{"data":{"id":"us/40-cfr-146.4","jurisdiction":"us","citation":"40 CFR 146.4","heading":"Criteria for exempted aquifers.","body":"An aquifer or a portion thereof which meets the criteria for an “underground source of drinking water” in § 146.3 may be determined under § 144.7 of this chapter to be an “exempted aquifer” for Class I-V wells if it meets the criteria in paragraphs (a) through (c) of this section. Class VI wells must meet the criteria under paragraph (d) of this section:\n(a) It does not currently serve as a source of drinking water; and\n(b) It cannot now and will not in the future serve as a source of drinking water because:\n(1) It is mineral, hydrocarbon or geothermal energy producing, or can be demonstrated by a permit applicant as part of a permit application for a Class II or III operation to contain minerals or hydrocarbons that considering their quantity and location are expected to be commercially producible.\n(2) It is situated at a depth or location which makes recovery of water for drinking water purposes economically or technologically impractical;\n(3) It is so contaminated that it would be economically or technologically impractical to render that water fit for human consumption; or\n(4) It is located over a Class III well mining area subject to subsidence or catastrophic collapse; or\n(c) The total dissolved solids content of the ground water is more than 3,000 and less than 10,000 mg/l and it is not reasonably expected to supply a public water system.\n(d) The areal extent of an aquifer exemption for a Class II enhanced oil recovery or enhanced gas recovery well may be expanded for the exclusive purpose of Class VI injection for geologic sequestration under § 144.7(d) of this chapter if it meets the following criteria:\n(1) It does not currently serve as a source of drinking water; and\n(2) The total dissolved solids content of the ground water is more than 3,000 mg/l and less than 10,000 mg/l; and\n(3) It is not reasonably expected to supply a public water system.","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER D—WATER PROGRAMS","PART 146—UNDERGROUND INJECTION CONTROL PROGRAM: CRITERIA AND STANDARDS","Subpart A—General Provisions"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"d80f69298b5faefdfeeb1fc0f899ed8dc3cde5f6004aec9c39892e7ad9dc2749","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-146.3","next":"us/40-cfr-146.5"},"notice":"GroundRules: Original legal text. Not legal advice."}