17.50.1312    MONITORING WELL ABANDONMENT

(1) The owner or operator of a solid waste management facility shall:

(a) completely seal all abandoned borings, water supply wells, and monitoring wells with grout or bentonite to prevent future contamination of ground water. The sealing materials must be continuous, physically and chemically stable, and have a hydraulic conductivity of less than 1 x 10^-5cm/sec;

(b) immediately abandon, after drilling and completion of soil testing, all boreholes not completed as a monitoring well, piezometer, or water supply well;

(c) for any borehole deeper than the well to be placed in it, seal with bentonite pellets or a bentonite slurry the portions of the borehole below the well screen; and

(d) conduct all abandonment activities in accordance with ARM 36.21.670 through 36.21.678 and 36.21.810.

History: 75-10-204, MCA; IMP, 75-10-204, MCA; NEW, 2010 MAR p. 317, Eff. 2/12/10.