'Safety First' in Utility Vegetation Management—Right?

On my first day of work in utility vegetation management (UVM), a seven-year-old girl was fighting for her life in a critical burn unit 200 miles from home.  A few days earlier, she had climbed into a pine tree, reached out and contacted a single-phase high-voltage distribution line operated by my new employer. After she was blown out of the tree and fell 30 ft to the ground, she was life-flighted to a medical center and treated for severe burns. Throughout my first year in UVM, she began her slow, painful recovery, and learned to live with permanent, debilitating injuries.  So went my introduction to UVM.

Sadly, many electrical contact victims don’t fare as well as the seven-year-old. During my ensuing 23-year career at that utility, four people lost their lives due to tree conflicts with power lines. Two were tree workers. That’s not unique or rare. Dr. John Ball, a professor at South Dakota State University, said electrocution is the third most common cause of work-related fatalities in the tree care industry. What’s more, tree conflicts with power lines have caused ruinous fires, resulting in catastrophic loss of life.

Safety: a UVM Priority

Clearly, safety is a serious matter in UVM, with potentially dire consequences for members of the communities we serve and for those with whom we work. We respond by making “safety first.” It’s a core value for utilities, UVM contractors and the Utility Arborist Association (UAA).

We prioritize the development of a safety culture. Progressive programs involve every team member from senior management to the newest groundworker. That dedication extends to the public, and we are committed to minimizing the likelihood of electric contact. We are also focused on mitigating wildfire risks, which are becoming increasingly challenging with climate change, poor forest health and an expanding wildland-urban interface. Our commitment is sincere, and safety is a central principle to our profession.

Reliability Focus?

Despite our commitment to safety, many UVM programs primarily schedule for reliability. There’s good reason for reliability-centered UVM. Transformative research on vegetation-caused outages by John Goodfellow, a consultant for BioCompliance Consulting, Inc. and Dr. B. Don Russell of Texas A&M, established that outages from vegetation growing into three-phase lines are rare, and they are nearly non-existent on single-phase lines. Rather, vegetation-caused outages are most often the result of trees or tree parts falling and mechanically tearing down electrical facilities. Evidence is mounting that 80% or more of vegetation-caused outages are caused by trees from off the right-of-way (ROW).

In response, reliability-based scheduling is gaining acceptance. In this approach, limited human and equipment resources are strategically deployed to optimize electrical service.  Stress is placed on tree risk assessment.  Further, three-phase lines are prioritized with emphasis on aligning vegetation management with protective device coordination to moderate the number of customers potentially affected by vegetation-caused outages.

I know from experience it works. Decades ago, I worked on a system where nine years lapsed between scheduled distribution vegetation maintenance (in a place where two or three years would have been warranted). Trees encroached to the extent that every time there was more than a breeze, lines were torn down. Tree-caused outages happened almost nightly. We responded by focusing on three-phase lines. The following year, the positive results on reliability were dramatic.

Unintended Consequences

As a result of the mounting evidence that vegetation-caused outages so seldom result from in-growth, we increasingly hear that “the problem isn’t around the lines.” More vegetation managers are concluding that systematic, routine line clearance “only buys air,” and resources should be redirected toward tree risk assessment and mitigation.

Line clearance cannot be deferred indefinitely. We know tree growth is relentless and, if left unchecked, the utility forest inevitably entangles power lines.  At some point, minimizing traditional line clearance work is counter-productive from both safety and reliability perspectives. The most appropriate scheduling of maintenance varies from one area and utility to another, but regular cycle work is central to effective UVM. Failure leads to hot spotting and a spiral of decline as costs and other problems mount, including increased safety risks.

Some argue that reliability and safety go hand in hand. To an extent that is true, but if reliability is the primary objective, single-phase maintenance can be de-emphasized because the risk of outages due to vegetative growth is statistically insignificant. However, allowing the utility forest to encroach into single-phase lines can provide access to them with potentially catastrophic consequences.

As the seven-year-old learned at such great cost, contacting a single-phase line can leave a victim just as injured, maimed, or dead as contacting a multi-phase line. Further, as trees are allowed to grow and entangle power lines, the risk for injury increases to qualified line-clearance arborists who clear them. It also intensifies risk for our municipal and commercial colleagues when high voltage lines are hidden by vegetation. Maintaining space between vegetation and power lines keeps them visible and top of mind, so arborists can maintain minimum approach distances. If we are committed to safety, we should not allow unreasonable working conditions—like high-voltage lines engulfed in vegetation—to develop.

Best Management Practices

A solution is to apply integrated vegetation management (IVM) best management practices, which advise us to set clearly defined management objectives. Risk mitigation should be the primary objective of any UVM program. Tolerance levels and action thresholds should be established and determined by site and vegetative factors to optimize IVM against the risk of unacceptable consequences.

Of course, those unacceptable consequences include both safety and reliability.  Artificial intelligence, remote sensing and traditional “boots-on-the- ground” evaluations (including tree risk assessment) should be leveraged to identify circuits of greatest safety concern, direct our resources to those first, then put every effort into power delivery optimization and other concerns.

As utility arborists, we put “safety first” as an ethical imperative, and we recognize our responsibility to mitigate safety risks for those who work for and with us, as well as for the public. We should also honor our commitment to “safety first” in UVM programs. Reliability-based scheduling is gaining traction based on sound science, but safety should take precedence in resource deployment. That is because somewhere in thousands of miles of line, a seven-year-old is climbing a tree, and this child deserves to go home safely.

Randall H. Miller ([email protected]) is the director of research and development for Eocene Environmental Group.