I would rethink your method of removing debris it will not work even if you crack the door a couple of inches. When you try to pump off the bottom the hose will clog and become very heavy and hard to manage. You will have to keep a proper mixture of water and solids for the pump to work the hose will gain a weight of 12 pounds per foot and sink.
Wait till you have the time and $ to dredge the pond 20 yds will not reduce the nutrient load.On average a 1 acre pond that is 30 years old will need 250 yds removed. This will vary with watershed and bio mass load from surronding area.
Good Luck
