40 CFR 267.111: What general standards must I meet when I stop operating the unit?

You must close the storage and treatment units in a manner that:

(a) Minimizes the need for further maintenance; and

(b) Controls, minimizes, or eliminates, to the extent necessary to protect human health and the environment, post-closure escape of hazardous waste, hazardous constituents, leachate, contaminated run-off, or hazardous waste decomposition products to the ground or surface waters or to the atmosphere; and

(c) Meets the closure requirements of this subpart and the requirements of §§ 267.176, 267.201, and 267.1108. If you determine that, when applicable, the closure requirements of § 267.201(tanks) or § 267.1108 (containment buildings) cannot be met, then you must close the unit in accordance with the requirements that apply to landfills (§ 264.310). In addition, for the purposes of post-closure and financial responsibility, such a tank system or containment building is then considered to be a landfill, and you must apply for a post-closure care permit in accordance with 40 CFR part 270.