Sounds like you and your company have done everything you can to prevent this - except for making the operators responsible for their own actions. Union shop or not, if someone was stood by these colums they would now most likely be dead - no union in the world would condone this. First off operator selection is important, responsible attitude is very important. The operator has to face consequences for their actions, maybe a fine system, loss of bonus, job demotion? As in life itself people have to be made responsible for their own actions, if you or your company are accepting full responsibility for your operators maybe thats the root cause of the problem ? (IMHO)