The U.S. Army plans to burn a rocket armed with deadly sarin nerve gas near Hermiston this morning, a turning point in the military's long effort to destroy chemical arms stored at the Umatilla Chemical Depot.

On Tuesday, guards and state regulators watched as workers loaded a pallet with 15 sarin rockets from a concrete storage bunker into a 9-ton steel container. A truck carried the deadly cargo less than a mile to an incinerator complex in the depot's northeastern corner, where the rockets would spend the night.

Barring any last-minute hitches, workers will drain the nerve agent from one of those rockets and send the emptied weapon into a 1,050-degree incinerator today, Army spokeswoman Mary Binder said. The drained sarin will be stored until the Army gathers enough to fire up a different incinerator for liquid chemicals, perhaps in a month.

A gradual start could see perhaps five more rockets drained and burned through Friday, said Dennis Murphey, who oversees Umatilla for the Oregon Department of Environmental Quality. He said DEQ workers would be on hand to watch the start of incineration. Regulators approved that startup last month, after deciding the depot's four-furnace incinerator plant met environmental and safety standards.

The Army delayed a planned Aug. 19 start of incineration to check several last-minute concerns. Those included monitors that scanned air from inside the incinerator buildings and found traces of surrogate chemicals, which are used in testing to mimic nerve agent. The amount of chemicals detected was within limits set by environmental permits.

After checking with the systems' manufacturers and workers at other chemical weapons incinerators, Umatilla workers determined that it is normal for the monitors to detect traces of such chemicals in the plant's air, Binder said.

"They're (chemical) levels that people breathe every day," she said. "You just don't measure them in your everyday life. Here, we do."

Binder said that the Army put new carbon in several hundred of the 2,700-plus carbon filters in the plant's ventilation system.

While the Army prepared to start the incinerator, foes continued legal fights they have waged since 1997, when Oregon regulators let the Army build an incinerator. Several environmental groups filed suits claiming that the state ignored cleaner and safer ways to destroy the weapons, such as through chemical treatments. Lower courts rejected many of those claims, but some are on appeal.

By Friday, incinerator foes will ask the Oregon Court of Appeals to block further incineration until its judges decide on a pending appeal, Portland lawyer Stuart Sugarman said. He said the court probably would not rule on that request before next week, meaning that the Army probably would incinerate several weapons.

"Once they begin burning, irreparable harm has been done. That's what we're trying to avoid," said Karyn Jones, a Hermiston activist involved in the lawsuits. "If I don't get my injunction (today), I may leave town for the day. That's how trusting I am."

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