v2.3.0.15
ASSET RETIREMENT OBLIGATION (Tables)
9 Months Ended
Sep. 30, 2011
ASSET RETIREMENT OBLIGATION 
Schedule of changes to asset retirement obligations
 
  Three months ended   Nine months ended  
 
  September 30, 2011   September 30, 2010   September 30, 2011   September 30, 2010  

Asset retirement obligation—beginning of period

  $ 9,860   $ 8,981   $ 9,478   $ 8,619  

Changes in estimated obligations

    (287 )       (287 )   10  

Accretion of discount

    184     176     566     528  
                   

Total asset retirement obligation—end of period

  $ 9,757   $ 9,157   $ 9,757   $ 9,157