No expenditure for improvement of property in an industrial development district, other than the expense of preparing and submitting a plan of improvement shall be made by a port district, and no property shall be acquired by it therefor except as provided for hereinbefore until it has been made a part of the comprehensive scheme of harbor improvements and industrial developments or amendments thereto.

That said comprehensive scheme or amendments thereto shall provide for the development or redevelopment of those marginal lands acquired and a provision for the continuing of the land uses which are hereby declared to constitute public uses and the purposes for which public moneys may be advanced and provide property acquired.