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Dos Pobres/San Juan Ground-Water Monitoring

Project Number: 9671BGJ
Project Chief: Jeff Cordova
Cooperating Agencies: Freeport-McMoRan Copper and Gold, City of Safford, AZ, Arizona Department of Water Resources
Period of Project: 2005 – At the close of the Phelps Dodge Safford Mine, currently projected for 2024

Mining operations, 11/20/07

In December of 2007 Freeport-McMoRan Copper and Gold, Inc.(FM) (formally Phelps Dodge Safford, Inc.) opened the Dos Pobres / San Juan Copper Mine in southeastern Arizona, about 8 miles north of the town of Safford in Graham County. This is the first major copper mine opened in Arizona since 1973. Mining operations are projected to require 5,533 acre-feet per year (acre-ft/yr) of ground-water, with a total demand of 88,528 acre-feet of groundwater over the life of the project.

The Gila River flows southeast to northwest through the Safford Valley approximately seven miles south of the project area. Both the San Carlos Apache Tribe and the Gila River Indian Community own water rights to the river of 6,000 acre-ft/yr and 303,288 acre-ft/yr, respectively. Additionally, the San Carlos Apache Tribe holds another Indian Trust Asset in ground water under the reservation.

The San Carlos Apache Tribe and the Bureau of Indian Affairs (BIA) have expressed concern that ground-water withdrawals for the mine project will negatively impact tribal Gila River water rights as well as the San Carlos Apache Tribe’s ground water supplies under the Reservation. To this end, a ground water modeling, monitoring and mitigation program was developed as part of the Environmental Impact Statement required for the Bureau of Land Management (BLM)-FM land exchange that is central to the project. The BLM requested that the United States Geological Survey, Arizona Water Science Center (USGS), provide oversight for this program.

The USGS’s long-term role in the project is to help ensure that the effects of mine-related pumpage on the regional aquifer are known and quantified. The USGS will be actively involved in the operation and quality control of the ground water monitoring plan, will provide technical input to and review any future recalibrations required to improve the ground water flow model of the area, and will maintain this project Web page to facilitate public access to project data. The USGS began its active involvement with the monitoring plan at the end of June, 2004 and will be involved with the project throughout the life of the mine and beyond.