NORTON - National Grid again will trim or remove trees threatening power lines near Norton homes.

The work is free through National Grid's hazard tree program.

According to the utility, 75 percent of tree-related power outages are caused by dead or dying, diseased or defective or structurally weak species.

National Grid arborist George Payton told selectmen that he'll work closely with Tree Warden Michael Tierney to answer customers' tree questions.

National Grid also soon will send letters to customers in areas targeted for hazardous tree assessments. A certified arborist will then evaluate the tree and explain the evaluation and recommendation to the customer.

"They do exactly what the customer wants with the tree," Payton said. "Our first objective isn't to take the tree down."

Special contractors will do the work and clean up afterward, Payton said.

The resident is offered the wood, which is otherwise trucked away.

A public hearing will be held for the removal of any town trees.

Residents in areas not targeted also may arrange for an arborist's visit by calling the toll-free number on their utility bill, Payton said.

Payton said he was unsure how many trees National Grid will remove this year.

However, last year, the utility removed 150 private trees and 54 town trees, Tierney said.

Over the last two months, National Grid has removed 30 hazardous town trees, he said.

"We've got a serious problem, because a lot of oaks died because of the gypsy moths," Tierney said. National Grid started the hazard tree program in Massachusetts in 2005.