All using agencies, either by or with the authorization of the head of the department under which the using agency operates, shall file with the City Purchasing Agent detailed requisitions or estimates of their requirements in goods and services in such manner, at such time and for such future periods as the Purchasing Agent shall prescribe.
A.
Unforeseen requirements. A using agency shall not be prevented from filing in the same manner with the Purchasing Agent, at any time, a requisition or estimate for any goods and services the need for which was not foreseen when the detailed estimates were filed.
B.
Revisory power of Purchasing Agent. The City Purchasing Agent shall examine each requisition or estimate and shall have the authority to revise it as to quantity, quality or estimated cost, but revision as to quality shall be in accordance with the standards and specifications established pursuant to this chapter.