Yeager landslide was a slow-motion disaster 5 years in the making

2015-05-03 | The Charleston Gazette

May 03--The man-made slope at Yeager Airport that collapsed in a massive landslide seven weeks ago, destroying a church and two homes and ultimately damaging 10 others, had slippage problems going back at least five years.

Those problems accelerated during the past 20 months, as airport officials and contracted engineers monitored the increasingly unstable slope, exchanging worried emails and potential solutions. The slow-motion disaster culminated in the hillside's collapse March 12. More than 130 people were evacuated due to the slide, and five families remain homeless, staying in hotels.

More than five years ago, airport officials found sand and silt -- materials known as "fines" -- collecting in a drainage gutter near the bottom of the slope, airport Director Rick Atkinson said Friday. They called Triad Engineering, the firm that designed the slope, to come check it out.

Triad came to inspect it and responded, exactly five years ago today.

Some minor sloughage has occurred along the surface of the reinforced slope at Runway 5," Dane Ryan, Triad's business development leader, wrote in a letter to Yeager on May 3, 2010. "In most cases the sloughage has been stopped by the secondary/slope protection grid. It is our opinion that this minor surficial movement is caused by minor slope erosion and not an indication of slope instability."

Triad recommended that the areas be re-seeded and mulched.

"So they're opining that this is some of the fines out of that and it's nothing with slope stability," Atkinson said in an interview last week. "Now, do I know that they were correct in that? You know, I have my doubts now, looking back, but that's what they said. Cast Baker guys shoveled the stuff out and they threw some more seed and that did seem to end that issue."

Cast Baker is the Pennsylvania-based contractor that led construction on the $25 million project, per Triad's designs.

So what caused the hillside to collapse five years later? No one seems to know, and if they do, with potential lawsuits looming, they're not saying.

Mike Baker, owner of Cast Baker, did not respond to a request for comment.

Dave Meadows, Triad's regional manager, said, "There's nothing I can say," and referred the Gazette-Mail to public relations consultant George Manahan, who did not return requests for comment.

Atkinson said Yeager does not have a working theory for what caused the man-made slope to fail, but it almost certainly has to do with water penetrating the fill.

"You know that 95 percent of all failures are the result of water," he said. "But why? And that answer hasn't been found."

He differentiated between ground water and surface water and said they didn't know which might be responsible.

"This is a historic failure," said George Koerner, director of the Geosynthetic Institute, a trade organization. "This is not common. This is one that will change the way these designs are done."

Koerner declined to speculate on possible reasons for the landslide, but added, "It's all the buzz in the industry."

Design of the Yeager slope began in 2003 and most of the construction was completed in 2007, although peripheral projects continued for several years after. The project, which made the slope significantly steeper than it had been, was plagued by environmental problems.

Triad pitched themselves to Yeager as the "premiere airport consulting firm in West Virginia" and said they were the "only local firm which can provide the specific airport related expertise as well as all of the additional services required for your projects."

The slope was created to support an extension to Runway 5 -- an Engineered Materials Arresting System. The EMAS is essentially a runaway truck ramp for planes. It is credited with saving 34 people in 2010, when a regional jet overran the runway during an aborted takeoff.

The 68,000-square-foot area consisted of 4,200 foam and cement blocks, each between 7 and 21 inches thick, that break down on contact to stop a plane. More than half of that area will be removed as Yeager attempts to stabilize the slide site.

The blocks sit on top of a crowned asphalt bed that is sloped for drainage purposes.

The 270-foot high slope that the asphalt sits on was constructed of 1.5 million cubic yards of fill, reinforced every three feet with horizontal sheets of synthetic mesh.

Triad's letter, along with thousands of other documents and communications which form the basis of this report, were provided by Yeager in response to requests made under West Virginia's public records law.

Those documents show semi-continuous problems with the EMAS bed and the underlying fill, although they really resurfaced around the summer of 2013.

For instance, a general airport inspection, conducted on Oct. 29, 2010, by Yeager staff in compliance with Federal Aviation Administration requirements, notes "EMAS damaged sections deteriorating."

Similar notations were made on other daily inspection forms around the same time.

In July 2013, airport officials noticed water coming off the slope.

"There is a substantial amount of water that is exiting the side of the fill and there is a large void on the slope filled with water," Atkinson emailed to Ryan, the Triad manager. "Grid is exposed in the area."

Ryan wrote back that they would be there the next morning,

That email seems to be the first of a sporadic and relatively informal correspondence that would continue for the next year and a half.

In addition to daily inspections of airport facilities, Yeager personnel also did weekly and monthly inspections specifically on the EMAS.

The first sign of trouble in these inspections doesn't seem to appear until September 2013.

"Large separation in blocks and shifting in blocks," Jeremiah Nunley, an airport maintenance worker, wrote on his Sept. 9, 2013 inspection. "Cracks in asphalt."

Cracks in the asphalt and shifting EMAS blocks were recurring themes, repeated dozens of times in EMAS inspections leading up to the time of the slide.

Two weeks after that inspection, Ryan emailed Atkinson.

"Have you noticed any movement since the cracks were sealed?" Ryan asked. Atkinson's response isn't clear from the emails.

A week later, Ryan asked via email, "Has there been any visual movement observed on the [Runway] 5 end?"

"The 5 end seems to be stable at this time," Atkinson wrote.

Yeager commissioned at least two engineering surveys over the next few months, both of which found movement in the EMAS, and one of which found the EMAS had shifted by several feet.

"The drop appears to be fairly uniform," Ryan wrote in November 2013 after viewing one of the surveys. "I had reported preliminarily that there was no significant horizontal movement. However, it does appear that the movement was in the direction of the corner."

Meanwhile, the troubling EMAS inspection reports continued.

Dec. 12, 2013: "Water running under EMAS onto road surface."

Jan. 9, 2014: "Areas with water flowing out from underneath EMAS to road surfaces. More outer blocks pulling away."

Apr. 24, 2014: "Outer blocks and many other blocks are pulling away from one another."

As the blocks separated and the asphalt cracked, airport officials made repairs, re-attaching the sealant tape that connects the EMAS blocks and patching cracks in the asphalt.

Movement in the underlying fill, of course, would likely cause separating blocks and cracked asphalt. At the same time, cracked asphalt would allow water into the fill, seemingly making movement more likely.

"It's a chicken-and-egg-type thing, and unfortunately we don't know," Atkinson said.

Last May, airport personnel noticed more cracking in the asphalt, and evidence of movement in the fill.

"The smaller trees down at the bottom above the house are leaning over further than they have been," Terry Sayre, the assistant airport director, wrote to Atkinson on May 5, 2014.

Atkinson forwarded the email to Ryan.

"See below," he wrote. "This doesn't sound good."

A month later, airport officials outlined steps they were preparing to take to "mitigate chances of introducing additional water into the fill."

They included diverting a ditch toward a gutter and checking, repairing and unclogging a 3-foot wide drainage pipe.

On June 10, 2014, Charleston got more than a half an inch of rain.

"Has anyone checked for additional movement of the slide after last night's rain?" Ryan wrote to Atkinson the next day.

"Yes, nothing of significance," Atkinson responded. "Looks like anything that does move will miss the house, including the big rock, if it does move."

After that big rain, Atkinson said Friday, he spoke casually about the slope with some people from the Keystone Apostolic Church (which was destroyed after the landslide).

"You know, we've always looked at that and wondered, man, what if that ever came down," Atkinson recalled church officials saying. "It looks like it's coming right at our church."

Three months later, in September 2014, Triad sent the airport a list of formal recommendations for dealing with the "dual slope failure between the toe of the reinforced soil slope and Keystone Drive."

The brief casualness of the previous emails was gone, and Triad wrote that they were "not responsible for any claims, damages or liability associated with any other party's interpretation of or re-use of these data."

Triad recommended repairing a pipe and clearing out a ditch which, Atkinson said, Yeager did.

Triad also made six other recommendations, all of which involved performing work on the fill itself. Yeager did not complete those recommendations, because, Atkinson said, they needed to see more specific planning.

Atkinson said the airport's general contractor was concerned about doing work on the unstable fill itself, without drilling for core samples to get more information.

"His concern [is] with taking out the soil below the existing slip and causing the whole fill to move and maybe kill a worker underneath the fill," Atkinson wrote to Ryan at the time.

Atkinson pushed for a core-drilling and whatever repairs were possible to be completed before winter.

The worrisome EMAS inspection reports continued unabated.

Dec. 23, 2014: "Cracks to southwest road surface appear to be getting larger by the week. Graveled area beside southwest road has large dip that has appeared within the week."

Jan. 28, 2015: "Cracks that were patched on 1/21/15 are starting to separate again. Cracks to road surfaces are separating weekly."

Feb. 17, 2015: "Several blocks pulling away from one another. Cracks to road surface getting larger daily. Hooving to road surface. Hooving to blocks center of EMAS."

On Jan. 13, 2015, two months before the slide, Sayre, the assistant airport director, spoke with a representative of Keystone Apostolic Church.

"He said they were concerned about the slip and it's stability," Sayre wrote to Atkinson. "I would expect further calls in the near future because they are concerned about the slip progressing and a collapse of the fill material. He said that they have been discussing it at the church."

Reach David Gutman at david.gutman@wvgazette.com, 304-348-5119 or follow @davidlgutman on Twitter.