From the factsheet:
In 2012, Earthworks released a report documenting the failure to capture and treat mine wastewater at U.S. operating copper mines accounting for 89% of U.S. copper production.1 The report found that 92% failed to capture and control mine wastewater, resulting in significant water quality impacts. This is an update to that effort. We reviewed government and industry documents for fifteen operating open-pit copper mines, representing 99% of U.S. copper production in 2015 – the most recent data on copper production available from the U.S. Geological Survey (see Table 1). Our research found similar results: 14 out of 15 (93%) failed to capture and control wastewater, resulting in significant water quality impacts (see Table 2). These unauthorized wastewater releases occurred from a number of different sources including uncontrolled seepage from tailings impoundments, waste rock piles, open pits, or other mine facilities, or failure of water treatment facilities, pipeline failures or other accidental releases.