First is waterline and front and back tow of dam staked? Site cleared? Once this is done you should be ready. I would let the dozer man prep the dam area and assist on the core ditch. That is a very important part of a sound dam. Especially one of this size. When we build lakes that are big enough to use a scraper we cut the waterline out usually a 3 to 1 slope approximately 4-5 feet to create weed free water line. With elevator scraper once you get the hang of it you should be able to cut a 3 to 1 slope with the scraper. As far as moving the dirt. We stockpile enough topsoil in order to cover the entire dam to the waterline when complete. After that we start hauling dirt to the dam. We do the dam in 3 sections. Left, Right and Middle which is last. The back half of the dam is topsoil/sand/clay mix whatever is ontop. The front half needs to be pure clay minimal mixing. We do 6-8" lifts for good compaction. You shouldnt have that problem with a scraper. Be sure if mixing not to leave strands of sand through dam because if you do the water will find its way through. Theres really not too much to worry about, take a full load everytime and put good clay in the front. What I have told you that we do is in south east texas and works for us. Not familiar with dirt where you are rocks ect. May be a little different approach if rocks are present. Hope this helps you some.