Minn. R. agency 144, ch. 4725, MONITORING WELLS, pt. 4725.6755

Current through Register Vol. 49, No. 10, September 3, 2024

Part 4725.6755 - PROTECTION OF MONITORING WELLS

Subpart 1.Casing, protective casing, and capping.

The inner casing of a monitoring well, and when installed, the protective outer casing as specified in subpart 2, item B, with bentonite grout in the annular space, must be covered with a cap or cover according to part 4725.2250, subpart 17. The protective outer casing may be covered with an overlapping cap or cover without a compression gasket.

A. Either the inner casing or the protective outer casing must be closed with a watertight, locked cap or a wrench-tightened, threaded metal cap.

B. The top of the well must be constructed to prevent entry of flood waters according to part 4725.4350, subpart 2.

C. A monitoring well cased with plastic must be protected with an outer steel protective casing as specified in subpart 2, item B.

Subp. 2.Protection.

A monitoring well must be protected by:

A. surrounding the casing with a concrete pyramid or cone that has horizontal dimensions of at least 24 inches by 24 inches at the established ground surface, that rises 12 inches above the established ground surface at the casing, and has a base with a mass of at least three cubic feet below the established ground surface;

B. installing a steel outer casing meeting the material standards of part 4725.2350 that is at least 3.0 inches in diameter greater than the inner casing, that extends at least two feet above and four feet below the established ground surface, and that has bentonite grout, neat-cement grout, or cement-sand grout in the annular space between the casings from the bottom of the outer casing to the established ground surface; or

C. placing three posts at least four inches square or four inches in diameter around the well at equal distances from each other and two feet from the casing. The posts must extend two feet above and four feet below the established ground surface or to a depth of two feet if each post is set in concrete to a depth of two feet. The posts must be made of reinforced concrete, decay-resistant wood, or ASTM Schedule 40 steel pipe capped with an overlapping, threaded, welded steel or iron cap, or be filled with cement.

Minn. R. agency 144, ch. 4725, MONITORING WELLS, pt. 4725.6755

17 SR 2773; 33 SR 211

Statutory Authority: MS s 103I.101; 103I.111; 103I.205; 103I.221; 103I.301; 103I.401; 103I.451; 103I.501; 103I.525; 103I.531; 103I.535; 103I.541; 103I.621; 144.05; 144.12; 144.383; 157.04; 157.08; 157.09; 157.13