Section 812.14. Drilled wells in bedrock formations.

  Bedrock wells shall be constructed according to the requirements of s. NR 812.12 and as follows:

(1)   General requirements for drilled wells terminating in bedrock formations.

(a) Steel well casing pipe meeting the requirements of s. NR 812.17 shall be used for bedrock wells. Thermoplastic well casing pipe may not be used for bedrock wells.

(b) The minimum diameter for bedrock wells is 6 inches.

(c) The minimum diameter for the upper enlarged drillhole for potable high capacity, school and wastewater treatment plant wells is 3 inches larger in diameter than the outside diameter of the well casing pipe or the outside diameter of the well casing pipe couplings, if used.

(d) The minimum depth for the upper enlarged drillhole and the well casing pipe is as specified in Tables I to IV.

(e) The well casing pipe shall be driven to a firm seat in the bedrock with a drive-shoe except when the upper enlarged drillhole extends 20 feet or more into the bedrock and the annular space is grouted before the lower drillhole is constructed, the use of a drive-shoe is optional.

(f) When well casing pipe is set in an upper enlarged drillhole extending 20 or more feet into bedrock, the well casing pipe shall be centered in the drillhole by one of the following methods:

1. A set of at least 3 centering guides shall be provided at every pipe joint within the bedrock to ensure an even annular space around the well casing pipe. A minimum of 2 sets shall be provided, one near the top of the bedrock and one at the bottom of the string of well casing pipe. This is depicted in figure 1, or

2. A drive-shoe may be welded or threaded onto the bottom of the string of well casing pipe and, if the well casing pipe extends more than 63 feet (that is, more than 3 standard pipe lengths) into the bedrock, at least one set of 3 centering guides shall be 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.

(g) Development of wells in shale formations is allowed by the department only when the shale is known to be firm enough so that the drillhole will stand open and the water pumped from the well is not turbid.

(h) When nonpotable high capacity wells and low capacity wells, except school and wastewater treatment plant wells, are completed in igneous or metamorphic crystalline bedrock, normally referred to as “granite" wells, an initial attempt shall be made to obtain water below the 40-foot depth. The drillhole shall extend to a depth of at least 150 feet, even though water in sufficient quantity may be encountered during drilling in the bedrock above the 40-foot depth. When adequate water quantity is not obtained below the 40-foot depth, the department may approve installation of less than 40 feet of well casing pipe for withdrawal of water from the bedrock above the 40-foot depth. Prior approval is required. Installation of less than 20 feet of grouted well casing pipe will not be approved without continuous chlorination. Installation of less than 25 feet of well casing pipe will not be approved unless the well casing pipe is permanently cement grouted all the way up to the ground surface.

(i) Wells may not be constructed open to both an unconsolidated formation and a bedrock formation without approval.

(j) 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 at least through the “Niagara" formation except in areas designated by the department as special well casing pipe depth areas. The department recommends that such wells also be cased and grouted through the “Maquoketa" shale formation. If a liner is used to case off the “Niagara" formation, the “Maquoketa" shale formation or both, it shall be installed in a manner conforming with the requirements of s. NR 812.21 (1) .

(k) Screens, installed with or without gravel-packs, may be installed in loosely cemented sandstone wells. The requirements for screen materials and installation of the screen in s. NR 812.13 (1) (e) and the requirements for gravel-packs in s. NR 812.16 apply to drilled wells in bedrock formations.

(L) An open bedrock drillhole may be underreamed to increase the size of a drillhole for gravel packing a screen in sandstone, setting a liner in a sloughing or contaminated formation or reducing the inflow velocity of water to a well. The underreaming may not commence closer than 5 feet below the bottom of the permanent well casing pipe unless the pipe is cement grouted in place to the depth required by Tables II & IV, in which case underreaming may commence directly below the bottom of the well casing pipe.

(m) Wells constructed with “hung" well casing pipe, i.e., well casing pipe, with a packer or grout flange installed on the bottom, suspended in an enlarged drillhole and grouted in place, require approval.

(2)   Percussion method requirements for drilled bedrock wells. The percussion method is a drilling method using a cable-tool drilling machine or a drilling method whereby the well casing pipe is driven or is set in an upper enlarged drillhole and then driven; soil or rock material inside or just below, but not more than one well casing pipe length below, is broken up or crushed with a drill bit; and the drill cuttings are removed from inside or just below the well casing pipe. This method may be performed with a cable-tool machine, a rotary machine with hammer or with a casing hammer. When using a rotary drilling machine with hammer or casing hammer for the percussion method, the drill cuttings inside and just below the well casing pipe may be removed with a rotary bit with the use of air or an approved drilling fluid aid.

(a) For nonpotable high capacity wells and for low capacity wells constructed by percussion methods in bedrock, except school and wastewater treatment plant wells:

1. When the depth to bedrock is at least 40 feet:

a. The well casing pipe may be driven, while drilling, from the ground surface to a firm seat in the top of bedrock without the use of an upper enlarged drillhole when the near surface unconsolidated material is of a caving nature, usually sand, to a depth of at least 10 feet or when granular bentonite of the 8-mesh size is either mounded around the top of the well casing pipe or placed in a starter drillhole and allowed to follow the well casing pipe down during driving. Any starter drillhole 10 feet deep or less is not an upper enlarged drillhole. Starter drillholes need not meet the minimum requirements for upper enlarged drillholes.

b. An upper enlarged drillhole at least 4 inches larger in diameter than the nominal diameter of the well casing pipe shall be constructed to at least the bottom of any non-caving layer or to the 20-foot depth whichever is the lesser when the near surface unconsolidated material to a depth of 10 feet is noncaving, usually clay, silt or hardpan. When steel well casing pipe assembled with welded joints is used and the annular space sealing material is placed with an approved pressure method, the diameter may be reduced to 2 inches larger than the nominal well casing pipe diameter. Rotary-air methods as specified in s. NR 812.12 (19) may be used.

c. When an upper enlarged drillhole is constructed it shall be kept filled up to within 10 feet of the ground surface with clay or sodium bentonite slurry with a mud weight of at least 11 pounds per gallon or with 8-mesh granular bentonite throughout the driving of the permanent well casing pipe. The pipe shall be driven to a firm seat in the bedrock.

d. When an upper enlarged drillhole is constructed, following completion of the driving of the well casing pipe, the annular space shall be filled with clay or sodium bentonite slurry having a mud weight of at least 11 pounds per gallon or with neat cement grout except that only neat cement grout may be used when the upper enlarged drillhole is constructed more than 5 feet into bedrock. Neat cement grout shall be placed according to the requirements of s. NR 812.20 . When temporary outer casing is used, it shall be removed during or immediately after sealing the annular space. When the upper enlarged drillhole extends deeper than the 40-foot depth and the annular space sealing material is clay or sodium bentonite slurry, the slurry shall be placed with a conductor pipe. When the upper enlarged drillhole extends deeper than the 100-foot depth, the annular space sealing material shall be pumped.

2. When the depth to bedrock is less than 40 feet or less than 30 feet for sandstone:

a. An upper enlarged drillhole shall be constructed to at least the 40-foot depth except when limestone or dolomite is encountered at a depth less than 10 feet from the ground surface, in which case the upper enlarged drillhole shall be constructed to at least the 60-foot depth or except when the bedrock is sandstone, in which case the upper enlarged drillhole shall be constructed to at least the 30-foot depth. When a caving unconsolidated formation is encountered, the upper enlarged drillhole shall be constructed by driving, while drilling, a temporary outer casing. The upper enlarged drillhole may be constructed only 2 inches larger in diameter than the nominal diameter of the permanent well casing pipe if the pipe is assembled with welded joints and if neat cement grout is placed into the annular space using an approved pressure method as specified in s. NR 812.20 . Otherwise the upper enlarged drillhole shall be constructed at least 4 inches larger in diameter than the nominal diameter of the well casing pipe,

b. The well casing pipe shall be set concentrically within the upper enlarged drillhole and driven to a firm seat in the bedrock, and

c. The annular space shall be sealed with neat cement grout according to the requirements of s. NR 812.20 . When temporary outer casing is used, it shall be removed during or after grouting. When the upper enlarged drillhole extends deeper than the 100-foot depth, the grout shall be placed with an approved pressure method.

(b) For potable high capacity, school and wastewater treatment plant wells constructed by percussion methods in bedrock:

1. When the depth to bedrock is at least 60 feet:

a. An upper enlarged drillhole at least 3 inches larger in diameter than the outside diameter of the well casing pipe or casing couplings, if used, shall be constructed to at least the 60-foot depth, or to at least the 100-foot depth if the well is for a wastewater treatment plant and there is a treatment pond or lagoon or sludge beds on the property. When an unconsolidated caving formation is encountered, the upper enlarged drillhole shall be constructed by driving, while drilling, a temporary outer casing,

b. The upper enlarged drillhole shall be kept filled up to within 10 feet of the ground surface with clay or sodium bentonite slurry with a mud weight of at least 11 pounds per gallon or with granular bentonite throughout the driving of the permanent well casing pipe. The well casing pipe shall be driven to a firm seat in the top of bedrock, and

c. The annular space shall be sealed with neat cement grout according to the requirements of s. NR 812.20 . An attempt shall be made to remove the temporary outer casing during or following grouting. It shall be removed if possible. When the upper enlarged drillhole extends deeper than the 100-foot depth, the grout shall be placed with an approved pressure method.

2. When the depth to bedrock is less than 60 feet:

a. An upper enlarged drillhole at least 3 inches larger in diameter than the outside diameter of the well casing pipe or casing couplings, if used, shall be constructed to least the 60-foot depth, or at least to the 100-foot depth if the well is for a wastewater treatment plant and there is a treatment pond or lagoon or sludge beds on the property. When an unconsolidated caving formation is encountered, the upper enlarged drillhole shall be constructed by driving, while drilling, a temporary outer casing,

b. The well casing pipe shall be set concentrically within the upper enlarged drillhole and driven to a firm seat in the bedrock, and

c. The annular space shall be sealed with neat cement grout according to the requirements of s. NR 812.20 . Temporary outer casing shall be removed during or after grouting. When the upper enlarged drillhole extends deeper than the 100-foot depth, the grout shall be placed with an approved pressure method.

(3)   Rotary method requirements for drilled bedrock wells. The rotary method for bedrock wells shall be a method whereby an upper enlarged drillhole is constructed to the intended depth of well casing pipe by using a circular rotating action applied to a string of hollow drilling rods having a drill bit attached to the bottom. The well casing pipe is set to the bottom of the drillhole and is not driven, except to drive to a firm seat in the top of bedrock.

(a) The upper enlarged drillhole constructed through the unconsolidated material above the bedrock shall be maintained at full diameter with drilling mud circulated with a suitable pump or with temporary outer casing. When temporary outer casing pipe is used, it shall be removed after the sealing process. An upper enlarged drillhole may be constructed to accommodate the setting and removal of temporary outer casing pipe if the drillhole is at least 2 inches larger in diameter than the nominal diameter of the temporary outer casing and is maintained at full diameter by circulating drilling mud. This is depicted in figure 2. Air or an approved foam may be used for constructing the upper enlarged drillhole if:

1. Bedrock is encountered above the 40-foot depth, 30-foot depth for sandstone, for nonpotable high capacity wells or for low capacity wells, except for school and wastewater treatment plant wells, or if bedrock is encountered above the 60-foot depth for potable high capacity, school or wastewater treatment plant wells, and

2. The unconsolidated material above the bedrock is clay, hardpan, or a similar material that will allow a drillhole to stand open.

3. If an approved foam is used, the foam concentration may not exceed one quart per 100 gallons of water, without approval.

(b) For nonpotable high capacity wells and low capacity wells constructed by rotary methods in bedrock, except school and wastewater treatment plant wells:

1. An upper enlarged drillhole at least 2 inches larger in diameter than the nominal diameter of the well casing pipe, shall be constructed according to par. (a) to a minimum depth as follows:

a. To the top of firm bedrock when the depth to firm bedrock is 40 feet or more, 30 feet or more for sandstone;

b. To the depth of the well casing pipe setting, but not less than 40 feet, 30 feet for sandstone, when the depth to bedrock is less than 40 feet, less than 30 feet for sandstone; or

c. To the depth of well casing pipe setting, but not less than 60 feet when the depth to firm limestone or dolomite is less than 10 feet below the ground surface.

2. The steel well casing pipe shall be set to the bottom of the upper enlarged drillhole and driven to a firm seat in the bedrock.

3. The annular space between the upper enlarged drillhole and the well casing pipe may be sealed with drilling mud and cuttings having a mud weight of at least 11 pounds per gallon or with neat cement grout, according to the requirements of s. NR 812.20 , except that only neat cement grout shall be used whenever the top of bedrock is encountered above the 40-foot depth, above the 30-foot depth for sandstone, or whenever the upper enlarged drillhole extends more than 5 feet into the top of the bedrock formation.

4. When the diameter of the upper enlarged drillhole is less than 4 inches larger in diameter than the nominal diameter of the well casing pipe, the well casing pipe shall be assembled with welded joints and the sealing material shall be placed using an approved pressure method as specified in s. NR 812.20 (2) (j) .

(c) For potable high capacity, school and wastewater treatment plant wells constructed by rotary methods in bedrock:

1. An upper enlarged drillhole at least 3 inches larger in diameter than the outside diameter of the well casing pipe or the outside diameter of the well casing pipe couplings, if used, shall be constructed according to par. (a) to a minimum depth of:

a. 60 feet or to the depth of bedrock if the top of bedrock is more than 60 feet below the ground surface; or

b. 100 feet if the well is to supply water for a wastewater treatment plant and there is a treatment pond or lagoon on sludge beds on the property.

2. The well casing pipe shall be set to the bottom of the upper enlarged drillhole and driven to a firm seat in the bedrock.

3. The annular space between the upper enlarged drillhole and the permanent well casing pipe shall be sealed with neat cement grout, according to the requirements in s. NR 812.20 .

History: 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.

Note

For the installation of pumps in wells with less than 25 feet of well casing pipe, see the requirement in s. NR 812.31 (2) (d) . Microsoft Windows NT 6.1.7601 Service Pack 1 - See PDF for diagram Figure 1. Minimum requirements for centering guides in bedrock wells. Microsoft Windows NT 6.1.7601 Service Pack 1 - See PDF for diagram Figure 2. Required rotary method for constructing and sealing upper enlarged drillholes to enable the setting and removal of a temporary outer casing in bedrock wells overlain by unconsolidated caving material. Microsoft Windows NT 6.1.7601 Service Pack 1