OAR 690-240-0046: Grouting of Uncased Boring

(1) Grouting of an uncased boring shall be completed after the heat exchange loop is installed. The boring shall be completed in a manner to allow ease in locating including but not limited to the use of marking or locating magnetic tape if maintenance or abandonment is necessary The area near land surface where the ground source heat pump boring will be connected to a manifold or to the closed loop system may be filled with earth materials. (2) Sealing shall be completed using active solids content bentonite grout slurry (minimum 20% active solids by weight) or high solids fluid mixture of cement. Controlled density fill (CDF), fly ash, drill cuttings or drilling fluids shall not be used in grouting the uncased boring. (3) Mixes of bentonite or cement slurry shall be installed by pumping through a grout pipe in a continuous operation from the bottom of the boring upward. The grout pipe shall extend the full depth of the borehole before pumping begins. Minimum slurry volume used shall be equal to or exceed the calculated annulus volume in the borehole. Grouting material shall surround all pipes remaining in the borehole. (4) The quality of the water in the boring shall not interfere with the proper hydration of bentonite.