Current through Register Vol. 49, No. 13, September 23, 2024
Subpart 1.
Grouting materials.
The following grout materials as listed in part 4725.0100 are
approved for filling an annular space between unconsolidated material or
bedrock and a casing:
A. neat-cement
grout, except that rapid setting cement must not be used with plastic
casing;
B. cement-sand grout;
and
C. bentonite grout when used in
unconsolidated materials.
Subp.
2.
Grouting requirements and methods.
The following general requirements apply to the grouting of
wells and borings.
A. Grouting must
start immediately on completion of drilling and be completed before placing a
well or boring in service.
B. The
annular space to be grouted must be protected from collapse and the
introduction of materials other than grout.
C. A steel plate, or a nontoxic metal,
rubber, or plastic grout basket may be attached to the casing within ten feet
of the bottom. Wood, burlap, or other organic material must not be
used.
D. Grout must be pumped under
pressure into the annular space from the bottom up to the established ground
surface or base of the pitless adapter or unit. Grout must be pumped through
the casing or through a tremie pipe placed within ten feet of the bottom of the
space to be grouted. The tremie pipe may be retracted as grouting proceeds;
however, the bottom of the tremie pipe must remain submerged in grout while
grouting.
E. Grout flowing out of
the annular space at the surface must meet the minimum specifications and
densities in this chapter before grouting may stop.
F. Dumping of grout is not allowed except
when the depth of the space to be grouted is less than ten feet.
Subp. 2a.
Wait on
cement.
Neat-cement grout or cement-sand grout must be allowed to set
a minimum of 24 hours. Rapid setting cement must be allowed to set a minimum of
12 hours. Drilling, development, or pump operation is prohibited during the
time the cement is setting.
Subp.
3.
Grouting depth requirement.
When constructing a well or boring with a method such as mud
or air rotary, auger, or jetting that creates an open annular space or drills a
bore hole larger than the casing or casing couplings outside diameter, a
grouting material specified in subpart 1 and the grouting methods specified in
subpart 2 must be used to fill the annular space between the casing and the
bore hole.
A. If the depth of the
casing is 50 feet or less, the grout must extend from the bottom of the casing,
top of the bentonite seal as specified in subpart 8, or top of the gravel pack,
to the established ground surface, or the base of the pitless adapter or
unit.
B. If the depth of the casing
is more than 50 feet, the annular space below 50 feet must be filled with
grout, except that the portion of the well or boring in an unconsolidated
formation below 50 feet in depth may be filled with cuttings. The cuttings must
be placed without bridging, and must be the unconsolidated materials taken from
the bore hole. The annular space above 50 feet must be filled from:
(1) a depth of at least 50 feet to the
established ground surface or the base of a pitless adapter or unit;
or
(2) the top of the bentonite
seal as specified in subpart 8 or the top of the gravel pack to the established
ground surface or the base of a pitless adapter or unit.
Subp. 4.
Grouting between
casings.
The annular space between an inner and outer casing must be
filled with neat-cement grout or cement-sand grout according to subpart
2.
Subp. 5.
Driving
casing.
When driving casing in an unconsolidated formation, a
cone-shaped depression or temporary outer casing filled with bentonite grout,
bentonite powder, or granular bentonite must be maintained around the outside
of the casing. The bottom of driven casing, except for a drive-point, temporary
casing, or outer casing that has a neat-cement or cement-sand grouted inner
casing must be equipped with a drive shoe in accordance with part 4725.2250,
subpart 15. Casing may only be driven through:
A. an unconsolidated formation;
B. sandstone bedrock including the St. Peter,
Jordan, Franconia, Ironton-Galesville, Mt. Simon, Hinckley, or Fond du Lac
formations;
C. ten feet or less of
limestone or dolomite bedrock including the Cedar Valley through Galena groups,
the Platteville formation, or the Prairie du Chien group;
D. ten feet or less of the St. Lawrence or
Eau Claire confining layers; and
E.
two feet or less of the Decorah or Glenwood confining layers.
Subp. 6.
Sealing bore hole
below screen.
If a bore hole extends more than ten feet below the bottom of
a screen, the bore hole must be filled with grout from the bottom of the bore
hole to within ten feet or less of the screen.
Subp. 7.
Grouting in bedrock.
The additional requirements in items A to C apply to grouting
a well or boring in bedrock.
A. When
bedrock is encountered in the construction of a well or boring, the casing must
be equipped with a drive shoe driven firmly into stable bedrock or the casing
must be grouted with neat-cement grout, or cement-sand grout from the bottom of
the casing to the top of the bedrock.
B. When the casing of a well or boring
extends more than ten feet into bedrock, or extends through any portion of a
bedrock confining layer, the casing must be installed in a bore hole 3.0 inches
larger, or 3.5 inches larger for casings deeper than 100 feet and larger than
12 inches inside diameter, than the outside diameter of the casing or
couplings, whichever is larger, and the annular space in bedrock must be
grouted with neat-cement grout or cement-sand grout, except that steel casing
may be driven more than ten feet in a sandstone formation.
C. If a cavern more than twice the diameter
of the bore hole exists or the grout level fails to rise after insertion of
either more than one cubic yard of grout or the quantity of grout necessary to
fill ten vertical feet of hole, then the following grouting materials and
methods may also be used in the portions where the conditions exist:
(1) pouring of a mixture of gravel or stone
aggregate not larger than one-half inch in diameter while simultaneously
pumping neat-cement grout or cement-sand grout through a tremie pipe in a ratio
not to exceed five parts aggregate to one part grout;
(2) pumping a mixture of gravel or stone
aggregate not larger than one-half inch in diameter and cement-sand grout or
neat-cement grout in a ratio not to exceed five parts gravel or aggregate to
one part Portland cement; or
(3)
pumping of alternate, equal thickness layers of cement-sand grout or
neat-cement grout and pouring gravel or stone aggregate not larger than
one-half inch in diameter. Individual layers of aggregate must not exceed ten
feet in thickness. Aggregate must not be emplaced in a confining layer.
Neat-cement grout or cement-sand grout must be pumped through
the casing or through a tremie pipe. The aggregate must be poured into the bore
hole at a rate that prevents bridging.
Subp. 8.
Bentonite seal between gravel
pack and grout.
A layer of bentonite pellets, bentonite chips, or granular
bentonite not to exceed five feet in thickness is allowed between a gravel pack
and grout. The bentonite pellets, bentonite chips, or granular bentonite must
not extend into a confining layer or extend more than ten feet above the static
water level, and must be poured without voids or bridging. A tremie pipe must
be inserted to within ten feet of the top of the pellets, chips, or granular
bentonite, and the annular space grouted to the established ground surface or
base of the pitless unit or adapter.
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
