Tree care crews work in a variety of environments: urban, rural, suburban and sometimes isolated, but all of these work sites will typically have one very important, and dangerous, item in common: electricity.
As much as the beauty and wonders of electricity may evoke a sigh of contentment as a refrigerated adult beverage is cracked open and the flat screen responds readily to the buttons on the remote, that same force can stop a beating heart, cause horrific burns or even blow holes right through equipment and flesh. This almost always present, powerful and dangerous force requires that all crew members be well trained and educated on how to identify electrical hazards, avoid them and, if present, know the safest way to work around them.
Dr. John Ball’s accident and fatality statistics have shown year after year that electricity plays a major role in injuring, or, more sadly, removing permanently from the workforce, those tree care personnel who either don’t have a knowledge and understanding of electrical hazards, or use a little knowledge or misinformation to make very bad decisions. As with most topics discussed in this column, there is no substitute for hands-on field education and training in electrical hazards, and there are a wide variety of organizations that instruct in this vitally important topic, but the basic information discussed here provides a good introduction to what tree professionals should be looking out for as they go about their daily routine of caring for trees.
Minimum Approach Distances for Non-line Clearance Qualified Arborists
Kilovolts phase to phase Feet Meters
0.0 to 50 10′ 3.05
50.1 to 72.5 10′ 9″ 3.28
72.6 to 121 12′ 4″ 3.76
138 to 145 13′ 2″ 4
161 to 169 14′ 4.24
230 to 242 16′ 5″ 4.97
345 to 362 20′ 5″ 6.17
500 to 550 26′ 8″ 8.05
785 to 800 35′ 10.55
Table 1 illustrates the minimum approach distances for non-line clearance qualified arborists, and as such should be obeyed in all situations. In short, a non-qualified climber or crew member should never be closer than 10 feet from any energized conductor and should be much farther away in the case of greater voltages. As can be seen in the table, higher voltage means more distance. Crew members would do well to remember that while electricity typically will travel through any conductive material in the shortest and most direct path to the ground, it can certainly also arc right through the air to a conductive material, depending on weather conditions, and thus continue its journey to the ground through the climber, tree or aerial lift.
Electrical contact may be either direct or indirect, but the end result is typically the same, with the voltage continuing on its merry way to the ground leaving behind damaged, or even dead, material and personnel.
Personal protective equipment
As mentioned, non-line clearance qualified personnel should never be nearer than 10 feet from an energized conductor, and with higher voltage should be even farther away. However, there are aspects of PPE that even these personnel need to be aware of for safety reasons.
Any hard hat or helmet that is used in the vicinity of electrical hazards must have an E rating and consist of a solid body with no vents or holes that would permit electricity to directly enter the brain housing group. In general, all climbing equipment is conductive to some degree, but in the presence of electrical hazards tree crews should take care not to use gear that is extremely conductive, such as wire-core lanyards, and use less or nonconductive options, such as fiberglass ladders and foam-filled poles. A common misconception is that the material, if present, coating many electrical lines is insulation. This material is weatherproofing at best, providing minimal, if any, insulation and should never be considered to provide any protection against the electricity in the wire.
This term describes the contact of any part of the climber or operator’s body with an energized conductor. Direct contact is often a consequence of a climber or aerial lift operator not fully inspecting the work site or all aspects of the tree’s canopy for the existence of overhead energized conductors. In addition, storm situations in which lines have reached the ground, are entangled in brush, or have even settled and snaked into a tree’s canopy after detachment from the poles can lead to direct contact. There is no better preventative measure for direct contact than a full and complete hazard inspection of the tree and work site by all crew members prior to work. After all, if you don’t know it’s there, it’s pretty hard to avoid.
Indirect contact is contact with an energized conductor through something other than the pieces and parts of the climber’s or operator’s body. It can happen through trees, branches, ropes, trucks, uninsulated aerial lifts, conductive tools or anything else you care to name that can conduct electricity. Indirect contact can also happen, particularly during storm situations, when an energized conductor has come in contact with a typically “safe” conductor such as a metal fence, cable lines or even the metal stripping lining some street curbs. This type of indirect contact possibility can be particularly hard to identify due to the possible distance away from the downed line that has “electrified” the fence or curb. Once again, the primary preventative measure for avoiding indirect contact is inspecting and recognizing the existence of electrical hazards, but also being mindful of how actions within the work plan — climbing and rigging lines, aerial lift booms, pole pruners, falling branches, etc. — may come into or affect the minimum approach distance, allowing the electricity a path to the crew indirectly.
This term describes a situation in which the ground itself has become “juiced.” The area of ground energized will vary with voltage levels, soil type and the amount of moisture present, but is often caused by downed lines in storm scenarios or through the outriggers on an uninsulated or poorly maintained aerial lift that has come in contact with a line. In the case of the energized truck, it is yet another reason for ground personnel to avoid standing around leaning against the truck while the operator works aloft.
Particularly dangerous and unique to ground faults is the possibility of step potential. In all likelihood the areas of the ground that are energized are all at differing levels and anxious to “even” themselves out. A crew member walking through such an area, or fleeing a suddenly energized truck, provides the conductor the electricity needs, entering through one foot, moving up through the body and then out through the other foot to a piece of ground with a lower voltage. One option to deal with this step potential is for the crew member to take very small shuffling steps, keeping their feet close together, to get out of the area of ground fault, thereby minimizing the possible voltage differences between one foot and the other.
All crew members should have the knowledge and training to react quickly and efficiently in the event of an electrical hazard accident. This should include items such as operating a bucket with an electrically incapacitated operator from the ground, having the number of the responsible utility readily available, methods and techniques for safely breaking line contact from the ground, and how to avoid becoming a “second” victim.
Electricity is something that is present, both benevolently and hazardously, in almost every day of tree care work. While the hazardous nature of electricity can never be eliminated, knowledge, training and awareness can go a long way toward helping tree care professionals work safely and efficiently in its presence. Regardless of whether a crew member is line clearance qualified or not, they must always remember that electricity is completely and totally nondiscriminatory: it will take the shortest path to the ground, whether it be tree, tool or flesh, so it’s best to avoid being in its path.