Tree Trimming

Trees are valuable assets in commercial, private, and public landscapes. Trees add aesthetic beauty, modify and enhance the environment, serve architectural and engineering functions, and increase property and community economic values. These same trees that enhance landscapes, however, are a major challenge for NBU. Most people have grown accustomed to reliable, uninterrupted electric, telephone, cable, water and sewer service in their homes and offices. Unfortunately, trees are one of the major causes of power outages in areas of overhead utility lines due to direct tree contact with lines, or to trees or tree limbs falling on the lines.  Tree root systems can also penetrate underground water and sewer lines and disrupt service.   

When trees contact live wires, they become conductors of electricity, causing power outages or creating dangerous situations for anyone coming in contact with the trees. NBU spends a considerable sum of money on labor and materials for tree pruning and removal annually.  This maintenance work is necessary to protect the public and utility company employees who service the lines, and to insure safe, reliable electrical service. While we do not want to risk losing this service, many of us dislike seeing trees removed or compromised in order to provide the service. The practice of planting tree species with potentially inappropriate mature heights greatly increases these problems. In addition, NBU incurs public relations problems and costs due to criticism of tree management within easements. Your easement document contains specific language granting NBU the right to remove and or trim trees which may endanger or interfere with the efficiency or maintenance of utilities.

Line clearance methods for existing utility line/street tree conflicts, such as natural, lateral, and directional pruning have been developed to minimize the impact of pruning on tree health. Directional growth trimming encourages the tree and new growth to grow away from the power lines and equipment.  In addition NBU uses a chemical treatment on cut branches of oak trees and on tree stumps to seal and prevent oak wilt infestation from the cut area. Unfortunately, people often find this necessary pruning to be aesthetically unacceptable. Because of the inherent danger of electric lines, any pruning needed within easement areas should only be carried out by professionals trained in line clearance pruning, never by homeowners.  NBU tree trimming professionals follow Best Management Practices for Utility Pruning of Trees.  These practices were developed from the residential and commercial tree care industry, utilities, the municipal and federal sectors, the landscape and nursery industries and other interested organizations and are documented in American National Standards Institute publication ANSI A300, part 1.

Additional options for dealing with utility line/street tree conflicts include the use of tree growth regulators, tree height control by pollarding (yearly pruning back to one trunk or branch area), and initiation of tree pruning far in advance of tree-line interception. Each of these options tries to prevent future conflict situations, but is still costly maintenance. Whole tree removal sometimes is the best alternative.

The best approach is to prevent street tree/utility line conflicts from arising in the first place. Where practical, new utility lines are constructed to avoid potential conflicts with trees either by installing lines underground or routing lines to avoid existing trees. Selection of appropriately sized trees prior to planting is critical to the trees' successful co-existence with overhead and underground utility lines. Proper selection and planting of trees near utility easements can improve the appearance of the landscape, prevent safety hazards, improve utility service reliability, and reduce line clearance expenses for NBU and our customers.

Before planting new trees, look overhead and all around the intended site. Note how far the tree planting site is from overhead utility lines and the easement. For plant selection, determine whether the proposed planting site falls into a low, medium or tall tree height zone (see illustration below). The low height zone extends 15 feet on either side of overhead wires. Plant large shrubs and small trees with mature heights of 20 feet or less within this area. To account for the width of taller trees, the medium height zone begins at least 15 feet from all utility lines and may include the area that frames a building or residence. Select trees that grow 40 feet or less for this zone. The tall height zone begins at least 35 feet from buildings and 65 feet from utility lines. Tall trees need additional space to permit adequate root development and to minimize structural storm damage. Select trees that grow taller than 40 feet for this area. Use tall trees in wooded lots, parks or other open areas where their height and spread can be appreciated without becoming a liability.


When selecting a particular tree species, consult a reference that will provide the tree's mature height and spread. When selecting urban trees, avoid those that require high maintenance (frequent pruning, control of major pest problems, etc.) or drop messy fruits, leaf litter and twigs. Look for trees that can tolerate generally adverse urban conditions (limited soil volume and moisture, compacted soil), and that have a slow to moderate (never fast) growth rate. Always follow proper tree and shrub planting guidelines and call 1-800-DIG-TESS before you dig any planting hole.

Trimming in Summary:

The trim distance NBU uses depends on the nature of the electrical equipment.  Primary power equipment is equipment that conducts current at several thousand volts.  It is the equipment associated with electrical distribution on the power grid.  Primary wire is most often bare and not insulated; however, it can also of the insulated variety.  Secondary power equipment is the electrical equipment and wire that supplies current to your residence.  It conducts current at a few hundred volts and always has insulation on the wiring.

For Primary equipment NBU will trim a minimum of 8 feet back from all wires and also remove all overhanging limbs and branches above the wires and equipment. We also remove all new or small trees that are growing directly under the line to prevent future tree contacts and trimming issues. 

For Secondary equipment NBU will trim a minimum of 3 feet and then recommends directional growth trimming away from the service drop and if possible the removal of any large limbs over the service drop that could fall and disrupt service to your premises

Around power poles NBU will trim a minimum of 3 feet. For any underground equipment we trim trees and clear shrubbery within 8 feet of any equipment door or entrance way.