For 32 years, the Charleston District has been operating the St. Stephen Dam and Powerhouse at the Cooper River Rediversion Project in St. Stephen, S.C., to control sedimentation in the Charleston Harbor and generate power as water moves from Lake Moultrie to the Santee River. The 84 megawatts of power produced by the three hydro turbine generator units inside the powerhouse can provide electricity for approximately 40,000 homes. That power is managed by Santee Cooper, one of the District’s closest partners.
There are currently 10 District employees who work at the powerhouse to ensure it stays maintained and operational and to troubleshoot any problems that may arise. These employees are critical to the needs of the region because the turbines have to be ready for use 24 hours a day, 365 days a year.
“Santee Cooper remotely operates our turbines from their facility and will turn them on whenever they need power,” said Joe Moran, chief of operations. “When they flip the switch, our turbines are operating at full power within 10 minutes.”
Except recently that didn’t happen exactly how it was supposed to. The St. Stephen Powerhouse serves as a “peaking power plant,” meaning that Santee Cooper usually turns the turbines on during periods of peak use, such as extremely hot or extremely cold days when power is at a premium and its customers are using a lot more energy. During the rare snow event in January that left an average of five inches of snow and sub-freezing temperatures in the area for five days, Santee Cooper customers were using a lot of energy and the utility company flipped the switch to turn on the District’s three turbines… but only two turned on.
“Our team got to work immediately to get the unit back up and running as soon as possible,” said Jim Carter, operations project manager at the powerhouse. “There are a lot of steps that have to be completed in a specific order to find the root cause of a problem like this one, so it can take some time to safely troubleshoot. Our guys had the turbine producing at full capacity for Santee Cooper in just 27 hours, which is fast for completing these steps.”
This down time was extremely rare for the powerhouse team. Routine maintenance is scheduled well in advance and, in 2017, the turbines were available to Santee Cooper 96.96 percent of the time. This is substantially above the District’s goal of 95 percent availability.
The District is committed to being available to produce the power needed by Santee Cooper, even though the 40,000 homes that can be powered by the St. Stephen Powerhouse is a drop in the bucket compared to the more than two million customers that are served by the utility company. The District also remains committed to the overall care of the facility, as the powerhouse will be turned over to Santee Cooper’s full control in 2035, as part of the agreement signed when it was constructed. Santee Cooper and the Charleston District work together to make sure the facility and turbines stay in good condition in order to keep the citizens of South Carolina warm in the winter and cool in the summer.