It probably won't stay that deep forever. You will have silt washing in and a lot of sand usually comes in off the sides when it starts filling. In my area, rain can be a rare blessing and having a deep water hole during dry times pays off. Prior to our record breaking July rains, I was 7 ft. low. You can pump some of it to get your bermuda growing on the dam. I did and that is the only reason I have any grass.