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Do the changes regarding monitor downtime in the MATS reporting revisions that became effective on 9/9/2020 mean that all downtime is now considered a deviation?

No, for MATS reporting purposes, certain situations can be a downtime event without being a deviation.  While it does not affect a unit's compliance status with respect to any emission limit, operating limit or work practice standard, the new revisions do treat any downtime that is associated with a monitoring system malfunction or out-of-control period as a deviation from the monitoring requirements of the rule.

63.10020 – paragraph (b) calls out the requirement to collect data from the monitoring systems at all times that the EGU is operating.

(b) You must operate the monitoring system and collect data at all required intervals at all times that the affected EGU is operating, except for required monitoring system quality assurance or quality control activities, including, as applicable, calibration checks and required zero and span adjustments, and any scheduled maintenance as defined in your site-specific monitoring plan. You are required to affect monitoring system repairs in response to monitoring system malfunctions and to return the monitoring system to operation as expeditiously as practicable.

Paragraph (d) explains that some downtime events are considered to be deviations while other downtime events are not deviations, if they qualify.

(d) Periods of monitoring system malfunctions or monitoring system out-of-control periods, repairs associated with monitoring system malfunctions or monitoring system out-of-control periods and required monitoring system quality assurance or quality control activities excluding zero and span checks must be reported as time the monitor was inoperative (downtime) under 63.10(c). Failure to collect required quality-assured data during monitoring system malfunctions, monitoring system out-of-control periods, or repairs associated with monitoring system malfunctions or monitoring system out-of-control periods is a deviation from the monitoring requirements.

A downtime event has occurred but is not deviation if the failure to collect the required quality-assured data is due to a non-monitoring malfunction, such as performing routine maintenance work. This routine maintenance work must be specified or listed in the Site Specific Monitoring Plan (SSMP). Another example of a “non-monitoring equipment malfunction” would be a power failure. Or in a rare case, a sample line becomes frozen in wintertime. The key is the fact that there was not a failed QA/QC check and that the maintenance work was defined previously in the SSMP.

How do I report monitoring system downtime/deviation events?

The reporting requirements will change in 2024.  But, for now, 63.10031(d) suggests that the deviation reporting is addressed by the excess emissions and downtime reporting defined under 63.10 and included in the current MATS semi-annual compliance reports.

63.10031(d) Excess emissions and deviation reporting. For EGUs whose owners or operators rely on a CMS to comply with an emissions or operating limit, the semiannual compliance reports described in paragraph (c) of this section must include the excess emissions and monitor downtime summary report described in 40 CFR 63.10(e)(3)(vi). However, starting with the first calendar quarter of 2024, reporting of the information under 40 CFR 63.10(e)(3)(vi) (and under paragraph (e)(3)(v), if the applicable excess emissions and/or monitor downtime threshold is exceeded) is discontinued for all CMS, and you must, instead, include in the quarterly compliance reports described in paragraph (g) of this section the applicable data elements in section 13 of appendix E to this subpart for any “deviation” (as defined in 40 CFR 63.10042 and elsewhere in this subpart) that occurred during the calendar quarter. If there were no deviations, you must include a statement to that effect in the quarterly compliance report.

The rule even suggest that the information from the MATS semi-annual compliance reports could be used to satisfy the requirement to report all deviations as part of your Title V semi-annual monitoring report required under Parts 70 and 71:

63.10031(e) Each affected source that has obtained a title V operating permit pursuant to part 70 or part 71 of this chapter must report all deviations as defined in this subpart in the semiannual monitoring report required by 40 CFR 70.6(a)(3)(iii)(A) or 40 CFR 71.6(a)(3)(iii)(A). If an affected source submits a semiannual compliance report pursuant to paragraphs (c) and (d) of this section, or two quarterly compliance reports covering the appropriate calendar half pursuant to paragraph (g) of this section, along with, or as part of, the semiannual monitoring report required by 40 CFR 70.6(a)(3)(iii)(A) or 40 CFR 71.6(a)(3)(iii)(A), and the compliance report(s) includes all required information concerning deviations from any emission limit, operating limit, or work practice requirement in this subpart, submission of the compliance report(s) satisfies any obligation to report the same deviations in the semiannual monitoring report. Submission of the compliance report(s) does not otherwise affect any obligation the affected source may have to report deviations from permit requirements to the permit authority.

Jon Konings

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