Colorado Department of Transportation crews will shut westbound Interstate 70 overnight Monday and Tuesday to erect temporary supports for a new cast-in-place concrete bridge over the highway.

The full closures run from 9 p.m. to 5 a.m. between the U.S. Highway 6 interchange at exit 244 near Idaho Springs. Drivers must exit, turn left under the highway and immediately re-enter westbound I-70. Flaggers guide traffic through the detour.

Poor weather could push the work to the same hours Dec. 17-18, officials warned. Motorists can text floydhill to 21000 for delay alerts.

The new bridge will carry westbound traffic in a straighter, safer alignment when the $700 million Floyd Hill Project finishes in 2028. Crews are adding a third westbound Express Lane, rebuilding curves and extending the Clear Creek frontage road.

No lane restrictions will occur from Dec. 20 through Jan. 5 to ease holiday travel, the agency said.

Travelers can check conditions on the project website or COtrip Planner app before heading into the mountains.