CHALLENGING TWO FLAWED ASSUMPTIONS ABOUT DEEP GEOLOGIC REPOSITORIES

Deep burial of dangerous waste has become mature practice in several countries. Since 1999, the US has joined the trend by filling the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico, with one category of radioactively and chemically contaminated waste. The WIPP uses excavations mined exclusively for waste disposal in thick Permian salt, in contrast to all other repositories in salt, which use former and current mines.

Two largely unexamined assumptions have strongly influenced past evaluations of potential repository sites. (1) For short-term operational safety, freshly mined excavations, carefully modeled, instrumented, and monitored were preferred over old mine workings. (2) For long-term performance assurance, e.g., to minimize the potential for future inadvertent human intrusion (IHI), known natural resources were avoided, unless such a “disincentive” was compensated for by other factors. Both assumptions deserve critical examination and should be discarded.

The most successful deep geologic waste repositories occupy mined-out portions of German potash mines; of course, they are located in areas at least formerly endowed in natural resources. More than hundred years of in-situ mining experience reduce the potential for unpleasant operational surprises. More than thirty years of uninterrupted disposal experience in old mines compare favorably to the significant chance for facing unexpected conditions in newly mined ground. Deep geologic repositories isolate dangerous waste forever in practical terms. What will constitute a natural resource in a few decades, centuries, or millennia, is unknown and unknowable. Today’s resource-barren region may be tomorrow’s valuable mineral deposit. To model the future risk of IHI based on current patterns of resource use is speculation, not science. The fact that IHI is less likely in an underground repository than in a land fill is sufficient rationale in favor of the former.

Site evaluation and selection for a repository is difficult enough without the need to address the deadweight of unwarranted assumptions. Eliminating counterproductive assumptions and requirements saves scarce resources, which preserves and improves our environment.