DHEC determines possible cause of Marlboro County dam breach
MARLBORO COUNTY, S.C. (WMBF) – State investigators have determined what may have caused a partial breach at a Marlboro County dam that caused flooding in the area.
The Department of Health and Environmental Control said it appears the Lake Wallace Dam breach on May 6 was caused by internal erosion, which is commonly called “piping failure.”
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The agency explained that internal erosion is one of the most common causes of failure among earthen dams. It occurs when water that naturally seeps through the dam begins to erode soil within the earthen embankment dam.
DHEC said its staff performed a routine inspection of Lake Wallace Dam on April 30 and there was no indication that the dam was at risk of a breach or failure.
The agency added that the investigation into the cause is ongoing and a report will be provided once it is finalized.
Meanwhile, an emergency order was issued on May 9 to the South Carolina Department of Natural Resources, which is the owner and operator of Lake Wallace Dam.
The emergency order mandates that SCDNR develop a plan of action that includes monitoring the structure and implementing interim risk reduction measures.
SCDNR must submit the plan of action by 5 p.m. May 16.
Lake Wallace Dam is classified as a high-hazard dam which means that the dam’s failure would likely result in loss of life.
DHEC said its condition assessment of Lake Wallace Dam has been rated as “poor.” It is one of nine high-hazard poor-rated dams in South Carolina. The agency added that it has been performing extensive technical reviews and engineering analyses of the dam for the past few years.
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