Building Alaska's Longest Single-Span Bridge: The Sterling Highway MP 45-60 project addresses congestion and increases safety.

• Author: Joyal, Brad

For nearly four decades, there have been conversations about upgrading the Sterling Highway between Sunrise Inn and the eastern entrance to Skilak Lake Road near Cooper Landing. Those upgrades are now underway as a part of the Department of Transportation and Public Facilities (DOT&PF) Sterling Highway MP 45-60 project, a development with an estimated cost of $375 million and a projected completion date of 2025. "It's hard to pin down the actual date, but I've heard 1982, or even maybe before, is when the first go at this environmental impact study started," says DOT&PF Project Manager Sean Holland. "We were finally able to get a record of decision in May 2018 that's letting us move forward with the Juneau Creek Alternative."

DOT&PF considered five alternatives--four build alternatives and a No Build option. In the end, the Juneau Creek Alternative was chosen and will include a new alignment section that will start at MP 46.2 and end at MP 56. A part of the project's new alignment section will be the construction of the Juneau Creek Bridge, which as planned will be the longest single-span bridge in Alaska.

"It's going to be a bridge that, depending on geology, will have a clear span of 450 to 825 feet," says Holland.

What the Project Will Solve

This project will address three problems with the Sterling Highway MP 45-60. It will reduce congestion; meet current highway design standards; and increase safety measures along the roadway. Holland notes that traffic jumps from about 1,000 vehicles traveling the highway per day in the winter to about 8,000 during the peak of dipnetting season in August. He estimates the new bypass will redirect the bulk of traffic and reduce congestion. "It should have a design speed of 60 miles per hour and a posted minimum of 55," Holland says. "Right now, we're slowing people down to 35. It's not uncommon--that occurs in other parts of the state--but it's not really a compatible use to have a highway go through a small community like that. This bypass is going to be able to redirect an estimated 70 percent of the traffic that goes through Cooper Landing now to the Juneau Creek Alignment."

In order to meet current highway design standards, Holland and DOT&PF are focused on creating 12-foot-wide lanes and 8-foot-wide shoulders. "The highway is classified as a rural highway--there are no shoulders there," says Holland. "A rural highway has a minimum of a 6-foot shoulder and preferably an 8-foot shoulder. Fifty...