McIntosh Perry provided engineering services for the Reed Narrows Bridge, which is located on Highway 71 in Northwestern Ontario and built in 1973. An underwater inspection revealed severe section loss and pitting of the steel piles, resulting from Microbial Influenced Corrosion (MIC). The bridge is a 164.6 m long, seven-span pre-stressed precast concrete girder structure. The superstructure is supported on conventional abutments and six piers (pile bents), each consisting of six concrete-filled, steel tube end bearing battered piles.
During the underwater inspection, the steel piles were noted as having severe section loss, organic scale, orange sulfate residue, severe pitting, and removal of the organic scale revealed a shiny steel surface. Based on these observed symptoms, it was concluded that the corrosion and section loss had been caused by MIC. The rehabilitation and strengthening of the steel piles consisted of polymer pile encapsulation. This involved the removal of the organic scale, installing underwater power actuated shear studs (to transmit force and bypass the zone of severe section loss), installing a reinforcing cage around the pile, installing an FRP jacket, and injecting the void between the steel pile and FRP jacket with epoxy grout. All of this was underwater.