Upon receiving the report and recommendations of the Harbor Commission, the board of supervisors shall consider and determine the feasibility of the project or projects submitted, may call upon the commission for further surveys and reports and shall determine (1) what harbor or harbors, and by what specific project or projects, or parts thereof, it will be in the interest of the county to improve, develop, or protect, (2) for which thereof, if any, moneys should be provided by the issuance of bonds of the county and the amount of bonds required to be issued and sold therefor, and (3) for which thereof, if any, moneys should be raised by the levy of a special tax at a specified rate over a specified number of years not exceeding 20 years.