A major transportation artery into Capitol Hill will be reopened Thursday morning marking the end of a year-long project to prepare Interstate 5 for the light rail tunnels connecting downtown to Capitol Hill.

In a media tour of the end point in the Seattle transit tunnel that will eventually connect to the light rail route, Sound Transit officials said that the Olive Way exit from northbound I-5 will be re-opened at 5 AM Thursday. The opening comes almost exactly a year after the offramp was closed as Sound Transit contractors began digging massive pits below the I-5 roadway to remove support pilings and poor soil that would hinder the light rail tunnel boring machine when it makes its journey beneath this area of the city as early as the end of next year. The $19.7 million project also involved cutting “windows” into the I-5 retaining walls beneath the Olive Way Exit for the tunnel boring machine to pass through as it completes the 3.15-mile route between downtown and the University of Washington.

Meanwhile, the Cherry St. onramp to north I-5 should also be reopened now that the Olive Way Exit work is complete.

During the Olive Way closure, most drivers used the Madison or James offramps as alternate routes to the Hill and many pedestrians enjoyed the easy crossing in front of the closed ramp as they made their way up or downhill on Olive Way.

Contractors on the $1.9 billion University Link light rail project are currently preparing the construction area on Broadway between Thomas and John for around-the-clock tunneling that will begin in 2011. Sound Transit was recently approved for a large project noise variance that will allow nighttime work on the project. The agency says the 24-hour schedule is necessary because it’s not safe to start and re-start the tunnel boring machine and that the project would take longer and subsequently cost more without the nighttime work. The 10 to 20-foot plywood construction noise walls around the Broadway site were recently painted a deep red as part of Sound Transit’s community art program.

As Wednesday morning’s tour, Sound Transit’s Rick Capka said the re-opening of the Olive Way exit was a milestone worthy of celebration. Capka, a resident engineer for Sound Transit, said the project was completed on time and under budget — and is a big step toward the start of tunneling and completing the University Link project on time.

Service is expected to begin in 2016.

Sound Transit took me and a camera person from every TV station in town underground to see this wall at the end of the transit tunnel.