Hazardous waste closure

Interim measures may be separate from the comprehensive Corrective Action plan but should be consistent with, and integrated with, any longer-term Corrective Action (e.g., corrective measure through an order, an op erating permit, a post-closure permit or interim status closure requirements). To the extent possible, interim measures should not seriously complicate the ultimate physical management of hazardous wastes or constituents, nor should they present or exacerbate a health or environmental threat. Interim measures may add additional costs or work to the comprehensive Corrective Action. Such added costs or work do not preclude implementation of an interim measure. 

The TSDF standards also establish requirements to ensure that hazardous waste management units are closed in a manner that protects human health and the environment. The closure provisions require the facility to stop accepting waste remove all waste from management units and decontaminate all soils, structures, and equipment. Some units (i.e., land treatment units, landfills, and surface impoundments) serve as places for the final disposal of hazardous waste. These land disposal units must comply with additional postclosure requirements to ensure proper long-term unit maintenance. 

Because closure and postclosure activities can be very expensive, the TSDF standards require owners and operators to demonstrate financial assurance. These provisions also require all TSDFs to set aside funds in order to compensate third parties for bodily injury and property damage that might result from hazardous waste management operations. 

The site conditions for an on-site landfill, such as location, geology, hydrogeology, physiography, climate, and so on, should also be suitable. Landfill should meet the minimum technology requirements and regulations for hazardous waste landfills such as double liners and leachate collection and removal systems, leak detection systems, closure procedures and final cover, and construction quality assurance.59... 

All devices classified as incinerators that burn hazardous waste must follow the Subpart O standards, with the following exception. The Regional Administrator must exempt an owner/operator applying for a permit from all of the incinerator standards in Subpart O, except waste analysis and closure, if the hazardous waste fed into an incinerator is considered as low-risk waste. The criteria for defining a waste as low risk are as follows4 ... 

At closure, the owner/operator must remove all hazardous waste and hazardous residues from the incinerator equipment site. In addition, throughout the operating period, if the residue removed from the incinerator is a hazardous waste, the owner or operator becomes a generator of hazardous waste and must manage the residue in accordance with the requirements applicable. 

FIGURE 26.2 Double-liner designs. (Adapted from U.S. EPA, Requirements for Hazardous Waste Landfill Design, Construction, and Closure, EPA/625/4-89/022, U.S. Environmental Protection Agency, Cincinnati, OH, August 1989.)... 

Final cover systems are another important component of waste containment systems used at landfills. While liner systems are installed beneath the waste, final cover (or closure) systems are installed over the completed solid waste mass. For hazardous waste landfills, 40 CFR 264 requires that the landfill be closed with a final cover system that meets certain performance criteria, most notably, that they have a permeability less than or equal to the permeability of any bottom liner system or natural subsoils present. U.S. EPA guidance documents517 recommend that final cover systems for hazardous waste landfills consist of at least the following, from top to bottom ... 

Filter layers, frost penetration, and cap-liner connections are other factors to consider in designing the closure system for a hazardous waste landfill. Before using geotextiles for filter layers in closures, one should conduct pressure tests and clogging tests on the material. Freeze-thaw cycles probably have little effect on membranes, but their impact on clay is still not known. Because of this lack of knowledge, membrane and clay layers should be placed below the frost penetration layer. Finally, a cap membrane should not be welded to the primary FML. Differential settlement in the cap can put tension on the cap membrane. In such a situation, the seam could separate and increase the potential for integration of the surface water collection system into the LDS. 

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