UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION IX 75 Hawthorne Street San Francisco, CA 94105·3901 

## AUG 12 

## 2010
VIA EMAIL AND U.S. MAIL
Jim Rexroad Avenal Power Center, LLC One Allen Center 500 Dallas Street, Level 31 Houston, TX77002
DearMr. Rexroad:
Thank you for the letters ofJune 28, 2010 and July 13,2010from your counsel, Jeffrey Holmstead, to Ms. Julie Walters, counsel for EPA Region 9, and Ms. Stephanie Talbert, counsel with the U.S. Department ofJustice. These letters provide the Avenal Power Center LLC's (Avenal orAPC) response to EPA's letter dated June 15,2010concerning Avenal's Supplemental N02 Air Quality Impact Analysis for the Avenal Energy Project (AEP) dated May 13,2010and submitted to EPA on May 14,2010. Avenal's supplemental analysis was intended to address the I-hournational ambient air quality standard (NAAQS) for nitrogen dioxide (N02), whichbecame effective April 12, 2010, for the AEP. EPA'sJune 15,2010letter stated that EPA had determined that significant additional information must beprovided by Avenal for EPAto evaluate whetheremissions from the AEP will cause orcontribute to ambient air pollution in excess ofthe Federal I-hourN02 standard. The EPA letterprovided further detail about 10 areas in Avenal's May 13,2010submittal in which EPAhad determined that additional information was necessary. Avenal's June 28, 2010 and July 13,2010letters indicate that Avenal believes that all necessary information has been submitted to EPA to demonstrate compliance with the I-hourN02 NAAQS. We disagree. While some ofthe requested information has been provided, we believe the submittals from Avenal to date do not contain all the information necessary for an acceptable I-hourN02 NAAQS compliance analysis. The text in Attachment 1below provides a detailed explanation ofwhy the information submittedbyAvenal to date is not adequate to demonstrate compliance with the I-hour N02 NAAQS and describes what additional information would be necessary for EPA to evaluate Avenal's analysis.
Avenal's June 28 and July 13 letters also reiterate Avenal's position that the I-hourN02 NAAQS does not apply to the AEP, butthat Avenal has provided additional modeling information for that standard in an effort to obtain its PSD permit in a timely manner. We certainlyunderstand Avenal's frustration with having to address the Federal I-hour N02

Printed on Recycled PaptrJim Rexroad Page 2

standard at this stage in the PSDpermit decisionmaking process, but we have nevertheless determined that Avenal must provide information to demonstrate that emissions from the AEP will not cause orcontribute to air pollution in excess ofthe I-hour NAAQS for N02, as required byCAA 165(a)(3). EPA interprets the Clean"Air Act and applicable regulations to require that PSD permits issued under 40 CPR 52.21 on or afterthe effective date ofthe Federal I-hour N02 standard, April 12,2010, must contain a demonstration that the source's allowable emissions will not cause or contribute to a violation ofthat standard. SeeApplicability of the Federal Prevention of SignificantDeterioration PermitRequirements to New andRevisedNational AmbientAir Quality Standards, authored by Stephen D. Page, Director, EPA Office ofAir Quality Planning and Standards, dated April 1,2010.

We note that in initial discussions with Avenal regarding the I-hour N02 NAAQS, Avenal indicated that it would work with EPA to develop a modeling protocol for this project appropriate for addressing the I-hourN02 NAAQS, and EPA agreed to this approach. However, Avenal chose to forgo obtaining EPA's input on the protocol and instead provided written submittals, starting with the May 13,2010 submittal, that contain information that we believe is inadequate or incomplete to demonstrate the AEP's compliance with the I-hourN02 NAAQS, as described in ourJune 15,2010letter and in Attachment 1below. EPA requested several weeks ago to meet with Avenal's technical staffto discuss in further detail EPA's comments on Avenal's I-hourN02NAAQS analysis as well as options for addressing those comments; however, Avenal representatives stated that Avenal did not wish to have such a discussion with EPA at that time. Weremain willing to have this technical discussion, and we encourage Avenal to contact us to discuss in detail Avenal's proposed approach for addressing EPA's remaining concerns, described below, prior to submitting additional information to us.
We would also like to note that Avenal's submittals to date pertaining to the Federal 1­ hour N02 standard rely heavily on information, data andjustifications previously submitted to EPA and other regulatory agencies concerning the project in the context ofanalyses for other standards. Avenal's June 28 letter states that it is puzzling that EPA would send its June 15 letter, late in the permitting process, that "completely ignores hundreds ofpages ofdata, analysis, and explanation that EPArequested long ago, that APC provided long ago, and that technical experts from EPA, APC, and other environmental agencies have already reviewed and found to be acceptable. Yet the June 15th letter and its attachment are focused almost entirely on issues that have already been resolved with EPA and are discussed in great detail for the permitting record."
As a technical and a legal matter, the information, data, protocols and analyses previously provided by Avenal to EPA and/or otherregulatory agencies for the purposes of demonstrating compliance with the Federal annual N02 standard orthe State I-hour N02Jim Rexroad Page 3

standard cannot simplybe assumed to demonstrate the AEP's compliance underthe Clean Air Act PSD program with the Federal I-hourN02 standard. Further, EPA did notpreviously accept or approve Avenal's use ofsuch information, data, protocols and analyses for the purposes ofdemonstrating compliance with the Federal I-hour N02 standard; indeed, that standard had notbeen finalized at the time such information was initially submitted and thus would not have been reviewed for that purpose.
Clean AirAct section I65(a)(3) requires the owner ofoperator ofa facility subject to PSD to demonstrate compliance with eachNAAQS. The demonstration to be provided bythe applicant pursuant to CAA I65(a)(3) must include a CAAPSD modeling analysis specific to each Federal standard that triggers PSD review. Technical modeling issues may vary depending
on the specific air quality standard and averaging period at issue. Thus, assumptions and justifications made with respect to one pollutant or averaging time may not be appropriate for demonstrating compliance with a different pollutant or averaging period. Further, State air quality standards that are notbased on a Federal standard may involve regulatory requirements different from those governing the PSD program. Inthe case ofthe AEP, information, data, protocols and analyses previously submitted by Avenal to EPA or other State and local regulatory agencies to demonstrate compliance with the annual N02 standard orwhich discuss the State I-hourN02 standard (which differs from the Federal I-hour N02 standard) cannotbe assumed appropriate for demonstrating compliance with the Federal I-hour N02 standard absent specific technicaljustification providedbythe applicant supporting their application for modeling under the PSD program for the Federal I-hourN02 standard. Inour view, acceptable justification for using much ofthe information previously submitted has not yetbeen provided by Avenal. In some areas, the information submitted is clearly inadequate for a I-hourN02 NAAQS modeling demonstration and must be supplemented with a complete analysis.
Avenal's letter dated July 13,2010 states that "EPAhas refused to approve [Avenal's] modeling, saying, among other things, that it wanted to finalize modeling guidance for the new I-hourN02 standard and then review [Avenal's] new modeling against that guidance." This statement is incorrect. EPA's June 15 letter did not state that EPAwould not review or approve Avenal's submittal pending the issuance offormal EPA guidance. The fact that EPAprovided a detailed response on June 15,2010to Avenal's submittal, priorto the issuance ofEPA's guidance onJune 28-29,2010, belies this statement. EPA's June 15,2010letter merely mentioned that we anticipated that an EPA guidance document on N02 modeling wouldbe issued very shortly, and discussed several areas in which we understood the guidance would provide further clarification, in order to provide Avenal with relevant information.
As noted in Avenal's July 13 letter, EPA did recently issue guidance relating to modeling for the I-hourN02NAAQS, with a cover memorandum entitled Guidance ConcerningJim Rexroad Page 4
Implementation of the I-hourN02NAAQSfor the Prevention of SignificantDeterioration Program, dated June 29, 2010, that included two attached guidance documents, one ofwhich
was entitledApplicability of Appendix WModeling Guidancefor the I-hour N02 National AmbientAir Quality Standard, dated June 28, 2010. These guidance documents provide EPA's current views on certain subjects relevant to the I-hourN02 NAAQS. The July 13 letter and its attachment describe why Avenal believes that its analysis addresses various components ofthe guidance. We have reviewed and considered that discussion in the July 13 letter, and our response is provided in Attachment 1below.

In light ofthe fact that Avenal has filed a lawsuit seeking a final PSD permit decision from EPA for the AEP, and the fact that it is not clear from previous discussions with Avenal whether Avenal will be providing additional modeling information for the I-hour N02 NAAQS,
we request that Avenal provide a written response to this letterby August 17, 2010 confirming that it intends to provide additional information andjustification that fully addresses EPA's remaining concerns as described in the detailed comments below. IfAvenal does not intend to fully address all those concerns, please describe those concerns that Avenal intends to further address and those it does not. IfAvenal does not indicate that it intends to provide additional information or analysis demonstrating compliance with the I-hourNAAQS byAugust 17,2010,
we plan to proceed with permit decisionmaking for the AEPbased on the informationreceived to date. On the otherhand, ifAvenal does plan to provide additional information, werequest that that information be providedbyno laterthan September 13,2010. Ifyou believe that additional time is needed for providing the requested information, we would be happy to discuss that with you. Sincerely,

.Gerardo Rios Chief, Air Permits Office

Attachment

cc (w/attachment, viaemail and U.S. Mail): Jeffrey R. Holmstead, Bracewell & Giuliani LLP Gary Rubenstein, SierraResearchATIACHMENT 1
On June 15,2010, EPAprovided a written response to Avenal's Supplemental N02 Air Quality Impact Analysis for the Avenal Energy Project dated May 13,2010. This supplemental analysis was intended to address the I-hournational ambient air quality standard (NAAQS) for nitrogen dioxide (N02), which became effective April 12, 2010. On June 28, 2010, the applicant provided a written response to EPA'sJune 15, 2010 letter. Ina letter dated July 13, 2010, the applicant provided some additional information concerning the analysis. This letterprovides EPA'sresponse to the applicant's June 28, 2010 submittal, as well as a response to certain aspects ofthe July 13 letter (and its attachment) where the letterprovided additional information from the June 28,2010letter. 

### SummaryofEPA'sResponses to Avenal'sJune 28, 2010 Letter, Paragraphs 1-12
Avenal's response provides sufficient information to address several ofthe comments made in EPA'sJune 15,2010letter. The information provided for downwash (paragraph 9) and operating emissions (paragraph 4) is adequate.
With respect to several otherissues, EPAbelieves that substantial additional information will berequired for review. Specifically, the information provided in the applicant's response for nearby sources (paragraph 1) andjustification for the method of adding modeled and monitored data (paragraphs 7 and 8) are not adequate.
EPA has also reviewed thejustification for the ambient and meteorological data (paragraphs 3, 10 and 11). Although the response does provide some information, based on previously submitted information for the annual N02 NAAQS, the level ofdetail provided is not sufficient for an analysis ofthe I-hourN02 NAAQS. While the facility impact was well below the annual N02 NAAQS

-- less than one percent ofthe standard

­

- the facility impact combined with background levels ofN02for the I-hourN02 NAAQS is nearthe standard, and therefore a more detailed analysis is warranted. In addition, the spatial and temporal distribution ofhourly N02leveisfrom the proposed facility and surrounding emissions cannot be assumed to be identical to the annual distribution, and therefore the previous analysis regarding representativeness for the annual N02NAAQS cannot simplybe referenced as being adequate to address the issue ofrepresentativeness for the I-hourN02NAAQS.
Thejustification for use ofthe non-regulatory-default PVMRM option in AERMOD is not sufficient, and needs to be expanded (paragraphs 2 and 12), including additional information on stack gas N02INOx ratios (paragraph 6). Some additional information regarding emissions (paragraph 5) also needs to beprovided.
These issues are discussed in greater detail below.EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 2



### Discussion ofEPA's responses to Paragraphs 1-12
The major headings below refer to the paragraph numbers in Avenal's June 28, 2010 response. 

### I. Paragraph 1
Comment 1in Attachment A to EPA's June 15,2010letter stated:
Avenal's May 13,2010 I-hourN02 submittal did not include necessary information indicating which, ifany, nearby sources were modeled orthe process used to determine which nearby sources shouldbe included. A full impact analysis should include modeling ofnearby sources as well as monitored background values. The recommendations for modeling for nearby sources are discussed in EPA's Guideline onAir QualityModels (40 CFR Part 51, Appendix W) Subsection 8.2.3, and relevant excerpts are quoted below. All sources expected to cause a significant concentration gradient in the vicinity ofthe source or sources underconsideration for emission limit(s) should be explicitly modeled. Please provide a description ofthe process used for determining which nearby sources shouldbe included in the modeling, as well as the modeling analysis for any such sources. EPA'sJune 15 letter also quoted relevant language from Guideline onAir Quality Models Subsection 8.2.3. Paragraph 1ofAvenal's June 28, 2010 refers to EPA's Comment 1, and states that "[t]he record for the AEP PSD permit already contains this information." Itcites information from two analyses: the Localized Impacts analysis previously provided by the applicant to the CaliforniaEnergy Commission (CEC), and the Additional Impact Analysis previously submittedbythe applicant (March 2009, Class II Impacts Analysis).
EPA does not believe that the information described in paragraph 1 ofAvenal's June 28,2010letterprovides an adequate basis on which EPAcan determine whether all sources expected to cause a significant concentration gradient in the vicinity ofthe source under consideration for emission limits have been considered. As discussed in more detail below, the information provided in the applicant's June 28,2010letter, including the attachments provided for the Localized Impact Analysis and Additional Impact Analysis, is not sufficient for EPAto determine ifthe recommendations in the Guideline onAir QualityModels (40 CFRPart 51, Appendix W, Subsection 8.2.3) have been met. A. Localized Impact Analysis
The applicant's June 28 response on this issue discusses the Localized Impacts analysis, which was provided to the CaliforniaEnergy Commission (CEC). The Localized Impact Analysis does not address nearby sources as recommended in the Guideline onAir QualityModels (40 CFRPart 51, Appendix W), Subsection 8.2.3. TheEPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 3
requirements ofthe CEC Localized Impact Analysis, as presented in Section 6.2.7.1.2 of the APC, differfrom PSD programcriteria in several significant aspects, such as excluding sources beyond six miles, andbeing limited to stationary sources. Inaddition, although the CEC Localized Impact Analysis includes a requirement to address existing sources, the applicant excluded existing sources from consideration. These issues are discussed in more detail below.
1. Applicant's June 28, 2010 response. The applicant's June 28,2010response states that "APC Section 6.2.7.1.2 (Localized Impacts) thoroughly discussed the criteriaused to evaluate whether any stationary sources existed within six miles that would qualifyto be explicitly included in a cumulative airquality modeling impact analysis. None were identified byeither the Applicant orthe SJVAPCD."
APC Section 6.2.7.1.2 (Localized Impacts) is presented here:
6.2.7.1.2 LocalizedImpacts The CEC has defined this local analysis as "acumulative airquality modeling impacts analysis ofthe project's typical operating mode in combination with other stationary source emissions sources within a six-mile radius which have received construction permits but are not yet operating, or are in the permitting process."[footnote omitted] Within the distance ofsix miles, three categories of projects with combustion sources were evaluated:

• Existing projects that have been in operation since at least January 2006. • Projects for which airpollutionpermits to construct have been issued and that began operation after 2006. • Projects for which air pollution permits to construct have not been issued, but are reasonably foreseeable. Existing projects that have been in operation since at least January 2006 are reflected in the ambient air quality data that have been used to represent background concentrations for the proposed project; consequently, no further analysis ofthe emissions from this category offacilities was performed.
The District was requested onJuly 19, 2007, to provide information on any sources that might be appropriate (Le., within 6 miles and with an emission increase ofat least 5 tons peryear for a criteriapollutant) for a cumulative air quality impact analysis, buthas not identified any. Consequently, no localized cumulative impact modeling analysis was performed for the proposed project.
2. Discussion ofapplicant's response. The applicant's reference to the CEC Localized Impact Analysis previously conducted for purposes ofits State and local permittingprocess does not demonstrate thatEPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 4

it has followed a technically adequate process for identifying all sources expected to cause a significant concentration gradient in the vicinity ofthe source under consideration for emission limits, which should be explicitlymodeled, in the context ofthe PSD program. The Localized Impact Analysis providedbythe applicant does not fully address all the factors germane to the identification ofnearby sources in the context of PSD modeling, as explained in more detail below.

a. CEC requirements differ from PSD criteria. First, the requirements ofthe CEC Localized Impact Analysis, as presented by the applicant, differ from PSD criteria in several significant aspects. The CEC has defined this local analysis as "acumulative air quality modeling impacts analysis ofthe project's typical operating mode in combination with other stationary source emissions sources within a six-mile radius". In contrast, the sources to be considered for inclusion in the PSD nearby source analysis are not limited to a six mile radius, and are not limited to stationary sources. Further, the PSD nearby source analysis is not limited to a modeling analysis ofthe project's typical operating mode.
b. Existing sources are not included in the applicant's response. Second, while both the CEC's definition ofa Localized Impact Analysis and EPA PSD recommendations for a nearby source analysis include consideration ofexisting sources, the applicant has chosen to exclude existing sources in its CEC Localized Impact Analysis, based on the assertion that "[e]xisting projects that have been in operation since at least January 2006 are reflected in the ambient airquality data that have been used to representbackground concentrations for the proposed project." The applicant provides no demonstration, however, ofhow the sources at issue are reflected in the ambient air quality data that have been used to represent background concentrations for the proposed project. This is particularly problematic in light ofthe fact that the existing projects are presumably within a distance ofsix miles ofthe source, whereas the background monitoring site is 28 miles away, at Hanford.
In addition, background monitoring datamay not reflect existing sources operating at their full operating capacity. 40 CFR Part 51, Appendix W, Subsection 8.2.1.c. states that "[s]ince sources don't typically operate at their maximum allowable capacity (which may include the use of 'dirtier' fuels), modeling is necessary to express the potential contribution ofbackground sources, and this impact would not be captured via monitoring. Backgroundconcentrations should be determined for each critical (concentration) averaging time."
40 CFR Part 51, Appendix W, Subsection 8.2.3.c. states: "Forcompliance with the short-term and annual ambient standards, the nearby sources as well as the primary source(s) should be evaluated using an appropriate Appendix A model with the emission input data shown in Table 8-1 or 8-2. When modeling a nearby source that does not have a permit and the emission limit contained in the SIP for a particular source category is greater than the emissions possible given the source's maximum physical capacitytoEPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 5
emit, the 'maximumallowable emission limit' for such a nearby source may be calculated as the emission rate representative ofthe nearby source's maximum physical capacity to emit, considering its design specifications and allowable fuels and process materials. However, the burden is on the permit applicant to sufficiently document what the maximum physical capacityto emit is for such a nearby source." Table 8-2: Point Source Model Emission Input Datafor NAAQS Compliance in PSD Demonstrations indicates that the appropriate emission input for nearby sources is the maximum allowable emission limit orfederally enforceable permit limit.

c. Adequate documentation ofthe District's response is not provided. Third, the applicant's June 28, 2010 response appears to rely inpart on the fact that the SanJoaquin Valley Air Pollution Control District (SJVAPCD) did not identify any sources in response to a July 19,2007letterrequesting that the District: identify any stationary source located within 6 miles ofthe Project, having a criteria pollutant emissionrate ofat least 5 tons per year, and which have received construction permits but are not yet operating, or are in the permittingprocess (i.e., existing emission sources are accounted for inbackground airquality monitoring). (Footnote 3 to Avenal's June 28, 2010 letter.)
The July 19, 2007 request is limited to sources within a six mile radius, is limited to stationary sources, and excludes existing sources, andtherefore is not consistent with what wouldbe acceptable for a nearby source analysis for PSD purposes, as described in more detail above. In addition, the applicant has provided limited documentation indicating what information was included in the SJVAPCD's response, and the basis (which inventories were reviewed, for example) for SJVAPCD's response. The applicant's June 28,2010response also notes that the analysis concludes, "no localized cumulative impact modeling analysis was performed for the proposedproject," based on SJVAPCD's response to the letterrequest described above. However, the concerns stated above regarding the limited scope ofthe localized impacts inquiry and analysis, andthe limited information provided about the District's response, apply equallyto the analysis's conclusion that no localized cumulative impact modeling analysis wouldbe performed.
d. Conclusion.
The information provided in the applicant's response concerning the Localized Impact analysis is not sufficient for EPAto determine whether all sources expected to cause a significant concentration gradient in the vicinity ofthe source under consideration for emission limits have been identified, consistent with EPA's Guideline onAirQuality Models, Subsection 8.2.3.EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 6

B. Additional Impact Analysis (or "Class II Impacts Analysis")
As further support for its approach to addressing nearby sources in response to EPA's comment, Avenal's June 28,2010response states, "InMarch 2009, a special study was.made in response to the EPARegion 9 request to conduct a Class II impacts analysis. That study included an additional search for other sources ofsignificance (i.e., excluding farm machines and rural roads) and potentially sensitive areas within the surrounding Class II region." Avenal also provides the Additional Impact Analysis as a reference for this study. However, Avenal's Additional Impact Analysis provides no discussion ordocumentation ofany search for nearby emission sources. Further, its conclusions regarding the project's impact area in the context ofthe annual N02 standard are inapplicable to the I-hour N02 standard, as discussedbelow.
1. Applicant's June 28,2010response. The applicant's June 28, 2010response states, "InMarch 2009, a special study was made in response to the EPA Region 9 request to conduct a Class II impacts analysis. That study included an additional search for other sources ofsignificance (Le., excluding farm machines and rural roads) and potentially sensitive areas within the surrounding Class II region. The results ofthat study were that:

• the project has no 'impact area' as defined byEPA guidance; and • no potentially sensitive state orfederal parks, forests, monuments, orrecreation areas are located within 50 km in this rural part ofthe Central Valley."
2. Discussion ofapplicant's response. The applicant's reference to its Class II impacts analysis (Additional Impact Analysis) does not demonstrate that it has followed a technically adequate process for identifying all sources expected to cause a significant concentration gradient in the vicinity ofthe source under consideration for emission limits, which shouldbe explicitly modeled, in the context ofthe PSD program. The Class II impacts analysis does not fully address all the factors germane to the identification ofnearby sources in the context of PSD modeling, as explainedbelow.

a. The Additional Impact Analysis does not provide information on nearby sources. First, the applicant's response indicates that as part ofits Additional Impact Analysis,l the applicant performed an additional search for other sources ofsignificance. However, the applicant's Additional Impact Analysis includes no discussion or documentation ofany search for nearby emission sources.

1We note that the Additional Impact Analysis, submitted as an attachment to the applicant's June 28, 2010 response, was originally prepared to address federal regulatory requirements, rather than as a special study.EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 7

b. The impact area discussed in the Additional Impact Analysis does not apply to the I-hourN02 standard. Second, the applicant's response states that "[t]heresults ofthat study were that the project has no 'impact area' as definedbyEPAguidance." While it is correct that the project has no impact area for the annual N02 standard, that does not hold true for the 1­ hour N02NAAQS, because the "noimpact area" conclusion for the annual N02 standard was based on the fact that the project impact was below the significant impact level (Sa) for the annual N02 NAAQS, and this sadoes not apply for the 1- hour N02 NAAQS. Therefore, this information does not provide information germane to the nearby source analysis for the I-hourN02NAAQS.
We note that the EPA guidance document issuedbyEPA's Office ofAir Quality Planning and Standards entitled General GuidanceforImplementing the I-hourN02 NationalAmbientAir Quality Standard in Prevention of SignificantDeterioration Permits, Including an Interim I-hourN02 SignificantImpactLevel, dated June 28, 2010, provides a recommended interim safor the I-hourN02NAAQS of4 ppb.

c. Discussion ofsensitive areas is not relevant to a nearby source emission discussion. Third, the applicant's response also indicates that no potentially sensitive state or federal parks, forests, monuments, orrecreation areas are located within 50 kmin this rural part ofthe Central Valley. This information addresses potentially sensitive areas and does not provide information regarding nearby emission sources. d. Conclusion.
The information provided in the applicant's response concerning the Additional Impact Analysis is not sufficient for EPA to determine whether all sources expected to cause a significant concentration gradient in the vicinity ofthe source under consideration for emission limits have been identified, consistent with EPA's Guideline onAir Quality Models, Subsection 8.2.3.
II. Paragraph 2
Avenal's paragraph 2 refers to the statement made on the first page ofEPA's June 15,2010letterthat "[k]ey input dataused in the PVMRM option within AERMOD needs to be discussed andjustified."
The information provided in paragraph 2 in Avenal's June 28, 2010 letter discusses the use ofthe ozone data submitted byAvenal in the PVMRM option within AERMOD, butdoes not provide adequatejustification for use ofthe ozone data in this context for purposes ofthe PSD program. In addition, otherkey input data used in the PVMRM option within AERMOD, such as stack gas N02INOxratios, need to beEPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 8

discussed andjustified. These issues are discussed in greater detail in the responses to paragraphs 6 and 12 below.
Avenal's response indicates that Avenal previously provided the ozone data at issue to EPA in Avenal's application for its PSDpermit. However, EPA did not have any basis to review the use ofthe data at that time, as the annual N02 NAAQS analysis that was submitted to meet PSD requirements did not use site-specific ozone data. The AFC prepared for the State air permitting process and citedbyAvenal in its June 28, 2010 response states on page 6.2-61 that, "Annual NOx impacts were converted to N02using the EPA-guidance Ambient Ratio Method and the nationwide default conversion ratio of 0.75 for the annual average N02/NOx ratio." The federal PSD requirements for the annual N02 NAAQS analysis were metbyusing an acceptable method, the Ambient Ratio Method. The nationwide default conversion ratio of0.75 is not site-specific, and does not rely on site-specific monitored ozone data. As a result, no ozone data was used for this analysis.
The AFC also includes an analysis for the State I-hour N02 standard, which concludes that the total impact for I-hourN02 (maximum facility impact and background) is 327.2 Ilglm3, shown on Table 6.2-31, Modeled Maximum Project Impacts, Avenal AFC, page 6.2-66. While the use ofthe non-regulatory-default PVMRM option in AERMOD and use ofthe hourly ozone data from the Hanford, CA monitoring station for this analysis was discussed on pages 6.2-60 and -61 ofthe AFC, this was not part ofthePSD annual N02 NAAQS analysis, and therefore was not reviewed or approvedbyEPA. At the time the AFC data was provided, EPAhad no reason for considering, and did not consider, the appropriateness ofthe use ofthe ozone data for an analysis relating only to the State's I-hourN02 standard. Paragraph 2 in Avenal's June 28,2010letter also states that"[t]he regulatory requirement ofrepresentativeness was satisfied bythe District's selection ofthe Hanford monitoring station as being the closest, and adequately close, source ofthe hourly ozone data. The use ofair quality and meteorological data from Hanford, which is 28 miles northeast ofthe project site, was discussed in Sections 2.4 (Data Requirements

­ Meteorological Data) and 2.5 (DataRequirements

- Ambient Monitoring Data) in the May 13,2010SupplementalN02Air QualityImpactAnalysis, and also discussed in AFC Sections 6.2.1.2 (Climate and Meteorology) and 6.2.3 (Existing Air Quality), Subsection 6.2.3.1 (Ozone). There are no developed stationary sources ofairpollution between Hanford and the project except for the Lemoore Naval Air Station, which is located 14 miles northeast ofthe project." [footnotes omitted]
The statements that the source is 28 miles northeast ofthe project site, is the closest source, and is adequately close, are not sufficient to show that the data is representative. The discussion ofrepresentativeness for ambient air quality data should be specific to the pollutant for the appropriate averaging time. Forexample, the discussion ofrepresentativeness for hourly ozone datain the SanJoaquin Valley should considerthe regional pattern ofozone in the San Joaquin Valley. The effect oflocal sources on the formation and destruction ofozone should be considered. Forexample, isEPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 9

the monitoring station near a roadway that maybe a local sink ofozone? Conditions at the project site shouldbe compared to conditions at monitoring sites in the San Joaquin Valley.


### III. Paragraph 3 Paragraph 3 in Avenal's June 28, 2010 response addresses the statement on the first page ofEPA'sJune 15,2010letterthat "documentation andjustification ofthe appropriateness ofthe meteorological and ambient airquality background data for the 1­ hour N02 analysis needs to be provided."
A discussion ofthe documentation andjustification ofthe appropriateness ofthe meteorological and ambient air qualitybackground datafor the I-hour N02 analysis provided in the applicant's June 28, 2010response is included in EPA'sresponse to paragraphs 10 and 11 below.


### IV. Paragraph 4
EPAhas reviewed Avenal's response to EPA's Comment 2 regarding the need to provide documentation ofthe source emission input data for averaging times appropriate for the federal I-hourN02 standard. The applicant has referenced these values in the FDOC, which was provided as an attachment to the response. These data were updated following Avenal's submission ofits original PSD application, as described below.
Withrespect to short-term, hourly emissionrates for NOx, the applicant noted the need to update the originallyestimatedrates for normal operations from the CTG + HRSG hourly rates of 13.47Ibslhr (without duct firing) and 17.13lbslhr (with duct firing) to 13.55 lbslhr and 17.20 lbslhr, respectively, for the purposes ofestablishing our PSD permit limits equivalent to 2.00 ppm NOx. The applicant has referenced these values in the FDOC, which was provided as an attachment to the response.
In addition to the update ofthe hourlyrate ofthe CTG+HRSG, an update was made for the natural gas-fired emergency generator. Theupdate was a reduction in the emission rate for NOx (grams perbrakehorsepower-hour, org/bhp-hr) for the natural gasfired emergency generator (which remained the same size) from 1.50 to 1.00 g/bhp-hr (equating to a revision from 2.841bslhrto 1.90 lbslhr). The emission rates for the auxiliaryboiler and diesel fire pump remained the same. Below summarizes EPA's understanding ofthe hourly NOx emission rate (lbslhr) for eachpiece ofequipment. Equipment NOx, emissions (not to exceed) CTG+HRSG (no ductburner) permitted: 13.55 lbslhr permitted: 2.0 ppm @ 15% 02 CTG+HRSG (with ductburner) permitted: 17.20lbslhr permitted: 2.0 ppm @ 15% 02 emergency generator permitted: 1.0 g/bhp-hrEPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 10

550 kW (or 860 hp) calculated: 1.9lbslhr (1.89Ibslhr) fire waterpump 288 hp permitted: 

### 304 g/bhp-hr calculated: 2.2 lbslhr (2.16 lbslhr) auxiliaryboiler 

### 37A MMBtulhr (HHV) permitted: 9.0 ppm @ 3% 02 calculated: 

### 0041 lblhr

EPA believes that the documentation presented in Paragraph 4 is sufficient, and the emission rates presented in the table above are appropriate for addressing compliance with the federal I-hourN02 standard.


### V. Paragraph 5
EPA has reviewed Avenal's response inparagraph 5 ofits June 28, 2010 letter to EPA's Comment 3 regarding the inclusion ofthe startup or shutdown emissions. In addition to the information cited in footnote 24 (i.e., EPA's June 2009 Statement ofBasis and Ambient Air Quality Impact Report), we acknowledge that EPA was in receipt ofthe initial PSD permit application information cited in footnote 25.
We understand Avenal's response to indicate that the existing information for startup and shutdown in the original PSD permit application has been proposed for the 1­ hour NAAQS airquality modeling evaluation. Based on Tables 6.2-1.1, 6.2-1.6, and 6.2­ 2.5, we note that the I-hour scenario is based on a combination ofthe following: (a) Case 4 (from vendor data) that represents 50% load and 101 degrees F; and (b) a cold start estimate of80 lbs/hour (each), which appears to be based on a compilation ofother facilities' cold start data.
Guideline onAir QualityModels (40 CFRPart 51, Appendix W, Subsection 8.1.2) Source Datarecommends that for point source applications, the load oroperating condition that causes maximum ground-level concentrations should be established. Where the source operates at substantially less than design capacity, and the changes in the stack parameters associated with the operating conditions could lead to higher ground level concentrations, loads such as 50percent and 75 percent ofcapacity should also be modeled. The information provided to date is insufficient and should demonstrate why the parameters for the proposed 50% load and 101 degrees F case represent the worstcase I-hourNOx scenario; i.e., why other loads (e.g., 60%, 75%) and other ambient conditions were not considered ordemonstrative ofthe worst-case I-hour NOx emission rate. 

### VI. Paragraph 6
EPA has reviewed Avenal's June 28 response to EPA's Comment4 regarding the in-stackratios. Avenal has selected the in-stack N02/NOxratio for the two combustion turbines as follows: equal to 0.25 for normal operations and equal to 

### 004 for startup and commissioning operations. Avenal has characterized these ratios as conservative, asEPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 11

derived from information related to the PalomarEnergy Center (Palomar) inEscondido, California, a facility that operates within the San Diego AirPollution Control District (SDAPCD). Avenal did not provide the specific background information cited for EPA in support ofthe selection process. Avenal stated that the ratios were "derived from source test data." EPA needs to confirm the proposed conservative ratios for use in the 1­ hour N02 NAAQS airquality modeling; therefore, we request the following:
A. SourceTest Operating Scenarios and Results: The applicant should provide the source test data, which the SDAPCD furnished, that Avenal has relied upon to develop the 0.25 and 

### 0040 ratios. This should include, at a minimum, source test results, source test support information to confirm test conditions and equipment operations, and the source test methodology. The applicant should confirm ifthe source test datarelied upon is a result ofemissions compliance testing or a result ofothercircumstances. Based on this information, the applicant should provide a discussion that demonstrates the representativeness and comparability ofthis information for Avenal's selection ofthe proposed ratios for normal, startup and commissioning operations.
B. Other Support Information (ifapplicable): We are not aware that source tests have generally been conducted during the startup and commissioningphases of operations specific for the collection ofinformation to determine the in-stack N02INOx ratio. Ifthe development ofthe normal, startup, and commissioningratios also were based on anothermethodes) otherthan source testing, the applicant should provide the information that Avenal has relied upon. For instance, ifcontinuous emissions monitoring also was relied upon, please provide a discussion that also demonstrates the representative and comparabilityofthis information for Avenal's selection ofthe proposed ratios. 

### C. San Diego APCD Recommendations: Avenal stated that the proposed instackratio values of0.25 and 

### 004 were"

... recommended by San Diego Air Pollution Control District for the modeling on another large-scale combined-cycle gas turbine project." The applicant should include the SDAPCD's recommendation andrationale.


### VII. Paragraph 7
EPArecognizes that detailed guidance regarding dispersion modeling for demonstrating compliance with the I-hourN02NAAQS was limited at the time of Avenal's May 13,2010, submittal. Additional guidance was issued onJune 28, 2010, in the form ofa clarification memorandum ontheApplicabilityof Appendix WModeling Guidance for the i-hourN02NationalAmbientAirQuality Standard. The first paragraph on page 5 ofthis N02clarification memorandum addresses the question of appropriate methods for combining modeled ambient concentrations with monitored background concentrations for comparison to the NAAQS in a cumulative analysis. The memorandum states that "[a] 'first tier' assumption thatmaybe appliedwithout further justification is to addthe overallhighesthourlybackgroundN02 concentration from a representative monitorto the modeleddesign value, basedon theform of the standard, for comparison to the NAAQS. Additional refinements to this 'first tier' approach basedEPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 12

on some level of temporalpairing of modeledandmonitored values maybe considered on a case-by-case basis, with adequatejustification anddocumentation." Although EPA'sJune 28, 2010 N02 clarification memorandum acknowledges that some level oftemporal pairing ofmodeled and monitored N02 concentrations may be appropriate in some situations, thejustificationregarding pairing on an hour-by-hour basis provided in Avenal's response, which states that the "approach guarantees meteorological consistency for each pairofbackground and modeled concentrations combined in each hour ofthe year," does not provide a sufficient rationale to support that approach in this case. There maybe sound technical arguments to account for consistency in terms ofthe meteorology affecting both background and modeled concentrations, but thejustification also needs to considerthe spatial representativeness ofthe monitored data as well, which is not addressed in Avenal's response to this comment. The aspect oftemporal pairing ofmodeled and monitored concentrations is also acknowledged in EPA's March 23, 2010 memorandum from Stephen Page regarding Modeling ProceduresforDemonstrating Compliance with PM2.5NAAQS, whereEPA indicates on page 8 that a SecondTier approach for combining modeled and monitored PM2.5 concentrations on a seasonal orquarterly basis maybe considered when the modeled primary PM2.5 impacts andbackground PM2.5 levels (including secondary PM2.5 formation) are not correlated on that time scale. Although the March 23, 2010 memo does not provide details regarding the recommended method for combining modeled and monitored PM2.5 concentrations on a seasonal orquarterly basis, the recent draft PM2.5 Hot Spot Conformity Guidance (EPA, 2010) recommends combining the average ofthe highest modeled 24-hour concentrations within each season/quarter to each ofthe eight highest 24-hour monitored background concentrations for that season/quarter, and then sorting the combined distribution to determine the cumulative design value (see Appendix K ofthe draft Hot Spot guidance). Note that the modeled and monitored concentrations are not paired on a day-by-day (or hour-by-hour) basis in this Second Tier approach for PM2.5, even though the spatial homogeneity of background levels ofPM2.5 on a dailybasis is likely to be much greater than the spatial homogeneity ofbackground levels ofN02 on an hourlybasis.
While the background ambient monitored N02 values, ifappropriatelyjustified, are presumed to berepresentative in a general sense ofbackground concentrations for purposes ofa cumulative impact assessment, pairing the monitored background values with modeled concentrations on an hour-by-hourbasis implies an assumption that the monitored concentrations are equally representative at each location within the modeling domain for eachhourofthe simulation. There is no technical orevenrational basis to support such a degree ofrepresentativeness in this case or any other case. Such a degree ofrepresentativeness would also be unreasonable to impose as a general requirement for use ofbackground monitored data, given the limited number ofmonitors available. However, any modeling approach developed regarding the use ofmonitoredbackground concentrations as part ofa cumulative impact assessment must take into account these limitations ofmonitored data.EPAResponse to Avenal Letters dated June 28, 2010and July 13, 2010 Page 13

Itappears that the approach used to combine hourly modeled and monitored NO

### z concentrations for comparison to the I-hourCalifornia Ambient Air Quality Standard (CAAQS) in Avenal's AFC submittal to the CEC was consistent with the approach recommended as the "firsttier" assumption for combining modeled and monitored NO

### z concentrations described in the June 28, 2010, N02 clarification memo. The results from the I-hour NO

### zCAAQS comparison summarized in Table 6.2-31 (6.2-66) ofthe APC show maximum I-hourAvenal facility impacts of 190 Jlg/m3

, combined with a background concentration of 137.2 Jlg/m3 to give a total impact of327.2 Jlg/m3

. This cumulative I-hour

### NOz impact is well above the EPA I-hour

### NOz standard, although we recognize that the I-hour modeled NO

### zconcentration documented in the APC is likely to be higher than the 98th-percentile ofthe annual distribution ofmaximum daily I-hour values used as the form ofthe I-hourEPA standard. However, the AFC results are also about 2.7 times higherthan the cumulative I-hour

### NOz impact reported in the May 13, 2010 submittal, which serves to highlight the significance ofthe issue raised byEPA in this comment, and to emphasize the importance ofhaving clearjustification and documentation ofthe approach taken for combining modeled and monitored concentrations for comparison to the NAAQS.
VIII. Paragraph 8 Paragraph 8 address EPA's commentthat Avenal's May 13,2010 I-hourN02 submittal labeled hours with missing ambient monitoredbackground N02 as missing for combined modeled and monitored impact, which effectively discards valid modeled data. The applicant's response states that "Although modeled concentrations are discarded when corresponding background concentrations are not available, the methodologyused faithfully follows the requirements in the I-hour N02NAAQS Final Rule, the only reasonably applicable regulatory guidance available at the time ofthis supplemental 1­ hour N02 analysis."
The procedures in Appendix S to 40 CFRPart 50, which are provided in the reference cited as "the onlyreasonably applicable regulatory guidance available at the time ofthis supplemental 1hourN02 analysis," apply to ambient monitored N02 concentrations and are notrelevant for modeled N02 concentrations. EPA disagrees that it is suitable to apply the currently available monitoring guidance for the I-hourN02 standard to modeling applications, as suggested byAvenal.
The applicant's response states that "EPA's suggestion that we should rely on guidance that has yet to be issued would appear unreasonable in light ofthe suitability of the currently available guidance with respect to monitoring compliance with this N02 standardby states." EPA's comment objects to discarding valid modeled data. The applicant should choose a method for combining modeled and monitored data that does not discard valid modeled data and which is consistent with Appendix W. EPA's guidance entitledApplicabilityof Appendix WModeling Guidance for the i-hourN02 NationalAmbientAir Quality Standard (June 28, 2010) maybeuseful in preparing an analysis ofthe I-hourN02NAAQS.EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 14

EPAbelieves that its objection that the Avenal's May 13,2010 I-hourN02 submittal labeled hours with missing ambient monitored background N02 as missing for combining modeled and monitored impact, which effectively discards valid modeled data, has not been adequately addressed.


### IX. Paragraph 9 Paragraph 9 in Avenal's June 28, 2010 response addresses Comment 6 in Attachment A to EPA'sJune 15,2010letter, which states: "Avenal'sMay 13,2010 1­ hour N02 submittal did not include any discussion ofhow building downwash is addressed."
We have reviewed the approach Avenal has taken for addressing building downwash, as described in its response, and believe that this approach is acceptable for Avenal's I-hourN02NAAQS analysis.


### X. Paragraph 10 Paragraph 10 in Avenal's June 28, 2010 response refers to Comment 7 in Attachment A to EPA's June 15,2010letter, which describes in detail the type of analysis that EPA guidelines indicate is appropriate to demonstrate the representativeness ofthe meteorological data. Although Avenal did provide some information regarding the surface meteorological station, the applicant's response does not fully address several of the issues raised in EPA's Comment 7, described as follows. Paragraph 3 in Avenal's June 28, 2010 response also addresses this issue, and refers to previous submittals that are based on the same material that is presented in paragraph 11, but does not provide additional information regarding the representativeness ofthe data.
EPA's Comment 7 states, "This analysis should include a discussion ofthe representativeness ofthe surface characteristics. The surface characteristics input to AERMET should bebased on the land cover characteristics in the vicinity ofthe meteorological tower." The information in Avenal's response states that "[t]he surface characteristics appropriate for the land uses surrounding the meteorological station at Hanford-namely surface roughness length, albedo, and Bowen Ratio-were computed bythe District." The information provided in the response does not adequately address EPA's comment. The response does not provide (1) information about the surface characteristics at the project site, (2) specific information about the surface characteristics for the meteorological station that were computedbythe District, or (3) a discussion of how the specific surface characteristics at the meteorological station are representative of the specific surface characteristics at the project site. Avenal should provide this information.
EPA's Comment 7 also states that "[0]thercandidate meteorological stations should be discussed." Noothercandidate meteorological stations are discussed in Avenal's June 28, 2010 response.EPA Response to Avenal Letters dated June 28, 2010 and July 13, 2010 Page 15

EPA's Comment 7 further states that [t]he representativeness oftheupper air station used for this analysis should be discussed." Avenal's June 28, 2010response states, ''The District's proposed Camp Pendleton meteorological data are representative ofconditions at the project site," and "[r]epresentativeness is bestevaluated when sites are climatologically similar, as are the project site and the Camp Pendleton meteorological monitoring station." However, the response does not provide an analysis supporting the conclusionthat the project site andthe Camp Pendleton meteorological monitoring station the project site are climatologically similar; this analysis shouldbe provided. Paragraph 10in Avenal's June 28, 2010response provides some information regarding the surface meteorological station. However, the following portion ofEPA's Comment 7 was not addressed: "[S]ince the spatial scope ofeachvariable couldbe different, representativeness shouldbejudgedfor eachvariable separately. Forexample, for a variable such as wind direction, the datamay need tobe collectedvery nearplume height tobe adequately representative, whereas, for a variable such as temperature, data from a station several kilometers awayfrom the source mayin some cases be considered tobe adequately representative." Avenal should address this issue in its analysis.
XI. Paragraph 11
Comment 8 in Attachment A to EPA's June 15,2010letter states that "Avenal's May 13, 2010 I-hourN02 submittal did not include any analysis showing the representativeness ofair quality data at the Hanford site with respect to the conditions at the project. The submittal should include the appropriate analysis, and othercandidate ambient airquality monitoring stations shouldbe discussed." In response, Avenal's June 28, 2010 letterrefers to previous submittals Avenal has made, butthese submittals do not provide an adequate analysis, as explained in more detail below. Paragraph 3 in Avenal's June 28,2010response also addresses this issue, andrefers to previous submittals that are based onthe same material that ispresentedinparagraph 11, butdoes notprovide additional informationregarding therepresentativeness ofthe data.
A. N02 datarepresentativeness has notbeen adequatelyjustifiedfor the I-hour NAAQS.
1. Summaryofinformationpresentedinparagraph 11 ofAvenal's June 28 response for representativeness ofN02 data. Paragraph 11 in Avenal's June 28 response first refers to Avenal's May 13, 2010 SupplementalN02Air QualityImpactAnalysis submittal, Section 2.5 (Data Requirements

- AmbientMonitoring Data) onpages 6 and7, which states:
Ambient N02 datacollected during the five-year modelingperiod of2000-2004 at the Hanford monitoring station were usedto characterize the representative ambient background concentrations. The ambientpollution levels monitored atEPA Response to Avenal Letters dated June 28, 2010 and July 13, 2010 Page 16

the Hanford monitoring station represent area-wide ambient conditions rather than the localized impacts ofany particular facility due to the lack ofany large local industrial sources in the Hanford area. Avenal also refers to Section 6 (Existing Ambient Air Quality Data) ofthe modeling protocol submitted to EPARegion 9 in August 2007. The representativeness justification presented in the protocol is limited to the fact that the Hanford monitoring site is nearest to the facility. The protocol states at Section 6:
6. EXISTING AMBIENT AIR QUALITY DATA Background ambient air quality data for the project area during 2004-2006 will be obtained from the following monitoring sites that are nearest to the project site by pollutant: • Hanford-South Irwin Street: 03 and N02
2. Thejustification for representativeness ofthe N02 datapresented in Avenal's June 28 response is not adequate for the I-hourN02NAAQS.
The discussion on representativeness presentedby Avenal and described above, i.e., that there is a lack ofany large local industrial sources in the Hanford area, and that the Hanford site is nearest to the facility, is not an adequate discussion of representativeness. The discussion ofrepresentativeness for ambient air quality data should include a discussion ofwhy the ambient pollution levels monitored at the Hanford monitoring station represent area-wide ambient conditions, not simplythat they do not represent localized impacts. The discussion shouldbe appropriate for the pollutant for the appropriate averaging time. Forexample, the discussion ofrepresentativeness for hourly N02 data in the San Joaquin Valley should include a discussion ofthe sources and conditions likelyto contribute to high hourly levels ofN02in the San Joaquin Valley. The project site should be compared to various monitoring sites in the San Joaquin Valley. This type ofinformation has not beenprovided.
3. N02 data were not previouslyreviewed or approvedbyEPA for the I-hourN02 NAAQS.
The N02 data Avenal proposes to use for the I-hourN02 NAAQS analysis were not used in the air quality analysis for the annual N02NAAQS conducted for Avenal's PSD permit. Because the impact for the facility was below the significance level for the annual N02 standard, the applicant did not conduct a full cumulative NAAQS analysis, which uses background monitoring data, for the annual N02 NAAQS. "These comparisons show that, except for I-hour CO, the maximum potential impacts are below the significant impact levels and no further analysis is required." (See Avenal APC 6.2­ 68).
As notedbythe APC (6.2-64, Table 6.2-28 Evaluation ofPreconstruction Monitoring Requirements), the Avenal Energy Project avoided preconstruction monitoring for the annual N02 standard, in part, for a different reason: the predicted airEPA Response to Avenal Letters dated June 28, 2010 and July 13.2010 Page 17
quality impacts ofthe project would not exceed defined monitoring de minimis levels known as significant monitoring concentrations. These de minimis levels do not apply to the I-hourN02 NAAQS.
The N02 ambient dataused for the annual N02 NAAQS analysis were not evaluatedbyEPA in that contextin light ofthe fact that the analysis did not use ambient N02 data, and the fact that the analysis had a project impactbelow the monitoring de minimis level. These factors are not present in the context ofthe I-hourN02NAAQS. Thus, EPA did not review or approve the information submitted at that time with respect to representativeness for the I-hourN02 NAAQS.
Avenal also refers to Section 6 (Existing Ambient Air Quality Data) ofthe modeling protocol submitted to EPARegion 9 in August 2007. This protocol was not reviewed at that time for the I-hour N02NAAQS becausethat standard did not exist at the time.
B. Ozone datarepresentativeness for use with the non-regulatory-default PVMRM option in AERMOD has not been adequatelyjustified for the I-hourN02 NAAQS.
1. Summary ofinformation presented in paragraph 11 ofAvenal's June 28 response for representativeness ofozone data.
Avenal refers to Section 6 (Existing Ambient Air Quality Data) ofthe modeling protocol submitted to EPA Region 9 in August 2007. The protocol states at Section 6:
6. EXISTING AMBIENT AIR QUALITY DATA Background ambient air quality data for the project area during 2004-2006 will be obtained from the following monitoring sites that are nearest to the project site by pollutant: • Hanford-South Irwin Street: 03 and N02
The representativenessjustification presented inthe protocol is limited to the fact that the Hanford monitoring site is nearest to the facility.
2. Ozone datarepresentativeness has not been adequatelyjustifiedbyAvenal.
The discussion ofrepresentativeness for ambient airquality data shouldbe appropriate for the pollutant and averaging time. Forexample, the discussion of representativeness for hourly ozone datain the SanJoaquin Valley should considerthe regional pattern ofozone in the San Joaquin Valley, as well as local sources and sinks of ozone. Conditions at the project site should be comparedto conditions at monitoring sites inthe SanJoaquin Valley.
3. Ozone data was notpreviouslyreviewed or approved byEPA for the I-hourN02 NAAQS.EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 18

EPA has not previously reviewed the ozone data included in the AFC. The Avenal AFC itselfindicates that ozone data was not used in the annual N02 analysis. The "Annual NOx impacts were converted to N02using the EPA-guidance Ambient Ratio Method and the nationwide default conversion ratio of0.75 for the annual average N02/NOxratio."z The federal requirements for the annual N02 NAAQS analysis were met byusing an acceptable method, the Ambient Ratio Method. The nationwide default conversion ratio is not site-specific and does not rely on site-specific ozone data. Thus, there was no reason for EPA to review and approve the ozone data in the context ofthe annual N02 analysis.
Avenal's June 28 response also states that "EPArefers to the modeling use of03 and N02background monitoring airquality datain Section 8.1 (Background Ambient Air Quality and Conditions) on page 24 ofthe June 2009 Statement of Basis andAmbient Air Quality ImpactReportFor a CleanAirActPrevention of SignificantDeterioration Permitwithout any qualifying comment." EPA did not review or approve the information submitted at that time with respect to representativeness for the I-hour N02 NAAQS; the I-hourN02 NAAQS did not exist at that time.
Avenal also refers to Section 6 (Existing Ambient Air Quality Data) ofthe modeling protocol submitted to EPA Region 9 in August 2007. This protocol was not reviewed at that time for the I-hour N02 NAAQS because the Federal I-hour N02 standard did not exist at the time.
C. Conclusion
Avenal still needs to provide an acceptable analysis showing the representativeness ofair quality data at the Hanford site with respect to the conditions at the project in the context ofthe I-hourN02 NAAQS.


### XII. Paragraph 12 Paragraph 12 refers to Comment 9 in Attachment A to EPA's June 15,2010letter, which states that "[t]his method for substituting missing 03 concentrations should be replaced with a clearly defined approachthat includes a reasonable assurance that substituted values will not result in underestimates ofambient N02 concentrations."
Avenal's June 28, 2010 response does not adequately address EPA's comment. EPA did not suggest that Avenal should "[a]rtificiallyreduc[e] the substituted concentrations to artificiallyincrease the resulting I-hourN02 concentration." Rather, EPA stated that Avenal should provide a "reasonable assurance that substituted values will not result in underestimates ofambient N02 concentrations." Avenal has not provided reasonable assurance that the method used

-- substituting concentrations with "hour-appropriate" values (e.g., from the previous day, orthe next day, for the same

2 Avenal Energy AFC 6.2-64)EPAResponse to Avenal Letters dated June 28, 2010 and July 13, 2010 Page 19
hour)

-- will not result in underestimates ofambient N02 concentrations. For example, Avenal has not indicated whetherthere were instances in which there were "hourappropriate" data for boththe daybefore and day afterthe date on which data was missing, and whether in any such cases it tookthe higher ofthe two values.
Avenal states that the informationit is relying on was submitted previously to EPA without comment from EPA. The fact that Avenal mayhave provided the approach it is now proposingto use for the I-hourN02NAAQS in submittals to EPA that preceded the issuance ofthis standard does not mean that EPAhas accepted this approach. EPAhas not previously reviewed or approved any method suggested by Avenal for substituting missing 03 concentrations for the I-hour N02 NAAQS.
Nor did EPA approve this method in the context ofthe annual N02 NAAQS. The PSDrequirements for an analysis ofthe annual N02 NAAQS analysis were met byusing the Ambient Ratio Method, using the nationwide default conversion ratio, which is not site-specific and does not rely on site-specific ozone data. 3 Accordingly, EPA'sJune 2009 Statement of Basis andAmbientAir Quality ImpactReportFor a CleanAirAct Prevention of SignificantDeterioration Permit, was based onthe Ambient Ratio Method and the nationwide default conversion ratio of0.75 for the annual average N02INOx ratio, which does not rely on ozone data. Therefore, EPA would have had no basis for examining a method for substituting missing ozone data in the context ofthe annual N02 NAAQS analysis.
Ozone data was discussed in information regarding the PVMRM option described in the APC, which was used to meet State requirements for modeling for the California 1­ hour N02 standard. The results ofthat analysis indicate that the total I-hourN02impact is**327!tg/m~.** This analysis was notpart ofthe PSD analysis, and therefore was not reviewed orapproved byEPA, and the appropriateness ofthe ozone data for this use was not reviewed byEPA.



### EPA's Response to Avenal'sJuly 

### 13,2010Letter andIts Attachment
Avenal's July 13,2010letterprovides some additional information regarding the adequacy ofAvenal's analysis in meeting the I-hourN02NAAQS. Many ofthe responses in the July 13 letterreiterate that these issues were addressed in Avenal's August 2007 protocol.
Avenal's response onpage 4 ofthe attachment to its July 13,2010letterprovides additional information regarding stack N02INOxratios. EPA has considered this information in its response to paragraph 6 ofthe June 28, 2010 letter, which is presented above.

3. Page 6.2-61 ofthe AFC states "Annual NOximpacts were converted to N02 using the EPA-guidance Ambient Ratio Method and the nationwide default conversionratio of0.75 for the annual average N02INOxratio."EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 Page 20

Avenal's response on page 5 and 6 ofthe attachment to its July 13,2010letter addresses 40 CFR Part 51, Appendix W, paragraph 3.2.2(e), regarding the use of alternative models. Inresponse, with respect to the various provisions in paragraph 3.2.2(e), EPA believes that:
Provision i. The model has received a scientific peerreview: This provision is adequately addressed.
Provision ii. The model canbe demonstrated to be applicable to the problemon a theoretical basis: This provision is not adequately addressed. That the project is located in an area ofhigh ozone concentrations does not necessarilyjustifythe use ofPVMRM, nor does it necessarily imply a particularbias orlackofbias in the results.
Provision iii. The data bases which are necessary to perform the analysis are available and adequate: We do not agree this provision is adequately addressed, for the reasons discussed in ourresponses above to paragraphs 2, 6, 11, and 12 ofthe June 28, 2010 letter.
Provision iv: Appropriate performance evaluations ofthe model have shown that the model is not biased toward underestimates: This provision is adequately addressed.
Provision v: A protocol on methods and procedures to be followed has been established: This provision is not adequately addressed, and was not approved in the previous submittals. Please provide a protocol that is consistent with the comments stated above.