Page 16 - TN Public Works Sept-Oct 2014 Vol.32 No.3
P. 16
By Alan Rauch
COAL ASH SPILL RECOVERY
STANTEC RECEIVES AWARD
Stantec has received the Grand Award from the American Council of Engineering
Companies of Kentucky (ACEC-KY). The award recognizes Stantec for its novel design
and comprehensive technical solution for the Tennessee Valley Authority’s (TVA)
recovery from the Kingston, Tennessee 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 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.
There From Day One
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
In December 2008, the dikes at TVA’s power station in with recovery efforts.
Kingston containing wet coal combustion ash failed, Today, TVA has achieved several key milestones at Kingston. During the first two years
and 5.4 million cubic yards of coal ash were released. after the spill, about 3 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.
New Containment Facility
The idea of placing large volumes of ash back within the failed area was met with initial
skepticism. 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 carefully 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.
On-site storage of the recovered ash with the By far, the most difficult design challenge was how to contain the ash in the event of a
perimeter containment structure represents TVA’s best large earthquake. Tennessee regulations require landfill facilities to withstand a 2500-year
option for meeting the goals of the project. 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 US.
Project On Schedule
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,” Zeller said.
TVA’s Kingston Fossil Plant supplies power that is critical to the regional economy. On-
A two-mile long perimeter containment structure site storage of the recovered ash, made possible with the perimeter containment structure,
has been built around the new 240-acre ash landfill, represents TVA’s best option for meeting both the economic and environmental goals of the
which is being capped with a flexible membrane project. The result has restored public confidence that a failure like the 2008 event would not
cover system. happen again at Kingston, not even during a major natural disaster such as an earthquake.
16 TPW September/October 2014
COAL ASH SPILL RECOVERY
STANTEC RECEIVES AWARD
Stantec has received the Grand Award from the American Council of Engineering
Companies of Kentucky (ACEC-KY). The award recognizes Stantec for its novel design
and comprehensive technical solution for the Tennessee Valley Authority’s (TVA)
recovery from the Kingston, Tennessee 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 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.
There From Day One
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
In December 2008, the dikes at TVA’s power station in with recovery efforts.
Kingston containing wet coal combustion ash failed, Today, TVA has achieved several key milestones at Kingston. During the first two years
and 5.4 million cubic yards of coal ash were released. after the spill, about 3 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.
New Containment Facility
The idea of placing large volumes of ash back within the failed area was met with initial
skepticism. 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 carefully 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.
On-site storage of the recovered ash with the By far, the most difficult design challenge was how to contain the ash in the event of a
perimeter containment structure represents TVA’s best large earthquake. Tennessee regulations require landfill facilities to withstand a 2500-year
option for meeting the goals of the project. 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 US.
Project On Schedule
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,” Zeller said.
TVA’s Kingston Fossil Plant supplies power that is critical to the regional economy. On-
A two-mile long perimeter containment structure site storage of the recovered ash, made possible with the perimeter containment structure,
has been built around the new 240-acre ash landfill, represents TVA’s best option for meeting both the economic and environmental goals of the
which is being capped with a flexible membrane project. The result has restored public confidence that a failure like the 2008 event would not
cover system. happen again at Kingston, not even during a major natural disaster such as an earthquake.
16 TPW September/October 2014
