# Technical Support Document for Determination that

the Cowtown Monitor is Ineligible for Comparison wi th

the Annual PM 2.5 

# NAAQS

**U.S. EPA Region 9**  **April 26, 2010**

# Cowtown and the Annual PM 2.5 

# NAAQS

**EPA has concluded that data from the PM 2.5**  

# monitor at the Cowtown monitoring station **(AQS ID: 04-021-3013) in Pinal County should not be compared to the annual PM**  **2.5** 

# NAAQS. **40 CFR 58.30(a) states that “(1) PM 2.5**  

# data that are representative, not of areawide but **rather, of relatively unique population-oriented mi croscale, or localized hot spot, or**  **unique population-oriented middle-scale impact site s are only eligible for comparison to**  **the 24-hour PM 2.5**  

# NAAQS” and “(2) There are cases where certain popu **lation- oriented microscale or middle scale PM**  **2.5** 

# monitoring sites are determined by the Regional **Administrator to collectively identify a larger reg ion of localized high ambient PM**  **2.5** 

# concentrations. In those cases, data from these pop **ulation-oriented sites would be eligible for comparison to the annual PM**  **2.5** 

# NAAQS.” **For example, if the PM 2.5**  

# monitoring site is adjacent to a unique dominating **local PM 2.5**  

# source or can be shown to have unique annual averag **e concentrations representative of a smaller than neighborhood spatial scale, then**  **data from a monitor at the site would only be eligible for comparison to the 24-hour PM**  **2.5** 

# NAAQS. **1** 

# However, if there are **potentially many such small scale impacts throughou t the monitoring region, then the**  **established monitoring site may be judged to be rep resentative of community-wide**  **exposure and eligible for comparison to the annual standard.**  **EPA has evaluated the comparability of data from th e Cowtown site to the annual PM**  **2.5** 

# standard on four criteria: the population oriented **monitoring, the spatial scale, localized hot spot conditions, and the uniqueness of the site** 
**,** Population-oriented monitoring: **40 CFR 58.1 states that “population-oriented monito ring (or sites) means**  **residential areas, commercial areas, recreational a reas, industrial areas where**  **workers from more than one company are located, and other areas where a**  **substantial number of people spend a significant fr action of their day”.** 
**There are four different feedlot facilities in the area: Sawyer Cattle Company, OK**  **Cattle Co., Maricopa Feedyard LLC, and Pinal Feedin g Co.**  **2,3** 

# Also, there is an **ethanol/ grain processing facility and a commercial composting facility located**  **nearby. The Cowtown site is representative of the c onditions that workers from**  **these various facilities may be exposed to and thus can be considered**  **“population-oriented.”The Pinal County 2009 annual network plan states that the**  **site’s type is “population/source impact”. This is an appropriate description of the** 

1 

# 40 CFR 58.30 (a) (1) **2** 

# Dun & Bradstreet Agricultural Data **3** 

# See Figure 1

# situation at hand and is consistent with EPA guidan **ce which states that “a site**

**may be population-oriented and at the same time be source oriented or reflective**  **of maximum concentration”. 4** 


# Spatial Scale: **The preamble to the 2006 monitoring regulations sta tes: “In practice, the majority**  **of PM 2.5**  

# monitors are deployed at neighborhood scale and lar **ger, meaning that they are located far enough from large emission sou**  **rces that they represent the fairly uniform air quality across an area with dime**  **nsions of at least a few kilometers and thus can be considered community ori**  **ented”. 5**  

# In addition, the **CFR states, specifically for PM 2.5**  

# , that a neighborhood scale site would represent **“conditions throughout some reasonably homogenous u rban sub-region with**  **dimensions of a few kilometers”. 6**  

# Based on available evidence, EPA believes **that the area of reasonably homogenous concentratio ns around this monitor is**  **considerable smaller than a few kilometers in diame ter or width. Moreover, the**  **area around the monitor, even extending out several kilometers, is definitely not**  **associated with community-wide exposure.**
**The Cowtown monitor is surrounded by agricultural f ields and cattle feedlots, and**  **does not represent the conditions expected in urban sub-regions or community**  **wide population PM 2.5**  

# exposure. Furthermore, the CFR gives an example o **f a neighborhood scale site: “such a site would likely**  **be located in a residential or commercial area having a high overall PM**  **2.5** 

# emission density but not in the **vicinity of any single dominant source”. 7**  

# The preamble also states “The EPA is **presently aware of fewer than ten PM 2.5**  

# monitors that are sited in relatively **unique population-oriented microscale areas, locali zed hot spots, or unique**  **population-oriented middle-scale areas. Such sites may have higher**  **concentrations than neighborhood scale sites on at least some days because**  **they may be close to and downwind of large emission sources, but the number of**  **people exposed to such concentrations is not large relative to the surrounding**  **communities”. 4**  

# It is very clear that the Cowtown monitor is locat **ed in the vicinity of a dominant source and does not meet this definit**  **ion of neighborhood scale and community-wide exposure.** 
**When determining the appropriate spatial scale for a particular site, the**  **homogeneity of the particulate matter concentration s, land use, and land surface**  **characteristics must also be considered. The Cowtow n site is located near a** 

4 

# Guidance **for Network Design and Optimum Site Exposure for PM 2.5**  

# and PM **10** 

# : EPA-454/R-99-022
5 

# 61264 Federal Register / Vol. 71, No. 200 / Tuesday **, October 17, 2006 / Rules and Regulations**
6 

# 40 CFR App. D 4.7.1 (c) (3) **7** 

# 40 CFR App. D 1.2 (d)

# number of cattle feedlots that have been shown, thr **ough chemical speciation 8**  

# , to

**contribute to elevated PM 2.5**  

# concentrations at the site. Analysis of wind and **pollution roses during exceedance days also shows t hat the Cowtown monitor is**  **significantly influenced by the cattle feedlots loc ated upwind. The majority of the**  **elevated concentrations occur during periods when t here are light winds (≤ 8**  **mph) from the South and Southeast. 9** 



# Due to the close proximity of a known source, the P **M 2.5**  

# concentrations measured **at the Cowtown site are higher in magnitude than su rrounding areas and do not**  **represent homogenous particulate concentrations in an area of a few**  **kilometers 10**  

# . In fact, modeling studies show that there are ver **y sharp gradients within several km of an emission sources.**  **11** 

# EPA guidance further explains that **“neighborhood scale monitors do not show significan t differences in particulate**  **concentrations with spacing of a few kilometers”. 12**  

# This suggests that a similar **monitor located a few kilometers away should experi ence the similar levels of**  **particulate matter. Again, due to the close proximi ty of a known source, it is**  **reasonable to assume that PM 2.5**  

# concentrations a few kilometers away may be **significantly different than those measured at the Cowtown site. Based on the**  **available information, the Cowtown monitor can be c onsidered to be**  **representative of an area smaller than a neighborho od spatial scale and does not**  **represent community-wide exposure. As stated in the Pinal County 2009 annual**  **network plan, the Cowtown monitor is representative of a microscale**  **environment.**
Localized Hot Spot: **The monitoring regulations have limited discussion about “hot-spots”. The term is**  **generally associated with areas of highest concentr ations whether it be from**  **mobile or multiple stationary sources. Microscale and middlescale monitors are**  **mentioned. 13**  

# For the purpose of this discussion, we will treat **hot-spot as synonymous with monitoring locations representing e**  **ither a micro or middlescale environment.** 
Uniqueness:
**PM 2.5**  

# concentrations recorded at this site are consistent **ly higher in magnitude than all surrounding sites in the county. Also, pre**  **liminary analysis shows that**

**8** 

# Pinal County Air Quality Control District Source A **pportionment Study: July 29, 2005 9**  

# See Figure 2 and Figure 3 **10** 

# See Figure 1 and 4 **11** 

# Brode, Review of TRC Comments on PM NAAQS (2006). 12 

# EPA-454/R-99-022
13 

# Federal Register / Vol. 71, No. 200 / Tuesday, Octo **ber 17, 2006 / Rules and Regulations**

# PM **2.5** 

# measurements at the Cowtown site are not correlated **to any other sites in**

**the area.**
**There are seven 14**  

# feedlots in Pinal County, and most are in the vici **nity of Cowtown. However, the Cowtown monitor may be repre**  **sentative of a relatively unique source of emissions. The monitor is immediat**  **ely downwind of the “Cowtown Complex” which consists of four different**  **cattle feedlot facilities: Sawyer Cattle Company, OK Cattle Co., Maricopa Feed**  **yard LLC, and Pinal Feeding Co**  **15** 

# . This accounts for a total of approximately 424 ac **res of feedlot facilities. Also, there is an ethanol/grain process**  **ing facility and a commercial composting facility located nearby. This source mix**  **represents a relatively unique situation in Pinal County.** 
**The remaining feedlots are located in the areas to both the East and West**  **Stanfield and South of Picacho Peak near the border of Pima County.**  **16** 

# The only **comparable situation to that of Cowtown is the “Red River Complex” west of**  **Stanfield, which has approximately 278 acres of fee dlot facilities that are in close**  **proximity to a number of dairies. This location may be considered different than**  **Cowtown: the feedlot sources are smaller and the ov erall source mix is**  **considerably different. Dairies have been shown to have lower PM**  **10** 

# emissions **than those of cattle feedlots. 17**  

# Also, the data show that the Stanfield PM **10** 

# monitor located approximately 4 km from the nearest **feedlot, records much lower PM**  **10** 

# concentrations: the 2006-2008 average PM **10** 

# expected exceedances at the **Cowtown station is approximately 10 times higher th an the Stanfield monitor.**  **18** 

# It **is reasonable to assume that this location also exp eriences lower PM**  **2.5** 

# concentrations than the Cowtown monitor. This is re **inforced by the Pinal County Source Apportionment Study that showed there was li**  **ttle contribution from the cattle feedlots at the Stanfield monitoring station**  **for both PM 10**  

# and PM **2.5** 

# . **19**



# The areas to the East of Stanfield and to the South **of Picacho Peak contain feedlots of much lesser size. The total areas of th**  **ese locations, the “Benedict Spread” and the “Red Rock Feedlot”, are approximate**  **ly 186 and 70 arces, respectively. While there are other feedlots within**  **Pinal County, it appears that the Cowtown monitor represents a relatively unique**  **monitoring location due to the size and composition of the nearby sources.** 

**14** 

# Pinal County Advanced Notice of Proposed Rule Maki **ng: April 9, 2009 15**  

# Dun & Bradstreet Agricultural Data **16** 

# See Figure 5 17 

# http://www.arb.ca.gov/ei/areasrc/arbmiscprocresfarm **op.htm 18**  

# 2009 Pinal County Annual Network Plan **19** 

# See Figure 6

# Conclusion

**40 CFR 58.30 – states that a “relatively unique pop ulation-oriented microscale, or**  **localized hot spot, or unique population-oriented m iddle-scale impact sites” is only**  **eligible for comparison to the 24-hour PM 2.5**  

# NAAQS, not the annual PM **2.5** 

# NAAQS. **Based on the analysis above, the Cowtown site shoul d be considered a relatively**  **unique, population-oriented, microscale site Furth ermore, the monitoring site is located**  **in close proximity to a “unique dominating local PM 2.5**  

# source” and is likely to have **“concentrations representative of a smaller than ne ighborhood spatial scale.”**  **Therefore, the PM 2.5**  

# data from the Cowtown site in Pinal County should n **ot be compared to the annual PM**  **2.5** 

# NAAQS.**Figure 1: PM 2.5** **Design Values #**  *****

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**C (** **50-Mile Buffer Mesa** **24-Hr DV: 17.6 Annual DV: 9.3** **Orange Grove 24-hr DV: 12.2** **Annual DV: 5.8 Children's Park** **24-hr DV: 11.9 Annual DV: 5.6** **South Phoenix 24-hr DV: 26.9** **Annual DV: 12 West Phoenix** **24-hr DV: 26.8 Annual DV: 11.6** **JLG Supersite 24-hr DV: 22** **Annual DV: 9.5 Casa Grande** **24-Hr DV: 19.9 Annual DV: 9.5** **Apache Junction 24-Hr DV: 13.1** **Annual DV: 6.6 Scottsdale** **24-Hr DV: 15.1 Annual DV: 7.7** Cowtown24-Hr DV: 47.8Annual DV: 21.6**296 37** **487 163** **67 429** **230 226** **201 118** **9 54** **47 45** **43 485** **482 461** **440 426** **418 410** **407 374** **341 333** **311 292** **285**Maricopa CountyPinal CountyPima CountyGila CountyLa Paz County**§  ̈** **¦**10**§  ̈** **¦**17**§  ̈** **¦**19**Emission Sources Within Fifty Miles of the Cowtown PM-2.5 Monitor** **AIR0901679_2 15 December 2009 Sources: NEI (2005), AQS (2009), TANA (2006), USGS** **(2006), ESRI (2006), Dunn and Bradstreet (2008)**



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**#** *****Feedlots Near Cowtown MonitorCowtown24-Hr DV: 47.8Annual DV: 21.6**! C** **( PM-2.5 Monitor Violating 2006 24-Hour Std** **! C** **PM-2.5 Monitor Attaining 2006 24-Hour Std #** *******Additional Cattle Operations (MFlagg) #** *******Feedlots #** *******Dairies Facilities Emitting > 1 TPY PM-2.5** **1 - 10 Tons Per Year 10.1 - 25 TPY** **25.1 - 50 TPY 50.1 - 100 TPY** **100.1 - 125 TPY City boundaries** **Res: 1 : 284550.498 High : 2786** **Low : 113 Numbers refer to corresponding OBJECTID record in E** **mitting_Facilites.xls** 

#  ̅**0 10 20 5 Miles** **Figure 2: Cowtown Pollution Rose 20** **Figure 3: Cowtown Wind Roses**20The different colors correspond to various levelsof PM2.5: Blue ≤ 30 μg/m3, Yellow 30-35 μg/m3, Red 35-40 μg/m3, and Black ≥ 40 μg/m3. Also, values meaured betweenOctober-April are shown as triangles, and values measured between May-September are shown as circles.**Figure 4: Spatial Scale Spatial Scale Surrounding Cowtown Monitor** **AIR0901679_4 30 December 2009 Sources: GlobeXplorer (April 1, 2008), Dunn and Bra** **dstreet (2008), Arizona State Land Department (Nov. 4, 2009)** 

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**C (** **50-Mile Buffer Mesa** **24-Hr DV: 17.6 Orange Grove** **24-Hr DV: 12.2 Children's Park** **24-Hr DV: 11.9 South Phoenix** **24-Hr DV: 26.9 West Phoenix** **24-Hr DV: 26.8 JLG Supersite** **24-Hr DV: 22 Casa Grande** **24-Hr DV: 19.9 Apache Junction** **24-Hr DV: 13.1 Scottsdale** **24-Hr DV: 15.1**Cowtown24-Hr DV: 47.8Maricopa CountyPinal CountyPima CountyGila CountyLa Paz County**Tohono O'Odham Gila River** **San Carlos Salt River** **Ak-Chin Fort McDowell** **White Mountain Tohono O'odham** Cluster 3Cluster 4Cluster 2Cluster 1**§  ̈** **¦**10**§  ̈** **¦**17**§  ̈** **¦**19**§  ̈** **¦**10**Cattle Operations Near Cowtown AIR0901679_5 12 January 2009** **Sources: NEI (2005), AQS (2009), TANA (2006), USGS (2006), ESRI (2006), Dunn and Bradstreet (2008)** 



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**#** *****Feedlots Near Cowtown MonitorCowtown24-Hr DV: 47.8**Cattle operations cluster boundaries !** **C (** **Violating PM-2.5 Monitor !** **C Active PM-2.5 Monitor** **#*********Additional Cattle Operations #** *******Feedlots #** *******Dairies Tribal Lands** **City boundaries 12,000+ feet** **~100 feet** 

#  ̅**0 10 20 5 Miles** **Figure 6: 2003 Speciation Results**