RSS FeedsClimate and Air Quality
Countywide emissions of the following criteria pollutants were assessed.
- Ozone (O3)
- Carbon monoxide (CO)
- Oxides of nitrogen (NOX)
- Sulfur dioxide (SO2)
- Particulate matter 10 and 2.5 microns or less in diameter (PM10 and PM2.5, respectively)
- Lead (PB)
Carbon monoxide modeling was performed for roadway segments with high daily traffic volumes using traffic data prepared by the project traffic engineers, Fehr & Peers. Regional climate and meteorology conditions were assessed, and precipitation patters were mapped. In addition, sensitive receptors and land uses were identified.
The existing air quality conditions in the County were characterized by assessing monitoring data collected for the region at the Jefferson Avenue monitoring station in the City of Napa. Air quality conditions within the County are such that it is listed as a non-attainment/maintenance area for several pollutants. It was determined that the Jefferson Avenue monitoring station has experienced three violations of the state 1-hour ozone standard; 24.4 violations of the state 24-hour PM10 standard; and no violations of the federal and state CO standard, federal 1-hour ozone standard, federal 8-hour ozone standard, and federal PM10 standard during the last 3 years for which complete data are available. PM2.5 is not monitored in Napa County. The U.S. Environmental Protection Agency (EPA) has classified Napa County as a nonattainment (other) “not classified/moderate” area, with a 2006 attainment deadline, for the 1-hour ozone standard, and a marginal nonattainment area for the 8-hour ozone standard. For the CO standard, the study area is classified as a moderate (≤ 12.7 ppm) maintenance area, while the rest of the County is classified as an unclassified/attainment area. The EPA has classified the County as an unclassified/attainment area for the PM10 and PM2.5 standards. The California Air Resources Board (ARB) has classified the County as a serious nonattainment area for the 1-hour ozone standard, and an attainment area for the CO standard. The ARB has classified the County as a nonattainment area for the PM10 and PM2.5 standards.
Although the County is designated as a non-attainment/maintenance area for several pollutants, monitoring data suggests that few violations of the NAAQS and CAAQS have occurred in the last few years, and air quality has been improving. Due to the relatively rural/agrarian nature of the County, it has relatively few traditional industrial/commercial sources of pollutants, and data from the ARB suggest that transport of some pollutants into the SFBAAB from neighboring air basins can adversely affect air quality within the County. Further, the bowl-shaped valley may also help to trap pollutants within the County.
