Section R. 325.1635 - Construction of wells; grouting driven casing wellsRule 135. A well that is constructed by cable tool, hollow rod, jetting, or other drilling method where the permanent casing is driven shall be grouted pursuant to either of the following provisions:
(a) Where temporary casing or oversized borehole is not used or where the temporary casing or oversized borehole is less than 25 feet in depth, dry granular bentonite shall be maintained around the permanent casing as it is being driven.(b) By installing a temporary casing or oversized borehole not less than 3 inches larger than the nominal size of the permanent casing and extending not less than 25 feet below the established ground surface and grouting the annular space surrounding the permanent casing pursuant to the provisions of R 325.1633a.Mich. Admin. Code R. 325.1635