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Columbia creeps closer to actually cleaning up polluting goo in Congaree River

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coal tar (copy)

Some coal tar from the bottom of the Congaree River washed up on shore last summer. The substance, discovered in 2010 by a kayaker, came from a former SCE&G gas plant and is believed to have leaked into the river in the early to mid-1900s. Provided

COLUMBIA — It took decades for coal tar to form a goopy layer on the bottom of the Congaree River by Columbia. Cleaning up the mess is taking years, too, but a resolution could be closer.

Last month, the S.C. Department of Health and Environmental Control submitted a revised cleanup plan to the U.S. Army Corps of Engineers. The plan was crafted by DHEC, Dominion Energy and other stakeholders to clean up much of the mess without disturbing the Congaree too much.

The Army Corps had balked at an earlier plan, concerned about how much diversion and disruption of the Congaree was involved.

Even under the revised plan, the river's flow will be disrupted for several hundred feet just south of the Gervais Street bridge. A rock dam will be built in the water along the Columbia side, creating an area that can be pumped dry. The water will be removed and then excavation can begin. 

"We have got to do this work in the dry," said Tom Effinger, director of environmental services for Dominion Energy.

Even though the mess has lay buried for decades, it still poses a risk and has to be cleaned up as much as possible, said Bill Stangler, the Congaree Riverkeeper, an advocate for the health of the waterways.

The goo smells like kerosene and can burn the skin of those river users who get into it, said Stangler, who stepped in the goo back when he was a river guide on the Congaree.

It has numerous chemicals considered toxic in it, and those could conceivably spread into water intakes for cities such as Cayce if the goo is not cleaned up, Stangler said. Current tests do not show the coal tar getting into municipal water systems.

The pollution was created by a power generation plant in the 1800s and early 1900s that used coal to create a gas for lights and heating in the city, but the byproduct was a gooey coal tar that was dumped on the edge of the Congaree. Gradually the mess seeped out across the river bottom and became buried under sediment.

The latest plan would remove about three-quarters of the industrial sediment and require less of the river to be dammed for the project.

DHEC is holding a virtual public hearing on Nov. 17 to get feedback about the plan and the issue. Information on the hearing can be found at 

The goo in question has been on the bottom of the Congaree for decades, but its rediscovery in 2010 produced a new call to clean up the mess. Now, the most likely date to start the work in May 2022, according to Effinger. 

That assumes that the Army Corps and other groups sign off on the plan in the interim. It's hoped to get Army Corps approval by early next year, and other approvals from many state and local agencies will be sought after that.

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Dominion is committed to clean up the mess, even though the cost will mount somewhere into the millions, Effinger said. Dominion accepted the responsibility as the purchaser of South Carolina Electric & Gas.

An environmental fund that is connected to the company's gas operations will absorb the cost. There should be no added cost to ratepayers from the project, however much it ends up costing, Effinger said. It's impossible to put an accurate number on the costs now because there are so many challenges to the project, he said.

One of the challenges of the project: the river periodically will rise high enough to flow over the earthen dam, flooding the work site.

Work crews will have to only disturb small areas for one day's work at a time and watch the weather to be ready for flooding, Effinger said. That should prevent the flowing of the disturbed coal tar down the river. 

Allowing the site to flood will keep the dam from pushing too much water elsewhere and causing damage, he said.

Another challenge: there may be dumped supplies from the Civil War, including possible cannonballs, in the muck at the site along with the coal tar. That material could have been dumped there to keep it out of Union hands as the troops of Gen. William T. Sherman threatened to take Columbia from Confederate forces near the end of the war.

Any historic materials will have to be carefully extracted and defused if necessary, then turned over to the state for study, Effinger said. 

The project is planned to work from May through October over at least three years, Effinger said. How long it takes is dependent on how much the river rises and what is unearthed, he said. Several delays per year are possible when years are as wet as 2020, he said.

It would be better to remove all the material off the bottom of the river rather than leave one-quarter, but a bigger project could cause flooding on the other bank. 

It's better to remove the toxins that are possible to reach under this project, Stangler said.

"This is the best plan that we have been given that has a chance of getting approved," he said.

The public gets its say this month, and the Army Corps should weigh in next year.

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