The Virginia Department of Transportation (VDOT) in cooperation with the Federal Highway Administration (FHWA), proposed a High Occupancy Vehicle (HOV) direct access ramp from the existing HOV lanes along Interstate 395 (I-395) to Seminary Road in Alexandria, VA. The study needed to address the potential air quality impacts associated with additional employee travel volumes related to the Mark Center at the nearby intersections and the I-395 on and off-ramps.
An air quality project level analysis was conducted for carbon monoxide (CO), particulate matter (PM) and Mobile Source Air Toxics (MSATs) from potential traffic impacts associated with the proposed I-395 HOV Ramp. A hot spot analysis for CO was required as expected traffic volumes will exceed the qualitative analysis threshold criteria and was conducted consistent with the VDOT Consulting Guide and EPA/FHWA guidance using the latest versions of MOBILE6.2 and CAL3QHC. The Project is located in a non-attainment area for PM2.5, however, based on the criteria specified in the Transportation Conformity Rule and associated guidance; the Project is not considered to be a "project of air quality concern" for particulate matter. Therefore, neither a qualitative nor quantitative analysis was required. A qualitative MSAT analysis was also conducted since the Project was considered to have low potential MSAT effects per FHWA NEPA guidance criteria.