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| 568 |
Screening Procedures for Quantitative MSATs Analyses |
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Status
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Cost
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Timeframe
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Air Quality
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Unmet
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Unknown
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Unknown
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Screening level procedures for quantitative mobile source air toxics (MSATs) analyses for transportation projects are needed to provide state and other transportation agencies a ready and inexpensive means to meet emerging NEPA requirements and screen projects for potential MSATs impacts while minimizing resource requirements and delays associated with detailed quantitative studies (especially those in developing areas of science such as MSATs) that should be reserved for only the largest projects or those with the greatest potential impacts. One approach would be to develop standardized worst-case MSATs analyses for typical major improvements such as new freeways, additions to existing freeways, and major transit improvements. The worst-case analyses would be based on worst-case assumptions for traffic, emissions, dispersion and exposure. Both case studies and screening software could be applied for this purpose. State transportation agencies could then make use of the worst-case analyses in one of two ways: 1) by reference to the case studies for various sample highway and transit projects developed in place of a detailed quantitative study. For example, if a state were planning a new four-lane freeway, it could refer to an AASHTO or federal reference-standard worst-case MSATs analysis for a hypothetical four- (or even a six-) lane highway. The state could add local data such as traffic and land use information and make an qualitative argument that traffic, emissions and exposure (especially of sensitive populations) for their planned project are less than the referenced worst-case and therefore their project would have lower potential impact than that presented in the reference case study. 2) by making use of screening-level software developed by FHWA and/or AASHTO to facilitate the development by local jurisdictions of worst-case analyses for MSATs, similar in concept to the Cal3Interface software recently developed by FHWA for streamlining project-level worst-case analyses for carbon monoxide (CO). The software would allow the selection of various roadway configurations (number of lanes, skew angles, intersections, grade separations, traffic volumes etc) to use in the worst case analyses. Worst-case assumptions for dispersion modeling could also be similar to that for CO modeling and include standard worst-case meteorological and receptor location assumptions. Worst-case assumptions for exposure modeling would address land use and associated human activity levels.
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The advantages of a federal/AASHTO lead in the development of case studies and ultimately screening level software include: 1. transparency and credibility, as the reference cases would not only be conducted by nationally recognized leaders in emission and exposure modeling, they would be subject to peer-review by national experts, 2. acceptance by the public, if the referenced worst-case studies are recognized as worse than what could reasonably be expected in most cases, and the studies have been conducted in an open process and led by national experts, 3. cost-effectiveness, as states would not have to unnecessarily and repeatedly conduct high cost detailed studies for their local jurisdictions if appropriate and accepted worst-case reference studies exist, 4. effectiveness, as the science will undoubtedly continue to evolve and the case studies will need to be updated, which can be systematically done (perhaps with scheduled periodic updates) at a national level, and 5. overall, similar to the experience with CO, a general worst-case approach for MSATs that incorporates applicable US DOT and EPA guidance and provides appropriate screening software would help states in the development of appropriate MSATs analyses while minimizing their costs and avoiding undue complexities and potential delays in their respective NEPA processes modeling would address land use and associated human activity levels.
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| Suggested By
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Posting Date
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Christopher Voigt, VDOT
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March 26, 2009
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