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Prairie Parkway Study Fine Particulate Matter (PM_2.5) Project Level Hot-Spot Analysis

6.0 Conclusions

In summary, based on the analysis and surrogate site monitoring data, it is determined that Prairie Parkway Preferred Alternative meets all the project level PM_2.5 conformity requirements, and that the Prairie Parkway project will not cause or contribute to a new violation of the PM_2.5 NAAQS, or increase the frequency or severity of a violation for the reasons listed below. Therefore, the Prairie Parkway Preferred Alternative meets the conformity hot-spot requirements in 40 CFR 93.116 and 93.123 for PM_2.5.

• PM_2.5 monitor sites with current traffic characteristics comparable to those estimated for the Preferred Alternative have current values below the 24-hour and annual PM_2.5 NAAQS. This is true for the project's overall maximum traffic level and freeway junction maximum traffic level at both the near-term worst case year 2016 and design year 2030.

• The development level at three of the four comparison PM_2.5 monitor locations are equal to or greater than those anticipated for the Prairie Parkway corridor by 2030. Monitor data for these locations therefore most likely reflects higher non-mobile source particulate matter emissions than would the development level anticipated in the Prairie Parkway corridor.

• The comparison PM_2.5 monitor locations are proximate enough to the corridor that there should be no difference in metrological conditions in comparison to the Prairie Parkway corridor.

• National and state data show a consistent downward trend in PM_2.5 emissions that is anticipated to decline even more due to technological improvements on new diesel vehicles from the 2007 heavy-duty engine standards and new clean fuels program. Regional PM_2.5 conformity analyses show reductions in PM_2.5 of 36% from 2010 to 2020 and a continued, slight, further decline between 2020 and 2030.

• Detailed, project level PM_2.5 monitoring data from the Dan Ryan Expressway reconstruction area has consistently been below the 24-hour PM_2.5 NAAQS. Current Dan Ryan traffic levels are many times higher than both the near-term and design year volumes estimated for the Prairie Parkway Preferred Alternative, and the Dan Ryan Expressway is located in an area far more densely developed than envisioned for any portion of the Prairie Parkway study area.