Section NR 812.16 - Gravel packs(1) CONDITIONS. A well driller or a well constructor may construct a screened well with a gravel pack under any of the following conditions:(a) In an unconsolidated formation well when the natural formation comprising the aquifer is very fine grained or when the aquifer formation is highly variable in size.(b) In loosely cemented sandstone aquifers that require screening to prevent sand pumping conditions.(c) In badly fractured or decomposed crystalline bedrock formations.(2) MATERIAL. The gravel or sand used to construct a gravel pack shall meet the requirements specified in s. NR 812.11(12).(3) SCREENS. Screens to be placed in gravel pack wells shall have a set of centering guides on the top and bottom of the screen to ensure an even gravel pack. The screen slot openings shall be sized to retain 90% of the gravel pack. Screen types and materials shall meet the requirements specified in s. NR 812.11(11). The screen may either be permanently welded or threaded onto the bottom of the well casing pipe or may be installed by pushing the screen to the bottom of the casing pipe and then pulling back the casing pipe to expose the screen.(4) PLACEMENT. Gravel packs shall be placed in accordance with all of the following requirements: (a) The gravel pack shall be placed through a tremie pipe placed in the annular space.(b) The gravel pack shall surround the entire screen and shall extend at least 2 feet above the top of the screen.(c) At least a 2-foot sand seal shall be placed upon the top of the gravel pack to prevent the required annular space sealing material from entering the gravel pack.(d) For potable wells, the gravel pack may not extend closer to the ground surface than the minimum depth for the upper enlarged drillhole specified in s. NR 812.152(3).(e) For nonpotable high capacity wells, the gravel pack may not extend more than 20 feet above the top of the screen.(5) THICKNESS. The diameter of the upper enlarged drillhole shall be sized to accommodate the thickness of the gravel pack. The gravel pack shall be at least 2 inches greater than the nominal radius of the screen.Wis. Admin. Code Department of Natural Resources NR 812.16
Cr. Register, January, 1991, No. 421, eff. 2-1-91; am. (3) (a), Register, September, 1994, No. 465, eff. 10-1-94.Amended by, CR 18-095: r. and recr. Register June 2020 No. 774, eff. 7/1/2020