Asset Retirement Obligations (Tables)

9 Months Ended

Jun. 30, 2021

Asset Retirement Obligation Disclosure [Abstract]


Asset Retirement Obligation Activity
	Nuclear		Non-Nuclear		Total
Balance at September 30, 2020	$	3,278	$	3,507	$	6,785	(1)
Settlements	(5)		(135)		(140)
Revisions in estimate	12		107		119
Additional obligation	—		30		30

Accretion (recorded as regulatory asset)	111		47		158

Balance at June 30, 2021	$	3,396	$	3,556	$	6,952	(1)

Note

(1) Includes $306 million and $345 million at June 30, 2021, and September 30, 2020, respectively, in Current liabilities.

The revisions in non-nuclear estimates increased the liability balance by $107 million for the nine months ended June 30, 2021. These increases were primarily driven by revisions of certain coal combustion residuals ("CCR") closure liabilities at Shawnee Fossil Plant ("Shawnee"), Paradise, and Colbert Fossil Plant ("Colbert"), resulting from revised engineering estimates for construction costs, new vendor bids, modified closure designs, and expected costs associated with post-closure care of the closed areas. In addition, TVA's use of a new CCR landfill at Shawnee resulted in a new obligation of $30 million.