Rosemont Conceptual Barrel Alternative Stormwater Control Features

This Technical Memorandum summarizes the conceptual stormwater control features anticipated for the Barrel Alternative associated with the proposed Rosemont Copper Project (Project) in Pima County, Arizona. A preliminary grading scheme was prepared for this alternative as shown on Figure 1 and is referred to as the Barrel Alternative Landform (Landform). The Landform consists of a Waste Rock Storage Area, a Dry Stack Tailings Facility encapsulated with waste rock, and a closed Heap Leach Facility, also encapsulated with waste rock. The proposed Barrel Alternative is designed to drain the majority of the stormwater off the Landform. Stormwater control on the Landform is accomplished primarily by drainage benches that intercept runoff from the slopes of the landform. Stormwater collected in the drainage benches exit the Landform via rock drop structures placed at select locations.