HERMISTON -- Real life did not totally cooperate with the annual emergency response exercise for communities surrounding the Umatilla Chemical Depot on Tuesday.

Instead of using the actual weather patterns as had been planned, the drill used "canned" weather -- from a computer program. And some of the emergency response vehicles that were to participate were delayed because of actual emergencies.

By 7 p.m., Hermiston Fire & Emergency Services had responded to one fire and three ambulance calls, one for an actual injury on the depot 35 miles south of the Tri-Cities.

Despite all that, area fire and police chiefs juggled the fictional chemical emergency and the real events just fine.

Tuesday's exercise was designed to test how area agencies would respond if an accident at the depot took place. In the fictional scenario, one rocket, and possibly a second, had exploded on the depot shortly after 5 p.m., and it was unclear if other M55 rockets filled with chemical agent also had been damaged.

The explosion sent a plume of nerve agent into the air, spreading toward Umatilla and the Columbia River.

This year, the exercise put additional emphasis on medical reception sites and decontamination, said Chris Brown, Oregon Chemical Stockpile Emergency Preparedness Program manager. That included increasing the number of "victims" who would go through decontamination centers set up in the area.

"We're estimating that somewhere in the neighborhood of 600 people will participate in the exercise," he said.

It also was the first year that the agencies in Umatilla and Morrow counties were to fully use the 450 megahertz tactical radio system to communicate, he said.

Oregon also set up reception centers for potential evacuees near the Wildhorse Casino on the Umatilla Indian Reservation and near Heppner for the first time.

Community response teams also were to be participating, Brown said Monday.

Tuesday during the exercise, one community response team from Stanfield responded to a Hermiston real fire call on Highway 207, just like they would have in an actual emergency.

In the Hermiston Safety Center, on the second floor of the Hermiston Fire Department, federal evaluators sat in the back of a cramped room observing how the group reacted to the scenario. The situations included hitches like a communication blackout where the phone lines went dead, making everyone resort to using cell phones and radios.

The exercise next year will take place in the new Hermiston Safety Center, which is being built adjacent to the existing fire department.

The group in the old safety center, which included representatives from Hermiston and Umatilla city fire and police departments, kept in contact with other teams in Pendleton, Heppner and on the depot by video conference. A map projected onto the wall showed the chemical plume spreading over the region.

Because the exercise started at 5 p.m., more first responders could participate in the drill, but area schools could not, Brown said.

Schools instead held their drills earlier in the day.

At Paterson School, the approximately 110 students evacuated and boarded buses at 1:30 p.m., said teacher Bob Stoddard. In a real chemical emergency, the buses would take students to Housel Middle School in Prosser, he said.

The exercise fits right in with the school's monthly building evacuation exercises, Stoddard said.

"It's just a step more to walk around to the front of the building and get on the buses," he said.

In Umatilla and Morrow counties, most students take shelter at their schools in rooms designed to not let the outside air in.