1. The history is pretty interesting.
Trees and wires conflicted from the beginning when they both tried to occupy the same space. In researching this topic, we came across a presentation featured at the 1981 International Society of Arboriculture’s annual conference, entitled “Reflections on Fifty Years of Utility Line Clearance” by Richard E. Abbott, who at the time was Davey Environmental Services’ vice president and general manager. Some highlights from this presentation, focused on the history of line clearance, include:
- Early on, linemen would go up the trees with their climbing spurs and remove interfering limbs.
- At one time, there were literally small armies working with crosscut saws and axes. In some instances, tent cities were set up to provide housing for these clearing workers.
- A rope, hand saw and pole runner were the principal tools of the early line clearer.
- Distribution primary circuit voltages were 4KV … today’s are more than 20 times higher.
- Brush and other debris were simply burned and horses were used for log skidding. All of this changed with the development of the lightweight gasoline-powered chain saw after World War II. Then, a bulldozer replaced the horses. Mechanical equipment has replaced labor, and so on.
- In the 1920s and 1930s, large groups of men with brush axes and hand saws spread out across the rights-of-way, cutting everything in their path. Brush disposal consisted of burning, but in many instances it was just left lying on the ground — re-clearing seemed a never-ending cycle.
- During World War II, the U.S. military conducted research on the use of chemical compounds that could kill living plants, depriving enemies of their food supply. But none of these chemicals, called “selective or phenoxy herbicides” were actually used in combat. However, they were used for right-of-way maintenance, serving as new technology to kill undesirable woody plant stems and roots — either species selectively or non-selectively.
- In many cases, backpack sprayer and hydraulic sprayers on old World War II military vehicles were the primary tools for chemical brush control.
- As time went on, the practice improved, with the development of specialized vehicles such as tracked bombardiers, modified log skidders and helicopters with invert emulsion technology.
2. Brush maintenance is crucial.
According to the Utility Arborist Association, in many circumstances, tree pruning around power lines is simply inappropriate. This is especially true in cases of very high voltage transmission lines where electricity can arc from the electric conductors to taller vegetation. Much of the vegetation on electric transmission and pipeline corridors is best maintained by converting the vegetation community that is dominated by tall growing trees to lower-growing vegetation. This conversion and subsequent maintenance is best accomplished using an integrated vegetation management strategy. The national standard (ANSI A300 Part 7) defines IVM as a system of managing plant communities in which managers set objectives; identify compatible and incompatible vegetation; consider action thresholds; and evaluate, select and implement the most appropriate control method or methods to achieve those objectives. From the UAA’s website: “The UAA encourages utilities to consider the Wire Zone-Border Zone (WZ-BZ) strategy in its implementation of IVM. The WZ-BZ strategy recognizes that plant species that are not compatible on some portions of the right-of-way may be compatible on others. This practice creates a more diverse plant community and a better habitat for many wildlife species.”
3. Longer contracts are trending up.
“One of the trends that we have seen more and more of [in utility line clearance] is longer termed contracts,” says John Hurst, regional manager at Wright Tree Service. “Not only are these contracts less expensive, but it encourages a strong partnership. In a single year, both the utility and the contractor have to look at new work, come to an agreement and then produce the work. This takes a lot of time on the contractor’s part. Our employees are also aware that it is only a single-year contract so many of them will be looking for more stability, and might begin to look elsewhere to find that. Higher turnover means more training and less efficiency.” Hurst also adds “With multi-year contracts, rates are generally stable for the length of the contract, with only a yearly negotiation for increases to cover expenses. In addition, our employees know they will have a job for more than one year and are less apt to leave. With that comes added production, safety and [better] morale leading to a more content workforce. All of this adds up to savings for the utility company.”
Read more: Exploring Utility Line Clearance