So I have a centipede lawn up on a hill. At the bottom of the the hill next to the curbing the ground is really wet and killing the grass. I took my soil prob and punched it 18 in in the gound. the top 3-4 inches was nice topsoil and the rest was thick sticky orange clay. I'm thinking the curbing cause a daming effect of the water running down the hill and the clay is keeping the water from draining. I was thinking to correct this I could take my prob and pull as deep a core as I could and fill the hole with sand. Figured this might help loosen the clay and help the water penetrate deep in the soil. Any ideas?