1



### EPA Technical Support Document i n Review of Colorado Department of Public Health and Environment’s Demonstration Package for the

April 1 and 2, 2015 Lamar Exceptional Event s

E XCEPTIONAL EVENT RUL E 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 section s contain definitions, criteria for EPA approval, procedural requirements, and requirements for air agency demonstrations, all of which must be met before
the EPA can concur under the EER on the exclusion of air quality data from regulatory decisions.

Und er 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 ev ent 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 t he 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 th e event.

This review applies the EPA’s “Interim Guidance of the Preparation of Demonstrations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Exceptional Events Rule” of May 2013, (Interim Guidance for High Wind Exceptional Events) in addition to the applicable statutory and regulatory provisions.

1 A natural event is further described in 40 CFR 50.1(k) as “an event in which human activity plays little or no direct causal role”.2

TABLE OF CONTENTS
Exceptional Event Rule Requirements

................................ ................................ ........................... 1
Summary

................................ ................................ ................................ ................................ ......... 3

Overview

................................ ................................ ................................ ................................ ..... 3 April 1 & 2, 2015

................................ ................................ ................................ ........................ 4
Not Reasonably Controllable or Preventable

................................ ................................ .................. 9 Anthropogenic sources of dust have reasonable controls in place:

................................ ........... 10 Reasonable controls have been effectively implemented and enforced:

................................ ... 12 Wind speed was high en ough to overwhelm the reasonable controls:

................................ ...... 19

Historical Fluctuations

................................ ................................ ................................ .................. 22
Clear Causal Relationship

................................ ................................ ................................ ............. 23 April 1, 2015

................................ ................................ ................................ ............................. 24 April 2, 2015

................................ ................................ ................................ ............................. 24
Affects Air Quality (AAQ)

................................ ................................ ................................ ........... 26

Natural Event

................................ ................................ ................................ ................................ 27

No Exceedance or Violation But For the Event

................................ ................................ ............ 28
Schedule and Procedural Requirements

................................ ................................ ........................ 28

Conclusion

................................ ................................ ................................ ................................ .... 293

SUMMARY

Overview

On December 4 , 2015 the Colorado Department of Public Health and Environment ( CDPHE ) submitted a demonstration (termed a Technical Support Document or TSD) for exceptional event
exceedance s of the 24

- hour PM 10 standard that occurred at the monitoring station in Lamar on April 1 and 2, 2015 . Table 1 summarizes the exceedance that CDPHE would like considered for exceptional event concurrence in the Air Quality System ( 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 Avg. (ug/m 3 ) CDPHE Request

to Consider for AQS Removal? April 1, 2015 Lamar Municipal

Building 0 8

- 99

- 0002 253 Yes

April 2 , 201 5 Lamar Municipal

Building 08

- 99

- 0002 419 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 s 1 and 2

.

Figure 1: Map of Desert, Four Corners, and Monitor Location with the PM 10 NAAQS Exceedance s4

Figure 2: Map of High Plains and Monitor Location with the PM 10 NAAQS Exceedances

April 1 & 2 , 2015 :

On April 1 and 2

, 2015 a strong upper level low pressure system transited southern Canada from west to east. An upper level trough extended south from the low, and the trough and associated cold fronts passed through eastern Colorado. The cold front remained in southeast C olorado from late April 1 through April 2, and the front passed over Lamar, Colorado the evening of April 1 and again twice on April 2. Strong surface winds associated with the trough and frontal passages occurred in the evening of both April 1 and April 2 . Of April 1, 2015, CDPHE said:

The exceedance in Lamar was the result of intense surface winds in the wake of a passing cold front. The surface winds in southeast Colorado were also likely enhanced by post

frontal thunderstorms moving to the north of Lam ar. These surface features were associated with a strong upper

- level trough that was moving across the western United States. The surface winds were predominantly out of a northerly direction which moved over dry soils in eastern Colorado, producing signif icant blowing dust

. 2

2 “TSD for the April 1 and 2, 2015 Lamar Exceptional Events,” December 4, 2015, page 7.5

Of the April 2, 2015 winds, CDPHE said:

In advance of the cold front the wind in southeast Colorado was predominantly out of a south to southeasterly direction and was quite gusty at times. However, the wind increased significa ntly on ce the cold front passed. ... By 8:00 PM MST, a significant amount of “bunching” of isobars was occurring in southeast Colorado behind the cold
front.

... This indicates that a strong pressure gradient was in place. Wind speed is directly proportional to the p ressure gradient, so a higher pressure gradient will produce stronger winds

... 3

EPA Figure 3 (April 1 at 5:00 pm MST) from CDPHE’s demonstration is described with :

The 700 mb level is located roughly 3 kilometers above mean sea level (MSL). This chart shows that a deep trough of low pressure was present at the 700 mb level at the onset of the blowing dust event of April 1, 2015, and that it was moving over eastern Colorado. 4

3 Ibid., 22.

4 Ibid., 8.6

Figure 3: 700 mb Upper Level Analysis at 5:00 pm MST on April 1, 2015 (CDPHE’ s TSD Figure 2) 5

Figure 4, also from the CDPHE demonstration, shows a similar view for April 2 at 5:00 pm MST. The low pressure system has progressed eastward, but the upper level trough continues to extend to the southwest into eastern Colorado.

5 Ibid., 9.7

Figu re 4: 700 mb Upper Level Analysis at 5:00 pm MST on April 2, 2015 (CDPHE’s TSD Figure 12) 6

Figure 5 from the CDPHE demonstration shows the surface level analysis for April 1 at 8:00 pm MST. A cold fro nt extends south and west of the low pressure system in southern Canada, and lies just south of Lamar, having passed over Lamar earlier that evening. A similar view in Figure 6, from 5:00 pm MST on April 2 shows the same front still in southern Colorado and again lying
over Lamar.

6 Ibid., 21.8

Figure 5: Surface Level Analysis at 8:00 pm MST on April 2 (CDPHE’s TSD Figure 4) 7

7 Ibid., 10.9

Figure 6: 700 mb Upper Level Analysis at 5 PM MST on April 2, 2015 at 5:00 pm MST (CDPHE’s TSD Figure 14) 8

Figures 2

- 10 and 12

- 23 from CDPHE’s demonstration (not all included here) use meteorology, radar imagery and monitoring analysis to support the evidence of wind direction and reach of the
dust storm into Lamar.

CDPHE provides a comprehensive description and discussion of these event s in Sections 2, 3, 4,
and 5 of the demonstration.

NOT REASONABLY CONTROLLA BLE 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 s peed, 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;

8 Ibid., 23.10

 The reasonable controls have been effectively implemented and enforced; and

 The wind speed was high enough to overwhelm the reasona ble controls. 9

The following nRCP analysis is broken down into three subsections that correspond to the three bullets above.

Anthropogenic sources of dust have reasonable controls in place:

In addressing reasonable controls, CDPHE provided detailed info rmation on the current set of required and voluntary controls in the Lamar area, including information on implementation of

s tate Regulations 1, 3, 6, and 9, rule effectiveness, compliance and public notification activities that occurred on the event day. As CDPHE states:

The APCD conducted thorough analyses and outreach with local governments to confirm that no unusual anthropogenic PM 10 - producing activities occurred in these areas and that despite reasonable control measures in place, high wind condition s overwhelmed all reasonably available controls

. ... This information shall confirm that no unusual anthropogenic actions occurred in the local areas of Lamar during this time. 10

CDPHE’s demonstration provides an analysis of the state and local controls in p lace to control
PM 10 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. 11

Lamar has the following controls in place: 12

9 “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 201 3, page 10.
10 “TSD for the April 1 and 2, 2015 Lamar Exceptional Events,” December 4, 2015, page 45.

11 Ibid., 45

- 47.
12 Ibid., 47

- 51.11

 A Natural Events Action Plan (NEAP) for High Wind Events completed in 2003, an d updated in 2012, which addresses public education, notification, and health advisory systems as well as implements Best Available Control Measures (BACM) 13 ;

 A PM 10 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) 14 ;

 State Implementation Plan (SIP) measures requiring owners/operators responsible for construction and/or maintenance of existi ng 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 th e 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. 15 Other BACM include installing 100,000 ft 2 of turf sod and irrigation at recreational open space Escondido Park, and fencing off and stabilizing lots that formerly contributed to fugitiv e dust;

 Other measures include: Art. XVII, Sec. 16

- 17

- 60 requiring off street parking lots to have a dust free surface, 16 and the Prowers County Land Use plan adopted in 2004 and amended in 2006; through it the county has authority over “construction, sitin g, health, fire, environmental codes, and other social concerns with provisions to minimize airborne dust” 17 ;

 Non

- enforceable measures include:

o The Colorado State University CO

- OP Extension Office efforts underway in the
Lamar area to encourage no

- or low

- till practices, outreach and education on soil management programs, and drought workshops to protect topsoil; 18

o Voluntary and s tate

- Only measures including weekly street sweeping and a city policy requir ing that new developments have paved streets; 19

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

13 Ibid., 47

- 48 and at: http://www.colorado.gov/airquality/tech_doc_repository.aspx?action=open&file=LamarNaturalE ventsActionPlan2012.pdf.

14 “TSD for the April 1 and 2 2015 Lamar Exceptional Events,” December 4, 2015, page 48.
15 Ibid., 49.
16 Ibid., 50.
17 Ibid., 51.
18 Ibid., 66.
19 Ibid., 48.12 the 60,000 acres now have a conservation plan and are enacting improvements created by each farmer/owner wi th costs of conservation improve ments split with the government; 20 and

o The Natural Resources Conservation Service (NRCS) is promoting: a rangeland management program, a tree planting program, a drip irrigation purchase program, a multi

- party drought respons e effort through the State of Colorado Governor’s office, and a program to incentivize erosion mitigation

. 21

 The United States Department of Agriculture (USDA) NRCS Conservation Reserve Program (CRP) includes conservation provisions in the Farm Bill which e ncourages farmers to contract with USDA to “place erodible cropland and other environmentally

sensitive land into long

- term conservation practices for 10

- 15 years” 22 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. Table 2 shows amounts of cropland under contract in surrounding counties in the years preceding the events.

Table 2 : Acres by County near Lamar Enrolled in the USDA NRCS CRP Program 23

COUNTY 2008 2009 2010 2011 2012 2013
Bent 25,649 25,700 24,056 24,412 33,886 23,566
Kiowa 216,307 217,881 187,394 192,222 177,100 181,169
Baca 260,040 258,469 161,147 274,281 277,508 264,071 Crowley 21,419 21,461 21,069 20,329 21,917 18,490
Otero 2,559 2,864 2,706 2,851 2,054 2,635
Las Animas 21,869 21,860 17,403 17,616 18,925 18,887 Cheyenne 142,075 140,071 94,852 113,753 122,862 99,074
Lincoln 155,505 155,425 137,099 145,248 118,948 116,289
Prowers 170,909 171,813 140,827 163,354 154,882 151,731
Total 1,016,333 1,015,544 786,554 954,066 928,082 875,912

Reasonable controls have been effectively implemented and enforced:

The following analysis corresponds to aerial maps provided by CDPHE identifying lots that could possibly contribute to anthropogenic blowing dust, and effectively explains the

20 Ibid., 68.

21 Ibid.

22 Ibid., 67.
23 Data for the USDA NRCS CRP program were provided as supplementary information per EPA request on April 17, 2014 by Ray Mohr of CDPHE.13

implementation of dust control in place for each lot, or explains the permit and monitoring history of the site, as applicable.

 Vegetation, signage, and/or other dust control measures are in place for undeveloped parcels of land in Lamar. Figures 7 and 8 below show that identified areas of soil disturbance north of the monitor have reasonable controls near the Lamar monitor. 24

o Sit e A is owned by Heath & Son & Turpin Trucking and HVH Transportation Inc., a large truck repair and freight service trucking company, respectively. It is a well

- maintained gravel lot

.
o Site B is a fenced watered

- as

- needed gravel lot shared by Prowers Area Transit and the defunct Cowboy Corral Storage, feed supply and grain storage companies. The transit company is on a concrete slab connecting to an asphalt road

.
o Site C is owned by Heath & Son & Turpin Trucking and is a well

- maintained gravel lot used for truck storage

.
o Site D is the Lamar Water Department and Lamar

- Prowers County Volunteer Fire Department and is a restricted access site of grated (sic) and watered gravel on an

as

- needed basis

.
o Site E is the power plant that hosts the monitor and is a res tricted access lot owned by Lamar Light and Power. It has been a gas fired boiler, natural gas power plant and coal

- fired 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 emer gency coal stockpile controlled through a water

- dust suppression system

.
o Site F is the Burlington Northern Santa Fe railroad and is covered in gravel 50 feet on either side of the tracks, surrounded by natural vegetation with xeriscape

.
o Site G is Colorad o Mills LLC sunflower oil and feed processing facility operating under CDPHE permit #95PR622. Permit conditions include 30% maximum opacity limit, PM limits, and an Operation and Maintenance Plan. The last inspection on 2/14/12 found no visible emissions, and in

- house monthly inspections and the use of cyclones for emission control demonstrate PM mitigation efforts

.

24 “ The APCD considers the enforceable conditions of the permit, including identified continuous controls such as gravel roads with miles per hour restrictions, compaction, re

vegetation, watering, and extraction limitation, to be technologically feasible and economically reasonable for a facility of this size in order to minimize fugitive particulate emissions for this site .” “TSD for the April 1 and 2 2015 Lamar Exceptional Events,” December 4, 2015, page 62.14 o Site H is partially owned by Century Link and is a fenced gravel lot with restricted access. The remainder of the site is a free chip

- sealed c rushed

- gravel parking lot for Prowers County Jail and the Prowers County Municipal Court that is maintained by the county

.
o Site I is owned by Prowers County and leased to the Colorado State Highway Patrol for office space. The lot is covered in gravel for dust suppression, drainage and erosion control. Lot has restricted access and a 5 mph speed limit

.
o Site J is owned by Ranco, a heavy duty construction trailer manufacturer. The property is covered in pavement, gravel, and natural vegetation, with no

unnat ural, disturbed areas that may have contributed to blowing dust

.
o Site K is owned by Valley G lass and the property has restricted access to a well maintained gravel lot;

Figure 7 : Lamar Site Assessment (CDPHE’s TSD Figure 35) 25

25 “TSD for the April 1 and 2 2015 Lamar Exceptional Events,” December 4, 2015, page 54.15

Figure 8 shows areas of dis turbed soil further north from the Lamar monitor than those shown in Figure 7.

 Site L is owned by All

- Rite Paving and Redi

- Mix Inc. and is a concrete batch plant permitted by CDPHE (#12PR1396). The facility is considered APEN exempt and emits
less than 1 t on per year of PM 10

. 26 Baghouse collection efficiency is 99%, there is a 20% opacity limit, and water sprays and magnesium chloride are used on storage piles and roads as needed. There is a 10 mph speed limit, transfer of materials occurs in enclosed areas, and the lot is fence d

.

 Site M is mined by Carder Inc. for sand and gravel and emits no more than 15 tons per year under CDPHE permit #99PR0180F. It is a wet mining operation to prevent fugitive dust, and uses the following preventative measures: watering as needed, re

- vegetat ion within one year of disturbance, compacting piles, 10 mph speed limit, and temporary roads are graveled and watered as needed

.

 Site O was mined by All

- Rite Paving and Redi

- Mix Inc. and was a concrete batch plant permitted by CDPHE. Baghouse collection efficiency was 99%, there was a 20% opacity limit, and water sprays and magnesium chloride were used on storage piles and roads as needed. There was a 10 mph speed limit, transfer of materials occurred in enclosed areas,
and the lot was fenced. 27 Partnering with the Division of Wildlife, the c ity of Lamar took over the lot in 2013 and has been reseeding it to create a fishing and wildlife park free of motorized vehicles. (It appears that All

- Rite Paving and Redi

- Mix Inc. moved to Site E, see below)

.

 Site P i s owned by the Ranchers Supply Co. Inc. and is a fenced 90% gravel lot for long

term oversize vehicle parking. It has a 10 mph policy, is watered as

- needed, and meets Air Quality Control Commission (AQCC) Regulation 1 requirements (Section III.D.1(a)

.

 Site Q is owned by Ranco, a heavy duty construction trailer manufacturer. The property is covered in pavement, gravel, and natural vegetation, with no unnatural, disturbed areas that may have contributed to blowing dust

.

 Site R is C.F. Mailer Composites Inc. and is a paved parking lot and surrounding natural vegetation with a short, maintained gravel road to a loading dock used once a day

.

 Site S is owned by Prowers County and leased to the Colorado State Highway Patrol for office space. The lot is covered in gravel for dust suppression, drainage, and erosion control. Lot has restricted access and a 5 mph speed limit

.

 Site T is Lamar Feed and Grain

– White Stone Farms, CDPHE permit #00PR0431. On the property is a grain receiving pit, shipping truck loadout st ation, grain storage, grain cleaning scalper and grain handling and milling systems. The permit includes dust control

measures: t otal PM, PM 10 and PM 2.5 annual emissions limitations, visible emissions not to exceed 20%, a ll equipment maintained consistent with good air pollution control

26 Ibid., p. 61.
27 Ibid., p. 6316

practices and the feed mill equipped with a mineral oil spray system to control PM
emissions

.

 Site U was Dragon EPS beginning in 1993, but merged in 2011 with Ranco (site Q and J above). CPDHE permit #08PR0603 issued 12/21 /11 covers paint booths and abrasive blasting units with the following PM controls: p ermitted annual TSP, PM 10 and PM 2.5 emission limits, High Volume Low Pressure paint spray guns, exhaust filters on paint spray booths, baghouse filters on blasting units, visible emissions not to exceed 20%, source must follow CPDHE operations and maintenance plan. It was last inspected on 11/9/11 and found to be in compliance

.

 Site V is a restricted access property that is naturally vegetated and appears to be
undisturbe d

.17

Figure 8: Lamar Site Assessment (CDPHE’s TSD Figure 44) 28

Site W, shown in Figure 9 (Figure 49 in the CDPHE demonstration) is the Robins Redi

- Mix Concrete Batch Plant approximately 4.5 miles north of the Lamar monitor. It opened in spring of 2010 and consists of a dry truck mix plant using a cement and a dry ash silo operated with pneumatic conveyers and bag houses to control 98% of emissions. In April 2010 CDPHE issued a permit exempt letter (10PR1310.XP) w hich includes PM point and

28 Ibid., 61.18

fugitive dust control measures such as: u ncontrolled PM cannot exceed 10 TPY and
uncontrolled PM 10 cannot exceed 5 TPY, and visible emissions cannot exceed 20%. The source waters the lot during processing and as

- needed, uses CDPHE Best Available Technology (BACT) for li mestone and ash handling, paving, wash

- down systems and enclosures.

Figure 9 : Site W, Robins Redi

- Mix Concrete Batch Plant (CDPHE’s TSD Figure 49) 29

According to CDPHE’s demonstration:

The APCD conducted thorough assessments to determine if the potential soil disturbances shown in Figure 34 through Figure 49 were present during the 2015 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 du ring the 2015, high wind events. Therefore, these sites were not significant contributors to fugitive dust in the Lamar area during the April 2015, high wind events

. 30

29 Ibid., 66.
30 Ibid.19

Wind speed was high enough to overwhelm the reasonable controls:

CDPHE provided EPA Ta bles 3 and 4 (CDPHE Tables 1 and 4 ) showing that sustained wind speeds associated with th ese event s were above 30 mph and gusts were above 40 mph. CDPHE previously established in its exceptional events demonstration for the January 19, 2009 event in Lamar, Colorado that wind speeds of 30 mph and/or gusts of 40 mph or higher have been shown to cause blowing dust in Colorado. T he sustained winds and gusts in Lamar exceed this Colorado
threshold

. T ransported dust from the upwind desert and arid plains region s appears to be a significant contribution to the exceedance , in addition to local winds overwhelming implemented local controls. EPA notes that the high local gust speeds in Lamar would likely be capable of overwhelming some local controls. Section 5 of the TSD provided by CDPHE supports this conclusion by describing in detail “Best Available Control Measures (BACM), other reasonable control measures, applicable federal, state, and local regulations, appropriate land use management, and an in

- depth analysis of potential areas of local soil disturbance for Lamar during the April 201 5 event s .” 31

31 Ibid., 45.20

Table 3 : Wind Speed Lamar , CO on April 1, 2015 (CDPHE’s TSD Table 1 ) 32

32 Ibid., 17.21

Table 4 : Wind Speed Lamar, CO on April 2, 2015 (CDPHE’s TSD Table 4) 33

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

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

 Regional wind and weather by hour, as well a s wind direction, through MesoWest; and

33 Ibid., 17.22

 Maps establishing the lack of regional precipitation and drought status from the USDA, NOAA and the National Drought Mitigation Center

. These analyses demonstrate through the weigh t of evidence the existence of high wind blowing dust event s originating upwind of the monitor in question.

Sections 2 and 5 of CDPHE’s demonstration show that the monitor in Lamar was affected by
PM 10 transport across a large region , with the main source areas located in ag ricultural areas in Colorado and Kansas . In addition to transport, the wind speeds associated with the event factor
into EPA’s evaluation of whether these events are nRCP in Lamar

. Therefore, the EPA
concludes that t hese events were nRCP pursuant to the Treatment of Data Influenced by the
EER

. Table 5 summarizes the EPA’s evaluation of CDPHE’s nRCP EE demonstration.

Table 5 : EPA’s Analysis of CDPHE’s TSD of nRCP
Exceedance
Date Reasonable

Controls Demonstration Citation Wind Speed

Demonstration Citation Sufficient

Quality of Evidence? EPA

Criterion Met?

April 1, 2015 Section 5: p. 45

- 69 Section 2: p. 7

- 19 Yes Yes

April 2, 2015 Section 5: p. 45

- 69 Section 2: p. 2 0

- 32 Yes Yes

HISTORICAL FLUCTUATI ONS
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 April 1 and 2, 20 15 data and a 5

- year time series of 24

- hour averages for the years of 20 10

- June
201 5

. The 201 0

- 2015 data set had 1, 875 samples, and each description below indicates the samples taken on these days ex ceed the typical samples for this site. CDPHE explains that for the
concentration measured on April 1, 2015 :

The PM 10 sample on April 1, 2015, at Lamar Municipal of 253  g/m 3 exceeds the 99th percentile value for all evaluation criteria and is the 11th largest sample of the dataset. The ten samples greater than the event sample are all associated with high wind events

. 34

34 Ibid., 33.23

CDPHE explains that for the concentration measured on Ap ril 2 , 201 5 :

The PM 10 sample on April 2, 2015, at Lamar Municipal of 419  g/m 3 exceeds the 99th percentile value for all evaluation criteria and is the 2nd largest sample of the dataset. The only sample greater than the event sample is associated with a high wind even t

. 35

The EPA “Interim Guidance on High Wind Exceptional Events” rec ommends that demonstrations also consider percentile ranks when dust impacted data is to be excluded. 36
CDPHE s tates that the percentile rank for these data are both at the 9 9 .5 percentile level

.

Since at least 2005 in these areas , values exceeding the NAAQS are only found during high wind dust events, including those in 2013 . This information indicates that values at the level seen on April 1 and 2, 201 5 are extremely rare in the absence of high wind dust exceptional events, and

t hat it is unlikely that any sources of PM 10 were involved in the 201 3 exceedance s other than wind

- blown dust. Therefore, the EPA concludes that these events were in excess of HF pursuant to the Treatment of Data Influenced by the EER. Table 6 summarizes th e EPA’s evaluation of CDPHE’s HF EE demonstration.

Table 6 : EPA’s Analysis of CDPHE’s TSD of HF
Exceedance
Date Exceedance

Location Historical Fluctuations

Demonstration Citation Sufficient Quality of Evidence? EPA

Criterion Met?

April 1, 2015 Lamar Municipal

Building Section 3: p. 33

- 38 Yes Yes

April 2 , 20 15 Lamar Municipal

Building Section 3: p. 38

- 43 Yes Yes

CLEAR CAUSAL RELATIO NSHIP

The 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 transpo rted 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

35 Ibid., 38.
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 20.24

emissions, and recorded concentrations; and, as appropriate, poll utant species

- specific information supporting a CCR between the event and the measured concentration. 37

Section 2 of CDPHE’s demonstration provides analyses that demonstrate the existence of high wind blowing dust event s originating north of the monitors in question , but including
south east ern Colorado contribution s

. April 1, 2015 :

The National Weather Service Pueblo, Colorado forecast discussion webpage issued at 4:12 am on April 1, 2015 stated that :

“ Models are showing potential for is ol[ate]d to sc[a]t[tered] high

- based convection developing this afternoon over the SE plains. Given surface dewpoints in the 20s...there is a potential for isol[ate]d dry lighting (sic)...and erratic gusty winds from virga and convective downdrafts.” 38

T he 3:08 pm forecast discussion from the Goodland, Kansas office o f the National Weather Service stated :

“ North winds will rapidly increase as the low level jet and rapid surface pressure rises move through the area. Gusts approaching 40 mph are certainty (sic) likely during the evening as a result. Due to the very dry conditions...there could be some blowing dust for locations that have not yet received rainfall.” 39

April 2 , 201 5 :
The NOAA Satellite Services Division was in agreement with the conclusion that blowin g dust was occurring in the wake of the cold front which passed over Lamar late on April 1 and then impacted Lamar again on April 2, 2015 . The Smoke Text Product from NOAA at 11:45 am MST on April 2 , 201 5 stated:

“ Further southwest and west, the aerosol i s more likely to be blowing dust behind the cold front that is dropping south through the Texas Panhandle.” 40

CDPHE issued a blowing dust advisory for southeast Colorado, including Lamar, at 12:00 pm MST :

37 See “Interim Guidance on the Preparation of Demonstrati ons 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.
38 TSD for the April 1 and 2, 2015 Lamar Exceptional Events,” December 4, 2015, page 13, citing http://mesonet.agron.iastate.edu/wx/afos/ as the source for the quote.
39 Ibid.
40 TSD for the April 1 and 2, 2015 Lamar Exceptional Events, December 4, 2015, page 18, citing http://www.ssd.noaa.gov/PS/FIRE/DATA/SMOKE/2015D021754.html as the source.25 “ Strong gusty winds will create areas of blowing dust through Thursday evening. Winds and the threat for blowing dust will decrease after about 10 PM.” 41

The Pueblo National Weather Service office forecast discussion at 7:57 pm MST stated:

This front has produced very gusty north winds...much stronger than originally anticipated...and these strong winds have kicked up an (sic) rather large area of dust and reduced visibilities. Therefore...dust advisory has been issued for portions of the SE plains through this evening until midnight. 42 (Source: http://mesonet.ag ron.iastate.edu/wx/afos/)

CDPHE generally summarizes that :

The PM 10 exceedances in Lamar would not have occurred if not for the following: (a) dry soil conditions over source regions with 30

- day precipitation totals below the threshold identified as a precondition for blowing dust; and (b) meteorological conditions that

c aused strong surface winds over the area of concern

. 43

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

- 2015, and associates the trends with high wind blowing dust events. It is titled Analysis of Lamar Dr ought Condition Severity and Blowing Dust: 1897

- 2015. The review finds some correlation between prolonged drought (as defined by 7

- year annual average) and blowing dust conditions in Lamar. The enclosure is at the end of this document.

EPA conclu des that t here was a CCR for the s e event s pursuant to the Treatment of Data Influenced by the EER. Table 7 summarizes the EPA’s evaluation of CDPHE’s CCR EE
demonstration.

41 Ibid., page 26, citing http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=04%2f02%2f2015 as the

source. 42 Ibid., citing http://mesonet.agron.iastate.edu/wx/afos/ as the source.
43 Ibid., 70.26

Table 7 : EPA’s Analysis of CDPHE’s TSD of CCR 44

Exceedance Date Clear Causal Relationship Demonstration Citation Sufficient Quality of Evidence? EPA

Criterion Met?

April 1, 2015 Section 2: p. 7

- 19 Yes Yes

April 2 , 201 5 Section 2: p. 20

- 32 Yes Yes

AFFECTS AIR QUALITY (AAQ)

As stated in EPA’s Interim Guidance for High Wind Exceptional Events Section 3.4, the 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 demons trations on the preceding three pages of this (EPA’s) TSD are cited in Table 8 . Additionally, CDPHE states that:

Since at least 2005, there has not been an exceedance that was not associated with high winds carrying PM 10 dust from distant sources in these areas. This is evidence that the events were associated with a measured concentration in excess of normal historical fluctuations including background. 45

Therefore, the EPA concludes that these events Affected Air Quality pursuant to the Treatment
of Data Influenced by the EER. Table 8 summarizes the EPA’s evaluation of CDPHE’s AAQ EE
demonstration.

Table 8 : EPA’s Analysis of CDPHE’s TSD of AAQ
Exceedance Date HF

and CCR Affects Air Quality Demonstration Citation Sufficient Quality of Evidence EPA

Criterion Met?

April 1, 2015 HF Section 3: p. 33

- 38 Yes Yes

CCR Section 2: p. 7

- 19 Yes Yes

April 2 , 201 5 HF Section 3: p. 38

- 43 Yes Yes

CCR Section 2: p. 20

- 32 Yes Yes

44 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.
45 TSD for the April 1 and 2, 2015 Lamar Exceptional Events , December 4, 2015, page 70.27

NATURAL EVENT

As stated in EPA’s Interim Guidance for High Wind Exceptional Events Section 6.3.6 the EPA will consider an event to be a natural event if both the nRCP and CCR requirements have been adequately demonstrated. CDPHE states that :

Due to the semi

- arid nature of parts of the state, Colorado is highly susceptible to windblown dust events. These events are often captured by various air quality monitoring equipment throughout the state, sometimes resulting in exceedances or violations of the
24

- hour PM10 NAAQS. Th is document contains detailed information about the large regional windblown dust events that occurred on April 1st and 2nd, 2015. The Colorado Department of Public Health and Environment (CDPHE) Air Pollution Control Division (APCD) has prepared this repo rt for the U.S. Environmental Protection Agency (EPA) to demonstrate that the elevated PM10 concentrations were caused by a natural event

. 46

CDPHE has sufficiently demonstrated the CCR and nRCP requirements for the April 1 and 2,
2015 event s

. There fore, the EPA concludes that the s e were natural event s pursuant to the Treatment of Data Influenced by the EER. Table 9 summarizes the EPA’s evaluation of CDPHE’s Natural Event EE demonstration.

Table 9 : EPA’s Analysis of CDPHE’s TSD of Natural Event
Exceedance Dat e nRCP or CCR Natural Event Demonstration Citation Sufficient Quality of Evidence? EPA

Criterion Met?

April 1, 2015 nRCP

- Anthropogenic Section 5: p. 45

- 69 Yes Yes

nRCP

- Wind Speed Section 2: p. 33

- 38 Yes Yes

CCR Section 2: p. 33

- 38 Yes Yes

April 2

, 201 5 nRCP

- Anthropogenic Section 5: p. 45

- 69 Yes Yes

nRCP

- Wind Speed Section 2: p. 38

- 43 Yes Yes

CCR Section 2: p. 38

- 43 Yes Yes

46 Ibid., 1.28

NO EXCEEDANCE OR VIO LATION BUT FOR THE E VENT
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 effect s of the event s

. 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:

Elevated 24

- hour PM 10 concentrations were recorded at the Lamar Municipal Building monitor on April 1st and 2nd, 2015. Both of the noted twenty

- four

- hour PM 10 concentrations were above the 90th percentile concentrations for their locations (see Section 3) and exceeded the 99th percentile value of any evaluation criteria. The statistical and meteorological data clearly show that but for these high wind blowing dust events, Lamar would not have exceeded the 24

- hour NAAQS on April 1st and 2nd, 2015. Since at least 2005, there has not been an exceedance that was not associated with high winds carrying PM10 dust from distant sources in these areas. This is evidence that the event was associated with measured concentrations in excess of normal historical fluctuations including backgro und

. 47

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 all well below the
24

- hour PM 10 NAAQS of 150 ug/m 3 , providing further support for CDPHE’s conclusion. Table
10 summarizes the EPA’s evaluation of CDPHE’s NEBF EE demonstration.

Table 10 : 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?

April 1, 2015 Section 6: p. 70 Yes Yes

April 2 , 201 5 Section 6: p. 70 Yes Yes

SCHEDULE AND PROCEDU RAL 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 cor rections were made to

47 Ibid., 70.29

the report based on internal staff review. Table 1 1 outlines EPA’s evaluation of these requirements.

Table 1 1 : EPA’s Analysis of Schedules and Procedural Criteria
Reference Demonstration

Citation for Compliance EPA

Criterion Met?

Did the State provide prompt public notification of the event? 40 CFR 50.14(c)(1)(i) Section 1: p. 5 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) Flag May 22,

2015 ; Initial Description April 29, 2016 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 4

, 2015 Yes

Was the public comment process followed and documented? 40 CFR 50.14(c)(3)(v) Section 1: p. 6 Yes

CONCLUSION

The 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 Colorado and western
Kansas into the Lamar area on April 1 and 2, 2015 . These high wind event s caused exceedance s of the 24

- hour PM 10 NAAQS at the Lamar PM 10 monitor

. The EPA concurs that the flagged
exceedance s at the Lamar monitor on the s e day s meet the definition of exceptional event s : the

event s affected air quality ; the events were n RCP ; and the events met the definition as natural

event s . Specifically, the EPA has determined that the event was nRCP due to high wind
cond itions that transported PM 10 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 and the wind speeds associated with the high wind dust event s provide sufficient evidence
to conclude that these events were nRCP. Furthermore, the EPA has determined that there is a30

CCR between the event and the measured exceedance, there would have been NEBF, and the
measured exceedance s are in excess of normal HFs.

The EPA finds that the weight of evidence is sufficient to concur on the flagging of the data for
the 24

- hour PM 10 NAAQS exceedance of 253 ug/m 3 at the Lamar monitor on April 1, 2015 and 419 ug/m 3 on April 2, 2015.

This concurrence does not constitute the EPA ’s final action regarding any matter on which the 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 the EPA completes notice and comment rulema king on those determinations.1 Enclosure

Analysis of Lamar Drought Condition Severity and Blowing Dust Events: 1897

- 2015

Due to the high number of exceedances in Lamar from 2008 to 2014 due to dust, the EPA conducted an historical analysis of the drought conditions in the surrounding area from 1897 to 2015. The results of which confirm that these events, while recurrent, can be considered highly unu sual and therefore truly exceptional events. The National Oceanic and Atmospheric Administration Climate Data Online service includes monthly and annual precipitation data for Lamar, Colorado beginning in 1897. When annual precipitation is plotted over tim e, two periods with seven consecutive years of below average precipitation are seen: 1931 through 1937 (The Dust Bowl years) and 2007 through 2013. Since both periods were seven years long, the running average of annual precipitation calculated over seven year intervals is a useful statistic for comparing multi

year drought severity. The two lowest periods for seven year running average s in the 119 year data set are centered on 1934 and 2010. The 1934 minimum, at 9.39 inches (seven year average) is consider ably lower than the 2010 level at 12.1 inches. These would be compared to the long term mean annual precipitation of 15.1 inches.

In the 7 years prior to 2007 (2000

- 2006), Lamar experienced dust storms leading to PM 10 exceedances on 8 days. For the seven y ear period of 2007 through 2013, Lamar experienced 17 dust storm days leading to exceedances, with an additional 8 exceedances in March and April 2014, before above average rainfall began in May 2014. Dust storm activity was therefore more than twice as he avy during the dry 2007

- 2013 period as in the preceding seven years with a mixture of both above and below normal precipitation.

Since above normal rains began in May 2014, three dust storms leading to exceedances have been observed, in December 2014, on A pril 1

- 2, 2015, and in August 2015. The two storms in the spring and summer of 2015 compares to 7 in the spring and summer of 2013 and 8 in 2014, suggesting that normal or above normal rainfall will significantly
decrease wind

- blown dust events in the area . Therefore, the EPA can conclude that the increased amount of exceedances is due to an extreme fluctuation in precipitation that is highly unusual, and the events are not characteristic of normal PM 10 conditions in and around Lamar.2

Figure 1: Annual Precipitation, Lamar, Colorado, 1897

- July 2015 1

In the 7 years prior to 2007 (2000

- 2006), Lamar experienced dust storms leading to PM 10 exceedances on 8 days. There were never more than two years in a row with PM 10 exceedances before a year with no exceedances was observed. For the seven year period of 2007 through 2013, Lamar experienced 17 dust storm days leading to exceedances, with an additional 8 exceedances in March and April 2014, before above average rainfal l began in May 2014. Five consecutive years (2011

- 2015) saw at least one PM 10 exceedance day during a dust storm. Dust storm activity was therefore more than twice as heavy during the dry 2007

- 2013 period as in the preceding seven years with a mixture of
b oth above and below normal precipitation. PM monitoring in Lamar began in 1975 with TSP monitoring. PM 10 monitoring was added in 1985. Mean TSP expected exceedance

counts 2 decreased from an initial level of 16 to 18 exceedances per year in 1976 and 1977

1 EPA Region 8 staff analysis conducted July 29, 2015 ; 2015 rainfall updated April 29, 2016

. 2 Expected exceedances for PM 10 correct the number of measured exceedances by correcting for unsampled days, in accordance with 40 CFR Part 50, Appendix K. TSP expected exceedances were calculated here in a similar manner to provide comparable data to PM 10

.3

to a level of 5 to 6 exceedances per year in 1985

- 1986. 3 Mean PM 10 expected exceedance counts were from zero to 3 expected exceedances per year from PM 10 monitoring inception until 2013, when the three year mean jumped to seven at the end of the seven year d ry spell. 4 The Lamar exceedance on May 22, 2008, one of two exceedance dust storms observed that year, occurred in the second of the seven years of consecutive below average precipitation.

Figure 2: Lamar Precipitation and PM Exceedances, 1975

- 2015, EPA Re gion 8 Analysis 5

3 CDPHE data in the EPA AQS d atabase, accessed by EPA Region 8 July 24, 2015.

4 Ibid.
5 EPA Region 8 staff analysis conducted July 29, 2015 ; 2015 rainfall updated April 29, 2016

.