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Flood led to discovery of unknown dams in Columbia area

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Broken dam at Lake Dogwood, lower Richland County.
Broken dam at Lake Dogwood, lower Richland County.

More dams crumbled and broke in the Columbia area than many people realized after historic October floods caused billions of dollars in property damage.

Since the Oct. 4 storm, engineers and public works employees have found at least 23 broken dams in Richland and Lexington counties that had not previously been identified by state regulators as having failed. Coupled with dams the state had already found, the additional discoveries bring to 45 the number of dams known to have breached in the two counties.

Most of the additional dams that breached are in rural Lexington County and are not regulated by the S.C. Department of Health and Environmental Control. But the breaks could prove costly to taxpayers and private landowners.

Lexington County taxpayers may be on the hook for as much as $7 million to fix roads damaged by dam failures and other flooding, according to preliminary estimates by county public works officials. Repairs for some could take up to a year.

The tab already promises to strain county finances even if federal disaster aid pays for some of the restoration, County Administrator Joe Mergo said.

Of the Lexington County roads damaged by broken dams that were discovered well after the floods, only two remain closed.

All told, Lexington County officials found 21 dams that were not identified by state officials in October as having failed or breached, records show. DHEC had identified only three broken dams in Lexington County, records show. Most of those discovered later were small farm ponds of a few acres in rural parts of the county that weren’t recorded anywhere, officials said.

County officials aren’t certain how many other similar ponds exist.

“There’s ponds like those dotted all over this county,” Lexington County Councilman Todd Cullum of Cayce said.

Richland County officials didn’t know of any dams not identified by state regulators as having broken. But at least two others not identified previously by the state have turned up below Fort Jackson in a mostly rural area off Leesburg Road. Those unregulated dams are at a small lake called Caughman’s Pond and at one unnamed pond, both in the tiny Jumping Run Creek watershed of Lower Richland.

A consultant’s letter to the state Department of Health and Environmental Control says the two unregulated dams broke upstream of two regulated dams, which also breached as a result of the October storm. The two regulated dams that failed are at Wilson Mill Pond and at Lake Dogwood.

The release of water from unregulated dams upstream “contributed to the overtopping and catastrophic failure of Wilson Mill Pond dam,’’ according to the Oct. 19 Chao and Associates letter to DHEC. A nearby road flooded after the Wilson Mill Pond dam broke.

Patricia Prince, who lives on Congress Road, said the cascade of water dumped mounds of sand and debris on her property. An engineer estimated the amount of sand to be at least 100 tons, Prince said.

“It is a mess,’’ she said. “The question now is how to clean it up.’’

State Sen. Katrina Shealy, R-Lexington, said she would not be surprised if more unregulated dams failed in her county than in Richalnd.

“We’ve got a lot more farm property,” she said, referring to ponds created for livestock and irrigation.

The Oct. 4 storm blasted the Columbia area with more than a foot of rain that weekend. It was considered one of the heaviest rainfalls seen in the area in years. Rising flood waters damaged thousands of homes and sent many people fleeing for high ground. Statewide, South Carolina suffered an estimated $12 billion in damage, according to a recent University of South Carolina report. The Columbia area was among the hardest hit.

DHEC officials said they are aware that counties are discovering more dams than originally listed. In addition to those dams identified by Lexington County and Chao and Associates, The State newspaper and Fort Jackson previously found three other broken dams not on DHEC’s list. Among those is the Pine Tree Dam in northeast Richland County. The dam is in the Gills Creek watershed.

Dave Hargett, a Clemson University adjunct professor who tracks dam safety issues, said it’s no surprise that more broken dams are being found in South Carolina.

Most of South Carolina’s dams are not regulated by the state, meaning oversight is solely up to the dam owners. DHEC regulates 2,400 dams and pays some attention to those, he said. South Carolina has 10,000 to 20,000 unregulated dams, according to the state emergency management agency.

But Hargett said unregulated dams also can be a danger to surrounding property if not maintained. Despite problems with regulated dams, Hargett said many unregulated dams are likely in worse shape.

“You’d expect a high frequency of failures,’’’ he said. “They are not noticed and reported (by DHEC) because they are off the radar.’’

Shealy suggested that DHEC could look at regulating more dams, especially those where state and county roads cross.

“You have to draw the line,” she said.

Staff writer Andrew Shain contributed.

Tim Flach: 803-771-8483. Sammy Fretwell: 803-771-8837, @sfretwell83

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