A state transportation commission has approved $20.4 million to repair a collapsed stretch of eastbound U.S. 36 in Westminster, which continues to sink at an inch per hour or 2 feet per day, Colorado Department of Transportation chief engineer Josh Laipply said.

CDOT selected Kraemer North America to rebuild the roadway between Wadsworth Boulevard and the Church Ranch Boulevard/West 104th Avenue exchange. The approval was given Thursday during the CDOT commission’s regular monthly meeting.

As of Tuesday, the length of the highway with the sinkhole was about 300 feet — almost the length of a football field.

Granite Construction, one of the companies involved in a recent expansion project on that section of U.S. 36, issued a statement Thursday that said it would cooperate with CDOT’s probe. The Watsonville, Calif.-based company was in a joint venture with Ames Construction, which has declined to comment.

“The roadway and structure at issue were substantially complete in 2013,” the company said. “Granite has reached out to (CDOT) to offer assistance and will cooperate in any investigation into the collapse. Until there is more verifiable detail on this road section, we cannot offer any additional information.”

Laipply didn’t have an exact timeline for the completion of the repairs but said it would be weeks before the road is operationally functional. It likely will take even longer before all the panels are back up and the road is back to its original condition.

“I’ll take the pieces as I can get them,” he said.

A retaining wall failed along the highway and a large crack that appeared Friday developed into a sinkhole. CDOT rerouted two eastbound lanes onto the westbound side of the highway.

The $20.4 million from the agency’s transportation contingency fund will be used to pay back emergency response, refund the Regional Transportation District for two days of free travel when the closure first occurred, and pay to rebuild the highway. After a determination of what caused the failure, the state would have to cover the full costs or it could demand the contractors that built the expansion project or maintained the roadway to reimburse the expenses.

The 5-year-old section of highway between Denver and Boulder began to fail because of “fat clay” that was saturated by water, Laipply said.

Once the clay layer absorbs water, it no longer holds up what’s above it, he added.

“We never expected that clay to fail,” Laipply said. “We hired folks to figure out what happened.”

CDOT crews are monitoring the other side of U.S. 36 as well, though Laipply said it’s out of an “abundance of caution” because the other side of the road is 100 percent safe and there’s nothing to indicate it could also sink.

“I’m concerned about every roadway,” Laipply said.

“We have other roadways that fail,” he added. He pointed out Colorado 325, which collapsed six days ago and cut off traffic to Rifle Falls State Park, according to the Summit Daily.

Staff writer Jon Murray contributed to this report.