HMMH evaluated the potential air quality impacts of proposed improvements to the interchange between I-81 and Fairfax Pike (Route 277) at Exit 307 in the Town of Stephens City, Virginia.
Analyses for potential impacts for CO were conducted for the roadway and associated intersections/interchanges that might be impacted by the project. Worst-case locations for the Build alternatives were identified from 12 signalized intersections along the study area and were ranked from worst to best based on peak volumes and Level of Service (LOS). The intersections were then screened for modeling using the 2016 FHWA-VDOT Programmatic Agreement (PA), which references screenings that were previously established based on worst-case modeling for typical intersections. Because all 12 signalized intersections and both the existing and proposed interchange meet the thresholds established in the PA; a CO qualitative analysis was conducted. A qualitative analysis was also conducted to evaluate potential impacts from Mobile Source Air Toxics (MSATs) in the Study Area.