Waste Disposal at the Pebble Mine
“The processing of ore promotes the dissolution and mobilization of elements present in the ore…Consequently, tailings undergo chemical reactions after their deposition in the repository and their composition changes over time.” 1
Tailings are one form of waste generated from mining. When mined. low grade porphery deposits, like the proposed Pebble prospect, will generate large volumes of waste2 . For example, processing 10 billion tons of ore can produce up to 9.9 billion tons of tailings. Mine tailings contain solids and liquids, metals, and processing chemicals. The solids are primarily clay, silt and sand. Some mined minerals and associated elements will occur in tailings, such as: aluminum, antimony, arsenic, barium, cadmium, copper, chromium, cobalt, iron, lead, manganese, mercury, molybdenum, nickel, selenium, silver, thallium, zinc, sulfides, and natural radioactive constituents. The composition of tailings depends on ore composition and processing chemicals used.
Tailing liquids will contain some processing chemicals (e.g., Cyanide, Xanthates, etc.) and petroleum products (e.g., diesel, oil, gas, etc.) 3. Tailings that contain reactive sulfides- which are present in the Pebble deposit, - can generate sulfuric acid if exposed to both air and water; thus they are often stored underwater4 . Both solid and liquid components of mine tailings can be toxic and impair natural ecosystem function if not contained properly.
- 1Lotterman, BG. 2007, Mine Wastes, Second Edition, characterization, treatment, environmental impacts. Page 154.
- 2Lotterman, BG. 2007, Pages 152-157
- 4U.S. EPA. 1994. Acid Mine Drainage Prediction, http://www.epa.gov/nps/acid_mine.html
Further Reading and References
Pebble Limited Partnership References
Independent Scientists References
Rico, M., G. Benito, A. R. Salgueiro, A. Diez-Herrero, and H. G. Pereira. 2008. Reported Tailings Dam Failures: A Review of the European Incidents in the Worldwide Context. Journal of Hazardous Materials. 152(2008)846-852. (pdf file 504 kb)