((a)) ** General exemption due to lack of alternate fuel supply, site limitations, or environmental requirements** After consideration of a petition (and comments thereon) for an exemption for a powerplant from the prohibitions of part A, the Secretary shall, by order, grant an exemption under this subsection for the use of natural gas or petroleum, if he finds that the petitioner has demonstrated that for the period of the proposed exemption, despite diligent good faith efforts—

((1)) it is likely that an adequate and reliable supply of coal or other alternate fuel of the quality necessary to conform with design and operational requirements for use as a primary energy source will not be available to such powerplant at a cost (taking into account associated facilities for the transportation and use of such fuel) which, based upon the best practicable estimates, does not substantially exceed the cost, as determined by rule by the Secretary, of the fuel that would be used as a primary energy source;

((2)) one or more site limitations exist which would ot  permit the location or operation of such a powerplant using coal or any other alternate fuel as a primary energy source; or

((3)) the prohibitions of could not be satisfied without violating applicable environmental requirements.

((b)) ** Temporary exemption based upon future use of synthetic fuels** After consideration of a petition (and comments thereon) for an exemption for a powerplant from the prohibitions of part A, the Secretary shall, by order, grant an exemption under this subsection for the use of natural gas or petroleum, if he finds that the petitioner has demonstrated that—

((1)) the petitioner will comply with the prohibitions of part A by the end of the proposed exemption by the use of a synthetic fuel derived from coal or another alternate fuel; and

((2)) the petitioner is not able to comply with such prohibitions by the use of such synthetic fuel until the end of the proposed exemption.

((c)) **, (d) Repealed. , , **

((e)) ** Duration of temporary exemptions**

((1)) Except as provided in paragraph (2), exemptions under this section for any powerplant may not exceed, taking into account any extension or renewal, 5 years.

((2))

((A)) An exemption under subsection (a)(1) may be granted for a period of more than 5 years, but may not exceed, taking into account any extension or renewal, 10 years.

((B)) An exemption under subsection (b) may be extended beyond the 5-year limit under paragraph (1), but such exemption, so extended, may not exceed 10 years.

((3)) If an exemption is granted for any powerplant before the powerplant is placed in service, the period before it is placed in service shall not be taken into account in computing the 5-year and the 10-year limitations of paragraphs (1) and (2).