When the Boards of 2 or more counties, through mutual agreement, wish to join to effectuate any part or all of this Act, they shall make written request to the Director, setting forth the geographical area and the Sections of this Act involved. Whenever, as ascertained from investigation, hearing, or otherwise, the Director determines it is advisable that these counties form a District, he may designate and establish such District. A District Board shall be formed and shall effectuate this Act as set forth for an individual county.