Section NR 812.14 - Drilled wells in bedrock formations A well driller or well constructor shall construct wells terminating in bedrock formations according to the requirements of s. NR 812.12 and the construction of wells in bedrock shall be completed to meet all of the following requirements:
(1) MINIMUM DIAMETER. The minimum diameter for bedrock wells is 6 inches.(2) CASING DEPTH. Minimum casing depth shall be measured from the ground surface. The following requirements apply to the minimum casing depth in bedrock formations: (a)Sandstone. Wells completed in sandstone bedrock shall have a minimum of 30 feet of casing.(b)Crystalline bedrock. Wells completed in crystalline igneous or metamorphic bedrock shall have a minimum of 40 feet of casing.(c)Limestone or dolomite. Wells completed in limestone or dolomite bedrock shall have a minimum casing depth as follows:1. Forty feet when the depth to the top of limestone or dolomite is equal to or greater than 20 feet below the ground surface.2. Sixty feet when the depth to the top of limestone or dolomite is less than 20 feet below the ground surface.(3) CASING MATERIAL AND INSTALLATION. (a)Material. Either steel or thermoplastic well casing pipe meeting the requirements of s. NR 812.11 (6) or (7) may be used as permanent casing for bedrock wells.(b)Centering. When well casing is set within an upper enlarged drillhole, it shall be centered within the drillhole to ensure an even annular space around the casing. When casing is placed in an upper enlarged drillhole that extends more than 80 feet below ground surface, a drive shoe or casing shoe shall be welded to the bottom of the casing and the casing shall be driven to a firm seat. The department may require, as a condition of an approval or in a special well casing area, that the well casing pipe be centered in the drillhole using any of the following methods: 1. A set of at least 3 centering guides provided at every pipe joint within the bedrock to ensure an even annular space around the well casing pipe. A minimum of 2 sets of 3 centering guides shall be provided, one near the top of the bedrock and one at the bottom of the string of well casing pipe.2. A drive shoe or casing shoe welded or threaded onto the bottom of the string of well casing pipe and, if the well casing pipe extends more than 63 feet into the bedrock, at least one set of 3 centering guides provided on the casing pipe within the bedrock. If only one set of guides is provided, it shall be installed within 5 feet of the top of the bedrock.(c)Hung casing pipe prohibition. Casing shall be set to the bottom of an upper enlarged drillhole unless the casing is installed in compliance with the requirements of par. (d).(d)Screens. Screens may be installed in loosely cemented sandstone wells. The requirements for screen materials and installation of the screen specified in s. NR 812.13 (4) and the requirements for gravel packs specified in s. NR 812.16 apply to drilled wells in bedrock formations.(e)Thermoplastic casing use restricted. Thermoplastic casing may only be placed in an upper enlarged drillhole and may not terminate in crystalline bedrock or be driven or jetted into place.(f)Damaged or deformed thermoplastic casing. A well using thermoplastic casing terminating in bedrock shall be free of cracks and free of deformation and the inside diameter shall remain within manufacturer's specifications after construction or reconstruction. A failed well constructed with thermoplastic casing shall have the casing removed or drilled out prior to filling and sealing.(g)Drilling tool use restricted. Drilling tools such as drill bits or stabilizers may not be placed in the thermoplastic well casing pipe nor may any drilling or reconstruction occur after placement of the well casing pipe in the well. This restriction does not prohibit the insertion of equipment for the development and cleaning of wells.(4) DRIVING OR ADVANCING CASING. A well driller or well constructor may drive or mechanically advance steel casing from the ground surface to the top of bedrock when the depth to the top of bedrock is equal to the minimum casing depths under sub. (3) or deeper. When steel casing is driven or mechanically advanced to the top of bedrock, it shall be completed in accordance with all of the following: (a)Drive shoe. The casing shall be equipped with a drive shoe or casing shoe meeting the requirements specified in s. NR 812.11 (10).(b)Annular space sealing. Clay slurry, sodium bentonite slurry, or granular bentonite shall be maintained around steel casing during advancement using any of the following methods: 1. When casing is driven or advanced from the ground surface, excavating a funnel-shaped depression around the casing to create a reservoir, which shall be kept filled with dry granular bentonite. The granular bentonite shall be kept dry at the surface during advancement.2. Filling a starter drillhole or temporary outer casing with clay slurry or sodium bentonite slurry and drill cuttings having a mud weight of at least 11 pounds per gallon, or with dry granular bentonite, which shall be maintained around the outside of the casing.3. Constructing an upper enlarged drillhole in accordance with sub. (5). The upper enlarged drillhole shall be kept filled to within 10 feet of the ground surface with clay slurry or sodium bentonite slurry and drill cuttings having a mud weight of at least 11 pounds per gallon, or with dry granular bentonite which shall be maintained around the outside of the casing.(c)Driving to a firm seat. Steel casing shall be driven or advanced to a firm seat into the top of bedrock.(d)Mechanically holding down thermoplastic casing. For a well constructed with thermoplastic casing, the casing may not be driven to a firm seat. However, the casing may be held down mechanically within an upper enlarged borehole during grouting to prevent the casing from floating.(5) UPPER ENLARGED DRILLHOLE. When a well is constructed with casing that extends 5 feet or more below the top of bedrock, an upper enlarged drillhole shall be constructed to the depth the casing is set. When a well driller or well constructor constructs an upper enlarged drillhole for any reason, it shall be constructed in accordance with all of the following: (a)Minimum diameter. The minimum diameter of an upper enlarged drillhole shall meet the following requirements:1. The upper enlarged drillhole shall be 4 inches greater than the nominal diameter of the casing when coupled joints are used.2. A well driller or well constructor may reduce the diameter of an upper enlarged drillhole to 2 inches greater than the nominal diameter of the casing when welded steel casing is used and the required sealing material, according to the requirements of sub. (7), is placed in the annular space between the upper enlarged drillhole and the well casing pipe using a pressure grouting method according to the requirements of s. NR 812.20.(b)Method of keeping hole open. A well driller or well constructor shall maintain an upper enlarged drillhole at full diameter during drilling by any of the following methods:1. Keeping the drillhole filled up to within 10 feet of the ground surface with drilling mud.2. Circulating bentonite drilling mud.3. Setting a temporary outer casing to the top of bedrock.4. Circulating air, air and water, or drilling foam when the drillhole is constructed through non-caving clay, silt, or hardpan.(c)Minimum depth. The minimum depth of an upper enlarged drillhole shall be one of the following: 1. To the final depth that the well casing is set.2. To the bottom of any clay formation, or 20 feet, whichever is less, when the casing is driven or advanced to the top of bedrock in accordance with sub. (4) (b) 3.3. For a well constructed using thermoplastic casing, to a depth not more than 5 feet into the top of firm limestone, dolomite, or shale.(d)Grouting. A well driller or well constructor shall grout an upper enlarged drillhole according to the requirements specified in sub. (7).(6) LOWER DRILLHOLE. A well driller or well constructor shall complete the drilling of a lower drillhole in accordance with all of the following: (a) The lower drillhole may not be constructed prior to grouting an annular space unless the casing is first driven to a firm seat in bedrock.(b) Drill cuttings may not fill an open annular space during the drilling of a lower drillhole, except when casing is driven or advanced to the top of bedrock in accordance with sub. (4) (b) 3.(c) Cement grout shall set for a minimum of 12 hours prior to drilling a lower drillhole.(7) GROUTING AND SEALING. A well driller or well constructor shall seal annular spaces using one of the pressure grouting methods specified in s. NR 812.20. Grouting material shall meet the requirements specified in s. NR 812.11 (15). A flowing well shall be grouted using the materials specified in s. NR 812.15. Potable high capacity wells shall be grouted using the materials specified in s. NR 812.152. A well driller or well constructor shall seal annular spaces with any of the following materials:(a) Sodium bentonite, sodium bentonite-sand, or a mixture of clay slurry or bentonite drilling mud and cuttings when the upper enlarged drillhole is less than or equal to 20 feet in depth.(b) Sodium bentonite, sodium bentonite-sand, neat cement or bentonite-cement when the upper enlarged drillhole extends less than 5 feet into the top of bedrock.(c) Neat cement or bentonite-cement when the upper enlarged drillhole extends 5 feet or more into the top of bedrock.(8) BENTONITE CHIPS IN FRACTURED FORMATIONS. A well driller or well constructor may use bentonite chips in an annular space when fractures, voids, or caverns are encountered that prevent the flow of grout at the surface. When bentonite chips are used by a well driller or well constructor to seal fractures in an annular space, the chips shall be placed in accordance with all of the following: (a) The upper enlarged drillhole shall be a minimum of 4 inches larger than the nominal diameter of the permanent casing and shall extend to the depth of any fractures, voids or caverns encountered greater than 20 feet below the ground surface.(b) The upper enlarged drillhole shall be free of drilling mud or cuttings.(c) Any bentonite chips placed below the water table shall be screened and poured in a manner that prevents bridging.(d) Any bentonite chips placed above the water table shall be hydrated using water meeting the requirements specified in s. NR 812.11 (14).(e) The volume of bentonite chips used shall be limited to the minimum needed to resume grouting according to the requirements specified in s. NR 812.20.(f) The number of bags or volume of chips used, the depth they were placed, and the reason they were needed shall be noted on the well construction report.(9) DUAL AQUIFER PROHIBITION. Wells may not be constructed open to both an unconsolidated formation and a bedrock formation.(10) WELLS CONSTRUCTED INTO THE MAQUOKETA SHALE. Wells constructed or reconstructed to withdraw water from any of the aquifers beneath the Maquoketa Shale and the Niagara formations in the eastern part of the state shall be cased and grouted into the Maquoketa Shale formation except in areas designated by the department as special well casing pipe depth areas. If a liner is used to case off the Niagara formation, the Maquoketa Shale formation or both, it shall be installed and grouted in place in accordance with s. NR 812.21.Wis. Admin. Code Department of Natural Resources NR 812.14
Cr. Register, January, 1991, No. 421, eff. 2-1-91; am. (1) (f) 2., (h), (j), (2) (a) 1. d., (3) (b) and (c), Register, September, 1994, No. 465, eff. 10-1-94.Amended by, CR 18-095: r. and recr., Register June 2020 No. 774, eff. 7-1-20; correction in (3) (b) 1., 2. made under s. 35.17, Stats., Register June 2020 No. 774, eff. 7/1/2020Amended by, CR 21-070: am. (3) (a), cr. (3) (e) to (g), am. (4) (intro.), (b) (intro.), (c), cr. (4) (d), (5) (c) 3. Register July 2022 No. 799, eff. 8/1/2022.