Response to Tetra Tech Memorandum dated 22 April 2011, Infiltration and Seepage Model

Tetra Tech prepared a technical memorandum Rosemont Facility Infiltration and Seepage — Response to Comments dated April 22, 2011. It was prepared in response to a technical review Infiltration, Seepage, Fate and Transport Modeling, Revision 1- Part 1 Infiltration and Seepage Model Components prepared by SRK Consulting on February 14, 2011. The Tetra Tech memorandum provided acceptable responses to all questions with the exception of two items below. We request clarification on Items 2 and 3.

• Input Data - Climate and Site Material Soil
• Heap Leach Facility Conceptual Model
• Steady-State and Transient Solutions