Empire Electric cooperative lines, poles and substation structures are engineered to withstand wind, rain and all kinds of weather. However, they can often be brought down with a fallen tree or large branch. And that will lead to lights out for someone.

Trees touching power lines drain electricity off the electrical system, cause flickering or blinking, and can cause line protection devices to take a circuit out of service. Voltage dips, caused when trees contact a power line, can damage appliances and sensitive electronics.

Vegetation management, including tree trimming and/or removal, is an important aspect of Empire Electric’s goal of delivering power to you that is safe, reliable, environmentally responsible and affordable. Empire Electric contracts this service to professional tree crews that cover the entire system about every three years.

In 2009, Empire Electric switched from ‘topping’ trees to the current scientifically-based method following ANSI standards. These newly-proven methods of tree trimming have increased safety, reliability, and expense.

Empire’s primary electric distribution lines operate at a minimum of 7,200 volts which are many times greater than the typical 120/240 volt household system. Both primary and secondary electric lines have the potential to kill or severely injure people who make contact with them, either directly or indirectly. Therefore, it is essential that only those who are properly trained in the practices and hazards associated with utility arboriculture engage in clearing vegetation from electric lines! Members of the public or arborists who are not qualified to work around electric lines should never attempt to clear trees and branches under these lines. While Empire’s tree pruning program cannot guarantee public safety, it can reduce the overall risk of accidents.

Reliability and expense are additional concerns of Empire Electric’s board of directors and the employees of the cooperative. Members expect that when they flip the switch, the power will be there. It is part of our mission as an electric utility to supply that power. Trees are among the most common causes of utility service interruption. Therefore, in addition to safety, pruning is undertaken to provide reliable electric service and the method we use permits us to control the expenses.

Utility pruning contractors remove only those branches necessary to ensure the effective intended use of the utility space and it is done on a three year cycle. Obtaining excessive clearance is needlessly costly, and may unnecessarily injure trees. At the same time, inadequate clearance could result in outages, damaged facilities, and/or safety hazards. Utility pruning specifications generally focus on the part of the tree with greatest potential to affect the electric lines. The remaining portions of tree pruning are outside the scope of work as it unnecessarily puts upward pressure on electric rates.

Recognized industry standards for pruning trees are carefully followed and expected growth patterns of trees are considered; some faster-growing trees may require more clearance than others.

Directional pruning is the standard Empire adopted and is the same standard used by a majority of electric utilities in Colorado. It is accomplished by pruning unwanted branches back to lateral branches or parent stems that are growing away from the electric lines. These lateral branches should be of sufficient size to become dominant, thus discouraging the growth of sprouts. Directional pruning is most effective when natural tree characteristics such as size, shape, and expected growth rate are taken into consideration.

The effect of directional pruning on the shape of the tree depends on the tree’s natural growth habit and where the tree is relative to the electric lines. Trees growing directly beneath electric lines will look different than a non-pruned mature tree. If large trees growing directly under electric lines are to be retained, it may be necessary to prune to smaller laterals in order to obtain the required clearance. Whenever practical, such trees should be removed and, if appropriate, replaced elsewhere on the property or replaced with compatible species.

Empire’s utility arborists are familiar with the characteristics of trees in our territory and they obtain clearances accordingly. For example, additional clearance is necessary on fast-growing or weak-wooded trees like Globe Willows. When minimum clearances are required, pruning cuts will be made at the next suitable lateral or parent limb beyond the specified distance whenever practical

Rounding over/topping are now discredited practices of indiscriminately stubbing the entire crown of a tree. This once widespread practice is now considered unacceptable because it severely damages trees and encourages rapid re-growth. Many tree species respond to topping with a flush of fast-growing sprouts, which rapidly overtake conductors. These sprouts grow quickly right back into the electric lines. In addition to safety issues, topping results in tree pruning cycles much less than our three year plan and costs all of the members money unnecessarily.

Safety, reliability and expense are driving Empire’s tree pruning practices. Empire would prefer that no trees occupy space under our overhead electric lines so that this expense could go to zero, but that is not practical. For those members who have trees growing under Empire’s power lines, Empire’s utility arborists will attempt to contact you prior to pruning the trees to inform you how directional pruning will affect your tree(s). An option is available for the arborist to completely remove and discard the entire tree, but it will be exercised at the owner’s discretion. Otherwise, directional pruning will be used.

The tree trimming program is part of the annual maintenance budget. There is no cost to individual consumers. If you desire additional information about directional pruning, feel free to contact Empire Electric at 565-4444.



Bobbe Jones is the Assistant Member Services Manager with Empire Electric, 801 N. Broadway, Cortez. Empire Electric Association is working with the community to save energy and money.