Infiltration, Seepage, Fate and Transport Modeling Report - Revision 2

Document ID: tetra-tech-infiltration-seepage-fate-transport-rev-2-201206

The Rosemont Copper Project (Project) is a proposed open pit mine located in Pima County, Arizona with an operational life of 20 to 25 years. This Project will require the construction of four (4) major facilities, which will include an Open Pit, a Waste Rock Storage Area, a Heap Leach Facility, and a Dry Stack Tailings Facility.

At the end of the mine life, final reclamation of the site will include demolition and closure of the Plant Site facilities and final regrading and revegetation of the Rosemont Ridge Landform. The Rosemont Ridge Landform is the consolidated and contoured earthen structure consisting of the Waste Rock Storage Area, the closed Heap Leach Facility encapsulated with waste rock, and the Dry Stack Tailings Facility, also encapsulated with waste rock. The Open Pit will remain as an excavation subject to natural processes of wind and water erosion, and geochemical weathering processes.

This investigation evaluates the environmental consequences of developing the Rosemont deposit, with a focus on the potential to impact the regional groundwater system following completion of the closure process. Post-closure impacts of the Open Pit have been characterized in a separate report titled Geochemical Pit Lake Predictive Model, Revision 1 for Rosemont Copper Project (Tetra Tech, 2010a). This report presents the results of the infiltration and seepage, and fate and transport modeling for the proposed Waste Rock Storage Area, the Heap Leach Facility, and the Dry Stack Tailings Facility.

Tetra Tech. 2012a. Infiltration, Seepage, Fate and Transport Modeling Report, Revision 2, Rosemont Copper Project. Tetra Tech Project No. 114-320884. Prepared for Rosemont Copper Company. Tucson, AZ: Tetra Tech. June.