(a) All drill holes sunk for the purpose of conducting exploration by drilling, including those drilled within a permitted mine operation, shall be capped, sealed or plugged in the manner described hereinafter.
(b) Drill holes that have artesian flow of groundwater to the surface shall be plugged with cement-based sealant material, as specified and in the manner described below, to prevent fluid communication and adverse changes in water quality or quantity.
(c) Drill holes that have encountered any ground water or saturated stratum shall be sealed utilizing sealant materials and emplacement methods as prescribed hereinafter to prevent fluid communication and adverse changes in water quality or quantity.
(d) "Sealant materials" are materials that are stable, have low permeability and possesses minimum shrinking properties such that they are optimal sealing materials for well plugging and drill hole abandonment. Sealant materials shall be either: - 1) a fluid mixture of water plus a cement-based or bentonite-based material, or
- 2) a dry bentonite- based material, either chips or pellets specifically designed for sealing drill holes. Sealant materials shall meet the technical requirements for making a proper seal, shall meet applicable recognized industry standards and shall be prepared according to manufacturer's directions for specific site requirements. The following are approved sealant materials:
- (i) Neat Cement Slurry must consist of a mixture of Portland Cement and not more than 6 gallons of clean water per bag (1 cubic foot or 94 pounds) of cement;
- (ii) Sand Cement Slurry must consist of a mixture of Portland Cement, sand, and water in the proportion of not more than 1 part by weight of sand to 1 part of cement with not more than 6 gallons of clean water per bag of cement (1 cubic foot or 94 pounds);
- (iii) Concrete Slurry must consist of a mixture of Portland Cement, sand and gravel aggregate, and water in the proportion of not more than 1 part by weight of aggregate to 1 part of cement with not more than 6 gallons of clean water per bag of cement;
- (iv) Cement/Bentonite Slurry must consist of a mixture of cement and bentonite in the proportion of not more than 6.5 gallons of water and 3 to 5 pounds of powdered bentonite per 94-pound sack of Portland cement;
- (v) High Solids Bentonite Slurry means an inorganic mixture with a slurry density of 9.4 lbs./gal. minimum (20%) by weight of solids bentonite, with polymers, water, or other additives for the yield/rate control, which forms a low permeability seal (not greater than 1 x 10-7 cm/sec), and is mixed to the manufacturer's specifications; and
- (vi) Nonslurry Bentonite must consist of chipped or pelletized bentonite varieties specifically designed to be used to seal drill holes.
- (vii) Abandonment Gel means a mixture of bentonite with polymers and other additives and water in the proportion of one (1) barrel of water to 15 pounds of abandonment material with a minimum slurry density of 8.6 lbs./ gal. Abandonment Gel used to seal boreholes shall meet the following specifications when using American Petroleum Institute Standard Procedures for Testing Drilling Fluids:
- (A) Ten minute gel strength of at least 20 lbs. / 100 sq. ft.
- (B) Filtrate volume not to exceed 13.5 cc.
- (C) Minimum Marsh Funnel viscosity of 60 sec. / quart.
(e) Sealant materials shall be emplaced in a manner that provides a water tight seal utilizing one of the following approved methods: - (i) By placing sealant materials by drill pipe, tremie pipe, or similar device in an upward direction from the bottom of the drill hole to within approximately five (5) feet of the ground surface; or
- (ii) By placing nonslurry bentonite from the bottom of the drill hole to within approximately five (5) feet of the ground surface. Nonslurry bentonite shall not be utilized unless the drill hole is four inches or greater in diameter and less than 500 feet in depth and the material must be placed in such a manner that a bridge does not occur. Nonslurry bentonite may not be placed in more than 300 feet of standing liquid.
(f) For any hole that has been sealed with a sealant material, the discoverer responsible for sealing the drill hole shall: - (i) Measure the depth of the top of the sealant material column with the appropriate equipment after sufficient time (minimum 24 hours) has been allowed for the column of sealant material to set up; and
- (ii) If the column of sealant material has dropped or fallen back, the discoverer shall continue to install sealant material until the top of the sealant material column remains at least 50 feet above the top of the uppermost saturated groundwater stratum; and
- (iii) Install uncontaminated fill material, drill cuttings or one of the approved sealant materials listed herein from the top of the sealant material column to within approximately 5 feet of the ground surface.
(g) If a hole is drilled without the use of drilling fluids and the bottom of the hole is above the preexisting natural elevation of the uppermost saturated groundwater stratum, the drill hole shall be abandoned by completely backfilling from the bottom of the drill hole to the surface with uncontaminated earthen material or drill cuttings or approved grout materials described herein. When using uncontaminated earthen material or drill cuttings as a backfill material, this material should be emplaced in a manner to promote settling and compaction and to minimize voids caused by bridging. If the drill hole is backfilled to the natural ground surface with dry nonslurry materials then no surface cap is necessary.
(h) All drill holes shall be backfilled to the surface with dry nonslurry materials or capped with a concrete cap set at least 2 feet below the ground surface and then backfilled to the surface with native earthen materials to ensure the safety of people, livestock, wildlife, and machinery in the area.
(i) Drill holes shall be capped or backfilled immediately after drilling and probing in accordance with W.S. 35-11-404(h). If it is necessary to temporarily delay the abandonment or keep the drill hole open for any reason, the drill hole must be securely covered with a temporary cap in a manner which will prevent injury to persons or animals. Drill holes shall not be left open for more than 30 days without specific authorization from the Administrator.
(j) For inspection and verification purposes, each drill hole shall be marked with a temporary marker that clearly identifies the name of the discoverer and the hole number until bond release is authorized. Holes shall not be marked with rebar, metal pipe or metal posts which could pose a hazard to people, livestock, wildlife or equipment.
(k) The Administrator may approve other drill hole abandonment procedures, and/or sealant materials, at the request of the discoverer.