I bought our house 4 years ago and the last 2 or 3 years I smell the drainfield and I find that one area of our yard or drainfield gray water is coming to the surface. I dug up the drainfield and put it lower in the ground it was only down about 6 inches. I also added about a foot of top soil. It just seems to have resurfaced closer to the tank. It now just comes to the surface and runs down my drive way. How can I fix it?