Since direct PM2.5 emissions are below the applicable SER for Case 4, the significant

15 impact analysis in this case would only address the potential contribution to secondary PM2.5

16 from NOx and/or SO2 precursor emissions, and would not require any modeling of direct PM2.5

17 emissions. As discussed above for Case 3, the assessment of the precursor emission impacts on

18 secondary PM2.5 formation for Case 4 may be: a) qualitative in nature; b) based on a hybrid of

19 qualitative and quantitative assessments utilizing existing technical work; or c) a full quantitative

20 photochemical grid modeling exercise. As with Case 3, the EPA anticipates that only a few

21 situations would require explicit photochemical grid modeling.

III.1 Assessing 1 Primary PM2.5 Impacts

2 The assessment of primary PM2.5 impacts from the proposed new or modifying source

3 should be consistent with Appendix W. As noted above, Appendix W recommends specific

4 models as “preferred” for specific types of applications, based on model performance evaluations

5 and other criteria. The purpose of recommending the use of a particular preferred model is to

6 ensure that the best-performing models are used in assessing PM impacts from a particular

7 project and are employed in a consistent fashion.11 In 2005, the EPA promulgated AERMOD as

8 the Agency’s preferred near-field dispersion model for a wide range of regulatory applications in

9 all types of terrain based on extensive developmental and performance evaluation.12 For

10 NSR/PSD modeling for the PM2.5 NAAQS, the AERMOD modeling system should be used to

11 model direct PM2.5 emissions unless another preferred model is more appropriate, such as the

12 Buoyant Line and Point source dispersion model (BLP), or the use of an alternative model can be

13 justified consistent with Section 3.2 of Appendix W.


n451 - n452 - n453 - n454 - n455 - n456 - n457 - n458 - n459 - n460 - n461 - n462 - n463 - n464 - n465 - n466 - n467 - n468 - n469 - n470 - n471 - n472 - n473 - n474 - n475 - n476 - n477 - n478 - n479 - n480 - n481 - n482 - n483 - n484 - n485 - n486 - n487 - n488 - n489 - n490 - n491 - n492 - n493 - n494 - n495 - n496 - n497 - n498 - n499 - n500



   Flag of Portugal 


 castellano: DISPER CUSTIC DESCAR RADIA    italiano:     


 français:    português:  






deutsch: DIS CUS  DES  RAD

castellano: DIS CUS DES  RAD   english: DIS CUS DES RAD  


 português: DIS CUS DES RAD   italiano:   DIS CUS  DES RAD


français:  DIS CUS DES RAD