Section 6.106 - Construction Standards(a) Siting and setback. All wells shall be located at least 10 feet from adjacent property lines and sewer lines, and at least 25 feet from potential sources of contamination that include but are not limited to septic tanks/fields, livestock pens, or material storage facilities.(b) Surface completion. Water well drillers drilling a shallow closed-loop geothermal injection well shall place a concrete slab or sealing block above the cement slurry around the well. (1) The slab or block shall extend at least two feet from the well in all directions and have a thickness of at least four inches. The slab or block shall be separated from the well casing by a plastic or mastic coating or sleeve to prevent bonding of the slab to the casing.(2) The surface of the slab shall be sloped so that liquid drains away from the well.(3) A pitless adapter may be used if: (A) the adapter is welded to the casing or fitted with another equally effective seal; and(B) the annular space between the borehole and the casing is filled with cement to a depth not less than 20 feet below the adapter connection.(c) Commingling prohibited. All shallow closed-loop geothermal injection wells shall be completed so that aquifers or zones containing waters that are known to differ significantly in chemical quality are not allowed to commingle and cause degradation of any aquifer containing fresh water.(d) Drilling and completion requirements. (1) Casing. Temporary casing may be installed to prevent overburden cave-in prior to the installation of tubing material and grouting of shallow closed-loop geothermal injection wells. If temporary casing is not installed, the completion of well construction should proceed as soon as possible upon completion of the borehole. If temporary casing is installed, it shall comply with the following requirements:(A) Steel well casing wall thickness shall be dependent on casing length and shall be determined using American Petroleum Institute (API) or American Water Works Association (AWWA) standards but in no circumstance shall have less than a.233-inch wall thickness.(B) Plastic well casing or screen shall not be driven. Plastic well casing shall meet the requirements specified in the ASTM Standard F480, Standard Specification for Thermoplastic Well Casing Pipe and Couplings Made in Standard Dimension Ratios (SDR) as amended and supplemented. Plastic casing shall also meet the American National Standards Institute (ANSI) standards for "Plastic Piping System Components and Related Materials."(C) If the use of a steel or polyvinyl chloride (PVC) sleeve is necessary to prevent possible damage to the casing, the steel sleeve shall be a minimum of 3/16 inches in thickness and the PVC sleeve shall be a minimum of ASTM D1785 Schedule 80 sun-resistant and 24 inches in length. Any sleeve shall extend 12 inches into the cement slurry.(D) Shallow closed-loop geothermal injection wells are not required to be cased into bedrock.(2) The water well driller shall backfill the annular space of a shallow closed-loop geothermal injection well from the surface to the total depth with grouting material in a manner that meets or exceeds good engineering practices and the gest current available technology. Grouting materials consist of a combination of bentonite, cement, thermally enhanced material, or a combination of such materials. In instances where boreholes will not support a grouting slurry, grouting alternatives, such as solid bentonite chip material may be used. Any other material used to backfill the annular space of a shallow-closed loop geothermal injection well must be approved by the Director.(3) Where no groundwater or only one zone of groundwater is encountered during drilling, grouting alternatives may be used to backfill up to 30 feet from the surface The water well driller shall fill the top 30 feet with grouting or grouting alternatives that have been approved by the Director.(4) At all times during the progress of work, the driller shall provide protection to prevent tampering with the well or introduction of foreign materials into the well.(5) Borehole diameter shall, at a minimum, allow for the insertion of a pipe sized to ensure all concrete is properly located, distributed, and cured based on the overall design and operation of the shallow closed-loop geothermal injection well. Loop tubing shall be installed for the purpose of filling the annulus between the tubing and the borehole with sand and grout material.(6) No section of the annulus between the heat exchange loop and borehole wall shall remain open after completion of the well.(7) For heat exchange loop material and connection requirements, the applicable American Society for Testing and Materials (ASTM) standards for the polyethylene (PE) pipe material shall be used. The heat exchange loop shall not be forced into the borehole or past an obstruction in such a manner that the structural integrity of the tubing may be compromised. This includes but is not limited to instances of cave-in, bedrock dislodgement, partial blockage, or overburden.(8) All heat exchange loop pipe connections to be placed in the borehole shall be connected by heat-fusion, electrofusion, or a similar joints process. In addition to heat fusion or electrofusion joints, non-metallic mechanical stab-type insert fittings shall meet applicable ASTM standards.(9) Wells that use a plastic loop require the placement of a high solids bentonite slurry grout with at least 20 percent solids by weight for any depth interval of the boring that is in a confining or semi-confining layer containing significant silt and/or clay.(10) If copper tubing is used for heat exchange applications, all below grade copper connections shall be joined by brazing using a filler material with a high melting temperature such as a material with 15% silver content or equivalent.(e) Heat Transfer Fluids. (1) Potable water, food grade propylene glycol, and USP-grade propylene glycol are the only antifreeze additives a water well driller may use for shallow closed-loop geothermal injection wells.(2) Any deviation from the approved antifreeze additives requires an individual permit.16 Tex. Admin. Code § 6.106
Adopted by Texas Register, Volume 50, Number 01, January 3, 2025, TexReg 0103, eff. 1/6/2025