HERMISTON -- Incineration of deadly nerve and mustard agents stored at the Umatilla Chemical Depot will be delayed until late spring or early summer, officials said this week.

Until now, officials had been projecting they would be ready to begin burning sometime before the end of the year.

Don Barclay, site project manager for the Umatilla facility, told the Chemical Stockpile Emergency Preparedness Program's governing board that problems with the deactivation furnace, which eventually will destroy explosives and rockets that contained the nerve agents, were the main cause of the change in schedule.

The depot, seven miles west of Hermiston, stores 220,604 munitions and containers filled with 7.4 million pounds of nerve and mustard agents. The aging weapons have been stored at the depot since the early 1960s.

Depot officials had said that they projected "people, plant and procedures" would be ready to begin disposal operations in December. A weekly update on depot operations faxed to reporters Friday morning repeated the December date.

But Barclay said it will be February or March before the facility is ready for operation. And it will probably be June before administrative procedures, such as getting approval from the state and the Army, are completed and incineration can begin.

The Oregon Department of Environmental Quality shut down the furnace in June because the levels of antimony and nickel emitted during testing exceeded amounts allowed by the state, although those emissions posed no threat to the public or the environment. DEQ gave Washington Demilitarization, the company handling incineration, permission to restart the furnace Aug. 22.

Barclay said fiberglass used during the surrogate burn to simulate munitions stuck to machine parts. He said the fiberglass was the wrong kind of material and created problems inside the furnace.

The burn was repeated successfully using a different kind of fiberglass. Test burning on the furnace was completed Monday.

Mary Alice Binder, depot spokeswoman, said test burning of surrogate materials will restart on the metal parts furnace sometime next month. Test burning on one liquid incinerator was finished in February.

Tests on the second liquid incinerator will take place near the end of this year.

There are two liquid incinerators, one metal parts furnace and a deactivation furnace.