CDOT to replace ‘structurally deficient’ emergency-access underpass

The Colorado Department of Transportation will begin construction to replace an emergency-access underpass near the Eisenhower/Johnson Memorial Tunnels next week, a project that is expected to run throughout the summer and fall and into next year.

In March 2020, CDOT began designs for the replacement of a structure known as “The Box,” located about 2 1/2 miles west of the tunnels, which serves as an underground access point for ambulances, law enforcement, tow companies and other emergency services. The existing roadway, a single-lane concrete box culvert, was built in the late 1960s during the original construction of Interstate 70 but is now considered “structurally deficient” and functionally obsolete, according to CDOT.

The underpass sits directly below I-70, and it is also considered vital to the integrity of the interstate above.

“This is leftover from the original I-70 roadway, which as we all know has had a lot of work done to it over the years and expanded,” said Elise Thatcher, communications manager with CDOT. “It was designed for a certain amount of load up above it, and as I-70 has grown, we’re really reaching the end point of how much that culvert can take.

“To be clear, we don’t think it’s going to collapse at any moment. We’re certainly not at that point, but we’re nearing the end of its lifespan, and it’s time to rebuild it. For example, there are cracks visible in the underpass. So it’s easy to immediately see when you’re down in that area that it needs to be replaced.”

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Construction on the project is scheduled to begin Wednesday, April 7, and will reconstruct about 1,900 feet of the access road and widen the underpass to two lanes. Thatcher noted that the contractor on the project, Kraemer North America, would be building the new underpass around the old one, so there shouldn’t be any closures on the interstate.

Instead, CDOT plans to close down one of the three westbound lanes between the tunnel and Silverthorne, which will keep two lanes of traffic moving and still provide emergency services with pullouts when necessary.

“In order to prevent major traffic impacts, we’re using a tried-and-true strategy for managing construction projects in this area,” Regional Transportation Director Michael Goolsby said in a press release. “By extending two westbound lanes further west from the tunnel and close to Silverthorne and Exit 205, we’re preventing a bottleneck from developing for westbound traffic. Three uphill eastbound lanes will be maintained throughout the duration of the project.”

Construction on the project will continue through fall. Work will be shut down over the winter to allow for ski traffic to make its way through the corridor as usual. Construction will resume in spring 2022, and the department expects to finish the new underpass by the end of next summer.