The U.S. Army has delayed the scheduled Thursday start of its chemical weapons incinerator west of Hermiston after finding several kinks during a final check of the plant.

The concerns range from delays in finishing pre-startup tasks to concerns about whether the facility's systems are working properly. For instance, engineers are wondering why monitors found traces of a "surrogate" -- a chemical used to simulate nerve agent in previous tests -- in air that had already passed through a filtration system.

Umatilla Chemical Depot officials hope they can fix their concerns and incinerate their first weapon -- a rocket armed with sarin nerve gas -- sometime next week. But an Army spokeswoman, Mary Binder, said officials are in no hurry to start and are more concerned with making sure the plant can work as designed.

"Safety's first, and we're serious about that," she said.

The Army's on-site project manager, Don Barclay, released a statement saying: "The project's philosophy is to stop work at any time when issues surface that need to be resolved. We want all our employees -- who question their work -- to stop, evaluate and seek resolution before proceeding."

Binder said workers found "several issues" to address before they could start processing any of the thousands of chemical weapons stored at the depot.

Reviews of earlier tests showed that vapor containing traces of surrogate chemicals made it past charcoal filters to emissions monitors in the plant air system. That system cleans air pumped through the plant. A separate system cleans and monitors emissions from the furnaces. Workers want to figure out where the surrogate chemicals came from and how they survived the filters, Binder said.

Slower than expected progress on work to "air wash" the main processing building, removing all traces of surrogate chemicals, also is delaying the start of weapons processing, she said.

"This most likely will not be the last time we have a schedule change. We've had it through the history of this project," Binder said. "There's always going to be something with a large facility like this."

Depot workers had planned to move a pallet of 15 sarin rockets from a concrete bunker to the incinerator complex today and process one rocket Thursday morning.

The delays give incinerator opponents more time to block the startup. Groups worried about the plant's safety and health effects tried but failed to get an injunction in Multnomah County Circuit Court on Monday.

The groups are filing to ask an appeals court to block the startup, but it could take that court several days to rule. An appeals court is already scheduled on Friday to hear an appeal of a previous case fighting the incineration.

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