As part of a statewide Environmental Services On-Call contract for the Virginia Department of Transportation (VDOT), HMMH assessed potential air quality impacts associated with the re-evaluation of the Study Alternatives of the Route 460 Location. An air quality impact assessment of peak carbon monoxide (CO) concentrations from the worst-case intersections and interchanges based on Level of Service (LOS) and traffic volumes was conducted. Mobile source emissions were derived using the EPA MOVES model while ambient pollutant concentrations at a variety of receptor locations were estimated using the EPA CAL3QHC model.
The analysis also evaluated potential impacts from Mobile Source Air Toxics (MSATs) in the Study area. Since the re-evaluation of the Study Alternatives will not add significant capacity to any of the existing and/or proposed new roadway networks where design year traffic is projected to be 140,000 to 150,000 annual average daily traffic (AADT) or greater, the Study Alternatives were best characterized as a project with “Low Potential MSAT Effects” under the 2012 FHWA interim guidance update document. Therefore, a qualitative analysis was conducted for this project consistent with the latest FHWA guidance.