(A) Abandonment of all exploratory borings shall be carried out in accordance with the following provisions.
(1) Abandonment, whether temporary or permanent, shall be undertaken immediately upon completion of drilling activities. When the test hole is to be abandoned, the city shall be notified so that the abandonment process may be inspected.
(2) Within 30 days of the completion of drilling or the drilling equipment leaving the site, whichever occurs first, an abandonment report shall be completed by the explorer, and filed with the city. The report shall include, but not be limited to, such things as water bearing formations encountered, method of construction used and method of abandonment. The abandonment report shall specify whether the boring is being temporary or permanently abandoned.
(B) A boring which is temporarily abandoned shall be constructed to prevent the introduction of surface contaminants into the boring and to prevent passage of water from one aquifer to another.
(1) At the minimum, a temporary abandoned boring shall be cased from bedrock or from the bottom of the boring if the boring terminates in unconsolidated materials, to a point one foot above the ground surface or, if in a floodplain, at least two feet above the level of the highest flood of record. The casing shall be protected with an overlapping can which will prevent any surface contamination from entering the boring.
(2) Any boring which is temporarily abandoned shall be marked and protected with four steel posts (schedule 40 pipe) of at least four-inch diameter at equal distance from each other, two feet from the center of the casing. Such posts shall be installed to a minimum depth of three feet into solid ground.
(3) A boring shall not be temporarily abandoned for more than two years.
(C) (1) Whenever the explorer determines that a boring needs not remain open any longer, or whenever the explorer is about to lose the right to explore, the explorer shall permanently abandon the boring. The boring shall be filled with grout to prevent contaminating materials from entering the water bearing ground formations.
(2) All materials, debris and obstructions that may interfere with sealing operations shall be removed from the boring.
(3) All casing and screen may be salvaged, except for casing that has been cemented in place.
(4) The top of the hole shall be fitted with ten feet of cement or concrete grout to within two feet of the land surface. Casing remaining in the hole shall be cut off at least six feet below the land surface. The remaining two feet of the hole shall be filled with native topsoil.
(5) When concrete or cement is used as a grout material, it shall be inserted in the boring through a grout pipe from the bottom of the boring upward to the surface under pressure.
(6) A permanently abandoned boring shall be filled and sealed using one or more of the following substances in accordance with geological materials penetrated.
(a) The section of a boring in unconsolidated deposits shall be filled with neat cement, concrete or heavy drilling fluid to provide a permeability no greater than the natural condition.
(b) The section of a boring in a rock formation shall be filled with neat cement or concrete.
(c) The section of a boring in a cavernous or crevice rock such as cavernous limestone or creviced granite shall be filled with concrete or neat cement and gravel or stone aggregate. At the top of cavernous or creviced formation, the filling shall be completed by a layer of neat cement or concrete extending at least ten feet into the above overlying formation and finished as provided in those rules.
(d) When a temporarily abandoned boring is permanently abandoned, a separate abandonment report shall be filed.
(Prior Code, § 345.07)