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.



JHM Certified Public Accountants Celebrates New Location

After nearly 40 years in their downtown location, Johnson, Hickey & Murchison Certified Public Accountants, a Chattanooga-based CPA firm, is moving to a new site just off Shallowford Road.   “The new location and fresh build-out have provided us with renewed energy and enthusiasm,” said Dean Krech, managing partner for JHM Certified Public Accountants. “We are so thrilled ... (click for more)

Blissful Wellness At Nutrition World Has Grand Reopening

Blissful Wellness at Nutrition World will host a grand reopening next week. It is at 6237 Vance Road Ste 8 Chattanooga, TN 37421. The week will include workshops, give a ways, and a free yoga class. For more information about the events of the week, contact Studio Manager Maggie Bailey at 423-298-8670 or visit Blissful Wellness on Facebook. (click for more)

City To Begin Shipping Much Of Its Garbage To Bradley County

City Public Works Administrator Justin Holland said the city plans to begin shipping much of its garbage to Bradley County. He said the deal is projected to extend the life of the city landfill at Birchwood by 15 years. Mr. Holland said Bradley County "has a huge landfill and takes garbage from Knoxville and other municipalities. It's regional." He said Bradley County charges ... (click for more)

Man Says He Did Nothing To Provoke Shooting At Bakewell Gas Station; Suspect Says Victim Was Coming Toward Him

A 33-year-old man who was shot in the face during a clash at a Bakewell gas station said he did nothing to provoke the shooting. The man charged said the victim cursed him, then started toward him. General Sessions Court Judge Clarence Shattuck, after a hearing on Tuesday, bound to the Grand Jury a charge of attempted first-degree murder against Donald Stuard II, 29, of Old Washington ... (click for more)

Something Beautiful Happened Monday Night - Not The Debate

Monday, Sept. 26, our first presidential debate happened; no minds were changed.  Yet something beautiful and important happened.  The Atlanta Falcons, my team, played the New Orleans Saints.  Instead of some irrelevant, broad based, screw America protest, the opposing teams locked arms in unity. I was impressed. I have been a Falcon Fan since 1971 when WMOC AM ... (click for more)

Roy Exum: Our 2.0 Embarrassment

Let’s pretend you are coming to a new and exciting world. You are on the jolly good ship “Mayflower” when some Miles Standish-type of a guy (he was the Pilgrim’s first cop) calls you into is presence and says, “Within two hours we are expected to stand on Plymouth Rock. Please come up with ten primary goals we should have in our public schools.” I believe you could do it within ... (click for more)