get a backhoe :-) Just joking, but you will need some muscle to pull them out if it's been a while. After you get them out, start hosing off the tubers and you will begin to see where you can pull them apart. Compost anything soft and just replant the firm tubers with preferably multiple growing tips.

Call all of your friends with ponds and give away the excess :-)

I had a big patch of mini cattails once that took 3 adults to pull out of the pond, we hacked it up and composted most of it. The liner beneath looked brand new, it was so clean.