Section NR 141.21 - Well developmentAll permanent groundwater monitoring wells shall be developed according to the requirements of section. Wells sealed with grout or slurry shall be developed after a minimum waiting period of 12 hours after installation is completed. The goal of well development is to produce water free of sediment and all drill cuttings and drilling fluids.
(1) WELLS THAT CANNOT BE PURGED DRY. All permanent groundwater monitoring wells that cannot be purged dry shall be developed by the following procedure: (a) Alternately surge and purge the well for a minimum of 30 minutes. The surge and purge cycle shall consist of several minutes of surging followed by several minutes of purging to remove the material collecting in the bottom of the well. The surging shall move formation water in and out of the well screen. The surging shall be accomplished by using either a bailer or surge block or by pumping the well sufficiently to cause a drawdown and then allowing the well to recover and repeating the process. Note: When a surge block is used, care should be taken to avoid drawing the annular space seal material into the filter pack or well screen.
(b) After the final surge and purge cycle is completed, the well shall be pumped or bailed until 10 well volumes of water are removed or until the well produces sediment free water. If sediment free water is not obtained any remaining sediment shall be removed from the bottom of the well. Well volume shall be calculated in the following manner: V1 + V2 = well volume
V1 = volume of water in well casing
V2 = volume of water in filter pack
N = porosity of filter pack
D1 = inside diameter of well casing
D2 = outside diameter of well casing
D3 = diameter of borehole
H1 = height of water column
H2 = length of sand used in filter pack and fine sand filter pack seal or the height of the water column in water table observation wells.
Note: There are 7.48 gallons per cubic foot.
H1 = height of water column
H2 = length of filter pack or the height of the water column in water table observation wells.
(2) WELLS THAT CAN BE PURGED DRY. All permanent groundwater monitoring wells that can be purged dry shall be developed in a manner which limits agitation by slowly purging the well dry. Wells which can be purged dry may not be surged and no water may be added to the well.Wis. Admin. Code Department of Natural Resources NR 141.21
Cr. Register, January, 1990, No. 409, eff. 2-1-90; am. (intro.), (1) (a) and (b) and (2), Register, June, 1991, No. 426, eff. 7-1-91.