All mud pits used to circulate fluids in and out of the hole during drilling, reworking or completion procedures shall be made of steel. Pits used only as reserve shall be permitted to be earthen pits, fully lined with plastic, at least six (6) mils thick, into which only nondeleterious substances may be disposed. Deleterious substances may only be disposed of in a steel reserve pit. Both deleterious and nondeleterious substances shall be removed to a proper disposal facility within fifteen (15) days after completion of the well. Said disposal facility shall be one which is approved for disposal by the State Corporation Commission. No earthen or steel reserve pit shall be located within six hundred sixty feet (660') of any developed area, park, school, church, public building, or place of public assembly. (1994 Code § 23.5-12)