Larvae feed beneath the bark, fatally damaging the tree by disrupting the movement of nutrients through the cambium. Within two to three years of infestation, the tree dies. Photo courtesy of Therese Poland, U.S. Forest Service.

Emerald Ash Borer: A Race Against Time

May 26, 2014
AEP takes a proactive approach to combating the emerald ash borer threat in Ohio.  

Why should electric utility managers be concerned about a small green beetle from Asia that only infests ash trees? The answer lies in the fact that in most of North America there are, or soon will be, thousands of dead or dying ash trees threatening the safety and reliability of power lines all because of that little green bug.

When the arrival of the emerald ash borer (EAB) was first confirmed in Detroit, Michigan, U.S., in 2002, no one knew how the economic and environmental costs might tally up. The impact of this pest is being compared to the destruction caused by the chestnut blight and Dutch elm disease of the previous century, but there is more critical infrastructure to protect today.

Now that this pest has been detected in 22 states and two Canadian provinces — and dead ash trees have fallen into power lines on blue-sky days — some electric utilities are learning the cost of not taking a proactive, focused approach to EAB mitigation.

This EAB-damaged ash tree is just one of millions, many of which pose a potential threat to power lines and passersby. Dead ash trees typically lose large limbs within two years and, after four years, larger trees will often fail at the base of the tree. This rapid decline threatens power reliability as well as the safety of tree workers trying to remove them.

The Initial Discovery

For a few years after the initial discovery of the EAB infestation, many government agencies and communities in Michigan, Ohio and Indiana hoped it could be confined by removing ash trees ahead of the infestation. For various reasons, this control effort did not work. By 2009, ash trees were failing at a significant rate, and it was clear the infestation would continue to spread.

Even now, there is no practical way to stop the ash tree species’ decline as a result of EAB. Although individual trees can be protected with repeated treatments of systemic pesticides, this is not a viable option for millions of ash trees in forests, wood lots and backyards, many of which are within falling distance of electric distribution and transmission lines throughout North America. Biological controls also are being tested, but researchers acknowledge these efforts will not stop the spread of EAB.

Meanwhile, utilities and municipalities are running out of time to manage the risk safely and efficiently.

AEP Ohio’s EAB mitigation program in the Columbus district begins with an Asplundh work planner identifying and marking ash trees outside the normal easement but within striking distance of lines, then contacting property owners for permission, followed by tree crews removing the trees. Asplundh collects and maintains data and documentation for AEP Ohio and PUCO review.

Avoid a Cycle and Budget Buster

Several utilities in Michigan, Ohio and Indiana, where EAB was detected earliest, have made a valiant effort to inventory ash trees on their rights-of-way and remove (or top for private removal) every ash tree within striking distance of electrical conductors. However, this work requires a significant amount of time to identify potential off-corridor threats and make customer arrangements to access them. Specialized equipment is often needed because dead ash trees are too unstable to climb.

Because of this extra time and equipment, simply absorbing EAB mitigation into a utility’s scheduled vegetation management cycle and budget is generally not sustainable. Mark Contat, manager of forestry services for Toledo Edison, a FirstEnergy company in northwestern Ohio, confirmed this. His utility’s EAB mitigation program began in 2009 with the removal of 380 ash trees during its normal vegetation management schedule. The following year, many more ash trees were falling and causing outages, so removals increased to more than 3,700 in 2010 and costs increased more than twelvefold.

Since the program began, Toledo Edison has removed approximately 15,000 ash trees from about 6,500 line miles (10,460 km). Contat reports that EAB mitigation has cost the utility an average of US$300 more per line mile.

AEP Ohio also came to understand the cost of this infestation as its Western Ohio district was the first to experience a large number of dead ash trees from EAB. Mike Chedester, supervisor of region forestry for the Western Ohio district, explained that much of the area is open farmland and not densely populated, but ash trees used to represent almost 20% of all trees in the region versus a 10% average statewide.

Initially, AEP Ohio was able to absorb the increased cost of EAB mitigation into its scheduled vegetation management program. However, as the impact of the pest became clearer in the urban and suburban Columbus district — and the costs/risks became greater — the utility proactively began to prepare a request to the Public Utilities Commission of Ohio (PUCO) in 2012.

Rich Simpson, supervisor of region forestry for AEP Ohio’s Columbus district, worked quickly with his foresters to formulate a plan and cost estimate for a dedicated EAB mitigation team. This would help to ensure work was done in an efficient and economical fashion, and the actual costs could be tracked better. The Columbus district plan was submitted to the PUCO and the request was approved in early 2013.

Track Results

In February 2013, AEP Ohio began its three-year program to identify and remove ash trees outside of its normal easement on 4,406 distribution line miles (7,091 line km) in the Columbus district. The objective is to mitigate ash trees that are at least 25 ft (8 m) tall and within 30 ft (9 m) either side of a single-phase conductor (60-ft [18-m] swath) or within 50 ft (15 m) either side of a three-phase conductor (100-ft [30-m] swath).

Asplundh Tree Expert Co., AEP’s vegetation management alliance partner, gathered a team of five experienced work planners, led by project coordinator Steve Young, to identify trees for removal and get permission to remove the trees. A skilled team of 15 Asplundh tree crews and two general forepersons perform the mitigation work in the wake of the work planners.

Young coordinates the activities of both groups so the work planners stay ahead of the tree crews as they move through each circuit. In addition, he communicates with municipal authorities, handles customer concerns, arranges for specialized equipment or planned outages, and maintains a database to track the units, hours, locations and refusals. This data is reported monthly to AEP Ohio and Asplundh management, and is available to the PUCO whenever requested.

In addition, the utility has brought representatives of the PUCO to observe the work planners and crews at work on the project.

“We are highly aware of the public impact of this program,” said Chedester, who has worked on the EAB problem with numerous communities in his territory, many of which are Tree City USA members. “AEP wants to be a good neighbor because we know we have to come back in four years. We have to make sure people understand that dealing with threats beyond the normal right-of-way will help reliability and safety.”

By the end of 2013, AEP Ohio was well on its way to meeting its goal of proactively cutting ash trees safely and efficiently before they fail. More than 13,700 ash trees were removed along 1,047 line miles (1,685 line km) in the Columbus district and there are still two more years of the EAB mitigation program to go. In addition, the PUCO approved an EAB mitigation program in the fall of 2013 for the nearby Newark district and this may continue into other AEP Ohio districts as the effects of the infestation are seen.

Learn from Others

Before EAB begins to kill trees, utilities can prepare by estimating the scale of the problem for their system. For example, in the fall of 2011, foresters from AEP’s Indiana Michigan Power — with assistance from Asplundh — sampled about 2% of the entire service territory and arrived at an estimate of 51,600 ash trees within falling distance of their lines systemwide. Of this number, an estimated 35,000 were posing an imminent threat to overhead lines based on the degree of mortality (“Ash Trees Under Siege” by B. Scott Bennett, Transmission & Distribution World, Vegetation Management supplement, June 2013).

The cost of obtaining this information is small in comparison to the cost and scale of the damage likely to occur, and it can help to justify a more proactive approach.

Utility management can only take a wait-and-see approach for so long. Simpson says that timing a request for financial support to mitigate EAB risk is almost as crucial as developing an efficient strategy to accomplish it. Although the PUCO and customers may want to wait to see some EAB-killed trees with their own eyes, waiting too long will increase the cost of mitigation.

“If you don’t get out ahead early enough, the outages creep up on you,” commented Contat, who is working to get the word out so utilities can prepare. He will be presenting information about Toledo Edison’s EAB experience at the Utility Arborist Association sessions during the annual conference of the International Society of Arboriculture in early August 2014. It will be an opportunity for utility arborists to learn from each other and find better ways to safely and efficiently manage the EAB risk. 

Kristin Wild ([email protected]) is a corporate communications writer at Asplundh Tree Expert Co. and a member of the Utility Arborist Association’s editorial committee.

Editor’s note: This article was prepared with information provided by Rich Simpson, supervisor of region forestry, AEP Ohio (South); Mike Chedester, supervisor of region forestry, AEP Ohio (North); Mark Contat, manager of forestry services, Toledo Edison; and Kevin Gibson, supervisor of Asplundh Tree Expert Co., Chillicothe, Ohio; and Steve Young, project coordinator, Asplundh Tree Expert Co., Millersport, Ohio.

Sidebar: Outage Risk from Emerald Ash Borer Infestations at LG&E and KU

By J.M. Sparkman, Environmental Consultants Inc.

Emerald ash borer (EAB) is a voracious wood-boring insect from China that, as its name implies, prefers to dine exclusively on ash. Unlike many wood-boring pests that mainly attack diseased or dying trees, the EAB is adept at attacking living, healthy ash trees, threatening to eradicate ash trees, with consequent devastating economic and ecological impacts (“Emerald Ash Borer Invasion of North America: History, Biology, Ecology, Impacts, and Management,“ Annual Review of Entomology, Vol. 59.)

Why Utilities Should Care

Since its discovery in Michigan in 2002, EAB has spread to more than 22 states and two Canadian provinces, killing tens of millions of trees along its path. Many of these trees now pose an immediate risk to overhead electric facilities. Utility vegetation management programs in the affected states and provinces are scrambling to mitigate interruptions resulting from dead ash trees and to understand the potential impacts to system reliability.

In the state where it all began, Consumers Energy has estimated that tree outages due to EAB will increase annual tree-caused outages by 150% in coming years if no corrective action is taken.

Emerald ash borer timeline of discovery within North America.

Utilities outside of the current known areas of infestation, but within the native range of susceptible ash species (primarily the entire eastern half of the U.S.), must also heed warning and begin to take proactive steps to understand EAB’s potential impact to their electrical systems. EAB illustrates a classic example of the pay-now-or-pay-later philosophy. Pay now to develop a mitigation strategy to proactively remove or treat all ash trees that could impact electrical facilities, thereby retaining cost control over their removals or treatments. Or, wait and pay later, after the trees have died, and risk escalated removal costs from catastrophic equipment damage, outages and lost revenue, as well as costs associated with negative customer impact. Consumers Energy estimated the reactive removal of dead ash trees was roughly threefold higher than the estimated proactive removal costs. The choice is clear.

LG&E and KU Case Study

Louisville Gas and Electric Co. (LG&E) and Kentucky Utilities Co. (KU) began noticing significant ash tree mortality around their system in early 2012. Recognizing the need for a long-term strategic solution to address the outage risks, LG&E and KU engaged the services of Environmental Consultants Inc. (ECI) to assist with quantifying the ash tree population on approximately 18,000 miles (28,968 km) of primary overhead distribution line and to develop an effective mitigation plan and budget specific to their needs.

ECI began by designing a random sample survey to estimate the population of ash trees with significant height and relative position to strike the overhead primary conductor should they fall. Data was collected by trained ECI survey personnel across 13 operations centers. Several height and distance measurements were taken for each tree tallied as well as multiple tree characteristics to ascertain the health, condition, diameter, proximity to conductors and other spatial factors for each tree.

Analysis and Results

The field data collected by ECI was analyzed and used to calculate line-strike probability for each tree tallied within the sample data. Factors such as tree elevation in relation to the primary conductor, total tree height, conductor height and horizontal distance from the conductor were considered in the probability calculation. Probability of line contact was estimated as the percentage of the fall radius that would impact the primary conductor. Line-contact probability coupled with the estimated number of ash trees capable of making line contact was used to approximate the potential impacts to service reliability.

The final mitigation plan provided LG&E and KU with several key results:

  • A workload estimate for the number of ash trees to be removed from the system
  • Ash population characteristics, including demographic breakouts, accessibility and current tree health
  • Line-strike probability percentages
  • Estimated cumulative reliability impacts
  • Budget requirements
  • Reactive versus proactive cost comparisons.

The bottom line: approximately 54,000 ash trees were estimated to have the potential to contact the LG&E and KU overhead distribution system. The cost to remove those risk trees was estimated at US$26.9 million over 10 years. Like Consumers Energy, it was estimated that the cost to proactively remove the trees is significantly cheaper than the alternative approach, although, in comparison, a conservative estimate for the reactive removal cost was only 22% higher at LG&E and KU. However, more importantly, the proactive approach was estimated to save LG&E and KU more than 16,000 tree-caused outages over the 10-year period.

LG&E and KU have supplemented their risk tree program with sufficient dollars to address the removal of healthy, as well as declining, ash trees. Their investment to date has resulted in tree outages remaining relatively flat from previous years.

“The EAB study with ECI provided LG&E and KU with a snapshot of the ash tree population, thus allowing LG&E and KU to effectively budget for a long-term solution,” stated Terry Wright, manager of forestry service at LG&E and KU.

J.M. Sparkman ([email protected]) is the manager for consulting services at Environmental Consultants Inc. (ECI).
His experience includes more than 25 years of UVM forestry including regional management responsibilities for a large investor-owned utility. His recent experience with ECI includes emerald ash borer risk assessments, numerous vegetation program assessments, utility benchmarking, and the design and implementation of regrowth studies.

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