I have a 4 X 7 Mile coolant pond which I need to calculate the surface volume of for evaporation calculations. The site has earthen berms running the length which extrude 10 feet above the water surface. The water surface has a 5 foot elevation difference from North to South (head). I tried using civil 3d 2011 but I can only get a flat surface calc. with cad. The calculations need to remove the area covered by the earthen berms.