40 CFR §147.2908

1. (a)After notice and opportunity for a public hearing, the Administrator may designate any aquifer or part of an aquifer as an exempted aquifer.
2. (b)An aquifer or its portion that meets the definition of a USDW may be exempted by EPA from USDW status if the following conditions are met:
   1. (1)It does not currently serve as a source of drinking water, and
   2. (2)It cannot now and will not in the future serve as a source of drinking water because:
      1. (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
      2. (ii)It is situated at a depth or location which makes recovery of water for drinking water purposes economically or technologically impractical; or
      3. (iii)It is so contaminated that it would be economically or technologically impractical to render that water fit for human consumption; or
   3. (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.