Its been almost 3 years since I started this thread and the damn dam still isn't fixed. The pipe finally rusted through and broke off right where the pipe goes underground into the damn. It is 24" corrugated 110 feet long. The drain pipe broke off about 2.5 feet lower than "normal water depth. With the loke lower than normal, I was able to dig a new spillway adjacent to emergency spillway. In the next couple weeks I will pour cement in new spillway. Then I will plug old pipe and start using new spillway.
My question is what is best way to plug the old pipe? So far, best idea I have heard is to ram a makeshift plug at least 6 feet into pipe then fill with hydraulic cement. Any other ideas? I'd like to plug it from the bottom, but that is 110 feet of cement = 12.8 cubic yards!!!