With regard to all contracts or purchases not in excess of the base amount of $18,500, subject to adjustment under section 11903.1 (relating to adjustments to base amount based on Consumer Price Index for All Urban Consumers), the following shall apply:
(1) The purchases or contracts shall be evidenced by note or memorandum in writing, signed by the officer or employee making the purchase or contract.
(2) Council, or the officer designated by council, shall approve all purchases or contracts, except council need not approve those purchases or contracts within the category of small or routine purchases or incidental expenses, as defined by ordinance.