The Colorado Department of Transportation says it will expand this stretch of I-25 south of Denver.

(Courtesy CDOT)

The last piece of funding needed to begin work on the notorious Interstate 25 "gap" south of Denver has fallen into place.

Colorado Department of Transportation spokeswoman Tamara Rollison confirmed Tuesday that the U.S. Department of Transportation has awarded a $65 million grant to El Paso County to go toward the $350 million project. It will add a lane in each direction in the 18-mile section of freeway that is currently only four lanes across between Monument and Castle Rock.

"We are definitely on track to begin construction on that project as early as August," Rollison said.

Motorists with fewer than three people in a car will have to pay to use the lanes, Rollison said. That's caused consternation among commuters. 

"Certainly there is a concern about express lanes," Rollison said. "But we have found in other facilities they have worked very well in improving safety and also reducing travel times across all lanes."

U.S. Rep. Doug Lamborn, R-Colorado Springs, said the grant is a "huge win for the entire Pikes Peak region."

"As I’ve worked with the Trump Administration over the last several months, my number one priority has been to secure this $65 million grant," Lamborn wrote in a tweet.

Construction should take about two years to complete, Rollison said.

Editor's Note: An earlier version of this story misidentified the party affiliation of Rep. Lamborn. We regret the error.