Moving the Moab Pile

Figure 1. The Moab Tailings Pile. Town of Moab in the background.

Here's another example of a project you've probably never heard of (I hadn't), where USA taxpayers will spend something like a billion dollars to move slightly radioactive material from one place to another. Between 1956 and 1983, one of the major USA mills for converting uranium ore to yellow cake, U3O8, was located just outside Moab, Utah on the Colorado River. The mill was built by the uranium king, Charlie Steen. It made the town of Moab.

The mill processed an average of 1400 tons of ore per day. In the process they built up a 16 million ton tailings Pile. The Pile covered 130 acres and was up to 80 feet high, Figure 1. The tailings are less radioactive than the incoming ore; but contain almost all the uranium daughter isotopes, Radium-226 and her progeny, which are almost all the activity associated with uranium.

In 2003, the dose rates on top of the Pile were 0.014 to 0.047 mSv/d for photons, and 0.041 to 0.052 mSv/d due to radon. Both are far below the tolerance dose of 1 mSv/d, and well below the background dose rates in parts of Kerala. The dose rates at the nearest residence, which is right on the edge of the mill property, were 0.0021 mSv/d photon and 0.0115 mSv/d radon. The background dose rates in the area are about 0.0022 mSv/d photon and 0.0044 mSv/d radon. In other words, at the edge of the mill the photon dose rate is background, and the radon dose rate is less than one-fourth the EPA action limit (8 mSv/y) for indoor radon.

The alleged motive for moving the Pile to somewhere else is contamination of the Colorado River, despite the fact that the radon daughters which represent almost all the dose rate, polonium, lead and bismuth, are all highly insoluble. (Some lead compounds such as lead carbonate are soluble, but they are unlikely to be produced in the Pile.)

The only semi-quantitative claims of river contamination I could find, including articles arguing strongly for moving the Pile, involved ammonia. Some articles claim ammonia levels in the river were 10 times EPA allowable. But I found no such claims for radioisotopes. Somebody must have measured the river contamination; but I did not find any real numbers.

Ammonia is highly soluble in water. That's why it hasn't boiled away. The Pile had no bottom liner but it is above the water table. Moab gets 9.5 inches of rain a year, which must have been the driving force for the ammonia, to get to the river.

One lesson I take away from this is that uranium mills should do a more careful job of removing ammonia and similar chemicals from the tailings. Ammonia should not even be part of the Pile. Ammonia is used late in the overall process, well after the uranium has been separated from the tailings. There was no need to mix the used ammonia solution into the tailings.

The other concern is a big flood washing the Pile into the river. But the actual floods to date have not breached the outer layers of the Pile.

Near as I can tell, we are spending 35 to 40 million dollars per year, over a 25 year period, 2010-2035, to move the Pile 30 miles away from the river. This will not change the radioactivity of the pile one whit. Total cost will likely be something like a billion.

You can argue that there are worse ways of spending taxpayer money. But my feeling is the locals are double dipping. Moab welcomed the mill when it was established, and benefited greatly from it. Now they want to turn the site into a gateway to the Arches National Park. If the locals want to move the pile, they should pay for it.

The federal taxpayer has funded something like 20 such tailings remediation programs in the US.