Transmission Lines and Reliability
Trees falling on power lines or branches coming in contact with power lines cause many transmission outages nationwide, according to the North American Electric Reliability Corporation (NERC), a regulatory organization that enforces reliability standards. In fact, the August 2003 blackout that disrupted service to many portions of the Northeast and Canada was traced in part to tree limbs coming in contact with transmission lines in Ohio.
Vegetation management crews maintain our transmission rights-of-way every 4 years. Transmission right-of-way widths vary according to the voltage of the transmission line and by land ownership or easement rights obtained when the line was built. Usually, trees located within the right-of-way that interfere or may potentially interfere with the operation of transmission facilities are removed. This may be accomplished using chain saws, EPA-approved herbicides, mechanical equipment, or a combination of methods.
Trees and Shrubs
Trees located beyond the edge of the right-of-way that potentially may interfere with transmission facilities are evaluated to determine whether pruning or removal is required. Trees adjacent to the right-of-way that are unhealthy, leaning or significantly encroaching the right-of-way are also pruned or removed.
Compatible shrubs that do not interfere with transmission facilities are not disturbed. A diverse mixture of perennial grasses, low growing shrubs and other ground cover preferred by birds, deer and small animals promote a thriving wildlife habitat. In this way, well-managed transmission rights-of-way provide food and cover wildlife need to survive.