At first glance, the new Mercers Bottom Transmission Station in West Virginia may not reveal the innovative construction approach beneath it.
To see the project's most notable feature, you have to look underground.
More than 300 prefabricated metal pile foundations were used in place of traditional cast-in-place concrete piers to support station structures. The project represents the largest deployment of prefabricated metal pile foundations in Appalachian Power Company (APCo) history.
The site near the Ohio River was well suited for this approach because the sandy riverside soil allowed the metal piles to be installed efficiently. Rather than relying on the traditional "dig, set and wait" process required for concrete foundations, crews were able to install the metal piles quickly and move directly to the next phase of construction.
Unlike concrete foundations, which can take one to four weeks to cure, metal piles can support their full load immediately after installation.
“This creates the potential for crews to follow quickly in setting structures and installing equipment, rather than waiting for concrete to cure,” said Todd Reed, transmission engineer. “We can reduce or nearly eliminate the waiting period between foundation installation and the next phase of work.”
Reed noted that individual metal piles can be installed in less than an hour.
Tommy Cooper, APCo transmission construction representative for the Mercers Bottom Station project, said the more than 300 foundations were installed in less than three months.
“These drive-in metal foundations were a significant time saver for us,” Cooper said. “The soil conditions were sandy and easy to drive them. Overall, it’s a good way to install a lot of foundations in a short amount of time.”
For APCo customers, that efficiency matters because it can help major transmission projects move forward more quickly and predictably. By shortening construction timelines when site conditions allow, the approach supports timely infrastructure upgrades that strengthen the electric grid and help deliver the reliable service customers count on every day.