1 

EPA Technical Support Document in Review of Colorado Department of 

Public Health and Environment’s Demonstration Package for the 

 March 11, March 15, March 18, March 29, March 30, March 31, April 23, 

April 29, and November 10, 2014 Lamar Exceptional Events 

EXCEPTIONAL EVENTS RULE REQUIREMENTS 

The Environmental Protection Agency (EPA) promulgated the Exceptional Events Rule (EER) in 2007, 

pursuant to the 2005 amendment of Clean Air Act (CAA) Section 319. 42 U.S.C. §7619. The EER added 

40 CFR 50.1(j), (k) and (l); 50.14; and 51.930 to the Code of Federal Regulations (CFR). These sections 

contain definitions, criteria for EPA approval, procedural requirements, and requirements for air agency 

demonstrations, all of which must be met before EPA can concur under the EER on the exclusion of air 

quality data from regulatory decisions. 

Under 40 CFR 50.14(c)(3)(iv), the air agency demonstration to justify exclusion of data must provide 

evidence that: 

• The event satisfies the criteria set forth in 40 CFR 50.1(j) for the definition of an exceptional 

event; 

• The event affects air quality; 

• The event is not reasonably controllable or preventable; and 

• The event is caused by human activity that is unlikely to recur at a particular location or 

[is] a natural event.1

• There is a clear causal relationship between the measurement under consideration and the event 

that is claimed to have affected the air quality in the area; 

• The event is associated with a measured concentration in excess of normal historical fluctuations, 

including background; and 

• There would have been no exceedance or violation but for the event. 

This review applies the EPA’s “Interim Guidance of the Preparation of Demonstrations in Support of 

Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Exceptional Events 

Rule” of May 2013, (Interim Guidance for High Wind Exceptional Events) in addition to the applicable 

statutory and regulatory provisions. 

 

1

 A natural event is further described in 40 CFR 50.1(k) as “an event in which human activity plays little or no direct 

causal role”. 
2 

Table of Contents 

Summary ....................................................................................................................................................... 4 

March 11, 2014 ......................................................................................................................................... 6 

March 15, 2014......................................................................................................................................................7 

March 18, 2014......................................................................................................................................................9 

March 29, 2014....................................................................................................................................................11 

March 30, 2014....................................................................................................................................................13 

March 31, 2014....................................................................................................................................................16 

April 23, 2014.......................................................................................................................................................18 

April 29, 2014.......................................................................................................................................................20 

November 10, 2014.............................................................................................................................................22 

Not Reasonably Controllable or Preventable ............................................................................................ 25 

March 11, 2014 ....................................................................................................................................... 27

March 15, 2014....................................................................................................................................................28 

March 18, 2014....................................................................................................................................................29 

March 29, 2014....................................................................................................................................................30 

March 30, 2014....................................................................................................................................................31 

March 31, 2014....................................................................................................................................................32 

April 23, 2014.......................................................................................................................................................33 

April 29, 2014.......................................................................................................................................................34 

November 10, 2014.............................................................................................................................................35 

Historical Fluctuations ................................................................................................................................ 51 

March 11, 2014 ....................................................................................................................................... 51

March 15, 2014....................................................................................................................................................51 

March 18, 2014....................................................................................................................................................51 

March 29, 2014....................................................................................................................................................51 

March 30, 2014....................................................................................................................................................51 

March 31, 2014....................................................................................................................................................52 

April 23, 2014.......................................................................................................................................................52 

April 29, 2014.......................................................................................................................................................52 

November 10, 2014.............................................................................................................................................52 

Clear Causal Relationship ........................................................................................................................... 53 

March 11, 2014 ....................................................................................................................................... 54

March 15, 2014....................................................................................................................................................54 

March 18, 2014....................................................................................................................................................55 

March 29, 2014....................................................................................................................................................55 

March 30, 2014....................................................................................................................................................56 

March 31, 2014....................................................................................................................................................59 

April 23, 2014.......................................................................................................................................................62 
3 

April 29, 2014.......................................................................................................................................................64 

November 10, 2014.............................................................................................................................................65 

Affects Air Quality ...................................................................................................................................... 66 

Natural Event .............................................................................................................................................. 67 

No Exceedance But For the Event .............................................................................................................. 69 

Schedule and Procedural Requirements ................................................................................................... 70 

Conclusion .................................................................................................................................................. 71 
4 

SUMMARY 

Overview 

On May 7, 2015 the Colorado Department of Public Health and Environment (CDPHE) submitted a 

demonstration (termed a Technical Support Document or TSD) for exceptional event exceedances of the 

24-hour PM10 standard that occurred at the monitoring station in Lamar on March 11, March 15, March 

18, March 29, March 30, March 31, April 23, April 29, and November 10, 2014. Table 1 summarizes the 

exceedance that CDPHE would like considered for exceptional event concurrence in the Air Quality 

System (AQS) database. 

Table 1: EPA PM10 Exceedance Summary of the 150 ug/m3 24-hour NAAQS 

Exceedance Date Monitor/Site Name AQS ID 24-hour Avg. 

(ug/m3

) 

CDPHE Request 

to Consider for 

AQS Removal? 

March 11, 2014 Lamar Municipal 

Building 

08-99-0002 387 Yes 

March 15, 2014 Lamar Municipal 

Building

08-99-0002 173 Yes

March 18, 2014 Lamar Municipal 

Building

08-99-0002 299 Yes

March 29, 2014 Lamar Municipal 

Building

08-99-0002 263 Yes

March 30, 2014 Lamar Municipal 

Building

08-99-0002 264 Yes

March 31, 2014 Lamar Municipal 

Building

08-99-0002 223 Yes

April 23, 2014 Lamar Municipal 

Building

08-99-0002 350 Yes

April 29, 2014 Lamar Municipal 

Building

08-99-0002 321 Yes

November 10, 2014 Lamar Municipal 

Building

08-99-0002 298 Yes

Lamar sits at 3,645 feet and is in southeastern Colorado on the Arkansas River. South and southwest of

Lamar are the high, semi-arid plains of New Mexico, north Texas, and the Oklahoma panhandle. Further 

west and southwest of Lamar are the deserts of the New Mexico, Utah, and Arizona Four Corners region. 

The areas described are shown in Figures 1 and 2. 
5 

Figure 1: Map of Desert, Four Corners, and Monitor Location with the PM10 NAAQS Exceedances 

Figure 2: Map of High Plains and Monitor Location with the PM10 NAAQS Exceedances 
6 

March 11, 2014: 

The exceedance in Lamar was the result of intense surface winds in the wake of a passing cold 

front. These surface features were associated with a strong upper-level trough that was moving 

across the western United States. The surface winds were predominantly out of a north to 

northeasterly direction which moved over dry soils in eastern Colorado, producing significant 

blowing dust.2

EPA Figure 3 from CDPHE’s demonstration visually demonstrate the passing cold front over 

southeastern Colorado at 5:00 AM and Figure 4 shows it moving over northern Texas at 11:00 AM. 

Figure 1 through Figure 11 from CDPHE’s demonstration (not all included here) use modeling, 

meteorology, and monitoring analysis to support the evidence of wind direction and reach of the dust 

storm into Lamar. 

Figure 3: Cold Front Surface Analysis at 5 AM on March 11, 2014 (CDPHE’s TSD Figure 4)3

 

2

 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 14. 

3

Ibid., 18. 
7 

Figure 4: Cold Front Surface Analysis at 11 AM on March 11, 2014 (CDPHE’s TSD Figure 5)4

March 15, 2014: 

The exceedance in Lamar was the result of intense surface winds which were produced by a very 

strong upper-level trough that was moving across the western United States. The surface winds 

were predominantly out of a northerly direction which moved over dry soils in eastern Colorado, 

producing significant blowing dust.5 

EPA Figures 5 and 6 from CDPHE’s demonstration show an: 

“upper-level trough associated with this storm system is shown on the 700 mb and 500 mb height 

analysis maps at 5:00 AM MST, March 15, 2014... These two charts show that a deep trough of 

low pressure was present at both the 700 and 500 mb level just a few hours before the onset of the 

blowing dust event of March 15 and that it was moving over the southwestern United States. This 

is a typical upper-air pattern for blowing dust events in Colorado”6

 

Figure 12 through Figure 19 in CDPHE’s demonstration (not all included here) use modeling, 

meteorology, and monitoring analysis to support the evidence of wind direction and reach of the dust 

storm into Lamar. 

 

4

“TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 18. 

5

Ibid., 28. 

6

Ibid., 28
8 

Figure 5: 700 mb Upper Level Trough Storm System Analysis at on March 15, 2014 (CDPHE’s TSD 

Figure 13)7

 

7

“TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 29.
9 

Figure 6: 500 mb Upper Level Trough Storm System Analysis at on March 15, 2014 (CDPHE’s TSD 

Figure 14)8

March 18, 2014: 

The exceedance in Lamar was the result of intense surface winds which were produced by a very 

strong upper-level trough that was moving across the western United States. The surface winds 

were predominantly out of a north to northwesterly direction which moved over dry soils in 

eastern Colorado, producing significant blowing dust.9

EPA Figures 7 and 8 from CDPHE’s demonstration show an: 

“upper-level trough associated with this storm system is shown on the 700 mb and 500 mb height 

analysis maps at 5:00 AM MST, March 18, 2014 ... These two charts show that a deep trough of 

 

8

“TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 30.

9

Ibid., 37. 
10 

low pressure was present at both the 700 and 500 mb level at the onset of the blowing dust event 

of March 18, 2014, and that it was moving over the southwestern United States. This is a typical 

upper-air pattern for blowing dust events in Colorado”10 

Figure 20 through Figure 28 in CDPHE’s demonstration (not all included here) use modeling, 

meteorology, and monitoring analysis to support the evidence of wind direction and reach of the dust 

storm into Lamar. 

Figure 7: 700 mb Upper Level Trough Storm System Analysis at on March 18, 2014 (CDPHE’s TSD 

Figure 21)11

 

10 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 38.

11 Ibid., 39.
11 

Figure 8: 500 mb Upper Level Trough Storm System Analysis at on March 18, 2014 (CDPHE’s TSD 

Figure 22)12

March 29, 2014: 

The exceedance in Lamar was the result of intense surface winds which were produced by a 

strong upper-level trough that was moving across the western United States. The surface winds 

were predominantly out of a south to southwest direction which moved over dry soils in southeast 

Colorado, producing significant blowing dust.13

EPA Figures 9 and 10 from CDPHE’s demonstration show the upper-level trough associated with this 

storm system at 700 mb height analysis maps at 11:00 AM MST, March 29, 2014. Figure 9 shows “that a 

 

12 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 40.

13 Ibid., 48. 
12 

deep trough of low pressure was entering southeast Colorado at the onset of the blowing dust event of 

March 29. In advance of this upper-level trough was a band of high winds ranging from 25-35 kts (29-40

mph), including over Lamar and areas downwind (south to southwest).”14 While Figure 10 shows: 

“that relatively deep atmospheric mixing was occurring over southeast Colorado at the same time 

the 700 mb jet streak was overhead. Mixing of 2.5-3.5 km above mean sea level (MSL) over 

Lamar and areas upwind would have been sufficient to transfer momentum to the surface from 

the zone of strong winds that were present at 700 mb (about 3 km above MSL).”15

Figure 29 through Figure 37 in CDPHE’s demonstration (not all included here) use modeling, 

meteorology, and monitoring analysis to support the evidence of wind direction and reach of the dust 

storm into Lamar. 

Figure 9: 700 mb Upper Level Trough Storm System Low Pressure Analysis on March 29, 2014 

(CDPHE’s TSD Figure 30)16

 

 

14 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 48.

15 Ibid., 48. 

16 Ibid., 49.
13 

Figure 10: 700 mb Upper Level Trough Storm System Mixed Layer Analysis on March 29, 2014 

(CDPHE’s TSD Figure 31)17

March 30, 2014: 

The exceedance was the result of an intense upper-level trough producing strong winds in 

southeast Colorado which transported blowing dust into the Lamar area. The surface winds were 

predominantly out of a west to southwest direction which moved over dry soils in southeast 

Colorado, producing significant blowing dust.18

EPA Figures 11 and 12 from CDPHE’s demonstration show an upper-level trough associated with this 

storm system at 700 mb height analysis maps at 5:00 AM MST and 11:00 AM MST, March 30, 2014. 

These two figures show: 

“As the trough moved over southeast Colorado (Figure 41) during the late evening hours of 

March 30, the winds aloft at 700 mb intensified. Directly over Lamar the 700 mb wind speeds 

ranged from 50-60 knots (57-69 mph) at 11:00 PM MST. Mixing at this time had decreased 

significantly (Figure 42), but still ranged from 3-5 km above MSL over the Lamar area.”19 

 

17 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 49.

18 Ibid., 57. 

19 Ibid., 58.
14 

Figure 11: 700 mb Upper Level Trough Storm System Wind Speed Analysis at 5:00 PM on March 30, 

2014 (CDPHE’s TSD Figure 39)20

Figure 12: 700 mb Upper Level Trough Storm System Wind Speed Analysis at 11:00 PM on March 30, 

2014 (CDPHE’s TSD Figure 41)21

 

20 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 59.

21 Ibid., 60.
15 

EPA Figures 13 and 14 show: 

“that a deep trough of low pressure was entering southeast Colorado at the onset of the blowing 

dust event of March 30. In advance of this upper-level trough was a band of high winds ranging 

from 35-45 kts (40-52 mph), including over Lamar and areas upwind (west to southwest)...

Mixing at this time had decreased significantly (Figure 42), but still ranged from 3-5 km above 

MSL over the Lamar area. As stated in the previous paragraph, the 700 mb level is about 3 km 

above MSL. This indicates that atmospheric mixing at 11:00 PM MST was still sufficient to mix 

down the very strong winds that were occurring at the 700 mb level at that time.”22

Figure 38 through Figure 51 in CDPHE’s demonstration (not all included here) use modeling, 

meteorology, and monitoring analysis to support the evidence of wind direction and reach of the dust 

storm into Lamar. 

Figure 13: 700 mb Upper Level Trough Storm System Mixed Layer Analysis at 5:00 PM on March 30, 

2014 (CDPHE’s TSD Figure 40)23

 

22 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 58 

23 Ibid., 59.
16 

Figure 14: 700 mb Upper Level Trough Storm System Mixed Layer Analysis at 11:00 PM on March 30, 

2014 (CDPHE’s TSD Figure 42)24

March 31, 2014: 

The exceedance in Lamar was the result of intense surface winds in the wake of a passing cold 

front. These surface features were associated with a strong upper-level trough that was moving 

across southeast Colorado. A secondary cold front passage later in the day also likely contributed 

to the PM10 exceedance. The surface winds in Lamar were predominantly out of a west to 

northwesterly direction which moved over dry soils in eastern Colorado, producing significant 

blowing dust.25

EPA Figures 15 and 16 from CDPHE’s demonstration show an upper-level trough associated with this 

storm system at 700 mb height analysis maps at 11:00 PM MST, March 31, 2014. Figure 15 shows “that a 

deep trough of low pressure was moving over southeast Colorado at the onset of the blowing dust event 

of March 31. Directly over Lamar the 700 mb wind speeds ranged from 50-60 knots (57-69 mph).”26

While the Figure 16 shows: 

 

 

24 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 60.

25 Ibid., 75.

26 Ibid., 78.
17 

“The atmosphere at this time was still fairly unstable as evidenced from the height of the mixed 

level shown in Figure 56. Over the Lamar area, mixing ranged from 3-5 km above mean sea level 

(MSL). The 700 mb level is located roughly 3 kilometers above MSL, so it is reasonable to 

believe that mixing was deep enough at 11:00 PM MST to transfer momentum to the surface 

from the zone of strong winds that were present at 700 mb. Winds of the magnitude found at 700 

mb would have been well in excess of wind speeds that are known to cause blowing dust in 

southeast Colorado (30 mph sustained winds, 40 mph gusts).”27

Figure 52 through Figure 63 in CDPHE’s demonstration (not all included here) use modeling, 

meteorology, and monitoring analysis to support the evidence of wind direction and reach of the dust 

storm into Lamar. 

Figure 15: 700 mb Upper Level Trough Storm System Low Pressure Analysis on March 31, 2014 

(CDPHE’s TSD Figure 55)28

 

27 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 78. 

28 Ibid., 78.
18 

Figure 16: 700 mb Upper Level Trough Storm System Mixed Layer Analysis on March 31, 2014 

(CDPHE’s TSD Figure 56)29

April 23, 2014: 

The exceedance in Lamar was the result of intense surface winds in the wake of a passing cold 

front. These surface features were associated with a strong upper-level trough that was moving 

across the western United States. Post-frontal thunderstorms with strong outflow winds may also 

have had a significant contribution to PM10 concentrations. The surface winds in Lamar were 

predominantly out of a north to northeasterly direction which moved over dry soils in eastern 

Colorado, producing significant blowing dust.30

EPA Figures 17 and 18 from CDPHE’s demonstration show that: 

The upper-level trough associated with this storm system is shown on the 700 mb and 500 mb 

height analysis maps at 5:00 PM MST, April 23, 2014 in Figure 65 and Figure 66, respectively. 

The 700 mb level is located roughly 3 kilometers above mean sea level (MSL) while the 500 mb 

level is approximately 6 kilometers above MSL. These two charts show that a deep trough of low 

pressure was present at both the 700 and 500 mb level at the onset of the blowing dust event of 

 

29 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 79.

30 Ibid., 89. 
19 

April 23 and that it was moving over the southwestern United States. This is a typical upper-air 

pattern for blowing dust events in Colorado.31

Figure 64 through Figure 75 in CDPHE’s demonstration (not all included here) use modeling, 

meteorology, and monitoring analysis to support the evidence of wind direction and reach of the dust 

storm into Lamar. 

Figure 17: 700 mb Upper Level Trough Storm System Analysis at on April 23, 2014 (CDPHE’s TSD 

Figure 65)32

 

31 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 90.

32 Ibid., 91.
20 

Figure 18: 500 mb Upper Level Trough Storm System Analysis at on April 23, 2014 (CDPHE’s TSD 

Figure 66)33

April 29, 2014: 

The exceedance in Lamar was the result of intense surface winds which were produced by a very 

strong upper-level trough that was moving across the central United States. The surface winds 

were predominantly out of a north to northwesterly direction which moved over dry soils in 

eastern Colorado, producing significant blowing dust.34

 

33 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 92.

34 Ibid., 103. 
21 

EPA Figures 19 and 20 from CDPHE’s demonstration show that: 

Eastern Colorado was on the western side of this slow moving, upper-level low where the winds 

were exceptionally strong. The North American Regional Reanalysis (NARR) 700 mb height 

analysis map of eastern Colorado shown in Figure 78 reveals that wind speeds over Lamar and 

upwind (north) ranged from 60-90 kts (69-103 mph) at 5:00 AM MST, April 29, 2014. By 

viewing Figure 79 we can see that relatively deep atmospheric mixing was occurring over eastern 

Colorado at the same time the 700 mb jet streak was overhead. Mixing of 3-5 km above MSL 

over Lamar and areas upwind would have been sufficient to transfer momentum to the surface 

from the zone of extremely strong winds that were present at 700 mb (about 3 km above MSL).35

Figure 76 through Figure 86 in CDPHE’s demonstration (not all included here) use modeling, 

meteorology, and monitoring analysis to support the evidence of wind direction and reach of the dust 

storm into Lamar. 

Figure 19: 700 mb Upper Level Trough Storm System Wind Speed Analysis at 5:00 AM on April 29, 

2014 (CDPHE’s TSD Figure 78)36

 

35 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 104.

36 Ibid., 105.
22 

Figure 20: 700 mb Upper Level Trough Storm System Mixed Layer Analysis on April 29, 2014 

(CDPHE’s TSD Figure 79)37

November 10, 2014: 

The exceedance in Lamar was the result of intense surface winds in the wake of a passing cold 

front. These surface features were associated with a strong upper-level trough that was moving 

across the western United States. The surface winds were predominantly out of a north to 

northeasterly direction which moved over dry soils in eastern Colorado, producing significant 

blowing dust.38

EPA Figures 21 and 22 from CDPHE’s demonstration show that: 

The upper-level trough associated with this storm system is shown on the 700 mb and 500 mb 

height analysis maps at 5:00 AM MST, November 10, 2014 in Figure 88 and Figure 89, 

respectively. The 700 mb level is located roughly 3 kilometers above mean sea level (MSL) while 

the 500 mb level is approximately 6 kilometers above MSL. These two charts show that a deep 

trough of low pressure was present at both the 700 and 500 mb level just a few hours before the 

 

37 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 105.

38 Ibid., 116. 
23 

blowing dust event of November 10, 2014, and that it was moving over the western United States. 

This is a typical upper-air pattern for blowing dust events in Colorado.39

Figure 87 through Figure 96 in CDPHE’s demonstration (not all included here) use modeling, 

meteorology, and monitoring analysis to support the evidence of wind direction and reach of the dust 

storm into Lamar. 

Figure 21: 700 mb Upper Level Trough Storm System Analysis at on November 10, 2014 (CDPHE’s 

TSD Figure 88)40

 

39 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 117.

40 Ibid., 117.
24 

Figure 22: 500 mb Upper Level Trough Storm System Analysis at on November 10, 2014 (CDPHE’s 

TSD Figure 89)41

CDPHE provides a comprehensive description and discussion of these events in Sections 2, 3, 4, and 5 of 

the demonstration. 

 

 

41 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 118.
25 

Not Reasonably Controllable or Preventable 

EPA evaluates whether an event was not Reasonably Controllable or Preventable (nRCP) at the time of 

the event by taking into account controls in place and wind speed, along with other factors. For natural 

sources of dust, a high wind dust event can generally be considered to be nRCP if winds are high enough 

to cause emissions from natural undisturbed areas. For anthropogenic sources of dust, a high wind dust 

event can be nRCP if: 

• The anthropogenic sources of dust have reasonable controls in place; 

• The reasonable controls have been effectively implemented and enforced; and, 

• The wind speed was high enough to overwhelm the reasonable controls.42 

In addressing reasonable controls, CDPHE provided detailed information on the current set of required 

and voluntary controls in the Lamar area, including information on implementation of State Regulations

1, 3, 6, and 9, rule effectiveness, compliance, and public notification activities that occurred on the event 

days. As CDPHE states: 

The APCD conducted thorough analyses and outreach with local governments to confirm that no 

unusual anthropogenic PM10-producing activities occurred in these areas and that despite 

reasonable control measures in place, high wind conditions overwhelmed all reasonably available 

controls... This information shall confirm that no unusual anthropogenic actions occurred in the 

local areas of Lamar during this time.43

CDPHE’s demonstration provides an analysis of the state and local controls in place to control PM10 

emissions. Although specifically focusing on Regulations 1, 3 and 6, these controls include CDPHE’s: 

• Regulation 1- Emission Control for Particulate Matter, Smoke, Carbon Monoxide, and Sulfur 

Oxides; 

• Regulation 3- Stationary Source Permitting and Air Pollutant Emission Notice Requirements; 

• Regulation 4- New Wood Stoves and the Use of Certain Woodburning Appliances During High 

Pollution Days; 

• Regulation 6- Standards of Performance for New Stationary Sources; and 

• Regulation 9- Open Burning, Prescribed Fire, and Permitting.44

CDPHE provided the documentation summarized in EPA Table 1, and displayed EPA Tables 2-10 

(CDPHE Tables 23-32) showing that sustained wind speeds associated with these events were above 30 

mph and gusts were above 40 mph. In fact the wind speeds for the events averaged 40 mph and the gusts 

averaged to 51.33 mph. CDPHE previously established in its exceptional events demonstration for the 

January 19, 2009 event in Lamar, Colorado that wind speeds of 30 mph and/or gusts of 40 mph or higher 

have been shown to cause blowing dust in Colorado.45 EPA Region 8 concurred with this analysis and 

accepts this as a legitimate threshold for evaluating blowing dust events in Colorado. The sustained winds 

 

42 “Interim Guidance on the Preparation of Demonstrations in Support of Requests to Exclude Ambient Air Quality 

Data Affected by High Winds Under the Exceptional Events Rule,” May 2013, page 10. 

43 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 182. 

44 Ibid., 182-184. 

45 “TSD for the January 19, 2009 Lamar Exceptional Event,” November 22, 2011. 
26 

and gusts in Lamar in 2014 exceed this Colorado threshold. Transported dust from the upwind desert and

arid plains regions appears to be a significant contribution to the exceedance, in addition to local winds 

overwhelming implemented local controls. EPA notes that the high local gust speeds in Lamar would 

likely be capable of overwhelming some local controls. Section 5 of the TSD provided by CDPHE 

supports this conclusion by describing in detail “Best Available Control Measures (BACM), other 

reasonable control measures, applicable federal, state, and local regulations, appropriate land use 

management, and an in-depth analysis of potential areas of local soil disturbance for Lamar during the

2014 events.”46

Table 1: Wind and Gust Highest Measured Speeds by Exceedance Date 

Exceedance Date Wind Speed in MPH Wind Gust in MPH 

March 11, 2014 39 48 

March 15, 2014 40 53 

March 18, 2014 43 52 

March 29, 2014 30 39 

March 30, 2014 33 48 

March 31, 2014 39 47 

April 23, 2014 45 59 

April 29, 2014 48 63 

November 10, 2014 43 53 

 

 

46 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 182.
27 

Table 2: Wind Speed Lamar, CO on March 11, 2014 (CDPHE’s TSD Table 1)47

 

47 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 20.
28 

Table 3: Wind Speed Lamar, CO on March 15, 2014 (CDPHE’s TSD Table 5)48

 

48 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 32.
29 

Table 4: Wind Speed Lamar, CO on March 18, 2014 (CDPHE’s TSD Table 7)49

 

49 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 42.
30 

Table 5: Wind Speed Lamar, CO on March 29, 2014 (CDPHE’s TSD Table 9)50

 

50 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 52.
31 

Table 6: Wind Speed Lamar, CO on March 30, 2014 (CDPHE’s TSD Table 10)51, 52

 

51 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 63.

52 Higher wind speed upwind of the Lamar meteorological monitor were contributing to regional aerosol haze 

covering all of Utah, northern Arizona, northern New Mexico, and over half of Colorado during the late afternoon 

prior to high winds reaching Lamar later in the evening, according to Naval Advanced Aerosol Prediction System 

Total Optical Depth Analysis for 5:00 PM and 11:00 PM on March 30, 2014. 
32 

Table 7: Wind Speed Lamar, CO on March 31, 2014 (CDPHE’s TSD Table 16)53

 

53 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 81.
33 

Table 8: Wind Speed Lamar, CO on April 23, 2014 (CDPHE’s TSD Table 18)54

 

54 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 98.
34 

Table 9: Wind Speed Lamar, CO on April 29, 2014 (CDPHE’s TSD Table 20)55

 

55 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 109.
35 

Table 10: Wind Speed Lamar, CO on November 10, 2014 (CDPHE’s TSD Table 23)56

 

56 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 121.
36 

Section 2 of CDPHE’s demonstration provides a complex meteorological analysis of the event, including: 

• Statewide PM10 monitoring maps; 

• Surface and upper air wind speed analysis from the National Oceanic and Atmospheric 

Administration (NOAA); 

• North American Regional Reanalysis (NARR) jet stream maximum winds; 

• Maps of real-time weather data from the National Center for Atmospheric Research (NCAR); 

• Regional wind and weather by hour, as well as wind direction, through MesoWest; 

• MODIS Terra satellite images demonstrating the blowing dust across the region; 

• Naval Advanced Aerosol Prediction System (NAAPS) forecasted dust concentrations; and 

• Maps establishing the lack of regional precipitation and drought status from U.S. Department of 

Agriculture (USDA), NOAA, and the National Drought Mitigation Center. 

These analyses demonstrate persuasively through the weight of evidence the existence of high wind 

blowing dust events originating far from the monitor in question. 

Lamar has the following controls in place:57

• A Natural Events Action Plan (NEAP) for High Wind Events completed in 2003, and updated in 

2012, which addresses public education, notification, and health advisory systems as well as 

implements Best Available Control Measures (BACM)58; 

• A PM10 Maintenance plan for the Lamar Attainment/Maintenance Area effective since Nov. 25, 

2005 with provisions for Prevention of Significant Deterioration (PSD) permitting requiring Best 

Available Control Technology (BACT) 59; 

• State Implementation Plan (SIP) measures requiring owners/operators responsible for 

construction and/or maintenance of existing or new unpaved roadway with traffic of over 200 

vehicles per day to stabilize the road to prevent fugitive dust (see Colorado Regulation 1); 

• City of Lamar BACM measures include: planting a wind-break of trees with drip-irrigation to 

control dust from the Lamar Transfer Station, establishing landfill controls such as opacity limits 

at 20%, fugitive dust at no more than 5.77 tons per year, and immediately shutting down the 

landfill when winds exceed 35 mph (per the “Operations and Closure Plan for the East Lamar 

Landfill” section 3.5.1, among other listed landfill controls.60 Other BACM include installing 

100,000 ft2

 of turf sod and irrigation at recreational open space Escondido Park, and fencing off 

and stabilizing lots that formerly contributed to fugitive dust; 

• Other measures include: Art. XVII, Sec. 16-17-60 requiring off street parking lots to be swept, 

The Prowers County Land Use plan adopted in 2004 and amended in 2006- through it the county 

has authority over “construction, siting, health, fire, environmental codes, and other social 

concerns with provisions to minimize airborne dust”61; 

 

57 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 184-188. 

58 Ibid., 184-185 and at: 

http://www.colorado.gov/airquality/tech_doc_repository.aspx?action=open&file=LamarNaturalEventsActionPlan 

2012.pdf.

59 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, 185. 

60 Ibid., 185-186. 

61 Ibid., 187-188. 
37 

• Non-enforceable measures include: 

o The Colorado State University CO-OP Extension Office efforts underway to encourage 

no- or low-till practices, outreach and education on soil management programs, and 

drought workshops to protect topsoil; 

o Voluntary and State-Only measures including weekly street sweeping and a city policy 

requirement that new developments have paved streets; 

o The Limestone-Graveyard Creeks Watershed Project which reduces soil erosion from 

60,000 acres along the Arkansas River, 2,000 of which are near Lamar. 99% of the 

60,000 acres now have a conservation plan and are enacting improvements created by 

each farmer/owner with costs of conservation improvements split with the government. 

o NRCS is promoting: a rangeland management program, a tree planting program, a drip 

irrigation purchase program, a multi-party drought response effort through the State of 

Colorado Governor’s office, and a program to incentivize erosion mitigation.62

• The United States Department of Agriculture (USDA) Natural Resources Conservation Service 

(NRCS) Conservation Reserve Program (CRP) includes conservation provisions in the Farm Bill 

which encourages farmers to contract with USDA to “place erodible cropland and other 

environmentally-sensitive land into long-term conservation practices for 10-15 years”63 in 

exchange for annual rental payments and cost-share assistance from the government. This 

mitigation strategy is a convincing argument for the existence of reasonable controls in place in 

the agricultural areas surrounding Lamar. Table 11 shows amounts of cropland under contract in 

surrounding counties in the years preceding the events. Figure 23 shows the location of these 

southeast Colorado counties relative to Lamar. Cheyenne and Kiowa counties are generally 

upwind of Lamar on days with winds from the north, while Otero, Bent, Las Animas and Baca, 

along with the bulk of Prowers county are upwind from Lamar when winds are from the south or 

southwest. 

Table 11: Acres by County near Lamar Enrolled in the USDA NRCS CRP Program64

 

COUNTY 2008 2009 2010 2011 2012 2013 

Bent 25,649 25,700 24,056 24,412 33,886 23,566 

Kiowa 216,307 217,881 187,394 192,222 177,100 181,169 

Baca 260,040 258,469 161,147 274,281 277,508 264,071 

Crowley 21,419 21,461 21,069 20,329 21,917 18,490 

Otero 2,559 2,864 2,706 2,851 2,054 2,635 

Las Animas 21,869 21,860 17,403 17,616 18,925 18,887 

Cheyenne 142,075 140,071 94,852 113,753 122,862 99,074 

Lincoln 155,505 155,425 137,099 145,248 118,948 116,289 

Prowers 170,909 171,813 140,827 163,354 154,882 151,731 

Total 1,016,333 1,015,544 786,554 954,066 928,082 875,912 

 

62 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 218-220.

63 Ibid., 219. 

64 Data for the USDA NRCS CRP program were provided as supplementary information per EPA request on April

17, 2014 by Ray Mohr of CDPHE.
38 

Figure 23: Southeast Colorado Counties 

• Vegetation, signage, and/or other dust control measures are in place for undeveloped parcels of 

land in Lamar. Figures 24-32 below show that identified areas of soil disturbance have reasonable 

controls near the Lamar monitor. 65

 

o Site A is owned by Heath & Son & Turpin Trucking and HVH Transportation Inc., a 

large truck repair and freight service trucking company, respectively. It is a wellmaintained gravel lot; 

 

65 “The APCD considers restricted vehicle speeds, maintained gravel, natural vegetation, restricted access, 

pavement, compaction, re-vegetation, watering, and extraction limitation to be the appropriate available and 

practical method that is technologically feasible and economically reasonable in order to minimize fugitive 

particulate emissions for these sites.” “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, pages 191-218.
39 

o Site B is a fenced watered-as-needed gravel lot shared by Prowers Area Transit and the 

defunct Cowboy Corral Storage, feed supply, and grain storage companies. The transit 

company is on a concrete slab connecting to an asphalt road; 

o Site C is owned by Heath & Son & Turpin Trucking and is a well-maintained gravel lot 

used for truck storage; 

o Site D is the Lamar Water Department and Lamar-Prowers County Volunteer Fire 

Department and is a restricted access site of grated (sic) and watered gravel on an asneeded basis; 

o Site E is the power plant that hosts the monitor and is a restricted access lot owned by 

Lamar Light and Power. It has been a gas fired boiler, natural gas power plant, and coalfired boiler until being shut down in November 2011. It was permitted under CDPHE 

permit #05PR0027 with the following dust control measures: high efficiency baghouses, 

water wash-down systems for all surfaces to prevent dust re-entrainment, all roads were 

paved and inspected daily and cleaned as needed while under the 1 ton per year APEN 

exemption, transfer locations were enclosed, and the emergency coal stockpile controlled 

through a water-dust suppression system; 

o Site F is the Burlington Northern Santa Fe railroad and is covered in gravel 50 feet on 

either side of the tracks, surrounded by natural vegetation with xeriscape; 

o Site G is Colorado Mills LLC sunflower oil and feed processing facility operating under 

CDPHE permit #95PR622. Permit conditions include 30% maximum opacity limit, PM 

limits, and an Operation and Maintenance Plan. The last inspection on 2/14/12 found no 

visible emissions, and in-house monthly inspections and the use of cyclones for emission 

control demonstrate PM mitigation efforts; 

o Site H is partially owned by Century Link and is a fenced gravel lot with restricted 

access. The remainder of the site is a free chip-sealed crushed-gravel parking lot for 

Prowers County Jail and the Prowers County Municipal Court that is maintained by the 

county; 

o Site I is owned by Prowers County and leased to the Colorado State Highway Patrol for 

office space. The lot is covered in gravel for dust suppression, drainage, and erosion 

control. Lot has restricted access and a 5 mph speed limit; 

o Site J is owned by Ranco, a heavy duty construction trailer manufacturer. The property is 

covered in pavement, gravel, and natural vegetation, with no unnatural, disturbed areas 

that may have contributed to blowing dust; 

o Site K is owned by Valley glass and the property has restricted access to a well 

maintained gravel lot; 

 
40 

Figure 24: Lamar Site Assessment (CDPHE’s TSD Figure 143)66

o Site L is owned by All-Rite Paving and Redi-Mix Inc. and is a concrete batch plant 

permitted by CDPHE (#12PR1396). The facility is considered APEN exempt and emits 

less than 1 ton per year of PM10.”67 Baghouse collection efficiency is 99%, there is a 20% 

opacity limit, and water sprays and magnesium chloride are used on storage piles and 

roads as needed. There is a 10 mph speed limit, transfer of materials occurs in enclosed 

areas, and the lot is fenced; 

o Site M is mined by Carder Inc. for sand and gravel and emits no more than 15 tons per 

year under CDPHE permit #99PR0180F. It is a wet mining operation to prevent fugitive 

dust, and uses the following preventative measures: watering as needed, re-vegetation 

within one year of disturbance, compacting piles, 10 mph speed limit, and temporary 

roads are graveled and watered as needed; 

o Site N is restricted access property that is naturally vegetated and undisturbed; 

 

66 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 191.
41 

o Site O was mined by All-Rite Paving and Redi-Mix Inc. and was a concrete batch plant 

permitted by CDPHE. Baghouse collection efficiency was 99%, there was a 20% opacity 

limit, and water sprays and magnesium chloride were used on storage piles and roads as 

needed. There was a 10 mph speed limit, transfer of materials occurred in enclosed areas, 

and the lot was fenced.68 Partnering with the Division of Wildlife, the City of Lamar took 

over the lot in 2013 and has been reseeding it to create a fishing and wildlife park free of 

motorized vehicles.; 

o Site P is owned by the Ranchers Supply Co. Inc. and is a fenced 90% gravel lot for longterm oversize vehicle parking. It has a 10 mph policy, is watered as-needed, and meets 

Air Quality Control Commission (AQCC) Regulation 1 requirements (Section 

III.D.1(a)); 

o Site Q is owned by Ranco, a heavy duty construction trailer manufacturer. The property 

is covered in pavement, gravel, and natural vegetation, with no unnatural, disturbed areas 

that may have contributed to blowing dust (duplicate of site J above); 

o Site R is C.F. Mailer Composites Inc. and is a paved parking lot and surrounding natural 

vegetation with a short, maintained gravel road to a loading dock used once a day; 

o Site S is owned by Prowers County and leased to the Colorado State Highway Patrol for 

office space. The lot is covered in gravel for dust suppression, drainage, and erosion 

control. Lot has restricted access and a 5 mph speed limit (duplicate of site I above); 

o Site T is Lamar Feed and Grain – White Stone Farms, CDPHE permit #00PR0431. On 

the property is a grain receiving pit, shipping truck loadout station, grain storage, grain 

cleaning scalper, and grain handling and milling systems. The permit includes dust 

control measures: Total PM, PM10 and PM 2.5 annual emissions limitations, visible 

emissions not to exceed 20%, All equipment maintained consistent with good air 

pollution control practices, and the feed mill equipped with a mineral oil spray system to 

control PM emissions; 

o Site U was Dragon EPS beginning in 1993, but merged in 2011 with Ranco (site Q and J 

above). CPDHE permit #08PR0603 issued 12/21/11 covers paint booths and abrasive 

blasting units with the following PM controls: Permitted annual TSP, PM10 and PM 2.5

emission limits, High Volume Low Pressure paint spray guns, exhaust filters on paint 

spray booths, baghouse filters on blasting units, visible emissions not to exceed 20%, 

source must follow CPDHE operations and maintenance plan. It was last inspected on 

11/9/11 and found to be in compliance; 

o Site V is a restricted access property that is naturally vegetated and appears to be 

undisturbed; 

o Site Y is a group of rotating crop fields, with a schedule to allow some fields to lay 

fallow between plantings; 

 

 
42 

Figure 25: Lamar Site Assessment (CDPHE’s TSD Figure 152)69

o Site W is the Robins Redi-Mix Concrete Batch Plant which opened in spring of 2010 and 

consists of a dry truck mix plant using a cement and a dry ash silo operated with 

pneumatic conveyers and bag houses to control 98% of emissions. In April 2010 CDPHE 

issued a permit exempt letter (10PR1310.XP) with includes PM point and fugitive dust 

control measures such as: Uncontrolled PM cannot exceed 10 TPY and uncontrolled 

PM10 cannot exceed 5 TPY, and visible emissions cannot exceed 20%. The source waters 

the lot during processing and as-needed, uses CDPHE Best Available Technology 

(BACT) for limestone and ash handling, paving, wash-down systems, and enclosures; 

 

69 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 199.
43 

Figure 26: Lamar Site Assessment (CDPHE’s TSD Figure 158)70

o Site AA is Parkview Elementary School with a well maintained gravel playground with a 

fence restricting vehicle access, all surrounded by trees to mitigate blowing dust; 

o Site BB is large parking lot for downtown businesses. It is mostly paved, with a small 

section covered in weeds (as opposed to bare dirt); 

o Site CC is an undeveloped lot with a traffic barricade to prevent cars driving on it. It is 

vegetated with weeds and grasses; 

o Site DD is a paved parking lot and therefore not a source for PM10; 

 

70 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 205.
44 

Figure 27: Lamar Site Assessment (CDPHE’s TSD Figure 160)71

o Site GG is County Acres RV Park. The park is well maintained gravel with recycled 

blacktop added to help with dust suppression; 

o Site HH is Lamar Community College’s Equine Complex. It is a well maintained and 

fenced property to restrict access; 

o Site II is the Lamar Ball Complex. It is fenced to limit access, covered in rotomilling 

(ground up asphalt) and pea gravel to help with dust control. It is owned by the City of 

Lamar, and the city drags the parking lots and applies water as needed for dust control. 

The rest of the property are grass fields and turf; 

o Site JJ is the Prowers County Fairgrounds. It is maintained by the county, grated 

annually, and watered frequently, especially during the high use season of April to 

September; 

o Site KK is restricted access property that is naturally vegetated and undisturbed; 

 

71 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 207.
45 

Figure 28: Lamar Site Assessment (CDPHE’s TSD Figure 164)72

o Site LL is the Prowers County – Walker Pit North sand and gravel production facility. It 

was issued a CDPHE permit exemption letter (09PR0038F.XP) on 7/6/10 with the 

following fugitive dust control measures: Comply with the developed dust control plan 

and Comply with production rate limit. The last inspection by CDPHE was on 3/29/14 

and found to be in compliance. Previously produced areas have been re-vegetated and the 

area is posted with a No Trespassing sign; 

 

72 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 209.
46 

Figure 29: Lamar Site Assessment (CDPHE’s TSD Figure 167)73

o Site MM is Washington Elementary School. It has a gravel playground and restricted 

access by a surrounding fence; 

 

73 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 212.
47 

Figure 30: Lamar Site Assessment (CDPHE’s TSD Figure 170)74

o Site NN is a metal recycling, welding, and custom fabrication business named Out West 

Equipment Co., Inc. and Lamar Scrap Salvage. The 3 acre lot is mostly gravel, and is 

watered on an as-needed basis; 

o Site OO is naturally vegetated, undisturbed land; 

o Site PP is restricted access property that is naturally vegetated and undisturbed; 

o Site QQ is restricted access, naturally vegetated, and undisturbed; and, 

 

74 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 214.
48 

Figure 31: Lamar Site Assessment (CDPHE’s TSD Figure 172)75

\ 

o Site RR is owned by Carder, Inc. and mined as a Hard Scrabble Pit for sand and gravel 

for road construction. It operates under CDPHE permit # 99PR0179FR and emits 8 TPY 

of PM10. It is a wet mining operation to control fugitive dust using the following control 

measures: watering disturbed areas as needed, re-vegetation within one year of 

disturbance, compacting of piles, mining moist materials, 10 mph speed limit, and 

temporary roads covered in gravel and watered as needed. 

 

75 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 215.
49 

Figure 32: Lamar Site Assessment (CDPHE’s TSD Figure 176)76

According to CDPHE’s TSD: 

The APCD conducted thorough assessments to determine if the potential soil disturbances shown 

in Figure 142 through Figure 176 [EPA Figures 24 through 32] were present during the 2014 

exceedances in Lamar. During the course of these assessments, the APCD discovered that these 

sites were either reasonably controlled or considered to be natural sources during the 2014 high 

wind events. Therefore, these sites were not significant contributors to fugitive dust in the Lamar 

area during the 2014 high wind events.77

Sections 2 and 5 of CDPHE’s demonstration show that the monitor in Lamar was affected by PM10

transport from outside the area, with the main source areas located in agricultural areas in Colorado, to the 

southwest in northwestern New Mexico, or to the north, including areas in Wyoming and Nebraska. In 

addition to transport, the spatial extent of elevated PM10 concentrations throughout southern Colorado and 

the wind speeds associated with the event factor into EPA’s evaluation of whether this event is nRCP in 

Lamar. Therefore, the EPA concludes that this event was nRCP pursuant to the Treatment of Data 

Influenced by the EER. Table 12 summarizes the EPA’s evaluation of CDPHE’s nRCP EE 

demonstration. 

 

76 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 217.

77 Ibid., 218.
50 

Table 12: EPA’s Analysis of CDPHE’s TSD of nRCP 

Exceedance 

Date 

Location Reasonable 

Controls 

Demonstration 

Citation

Wind Speed 

Demonstration 

Citation

Sufficient 

Quality of 

Evidence?

EPA 

Criterion 

Met?

March 11, 

2014 

Lamar Municipal 

Building 

Section 5: p. 182-

220 

Section 2: p. 14-27 Yes Yes 

March 15, 

2014 

Lamar Municipal 

Building

Section 5: p. 182-

220

Section 2: p. 28-37 Yes Yes 

March 18, 

2014 

Lamar Municipal 

Building

Section 5: p. 182-

220

Section 2: p. 38-47 Yes Yes 

March 29, 

2014 

Lamar Municipal 

Building

Section 5: p. 182-

220

Section 2: p. 48-57 Yes Yes 

March 30, 

2014 

Lamar Municipal 

Building

Section 5: p. 182-

220

Section 2: p. 58-75 Yes Yes 

March 31, 

2014 

Lamar Municipal 

Building

Section 5: p. 182-

220

Section 2: p. 76-89 Yes Yes 

April 23, 

2014 

Lamar Municipal 

Building

Section 5: p. 182-

220

Section 2: p. 90-102 Yes Yes 

April 29, 

2014 

Lamar Municipal 

Building

Section 5: p. 182-

220

Section 2: p. 103-115 Yes Yes 

November 

10, 2014 

Lamar Municipal 

Building

Section 5: p. 182-

220

Section 2: p. 116-128 Yes Yes 

 
51 

Historical Fluctuations 

EPA evaluates whether a measured exceedance is in excess of Historical Fluctuation (HF) by taking into

account the level of the exceedance in relation to historical data, which is typically 3 to 5 years. 

To demonstrate that this requirement was met, CDPHE provided a statistical analysis of the 2014 24-hour 

average data, 6-year time series of 24-hour averages for the years of 2008-2014, and monthly data 

showing that all readings greater than 100 μg/m3 might be considered statistical outliers. The 2014 data 

set had 1,997 samples, and each description below indicates the samples taken on these days clearly 

exceed the typical samples for this site. CDPHE explains that for the concentration measured on March 

11, 2014: 

The PM10 sample on March 11, 2014, at Lamar Municipal of 387 μg/m3 exceeds the 99th 

percentile value for all evaluation criteria and is the 3rd largest sample of the dataset and the 

largest sample in any March. Both samples greater than the event sample are associated with high 

wind events.78

 

CDPHE explains that for the concentration measured on March 15, 2014: 

The PM10 sample on March 15, 2014, at Lamar Municipal of 173 μg/m3 exceeds the 99th 

percentile value for all evaluation criteria and is the 14th largest sample of the dataset. All 

thirteen samples greater than the event sample are associated with high wind events.79

CDPHE explains that for the concentration measured on March 18, 2014: 

The PM10 sample on March 18, 2014, at Lamar Municipal of 299 μg/m3

 exceeds the 99th 

percentile value for all evaluation criteria and is the 6th largest sample of the dataset. The five 

samples greater than the event sample are associated with high wind events.80

CDPHE explains that for the concentration measured on March 29, 2014: 

The PM10 sample on March 29, 2014, at Lamar Municipal of 263 μg/m3 exceeds the 99th 

percentile value for all evaluation criteria and is the 8th largest sample of the dataset. The seven 

samples greater than the event sample are associated with high wind events.81

CDPHE explains that for the concentration measured on March 30, 2014: 

The PM10 sample on March 30, 2014, at Lamar Municipal of 264 μg/m3

 exceeds the 99th 

percentile value for all evaluation criteria and is the 7th largest sample of all samples from 2009 

 

78 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 129.

79 Ibid., 134.

80 Ibid., 139.

81 Ibid., 144.
52 

through August, 2014. All six samples greater than the event sample are associated with high 

wind events.82

CDPHE explains that for the concentration measured on March 31, 2014: 

The PM10 sample on March 31, 2014, at Lamar Municipal of 223 μg/m3

 exceeds the 99th 

percentile value for all evaluation criteria and is the 10th largest sample of the dataset. The nine 

samples greater than the event sample are associated with high wind events.83

CDPHE explains that for the concentration measured on April 23, 2014: 

The PM10 sample on April 23, 2014, at Lamar Municipal of 350 μg/m3 exceeds the 99th 

percentile value for all evaluation criteria and is the 4th largest sample of the dataset. The three 

samples greater than the event sample are associated with high wind events.84

CDPHE explains that for the concentration measured on April 29, 2014: 

The PM10 sample on April 29, 2014, at Lamar Municipal of 321 μg/m3 exceeds the 99th 

percentile value for all evaluation criteria and is the 5th largest sample of the dataset. The four 

samples greater than the event sample are associated with high wind events.85

CDPHE explains that for the concentration measured on November 10, 2014: 

The PM10 sample on November 10, 2014, at Lamar Municipal of 298 μg/m3

 exceeds the 99th 

percentile value for all evaluation criteria and is the 7th largest sample of the dataset. The six 

samples greater than the event sample are associated with high wind events.86

The EPA “Interim Guidance on High Wind Exceptional Events” recommends that demonstrations also 

consider percentile ranks when dust impacted data is excluded.87 CDPHE States that the percentile rank 

for these areas is 99% and above for the monitor in question on all nine days in question. 

Included with this TSD is an enclosure which analyzes drought conditions in the Lamar area from 1897-

2015, and associates the trends with high wind blowing dust events. It is titled Analysis of Lamar Drought 

Condition Severity and Blowing Dust: 1897-2015. The review finds some correlation between prolonged

drought (as defined by 7-year annual average) and blowing dust conditions in Lamar. The enclosure is at 

the end of this document. 

Since at least 2005 in these areas, values exceeding the 24-hour PM10 NAAQS are only found during high 

wind dust events, including those in 2014. This information indicates that values at the level seen during 

 

82 Ibid., 149.

83 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 154.

84 Ibid., 159.

85 Ibid., 164.

86 Ibid., 169.

87 See “Interim Guidance on the Preparation of Demonstrations in Support of Requests to Exclude Ambient Air 

Quality Data Affected by High Winds Under the Exceptional Events Rule” of May 2013, page 20.
53 

2014 are extremely rare in the absence of high wind dust exceptional event impacts, and that it is unlikely 

that any sources of PM10 were involved in the 2014 exceedances other than wind-blown dust. Therefore, 

the EPA concludes that this event was in excess of HF pursuant to the Treatment of Data Influenced by 

the EER. Table 13 summarizes the EPA’s evaluation of CDPHE’s HF EE demonstration. 

Table 13: EPA’s Analysis of CDPHE’s TSD of HF 

Exceedance 

Date 

Exceedance 

Location 

Historical Fluctuations 

Demonstration Citation 

Sufficient 

Quality of 

Evidence? 

EPA Criterion 

Met? 

March 11, 

2014 

Lamar Municipal 

Building 

Section 3: p. 129-134 Yes Yes 

March 15, 

2014 

Lamar Municipal 

Building 

Section 3: p. 134-139 Yes Yes 

March 18, 

2014 

Lamar Municipal 

Building 

Section 3: p. 139-144 Yes Yes 

March 29, 

2014 

Lamar Municipal 

Building 

Section 3: p. 144-149 Yes Yes 

March 30, 

2014 

Lamar Municipal 

Building 

Section 3: p. 149-154 Yes Yes 

March 31, 

2014 

Lamar Municipal 

Building 

Section 3: p. 154-159 Yes Yes 

April 23, 2014 Lamar Municipal 

Building 

Section 3: p. 159-164 Yes Yes 

April 29, 2014 Lamar Municipal 

Building 

Section 3: p. 164-169 Yes Yes 

November 10, 

2014 

Lamar Municipal 

Building 

Section 3: p. 169-174 Yes Yes 

Clear Causal Relationship 

EPA considers a variety of evidence when evaluating whether there is a Clear Causal Relationship (CCR)

between the measurement under consideration and the event that is claimed to have affected the air 

quality in the area. Demonstrations should include documentation showing that the event in fact occurred 

and that emissions related to the event were transported in the direction of the monitor(s) where 

measurements were recorded; the size of the area affected by the transported emissions; the relationship 

in time between the event, transport of emissions, and recorded concentrations; and, as appropriate, 

pollutant species-specific information supporting a CCR between the event and the measured 

concentration.88

 

Section 2 of CDPHE’s demonstration provides analyses from NOAA’s National Weather Service (NWS) 

that demonstrate the existence of high wind blowing dust events originating far southwest or far north of 

the monitors in question, but including southern Colorado’s contribution: 

 

88 See “Interim Guidance on the Preparation of Demonstrations in Support of Requests to Exclude Ambient Air 

Quality Data Affected by High Winds Under the Exceptional Events Rule” of May 2013, pages 21-22. 
54 

March 11, 2014: 

The National Oceanic and Atmospheric Administration (NOAA) Satellite Services Division was 

in agreement with the conclusion that blowing dust was occurring in southeast Colorado. The 

Smoke Text Product from NOAA at 11:00 AM MST on March 11, 2014 stated: 

“Several large plumes of blowing dust/sand were observed over southeast Colorado and 

far western Kansas moving to the south towards the Oklahoma Panhandle.” (Source: 

http://www.ssd.noaa.gov/PS/FIRE/DATA/SMOKE/2014/2014C111803.html) 

Additionally, the Pueblo office of the National Weather Service and the Colorado Department of 

Public Health and Environment issued Blowing Dust Advisories for southeast Colorado in 

anticipation of the blowing dust event of March 11, 2014. Text from these advisories includes: 

“Visibilities...will drop to less than 1 mile at times due to blowing dust...particularly 

down wind of plowed fields or in areas where vegetation growth has been limited by long 

term drought and soils remain loose.” (Source: http://mesonet.agron.iastate.edu/wx/afos/) 

“People with heart or lung disease, older adults, and children in the affected area should 

reduce prolonged or heavy indoor and outdoor exertion.” (Source: 

http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=03%2f11%2f2014)89

March 15, 2014: 

The National Oceanic and Atmospheric Administration (NOAA) Satellite Services Division was 

in agreement with the conclusion that blowing dust was occurring in southeast Colorado. The 

Smoke Text Product from NOAA at 5:45 PM MST on March 15, 2014 stated: 

“Strong northerly winds are kicking up dust/sand and loose soils across much of SE 

Colorado south of US40 in Lincoln and Cheyenne counties where individual narrow N-S 

bands/plumes consolidated and became moderately to dense sand strom (sic) across E 

Animas and Baca counties before moving into NM, Texas county OK and far NW 

portions of the TX panhandle as far south as I-40 in Quay county.” (Source: 

http://www.ssd.noaa.gov/PS/FIRE/DATA/SMOKE/2014/2014C160051.html) 

Additionally, both the Pueblo office of the National Weather Service and the Colorado 

Department of Public Health and Environment issued Blowing Dust Advisories for southeast 

Colorado in anticipation of the blowing dust event of March 15, 2014. Text from these advisories 

includes: 

“A few areas may see visibility near zero in and around exposed fields.” (Source: 

http://mesonet.agron.iastate.edu/wx/afos/) 

“People with heart or lung disease, older adults, and children in the affected area should 

reduce prolonged or heavy indoor and outdoor exertion.” (Source: 

http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=03%2f15%2f2014)90

 

89 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 24.

90 Ibid., 34.
55 

March 18, 2014: 

The National Oceanic and Atmospheric Administration (NOAA) Satellite Services Division was 

in agreement with the conclusion that blowing dust was occurring in southeast Colorado. The 

Smoke Text Product from NOAA at 9:45 AM MST on March 18, 2014 stated: 

“A fairly large area of dust, partially obscured by clouds, was seen moving southsoutheast across southeastern Colorado and extreme southwestern Kansas.” (Source: 

http://www.ssd.noaa.gov/PS/FIRE/DATA/SMOKE/2014/2014C181714.html) 

Additionally, the Pueblo office of the National Weather Service issued a Dust Storm Warning for 

southeast Colorado while the Colorado Department of Public Health and Environment issued a 

Blowing Dust Advisory in anticipation of the blowing dust event of March 18, 2014. Text from 

these advisories includes: 

“Significant amounts of blowing dust will likely occur which will reduce visibility to 

around 1⁄4 mile throughout the day.” (Source: http://mesonet.agron.iastate.edu/wx/afos/) 

“People with heart or lung disease, older adults, and children in the affected area should 

reduce prolonged or heavy indoor and outdoor exertion.” (Source: 

http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=03%2f18%2f2014)91

March 29, 2014: 

The blowing dust of March 29, 2014 was not only observed, but also anticipated. The Navy 

Aerosol Analysis and Prediction System (NAAPS) accurately forecast that blowing dust would be 

an issue in southeast Colorado during the late morning and afternoon hours. Figure 35 [EPA 

Figure 33] shows the output from this model covering the time period from 18Z (11:00 AM 

MST), March 29 to 0Z (5:00 PM MST, March 29), March 30. The NAAPS system models 

blowing dust emissions and transport based on soil moisture content, soil erodibility factors and a 

variety of meteorological factors known to be conducive to blowing dust.92 The forecast panel in 

the upper left of Figure 35 [EPA Figure 33] clearly shows above normal Total Optical Depth 

values attributed to dust over southeast Colorado. 

Additionally, the Colorado Department of Public Health and Environment (CDPHE) was alerted 

to blowing dust on March 29, 2014 and consequently issued a Blowing Dust Advisory for most of 

southeast Colorado. Text from that advisory includes: 

“Strong gusty winds will bring a threat for blowing dust to portions of southeastern 

Colorado.” and, “People with heart or lung disease, older adults, and children in the 

affected area should reduce prolonged or heavy indoor and outdoor exertion.” (Source: 

http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=03%2f29%2f2014)93

The NAAPS system models blowing dust emissions and transport based on soil moisture content, soil 

erodibility factors and a variety of meteorological factors known to be conducive to blowing dust. The

forecast panel in the lower left of Figure 34 shows an area of highly elevated surface dust concentrations 

over much of New Mexico, and the optical depth panel on the upper left shows dust continuing over 

 

91 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 44.

92 For a description of NAAPS see: http://www.nrlmry.navy.mil/aerosol_web/Docs/globaer_model.html

93 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 53.
56 

southeastern Colorado into Kansas. This model output suggests that this drought-stricken region was a 

major source region for blowing dust on March 29, 2014 in Lamar. 

Figure 34: National NAAPS Analysis for March 29, 2014 (CDPHE’s TSD Figure 35)94 

March 30, 2014: 

The blowing dust of March 30, 2014 was not only observed, but also anticipated. The Navy 

Aerosol Analysis and Prediction System (NAAPS) accurately forecast that blowing dust would be 

an issue in southeast Colorado during the afternoon and evening hours. Figure 48 [EPA Figure 

34] shows the output from this model covering the time period from 18Z (11:00 AM MST), 

 

94 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 55.
57 

March 30 to 0Z (5:00 PM MST, March 30), March 31 while Figure 49 shows the same model for 

the time period of 0Z (5:00 PM MST, March 30), March 31 to 6Z (11:00 PM MST, March 30), 

March 31. The NAAPS system models blowing dust emissions and transport based on soil 

moisture content, soil erodibility factors and a variety of meteorological factors known to be 

conducive to blowing dust... The forecast panels in the upper left quadrant of both EPA Figures 

34 and 35 [CDPHE Figures 48 and 49] clearly show Total Optical Depth values increasing in 

southeast Colorado to above normal levels. The green and yellow shading indicates that those 

enhanced values are attributed to dust. 

Additionally, the Colorado Department of Public Health and Environment (CDPHE) was alerted 

to blowing dust on March 30, 2014 and consequently issued a Blowing Dust Advisory for most of 

southeast Colorado. Text from that advisory includes: 

“Strong gusty winds will bring a threat for blowing dust to portions of southwestern, 

southern and southeastern Colorado.” and, “People with heart or lung disease, older 

adults, and children in the affected area should reduce prolonged or heavy indoor and 

outdoor exertion.” (Source: 

http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=03%2f30%2f2014).

95

The NAAPS system models blowing dust emissions and transport based on soil moisture content, soil 

erodibility factors and a variety of meteorological factors known to be conducive to blowing dust. The

forecast panel in the lower left of Figures 35 and 36 shows an area of highly elevated surface dust 

concentrations over Utah, Arizona, New Mexico, Colorado, Texas, and Kansas (and continuing northeast) 

and the optical depth panel on the upper left of Figures 32 and 33 show dust at 5 pm over Utah, Arizona, 

New Mexico, Colorado, and Texas, moving by 11 PM towards Kansas, Nebraska, and Wyoming. This 

model output suggests that this drought-stricken region was a major source region for blowing dust on 

March 30, 2014 in Lamar. 

 

95 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 67.
58 

Figure 35: National NAAPS Analysis for 5 PM March 30, 2014 (CDPHE’s TSD Figure 48)96

 

 

96 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 72.
59 

Figure 36: National NAAPS Analysis for 11 PM March 30, 2014 (CDPHE’s TSD Figure 49)97

 

March 31, 2014: 

The blowing dust of March 31, 2014 was not only observed, but also anticipated. The Navy 

Aerosol Analysis and Prediction System (NAAPS) accurately forecast that blowing dust would be 

an issue in southeast Colorado during the morning hours of March 31. Figure 60 [EPA Figure 36] 

shows the output from this model covering the time period from 6Z (11:00 PM MST, March 30), 

March 31 to 12Z (5:00 AM MST), March 31 while Figure 61 [EPA Figure 37] shows the same 

model for the time period of 12Z (5:00 AM MST), March 31 to 18Z (11:00 AM MST), March 31. 

 

97 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 73.
60 

The NAAPS system models blowing dust emissions and transport based on soil moisture content, 

soil erodibility factors and a variety of meteorological factors known to be conducive to blowing 

dust. The forecast panels in the upper left of both Figure 60 and Figure 61 [EPA Figures 36 and 

37] clearly show Total Optical Depth values in southeast Colorado above normal levels. The 

green and yellow shading indicates that those enhanced values are attributed to dust. 

Additionally, the Colorado Department of Public Health and Environment (CDPHE) was alerted 

to the threat for blowing dust on March 31, 2014 and consequently issued a Blowing Dust 

Advisory for most of southeast Colorado, including the Lamar area. Text from that advisory 

included: 

“Strong gusty winds will bring a threat for blowing dust to large portions of eastern 

Colorado.” and, “People with heart or lung disease, older adults, and children in the

affected area should reduce prolonged or heavy indoor and outdoor exertion.” (Source: 

http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=03%2f31%2f2014).

98

The NAAPS system models blowing dust emissions and transport based on soil moisture content, soil 

erodibility factors and a variety of meteorological factors known to be conducive to blowing dust. The

optical depth panel on the upper left of Figures 37 and 38 show dust at 5 AM over Arizona, New Mexico,

Colorado, Texas, Oklahoma, Kansas, Nebraska, and Wyoming, and then moving northwest by 11 AM. 

 This model output suggests that this drought-stricken region was a major source region for blowing dust 

on March 31, 2014 in Lamar. 

Figure 37: National NAAPS Analysis for 5 AM March 31, 2014 (CDPHE’s TSD Figure 60)99

 

 

98 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, pages 85-86.

99 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 86.
61 

Figure 38: National NAAPS Analysis for 11 AM March 31, 2014 (CDPHE’s TSD Figure 61)100

 

 

100 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 87.
62 

April 23, 2014: 

Radar imagery provides strong supporting evidence that a regional dust storm was taking place on 

April 23, 2014. The Pueblo radar image at 6:14 PM MST, April 23 (Figure 72) [EPA Figure 38] 

shows a suspected line of dust (circled in red) approaching Lamar and La Junta from the north. 

This band of blowing dust was likely produced by several factors; including the cold front 

passage described earlier combined with strong outflow winds from post-frontal thunderstorms 

which were impacting northeast Colorado. Figure 73 [EPA Figure 40] displays the 1-km radar 

mosaic from the central Rockies at 4:25 PM MST and shows one particularly intense 

thunderstorm in northeast Colorado (circled in red) with discernible areas of outflow visible to its 

south (green arrow). These areas of outflow would continue to move southward and remained 

intact nearly two hours later in Figure 72 [EPA Figure 39]. Also note that the radar return from 
63 

Figure 72 [EPA Figure 39] has a distinct bow echo pattern which is often associated with strong, 

sometimes damaging, winds that spread outward from the bottom of storms.101

Figure 39: National NAAPS Analysis for 11 AM March 31, 2014 (CDPHE’s TSD Figure 72)102

 

Figure 40: National NAAPS Analysis for 11 AM March 31, 2014 (CDPHE’s TSD Figure 73)103

 

 

101 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 100.

102 Ibid., 101.

103 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 101.
64 

April 29, 2014: 

The National Oceanic and Atmospheric Administration (NOAA) Satellite Services Division was 

in agreement with the conclusion that blowing dust was occurring in eastern Colorado. The 

Smoke Text Product from NOAA at 7:00 PM MST on April 29, 2014 stated: 

“An expansive area of dust is moving from the central plains south into the Texas 

Panhandle this evening. Through sunset, the dust is seen reaching from eastern Colorado 

down through central Texas.” (Source: 

http://www.ssd.noaa.gov/PS/FIRE/DATA/SMOKE/2014/2014D300316.html) 

Additionally, the Pueblo office of the National Weather Service issued a Dust Storm Warning for 

southeast Colorado while the Colorado Department of Public Health and Environment issued a 

Blowing Dust Advisory in anticipation of the blowing dust event of April 29, 2014. Text from 

these advisories includes: 

“Wrap around north flow around a deep storm system over the upper Midwest will 

produce high winds and widespread blowing dust through this afternoon.” (Source: 

http://mesonet.agron.iastate.edu/wx/afos/) 

“Extremely gusty winds will produce areas of blowing dust to portions of eastern 

Colorado for much of Tuesday.” (Source: 
65 

http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=04%2f29%2f2014)

104

November 10, 2014: 

The National Oceanic and Atmospheric Administration (NOAA) Satellite Services Division and 

the National Weather Service (NWS) office in Pueblo were in agreement with the conclusion that 

blowing dust was occurring in southeast Colorado. The Smoke Text Product from NOAA at 7:45 

PM MST on November 10, 2014 stated: 

“There is a large and significant area of blowing dust that can be seen moving towards 

the south/southeast across southeastern Colorado and into northeastern New Mexico.” 

(Source: http://www.ssd.noaa.gov/PS/FIRE/DATA/SMOKE/2014/2014K110313.html) 

While the NWS Forecast Discussion at 3:50 PM MST stated: 

“Arctic front came through the eastern plains this afternoon...in typical fashion...ahead of 

schedule. 50-60 mph N to NE wind gusts along and behind FROPA...with blowing dust.” 

(Source: http://mesonet.agron.iastate.edu/wx/afos/) 

Additionally, the Colorado Department of Public Health and Environment (CDPHE) issued a 

Blowing Dust Advisory for southeast Colorado, including Lamar, at 1:00 PM MST. Included in 

the advisory text: 

“Strong gusty winds with a cold front will create areas of blowing dust through Monday 

evening.” (Source: 

http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=11%2f10%2f2014)

105

CDPHE generally summarizes that: 

The PM10 exceedances in Lamar would not have occurred if not for the following: (a) dry soil 

conditions over source regions with 30-day precipitation totals below the threshold identified as a 

precondition for blowing dust; and (b) meteorological conditions that caused strong surface winds 

over the area of concern. Surface weather observations provide strong evidence that dust storms 

took place on March 11, 2014, March 15, 2014, March 18, 2014, March 29, 2014, March 30, 

2014, March 31, 2014, April 23, 2014, April 29, 2014, and November 10, 2014. The 

meteorological conditions during these events in 2014 caused regional surface winds over 30 mph 

with gusts exceeding 40 mph. These speeds are above the thresholds for blowing dust identified 

in EPA draft guidance and in detailed analyses completed by the State of Colorado.106

EPA concludes that there was a CCR for these events pursuant to the Treatment of Data Influenced by the 

EER. Table 14 summarizes the EPA’s evaluation of CDPHE’s CCR EE demonstration. 

 

104 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 112.

105 Ibid., 125.

106 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 221.
66 

Table 14: EPA’s Analysis of CDPHE’s TSD of CCR107

Exceedance Date Clear Causal Relationship 

Demonstration Citation 

Sufficient Quality 

of Evidence? 

EPA Criterion 

Met? 

March 11, 2014 Section 2: p. 24 Yes Yes 

March 15, 2014 Section 2: p. 34 Yes Yes 

 March 18, 2014 Section 2: p. 44 Yes Yes 

March 29, 2014 Section 2: p. 53-55 Yes Yes 

March 30, 2014 Section 2: p. 69-73 Yes Yes 

March 31, 2014 Section 2: p. 85-87 Yes Yes 

April 23, 2014 Section 2: p.100-101 Yes Yes 

April 29, 2014 Section 2: p. 112 Yes Yes 

November 10, 2014 Section 2: p. 125 Yes Yes 

Affects Air Quality (AAQ) 

As stated in EPA’s Interim Guidance for High Wind Exceptional Events Section 3.4, EPA will consider 

events to have affected air quality if the CCR and HF requirements have been adequately demonstrated. 

The information presented in the HF and CCR demonstrations on the preceding three pages of this 

(EPA’s) TSD are cited in Table 15. Additionally, CDPHE states that: 

Since at least 2005, there has not been an exceedance that was not associated with high winds 

carrying PM10 dust from distant sources in these areas. This is evidence that the events were 

associated with a measured concentration in excess of normal historical fluctuations including 

background.

108

Therefore, the EPA concludes that this event Affected Air Quality pursuant to the Treatment of Data 

Influenced by high wind under the EER. Table 15 summarizes the EPA’s evaluation of CDPHE’s AAQ 

EE demonstration. 

 

107 See “Interim Guidance on the Preparation of Demonstrations in Support of Requests to Exclude Ambient Air 

Quality Data Affected by High Winds Under the Exceptional Events Rule” of May 2013 page 21.

108 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 221.
67 

Table 15: EPA’s Analysis of CDPHE’s TSD of AAQ 

Exceedance 

Date 

HF and 

CCR 

Affects Air Quality 

Demonstration Citation 

Sufficient 

Quality of 

Evidence 

EPA 

Criterion 

Met? 

March 11, 

2014 

HF Section 3: p. 129-134 Yes Yes

CCR Section 2: p. 24 Yes Yes

March 15, 

2014 

HF Section 3: p. 134-139 Yes Yes

CCR Section 2: p. 34 Yes Yes

March 18, 

2014 

HF Section 3: p. 139-144 Yes Yes

CCR Section 2: p. 44 Yes Yes

March 29, 

2014 

HF Section 3: p. 144-149 Yes Yes

CCR Section 2: p. 53-55 Yes Yes

March 30, 

2014 

HF Section 3: p. 149-154 Yes Yes

CCR Section 2: p. 69-73 Yes Yes

March 31, 

2014 

HF Section 3: p. 154-159 Yes Yes

CCR Section 2: p. 85-87 Yes Yes

April 23, 

2014 

HF Section 3: p. 159-164 Yes Yes

CCR Section 2: p.100-101 Yes Yes

April 29, 

2014 

HF Section 3: p. 164-169 Yes Yes

CCR Section 2: p. 112 Yes Yes

November 

10, 2014 

HF Section 3: p. 169-174 Yes Yes

CCR Section 2: p. 125 Yes Yes

Natural Event 

As stated in EPA’s Interim Guidance for High Wind Exceptional Events Section 6.3.6, EPA will consider 

an event to be a natural event if both the nRCP and CCR requirements have been adequately 

demonstrated. CDPHE states that:
68 

Due to the semi-arid nature of parts of the state, Colorado is highly susceptible to windblown dust 

events. These events are often captured by various air quality monitoring equipment throughout 

the state, sometimes resulting in exceedances or violations of the 24-hour PM10 NAAQS. This 

document contains detailed information about the large regional windblown dust events that 

occurred in 2013. The Colorado Department of Public Health and Environment (CDPHE) Air 

Pollution Control Division (APCD) has prepared this report for the U.S. Environmental 

Protection Agency (EPA) to demonstrate that the elevated PM10 concentrations recorded in 2014 

in Lamar, Colorado, were caused by natural events.

109

CDPHE has sufficiently demonstrated the CCR and nRCP requirements for the 2014 events. Therefore, 

the EPA concludes that these were natural events pursuant to the Treatment of Data Influenced by high 

winds under the EER. Table 16 summarizes the EPA’s evaluation of CDPHE’s Natural Event EE 

demonstration. 

Table 16: EPA’s Analysis of CDPHE’s TSD of Natural Event 

Exceedance 

Date 

nRCP or CCR Natural Event Demonstration 

Citation 

Sufficient 

Quality of 

Evidence?

EPA 

Criterion 

Met? 

March 11, 

2014 

nRCP- Anthropogenic Section 5: p. 182-220 Yes Yes 

nRCP-Wind Speed Section 2: p. 14-27 Yes Yes 

CCR Section 2: p. 24 Yes Yes 

March 15, 

2014 

nRCP- Anthropogenic Section 5: p. 182-220 Yes Yes 

nRCP-Wind Speed Section 2: p. 28-37 Yes Yes 

CCR Section 2: p. 34 Yes Yes 

March 18, 

2014 

nRCP- Anthropogenic Section 5: p. 182-220 Yes Yes 

nRCP-Wind Speed Section 2: p. 38-47 Yes Yes 

CCR Section 2: p. 44 Yes Yes 

March 29, 

2014 

nRCP- Anthropogenic Section 5: p. 182-220 Yes Yes 

nRCP-Wind Speed Section 2: p. 48-57 Yes Yes 

CCR Section 2: p. 53-55 Yes Yes 

 

109 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 1.
69 

Table 16 (cont.): EPA’s Analysis of CDPHE’s TSD of Natural Event 

Exceedance 

Date 

nRCP or CCR Natural Event Demonstration 

Citation 

Sufficient 

Quality of 

Evidence?

EPA 

Criterion 

Met? 

March 30, 

2014 

nRCP- Anthropogenic Section 5: p. 182-220 Yes Yes 

March 30, 

2014 

nRCP- Anthropogenic Section 5: p. 182-220 Yes Yes 

nRCP-Wind Speed Section 2: p. 58-75 Yes Yes 

CCR Section 2: p. 69-73 Yes Yes 

March 31, 

2014 

nRCP- Anthropogenic Section 5: p. 182-220 Yes Yes 

nRCP-Wind Speed Section 2: p. 76-89 Yes Yes 

CCR Section 2: p. 85-87 Yes Yes 

April 23, 

2014 

nRCP- Anthropogenic Section 5: p. 182-220 Yes Yes 

nRCP-Wind Speed Section 2: p. 90-102 Yes Yes 

CCR Section 2: p.100-101 Yes Yes 

April 29, 

2014 

nRCP- Anthropogenic Section 5: p. 182-220 Yes Yes 

nRCP-Wind Speed Section 2: p. 103-115 Yes Yes 

CCR Section 2: p. 112 Yes Yes 

November 

10, 2014 

nRCP- Anthropogenic Section 5: p. 182-220 Yes Yes 

nRCP-Wind Speed Section 2: p. 116-128 Yes Yes 

CCR Section 2: p. 125 Yes Yes 

No Exceedance or Violation But For the Event 

Generally, the No Exceedance or Violation But for the Event (NEBF) demonstration is similar to the 

demonstration of the nRCP and CCR requirements, and should show that the measured concentration 

would have been below the applicable NAAQS without the effects of the events. 
70 

CDPHE provides a summary of the analysis and information presented in the demonstration that show 

both the nRCP and CCR requirements have been met and states that: 

Both wind speeds and soil moisture in surrounding areas were conducive to the 

generation of significant blowing dust. Multiple sources of data for the events in question 

and analyses of past dust storms in this area prove that these were natural events and, 

more specifically, significant natural dust storms originating outside the monitored areas. 

“But for” the large regional dust storms on March 11, 2014, March 15, 2014, March 18, 

2014, March 29, 2014, March 30, 2014, March 31, 2014, April 23, 2014, April 29, 2014, 

and November 10, 2014, these exceedances would not have occurred.110 

Therefore, the EPA concludes that there would have been NEBF pursuant to the Treatment of Data 

Influenced by high winds under the EER. While not explicitly stated in the documentation, EPA notes 

that PM10 concentrations before the periods of high winds on the event days were all well below the 24-

hour PM10 NAAQS of 150 ug/m3

, providing further support for CDPHE’s conclusion. Table 17 

summarizes the EPA’s evaluation of CDPHE’s NEBF EE demonstration. 

Table 17: EPA’s Analysis of CDPHE’s TSD of NEBF 

Exceedance Date No Exceedance But For the Event 

Demonstration Citation 

Sufficient 

Quality of 

Evidence? 

EPA Criterion 

Met? 

March 11, 2014 Section 6: p. 221 Yes Yes

March 15, 2014 Section 6: p. 221 Yes Yes

March 18, 2014 Section 6: p. 221 Yes Yes

March 29, 2014 Section 6: p. 221 Yes Yes

March 30, 2014 Section 6: p. 221 Yes Yes

March 31, 2014 Section 6: p. 221 Yes Yes

April 23, 2014 Section 6: p. 221 Yes Yes

April 29, 2014 Section 6: p. 221 Yes Yes

November 10, 2014 Section 6: p. 221 Yes Yes

Schedule and Procedural Requirements 

In addition to technical demonstration requirements, 40 CFR 50.14(c) specifies the schedule and 

procedural requirements an air agency must follow to request data exclusion. CDPHE received no 

 

110 “TSD for the 2014 Lamar Exceptional Events,” May 7, 2015, page 221. 
71 

external comments during the 30 day comment period, but minor corrections were made to the report 

based on internal staff review. Table 18 outlines EPA’s evaluation of these requirements. 

Table 18: EPA’s Analysis of Schedules and Procedural Criteria 

Reference Schedules and 

Procedural 

Criteria 

Demonstration 

Citation 

EPA 

Criterion 

Met? 

Did the State provide prompt public 

notification of the event? 

40 CFR 50.14(c)(1)(i) Section 1: p.12 Yes 

Were flags and initial description 

placed on the data by July 1st of the 

following year? 

40 CFR 50.14(c)(2)(iii) Section 1: p.12-13 Yes 

Was the demonstration submitted 

within 3 years of the end of the quarter 

in which the event occurred and 12 

months prior to the date that any 

regulatory decision must be made by 

EPA? 

40 CFR 50.14(c)(3)(i) May 7, 2015 Yes 

Was the public comment process 

followed and documented? 

40 CFR 50.14(c)(3)(v) Section 1: p.13 Yes 

CONCLUSION 

EPA has reviewed documentation provided by CDPHE to support claims that dust emissions generated 

by high winds resulted in PM10 transport from arid regions in Colorado, Arizona, New Mexico, western 

Texas, Wyoming, Nebraska, and western Kansas into the Lamar area during 2014. These high wind 

events caused exceedances of the 24-hour PM10 NAAQS at the location identified in Table 1 of this

document on March 11, March 15, March 18, March 29, March 30, March 31, April 23, April 29 and 

November 10, 2014, in Lamar. EPA concurs that the flagged exceedances at the Lamar monitor on these 

days meet the definition of an exceptional event: the events affected air quality, were nRCP, and met the 

definition as natural events. Specifically, EPA has determined that the event was nRCP due to high wind 

conditions that transported PM10 from sources outside of the immediate Lamar area and also subsequently 

may have overwhelmed some reasonable controls within Lamar. Also, regardless of transport into the 

area, information pertaining to the controls implemented within the affected area, the spatial extent of 

elevated PM10 concentrations measured in the area, and the wind speeds associated with the high wind 

dust events provide sufficient evidence to conclude that this event was nRCP. Furthermore, EPA has 

determined that there is a CCR between the event and the measured exceedance, there would have been 

NEBF, and the measured exceedances are in excess of normal HFs. 
72 

EPA finds that the weight of evidence is sufficient to concur on the flagging of the data for the 24-hour 

PM10 NAAQS exceedance of 387 μg/m3

 at the Lamar Power Plant monitor on March 11, 173 μg/m3 on 

March 15, 299 μg/m3 on March 18, 263 μg/m3 on March 29, 264 μg/m3 on March 30, 223 μg/m3 on 

March 31, 350 μg/m3

 on April 23, 321 μg/m3 on April 29, and 298 μg/m3 on November 10, 2014. 

This concurrence does not constitute final EPA action regarding any matter on which EPA is required to

provide an opportunity for public comment. In particular, this applies to determinations regarding the

attainment status or classification of the area. Final actions will take place only after EPA completes 

notice and comment rulemaking on those determinations.