ADEQ reviewing FMI toxic spill
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Whether the Arizona Department of Environmental quality penalizes the Freeport McMoRan Morenci copper mine for an Oct. 30 toxic spill into Chase Creek is uncertain.
The 168,000-gallon spill came within 120 feet of reaching the San Francisco River but was stopped by small earthen dams hastily constructed in the creek at its confluence with the river in Clifton.
The ADEQ released a preliminary report Monday summarizing the cause of the spill and action taken by FMI to mitigate it. ADEQ spokesman Mark Shaffer said the state agency is reviewing whether FMI violated its Aquifer Protection Permit or Arizona Pollution Discharge Elimination System regulations and if any action against FMI is warranted.
According to ADEQ, the sulfuric acid electrolyte solution spilled into the creek when an accidental cross connection between a solution pipe and the Chase Creek diversion pipe occurred. The creek is diverted through a pipe around the copper mine and returned to the creek's bed about two miles north of Clifton.
The toxic solution spilled into the creek is used in the mine's solvent extraction-electrowinning process to extract copper from low-grade ore.
The 168,000-gallon estimate was reached by calculating the volume of solution missing from a storage tank connected to the pipeline.
More than a week and the likely cost of hundreds of thousands of dollars later, the spill has been cleaned up.
Mine crews worked around the clock from the time of the spill until the weekend. About 200 workers were involved. Some of them were contract workers who had recently been laid off due to the recent copper market crash.
Activity appeared frantic through the week at the center of Clifton, where large equipment and several small earth movers, known as bobcats, were brought in for the cleanup. The bobcats were lowered into the creekbed by a crane.
Workers dug to a depth of about 4 feet in removing dirt from the creek. The dirt was replaced with clean soil trucked in from elsewhere.
Activity centered around the Circle K convenience store, which is located close to the confluence of Chase Creek and the San Francisco.
