The board of directors of the authority shall appoint an executive director who shall not be a member of the board and who shall serve at the pleasure of the board and receive such compensation as shall be fixed by the board. He shall be the chief administrative officer of the authority and shall direct and supervise administrative affairs and technical activities in accordance with the directives of the board. He shall approve all accounts for salaries, allowable expenses of the authority or of any employee or consultant thereof, and expenses incidental to the operation of the authority. He shall perform such other duties as may be directed by the board in carrying out the purposes of this chapter. The executive director and all other employees of the authority shall be exempt from the classified service. The executive director shall attend all meetings of the board, keep a record of the proceedings of the authority and shall maintain and be custodian of all books, documents and papers filed with the authority and of the minute book or journal of the authority and of its official seal. He may cause copies to be made of all minutes and other records and documents of the authority and may give certificates under the official seal of the authority to the effect that such copies are true copies, and all persons dealing with the authority may rely upon such certificates.