The National Academies

NCHRP Synthesis 20-05/Topic 51-18 [New]

Practices for Project-Level Analyses for Air Quality
[ NCHRP 20-05 (Synthesis of Information Related to Highway Practices) ]

  Project Data
Funds: $45,000
Staff Responsibility: Tanya Zwahlen
Fiscal Year: 2019

Preliminary Scope

Air quality project-level analyses (PLAs) that state departments of transportation (DOTs) are required to prepare for purposes of the National Environmental Policy Act (NEPA) and the EPA transportation conformity rule have become more complicated, time-consuming and costly to prepare due to the issuance of new regulatory models for transportation and associated guidance by EPA in 2010.

The objective of this synthesis is to summarize existing practices related to project-level analysis for air quality.

Information to be gathered will include:

• How programmatic agreements, pre-vetted modeling inputs, template tools and documentation are used by state DOTs
• Scoping practices and appropriately budgeting time and cost for consultant analyses by project type, pollutant and level of public interest
• How DOTs approach scoping, screening, modeling and analysis for all regulatory pollutants, mitigation, quality assurance and control (QA/QC), consultation, risk management, and documentation.
• Modeling and analysis used by DOTs including traffic, emission (including construction), and dispersion modeling (including the determination of background concentrations), and qualitative analyses
• Whether and when qualitative analyses are used where applicable.
• Regulatory pollutants include carbon monoxide (CO), particulate matter (PM), mobile source air toxics (MSATs), indirect effects and cumulative impacts (IECI), and, where required locally, greenhouse gases (GHGs.)

Information will be collected through literature review, survey of DOTs, and follow-up interviews with selected agencies for the development of case examples. The case examples will include sample documentation and sets of model input and output files for all typical project types. Information gaps and suggestions for research to address those gaps will be identified.

Information Sources (Partial):
• NCHRP 25-25 Task 78, “Programmatic Agreements for Project-Level Air Quality Analyses”, 2015. http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3311 This study developed templates for clearing projects (typically ones of smaller scope or expected impacts) for one pollutant (CO). An update is in progress under Task 104. • NCHRP 25-25 Task 96, “Quick Reference Guide for Traffic Modelers for Generating Traffic and Activity Data for Project-Level Air Quality Analyses”, 2018 http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3971 This recent report was designed as a supplement to NCHRP 765, which is the standard reference for traffic for project-level design purposes and may serve as a good example of the level of detail and coverage proposed for the air quality BPs.
• NCHRP 08-101, “Enhanced Truck Data Collection and Analysis for Emissions Modeling”, in progress (expected publication early 2019) http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3860
• NCHRP 25-38, “Input Guidelines for Motor Vehicle Emissions Simulator Model”, 2014. http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3191
• NCHRP 25-25 Task 89, “Establishing Representative Background Concentrations for Quantitative Hot-spot Analyses for Particulate Matter”, 2014http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3514
• CalTrans, “Quantitative Particulate Matter Hot-Spot Analysis Best Practices Guidebook”, Version 2.0, CTAQ-RT-17-317.02.6, 2017. See: http://www.dot.ca.gov/env/air/docs/pm-hot-spot-best-practices- guidebook.pdf
• CalTrans, “Streamlining Air Quality Dispersion Modeling to Support Quantitative Particulate Matter Hot-Spot Analysis”, CTAQ-RT-17-317.12.29, 2017. See: http://www.dot.ca.gov/env/air/docs/dispersion-modeling-support- pm-hot-spot-analysis.pdf
• AASHTO, “Addressing Air Quality Issues in the NEPA Process for Highway Projects,” 2017, 22 pages. See: https://environment.transportation.org/center/products_programs/practitioners_handbooks. aspx#17 

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