US Copper Porphyry Mines

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The track record of water quality impacts resulting from pipeline spills, tailings failures and water collection and treatment failures.

Revised Nov 2012

From the report:

The Pebble Mine is proposed for development at the headwaters of the Bristol Bay watershed in southwest Alaska, which supports the world’s largest wild sockeye salmon fishery. According to current ore estimates, the Pebble Mine would be the largest copper porphyry mine in the U.S., if constructed.

Currently, the U.S. Environmental Protection Agency (EPA) is completing a watershed assessment to evaluate the potential impacts of large-scale mining on water quality and fishery resources using a mine scenario that reflects the expected characteristics of mining operations at the Pebble deposit.

The purpose of this report is to compile the record of pipeline, seepage control and tailings impoundment failures at operating copper porphyry mines in the U.S., and to document associated water quality impacts.

We reviewed state and federal documents and a federal database for fourteen copper porphyry mines currently operating in the U.S. with respect to three failure modes: pipeline spills or other accidental releases, tailings spills or tailings impoundment failures, and failure to capture and treat mine seepage.

The 14 mines represent 87% (14 out of 16) of currently operating copper porphyry mines, and 89% of U.S. copper production in 2010 – the most recent data on copper production available from the U.S. Geological Survey. The mines were chosen based on an operating record of more than five years. These mines provide a representative view of the types of environmental impacts resulting from the development of copper porphyry deposits, focusing on pipeline spills, tailings failures, and water collection and treatment failures.

Our research shows that copper porphyry mines are often associated with water pollution associated with acid mine drainage, metals leaching and/or accidental releases of toxic materials. We found that all of the mines experienced at least one failure, with most mines experiencing multiple failures.