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III. ENVIRONMENTAL SETTING,IMPACTS AND MITIGATION MEASURES B. AIR QUALITY TABLE III.B-2 AIR POLLUTANT SUMMARY IN THE VICINITY OF THE PROJECT SITE, 1993-1997 oncen c t' C a tt ons,by Yeara Pollutant Std.b 1993 1994 1995 1996 1997 Ozone: Highest 1-hour-average concentration,ppmc 0.09 0.11 0.13 0.13 0.12 0.10 Number of violationsd 7 8 8 4 1 Carbon Monoxide: Highest 1-hour-average concentration,ppm 20 I0 10 10 9 8 Number of violations 0 0 0 0 0 Highest 8-hour-average concentration,ppm 9.0 6.3 7.1 4.5 6.5 3.5 Number of violations 0 0 0 0 0 Suspended Particulate(PM-10): Highest 24-hour-average concentration,µg/m3 c 50 104 109 109 127 98 Violations/Samplese 15/58 11/59 4/49 4/60 5/60 Annual Geometric Mean, gg/m3 30 32.0 32.6 23.8 23.7 26.8 a Pollutant data were collected at ARB's monitoring station on Hazelton Street in Stockton. b State standard,not to be exceeded. dppm:parts per million;pg/m3:micrograms per cubic meter. For ozone, "number of violations"refers to the number of days in a given year during which excesses of the state standard were recorded. e Indicates the number of violations and the number of samples taken in a given year. NOTE: Bold values are in excess of applicable standard;NA=Not Available SOURCE: ARB, 1993, 1994, 1995, 1996 and 1997 reactive organic gases(ROG)and nitrogen oxides(NOx). ROG and NOx,which are emitted directly to the atmosphere, are known as precursor compounds for ozone. Significant ozone production generally requires ozone precursor presence for approximately three hours in a stable atmosphere with strong sunlight. Ozone is a regional air pollutant because its precursors are transported and diffused by wind concurrently with ozone production. While ozone in the upper atmosphere protects the earth from harmful ultraviolet radiation, high concentrations of ground level ozone can adversely affect the human respiratory system. Many respiratory ailments, as well as cardiovascular diseases, are aggravated by exposure to high ozone levels (SJVUAPCD, 1998a). Table III.B-2 shows that the number of days during which ozone concentrations violated the state standard in Stockton was notably lower in 1997 than in the previous four years. Based on the data from 1993 through 1997, ozone concentrations in Stockton violate the state ozone standard on an average of about 6 days per year. Major sources of ROG emissions in the San Joaquin Valley are mobile sources,solvents and other area sources, and oil and gas production. On-road motor vehicles and fuel combustion account for roughly 47 and 32 percent of the San Joaquin Valley's total NOx emissions,respectively (SJVUAPCD, 1998a). Storkton Sravenger Transfer Station Erpansion III.13.5 ESA 1990190