After a 10-year court battle, a judge on Tuesday told Oregon's Department of Environmental Quality it must reassess whether a chemical weapons incinerator is good enough and safe enough to destroy 2,300 tons of mustard gas stored at Umatilla Chemical Depot.

Circuit Judge Michael H. Marcus did not halt ongoing incineration of nerve agent at the plant near Hermiston. But he said that the DEQ needs to consider changes in the plant's design and operations made since the incinerator was approved in 1997 before it starts processing mustard gas, a blister agent. That's key because tests have shown U.S. mustard gas to be contaminated with mercury at higher levels than previously thought.

"I don't think under this ruling they could start the mustard processing," said Mick Harrison, an Indiana lawyer who worked on the case for environmental groups including GASP, an Oregon group opposed to incineration. "It's a substantial victory."

Harrison and Portland lawyer Stuart Sugarman said that it would be safer to treat the mustard gas with a water neutralization process. That creates liquid waste to be disposed of, but it would not incinerate the mercury.

But Marcus' ruling said the DEQ could still reasonably decide to incinerate the mustard gas and some secondary waste, such as chemical protection suits, also addressed in the lawsuit. He just ordered a more thorough look at the best options for disposing of those items.

That review probably couldn't be completed until some time in 2008, said Rich Duvall, administrator of DEQ's Chemical Demilitarization Program. Duvall said Tuesday that he hadn't heard a full interpretation of the ruling from state lawyers and didn't know exactly what the review would involve. But he said the facility might have to delay processing mustard gas, work that otherwise may have started in late 2008.