It's nature's equivalent of David versus Goliath. In this instance David happens to be 7 mm long and Goliath is the U.S. Department of Energy and the scientific community.

Their battleground is the Idaho National Engineering Laboratory (INEL) in southern Idaho where harvester ants are stymieing waste disposal efforts by doing what ants do best - digging below and moving dirt above.

But this dirt is hotter than the typical arid soil of the Snake River Plain. It contains low-level radioactive waste.

Armed with money from the Energy Department, University of Idaho scientists are studying methods to prevent the ants from disturbing radioactive contaminants by digging vertical tunnels in the soil. The tunnels allow deeper percolation of water, and more moisture means more entry to radioactive waste.

Seven million cubic feet of government waste is currently stored in disposal sites at INEL, including more than 300,000 pounds of debris from the core of the infamous Three Mile Island nuclear plant and 1,276 pounds of plutonium, also classified as "government nuclear waste."

Scientists James "Ding" Johnson and Paul Blom are in the second year of a three-year study of "biobarriers' against harvester ants. Their research tools are plexiglass ant farms that house some 5,000 industrious ants. The four-foot-tall farms contain four sections of pipe with different colored soil or gravel mix. The deepest of the four levels simulates the radioactive soil. If that particular color of gravel makes it to the top of the ant farm, then the barrier is marked a failure and another material is tested.

Finding just the right substance or the exact combination of materials is proving to be a challenge because the scientists must design the biobarrier with other creatures in mind. In the southern desert of Idaho where INEL is located, rodents are also digging.

"Ants walk through cobble that can stop small mammals, but ants can't get through gravel those same mammals can," Blom said. "We're trying to find just how much gravel to use and which particle size will stop the ants."

Doyle Markham, senior research ecologist at the INEL, said the number of ant dens and the quantity of contaminated soil they disturb are minor, but he is certain that the density of the dens will grow if they continue unchecked. For a biobarrier to meet waste disposal requirements set by the Environmental Protection Agency, it must last for more than 500 years.

Tim Reynolds, another research ecologist at the INEL, said, "If the biobarrier is a success - and we think it will be - this will be a resource to handle any type of waste you can imagine, including medical, chemical and biological waste."

The lifetime of an ant colony is estimated at 17 to 50 years. Harvester ants were noticed years ago when large, circular disks were spotted from the air - a sign of vegetation clearing around ants' nests.

The first scientific report of the harvester ants' presence in southern Idaho was written in 1932. The first report of the possible threat to storage facilities at the INEL appeared in 1991, in the Journal of the Idaho Academy of Science.

The INEL, established in 1949 as the National Reactor Testing Station, contains the largest concentration of nuclear reactors in the world. Over its 44-year history, 52 reactors have been built on the 890-square-mile site. Fourteen of the reactors are operable; the others have been phased out.

* Stephen Lyons

The writer is a poet and journalist in Moscow, Idaho.