ASSET RETIREMENT OBLIGATIONS (Tables)

3 Months Ended

Mar. 31, 2022

ASSET RETIREMENT OBLIGATIONS [Abstract]

Asset Retirement Obligations Operating Costs

	Three Months Ended
	March 31
in millions	2022	2021
ARO Operating Costs
Accretion	$          3.5	$          3.2
Depreciation	2.4	2.7
Total	$          5.9	$          5.9

Reconciliations of Asset Retirement Obligations

	Three Months Ended
	March 31
in millions	2022	2021
Asset Retirement Obligations
Balance at beginning of year	$       315.2	$       283.2
Liabilities incurred	2.3	0.9
Liabilities settled	(1.3)	(2.7)
Accretion expense	3.5	3.2
Revisions, net	0.0	0.8
Balance at end of period	$       319.7	$       285.4