Tucson AMA Metal Mining Facilities

Fact Sheet

• Four metal mines are currently operating in the Tucson AMA:  Phelps Dodge Sierrita, Phelps Dodge Twin Buttes, ASARCO Mission, and ASARCO Silver Bell.  All of these, except for Silver Bell, are located south of the City of Tucson in the Sahuarita and Green Valley areas.  An AMA is an Active Management Area.  Much of Arizona is divided into five AMAs (Prescott AMA, Phoenix AMA, Pinal, AMA, Tucson AMA, and Santa Cruz AMA..), each having its own water resource and conservation goals.

• Copper and Molybdenum are the primary products of the metal mines in the Tucson AMA.  Silver and rhenium are also by-products of the mining process.

• The predominant mining technique used is open pit mining followed by milling and flotation.  Surface leaching, "in situ" mining, and underground mining are also used in the AMA.

• In 2000, in the Tucson AMA, Phelps Dodge used approximately 25,400 AF of groundwater and ASARCO used approximately 13,400 AF of groundwater.  (Note: One AF (acre-foot) equals 325,851 gallons.)

• Over the last decade, the Tucson AMA metal mines have used an average of approximately 40,000 AF of groundwater per year. This water accounts for approximately 13 percent of the total water use in the Tucson AMA.

• The Arizona Department of Water Resources (ADWR) regulates water use in any metal mine that uses over 500 AF of water per year.  There are conservation measures that each mine must follow in order to stay in compliance with ADWR regulation.

• A major mining conservation measure requires that the transport of tailings, the slurry of water and fine grain rock left over from the milling operation, be an average density of 48 percent solids, depending on the age of the facility.

• Arizona mining produces 64% of all the copper produced in the United States (Source:  Governor's Water Management Commission, December 2000).

• Until recently, the mines have not seriously considered the use of Central Arizona Project (CAP) Water because of water quality issues, lack of infrastructure, economic considerations, and reliability concerns.  This appears to be changing.  In October 2000, ASARCO signed an agreement with the City of Tucson to purchase up to 5,000 AF of CAP water per year.  ASARCO will use this CAP water on a trial basis.  This is an important first step to using renewable supplies in Tucson's metal mines.

(Source: Arizona Department of Water Resources' handout)