An Army report issued late Tuesday estimates that taxpayers will save at least $347 million under a plan to treat chemical-weapon disposal waste at a DuPont Co. plant along the Delaware River.

Military officials developed the cost-benefit analysis after Congress called last year for proof that the hotly contested plan was cheaper than other methods for destroying the VX nerve agent waste at the site of a neutralization complex in Newport, Ind.

Army officials said Tuesday the same study found the VX stockpile would be destroyed 57 months sooner if contractors use DuPont's Chambers Works industrial wastewater plant in Deepwater, N.J., for final disposal of the broken-down VX.

More than 1,200 tons of VX, one of the most-deadly chemical weapons ever made, were stored at Newport and targeted for destruction under an international treaty. About 180 tons already has been neutralized, with the remnants awaiting shipment to Deepwater.

"This demonstrates that our proposal for off-site treatment provides significant and substantial benefit to the taxpayer," said Col. Jesse L. Barber, CMA's Alternative Technologies and Approaches Project manager.

David Keifer, conservation chairman for the Sierra Club Delaware Chapter, said the organization remains opposed to DuPont's plans for treating the Army waste.

"To the best of my knowledge, nothing has changed," Keifer said. "It's a bad idea. I'm not one for frittering away the taxpayers' money, but health and things of that nature are a very major concern to the Sierra Club."

Citizen and environmental groups have called on the Army to complete all treatment at Newport, citing transportation risks and concerns about pollution from DuPont's wastewater discharge to the river. New Jersey has publicly barred DuPont from handling the waste pending further study and approval of a state permit amendment.

The wastewater DuPont wants to treat mostly contains a caustic liquid similar to drain cleaner, but also carries small amounts of potentially toxic compounds left over from the VX neutralization. The Environmental Protection Agency recently concluded that DuPont can safely treat the material without excessive risk to the river or aquatic life.

A related report from the Centers for Disease Control and Prevention is expected to be released shortly on transportation hazards and other concerns.

Contact Jeff Montgomery at 678-4277 or jmontgomery@delawareonline.com.