## Air Quality Demonstration: SIP Revision for CPV Sentinel Energy Project

Air Quality Impacts The impacts to regional air quality resulting from the proposed Sentinelpower plant were analyzed for three primary criteria air pollutants: ozone, PM2.5 and PMl0. This analysis examines the regional impacts for two air basins for which the District hasjurisdiction including the South Coast Air Basin and the Coachella Valley portion of the Salton SeaAir Basin. More specifically,the impacts of the project are analyzed for 8-hour average ozone, 24-hour and annual average PM2.5 and PMI0. U.S. EPA has designated the South Coast Air Basin as extreme non- attainment for ozone and the Coachella Valley as Severe-15. This means that the South Coast Air Basin must attain the federal standard by 2024 and the Coachella Valley by 201 8. In addition, both air basins are designated as severe nonattainment for 24-hour average PM10. Furthermore, the South CoastAir Basin is one of two regions in California that is designated as non-attainment for annual average PM2.5 with an attainment date of 2015. In contrast, the Coachella Valley has been in compliance with the federal PM2.5 standards with observed concentrations typically at values of only

.a- two thirds ofthe NAAQS. The South Coast Air Basin and Coachella Valley have been in compliance with the federal air quality standards for SO2 and NO2 for more than a decade. The South Coast Air Basin and Coachella Valley are both expected to continue to be in compliance with the recent proposed revisions to the federal standard for each criteria pollutant. California has recently lowered the state annual NO2 air quality standard (below the corresponding federal level) and the Basin was designated in February 20 10 as non-attainment. It is important to note that the degree the Basin was found to in excess of the standardswas fractional and is expectedto be remedied shortly due to oxide ofnitrogen controls scheduled to be implemented to meet the 2015 PM2.5 attainment date. Regional Simulation Methodology To determine the air quality impact due to the Sentinel project, future-year concentrations of ozone and PM2.5 were simulated using the project emissions and then compared to the predicted baseline future year air quality. The simulated impacts to future year air quality were determined using the 2007 AQIVIP air quality modeling methodology. The years selected for simulations included 2014 for PM2.5 and 2023 for ozone. Briefly, the regional impacts are simulated by using National Weather Service (NWS) numerical meteorological model data to provide the characterization ofthe hourly weather



### -. that is coupled with apeer reviewed regional air quality dispersion platform that reacts and transports emissionsthroughout a modeling domain. The 2007 AQMP modeling domain extends from 100 kilometers west of Palos Verdes Peninsula east through Joshua Tree National Monument. The southern boundary ofthe modeling domain extends into Mexico and the northern extent of the domain touches the San Joaquin Valley. Air quality impactswere simulated for a 5 

### X 5 kilometer grid. The South Coast Air Basin and Coachella Valley areboth fully represented in the modeling domain.
The 2007 AQMP used a the state-of-the art modeling platform which utilized the combination ofthe Comprehensive Air Quality Model with Extensions (CAMx) dispersion model with the "one atmosphere" chemistry mechanism to simulate annual average particulate air quality and CAMx with the SAPRC99 chemistry mechanism to simulate episodic gaseous ozone air quality. TheMM5 meteorological model provided critical meteorological inputs for the daily and annual simulations. The simulations utilized mobile source emissions provide by CARB7s 

## EMFAC~M~ and the growth and planning assumptions provided by SCAGfromtheir Interim 2007 Regional Transportation Plan. Point and areas source emissions profiles were developed jointly by the District and CAW. A comprehensive discussion ofthe modeling techniques, input data and model performance is provided in Appendix V ofthe 2007 AQMP, availableat www.aqmd.govlaqmp/07aqmp/aqmp/Appendix V.pdf.
As described in Appendix V ofthe 2007 AQMP, the regional numerical air quality projections followed U.S. EPA guidanceusing relative response factors 

### (RRF)to estimate future year ozone and PM2.5 design values to determine future year attainment ofthe respective 8-hour average and annual average standards. TheRRFs were used to adjust simulated future year air quality by accounting for variance in the model performance.

The ozone simulations were conducted using the CAMx/MM5/SAPRC99 platform for a series ofmeteorological episodes identified in the 2007 AQMP attainment demonstration. Two indices are presented in the air quality analysisto characterize the impact ofthe projects: the ozone air quality impact tothe area in each air basin having the projected maximum concentration; and,the average ozone impacts predicted throughout each ofthe basins. The ozone simulations were conducted for the 2023 baseline and the baseline plus the Sentinel power plant emissions. The impact of the project was estimated by calculating the difference in the simulated impacts for the two emissions scenarios.

The annual PM2.5 simulations were generated for the CAMx/MM5/One-Atmosphere platform for every hour in the year for 2014 for the 2007 AQMP baseline emissions and those for the Sentinel project. The emissions from the proposed source are combustion related and almost exclusively inthe fineparticulate size distribution. Similarly, the projected secondary formation ofparticulates is expected to be concentrated inthe fine size scale aswell. As a consequence, this analysis assumes that the PM2.5 and PM10 impacts arethe same. Future year annual average PMlO concentration impacts were assumed equivalent to the PM2.5 impact for both the annual and 24-hour averaging periods. 

### Visibility Visibility impacts to nearby Joshua Tree, San Gorgonio, SanJacinto Class

### I wilderness 

## . areas were estimated using the CAMxpredicted PM2.5 and gaseous air quality coupledwith the Interagency Monitoring of Protected Visual Environments (IMPROVE) methodology. The EPA sponsored IMPROVEprogram was established to provide background measurements and visual range calculation in support of the federal Regional Haze Rule visibility standard attainment. The IMPROVE technique utilizes empirical relationship visibility-air quality equationsto provide visual range in miles which can be converted into deciviews. The deciviewis an index that scales humanly-perceived changes in visual air quality. The deciview increases as haze increases (and visual range decreases). In general, perception ofvisibility beyond 8-10 miles is very subjective and subtle changes in range are not easily detected by the eye. (Until recent upgrades in automated monitoring, many military airports would not report range more than 

### 8 miles). The deciview index is directly used as the metric for visibility assessment in the federal Regional Haze Rule criterion. A deciview is approximately a 10%change in the light extinction reading. Impacts from sourcesthat result in a 0.5 deciview reduction are considered by EPA to be significant. 

### Air Quality Impacts
Table 

### 1 summarizesthe predicted 8-hour ozone and PM2.51PM10 impactsto the Coachella Valley and Basin. Ozone The maximum increase in 8-hour average ozone concentrationspredicted for the Coachella Valley was at 0.3 ppb. Thepredicted increaseto maximum ozone in the South Coast Air Basin due to the Sentinel power plant was 0.1 ppb. The predicted average Coachella Valley ozone impact was valued at 0.1 ppb and the average South Coast Air Basin impact at less than 0.1 ppb. The 2007 AQMP Basin ozone attainment demonstration indicated that with full implementation ofthe control strategy the Basin would meet the federalNAAQS in 2024 with a predicted maximum 8-hour concentrationof 83ppb and remain in attainment through 2030. The additional maximum ozone impact duetothe Sentinelplant (0.1 ppb) would not jeopardize the Basin ozone attainment. The 2007 AQMP Coachella Valley ozone attainment demonstrationprojected attainment ofthe NAAQS in 201

### 8 with apredicted maximum average concentration of 81 ppb. The projected maximum 8-hour average concentration increase (0.3 ppb) dueto the Sentinel power plant would not result in a delay ofthe observed ozone attainment.

### Table 1 Simulated Total Sentinel Project Regional Air Quality Impacts

Averaging

Period

Annual PM2.5 

# p I I I I I &Hour Basin Average Scenario 

# ~ Impact

I I I I I Ozone

24-Hr



### PM2.5 and 

### PMlO Basin Maximum

Station Impact

PMlO 

# 1 0.01 <pg/m3 

# 1
Annual

As previously discussed, this analysis assumes that -thePM2.5 and PM10 impacts are the same. The maximum impactto the Coachella Valley annual average PM2.5 due to the Sentinel project was predicted at 0.03 pg/m3in2014. The average valley impact was predicted to be lessthan 0.02 pg/m3. The proposed project would result in a 0.01 pgim3of increase to the South Coast Air Basin annual average PM2.5 with an average impact of less than 0.01 throughout the area. I I I PMlO 

# 1 0.01 < pdm3 

## ( 0.01 pg/m3 0.015 pg/m3 

# 1 0.03 pg/m3 

# 1

Theproject was predicted to generate a maximum 24-hour PM2.5 impact of 0.07 pg/m3in the Coachella Valley. The maximum predicted 24-hour average in the Basin from the project is valued at 0.1pg/m3in 2014. The average predicted PM2.5 concentration impacts to the Coachella Valley and Basin were predicted to be lessthan 0.5 pg/m3and 0.01< pg/m3respectively. The predicted particulate impacts would not result in a delay of the 2014 Basin PM2.5 attainment or impact the Coachella Valley and Basin 24-hour average PM10federal standard attainment demonstrations. Coachella Valley Average Impact

I



### Visibility Impact Coachella Valley Maximum

Station Impact

0.1 ppb 0.1< ppb

Table 2 summarizesthe proposed Sentinelpower plant's impact to visibility atthe nearby Class-I areas (San Gorgonio, San Jacinto and Joshua TreeNational Monument). The baseline values of deciview forthe three Class I areas range from 11.3to 14.0. The average baseline visual range for the Class I areas is more than 60 miles. The Sentinel



## ... power plant would result in a minor increase in deciviews (0.006 deciview or less in all cases). These impacts, however, would not be significant based on U.S. EPA criteria. When translated to miles of visual range, the power plant would lower visual range to the Class 

### I areas by less than 3 one hundredths ofa mile. 0.3 ppb 

# ~ 0.2 ppbTable2 Impacts to Visibility at Class-I Wilderness Areas Measured in Deciview and Visual Range (miles)

- 13.037 0.004 67.7 17 -0.026

P SanJacinto -0.03 1

Area Impacted Baseline Deciview

Joshua Tree Difference in Deciviews

11.251 Baseline Visual Range (miles)

0.006 Difference in Miles

90.694 -0.035 

# 1