1. Presents:/slides/greg/PSAT_11-17-03.ppt Modeling Options for Proposed BART Rule Two roles for modeling in proposed BART rule > Does a potential BART-eligible source contribute to visibility impairment at a Class I area (max 24-hr) > What is degree of visibility improvement due to BART controls at a specific facility Do BART controls result visibility improvements of > 0.5 dV averaged across 20% worst modeled days Once a facility is BART-eligible, then all visibility precursor species must be considered (SOx, NOx, PM and VOC) > For most sources SO4 and NO3 will be primary pollutants of interest (SOx and NOx emissions)

2. Presents:/slides/greg/PSAT_11-17-03.ppt Modeling Options for Proposed BART Rule CALPUFF – Lagrangian non-steady-state Gaussian puff model with simplified parameterized chemistry Advantages > Simple integrated modeling package w/ GUIs available > Computationally efficient for a few sources > EPA guideline model for > 50 km and PSD pollutants (SO2, NO2 and PM) > Mentioned in proposed BART rule Disadvantages > Chemistry incorrect and out of date (1982) > SO4 and NO3 estimates likely not accurate and reliable

3. Presents:/slides/greg/PSAT_11-17-03.ppt Modeling Options for Proposed BART Rule SCICHEM – Second Order Closure Lagrangian non- steady-state model with full chemistry – requires 3-D fields of concentrations Advantages > Treats full nonlinear chemistry > Less computationally demanding than a photochemical grid model (PGM) for a few sources Disadvantages > Not easy to use and not widely used > Uncertainty in applicability, hasn’t been demonstrated for this type of application > Need 3-D fields without BART source(s) > More computationally demanding than CALPFF

4. Presents:/slides/greg/PSAT_11-17-03.ppt Modeling Options for Proposed BART Rule CMAQ – One-atmosphere photochemical grid model Advantages > Full chemistry > Will be set up for 36 km inter-RPO grid and several RPO 12 km grids Disadvantages > Coarse grid resolution (36/12 km) and one-way grid nesting limit ability to resolve point sources and get correct chemistry (Plume-in-Grid may help) > How to get single source impacts: > Zero-out? > TSSA Source Apportionment? > Computationally demanding

5. Presents:/slides/greg/PSAT_11-17-03.ppt Modeling Options for Proposed BART Rule CAMx – One-atmosphere photochemical grid model Advantages > Same as CMAQ > Two-way nesting and flexi-nesting can better resolve point source plumes > PSAT may be useful Disadvantages > How to get single source impacts: > Zero-out? > TSSA Source Apportionment? > Computationally demanding

6. Presents:/slides/greg/PSAT_11-17-03.ppt Modeling Options for Proposed BART Rule One potential approach using CAMx/PSAT Address each state one at a time Center 12 km modeling grid over state to include all key nearby Class I area Develop BCs from 36 km Inter-RPO grid 2002 run Add 4 km flexi-nest over state of interest Base Case run and zero-out all BART-eligible sources to identify most important visibility species (i.e., SO4 and NO3) Apply PSAT with ~30 BART-eligible facilities as separate source groupings Post-process to estimate each BART-eligible facility’s visibility impacts at Class I areas