Ozone National Air Quality Standard Review WESTAR Fall Business Meeting Boise, Idaho September 2006

Ozone NAAQS Review - History Current review process started in 2005 Comprehensive assessment of the latest scientific and technical information Criteria Document published in August 2005 EPA staff assessment in November 2005 – 1 st Draft Staff Paper Clean Air Scientific Advisory Committee (CASAC) reviewed EPA released Final Criteria Document March 2006

EPA released 2 nd Draft Staff Paper July 18, 2006 Comments received until September 18, 2006 EPA expects to issue Final Staff Paper sometime this fall (perhaps October)

EPA Administrator will consider: Final Staff Paper CASAC Comments Public Comments Final Decision to revise or retain the ozone standard is expected by March 28, 2007 Final Action is expected by Dec. 19, 2007

Options from the EPA 2 nd Draft Staff Paper

Clean Air Scientific Advisory Committee Met August 24 – 25, 2006 and recommended lowering the standard Current 8 hour O 3 standard = 0.08 parts per million (ppm) CASAC, no more than ppm Should consider or 0.060

Clean Air Science Advisory Committee The current standard is not protective EPA should eliminate the rounding convention The upper end should be ppm The risk assessment should include all ozone, man made and natural

Ozone Values in Western National Parks

Are the WRAP CMAQ model results a useful guide for rural ozone analysis? Is the model providing good estimates of hourly ozone production and depletion? Compare observed ozone at the 6 monitors in the domain with model estimates  Statistical metrics Mean normalized bias Mean normalized error  Time series charts Tools used  GIS  Perl programming  Additional scripts from the RMC  HYSPLIT

Evaluation Metrics Mean Normalized Bias (MNB): A value of zero would indicate that the model over predictions and model under predictions exactly cancel each other out. Mean Normalized Gross Error (MNGE): A value of zero would indicate that the model exactly matches the observed values at all points in space/time. Previous guidance in the modeling community set a goal of: MNB <= 15% and MNGE of <= 25%. This was based on the experience of actual model performance over the years.

Results Goal<= 15%<= 25% MonitorMNBMNGE Rocky Mountain N.P.4%16% Mesa Verde N.P.3%14% Centennial, WY-4%10% Pinedale, WY-2%13% Gothic, CO7%17% Canyonlands N.P.-3%12%

Modeling Results Time Series Charts

Modeling Results July 12-14, 2002