20. Where a groundwater withdrawal facility is plugged, the plugging must meet the following conditions:
(1) a material not likely to degrade the quality of the groundwater must be used;
(2) the well casing must be exposed to a depth of at least 1 m below the surface of the ground;
(3) the well casing must be cut off at the bottom of the excavation;
(4) the portion of the casing open to the aquifer must be filled with clean sand;
(5) the remaining portion of the casing must be filled with pure bentonite or a cement bentonite mix;
(6) a concrete slab must be placed over the end of the casing;
(7) the excavation must be filled using the soil initially excavated.
This section also applies to an observation well.