Two drilling crew members were electrocuted when the boom of their drill rig contacted a high-voltage overhead power line.

The victims were employed by a company hired to find and blast large rocks that lay in the path of new gas lines. As a preliminary step, the two workers were drilling test bores alongside a roadway to search for rocks. The drill operator had 12 years of experience at his job. Although his co-worker was employed primarily as shop mechanic, he occasionally assisted in the field as a driller or laborer. The drill rig used was a small, self-propelled tracked vehicle with a 27-foot (nine-meter) boom. The rig was powered by a large air compressor that was towed behind a dump truck. The operator worked the controls while standing behind the drill rig.

The incident took place on a dry, clear, hot summer day. There were no witnesses, but evidence suggests it occurred as the two men were moving the rig off the road at the end of the work day. Apparently the mechanic was operating the rig while the drill operator moved the compressor hose. As they moved the rig up a small incline at the side of the road, the raised boom might have made the rig unstable. It appears the mechanic stopped the rig and was moving the boom sideways when it contacted the 7,200-volt overhead power line.

The two workers were electrocuted. The mechanic received the shock through the drill rig as he stood holding the rig controls. The power passed through the steel-reinforced air hose to the second victim. The medical examiner determined the cause of the two deaths as electrocution accompanied by severe body burns.

How can similar incidents be prevented?

• Workers must maintain minimum safe clearance distances in keeping with regulations.
• Utility companies should be asked to shut off power, and lines should be tested before work is done within safe clearance distances. Alternatively, utility companies should be asked to isolate lines with insulating hoses or blankets.
• Workers must be trained to use equipment safely. Signs should indicate the height of equipment such as this boom, which in this case reached higher than the power line.