January 4, 2009 – After a blowout five years ago on the wall of a massive, above-ground coal ash landfill at TVA’s Kingston power plant, engineers were under pressure to find a fix that was not only viable, but also economical.
The blowout wasn’t large but indicated that something was not quite right inside the 98-acre mound of sludge.
Water was tunneling in the layers of ash and creating pressure points on the dike holding the structure in place.
How the Tennessee Valley Authority decided to stabilize Kingston’s ash landfill would have implications for its many other elevated waste dumps, an important tool in the agency’s strategy to maximize its storage on-site and avoid more costly options.
A Tennessean review of state records and some TVA documents shows that top officials rejected solutions that were deemed “global fixes” because they were simply too costly. The most expensive option was listed at $25 million.
In the end, TVA chose to install a series of trenches and other drainage mechanisms to try to relieve the water pressure and give the walls more stability.
On Dec. 22, the walls gave way.
A dark avalanche of coal ash sludge rolled over more than 300 acres around 1 a.m., knocking one home off its foundation and damaging others, toppling trees, filling two inlets of the Emory River and raising health and environmental concerns in nearby neighborhoods and for miles downstream.
Remarkably, no lives were lost.
But the cleanup could cost far more than the most expensive options TVA once considered.
State to boost scrutiny
TVA officials say they are investigating why the mountain of ash collapsed. So far, they have said heavy rains and freezes probably triggered the disaster.
Before the break, plant officials had been monitoring the dike and recent repairs.
“They had not seen any indications that there was some type of imminent problem with the dike,” said TVA spokesman Mike Harris. “They were evaluating the situation as it went along.”
One engineer who reviewed TVA’s Feb. 15, 2008, Annual Ash Pond Dike Stability Inspection report questioned TVA’s evaluation.
The stability report was perplexing, he said, because it contained information about seeps, erosion and other issues, but no information to back up the claim that the dike was indeed stable.
“Obviously, it failed because of slope instability. … I don’t see that really being addressed,” said Bruce Tschantz, a dam safety consultant who was the first U.S. chief of federal dam safety for the Federal Emergency Management Agency. There was no information about the pressure inside the landfill in relation to the seepages and cohesiveness of the material, for example.
The ash disposal site is regulated by the state of Tennessee’s Department of Environment and Conservation and was classified as a Class II industrial landfill.
TVA had to get approval from the state when it made changes to the landfill. For example, the state approved the installation of the drainage trenches in 2005, and did periodic visual inspections.
Gov. Phil Bredesen suggested last week, however, that too much deference has been paid to federal agencies, including the TVA, over the years, and that TVA should expect closer scrutiny in the future.
He called for inspections of all of TVA’s ash facilities and a review of state environmental regulations, which could result in the state’s taking back some of the responsibilities it may have ceded to federal authorities.
Troubles were apparent early
The Kingston power plant, one of TVA’s largest, began producing electricity in the 1950s at the base of a peninsula formed by the Clinch and Emory river embayment of Watts Bar Lake — part of the Tennessee River system.
Each year, about 360,000 tons of powdery fly ash is produced as a byproduct of burning coal. It contains trace amounts of arsenic, lead, mercury, beryllium and other potentially toxic substances. Environmentalists have tried unsuccessfully to have it regulated as hazardous waste.
The Kingston ash pile has slowly grown and, in 2000, TVA requested and the state issued a landfill permit.
Ash has accumulated at all the power producer’s 11 coal-fired power plants, helped by Tennessee consistently being among the top — some years it’s No. 1 — electricity users in the nation.
Some of TVA’s coal-burning plants add water to the fine ash to collect and store it, and others keep it dry.
The Kingston ash facility, a wet version, is unusual for having been built so high.
Before the cataclysmic break on Dec. 22, the stashed ash towered about 60 to 65 feet above Swan Pond Road, which skirted it.
The walls were made of the heavy chunks of ash that fall to the bottom of the plant’s burners. The wet fly ash was deposited inside the walls after being dredged out of settling ponds. TVA refers to the landfill as dredge cells.
State records show troubles were apparent not long after the state issued the landfill permit.
In mid-November 2003, a blowout caused the shutdown of the landfill, and an emergency dredge cell was set up next to it while an investigation took place.
Blame was placed on “piping” and excessive seepage — both water issues.
Water from the ash and also from rain can accumulate. If the liquid gathers and finds weak points, it can channel through the ash, leaving a pipeway for more water to move through, undermining the structure.
A Dec. 22, 2003, report listed several repair alternatives, including converting to a dry ash collection system, a liner over the entire landfill, a vibrating beam cutoff wall and a new dredge cell.
Safer method cost most
A dry collection system — a method that is more labor intensive — is considered more environmentally safe for waterways and groundwater than the wet method. It also was the most expensive fix at $25 million, according to the TVA report. The liner installation was estimated at $5 million, but TVA noted that it would set “a precedence for all other dredge cells” and “take a long time to construct.”
The cheapest option, a new dredge cell, would cost $480,000 and was a possibility for the short term, according to TVA in 2003, but could be viewed as a lateral expansion that would require the onus of a major permit modification, the update said.
TVA decided to hire an outside firm, Parsons E&C, now WorleyParsons, to develop the plan to repair the landfill.
In April 2005, TVA submitted a proposal for repair, backed with analysis by Parsons, and reviewed by a peer engineering firm, GeoSyntec. The solution would include a series of trench drains at different levels on the dike, another drain at the base of the mound and a riprap channel.
Trench drains were not mentioned in the earlier 2003 options.
“Effectiveness, constructability, economics and practical experience led TVA to focus its efforts on trench drains as the preferred fix,” the April 2005 TVA report said. TVA urged quick approval of its plans so it could make repairs and resume dredging.
The state signed off, without any apparent dissension.
“Nothing showed anyone had any concerns,” said Glen Pugh, division manager with the state’s environmental agency’s solid waste management in Nashville. “We don’t reproduce the studies, but we look at the results.”
The fix was viewed as a minor modification to TVA’s landfill permit, and work was completed in October 2005.
Wall ruptured in 2006
Failure followed in 2006, with another rupture loosing water and ash from a nearby section of wall.
Though TVA officials have referred to it as “a small blowout” today, concerns were high enough afterward to install special wells to pull out water from behind the dike and to add 30 shallow piezometers, slim wells sunk into the landfill that measure water levels and help gauge pressure.
“The monitors in place did not show any indications of any immediate problems,” TVA’s Harris said.
Gil Francis, another TVA spokesman, dismissed any comparison to the previous break.
“It was a 5-by-5-foot section with seepage that released some ash,” he said of the 2006 event, adding that it was properly repaired. “That was not the section that failed with this incident.”
Meanwhile, another matter hovered over the landfill. By about 2015, at the current rate of disposal, it would be full.
The maximum elevation could be about 815 feet above sea level — with the last level intended to be a mound of dry ash covered with a layer of earth and grass.
“They were at 790 feet” in 2006, Pugh said. “They weren’t far from reaching the maximum.”
The Kingston plant planned to add new air filtering equipment in 2009. The new scrubbers would remove additional waste from air emissions, which would mean a more than doubling of the waste stream with at least 372,000 tons of a new byproduct, gypsum. The gypsum waste could be sold — it’s used in Sheetrock — but TVA would store the rest on-site as needed with the fly ash.
It proposed to expand the dredge cells laterally, into the adjacent ash settling pond, to handle the additional waste, according to a March 2006 report.
In mid-November 2007, engineers recommended a halt to the dredging as a preventive measure “to avoid another blowout” going into the winter months.
Within a few months, the ash pile began drying out without the addition of new wet ash, and dust had become an issue.
This potentially toxic dust carries sharp-edged bits of silica — like the building-materials dust in the air that sickened workers in New York after the 9/11 attacks.
Dredging restarted for one day and then a decision was made to spray the cells with a coating to try to seal the material, the report said.
A February dike stability inspection said the slopes “appeared to be in sound condition” and dredging resumed in March. Erosion and gullies were noted in the February report, but some seeps along the toe of the dike — known since the early 1980s — were not visible during the inspection.
The February report included many recommendations, including taking action that would “allow an additional release of water from the dikes.”
Plant operators were commended for mowing the landfill slopes. Trees too large to be mowed should be cut, the stumps removed, the area backfilled with soil and seeded, the report said.
“They mentioned small trees being removed,” said Tschantz, the dam safety consultant. “I’m wondering if trees had a role to play. You don’t just pull those things out. The root channels have to be filled and compacted.”
Water can run along roots, or the channels if roots are removed, weakening a dike.
‘Substantial’ cleanup costs
The Tennessean’s request for interviews this week with TVA engineers was not granted.
But there are clearly many wild cards in the quest to determine what went wrong. Rains had dropped almost 5 inches of water in December, compared with the usual 2.8 inches, officials said.
A small earthquake, which did no damage, was reported by the U.S. Geological Service just northeast of Knoxville a few days before the coal ash disaster.
Aside from figuring out what happened, officials also have to total up possible costs.
Slow leaks from ash ponds in Maryland and Montana have resulted in $45 million and $25 million settlements.
PPL Corp. has estimated its cleanup costs from leaking ashy water from a coal-burning plant in Pennsylvania at $37 million.
In TVA’s case, the equivalent of more than a billion gallons of ash sludge blew out all at once.
“I do not know what the costs will be,” Neil Carriker, TVA’s environmental unit chief, said at a news conference last week. “I can guarantee you it will be substantial.”