The following sealing materials are acceptable to seal a well: Concrete when mixed at five 94-pound sacks of Portland cement per yard of concrete; Neat Portland cement grout when mixed in accordance with Regulation .19 of this chapter; A mixture of five 94-pound sacks of Portland cement and 1 cubic yard sand; Bentonite, if used: As a slurry mixed at 2 pounds per gallon of water; or In chip or pellet form; and Combinations of these materials. Drilling fluid may not to be used to seal a well. Fill Materials. Clay, silt, sand, gravel, crushed stone, mixtures of these materials, and sealing materials may be used as a filler in sealing a well. In the sealing of an unsuccessful well in Hydrogeologic Areas 3, 4, and 5, the drill cuttings may be used as fill material. Material containing organic matter may not be used. The Approving Authority may require that fill material be disinfected.