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Mills River board grills AVL official on wall collapse

MILLS RIVER — Presenting the first full public explanation of the failure of a 40-foot-high retaining wall above Ferncliff Park Drive, the Asheville Regional Airport's second-in-command defended the wall engineering and said repairs should be done within eight weeks of receiving new wall panels.


"The wall was, is and remains a sound design," Michael Reisman, the director of development and operations for the airport, told the Mills River Town Council Thursday night. "There was nothing wrong with the design of the wall. The failure of the wall was not related to the design. It was related to storm drain issues that we had behind the wall before we had the opportunity to get the permanent storm drains in place. The temporary stuff unfortunately failed on us and didn't hold up."
Reisman gave the town council a step-by-step explanation of the design of the 1,200-foot retaining wall and what caused either end to buckle on Christmas Eve. He vowed that the airport and its contractors would fix the wall and repair damage to wetlands caused by heavy rains and the drainage failure. He told the council, too, that a state incentive grant assures that the NCDOT will plant "extensive landscaping" along the tall wall and across the road to improve the view for thousands of tourists who are expected to visit the Sierra Nevada brewery.
Reisman emphatically reassured the town council that the stormwater that caused the wall collapse never threatened to break the thick plastic liners that envelope tons of coal ash the airport has used as construction fill.
Michael Reisman Michael Reisman "It's a valid concern," the airport official responded when Councilman Roger Snyder raised the question. "The coal ash and the vessel that contains the coal ash on the airport was never in jeopardy of being breached as a result of this. The closest any part of the wall is about ninety to a hundred feet, in that general range.
"The coal ash is contained within a completely sealed encapsulated heat-welded vessel which quite honestly you'd really have to go out there with a piece of equipment to try to puncture that thing before it would probably tear. ... It's very difficult to get it to move as well."
Even so, Snyder pressed Reisman on what would happen when the contractor pounded the ground to build a temporary taxiway for heavy jets. "When you're out there packing this down with big ol' equipment, getting ready to pave, you're saying there's no chance of this stuff leaching out, leaking out, whatever you want to call it?"
"The way the system is designed," Reisman responded, "is if there was anything leaching or leaking it would leach or leak down to the bottom and the liner system at the bottom is designed to capture anything like that and carry it into self-contained chamber onsite at the airport."

Wall intact

Reisman said the storm that dumped an inch and a half of rain on Dec. 23 came after the contractor had just completed grading of hundreds of acres. Hydroseeding to hold the dirt and prevent erosion had not taken hold when rainwater washed dirt toward the wall and overwhelmed a temporary drainage system.
"The site actually stood up pretty well to several heavy rains that we had throughout the course of the construction project," he said. "However, on the night of Dec. 23rd we had about a one and a half inch rainstorm overnight. The storm itself was nothing out of the ordinary or special in terms of what we experienced. However, we did have an issue where some siltation and blockage occurred in the temporary storm drain that was behind the wall in two locations on both the north and south ends. Once those storm drains blocked up, we ultimately had backing up. We had water ponding back there and ultimately the water encroached behind the wall and down the inside of the wall, causing a significant amount of erosion and ultimately the movement and the failure that you've probably all seen at this point on both the north and south end of the entire wall system.
"It's important to point out that the main run of the wall — the roughly eight- or nine-hundred feet of that center section — was never damaged and is not damaged," he added. "There was no problems with it whatsoever. It was really where the tapered ends were on both ends."
Despite the appearance of the wall, there was no risk that the loose panels would plummet down onto Ferncliff Park Drive, he said.
"Every one of those panels is actually attached all the way across the back to a very heavy gauge geogrid system that extends about a hundred feet into the earth behind the wall," he said. "So even though the erosion washed away, even though those panels looked like they shifted and were moving — which they were — they were really never in danger of falling because they were connected on the back by that geogrid system that was being held to the ground by the earth."

Wall creates 'negative appearance'


Mud and water ran off from site and into wetlands across Ferncliff Park Drive above the French Broad River, triggering in a citation from the state Department of Environment and Natural Resources. Reisman said the airport had drafted a correction plan for the violation.
IMG 5709Mayor Larry Freeman questions Michael Reisman about the airport wall collapse."There was some discussion about how the silt may have left the airport property and damaged adjacent property," he said. "That adjacent property is airport property. So yes, it did go under Ferncliff Park Drive but that parcel down to the river on the other side is also airport-owned. So there was no other private property damaged other than airport property."
Once DENR approves the plan, contractors will begin work to repair the damage. "Very preliminarily, it does not appear overly substantial," he said. "It appears to be more in the minor range."
Snyder also brought up the cosmetics of the wall, suggesting that the entry to the Sierra Nevada brewery looks unattractive. Imagine a tourist, he said, turning off Highway 280 and heading toward Sierra Nevada.
"I look to my left and see these silt ponds and I look to my right and see this great wall," he said. "I would almost think that it would be a negative appearance.
"I would agree with you," Reisman responded. "There will be some extensive landscaping on either side of Ferncliff Park Drive."
As part of the improvements for the road paid for by a state economic development incentive, the NCDOT will do the work. "I've seen the landscape plan. It's actually going to look I think pretty darn nice," he said. "But the state had intentionally held off on putting in the landscaping until after the wall was built."

The Town Council took no official action. Freeman urged Reisman to stay in contact and update the council on the construction.