6. Fixed Assets and Asset Retirement Obligations

Fixed Assets

Fixed assets consisted of the following:

		0000000			0000000
	December 31,
	2011			2010
Land, buildings and improvements	$	13,140		$	14,335
Pipelines and related assets		167,865			156,805
Machinery and equipment		46,233			29,433
Transportation equipment		21,732			29,249
Marine vessels		262,216			122,992
Office equipment, furniture and fixtures		3,778			3,742
Construction in progress		14,236			4,493
Other		11,938			12,290

Subtotal		541,138			373,339
Accumulated depreciation		(124,213	)		(108,283	)

Total	$	416,925		$	265,056

Depreciation expense was $27.3 million, $22.5 million and $25.2 million for the years ended December 31, 2011, 2010, and 2009, respectively.

Asset Retirement Obligations

A reconciliation of our liability for asset retirement obligations is as follows:


Asset retirement obligations as of December 31, 2009	$	4,838
Accretion expense		341

Asset retirement obligations as of December 31, 2010		5,179
Liabilities incurred and assumed in the current period		349
Accretion expense		372

Asset retirement obligations as of December 31, 2011	$	5,900