Any septic tank that is not being used must have the sewage removed by a licensed sanitary disposal contractor. The top cover of the septic tank must be removed and crushed into the septic tank. The septic tank is then filled with sand, gravel, earth, concrete or other approved material. The Environment Division recommends that sand or gravel be used.

The septic tank must be inspected by an Environmental Health Specialist prior to its being covered with soil. There is an application that must be submitted with the required fee prior to the inspection of the decommissioned tank. 

More Information
Plugging Cisterns, Cesspools, Septic Tanks, and Other Holes
(Publication from the Kansas State University Agricultural Experiment Station and Cooperative Extension Office)