A Canadian Pacific Railway (CP) freight train derailed six tank cars. There were no injuries in the accident and the tank cars were safely removed without spill or damage to the environment.

The investigation determined that train handling did not contribute to the accident, and the CP inspections of the bridge before the collapse exceeded Transport Canada requirements.

The original single track bridge had been built in 1897, was expanded to accommodate an additional two tracks in 1912, and another bridge for a fourth track was added in 1969. The bridge failed at Pier No 2 of the original bridge under the 67th and 68th cars.

A comprehensive examination of the bridge failure was conducted. It revealed that flood water flow had attacked the shale bedrock/clay pier foundation, eroding and undermining it. Scouring action of the flooding Bow River on the downstream end of Pier No 2 resulted in a loss of foundation support to the pier.

The investigation also highlighted that the unified command structure initiated by the City of Calgary Fire Department worked well in securing the site and in developing and executing the plan to safely remove the derailed cars from the bridge.

Following the accident, Transport Canada issued a number of safety communications regarding bridge inspections to all railway companies. In addition, CP revised its bridge inspection practices and its inspector training programme and is investing in research for the early detection of scour and erosion at railway bridges.