The owner or lessee of private wharves, piers and bulkheads within the municipality shall at all times keep and maintain the adjoining dock or docks clean and free from obstructions, and the municipality may, upon default for thirty days after service of notice upon any such owner or lessee, cause said dock or docks to be cleaned and freed from obstructions, and apportion the cost thereof among the owner, owners, lessee and lessees of the wharves, piers and bulkheads adjoining such dock or docks in proportion to the extent that their wharves, piers or bulkheads have the privilege of the use of such dock or docks. The cost so apportioned shall be a lien upon the property to the same extent and enforced and collected as liens for assessments for local improvements are enforced and collected.