New weapon in the search for buried munitions on Cape Cod
By GEORGE BRENNAN | Cape Cod Times, Hyannis, Mass. | Published: August 30, 2013
CAMP EDWARDS, Mass. — For seven decades, munitions were fired, tested and dumped in a 300-plus-acre site known as the Central Impact Area as soldiers trained for war.
In the ongoing battle to clean up the collection of rockets, mortars and grenades — some of them still volatile — the Army Impact Area Groundwater Study Program is employing the U.S. Army Corps of Engineers to use metal mapping technology to find what's buried beneath the pitch pine and rugged terrain at this Upper Cape military base.
On a tour of the former target range Wednesday, Elise Goggin, a geophysicist for the Army Corps, demonstrated how the MetalMapper works using a combination of GPS and electromagnetic sensors that transmit electric currents into the ground to find unexploded ordnance, also known as UXOs. From the data collected, Goggin can determine whether what lies below is a munition that requires digging up and further inspection or is a harmless fragment of metal.
"It allows us to get a better idea of what is under the ground," Goggin said during a briefing for environmental stakeholders and the military. Preliminary results show the system is effective in sorting through what Goggin called the clutter of metal fragments to find both inert munitions and those rare finds of mortar rounds that could still pack an explosive punch.
Those volatile finds account for about 1 percent of the UXOs unearthed in recent test areas, Goggin said.
When they're found, the live rounds are detonated in a safe location on the base under a small hill of sand, Maj. Shawn Cody, director of the Army's cleanup program, said. "For multiple reasons, we don't want these UXOs hanging around," Cody said.
The MetalMapper looks like the frame of a washing machine being pulled along behind a John Deere tractor. It comes into play after another metal-detecting process, known as an EM-61, narrows the search area.
During the tour, Goggin demonstrated how, by using the data collected from the mapping system, she could determine what type of munition was placed underneath it based on the curves of the lines from electromagnetic currents. Just to keep the system honest, one of the options was a twisted piece of scrap metal, a common find beneath the base.
Goggin's first attempt didn't work, but with some adjustments, she was able to determine that an 81 mm mortar was placed underneath.
When Cody switched it out, the data on her portable computer screen detected the change. "I'm a little nervous, but I think it's a piece of scrap metal," Goggin said.
The MetalMapper is accurate to depths of about 4 feet and can cover about 200 points of interest in a day, Goggin said.
The Army is under orders from the Environmental Protection Agency to remove UXOs from 50 acres of the impact area. The munitions are believed to be one of the sources of groundwater contamination beneath the base.
The metal mapping technology will reduce the cost of the source cleanup because eventually only the targets of interest will have to be dug up instead of having to clear and sift through every acre, Cody said.
"I think it shows a lot of promise," Lynne Jennings, base cleanup manager for the EPA, said after Wednesday's tour. Other technologies tried at the base, including robotics and bomb-sniffing dogs, have proved costly.
Initial estimates indicated it would cost $1 million per acre to clear the impact area of UXOs, but with the use of metal mapping that has now dropped to $300,000 per acre, Jennings said. "I think they can do even better," she said.
The EPA plans to impose a system of checks and balances, Jennings said. Among the efforts will be random digs for UXOs, a quarter acre at a time, to compare with results from areas where metal mapping is used, she said.
"We're pretty excited about this cutting-edge technology and that we have it here," Jennings said.