Since 1978, the Army has spent millions of dollars to dig it up, pump it out of the groundwater and break it up with hydrogen peroxide injected underground. These efforts have removed tons of contaminated water and clay, most notably in areas of the Anniston Army Depot where for decades workers dumped the acid-like waste into unlined ponds and trenches.
In addition to being elusive, TCE is profoundly bad for your health.
A toxic mix
Drinking small amounts of TCE for a long time may cause liver and kidney damage and impaired fetal development and weaken the immune system. A growing body of research also links the compound to certain kinds of cancer, although the federal government hasn't formally recognized it as a carcinogen.
The Environmental Protection Agency decreed in 1989 that water containing a TCE concentration of fewer than 5 parts per billion is safe to drink regularly. By comparison, water may contain up to 10 parts per billion of arsenic and still be OK, according to the agency.
In other words, TCE is thought to be twice as toxic as arsenic.
"When I started doing this work, (the allowable TCE concentration) was 40 parts per billion, then 20 parts per billion, then five parts per billion," said Dr. David Ozonoff, an environmental health professor at Boston University and a TCE expert.
"That tells you there's a lot of uncertainty about it."
For a manmade chemical, TCE is surprisingly ubiquitous. As many as one-third of the nation's public water supplies contain at least trace amounts of the substance, the federal government estimates.
The widespread pollution is a side effect of TCE's popularity as a one-size-fits-all compound. It has been an ingredient in spot removers, dry-cleaning chemicals and correction fluid, among other things. Doctors even used TCE, under the brand name Trilene, as an anesthetic until the government banned it for that use in 1977.
For many of the stories, the setting is a military base where the substance spilled or got dumped onto the ground.
"The military is the largest owner of Superfund contaminated sites in the country, and TCE is one of the most toxic chemicals at them, except for fuel," said Lenny Siegel, director of the Center for Public Environmental Oversight, a California group that tracks toxic pollution nationwide.
Where the water goes
The Anniston Army Depot's saving grace — what has helped it avoid becoming the next Camp Lejeune — is that no one drinks the groundwater directly beneath the installation. No one has complained of getting sick.
But, as in real estate, pollution is all about location. And this particular pollution happens to be a mere 1.5 miles north of where the city of Anniston's main drinking water supply, Coldwater Spring, bubbles up from the ground.
Although they lack conclusive evidence, scientists suspect leached rainwater is washing the depot's TCE in drips and drabs into the spring.
The same forces that created the spring are to blame for that uncertainty. The spring and the depot sit at the base of Coldwater Mountain, which itself sits at the southern toe of the Appalachian Mountains. The violent geologic spasms that created the mountain also left huge cracks, or fractures, underground.
One of the fractures happens to wind its way to the surface just east of present-day Alabama 202 and north of U.S. 78, forming Coldwater Spring. The others remain below ground — invisible and unknown.
Rain leaches into the earth, filling the fractures. And the underground cracks splay and twist like three-dimensional rivers. Ron Grant, the former director of risk management at the depot, said he's had separate contractors tell him that the depot's groundwater flows north, south, east and west away from the site.
Another complication is that the Jacksonville Fault runs northeast to southwest along the southern edge of the depot, where the TCE contamination is most potent. The fault is highly fractured. And geologists aren't sure whether the fault acts as a conduit or a barrier to the pollution.
"We've been doing this for quite a while, and we still don't have a complete handle on it," said Ben Bentkowski, the EPA hydrologist assigned to the depot Superfund site. "It's half-science, half-art, and you really don't know the truth until you drill."
The fault runs beneath the spring, so in that regard it doesn't matter whether the fault zone impedes the TCE plumes or acts like a watery highway, said David Steffy, a geology professor at Jacksonville State University. He also is a member of the restoration advisory board, a citizen watchdog group that oversees the depot cleanup.
The trouble with the depot's TCE waste is finding it. Most of it is hidden in countless fractures deep below the ground.
"We're just kind of victimized by the geology," said Grant, who now sits on the same watchdog group as Steffy.
'The option seemed the best'
By the late 1980s, workers had removed most of the TCE-tainted soil. Now, their attention turned to a bigger headache: the toxics in the groundwater.
In the early 1990s, the depot installed a network of 15 wells designed to pump up the industrial area's polluted groundwater. Pipes transported the water to one of three treatment plants.
"Of the options that were identified at the time, that seemed the best," Grant said.
But from the outset, the "pump and treat" system was a mess. Iron and microbial slime fouled the pumps and pipes, reducing their pumping capacity to a third of their designed capability. By the end of the decade, consultants declared that the pumps had done nothing to reduce the concentration or extent of the TCE plume.
The depot overhauled the pump system in 2001. Three treatment plants became one. As a result, TCE concentrations did taper off, but the wells still don't capture enough of the contaminant to be considered a long-term solution, said Pat Smith, an environmental engineer at the depot.
Today the wells remove about a pound of TCE a day, he estimated.
"It's hit or miss," he said. "When you drill a well into fractured rock, you don't know if you're going to hit a fracture or not."
The only way to ensure complete TCE removal with a "pump and treat system," Grant said, is to drill an "infinite" number of wells across the contaminated area.
With no better option at hand, officials continue to run the pump system at a cost of $250,000 a year.
About eight years ago, depot officials quietly began exploring a bureaucratic answer to their problem. They hired a consultant, Malcolm Pirnie, and began building a case for a technical impracticability waiver from the EPA.
"That was the way we were going to go because we didn't see any way of meeting (cleanup goals)," Smith said.
The waiver, if granted, allows polluters to back away from having to meet the typical Superfund goal of scrubbing groundwater to the point that it is safe for drinking.
Polluters still must do whatever is necessary to make sure the pollution doesn't hurt the public. And they must perform reviews every five years to check if any emerging technologies have popped up that might further the cleanup.
The EPA insists that the process does not amount to a free pass for polluters. The 1993 EPA guidance document states that the impracticability waiver is designed to promote "the careful and realistic assessment of technical capabilities at hand."
Smith, for his part, said, "It's not a walk-away situation. We still have to protect the public and new technologies."
Although the waivers were intended to be temporary, none of the 48 waiver-approved sites across the country had come off the list as of 2006, according to an analysis by the firm Malcolm Pirnie.
"That tells you something," said Steffy, the JSU professor. "You really shouldn't enter into it haphazardly."
The EPA and ADEM have signaled they aren't ready to sign off on the waiver. Both agencies told the Army about two years ago to refocus on cleaning up the most contaminated part of the site, the area beneath the industrial complex. The initially proposed "waiver zone" included land well outside the installation as far as Coldwater Spring.
But if the new study fails to turn up any workable way forward, Smith said, the Army will once again pursue a waiver.
The way forward
So the Army Depot finds itself casting for a contractor to give the cleanup one last detailed look. The installation is in negotiations with a California-base environmental consulting firm called Tetra Tech, Smith said.
A handful of technologies are on the table. One would have the Army inject hydrogen peroxide and iron into the earth to make the contamination fizz its way up to the surface. Another involves burying electrodes into the ground to boil the TCE out of the water. Others will be reviewed as well.
Each has its pros and cons, Smith said. The question will be whether a solution can be implemented that is cost effective and has a reasonable timetable.
"We are stewards of the taxpayer money," the environmental engineer said. "We won't allow an inefficient or ineffective technology to go forward."
Meeting the EPA cleanup requirements, though, might get a lot tougher soon.
The agency is considering whether to change the longstanding 5-part-per-billion drinking water standard for TCE. A final decision is expected in 2010.
A 2001 EPA assessment found that the compound is up to 65 times more toxic than previously believed. All signs point to a significant reduction in the contaminant's allowable concentration, perhaps to as low as 1 part per billion.
The Anniston depot's Smith isn't sure how he will meet a lower concentration.
"We are at a point where it's technically impracticable to reach 5 (parts per billion)," he said, "so 1 (part per billion) would be even harder."
Coming Tuesday: Army looks to reduce but not cease TCE use.
Jeremy Cox was a 2008 Knight Fellow in Community Journalism at The Anniston Star and the University of Alabama.