(a) Nitrogen oxides (NOX ) monitoring. The owner or operator of each unit subject to the emission specifications in §117.1105 of this title (relating to Emission Specifications for Reasonably Available Control Technology (RACT)), shall install, calibrate, maintain, and operate a continuous emissions monitoring system (CEMS) or predictive emissions monitoring system (PEMS) to measure NOX on an individual basis.
  (1) Each CEMS or PEMS is subject to the relative accuracy test audit relative accuracy requirements of 40 Code of Federal Regulations (CFR) Part 75, Appendix B, Figure 2, except the concentration options (parts per million by volume (ppmv) and pound per million British thermal units (lb/MMBtu)) do not apply. Each CEMS or PEMS must meet either the relative accuracy percent requirement of 40 CFR Part 75, Appendix B, Figure 2, or an alternative relative accuracy requirement of ± 2.0 ppmv from the reference method mean value.
  (2) Each CEMS or PEMS is subject to the requirements of §117.8110 of this title (relating to Emission Monitoring System Requirements for Utility Electric Generation Sources).
  (3) Each PEMS must predict NOX emissions in the units of the applicable emission limitations of this division and PEMS and fuel flow meters must be used to demonstrate continuous compliance with the emission specifications of this division.
(b) Acid rain peaking units. In lieu of the NOX monitoring requirements in subsection (a) of this section, the owner or operator of each peaking unit as defined in 40 CFR §72.2, may monitor operating parameters for each unit in accordance with 40 CFR Part 75, Appendix E, and calculate NOX emission rates based on those procedures.
(c) Totalizing fuel flow meters. The owner or operator of each unit subject to the emission specifications in §117.1105 of this title and each unit using the exemption in §117.1103(1) of this title (relating to Exemptions) shall install, calibrate, maintain, and operate totalizing fuel flow meters to individually and continuously measure the gas and liquid fuel usage. A computer that collects, sums, and stores electronic data from continuous fuel flow meters is an acceptable totalizer. In lieu of installing a totalizing fuel flow meter on a unit, an owner or operator may opt to assume fuel consumption at maximum design fuel flow rates during hours of the unit's operation.
(d) Run time meters. The owner or operator of a unit using the exemption of §117.1103(2) of this title shall record the operating time hours with an elapsed run time meter.
(e) Loss of exemption. The owner or operator of any unit claimed exempt from the emission specifications of this division using the exemptions in §117.1103(1) or (2) of this title, shall notify the executive director within seven days if the applicable limit is exceeded.
  (1) If the limit is exceeded, the exemption from the emission specifications of this division is permanently withdrawn.
  (2) Within 90 days after loss of the exemption, the owner or operator shall submit a compliance plan detailing a plan to meet the applicable compliance limit as soon as possible, but no later than 24 months after exceeding the limit. The plan must include a schedule of increments of progress for the installation of the required control equipment.
  (3) The schedule is subject to the review and approval of the executive director.
(f) Data used for compliance. The methods required in this section must be used to demonstrate compliance with the emission specifications of §117.1105 of this title and the system cap in §117.1120 of this title (relating to System Cap). For enforcement purposes, the executive director may also use other commission compliance methods to determine whether the unit is in compliance with applicable emission specifications.
  (1) For units complying with the NOX emission specifications of §117.1105 of this title in pounds per million British thermal units (lb/MMBtu) on a rolling 30-day average basis, the rolling 30-day average is calculated for each day that fuel was combusted in the unit, and is the total NOX emissions (in pounds) from the unit for the preceding 30 days that fuel was combusted in the unit, divided by the total heat input (in MMBtu) for the unit during the same 30-day period.
  (2) For any electric generating facility (EGF) complying with the system cap in §117.1120 of this title (relating to System Cap) in pounds per day on a rolling 30-day average basis, the rolling 30-day average is calculated for each day and is the average of the total pounds of NOX emissions per day from all EGFs included in the system cap for the preceding 30 days.
(g) Data Substitution. The missing data procedures specified in 40 CFR Part 75, Subpart D (Missing Data Substitution Procedures) must be used to provide substitute emissions compliance data during periods when the NOX monitor is off-line except as follows.
  (1) A peaking unit, as defined in 40 CFR §72.2, subject to 40 CFR Part 75, Appendix E, may use the missing data procedures specified in 40 CFR Part 75, Appendix E, §2.5 (Missing Data Procedures).
  (2) A PEMS for units not subject to the requirements of 40 CFR Part 75 may use calculations in accordance with §117.8110(b) of this title (relating to Emission Monitoring System Requirements for Utility Electric Generation Sources).

Source Note: The provisions of this §117.1140 adopted to be effective May 16, 2024, 49 TexReg 3347