The Department of Environmental Quality (DEQ) received an amendment application from Sibanye Stillwater Mining Company on December 4, 2017, proposing to expand the impoundment at the East Boulder mine. The Sibanye Stillwater Mining Company operates this mine under Operating Permit No. 00149. The mine is located in portions of Sections 11, 19, 20, 20, 26-29, and 33-35 in Township 4 South, Range 13 East and Sections 9, 10, 16, 17, 19, 20, and 21 in Township 3 South, Range 13 East in Sweet Grass County.
If approved, the proposed amendment would allow a “raise” of the currently permitted tailings impoundment. The proposed amendment would raise the currently approved Stage 5 lift an additional fourteen feet in elevation and add 1.8 million cubic yards of tailings capacity. The amendment would add approximately 6.4 acres to the currently permitted disturbance area for a total of about 335 acres of disturbance.