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 – 1st Draft

Staff Paper Clean Air Scientific Advisory Committee (CASAC)

reviewed EPA released Final Criteria Document March 2006

EPA released 2nd 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 2nd Draft Staff Paper

Options from 2nd Draft Staff paper Primary Standard Secondary Standard Current 8-hr Ozone Standard 0.080 ppm based on the 3-year

average of the 4th highest concentration recorded at each monitor.

Same as Primary

EPA Staff Paper option #1

Same as current standard Same as current standard

EPA Staff Paper option #2 Revise to 0.070 ppm based on the three year average of the 4th highest concentration recorded at each monitor.

3-month, 12-hr SUM061 Range (15-38 ppm-hr), or W1262

Range (13-35 ppm-hr)

Clean Air Scientific Advisory Committee Met August 24 – 25, 2006 and recommended

lowering the standard Current 8 hour O3 standard = 0.08 parts per

million (ppm) CASAC, no more than 0.070 ppm Should consider 0.055 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 0.070 ppm The risk assessment should include all

ozone, man made and natural

Ozone Values in Western National ParksWestern National Parks

4th Highest 8-Hour Maximum Value 1994-2004

0.050

0.060

0.070

0.080

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

PP

M

Canyonlands, Utah Craters of the Moon, Idaho Death Valley, Calif.

Great Basin, Nevada Grand Canyon, Arizona Rocky Mountain, Colorado

Saguaro, Arizona Yellowstone, Wyoming NAAQS Standard = 0.070 ppm

NAAQS = 0.070 ppm

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%

Monitor MNB MNGE

Rocky Mountain N.P. 4% 16%

Mesa Verde N.P. 3% 14%

Centennial, WY -4% 10%

Pinedale, WY -2% 13%

Gothic, CO 7% 17%

Canyonlands N.P. -3% 12%

Modeling ResultsTime Series Charts

Canyonlands

0

20

40

60

80

100

120

1 53 105 157 209 261 313 365 417 469 521 573 625 677 729 781 833 885 937 989 1041 1093 1145 1197 1249 1301 1353

Hour

PP

B Obs

Model

Modeling ResultsJuly 12-14, 2002

Mesa Verde

30

40

50

60

70

80

90

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69

Hour

PP

B ObsModel