USGS Assesses Baseline Conditions Prior to Uranium Mining near Grand Canyon National Park

Scientists have collected and analyzed 84 environmental samples to establish baseline data prior to any active uranium mining activities at the Canyon Uranium Mine, located south of Grand Canyon National Park.  This baseline information will play an important role in assessing if contaminants escape from the mine site and how they would move through the environment once mining operations begin.

Canyon Mine is currently not producing any uranium ore. The mine is located within the public lands acreage in northern Arizona that the Department of the Interior withdrew in 2012 from consideration for new uranium mining claims for 20 years. However, Canyon Mine can still produce uranium ore, because it is one of four pre-existing mines that were permitted before the 2012 decision.

“A key factor in Interior’s 2012 decision was the limited amount of scientific data available to assess potential uranium extraction effects on the Grand Canyon and surrounding areas,” said USGS director Suzette Kimball. “Fortunately, the USGS has expertise across the country in collecting baseline data and analyzing samples for water and sediment quality.”

USGS scientists have worked with the mine owners to collect samples for the baseline data study.

“Getting into the Canyon Mine area before any ore is extracted has provided an excellent opportunity to get high-quality baseline data,” said USGS scientist Katie Walton-Day, who leads the research team on this project. “That data are necessary to quantitatively assess off-site migration, if any, of mine-related contaminants resulting from future ore extraction activities at the Canyon Mine.”

Baseline data from the study includes analysis of 33 contaminants in the 84 samples, including uranium, arsenic, molybdenum and vanadium. The following chart provides some of the results:

Chemical constituent

   Inside mine perimeter (n = 3)

         Low         Mean        High

 Outside mine perimeter (n = 72)

       Low         Mean          High

Uranium

          3.3            5.6            9.9

        1.4            2.0              6.2

Arsenic

        23             35             58

        7.1          10               18

Molybdenum

          1.4            2.1            3.2

         0.75         1.1              2.4

Vanadium

        43             52             57

       29             45              59

In addition to establishing the baseline in soils and stream sediments around the mine site, USGS scientists are studying the plant and animal life in the area to determine which species to monitor once mining begins.

“Biologists are looking at what types of species live here, how many of each species there are, and even what levels of contaminants are already in their tissues,” said USGS scientist David Naftz, lead author of the study. “When combined with the soil and sediment samples, we’ll have a really clear snapshot of what conditions are like here before any uranium ore is extracted.”

The results of the study were published this week in the journal Geoderma Regional. More information about the study can be found here. The approach and baseline data are part of a long-term comprehensive study designed by USGS to establish radiological and chemical baselines and environmental pathways of exposure within and surrounding the Canyon Uranium Mine, in northern Arizona prior to ore extraction.

The USGS Toxic Substances Hydrology Program and Environmental Health Mission Area provide objective scientific information on environmental contamination to improve characterization and management of contaminated sites, to protect human and environmental health, and to reduce potential future contamination problems.