EXHIBIT 4-2_55A_BRISTOL WIDENING TECHNICAL STUDIES

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Long -Term Air Quality Projections Microscale analyses were made at four intersections within the project limits where typical sensitive receptors were located. Carbon monoxide concentrations were estimated adjacent to these intersections using "worst case" assumptions and the California Department of Transportation Line Source Dispersion Model Caline I 3. This model is approved for use by both the EPA and the Federal Highway Administration (FHWA) . Because of the relative inertness of carbon monoxide in the photochemical smog formation process, and limitations of know- ledge on dispersion characteristics of other air pollutant spe- cies, carbon monoxide was selected as the indicator of impact. NOx and HC were not considered because they are unstable and undergo changes to become secondary pollutants; therefore, the roadway's contribution to these pollutant concentrations cannot be accurately assessed. Nitric oxide (NO) concentrations can be predicted but there is no ambient air quality standard for NO. Nitrogen dioxide (which is the major constituent of NOx) concentrations cannot be determined from conventional non - reactive models. Similarly, an accurate method to determine a roadway's contribution to local levels of SOx and particulate matter is not yet available. Secondary pollutants are a large -scale phenomenon, and should be analyzed on a regional basis rather than a local one. j The "worst case" assumptions made in the Caline 3 modeling pro- If cess included: wind speed of 1 meter per second, wind direction parallel to the road, peak hour traffic volumes, and atmospheric stability class of F (most stable) for 1 --hour averages and class D for 8 -hour averages. The Appendix (page 9) provides additional details and Caline 3 assumptions. The results appear in Table 3 -4 and represent "worst case" condi- tions. Actual levels would probably be less. Three scenarios were analyzed based upon traffic volumes for 1987 and for future year 2005 conditions both with and without the project. As shown in Table 3 -4, the future design year carbon monoxide concentrations adjacent to the intersections most affected by the project will not equal or exceed the 35 ppm 1 -hour federal stan- dard with or without the roadway widening proposed. Addi- tionally, the 20 ppm 1 -hour state standard should not be exceeded after completion of the proposed project. Conversely, state 1- hour standard exceedances may occur in the future design year under the "No- Build" condition at the intersections analyzed. Ambient CO levels in the design year (9.5 ppm) are projected to exceed the 8 -hour state and federal standards (9.0 ppm) in the project vicinity. However, CO contributions at the intersections W