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Modeling Options for Proposed BART Rule

Explore different modeling options for implementing the proposed BART rule, focusing on visibility improvements and precursor pollutants. Understand advantages and disadvantages of CALPUFF, SCICHEM, CMAQ, and CAMx models for assessing BART-eligible sources. Learn about the application of CAMx/PSAT approach for single-source impacts evaluation.

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Modeling Options for Proposed BART Rule

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  1. 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) Presents:/slides/greg/PSAT_11-17-03.ppt

  2. 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50 km and PSD pollutants (SO2, NO2 and PM) • Mentioned in proposed BART rule • Disadvantages • Chemistry incorrect and out of date (1982) • SO4 and NO3 estimates likely not accurate and reliable Presents:/slides/greg/PSAT_11-17-03.ppt

  3. 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 Presents:/slides/greg/PSAT_11-17-03.ppt

  4. 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 Presents:/slides/greg/PSAT_11-17-03.ppt

  5. 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 Presents:/slides/greg/PSAT_11-17-03.ppt

  6. 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 Presents:/slides/greg/PSAT_11-17-03.ppt

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