DENVER, CO The Federal Highway Administration and Colorado Department of Transportation said that they have signed a formal finding of no significant impact that helps pave the way for CDOT to begin work in Denver, Colorado, on a major project to add toll lanes and extra capacity to state road 470.

That east-west route in the southern metro area is now a heavily congested four-lane divided highway of non-toll lanes, where rush-hour traffic slowed to about 24 miles per hour in 2013 instead of the posted 65 miles per hour, and traffic volume is projected to grow sharply in the next 20 years.

The finding is part of a C-470 corridor revised environmental assessment. Here is the finding document.

The C-470 project would add toll lanes in each direction for 13.75 miles, at an estimated cost of $385 million, with a first phase of construction building most of it during 2016-2018.

CDOT and the FHWA said proposed improvements include adding one tolled express lane in each direction on C-470 between Interstate 25 and Kipling Parkway, with a second tolled express lane westbound between I-25 and Lucent Boulevard, and eastbound between Broadway and I-25.

Those new lanes and any new auxiliary lanes where needed would supplement the existing non-tolled general-purpose lanes. The project includes pavement reconstruction, alignment improvements and direct-connect ramps at the C-470 and I-25 interchange.

The work will also replace bridges over the South Platte River and widen other bridges throughout the corridor.

CDOT will build, manage, own and operate the toll lanes. The project is also supported by an area C-470 Corridor Coalition, and partial funding is provided to CDOT from Douglas County.