HERMISTON -- The Umatilla Chemical Depot marks its first year of burning chemical weapons today -- a year marked by a few worker mistakes, unexpected fires and more than 30,000 unstable chemical rockets destroyed.

While it took the depot's incinerator all day to destroy the first rocket a year ago, a third of the total stockpile of 91,442 rockets has been destroyed, and depot officials are looking forward.

That future should see work begin soon on destroying 750-pound bombs filled with GB sarin, and the start to burning of VX nerve agent and possibly mustard in about a year.

If all goes as scheduled, the entire deadly stockpile will be destroyed in about five years. And that means the facility near Hermiston is on track to meet an international treaty deadline calling for the nation's chemical stockpile to be destroyed by 2012, said Don Barclay, depot site project manager.

The first job is to destroy the stockpile of GB sarin-filled M55 rockets, said Doug Hamrick, project general manager for Washington Group International, the company hired to operate the incinerator.

The rockets are considered the most dangerous item in the stockpile because they contain aging explosives. Officials estimate it will take about another year to finish destroying the rockets.

But before the rockets are finished, the plant will start destroying bulk GB agent, probably in the next few weeks.

Once the facility starts processing the bulk containers of GB nerve agent -- which include 750-pound, 500-pound and 1-ton containers -- the incinerator will be able to continue destroying munitions when the rocket processing lines are down for maintenance, Barclay said.

Because the bulk munitions don't have explosives, they are not processed in the explosive containment rooms that the rockets must run through, he said.

The bombs can be punctured and drained on a separate line, then put through the metal parts furnace to burn any residual agent. Because the bombs don't have explosives, however, doesn't mean the process will be easy because it still involves handling aging munitions, Hamrick warned.

"Each different kind of munition will present its own problems," he said. But he added that he believes workers at the facility are up to the challenge.

Still, the past year has seen mishaps. The first day of processing was halted when a worker bumped an emergency stop button. And since then, the plant has twice shut down because of workers' errors, although no one has been hurt.

The plant also has had four fires since April in which M55 rockets filled with GB sarin nerve agent caught fire as their motor sections were being cut up. The last fire was at the end of July.

The exact cause of the fires is unknown, and there appears to be no way to predict which rockets might catch fire. Yet Barclay and Hamrick said they are confident fire suppression measures installed in the rooms where the rockets are cut up mean the building can withstand the fires and continue destroying rockets.

Hamrick said he is confident the next year will not show a repeat of the errors that led to some of the shutdowns. His optimism is shared by some others.

"We've not seen a repetition of some of the early stumbles," said Dennis Murphy, administrator of the Oregon Department of Environmental Quality's chemical demilitarization program. Murphy said his staff is pleased with what they've seen and gratified to see more than a third of the rockets destroyed.

There still are potential hitches, however.

The Oregon Supreme Court recently agreed that GASP, a group opposed to the incinerator, should get its chance in court to argue about the legality of the incinerator's permits. Ultimately, the 1997 case, commonly called GASP I, asks that the permits be revoked.

In the meantime, however, the facility is continuing to make progress in destroying the deadly stockpile.

Barclay compared the incinerator work force to a "diamond in the rough" when the plant started up. Officials knew it would be a slow start-up process, he said.

However, he added, "What I'm seeing at this point when I step back, I'm seeing a diamond, a cut diamond."