Old Skeena River Bridge is a 9 span, 1120’ (341 m) long, steel vehicle bridge over the Skeena River in Terrace, BC. The bridge has:

• One 50’ (15.2 m) steel stringer south approach span
• Four 140’ (42.7 m) steel deck truss spans
• One 160’ (48.8 m) steel deck truss span
• One 250’ (76.2 m) steel through truss main span
• Two 50’ (15.2 m 15.2 m) steel stringer north approach spans

The bridge operates as a single lane alternating structure with traffic light controls at each end, & it is restricted to carry only passenger vehicles weighing less than 4,000 kg (4.4 tons).

The bridge was constructed in 1924 & has undergone a number of major rehabilitations. Prior to the latest rehabilitation, it had been experiencing heavy corrosion which, if not addressed, could lead to the permanent closure of the bridge. Due to the anticipated replacement cost & the presence of more modern bridges nearby, a new bridge at this location may not be practical, so its historic service to the community could be lost forever.

The Primary Objective was to extend the service life of the bridge as long as possible while targeting only critical components of the structure to manage costs, including:

• Maintaining the existing 4000 kg vehicle restriction.
• Repairing or replacing damaged or badly corroded components.
• Replacing all expansion bearings.
• Recoating the entire structure.

Secondary Objectives included:

• Allowing use of a 21 tonne bridge inspection vehicle.
• Installing pedestrian refuge bays to allow passing on the narrow sidewalk.
• Repairing deteriorated substructure concrete.

Morrison Hershfield was retained to conduct a bridge renewal study, condition assessment & rehabilitation design in an attempt to extend the service life of this historic structure as long as possible due to a high bridge replacement cost.

The project was completed 4 months ahead of schedule, & with regular maintenance, the service life is expected to continue for at least 30 more years.

• Load Evaluation: MH prepared a sophisticated 3D model to assess the bridge’s capacity for vehicle & wind loads. MH justified use of a 21.1-tonne snooper inspection vehicle (previously restricted to 4 tonnes) by strategic positioning on the bridge deck. MH also analyzed wind loading during coating operations, determining permitted enclosures & temporary bracing requirements.
• Close-Proximity Inspection: MH conducted a 3-day snooper truck inspection, assessing the bridge’s condition, coating deterioration, & identifying severe structural steel losses in truss spans.
• Condition Reporting: MH compiled a comprehensive inspection report, featuring field photos, condition ratings, mapping of components with notable deterioration, & recommendations for structure rehabilitation.
• Coating Assessment: MH assessed coating deterioration, providing a memo with site photos, estimation of remaining coating service life, comparison of renewal options, cost estimates, & LCCA.
• Bridge Rehabilitation Design: MH designed repairs for structural steel & gusset plates with severe corrosion & section loss. Deteriorated roller bearings were replaced with new elastomeric sliding bearings. A deficient cap beam was replaced, & 6 pedestrian refuge bays were added for enhanced passage.
• Construction Services: MH swiftly addressed additional member deterioration during construction, revealed during sand-blasting. Design details considered available steel plate & member sizes for on-site repairs.

• Bridge gained additional 30+ years of service life
• Load rating justified use of snooper truck for future inspections
• Staged coating enclosures allowed concurrent work on multiple spans
• Temporary lateral bracing used to accommodate bridge coating enclosure
• 6 sidewalk refuge bays added
• Full recoat of structure with 3-part epoxy
• Replaced all expansion bearings
• Repaired/replaced corroded steel members
• Contractor worked year-round & completed 4 months ahead of schedule