A Multnomah County Circuit Court judge declined to block the startup of a chemical weapons incinerator Monday, as workers readied the plant to destroy a rocket containing nerve gas.

The Army is planning to process a rocket Thursday morning, after Judge John Wittmayer turned down a motion for an injunction filed by local activists who fear the plant is not safe or ready to begin.

But the activists have not given up hope of stopping this week's incineration at the Umatilla Chemical Depot outside Hermiston, said Richard Condit, one of their attorneys. Condit and others are working to get a hearing before an appeals court today or tomorrow, and will again ask for an injunction against starting the incinerator.

The activists are scheduled on Friday to argue an appeal of a years-old suit, claiming the state was wrong to approve burning the weapons in the first place. They hope to persuade a court to forestall the incineration at least until that appeal is heard.

"We face an uphill battle, but we're confident that the court of appeals will see it in a better light" than did Wittmayer, Condit said.

While opponents work for a hearing, laborers at the depot are preparing to start the incinerator, seven years in the making.

"We are doing our final internal reviews at the moment, just working through all the procedures on our final checklist," Army spokeswoman Mary Binder said. "At this particular point it looks good" to start on Thursday.

Crews would move a pallet of 15 rockets armed with sarin nerve gas from a storage bunker to the incinerator Wednesday, Binder said. Thursday, they would drain the nerve gas from the rocket and send the rocket but not the sarin into a high-temperature furnace. Incineration of nerve agent probably would not start for about a month, she said.

State Department of Environmental Quality workers will observe the whole process, said Dennis Murphey, who administers DEQ's Chemical Demilitarization Program.

The incinerator must destroy about 91,000 sarin rockets, which will take more than a year, before moving on to tons of other chemical weapons, Murphey said. It could take six years to destroy all the weapons, Binder said.

Andy Dworkin: 503-221-8239; andydworkin@news.oregonian.com