1 

EPA Technical Support Document in Review of Colorado Department of 

Public Health and Environment’s Demonstration Package for the 

November 5, 2011, Lamar Exceptional Event 

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. 

SUMMARY 

Overview 

On December 24, 2013 the Colorado Department of Public Health and Environment (CDPHE) submitted 

a demonstration (termed a Technical Support Document or TSD) dated November 20, 2013 for an 

exceptional event exceedance of the 24-hour PM10 standard that occurred at the monitoring station in

 

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 

Lamar on November 5, 2011. 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? 

November 5, 2011 Lamar Power Plant 08-99-0001 192 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 Figure 1. 

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

In its exceptional event demonstration package CDPHE describes the November 5, 2011 event as: 

the result of a combination of synoptic and mesoscale weather events which generated very 

intense surface winds. In the synoptic scale, high winds were produced throughout much of the 

region... by a vigorous cold front and surface low pressure system associated with an upper-level 

trough. The surface winds were predominantly out of a south to southwesterly direction and 

moved over dry soils that stretched from southeast Colorado southward into northern Mexico. 

Contributing at the smaller mesoscale were very strong outflow winds from collapsing 
3 

thunderstorms in southeast Colorado and northeast New Mexico. This series of events led to the 

occurrence of blowing dust in and around Lamar during the late morning and early afternoon 

hours of November 5, 2011.2 

CDPHE provides a comprehensive description and discussion of this event in Sections 2, 3, 4, and 5 of 

the demonstration. As noted in the figure below, the high wind event caused dust to blow and affected air 

quality in this area. 

EPA Figures 2 and 3 from CDPHE’s demonstration visually demonstrate wind speed at an elevation of 

roughly 19,000 feet above sea level over southern and eastern New Mexico, western Texas, and northern 

Mexico into south and southeastern Colorado at 8:00 AM mountain standard time on November 5. 

Figures 1-39 from CDPHE’s demonstration use modeling, meteorology, and monitoring analysis to 

support the evidence of wind direction and reach of the dust storm into Lamar. 

Figure 2: Map of Wind Speed and Direction on November 5, 2011 (CDPHE’s TSD Figure 15)3

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; 

 

2

 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 11. 

3

 Ibid., 35. 
4 

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

• The wind speed was high enough to overwhelm the reasonable controls.4

 

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 

day. As CDPHE states: 

The [CDPHE Air Pollution Control Division] APCD conducted thorough analyses and outreach 

with local governments to confirm that no unusual anthropogenic PM10-producing activities 

occurred in Lamar 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 Lamar during this time.5

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.6

CDPHE provided the documentation listed in Figures 3, 4, and 5 showing that sustained wind speeds 

associated with this event were above 30 mph and gusts were above 40 mph (CDPHE Table 1)7. For 

example, in Lamar the sustained surface winds of up to 50 mph with gusts up to 68 mph were measured 

on November 5, 2011. 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 (attached as appendix A of CDPHE’s 

demonstration). The sustained winds and gusts in Lamar exceed this Colorado threshold. And wind 

speeds in Las Vegas and Raton, NM exceeded the established thresholds, helping indicate that the winds

and some regional dust originated southwest of the monitor. Given the wind direction evidence of Figure 

2 above, 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 

 

4

 “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. 

5

 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 69. 

6

 Ibid., 69-71. 

7

 Ibid., 20, 27- 28. 
5 

local regulations, appropriate land use management, and an in-depth analysis of potential areas of local 

soil disturbance for Lamar during the November 5, 2011, event.”8

Figure 3: Wind Speed Lamar, CO on November 5, 2011 (CDPHE’s TSD Table 1) 

 

8

“TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 69.
6 

Figure 4: Wind Speed Las Vegas, NM on November 5, 2011 (CDPHE’s TSD Table 8)
7 

Figure 5: Wind Speed Raton, NM on November 5, 2011 (CDPHE’s TSD Table 9)

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; 

• NOAA HYSPLIT modeling of wind trajectories; 

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

• Naval Advanced Aerosol Prediction System (NAAPS) forecasted dust concentrations; 
8 

• NOAA Geostationary Satellite Server (GOES) Aerosol Smoke Product (GASP) Optical Depth 

Images; 

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

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

• Maps of elevated friction velocities in the region from the NOAA National Centers for 

Environmental Prediction (NCEP) North American Model. 

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

blowing dust event originating far southwest of the monitor in question. 

Lamar has the following controls in place:9

• 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)10; 

• 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) 11; 

• 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.12 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”13; 

• 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 

requirements that new developments have paved streets; 

o The Limestone-Graveyard Creeks Watershed Project reduces soil erosion from 60,000 

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

 

9

 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 71-76 

10 Ibid., Appendix C. 

11 Ibid., 72. 

12 Ibid., 72-73. 

13 Ibid., 74-75. 
9 

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.14

• 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”15 in 

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

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

agricultural areas surrounding Lamar. The following amounts of cropland were under contract in 

surrounding counties. 

Figure 6: Acres by County near Lamar Enrolled in the USDA NRCS CRP Program 

2007 2008 2009 2010 2011 

Bent 25,586 25,649 25,700 24,056 24,412 

Kiowa 214,879 216,307 217,881 187,394 192,222 

Baca 263,357 260,040 258,469 161,147 274,281 

Crowley 22,032 21,419 21,461 21,069 20,329 

Otero 2,624 2,559 2,864 2,706 2,851 

Las Animas 21,983 21,869 21,860 17,403 17,616 

Cheyenne 143,948 142,075 140,071 94,852 113,753 

Lincoln 156,328 155,505 155,425 137,099 145,248 

Prowers 173,030 170,909 171,813 140,827 163,354 

Total 1,023,767 1,016,333 1,015,544 786,554 954,066 

Winds on November 5, 2011 from the southwest passed through Bent, Baca, and Las Animas 

Counties on their way to Lamar in Prowers County. CRP acreage in upwind and surrounding 

counties is shown in Figure 6. 

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

land in Lamar. Figure 7 below shows that identified areas of soil disturbance have reasonable 

controls near the Lamar monitor. 

o Site H 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.16

 

 

14 TSD for the November 5, 2011 Lamar Exceptional Event,” November 20, 2013, pages 119-122.

15 Ibid., 121. 

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

pavement, compaction, revegetation, 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 November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 77.
10 

o Site I 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.17 

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

used for truck storage.18

 

o Site K 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.19

 

o Site L 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.20

 

o Site M 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.21

 

o Site O 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 

county22. 

 

17, 18, 19, 20, 21, 22 “The APCD considers restricted vehicle speeds, maintained gravel, natural vegetation, restricted 

access, pavement, compaction, revegetation, 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 November 5, 2011, Lamar Exceptional Event,” November 20, 

2013, pages 77-80.
11 

Figure 7: Lamar Site Assessment (CDPHE’s TSD Figure 42)

• Vegetation and dust control measures are discussed below for the following parcel in Figure 8: 

o Site N is owned and mined by Carder Inc for sand and gravel under CDPHE permit 

#99PR0179F. It emits 8 tons per year of PM10 and is a wet mining operation employing 

the following dust control 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.23, 24

 

23, 24 “The APCD considers restricted vehicle speeds, maintained gravel, natural vegetation, restricted access, 

pavement, compaction, revegetation, 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 November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 

81.
12 

Figure 8: Lamar Site Assessment CDPHE’s TSD Figure 49) 

According to CDPHE’s TSD: 

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

in Figure 42 through Figure 49 [EPA Figures 7 and 8] were present during the 2011 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 November 5, 2011, 

high wind event. Therefore, these sites were not significant contributors to fugitive dust in the 

Lamar area during the November 5, 2011, high wind event.25

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 and to 

the southwest in northwestern New Mexico. 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 2 summarizes the EPA’s 

evaluation of CDPHE’s nRCP EE demonstration. 

 

25 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 82.
13 

Table 2: 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?

November 5, 

2011 

Lamar Power 

Plant 

Section 5: p. 69-84 Section 2: p.9-

52, esp. p.20 

Yes Yes 

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 2011 24-hour 

average data, 5-year time series of 24-hour averages for the years of 2006-2011, and monthly data 

showing that all readings greater than 100 μg/m3 might be considered statistical outliers. CDPHE explains 

that for the concentration measured on November 5, 2011: 

The PM10 sample on November 05, 2011, at Lamar Power of 192 μg/m3 is the largest sample 

recorded among all November samples, is the maximum value for all 2011 data, and is the fourth 

largest sample value for the entire dataset. The three samples greater than the event sample are all 

associated with a high wind event. There are 2181 samples in this dataset. The sample of 

November 05, 2011, clearly exceeds the typical samples for this site.26 

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

consider percentile ranks when dust impacted data is excluded.27 CDPHE States that the percentile rank 

for these areas is 99.9% and above for the monitor in question. See Figure 9 (CDPHE’s TSD Table 16) 

below. 

Figure 9: Percentile Analysis (CDPHE’s TSD Table 16)

28

 

26 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 55. 

27 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. 

28 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 54.
14 

Since at least 2005 in these areas, values exceeding the NAAQS are only found during high wind dust 

events, including November 5, 2011. This information indicates that values at the level seen on November 

5, 2011 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 November 5, 2011 exceedance other than windblown dust. Therefore, the EPA concludes that this event was in excess of HF pursuant to the Treatment

of Data Influenced by the EER. Table 3 summarizes the EPA’s evaluation of CDPHE’s HF EE 

demonstration. 

Table 3: EPA’s Analysis of CDPHE’s TSD of HF 

Exceedance 

Date 

Exceedance 

Location 

Historical Fluctuations 

Demonstration Citation 

Sufficient 

Quality of 

Evidence? 

EPA Criterion 

Met? 

November 5, 

2011 

Lamar Power Plant Section 3: p.53-61 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.29

 

Section 2 of CDPHE’s demonstration provides analyses that demonstrate the existence of a high wind 

blowing dust event originating far southwest of the monitors in question, but including significant 

southern Colorado contribution. 

Figure 10 below (CDPHE Figure 31) shows the output for blowing dust from the Navy Aerosol Analysis 

and Prediction System (NAAPS) Global Aerosol Model for 11 AM (18Z) on November 5, 2011. 

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.30 The 

forecast panel in the lower left of Figure 31 shows an area of highly elevated surface dust concentrations 

over much of New Mexico and southeast Colorado. This model output suggests that this drought-stricken 

region was a major source region for blowing dust on November 5, 2011, in Lamar.31

 

29 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. 

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

31 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 49.
15 

Figure 10: NAAPS Forecasted Dust Concentration for Nov. 5, 2011 at 11 am (CPDHE’s Figure 31)32

NOAA’s Smoke Text Product Satellite Services Division described the November 5, 2011 event as 

follows: 

Gusty winds along a cold front kicked up a rather extensive area of thin to moderate density 

blowing dust which extended from southern New Mexico/far western Texas (near and SE of El 

Paso)/northern Mexico to western Oklahoma and western Kansas. NOAA scientists with 

expertise in the analysis of dust storms have indicated that a regional dust storm occurred in 

areas in close proximity to southeast Colorado and also in known source regions for Lamar 

blowing dust events on November 5, 2011. [CDPHE’s emphasis]33

 

 

32 Ibid., 50.

33 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 49.
16 

CDPHE generally summarizes that: 

The PM10 exceedance in Lamar on November 5, 2011, would not have occurred if not for the 

following: (a) dry soil conditions over southeast Colorado, southern and eastern New Mexico, 

western Texas, and northern Mexico with 30-day precipitation totals below were near or below 

0.5 inches (Figure 20 and Figure 21); (b) a combination of synoptic and mesoscale weather 

events; (In the synoptic scale, high winds were produced throughout much of the region by a 

vigorous cold front and surface low pressure system associated with an upper-level trough. 

Contributing at the smaller mesoscale were very strong outflow winds from collapsing 

thunderstorms.) (c) friction velocities over a wide area of southeast Colorado, southern and 

eastern New Mexico, western Texas and northern Mexico that were high enough to allow 

entrainment of dust from natural sources with subsequent transport of the dust to southeastern 

Colorado in strong winds.34

CDPHE further states that “The statistical and meteorological data clearly shows that but for this high 

wind blowing dust event, Lamar would not have exceeded the 24-hour NAAQS on November 5, 2011”.35

Therefore, the EPA concludes that there was a CCR for this event pursuant to the Treatment of Data 

Influenced by the EER. Table 4 summarizes the EPA’s evaluation of CDPHE’s CCR EE demonstration. 

Table 4: EPA’s Analysis of CDPHE’s TSD of CCR36

Clear Causal Relationship Demonstration 

Citation 

Sufficient Quality of 

Evidence? 

EPA Criterion 

Met? 

Section 2: p.9-52, Figures 1-33 Yes Yes 

Section 2: p.9, 20-33, Tables 1-14 Yes Yes 

Section 2: p.49 Yes Yes 

Section 4: p.62-68 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 5. 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 Lamar. This is evidence that the event was associated 

with a measured concentration in excess of normal historical fluctuations including background.37

 

34 Ibid., 9.

35 Ibid., 85. 

36 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. 

37 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 85.
17 

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

Influenced by the EER. Table 5 summarizes the EPA’s evaluation of CDPHE’s AAQ EE demonstration. 

Table 5: EPA’s Analysis of CDPHE’s TSD of AAQ 

HF and 

CCR 

Exceedance Location Affects Air Quality 

Demonstration Citation 

Sufficient 

Quality of 

Evidence 

EPA 

Criterion 

Met? 

HF Lamar Power Plant Section 3: p.53-61 Yes Yes

CCR Lamar Power Plant 

Section 2: p.9-52, Figures 1-

33 

Yes Yes

Section 2: p.9, 20-33, Tables 

1-14 

Yes Yes

Section 2: p.49 Yes Yes

Section 4: p.62-68 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,

Multiple sources of data for the event in question and analyses of past dust storms in this area 

prove that this was a natural event and, more specifically, a significant natural dust storm 

originating in southern and eastern New Mexico, western Texas, and northern Mexico. But for 

the dust storm on November 5, 2011, this exceedance would not have occurred... MODIS 

satellite imagery shows that southeast Colorado and points to the south and southwest of 

Colorado were source regions for blowing dust in Lamar on November 5. .... The observations of 

winds above blowing dust thresholds and restricted visibilities in the areas of concern 

demonstrate that this is a natural event that cannot be reasonably controlled or prevented.38

CDPHE has sufficiently demonstrated the CCR and nRCP requirements for the November 5, 2011 event. 

Therefore, the EPA concludes that this was a natural event pursuant to the Treatment of Data Influenced 

by the EER. Table 6 summarizes the EPA’s evaluation of CDPHE’s Natural Event EE demonstration. 

 

38 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 86.
18 

Table 6: EPA’s Analysis of CDPHE’s TSD of Natural Event 

nRCP or CCR Exceedance 

Location 

Natural Event 

Demonstration 

Citation 

Sufficient 

Quality of 

Evidence? 

EPA 

Criterion 

Met? 

nRCPAnthropogenic Lamar Power 

Plant

Section 5: p. 69-84 Yes Yes

nRCP-Wind Speed Lamar Power 

Plant

Section 2: p.9-52, esp. 

p.20

Yes Yes

CCR Lamar Power 

Plant

Section 2: p.9-52, 

Figures 1-33

Yes Yes

Section 2: p.9, 20-33, 

Tables 1-14

Yes Yes

Section 2: p.49 Yes Yes

Section 4: p.62-68 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 affect of the event. 

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: 

The PM10 sample at Lamar Power (192 μg/m3) exceeded the 99th percentile for any evaluation 

criteria and is the maximum value for all 2011 data. The statistical and meteorological data 

clearly shows that but for this high wind blowing dust event, Lamar would not have exceeded the 

24-hour NAAQS on November 5, 2011. Since at least 2005, there has not been an exceedance 

that was not associated with high winds carrying PM10 dust from distant sources in Lamar. This is 

evidence that the event was associated with a measured concentration in excess of normal 

historical fluctuations including background.39 

Therefore, the EPA concludes that there would have been NEBF pursuant to the Treatment of Data 

Influenced by 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 at or below 55 ug/m3

 prior to and 

below 25 ug/m3 after the event; all well below the 24-hour PM10 NAAQS of 150 ug/m3, providing further 

 

39 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 85. 
19 

support for CDPHE’s conclusion. Table 7 summarizes the EPA’s evaluation of CDPHE’s NEBF EE 

demonstration. 

Table 7: 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? 

November 5, 2011 Section 6: p.85-86 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 

external comments during the 30 day comment period, but minor corrections were made to the report 

based on internal staff review. Table 8 outlines EPA’s evaluation of these requirements. 

Table 8: 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.7 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.7 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) December 24, 2013 Yes 

Was the public comment process 

followed and documented? 

40 CFR 50.14(c)(3)(v) Section 1: p.8 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 southern and eastern New Mexico, western 
20 

Texas, and northern Mexico into the Lamar area on November 5, 2011. This high wind event caused an 

exceedance of the 24-hour PM10 NAAQS at the location identified in Table 1 of this document on 

November 5, 20011, in Lamar. EPA concurs that the flagged exceedance at the Lamar monitor on this day 

meets the definition of an exceptional event: the event affected air quality, was nRCP, and met the 

definition of a natural event. 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 event 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 exceedance is in excess of normal HFs. 

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 192 ug/m3

 at the Lamar Power Plant monitor on November 5, 2011. 

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. 
1 

EPA Technical Support Document in Review of Colorado Department of 

Public Health and Environment’s Demonstration Package for the 

November 5, 2011, Lamar Exceptional Event 

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. 

SUMMARY 

Overview 

On December 24, 2013 the Colorado Department of Public Health and Environment (CDPHE) submitted 

a demonstration (termed a Technical Support Document or TSD) dated November 20, 2013 for an 

exceptional event exceedance of the 24-hour PM10 standard that occurred at the monitoring station in

 

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 

Lamar on November 5, 2011. 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? 

November 5, 2011 Lamar Power Plant 08-99-0001 192 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 Figure 1. 

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

In its exceptional event demonstration package CDPHE describes the November 5, 2011 event as: 

the result of a combination of synoptic and mesoscale weather events which generated very 

intense surface winds. In the synoptic scale, high winds were produced throughout much of the 

region... by a vigorous cold front and surface low pressure system associated with an upper-level 

trough. The surface winds were predominantly out of a south to southwesterly direction and 

moved over dry soils that stretched from southeast Colorado southward into northern Mexico. 

Contributing at the smaller mesoscale were very strong outflow winds from collapsing 
3 

thunderstorms in southeast Colorado and northeast New Mexico. This series of events led to the 

occurrence of blowing dust in and around Lamar during the late morning and early afternoon 

hours of November 5, 2011.2 

CDPHE provides a comprehensive description and discussion of this event in Sections 2, 3, 4, and 5 of 

the demonstration. As noted in the figure below, the high wind event caused dust to blow and affected air 

quality in this area. 

EPA Figures 2 and 3 from CDPHE’s demonstration visually demonstrate wind speed at an elevation of 

roughly 19,000 feet above sea level over southern and eastern New Mexico, western Texas, and northern 

Mexico into south and southeastern Colorado at 8:00 AM mountain standard time on November 5. 

Figures 1-39 from CDPHE’s demonstration use modeling, meteorology, and monitoring analysis to 

support the evidence of wind direction and reach of the dust storm into Lamar. 

Figure 2: Map of Wind Speed and Direction on November 5, 2011 (CDPHE’s TSD Figure 15)3

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; 

 

2

 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 11. 

3

 Ibid., 35. 
4 

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

• The wind speed was high enough to overwhelm the reasonable controls.4

 

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 

day. As CDPHE states: 

The [CDPHE Air Pollution Control Division] APCD conducted thorough analyses and outreach 

with local governments to confirm that no unusual anthropogenic PM10-producing activities 

occurred in Lamar 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 Lamar during this time.5

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.6

CDPHE provided the documentation listed in Figures 3, 4, and 5 showing that sustained wind speeds 

associated with this event were above 30 mph and gusts were above 40 mph (CDPHE Table 1)7. For 

example, in Lamar the sustained surface winds of up to 50 mph with gusts up to 68 mph were measured 

on November 5, 2011. 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 (attached as appendix A of CDPHE’s 

demonstration). The sustained winds and gusts in Lamar exceed this Colorado threshold. And wind 

speeds in Las Vegas and Raton, NM exceeded the established thresholds, helping indicate that the winds

and some regional dust originated southwest of the monitor. Given the wind direction evidence of Figure 

2 above, 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 

 

4

 “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. 

5

 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 69. 

6

 Ibid., 69-71. 

7

 Ibid., 20, 27- 28. 
5 

local regulations, appropriate land use management, and an in-depth analysis of potential areas of local 

soil disturbance for Lamar during the November 5, 2011, event.”8

Figure 3: Wind Speed Lamar, CO on November 5, 2011 (CDPHE’s TSD Table 1) 

 

8

“TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 69.
6 

Figure 4: Wind Speed Las Vegas, NM on November 5, 2011 (CDPHE’s TSD Table 8)
7 

Figure 5: Wind Speed Raton, NM on November 5, 2011 (CDPHE’s TSD Table 9)

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; 

• NOAA HYSPLIT modeling of wind trajectories; 

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

• Naval Advanced Aerosol Prediction System (NAAPS) forecasted dust concentrations; 
8 

• NOAA Geostationary Satellite Server (GOES) Aerosol Smoke Product (GASP) Optical Depth 

Images; 

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

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

• Maps of elevated friction velocities in the region from the NOAA National Centers for 

Environmental Prediction (NCEP) North American Model. 

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

blowing dust event originating far southwest of the monitor in question. 

Lamar has the following controls in place:9

• 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)10; 

• 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) 11; 

• 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.12 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”13; 

• 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 

requirements that new developments have paved streets; 

o The Limestone-Graveyard Creeks Watershed Project reduces soil erosion from 60,000 

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

 

9

 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 71-76 

10 Ibid., Appendix C. 

11 Ibid., 72. 

12 Ibid., 72-73. 

13 Ibid., 74-75. 
9 

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.14

• 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”15 in 

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

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

agricultural areas surrounding Lamar. The following amounts of cropland were under contract in 

surrounding counties. 

Figure 6: Acres by County near Lamar Enrolled in the USDA NRCS CRP Program 

2007 2008 2009 2010 2011 

Bent 25,586 25,649 25,700 24,056 24,412 

Kiowa 214,879 216,307 217,881 187,394 192,222 

Baca 263,357 260,040 258,469 161,147 274,281 

Crowley 22,032 21,419 21,461 21,069 20,329 

Otero 2,624 2,559 2,864 2,706 2,851 

Las Animas 21,983 21,869 21,860 17,403 17,616 

Cheyenne 143,948 142,075 140,071 94,852 113,753 

Lincoln 156,328 155,505 155,425 137,099 145,248 

Prowers 173,030 170,909 171,813 140,827 163,354 

Total 1,023,767 1,016,333 1,015,544 786,554 954,066 

Winds on November 5, 2011 from the southwest passed through Bent, Baca, and Las Animas 

Counties on their way to Lamar in Prowers County. CRP acreage in upwind and surrounding 

counties is shown in Figure 6. 

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

land in Lamar. Figure 7 below shows that identified areas of soil disturbance have reasonable 

controls near the Lamar monitor. 

o Site H 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.16

 

 

14 TSD for the November 5, 2011 Lamar Exceptional Event,” November 20, 2013, pages 119-122.

15 Ibid., 121. 

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

pavement, compaction, revegetation, 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 November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 77.
10 

o Site I 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.17 

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

used for truck storage.18

 

o Site K 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.19

 

o Site L 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.20

 

o Site M 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.21

 

o Site O 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 

county22. 

 

17, 18, 19, 20, 21, 22 “The APCD considers restricted vehicle speeds, maintained gravel, natural vegetation, restricted 

access, pavement, compaction, revegetation, 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 November 5, 2011, Lamar Exceptional Event,” November 20, 

2013, pages 77-80.
11 

Figure 7: Lamar Site Assessment (CDPHE’s TSD Figure 42)

• Vegetation and dust control measures are discussed below for the following parcel in Figure 8: 

o Site N is owned and mined by Carder Inc for sand and gravel under CDPHE permit 

#99PR0179F. It emits 8 tons per year of PM10 and is a wet mining operation employing 

the following dust control 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.23, 24

 

23, 24 “The APCD considers restricted vehicle speeds, maintained gravel, natural vegetation, restricted access, 

pavement, compaction, revegetation, 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 November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 

81.
12 

Figure 8: Lamar Site Assessment CDPHE’s TSD Figure 49) 

According to CDPHE’s TSD: 

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

in Figure 42 through Figure 49 [EPA Figures 7 and 8] were present during the 2011 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 November 5, 2011, 

high wind event. Therefore, these sites were not significant contributors to fugitive dust in the 

Lamar area during the November 5, 2011, high wind event.25

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 and to 

the southwest in northwestern New Mexico. 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 2 summarizes the EPA’s 

evaluation of CDPHE’s nRCP EE demonstration. 

 

25 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 82.
13 

Table 2: 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?

November 5, 

2011 

Lamar Power 

Plant 

Section 5: p. 69-84 Section 2: p.9-

52, esp. p.20 

Yes Yes 

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 2011 24-hour 

average data, 5-year time series of 24-hour averages for the years of 2006-2011, and monthly data 

showing that all readings greater than 100 μg/m3 might be considered statistical outliers. CDPHE explains 

that for the concentration measured on November 5, 2011: 

The PM10 sample on November 05, 2011, at Lamar Power of 192 μg/m3 is the largest sample 

recorded among all November samples, is the maximum value for all 2011 data, and is the fourth 

largest sample value for the entire dataset. The three samples greater than the event sample are all 

associated with a high wind event. There are 2181 samples in this dataset. The sample of 

November 05, 2011, clearly exceeds the typical samples for this site.26 

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

consider percentile ranks when dust impacted data is excluded.27 CDPHE States that the percentile rank 

for these areas is 99.9% and above for the monitor in question. See Figure 9 (CDPHE’s TSD Table 16) 

below. 

Figure 9: Percentile Analysis (CDPHE’s TSD Table 16)

28

 

26 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 55. 

27 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. 

28 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 54.
14 

Since at least 2005 in these areas, values exceeding the NAAQS are only found during high wind dust 

events, including November 5, 2011. This information indicates that values at the level seen on November 

5, 2011 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 November 5, 2011 exceedance other than windblown dust. Therefore, the EPA concludes that this event was in excess of HF pursuant to the Treatment

of Data Influenced by the EER. Table 3 summarizes the EPA’s evaluation of CDPHE’s HF EE 

demonstration. 

Table 3: EPA’s Analysis of CDPHE’s TSD of HF 

Exceedance 

Date 

Exceedance 

Location 

Historical Fluctuations 

Demonstration Citation 

Sufficient 

Quality of 

Evidence? 

EPA Criterion 

Met? 

November 5, 

2011 

Lamar Power Plant Section 3: p.53-61 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.29

 

Section 2 of CDPHE’s demonstration provides analyses that demonstrate the existence of a high wind 

blowing dust event originating far southwest of the monitors in question, but including significant 

southern Colorado contribution. 

Figure 10 below (CDPHE Figure 31) shows the output for blowing dust from the Navy Aerosol Analysis 

and Prediction System (NAAPS) Global Aerosol Model for 11 AM (18Z) on November 5, 2011. 

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.30 The 

forecast panel in the lower left of Figure 31 shows an area of highly elevated surface dust concentrations 

over much of New Mexico and southeast Colorado. This model output suggests that this drought-stricken 

region was a major source region for blowing dust on November 5, 2011, in Lamar.31

 

29 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. 

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

31 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 49.
15 

Figure 10: NAAPS Forecasted Dust Concentration for Nov. 5, 2011 at 11 am (CPDHE’s Figure 31)32

NOAA’s Smoke Text Product Satellite Services Division described the November 5, 2011 event as 

follows: 

Gusty winds along a cold front kicked up a rather extensive area of thin to moderate density 

blowing dust which extended from southern New Mexico/far western Texas (near and SE of El 

Paso)/northern Mexico to western Oklahoma and western Kansas. NOAA scientists with 

expertise in the analysis of dust storms have indicated that a regional dust storm occurred in 

areas in close proximity to southeast Colorado and also in known source regions for Lamar 

blowing dust events on November 5, 2011. [CDPHE’s emphasis]33

 

 

32 Ibid., 50.

33 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 49.
16 

CDPHE generally summarizes that: 

The PM10 exceedance in Lamar on November 5, 2011, would not have occurred if not for the 

following: (a) dry soil conditions over southeast Colorado, southern and eastern New Mexico, 

western Texas, and northern Mexico with 30-day precipitation totals below were near or below 

0.5 inches (Figure 20 and Figure 21); (b) a combination of synoptic and mesoscale weather 

events; (In the synoptic scale, high winds were produced throughout much of the region by a 

vigorous cold front and surface low pressure system associated with an upper-level trough. 

Contributing at the smaller mesoscale were very strong outflow winds from collapsing 

thunderstorms.) (c) friction velocities over a wide area of southeast Colorado, southern and 

eastern New Mexico, western Texas and northern Mexico that were high enough to allow 

entrainment of dust from natural sources with subsequent transport of the dust to southeastern 

Colorado in strong winds.34

CDPHE further states that “The statistical and meteorological data clearly shows that but for this high 

wind blowing dust event, Lamar would not have exceeded the 24-hour NAAQS on November 5, 2011”.35

Therefore, the EPA concludes that there was a CCR for this event pursuant to the Treatment of Data 

Influenced by the EER. Table 4 summarizes the EPA’s evaluation of CDPHE’s CCR EE demonstration. 

Table 4: EPA’s Analysis of CDPHE’s TSD of CCR36

Clear Causal Relationship Demonstration 

Citation 

Sufficient Quality of 

Evidence? 

EPA Criterion 

Met? 

Section 2: p.9-52, Figures 1-33 Yes Yes 

Section 2: p.9, 20-33, Tables 1-14 Yes Yes 

Section 2: p.49 Yes Yes 

Section 4: p.62-68 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 5. 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 Lamar. This is evidence that the event was associated 

with a measured concentration in excess of normal historical fluctuations including background.37

 

34 Ibid., 9.

35 Ibid., 85. 

36 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. 

37 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 85.
17 

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

Influenced by the EER. Table 5 summarizes the EPA’s evaluation of CDPHE’s AAQ EE demonstration. 

Table 5: EPA’s Analysis of CDPHE’s TSD of AAQ 

HF and 

CCR 

Exceedance Location Affects Air Quality 

Demonstration Citation 

Sufficient 

Quality of 

Evidence 

EPA 

Criterion 

Met? 

HF Lamar Power Plant Section 3: p.53-61 Yes Yes

CCR Lamar Power Plant 

Section 2: p.9-52, Figures 1-

33 

Yes Yes

Section 2: p.9, 20-33, Tables 

1-14 

Yes Yes

Section 2: p.49 Yes Yes

Section 4: p.62-68 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,

Multiple sources of data for the event in question and analyses of past dust storms in this area 

prove that this was a natural event and, more specifically, a significant natural dust storm 

originating in southern and eastern New Mexico, western Texas, and northern Mexico. But for 

the dust storm on November 5, 2011, this exceedance would not have occurred... MODIS 

satellite imagery shows that southeast Colorado and points to the south and southwest of 

Colorado were source regions for blowing dust in Lamar on November 5. .... The observations of 

winds above blowing dust thresholds and restricted visibilities in the areas of concern 

demonstrate that this is a natural event that cannot be reasonably controlled or prevented.38

CDPHE has sufficiently demonstrated the CCR and nRCP requirements for the November 5, 2011 event. 

Therefore, the EPA concludes that this was a natural event pursuant to the Treatment of Data Influenced 

by the EER. Table 6 summarizes the EPA’s evaluation of CDPHE’s Natural Event EE demonstration. 

 

38 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 86.
18 

Table 6: EPA’s Analysis of CDPHE’s TSD of Natural Event 

nRCP or CCR Exceedance 

Location 

Natural Event 

Demonstration 

Citation 

Sufficient 

Quality of 

Evidence? 

EPA 

Criterion 

Met? 

nRCPAnthropogenic Lamar Power 

Plant

Section 5: p. 69-84 Yes Yes

nRCP-Wind Speed Lamar Power 

Plant

Section 2: p.9-52, esp. 

p.20

Yes Yes

CCR Lamar Power 

Plant

Section 2: p.9-52, 

Figures 1-33

Yes Yes

Section 2: p.9, 20-33, 

Tables 1-14

Yes Yes

Section 2: p.49 Yes Yes

Section 4: p.62-68 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 affect of the event. 

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: 

The PM10 sample at Lamar Power (192 μg/m3) exceeded the 99th percentile for any evaluation 

criteria and is the maximum value for all 2011 data. The statistical and meteorological data 

clearly shows that but for this high wind blowing dust event, Lamar would not have exceeded the 

24-hour NAAQS on November 5, 2011. Since at least 2005, there has not been an exceedance 

that was not associated with high winds carrying PM10 dust from distant sources in Lamar. This is 

evidence that the event was associated with a measured concentration in excess of normal 

historical fluctuations including background.39 

Therefore, the EPA concludes that there would have been NEBF pursuant to the Treatment of Data 

Influenced by 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 at or below 55 ug/m3

 prior to and 

below 25 ug/m3 after the event; all well below the 24-hour PM10 NAAQS of 150 ug/m3, providing further 

 

39 “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 2013, page 85. 
19 

support for CDPHE’s conclusion. Table 7 summarizes the EPA’s evaluation of CDPHE’s NEBF EE 

demonstration. 

Table 7: 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? 

November 5, 2011 Section 6: p.85-86 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 

external comments during the 30 day comment period, but minor corrections were made to the report 

based on internal staff review. Table 8 outlines EPA’s evaluation of these requirements. 

Table 8: 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.7 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.7 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) December 24, 2013 Yes 

Was the public comment process 

followed and documented? 

40 CFR 50.14(c)(3)(v) Section 1: p.8 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 southern and eastern New Mexico, western 
20 

Texas, and northern Mexico into the Lamar area on November 5, 2011. This high wind event caused an 

exceedance of the 24-hour PM10 NAAQS at the location identified in Table 1 of this document on 

November 5, 20011, in Lamar. EPA concurs that the flagged exceedance at the Lamar monitor on this day 

meets the definition of an exceptional event: the event affected air quality, was nRCP, and met the 

definition of a natural event. 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 event 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 exceedance is in excess of normal HFs. 

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 192 ug/m3

 at the Lamar Power Plant monitor on November 5, 2011. 

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.