T&D World Magazine

VM Funding

In the recent Utility Arborist Newsline, Utility Arborist Association President Will Nutter said, “Most vegetation managers I work with spend very little time in the field or on crews. Most are in meetings, responding to utility requests, or defending the program. They’re on the defense several times each year, struggling to keep the funding promised to them at the beginning of the year.” He went on to say “I know we can do better at defending our programs and specifications if we work more as a team.”

Before we can justify and defend VM funding we need to have the facts and a means of articulating the necessity of that funding both internally and externally. When we need to justify funding to regulators, interveners and the public in general, it would help greatly if the entire utility industry were on the same page. To facilitate such communication, I will be doing a series of articles, beginning with this one, on VM funding. So, we will begin with a question.

Is there a specific annual amount that needs to be spent on VM?

My answer is yes. If you would like to have a sustainable least-cost VM program that simultaneously minimizes tree-related outages, there is a specific minimum that needs to be invested annually in the VM program.

Arriving at this conclusion is facilitated by thinking in terms of the utility forest. Annual changes in a forest are biomass additions and losses. For the utility forest the primary drivers of VM workload are tree growth and tree mortality. Consequently, the expansion of that workload can be defined by a logistic curve.

In forestry terms, the annual addition of biomass is referred to as the annual volume increment (AVI). For the utility forest, the focus being the protection of utility assets, the AVI is composed not only of the biomass additions but also the trees that have become decadent and need to be assessed and pruned or removed to eliminate the hazard. VM funding adequate to remove the AVI holds the system in equilibrium. It is the equivalent of paying the interest accrued on a debt over the year. The following year is begun with the same amount of debt, and assuming no change in the interest rate, the interest that accrues over the following year will be the same.

That explains how to attain a sustainable VM program. How do we realize the “least-cost” VM program? Understanding that the VM workload can be described by a logistic curve suggests that workload may be held at equilibrium at any number of points along the curve. While true, the best economy is achieved in holding the curve as low as possible because that is where the value of the AVI is minimized.

In field-applicable terms, how is the AVI minimized? That would be by using integrated VM and prioritizing the most cost-effective methods for the most pervasive use. It would include establishing early successional plant communities, using herbicides, matching mower type to brush density and diameter and choosing a pruning and hazard tree cycle that balances travel and set up charges with the increased safety risks and additional disposal costs associated with longer maintenance cycles.

If funding that permits removal of the AVI provides the least-cost VM program, then any deferred VM cannot be least-cost. Understanding that the VM workload can be described by a logistic curve, leads to the conclusion that the deferred workload will expand exponentially. For information on the scale of this expansion and what the implications are for future funding requirements follow the links provided above or see the articles below under "Highlights."

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