But six years later, after a million rounds have been fired at the base's shooting ranges, new information suggests the green bullets may not be much better for the environment than the lead ones.
"It's frustrating," Col. William FitzPatrick of the National Guard's Environmental Readiness Center said Thursday. "You're doing what you think are the right things. As science evolves, you wonder, 'Am I in front of the curve, or behind?"'
The green bullets are made of nylon and tungsten, a metal that supposedly does not seep into ground as quickly as lead. That's important because the aquifer below the base supplies upper Cape Cod with drinking water.
But conventional wisdom about tungsten has been challenged by tests done in recent years at the Stevens Institute of Technology in Hoboken, N.J.
Lab tests there found in 2002 that tungsten was not insoluble and that it could travel through soil under certain conditions. It also found that tungsten enables lead to move through the soil more quickly.
The Army has now begun field tests on how tungsten moves through the ground.
Camp Edwards is part of the Massachusetts Military Reservation, which covers 30 square miles. It's been a major training center for decades.
The camp has had a history of environmental problems since it opened in 1911.
Jet fuel, solvents and other pollutants contaminated the aquifer and the groundwater is now under constant monitoring.
In 1997, the U.S. Environmental Protection Agency ordered target practice halted at the camp and ordered a clean-up of lead buried in and around the berms at the base shooting ranges.
Lead was later found 19 feet underground and moving toward the aquifer — though it never reached the water.
For now, the tungsten bullets are still officially considered safe by the Department of Defense, and they are still used at the base.