This document provides a reference resource to EPA and other staff addressing characterization and cleanup of abandoned mine sites. It was developed by the Environmental Protection Agency as a resource for project managers working on addressing the environmental concerns posed by inactive mines and mineral processing sites. The information contained in the Handbook is not policy or guidance, rather it a compendium of information gained during many years of experience on mine site cleanup projects. This information was developed primarily for EPA staff, but may also prove useful to others working on mine site characterization and cleanup projects, including: states, other federal agencies, tribes, local government, public interest groups, and private industry. Handbook users are encouraged to refer to appropriate agency guidance and/or policy during development of site specific mine site investigation and cleanup projects. This handbook focuses on environmental hazards at abandoned mining sites. At many sites, however, physical hazards (e.g., open shafts or adits, unstable buildings, unstable slopes, etc.) present a safety hazard to the investigators and/or general public. These safety hazards also deserve careful consideration in developing site management strategies but are not considered in this document.