MULTIPLE USE OF NEW AND OLD UNDERGROUND EXCAVATIONS

Deep underground laboratories and geologic repositories occupy both recent excavations and openings that were mined long ago. Examples include still active salt and potash mines that isolate chemically toxic waste, road tunnel branches in dolomite that house physics experiments, silos carved into basement rock that hold radioactive waste, active and former ore mines that host neutrino observatories, specially excavated spaces in igneous and argillaceous rocks that serve as underground research laboratories, and rooms in rock salt that were excavated exclusively for radioactive waste disposal.

The Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM, represents the latter option. It is a deep geologic repository in rock salt for radioactive waste characterized by long-lived radionuclides and no significant heat generation. Extensive modeling and monitoring compiled the probably most comprehensive body of site-specific scientific information about excavation behavior. WIPP has hosted experiments in the past and is providing additional space for science. Its special status as an active government project favors cost-effective secondary use for purposes that do not conflict with its primary mission.

Old mines are not usually as well characterized as WIPP excavations. But they enjoy the advantage of practical experience accumulated during much longer spans of time. A century- old and still operating German potash mine, for example, keeps wastes with infinite half-lives retrievable for several decades. Some old mines are also well suited to host long-term science experiments, e.g., Soudan, Creighton, and Kamioka.

Future use of underground mines for both waste disposal and science experiments will profit from concurrent consideration of primary resource extraction and secondary opportunities during mine planning. It will also benefit from the massive quantity of scientific data collected and interpreted in non-commercial underground excavations.