EVERETT — It’s year-round work maintaining such a vast electrical system and a fair amount of the toil gets done in the favorable conditions summer brings.

This year, improvements and preventative maintenance projects are expected to cost the Snohomish County PUD around $60 million.

Over the past two years, the Snohomish County PUD assessed and treated more than 25,000 poles among the 115,000 in the system. It’s replacing roughly 700 this year.

Old poles have an expected life of about 40 years and newer ones 60 years, said Neil Neroutsos, a spokesman for the state’s largest public utility district.

The PUD also is replacing 30 to 40 miles of aging underground cable. That’s a fraction of the 3,100 miles of underground line within the system. Overhead lines account for 3,300 miles.

The life expectancy for underground line is about 60 years. Some of the early buried line wasn’t made to the same standard as later line and has needed more frequent replacement. The PUD has been able to extend the life of some of its underground line by 20 years by injecting it with a silicon type liquid, Neroutsos said.

Work also is continuing on the Beverly Park substation in Everett where the utility’s largest transformer is being installed. It’s more than 30 feet long and 16 feet high and is expected to bolster reliability for customers throughout the region.

“The larger transformer can handle a higher voltage level,” Neroutsos said. “It gives us more options in terms of our BPA power supply and how it’s delivered.”

The expected completion date for the Beverly Park project is spring 2018.

A new Eagle Creek Substation is being built in Arlington along with upgrades to substations in East Arlington and Oso. That should help provide backup power in north areas of the county, which often are hit hard by weather and outages.

Substations also are being rebuilt in Smokey Point and north Everett and substations in Monroe and the Mill Creek-Seattle Hill area are getting equipment upgrades.

The PUD also has moved some poles and wires to accommodate development and construction projects, including the city of Everett’s bridge linking Grand Avenue Park and West Marine Drive on the water front.

PUD crews often work closely with developers during the summer, Neroutsos said.

Summer “is consistent with some of the home and other construction that goes on,” he said. “We can work with the developers to provide for their electrical needs consistent with the time of their projects.”

Eric Stevick: 425-339-3446; stevick@heraldnet.com.