(a) If you demonstrate continuous compliance using a CEMS for measuring SO2 emissions, excess emissions are defined as the applicable averaging period, either 4-operating-hour or 30-operating-day, during which the average SO2 emissions from your stationary combustion turbine measured by the CEMS exceeds the applicable SO2 emissions standard specified in § 60.4330a as determined using the procedures specified in this section that apply to your stationary combustion turbine.

(b) You must install, calibrate, maintain, and operate a CEMS for measuring SO2 concentrations and either O2 or CO2 concentrations at the outlet of your stationary combustion turbine, and record the output of the system.

(c) The 1-hour average SO2 emissions rate measured by a CEMS must be expressed in ng/J or lb/MMBtu heat input and must be used to calculate the average emissions rate under § 60.4330a.

(d) You must use the procedures for installation, evaluation, and operation of the CEMS as specified in § 60.13 and paragraphs (d)(1) through (3) of this section.

(1) Each CEMS must be operated according to the applicable procedures under Performance Specifications 1, 2, and 3 in appendix B to this part;

(2) Quarterly accuracy determinations and daily calibration drift tests must be performed according to Procedure 1 in appendix F to this part; and

(3) The span value of the SO2 CEMS at the outlet from the SO2 control device (or outlet of the stationary combustion turbine if no SO2 control device is used) must be 125 percent of either the highest applicable standard or highest potential SO2 emissions rate of the fuel combusted. Alternatively, SO2 span values determined according to section 2.1.1 in appendix A to part 75 of this chapter may be used.

(e) If you have installed and certified a SO2 CEMS that meets the requirements of part 75 of this chapter, the Administrator or delegated authority can approve that only quality assured data from the CEMS must be used to identify excess emissions under this subpart. You must report periods where the missing data substitution procedures in subpart D of part 75 are applied as monitoring system downtime in the excess emissions and monitoring performance report required under § 60.7(c).

(f) All required fuel flow rate, steam flow rate, temperature, pressure, and megawatt data must be reduced to hourly averages.

(g) Calculate the hourly average SO2 emissions rate, in units of the emissions standard under § 60.4330a, using lb/MMBtu for units complying with the input-based standard or using equation 1 to paragraph (g)(1) of this section for units complying with the output-based standard:

(1) For simple cycle operation:

Equation 1 to Paragraph (g)(1) Where: E = Hourly SO2 emissions rate, in lb/MWh; (SO2)h = Average hourly SO2 emissions rate, in lb/MMBtu; Q = Hourly heat input rate to the stationary combustion turbine, in MMBtu, measured using the fuel flow meter(s), e.g., calculated using Equation D-15a in appendix D to part 75 of this chapter, an O2 or CO2 CEMS and a stack flow monitor, or the methodologies in appendix F to part 75 of this chapter; and P = Gross or net energy output of the stationary combustion turbine in MWh.

(2) The gross or net energy output is calculated as the sum of the total electrical and mechanical energy generated by the stationary combustion turbine; the additional electrical or mechanical energy (if any) generated by the steam turbine following the heat recovery steam generating unit; the total useful thermal energy output that is not used to generate additional electricity or mechanical output, expressed in equivalent MWh, minus the auxiliary load as calculated using equations 2 and 3 to this paragraph (g)(2); and any auxiliary load.

Equation 2 to Paragraph (g)(2) Where: P = Gross energy output of the stationary combustion turbine system in MWh; (Pe)t = Electrical or mechanical energy output of the stationary combustion turbine in MWh; (Pe)c = Electrical or mechanical energy output (if any) of the steam turbine in MWh; PeA = Electric energy used for any auxiliary loads in MWh; Ps = Useful thermal energy of the steam, measured relative to ISO conditions, not used to generate additional electric or mechanical output, in MWh; Po = Other useful heat recovery, measured relative to ISO conditions, not used for steam generation or performance enhancement of the stationary combustion turbine; and T = Electric Transmission and Distribution Factor. Equal to 0.95 for CHP combustion turbine where at least 20.0 percent of the total gross useful energy output consists of electric or direct mechanical output and 20.0 percent of the total gross useful energy output consists of useful thermal output on an annual basis. Equal to 1.0 for all other combustion turbines. Equation 3 to Paragraph (g)(2) Where: Ps = Useful thermal energy of the steam, measured relative to ISO conditions, not used to generate additional electric or mechanical output, in MWh; Qm = Measured steam flow rate in lb; H = Enthalpy of the steam at measured temperature and pressure relative to ISO conditions, in Btu/lb; and 3.413 × 10 6 = Conversion factor from Btu to MWh.

(3) For mechanical drive applications complying with the output-based standard, use equation 4 to this paragraph (g)(3):

Equation 4 to Paragraph (g)(3) Where: E = SO2 emissions rate in lb/MWh; (SO2)m = SO2 emissions rate in lb/h; BL = Manufacturer's base load rating of turbine, in MW; and AL = Actual load as a percentage of the base load rating.

(h) For each stationary combustion turbine demonstrating compliance on a heat input-based emissions standard, excess SO2 emissions are determined on a 4-operating-hour averaging period basis using the SO2 CEMS data and procedures specified in paragraphs (i)(1) and (2) of this section and as applicable to the SO2 emission standard.

(1) For each 4-operating-hour period, compute the 4-operating-hour rolling average SO2 emissions as the heat input weighted average of the hourly average of SO2 emissions for a given operating hour and the 3 operating hours preceding that operating hour using the applicable equation in paragraph (i)(2) of this section. Calculate a 4-operating-hour rolling average SO2 emissions rate for any 4-operating-hour period when you have valid CEMS data for at least 3 of those hours (e.g., a valid 4-operating-hour rolling average SO2 emissions rate cannot be calculated if 1 or more continuous monitors was out-of-control for the entire hour for more than 1 hour during the 4-operating-hour period).

(2) If you elect to comply with the applicable heat input-based emissions rate standard, calculate both the 4-operating-hour rolling average SO2 emissions rate and the applicable 4-operating-hour rolling average SO2 emission standard using equation 5 to this paragraph (h)(2).

Equation 5 to Paragraph (h)(2) Where: E = 4-operating-hour rolling average SO2 emissions (lb/MMBtu or ng/J); Ei = Hourly average SO2 emissions rate or emissions standard for operating hour “i” (lb/MMBtu or ng/J); and Qi = Total heat input to stationary combustion turbine for operating hour “i” (MMBtu or J as appropriate).

(i) For each combustion turbine demonstrating compliance on an output-based standard, you must determine excess emissions on a 30-operating-day rolling average basis. The measured emissions rate is the SO2 emissions measured by the CEMS for a given operating day and the 29 operating days preceding that day. Once each operating day, calculate a new 30-operating-day average measured emissions rate using all hourly average values based on non-out-of-control SO2 emission data for all operating hours during the previous 30-operating-day operating period. Report any 30-operating-day periods for which you have less than 90 percent data availability as monitor downtime. Calculate both the 30-operating-day rolling average SO2 emissions rate and the applicable 30-operating-day rolling average SO2 emissions standard using equation 6 to this paragraph (i).

Equation 6 to Paragraph (i) Where: E = 30-operating-day average SO2 measured emissions rate (lb/MWh or ng/J); Ei = Hourly average SO2 measured emissions rate for non-out-of-control operating hour “i” (lb/MMBtu or ng/J); Qi = Total heat input to stationary combustion turbine for non-out-of-control operating hour “i” (MMBtu or J as appropriate); Pi = Total gross energy output from stationary combustion turbine for non-out-of-control operating hour “i” (MWh or J); and n = Total number of non-out-of-control operating hours in the 30-operating-day period.

(j) At a minimum, non-out-of-control CEMS hourly averages shall be obtained for 90 percent of all operating hours on a 30-operating-day rolling average basis.