Abstract
The Grand Canyon region in northern Arizona is a home or sacred place of origin for many Native Americans and is visited by over 6 million tourists each year. Some of the highest-grade uranium ore in the United States also is found in the Grand Canyon region, hosted in solution-collapse breccia pipes that are unique in the world for uranium deposits. In 2012, the U.S. Department of the Interior withdrew about 1 million acres of federal land near Grand Canyon from new uranium mining activities through 2032, citing a lack of information on potential effects from mining on cultural, biological, and water resources in the area. Since 2014, the U.S. Geological Survey (USGS) has planned and conducted scientific investigations to address the uncertainties of potential uranium-mining impacts noted in the Record of Decision (ROD) and to provide information to decision makers who will determine if the mining withdrawal should be eliminated, extended, or made permanent. This talk will discuss results from investigations related to regional water resources including developing a conceptual model of the regional and perched groundwater systems in the area, investigating the concentration of uranium and associated trace elements in the Colorado River and major tributaries, and establishing baseline concentrations of uranium and arsenic in groundwater in the region.
Bio
Fred Tillman is a Research Hydrologist with the USGS Arizona Water Science Center in Tucson. He joined USGS in 2006 after 2.5 years as a post-doc with the USEPA Office of Research and Development in Athens, GA, following graduate studies in engineering at the University of Virginia. Fred has led a number of water-resources investigations at USGS including evaluating projected changes in groundwater recharge in the Colorado River basin, understanding salinity loading and fluctuations in the Colorado River, and assessing the connection between groundwater systems on the west coast of the Island of Hawai‘i, among others.
Learn more about Dr. Tillman's work at: https://www.usgs.gov/staff-profiles/fred-d-tillman