
	June 30, 2025			December 31, 2024			Estimated Useful Lives (In Years)
Gathering systems	$	11,845.5		$	11,575.0		5 to 20
Processing and fractionation facilities		10,037.1			9,543.3		5 to 25
Terminaling and storage facilities		1,550.0			1,469.1		5 to 25
Transportation assets		4,436.5			4,131.5		10 to 50
Other property, plant and equipment		572.8			537.7		3 to 25
Land		209.2			198.6		—
Construction in progress		2,003.1			1,702.9		—
Finance lease right-of-use assets		434.8			401.3		5 to 14
Property, plant and equipment		31,089.0			29,559.4
Accumulated depreciation, amortization and impairment		(12,068.7	)		(11,496.7	)
Property, plant and equipment, net	$	19,020.3		$	18,062.7

Intangible assets		4,378.0			4,378.0		10 to 20
Accumulated amortization and impairment		(2,563.6	)		(2,400.6	)
Intangible assets, net	$	1,814.4		$	1,977.4

During the three and six months ended June 30, 2025, depreciation expense was $292.2 million and $578.3 million, respectively. During the three and six months ended June 30, 2024, depreciation expense was $255.3 million and $502.5 million, respectively.

Intangible assets consist of customer contracts and customer relationships acquired in prior business combinations. The fair values of these acquired intangible assets were determined at the dates of acquisition based on the present values of estimated future cash flows. Amortization expense attributable to these assets is recorded over the periods in which we benefit from services provided to customers.

During the three and six months ended June 30, 2025, amortization expense was $81.5 million and $163.0 million, respectively. During the three and six months ended June 30, 2024, amortization expense was $93.3 million and $186.6 million, respectively.

The estimated annual amortization expense for intangible assets is approximately $326.0 million, $279.8 million, $252.2 million, $234.0 million and $214.1 million for each of the years 2025 through 2029, respectively.