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The Evolution of Reliability-driven Utility Vegetation Management

By Sara Sankowich


More than a decade ago, I worked for a utility company as an associate arborist. I was just starting out, and I remember the system arborist discussing a vegetation-related situation. Our company, as part of an electric infrastructure improvement project, had planned a new, three-phase line down a town’s main road where an historic, beloved oak tree stood in the way. While the project planners hadn’t thought about trees on this road being an issue, several town residents objected to the notion of this particular tree being pruned or cut down. Relocating the line one street over, where vegetation was not an issue, was the logical compromise to keep everyone happy. Had the vegetation management department been consulted during the initial planning phase, the design would have originated with this important aspect in mind; instead, it had to be revised, costing unnecessary time, money and effort.

Arborists have always been a component of a utility’s operations team, but, historically, vegetation management was only a small part of the big picture, and secondary to the core business of electricity distribution. Often, arborists were not included in early-stage planning of electrical projects; in fact, they frequently functioned without planning and strategy interaction with other departments. An example of this independent vegetation management structure was evident in how maintenance pruning was coordinated and scheduled by many utility system arborists at the time. It was common to see maintenance pruning organized by vegetation management areas or trim zones, taking into account municipalities and geographic areas for scheduled pruning, which made the process and implementation of pruning easier for workers and the public. Trim zones, however, did not encompass the electrical circuit layout, how power flows, and the number of customers served. After collaborating with engineering and electrical operations, system arborists consider these factors critical today, explaining why the evolution from trim zones to circuit pruning has become more prominent over the years.


Factors leading to change

During the past 10 to 15 years, the role of the arborist within a utility company has changed dramatically, and vegetation management has become a core part of a utility’s overall reliability strategy. Several factors have led to this cultural shift, including an increase in frequency and severity of storms, increased societal reliance on power, the Northeast’s aging forests, and economic constraints.


Severe weather

According to the U.S. National Climate Assessment, New England alone has seen a dramatic 71 percent upswing in extreme precipitation from 1958 to 2012, resulting in greater damage to infrastructure. Trees have the potential to cause outages even in the fairest of weather, be it from a broken limb or a fallen tree. Extreme precipitation — such as heavy and frequent snow falls, ice storms, and hurricane activity — can raise those odds even higher. As a result, utilities see value in a more proactive approach to reducing the risk of tree and limb failure through advanced vegetation management and storm resiliency projects.


Reliance on power

As a society, we have come to rely on continuous power to support our lifestyle, and any power interruption causes great disruption to individuals and businesses alike. For example, with more and more people working from home at all hours of the day and night, they expect that they will have access to continuous, uninterrupted power. If an interruption does occur, even during a storm event, it is assumed that power will be restored quickly. Loss of power can also distress a business; the inability to operate results in loss of productivity, loss of revenue, and added costs to reset and restart sensitive equipment.


Aging forests

Tree-related interruptions are one of the top causes of power outages, and in New England, the aging urban forest certainly doesn’t help the situation. As stated by Lloyd Irland in his book, The Northeast’s Changing Forest, “Visitors to upstate New York and New England often remark on the oddity of stone walls rambling through the roadside woodlands. Many are surprised to hear that large areas have been out of farm production so long that they have grown several successive crops of trees.” Land that was previously cleared for pasture has gone through the natural reforestation process and the accompanying successional stages, resulting in a forest that is reaching and passing maturity. Older trees are more susceptible to pest infestation, disease, and damage from severe weather, leaving the urban forest in poor health and raising the rate of tree mortality.


Economic constraints

With municipalities cutting back on budgets for tree care due to economic constraints, and residential tree owners unable to afford tree maintenance on their own properties, the onus to prevent these deteriorating trees from falling on the public way falls on utilities when power lines are present. This presents challenges in areas that are heavily treed and also are struggling economically.


Reliability-driven vegetation management gains prominence

Combined, the factors described above have led to an increased occurrence of tree and power line conflict, and increased focus on mitigating power interruptions. Due to these external influences, vegetation management is now an integral part of utility operations, and has resulted in the following best practices for utility vegetation management:

  1. The system arborist or vegetation manager now plays a key role in company operations and strategy. Vegetation management is either integrated into operations or works closely with operations, and interfaces with other departments regularly. For example, in the past, when a new substation was being developed, an arborist may have been brought in as part of the execution phase, but may not have been part of the planning phase. Today, an arborist is often included in the initial planning phase, and plays an active part in the planning and design of the substation — from assessing tree-related impact and future maintenance concerns to advising on size and easement language required for the rights-of-way.
  2. Vegetation management is no longer “under the radar.” In fact, communications and outreach are essential to a program’s success. Vegetation management is often the most costly maintenance expense for a utility, and, as a result, regulators watch spending with a keen eye to ensure the utility arborists are operating in the best interest of the customers. Frequent communication to elected officials and regulators through presentations, videos, and written materials has helped utilities share critical information about their vegetation management plans. Customer education has also become an extremely important component of a utility arborist’s job. When tree workers are in the field interacting with customers, they have an opportunity to communicate to customers about “right tree, right place.” From the utility perspective, this is the idea that, before planting any tree, customers should choose a species and location that looks at the tree’s mature size, and advises planting with this future size in mind to keep the tree clear of overhead wires and away from underground electric lines. Proper tree species selection and placement help avoid utility line conflicts in the future — and, therefore, help prevent future outages and future pruning needs. An added bonus: the right tree might provide shade or a windscreen to a home and lower a consumer’s utility costs.
  3. Vegetation management program strategies look to drive reliability improvement; and advanced vegetation management programs are implemented for targeted reliability initiatives. Pruning programs are reliability-based and keep electric circuitry in mind. Hazard tree mitigation programs are targeted for critical circuits. There are now storm “hardening” or resiliency programs in place that look to make critical sections of select circuits more resilient to major storm events. Unitil’s Storm Resiliency Program, or SRP, removes numerous hazard trees and all branch overhang from over critical portions of selected circuits that deliver power to critical municipal infrastructure and community essentials.
  4. Vendor selection is prioritized around reaching a common goal. There is a greater emphasis on selecting qualified vendors that demonstrate the ability to complete safe, quality work on time, efficiently and effectively, while driving toward utility goals of reliability, safety and customer satisfaction.


The future of vegetation management

As the utility industry evolves, the future of vegetation management will include even more monitoring: monitoring storm footprints and impact on the urban forest after they have come and gone, and monitoring pest/disease footprints and impact on the urban forest surrounding the electric lines. The methods by which these areas are monitored will rely more heavily on technology. Where we used to execute a field ground patrol, we are now able to use LiDAR data, spectral imaging, high-definition video monitoring, satellites, and GIS to review annual maintenance and look for concerns or hazards along our rights-of-way. With all of this data and technology, we can prioritize work and manage to a specific field condition and desired outcome. We can make smarter, better decisions about vegetation management, and positively impact the delivery of safe and reliable electric service.


Vegetation management has evolved during a relatively short period of time. It is now an integral component of utility operations, standing side by side with pole and line maintenance. No longer relegated to the sidelines and overlooked during strategic planning, the role of the utility system arborist is a critical component of a utility’s overall reliability strategy. It is an exciting time to be a system arborist.


Sara Sankowich is system arborist at Unitil, a public utility holding company, headquartered in Hampton, New Hampshire, that provides electric and natural gas distribution services in New England.

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