Next to a Macon city park, a contaminated former industrial site is being “greened” twice over: Hundreds of trees were planted there recently, so their roots will act as straws to drink up contaminated groundwater.
The method, called phytoremediation, uses plants to break down organic pollutants into harmless materials within the plant’s tissues. Some plants also can absorb other pollutants, like heavy metals, that can’t be broken down.
The Southern Wood Piedmont site next to Freedom Park is one of the first hazardous waste sites in Georgia to use the technique, said David Brownlee, acting manager of the hazardous sites response program of the Georgia Environmental Protection Division.
“This is not a common remediation approach, so we are proceeding somewhat cautiously and not all sites would be good candidates,” he wrote in an e-mail. “The Southern Wood Piedmont site, though, is a good candidate with controlled access, a large area for the pilot test, and an existing groundwater recovery system. We are hopeful that this ‘green’ technology will be successful at the site.”
To see if the method works there, 376 trees, all about a year old, were planted a few weeks ago on land where railroad ties and telephone poles were once treated with creosote. EPD documents indicate the treated wood was propped up on railroad tracks to allow the preservative to drip off.
The 84 acres just outside the city limits have been home to industry since 1850. The Confederate States of America once manufactured gunpowder there. A few years later textile and fertilizer factories were run there by the Freedman’s Bureau, which helped freed slaves.
Since 1926, when Central of Georgia Railroad bought the land, it was a creosoting operation, most recently owned by Southern Wood Piedmont from 1972 to 1986.
Both Southern Wood Piedmont and the Central of Georgia Railroad are considered responsible for cleanup of contamination there. State environmental documents show that Central of Georgia’s parent company, Norfolk Southern Corp., took the lead on cleanup activities starting in 2010.
The site was among the first added to Georgia’s hazardous site registry in 1994 because it is contaminated with hydrocarbons and dioxins, and the groundwater is contaminated with benzene, napthalene, toluene and xylenes.
Some of these are considered or suspected of being carcinogens, although human contact with them is limited because there are no residential wells nearby.
Contamination extends off the site to a portion of Freedom Park, according to EPD documents.
The state ranks the site as having the highest priority for corrective action.
Removal of contaminated soil began in 1986, according to a 2001 compliance status report by Southern Wood Piedmont. Dirt up to 3 feet below the surface was carted off and replaced with fill, and surface ponds on the property were filled and capped.
But that eliminated only the worst of the pollution.
Now the trees may start to play a bigger role.
“If you think about putting in plants, the public is happier because it’s greener, you’re fixing carbon dioxide, you’re improving the environment and degrading the chemicals,” said Richard Meagher, a University of Georgia genetics professor who was a pioneer in phytoremediation.
It’s also generally far cheaper than many other methods, because once the trees are planted, the remaining costs are mostly just monitoring.
In contrast, he said, “If you just remove the dirt, then somebody in Alabama gets your contaminated dirt because they’re poorer than we are. ... It’s really pathetic that this hasn’t been used all the time.”
Phytoremediation has been researched for 30 years, but even five to 10 years ago, Meagher said, the EPD would not accept it as a treatment option. He said a small but profitable industry has grown up around traditional cleanup methods, and engineers who have worked as both regulators and contractors were unwilling to try something new.
“Politics and finances are the problem,” he said.
But part of the problem might also be that phytoremediation can take a long time.
“It’s a viable corrective measure,” Collins said. “But because of the long-term nature of it, EPD hasn’t been able to evaluate those completely.”
Brownlee said EPD is considering only two other phytoremediation projects, another Norfolk Southern cleanup in Savannah and a groundwater control project in Baxley.
Norfolk Southern spokeswoman Susan Terpay said the company has found success with the method at a similar site in Oneida, Tenn., using about 1,100 hybrid poplars to absorb creosote contamination from soil and groundwater.
Meagher said phytoremediation can take as little as five or six years and works well with hydrocarbons like the ones at Southern Wood Piedmont.
And many such sites using traditional cleanup methods have remained contaminated for decades.
Southern Wood Piedmont had tried a “bioplug” method that involved injecting water into the ground to speed up the breakdown of chemicals, but both Norfolk Southern and EPD officials agreed last year that it wasn’t working, Collins said.
The tree roots are now intended to reduce both the soil and shallow ground water contamination. For the deeper ground water pollution, Norfolk Southern will continue to pump out and treat groundwater before returning it to the ground or using it to water the trees, according to Norfolk Southern’s phytoremediation work plan.
Meagher said phytoremediation projects won’t be successful unless they are based on scientific studies to be sure the plants being used are effective for removing the target pollutants.
Norfolk Southern chose red maple and sweet gum trees because they are hardy, they grow quickly, and they take up a lot of water, according to the company’s work plan.
“While it will take up to five years to assess the full impact of the tree-planting, we should have some initial results by the end of the first growing season” this fall, Terpay said in an e-mail. “One of the success factors we will be looking for is to see if the trees’ bark is absorbing some of the substances in the creosote. If successful, we could embark on a full-scale planting at the site.”
To contact writer S. Heather Duncan, call 744-4225.