All work or other public improvement which is: (i) not to be paid for in whole or in part by special assessment or special taxation; (ii) does not involve a contract with the federal government or an agency thereof; and (iii) the expense of which will exceed ten thousand dollars ($10,000.00), and all purchases, orders or contracts for supplies, materials, equipment or contractual services not involved in public works projects, when the estimated cost thereof shall exceed ten thousand dollars ($10,000.00), shall be purchased from the lowest responsible bidder, after due notice inviting bids, unless competitive bidding is waived by a vote of two-thirds of the aldermen then holding office on the city council. (Ord. 977 § 1 (part), 1992: prior code § 2-4-8(B))