Got my yard leveled and lots of glass and other things found in dirt in the ground. Going to install the rails and bricks tomorrow (weather permiting). Is there anything I could lay on the ground before putting down the sand to protect my liner, something I can get from Home Depote? Or is the 4 inches of sand enough? Its going to be a 28 foot ABG pool with a slight scoop in the center with a deep part of about 6 feet, 4 foot sides;if everything goes well. No one here ever built one before but lots of reading and building other things. Have the laser level, Escavator loaning us his. Thanks, Kim