## Proposed Replacement of CALINE3 with AERMOD in Appendix W NPRM 11 th 

### Modeling Conference Research Triangle Park, NC August 12, 2015 Chris Owen U.S . EPA/OAQPS/AQAD/AQMG 1

## CALINE3 workgroup • Chris Owen (OAQPS) • James Thurman (OAQPS) • Laura Berry (OTAQ) • David Heist (ORD) • Mike Leslie ( Region 5) • Meg Patulski (OTAQ) • Sue Kimbrough (ORD) 2

## Summary of EPA proposed actions for mobile source modeling • Propose to replace CALINE3, CAL3QHC, and CAL3QHCR with AERMOD as the Appendix A preferred dispersion model for all mobile source modeling of inert pollutants • Proposal is based on the following:

– AERMOD has updated dispersion science relative to CALINE3

– Model intercomparisons show that AERMOD outperforms CALINE3

– Simplified implementation of mobile source modeling for CAA requirements • Updates to Sections 4.2.3 and 7.2.3 of the proposed Appendix W 3

## CALINE3 Background/History • CALINE3 developed by Benson (1979).

– Dispersion theory based on “P - G stability classes”

– Single meteorological condition • CAL3QHC developed from CALINE3 for screening

– Adds queueing algorithm for emissions from intersections • CAL3QHCR developed from CAL3QHC for refined analyses

– Adds the ability to use 1 -year of meteorological data, hourly emissions variation, additional averaging periods

– Met preprocessor only available for very old met data • CALINE3 replaced by CALINE4 (Benson, 1984) 4

## AERMOD Background/History • Promulgated as the EPA’s preferred dispersion model for most applications in 2005 revisions to Appendix W • Reflects state of the science dispersion model formulation, i.e.,

– Planetary boundary layer (PBL) scaling parameter to characterize stability and determine dispersion rates

– Monin - Obukhov (M - O) similarity profiling of winds near the surface

– In replacing ISC3 in 2005, one of the major technical advancements was to replace the P - G stability class dispersion estimates (same as CALINE3) with the turbulence - based dispersion rates consistent with PBL and M - O 5

## Model Performance Evaluations and Intercomparisons • Result summaries in the following slides are based on Heist et al. (2013), Estimating near- road pollutant dispersion: A model inter-comparison, Trans. Res. D., 93- 105 • Published findings from two field studies with emissions of SF6 tracer specifically designed for evaluation of mobile emission modeling

– CALTRANS99 tracer experiment

– Idaho Falls barrier tracer experiment 6

### CALTRANS Study: Model performance summary

7 • Model statistics show that AERMOD/RLINE almost identical • CALINE overpredicts • Q - Q plot shows that AERMOD is best at highest concentrations CALINE3 CALINE4 CALINE3 CALINE4

### Idaho Falls Tracer Study : Model performance summary

8 • Q - Q plot shows that AERMOD/RLINE is best at highest concentrations

• Model statistics show that AERMOD/ADMS almost identical • CALINE underpredicts CALINE4 CALINE4

## Streamlined implementation for mobile sources • Appendix W NPRM will bring commonality and consistency in modeling analyses for EPA regulatory applications

– AERMOD already preferred for PM2.5, PM10

– One model for mobile sources rather than 4

– AERMOD has more options for source characterization and computation of design values

– FAA uses AERMOD in their EDMS/AEDT 

### • EPA fully supports AERMOD with continued development and updates to meet regulatory needs and issues 9

## EPA Transition Plans Under Appendix W NPRM • EPA is taking comment on transition period from CALINE3 to AERMOD in NPRM

– P roposing a 1 year transition period after final rule, i.e., slightly less than 2 years from now until formal transition to AERMOD 

### • EPA plans to provide training

– Training package with examples

– Webinars and trainings for stakeholders

– Air Pollution Training Institute course # 423, Air pollution dispersion models

– Project level training for Hot-spot analyses 10

## Relevant docket items • Document Title: Technical Support Document (TSD) for Replacement of CALINE3 with AERMOD for Transportation Related Air Quality Analyses, EPA Document EPA-454/B- 15 -002 • http:// www.epa.gov/ttn/scram/11thmodconf/CAL3_A ERMOD_Replacement_TSD.pdf

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