Owner/Client
Hecla Greens Creek Mining Company
Location
Admiralty Island, AK
CEC Services
- Air Compliance and Permitting
- Air Dispersion Modeling
- Site Characterization
- Environmental Monitoring/Compliance
- O & M of Control Systems
Owner Objective
Hecla Greens Creek Mining Company is a wholly owned subsidiary of Hecla Mining Company of Coeur d’Alene, Idaho. Hecla is the largest primary silver mining company in the United States and is the oldest precious metals mining company listed on the New York Stock Exchange.
Hecla operates the Greens Creek Mine, which is an underground silver, lead, and zinc mine located on the northern portion of Admiralty Island, Alaska. Admiralty Island is a National Monument managed by the U.S. Forest Service, Tongass National Forest. Because it is accessible only by shuttle boat or charter air service, it is considered remote. Mill tailings placed for final disposal on the 80- acre dry stack tailings storage facility (TSF) contain measureable levels of zinc and lead. During dry periods (between the middle of November and the end of February), the surface of the TSF is subject to scouring wind events that deposit particulate (fugitive emissions) containing levels of zinc and lead south onto National Monument lands and potentially on the surface of the adjacent Stephens Passage, part of the Alaskan Inland Waterway. The TSF fugitive emission issue has been a regulatory and public relations issue for Hecla for over 10 years. In particular, the residents of Angoon, a native Alaskan village south of the mine site, have raised concerns that the deposition of lead and zinc dust on terrestrial vegetation and wildlife; along with the potential introduction of these materials to marine wildlife, it has impacted Angoon’s historic subsistence lifestyle. Hecla requested CEC to evaluate and develop a solution to control the fugitive emissions from the TSF.
CEC Approach
CEC realized that controlling the fugitive emissions from the TSF surface would be similar to managing and controlling fugitive emissions and odors from large landfill sites. In coordination with CEC’s teaming partner, NCM Odor and Dust Control, CEC designed and installed a high volume mister/atomizer system. A key task involved designing a cost-effective system. The dust dispersion modeling completed for the project indicated that the mine site only needed to control emissions from a 3–5-acre working area on the larger 80-acre TSF surface to eliminate downwind dust deposition on the National Monument lands and the Inland Waterway. This working area is dynamic and shifts location on a regular basis with regard to TSF operations. In coordination with Hecla, the mister/atomizer system is designed as a portable unit that will be moved as needed to provide dust control on the 5-acre working area. Hecla will place a temporary cover on the remaining open TSF areas to control fugitive emissions as appropriate.
The mister/dust control system was installed on a temporary location on the TSF in October 2018. Hecla will move the system as needed based on routine TSF operations and wind events during the 2018–2019 season. Installation of the system has assisted Hecla in meeting regulatory goals with regard to controlling fugitive emissions from the TSF.
