Yucca Mountain, located on the Nevada Test Site, is being considered as a potential repository site for spent nuclear fuel and high-level radioactive waste. To determine the suitability of Yucca Mountain as a repository, the Department of Energy constructed an underground Exploratory Studies Facility (ESF) where tests and experiments will be performed. This book addresses safety issues which will impact the construction and operation of the ESF and other similar underground facilities. The authors discuss proactive strategies for underground safety management with an emphasis on planning for safety, safety regulations, and the enforcement of such regulations. Also included are illustrations of successful approaches in creating a safe environment for those who work underground.