Section 503.9 - Use of mixtures-general requirement for certain permanent exemptions(a)Criteria. To qualify for a permanent exemption, except in the case of an exemption for fuel mixtures, section 213(a)(1) of the Act requires a demonstration that the use of a mixture of natural gas and petroleum and an alternate fuel for which an exemption under 10 CFR 503.38 (Fuel mixtures) would be available, would not be economically or technically feasible.(b)Evidence. The petition must include the following evidence in order to make the demonstration required by this section: (1) Duly executed certifications to the criteria set forth in paragraph (a) of this section; and(2) Exhibits containing the basis for the certifications submitted under this section (including those factual and analytical materials deemed by the petitioner to be sufficient to support its certifications to this general requirement.)46 FR 59903, Dec. 7, 1981, as amended at 54 FR 52894, Dec. 22, 1989 In meeting this general requirement, OFE will require a petitioner to examine only mixtures of oil and coal and natural gas and coal, or, where petitioner wishes to examine an additional or substitute mixture, such other alternate fuels as OFE and the petitioner agree are reasonable to petitioner's circumstances.