Achieving the Perfect Transmission Right of Way

Ensure reliability while providing habitat for wildlife

by Sam Quattrocchi

A well-managed right of way provides significant value for a variety of wildlife, as vegetation management practices have created early successional habitats. That’s one of the most significant findings of a 54-year study on electric transmission rights of way.

The State Game Lands 33 Research and Demonstration Project is the longest continuous and most comprehensive study documenting the effects of mechanical and herbicidal maintenance practices on plants and animals along electric transmission rights of way.
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“Through effective ROW management practices, we have been able to maintain the status quo. And in many parts of the eastern United States, the forests are maturing and habitats such as this are at a premium,” said Dr. Rich Yahner, Penn State University professor of wildlife conservation and lead researcher on the State Game Lands 33 Research and Demonstration Project.

The project began in 1953 when Pennsyl-vania Electric Company, now a wholly owned subsidiary of FirstEnergy Corp., and Asplundh Tree Expert Co. teamed up with researchers and the Pennsylvania Game Commission. Along the way, Dow AgroSciences also became a cooperator.

Today, the project is the longest continuous and most comprehensive study documenting the effects of mechanical and herbicidal maintenance practices on plants and animals along electric transmission rights of way. The original objectives of the project remain the same: to compare the effectiveness of commonly used mechanical and herbicidal maintenance treatments on control of undesirable trees and development of tree-resistant plant cover types, and to determine the effects of these practices on wildlife habitat.

Integrated Vegetation Management Aids Reliability

The “wire zone-border zone” method of vegetation management was implemented in 1982, dividing the area along the right of way into two sections. The wire zone is the area directly beneath the power line, plus 10 feet on each side. In the wire zone, the goal is to produce a community of grasses, forbs (an herb other than grass) and low-growing shrubs. The border zone is the 20-foot-plus area on each side of the wire zone. Low- to medium-sized shrubs and low trees fill this area, which meets the natural forest.

The wire zone-border zone method helps vegetation managers achieve the perfect right of way, one that is accessible and free of troublesome trees that could cause reliability issues. In addition, the research shows that this variety of vegetation is conducive to attracting wildlife.

To study the impact of vegetation management practices on this environment, the project land is divided into several sections where various treatment methods are used, including handcutting, low-volume basal spray, stem-foliage spray, mowing and mowing plus herbicide. Vegetation in each area is measured prior to a treatment and monitored several years post-treatment to determine the effectiveness of each method.

Mechanical and herbicidal treatments were last conducted on the right of way in 2000, including low-volume basal spray using Garlon 4 herbicide at 25 percent and basal oil at 75 percent. In 2005, Yahner and his team measured and recorded all undesirable or target trees at least 1 foot in height within sections of the wire zone and compared that to numbers found in 2004. The findings showed target trees continued to invade the right of way, where the average number of undesirable trees in the handcut units was 2,425 per acre. But the number of target trees in areas where herbicides and mechanical means were used averaged only 254 per acre.

The wire zone-border zone method helps vegetation managers achieve the perfect right of way, one that is accessible to ensure reliability and conducive to attracting wildlife.
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“These low densities attest, in part, to the effectiveness of integrated vegetation management for maintenance of electric utility transmission rights of way,” Yahner said, “especially when compared to the numbers found on handcut units, which indicates out-of-control management of undesirable tree species in the absence of herbicidal and mechanical treatments.”

Impact on Wildlife Often Surprising

In addition to measuring vegetation growth during the past 50-plus years, each of these areas and management methods have been monitored and examined for their effect on wildlife. Since 1982, a series of studies has focused on songbirds, small mammals, butterflies, amphibians and reptiles. Some results might come as a surprise.

Butterfly populations were studied on the right of way in 1989 and 1990 to determine if herbicidal spray maintenance had any adverse effects on the population. This study was crucial because butterflies pollinate wildflowers, provide food for wildlife and add natural beauty. Fourteen species were observed on the handcut unit compared to 20 on the high-volume basal spray unit and 19 to 20 on the mowing plus herbicide units, indicating that herbicide spray did not have a detrimental impact on butterfly populations at all.

Amphibians and reptiles serve as indicators of a healthy ecosystem and play important roles in the food chain. Nine species of amphibians and reptiles were found on the right of way; six were identified in the stem-foliage spray unit and three in the handcut unit. In contrast, only two species were found in the nearby forest. The species identified included Redback salamanders, Northern Redbelly snakes and Northern Ringneck snakes. Snakes were observed mainly in the wire zones, with salamanders primarily in the border zones.

Birds also depend on early successional habitats for breeding and nesting, and were studied along State Game Lands 33 in 1991 and 1992, and again in 2002 and 2003. The studies showed that bird populations along the right of way are high, and also confirmed that more than 10 different bird species are nesting in the area and have been relatively successful in raising their young. In the earlier study, the rate of success for all species combined was 68 percent. In 2003, the rate of success declined slightly to 65 percent, in part due to abundant nest predators such as the Eastern chipmunk.

The American woodcock is a migratory game bird whose population has been declining for years in the northeastern U.S. as a result of forest maturation and conversion of farmland to forestland. In spring 2000, the project began monitoring the American woodcock. In the first year, one was documented; by 2005, the number had risen to seven. Based on six years of data available thus far, the area provides suitable courtship sites for the woodcock, especially along the border zones where there is cover for the singing males. The study needs to continue for a few more years to produce more meaningful results.

The contributions the State Game Lands 33 Research and Demonstration Project has made to the industry are crucial, and with the industry’s support will continue to evolve and provide useful information for years to come.


Sam Quattrocchi is an International Society of Arboriculture certified vegetation manager and herbicide trainer who has worked with Dow AgroSciences for more than 25 years. He can be reached at

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