By Kim Smiley
On Sunday August 11, 2013, guests at a resort near Orlando, Florida woke to creaking sounds and breaking windows. About 10 minutes after the disturbances began a portion of the luxury resort villa was swallowed up by a sinkhole that had formed with little warning. Luckily, there was enough time to evacuate the resort and no one was injured, but guests lost most of their luggage, including purses and wallets, and the resort obviously suffered significant damage.
This incident can be analyzed by building a Cause Map, or visual root cause analysis. A Cause Map shows the cause-and-effect relationships between the different causes that contributed to an issue. This can help guide an investigation and is useful when developing solutions to prevent similar problems from occurring in the future. Cause Maps can also be used to help explain the issue to somebody who was not involved with the investigation. To view a high level Cause Map of this specific issue, click on “Download PDF” above.
A sinkhole forms when a void is created underground and the earth ceiling over the void collapses into it. Voids typically form when there is a limestone or similar rock deposit underground that is dissolved by slightly acidic groundwater. This region in central Florida is well known for sinkholes because these types of underground deposits are relatively common in the area. Over pumping of groundwater can also cause the ground to settle, possibly forming a void. There is concern that the rapid pace of development in this area has had an impact on the groundwater and may potentially be helping fuel the formation of sinkholes. There was also record rain fall in July in Orlando and the additional water may have caused the ceiling over the void to be heavier than normal and more likely to collapse.
There rarely are easy answers, but sinkholes seem to be a particularly tricky problem to solve. They are unpredictable and there is typically little warning before they develop. Prior to the resort being constructed, the site underwent geological testing and the ground was found to be stable so something more than basic geological testing will be needed to solve this problem. Well planned development and careful management of ground water may help limit the development and impact of sinkholes, but there will be strong economic pressure to develop more and more land in the booming Orlando area. Insurance seems to be one of the best solutions to date. Florida law requires insurance companies to cover “catastrophic ground collapse” so that property owners at least have an economic safety net in the event of a sinkhole. The only good thing about sinkholes is that they generally take a little time to form like the recent resort sinkhole. There will be property damage from sinkholes in the future, but hopefully there will also be time to evacuate everybody like there was this case.