40 CFR § 144.19 - Transitioning from Class II to Class VI.
(a) Owners or operators that are injecting carbon dioxide for the primary purpose of long-term storage into an oil and gas reservoir must apply for and obtain a Class VI geologic sequestration permit when there is an increased risk to USDWs compared to Class II operations. In determining if there is an increased risk to USDWs, the owner or operator must consider the factors specified in § 144.19(b).
(b) The Director shall determine when there is an increased risk to USDWs compared to Class II operations and a Class VI permit is required. In order to make this determination the Director must consider the following:
(1) Increase in reservoir pressure within the injection zone(s);
(2) Increase in carbon dioxide injection rates;
(3) Decrease in reservoir production rates;
(4) Distance between the injection zone(s) and USDWs;
(5) Suitability of the Class II area of review delineation;
(6) Quality of abandoned well plugs within the area of review;
(7) The owner's or operator's plan for recovery of carbon dioxide at the cessation of injection;
(8) The source and properties of injected carbon dioxide; and
(9) Any additional site-specific factors as determined by the Director.