This proposed rule would revise the definitions, monitoring, recordkeeping, and reporting requirements associated with the allowance trading programs (e.g., Acid Rain, Cross State Air Pollution Rule etc.) implemented by EPA in conjunction with States. EPA periodically revises these regulations in order to update test methods incorporated by reference, correct known errors, clarify, and otherwise modify provisions where necessary to ensure that the requirements remain current, and provide flexibility. The proposed rule would also update or remove other provisions of the Acid Rain Program that applied only in earlier phases of the program.