1. Ozone and nitrogen deposition from Colorados Craig powerstation

2. NOx from Craig The Craig powerstation is the largest uncontrolled NOx source in the state (~18k tons/yr) NPS is lobbying EPA for stricter controls (i.e., SCR on all three boilers) What is the impact in terms of Ozone Nitrogen dep PM nitrate

3. Approach Reduce NO and NO2 emissions from Craig w.r.t. three proposed scenarios NPS option is most stringent with full SCR Reduce NOx from ~18k tons/yr to ~3k tons/yr Run CAMx for a year (2005) with 12km 4CAQTF inputs

4. Regional N dep from Craig

5. ROMO N dep from Craig

6. Peak ozone impacts from Craig

7. Ozone from Craig at Flat Tops WA

8. VOC vs. NOx from OMI HCHO NO2 HCHO/NO2 HCHO and NO2 can be detected from the OMI satellite, and provide indicator species to help assess whether a region is VOC or NOx limited. HCHO/NO2 > 1 Suggests NOx limited (Duncan et al., 2010) Craig

9. ROMO nitrate from Craig

10. Summary Given VOC/NOx ratios in northwestern CO, NOx controls should be effective for reducing ozone, N dep, and haze NOx emissions from O&G development in the region (Uintah, Piceance, and SW Wyo) are also a concern Emissions at the surface: shorter transport? This sector is growing, and NOx controls may be harder to apply

11. Summary (contd) The benefits from full SCR at Craig could be significant: Ozone: 2 – 6 ppb (8 hr avrg) ozone reduction at Flat Tops WA 1 – 2 ppb at ROMO N dep: 0.2 kg N/ha/yr reduction at Mt Zirkel 0.14 kg N/ha/yr reduction at ROMO PM nitrate: 0.6 ug/m3 reduction at ROMO

12. Summary (contd) Nitrate behavior seems a little strange N dep at ROMO was ~linear w.r.t. to reductions Next time should use plume-in-grid to better capture high NOx chemistry