(a) The driller or person/entity engaged in construction of a water well shall have in their possession, at the well site, a copy of the approved permit or the permit number.
(b) Knowledge of the properties and depth of the producing aquifer zone, the nature of the overlying formations, and the proposed use of the well will dictate the type of construction required. The following described well types are established: - (i) Type I - Dug Wells - Dug wells are excavations that penetrate from the ground surface down to the first-encountered aquifer. Dug wells are usually simple pits, elongate trenches, or large diameter, lined shafts constructed by hand or using excavating machinery (e.g., a backhoe). A typical construction diagram for Type I wells is illustrated in Appendix C-l.
- (ii) Type II - Natural Filter Wells - Natural Filter Wells are constructed to obtain water at various depths from unconsolidated alluvial/colluvial deposits or severely weathered rock material that can be effectively stabilized and developed after placement of perforated casing or well screen. Wells of this type are usually completed into an unconfined aquifer (confined, perched conditions may be encountered) and may be dug or constructed by jetting, boring, driving, drilling, or a combination of methods. Horizontal wells that drain water from very coarse sand and gravel-sized material and often located near streams are considered Natural Filter Wells. A typical construction diagram for Type II wells is illustrated in Appendix C-2.
- (iii) Type III - Artificial Filter Wells - Artificial Filter Wells are also referred to as "gravel pack," "sand pack," or "filter pack" wells. This type of well is designed to obtain water from unconsolidated to poorly consolidated deposits or bedrock formations by placing filter pack in the annulus, opposite the completion interval. The filter pack (or material contained in "channel pack" well screen) acts as a formation stabilizer, a filter to prevent fine-grained material from entering the well, and also serves to increase the yield of the well. This type of well is constructed by boring or drilling. A typical construction diagram for Type III wells is illustrated in Appendix C-3.
- (iv) Type IV - Partially-Cased Open Borehole Wells - Partially-Cased Open Borehole Wells are also referred to as "open-hole" wells. This type of well is designed to obtain water from consolidated formations that are stable enough to preclude the need for perforated casing or well screen. Overlying formations, however, are cased and sealed to prevent caving and cross-connection of water from vertically separate aquifers. Flowing wells are commonly the result of this type of well construction when head elevation is greater than ground surface elevation. A typical construction diagram for Type IV wells is illustrated in Appendix C-4.
- (v) Type V - Fully-Cased Wells - Fully-Cased Wells are drilled to produce water from an aquifer containing multiple water-bearing intervals. Water production is achieved by screening and/or perforating opposite one or more of the most viable water-producing aquifer zones. Overlying formations are cemented or grouted off to prevent caving and aquifer cross-connection. Wells of this type are usually drilled relatively deep and generally intercept aquifers under confined conditions. A typical construction diagram for Type V wells is illustrated in Appendix C-5.
- (vi) Type VI - Conversion of Existing Oil or Gas Wells, or Exploration Test Wells into Water Wells.
- (A) Existing oil and gas wells, seismic test holes, or mineral exploration holes may be converted for use as water wells, provided that the wells can be completed to conform to minimum construction standards cited herein.
- (B) Information on geologic conditions encountered in the well at the time of the original well drilling shall be used to determine what special construction standards shall be met in order to eliminate all movement of pollutants into the well or along the annular space. If no original geologic information is available, a specified borehole log suite may be required to supplement known information.
- (C) A permit to appropriate ground water must be obtained from the State Engineer prior to commencing construction of the well.
- (D) Before any oil or gas exploration hole or well is converted for use as a water well, the Wyoming Oil & Gas Conservation Commission should be contacted in order to comply with that Commission's regulations.
(c) Annulus. - (i) If a fill pipe for gravel is installed, the diameter of the well bore must be four (4) inches larger than the largest diameter of the casing plus the largest diameter of the fill pipe for gravel. A fill pipe for gravel or any other pipe to provide access to the interior of the well bore must be completely surrounded by the seal.
- (ii) All wells shall be constructed with at least a 2-inch annular space surrounding the outermost casing and extending not less than 20-feet below ground surface.
(d) Casing. - (i) Casing, surface casing (conductor pipe), liners, and screens shall be of new or new-like contaminant-free material and free of pits, cracks, breaks, and corrosion. All pipe, casing, couplings, and screen must meet applicable ASTM, API, NSF, and/or AWWA standards. Casing shall be of adequate strength and durability to protect the well against structural failures during construction and use and protect against the entrance of contaminants during the expected life of the well.
- (ii) All casing shall be selected in accordance with the design of the well, depth of the well, and conditions at the well site. The most common casing materials allowed for use are carbon-steel and thermoplastic (PVC). Less common casing materials such as pre-cast concrete, fiberglass, stainless steel, aluminum, various alloy and non-ferrous metal casing types are allowable where use/conditions dictate and steel or plastic cannot be used. Choice of casing material, diameter, and wall thickness shall be based on:
- (A) Maximum Pumping Rate and Flow Capacity Over the Life of the Well: The production casing shall be greater than or equal to one nominal size larger than the down-hole pump assembly.
- (B) Geology and Aquifer Conditions: Where multiple casings are warranted (surface casing, liners, screens, etc.), provisions shall be incorporated to prevent misalignment, to seal/secure the annulus between casings, and to prevent or secure from borehole caving.
- (C) Installation Method: Difficulty in handling and load strength must be considered for various well designs, depths of drilling, specific geologic conditions, and grouting requirements. Re-entered wells (e.g., for liner placement or plugging back and completing abandoned oil and gas test wells) should be assessed for competency of the existing casing.
- (D) Plumbness and Alignment: A well shall drift off plumb no more than one degree per 100 feet of borehole. The alignment shall allow a 40-foot long section of pipe, -inch less than the inside diameter of the casing, to pass freely from the top of the casing through anticipated pump setting depth.
- (E) Water Quality: The effects of formation waters that may cause corrosion, cross-connection of vertically separate aquifers, bacterial growth, surface water influx, etc., shall be avoided by proper casing selection and installation.
- (F) Well Devices: Decisions on casing material and dimensions also depend on outfitting of the well which may include choice of pumps, motors, wiring, transducers, sampling tools, floats, adapters, airline, caps, seals, etc.
- (iii) All casing types must achieve watertight connections according to directions from the manufacturer.
- (A) Metal pipe must be welded or joined with threaded couplings. If the joints are welded, the weld shall be made using welding rods of equal quality to the most noble metal, shall be at least as thick as the wall thickness of the well casing, and shall be fully penetrating. Spot welding of joints is prohibited.
- (B) PVC pipe may be glued, flush joint thread and coupled, or spline-lock coupled.
- (C) All solvents, pipe dope, and glue must be NSF approved or an acceptable equivalent. Rivets or screws used in the casing joints shall not penetrate the inside of the casing.
- (iv) Casing shall be installed in accordance with the drilling method used, borehole condition, formation characteristics, and comprehensive/tensile strength of the casing material. Only steel casing, equipped with proper drive shoe or drive point, can be used if the casing is to be installed by jacking or driving. PVC casing shall be installed only in an oversized drilled hole without driving. PVC casing shall conform to industry standards and shall be manufactured for the purpose of water well casing.
- (v) Casing made of, or which has been exposed to, hazardous or potentially harmful materials, such as asbestos, shall not be used.
(e) Lost Circulation Material. - (i) The introduction of lost circulation materials (LCMs) shall be limited to those products which will not present a potential medium for bacterial growth or contamination. Only LCMs which are non-organic and can be safely broken down and removed from the borehole may be utilized. Cottonseed hulls, shredded newspaper, or cedar chips are examples of LCMs which are not allowed.
(f) Well Completion. - (i) Well completion refers to the method employed to allow water to enter the well from one aquifer. This is accomplished via perforations in the casing or well screens set adjacent to water-bearing intervals or by allowing water to enter the well through the open bottom of the casing. Multiple completions, or wells completed into two or more vertically separate aquifers, are not allowed
- (A) The well driller shall:
- (I) Install well screens constructed of material which is compatible with adjoining casing and is corrosion resistant.
- (II) Install well screens or well intakes that prevent the continued production of sand, silt, or turbid water.
- (III) Not install screen or perforated casing within the zone of maximum dynamic pumping level to prevent cascading water, except in the case of monitor wells, recovery wells or test wells.
- (B) Type II and III wells shall be constructed with well screen (as defined in Chapter 2) commercially manufactured for the purpose of well construction and sized appropriately for the grain size of the aquifer materials to be developed by the well.
(g) Filter Pack.
Filter pack (or gravel pack) material shall consist of clean, well-rounded, chemically stable grains that are smooth and uniform. The filter material should not contain more than 2% by weight of thin, flat, or elongated pieces and should not contain organic impurities or contaminants of any kind. Type III Wells should be gravel (filter) packed opposite the perforated or screened zone(s) and no more than five (5) feet above the zone(s). The interval above the gravel pack must be sealed, as described in these rules, to prevent fluid cross-contamination from the surface or from a shallow aquifer.
- (i) All filter material shall be placed using a method that through common usage has been shown to minimize bridging of the material between the borehole and the casing and excessive segregation of the material after it has been introduced into the annulus and before it settles into place.
- (ii) It is not acceptable to place filter material by pouring from the ground surface unless proper sounding devices are utilized to measure dynamic filter depth, evaluate pour rate, and minimize bridging and formation of voids.
(h) Well Sealing/Grouting. - (i) Well casing shall be sealed to prevent vertical movement or leakage of fluid in the annular space between casing and borehole wall. Non-Slurry bentonite grouts must be in place before significant hydration occurs. Plans for well construction shall include allowances for maximum effective emplacement of grout as a seal to protect the source aquifer and/or assure structural integrity of the entire cased well. Well cuttings are not allowed to be used as grout, filler, or aggregate material for well sealing.
- (ii) Selection of grouting material shall meet the technical requirements for making a proper seal. Grout products shall meet applicable ASTM, API, NSF, AWWA, or other recognized industry standards. Grout shall be prepared according to manufacturer's directions and shall be mixed as engineered for specific site requirements. Water wells permitted under the DEQ-WQD may alternately use any grout mixture specified by DEQ-WQD. For all other wells, the following are approved grout materials:
- (A) Neat Cement Grout 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.
- (B) Sand Cement Grout 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).
- (C) Concrete Grout Slurry must consist of a mixture of Portland Cement, sand and gravel aggregate, and water in the proportion of at least 1 part by weight of aggregate to 1 part of cement with not more than 6 gallons of clean water per bag of cement.
- (D) Nonslurry Bentonite Grout must consist of chipped or pelletized bentonite varieties that are hydrated to manufacturer's specifications.
- (E) Cement/Bentonite Grout 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.
- (F) Bentonite Grout Slurry means an inorganic mixture of a minimum 20% by weight 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.
- (iii) All wells shall have an annular surface seal of grout extending not less than 20 feet below ground surface or to useable water below ground surface. The surface seal must be placed in at least a 2-inch annular space. The completed surface seal must fully surround the outermost casing, be evenly distributed, and be free of voids.
- (A) If a temporary surface casing is utilized, the surface casing shall be removed in conjunction with the placement of the seal. Alternatively, conductor casing may be sealed permanently in place to a depth of at least 20 feet with a minimum 2-inch annular seal between the largest outside diameter of the surface casing and borehole wall. If the temporary surface casing is to be removed, the surface casing shall be withdrawn as sealing material is placed between the outermost permanent well casing and borehole wall. The sealing material shall be kept at a sufficient height above the bottom of the temporary surface casing as it is withdrawn, to prevent caving of the borehole wall.
- (iv) Type I wells, as defined in this section, (b)(i), shall be constructed with a watertight curbing extending, at a minimum, from 18 inches above the natural ground level to the static water level. The curbing shall consist of poured cement grout or casing surrounded by cement grout. Concrete block with cement grout and rock with cement grout may also be used. The poured cement grout shall not be less than 6-inches thick. If casing is to be used, the minimum annular space between the casing and the borehole shall be three inches. A typical construction diagram for Type I wells is illustrated in Appendix C-l.
- (v) Type III Wells, as defined in this section, (b)(iii), shall be grouted from immediately above the gravel packed interval and shall terminate at the ground surface or at the base of a pitless adaptor. The seal shall close off all zones above the gravel-packed interval. If a gravel tube is installed, it shall be sealed with a water-tight cap. A typical construction diagram for Type III wells is illustrated in Appendix C-3.
- (vi) Type IV Wells, as defined in this section, (b)(iv), shall have the entire production casing string grouted from bottom to top before well completion. The well shall be drilled and cased at least 10 feet into the upper portion of the target aquifer. If permeability factors or hydrostatic conditions in the target aquifer will jeopardize a successful grout job, then the well shall be drilled, cased and cemented into the first overlying formation which will provide for secure sealing and completion. According to W.S. § 41-3-909(a)(vii), flowing and non-flowing wells are required to be "... constructed and maintained as to prevent the waste of underground water either above or below the land surface." Grouting shall be accomplished by either one or several methods in which grout is pumped directly in the annulus (by tremie or grout pipe) or circulated to the annulus by positive displacement from inside the casing. Before grouting, clean water or other suitable drilling fluid mixture shall be circulated to clear the borehole and provide conditions for optimal bonding. Engineered grout volume calculations must include an excess allowance (e.g. 25%, 50%, 100%, etc.) for losses in the subsurface. It is allowed to introduce cement or concrete (e.g. Redi-Mix) from the land surface to finish a grout job so long as a complete seal is attained. A cement bond log of the well may be required to assure that an adequate seal was set in place. If leaks occur around the well casing or adjacent to the well, the driller shall complete the well with seals, packers, and/or grout to eliminate the leak. A typical construction diagram for Type IV wells is illustrated in Appendix C-4.
- (vii) Type V Wells, as defined in this section, (b)(v), shall be grouted from the ground surface or the base of the pitless adapter to the bottom of the casing. A typical construction diagram for Type V wells is illustrated in Appendix C-5.
(i) Well Development - Following construction, all wells shall be cleaned and developed to remove drilling fluids, drill cuttings, and other foreign materials. Proper well development functions to establish the best hydraulic connection between the well and the source aquifer. The well driller shall develop every new well until the produced water does not contain appreciable amounts of sand, silt, or turbidity. Chemicals used as development aids such as agents used in acid fracturing, carbon dioxide (CO2) injection, formation deflocculation treatment, etc., are also allowed; however, notification to WDEQ-WQD is required prior to application or introduction of a foreign substance into a well that is a public water supply source.