Property and Equipment

The following is a summary of property and equipment at December 31, 2018 and December 31, 2017:



	December 31, 2018			December 31, 2017
Automobiles and trucks	$	1,709		$	1,940
Building and improvements	43,628			38,062
Construction equipment	161,113			166,203
Vessels and other equipment	90,217			85,113
Office equipment	8,061			8,039
	304,728			299,357
Less: accumulated depreciation	(195,373		)	(191,407		)
Net book value of depreciable assets	109,355			107,950
Construction in progress	2,785			245
Land	35,863			38,083
	$	148,003		$	146,278

At December 31, 2018, the Company has $9.2 million of assets, net of accumulated depreciation, under capital leases which are reflected in the above table.

For the years ended December 31, 2018, 2017 and 2016, depreciation expense was $28.4 million, $24.8 million and $26.9 million, respectively. Substantially all depreciation expense is included in the cost of contract revenue in the Company’s Consolidated Statements of Operations. Substantially all of the assets of the Company are pledged as collateral under the Company's Credit Agreement (as defined in Note 12).

Substantially all of the Company’s long-lived assets are located in the United States.

The Company reviews property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. Assets to be disposed of are separately presented in the balance sheet and reported at the lower of the carrying amount or the fair value, less the costs to sell, and are no longer depreciated. Approximately $6.4 million were classified as held for sale on the Company's Consolidated Balance Sheet at December 31, 2016. During the year ended December 31, 2017, approximately $5.4 million of these assets were sold for cash of $4.5 million. The difference of $0.9 million is classified as a loss on the sale of assets on the Consolidated Statements of Operations. The remaining assets held for sale of $1.0 million was classified as a total loss as a result of Hurricane Harvey. Insurance claims of approximately $0.9 million were received in the fourth quarter of 2017. The difference of $0.1 million is classified as a loss on disposal of assets on the Consolidated Statements of Operations. No assets remained as held for sale on the Company's Consolidated Balance Sheet at December 31, 2017 or December 31, 2018.