The Waste Isolation Pilot Plant (WIPP) is an underground facility operated by the US Department of Energy (DOE) for permanent disposal of transuranic waste. The compliance of the WIPP to the US Environmental Protection Agency regulations, as assessed by the performance assessment process, is demonstrated by comparison of potential releases to the regulatory limits. In the Compliance Certification Application the potential for solids release to the surface exists only for “disturbed” scenarios, whereby the repository is intersected by an exploratory borehole at some time during the regulatory period of 10,000 years. Releases for this scenario are dominated by three mechanisms associated with the hypothetical scenario. These mechanisms are “cuttings”; the removal of solid materials by the action of drilling, “cavings”; the removal of solids by erosion by the circulating mud, and “spallings”; the removal of solids by a gas-driven blow-out.