February 2 , 2012

Mr. Gerardo Rios Chief, Permits Office U.S. EPA Region 9

75 Hawthorne Street San Francisco, CA 94105

Subject: Pio Pico Energy Center PSD Permit Application

1

- Hour Ozone Compliance Demonstration

Dear Mr. Rios:

As requested by EPA during the December 9, 2011 meeting between representatives of EPA and Pio Pico Energy Center, LLC (Applicant), we are herein submitting additional

information on behalf of the Applicant. Specifically, EPA requested additional

informat ion from the Applicant, using background concentrations from the El Cajon and Otay Mesa monitoring stations.

It should be noted that the Applicant submitted the proposed modeling protocol for the Pio Pico Energy Center (Project) to EPA on December 1, 20 10, with a request for review and comment, consistent with EPA’s policy encouraging early consultation on modeling

issues. 1 EPA did not respond to the Applicant’s request. In the absence of any questions or concern expressed by EPA regarding the protocol

, the Applicant proceeded with modeling and analysis consistent with the protocol, and has expended considerable time and effort in reliance on EPA’s tacit approval. 2



### Background

The Applicant has previously provided air quality analyses demonstrating compliance with federal National Ambient Air Quality Standards (NAAQS) as part of its application for a PSD permit. The demonstration of compliance with the new 1

- hour NO 2 standard

1 Appendix W, Section 10.2.1: “[e]very effort should be made by the Regional Office to meet with all parties involved in a SIP revision or a PSD permit application prior to the start of any work on such a project. During this meeting, a protocol should be established between the preparing and reviewing parties to define the procedures to be followed, the data to be collected, the model to be used, and the analysis of

the source and concentration data.”

2 It should also be noted that during the December 9 me eting EPA staff indicated that any additional concerns regarding modeling issues would be documented in a letter to Applicant on or before December 16, 2011. To date, no such letter has been received and several calls have been placed to EPA modeling

staf f to confirm that any remaining issues have been resolved. However, no calls have been returned. Applicant has therefore proceeded on the assumption that EPA’s requests for additional information about modeling issues have been fully addressed. 

## sierra research

1801 J Street Sacramento, CA 95811 Tel: (916) 444

- 6666 Fax: (916) 444

- 8373

Ann Arbor, MI Tel: (734) 761

- 6666 Fax: (734) 761

- 6755Gerardo Rios

- 2

- February 2 , 2012

was made using Chula Vista monitoring data to characterize regional backgr ound concentrations throughout the entire region. Several non

- project sources were also explicitly modeled as nearby sources to determine the cumulative impact of the project and the existing background. During the December 9 meeting, EPA staff suggested that other monitoring sites might provide a more accurate characterization of background concentrations. Specifically, EPA suggested El Cajon (because it is located approximately the same distance from the ocean as the Project, whereas the Chula Vista

st ation is much closer to the ocean) and the station located at the Otay Mesa border crossing.

While the Applicant disagrees with EPA’s belief that these alternate stations offer any better characterization of regional background than does the Chula Vista station, the Applicant agreed to perform additional analysis to support its PSD application. Specifically, the Applicant agreed to perform a compliance demonstration using El Cajon data as the background concentration at receptors that are closer to El C ajon than to

Chula Vista. 3 The Applicant also agreed to use Otay Mesa data at receptors within 0.5 km of the Otay Mesa station. The additional analysis does not require additional dispersion modeling, and has been performed by replacing Chula Vista backg round NO 2 data at some receptors with El Cajon data or Otay Mesa data, as appropriate.



### El Cajon Data

As noted above, the Applicant agreed to apply El Cajon dat a to all receptors closer to

El Cajon than to Chula Vista. As a screening step, the Applicant applied the El Cajon data to all receptors. The result was that compliance was demonstrated at all receptors, and therefore compliance was demonstrated at the subset closest to El Cajon. The highest 5

- year average of the 98 th percentile cumulative impac t (project plus nearby sources plus regional background) was 173 μg/m 3 . This can be compared to the value reported in the AFC (179 μg/m 3 ) and the standard (188 μg/m 3 ). Because no non

complying receptors were identified, it was unnecessary to limit the an alysis to any particular subset. No further analysis was performed, and additional details are provided

on the worksheet being provided with this letter

.



### Otay Mesa Data

The Otay Mesa station is located at the U

. S

. - Mexico border and is heavily impacted by border traffic. This includes a significant number of vehicles that are not equipped with California emission controls. The monitor shows significant spikes in concentrations during morning and evening rush hours. Because the monitor is directly imp acted by nearby emissions, it cannot be considered representative of background concentrations. Nevertheless, EPA requested that Otay Mesa data be used to evaluate cumulative impacts at receptors within 0.5 km of the station.

3 Lett er, Steve Hill to Gerardo Rios, Pio Pico Energy Center PSD Permit Application Modeling Questions, December 1, 2011

.Gerardo Rios

- 3

- February 2 , 2012

The Otay Mesa station lies j ust outside the Project’s NO 2 impact area. There is only one receptor within 0.5 km of the station that has a project impact above the NO 2 SIL, and there is only one hour in the 5

- year evaluation period where the NO 2 impact from the project exceeds the SI L.

Synthetic Background Concentration Profile

– Previous compliance demonstrations used a conservative synthetic background concentration profile. The profile used in previous demonstrations was constructed by determining, for each month in the 5

- year evaluation period, the maximum concentration for each clock hour during a calendar month. These values were used to construct 60 daily concentration profiles, one for each calendar

month in the five

- year evaluation period.

For the present analysis, a different procedure was used. Following EPA guidance

, 4

multi

- year averages of the 98 th percentile of available background concentrations were calculated by season and hour

- of

- day. The guidance recommends using the 3 rd highest

value for each season and ho ur

- of

- day combination in the evaluation period. The multi

year average for each season is then calculated. This procedure results in four daily profiles, one for each season. The modeled project impact for each hour was then added to the background conc entration in the appropriate seasonal profile. Any resulting value above the standard would be a potential violation.

Using this methodology, the maximum cumulative impact (Project plus nearby sources plus background) at the receptor was determined to be 164 μg/m 3 , which is below the NAAQS of 188 μg/m 3 . The cumulative impact during the one hour when the project’s impact exceeded the SIL was 148 μg/m 3 . See the enclosed worksheet for additional

detail.

If you have any questions regarding this informatio n, please contact the Applicant’s representative David Jenkins at (317) 431

- 1004, or Gary Rubenstein or me at (916) 444

- 6666.

Sincerely,

Steve Hill

cc: John McKinsey, Stoel Rives LLP David Jenkins, Apex Power Group Steve Moore, San Dieg o Air Pollution Control District

Enclosure: CD

4 Fox, Tyler, Additional Clarification Regarding Application of Appendix W Modeling Guidance for the 1

- hour NO 2 National Ambient Air Quality Standard (March 1, 2011). p. 19