Current through Vol. 41, No. 13, March 15, 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.
