Duquesne Light controls vegetation growth through the responsible use of herbicides.
In 2008, Duquesne Light Co. Initiated an Interim-Cycle Selective Herbicide application program on select transmission rights-of-way (ROW) to reduce future maintenance. This effort will greatly diminish the risk of vegetation growth, keeping the floor of the treated ROW from encroaching upon overhead conductors.
As with any successful program, Duquesne Light Co. (Pittsburgh, Pennsylvania) will have to overcome some hurdles. Still, considering the utility used virtually no herbicides less than two decades ago, Duquesne Light has made great strides in its utility vegetation management (UVM) program.
Utility professionals charged with the task of managing ROW vegetation experience a wide variety of challenges in an ever-changing environment. UVM is a strategy that involves controlling undesirable vegetation by selecting and applying a variety of environmentally sound, cost-effective techniques. These techniques include biological, chemical, mechanical, manual and cultural practices.
The 1962 release of Silent Spring, written by Rachel Carson, a native of Springdale, Pennsylvania, brought unprecedented attention to pesticides, notably the effects of the insecticide DDT, which made many question the technologies of the day. Carson's work spurred change in national pesticide policies and inspired interest in the general public about all types of pesticides, a category of which includes herbicides. This awareness has had substantial impact on the use of chemicals in both past and present UVM programs.
The scrutiny of today's world intensifies the need for proper implementation of UVM best practices. Among the issues facing vegetation managers are public perception and regulatory oversight regarding environmental, social and economic issues. Rising concerns over climate change, protection of rare and endangered species, and preservation of green space, groundwater, riparian and culturally sensitive habitats are just a few examples of the environmental challenges vegetation managers face.
Compliance requirements when these situations are encountered vary significantly from state to state within the U.S. and from the U.S. to other countries. Depending on the specifics, vegetation managers must seek out environmentally sensitive and effective alternatives to achieve UVM goals. Selected tools must produce the desired end results and be financially viable.
DUQUESNE LIGHT'S HISTORICAL OVERVIEW
For more than a decade, Duquesne Light underestimated the value of herbicides as an integral tool in the control of incompatible, tall-growing species on its ROW. The utility's UVM program involved essentially no use of this valuable tool because of the then-held internal and external misconceptions about these chemical agents and the concerns about public opposition to the use of herbicides.
Therefore, vegetation on the ROW was mechanically cut using heavy equipment such as hydro-axes and brush hogs, or manually using handheld chain saws or brush saws. Rough terrain within the service territory limits the extent of ROW suitable for mowing operations, so cutting by hand was the most common practice. The mechanical/manual cutting compounds the problem of incompatible, tall-growing species.
With mechanical/manual cutting techniques, the root system of each individual plant is relatively unaffected after the removal of the aboveground portion of the stem — similar to mowing a lawn heavily inundated with weeds. The remaining belowground root system that stores food reserves for the entire plant unleashed tremendous energy, resulting in the proliferation of numerous sprouts from suppressed buds at the root collar of individually cut stumps. Each newly developed shoot resulted in yet another incompatible tall-growing stem to manage.
While many tree species sprout only from the root collar of the cut stump, there are several species prevalent in southwestern Pennsylvania that have the ability to reproduce sucker growth from the plant's root system, in addition to resprouting from the root collar of the cut stump. Root-suckering species such as sassafras, black locust and ailanthus (tree of heaven) respond to cutting by a rapid flush of sucker growth occurring from both the stump and the extensive root system of the established plant. This dynamic invasion of root-suckering species typically produces hundreds of new undesirable stems per acre, unless controlled through the use of herbicides.
The resprouting that occurs from cutting activities is only one source of growth on utility ROW. By clearing away tall-growing trees and brush, areas previously sheltered from sunlight and moisture become excellent sites for the germination of a host of seeds, which lay dormant in the seedbed on the ROW floor. Disturbance on the ROW by mechanical/manual maintenance activities results in an explosion of new growth flourishing from the lack of competition.
NECESSITY FOR UVM
A well-managed UVM program is essential for the safe, reliable delivery of electricity. The Northeast blackout of Aug. 14, 2003, clearly identified the vulnerability of eastern North America's electrical transmission grid to unmanaged vegetation.
Due to this incident, which affected an estimated 50 million people, the North American Electric Reliability Corp. (NERC), under the direction of the Federal Energy Regulatory Commission (FERC), developed and implemented the first UVM Standard FAC-003. The standard was put in place to improve the reliability of the electric transmission systems by doing the following:
Preventing outages from vegetation located on transmission ROW
Minimizing outages from vegetation located adjacent to ROW
Maintaining clearances between transmission lines and vegetation on and along transmission ROW
Reporting vegetation-related outages of the transmission systems to the respective organizations.
Noncompliance with this standard carries the possibility of sanctions imposed against the involved utility.
The ecological succession of plants explains nature's invasion of these open corridors by vegetation that threatens the reliability of electrical service. It is an industry best practice to establish and manage low-growing, stable plant communities on ROW floors to avoid encroachment upon overhead conductors. However, nature is rarely held in check and makes the management of desirable plant communities a perpetual challenge for the vegetation manager.
With the establishment of desirable plant communities, the density of undesirable stems is reduced, which may support the extension of treatment cycles. As the density of undesirable stems is reduced by herbicides, the established low-growing plant community serves as a barrier to the establishment of new undesirable stems, due to the competition for soil, nutrients, water and sunlight.
WHAT TO CONSIDER
The responsible use of herbicides in a UVM program to selectively manage vegetation on the ROW floor has very positive implications for reliability. When compared to mechanical/manual cutting, selective herbicide applications are highly effective — both in the near and long term — in reducing the densities of tall-growing, undesirable plants while promoting desired species.
The condition of the ROW vegetation is of utmost importance when selecting the appropriate herbicide application. Application choice is generally driven by the height, density and species of the vegetation involved. When the established vegetative cover has extended beyond the capabilities of proper herbicide applications, mechanical cutting may be the only, and unfortunately the most costly, option. An herbicide treatment following mechanical/manual cutting will reduce the number of tall-growing undesirables and is strongly recommended for the recovery of an unmanaged ROW.
A sound understanding of the economics involved with particular management techniques enables UVM professionals to address particular situations and achieve desired outcomes.
With the objective of managing ROW vegetation to coexist with electrical facilities, vegetation managers must make conscious efforts to work with nature, not against it. A resourceful manager will use a combination of mechanical/manual and chemical means for managing ROW.
First, the state of a utility's UVM program must be determined. Are the ROW in an unmanaged or a managed state? Simply put, have budgets for UVM activities been steadily supported by those determining the annual funding levels, or does vegetation management remain the area where budgets are first reduced when cash-flow issues arise? Be mindful that vegetation-related interruption levels share an inverse relationship with appropriate funding levels.
AN INTEGRAL COMPONENT
In an unmanaged state, vegetation has been permitted to grow unchecked to the extent where height and density prohibit the responsible and economical use of herbicides for control. Mechanical/manual clearing becomes the only option at this stage. The cost of recovery is extremely high and, ideally, for those who learn from experience, should only be performed once. In a managed operational mode, using a long-term approach, the vegetation manager strategically plans to sustain younger, diversified plant communities that can be readily controlled through the selective use of herbicides.
The incorporation of herbicides into a program serves several purposes:
The economic benefit of herbicide applications when compared to mechanical/manual operations is evident when viewed over the long term. Over time, proper herbicide applications can ultimately reduce the amount of work, and thereby the associated labor, equipment and material costs.
The establishment of desirable, low-growing flora through the selective use of herbicides makes a vast difference in the accessibility to a ROW during troubleshooting or maintenance activities.
The selective use of herbicides is more environmentally sensible than mechanical/manual techniques. The professional applicator, knowledgeable in species identification, selects the desired plant cover by treating only undesirable species, and chooses the appropriate application and herbicides to achieve this objective. The applicator must determine whether the site involved is terrestrial or aquatic, and then apply specific herbicides suited to the site's environmental considerations.
Mechanical mowing is a nonselective method that reduces all vegetation to the ground level. The resulting soil compaction and disturbance from mowing operations can create potential erosion and sedimentation problems. Additionally, equipment used in mowing and hand-cutting operations introduces synthetic chemicals such as bar and chain oil, gasoline and other petroleum-based products into the environment. These products take years to degrade and have the potential to enter both surface and ground water. The risk of water contamination is minimal with the proper selection and application of herbicides.
Herbicide applications are a safe method for managing vegetation considering line clearance and utility workers, property owners and the general public. Mechanical mowers can hurl pieces of wood, rocks and other debris substantial distances from the work site at an extremely high speed. Additionally, stubble remaining from mown vegetation can be sharp or shattered, and may present hazards for those walking the ROW. While cutting by hand presents this same hazard, it also introduces the potential for chain saw accidents when heavy brush-cutting is required.
Herbicides can enhance the aesthetics and wildlife habitat of a ROW. The world's longest ongoing study of the effects of mechanical versus herbicide applications, resulting plant cover and wildlife benefits has been researched for 56 years. Initiated in 1953 by Dr. William Bramble and Dr. William Byrnes, this project, now overseen by Dr. Richard Yahner, professor of the Wildlife Conservation at Penn State University, involves a 230-kV transmission ROW on State Game Lands No. 33 in central Pennsylvania. Through the selective use of herbicides, diversity-rich vegetative cover types were established that provide abundant food and shelter for a diverse population of wildlife.
The vegetation manager must be cognizant of user and public perceptions relating to herbicides. In many cases, this perception is negative, so education is essential for addressing and dispelling preconceived notions. With acceptance of this tool by the workforce and landowners, proper mixing, application, transport and storage of this material are essential for ultimate success.
Implementation of the use of herbicides in Duquesne Light's UVM program has served the utility and its customers well. Consequently, vegetation management support and funding have been relatively stable across the service territory since the 1990s.
UVM managers are challenged to accomplish more work with limited budgets. Herbicides, over the long term, are more effective from both a cost and UVM perspective because they can extend maintenance periods.
By responsibly managing UVM budgets, the utility will be better positioned to reduce the frequency of vegetation-related interruptions. The primary reason that Duquesne Light and all electric utilities perform ROW vegetation management is to provide safe, reliable electrical service. Duquesne Light takes great pride in providing energy reliably, and its supported UVM program is a key factor in the utility's success.
Jennifer Arkett (firstname.lastname@example.org) is Duquesne Light Co.'s vegetation management coordinator, a licensed Pennsylvania Department of Agriculture commercial applicator and an International Society of Arboriculture (ISA) certified arborist. A University of Michigan and Kent State University graduate, she has served as president of the Utility Arborist Association (UAA) and as a member of the ISA Certification Test Committee. She is presently active as a member of the ISA Public & Industry Relations Committee and UAA NERC Audit Certification Committee.