Eversource Project Designed To Thwart Flying Manhole Covers

CONNECTICUT — Eversource is replacing thousands of manhole covers across Connecticut with safety devices designed to prevent the heavy covers from being propelled into the air when pressure builds up in the underground electrical system.

The utility, which operates more than 6,800 miles of underground electric lines in Connecticut, has installed about 325 energy-release manhole covers since 2024, with additional installations planned across the state.

The upgraded covers are designed to release built-up pressure without becoming completely dislodged, reducing potential safety risks for pedestrians and others nearby.

“Every energy-release cover that’s installed makes the system and surrounding area safer,” Eversource President of Connecticut Electric Operations Don Scacco said.

The company has approximately 8,000 additional manhole covers it plans to replace over the next 10 years, Scacco said. Eversource is prioritizing locations with heavy pedestrian traffic, including outdoor dining areas and busy downtown districts.

The covers use a swivel-lock latch that keeps them attached to their frames. When pressure builds beneath the surface, the cover lifts about 4 inches to release the pressure before returning to its original position. The modified covers can still be opened normally when crews need access to the underground electrical system.

Eversource said underground electrical infrastructure can be affected by extreme heat and cold, freeze-thaw cycles, moisture and vibration. Equipment malfunctions and cable failures also can cause pressure to build up. Corrosion, which can be accelerated by road salt used during winter weather, is another potential factor.

The company said it monitors the underground system through maintenance inspections, atmospheric sensors in manholes that provide real-time alerts and specialized vehicles that scan for potential hazards.

The installations have been completed in several Connecticut communities, including Hartford, West Hartford, Bloomfield, Waterbury, Stamford, Norwalk, Greenwich, Torrington, Manchester and Meriden. An additional cover is being installed in East Hartford.

Eversource said the technology is intended to improve public safety while allowing crews to maintain access to underground electrical equipment.