Fixed Assets and Mineral Leaseholds

Fixed Assets

Fixed assets consisted of the following:



	September 30, 2017			December 31, 2016
Crude oil pipelines and natural gas pipelines and related assets	$	3,004,618		$	2,901,202
Alkali facilities, machinery, and equipment	617,878			—
Onshore facilities, machinery, and equipment	757,874			427,658
Transportation equipment	17,995			17,543
Marine vessels	898,582			863,199
Land, buildings and improvements	103,774			55,712
Office equipment, furniture and fixtures	9,681			9,654
Construction in progress	58,069			440,225
Other	53,821			48,203
Fixed assets, at cost	5,522,292			4,763,396
Less: Accumulated depreciation	(681,900		)	(548,532		)
Net fixed assets	$	4,840,392		$	4,214,864

Mineral Leaseholds

Our Mineral Leaseholds, as relating to our recently acquired Alkali Business, consist of the following:



	September 30, 2017
Mineral leaseholds	623,137
Less: Accumulated depletion	(381		)
Mineral leaseholds, net	$	622,756

Our depreciation and depletion expense for the periods presented was as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Depreciation expense	$	57,117	$	46,909	$	157,438	$	135,428
Depletion Expense	381		—		381		—

Asset Retirement Obligations

We record AROs in connection with legal requirements to perform specified retirement activities under contractual arrangements and/or governmental regulations.

The following table presents information regarding our AROs since December 31, 2016:



ARO liability balance, December 31, 2016	$	213,726
Accretion expense	8,257
Change in estimate	7,875
Acquisitions	2,444
Divestitures	(7,649		)
Settlements	(21,252		)
Other	240
ARO liability balance, September 30, 2017	$	203,641

Of the ARO balances disclosed above, $19.3 million and $22.4 million is included as current in "Accrued liabilities" on our Unaudited Condensed Consolidated Balance Sheet as of September 30, 2017 and December 31, 2016, respectively. The remainder of the ARO liability as of September 30, 2017 and December 31, 2016 is included in "Other long-term liabilities" on our Unaudited Condensed Consolidated Balance Sheet.

With respect to our AROs, the following table presents our forecast of accretion expense for the periods indicated:



Remainder of	2017	$	2,741
	2018	$	9,686
	2019	$	8,782
	2020	$	9,378
	2021	$	10,014

Certain of our unconsolidated affiliates have AROs recorded at September 30, 2017 relating to contractual agreements and regulatory requirements. These amounts are immaterial to our Consolidated Financial Statements.