Prior to the issuance of any bonds hereunder, and precedent to the inauguration of this program, the following steps shall be taken:
Any such board of supervisors is authorized to employ competent engineers or technical assistants to make necessary preliminary plans and specifications and estimates of cost of the construction of any causeways or bridges or other structures in connection with any proposed project or projects which the board may deem necessary and proper. After said preliminary plans, specifications and estimates of cost have been approved by said board, the same shall be filed in the office of the chancery clerk of such county;
Such board of supervisors shall obtain approval by the proper United States governmental authorities of the building of the proposed project, or projects, with regard to questions of navigation.