I am in the process of renovating a small 60yo+ heavily silted 0.9acre pond in Lafayete LA. Took about 6 months with a trash pump trying to get it dry before we could get a tiny excavator in there. Used that to dig a drainage trench which we are now pumping out of (allowing us to pump water from below the nominal pond bottom) which has allowed the pond to "fully" dry enough for real work. All in all, probably took 10 months from when we started pumping to being ready for work. Cost aside, time may be a factor to think about too - depending on the condition of the soil on the pond bottom.

Kris