Expert witness blasts TVA over coal ash spill

Sep 28 - McClatchy-Tribune Regional News - Ed Marcum The Knoxville News-Sentinel, Tenn.

Liike a paper bag sitting on a mound of gelatin -- just add water and you've got a mess.

That's how plaintiffs' expert witness B. Dan Marks described what happened when a coal fly ash impoundment failed at TVA's Kingston Fossil Plant, 2008. If soil becomes saturated enough, it will fail in a similar way paper does when it becomes soaked, Marks said during testimony in U.S. District Court Tuesday.

"This is so much like putting water in a paper sack and putting it on top of Jell-O," said Marks, a geotechnical engineer, former University of Tennessee professor and owner of Marks Enterprises, which specializes in designing, maintaining and inspecting dams.

"As the sack becomes saturated, you will start seeing water squirting out at different places because the bag is weaker in some places than in others. Then you have the Jell-O, which is soft but is compressing the bag as you add water. You get to a certain level and the next teaspoon of water you put in there -- poof! She's gone."

Marks said it comes down to pore pressure, which he described as pressure that water held between the particles of soil exerts against the ability of the soil to hold itself together. The dike that failed at Kingston in 2008 was under great stress from ground water pressure, there were signs of this that TVA employees misidentified during inspections as erosion, and the weakened structure finally disintegrated, Marks said. He believes the addition of more coal ash sludge before the incident was the likely trigger.

This view conflicts with the conclusion of a root cause analysis that TVA commissioned after the spill and which put much blame on a layer of unstable soil under the ash holding cell that collapsed. It also runs counter to testimony from TVA engineer Jamey Dotson, who spent nearly two days on the stand. About 230 plaintiffs are suing TVA over the 2008 spill, which sent 5.4 million cubic yards of coal ash into the Emory River and over 300 acres of the countryside.

Dotson's testimony wrapped up Tuesday morning, and some of it was at odds with what Marks had to say. Under questioning by TVA lawyer Brent Marquand, Dotson said the monitoring of water pressure levels in the dikes at Kingston before the collapse did not show levels that met a threshold at which he would have been alerted by those doing the monitoring. Dotson was responsible for responding to issues with the coal ash storage area at the Kingston power plant, which generates electricity by burning coal.

Under questioning by plaintiffs' attorney David Byrne, Dotson conceded there were spikes in ground water pressure readings in November 2008 in monitoring devices near the spot where the initial collapse would later occur, but he said the readings could have been influenced by elevated river levels, heavy rainfall or other factors.

Marks discounted the effect of rain and said the November readings, in which the three measuring devices at the dike recorded water level increased of three to five feet, should have been red flags under any circumstances. Under questioning by plaintiffs' attorney Gary Davis, Marks also criticized TVA for not making sure the engineers who inspected the ash storage area were property trained and followed procedures. He criticized the engineers for not turning in their last inspection report until after the ash spill.

"Why would you do a dam report after the dam has failed?" he said.