### Summary	of	Interagency	Working	Com ments	on	Draft	Language	under EO12866/13563	Interagency	Review.		Subject	to	Further	Policy	Re view.

Environmental Protection Agency (EPA): Draft Guidance

Supplemental Exceptional Events Implementation Guidance

RIN 2060-ZA21

General Comments

1) The draft guidance addresses wildfire events . Has EPA guidance for prescribed fire events that describes the technical pr ocess for such a demonstration under the Exceptional Events Rule? Given the similari ties in how an assessment would likely be done, it might best be contained in th is document instead of elsewhere.

Response: The preamble to the proposed Excepti onal Events Rule revisions explains that the Draft Wildfire Ozone Guidance document is limited to wildfire event types, while also recognizing the technical section of the guidance document (Section 3) may be appropriate for application to prescribed fi re events. The Notice of Proposed Rulemaking (NPRM) invites comment on whether it is necessary to expand the scope of the final guidance, and if so, whether the wildfire ozone guidance document should be expanded to cover other fire types or if a separate document should be developed. Given that the prescribed fire-related elements of the rule revisions are at the propos al stage, we believe that it is appropriate to cove r only wildfire event types with this proposed guidance. We will consider this interagency comment suppor ting the expansion of the scope of this guidance document in combination with any comments received during the public comment period following the Notice of Availab ility for this guidance when determining whether (and in what format) to i ssue prescribed fire guidance.

2) Reviewer recommends clarifying how an air agency would know what Tier their EER demonstration would fall into, specifically whether Tier 2 or Ti er 3 evidence should apply. It is unclear where the line between Tier 2 and Tier 3 is . Thus, this could result in

situations where states must submit under diffe rent tiers although the facts may be similar and potentially creates signifi cant regulatory uncertainty.

Response: The tiered approach proposed in th e guidance document is intended to help air agencies determine the level of evidence that may be appropriate to meet the Exceptional Events Rule’s regulatory re quirements for data exclusion requests. The individual event characteristics, event/monitor relationships, and the typical O 3 concentrations in the area of focus will help determine the appropriate demonstration tier. Additionally, the initial discussions between the submitting air agency and the reviewing EPA regional office will help the air agency determine the appropriate tier for the demonstrat ion. (The Exceptional Events Rule revisions NPRM proposes that these conversations take place before the affected air agency begins developing a ny demonstration.) Specifically, the guidance proposes that events that do not meet the Tier 1 (unique O 3 concentration) or Tier 2 (Q/D

and 99 th percentile or higher O 3 concentration) factors, should pursue a Tier 3 demonstration. However, the appropriate ev idence for a Tier 3 de monstration will be determined on a case-by-case basis. Discu ssions between the air agency and the EPA regional office will be help determine the evid ence to support the Tier 3 demonstration.

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2 We have modified the language in section 3.6 (page 22) to include a reminder of the importance of air agency/EPA regional office discussions:

”As discussed in Section 3.3, air agencies may need additional detail to satisfy the clear causal relationship element for events not meeti ng the Tier 1 or Tier 2 key factors. This

section describes the additional evidence that may be appropriate for inclusion in for

these Tier 3 event demonstrations. The appropriate level of evidence should be discussed between the submitting air agency and the EPA regional office during the Initial

Notification discussions .”

Specific Comments

1) Page 8-9 Bulleted section: Emergency monitoring data and operational smoke forecasts which include model output for the surface ar e a common part of the Wildland Fire Air Quality Response Program and reviewer recommends including this here.

Response: We have added the operational smoke forecasts as a potential piece of evidence on the list on page 8-9:

“Smoke forecasts based on meteorology and bur n conditions; these are often provided as part of the Wildland Air Quality Response Program.”

We have also added text to page 19 of the guidance document (showing fire impacts reach the monitor) to explain that non-regulat ory monitoring data may be used to support the clear causal relationship el ement of the demonstration:

“While fires generate emissions of CO, NO, NO 2 , VOCs, PM 10 , and PM 2.5 , anthropogenic sources, such as from industrial and vehicu lar combustion, also em it these pollutants. Therefore, the air agency should distinguish the difference in th e non-event pollutant behavior ( e.g ., concentration, timing, ratios, and/or spatial patterns) from the behavior during the event impact to more clearly show that the emissions from the fire(s) affected the monitor(s). Evidence from regulatory and non-regulatory ( e.g. , special purpose, emergency) monitors may be us ed to support these analyses. ”

2) Page 13: General Comment on 3.4.2 Trajectory Analys is section: Given the prevalence and ease of use of the HYSPLIT system, re viewer recommends that more detailed guidance on it use be offered in Appendix A.3.

a. As part of that guidance, reviewer recommends an enhanced discussion on selection of meteorological database th at is used for construction of back trajectories. If trajectories are used in areas of highly complex terrain and sourcereceptor relationships are relatively clos e (10’s – 100km), the resolution of the routinely used meteorological databa ses for HYSPLIT may not adequately capture the meteorological conditions which governed source-receptor relationships for a particular event. Careful consider ation should be used when

### Summary	of	Interagency	Working	Com ments	on	Draft	Language	under EO12866/13563	Interagency	Review.		Subject	to	Further	Policy	Re view.

3 selecting meteorological databases, as th ese will largely determine the accuracy of the trajectory for a given event.

Response: We have added the following te xt to page 51 of the guidance document (Appendix 3) to further address the importa nce of meteorological database choice:

“If trajectories are used in areas of hi ghly complex terrain and source-receptor relationships are relatively close (10’s – 100 km), the resolution of some of the routinely used meteorological databases for HYSPL IT may not adequately capture the meteorological conditions that govern source-recep tor relationships for a particular event.

Careful consideration should be used when se lecting meteorological databases, as these will largely determine the accuracy of the traj ectory for a given event. More information on meteorological databases and their appl icability to HYSPLIT can be found at https://ready.arl .noaa.gov/archives.php .”

3) Page 14 and page 21: On sentence: Air agencies could use other trajectory models, such as FLEXPART to demonstrate expected tr ansport. Appendix A3 contains additional information on trajectory analyses. FLEXPART is not a trajectory model, but rather is a full Lagrangian Particle Dispersion Model (LPDM). The companion trajectory model, FLEXTRA, has not been updated in years and is not compatib le with any modern source of meteorological data. Howeve r, FLEXPART itself is a viable tool for establishing an understanding of source-receptor relations hips (SRR). Reviewer recommends that Appendix A.3 be updated to reflect use of inverse or adjoint LPDM methods (FLEXPAR or STILT models). Adjoint methods are more suitable when multiple monitors have been influenced by a single event.

a. References include the following:

i. M. Maione et al.: Estimates of Euro pean emissions of methyl chloroform

. Atmos. Chem. Phys., 14, 9755–9770, 2014

ii. X.L. Pan, et al.: Using Bayesian optimization and FLEXPART tracer

model to evaluate CO emission in East China in springtime. Env. Sci. and Poll. Res., 21, 3873 - 3879, 201

Response: We have removed the explicit me ntion of the FLEXPART model in this version of the guidance document because, as a result of this comment, we are now aware of potential inconsistencies in our description of these analytical tools. Prior to finalizing this guidance we will research the appropriate description and use of FLEXPART or STILT dispersion models for investigating source-receptor relationships and will consider adding information, as appropriate, to the final guidance. In the draft guidance, we have revised the language on page 14 (and again on page 21) to read:

“Air agencies could us e other trajectory models , such as FLEXPART, to demonstrate expected transport. Exceptional events demonstrations using other trajectory models should contain enough background information and detail supporting model application to allow reviewers to thoroughly understand the model and to repr oduce the results if

necessary. ”

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4 4) Page 14 on 3.5: Key Factors of and Suggested Evidence to Include in Tier 2

Demonstrations. Another anal ytical technique overlooked he re which could be used to demonstrate the presence of smoke on a particular date at multiple monitors is the use of receptor modeling techniques such as PMF. EPA Region 7 in 2004 demonstrated that using strength of PMF biomass burning prof iles from either STN data or IMPROVE on dates that coincide with O3 exceedances, coupl ed with use of inverse LPDM techniques can clearly indicate the presence of smoke influence on ozone events. Reviewer recommends that this technique also be in cluded as a possible Tier II analytical technique. EPA Region 7 published a report in 2004 on the analysis of O3 exceedances in the KC metro area in April 2003 and the possi bility of influence from the Flint Hills

fires contribution to these events. Th ese procedures are documented there.

Response: We thank the reviewer for bringi ng the EPA Region 7 report to our attention. The authors of this guidance document were not aware of the report and agree that PMF analyses might be useful in establishing clea r causal relationships be tween fire events and

monitored O 3 concentrations. Prior to finalizing this guidance, we will investigate the use of PMF analysis for fire-related O 3 exceedances and, if appropriate, we will add language to the final guidance document.

5) Page 15 on 3.5.1 : Reviewers support the notion of simp lified tool development for Tier I and Tier II demonstrations, but have general concerns about th e usefulness of Q/d as tool for this purpose. As EPA states, both the a ppropriate ratio of NOx to rVOC and sunlight are necessary for ozone formation. Simple addition of NOx and rVOC emissions is not sufficient to describe Q because the ratio of NOx to rVOC determines whether there is ozone formation. Near the fire, ozone may be consumed rather than generated, and smoke plumes may impede photochemistry. Ev en though Q/d is used in conjunction with

two other indictors within tie r 2, the reviewer does not be lieve that Q/d is a useful surrogate and supports discus sion on another approach. 1

Response: We thank the reviewer for suppor ting the tier-based approach and for recommending an alternative tool. We agree that the Q(NOx+VOC)/D tool is a simplified representation of very complex chemistry, but we believe that it can be used, in combination with high O 3 concentrations, to indicate conditions where O 3 impacts from fires are likely to occur. Ou r investigation of other scre ening tools is ongoing. If we

receive additional information about altern ate approaches during the upcoming public comment period, we will consider changes to the screening tool/key factor. Additionally, air agencies can use results from tools not described in the guidance document to support

their demonstrations.

6) Page 23 on 3.6.4: Reviewer recommends providing be tter references for useful techniques that can use climat ology for ozone events include:

a. Eder, Brian K., Jerry M. Davis, and Pe ter Bloomfield (1993): A Characterization of the Spatiotemporal Variability of N on-Urban Ozone Concentrations Over the Eastern United States. Atmospheric Environment 27A, 2645-2668.

1 http://wrapfets.org/deasco3.cfm

### Summary	of	Interagency	Working	Com ments	on	Draft	Language	under EO12866/13563	Interagency	Review.		Subject	to	Further	Policy	Re view.

5 b. Brian K. Eder, Jerry M. Davis, a nd Peter Bloomfield, 1994: An Automated Classification Scheme Designed to Bette r Elucidate the Dependence of Ozone on Meteorology. J. Appl. Meteor., 33, 1182–1199.

c. B. Anderson, and Davis, M. 2004: Analys is of April 12-13, 2003 Kansas City Ozone Exceedances. EPA Region 7 Technical Report.

Response: We thank the review er for identifying these references, which we have added

as citations in section 3.6.4.

7) Page 27: Reviewer recommends modifying the sentence to state:

a. Note: if a prescribed fire was declared to be a wildfire, then the air agency should supplement the language above with additiona l detail as to the conditions of the prescribed fire that led to the fire ma nager’s decision that the fire should be treated as a wildfire, fo r example if the prescribed fire escaped secure containment lines and required suppression al ong all or part of its boundary or if the prescribed fire escaped as a result of quickly changing weather and no longer

mets meets the resource objectives ( e.g. , smoke impact, flame height).

Response: We have corrected this error.

8) Page 28 on 5.2: Reviewer recommends clarifying or removing the second paragraph as unnecessary in a demonstration. Whether a w ildfire originated under the jurisdiction of an air agency or a state or federal land ma nagement agency is not relevant as the EER

defines wildfire as not reasonabl y controlled or preventable.

Response: We have incorporated the reviewer’s suggested edits.