Usually some portion of your dirt work is up and out of the pond.

Why not push some dirt into your 20' deep areas? I would imagine you could construct some fairly steep humps and maybe compact one lift over them. They should last a long time since there should be almost zero wave action in a pond that size at 20' deep.

It is always easier to doze dirt downgrade rather than up.

Are you going to have any big tree trunks and root balls to be excavated within the pond boundaries? Maybe put one of those on top of the hump, and another one beside the hump?

I bet if you look at the pond area after they strip the vegetation and top soil, you can envision some good structure to create or enhance in the deeper water areas - and it might even save you some money on dozer time!