'Uranium rush' prompts Grand Canyon fears
A new "gold rush" is under way in the American West, but this time the prospectors are out for another metal: uranium.
The Grand Canyon region in the US state of Arizona holds one of the nation's largest concentrations of high grade uranium, the fuel for nuclear power.
As global demand for nuclear power has increased so has interest in the metal and, across the south-west, companies are seeking permission to restart uranium mining.
In the US, President Barack Obama has called for an increase in nuclear power to help reduce the country's dependence on foreign oil.
The US government is currently weighing the costs and benefits of mining, with Arizona Congressman Raul Grijalva proposing a ban on mining near the Grand Canyon.
But with the increase in uranium exploration come concerns about the future of the Grand Canyon, a Unesco World Heritage Site and one of America's foremost natural wonders.
And Native American populations living near uranium mines fear exploration could contaminate their drinking water.
For now, the sole active uranium mine near the Grand Canyon's northern rim is run by Denison Mines Corporation, a Canadian firm.
The Arizona 1 mine employs 30 miners, and the firm says it goes to great lengths to protect them in the hazardous environment.
Among other precautions, large fans pump clean air into the mine and suck out most of the radioactive radon gas, while workers spray water across the site to keep down potentially harmful dust. The firm also says past accidents were swiftly and effectively cleaned up.
On a recent trip into the mine, none of the miners wore masks, and their hands and face were caked with uranium ore.
"It washes off," miner Cody Behuden, 28, told the BBC while licking his ore-caked lips.
Vice-president of US operations Harold Roberts said the miners were under no danger from ingesting uranium.
Dr Lee Grier, a biologist at University of California at Riverside, said exposure to uranium can be harmful, and the Navajo Native American reservation nearby is still is grappling with contamination from previous uranium mining and milling done by other companies. Those companies now no longer exist.
"The danger with long term exposure is that people breathe it, ingest it or it seeps through the skin," he said.
"These particles start bombarding tissues and cause wild uncontrolled cell growth like cancer."
After the ore is hauled from the mine, Denison Mines ships it north to a mill in the US state of Utah where the uranium is extracted by dissolving the ore in acid. The resulting product, called yellow cake, is then used in nuclear fuel rods.
The waste from the milling process is 80% more radioactive than yellow cake and has a half-life of 4.7 billion years. Thousands of tonnes of waste are buried in containers lined with 60mm (2.4in) of plastic.
Federal law requires the company to design the facility to last more than 200 years, and an insurance bond ensures funds will be available to maintain the facility.
The US Geological Survey (USGS) has been investigating mining risks in the Grand Canyon area in a six-month study.
Its research focuses on whether during mining, uranium could contaminate the area and seep into ground water.
The Colorado River supplies drinking water to some 30 million people from Los Angeles to Las Vegas.
"Theoretically uranium could get into the water supply," said Andrea Alpine, senior adviser on the USGS uranium project.
Geologist Jim Otton, who contributed to the survey, said mining results in increased contamination.
When uranium comes into contact with oxygen it becomes soluble in water, which increases the chance of contamination. Radioactive dust can also be blown away by the wind or washed away by rain.
This is what Carletta Tilousi of the Havasupai Indian tribe fears most. The Havasupai live on the bottom of the Grand Canyon and derive water from the rim.
"Mining companies are pursuing uranium for their own profit," she said.
"But the only benefit that we are going to get is a source of contamination. We are concerned about the future of our children, that's why we fight this."