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Thus, on a short and long -term basis, the proposed project will have a <br />beneficial impact on ambient air quality in terms of CO, THC, and the <br />secondary pollutants formed as a result of these primary pollutants. The <br />project will, however, increase the localized effects of NOx by accommodating <br />more vehicles at higher speeds within the roadbed and thereby increasing the <br />concentration of this pollutant adjacent to the roadbed. <br />Table 14 <br />Project- Related Motor Vehicle <br />Emission Inventory Comparison) <br />(Pounds/Day) <br />Scenario <br />-------------------------------------------- <br />CO <br />THC <br />NOx <br />Sox <br />Parts <br />-------------------------------------------- <br />1987 (Current Year) <br />- No Project <br />7,792 <br />790 <br />583 <br />69 <br />108 <br />- Project <br />NA <br />NA <br />NA <br />NA <br />NA <br />- Change with Project <br />NA <br />NA <br />NA <br />NA <br />NA <br />2006 (Future Year) <br />- No- Project 9,162 947 <br />- Project 5,496 571 <br />- Change with Project -3,666 -376 <br />Note: NA = Not Available. <br />1 Values are the same for all three alternatives. <br />Source: Endo Engineering <br />520 90 122 -^ <br />525 90 122 -. <br />+5 0 0 <br />Microscale analyses were made at four intersections within the project limits <br />where typical sensitive receptors were located. Carbon monoxide <br />concentrations were estimated adjacent to these intersections using "worst <br />case" assumptions and the California Department of Transportation Line <br />Source Dispersion Model Caline 3. This model is approved for use by both <br />the EPA and the Federal Highway Administration (FHWA). <br />Because of the relative inertness of carbon monoxide in the photochemical <br />smog formation process, and limitations of knowledge on dispersion <br />characteristics of other air pollutant species, carbon monoxide was selected as <br />the indicator of impact. NOx and HC were not considered because they are <br />unstable and will undergo changes to become secondary pollutants; therefore, <br />the roadway's contribution to these pollutant concentrations cannot be <br />accurately assessed. <br />Nitric oxide (NO) concentrations can be predicted, but there is no ambient air <br />quality standard for NO. Nitrogen dioxide (which is the major constituent of <br />NOx) concentrations cannot be determined from conventional non - reactive <br />models. Similarly, an accurate method to determine a roadway's contribution <br />to local levels of SOx and particulate matter is not yet available. Secondary <br />IV -12 <br />