Fatality Investigation Report
FACE Facts
Fatality Assessment and Control Evaluation (FACE) Project

Drill Crew Electrocuted by High Voltage Overhead Power Line

Background

The victims were employed by a small drilling and blasting company, which had been 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 primarily employed 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 high boom. The rig was powered by a large air compressor that was towed behind a dump truck. The compressor was attached to the drill rig with a 4 inch diameter steel-reinforced air hose. The operator worked the controls while standing behind the drill rig. To move the rig, it was necessary for one person to stand behind the rig to operate the controls while a second person lifted the air hose. This prevented the hose from dragging on the ground.

The Incident

The incident took place on a dry, clear, hot summer day. There were no witnesses, but evidence suggests that 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 may have made the rig unstable. (According to company policy, the boom should have been lowered before moving the rig.) It appears the mechanic stopped the rig and was moving the 27 foot boom sideways when it contacted the 26 3/4 foot high, 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.

Recommendations

1. Employers must ensure that workers maintain a minimum distance of ten feet between equipment and power lines, in keeping with federal and state regulations. Where safe clearance is difficult to maintain, the following precautions should be taken:
   
   
   • Change equipment or work practices to maintain the proper clearance; for example in this case using a shorter boom.
   • Ask the local utility company to shut off power to the lines. The lines should be tested to make sure that they are not carrying power before beginning work nearby.
   • Ask the utility company to isolate the power lines with insulating hoses and blankets. Note: This step may not be adequate to insulate against contacts with heavy equipment.
   
   
2. Employers should ensure that employees are properly trained in the safe operation of equipment and that safety procedures are followed at all times. All employee training programs should be in writing.
   
   
3. Drilling equipment should be posted with signs warning of the danger of contact with overhead power lines. Signs should also indicate the height of the drill boom.