Fixed Assets, Mineral Leaseholds, and Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2019

Fixed assets, net consisted of the following:



	September 30, 2019			December 31, 2018
Crude oil pipelines and natural gas pipelines and related assets	$	2,922,029		$	2,918,285
Alkali facilities, machinery, and equipment	563,654			533,924
Onshore facilities, machinery, and equipment	626,492			639,023
Transportation equipment	19,484			20,102
Marine vessels	969,432			951,597
Land, buildings and improvements	225,334			222,242
Office equipment, furniture and fixtures	20,889			20,505
Construction in progress	132,229			94,025
Other	41,891			41,155
Fixed assets, at cost	5,521,434			5,440,858
Less: Accumulated depreciation	(1,212,062		)	(1,023,825		)
Net fixed assets	$	4,309,372		$	4,417,033

Our Mineral Leaseholds, relating to our 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,
	2019		2018		2019		2018
Depreciation expense	$	77,228	$	85,282	$	222,106	$	224,546
Depletion expense	1,204		722		3,488		2,913

The following table presents information regarding our AROs since December 31, 2018:



ARO liability balance, December 31, 2018	$	239,865
Accretion expense	6,825
Changes in estimate	(14,377		)
Settlements	(36,028		)
ARO liability balance, September 30, 2019	$	196,285

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