I know of no studies and I doubt that many records are kept nor is there a central record base to my knowledge The closer you get to a hazardous utility the more hand digging/working is needed and I think that there are hundreds of 'pecker', jack hammer etc strikes on hazardous utilities on a daily basis even though there is very good detection kit out there; but its expensive and the supplied drawings are poor to say the least Its almost certain that a 'strike' will happen so 'foreseability' is not an issue and the aftermath is hardly ever recorded in the press as they are just not interested in such work related accidents