Chris,
after looking at your pictures, I would pump it out it would take a day with the proper pump. And then hire a track-hoe to clean it up spread the dirt on the down side seed and straw.I would put in two silt traps at inflow ,judging by the shape of it. There is a difference between silt and biomass which do you have. Aeration will not reduce yiur silt load but work on Biomass.Your banks might be to steep for equipment ,but it was built with a machine.Also the spillway or overflow is in the wrong spot,while the Hoe is in there he can ease the inboard banks.You might want to put a 10" culvert pipe where the chair is ,instead of water erroding steep bank.
Good Luck
Scott
