On Jan. 15, testing begins on new procedures to eliminate the main source of groundwater contamination
By Joe Walker firstname.lastname@example.org
The $3.2 million process, called six-phase heating, uses electrical resistance to heat the ground far below the surface and vacuum out vaporized contamination for carbon-filter treatment. Hexagonally arrayed electrodes are buried 100 feet deep near the southwest corner of a cleaning building called C-400 where the now-banned hazardous degreaser trichloroethylene (TCE) was used extensively for decades to clean uranium-enrichment machinery.
Historic spills have left almost 180,000 gallons of TCE beneath the building, some at concentrations more than 20,000 times greater than the federal safe drinking water standard of 5 parts per billion. That level, at which municipal water systems must treat to remove TCE, is equivalent to five kernels of corn in a silo 45 feet high and 15 feet wide. Molasses-like globs of the hidden, heavier-than-water chemical have lodged in underground rock fissures, feeding traces of TCE into the aquifer almost indefinitely.
"At the rate the TCE dissolves, if we relied on nothing but pump-and-treat systems, we'd be doing that for hundreds of years," said Greg Cook, spokesman for Bechtel Jacobs, lead environmental contractor at the site for the Department of Energy.
His and other firms hope a four-month trial run of the electrodes will prove much more effective than other processes, notably two ongoing pump-and-treat systems on the northeastern and northwestern plant boundaries.
"This isn't something you just go down and pump out. That's part of the difficulty," Cook said. "It doesn't flow like water. It sits at the bottom of an aquifer in kind of a thick mass and doesn't readily dissolve."
Digging up soil is impractical because much of the contamination is under the building, which is still in use, Cook said. The Energy Department expects the test will show the electrode process can remove 99 percent of the solvent from soil and groundwater. Monitoring wells will calculate the effectiveness.
"We're really hoping this technology will prove out well," said Don Seaborg, DOE site manager. "It (C-400 area) has been called the mother lode of contamination. If the process works here, it will work anywhere. That's why we're trying it here."
Tests in recent years have shown the difficulty of adapting cleanup techniques for the very deep, comparatively swift groundwater beneath the plant.
One trademark process called Lasagna, which ran for two years until last December, worked well in a relatively shallow clay layer that had trapped TCE in a one-acre area of the plant. Seaborg said Lasagna also heated the soil, but merely at 50 feet deep in an area between the aquifer and surface.
Although the electrodes have been used elsewhere at 100 feet, they have not been tested at the Paducah plant's groundwater velocities of one to two feet daily, said John Farrell, who is managing the cleaning building work for Bechtel Jacobs. Among other things, the test will show if the system can provide enough heat to vaporize TCE despite the cooling effect of the water, he said.
A second system, tried in late 2001, involved injecting iron filings into a gummy base of food material in the ground to form a filter — about 100 feet long and 120 feet deep — to break down the degreaser as it flowed. Cold weather lowered the viscosity of the gum.
"The injection process did not go as well as expected and we couldn't effectively get the barrier in the ground," Cook said. "It had been used effectively at other plant sites at shallower depths."
The pump-and-treat systems attack the heaviest concentrations of TCE but do nothing for the sources, he said. "In both those cases, we're catching already-contaminated groundwater and trying to clean it up. Without removing the source, you have a perpetual problem."
Through summer 2000, pumping and treating had released more than 700 million gallons of drinkable water back into the aquifer, yet the process is painstakingly slow. Although the two systems handle more than half a million gallons — enough to supply a town of nearly 5,000 people — the area of groundwater with TCE contamination above drinking-water standards is about two miles wide. The pump-and-treat plants' average daily yield is only enough TCE to fill roughly a two-liter bottle.
"Nothing we can do out here economically and physically can clean it up 100 percent," Farrell said, noting the importance of eliminating the cleaning-building source. "The cost would be horrendous."
Cook said another reason for getting rid of the huge TCE deposit beneath C-400 is that it may be "masking" other sources of the chemical.
TCE, a colorless or blue organic liquid with a chloroform-like odor, is suspected to cause cancer in humans if ingested at high enough quantities over a long period of time. Starting in 1988, traces generally below safe drinking water standards were found in a few residential wells near the plant. Since then, the Energy Department has replaced wells at nearly 100 homes with municipal water.
Seaborg said repeated tests have not detected TCE in the Ohio River. One reason may be the sheer dilution factor; another may be the back pressure of the river against the groundwater.
The chemical was banned at the plant in 1993 after being used for more than 40 years to clean equipment. The Energy Department says a damaged drain in C-400 went undetected for many years, allowing thousands of gallons of the degreaser to leak into the ground. However, some former C-400 workers blame laxity in following procedures from managers on down.
Retiree Harold Hargan of Mounds, Ill., said workers dipped the processing equipment into huge vats filled with TCE. Had the equipment been properly rigged, the degreaser would have drained back into the vat after the equipment was removed, he said. Instead, it was routinely spilled on the floor and at least 5,000 pounds washed into drains during a 10-year period, he estimates.
Hargan made his claims in testimony last fall before a federal grand jury investigating past environmental practices at the plant.