Wisconsin Administrative Code
Department of Natural Resources
NR 800 - Environmental Protection - Water Supply
Chapter NR 812 - Well Construction And Pump Installation
Subchapter III - Requirements for New Pump Installations and Water Treatment
Section NR 812.36 - Pits

Universal Citation: WI Admin Code ยง NR 812.36

Current through August 26, 2024

(1) APPROVALS TO CONSTRUCT PITS. A pit structure that is completely or partially below the ground surface or below a building floor used for the housing of wells, off-set pumps, pressure tanks, or heads of pressure tanks may not be constructed without prior written approval from the department under s. 812.09. Pits used only for the housing of valves are exempt from the requirements of this section except that a pit used for this purpose shall be watertight, may not be connected to a sewer, shall be drained to permeable soil or to the ground surface and may not be subject to flooding

(2) SPECIFICATION FOR NEW PITS. Pits shall conform to Figure 8 of ch. NR 812 Appendix and all of the following minimum specifications:

(a) Dimensions.
1. 'Area.' Five square feet of free floor area shall be provided for each square foot of area required for any pump installation equipment. The inside area of a pit may not be less than 24 square feet.

2. 'Width.' The width of the pit shall be not less than 2/3 of the length.

3. 'Height.' The height inside shall be at least 6 feet, but not less than 6 inches higher than any equipment installed in the pit.

4. 'Walls, floor and roof thicknesses.' The wall thickness shall be at least 6 inches and waterproof. The floor thickness shall be at least 4 inches when the floor bears on a footing. Floors used as a wall footing shall be at least 6 inches thick from the outside edge of the floor to a point at least one foot inside the wall of the pit. The roof thickness shall be at least 5 inches.

(b) Construction.
1. 'Material.' The pit shall be constructed of reinforced poured concrete thoroughly puddled in place. The concrete shall be prepared to meet the requirements specified in s. NR 812.11(15) (e) or by using clear water and washed sand and gravel or crushed rock in the following proportions: 1 part cement, 2 parts sand, and 3 parts gravel. The water-cement ratio may not exceed 6 gallons of water per 94 pounds of cement. A 6-bag concrete mix per cubic yard with a 28-day design strength of at least 3,000 lbs. per foot and a slump test of no more than 3 inches may be used.

2. 'Watertight juncture.' The junction of walls, floor and roof shall be made watertight by use of water stops or keyed joints. Conduits or similar connection with the pit shall be watertight.

3. 'Reinforcement.' The deck or pit roof and walls of the pit structure shall be reinforced with bars or wire mesh to insure strength and durability.

4. 'Elevation of pit roof.' The pit roof, deck or wall top shall be above the ground surface.

(c) Manhole opening.
1. 'Placement.' The pit shall be provided with a manhole opening. The opening shall be located directly over the well, unless the well casing pipe itself extends through the roof, or if a capped section of well casing pipe at least equal in diameter to the well casing pipe is cast into the pit roof directly over the well.

2. 'Size.' The manhole opening shall be at least 20 inches square or 20 inches in diameter and shall be sufficiently large to allow entrance or removal of any unit or equipment to be installed in the pit.

3. 'Curbing.' The manhole opening shall be provided with a raised concrete curbing at least 4 inches thick. The curbing shall extend at least 4 inches above the pit roof.

4. 'Cover.' A structurally substantial, watertight, overlapping, tight-fitting, cover with skirted sides at least 3 inches high shall be provided for the manhole. The department recommends that a welded sheet steel cover be used, but a cover made out of lumber and covered in turn with sheet metal or tin may be acceptable if waterproof.

5. 'Exceptions.' A watertight, cast iron manhole frame and cover with a gasket may be substituted for a curbed manhole. When the pit is an alcove adjoining a basement foundation, a watertight concrete plug may be substituted for a curbed manhole if the roof of the pit terminates in a walkway, breezeway, patio or porch, providing the pit is reasonably accessible.

(d) Drainage.
1. 'Gravity drain.' The pit shall be drained by a watertight gravity drain discharging to the ground surface at a point at least 8 feet from the well. The drain shall be constructed of materials conforming to ch. SPS 384 and shall have a minimum diameter of 2 inches with a screened outlet.

2. 'Alcoves.' An alcove may be drained to the basement floor if the pit floor slopes toward the basement and if the basement is adequately drained. If the basement is not adequately drained, a gravity drain shall be provided for the pit. The pit floor shall be one foot above the basement floor.

(e) Termination of well casing pipe. The well casing pipe shall terminate at least 12 inches above the pit floor and be provided with an approved watertight seal.

(f) Venting.
1. 'Pit.' A pit should be vented with 2, 2-inch diameter or larger galvanized steel pipes located in opposite corners, one pipe to extend to within one foot of the pit floor and the other to extend only through the pit roof. If used, the upper end of the vent pipes shall terminate with return bends and screened outlets.

2. 'Well.' The well vent pipe shall extend to the top of the pit and terminate with a return bend and a screened outlet.

(g) Pump installation. The free space in the pit around the well casing pipe shall be maintained so that the top of the well casing pipe is readily accessible for installation, adjustment or removal of an approved well seal and for the installation and removal of the pump or piping.

(3) DRIVEWAY RAMPS. If a well must be located in a driveway, parking area, walkway or other high traffic area due to small lot size, accessibility constraints or inability to otherwise meet the minimum separation distance requirements of s. NR 812.08, the well may be contained within a driveway ramp structure without department approval provided the driveway ramp meets the specifications of this subsection.

(a) Relation to floodplain. Driveway ramps may not be constructed in a floodway or floodplain.

(b) Construction specifications. Driveway ramps shall conform to Figure 9 of ch. NR 812 Appendix and all of the following minimum specifications:
1. 'Nonpressurized conduit.' If the well has a nonpressurized conduit, the pump installer shall evaluate the integrity of the non-pressurized conduit and its connection to the well casing pipe by performing a pressure test. If the nonpressurized conduit fails the pressure test, the nonpressurized conduit shall be eliminated and the installation shall be changed to a pitless connection in accordance with s. NR 812.42(11) (e). Wells with nonpressurized conduits must be vented to the ceiling in the basement and shall have the pump cables enter through a conduit.

2. 'Construction.' The top of the well shall be contained within a manhole and frame that is set on a concrete ring. The manhole shall be water-tight with a gasketed seal and shall be bolted securely to the frame. The manhole must be surrounded by concrete or asphalt that is sloped so that surface water does not flow toward or pond on the manhole cover.

3. 'Height of well.' The top of the well casing pipe shall terminate a minimum of four inches above the original grade of the driveway, parking lot or sidewalk.

4. 'Well seal.' The top of the well shall be sealed watertight with an approved sanitary well seal.

5. 'Conduit for electrical cable.' Conduit for electrical wiring shall be protected and sealed to comply with s. NR 812.30(5). If the conduit extends from the well seal to a basement, the end of the conduit shall be sealed with a watertight, vermin-proof seal.

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