Gabe Cavallaro

gcavallaro@newsleader.com

WAYNESBORO - It's like a pair of pants that are too big — first you put on a belt, but then to make sure they stay up, you put on suspenders too.

At least that's how Mike Liberati, the principal project director for DuPont's project targeted at stopping mercury from continuing to enter the South River, explains it.

DuPont completed the first section of the mercury removal process in Waynesboro last Wednesday, covering about 800 feet of riverbank in the Constitution Park area, which amounts to a little less than one-sixth completion of the first phase of the project.

Mercury has accumulated in the riverbank soil over the years and so when those banks erode, that mercury-coated soil enters the river, which is why fish in the river have continued to build up high levels of mercury decades after the former DuPont plant stopped leaking the chemical into the river.

The "belt and suspenders" plan, launched back in November 2016, first aims to remove the mercury from the soil and also is designed to stop water runoff potentially containing mercury-coated soil, called "baseflow," from entering the river, Liberati said.

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"Everyone's always asking about the 'what-ifs' — this addresses the 'what-ifs,'" he said.

They first identified the banks with elevated mercury levels that were eroding, as not all of the South River's banks are causing the problem and need to be addressed, Liberati said. Then came excavation of those banks, which he admits disturbed them "pretty severely" and so DuPont is picking its spots on which areas to target.

"What we’re doing is invasive," he said. "Before we do more of it and spend the money, let’s make sure it’s effective."

They dug up the banks, and filled them back in a "layer-cake-fashion," starting with a sand-biochar mixture, which is the key component to removing the mercury. Biochar, which is typically used agriculturally, was discovered to be very effective at absorbing mercury when DuPont was testing a wide range of possible materials to use — Liberati said he's not aware of any other instance in which biochar has ever been used for remediation.

Everything is held in place using a honeycomb-shaped "geocell" and then the soil is filled back in and a range of native vegetation is planted on top, which should bloom within a year, Liberati said.

It's also important to note that this project is completely distinct from restoration of the river, as restoration is about recovering and recouping lost resources, whereas remediation targets stopping the mercury problem from continuing on, he said.

They hope to begin work on the next section of the remediation project this spring, Liberati said.