When field tests recently found contamination from Delaware's worst toxic waste site drifting into a deep aquifer, the discovery confirmed what some regulators had long feared: The pollution from an abandoned Delaware City chemical plant could pose a threat to a key source of drinking water.
Now regulators are faced with the daunting task of figuring out whether the cancer-causing pollutants can spread farther and, if so, how to stop them.
One pollutant, the carcinogen benzene, was detected in the upper part of the Potomac Aquifer under the former Metachem Products site at more than three times the level allowed in drinking water, officials said last week. None of the public water supply wells around the site are in immediate danger, regulators said, and public health officials said they will test all wells within a one-mile radius in coming weeks.
Scientists said the meandering, 100-million-year-old seams and clumps of wet sand that make up the Potomac Aquifer are only partly understood. In some areas the water-filled deposits lie hundreds of feet below the surface, snaking through prehistoric clay and mud the way chocolate is laced through a marble cake. Getting a fix on what is happening in the aquifer can confound well-drillers and pollution-tracking experts.
One concern is that drilling into the area to do more tests could open up new pathways for the pollution in an aquifer that supplies northern Delaware with 30 percent of its water.
"We are as alarmed as you," John B. Blevins, director of Air and Waste Management for the Department of Natural Resources and Environmental Control, told members of the public who attended a briefing at Southern Elementary School last week.
Environmental Protection Agency managers said the quest for answers will require groundbreaking research extending to the very bedrock under and around the Metachem site.
The EPA-financed investigation approved last week could include ground-penetrating radar to help environmental engineers explain how the chemicals trickled past the clay barriers that policy-makers counted on to protect the aquifer from Metachem's pollution.
New monitoring wells also are planned, along with evaluations of contamination levels in the air, shallow groundwater, surrounding soils and wetlands, and nearby streams. Studies will cover about 76 acres around and under the factory, which covers only 26 acres of the total.
A toxic property
Metachem's former owners purchased the plant from the former Standard Chlorine of Delaware Inc. in December 1998 and abandoned the operation to the government in May 2002, leaving behind more than $60 million in debts and more than 40 million pounds of toxic chemicals. The factory produced chlorinated benzenes, a type of toxic, long-lived chemical used for herbicides and pesticides. Some of the company's products in the past were used to make Agent Orange, a now-banned herbicide used in Vietnam.
Millions of pounds of chemicals spilled from the plant over the years. Much of the spilled material remains under and around the plant, trickling into Red Lion Creek and a tributary, as well as soaking into groundwater.
Just above the Potomac aquifer, in wet sands 70 feet down, some cancer causing compounds from Metachem have been found at concentrations as high as 28,000 times the federal drinking water limit.
Hilary Thornton, EPA project manager, said state and federal officials will meet Tuesday to consider interim steps to contain this relatively shallow groundwater. One option calls for surrounding the area with a buried wall up to 70 feet deep and more than a mile long.
"It doesn't give us a great deal of comfort," said Delaware City Manager Paul H. Morrill Jr. after learning that the contaminants could threaten 700-foot deep Potomac wells used by the city.
Addressing the concerns of Morrill and others may be costly.
Even before last week's announcement, officials had estimated waste disposal and pollution cleanup costs at the Metachem site could top $100 million. The EPA has spent more than $13 million on emergency disposal and stabilization work.
Thornton said contractors will be paid about $2.6 million to study the contaminated aquifer and other problems and prepare a recommendation for permanent solutions.
"Of course it should be looked at, to see where the contamination is and what the potential is for that contamination to move through this system," said Delaware Geological Survey director John H. Talley. "The Potomac formation is an extremely complex aquifer system, and it's very difficult to trace."
Thomas E. McKenna, a researcher for the geological survey, said Potomac water creeps slowly through sand channels formed by rivers that were on the surface in the Cretaceous period, 65 million to 140 million years ago. Mud and clay make up about 80 percent of the layer, with water moving most easily through the sandy channels. Water trickles down from more-recently formed and shallower aquifers to keep the system filled and moving.
"The sands come and go," McKenna said. "You can move 500 meters from a well that's got gangbuster [water-filled] sand and you might hit 600 feet of clay."
The past catches up
Although Metachem was assigned to the nation's list of top-priority federal toxic cleanup sites in 1987, comprehensive sampling of the Potomac aquifer began only last year. Federal officials said last week the factory's owners repeatedly fought efforts to test the aquifer for contamination between 1987, when a series of chemical spills landed the site on the Superfund cleanup list, and 2002, when the plant was shut down.
"For years, the EPA had discussions with Standard Chlorine and Metachem about an investigation of the Potomac, their insistence always was there's no contamination," Thornton said. "When the bankruptcy occurred, the EPA took over and we set the wheels in motion to investigate."
The agency's recent findings have sparked protests from some community and environmental groups who criticized state and federal regulators for failing to closely regulate Metachem and its previous owners, Standard Chlorine of Delaware.
"It was sort of wishful thinking to believe that the contamination would never get into the deep aquifer," said Seth W. Ross, a Delaware Nature Society member who has followed the problem for years. "They've got to contain it, and they're going to have to monitor that for years and years."
Reach Jeff Montgomery at 678-4277 or jmontgomery@delawareonline.com.
source: http://www.delawareonline.com/newsjournal/local/2004/02/08answerssoughton.html 8feb04
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