Bennettsville dam failure blamed on internal erosion, state regulators say

BENNETTSVILLE, S.C. (WBTW) — Internal erosion is to blame for a May 6 breach of the Lake Paul Wallace Dam in Marlboro’s largest city — and the structure remains in need of critical repairs, state regulators said on Monday.

“Based on the data and information we have today, it appears the type of failure that occurred at Lake Wallace Dam was internal erosion, commonly called “piping failure.” Internal erosion is one of the most common causes of failure among earthen dams,” DHEC spokeswoman Laura Renwick said. “It occurs when water that naturally seeps through the dam begins to erode soil within the earthen embankment dam. This can happen without there being any surficial sign of soil movement.”

The state Department of Health and Environmental Control on Tuesday issued an emergency order to sister agency Department of Natural Resources, demanding a summary of planned repairs and safety measures being taken to prevent more damage.

A wall holding back the 300-acre lake cracked about 5:30 p.m., sending waters coursing into the city’s Shady Rest and Richardson Park communities, prompting evacuations and forcing a virtual learning day for Marlboro School District.

There were no reported injuries.

Bennettsville Mayor Leith Fowler said during an after-action meeting the situation could have been much worse.

“I truly believe we missed a bullet on this one. I think now we’ve got a chance to do the right thing and fix the dam, fix the creek and try to protect the neighborhoods,” he said.

Marlboro County leaders echoed that .

“We believe this should be the final straw. Moving forward, we will collaborate with local, state, and federal authorities to find lasting and efficient solutions to a longstanding issue,” officials wrote to the county’s Facebook page last week.

The dam was most recently inspected on April 30. It’s one of nine “high-hazard” dams in poor condition statewide, DHEC said. It was built in 1955.

That report is due by 5 p.m. on Thursday.

Officials said a sinkhole developed after the April 30 dam review.

Of South Carolina’s 2,430 dams, 75% are considered “high-hazard,” and they’re an average of 66 years old, according to a national inventory maintained by the U.S. Army Corps of Engineers.

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Adam Benson joined the News13 digital team in January 2024. He is a veteran South Carolina reporter with previous stops at the Greenwood Index-Journal, Post & Courier and The Sun News in Myrtle Beach. Adam is a Boston native and University of Utah graduate. Follow Adam on X, formerly Twitter, at @AdamNewshound12 . See more of his work here .

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