Good topsoil to 3 feet then solid clay to the earths core! I had no problems with the pond holding water, but my septic system for our home became a major issue when the home was built. Of course it was nothing $$$ could'nt fix.
Welcome to my world. 90% of the septic systems around here eventually have a spade dig a hole and open the end to drain. Which is completely illegal, but it happens. When we put in a new drain field, loads and loads of crushed 2-3" limestone lateral rock in a deep backhoe trench covered with fabric before the soil went back in. So far, so good. Septic systems in clay pan soils are a challenge.
