((a)) ** Underground source of drinking water** No hazardous waste may be disposed of by underground injection—

((1)) into a formation which contains (within one-quarter mile of the well used for such underground injection) an underground source of drinking water; or

((2)) above such a formation.

((b)) ** Actions under Comprehensive Environmental Response, Compensation, and Liability Act** Subsection (a) shall not apply to the injection of contaminated ground water into the aquifer from which it was withdrawn, if—

((1)) such injection is—

((A)) a response action taken under section 9604 or 9606 of this title, or

((B)) part of corrective action required under this chapter

((2)) such contaminated ground water is treated to substantially reduce hazardous constituents prior to such injection; and

((3)) such response action or corrective action will, upon completion, be sufficient to protect human health and the environment.

((c)) ** Enforcement** In addition to enforcement under the provisions of this chapter, the prohibitions established under paragraphs (1) and (2) of subsection (a) shall be enforceable under the Safe Drinking Water Act [ et seq.] in any State—

((1)) which has adopted identical or more stringent prohibitions under part C of the Safe Drinking Water Act [ et seq.] and which has assumed primary enforcement responsibility under that Act for enforcement of such prohibitions; or

((2)) in which the Administrator has adopted identical or more stringent prohibitions under the Safe Drinking Water Act [ et seq.] and is exercising primary enforcement responsibility under that Act for enforcement of such prohibitions.

((d)) ** Definitions** The terms “primary enforcement responsibility”, “underground source of drinking water”, “formation” and “well” have the same meanings as provided in regulations of the Administrator under the Safe Drinking Water Act [ et seq.]. The term “Safe Drinking Water Act” means title XIV of the Public Health Service Act.42 U.S.C. 300f