Draft Environmental Impact Report - East Bay Municipal Utility District

3.7.2 Setting/Regulatory FrameworkMeteorologyEstates Reservoir Replacement Draft Environmental Impact ReportAir QualityTemperatures in the Oakland area average about 60 degrees Fahrenheit annually, withsummer highs in the mid-70s and winter lows in the mid-40s. Precipitation averagesabout 20 inches per year throughout much of the Bay Area, although annualprecipitation varies markedly from year to year. Winds in the Oakland area aretypically out of the west, west-northwest, and northwest (about 50 percent of the time).All other wind directions occur no more than 7 percent of the time, individually, andcalm conditions occur during 16 percent of annual observations. Annual average windspeeds in the central Bay Area are 8.7 miles per hour (mph) or 3.9 meters per second(NOAA 2008).During the day, localized emissions are funneled in a southeastward direction. Atnight, emissions are less readily ventilated and travel in more random directions.During the daytime, there is usually little potential for large-scale stagnation, withwinds traveling at an average speed of about 8 to 9 mph. However, winds at night areless than 2 to 3 mph, about one-third of the time. Local radiation temperatureinversions (where the ground is cooler than the air) may combine with these lightwinds to create localized air stagnation during the night near localized emissionsources (e.g., freeways) (BAAQMD 2008b).Criteria Air PollutantsA criteria or regulated air pollutant is any air pollutant for which ambient air qualitystandards have been set by the USEPA or the CARB. Primary air quality standards areestablished to protect human (public) health. Secondary air quality standards aredesigned to protect public welfare from effects such as diminished production andquality of agricultural crops, reduced visibility, degraded soils, materials andinfrastructure damage, and damaged vegetation. Criteria pollutants include ozone (O 3 ),nitrogen dioxide (NO 2 ), carbon monoxide (CO), sulfur dioxide (SO 2 ), respirableparticulate matter (PM 10 ), and fine particulate matter (PM 2.5 ). The six most prevalentcriteria pollutants and their potential health effects are described below:OzoneOzone (O 3 ) is a pungent, colorless, toxic gas and is the major air pollutant of concernin California. O 3 is formed in the atmosphere by a series of complex chemicalreactions and transformations in the presence of sunlight. Nitrogen oxides (NO x ) andreactive organic compounds (ROC) 16 are the principal constituents in these reactions.Nitrogen oxide NO x and ROC emissions are predominantly attributed to mobilesources (on-road motor vehicles and other mobile sources) in the Bay Area(CARB 2007). Ozone can chemically burn and cause narrowing of airways, forcing16 Also referred to as reactive organic gases or volatile organic compounds.sb09_001.doc 3-7.3 7/22/2009