Risk assessment of nonhazardous oil-field waste disposal in salt caverns.
Salt caverns can be formed in underground salt formations incidentally as a result of mining or intentionally to create underground chambers for product storage or waste disposal. For more than 50 years, salt caverns have been used to store hydrocarbon products. Recently, concerns over the costs and environmental effects of land disposal and incineration have sparked interest in using salt caverns for waste disposal. Countries using or considering using salt caverns for waste disposal include Canada (oil-production wastes), Mexico (purged sulfates from salt evaporators), Germany (contaminated soils and ashes), the United Kingdom (organic residues), and the Netherlands (brine purification wastes). In the US, industry and the regulatory community are pursuing the use of salt caverns for disposal of oil-field wastes. In 1988, the US Environmental Protection Agency (EPA) issued a regulatory determination exempting wastes generated during oil and gas exploration and production (oil-field wastes) from federal hazardous waste regulations--even though such wastes may contain hazardous constituents. At the same time, EPA urged states to tighten their oil-field waste management regulations. The resulting restrictions have generated industry interest in the use of salt caverns for potentially economical and environmentally safe oil-field waste disposal. Before the practice can be implemented commercially, however, regulators need assurance that disposing of oil-field wastes in salt caverns is technically and legally feasible and that potential health effects associated with the practice are acceptable. In 1996, Argonne National Laboratory (ANL) conducted a preliminary technical and legal evaluation of disposing of nonhazardous oil-field wastes (NOW) into salt caverns. It investigated regulatory issues; the types of oil-field wastes suitable for cavern disposal; cavern design and location considerations; and disposal operations, closure and remediation issues. It determined that if caverns are sited and designed well, operated carefully, closed properly, and monitored routinely, they could, from technical and legal perspectives, be suitable for disposing of oil-field wastes. On the basis of these findings, ANL subsequently conducted a preliminary risk assessment on the possibility that adverse human health effects (carcinogenic and noncarcinogenic) could result from exposure to contaminants released from the NOW disposed of in salt caverns. The methodology for the risk assessment included the following steps: identifying potential contaminants of concern; determining how humans could be exposed to these contaminants; assessing contaminant toxicities; estimating contaminant intakes; and estimating human cancer and noncancer risks. To estimate exposure routes and pathways, four postclosure cavern release scenarios were assessed. These were inadvertent cavern intrusion, failure of the cavern seal, failure of the cavern through cracks, failure of the cavern through leaky interbeds, and partial collapse of the cavern roof. Assuming a single, generic, salt cavern and generic oil-field wastes, potential human health effects associated with constituent hazardous substances (arsenic, benzene, cadmium, and chromium) were assessed under each of these scenarios. Preliminary results provided excess cancer risk and hazard index (for noncancer health effects) estimates that were well within the EPA target range for acceptable exposure risk levels. These results lead to the preliminary conclusion that from a human health perspective, salt caverns can provide an acceptable disposal method for nonhazardous oil-field wastes.
- Research Organization:
- Argonne National Lab., IL (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 10683
- Report Number(s):
- ANL/EA/CP-95861; TRN: US0103981
- Resource Relation:
- Conference: 1998 Pacific Basin Conference on Hazardous Waste, Honolulu, HI (US), 04/20/1998--04/24/1998; Other Information: PBD: 10 Mar 1998
- Country of Publication:
- United States
- Language:
- English
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