December 04, 2007

Researchers tackle run-off, soil issues at Fort Knox

by K.C. Jaehnig

CARBONDALE, Ill. — Take Army tanks. Add a fragile, Kentucky limestone plain. Mix often, over decades, and you get some idea of the environmental challenge facing a team of researchers from Southern Illinois University Carbondale.

Hydrologists Karl W.J. Williard and Jon E. Schoonover with forestry colleagues John W. Groninger, James J. Zaczek and Charles M. Ruffner are trying to figure out how much water is running off tank training areas at Fort Knox, how much soil it's taking with it and what kind of soil and plant life is left for them to work with in restoring the land.

"That part of Fort Knox has been utilized for tank training since the '40s," Williard said.

"The problem is the amount of erosion and (the resulting) transported sediment it's caused. Sediment is the No. 1 water quality problem in the world. Sediment also can be particularly harmful to some aquatic organisms. There are threatened and endangered species in the sinkholes and caves and a trout hatchery nearby."

Fort Knox, 35 miles south of Louisville, occupies 109,000 acres in the north-central part of the state. The tank training area lies near the fort's western edge on a barren plateau, crisscrossed by treadmarks, which serves as the headwater for streams feeding into Otter Creek and an underground aquifer that also supplies drinking water for the military installation.

The training area's terrain presents a particular challenge for this kind of work. Much of Kentucky, including the part where Fort Knox sits, contains geological features — sinkholes, springs, "sinking" streams that disappear into underground channels and then pop up again elsewhere — formed as water dissolved the underlying, porous rock.

"It's like a maze underground with different channels going a lot of different directions," Williard said. "It makes our job a lot harder."

Williard said their job — assessing, then managing the flow of water and sediment — differs markedly from "the way things have always been done."

"Historically, what the Army did was to reseed these areas, keep them off limits while the vegetation grew back, then let the tanks back on and in three to six months, they were right back where they started," he said. "They want to rethink that, and they have given us a lot of latitude in developing our plan.

"We're going to map out where the water is concentrating on the soil surface and then put in sediment retention basins or ponds that can catch the runoff and retain the sediment before it gets to Otter Creek or a sinkhole."

They also are taking a closer look at where that sediment winds up.

"We want to determine if it's going into the sinkhole and if it is, whether it's moving through or staying put, plugging it up," Schoonover said.

"We've seen some evidence that fine sediments are moving through the underground sinkhole networks and ending up in receiving streams downslope. Sediment accumulation in the downslope areas of Fort Knox can potentially threaten the trout nursery and endangered crayfish that inhabit the caves connected to the sinkhole networks."

In addition, the researchers will plant wide swathes of hardy trees, shrubs and grasses around the sinkholes to slow the accumulation of water and sediment. Not that it will be easy.

"It takes a long time, 500 years or so, to develop one inch of topsoil," Schoonover said.

"They've lost thousands of years of topsoil — they're down to the clay subsoil now — and you just don't get that back. It will make it harder to re-vegetate because there's nothing much left in the way of nutrients."

The project, which includes an assessment period to see how well their management strategies are working, should end sometime in 2010. The knowledge they gain will go on forever.

"The neat thing is we're picking up techniques that may be used in different environments," Williard said.

"Ultimately, we're trying to remedy a problem, and I think we will be able to take that remedy to other places."