The Army plans to pump out and treat ground water in the Edgewood area of Aberdeen Proving Ground that is contaminating a creek with mustard gas agent and other dumped toxins.

The proposal is designed tostop further pollution of Watson Creek until technology is developedto clean up the Old O-Field on the base. The U.S. Environmental Protection Agency placed the O-Field on its Superfund list of the nation's most hazardous waste sites in February 1990.

The 4.5-acre O-Field was used in the 1940s and 1950s as a dump site for chemical warfare agents, munitions and other hazardous wastes left over from the proving ground's military testing programs.

TheAPG plan to treat the ground water is only a stopgap measure for thenext three to five years. During that time, the army will study how to decontaminate the creek and remove toxins that have leaked throughthe landfill and poisoned the ground water aquifer.

The pollutiondoes not affect supplies of residential drinking water and is contained within APG on a peninsula surrounded by the Gunpowder and Bush rivers and the Chesapeake Bay.

"There is no significant health risk from the site, but we still feel we need to stop the ground water from migrating and further contaminating Watson Creek," said project manager Cynthia Couch, an APG environmental engineer.

The water tablehas been contaminated beneath the dump, bounded on the west by the Gunpowder River and on the north and east by Watson Creek.

The areais fenced and the only human activity is sampling test wells to monitor any environmental threat.

Despite the contamination of Watson Creek, APG has not collected extensive data on its effect on aquatic and wildlife in the area. But the Army says that the creek might havebeen degraded as a nursery area for several fish species and that wildlife feeding appears to be at risk from exposure to poisonous heavymetals found to be contaminating the water, such as arsenic and cadmium.

"As long as the source of pollution is there, the ground water will continue to be contaminated," Couch said.

But the contaminants provide virtually no risk to humans. The Army estimates that a person swimming in the Gunpowder River at the mouth of Watson Creek -- a restricted area -- would run a four in 1 million additional increase risk of cancer.

The APG cleanup would involve diverting the aquifer from its northeasterly flow into the creek through a system of 14wells. The water would be pumped from the wells through a treatment plant, where it would be decontaminated and discharged into either Watson Creek or Gunpowder River.

The treatment plant would rely on acombination of ultraviolet light and hydrogen peroxide or ozone to destroy organic pollutants and chemical separation of the water and inorganic contaminants. The contaminants would produce a residue to be scraped from filters for disposal off-site.

The APG plan would cost almost $1.9 million to construct the pumping system and treatment plant and another $467,000 to operate annually. If no solution is found to extract and dispose of the hazardous waste safely, the project could end up becoming a perpetual containment effort.

"If we were to find some magic wand, we could clean up the source of contaminationusing microorganisms or something," Couch said. "But right now thereis no technology to do that."

The public can comment on the cleanup plan through Aug. 17. A public hearing is scheduled for 7 p.m. Thursday at the proving ground's Edgewood Area Conference Center, at Hoadley and Austin roads.

APG officials will also discuss their finding of no safety or environmental risks from the White Phosphorous Undewater Munitions Burial Area in the shallow waters of Mosquito Creek between Black Point and Gull Island.

The area reportedly was used as an aquatic dumping ground in the 1920s, but APG studies have neverbeen able to confirm the location.

An investigation in 1988 and sediment sampling in 1989 have led APG officials to conclude that whatever hazards might have been present no longer exist.

APG's plans for the O-Field have not produced much comment from the public. But the installation's efforts to clean up toxic waste sites have won praise from environmentalists and citizen groups who have been critical of separate plans to incinerate mustard gas agent and other chemical warfare waste awaiting disposal.

"They're really making an effort to rectify past mistakes," said Helen Richick, who monitors environmental matters at APG for Concerned Citizens of Harford County, a Joppatowne-based citizens watchdog group.

But Richick, who also monitorsAPG's Technical Review Committee for the county's General Assembly delegation, added that "there's an incredible amount of work to do. There's no telling how long it will take."

APG has been developing, testing and dumping chemical warfare agents and other munitions sinceWorld War I, leading the EPA to put the entire 13,000-acre Edgewood area on its Superfund list last year.

The cleanup of O-Field beganin 1949. But the first effort only compounded the problem, accordingto the new ground water containment proposal.

A non-corrosive chemical was applied to the field in an attempt to detoxify mustard gas that had been scattered over the site by spontaneous detonations. Butthe degraded agent showed up in ground water, which in turn became contaminated with lethal chlorinated hydrocarbons.

APG environmental engineer Couch said there will be no such risk this time. "They were going into the landfill and handling the munitions and handling the(mustard gas) agent, and we're not even going to go on to the site,"she said.

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