Iowa Code § 468.47: Evidence — conclusive presumption.

At such hearing, the board may hear evidence both for and against the approval of said report or any portion thereof, but it shall not be competent to show that any of the lands in said district assessed for benefits or against which an apportionment of costs and expenses has been made will not be benefited by such improvement in some degree. Any interested party may be heard in argument in person or by counsel.