement to improve driver visibility, the Twin Tunnels fact sheet stated.
The westbound bore is on schedule to open before the end of the year. When it does, the Twin Tunnels will be renamed Veterans Memorial Tunnels, in accordance with state legislation passed in April.
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