Section 97.505 - Retired unit exemption(a)(1) Any CSAPR NOX Ozone Season Group 1 unit that is permanently retired shall be exempt from § 97.506(b) and (c)(1) , § 97.524 , and §§ 97.530 through 97.535 .(2) The exemption under paragraph (a)(1) of this section shall become effective the day on which the CSAPR NOX Ozone Season Group 1 unit is permanently retired. Within 30 days of the unit's permanent retirement, the designated representative shall submit a statement to the Administrator. The statement shall state, in a format prescribed by the Administrator, that the unit was permanently retired on a specified date and will comply with the requirements of paragraph (b) of this section.(b)(1) A unit exempt under paragraph (a) of this section shall not emit any NOX, starting on the date that the exemption takes effect.(2) For a period of 5 years from the date the records are created, the owners and operators of a unit exempt under paragraph (a) of this section shall retain, at the source that includes the unit, records demonstrating that the unit is permanently retired. The 5-year period for keeping records may be extended for cause, at any time before the end of the period, in writing by the Administrator. The owners and operators bear the burden of proof that the unit is permanently retired.(3) The owners and operators and, to the extent applicable, the designated representative of a unit exempt under paragraph (a) of this section shall comply with the requirements of the CSAPR NOX Ozone Season Group 1 Trading Program concerning all periods for which the exemption is not in effect, even if such requirements arise, or must be complied with, after the exemption takes effect.(4) A unit exempt under paragraph (a) of this section shall lose its exemption on the first date on which the unit resumes operation. Such unit shall be treated, for purposes of applying allocation, monitoring, reporting, and recordkeeping requirements under this subpart, as a unit that commences commercial operation on the first date on which the unit resumes operation. 76 FR 48406 , Aug. 8, 2011, as amended at 86 FR 23186 , Apr. 30, 2021