HERMISTON -- Two fires erupted at the Umatilla Chemical Agent Disposal Facility over the weekend, quickly extinguished by the facility's fire suppression system.

One fire occurred Friday morning about 2:45 in Explosive Containment Room B during processing of a M55 rocket. The other fire occurred on Saturday about 12:39 p.m. Both rockets had been punched and drained of their GB sarin agent and were being chopped for the incinerator when the fires occurred. Both fires happened at the fifth shear.

According to Hal McCune, protocol officer for Washington Group International, the contractor for UMCDF, the fires are not unexpected.

"We are processing the lot that had previously caused fires," McCune said. "It is not unexpected."

Rocket fires in the ECRs have been occurring since start-up at the facility in September of 2004. After investigation by the Army, the most probable cause for the fires was related to the movement of nitroglycerin within the rocket motor assembly which formed concentrated droplets of liquid nitroglycerin. Due to the volatility of nitroglycerin, when struck with the rocket shear blade during the disposal process, the concentrations could initiate a small fire.

In order to reduce the likelihood of rocket fires, the UMCDF has increased the amount of water used in the cutting area, as well as other measures to ensure the problem does not happen again. These actions appear to have helped reduce the number of fires.

Fires broke out at the facility on April 7 and 23 and on May 18 as M55 GB rockets were being sheared into pieces before being fed into an incinerator for destruction. The shear blade hit the propellant during the fifth shear. The blade cuts each rocket into eight sections. Each time a fire occurred in the Explosive Containment Room, the fires were contained in the room.

The Oregon Department of Environmental Quality halted processing of rockets while an investigation was held after the May 18 fire. Work resumed on June 9 after a review by DEQ indicated it was safe to continue processing rockets.

The propellant in the three rockets which caught on fire was manufactured in October 1962. Samples of M55 rocket propellant had been shipped to Picatinny Arsenal in New Jersey for testing.

The last fire at the facility occurred March 19.