With torrential rain forecast for SC, are dams safer than in 2015? Here’s what we know

Nearly a decade after dams broke across South Carolina from an historic rainstorm, government officials are hoping efforts since then have been enough to prevent a repeat of the 2015 disaster that caused flooding like few people had ever seen in the state.

Since the October 2015 flood, scores of aging, earthen dams have been rebuilt or improved in an effort to prevent failures like those nine years ago.

At the time, at least 70 dams regulated by the state — including a string of them that form residential lakes in Columbia’s Gills Creek watershed — fell apart or breached in the intense rainfall.

Among those were dams at Spring Lake, Cary Lake and Lower Rockyford Lake, all in the eastern Columbia-Forest Acres area. A federal dam on Fort Jackson, the one at Semmes Lake, also broke, sending a torrent of water into the Kings Grant neighborhood and lower Devine Street.

Collectively, the cascading effect of the failed dams flooded major roads that almost never flood. One unsuspecting Columbia resident drowned on lower Devine Street when he drove his car into the water, sparking a wrongful death lawsuit against the federal government. The suit was not successful, even though federal records show that inspectors had found deficiencies in the Semmes Lake dam years before.

Lower Devine Street was impassable for days, resembling a small lake. All told, nine people died in the Columbia area during the flood.

Many dams in the Gills Creek watershed were rebuilt or repaired after 2015 and the state has beefed up its dam safety program., although reports show the state still needs to make more progress in overseeing dams.

Some dams in South Carolina that were not fixed after the 2015 flood failed in later storms, including Hurricane Florence in 2018. At one point in 2018, state regulators said about 150 dams that had developed problems from the 2015 storm and a 2016 hurricane needed repair.

Legislators have been reluctant to tighten regulations for some dams, particularly those in rural areas, because of the cost private property owners could incur fixing them and maintaining them.

South Carolina has about 20,000 dams that are not regulated by the state, according to a study done for the state environmental department in 2020. But during Tuesday’s news conference, Reece said there are about 40,000 dams in South Carolina.

The American Society of Civil Engineers noted in a recent rating of the nation’s infrastructure that South Carolina has limited resources to support dam maintenance and repairs. Spending in South Carolina on high hazard dams falls under the national average of $4,875 per dam, the association says.

Questions also have surfaced about federal oversight, but a fort official expressed confidence that the Semmes Lake dam will hold up. Semmes Lake has since been renamed Inchon Lake. The dam is now designed to withstand substantially more rainfall than the dam that blew out in 2015, a fort spokesman said.

“The community should have high confidence in the rebuilt dam,’’ spokesman Thomas Byrd said in an email Monday.

Still, state officials said they were on the lookout for problems across South Carolina. On Tuesday, officials in Colleton County warned the public that the McGrady Dam has the potential to fail. People in parts of the area between Cavanaugh and Edward roads should evacuate, the Colleton Fire Department said in a tweet.

DHEC officials later said that dam was not failing, but another small one had been reported to have breached in a rural area. The water drained into a nearby creek and did not flood homes or roads, the state’s top environmental regulator said.

Myra Reece, who heads the state’s environmental agency, said during a news conference Monday that the department had looked at 19 dams that it had questions about.

She did not identify the dams during the session with reporters Monday or during a second news conference Tuesday. She also did not say what part of South Carolina they are located in. Reece said, however, that DHEC found “no urgent issues’’ with the dams from its assessment.

“Our team conducted pre-storm assessments of dams we felt might be vulnerable to this type of intense storm, and we are working with the owners.”

Bailey Parker, director of the Gills Creek Watershed Association, said she’s encouraged that multiple dams are in better shape today than nine years ago and dam owners are working together to manage them. But Parker and those who live in the watershed are on watch for signs of trouble, she said.

“People are nervous,’’ Parker said. “I don’t want people to be nervous, but I appreciate that they remember what happened and realize it could happen again..’’

Parker said the looming rainfall has people “on edge. It could be nothing or it could be a repeat of 2015.’’

As of Monday afternoon, the forecast for Columbia did not show rainfall amounts like those that fell in 2015. About 20 inches of rain fell over a weekend that year. The forecast for the Columbia area was showing rainfall of up to 6 inches by Thursday.

But National Weather Service forecasters concede the track of Tropical Storm Debby in the Midlands contains uncertainty.

“The heaviest rain looks to be off to the east (of Columbia), but it really is going to come down to where exactly Debby is going to go for the rest of the week,’’ said Chris Rohrbach, a meteorologist with the weather service.

Statewide, South Carolina has more than 2,300 state regulated dams, more than a third of which pose high or significant hazards to people and property if they break. Many of the dams are earthen structures and some were built decades ago.

All told, 169 high hazard dams in 2020 were rated poor or unsatisfactory, according to the state environmental department report that year. But overall, the 2020 report said 60% of the dams that breached in October 2015 were repaired, removed or exempted from regulation. At the time, about 20 percent were being repaired or scheduled for repairs.

State regulated dams are typically smaller dams that hold back the waters of moderate sized lakes, such as Forest Lake in Columbia. Large dams at reservoirs like Lake Murray are regulated by the federal government.

Because of concerns about dams, the S.C. Department of Environmental Services urged dam and lake owners to clear spillways that might be clogged, lower water levels and monitor the dams during the next several days.

The operators of Cary Lake, Spring Lake, Forest Lake, and Lake Katherine began releasing water Sunday to lower water levels in advance of the storm, Parker said in an Instagram post.

The stability of dams is not an issue only in the Columbia area. Other parts of the state, particularly the eastern and northwestern parts of South Carolina, have clusters of dams — and some of them failed during the 2015 storm.

Meanwhile Monday, state officials said the water levels had been lowered in some of the state’s major lakes, including lakes Marion and Moultrie between Columbia and Charleston, as well as Lake Murray near Columbia.

This story has been updated with additional information about dam safety and dams that have not been repaired.. The number of unregulated dams has been updated.

Staff Writer Ted Clifford contributed to this story.