An oil and gas operator is preparing its annual air and GHG reports. Operating hours for one compressor were never recorded in June. A required gas composition analysis was not completed, and the annual workbook contains an August throughput estimate that has not been reviewed since the quarterly reporting check.
The examples below draw on EPA's Greenhouse Gas Reporting Program. State air emissions inventories may require different methods for handling the same missing records.
Missing reporting data usually shows up in a few concrete ways: operating hours that were never recorded, a laboratory analysis that was not completed or that arrived without the stream, units, or dates the method expects, activity data that stops short of the reporting period, or an engineering estimate already in the annual workbook without the records, assumptions, and calculation steps another reviewer would need to reproduce it. These problems may not be apparent from the completed annual emissions total.
If the problem is a historian export whose tag, units, or intervals cannot be trusted, that is covered in SCADA data for emissions reporting in oil and gas.
Consider the missing compressor operating hours for June. The unit ran, but the hours are not in the file. Those monthly records may be how the team builds the annual hours the compressor spent in each operating mode. For a centrifugal compressor calculated from as-found measurements, that annual mode time is the figure the calculation uses. The calculation does not ask for a separate June total, and it does not name zero or the previous June as the substitute. The annual mode time is the input in equation W-21.
The team first needs to determine whether the missing June records affect a parameter required by the reporting method or an intermediate calculation in the workbook. The calculation can specify a substitute for missing activity data and say nothing about a figure that exists only in the workbook.
If the missing figure is activity data and no other provision addresses it, the rule calls for a best available estimate from applicable process data. Run logs and other operating records may show when the compressor operated or was down, providing evidence for the estimate. Entering zero reports that the compressor spent no time in the mode. That figure still has to follow the method and the process data, not the fact that June's record is blank. The activity-data provision is § 98.235(g). How the selected calculation uses it is covered in EPA Subpart W.
Consider a facility that missed a required quarterly gas composition sample for an acid gas removal vent. The unit operated during the quarter, but no valid sample was collected. For this calculation, Subpart W specifies how the missing measurement must be handled. The substitute is the average of the quality-assured values immediately before and after the gap. If the later value is not available by the end of the reporting year, the earlier value may be used. That sampling requirement, where no continuous analyzer is available, is in § 98.233(d)(6), and the substitute is in § 98.235(b).
Other calculations handle a missing composition differently. A missed annual sample has to be repeated, and a sample collected in a later year cannot be used for that later year's emissions (§ 98.235(c)). Where the method already calls for the most recent available analysis, that analysis is the required input, not a fill-in for a sample that was never taken (§ 98.233(u)(2)(i)). The rule does not set a maximum age for that analysis.
The August throughput estimate is already inside the annual total. An analyst entered it so a quarterly check could be completed. The team has to determine whether this throughput figure is activity data the calculation requires. If it is, and no other provision controls, the same activity-data rule calls for a best available estimate from available process data. Missing fuel-use records in a Subpart C calculation are also a best available estimate, and the procedures used have to be documented and retained (§ 98.35(b)(2)). Completing the quarterly check does not establish which of those situations this estimate is, or whether the process data behind it are still available.
The analyst who prepared the August estimate considers it reasonable, because the quarterly check had to be finished. The environmental lead has not accepted it. The workbook does not show which provision allows an estimate for this throughput parameter, or which process data were used. The submission approver needs to know whether the estimate has been reviewed.
The preparer can recommend the estimate. The lead can withhold acceptance until the provision and the supporting records are identified. If the estimate has not received the internal review the operator requires, it should not be treated as an accepted reporting value. That review is the operator's control. Greenhouse Gas Reporting Program recordkeeping does not require a named approver, and the approval does not change the substitute the applicable provision specifies.
When a Subpart W missing-data procedure is used, the file has to show the emission source type, the circumstance that created the gap, the provision that applies, the calculation or analysis used to develop the substitute, and the substitute value (§ 98.237(f)). For an engineering estimate, the same recordkeeping section also requires the inputs and outputs and an explanation of how company records or the estimate were used. An approval record alone does not document the source data, assumptions, or calculation used to produce the estimate.
The reviewer needs enough supporting information to reconstruct the figure: which months of throughput were unavailable, which process data were used and what they showed, the assumptions, and the calculation steps. The name of the person who accepted the estimate can sit in the same file. That name is an internal control, not part of the required missing-data record.
What a verifier expects to see with a reported emissions figure, beyond this calculation record, is covered in emissions assurance and verification in oil and gas.
Before submission, the reporting team needs to confirm which missing-data procedure applies, calculate the substitute accordingly, and retain the required supporting records. An internal exception log does not replace those steps.
For a Greenhouse Gas Reporting Program report, the submission includes information on the missing-data procedures that were used (§ 98.236(bb)). For a quarterly measurement, that report uses the number of quarters a procedure was used. That disclosure is not a requirement of every air or GHG program.
An unresolved August estimate remains a reporting issue at the deadline when the file still lacks the provision that allows the estimate and the analysis that produced it. How an open exception is carried across the reporting program, including when more than one report uses the same activity data, is part of running an in-house compliance reporting program.
The workbook is sufficient when the reported figure follows the applicable provision and another reviewer can follow the process data through the calculation steps. The existing workbook and the files around it are enough when the team can consistently keep the calculation records, the source data, and the approvals together for the facilities it reports.
The issue is likely to recur when the calculation basis exists only in overwritten cells or in emails that cannot be retrieved. When the workbook has become the place that holds the calculations, the reviews, and the supporting records, that threshold is covered in when spreadsheets stop working for emissions management.
For teams managing these decisions across multiple facilities or reporting periods, keeping source records, calculation methods, and review history together can reduce the work required to reconstruct an estimate or resolve a missing parameter. A reporting platform can hold those records with the calculation. It does not determine what the method allows. Teams evaluating a platform for that work can use the emissions reporting software guide.
Validere keeps a calculation traceable to its operational source and the methodology behind it. The reporting team still determines which substitute the applicable provision permits and whether the supporting records are sufficient. See how Validere supports regulatory air and GHG reporting.
Not simply because the June record is missing. The reported annual mode hours have to follow the applicable method and the process data for that mode. Subpart W does not treat a blank June as zero, and it does not name the previous June as the substitute. A best available estimate can be zero when the process data show the compressor spent no time in the mode.
No. An internal flag records that the sample or the activity record is absent. The parameter is ready when the applicable provision specifies the substitute and the record for that substitute is in the file. Greenhouse Gas Reporting Program reports include the missing-data procedures that were used. Other programs may not.
The person the operator has authorized to accept the figure for that calculation. That person may be neither the analyst who prepared the estimate nor the person who signs the report. The approval is an internal control. It is not part of the required missing-data record, and it does not change the substitute the provision specifies.
No. The total can include a substitute under a missing-data provision, a gas analysis the method already requires, or a best available estimate. An estimate still needs the record the applicable provision requires.