Think of them as a sour note from Hanford for the late singing cowboy Roy Rogers and the Sons of the Pioneers.

I'll keep rollin' along.

Deep in my heart is a song.

Here on the range I belong.

Driftin' along with the tumblin' tumbleweeds.

Twwaaaannng! Klunk!

They are tumbleweeds in central Hanford, out there sucking up contaminated ground water before tumbling about in the wind and scattering radioactivity here and there.

And a November Department of Energy report notes that more radioactive tumbleweeds have been showing up.

The numbers tell part of the tale: Eleven contaminated tumbleweeds were found in 1995, 19 in 1996, 39 in 1997, and 20 in the first six months of 1998.

Hanford officials say the increase is mostly linked to increased efforts to find radioactive tumbleweeds and expanding the monitored areas from 8,786 acres in 1995 to 11,376 acres in 1998.

Of Hanford's roughly 1,100 documented findings of contaminated vegetation in the past 50 years, more than 80 percent were tumbleweeds.

Almost all the contaminated tumbleweeds bounce around central Hanford's 200 Area, where the ground underneath is crisscrossed by numerous plumes of radioactive contaminants.

The weeds - more formally known as Russian thistle - have roots that can stretch 15 feet deep in search of water, which at Hanford is likely to be contaminated.

Radioactive strontium 90 is common in tumbleweeds, which absorb the radionuclides into their tissue.

The plants usually grow to 3 or 4 feet tall before they break off to scatter seeds as the wind blows them around.

At Hanford, they also scatter bits and pieces of radioactive material.

The radioactivity in each piece is slight, but the pieces are a symptom of an ongoing Hanford problem: controlling myriad ways that nature conspires to spread radioactivity.

Add mice and various bugs to the list.

They track through Hanford's contaminated nooks and crannies, then walk or fly off, spreading radioactivity.

Those specks can be picked up on workers' shoes and tracked off-site. In September, that led to contaminated socks showing up in a worker's laundry hamper at home.

In 1996, a contaminated mouse made it to the Tri-Cities Food Bank in north Richland.

And this past fall, a couple dozen contaminated fruit flies scattered radioactive specks around the 200 Area.

Then contaminated trash showed up in the Richland landfill, and the city temporarily closed the landfill to Hanford. Trash was hauled back to Hanford, while new procedures were hammered out between Hanford and the city.

So Atomic Age tumbleweeds are taken seriously at Hanford.

In fact, the November DOE report calculated Fluor's seven-company team spent $1.68 million in fiscal 1998 to control vegetation like tumbleweeds and various critters ranging from mice to bugs.

The report said that figure includes some unnecessarily high overhead costs that could be reduced if the program was better coordinated within Fluor's team and with another prime contractor, Bechtel Hanford Inc.

Bechtel spent another $451,000 on herbicide spraying in 1998, the report said.

Efforts to improve planning and coordination are under way, said Fluor and DynCorp Tri-Cities Services officials.

The November report was prompted by a pair of employee complaints that the tumbleweeds were not being tackled in a timely manner.

So Hanford workers are now systematically surveying Hanford, including checking tumbleweeds.

"There might be 50 tumbleweeds, and we'll find one with some radioactivity,"said Greg Perkins, Fluor Daniel Hanford's director of radiation protection.

Contaminated tumbleweeds are stuffed into bags, then crushed and buried in central Hanford's low-level waste trenches.

But such cleanup is expensive. Strict radioactivity handling requirements bump up the costs of gathering and burying contaminated tumbleweeds - which can run $27,000 to $160,000 per acre, depending on the degree of infestation.

The November report also stressed preventing the tumbleweeds from sucking up contaminants in the first place.

That means spraying herbicides to stop the growth of tumbleweeds - for about $343 per acre.

Perkins explained the work isn't as simple as it sounds. "You can't go out and blanket an area with spray. Certain (rare and sensitive) plants have to be protected, and you can't arbitrarily kill those off," he said.

Contaminated areas also have to be checked and sprayed repeatedly because roaming tumbleweeds - each capable of spreading 200,000 seeds - repopulate themselves very fast, said Tom Harper, Fluor Daniel Hanford's director of infrastructure.