Uranium mining ban near Grand Canyon all politics, no science

Uranium poses no danger to drinking water supply

An article in the April 25, 2014, Arizona Daily Star “Controversial uranium mine north of Canyon to stay open” reopens the fear that radioactive dust or uranium ore will find its way into the Colorado River which supplies drinking water for much of Arizona, California, and parts of Nevada. But that fear is without scientific basis.

There are over 1,300 known or suspected breccia pipes in the region, many of which contain uranium oxide as well as sulfides of copper, zinc, silver, and other metals. According to the Arizona Geological Survey, “Total breccia-pipe uranium production as of Dec. 31, 2010, has been more than 10,700 metric tons (23.5 million pounds) from nine underground mines, eight of which are north of Grand Canyon near Kanab Creek.”

On January 9, 2012, the Obama administration announced a 20-year ban on new mining claims on public land near Grand Canyon National Park. The ban will not affect about 3,000 existing claims in the area. A principal stated reason for the ban was to forestall possible contamination of Colorado River water resulting from a mining accident. But dangerous uranium contamination from an accident is extremely unlikely according to a study by the Arizona Geological Survey:

To examine one potential impact of uranium mining in the Grand Canyon region on uranium levels in Colorado River water, Dr. Jon Spencer (AZGS Senior Geologist) and Dr. Karen Wenrich (Consulting Geologist) posed a hypothetical, worst-case, scenario involving an accidental spill of the entire contents of an ore truck hauling 30 metric tons (66,000 pounds) of uranium ore containing one percent uranium (ore grades in northern Arizona are typically somewhat lower), followed by flash-flood transport and dissolution of all spilled uranium into the Colorado River. In this scenario, the ore is pulverized and dissolved within a single year, releasing 300 kg (661 pounds) of uranium directly into river waters.

The result: uranium concentration of Colorado River waters would increase from 4.00 ppb (parts per billion by mass) to 4.02 ppb. To write those numbers as decimals, the uranium concentration would rise from 0.000000400% to 0.000000402%. That increase would be masked by natural uranium-concentration variations as determined by measurements reported in a recent U.S. Geological Survey study. Furthermore, the uranium content of Colorado River waters would remain well below the 30 ppb Maximum Contaminant Level set by the Environmental Protection Agency for safe drinking water.

The small change in dissolved uranium content of Colorado River water as a result of this hypothetical accident is due to the very large annual volume of river water that passes through the Grand Canyon and the approximately 60 metric tons of dissolved uranium that is naturally carried by the river each year.

The study is: Spencer, J.E. and Wenrich, K, 2011, Breccia-pipe uranium mining in the Grand Canyon region and implications for uranium levels in Colorado River water. Arizona Geological Survey OFR-11-04, 13 p. It may be downloaded here.

A U.S. Geological Survey report issued in 2010, provided data showing that the river carries an average of 120,000 lbs (a range of 40-80 tons) of uranium down the Grand Canyon every year. The uranium is apparently eroded from normal crustal concentrations over the large drainage area of the Colorado River basin.

Reference: Hydrological, Geological, and Biological Site Characterization of Breccia Pipe Uranium Deposits in Northern Arizona, Edited by Andrea E. Alpine, USGS SIR 2010-5025, download here.

Besides eliminating hundreds of potential jobs, this decision denies the U.S. resources to produce electricity. This decision seems to be part of Obama’s plan to make electricity costs “skyrocket” so that wind and solar energy appear more attractive.