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Residents of Carlin, NV, worry that groundwater pumping at Carlin Trend mines is drying up local wells. | Photo Credit: GBRW Great Basin open pit mines are so deep that they reach below the groundwater table. Therefore, groundwater must be pumped from around the pits to keep the water from seeping inside while mining occurs. These mines have drained up to 70,000 gallons of groundwater per minute, and the pumps run 24 hours per day. The state of Nevada provides very little oversight of the mines' use of groundwater.
As a result, water mining pollutes and often wastes the state's future groundwater resources. Springs and streams in northern NV are drying up. Surface water is contaminated with arsenic and other heavy metals, and groundwater is contaminated when water is reinjected into the aquifer, leaving less water for wildlife and other uses.
At Newmont's Lone Tree mine, the mine's discharge water continues to violate water quality standards for boron, unionized ammonia and pH. | Photo Credit: GBRW
After a mine closes, the problem gets worse. While the mine is in operation, pumping drains the aquifer in the area surrounding the open pit, creating an area devoid of water or a "cone of depression." When the mine closes and pumping stops, the groundwater is sucked back into the cone of depression as the system tries to reach equilibrium. The pit?formerly full of rock, but now empty?will pull groundwater from the surrounding area for decades, and it can affect surface and groundwater flows up to 50 square miles away. The mining industry has insisted that impacts from water mining are minimal and won't be felt until late this century. Yet a Bureau of Land Management Study in 1999 discovered that impacts from water mining occurred within 10 years, and that the impacts were severe. Not only were groundwater and surface water flows affected, but sinkholes appeared within 10 miles of the Barrick Goldstrike mine. Draw-down of the water table there reached 1,500 feet.
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