Over the course of a year, Continental and the MU researchers experimented with various formulas and, in 2003, ended up blending, composting and placing about 80,000 tons over four acres at depths of 10 to 15 feet. They also constructed a smaller test plot and equipped it with moisture content sensors, temperature gauges, water collection devices and a rain gauge to quantify the rate and depths to which rainfall infiltrates the blended soil.

On the 4-acre site, they've planted reclaimed areas with native grasses, shrubs and trees to begin biological processes associated with naturally occurring soil. The researchers surmise that, once established with native growth, the artificial soil layer will become what they call an "evapo-transpirative" barrier against the concentrated CKD below.

The idea is to create a layer that will keep water from the CKD pile. "Our desired goal would be to have our soil resemble a real, native Missouri soil," says David Hammer. One hurdle the researchers face is that the CKD included in the artificial soil can contain heavy metals. Metals are also sometimes found in organic sewage sludge.

How do these materials behave in this system? The only way to find out was to look. They opened two pits in the artificial soil -- one where material had been in place for 18 months and another for 6 months. Where the organic layer and mineral layers of the artificial soil meet, the researchers saw a green-tinted layer in various stages of becoming cement-like. They suspect the green tint is a sign of organic acids and heavy metals chelating, or binding up with one another, which makes the metals more stable.

"The word chelate is derived from the word claw," Hammer explains. "It's like a claw-like hand is reaching out from the organic material and grabbing the heavy metal molecule and taking it with it. Heavy metals are often immobilized in this way by organic acids, which is a good thing."

Having a cement-like barrier is advantageous because it can capture the heavy metals. This layer is also acting as a physical barrier to water working its way down into the system. It could also be a problem, however. If the organic layer above it decomposes and erodes, the green-tinted cement layer would become exposed.

"It's a little different from other approaches I'm familiar with because they are chemically creating this layer, a physical barrier to prevent water from entering the CKD," says Jim Dwyer, a contaminants biologist with the U.S. Fish and Wildlife Service who coordinates Superfund clean up efforts in a tri-state region. "Another question to ask is what are the concentrations of the metals that are contained in this organic matter, and how biologically tied up are those metals."

Dwyer also says that one of the biggest factors affecting the success of land-reclamation projects -- whether the land has mine tailings, slag or CKD on it -- lies in understanding water and how it works in that environment.

Since potential toxins move via water, Likos must measure how effective the artificial soil is as a hydraulic barrier. Also important is learning how the soil matures and what kind of changes it will undergo. How will changes associated with the artificial soil's transition from a "young" soil to a "mature" one compare with the real thing? At what rate will the organic layer decompose and weather? How quickly will acids from the organic layer move into the mineral layer? All these questions bear on the artificial soil's usefulness.

"We're putting an artificial thing into a natural environment, and nature's going to want to change it around," Likos says. "So we're very interested in predicting how this pretty simple, two-layer system is going to self-partition into distinct horizons or soil-layering."

As the project continues, the researchers will excavate observation trenches to examine the horizon development and predict the equilibrium soil profile -- that is, when enough plants and shrubs are growing on top to keep the soil supplied with a balance of organic material that keeps pace with decomposition. After they have collected some of this data, the next step will involve generating a computer model of the system to see how it might behave over time.

"I hope to be able to show it can work here as a hydraulic barrier as well as a barrier to contaminant transport," Likos says. "Because I'm a civil engineer, I'll of course be thinking about what other applications the artificial soil could have."