Timing is everything (except when it’s not)

A view of J. Strom Thurmond Dam while its gates are being repaired. Counting from the right, repairs on the first 6 gates have been completed. Photo: Scott Hyatt

Seepage is visible on the sides of the spillway. Photo: Scott Hyatt

It’s safe to say the last few months have been good to the basin in terms of rainfall.

In May, Hartwell and Thurmond blew their averages out of the water, receiving more than double their normal precipitation (9.6 and 7.4 inches versus their 4.5 and 3.6 inch averages, respectively).

So why, now that we’re at full pool after enduring one of the worst droughts in the basin’s history, did the Corps of Engineers decide to start a maintenance project on Thurmond’s gates, which requires keeping the pool at 329 feet above mean sea level?

And for that matter, weren’t the gates already fixed a few years ago?

Several stakeholders have asked these and other relevant questions about the project and the timing of it all. The simple answer is: It’s complicated.

“We’ve known about the gates and have been asking for money for a number of years,” said Scott Hyatt, operations project manager at J. Strom Thurmond Project. “This year it finally came through.”

Hyatt recounted the timeline leading to the current repairs, which began in 2010 – two years before the last drought.

That year, the project received funding through the 2009-2010 infrastructure stimulus package that allowed for the dam’s gates to be re-coated. These industrial coatings usually last for 20-30 years and the previous coat was 30 years old.

While conducting this maintenance, workers discovered pitting in the gates caused by water erosion for the past 60 years and also that several seals needed to be replaced.

The only problem: Because of stipulations that came with the stimulus program, the funding for the recoating could not be used to repair the pitting or the seals. These repairs are funded through normal appropriations / maintenance channels.

So after requesting funding through these channels, the pitting repairs were completed in 2012-2013.

Additional budgetary requests were finally successful and the project received funding to repair the seals in March-April 2017. The contract was awarded in September and after the contractors manufactured the seals, they began installing them in January of this year.

The repair process

To repair the seals, workers use a floating bulkhead that functions like a cork. The bulkhead is sunk and positioned between the spillway crest and the gate (where the gate makes contact with the dam). The workers can then raise the gate to access the seal safely and the bulkhead functions as a temporary seal.

Workers can then replace the seal, lower the gate and move to the next gate. Keeping the reservoir level at 329 feet above sea level allows the workers to safely perform the maintenance. If the lake is higher, wind action and boat wakes will cause waves to overtop the bulkhead, sending water crashing down on the work area and creating a very dangerous situation for workers.

During the past repairs, wave action sent water over the bulkhead that bent large metal scaffolding and handrails.

If you’ve noticed a trickle of water running down the spillway, this is one indication of leakage in the seal. However, this water is actually measured, recorded and accounted for as part of the published releases. Repairing the seals will direct that flow through the power plant while ensuring the operational integrity of the spillway gates.

The entire process – repairing the seals on 23 gates – should be finished by the end of the year.

~ Jeremy S. Buddemeier, Corporate Communication Office

About US Army Corps of Engineers Savannah District

The U.S. Army Corps of Engineers Savannah District oversees a multi-million dollar military construction program at 11 Army and Air Force installations in Georgia and North Carolina. We also manage water resources across the Coastal Georgia region, including maintenance dredging of the Savannah and Brunswick harbors; operation of three hydroelectric dams and reservoirs along the upper Savannah River; and administration of an extensive stream and wetland permitting and mitigation program within the state of Georgia. Follow us on Twitter @SavannahCorps and on Facebook.com/SavannahCorps
This entry was posted in Flood Risk Management, Hydropower and tagged , , , , , , , , , . Bookmark the permalink.