Project Overview
A short construction season, harsh weather conditions, and extremely heavy loads were just a few of the challenges PND overcame when designing the Nigliq Channel Bridge across the Colville River on Alaska’s remote North Slope. The award-winning bridge is a throughway critical for accessing, producing, and transporting thousands of barrels of oil per day, acting as a key component for careful resource extraction in the National Petroleum Reserve―Alaska.
PND designed the 1,420-foot bridge as an easily launchable twin-box-girder superstructure prefabricated in eight sections in the Pacific Northwest. The bridge components were transported to the site, then stored on a multiseason ice pad before on-site assembly. The bridge was incrementally launched horizontally across nine piers. To address the wide variety of frozen ground conditions at the site, PND’s substructure design used multiple configurations of steel pipe piles, including driven piles with our trademarked SPIN FIN™ tips for extra bearing capacity in shallow thawed zones.
The Nigliq Bridge is the first and longest launched bridge constructed in North America north of the Arctic Circle. PND’s launchable bridge design minimized the project’s environmental footprint, allowed for quick deployment during the limited ice road season, and maximized safety by drastically reducing the number of work-at-height field hours compared to standard bridge construction.
Our Role
- Geotechnical Engineering: designed a complex assortment of foundation solutions due to the wide variety of frozen ground conditions at the site and performed engineering predictions of adfreeze behavior in high-salinity permafrost soils
- Structural Engineering: used a launchable box girder superstructure to meet the project’s critical schedule for completion and incorporated SPIN FIN piles into the design to ensure bridge stability
- Civil Engineering: designed the 1,420-foot Nigliq Bridge, plus three other significant bridges, a 6-mile gravel road, resource development gravel pad, and a multiseason ice pad
- SPIN FIN: used SPIN FIN tips for extra bearing capacity
Launching Innovation Across an Arctic River
PND engineered the Nigliq Bridge with a box girder design facilitating easy launch across the Colville River. The bridge’s foundation system consists of piles embedded in complex geotechnical conditions ranging from thawed to permafrost soils.
The bridge consists of eight spans up to 200 feet long each, providing access for heavy oil field service vehicles weighing up to 175 tons. PND engineered the bridge to support six pipelines along its downstream side, protecting them against ice floes up to 6 feet thick and 200 feet wide. Construction challenges included the project’s remote location and extreme climate, with wind chills plunging to -65°F, blizzards, extended darkness, and limited access due to seasonal ice road restrictions. PND launched the bridge during fall months to allow construction during the ice road offseason. PND’s innovative strategies facilitated expedient project completion.
"This bridge is an engineering feat. Launching a girder system is hard enough in ideal conditions, but to do so under extreme conditions is an accomplishment to be lauded.”
Feet
length of the Nigliq Bridge
Spans
comprise the Nigliq Bridge
Feet
maximum span length
