If Connecticut Siting Council approval is granted this summer, Eversource will begin work to upgrade the 11.3-mile transmission line connecting Madison’s Green Hill Road substation with Old Saybrook’s Bokum Road substation this fall. The wooden monopoles in the existing transmission line will be replaced with new, steel monopoles of a similar brown color.

Like the current poles, the new poles will have three arms, two on one side and one on the other, and a single shield wire attached at the top of the pole and running from pole to pole.

“This is a structural replacement project that will replace existing transmission structures with new ones that conform to national standards,” said Eversource spokesman Frank Poirot. “By replacing these poles now, we’re repairing them in a planned and orderly way rather than in an emergency restoration.”

The existing transmission line starts at Madison’s Green Hill Road substation and then runs overland through Killingworth, Clinton, Westbrook, and Essex, before reaching its endpoint at Old Saybrook’s Bokum Road substation.

An evaluation by ISO New England identified this stretch of aging power line infrastructure as needing an upgrade to bring it up to current standards.

“This project is part of our proactive maintenance,” said Poirot. “These [wooden] poles have been out there for a long time.”

The infrastructure upgrade project will have several phases. The pre-construction phase is underway now. This begins with aerial surveys of the transmission line to identify the pole locations.

Once this is completed, the transmission line route must be prepared for the heavy equipment that will be needed to remove the old poles, drill a hole for the new pole, and to pour foundations for the new pole. Gravel access roads and then gravel or wooden pads on which the heavy equipment can safely rest will be built. As part of this phase, some trees that obstruct access or that could interfere with the line will be removed and others, trimmed.

The transmission pole replacement phase of the project should start this fall and continue into spring 2019. Restoration of the right of way may continue into fall 2019 in some areas.

Poirot said that customers should not experience power interruptions from this project either during the pre-construction or construction phases. When a new pole is installed, the wire attached to the old pole next to it will simply be moved to the new pole.

Traffic will experience minimal impact as the transmission line crosses but does not follow along any roadways.

In the final phase of the project, helicopters will be used to help crews string the shield wire line between the line’s poles. The new shield wire, unlike the current shield wire, will have a fiber-optic core to speed data communications between substations. The outer portion of the new shield wire will, like the current wire, continue to provide lightning protection for the electric transmission lines attached to the poles below it.

According to Poirot, the contractors tapped for this work will likely have more than one crew working at different sites at the same time. Eversource also plans to announce to the line’s neighbors in advance when work will begin and of the dates when helicopters will be used.

The final phase of the pole replacement project will include some re-vegetation and restoration of the work sites, according to Poirot.

Editor's note: An earlier version of the story stated that construction would begin this spring; construction may start in fall 2018 if Connecticut Siting Council approval is granted.