ABSTRACT
Thorough scientific and engineering characterization of crushed salt assures that access shafts will not become avenues for hazardous material migration from the Waste Isolation Pilot Plant (WIPP). Essential work to characterize engineering properties, construction methods, and constitutive modeling underpins the shaft seal design, construction, and analysis. A comprehensive shaft seal system design and analysis, independent technical review, and critical acceptance were milestones along the path to regulatory compliance. After approximately a decade of regulatory interactions, the WIPP began underground disposal operations in March 1999. This historic achievement is due in part to a rigorous, unassailable shaft seal system. The WIPP itself is a full-scale geologic repository located in the bedded salt of the Salado Formation at a depth of 655 meters. Four shafts connect the underground facility to the surface. Compacted crushed salt placed near the bottom of each shaft provides a primary seal element. The technical basis for crushed salt use as a seal component was established by extensive research undertaken by Sandia National Laboratories and RESPEC.
