Nothing in this act shall prevent the use of any available federal or state aid or both by the county carrying out one or more of the purposes authorized by this act. The bonds issued under the authority of this act shall be issued and retired in accordance with the provisions of the general bond law except that they shall be retired over a period of not more than twenty (20) years, may be issued in addition to all other bonds authorized to be issued by counties, and no statute limiting the outstanding indebtedness which a county may have shall apply to any bonds issued under the provisions of this act.