Hazardous Waste Program

Closure Requirements

From the archives of the Enforcement and Compliance Listserv for Hazardous Waste Generators

May 1, 2006

What is proper closure for a hazardous waste generator? Many generators may not be clear on their responsibilities when they cease using an area or a unit, such as a tank, used for accumulating hazardous waste. Often when a business moves, or stops generating hazardous waste, the proper closure of these areas or units is overlooked. The requirements for proper closure originate in 40 CFR 262.34, as incorporated and modified by the Missouri regulations. Both small and large quantity generators must comply with certain disposal and decontamination requirements once they cease operating accumulation areas or units.

Large Quantity Generators (LQG) must comply with the generic federal closure requirements in 40 CFR 265.111(a) and (b) and 265.114, and the unit-specific federal closure requirements found in Part 265, Subpart I (containers), Subpart J (tanks), Subpart W (drip pads), and Subpart DD (containment buildings). The closure requirements include removing and decontaminating all equipment, structures, and soil to minimize the need for further maintenance and prevent post-closure escape of hazardous waste. Please Note: In Missouri the requirements found in 10 CSR 25-5.262(2)(C)2.A require Small Quantity Generators (SQGs) that accumulate large quantities of hazardous waste (over 1,000 kilograms) to meet the above LQG closure requirements as well.

Hazardous waste tank closures can be especially critical. When a LQG (or a SQG that stores over 1,000 kilograms of hazardous waste) stops using its hazardous waste tanks, the facility must conduct an evaluation pursuant to 40 CFR 265.197(a) and (b). After the evaluation, the business must take appropriate actions to deal with any contamination of soils, structures or other surroundings. If it is necessary to leave contamination in place, the facility may be required to conduct an interim status closure, and could potentially trigger post-closure permit requirements. Ideally, tank releases are detected during the operating life of the tank, but this final evaluation provides an additional check and response when the tank ceases operation.

Regardless of the volume of waste accumulated, SQGs must always follow the special requirements for accumulating hazardous waste in tanks, including closure requirements found in 40 CFR 265.201 in Sub-part J of part 265.

Although there are no specific closure requirements for Conditionally Exempt Small Quantity Generators (CESQGs), all hazardous waste must be managed in a way that does not threaten human health or the environment, or create a public nuisance. Both common sense and good housekeeping should be used by CESQGs to close hazardous waste areas or units. For more information on all CESQG requirements, see Management of Conditionally Exempt Small Quantities of Hazardous Waste, Fact Sheet--PUB128 .

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If you need further assistance, please email or contact the Department of Natural Resources' Hazardous Waste Program at 573-751-7560 or 800-361-4827.