Violent, Costly Flood Inundates Alberta
Premier Alison Redford says it will take Alberta, Canada, a decade and $5 billion to recover and rebuild from a once-in-a-century flood that tore through the southern portion of the province on June 20. Damage was extensive in Calgary, where a state of emergency extended into July as floodwaters receded.
Tens of thousands of homes and businesses remained without power and roads and bridges were closed as engineers and inspection staff worked 24/7 to assess the damage and begin recovery and cleanup.
"June is always the runoff month from the mountains here, so we do see elevated water levels but certainly nothing like this," Craig MacFarlane, Calgary's chief structures engineer, told ENR. "We closed most of the bridges on the Bow and Elbow rivers because the water levels had come up high enough that they were impacting the superstructures."
The city hired locally based PCL Construction's Southern Alberta Division to coordinate the reconstruction of bridge abutments and approaches on the main downtown arteries.
"The force of the river washed out the gravel around the bridges, so there was no way to get on them," said Rob Otway, PCL district manager. "We're coordinating contractors to backfill and do some temporary paving to get the roads back in operation."
Early in the morning on June 27 in the city's center, the Bonnybrook Bridge buckled and dropped about a half meter, stranding a 102-car Canadian Pacific Railway freight train above the swollen Bow River. Canadian Pacific crews safely transferred petroleum diluent from six damaged railcars into railcars placed on an uncompromised adjacent bridge.
MacFarlane says the buckled bridge, a pony-truss structure built in the late 1800s, rests on piers embedded in river gravel. "There was five feet of gravel that was eroded due to flooding ,which caused the pier to slough at one end and lose support for one side of the bridge. That end settled down to bedrock, which is why it didn't collapse completely."
Calgary Mayor Naheed Nenshi criticized Canadian Pacific, which is exempt from municipal bridge-inspection rules, but the railroad said the bridge had been inspected 18 times since flooding began.
