The West Desert Trails are unmaintained trails located on approximately 1,830 acres of open space adjacent to the Sierrita Mine in Green Valley, Arizona. This property was purchased by Freeport-McMoRan Sierrita Inc. in 2012. In 2014, Sierrita completed the installation of groundwater extraction wells and related infrastructure in accordance with the sulfate mitigation effort.

Access to the property is only allowed through existing gates and trails. The land is intended to be managed for conservation purposes with the caveat that Sierrita maintains the ability to conduct mitigation operations.  For more information on the mitigation plan please visit our website https://fcx.com/sierrita

Current Update 2-9-2023 New Mitigation Wells 

Freeport-McMoRan Sierrita will begin a project to replace an older mitigation well and install another one on company­ owned property in the West Desert Trails area. This is continuation of an effort that began in June 2006 when Sierrita signed a Mitigation Order on Consent (MOC) with the Arizona Department of Environmental Quality. 

Under the MOC, Sierrita is to undertake mitigation so drinking water supplies do not exceed 250 mg/I of sulfate at the point of drinking water use due to operation of the Sierrita Tailings lmpoundment. While not considered hazardous by environmental regulations, sulfate can be produced when sulfide minerals, such as those found naturally in Sierrita and elsewhere, are exposed to air and water.

Mitigation is accomplished through the installation and operation of groundwater wells, monitoring, groundwater modeling and reporting to ADEQ to help ensure proper functioning as required by the MOC. In 2014, Sierrita completed the construction of the groundwater pumping system to supply its mining operations with water from the sulfate plume as defined in the Mitigation Plan. Ongoing maintenance on the current pumping system has occurred since 2014, and the two wells will continue to support these pumping efforts.

At the end of 2022, Sierrita reported the mitigation plan pumping has had positive effects on plume stabilization and control. More information on the MOC can be found at https://www.fcx.com/sierrita or by visiting the Joyner-Green Valley Library.