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February 20, 2024

Granite's CM/GC contract to fix Denali Park landslide tops $207M

BGC/Jacobs image from NPS [enlarge]
The steel bridge will span 475 feet across the landslide area.

Granite Construction earlier this month was awarded the final $112 million construction option to fix Denali Park Road, part of which was slowly swept away in 2021 by an ongoing landslide in Alaska's Denali National Park. This brings Granite's total value of its construction manager/general contractor contract and options to $207.79 million.

Granite is working with the Federal Highway Administration and National Park Service to build a 475-foot-long bridge over the active slide area on Polychrome Mountain.

“We are pleased to have effectively delivered preconstruction services and successfully negotiated all the construction phase contracts,” said Derek Betts, Granite vice president of regional operations, in a news release. “As a partner with the FHWA and NPS, we look forward to building this critical bridge and providing the public with access to the western half of the park that has been cut off by a landslide since 2021.”

The bridge will be a single-span steel truss standing 50 feet tall and 24 feet wide. Granite said supporting the bridge and improving ground conditions will require a combination of earthwork, micro piles, rock anchors, soil nails, precast/post-tensioned concrete abutments, and thermosyphons. According to Granite, thermosyphons are part of a passive heat exchange system designed to prevent permafrost from thawing and creating instability. NPS's project website indicates there will be 23 thermosyphons around the eastern abutment of the bridge.

Photo via Business Wire [enlarge]
Granite is using drill rigs for its earthwork operations.

Construction of the project began in 2023 with mobilization, development of a worker camp, pioneering access across the landslide, blasting, and mass earthwork. Work planned for this season includes completion of mass earthwork, construction of the bridge abutments, installation of a temporary launching system, and partial erection of the bridge.

Project designers Jacobs and BGC Engineering decided to use the unique bridge erection process due to the site's complex geology, steep slope and remote location. Crews will first assemble the permanent bridge truss cantilevering out from a temporary launch beam installed adjacent to the east abutment. Then a temporary truss (launch nose) will be built within the permanent truss and incrementally moved westward to bear on a receiving tower placed on the west abutment, at which point it will be rigidly attached to the permanent truss. The combined assembly (permanent truss and launch nose) will be incrementally moved westward until the permanent truss bears on the receiving tower and is then lowered into place on the west abutment.

Bridge erection will continue through 2025, along with launching of the structure to span the landslide. For the 2026 season, construction will include setting precast bridge approaches, building a retaining wall, installing thermosyphon condensers, coating the bridge deck, and demobilization.

NPS said the project should be finished by mid-2026, but the full length of the road won't likely reopen to the public and bus service until 2027.

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