28 rosemont copper - a bridge to a sustainable future

Noise

TITLE: Background Ambient Noise StudyRELEASE DATE: October 2008PREPARED BY: Tetra TechBrief Summary: Because there are areas of rural residences

along Highway 83 and near the southern portion of the Rosemont Copper project, Rosemont commissioned a study of the noise conditions in the project area. The study conducted by Tetra Tech over a five-day period in 2008 involved concurrent ambient noise monitoring at multiple locations within or near the proposed operations area. A preliminary evaluation also was made of the noise decline between the southern portion of the proposed operations area and the nearest residences. The study demonstrated the low background noise conditions expected for areas with limited development and few major roadways.

TITLE: Supplemental Noise Study RELEASE DATE: April 2009PREPARED BY: Tetra TechBrief Summary: On behalf of Rosemont Copper, Tetra

Tech conducted sound measurements, noise modeling, and noise predictions for the area around the proposed Rosemont project site.

Ambient noise in the project area was monitored for 72 consecutive hours at five locations and for 48 consecutive hours at three locations.

Noise studies looked at the projected noise levels from the Rosemont project operations and their potential impact on surrounding roadways and urban areas .

Noise

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Additional noise monitoring was conducted at an active copper mine in October 2008. The results indicated:

•Except in the immediate vicinity of the active pit or within 100 feet of active haul roads, noise levels measured at an active copper mine were similar to the ambient noise levels currently at the Rosemont Copper project area.

•During blasting operations at the active copper mine, the blast was not detectable with terrain shielding about one mile from the pit or at a location without terrain shielding about 1.1 miles from the pit.

Tetra Tech concluded that maximum construction noise levels and operational noise from the plant site and motorized equipment generally would not be audible beyond the boundaries of the proposed Rosemont project boundaries; and blast noise levels from the proposed project site would be comparable to, or less than, the maximum noise levels that currently occur several times per hour during daytime periods. The blast noise would likely be undetectable indoors.

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