E.2.5  Select Receptor Site Locations  The locations at which concentrations are estimated are known as “receptors”. EPA’s  Guideline  on Air Quality Models 105  provides guidance on the selection of receptor sites and recommends  that receptor sites be placed to estimate the highest potential concentrations.  When completing a CO hot-spot analysis, receptors should be placed at each approach on both  sides of the roadway where traffic queues develop (i.e., at least three meters from each of the  traveled roadways which make-up the intersection). Other examples of reasonable receptor sites  include the following:  For further guidance on the selection of receptor locations for CO hot -spot analyses, refer to  EPA’s  Guideline for Modeling Carbon Monoxide from Roadway Intersection 106  .  Additionally, the selection of receptor sites for PM hot-spot analyses should be determined on a  case-by-case basis taking into account project -specific factors that may influence areas expected high concentrations, such as prevailing wind directions, monitor locations, topography,  and other factors. Typically, receptors should be sited as near as five meters from a source (e.g.,  the edge of a traffic lane or a source in a terminal. For further guidance on the selection receptor locations for PM hot-spot analyses refer to EPA’s  Transportation Conformity Guidance  for Quantitative Hot-spot Analyses in PM$_{2.5 }$and PM$_{10 }$ Nonattainment and Maintenance Areas  mentioned above.  EPA recommends that receptors s hould be positioned to represent concentrations near -ground  level, generally at a height of 1.8 meters (approximately 6 feet) above grade. Receptors should  also be placed at higher elevations  (if needed) to represent concentrations at different  heights  along multi-story buildings, such as apartment or office buildings.  Finally, when completing air quality modeling for Build and No-B uild scenarios, receptors  should be placed in the same locations in both scenarios so that direct comparisons can be made  between the concentrations calculated at each receptor.  105  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.  106  EPA,  Guideline for Modeling Carbon Monoxide from Roadway Intersections ,  http://www.epa.gov/scram001/guidance/guide/coguide.pdf.  97$_{ }$ • Sidewalks to which the general public has access on a continuous basis;  • A vacant lot near an intersection, where the general public would have continuous access;  • Portions of a nearby parking lot to which pedestrians have continuous access;  • In the vicinity of parking lot entrances and exits, provided a nearby area contains a public  sidewalk, residences, or structures to which the general public is likely continuous access; and  • Property lines of residences, hospitals, rest homes, schools, playgrounds, and entrances and ground-level air intakes to all other buildings.  APPENDIX E$_{ }$