About 15 years ago, we had a sidewalk that went across the lawn to the front corner out at the end of the driveway. For convenience, we had the sidewalk removed and had a walk installed that ran directly to the driveway to the side instead of all the way out near the street. We watched the walkway being broken up and removed. A load of topsoil was delivered and the whole front (only about 35' square) was covered to smooth it out and new seed was planted. All is well - grass is green. UNTIL we get a dry spell. Any time we get a dry spell you will note that the area where the original sidewalk was will begin to turn brown and the "ghost" of the old sidewalk can be seen. I assume it has something to do with whatever leeches out of concrete that stays in the ground is causing this, but I don't know exactly what. Anyone know?