EGLE holds public hearing on Eagle Mine paste-backfill project; air permit draft and mining-permit amendment open for comment

An informational session and public hearing March 5 convened by the Michigan Department of Environment, Great Lakes, and Energy (EGLE) covered Eagle Mine’s request to add a paste backfill process, construct an enclosed tailings storage addition to the mine’s core storage area (COSA), install a cement silo and a borehole to deliver paste underground, and to increase the facility’s allowed annual ore-truck count from 17,140 to 17,703.

Why it matters: EGLE’s Air Quality Division (AQD) is the decision maker on the draft air permit to install the paste backfill equipment; EGLE’s Geologic Resources Management Division (GRMD) is separately considering an amendment to the mine’s nonferrous metallic mining permit. Both reviews evaluate potential air and geochemical impacts and set conditions that the mine must follow if permits are approved. Public comments submitted during the stated comment periods will be reviewed before EGLE issues any final decisions.

AQD overview and draft permit details Andy Drury, lead air quality permit engineer for the Eagle Mine application, described AQD’s regulatory role, the technical review steps and the draft permit conditions. AQD evaluated emissions from the entire facility (including onsite truck traffic and fugitives) and performed dispersion modeling for criteria pollutants (including PM10 and PM2.5) and toxic air contaminants. Drury said the modeling shows the facility’s projected emissions would meet National Ambient Air Quality Standards and EGLE health-based screening levels for toxic air contaminants under the scenarios modeled.

Drury summarized the main elements of the proposed air-permit changes: operation of a paste backfill process (mixing dewatered tailings from the Humboldt Mill with cement in a screen and mixer, then pumping paste underground via a new borehole and pipe), an enclosed addition to the COSA to store dewatered tailings, a new cement silo with a bin-vent filter, and visible-emission and fugitive-dust controls for the new equipment and onsite…