23 C.F.R. § 172.9
(a) Contract types. The contracting agency shall use the following types of contracts:
(3) On-call or indefinite delivery/indefinite quantity (IDIQ). A contract for the performance of services for a number of projects, under task or work orders issued on an as-needed or on-call basis, for an established contract period. The procurement of services to be performed under on-call or IDIQ contracts shall follow either competitive negotiation or small purchase procurement procedures, as specified in § 172.7. The solicitation and contract provisions shall address the following requirements:
(iv) If multiple consultants are to be selected and multiple on-call or IDIQ contracts awarded through a single solicitation for specific services:
(B) Specify the procedures the contracting agency will use in competing and awarding task or work orders among the selected, qualified consultants. Task or work orders shall not be competed and awarded among the selected, qualified consultants on the basis of costs under on-call or IDIQ contracts for services procured with competitive negotiation procedures. Under competitive negotiation procurement, each specific task or work order shall be awarded to the selected, qualified consultants:
(1) Through an additional qualifications-based selection procedure, which may include, but does not require, a formal RFP in accordance with § 172.5(a)(1)(ii); or
(2) On a regional basis whereby the State is divided into regions and consultants are selected to provide on-call or IDIQ services for an assigned region(s) identified within the solicitation.
(b) Payment methods.
(c) Contract provisions.
(1) All contracts and subcontracts shall include the following provisions, either by reference or by physical incorporation into the language of each contract or subcontract, as applicable:
(d) Contract administration and monitoring—(1) Responsible charge. A full-time, public employee of the contracting agency qualified to ensure that the work delivered under contract is complete, accurate, and consistent with the terms, conditions, and specifications of the contract shall be in responsible charge of each contract or project. While an independent consultant may be procured to serve in a program or project management support role, as specified in § 172.7(b)(5), or to provide technical assistance in review and acceptance of engineering and design related services performed and products developed by other consultants, the contracting agency shall designate a public employee as being in responsible charge. A public employee may serve in responsible charge of multiple projects and contracting agencies may use multiple public employees to fulfill monitoring responsibilities. The term responsible charge is intended to be applied only in the context defined within this regulation. It may or may not correspond to its usage in State laws regulating the licensure and/or conduct of professional engineers. The public employee's responsibilities shall include:
(e) Contract modification.
(5) For any additional engineering and design related services outside of the scope of work established in the original request for proposal, a contracting agency shall: