I always wondered what the possibility of creating a new core behind the dam, and fill with good material from somewhere nearby to make a short dam with a pipe or breach all set for draining. Then breach the old dam, let the water out, then move the old dam plus new clay/bentonite into the new dam location. It would then prevent machinery from spending too much time in the muddy bowl of the pond. It would have the additional benefit if enlarging the pond which we all hate.
