Stantec’s Support Of TVA’s Coal Ash Spill Recovery Earns Awards For Engineering Excellence

Wednesday, June 4, 2014
The Kingston Coal Ash Spill/Failure of 2008
The Kingston Coal Ash Spill/Failure of 2008

Stantec has received the Grand Award from the American Council of Engineering Companies of Kentucky. The award recognizes Stantec for its design and technical solution for the Tennessee Valley Authority’s recovery from the Kingston coal ash spill. The project also received a National Recognition Award at the ACEC 2014 Engineering Excellence Awards competition.  

In December 2008, the dikes at TVA’s power station in Kingston, Tennessee containing wet coal combustion ash failed, and 5.4 million cubic yards of coal ash were released. The ash slurry flowed out from the site, impacting the adjacent Emory River In the aftermath, TVA committed more than $1 billion for the response, clean up, and site restoration. 

Stantec’s team was at Kingston within hours after the spill to assist TVA with emergency actions. As the recovery progressed, Stantec developed a site closure scheme, completed detailed engineering designs for a containment structure, and remained on-site to help with recovery efforts.  

Today, TVA has achieved several key milestones at Kingston. During the first two years after the spill, about three million cubic yards of ash dredged from the river was shipped by rail to a permitted, off-site landfill. Since then, the remainder of the released material has been excavated and stacked back inside the footprint of the failed impoundment facility. A two-mile long perimeter containment structure has been built around the new 240-acre ash landfill, which is being capped with a flexible membrane cover system.  In 2014, Stantec’s design was recognized by ACEC for engineering excellence.

The idea of placing large volumes of ash back within the failed area was met with initial skepticism, said officials. To prove it could be done without causing another failure, a test embankment was built across six acres of the failed dredge cell. Geotechnical instrumentation was installed to measure water pressures and movements within the underlying ash. Stantec established criteria and monitored conditions. In the end, more than 250,000 cubic yards of ash were safely stacked to a height of 45 feet above the failed surface. In addition to restoring confidence, the test program established protocols that would be followed throughout the project.

By far, the most difficult design challenge was how to contain the ash in the event of a large earthquake, said officials. Tennessee regulations require landfill facilities to withstand a 2500-year earthquake. Engineering analyses showed that these events would liquefy the sandy soils underlying the ash landfill.

Borrowing an approach used elsewhere to stabilize large embankment dams, Stantec designed a grid of buried walls that enclose the ash landfill. The engineering design was complex and required advanced numerical modeling of the seismic behavior, using both dynamic 2D and static 3D structural analyses. The design was subject to extensive independent review and regulatory oversight. The completed retaining structure, built to depths of 70 feet, is one of the largest walls of its type ever constructed in the U.S. 

Craig Zeller, EPA’s project manager at the site, sees how far the cleanup project has come. “It was a daunting project at the start. But five years later, after dredging, digging, and stacking ash day after day, week after week, the end is in sight. The project is on schedule. Ash is out of the river. The perimeter walls are done. The environmental restoration is underway. Kingston is a fantastic case study for a large-scale cleanup,” Mr. Zeller says.

TVA’s Kingston, Tennessee, Fossil Plant supplies power that is critical to the regional economy. On-site storage of the recovered ash, made possible with the perimeter containment structure, represents TVA’s best option for meeting both the economic and environmental goals of the project. The result has restored public confidence that a failure like the 2008 event would not happen again at Kingston, not even during a major natural disaster like an earthquake, said officials.



CBL & Associates Declares Common Stock Dividend And Preferred Stock Dividend

CBL & Associates Properties, Inc. on Friday announced that its Board of Directors has declared a quarterly cash dividend for the company’s Common Stock of $0.265 per share for the quarter ending March 31. The dividend is payable on April 17 to shareholders of record as of March 30.  The Board also declared a quarterly cash dividend of $0.4609375 per depositary share ... (click for more)

Covenant Transport To Pay $30,000 To Settle EEOC Disability Discrimination Suit

Covenant Transport, Inc. will pay $30,000 and furnish other relief to settle a disability discrimination lawsuit filed by the U.S. Equal Employment Opportunity Commission, the federal agency announced Friday.   The EEOC’s suit had charged that Covenant discriminated against an applicant for a commercial truck driver position on the basis of his disability. Covenant conditionally ... (click for more)

2 Homes Totally Destroyed By Fire On Sunday In Separate Blazes

Two homes were totally destroyed by fire in separate blazes on Sunday afternoon. At  5 p.m. , a neighbor called 911 reporting a house fire at 3910 Fairmont Pike on Signal Mountain. Walden's Ridge Emergency Services responded and arrived on the scene reporting a fully involved house fire. A mutual aid response was requested for additional manpower and apparatus ... (click for more)

Signal School Study Says Under Own School System Much More Could Go To The Classroom; Lennon Says Getting Land, Buildings A Major Issue

A panel studying a new school system operated by Signal Mountain concluded that much more money could go directly into the classroom, helping students further increase their potential.   However, County School Board member Kathy Lennon said how the town would be able to acquire the land and buildings is a major issue.   A group of Signal Mountain residents ... (click for more)

CVB Should Share Financials With The Home Folks

The recent debate over the Convention and Visitor's Bureau's funding and budget has gotten ugly. A Hamilton County commissioner has asked questions and made comments about the CVB. The director of the CVB has organized a campaign to dismiss the commissioner's questions and comments. The children on the playground are choosing sides and nothing useful seems to be happening. It's ... (click for more)

Roy Exum: The Eye Of The Storm

There is a very serious building in Norman, Okla., that houses the nation’s Storm Prediction Center for the National Oceanic and Atmospheric Administration and the National Weather Service. According to a Four-Day Forecast released on Sunday, north Alabama and the Chattanooga area are in the middle of the bulls eye for the United States. Yes, it was about 40 degrees and sunny ... (click for more)