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(1) Perforations above the lowest expected static water level shall not be permitted. Wells may be completed with perforations as follows:

(a) in-place perforations with star, mills knife, similar type perforators, millslotted, sawed, or drilled;

(b) perforated inner casing, either torch-cut, millslotted or punched. Such inner casing may be of steel, plastic or other suitable corrosion-resistant material, but if other than steel, a full evaluation of the structural stability of the inner casing must be made prior to its placement. They may be used in a natural development or gravel packed type of construction. Where appropriate, the top of the inner casing shall be fitted with suitable packers or sealing material and sealed to the well casing.

(2) Casing perforations that allow the well casing to act as a conduit for deleterious interflow between aquifers shall not be permitted. (That is, interflow where waters of different heads, temperatures, or quality mix causing deleterious effects.)

(3) Perforations shall not be placed to allow cascading water within the well casing during static conditions.

(4) Perforations shall not be placed to allow upward artesian flow from one aquifer to another.

History: 37-43-202(3), MCA; IMP, 37-43-202(3), MCA; NEW, 1986 MAR p. 1699, Eff. 10/17/86; AMD, 1991 MAR p. 913, Eff. 6/14/91; AMD, 1997 MAR p. 65, Eff. 1/17/97.

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