Current through Register Vol. 49, No. 13, September 23, 2024
Subpart 1.
Permanent sealing
required.
The explorer must permanently seal an exploratory boring that
is not temporarily sealed or that is required to be permanently sealed under
part 4727.1100, subpart 2.
Subp.
2.
Sealing with grout.
An exploratory boring must be permanently sealed by filling
the boring, including any open annular space, with grout. The grout must be
pumped through a tremie pipe or the casing from the bottom of the annular space
or boring upward to within two feet of the established ground surface. The
bottom of the tremie pipe must remain submerged in grout while grouting.
Subp. 3.
Removal of
obstruction, debris.
Materials, debris, and obstructions that may interfere with
permanent sealing must be removed from the exploratory boring. Casing may be
salvaged, except casing that has been cemented in place.
Subp. 4.
Grouting an annular
space.
Open annular space surrounding a casing must be grouted
by:
A. filling the annular space with
grout according to subpart 2;
B.
removing the casing and filling the boring with grout. If casing is to be
removed from a collapsing formation, grout must be inserted so the bottom of
the casing remains submerged in grout;
C. perforating the casing with a minimum of
one 1/2-square-inch hole in each foot of casing and forcing grout through the
perforations; or
D. ripping a
minimum of five feet of casing for every 20 feet of casing and forcing grout
through the ripped casing, except that casing must be ripped through the entire
length of a confining layer.
Subp.
5.
Additional sealing requirements; unconsolidated
materials.
The additional requirements in items A and B apply to the
permanent sealing of a boring in unconsolidated materials.
A. The portion of a boring in unconsolidated
material must be filled with high solids bentonite grout or neat cement grout.
Concrete grout is approved for grouting only in the dry portion of the hole.
The grout must be pumped through a tremie pipe or the casing from the bottom of
the boring upward to within two feet of the established ground
surface.
B. The portion of a boring
in kaolin clay may be sealed with kaolin clay in addition to the grout
materials in item A. Up to 20 percent water by volume may be added to the
kaolin clay to allow for placement. The kaolin clay, or kaolin clay and water
mixture, must be inserted through a tremie pipe or the casing.
Subp. 6.
Additional sealing
requirements; bedrock.
The additional requirements in items A and B apply to the
permanent sealing of a boring in bedrock.
A. The portion of a boring in bedrock must be
filled and sealed through the entire interval of the bedrock with neat cement
grout, except that:
(1) concrete grout may be
used above the water level;
(2) in
that portion of igneous or metamorphic bedrock that does not contain
water-bearing fractures or voids and that is at least 250 feet below the top of
the igneous or metamorphic bedrock, a plug or packer may be installed. The bore
hole above the packer must be filled with grout and the bore hole below the
packer may be left without grout; and
(3) if the grout level fails to rise after
insertion of more than one cubic yard of grout or the quantity of grout
necessary to fill ten vertical feet of hole, or if a cavity more than twice the
diameter of the bore hole exists, then the following grouting materials and
methods may be used in the portions where the conditions exist:
(a) pouring a mixture of gravel or stone
aggregate not larger than one-half inch in diameter while simultaneously
pumping neat cement grout or concrete grout in a ratio not to exceed five parts
aggregate to one part grout;
(b)
pumping a mixture of gravel or stone aggregate not larger than one-half inch in
diameter and concrete grout or neat cement grout in a ratio not to exceed five
parts gravel to one part Portland cement; or
(c) alternately pumping concrete or neat
cement grout and pouring gravel or stone aggregate not larger than one-half
inch in diameter in layers of equal thickness. Individual layers of aggregate
must not exceed ten feet in thickness. Aggregate must not be placed in a
confining layer.
B. Neat cement grout or concrete grout must
be pumped through the casing or a tremie pipe. The aggregate must be poured
into the bore hole at a rate that prevents bridging.
Subp. 7.
Sealing flowing boring.
An exploratory boring from which groundwater flows above the
established ground surface must be permanently sealed with neat cement grout.
The discharge from a flowing exploratory boring must be stopped and the boring
sealed according to this part.
Statutory Authority: MS s
103I.101