“The Sonoita Plain is home to many working ranches and farms, including wineries, which underscore the economic importance of available water resources,” says Emily Brott, a project manager for the Sonoran Institute. “Placing a new open-pit mine in this area, we believe, will jeopardize and even possibly eliminate these water resources – which would be devastating to the local economy.” The Sonoita Plain area also includes sensitive native grasslands and the Las Cienegas National Conservation Area.
The report used geologic and hydrologic information from the mine area to create a model that could forecast the impact of the mine on area water resources. According to the author, Dr. Waite R. Osterkamp, a Research Hydrologist, Emeritus with the United State Geological Survey (USGS), open-pit mining in the area could decrease or even eliminate these water sources by draining water from the carbonate rocks—the limestone and dolomites—that are the main “transmitters” of water in the area.
“The open pit mine will go through the carbonate rocks to a level that is considerably lower than what the level is of those rocks underlying the Sonoita Plain,” says Dr. Osterkamp. “The potential, therefore, is that there can be drainage into the open pit that will dewater, partially or even completely, the carbonate rocks—and dry up wells, dry up springs, eliminate the water resource of the entire area.”
Dr. Osterkamp is currently on the Board of the Appleton-Whittell Research Ranch in Elgin, Arizona. An independent study conducted by Dr. Larry Winter of the University of Arizona also suggested the likelihood of significant water-level declines.
“Given this new information, we are calling on the Forest Service to conduct new detailed and independent investigations into the impact on area water resources before any decision is reached on the mine,” says Brott. “We believe that the Forest Service’s Draft Environmental Impact Statement (DEIS) on the proposed Rosemont Mine inadequately examines the potential impacts to the surface and ground-water resources of the Sonoita Plain.” Brott indicated that the Institute has formally filed the study with the Forest Service.
Visit the Sonoran Institute website at www.sonoraninstitute.org to download a copy of the report, and to view video interviews with Emily Brott and Dr. Osterkamp about his study.
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