It only takes a few Grand Canyon hikes to realize the importance of its springs and other water sources. When refilling a water bottle in the cool depths below multi-colored rock walls, listening to a summer frog symphony at sunset or maybe snapping an icicle from a weeping ledge in winter, it’s clear that the living desert depends on its pockets of water.

That’s why, as a hydrologist and longtime Grand Canyon hiker, boatman and scientist, I am profoundly concerned about continued uranium mining in or near it. It has great potential to irreparably harm Grand Canyon springs and the plants and animals that depend on them.

I am concerned because industry and agency officials are relying on a justification that isn’t supported by past investigations, research or data to promote uranium mining in the Grand Canyon region. Specifically, they claim that mining will have minimal impact on springs, people and ecosystems there.



Instead, the science shows that it is unreasonable to assume that uranium deposits, when disturbed by mining, can’t leak into groundwater. The deposits in the Grand Canyon are typically found in geologic features known as breccia pipes, formed millennia ago when caves in the main groundwater system collapsed, leaving shattered, rock-filled chimneys that extend upwards thousands of feet to the canyon’s rim. These chimneys act as conduits that have allowed groundwater to move vertically through the rock layers over thousands of years. The vertical movement of groundwater combined with low oxygen levels caused the uranium deposits to form over millennia. Inserting a mine shaft into these features disrupts geologic formations, increases the permeability and oxygenation of these vertical pipes and increases the ability of ore deposits to be suddenly dissolved, mobilized and carried with groundwater.

It is unreasonable to assume that elevated concentrations of dissolved uranium cannot be mobilized and will not reach the Grand Canyon’s springs. It is also risky for industry to assume that mining activities, such as the sinking of mining shafts and pumping of groundwater, have no potential to redirect groundwater movement and negatively impact spring flow and associated wildlife habitats.

Similar claims of mining’s minimal impact are made often worldwide, but they are typically supported and validated by rigorous monitoring programs involving a suite of monitoring wells around a site, regular sampling and chemical analysis of water in these wells and surrounding springs, and regularly updated hydrologic and hydrochemical mathematical modeling which simulates and predicts groundwater flow and potential pollutant movement. The uranium mining operations in the Grand Canyon region have no such rigorous or extensive well-monitoring program, no consistent system to test water quality in mine seeps and no regular spring monitoring.

In the 1990s, my research team found uranium concentrations many times over the regulatory maximum contaminant level for safe drinking water in Horn Creek, one of the many side canyons of the Grand Canyon which drain to the Colorado River. This creek is directly below the site of the abandoned Orphan Uranium Mine, which operated on the rim of the Grand Canyon from the late 1940s to 1970. Horn Creek’s aqueous uranium isotopic ratio, like a fingerprint, links mining activity to its high uranium concentrations in water. In the US the Centers for Disease Control and Prevention note that ingested uranium can increase a person’s risk of kidney damage and estimated lifetime risk of cancer.

Some mining representatives have implied that the cosmetic fix of cleaning up the surface of old mining sites is evidence of zero subsurface pollution. But because groundwater flow can be very slow, the effects of groundwater contamination may take years, decades or even centuries to fully manifest. The lack of clear and consistent groundwater monitoring undercuts industry claims that mining near the Grand Canyon has caused and will cause no harm.

Across the United States, responsible mining operators and regulators work hard to account for the long-term effects of mining activities by making realistic projections of what those effects will be. They ensure credible, continuing and complete monitoring, accountability for past mistakes and true adherence to a precautionary principle that does not allow short-term gain to outweigh public and ecological safety. If there is any place in the world where this precautionary principle should be put into practice, it is the Grand Canyon.