Technical Reports

The goal of this survey was to obtain ground and airborne measurements of sky brightness in a specified 250 square mile area, roughly centered on the Santa Rita Mountain Range of southern Arizona. These measurements are intended to serve as an epoch October – November, 2011 baseline of sky brightness and local light at night (LAN).

Neither the existing 2006 Pima County Outdoor Lighting Code (PCOLC) nor the draft 2011 PCOLC have jurisdiction over the Project site for the development as proposed. However, as part of its commitment to best possible environmental practices, Rosemont Copper Company (Rosemont) will voluntarily employ an advanced light pollution mitigation plan. The plan will include the use of state of the art lighting equipment and controls to minimize environmental impact to levels below the intent of the PCOLC, including other comparable modern light pollution control standards. Importantly, the plan must also comply with the project’s operational safety requirements prescribed by the Mine Safety and Health Administration (MSHA).
To assess the baseline night sky condition and to allow future measurements, advanced aerial methods will be employed. Aerial surveys have already identified current sources and intensities of light pollution throughout the region as well as characterizing the baseline night sky. Measurements may be made in the future to determine the impact of the Project, its compliance with established goals and mitigation methods, and to identify other newly introduced sources of light pollution in the Tucson region and their relative impacts. The result is expected to be a lighting installation that generates about 10-15% of the amount of environmental light that, per the PCOLC, would normally be allowed by a similar commercial development of the same scale in the same location using conventional lighting systems on a similarly sized parcel.

STEM Laboratory, Inc. (STEM) is undertaking a comprehensive survey of light at night (LAN) and sky brightness in the Pima County, Arizona area. STEM submits here our Progress Letter Report covering the project period 1 March 2012 through 31 March 2012.