Examining the Potential Impacts to Wetlands and Water Bodies Due to Mineral Exploration, Pebble Copper-Gold Prospect, Southwest Alaska

The majority of mining ventures do not make it past the stage of discovery. There is, however, no detail in the literature on the impacts on natural waters of mineral exploration drilling. A copper-goldmolybdenum mining deposit in Alaska was extensively investigated and partially reclaimed until 2012; however, in 2016, full reclaim of drill sites remained incomplete. Copper, a highly valued resource in this region, is sub-lethally toxic to salmon. Nine sites had reported impacts from 109 inspected sites due to un-reclaimed drill-holes or drill waste disposal activities. Artesian waters at the drill stem at seven sites resulted in surface water or sediment elevated at neutral pH in aluminium , iron, copper, or zinc. The concentrations of copper at artesian sites were < 0.4, 0.7, 2, 7, 15, 76, and 215 μg / L; the latter four in the state of Alaska surpassed the requirements for water quality. It is understood that drilling waste is disposed of in ponds and unlined sumps. Copper declined from 511 at one of five sampled ponds, However, in the only sump region with historical evidence, copper increased over five years from 0.3 to 1.8 μg / L at a downgradient wetland spring to 8 μg / L over nine years. This study describes forms and origins of pollutants and can be used to direct potential studies of ecotoxicity and strengthen regulatory oversight. The findings of this research provide guidance on the causes and forms of pollution. Future research should sample pond soil, where drill waste pollutants can be sequestered, and analyse drill waste sumps for leaching proof. It will be in the public interest for state regulators, during inspections, to perform water , soil, or sediment monitoring to track improvements in the ecosystem where drill holes are not completely and permanently reclaimed.

Author (s) Details

Dr. Kendra Zamzow
Center for Science in Public Participation, Chickaloon, AK 99674, USA.

David M. Chambers
Center for Science in Public Participation, Bozeman, MT 59715, USA.

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