I have owned my home for 5 years. Last week I had my septic inspected and drained for the 2nd time since I purchased the home. To my surprise the technician dug up and and drained a second septic tank. It was completely buried with the exception of one small part that I assumed was part of the first tank. The first tank is 1500 gallons, the second is 1000 gallons. I am concerned about this second tank, I can't imagine needing two tanks. The fact that it was completely buried makes me think it was defective, or for some other reason abandoned and purposely buried. Anyone have any experiences like this?