Amendment 10 - Montana Resources

The Yankee Doodle Tailings Impoundment (YDTI) is the tailings storage facility for the mine. The YDTI was originally constructed in 1963 using rockfill obtained from Berkeley Pit stripping operations and has been continuously expanded to elevation (EL.) 6,400 ft using rockfill from the Berkeley Pit (until 1982) and from the Continental Pit (beginning in 1986). The mine operating permit allows for continued mining in the Continental Pit, rockfill disposal areas and ancillary facilities with the exception of the YDTI.

Amendment 10 was to allow for continued filling of the facility with embankment crests of EL. 6,450 ft. This created capacity for tailings storage for approximately 12 additional years. Design documents for Amendment 10 were reviewed by the YDTI Independent Review Panel (IRP), who are charged with evaluating whether the expansion is designed, operated, monitored, and closed using the most applicable, appropriate, and current technologies and techniques practicable, given site-specific conditions and concerns. The IRP issued their Report on the Design Document for the expansion, with final permit modification approval being issued by the Department of Environmental Quality (DEQ).