The Tennessee Valley Authority is shifting into the next phase of its cleanup of the massive coal-ash spill near Knoxville. That’s where an earthen dam burst in December of 2008, spilling millions of tons of ash sludge, which is what’s left over after coal is burned for energy and dumped in a lake. And now TVA says it will keep some of the ash from the cleanup on site.

For the last year TVA has focused on dredging ash out of the nearby Emory River. Now it’s turning its efforts to the roughly two million cubic yards of ash on land and in the river’s shallows.

The Environmental Protection Agency’s Craig Zeller is overseeing the cleanup effort. He says some 700 workers are on the site, which runs 24 hours a day, six days a week, with the seventh spent maintaining equipment.

“The pieces of yellow iron on this project are too many to count. We’ve got a fleet of articulated dumptrucks…God, I’d say dozens of long-stick excavators, clamshells, 12 water trucks for dust suppression…it’s quite an amazing place.”

The next phase of the cleanup will take years, and Zeller says the ash will be stored on site. He says TVA is engineering new safeguards for storing the ash, including thousands of underground cement reinforcements. And he says the goal is to safeguard against another spill, even in the event of an earthquake.

Before the 2008 spill, when the plant burned coal for energy, it dumped what was left in a man-made lake. This time, TVA will effectively bury that ash under several feet of clay and topsoil.

To make sure nothing like the spill happens again, Zeller says they’ll surround the 250-acre ash cell with a lattice of underground reinforcements.

“What we’ll do is auger down 60 to 70 feet through saturated ash and key into the underlying shale bedrock. And as we withdraw the auger bits that are going to be eight foot in diameter, we’re going to be injecting 25 percent Portland cement.”

Zeller says that should be able to withstand a magnitude 6 earthquake some 20 miles from the site. And he says workers will drill the first test holes this month.

EXTRA:

“It’s going to require over 12 thousand eight-foot-diameter auger borings, and 260 thousand cubic yards of cement, so it’s going to be a very large civil engineering project, that again is being done to make sure that what happened December 22, 2008, never happens again at this cell.”