Is the Grand Canyon radioactive?

Is there radioactive material lurking beneath one of America’s greatest natural wonders? In this video, we dig deep into the geology of the Grand Canyon to explore the presence of uranium, historical mining activity, and potential radiation concerns. Whether you're a curious traveler, science enthusiast, or just love a good mystery, join us for a fascinating look at the intersection of nature and nuclear science.

• Is the Grand Canyon radioactive? The short answer is, to a certain degree, yes.

• At the Grand Canyon, uranium is most commonly found in breccia (bre-she-a) pipes–essentially a tube of dissolved tube of rubble that can contain elements like copper, gold, and to our interest, uranium.

• There are likely two springs in the Grand Canyon area that have an elevated level of radioactivity simply because of the natural occurrence of these breccia pipes; however, these are in infrequently visited areas. But in general, undisturbed, the naturally occurring minerals in the Grand Canyon pose no risk for visitors.

• Undisturbed, that is. It is not well known that the first industry at Grand Canyon was mining, not tourism.

• For example the Last Chance Mine on Horseshoe Mesa started in the 1890's mining copper, closing in 1907. The Park Service put two signs warning of the risk of radioactive exposure near the mine as uranium was present in the tailings, despite the fact they were mining copper. Those signs are still there today, although the extent of the risk remains ambiguous.

• But, starting in the nuclear era, uranium became a valuable resource. There have been a number of uranium mines operating near the park, for example the Pinyon Plain Mine is operating south of the park within 10 miles of the rim, and it is within a national monument’s boundaries, but it was grand fathered in.

• Some of those trucks you see barreling down the highway on your way into Grand Canyon may be carrying uranium!

• And it is a little known fact that one of the richest uranium mines in the US was located right on the rim of the Grand Canyon!

• Located just Two Miles West of the Historic Village between Powell and Maricopa Points, the Orphan Mine was the richest uranium mine in the US, and operated from the 1950's through 1969.

• And here is the unbelievable part, for all the years the uranium mine operated, a hotel with outdoor dancing and an outdoor swimming pool operated alongside it!

• The hotel gift shop even sold uranium samples!

• Now, all of these things make dramatic and interesting stories, but the important question to most people is, is there any risk?

• The Orphan Mine site currently has a double fence and a locked gate. Several evaluations have been done of the risk the site may pose, but there seems to be no conclusive evidence it is dangerous for a casual visitor. The same with the mine tailings on Horseshoe Mesa.

• Likely there is little risk from a brief visit to the surface of these mine sites.

• But it turns out that uranium mining has its biggest impact on ground water, and that is an issue here. Contamination from the Orphan Mine is a concern because uranium in oxidized form is highly soluble and mobile in water. That means it can travel through groundwater and end up in springs that people and wildlife rely on.

• While most springs in the Grand Canyon region meet federal safety standards, a handful—especially near the Orphan Mine—do not. And because groundwater moves slowly through fractured rock, contamination could persist for decades or even centuries.

• The EPA says the Maximum Contaminant Level for Uranium is 30 micrograms per liter–I will just say 30 units.

• A handful of Springs down-Canyon and to the North of the Orphan Mine exceed this level. In particular, Springs in the Horn Creek area, one of which has a level of 293 units, almost ten times the maximum acceptable level. Salt Springs also exceeds the maximum level slightly.

• Both Horn Creek and Salt Springs are on the Tonto Trail between Bright Angel and Hermit Trail.

• I hiked to Horn Creek twice this year and I saw no warning signs about the radiation risk. In fact, the one sign with the name Horn Creek was on the ground and I did not even see it until after I was in the area for ½ an hour.

• So, is the Grand Canyon radioactive? The answer is nuanced. Yes, uranium is naturally present in the rocks. Yes, some areas—like near the Orphan Mine—have unsafe water. But no, the park as a whole is not dangerously radioactive.