BOURNE, Mass. – Soil contaminated by explosives at the Army’s Camp Edwards may be treated by covering it up with organic material such as cranberry hulls and letting microbes eat away at the contamination.

The Army believes compost could clean up the tainted soil faster and cheaper than other treatment methods, including incinerating the soil.

But the U.S. Environmental Protection Agency has yet to approve the composting option, which the agency fears may not be effective.

EPA officials who oversee the base’s cleanup fear composting won’t be as effective as other methods because the Army proposes to lay organic material on top of contaminated soil, rather than churn the soil up – a precaution to ensure potentially volatile unexploded ordnance at the site won’t be disturbed.

The EPA also worries that composting won’t treat contaminated soil deep below ground, the Cape Cod Times reported Monday.

The Army is trying to clean up munitions left over from live-fire training conducted until 1997 on a 330-acre section of Camp Edwards. The camp is part of the Massachusetts Military Reservation, which covers 30 square miles and includes four towns on upper Cape Cod: Bourne, Sandwich, Falmouth and Mashpee.

The Army has proposed laying about a foot of locally acquired organic materials – possibly cranberry hull – on top of the tainted soils. As it decomposes, bacteria will also eat the explosives on the surface and to a shallow depth.

“The composting is something that really works,” said Ben Gregson, a project manager. “It destroys the explosives by natural activity.”

Ocean Spray, a cranberry growers’ cooperative, has already provided the Army with five gallons of cranberry wastewater – biological materials left over from its Milford plant – to test their plans.

If the EPA consents, the Army hopes to conduct tests at three of the most contaminated sites this spring.

The Army’s Groundwater Study Program is already treating underground plumes of contamination in other parts of the base.

Investigators have used several different methods to rid the base of tainted soils, including heating soil to very high temperatures and cooking off contamination – and everything else in the soil. Army officials have also carted away some soils to be disposed of in special landfills.