The year I graduated from high school, I was hired for the summer at the local pulp and paper mill, after a couple of days they gave me and another guy to the pipe shop for a special project; we had to dig out a section of 36" water main. It was located behind the bleach plant, about 10-12' deep at the bottom of the pipe. Our tools were two shovels, a rope with a snatch block, a five gallon bucket, and a 4" diaphragm pump to keep the water down to 6" in the bottom of the hole. At the foundation of the bleach plant there was a space that had water and chlorine paper blowing out of it. After we had a good deal of it dug out a backhoe was brought in to dig out the other end of the hole. He got about two buckets out before hitting an overhead 2" pipe and breaking the flange, said pipe was carrying 98% sulfuric acid @90# pressure.
After the acid was cleaned up (washed down into our hole) the operator was taken to the ER, and the now paint free backhoe was towed off, we went back to work with our shovels and bucket. The water was now warm from the acid. When we were in the hole we wore: hard that, goggles, gas mask, neoprene rain suits, neoprene gloves and neoprene boots.
I don't know how much material we dug out of that hole but the pile was pretty big when we were done.
The fun part was jackhammering out the foundation wall around the pipe, yes the pipe was carrying water a pressure when we were working on it!
It worked out well in the end, he was assigned to the pipe shop as a helper and I was assigned to the electrical shop as a helper and spent the rest of the summer overhauling big 3 phase motors.