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Ralph Morris and Abby Hoats ENVIRON International Corporation

Interim 2009 8-Hour Ozone Design Value Projections for St. Louis. Ralph Morris and Abby Hoats ENVIRON International Corporation St. Louis 8-Hour Ozone/PM 2.5 Workgroup Meeting March 20, 2006. 8-Hour Ozone Design Value Projections.

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Ralph Morris and Abby Hoats ENVIRON International Corporation

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  1. Interim 2009 8-Hour Ozone Design Value Projections for St. Louis Ralph Morris and Abby Hoats ENVIRON International Corporation St. Louis 8-Hour Ozone/PM2.5 Workgroup Meeting March 20, 2006

  2. 8-Hour Ozone Design Value Projections • EPA’s “Guidance on the Use of Models and Other Analyses in Attainment Demonstrations for the 8-hour Ozone NAAQS” Final, October 2005 • Project future-year design values using model derived Relative Reduction Factors (RRFs) • RRFs = Modeled 2009 / Modeled 2002 • Apply RRFs to current-year baseline 8-hour ozone Design Values (DVB) to estimate future-year Design Values (DVF) • DVF = RRF x DVB • DVF < 85.0 ppb for modeled demonstration of attainment

  3. Steps in the 8-Hour O3 DV Projections • Calculate Monitor-Specific Baseline 8-hr O3 Design Value (DVB) from observations • Calculate modeled RRF • RRF is ratio of modeled future-year to current-year daily maximum 8-hr O3 concentrations near the monitor (averaged over several days) • Calculate Future-Year 8-hr O3 Design Value: DVF = RRF x DVB • Check Whether DVF < 85 ppb at all Monitors • Apply Unmonitored Areas Attainment Test

  4. 8-Hour Ozone Design Value Projections • How to define Baseline Design Value (DVB) for 8-hour Ozone Projections? • 8-Hour Ozone Design Values defined as the average of fourth highest daily maximum 8-hour ozone concentrations at a monitor over 3 years • EPA Guidance: Define DVB as the average of three Design Value periods that centered on the baseline inventory or modeled year (2002) • DVB = 1/3 x (DV2000-2002+DV2001-2003+DV 2002-2004) • Round to nearest tenth of a ppb • Site-specific • Weights fourth highest 8-hour ozone in 2000, 2001, 2002, 2003 and 2004 by 1, 2, 3, 2, 1, respectively

  5. 8-Hour Ozone Design Value Projections • How to define RRFs? • Select highest estimated daily maximum 8-hour ozone near the monitor • Near defined within ~15 km (7x7 5-km; 3x3 12-km; 1 cell 36-km) • We used 7x7 array for St. Louis 4-km modeling • May not select same cell in 7x7 array in 2002 and 2009 scenarios • RRF is defined as the ratio of the average future-year to average current-year 8-hour ozone near each monitor for which the current-year 8-hour ozone is greater than the threshold • EPA Guidance recommends 85 ppb threshold • EPA Guidance recommends at least 10 modeling days be used in the attainment test with 5 days absolute minimum • Two issues can be in conflict

  6. 8-Hour Ozone Design Value Projections • June (15 days), July (15 days) and Aug (8 days) 2002 episodes used (38 days total) • Goal is at least 10 modeled days in RRF calculations, with 5 days absolute minimum • Used 2002 Base Case 8-hour ozone cutoff thresholds of 70, 75, 80 and 85 ppb • For Southeast States (AL, GA, NC, VA) performed 8-hour attainment demonstration using variable threshold starting at 85 ppb and reducing 1 ppb until 10 modeling days used with floor at 70 ppb • Present results for 85 ppb threshold as in EPA guidance

  7. 8-Hour Ozone Design Value Projections • 2002 Base 3 Emissions • Still undergoing updates and refinements • 2009 Base 3 Emissions • Interim 2009 On-the-Books (OTB) Base Case • Some questions on IPM emissions allocations • Missouri EGU emissions overstated? • Still need to add in permitted sources • Will we need to modify growth factors? • Additional QA of Growth and Control Factors Warranted • Results are Interim and Will Change

  8. 2009 8-Hour Ozone Projected DVFs 85 ppb Threshold; Red Line = NAAQS 85 ppb; Dotted Line 82/87 ppb WOE Levels

  9. Number Days > 85 ppb; EPA Guidance Recommends at Least 10 Days with 5 Days Absolute Minimum

  10. St. Louis Monitoring Sites 86 90 86 88 86 88

  11. 2009 8-Hr O3 Projections using CAMx, Base 3 Emissions, 3 St. Louis Episodes and 85 ppb Threshold Final DVF is Truncated; Maximum StL DVF = 81 ppb

  12. Projections at Unmonitored Areas • Interpolated fields of Baseline Design Values • Interpolate monitored DVB to create spatial fields • Adjust DVB spatial fields using gridded model output gradients from current-year base case • Apply gridded modeled RRFs • Determine if any unmonitored area DVFs exceed the NAAQS • EPA developing software to perform this (not done for St. Louis yet) • “Violations” in unmonitored areas handled on case-by-case basis • Analyze uncertainties • Placement of additional monitors • Additional controls

  13. Supporting and WOE Analysis • Corroborate and Weight of Evidence (WOE) Analysis Recommended in addition to Modeled Attainment test (DVF) • Required if DVF between 82 ppb and 87 ppb • If DVF 88 ppb or higher EPA Guidance suggest not amount of WOE analysis would be convincing • Other study’s (e.g., MRPO, CAIR, 5 States) • Additional Models and Modeling Metrics, Data Analysis (e.g., Trends), Receptor Modeling, etc. • Recommend St. Louis pursue this path also

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