ARCHIVED REPORTS LEC APPLICATION FOR CERTIFICATION

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5.1 AIR QUALITY • 250-meter resolution from 1 km out to at least 10 km from the site. When maximum impacts occurred in the 100-or 250-meter spaced areas,additional refined receptor grids with 25-meter resolution were placed around each maximum coarse grid impact and extended out to a distance of two coarse grid spacings from the coarse grid maxima in all directions from that point of impact. Concentrations within the facility fence line,representing property controlled by NCPA,were not calculated. 5.1.5.5 Meteorological Data Selection SJVAPCD has prepared meteorological data sets applicable to most locations in the district and has processed them,using AERMET (Version 06341), into the format required by AERMOD. Hourly surface meteorological data (e.g.,hourly wind speed and direction, temperature) for Stockton during the period 2000-2004 were obtained from the SJVAPCD's modeling website.10,11 The Stockton monitoring station is located approximately 16 miles south-southeast of the project site. Upper air data from the Oakland International Airport monitoring station located approximately 56 miles southwest of the project site and approximately 60 miles west-southwest of the surface data station were used by SJVAPCD in creating the model-ready data set. The surface characteristics appropriate to the land uses surrounding the meteorological station at Stockton (surface roughness length,albedo, and Bowen Ratio)were developed by SJVAPCD for the met station site following the guidance published by EPA in September 2005. Although this earlier guidance has been updated by EPA with the development of AERSURFACE (Version 08009) software (released on January 9,2008),SJVAPCD staff believe that surface characteristics developed using AERSURFACE are not appropriate for use in the San Joaquin Valley. AERSURFACE obtains land use data from 1992 US Geological Survey National Land Cover Data. Because of the large amount of development in the valley since 1992,SJVAPCD staff believes that the land use data used by AERSURFACE is outdated. SJVAPCD staff has indicated that EPA staff has agreed that the older guidance can continue to be used for projects in the San Joaquin Valley.12 EPA requires the use of meteorological data that would be representative of atmospheric dispersion conditions at the source and at locations where the source may have a significant impact on air quality.Specifically,the meteorological data requirement originates in the Clean Air Act at Section 165(e)(1),which requires an analysis"of the ambient air quality at the proposed site and in areas which may be affected by emissions from such facility for each pollutant subject to regulation under [the Act] which will be emitted from such facility." This requirement and EPA's guidance on the use of onsite monitoring data are also outlined in the"On-Site Meteorological Program Guidance for Regulatory Modeling Applications" (1987b). The representativeness of the data depends on: (a) the proximity of the meteorological monitoring site to the area under consideration, (b) the complexity of the topography of the area, (c) the exposure of the meteorological sensors,and (d) the period of time during which the data are collected. District staff has determined that the Stockton meteorological data set 10 http://www.valleyair.org/busind/pto/Tox_Resources/AirQualityMonitoring.htm 11 In the June 5,2008 comment letter,the SJVAPCD indicated that more than 10 percent of the meteorological data for year 2001 are missing,and that modeling results for that year should be used with caution.While all five years will be used in the modeling analyses,any modeling results based on 2001 met data will be flagged. 12 Villalvazo,Leland,personal communication with Eric Walther of Sierra Research,April 23,2008. 5.1-36 SAC/3713221082410013(LEC_5.1_AIR_QUALITY.DOC)