TransActions - January 2002 (Vol 102)

Efficient Vegetation Management: Highest Quality for the Lowest Cost

How much does your utility spend on right-of-way brush control? The budget for an electric distribution system in the Southeast with approximately 2,500 miles of primary line can run $1,000,000 or more annually. To ensure that you are getting the most for your money, ask yourself two questions.

1. Is the current vegetation control plan effective.

2. Is it efficient?

The primary objective of vegetation management is to keep trees and brush from interfering with the conductors and to provide linemen and equipment access to the structures. An effective maintenance program is evidenced by a low number of outages caused by trees and minimal line loss.  Providing reasonable access to the structures for linemen and equipment reduces the time necessary to restore power during major storms.  This results in shorter outage periods per consumer.  Reducing line loss and outages increases customer satisfaction through reasonable electric bills and reliable service.  However, if the vegetation control program is not examined carefully, money can be wasted in the treatment process or by maintaining an unnecessary high degree of control. If this happens, the savings realized from effectiveness are lost in inefficiency. 

Budgets are a function of treatment costs and the interval between applications.  Generally, a specific area is treated one year then left alone for several years. When the vegetation grows to a height that it interferes with the conductors, it is treated again. This rotation is called the clearing or treatment cycle. If the clearing cycle is too long, trees will grow into the lines. If it is too short, funds may be allocated for needless services. Maximum efficiency is achieved when the trees and brush are re-cleared and trimmed just prior to them interfering with the conductors or impeding access to the structures. The optimum clearing cycle keeps the lines clear and uses minimum labor and equipment to obtain the maximum length of time between treatments. This goal can be achieved by accurate evaluation of the existing program and development of a comprehensive vegetation management plan.

Evaluation

• Survey the system environment - Determine the species and density of brush growing on the right-of-way. Review the system to gauge the percentage of actual trees and brush that must be cleared along a given circuit.  A complete ride-through inspection of the system will aid in assessing the vegetation and topography.

• Analyze the current program - Research the last five years of activity to determine past treatment cycles. Examine outage reports and line loss records to determine the effectiveness of the past vegetation control program. Calculate the annual expenditures by reviewing the right-of-way clearing financial records.  Review the operating maps and records to determine the volume of right-of-way that has been cleared and trimmed.  Form conclusions based on the historical appraisal such as cost per mile, labor and equipment requirements, and continuing treatment costs.

• Inspect the labor force - List the equipment and personnel dedicated to right-of-way maintenance. Measure performance rates for the various combinations of crews, tractors, chippers, trucks, and specialized machines. If both in-house crews and contractors are used, the performance rates and cost should be separated.

Planning

• Develop clearing and trimming schedules - Based on the utility's clearing history; determine when each circuit is to be scheduled for clearing and trimming. It is best to accomplish both operations in the same year. Organize the various circuits into manageable areas. This will reduce mobilization costs created by jumping around the system in an unorganized manner.  If the system has not been maintained systematically, hot spot clearing may be necessary to delay full treatment of overgrown circuits until they can be scheduled into a logical rotation.

• Establish unit cost - Measure the length of each circuit to establish unit cost. The planner has two choices to accomplish this task.

1. System Maps - Obtain the mileage from the existing detail maps or circuit diagrams.  Although this method is reasonably accurate, it can only be used on a circuit-mile type management plan. The circuit-mile includes vegetation plus all open areas such as fields, roads, and yards. If contractors are used, they must estimate the actual amount of vegetation to be treated less the open areas and formulate their bids accordingly. The bidders may spend their own money to measure the vegetation and pass it on in the bid price, or simply bid a higher unit price to compensate for the estimating.

2. GPS Field Survey - Make a field inventory using GPS coordinates and data management software to accurately measure the volume of trees and brush.  Once the data is obtained, it can be converted into specific contract units unique to the type of treatment needed to clear the brush. The "brush acre" is becoming the more preferred unit as mechanical clearing is combined with the application of herbicides. Knowing the actual amount of vegetation to be cleared, trimmed, or sprayed produces the lowest contract bid prices. It also provides an accurate basis to measure the performance of in-house crews, as well as contract crews.  Although this method increases the planning costs, they are usually recouped from the significant savings realized from the lower contract bid prices.

• Choose in-house or contract work force - Decide whether to use independent contractors or in-house crews and equipment to implement the management plan.  Be careful with this decision. Choosing a total in-house work force can result in a dramatic increase in overhead expenditures. During hard times, vegetation control is usually the first budget item to be cut by managers.  Should this happen, a large in-house force could face layoffs. This decision must be based on carefully prepared performance rates and costs for both contract and in-house work forces. 

• Determine the clearing cycle - Based on brush species and growth rates determine the clearing cycle. Specify the circuits to be cleared each year, and budget the annual cost based on a per unit value. Prepare an annual clearing and trimming schedule for the complete clearing cycle.

Herbicides
Proper application of herbicides can greatly improve efficiency by extending the clearing cycle. This is achieved mainly through a major reduction in sprout growth. Sprouts from old stumps can reach heights of twenty feet in three years. Seeded-in growth takes considerably longer. Depending on the environment, clearing cycles of seven years can be realized.  Effective "mechanical clearing only" programs typically run for a five-year cycle at $1,000,000 per year cost.  By extending the cycle to seven years, savings of $2,000,000 less the cost of herbicide application can be achieved.  Herbicide treatment costs for a 2,500-mile system that is about 65% vegetated typically run between $100,000 to $150,000 per year.

Analysis of the species and density of the brush plus environmental conditions is necessary to accurately prescribe the correct chemical tank mix. The chemical must enter the vascular system of the plant to be effective.  Plants with thick leaf cuticles such as waxmyrtle usually require a different treatment than non-waxy species such as sweetgum. Herbicides applied near water or wetlands must be safe and labeled for these sensitive areas.  Apply all herbicides according to the species and rates shown on the label. A registered forester or certified arborist is well suited for this type of work and can properly select a prescription that will be both effective and safe for the environment.

The method of application is important for effective kill and customer acceptance. Low volume backpack spraying maintains a lower profile in populated areas while tractor or truck spraying may work best for remote areas. Many of the contractors have GPS receivers installed in their      equipment. They can utilize the GPS coordinates obtained in the initial survey to start and stop the application for a specified area.

The vegetation manager and not the vendor should specify the chemicals, rates, and method of application.  He or she should also monitor the field treatment to see that the prescription is being properly applied. This will ensure an effective kill and prevent damage to the environment.  In most situations, a commercial pesticide applicator's license is required for this type of administration and monitoring.  Defining the specific chemicals, rates, and brush acres will produce the lowest contract bid prices.

Implementation
A well-prepared management plan will be effective only if it is implemented properly.  To realize savings and extend the rotation, the clearing crews must adhere to the schedules and treatment areas.  Proper application of herbicides including prescription, timing, rate, and volume are crucial for an effective kill.  A unit cost contract will encourage contractors to finish on time.  In-house crews should be continually supervised and kept focused. Try to prevent the mainline crews from jumping about the system. If hot-spot clearing is needed, dedicate a small crew specifically for this task.

Prepare a detailed contract to protect the utility and ensure that the work is properly done.  It should include specifications, insurance needs, hold harmless agreements, special environmental conditions, and performance schedules.  Prepare separate contracts for clearing and herbicide application.  A well-prepared contract will obtain the lowest bid prices and produce the highest level of performance.

In densely populated areas, property owners do not easily accept right-of-way clearing and trimming. The improper pruning of yard trees causes many hard feelings.  Education and good contract administration can help alleviate this distress.  Provide pre-application conferences for the contractors and in-house crews. Instruct them on proper interaction with customers and complaint handling.  Send an arborist or urban forester ahead of the crews to talk with the customers prior to trimming or cutting their trees.  Explain the necessity for the work and show the property owner that the utility cares about their trees but must maintain clearance from the lines to provide for safety and reliability. The utility should consider a tree replacement program to mitigate tall growing trees beneath electric lines by removing them and planting species that mature at fifteen to twenty feet.  Consider applying tree growth regulator chemicals to decelerate the growth and delay future trimming. Monitor the pruning of yard trees to ensure that proper pruning techniques as specified in the contract are being correctly applied.  Make sure that the brush is removed and the yard is left as it was found.  Settle complaints quickly. Do not let the customer's dissatisfaction fester over an unreasonable length of time.  He or she may own the land needed for a future line extension to a large industrial customer.

Make a final inventory and inspection of the work soon after it is completed for each section.  Check to see that the clearing and trimming meets the contract specifications. Inspect the percent vegetation kill for the herbicide during the next year's growing season. Inventory the actual brush acres treated including all field changes approved by the owner. Calculate final payment based on the inventory and close the contract.

Summary
Effective vegetation management requires research, evaluation, planning and implementation. Efficiency is achieved when these tools are integrated into a vegetation management plan that keeps the trees and brush from interfering with the conductors and provides access to the lines for the lowest possible cost. If the management plan is well prepared, its implementation will promote customer satisfaction through reduced outage time and competitive electric power rates.

It is apparent that the responsibility for evaluation and design is no simple task. Utilities are increasingly turning to professionals for help in evaluating and developing efficient vegetation management programs. A forester or arborist, educated and trained in vegetation management, can spot trends and problems not seen by linemen, superintendents, or engineers. The professional forester can develop a right-of-way management plan based on sound biological principles that is both adequate and cost effective. Compared to the amount of money spent for annual maintenance, the cost for professional evaluation is insignificant and is usually recouped many times over in increased efficiency.

Professional Services
Hi-Line Engineering prepares and implements vegetation control plans The staff includes registered foresters, certified arborists, and commercial pesticide applicators. Services include GPS data collection and GIS mapping of right-of-way vegetation.  Hi-Line Engineering is a full service firm providing electrical distribution system evaluation, planning, design, and right-of-way management services.

For more information, contact Richard Lovelace at 334-887-3297 or by e-mail at richard.lovelace@hi-line.gdsassociates.com.

HERE'S YOUR CHANCE TO WIN A CRYSTAL BALL!

Guess where natural gas prices will be on April 30.
Not too many people in the utility industry will disagree that natural gas has become the fuel of choice for new electric power generation.  However, there appears to be considerable uncertainty over what the price of natural gas will be in the future.  Until the year 2000, changes in price had been stable over time.  Average wellhead prices for natural gas fluctuated around $2 per million for nearly a decade.  However, during 2000, prices increased dramatically as supply and demand forces took effect. 

Due to recent price fluctuations and uncertainty regarding near term supply and demand, the outlook for natural gas prices has become somewhat clouded.  The following graph shows how prices rose during 2000 and then returned to levels just above the long-term average. 

The graph also shows how the pricing of natural gas futures contracts has decreased considerably since April 2001. How confident are you in using this information as a gauge of prices for the coming months and year? In it's December 2001 Short-Term Energy Outlook, the Energy Information Administration projects average spot wellhead prices to fall from $6.48 per thousand cubic feet last winter to $2.15 per cubic feet this winter.