Scott, did the beaver move the chunk rock away from the dam to dig the hole too? The little bugger that did ours went in about 30 ft, then did a "T" and that went another 30ft each way with an air hole at the "T". If I remember right it took three weeks to bring the water level down a couple of feet to to where it could be filled in and repaired with a bull dozer. Our probelm was solved with a 330 connibear trap in front of the hole before the heavy machinery went to work. ;\)