1



## EPA Technical Support Document i n Review of Colorado Department of Public Health and Environment’s Demonstration Package for the April 3 , 20 11 , Alamosa and Lamar Exceptional Event

EXCEPTIONAL EVENTS RULE REQUIREMENTS

The Environmental Protection Agency ( EPA ) promulgated the Exceptional Events Rule (EER) in 2007, pursuant to the 2005 amendment of Clean Air Act (CAA) Section 319. 42 U.S.C. §7619. The EER added 40 CFR 50.1(j), (k) and (l); 50.14; and 51.930 to the Code of Federal Regulations (CFR). These se ctions contain definitions, criteria for EPA approval, procedural requirements, and requirements for air agency demonstrations, all of which must be met before EPA can concur under the EER on the exclusion of air quality data from regulatory decisions.

Un der 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 e vent 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 t he event.
This review applies the EPA’s “Interim Guidance of the Preparation of Demonstrations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Exceptional Events Rule” of May 2013, (Interim Guidance for High Wind Exceptional Events) in addition to the applicable statutory and regulatory provisions.



## SUMMARY

Overview

Colorado Department of Public Health and Environment ( CDPHE ) submitted a demonstration (termed a Technical Support Document or TSD) dated November 20
, 201 3 for an exceptional event exceedance of the 24

- hour PM 10 standard that occurred at the monitoring station s in Alamosa and Lamar on April 3 , 20 11 . Table 1 summarizes the exceedance s that CDPHE would like considered for exceptional event concurrence in the Air Quality System ( AQS ) database.

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 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 3
, 2011 Alamosa

- Municipal Building 08

- 0 03

- 0003 3 7 2 Yes

Alamosa

- Adams State College 08

- 003

- 0001 295 Yes Lamar Power Plant 08

- 099

- 0001 169 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 the San Luis Valley. To the southwest of Alamosa are the deserts of the New Mexico, Utah, and Arizona Four C orners 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 plains of New Mexico, north Texas, and the Oklahoma panhandle

. The areas described are shown in Figure 1.

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

In its exceptional event demonstration package
, CDPHE describes the April 3 , 20 11 event as:

the consequence of high winds from an intensifying surface low pressure system and vigorous cold front. These surface features were associated with a strong upper

- level trough that was moving across the western United States. The prefrontal surface winds were out of a west to southwesterly direction and moved over dry soils in Arizona, northwest New Mexico, southeast Utah and southern Colorado producing significant blowing dust. Behind the cold front the winds3

were northerly which moved over dry soils in easte rn Colorado, consequently also producing significant amounts of blowing dust

. 2

CDPHE provides a comprehensive description and discussion of this overnight event in Sections 2, 3, 4, and 5 of the ir TSD . As noted in the figure below, the high wind event cau s ed dust to blow and affected air quality in this area.
EPA Figure 2 from CDPHE’s TSD 3 visually demonstrates wind speed and direction at an elevation of roughly 19,000 feet above sea level over northeastern Arizona, southeastern Utah, and northwestern New Mexico into south and south eastern Colorado at 11:00 AM mountain standard time on April 3 . Figures 1

- 39 from CDPHE’s TSD use modeling, meteorology, and monitoring analysis to support the eviden ce of wind direction into Alamosa and Lamar

. EPA acknowledges that the winds originated from arid regions in Arizona, northwest New Mexico, southeast Utah and blew into the San Luis Valley of Colorado into the Alamosa area, and from northwest New Mexico a nd eastern Colorado blowing into the Lamar area. However, EPA analysis of the data indicates that significant amounts of dust was not transported across state lines, and that arid natural climate and surrounding agricultural lands were most likely a signif icant source of monitored dust.

Figure 2: Map of Wind Speed and Direction on April 3 , 20 11 (CDPHE’s TSD Figure 14 )

2 “ TSD for the April 3 , 20 11
, Alamosa & Lamar Exceptional Event,” November 20 , 201 3 , page 11

. 3 Ibid., 19.4

Not Reasonably Controllable or Preventable

EPA evaluates whether an event was n ot 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:

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

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

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

In addressing reasonable controls, CDPHE provided detailed information on the current set of required and voluntary controls in the Alamosa and Lamar area s , including information on implementation of State Regulations 1, 3, 6, and 9, rule effectiveness, compliance, and public notification activities that occurred on the event day. As CDPHE states :

The [CDPHE Air Pollution Control Division] APCD conducted thorough analyses and outreach with local gove rnments 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. The following subsections describe 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 each affected community during the April 3, 2011 event. This information shall confirm that no unusual anthropogenic actions occurred in the local areas of Alamosa and Lamar during this time. 5

CDPHE’s TSD provides an analysis 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 Oxides;

 Regulation 3

- Stationary Source Permitting and Air Pollutant Emission Notice Requirements;

 Regulation 4

- New Wood Stoves and the Use of Certain Woodburning Appliances During High Pollution Days;

 Regulation 6

- Standards of Performance for New Stationary Sources; and

 Regulation 9

- Open Burning, Prescribed Fire, and Permitting. 6

CDPHE provided the documentation listed in Figures 3
, 4 , 5, and 6 showing that sustained wind speeds associated with these events were above 30 mph and gusts were above 40 mph (CDPHE tables 12 , 13, and 14 ) 7 . For example, in Alamosa the sustained surface winds of up to 5 1 mph with gusts up to 7 0 mph

4 “Interim Guidance on the Preparation of Demonstrations in Support of Requests to Exclude Ambient Air Quality Data Affected by High Winds Under the Exceptional Events Rule,” May 2013, page 10.
5 “ TSD for the April 3 , 20 11
, Alamosa & Lamar Exceptional Even t,” November 20 , 201 3 , page 88

. 6 Ibid., 88

- 90.

7 Ibid., 31

- 32, 43

- 44.5

were measured on April 3, 20 11 , while Lamar saw sustained surface wind speeds of up to 44 mph and gusts up to 59 mph. CDPHE previously established in its exceptio nal events TSD for the January 19, 2009 event in Lamar, Colorado that wind speeds of 30 mph and/or gusts of 40 mph or higher have been shown to cause blowing dust in Colorado (attached as appendix A of CDPHE’s TSD ). T he sustained winds and gusts in both Al amosa and Lamar exceed this Colorado threshold

. However, although wind speeds in Farmin g ton and Gallup, NM exceeded the established thresholds and help indicate that the winds originated southwest of the monitors , wind speeds in Alamosa and Lamar are high er than upwind monitors

. High resolution satellite imagery is available at the approximate time of the peak winds in Farmington and Gallup, and the large dust plumes in northwest New Mexico and northeast Arizona, visible in other, previous high wind dust events, are not visible on April 3, 2011. Given the wind direction evidence of Figure 2 above, the upwind desert and arid plains region s appears to be a less significant contribution to the exceedance than was local winds overwhelming implemented local controls. EPA notes that the high local gust speeds in Alamosa and Lamar would likely be capable of overwhelming some local controls. Section 5 of the TSD provid ed 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 potentia l areas of local soil disturbance for the affected community.” 8

8 “ TSD for the April 3 , 20 11
, Alamosa & Lamar Exceptional Event,” November 20 , 201 3, page 88.6

Figure 3: Wind Speed in Alamosa, CO on April 3, 20 11 (CDPHE’s TSD Table 1 )7

Figure 4: Wind Speed Lamar , CO on April 3 20 11 (CDPHE’s TSD Table 2 )8

Figure 5: Wind Speed in Farmington, NM on April 3, 2011 (CDPHE’s TSD Table 13)9

Figure 6: Wind Speed in Gallup, NM on April 3, 2011 (CDPHE’s TSD Table 14)

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

 Statewide PM 10 monitoring maps;

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

 North American Regional Rea nalysis (NARR) jet stream maximum winds;

 Maps of real

- time weather data from the National Center for At mospheric Research (NCAR);

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

 NOAA HYSPLIT modeling of wind trajectories;

 Naval Advanced Aerosol Prediction System (NAAPS) forecasted dust concentrations;10

 NOAA Geostationary Sa tellite Server (GOES) Aerosol Smoke Product (GASP) Optical Depth Images ;

 Maps establishing the lack of regional precipitation and drought status from U.S. Department of Agriculture (USDA), NOAA, and the National Drought Mitigation Center; and

 Maps of ele vated friction velocities in the region from the NOAA National Centers for Environmental Prediction (NCEP) North American Model.

These analyses demonstrate persuasively through the weight of evidence the existence of a high wind blowing dust event origina ting far southwest of the monitor in Lamar and south

- southwest of the monitors in Alamosa

.

ALAMOSA:

Alamosa has the following controls in place:

 Natural Events Action Plan (NEAP) 9 for high wind events , completed in May 2003, addresses public health programs, public notification, and implements Best Available Control Measures (BACM). CDPHE ensured in 2007 and 2013 that the NEAP was implemented satisfactorily (see Colorado Regulation 1);

 City Code of Ordinances : Article VII of Section 21

- 140(5) addre sses dust control at homes; Article V Sec. 17

- 87(3) requires pavement of new roads/alleys (see Colorado Regulation 1); and Article VI Sec. 21

- 119(3) requires new commercial establishments to install underground irrigation (see Colorado Regulation 3). 10

In addition, Alamosa conducts street sweeping, has irrigated and installed vegetative cover on all city parks, encourages low tilling and other soil conservation practices outside of town through the Colorado State University Co

- Op Extension Office and the N atural Resources Conservation Service. Since 2008 t he Mosca

- Hooper Conservation District has been working with the Natural Resources Conservation Service to implement the Colorado State Forest Service’s program to plant between 2,805 and 7,432 trees per ye ar to prevent wind erosion in the area. 11 Lastly, Alamosa and nearby counties participate in the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Conservation Reserve Program ( CRP ) , but not at the scale that the c ounties near Lamar do. In 2014, more farmers began participating in the program, mostly due to concerns over depletion of the underground aquifer. By attempting to preserve the aquifer the farmers obtain a secondary benefit of controlling local dust source s.

9 “ TSD for the April 3 , 20 11
, Alamosa & Lamar Exceptional Event,” November 20 , 201 3
, Appendix D

. 10 Ibid., 91 and 93.
11 Ibid., 93

- 94

.11

Figure 12: Area Acres by County near Alamosa Enrolled in the USDA NRCS CRP Program 12

2007 2008 2009 2010 2011 2012 2013 2014

A lamosa 0 0 0 0 0 0 0 1,346

C onejos 32 32 32 32 32 32 70 70

C ostilla 0 0 13 13 13 13 13 13

M ineral 0 0 0 0 0 0 0 0 R io G rande 1 1 1 0 0 0 0 130 S aguache 0 0 0 0 0 0 0 558

Maps of eight undeveloped parcels of land in town are included that were determined to be reasonably controlled or considered natural sources. All eight parcels near the Adams State College monitor are covered with vegetation and five of those eight are confirmed to be irrigated. The three remaining sites in F igure 13 (Sites B, E, and H) are naturally vegetated and satellite images show minimal soil disturbance. 13

Figure 13 : Alamosa Site Assessment

- Adams State College Monitor (CDPHE’s TSD Figure 63)

A map is also included of eight undeveloped parcels of land in town near the Alamosa Municipal Building monitor (Figure 14). The five sites of potential concern are c overed with vegetation and two of

12 A nalysis for the six counties of the San Luis valley show very low participation in Conservation Reserve or Conservation Reserve Enhancement Programs. An January 12, 2012 article by Circle of Blue.org ( http://www.circleofblue.org/waternews/2012/world/food

- vs

- water

- high

- commodity

- prices

- complicate

- a quifer

protection

- in

- colorados

- san

- luis

- valley/ ) describes how high agricultural product prices and relatively low costs of ground water make ongoing irrigation and agricultural production in the valley more economically viable than the reserve program set aside payments made available to date in farm legislation.
13 “TSD for the April 3 , 20 11
, Alamosa & Lamar Exceptional Event,” November 20 , 201 3, pages 95

- 101

.12

those five include a maintained gravel rail yard (site J), a maintained gravel parking lot, irrigated field, cement basketball court, and a small hard

- pack clay BMX track (site L) . The three remaining sites in F igure 14 ( Sites M, N, and K ) are naturally vegetated and satellite images show minimal soil disturbance. 14

The state has shown there are reasonable and preventable controls in place for the Alamosa area.

Figure 14 : Alamosa Site Assessment

- Alamosa Municipal Building Monitor (CDPHE’s TSD Figure 63)

LAMAR:

Lamar has the following controls in place 15 :

 A Natural Events Action Plan (NEAP) for High Wind Events completed in 2003 , and updated in 2012, which addresses public education, notification, and health advisory system s as well as implements Best Available Control Measures (BACM) 16 (see Colorado Regulation 1) ;

 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) 17 (see Colorado Regulation 3) ;

 State I mplementation 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 Regulatio n 1) ;

 City of Lamar BACM measures include: planting a wind

- break of trees with drip

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

14 “ TSD for the April 3 , 20 11
, Alamosa & Lamar Exceptional Event,” November 20 , 201 3, page s 102

- 1 05.
15 Ibid., 107

- 111

. 16 Ibid., Appendix E ; the Natural Events Action Plan was updated in 2012, after the April 3, 2011 event

. 17 Ibid., 107 ; the PM10 Maintenance Plan was updated in 2012, after the April 3, 2011 event

.13

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. 18 Other BACM include installing 100,000 ft 2 of turf sod and irrigati on at recreational open space Escondido Park, and fencing off and stabilizing lots that formerly contributed to fugitive dust (see Colorado Regulation 1) ;

 Other measures include : Lamar Charter and Code, Art. XVII, Sec. 16

- 17

- 60 requiring off street parking lots to be swept and t he Prowers County Land Use P lan adopted in 2004 and amended in 2006 whereby the county has authority over “construction, siting, health, fire, environmental codes, and other social concerns with provisions to minimize airborne dust” 19 (see Colorado Regulation 1) ;

 Non

- enforceable measures include:

o The Colorado State University CO

- OP Extension Office efforts underway to encourage

no

- or low

- till practices, outreach and education on soil management programs, and drought workshops to pro tect topsoil.

o Voluntary and State

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

o The Limestone

- Graveyard Creeks Watershed Project reduces soil erosion from 60,000 acres along the Arka nsas River, 2,000 of which are near Lamar. O f the 60,000 acres , 99% now have a conservation plan and are enacting improvements created by each farmer/owner with costs of conservation improvements split with the government.

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

- party drought response effort through the State of Colorado Governor’s office, and a program to incentivize erosion mi tigation. 20

 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 conservation practices for 10

- 15 years” 21 in ex change for annual rental payments and cost

- share assistance from the government. This mitigation strategy further supports the existence of reasonable controls in the surrounding agricultural areas
, especially due to the finding that the dust originated in the counties surrounding Lamar. The following amounts of cropland were under contract in surrounding counties.

18 “TSD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013, page 108.
19 Ibid., 110.

20 Ibid., 119

- 122.

21 Ibid., 121.14

Figure 7 : Acres by County near Lamar Enrolled in the USDA NRCS CRP Program

2007 2008 2009 2010 2011 Bent 25,586 25,649 25,700 24,056 24,412 Kiowa 214,879 216,307 217,881 187,394 192,222 Baca 263,357 260,040 258,469 161,147 274,281 Crowley 22,032 21,419 21,461 21,069 20,329 Otero 2,624 2,559 2,864 2,706 2,851 Las Animas 21,983 21,869 21,860 17,403 17,616 Cheyenne 143,948 142,075 140,071 94,852 113,753 Lincoln 156,328 155,505 155,425 137,099 145,248 Prowers 173,030 170,909 171,813 140,827 163,354 Total 1,023,767 1,016,333 1,015,544 786,554 954,066

 Vegetation, signage, and /or other dust control measures are in place for undeveloped parcels of land in Lamar . Figure 8 below identifies the potential areas of soil disturbance. In Figure 8 :

o Site A 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 Co m mission ( AQCC ) Regulation 1 requirements (Section III.D.1(a). 22

o Site B is owned by Ranco Construction Trailer Manufacturing and consists of pavement, gravel, and naturally vegetated areas with restricted access

. 23

o Site C is owned by Prowers County and rented to the Colorado State Patrol

. It is a fenced, restricted access, gravel lot with a 5 mph limit, and drainage and erosion control

measure s per AQCC Regulation 1 requirements (Section III.D.1(a) )

. 24

o Site D 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. 25

o Site F 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. Th ere was a 10 mph speed limit, transfer of materials occur r ed in enclosed areas, and the lot was fenced. 26 Partnering with the Division of Wildlife, the City of Lamar took

22 , 23, 24, 25, 26 “The APCD considers restricted vehicle speeds

, maintained gravel , natural vegetation, restricted access, pavement, compaction, revegeta tion, watering, and extraction limitation to be the appropriate available and practical method that is technologically feasible and economically reasonable in order to minimize fugitive particulate emissions for th e s e site s

. “TSD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013,
page s 113 and 114.15 over the lot in 2013 and has been reseeding it to create a fishing and wildlife park f ree of motorized vehicles . (It appears that All

- Rite Paving and Redi

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

Figure 8 : Lamar Site Assessment (CDPHE’s TSD Figure 76)

 Vegetation and dust control measures are also in place for undeveloped parcels of land North of Lamar. Figure 9 below identifies the potential areas of soil disturbance. The state has shown there

are reasonable and preventable controls

. In Figure 9 :

o Site E is also 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
. ” 27 As with Site F above, baghouse collection efficiency is 99%, there is a 20% opacity limit, and water sprays and magnesium chloride are used on storage piles and roads as needed. There is a 10 mph speed limit, transfer of materials occurs in enclosed areas, and the lot is fenced. 28

o Site G is mined by Carder Inc. for sand and gravel and emits no more than 15 tons per
year under CDPHE pe rmit #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 gravel ed a nd watered as needed 29
, 30 ;

27 , 28, 29, 30 “The APCD considers restricted vehicle speeds

, maintained gravel , natural vegetation, restricted access, pavement, compaction, revegetation, watering, and extraction limitation to be the appropriate available and practical method that is technologically feasible and economically reasonable in order to minimize fugitive particulate emissions for th e s e site s

. “TSD for the April 3, 2011, Alamosa & Lamar Excepti onal Event,” November 20, 2013, page s 114 and 115.16

Figure 9 : Lamar Site Assessment (CDPHE’s Figure 78 in the CDPHE’s TSD)

 Vegetation and dust control measures are also in place for undeveloped parcels of land northwest of Lamar. Figure 10 below identifies the potential areas of soil disturbance. The state has shown there are reasonable and preventable controls

. In Figure 1 0 :

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

maintained gravel lot. 31

o Site I is a fenced
, watered

- as

- needed gravel lot shared by Prowers Area Transit and the defunct Cowboy Corral Storage, feed supply
, and grain storage companies. The transit company is on a concrete slab connecting to an asphalt road. 32 Site J is owned by Heath & Son & Turpin Trucking and is a well

- maintained gravel lot used for truck storage. 33

o Site K is the Lamar Water Department and Lamar

- Prowers County Volunteer Fire Department and is a restricted site of gra d ed and wat ered gravel on an as

- needed basis. 34

o Site L is the power plant that hosts the monitor and is a restricted 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

31 , 32, 33 , 34 “The APCD considers restricted vehicle speeds

, maintained gravel , natural vegetation, restricted access, pavement, compaction, revegetation, watering, and extraction limitation to be the appropriate available and practical method that is technologically feasible and economically reasonable in order to minimize fugitive particulate emissions for th e s e site s

. “TSD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013,
page s 115, 116, and 117.17 wash

- down systems for all surfaces to prevent dust re

- entrainment, all roads were paved and inspected daily and cleaned as needed while under the 1 ton per year APEN exemption , transfer locations were enclosed, and the emergency coal stockpile controlled through a water

- dust suppression system. 35

o Site M is the Burlington Northern Santa Fe railroad and is covered in gravel 50 feet on either side of the tracks, surrounded by natural vegetation with xer i scape 36 ; and

Figure 1 0 : Lamar Site Assessment (CDPHE’s TSD Figure 79)

 Vegetation and dust control measures are also in place for undeveloped parcels of land w est of Lamar. Figure 1 1 below identifies the potential areas of soil disturbance. Site N is owned and mined by Carder Inc for sand and gravel under CDPHE permit #99PR0179F. It emits 8 tons per year of PM 10 and is a wet mining operation employing the following dust control measure s:, re

vegetation within one year of disturbance, compacting piles, 10 mph speed limit, and temporary roads are gravel ed and watered as needed. 37
, 38

The state has shown there are reasonable and preventable controls in place for the Lamar area.

35 , 36, 37, 38 “The APCD considers restricted vehicle speeds

, maintained gravel , natural vegetation, restricted access, pavement, compaction, revegetation, watering, and extraction limitation to be the appropriate available and practical method that is technologically feasible and economically reasonable in order to minimize fugitive particulate emissions for th e s e site s

. “TSD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013,
page s 118, 119, and Appen dix D.18

Figure 1 1 : Lamar Site Assessment ( CDPHE’s TSD Figure 84)

According to CDPHE’s TSD:

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 th at despite reasonable control measures in place, high wind conditions overwhelmed all reasonably available controls

. 39

Sections 2 and 5 of CDPHE’s TSD assert that the monitor s in Alamosa and Lamar w ere affected by PM 10 transport from outside the immediate area of the monitor , with the main source areas from arid regions in Arizona, northwest New Mexico, southeast Utah and the San Luis Valley of Colorado into the Alamosa

area, and from northwest New Mexico and eastern Colorado into the Lamar area. EPA analy sis indicates that the wind was stronger locally, and that dust from surrounding areas within Colorado were the most likely sources of the exceedances, especially in Lamar. In addition to transport, the spatial extent of elevated PM 10 concentrations throughout southern Colorado and the wind speeds associated with the event contribute to EPA’s evaluation of whether this event is nRCP in Alamosa and Lamar

. The EPA concludes that wind speeds on April 3, 2011 did exceed the blowing dust th resholds of 30 mph or greater and gusts of 40 mph or greater at which the CDPHE expects stable surfaces (i.e., controlled anthropogenic and undisturbed natural surfaces) to be overwhelmed, given that wind speeds were as high as 51 mph with wind gusts up to 70 mph. Therefore, the EPA concludes that this event was not reasonably controllable pursuant to the Treatment of Data Influenced by Exceptional Events rule. Table 2 summarizes the EPA’s evaluation of CDPHE’s nRCP EE demonstration.

39 “TSD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013, page 88

.19

Table 2: EPA’s Analy sis of CDPHE’s TSD of nRCP
Exceedance Date Location Reasonable Controls TSD Citation Wind Speed

TSD Citation Sufficient

Quality of Evidence? EPA

Criterion Met?

April 3, 2011 Alamosa

Adams State College Section 5: p. 88

- 101 Section 2: p. 11

- 62 , esp. p. 31 Yes Yes

Alamosa Municipal Building Section 5: p. 88

- 94,

102

- 106 Section 2: p.11

-

62, esp. p.31 Yes Yes

Lamar Power Plant Section 5: p. 107

- 122 Section 2: p.11

- 62, esp. p.32 Yes Yes

Historical Fluctuations

EPA evaluates whether a measured exceedance is in excess of Historical Fluctuation (HF) by taking into account the level of the exceedance in relation to historical data, which is typically 3 to 5 years.

To demonstrate that this requirement was met, CDPHE provided a statistical analysis of the 2011 24

- hour
average data
, 5

- year time series of 24

- hour averages for the years of 200 6

- 20 11 , and monthly data showing that all readings greater than the NAAQS thres hold of 1 5 0  g /m 3 might be considered statistical outliers . CDPHE explains that for the concentration measured on April 3, 20 11 :

Of those samples in excess of 150  g/m 3 all three are the maximum value for any sample taken in April. The samples at Alamosa ASC, Alamosa Muni and Lamar Power on April 3, 2011, exceeded the 99th% value of any evaluation criteria. 40

The EPA “Interim Guidance on High Wind Exceptional Events” recomme nds that TSD s also consider percentile ranks when dust impacted data is excluded. 41 CDPHE s tates that the percentile rank for these areas is 99.4% and above for the th r ee monitors in question. See Figure 1 5 below

.

40 “TSD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013, page 65

. 41 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 20.20

Figure 1 5 : Percentile Analysis ( CDPHE’s TSD Table 16 ) 42

Since at least 2005 in these areas , values exceeding the NAAQS are only found during high wind dust events, including April 3, 20 11 . This information indicates that values at the level seen on April 3, 20 11 are extremely rare in the absence of high wind dust exceptional event impacts, and that it is unlikely that any sources of PM 10 were involved in the April 3, 20 11 exceedance s other than wind

- blown dust. Therefore, the EPA concludes that this event was in excess of historical fluctuations pursuant to the Treatment of Data Influenced by Exceptional Events rule. Table 3 summarizes the EPA’s evaluation of CDPHE’s HF EE demonstration.

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

Loc ation Historical Fluctuations TSD Citation Sufficient

Quality of Evidence? EPA Criterion

Met?

April 3, 2011 Alamosa Adams

State College Section 3: p.63

- 68, 76

- 78 Yes Yes

Alamosa Municipal Building Section 3: p.63

- 65, 68

- 71, 76

- 78 Yes Yes

Lamar Power Plant Section 3: p.63

- 65, 71

- 78 Yes Yes

Clear Causal Relationship

EPA considers a variety of evidence when evaluating whether there is a Clear Causal Relationship (CCR) between the measurement under consideration and the event that is claimed to h ave 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,

42 “TSD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013, page 64

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pollutant species

- specific information supporting a CCR between the event and the measured concentration. 43

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

 Statewide PM 10 monitoring maps;

 Surface and upper air wind speed analysis from NOAA ;

 NARR jet stream maximum winds;

 Maps of real

- time weather data from NCAR;

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

 NOAA HYSPLIT modeling of wind trajectories;

 NAAPS forecasted dust concentrations;

 NOAA GOES GASP Optical Depth Images;

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

 Maps of elevated friction velocities in the region from the NOAA NCEP North American Model.

These analyses demonstrate the exist ence of a high wind blowing dust event originating far southwest of the monitors in question.

NOAA’s Smoke Text Product Satellite Services Division described the April 3, 20 11 event as follows,

A few areas of blowing dust

... could be seen moving southward through parts of far eastern Colorado and into western Kansas where high winds have picked up after the passage of a cold front this evening

. 44

CDPHE generally summarizes that :
The exceedances were the consequence of high winds from an intensifying surfa ce low pressure system and vigorous cold front. These surface features were associated with a strong
upper

- level trough that was moving across the western United States. The prefrontal surface winds were out of a west to southwesterly direction and moved o ver dry soils in Arizona, northwest New Mexico, southeast Utah and southern Colorado producing significant blowing dust. Behind the cold front the winds were northerly which moved over dry soils in eastern Colorado, consequently also producing significant amounts of blowing dust. 45

CDPHE further states that “ 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 April 3, 2011 ”. 46 EPA acknowledges the wind direction originating south and southwest of the monitors, but considers local sources of dust to be responsible for the exceedances, especially in Lamar. Therefore, the EPA concludes that there was a clear causal relationship for this event pursuant to the Treatment of Data

43 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.

44 “TSD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013, page 58

. 45 Ibid., 11

. 46 Ibid., 123.22

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

Table 4: EPA’s Analysis of CDPHE’s TSD of CCR 47 Clear Causal Relationship TSD Citation Sufficient Quality of Evidence? EPA Criterion Met?

Section 2: p. 11

- 62 , Figures 1

- 3 9 Yes Yes

Section 2: p. 11 , 3 1

- 4 4 , Tables 1

- 1 4 Yes Yes

Section 2: p. 58 Yes Yes

Section 4: p. 79

- 87 Yes Yes

Affects Air Quality (AAQ)

As stated in EPA’s Interim Guidance for High Wind Exceptional Events Section 3.4, EPA will consider events to have affected air quality if the CCR and HF requirements have been adequately demonstrated. The information presented in the HF and CCR demonstrations on the preceding three pages of this (EPA’s) TSD are cited in Table 5. Additionally, CDPHE states that:

This event produced the maximum value for any sample taken in April and exceeded the 99th%

v alue of any evaluation criteria... This is evidence that the event was associated with a mea sured concentration in excess of normal historical fluctuations including background. 48

Therefore, the EPA concludes that this event affected air quality pursuant to the Treatment of Data Influenced by Exceptional Events rule. Table 5 summarizes the EPA’s e valuation of CDPHE’s AAQ EE demonstration.

47 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.

48 “TSD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013, page 123

.23

Table 5: EPA’s Analysis of CDPHE’s TSD of AAQ HF and CCR Exceedance Location Affects Air Quality TSD Citation Sufficient

Quality of Evidence EPA

Criterion Met?

HF Alamosa Adams State

College Section 3: p.63

- 68, 76

- 78 Yes Yes

Alamosa Municipal Building Section 3: p.63

- 65, 68

- 71, 76

- 78 Yes Yes

Lamar Power Plant Section 3: p.63

- 65, 71

- 78 Yes Yes

CCR All Three Monitoring

Sites Section 2: p.11

- 62, Figures 1

- 39 Yes Yes

Section 2: p.11, 31

- 44, Tables

1

- 14 Yes Yes

Section 2: p.58 Yes Yes

Section 4: p.79

- 87 Yes Yes

Natural Event

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

, EPA will consider an event to be a natural event if both the nRCP and CCR requirements have been adequately demonstrated. CDPHE states that

, Multiple sources of data for the event in question and analyses of past dust storms in this area prove that this was a natural event and, more specifically, a significant natural dust storm originating in northeastern Arizona, northwestern New Mexico, and southeastern Utah and spreading into southeastern Colorado. But for the dust storm on April 3, 2011, this exceedance would not have occurred.

. . . GASP satellite imagery shows that the desert regions of northeast Arizona and northwest New Mexico along with the arid plains of eastern Colorado were source regions for the blowing dust on April 3. This is consistent with the climatology for many dust storms in Colorado as described in the Grand Junction, Colorado, Blowing Dust Climatology report contained in Appendix A and the Lamar, Colorado, Blowing Dust Climatology in Appendix B, both found at the end of this document. The observations of winds above blowing dust thresholds and re stricted visibilities in the areas of concern demonstrate that this is a natural event that cannot be reasonably controlled or prevented. 49

EPA acknowledges that the winds originate from arid regions in Arizona, northwest New Mexico, southeast Utah and ble w into the San Luis Valley of Colorado into the Alamosa area, and from northwest New Mexico and eastern Colorado blowing into the Lamar area. However, EPA analysis of the data indicates that significant amounts of dust do not appear to have been transporte d across state lines, and that in fact the arid natural climate and surrounding agricultural lands within Colorado were the more

49 “TSD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013, page 124

.24

probable source of monitored dust. Regardless, s ufficient local controls were in place and were likely overwhelmed by the wind speed. CDPHE has sufficiently demonstrated the CCR and nRCP requirements for the April 3, 2011 event. Therefore, the EPA concludes that this was a natural event pursuant to the Treatment of Data Influenced by Exceptional Events rul e. Table 6 summarizes the EPA’s evaluation of CDPHE’s Natural Event EE demonstration.

Table 6: EPA’s Analysis of CDPHE’s TSD of Natural Event nRCP or CCR Exceedance Location Natural Event TSD Citation Sufficient Quality

of Evidence? EPA

Criterion Met?

nRCP

Anthropogenic Alamosa Adams

State College Section 5: p. 88

- 101 Yes Yes

Alamosa Municipal Building Section 5: p. 88

- 94, 102

- 106 Yes Yes

Lamar Power Plant Section 5: p. 107

- 122 Yes Yes

nRCP

- Wind Speed Alamosa Adams State College Section 2: p.11

- 62, esp. p.31 Yes Yes

Alamosa Municipal Building Section 2: p.11

- 62, esp. p.31 Yes Yes

Lamar Power Plant Section 2: p.11

- 62, esp.

p.32 Yes Yes

CCR All Three

Monitoring Sites Section 2: p.11

- 62, Figures 1

- 39 Yes Yes

Section 2: p.11, 31

- 44, Tables 1

- 14 Yes Yes

Section 2: p.58 Yes Yes

Section 4: p.79

- 87 Yes Yes

No Exceedance or Violation But For the Event

Generally, the No Exceedance or Violation But for the Event (NEBF) demonstration is similar to the demonstration of the nRCP and CCR requirements, and should show that the measured concentration would have been below the applicable NAAQS without the affect of the event.

CDPHE provides a summary of the analysis and information presented in the TSD that show both the nRCP and CC R requirements have been met and states that:

This event produced the maximum value for any sample taken in April and exceeded the 99th% value of any evaluation criteria. The statistical and meteorological data clearly shows that but for25

this high wind blowing dust event, Alamosa and Lamar would not have exceeded the 24

- hour NAAQS on April 3, 2011. 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 fluctuations including background

. 50

Therefore, the EPA concludes that there would have been no violation but for the event pursuant to the Treatment of Da ta Influenced by Exceptional Events rule. While not explicitly stated in the TSD , EPA notes that PM 10 concentrations before the periods of high winds on the event days were below the 24

- hour PM 10 NAAQS, providing further support for CDPHE’s conclusion. Tab le 7 summarizes the EPA’s evaluation of CDPHE’s NEBF EE demonstration.

Table 7: EPA’s Analysis of CDPHE’s TSD of NEBF Exceedance Date No Exceedance But For the Event TSD Citation Sufficient Quality of Evidence? EPA Criterion Met?

April 3, 2011 Section 6: p.124

- 125 Yes Yes

Schedule and Procedural Requirements

In addition to technical demonstration requirements, 40 CFR 50.14(c) specifies the schedule and procedural requirements an air agency must follow to request data exclusion. CDPHE received no

extern al comments during the 30 day comment period, but minor corrections were made to the report based on internal staff review. Table 8 outlines EPA’s evaluation of these requirements.

Table 8: EPA’s Analysis of Schedules and Procedural Criteria Reference Schedules and Procedural Criteria TSD Citation EPA

Criterion Met?

Did the State provide prompt public notification of the event? 40 CFR 50.14(c)(1)(i) Section 1: p.9 Yes

Were flags and initial description placed on the data by July 1 st of the following year? 40 CFR 50.14(c)(2)(iii) Section 1: p.9 Yes

Was the demonstration submitted within 3 years of the end of the quarter in which the event occurred and 12 months prior to the date that any regulatory decision must be made by EPA? 40 CFR 50.14(c)(3)(i) December 24, 2013 Yes

Was the public comment process followed and documented? 40 CFR 50.14(c)(3)(v) Section 1: p. 10 Yes

50 “T SD for the April 3, 2011, Alamosa & Lamar Exceptional Event,” November 20, 2013, page 123

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## CONCLUSION

EPA has reviewed the TSD provided by CDPHE to support claims that dust emissions generated by high winds resulted in PM 10 transport from arid regions in Arizona, northwest New Mexico, southeast Utah and the San Luis Valley of Colorado into the Alamosa area, and from northwest New Mexico and eastern Colorado into the Lamar area on April 3, 2011. EPA ackn owledges that the winds originate d from arid regions in Arizona, northwest New Mexico, southeast Utah and blew into the San Luis Valley of Colorado into the Alamosa area, and from northwest New Mexico and eastern Colorado blowing into the Lamar area. Howev er, EPA analysis of the data indicates that significant amounts of dust do not appear to have been transported across state lines, and that in fact the arid natural climate and surrounding agricultural lands within Colorado were the more probable source of monitored dust, and that sufficient local controls in place were likely overwhelmed by the wind speed. This high wind event caused exceedances of the 24

- hour PM 10 NAAQS at the locations identified in Table 1 of this documen t on April 3, 2011, in Alamosa and Lamar. EPA concurs that the flagged exceedances at the Alamosa and Lamar monitors on this day meet the definition of an exceptional event: the exceedances affected air quality, were nRCP, and met the definition of a natu ral event. Specifically, EPA has determined that the event was nRCP due to high wind conditions that entrained PM 10 from sources in the vicinity of the Alamosa and Lamar areas and overwhelmed reasonable controls within Alamosa and Lamar. Also, regardless of transport into the areas, information pertaining to the controls implemented within the affected areas, the spatial extent of elevated PM 10 concentrations measured in the areas, and the wind speeds associated with the high wind dust event provide suffic ient evidence to conclude that these events were nRCP. Furthermore, EPA has determined that there is a CCR between the events and the measured exceedances, there would have been NEBF, and the measured exceedances are in excess of normal HFs. EPA finds tha t the weight of evidence is sufficient to concur on the flagg ed data for the NAAQS exceedance of 298 ug/m 3 at the Alamosa Adams State College monitor, 392 ug/m 3 a t the Alamosa Municipal Building monitor, and 169 ug/m 3 at the Lamar Power Plant monitor on April 3, 2011

. This concurrence does not constitute final EPA action regarding any matter on which EPA is required to provide an opportunity for public comment. In particular, this applies to determinations regarding th e attainment status or classification of the area. Final actions will take place only after EPA completes notice and comment rulemaking on those determinations.