Current through Vol. 42, No. 1, September 16, 2024
(a)
General requirements.
(1)
Applicability of minimum
standards. The minimum standards set forth herein apply to all heat
exchange wells as defined in
785:35-1-2, whether constructed
by a person having a valid license or by any other person. Minimum standards
shall include regulation of the drilling of the borehole, installation of
casing, installation of heat loop pipe, grouting of the well, and installation
of the heat loop pipe up to the connection of the heat loop pipe to the
facility circulation equipment .
(2)
Prohibition against other
uses. Heat exchange wells shall not be used for any purpose other than
heat exchange. After completion, heat exchange wells shall not be converted to
any other type of well unless written approval is obtained from the Board. The
licensee shall ensure that the heat exchange well is constructed according to
the rules.
(3)
Maximum
protection of groundwater required. Construction of heat exchange wells
shall provide maximum protection to the groundwater from surface contaminants
and movement and migration of water from one zone or aquifer to
another.
(b)
Location of heat exchange wells.
(1) A vertical heat exchange well shall be
located on a site so that surface water will not pool or pond around or within
ten (10) feet of the heat exchange well location.
(2) Placement of a heat exchange well must
meet or exceed standards as set forth by section
785:35-7-1(b)
relating to location requirements for groundwater wells except as set forth in
paragraph 3 of this subsection.
(3) If not prohibited by the owner of the
well or other federal or state agency requirements, heat exchange wells may be
located closer to a possible source of pollution than the minimum distances
specified in Section
785:35-7-1(b) if
all of the following conditions are met:
(A)
The possible pollution source is not a wastewater lagoon, septic tank,
absorption field, or aerobic sprinkler system .
(B) The well annulus is completely sealed as
described in paragraph 7 of subsection (c) of this section.
(c)
Construction
standards for vertical closed-loop exchange wells. Vertical closed-loop
heat exchange wells shall be constructed in accordance with this subsection.
Site specific conditions shall be assessed to determine the best method and
materials to be used for grouting the well annulus to provide protection of the
groundwater per paragraph 3 of subsection (a) . In addition, but not as an
alternative, to the requirements stated in (1) through (8) of this subsection,
methods and materials for construction of heat exchange wells that meet or
exceed recommendations specified in "Grouting for Vertical Geothermal Heat Pump
Systems Engineering Design and Field Procedures Manual", International Ground
Source Heat Pump Association, Oklahoma State University, 2015, and in
"ANSI/CSA/IGSHPA C448 Series-16, Design and installation of ground source heat
pump systems for commercial and residential buildings", American National
Standards Institute, 2016, may be used for construction of vertical closed-loop
heat exchange wells.
(1)
Casing
material. If permanent casing is needed in a vertical closed-loop heat
exchange well, it must meet standards set out in Section
785:35-7-1 for steel and for
plastic.
(2)
Heat exchange
loop material. The material used to construct the heat exchange loop
must meet or exceed standards set forth by Clause 5.4 of ANSI/CSA/IGSHPA
C448.0.
(3)
Connecting
closed-loop pipe. All pipe joints and fittings installed and buried
shall meet or exceed standards set forth by Clause 5.4 of ANSI/CSA/IGSHPA
C448.0 . Glued or clamped joints shall not be used below ground unless the
joint or connection serves as a service outlet and the joint or connection is
not covered with earth material. Joints must not leak after assembly. All
indoor piping and fittings should meet or exceed standards set forth by Clause
5.5 of ANSI/CSA/IGSHPA C448.0.
(4)
Heat transfer fluid. Approved fluids for use inside the heat
exchange loop include potable water, food-grade or USP-grade propylene glycol,
and solutions in which remediation of leaks would occur through dissipation. A
release of the fluid to the groundwater must not violate Oklahoma Water Quality
Standards set forth in Chapter 45, OAC 785.
(5)
Borehole specifications.
(A)
Borehole diameter. The
borehole for vertical closed-loop heat exchange wells must have a sufficient
diameter to accommodate the heat exchange loop u-bend assembly, tremie pipe,
and placement of grout to surround all heat exchange loop pipe.
(B)
Exploratory borehole. The
first borehole drilled for the vertical closed-loop heat exchange system shall
be considered an exploratory borehole. A subsequent borehole may also be
considered an exploratory borehole if the well driller encounters subsurface
conditions that include, but are not limited to, lost circulation conditions,
hydrocarbons or hazardous gases, and changes in groundwater chemistry.
(C)
Lost circulation
conditions. If caves or large fractures are encountered in drilling the
exploratory borehole or any subsequent borehole, grouting may not be possible
and the Board must pre-approve completion of the vertical closed-loop heat
exchange system in such conditions based on plans to bridge and seal zones of
lost circulation.
(D)
Hydrocarbons and hazardous gases. If hazardous gases or
hydrocarbons are observed in drilling the exploratory borehole or any
subsequent borehole, the Board must be notified immediately. Completion of the
vertical closed-loop heat exchange system shall be prohibited without Board
approval.
(E)
Groundwater
chemistry. Chemistry of groundwater encountered in drilling the
exploratory borehole, or any subsequent borehole shall be used to inform grout
selection. Instructions provided by the grout manufacturer must be followed to
provide protection of the groundwater per paragraph 3 of subsection (c) of this
section. The grout manufacturer shall be consulted as required.
(6)
Grouting of vertical
heat exchange wells. Grouting and filling the annulus of a heat exchange
well must be completed immediately after the well is drilled to avoid cave-in
of the uncased hole.
(7)
Grouting methods and materials for vertical closed-loop heat exchange
wells. Grouting methods for vertical closed-loop heat exchange wells
shall meet or exceed standards provided by Clause 5.8 of ANSI/CSA/IGSHPA C448.0
and Clause 6.3 of ANSI/CSA/IGSHPA C448.3 except where standards set forth by
this Section provide exceptions. The following methods and materials are
approved for grouting the annulus of vertical closed-loop heat exchange wells,
provided that standards set forth by 785:35-7-1.1(c)(5)(E) shall also apply:
(A) A grout seal shall be installed from the
total depth of the borehole up to the connecting trench and must be composed of
one of the following materials:
(i) Portland
cement;
(ii) Sand-cement mixed at
a ratio of not more than 188 pounds of sand to one 94-pound sack of Portland
cement and seven (7) gallons of water;
(iii) High solids bentonite grout with a
minimum solids content of 20 percent by weight. Clean silica sand may be added
to the slurry;
(iv) Bentonite
pellets or chips; or
(v) Approved
thermally enhanced grouts and non-cement grouts which meet standards set forth
by Clause 5.8 of ANSI/CSA/IGSHPA C448.0 and Clause 6.3 of ANSI/CSA/IGSHPA
C448.3
(B) Bentonite
chip or pellet fill material installed shall be hydrated immediately after
installation if installed in the unsaturated zone.
(C) When non-slurry sealing materials are
used, only chipped or pelletized sodium bentonite varieties that are designed
to fall through standing water are acceptable when sealing the annulus of a
well that is below the water level in the saturated zone. The borehole shall be
flushed clean of all drilling mud and debris left over from the drilling
operation so that the bentonite products designed for this type of installation
will gravity feed without obstruction. Material shall be introduced in a manner
to prevent bridging of the materials in the borehole annulus. A measuring
device such as a tagline shall be used to measure and document placement of the
materials installed.
(D) Slurry
mixes of bentonite grout or Portland cement shall be installed by pumping
through a tremie pipe in a continuous operation using a positive displacement
method. Polymer additives designed to retard swelling are acceptable for use
with the bentonite grout or Portland cement. The tremie pipe will extend the
full depth of the borehole before pumping begins. The borehole diameter shall
be of adequate size to allow proper placement of materials using this method.
Slurry volume used must equal the annulus volume of the borehole.
(8)
Concentric tube heat
exchangers. Concentric tube heat exchangers that meet or exceed the
requirements of this Section are approved.
(d)
Construction standards for
open-loop and return heat exchange wells.
(1) Groundwater wells and water return wells
used in open-loop heat exchange must meet the minimum construction standards
set forth in Section
785:35-7-1 relating to
groundwater.
(2) Groundwater used
in the open loop heat exchange system must remain untreated and be returned to
the same aquifer from which the groundwater was withdrawn.
(e)
Construction standards
for horizontal closed-loop heat exchange systems. Horizontal closed-loop
heat exchange systems constructed by trenching or digging are exempt from
grouting requirements, provided that no part of the horizontal loop is
constructed at or below the highest anticipated groundwater level. Horizontal
closed-loop heat exchange systems constructed by boring or drilling must be
grouted according to standards set forth by paragraph 7 of subsection (c) of
this Section. All other construction for horizontal closed-loop heat exchange
systems shall meet or exceed standards set forth by subsection (c) of this
Section.
Added at 20 Ok Reg 2608,
eff 7-11-03; Amended at 21 Ok Reg 3169, eff 7-25-03 through 7-14-04
(emergency)1; Amended at 21 Ok Reg 3180, eff
9-13-04; Amended at 23 Ok Reg 3078, eff 7-27-06; Amended at 25 Ok Reg 1444, eff
5-27-08
1This emergency action expired
without being superseded by a permanent action. Upon expiration of an emergency
amendatory action, the last prior permanent text is reinstated. Therefore, on
7-15-04 (after the expiration of the emergency action), the text of section
785:35-7-1.1 reverted back to the permanent text that became eff 7-11-03, as
was last published in the 2003 OAC Supplement, and remained as such until
amended again by permanent action on
9-13-04.
