Fixed Assets and Asset Retirement Obligations

12 Months Ended

Dec. 31, 2019

Fixed Assets And Asset Retirement Obligations [Abstract]

Fixed Assets and Asset Retirement Obligations

Fixed Assets, Mineral Leaseholds and Asset Retirement Obligations

Fixed Assets

Fixed assets consisted of the following:



	December 31,
	2019			2018
Crude oil pipelines and natural gas pipelines and related assets	$	2,891,489		$	2,918,285
Alkali facilities, machinery, and equipment	591,547			533,924
Onshore facilities, machinery, and equipment	640,376			639,023
Transportation equipment	19,864			20,102
Marine vessels	979,171			951,597
Land, buildings and improvements	238,451			222,242
Office equipment, furniture and fixtures	22,645			20,505
Construction in progress	115,162			94,025
Other	41,891			41,155
Fixed assets, at cost	5,540,596			5,440,858
Less: Accumulated depreciation	(1,246,121		)	(1,023,825		)
Net fixed assets	$	4,294,475		$	4,417,033

Mineral Leaseholds

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



	December 31, 2019			December 31, 2018
Mineral leaseholds	$	566,019		$	566,019
Less: Accumulated depletion	(10,194		)	(5,538		)
Mineral leaseholds, net	$	555,825		$	560,481

Depreciation expense was $295.6 million, $286.0 million and $226.0 million for the years ended December 31, 2019, 2018, and 2017, respectively. Depletion expense was $4.7 million, $4.0 million, and $1.5 million for the years ended December 31, 2019, 2018 and 2017, respectively.

On October 11, 2018, we completed the divestiture of our Powder River Basin midstream assets, included in our Onshore Facilities and Transportation segment, and received total net proceeds of approximately $300 million. This sale resulted in a gain of $38.9 million recorded in Gains on assets sales in the Consolidated Statements of Operations. Additionally, we recorded an impairment expense of $21.2 million on our remaining non-core midstream assets in the Powder River Basin as the carrying value exceeded the fair value in the current market at December 31, 2018. We divested these assets during the fourth quarter of 2019.

During 2018, we also recorded impairment expense of $82.0 million associated with certain of our non-core offshore gas assets in the Gulf of Mexico due to a change in contractual arrangements during the fourth quarter. Included in this amount is the acceleration in timing of the abandonment of one of our offshore hub platforms and pipelines and the write-off of its associated asset retirement obligation assets. The fair value of our assets was determined based on present value techniques.

Asset Retirement Obligations

We record AROs in connection with legal requirements to perform specified retirement activities under contractual arrangements and/or governmental regulations. For any AROs acquired, we record AROs based on the fair value measurement assigned during the preliminary purchase price allocation.

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



December 31, 2017	$	198,187
Accretion expense	10,509
Revisions in timing and estimated costs of AROs	44,319
Settlements	(13,150		)
December 31, 2018	239,865
Accretion expense	9,402
Revisions in timing and estimated costs of AROs	(20,529		)
Settlements	(53,657		)
December 31, 2019	$	175,081

At December 31, 2019 and December 31, 2018, $26.6 million and $67.5 million are included as current in "Accrued liabilities" on our Consolidated Balance Sheets, respectively. Revisions in timing and estimated costs during 2019 and 2018 are primarily attributable to the accelerated timing and revised costs associated with the abandonment of certain of our non-core offshore gas assets in the Gulf of Mexico. The remainder of the ARO liability at each period is included in "Other long-term liabilities" on our Consolidated Balance Sheet.

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



2020	$	8,860
2021	$	8,939
2022	$	9,417
2023	$	10,081
2024	$	10,792

Certain of our unconsolidated affiliates have AROs recorded at December 31, 2019 relating to contractual agreements and regulatory requirements. These amounts are immaterial to our Consolidated Financial Statements.