William E. Cobb
Director, Environmental Department May 11, 2005
Patrick J. Cunningham
Deputy Director
Arizona Department of Environmental Quality
1110 West Washington Street
Phoenix, Arizona 85007
Re: Aesthetic Sulfate Impacts
Dear Mr. Cunningham:
As we have recently discussed, this letter confirms Phelps Dodge's voluntary commitment to address certain aesthetic sulfate impacts to drinking water supply wells located down-gradient from the Phelps Dodge Sierrita and Phelps Dodge Copper Queen mines. Specifically, Phelps Dodge agrees to find appropriate alternatives (e.g., source replacement, well replacement) for any down-gradient drinking water supply wells' at these two sites during the time that the wells have documented sulfate concentrations in excess of 500 mg/L. To ensure the enforceability of this voluntary commitment, Phelps Dodge is willing to memorialize its commitment by letter agreement with ADEQ or by participation in an agency voluntary performance program. Of course, Phelps Dodge will address potential human health impacts (i.e., mild short-term laxative effects including diarrhea) from sulfate, which may occur at levels above 1,200 mg/L, under applicable regulatory permits such as the pending aquifer protection permits for both sites.
Very truly yours,
s/William E. Cobb
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One North Central Avenue, Phoenix, AZ 85004 . (602) 366-7826