10. Long-Lived Asset Impairment

We review long-lived assets, including property, plant and equipment and identifiable intangibles that are being amortized, for impairment whenever events or changes in circumstances, including the removal of compressor units from our active fleet, indicate that the carrying amount of an asset may not be recoverable.

During the three and six months ended June 30, 2017 and 2016, we reviewed the future deployment of our idle compression assets for units that were not of the type, configuration, condition, make or model that are cost efficient to maintain and operate. Based on these reviews, we determined that certain idle compressor units would be retired from the active fleet. The retirement of these units from the active fleet triggered a review of these assets for impairment, and as a result of our review, we recorded an asset impairment to reduce the book value of each unit to its estimated fair value. The fair value of each unit was estimated based on either the expected net sale proceeds compared to other fleet units we recently sold and/or a review of other units recently offered for sale by third parties, or the estimated component value of the equipment we plan to use.

In connection with our review of our idle compression assets during the three and six months ended June 30, 2017 and 2016, we evaluated for impairment idle units that had been culled from our fleet in prior years and were available for sale. Based upon that review, we reduced the expected proceeds from disposition for certain of the remaining units and recorded additional impairment to reduce the book value of each unit to its estimated fair value.

The following table presents the results of our impairment review for the three and six months ended June 30, 2017 and 2016:



	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Idle compressor units retired from the active fleet	60		130		140		210
Horsepower of idle compressor units retired from the active fleet	23,000		39,000		51,000		72,000
Impairment recorded on idle compressor units retired from the active fleet (in thousands)	$	5,508	$	10,733	$	13,753	$	20,593
Additional impairment recorded on available-for-sale compressor units previously culled (in thousands)	$	—	$	3,075	$	—	$	3,075