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Landfill Accounting | 9 Months Ended
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Sep. 30, 2025
Landfill Accounting [Abstract] |
Landfill Accounting | 6.LANDFILL ACCOUNTING At September 30, 2025, the Company’s landfills consisted of 101 owned landfills, five landfills operated under life-of-site operating agreements and seven landfills operated under limited-term operating agreements. The Company’s landfills had site costs with a net book value of $3,333,798 at September 30, 2025. For the Company’s landfills operated under limited-term operating agreements and life-of-site operating agreements, the owner of the property (generally a municipality) usually owns the permit and the Company operates the landfill for a contracted term. Where the contracted term is not the life of the landfill, the property owner is generally responsible for final capping, closure and post-closure obligations. The Company is responsible for all final capping, closure and post-closure liabilities at the landfills it operates under life-of-site operating agreements. The Company’s internal and third-party engineers perform surveys at least annually to estimate the remaining disposal capacity at its landfills. Many of the Company’s existing landfills have the potential for expanded disposal capacity beyond the amount currently permitted. The Company’s landfill depletion rates are based on the remaining disposal capacity, considering both permitted and probable expansion airspace, at the landfills it owns and landfills it operates, but does not own, under life-of-site agreements. The Company’s landfill depletion rate is based on the term of the operating agreement at its operated landfill that has capitalized expenditures. Expansion airspace consists of additional disposal capacity being pursued through means of an expansion that has not yet been permitted. Expansion airspace that meets certain criteria is included in the estimate of total landfill airspace. Based on remaining permitted capacity as of September 30, 2025, and projected annual disposal volumes, the average remaining landfill life for the Company’s owned landfills and landfills operated under life-of-site operating agreements is estimated to be approximately 31 years. As of September 30, 2025, the Company is seeking to expand permitted capacity at six of its owned landfills and considers the achievement of these expansions to be probable. Although the Company cannot be certain that all future expansions will be permitted as designed, the average remaining life, when considering remaining permitted capacity, probable expansion capacity and projected annual disposal volume, of the Company’s owned landfills and landfills operated under life-of-site operating agreements is approximately 33 years. The estimated remaining lives of the Company’s owned landfills and landfills operated under life-of-site operating agreements range from one to several hundred years, with approximately 90% of the projected annual disposal volume from landfills with remaining lives of less than 70 years. During the nine months ended September 30, 2025 and 2024, the Company expensed $197,920 and $207,887, respectively, related to landfill depletion at owned landfills and landfills operated under life-of-site agreements. The Company reserves for estimated final capping, closure and post-closure maintenance obligations at the landfills it owns and landfills it operates under life-of-site operating agreements. The Company calculates the net present value of its final capping, closure and post-closure liabilities by estimating the total obligation in current dollars, inflating the obligation based upon the expected date of the expenditure and discounting the inflated total to its present value using a credit-adjusted risk-free rate. Any changes in expectations that result in an upward revision to the estimated undiscounted cash flows are treated as a new liability and are inflated and discounted at rates reflecting market conditions. Any changes in expectations that result in a downward revision (or no revision) to the estimated undiscounted cash flows result in a liability that is inflated and discounted at rates reflecting the market conditions at the time the cash flows were originally estimated. This policy results in the Company’s final capping, closure and post-closure liabilities being recorded in “layers.” The Company’s discount rate assumption for purposes of computing “layers” for final capping, closure and post-closure liabilities is based on its long-term credit adjusted risk-free rate. The Company’s discount rate assumption for purposes of computing 2025 and 2024 “layers” for final capping, closure and post-closure obligations was 5.50% for both periods. The Company’s long-term inflation rate assumption is 2.75% for each of the years ending December 31, 2025 and 2024. The resulting final capping, closure and post-closure obligations are recorded on the Condensed Consolidated Balance Sheets along with an offsetting addition to site costs which is amortized to depletion expense as the remaining landfill airspace is consumed. Interest is accreted on the recorded liability using the corresponding discount rate. During the nine months ended September 30, 2025 and 2024, the Company expensed $35,793 and $22,768, respectively, related to final capping, closure and post-closure accretion expense. In the event that changes in an estimate for a closure and post-closure liability are associated with a significant change in facts and circumstances at a landfill or a non-operating section of a landfill, corresponding adjustments to recorded liabilities and Impairments and other operating items are made as soon as is practical. The following is a reconciliation of the Company’s final capping, closure and post-closure liability balance from December 31, 2024 to September 30, 2025: ​
​ | ​ | ​ | ​
Final capping, closure and post-closure liability at December 31, 2024 |  | $ | 860,123
Liability adjustments | ​ |  | 37,482
Accretion expense | ​ |  | 35,793
Closure payments | ​ |  | (223,380)
Foreign currency translation adjustment | ​ |  | 2,918
Final capping, closure and post-closure liability at September 30, 2025 | ​ | $ | 712,936
​ Liability adjustments of $37,482 for the nine months ended September 30, 2025, represent non-cash changes to final capping, closure and post-closure liabilities and are recorded on the Condensed Consolidated Balance Sheets along with an offsetting addition to site costs, which is amortized to depletion expense as the remaining landfill airspace is consumed. At September 30, 2025 and December 31, 2024, the current portion of final capping, closure and post-closure liabilities, included in Accrued Liabilities on the Condensed Consolidated Balance Sheets, was $161,230 and $199,735, respectively, and the long-term portion of final capping, closure and post-closure liabilities, included in Other long-term liabilities on the Condensed Consolidated Balance Sheets, was $551,706 and $660,388, respectively. The Company performs its annual review of its cost and capacity estimates in the first quarter of each year. In the event that changes in an estimate for a closure and post-closure liability are associated with a significant change in facts and circumstances at a landfill or a non-operating section of a landfill, corresponding adjustments to recorded liabilities and Impairments and other operating items are made as soon as is practical. At September 30, 2025 and December 31, 2024, $9,771 and $8,852, respectively, of the Company’s restricted cash balance and $79,900 and $77,855, respectively, of the Company’s restricted investments balance was for purposes of securing its performance of future final capping, closure and post-closure obligations.

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- Definition The entire disclosure for an asset retirement obligation and the associated long-lived asset. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481850/410-20-50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org/410-20/tableOfContent Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -SubTopic 20 -Topic 410 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481850/410-20-50-2 + Details
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