§  75.31 Initial missing data procedures.

(a) During the first 720 quality-assured monitor operating hours following initial certification (i.e., the date and time at which quality assured data begins to be recorded by the CEMS) of an SO2 pollutant concentration monitor, or a CO2 pollutant concentration monitor (or an O2 monitor used to determine CO2 concentration in accordance with appendix F to this part), or an O2 or CO2 diluent monitor used to calculate heat input or a moisture monitoring system, and during the first 2,160 quality-assured monitor operating hours following initial certification of a flow monitor, or a NOX-diluent monitoring system, or a NOX concentration monitoring system used to determine NOX mass emissions, the owner or operator shall provide substitute data required under this subpart according to the procedures in paragraphs (b) and (c) of this section. The owner or operator of a unit shall use these procedures for no longer than three years (26,280 clock hours) following initial certification.

(b) SO2, CO2, or O2 concentration data and moisture data. For each hour of missing SO2 or CO2 pollutant concentration data (including CO2 data converted from O2 data using the procedures in appendix F of this part), or missing O2 or CO2 diluent concentration data used to calculate heat input, or missing moisture data, the owner or operator shall calculate the substitute data as follows:

(1) Whenever prior quality-assured data exist, the owner or operator shall substitute, by means of the data acquisition and handling system, for each hour of missing data, the average of the hourly SO2, CO2 or O2 concentrations or moisture percentages recorded by a certified monitor for the unit operating hour immediately before and the unit operating hour immediately after the missing data period.

(2) Whenever no prior quality assured SO2, CO2 or O2 concentration data or moisture data exist, the owner or operator shall substitute, as applicable, for each hour of missing data, the maximum potential SO2 concentration or the maximum potential CO2 concentration or the minimum potential O2 concentration or (unless Equation 19-3, 19-4 or 19-8 in Method 19 in appendix A to part 60 of this chapter is used to determine NOX emission rate) the minimum potential moisture percentage, as specified, respectively, in sections 2.1.1.1, 2.1.3.1, 2.1.3.2 and 2.1.5 of appendix A to this part. If Equation 19-3, 19-4 or 19-8 in Method 19 in appendix A to part 60 of this chapter is used to determine NOX emission rate, substitute the maximum potential moisture percentage, as specified in section 2.1.6 of appendix A to this part.

(c) Volumetric flow and NOX emission rate or NOX concentration data. For each hour of missing volumetric flow rate data, NOX emission rate data or NOX concentration data used to determine NOX mass emissions:

(1) Whenever prior quality-assured data exist in the load range corresponding to the operating load at the time the missing data period occurred, the owner or operator shall substitute, by means of the automated data acquisition and handling system, for each hour of missing data, the average hourly flow rate or NOX emission rate or NOX concentration recorded by a certified monitoring system. The average flow rate (or NOX emission rate or NOX concentration) shall be the arithmetic average of all data in the corresponding load range as determined using the procedure in appendix C to this part.

(2) Whenever no prior quality-assured flow or NOX emission rate or NOX concentration data exist for the corresponding load range, the owner or operator shall substitute, for each hour of missing data, the average hourly flow rate or the average hourly NOX emission rate or NOX concentration at the next higher level load range for which quality-assured data are available.

(3) Whenever no prior quality assured flow rate or NOX emission rate or NOX concentration data exist for the corresponding load range, or any higher load range, the owner or operator shall, as applicable, substitute, for each hour of missing data, the maximum potential flow rate as specified in section 2.1.4.1 of appendix A to this part or shall substitute the maximum potential NOX emission rate or the maximum potential NOX concentration, as specified in section 2.1.2.1 of appendix A to this part.

[64 FR 28601, May 26, 1999]