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U 3.3 Air Quality and Climate Change l 3.3 Air Quality and Climate Change 3.3.1 Introduction This section provides an overview of existing air quality in the project area,the air quality regulatory ' framework to which the project is subject,.and an-analysis of potential air quality impacts that could result from the project. 3.3.2 Setting Existing Air Quality Conditions General Meteorology and Topography The primary factors that determine air quality are the locations of air pollutant sources and the amounts of pollutants emitted. Meteorological and topographical conditions,however, also are II important. Factors such as wind speed and direction,and air temperature gradients interact with #� physical landscape features to determine the movement and dispersal of criteria air pollutants. The project lies within the San Joaquin Valley Air Basin(SJVAB), basically a flat area bordered on the east by the Sierra Nevada Mountains;on the west by the Coast Ranges; and to the south by the Tehachapi Mountains. Airflow in the SJVAB is primarily influenced by marine air that enters through the Carquinez Straits where the San Joaquin-Sacramento Delta empties into the San Francisco Bay (SJVAPCD, 2002). The region's topographic features restrict air movement through and out of the basin. As a result,the SJVAB is highly susceptible to pollutant accumulation over time r (SJVAPCD, 2002). Frequent transport of pollutants into the SJVAB from upwind sources also contributes to poor air quality. Wind speed and direction play an important role in dispersion and transport of air pollutants,During rill summer periods, winds usually originate from the north end of the San Joaquin Valley and flow in a south-southeasterly direction through the valley,through the Tehachapi pass and into the neighboring Southeast Desert Air Basin. During winter months, winds occasionally originate . �. from the south end of the valley and flow in a north-northwesterly direction, Also, during winter months,the valley experiences light,variable winds,less than 10 miles per hour(mph).Low wind speeds, combined with low inversion layers in the winter, create a climate conducive to high .a concentrations of certain air pollutants. The SJVAB has an inland Mediterranean climate that is characterized by warm,dry summers and cooler winters. Summer high temperatures often exceed 100 degrees Fahrenheit(°F), averaging from the low 90s in the northern part of the valley to the high 90s in the south. The daily summer temperature variation can be as high as 30°F. Winters are for the most part mild and humid.Average high temperatures during the winter are in the 50s, while the,average daily low temperature is approximately 45 degrees 'F. F Munn 8 Perkins Quarry Excavation Permit 3.3-1 PSA 1211086 Draft SIR April 2011