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Four Corners Power Plant and Navajo Mine Energy Project Final Environmental Impact Statement 4.1 Air Quality The proposed project is located in the Four Corners region of northwestern New Mexico within the San Juan Air Basin (Figure 4.1-1). This air basin comprises the Four Corners region of northwest New Mexico, southwest Colorado, southeast Utah, and northeast Arizona. For the purposes of this EIS, the Proposed Action area encompasses a 300-kilometer (km) (186-mile) radius from FCPP, which includes the Navajo and Hopi tribal trust lands, consistent with EPA’s area of evaluation for the FIP for FCPP. San Juan Basin air quality is generally good and meets EPA ambient air quality standards. Primary issues of concern in this region include regional haze and visibility issues, as well as the potential deposition of metals from air to soil and water as a result of industrial air emissions. The Navajo Mine and FCPP are located on Navajo tribal trust land; therefore, air emissions and air quality are under the jurisdiction of the NNEPA) and overseen by the EPA Region IX in San Francisco.1 Federal and tribal law defines criteria pollutants to include the following: reactive or volatile organic compounds (ROCs or VOCs), nitrogen oxides (NOX as NO and NO2), ozone (O3), carbon monoxide (CO), sulfur dioxide (SO2), respirable particulate matter (PM10), and fine particulate matter (PM2.5). Of these, VOCs and NOX are precursors of ground-level photochemical O3, which can result in decreased visibility and haze. In addition, the EPA published a Final Ruling regarding the Source Specific FIP to implement BART at the FCPP in August 2012, which provides requirements for future operation of the plant. The FIP and associated BART requirements have been determined and as such comprise part of the environmental baseline for assessing the consequences of the Proposed Action and alternatives. A detailed discussion of the regulatory framework regarding air quality and air emissions as applicable to the proposed Project is provided below. Coal mining would cause air emissions from combustion of motor fuels (diesel and gasoline) used to operate mining equipment, portable equipment, and support vehicles. Mining activities also cause air emissions from explosives detonation (NO2, SO2, and CO) and fugitive dust (PM10 and PM2.5) from earthmoving activities. Power plant operation and maintenance would cause air emissions from the combustion of coal in boilers as well as motor fuels (diesel and gasoline) used in off-road equipment, portable equipment, and support vehicles. Support activities include switchyard and transmission line maintenance near the plant. Several quantitative models were conducted to evaluate the potential air quality impacts of the Proposed Action and alternatives. These include calculations of mobile and stationary source emissions in comparison to Federal standards, air deposition modeling, O3 Assessment; and plume visibility. Each of these models, their results, and implications with regard to potential impacts are described in the environmental consequences section. Human health risk assessment of hazardous air pollutants (HAPs), diesel particulate matter, and fugitive dust are presented in Section 4.17, Health and Safety. These issues are also mentioned in this section. 4.1.1 Regulatory Compliance Framework 4.1.1.1 Air Quality Standards Air quality in a given location is determined by the concentration of various pollutants in the atmosphere. National Ambient Air Quality Standards (NAAQS) have been established by the EPA under the CAA of 1970 (amended 1977 and 1990, 42 USC 7401 et seq.). The NAAQS represent maximum levels of background pollution that are considered safe, with an adequate margin of safety, to protect public health (primary standards) and welfare (secondary standards such as diminished production and quality of agricultural crops, reduced visibility, degraded soils, materials and infrastructure damage, and damaged 1 In 2005, the Nation and owners of the FCPP entered into a VCA under which FCPP agreed to apply for and obtain a CAA Title V operating permit from NNEPA provided, among other things, that permit requirements would be no more stringent than federal requirements unless FCPP agreed to more stringent requirements and the administration and enforcement of the permit would be no more stringent than what EPA would do and that would be required under federal court decisions. May 2015 Air Quality 4.1-1 Four Corners Power Plant and Navajo Mine Energy Project Final Environmental Impact Statement vegetation). Recently, the EPA has proposed developing new secondary standards for SO2 and NOX aimed at reducing the impacts of atmospheric deposition on surface waters (Government Accounting Office [GAO] 2013). Individual states have the option to adopt more stringent standards and to include other pollution sources. However, all states in the Four Corners region – New Mexico, Arizona, Utah, and Colorado – have adopted NAAQS in lieu of adopting more stringent state standards. Also, the sovereign nations – Navajo Nation, Hopi Tribe, and Southern Ute Indian Tribe – use NAAQS as tribal standards. The Navajo Mine and FCPP are located on Navajo tribal trust lands; therefore, air emissions and air quality are under the jurisdiction of the NNEPA and overseen by the EPA Region IX in San Francisco. Federal and tribal law defines criteria pollutants to include O3, NO2, CO, SO2, PM10, PM2.5, and lead (Pb). Elimination of tetraethyl lead in motor gasoline has eliminated emissions of Pb from vehicles and portable equipment, although tetraethyl lead is still used in some types of aviation gasoline. O3 is not directly emitted, rather, its precursors NOX and VOC are the pollutants which react with sunlight to form ground- level photochemical O3 and contribute to regional haze, along with SO2 and particulate matter. Criteria emissions – also referred to as regulated pollutants – caused by the Action include ROCs or VOCs, NOX as NO and NO2, CO, SO2, PM10, and PM2.5. Each pollutant is described below. Ozone (O3) Ground-level O3 is a secondary pollutant formed in the atmosphere by a series of complex chemical reactions and transformations in the presence of sunlight. NOX and VOCs are the principal constituents in these reactions. An important source of NOX and VOC emissions is the high-temperature combustion of fossil fuels such as in motor vehicle engines and power plant boilers. Thus, regulation and control of NOX and VOCs from these sources is essential to reduce the formation of ground-level O3. O3 is a strong irritating gas that can chemically burn and cause narrowing of airways, forcing the lungs and heart to work harder to provide oxygen to the body. A powerful oxidant, O3 is capable of destroying organic matter, including human lung and airway tissue. O3 damages cells in the lungs, making the passages inflamed and swollen. O3 also causes shortness of breath, nasal congestion, coughing, eye irritation, sore throat, headache, chest discomfort, breathing pain, throat dryness, wheezing, fatigue, and nausea. It can damage alveoli, the individual air sacs in the lungs where oxygen and CO2 are exchanged. O3 has been associated with a decrease in resistance to infections. People most likely to be affected by O3 include the elderly, the young, and athletes. O3 may pose its worst health threat to people who already suffer from respiratory diseases such as asthma, emphysema, and chronic bronchitis (VCAPCD 2003). Nitrogen Dioxide (NO2) NO2 is formed in the atmosphere primarily by the rapid reaction of the colorless gas nitric oxide (NO) with atmospheric oxygen. It is a reddish brown gas with an odor similar to that of bleach. NO2 participates in the photochemical reactions that result in O3. The greatest source of NO, and subsequently NO2, is the high-temperature combustion of fossil fuels such as in motor vehicle engines and power plant boilers. NO2 and NO are referred to collectively as NOX. NO2 can irritate and damage the lungs, cause bronchitis and pneumonia, and lower resistance to respiratory infections such as influenza. Researchers have identified harmful effects, similar to those caused by ozone, with progressive changes over four hours of exposure causing impaired pulmonary function, increased incidence of acute respiratory disease, and difficult breathing for both bronchitis sufferers and healthy persons (Ventura County Air Pollution Control District [VCAPCD] 2003). 4.1-2 Air Quality May 2015 This Page Intentionally Left Blank Four Corners Power Plant and Navajo Mine Energy Project Final Environmental Impact Statement Carbon Monoxide (CO) CO is a common, colorless, odorless, highly toxic gas. It is produced by natural and anthropogenic (caused by human activity) combustion processes. The major source of CO is incomplete combustion of carbon-containing fuels (primarily gasoline, diesel fuel, natural gas, and coal). However, it also results from combustion processes including forest fires and agricultural burning. Ambient CO concentrations are generally higher in the winter, usually on cold, clear days and nights with little or no wind. Low wind speeds inhibit horizontal dispersion, and surface inversions inhibit vertical mixing. Traffic-congested intersections have the potential to result in localized high CO levels. When inhaled, CO does not directly harm the lungs. The impact from CO is on oxygenation of the entire body. CO combines chemically with hemoglobin, the oxygen transporting component of blood. This diminishes the ability of blood to carry oxygen to the brain, heart, and other vital organs. Red blood cells have 220 times the attraction for CO as for oxygen. This affinity interferes with movement of oxygen to the body’s tissues. Effects from CO exposure include headaches, nausea, and death. People with heart ailments are at risk from low-level exposure to CO. Also sensitive are people with chronic respiratory disease, the elderly, infants and fetuses, and people suffering from anemia and other conditions that affect the oxygen carrying capacity of blood. High CO levels in a concentrated area can result in asphyxiation.

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