3. Property and Equipment

Property and equipment consist of the following (in thousands):

	Estimated Useful
	Life (Years)		September 30, 2017			December 31, 2016
Land		—	$	875		$	875
Buildings	39-40			17,389			17,389
Building improvements	5-40			34,957			34,957
Machinery and equipment	3-15			62,768			62,992
Furniture, fixtures and office equipment	5-10			3,556			3,556
Computer equipment and software		3		8,531			8,531
Construction in progress		—		—			202
				128,076			128,502
Less accumulated depreciation				(100,702	)		(99,575	)
Total property and equipment, net			$	27,374		$	28,927

Depreciation expense related to property and equipment for the three and nine months ended September 30, 2017 and 2016 was as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Depreciation expense	$	454	$	597	$	1,350	$	1,775

Management evaluated certain equipment that was not yet in service and determined that since the equipment was not being used and there was no current estimated date for installation and therefore no future cash flows associated with the equipment, a write-down of construction in progress of approximately $0.1 million and $0.2 million was recorded during the three and nine months ended September 30, 2017, respectively. An impairment of $0.7 million was charged to the individual asset groups for the nine months ended September 30, 2016.

On January 6, 2017, the Company and Rexford Industrial Realty, L.P. (“Rexford”) entered into an Agreement of Purchase and Sale and Joint Escrow Instructions (the “Purchase Agreement”), pursuant to which the Company agreed to sell and Rexford agreed to purchase certain parcels of real estate owned by the Company in Valencia, California and certain related improvements, personal property, equipment, supplies and fixtures (collectively, the “Property”) for $17.3 million. This asset in the amount of $16.7 million was classified as held for sale as of December 31, 2016. The sale and purchase of the Property for $17.3 million pursuant to the terms of the Purchase Agreement, as amended, was completed on February 17, 2017. Net proceeds were $16.7 million after deducting broker’s commission and other fees of approximately $0.6 million paid by the Company. Net proceeds received approximated the carrying value of the asset held for sale.