Conn. Agencies Regs. § 25-128-49a
Geothermal bore holes shall be terminated a minimum of four (4) feet below the proposed finished grade and shall be fed to the point of termination. If piping running between bore holes and the heated structure is shallower than four (4) feet below finished grade, measures shall be taken to prevent long term damage to the tubing from freeze-thaw cycles and accidental damage. Bore holes terminating in a structure shall be terminated flush with the finished floor. Casing, if used during bore hole drilling, shall be capped from the time of installation until the installation of the geothermal system piping. As the bore hole is being grouted, the casing may be withdrawn. Figures 6 and 7 in section 25-128-64 of the Regulations of Connecticut State Agencies set forth examples of bore hole termination for geothermal bore holes.
Conn. Agencies Regs. § 25-128-49a