Science for Decision Making on Uranium Mining in Arizona

Investigating Potential Impacts from Uranium Mining on Grand Canyon Regional Groundwater Resources

At Pinyon Plain (formerly Canyon) Mine

Uranium and other chemical constituents associated with breccia pipe deposits occur naturally in soil, sediment, groundwater, and surface water, and from the weathering and leaching of ore deposits. Mining of breccia pipes has the potential to enhance release of chemical constituents (such as uranium and associated trace elements) into the environment, which can then expose soil, water and biological resources to mining-related contaminants.

Determining the relative contribution of radiochemical and chemical constituents in regional and local groundwater resources from mining activities is problematic and challenging without an understanding of background concentrations. The potential for increased exposure resulting from mining activities has not been well characterized in the Grand Canyon region because regional/background concentrations of uranium and other trace elements in groundwater are largely unknown and there is a general lack of understanding regarding the local and regional groundwater flow systems.

Water movement through breccia pipes and associated ring fractures during natural pre-mining conditions and once the pipe is opened for mining is not well understood.

Questions this study could help answer

  • How does groundwater interact with breccia pipes? With mineralized breccia pipes? How might this interaction change during/after mining?
  • What changes in water chemistry would be expected if mining activities were impacting groundwater resources?
  • When would potential impacts from mining on groundwater be observed?
  • Where would potential impacts first be noticed?


Determine how mining-related chemical constituents move through the environment to help identify potential impacts to groundwater resources.



Specific Tasks

Task 5a: Compile/evaluate existing and newly collected monitoring data from various agencies/sources
Task 5b: Collect/analyze water and sediment samples from streams and springs
Task 8a: Continue evaluation/analysis of Uranium Activity Ratio analysis
Task 9: Drill and develop groundwater monitoring wells


Beisner, K.R., Solder, J.E., Tillman, F.D., Anderson, J.R., Antweiler, R.C., 2020, Geochemical characterization of groundwater evolution south of Grand Canyon, Arizona (USA), Hydrogeology Journal,

Principal Investigators

Kimberly Beisner
Arizona and New Mexico Water Science Centers

Fred Tillman
Arizona Water Science Center


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Photo Gallery

Pinyon Plain Mine (formerly Canyon Mine) observation well

Pinyon Plain (formerly Canyon) Mine Gallery

Sites with Related Activities

Arizona 1 || Pinenut || Regional Studies