A. Whenever a well penetrates one or more aquifers containing water the quality of which is such that the quality of water produced by the well, or the quality of water in other aquifers, will be significantly reduced if the waters are allowed to intermingle, the aquifer containing the low quality water shall be sealed so as to prevent such intermingling. Whenever an aquifer is required to be sealed, a ten foot annular seal shall be formed in the confining formations, except that where the well shaft ends in the aquifer to be sealed, the seal need not be extended into the lower confining formation so long as the bottom of the shaft is sealed. There shall be no casing perforations in the aquifer to be sealed.
B. When drilling a well, if the driller drills through a layer of clay which is twenty (20) feet or more in thickness, the casing shall not be perforated both above and below the clay if both the following conditions occur:
1. The difference in water quality above and below the clay is more than five hundred (500) micromhos as specified electrical conductance or more than three hundred (300) milligrams per liter as total dissolved solids; and
2. The well is located in an area which is designated by the building official as a salinity problem area on a current map of the known salinity problem areas in the city prepared by, and on file in the office of, the building official. Said map shall be revised by the building official from time to time to show the areas in the city where salinity problems are known to exist after consultation with well drillers generally and other interested groups and individuals. (Prior code § 7802)