text: In accordance with SFAS 143, changes due to revision of the estimates of the amount or timing of the 
  original undiscounted cash Öows used to record a liability are recognized by increasing or decreasing the 
  carrying amount of the asset retirement obligation liability and the carrying amount of the related asset. 
  Upward revisions in the amount of undiscounted estimated cash Öows used to record a liability must be 
  discounted using the credit-adjusted, risk-free rate in eÅect at the time of the change. Downward revisions in 
  the amount of undiscounted estimated cash Öows used to record a liability must be discounted using the 
  credit-adjusted, risk-free rate that existed when the original liability was recognized. 
  
  The Company reviews its calculations with respect to landÑll asset retirement obligations at least 
  annually. If there is a signiÑcant change in the facts and circumstances related to a landÑll during the year, the 
  Company will review its calculations for the landÑll as soon as practical after the signiÑcant change has 
  occurred. 
  
  The following table summarizes the actual activity in the Company's asset retirement obligation liabilities 
  for the years ended December 31, 2004 and 2003 and the pro forma activity for the years ended December 31, 
  2003 and 2002 assuming SFAS 143 were eÅective as of January 1, 2002: 