ASSET RETIREMENT OBLIGATIONS (Tables)

9 Months Ended

Sep. 30, 2023

ASSET RETIREMENT OBLIGATIONS [Abstract]

Asset Retirement Obligations Operating Costs

	Three Months Ended		Nine Months Ended
	September 30		September 30
in millions	2023	2022	2023	2022
ARO Operating Costs
Accretion	$          3.5	$          3.6	$        10.3	$        10.7
Depreciation	2.2	2.4	6.6	7.2
Total	$          5.7	$          6.0	$        16.9	$        17.9

Reconciliations of Asset Retirement Obligations

	Three Months Ended		Nine Months Ended
	September 30		September 30
in millions	2023	2022	2023	2022
Asset Retirement Obligations
Balance at beginning of period	$       311.6	$       321.1	$       311.3	$       315.2
Liabilities incurred	0.0	19.2	0.0	21.5
Liabilities settled	(1.9)	(2.3)	(8.4)	(5.6)
Accretion expense	3.5	3.6	10.3	10.7
Revisions, net	2.3	(1.6)	2.3	(1.8)
Balance at end of period	$       315.5	$       340.0	$       315.5	$       340.0