Certain Balance Sheet Information

Inventories

Inventories consisted of the following at September 30, 2012 and 2011, respectively (in millions):



	September 30,
	2012		2011
Parts and supplies	$	4.2	$	3.7
Natural gas	0.4		0.6
Raw materials	0.2		0.2
Finished goods	0.8		0.6
Total inventories	$	5.6	$	5.1

Property, Plant and Equipment

Property, plant and equipment consisted of the following at September 30, 2012 and 2011, respectively (in millions):



	September 30,
	2012		2011
Plant equipment	$	225.3	$	173.4
Salt deposits	41.6		41.6
Land and buildings	393.3		358.0
Vehicles	3.0		2.5
Construction in progress	331.4		169.6
Base gas	73.1		71.1
Office furniture and equipment	1.0		0.7
	1,068.7		816.9
Less: accumulated depreciation	200.8		152.9
Total property, plant and equipment, net	$	867.9	$	664.0

Depreciation expense totaled $47.8 million, $40.8 million and $38.5 million for the years ended September 30, 2012, 2011 and 2010, respectively. Depletion expense totaled $0.2 million for the years ended September 30, 2012, 2011 and 2010.

Intangible Assets

Intangible assets consisted of the following at September 30, 2012 and 2011, respectively (in millions):



	September 30,
	2012			2011
Customer accounts	$	38.3		$	39.5
(accumulated amortization—customer accounts)	(13.4		)	(12.7		)
Covenants not to compete	—			7.5
(accumulated amortization—covenants not to compete)	—			(7.0		)
Deferred financing	5.2			—
(accumulated amortization—deferred financing costs)	(0.8		)	—
Total intangible assets, net	$	29.3		$	27.3

Amortization and interest expense associated with the above described intangible assets for the years ended September 30, 2012, 2011 and 2010, amounted to $3.3 million, $2.9 million and $3.7 million, respectively.