April 23, 2025,
Unanticipated increases in metal contaminants in Davidson Canyon stream flows could be related to ongoing Copper World earth moving activities on the eastern slope of the Santa Rita Mountains, University of Arizona researchers are warning.
The water testing was conducted in a stretch of Davidson Canyon south of its confluence with Cienega Creek. This section of Davidson Canyon is designated as an Outstanding Arizona Water by the Arizona Department of Environmental Quality. Outstanding Arizona Waters are protected by state law from water quality degradation.
Recent data collected by the UofA scientists was summarized in a memo from County Administrator Jan Lesher to the Pima County Board of Supervisors.
“More recently, there were unanticipated increases in metal contaminants in the water, including dissolved copper, lead, arsenic, and zinc. Although high concentrations occur primarily in storm flow, the elevated concentrations of contaminants in base flow samples have been found as well, suggesting a degradation in the water quality,” Lesher states in the memo.
“Dr. (Jennifer) McIntosh hypothesizes that the increased metals concentrations might be related to growing disturbance of the metalliferous soil associated with ground preparations for the Copper World Project. The below series of photos show the increased disturbance of the mountaintop during this sampling period showing increased metal concentrations.”
UofA researchers are monitoring water quality in Davidson Canyon and Cienega Creek under a long term contract with the Pima County Regional Flood Control District.
Davidson Canyon and Cienega Creek provide an important source of renewable surface water supply for the City of Tucson.
Read or download the full report here
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