N.J. Stat. Ann. § 40:65-7

In any case in which the owner or owners of the real estate affected are required to bear the whole cost of the improvement after the passage of the ordinance therefor, and notice given as in sections 40:65-2 to 40:65-5 of this Title directed, the owner of any real estate affected by such improvement shall fail to make such improvement as required by the ordinance, or in any case in which the whole cost of said improvement is not to be borne by the owner or owners of the real estate affected thereby, the governing body may cause the improvement to be made under supervision of the proper municipal officer, or may award a contract or contracts therefor.