NAC534.380. Construction of well: Seals.

     1. Except as otherwise provided in subsection 2, before the drill rig is removed from the drill site of a well, the annular space between the well bore and the casing must be sealed to a minimum depth of 50 feet below ground level by:

     (a) Placing neat cement, cement grout, concrete grout or bentonite chips from the sealing depth to 20 feet from the surface; and

     (b) Placing neat cement, cement grout or concrete grout from 20 feet below the surface to the surface.

Ê If sodium bentonite chips are placed in the annular space, the chips must be placed in such a manner that a bridge does not occur. If bentonite chips are poured in standing water, the bentonite chips must be screened to eliminate the fines.

     2. Before the drill rig is removed from the drill site of a well, the annular space between the well bore and the casing must be sealed to a depth of greater than 50 feet below ground level if sealing to such a depth is required by subsection 1 of NAC 534.370, NAC 534.375, subsection 1 of NAC 534.378 or paragraph (b) of subsection 1 of NAC 534.390. If the well is regulated by the Bureau of Safe Drinking Water of the Division of Environmental Protection of the State Department of Conservation and Natural Resources, the annular space must be sealed in accordance with NAC 445A.66905.

     3. The casing must be centered as nearly as practicable in the well bore to allow the sanitary seal to surround the casing.

     4. If a temporary conductor casing is used, it must be withdrawn during the placement of the grout.

     5. If a pitless adapter is used in domestic or small commercial wells:

     (a) The sanitary seal must begin not more than 5 feet below ground level;

     (b) The sanitary seal must extend at least 50 feet below the bottom elevation of the pitless adapter; and

     (c) The portion of the casing above the sanitary seal must be backfilled to ground level with uncontaminated soil which is compacted.

     6. A pipe used to feed gravel through the cement seal or to provide access to the interior of the well must be fitted with a watertight cap.

     7. A licensed well driller must place the seal or directly supervise the placement of the seal.

     8. The seal must be placed:

     (a) In the annular space within 3 days after the casing is set and before the drill rig is removed from the drill site.

     (b) In one continuous mass from the minimum depth of 50 feet below ground level to the surface.

     (c) By tremie pipe in an upward direction to displace the fluid to the surface of the ground, if any fluid is standing in the well bore above the sealing depth.

     9. The diameter of the well bore must be at least 4 inches larger than the largest diameter of the outside of the outermost casing to be used, including any joints or collars. If a fill pipe for gravel is installed, the diameter of the well bore must be 4 inches larger than the largest diameter of the casing plus the largest diameter of the fill pipe for gravel. A fill pipe for gravel or any other pipe to provide access to the interior of the well must be completely surrounded by the seal. A conductor casing may be used to convey the gravel pack. If a conductor casing is used:

     (a) The diameter of the well bore must be at least 4 inches larger than the largest diameter of the conductor casing; and

     (b) The annular space between the conductor casing and the well bore must be sealed.

     10. A watertight seal must be installed at the surface level between the conductor casing and the production casing to prevent any contaminants from entering the gravel pack conductor area. A welded plate or a seal consisting of neat cement, cement grout or concrete grout from a minimum depth of 10 feet below ground level to the surface must be used. If a welded plate is used, the entire length of the plate must be welded to the conductor casing and production casing.

     [St. Engineer, Drilling Wells Reg. §§ 3.02-3.13 & 3.16, eff. 5-19-81]—(NAC A 1-9-90; 12-30-97; R009-06, 6-1-2006; R039-12, 6-29-2012)