HILO, Hawai'i — Crews digging up World-War II-era grenades, shells and mines as part of a federal cleanup in the Waimea and Waikoloa areas have also encountered some other unexpected relics of Hawai'i's past, including hundreds of horseshoes.

Chuck Streck, ordnance program manager for the Honolulu district of the U.S. Army Corps of Engineers, said the teams clearing former U.S. Marine training and target areas for the past four years have cleared about 6,600 acres of land of a surprising array of weaponry, ranging from unexploded 155 mm artillery shells to Japanese bayonets.

"We keep on being surprised," Streck said. "We have to have one of the highest varieties of different types of ordnance that has been encountered on any one property."

The crews have been working to clear the surface and subsurface in bands of land around neighborhoods in Waimea, Waikoloa, Lalamilo and 'Ouli to try to reduce the risk of accidents involving unexploded ordnance.

In all, the federal government has identified about 55,000 acres in West Hawai'i that need to be cleared, and the U.S. Army Corps of Engineers has just announced that another $9.99 million has been allocated for the project. Streck said that money will probably be enough to clear another 1,500 acres over the next year.

Contractor American Technologies Inc. detects the higher densities of the metal weapons compared to the surrounding rock and soil, and Streck said most of the old ordnance is on or near the surface.

Along the way, crews using electromagnetic sensors have made some odd finds.

Close to four dozen Japanese rounds were discovered, and, although federal records indicate there would be no land mines in the area, the crews discovered plenty, Streck said.

There was also the more predictable array of nearly 1,800 live mortar rounds, rockets, bazooka rounds, hand grenades and artillery shells, with crews discovering about 100 different types of weapons.

Another find was a World War I officer's pistol that was still fully loaded but rusted beyond all repair. The training area opened in World War II and closed in 1946, so it isn't clear who would have brought such a weapon to the training area or why, he said.

Crews have disposed of more than 100 tons of shrapnel and scrap metal, and also found caches of horseshoes, he said.

"When you get a bunch of horseshoes that are buried underground, it gives you the same kind of signature as a large piece of ordnance would, so they've been dug up just as carefully as everything else," he said.

In the coming year the crews will continue work on the site of a planned new district park off Mamalahoa Highway near the Parker Ranch headquarters, as well as land in Lalamilo and near the Waikoloa stables, he said.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.