Section 812.15. Flowing wells.

 

(1)  When a flowing well is constructed, in an area where the well driller or well constructor knows flowing wells exist, flow of water up the outside of the well casing pipe shall be prevented. Flowing well construction shall comply with the requirements of ss. NR 812.12 to 812.14 , including Tables I to IV, and the additional requirements of sub. (2) and (3) . Flowing wells may occur in the following areas:

(a) The aquifer is not confined and is in a discharge area, usually near a river, lake or stream as depicted in figure 3; or

(b) The aquifer is confined by an overlying impermeable geologic formation as depicted in figure 4.

(2)  A flowing well shall meet the construction requirements of sub. (3) with the following modifications:

(a) If the flowing well is a potable high capacity, school or wastewater treatment plant well:

1. The reference depth to the aquifer is 60 feet rather than 40 feet or 30 feet for sandstone, except when the well is installed for a wastewater treatment plant that has a treatment pond or lagoon or sludge beds on the property, the reference depth to the aquifer is 100 feet.

2. The upper enlarged drillhole shall be 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.

3. The annular space shall be sealed with cement grout as specified in s. NR 812.20 .

(b) If the flowing well is a sandstone bedrock well, and is a nonpotable high capacity well or a low capacity well, except for school and wastewater treatment plant wells, the reference depth to the sandstone bedrock aquifer is 30 feet rather than 40 feet as for other types of bedrock.

(3)  A flowing well shall be constructed according to the requirements of this subsection as follows:

(a) Aquifer not confined. Flowing wells constructed in areas where the aquifer is not confined shall be constructed as follows:

- See PDF for diagram Figure 3. A flowing well in an unconfined aquifer.

1. When the flowing well is constructed using percussion methods:

a. An upper enlarged drillhole shall be constructed. Any portion of the upper enlarged drillhole constructed into unconsolidated material shall be constructed with temporary outer casing at least 4 inches larger in diameter than the nominal diameter of the well casing pipe. If, for bedrock wells, the top of bedrock is less than 40 feet from the ground surface or less than 30 feet for sandstone, the temporary outer casing shall be driven with a drive-shoe to a firm seat in the top of bedrock, and the remainder of the upper enlarged drillhole shall be constructed the same diameter as the inside diameter of the temporary outer casing.

b. When the well casing pipe is set to the bottom of the temporary outer casing and driven through unconsolidated material, either into an unconsolidated aquifer, or to the top of a bedrock aquifer, the temporary outer casing shall be filled up to within 10 feet of the ground surface with a clay or sodium bentonite slurry and cuttings having a mud weight of at least 11 pounds per gallon throughout the driving.

c. When the upper enlarged drillhole extends more than 5 feet into the top of bedrock and there is a strong flow up the drillhole, the flow up the annular space shall be reduced with a packer installed surrounding the bottom of the well casing pipe. The well casing pipe shall be driven with a drive-shoe to a firm seat into the top of bedrock and the required neat cement grout shall be pumped through a conductor (tremie) pipe.

2. When a flowing well is constructed using rotary methods, heavy drilling mud having a mud weight of at least 11 pounds per gallon shall be circulated during the construction of the upper enlarged drillhole.

(b) Aquifer is confined, is more than 40 feet from the ground surface and the confining bed is unconsolidated. Flowing wells constructed in areas where the aquifer is confined, is more than 40 feet from the ground surface and the confining bed is unconsolidated, usually clay or hard pan, shall be constructed as follows:

- See PDF for diagram Figure 4. A flowing well in a confined aquifer.

1. When such a flowing well is constructed using percussion methods:

a. As depicted in figures 5 and 6, a temporary outer casing at least 4 inches larger in diameter than the nominal diameter of the permanent well casing pipe shall be driven, while drilling, about halfway, if known, through the unconsolidated confining bed, but not less than the depth required in Tables I to IV.

b. The well casing pipe, with drive-shoe, shall be set to the bottom of the temporary outer casing and driven, while drilling, through the remainder of the confining bed and either into the unconsolidated aquifer, or to the top of a bedrock aquifer. The annular space shall be filled up to within 10 feet of the ground surface with a clay or sodium bentonite slurry and cuttings with a mud weight of at least 11 pounds per gallon during the driving of the well casing pipe. The annular space shall be subsequently sealed, as specified in Tables I to IV, with neat cement grout or with a clay or sodium bentonite slurry according to the requirements of s. NR 812.20 .

c. The well shall be completed in the manner prescribed in Tables I to IV and ss. NR 812.12 to 812.14 , and the temporary outer casing shall be removed, if possible, during the sealing of the annular space.

2. When such a flowing well is constructed using rotary methods:

a. As depicted in figures 7 and 8, the well shall be constructed double-cased. The size of the inner well casing pipe shall have a nominal diameter not less than 4 inches for unconsolidated wells and not less than 6 inches for bedrock wells.

b. An outer upper enlarged drillhole at least 2 inches larger in diameter than the nominal diameter of the outer well casing pipe shall be constructed, by circulating drilling mud, from the ground surface to about halfway, if known, through the unconsolidated confining bed, but to a depth not less than the depth required by Tables I to IV.

c. An outer well casing pipe meeting the specifications of temporary outer casing described in s. NR 812.17 and assembled with welded joints shall be set to the bottom of the outer upper enlarged drillhole. Threaded and coupled well casing pipe may be used if the upper enlarged drillhole is constructed 4 inches larger in diameter than the nominal diameter of the well casing pipe. The annular space shall be sealed according to the requirements of s. NR 812.20 with clay or sodium bentonite slurry and cuttings having a mud weight of at least 11 pounds per gallon, or with neat cement grout.

d. An inner upper enlarged drillhole, the same diameter as the inside diameter of the outer well casing pipe, shall be constructed, by circulating drilling mud and cuttings with a mud weight of at least 11 pounds per gallon, through the remainder of the unconsolidated confining bed and either into an unconsolidated aquifer or to the top of a bedrock aquifer.

e. The inner well casing pipe shall have a nominal diameter 2 inches smaller than the nominal diameter of the outer well casing pipe, shall meet s. NR 812.17 and Table V requirements and shall be set to the bottom of the inner upper enlarged drillhole, and, if the aquifer is bedrock, driven to a firm seat with a drive-shoe. The annular space may be sealed with the drilling mud and cuttings or with neat cement grout, except when the inner upper enlarged drillhole extends more than 5 feet into bedrock, in which case the annular space shall be sealed with neat cement grout according to the requirements of s. NR 812.20 .

f. The well shall be completed in the manner prescribed in Tables I to IV and by s. NR 812.14 .

(c) Aquifer is confined, is more than 40 feet from the ground surface and the confining bed is bedrock. Flowing wells constructed in areas where the aquifer is confined, is more than 40 feet from the ground surface and where the confining bed is bedrock shall be constructed as follows:

1. When such a flowing well is constructed using percussion methods:

a. As depicted in figure 9, a temporary outer casing at least 4 inches larger in diameter than the nominal diameter of the well casing pipe shall be driven, while drilling, from the ground surface to a firm seat in the top of bedrock confining bed.

b. An upper enlarged drillhole the same diameter as the inside diameter of the temporary outer casing shall be constructed from the bottom of the temporary outer casing about halfway, if known, through the bedrock confining bed. The depth of this upper enlarged drillhole may not be less than the depth required in Tables I to IV.

c. The well casing pipe with a drive shoe shall be set to the bottom of the upper enlarged drillhole and driven to a firm seat in the bedrock confining bed.

- See PDF for diagram

- See PDF for diagram - See PDF for diagram - See PDF for diagram - See PDF for diagram - See PDF for diagram

d. The annular space shall be sealed with neat cement grout according to the requirements of s. NR 812.20 and the temporary outer casing shall be removed if possible.

e. After waiting 24 hours following grouting, a lower drillhole the same diameter of the inside diameter of the permanent well casing pipe shall be constructed from the bottom of the permanent well casing pipe through the remainder of the confining bed into the bedrock aquifer.

f. For confined aquifers under high artesian pressure that produce a flow from the well greater than or equal to 70 gallons per minute, the department recommends that a flow pipe meeting Table V requirements be installed watertight with a packer from the bottom of the well casing pipe at least 10 feet into the aquifer to prevent the erosive action of the water entering the well so as to reduce the danger of water cutting a channel around the well casing pipe. In addition, the department recommends that a suitable piping arrangement, with a watertight packer or seal, be provided for the top of the well casing pipe to prevent excess pressure build-up or unnecessary flow or loss of artesian pressure.

g. The department recommends that a flow pipe as described in subd. 1. f. also be installed when the confining bed produces turbid water.

2. When such a flowing well is constructed using rotary methods:

a. As depicted in figure 10, an upper enlarged drillhole at least 2 inches larger in diameter than the nominal diameter of the well casing pipe shall be constructed about halfway, if known, through the bedrock confining bed. The depth of the upper enlarged drillhole may not be less than that required by Tables I to IV.

b. The well casing pipe assembled with welded joints shall be set to the bottom of the upper enlarged drillhole and driven to a firm seat in the bedrock confining bed. Threaded and coupled well casing pipe may be used if the upper enlarged drillhole is constructed 4 inches larger in diameter than the nominal diameter of the well casing pipe.

c. The annular space shall be sealed with neat cement grout by using an approved pressure method according to the requirements of s. NR 812.20 .

d. The well shall be completed according to the percussion method requirements of subd. 1. e. to g.

(d) Aquifer is confined and less than 40 feet from the ground surface. When flowing wells are constructed in areas where the aquifer is confined and lies less than 40 feet below the ground surface, the wells shall be double-cased as follows:

1. An upper enlarged drillhole shall be constructed for both the outer well casing pipe and the inner well casing pipe. The size of the upper enlarged drillholes for both the outer and inner well casing pipes and the methods of their construction are the same as described in pars. (b) and (c) when the aquifer is greater than 40 feet below the ground surface.

2. The outer well casing pipe shall extend about halfway through the overlying confining bed and shall be sealed in place according to the grouting and sealing requirements of s. NR 812.20 . If the confining bed is bedrock, the portion of the upper enlarged drillhole constructed into the overlying unconsolidated material above the confining bed shall be constructed by driving, while drilling, a temporary outer casing to the top of the confining bed. The outer well casing pipe shall meet, at a minimum, the specifications for temporary outer casing of s. NR 812.17 (1) (a) .

3. The inner well casing pipe shall extend into the aquifer to a depth not less than the depth required in Tables I to IV. It shall be set in the inner upper enlarged drillhole, driven to firm seat if in bedrock and shall be sealed in place according to the grouting and sealing requirements of s. NR 812.20 .

4. The methods of placement of the outer and inner well casing pipes shall also be the same as described in pars. (b) and (c) for those cases where the aquifer is encountered at a depth greater than 40 feet below the ground surface.

5. The size of the inner well casing pipe shall have a nominal diameter not less than 4 inches for unconsolidated formation wells and not less than 6 inches for bedrock wells.

6. When the confining bed is limestone or dolomite and lies 10 feet or less below the ground surface, the inner upper enlarged drillhole and the inner well casing pipe shall extend to at least the 60-foot depth.

History: Cr. Register, January, 1991, No. 421 , eff. 2-1-91; am. (2) and (3) (intro.), (b) 2. e. and Figure 6, Register, September, 1994, No. 465 , eff. 10-1-94; CR 13-099 : r. and recr. Figures (5) (b) 1., (6) (b) 1., (7) (b) 2., (9) (c) 1., (10) (c) 2., Register September 2014 No. 705 , eff. 10-1-14.