My advice is build a new pond in a different location if that option is available. If the current pond is strategically located and the only option is cleaning it out it can be done but it likely will cost as much if not more than building an entirely new pond. I have built 4 ponds from scratch and have cleaned out and renovated three old ponds, one of my own, one for my daughter and one for a son.
Here is a link to my experience cleaning out my son's old pond. The dam had failed numerous years earlier (washed out the overflow pipe) and it was an almost dry bed when I started. Maybe it will give you some ideas or more questions to ask.
Reclaiming a 50 year old pond If I would have had an excavator to help the dozer out the job would have been twice as easy. I have a 12 yard scraper pulled by a rubber track tractor that moves dirt very efficiently but in muck it is useless and I did not even take it to the job. I worked with what I had for equipment but in retrospect an excavator would have been really nice.
My son and his young family use the pond extensively every year since it has been cleaned out. Probably one of the best things I have done for them.
