Kelly-I like the idea too. I have always liked when people start "thinking outside the box". The biggest obstacle in that would be getting some kind of sealant deep into that tunnel ( I think he said 30'?) and then getting the new pipe to stick good enough to it so there isn't even a hairline crack. Possiblly several jacks inserted deep into the tube would work like you said. To bad there insn't a fluid that you could just pour down the tube and let it settle out level and turn solid AND seal to the pipe. Then you wouldn't have to worry about even putting in additional pipe.

Another half baked idea... Would it be possible to insert a flexible drain pipe down and thru the old pipe all the way to the outlet? Seal of the inlet end so water can't get between the old and new line, forcing the new pipe to be used. This would only work if the old pipe it isn't rusted out at the pond side and the leak is happining after it goes into the groundwork of the dam. Bad news to this would be the new line is smaller than the old one, possibly causing the spillway to be used.

Laneman - Are we to assume the pond is now draind down to the horizontal level of this old pipe?