Nothing herein is intended to be a substitute for any other method or system for financing of projects, particularly those in section 5-101 of article 29 of the Annotated Code of Maryland, as amended, it being intended to provide for a supplementary source of funds where the scheduled construction has been determined to be needed by the county council for the public purposes of this article. Nothing in this chapter authorizes the county council to construct or maintain sewer systems. Assessments levied in an assessment district under this chapter shall be used only for financing sewer systems within that district or related to the district or the system therein. (1971 L.M.C., ch. 1, § 1.)