I have cleaned out several ponds by trenching to draw down the water and then used a large excavator sitting on the dike, like a Cat 225 to dig a sump inside the pond. A small dozer, like a Cat D3 then can push the muck to the sum where the ecavator will lift it out and depoist it on the rear side of the dike. This should cost $2-$3k for a one acre pond. Using a large excavator it takes only 8 hours for an acre pond where the muck was 2'-6' deep.
