Tests to continue on ground water in Nye County

Tuesday, March 7, 2000 | 11:08 a.m.

Radiation

There are three types of radiation from both natural and man-made sources. They are:

Although the Department of Energy released its results on ground water in Nye County that show radiation is not above natural levels in local rocks, further testing continued Monday.

Nye County officials reported last week that a single, unfiltered water sample taken at a depth of 400 feet measured radiation at 25 times above the safe drinking water limit.

Additional samples of drinking water were collected from a school and a senior center in Amargosa Valley on Monday, said Nye County Commissioner Jeff Taguchi, who represents residents of the district where the sample was taken.

"In the interest of assuring people their water is safe to drink, we continued testing," Taguchi said.

Earlier tests at the Ponderosa Dairy, Nevada's largest organic milk supplier, did not show radioactive contamination.

"Results of water samples taken by the Department of Energy have shown that accounts of high radiation in ground water outside the boundaries of the Nevada Test Site are in error," DOE spokeswoman Nancy Harkess said late Monday.

The DOE said its tests in Nye County water recorded alpha radiation ranging from 6.77 to 7.03 picocuries per liter, while Southern Nevada's tap water has averaged as high as 4.1 picocuries per liter for alpha.

A picocurie is a trillionth of a curie, a measure of radiation.

For beta radiation in Nye, the DOE measured between 6.16 to 6.51 picocuries per liter. The limit is 50 picocuries per liter.

Southern Nevada tap water has reached as high as 9.7 picocuries per liter.

"Your Las Vegas tap water is higher than the Nye County source," Harkess said.

No specific source of Nye County's radiation has been identified. Results could take weeks to pinpoint a source, Harkess said. Separate test results by Nye County and the state of Nevada are not expected to be complete until next week.

The DOE has spent $170 million to monitor ground water that runs off the Nevada Test Site -- where 928 nuclear warhead experiments were conducted from 1951 until 1992 -- said Carl Gertz, in charge of DOE's environmental monitoring efforts.

Earlier studies by UNLV and the Environmental Protection Agency show that some areas in Nevada contain higher levels of natural radiation than amounts found after nuclear bomb experiments, experts said.

Volcanic activity and earthquakes bring the radioactive rocks closer to the surface. Ground water can become contaminated by contact with radioactive soils and stones.

Both UNLV and EPA studies confirmed that the Great Basin's rocks are churning, bringing radioactivity from deep within the Earth to the surface. Volcanic rocks and granite tend to contain more natural radioactivity from uranium, radon and thorium, scientists said.

Nevada is the third most seismically active state behind California and Alaska.

So the higher level of radiation found by Nye County experts at 400 feet in a water well near the Test Site could be a "hot spot" coming from rock and soils, not old atomic bomb experiments, scientists say.

If that's the case, Nye's discovery does not prove there is a danger that radiation from Test Site explosions is migrating with ground water.

Even if there is migration, it would not flow toward the Las Vegas Valley, 65 miles southeast of the Test Site. It would flow southward, through Amargosa Valley to California.

The Las Vegas Valley has some of the lowest levels of natural radiation in the country, UNLV health physicist Bill Johnson said. "The only place lower is Florida."

The sediments that washed out of the Spring Mountains and formed the valley never were radioactive, Johnson said.

"The radiation was not there, so the valley was built on clean fill," he said.

In contrast, central Nevada, from north of the Test Site to Tonopah, contains some of the most radioactive rocks around, all of it from natural sources, he said.

Nevada is not alone in having to deal with naturally occurring radiation. On the East Coast, water users and those drawing from deep wells have to worry about radium and radon gas. In deep wells, 600 feet or deeper, radon is trapped and may enter rural homes, Johnson said. If the water sits in a holding tank for a day or two, however, the radon evaporates.

Scott Faller, a radiation expert working at the EPA laboratory in Las Vegas, said high levels of radon gas have been found in well water near Prescott, Ariz. The radiation discovered in Nye County's well, he noted, could come from natural elements trapped deep in the rock.

UNLV chemistry professor Vernon Hodge has tracked radiation all over the world, including an investigation into plutonium from above-ground nuclear weapons tests that could end up in ocean fish. Above-ground testing by the United States and the former Soviet Union ended in 1963.

Mary Manning covers environmental issues for the Sun. She can be reached by phone at (702) 259-4065 or by e-mail at manning@lasvegassun.com