If you felt the ground shake this past weekend, you’re not alone. Many people throughout the Savannah River Basin (and beyond) reported tremors during two earthquakes Feb. 14 and Feb. 16. But rest assured, the U.S. Army Corps of Engineers dams are safe and sound.
According to reports from the U.S. Geological Survey (USGS), a 4.1 magnitude earthquake occurred at 10:23 p.m. on Feb. 14. It was centered 7 miles west of Edgefield, S.C., but news reports say it was felt as far west as Atlanta and as far north as Hickory, N.C. (about 150 miles away). An aftershock quake was recorded on Feb. 16 at 3:23 p.m., registering 3.2 magnitude and occurring in the same area as the first quake.
Following each quake, our team immediately began inspecting the Thurmond, Russell and Hartwell dams and their related embankments and structures, including the two diversion dams at Clemson University. Onsite operators did immediate visual checks with security cameras. We also brought in additional personnel to do on-site inspections and take numerous data readings at the dams.
All preliminary inspections are now complete and no structural damages or abnormalities were reported.
“There are many factors we must look at when seismic activity occurs near the dams, including not just the concrete structure and the earthen embankments, but also the spillway gates, the penstocks, and the inner workings of the dam and power plant,” said Beth Williams, dam and levee safety program manager.
“Due to the quick action of personnel on site at the projects, we had enough information to make a determination on public safety and structural integrity within hours,” Williams said.
The dams are integrated with multiple instruments so Corps employees can quickly and efficiently measure water pressure, uplift pressure, seepage, and other factors. This data is recorded routinely throughout the year, in addition to immediately following earthquakes or other emergency events.
“Earthquakes are not uncommon in the greater Augusta area,” Williams said. “According to the USGS there have been more than 20 earthquakes in the last 40 years within 30 miles of Augusta. Most of these are a much lower magnitude than the one experienced Friday night and are not noticeable by humans. Fortunately, the dams were engineered with large earthquakes in mind and built to withstand reasonable occurrences like this one.”
Williams said ground motions at the Thurmond Dam produced by this weekend’s earthquake are considered a “300-year” event. Essentially, this means there is about a 0.3 percent chance of experiencing ground motion of this magnitude at the Thurmond Dam each year.
“The integrity of our structures and public safety is our key concern after an earthquake,” Williams said. “Our professionals demonstrated this commitment by working through the weekend to provide 360-degrees of oversight on all dams and related structures.”
~By Tracy Robillard, public affairs specialist