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Air Quality <br />Affected Environment <br />Air quality information presented in this section is qualitative and is based primarily on existing <br />data and published literature. This section focuses primarily on ambient air quality in the <br />Eugene/Springfield area. Lane County, including Eugene and Springfield, is an attainment area <br />for all national ambient air quality standards. <br />Climate <br />The climate of the Eugene/Springfield area is predominantly mid-latitude and is influenced by <br />proximity to the Pacific Ocean, with a dry season and pleasant temperatures during the summer, <br />and mild but rainy winters. Temperatures in the Eugene/Springfield area average approximately <br />52.4 degrees Fahrenheit (°F). The average daily maximum temperature is 63.2°F, and the <br />average daily minimum temperature is 41.7°F. The Eugene/Springfield area has an average <br />annual rainfall of 46.6 inches. From late fall through early spring, prevailing winds are from the <br />south, while late spring to early fall winds are generally from the north (LRAPA 2000). Local <br />variations in climate are influenced by terrain, including structures, and paved areas that affect <br />local climate differently than natural vegetation. <br />Air Pollution and Sources <br />Air quality is affected by weather, demography, land uses, and geography. Meteorological <br />events have a major influence on air pollution levels as well as the formation and persistence of <br />,' air pollution. Natural weather processes usually cleanse the air by dispersing pollutants through <br />- chemical reactions, deposition, condensation, or the scrubbing action of rain. Many activities in <br />densely populated areas produce emissions of pollutants that in combination produce <br />~_ , <br />concentrations high enough to be of concern. Large, confined valleys are known for poor <br />ventilation (due to high ground on either side of the valley) yet are desirable locations for <br />industrial development. The combination of these factors often results in high pollutant <br />concentrations (Oregon Department of Environmental Quality 1995). <br />~; <br />There are many sources of air pollutants in urban areas such as the Eugene/Springfield area. <br />~ Approximately 90 percent of carbon monoxide measured in urban areas is produced by motor <br />L. i <br />vehicles. Carbon monoxide levels are typically higher during the winter months, especially <br />during air stagnation periods. Ground-level ozone, or smog, is formed when volatile organic <br />G compounds and nitrogen oxides react chemically in sunlight and when temperatures are over <br />90°F. Temperatures rarely exceed 90°F in the Eugene/Springfield area, so this is generally not a <br />~- major concern. However, ozone levels have approached federal standards in recent years <br />(LRAPA 2000). Ozone can lower human resistance to head colds and pneumonia and can cause <br />irritation to the nose, throat, and lungs. Emissions from motor vehicles, gasoline and paint <br />New Federal Courthouse 87 Final EIS <br />