Current through Register Vol. 49, No. 13, September 23, 2024
Subpart 1.
General construction.
A temporarily sealed exploratory boring from which
groundwater flows above the established ground surface without pumping and
which does not require special construction under subpart 2 must be constructed
to prevent erosion of the aquifer and confining layer. Casing must be installed
into the flowing aquifer to prevent water flowing up the outside of the casing
by either:
A. driving steel casing
into the flowing aquifer according to part 4727.0980, subpart 6; or
B. grouting the annular space surrounding the
casing with neat cement grout according to part 4727.0980, subpart 3.
Subp. 2.
Special
construction required.
A temporarily sealed exploratory boring must be constructed
according to subpart 3 when:
A. the
artesian flow rate at the established ground surface is greater than 70 gallons
per minute;
B. the artesian
pressure at the established ground surface exceeds ten pounds per square inch;
or
C. the commissioner designates
an area where the use of standard construction techniques have resulted in
uncontrolled flows or where hydrogeologic conditions such as eroded or unstable
confining layers require special construction to successfully complete an
exploratory boring and confine the artesian pressure.
Subp. 3.
Special construction
standards.
A temporarily sealed exploratory boring requiring special
construction under subpart 2 must be constructed by:
A. installing an outer steel casing into, but
not penetrating the entire thickness of, the confining layer overlying the
flowing aquifer by:
(1) driving steel casing
according to part 4727.0980, subpart 6; or
(2) drilling a bore hole a minimum of 3.25
inches larger than the outside diameter of the casing or couplings, whichever
is larger, installing steel casing into the confining layer, and pumping neat
cement grout into the annular space surrounding the casing from the bottom of
the casing to the established ground surface;
B. drilling through the confining layer into
the aquifer;
C. installing an inner
casing, which is 3.25 inches smaller than the bore hole, into the aquifer;
and
D. grouting the annular space
surrounding the inner casing with neat cement grout according to part
4727.0980, subpart 3.
Subp.
4.
Flow control.
A temporarily sealed flowing exploratory boring must be
provided with flow control capable of stopping all flow.
Statutory Authority: MS s
103I.101
