Draft Comments Wyoming Draft Haze SIP

September 29, 2009

Pat Brewer

Section 2 and 3 describe the WY Class I areas and the visibility monitoring data that define the 20% 

worst and 20% best visibility days at these areas. It would be helpful to at least cite references, if not 

include in the SIP, discussions how light extinction and deciview are calculated from IMPROVE 

measurements (sections 2 and 3), and how relative response factors are calculated to project future 

visibility (Section 5). 

In Section 4, WY reports emissions from the WRAP 2002d and 2018PRPb inventories. WY should clarify 

that you accept WRAP emissions projections for WY sources as representative of all WY controls by 

2018. In particular, are all WY BART reductions included in WRAP 2018PRPb? If some or all of WY BART 

NOx controls are missing from the WRAP 2018PRPb, benefits from these controls are missing from the 

WRAP CMAQ 2018 projections and PSAT source attribution that are the basis for WY’s reasonable 

progress analyses. Table 4.3-1 reports a 7% decrease in NOx emissions by 2018 from point sources. If a 

larger reduction is expected from BART, it would be helpful in Table 4.3-1 to separately list BART EGU, 

non-BART EGU, and industrial point. The majority of the NOx reductions projected for 2018 are due to 

reductions in the mobile onroad and nonroad sectors. The projected increase in NOx emissions from oil 

and gas (132%) indicates that NOx controls for oil and gas should be considered as part of reasonable 

progress analyses. 

In Section 5, WY cites WRAP CAMx-PSAT analyses of contributions to SO4 and NO3 from different source 

regions and CMAQ projections of 2018 progress. The inventories and models are subtly different so you 

are seeing subtle differences in the results. It would be helpful to make that clearer in the discussion on 

page 48. For example, how are SO2 emissions in WY different between the two sets of inventories? 

Only 2002pland and 2018PRPb are presented in section 4. Using CAMx-PSAT and 2002planc and 2018 

baseb emissions, Figures 5.2-1 through 5.2-3 indicate that SO4 mass does not change on 20% worst days 

between 2002 and 2018, despite SO2 reductions. Figures 5.2.1-1 through 5.2.1-3 also indicate slight 

increases in WY contributions to SO4 at the WY Class I areas in 2018 on the 20% worst days and slight 

increase in WRAP contributions to SO4 at Bridger. Using CMAQ and 2002pland and 2018PRPb 

emissions, Table 5.3.1-1 through 5.3.1-3 indicates the sulfate contributions to light extinction do 

decrease between 2002 and 2018. The differences in results are subtle but important if WY is citing 

these results to conclude that you do not need to consider SO2 reductions beyond those covered under 

the Section 309 SIP. 

Section 7: Reasonable Progress Goals:

Section 7.5 (p 123) indicates that WY Reasonable Progress Goals for 20% Worst Days and 20% Best Days 

for Wyoming Class I areas are based on primarily on results of WRAP CMAQ modeling for 2018. It would 

be helpful to make clear that RPGs listed in Table 7.5-1 are the results of WRAP 2018b modeling without 

any additional controls beyond WRAP 2018b modeling. 

WYs uses Q/d > 10 as an indicator of sources that should be considered for additional NOx controls for 

reasonable progress. Without more specific guidance from EPA, there is precedence that other states 
have used similar approach to screen sources. This criteria identifies only two units at Dave Johnson 

EGU, one unit at the Mountain Cement plant, and oil and gas exploration and productions. Highly cost 

effective NOx controls were identified in all cases. On page 125 item 4, WY indicates that significant 

reductions will be made from BART controls for coal fired power plants “as well as additional reductions 

committed to in the long term strategy.” Yet no additional NOx controls were included in WY’s long 

term strategy for controls by 2018. Rather in Section 8.3 WY suggests that it will evaluate additional 

controls by the 2013 review. WY needs to make stronger commitments for additional controls for these 

sources, particularly for oil and gas. Given the large increases in NOx emissions projected from oil and 

gas, WY needs to make a commitment to control future growth in emissions. 

WY asserts that uniform rate of progress will not be met because much of the contribution is from 

uncontrollable sources. We believe that WY should do more to adapt controls for reasonable progress 

where they are cost effective because WY is not meeting URP for sulfate and only barely meeting URP 

for nitrate, those pollutants which WY can control. 

Section 8.1.2.1: Class I areas affected by Wyoming Emissions

WY cites WRAP PSAT analyses that project WY’s contributions to SO4 and NO3 at Class I areas in 

neighboring states and cites consultation through the WRAP process.

WY’s long term strategy includes discussion of existing programs, including EPA discussions with Canada 

and Mexico over international emissions, existing WY control programs, natural events plan, measures 

to mitigate impacts from construction activities, and Smoke Management techniques. We ask that WY 

include in their discussion of New Source Review and Prevention of Significant Deterioration

requirements recognition of visibility improvement goals so that progress in reducing emissions from 

existing sources is not offset by growth in new sources. We already are seeing such an offset due to 

increased emissions from oil and gas activities.