Landfill begins process of capping 90 acres of closed cells

May 18—The process of covering 10 closed cells spanning 90 acres at the Decatur-Morgan County Regional Landfill in Trinity will begin soon as part of an effort to limit the leaching of industrial toxins into groundwater and the river.

3M Co. in 2021 agreed to pay up to $22.2 million to cover the 10 cells with four synthetic liners separated by layers of soil. The agreement was part of a $98.4 million settlement with the city of Decatur, Morgan County and Decatur Utilities.

The settlement focuses on reducing levels of per- and polyfluoroalkyl substances (PFAS). PFAS are called "forever chemicals" because they don't break down in the environment. PFAS-contaminated leachate from the landfill enters the groundwater or is piped to the DU wastewater treatment plant.

Because the chemicals do not decompose, they leave the DU wastewater treatment plant in one of two ways. Either they are discharged into the river — contributing to health advisories on fish consumption and contamination of downstream drinking water intakes — or they are trucked back to the landfill in heavily contaminated sludge.

"When groundwater hits our garbage and trash, it makes leachate. Our leachate goes into the DU wastewater system," landfill Director Wanda Tyler said. "That wastewater is taken care of by DU and then the sludge from the DU wastewater process comes back to the landfill."

The 10 cells are the oldest at the landfill and were closed before 1991, when the Environmental Protection Agency started requiring landfill cells to be lined at the base and to have a liner on top once the cell was closed. The liners' purpose was to limit the amount of leachate created as rainwater enters a closed landfill cell.

"The idea is that if you seal the mound, which is the cell, if you seal it a certain way then the water won't infiltrate and penetrate into our groundwater," Tyler said. "Everything is now compacted into these mounds and you're going to put something over it to seal it so you will not have those leaks of those forever chemicals."

Tyler compared the capping to putting a hat on in the rain. The cap will prevent rainwater from entering the closed cells, thus preventing the accumulation of contaminated leachate.

According to the EPA, PFAS exposure may lead to decreased fertility, increased high blood pressure in pregnant women, developmental defects or delays in children, including low birth weight and accelerated puberty or behavioral changes. Exposure to the chemicals may also cause an increased risk of prostate, kidney and testicular cancers, compromised immune systems and reduced vaccine response, increased cholesterol levels and hormonal imbalances.

The groundwater will continue to be tested after the capping, Tyler said.

Tyler said the cell caps will be layered.

"There will be a lot of dirt because the slopes of those cells have to be managed," she said. "You can't just put things on it in order to cap it so there'll be a lot of dirt and I'm sure there'll be some geosynthetics. Then more dirt and then some other layer so we can grow grass on it."

The civil engineering firm Pugh Wright McAnally is overseeing the capping process.

"The cells will be capped with a combination of soil, geo-composite and geomembrane," said Pugh Wright Vice President Nathan Tomberlin. Geo-composite and geomembrane are plastic-like materials.

There are still steps to take before the capping work begins, Tyler said.

"We're still waiting for ADEM (the Alabama Department of Environmental Management) to approve our plan. We'll know I guess in the next couple of months," she said. "Then after that you have to go out for bid to award the job."

Tomberlin said the construction is slated to be completed by mid to late 2025.

At its May 9 meeting, the Morgan County Commission approved the capping. Tomberlin said it will now have to be approved by the Decatur City Council after a public hearing at the June 5 council meeting.

At Monday's council meeting, the council approved testing for cell 16, which Tyler said is in construction to be opened. She said the weather has delayed getting into the new cell.

"You have to put down a clay liner, a sand permeability layer then geosynthetics," she said. "Every part of it has to go through certain testing and documentation, certain parameters that we have to keep ADEM informed."

There are a total of 19 cells at the landfill. Cells 12 and 13 were capped in 2018, and cell 14 will be capped next, Tyler said.

The council on Monday also approved a five-year permit renewal payment for the landfill in the amount of $37,270. The fee will be paid to ADEM and will come out of the landfill department's budget.

—erica.smith@decaturdaily.com or 256-340-2460.