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Property, Plant, and Equipment
3 Months Ended
Mar. 31, 2024
Property, Plant and Equipment [Abstract]  
Property, Plant, and Equipment
8. PROPERTY, PLANT, AND EQUIPMENT

A summary of the historical cost of property, plant, and equipment is as follows:
thousandsEstimated Useful LifeMarch 31,
2024
December 31,
2023
LandN/A$12,442 $12,504 
Gathering systems – pipelines30 years5,935,848 5,890,607 
Gathering systems – compressors15 years2,602,110 2,553,602 
Processing complexes and treating facilities25 years3,775,379 3,745,332 
Transportation pipeline and equipment
3 to 48 years
259,227 259,314 
Produced-water disposal systems
20 years1,103,001 1,098,616 
Assets under constructionN/A560,417 479,368 
Other
3 to 40 years
909,211 906,088 
Total property, plant, and equipment15,157,635 14,945,431 
Less accumulated depreciation5,432,343 5,290,415 
Net property, plant, and equipment$9,725,292 $9,655,016 

“Assets under construction” represents property that is not yet placed into productive service as of the respective balance sheet date and is excluded from capitalized costs being depreciated.
Long-lived asset impairments. During the three months ended March 31, 2023, the Partnership recognized a long-lived asset impairment of $52.1 million for assets located in the Rockies due to a reduction in estimated future cash flows resulting from a contract termination notice received in the first quarter of 2023. This asset was impaired to its estimated fair value of $22.8 million. The fair value was measured using the income approach and Level-3 fair value inputs. The income approach was based on the Partnership’s projected future EBITDA and free cash flows, which requires significant assumptions including, among others, future throughput volumes based on current expectations of producer activity and operating costs.