The Tennessee Valley Authority said Oct. 21 that it recently completed a $16 million project to close the dry ash stack at the now-retired Colbert Fossil Plant in Colbert County, Ala.
Started in the summer of 2015, this 67-acre project involved the installation of over 2.8 million square feet of plastic liner, 255,000 tons of soil (enough to cover the site to a depth of 18 inches) and 2.7 million square feet of sod.
“By following TVA project management procedures, the joint project team worked collectively within their disciplines by incorporating lessons learned and other closure experiences to complete the Stack 5 project under budget, ahead of schedule and with no safety instances,” said Kris Johnson, general manager, Civil Project Management.
When the decision was made to shut down the coal-fired generating facility, the team recognized an opportunity to accelerate closure of Stack 5 by more than a year by shifting the last few months of coal ash placement to an adjacent Pond 4. Using lessons learned from a pond closure at Widows Creek, the team recommended eliminating a 6-inch topsoil layer and placing sod instead, which saved two months of construction time and more than $1 million.
A cloth layer above the plastic liner keeps rainwater off the stack. This cover system will be monitored by TVA for the next 30 years. Groundwater also will be monitored and results reported to the Alabama Department of Environmental Management.
TVA removed Colbert Units 1-4, with a summer net capability of 712 MW, from service in March 2016. Colbert Unit 5 was removed from service in 2013, and all five Colbert units were offically retired on April 16, 2016.