Yucca water runoff raises concern: Floods may pose radiation risk to communities

Tuesday, May 8, 2001 | 10:54 a.m.

Floodwater draining from Yucca Mountain is raising concerns that radiation could be carried into the environment.

New research also shows that similar drainage occurred at the Nevada Test Site, where atomic testing occurred from 1951 to 1992.

The research raises the possibility that radiation from a proposed high-level nuclear waste repository at Yucca Mountain or from the Test Site could be carried into nearby communities.

It is the first scientific evidence of water runoff heading from Yucca Mountain or the Test Site to populated areas. Yucca Mountain, 90 miles northwest of Las Vegas, is the only site being studied to permanently store 77,000 tons of commercial and defense waste. There has never been proof of radioactive contamination off the Test Site.

In addition, a U.S. Geological Survey study showed flash flooding in the 300-square-mile area including Yucca Mountain and the Test Site could close highways -- disrupting the transportation of nuclear waste -- and could interfere with above-ground repository operations.

During peak operations at a proposed repository, up to three truckloads a day could arrive at Yucca Mountain.

"That is a very significant development," a spokesman for Rep. Shelley Berkley, D-Nev., said. "It is very clear that water threatens the mountain. There is proof of major flooding on Yucca Mountain itself."

But the Energy Department, which is charged with studying Yucca Mountain's suitability as a repository site and would build and operate a repository if it is approved, downplayed the findings.

"It's not news that the area floods," DOE Yucca Mountain Project spokeswoman Gayle Fisher said. "That's why it's called Fortymile Wash."

The observations made by USGS scientists during storms in 1995 and 1998 will have to be considered in an environmental impact study under way on the proposed repository at Yucca Mountain.

The floods showed that the Amargosa River "has the potential to transport dissolved and particulate matter well beyond the boundary of the NTS (Nevada Test Site) and the Yucca Mountain area during periods of moderate to severe streamflow," the report concluded.

The Amargosa River, draining both areas at the Test Site and Yucca Mountain, usually runs underground, but exceptionally wet years in 1995 and 1998 caused the river to flow at the surface.

Contaminated water could travel as far as Death Valley in California, the report found.

A USGS report that began as a study of how much rainwater might penetrate Yucca Mountain's surface turned into a flash flood investigation, USGS hydrologist Daron Tanko said.

Scientists had believed that runoff from storms would not drain into the river from the Test Site, 65 miles northwest of Las Vegas, where more than 1,000 nuclear weapons exploded above and below ground.

However, in 1995 and 1998 storms dumped so much rain down Fortymile Wash at Yucca Mountain and Topopah Wash at Little Skull Mountain that runoff flowed into the Amargosa River and flooded Badwater Basin, a dry lake bed in Death Valley, Calif. A weeklong storm in February 1998 again caused the river to run and closed U.S. 95 for two days.

Such floods in wetter periods could occur every three or four years, Tanko said.

A major flood occurred at Yucca Mountain and in the nearby town of Beatty in 1969, probably one of the largest inundations in that area's history, co-author Pat Glancy said.

"That was probably the biggest flow we ever saw in Fortymile Wash," Glancy said. "Fortymile Wash does go on a rampage every once in a while."

The DOE draft environmental impact report does not consider runoff into Fortymile Wash or Topopah Wash, the subjects of the USGS report.

It does estimate that nine to 12 feet of water could flow in the Midway Valley Wash next to nuclear waste-handling operations at the northeast end of the repository during a 100-year flood. That water path flows away from populated areas and ends on Test Site property.

To avoid those floodwaters, the DOE plans to build facilities away from flood-prone areas and divert runoff into constructed channels.

The DOE's final environmental impact study is expected to be released at the end of this year.

Berkley said she thought the USGS findings were significant enough to include them in her testimony before the Senate Energy and Water Appropriations Subcommittee this week.