### Attachment A

The State of Wyoming 2008 8

- H our Ozone Infrastructure SIP

Element 110(a)(2)(D)(i)(I) Support DocumentsWDEQ

- AQD 2008 8

- H our Ozone Infrastructure SIP ( Attachment A )

December 2013

2 Attach ment A

Interstate and International Transport Provisions for the 2008 8

- H our Ozone NAAQS

The Wyoming Department of Environmental Quality

- Air Quality Division (AQD) has identified

nearby nonattainment areas from the U.S. Environmental Protection Agency’s (EPA’s) map of 8

- Hour Ozone Nonattainment Areas ( Figure 1 ) and evaluated the potential likelihood of impact

from emissions in Wyoming to those nonattainment areas. The only ozone nonattainment area

identified is the Denver

- Boulder

- Greeley

- Ft. Collins

- Loveland, Co lorado nonattainment area

( Denver NAA) . The Denver NAA is designated as “marginal” nonattainment for the 2008 8

-

hour ozone National Ambient Air Quality Standard ( NAAQS ) . A “marginal” rating is the least

significant rating of nonattainment possible.

Th e primary objective of the Cheyenne NCore Multi

- Pollutant Monitoring Project is to obtain

ambient air quality and meteorological data for the purposes of incorporating it into the EPA’s

National Core (NCore) Monitoring Network. NCore m onitoring methods an d strategies focus on

the deployment of instrumentation to target air pollutants originating from the Cheyenne area,

their concentrations, and their direction and extent of travel. As seen in Figure 2 , the Cheyenne

NCore ambient air and meteorological mon itoring station is centrally located in the city of

Cheyenne, W yoming in the extre me southeastern portion of the S tate . Cheyenne is also the

closest capital city in Wyoming with an approximate county

- wide population of 91,000 citizens

( Figure 3 ) within pr oximity to the Denver NAA that hosts an expansive approximate population

of 3 million ( Figure 3 ). The Denver NNA is located approximately 30 miles directly south of the

southeastern Wyoming border (Figures 4 and 5 )

.

Meteorological data collected along with air quality parameters at the Cheyenne NCore

monitoring station are used to better understand the local conditions and transport of air

pollutants. The 2011 annual and quarterly wind rose s produced for the Wyoming Air Quality

Monitoring Network Annua l Summary at the Cheyenne NCore Soccer Complex monitoring

station (Figures 6 and 7 ), and a composite wind rose from Cheyenne for the y ears 2006 through

2010 (Figure 8 )

, show that prevailing winds in Cheyenne, Wyoming come from the west,

northwest indicatin g that the transport of air pollutants is away from the Denver NAA.

The Che yenne NCore monitoring station became operational June 2010 , and provides two years

of ambient air quality data to assess . O zone data for the year 2011 and three (3) quarters of the

year 2012 gathered from the Cheyenne NCore station shows relativ ely low concentrations of

ozone, where no one (1) day in either year exceeded the 2008 8

- hour ozone NAAQS ( Table 1 )

. The combination of prevailing wind flow and low 8

- hour ozone concentr ation values indicate

that the Denver NAA is not, and has not been

, significantly influenced by the transport of ozone

and/or its precursors from Wyoming.

Other downwind, or potentially do wnwind S tates such as North Dakota, South Dakota , Nebraska

and Kan sas do not have any areas designated as nonattainment for the 2008 8

- hour ozone

standard. Based on this information, the State of Wyoming believes that ozone and ozone

precursor emissions from Wyoming do not contribute to nonattainment or interfere with

m aintenance of the 2008 8

- hour ozone NAAQS in another S tate.WDEQ

- AQD 2008 8

- H our Ozone Infrastructure SIP ( Attachment A )

December 2013

3 Figure 1.WDEQ

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December 2013

4 F igure 2

.WDEQ

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5 Figure 3.WDEQ

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6 Figure 4

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7 Figure 5

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8 Figure 6

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9 Figure 7

.WDEQ

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10 Figure 8

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11

Table 1. Cheyenne NCore Rolling 8

- H our Ozone Summary

NAAQS/WAAQS 1 Measured Value

2012

Jan. 1

– Sept. 30, 2012 2

Running 3 rd Quarter 75 ppb 3 Highest Daily Max: 73 ppb

4 th Highest Daily Max: 68 ppb

2011 Annual 75 ppb Highest Daily Max: 70 ppb

4 th Highest Daily Max: 67 ppb

1 National Ambient Air Quality Standards/Wyoming Ambient Air Quality Standards.

2 The 2012 4 th Quarter and Annual reports are being finalized and unavailable at this time.

3 To attain the O 3 standar d, the 3

- year average of the fourth

- highest daily maximum 8

- hour average O 3

concentrations must not exceed the standard.