No owner of any dock or wharf property on the said avenue shall extend the same into the channel of the river beyond the present limits thereof, or to the wharf line now established by ordinance, unless a full and sufficient release of damages to the said city caused, or to be caused by the widening of said avenue as aforesaid, shall have been first filed in the office of and approved by the city solicitor: Provided, That in case such damages shall have been already assessed and paid to such owner prior to such extension, then the damages so paid, with interest, shall be first refunded to said city.
53 P.S. § 16858