(1) The board may authorize the exemption of an aquifer from classification as an underground source of drinking water provided the aquifer:
(a) does not currently serve as a source of drinking water; and
(b) is not reasonably expected to serve as a source of drinking water because:
(i) the aquifer produces, or is capable of producing, mineral, hydrocarbon, or geothermal energy in commercial quantities; or
(ii) the aquifer is situated at a depth or location which makes recovery of the water for drinking water purposes economically or technologically impractical; or
(iii) the aquifer is so contaminated that it would be economically or technologically impractical to render the water fit for human consumption; or
(iv) the aquifer is located above a Class III well mining area subject to subsidence or catastrophic collapse; or
(c) the total dissolved solids content of the groundwater is more than 3000 and less than 10,000 milligrams per liter and the aquifer is not reasonably expected to supply a public water system.
(2) Exempt aquifers will include:
(a) any aquifer or portion of an aquifer exempted by EPA prior to the effective date of these regulations;
(b) any aquifer or portion of an aquifer exempted by the board after the effective date of these regulations subsequently proposed after notice and hearing, provided such exemption is approved by EPA as required in 40 Code of Federal Regulations, part 144.7(b)(3);
(c) any aquifer or portion of an aquifer exempted by the board as part of a public hearing on an application for an enhanced recovery or area injection permit or other Class II well; or
(d) any aquifer or portion of an aquifer proposed by the board for exemption as part of the UIC primacy delegation or subsequently proposed after notice and hearing, provided such exemption is approved by EPA.