The objective of this study was to determine the gas injection rates needed to develop and maintain slight pressures within a mine over ambient conditions during changes in the barometric pressure. The ultimate aim of the project was to determine the feasibility of blanketing an abandoned deep mine with an inert gas in order to eliminate the acid mine drainage. Pressurization tests were conducted at two typical abandoned deep mine sites in southwestern Pennsylvania. The study also included a state-of-the-art evaluation of existing technology which could be used to locate points of gas leakage from deep mines. The findings of this literature survey were implemented in several full-scale leak detection experiments. (Modified author abstract)