All annular seals shall be of neat cement grout, quick setting cement or bentonite the composition of which shall conform to requirements of Subsection 9 of Part II of Chapter II of state of California Department of Water Resources Bulletin No. 74 which is referred to, adopted and made a part of this chapter with the same effect as if fully set forth herein. The building official may accept other materials when they have been demonstrated to form acceptable seals which preclude the vertical movement of water along the outside of the well casing. All annular seals shall be poured in one continuous process unless otherwise specified on the permit. The annual seal shall be a minimum of two inches thick at all depths, except the annular seal for hardrock wells shall be a minimum of one inch thick at all depths. In no event shall the thickness of an annular seal be less than three times the diameter of the largest aggregate used in the sealing material. (Prior code § 7803)