The rock farm had a sewer line so to speak. 16" steel, about 1/2 mile of it, carries the silt and fines away from the plant. Every now and again the rockheads would lose a sand screen and plug that sucker up. Across flat ground it was pretty well exposed for just such events. only once did we have to excavate to find the plug up. Cut a hole in the pipe, flush it down hill, weld the pipe back together. Oy Vey.