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www.arborage.com Arbor Age / May 2014 17 distance. Minimum approach distances will be discussed in greater detail later, but the key number for non-line clearance tree folk to keep in mind is 10 feet, meaning don't get closer than that to any line; and larger lines with even greater voltage will require greater distances. How close is too close? The table to the right shows a variety of minimum approach distances for tree folk who are not line clearance certifi ed. The folks who have had the specialized training and instruction, along with tools and equipment, to be line clearance certi- fi ed use a different table, which takes into account their skills, knowledge and abilities. Confusion is often expressed by tree care personnel in regard to the table — the most common comment being that if they don't know how much "electric" the line is carrying, how can they know how far away they need to stay? As can be seen from the table, nobody except for line clearance folk should be within 10 feet of an energized conductor. As to how many volts the line may be carrying, a rough estimate may be gained by looking at the number of insulators at the pole — more insulators mean more volts, which means more distance. There are a wide variety of classes and training seminars available that will help tree crews decipher how much "electric" may be in a given line; and most utility/power companies and crews are happy to pass on this vital information to curious tree care crews or companies; after all, they will have to clean up the mess if something goes "zap." Electricity, given the right atmospheric conditions and voltage levels can easily arc through the air to a crew member who just wanted to get "a little bit closer." Stay the proper distance away, and keep the gear/ equipment the proper distance away, or, if unsure, very far away; and the voltage will not be able to show how badly it wishes to return to the ground through a body or piece of equipment. Direct contact Many electrical interactions between tree crews and utility lines happen without the crew even recognizing that "electric" was present. It usually involves a crew, climber or crane/lift opera- tor who hasn't evaluated the tree and site for hazards. In essence, nobody ever saw the utility line on the back side of the tree or disappearing into the canopy and somebody moves or swings right into it. Direct contact can also happen when the worker knows the line is there, but has gotten busy and has a moment of inattention, and some form of "zap" is the result. Storm clean-up or work situations can also be ripe with direct contact possibili- ties. There may be any number of lines down, tangled in brush, or settled down on top of trees — all of them "live" and looking for a quick and easy path to the ground. Knowledge of the minimum approach distances, with a good pre-work hazard inspection, will go a long way toward preventing the possibility of direct contact. Indirect contact paths This type of path for the "electric" is typically when some- thing unrelated to the worker's body comes into contact with a line or gets inside the line's safe approach distance. The electricity travels through whatever this non-body part might be, because it just don't care, and runs into a human body, which has all kinds of conducting water in it at the end. The conducting non-body part could be any number of things including the tree being climbed, branches, conductive tools or lifts, and even climbing Line clearance may often take place in fairly isolated rural settings. Kilovolts phase to phase feet meters 0.0 to 50.0 10' 3.05 50.1 to 72.5 10' 9" 3.28 72.6 to 121.0 12' 4" 3.76 138.0 to 145.0 13' 2" 4.00 161.0 to 169.0 14' 4.24 230.0 to 242.0 16' 5" 4.97 345.0 to 362.0 20' 5" 6.17 500.0 to 550.0 26' 8" 8.05 785.0 to 800.0 35' 10.55 Photo by Mike Schronk, Carolina Tree