Emergency crews in Calgary, already overworked from the heavy flooding in the area, have another potential emergency to mitigate. In the very early morning of June 27, a rail bridge over the Bow River collapsed, just as the end of a long train went across. The last six cars – five of which contained petroleum products, the last empty – derailed and are now precariously balanced on the collapsed bridge (but remain out of the river).
Emergency plans have been implemented to reduce the risk of the public in the area. Capturing the cause-and-effect relationships that are resulting in the risk to the area can show how the emergency actions are acting on causes and potential causes to keep the public and the environment safe. A visual representation of this type of root cause analysis is called a Cause Map. The Cause Map has three steps.
First, we capture the what, when and where of the incident in a problem outline. We also capture any differences such as the heavy recent flooding in the area. Differences that we capture may or may not turn out to be causally related to the problem, but investigating the possibility is important.
The remainder of the outline is the impact to the goals. Any “problem” is in fact an impact to one or more of an organization’s goals. Framing the problem with respect to an organization’s goals ensures that solutions act to reduce these impacts and decrease disagreement about what the problem really is. In this case, the safety goal is impacted due to the potential for injuries (though there have not been any associated with the derailment or response yet). The potential leak of petroleum products is an impact to the environmental goal. The area surrounding the train was evacuated, which can be considered an impact to the customer service goal. (Frequently organizations will consider the surrounding communities as part of their customer base.) The production/schedule goal is impacted because the bridge is unusable. The damage to the bridge and potential damage to the cars (as yet unknown, because of their unstable position) are impacts to the property/materials goal. Lastly, the manpower being spent on emergency response and securing the train cars is an impact to the labor/time goal.
Once the impacts to the goals have been determined, the analysis begins with these impacted goals and is continued by asking “Why” questions. For example, the risk of injury is caused by the potential leak of petroleum products. The potential leak is due to the potential damage to the rail cars and the product contained within 5 of the cars. Removing either of these causes reduces the risk of the effect. In this case, plans are being made to remove the product from the trains to reduce the risk of both the safety and environmental impact. The rail cars are being secured so that further bridge collapse will have less impact on the structural stability of the cars.
The evacuation – removing the people from the area – also serves to reduce the risk of injury. To reduce the potential environmental impact, booms have been installed down-river in case of product leak. Of course, these are emergency, short-term solutions designed to reduce the impact of collapse and derailment. Solutions to the issue of the bridge collapse and its causes will be looked at in more detail once the cars have been safely removed.
While the investigation of the issue is still ongoing, the information that is currently known can be added to the Cause Map. The structural failure that led to the bridge collapse appears to be caused by scouring of a support pier caused by the sudden influx of water related to the flooding in the area. Concerns about how quickly the damage was discovered are a concern. While investigations had been stepped up as a result of the flood, concerns from the city – which does not have jurisdiction for its own inspections – that the rail company’s inspections were insufficient will certainly be investigated. It’s also been determined that the bridge – unlike others in the area – was not built into the bedrock, decreasing its strength, though how much of a role that played in the collapse is yet to be determined. When more information is known, it can be added to the Cause Map.
To view the Outline and Cause Map, please click “Download PDF” above.