What's the best (easiest) way to find out where a copper cable is buried? It's been close to 25 yrs ago, but I saw a guy drag it off w/a dozer and bury it, so it won't be real deep, 7-8 feet, but it was for 4160 volts, so there would be a lot of copper there, as it was a hundred feet or so long. How deep do rental units detect? Or should I get in cahoots w/a backhoe guy?