70 ILCS 1865/19
Regular meetings of the Board shall be held at least once in each calendar month, the time and place of such meetings to be fixed by the Board. Four members of the Board shall constitute a quorum for the transaction of business. All action of the Board shall be by ordinances or resolution and the affirmative vote of at least 4 members shall be necessary for the adoption of any ordinance or resolution. All such ordinances and resolutions before taking effect shall be approved by the chairman of the Board, and if he approves thereof he shall sign the same, and such as he does not approve he shall return to the Board with his objections thereto in writing at the next regular meeting of the Board occurring after the passage thereof. But in the case the chairman fails to return any ordinance or resolution with his objections thereto by the time aforesaid, he shall be deemed to have approved the same and it shall take effect accordingly. Upon the return of any ordinance or resolution by the chairman with his objections, the vote by which the same was passed shall be reconsidered by the Board, and if upon such reconsideration said ordinance or resolution is passed by the affirmative vote of at least 5 members, it shall go into effect notwithstanding the veto of the chairman. All ordinances, resolutions and all proceedings of the District and all documents and records in its possession shall be public records, and open to public inspection, except such documents and records as are kept or prepared by the Board for use in negotiations, legal actions or proceedings to which the District is a party.
70 ILCS 1865/19