(1) The following special sealing methods may be required in situations where different techniques are necessary to protect aquifers.

(2) In drilled wells that penetrate an aquifer overlain by clay or other unconsolidated deposits such as sand and gravel in which significant (at least 6 feet thick) interbeds of clay are present, the well casing may be terminated in such clay strata, provided that the casing be sealed in substantially the same manner as is required in the case of consolidated formations (see ARM 36.21.655 and Figure 3C at the end of this subchapter) .