Section 0400-45-09-.17 - GEOTHERMAL WELL CONSTRUCTION STANDARDS FOR CLOSED LOOP GEOTHERMAL BOREHOLES(1) Location of Closed Loop Geothermal Boreholes(a) The construction of a closed loop geothermal borehole is prohibited at other than a safe distance from any potential source of contamination. The minimum safe distances shall apply for the sources listed below: Source of structure | Minimum Distances |
Sewer Line | 10 feet |
Septic Tanks | 25 feet |
Springs | 100 feet |
Septic Drain Fields | 25 feet |
Water Wells | 100 feet |
House to septic tank connection | 10 feet |
House to sewer line connection | 10 feet |
(2) Source of Drilling Water for Closed Loop Geothermal Boreholes(a) All water used in drilling and construction of a closed loop geothermal borehole shall be from a public water supply, water well or protected spring box.(b) Water used in the drilling or construction process shall be treated with enough chlorine product to retain a free chlorine residual of at least two (2) parts per million unless the water is obtained on site from a direct connection to a public supply equipped with a proper cross connection protection device.(c) Drilling fluids and additives shall be materials specified by the manufacturer for use in either water or geothermal well drilling or construction and approved by the Department.(d) During the course of drilling a closed loop geothermal borehole with air rotary equipment, a minimum of one gallon per minute (1) of water must be injected or added into the air stream unless the drill rig is equipped and uses a dust cyclone to control dust. The amount of water injected shall be sufficient to control dust and to keep the borehole cleaned out.(e) Petroleum based products or byproducts spilled or leaked from a drill rig in any quantity greater than one (1) quart shall be removed from the drilling area before the drill rig is removed from the borehole being constructed.(3) Grouting for Closed Loop Geothermal Boreholes(a) The entire borehole surrounding the closed loop shall be filled with a grout material approved by the Department. A cover from land surface to five (5) feet below land surface comprised of native soil material may be used in closed loop geothermal boreholes.(b) Grout in closed loop geothermal boreholes is to be composed of cement, a bentonite cement mixture, high solids sodium bentonite or other grout material approved by the Department. Thermal grout, Thermal Grout Lite and Mix 111 Grout are three specific type grouts approved by the board for the grouting and closure of closed loop geothermal boreholes.1. Cement grout shall be composed of Class A, Type I Portland Cement mixed with not more than six (6) gallons of clean water per bag (one cubic foot or 94 pounds) of cement with a density of 15 to 16 pounds per gallon, or to manufacturer's specifications.2. Bentonite-cement grout shall be composed of powdered bentonite (less than 5% by weight) mixed at not more that 8 gallons of water to the bag, with a density of 14 to 15 pounds per gallon, or to manufacturer's specifications.3. High solids sodium bentonite grout shall have minimum of 20% solids and be mixed per manufacturer's specifications with water and/or other required additives.(c) All grouting shall be accomplished using forced injection to emplace the grout. When emplacing the grouting material, the tremie pipe shall be lowered to the bottom of the zone to be grouted. The tremie pipe shall be kept full continuously from start to finish of the grouting procedure, with the discharge end of the tremie pipe being continuously submerged in the grout until the zone to be grouted is completely filled.(d) The driller shall take all steps necessary to maintain safety around the borehole until the closed loop is installed and grouted in the borehole. Each ungrouted borehole or loop shall have a protective cover, or sand bag placed over the open borehole. The closed loop u-bend or dropline pipe shall be placed into the borehole to its proper depth and grouted in place within five (5) days of drilling each borehole unless the u-bend dropline pipe has been installed to its maximum depth with a dedicated tremie pipeline. Each u-bend dropline pipe opening shall be taped or crimped or covered at land surface after installation of the loop. All Closed Loop Geothermal Boreholes shall be grouted in-place within fifteen (15) days of being drilled. (e) When high solids bentonite grouts are used, a cover at the land surface at least the width of the borehole made of suitable materials, as approved by the Department, such as native soils, gravel, sand or thermoplastic material sufficient to support the weight of normal foot traffic shall be used as a covering for each borehole.(f) Boreholes that encounter caves or large fractures below thirty (30) feet from land surface that prohibit the use of standard grouting procedures shall use one of the following materials to fill these intervals up to a maximum of thirty (30) feet in each well;1. Chipped or granular bentonite;2. Clean washed gravel 1/2 inch diameter or less;3. Clean washed coarse sand; and4. Liner casing shall consist of steel casing if the casing is permanently installed in the borehole(g) All drilled boreholes must be drilled to a minimum of four (4) inches in diameter or larger to allow for installation of the loop and tremi pipe unless prior approval has been granted by the Department. Well depths shall not exceed five hundred (500) feet unless prior approval has been granted by the Department.(h) Geothermal systems consisting of five (5) boreholes or greater shall not be located within well head protection areas unless prior approval has been granted by the Department in writing. The driller must contact the Department to determine if a site is located within a well head protection area designated by the Department. The Director may set any conditions deemed necessary to protect the well head protection area,(i) A licensed geothermal driller or loop installer may request a variance from the Director to convert an existing water well into a closed loop geothermal well. A geothermal report is required within sixty (60) days upon completion of conversion if approved by the Department. There is no Notice of Intent or fee required for this conversion. The Director may approve or disapprove any request for conversion and set additional conditions as deemed necessary by the Director to protect the ground water resource.(j) A licensed geothermal well driller may request a variance from the Department to convert a geothermal borehole at a geothermal system to a water well. A Notice of Intent fee and specific water well driller report for the converted well is required within sixty (60) days upon completion of converson if approved by the Department. The Department may approve or disapprove any request for conversion and set additional conditions as deemed necessary by the Department to protect the ground water resource.(4) Reporting of Closed Loop Geothermal Boreholes(a) A "Report of Well Driller" for a closed loop geothermal borehole system shall be submitted by the driller to the Department within sixty (60) days after the drilling or closure of the last closed loop borehole in the system at the site. A Report of Well Driller shall also be submitted for a closed loop geothermal test borehole if drilled on the site to determine geology or heat transfer characteristics within sixty (60) days after drilling the borehole. See also paragraph (14) of this rule for Notice of Intent requirements for drilling.(b) The report shall be true and accurate. Borehole footage shall be accurate to the nearest foot of measurement. The report shall include as a minimum the following accurate information about the system:1. Name and address of the person for whom the closed loop geothermal boreholes were drilled;2. The location of the system as denoted by county, street address and road name;3. The location of the system as denoted by latitude and longitudinal coordinates of the center of the system, a diagram of the closed loop geothermal boreholes, and identification of other wells on the property and the location of the septic tank, field lines or sewer lines on the property. The accuracy of the coordinates must be to the nearest second of the location;4. The date the last closed loop geothermal borehole was drilled at the system site and additional information as required by the Department;5. The licensed driller's name and contractor identification number, general specifications of the closed loop geothermal borehole such as depth, diameter, backfill and closed loop information;7. For systems with ten or less closed loop boreholes, the driller is required to provide a master plat to both the owner and Division of Water Resources of the location of each borehole. The plat shall include related distances from major buildings, septic tanks and field lines and sewer lines and be submitted with the Report of Well Driller within sixty (60) days upon completion of drilling of the last borehole on a given project. Site plans drawn up by a licensed engineer may be used if the driller is unable to provide a master plat;8. For systems with eleven or more boreholes. The driller is required to provide a master plat to the owner of the property. The plat shall include related distances from major buildings, septic tanks and field lines and sewer lines. The driller shall also submit a Report of Well Driller to the Division of Water Resources within sixty (60) days upon completion of drilling of the last borehole on a given project. Site plans drawn up by a licensed engineer may be used if the driller is unable to provide a master plat.(5) A geothermal driller license or closed loop installer license is required to install a closed loop dropline or u-bend loop in a closed loop geothermal borehole. In a closed-loop geothermal borehole, the material used to make up the heat-exchange loop that is placed in the ground or into a body of water must be composed of high-density polyethylene or other material approved by the Department. All closed loop material placed in the borehole must be installed and grouted within fifteen (15) days upon completion of drilling of each borehole. Each loop will be pressure tested to 100 pounds per square inch (psi) and maintain constant pressure for twenty (20) minutes before grouting and placement of loop into service. The entire system shall be free of leaks or pressure loss. (a) High Density Polyethylene Pipe. This pipe must be manufactured in accordance with dimensional specifications of ASTM D-2513 or ASTM F-714 and must have a minimum cell classification of PE345434C up to PE345464C when tested under ASTM D-3350 to be acceptable for use in closed-loop heat pump systems. No other pipe shall be used for closed loop installation unless approved by the Department.(6) Connecting Closed-Loop Pipe. The pipe must be thermally fused according to the pipe manufacturer's specifications and must not leak after assembly. No other connection method shall be used unless approved by the Department.(7) Heat Transfer Fluid. The fluid used inside the closed-loop assembly must be composed of:(a) Heat transfer fluids: 1. Pure glycerin solution-glycerin must be ninety-six and one-half (96.5%) United States pharmacopoeia grade;2. Food grade propylene glycol;3. Dipotassium phosphate;7. Other fluids as may be approved in advance by the Division.(b) It is the responsibility of the closed loop installer, driller, primary geothermal heat pump installer and owner to become familiar with the safe and proper use of these fluids and to take necessary precautions to ensure ground water protection.(8) Boreholes with closed loop u-bend material in the borehole shall have all heat transfer fluid removed from the closed loop before borehole abandonment. This fluid shall be disposed in accordance with manufacturers specifications. The closed loop u-bend material shall either be completely removed from the borehole before closure and the borehole closed in accordance with subparagraph (10)(a) of this rule or the loop shall be pumped full of cement grout or bentonite or other material approved by the Department. The driller shall denote on the geothermal well abandonment report how much grout or bentonite was used in sealing the closed loop or u-bend material. The upper portion of the borehole to five feet below land surface may be filled with compacted earth or same material to fill the closed loop.(9) The driller or person holding a license for well closure shall backfill and abandon any drilled closed loop borehole in accordance with subparagraph (10)(a) of this rule not intended for use within 15 days after the drill rig leaves the property. The driller shall take all steps necessary to maintain safety around the site until the closure process is completed. Prior to closing any such borehole the driller shall: (a) Check the entire depth of the borehole for obstructions that may interfere with sealing operations and remove them, and(b) Thoroughly chlorinate the borehole prior to sealing by the addition of sufficient quantities of liquid bleach or dry hypochlorite granules to produce a free chlorine residual of 25 parts per million (ppm).(10) Closed loop borehole plugging and abandonment shall be accomplished by a licensed driller by the following methods:(a) For closed loop boreholes without thermal transfer pipe, or closed loops installed, a cement grout or bentonite or other approved sealing material approved by the Department shall be placed in the borehole from two (2) feet below land surface to a minimum of twenty-five (25) feet below land surface. Native soil may be used to backfill the borehole from land surface to two feet below land surface or the driller may use cement or bentonite to land surface. The borehole twenty-five (25) feet below land surface shall be filled with either bentonite, cement grout, clean crushed stone one half inch in diameter or less, well cuttings, puddled clay, sand or combined mixture of any of these listed materials. Backfill shall remain level with land surface.(b) The grout material used in the plugging and abandonment of a closed loop borehole shall consist of a mixture of Portland Class A cement or quick setting cement in a ratio of not over six (6.0) gallons of water per ninety-four (94) pound sack of cement, or a high solids bentonite grout with a minimum of 20% solids and a weight of no less than nine and two tenths (9.2) pounds per gallon as measured by a standard mud balance or other type grout material approved by the Department. The use of bentonite, in chip or tablet form, ranging in size from one-quarter (1/4") inch to three-quarters (3/4) of an inch will be allowed as an alternate seal to slurry grouting. The bentonite shall be mixed and applied in accordance with the manufacturer's recommendations. The use of low solids bentonite drilling clay (designed for use as a drilling fluid to form a filter cake on the side walls of the borehole and to increase viscosity of water) is prohibited for use as a grout or sealing material except as an additive. If bentonite is used as a sealing material, only bentonite grout, bentonite tablets, or bentonite chips, approved by the National Sanitation Foundation (NSF) or American National Standards Institute (ANSI) certified parties as meeting NSF product standard 60 or 61 shall be approved by the Department as appropriate grouting or sealing material.(c) Placement of the backfill material shall be done in such a way that there are no bridges or gaps in the borehole. The top of the backfill material shall remain level with land surface.(11) Boreholes extending into more than one aquifer shall be filled and sealed in such a way that exchange of water from one aquifer to another is prevented.(12) The driller or person holding a license for well closure may submit a written petition for an alternative method of borehole abandonment. Any alternate method of filling and sealing a well shall be submitted to the Director for review and written approval prior to sealing a borehole by such method. In an emergency or in exceptional instances, the Department will respond to a verbal request provided the applicant submits a written application within ten (10) days of the verbal application.(13) Every licensed driller or person holding a license for well closure, within sixty (60) days of abandonment of a closed loop borehole, shall submit a report of the abandonment of the borehole to the Department. The well abandonment report shall be made on a form provided by the Department or a reasonable facsimile approved by the Department. The report shall include the same information as required on the completion report and shall include specific information on how the borehole was closed and the placement and type of backfill placed in the borehole. The abandonment report shall be signed by the licensed driller or person holding a license for well closure.(14) Notice of Intent required to drill geothermal closed loop well system. (a) A Notice of Intent to drill a closed loop geothermal borehole system must be submitted by the property owner or the licensed well driller to the Director in the manner prescribed by the Department, prior to commencement of drilling a water well or a closed loop geothermal borehole system in Tennessee. The licensed driller is required to have sufficient documentation that a Notice of Intent was submitted to the Division of Water Resources before beginning operations at a drill site. Sufficient documentation for a Notice of Intent being filed may include one of the following:1. Fee receipt of the Notice of Intent.2. Confirmation number of the Notice of Intent or other approved format approved by the Director and issued by the Department.(b) The Notice of Intent fee or copy of the receipt for a Notice of Intent fee shall accompany the submission of the driller's report. No well or borehole shall be drilled unless the driller has documentation that a Notice of Intent has been filed. All well reports shall be submitted with documentation of the Notice of Intent fee being paid. Documentation of the fee being paid shall consist of the receipt originating from a Notice of Intent or money collected and enclosed with the original driller's report by the driller for the Notice of Intent. A Notice of Intent and fee is not required for well closure, deepening or reworking any closed loop geothermal borehole. The amount of the Notice of Intent fee shall be reviewed by the Department at least every five (5) years and shall currently be scheduled as follows: 1. | Geothermal well system (closed loop), ten boreholes or less | $ 75 |
2. | Geothermal well system (closed loop) eleven to fifty boreholes | $150 |
3. | Geothermal well system (closed loop) fifty-one boreholes or greater | $500 |
4. | Closed Loop test hole for thermal conductivity and geology | $ 75 |
(c) The requirement to furnish the Department a Notice of Intent fee payment shall not apply to closed loop geothermal boreholes drilled in any local jurisdiction which is authorized, by private act or pursuant to the provisions of an adopted "home rule" charter, to regulate the location and construction of these wells and which has established a fee for the inspection of both geothermal and water wells approved by the Commissioner.(d) A Notice of Intent fee shall not apply to any property owner who within the past five years has filed a Notice of Intent and paid the fee for the same property. The property owner or driller must identify on the new Notice of Intent submitted for the property the identification number from the first Notice of Intent fee submitted.(e) Checks returned for insufficient funds will be charged an established check processing fee and the Division will seek payment from the individual responsible for writing the check.(f) A Notice of Intent shall expire one hundred and eighty days from the original date filed by the well driller or homeowner.(g) When strict compliance with these standards is impractical, the driller or installer shall make application to the Department for approval of an alternative standard prior to the work being done. The Department may grant the request for an alternative standard if it determines the proposed standards offer an equivalent or higher level of protection to the environment. In an emergency or in exceptional instances, the Department will respond to a verbal request provided the applicant submits a written application within ten (10) ten days of the verbal application.Tenn. Comp. R. & Regs. 0400-45-09-.17
Original rule filed October 16, 2012; effective January 14, 2013. Rule renumbered from 1200-04-09. Amendments filed June 19, 2015; effective 9/17/2015.Authority: T.C.A. §§ 69-10-101 et seq. and 4-5-201 et seq.