Alaska Railroad Corp.’s Northern Rail Tanana River bridge

Project Summary

The Alaska Railroad Corp. (ARRC) selected Hanson Alaska LLC, a wholly owned subsidiary of Hanson Professional Services Inc., to provide engineering services for a proposed rail line extension from the south bank of the Chena Floodway near Eielson Air Force Base to Delta Junction, Alaska.

Major elements of the proposed extension project include:

• approximately 80 miles of new railroad track to be constructed to Federal Railroad Administration Class 5 track standards, 
• 14 bridges on the proposed action alignment, including a 3,300-foot-long bridge over the Tanana River, 
• an access road for joint use by the military and ARRC maintenance personnel,
• facilities for passengers, freight and maintenance operations at the terminus in Delta Junction and
• ancillary railroad support facilities, including but not necessarily limited to power, wayside signals and communications towers and facilities.

The primary objectives of the project are to:

• support commercial freight needs for communities and businesses, including the agricultural, mining and petrochemical sectors,
• support passenger service needs and area tourism by providing a safe and reliable transportation alternative to the Richardson Highway and
• provide improved access to the military training areas on the west side of the Tanana River.

In 2006 and 2007, Hanson evaluated several alignment alternatives to identify a proposed action alignment for the Surface Transportation Board to consider in an environmental impact statement. The proposed action alignment was refined and developed into a conceptual plan set in November 2007.

Hanson also conducted a conceptual design study to determine the preliminary configuration of three “standard” bridges defined as short spans (less than 40 feet), medium spans (60 to 80 feet) and long spans (more than 100 feet). These standard bridges will be used in evaluating the numerous proposed routes for the Northern Rail Extension, along with other considerations, to select a preferred route.

This report focused on the preliminary planning and conceptual configuration to be used throughout the route and to serve as the basis for opinion of probable construction costs for the majority of bridges. Compiling this report involved investigating numerous types of superstructure construction materials and researching typical local construction practices and climate restrictions, and Alaska-specific material availability.

In 2011, Hanson provided final engineering services for Phase 1 of the project, which consisted of a 3,300-foot-long crossing of the braided Tanana River, two smaller railroad bridges over Tanana River sloughs, and a mile of railroad embankment to connect the structures near Salcha, Alaska. This design addressed significant geotechnical, hydrologic, environmental and seismic issues. Hanson provided office engineering support to ARRC during construction of Phase 1.

The new bridge is designed to serve roadway and railroad traffic with a single bimodal deck. A ribbon-cutting ceremony for Alaska’s longest bridge — the Tanana River Bridge — was held Aug. 5, 2014.