In 2002, the Sierra Club legally challenged the U.S. Department of Transportation (DOT) Federal Highway Administration (FHWA) and the Nevada Department of Transportation's (NDOT) National Environmental Policy Act (NEPA) environmental document related to the proposed widening of U.S. 95 in Las Vegas, Nevada. FHWA entered into a Settlement Agreement with Nevada DOT and the Sierra Club, wherein the FHWA agreed to undertake a research effort to characterize the impact and behavior of particulate matter with aerodynamic diameter less than 2.5 microns (PM2.5) and MSATs near highways.1
The FHWA and U.S. Environmental Protection Agency (U.S. EPA) determined that it would be in the best interest of both organizations to implement this project in a collaborative manner, allowing a more effective utilization of staffing and resources. The first study was conducted in the city of Las Vegas, Nevada in the vicinity of I-15. The site location was just south of the I-15 and Russell Road interchange and just north of the I-15 and I-215 interchange. This was completed in mid-December, 2009. Detroit was the second study city. A site was selected for Detroit in collaboration with FHWA, Michigan DOT, Southeast Michigan Council of Government and EPA. The site selected for Detroit was along I-96, east of Telegraph Road (US 24) (Figure 1).
The objective of the study conducted under this Protocol was to determine MSAT concentrations and variations in concentrations as a function of distance from the highway and to establish relationships between MSAT concentrations as related to highway traffic flows including traffic count, vehicle types, and speed; meteorological conditions such as wind speed and wind direction; and other air pollutants emitted from motor vehicles such as carbon monoxide (CO) and oxides of nitrogen (NOX).2 This report focuses on carbon monoxide (CO), nitrogen oxide (NO), nitrogen dioxide (NO2), oxides of nitrogen (NOX), black carbon (BC), particulate matter less than 10 microns (PM10), PM2.5, PM Coarse, and MSAT (1-3, butadiene, benzene, acrolein, formaldehyde, acetaldehyde) measurements (Table 1).
FHWA's "detailed monitoring protocol" outlined a uniform approach to conduct this study, as well as future related studies, for evaluating mobile source contributions to air toxic compounds and PM2.5 and their dispersion patterns2. This protocol was peer reviewed by other federal agencies (EPA and DOE), State environmental and transportation agencies, the Sierra Club, and academic institutions. A more detailed examination of the monitoring protocol indicates that for each city, continuous monitoring and integrated sample collection was required at four monitoring sites located at distances ranging from roadside to 300 meters (m). In addition, wind speed and wind direction were required at each site. Moreover, monitoring for the complete suite of meteorological parameters was required at the monitoring station positioned 50 to 150 m from the roadway (100 meter downwind).