In 2020, the Company's shareholders approved the Clean Harbors, Inc. 2020 Stock Incentive Plan (the "2020 Plan"). The 2020 Plan provides for future awards of up to 2.5 million shares of the Company’s common stock (subject to certain anti-dilution adjustments) in the form of stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards. The 2020 Plan is administered by the Compensation and Human Capital Committee of the Company’s Board of Directors.

The Company grants restricted stock awards and performance stock awards. The restricted stock awards generally vest over three to five years subject to continued employment. The performance stock awards vest depending on the satisfaction of certain performance conditions typically based on revenue, Adjusted EBITDA margin, return on invested capital and a measure of workplace safety. In addition, performance stock awards include continued service conditions subsequent to the attainment of any performance conditions.

Total stock-based compensation cost recognized for the years ended December 31, 2023, 2022 and 2021 was $20.7 million, $26.8 million and $18.8 million, respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation expense was $3.5 million, $5.0 million and $3.5 million for the years ended December 31, 2023, 2022 and 2021, respectively.

The following table summarizes information about restricted stock awards for the year ended December 31, 2023:


Restricted Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2023	427,142	$	84.64
Granted	209,431	140.32
Vested	(170,060)	76.26
Forfeited	(51,890)	102.11
Balance at December 31, 2023	414,623	$	114.02

As of December 31, 2023, there was $34.5 million of total unrecognized compensation cost arising from restricted stock awards. This cost is expected to be recognized over a weighted average period of 2.9 years. The total fair value of restricted stock vested during 2023, 2022 and 2021 was $26.5 million, $16.4 million and $17.7 million, respectively.

Performance stock awards are subject to performance criteria established by the Compensation and Human Capital Committee of the Company's Board of Directors prior to or at the date of grant. The vesting of the performance stock awards is based on achieving targets currently based on revenue, Adjusted EBITDA Margin, Return on Invested Capital and Total Recordable Incident Rate. In addition, performance stock awards include continued service conditions.

The following table summarizes information about performance stock awards for the year ended December 31, 2023:


Performance Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2023	213,679	$	91.62
Granted	120,765	131.18
Vested	(111,924)	90.56
Forfeited	(41,236)	111.50
Balance at December 31, 2023	181,284	$	114.10

As of December 31, 2023, there was $3.3 million of total unrecognized compensation cost arising from unvested performance stock awards deemed probable of vesting. The total fair value of performance awards vested during 2023, 2022 and 2021 was $17.0 million, $11.1 million and $15.0 million, respectively.