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Prairie Parkway Study Fine Particulate Matter (PM2.5) Project Level Hot-Spot Analysis

5.4 PM2.5 Hot-spot Analysis Approach

The Prairie Parkway project proposes a new roadway improvement where there is currently no comparable transportation facility. There is no logical initial condition to use in comparing localized PM2.5 concentrations for build conditions because there is neither a comparable facility nor PM2.5 monitor data at the project location. Relying on the March 2006 joint EPA and FHWA guidance for conducting PM2.5 hot-spot analyses, this analysis follows the "Comparison to another location with similar characteristics" or surrogate approach described in Chapter 4 of the March 2006 joint EPA and FHWA qualitative hot-spot analysis guidance. The preamble to the July 1, 2004, revision to the transportation conformity rule (69 Federal Register 40004) requires that project-level analyses consider the year (or years) of expected peak mobile source emissions from the project. For PM2.5 this is expected to be a near term year, such as the first year of operation of the project, because emission rates from vehicles are predicted to decline significantly between the project's opening year and its design year due to lower tailpipe emissions from fleet turnover and national vehicle emissions control programs. A particular opening year for this project has not been established; so for consistency with the analysis years used in the DEIS and FEIS, 2016 and 2030 represent near-term, expected peak emissions and design years respectively.

For the reason stated in section 5.1 above, this analysis does not consider PM2.5 precursors, re-entrained road dust or construction emissions. The project's major design features are consistent with those used in the last regional PM2.5 conformity determination. No PM2.5 mitigation or control measures are anticipated as part of this project's implementation.

5.4.1 Surrogate Site Selection

Existing PM2.5 monitor locations in Illinois were reviewed to identify sites that could serve as surrogates for this analysis. Acceptable surrogate sites should have similar, or greater, ADT and diesel vehicle traffic levels compared to the values forecast for the Prairie Parkway Preferred Alternative; development levels like those forecast for the project study area; and comparable average meteorological conditions. Information about the four PM2.5 monitor sites chosen as surrogates was presented previously in Table 4. These sites all have comparable or higher total traffic levels; HCV shares near the regional average or above the project's estimated diesel share; are all east of the project area in more developed parts of the region; but are physically close enough that metrological conditions such as temperature, humidity, etc. are similar.

5.4.2 Proposed Improvement Forecast Traffic

Table 6 shows the maximum mainline traffic level estimate for the Preferred Alternative and arterial cross road for the near-term, worst case year (2016) and design year (2030). The maximum freeway mainline traffic level is on the section between the US-34 and IL-71 interchanges, with US-34 having higher traffic levels at its interchange with the Prairie Parkway than IL-71. Forecast 2030 traffic is from regional travel simulations that were done as part of the project's Phase 1 Engineering Study, while those for the near-term, worst case year 2016 were interpolated using 2000 base and 2030 design year forecasts.

Table 6 - Preferred Alternative - Mainline Traffic
Roadway Year ADT
(2-Way)
HCV
(2-Way)
Combined
ADT
Combined
HCV
           
Prairie Parkway 2016 28,600 5,700 50,500 7,100
14%
US-34 2016 21,900 1,400
         
Prairie Parkway 203050,000 8,900 80,300 12,100
15%
US-34 2030 30,300 2,100

In addition to maximum freeway traffic level, another worst case PM2.5 condition can occur at freeway/freeway junctions. The Prairie Parkway Preferred Alternative maximum combined freeway/freeway terminal volume will be at its southern terminus with I-80. Table 7 shows the near-term (2016) and design year (2030) traffic estimates for the Preferred Alternative at this point.

>Table 7 - Preferred Alternative - Terminal Point Traffic
Roadway Year ADT
(2-Way)
HCV
(2-Way)
Combined
ADT
Combined
HCV
           
Prairie Parkway2016 13,400 2,700 53,800 16,200
30%
I-80 2016 40,400 13,500
           
Prairie Parkway 2030 23,400 4,700 70,000 20,100
29%
I-80 2030 46,600 15,400

5.4.3 Surrogate Site Comparisons

This PM2.5 hot-spot analysis is for a project extending more than 30 miles. Conditions will obviously vary over the project length in terms of volume of traffic, flow along the mainline or near interchanges, at connections to other expressways, level of development, type of area etc. The use of multiple surrogates is the best means of matching such a range of conditions and so ensuring a robust analysis. Consistent with the PM2.5 hot-spot guidance, traffic comparisons are made using the expected peak mobile source emission year 2016 and design year 2030 project traffic estimates. Table 8 summarizes the comparison data for 2016 and Table 9 summarizes the data for 2030. Overall conditions at each of the four surrogate PM2.5 monitor sites are discussed below.

Table 8 - Surrogate to Preferred Alternative to 2016 Comparison
    Comparison traffic Project traffic Monitor data  
Comparison
Monitor
Comparison
roadways
Combined
2005 ADT
Combined
2005 HCV
Combined
2016 ADT
Combined
2016 HCV
2004-
2006
μg/m3
24-hour
2004-
2006
μg/m3
annual
Project traffic condition
Aurora I-88 & IL-31 80,200 9,000 50,500 7,100 34.5 13.0 Max volume between
US-34 & IL-71
Elgin I-90 & IL-31 141,700 12,850 50,500 7,100 32.3 14.3 Max volume between
US-34 & IL-71
Joliet I-80 & IL-7 109,400 19,550 50,500 7,100 33.4 13.2 Max volume between
US-34 & IL-71
Joliet I-55 & US-52 90,400 16,500 50,500 7,100 33.4 13.2 Max volume between
US-34 & IL-71
Braidwood I-55 & IL-129 90,400 16,500 50,500 7,100 29.7 11.1 Max volume between
US-34 & IL-71
Joliet I-80 & I-55 152,000 19,800 53,800 16,200 33.4 13.2Max terminal volume at
I-80

Table 9 - Surrogate to Preferred Alternative to 2030 Comparison
    Comparison traffic Project traffic Monitor data  
Comparison
Monitor
Comparison
roadways
Combined
2005 ADT
Combined
2005 HCV
Combined
2016 ADT
Combined
2016 HCV
2004-
2006
μg/m3
24-hour
2004-
2006
μg/m3
annual
Project traffic condition
Aurora I-88 & IL-31 80,200 9,000 80,300 12,100 34.5 13.0 Max volume between
US-34 & IL-71
Elgin I-90 & IL-31 141,700 12,850 80,300 12,100 32.3 14.3 Max volume between
US-34 & IL-71
Joliet I-80 & IL-7 109,400 19,550 80,300 12,100 33.4 13.2 Max volume between
US-34 & IL-71
Joliet I-55 & US-52 90,400 16,500 80,300 12,100 33.4 13.2 Max volume between
US-34 & IL-71
Braidwood I-55 & IL-129 90,400 16,500 80,300 12,100 29.7 11.1 Max volume between
US-34 & IL-71
Joliet I-80 & I-55 152,000 19,800 70,000 20,100 33.4 13.2 Max terminal volume at
I-80

5.4.3.1     Aurora

The Aurora monitor (0890007) is located approximately one-half mile south of I-88 just west of the IL-31 interchange. This is a relatively new monitoring site and so data are available only for 2005 and 2006. The level of development in the area surrounding the monitor is as high as or higher than anticipated for any location along the Prairie Parkway corridor - the City of Aurora 2000 population was 142,990 while 2030 estimated population for all of Kendall County is 176,607. The combined 2005 ADT at this monitor site is almost 60% higher than the project's 2016 traffic estimate and equal to the project's 2030 traffic forecast. The combined 2005 HCV traffic at this monitor site is approximately 25% higher than the project's 2016 truck traffic estimate, but almost 35% below the project's 2030 truck traffic forecast. Both the 24-hour and annual monitor values are below their respective standards at this location. Note that because this is a new monitor site, data are averaged for only two years not three.

5.4.3.2     Elgin

The Elgin monitor (0890003) is located approximately 1.2 miles south of I-90 just east of the IL-31 interchange. This monitor is located in a mature, built out section of the City of Elgin that is developed to a higher level than anticipated for the Prairie Parkway corridor - the City of Elgin 2000 population was 94,487 while 2030 estimated population for all of Kendall County is 176,607. The combined 2005 ADT at this monitor site is more than double the project's 2016 traffic estimate and approximately 75% higher than the project's 2030 traffic forecast. The combined 2005 HCV traffic at this monitor site is 80% higher than the project's 2016 truck traffic estimate and still 6% above the project's 2030 truck traffic forecast. Both the 24-hour and annual monitor values are below their respective standards at this location.

5.4.3.3     Joliet

The Joliet monitor (1971002) is located in the vicinity of the junction of I-80 and I-55 on the near west side of the City of Joliet. It is approximately one mile north of I-80 east of the IL-7 interchange, and approximately 3.6 miles east of I-55 just north of the US-52 interchange. This monitor is located in a mature, built out section of the City of Joliet that is developed to a higher level than anticipated for the Prairie Parkway corridor - the City of Joliet 2000 population was 106,221 while 2030 estimated population for all of Kendall County is 176,607. Because this monitor is near the junction of two existing freeways, it is reasonable for comparisons to be made to both maximum project section traffic level and maximum traffic level at the project's junction with existing freeways.

The 2005 combined traffic at I-80 and IL-7 is slightly more than twice the project's 2016 traffic estimate and still 36% higher that the project's forecast 2030 traffic. The combined 2005 HCV at I-80 & IL-7 is 175% of the project's estimated 2016 HCV traffic and 60% higher than the project's forecast 2030 traffic.

The 2005 combined traffic at I-55 and US-52 is 80% higher than the project's 2016 estimated traffic and 12% higher than the project's forecast 2030 traffic. The combined 2005 HCV traffic at I-55 and US-52 is 130% higher than the project's 2016 estimated HCV traffic and 36% higher than the project's forecast 2030 HCV traffic.

The 2005 combined traffic at the junction of I-80 and I-55 is approximately three times that of the Preferred Alternative's 2016 traffic level at its terminus with I-80 and somewhat more than double the project's 2030 traffic at this same point. The combined HCV traffic at the junction of I-80 and I-55 is 22% higher than the project's 2016 HCV estimate and just slightly less than the project's forecast 2030 HCV traffic level. Both the 24-hour and annual monitor values are below their respective standards at this location.

5.4.3.4     Braidwood

The Braidwood monitor (1971001) is located approximately 1.8 miles south of I-55 just west of the IL-129 interchange. This monitor is located in an exurban town that is currently developed to a level comparable to the lower to moderate levels anticipated for the Prairie Parkway corridor. The 2005 combined ADT at this monitor site is 27% lower than the project's 2016 traffic estimate and only about half of the project's estimated 2030 traffic level. The combined HCV traffic at this monitor site is 10% higher than the project's 2016 estimate HCV traffic, but 55% lower than the project's 2030 forecast HCV traffic. Both the 24-hour and annual monitor values are significantly below their respective standards at this location.

Updated: 07/06/2011
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