ASSET RETIREMENT OBLIGATIONS (Tables)

6 Months Ended

Jun. 30, 2023

ASSET RETIREMENT OBLIGATIONS [Abstract]

Asset Retirement Obligations Operating Costs

	Three Months Ended		Six Months Ended
	June 30		June 30
in millions	2023	2022	2023	2022
ARO Operating Costs
Accretion	$          3.4	$          3.6	$          6.9	$          7.1
Depreciation	2.2	2.4	4.3	4.8
Total	$          5.6	$          6.0	$        11.2	$        11.9

Reconciliations of Asset Retirement Obligations

	Three Months Ended		Six Months Ended
	June 30		June 30
in millions	2023	2022	2023	2022
Asset Retirement Obligations
Balance at beginning of period	$       311.9	$       319.7	$       311.3	$       315.2
Liabilities incurred	0.0	0.0	0.0	2.3
Liabilities settled	(3.7)	(2.0)	(6.6)	(3.3)
Accretion expense	3.4	3.6	6.9	7.1
Revisions, net	0.0	(0.2)	0.0	(0.2)
Balance at end of period	$       311.6	$       321.1	$       311.6	$       321.1