United Civil partnered with WA Chester in relocating Circuit 1697 & 1710 on United Illuminating’s Pequonnock Substation 115kV High-Pressure-Gas-Filled Cable project. This multiphase project connected the existing 115kV transmission line to the old GIS substation from the new expansion further inland and involved significant environmental/climate mitigation.

With this area highly prone to costal flooding, implementing a high-pressure-gas-filled-cable-system at this site was environmentally proactive as a potential leak of nitrogen gas from the steel conduits has a far lower environmental impact than a leak from fluid-filled system.

Our crews installed a precast splice vault over the existing transmission line which required extensive dewatering of soil and contaminated water treatment as the vault was installed approximately 30 feet from the Bridgeport Harbor shoreline. UC deployed a water treatment system consisting of (2) 18,000-gallon weir tanks in series, a three-level bag filter system and a carbon treatment system.

The vault installation required a 14’ deep excavation, 8’ below the water table. To control the tidal water elevation, UC installed a 50’x16’ slide rail shoring system 14’ deep with a wellpoint system around the perimeter. All contaminated soil excavated in this area was properly handled and disposed of at an approved facility.