Or the human error was the data house didn't understand what the contractor was going to do, which is a common failing.
Unfortunately we don't know what the contractor was there to do, he may have been there to work on the failsafe system, or a part of it. Because of this we can't say whether procedures etc were there or not, they probably are in place, but either not used, not understood or have errors in them.
I'm afraid, due to my background in process safety, I take statements like 'never happens again' related to procedures with a pinch of salt, humans make mistakes, whether that is in writing the procedure, failing to follow the procedure in the correct order, just not understanding it but trying to muddle through or just not using it/forgetting its there. Human error can be reduced but it can't be complete mitigated against, there is some research by a chap called Kirwan called 'Guide to Practical Human Reliability Assessment', a person doing a simple task that requires care is likely to make an error once in a hundred times.
I'm afraid we are just not that reliable, especially if there is a stressful situation
Paul
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