D.C. Mun. Regs. tit. 27, § 2104
2104.1 When ordering from a single-award schedule, the contracting officer shall place orders directly with the schedule contractor at the price shown in the schedule.
2104.2 Except as provided in §2104.3, when ordering from a multiple-award schedule, the contracting officer shall place orders with the schedule contractor offering the lowest delivered price available.
2104.3 The contracting officer shall justify any order over five hundred dollars ($500) per line item placed at other than the lowest price. Justification for ordering a higher priced item may be based on any of the following considerations:
(a) Delivery time in terms of actual need that cannot be met by a contractor offering a lower price;
(b) Specific or unusual requirements, such as differences in performance characteristics;
(c) Compatibility with existing equipment or systems; or
(d) Trade-in considerations that favor a higher priced item and produce the lowest net cost.
SOURCE: Final Rulemaking published at 35 DCR 1518 (February 26, 1988).