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Summary of WRAP Policy

1. Pursuant to 40 CFR 51.309(d)(3), the WRAP directs its Technical Oversight Committee 

(TOC) to track emissions and to describe the tracking process in such a way that can be 

included in state and tribal implementation plans. At a minimum, using the most recent 

state emission inventories available, the TOC should produce a report for each five-year 

implementation plan revision on the current and projected emissions in the clean air 

corridor and in areas outside the corridor and compare these emissions to a 1996 baseline 

for purposes of this section.

2. Pursuant to 40 CFR 51.309(d)(3)(i), the WRAP identifies one clean air corridor as shown 

in Figure 1. For ease of administration, the corridor's boundary follows county lines.

3. Pursuant to 40 CFR 51.309(d)(3)(ii), the WRAP has examined patterns of growth in the 

corridor and finds that they are not causing significant emission increases that could have 

or are having visibility impacts at one or more of the 16 Class I areas. Nor, at this time, 

are such emission increases expected during the first planning period (2003-2018). 

Analyses performed by the Grand Canyon Visibility Transport Commission found that an 

increase of 25% in weighted emissions would result in a 0.7 dv reduction in visibility,

whereas the weighted emission increase expected by 2018 is only 4%.

4. Pursuant to 40 CFR 51.309(d)(3)(iii), the WRAP has examined emissions growth in areas 

outside the corridor and finds that significant emissions growth is not occurring that 

could begin or is beginning to impair the quality of the air in the corridor and thereby 

lead to visibility degradation for the least impaired days in one or more of the 16 Class I

areas.

5. Since impairment of air quality in clean air corridors has not been identified pursuant to 

40 CFR 51.309(d)(3)(ii) and (iii), the WRAP finds no requirement under 40 CFR 

51.309(d)(3)(iv) for further visibility impact analysis or additional emission reduction 

measures until at least the next SIP revision (2008). However, the WRAP encourages its 

appropriate technical activities - such as the Causes of Haze report - to take into account 

the assessment and protection of clean air corridors.

6. Pursuant to 40 CFR 51.309(d)(3)(v), the WRAP finds no other clean air corridors beyond 

the corridor identified in Figure 1.

Conclusion

While the area to the northwest of the Colorado Plateau delivers clean air to the Plateau on the 

cleanest days, emissions from throughout much of the region affect the Class I areas on the 

Plateau. Thus, emissions throughout the WRAP region will be tracked carefully. Ongoing 

WRAP efforts to improve the quality of inventories and the models used to make projections, 

and to produce a periodic Causes of Haze report, will bring increased understanding of the role 

that clean air corridors play in protecting the cleanest days. In the final analysis, the indicator of 

success or failure will be whether the measured light extinction at the Class I areas on the 
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Colorado Plateau improves or declines on the cleanest days. Any indication of deterioration on 

the cleanest days should trigger an immediate investigation of the cause, as well as efforts to 

correct the problem.