• Select receptor site locations :  • Select dispersion models and calculate concentrations at selected intersection(s) : 96  • Determine background concentrations :  • Tabulate results :  − Representative background concentrations should be added to the predicted  worst-case project-level concentration and compared to the NAAQS. If  project  does not conform, consider mitigation or control measure(s).  − Background  concentrations  are  typically  obtained  from  a  representative  background monitoring site not affected by the intersection(s) of interest.  − The locations at which concentrations are estimated are known as receptors.  Generally receptors are located  along the roadway where the general public is  likely to have continuous access.  94 Re-entrained road dust must be included in all PM$_{10 }$hot-spot analyses. Because road dust is a significant  component of PM$_{10 }$inventories, EPA has historically required road dust emissions to be included in all  conformity analyses of direct PM$_{10 }$emissions – including hot-spot analyses. See the March 2006 final rule (71  FR 12496-98).  95 Emissions from construction-related activities are not required to be included in PM hotspot analyses if such  emissions are considered temporary as defined in 40 CFR 93.123(c)(5) (i.e., emissions which occur only during  the construction phase and last five years or less at any individual site).  96 Appendix W to Part 51  – Guideline on Air Quality Models , http://www.ecfr.gov/cgi-bin/text- idx?SID=e6a5b817b94abf58460f48c032d9a39c&node=40:2.0.1.1.2.23.11.5.37&rgn=div9, describes both  AERMOD and CAL3QHC/CAL3QHCR as being appropriate for modeling line sources.  67$_{ }$ Aviation Emissions and Air Quality Handbook  The last step of the process f or conducting a quantitative CO and/or  PM$_{10 }$ and PM$_{2.5 }$ hot-spot  analysis is to document the analysis and results. For both project -level air quality requirements  under the CAA and those under the NEPA, it is always necessary to complete emissions and air  quality modeling on the project/action and compare the resulting values to the relevant NAAQS.  Table 7-3  ( CO Intersection Hot-Spot Results ) and  Table 7-4  ( PM Intersection Hot-Spot Results )  provide a sample format for reporting CO, PM$_{10}$, and PM$_{2.5 }$ impacts of roadway traffic from a  hot-spot analysis, respectively. As shown, CO results are typically presented in ppm and  PM$_{10 }$ and PM$_{2.5 }$results in µg/m$^{3 }$and all results include background concentrations.  7.2.4.  Roadway Dispersion Modeling Results  − For quantitative hot-spot analyses the EPA-recommended models for CO and  PM$_{10 }$ and PM$_{2.5 }$ are CAL3QHC and AERMOD/ CAL3QHCR, respectively.  CAL3QHCR is recommended for  CO when a CAL3QHC analysis with  conservative assumptions indicates a potential to exceed the NAAQS. 