The vegetation management program at Pepco (Washington, D.C.) began with a simple routine operation of scheduled maintenance for trimming trees and clearing rights-of-way (R/Ws).

Today, the extended process also involves an evaluation of trimming as it affects feeder reliability and a new meadow management program.

In 1995 and 1996, trees caused 11% of Pepco's total primary sustained outages. Two-thirds of the outages were caused either by branches or by uprooted trees falling into the overhead conductors. Routine scheduled maintenance did not aggressively address these two problems. Therefore, those directly involved developed solutions to reduce these kinds of outages by eliminating overhanging limbs and removing trees that could cause outages.

The utility discovered ways to detect diseased trees that were a hazard to the system. Additionally, Pepco's forester and the contractor's general foreman worked together to inspect all completed work to identify skips and improperly trimmed trees, resulting in improvements in the work.

In 1999, Pepco's focus was to reduce the number of tree-caused outages. Pepco not only completed the work on time, it also improved field operations; increased the scheduling and efficiency of its non-routine/scheduled work; improved customer and governmental communications; and converted its existing R/W maintenance work to a meadow management program. Pepco accomplished these activities while saving time, reducing costs and improving system reliability.

Contractor Relations

Pepco contractors train and develop their work forces to concentrate on improved system reliability, minimized environmental impact and cost reduction. Pepco developed a program of “predictable consistency” by leveling the workload over the calendar year and negotiating long-term contracts. These consistencies provide projectable revenue streams for contractors as well as work security for employees. All scheduled work is unitized so that payments are based on predetermined work units, which encourages contractors to strive for increased efficiency and improved performance. Since 1999, Pepco has continued to successfully complete all scheduled system work on budget, even during the history-making Hurricane Floyd in September 1999 and the September 2001 tornado.

System-reliability statistics continue to improve as a result of a multifaceted program that draws on internal and external resources. In 1999, Pepco's team of professional foresters doubled from three to six, helping the utility achieve increased inspection of the scheduled work. Pepco also was able to improve communications with customers, municipal representatives, regulatory authorities and community action groups. Using all personnel from both in-house staff and contractors, the utility was able to identify all reliability problems, which has reduced the costly reactive response to system outages caused by tree contact during storms or simply to answer a customer's request for mid-cycle pruning.

Perhaps the single most-effective change Pepco made to improve reliability was to institute a 100% inspection of the completed scheduled work. Its system is trimmed on a two-year schedule, in accordance with Mary-land's Roadside Tree Law, amounting to about 2400 pole-miles (3862 pole-km) per year. Pepco issues the work packages to its contractors and includes plats and specific details about the work. Upon completion of the plat, the contractor's general foreman and a Pepco forester inspect the plat together. Each span is inspected and any skips or improperly trimmed trees are listed on an inspection sheet. Both parties sign the sheet, which is then returned to the crew responsible for completing the work on the plat outlined on the inspection sheet.

When Pepco began this joint inspection, approximately 10% of the plats did not require further work. The crews' work practices and knowledge of the job requirements have evolved to the point where more than 75% of the plats inspected now do not require further work. In addition to improved productivity and accountability, this process has the added benefit of improving reliability by ensuring that all spans in the area are clear.

The Work Routine

The scheduled work is based on trimming trees to maintain line clearances for at least two years. That is, the tree will not contact wires even during 25 mph winds during this time. All pruning is done in accordance with the latest version of ANSI and OSHA standards. In preparation for trimming, an inspection is undertaken to identify dead, diseased and hazardous trees or limbs. The contractor receives work orders addressing these items, which then are assigned to special crews to minimize possible disruption of regularly scheduled work.

Another solution for maintaining the work schedules involved the necessary post-storm cleanup, in which Pepco would dispose of private or municipally owned tree debris. This tied up crews that normally would be working on specific maintenance jobs, resulting in delayed schedules and responses to existing customer service requests. Pepco discontinued its “free municipal” work and concentrated on its core business. This action provided work for private contractors hired by the municipalities to do the cleanup work.

Updating the Maintenance Work

Prior to 1999, “unscheduled work” was the one line item that comprised 25% of the total vegetation management budget, which covered:

  • Customer requests

  • Assistance with public and private removals

  • Feeder reliability work

  • Storm restoration

  • Standby during inclement weather

  • Miscellaneous work to resolve claims.

In 1999, Pepco developed spreadsheets and assigned charge-function numbers to the various activities. Based on statistics from previous years, this change now has evolved, making it possible to predict how much Pepco will spend on each activity. For example, the utility can track how much it spends on crews that it holds as “stand bys” in anticipation of inclement weather. It also can track weather data involving wind speed and precipitation, duration of the storm and customer requests. By using historical data, outage personnel can estimate the number of crews required to handle a predicted storm.

Another type of previously unscheduled work — that is now scheduled — is “tops for removals” (TFR). A TFR involves trimming trees so nonqualified tree trimmers can remove the rest of the tree safely and without violating the minimum-approach distances to energized conductors set by OSHA. In this respect, Pepco tracked the cost of the TFR activity using criteria such as DBH (diameter at breast height), location and wire configuration to develop unit prices that enabled the utility to predict annual costs for budget purposes.

Along with TFRs, which comprise 25% of customer requests, other types of requests also are tracked, prioritized and scheduled. By scheduling work, instead of just sending out crews every time it receives a customer call, the utility reduced the cost and increased the efficiency in resolving each request.

Improved Relations with the State

Maryland's Department of Natural Resources (DNR) has a comprehensive system for protecting its urban forest. Included is the requirement that contractors who perform work in the state for a fee must have a state-licensed tree expert on staff. Pepco finds it advantageous to work with regulatory officials, for example, developing a partnership with the DNR Forest Service to achieve a successful vegetation management program.

The utility participated in training DNR personnel in electric-system operations to provide awareness and knowledge of system reliability and the necessity for trimming around energized circuits. DNR staff cultivated working relationships with forest rangers in the field, project foresters on a regional basis and with the program coordinator at the state level. These relationships opened lines of communication, which helped to diffuse problems with individual customers, provided a forum for discussion and interpretation of state laws and regulations, and created a streamlined framework to obtain permits in an efficient manner.

The decision to work for the conservation of the Kentucky coffee tree is an example of how a good working relationship evolves with the DNR. This tree was slated for removal as part of a highway ramp construction project. Pepco scheduled meetings between the Maryland State Highway Administration (MSHA), the DNR Forest Service, the construction contractor, the developer and its own construction personnel. The utility forestry staff worked with each agency to resolve problems and was successful in building a coalition to support the effort to save the tree. Pepco reconfigured the construction of its overhead and underground facilities, and performed trimming where necessary. The MSHA redesigned the roadway to avoid infringing on the critical root zone of the tree. The tree was saved. The conservation of the tree is a credit to the work and determination exhibited by staff in building strong partnerships with local and state agencies.

Another activity resulting from the 1995/1996 tree-caused outage study was the implementation the Proactive Reliability Operations Aggressive Circuit Trimming (PROACT) program. For the majority of the distribution system, the consistent routine of trimming every two years resulted in a high degree of system reliability. The tree-caused outage study indicated that the problem resided with whole trees toppling over and onto the feeder, or with large limbs or treetops breaking out and contacting the conductors.

When PROACT was adopted in 1999, the operation was improved dramatically for the subtransmission feeders located along public streets in suburban and urban areas, often with a mature tree canopy. The PROACT program protects the feeder by eliminating all overhanging limbs and hazardous trees along the entire circuit. The crews involved in the program are highly dedicated and are teamed with a permission specialist, who is charged with the responsibility for obtaining the necessary permission to work on targeted trees. These trees may be privately owned or in public spaces under the jurisdiction of the DNR and protected by the Roadside Tree Law.

Meadow Management

An additional project intended to ensure service reliability involved a new vegetation management program called meadow management. The program is intended to focus on reliability as well as on responsibility for environmental stewardship with respect to transmission R/Ws.

Tall-growing trees naturally invade R/Ws and may impinge on the overhead conductors. The principle management objective is to remove these undesirable trees and to cultivate low-growing, relatively stable plant communities by mowing and treating the areas with herbicides, such as ACCORD, which is supplied by BASF (Research Triangle, North Carolina, U.S.), to reduce stem density. As crews work in the R/Ws, daily inspections monitor progress. In addition to inspecting the work, the inspector also meets with adjacent property owners and customers to address any questions before work begins.

Pepco established several partnerships with many organizations to enhance wildlife habitat and to improve water quality in streams that cross the utility's property. An example is the Stream Relief program, in which inspectors worked with contractors and the Maryland Youth Conservation Corps to clean up many of the waterways that cross R/Ws in preparation for the planting of low-growing plants to reduce water temperatures and to promote clean water. Another example is the Bayscapes program — the result of a partnership between the U.S. Fish and Wildlife Service and a local municipality — which concentrates on a 230-kV R/W. This area acts as a filter to improve water quality to the Chesapeake Bay, where contractors mow, disc and plant wildflowers.

Measurable Results

New approaches and initiatives are evolving to increase the value of R/Ws through management of property based on ecological resource valuation. Practicing environmental stewardship encourages partnering with wildlife support groups, environmental government agencies and other interested groups to achieve corporate goals. The outcome of the vegetation management program has been a dramatic reduction in tree-caused outages, improved relationships with local and state officials, better communication with customers, partnerships with various interested groups and greater efficiency. The program will continue to evolve and eventually will become part of an enhanced GIS program. The National Arbor Day Foundation recently recognized Pepco as a Tree Line USA utility for its vegetation management program.


Contributing to this article were members of the vegetation management team that include Pat Byrne, Rick Clark, Steve Genua, Jennifer Gillen, Dan Landry, Nathan McElroy and Dave Paduda.

Cindy Devlin Musick is a staff forester at Pepco, where she has worked in utility forestry since 1991. Her previous employment was with the Bureau of Land Management in Red Rocks Lake, Montana. She received the BS degree in forest resource management from West Virginia University and the MS degree in environmental science and policy from Johns Hopkins University. Musick is a licensed forester and a certified arborist, a member of the International Society of Arboriculture and the Society of American Foresters.