I was going to say metal detector also. some actually tell you how deep. Then mark it with marking paint, and then dig with a hand shovel, from the side and using only your arm strength , no jumping on the shovel with your feet. Then make test holes every three feet or so to locate the depth. once youve done that the length, it will be lot easier to dig the length with your shovel and the majority of the depth can be pretty quick. I had one instance where Miss Utility told me where the line was, but it was actually 10 feet to the right the entire way. They were locating something else apparently. In another instance, they confirmed nothing was buried in an area and when the back hoe came in, they went through the water line to the house and lots of water. They obviously were liable thankfully. Once you find it, I would consider coming up with a solution to put a a protective layer over, like a couple inches of concrete or something in the ditch, just to give you a layer of protection in the future. It wouldnt take much.
When I was in grad school at UofMO in the early 1990s, we lived out west of Columbia, on US40. The MAIN transcontinental telephone cable ran right through our front yard…they were really paticular about that…had a guy who flew the route from St.Louis to Kansas City, every day looking for any indication that someone might be thinking about doing any excavation in the vicinity of the cable. Showed up at our door one day when he saw a backhoe…landowner was getting ready to run a new waterline from the well to the house; he had to hand-dig to show them where the cable was, and stay there until the new waterline was run and the trench was backfilled.
If they had cut that cable…
Ha. My Verizon cable is maybe 4 inches. I know, because they cut my irrigation when they installed it, so I had to muck with it when i fixed the irrigation. (The irrigation is just plastic tubing that I installed, and it’s only a little above the Verizon cable.)