There had been a wet spot beside a putting green for year's, it finally got big enough to be a real problem and needed to be fixed. I took a probe to get an idea of what i had to do and i kept hitting something solid and it wasn't pipe. I started to dig this thing by hand. After a whole day, i had a trench 10 feet long, 4 feet deep and 2 feet wide and all i had uncovered was a concrete blob. At this point i brought in the backhoe. This is highly unusual, i never dig up irrigation leak's with machinery like that, it cause's way too much damage. By the time we had this thing exposed, there was a gigantic hole and we used 35 4' x 8' sheet's of plywood as a base for this mountain of soil. A assistant who had been there forever told me that year's earlier, when they thought they had this problem fixed, they brought in a concrete mixer truck with a yard of concrete and poured it on top of the pipe. This thrust block (i use that term loosely, but technically that's what it was) was so heavy that the backhoe couldn't pull it out of the hole. We had to dig the hole deeper and drop this blob below where the new pipe ran. In the end i used three 80 Lb. bag's of quik-crete for a new thrust block. This turned out to be a major ordeal. See the illustration.