Where a well penetrates one or more aquifers containing water the quality of which is such that the quality of water in other aquifers will be significantly reduced if the waters are allowed to intermingle, in addition to the impervious seal required by Section 13.16.580, the building official shall require that the shaft be sealed at such depths and in such a manner that no such intermingling of waters will occur through the shaft or through the annular space. (Prior code § 7819)