18 CFR §284.9

1. (a)Interruptible transportation availability.
   1. (1)An interstate pipeline that provides firm transportation service under subpart B or G of this part must also offer transportation service on an interruptible basis under that subpart or subparts and separately from any sales service.
   2. (2)An intrastate pipeline that provides transportation service under Subpart C may offer such transportation service on an interruptible basis.
   3. (3)Service on an interruptible basis means that the capacity used to provide the service is subject to a prior claim by another customer or another class of service and receives a lower priority than such other classes of service.
2. (b)The provisions regarding non-discriminatory access, reasonable operational conditions, and limitations contained in § 284.7 (b), (c), and (f) apply to pipelines providing interruptible service under this section.
3. (c)Reservation fee. No reservation fee may be imposed for interruptible service. A pipeline's rate for any transportation service provided under this section may not include any minimum bill provision, minimum take provision, or any other provision that has the effect of guaranteeing revenue.