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4.Environmental Analysis — The SJVAB consists of a continuous inter-mountain valley approximately 250 miles long and — averaging 80 miles wide. On the western edge is the Coast Mountain range, with peaks reaching 5,020 feet,and to the east of the valley is the Sierra Nevada Range with some peaks exceeding 14,000 feet. The Tehachapi Mountains form the southern boundary of the valley. The region's — topographic features act to restrict air movement through and out of the air basin. Airflow in the SJVAB is primarily influenced by marine air that enters through the Carquinez Strait, where the San Joaquin-Sacramento Delta empties into the San Francisco Bay. The SJVAB is highly — susceptible to pollutant accumulation over time. Frequent transport of pollutants into the SJVAB from upwind sources contributes to poor air quality. Air quality in the project area is influenced mostly by pollutant transport from upwind areas, such as the Sacramento and San Francisco Bay metropolitan areas,but also by local emissions sources, such as wood-burning stoves and fireplaces during the winter months and motor vehicles using roadways. San Joaquin County's major air quality problems occur from late spring through early winter. From May to October, high ozone levels are a recurring problem due to the region's intense heat and sunlight.Pollution problems also occur from October through January due to frequent strong — temperature inversions, which trap pollutants near the earth's surface. These stagnant air conditions can last for weeks at a time. During these periods,CO levels rise. Visibility-reducing particulates are a problem much of the year. Dust from spring winds and agricultural operations, including agricultural burning, account for most of the area's particulates. Climate — Air quality is affected by the rate,amount, and location of pollutant emissions and the associated meteorological conditions that influence pollutant movement and dispersal. Atmospheric — conditions including wind speed, wind direction, and air temperature, in combination with local surface topography(i.e.,geographic features such as mountains and valleys),determine the effect of air pollutant emissions on local air quality. — The San Joaquin Valley is characterized by an inland Mediterranean climate that is typified by warm,dry summers and cooler winters. Summer high temperatures often exceed 100°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 great as 30°F. Generally,winters are mild and humid. Average high temperatures during the winter are in the 50s, while the average daily low temperature is about 45°F. The SJVAB averages over 260 sunny days per year. Annual rainfall varies from north to south, with the northern counties experiencing as much as 11 inches of rainfall and the southern counties experiencing as little as four inches per year. Nearly 90 percent of the annual precipitation in the SJVAB falls between November and April. Wind speed and direction play an important role in dispersion and transport of air pollutants. During summer periods airflow in the region is primarily influenced by marine air that enters through the Carquinez Strait. Winds usually originate out of the north end of the San Joaquin — Valley and flow in a south-southeasterly direction through the Valley, through the Tehachapi Pass RMC Pacific Vernalis Quarry Mining and Redamation Project 4.6-2 ESA/203015 Draft Environmental Impact Report May 2006