A client contacted me to open up a trench so that plumber could connect the sewer line county out of his new home construction to the county sewer line. Why they didn't do it before they completed backfilling around the foundation, I don't know. The challenge for me is the house is built into the side of a hill. I didn't do the excavation for the foundation, but was called in to help bust up some rock. There was a lot of rock in the hillside and there's limited space. It was showed and told to me that there was only one line in the ground and it was marked. However, that proved not to be the case. When I hit the first vein of 57 stone, I stopped digging. As I was clearing the trench for personnel access, I came across another vein of 57 stone and exposed a pipe. Something wasn't adding up. I came across 2 distinct gravel veins, at different depths, and in different locations. Obviously, there's more than one line running through the area. I called the owner and explained my findings to him and he says 'oh yeah, there's a 3" force main and 8" sewer line in that area. I wonder why only one was marked? It had been awhile since I last looked at the site plans. The owner didn't sound too confident on the locations and depth. And, given the amount of backfill on the hillside, I was suspect of the accuracy of the markings as well. So, once I got through what I knew was backfill, I took shallow bites. It was all 'discovery' excavation after that. Fortunately, I didn't damage anything and was able to locate the pipes without issue. Lesson - Refresh/review and verify plans yourself, If you have any questions on utility locations, call out Ms. Utility back out for marking, and go slow! Now, just waiting for the plumber to get out there and do his thing so I can fill that hole back up.