Protection of ground water sources

1. Minimum protective depths of wells. All wells shall be watertight to exclude contamination. Wells shall be designed to seal off formations that are or may be contaminated or undesirable. Unless approved otherwise by the department, the annular space between a well hole excavation and the outside of the well casing shall be filled with neat cement grout, high-solids bentonite clay grout, bentonite chips, or bentonite tablets at least one and one-half inches [3.81 centimeters] in thickness from a depth of not less than thirty feet [9.1 meters] to the ground surface or the upper end of the well casing if a pitless unit or adapter is installed. Wells with a depth of thirty feet [9.1 meters] or less shall be grouted from within two feet [60.96 centimeters] of the top of the well screen to the ground surface or the upper end of the well casing if a pitless unit or adapter is installed. Greater depths are preferable and may be required for specific installations as determined by review of the plans and specifications. The annular space of wells constructed in unconsolidated formations without overlying confining beds and static water levels less than thirty feet [9.1 meters] below the ground surface shall be filled with neat cement grout, high-solids bentonite clay grout, bentonite chips, or bentonite tablets at least one and one-half inches [3.81 centimeters] in thickness from the static water level or a depth of not less than ten feet [3.0 meters], whichever is greater, to the ground surface or the upper end of the well casing if a pitless unit or adapter is installed. Driven well casing may, when conditions warrant, be installed without grouting. 2. Required protection for various sources. a. Radial collector wells. The location of all caisson construction joints and porthole assemblies shall be indicated. The caisson wall shall be substantially reinforced. Radial collectors shall be in areas and at depths approved by the department. Provisions shall be made to assure minimum vertical rise. The top of the caisson shall be covered with a watertight floor. All openings in the floor shall be curbed and protected from entrance of foreign material. Pump discharge piping shall not be placed through caisson walls. b. Dug or bored wells. Dug or bored wells greater than two feet [60.96 centimeters] in diameter shall be developed only where geological conditions preclude the development of a satisfactory drilled well. Every dug or bored well shall have a continuous watertight casing. The section of casing in the producing zone serving as the well screen shall readily admit water and be structurally sound to withstand external pressures. The open space between the excavation and the installed casing shall be sealed with neat cement grout, high-solids bentonite clay grout, bentonite chips, or bentonite tablets. The watertight casing shall extend at least twelve inches [30.48 centimeters] above finished ground surface. A cover slab at least four inches [10.16 centimeters] thick, adequately reinforced and having a diameter sufficient to overlap the lining by two inches [5.08 centimeters] shall be provided. The slab shall be constructed without joints. The top of the slab shall be sloped to drain to all sides and a watertight joint made where the slab rests on the well casing using cement mortar or a mastic compound. A manhole, if installed, shall be provided with a curb cast in the slab and extending at least four to six inches [10.16 to 15.24 centimeters] above the slab. The manhole shall have a watertight overlapping cover extending down around the curb by at least two inches [5.08 centimeters]. Adequate sized pipe sleeve or sleeves shall be cast in place in the slab to accommodate the type of pump or pump piping proposed for the well. c. Infiltration wells. Infiltration wells may be considered where geological conditions preclude possibility of developing an acceptable drilled well. The area around the well shall be under the control of the water purveyor for a distance acceptable to or required by the department. The flow in the lines shall be by gravity to a collecting well. The water shall be continuously chlorinated to assure bacterial purity. d. Flowing wells. The construction of flowing wells shall be in compliance with North Dakota Century Code chapter 61-20. The construction of flowing wells shall be such that the flow from them can be controlled. Well casing shall be installed, and the annular space grouted with neat cement to form a tight seal. The neat cement grout shall extend upward from within twenty feet [6.1 meters] of the top of the aquifer to the ground surface or the upper end of the well casing if a pitless unit or adapter is installed. Well casings shall be joined in a watertight manner. Flow control should consist of valved pipe connections, watertight pump connections, or receiving reservoirs set at an elevation corresponding to the artesian head. e. Existing wells. The department shall be consulted for requirements concerning the reconstruction of existing wells.