The Twin tunnels project proposes to add a third eastbound travel lane on I-70 between the Idaho Springs East Interchange (milepost 241) to the base of Floyd Hill (milepost 244) where a three-lane highway section currently exists. The project is approximately two and a half miles long and includes widening the eastbound bore of the Twin tunnels.

This report provides information on life cycle cost analysis (LCCA) as applied to CDOT's roadways. It describes the methodology CDOT uses to select discount rates to be used in LCCA calculations. It also summarizes pavement selection terminology for deterministic and probabilistic LCCA procedures.