Whenever the owner or owners, or lessee or lessees, of any wharf, pier, or bulkhead shall fail to keep and maintain the adjoining dock or docks cleaned and free from obstruction, it shall be lawful for the President of the Commissioners, upon default for thirty days after the service of notice on such owner or owners, lessee or lessees, to clean or cause said dock or docks to be cleaned and freed from obstructions, and to apportion the expense thereof among the owner or owners, lessee or lessees, of the wharves, piers, and bulkheads adjoining such dock or docks, in proportion to the extent of their wharves, piers, or bulkheads having the privilege of use of such dock or docks; and to collect the cost and expense of the same by filing liens therefor, in the name of the Commonwealth of Pennsylvania, and issuing process thereupon as is provided by law in the case of liens filed for work done by a municipal corporation; and all liens for the said work shall be filed by the Attorney General of the Commonwealth, and shall have the same force and effect as in the case of liens for municipal work under existing laws: Provided, That, for the purposes of this section, the Commissioners shall not have jurisdiction within any city of the first class.