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COMMITMENTS AND CONTINGENCIES - Schedule of Environmental Liability Associated with Southbridge Landfill (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Ending balance | $ 5,747 |
Southbridge Landfill |  |
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Beginning balance | 5,173 | $ 5,936
Accretion expense | 124 | 0
Obligations incurred | 0 | 152
Obligations settled | (701) | (915)
Ending balance | $ 4,596 | $ 5,173

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