The 125-year-old stone masonry dam that holds in place up to 2.8 million tons of toxic sediment in Lake Conestee Nature Park poses a serious environmental and economic threat if it were to fail, a catastrophe that would affect water supplies, destroy riverfront properties and cost hundreds of millions of dollars to clean up, said the dam’s owner.
Lake Conestee, located on the Reedy River just south of the city of Greenville near Mauldin, acts as a receptor of chemicals that flowed downstream for decades as part of Greenville’s industrial legacy, especially in the era before the Clean Water Act restricted the types of waste that could be discharged into the river.
Over time, the waste mixed in with sediment that washed downstream until it settled behind the Lake Conestee dam and filled in much of Lake Conestee.
And there the contaminants sit, a threat just below the surface, upstream from more than 250 riverfront homes in Greenville County and within striking distance of Lake Greenwood, the main drinking water source for the city of Greenwood.
If that dam were to fail, it would cause untold damage downstream, said Dave Hargett, founder and executive director of the Conestee Foundation, a nonprofit that purchased the lake property and dam in 2000. The foundation studied the site, made repairs to the dam and opened a pristine nature park in the center of Greenville County seven years later.
In December, inspectors from the state Department of Health and Environmental Control rated the dam in poor condition due to deterioration of mortar and because of water seeping through porous cracks in the hand-built structure. It’s also not keyed into the bedrock, which puts it at risk of slipping if an earthquake or major flood strikes the Upstate, Hargett said.
“We roll the dice every day,” he said.
Failure would close Conestee Road, which runs just south of the dam, and would disrupt businesses between Mauldin and the South Carolina Technology and Aviation Center. Water mixed with contaminated sediment would flow downstream toward Boyd Mill Pond in Laurens and eventually into Lake Greenwood.
Request for funds
Now the foundation hopes state lawmakers will see the need to quickly put in place a plan to replace the dam. Hargett has met with DHEC director Catherine Heigel on site and explained the potential calamity. He asked DHEC to include a budget proviso this year for $185,000 to fund a final study by an engineering firm to identify a solution that would protect the water source and lake for the next 100 years.
The health department supports the foundation’s request for a study because the dam’s failure “would potentially pollute drinking water sources for communities downstream,” adding broader health impacts for the region beyond flooding, said DHEC spokeswoman Jennifer Read.
The House Ways and Means healthcare subcommittee is scheduled to vote this week on whether the proviso should be included in the budget, said Rep. Garry Smith, R-Simpsonville, a member of the subcommittee whose district lies downstream from the dam.
“I feel very confident that it will go through,” Smith said Friday. “It’s a project (Heigel) supports and DHEC supports because of the possibility of contamination of water supplies downstream and the damage that could be done if the dam were to break, both from the erosion and also from the chemicals in the sediment.”
The most likely solution will be to construct a new dam, which would cost between $30 million and $40 million, Hargett said.
The small nonprofit would never be able to raise funds to pay for it, and Hargett doesn’t want state taxpayers to have to pick up the tab for an issue created by industry. With the Trump administration floating the idea of a massive infrastructure investment, Hargett said this study would allow the dam to be shovel-ready if federal funds become available.
The other option, he said, would be to go after responsible parties under the Environmental Protection Agency’s Superfund laws.
More than a thousand industrial sites – coal plants, textile mills, dyeing operations and more – may have contributed to the contaminated sediment through the years. They left a smorgasbord of chemicals that attach to the soil and remain, including heavy metals like lead, pesticides and cancer-causing chemical compounds such as polychlorinated biphenyls (PCBs) and polynuclear aromatic hydrocarbons (PAHs.)
Removing the dam entirely isn’t an option for that reason, Hargett said. Digging up and removing the affected sediment would cost in excess of $1 billion, he said.
The dam was in failure when the Conestee Foundation used settlement funds from the 1996 Colonial Oil Pipeline spill to purchase the lake and dam in 2000.
The group made repairs the following year to shore up the dam and made major repairs again in 2011.
“We’ve done all we can do as a little nonprofit that’s taken this thing on,” Hargett said. “We’ve spent a lot of money of our own already which we’ve gotten mostly from federal sources. We just can’t do any more.”
Sampling over the course of eight years through 2008 determined the best course of action was to leave the toxic sediment in place and continue to monitor it, Hargett said.
Conestee is a prime example of what could be done with a federal Brownsfield site, he said. Once the safety studies were completed and showed no harm if the sediment was left in place, the foundation was allowed to move forward with a plan to build a nature park on the land.
Lake Conestee Nature Park opened 10 years ago with a section of trails through the swampy wetlands.
Now the park has grown to more than 400 acres with the acquisition of several adjacent farms. It now boasts more than 12 miles of trails, six of them paved, and more than 4,000 feet of boardwalks and decks that overlook what remains of the lake. The park, once a neglected area nearly devoid of animal life, now boasts more than 200 bird species and has been classified as an Important Bird Area of Global Significance by the National Audubon Society.
More than 60,000 people visit the park each year, including more than 3,000 students who come for the park’s nature education program.
The foundation has embarked on a new goal to build a permanent education center near the park’s main entrance on Mauldin Road. It would act as the park’s headquarters and could host field trips and other events along banks of the Reedy River.
The foundation launched that fundraising effort at the start of the year. The building would cost about $1 million and take a year to construct, Hargett has said.
Hargett doesn’t know exactly what would happen to the park if the dam failed but said it would significantly change, he said.
Miles of the Reedy River downstream and the park itself could be reclassified as a Superfund site if the dam failed, he warned in a statement making his case to DHEC for the study funds.
There’s also potential for development at the former Conestee Mill immediately downstream from the dam and directly in its path.
The mill is being used as a rug warehouse now, but it was approved for a mixed-use development by Greenville County in 2008, although plans fell through. Developers have shown interest in the site since then, though development plans have not yet been filed.
If the former mill were redeveloped it would raise the dam’s classification to high hazard – the highest classification – because its failure would then likely result in the loss of life, Hargett said.
“This is a critical issue,” he said.
In his report to DHEC, Hargett said the dam continues to gradually disintegrate. Its failure, he said, is certain. The only uncertainty is when.