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Modeling Options for Proposed BART Rule

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

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50 km and PSD pollutants (SO2, NO2 and PM) • Mentioned in proposed BART rule • Disadvantages • Chemistry incorrect and out of date (1982) • SO4 and NO3 estimates likely not accurate and reliable Presents:/slides/greg/PSAT_11-17-03.ppt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