generally prune more trees in public rights-of-way than all other parties
combined. And, underground services have a similar impact. Trees and overhead
lines have been getting in each other's way ever since the first utility pole
was erected along a tree lined street. Initially, trees were considered
obstructions to the electrification of a nation. Lines were built and the
public got electric power, often at the expense of trees.
It should come as no surprise, that the public has long complained about the seeming insensitivity to trees displayed by utility pruning programs. At the same time, utility arborists have legitimate objections about common tree planting practices in utility rights-of-way. Both trees and overhead lines have a legitimate place in human communities. For this reason, it is prudent for every community to take a close look at the practices of local utility companies and the way those practices affect the urban forest. To develop a constructive working relationship, it's important to understand the opportunities for cooperation as well as conflict. Minimizing conflicts requires an examination of the goals and objectives of each function.
The local utility company is responsible for maintaining safe and reliable electrical service to its customers. Trees growing near overhead lines can pose a threat to reliability and public safety, so trimming and removing trees along the "utility strip" is one important utility function. Simply put, utilities manage the portion of the urban forest growing near overhead power lines. However, the community is responsible for maintaining and preserving all components of the urban forest, including parks, greenways, and street trees growing in the "utility strip."
A municipal arborist views the urban tree as a generalist; each tree is a valuable and integral part of the entire urban forest. Condition, vigor, size, and maintenance needs are items that require attention for the good of the community. On the other hand, a utility arborist focuses on trees as they relate to overhead lines. The goal of a utilities tree trimming efforts is that clearance be obtained between the power lines and the trees. When the need for line clearance work is assessed, the decision to trim or remove is made from that perspective. Work closely with your local utility to broaden priorities and benefit the urban forest as well as the utility system.
Some utilities have developed vegetation management plans, which are similar to municipal street tree management plans. Before scheduled maintenance is performed, a crew conducts a pre-job survey of the tree work along the line. This inventory identifies the amount of trimming and tree removal work required. Inventory information also helps allocate labor and equipment resources, and establish crew makeup and work practices.
"Round-over" or "topping" techniques of pruning are not acceptable standards for tree trimming.
|Planting inappropriate tree species under
power lines creates a difficult situation for both the utility and the
community. For example, trying to control the height of trees with the genetic
drive to grow eighty feet tall poses a real maintenance challenge. As long as
the wrong trees are planted in the wrong place, utilities will be obligated to
prune them or remove them altogether. To minimize this, many utilities have
developed tree lists suggesting alternatives to such favorites as oaks, maples,
London plane trees, and other tall-growing species. The recommended species are
selected for low maintenance, insect and disease resistance, availability, and
beauty. Mature height must be 25 feet or less.
Normally, the utility's vegetation management budget is significantly larger than the community's urban forestry budget. Cooperation allows both organizations to extend their resources. In large and small communities alike, utility efforts represent the most significant force for change in the urban forest. Where a community lacks resources, a cooperative effort may represent the only way to manage the urban forest.
In many communities, a history of cooperation exists between the local utilities and government agencies. For example, cooperation was common during efforts to remove elm trees during the peak of the Dutch elm disease in the late 1960's and early 1970's. If such a relationship does not exist, one should be initiated immediately.
Cooperation occurs in situations where both parties benefit by working together. In many cities, the continual decline of "old growth, even age" trees along streets and in parks poses a hazard recognized by both utilities and communities. But, this situation also presents an opportunity to improve the composition of the urban forest through a cooperative program of tree removal and replacement. Selectively removing the overlymature trees and replanting with more desirable species-those more compatible with urban conditions-creates a new urban forest.
Conflicting ideas will not disappear overnight. For example, it may be difficult to reconcile the public's desire for streets shaded by majestic trees with the utility's need to eliminate interference between trees and overhead lines. Where appropriate small scale street trees can be integrated into the community's planting plan. In other cases, pruning practices that appeal to community aesthetics may be needed. Overall, a joint effort will lead to a compromise that comes closest to meeting the needs of both groups.
In many communities, trees are caught between utilities trimming from the top down and communities trimming from the bottom up. This creates serious problems for the trees. Maintaining reliable and safe service is the main mission of utilities, and it requires clearance between trees and distribution lines.
While not universally practiced, many utility companies continue the practice of "topping" or "round-over" pruning. This technique describes a method of pruning where cuts are made at arbitrary points on a branch along a uniform plane within the crown. The resulting crown form is artificially uniform following pruning. Unfortunately, topping causes more problems than it solves. Because the tree sprouts grow rapidly, the tree must be pruned frequently.
Two commonly accepted pruning alternatives are "lateral drop crotch pruning," also known as "natural pruning," and "side-pruning." Lateral or natural pruning requires the tree trimmer to pick out the branches growing toward the lines and remove them where they attach to the next lateral limb. Properly placed cuts produce few sprouts and natural growth rates. The next cycle of trimming requires fewer cuts than the topping approach, because the problem branches were removed during the previous cycle and sprout growth has been slower. This method is used both on trees growing beneath or to the side of utility lines.
When the wrong species has been planted directly underneath the power lines, there may be no other alternative short of removal and replanting.
Increasingly, utilities install underground distribution lines that require trenches. These trenches frequently damage tree roots, which slows tree growth, and leads to decline of the crown and root system. Branches may die, increasing the chances of wind damage and invasion of wood decaying fungi or insects. Augering, tunneling, or boring through the root zone of the tree will cause less damage to the root system.
|Safety and liability are issues of concern to everyone. Dead or dying trees in a park or along a street will eventually fall, possibly causing injuries or fatalities. If such trees are close to overhead power lines, their failure could tear down lines and poles, causing outages and other damage. Trees with low branches may tempt climbers and pose a safety concern. Someone climbing into the crown of the tree, particularly a child, risks touching a high voltage wire and suffering serious injury or death. Vehicular and pedestrian traffic is another concern. Street trees must be managed to ensure visibility and clearance for street lights and signs.||
Height reduction pruning by "topping" causes more problems than it solves.
The utility and the community are both responsible to the public. By working together they can obtain better results than by working alone. Communication is the key. Coordinating work plans and schedules increases efficiency. And, cooperation reduces the need for restrictive municipal regulations.
Through cooperation the utility will become more aware of the impacts that their operations have on the urban forest. Utilities with a negative image-whether justified or not- may be eager to demonstrate their helpful attitude.
Height reduction pruning using this "natural" or "drop crotch" technique is the correct way to "top" a tree.
|Through cooperative efforts, utilities are becoming more sensitive to the value of incorporating sound, arboriculture techniques into their vegetation management programs. And, municipal arborists are beginning to recognize utilities as an arboriculturally.|