Current through Register Vol. 48, No. 12, March 22, 2024
a) Drift or Earth Cover Less Than 30 Feet in
Thickness
1) The well casing shall extend to a
depth of at least 40 feet below finished ground surface. The diameter of the
drill hole shall be a minimum of 3 inches greater than the outer diameter of
the casing or coupling, whichever is greater. The annular space shall be
pressure grouted as provided for in Section
920.90(h).
If plastic casing is installed, it shall be installed in accordance with
Section
920.90(g).
(See Illustration D.)
2) If a well
is drilled to obtain water below the upper bedrock formation, it shall comply
with subsection (a)(1) and the well casing shall be seated firmly in rock. When
a liner is installed through the casing, the annular space between the casing
and the liner shall be pressure grouted in accordance with Section
920.90(h).
If the upper bedrock formation is a water-bearing formation, the liner shall be
installed in accordance with Section
920.40(c).
b) Drift or Earth Cover Over 30
Feet in Thickness
1) When an oversized drill
hole is constructed for the installation of the casing and the annular space is
to be grouted through a tremie pipe installed in the annular space, the
diameter of the drill hole shall be a minimum of 3 inches greater than the
outer diameter of the casing or coupling, whichever is greater. After the
casing is installed, the annular space shall be grouted as provided for in
Section
920.90(h).
The annular space shall be grouted from the bottom of the casing to ground
level. The tremie pipe shall be installed to the bottom of the annular space.
No device shall be installed to prevent the tremie pipe from being installed
into the annular space or to prevent the grout from filling the annular space.
(See Illustration E.)
2) When grout
is pumped into the annular space through the inside of the casing, the diameter
of the drill hole shall be a minimum of 2 inches greater than the outer
diameter of the casing or coupling, whichever is greater. The entire length of
casing shall be grouted as provided in Section
920.90(h).
If plastic well casing is installed, it shall be installed as required in
Section
920.90(g).
3) When the casing is installed by
mechanically driving the casing, an oversized hole shall be constructed to a
depth of at least 10 but not more than 20 feet to allow removal of the drive
nipple and installation of a joint of casing. While the casing is being driven,
the bottom of the oversized hole shall be filled with granulated bentonite or
natural clay mixture. After the casing is installed, either the annular space
that exists around the well casing shall be grouted as required in Section
920.90(h)
or, when the diameter of the oversized hole is a minimum of 3 inches greater
than the outer diameter of the casing or coupling, whichever is greater, the
annular space that exists around the well casing can be filled with bentonite
or natural clay. (See Illustration F.)
c) Flowing Artesian Well. A well that is
constructed in a location where flowing artesian conditions are encountered or
expected to occur shall be grouted to protect the artesian aquifer, prevent
erosion of overlying geologic materials, and confine the flow to within the
casing. Initial drilling operations shall extend into but not through the
formation confining the water. The casing shall be installed and the annular
opening between drill hole and casing shall be pressure grouted in accordance
with Section
920.90(h).
If plastic casing is installed, it shall be installed in accordance with
Section
920.90(g).
The hole shall then be extended into the artesian formation. Flow control from
the well shall be provided by valved pipe connections, watertight pump
connections, or receiving reservoirs set at an altitude corresponding to the
artesian head. The flowing well discharge control shall be provided to conserve
groundwater and to prevent the loss of artesian head by preventing or reducing
continuous discharges. A flow discharge pipe, where installed, shall not be
directly connected to a sewer or other source of contamination.