The board, as corporate authority of a forest preserve district, shall have power to pass and enforce all necessary ordinances, rules and regulations for the management of the property and conduct of the business of such district. The president of such board shall have power to appoint a secretary and an assistant secretary, and treasurer and an assistant treasurer and such other officers and such employees as may be necessary, all of whom, excepting the treasurer and attorneys, shall be under civil service rules and regulations, as provided in Section 17 of this Act. The assistant secretary and assistant treasurer shall perform the duties of the secretary and treasurer, respectively, in case of death of said officers or when said officers are unable to perform the duties of their respective offices because of absence or inability to act. All contracts for supplies, material or work involving an expenditure by forest preserve districts in excess of $30,000 shall be let to the lowest responsible bidder, after due advertisement, excepting work requiring personal confidence or necessary supplies under the control of monopolies, where competitive bidding is impossible, or as otherwise provided in the Forest Preserve District and Conservation District Design-Build Authorization Act. Contracts for supplies, material or work involving an expenditure of $30,000 or less may be let without advertising for bids, but whenever practicable, at least 3 competitive bids shall be obtained before letting such contract. Notwithstanding the provisions of this Section, a forest preserve district may establish procedures to comply with State and federal regulations concerning affirmative action and the use of small businesses or businesses owned by minorities or women in construction and procurement contracts. All contracts for supplies, material or work shall be signed by the president of the board or by any such other officer as the board in its discretion may designate.
     Salaries of employees shall be fixed by ordinance.