Colorado’s Twin Tunnels Widening Begins

Thu September 05, 2013 - West Edition
Lori Tobias


Contractors fully expect to make their December deadline and they’ve taken a number of steps to make sure that happens safely. Three crews work the 24-hour period with three full-time safety managers on each shift.
Contractors fully expect to make their December deadline and they’ve taken a number of steps to make sure that happens safely. Three crews work the 24-hour period with three full-time safety managers on each shift.
Contractors fully expect to make their December deadline and they’ve taken a number of steps to make sure that happens safely. Three crews work the 24-hour period with three full-time safety managers on each shift. The blasting is conducted throughout the day, creating closures that last about 20 to 30 minutes. Traffic is stopped a safe distance from the tunnels prior to the blasting. The $110 million project is the largest and among the first Construction Manager General Contractor projects the Colorado Department of Transportation has awarded, said Bob Smith, CDOT project engineer, and it’s been on the state’s wish list f It is believed to be one of only a very few highway tunnels in the United States to be widened rather than completely replaced.

On a good day, the 60 mi. (97 km) drive home on I-70 from Colorado’s mountain play land takes about an hour. On a bad day — and there are many — you can expect to triple the drive time home. Throw in an accident and there’s no telling when you’ll make it.

That’s all about to change. Contractors have begun work to widen 3 mi. (4.8 km) of eastbound lanes from Idaho Springs to the bottom of Floyd Hill, including the widening of an existing tunnel and a new bridge.

“It’s a very big deal,” said CDOT spokesman Bob Wilson. “That corridor has suffered with increased traffic since the highway was originally built in 1961. It will make the highway three lanes all the way from Idaho Springs to Denver.”

It is believed to be one of only a very few highway tunnels in the United States to be widened rather than completely replaced, said Wilson. The others are tunnels in the Great Smokey National Park and the Zion National Park.

The $110 million project is the largest and among the first Construction Manager General Contractor (CMGC) projects the Colorado Department of Transportation has awarded, said Bob Smith, CDOT project engineer, and it’s been on the state’s wish list for at least 15 years.

CMGC projects allow the owner and contractor to share the risk, and it creates an environment that is less tense with fewer disputes and a working environment more conducive to getting the job done, said Benjamin Acimovic, CDOT project manager of Twin Tunnels and chair of the CMGC committee.

The process begins with a Request for Proposals, from which prospective contractors are selected to be interviewed. The project is awarded not to the lowest bidder, but to the contractor who seems to have the most expertise for the job.

In this case, that is Kraemer/Obayashi Joint Venture.

Once the contractor is selected, then they talk price.

“They give us what their take is of the project,” said Smith. “We select totally based on their fit for the job. We get prices and negotiate, then go with independent cost estimator to make sure they were with 10 percent of our independent cost estimate.”

Kraemer/Obayashi Joint Venture began preconstruction work in 2012, upgrading an existing frontage road, then rerouting traffic from the tunnel onto it.

“Time and access are the two biggest challenges,” said Matt Hogan, construction manager of Kraemer/Obayashi. “We spent a year in pre-construction with CDOT and the designer to refine the design. CDOT gave us the direction that we could close the tunnel on April 1 and we’re under mandate to have three lanes open by Dec. 21 of this year. We are working 24 hours a day, six days a week inside the tunnel, excavating the tunnel from both headings, to meet that goal.”

Crews are using state-of-the-art blasting techniques to excavate the tunnel and expect to remove 19,700 cu. yd. (15,061 cu m) — or about 2,000 dump truck loads.

“It’s drill and blast,” said Hogan. “We have two Atlas Copco E2C boomer model drills on site. They’re expensive drills.”

They’re also working with a Fletcher single boom jumbo, two Liebherr 932 tunnel excavators and two robotic shotcrete placing booms. Hogan describes the latter as “a robotic arm that is controlled remotely and carries placing hose to the nozzle at the end of the robot to allow for placement of Shotcrete without the need to put workers below unsupported ground.”

The blasting is conducted throughout the day, creating closures that last about 20 to 30 minutes. Traffic is stopped a safe distance from the tunnels prior to the blasting. Once the blasting is completed, workers inspect the westbound tunnel — which is not under construction — to ensure it is safe for motorists. Eastbound travelers are moved to the detour route around the tunnel. There is no blasting during high volume traffic periods.

Workers also will remove the 18-in. (45.7 cm) concrete liner of the existing 800-ft. (244 m) tunnel. They’ll widen the tunnel from two to three lanes, and expand the currently 2 ft. (.6 m) shoulders to 4 and 10 ft. (1.2 and 3 m) shoulders. Once that’s done, they’ll install a new concrete liner.

While it is technically widening the tunnel already in place, for all intents and purposes, “It’s basically rebuilding the tunnel,” said Smith. “There’s another tunnel right next to it, so it’s not like you can go in there and go hog wild. We’re constantly monitoring the westbound tunnel and there is a fuel plant right next to us we have to monitor.”

The new lane will add capacity on the Interstate, but the anticipated improvement will be more than just the ability to handle more volume.

“The importance of this project is that it has been a historic pinch point along the corridor,” Wilson said. “A lot of it has to do with human psychology, the black hole effect. As you go into a tunnel people tend to slow down. So heading back to Denver, the tunnel automatically slowed people down.”

The new tunnel will be wider and brighter. The widened shoulders also will help.

“There are no real shoulders now, Wilson said. “That also creates a confining effect that slows people down. It will be more inviting.”

There also will be a new three-span bridge. The current bridge has a tight curve, which also lends to the traffic problems. The new bridge will be less steep with softer curves, Wilson said.

Contractors fully expect to make their December deadline and they’ve taken a number of steps to make sure that happens safely.

Three crews work the 24-hour period with three full-time safety managers on each shift. There are daily safety meetings, as well as bi-weekly safety meetings to keep workers abreast of rapidly changing conditions on the job. They’ve also set up an incentive program that rewards workers over three periods for safety, quality and production.

“I really do believe we’ve created a culture up here where safety and production go hand in hand,” said Hogan. “We’ve made vast improvements regarding the safety on the project. We’re going to create a job everyone can be proud of when we’re done.”