1



### EPA Technical Support Document i n Review of Colorado Department of Public Health and Environment’s Demonstration Package for the March 18 and April 2 , 201 2 Lamar and Alamosa 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 Regulatio ns (CFR). These sections 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 reg ulatory decisions.

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

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

 The event affe cts air quality ;

 The event is not reasonably controllable or preventable ; and

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

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

 The event is associated with a measured concentration in excess of normal historical fluctuations, including background; and

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

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

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

TABLE OF CONTE NTS
Excep tional Event Rule Requirements

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

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

Overview

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

March 18, 2012:

................................ ................................ ................................ ...................... 4
April 2, 2012:

................................ ................................ ................................ .......................... 7
Not Reasonably Controllable or Preventable

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

................................ ........... 11

Lamar Specific Controls

................................ ................................ ................................ ....... 11
Alamosa Specific Controls

................................ ................................ ................................ ... 14

Re asonable controls have been effectively implemented and enforced:

................................ ... 15

Alamosa Disturbed Area Analysis

................................ ................................ ........................ 19
Lamar Disturbed Area Analysis

................................ ................................ ............................ 21
Wind speed was high enough to overwhelm the reasonable controls

................................ .. 30

Historical Fluctuations

................................ ................................ ................................ .................. 35 Clear Causal Relationship

................................ ................................ ................................ ............. 37
March 18, 2012

................................ ................................ ................................ ......................... 37 April 2, 2012

................................ ................................ ................................ ............................. 38

Affects Air Quality (AAQ)

................................ ................................ ................................ ........... 39

Na tural Event

................................ ................................ ................................ ................................ 40

No Exceedance or Violation But For the Event

................................ ................................ ............ 41 Schedule and Procedural Requirements

................................ ................................ ........................ 42

Conclusion

................................ ................................ ................................ ................................ .... 433

S UMMARY

Overview
On March 10 , 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 s in Lamar and Alamosa, Colorado, on March 18 and April 2 , 201 2 . 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

- h our NAAQS
Exceedance Date Monitor/Site Name AQS ID 24

- hour Avg. (  g/m 3 ) CDPHE Request

to Consider for AQS Removal? March 18, 2012 Alamosa

- Adams

State College 08

- 003

- 000 1 324 Yes

March 18, 2012 Alamosa Municipal Building 08

- 003

- 000 3 237 Yes

March 18, 2012 Lamar Power Plant 08

- 0 99

- 000 1 220 Yes

March 18 , 201 2 Lamar Municipal Building 0 8

- 0 99

- 000 2 242 Yes

April 2, 2012 Alamosa

- Adams

State College 08

- 003

- 000 1 389 Yes

April 2 , 20 12 Lamar Municipal

Building 08

- 99

- 0002 163 Yes

Alamosa, Colorado lies in the broad, flat, high elevation San Luis Valley of the upper Rio Grande River. Alamosa is at an elevation of 7

, 600 feet, and is between the South San Juan and Sangre de Cristo Mountain ranges. Alamosa is generally surrounded by agricultural lands within

t he San Luis Valley. To the southwest of Alamosa are the deserts of the New Mexico, Utah, and Arizona Four Corners region. 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 p lains of New Mexico, north Texas, and the Oklahoma panhandle. The areas described are shown in Figure 1.4

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

March 18 , 201 2 : On March 18, 2012 a powerful late winter storm system crossed the Rocky Mountain states

. Strong southerly winds in advance of the storm’s cold front induced blowing dust in southern Colorado, as well as in central and southern New Mexico. An upper level troug h extended south from the low, and the trough and associated cold fronts passed through eastern Colorado in the
afternoon . Of March 18, 2012 , CDPHE said:

The exceedances in Alamosa and Lamar were the result of intense surface winds in advance of an approa ching cold front. These surface features were associated with a strong upper

- level trough that was moving across the western United States. The surface winds were predominantly out of a south to southwesterly direction and moved over erodible dry soils in New Mexico and southern Colorado producing significant blowing dust. This storm system transported PM 10 dust into the southern and southeastern portions
of Colorado

. 2

2 “TSD for the March 18, 2012 Alamosa and Lamar Exceptional Events,” March 10, 2015, page 7

- 8.5

EPA Figure 2 ( March 18, 2012 at 5:00 pm MST) from CDPHE’s demonstration is described with :

Significant surface features during this period of time included a cold front that swept across Colorado. This front was associated with a strong area of surface low pressure that was slowly moving northward through northwestern Wyoming.

In addition , the upper level trough with this storm system aided in producing very strong winds at the surface. 3

Figure 2 : Surface Level Analysis at 5:00 pm MST on March 18, 2012 (CDPHE’s TSD Figure 6 ) 4

Figure 3 (Figure 9 from the CDPHE demonstration ) shows the 700 mb level analysis for March
18 , 2012 at 5 :00 pm MST. An upper level trough extends from two upper level lows in the northeast Pacific and western Canada southeast through the western U. S. and into northwestern
Mexico

.

3 Ibid., 11.

4 Ibid.6

Figure 3 : 700 mb Level Analysis a t 5:00 pm MST on March 18, 2012 (CDPHE’s TSD Figure 9 ) 5

Figure 4 (Figure 26 from the CDPHE demonstration) shows National Oceanic and Atmospheric Administration (NOAA) reanalysis of 700 mb (approximately 3 km elevation) wind speeds at 11:00 am on March 18 , 2012. Only wind speeds greater than 30 knots (34.5 mph) are shown. Blue areas have winds of 30 to 45 knots (34.5 to 52 mph), green areas have winds 45 to 53 knots (52 to 61 mph), and yellow and orange areas have winds of 53 to 70 knots (61 to 81 mph).
Al amosa is shown at the edge of the 30 knot zone, while winds in the area of Lamar are on the order of 60 knots (69 mph). EPA has overlayed PM 10 data from AQS for New Mexico, Alamosa and Lamar, showing widespread PM 10 dust impacts coinciding with the high wi nd region.

5 Ibid., 14.7

Figure 4 : 700 mb Modeled Wind Speed at 11:00 am MST on March 18, 2012 (CDPHE’s TSD Figure 26 ) ; 6 PM 10 Data Added by EPA

Figures 4

- 1 3 and 23

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

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

April 2, 2012 : On April 2, 2012 a powerful spring storm system crossed the Rocky Mountain states

. The PM 10 monitors in both Alamosa and Lamar, Colorado were impacted by dust transported by strong surface winds in the wake of the passing cold front. In Alamosa, surface winds were from the

6 Ibid., 45.8

south and southeast, while in Lamar, post frontal winds were from the north. CDPHE descr ibed the April 2, 2012 event as:

The exceedance in Alamosa was the result of intense surface winds produced by a very tight pressure gradient in the wake of a passing cold front. The surface winds were predominantly out of an east to southeast direction and were likely enhanced by some of the mountain passes found in the Sangre De Cristo range that bounds the eastern side of the San Luis Valley. These wind s moved over dry soils which resulted in significant blowing dust in Alamosa. Lamar was likewise impacted by post

- frontal winds, but from a northerly direction. Lamar also received a brief period of strong outflow winds from evening thunderstorms located t o the east in southwest Kansas. Blowing dust produced by those downburst winds also likely contributed to the PM 10 exceedance recorded in Lamar. All of the surface features which aided in producing blowing dust in Alamosa and Lamar were associated with a s trong upper

- level trough that was moving across the western United States. This storm system transported PM 10 dust into the southern and southeastern portions of Colorado. 7

EPA Figure 5 ( April 2, 2012 at 11 :00 a m MST , Figure 7 from CDPHE’s demonstration ) is
described with :

Significant surface features at 5 AM MST

. . . included an increasing amount of “bunching” of isobars in northeast Colorado and western Nebraska, indicating that a strong pressure gradient was developing. Wind speed is directly propor tional to the pressure gradient, so a higher pressure gradient will produce stronger winds

. . . . This tightening of the isobars spread southward as a cold front continued to move away from southeast Colorado. By 11 AM MST (18Z, Figure 7) the pressure gra dient had become particularly strong between the plains of eastern Colorado and the San Luis Valley of
south

- central Colorado. This was in response to a building ridge of high pressure in eastern Colorado interacting with an intense low pressure trough ext ending from north

central New Mexico northward into south

- central Colorado. 8

7 “TSD for the April 2, 2012 Alamosa and Lamar Exceptional Event,” March 10, 2015, page 1

- 2.
8 Ibid., 13.9

Figure 5 : Surface Level Analysis at 11:00 am MST on April 2, 2012 (CDPHE’s TSD Figure 7 ) 9

Figure 6 (Figure 4 from the CDPHE demonstration ) shows the 700 mb level analysis for April 2,
2012 at 5:00 am MST. An upper level trough extends from two upper level lows in north western and central Canada south through the U. S. Rocky Mountain states and into northwestern Mexico.

9 Ibid.10

Figure 6 : 700 mb Level Analysis at 5:00 am MST on April 2 , 2012 (CDPHE’s TSD Figure 4 ) 10

Figures 4

- 7 and 8

- 1 8 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 and Alamosa

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

NOT REASONABLY CONTROLLA BLE OR PREVENTABLE

The EPA evaluates whether an event was not Reasonably Controllable or Preventable (nRCP ) at the time of the event by taking into account controls in place and wind speed, along with other factors. For natural sources of dust, a high wind dust event can generally be considered to be nRCP if winds are high enough to cause emissions from natura l undisturbed areas. For anthropogenic sources of dust, a high wind dust event can be nRCP if:

10 Ibid., 12.11

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

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

 The wind speed w as high enough to overwhelm the reasonable controls. 11

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 information 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 acti vities
that occurred o n 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 conditions overwhelmed all reasonably available controls

. ... This information shall confirm that no unusual anthropogenic actions occurred in the local areas of Lamar during this time. 12

CDPHE’s demonstration provides an analys is of the state and local controls in place 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 Oxid es;

 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 Stationar y Sources; and

 Regulation 9

- Open Burning, Prescribed Fire, and Permitting. 13

Lamar Specific Controls Lamar has the following controls in place: 14

11 “Interim Guidance on the Preparation of Demonstrations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Exceptional Events Rule,” May 2013, page 10.
12 “TSD for the April 2, 2012 Lamar Exceptional Events,” March 1 0, 2015, page 53.
13 Ibid., 53

- 55.
14 Ibid., 67

- 71.12

 A Natural Events Action Plan (NEAP) for High Wind Events completed in 2003, and updated in 2012, which addres ses public education, notification, and health advisory systems
, as well as implements Best Available Control Measures (BACM) 15 ;

 A PM 10 Maintenance plan for the Lamar Attainment/Maintenance Area effective since
Nov ember 25, 2005 with provisions for Prevention of Significant Deterioration (PSD) permitting requiring Best Available Control Technology (BACT) 16 ;

 State Implementation Plan (SIP) measures requiring owners/operators responsible for construction and/or maintenance of existing or new unpaved roadway with traffic of over 200 vehicles per day to stabilize the road to prevent fugitive dust (see Colorado Regulation 1);

 City of Lamar BACM measures include: planting a wind

- break of trees with drip

irrigation to control dus t from the Lamar Transfer Station, establishing landfill controls such as opacity limits at 20%, fugitive dust at no more than 5.77 tons per year, and immediately shutting down the landfill when winds exceed 35 mph (per the “Operations
and Closure Plan for the East Lamar Landfill” section 3.5.1), among other listed landfill
controls. 17 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 fugitive dust;

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

- 17

- 60 requiring off street parking lots to be swept

. The Prowers County Land Use plan adopted in 2004 and amended in 2006

- through it the county has authority over “construction, siting, health, fire, environmental codes, and other social concerns with provisions to minimize airborne dust” 18 ;

 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 pract ices, conduct outreach and education on soil management programs, and hold drought workshops to protect topsoil;

o Voluntary and s tate

- o nly measures including weekly street sweeping and a city policy requiring that new developments have paved streets;

o The L imestone

- Graveyard Creeks Watershed Project , which reduces soil erosion from 60,000 acres along the Arkansas River, 2,000 of which are near Lamar. 99% of the 60,000 acres now have a conservation plan and are enacting improvements created by each farmer/own er with costs of conservation improvem ents split with the government; and

15 Ibid., 67 and at: http://www.colorado.gov/airquality/tech_doc_reposit ory.aspx?action=open&file=LamarNaturalE ventsActionPlan 2012.pdf.
16 “TSD for the April 2, 2012 Lamar Exceptional Events,” March 10, 2015, page 67

- 68.
17 Ibid., 69.
18 Ibid., 70.13 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 res ponse effort through the State of Colorado Governor’s office, and a program to incentivize erosion mitigation. 19

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

sensitive land into long

- term conservation practices for 10

- 15 years” 20 in exchange for annual rental payments and cost

- share assistance from the government. T his mitigation strategy is a 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.

Ta ble 2 : Acres by County near Lamar Enrolled in the USDA NRCS CRP Program 21

COUNTY 2008 2009 2010 2011 2012 2013 201 4
Bent 25,649 25,700 24,056 24,412 33,886 23,566 3 3,56 7
Kiowa 216,307 217,881 187,394 192,222 177,100 181,169 1 77,788
Baca 260,040 258,469 161,147 274,281 277,508 264,071 26 7

, 732 Crowley 21,419 21,461 21,069 20,329 21,917 18,490 21,26 0
Otero 2,559 2,864 2,706 2,851 2,054 2,635 2, 014 Las Animas 21,869 21,860 17,403 17,616 18,925 18,887 1 9,839 Cheyenne 142,075 140,071 94,852 113,753 122,862 99,074 122,218
Lincoln 155,505 155,425 137,099 145,248 118,948 116,289 11 4,581
Prowers 170,909 171,813 140,827 163,354 154,882 151,731 15 5,065
Total 1,016,333 1,015,544 786,554 954,066 928,082 875,912 914 , 064

19 Ibid., 90

- 91

. 20 Ibid., 90

. 21 Data for the USDA NRCS CRP program were provided as supplementary information per EPA request on April 17, 2014 by Ray Mohr of CDPHE . Data for 2014 was added by the EPA

.14

Alamosa Specific Controls The following controls are in place in and around Alamosa: 22

 A Natural Events Action Plan (NEAP) for High Wind Events completed in 2003, which addresses public education, notification, and health advisory systems, as well as implements BACM ; 23

 P rovisions for PSD permitting requiring BACT ; 24

 SIP measures requiring owners/operators responsible for construction and/or maintenance of existing or new unpaved roadway with traffic of over 200 vehicles per day to stabilize the road to prevent fugitive dust (see Colorado R egulation 1);

 City of Alamosa control measures include: requirements that all new streets and alleys be paved ; requirements for underground automatic irrigation for landscaping at new large commercial and retail establishments; 25

 Alamosa County control meas ures include : dust from feed lots, animal waste treatment or animal waste collection must be confined to the agricultural property; proposed oil and gas well installations must pave or otherwise abate dust from interior transportation networks; roads, driv eways, parking lots and loading/unloading areas within 500 feet of any lot line must be graded and paved; off

- street parking or vehicle use areas must be surfaced with asphalt, concrete or similar dustless material and maintained; dust control plans for se lected construction or development projects; 26 and

 The USDA NRCS 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 conserv ation practices for 10

- 15 years” 27 in exchange for annual rental payments and cost

- share assistance from the government. CRP acreage in the San Luis Valley counties of Colorado is much smaller than in the area around Lamar in southeast Colorado. A new Conse rvation Reserve Enhancement Program aimed at water conservation was initiated in 2012, 28 which is reflected in the larger acreages enrolled i n 2014 as shown in Table 3

.

22 “TSD for the April 2, 2012 Alamosa and Lamar Exceptional Event”

, 5 7

- 59

. 23 Ibid., 55 and at: http://www.colorado.gov/airquality/tech_doc_repository.aspx?action=open& file=AlamosaNatur alEventsActionPlan2003.pdf.

24 “TSD for the April 2, 2012 Lamar Exceptional Events,” March 10, 2015, page 67

- 68.
25 Ibid., 56.
26 Ibid., 57

- 58.
27 Ibid., 90.
28 “USDA and Colorado Announce Rio Grande Basin Water Conservation Project Agreement”, USDA Farm Service Agency, Office of Communications, September 20, 2012, http://www.fsa.usda.gov/FSA/printapp?fileName=nr_20120920_rel_0304.html&newsType=new srel15

Table 3 : Acres by County in the San Luis Valley Enrolled in the USDA NRCS CRP Program 29

COUNTY 2008 2009 2010 2011 2012 2013 2014
Alamosa 0 0 0 0 0 0 1,347 Conejos 32 32 32 32 32 70 51
Costilla 0 13 13 13 13 13 13
Mineral 0 0 0 0 0 0 0
Rio Grande 1 1 0 0 0 0 130 Saguache 0 0 0 0 0 0 672
Total 33 46 45 45 45 83 2,213

Reasonable controls have been effectively implemented and enforced:

Surface winds on March 18, 2012 were from the south in both Alamosa and Lamar . On April 2, 2012, winds were from the east and southeast in Alamosa, and from the north in Lamar. The wind directions ar e shown in EPA figures 7

- 10. With these differing wind directions, CDPHE evaluated areas with disturbed soil upwind from the impacted monitors in the relevant directions on the two days.

29 United States Department of Agriculture, Farm Service Agency, Conservation Reserve Program S tatistics, http://www.fsa.usda.gov/programs

- and

- services/conservation

programs/reports

- and

- statistics/c onservation

- reserve

- program

- statistics/index , accessed February 2, 2016

.16

Figure 7: Surface Wind Direction in Alamosa on March 18, 2012 (CDPH E Figure 67) 30

30 “TSD for the March 18, 2012 Alamosa and Lamar Exceptional Event”, March 10, 2015, page 89.17

Figure 8: Surface Wind Direction in Lamar on March 18, 2012 (CDPHE Figure 73) 31

31 Ibid., 99.18

Figure 9: Surface Wind Direction in Alamosa on April 2, 2012 (CDPHE Figure 34) 32

Figure 10: Surface Wind Direction in Lamar on April 2, 2012 (CDPHE Figure 45) 33

32 “TSD for the April 2, 2012 Alamosa and Lamar Exceptional Event”, March 10, 2015, page 60.
33 Ibid., 72.19

Alamosa Disturbed Area Analysis
Potential area s of disturbed soil south of the Adams State College monitoring site in Alamosa evaluated by the CDPHE are shown in Figure 11

. Figure 11: Potential Disturbed Soil Areas Upwind of the Adam’s State College Monitor on March 18, 2012 (CDPHE Figure 59) 34

Site A in Figure 11 (approximately 85 acres) is zoned outside of the city’s limits by the city as a “Parcel

. ” The eastern portion of Area A is being considered for annexation into the c ity. Site A

cont ains a combination of relatively dense grass and brush cover, periodic ponds and puddles, and dry soil in locations where ponds and puddles have dried. Sites D and C are similar. C DPHE notes that “ Sites A, C and D are noted by Alamosa’s Public Works Direct or and County Health Director to be vacant land with natural vegetation (i.e. shrubland, mostly Chico bush) with no artificial irrigation and no access restriction. The c ity emphasizes that the areas are not suited for motorized travel. These lots are not considered to be anthropogenically disturbed soils and should be considered to be natural sources. If future high wind or other exceptional events occur,
the APCD will re

- assess these lots to determine if they are still natural sources.” 35

34 “TSD for the March 18, 2012 Alamosa and Lamar Exceptional Event”, March 1 0 , 2015, page 89.
35 Ibid., 86.20

Site B in Figure 11 (approximately 22 acres) is zoned outside of the city’s limits. Site E (approximately 30 acres) is zoned mostly as a “Commercial Business

. ” There is a small portion in the northeast corner that is zoned outside of the city’s limits. Site F (approximatel y 23 acres) is zoned as “Commercial business

, ” “Residential High” and a small portion as “Industrial

. ” Sites B, E, and F are naturally vegetated and partially irrigated. The sites are minimally (if at all)
disturbed soil areas as of “ this writing

. ” 36

Figure 7 show ed additional potential disturbed soil areas upwind of the Alamosa Municipal Building monitor on March 18, 2012. Site G is zoned by the city as “Commercial Business” and is undisturbed gravel, dirt, and natural vegetation. The railroad runs th rough this narrow strip of land rendering it unlikely to be developed in the future. 37 Site H is zoned by the city as “Commercial Business” and “Industrial

. ” It is private property with restricted access located just south of the rail yard. The land is natu rally vegetated and undisturbed. 38 Site I is zoned by the city as “Commercial Business” , but is now “Friends” Park

. Friends Park has a well maintained gravel parking lot, a cement basketball court, an irrigated field, and a small hard packed clay
BMX bike d irt track. The park is well maintained by the c ity, which implements reasonable dust control measures on a regular basis. 39 Site J (approximately 9 acres) is zoned by the city as “Residential Medium

. ” It is a vacant lot behind a small apartment building. Th e land is natural and undisturbed. There is no irrigation but natural vegetation is present. The soil has a crust on the surface. When asked, residents of the adjacent apartment complex did not complain about blowing dust coming from Site J. 40 Site K (appro ximately 26 acres) is zoned by the city as “Residential Medium”. It is vacant land that is naturally vegetated and undisturbed. 41

Figure 12 s how s areas of potentially disturbed soil upwind from the Adam’s State College monitor in Alamosa on April 2, 2012 . E ach of these sites were discussed above for the March 18

, 2012 event, with site A of Figure 12 corresponding to site H of Figure 7, site B of Figure 12 corresponding to site G of Figure 7, site D of Figure 12 corresponding to site I of Figure 7 and site C of Figure 12 corresponding to site B of Figure 11. 42

36 Ibid., 86.
37 Ibid., 90.
38 Ibid.
39 Ibid., 90

- 91
40 Ibid., 91.
41 Ibid.

42 “TSD for the April 2, 2012 Alamosa and Lamar Excep tional Event”, March 10, 2015, page 61.21

Figure 12: Potential Disturbed Soil Areas Upwind of the Adam’s State College Monitor on April 2

, 2012 (CDPHE Figure 36) 43

Lamar Disturbed Area Analysis Figure 13 shows areas of potential soil disturbance upwind of the Lamar PM 10 monitors on March 18, 2012. 44 Site A is the Lamar Power Plant where the Power Plant PM 10 monitor resides. Particulate matter emissions are controlled in compliance with CDPHE permit No. 05PR0027, which includes the follo wing provisions:

 Limestone and ash handling, processing, and storage are controlled by high efficiency baghouses.

 Water wash

- down

- systems are used for flushing down any accumulated dust on walkways, platforms, and other surfaces to prevent re

- entrainment o f the dust into the atmosphere.

 On

- site haul roads are paved, and are inspected at least once each day during which hauling activities occur, and cleaned as needed. These activities emit less than 1 ton per year of PM 10 and are APEN Exempt.

 All transport vehicles carrying substances that potentially generate fugitive particulate matter emissions (such as trucks containing limestone, inert material, or ash) are fully enclosed, or covered with a mechanical closing lid or a tight tarp

- like cover at all times while on the facility grounds except during loading/unloading operations.

43 Ibid.
44 “TSD for the March 18, 2012 Alamosa and La mar Exceptional Event”, March 1 , 2015, page 63.22

 Emissions from emergency coal stockpile are effectively controlled with a water dust suppression system.

Access to the power plant is restricted by security fences. CDP HE considers the controls a combination of BACT for the limestone and ash handling, paving, wash

- down systems and enclosures, and reasonable controls otherwise. 45

Figure 13: Potential Disturbed Soil Areas Upwind of the Lamar PM 10 monitors on March 18, 2012 (CDPHE Figure 74) 46

45 Ibid., 101.
46 Ibid., 63.23

Other potentially disturbed soils in Figure 13 are characterized as follows:

 Site B 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;

 Site C 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 conne cting to an asphalt road;

 Site D 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;

 Site E is Colorado Mills LLC sunflower oil and feed processing f acility operating under CDPHE permit #95PR622. Permit conditions include 30% maximum opacity limit, PM limits and an Operation and Maintenance Plan. The last inspection on February 14, 2012 found no visible emissions, and in

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

 Site F is partially owned by Century Link and is a fenced gravel lot with restricted access. The remainder of the site is a free chip

- sealed crushed

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

Figure 14 shows additional potential disturbed areas further south of the PM 10 monitors relevant for the March 18, 2012 event. 47 The areas identified are characterized as follows: 48

 Site G is a paved parking lot ;

 Site H is naturally vegetated undisturbed land with restricted access abutting the southeast edge of Lamar ;

 Site I is the Lamar Ball Complex at approximately 100 Savage St ., which has limited access through fencing. Recycled asphalt and gravel has been applied to reduce dust in the areas around the ball diamonds. Parking areas are periodically dragged and watered as
needed to control dust ; and

 Site J is the Lamar County Fai rgrounds. The land is maintained by the county and is graded annually and watered frequently during most of the year.

47 Ibid., 63.
48 Ibid., 108.24

Figure 14 : Additional Potential Disturbed Soil Areas Upwind of the Lamar PM 10 monitors on March 18, 2012 (CDPHE Figure 81) 49

Winds were from the north for the April 2, 2012 event.

 Vegetation, signage, and/or other dust control measures are in place for undeveloped parcels of land in Lamar. EPA Figures 15

- 16 (CDPHE Figures 46 and 55 ) below show
that identified areas of soil dist urbance have reasonable controls near the Lamar Municipal Building monitor. 50

49 Ibid., 107.
50 Ibid., p. 72.25 o Site A is owned by Heath & Son & Turpin Trucking and HVH Transportation Inc., a large truck repair and freight service trucking company, respectively. It is a well

- maintained g ra vel 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 owne d by Heath & Son & Turpin Trucking and is a well

- maintained

gra vel 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 o n an

as

- needed basis.

o Site E is a power plant with a restricted 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 exem ption, t ransfer locations were enclosed and the emergency coal stockpile controlled through a water

- dust suppression system.

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

o Site G is Colorado Mills LLC sunflower oil and feed processing facility operating under CDPHE permit #95PR622. Permit conditions include 30% maximum opacity limit, PM limits, and an Operation and Maintenance Plan. The last inspection on February 14, 2012 found no visible emissions, and in

- house monthly inspections and the use of cyclones for emission control dem onstrate PM mitigation efforts.

o Site H is partially owned by Century Link and is a fenced gravel lot with
restricte d access. The remainder of the site is a free chip

- sealed crushed

- gravel parking lot for Prowers County Jail and the Prowers County Municipal Court t hat 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. The l ot has restricted access and a 5 mph speed limit.

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

o Site K is owned by Valley glass and the property has restricted access t o a well maintained gravel lot.26

Figure 15 : Potential Disturbed Soil Areas Upwind of the Lamar PM 10 monitors on April 2, 2012 (CDPHE Figure 46) 51

Figure 16 shows additional potential areas of disturbed soil north (upwind) of the Lamar Municipal Building monitor on April 2, 2012.

o Site L is owned by All

- Rite Paving and Redi

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

. 52 Baghouse collection efficiency is 99%, there is a 20% opacity limit, and water sprays and magnesium

51 “TSD for the April 2, 2012 Alamosa and Lamar Exceptional Event”, March 10, 2015, page 43

.27 chloride are used on storage piles and roads as needed. There is a 10 mph speed limit, transfer of materials occurs in enclosed areas, and the lot is fenced

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

- vegetation within one year of disturbance ; compacting piles ; 10 mph speed limit ; and temporary roads are graveled and watered as needed.

o Site N is naturally vegetated and undisturbed

.
o Site O was mined by All

- Rite Paving and Redi

- Mix Inc. and was a concrete batch plant permitted by CDPHE. Baghouse collection efficiency was 99%, there w as 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. Partnering with the Division of Wildli fe, 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 I nc. moved to Site E, see below).

o Site P is 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

r equirements (Section III.D.1(a) )

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

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

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

o Site T is Lamar Feed and Grain

– White Stone Farms, CDPHE permit #00PR0431. On the property is a grain receiving pit, shipping truck loadout station, grain storage, grai n cleaning scalper, and grain handling and milling systems. The permit includes dust control measures for t otal PM, PM 10 and PM 2.5 annual emissions limitations and visible emissions not to exceed 20%

. All equipment is maintained consistent with good air p ollution control practices, and
the feed mill is equipped with a mineral oil spray system to control PM emissions.

o Site U was Dragon EPS beginning in 1993, but merged in 2011 with Ranco (site Q and J above). CPDHE permit #08PR0603 issued December 21, 2011 covers paint booths and abrasive blasting units with the following PM controls: p ermitted annual TSP, PM 10 and PM 2.5 emission limits, h igh v olume l ow p ressure paint28 spray guns, exhaust filters on paint spray booths, baghouse filters on blasting units, visi ble emissions not to exceed 20% and source must follow CPDHE operations and maintenance plan. It was last inspected on November 9, 2011 and found to be in compliance.

o Site V is a restricted access property that is naturally vegetated and appears to be
undi sturb ed.

o Site W is a group of rotating crop fields, with a schedule to allow some fields to lay fallow between plantings; and

o Site X is the Robins Redi

- Mix Concrete Batch Plant which opened in spring of 2010 and consists of a dry truck mix plant using a cement and a dry ash silo operated with pneumatic conveyers and bag houses to control 98% of emissions. In April 2010 CDPHE issued a permit exempt letter (10PR1310.XP) w hich includes PM point and fugitive dust control measures such as: u ncontrolled PM

cann ot 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 BACT for limestone and ash handling, paving, wash

down systems and enclosures

.29

Fig ure 16: Additional Potential Disturbed Soil Areas Upwind of the Lamar PM 10 monitors on April 2, 2012 (CDPHE Figure 55 ) 53

According to the CDPHE TSDs,

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

. . . were pre sent during the 2012 exceedance in Lamar. During the course of these assessments, the APCD discove red that these sites were reasonably controlled or considered to be natural sources during the April 2, 2012, high wind event. Therefore, these sites were not significant contributors to fugitive dust in the Lamar area during the April 2, 2012, high wind event. 54

53 “TSD for the April 2, 2012 Alamosa and Lamar Exceptional Event”, March 10, 2015, page 81.
54 Ibid., 88.30

Wind speed was high enough to overwhelm the reasonable controls CDPHE provided the documentation summarized in EPA Table 4, an d included in EPA Tables
5

- 8 (CDPHE Tables 1 and 2 of each of the two demonstrations ) showing that sustained wind speeds associated with these event were above 30 mph and gusts were above 40 mph. CDPHE previously established in its exceptional events demonstration for t he 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. The sustained winds and gusts in Lamar exceed this Colorado threshold. Transported dust from the upw ind desert and arid plains regions appears to be a significant contribution to the exceedance, in addition to local winds overwhelming implemented local controls. EPA notes that the high local gust speeds in Lamar would likely be capable of overwhelming so me 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, app ropriate land use

ma nagement and an in

- depth analysis of potential areas of local soil disturbance for each affected community ” for Alamosa and Lamar during the March and April 201 2 events. 55

Table 4 : Wind and Gust Highest Measured Speeds by Exceedance Date

Exceedance Date Wind Speed in mph Wind Gust in mph

March 18, 2012 Alamosa 4 5 5 6
March 18, 2012 Lamar 4 0 51
April 2, 2012 Alamosa 41 5 4
April 2, 2012 Lamar 35 54

55 “TSD for the March 18, 2012 Alamosa and Lamar Exceptional Event”, March 10, 2015,
page 77; “TSD for the April 2, 2012 Alamosa and Lamar Exceptional Event”, March 10, 2015,
page 53

.31

Table 5 : Wind Speed Alamosa , CO on March 18, 2012 (CDPHE’s TSD Table 1) 56

56 “TSD for the March 18 , 2012 Alamosa and Lamar Exceptional Event”, March 10, 2015,
page 20

.32

Table 6 : Wind Speed Lamar, CO on March 18 , 201 2 (CDPHE’s TSD Table 2 ) 57

57 Ibid., 21

.33

Table 7 : Wind Speed Alamosa , CO on April 2 , 201 2 (CDPHE’s TSD Table 1 ) 58

58 “TSD for the April 2 , 20 12 Alamosa and Lamar Exceptional Event”, March 10, 2015, page 16

.34

Table 8 : Wind Speed Lamar, CO on April 2 , 201 2 (CDPHE’s TSD Table 2 ) 59

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

 Surface and upper air wind speed analysis from NOAA;

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

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

 Webcam imagery showing visibility impairment due to blowing dust ;

 NOAA HYSPLIT Model b acktrajectories ;

 GOES Satellite imagery of surface dust plumes ; and

 NEXRAD radar imagery of windblown dust fronts

.

59 Ibid., 17

.35

These analyses demonstrate through the weight of evidence the existence of high wind blowing dust events originating upwind of the monitor in question.

Sections 2 and 5 of CDPHE’s demonstration s show that the monit or s in Alamosa and Lamar

w ere affected by PM 10 transport across a large region, with the main source areas located in agricultural areas in Colorado. In addition to transport, the wind speeds associated with the event factor into EPA’s evaluation of whethe r th ese event s are nRCP in Alamosa and Lamar. Therefore, the EPA concludes that th e s e event s w ere nRCP pursuant to the Treatment of Data Influenced by the EER. Table 9 summarizes the EPA’s evaluation of CDPHE’s nRCP EE
demonstration.

Table 9 : EPA’s Analy sis of CDPHE’s TSD of nRCP
Exceedance
Date Reasonable

Controls Demonstration Citation Wind Speed

Demonstration Citation Sufficient

Quality of Evidence? EPA

Criterion Met?

March 18, 2012 Alamosa Section 5: p. 45

- 94 Section 2: p. 9

- 55 Yes Yes

March 18, 2012 Lamar Section 5: p. 94

- 111 Section 2: p. 9

- 55 Yes Yes

April 2, 201 2 Alamosa Section 5: p. 79

- 6 7 Section 2: p. 9

- 32 Yes Yes

April 2, 201 2 Lamar Section 5: p. 67

- 91 Section 2: p. 9

- 32 Yes Yes

HISTORICAL FLUCTUATI ONS

The 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 March 18 and April 2, 201 2 data and a 6

- year time series of 24

- hour averages for the years of
20 07

- 2012 . The 20 07

- 201 2 data set had between 1839 and 2181 samples for the four monitors
found in Lamar and Alamosa , and each description below indicates the samples taken on these days exceed the typical samples for this site. Table 10 summarizes the statistical assessment of the March 18 and April 2, 2012 PM 10 data.36

Table 10: Statistical Analysis of March 18 and April 2, 2012 Samples Compared to 2007

- 2012
Data

Sample Concentration

,  g/m 3 Rank Percentile

March 18, 2012 Alamosa Adams State 324 4 th of 1839 99.8th

March 18, 2012 Alamosa Municipal Building 237 5 th of 2048 99.8th

March 18, 2012 Lamar Power Plant 220 4 th of 2181 99.8th

March 18, 2012 Lamar Municipal Building 2 42 1 st of 21 14 99. 95 th

April 2, 2012 Alamosa Adams State College 389 2 nd of 1839 99.9th

April 2, 2012 Lamar Municipal Building 163 4 th of 2114 99.8th

The EPA “Interim Guidance on High Wind Exceptional Events” recommends that demonstrations also consider percentile ranks when dust impacted data is to be excluded. 60

Since at least 2005 in these areas, values exceeding the NAAQS are only found during high wind dust events, including those in 20 1 2 . This information indicates that values at the level seen on March 18 and April 2, 201 2 are extremely rare in the absence of high wind dust exceptional events, and that it is unlikely that any sources of PM 10 were involved in the 201 2 exceedances other than wind

- blown dust. Therefore, the EPA concludes that th ese event s w ere in excess of HF pursuant to the Treatment of Data Influenced by the EER. Table 11 summarizes the EPA’s evaluation of CDPHE’s HF EE demonstration.

60 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 20.37

Table 11 : EPA ’s Analysis of CDPHE’s TSD of HF
Exceedance
Date Exceedance

Location Historical Fluctuations

Demonstration Citation Sufficient Quality of Evidence? EPA

Criterion Met?

March 18 , 201 2 Alamosa Section 3: p. 56

- 69 Yes Yes

March 18 , 201 2 Lamar Section 3: p. 56

- 69 Yes Yes

April 2, 201 2 Alamosa Section 3: p. 3 3

- 43 Yes Yes

April 2, 201 2 Lamar Section 3: p. 3 3

- 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 transported
in the direction of the monitor(s) where measurements were recorded; the size of the area affected by the transported emissions; the relationship in time between the event, transport of emissions, and recorded concentrations; and, as appropriate, pollutant s pecies

- specific information supporting a CCR between the event and the measured concentration. 61

Section 2 of CDPHE’s demonstration s provides analyses that demonstrate the existence of high wind blowing dust events upwind of the monitors in question, but in cluding southeastern
Colorado contributions.

March 18 , 201 2 : The CDPHE demonstration for March 18, 2012 states that:

S tations upwind from Alamosa and Lamar, predominantly in New Mexico, also reported numerous hours of blowing dust and/or haze along with significantly diminished visibility. It should be noted that many of the blowing dust conditions upwind from Alamosa and Lamar occurred several hours earlier in the day. This suggests the possibility that at least some portion of the dust that produced the exceedances in Alamosa and Lamar was transported from outside of Colorado. 62

61 See “Interim Guidance on the Preparation of Demonstrations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Exceptional Events Rule” of May 2013, pages 21

- 22.
62 “TSD for the March 18, 2012 Alamosa and Lamar Exceptional Events,” March 10, 2015, page 18.38

April 2, 201 2 :

The CDPHE demonstration for April 2, 2012 states that :

The Denver and Pueblo National Weather Service (NWS) forecast offices issue weather information and alerts f

or all of south

- central and eastern Colorado, including Alamosa and Lamar. The NWS office in Cheyenne, Wyoming monitors the Nebraska Panhandle, a suspected source area that contributed to the blowing dust in eastern Colorado on April 2, 2012. Appendix B pr ovides several warnings, advisories and discussions from the Denver, Pueblo and Cheyenne NWS offices for April 1, 2012 to April 2, 2012. The text from these products, particularly those highlighted in yellow, clearly show that the NWS anticipated high wind s and blowing dust. Additionally, the Colorado Department of Public Health and Environment (CDPHE) issued a Blowing Dust Advisory for portions of eastern Colorado and the San Luis Valley on April 2, 2012. 63

In addition, the NOAA smoke and dust text products for April 2 , 2012 state that:

Several areas of blowing dust continue to originate in Colorado. Southward moving dust was visible at sunrise in Cheyenne, Lincoln, Crowley and Pueblo Counties. 64

Additionally:

A deep storm center over New Mexico was producing strong winds over the southwest Plains from northern Mexico into west Texas that was kicking up a broad area of blowing dust. The dust was mainly originating from several sources in northern Chihuahua and west Texas in the vicinity of Midland and Lubbock. The dust was curling counterclockwise across the region and extended to near Wichita Falls and the Texas Panhandle by sunset. Another smaller area of blowing dust was seen this afternoon north of the storm center in the Great Sand Dunes National Preserve of south central Colorado. This area was moving o [ sic ] the west. 65

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 Analysi s of Lamar Drought Condition Severity and Blowing Dust: 1897

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

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

The E PA concludes that there was a CCR for these events pursuant to the Treatment of Dat a Influenced by the EER. Table 1 2 summarizes the EPA’s evaluation of CDPHE’s CCR EE
demonstration.

63 “TSD for the April 2 , 2012 Alamosa and Lamar Exceptional Events,” March 10, 2015, page 32

. 64 Satellite imagery analysis through 1530z April 2, 2012, NOAA Smoke and Dust text product, Ib id., p. B

- 10.
65 Ibid., p. B

- 10 & B

- 11.39

Table 1 2 : EPA’s Analysis of CDPHE’s TSD of CCR 66
Exceedance Date Clear Causal Relationship Demonstration Citation Sufficient Quality of Evidence? EPA

Criterion Met?

March 18, 2012 Section 2: p. 9

- 55 Yes Yes

April 2, 201 2 Section 2: p. 9

- 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 1 3 . 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 thes e areas. This is evidence that the event was associated with a measured concentration in excess of normal historical fluctuations including background. 67

Therefore, the EPA concludes that th ese event s Affected Air Quality pursuant to the Treatment of Data Influenced by the EER. Table 1 3 summarizes the EPA’s evaluation of CDPHE’s AAQ
EE demonstration.

66 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.

67 “TSD for the March 18 , 2012 Alamosa and Lamar Exceptional Events,” March 10, 2015, page 92; “TSD for the April 2 , 2012 Alamosa and Lamar Exceptional Events,” March 10, 2015, page 111

.40

Table 1 3 : EPA’s Analysis of CDPHE’s TSD of AAQ
Exceedance Date HF

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

Criterion Met?

March 18, 2012 HF Section 3: p. 56

- 69 Yes Yes

CCR Section 2: p. 9

- 55 Yes Yes

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

- 43 Yes Yes

CCR Section 2: p. 9

- 32 Yes Yes

NATURAL EVENT

As stated in the 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

- h our PM 10 NAAQS. This document contains detailed information about the large regional windblown dust events that occurred on ” March 18 and April 2, 2012

. “ The Colorado Department of Public Health and Environment (CDPHE) Air Pollution Control Division (APCD) has prepared this report for the U.S. Environmental Protection Agency (EPA) to demonstrate that the elevated PM 10 concentrations were caused by a natural

event

. 68

CDPHE has sufficiently demonstrated the CCR and nRCP requirements for the March 18 and April 2, 2012 events. Therefore, the EPA concludes that these were natural events pursuant to the Treatment of Data Influenced by the EER. Table 1 4 summarizes the EPA’s evaluation of CDPHE’s Natural Event EE demonstration.

68 “TSD for the March 18 , 2012 Alamosa and Lamar Exceptional Events,” March 10, 2015, page 1; “TSD for the April 2 , 2012 Alamosa and Lamar Exceptional Events,” March 10, 2015, page 1

.41

Table 1 4 : EPA’s Analysis of CDPHE’s T SD of Natural Event
Exceedance Date nRCP or CCR Natural Event Demonstration Citation Sufficient Quality of Evidence? EPA

Criterion Met?

March 18, 2012 nRCP

- Anthropogenic Section 5: p. 45

- 111 Yes Yes

nRCP

- Wind Speed Section 2: p. 9

- 55 Yes Yes

CCR Section 2: p. 9

- 55 Yes Yes

April 2, 2015 nRCP

- Anthropogenic Section 5: p. 79

- 91 Yes Yes

nRCP

- Wind Speed Section 2: p. 9

- 32 Yes Yes

CCR Section 2: p. 9

- 32 Yes Yes

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 events.

CDPHE provides a summary of the analysis and information presented in the demonstration that show both the nRCP and CCR requirements have been met for the March 18, 2012 exceedances,
and states that:

Elevated 24

- hour PM 10 concentrations were recorded in parts of Colorado on March 18, 2012. All of the noted March 18, 2012, twenty

- four

- hour PM 10 concentrations were above the 90th percentile concentrations for their locations (see Table 22). This event produced the maximum va lue for any sample taken in April and exceeded the 99th% value of any evaluation criteria. The statistical and meteorological data clearly shows that but for this high wind blowing dust event, Alamosa and Lamar would not have exceeded
the 24

- hour NAAQS on March 18, 2012. 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 event was associated with a measured
concentration in excess of normal historical fl uctuations including background

. 69

Similarly for the April 2, 2012 exceedances, CDPHE states:

69 “TSD for the March 18 , 2012 Alamosa and Lamar Exceptional Events,” March 10, 2015, page 111

.42

Elevated 24

- hour PM 10 concentrations were recorded in parts of Colorado on April 2, 2012. All of the noted April 2, 2012, twenty

- four

- hour PM 10 concentrations were above the 90th percentile concentrations for their locations (see Table 9). This event exceeded the 99th percentile value for the entire dataset. The statistical and meteorological data clearly shows that but for this high wind blowi ng dust event, Alamosa and Lamar would not have exceeded the 24

- hour NAAQS on April 2, 2012. 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 evide nce that the event was associated with a measured concentration in excess of normal historical fluctuations including background. 70

Therefore, the EPA concludes that there would have been NEBF pursuant to the Treatment of Data Influenced by the EER. While n ot explicitly stated in the documentation, the 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 1 5 summari zes the EPA’s evaluation of CDPHE’s NEBF EE demonstration.

Table 1 5 : EPA’s Analysis of CDPHE’s TSD of NEBF
Exceedance Date No Exceedance But For the

Event Demonstration Citation Sufficient Quality of Evidence? EPA Criterion

Met?

March 18, 2012 Section 6: p. 111 Yes Yes

April 2, 201 2 Section 6: p. 92 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 corrections were made to the report based on internal staff review. Table 1 6 outlines EPA’s evaluation of these requirements.

70 “TSD for the April 2, 2012 Alamosa and Lamar Exceptional Eve nts,” March 10, 2015, page 92.43

Table 1 6 : EPA’s Analysi s 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) March 18, 2012 Section 1: p. 7 Yes

April 2, 2012 Section 1: p. 7. Were flags and initial description placed on the data by July 1 st of the following year? 40 CFR 50.14(c)(2)(iii) March 18, 2012:

Flag April 18, 2012; Initial Description May 30, 2013 No

April 2, 2012: Flag April 27, 2012; Initial Description May 30, 2012 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) March 10 , 2015 Yes

Was the public comment process followed and documented? 40 CFR 50.14(c)(3)(v) March 18, 2012

Section 1: p. 8 Yes

April 2, 2012 Section 1: p. 8.

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 upwind states into the Lamar and Alamosa areas on March 18 and April 2, 2012 . These high wind events
caused exceedances of the 24

- hour PM 10 NAAQS at the Lamar and Alamosa PM 10 monitor. EPA concurs that the flagged exceedances at the Lamar and Alamosa monitor s on these days meet the definition of exceptional events: the events affected air quality, were nRCP, and met the definition as natural events. Specifically, the EPA has de termined that the event was nRCP due44

to high wind conditions that transported PM 10 from sources outside of the immediate Lamar and
Alamosa area s and also subsequently may have overwhelmed some reasonable controls within
Lamar and Alamosa . 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 events provide sufficient evidence to conclude that th ese event s were nRCP. Furthermore,
the EPA has determined that there is a CCR between the event and the measured exceedance, there would have been NEBF, and the measured exceedances are in excess of normal HFs.

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

- hour PM 10 NAAQS exceedance s at the Lamar and Alamosa monitor s on March 18 and April 2 , 201 2.

This concurrence does not constitute final EPA action regarding any matter on which the EPA is required to provide an opportunity for public comm ent. 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 rulemaking 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 unusual 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 precipit ation is plotted over time, 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 precipitati on 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 considerably 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 o n 8 days. 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 rainfall began in May 2014. Dust storm activity was theref ore more than twice as heavy 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 observe d, in December 2014, on April 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

- blow n 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 Lama r.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
be fore 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 rainfall 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 both above and b elow 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 to a level of 5 to 6 exceedances per year in 1985

- 1986. 3 Mean PM 10

1 EPA Region 8 staff analysis conducted July 29, 2015.

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 CDPHE data in the EPA AQS database, accessed by EPA Region 8 July 24, 2015.3

expected exceedance counts were from zero to 3 expected exceedances per year from PM 10 monitoring inceptio n until 2013, when the three year mean jumped to seven at the end of the seven year dry 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

avera ge precipitation.

Figure 2: Lamar Precipitation and PM Exceedances, 1975

- 2015, EPA Region 8 Analysis 5

4 Ibid.
5 EPA Region 8 staff analysis conducted July 29, 2015.