The powers and rights granted to port districts and public agencies by the provisions of this chapter are in addition and supplemental to and not in substitution of the powers and rights heretofore or hereafter granted to such districts and public agencies by any other law or city charter, and no limitations or restrictions or proceedings for the exercise of powers and rights by port districts and public agencies contained in any other laws or city charters shall apply to the exercise of powers and rights granted by the provisions of this chapter, and the provisions of this chapter shall be liberally construed to permit the accomplishment of the purposes hereof.