New bridge for environmentally sensitive, remote location

New Coal River Bridge
Alaska Highway, British Columbia, Canada
Public Works and Government Services Canada
Public Works and Government Services Canada
Industry Sector
Service Area
Basic Engineering; Facility Assessments; Infrastructure Services

Constructed in 1943 with a steel girder span and concrete deck, the old Coal River Bridge had reached the end of its economic life and PWGSC retained. Ausenco to design a replacement bridge over the Coal River.

The project presented some significant design challenges including: remoteness of site for construction, crossing of a sensitive fish bearing river, and extreme annual temperature range (-49C to +43C).

We reviewed a number of bridge structural options, including schemes with piers in or out of the river, using both concrete and steel construction. Evaluation of these schemes concluded that an arch, which avoided instream works, was the most suitable structural system.

A twin steel arch with a clear span of 100 metres was designed with the superstructure consisting of 13 spans with precast concrete panels with a cast in place overlay supported on steel stringers and floor beams.

The thrust blocks for the arches, located on each bank, are supported by mini-piles. The design, which incorporates mechanically stabilised earth type abutments, was developed to minimise the amount of site fabrication and construction.

The majority of the bridge components were manufactured offsite and transported to the bridge site by road.