the increase in interest expense during the year ended december 31 , 2009 versus 2008 is primarily due to the additional debt we assumed as a result of the allied acquisition . interest expense also increased as a result of accreting discounts applied to debt or imputing interest on environmental and risk reserves assumed from allied . the debt we assumed from allied was recorded at fair value as of december 5 , 2008 . we recorded a discount of $ 624