A new bridge across the Kitimat River

Replacing a 69-year-old bridge

A 69-year-old highway bridge provided the only connection across the Kitimat River between the municipality of Kitimat, BC, and its industrial lands. With the industrial lands becoming increasingly busy due to the growth of LNG Canada, the bridge required replacement or major repairs to accommodate the growing amount of industrial traffic crossing back and forth.

Ultimately, the District of Kitimat made the decision to replace the bridge through a Design-Build contract awarded to the Ledcor-Haisla Limited Partnership. Brybil Projects, a subsidiary of the Associated Engineering Group of Companies, was the lead design consultant for the project. Thurber acted as a sub-consultant to Associated Engineering, providing geotechnical engineering, construction materials testing, and metal leaching/acid rock drainage (ML/ARD) services.

The new two-lane bridge opened on July 31, 2023. It is 230 metres long and consists of four spans, 1,000 metres of realigned road approaches, upgraded drainage infrastructure, roadway lighting, erosion and scour protection, and private utilities.

Geotechnical

Thurber provided the following services for the Haisla Bridge project:

• Geotechnical investigations to characterize the soil strata and bedrock along the bridge alignment, which included test hole drilling at the east and west piers, downhole shear wave velocity testing for seismic classification, laboratory testing of soil and bedrock samples, and mapping of bedrock outcrops near the bridge alignment.
• Geotechnical design of the new bridge foundations and approach fills. The Kitimat area is subject to moderate to high seismic hazards; the new bridge needed to be designed to withstand seismic demands from the 2,475-year earthquake event, which were determined from site response and liquefaction triggering analyses.
• Geotechnical design of new rock cuts, catchment ditches, and roadway embankments as part of the realignment and upgrading of Haisla Boulevard on both sides of the new bridge.
• Construction field reviews of the roadway subgrade, utility trenches, and during pile drilling/driving in accordance with project requirements.
• Geotechnical design of crane pads and temporary pavements during construction.

ML/ARD assessment

The Ministry of Transportation and Infrastructure BC (MOTI) requires ML/ARD assessment for all highway projects that involve the disturbance or use of more than 1000 m3 of rock materials, including bedrock disturbance in rock cuts or importation of rock material from quarries or talus slopes. The presence of ML/ARD in rock disturbed by or imported to a project site can have significant environmental impacts.

Thurber provided ML/ARD assessments for the quarried rock used in the Haisla bridge construction and erosion protection, and the rock cuts generated by the bridge re- alignment along Haisla Boulevard. As part of this assessment, we identified an area of potential acid generation next to the existing roadway. This required modifications to the roadway design to avoid disturbing the bedrock in the ARD-prone area.

We conducted site visits, visual identification of the local geological conditions, collection of rock samples and interpretation of laboratory-based static assessment data, quarry assessment, and review of third-party assessment reports for other rock quarries in the area. We also provided follow-up monitoring of the quarry contractor’s field operations to confirm the effectiveness of material sorting to segregate ARD-prone from lower-risk rock material.