BOSTON — The state’s largest utility is embroiled in a dispute over plans to clear-cut trees near power distribution lines.

National Grid, which serves about 1.3 million electric customers in Massachusetts, asked the state Department of Public Utilities for permission to expand a program for clearing “hazard” trees by allowing it to remove ash trees infected with the emerald ash borer and oak trees infested with gypsy moths within striking distance of its transmission systems.

The company, which made the request last year as part of a rate hike that went into effect Nov. 1, wanted to pass along the $74 million cost to its consumers.

Regulators rejected the request, but the utility has asked them to reconsider. A decision is pending.

Attorney General Maura Healey’s office, which opposed the plans, said the cost is excessive and trees with gypsy moths shouldn’t be included.

In filings with regulators, her office said it didn’t object to National Grid’s efforts to remove hazardous vegetation from its service territory, but the company’s accelerated plan “would result in unnecessary charges to ratepayers and would deprive the commonwealth of the benefits from otherwise healthy oak trees and, as such, should be rejected.”

Environmental groups say while there may be justification to remove infected ash trees, there’s no reason oak trees with gypsy moths should be cut.

“It’s overkill,” said Jack Clarke, director of public policy and government relations at the Massachusetts Audubon Society. “To use gypsy moth infestation as an excuse to clear cut otherwise healthy trees, and then pass the costs onto ratepayers, is pretty outrageous.”

Hazardous trees

Last year, regulators approved a $9 million pilot project allowing National Grid to prune and cut down trees in areas that have experienced tree-related outages. The company has argued in filings that expanding the program is crucial to ensuring that hazardous trees don’t fall on its lines during storms.

“With an estimated stocking density of over 190 trees per mile, the company’s electric system is vulnerable to harsh conditions during major weather events, which are becoming more common and more severe due to climate change,” the company said. “These events can cause substantial damage to the system and cause interruptions, which last for multiple days.”

From 2016 to 2018, National Grid averaged 2,738 tree-related interruptions a year, a 44% increase from the annual interruptions from 2010 to 2015, the company said.

National Grid has also asked regulators to shorten its five-year pruning cycle for trees near its distribution system to four years, similar to other utilities.

Massachusetts utilities have been under growing scrutiny from state regulators to upgrade and harden their infrastructure to prevent outages.

Last year, National Grid was fined $750,000 for what state regulators described as inadequate preparation and response to a destructive 2017 wind storm that knocked down hundreds of trees, cutting off power to tens of thousands of homes and businesses in the Merrimack Valley.

Local officials blasted the company for not restoring service quickly enough.

A state investigation concluded the utility did not properly classify the storm and reduced the amount of resources available to customers in 166 communities.

Moth infestation

Officials at the Department of Public Utilities noted the company is proposing to cut down an unknown number of oak trees, but it hasn’t conducted a risk assessment of the gypsy moth infestation.

“Infested oak trees do not always succumb to the gypsy moth, and the company agreed that the gypsy moth will not kill 100% of the oak trees in Massachusetts,” the agency wrote in a 2018 filing. “Thus, it is unclear how many infested oak trees in the company’s service territory pose a certain risk of dying and striking the company’s electric infrastructure.”

The company said in some areas it will need to employ a “ground to sky” clearing of trees and other vegetation to protect power lines and transformers.

The emerald ash borer is an Asian beetle that has run like a buzzsaw through North America, killing tens of millions of trees in at least 35 states.

Arborists say while there are treatments to prevent its spread, there is no cure for a tree that is infested.

“If you don’t treat your ash trees, they will die. There’s no if, ands or buts about it,” said Russell Holman, a certified arborist with Arborway Tree Care Inc. and board member of the Massachusetts Arborist Association. “There’s no resistance to it, no natural predators, and we know that 100% of the native ash trees will die from that infection.”

He said ash trees that have been infested degrade so quickly — often within 10 years — that “they become a hazard almost immediately.”

As for oak trees, gypsy moths have been around since the late 1800s. The need to remove trees before they die is less certain, Holman said.

There are treatments and natural controls — a virus and fungus that thrive during wet years — which can eradicate a gypsy moth caterpillar infestation before they destroy an oak tree.

“It’s definitely not the same,” said Holman. “There are certainly trees that die from gypsy moths, but it’s not a case where all of the infected oak trees are going to die.”

Christian M. Wade covers the Massachusetts Statehouse for North of Boston Media Group’s newspapers and websites. Email him at cwade@cnhi.com.

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