A detailed engineer’s estimate of the construction cost of the project, given under oath, shall be submitted to the purchasing division. The contract shall be let to the lowest responsible bidder, if any, whose bid does not exceed the estimate, taking into consideration conformity with the specifications, terms of delivery and other conditions imposed in the invitation for bids. (Ord. 79 § 1, 12-1-92; C.O. 17 § 13, 1-30-71.)