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Decommissioning and Other Provisions | 12 Months Ended
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Dec. 31, 2021
Other Provisions, Contingent Liabilities And Contingent Assets [Abstract] |
Decommissioning and Other Provisions | Decommissioning and Other Provisions The change in decommissioning and other provision balances is as follows:
| Decommissioning and restoration | Other provisions | Total
Balance, Dec. 31, 2019 | 501 |  | 45 |  | 546 |
Liabilities incurred | 1 |  | 34 |  | 35 |
Liabilities settled | (18) |  | (19) |  | (37) |
Accretion | 30 |  | — |  | 30 |
Acquisition of liabilities | 1 |  | — |  | 1 |
Revisions in estimated cash flows | 61 |  | 11 |  | 72 |
Revisions in discount rates(1) | 36 |  | — |  | 36 |
Reversals | — |  | (6) |  | (6) |
Change in foreign exchange rates | (4) |  | — |  | (4) |
Balance, Dec. 31, 2020 | 608 |  | 65 |  | 673 |
Liabilities incurred | 8 |  | 22 |  | 30 |
Liabilities settled (Note 36) | (18) |  | (62) |  | (80) |
Accretion | 32 |  | — |  | 32 |
Acquisition of liabilities | 2 |  | — |  | 2 |
Revisions in estimated cash flows | 167 |  | 12 |  | 179 |
Revisions in discount rates | (6) |  | — |  | (6) |
Reversals | — |  | (3) |  | (3) |
Balance, Dec. 31, 2021 | 793 |  | 34 |  | 827 |
(1) Discount rates at Dec. 31, 2020, are generally lower than those at Dec. 31, 2019, due to decreases in the underlying risk-free US and Canadian benchmark yields and changes in credit spreads due to volatility within the market as a result of COVID-19. On average, these rates decreased by approximately 0.3 to 0.9 per cent.
| Decommissioning and restoration | Other | Total
Balance, Dec. 31, 2020 | 608 |  | 65 |  | 673 |
Current portion | 21 |  | 38 |  | 59 |
Non-current portion | 587 |  | 27 |  | 614 |
Balance, Dec. 31, 2021 | 793 |  | 34 |  | 827 |
Current portion | 35 |  | 13 |  | 48 |
Non-current portion | 758 |  | 21 |  | 779 |
A. Decommissioning and Restoration A provision has been recognized for all generating facilities and mines for which TransAlta is legally, or constructively, required to remove the facilities at the end of their useful lives and restore the sites to their original condition. TransAlta estimates that the undiscounted amount of cash flow required to settle these obligations is approximately $1.6 billion, which will be incurred between 2022 and 2072. The majority of the costs will be incurred between 2025 and 2050. In 2021, the Company adjusted the wind assets decommissioning and restoration provision as estimates were updated a fter the review of a recent engineering study on the decommissioning costs of the wind sites. The Company's current best estimate of the decommissioning and restoration provision increased by $120 million. The change in estimate is unrelated to the tower failure identified in the fourth quarter of 2021. The Company also increased the decommissioning and restoration provision by approximately $47 million for the Sundance and Keephills Units included in the Gas and Energy Transition segments to reflect the change in the timing of the expected reclamation work resulting from asset retirements and change in useful lives. These changes resulted in an increase in the related assets in PP&E. At Dec. 31, 2021, the Company had provided a surety bond in the amount of US$147 million (2020 – US$147 million) in support of future decommissioning obligations at the Centralia coal mine. At Dec. 31, 2021, the Company had provided letters of credit in the amount of $188 million (2020 – $131 million) in support of future decommissioning obligations at the Highvale mine. In the fourth quarter of 2020, the Company adjusted the Sarnia decommissioning and restoration provision to reflect an updated engineering study. The Company's current best estimate of the decommissioning and restoration provision decreased by $15 million. This resulted in a decrease in the related assets in PP&E. In the third quarter of 2020, the Company adjusted the Highvale mine decommissioning and restoration provision to reflect the mine closure advancement, an updated mine plan and current mining activity including increased volume of material movement. The Company's current best estimate of the decommissioning and restoration provision increased by $75 million. This resulted in an increase in the related assets in PP&E. B. Other Provisions Other provisions also include provisions arising from ongoing business activities and include amounts related to commercial disputes between the Company and customers or suppliers. Information about the expected timing of settlement and uncertainties that could impact the amount or timing of settlement has not been provided as this may impact the Company’s ability to settle the provisions in the most favourable manner. During the third quarter of 2021, an onerous contract provision for future royalty payments of $14 million was recognized as a result of a decision to accelerate the plans to shut down the Highvale mine, with the effect that any remaining future royalty payments related to the extraction of coal has no future economic benefit. Payments required under the royalty contract will continue through 2023. At Dec. 31, 2021, the remaining balance of the provision was $14 million. During the fourth quarter of 2020, an onerous contract provision of $29 million was recognized as a result of a decision to accelerate plans to eliminate coal as a fuel source at the Sheerness facility by the end of 2021. The last coal shipment was received during the first quarter of 2021, while payments required under the contract will continue until 2025. At Dec. 31, 2021, the remaining balance of the provision was $14 million.

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