The Colorado Department of Transportation says the work will continue through October. One lane will remain open to traffic.
The project will replace 3 miles of asphalt in the westbound lanes. There will also be 3 miles of guardrail improvements in the westbound lanes and 12 miles of guardrail replacements in the eastbound lanes from the tunnel to Georgetown.
Crews plan to repave two miles of westbound I-70 a day and will impact one lane at a time. In total, approximately 20,000 linear feet of guardrail will be repaired or replaced.
CDOT says the improvements will cost $6.5 million.