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19. Provision for Asset Retirement Obligation - Fuel Tanks (Tables)
12 Months Ended
Dec. 31, 2017
Provision For Asset Retirement Obligation - Fuel Tanks Tables  
Changes in the provision for asset retirement obligation
  2017   2016   2015
Initial balance 77,564   74,716   70,802
Additions (new tanks) 537   483   625
Expense with tanks removed (15,432)   (2,785)   (3,949)
Accretion expense 2,105   5,150   7,238
Final balance 64,774   77,564   74,716
           
Current 4,799   4,563   5,232
Non-current 59,975   73,001   69,484