Sulfuric Acid Spills
Traditionally, hard rock mining has to use a leaching solution to extract the desired metal from the rock with copper. In the case of copper, sulfuric acid is used. Therefore, there are large quantities of sulfuric acid on-site. See Leach Solution Ponds data on the Duval/Sierrita site. The leach solution has to be piped from the ponds to the leach site. Then when the leaching is completed, the leach solution is recycled. Does it ever become so saturated that it has to be filtered? If so, how is the leachate disposed of?
Further, there are regular spills of Sulfuric Acid at the plant. The officials claim that they move the contaminated soil. Where do they move it to? What is the impact on Groundwater? I have attempted with no success to have ADEQ and EPA look at the figures to determine if they were what were causing the spikes in the sulfate data at all the Community Water Company Wells.
The spills do not occur in the same locations, they are not of the same quantity, and they do not necessarily have the same percentage of Sulfuric acid. Therefore, as they run down the hill, it could take different lengths of time to reach the aquifer. Assuming the liquid solution seeks out rifts, faults and gullies in its downhill route, one would also expect it to arrive with a faster speed than the tailings seepage, therefore, it will reach the aquifer faster,and have some force to spread out further when it reaches the aquifer. Another clear indicator of a solution different than tailings seepage is impacting the wells is the high percentage of sulfate shown in the water quality data at the time of the spikes. The fact that the Sulfate and TDS values gradually spike up and gradually go back down is not characteristic of tailings pond seepage.
These Hazardous Material Incidents of Sulfuric Acid also occur at other copper mines in Pima County: