On Thursday, a worker with a chain saw in a cherry picker carved off the upper boughs and branches of a sweet gum tree sending them toppling to the ground adjacent to Connecticut Light & Power's main transmission line.

While some smaller trees might be pared back, the sweet gum tree is among the taller group of trees that will need to come down to protect power lines, the workmen said.

The work was the beginning of a joint effort between CL&P, Metro-North Railroad, and the Connecticut Department of Transportation to select and cut down trees both on the state owned property as well as privately owned land that are a risk to damage the nearby utility and the railroad's power transmission systems and cause power and rail service outages, CL&P spokeswoman Tricia Taskey Modifica said.

Connecticut Light & Power's main transmission lines run parallel and power the New Haven Line's overhead catenary wires, both of which have been damaged by felled trees and branches in major storms in recent years, Modifica said.

Similar efforts along the New Haven Line will continue through June, according to Modifica.

"Since all of our systems are interconnected, this work is expected to improve reliability to all of our customers in lower Fairfield County," Modifica said. "This project is all about improving reliability for our customers in that part of the state, so all trees being trimmed or removed pose a direct threat to our electric system."

In addition to the New Haven Line, the transmission system supplies power to roughly 83,000 customers in Stamford and Greenwich, Modifica said.

While some higher voltage lines require greater clearance zones, the utility's guidelines call for maintaining an average clearance zone of eight feet along electric lines, 15 feet above the lines and 10 feet below, according to the utility.

Two weeks ago, owners of neighboring properties including residential customers were sent notices by the utility about the work, and CL&P representatives began meeting on an individual basis with private property owners about any planned tree removals on their land, Modifica said.

The work is part of a $300 million plan submitted by CL&P in July 2012 to the Connecticut Public Utility Regulatory Authority to protect infrastructure from storm damage that also includes measures to strengthen wires and poles in the transmission system from storms.

An 85-foot tree that fell during a storm last August knocked out power to about 30,000 CL&P customers and brought the New Haven Line to a halt.

Under the established process, private property owners who question the selection of trees for removal should contact the utility or the state Department of Transportation.

Connecticut Department of Transportation Commissioner James Redeker said that the effort will reduce the duration and cost to repair future storm related outages on the transmission line.

"Power and service disruptions are a major source of aggravation for commuters, not to mention businesses and homeowners and a major expense for us all when they occur," Redeker said.

martin.cassidy@scni.com; 203-964-2264.