40 CFR 147.2908 - Aquifer exemptions.
(1) It does not currently serve as a source of drinking water, and
(2) It cannot now and will not in the future serve as a source of drinking water because:
(i) It is hydrocarbon producing, or can be demonstrated by a permit applicant as a part of a permit application for a Class II operation to contain hydrocarbons that are expected to be commercially producible (based on historical production or geologic information); or
(ii) It is situated at a depth or location which makes recovery of water for drinking water purposes economically or technologically impractical; or
(iii) It is so contaminated that it would be economically or technologically impractical to render that water fit for human consumption; or
(3) The Total Dissolved Solids content of the groundwater is more than 3,000 and less than 10,000 mg/1 and it is not reasonably expected to supply a public water system.