1



## EPA Technical Support Document in Review of Colorad o Department of Public Health and Environment’s Demonstration Packa ge for the

November 5, 2011, Lamar Exceptional Event
EXCEPTIONAL EVENTS RULE REQUIREMENTS

The Environmental Protection Agency (EPA) promulgat ed the Exceptional Events Rule (EER) in 2007, pursuant to the 2005 amendment of Clean Air Act (CA A) Section 319. 42 U.S.C. §7619. The EER added 40 CFR 50.1(j), (k) and (l); 50.14; and 51.930 to t he Code of Federal Regulations (CFR). These section s contain definitions, criteria for EPA approval, pro cedural requirements, and requirements for air agen cy 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 demons tration to justify exclusion of data must provide evidence that:

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

• The event affects air quality;

• The event is not reasonably controllable or prevent able; and

• The event is caused by human activity that is unlik ely to recur at a particular location or [is] a natural event. 1

• There is a clear causal relationship between the me asurement under consideration and the event that is claimed to have affected the air quality in the area;

• The event is associated with a measured concentrati on in excess of normal historical fluctuations, including background; and

• There would have been no exceedance or violation bu t 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 Affect ed 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 Pub lic Health and Environment (CDPHE) submitted a demonstration (termed a Technical Support Documen t or TSD) dated November 20, 2013 for an exceptional event exceedance of the 24-hour PM 10 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 lit tle or no direct causal role”.2

Lamar on November 5, 2011. Table 1 summarizes the e xceedance that CDPHE would like considered for exceptional event concurrence in the Air Quality Sy stem (AQS) database.

Table 1: EPA PM 10 Exceedance Summary of the 150 ug/m 3 24-hour NAAQS Exceedance Date Monitor/Site Name AQS ID 24-hour Av g. (ug/m 3 ) 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 Col orado 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 PM 10 NAAQS Exceedance

In its exceptional event demonstration package CDPH E describes the November 5, 2011 event as:
the result of a combination of synoptic and mesosca le 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 pr essure 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 str ong outflow winds from collapsing3

thunderstorms in southeast Colorado and northeast N ew Mexico. This series of events led to the occurrence of blowing dust in and around Lamar duri ng the late morning and early afternoon hours of November 5, 2011. 2

CDPHE provides a comprehensive description and disc ussion of this event in Sections 2, 3, 4, and 5 of the demonstration. As noted in the figure below, th e high wind event caused dust to blow and affected air quality in this area.
EPA Figures 2 and 3 from CDPHE’s demonstration visu ally demonstrate wind speed at an elevation of roughly 19,000 feet above sea level over southern a nd 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 modelin g, 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 Novemb er 5, 2011 (CDPHE’s TSD Figure 15) 3

Not Reasonably Controllable or Preventable
EPA evaluates whether an event was not Reasonably C ontrollable 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 general ly be considered to be nRCP if winds are high enoug h 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 c ontrols in place;

2 “TSD for the November 5, 2011, Lamar Exceptional E vent,” November 20, 2013, page 11.
3 Ibid., 35.4

• The reasonable controls have been effectively imple mented and enforced; and,

• The wind speed was high enough to overwhelm the rea sonable controls. 4
In addressing reasonable controls, CDPHE provided d etailed 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 th e event day. As CDPHE states:
The [CDPHE Air Pollution Control Division] APCD con ducted thorough analyses and outreach with local governments to confirm that no unusual a nthropogenic PM 10 -producing activities occurred in Lamar and that despite reasonable contr ol measures in place, high wind conditions overwhelmed all reasonably available controls.... Thi s information shall confirm that no unusual anthropogenic actions occurred in Lamar during this time. 5

CDPHE’s demonstration provides an analysis of the s tate and local controls in place to control PM 10 emissions. Although specifically focusing on Regula tions 1, 3 and 6, these controls include CDPHE’s:

• Regulation 1- Emission Control for Particulate Matt er, 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 Certai n Woodburning Appliances During High Pollution Days;

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

• Regulation 9- Open Burning, Prescribed Fire, and Pe rmitting. 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 gu sts 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 i n 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 La mar exceed this Colorado threshold. And wind speeds in Las Vegas and Raton, NM exceeded the esta blished thresholds, helping indicate that the winds and some regional dust originated southwest of the monitor. Given the wind direction evidence of Figur e 2 above, transported dust from the upwind desert an d arid plains regions appears to be a significant contribution to the exceedance, in addition to loca l winds overwhelming implemented local controls. EP A notes that the high local gust speeds in Lamar woul d likely be capable of overwhelming some local controls. Section 5 of the TSD provided by CDPHE su pports this conclusion by describing in detail “Bes t Available Control Measures (BACM), other reasonable control measures, applicable federal, state, and

4 “Interim Guidance on the Preparation of Demonstrat ions in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Exceptional E vents Rule,” May 2013, page 10. 5 “TSD for the November 5, 2011, Lamar Exceptional E vent,” 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 loc al soil disturbance for Lamar during the November 5, 2 011, 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 Ev ent,” November 20, 2013, page 69.6

Figure 4: Wind Speed Las Vegas, NM on November 5, 2 011 (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 compl ex meteorological analysis of the event, including:

• Statewide PM 10 monitoring maps;

• Surface and upper air wind speed analysis from the National Oceanic and Atmospheric Administration (NOAA);

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

• Maps of real-time weather data from the National Ce nter 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 blow ing dust across the region;

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

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

• Maps establishing the lack of regional precipitatio n 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 Mode l.
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 E vents completed in 2003, and updated in 2012, which addresses public education, notificati on, and health advisory systems as well as implements Best Available Control Measures (BACM) 10 ;

• A PM 10 Maintenance plan for the Lamar Attainment/Maintena nce 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 f ugitive dust (see Colorado Regulation 1);

• City of Lamar BACM measures include: planting a win d-break of trees with drip-irrigation to control dust from the Lamar Transfer Station, estab lishing 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 “Operati ons and Closure Plan for the East Lamar Landfill” section 3.5.1, among other listed landfil l controls. 12 Other BACM include installing 100,000 ft 2 of turf sod and irrigation at recreational open sp ace Escondido Park, and fencing off and stabilizing lots that formerly contributed to f ugitive dust;

• Other measures include: Art. XVII, Sec. 16-17-60 re quiring off street parking lots to be swept, The Prowers County Land Use plan adopted in 2004 an d amended in 2006- through it the county has authority over “construction, siting, health, f ire, 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 Offic e efforts underway to encourage no- or low-till practices, outreach and education o n 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 stree ts;

o The Limestone-Graveyard Creeks Watershed Project re duces 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 E vent,” 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 impro vements created by each farmer/owner with costs of conservation improvement s 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 incent ivize 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 conse rvation 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 th e 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. C RP acreage in upwind and surrounding counties is shown in Figure 6.

• Vegetation, signage, and/or other dust control meas ures 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 an d 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 Even t,” November 20, 2013, pages 119-122.
15 Ibid., 121.
16 “The APCD considers restricted vehicle speeds, main tained gravel, natural vegetation, restricted acces s, pavement, compaction, revegetation, watering, and e xtraction limitation to be the appropriate available and practical method that is technologically feasible and economi cally reasonable in order to minimize fugitive part iculate 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 sha red by Prowers Area Transit and the defunct Cowboy Corral Storage, feed supply, and gra in storage companies. The transit company is on a concrete slab connecting to an asph alt road. 17

o Site J is owned by Heath & Son & Turpin Trucking an d is a well-maintained gravel lot used for truck storage. 18

o Site K is the Lamar Water Department and Lamar-Prow ers County Volunteer Fire Department and is a restricted access site of grate d (sic) and watered gravel on an asneeded basis. 19

o Site L is the power plant that hosts the monitor an d is a restricted access lot owned by Lamar Light and Power. It has been a gas fired boil er, 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 me asures: 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 whi le under the 1 ton per year APEN exemption, transfer locations were enclosed, and th e 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 ve getation 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-se aled crushed-gravel parking lot for Prowers County Jail and the Prowers County Municipa l Court that is maintained by the county 22

.

17, 18, 19, 20, 21, 22 “The APCD considers restricted vehicle speeds, main tained gravel, natural vegetation, restricted access, pavement, compaction, revegetation, waterin g, and extraction limitation to be the appropriate available and practical method that is technologically feasible a nd economically reasonable in order to minimize fug itive 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 an d gravel under CDPHE permit #99PR0179F. It emits 8 tons per year of PM 10 and is a wet mining operation employing the following dust control measures: watering as ne eded, 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, main tained gravel, natural vegetation, restricted acces s, pavement, compaction, revegetation, watering, and e xtraction limitation to be the appropriate availabl e and practical method that is technologically feasible and economi cally reasonable in order to minimize fugitive part iculate emissions for these sites..” “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 201 3, page 81.12

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

According to CDPHE’s TSD:
The APCD conducted thorough assessments to determin e 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, t he APCD discovered that these sites were either reasonably controlled or considered to be na tural sources during the November 5, 2011, high wind event. Therefore, these sites were not si gnificant contributors to fugitive dust in the Lamar area during the November 5, 2011, high wind e vent. 25

Sections 2 and 5 of CDPHE’s demonstration show that the monitor in Lamar was affected by PM 10 transport from outside the area, with the main sour ce areas located in agricultural areas in Colorado and to the southwest in northwestern New Mexico. In additi on to transport, the spatial extent of elevated PM 10 concentrations throughout southern Colorado and the wind speeds associated with the event factor into EPA’s evaluation of whether this event is nRCP in L amar. Therefore, the EPA concludes that this event was nRCP pursuant to the Treatment of Data Influenc ed 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 Ev ent,” 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 e xcess 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-hou r average data, 5-year time series of 24-hour average s for the years of 2006-2011, and monthly data showing that all readings greater than 100 μ g/m 3 might be considered statistical outliers. CDPHE ex plains that for the concentration measured on November 5, 2011:

The PM 10 sample on November 05, 2011, at Lamar Power of 192 μ g/m 3 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 th ree samples greater than the event sample are all associated with a high wind event. There are 2181 s amples in this dataset. The sample of November 05, 2011, clearly exceeds the typical samp les for this site. 26

The EPA “Interim Guidance on High Wind Exceptional Events” recommends that demonstrations also consider percentile ranks when dust impacted data i s 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 E vent,” November 20, 2013, page 55.
27 See “Interim Guidance on the Preparation of Demons trations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Excep tional Events Rule” of May 2013, page 20.
28 “TSD for the November 5, 2011, Lamar Exceptional Ev ent,” November 20, 2013, page 54.14

Since at least 2005 in these areas, values exceedin g the NAAQS are only found during high wind dust events, including November 5, 2011. This informatio n indicates that values at the level seen on Novemb er 5, 2011 are extremely rare in the absence of high w ind dust exceptional event impacts, and that it is unlikely that any sources of PM 10 were involved in the November 5, 2011 exceedance o ther 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 t he 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 occurr ed and that emissions related to the event were transp orted in the direction of the monitor(s) where measurements were recorded; the size of the area af fected by the transported emissions; the relationsh ip 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 analyse s 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 concentrat ions over much of New Mexico and southeast Colorado. Thi s model output suggests that this drought-stricken region was a major source region for blowing dust o n November 5, 2011, in Lamar. 31

29 See “Interim Guidance on the Preparation of Demons trations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Excep tional 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 Ev ent,” 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 Divisi on described the November 5, 2011 event as follows:
Gusty winds along a cold front kicked up a rather e xtensive area of thin to moderate density blowing dust which extended from southern New Mexic o/far western Texas (near and SE of El Paso)/northern Mexico to western Oklahoma and weste rn Kansas. NOAA scientists with expertise in the analysis of dust storms have indic ated 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 Ev ent,” November 20, 2013, page 49.16

CDPHE generally summarizes that:

The PM 10 exceedance in Lamar on November 5, 2011, would not have occurred if not for the following: (a) dry soil conditions over southeast C olorado, southern and eastern New Mexico, western Texas, and northern Mexico with 30-day prec ipitation totals below were near or below 0.5 inches (Figure 20 and Figure 21); (b) a combina tion of synoptic and mesoscale weather events; (In the synoptic scale, high winds were pro duced 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 str ong outflow winds from collapsing thunderstorms.) (c) friction velocities over a wide area of southeast Colorado, southern and eastern New Mexico, western Texas and northern Mexi co that were high enough to allow entrainment of dust from natural sources with subse quent transport of the dust to southeastern Colorado in strong winds. 34

CDPHE further states that “The statistical and mete orological data clearly shows that but for this hig h wind blowing dust event, Lamar would not have excee ded the 24-hour NAAQS on November 5, 2011”. 35 Therefore, the EPA concludes that there was a CCR f or 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 CCR 36 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 E xceptional 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 demonst rations on the preceding three pages of this (EPA’s) TSD are cited in Table 5. Additionally, CDP HE states that:
Since at least 2005, there has not been an exceedan ce that was not associated with high winds carrying PM 10 dust from distant sources in Lamar. This is evidenc e that the event was associated with a measured concentration in excess of normal h istorical fluctuations including background. 37

34 Ibid., 9.
35 Ibid., 85. 36 See “Interim Guidance on the Preparation of Demons trations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Excep tional Events Rule” of May 2013 page 21.
37 “TSD for the November 5, 2011, Lamar Exceptional Ev ent,” November 20, 2013, page 85.17

Therefore, the EPA concludes that this event Affect ed 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 E xceptional 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 speci fically, a significant natural dust storm originating in southern and eastern New Mexico, wes tern 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 La mar 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 canno t be reasonably controlled or prevented. 38

CDPHE has sufficiently demonstrated the CCR and nRC P requirements for the November 5, 2011 event. Therefore, the EPA concludes that this was a natura l event pursuant to the Treatment of Data Influence d 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 Ev ent,” November 20, 2013, page 86.18

Table 6: EPA’s Analysis of CDPHE’s TSD of Natural E vent 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 t he 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 inform ation presented in the demonstration that show both the nRCP and CCR requirements have been met an d states that:

The PM 10 sample at Lamar Power (192 μ g/m 3 ) exceeded the 99 th 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 d ust event, Lamar would not have exceeded the 24-hour NAAQS on November 5, 2011. Since at least 2 005, there has not been an exceedance that was not associated with high winds carrying PM 10 dust from distant sources in Lamar. This is evidence that the event was associated with a measu red 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 PM 10 concentrations before the periods of high winds on the event days were at or below 55 ug/m 3 prior to and below 25 ug/m 3 after the event; all well below the 24-hour PM 10 NAAQS of 150 ug/m 3 , providing further

39 “TSD for the November 5, 2011, Lamar Exceptional E vent,” 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 t o 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 EP A’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 1 st 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 PM 10 transport from arid regions in southern and easter n New Mexico, western20

Texas, and northern Mexico into the Lamar area on N ovember 5, 2011. This high wind event caused an exceedance of the 24-hour PM 10 NAAQS at the location identified in Table 1 of this document on November 5, 20011, in Lamar. EPA concurs that the f lagged exceedance at the Lamar monitor on this day meets the definition of an exceptional event: the e vent affected air quality, was nRCP, and met the definition of a natural event. Specifically, EPA ha s determined that the event was nRCP due to high wi nd conditions that transported PM 10 from sources outside of the immediate Lamar area an d also subsequently may have overwhelmed some reasonable controls withi n Lamar. Also, regardless of transport into the area, information pertaining to the controls implem ented within the affected area, the spatial extent of elevated PM 10 concentrations measured in the area, and the wind s peeds 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 an d the measured exceedance, there would have been NEBF, and the measured exceedance is in excess of n ormal HFs.
EPA finds that the weight of evidence is sufficient to concur on the flagging of the data for the 24-h our PM 10 NAAQS exceedance of 192 ug/m 3 at the Lamar Power Plant monitor on November 5, 20 11.

This concurrence does not constitute final EPA acti on regarding any matter on which EPA is required to provide an opportunity for public comment. In parti cular, this applies to determinations regarding the attainment status or classification of the area. Fi nal actions will take place only after EPA complete s notice and comment rulemaking on those determinatio ns.1



## EPA Technical Support Document in Review of Colorad o Department of Public Health and Environment’s Demonstration Packa ge for the

November 5, 2011, Lamar Exceptional Event
EXCEPTIONAL EVENTS RULE REQUIREMENTS

The Environmental Protection Agency (EPA) promulgat ed the Exceptional Events Rule (EER) in 2007, pursuant to the 2005 amendment of Clean Air Act (CA A) Section 319. 42 U.S.C. §7619. The EER added 40 CFR 50.1(j), (k) and (l); 50.14; and 51.930 to t he Code of Federal Regulations (CFR). These section s contain definitions, criteria for EPA approval, pro cedural requirements, and requirements for air agen cy 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 demons tration to justify exclusion of data must provide evidence that:

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

• The event affects air quality;

• The event is not reasonably controllable or prevent able; and

• The event is caused by human activity that is unlik ely to recur at a particular location or [is] a natural event. 1

• There is a clear causal relationship between the me asurement under consideration and the event that is claimed to have affected the air quality in the area;

• The event is associated with a measured concentrati on in excess of normal historical fluctuations, including background; and

• There would have been no exceedance or violation bu t 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 Affect ed 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 Pub lic Health and Environment (CDPHE) submitted a demonstration (termed a Technical Support Documen t or TSD) dated November 20, 2013 for an exceptional event exceedance of the 24-hour PM 10 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 lit tle or no direct causal role”.2

Lamar on November 5, 2011. Table 1 summarizes the e xceedance that CDPHE would like considered for exceptional event concurrence in the Air Quality Sy stem (AQS) database.

Table 1: EPA PM 10 Exceedance Summary of the 150 ug/m 3 24-hour NAAQS Exceedance Date Monitor/Site Name AQS ID 24-hour Av g. (ug/m 3 ) 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 Col orado 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 PM 10 NAAQS Exceedance

In its exceptional event demonstration package CDPH E describes the November 5, 2011 event as:
the result of a combination of synoptic and mesosca le 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 pr essure 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 str ong outflow winds from collapsing3

thunderstorms in southeast Colorado and northeast N ew Mexico. This series of events led to the occurrence of blowing dust in and around Lamar duri ng the late morning and early afternoon hours of November 5, 2011. 2

CDPHE provides a comprehensive description and disc ussion of this event in Sections 2, 3, 4, and 5 of the demonstration. As noted in the figure below, th e high wind event caused dust to blow and affected air quality in this area.
EPA Figures 2 and 3 from CDPHE’s demonstration visu ally demonstrate wind speed at an elevation of roughly 19,000 feet above sea level over southern a nd 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 modelin g, 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 Novemb er 5, 2011 (CDPHE’s TSD Figure 15) 3

Not Reasonably Controllable or Preventable
EPA evaluates whether an event was not Reasonably C ontrollable 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 general ly be considered to be nRCP if winds are high enoug h 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 c ontrols in place;

2 “TSD for the November 5, 2011, Lamar Exceptional E vent,” November 20, 2013, page 11.
3 Ibid., 35.4

• The reasonable controls have been effectively imple mented and enforced; and,

• The wind speed was high enough to overwhelm the rea sonable controls. 4
In addressing reasonable controls, CDPHE provided d etailed 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 th e event day. As CDPHE states:
The [CDPHE Air Pollution Control Division] APCD con ducted thorough analyses and outreach with local governments to confirm that no unusual a nthropogenic PM 10 -producing activities occurred in Lamar and that despite reasonable contr ol measures in place, high wind conditions overwhelmed all reasonably available controls.... Thi s information shall confirm that no unusual anthropogenic actions occurred in Lamar during this time. 5

CDPHE’s demonstration provides an analysis of the s tate and local controls in place to control PM 10 emissions. Although specifically focusing on Regula tions 1, 3 and 6, these controls include CDPHE’s:

• Regulation 1- Emission Control for Particulate Matt er, 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 Certai n Woodburning Appliances During High Pollution Days;

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

• Regulation 9- Open Burning, Prescribed Fire, and Pe rmitting. 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 gu sts 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 i n 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 La mar exceed this Colorado threshold. And wind speeds in Las Vegas and Raton, NM exceeded the esta blished thresholds, helping indicate that the winds and some regional dust originated southwest of the monitor. Given the wind direction evidence of Figur e 2 above, transported dust from the upwind desert an d arid plains regions appears to be a significant contribution to the exceedance, in addition to loca l winds overwhelming implemented local controls. EP A notes that the high local gust speeds in Lamar woul d likely be capable of overwhelming some local controls. Section 5 of the TSD provided by CDPHE su pports this conclusion by describing in detail “Bes t Available Control Measures (BACM), other reasonable control measures, applicable federal, state, and

4 “Interim Guidance on the Preparation of Demonstrat ions in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Exceptional E vents Rule,” May 2013, page 10. 5 “TSD for the November 5, 2011, Lamar Exceptional E vent,” 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 loc al soil disturbance for Lamar during the November 5, 2 011, 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 Ev ent,” November 20, 2013, page 69.6

Figure 4: Wind Speed Las Vegas, NM on November 5, 2 011 (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 compl ex meteorological analysis of the event, including:

• Statewide PM 10 monitoring maps;

• Surface and upper air wind speed analysis from the National Oceanic and Atmospheric Administration (NOAA);

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

• Maps of real-time weather data from the National Ce nter 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 blow ing dust across the region;

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

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

• Maps establishing the lack of regional precipitatio n 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 Mode l.
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 E vents completed in 2003, and updated in 2012, which addresses public education, notificati on, and health advisory systems as well as implements Best Available Control Measures (BACM) 10 ;

• A PM 10 Maintenance plan for the Lamar Attainment/Maintena nce 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 f ugitive dust (see Colorado Regulation 1);

• City of Lamar BACM measures include: planting a win d-break of trees with drip-irrigation to control dust from the Lamar Transfer Station, estab lishing 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 “Operati ons and Closure Plan for the East Lamar Landfill” section 3.5.1, among other listed landfil l controls. 12 Other BACM include installing 100,000 ft 2 of turf sod and irrigation at recreational open sp ace Escondido Park, and fencing off and stabilizing lots that formerly contributed to f ugitive dust;

• Other measures include: Art. XVII, Sec. 16-17-60 re quiring off street parking lots to be swept, The Prowers County Land Use plan adopted in 2004 an d amended in 2006- through it the county has authority over “construction, siting, health, f ire, 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 Offic e efforts underway to encourage no- or low-till practices, outreach and education o n 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 stree ts;

o The Limestone-Graveyard Creeks Watershed Project re duces 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 E vent,” 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 impro vements created by each farmer/owner with costs of conservation improvement s 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 incent ivize 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 conse rvation 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 th e 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. C RP acreage in upwind and surrounding counties is shown in Figure 6.

• Vegetation, signage, and/or other dust control meas ures 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 an d 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 Even t,” November 20, 2013, pages 119-122.
15 Ibid., 121.
16 “The APCD considers restricted vehicle speeds, main tained gravel, natural vegetation, restricted acces s, pavement, compaction, revegetation, watering, and e xtraction limitation to be the appropriate available and practical method that is technologically feasible and economi cally reasonable in order to minimize fugitive part iculate 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 sha red by Prowers Area Transit and the defunct Cowboy Corral Storage, feed supply, and gra in storage companies. The transit company is on a concrete slab connecting to an asph alt road. 17

o Site J is owned by Heath & Son & Turpin Trucking an d is a well-maintained gravel lot used for truck storage. 18

o Site K is the Lamar Water Department and Lamar-Prow ers County Volunteer Fire Department and is a restricted access site of grate d (sic) and watered gravel on an asneeded basis. 19

o Site L is the power plant that hosts the monitor an d is a restricted access lot owned by Lamar Light and Power. It has been a gas fired boil er, 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 me asures: 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 whi le under the 1 ton per year APEN exemption, transfer locations were enclosed, and th e 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 ve getation 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-se aled crushed-gravel parking lot for Prowers County Jail and the Prowers County Municipa l Court that is maintained by the county 22

.

17, 18, 19, 20, 21, 22 “The APCD considers restricted vehicle speeds, main tained gravel, natural vegetation, restricted access, pavement, compaction, revegetation, waterin g, and extraction limitation to be the appropriate available and practical method that is technologically feasible a nd economically reasonable in order to minimize fug itive 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 an d gravel under CDPHE permit #99PR0179F. It emits 8 tons per year of PM 10 and is a wet mining operation employing the following dust control measures: watering as ne eded, 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, main tained gravel, natural vegetation, restricted acces s, pavement, compaction, revegetation, watering, and e xtraction limitation to be the appropriate availabl e and practical method that is technologically feasible and economi cally reasonable in order to minimize fugitive part iculate emissions for these sites..” “TSD for the November 5, 2011, Lamar Exceptional Event,” November 20, 201 3, page 81.12

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

According to CDPHE’s TSD:
The APCD conducted thorough assessments to determin e 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, t he APCD discovered that these sites were either reasonably controlled or considered to be na tural sources during the November 5, 2011, high wind event. Therefore, these sites were not si gnificant contributors to fugitive dust in the Lamar area during the November 5, 2011, high wind e vent. 25

Sections 2 and 5 of CDPHE’s demonstration show that the monitor in Lamar was affected by PM 10 transport from outside the area, with the main sour ce areas located in agricultural areas in Colorado and to the southwest in northwestern New Mexico. In additi on to transport, the spatial extent of elevated PM 10 concentrations throughout southern Colorado and the wind speeds associated with the event factor into EPA’s evaluation of whether this event is nRCP in L amar. Therefore, the EPA concludes that this event was nRCP pursuant to the Treatment of Data Influenc ed 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 Ev ent,” 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 e xcess 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-hou r average data, 5-year time series of 24-hour average s for the years of 2006-2011, and monthly data showing that all readings greater than 100 μ g/m 3 might be considered statistical outliers. CDPHE ex plains that for the concentration measured on November 5, 2011:

The PM 10 sample on November 05, 2011, at Lamar Power of 192 μ g/m 3 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 th ree samples greater than the event sample are all associated with a high wind event. There are 2181 s amples in this dataset. The sample of November 05, 2011, clearly exceeds the typical samp les for this site. 26

The EPA “Interim Guidance on High Wind Exceptional Events” recommends that demonstrations also consider percentile ranks when dust impacted data i s 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 E vent,” November 20, 2013, page 55.
27 See “Interim Guidance on the Preparation of Demons trations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Excep tional Events Rule” of May 2013, page 20.
28 “TSD for the November 5, 2011, Lamar Exceptional Ev ent,” November 20, 2013, page 54.14

Since at least 2005 in these areas, values exceedin g the NAAQS are only found during high wind dust events, including November 5, 2011. This informatio n indicates that values at the level seen on Novemb er 5, 2011 are extremely rare in the absence of high w ind dust exceptional event impacts, and that it is unlikely that any sources of PM 10 were involved in the November 5, 2011 exceedance o ther 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 t he 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 occurr ed and that emissions related to the event were transp orted in the direction of the monitor(s) where measurements were recorded; the size of the area af fected by the transported emissions; the relationsh ip 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 analyse s 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 concentrat ions over much of New Mexico and southeast Colorado. Thi s model output suggests that this drought-stricken region was a major source region for blowing dust o n November 5, 2011, in Lamar. 31

29 See “Interim Guidance on the Preparation of Demons trations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Excep tional 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 Ev ent,” 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 Divisi on described the November 5, 2011 event as follows:
Gusty winds along a cold front kicked up a rather e xtensive area of thin to moderate density blowing dust which extended from southern New Mexic o/far western Texas (near and SE of El Paso)/northern Mexico to western Oklahoma and weste rn Kansas. NOAA scientists with expertise in the analysis of dust storms have indic ated 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 Ev ent,” November 20, 2013, page 49.16

CDPHE generally summarizes that:

The PM 10 exceedance in Lamar on November 5, 2011, would not have occurred if not for the following: (a) dry soil conditions over southeast C olorado, southern and eastern New Mexico, western Texas, and northern Mexico with 30-day prec ipitation totals below were near or below 0.5 inches (Figure 20 and Figure 21); (b) a combina tion of synoptic and mesoscale weather events; (In the synoptic scale, high winds were pro duced 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 str ong outflow winds from collapsing thunderstorms.) (c) friction velocities over a wide area of southeast Colorado, southern and eastern New Mexico, western Texas and northern Mexi co that were high enough to allow entrainment of dust from natural sources with subse quent transport of the dust to southeastern Colorado in strong winds. 34

CDPHE further states that “The statistical and mete orological data clearly shows that but for this hig h wind blowing dust event, Lamar would not have excee ded the 24-hour NAAQS on November 5, 2011”. 35 Therefore, the EPA concludes that there was a CCR f or 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 CCR 36 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 E xceptional 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 demonst rations on the preceding three pages of this (EPA’s) TSD are cited in Table 5. Additionally, CDP HE states that:
Since at least 2005, there has not been an exceedan ce that was not associated with high winds carrying PM 10 dust from distant sources in Lamar. This is evidenc e that the event was associated with a measured concentration in excess of normal h istorical fluctuations including background. 37

34 Ibid., 9.
35 Ibid., 85. 36 See “Interim Guidance on the Preparation of Demons trations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Excep tional Events Rule” of May 2013 page 21.
37 “TSD for the November 5, 2011, Lamar Exceptional Ev ent,” November 20, 2013, page 85.17

Therefore, the EPA concludes that this event Affect ed 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 E xceptional 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 speci fically, a significant natural dust storm originating in southern and eastern New Mexico, wes tern 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 La mar 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 canno t be reasonably controlled or prevented. 38

CDPHE has sufficiently demonstrated the CCR and nRC P requirements for the November 5, 2011 event. Therefore, the EPA concludes that this was a natura l event pursuant to the Treatment of Data Influence d 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 Ev ent,” November 20, 2013, page 86.18

Table 6: EPA’s Analysis of CDPHE’s TSD of Natural E vent 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 t he 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 inform ation presented in the demonstration that show both the nRCP and CCR requirements have been met an d states that:

The PM 10 sample at Lamar Power (192 μ g/m 3 ) exceeded the 99 th 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 d ust event, Lamar would not have exceeded the 24-hour NAAQS on November 5, 2011. Since at least 2 005, there has not been an exceedance that was not associated with high winds carrying PM 10 dust from distant sources in Lamar. This is evidence that the event was associated with a measu red 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 PM 10 concentrations before the periods of high winds on the event days were at or below 55 ug/m 3 prior to and below 25 ug/m 3 after the event; all well below the 24-hour PM 10 NAAQS of 150 ug/m 3 , providing further

39 “TSD for the November 5, 2011, Lamar Exceptional E vent,” 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 t o 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 EP A’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 1 st 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 PM 10 transport from arid regions in southern and easter n New Mexico, western20

Texas, and northern Mexico into the Lamar area on N ovember 5, 2011. This high wind event caused an exceedance of the 24-hour PM 10 NAAQS at the location identified in Table 1 of this document on November 5, 20011, in Lamar. EPA concurs that the f lagged exceedance at the Lamar monitor on this day meets the definition of an exceptional event: the e vent affected air quality, was nRCP, and met the definition of a natural event. Specifically, EPA ha s determined that the event was nRCP due to high wi nd conditions that transported PM 10 from sources outside of the immediate Lamar area an d also subsequently may have overwhelmed some reasonable controls withi n Lamar. Also, regardless of transport into the area, information pertaining to the controls implem ented within the affected area, the spatial extent of elevated PM 10 concentrations measured in the area, and the wind s peeds 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 an d the measured exceedance, there would have been NEBF, and the measured exceedance is in excess of n ormal HFs.
EPA finds that the weight of evidence is sufficient to concur on the flagging of the data for the 24-h our PM 10 NAAQS exceedance of 192 ug/m 3 at the Lamar Power Plant monitor on November 5, 20 11.

This concurrence does not constitute final EPA acti on regarding any matter on which EPA is required to provide an opportunity for public comment. In parti cular, this applies to determinations regarding the attainment status or classification of the area. Fi nal actions will take place only after EPA complete s notice and comment rulemaking on those determinatio ns.