For closure wastes, there are several methods for determining whether the waste poses residual hazards. Typically, generator knowledge2 and standard methods such as those provided in the EPA publication SW-846 are used to determine if a waste meets the release criteria. When these are not available, new methods may have to be developed and validated. This may be time- and resource-intensive.
Careful materials management is a key to successful facilities closure. Decontamination, reuse, recycle, and disposal options for equipment and secondary waste materials generated during closure should be identified. Protocols for segregation of generated hazardous and nonhazardous materials should then be implemented, including planning for prevention of cross-contamination. This will require proper identification and inventory control of these materials. A time line for risk-based disposition of all materials resulting from closure should be developed. Prior regulatory agreement and approval should be obtained for reuse, recycling, and disposal of all materials. In addition, protocols that have been established to prevent releases from stored waste should be continued.
“Generator knowledge” is an evaluation method for hazardous waste that is commonly accepted and defined by the EPA and individual states based on some or all of the following information (EPA, 2005):
1. Facility process flow diagram or narrative description of the process generating the waste (should be used in most cases).
2. Chemical makeup of all ingredients or materials used in the process that generates the waste (should be used in most cases).
3. List of constituents that are known or believed to be by-products or side reactions of the process that produces the waste.
4. Material safety data sheets and/or product labels or substances used in the process that generates the waste.
5. Data obtained from approved methods of sampling and laboratory analysis of waste generated from the same process using the same ingredients/materials.
6. Data obtained from literature regarding waste produced from a similar process using the same ingredients/materials.
7. Documentation of product specifications or input materials and output products.