The rainiest months in Chowan County, North Carolina, are July and August. This poses a prominent challenge when a team is tasked with building a foundation for a new substation in September and is welcomed with swampy, waterlogged soil.

The solution? A 200-year-old renowned technology with a reputation for successfully carrying the weight of buildings and bridges for decades.

As part of Dominion Energy’s Grid Transformation Plan to improve grid reliability and security, the Pembroke Creek Substation came to life to enhance power capacity, stability and responsiveness to outages.

With a tight turnaround schedule and difficult soil conditions, traditional drilled shaft deep foundations — which require excavations and concrete placement below ground — weren’t ideal. So, a team of geotechnical and structural engineers worked in tandem to determine a suitable foundation system.

The key to this challenge was going back to the basics; if your boots can sink within seconds of stepping into the field, then maybe concrete isn’t the best option. But helical piles could deliver a faster, more cost-effective construction foundation.

“With situations like these, it’s important to collaborate with team members of different backgrounds and experiences. Using helical piles as an option wasn’t something new for us but it isn’t too common within the transmission and distribution industry,” says Matthew Bauer, technical consultant at Burns & McDonnell. “Like many projects before, we’ve had to utilize relationships with vendors to quickly pivot when faced with supply chain issues, material shortages and — as in this case — design changes. But with collecting and analyzing data throughout the construction process, we can better predict and plan for future projects with greater efficiency.”

The solution to use helical piles — designed by Burns & McDonnell, with fabrication and installation by AZCO, a Burns & McDonnell subsidiary — proved to have multiple perks. For one, the piles reduced the labor required on-site as the piles were prefabricated off-site and installed by a smaller, more specialized crew. Where soil conditions varied, the installation process was adjusted in real-time, providing immediate feedback through the torque required to drive the piles. This foundation method reduced safety risks by eliminating open excavations and minimizing the on-site footprint, as the helical piles were prefabricated off-site and only required a few craft members for on-site installation. It also reduced vehicle traffic by eliminating off-site spoil removal and concrete deliveries. Lastly, the piles improved grounding performance of the station by providing a deep path to low-resistivity soils.

“It’s safe to say that it takes a village of self-performing, engineer-procure-construct (EPC) professionals to safely and reliably fill in 282 helical piles as a foundation for the substation," says Patrick Choudoir, project development manager at AZCO. "We sourced almost 180 tons of steel for this project. Securing the piping took specific collaboration so that lead times met the schedule and the lengths required aligned with some of the calculated embedment depths. Our one-team approach and established procedures allowed us to focus on execution, leveraging our existing culture and technologies to deliver a quality result ahead of schedule.”

This project not only meets technical and scheduling goals but also supports the community’s needs and aspirations. It’s a foundation for community resilience and a catalyst for continued development and innovation in the region. It marks a step closer to Dominion Energy’s plans for Chowan County.

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Thought Leader

Matt Bauer

Associate Technical Consultant
Burns & McDonnell

Patrick Choudoir

Project Development Manager
AZCO

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