By Dennis Seid/NEMS Daily Journal
TUPELO – To supply electricity to its customers in seven states, the Tennessee Valley Authority uses more than 13,000 miles of transmission lines.
But those transmission lines need to be relatively clear of vegetation, i.e., trees, that could interfere with that delivery.
In fact, TVA spends about $20 million a year on what it calls right-of-way vegetation management, which includes removing property owners’ trees.
“Power lines and trees don’t mix,” said John Dooley, TVA’s West Area Line Applied Services manager.
High voltage lines – which carry 100,000 volts or more – can arc to trees, buildings or other nearby objects and cause fire, property damage or costly power outages.
Through aerial surveys and other methods, TVA regularly checks to keep trees clear.
The industry standard is to not have trees over 15 feet under power lines. And the width of the rights of way can vary, from 75 feet to 200 feet.
“Those lines can sag 15 to 25 feet, so it’s important that we keep those rights of way,” Dooley said.
The 2003 blackout in the northeastern U.S. affected 50 million people and cost and estimated $6 billion in total economic damages. A tree was the root cause of the blackout, Dooley said.
“So the industry as a whole set minimum clearances for the lines across the country,” he said.
Recently, TVA was fined $175,000 due to a power interruption caused by a tree. A willow tree grew almost 30 feet in a right of way in Alabama, and when it grew within 10 feet of a 500,000-volt line, the line “flashed over” and triggered an outage.
But under mandatory guidelines, TVA – or any utility that doesn’t maintain its rights of way – could be fined up to $1 million a day.
No wonder TVA wants to get the word out on its vegetation management program.
TVA will contact customers with a “door-hanger” notice to let them know work will begin within 14 days if it has to remove any trees.
The TVA doesn’t merely trim the trees because it’s too costly to maintain that much vegetation on some 50,000 properties across its coverage area.
It’s easier to cut down the trees instead. TVA will mulch the downed trees back into the tree line if they’re in a remote area. If the trees are on personal property, it can use a chipper to take care of them. Or, if the owner wishes, he or she can keep the trees to use for firewood.
And if needed, TVA reseeds and hays the affected areas and cleans it up to leave it as it was before the trees were removed. It also provides a list of compatible trees and shrubs homeowners can plant.
“Everything goes back to keeping things safe and keeping the electricity on,” Dooley said.