Seward Highway Rehabilitation Milepost 75-90

CLIENT Alaska Department of Transportation

Location Turnagain Arm, AK

The Seward Highway Rehabilitation project involves the widening and realignment of 15 miles of roadway, as well as replacing eight bridges. 

This area of Southcentral Alaska exhibited severe subsidence and infrastructure failure during the 1964 Great Alaska Earthquake, and design of the new embankment and bridges must accommodate the potential effects from future earthquake events. The Seward Highway serves as the sole vehicular transportation route between Southcentral Alaska and the Kenai Peninsula, and is heavily traveled, especially in the summer.

Shannon & Wilson assembled a team to conduct geotechnical explorations, which included more than 100 geotechnical borings, down hole shear wave velocity measurements, and seismic refraction. We completed this work to support recommendations for embankment and bridge foundations, as well as borrow source development along the alignment.

The project encountered significant challenges, including marine mammal observers (Beluga Whale watch) for overwater exploration work; coordination with the Alaska Railroad; adherence to permit stipulations from Alaska DNR, USACE, ADF&G and UFSF; and potential deep liquefaction hazards at the bridge locations.


Kyle Brennan
Vice President, Anchorage Office Manager

Ryan Collins

Stafford Glashan
Senior Engineer

Thomas Keatts
Senior Engineer

Brentton Leeper
Geotechnical Staff

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