Wisconsin Administrative Code
Department of Natural Resources
NR 800 - Environmental Protection - Water Supply
Chapter NR 811 - Requirements For The Operation And Design Of Community Water Systems
Subchapter II - Source Development - Groundwater
Section NR 811.19 - Special requirements for limestone or dolomite wells
Current through August 26, 2024
This section applies to wells drilled in formations commonly referred to as limestones and dolomites in Wisconsin. This includes the Niagara dolomite, the Galena-Platteville dolomite and the Prairie du Chien dolomite. When an acceptable sandstone aquifer can be utilized, construction of limestone or dolomite wells should be avoided. The following requirements apply to wells located in limestone and dolomite aquifers which are not overlain by consolidated shale or sandstone formations.
(1) At a minimum, continuous disinfection, and possibly detention, shall be provided when the department determines that additional protection is necessary.
(2) Continuous disinfection shall be provided for wells with less than 60 feet of grouted casing.
(3) If the depth of unconsolidated material overlying the limestone is 60 feet or greater for a minimum radius of one-half mile and there is no record of sinkholes, quarries, improperly constructed wells, or outcrops within that area, the minimum depth of grouted casing shall be 60 feet. The department may require greater depths of grouted casing in areas where there is known bacteria or nitrate concentrations exceeding drinking water standards. The casing shall be installed to a depth of 10 feet below the anticipated pumping water level unless the department waives this requirement after finding it unnecessary in meeting the requirements of this chapter.
(4) If the depth of unconsolidated material is more than 60 feet and only 60 feet of grouted casing is required by the department, the casing shall be seated in firm limestone.
(5) If the depth of unconsolidated material is less than 60 feet at the well site or within one-half mile of the well site, the water system owner shall contact the department to determine the required minimum depth of grouted casing. An inner casing size of at least 12 inches in diameter shall be required to permit the installation of a grouted liner at a future date if the water from the well shows evidence of contamination. The department may waive the casing size requirement if it is demonstrated that it is unnecessary to meet the requirements of this chapter, but in that case a minimum of 100 feet of grouted casing is required.
