Submitted to: Submitted by: Arizona Public Service AECOM Phoenix, AZ Fort Collins, Colorado 60221977 July 2013 

### Environment



# Four Corners Power Plant and Navajo Mine Energy Project Environmental Impact Statement Ozone Impact AssessmentAECOM Environment ES

- 1

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# Executive Summary

The Arizona Power Service (APS) operates the Four Corners Power Plant (FCPP), a privately owned and operated coal

- fired po wer plant located on the Navajo Nation, about 25 miles west of Farmington, New Mexico. The APS contracted AECOM to assist in gathering data in support of the preparation of an Environmental Impact Statement (EIS). The EIS will be prepared to analyze the ef fects of related proposed federal undertakings in accordance with the National Environmental Policy Act of 1969 (NEPA), 42 U nited States Code 4231

– 4347; the Council on Environmental Quality’s regulations for implementing NEPA, 40 CFR Parts 1500 through 150 8; and the Department of the Interior’s (DOI) NEPA regulations, 43 CFR Part 46, the Office of Surface Mining Reclamation and Enforcement (OSM), Western Region (WR), Denver, Colorado. The OSM is the lead federal agency. APS’ proposed action to be analyzed i n the EIS includes a lease amendment for the FCPP, rights

- of

- way (ROWs) renewals, ceasing operations of Units 1, 2
, and 3, installing SCR controls on the two remaining operating units (4 and 5), and continuing operations of the transmission lines and ancil lary facilities. Other connected actions include development of a new coal mine permit area, called the Pinabete Permit, located adjacent to the FCPP on the Navajo Nation by BHP Navajo Coal Company (BNCC) and continued operations of transmission lines asso ciated with the FCPP that are operated by Public Service Company of New Mexico (PNM). This EIS is in response to the proposed Lease Amendment No. 3 for the FCPP site and renewal of ROW for existing FCPP facilities. This modeling work focuses exclusively on the assessment of ozone air quality impacts associated with the proposed lease renewal and grant issuance. The assessment is conducted by modeling the FCPP emissions in combination with other regional emissions sources and comparing the resulting ozone co ncentrations to the United States Environmental Protection Agency’s (USEPA) 2008 8

- hour ozone National Ambient Air Quality Standard (NAAQS). Ozone impacts were assessed near the FCPP, at existing ozone monitors, and at 88 Class I and sensitive Class II are as. The approach used in this modeling work relies on the input data, configurations, supporting information, and modeling platform developed for the Four Corners Air Quality Study (FCAQS). The FCAQS, which encompasses the FCPP project area, was conducted with the Comprehensive Air Quality model with extensions (CAMx) to assess air quality conditions in the Four Corners region and evaluate the potential future impacts of various control scenarios in 2018. The FCAQS modeling was performed using 12

- kilometer ( km ) , and 4

- km grid cell resolution for two modeling domains

. The FCAQS also performed a model performance evaluation of CAMx results by comparing modeled concentrations to ambient measurements. This evaluation found that model performance for ozone was wi thin the established USEPA acceptance criteria for most months, indicating CAMx is adequate for ozone modeling. Using the FCAQS modeling platform, AECOM simulated ozone concentrations for the year 2005 and two future year 2018 scenarios to assess the impac ts of the proposed FCPP proposed action. The 2005 Baseline simulation was conducted using the 2005 FCAQS regional emissions inventory to provide an assessment of current air quality conditions and for comparison to future year model

- predictions

. The 2018 No Action (NA) Alternative simulation was developed to reflect the scenario that the FCPP lease is not renewed and the FCPP would be shut down. Therefore, the FCPP has zero emissions for the 2018 NA Alternative emissions inventory. The other regional emiss ions for the 2018 NA Alternative emissions inventor y were based on FCAQS Mitigation Scenario #4 which applies co ntrol measures to nitrogen oxides (NO X ) and sulfur dioxide (SO 2 ) from coal

- fired power plants , as well as NO X and Volatile Organic Compounds (VO C) controls to oil and gas sources in San Juan and Rio Arriba counties in New Mexico. In addition, FCAQS Mitigation Scenario #4 was updated with the most current information available for Electric Generating Units (EGU) in the 4

- km domain, including the Sa n Juan Generating Station (SJGS).

The 2018 Proposed Action (PA) emissions are identical to the NA Alternative, except for the FCPP. The modeled emissions for the FCPP were provided by APS

.AECOM Environment ES

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 The emissions inventories for the 2005 Baseline, 2018 NA Alternati ve, and 2018 PA were processed through the Sparse Matrix Operator Kernel Emissions (SMOKE) model to produce surface and elevated hourly, gridded, speciated, emissions for the CAMx air quality model. Using the SMOKE processed emissions and FCAQS model

- ready meteorological inputs and ancillary data, CAMx was used to perform ozone modeling to assess the FCPP PA impacts on the Four Corners region. Ozone was modeled from May through August as the obs erved ozone concentrations are highest during the summer months in this region

. The CAMx configuration options used in this modeling work were based on the FCAQS, except for the Plume

- in

- Grid ( PiG ) sub

- model setting. The PiG sub

- model was required for FCPP and SJGS to better represent the early chemical and transport evolution of the NO X plumes associated with these sources.
The results of these three CAMx simulations were post

- processed to perform the following analyses: 1) comparison of modeled concentrations to the 8

- hour ozone NAAQS, 2) model attainment tests for monito red and unmonitored areas, and 3) assessment of the ozone impacts due to the PA.

Model

- predicted ozone concentrations were further post

- processed with AECOM’s Impact Assessment Suite (IAS) and US EPA’s Model Attainment Test Software (MATS). The IAS w as designed to read model predicted concentrations at specified receptor sites and produce values that could be compared to the ozone NAAQS and also to provide suitable input files for MATS

. The IAS calculated the model

predicted fourth highest daily maxim um 8

- hour average ozone concentrations at Class I and sensitive Class II areas for comparison to the NAAQS for the 2005 Baseline, 2018 NA Alternative, and 2018 PA simulations. The IAS results are referred to as the absolute model

- predicted impacts.
Ozone m odel attainment demonstration was performed using MATS. The model

- predicted impacts are adjusted for monitored concentrations. MATS results are referred to as model

- adjusted impacts. The MATS tool was designed to project future ozone concentrations at loca tions of ozone monitors and also locations removed from monitors based on ambient ozone measurements. Projections were based on applying a RRF to an ozone design value, which is estimated from the 5

- year weighted average of the fourth highest daily maximum 8

- hour average monitored values. The MATS also calculated ozone concentrations for sites removed from monitor locations by using two types of spatial interpolation: 1) between “ neighbor ” monitors and 2) between “ neighbor ” monitors but relying on model da ta to perform gradient adjustments. This analysis provides the MATS calculated fourth

- highest daily maximum 8

- hour average ozone concentrations for monitor locations and also spatial interpolation values for unmonitored Class I and sensitive Class II areas . The MATS was run for the 4

- km domain for both the 2018 NA Alternative and PA scenarios for comparison to the NAAQS.

M odel result s and comparisons were presented in different tabular and gr aphical format analysis. Regional comparisons showed that there is an overall decrease in cumulative ozone concentrations for the 2018 year simulations relative the 2005 B aseline

. The largest changes occur in the western and central areas of the 4

- km domain where the model

- predicted fourth

- highest daily maximum 8

- hour

av erage ozone concentrations decrease by 5 to 7 parts per billion ( ppb )

. The only locations where ozone is observed to increase occur in San Juan County in New Mexico, in an area immediately downwind of the FCPP. The maximum increase in the fourth

- highest 8

- hour ozone concentrations between the 2018 NA Alternative and 2005 Baseline was 3.5 ppb . This increase occurs in a region where ozone concentrations do not exceed the NAAQS.

The PA ozone impacts were estimated as the difference between 2018 PA and the 201 8 NA Alternative simulations. This difference in the model concentrations was examined using three methods: 1) absolute values , 2) monitored area analysis, and 3) unmonitored area analysis

. In general, the largest impacts range between 2 to 4.7 ppb. These impacts occur almost entirely in San Juan County, New Mexico about 11 miles southeast of the FCPP and about 16 miles southwest of Farmington. The absolute model predicted results indicate that in 2005, t welve Class I and sensitive Class II areas exceeded t he NAAQS

, but by 2018 only three of these areas may exceed the NAAQS. These areas include La Garita Wilderness Area, Grande Messa National Forest, and Rio Grande National Forest. The FCPP does not contribute to the ozo ne concentrations in any of these area s (i.e.

, the FCPP contribution in these areas is 0.0 ppb). Importantly, the absolute model predicted ozone concentration for the PA at the Navajo Nation is just below the NAAQS. The model

- predicted FCPP contribution to this area is 0.7 ppb of ozone.AECOM Environment ES

- 3

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 The mo nitored area analysis indicates that in 2005 one monitor exceeded the NAAQS, but that by 2018 no monitors in the 4

- km modeling domain would exceed the NAAQS.
Similar to the absolute model

- predicted impacts, t he unmonitored area analysis indicates that in 2005 there were nine Class I and sensitive Class II areas with modeled ozone exceed e nces, but that by 2018 the ozone concentrations in these areas will decrease and only one area (Sandia Mountain Wildern ess Area) may have ozone exceede nces. The FCPP contri butes 0.1 ppb at Sandia Mountain. Importantly, using this method to predict future ozone concentrations, the ozone levels at the Navajo Nation are notably lower than the absolute model impacts and the contribution of the FCPP to this area is between 0.0 an d 0.1 ppb. Overall, the model

- predicted future ozone concentrations are similar regardless of the methods used to analyze the results . In general, ozone concentrations are predicted to decrease in 2018 throughout the 4

- km modeling domain relative to condit ions in 2005 . Ozone impacts from the FCPP under the Proposed Action do not contribute to areas that may continue to have ozone concentrations that exceed the NAAQS in 2018

.AECOM Environ ment AA

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# List of Acronyms

APS Arizona Public Service Company
BART Best Available Retrofi t Technology BC boundary concentration BIA Bureau of Indian Affairs BLM Bureau of Land Management BNCC BHP Navajo Coal Company CAMx comprehensive air quality model with extensions CB05 Carbon Bond 2005 CEM S Continuous Emissions Monitoring System CFR Code of Federal Register CO carbon monoxide °C degrees Celsius dd decimal degrees DVC current year design value DVF future year design value EGU electric generating units EIS Environmental Impact Statement FCAQS Four Corners Air Quality Study FCP P Four Corners Power Plant GEOS

- C hem Go ddard Earth Observing System

- C hemical GREASD Greatly Reduced Execution and Simplified Dynamics g/kg grams per kilogram g/m 3 grams per meter cubed IA Index of Agreement IAS Impact Assessment Suite IC initial co ncentration IMPROVE Interagency Monitoring of Protected Visual Environments IR Indian Reservation ISORROPIA Inorganic Aerosol Thermodynamics/Partitioning scheme K degrees Kelvin km kilometer LCC Lambert Conformal Conic

m meter MATS Model Attainment T est Software MEGAN Model Emissions of Gases and Aerosols from Nature mb millibars MM5 Mesoscale Model version 5 MSL mean sea level MW megawatt m/h meters per hourAECOM Environ ment AA

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 m/s meters per second

m 2 /s meters squared per second NA No Action NAAQS National Amb ient Air Quality Standards NASA National Aeronautics and Space Administration NCAR National Center for Atmospheric Research
NEPA National Environmental Policy Act NH 3 ammonia NM National Monument NNEPA Navajo Nation Environmental Protection Agency NP National Park NPDES National Pollutant Discharge Elimination System NOAA National Oceanic and Atmospheric Administration NO nitrogen oxide NO 2 nitrogen dioxide NO 3 nitrate NO X nitrogen oxides NWS National Weather Service O 2 molecular oxygen O 3 o zone OSM Office of Surface Mining Reclamation and Enforcement
PA Proposed A ction PGM photochemical grid model PiG Plume

- in

- Grid
PM particulate matter PM 2.5 particulate matter with an aerodynamic diameter if 2.5 microns or less PM 10 particulate matte r with an aerodynamic diameter if 10 microns or less PNM Public Service Company of New Mexico ppb parts per billion
ppm parts per million PPM Piecewise Parabolic Method PSU Pennsylvania State University QA quality assurance RADM Regional Acid Deposi tion Model ROW right

- of

- way RPO Regional Planning Organization RRFs relative response factors SCC source classification code SCR Selective Catalytic Reduction SIP State Implementation Plan SJGS San Juan Generating Station SMCRA Surface Mining Contr ol and Reclamation Act SMOKE Sparse Matrix Operator Kernel Emissions SOAP Secondary Organic Aerosol Formation/Partitioning schemeAECOM Environ ment AA

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 SO 2 sulfur dioxide SO 4 sulfate TDL Techniques Development Lab TOMS Total Ozone Mapping Spectrometer tpy tons per year U SACE U.S. Army Corps of Engineers USEPA U.S. Environmental Protection Agency VOC volatile organic compound WA Wilderness Area WRAP Western Regional Air Partnership WSA Wilderness Study Area
2

- D two

- dimensional 3

- D three

- dimensionalAECOM Environment i

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# Contents

Execut ive Summary

................................ ................................ ................................ ............................... ES

- 1

1.0 Introduction

................................ ................................ ................................ ................................ ..... 1

- 1

1.1 Modeling Overview

................................ ................................ ................................ ................ 1

- 2

1.2 Conte nts of the Modeling Report

................................ ................................ .......................... 1

- 4

2.0 Regional Emissions Inventory

................................ ................................ ................................ ...... 2

- 1

2.1 2005 Baseline

................................ ................................ ................................ ........................ 2

- 3

2.2 2018 No Action Alternative

................................ ................................ ................................ ... 2

- 6

2.3 2018 Proposed Action Alternative

................................ ................................ ........................ 2

- 7

3.0 Modeling Approach

................................ ................................ ................................ ........................ 3

- 1

3.1 Gridded Meteorological Data

................................ ................................ ................................ 3

- 1

3.2 Emissions Modeling

................................ ................................ ................................ .............. 3

- 1

3 .3 CAMx Modeling

................................ ................................ ................................ ..................... 3

- 3

3.4 CAMx Post

- Processing

................................ ................................ ................................ ......... 3

- 5 3.4.1 Assessment Areas

................................ ................................ ................................ . 3

- 5 3.4.2 Ozone Impact Assessment

................................ ................................ .................... 3

- 7 3.4.3 Ozone Model Attainment Test at Monitored Locations

................................ ........ 3

- 9 3.4.4 Ozone Model At tainment Test Removed from Monitors

................................ ...... 3

- 9

4.0 Modeling Results

................................ ................................ ................................ ............................ 4

- 1

4.1 Absolute Model

- Predicted Ozone Concentrations

................................ ............................... 4

- 2 4.1.1 2005 Baseline Compared to the 2018 No Action Alternative

............................... 4

- 2 4.1.2 2005 Baseline Compared to the 2018 Proposed Action

................................ ...... 4

- 4 4.1.3 2018 Proposed Action Compared to the 2018 No Action Alternative

.................. 4

- 4 4.1.4 Ozone Concentrations at Class I and Sensitive Class II Ar eas

......................... 4

- 10

4.2 Model

- Adjusted Ozone Concentrations

................................ ................................ ............. 4

- 13

5.0 Summary

................................ ................................ ................................ ................................ .......... 5

- 1

6.0 References

................................ ................................ ................................ ................................ ....... 6

- 1AECOM Environment ii

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# List of Appendices

Appendix A

- Analysis of FCAQS Emissions Inventory and CAMx Model Sensitivity



# List of Tables

Table 1

- 1 MM5 and CAMx Domain Dimensions

................................ ................................ ................. 1

- 3
Table 1

- 2 RPO Unified Grid Definition

................................ ................................ ................................ 1

- 3
Table 2

- 1 FCAQS Regional Emissions Invent ory Summary

................................ .............................. 2

- 2
Table 2

- 2 2005 Baseline 4

- km Domain Major EGUs Emissions

................................ ........................ 2

- 4
Table 2

- 3 FCPP Units 1

- 5 Stack Parameters

................................ ................................ ..................... 2

- 4
Table 2

- 4 2005 Baseline 4

- km Domain Emissions by Source Category

................................ ........... 2

- 4
Table 2

- 5 SJGS 2018 Emissions

................................ ................................ ................................ ......... 2

- 6
Table 2

- 6 2018 NA Alternative 4

- km Domain Emissions by Source Category

................................ .. 2

- 7
Table 2

- 7 FCPP 2018 PA Emissions

................................ ................................ ................................ .. 2

- 7
Table 2

- 8 FCPP Unit 4

- 5 Stack Parameters

................................ ................................ ....................... 2

- 8
Table 2

- 9 2018 PA 4

- km Domain Emissions by Source Category

................................ .................... 2

- 8
Ta ble 3

- 1 CAMx

- Required Meteorological Data

................................ ................................ ................. 3

- 1
Table 3

- 2 CAMx Air Quality Model Configurations

................................ ................................ ............. 3

- 4
Table 4

- 1 Maximum 1

- hour daily Ozone Difference between 2018 PA and NA Alternative

............. 4

- 7
Table 4

- 2 Fourth

- Highest Daily Maximum 8

- hour Average Ozone Concentrations at Class I and Sensitive Class II Areas

................................ ................................ ............................. 4

- 10
Table 4

- 3 MATS 8

- Hour Ozone Design Values for 2005 and 2018 at Monitoring Sites Located within the 4

- km Domain

................................ ................................ ....................... 4

- 15
Table 4

- 4 MATS 8

- Hour Ozo ne Design Values for 2005 and 2018 at Unmonitored Sensitive Class I and II Areas Located within the 4

- km Domain

................................ ..... 4

- 16AECOM Environment iii

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# List of Figures

Figure 1

- 1 FCAQS MM5 and CAMx Model Domains

................................ ................................ .......... 1

- 5 Figure 1

- 2 FCPP with the CAMx 12

- km and 4

- km Domains

................................ ............................... 1

- 6 Figure 2

- 1 4

- km CAMx Domain and EGUs

................................ ................................ .......................... 2

- 5 Figure 3

- 1 Class I and Sensitive Class II Areas of Concern

................................ ................................ 3

- 8 Figure 3

- 2 MATS Ozone Monitors in the Four Corners States

................................ ......................... 3

- 10 Figure 4

- 1 Model

- predicted Fourth

- Highest Daily Maximum 8

- hour Average Ozone Concentrations: 2005 Baseline and 2018 NA Alternative

................................ .................. 4

- 3 Figur e 4

- 2 Model

- predicted Fourth

- Highest Daily Maximum 8

- hour Average Ozone Concentrations: 2005 Baseline and 2018 PA

................................ ................................ ..... 4

- 5 Figure 4

- 3 Model

- predicted Fourth

- Highest Daily Maximum 8

- hour Average Oz one Concentrations: 2018 NA Alternative and PA

................................ ................................ .... 4

- 6 Figure 4

- 4 2018 NA Alternative and PA Model

- Predicted Hourly Average Ozone and NO X on July 16

................................ ................................ ................................ .................... 4

- 8 Figure 4

- 5 2018 NA Alternative and PA Model

- Predicted Hourly Average Ozone and NO X on August 2

................................ ................................ ................................ ................. 4

- 9AECOM Environment 1

- 1

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# 1.0 Introduction

The Arizona Public Service Company (APS) operates the Four Corners Power Plant (FCPP) , a privately owned and operated coal

- fired power plant located on the Navajo Nation, about 25 miles west of Farmington, New Mexico

. The facility currently consists of five boiler electric generating units (Units 1

- 5), with a total capacity of approximatel y 2, 100 megawatts (MW)

. The current FCPP lease expires in 2016. Under the proposed action, Units 1, 2, and 3 will be permanently retired prior to the FCPP lease expiration

. Units 4 and 5 with a total capacity of 1,5 40 MW will continue to operate after 2016

.
The APS contracted AECOM to assist APS in gathering data to submit to Office of Surface Mining Reclamation and Enforcement (OSM) to be used in preparation of an environmental impact statement (EIS)

. The EIS is needed to support the following proposed Fe deral actions:

• Approval from Bureau of Indian Affairs ( BIA ) of Lease Amendment No.3 for the FCPP site, which has been signed by the Navajo Nation after Navajo Nation Council approval

.

• Issuance by BIA of renewed right

- of

- way (ROW s ) for existing facilities f or the FCPP and its switchyards
, and ancillary facilities
, a 500

- kilovolt (kV ) transmission line and two 345

- kV transmission lines and ancillary transmission line facilities (including the Moenkopi Switchyard )

, an associated 12

- kV line, and access road

.
Co ncurrent with the proposed FCPP lease amendment approval and renewed ROWs grant actions, BHP Navajo Coal Company (BNCC) proposes to develop a new permit area, called the Pinabete Permit, which is located adjacent to the FCPP on tribal trust lands on the Na vajo Nation

. The new Pinabete Permit area would, in conjunction with the mining of any reserves remaining within the existing Navajo Mine Permit area (Federal Surface Mining Control and Reclamation Act [ SMCRA ] Permit NM0003F), supply low

- sulfur coal to the FCPP at a rate of approximately 5.8 million tons per year. Development of the Pinabete Permit area and associated coal reserves would use surface mining methods and, based on current projected customer needs, would supply coal to FCPP for up to 25 years b eginning in 2016. The proposed Pinabete Permit area would include previously permitted but undeveloped coal reserves within Area IV North of the Navajo Mine Lease, and unpermitted and undeveloped coal reserves in a portion of Area IV South of the existing Navajo Mine Lease. Full implementation of the proposed Pinabete Permit is expected to require specific federal actions that will be addressed in the EIS, including :

• Approval from the OSM of the new SMCRA permit.

• Approval from the Bureau of Land Managemen t ( BLM ) of a revised Mine Plan developed for the proposed maximum economic recovery of coal reserves.

• Approval of a Section 404 Individual Permit from the U.S. Army Corps of Engineers ( USACE ) for the impacts to waters of the United States from proposed min ing activities.

• Approval of a Section 402 National Pollutant Discharge Elimination System (NPDES) permit or permit revision from the U

. S

. Environmental Protection Agency ( US EPA )

.

• Approval by the BIA of a proposed realignment for approximately 2.8 miles of BIA 3005/Navajo Road N

- 5082 (Burnham Road) in Area IV South to avoid proposed mining areas.

• Approval or grant of other associated facilities, permits, or ROWs for access and haul roads, power supply for operations, and related facilities.AECOM Environment 1

- 2

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 This report focus es exclusively on the assessment of the ozone ambient air quality impacts associated with the proposed lease renewal and grant issuance. The assessment was conducted by modeling the FCPP emissions in combination with other regional emissions sources and co mparing the r esulting ozone concentration to the USEPA ’s 2008 8

- hour ozone National Ambient Air Quality Standards (NAAQS). Assessment of sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), particulate matter (PM) with aerodynamic diameters less than or equal to 2.5 and 10 microns (PM 2.5 , PM 10 , respectively), carbon monoxide (CO), and lead impacts are addressed in a separate report ( AECOM 2013 )

.

1.1 Modeling Overview The objective of this modeling work was to estimate the change in ozone air quality impacts associated with the proposed future operations of the FCPP relative to current conditions

. Ozone impacts were assessed near the FCPP, at existing ozone monitors; at Class I areas identified in the Clean Air Act (CAA) Amendments of 1977, and at sensitive Class II are as. T his assessment was performed with the C omprehensive A ir Q uality M odel with E xtensions (CAMx) ( ENVIRON 2008 )

. The use of the CAMx model for analyzing air quality impacts has been well established in the scientific community, and the model has been use d for many previous modeling studies in the western U.S., including the Four Corners Air Quality Study (FCAQS) (ENVIRON 2009) . The Pen nsylvania State University / National Center for Atmospheric Research ( PSU/ NCAR ) Mesoscale Model version 5 (MM5) and the Spa rse Matrix Operator Kernel Emissions (SMOKE) (Coats 1995; Houyoux and Vukovich 1999) model s w ere used in combination with CAMx for this project. Collectively, these models will be referred to hereafter as the CAMx modeling system. The version of the CAMx m odeling system used for this work includes:

• The MM5 (version 5) is a meteorological model that generates hourly

, gridded meteorological data required as inputs to the CAMx and SMOKE models.

• The SMOKE modeling system (version 2.4) is an emissions modeling s ystem that generates hourly, gridded, and speciated emissions inputs of mobile, non

- road, area, point, fire, and biogenic emissions sources for photochemical grid models.

• The CAMx modeling system (version 4.51) is a ‘One

- Atmosphere’ photochemical grid mode l (PGM) capable of addressing ozone and other criteria pollutants, visibility, and acid deposition at the regional and urban scale.

To be consistent with previous regional modeling and publicly available information, the project approach relie d on the inpu t data, configurations, and supporting information developed for the FCAQS (ENVIRON 2009) . The FCAQS was developed specifically to assess air quality conditions in the Four Corners region and evaluate potential changes in year 2018 due to various control s cenarios.

The FCAQS provide d an ozone modeling platform that encompasses the FCPP project area and is appropriate for use in an EIS. All model domains in the FCAQS CAMx modeling system , which also are used for this project
, are shown in Figure 1

- 1 and lis ted in Table 1

- 1

. The CAMx nested system uses domains with 36

- kilometer (km), 12

- km, and 4

- km nested grid cells, hereafter referred to as the 36

- km, 12

- km, and 4

- km domains. All model domains use d the map projection from the Regional Planning Organizations ’ (RPO) unified grid. The RPO unified grid consists of a Lamber t Conformal Conic (LCC) map projection using the projection parameters listed in Table 1

- 2

. The location of the FCPP is shown relative to the 12

- km and 4

- km CAMx domains in Figure 1

- 2

.AECOM Environment 1

- 3

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013

Table 1

- 2 RPO Unified Grid Definition

Parameter Value Projection LCC

Datum World Geodetic System 1984
Standard Parallel 1 33° latitude
Standard Parallel 2 45° latitude
Central Meridian

- 97° lon gitude Latitude of Origin 40° latitude

Consistent with the FCPP EIS project objectives, AECOM simulat ed the ozone concentrations for the year 2005 as well as two future year simulations for 2018 using the FCAQS modeling platform

. As part of this modelin g work , the FCAQS emissions inventory was reviewed and updated if more recent data were available. The details of the model simulations are summarized below:

• 2005 Baseline . The analysis of current air quality conditions used the FCAQS 2005 (ENVIRON 2009) e missions inventory for the model domain described in more detail in Section 2.1

. Modeling year 2005 emissions establishe d baseline air quality levels against which future year project and cumulative impacts were evaluated. In addition, the baseline run was critical for establishing any potential model bias and errors that may exist relative to observations so that the bias and errors in model

- predicted future year impacts can be assessed

.

• 2018 No Action Alternative . The No Action (NA) Alternative use d the same regional emissions as the Proposed Action (PA) but without any emissions contribution from the FCPP. The emissions inventory for this analysis is described in more detail in Section 2. 2 . This modeling scenario include d all other regional emissions sou rces in order to assess cumulative future air quality impacts for comparison to the PA.

• 2018 Proposed Action . A project

- specific emissions inventory was developed for the PA . The development of this emissions inventory is described in more detail in Secti on 2. 3

. The PA emissions inventory was modeled in conjunction with other regional emissions sources, identical to the NA Alternative . The potential air quality impacts due to the FCPP proposed emissions were assessed by comparing the modeled impacts for th e PA to the NA Alternative

. Table 1

- 1 MM5 and CAMx Domain Dimensions

Model Model Domain Number of Grid Cells (X,Y) Domain Coordinates (Southwest to Northeast Corner in km )

MM5 36

- km 165x129 (

- 2952,

- 2304 ) to (2592, 2304 )

12

- km 178x157 (

- 2376
, - 1080) to (

- 252, 792)

4

- km 172x167 (

- 1272,

- 672) to (

- 588,

- 8)
CAMx and SMOKE 36

- km 148x112 (

- 2736,

- 2088) to (2592, 1944)

12

- km 167x137* (

- 2316,

- 912) to (

- 312, 732)

4

- km 101x 92* (

- 1192,

- 508) to (

- 788,

- 140)

* The se values include buffer cells.AECOM Environment 1

- 4

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 The CAMx model results were post

- processed to derive results : 1) for comparison to the 8

- hour ozone NAAQS ; 2) for conducting the ozone model attainment tests for both monitored and unmonitored areas ; and 3) to analyze the ozone impacts due to the PA

. Section 3. 4 provides additional information on how model results were post

- processed for future year impacts assessment.

1.2 Contents of the Modeling Report In a very simplified sense, ozone impacts were evaluated using a three

- step pro cess: 1) estimate and process all regional emissions ; 2) model the emissions ; and 3) compare the modeled impacts to applicable standards. The first step in the process was the emissions development ; Chapter 2 .0 describes the regional emissions inventory d eveloped for the baseline and future emissions scenarios. Chapter 3 .0 describes the photochemical grid model system inputs, procedures and options used in this analysis , and methods used to post

- process model results

. Chapter 4 .0 presents the model results and compares results to the 8

- hour ozone NAAQS. Chapter 5 .0 summarizes the ozone impacts . References are provided in Chapter 6 .0

.Alabama Arkansas Arizona California Colorado Delaware

Florida Georgia Iowa Idaho

Illinois Indiana

Kansas Kentucky

Louisiana Mass. Maine

Michigan Minnesota

Missouri

Mississippi Montana

N. Carolina North Dakota

Nebraska

New Mexico Nevada New York

Ohio

Oklahoma Oregon

Penn.

S. Carolina South Dakota

Tennessee

Texas Utah

Virginia Washington

Wisconsin

W. Virginia Wyoming C A N A D A

M E X I C O 

### Legend

APS Four Corners Power Plant
36-km CAMx Domain
12-km CAMx Domain
4-km CAMx Domain
36-km MM5 Domain
12-km MM5 Domain
4-km MM5 Domain



### Four Corners Power Plant

Ozone Modeling Study

Figure 1-1 FCAQS MM5 and CAMx Model Domains 0 500 1,000 250 Kilometers 0 250 500 125 Miles

1:29,000,0006666666666666XSouthDakotaTexasMEXICO§ ̈¦80§ ̈¦10§ ̈¦40§ ̈¦15§ ̈¦84§ ̈¦25§ ̈¦20§ ̈¦8§ ̈¦76§ ̈¦17§ ̈¦19§ ̈¦27§ ̈¦82§ ̈¦15§ ̈¦15§ ̈¦84§ ̈¦25§ ̈¦84§ ̈¦94§ ̈¦10§ ̈¦40§ ̈¦40§ ̈¦80§ ̈¦25§ ̈¦70§ ̈¦90§ ̈¦5§ ̈¦5SanFranciscoDenverSan JoseLos AngelesSan DiegoPhoenixEl PasoLas VegasSalt Lake CityCasperRapid CityBillingsArizonaCaliforniaColoradoIdahoMontanaNorthDakotaNebraskaNewMexicoNevadaOregonUtahWyomingLegendXAPS Four Corners Power Plant6CityInterstate Highway4-km CAMx Domain12-km CAMx DomainFour Corners Power PlantOzone Modeling StudyFigure 1-2FCPP with the CAMx12-km and 4-km Domains0200400100Kilometers010020050Miles1:9,900,000oAECOM Environment 2

- 1

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# 2.0 Regional Emissions Inventory

For regional photochemical modeling, it is essential to model the emissions from all source categories in the model domain s . The performance of the air quality model depends on its ability to simulate the complex interactions between primary emissions sources and meteorological conditions. For this analysis
, the FCPP emissions for both the 2005 Baseline and future years were obtained in consultation

w ith APS

. Regional emissions for all other sources were obtained from the FCAQS.

For the FCAQS, emissions from 2005 were modeled as well as multiple emissions scenarios for year 2018 (ENVIRON 2009)

. The following is a summary of the FCAQS emissions inventor ies that are relevant to the FCPP EIS project :

• 2005 Base Case emissions :

− E missions for a ll area and point sources outside the 4

- km domain were obtained by linearly interpolatin g between Western Regional Air Partnership ( WRAP ) 2002 emissions inventory and the WRAP 2018 Preliminary Reasonable Progress 2018 ( PRP18 ) emissions inventory (Fields et al. 2007)

.

− The 4

- km domain emissions inventories were updat ed for the following emission categories: oil and gas, electric generating units ( EGUs ) , non
- EGUs, mobile , and fugitive dust

.

• 2018 Base Case emissions :

− E missions for all point and area sources outside the 4

- km domain were obtained directly from the WRAP PRP18. 1

− The 4

- km domain emissions inventories were updated for the following emission categories: oil and gas , EGUs, non

- EGUs, mobile, and fugitive dust

.

• 2018 Mitigation Scenario #4 :

− Application of control measures for nitrogen oxide ( NO X ) and SO 2 emissions from coal

- fired power plants in the Four Corners region.

− Application of control measures for NO X and v olatile organic compound ( VOC ) emissions from oil and gas sources in San Juan and Rio Arriba counties in New Mexico. The controls were applied to both area and point source emissions from oil and gas equipment

.

• The following emission categories remained co nstant between all model scenarios:

− The emissions inventories for ammonia . The 4

- km domain emissions were developed specifically for FCAQS

.

− The biogenic emissions

. These emissions were d eveloped for all three modeling domains using the Model Emissions of Gases and Aerosols from Nature (MEGAN) version 2.0

.

− Wildfires and prescribed fires . These emissions were obtained for the 12

- km and 4

- km domains from National Center for Atmospheric Research (NCAR) 2005 fire database (NCAR 2005).

Table 2

- 1 summarizes the F CAQS regional emissions inventories for year s 2005 and 2018

.

1 Additional processing was required to convert the 36

- km gridded area source emissions into 12

- km grid cells in

the 12

- km domain. The 3 6

- km gridded area source emissions were evenly divided into each of the nine 12

- km grid cells contained within a single 36

- km grid cell.AECOM Environment 2

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013

Table 2

- 1 FCAQS Regional Emissions Inventory Summary

Emissions Component Domain FCAQS Data Sources and Supporting Information

2005 B ase Case

Are a 36

- km domain Linear interpolation between WRAP Plan02d and WRAP PRP18; include s road dust and fugitive dust emissions

12

- km domain, excluding the 4

- km domain Disaggregated 36

- km resolution emissions to 12

- km x 12

- km grid cells

4

- km domain Updated e missions including oil and gas sources from WRAP Phase II
On

- Road 36

- km, 12

- km, and 4

- km domains SMOKE

- MOBILE6

Off

- Road 36

- km, 12

- km, and 4

- km domains Linear interpolation between WRAP Plan02d and WRAP PRP18; include locomotive, aircraft and other non

- r oad

sources Biogenic 36

- km, 12

- km, and 4

- km domains SMOKE

- MEGAN

Point 36

- km domain EGU, non

- EGU, and Oil and Gas emissions from both Tribal and State sources with revised sources in 4

- km region

36

- km domain 2005 NCAR fire database

2018 Base Case and Mitigation Scenario #4

Area 36

- km domain WRAP PRP18; include s road dust and fugitive dust emissions

12

- km domain, excluding the 4

- km domain Disaggregated 36

- km resolution emissions to 12

- km x 12

- km grid cells

4

- km domain Revised emissions including oil and gas

sources
On

- Road 36

- km, 12

- km, and 4

- km domains SMOKE

- MOBILE6

Off

- Road 36

- km, 12

- km, and 4

- km domains WRAP PRP18; include s locomotive, aircraft and other non

- road sources Biogenic 36

- km, 12

- km, and 4

- km domains SMOKE

- MEGAN ; same as 2005

Poi nt 36

- km domain EGU, non

- EGU, and Oil and Gas from both Tribal and State sources with revised sources in 4

- km domain

36

- km domain 2005 NCAR fire database; same as 2005

The FCAQS regional emissions inventories were updated for the FCPP EIS to include m ore recent information. The FCAQS 2005 Base Case emissions inventory is the basis for the FCPP EIS 2005 Baseline emissions inventory and the FCAQS 2018 Mitigation Scenario #4 is the basis for the FCPP EIS 2018 NA Alternative and PA emissions inventories

. T he updates that were made to the FCAQS were limited to those changes that are relevant for evaluating ozone impacts in the vicinity of the FCPP

.AECOM Environment 2

- 3

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Given the objectives of this project and availability of more recent information, AECOM updated the FCAQS 4

- km domain EGU point source inventory. The updates were limited to the 4

- km domain since this is the area most relevant for the FCPP. The updates were based on the most current information for both 2005 and projected future EGU operations. The following change s were made to the FCAQS 4

- km EGU inventory :

• FCPP annual emissions were updated for all model scenarios ;

• The temporal variably of the FCPP emissions were adjusted to have a constant emission rate for all model scenarios (APS 2013);

• The stack parameters for FCPP Units 1

- 5 were updated for all model scenarios;

• The locations of all the major EGU point sources in the 4

- km domain were revised to reflect their

correc t latitude and longitude values for all model scenarios ; and

• San Juan Generating Station (SJGS) an nual emissions were updated for the 2018 NA Alternative and PA. Since the emissions inventory was revised for assessing ozone impact s , the emissions inventory improvements focused on ozone precursors (NOx and VOC). As part of this effort, the Navajo Mine

e missions for the PA were reviewed. Importantly, the proposed activities and operations at the Navajo Mine would not emit ozone precursors (NOx and VOC) in sufficient quantities to impact ozone formation (AECOM 2013). Therefore, the Navajo Mine emissions we re not explicitly modified for the NA Alternative and PA.

The following sections provide more detailed information about the updates made to the FCAQS emissions inventories for the purposes of assessing FCPP ozone impacts.

2.1 2005 Baseline

The 2005 Baseline regional emissions inventory was based on the 2005 FC A QS Base Case emissions inventory for all source categories, except that the FCPP emissions were updated based on data from APS (2013)

. The ozone precursors emitted from the FCPP primarily occur due to t he combustion of coal in the main coal

- fired boilers (Units 1

- 5). Smaller amounts of precursor emissions also are emitted from the ancillary equipment, such as the recently permitted gas

- fired auxiliary boiler and vehicle exhaust.

The modeled FCPP 2005 Ba seline emissions are shown in Table 2

- 2 with the emissions for the largest EGUs in 4

- km domain. T he Mohave Generating Station was shut down on 2005. Therefore, this EGU was removed from the modeled emissions inventory. All emissions are provided in tons pe r year (tpy). While this project focused on ozone impacts, the FCAQS assessed the impacts of multiple pollutants. For completeness, all modeled emissions are shown in Table 2

- 2

. The locations of the EGUs within the 4

- km domain are shown in Figure 2

- 1

.
In a ddition to updating the total FCPP emissions, the temporal variability of the FCPP emissions and the stack parameters also were revised for the purposes of this project. Based on information from APS (2013), the FCPP emissions were modeled with a constant emissions rate throughout the model period. The exhaust gases from Units 1

- 5 were modeled as one single stack with an effective average diameter calculated from the values from all the units. Table 2

- 3 summarizes the exhaust stack parameters provided by en gineers at APS, which are used for the 2005 Baseline model simulation (APS 2013).

The modeled 2005 Baseline 4

- km domain emissions are summarized in Table 2

- 4 for all source categories.AECOM Environment 2

- 4

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013

Table 2

- 2 2005 Baseline 4

- km D omain Major EGUs Emission s

Facility Name Latitude (dd) Longitude (dd) 2005 Emissions (tpy) 1

CO NH 3 NO X PM 10 PM 2.5 SO 2 VOC

Four Corners Power Plant 36.689162

- 108.479631 2,411 0 44,587 1,408 704 13,712 12

San Juan Generating Station 36.802150

- 108.438205 1
, 53 4 0 26
, 82 9 1
, 5 20 393 16
, 636 185

Escalante Station 35.415965

- 108.082289 20 3 4 3
, 79 9 19 7 1
, 293 0

Reeves Generating Station 35.171700

- 106.599700 1
, 40 6 5 151 0 5 0 8

Milagro Cogeneration Plant 36.736700

- 107.941700 0 0 110 0 0 3 0

Anima s Power Plant 36.724885

- 108.191808 16 0 61 0 0 0 58

Delta Person Generating Station 35.027592

- 106.643502 1 1 4 4 0 0 0

1 For the assessment of ozone impacts, 2005 is selected as the “ baseline year ” based on availability of input data . A baseline

year i s necessary to conduct an ozone attainment test in accord with USEPA guidance (2007). This is not an increment consuming baseline assessment.

Table 2

- 3 FCPP Units 1

- 5 Stack Parameters

Parameter Units Units 1

- 5 Merged Stack

Latitude decimal degrees (dd) 36.689162 Longitude dd

- 108.479631 Stack Height m eters (m) 115.824
Effective Diameter m 8.6868 Gas Exit Velocity meters per hour ( m/h ) 87782.4 Stack Gas Exit Temperature d eg rees Kelvin ( K ) 327.00

Table 2

- 4 2005 Baseline 4

- km D omain Emissions by S ource C ategory

Pollutant

(tpy) Area On

road Off

road Biogenic Area Oil & Gas Point Oil & Gas EGU Non

EGU Total

NO X 16,477 39,340 15,717 1,834 38,832 29,998 72,668 6,997 221,863

SO 2 5,789 669 809 0 136 602 30,518 4,938 43,461

VOC 32,989 23,499 11,690 238,471 110,862 11,410 299 2,429 431,649

PM 10 37,224 1,197 1,224 98,640 24 168 990 3,018 142,485

# X W

X W

X

W X W X W

X

W 6

6 6

6
6 6

6 6

6 

# X FCPP



# §  ̈ ¦ 40 

# §  ̈ ¦ 25 

# Arizona Colorado

New Mexico Utah

Durango

Shiprock Farmington

Window Rock Gallup

Santa Fe

Rio Rancho

Albuquerque

Los Lunas San Juan Generating Station

Escalante

Station

Reeves Generating Station

Milagro Cogeneration Plant Animas Power Plant

Delta Person Generating Station San Juan

Navajo Coconino

Apache

Cibola San Juan

McKinley Garfield

Kane
San Juan Dolores

La Plata Montezuma

Catron San Miguel Montrose

Ouray

Saguache Gunnison Chaffee Fremont

Torrance Hinsdale

Rio

Arriba

Taos

San Miguel

Valencia Mora

Santa Fe Los Alamos

Sandoval

Bernalillo Mineral

Rio Grande Alamosa

Costilla Archuleta Conejos 

## Legend



# X APS Four Corners Power Plant 

# X W EGUs in 4-km Domain


### 6 City
4-km CAMx Domain Interstate Highway County



### Four Corners Power Plant Ozone Modeling Study

Figure 2-1 4-km CAMx Domain and EGUs 0 40 80

20 Kilometers 0 20 40 10
Miles

1:2,100,000 

# o

AZ CA CO

ID

KS MT ND

NE

NM NV

OK OR SD

TX UT WA

WY CANADAAECOM Environment 2

- 6

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 2.2 2018 No Action Alternative

The 2018 NA Alternative emissions inventory was developed to reflect the scenario that the FCPP lease is not renewed and the FCPP would be shut down. Therefore, the FCPP has zero emissions for the 2018 NA Alternative emissions inventory.

As described previously, an assessment of ozone impacts requires inclusion of all regional emissions

sources. For the purposes of assessing the NA Alternative ozone concentrations, the FCAQS 2018 Mitigation Scenario #4 was selected

. As described in Appendix A , the emissions inventory for the FCAQS Mitigation Scenario #4 is potentially more accurate for the Four Corners area than the original 2018 Base Case emissions inventory. As summarized previously, t he FCAQS Mitigation Scenario #4 contains the following differences from the 2018 B ase C ase inventor y :

• Application of control measures for NO X and SO 2 emissions from coal

- fired power plants in the Four Corners region.

• Application of control technologies to oil and ga s source s for NO X and VOC emissions in San Juan and Rio Arriba counties in New Mexico. The changes include both area and point sources for oil and gas inventories.

S ince the FCAQS was finalized, updated emissions information has become available for the oil and ga s sources in the Four Corners area

. Appendix A presents a comparison of the FCAQS modeled oil and gas emissions relative to the most recent oil and gas emissions inventory data.

The only updates made to FCAQS Mitigation Scenario #4 for the NA Alternative are : 1) removal of the FCPP emissions; 2 ) revised SJGS 2018 emissions provided by Public Service Company of New Mexico (PNM) as summarized in Table 2

- 5 (PNM 2013) ; and 3 ) the locations (latitude and longitude) of EGUs located in the 4

- km domain (as shown in Table 2

- 2 and Figure 2

- 1 )

. The SJGS emissions were updated for both the 2018 NA Alternative and PA emissions inventories. The SJGS 2018 annual emissions were obtained from PNM ( 2013). The modeled 2018 SJGS emissions inventory is shown in Table 2

- 5 . Thes e emissions were based on the August 22, 2011 New Mexico Regional Haze Federal Implementation Plan and conservatively assumes an 85 percent capacity factor. After the modeling was initiated for this project, PNM signed a tentative agreement with New Mexico Environmental Department and USEPA to develop an alternative State Implementation Plan (SIP) to revise the SGJS emissions by 2018. The SGJS emissions under this revised plan were expected to be similar to the data shown in Table 2

- 5 for SIP potential futu re emissions. The SJGS potential future SIP emissions are provided for informational purposes only.

Table 2

- 5 SJGS 2018 Emissions
2018 (tpy)
CO NH 3 NO X PM 10 PM 2.5 SO 2 VOC

Modeled 2018 Emissions 33,507 90 3,500 3,884 2,800 10,500 210

SIP Potential Future Emissions 18,615 ND 8,011 1,185 1,185 3,483 105

Note: ND = No Data.AECOM Environment 2

- 7

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 2

- 6 summarizes the modeled 2018 NA Alternative 4

- km domain emissions by source category

.

Table 2

- 6 2018 NA Alternative 4

- km D omain E missions by S ource C ategory

Pollutant

(tpy) Area On

road Off

road Biogenic Area Oil & Gas Point Oil & Gas EGU Non

EGU Total

NO X 21,231 13,385 8,743 1,834 39,639 26,216 10,054 7,770 142,210

SO 2 13,428 180 66 0 142 715 8,027 5,763 50,127

VOC 41,906 11,094 8,193 238,471 65,950 15,945 581 2,738 421,134

PM 10 54,934 883 655 98,640 26 116 5,889 1,814 162,957

2.3 2018 Proposed Action Alternative

The PA emissions are identical to the NA Alternative, except for the FCPP. T he modeled emissions for the FCPP were obtained by personal communication with APS and are consistent with the EIS NAAQS study (AECOM 2013). Units 4 and 5 are cell burner, pulverized coal

- fired boilers equipped with lime spray towers and baghous es for SO 2 and PM control. Under the PA , SCR controls will be installed as part of the Best Available Retrofit Technology ( BART ) agreement (USEPA 2012). Emission rates from Units 4 and 5 were derived based on actual hourly data, the current Title V operati ng permit (NNEPA 2008) for FCPP, as well as from the final BART rule (USEPA 2012) for NO X and PM

. The emission rates for NO X , SO 2 , PM 10 , PM 2.5 , and CO emissions were consistent with the NAAQS compliance assessment (AECOM 2013). Ammonia (NH 3 ) and VOC emissi ons were provided by personal comm unication with APS (APS 2013). The modeled FCPP 2018 PA emissions are shown in Table 2

- 7

.

Table 2

- 7 FCPP 2018 PA Emission s

Facility Name 2018 (tpy)

CO NH 3 NO X PM 10 PM 2.5 S O 2 VOC

Four Corners Power Plant 1654.2 87 5789.6 1075.4 729.7 11224.7 8

Table 2

- 8 summarizes the PA modeled stack parameters for Units 4 and 5. Similar to the 2005 Baseline scenario , the exhaust gases from Units 4 and 5 were modeled as one single stack with an effective average diameter calculated from the values of both units

. The stack location and height are identical to the 2005 Baseline modeling; however, the temperature and exhaust velocity are based on actual hourly data measured from 2009 through 2011.AECOM Environment 2

- 8

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013

Table 2

- 8 FCPP Unit 4

- 5 Stack Parameters

Units Units 4

- 5 Merged Stack

Latitude dd 36.689162 Longitude dd

- 108.479631 Stack Height m 115.824
Effective Diameter m 12.28 Gas Exit Velocity 1 m/h 7416 0 Stack Gas Exit Temperature 1 K 327.00

1 The exhaust parameters coincide with a 99 th percentile heat input rate of 7,411 MMBtu/hr for

each of Units 4 and 5.

The modeled 2018 PA emissions inventory is shown for all sources within the 4

- km domain in Tabl e 2

- 9

.

Table 2

- 9 2018 PA 4

- km D omain E missions by S ource C ategory

Pollutant

(tpy) Area On

road Off

road Biogenic Area Oil & Gas Point Oil & Gas EGU* Non

EGU Total

NO X 21,231 13,385 8,743 1,834 39,639 26,216 19,344 7,770 142,210

SO 2 13,428 180 66 0 142 715 29,752 5,763 50,127

VOC 41,906 11,094 8,193 238,471 65,950 15,945 799 2,738 421,134

PM 10 54,934 883 655 98,640 26 116 9,419 1,814 162,957

* The values include PA emissions for FCPP.AECOM Environment 3

- 1

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# 3.0 Modeling Approach

The air quality modeling and input data use d the FCAQS modeling platform, as mentioned previously. This modeling platform consist ed of the following key components: 1) a meteorological modeling simulation using the PSU / NCAR Mesoscale Model version 5 (MM5 ) (Dudhia 1993) ; 2) emission inventories processed with the SMOKE emission processing system ; and 3) air quality modeling simulations using the CAMx model.

The modeling domains used in this modeling work were identical to those in the FCAQS, which were
co mprised of a 36

- km , 12

- km , and 4

- km nested grids ( F igure 1

- 1 )

. The modeling conducted for this analysis was only performed for the nested12

- km and 4

- km domains because: a) the FCAQS analysis and most of the important updates to the emissions inventory wer e done for these two domains; b) the 12

- km domain encompasses most of the western U .S. , which captures any potential regional effects that could impact the 4

- km domain ; and c) the FCPP is located within the 4

- km domain. The following sections provide more detailed information about the setup, configuration, and data sources for each model used for this modeling work

.

3.1 Gridded Meteorological Data The FCAQS developed gridded meteorological data for the year 2005 using the MM5 . These gridded meteorological data were processed for CAMx modeling using the MM5CAMx processor. The 2005 gridded meteorological files were used for all modeling scenarios for this project ( i.e., the 2005 Baseline
, 2018 NA Alternative
, and 2018 PA ). The meteorological data are consistent w ith the parameters required for CAMx as shown in Table 3

- 1

. Detailed information about the set up and results of the MM5 modeling and the post

- processing to CAMx

- ready meteorological input can be found in the FCAQS (ENVIRON 2009).

Table 3

- 1 C AM x - Required Meteorological Data

CAMx Input Parameter Description Layer interface height (m) three

- dimensional ( 3

- D ) , hourly, gridded
, time

- varying layer heights Winds (m/s) 3

- D , hourly, gridded wind vectors Temperatur e (K) 3

- D , hourly, gridded temperature and 2D , hourly, gridded surface temperature Pressure (mb) 3

- D , hourly, gridded pressure Vertical Diffusivity (m 2 /s) 3

- D , hourly, gridded vertical exchange coefficients Water Vapor (ppm) 3

- D , hourly, gridded water vapor mixing ratio Clouds and Rainfall (g/m 3 ) 3

- D , hourly, gridded cloud and rain liquid water content Land use types two

- dimensional ( 2

- D ) gridded land use/land cover distribution

3.2 Emissions Modeling The SMOKE emissions modeling system (Coats 1995; Ho uyoux and Vukovich 1999) was used to generate the hourly, gridded, speciated model

- r eady emissions inputs for the 2005 Baseline, the 2018 NA Alternative , and 2018 PA modeling scenarios. The emissions described in Chapter 2 .0 were processed and formatted in two types of emissions input files: surface and elevated emissions. Surface emissions consist of area sources, on
- road and non

- road (mobile) sources, as well as fugitive dust,AECOM Environment 3

- 2

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 ammonia, and biogenic emissions. These sources were then gridded for the CAMx nested system for domains with 36

- km, 12

- km, and 4

- km grid cells. Elevated emissions consist of major point sources including EGU, non

- EGU point sources (including oil and gas sources), and fires. For elevated sources, the plume rise for each source was ca lculated by CAMx from stack parameters and hourly meteorological conditions to place the emissions in the appropriate vertical layer.

For this project , the SMOKE configuration parameters and data inputs were consistent with FCAQS. The following SMOKE proce ssing routines that were used for this work :

• Spatial Allocation

. The spatial resolution of the emissions must match the CAMx grid cells for each domain. Initial area , on
- road, and non

- road emission inventories were spatially resolved at the county level, a nd county

- level emissions were allocated to the grid cells within each county based on spatial surrogates . Spatial surrogates were based on attributes such as population, land use category, and economic activity. The USEPA has developed spatial surrogates which were used for spatially allocating all non

- oil and gas emissions. Oil and gas area emissions were spatially allocated based on well location and production information.

• Temporal Allocation

. Initial emissions data were provided for different averaging periods depending on each source type. Source types with annual or short

- term emission rates were adjusted to seasonal or monthly profiles accounting for day

- of

- week and hour

- of

- day differences. Area sources, including non

- road and dust emissions were all ocated by monthly, daily, and hourly profiles provided by the USEPA. Biogenic and on

- road emissions were modeled using hourly meteorological data. Point sources, including continuous emissions monitoring system ( CEM S ) and fire emissions, were modeled with available day

- specific, or hour

- specific emissions and meteorology. In this modeling work , the emissions rates from the FCPP were assumed constant throughout the modeling period to reflect an expected constant capacity factor of 91 percent.

• Chemical Specia tion

. Emission inventories do not routinely include estimates of every chemical species emitted; rather
, total emissions are reported for similar pollutants. Emissions of total VOC were converted to estimates of carbon bond types as required by the Carbon Bond 2005 (CB05) chemical mechanism (Yarwood et al. 2005). Total NO X emissions were allocated to nitrogen oxide (NO) and NO 2 components. The PM was allocated to coarse PM, nitrate, sulfate, organic carbon, elemental carbon, and other fine particulates. The SMOKE model includes default speciation profiles by source classification codes (SCC). These profiles are based on USEPA’s default data as well as on various updates and improvements incorporated to account for variations in fuels, solvent composition, an d chemical mechanisms used in air quality models.

• Elevated Sources

. All sources were treated by SMOKE as potentially elevated. The Plume

- in

Grid (PiG) sub

- model that tracks the dispersion and chemical evolution of individual plume segments within the large r grid model framework was invoked to handle large stationary sources in the 4

- km domain such as FCPP and SJGS

.

• Quality Assurance

. The SMOKE model includes quality assurance (QA) and reporting features to keep track of the adjustments at each processing st age and ensure that data integrity is not compromised. The QA tools from SMOKE were used to provide summary plots and tables of emissions.

Importantly, t he revisions to the FCAQS emissions described in Chapter 2 .0 only affected the elevated point source em issions, the surface level emissions files from the FCAQS were used without any modifications. Additional SMOKE p rocessing steps were performed for the elevated point sources described in Chapter 2 .0 . The following steps were performed for all elevated emi ssions files modeled for this project :AECOM Environment 3

- 3

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 1. Removing (zeroing out) point sources emissions in the 4

- km domain from the original 36

- km binary point source files.

2. Processing point source emissions for sectors
, including EGU, non
- EGU

, and point oil and gas, throug h SMOKE to create pre

- CAMx point source files in ASCII format.

3. Converting non

- PiG point sources in ASCII into CAMx

- ready binary format.

4. Processing FCPP and SJGS to setup their emissions to be handled by the PiG sub

- model and converting them to CAMx

- ready b inary format.

5. Merging PiG, non

- PiG and point

, fire emissions into final merged CAMx

- ready point source emissions.

Given the complexity involved in the modification of the point sources in the 4

- km domain , these steps were followed to first reproduce the F CAQS inventories identically. This served as a verification step to ensure the results from FCAQS were reproducible and make sure there were no oversights in the generation of the updated inventory. Once verified, the same steps were applied to the revisio ns of the point sources emissions in the 4

- km domain as described in Chapter 2.0

.

3.3 CAMx Modeling The ozone modeling performed was conducted with CAMx. In addition to appropriate meteorological and emissions input data described in previous sections, the PGM requires input files that configure and setup each simulation, define the chemical mechanism to be used, and describe the photochemical conditions, surface characteristics, initial/boundary conditions, emissions rates, and various meteorological fields ov er the entire modeling domain. Relevant CAMx model inputs include:

• T hree

- dimensional
, hourly meteorological fields generated, which for this modeling work were generated by the FCAQS with the M M5CAMx processor

.

• T wo
- dimensional
, low

- level (surface layer) em issions and elevated point source emissions generated b y the SMOKE emissions processor

.

• I nitial concentration (IC) and boundary concentration (BC) inputs generated by the CAMx IC/BC processors

.

• A lbedo/Haze/ O zone Column input file

.

• P hotolysis rates look up table

.

• Land use and topography data

.

T he main CAMx configuration options in this modeling work were identical to those used in the FCAQS

. These options are summarized in Table 3

- 2

. The CAMx model was set up on the 12

- km and 4

- km domains using two

- way grid nesting. The base configuration of CAMx use d the vertical layers that are aggregated from 34 MM5 layers to 19 CAMx layers spanning the depth between the surface and approximately 15 km above mean seal level (MSL). The Piecewise Parabolic Method (PPM) advec tion solver was used along with the spatially varying horizontal diffusion approach. Vertical diffusion in CAMx

was modeled by K

- theory.AECOM Environment 3

- 4

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 3

- 2 CAMx Air Quality Model Configurations
Science Options Config uration Details

Vertical Grid Mesh 19 layers Aggregated from 34 MM5 layers

Grid Interaction One

- way nesting from the 36

- km domain to the 12

- km domain Two

- way nesting between the 12

- km domain and 4

- km domain

Initial Conditions 5 days full spin

- up for 1 2

- km and 4

- km domains using initial concentration derived from 36

- km results Started on April 25, 2005

Boundary Conditions Goddard Earth Observing System

- chemical (GEOS

- Chem) 2002 annual run as prepared by WRAP Contains daily 3

- h ou r averages gridded co ncentrations

Chemistry Gas Phase Chemistry CB05 Aerosol Chemistry ISORROPIA equilibrium Cloud Chemistry RADM

- type aqueous chemistry Meteorological Processor MM5CAMx Horizontal Transport K

- theory with grid size dependent on coefficient of hor izontal eddy diffusion Vertical Transport K

- theory Lower limit of vertical eddy diffusivity = 1.0 Deposition Scheme Zhang wet and dry deposition

Plume

- in

- Grid Greatly Reduced Execution and Simplified Dynamics (GREASD) PiG PiG approach aimed at tre ating the early chemical evolution of large NO X plumes. Applied to FCPP and SJGS point sources only.

Numerics Gas Phase Chemistry Solver Chemical Mechanism Compiler Fast Solver

Horizontal Advection Scheme PPM scheme Integration Time Step Wind sp eed dependent

The CAMx configuration also includes the CB05 gas phase photochemical mechanism (Yarwood et al. 2005). The CB05 gas

- phase photochemical mechanism contains 156 reactions involving 52 chemical species. The VOC species were treated using a lu mped bond approach in which actual VOC species are represented in the CB05 mechanism by model species that are designed to represent certain carbon bond types. This approach was used to reduce the total number of VOC species represented in the photochemica l model. The CAMx is a ‘one

- atmosphere’ model which means that in addition to theAECOM Environment 3

- 5

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 algorithms that estimate the fate of ozone , PM formation also is included through aqueous chemistry (Regional Acid Deposition Model [RADM]), Inorganic Aerosol Thermodynamics/ partitioning (ISORROPIA), and Secondary Organic Aerosol Formation/partitioning (SOAP) schemes. The particulate chemistry mechanism utilizes products from the gas phase photochemistry for production of sulfate (SO 4 ), nitrate (NO 3 ), condensable organic gases , and chloride. Mineral NO 3 is included in the calculation of aerosol NO 3 formation

. N one of the other PM or gas

- phase species , however, were reported in this analysis.

An important aspect of the FCAQ S was the comprehensive model evaluation of CAMx result s by comparing model predictions to measurements of ambient air pollutant concentrations. The FCAQS found that the model performance for ozone for most months was within the established US EPA acceptance criteria of ±15 percent bias envelope and that all mo nths were within the 35 percent error envelope. T he bias also decreased during summer months, which indicates that CAMx exhibits the largest under predictions for the highest ozone concentrations. O verall the model performance for ozone
, however, was adequ ate in replicating rural levels of ozone throughout the modeling of the 2005 Baseline and over the 4

- km domain that covered the Four Corners area.

The focus of this analysis was on the periods when ozone formation is the largest; as a result
, the modeling period of May through August was selected to evaluate the ozone impacts that can be attributed to the FCPP since maximum ozone concentrations typically occur during summer season in this region.

The PiG sub

- model was invoked to adequately simulate the che mistry and transport of concentrated point source plumes within the grid model framework. The PiG was invoked to handle the emissions from FCPP and SJGS . The PiG option has been primarily used for simulating elevated point source plumes within a grid model

. In addition to the meteorology and emissions inputs, the CAMx model requires ancillary data, including initial and boundary concentrations for all chemical species, and ozone column data for calculating photolysis rates. The source of all the ancillary d ata used in this modeling work are described in detail in the FCAQS report (ENVIRON 2009).

3.4 CAMx Post

- Processing The USEPA metrics for predicting future attainment of the ozone NAAQS are based on the modeled ozone concentrations at a monitor location. For this analysis, the project area contains some available ozone measurements, but not near the sensitive areas. Therefore, it is desirable to examine the ozone impacts both at the monitors and at areas removed from monitors. The ozone impacts were analyzed a t Class I and sensitive Class II areas shown in Figure 3

- 1

. The ozone model attainment test was performed through the use of the Model Attainment Test Software (MATS) ( Abt Associates, Inc. 2009 ) as well as AECOM’s Impact Assessment Suite (IAS) ; both assess ment tools and methodologies are described in the following sections.

3.4.1 Assessment Areas Ozone impacts will be evaluated at the following Class I and sensitive Class II areas:

Class I Areas

• Bandelier Wilderness Area (WA)

• Canyonlands National Park (NP)

• La Ga rita WA

• Mesa Verde NP • Pecos WA

• Petrified Forest NP

• San Pedro Parks WA

• Weminuche WAAECOM Environment 3

- 6

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Class II Area s

• Acoma Indian Reservation (IR)

• American Flats

• Aztec Ruins National Monument (NM)

• Bisti/De

- Na

- Zin WA

• Bridger Jack Mesa Wilderness Study Area (WSA)

• Butler Wash WSA

• Cahone Canyon WSA

• Canoncito IR

• Canyon de Chelly NM

• Carson NF

• Chaco Culture National Historic Park

• Chama Rover Canyon WA

• Cheese Box Canyon WSA

• Cibola NF

• Cochiti IR

• Cross Canyon WSA

• Cruces Basin WA

• Dark Canyon WA

• Dome WA

• El Malpais NM

• El Morro NM

• Fish C reek Canyon WSA

• Glen Canyon National Recreation Area

• Grand Mesa, Uncompahgre, and Gunnison NFs

• Handies Peak WSA

• Hopi IR

• Hovenweep NM

• Hubbell Trading Post National Historic Site

• Jemez IR

• Jemez National Recreation Area

• Jicarilla Apache IR

• Laguna IR

• Little Ro ckies WSA

• Lizard Head WA

• Mancos Mesa WSA

• Manti

- Lasal NF

• McKenna Peak WSA

• Menefee Mountain WSA

• Mesa Verde WA

• Middle Point WSA

• Monte Vista National Wildlife Refuge

• Mount Sneffels WA

• Nambe IR • Natural Bridges NM

• Navajo Nation

• Ojito WA

• Pecos National Historical Park

• Petrified Forest National WA

• Petroglyph NM

• Pojoaque IR

• Powderhorn WA (BLM)

• Powderhorn WA (USFS)

• Powderhorn WSA (BLM)

• Ramah Navajo IR

• Redcloud Peak WSA

• Rio Grande NF

• Road Canyon WSA

• San Felipe IR

• San Ildefonso IR

• San Juan NF

• San Juan IR

• Sandia IR

• Sand ia Mountain WA

• Santa Ana IR

• Santa Clara IR

• Santo Domingo IR

• Slickhorn Canyon WSA

• Santa Fe NF

• South San Juan WA

• Southern Ute IR

• Squaw/Papoose Canyon WSA

• Tesuque IR

• Uncompahgre WA (BLM)

• Uncompahgre WA (USFS)

• Ute Mountain IR

• Weber Mountain WSA

• West Malpais WA

• Yucca House NM

• Zia IR

• Zuni IRAECOM Environme nt 3

- 7

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 The locations of these Class I and Class II sensitive areas within the 4

- km d omains are shown in Figure 3

- 1

. These areas are managed by a number of Federal Agencies and include National Parks, Wilderness Areas and tribal lan ds among others. Ambient ozone concentrations for both the 2005 Baseline and 2018 future year modeling results are r eported in Chapter 4 .0 f or all of these areas. M odel result s and comparisons also are presented in both tabular and gr aphical format.

3.4.2 Ozone Impact Assessment AECOM’s IAS was developed to post

- process model results into the format required for assessment and comparison with applicable standards and thresholds. Photochemical models produce hourly values of pollutant concentrations, such as ozone , at each grid cell. T hese results often need to be evaluated over different spatial and temporal scales, such as Class I or sensitive Class II areas , and various averaging periods like 8

- hour averages or annual averages . The IAS was designed to post

- proce ss CAMx model results. The following processing methods were used for this project :
a) Selecting model

- predicted hourly concentrat ions for applicable species to compute appropriate temporal average concentrations. The hourly concentrations and averages can be compared to applicable NAAQS for a given set of receptors within a modeling domain. The results from this step are reported and referred to as the “ absolute ” model

- predicted impacts

. b) Selecting model

- predicted hourly concentrations and processing the data to produce files for input into the MATS tool. The MATS tool requires model estimated daily maximum 8

- hour ozone concentrations for each grid cell in the modeling domains

. The results from the MATS tools are referred to as the “ model

- adjusted ” impacts. Mor e information about the MATS tool is provided in the following section.

In addition to the CAMx output files, the only data required by the IAS is a file containing the locations of the assessment areas . This file was prepared using ESRI ’s ArcGIS software by intersecting the Class I and sensitive Class II areas shown in Figure 3

- 1 with the 4

- km domain grid cells.

To calculate the absolute model

- predicted impacts f or each assessment area , the IAS calculates the 8

- hour ozone NAAQS following this process:

1. Calc ulate rolling 8

- hour averages from the hourly model

- predicted ozone concentrations fo r each model grid cell within an assessment area ;
2. Obtain the daily maximum value from step 1 for each assessment area in model grid ; and

3. Rank all the values calculated i n step 2 from largest to smallest for each assessment area and select the fourth

- highest value. This provides the model

- predicted fourth highest daily maximum 8

- hour average ozone concentration for each assessment area. This value is consistent with the st atistical form of the 8

- hour ozone NAAQS

.
To calculate the model

- predicted impacts for the MATS tool, steps 1 and 2 were conducted for the full 4

- km model domain and the results are formatted to be compatible with the MATS tool.

# 6

6 6

6 6 6

6 6

6 

# X Mount Sneffels Wilderness Powderhorn Wilderness Powderhorn Wilderness SA

Santa Fe NF 

# §  ̈ ¦ 40 

# §

 ̈ ¦ 25 

# Arizona Colorado

New Mexico Utah

Durango

Shiprock

Farmington

Window Rock Gallup Santa Fe

Rio Rancho

Albuquerque

Los Lunas Acoma IR Canoncito IR Cochiti IR Hopi IR

Isleta IR Jemez IR Jicarilla

Apache IR

Laguna IR Nambe IR Navajo IR

Picuris IR

Pojoaque IR

Ramah Navajo IR San Felipe IR San Ildefonso IR San Juan IR

Sandia IR Santa Ana IR Santa Clara IR

Santo Domingo IR Southern Ute IR

Taos IR

Tesuque IR Ute Mountain IR

Zia IR

Zuni IR Carson NF

Cibola NF Grand Mesa, Uncompahgre and Gunnison NFs

Manti-Lasal NF

Pike and San Isabel NFs

Rio Grande NF

San Juan NF

Santa Fe NF Hubbell Trading Post National Historic Site Chaco Culture National Historical Park

Pecos National Historical Park Aztec Ruins NM

Canyon de Chelly

El Malpais El Morro NM Hovenweep NM

Natural Bridges NM

Navajo NM

Petroglyph Canyonlands NP

Capitol Reef NP

Mesa Verde NP

Petrified Forest NP Glen Canyon National Recreation Area

Jemez National Recreation Area Monte Vista National Wildlife Refuge

Bisti/De-Na-Zin Wilderness

Cebolla Wilderness Ojito Wilderness

West Malpais Wilderness Bandelier Wilderness Mesa Verde Wilderness

Petrified Forest National Wilderness Area Chama River Canyon Wilderness Cruces Basin Wilderness Dark Canyon Wilderness

Dome Wilderness La Garita Wilderness

Lizard Head Wilderness

Manzano Mountain Wilderness Pecos Wilderness San Pedro Parks Wilderness

Sandia Mountain Wilderness South San Juan Wilderness Weminuche Wilderness Amercian Flats Bridger Jack Mesa Wilderness SA Butler Wash Wilderness SA

Cahone Canyon Wilderness SA

Cheese Box Canyon Wilderness SA Cross Canyon Wilderness SA Fiddler Butte Wilderness SA

Fish Creek Canyon Wilderness SA Handies Peak Wilderness SA Little Rockies Wilderness SA

Mancos Mesa Wilderness SA McKenna Peak Wilderness SA

Menefee Mountain

Wilderness SA Middle Point Wilderness SA Mount Hillers Wilderness SA

Redcloud Peak Wilderness SA

Road Canyoon Wilderness SA

San Luis Hills Wilderness SA Slickhorn Canyon Wilderness SA Squaw/Papoose Canyon Wilderness SA

Weber Mountain Wilderness SA

Santa Fe NF

Santa Fe NF Carson NF

Cibola NF Cibola NF Uncompahgre Wilderness

Laguna IR San Juan NF

Carson NF

Santa Fe NF 

## Legend



# X APS Four Corners Power Plant 

# 6 City Interstate Highway
4-km CAMx Domain
Class I Area of Concern Class II Area of Concern



### Four Corners Power Plant Ozone Modeling Study

Figure 3-1 Class I and Sensitive Class II Areas of Concern 0 40 80

20 Kilometers 0 20 40 10
Miles

1:2,100,000 

# o

AZ CA CO

ID

KS MT ND

NE

NM NV

OK OR SD

TX UT WA

WY CANADAAECOM Environme nt 3

- 9

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 3.4.3 Ozone Model Attainment Test at Monitored Locations The USEPA guidance for projecting future 8

- hour ozone concentrations recommends using the PGM in a relative sense to s cale current observed 8

- hour design values (USEPA 2007). A design value is defined as a 5

- year average of the fourth

- highest daily maximum 8

- hour ozone concentration at a monitor. The locations of all monitors used for this assessment are shown in Figure 3

- 2 . Model scaling factors called relative response factors (RRFs) were used to scale the observed design values in order to predict future year design values. The RRFs are the ratio of the future year (or the control case) to the current year modeled 8

- hou r ozone concentrations near a monitor site. The USEPA has defined “ near the monitor ” to be approximately 15 km from the monitor location. The future year design value (DVF) is obtained from the current year design value (DVC) using the relationship:

DVF = DVC x RRF

The RRFs were calculated for all days in which the current year modeled 8

- hour ozone value is above a threshold. The USEPA currently recommends a threshold between 70 and 85 ppb; this modeling work
, however, set a lower threshold of 40 ppb to acc ommodate an adequate number of days and to accommodate a potentially lower ambient standard for ozone. This was done so that the model response to future changes in emissions is considered only on high ozone days of comparable conditions to the days used t o produce the DVC. The USEPA allows a reduction of the threshold value to 70 ppb to meet the minimum day requirements. These procedures were developed mainly for urban ozone

non
- attainment areas where ozone concentrations are much higher than those measure d in this project

area.
To perform the 8

- hour projections, the USEPA has developed the MATS (Abt Associates Inc. 2009) tool that uses modeling results, 8

- hour ozone design values, and follows USEPA guidance (USEPA 2007) to project 8

- hour ozone concentratio ns that reflect the change in emissions from the baseline to an alternative emissions scenario. The MATS ozone design values were calculated in accordance with 40 CFR Part 50.10, and Appendix I to Part 50.

The USEPA modeling guidance procedures (USEPA 2007 ) recommends using a DVC based on a 5

- year average of 8

- hour ozone design values centered on the modeling year. For the 2005 Baseline modeling, this means the DVC was the weighted average of the fourth

- highest 8

- hour ozone value at a monitor from 2003, 200 4, 2005, 2006, and 2007. To develop RRFs, USEPA guidance recommends using current and future modeling results for all days in which the current year daily maximum 8

- hour ozone concentration near the monitor exceeds a threshold value. The maximum modeled da ily maximum 8

- hour ozone concentration was picked from a 7x7 array of grid cells centered on the monitor in the 4

- km domain . This analysis follows the USEPA recommendation of using an 8

- hour ozone threshold based on a minimum of 5 days, although greater th an 10 days is preferred. The 8

- hour ozone projections using the MATS tool were performed twice using the 2005 Baseline simulation to forecast ozone concentrations for the 2018 NA Alternative and PA scenarios.

3.4.4 Ozone Model Attainment Test Removed from Monito rs
The US EPA’s guidance on model attainment demonstration ( USEPA 2007 ) suggests that an assessment of the impacts in areas removed from monitor locations is a recommended supplemental analysis that needs to be performed as part of the demonstration

. The in formation from this type of test can help to determine if further action is required despite passing the modeled attainment test at all monitoring sites. Additionally
, it also helps to determine if any unmonitored sensitive areas could b e subjected to pote ntial exceed e nces to the NAAQS. It is important , however, to emphasize that this type of analysis is subject to larger uncertainty than the analysis of monitored areas. The MATS unmonitored screening analysis was used to prepare spatial fields of the proje cted future year ozone design values throughout the 4

- km

.

# 6

6 6

6
6 6

6 6

6 ! (

! ( ! (

! ( ! ( ! ( ! (

! ( ! ( ! ( ! ( ! ( ! ( ! ( ! ( ! ( 

# X

350010027 

# §  ̈ ¦ 40 

# §  ̈ ¦ 25 

# Arizona Colorado

New Mexico Utah

Durango

Shiprock Farmington

Window Rock Gallup

Santa Fe

Rio Rancho

Albuquerque

Los Lunas 80671004

80677003 80830101

350010023 350010019 350010024 350010029 350011012

350011013 350011014 350431001 350431003 350439004 350450009 350451005 San Juan

Navajo Coconino

Apache

Cibola San Juan

McKinley Garfield

Kane
San Juan Dolores

La Plata Montezuma

Catron San Miguel Montrose

Ouray

Saguache Gunnison Chaffee Fremont

Torrance Hinsdale

Rio

Arriba

Taos

San Miguel

Valencia Mora

Santa Fe Los Alamos

Sandoval

Bernalillo Mineral

Rio

Grande Alamosa

Costilla Archuleta Conejos 

## Legend



# X APS Four Corners Power Plant

! ( Ozone Monitor 

### 6 City
4-km CAMx Domain Interstate Highway County



### Four Corners Power Plant Ozone Modeling Study

Figure 3-2 MATS Ozone Monitors in 4-km Domain 0 40 80

20 Kilometers 0 20 40 10
Miles

1:2,100,000 

# o

AZ CA CO

ID

KS MT ND

NE

NM NV

OK OR SD

TX UT WA

WY CANADAAECOM Environme nt 3

- 11

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Further details on this type of analysis can be found on the MATS user’s guide (Abt As sociates, Inc. 2009)

, but MATS can provide spatial f ield results. Th at is, MATS can provide air pollution estimates made at the center of each grid cell in a specified modeling domain.

The following types of spatial f ie lds were calculated for ozone:

• Basel ine

– interpolate monitor data to spatial field. This is an interpolation of baseline monitor values at each grid cell. The MATS identifies the “ neighbor ” monitors for each grid cell and then calculates an inverse

- distance

- weighted average of the monitor v alues at each grid cell.

• Baseline

– interpolate gradient

- adjusted monitor data to spatial field. This is an interpolation of model

- adjusted baseline monitor values at each grid cell. The MATS identifies the “ neighbor ” monitors for each grid cell, it adjust s the monitor values to account for the modeled spatial gradient, and then calculates an inverse

- distance weighted average of the monitor values.

• Forecast

– interpolate monitor data to spatial field. Temporally a djust. This is an interpolation of baseline monitor values at each grid cell that are then temporally adjusted to a future year. The MATS calculates the Baseline

- interpolate monitor data to spatial field and multiplies it with a RRF.

• Forecast

– interpolate gradient

- adjusted monitor data to spatial field. Temporally adjust. This is an interpolation of model

- adjusted baseline monitor values at each grid cell that are then temporally adjusted to a future year. The MATS calculates the Baseline interpolate gradient

adjusted monitor data to spatial field and multiplies it with a RRF.

The MATS tool was used to obtain estimates of the spatial fields described above for each of the modeling scenarios considered in this project

. Although the information provided by MATS is gridded data for the entire 4

- km dom ain, only a subset is presented for this analysis. Chapter 4.0, summarizes the spatial field ozone design v alues for 2005 and 2018 at the unmonitored Class I and sensitive Class II areas listed on Section 3. 4 .1. The se valu es were obtained with the help of Esri’s ArcGIS software and MATS output. ArcGIS was used to locate the centroid of each sensitive area that intersects the 4

- km domain and identify the nearest MATS’s spatial field values to each sensitive area centroid

.AECOM Environment 4

- 1

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# 4.0 Modeling Results

In order to eval uate the impacts of the PA and compare the results to ozone NAAQS, the model scenarios described in Chapter 1.0 were modeled using the emission inventory described in Chapter 2.0. Model results were process ed using the methods described in Chapter 3.0 to c ompare results with the 8

- hour ozone NAAQS. M odel results were processed and presented in two different ways. The absolute model results are model

- predicted concentrations without any adjustment from actual monitored values. These results were processed wi th the IAS tool to put model values in a form that can be directly compared to the ozone NAAQS. The second processing method uses the MATS tool to adjust model results with actual monitoring values. This second method accounts for model bias and the inter

- annual variability in ozone concentrations at monitoring locations. Results from both methods are reported and analyzed in the following subsections.

In this section
, the predicted model concentrations are compared to the ozone NAAQS. The primary and

seco ndary NAAQS are defined as the 3

- year average of the annual fourth

- highest daily maximum 8

- hour ozone concentration may not exceed a level of 75 ppb (CFR 2008)

. Although modeling results were only available for less than a 3

- year period, the averaging form required by the standard has been taken into account to perform these comparisons.

Modeled results should be interpreted in consideration of know model limitations. The FCAQS performed

a comprehensive model evaluation by comparing CAMx model predictions to measurements of ambient air pollutant concentrations. The FCAQS found that the ozone model performance for most months was within the established USEPA acceptance criteria of ±15 percent bias envelope and that all months were within the 35 percent error envelope. The bias also decreased during summer months, which indicates that CAMx exhibits the largest under predictions for the highest ozone concentrations. Overall the model performance for ozone, however, was adequate in replicating rural levels of oz one throughout the 2005 Baseline modeling over the 4

- km domain that covered the Four Corners area.

The following analyses are presented in this section :

• Absolute model concentrations were compared between:

− T he 2005 Baseline and the 2018 NA Alternative for the fourth

- highest daily maximum 8

- hour concentrations.

− T he 2005 Baseline and the 2018 PA for the fourth

- highest daily maximum 8

- hour concentrations.

− T he 2018 NA Alternative and the 2018 PA for both the fourth

- highest daily maximum 8

- hour concentrations an d the overall daily maximum 1

- hour concentrations.

− T he 2018 NA Alternative and the 2018 PA at Class I and sensitive Class II areas. Results also are compared to NAAQS

.

• Model

- adjusted concentrations were compared between:

− T he 2018 NA Alternative and the 201 8 PA at monitored locations. Results also are compared to NAAQS and the 2005 design values.

− T he 2018 NA Alternative and the 2018 PA at unmonitored Class I and sensitive Class II areas. Results also are compared to NAAQS and the 2005 design values.AECOM Environment 4

- 2

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 4.1 Absolute Model

- Predicted Ozone Concentrations This section reports and analyzes the absolute model

- predicted ozone concentrations from all modeling scenarios. Model

- adjusted ozone concentrations that are consistent with US EPA’s guidance on ozone model attainment d emonstrations are reported and analyzed in Section 4.2.

4.1.1 2005 Baseline Compared to the 2018 No Action Alternative Figure 4

- 1 depicts the spatial extent of model

- predicted cumulative ozone concentrations including the 2005 Baseline, the 2018 NA Alternative, and the differences between these scenarios

. The figure provides the model

- predicted fourth

- highest daily maximum 8

- hour average ozone concentrations at the surface layer for each grid cell . The model results presented in this spatial figure are consistent with the form of the 8

- hour ozone NAAQS, except that the model estimates only include the values from May to August. A direct comparison to the NAAQS would require an average over a 3

- year period. Importantly, the timing of the fourth

- highest value in the figure can vary from one grid cell to the next, and thus the values shown in the figures are not matched in time. The model results from the NA Alternative scenario represent the estimated future 2018 ozone concentrations that result from changes of all t he domain

wide emissions except for the FCPP, whose contributions were entirely removed from the inventory as explained in Section 2.2.

The modeled spatial concentrations in 2005 are shown in Figure 4

- 1 a

. Figure 4

- 1 a illustrates that the modeled peak fourt h

- highest daily maximum 8

- hour av erage ozone concentration in the 4

- km domain i n 2005 was 73.1 ppb and occur in Rio Arriba County, New Mexico (36.97 ° N, 107.38 ° W) right on the northeast edge of the San Juan Basin oil and gas field

. In general, the largest c oncentrations occur in San Juan and Rio Arriba c ounties in New Mexico where model

- predicted ozone exceeds 70 ppb. Other regions with relatively high concentrations were La Plata, Archuleta, Conejos, Mineral and Rio Grande counties in Colorado where ozone c an reach up to 70 ppb. In general for the 2005 Baseline
, Figure 4

- 1a shows spatial patterns that reflect ozone formation downwind from, or to the east of, important NO X and VOC (ozone precursors) sources. This is consistent with both the location of EGU an d oil and gas emissions sources in the 4

- km domain and the typical synoptic westerly transport in the region. It is important to remember that the ozone concentrations for this figure represent the cumulative effect of all the sources in the region and not just sources from FCPP during the 2005 Baseline year.

Figure 4

- 1b shows the model

- predicted fourth

- highest daily maximum 8

- hour average ozone concentrations at the surface layer for each grid cell for the 2018 NA Alternative. Figure 4

- 1 b illustrates that the modeled peak fourth

- highest daily maximum 8

- hour av erage ozone concentration in the 4

- km domain i n 2018 was 69.9 ppb and occur at about 16 miles southeast of the maximum concentrations for the 2005 Baseline. A qualitative assessment of Figures 4

- 1a and 4

- 1b show that although the spatial distribution of ozone concentrations are very similar in both figures, the 2018 NA Alternative concentrations show an overall decrease relative to the 2005 Baseline. For instance, the modeled peak fourth

- highest concen tration within the 4

- km domain decreases by 3 pbb in 2018 relative to 2005, while the domain

- wide average concentration decreases from 63.9 ppb in 2005 to 61.6 ppb in 2018.

To examin e in more detail the changes that occur between the base year and the NA Alternative scenario, Figure 4

- 1c shows the spatial difference between model

- predicted fourth

- highest daily maximum 8

- hour average ozone concentration in the 2018 NA Alternative and the 20 05 Baseline model simulations (i.e., the difference between Figure 4

- 1b and 4

- 1a )

. Figure 4

- 1c confirms that there is an overall domain

- wide decrease in ozone concentrations in 2018 relative to 2005. The most notable changes occur in the western and central areas of the domain where there is a 5 to 7 ppb decrease in the mo del

- predicted fourth

- highest daily maximum 8

- hour average ozone concentration s. The only locations with increases in ozone occur in San Juan County in New Mexico, which are immediatelyFour Corners Power Plant Ozone Modeling Study

Figure 4-1 Model-predicted Fourth Highest Daily Maximum 8-hour Average Ozone Concentrations:

2005 Baseline and 2018 NA Alternative 25 40 Weminuche Wilderness

San Pedro

Parks Wilderness La Garita Wilderness

Bandelier Wilderness

Petrified Forest NP Mesa Verde NP

Albuquerque Santa Fe Farmington

0 5 0 1 0 0 25

Miles 0 8 0 1 6 0 40

Kilometers TX CA MT

AZ ID

NV

NM CO OR

UT WY

KS SD

NE ND

OK WA 25 40 Weminuche Wilderness

San Pedro

Parks Wilderness La Garita Wilderness

Bandelier Wilderness

Petrified Forest NP Mesa Verde NP

Albuquerque Santa Fe Farmington

1:4,500,000 Legend

APS Four Corners Power Plant City
Class I Areas Interstate Highway State Boundary County Boundary

25 40 Weminuche Wilderness

San Pedro

Parks Wilderness La Garita Wilderness

Bandelier Wilderness

Petrified Forest NP Mesa Verde NP

Albuquerque Santa Fe Farmington ppb 70

67.5

65

62.5

60

57.5

55 ppb 70

67.5

65

62.5

60

57.5

55

ppb 5

4

3

2

1

0

-1

-2

-3

-4

-5 a) 2005 Baseline b) 2018 NA Alternative

c) 2018 NA Alternative - 2005 BaselineAECOM Environment 4

- 4

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 downwind of the location of FCPP. The main reason for the increase in ozone concentrations in 2018 relative to 2005 is the reduction in the NO emissions from the FCPP. In fact, this decrease is such that FCPP’s NO X emissions for the NA Alternative are exactly zero. During 2005, the ozone concentrations

were lower in the area surrounding the FCPP due to the chemical reaction of ozone with NO emit ted from the power plant. In the presence of NO, ozone is chemically transformed into oxygen (O 2 ), and NO is converted into NO 2 . When the emissions of NO decrease in the future year 2018, ozone is no longer converted into O 2 , and the net effect is an incre ase in the ozone concentrations immediately downwind from the source. The maximum increase in the fourth

- highest 8

- hour ozone concentrations between the 2018 NA Alternative and 2005 Baseline is 3.5 ppb. It is important to note, however, that this increase occurs in an area where ozone concentrations range only from 65 to 70 ppb and that model

- predicted

ozone concentrations in the vicinity of the FCPP peaks at 69 ppb.

4.1.2 2005 Baseline Compared to the 2018 Proposed Action Figure 4

- 2 depicts the spatial extent of model

- predicted cumulative ozone concentrations including the 2005 Baseline, the 2018 PA, and the differences between these scenarios. The figure provides the model

- predicted fourth

- highest daily maximum 8

- hour average ozone concentrations at the surface layer for each grid cell . The model results presented in this spatial figure are consistent with the form of the 8

- hour ozone NAAQS, except that the model estimates only include the values from May to August. A direct comparison to the NAAQS would require an average over a three year period. Importantly, the timing of the fourth

- highest value in the figure can vary from one grid cell to the next, and thus the values shown in the figures are not matched in time. The model results from the PA scenario represe nt the estimated future (2018) ozone concentrations that result from changes of all the domain

- wide emissions including those from the FCPP, whose contributions are detailed in S ection 2.3

. Comparison between Figures 4

- 1 and 4

- 2 shows that domain

- wide ozon e concentrations for the future year 2018 are very similar indicating that the FCPP contribution is minor . This is confirmed by comparing Figures 4

- 1c and Figure 4

- 2c . Each of these figures presents the difference between PA and NA Alternative to the 2005 Baseline, respectively. The domain

- wide spatial patterns in these figures are similar with the exception of larger differences immediately downwind of the FCPP. The spatial extent of ozone concentrations subject to the largest impacts from the FCPP can be estimated from these figures to be no larger than approximately 32 km east of the power plant.

4.1.3 2018 Proposed Action Compared to the 2018 No Action Alternative The following sections present several analyses that estimate d the potential future impacts for t he 2018 PA. These estimates were based on the evaluation of absolute modeling results from both the 2018 NA Alternative and PA scenarios. Since the 2018 NA Alternative and the 2018 PA model simulations were identical except for the change in the FCPP emiss ions, the impacts of the power plant can be isolated by comparing these results.

4.1.3.1 Fourth

- Highest 8

- Hour Average Ozone Concentrations
Similar to Figure 4

- 1
, Figure 4

- 3 depicts the spatial extent of model

- predicted fourth

- highest daily maximum 8

- hour averag e ozone concentrations for three analyses : the 2018 NA Alternative , the 2018 PA , and the differences between the 2018 PA and the 2018 NA Alternative.

Comparison of Figure 4

- 3a and 4

- 3b shows that the spatial patterns of the fourth

- highest daily maximum 8

- hour average ozone concentrations are very similar between the PA and the NA Alternative. For both modeling scenarios, the highest ozone concentrations, ranging from 60 to 70 ppb, are found mostly in the northeastern portion of the 4

- km domain. The fourth

- highest daily maximum 8

- hour average ozone concentration in the vicinity of the FCPP ranges from 65 to 70 ppb. Additionally, the largest and smallest values of the fourth

- highest daily maximum 8

- hour average ozone concentrations throughout the 4

- km model d omain are 70.1 ppb and 43.6 ppb, respectively.Four Corners Power Plant Ozone Modeling Study

Figure 4-2 Model-predicted Fourth Highest Daily Maximum 8-hour Average Ozone Concentrations:

2005 Baseline and 2018 PA 25 40 Weminuche Wilderness

San Pedro

Parks Wilderness La Garita Wilderness

Bandelier Wilderness

Petrified Forest NP Mesa Verde NP

Albuquerque Santa Fe Farmington

0 5 0 1 0 0 25

Miles 0 8 0 1 6 0 40

Kilometers TX CA MT

AZ ID

NV

NM CO OR

UT WY

KS SD

NE ND

OK WA 25 40 Weminuche Wilderness

San Pedro

Parks Wilderness La Garita Wilderness

Bandelier Wilderness

Petrified Forest NP Mesa Verde NP

Albuquerque Santa Fe Farmington

1:4,500,000 Legend

APS Four Corners Power Plant City
Class I Areas Interstate Highway State Boundary County Boundary

25 40 Weminuche Wilderness

San Pedro

Parks Wilderness La Garita Wilderness

Bandelier Wilderness

Petrified Forest NP Mesa Verde NP

Albuquerque Santa Fe Farmington ppb 70

67.5

65

62.5

60

57.5

55 ppb 70

67.5

65

62.5

60

57.5

55

ppb 5

4

3

2

1

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-1

-2

-3

-4

-5 a) 2005 Baseline b) 2018 PA

c) 2018 PA - 2005 BaselineFour Corners Power Plant Ozone Modeling Study

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F3$±1$$OWHUQDWLYHAECOM Environment 4

- 7

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Figure 4

- 3c depicts the spatial differences between model

- predicted fourth

- highest daily maximum 8

- hour average ozone c oncentration in 2018 PA and the 2018 NA Alternative (i.e., the difference between Figure 4

- 3b and 4

- 3a ) . The maximum model

- predicted difference between the PA and the NA Alternative is 4.7 ppb, which occurs downwind of the FCPP. This maximum difference is located about 11 miles southeast of the FCPP and about 16 miles southwest of Farmington, New Mexico. Most of the impacted areas show a 2 to 4 ppb increase in ozone concentrations and are located entirely in San Juan and McKinley counties in New Mexico. Fig ure 4

- 3c also demonstrates that the largest impacts from the FCPP are more likely to be located east of the FCPP, which reflects the typical westerly transport in the region.

4.1.3.2 Daily Maximum 1

- Hour Average Ozone Concentrations

In order to evaluate the maxim um model

- predicted ozone impact attributable to the FCPP, the 2018 NA Alternative 1

- hour average ozone concentrations were subtracted from the 2018 PA 1

- hour average ozone concentrations. Table 4

- 1 shows the five largest values of the daily 1

- hour differen ce between the 2018 future scenarios for the entire modeling period along with the date when they occur and their approximate location. The maximum model

- predicted ozone impacts a ttributable to the FCPP occurs during the summer mostly in July and August. T he impacts are located to the east of the FCPP, with the largest impact (15.8 ppb) at about 12 miles to the southeast of FCPP, while the fifth largest impact (13.1 ppb) is located approximately 29 miles southeast of the FCPP.

Table 4

- 1 Maximum 1

- hour daily Ozone D ifference between 2018 PA and NA Alternative

Difference between

2018 PA and NA Alternatives O zone Values (ppb) Date A ssociated to L argest D ifference Latitude (degrees) Longitude (degrees)

15.8 July 1 6 36.58811

- 108.32195

15.1 August 2 36.67785

- 108.15470

14.9 August 9 36.76324

- 108.39458

- 13.3 July 13 36.54767

- 108.36091

13.1 August 26 36.43069

- 108.07183

In order to examine the spatial extent of the potential impacts from the FCPP, isopleths of absolute model

- predicted ozone concentration for 2018 NA Alternative and PA and their difference for the two largest episodes identified in Table 4

- 1 are presented in Figures 4

- 4 and 4

- 5

. Figure 4

- 4 presents model results for July 16 at 14:00 MST while Fi gure 4

- 5 presents results for August 2 at 13:00 MST. Both figures show ozone concentrations on the upper panel and NO X concentrations on the lower panel.

On July 16, the maximum modeled 1

- hour ozone concentration in the 4

- km domain is 78.6 ppb for both th e 2018 NA Alternative and PA. Figure 4

- 4c shows that the FCPP contributes 15.8 ppb to the modeled ozone concentrations. Although this region generally has westerly transport for this period, Figure 4

- 4c indicates southeasterly transport occurs during July 16 as shown by the direction of the ozone plume.

On August 2, the maximum modeled 1

- hour ozone concentration in the 4

- km domain is 69.3 ppb for both the 2018 PA and the NA Alternative. Figure 4

- 5 c shows that the FCPP contributes 15.1 ppb to the modeled oz one concentrations. It is likely the meteorological conditions during August 2 were more stagnant than the July 16 period due to the spatial concentrations of ozone in the vicinity of the FCPP.AECOM Environment 4

- 8

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 (a) NA Alternative (b) PA (c) PA

- NA

Figure 4

- 4 2018 NA Alternative and PA Model

- Predicted Hourly Average Ozone and NO X on July 16AECOM Environment 4

- 9

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 (a) NA Alternative (b) PA (c) PA

- NA

Figure 4

- 5 2018 NA Alternative and PA Model

- Predicted Hourly Average Ozone and NO X on August 2AECOM Environment 4

- 10

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 4.1.4 Ozone Concentrations at Class I and Sensitive Class II Areas

Table 4

- 2 presents the absolute model

- predicted ozone concentrations for the Class I and sensitive Class II areas listed in Section 3. 4 .1 and shown in Figure 3

- 1

. The reported ozone values are the model

- predicted fourt h

- highest daily maximum 8

- hour average concentrations that occur in any grid cell that contains the Class I or sensitive Class II area and were estimated with the IAS tool

. As shown in Table 4

- 2 , there are 12 sensitive areas with model

- predicted ozone conc entrations that exceed the NAAQS in 2005. Consistent with the results discussed previously, overall ozone concentrations decrease in 2018 relative to 2005. The number of sensitive areas with predicted NAAQS exceed e nces decreases from 12 areas in 2005 to on ly four areas in the 2018 PA and three areas in the NA Alternative model scenarios. These four areas with model

- predicted ozone concentrations that exceed the NAAQS in the PA are La Garita WA, Grand Mesa, Uncompahgre, and Gunnison NF s, Navajo Nation, and R io Grande NF. The contribution of the FCPP to these exceed e nces can be estimated by evaluating the difference between the 2018 PA and NA Alternative. In La Garita WA, Grand Mesa, Uncompahgre, and Gunnison NF s, and Rio Grande NF, the difference between the 2018 PA and NA Alternative is 0.0 ppb, indicating that the FCPP does not contribute to any modeled ozone impacts that exceed the NAAQS. Importantly, the absolute model predicted ozone concentration for the PA at the Navajo Nation is just below the NAAQS. T he model

- predicted FCPP contribution to the Navajo Nation is 0.7 ppb of ozone.

For all other areas in Table 4

- 2 , the difference between the model

- predicted 2018 PA and NA Alternative is 0.0 ppb with the exception of 43 sensitive areas where the model

- predi cted impacts due to the PA range from 0.1 to 0.9 ppb. The maximum impact of the PA (0.9 ppb) occurs at Ute Mountain IR in Colorado and New Mexico and also at Chaco Culture National Historic Park in New Mexico. The model

predicted fourth

- highest daily avera ge 8

- hour ozone concentrations at Ute Mountain and Chaco Culture National Historic Park are 63.8 ppb and 67.8 ppb respectively under the 2018 PA, which is well below the 75 ppb NAAQS.

Table 4

- 2 Fourth

- Highest D aily M aximum 8

- hour A verage O zone C oncentrations at Class I and Sensitive Class II Areas

Receptor Site 2005 Ozone Values (ppb) 2018 PA Ozone Values (ppb) 2018 NA Alternative Ozone Values (ppb) Difference Between PA

and NA Alternative Ozone Values (ppb)

CLASS I AREAS

Bandelier WA 1 69.1 66.8 66.4 0.4 Canyonlands NP 2 62.5 61.0 61.0 0.0

La Garita WA 76.3 75.4 75.4 0.0

Mesa Verde NP 67.3 65.0 64.7 0.3

Pecos WA 69.0 66.9 66.9 0.0

Petrified Forest NP 69.9 68.0 68.0 0.0

San Pedro Parks WA 70.1 67.5 6 7.5 0.1

Weminuche WA 75.6 74.8 74.8 0.0

CLASS II AREAS

Acoma IR 3 66.6 63.3 63.1 0.2

American Flats 74.7 73.9 73.9 0.0AECOM Environment 4

- 11

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 4

- 2 Fourth

- Highest D aily M aximum 8

- hour A verage O zone C oncentrations at Class I and Sensitive Class II Areas

Receptor Site 2005 Ozone Values (ppb) 2018 PA Ozone Values (ppb) 2018 NA Alternative Ozone Values (ppb) Difference Between PA

and NA Alternative Ozone Values (ppb)

Aztec Ruins NM 4 71.0 68.7 68.7 0.0

Bisti/De

- Na

- Zin WA 68.0 62.9 62.2 0.7 Bridger Jack Mesa WSA 5 62.5 61.2 61.2 0.0

Butler Wash WSA 62.7 61.1 61.1 0.0 Cahone Canyon WSA 64.9 61.6 61.4 0.2

Canoncito IR 65.7 62.9 62.8 0.2 Canyon de Chelly NM 65.8 61.9 61.9 0.0

Carson NF 75.3 72.1 71.9 0.1

Chaco Culture National Historic Park 68.9 63.8 62.9 0.9 Chama Rover Canyon WA 72.6 69.6 6 9.6 0.1 Cheese Box Canyon WSA 62.9 62.0 62.0 0.0

Cibola NF 72.3 70.5 70.3 0.1

Cochiti IR 70.9 69.2 69.1 0.1 Cross Canyon WSA 64.5 61.4 61.1 0.3

Cruces Basin WA 73.0 70.0 69.8 0.2 Dark Canyon WA 65.3 64.2 64.2 0.0

Dome WA 68.2 66.0 65.5 0.5 El Malpa is NM 66.0 63.4 63.3 0.1

El Morro NM 65.0 63.2 63.1 0.1 Fish Creek Canyon WSA 65.0 62.3 62.3 0.0 Glen Canyon National Recreation Area 67.7 65.5 65.5 0.0
Grand Mesa, Unc ompahgre, and Gunnison NF 76.3 75.4 75.4 0.0

Handies Peak WSA 75.2 74.3 74.3 0.0

H opi IR 62.7 60.5 60.5 0.0 Hovenweep NM 65.7 62.0 61.6 0.4 Hubbell Trading Post National Historic Site 58.9 56.6 56.6 0.0

Jemez IR 67.3 65.5 65.2 0.3

Jemez National Recreation Area 68.6 66.3 66.0 0.3 Jicarilla Apache IR 75.3 72.4 71.9 0.5AECOM Environment 4

- 12

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 4

- 2 Fourth

- Highest D aily M aximum 8

- hour A verage O zone C oncentrations at Class I and Sensitive Class II Areas

Receptor Site 2005 Ozone Values (ppb) 2018 PA Ozone Values (ppb) 2018 NA Alternative Ozone Values (ppb) Difference Between PA

and NA Alternative Ozone Values (ppb) Laguna IR 68 .1 64.9 64.6 0.3

Little Rockies WSA 67.3 65.2 65.2 0.0

Lizard Head WA 72.2 71.4 71.4 0.0

Mancos Mesa WSA 66.7 64.5 64.5 0.0

Manti

- Lasal NF 66.3 65.4 65.4 0.0

McKenna Peak WSA 66.2 65.1 65.1 0.0

Menefee Mountain WSA 65.9 64.8 64.6 0.2

Mesa Verde WA 6 6.1 65.0 64.6 0.5

Middle Point WSA 64.7 62.7 62.7 0.0 Monte Vista National Wildlife Refuge 69.4 68.4 68.4 0.0

Mount Sneffels WA 72.8 71.8 71.8 0.0

Nambe IR 69.7 67.5 67.4 0.1 Natural Bridges NM 64.0 63.2 63.2 0.0 Navajo Nation 78.7 74. 9 74.3 0.7 Oj ito WA 64.1 61.8 61.8 0.0

Pecos National Historical Park 65.3 63.1 63.0 0.0

Petrified Forest National WA 68.7 66.9 66.9 0.0 Petroglyph NM 69.4 67.7 67.7 0.1 Pojoaque IR 65.1 63.0 62.9 0.1 Powderhorn WA (BLM) 74.0 73.0 73.0 0.0 Powderhorn WA (USFS) 73 .9 72.9 72.9 0.0 Powderhorn WSA (BLM) 71.8 70.8 70.8 0.0 Ramah Navajo IR 67.3 66.5 66.5 0.0

Redcloud Peak WSA 75.0 74.1 74.1 0.0

Rio Grande NF 76.1 75.2 75.2 0.0 Road Canyon WSA 65.1 61.1 61.1 0.0 San Felipe IR 72.4 70.4 70.4 0.1

San Ildefonso IR 66 .0 63.9 63.6 0.3

San Jua n NF 75.1 74.3 74.3 0.0

San Juan IR 67.3 66.1 66.1 0.0AECOM Environment 4

- 13

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 4

- 2 Fourth

- Highest D aily M aximum 8

- hour A verage O zone C oncentrations at Class I and Sensitive Class II Areas

Receptor Site 2005 Ozone Values (ppb) 2018 PA Ozone Values (ppb) 2018 NA Alternative Ozone Values (ppb) Difference Between PA

and NA Alternative Ozone Values (ppb)

Sandia IR 71.9 70.7 70.6 0.1

Sandia Mountain WA 72.0 70.1 70.0 0.1

Santa Ana IR 72.6 70.7 70.7 0.1

Santa Clara IR 71.1 68.3 67.9 0.3 Santo Domingo IR 70.9 68.6 68.5 0.1 Slickhorn Canyon WSA 65.4 62.3 62.3 0.0

San ta Fe NF 73.5 70.6 70.5 0.1

South San Juan WA 74.6 73.8 73.8 0.0

Southern Ute IR 74.6 72.0 71.7 0.3 Squaw/Papoose Canyon WSA 65.1 61.0 60.8 0.2 Tesuque IR 67.4 65.5 65.4 0.1 Uncompahgre WA (BLM) 75.0 74.2 74 .2 0.0 Uncompahgre WA (USFS) 75.0 74.1 74.1 0.0

Ute Mountain IR 73.8 67.8 67.0 0.9

Weber Mountain WSA 66.3 65.0 64.5 0.4 West Malpais WA 62.1 61.3 61.3 0.0

Yucca House NM 65.2 60.5 60.5 0.1

Zia IR 67.2 65.2 65.1 0.1

Zuni IR 66.5 64.8 64.8 0.0

1 WA = Wilderness Area.

2 NP = National Park.

3 IR = Indian Reservation.

4 NM = National Monument.

5 WSA = Wilderness Study Area.

Notes: Model

- predicted concentrations that exceed 75 ppb are shown in red text. Information in parentheses indicates agency managin g sensitive area.

4.2 Model

- Adjusted Ozone Concentrations The 2005 design values were calculated based on actual monitoring data over a 5

- year monitoring record. Application of design value concentrations to model results was used to present the modeling

re sults in a form consistent with the NAAQS and reduces model uncertainty and biases that could result from using absolute model predictions alone.AECOM Environment 4

- 14

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 4.2.1.1 Ozone Impact Assessment in Monitored Areas

Table 4

- 3 provides the ozone design values estimated by MATS for 20 05 and 2018 at 16 monitoring sites located within the 4

- km modeling domain. Note that red text in the table indicates design values that exceed 75 ppb

. The 2005 design values were calculated exclusively from measured ozone concentrations. As shown in Table 4

- 3 , there is only one monitor (site ID 350011012 ) with design values in 2005 that exceed the 8

- hour ozone NAAQS (77 ppb). This site is located northeast of Albuquerque in Bernalillo County, New Mexico. In general, the future year design values decrease r elative to 2005, and this is consistent with the results presented in Section 4.1 for absolute model predictions. As shown in Table 4

- 3 , there are no monitors within the 4

- km domain with design values that exceed the 8

- hour ozone NAAQS under both the 2018 NA Alternative and PA

. This reduction in ozone levels is attributable to reduced regional emissions, including those from the FCPP, relative to 2005.

For all monitor locations, the contribution from the FCPP was calculated as the difference between the PA and NA Alternative design values, and these results also are shown in Table 4

- 3

. The ozone contribution attributable to FCPP is 0.0 ppb for all monitors close to exceeding the NAAQS in 2018, such as the aforementioned Albuquerque, New Mexico monitor (site ID 350011012 )

. Furthermore, this monitor is located at a considerable distance from the FCPP. There are 11 monitors with a predicted non

- zero contribution to ozone that is attributable to the PA. These contributions range from 0.1 to 1.0 ppb. The largest i mpact of the PA at an existing monitor is 1.0 ppb, which occurs in Farmington, New Mexico (site ID 350451005). Importantly, none of the monitoring sites that are predicted to have an increase in ozone concentrations under the PA have a design value that ex ceeds the NAAQS either in 2005 or in 2018.

4.2.1.2 Ozone Impact Assessment in Unmonitored Areas In addition to assessing the ozone impacts in areas with monitors, areas without monitors were assessed using the MATS tool in order to evaluate all areas where future year design values could be greater than the NAAQS

. It should be noted that due to lack of measurement data, the analysis of ozone attainment test in the unmonitored areas can be more uncertain than in places where monitoring data are available. As a resu lt, the unmonitored area analysis should be treated as a separate test from the monitor based attainment test. The current work provides results from the unmonitored area analysis as a supplemental analysis. The receptors chosen for this analysis include t he Class I and sensitive Class II areas listed in Section 3. 4 .1 that are within the 4

- km domain. The methodology used to obtain the values presented in Table 4

- 4 is detailed in S ection 3. 4 .4.

Table 4

- 4 shows ozone design values estimated by MATS for 2005 a nd 2018 at unmonitored areas. The 2005 Baseline column represents ozone concentrations at 88 sensitive areas from the interpolation of available monitor data for 2005 (spatial field baseline). In 2005, there are no receptors that exceed the ozone NAAQS. Be cause 2018 ozone design values generally decrease from 2005, there are no receptors that exceed the ozone NAAQS in the future year either. The difference between PA and NA Alternative is seen in 60 sensitive areas with differences ranging from 0.1 to 1.0 p pb due to impacts from the FCPP. The maximum impact of 1.0 ppb occurs at Bisti/De

- Na

- Zin WA , which has a future design value of 65.8 ppb.

Table 4

- 4 also shows interpolated gradient

- adjusted ozone concentrations for Class l and sensitive Class II areas. Whe n these gradient

- adjusted values are examined, the baseline 2005 ozone concentrations exceed the NAAQS at only nine receptors. Only one site, Sandia Mountain WA, shows ozone exceed e nces of the NAAQS in the 2018 future year scenarios. The difference between the 2018 PA and NA Alternative for Sandia Mountain WA is 0.1 ppb, indicating some impacts from the FCPP. The ozone values for both the 2018 NA Alternative and PA, however, exceed the NAAQS. The difference between PA and NA Alternative are non

- zero for 60 sensitive areas with predicted FCPP contributions ranging from 0.1 to 1.0 ppb. The maximum impact of 1.0 ppb occurs at Bisti/De

- Na

- Zin WA , which has a future ozone design value of 62 ppb.AECOM Environment 4

- 15

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013

Table 4

- 3 MATS 8

- Ho ur Ozone Desi gn Values for 2005 and 2018 at M onitoring S ites L ocated within the 4

- km D omain

Location Site ID Latitude (degrees) Longitude (degrees) 2 005 Baseline Ozone Design Value (ppb) 2018 PA Ozone Value (ppb) 2018 NA Alternative Ozone Value (ppb) Diff erence between PA and NA Alternative Ozone Values (ppb) Bernalillo County, New Mexico 350010019 35.10728

- 106.56359 72.3 70.6 70.5 0.1 Bernalillo County, New Mexico 350010023 35.13430

- 106.58520 71.0 69.0 68.9 0.1 Bernalillo County, New Mexico 350010024 35.06310

- 106.57879 72.3 70.6 70.5 0.1 Bernalillo County, New Mexico 350010027 35.15390

- 106.69715 71.7 69.5 69.4 0.1 Bernalillo County, New Mexico 350010029 35.01708

- 106.65739 69.0 67.1 67.1 0.0 Bernalillo County, New Mexico 350011012 35.18520

- 106.5 0815 77.0 74.9 74.9 0.0 Bernalillo County, New Mexico 350011013 35.19324

- 106.61382 73.7 71.7 71.7 0.0 Bernalillo County, New Mexico 350011014 35.20220

- 106.64927 70.3 68.0 68.0 0.0

La Plata County, Colorado 80671004 37.30389

- 107.48417 72.0 69.8 69.6 0 .2 La Plata County, Colorado 80677003 37.10258

- 107.87022 63.7 60.3 60.1 0.2 Montezuma County, Colorado 80830101 37.19833

- 108.49028 72.0 65.1 64.7 0.4 Sandoval County, New Mexico 350431001 35.29944

- 106.54833 67.7 65.6 65.5 0.1 Sandoval County, New Me xico 350431003 35.23806

- 106.64944 73.3 70.9 70.9 0.0 Sandoval County, New Mexico 350439004 35.61528

- 106.72444 71.0 68.6 68.3 0.3 San Juan County, New Mexico 350450009 36.74222

- 107.97694 69.7 66.5 66.2 0.3 San Juan County, New Mexico 350451005 36.7966 7

- 108.47250 71.3 68.1 67.1 1.0

Note: Design value concentrations that exceed 75 ppb are shown in red text.AECOM Environment 4

- 16

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 4

- 4 MATS 8

- Hour Ozone Design Values for 2005 and 2018 at U nmonitored S ensitive Class I an d II A reas L ocated within the 4

- km D omain

Site Name Interpolated Ozone Concentration (ppb) Interpolated Gradient

- Adjusted Ozone Concentration (ppb)

2005 Baseline 2018 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative 2005 Baseline 20 18 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative

CLASS I AREAS

Bandelier WA 1 71.4 68.6 68.4 0.2 71.5 68.7 68.5 0.2
Canyonlands NP 2 71.8 69.4 69.4 0.0 65.4 63.2 63.2 0.0

La Garita WA 71.9 70.7 70.7 0.0 75.4 74.2 74 .1 0.1

Mesa Verde NP 71.4 68.4 68.1 0.3 69.5 66.5 66.3 0.2

Pecos WA 71.8 69.3 69.2 0.1 75.0 72.4 72.3 0.1

Petrified Forest NP 70.8 67.9 67.9 0.0 68.1 65.3 65.3 0.0

San Pedro Parks WA 71.3 68.6 68.3 0.3 73.4 70.6 70.3 0.3

Weminuche WA 69.5 68.0 67.9 0. 1 70.1 68.6 68.5 0.1

CLASS II AREAS

Acoma IR 3 70.5 68.2 68.1 0.1 66.5 64.3 64.2 0.1

American Flats 70.0 68.8 68.7 0.1 72.3 71.0 71.0 0.0

Aztec Ruins NM 4 69.0 65.8 65.5 0.3 70.9 67.6 67.3 0.3

Bisti/De

- Na

- Zin WA 70.5 65.8 64.8 1.0 66.4 62.0 61.0 1.0 Bridger Jack Mesa WSA 5 71.8 69.0 68.9 0.1 65.2 62.7 62.6 0.1

Butler Wash WSA 71.8 69.7 69.7 0.0 66.7 64.7 64.7 0.0
Cahone Canyon WSA 71.8 67.5 67.3 0.2 67.5 63.5 63.2 0.3

Canoncito IR 70.5 67.9 67.8 0.1 67.8 65.3 65.2 0.1AECOM Environment 4

- 17

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 4

- 4 MATS 8

- Hour Ozone Design Values for 2005 and 2018 at U nmonitored S ensitive Class I an d II A reas L ocated within the 4

- km D omain

Site Name Interpolated Ozone Concentration (ppb) Interpolated Gradient

- Adjusted Ozone Concentration (ppb)

2005 Baseline 2018 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative 2005 Baseline 20 18 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative
Canyon de Chelly NM 70.9 67.7 67.6 0.1 64.6 61.7 61.6 0.1

Carson NF 70.1 66.8 66.6 0.3 72.6 69.1 68.9 0.3

Chaco Culture National Historic Park 70.5 67.3 66.9 0.4 67.1 64.0 63.6 0.4

Chama Rover Canyon WA 71.3 67.3 67.0 0.3 73.8 69.7 69.4 0.3
Cheese Box Canyon WSA 71.4 69.0 69. 0 0.0 66.3 64.1 64.1 0.0

Cibola NF 71.5 69.6 69.6 0.1 72.0 70.1 70.1 0.0

Cochiti IR 71.6 68.6 68.4 0.2 73.1 70.0 69.9 0.1
Cross Canyon WSA 71.8 66.2 65.7 0.5 67.3 62.0 61.6 0.4

Cruces Basin WA 71.4 69.2 69.1 0.1 75.8 73.5 73.4 0.1
Dark Canyon WA 71.5 69.9 69.9 0.0 68.9 67.4 67.4 0.0

Dome WA 71.4 68.6 68.3 0.3 72.0 69.2 68.9 0.3
El Malpais NM 70.5 68.1 68.1 0.0 66.9 64.6 64.6 0.0

El Morro NM 70.5 68.0 68.0 0.0 65.2 62.9 62.9 0.0
Fish Creek Canyon WSA 71.5 68.1 67.9 0.1 66.7 63.5 63.4 0.1
Glen Canyo n National Recreation Area 71.4 68.5 68.5 0.0 66.8 64.1 64.1 0.0

Grand Mesa, Uncompahgre, and Gunnison NFs 70.7 68.9 68.8 0.1 69.1 67.3 67.2 0.1AECOM Environment 4

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 4

- 4 MATS 8

- Hour Ozone Design Values for 2005 and 2018 at U nmonitored S ensitive Class I an d II A reas L ocated within the 4

- km D omain

Site Name Interpolated Ozone Concentration (ppb) Interpolated Gradient

- Adjusted Ozone Concentration (ppb)

2005 Baseline 2018 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative 2005 Baseline 20 18 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative

Handies Peak WSA 70.0 69.0 68.8 0.2 72.0 70.9 70.8 0.1
Hopi IR 70.8 68.0 68.0 0.0 63.4 60.9 60.9 0.0

Hovenw eep NM 71.8 65.3 64.6 0.7 68.7 62.5 61.8 0.7
Hubbell Trading Post National Historic Site 70.8 68.3 68.3 0.0 65.1 62.8 62.8 0.0

Jemez IR 71.1 68.6 68.3 0.3 70.8 68.3 68.0 0.2

Jemez National Recreation Area 70.2 68.0 67.8 0.2 70.8 68.6 68.4 0.2

Jicarilla Apache IR 70.6 67.6 67.4 0.3 74.7 71.5 71.3 0.2
Laguna IR 70.5 67.8 67.7 0.1 68.3 65.7 65.6 0.1

Little Rockies WSA 71.4 69.1 69.1 0.0 67.0 64.9 64.8 0.1

Lizard Head WA 69.3 67.4 67.3 0.1 68.5 66.6 66.5 0.1

Mancos Mesa WSA 71.4 68.3 68.3 0.0 67.6 64.7 64.6 0.1

Manti

- Lasal NF 71.5 69.9 69.9 0.0 68.4 66.8 66.8 0.0

McKenna Peak WSA 69.9 67.1 66.9 0.2 65.1 62.5 62.3 0.2

Menefee Mountain WSA 69.8 67.7 67.6 0.1 66.9 64.9 64.8 0.1

Mesa Verde WA 70.9 68.4 68.3 0.1 69.4 67.0 66.8 0.1

Middle Point WSA 71.4 6 9.5 69.5 0.0 65.5 63.7 63.7 0.0

Monte Vista National Wildlife Refuge 71.9 70.7 70.5 0.2 73.3 72.1 71.9 0.2AECOM Environment 4

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 4

- 4 MATS 8

- Hour Ozone Design Values for 2005 and 2018 at U nmonitored S ensitive Class I an d II A reas L ocated within the 4

- km D omain

Site Name Interpolated Ozone Concentration (ppb) Interpolated Gradient

- Adjusted Ozone Concentration (ppb)

2005 Baseline 2018 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative 2005 Baseline 20 18 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative

Mount Sneffels WA 69.3 67.8 67.7 0.1 68.4 66.9 66.9 0.0

Nambe IR 71.7 69.4 69.3 0.1 70.4 68.1 68.0 0.1
Natural Bridges NM 71.4 68.6 68.6 0.0 66.4 63.8 63.8 0.0
Navajo Nation 71.0 68.5 68.5 0.1 65.6 63.3 63.3 0.0
Ojito WA 70.7 68.2 68.2 0.0 67.8 65.4 65.4 0.0

Pecos National Historical Park 72.2 70.5 70.4 0.1 75.1 73.3 73.2 0.1

Petrified Forest National WA 70.8 67.7 67.7 0.0 68.2 65.2 65.2 0.0

P etroglyph NM 71.6 69.1 69.0 0.1 72.4 69.9 69.9 0.0
Pojoaque IR 71.7 69.5 69.5 0.0 70.1 68.0 67.9 0.1
Powderhorn WA (BLM) 71.9 70.7 70.7 0.0 75.2 73.9 73.9 0.0
Powderhorn WA (USFS) 71.9 70.8 70.8 0.0 75.5 74.4 74.4 0.0
Powderhorn WSA (BLM) 71.9 70.5 70. 5 0.0 73.6 72.2 72.2 0.0
Ramah Navajo IR 70.7 67.7 67.7 0.0 66.2 63.4 63.4 0.0

Redcloud Peak WSA 71.9 70.7 70.6 0.1 74.9 73.6 73.5 0.1

Rio Grande NF 71.9 70.6 70.5 0.1 74.8 73.5 73.4 0.1
Road Canyon WSA 71.4 67.8 67.7 0.1 66.8 63.5 63.3 0.2
San Felipe IR 71.3 68.1 68.1 0.0 73.9 70.6 70.6 0.0

San Ildefonso IR 71.5 69.1 69.0 0.1 69.1 66.8 66.7 0.1AECOM Environment 4

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 4

- 4 MATS 8

- Hour Ozone Design Values for 2005 and 2018 at U nmonitored S ensitive Class I an d II A reas L ocated within the 4

- km D omain

Site Name Interpolated Ozone Concentration (ppb) Interpolated Gradient

- Adjusted Ozone Concentration (ppb)

2005 Baseline 2018 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative 2005 Baseline 20 18 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative

San Juan IR 71.5 68.7 68.5 0.2 69.7 67.0 66.8 0.2

San Juan NF 71.9 69.9 69.8 0.1 72.9 70.9 70.7 0.2

Sandia IR 71.8 69.4 69.4 0.0 73.6 71.2 71.1 0.1

Sandia Mountain WA 72.4 70.3 70.2 0.1 78.8 76.5 76.4 0.1

Santa Ana IR 70.3 67.8 67.8 0.0 72.0 69.5 69.4 0.1

Santa Clara IR 71.4 69.1 68.8 0.3 72.4 70.0 69.7 0.3

Santa Fe NF 71.5 68.9 68.7 0.2 72.1 69.5 69.3 0.2 Santo Domingo IR 71.5 68.2 68.0 0.2 72.4 69.1 6 8.9 0.2
Slickhorn Canyon WSA 71.4 67.6 67.5 0.1 67.5 63.9 63.8 0.1

South San Juan WA 71.4 69.1 68.9 0.2 75.0 72.6 72.3 0.3

Southern Ute IR 67.3 64.4 64.3 0.1 67.1 64.2 64.1 0.1
Squaw/Papoose Canyon WSA 71.8 66.5 65.9 0.6 67.7 62.7 62.2 0.5
Tesuque IR 71.7 69.4 69.4 0.0 70.4 68.1 68.1 0.0
Uncompahgre WA (BLM) 69.4 68.1 68.0 0.1 71.4 70.0 70.0 0.0 Uncompahgre WA (USFS) 71.9 70.7 70.7 0.0 75.2 74.0 74.0 0.0

Ute Mountain IR 71.8 65.1 64.3 0.8 74.5 67.5 66.7 0.8

Weber Mountain WSA 70.4 67.9 67.8 0.1 68. 6 66.2 66.1 0.1
West Malpais WA 70.5 68.3 68.2 0.1 66.3 64.2 64.1 0.1AECOM Environment 4

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 4

- 4 MATS 8

- Hour Ozone Design Values for 2005 and 2018 at U nmonitored S ensitive Class I an d II A reas L ocated within the 4

- km D omain

Site Name Interpolated Ozone Concentration (ppb) Interpolated Gradient

- Adjusted Ozone Concentration (ppb)

2005 Baseline 2018 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative 2005 Baseline 20 18 PA 2018 NA Alternative Difference between 2018

PA and NA Alternative

Yucca House NM 71.8 66.6 66.2 0.4 71.1 66.0 65.5 0.5

Zia IR 71.2 68.6 68.4 0.2 69.8 67.3 67.1 0.2

Zuni IR 70.8 67.7 67.6 0.1 64.5 61.7 61.6 0.1

1 WA = Wilderness Area.

2 NP = Nation al Park.

3 IR = Indian Reservation.

4 NM = National Monument.

5 WSA = Wilderness Study Area.

Notes: Model

- predicted concentrations that exceed 75 ppb are shown in red text. Information in parentheses indicates agency managing sensitive area.AECOM Env ironment 5

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# 5.0 Summary

Th e APS operates the FCPP, a privately owned and operated coal

- fired power plant located on the Navajo Nation, about 25 miles west of Farmington, New Mexico. The APS contracted AECOM to assist in gathering data to submit to the OSM for the preparation of an EIS. This EIS is in response to the proposed Lease Amendment No. 3 for the FCPP site and renewal of ROWs for existing FCPP facilities. This modeling work focuses exclusively on the assessment of ozone ambient air quality impacts associated with the propose d lease renewal and grant issuance. The assessment is conducted by modeling the FCPP emissions in combination with other regional emissions sources and comparing the resulting ozone concentrations to the USEPA’s 2008 8

- hour ozone NAAQS. Ozone impacts were assessed near the FCPP, at existing ozone monitors, at Class I areas, and sensitive Class II areas.

The approach used in this modeling work relies on the input data, configurations, supporting information, and modeling platform developed for the FCAQS (ENV IRON 2009). The FCAQS, which encompasses the FCPP project area, was conducted to assess air quality conditions in the Four Corners region and evaluate the potential future impacts of various control scenarios in 2018. The FCAQS modeling used the CAMx model ing system, a modeling platform that includes the MM5 meteorological model, the SMOKE emissions processing system, and the CAMx photochemical grid model. The FCAQS also provided the modeling domains that consist of 12

- km and 4

- km nested grid cells that wer e used for all simulations.

AECOM estimated the impacts on ozone concentrations due to the emissions from the FCPP by using this modeling platform to simulate the following scenarios :

• 2005 Baseline

. The 2005 Baseline simulation used the FCAQS 2005 (ENVIRON 2009) emissions inventory for an analysis of current air quality conditions. Modeling emissions in the year 2005 established baseline air quality levels against which future year project and cumulative impacts were evaluated.

• 2018 No Action Alternative . T he NA Alternative simulation was based on the FCAQS 2018 Mitigation Scenario #4 and include d impacts all regional emissions except for contributions from the FCPP. Mitigation Scenario #4 applied aggressive control measures for NO X and SO 2 from coal

- fired p ower plants in the Four Corner’s region as well as control technologies for oil and gas sources of NO X and VOCs in San Juan and Rio Arriba counties in New Mexico.

• 2018 Proposed Action

. The PA simulation also was based on the FCAQS 2018 Mitigation Scenario #4 and included contributions from the proposed future emissions of the FCPP. Potential air quality impacts from the FCPP proposed emissions were assessed by comparing modeled impacts of the PA to the NA Alternative.

As part of this modeling work, the FCAQ S emissions inventories were reviewed and updated for these three scenarios. APS provided updated emissions for the FCPP that are consistent with the final BART rule. The FCAQS regional emissions inventory was updated with emissions and parameter informati on for other EGUs in the 4

- km domain as well
, particularly the SJGS.

Updated FCAQS emissions inventories were processed through SMOKE to produce surface and elevated hourly, gridded, and speciated model

- ready emissions for the three scenarios described. Th e CAMx then used these SMOKE processed emissions and FCAQS model

- ready meteorological inputs and ancillary data to perform ozone modeling to assess the FCPP PA impacts on the Four Corners region. The selected modeling period spans from May through August b ecause observed ozone concentrations are usually the highest during the summer months in this region. Most of the main CAMx configuration options used in this modeling work were based on the FCAQS, except for the PiG sub

- model setting. The PiG sub

- model wa s required for FCPP and SJGS to better represent t he early chemical and transport evolution of large NOx plumes associated with these sources.AECOM Env ironment 5

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 The CAMx was shown to be appropriate for this modeling work by a comprehensive model evaluation of CAMx results in the FCAQS. The FCAQS evaluated model performance by comparing modeled concentrations to ambient measurements. This evaluation found that model performance for ozone was within the established USEPA acceptance criteria for most months, indicating CAMx is adequate for modeling ozone for the 2005 Baseline simulation.

The results of the three CAMx simulations were post

- processed to p erform the following analyses: 1) comparison of modeled concentrati ons to the 8

- hour ozone NAAQS, 2) model attainment tests for monito red and unmonitored areas, and 3) assessment of the ozone impacts due to the PA. Ozone impacts were assessed at ozone monitor locations as well as 88 unmonitored Class I and sensitive Class II areas in the 4

- km domain.

Model

- predicted ozone concentr ations were further post

- process ed with AECOM’s IAS and EPA’s MATS tools. The IAS was designed to read model predicted concentrations at specified receptor sites and produce values that could be compared to the ozone NAAQS and also to provide suitable inpu t files for MATS

. The IAS calculated the model

- predicted fourth highest daily maximum 8

- hour average ozone concentrations at Class I and sensitive Class II areas for comparison to the NAAQS for the 2005 Baseline, 2018 NA Alternative, and 2018 PA simulation s.

Ozone model attainment demonstration was performed using MATS. The MATS tool was designed to project future ozone concentrations at locations of ozone monitors and also locations removed from monitors based on ambient ozone measurements. Projections we re based on applying a RRF to an

ozone design value, which is estimated from the 5

- year weighted average of the fourth highest daily maximum 8

- hour average monitored values. The MATS also calculated ozone concentrations for sites removed from monitor locat ions by using two types of spatial interpolation : 1) between “ neighbor ” monitors , and 2) between “ neighbor ” monitors but relying on model data to perform gradient adjustments

. This analysis provides the MATS calculated fourth

- highest daily maximum 8

- hour a verage ozone concentrations for monitor locations and also spatial interpolation values for unmonitored Class I and sensitive Class II areas. The MATS was run for the 4

- km domain for both the 2018 NA Alternative and PA scenarios for comparison to the NAAQS

. Qualitative assessment of the spatial distribution of ozone concentrations between the baseline and future simulations indicate d an overall decrease in ozone levels in 2018 relative to 2005

. In particular for the NA Alternative simulations, domain

- wide a verage concentration decrease d from 63.9 ppb in 2005 to 61.6 ppb in 2018. The most notable changes occur in the western and central areas of the 4

- km domain where the model

- predicted fourth

- highest daily maximum 8

- hour average ozone concentrations decrease d by 5 to 7 ppb. The only locations where ozone is observed to increase occur in San Juan County in New Mexico, which are immediately downwind of the location of FCPP. The maximum increase in the fourth

- highest 8

- hour ozone concentrations between the 2018 NA Alternative and 2005 Baseline was 3.5 ppb. This increase occur s in an area where ozone concentrations do not exceed the NAAQS (values range between 65 to 70 ppb) and concentrations in the vicinity of the FCPP peaks at 69 ppb.

Results show that the FCPP contributions generally range from 0.0 to 0. 9 ppb over the 4

- km domain. Qualitative assessment of the spatial distribution of ozone concentrations between the baseline and both future simulations yield similar spatial patterns, with the exception of some differences immediately downwind of the FCPP.

The impacts of the FCPP under the PA were estimated as the difference between 2018 PA and the 2018 NA Alternative simulations

. For both modeling scenarios, the highest ozone concentrations, ranging from 60 to 70 ppb, are found mostly in the northeastern portion of the 4

- km domain. The maximum model

predicted difference between the PA and the NA Alternative is 4.7 ppb, which occurs downwind of the FCPP. This maximum difference is located about 11 miles southeast of the FCPP and about 16 milesAECOM Env ironment 5

- 3

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 southwest of Farmington, New Mexico. Most of the impacted areas show a 2 to 4 ppb increase in ozone concentrations and are located entirely in San Juan and McKinley counties in New Mexico.

The impacts on receptors defined as Class I and sensitive Class II areas in this analysis was examined with various approaches. Examination of absolute model concentrations indicates that in general the number of sensitive ar eas with predicted NAAQS exceede nces decrease from 12 areas in 200 5 to only three areas in the NA Alternative model scenarios. The affected areas are La Garita WA, Grand Mesa, Uncompahgre, and Gunnison NFs, and Rio Grande NF. T he FCPP , however, does not contribute to their modeled impacts since the difference between the 2018 PA and NA Alternative is 0.0 ppb

. Importantly, the absolute model predicted ozone concentration for the PA at the Navajo Nation is just below the NAAQS. The model

- predicted FCPP contribution to the Navajo Nation is 0.7 ppb of ozone. For all other are as the impacts from the FCPP are 0.0 ppb except for 43 sensitive areas where the model

- predicted impacts due to the FCPP range from 0.1 to 0.9 ppb. The maximum impact (0.9 ppb) occurs at Ute Mountain IR in Colorado and New Mexico and also at Chaco Culture National Historic Park in New Mexico. I n both areas , however, the model concentrations are well below the NAAQS. Examination of model concentrations adjusted with monitored data as provided by MATS indicate that there is only one monitor (site ID 350011012 ) with design values in 2005 that exceed the 8

- hour ozone NAAQS (77 ppb). This site is located northeast of Albuquerque in Bernalillo County, New Mexico

. The analysis indicates that there are no monitors within the 4

- km domain with design values that excee d the 8

- hour ozone NAAQS under both the 2018 NA Alternative and PA. There are 11 monitors with a predicted non

- zero contribution to ozone that is attributable to the PA. These contributions range from 0.1 to 1.0 ppb. The largest impact of the PA at an exis ting monitor is 1.0 ppb, which occurs in Farmington, New Mexico (site ID 350451005). Importantly, none of the monitoring sites that are predicted to have an increase in ozone concentrations under the PA have a design value that exceeds the NAAQS either in 2005 or in 2018.

Finally
, the examination of ozone impacts in unmonitored areas shows that in 2005 there are no sensitive areas that exceed the ozone NAAQS. This analysis is subject to more uncertainty relative to the monitored analysis, but it does show s imilar conclusions as the other type s of results presented. Because 2018 ozone design values generally decrease from 2005, there are no receptors that exceed the ozone NAAQS in the future year either. The difference between PA and NA Alternative is seen in 60 sensitive areas with differences ranging from 0.1 to 1.0 ppb due to impacts from the FCPP. The maximum impact of 1.0 ppb occurs at Bisti/De

- Na

- Zin WA , which has a future design value of 65.8 ppb.

Overall, the model

- predicted future ozone concentrations are similar regardless of the methods used to analyze the results. In general, ozone concentrations are predicted to decrease in 2018 throughout the 4

- km modeling domain relative to conditions in 2005. Ozone impacts from the FCPP under the Proposed Action do not contribute to areas that may continue to have ozone concentrations that exceed the NAAQS in 2018.AECOM Env ironment 6

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FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# 6.0 References

Abt Associates Inc. 2009. Modeled Attainment Test Software User's Manual. Prepared for Office of Air Quality Planning and Standards, U SEP A , Research Triangle Park, N orth Carolina

. March 2009

. AECOM. 2013. Four Corners Power Plant and Navajo Mine Environmental Impact Statement NAAQS Compliance Modeling Study. Prepared for Arizona Public Service. May 2013.

Arizona Public Service. 2013. Person al communication between Alan Papp, Richard Grimes (APS) and Marco Rodriguez (AECOM). February 2013.

Code of Federal Registrations (CFR) . 2008. Ozone National Ambient Air Quality Standard. 73 FR 16436. March 27, 2008.

Coats, C. J., Jr. 1995. High Performa nce Algorithms in the Sparse Matrix Operator Kernel Emissions (SMOKE) Modeling System, MCNC Environmental Programs, Research Triangle Park, North Carolina. 1995.

ENVIRON International Corporation (ENVIRON). 2009. Air Quality Modeling Study for the Four Cor ners. Prepared for New Mexico Environment Department Air Quality Bureau. June 2009. Internet website: http://www.nmenv.state.nm.us/aqb/4C/Modeling.html.

ENVIRON International Corporation (ENVIRON). 2008. User’s Guide Comprehensive Air Quality Model with E xtensions Version 4.50. ENVIRON International Corporation, Novato, California. September 2008.

Fields, P. G., M. E. Wolf, T. Moore, and L. Gribovice. 2007. Developing the WRAP Point and Area Source Emissions Projects for the 2018 Reasonable Progress Milest one for Regional Haze Planning

. Presented at 16 th Annual International Emission Inventory Conference Emission Inventories: “ Integration , Analysis, and Communications

. ” May 14

- 17, 2007.

Houyoux, M. R. and J. M. Vukovich. 1999. Updates to the Sparse Matrix O perator Kernel Emissions (SMOKE) Modeling System and Integration with Models

- 3. Presented at The Emission Inventory: Regional Strategies for the Future, Raleigh, North Carolina, Air & Waste Management Association. October 26

- 28, 1999.

National Aeronautics and Space Administration (NASA). 2013. GEOS

- Chem Model. April 2013. Internet website: http://acmg.seas.harvard.edu/geos/

. National Center for Atmospheric Research (NCAR). 2005

. Fire Emission Factors and Emission Inventories. 2005. Internet website: http:/ /bai.acd.ucar.edu/Data/fire/

.

N avajo Nation Environmental Protection Agency (N NEPA )

. 2008

. Arizona Public Service Four Corners Power Plant Title V Operating Permit. August 2008. Internet website: http://www.navajonationepa.org/airqty/Pdf_files/FCPPpermit8

- 1

- 2008.pdf

. Public Service Company of New Mexico (PNM ). 2013

. Personal communication between Mark Williams (PNM) and Marco Rodriguez (AECOM). February 2013.
United States Environmental Protection Agency ( USEPA ). 2012

. Source Specific Federal Implementation Plan for Implementing Best Available Retrofit Technology for Four Corners Power Plant

. 77FR 51620

. August 24, 2012.AECOM Env ironment 6

- 2

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 United States Environmental Protection Agency ( USEPA ). 2007 . Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze. USEPA , Office of Air Quality and Planning Standards, Research Triangle Park, North Carolina. EPA 454/B

- 07

- 002. April 2007.

Yarwood, G., S. Rao, M. Yocke, and G. Z. Whitten. 2005. Updates to the Carb on Bond Mechanism: CB05. USEPA Final Report, 161 pp. 2005. Internet website: http://www.camx.com/publ/pdfs/CB05_Final_Report_120805.pdf

.AECOM Environment

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 

# Appendix A

Analysis of FCAQS Emissions Inventory and CAMx Model SensitivityAECOM Environment A

- 1

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Updated emissions information has become available for the oil and gas sources in the Four Corners

area since the FCAQS was finalized. This appendix presents a comparison of the oil and gas emissions modeled in the FCAQS and the most recent oil and gas emissions inventory data. This information is used to support two points:

1. That the Mitigation Scenario #4 emissions inventory is potentially a more accurate assessment of potential future emissions in the Four Corners area than the original 2018 Base Case emissions inventory; and

2. A revised model p erformance evaluation is not required based on results that the FCAQS 2018 model impacts are relatively insensitive to the changes in the base year oil and gas emissions inventory.

Emissions Inventory Comparison The oil and gas emissions inventory modeled in the FCAQS 2005 Base Case is shown in Table 1

. These emissions are compared to the latest available emissions inventory for this area, which is the Western Regional Air Partnership (WRAP) Phase III Emissions Inventory for the North and South San Juan Ba sins for year 2006. Since the FCAQS was completed, the estimated emissions from oil and gas sources near the Four Corners Power Plant have decreased by approximately 50 percent for Volatile Organic Compounds (VOC), carbon monoxide (CO), and sulfur dioxide (SO 2 ); decreased by approximately 25 percent for nitrogen oxides (NO x ); and increased by approximately 250 percent for particulate matter with an aerodynamic diameter of 10 microns or less (PM 10 ).

Table 1 Comparison of the North and South San Juan Basins O il and Gas Emissions Inventories for the FCAQS 2005 Base Case and 2006 WRAP Phase III

Oil and Gas Emissions VOC (tpy) NO x (tpy) CO (tpy) SO 2 (tpy) PM 10 (tpy) FCAQS 2005 Base Case (Phase II) 119,959 64,252 53,292 686 171

WRAP Phase III 2006 62,296 46,270 28,132 306 620 Difference (tpy)

- 57,664

- 17,982

- 25,161

- 380 449 Percent Change (%)

- 48

- 28

- 47

- 55 262

Table 2 shows how the entire FCAQS 2005 Base Case emissions inventory would change (i.e. the emissions from all sources in the 4

- kilometer (km) mod eling domain, not just the emissions from the oil and gas sector) if the study had used the WRAP Phase III oil and gas emissions in Table 1 instead of the Phase II emissions. As shown in Table 2 , the total emissions in the 4

- km modeling domain would be app roximately 13 percent lower for VOC, 8 percent lower for NO x , and less than 1 percent different for SO 2 and PM 10 .
Table 2 Comparison of the FCAQS 2005 Base Case Emissions between the Phase II Emissions and the Phase III Emissions

4

- km Domain VOC (tpy) NO x (tpy) CO (tpy) SO 2 (tpy) PM 10 (tpy)
Modeled FCAQS 2005 Base Case (Phase II) 431,649 221,863 NA 43,461 142,485 FCAQS 2005 Base Case Replaced with Phase III 373,985 203,881 NA 43,081 142,934 Percent Change (%)

- 13.4

- 8.1 NA

- 0.9 0.3AECOM Environment A

- 2

FCPP/Navajo Mine EIS Ozone Impact Assessment July 2013 Table 3 compares t he 4

- km Domain Oil and Gas emissions for the 2018 Base Case to the 2018 Mitigation Scenario #4. As shown in Table 3 , the 4

- km domain oil and gas emissions would be approximately 45 percent lower for VOC, and 15 percent lower for NO x . These percent changes are relatively similar to the estimated changes in the 2005/2006 emissions inventory shown in Table 1

.
Table 3 Comparison of the 4

- km Domain Oil and Gas Emissions Inventories for the 2018 Base Case and 2018 Mitigation Scenario #4

Oil and Gas Emissions VOC (tpy) NO x (tpy) SO 2 (tpy) PM 10 (tpy)
2018 Base Case 149,227 78,040 857 162 2018 Mitigation Scenario #4 81,895 65,855 857 142 Difference (tpy)

- 67,332 12,185 0 20 Percent Change (%)

- 45.12 15.61 0.00 12.35

Implications of Emissions Inventory on Ozone Concentrations Since the objective of the ozone modeling is to assess the changes in the concentration of ozone that is attributable to the project, it is important to understand how the changes in the emissions inventory relate to changes in the modeled ozone concentrations. As part of the FCAQS, the sensitivit y of ozone concentrations to changes in NOx and VOC ratios were investigated using a Higher

- Order Direct Decoupled (HDDM) method 2

. Importantly, t he HDDM analysis was performed only on the days and l ocations with the highest modeled impact, so the applicability of the results of the HDDM is limited to these conditions 3 . HDDM results from the FCAQS shows that a potential reduction of 13% in VOC and 8% in NOx emissions 4 would resu lt in ozone reductions of 2 ppb in Navajo Lake area when ozone exceeds 65 ppb on average, and no change in ozone concentrations at Mesa Verde

.

2 ENVIRON International Corporation (ENVIRON). 2010.Addendum to the Air Quality Modeling Study for the Four Corners. Pr epared for New Mexico Environment Department Air Quality Bureau. April 2010. Internet website: http://www.nmenv.state.nm.us/aqb/4C/Documents/FourCornersModelingAddendum_5April2010.pdf
3 HDDM was performed for only the days when ozone exceeded 65 ppb in Jul y 2005 at Navajo Lake and Mesa Verde.

4 Note that these percent changes in emissions are consistent with the emission differences that would occur if the FCAQS were to be revised to include the updated oil and gas emissions inventory, as shown in Table 2

.