v3.24.0.1
Landfill and Environmental Costs
 12 Months Ended
Dec. 31, 2023
Environmental Remediation Obligations [Abstract]  
Landfill and Environmental Costs LANDFILL AND ENVIRONMENTAL COSTS
As of December 31, 2023, we owned or operated 207 active landfills with total available disposal capacity estimated to be 5.1 billion in-place cubic yards. Additionally, we have post-closure responsibility for 126 closed landfills.
Accrued Landfill and Environmental Costs
A summary of our accrued landfill and environmental liabilities as of December 31 follows:
20232022
Landfill final capping, closure and post-closure liabilities$1,937.2 $1,786.4 
Environmental remediation485.4 487.5 
Total accrued landfill and environmental costs2,422.6 2,273.9 
Less: current portion(141.6)(132.6)
Long-term portion$2,281.0 $2,141.3 
Final Capping, Closure and Post-Closure Costs
The following table summarizes the activity in our asset retirement obligation liabilities, which includes liabilities for final capping, closure and post-closure, for the years ended December 31:
202320222021
Asset retirement obligation liabilities, beginning of year$1,786.4 $1,507.3 $1,346.4 
Non-cash additions61.4 60.1 47.2 
Acquisitions, net of divestitures and other adjustments12.3 173.5 32.1 
Asset retirement obligation adjustments40.1 20.0 58.5 
Payments(60.8)(64.6)(59.6)
Accretion expense97.9 89.6 82.7 
Foreign currency translation(0.1)0.5 — 
Asset retirement obligation liabilities, end of year1,937.2 1,786.4 1,507.3 
Less: Current portion(72.4)(75.2)(68.4)
Long-term portion$1,864.8 $1,711.2 $1,438.9 
We review annually, in the fourth quarter, and update as necessary, our estimates of asset retirement obligation liabilities. As a result, we increased amortization expense by $5.2 million, $5.8 million and $6.9 million for the years ended December 31, 2023, 2022 and 2021, respectively, primarily related to changes in estimates and assumptions concerning the anticipated waste flow, cost and timing of future final capping, closure and post-closure activities.
The expected future payments for final capping, closure and post-closure as of December 31, 2023 follows: 
2024$72.4 
202596.5 
202691.9 
2027116.7 
2028120.9 
Thereafter7,020.0 
$7,518.4 
The estimated remaining final capping, closure and post-closure expenditures presented above are not inflated and not discounted and reflect the total estimated future payments for liabilities which include those incurred and recorded as of December 31, 2023 as well as liabilities yet to be incurred over the remaining life of our landfills.
Environmental Remediation Liabilities
We accrue for remediation costs when they become probable and can be reasonably estimated. There can sometimes be a range of reasonable estimates of the costs associated with remediation of a site. In these cases, we use the amount within the range that constitutes our best estimate. If no amount within the range appears to be a better estimate than any other, we use the amount that is at the low end of such range. It is reasonably possible that we will need to adjust the liabilities recorded for
remediation to reflect the effects of new or additional information, to the extent such information impacts the costs, timing or duration of the required actions. If we used the reasonably possible high ends of our ranges, our aggregate potential remediation liability as of December 31, 2023 would be approximately $375 million higher than the amounts recorded. Future changes in our estimates of the cost, timing or duration of the required actions could have a material adverse effect on our consolidated financial position, results of operations and cash flows.
The following table summarizes the activity in our environmental remediation liabilities for the years ended December 31:
202320222021
Environmental remediation liabilities, beginning of year$487.5 $454.9 $462.8 
Net additions charged to expense2.0 2.9 0.5 
Payments(54.9)(54.7)(57.1)
Accretion expense (non-cash interest expense)18.2 17.3 17.1 
Acquisitions, net of divestitures and other adjustments32.6 67.1 31.6 
Environmental remediation liabilities, end of year485.4 487.5 454.9 
Less: current portion(69.2)(57.4)(56.1)
Long-term portion$416.2 $430.1 $398.8 
The expected undiscounted future payments for remediation costs as of December 31, 2023 follows:
2024$69.2 
202565.3 
202654.7 
202742.9 
202829.6 
Thereafter281.0 
$542.7 
The following is a discussion of certain of our significant remediation matters:
Bridgeton Landfill. During the year ended December 31, 2023, we paid $13.6 million related to management and monitoring of the remediation area for our closed Bridgeton Landfill in Missouri. We continue to work with state and federal regulatory agencies on our remediation efforts. From time to time, this may require us to modify our future operating timeline and procedures, which could result in changes to our expected liability. As of December 31, 2023, the remediation liability recorded for this site was $73.6 million, of which approximately $13.2 million is expected to be paid during 2024. We believe the remaining reasonably possible high end of our range would be approximately $141 million higher than the amount recorded as of December 31, 2023.
West Lake Landfill Superfund Site. Our subsidiary Bridgeton Landfill, LLC is one of several currently designated Potentially Responsible Parties for the West Lake Landfill Superfund site (West Lake) in Missouri. On September 27, 2018, the United States Environmental Protection Agency (EPA) issued a Record of Decision Amendment for West Lake that includes a total undiscounted cost estimate of $229 million over a four to five year design and construction timeline. On March 11, 2019, the EPA issued special notice letters under the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) to Bridgeton Landfill, LLC and the other currently designated Potentially Responsible Parties to initiate negotiations to implement the remedy. At this time we are neither able to predict the final design of that remedy, nor estimate how much of the future response costs of the site our subsidiary may agree or be required to pay. During any subsequent administrative proceedings or litigation, our subsidiary will vigorously contest liability for the costs of remediating radiologically-impacted materials generated on behalf of the federal government during the Manhattan Project and delivered to the site by an Atomic Energy Commission licensee and its subcontractor. Currently, we believe we are adequately reserved for our expected remediation liability. However, subsequent events related to remedy design, divisibility, or allocation may require us to modify our expected remediation liability.