In July 2002, Nashville Electric Service (NES) announced an accelerated vegetation management program designed to reduce the number of power outages that customers experience while protecting the health of their trees. The trees in Nashville, Tennessee, are a major attribute to making the city such a beautiful place to live. Now in the second three-year trim cycle, NES's vegetation management team has learned many lessons about working with customers and city leaders. And, almost more importantly, the team has learned how to better manage its contractors — the trimming and tree-removal crews on the front line.

Environmental Consultants Inc. (ECI; Southampton, Pennsylvania) conducted a study on NES's line-clearance program and found that NES had the highest number of tree-caused outages per 100 miles of line of any of the 110 utilities ECI has studied. With a ranking 10 times higher than that of best-practice utilities, NES took the report to heart.

Inside NES

NES's vegetation management department consists of 10 personnel. The manager of vegetation management is accountable for the overall vegetation management functions. His office includes a planner/coordinator and a one-person support staff. Each of the five senior utility arborists on staff is an International Society of Arboriculture (ISA)-certified arborist and utility specialist. The arborists are responsible for planning, scheduling and coordinating the work for the vegetation management contractors, including tree trimming, bush hog, grass mowing, substation chemical vegetation control, tree replacement, as well as ACRT auditors and work planners. The department also includes two utility arborist trainees. At the start of the new program, a retired employee was also brought back temporarily to maintain statistical data as well as develop charts and graphs to help track and analyze data.

Our No. 1 goal was to communicate to our customers that we wanted to keep trees healthy and alive, while making sure they didn't interfere with electrical lines, which could result in outages. Early (and often) in the program, NES communicated to its customers the fact that, while we understood the important aesthetic, recreational, historical, economic and environmental role trees play in our urban environment, we also knew many of these trees were planted directly under or too close to power lines.

Our Front Line

In order to get to the required clearance and a three-year trim cycle, NES increased its annual vegetation management budget by approximately 35%; the amount of contracted trimming and removal escalated accordingly. We outsource all of our trimming and tree removal to contractors. We knew we had a public relations challenge on our hands and understood that the key to the success of taking back our corridors was dependent on the performance of our contractors — both in their quality of work and their interaction with our customers.

We have three main contracts that we maintain directly with our vegetation management program. Our Time and Material (T&M) contracts are for a three-year period with two one-year options to renew with prices fixed. Our Unit Trim and Removal contracts are for three years with set prices. Our Lump Sum contracts are for one year with unit prices for removals. Prices on all bids are fixed, so there is no negotiation.

Given the volume of work and the increased number of crews working in our corridors, the key was to clearly spell out the required trimming procedures and specifications. NES's tree-trimming guidelines are set by Nashville's Metro Tree Ordinance and recommended by the ISA. All contractors working on the system are required to spend time in the classroom before they ever set foot or equipment on NES's corridors. The degree to which a tree is trimmed depends on several factors: the tree species, voltage of power lines and how close branches are to those lines. We discuss our guidelines and trimming and removal standards and procedures with new crews and monitor them closing during their week on the job. Our guidelines are applied consistently across the board, from the highly affluent to the less affluent neighborhoods.

Contractors working on the NES's system come from numerous backgrounds in Tennessee, nationally and internationally. They include ABC Professional Tree Services Inc. (Houston, Texas), Asplundh Tree Expert Co. (Willow Grove, Pennsylvania), Seelbach and Co. (Lawrenceville, Georgia, U.S.), Townsend Tree(Parker City, Indiana), Trees Inc. (Houston) and Wolf Tree (Knoxville). Many bring personnel and their families with them to Nashville and often stay, seeking other employers when their contract runs out.

Train and Monitor

ACRT Inc. audits 100% of the contractors' work. NES staff and ACRT auditors drive through areas where the contractors are working to inspect work on a regular basis. This enables us to correct any problems quickly instead of letting them mount. If we find crews or personnel who are not sufficiently trained, we request that they not work on our system until they receive further training by the contractor. We also may ask a contractor to send trainers on the system to work with the crews.

NES staff is in the process of working with some contractors who are trying to develop a training standard, but it has been slow going. A comprehensive training program for utility tree-trimming contractors that is easy to administer does not exist. Most training material is sparse and piecemeal. For liability reasons, safety programs are the contractors' responsibility. This helps to ensure a safer workplace, as contractors take ownership of their workers' safety.

Contractor Operations

Each contractor has at least one on-site supervisor. Depending upon the number of crews, the contractor might have multiple supervisors, with one lead supervisor. A crew visited on a daily basis and sent a weekly report. We also meet with the contractor executives quarterly, if not more frequently.

Crew numbers vary depending upon startup or ending contracts and demand. During our first trim cycle, we kept our initial T&M contract of 26 crews and had anywhere between 40 to 60 Lump Sum contract crews on the system at any one time. Later in the cycle, we added 10 contract Unit Removal crews. Presently we have as many as 53 crews doing Lump Sum and Unit Removal, 15 crews working with Unit Trim and Unit Removal, and 13 T&M crews working on the system. A few T&M specialty crews alternate between stump grinder and crane truck.

Lump Sum with Unit Removal, Unit Trim and Unit Removal crews can use whatever equipment they need. A typical contractor has 55-ft bucket crews, backyard buckets, chippers, crane trucks, knuckle boom loaders and a 70-ft bucket. Our “combo” crews typically consist of two to three workers who do both manual (climbing) and bucket work.

Think Outside The Box

Any vegetation management team faced with such an ambitious undertaking needs to try new things, accept failure and then move on. For example, we thought, ideally, that tree trimming and tree removal should be one operation. A one-stop operation simply made sense. However, in reality, we had to make a choice because the initial prices we received from contractors were too high. We could either extend the rotation from three to five years, or separate the operations and have a trimming operation and a tree-removal operation. We chose to have two separate operations.

Our tree-removal goal was to remove trees smaller than 12 inches in diameter in order to gain control over future in-growth. The industry average cost for tree removal is $38 to $46 per tree. Our first Unit Tree Removal bids were upwards of $125-plus per tree. T&M crew removal costs were $60 to $90 per tree on average. And with a backlog of up to one year for tree removals, customers complained that we were taking too long.

After multiple requests for proposals, vendors began bidding an average of $35 to $55 per tree removal. Upon receiving three bids during the second trim cycle, from several companies that were comfortable enough with our removal and trim prices, we selected them for Unit Trimming and Unit Removal contracts. In March 2006, nine months after we finished the first cycle, we finally completed our backlog of removals.

Per Mile Costs

When we began the revised vegetation management program in July 2002, we were trimming as many as 200 trees per mile. Our pruning costs averaged $3744 per mile. Our removal costs per mile were similar. Add to these figures approximately $500 per mile for work planning and auditing. In our second trim cycle, which began in June 2005, we have noticed a decline in the per-mile cost. Trimming cost have dropped between 25% and 30%, and we will probably have a 40% to 60% drop in cost per mile for removals.

Our goal is to trim approximately 1600 miles to 1800 miles per year in order to maintain a three-year trim cycle. We try to bid out one Lump Sum contract per quarter. The contracts are for one year, and in order to meet our goals, contract specifications dictate that the contractor must complete one-twelfth of his or her awarded bid miles per month.

Reaping the Results

When we started this new program, there were times the staff in vegetation management felt like the floor, ceiling and walls had been knocked out from around them. But regardless of their comfort level, or I should say lack thereof, we completed a monumental task of trimming an enormous amount of trees and vegetation from our system in just three years. And now we are reaping the results: a well-established, well-funded vegetation management program with excellent service reliability that benefits both the customer and NES. Our outage numbers have decreased by 19%, and we are consistently meeting service reliability goals that we had never been able to reach in the past.


Glenn Springer, vegetation manager at Nashville Electric Service, has a bachelor's degree in forestry. He has 18 years of experience in utility vegetation management and 32 years of experience in the forestry field, including serving eight years as one of nine district foresters in the State of Tennessee. Springer is a past chairman and has served on the Metro Davidson County Tree Advisory Committee for the past 12 years. He has made numerous presentations on lateral trimming and utility trimming to various local groups and others representing communities and utilities across Tennessee. gspringer@nespower.com

Third-Party Auditing

Third-party partnerships with utility forestry-consulting firms often play a strategic part in successful vegetation management programs because they provide work planners and auditors. These professionally trained utility arborists provide appraisal of the work to be done, notify the property owners, and train the contracted crews and schedule the daily work.

The tree management consultant is often responsible for the auditing of the contractor's work, patrolling the jobsites and conducting final inspections of completed work. Verifying the contractors completed work may include:

  • Tree/conductor clearances
  • Clean up
  • Herbicide/stump treatment applications
  • Safety violations (hangers left in trees)
  • Skipped trees or missed taps.

In many cases, the contractor is not paid until he auditor deems the work has been completed according to the utilities trimming specifications.

Some third-party consultants who use pen tablet computers have developed custom software applications that enable them to collect all data electronically in the field. This information is warehoused in a central database and is used to print a multitude of reports, including work maps and work manifests used to monitor all aspects of the vegetation program. Additionally, reverse invoicing for the tree-trimming contractors can be generated from the software.

Because the consultant's team is so close to the day-to-day work, the contractors and the public, they also provide an important role in public relations, both in proactive communications with the customers and following up with “refusals.”