If, at the time of the hearing, the commission shall find that the improvement would be conducive to the public convenience, welfare, benefit or utility, and the cost thereof is not excessive, and no claim shall have been filed for damages, it may adopt the tentative plan as final or may modify the plan, provided said modification will not, to any greater extent than the tentative plan, materially and adversely affect the interests of littoral or riparian owners.
C93, §464A.4