BOISE - Contractors and staff at Boise's Gowen Field are working to make sure the past doesn't come back to haunt them.

Using sound waves, digital maps and federal dollars, they are searching where bombs, grenades and ammunition were once stored.

Two areas are of special interest: a large field along Gowen Road that until the 1970s served as a munitions storage area; and the grounds around an old Marine Corps barracks.

The Idaho National Guard has Military Munitions Response Programs at military properties across the state, said Maj. Jim Hawkes, an environmental manager at the base.

The program cleans up former training ranges and munitions storage areas, making them safe for other purposes, Hawkes said.

The process started in the past decade and gained steam the past couple of years.

"It's a positive thing," Hawkes said.

The old bunkers and munitions buildings have been torn down. At Gowen, the former storage area is fenced off and empty, said Capt. Tony Vincelli, Idaho Air Guard spokesman.

"You can't really do anything with the area until the debris is cleared up," Vincelli said. "And the area hasn't been used in 40 years."

A contractor surveyed those sites with special equipment, identifying "anomalies" that show up as deep red swaths on a high-tech map.

Most likely, those red splotches are construction debris, said Senior Airman Heidi Caye, a base environmental expert.

"That's what we are hoping it is," Caye said. "But we have to make sure."

Between now and May 18, the base's environmental experts and a contractor will dig up those anomalies.

If contractors find any grenades, bombs or other dangerous materials, the area will be cordoned off and the explosives destroyed, Caye said.

"We are not expecting to find a bomb," she said.

Across the airfield on a Tuesday earlier this month, another contractor was using huge equipment to demolish and haul away an old "hush house." The building had been used to test jet engines.

Environmental studies showed that the soil beneath the structure could be contaminated with jet fuel. A nearby site was used to burn fuel, Caye said, before base managers ended that practice.

Once the last vestiges of the old building are removed, any contaminated soil will be scraped up and replaced, Caye said.

The work is being done under Department of Environmental Quality regulations, Caye said.