Fixed Assets and Mineral Leaseholds (Tables)

9 Months Ended

Sep. 30, 2018

Fixed assets consisted of the following:



	September 30, 2018			December 31, 2017
Crude oil pipelines and natural gas pipelines and related assets	$	2,900,469		$	3,028,657
Alkali facilities, machinery, and equipment	515,226			497,601
Onshore facilities, machinery, and equipment	638,726			692,364
Transportation equipment	20,352			21,483
Marine vessels	946,377			918,953
Land, buildings and improvements	220,823			223,186
Office equipment, furniture and fixtures	18,898			18,112
Construction in progress	97,313			151,768
Other	47,800			48,891
Fixed assets, at cost	5,405,984			5,601,015
Less: Accumulated depreciation	(882,833		)	(734,986		)
Net fixed assets	$	4,523,151		$	4,866,029

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

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



	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Depreciation expense	$	85,282	$	57,117	$	224,546	$	157,438
Depletion expense	722		381		2,913		381

The following table presents information regarding our AROs since December 31, 2017



ARO liability balance, December 31, 2017	$	198,187
Accretion expense	7,437
Changes in estimate	18,913
Settlements	(9,481		)
ARO liability balance, September 30, 2018	$	215,056

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