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, TX 77002 

Dear Mr. Rexroad: 

Thank you for the letters of June 28, 2010 and July 13,2010 from your counsel, Jeffrey 

Holmstead, to Ms. Julie Walters, counsel for EPA Region 9, and Ms. Stephanie Talbert, counsel 

with the U.S. Department of Justice. These letters provide the Avenal Power Center LLC's 

(Avenal or APC) response to EPA's letter dated June 15,2010 concerning Avenal's 

Supplemental N02 Air Quality Impact Analysis for the Avenal Energy Project (AEP) dated May 

13,2010 and submitted to EPA on May 14,2010. Avenal's supplemental analysis was intended 

to address the I-hour national ambient air quality standard (NAAQS) for nitrogen dioxide 

(N02), which became effective April 12, 2010, for the AEP. 

EPA's June 15,2010 letter stated that EPA had determined that significant additional 

information must be provided by Avenal for EPA to evaluate whether emissions from the AEP 

will cause or contribute to ambient air pollution in excess of the Federal I-hour N02 standard. 

The EPA letter provided further detail about 10 areas in Avenal's May 13,2010 submittal in 

which EPA had determined that additional information was necessary. Avenal's June 28, 2010 

and July 13,2010 letters indicate that Avenal believes that all necessary information has been 

submitted to EPA to demonstrate compliance with the I-hour N02 NAAQS. We disagree. 

While some of the requested information has been provided, we believe the submittals from 

Avenal to date do not contain all the information necessary for an acceptable I-hour N02 

NAAQS compliance analysis. The text in Attachment 1 below provides a detailed explanation 

of why the information submitted by Avenal 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-hour N02 

NAAQS does not apply to the AEP, but that Avenal has provided additional modeling 

information for that standard in an effort to obtain its PSD permit in a timely manner. We 

certainly understand Avenal's frustration with having to address the Federal I-hour N02 

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Jim Rexroad 

Page 2 

standard at this stage in the PSD permit decisionmaking process, but we have nevertheless 

determined that Avenal must provide information to demonstrate that emissions from the AEP 

will not cause or contribute to air pollution in excess of the I-hour NAAQS for N02, as required 

by CAA 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 after the effective date of the 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 of that standard. See Applicability ofthe Federal 

Prevention ofSignificant Deterioration Permit Requirements to New and Revised National 

Ambient Air Quality Standards, authored by Stephen D. Page, Director, EPA Office of Air 

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-hour N02 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-hour N02 

NAAQS, as described in our June 15,2010 letter and in Attachment 1 below. EPA requested 

several weeks ago to meet with Avenal's technical staff to discuss in further detail EPA's 

comments on Avenal's I-hour N02 NAAQS 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. We remain 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 and justifications previously submitted to 

EPA and other regulatory agencies concerning the project in the context of analyses 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 of pages of data, analysis, 

and explanation that EPA requested 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 other regulatory agencies for the purposes of 

demonstrating compliance with the Federal annual N02 standard or the State I-hour N02 
Jim Rexroad 

Page 3 

standard cannot simply be assumed to demonstrate the AEP's compliance under the Clean Air 

Act PSD program with the Federal I-hour N02 standard. Further, EPA did not previously 

accept or approve Avenal's use of such information, data, protocols and analyses for the 

purposes of demonstrating compliance with the Federal I-hour N02 standard; indeed, that 

standard had not been finalized at the time such information was initially submitted and thus 

would not have been reviewed for that purpose. 

Clean Air Act section I65(a)(3) requires the owner of operator of a facility subject to 

PSD to demonstrate compliance with each NAAQS. The demonstration to be provided by the 

applicant pursuant to CAA I65(a)(3) must include a CAA PSD 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 not based on a Federal standard may involve regulatory requirements 

different from those governing the PSD program. In the case of the 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 or which discuss 

the State I-hour N02 standard (which differs from the Federal I-hour N02 standard) cannot be 

assumed appropriate for demonstrating compliance with the Federal I-hour N02 standard absent 

specific technical justification provided by the applicant supporting their application for 

modeling under the PSD program for the Federal I-hour N02 standard. In our view, acceptable 

justification for using much of the information previously submitted has not yet been provided 

by Avenal. In some areas, the information submitted is clearly inadequate for a I-hour N02 

NAAQS modeling demonstration and must be supplemented with a complete analysis. 

Avenal's letter dated July 13,2010 states that "EPA has refused to approve [Avenal's] 

modeling, saying, among other things, that it wanted to finalize modeling guidance for the new 

I-hour N02 standard and then review [Avenal's] new modeling against that guidance." This 

statement is incorrect. EPA's June 15 letter did not state that EPA would not review or approve 

Avenal's submittal pending the issuance of formal EPA guidance. The fact that EPA provided a 

detailed response on June 15,2010 to Avenal's submittal, prior to the issuance of EPA's 

guidance on June 28-29,2010, belies this statement. EPA's June 15,2010 letter merely 

mentioned that we anticipated that an EPA guidance document on N02 modeling would be 

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-hour N02 NAAQS, with a cover memorandum entitled Guidance Concerning 
Jim Rexroad 

Page 4 

Implementation ofthe I-hour N02 NAAQS for the Prevention ofSignificant Deterioration 

Program, dated June 29, 2010, that included two attached guidance documents, one of which 

was entitled Applicability ofAppendix W Modeling Guidance for the I-hour N02 National 

Ambient Air Quality Standard, dated June 28, 2010. These guidance documents provide EPA's 

current views on certain subjects relevant to the I-hour N02 NAAQS. The July 13 letter and its 

attachment describe why Avenal believes that its analysis addresses various components of the 

guidance. We have reviewed and considered that discussion in the July 13 letter, and our 

response is provided in Attachment 1 below. 

In light of the 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 letter by August 17, 2010 confirming 

that it intends to provide additional information and justification that fully addresses EPA's 

remaining concerns as described in the detailed comments below. If Avenal 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-hour NAAQS by August 17,2010, 

we plan to proceed with permit decisionmaking for the AEP based on the information received to 

date. On the other hand, if Avenal does plan to provide additional information, we request that 

that information be provided by no later than September 13,2010. If you 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, via email and U.S. Mail): 

Jeffrey R. Holmstead, Bracewell & Giuliani LLP 

Gary Rubenstein, Sierra Research 
ATIACHMENT 1 

On June 15,2010, EPA provided 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-hour national 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's June 15, 

2010 letter. In a letter dated July 13, 2010, the applicant provided some additional 

information concerning the analysis. This letter provides EPA's response to the 

applicant's June 28, 2010 submittal, as well as a response to certain aspects of the July 13 

letter (and its attachment) where the letter provided additional information from the June 

28,2010 letter. 

Summary of EPA's Responses to Avenal's June 28, 2010 Letter, Paragraphs 1-12 

Avenal's response provides sufficient information to address several of the 

comments made in EPA's June 15,2010 letter. The information provided for downwash 

(paragraph 9) and operating emissions (paragraph 4) is adequate. 

With respect to several other issues, EPA believes that substantial additional 

information will be required for review. Specifically, the information provided in the 

applicant's response for nearby sources (paragraph 1) and justification for the method of 

adding modeled and monitored data (paragraphs 7 and 8) are not adequate. 

EPA has also reviewed the justification 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 of detail 

provided is not sufficient for an analysis of the I-hourN02 NAAQS. While the facility 

impact was well below the annual N02 NAAQS -- less than one percent of the standard ­

- the facility impact combined with background levels of N02 for the I-hour N02 

NAAQS is near the standard, and therefore a more detailed analysis is warranted. In 

addition, the spatial and temporal distribution of hourly N02leveis from 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 N02 NAAQS cannot simply be referenced as being adequate to address the issue 

of representativeness for the I-hour N02 NAAQS. 

The justification for use of the 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 be provided. 

These issues are discussed in greater detail below. 
EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 

Page 2 

Discussion of EPA'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 1 in Attachment A to EPA's June 15,2010 letter stated: 

Avenal's May 13,2010 I-hour N02 submittal did not include necessary 

information indicating which, if any, nearby sources were modeled or the process 

used to determine which nearby sources should be included. A full impact 

analysis should include modeling of nearby sources as well as monitored 

background values. The recommendations for modeling for nearby sources are 

discussed in EPA's Guideline on Air Quality Models (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 of the source 

or sources under consideration for emission limit(s) should be explicitly modeled. 

Please provide a description of the process used for determining which nearby 

sources should be included in the modeling, as well as the modeling analysis for 

any such sources. 

EPA's June 15 letter also quoted relevant language from Guideline on Air Quality 

Models Subsection 8.2.3. 

Paragraph 1 of Avenal'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." It cites 

information from two analyses: the Localized Impacts analysis previously provided by 

the applicant to the California Energy Commission (CEC), and the Additional Impact 

Analysis previously submitted by the applicant (March 2009, Class II Impacts Analysis). 

EPA does not believe that the information described in paragraph 1 of Avenal's 

June 28,2010 letter provides an adequate basis on which EPA can determine whether all 

sources expected to cause a significant concentration gradient in the vicinity of the source 

under consideration for emission limits have been considered. As discussed in more 

detail below, the information provided in the applicant's June 28,2010 letter, including 

the attachments provided for the Localized Impact Analysis and Additional Impact 

Analysis, is not sufficient for EPA to determine if the recommendations in the Guideline 

on Air Quality Models (40 CFR Part 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 California Energy Commission (CEC). The 

Localized Impact Analysis does not address nearby sources as recommended in the 

Guideline on Air Quality Models (40 CFR Part 51, Appendix W), Subsection 8.2.3. The 
EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 

Page 3 

requirements of the CEC Localized Impact Analysis, as presented in Section 6.2.7.1.2 of 

the APC, differ from PSD program criteria in several significant aspects, such as 

excluding sources beyond six miles, and being limited to stationary sources. In addition, 

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 28,2010 response states that "APC Section 6.2.7.1.2 

(Localized Impacts) thoroughly discussed the criteria used to evaluate whether any 

stationary sources existed within six miles that would qualify to be explicitly included in 

a cumulative air quality modeling impact analysis. None were identified by either the 

Applicant or the SJVAPCD." 

APC Section 6.2.7.1.2 (Localized Impacts) is presented here: 

6.2.7.1.2 Localized Impacts 

The CEC has defined this local analysis as "a cumulative air quality modeling 

impacts analysis of the 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 of six 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 air pollution permits 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 of the emissions from this category of facilities was performed. 

The District was requested on July 19, 2007, to provide information on any 

sources that might be appropriate (Le., within 6 miles and with an emission 

increase of at least 5 tons per year for a criteria pollutant) for a cumulative air 

quality impact analysis, but has not identified any. Consequently, no localized 

cumulative impact modeling analysis was performed for the proposed project. 

2. Discussion of applicant's response. 

The applicant's reference to the CEC Localized Impact Analysis previously 

conducted for purposes of its State and local permitting process does not demonstrate that 
EPA 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 of the source under consideration 

for emission limits, which should be explicitly modeled, in the context of the PSD 

program. The Localized Impact Analysis provided by the applicant does not fully 

address all the factors germane to the identification of nearby sources in the context of 

PSD modeling, as explained in more detail below. 

a. CEC requirements differ from PSD criteria. 

First, the requirements of the 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 "a cumulative air quality modeling impacts analysis of the 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 of the project's typical operating mode. 

b. Existing sources are not included in the applicant's response. 

Second, while both the CEC's definition of a Localized Impact Analysis and EPA 

PSD recommendations for a nearby source analysis include consideration of existing 

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 air quality data that have been used to 

represent background concentrations for the proposed project." The applicant provides 

no demonstration, however, of how 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 of the fact that the existing projects are 

presumably within a distance of six miles of the source, whereas the background 

monitoring site is 28 miles away, at Hanford. 

In addition, background monitoring data may 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 of background sources, and this impact would not be captured 

via monitoring. Background concentrations should be determined for each critical 

(concentration) averaging time." 

40 CFR Part 51, Appendix W, Subsection 8.2.3.c. states: "For compliance 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 capacity to 
EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 

Page 5 

emit, the 'maximum allowable emission limit' for such a nearby source may be 

calculated as the emission rate representative of the 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 capacity to emit is for such a nearby source." Table 8-2: Point 

Source Model Emission Input Data for NAAQS Compliance in PSD Demonstrations 

indicates that the appropriate emission input for nearby sources is the maximum 

allowable emission limit or federally enforceable permit limit. 

c. Adequate documentation of the District's response is not provided. 

Third, the applicant's June 28, 2010 response appears to rely in part on the fact 

that the San Joaquin Valley Air Pollution Control District (SJVAPCD) did not identify 

any sources in response to a July 19,2007 letter requesting that the District: 

identify any stationary source located within 6 miles of the Project, having a 

criteria pollutant emission rate of at least 5 tons per year, and which have received 

construction permits but are not yet operating, or are in the permitting process 

(i.e., existing emission sources are accounted for in background air quality 

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, and therefore is not consistent with 

what would be 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 28,2010 response also notes that the analysis concludes, "no 

localized cumulative impact modeling analysis was performed for the proposed project," 

based on SJVAPCD' s response to the letter request described above. However, the 

concerns stated above regarding the limited scope of the localized impacts inquiry and 

analysis, and the limited information provided about the District's response, apply 

equally to the analysis's conclusion that no localized cumulative impact modeling 

analysis would be performed. 

d. Conclusion. 

The information provided in the applicant's response concerning the Localized 

Impact analysis is not sufficient for EPA to determine whether all sources expected to 

cause a significant concentration gradient in the vicinity of the source under consideration 

for emission limits have been identified, consistent with EPA's Guideline on Air Quality 

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 28,2010 response states, "In March 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 of significance (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 or documentation of any search for nearby emission sources. Further, its 

conclusions regarding the project's impact area in the context of the annual N02 standard 

are inapplicable to the I-hour N02 standard, as discussed below. 

1. Applicant's June 28,2010 response. 

The applicant's June 28, 2010 response states, "In March 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 of significance (Le., excluding 

farm machines and rural roads) and potentially sensitive areas within the surrounding 

Class II region. The results of that study were that: 

•	 the project has no 'impact area' as defined by EPA guidance; and 

•	 no potentially sensitive state or federal parks, forests, monuments, or recreation 

areas are located within 50 km in this rural part of the Central Valley." 

2. Discussion of applicant'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 of the source under consideration for emission limits, which should be explicitly 

modeled, in the context of the PSD program. The Class II impacts analysis does not fully 

address all the factors germane to the identification of nearby sources in the context of 

PSD modeling, as explained below. 

a. The Additional Impact Analysis does not provide information on nearby sources. 

First, the applicant's response indicates that as part of its Additional Impact 

Analysis,l the applicant performed an additional search for other sources of significance. 

However, the applicant's Additional Impact Analysis includes no discussion or 

documentation of any search for nearby emission sources. 

1 We 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-hour N02 standard. 

Second, the applicant's response states that "[t]he results of that study were that 

the project has no 'impact area' as defined by EPA guidance." 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 N02 NAAQS, because the "no impact 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 sa does not apply for the 1- hour N02 

NAAQS. Therefore, this information does not provide information germane to the 

nearby source analysis for the I-hour N02 NAAQS. 

We note that the EPA guidance document issued by EPA's Office of Air Quality 

Planning and Standards entitled General Guidance for Implementing the I-hour N02 

National Ambient Air Quality Standard in Prevention ofSignificant Deterioration 

Permits, Including an Interim I-hour N02 Significant Impact Level, dated June 28, 2010, 

provides a recommended interim sa for the I-hour N02 NAAQS of 4 ppb. 

c.	 Discussion of sensitive 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, or recreation areas are located within 50 km in this 

rural part of the 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 of the source under consideration 

for emission limits have been identified, consistent with EPA's Guideline on Air Quality 

Models, Subsection 8.2.3. 

II. Paragraph 2 

Avenal's paragraph 2 refers to the statement made on the first page of EPA's June 

15,2010 letter that "[k]ey input data used in the PVMRM option within AERMOD needs 

to be discussed and justified." 

The information provided in paragraph 2 in Avenal's June 28, 2010 letter 

discusses the use of the ozone data submitted by Avenal in the PVMRM option within 

AERMOD, but does not provide adequate justification for use of the ozone data in this 

context for purposes of the PSD program. In addition, other key input data used in the 

PVMRM option within AERMOD, such as stack gas N02INOx ratios, need to be 
EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 

Page 8 

discussed and justified. 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 PSD permit. However, EPA did not have any 

basis to review the use of the 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 cited by Avenal in its June 28, 2010 

response states on page 6.2-61 that, "Annual NOx impacts were converted to N02 using 

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 met by using an acceptable method, the Ambient 

Ratio Method. The nationwide default conversion ratio of 0.75 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-hour N02 (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 of the non-regulatory-default 

PVMRM option in AERMOD and use of the hourly ozone data from the Hanford, CA 

monitoring station for this analysis was discussed on pages 6.2-60 and -61 of the AFC, 

this was not part ofthe PSD annual N02 NAAQS analysis, and therefore was not 

reviewed or approved by EPA. At the time the AFC data was provided, EPA had no 

reason for considering, and did not consider, the appropriateness of the use of the ozone 

data for an analysis relating only to the State's I-hour N02 standard. 

Paragraph 2 in Avenal's June 28,2010 letter also states that"[t]he regulatory 

requirement of representativeness was satisfied by the District's selection of the Hanford 

monitoring station as being the closest, and adequately close, source of the hourly ozone 

data. The use of air quality and meteorological data from Hanford, which is 28 miles 

northeast of the project site, was discussed in Sections 2.4 (Data Requirements ­

Meteorological Data) and 2.5 (Data Requirements - Ambient Monitoring Data) in the 

May 13,2010 Supplemental N02 Air Quality Impact Analysis, 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 of air pollution 

between Hanford and the project except for the Lemoore Naval Air Station, which is 

located 14 miles northeast of the project." [footnotes omitted] 

The statements that the source is 28 miles northeast of the project site, is the 

closest source, and is adequately close, are not sufficient to show that the data is 

representative. The discussion of representativeness for ambient air quality data should 

be specific to the pollutant for the appropriate averaging time. For example, the 

discussion of representativeness for hourly ozone data in the San Joaquin Valley should 

consider the regional pattern of ozone in the San Joaquin Valley. The effect of local 

sources on the formation and destruction of ozone should be considered. For example, is 
EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 

Page 9 

the monitoring station near a roadway that may be a local sink of ozone? Conditions at 

the project site should be 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 of EPA's June 15,2010 letter that "documentation and justification of the 

appropriateness of the meteorological and ambient air quality background data for the 1­

hour N02 analysis needs to be provided." 

A discussion of the documentation and justification of the appropriateness of the 

meteorological and ambient air quality background data for the I-hour N02 analysis 

provided in the applicant's June 28, 2010 response is included in EPA's response to 

paragraphs 10 and 11 below. 

IV. Paragraph 4 

EPA has reviewed Avenal's response to EPA's Comment 2 regarding the need to 

provide documentation of the source emission input data for averaging times appropriate 

for the federal I-hour N02 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 of its original PSD application, as described below. 

With respect to short-term, hourly emission rates for NOx, the applicant noted 

the need to update the originally estimated rates 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 of establishing 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 of the hourly rate of the CTG+HRSG, an update was 

made for the natural gas-fired emergency generator. The update was a reduction in the 

emission rate for NOx (grams per brakehorsepower-hour, or g/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 2.841bslhr to 1.90 lbslhr). The emission rates for the 

auxiliary boiler and diesel fire pump remained the same. Below summarizes EPA's 

understanding of the hourly NOx emission rate (lbslhr) for each piece of equipment. 

Equipment NOx, emissions (not to exceed) 

CTG+HRSG 

(no duct burner) 

permitted: 13.55 lbslhr 

permitted: 2.0 ppm @ 15% 02 

CTG+HRSG 

(with duct burner) 

permitted: 17.20 lbslhr 

permitted: 2.0 ppm @ 15% 02 

emergency generator permitted: 1.0 g/bhp-hr 
EPA 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 water pump 

288 hp 

permitted: 304 g/bhp-hr 

calculated: 2.2 lbslhr (2.16 lbslhr) 

auxiliary boiler 

37 A 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-hour N02 standard. 

V. Paragraph 5 

EPA has reviewed Avenal's response in paragraph 5 of its June 28, 2010 letter to 

EPA's Comment 3 regarding the inclusion of the startup or shutdown emissions. In 

addition to the information cited in footnote 24 (i.e., EPA's June 2009 Statement of Basis 

and Ambient Air Quality Impact Report), we acknowledge that EPA was in receipt of the 

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 air quality 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 of the following: (a) Case 

4 (from vendor data) that represents 50% load and 101 degrees F; and (b) a cold start 

estimate of 80 lbs/hour (each), which appears to be based on a compilation of other 

facilities' cold start data. 

Guideline on Air Quality Models (40 CFR Part 51, Appendix W, Subsection 

8.1.2) Source Data recommends that for point source applications, the load or operating 

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 50 percent and 75 percent of capacity 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-hour NOx scenario; i.e., why other loads (e.g., 60%, 75%) and other ambient 

conditions were not considered or demonstrative of the worst-case I-hour NOx emission 

rate. 

VI. Paragraph 6 

EPA has reviewed Avenal's June 28 response to EPA's Comment 4 regarding the 

in-stack ratios. Avenal has selected the in-stack N02/NOx ratio 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, as 
EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 

Page 11 

derived from information related to the Palomar Energy Center (Palomar) in Escondido, 

California, a facility that operates within the San Diego Air Pollution Control District 

(SDAPCD). Avenal did not provide the specific background information cited for EPA 

in support of the 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 air quality modeling; therefore, we request the following: 

A. Source Test 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 if the source test data relied 

upon is a result of emissions compliance testing or a result of other circumstances. Based 

on this information, the applicant should provide a discussion that demonstrates the 

representativeness and comparability of this information for Avenal's selection of the 

proposed ratios for normal, startup and commissioning operations. 

B. Other Support Information (if applicable): We are not aware that source tests 

have generally been conducted during the startup and commissioning phases of 

operations specific for the collection of information to determine the in-stack N02INOx 

ratio. Ifthe development of the normal, startup, and commissioning ratios also were 

based on another methodes) other than source testing, the applicant should provide the 

information that Avenal has relied upon. For instance, if continuous emissions 

monitoring also was relied upon, please provide a discussion that also demonstrates the 

representative and comparability of this information for Avenal's selection of the 

proposed ratios. 

C. San Diego APCD Recommendations: Avenal stated that the proposed instack ratio values of 0.25 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 and rationale. 

VII. Paragraph 7 

EPA recognizes that detailed guidance regarding dispersion modeling for 

demonstrating compliance with the I-hour N02NAAQS was limited at the time of 

Avenal's May 13,2010, submittal. Additional guidance was issued on June 28, 2010, in 

the form of a clarification memorandum on the Applicability ofAppendix W Modeling 

Guidance for the i-hour N02 National Ambient Air Quality Standard. The first 

paragraph on page 5 of this N02 clarification 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 that may be applied withoutfurther 

justification is to add the overall highest hourly background N02 concentration from a 

representative monitor to the modeled design value, based on the form ofthe standard, 

for comparison to the NAAQS. Additional refinements to this 'first tier' approach based 
EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 

Page 12 

on some level oftemporal pairing ofmodeled and monitored values may be considered 

on a case-by-case basis, with adequate justification and documentation." 

Although EPA's June 28, 2010 N02 clarification memorandum acknowledges 

that some level of temporal pairing of modeled and monitored N02 concentrations may 

be appropriate in some situations, the justification regarding pairing on an hour-by-hour 

basis provided in Avenal's response, which states that the "approach guarantees 

meteorological consistency for each pair of background and modeled concentrations 

combined in each hour of the year," does not provide a sufficient rationale to support that 

approach in this case. There may be sound technical arguments to account for 

consistency in terms of the meteorology affecting both background and modeled 

concentrations, but the justification also needs to consider the spatial representativeness 

of the monitored data as well, which is not addressed in Avenal's response to this 

comment. 

The aspect of temporal pairing of modeled and monitored concentrations is also 

acknowledged in EPA's March 23, 2010 memorandum from Stephen Page regarding 

Modeling Proceduresfor Demonstrating Compliance with PM2.5 NAAQS, where EPA 

indicates on page 8 that a Second Tier approach for combining modeled and monitored 

PM2.5 concentrations on a seasonal or quarterly basis may be considered when the 

modeled primary PM2.5 impacts and background 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 or quarterly basis, the recent 

draft PM2.5 Hot Spot Conformity Guidance (EPA, 2010) recommends combining the 

average of the highest modeled 24-hour concentrations within each season/quarter to 

each of the 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 of the 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 of PM2.5 on a daily basis is likely to be much greater than the spatial 

homogeneity of background levels of N02 on an hourly basis. 

While the background ambient monitored N02 values, if appropriately justified, 

are presumed to be representative in a general sense of background concentrations for 

purposes of a cumulative impact assessment, pairing the monitored background values 

with modeled concentrations on an hour-by-hour basis implies an assumption that the 

monitored concentrations are equally representative at each location within the modeling 

domain for each hour of the simulation. There is no technical or even rational basis to 

support such a degree of representativeness in this case or any other case. Such a degree 

of representativeness would also be unreasonable to impose as a general requirement for 

use of background monitored data, given the limited number of monitors available. 

However, any modeling approach developed regarding the use of monitored background 

concentrations as part of a cumulative impact assessment must take into account these 

limitations of monitored data. 
EPA Response to Avenal Letters dated June 28, 2010 and July 13, 2010 

Page 13 

It appears that the approach used to combine hourly modeled and monitored NOz 

concentrations for comparison to the I-hour California Ambient Air Quality Standard 

(CAAQS) in Avenal's AFC submittal to the CEC was consistent with the approach 

recommended as the "first tier" assumption for combining modeled and monitored NOz 

concentrations described in the June 28, 2010, N02 clarification memo. The results from 

the I-hour NOz CAAQS comparison summarized in Table 6.2-31 (6.2-66) of the APC 

show maximum I-hour Avenal facility impacts of 190 Jlg/m3

, combined with a 

background concentration of 137.2 Jlg/m3 to give a total impact of 327.2 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 NOz concentration documented in the APC is likely to 

be higher than the 98th-percentile of the annual distribution of maximum daily I-hour 

values used as the form of the I-hour EPA standard. However, the AFC results are also 

about 2.7 times higher than the cumulative I-hour NOz impact reported in the May 13, 

2010 submittal, which serves to highlight the significance of the issue raised by EPA in 

this comment, and to emphasize the importance of having clear justification and 

documentation of the approach taken for combining modeled and monitored 

concentrations for comparison to the NAAQS. 

VIII. Paragraph 8 

Paragraph 8 address EPA's comment that Avenal's May 13,2010 I-hour N02 

submittal labeled hours with missing ambient monitored background 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 methodology used 

faithfully follows the requirements in the I-hour N02 NAAQS Final Rule, the only 

reasonably applicable regulatory guidance available at the time of this supplemental 1­

hour N02 analysis." 

The procedures in Appendix S to 40 CFR Part 50, which are provided in the 

reference cited as "the only reasonably applicable regulatory guidance available at the 

time of this supplemental 1 hour N02 analysis," apply to ambient monitored N02 

concentrations and are not relevant for modeled N02 concentrations. EPA disagrees that 

it is suitable to apply the currently available monitoring guidance for the I-hour N02 

standard to modeling applications, as suggested by Avenal. 

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 of the suitability of 

the currently available guidance with respect to monitoring compliance with this N02 

standard by 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 entitled Applicability ofAppendix W Modeling Guidance for the i-hour N02 

National Ambient Air Quality Standard (June 28, 2010) may be useful in preparing an 

analysis of the I-hour N02 NAAQS. 
EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 

Page 14 

EPA believes that its objection that the Avenal's May 13,2010 I-hour N02 

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's June 15,2010 letter, which states: "Avenal's May 13,2010 1­

hour N02 submittal did not include any discussion of how 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-hour N02 NAAQS analysis. 

X. Paragraph 10 

Paragraph 10 in Avenal's June 28, 2010 response refers to Comment 7 in 

Attachment A to EPA's June 15,2010 letter, which describes in detail the type of 

analysis that EPA guidelines indicate is appropriate to demonstrate the representativeness 

of the 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 of the data. 

EPA's Comment 7 states, "This analysis should include a discussion of the 

representativeness of the surface characteristics. The surface characteristics input to 

AERMET should be based on the land cover characteristics in the vicinity of the 

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 

by the 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 computed by the 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]ther candidate meteorological stations 

should be discussed." No other candidate 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 ofthe upper air 

station used for this analysis should be discussed." Avenal's June 28, 2010 response 

states, ''The District's proposed Camp Pendleton meteorological data are representative 

of conditions at the project site," and "[r]epresentativeness is best evaluated 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 conclusion that the project site and the Camp Pendleton meteorological 

monitoring station the project site are climatologically similar; this analysis should be 

provided. 

Paragraph 10 in Avenal's June 28, 2010 response provides some information 

regarding the surface meteorological station. However, the following portion of EPA's 

Comment 7 was not addressed: "[S]ince the spatial scope of each variable could be 

different, representativeness should be judged for each variable separately. For example, 

for a variable such as wind direction, the data may need to be collected very near plume 

height to be adequately representative, whereas, for a variable such as temperature, data 

from a station several kilometers away from the source may in some cases be considered 

to be adequately representative." Avenal should address this issue in its analysis. 

XI. Paragraph 11 

Comment 8 in Attachment A to EPA's June 15,2010 letter states that "Avenal's 

May 13, 2010 I-hour N02 submittal did not include any analysis showing the 

representativeness of air quality data at the Hanford site with respect to the conditions at 

the project. The submittal should include the appropriate analysis, and other candidate 

ambient air quality monitoring stations should be discussed." In response, Avenal's June 

28, 2010 letter refers to previous submittals Avenal has made, but these submittals do not 

provide an adequate analysis, as explained in more detail below. 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 of the data. 

A. N02 data representativeness has not been adequately justified for the I-hour 

NAAQS. 

1. Summary of information presented in paragraph 11 of Avenal's June 28 response for 

representativeness of N02 data. 

Paragraph 11 in Avenal's June 28 response first refers to Avenal's May 13, 2010 

Supplemental N02 Air Quality Impact Analysis submittal, Section 2.5 (Data 

Requirements - Ambient Monitoring Data) on pages 6 and 7, which states: 

Ambient N02 data collected during the five-year modeling period of 2000-2004 

at the Hanford monitoring station were used to characterize the representative 

ambient background concentrations. The ambient pollution levels monitored at 
EPA 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 of any particular facility due to the lack of any large 

local industrial sources in the Hanford area. 

Avenal also refers to Section 6 (Existing Ambient Air Quality Data) of the modeling 

protocol submitted to EPA Region 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. The justification for representativeness of the N02 data presented in Avenal's June 28 

response is not adequate for the I-hour N02 NAAQS. 

The discussion on representativeness presented by Avenal and described above, 

i.e., that there is a lack of any 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 of representativeness for ambient air quality data 

should include a discussion of why the ambient pollution levels monitored at the Hanford 

monitoring station represent area-wide ambient conditions, not simply that they do not 

represent localized impacts. The discussion should be appropriate for the pollutant for the 

appropriate averaging time. For example, the discussion of representativeness for hourly 

N02 data in the San Joaquin Valley should include a discussion of the sources and 

conditions likely to contribute to high hourly levels of N02 in the San Joaquin Valley. 

The project site should be compared to various monitoring sites in the San Joaquin 

Valley. This type of information has not been provided. 

3. N02 data were not previously reviewed or approved by EPA for the I-hour N02 

NAAQS. 

The N02 data Avenal proposes to use for the I-hour N02 NAAQS analysis were 

not used in the air quality analysis for the annual N02 NAAQS 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 noted by the APC (6.2-64, Table 6.2-28 Evaluation of Preconstruction 

Monitoring Requirements), the Avenal Energy Project avoided preconstruction 

monitoring for the annual N02 standard, in part, for a different reason: the predicted air 
EPA Response to Avenal Letters dated June 28, 2010 and July 13.2010 

Page 17 

quality impacts of the project would not exceed defined monitoring de minimis levels 

known as significant monitoring concentrations. These de minimis levels do not apply to 

the I-hour N02 NAAQS. 

The N02 ambient data used for the annual N02 NAAQS analysis were not 

evaluated by EPA in that context in light ofthe fact that the analysis did not use ambient 

N02 data, and the fact that the analysis had a project impact below the monitoring de 

minimis level. These factors are not present in the context of the I-hour N02 NAAQS. 

Thus, EPA did not review or approve the information submitted at that time with respect 

to representativeness for the I-hour N02 NAAQS. 

Avenal also refers to Section 6 (Existing Ambient Air Quality Data) of the 

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 that standard did not exist at 

the time. 

B. Ozone data representativeness for use with the non-regulatory-default PVMRM 

option in AERMOD has not been adequately justified for the I-hour N02 NAAQS. 

1. Summary of information presented in paragraph 11 of Avenal's June 28 response for 

representativeness of ozone data. 

Avenal refers to Section 6 (Existing Ambient Air Quality Data) of the 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 representativeness justification presented in the protocol is limited to the fact that the 

Hanford monitoring site is nearest to the facility. 

2. Ozone data representativeness has not been adequately justified by Avenal. 

The discussion of representativeness for ambient air quality data should be 

appropriate for the pollutant and averaging time. For example, the discussion of 

representativeness for hourly ozone data in the San Joaquin Valley should consider the 

regional pattern of ozone in the San Joaquin Valley, as well as local sources and sinks of 

ozone. Conditions at the project site should be compared to conditions at monitoring 

sites in the San Joaquin Valley. 

3. Ozone data was not previously reviewed or approved by EPA for the I-hour N02 

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 itself indicates that ozone data was not used in the annual N02 analysis. 

The "Annual NOx impacts were converted to N02 using the EPA-guidance Ambient 

Ratio Method and the nationwide default conversion ratio of 0.75 for the annual average 

N02/NOx ratio."z The federal requirements for the annual N02 NAAQS analysis were 

met by using 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 of the 

annual N02 analysis. 

Avenal's June 28 response also states that "EPA refers to the modeling use of 03 

and N02 background monitoring air quality data in Section 8.1 (Background Ambient 

Air Quality and Conditions) on page 24 of the June 2009 Statement ofBasis and Ambient 

Air Quality Impact Report For a Clean Air Act Prevention ofSignificant Deterioration 

Permit without 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-hour N02 NAAQS did not exist at that time. 

Avenal also refers to Section 6 (Existing Ambient Air Quality Data) of the 

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 of air quality data at the Hanford site with respect to the conditions at 

the project in the context of the I-hour N02 NAAQS. 

XII. Paragraph 12 

Paragraph 12 refers to Comment 9 in Attachment A to EPA's June 15,2010 letter, 

which states that "[t]his method for substituting missing 03 concentrations should be 

replaced with a clearly defined approach that includes a reasonable assurance that 

substituted values will not result in underestimates of ambient N02 concentrations." 

Avenal's June 28, 2010 response does not adequately address EPA's comment. 

EPA did not suggest that Avenal should "[a]rtificially reduc[e] the substituted 

concentrations to artificially increase the resulting I-hour N02 concentration." Rather, 

EPA stated that Avenal should provide a "reasonable assurance that substituted values 

will not result in underestimates of ambient N02 concentrations." Avenal has not 

provided reasonable assurance that the method used -- substituting concentrations with 

"hour-appropriate" values (e.g., from the previous day, or the next day, for the same 

2 Avenal Energy AFC 6.2-64) 
EPA Response to Avenal Letters dated June 28, 2010 and July 13, 2010 

Page 19 

hour) -- will not result in underestimates of ambient N02 concentrations. For example, 

Avenal has not indicated whether there were instances in which there were "hourappropriate" data for both the day before and day after the date on which data was 

missing, and whether in any such cases it took the higher of the two values. 

Avenal states that the information it is relying on was submitted previously to 

EPA without comment from EPA. The fact that Avenal may have provided the approach 

it is now proposing to use for the I-hour N02 NAAQS in submittals to EPA that 

preceded the issuance of this standard does not mean that EPA has accepted this 

approach. EPA has 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 of the annual N02 NAAQS. The 

PSD requirements for an analysis of the annual N02 NAAQS analysis were met by using 

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's June 

2009 Statement ofBasis and Ambient Air Quality Impact Report For a Clean Air Act 

Prevention ofSignificant Deterioration Permit, was based on the Ambient Ratio Method 

and the nationwide default conversion ratio of 0.75 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 of the 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 of that analysis indicate that the total I-hour N02 impact 

is 327!tg/m~. This analysis was not part of the PSD analysis, and therefore was not 

reviewed or approved by EPA, and the appropriateness of the ozone data for this use was 

not reviewed by EPA. 

EPA's Response to Avenal's July 13,2010 Letter and Its Attachment 

Avenal's July 13,2010 letter provides some additional information regarding the 

adequacy of Avenal's analysis in meeting the I-hour N02 NAAQS. Many ofthe 

responses in the July 13 letter reiterate that these issues were addressed in Avenal's 

August 2007 protocol. 

Avenal's response on page 4 of the attachment to its July 13,2010 letter provides 

additional information regarding stack N02INOx ratios. EPA has considered this 

information in its response to paragraph 6 of the June 28, 2010 letter, which is presented 

above. 

3. Page 6.2-61 of the AFC states "Annual NOx impacts were converted to N02 using the EPA-guidance 

Ambient Ratio Method and the nationwide default conversion ratio of 0.75 for the annual average 

N02INOx ratio." 
EPA Response to Avenal Letters dated June 28, 2010 and July 13,2010 

Page 20 

Avenal's response on page 5 and 6 of the attachment to its July 13,2010 letter 

addresses 40 CFR Part 51, Appendix W, paragraph 3.2.2(e), regarding the use of 

alternative models. In response, with respect to the various provisions in paragraph 

3.2.2(e), EPA believes that: 

Provision i. The model has received a scientific peer review: 

This provision is adequately addressed. 

Provision ii. The model can be demonstrated to be applicable to the problem on a 

theoretical basis: 

This provision is not adequately addressed. That the project is located in an area 

of high ozone concentrations does not necessarily justify the use of PVMRM, nor 

does it necessarily imply a particular bias or lack of bias 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 our responses above to paragraphs 2, 6, 11, and 12 of the June 28, 2010 letter. 

Provision iv: Appropriate performance evaluations of the 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.