In 2015, a 1,000 year flood devastated residents across central South Carolina. Historic rainfall from October 1st to 5th caused the failure of dozens of dams across the state, displacing families, eroding the landscape and, sadly, claiming 19 lives. In response to the dam failures, inspectors from the SC Department of Health and Environmental Control issued emergency orders for 75 dams across the state. With an average age of 80 years, it is unlikely these dams were built to pass capacity requirements consistent with current regulations. Thus, the need for an expansive effort to update, repair and replace the deficient structures.
It was much easier than painting. We just had to deliver the steel to the galvanizer and let them take it from there
After the flood, regulators began demanding significant changes to the current standards while reviewing and approving designs for replacements. They determined it was necessary to take a new approach for the reconstruction of the dams and their surrounding structures but costs still needed to be reasonable.
The dam at Barr Lake was one that collapsed during the 2015 floods. Located west of Lexington on Twelve-mile Creek, it holds a storage capacity of 243 acre-feet. The new dam was designed to be the centerpiece of a new housing development with more than 300 proposed home sites. The new concrete spillways include bridges at the dam crest.
The new construction designs and regulations focused on longevity. Access for inspection, serviceability and maintenance would be a critical addition to ensure the safety of the structure over the anticipated lifespan. The life-span goals were therefore expanded to the catwalk design. The solution had to be able to withstand the marine environment, be compatible with concrete, and last as long as the dam itself. Historically, catwalks were made of wood; however, the project team knew lumber would not meet project goals. When the team learned about the values of hot-dip galvanized steel, they knew they found their solution.
Galvanized steel works well with concrete. In fact, galvanized rebar is growing in popularity because it can withstand much higher concentrations of chloride in the concrete than black steel. By galvanizing the catwalk, they greatly extend maintenance cycles allowing their focus to remain on the operation of the dam and its overall condition. Another benefit of selecting galvanizing for this project was the reduced construction times. Residents in the area were already suffering through years of construction, road closures, and cleaning up from the flooding. Getting everything back up and running as quick as possible would help alleviate some of these difficulties.
The fabricator for this project, Palmetto Metal Designs, had never used hot-dip galvanizing in the past. Exposure to the protective coating through this project will likely have a lasting affect on their recommendations for corrosion control in the future. “I like it for its corrosion resistance plus it’s inexpensive,” Lance Lasseigne from Palmetto Metal Designs expressed. “It was much easier than painting. We just had to deliver the steel to the galvanizer and let them take it from there.”
Although triggered by unfortunate events, the replacement of these dams has provided engineers a wealth of new experience in dam construction. It has also highlighted the need for long-lasting support structures to ensure inspection requirements and maintenance can be easily completed. The galvanized steel catwalks turned out to be a stress-free, economic solution that would be easily repeatable at other dam sites across the nation.
Water & Marine
Lexington, SC United States
Coating Durability, Corrosion Performance, Sustainability
7 catwalks (total span of 140’), 14 plates, 3 tube columns, 9 channels, 9 beams
Palmetto Metal Design
Valmont Coatings - Columbia Galvanizing
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