I have a good size hole in my damm around the exit side of an old stand pipe which is no longer in use. I could see water bubbling from around it and took a good look. I discovered a hole so deep that i couldn't reach the bottom with a shovel. I have a siphon system that replaced the stand pipe. The water has lowered enough so that it has lost suction. The pipe appears to be in good shape. I think the leak is around the pipe and not from it. Any suggestions on how to deal with this? Thanks in advance.