Outages and equipment failures related to overgrown and/or fallen vegetation – trees and other vegetation – are among the biggest challenges to AEP's service reliability. To meet AEP's standards for transmission and distribution system reliability, we must manage vegetation in, and along, our rights-of-way (ROW). We manage vegetation growth immediately surrounding our power lines with a combination of performance-based (such as targeting low-performing circuits) and cycle-based (regularly scheduled) maintenance strategies.
Outages and equipment failures related to overgrown and/or fallen vegetation – trees and other vegetation – are among the biggest challenges to AEP's service reliability.
Executing an effective tree-trimming cycle across our service area is a significant expense that has a direct effect on service reliability and customer satisfaction. During the past five years, AEP has spent more than $1.78 billion on vegetation management, including $388 million in 2018. We carefully manage our programs to ensure they are cost-effective; we do this by using a variety of tools and techniques to manage vegetation. But challenging terrain in parts of our service territory can often limit the options we can use. For example, in the mountains of West Virginia, Appalachian Power (APCo) regularly uses helicopters for aerial inspections, herbicide applications and tree trimming. In these rugged, undeveloped areas, the use of helicopters reduces impacts to the local environment by eliminating the need to build access roads to each structure. It is also a safer alternative than having workers hike through thick forests and climb steep terrain with chainsaws, tree climbing equipment, and backpack spray units loaded with herbicide.
Our operating companies continue to work with state regulatory commissions for approval to implement more aggressive and proactive cycle-based vegetation management programs. Such management cycles have already been established in Ohio, Oklahoma and Kentucky. In West Virginia, where vegetation growing into and trees falling onto power lines are major causes of outages, 2018 marked the fourth year of a program to aggressively clear all distribution circuits end-to-end to establish a formal vegetation management cycle.
In 2019, Kentucky Power's five-year trimming cycle began across its entire service area. The increased trimming efforts we've used to prepare for this new cyclic program have resulted in significant reductions in tree-caused outages. Since 2010, Kentucky Power has cleared nearly 10,000 miles of overhead lines in its service territory, reducing outages caused by trees inside the ROW by over 70 percent.
Falling trees and limbs from outside the traditional ROW are increasingly a major threat to reliability. When a heavy tree or tree limb hits a power line, the poles and wires are often broken, extending the time it takes to restore service to customers. In 2018, falling trees accounted for approximately 24 percent of the total AEP customer minutes of interruption, and, over the past five years, we have seen the number of these outages caused by trees outside of the ROW increase by 29 percent across our system. The largest increases in outages due to this are in APCo and AEP Ohio, with 72 percent and 80 percent increases, respectively. Ash trees are a prevalent species in eastern forests and infestations of the emerald ash borer insects that kill these trees are primary contributors to downed trees and outages.
In 2018, AEP spent approximately $103 million on proactive tree removals – including approximately $11 million to widen "up-the-hill" ROWs in targeted areas above our transmission lines in the mountains of West Virginia and Kentucky.
With the increase in outages caused by trees outside of the ROW and with sensitivity toward the customer experience, AEP Ohio conducted a yearlong review of its forestry program which resulted in several changes to our vegetation management approach. In addition, we are using historical data to help us more methodically maintain at-risk circuits.
We have also stepped up our community outreach to alert residents of upcoming tree maintenance and hazard-tree work that is scheduled in their neighborhood. Our intent is to keep customers more informed about the work we are doing and what they should expect during these projects.