In order to establish efficient procedures for the purchase of supplies, equipment and services; to secure for the City supplies, equipment and services at the lowest competitive cost commensurate with quality needed and with due consideration to disposability; to exercise positive financial control over purchases; to clearly define authority for the purchasing functions; to assure the quality of purchases; and to buy without favor or prejudice, a purchasing system is adopted and shall control the procedure for all purchases except as otherwise provided by law. (Ord. 2483 § 1 (part), 1983).