Major Scientific Issues for the WIPP–and How They Were Resolved

Wendell D Weart, Sandia National Laboratory Fellow, Retired

The Waste Isolation Pilot Plant was sited in 1975, certified for operation by the Environmental Protection Agency (EPA) in May 1998 and began operation in March 1999. Throughout this period there were numerous scientific issues that were the subject of intense debate within the project, with oversight groups and eventually with the EPA certifier. In this presentation I elaborate on a few of the more prominent issues and discuss how the issues were resolved.

The first concerns to arise were related to site selection issues having to do with geologic structure and hydrogeology, namely salt deformation and dissolution and potential breccia pipe development. A site characterization program subsequently examined the site in detail, including the underground, and addressed such issues as the hydrologic model for the Rustler aquifers, underground brine seepage, faster than anticipated salt creep, and brine reservoirs in the underlying Castile formation. During the certification process, the long-term performance of the WIPP addressed a multitude of issues, some of which were the sealing of the repository, gas generation from the emplaced waste, and the solubility and resultant transport of radioactive isotopes through the Rustler aquifer if release via human intrusion. After EPA certification, issues continued to arise, principally with RCRA and details of certifying the waste at generator sites to meet State of New Mexico requirements. The numerous political and legal issues, which in their own way were equally challenging, are not addressed in this discussion.