40 C.F.R. § 147.2911
All Class II wells shall be cased and cemented to prevent movement of fluids into USDWs. The Regional Administrator shall review inventory information, data submitted in permit applications, and other records, to determine the adequacy of construction (completion) or existing injection wells. At the Regional Administrator's discretion, well casing and cementing may be considered adequate if it meets the BIA requirements that were in effect at the time of construction (completion) and will not result in movement of fluid into an USDW. If the Regional Administrator determines that the construction of a well authorized by rule is inadequate, he shall require a permit, or he shall notify the owner/operator and the owner/operator shall correct the problem according to instructions from the Regional Administrator. All corrections must be completed within one year of owner/operator notification of inadequacies.
40 C.F.R. §147.2911