For more reading on how to renovate a pond without rotenone see these links that I found by searching.
Hydrated lime
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=300154http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=386504http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=383641Hydrated lime and green walnut hulls – husks. Black Walnuts are readily available now wherever there are the trees. It was a good year for black walnut production.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=228909Bleach will work but some consider it risky in terms of environmental effects. Trihalomethanes have to be monitored by water treatment plants to insure they are not too high after chlorine treatment.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=149891Google rotenone fish toxicant for all sorts of information about it. Just FYI contact a local pond management company to see how much they charge to kill the low water pool of the pond. Contact local game warden or DNR for info about closest place that deals with or applies rotenone the fish toxicant.
If you only have bass and BG in the old pond these species should kill pretty easily with hydrated. Catfishes, bullheads, and green sunfish are resistant, may be harder to kill and need higher dosages.
