After decades of delay, the U.S. Forest Service is seeking public comments about a slow-motion contamination risk — the radioactive dirt piles left over from now-abandoned uranium mines in the Young Ranger District along popular Workman Creek in the Sierra Anchas.
During the boom years of uranium mining in the 1950s and 1970s, mining companies dug “dozens” of mine shafts following veins of the naturally occurring, radioactive mineral. Most of the once-sealed mine shafts are now open after vandals pried loose the timbers and tore down the warning signs. The mine shafts still have radiation levels that could cause cancer and other health problems.
Moreover, the mining companies left faintly radioactive tailings at the entrance to the mine shafts and in several sites along Workman Creek where they dumped the ore waste, including two public campsites, currently closed.
Many of these tailings dump sites lie along Workman Creek, which drains into Roosevelt Lake, which is a drinking water reservoir for Phoenix. Tests show sufficiently high radiation levels in the creek that the Forest Service advises people against eating fish caught in the creek. However, no dangerous levels of radiation have reached Roosevelt Lake, say Forest Service officials.
David Frew, recreation lands and minerals staff officer for the Young Ranger District, said the Forest Service has opened the public comment period on possible solutions to the problem and in the meantime is struggling to at least post signs at all the potentially hazardous sites and abandoned mines.
“The major message for people is — stay out, stay alive,” said Frew of the numerous open mine tunnels that would still light up a Geiger counter.
“Many of them were boarded up, but people have broken into them over the years. We tried a whole signage program, but people take them down.”
The shafts and the tailings piles contain arsenic, uranium and radium-266.
A Geiger counter taken into one of the mines would register an “evacuation level,” said Frew.
“That means you’d evacuate the area due to the health risk.”
However, the levels outside the mine remain relatively low, he said.
“You get radiation exposure riding in an airplane or in a lot of basements, due to radon. Just being in Arizona exposes you to elevated levels,” due to naturally occurring radiation in many types of rock, said Frew.
The Forest Service commissioned a study of the extent of the problem and now seeks public comments on that study.
A copy of the study is available at www.fs.fed.us/tonto or by calling the Forest Service and arranging a time to go to the offices in Phoenix or Young to review the documents. The Forest Service will continue gathering comments until March 3, before making a decision on a cleanup plan.
Although federal officials have known for years of the contamination along the creek that empties into Roosevelt Lake, they still have no idea how much a cleanup will cost.
“In some places, we could put (the tailings) back into the mine” and seal off the entrance, said Frew.
“In other cases, you’d look at taking the topsoil away and hauling it to a storage site.”
The current study examines various options, although Frew said the Forest Service has no money at present to implement any of the potentially expensive remedies.
“It’s going to be a lot of money — we can’t say for sure,” he said.
The Forest Service also has no idea how many miles of tunnels were dug, following the veins laced with uranium during the boom years in the 1950s. Most of the mining claims have been abandoned and it’s unclear whether the government can require any modern corporations to assist in the cleanup, although Westinghouse was one of the major corporations engaged in the exploratory mining.
Most of the mining sites have perhaps half a dozen shafts, most extending for only several hundred yards — but some potentially boring much deeper into the mountain. The shafts generally follow a layer of dripping quartzite that runs throughout the Sierra Anchas and which is associated with a low-grade of uranium.
“If you think of the mountain as a cake, this layer runs right through it,” said Frew.
The tailings and abandoned mine shafts represent one small, local toll in the rush after the invention of the atom bomb to mine enough of the dense, weakly radioactive material to build thousands of warheads and fuel nuclear power plants. Other fallout from that boom in exploration locally before doctors understood fully the low-term effects of low-level radiation includes a raft of cancer cases among Navajo miners.
In it’s natural form, uranium is about 70 percent more dense than lead, but less dense than .99999 gold.
The silvery gray element has more neutrons and protons packed into the core than any other naturally occurring element and binds readily to other non-metallic elements.
To become explosive, it must be chemically extracted for the other elements with which it bonds — usually with acids. Once purified and concentrated, it can be readily split apart.
The fragments go flying off and split apart other sufficiently concentrated atoms, leading to a chain reaction fission explosion, which was the basis of the first atomic bomb using uranium 235. Later bombs used more concentrated and refined forms.
Hydrogen bombs use a nuclear fission explosion to create the temperature and pressure necessary to trigger a fusion reaction in a concentrated plutonium fuel, unleashing a much greater explosion through the fusion of hydrogen atoms — the same reaction that powers the sun.