(1) The
following special sealing methods may be required in situations where different
techniques are necessary to protect aquifers.
(2) When permanent surface
casing is installed, the well bore shall have a diameter of at least 3 inches
greater than the surface casing for the introduction of sealing materials. A
watertight seal shall be installed at the top of the gravel pack between the
permanent surface and production casing. Sealing procedures and installation of
gravel fill pipes are substantially the same as in ARM 36.21.659 above. If a
temporary casing is used to maintain the oversized drill hole, the annular
space to be sealed under conditions of ARM 36.21.659 and 36.21.660 shall be
kept full with cement grout or bentonite clay grout as the temporary casing is
withdrawn (see Figure 4B at the end of this sub-chapter) .
(3) If a clay layer or other formation of low permeability is not encountered before reaching the top of the
water-bearing zone, the upper drill hole and unperforated production casing
shall extend to a minimum depth of 18 feet below land surface. Sealing
procedures, installation of gravel fill pipes and temporary casing are
substantially the same as in ARM 36.21.659 and 36.21.660.