Consideration of the future in the WIPP regulations: Policy and practice

The US Environmental Protection Agency (USEPA) published final regulations for the disposal of transuranic and certain other radioactive waste in 1993. These regulations contain standards that limit the amount of specific radionuclides that may be released from a disposal site over 10,000 years. The USEPA was directed by the United States Congress to develop criteria based on the general disposal regulations specifically for the Waste Isolation Pilot Plant (WIPP), a disposal site in New Mexico that is owned and operated by the U.S. Department of Energy (USDOE). EPA published the WIPP compliance criteria in 1996. Because transuranic waste will remain radioactive for many thousands of years, any prediction of the WIPP's performance will involve a significant amount of uncertainty regarding the factors that could affect containment. In an effort to constrain potentially endless speculation about future events, the USEPA specified in the WIPP compliance criteria the manner in which the USDOE must consider important events and processes that may occur at the WIPP site. This paper identifies and briefly explains the basis for USEPA's assumptions governing consideration of future events. The paper then reviews some significant issues that arose during USEPA's rulemaking for the final WIPP certification, and explains the effect these issues had on USEPA's decision making. Performance criteria for a disposal site inevitably must make assumptions about the future if the results of the performance assessment are to be meaningful. When forming assumptions, the regulatory agency must balance what is known about present conditions against what may happen despite our best predictions. Because assumptions about the future are likely to be controversial, they must be based as much as possible on concrete evidence. A strong factual foundation for assumptions, as well as an overall conservative approach that maximises negative consequences, can help to alleviate controversy and increase public confidence