The governing body of any county notified of the proposed establishment of a sewage system or of the extension of any existing sewage system under § 15.2-2126 is authorized to disapprove the same, if it finds that such sewage system is not capable of serving the proposed number of connections by reason of inadequate pipes, conduits, pumping stations, force mains, or sewage treatment plants or is otherwise inadequate to render the proposed service. If, at the expiration of seventy days from the date on which the applicant appeared before the governing body, such governing body has not disapproved the application, the applicant may proceed with the construction and installation of such sewage system, provided he first gives notice to the chairman of the governing body by registered mail of his intention to proceed.