The offer comes more than two years after the Geyserville-area casino operated by the Dry Creek Rancheria Band of Pomo Indians defaulted on interest payments on $165 million owed to bond holders. River Rock Casino, which took a financial blow after the bigger, glitzier Graton Resort and Casino opened nearly three years ago, is offering to restructure its overdue debt, but in a deal that would pay bondholders a fraction of what they are owed.