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Alternatives to Air Quality Modeling for Project Level Conformity


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Suggested Citation:
Kear, Tom P. and Vicente J. Garza (1996) Alternatives to Air Quality Modeling for Project Level Conformity. Institute of Transportation Studies, University of California, Davis, Presentation Series UCD-ITS-RP-96-23

Presented at the Transportation Research Board Transportation & Air Quality Committee (A1F03). 1996 Summer Conference: "Regional Transportation and Air Quality Planning: Expanding the Dialogue, Advancing the Practice", Irvine, CA

Approaches that simplify project-level conformity determinations by combining air quality planning, microscale monitoring and project conformity analysis are presented.

Under the Clean Air Act Amendments of 1990, transportation projects may not create, or worsen existing violations of air quality standards. Projects with characteristics that may potentially increase emissions must demonstrate that they will not have a detrimental effect on local air quality. For carbon monoxide, this demonstration is commonly made with dispersion models.

Regional air quality plans map out how a nonattaininent area intends to come into compliance with, and maintain air quality standards. Estimates of regional emissions are compared with permissible emission levels, given the area's carrying capacity and air quality standards. Though some of the data relied upon to demonstrate attainment is gathered at microscale-level monitors, localized impacts of future traffic growth at specific intersections and links are not necessarily considered.

A proposal is introduced that places more emphasis on estimation of micro scale effects of traffic growth in the air quality planning process. Through incorporation of hot-spot analysis of (or demonstrating that the monitoring network adequately characterizes) each region's "worst" links and intersections a measure is established to which new projects could be compared. This suggests an implicit demonstration of conformity for "lesser" projects. The regulatory ftamework for this change is outlined and the implications for air quality planning and conformity processes are reviewed.