The Colorado Dept. of Transportation began repairs July 18 on the sinkhole on U.S. 24 over Tennessee Pass and will finish the week of August 6. The highway will remain closed in both directions to all traffic, including bicyclists, from mile marker (MM) 162 to MM 166. 

Photo courtesy of CDOT
CDOT began work July 18 to repair a 35-ft-wide sinkhole on U.S. 24 over Tennessee Pass.

Hayward Baker Inc. won the repair bid with a contract amount of $829,748.65. Incentives are part to the contract. If Hayward Baker can open one lane or both lanes of the highway by August 6, it will receive an additional $5,000 per day for early opening. Conversely, the firm will be assessed a disincentive of $5,000 for each day the highway remains closed past August 6. The total cost of repairs, including traffic control, design, etc. is estimated to be $1.5 million.

The situation was likely caused when wooden braces of a 100-year-old mining tunnel that runs under the road collapsed and opened up the 30-ft-plus diameter sinkhole.

CDOT began the expedited emergency bidding process for highway repairs after the sinkhole opened up on July 9. After receiving repair bids, CDOT selected the contractor based on the lowest bid amount and the time estimated to complete the project.

To repair the sinkhole and the highway, crews will be constructing a grout containment barrier on the north and south sides of the highway to contain the fill zone. Then, a thinner grout material will be poured into the void followed by a pressurized grout to fill any remaining voids, which will also compress the existing materials underneath the highway to strengthen the roadway platform. Once the void has been stabilized, crews will mill and pave a three-in. layer of asphalt to create a seamless transition for motorists over the former sinkhole site.

CDOT says it continues to work with state historians and is referencing its archives to build a full history of the tunnel and the roadway.

Repairs are scheduled to be complete ahead of when the USA Pro Challenge plans to go through the area, barring any changes based on weather, natural disasters and other unforeseen circumstances, CDOT says.