I have a 7 A. pond in my back yard. When I moved in it had 2 ft of water in it and a leaky dam. It has a 2.5 sq mile watershed. There is 666 cu ft/sec of water that goes over the spillway that is in bad shape. My ex and I drained it and removed 5000 dump truck loads of clay out and repaired the dam. Now a contractor is going to finish it and take the dirt. He has dug in the middle of the pond 8' down and hit shale. There is 6" of water it in now in a dry spring. He says I dont need a clay botton "Look its holding water now" Is he right? Everything I read says you have to have a clay bottom. Help!