I had a hell of a time getting that pipe unclogged. After I got the flow going, they when up in the pipe 7-8" and sealed it up. At first I cut a pole from a dead treelimb and thought I can jam it a few times and break it up. Didn't work. So I got a fruit picker on a 10' pole, and tried to corkscrew it with the basket. I was up to my shoulder and had only managed to push it in further. Finally I got a 20' telescopic pruning handsaw, removed the blade, and duct taped a potato rake to it. By this point the blockage was about 15' into the pipe. I was able to rotate the rake against it and piece by piece grab off twigs and debris. Finally I got a got a good hold on a chunk of debris and that got the flow started again. Kept at it as much as I could and opened it up good. There is still some junk in there about 20' in. The PVC pipe goes down through the dam. So it I couldn't get it lose it would be an expensive fix.
I don't know if there's anymore beavers in there, I guess I'll find out in the next few days.