Spanish Ontario - On 1 Nov 2015 a Huron Central Railway (HCRY) freight train lost three locomotives and 13 cars.
The Transportation Safety Board (TSB) was called in to investigate what could have occurred.
After two years, the TSB has closed the investigation and released Investigation Report R15H0092 on its findings.
The TSB stated the HCRY crew felt one of the locomotives dip and pull.
When the crew looked to see what was happening behind them, they saw sparks coming from the second locomotive.
This caused the crew to initiate the emergency brake application and inspect the train.
The crew found three locomotives and the 13 cars had disconnected from the train where the track had collapsed.
High levels of rain leading up to the train derailment had caused the roadbed to weaken.
In October 2015, the area had received 134.4 milimetres of rain.
Some of the HCRY cars that had derailed were submerged in two feet of water and clay soil.
Upon inspection, the TSB noted that the roadbed was destroyed for 225 feet.
While inspecting the track, there were 39 joint defects.
"These defects included 10 cracked or broken joint bars," stated the TSB report.
"One cracked joint bar was located at a rail joint that had been marked during a rail flaw test due to the presence of an internal rail defect. The remaining joint defects included loose, bent, or missing bolts, and broken or missing tie plates. At the time of the occurrence, no slow orders were in effect at that location."
The report stated that the joints had not been loose, but rather the stress of water saturation had resulted in the reduced stability of the track.
The concrete culvert situated where the collapse occurred had restricted water flow, which caused the culvert to either collapse, sink, or become blocked.
The last culvert inspection occurred in 2013, two years prior to the train derailment.
Restoration of the track had occurred in 2014.
"The derailment location had a history of track and roadbed instability," stated the report.
"Specifically, frequent track maintenance had been required, including track surfacing, shimming, rail pull-apart, and low joints. These maintenance activities were generally required as a result of poor drainage. Despite the fact that Huron Central Railway had adopted the Transport Canada (TC) Guideline for Culvert Safety Management and had a history of track instability and frequent track maintenance, there was no indication that the problem was fully understood nor was a more permanent mitigation established."
If conditions related to drainage are not identified and fixed, it speeds up the process for the track to become unstable.
The TSB investigates transportation safety, but do not assign fault or determine guilt or criminal liability.