# 75.34 Units with add-on emission controls.
(a) The owner or operator of an affected unit equipped with add-on SO<sub>2</sub> and/or NO<sub>X</sub> emission controls shall provide substitute data in accordance with paragraphs (a)(1), through (a)(5) of this section for each hour in which quality-assured data from the outlet SO<sub>2</sub> and/or NO<sub>X</sub> monitoring system(s) are not obtained.
(1) The owner or operator may use the missing data substitution procedures specified in §§ 75.31 through 75.33 to provide substitute data for any missing data hour(s) in which the add-on emission controls are documented to be operating properly, as described in the quality assurance/quality control program for the unit, required by section 1 in appendix B of this part. To provide the necessary documentation, the owner or operator shall, for each missing data period, record parametric data to verify the proper operation of the SO<sub>2</sub> or NO<sub>X</sub> add-on emission controls during each hour, as described in paragraph (d) of this section. For any missing data hour(s) in which such parametric data are either not provided or, if provided, do not demonstrate that proper operation of the SO<sub>2</sub> or NO<sub>X</sub> add-on emission controls has been maintained, the owner or operator shall substitute (as applicable) the maximum potential NO<sub>X</sub> concentration (MPC) as defined in section 2.1.2.1 of appendix A to this part, the maximum potential NO<sub>X</sub> emission rate, as defined in § 72.2 of this chapter, or the maximum potential concentration for SO<sub>2</sub>, as defined by section 2.1.1.1. Alternatively, for SO<sub>2</sub> or NO<sub>X</sub>, the owner or operator may substitute, if available, the hourly SO<sub>2</sub> or NO<sub>X</sub> concentration recorded by a certified inlet monitor, in lieu of the MPC. For each hour in which data from an inlet monitor are reported, the owner or operator shall use a method of determination code (MODC) of “22” (see Table 4a in § 75.57). In addition, under § 75.64(c), the designated representative shall submit as part of each electronic quarterly report, a certification statement, verifying the proper operation of the SO<sub>2</sub> or NO<sub>X</sub> add-on emission control for each missing data period in which the missing data procedures of §§ 75.31 through 75.33 were applied; or
(2) This paragraph, (a)(2), applies only to a unit which, as provided in § 75.74(a) or § 75.74(b)(1), reports NO<sub>X</sub> mass emissions on a year-round basis under a state or Federal NO<sub>X</sub> mass emissions reduction program that adopts the emissions monitoring provisions of this part. If the add-on NO<sub>X</sub> emission controls installed on such a unit are operated only during the ozone season or are operated in a more efficient manner during the ozone season than outside the ozone season, the owner or operator may implement the missing data provisions of paragraph (a)(1) of this section in the following alternative manner:
(i) The historical, quality-assured NO<sub>X</sub> emission rate or NO<sub>X</sub> concentration data may be separated into two categories, i.e., data recorded inside the ozone season and data recorded outside the ozone season;
(ii) For the purposes of the missing data lookback periods described under §§ 75.33 (c)(1), (c)(2), (c)(3) and (c)(5) of this section, the substitute data values shall be taken from the appropriate database, depending on the date(s) and hour(s) of the missing data period. That is, if the missing data period occurs inside the ozone season, the ozone season data shall be used to provide substitute data. If the missing data period occurs outside the ozone season, data from outside the ozone season shall be used to provide substitute data.
(iii) A missing data period that begins outside the ozone season and continues into the ozone season shall be considered to be two separate missing data periods, one ending on April 30, hour 23, and the other beginning on May 1, hour 00;
(iv) For missing data hours outside the ozone season, the procedures of § 75.33 may be applied unconditionally, i.e., documentation of the operational status of the emission controls is not required in order to apply the standard missing data routines.
(3) For each missing data hour in which the percent monitor data availability for SO<sub>2</sub> or NO<sub>X</sub>, calculated in accordance with § 75.32, is less than 90.0 percent and is greater than or equal to 80.0 percent; and parametric data establishes that the add-on emission controls were operating properly (*i.e.* within the range of operating parameters provided in the quality assurance/quality control program) during the hour, the owner or operator may:
(i) Replace the maximum SO<sub>2</sub> concentration recorded in the 720 quality-assured monitor operating hours immediately preceding the missing data period, with the maximum controlled SO2 concentration recorded in the previous 720 quality-assured monitor operating hours; or
(ii) Replace the maximum NO<sub>X</sub> concentration(s) or NO<sub>X</sub> emission rate(s) from the appropriate load bin(s) (based on a lookback through the 2,160 quality-assured monitor operating hours immediately preceding the missing data period), with the maximum controlled NO<sub>X</sub> concentration(s) or emission rate(s) from the appropriate load bin(s) in the same 2,160 quality-assured monitor operating hour lookback period.
(4) The designated representative may petition the Administrator under § 75.66 for approval of site-specific parametric monitoring procedure(s) for calculating substitute data for missing SO<sub>2</sub> pollutant concentration, NO<sub>X</sub> pollutant concentration, and NO<sub>X</sub> emission rate data in accordance with the requirements of paragraphs (b) and (c) of this section and appendix C to this part. The owner or operator shall record the data required in appendix C to this part, pursuant to § 75.58(b).
(5) For each missing data hour in which the percent monitor data availability for SO<sub>2</sub> or NO<sub>X</sub>, calculated in accordance with § 75.32, is below 80.0 percent and parametric data establish that the add-on emission controls were operating properly (*i.e.* within the range of operating parameters provided in the quality assurance/quality control program),in lieu of reporting the maximum potential value, the owner or operator may substitute, as applicable, the greater of:
(i) The maximum expected SO<sub>2</sub> concentration or 1.25 times the maximum hourly controlled SO<sub>2</sub> concentration recorded in the previous 720 quality-assured monitor operating hours;
(ii) The maximum expected NO<sub>X</sub> concentration or 1.25 times the maximum hourly controlled NO<sub>X</sub> concentration recorded in the previous 2,160 quality-assured monitor operating hours at the corresponding unit load range or operational bin;
(iii) The maximum controlled hourly NO<sub>X</sub> emission rate (MCR) or 1.25 times the maximum hourly controlled NO<sub>X</sub> emission rate recorded in the previous 2,160 quality-assured monitor operating hours at the corresponding unit load range or operational bin;
(iv) For the purposes of implementing the missing data options in paragraphs (a)(5)(i) through (a)(5)(iii) of this section, the maximum expected SO<sub>2</sub> and NO<sub>X</sub> concentrations shall be determined, respectively, according to sections 2.1.1.2 and 2.1.2.2 of appendix A to this part. The MCR shall be calculated according to the basic procedure described in section 2.1.2.1(b) of appendix A to this part, except that the words “maximum potential NO<sub>X</sub> emission rate (MER)” shall be replaced with the words “maximum controlled NO<sub>X</sub> emission rate (MCR)” and the NO<sub>X</sub> MEC shall be used instead of the NO<sub>X</sub> MPC.
(b) For an affected unit equipped with add-on SO<sub>2</sub> emission controls, the designated representative may petition the Administrator to approve a parametric monitoring procedure, as described in appendix C of this part, for calculating substitute SO<sub>2</sub> concentration data for missing data periods. The owner or operator shall use the procedures in §§ 75.31, 75.33, or 75.34(a) for providing substitute data for missing SO<sub>2</sub> concentration data unless a parametric monitoring procedure has been approved by the Administrator.
(1) Where the monitor data availability is 90.0 percent or more for an outlet SO<sub>2</sub> pollutant concentration monitor, the owner or operator may calculate substitute data using an approved parametric monitoring procedure.
(2) Where the monitor data availability for an outlet SO<sub>2</sub> pollutant concentration monitor is less than 90.0 percent, the owner or operator shall calculate substitute data using the procedures in § 75.34(a) (1) or (2), even if the Administrator has approved a parametric monitoring procedure.
(c) For an affected unit with NO<sub>X</sub> add-on emission controls, the designated representative may petition the Administrator to approve a parametric monitoring procedure, as described in appendix C of this part, in order to calculate substitute NO<sub>X</sub> emission rate data for missing data periods. The owner or operator shall use the procedures in § 75.31 or 75.33 for providing substitute data for missing NO<sub>X</sub> emission rate data prior to receiving the Administrator's approval for a parametric monitoring procedure.
(1) Where monitor data availability for a NO<sub>X</sub> continuous emission monitoring system is 90.0 percent or more, the owner or operator may calculate substitute data using an approved parametric monitoring procedure.
(2) Where monitor data availability for a NO<sub>X</sub> continuous emission monitoring system is less than 90.0 percent, the owner or operator shall calculate substitute data using the procedure in § 75.34(a) (1) or (2), even if the Administrator has approved a parametric monitoring procedure.
(d) In order to implement the options in paragraphs (a)(1), (a)(3) and (a)(5) of this section; and §§ 75.31(c)(3) and 75.72(c)(3), the owner or operator shall keep records of information as described in § 75.58(b)(3) to verify the proper operation of all add-on SO<sub>2</sub> or NO<sub>X</sub> emission controls, during all periods of SO<sub>2</sub> or NO<sub>X</sub> emission missing data. If the owner or operator elects to implement the missing data option in paragraph (a)(2) of this section, the records in § 75.58(b)(3) are required to be kept only for the ozone season. The owner or operator shall document in the quality assurance/quality control (QA/QC) program required by section 1 of appendix B to this part, the parameters monitored and (as applicable) the ranges and combinations of parameters that indicate proper operation of the controls. The owner or operator shall provide the information recorded under § 75.58(b)(3) and the related QA/QC program information to the Administrator, to the EPA Regional Office, or to the appropriate State or local agency, upon request.
[60 FR 26567, May 17, 1995, as amended at 61 FR 59160, Nov. 20, 1996; 64 FR 28604, May 26, 1999; 67 FR 40438, June 12, 2002; 73 FR 4348, Jan. 24, 2008; 76 FR 17312, Mar. 28, 2011]