The contract for the state’s biggest highway project in history was finalized Thursday when the Colorado Department of Transportation and its private contractor reached financial close on the reconstruction and expansion of I-70 across north Denver.

And CDOT’s $2.35 billion overall cost of the project over the next 30-plus years has dropped slightly, by about $10 million, due to lower than expected interest costs the agency will pay as part of the public-private contract.

The $1.3 billion construction project calls for sinking a portion of I-70 east of I-25 and expanding the road by adding a toll lane in each direction between I-25 and Chambers Road. The project's overall price tag rises when 30 years of annual payments from CDOT to the private contractor are factored in.

Construction is expected to start next summer.

More details about the partnership and the project can be found at the Denver Business Journal.