(a) All drill holes sunk for the purpose of conducting exploration, including those drilled within the permit area of a surface coal mining and reclamation operation, by drilling 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. - (i) When the underground pressure head producing flow is such that a counter pressure must be applied to force a sealant into the drill hole, this counter pressure shall be maintained for the length of time required for the cementing mixture to set.
- (ii) The minimum time that must be allowed for materials containing cement to "set" shall be in accordance with ASTM C150 or API RP 10B.
(c) Drill holes that have encountered any groundwater 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 (1 x 10-7 cm/sec or less) and possesses minimum shrinking properties such that they are optimal sealing materials for well plugging and drill hole abandonment. Used drilling muds are not acceptable.
(e) 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 more than six (6) gallons of clean water per bag of cement (one (1) cubic foot or ninety-four (94) pounds);
- (ii) Sand Cement Slurry must consist of a mixture of Portland Cement, sand and water in the proportion of not more than one (1) part by weight of sand to one (1) part of cement with not more than six (6) gallons of clean water per bag of cement (one (1) cubic foot or ninety-four (94) pounds);
- (iii) Concrete Slurry must consist of a mixture of Portland Cement, sand and gravel aggregate and water in a proportion of not more than one (1) part by weight of aggregate to one (1) part of cement with not more than six (6) gallons of clean water per bag of cement (one (1) cubic foot or ninety-four (94) pounds);
- (iv) Cement/Bentonite Slurry must consist of a mixture of cement and bentonite in the proportion of not more than six and a half (6.5) gallons of water and three (3) to five (5) pounds of powdered bentonite per bag of cement (one (1) cubic foot or ninety-four (94) pounds);
- (v) High Solids Bentonite Slurry means an inorganic mixture with a slurry density of nine and four tenths (9.4) pounds per gallon (lbs/gal) minimum twenty percent (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 one (1) x 10-7 cm/sec) and is mixed to the manufacturer's specifications;
- (vi) Nonslurry Bentonite must consist of chipped or pelletized bentonite varieties specifically designed to be used to seal drill holes; and
- (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 fifteen (15) pounds of abandonment material with a minimum slurry density of eight and six tenths (8.6) pounds per gallon (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 twenty (20) pounds per one hundred (100) square feet (20 lbs/100 sq. ft.);
- (B) Filtrate volume not to exceed thirteen and one half (13.5) cubic centimeters (cc); and
- (C) Minimum Marsh Funnel viscosity of sixty (60) seconds per quart.
(f) 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 (4) inches or greater in diameter and less than five hundred (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 three hundred (300) feet of standing liquid.
(g) For any drill 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 of twenty-four (24) hours) has been allowed for the column of sealant materials to set up;
- (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 fifty (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 five (5) feet of the ground surface.
(h) 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 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.
(i) All drill holes shall be backfilled to the surface with dry nonslurry materials or capped with a concreted cap set at least two (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.
(j) Drill holes shall be capped or backfilled immediately after drilling and probing in accordance with W.S. § 35-11-404(h) (2015). 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 thirty (30) days without specific authorization from the Administrator.
(k) 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. Drill holes shall not be marked with rebar, metal pipe or metal posts which could pose a hazard to people, livestock, wildlife or machinery.
(l) The Administrator may approve other drill hole abandonment procedures and/or sealant materials at the request of the discoverer.
020-14 Wyo. Code R. § 14-2