This excerpt taken from the PBR 6-K filed Mar 31, 2009.
3.2 Decrease in recoverable value of assets (Impairment)
The CPC 01 defines procedures aimed at ensuring that the companys assets are not recorded in the accounting at a value higher than that liable to be recovered through use or sale. If there is clear evidence that assets are valued at a value that is not recoverable in the future, the company must immediately recognize the devaluation through the recording of a provision for losses.
The evaluations are made considering the smallest cash generating unit, when applicable, calculated based on the future cash flow model, discounted by the interest rates before taxes.
The Company already adopted this procedure, however, the losses that are recorded as provisions, according to the current procedure, may be reversed if there are indications that provide clear evidence of this recovery.