Section NR 141.19 - Borehole diameter(1) BOREHOLES IN UNCONSOLIDATED GEOLOGIC FORMATION. For all permanent groundwater monitoring wells in unconsolidated geologic formations, the borehole diameter shall meet the following requirements: (a) If hollow stem augers are used, their inside working diameter shall be at least 2 1/4 inches greater than the inside diameter of the permanent well casing.(b) If solid stem augers are used, their outside diameter shall be at least 4 inches greater than the inside diameter of the permanent well casing.(c) If an air or mud rotary method is used, the borehole diameter shall be at least 4 inches greater than the inside diameter of the permanent well casing. If a temporary outer casing is used, the inside diameter of the temporary outer well casing shall be at least 4 inches greater than the inside diameter of the permanent well casing. The temporary outer casing shall be pulled as the annular space is being sealed. Note: The dual-tube or triple-tube reverse rotary systems are rotary methods.
(d) If percussion methods, including the rotary wash, wash down and wash bore methods, with a temporary outer casing are used, in unconsolidated geologic formations, the inside diameter of the temporary outer casing shall be at least 4 inches greater than the inside diameter of the permanent well casing. The temporary outer casing shall be removed during the sealing of the annular space.(2) BOREHOLES IN BEDROCK GEOLOGIC FORMATIONS. For all permanent groundwater monitoring wells installed deeper than 2 feet past the top of the bedrock, the borehole diameter shall meet the following requirements: (a) If an air or mud rotary method is used to construct the monitoring well, the requirements of sub. (1) (c) shall be followed. (b) If percussion methods are used to construct the monitoring well, the requirements of sub. (1) (d) shall be followed.Wis. Admin. Code Department of Natural Resources NR 141.19
Cr. Register, January, 1990, No. 409, eff. 2-1-90.