Repairs planned for worn Glenn Highway bridges over Knik River

Jan. 21—PALMER — A pair of worn highway bridges spanning the Knik River in Mat-Su and known by commuters as a hazard are expected to get their first major overhaul, with state transportation officials looking to start work as soon as this summer.

The spans between Mile 30 and 31 on the Glenn Highway are used by thousands of drivers daily, many of them making the commute to and from Anchorage. The bridges have been the scene of numerous vehicle accidents thanks to the combination of ice, rutted surfaces and a lip where the bridge and road meet.

The southbound bridge was constructed as part of a Glenn Highway project in 1990, but the northbound bridge is much older, originally built in 1965 when the highway was rerouted to its current course over the Palmer Hay Flats rather than through Butte, state officials say.

The repairs, along with similar work on the northbound Peters Creek bridge, will be paid for through federal funds, officials say. They are expected to cost between $10 million and $20 million depending on the extent of work necessary, traffic control methods and how long construction takes, they say.

With record snowfall this winter, Glenn Highway drivers have reported challenging conditions over the Knik River bridges, particularly on the older span.

The northbound bridge was the site of a seven-car collision on Christmas Day caused by icy conditions, Alaska State Troopers said in an online report. About 90 accidents occurred in the miles on or just south and north of the bridges between 2018 and early this month, according to data provided by the troopers.

The Knik River bridge repairs are expected to begin this summer, though it's possible that start date could push into next year due to planning delays and the complexity of the work, said Christina Huber, a project manager for the Alaska Department of Transportation and Public Facilities. For example, bids for a construction contractor are not yet done — they're scheduled to open in the next six weeks — even though preliminary plans for the work are complete, Huber said.

Because some of the construction requires the weather to be not too cold or wet, work is likely to extend over two summers once it gets underway, she said. Plans call for each bridge to be closed for up to a month while the work is done, with traffic routed onto the other span during the closure.

Scheduled fixes include completely replacing the joints used where the bridge meets the highway and swapping the decks' current concrete with a new concrete that will better bond with future repairs, Huber said. Crews will also be removing a deicing system installed in the bridges in 2006 but out of commission since 2017 due to repair and upkeep problems.

Once bridge repairs start, state officials say they are hoping to avoid the kind of hourslong delays caused by construction at the Mirror Lake exit in 2021. Huber's team is using computer modeling that maps out potential delays and projects alternate patterns such as adding an extra lane of traffic to the bridge not under construction, she said.

The construction will bring the first major fixes ever done on either bridge span, Huber said.

"We don't rush out there and close these bridges and mess around with them every day," she said. "When we do it, it's because it really needs it and we're trying to do it as efficiently as we can."

Questions about the project can be sent by email to Huber at christina.huber@alaska.gov.