Current through Register Vol. 47, No. 17, September 10, 2024
8.1
Type A Geothermal Well (defined in Rule 4.2.28)- is generally constructed in
one of three configurations. For purposes of these Rules, the three
configurations are designated as a Type A-OS well (open system), a Type A-CLH
well (horizontal closed-loop system), and a Type A-CLV well (vertical
closed-loop system). Definitions for the geothermal well types are provided in
Rule 4.
8.2 Type A-OS Well
Construction- A Type A-OS well is constructed to withdraw a geothermal fluid
from a subsurface aquifer or reservoir for extraction and utilization of the
thermal attributes of the produced fluid. Therefore, a Type A-OS well is
considered to be a "well" as defined in Section
37-91-102(16)(a),
C.R.S. (2003), and its construction is under the jurisdiction and authority of
the State Board of Examiners of Water Well Construction and Pump Installation
Contractors.
8.2.1 Licensed Contractor
Required- All well construction, repair, modification or plugging and all
installation, repair or modification of producing equipment for a Type A-OS
well shall be performed by a licensed contractor, a direct employee of a
licensed contractor, or a person under the continuous on-site supervision of a
licensed contractor having a valid license issued by the State Board of
Examiners of Water Well Construction and Pump Installation
Contractors.
8.2.2 Compliance with
Water Well Construction Rules- Well construction and the installation of
production equipment in a Type A-OS well shall conform, at a minimum, with the
well construction, pump installation, well plugging, and disinfection standards
of the Water Well Construction Rules, 2 CCR 402-2, and shall comply with any
additional standards specifically established by these Geothermal Rules or
specified in the conditions of approval stated on a valid geothermal well
permit issued by the State Engineer.
8.2.3 Well Head and Protection Equipment-
When temperatures greater than one hundred and twenty (120) degrees Fahrenheit
or flowing conditions are encountered during the construction of a Type A-OS
well, the owner or operator shall install and maintain in good working order
blowout preventers and equipment to prevent the uncontrolled flow of fluid, and
shall provide protective equipment for on-site personnel.
8.3 Construction Materials for Type A-CLH and
Type A-CLV Wells- Construction materials to be buried below the ground surface
or submerged in water for the construction of a loop field for a geoexchange
system shall, at a minimum, meet the standards of these Rules. Where geologic,
hydrologic, or thermal conditions require the use of materials exceeding the
standards of these Rules, the certified individual shall be responsible for
ensuring that the proper materials are used to protect the public health,
ground water resources, and the environment.
8.3.1 The circulating pipes installed below
ground level shall consist of high density polyethylene (HDPE) pipe meeting the
standards specified in Section 1 of the International Ground Source Heat Pump
Association, Oklahoma State University, publication "Closed-Loop/Geothermal
Heat Pump Systems: Design and Installation Standards 2000", or vinyl coated
copper tubing specifically designed for use in geothermal applications.
8.3.1.1 All buried HDPE connections, joints
and fittings shall be heat fused in accordance with the manufacturer's
specifications. Copper tubing shall be brazed utilizing the nitrogen brazing
technique or as otherwise specified by the manufacturer. Testing shall be
accomplished as specified in Rule 8.6.
8.3.1.2 Threaded connections or clamps shall
not be used below ground level on any HDPE or copper tubing unless the joint is
a service outlet that can be visually observed and inspected.
8.3.2 Grout materials approved by
the State Engineer include the following:
a.
neat cement;
b. cement-bentonite
mixtures;
c. cement-fly ash
mixtures;
d. high solids bentonite
(at least thirty (30) percent solids by weight); and,
e. thermally enhanced grouts (cement-sand or
bentonite-sand).
8.3.2.1 All grout
materials shall be mixed by the method and in the proportions specified by the
manufacturer. Excess water shall not be used in the preparation of grout
materials. The type and amount (by weight) of each constituent used in the
grout mixture shall be reported on a form prescribed by the State
Engineer.
8.3.3 Only a
non-toxic fluid shall be used in a Type A-CLH or Type A-CLV well. Fluids
approved by the State Engineer are:
a. potable
water;
b. aqueous solution of
sodium or calcium chloride;
c.
aqueous solution of potassium acetate containing less than one (1) percent
corrosion inhibitors;
d. food grade
propylene glycol;
e. methanol-water
solution up to twenty (20) percent methanol by volume;
f. ethanol-water solution up to twenty (20)
percent ethanol by volume; and,
g.
R-22 refrigerant is approved for use in a closed-loop direct exchange (DX)
system.
Use of any fluid or vapor not specified in this Rule requires
a variance from the State Engineer prior to its use (see Rule 14).
8.4 Type
A-CLH Well Construction (horizontal closed-loop)- Installation shall be in
accordance with manufacturer and designer specifications and must be performed
by or under the supervision of a certified individual. A Type A-CLH well need
not be constructed by or under the supervision of a water well construction
contractor licensed by the State Board of Examiners of Water Well Construction
and Pump Installation Contractors.
8.4.1
Trenches or excavations for horizontal pipe/tubing loops shall be back-filled
with materials no more permeable than the surrounding soil. Back-fill materials
shall be clean and free of contaminants and shall be adequately compacted to
minimize the potential for forming a depression or sump that would allow
infiltration of surface run-off or other fluids.
8.4.2 A Type A-CLH well with loops designed
for submergence in a body of water shall be equipped and tested in accordance
with Rules 8.5 and 8.6 . The certified individual shall take all necessary
precautions to prevent leakage or spillage of the circulating fluid into the
surface water reservoir that may adversely affect human health or the
environment, and shall be equipped to contain any such leak or spill that may
occur.
8.5 Type A-CLV
Well Construction (vertical closed-loop)- The well shall be constructed in such
a manner as to confine underground fluids in the aquifers in which they are
encountered and to prevent contamination of surface or ground water resources.
Installation shall be in accordance with manufacturer and designer
specifications and must be performed by or under the supervision of a certified
individual. A Type A-CLV well need not be constructed by or under the
supervision of a water well construction contractor licensed by the State Board
of Examiners of Water Well Construction and Pump Installation Contractors.
8.5.1 Boreholes drilled for a Type A-CLV well
shall be of sufficient diameter so that there is not less than one (1) inch of
space between the tubing or piping installed and the borehole wall to ensure
proper grouting and sealing.
8.5.2
Boreholes for a Type A-CLV well shall be entirely filled with only approved
grout materials. Grout shall be placed as a slurry through a tremie pipe and
shall be placed in one continuous operation from the bottom of the hole upward.
All grout shall be pumped and shall not be poured from the surface. Drilling
fluids, drill cuttings or shale slurries are not grout materials and shall not
be used to backfill boreholes constructed for a Type A-CLV well.
8.5.3 Grout shall be placed as soon as
possible after installation of the pipe or tubing loop to prevent collapse of
the borehole and the potential for an incomplete grout seal. Should such
collapse occur, the pipe or tubing shall be removed, the borehole cleaned or
re-drilled, and the pipe or tubing inspected and re-tested prior to
installation. All reasonable attempts shall be made to remove the pipe from
damaged boreholes. If the remaining pipe cannot be removed without damage to
the bulk of the pipe in place, the loop and borehole shall be plugged pursuant
to Rule 11.5.
8.5.4 In boreholes
that penetrate a confining layer or layers, a minimum of forty (40) feet of
cement grout shall be placed opposite each confining layer between ground water
aquifers encountered in each borehole.
8.6 Testing of a Type A-CLH or Type A-CLV
Well- All pipe/tubing, connections, joints and fittings which will be installed
underground or submerged in water shall be tested at the designed working
pressure prior to installation and visually inspected for leaks. Once
installed, the underground or submerged portion of the closed loop shall be
pressure tested at one hundred and fifty (150) percent of the designed working
pressure for a minimum of thirty (30) minutes, and/or to the pipe
manufacturer's testing specifications, whichever is greater. Pressures shall
not decline by more than ten (10) percent during the test.
8.7 All geoexchange systems shall be equipped
with a pressure shutdown switch.
8.8 Limits of a Type A Geothermal Well
Exceeded- All well construction operations shall be suspended and the State
Engineer shall be notified immediately when geothermal fluid temperature
greater than two hundred and twelve (212) degrees Fahrenheit is encountered
during the construction of a Type A geothermal well. No further construction
shall be allowed unless a permit for a Type B geothermal well has been approved
by the State Engineer and the well complies with the construction standards for
a Type B well.
