U.S. Mines Pollute Water Despite Predictions of Low Impact, Says Report

Water quality near U.S. mines is frequently worse than predicted by regulators.

A new report reveals that the vast majority of U.S. metal mines pollute clean water even though the required environmental impact assessments predicted they wouldn’t. The report, Comparison of Predicted and Actual Water Quality at Hardrock Mines, highlights the costs to the environment and the public that are created when predictive models fail to reflect real-life consequences. Report authors Jim Kuipers, a mining engineer, and Ann Maest, an environmental geochemist, recommend creating more accurate models to assess mines’ effects on water quality.

U.S. federal law requires that regulators use scientific approaches to predict the environmental impacts of proposed mine sites before permits may be issued. Yet according to the report, 76 percent of the 25 mines studied contributed to contamination of nearby water sources, at levels exceeding permissible water quality standards, even though assessments predicted that all of the mines would comply with standards. Such discrepancies, often the result of failed mine mitigation efforts, are detrimental to municipal, agricultural, and rural water supplies as well as wildlife and certain industries, the report authors say.

Taxpayers are frequently the losers when water quality predictions are not estimated accurately. According to the U.S. Environmental Protection Agency (EPA), the cost of cleaning up all mines listed on the Superfund National Priorities List of abandoned or uncontrolled hazardous waste sites would total some $20 billion—nearly three times the EPA’s 2007 fiscal year budget request. And a growing number of communities require water treatment in perpetuity because of contamination from nearby mines, the report notes.

To provide regulators and citizens with more accurate predictions of proposed mines’ effects on water quality, the report recommends improving public access to predictions and results, ongoing reviews of predictions during the mining process, consultation of predictions for other mines for comparison, and changing the procedure for selecting consultants (who currently tend not to be rehired when they predict poor water quality for a proposed mine site). Major hardrock mines are located in 14 U.S. states (Alaska, Arizona, California, Colorado, Idaho, Michigan, Montana, Nevada, New Mexico, South Carolina, South Dakota, Utah, Washington, and Wisconsin), though the vast majority (178 of 183) are located in the west, mainly in Nevada. Sixty-three percent of the mines produce gold and/or silver and 66 percent use cyanide heap or vat leaching to extract the ore, according to the report.

This story was produced by Eye on Earth, a joint project of the Worldwatch Institute and the blue moon fund. View the complete archive of Eye on Earth stories, or contact Staff Writer Alana Herro at aherro [AT] worldwatch [DOT] org with your questions, comments, and story ideas.