The Mercer County Local Emergency Planning Committee members on Wednesday morning conduct a full-scale hazardous material exercise at the Mercer County Fairgrounds. The drill is required every four years by the state, county EMA director Mike Robbins said. Numerous county and city departments and agencies reacted to a scenario in which highly flammable ethanol is released after an accident between a pickup truck and tractor-trailer. Robbins said the exercise went well.