(a) All wells that are no longer useful (including test wells) must be plugged in order to ensure that groundwater supply is protected and preserved for further use and to eliminate the potential physical hazard. A well is considered "abandoned" when it has not been used for a period of one year, unless the owner demonstrates their intention to use the well again by properly maintaining the well in such a way that: - (i) The well has no defects that will allow the impairment of quality of water in the well or in the water bearing formations penetrated.
- (ii) The well is covered and the cover is watertight.
- (iii) The well is marked so that it can be clearly seen.
- (iv) The area surrounding the well is kept clear of brush or debris.
Observation or test wells used in the investigation or management of usable sources of groundwater by state agencies or by engineering or research organizations are not considered "abandoned" so long as they are maintained for this purpose. These wells shall be covered with an appropriate cap, and labeled for their particular use.
(b) Preliminary work. Before a well is plugged and abandoned, it shall be investigated by the permittee (owner/ operator) to determine its condition, details of construction and whether there are obstructions that will interfere with the process of filling and sealing.
(c) Filling and sealing. Following are requirements to be observed when plugging wells: - (i) Wells wholly situated in unconsolidated material in an unconfined groundwater zone shall have the uppermost thirty (30) feet sealed with impervious material. The remainder of the well shall be filled with clay, sand, or other suitable inorganic matters as described in paragraph e.
- (ii) Wells penetrating several aquifers or formations containing usable water sources shall have the uppermost thirty (30) feet sealed with an impervious material. All screened or perforated intervals shall be sealed to prevent vertical movement of waters from the producing or injected formation. Impervious material shall be placed opposite the confining formation above and below (and including) the screened or perforated interval for a minimum of fifty (50) feet or more.
- (iii) Any uncased hole below the well shoe shall be filled with an impervious material as described in paragraph e. to a depth of at least fifty (50) feet above the shoe.
- (iv) Whenever production casing has been severed or inadvertently removed the well bore shall be filled with impervious material from a point fifty (50) feet below to a point 50 feet above the point of severance or to the surface limit.
- (v) Wells penetrating creviced or fractured rock shall have the portions of the well opposite this formation sealed with neat cement, sand cement grout or concrete. If these formations extend to considerable depth, alternate layers of coarse stone and cement grout or concrete may be used to fill the well.
- (vi) Wells in nonfractured, consolidated formations shall have the uppermost thirty (30) feet filled with impervious material and the non-creviced, consolidated formation portion of the well may be filled with clay or other suitable material.
(d) Placement of material. The following requirements shall be observed in placing fill or sealing a plugged or abandoned well. - (i) No material shall be placed in the well unless the Administrator has been notified that plugging and abandonment operations are to commence. A minimum of thirty (30) days notice must be given.
- (ii) The well shall be filled with the appropriate material as described in paragraph e. from the bottom of the well up.
- (iii) Sealing materials shall be placed in the interval or intervals to be sealed by methods that prevent free fall, dilution and/or separation of aggregates from cementing materials.
- (iv) When the underground pressure head producing flow is such that a counterpressure must be applied to force a sealing material into the annular space, this counterpressure shall be maintained for the length of time required for the cementing mixture to set as specified in Section 6, paragraph (c) (viii) of this part.
- (v) To ensure that the well is filled and there has been no bridging of the material, verification shall be provided that the volume of material placed in the well installation at least equals the volume of the empty hole.
(e) Material. Requirements for sealing and fill materials are as follows. - (i) Impervious sealing materials. Sealing materials shall have a permeability of 10 - 7 cm/sec or less. Impervious materials include neat cement, sand-cement grout, concrete, and bentonite clay as described in Section 6, paragraph (c). Used drilling muds are not acceptable.
- (ii) Filler material. Materials such as clay, silt, sand, gravel, crushed stone, native soil, and mixtures of these materials, as well as those described in paragraph (i) above may be used as filler material. Material containing organic matter or used drilling muds shall not be used.
(f) Markings. The top of the plug of any plugged and abandoned well shall show clearly, by permanent markings, whether inscribed in the cement or on a steel plate embedded in the cement, the permit number, well identification number and date of plugging.
(g) Reports. Within fifteen (15) days after a well has been plugged and abandoned, the owner shall file a plugging record with the Water Quality Division.
020-26 Wyo. Code R. § 26-11