1 

Technical Support Document

For the April 28 & 29, 2010, 

Alamosa, Pagosa Springs, and 

Durango Exceptional Event

Prepared by the Technical Services Program

Air Pollution Control Division

Colorado Department of Public Health and 

Environment

May 17, 2013
1 

Executive Summary

In 2005, Congress identified a need to account for events that result in exceedances of the National 

Ambient Air Quality Standards (NAAQS) that are exceptional in nature1 (e.g., not expected to reoccur or 

caused by acts of nature beyond man-made controls). In response, EPA promulgated the Exceptional 

Events Rule (EER) to address exceptional events in 40 CFR Parts 50 and 51 on March 22, 2007 (72 FR 

13560). On May 2, 2011, in an attempt to clarify this rule, EPA released draft guidance documents on the 

implementation of the EER to State, tribal and local air agencies for review. The EER allows for states 

and tribes to “flag” air quality monitoring data as an exceptional event and exclude those data from use in 

determinations with respect to exceedances or violations of the NAAQS, if EPA concurs with the 

demonstration submitted by the flagging agency. 

Due to the semi-arid nature of parts of the state, Colorado is highly susceptible to windblown dust events. 

These events are often captured by various air quality monitoring equipment throughout the state, 

sometimes resulting in exceedances or violations of the 24-hour PM10 NAAQS. This document contains 

detailed information about the large regional windblown dust event that occurred on April 28 and 29, 

2010. 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 PM10 concentrations were caused by a natural event. 

On Wednesday April 28, 2010, PM10 exceedances greater than the 24-hour NAAQS of 150 μg/m3 were 

recorded at the Adams State College (08-003-0001) monitor in Alamosa with a concentration of 285 

μg/m3

, the Alamosa Municipal Building (08-003-0003) monitor with a concentration of 236 μg/m3, and 

the Pagosa Springs School (08-007-0001) monitor with a concentration of 181 μg/m3

. Additionally on 

April 28, 2010, an exceptionally high sample (greater than the 99th percentile for the site) was recorded at 

the PM10 monitor in Mt. Crested Butte (08-051-0007) (123μg/m3

). On Thursday April 29, 2010, 

exceedances greater than 150 μg/m3 were recorded at the Pagosa Springs School (08-007-0001) monitor 

with a concentration of 162 μg/m3

 and the Durango River City Hall (08-067-0004) monitor with a 

concentration of 226 μg/m3

. Additionally on April 29, 2010, high samples were taken at the Alamosa 

PM10 monitors at Adams State College (08-003-0001) (92 μg/m3

) and the Municipal Building (08-003-

0003) (94 μg/m3

). These exceedances and other high concentrations across Colorado are plotted on the 

maps for April 28 and 29 in Figure 1 and Figure 2, respectively. 

All of the noted April 28 and 29, 2010, twenty-four-hour PM10 concentrations were above the 90th

percentile concentrations for their locations (see Table 24 and Table 25). The statistical data and 

meteorological analysis clearly shows that but for this high wind blowing dust event, Alamosa, Pagosa 

Springs, and Durango would not have exceeded the 24-hour NAAQS on April 28 and 29, 2010. Since at 

least 2005, there has not been an exceedance that was not associated with high winds carrying PM10 dust 

from distant sources in these areas. This is evidence that the event was associated with a measured 

concentration in excess of normal historical fluctuations including background. 

This large regional dust storm adversely affected the air quality exceeding the 24-hour PM10 NAAQS in 

Alamosa, Pagosa Springs, and Durango and impacted PM10 concentrations at several other monitoring 

stations in Colorado. Since at least 2005, there has not been an exceedance that was not associated with 

high winds carrying PM10 dust from distant sources in these areas. APCD is requesting exclusion for each 

of the samples taken at the Adams State College monitor in Alamosa, the Alamosa Municipal Building 

monitor, the Pagosa Springs School monitor and the Durango monitor. 

 

1 Section 319 of the Clear Air Act (CAA), as amended by section 6013 of the Safe Accountable Flexible EfficientTransportation Equity Act: A Legacy for Users (SAFE-TEA-LU of 2005, required EPA to propose the Federal 

Exceptional Events Rule (EER) no later than March 1, 2006.
2 

Specifically, these high values taken on April 28 and 29, 2010, were the consequence of strong 

southwesterly prefrontal surface winds over dry soils which caused significant blowing dust across much 

of Arizona, northwest New Mexico, southeast Utah and southwest Colorado. These winds were the result 

of a significant surface low pressure and surface cold front associated with a major upper-level trough that 

was moving across the Western United States. This single storm system caused blowing dust during the 

afternoon and evening hours of April 28 that continued through the morning hours of April 29. It 

transported PM10 dust into the southwestern portion of Colorado. 

Widespread restrictions to visibility occurred in northeastern Arizona, northwestern New Mexico, and 

southwestern Colorado. The weather system causing the winds affected southwestern Colorado during the 

afternoon and evening hours on April 28 and during the early morning hours of April 29 as the effects of 

the system shifted east and south. These observations contribute to the body of evidence that shows that a 

regional dust storm caused the PM10 exceedances at the monitoring sites in question.

EPA‘s June 2012 draft 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 states “the EPA 

will accept a threshold of a sustained wind of 25 mph for areas in the west provided the agencies support 

this as the level at which they expect stable surfaces (i.e., controlled anthropogenic and undisturbed 

natural surfaces) to be overwhelmed...” In addition, in both eastern and western Colorado it has been 

shown that wind speeds of 30 mph or greater and gusts of 40 mph or greater can cause blowing dust (see 

reference for the Technical Support Document for the January 19, 2009 Lamar Exceptional Event and 

Attachment A - Grand Junction, Colorado, Blowing Dust Climatology at the end of this document). For 

this blowing dust event, it has been assumed that sustained winds of 25 mph and higher or wind gusts of 

40 mph and higher can cause blowing dust in Arizona, New Mexico, and Colorado. Observations for 

Cortez, Durango, Montrose, Alamosa, and Colorado Springs showed sustained wind speeds were as high 

as 47 mph and wind gusts were as high as 64 mph on April 28 and 29, 2010, and these are well above the 

identified blowing dust thresholds. Outside of Colorado, sustained wind speeds were as high as 53 mph 

and wind gusts were as high as 70 mph on April 28 and 29, 2010. 

The Albuquerque, Flagstaff, and Grand Junction NWS Forecast Offices issue weather warnings and 

advisories for northeast Arizona, most of New Mexico, eastern Utah, and western and southwestern 

Colorado. The weather warnings and advisories issued by theses offices for April 28 and 29, 2010, are 

presented in Appendix B. These warnings and advisories show that strong winds and areas of blowing 

dust were expected and experienced across this region on these days.

The blowing dust climatology for the Four Corners area indicates that the area can be susceptible to 

blowing dust when winds are high. Landform imagery shows that northeastern Arizona and southeastern 

Utah in particular have experienced a long-term pattern of wind erosion and blowing dust when winds 

have been southwesterly and blowing into western and southern Colorado. Forecast products from the 

Navy Aerosol Analysis and Prediction System model provide evidence for a widespread blowing dust 

event in the Four Corners states, suggesting that significant source regions for dust transported into 

Colorado were located in arid regions of Arizona, Utah, and New Mexico. NOAA HYSPLIT forward and 

backward trajectories provide clear supporting evidence that dust from desert regions of northwest New 

Mexico and Arizona caused the PM10 exceedances measured across portions of southwestern Colorado on 

April 28 and 29, 2010. Soils in the Four Corners area and in northeastern Arizona, southeastern Utah, and 

extreme northwestern New Mexico in particular were dry enough to produce blowing dust when winds 

were above the thresholds for blowing dust. 

The Drought Monitor map of the western U.S. for April, 2010, shows that much of southeastern Utah, 

northeastern Arizona, and portions of extreme northwestern New Mexico had below normal soil moisture. 

Northeastern Arizona was classified as Abnormally Dry with an area of Moderate to Severe Drought in 
3 

the Painted Desert region. Soils in southeastern Utah, northwestern New Mexico, and northeastern

Arizona in particular were dry enough to produce blowing dust when winds were above the thresholds for 

blowing dust. At these locations of concern sustained wind speeds were as high as 53 mph and wind gusts 

were as high as 70 mph on April 28 and 29, 2010.

Surface weather maps for the Four Corner States show evidence of widespread blowing dust and winds 

above the threshold speeds for blowing dust on April 28 and 29, 2010. MODIS and GOES satellite 

imagery shows that the Painted Desert and Four Corners area in general were source regions for the 

blowing dust that spanned April 28 and 29, 2010. 

MODIS and GOES satellite imagery shows that the Painted Desert and Four Corners area in general were 

source regions for the blowing dust that spanned April 28 and 29, 2010. 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 of this document. The observations of winds above 

blowing dust thresholds and restricted visibilities in the areas of concern demonstrate that this is a natural 

event that cannot be reasonably controlled or prevented. 

The Center for Snow and Avalanche Studies has been studying the effects of wind-blown desert dust from 

Arizona, New Mexico, and Utah on snowpack albedo and snowmelt in the San Juan Mountains of 

Colorado. The Center for Snow and Avalanche Studies lists April 28, 2010, as one of nine Dust-on-Snow 

events for the 2009/2010 water year, and this provides clear supporting evidence that a regional blowing 

dust event with long-range transport caused the PM10 exceedances measured across portions of Colorado 

on April 28, 2010. Snow cover data provide strong evidence that a widespread, regional, blowing dust 

event caused exceedances at these locations. In addition, scientists at the NOAA Satellite Services 

Division reported significant dust transport from northeastern Arizona and northwestern New Mexico into 

Colorado during this event. 

Friction velocities provide a measure of the near-surface meteorological conditions necessary to cause 

blowing dust. Friction velocities were high enough to sustain blowing dust over undisturbed soils in each 

of the Four Corners states during this event.

The PM10 exceedances in Alamosa, Pagosa Springs and Durango on April 28 and 29, 2010, would not 

have occurred if not for the following: (a) dry soil conditions over southeastern Utah, northeastern 

Arizona, portions of extreme northwestern New Mexico, and portions of southern Colorado with 30-day 

precipitation totals below the thresholds for blowing dust; (b) a strong surface and upper-level low 

pressure system that caused widespread strong gusty winds through a deep layer of the atmosphere over 

the area of concern; and (c) friction velocities over the desert regions of northwest New Mexico, Utah, 

Arizona and much of Colorado that were high enough to allow entrainment of dust from natural sources 

with subsequent transport of the dust into (or within) Colorado in strong, southwesterly winds. These 

PM10 exceedances were due to an exceptional event associated with regional windstorm-caused emissions 

from erodible soil sources over a large area of Arizona, northwest New Mexico, southeast Utah and 

southwest Colorado. These sources are not reasonably controllable during a significant windstorm under 

abnormally dry or moderate drought conditions.

APCD is requesting concurrence on exclusion of the PM10 values from Alamosa-Adams State 

College (08-003-0001), Alamosa-Municipal Building (08-003-0003), and Pagosa Springs-Middle 

School (08-007-0001) on April 28, 2010. 

APCD is requesting concurrence on exclusion of the PM10 values taken at Pagosa Springs-Middle 

School (08-007-0001) and Durango-River City Hall (08-067-0004) on April 29, 2010.
4 

Table of Contents

1.0 Exceptional Events Rule Requirements............................................................................................. 9

1.1 Procedural Criteria ........................................................................................................................ 9

1.2 Documentation Requirements..................................................................................................... 10

2.0 Meteorological analysis of the April 28/29, 2010, blowing dust event and PM10 exceedance – 

Conceptual Model and Wind Statistics .......................................................................................... 11

3.0 Evidence-Ambient Air Monitoring Data and Statistics................................................................... 62

3.1 Historical Fluctuations of PM10 Concentrations in Alamosa, Pagosa Springs, and Durango ..... 62

3.2 Wind Speed Correlations ............................................................................................................ 74

3.3 Percentiles................................................................................................................................... 76

4.0 News and Credible Evidence........................................................................................................... 79

5.0 Not Reasonably Controllable or Preventable: Local Particulate Matter Control Measures............. 92

5.1 Alamosa ...................................................................................................................................... 94

5.2 Pagosa Springs.......................................................................................................................... 102

5.3 Durango..................................................................................................................................... 107

6.0 Summary and Conclusions............................................................................................................ 114

7.0 References..................................................................................................................................... 116
5 

Figures 

Figure 1: 24-hour PM10 concentrations for April 28, 2010..........................................................................................12

Figure 2: 24-hour PM10 concentrations for April 29, 2010..........................................................................................13

Figure 3: Surface analysis for 12Z April 28, 2010,or 5 AM MST April 28, 2010. .....................................................13

Figure 4: Surface analysis for 00Z April 29, 2010 or 5 PM MST April 28, 2010 ......................................................14

Figure 5: Surface analysis for 12Z April 29, 2010 or 5 AM MST April 29, 2010. .....................................................14

Figure 6: Surface analysis for 18Z April 29, 2010 or 11 AM MST April 29, 2010. ...................................................15

Figure 7: 500 mb analysis for 12Z April 28, 2010, or 5 AM MST April 28, 2010 .....................................................15

Figure 8: 500 mb analysis for 18Z April 28, 2010 or 11 AM MST April 28, 2010. ...................................................16

Figure 9: 700 mb analysis for 18Z April 28 2010, or 11 AM MST April 28, 2010. ...................................................16

Figure 10: Height of the mixed layer the NAM12 analysis at 18Z April 28, 2010 or 11 AM MST April 28, 2010. . 17

Figure 11: 700 mb analysis for 00Z April 29, 2010 or 5 PM MST April 28, 2010 .....................................................18

Figure 12: Height of the mixed layer from the NAM12 analysis at 00Z April 29, 2010 

or 5 PM MST April 28, 2010.....................................................................................................................18

Figure 13: 500 mb analysis for 12Z April 29, 2010 or 5 AM MST April 29, 2010. ...................................................19

Figure 14: 500 mb analysis for 12Z April 29, 2010 or 5 AM MST April 29, 2010. ...................................................19

Figure 15: 700 mb analysis for 12Z April 29, 2010 or 5 AM MST April 29, 2010. ...................................................20

Figure 16: Height of the mixed layer from the NAM12 analysis at 12Z April 29, 2010 

or 5 AM MST April 29, 2010. ...................................................................................................................20

Figure 17: NCAR RAP DEN sector surface analysis for 2243Z April 28, 2010 or 3:43 PM MST April 28, 2010. ...22

Figure 18: NCAR RAP DEN sector surface analysis for 0143Z April 29, 2010 or 6:43 PM MST April 28, 2010. ...23

Figure 19: NCAR RAP DEN sector surface analysis for 0743Z April 29, 2010 or 0:43 AM MST April 29, 2010....24

Figure 20: NOAA HYSPLIT 18-hour forward trajectories for northeast Arizona and northwest New Mexico for 5 

PM MST April 28 (00Z April 29), 2010....................................................................................................47

Figure 21: NOAA HYSPLIT 12-hour back trajectories for Durango, Colorado for each hour from 3 AM MST April 

28, 2010 to 3 PM MST April 28, 2010......................................................................................................48

Figure 22: NOAA HYSPLIT 12-hour back trajectories for Durango, Colorado for each hour from 11 AM MST 

April 28, 2010 to 11 PM MST April 28, 2010...........................................................................................49

Figure 23: NOAA HYSPLIT 12-hour back trajectories for Pagosa Springs, Colorado for each hour from 3 AM MST 

April 28, 2010 to 3 PM MST April 28, 2010.............................................................................................50

Figure 24: NOAA HYSPLIT 12-hour back trajectories for Pagosa Springs, Colorado for each hour from 11 AM 

MST April 28, 2010 to 11 PM MST April 28, 2010..................................................................................51

Figure 25: NOAA HYSPLIT 12-hour back trajectories for Alamosa, Colorado for each hour from 3 AM MST April 

28, 2010 to 3 PM MST April 28, 2010......................................................................................................52

Figure 26: NOAA HYSPLIT 12-hour back trajectories for Alamosa, Colorado for each hour from 11 AM MST 

April 28, 2010 to 11 PM MST April 28, 2010...........................................................................................53

Figure 27: NAAPS forecasted dust concentrations for 5 PM April 28 (00Z April 29), 2010......................................54

Figure 28: Dust-on-Snow Deposition Events Log at the Senator Beck Basin Study Area on Red Mountain Pass, 

Colorado. ...................................................................................................................................................55

Figure 29: MODIS Aqua satellite afternoon image of Arizona on April 28, 2010 showing plumes of blowing dust in 

the Four Corners area.................................................................................................................................56

Figure 30: GOES visible satellite image for 3:02 PM MST April 28, 2010 showing plumes of blowing dust in the 

Four Corners area. .....................................................................................................................................57

Figure 31: GOES visible satellite image for 4:45 PM MST April 28, 2010 showing plumes of blowing dust in the 

Four Corners area. .....................................................................................................................................58

Figure 32: Total precipitation in inches for April 2010...............................................................................................59

Figure 33: Drought status for the Colorado on April 27, 201060.................................................................................60

Figure 34: Friction velocities from the NOAA NCEP North American Model (5 PM MST April 28).......................61

Figure 35: Friction velocities from the NOAA NCEP North American Model (11 PM MST April 28).....................61

Figure 36: Alamosa ASC PM10 Time Series ...............................................................................................................65

Figure 37: Alamosa ASC PM10 Histogram..................................................................................................................65

Figure 38: Monthly Alamosa ASC PM10 Box and Whisker Plot.................................................................................66

Figure 39: Monthly Alamosa ASC PM10 Box and Whisker Plot (expanded view).....................................................66

Figure 40: Alamosa Municipal PM10 Time Series.......................................................................................................67

Figure 41: Alamosa Municipal PM10 Histogram.........................................................................................................68

Figure 42: Monthly Alamosa Muni PM10 Box and Whisker Plot................................................................................68
6 

Figure 43: Monthly Alamosa Muni PM10 Box and Whisker Plot (expanded view) ....................................................69

Figure 44: Pagosa Springs ASC PM10 Time Series.....................................................................................................70

Figure 45: Pagosa Springs ASC PM10 Histogram......................................................................................................70

Figure 46: Monthly Pagosa Springs PM10 Box and Whisker Plot...............................................................................71

Figure 47: Monthly Pagosa Springs PM10 Box and Whisker Plot (expanded view) ...................................................71

Figure 48: Durango PM10 Time Series........................................................................................................................72

Figure 49: Durango PM10 Histogram...........................................................................................................................73

Figure 50: Monthly Durango PM10 Box and Whisker Plot..........................................................................................73

Figure 51: Monthly Durango PM10 Box and Whisker Plot (expanded view)..............................................................74

Figure 52: Wind Speed Graphs for Select Areas in Southwest Colorado, Northeast Arizona and 

Northwest New Mexico .............................................................................................................................75

Figure 53: PM10 Concentrations, Select Affected Sites (04/22/2010 – 05/05/2010)...................................................76

Figure 54: Monthly Percentile Plots for Alamosa ASC, Alamosa Muni, Durango, Mt Crested Butte, 

and Pagosa Springs....................................................................................................................................77

Figure 55: Relative positions of Adam's State College PM10 Monitor and potential disturbed soil ............................97

Figure 56: 2011 City of Alamosa Zoning Map............................................................................................................98

Figure 57: Sites B, E, and H with natural vegetation...................................................................................................99

Figure 58: Relative positions of Municipal Building PM10 Monitor and potential disturbed soil .............................100

Figure 59: Relative positions of Pagosa Springs PM10 monitor and known or potential disturbed soil.....................104

Figure 60: View of the fence surrounding the vacant lot (Site A).............................................................................105

Figure 61: Yamaguchi Park.......................................................................................................................................106

Figure 62: Site of the new Smith Sports Complex ....................................................................................................110

Figure 63: Three Springs Southern Open Space and the Three Springs Confluence Park 

before Completion ...................................................................................................................................111

Figure 64: Relative positions of Durango PM10 Monitor and potential disturbed soil ..............................................112
7 

Tables 

Table 1: Wind and weather observations for Winslow, Arizona reported by the University of Utah 

MesoWest site for April 28, 2010. ................................................................................................................26

Table 2: Wind and weather observations for Winslow Arizona reported by the University of Utah 

MesoWest site for April 29, 2010. ................................................................................................................27

Table 3: Wind and weather observations for Hopi, Arizona reported by the University of Utah 

MesoWest site for April 28, 2010. ................................................................................................................28

Table 4: Wind and weather observations for Hopi, Arizona reported by the University of Utah 

MesoWest site for April 29, 2010. ................................................................................................................29

Table 5: Wind and weather observations for Window Rock, Arizona reported by the University of Utah 

MesoWest site for April 28, 2010. ................................................................................................................30

Table 6: Wind and weather observations for Window Rock, Arizona reported by the University of Utah 

MesoWest site April 29, 2010.......................................................................................................................31

Table 7: Wind and weather observations for Gallup, New Mexico reported by the University of Utah 

MesoWest site for April 28, 2010. ................................................................................................................32

Table 8: Wind and weather observations for Gallup, New Mexico, reported by the University of Utah 

MesoWest site for April 29, 2010. ................................................................................................................33

Table 9: Wind and weather observations for Farmington, New Mexico reported by the University of Utah 

MesoWest site for April 28, 2010. ................................................................................................................34

Table 10: Wind and weather observations for Farmington, New Mexico reported by the University of Utah 

MesoWest site for April 29, 2010................................................................................................................35

Table 11: Wind and weather observations for Cortez, Colorado reported by the University of Utah 

MesoWest site for April 28, 2010................................................................................................................36

Table 12: Wind and weather observations for Cortez, Colorado reported by the University of Utah 

MesoWest site for April 29, 2010................................................................................................................37

Table 13: Wind and weather observations for Durango, Colorado reported by the University of Utah 

MesoWest site for April 28, 2010................................................................................................................38

Table 14: Wind and weather observations for Durango, Colorado reported by the University of 

Utah MesoWest site for April 29, 2010.......................................................................................................39

Table 15: Wind and weather observations for Montrose Colorado, reported by the University of Utah 

MesoWest site for April 28, 2010................................................................................................................40

Table 16: Wind and weather observations for Montrose, Colorado reported by the University of Utah 

MesoWest site for April 29, 2010................................................................................................................41

Table 17: Wind and weather observations for Alamosa, Colorado reported by the University of Utah 

MesoWest site for April 28, 2010................................................................................................................42

Table 18: Wind and weather observations for Alamosa, Colorado reported by the University of Utah 

MesoWest site for April 29, 2010................................................................................................................43

Table 19: Wind and weather observations for Pagosa Springs, Colorado reported by the University of Utah 

MesoWest site for April 28, 2010................................................................................................................44

Table 20: Wind and weather observations for Pagosa Springs, Colorado reported by the University of Utah 

MesoWest site for April 29, 2010................................................................................................................45

Table 21: PM10 Monitoring Data Summary (Affected Sites) ......................................................................................63

Table 22: Data Summary between 2005 and 2011 ......................................................................................................63

Table 23: Month and Year PM10 Monitoring Data Summary......................................................................................64

Table 24: Various Percentile Values for Each Site from all April Data compared to April 28, 2010 .........................78

Table 25: Various Percentile Values for Each Site from all April Data compared to April 29, 2010 .........................78

Table 26: State Regulations Regulating Particulate Matter Emissions........................................................................92

Table 27: Rules and Ordinances Regulating Particulate Matter Emissions in Alamosa..............................................94

Table 28: Number of seedlings sold in Alamosa per year. ..........................................................................................96

Table 29: Rules and Ordinances Regulating Particulate Matter Emissions in Archuleta County .............................102

Table 30: Rules and Ordinances Regulating Particulate Matter Emissions in Durango............................................107
8 

List of Appendices

Appendix A - Grand Junction, Colorado, Blowing Dust Climatology 

Appendix B - Weather Warnings and Blowing Dust Advisories for April 28/29, 2010 

Appendix C - Final Natural Events Action Plan for High Wind Events, Alamosa, Colorado 

Appendix D - Copy of Affidavit of Public Notice 
9 

1.0 Exceptional Events Rule Requirements

In addition to the technical requirements that are contained within the EER, procedural requirements must 

also be met in order for EPA to concur with the flagged air quality monitoring data. This section of the 

report lays out the requirements of the EER and discusses how the APCD addressed those requirements. 

1.1 Procedural Criteria

This section presents a review of the procedural requirements of the EER as required by 40 CFR 50.14 

(Treatment of Air Quality Monitoring Data Influenced by Exceptional Events) and explains how APCD 

fulfills them. 

The Federal EER requirements include public notification that an event was occurring, the placement of 

informational flags on data in EPA’s Air Quality System (AQS), submission of initial event description, 

the documentation that the public comment process was followed, and the submittal of a demonstration 

supporting the exceptional events flag. ACPD has addressed all of these procedural and documentation 

requirements. 

Public notification that event was occurring (40 CFR 50.14(c)(1)(i)) 

APCD issued Blowing Dust Advisories for western, central, and southern Colorado advising citizens of 

the potential for high wind/dust events on April 28 and 29, 2010. This area includes: Grand Junction, 

Rifle, Montrose, Aspen, Pagosa Springs, Delta, Cortez, Durango, Telluride, Alamosa, and nearby towns 

(i.e. Pagosa Springs and Crested Butte). The advisories that were issued on April 28 and 29, 2010, can be 

viewed at: http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=04%2f28%2f2010 and 

http://www.colorado.gov/airquality/forecast_archive.aspx?seeddate=04%2f29%2f2010 and are included in 

Appendix B. 

Place informational flag on data in AQS (40 CFR 50.14(c)(2)(ii)) 

APCD and other applicable agencies in Colorado submit data into EPA’s AQS. Data from both filterbased and continuous monitors operated in Colorado are submitted to AQS. 

When APCD and/or another agency operating monitors in Colorado suspects that data may be influenced 

by an exceptional event, APCD and/or the other operating agency expedites analysis of the filters 

collected from the potentially-affected filter-based air monitoring instruments, quality assures the results 

and submits the data into AQS. APCD and/or other operating agencies also submit data from continuous 

monitors into AQS after quality assurance is complete. 

If APCD and/or the applicable operating agency have determined a potential exists that the sample value 

has been influenced by an exceptional event, a preliminary flag is submitted for the measurement when 

the data is uploaded to AQS. The data are not official until they are certified by May 1st of the year 

following the calendar year in which the data were collected (40 CFR 58.15(a)(2)). The presence of the 

flag can be confirmed in AQS. 

Notify EPA of intent to flag through submission of initial event description by July 1 of calendar year 

following event (40 CFR 50.14(c)(2)(iii)) 

In early 2011, APCD and EPA Region 8 staff agreed that the notification of the intent to flag data as an 

exceptional event would be done by submitting data to AQS with the proper flags and the initial event 

descriptions. This was deemed acceptable, since Region 8 staff routinely pull the data to review for 

completeness and other analyses. 

On April 28, 2010, three PM10 sample values greater than 150 μg/m3 were taken at multiple sites across 

southwestern Colorado during the high wind event that occurred that day. These were the monitors 

located in Alamosa at Adams State College (SLAMS), Alamosa Municipal Building (SLAMS), and 
10

Pagosa Springs (SLAMS). In addition, a high value greater than the 99th percentile was recorded at the 

Mt. Crested Butte PM10 monitor. All of these monitors are operated by APCD in partnership with local 

operators. 

On April 29, 2010, two PM10 sample values greater than 150 μg/m3 were taken at multiple sites across 

southwestern Colorado during the high wind event that occurred that day. These were the monitors 

located in Pagosa Springs (SLAMS), and Durango (SLAMS). Both of these monitors are operated by 

APCD in partnership with local operators. 

Document that the public comment process was followed for event documentation (40 CFR 

50.14(c)(3)(iv)) 

APCD posted this report on the Air Pollution Control Division’s webpage for public review. APCD 

opened a 30-day public comment period on May 28, 2013. A copy of the public notice certification, along 

with any comments received, will be submitted to EPA, consistent with the requirements of 40 CFR 

50.14(c)(3)(iv). See Appendix D for a copy of the affidavit of public notice. 

Submit demonstration supporting exceptional event flag (40 CFR 50.14(a)(1-2)) 

At the close of the comment period, and after APCD has had the opportunity to consider any comments 

submitted on this document, APCD will submit this document, along with any comments received (if 

applicable), and APCD’s responses to those comments, to EPA Region VIII headquarters in Denver, 

Colorado. The deadline for the submittal of this demonstration package is June 30, 2013. 

1.2 Documentation Requirements

Section 50.14(c)(3)(iv) of the EER states that in order to justify excluding air quality monitoring data, 

evidence must be provided for the following elements: 

a. The event satisfies the criteria set forth in 40 CFR 501(j) that: 

(1) the event affected air quality, 

(2) the event was not reasonably controllable or preventable, and 

(3) the event was caused by human activity unlikely to recur in a particular location or 

was a natural event;

b. There is a clear causal relationship between the measurement under consideration and the 

event; 

c. The event is associated with a measured concentration in excess of normal historical 

fluctuations; and 

d. There would have been no exceedance or violation but for the event. 
11

2.0 Meteorological analysis of the April 28/29, 2010,

blowing dust event and PM10 exceedance – Conceptual 

Model and Wind Statistics

On April 28 and 29 of 2010, a strong spring storm system caused multiple exceedances of the twentyfour-hour PM10 standard in southwest Colorado. On Wednesday April 28, 2010, exceedances were 

recorded at the Adams State College monitor in Alamosa with a concentration of 285 μg/m3

, the Alamosa 

Municipal Building monitor with a concentration of 236 μg/m3

, and the Pagosa Springs School monitor 

with a concentration of 181 μg/m3

. On Thursday April 29, 2010, exceedances were recorded at the 

Pagosa Springs School monitor with a concentration of 162 μg/m3

 and the Durango monitor with a 

concentration of 226 μg/m3

. These exceedances and other concentrations across Colorado are plotted on 

the maps for April 28 and 29 in Figure 1 and Figure 2, respectively. These exceedances were the 

consequence of strong southwesterly prefrontal surface winds over dry soils which caused significant 

blowing dust across much of Arizona, northwest New Mexico, southeast Utah and southwest Colorado. 

Strong winds were the result of a significant surface low pressure and surface cold front associated with a 

major upper-level trough that was moving across the Western United States. This single storm system 

caused blowing dust during the afternoon and evening hours of April 28 that continued through the 

morning hours of April 29. 

EPA‘s June 2012 draft 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 states “the EPA 

will accept a threshold of a sustained wind of 25 mph for areas in the west provided the agencies support 

this as the level at which they expect stable surfaces (i.e., controlled anthropogenic and undisturbed 

natural surfaces) to be overwhelmed...” In addition, in both eastern and western Colorado it has been 

shown that wind speeds of 30 mph or greater and gusts of 40 mph or greater can cause blowing dust (see 

reference for the Technical Support Document for the January 19, 2009 Lamar Exceptional Event and 

Attachment A - Grand Junction, Colorado, Blowing Dust Climatology at the end of this document). For 

this blowing dust event, it has been assumed that sustained winds of 25 mph and higher or wind gusts of 

40 mph and higher can cause blowing dust in Arizona, New Mexico, and Colorado. 
12

Table 11 through Table 20 list wind observations for Cortez, Durango, Montrose, Alamosa, and Colorado 

Springs, respectively. It will be shown that this storm system caused winds that met these criteria at many 

of the weather stations in the affected region on April 28 and 29, 2010. 

The surface weather associated with this storm on April 28, 2010, is presented in Figure 3 and Figure 4, 

the surface analyses for 5 AM MST and 5 PM MST April 28, respectively. Surface weather on April 29, 

2010, is presented in Figure 5 and Figure 6, the surface analyses for 5 AM MST and 11 AM MST April 

29, respectively. Significant surface features in Figure 3, Figure 4, Figure 5, and Figure 6 include the 

cold front moving across the Great Basin and Colorado, the surface low pressure complex with a center 

forming in Colorado, and a semi-stationary front moving slowly southward across Colorado. 

The upper-level trough associated with this storm is shown in Figure 7, Figure 8 and Figure 9. Figure 7

and Figure 8 show the 500-mb height analysis maps for 5 AM and 11 AM MST, respectively on April 28. 

The 500 mb level is roughly 6 kilometers above mean sea level (MSL). These two maps show that a deep 

trough was located in the western United States. Figure 8 shows the jet stream maximum winds around 

the base of the trough from California through Wyoming. Figure 9 shows the trough at the 700 mb level 

which is approximately 3 kilometers MSL. Upper-level winds at the base of the trough ranged from 40 to 

100 knots, with a wind speed maximum over northern Arizona at 700 mb (Figure 9). 

Figure 1: 24-hour PM10 concentrations for April 28, 2010.
13

Figure 2: 24-hour PM10 concentrations for April 29, 2010.

Figure 3: Surface analysis for 12Z April 28, 2010, or 5 AM MST April 28, 2010 (source: 

http://nomads.ncdc.noaa.gov/ncep/NCEP).
14

Figure 4: Surface analysis for 00Z April 29, 2010, or 5 PM MST April 28, 2010 (source: 

http://nomads.ncdc.noaa.gov/ncep/NCEP).

Figure 5: Surface analysis for 12Z April 29, 2010, or 5 AM MST April 29, 2010 (source: 

http://nomads.ncdc.noaa.gov/ncep/NCEP).
15

Figure 6: Surface analysis for 18Z April 29, 2010, or 11 AM MST April 29, 2010 (source: 

http://nomads.ncdc.noaa.gov/ncep/NCEP).

Figure 7: 500 mb (about 6 kilometers above sea level) analysis for 12Z April 28, 2010, or 5 AM MST April 28, 2010 

(source: http://nomads.ncdc.noaa.gov/ncep/NCEP).
16

Figure 8: 500 mb (about 6 kilometers above sea level) analysis for 18Z April 28, 2010, or 11 AM MST April 28, 2010, 

showing wind speeds in knots. Only speeds greater than 40 knots are plotted. (source: RUC 13 km analysis 

http://nomads.ncdc.noaa.gov/data.php?name=access#hires_weather_datasets).

Figure 9: 700 mb (about 3 kilometers above sea level) analysis for 18Z April 28, 2010, or 11 AM MST April 28, 2010, 

showing wind speeds in knots. Only speeds greater than 40 knots are plotted. (source: RUC 13 km analysis 

http://nomads.ncdc.noaa.gov/data.php?name=access#hires_weather_datasets).
17

The upper level trough affected winds near the surface in two ways. First of all, the trough generated a 

surface low-pressure system with strong pressure gradients that caused strong winds at the surface. 

Secondly, momentum associated with the strong winds aloft at the base of the trough was mixed to the 

surface because of deep vertical mixing in the area of the strong winds aloft. Figure 10 shows the height 

of the top of the mixed layer in MSL at 11 AM on April 28, 2010. Mixing as deep as 3 to 6 kilometers 

MSL would have been sufficient to mix momentum to the surface from the zone of strong winds evident 

at 700 and 500 mb over the Four Corners area and southern Colorado. When blowing dust occurs with 

strong winds at the surface and aloft and deep mixing, dust can be suspended for many hours and 

transported long distances. These conditions are the hallmarks of a regional dust transport event.

Figure 11 and Figure 12 show the winds at 700 mb and the height of the mixed layer, respectively, at 5 

PM MST on April 28, 2010. Both the extent of the wind speed maximum and the depth of the mixing 

had increased since 11 AM MST. Figure 12 shows that the mixing was as deep as 3 to 9 kilometers MSL 

in the Four Corners area and all of Colorado.

Figure 13 and Figure 14 show the 500-mb height analysis map and winds for 5 AM on April 29, 2010. 

By this time, the center of the trough had moved over Montana, and the jet stream maximum winds 

extended from California through Arizona and into New Mexico and the southern half of Colorado. 

Figure 15 shows the 700 mb analysis and winds at 5 AM on April 29, 2010. An area of strong winds was 

located over south-central Colorado. The mixing height analysis for 5 AM is presented in Figure 16. 

Mixing was as deep as 3 to 9 kilometers MSL in central and south-central Colorado and northern New 

Mexico. The coincidence of deep mixing and strong winds aloft would have enabled the transfer of 

momentum from the upper level winds to the surface in these areas.

Figure 10: Height of the mixed layer in kilometers above sea level from the NAM12 analysis at 18Z April 28, 2010, or 11 

AM MST April 28, 2010, showing mixing as deep as 3 to 6 kilometers MSL in the Four Corners area.
18

Figure 11: 700 mb (about 3 kilometers above sea level) analysis for 00Z April 29, 2010, or 5 PM MST April 28, 2010, 

showing wind speeds in knots. Only speeds greater than 40 knots are plotted. (source: RUC 13 km analysis 

http://nomads.ncdc.noaa.gov/data.php?name=access#hires_weather_datasets ). 

Figure 12: Height of the mixed layer in kilometers above sea level from the NAM12 analysis at 00Z April 29, 2010, or 5 

PM MST April 28, 2010, showing mixing as deep as 3 to 9 kilometers MSL in the Four Corners area and all of Colorado.
19

Figure 13: 500 mb (about 6 kilometers above sea level) analysis for 12Z April 29, 2010, or 5 AM MST April 29, 2010 

(source: National Weather Service fax maps http://nomads.ncdc.noaa.gov/ncep/NCEP).

Figure 14: 500 mb (about 6 kilometers above sea level) analysis for 12Z April 29, 2010, or 5 AM MST April 29, 2010, 

showing wind speeds in knots. Only speeds greater than 40 knots are plotted. (source: RUC 13 km analysis 

http://nomads.ncdc.noaa.gov/data.php?name=access#hires_weather_datasets ).
20

Figure 15: 700 mb (about 3 kilometers above sea level) analysis for 12Z April 29, 2010, or 5 AM MST April 29, 2010, 

showing wind speeds in knots. Only speeds greater than 40 knots are plotted. (source: RUC 13 km analysis 

http://nomads.ncdc.noaa.gov/data.php?name=access#hires_weather_datasets ). 

Figure 16: Height of the mixed layer in kilometers above sea level from the NAM12 analysis at 12Z April 29, 2010, or 5 

AM MST April 29, 2010, showing mixing as deep as 3 to 9 kilometers MSL in central and south-central Colorado and 

northern New Mexico.
21

The combination of strong winds aloft, deep mixing, and the tight surface pressure gradient associated 

with the surface low pressure system caused surface winds of up to 53 mph with gusts to 70 mph. Winds 

of this strength will cause blowing dust if soils are dry. Recall that wind speeds of 30 mph or greater 

and/or gusts of 40 mph or higher have been shown to cause blowing dust in Colorado (see reference for 

the Natural Events Action Plan for High Wind Events - Lamar, Colorado and the Technical Support 

Document for the January 19, 2009, Lamar Exceptional Event and Attachment A - Grand Junction, 

Colorado, Blowing Dust Climatology at the end of this document). The synoptic weather conditions on 

April 28 and 29, 2010, (illustrated in Figure 3 through Figure 16) show that the conditions necessary for 

widespread strong gusty winds and transport of blowing dust were in place over the area of concern on 

April 28 and 29, 2010. 

Figure 17, Figure 18, and Figure 19 show surface weather observations for 3:43 PM MST and 6:43 PM 

April 28, and12:43 AM April 29, respectively. These maps cover Colorado and the areas of Arizona, 

Utah, and New Mexico that were upwind of the portions of Colorado that experienced exceedances of the 

PM10 standard. These surface analyses shows that winds above 30 mph with gusts above 40 mph 

occurred in areas south of the stationary front and surface low pressure complex shown Figure 4, Figure 

5, and Figure 6. On the map in Figure 17, the station plot for Chama, NM, (E33) is accompanied by a 

dollar sign which is the weather symbol for dust or sand raised by wind at the time of the observation. 

The infinity sign is the weather symbol for haze. This symbol is associated with stations across 

southwestern Colorado and central Colorado as far east as Colorado Springs (COS). Haze is often 

reported during dust storms, and in these dry windy events, haze typically refers to blowing dust. Note 

that haze was reported both in the valley locations like Cortez (CEZ), Farmington (FMN), Alamosa 

(ALS) and Durango (DRO) and in mountain valleys like Telluride (TEX). Additional surface weather 

maps not included here show that there was haze reported in portions of southwest Colorado and 

neighboring states from early afternoon on April 28 through early morning on April 29. Surface weather 

maps for the Four Corners states show evidence of widespread blowing dust and winds above the 

threshold speeds for blowing dust on April 28 and 29, 2010. 
22

Figure 17: NCAR RAP Real-Time Weather Data website DEN sector surface analysis for 2243Z April 28, 2010, or 3:43 

PM MST April 28, 2010 (source: http://www.rap.ucar.edu/weather/).
23

Figure 18: NCAR RAP Real-Time Weather Data website DEN sector surface analysis for 0143Z April 29, 2010, or 6:43 

PM MST April 28, 2010 (source: http://www.rap.ucar.edu/weather/).
24

Figure 19: NCAR RAP Real-Time Weather Data website DEN sector surface analysis for 0743Z April 29, 2010, or 0:43 

AM MST April 29, 2010 (source: http://www.rap.ucar.edu/weather/).
25

Table 1 through Table 10 contain the surface weather observations for Winslow, Hopi, and Window 

Rock, Arizona, and Gallup and Farmington, New Mexico for April 28 and 29. These locations are either 

in or near the areas in northeastern Arizona and northwestern New Mexico that are known sources for 

blowing dust as described in Attachment A (Grand Junction, Colorado, Blowing Dust Climatology - at 

the end of this document). At these locations wind speeds were as high as 53 mph and wind gusts were as 

high as 70 mph, and these are well above the blowing dust thresholds already identified. 

Table 11 through Table 20 list observations for Cortez, Durango, Montrose, Alamosa, and Pagosa

Springs, respectively. These are the National Weather Service sites in Colorado south of the stationary 

front in Figure 4, Figure 5, and Figure 6. These sites also experienced many hours of reduced visibility 

and wind speeds and gusts at or above the thresholds for blowing dust. Observations of wind speeds and 

gust speeds above the blowing dust thresholds and reduced visibilities on April 28 and 29 at weather 

stations in northeastern Arizona, northwestern New Mexico, and southwestern Colorado show that a 

regional dust storm event occurred under southwesterly flow. The weather system causing the winds 

affected southwestern Colorado during the afternoon and evening hours on April 28 and during the early 

morning hours of April 29 as the effects of the system shifted east and south. These observations 

contribute to the body of evidence that shows that a regional dust storm caused the PM10 exceedances at 

the monitoring sites in question. 
26

Table 1: Wind and weather observations for Winslow, Arizona, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 28, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 

28

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:56 58 23 6 170 10

1:56 60 22 7 180 10

2:56 61 21 9 210 10

3:56 61 21 14 200 10

4:56 60 23 8 180 10

5:56 59 21 10 160 10

6:56 60 17 10 160 10

7:56 65 14 27 32 210 10

8:56 67 15 21 28 220 10

9:56 71 12 31 39 210 10

10:56 74 17 25 41 210 lt rain 10

11:56 75 18 33 48 210 lt rain 10

12:56 77 16 28 41 220 10

13:56 79 11 33 45 220 10

14:56 77 12 37 46 220 lt rain 10

15:56 75 15 35 59 210 7 

16:21 73 15 53 67 220 haze 1.75

16:41 73 16 50 62 220 lt rain 0.75

16:46 73 16 53 69 220 lt rain 0.5

16:56 72 17 51 69 220 lt rain 0.5

20:56 64 30 43 62 210 8 

21:56 61 35 45 64 210 haze 4

22:18 61 36 46 70 220 haze 1.75

22:25 61 36 48 66 220 haze 2 

22:47 61 34 51 60 220 haze 4 

22:56 59 33 47 60 220 haze 4

23:08 59 31 47 61 220 haze 2.5

23:16 59 31 44 63 220 haze 4 

23:56 59 36 46 58 210 10
27

Table 2: Wind and weather observations for Winslow, Arizona, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 29, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 

29

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:56 58 44 46 61 210 9 

1:56 57 44 45 58 210 10

2:56 54 43 41 58 210 10

3:56 53 35 40 54 220 10

4:56 52 32 33 47 210 10

5:56 51 29 28 39 220 10

6:56 52 29 25 42 220 10

7:56 53 28 32 44 230 10

8:47 66 30 7 18 240 30

8:56 56 28 28 41 230 10

9:56 54 30 23 39 240 10

10:56 54 24 36 50 240 8 

11:56 53 28 18 33 220 10

12:56 54 23 26 37 240 10

13:56 55 21 26 39 210 10

14:56 51 33 35 47 270 haze 2.5

15:00 50 37 36 47 280 haze 1.5

15:08 48 40 34 46 280 haze 1.5

15:16 48 40 32 47 280 haze 3

15:56 48 39 26 38 270 9 

16:56 46 43 10 23 250 10

17:10 45 45 17 22 240 10

17:26 43 49 21 33 290 10

17:53 43 52 19 36 260 9 

17:56 42 53 16 31 320 9 

18:56 41 52 17 250 10

19:56 41 56 5 30 10

20:56 38 70 7 310 10

21:56 37 67 5 260 10

22:56 38 62 7 230 10

23:56 39 55 8 210 10

 
28

Table 3: Wind and weather observations for Hopi, Arizona, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 28, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 28

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:13 53 27 6 10 207

1:13 52 28 3 12 219

2:13 48 32 2 8 271

3:13 47 32 0 4 220

4:13 49 30 6 9 248

5:13 49 30 7 9 241

6:13 52 28 11 16 208

7:13 56 26 16 21 197

8:13 63 18 19 29 188

9:13 66 17 24 34 216

10:13 69 18 28 37 222

11:13 72 19 26 37 222

12:13 73 18 28 40 222

13:13 75 17 25 41 223

14:13 74 18 29 43 216

15:13 73 18 31 46 229

16:13 71 19 34 48 218

17:13 69 21 31 45 221

18:13 65 25 34 46 230

19:13 62 28 30 47 229

20:13 60 32 31 45 237

21:13 58 34 30 45 234

22:13 57 37 29 39 232

23:13 54 36 24 36 221
29

Table 4: Wind and weather observations for Hopi, Arizona, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 29, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 29

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:13 53 32 29 42 223

1:13 52 35 26 39 240

2:13 51 42 23 34 240

3:13 50 45 27 38 222

4:13 48 37 21 35 246

5:13 45 40 22 32 280

6:13 42 41 18 34 284

7:13 42 32 24 32 284

8:13 43 32 24 36 277

9:13 44 31 22 38 271

10:13 45 30 20 32 280

11:13 47 35 16 31 325

12:13 48 31 17 29 283

13:13 45 50 25 38 325

14:13 47 34 19 29 314

15:13 41 73 13 40 317

16:13 43 52 14 21 311

17:13 42 53 16 34 339

18:13 40 46 10 15 292

19:13 35 73 15 25 283

20:13 35 75 5 21 262

21:13 35 55 14 18 276

22:13 34 74 5 16 224

23:13 32 77 5 9 215

 
30

Table 5: Wind and weather observations for Window Rock, Arizona, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 28, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 28

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:53 54 25 10 230 10

1:53 52 28 12 220 10

2:53 51 29 6 180 10

3:53 52 27 10 190 10

4:53 50 30 9 180 10

5:53 49 31 9 170 10

6:53 48 34 8 180 10

7:53 51 33 7 190 10

8:53 54 31 15 24 210 10

9:53 58 23 27 37 230 10

10:53 61 20 31 43 230 10

11:53 64 19 29 45 230 10

12:53 66 16 35 51 230 10

13:53 69 15 33 48 220 10

14:53 70 15 33 51 220 10

15:53 71 16 33 51 250 10

16:53 69 16 30 48 230 10

17:53 67 18 33 48 240 10

18:53 64 21 36 54 230 10

19:53 60 25 28 44 220 10

20:53 58 26 27 35 220 10

21:53 56 29 22 37 220 10

22:53 54 32 20 32 220 10

23:53 53 35 25 33 230 10
31

Table 6: Wind and weather observations for Window Rock, Arizona, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 29, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 29

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:53 52 44 25 41 240 10

1:53 51 48 25 43 230 10

2:53 50 50 24 37 230 10

3:53 49 48 25 41 230 10

4:53 49 48 23 40 220 10

5:53 46 51 29 40 230 10

6:53 45 53 32 40 230 10

7:53 46 51 29 45 220 10

8:53 48 37 32 48 240 10

9:53 49 25 37 47 240 10

10:53 46 34 20 30 260 10

11:53 47 35 21 37 270 lt rain 10

12:43 43 52 18 33 280 haze 4

12:53 41 55 18 31 270 haze 5

13:01 39 70 18 33 270 haze 1.75

13:19 37 75 14 24 280 lt snow 1.25

13:32 37 70 12 25 290 lt snow 2

13:40 39 65 15 24 300 lt snow 4

13:53 40 59 12 21 300 9

14:39 43 42 24 31 260 10

14:53 45 36 27 37 260 10

15:41 43 42 32 40 260 haze 4

15:49 39 60 14 40 280 haze 2.5

15:53 39 57 12 22 280 haze 5

16:53 41 41 16 31 240 10

17:03 37 65 18 31 280 haze 1.75

17:15 37 70 15 22 290 lt snow 3

17:25 37 65 13 280 10

17:48 36 69 10 280 lt snow 2.5

17:53 34 79 9 270 lt snow 1.5

18:01 34 80 8 230 lt snow 3

18:14 34 80 13 21 270 lt snow 1.75

18:20 34 80 9 21 270 lt snow 0.75

18:25 34 80 9 280 lt snow 1

18:31 34 80 6 260 lt snow 3

18:50 34 75 13 18 260 10

18:53 34 75 8 18 270 lt snow 9

19:17 34 80 13 280 lt snow 2

19:22 32 86 10 260

lt snow; 

fog 0.75

19:32 32 80 7 250 lt snow 2 

19:34 32 80 6 250 lt snow 4
32

Table 7: Wind and weather observations for Gallup, New Mexico, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 28, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 28

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:53 55 24 15 220 10

1:53 54 26 13 20 220 10

2:53 52 28 13 210 10

3:53 50 30 10 180 10

4:53 48 32 6 170 10

5:53 50 30 13 210 10

6:53 50 33 16 210 10

7:53 52 33 21 27 220 10

8:53 56 31 20 27 230 10

9:53 59 27 30 38 230 10

10:53 63 22 31 43 220 10

11:53 63 20 31 56 230 10

12:53 67 19 32 45 230 10

13:53 69 15 38 47 240 10

14:53 71 14 37 56 240 10

15:53 72 15 36 52 230 10

16:53 70 17 39 54 230 10

17:53 68 18 33 51 220 10

18:53 65 21 33 45 220 10

19:53 61 24 30 43 210 10

20:53 59 26 32 43 220 10

21:53 58 28 28 36 220 10

22:53 57 29 23 35 220 10

23:53 56 31 27 37 220 10
33

Table 8: Wind and weather observations for Gallup, New Mexico, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 29, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 29

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:53 55 34 28 43 230 10

1:53 53 39 21 29 220 10

2:53 51 44 18 25 240 10

3:53 50 41 29 45 230 10

4:53 50 39 36 50 230 10

5:53 48 44 32 47 230 10

6:53 46 49 27 45 230 10

7:53 48 49 28 44 240 10

8:53 50 46 38 57 240 10

9:53 52 36 31 53 230 10

10:53 51 29 33 51 250 10

11:53 48 34 28 52 240 10

12:53 48 34 31 40 250 10

13:53 42 55 18 29 290 10

14:36 45 49 29 40 250 9

14:53 43 49 29 46 260 9

15:00 43 49 29 38 270 10

15:53 43 43 23 36 270 10

16:53 44 33 32 45 280 10

17:53 43 41 25 32 270 10

18:36 34 80 20 32 280 lt snow 0.75

18:46 34 86 17 25 270

lt snow; 

fog 2

18:53 35 78 21 28 260 9

19:53 34 79 12 250 lt snow 9

20:53 32 75 13 240 10

21:53 32 81 15 230 lt snow 8

22:53 31 89 7 220 10

23:53 31 82 8 210 10
34

Table 9: Wind and weather observations for Farmington, New Mexico, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 28, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 

28

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in mph

Wind 

Gust in 

mph

Wind 

Direction 

in Degrees Weather

Visibility 

in miles

0:53 62 20 14 290 10

1:53 60 21 5 200 10

2:53 57 24 0 10

3:53 53 31 8 90 10

4:53 53 31 8 90 10

5:53 52 32 9 90 10

6:53 51 35 8 70 10

7:53 55 29 4 80 10

8:53 62 21 4 120 10

9:53 66 13 10 210 10

10:53 69 15 15 25 210 10

11:53 71 13 18 28 220 10

12:53 74 12 23 30 210 haze 6

13:53 76 11 23 37 250 10

14:53 78 10 30 39 260 9

15:09 79 9 35 43 240 haze 2

15:53 76 13 33 46 240 haze 2

16:00 75 13 31 45 250 haze 5

16:53 78 12 28 43 240 haze 5 

17:53 74 14 35 44 240 haze 4

18:06 73 13 33 45 240 haze 4

18:23 73 13 25 40 240 haze 5

18:42 72 14 36 43 230 haze 3

18:53 72 13 29 50 230 haze 2.5

19:04 72 14 33 46 230 haze 3

19:53 68 15 29 46 240 haze 4

20:04 68 16 31 41 250 haze 4

20:53 66 17 24 40 250 haze 4

21:35 64 19 25 33 240 7

21:53 64 20 20 31 240 7

22:53 62 22 20 29 250 8 

23:40 61 23 29 38 250 haze 6

23:53 61 23 24 36 240 haze 5
35

Table 10: Wind and weather observations for Farmington, New Mexico, reported by the University of Utah MesoWest 

site (http://www.met.utah.edu/mesowest/) for April 29, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 

29

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in mph

Wind 

Gust in 

mph

Wind 

Direction 

in Degrees Weather

Visibility 

in miles

0:19 61 25 20 31 250 haze 6

0:53 59 27 18 29 250 haze 6

1:45 59 27 22 33 250 haze 4

1:53 58 26 23 36 240 haze 3

2:05 57 26 22 41 250 haze 2.5

2:14 57 28 25 36 250 haze 2.5

2:21 57 26 22 37 250 haze 3

2:53 57 23 29 43 260 haze 4

3:02 55 24 23 38 260 haze 4

3:36 55 28 23 36 250 7

3:53 55 32 20 35 250 8

4:53 55 35 16 28 260 10

5:39 54 38 13 21 250 haze 6

5:53 54 40 14 23 240 haze 6

6:28 54 35 24 37 240 haze 4

6:53 53 33 23 40 240 haze 4

7:01 52 35 24 33 240 haze 6

7:53 51 35 20 38 270 9

8:53 50 34 20 30 280 10

9:53 46 49 20 34 300 10

10:53 48 42 25 32 290 10

11:53 48 35 22 27 250 10

12:53 51 29 24 30 270 10

13:53 51 26 21 32 270 10

14:53 47 37 18 30 300 10

15:53 47 31 21 31 280 10

16:53 48 27 16 29 290 10

17:53 40 57 17 29 330 lt rain 5

18:53 43 43 15 25 320 10

19:53 41 42 9 290 10

20:53 39 46 8 290 10

21:53 38 48 7 290 10

22:53 38 54 18 290 10

23:53 38 50 13 270 10
36

Table 11: Wind and weather observations for Cortez, Colorado, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 28, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 28

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:53 61 21 10 220 10

1:53 61 22 14 23 220 10

2:53 54 31 7 200 10

3:53 49 41 7 200 10

4:53 48 40 5 270 10

5:53 47 44 0 10

6:53 48 42 0 10

7:53 53 36 6 200 10

8:53 59 27 12 17 190 10

9:53 61 21 16 28 210 10

10:53 67 20 20 31 220 10

11:53 70 20 22 29 190 10

12:53 70 18 23 41 210 9

13:53 72 17 30 43 210 8

14:53 74 17 25 43 220 8 

15:53 75 18 29 39 230 haze 5

16:53 72 17 24 43 240 haze 5

17:53 69 18 27 41 240 haze 4 

18:53 68 19 29 41 250 haze 4

19:53 67 22 31 41 220 haze 3

20:53 64 24 33 44 220 haze 4 

21:53 62 27 23 39 220 haze 4

22:53 60 30 29 41 220 haze 4

23:53 58 33 30 41 220 haze 5 
37

Table 12: Wind and weather observations for Cortez, Colorado, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 29, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 29

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:53 57 33 25 39 220 7

1:53 56 34 29 41 220 7 

2:53 54 34 27 40 220 10

3:53 51 35 27 38 220 9

4:53 51 35 16 30 230 10

5:53 49 36 16 30 240 10

6:53 48 39 23 32 240 10

7:27 43 56 15 21 320 10

7:53 41 62 10 320 10

8:53 40 70 13 280 lt rain 10

9:39 37 87 10 210 lt snow 7

9:53 37 89 10 170 lt snow 8

10:03 37 87 7 170

unknown 

prcp 9 

10:53 43 49 23 35 210 10

11:53 46 49 21 32 320 10

11:59 41 61 18 25 320 10

12:22 37 75 10 21 320 lt snow 5

12:50 41 65 7 360 10

12:53 42 64 7 20 10

13:33 37 75 10 18 270 lt snow 7

13:39 36 75 10 22 270 lt snow 2 

13:43 36 80 14 22 270 lt snow 1.5

13:48 34 86 13 23 280

lt snow; 

fog 0.75

13:53 33 88 5 23 240

lt snow; 

fog 0.75

13:58 34 80 5 140

lt snow; 

fog 1.25

14:00 34 86 7 150

lt snow; 

fog 2.5

14:07 37 81 10 170 9

14:15 37 87 9 150 10

14:53 42 57 14 200 10

15:48 36 75 21 33 340 10

15:53 36 73 20 30 340 10

16:13 36 75 13 27 330 lt snow 2 

16:16 34 86 13 27 330

lt snow; 

fog 1.25

 
38

Table 13: Wind and weather observations for Durango, Colorado, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 28, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 28

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:53 50 33 0 10

1:53 50 32 5 140 10

2:53 49 34 0 10

3:53 48 39 4 30 10

4:53 45 47 5 20 10

5:53 41 60 5 40 10

6:53 43 53 8 90 10

7:53 47 48 7 60 10

8:53 50 42 6 120 10

9:53 54 35 7 100 10

10:53 59 26 0 10

11:53 64 18 12 23 230 10

12:53 66 18 17 29 210 10

13:53 69 15 25 40 220 10

14:53 68 15 22 37 240 10

15:53 69 15 24 37 230 7

16:53 69 17 32 54 240 haze 5

17:53 68 19 27 41 240 haze 6

18:53 66 18 28 43 230 haze 6

19:53 63 19 33 44 230 haze 4

20:53 61 21 25 40 230 haze 5

21:44 61 22 22 43 240 haze 3

21:53 59 23 24 36 240 haze 2.5

22:53 58 26 28 33 250 haze 2.5

23:05 57 26 24 38 240 haze 3

23:18 57 26 28 44 240 haze 2.5

23:36 55 28 31 40 250 haze 2.5

23:51 55 28 30 46 240 haze 2

23:53 56 28 29 44 250 haze 2 
39

Table 14: Wind and weather observations for Durango, Colorado, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 29, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 29

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:39 54 32 20 29 230 haze 3

0:53 54 31 27 36 230 haze 4

1:53 52 35 21 36 230 haze 4

2:53 51 32 21 33 240 haze 6

3:53 49 29 23 35 240 8

4:53 48 32 16 25 240 9

5:53 48 44 28 40 240 10

6:53 48 40 27 39 250 9

7:53 43 53 18 28 280 10

8:53 44 47 23 30 280 10

9:53 44 45 31 38 250 10

10:53 44 49 23 36 250 10

11:53 40 50 15 27 250 9

12:06 39 52 22 25 270 9

12:19 41 45 20 28 220 10

12:53 44 38 14 29 250 10

13:53 46 30 24 33 270 10

14:53 43 41 21 31 270 10

15:53 43 36 17 27 280 10

16:53 44 29 24 37 240 10

17:53 42 37 17 29 280 10

18:53 39 39 15 21 350 10

19:53 37 38 10 320 10

20:53 35 36 9 330 10

21:53 32 47 7 230 10

22:53 31 61 4 250 10

23:53 30 63 6 230 10

 
40

Table 15: Wind and weather observations for Montrose, Colorado, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 28, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 28

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:53 63 18 10 140 10

1:53 64 15 29 46 220 8

2:53 63 16 9 150 10

3:53 61 16 9 21 140 10

4:53 60 19 16 23 130 10

5:53 58 22 4 130 10

6:53 60 20 10 23 110 10

7:53 60 21 21 31 210 10

8:53 64 18 30 41 210 10

9:53 66 16 35 46 210 10

10:53 68 15 32 44 230 10

11:53 70 15 32 45 220 10

12:53 72 15 28 41 210 10

13:53 70 16 30 40 210 10

14:53 74 13 29 45 220 10

15:53 75 14 16 44 230 10

16:53 73 12 32 45 220 10

17:53 72 11 29 43 230 10

18:53 70 13 25 48 220 7

19:53 67 16 33 50 220 haze 5

20:53 66 17 29 43 220 haze 6

21:21 64 19 28 39 220 7

21:53 65 18 32 48 220 haze 6

22:53 63 22 24 40 220 8

23:53 61 23 47 64 200 7
41

 Table 16: Wind and weather observations for Montrose, Colorado, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 29, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 29

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:53 59 27 24 35 220 10

1:53 58 30 18 39 210 10

2:29 43 65 23 32 330 lt rain 10

2:53 37 82 16 25 340 lt rain 10

3:08 36 93 15 340 lt rain 10

3:34 36 93 12 330 lt rain 10

3:53 34 96 9 320

lt snow; 

fog 6 

4:11 34 100 8 320

lt snow; 

fog 5

4:43 34 100 8 330

lt snow; 

fog 4 

4:53 33 100 5 340

lt snow; 

fog 2

5:20 34 100 4 10

lt snow; 

fog 3 

5:30 34 100 5 360

lt snow; 

fog 2.5

5:37 34 100 4 

lt snow; 

fog 3 

5:44 34 93 5 330

lt snow; 

fog 2

5:46 34 93 4 330

lt snow; 

fog 1.75

5:53 33 96 4 350

lt snow; 

fog 1.25

6:00 34 100 0 

lt snow; 

fog 1.25

6:08 34 93 6 350

lt snow; 

fog 2

6:27 34 93 7 360

lt snow; 

fog 1.75

6:43 32 100 9 350

lt snow; 

fog 1

6:51 32 93 10 340

lt snow; 

fog 0.75

6:53 32 96 9 350

lt snow; 

fog 0.75

7:53 31 100 8 320

mod snow; 

ice fog 0.5

8:53 31 100 0

hvy snow; 

ice fog 0.25

 
42

Table 17: Wind and weather observations for Alamosa, Colorado, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 28, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 28

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility

in miles

0:52 50 29 15 200 10

1:52 47 37 13 190 10

2:52 49 36 9 180 10

3:52 48 34 13 140 10

4:52 41 52 8 140 10

5:52 45 43 18 170 10

6:52 43 49 13 150 10

7:52 52 32 17 27 180 10

8:52 56 26 17 170 10

9:52 58 25 24 36 170 10

10:16 63 20 24 33 230 10

10:52 62 20 24 32 230 10

11:52 64 20 22 32 200 10

12:52 68 17 21 33 230 10

13:52 69 15 24 33 230 10

14:52 69 15 40 48 220 haze 5

15:35 70 15 41 55 240 haze 2.5

15:52 69 17 36 51 240 haze 4

16:52 68 16 36 48 240 haze 5

17:52 64 19 41 55 220 haze 3

17:55 64 19 37 56 230 haze 2.5

18:03 64 19 33 47 240 haze 3

18:52 61 21 32 50 230 haze 4

19:04 61 22 31 53 220 haze 4

19:52 60 24 30 39 220 haze 5

20:18 59 25 30 48 230 haze 5

20:52 60 23 36 52 220 haze 4

21:48 57 26 29 47 220 8

21:52 57 28 32 44 220 8

22:52 55 30 28 46 220 10

23:52 54 31 37 48 220 10
43 

 Table 18: Wind and weather observations for Alamosa, Colorado, reported by the University of Utah MesoWest site 

(http://www.met.utah.edu/mesowest/) for April 29, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 29

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed in 

mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:52 52 33 35 47 220 10

1:52 51 35 35 54 220 8

2:52 50 37 37 46 230 10

3:52 48 39 36 51 220 9

4:52 45 47 25 32 240 10

5:52 43 60 23 32 240 lt rain 10

6:12 39 81 24 39 240 lt rain 9

6:52 40 83 30 41 220 lt rain 9

7:52 40 79 35 41 230 lt rain 10

8:47 36 93 38 50 250

lt snow; 

fog 1.5

8:52 34 92 32 50 230

lt snow; 

fog 1 

8:59 37 87 35 47 230

lt snow; 

fog 2

9:07 39 81 33 43 240 9

9:16 43 70 35 43 240 10

9:52 44 67 31 37 230 10

10:52 49 46 27 40 240 10

11:52 50 37 29 38 260 10

12:52 50 37 25 41 240 10

13:52 49 36 27 37 220 10

14:52 49 31 24 36 270 10

15:52 45 40 22 28 250 10

16:52 46 34 28 35 280 10

17:52 45 32 31 43 270 10

18:52 38 48 20 28 280 10

19:52 34 59 8 210 10

20:36 34 47 15 340 10

20:52 34 45 20 23 330 10

21:52 32 58 9 290 10

22:52 29 66 4 360 10

23:52 30 58 8 320 10

 
44

Table 19: Wind and weather observations for Pagosa Springs, Colorado, reported by the University of Utah MesoWest

site (http://www.met.utah.edu/mesowest/) for April 28, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 28

Temperature 

Degrees F

Relative 

Humidity

in %

Wind 

Speed 

in mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:15 43 45 0 thunder 10

2:15 45 39 0 10

3:15 46 34 7 140 10

4:15 39 60 0 10

5:15 41 56 0 10

6:15 39 65 0 10

7:15 43 56 0 10

8:15 46 39 0 10

9:15 50 32 6 160 10

10:15 52 30 7 160 10

11:15 54 28 4 250 10

12:15 57 21 8 220 10

13:15 61 18 10 32 210 10

14:15 61 18 25 33 220 10

15:15 63 17 25 36 230 10

16:15 61 17 23 38 220 10

16:55 63 16 31 41 210 haze 5

17:15 63 16 18 35 210 haze 5

17:35 63 19 25 40 210 haze 5 

17:55 63 19 29 39 220 haze 5

18:15 63 20 27 36 220 haze 5 

18:35 63 19 23 41 220 haze 5 

18:55 61 20 25 37 220 haze 5

19:15 61 20 29 43 220 haze 5 

19:35 61 20 28 44 220 haze 5

19:55 59 21 16 30 220 haze 5

20:15 59 20 23 41 220 7 

20:55 59 18 29 40 220 7 

21:35 55 22 24 40 220 7

21:55 55 24 25 41 230 7 

22:15 55 24 30 39 230 haze 5

22:35 54 26 24 41 220 haze 5

22:55 54 28 28 37 220 haze 5 

23:15 54 28 23 37 220 7

23:35 54 28 20 32 220 7

23:55 54 28 20 37 220 7 
45

Table 20: Wind and weather observations for Pagosa Springs, Colorado, reported by the University of Utah MesoWest 

site (http://www.met.utah.edu/mesowest/) for April 29, 2010. 

Speeds at or above the blowing dust thresholds, weather, and visibility (caused by or reduced by dust) 

have been highlighted in yellow. 

Time 

MDT 

April 29

Temperature 

Degrees F

Relative 

Humidity 

in %

Wind 

Speed 

in mph

Wind 

Gust in 

mph

Wind 

Direction 

in 

Degrees Weather

Visibility 

in miles

0:15 52 30 32 44 220 7 

0:35 52 30 30 43 220 7

0:55 52 30 28 47 220 7 

1:15 50 32 30 44 220 7 

1:35 50 32 31 44 230 7

1:55 50 32 27 44 230 7 

2:15 50 34 23 38 220 haze 5

2:35 50 34 22 32 210 haze 5

2:55 48 37 28 35 220 5 

3:15 48 34 31 45 220 haze 4

3:35 46 34 22 43 220 haze 3

3:55 46 34 20 39 230 haze 4 

4:15 46 31 24 39 220 haze 4

4:35 46 31 23 32 220 haze 5

4:55 45 33 22 38 230 7 

5:15 45 39 22 32 250 10

5:35 45 45 24 40 250 10

5:55 43 56 20 31 250 10

6:15 43 56 16 27 250 10

6:35 43 56 9 18 220 10

6:55 43 61 20 25 200

mod 

drizzle 7

7:15 41 70 15 25 210

unknown 

prcp 5 

7:35 39 75 25 38 250

unknown 

prcp 7

7:55 37 81 25 36 250 lt snow 4

8:15 36 87 18 41 240 lt snow 4 

9:15 36 93 15 24 240 fog 5

10:15 36 87 12 24 240 lt snow 7

11:15 36 80 18 28 250 lt snow 4 

13:15 37 65 21 43 270 10

13:35 37 56 16 23 270 10

13:55 37 52 15 27 230 10

14:15 37 52 8 220 10

14:35 39 41 21 30 230 10
46

The Albuquerque, Flagstaff, and Grand Junction NWS Forecast Offices issue weather warnings and 

advisories for northeast Arizona, most of New Mexico, eastern Utah, and western and southwestern 

Colorado. The weather warnings and advisories issued by theses offices for April 28 and 29, 2010, are 

presented in Attachment B. These warnings and advisories show that strong winds and areas of blowing 

dust were expected and experienced across this region on these days.

Figure 20 shows the NOAA HYSPLIT 18-hour forward matrix trajectories (Draxler and Rolph, 2012) for 

northeast Arizona and northwest New Mexico starting at 5 PM MST April 28, 2010 (see the following 

link for more information on HYSPLIT: http://ready.arl.noaa.gov/HYSPLIT.php ). This analysis shows 

transport of air from this region into Colorado on April 28. HYSPLIT 12-hour back trajectories for 5 PM 

and 11 PM April 28, 2010, for Durango, Pagosa Springs, and Alamosa, respectively, are presented in 

Figure 21 through Figure 26. These also show that Arizona and northwest New Mexico were source 

regions for air transported into Colorado on April 28. NOAA HYSPLIT forward and backward 

trajectories provide clear supporting evidence that dust from desert regions of northwest New Mexico and 

Arizona caused the PM10 exceedances measured across portions of southwestern Colorado on April 28 

and 29, 2010. 

Figure 27 shows the output for blowing dust from the Navy Aerosol Analysis and Prediction System 

(NAAPS) Global Aerosol Model for 5 PM April 28 (00Z April 29), 2010 (source: 

http://www.nrlmry.navy.mil/aerosolbin/aerosol/display_directory_all?DIR=/web/aerosol/public_html/globaer/ops_01/wus/ ). The NAAPS 

system models blowing dust emissions and transport based on soil moisture content, soil erodibility 

factors, and a variety of meteorological factors known to be conducive to blowing dust (for a description 

of NAAPS see: http://www.nrlmry.navy.mil/aerosol_web/Docs/globaer_model.html ). 

The forecast panel in the lower left of Figure 27 shows blowing dust generation over northeast Arizona, 

portions of southern Utah, and northwest New Mexico. The NAAPS model can overestimate dust 

emissions, and in this case it shows high concentrations of dust in southeast Colorado that were not 

actually observed. The model output, however, does suggest that Four Corners areas of Arizona, New 

Mexico, and Utah were major source regions for blowing dust on April 28, 2010. Forecast products from 

the Navy Aerosol Analysis and Prediction System model provide evidence for a widespread blowing dust 

event in the Four Corners states, suggesting that significant source regions for dust in Colorado were 

located in arid regions of Arizona, Utah, and New Mexico. 
47

Figure 20: NOAA HYSPLIT 18-hour forward trajectories for northeast Arizona and northwest New Mexico for 5 PM 

MST April 28 (00Z April 29), 2010, (source: NOAA Air Resources Laboratory at: 

http://ready.arl.noaa.gov/HYSPLIT.php). 
48

Figure 21: NOAA HYSPLIT 12-hour back trajectories for Durango, Colorado, for each hour from 3 AM MST April 28, 

2010, to 3 PM MST April 28, 2010 (source: NOAA Air Resources Laboratory at: 

http://ready.arl.noaa.gov/HYSPLIT.php).
49

Figure 22: NOAA HYSPLIT 12-hour back trajectories for Durango, Colorado, for each hour from 11 AM MST April 28, 

2010, to 11 PM MST April 28, 2010 (source: NOAA Air Resources Laboratory at: 

http://ready.arl.noaa.gov/HYSPLIT.php).
50

Figure 23: NOAA HYSPLIT 12-hour back trajectories for Pagosa Springs, Colorado, for each hour from 3 AM MST 

April 28, 2010, to 3 PM MST April 28, 2010 (source: NOAA Air Resources Laboratory at: 

http://ready.arl.noaa.gov/HYSPLIT.php).
51

Figure 24: NOAA HYSPLIT 12-hour back trajectories for Pagosa Springs, Colorado, for each hour from 11 AM MST 

April 28, 2010, to 11 PM MST April 28, 2010 (source: NOAA Air Resources Laboratory at: 

http://ready.arl.noaa.gov/HYSPLIT.php).
52

Figure 25: NOAA HYSPLIT 12-hour back trajectories for Alamosa, Colorado, for each hour from 3 AM MST April 28, 

2010, to 3 PM MST April 28, 2010 (source: NOAA Air Resources Laboratory at: 

http://ready.arl.noaa.gov/HYSPLIT.php).
53

Figure 26: NOAA HYSPLIT 12-hour back trajectories for Alamosa, Colorado, for each hour from 11 AM MST April 28, 

2010, to 11 PM MST April 28, 2010 (source: NOAA Air Resources Laboratory at: 

http://ready.arl.noaa.gov/HYSPLIT.php). 
54

Figure 27: NAAPS forecasted dust concentrations for 5 PM April 28 (00Z April 29), 2010 (source: 

http://www.nrlmry.navy.mil/aerosolbin/aerosol/display_directory_all?DIR=/web/aerosol/public_html/globaer/ops_01/wus/ ).

The Center for Snow and Avalanche Studies has been studying the effects of wind-blown desert dust from 

Arizona, New Mexico, and Utah on snowpack albedo and snowmelt in the San Juan Mountains of 

Colorado. Figure 28 is the Center’s log of events that are associated with deposits or layers of windblown dust on or within the snowpack of the San Juan Mountains. The Center for Snow and Avalanche 

Studies lists April 28, 2010, as one of nine Dust-on-Snow events for the 2009/2010 water year, and this 

provides clear supporting evidence that a regional blowing dust event with long-range transport caused 

the PM10 exceedances measured across portions of Colorado on April 28, 2010. 
55

Figure 28: Dust-on-Snow Deposition Events Log at the Senator Beck Basin Study Area on Red Mountain Pass, Colorado. 

(source: Chris Landry. 9/24/2010).

Figure 29 shows the MODIS Aqua satellite image for the Four Corners region, Utah, Arizona, New 

Mexico, and Colorado for April 28, 2010. Areas of blowing dust can be seen in Utah, Arizona, and New 

Mexico. Plumes of blowing dust originating in the Painted Desert region of northeastern Arizona and 

northwest New Mexico stretched across southwest Colorado and southeastern Utah. Figure 30 and Figure 

31 show the GOES visible satellite imagery for the same region for 3:02 PM MST and 4:45 PM MST, 

respectively. These images show the increase in dust in the region as the afternoon progressed and the 

extension of the plume across Alamosa and the San Luis Valley area and onto the plains of southeastern 

Colorado. Satellite imagery that shows the plumes after sunset on April 28, 2010, and during the early 

morning hours of April 29, 2010, is not available because of nighttime darkness and cloud cover. 

MODIS and GOES satellite imagery shows that the Painted Desert and Four Corners area in general were 

source regions for the blowing dust that spanned April 28 and 29, 2010. 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 Attachment A of this document. 

Colorado Dust-on-Snow (CODOS)

Dust-on-Snow Deposition Events Log

Thanks to our original National Science Foundation research grants for collaborative research (grants ATM-0432327 to 

Painter at National Snow and Ice Data Center and ATM-0431955 to Landry at Center for Snow and Avalanche Studies), 

and to the subsequent support of the Colorado Dust-on-Snow program by Colorado water districts the State of Colorado, 

the U.S. Bureau of Reclamation, and others, this program has accumulated several seasons of dust-on-snow observations 

at our Senator Beck Basin Study Area (SBBSA) at Red Mountain Pass, summarized in the table below. It is reasonable to 

assume that our skill at detecting dust-on-snow events has improved and that we may have failed to observe very small 

events during the early years of this work. Therefore the table represents an absence of events in grey for the first two 

years of observation but thereafter indicates an absence of observed events as “0” (zero).

Dust-on-Snow Events Documented per Month, by Winter

Senator Beck Basin Study Area at Red Mountain Pass – San Juan Mountains

Oct Nov Dec Jan Feb Mar Apr May Jun Total

2002/2003 2 1 3

2003/2004 2 1 3

2004/2005 0 0 0 0 0 1 2 1 0 4

2005/2006 0 0 1 0 1 1 3 2 0 8

2006/2007 0 0 1 0 1 1 3 1 1 8

2007/2008 0 0 0 0 0 3 3 1 0 7

2008/2009 1 0 1 0 1 4 5 0 0 12 

2009/2010 1 0 0 0 0 1 4 3 0 9

Dates of the events, by winter/spring season, were as follows (WY = Water Year):

2002/2003 (WY2003): Feb 3, Feb 22, Apr 2-3

2003/2004 (WY 2004): Apr 17, Apr 28, May 11

2004/2005 (WY 2005): Mar 23, Apr 4, Apr 8, May 9

2005/2006 (WY 2006): Dec 23, Feb 15, Mar 26, Apr 5, Apr 15, Apr 17, May 22, May 27

2006/2007 (WY 2007): Dec 17, Feb 27, Mar 27, Apr 15, Apr 18, Apr 24, May 4, Jun 6

2007/2008 (WY 2008): Mar 16, Mar 26-27, Mar 30-31, Apr 15, Apr 21, Apr 30, May 12

2008/2009 (WY 2009): Oct 11, Dec 13, Feb 27, Mar 6, Mar 9, Mar 22, Mar 29, Apr 3, Apr 8, Apr 15, Apr 24, Apr 25

2009/2010 (WY 2010): Oct 27, March 30, April 3, April 5, April 12, April 28, May 9, May 11, May 22
56

The Smoke Text Product from NOAA’s Satellite Services Division - Descriptive Text Narrative for 

Smoke/Dust Observed in Satellite Imagery through 0115Z April 29, 2010, (6:15 PM MST April 28) 

(http://www.ssd.noaa.gov/PS/FIRE/DATA/SMOKE/2010/2010D290159.html ) - describes dust from 

Arizona and New Mexico moving into Colorado: 

“A significant area of blowing dust is being picked up across parts of NE Arizona and NW New 

Mexico and moving ENE across a large section of Colorado and beginning to reach parts of W 

Nebraska and Kansas. There are very high winds across the region.”

Figure 29: MODIS Aqua satellite afternoon image of Arizona on April 28, 2010, showing plumes of blowing dust in the 

Four Corners area, with the greatest plume densities in the Painted Desert and northwest New Mexico areas north of I-40 

(source: http://ge.ssec.wisc.edu/modis-today/index.php ). 
57

Figure 30: GOES visible satellite image for 3:02 PM MST April 28, 2010, showing plumes of blowing dust in the Four 

Corners area, with the greatest plume densities in the Painted Desert and northwest New Mexico areas north of I-40 and 

extending into southern Colorado and the cloud-free San Luis Valley just north of Colorado-New Mexico border in southcentral Colorado (source: http://weather.rap.ucar.edu/satellite/). 
58

Figure 31: GOES visible satellite image for 4:45 PM MST April 28, 2010,showing plumes of blowing dust in the Four 

Corners area, with the greatest plume densities in the Painted Desert, extreme southeast Utah, and northwest New Mexico 

areas north of I-40 and extending into southern Colorado and the cloud-free San Luis Valley just north of Colorado-New 

Mexico border in south-central Colorado (source: http://weather.rap.ucar.edu/satellite/). Dust is also visible in southeast 

Colorado east of the Southern Front Range.

The U.S. Geological Survey (USGS) Southwest Geographic Science Team: Dust Monitoring web pages 

(http://sgst.wr.usgs.gov/dust_detection/dust-events/2010-2/april-28th-2010/ and 

http://sgst.wr.usgs.gov/dust_detection/dust-events/2010-2/april-29th-2010/ ) list April 28 and 29, 2010, as 

a dust event days. The web page for the April 28, 2010, event has various satellite pictures, videos, and 

time lapse imagery of the dust storm. This web page provides the following characterization for this 

event:

“A strong pacific storm front moved through the southwest today, bringing very strong winds 

cold temperatures and snow in the higher elevations. The dominant wind direction was out of the 

south-west. Severe dust was viewable from satellite by both visible band and thermal imaging in 
59

the Four Corners area. Activity was apparent from mid morning on to well after sunset. Interstate 

40 in Arizona was closed from Belmont to Winslow for most of the day.” 

USGS Scientists with expertise in the analysis of dust storms have indicated that a regional dust storm 

occurred in the Four Corners area on April 28, 2010. They also provide evidence for the dust storm on 

April 29, when the daytime effects of the storm were most pronounced in New Mexico, Texas, and 

Mexico.

Figure 32 shows the total precipitation in inches for the western U.S. for the month of April 2010. It 

shows that much of southeastern Utah, northeastern Arizona, and portions of extreme northwestern New 

Mexico had less than 0.5 inches of precipitation in April. This is an approximate threshold below which 

blowing dust can occur in the Painted Desert area when winds are above the blowing dust thresholds. 

The precipitation hreshold is reported in Attachment A that shows that blowing dust occurs in 

northeastern Arizona source regions when soils are dry (typically less than 0.5 inches in a 30-day period 

at Hopi, Arizona) and winds are strong. Figure 33 is the Drought Monitor report for the western U.S. It 

shows that northeastern Arizona was classified as Abnormally Dry with an area of Moderate to Severe 

Drought in the Painted Desert region. Soils in the Four Corners area and in northeastern Arizona, 

southeastern Utah, and extreme northwestern New Mexico in particular were dry enough to produce 

blowing dust when winds were above the thresholds for blowing dust. 

Figure 32: Total precipitation in inches for April 2010 (source: 

http://www.hprcc.unl.edu/maps/current/index.php?action=update_region®ion=WRCC ).
60

Figure 33: Drought status for the Colorado on April 27, 2010 (source: the USDA, NOAA, and the National Drought 

Mitigation Center at: http://drought.unl.edu/dm/archive.html).

In a 1997 paper “Factors controlling threshold friction velocity in semiarid and arid areas of the United 

States” (Marticorena et al., 1997), the authors characterized the erodibility of both disturbed and 

undisturbed desert soil types. The threshold friction velocity, which is described in detail in this paper, is 

a measure for conditions necessary for blowing dust and is higher for undisturbed soils and lower for 

disturbed soils. 

Friction velocities have been calculated for 5 PM MST and 11 PM MST April 28 using the NAM12 

model (data source: http://nomads.ncdc.noaa.gov/data.php?name=access#hires_weather_datasets ). These 

friction velocities are shown in Figure 34 and Figure 35, respectively. According to Marticorena and 

coauthors (1997), even undisturbed desert soils normally resistant to wind erosion will be susceptible to 

emission of blowing dust when threshold friction velocities are greater than about 1.0 to 2.0 meters per 

second. These figures show that a wide area of northern Arizona, northwestern New Mexico, 

southeastern Utah, and southwestern Colorado had friction velocities above 1.0 meters per second during 

the second half of the day on April 28. High values were present within the Little Colorado River Valley 

and Painted Desert region of northeastern Arizona where satellite imagery shows the eruption of large 

plumes of blowing dust and where 30-day precipitation totals were below 0.5 inches. Note that blowing 

dust will typically only occur where friction velocities are high and the soils are dry and not protected by 

vegetation, forest cover, boulders, rocks, etc. This is why blowing dust occurred in the desert and more 

arid areas of northeastern Arizona, and northwestern New Mexico on April 28 and 29, 2010. 

The elevated friction velocities shown in Figure 34 and Figure 35, the data on soil moisture conditions 

presented elsewhere in this report, and the prevalence of winds above blowing dust thresholds (all 

occurring in traditional source regions in northeastern Arizona and northwestern New Mexico) prove that 

this dust storm was a natural event that was not reasonably controllable or preventable. 
61

Figure 34: Friction velocities in meters/second from the NOAA NCEP North American Model with 12 kilometer grid 

spacing at 00Z April 29, 2010 (5 PM MST April 28).

Figure 35: Friction velocities in meters/second from the NOAA NCEP North American Model with 12 kilometer grid 

spacing at 06Z April 29, 2010 (11 PM MST April 28).
62

3.0 Evidence-Ambient Air Monitoring Data and Statistics

PM10 concentrations that exceeded the level of the twenty-four-hour PM10 NAAQS were monitored 

across a broad geographical area of Colorado on April 28 and 29, 2010. On Wednesday April 28, 2010, 

exceedances greater than 150 μg/m3 were recorded at the Adams State College (“ASC”) monitor in 

Alamosa with a concentration of 285 μg/m3

, the Alamosa Municipal Building (“Muni”) monitor with a 

concentration of 236 μg/m3

, and the Pagosa Springs School monitor with a concentration of 181 μg/m3. 

Additionally on April 28, 2010, an exceptionally high sample (greater than the 99th percentile for the site) 

was recorded at the PM10 monitor in Mt. Crested Butte (123μg/m3

). On Thursday April 29, 2010, 

exceedances greater than 150 μg/m3

 were recorded at the Pagosa Springs School monitor with a 

concentration of 162 μg/m3 and the Durango monitor with a concentration of 226 μg/m3

. Additionally on 

April 29, 2010, high samples were taken at the Alamosa PM10 monitors at Adams State College 

(92μg/m3

) and the Municipal Building (94μg/m3). These high values would not have occurred if not for 

the following: (a) dry soil conditions over southeastern Utah, northeastern Arizona, portions of extreme 

northwestern New Mexico, and portions of southern Colorado with 30-day precipitation totals below the 

thresholds for blowing dust; (b) a strong surface and upper-level low pressure system that caused 

widespread strong gusty winds through a deep layer of the atmosphere over the area of concern; and (c) 

friction velocities over the desert regions of northwest New Mexico, Utah, Arizona and much of Colorado 

that were high enough to allow entrainment of dust from natural sources with subsequent transport of the 

dust into (or within) Colorado in strong, southwesterly winds. These exceedances and other high 

concentrations across Colorado are plotted on the maps for April 28 and 29, 2010, in Figure 1 and Figure 

2, respectively. The high values on both days were the consequence of strong southwesterly prefrontal 

surface winds over dry soils which caused significant blowing dust across much of Arizona, northwest 

New Mexico, southeast Utah and southwest Colorado. These winds were the result of a significant 

surface low pressure and surface cold front associated with a major upper-level trough that was moving 

across the Western United States. 

Section 2 provides the meteorological evidence for the spatial extent of this regional blowing dust event 

including the dust on snow data from the Colorado Dust-on-Snow (CODOS) network. The CODOS 

network clearly shows that the spatial extent of this dust storm was quite large, covering thousands of 

square miles. 

The APCD reviewed PM10 monitoring data in Western Colorado in the path of the dust storm (see Section 

3.1). The PM10 concentrations at affected sites were compared using time series plots for a number of 

days pre and post event (see Figure 52). The PM10 time series graphs clearly show that the regional 

blowing dust storm adversely affected the air quality in Alamosa, Pagosa Springs and Durango on April 

28 and 29, 2010. PM10 samples the day before and the day two days after the event were typical of 

samples at each affected site. 

3.1 Historical Fluctuations of PM10 Concentrations in Alamosa, Pagosa Springs, and 

Durango 

This evaluation of PM10 monitoring data for sites affected by the April 28-29, 2010, event was made 

using valid samples from hi-vol PM10 samplers in Alamosa, Pagosa Springs, and Durango from 2005 

through 2011. APCD has been monitoring PM10 concentrations in these areas since 1985. On-going data 

collection at all the sites affected by the event began in 2005; therefore, the data in this analysis is from 

January 2005 through the end of 2011. The overall data summary for the affected sites is presented in 

Table 21 with all data values in μg/m3

: 
63

Table 21: PM10 Monitoring Data Summary (Affected Sites)

Alamosa ASC Alamosa Muni

Pagosa 

Springs 

Mt. Crested 

Butte Durango 

04/28/10 285 236 181 123 n/a

04/29/10 92 94 162 28 226

Mean 22.1 27.9 22.7 20.8 20.7 

Median 18 23 20 17 18 

Mode 16 20 16 11 16

SD 24.0 26.8 17.0 14.6 18.8

Variance 578.3 716.4 290.6 213.5 355.3 

Minimum 1 1 2 1 3 

Maximum 473 635 349 168 320

Count 2214 2168 2287 2262 811

Table 21 demonstrates the spatial scope of this event, addressed elsewhere in this document, was broad 

and had an impact on PM10 concentrations at multiple sites covering an extensive geographical area. 

Since the event will affect attainment status of only Alamosa, Pagosa Springs, and Durango only these 

data sets will be discussed in detail. The attainment status of the other site (Mt. Crested Butte) will not be 

affected by this event. It is a certainty that the sampler in Mt. Crested Butte was affected by the event to 

the same extent as Alamosa, Pagosa, and Durango and so it is included here to help define the 

geographical extent of the affected area. A snapshot summary of data from all those sites affected by the 

event is presented in Table 22, along with the approximate percentile value that data point represents for 

each site for their unique historical data sets, for the month of the event (every sample in any April), and 

for the year of the event. All percentile calculations presented anywhere in this section were made using 

the entire dataset, including known high wind events. There is no difference between the two datasets 

(with and without high wind events) in regards to percentile calculations. All data sets were restricted to 

valid samples from the interval 2005 – 2011. 

Table 22: Data Summary between 2005 and 2011

Evaluation Alamosa 

ASC

Alamosa Muni Pagosa 

Springs

Mt. Crested 

Butte

Durango

4/28/2010 285 μg/m3 236 μg/m3 181 μg/m3 123 μg/m3 n/a

4/29/2010 92 μg/m3 94 μg/m3 162 μg/m3 28 μg/m3 226 μg/m3

Overall 99.68% Max Value Max Value* 99.87% 99.98%

All April 98.95% Max Value Max Value* 99.37% 99.96%

2010 #N/A Max Value Max Value* 99.72% #N/A

*The ‘Max Value’ notation refers to the 28 April sample value

This event produced the maximum value in three of the five datasets and exceeded the 98th% value of 

any evaluation criteria for the other two sites. The overall magnitude and broad geographical extent of 

affected sites suggests that there was a common contribution to each sample from other than local 

sources.

Those data sets for sites with samples for which exclusion is being requested are further summarized by 

month. As with previous submittals these summaries (see charts, below) present no obvious ‘season’; 

PM10 levels at any particular site in Colorado do not necessarily fluctuate by season. Of greater

importance affecting day-to-day, typical PM10 concentrations are local sources, e.g. road sanding and 
64

sweeping, local burning from agriculture and residential heating, vehicle contributions via road dust, 

unpaved lots or roads, etc. While the historic monthly mean values for the affected sites can be higher 

during the winter and spring months there is little month-to-month variation. Additionally, some of the 

sites exhibit monthly medians over this period (winter/spring) that are generally lower than other months 

of the year. This time frame (winter and early spring) is that which is most likely to experience the 

regional meteorological and dry soil conditions exhibited during this event and discussed elsewhere in 

this document. Although the maximum values for these months (winter/spring) are the highest in the data 

set the ‘typical’ data (i.e. day-to-day, reflective of local conditions) are similar or lower than the same 

‘typical’ data for the rest of the year. The summary data for the month of April (all samples in any April) 

and for 2010 for Alamosa ASC, Alamosa Muni, Pagosa Springs, and Durango are presented in Table 23: 

Table 23: Month and Year PM10 Monitoring Data Summary

Site: Alamosa ASC Pagosa Springs Durango

April 2010 April 2010 April 2010 

Mean 27.9 23.5 31.2 24.3 34.4 25.3

S.E. 2.7 1.5 2.6 1.6 6.2 3.6

Median 18 19 24 18 19.5 18 

Mode 11 20 23 18 13 18

SD 38.0 26.5 36.9 28.7 51.4 37.7

Minimum 1 2 2 4 6 3

Maximum 295 285 349 349 320 320 

Count 192 314 195 310 68 111

Alamosa Adams State College – 080030001 

The PM10 sample on April 28, 2010, at Alamosa ASC of 285 μg/m3 exceeds the 99th percentile value for 

all April data, exceeds the 99th percentile value for all 2010 data, and is greater than the 99th percentile 

value (97 μg/m3

) for the entire dataset. Overall, this sample is the fifth highest sample in the entire data 

set and the largest sample in 2010. The four samples greater than the event sample are all associated with 

high wind events. There are 2214 samples in this dataset. The sample of April 28, 2010, clearly exceeds 

the typical samples for this site.

Figure 36 through Figure 39 graphically characterize the Alamosa ASC PM10 data. The first is a simple 

time series; every sample in this dataset (2005 – 2011) greater than 150 μg/m3 is identified. Note the 

overwhelming number of samples occupying the lower end of the graph; an interested reader can count 

the number of samples greater than 100 μg/m3

. Of the 2214 samples in this data set less than 1% are 

greater than 100 μg/m3

. 
65

Figure 36: Alamosa ASC PM10 Time Series

Figure 37 is a simple histogram, demonstrating the overwhelming weight of samples on the low end of 

the curve. Over 60% of the samples in this data set are less than 20 μg/m3

. Even in the highly variable 

month of April, the month with the largest sample standard deviation, 90% of the samples are less than 50 

μg/m3

. Clearly the sample on April 28, 2010, exceeds what is typical for this site.

Figure 37: Alamosa ASC PM10 Histogram

473, 056 Jun 2007

440, 01 Dec 2011

424, 10 Feb 2006

295, 03 Apr 2011

285, 28 Apr 2010

260, 22 May 2010

160, 11 May 2010

158, 15 Feb 2006

207, 05 Oct 2009 185, 05 Apr 2010 

0 

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350

400

450

500

11/09/04 03/24/06 08/06/07 12/18/08 05/02/10 09/14/11

Concentration, 

μg/m3 

Sample Date

Alamosa ASC PM10

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

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100110120130140150

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Frequency

Concentration, μg/m3 

Alamosa ASC PM10 Histogram

Frequency

Cumulative %
66

The monthly box-whisker plot in Figure 38 highlights the consistency of the majority of data from month 

to month. Note the greater variability (wider inner-quartile range) and greater range of the data through 

the winter and early spring months that’s accompanied by typically greater monthly maxima. Recall, this 

time period experiences a greater number of days with meteorological conditions similar to those 

experienced on April 28, 2010. Although these high values affect the variability and central tendency 

(average) of the dataset they aren’t representative of what is typical at the site. 

Figure 38: Monthly Alamosa ASC PM10 Box and Whisker Plot

The box and whisker plots graphically represent the overall distribution of each data set including the 

mean ( ), the inner quartile range ( IQR, defined to be the distance between the 75th% and 25th%), 

the median (represented by the horizontal black line) and two types of outliers identifed in these plots: 

outliers greater than 75th% +1.5*IQR ( )and outliers greater than 75th% + 3*IQR ( ). The outliers 

that satisfy the last criteria and are greater than 150 μg/m3 are labeled with sample value and sample date. 

Each of these outliers is associated with a known high-wind event similar to that of 05 April.

The presence of the extreme values distorts the graph, losing definition and distorting information 

presented across the range where the majority of data resides. The same plot graphed to 100 μg/m3

, 

which includes almost 99% of all the data, is presented in Figure 39. 

Figure 39: Monthly Alamosa ASC PM10 Box and Whisker Plot (expanded view)

424, 10 Feb 2006

158, 15 Feb 2006 

295, 11 Apr 2011

185, 05 Apr 2010

260, 22 May 2010

160, 11 May 2010

473, 06 Jun 2007

207, 05 Oct 2009

440, 01 Dec 2011

285, 28 Apr 2010

0 

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150

200

250

300

350

400

450

500

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Concentration (

μg/m3) 

Month

0 

10

20

30

40

50

60

70

80

90

100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Concentration (

μg/m3) 

Month
67

Note the degree to which the April (among other months) data is skewed. The mean (27.8 μg/m3) is 

greater than the 75th percentile value (26 μg/m3

). This is due to the presence of a handful of extreme 

values and can create the perception that those months experiencing these high wind events are somehow 

‘dirtier’ than other months of the year. This data exposes that perception as flawed as the typical data is 

similar to every other month of the year. The sample of April 28, 2010, clearly exceeds the typical data at 

this site.

Alamosa Municipal – 080030003 

The PM10 sample on April 28, 2010, at Alamosa Muni of 236 μg/m3 exceeds the 99th percentile value for 

all April data, is the maximum value for all 2010 data, and is greater than the 99th percentile value (110 

μg/m3

) for the entire dataset. Overall, this sample is the fifth highest sample in the entire data set and the 

largest sample in 2010. The four samples greater than the event sample are all associated with high wind 

events. There are 2168 samples in this dataset. The sample of April 28, 2010, clearly exceeds the typical 

samples for this site.

Figure 40 through Figure 43 graphically characterize the Alamosa Muni PM10 data. The first is a simple 

time series, the sample of April 28, 2010, is identified. Note the overwhelming number of samples 

occupying the lower end of the graph; an interested reader can count the number of samples greater than 

100 μg/m3

. Of the 2214 samples in this data set less than 1% are greater than 110 μg/m3. 

Figure 40: Alamosa Municipal PM10 Time Series

Figure 41 is a simple histogram, demonstrating the overwhelming weight of samples on the low end of 

the curve. Over 60% of the samples in this data set are less than 20 μg/m3

. Even in the highly variable 

month of April, the month with the largest sample standard deviation, 90% of the samples are less than 50 

μg/m3

. Clearly the sample on April 28, 2010, exceeds what is typical for this site.

635, 01 Dec 2011

494, 06 Jun 2007

372, 03 Apr 2011

289, 10 Feb 2006

213, 14 Apr 2006 236, 28 Apr 2010

206, 15 Feb 2006 194, 22 May 2010 181, 28 Apr 2006

161, 11 May 2010 160, 26 Jun 2006 

157, 08 Apr 2009

0 

100

200

300

400

500

600

700

11/09/04 03/24/06 08/06/07 12/18/08 05/02/10 09/14/11

Concentration, 

μg/m3 

Sample Date

Alamosa Municipal PM10
68

Figure 41: Alamosa Municipal PM10 Histogram

The monthly box-whisker plot in Figure 42 highlights the consistency of the majority of data from month 

to month. Note the greater variability (wider inner-quartile range) and greater range of the data through 

the winter and early spring months that’s accompanied by typically greater monthly maxima. Recall, this 

time period experiences a greater number of days with meteorological conditions similar to those 

experienced on April 28, 2010. Although these high values affect the variability and central tendency 

(average) of the dataset they aren’t representative of what is typical at the site. 

Figure 42: Monthly Alamosa Muni PM10 Box and Whisker Plot

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

100.00%

0 

100

200

300

400

500

600

700

800

Frequency

Concentration (μg/m3) 

Alamosa Muni PM10 Histogram

Frequency

289, 10 Feb 2006

206, 15 Feb 2006

372, 03 Apr 2011

236, 28 Apr 2010 

181, 28 Apr 2006213, 14 Apr 2006

157, 08 Apr 2009

194, 22 May 2010

494, 06 Jun 2007

160, 26 Jun 2006

635, 01 Dec 2011

0 

100

200

300

400

500

600

700

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Concentration (

μg/m3) 

Month
69

The presence of the extreme values distorts the graph, losing definition and distorting information 

presented across the range where the majority of data resides. The same plot graphed to 100 μg/m3

, 

which includes almost 99% of all the data, is presented in Figure 43. 

Figure 43: Monthly Alamosa Muni PM10 Box and Whisker Plot (expanded view)

Note the degree to which the April (among other months) data is skewed. The mean (35.4 μg/m3) is 

greater than the 75th percentile value (35 μg/m3

). This is due to the presence of a handful of extreme 

values and can create the perception that those months experiencing these high wind events are somehow 

‘dirtier’ than other months of the year. This data exposes that perception as flawed as the typical data is 

similar to every other month of the year. The sample of April 28, 2010, clearly exceeds the typical data at 

this site.

Pagosa Springs Middle School - 080070001 

The PM10 samples on April 28 and 29, 2010, at Pagosa Springs of 181 μg/m3

 and 162 μg/m3, respectively, 

both exceed the 97th percentile value for any April, exceed the 99th percentile value for any data in 2010, 

and exceed the 99th percentile value for all data in this data set. There are 2287 samples in this dataset. 

The samples of April 28 and 29, 2010, clearly exceed the typical samples for this site.

Figure 44 through Figure 47 graphically characterize the Pagosa Springs PM10 data. The first is a simple 

time series, the samples of April 28 and 29, 2010, have been identified. Note the overwhelming number 

of samples occupying the lower end of the graph; an interested reader can count the number of samples 

greater than 100 μg/m3

. Of the 2287 samples in this data set less than 1% are greater than 110 μg/m3. 

0 

10

20

30

40

50

60

70

80

90

100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Concentration (

μg/m3) 

Month
70

Figure 44: Pagosa Springs ASC PM10 Time Series

Figure 45 is a simple histogram, demonstrating the overwhelming weight of samples on the low end of 

the curve. Over 50% of the samples in this data set are less than 20 μg/m3

. Even in the highly volatile 

month of April the month with the largest sample standard deviation, 95% of the samples are less than 50 

μg/m3

. Clearly the samples on April 28 and 29, 2010, exceed what is typical for this site.

Figure 45: Pagosa Springs ASC PM10 Histogram

181, 28 Apr 2010

200, 11 May 2010

225, 03 Apr 2009

162, 29 Apr 2010

162, 29 Apr 2010

188, 25 Apr 2009

182, 06 Apr 2009

349, 05 Apr 2010

255, 22 Mar 2009

0 

50

100

150

200

250

300

350

400

11/09/04 03/24/06 08/06/07 12/18/08 05/02/10 09/14/11

Concentration, 

μg/m3 

Sample Date

Pagosa Springs PM10

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

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90.00%

100.00%

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100110120130140150

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Frequency

Concentration, μg/m3 

Pagosa Springs PM10 Histogram

Frequency

Cumulative %
71

The monthly box-whisker plot in Figure 46 highlights the consistency of the majority of data from month 

to month. Note the greater variability (wider inner-quartile range) and greater range of the data through 

the winter and early spring months that’s accompanied by typically greater monthly maxima. Recall, this 

time period experiences a greater number of days with meteorological conditions similar to those 

experienced on April 28 and 29, 2010. Although these high values affect the variability and central 

tendency of the dataset they aren’t representative of what is typical at the site.

Figure 46: Monthly Pagosa Springs PM10 Box and Whisker Plot

As with the previous box and whisker plots outliers greater than 150 μg/m3 are identified by concentration 

and date. Each of these outliers is associated with a known high-wind event similar to that of April 28 

and 29, 2010. The presence of the extreme values distorts the graph, losing definition and distorting 

information presented across the range where the majority of data resides. The same plot graphed to 100 

μg/m3

, which includes almost 99% of all the data, is presented in Figure 47. 

Figure 47: Monthly Pagosa Springs PM10 Box and Whisker Plot (expanded view)

255, 22 Mar 2009

349, 05 Apr 2010

225, 03 apr 2009

188, 25 Apr 2009

181, 28 Apr 2010 162, 29 Apr 2010

200, 11 May 2010

187, 22 May 2010

0 

50

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400

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Concentration 

μg/m3 

Month

0 

10

20

30

40

50

60

70

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100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Concentration 

μg/m3 

Month
72

Durango River City Hall - 080670004 

The PM10 sample on April 29, 2010, at Durango of 262 μg/m3 is the 2nd largest sample in the data set, is 

the 2nd largest in any April and is the 2nd largest sample in all of 2010. There are 811 samples in this 

dataset. The sample of 29 April clearly exceeds the typical samples for this site.

Figure 48 through Figure 51 graphically characterize the Durango PM10 data. The first is a simple time 

series graph, every sample in this dataset (2005 – 2011) greater than 150 μg/m3 is identified. As with the 

previous time series an overwhelming number of samples occupy the lower end of the graph, over 99% of 

all the samples in this dataset are less than 75 μg/m3

. Of the 811 samples in this data set exactly four are 

greater than 150 μg/m3 ; all four of these samples are related to high wind events similar to this event. 

Clearly the April 29, 2010, sample is not typical of samples at this site.

Figure 48: Durango PM10 Time Series

Figure 49 is a simple histogram, demonstrating the overwhelming weight of samples on the low end of 

the curve. Almost 50% of the samples in this data set are less than 20 μg/m3

. Even in the highly volatile 

month of April, the month with the largest sample standard deviation, 90% of the samples are less than 50 

μg/m3

. Clearly, the sample on April 29, 2010, exceeds what is typical for this site.

198, 27 Feb 2009

198, 27 Feb 2009

226, 29 Apr 2010

203, 25 Apr 2009

320, 05 Apr 2010 

0 

50

100

150

200

250

300

350

11/09/04 03/24/06 08/06/07 12/18/08 05/02/10 09/14/11

Concentration, 

μg/m3 

Sample Date

Durango PM10
73

Figure 49: Durango PM10 Histogram

The monthly box-whisker plot, below, highlights the consistency of the majority of data from month to 

month. Note the greater variability (wider inner-quartile range) and greater range of the data through the 

winter and early spring months that’s accompanied by typically greater monthly maxima. Recall, this 

time period experiences a greater number of days with meteorological conditions similar to those 

experienced onApril 29, 2010. Although these high values affect the variability and central tendency of 

the dataset they aren’t representative of what is typical at the site.

Figure 50: Monthly Durango PM10 Box and Whisker Plot

As with the previous box and whisker plots outliers greater than 150 μg/m3 are identified by concentration 

and date. Each of these outliers is associated with a known high-wind event similar to that of April 29, 

2010. The presence of the extreme values distorts the graph, losing definition and distorting information 

presented across the range where the majority of data resides. The same plot graphed to 100 μg/m3

, 

which includes almost 99% of all the data, is presented in Figure 51. 

198, 27 Feb 2009

320, 5 Apr 2010

226, 29 Apr 2010

203, 25 Apr 2009

0 

50

100

150

200

250

300

350

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Concentration (

μg/m3) 

Month
74

Figure 51: Monthly Durango PM10 Box and Whisker Plot (expanded view)

3.2 Wind Speed Correlations 

Wind speeds around the region (Southwest Colorado, Northeast Arizona, Northwest New Mexico) 

increased early in the morning April 28, 2010, and stayed high through late afternoon of April 29, 2010, 

gusting to speeds in excess of 60 mph. The charts in Figure 52 display wind speed (mph) as a function of 

date from six widely dispersed stations across the region. Every one of these stations, despite being in 

completely disparate locations, exhibits nearly the same behavior in regards to the sustained high winds 

from April 28 and 29, 2010. 

0 

10

20

30

40

50

60

70

80

90

100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Concentration (

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Month
75

Figure 52: Wind Speed Graphs for Select Areas in Southwest Colorado, Northeast Arizona, and Northwest New Mexico 

(Wind Speed data courtesy of University of Utah, Mesowest)

Figure 53 plots PM10 concentrations from the affected sites for a small number of days prior to and 

following the sample(s) of April 28 and 29, 2010. 
76

Figure 53: PM10 Concentrations, Select Affected Sites (04/22/2010 – 05/05/2010)

Figure 53 precisely mimics the plots for wind speed in Figure 52. Although not every sample from April 

28 and 29, 2010, is in excess of 150 μg/m3 the elevated concentrations are clearly associated with the 

elevated wind speeds. Given the spatial dislocation of the sites (meteorological and PM10) the 

relationship between the two data sets would suggest that the regional high winds had a similar effect on 

PM10 samples in across a broad spatial region in Colorado from April 28 and 29, 2010. 

3.3 Percentiles

Monthly percentile plots for each site demonstrate a high degree of association between monthly median 

values and relatively high monthly percentile values, e.g. the r2 value between the Alamosa ASC monthly 

90th percentile and the Alamosa ASC monthly median is 0.699. The same value(s) for Pagosa Springs and 

Durango are 0.827 and 0.613, respectively. As the percentile value decreases (i.e. 85%, 75%, etc) the 

correlation between those values and the median increases sharply. The monthly percentile plots for each 

site are presented in Figure 54 (the black line is the 85th percentile):
77

Figure 54: Monthly Percentile Plots for Alamosa ASC, 

Alamosa Muni, Durango, Mt Crested Butte, and Pagosa 

Springs

It is certainly the case that monthly median values are indicative of typical, day to day concentrations. 

Additionally, there is a range of samples that are a product of normal variation subject to typical, day to 

day local effects. This range may be restricted to percentile values that are well correlated with the 

median. For these data sets a conservative estimate of the percentile value that is reflective of typical, day 

to day variation is the 90th percentile value. A different way to phrase this may be that most of the 

variability in the monthly 90th percentile values can be explained by the variation in monthly medians. If 
78

we take the 90th percentile as an estimate of the maximum contribution that could have come from local 

sources then the portion of the sample concentration remaining would be due to the event. Nearly all of 

the variation in the monthly 84th percentile values can be explained by the variation in monthly medians; 

for these five sites the correlation between the median and 84th percentile values vary from an r2

 = 0.69 

(Mt. Crested Butte) to an r2

 = 0.93 (Alamosa Muni). Table 24 and Table 25 identify various percentile 

values for each site from all April data for both sample dates. The range estimate in the ‘Est. Conc. 

Above Typical’ column is derived using the difference between the actual sample value and the 90th

percentile as the minimum event contribution estimate and the difference between the actual sample value 

and the 84th percentile as the maximum event contribution estimate.

Table 24: Various Percentile Values for Each Site from all April Data compared to April 28, 2010

Site

Event Day 

Concentration 

(April 28th) 

(μg/m3) 

April 

Median 

(μg/m3

) 

April 

Average 

(μg/m3

) 

April 75th

% (μg/m3

) 

April 84th

% (μg/m3

) 

April 90th

% (μg/m3

) 

Est. Conc. 

Above 

Typical 

(μg/m3

) 

Alamosa 

ASC

285 18 27.8 26 33 47 238 - 252

Alamosa 

Muni

236 23 35.5 35 42 60 176 - 194

Pagosa 

Springs

181 24 34.0 30 34 41 140 - 147

Mt. Crested 

Butte

123 19 31.2 26 31 39 84 - 92

Durango n/a 19 34.4 30 40 51 n/a

Table 25: Various Percentile Values for Each Site from all April Data compared to April 29, 2010

Site

Event Day 

Concentration

(April 29th) 

(μg/m3)

April 

Median 

(μg/m3)

April 

Average 

(μg/m3)

April 75th

% (μg/m3)

April 84th

% (μg/m3)

April 90th

% (μg/m3)

Est. Conc. 

Above 

Typical 

(μg/m3)

Alamosa 

ASC

92 18 27.8 26 33 47 45 - 59

Alamosa 

Muni

94 23 35.5 35 42 60 34 - 52

Pagosa 

Springs

162 24 34.0 30 34 41 121 - 128

Mt. Crested 

Butte

28 19 31.2 26 31 39 n/a

Durango 226 19 34.4 30 40 51 175 - 186

Clearly, there would have been no exceedance but for the additional contribution provided by the event. 

Since the local anthropogenic sources are well controlled in Alamosa, Pagosa Springs, and Durango and 

the sustained surface wind speeds were well above 25 mph in the region of the dust storm, it follows that 

the dust was transported into the region on April 28 and 29, 2010. The size, extent, and origination of the 

blowing dust storm made the event not preventable and it could not be reasonably controlled. Statistical 

data clearly shows that but for this high wind blowing dust event Alamosa, Pagosa Springs, and Durango 

would not have exceeded the 24-hour NAAQS on April 28 and 29, 2010. 
79

4.0 News and Credible Evidence

NEWS: Wed. April 28, 2010

Apr 28th @ 4:30 pm in News by Scott Staley 

High winds have hit just about all of the Western Slope this afternoon. And in some cases the winds have become quite inconvenient. 

The Daily Sentinel reports that some Grand Junction residential and commercial trash customers won’t have their trash picked up until Thursday, as 

high winds forced the closure of the Mesa County Landfill this morning. The city’s recycling service was also forced to close because of the wind but 

should reopen tomorrow. Much of the western slope has been under a High wind warning which remains in effect until 9pm tonight. Then look for a 

drastic drop in temperatures tomorrow and Friday....

Source: Daily Sentinel (Posted 5:05p by Jim Kapp)

The Colorado Senate has endorsed adding a “zipper” lane on Interstate 70 to ease weekend traffic. The Daily Sentinel reports Senators 

unanimously passed a bill today that’s aimed at prodding the Colorado Department of Transportation to move ahead with the idea. CDOT is already 

studying whether it’s feasible to use moveable concrete barriers to temporarily add an extra eastbound lane, known as the “zipper lane”....

Source: Daily Sentinel (Posted 4:25p by Jim Kapp)

Dozens of people gathered in Clifton last night for a candlelight vigil to honor Buddy the dog, who was dragged to death on the Colorado 

National Monument this winter. According to KJCTthe Lebers, who owned Buddy, hope that last night’s vigil will help people remember not just 

Buddy, but other animals who are victims of neglect and cruelty....

Source: KJCT (Posted 4:26p by Jim Kapp)

http://coloradoradio.com/2010/04/28/news-wed-april-28-2010-2/

NEWS: Friday April 30, 2010

Apr 30th @ 6:41 am in News by Scott Staley 

A Freeze Watch remains in effect from late tonight through Saturday morning. Freezing temperatures are expected. If plants and trees are left 

unprotected they risk freeze damage. The National Weather Service says sub-freezing temperatures could kill crops and other sensitive vegetation.

Source: National Weather Service (Posted 6:41a)

This freeze is the last thing Mattics Orchards needs right now as late night winds Wednesday and snow early yesterday have caused serious 

damage to some of their property, leaving crops exposed to the cold air. Orchard owner Pete Mattics estimates the damage between $6,000-$10,000. 

A greenhouse was destroyed, a chunk of roof from a packing shed knocked down power lines, disabling a transformer and scattered pieces of roof 

throughout the crop fields. Winds were recorded as high as 66mph in the area Wednesday night. Mattics Orchards is headquartered in Olathe. The 

damaged greenhouse is where crops were growing for kids in the Montrose County School District. Its unknown how much the storm and freeze will 

affect their business.

Source: Daily Press (Posetd 6:41a)

The supply of cinders used to treat Ouray County’s paved roads in the winter is running low, and might be depleted within 7-10 years. The 

County is looking at options on what to do when that happens. According to The Watch, Ouray County spends about $30,550 a year to have the 

cinders hauled in from Nucla. Future options include hauling a salt/sand mixture from Montrose for an estimated cost of $83,000 a year or go with 

magnesium chloride which would initially cost about $125,000. The topic is up for discussion next month.

Source: The Watch (Posted 6:39a)

Governor Ritter signed a 20 billion dollar state budget bill on Thursday, calling it a tough but balanced budget that reflects tough times. But fiscal 

policy analyst Terry Scanlon with the Colorado Fiscal Policy Institute says cuts in state spending could wind up being too tough on Coloradans that 

need the most help. He says that funding goes towards programs dealing with children in foster care or that were in abusive homes among other 

situations. Scanlon says it’s possible the budget situation could be even worse next year if ballot initiatives to further limit government pass in the fall. 

The new budget goes into effect July 1st.

Source: Colorado News Connection (Posted 6:39a)

http://coloradoradio.com/2010/04/30/news-friday-april-30-2010-2/
80

High winds expected through evening

Posted: Apr 28, 2010 4:55 PM by Greg Boyce 

Updated: Apr 28, 2010 4:55 PM

Rating:

0.0 (0 votes)

Wind is the word in Southern Colorado. A High Wind Warning is in effect until midnight along the southern I-25 corridor 

and the Wet Mountains.

The strongest winds are expected late Wednesday afternoon and evening. Winds of 35 to 45 miles an hour will be 

common south of Pueblo, from Westcliffe to Trinidad, with gusts of 75 miles an hour possible.

This will make travel difficult along I-25.

Topics: wind, warning, pueblo, westcliffe, trinidad, walsenburg, I-25
81

Weatherblog: Incoming storm could bring more desert dust Posted on April 27, 2010 by Bob Berwyn

Evening casts a blue light over Dillon Reservoir.

Strong cold front will bring high winds, cold temperatures and snow at the end of the week

By Bob Berwyn

SUMMIT COUNTY — Enjoy Tuesday and Wednesday, because a cold and windy storm is set 

to roll out of the Great Basin and into the Colorado Plateau and the Rockies Thursday. Winds in 

advance of the system could bring another layer of desert dust to parts of the Rockies Wednesday 

night. 

Snow banners streaming off the Gore and Tenmile Ranges Tuesday morning indicated the 

approach of strong high-level winds. Wind speeds could approach 60 MPH over the higher 

elevations Wednesday. 

The Pacific weather system will initially bring high winds and unseasonably cold temperatures, 

along with chance of snow on and off through early next week, according to the Grand Junction 

National Weather Service office, where forecasters said they’re leaning toward issuing winter 

storm watches or advisories in the coming days. 

In their forecast discussion, the Grand Junction-based forecasters wrote that they’re having a 

hard time remembering a system with these types of wind speeds. A wind advisory with a red 

flag fire warning is in effect for parts of the West Slope. Temperatures will drop sharply with 

arrival of a strong cold front. 

But until the front arrives late Wednesday, look for temperatures to climb into the 40s and 50s 

across the Summit-Vail forecast area. The warm weather is expected to trigger wet and loose 

snow avalanches in the backcountry from the recent storm that brought significant accumulations 

to the higher mountain areas. 

Backcountry observers reported drifts and slabs as deep as four to five feet, setting the stage for 

potentially large snow slides. Suspect areas include cornices and slopes below rocky areas that 

can quickly heat and weaken the surrounding snowpack. Check in with the Colorado Avalanche 

Information Center for general backcountry avalanche information and updates Wednesday, 

Friday and Sunday through the end of May.

About these ads

http://summitcountyvoice.com/2010/04/27/weatherblog-incoming-storm-could-bring-more-desert-dust/
82
83

(NOTE: CoCoRaHS “Daily Comments” reports are submitted at approx. 7:00 a.m.)
84

(NOTE: CoCoRaHS “Daily Comments” reports are submitted at approx. 7:00 a.m.)
85

(NOTE: CoCoRaHS “Daily Comments” reports are submitted at approx. 7:00 a.m.)
86

Wednesday, April 28, 2010

Way Too Windy

We spent a very windy night at Great Sand Dunes, and

even though we planned on staying a second night, we

decided to break camp and look elsewhere to camp for

our second night. We read the weather forecast at the

Visitor's Center and there were to be wind gusts of up

to 60 mph this evening. Even though our tent did well

last night, we didn't have that great of a time because we

couldn't sit outside and enjoy our campsite. We decided

to head west in hopes that the weather would be better.

Along they way, we saw a large elk herd that reminded

us of when we lived in Estes Park upwards of 200 elk

would gather in our yard at the same time.

This part of Colorado has quite a few farms where bison

are raised. It was interesting watching them and it's

quite relieving to know that they aren't as endangered

as they were even a generation ago.
87

As we drove west, through southern Colorado, we traveled a

few roads through country we hadn't visited before. We went

through Pagosa Springs and when we got to Durango, we

stopped at the Public Lands Office to check the weather.

We had thought about stopping for the night near Dolores

and Canyons of the Ancients National Monument, but found

that it was going to be even windier there than at Great

Sand Dunes. We even thought about staying at Hovenweep

National Monument, which is even farther west. It was very

windy there as well. It seemed at times that the whole state

of Utah was blowing east into Colorado. The skies had such

a hazy, dusty look. We decided to cut our losses and head

home for the night. We headed north and visited the small

resort/ski town of Telluride. We decided we would visit

later in the summer since it looked like a pretty neat place.

Later, we drove the the small town of Ridgway where we

saw this old firehouse and fire truck. They also have an

interesting railroad museum there that we might check out

at a later date. Overall, we spent a long day in the car, but

it was fun to see so many places we hadn't seen before.

Posted by Tom at 10:24 PM 1 comments 

http://bigblueglobe.blogspot.com/2010_04_01_bigblueglobe_archive.html
88

 

04-28-2010, 09:28 PM

jim9251

Status: "Living in paradise" (set 5 days ago)

 

Location: Western Colorado

3,833 posts, read 2,073,549 times

Reputation: 4880

The dust storm is kinda sucking the oxygen out of the air and it's a bit difficult to breathe 

without getting a mouthful of dirt, but I haven't had allergy problems since I moved here. I 

expected wind since this is the windy season, but wasn't told about the dust storms. Utah 

can have their dirt back. But I know it will be back to fresh, crisp mountain air in a day or 

two.

 

04-29-2010, 07:52 AM

CosmicWizard Location: Wherabouts Unknown!

6,825 posts, read 8,322,753 times

Reputation: 7113

Get used to it Jim...it happens from time to time. Last summer, when it rained, the rain was 

full of dust, and it did a real number on the windows and cars. Before I lived in the desert, I 

experienced rain as something that cleaned my car, not something that splatterd it with 

mud drops. I'm sure you'll soon have a chance to experience first hand what I'm talking 

about.

This morning in Grand Junction reminds me of the good ole days in southeatern PA when I 

was growing up. Yesterday the temp was almost 80, and this morning it's snowing hard 

enough to coat the grass and rooftops with a nice white dusting.

 

04-29-2010, 08:04 AM

jim9251

Status: "Living in paradise" (set 5 days ago)

 

Location: Western Colorado

3,833 posts, read 2,073,549 times

Reputation: 4880

Already did that, rained mud here last week. That was different.

And now it's snowing.

 

04-29-2010, 09:17 AM

80skeys Location: Sunnyvale, CA

3,314 posts, read 3,274,810 times

Reputation: 1090

Quote:

Originally Posted by jim9251

I discovered something I do not like about living here. The dust storms. Everything is 

brown, the sky, the air, and there's this dirt taste in my mouth. Yecch.

Unfortunately we live on the Western slope. To the west of us is nothing but hundreds of 

miles of open, unprotected deserts of Utah. Nothing to hold down the sand.

 
89

04-29-2010, 09:49 AM

CosmicWizard Location: Wherabouts Unknown!

6,825 posts, read 8,322,753 times

Reputation: 7113

80skeys wrote:

Unfortunately we live on the Western slope

Just curious, what do you find unfortuante about living on the western slope? I've always 

considered it my good fortune to be living on the western slope! 

 

04-29-2010, 11:15 AM

80skeys Location: Sunnyvale, CA

3,314 posts, read 3,274,810 times

Reputation: 1090

Quote:

Originally Posted by CosmicWizard

80skeys wrote:

Unfortunately we live on the Western slope

Just curious, what do you find unfortuante about living on the western slope? I've always 

considered it my good fortune to be living on the western slope!

I meant in the context of the dust storms and wind.

 

04-30-2010, 12:47 PM

mrgoodwx Location: Albuquerque

669 posts, read 821,352 times

Reputation: 587

Yep...it does.

Quote:

Originally Posted by 80skeys

Not just a Colorado phenomenon. That type of thing happens in AZ and NM too.

It's the last day of April. We had several snow showers this morning on the eastern edge of 

Albuquerque, where I live up against the Sandia Mountains. This is much better than 

watching pieces of western New Mexico and Arizona fly by overhead...driven by wind gusts 

to 70 mph.

04-30-2010, 03:09 PM

jim9251

Status: "Living in paradise" (set 5 days ago)

 

Location: Western Colorado

3,833 posts, read 2,073,549 times

Reputation: 4880

It has snowed, heavy here the past two days. No more dust or winds. Just snow. I'm a Ham 

Radio operator and when I tell guys in Cuba, or South America it's snowing here I always 

get a "IT'S WHAT?" Hopefully it's nice for the big hot air balloon festival and car show next 

weekend here!

 

05-04-2010, 09:40 AM
90

jim9251

Status: "Living in paradise" (set 5 days ago)

 

Location: Western Colorado

3,833 posts, read 2,073,549 times

Reputation: 4880

Well after a dust storm, winds clocked at 100mph, snow, snow and a blizzard Sunday 

evening, MOnday May 3rd was clear, crisp, bright sunshine and deep blue sky.

Here is a photo of Mt Lamborn over Paonia Monday and again today. How fast the snow 

melts in the sunshine. The San Juans by my town are still snowpacked.
91

 

05-04-2010, 12:47 PM

CALIFRE Location: Way Out West...

82 posts, read 64,829 times

Reputation: 107

Beautiful Jim, Always enjoy your pics. I have a similar view of Mt. Lamborn from property in 

the area, I'm planning to build and settle in a few years.

Maybe spring has finally sprung on the Western slope??

Read more: http://www.city-data.com/forum/colorado/693202-retiring-colorado-western-slope-grand-junction18.html#ixzz2SiG8Tivj

http://www.city-data.com/forum/colorado/693202-retiring-colorado-western-slope-18.html
92

5.0 Not Reasonably Controllable or Preventable: Local 

Particulate Matter Control Measures

While it is likely that some dust was generated within the local communities as gusts from the regional 

dust storm passed through the area, the amount of dust generated locally was easily overwhelmed by, and 

largely unnoticeable as compared to the dust transported in from the source regions of the dust storm. 

The following sections will describe in detail the regulations and programs in place designed to control 

PM10 in each affected community. These sections will demonstrate that the event was not reasonably 

controllable, as laid out in Section 50.1(j) of Title 40 CFR 50, within the context of reasonable local 

particulate matter control measures. As shown from the meteorological and monitoring analyses 

(Sections 2 and 3), the source region for the associated dust that occurred during the April 5, 2010 event 

originated outside of the monitored areas, primarily from the desert regions of northern and central 

Arizona and northwestern New Mexico. 

The Colorado Air Pollution Control Division (Division) conducted thorough analyses and outreach with 

local governments to confirm that no unusual anthropogenic PM10-producing activities occurred in these 

towns 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 5, 2010 event, as well as subsequent outreach designed to 

administer these activities. This information shall confirm that no unusual anthropogenic actions 

occurred in the local areas of Alamosa, Pagosa Springs, or Durango during this time. 

Regulatory Measures- State

The Division’s regulations on PM10 emissions are summarized in Table 26. 

Table 26: State Regulations Regulating Particulate Matter Emissions

Rule/Ordinance Description

Colorado Department of Public Health and 

Environment 

Regulation 1- Emission Control For Particulate 

Matter, Smoke, Carbon Monoxide, And Sulfur 

Oxides 

Applicable sections include but are not limited to:

Everyone who manages a source or activity that is 

subject to controlling fugitive particulate emissions 

must employ such control measures and operating 

procedures through the use of all available practical 

methods which are technologically feasible and 

economically reasonable and which reduce, prevent 

and control emissions so as to facilitate the 

achievement of the maximum practical degree of 

air purity in every portion of the State. Section 

III.D.1.a) 

Anyone clearing or leveling of land greater than 

five acres in attainment areas or one acre in nonattainment areas from which fugitive particulate 

emissions will be emitted are required to use all 

available and practical methods which are 

technologically feasible and economically 

reasonable in order to minimize fugitive particulate 
93

Rule/Ordinance Description

emissions.(Section III.D.2.b)

Control measures or operational procedures for 

fugitive particulate emissions to be employed may 

include planting vegetation cover, providing 

synthetic cover, watering, chemical stabilization, 

furrows, compacting, minimizing disturbed area in 

the winter, wind breaks and other methods or 

techniques approved by the Division. (Section 

III.D.2.b) 

Any owner or operator responsible for the 

construction or maintenance of any existing or new 

unpaved roadway which has vehicle traffic 

exceeding 200 vehicles per day in the 

attainment/maintenance area and surrounding areas 

must stabilize the roadway in order to minimize 

fugitive dust emissions (Section III.D.2.a.(i))

Colorado Department of Public Health and 

Environment 

Regulation 3- Stationary Source Permitting and Air 

Pollutant Emission Notice Requirements 

Construction Permit required if a land development 

project exceeds 25 acres and spans longer than 6 

months in duration (Section II.D.1.j) 

Colorado Department of Public Health and 

Environment 

Regulation 6- Standards of Performance for New 

Stationary Sources 

Implements federal standards of performance for 

new stationary sources including ones that have 

particulate matter emissions. (Section I) 

Colorado Department of Public Health and 

Environment 

Regulation 9- Open Burning, Prescribed Fire, and 

Permitting

Prohibits open burning throughout the state unless 

a permit has been obtained from the appropriate air 

pollution control authority. In granting or denying 

any such permit, the authority will base its action 

on the potential contribution to air pollution in the 

area, climatic conditions on the day or days of such 

burning, and the authority’s satisfaction that there 

is no practical alternate method for the disposal of 

the material to be burned. Among other permit 

conditions, the authority granting the permit may 

impose conditions on wind speed at the time of the 

burn to minimize smoke impacts on smokesensitive areas. (Section III) 

Federal Motor Vehicle Emission Control Program The federal motor vehicle emission control 

program has reduced PM10 emissions through a 

continuing process of requiring diesel engine 

manufacturers to produce new vehicles that meet 

tighter and tighter emission standards. As older, 

higher emitting diesel vehicles are replaced with 

newer vehicles; the 

PM10 emissions in areas will be reduced.
94

5.1 Alamosa

Natural Events Action Plan (NEAP)

The Final NEAP for High Wind Events in Alamosa, Colorado was completed in May 2003. The NEAP 

addresses public education programs, public notification and health advisory programs, and determines 

and implements Best Available Control Measures (BACM) for anthropogenic sources in the Alamosa 

area. The Division followed up with the City and County of Alamosa in January 2007 and in the spring 

of 2013 on whether the NEAP mitigation measures and commitments were satisfied, the results of which

are detailed below. The City of Alamosa, Alamosa County, the Division, and participating federal 

agencies worked diligently to identify contributing sources and to develop appropriate BACM as required 

by the Natural Events Policy. 

Regulatory Measures- City

The Division and the City of Alamosa are responsible for implementing regulatory measures to control 

emissions from agricultural sources, stationary sources, fugitive dust sources, and open burning within 

Alamosa. Alamosa’s ordinances of PM10 emissions are summarized in Table 27. 

Table 27: Rules and Ordinances Regulating Particulate Matter Emissions in Alamosa

Rule/Ordinance Description

City of Alamosa Code of Ordinances 

Article VII of Section 21-140 (5)

Addresses dust control for home occupations

City of Alamosa Code of Ordinances 

Article V Sec. 17-87(3))

Requires all new roads and alleys to be paved

City of Alamosa Code of Ordinances 

(Article VI Sec. 21-119(g)(3)). 

New large commercial/retail establishments must 

install underground automatic irrigation systems 

for all landscaped areas

City of Alamosa 

The City of Alamosa has been active in addressing potential PM10 sources within the Alamosa area 

through various efforts. Some of these efforts, plus other potential future measures, include the adoption 

of local ordinances to reduce PM10. Copies of current ordinances and any related commitments are 

included in the NEAP in Appendix C. According to the City’s Public Works Director, as of 2013, the City 

is planning on adding additional dust control best management practices to the International Building 

Codes that are adopted by the city in the next update. The best management practices will include 

requiring a Dust Control Plan for any site that is issued a clearing permit for any site over 2 acres. The 

City is also currently (as of 2013) working on revising part of their landscaping ordinances to require 

mulch in areas that are not vegetated or covered by rock to help mitigate fugitive particulate emissions. 

These efforts have been stalled in the past due to employee turnover at City Manager’s Office. 

Street Sweeping 

The City of Alamosa sweeps on an every 4-week schedule or as needed, as determined by local officials 

on a case by case situation (e.g., following each snowstorm and/or where sand was applied). Sweeping 

occurs on every single City street with an emphasis on the downtown corridor where public exposure is 

expected to be greatest. As of Spring 2013, street sweeping in the downtown corridor currently takes 

place twice per week according to the City’s Public Works Director. 

According to the City’s Public Works Director, the city (as of 2013) owns an Elgin Pelican (mobile 

mechanical sweeper) and a Tymko 600 (brush-assisted head) street sweeper. As of June 2013, the City 
95

will also own a new Elgin Broom Badger street sweeper at which time the Tymko 600 will be sent in for 

a re-build. The new Elgin Broom Badger street sweeper can be used in the winter months when the 

Tymko cannot due to freezing of the water delivery system. 

Unpaved Roads within the City 

The City of Alamosa (as of 2008) requires all new roads and alleys to be paved according to the 

Municipal Code (Article V Sec. 17-87(3)) and some existing unpaved roads are being treated with dust 

suppressants until all underground utilities are installed. No new development is allowed until paving is 

complete unless a performance bond is in place. 

According to the City’s Public Works Director, as of 2013, less than 3% of City roads are unpaved; most 

of these unpaved roads are legacy annexations. One of these unpaved roads is scheduled for paving this 

year (2013). The remaining unpaved roads are all low traffic (less than 100 ADT) and the City continues 

to seek funding sources for paving these streets.

Sod/Vegetative Cover Projects in the City of Alamosa 

As of 2008, the City of Alamosa placed vegetative cover in all city parks and has installed irrigation 

systems to maintain the cover. As of 2013, the City has been emphasizing more low-water use 

landscaping with shrubs, mulch, etc. including both organic and rock. All turf areas do have irrigation 

systems which utilize drip systems for specimen plantings.

Alamosa County 

Alamosa County has also been active in addressing blowing dust as detailed below. 

Unpaved Roads 

Alamosa County continues to address unpaved roads and lanes that are anticipated to contribute to PM10

emissions in the community. As of 2002, Alamosa County was nearing the end of its five-year road 

paving plan and was developing their next plan with the intention of paving on a yearly basis, based on 

traffic, community needs/priorities, and funding availability. 

In 2002, Alamosa County addressed approximately ten (10) miles of unpaved roads. This includes the 

stabilization of approximately five section roads, the seal coating of two roads, and the overlay (repaving) 

of four (4) additional roads. 

In 2003, approximately 14 miles of roads were paved. This includes the Seven Mile Road (three miles 

long), Road 109 (one mile long), and 10th Street (also one mile long). These roads are in close proximity 

to the City of Alamosa, are upwind (prevailing) from the city, and have heavy traffic. Paving is 

anticipated to greatly reduce blowing dust and impacts in the vicinity. 

No paving projects took place between 2004 and 2010 due to lack of funding. Between 2010 and 2013, 

the County was able to get funding but only for maintenance paving on previously paved roads that 

needed repair. Now that the county is caught up on maintenance paving, it is focusing on paving the 

remaining unpaved roads. The County’s goal is to pave about 2.5 miles of unpaved road per year 

depending on funding availability. 

As of 2013, Alamosa County has funding to pave approximately 2.5 miles of County Road 106 North 

(located north of Alamosa off of Highway 17) which is currently unpaved. After this paving project the 

County will only have 2.5 miles of unpaved road remaining on the 106 North which is anticipated to be 

paved in the summer of 2014. 
96

In the summer time the County regularly hauls water and wets down the unpaved roads (mostly gravel, 

clay and sand) to reduce the fugitive particulate emissions. The County wets the unpaved roads on an as 

needed basis based on weather conditions and traffic volume. In addition, when it gets cold enough in the 

area, the County wets down some of the more sandy roads. Once the water soaks in and freezes, good 

dust suppression is seen. Road construction areas are being dampened with water for dust control. These 

practices reduce PM10 emissions in and near Alamosa. This control measure is balanced with the 

availability of water in the area. 

Alamosa County used to assess the need to use MgC12 treatment on roads in front of residences that 

request such service. This practice stopped in 2004 when funding was lost. Assessments included the 

sensitivity to dust of residents, the materials of the road base for safety reasons, and possible 

environmental concerns of the neighborhood. Most requests for treatment are were granted. Other areas 

for treatment, such as commercial construction zones or gravel pits, are investigated on a case by case 

basis. The County hopes to be able to start offering this service again when funding is restored. 

Dust Control Plans 

Alamosa County requires dust control plans for selected construction/developments. The dust control 

plans are typically done through a negotiated agreement by the Alamosa Land Use Department and is 

supported by zoning codes. 

The County may update the Comprehensive Plan to include a dust control plan. The Land Use 

Administrator is researching the potential for a dust control ordinance. This effort is anticipated to reduce 

PM10 emissions in Alamosa, especially as it relates to impacts on the community and high recorded PM10

values. At the time of this submittal (June 2013), this effort is still underway. 

Wind Erosion of Open Areas 

To reduce PM10 emissions from open areas outside of the City limits, low tilling and other soil 

conservation practices continue to be utilized in the community. The Mosca-Hooper Conservation District 

and Natural Resources Conservation Service is working on education efforts to promote cover crops and 

no-till agriculture. In addition, the community is using in strategic areas the Colorado State Forest Service’s

 program to purchase and plant shelter trees to reduce wind erosion in open areas. Nursery seedlings from 

the program have been sold in Alamosa County since 1956. The number of seedlings sold has varied over 

the last few years as illustrated in Table 28. 

Table 28: Number of seedlings sold in Alamosa per year.

Year: 2008 2009 2010 2011 2012 2013

Seedlings 

Sold:

7,432 5,963 2,805 4,197 3,327 4,231

These trees have a demonstrated advantage for the community and for air quality. Once the trees reach 

maturity, it is anticipated that the equivalent of 112 miles of double-rowed trees will be in place. The 

survival rate of the tree seedlings varies but according to the District Coordinator for the Seedling Tree 

Program, potted seedlings have about a 60% to 80% survival rate and the bare root seedlings have about a 

40 to 60% survival rate. The Seedling Program recommends Siberian elm and Rocky Mountain juniper 

trees for low maintenance, drought resistance windbreaks in the valley, but offers over 40 varieties to suit 

specific site conditions. The Colorado State Forest Service and the Mosca-Hooper Conservation District 

promote the windbreak program through workshops and consulting landowners. 

In addition, there is ongoing planting of trees (approximately 50) on newly developed Alamosa County 

property south/southwest of Alamosa (prevailing winds from southwest) and the Airport south of 
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Alamosa for added air quality improvement. Also, The Bureau of Reclamation has an ongoing project to 

plant windbreaks along their Closed-Basin Canal. 

Windblown Dust from Disturbed Soils

Alamosa has a semi-arid climate with approximately 7.25 inches of precipitation annually. The San Luis 

Valley, as noted within 25 miles of the San Luis Valley Regional Airport in Alamosa, is primarily 

comprised of forests (43%) and shrublands (42%). Consequently, soils in all areas are typically a 

mixture of silt and sand with limited vegetation due to low precipitation. In winter and spring, 

windstorms are common, especially in drier years. It is due to these high velocity windstorms that 

Alamosa experiences most of the PM10 problems for the area. Figure 1 illustrates potential areas of local 

soil disturbance that have been evaluated by the Division for the Alamosa Adams State PM10 monitor. 

Figure 55: Relative positions of Adam's State College PM10 Monitor and potential disturbed soil. (Image from Google 

Earth 2007)

A B

C

D E

F G H
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Figure 56: 2011 City of Alamosa Zoning Map (Provided by the Public Works Department)

Site A in Figure 55 (approximately 85 acres) is East of Rd S 108 and South of Chico St. It is zoned 

outside of the city’s limits by the city as a “Parcel” as shown in Figure 56. The eastern portion of Area A 

is being considered for annexation into the City. 

Site C in Figure 55 (approximately 25 acres) is north of 10th St, West of Road 108, and east of Craft St. It 

is zoned outside of the city’s limits by the city as a “Parcel” as shown in Figure 56. 

Site D in Figure 55 (approximately 34 acres)is north of 10th street, east of Rd S 108, west of Park Ct, and 

south of 8th St. It is zoned outside of the city’s limits by the city as a “Parcel” as shown in Figure 56. 

Site F in Figure 55 (approximately 31 acres)is south of 10th St, east of Craft Dr, west of S Rd 108, and 

North of Coop Rd. It is zoned outside of the city’s limits by the city as a “Parcel” as shown in Figure 56. 

Site G in Figure 55 (approximately 41 acres) is east of S Rd 108, north of Coop Rd, west of Earl St, and 

South of 10th St. It is zoned outside of the city’s limits by the city as a “Parcel” as shown in Figure 56. 

Sites A, C, D, F, and G are noted by the City of Alamosa’s Public Works Director 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 City 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 as of this writing. If future high wind or other exceptional events occur, the Division 

will re-assess these lots to determine if they are still natural sources. 

Site B in Figure 55 (approximately 22 acres) is south of Highway 160 and north east of Tremont St. It is 

zoned outside of the city’s limits by the city as a “Parcel” as shown in Figure 56. Site E in Figure 55

(approximately 30 acres) is north of 10th St, south of 8th St, east of Park Ct, and west of West Ave. It is 

zoned mostly as a “Commercial Business” as shown in Figure 56. There is a small portion in the top right 

corner that is zoned outside of the city’s limits by the city as a “Parcel”. Site H (approximately 23 acres) 

in Figure 55 is east of Earl St, south of 10th St, and north of Rd 8 S. It is zoned as “Commercial business”, 

“Residential High” and a little “Industrial” as shown in Figure 56. Sites B, E, and H are naturally 
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vegetated and potentially irrigated as shown in Figure 57. Figure 57 demonstrates that these sites are 

minimally (if at all) disturbed soil areas as of this writing. 

Figure 57: Sites B, E, and H with natural vegetation (Google Earth 2007)

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

Figure 55 were present during the 2010 exceedances. During the course of these assessments, the 

Division discovered that these sites were either reasonably controlled or considered to be natural sources 

during the April 5, 2010 high wind event. Therefore, these sites were not significant contributors to 

fugitive dust in the Alamosa area during the April 5, 2010 high wind event. 

The Division is currently investigating the applicable area around the Alamosa Municipal Building (08-

003-0003) PM10 monitor in coordination with the County and City of Alamosa, shown in Figure 1. The 

Division commits to submitting an Addendum similar to the analysis for the Alamosa Adams State PM10

monitor and other monitoring sites. Figure 58 illustrates potential areas of local soil disturbance that have 

been evaluated by the Division for the Alamosa Municipal Building (08-003-0003) PM10 monitor. 

B

E

H
100

Figure 58: Relative positions of Municipal Building PM10 Monitor and potential disturbed soil. 

(Image from Google Earth 2007) 

Sod and Vegetative Projects in the County 

The development and construction of a local park, Eastside Park, is complete in Alamosa County. It has 

been completed with turf grass, shrubs, and landscape rock. No exposed soil remains. 

Numerous other projects to reduce blowing dust and its impacts have happened or are happening at the 

County Airport. For example: 

• Through additional grounds maintenance of the 40-acre Alamosa County airport south of the 

city, “Xeriscape” has been installed for aesthetics and dust control. 

• Decorative rock and xeriscape have been implemented in the landscaping of the Alamosa 

County property (2007-2012). These measures have directly abated blowing dust at the 

Airport. 

• Also, the widening of the airport’s safety areas (250 feet on either side of the runway) is 

complete and seeding of natural grasses was incorporated in the project. Trees and grass were 

incorporated in the approaches to the airport and have provided additional wind-break 

advantages to South Alamosa. 
101

In other areas where watering is a problem, xeriscape (the use of native drought resistant vegetation 

and/or rock cover) is being encouraged for County owned property and for all other property owners. 

Colorado State University Co-Op Extension Office 

In response to extremely dry conditions, the need to maintain area topsoil, and reduce impacts, the 

Colorado State University Co-Op Extension Office of Alamosa County provides the following outreach 

efforts and recommendations: 

• Modification of grazing practices to improve protective crop cover 

• Increasing crop residues left in the fields to reduce blowing dust 

• Planting of Fall crops to maintain fields 

• Application of manure to protect top soils from blowing away 

• Staggering of the harvest to minimize blowing dust 

• Outreach programs on soil conservation efforts 

• Development of outreach/education materials (e.g., news articles, newsletters, fact sheets, etc.), 

and 

• Attendance at Statewide workshop to educate other Co-Op offices to various practices to reduce 

blowing top soil and minimize impacts.

 

These control strategies are not meant to be enforceable. They are meant only to demonstrate the regional 

nature of cooperation in addressing blowing dust and its impacts on the community. 

Natural Resources Conservation Service (NRCS)

Alamosa County is a predominately agricultural area where limited water, coupled with the frequent high 

winds experienced during late fall and early spring, can destroy crops, encourage pests, and damage soil 

surfaces lending them susceptible to wind erosion. Thus, activities that improve the topsoil and prevent its 

lifting during high wind events are encouraged. Some notable NRCS and agricultural examples include: 

• Local Conservation Districts and farmers hold monthly meetings as an informal Soil Health 

Group, discussing ways to improve soil health. Cover crops, compost applications, and 

reduced tillage are the targeted practices. Public tours are held twice a year.

• NRCS continues to work with area farmers in the development of conservation compliance 

plans to also protect topsoil;

• NRCS encourages planting perennial grasses or the leaving weeds undisturbed or mowed on 

the corners of center pivots (instead of tilling that might lead to open, barren lands) to reduce 

soil blowing; 

• NRCS “cost shares” on soil health practices and perennial grass seeding conservation practices 

with local farmers to prevent soil erosion, and;

• The NRCS is working with Colorado State University, local Water Conservation District, and 

Farm Service Agency to encourage retirement of marginal cropland in the Conservation 

Enhanced Reserve Program (CREP) and seeding those acreages back to native grass, forbs 

and shrubs. 

Other successful agricultural practices encouraged in the area include: timing of tillage, crop rotation, 

amount of crop residue left on the land, and proper water usage. These control strategies are not meant to 

be enforceable. They are meant only to demonstrate the regional nature of cooperation in addressing 

blowing dust and its impacts on the community. 

Please refer to the Final NEAP in Appendix C for more detail if needed. 
102

5.2 Pagosa Springs 

Regulatory Measures- City and County

The Division and the Archuleta County are responsible for implementing regulatory measures to control 

emissions from agricultural sources, stationary sources, fugitive dust sources, and open burning within 

Pagosa Springs. Archuleta County regulations of PM10 emissions are summarized in Table 29.

Table 29: Rules and Ordinances Regulating Particulate Matter Emissions in Archuleta County

Rule/Ordinance Description

Pagosa Springs 

Land Use and Development Code 6.6.3(h)

Requires that all new developments have paved 

streets.

Pagosa Springs 

Land Use and Development Code 6.6.3(m)(i) 

All new roads having a projected trip generation of 

200 or greater ADT (average daily traffic) shall be 

paved. 

The following control measures resulted in the area‘s attainment of the PM10 NAAQS, and these 

measures should ensure continued maintenance of the PM10 NAAQS through the year 2021, which is the 

duration of the maintenance period. 

Control of Emissions through Road Paving 

The Town of Pagosa Springs paved 6.5 miles of unpaved roads during 1992, 1993, and 1994 in order to 

reduce PM10 emissions. This strategy was adopted locally in 1991 and included in State regulation in 1992 

(Section I.B. of the State Implementation Plan-Specific Regulations for Nonattainment - 

Attainment/Maintenance Areas (Local Elements)). The rule was approved by EPA in 1994 and was 

removed from the Colorado regulation in 2000 as the paving requirements had been completed. 

Street Sanding Controls

There is a requirement that any user that applies street sanding material on Highway 160 and 

Highway 84 in the Pagosa Springs attainment/maintenance area must use materials containing less than 

one percent fines. Users of street sand on these highways must also use 15 percent less sand than an 

established base sanding amount. These strategies were adopted in 1992 and approved by EPA in 1994, 

and they are defined in detail in Sections I.B. and C., respectively, of the ―State Implementation PlanSpecific Regulations for Nonattainment -Attainment/Maintenance Areas (Local Elements) Regulations (5 

CCR 1001-20). 

Control of Emissions from Stationary Sources 

Although there are no stationary sources located in the Pagosa Springs attainment/maintenance 

area, the State‘s comprehensive permit rules will limit emissions from any new source that may, in the 

future, locate in the area. These rules are outlined in Table 26. 

As indicated above, emissions from new or modified major stationary sources emissions of PM10 are 

controlled under AQCC Regulation No. 3's nonattainment-area (NAA) new source review (NSR) 

permitting requirements. The NSR provisions require all new and modified major stationary sources to 

apply emission control equipment that achieves the "lowest achievable emission rate" (LAER) and to 

obtain emission offsets from other stationary sources of PM10. 

The EPA approval of the original PM10 Maintenance Plan, effective on 08/14/01, reinstates the prevention 

of significant deterioration (PSD) permitting requirements in the Pagosa Springs Attainment/Maintenance 

area. The federal PSD requirements are considered a relaxation from the NAA NSR requirements, as 

LAER is no longer required and is replaced by the less stringent "best available control technology" 

(BACT), along with the removal of the requirement to offset PM10 emissions. The future reapplication of 
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NAA NSR provisions appears unlikely in the Pagosa Springs Attainment/Maintenance area based on 

current PM10 monitoring trends. 

Voluntary and State-Only Measures

In addition to the mandatory control measures discussed above, there are other activities that result in the 

reduction of PM10 emissions that are not classified as “federally enforceable control measures.” Some 

notable examples include:

The Town of Pagosa Springs has historically cleaned Highway 160 in town throughout the winter and 

spring using regenerative air vacuum sweepers. The frequency of this voluntary sweeping/cleaning has 

been about once after each street sanding deployment. The Town of Pagosa Springs is committed to 

regularly vacuum sweep/clean Highway 160 within four days of the roadway becoming free and clear of 

snow and ice following each street sanding deployment, as weather, temperature, and street conditions 

permit, between the intersections of Highway 84 to the east and 14th street to the west. The town also 

street sweeps regularly on the side streets.

The Town of Pagosa Springs encourages private businesses to properly clean/sweep private parking lots 

on a regular basis. These strategies are considered to be voluntary local initiatives intended to reduce 

PM10 emissions. These strategies are not intended to be federally enforceable. 

Archuleta County annually teats about 95 miles of unpaved roadways that exceed 200 ADT with MgCl2 

to control dust and stabilize the road according to the County Public Works Director. 

Windblown Dust from Disturbed Soils

Pagosa Springs has a semi-arid climate with approximately 17 inches of precipitation annually. The town 

is located about 35 miles north of the New Mexico border at 7,000 feet. This area is considered a high 

desert plateau, creating an unusually mild climate. In winter and spring, regional windstorms are 

common, especially in drier years. It is during these high velocity windstorms that Pagosa Springs 

experiences PM10 issues. Figure 59 illustrates potential areas of local soil disturbance that have been 

evaluated by the Division.
104

Figure 59: Relative positions of Pagosa Springs PM10 monitor and known or potential disturbed soil. (Image from EPA)

Site A in Figure 59 shows a 1 acre vacant lot that previously contained a small convenience store which 

was torn down by the new owner between March and April of 2006. Division conversations with 

neighboring local business owners indicate the owner seeded the vacant lot (site A) with grass soon after 

demolishing the building. According to several nearby businesses and a court house clerk, the lot has been 

under continuous vegetative cover since the seeding in 2006. The grass is well maintained and is enclosed 

by a small fence (shown in Figure 60) to deter people from walking on the grass. Moreover, the lot is not 

used for parking or storage. 

 

D

C

A

B
105

Figure 60: View of the fence surrounding the vacant lot (Site A) - Google Image 12-2007

Site B in Figure 59 (approximately 2 acres) shows The Springs Resort and Spa. The resort underwent an 

expansion; construction began in June 2008 and was completed in May 2009. By April 2009, the entire 

construction site was paved and the building was constructed; the interior was just being finished. 

Therefore, this project was completed and did not contribute to the April 5, 2010 exceptional event. 

Site C in Figure 59 is a 35-acre area of vacant land. According to the Pagosa Springs Parks Department, 

the area is private property and is entirely naturally vegetated because of a continuous supply of ground 

water from the nearby stream. The Parks Department also indicates that off-road recreational vehicles are 

prohibited on the property. The Parks Department is very aware of dust prevention practices and does not 

believe that the area is a significant source of dust during high winds. With regard to AQCC Regulation 1 

requirements (Section III.D.2.b), the Division considers the natural vegetation with regular ground water 

availability due to the low-lying terrain to be the appropriate available and practical method that is 

technologically feasible and economically reasonable in order to minimize fugitive particulate emissions 

for this lot at this time. Local sources, including the Pagosa Daily Post, cite the proposed future 35-acre 

hotel expansion (Site C) to be projected to occur in several phases over a 10-15 year time period. 

The Division will conduct appropriate outreach and compliance assistance so the hotel is aware of 

potentially applicable AQCC Regulation 1 (Section III.D.2.b) and Regulation 3 (Construction Permit 

required if the project exceeds 25 acres and spans longer than 6 months in duration) requirements for 

future construction projects. The Division has specific Air Pollutant Emissions Notices (APENs) for land 

development and associated guidance documents posted on its website for these type of sources. 

Additionally, the Division has staff that conducts Small Business Assistance outreach as warranted. 

Compliance and enforcement inspectors from the Division are assigned regions throughout the state. As 

part of their workplans, they are required to be reasonably (within 1-2 business days) responsive to 

community and local government concerns and complaints regarding air quality issues, including fugitive 

dust. 

Site D in Figure 59 is Yamaguchi Park, a 16-acre park consisting mostly of well-maintained turf and 

some stabilized clay associated with a baseball field. The entire park is irrigated on a regular basis to both 

maintain the vegetation and to mitigate dust. In the fall of 2008, Pagosa Springs hydro-seeded the park 

and vegetation emerged around April 2009 which was watered on a regular basis to help the vegetation 

grow. In Figure 61 below, it is apparent that the park has well maintained vegetation and a small amount 

of stabilized clay. With regard to AQCC Regulation 1 requirements (Section III.D.2.b), the Division 

considers hydro-seeding to be the appropriate available and practical method that is technologically 

feasible and economically reasonable in order to minimize fugitive particulate emissions for this 

magnitude of construction project. 
106

Figure 61: Yamaguchi Park- Google Image from 10-2011

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

Figure 5 were present during the 2010 exceedances. During the course of these assessments, the Division 

discovered that these sites were reasonably controlled during the April 5, 2010 high wind event. 

Therefore, these sites were not significant contributors to fugitive dust in the Pagosa Springs area during 

the April 5, 2010 high wind event.
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5.3 Durango 

Regulatory Measures- City and County

The Division, the City of Durango, La Plata County, and the Southern Ute Indian Tribe are responsible 

for implementing regulatory measures to control emissions from agricultural sources, stationary sources, 

fugitive dust sources, and open burning within Durango. A summary of regulations regarding PM10

emissions is in Table 30. 

Table 30: Rules and Ordinances Regulating Particulate Matter Emissions in Durango

Rule/Ordinance Description

City of Durango’s Municipal Code 

No. 10-1-22 (b)(6 &8) 

Requires that all temporary (not to exceed eighteen 

months) office structures parking areas must have 

all weather surface gravel to eliminate exposed dirt. 

Also, the landscaping must have vegetative ground 

cover in all areas not covered by the building, 

pavement, or gravel.

City of Durango’s Municipal Code 

Ord. No. 10-1-6 (a) “Vehicular Circulation Areas” 

Ord. No. 10-1-28 (a) “Driveways”

Ord. No. 10-2-1 (m)(6) “On-site Parking”

Ord. No. 4-3-12 (d)(1) 

All developed vehicular traffic areas, driveways, 

on-site parking areas, and off-site parking districts 

are required to be properly graded for drainage and 

surfaced with concrete, asphaltic concrete, or any 

other dust-free surface materials, and maintained in 

good condition, free of weeds, dust, trash, and 

debris

City of Durango’s Municipal Code 

Ord. No. 10-1-8 “Pollution”

Dust from developments is required to be 

effectively minimized to not be injurious to the 

neighborhood or detrimental to the general public

City of Durango’s Municipal Code 

Ord. No. 10-1-17 (f)(14)”Recycling Facilities”

Recycling facilities are permitted and encouraged 

for redemption and recycling of reusable materials 

in order to reduce litter. These facilities are not 

allowed to produce dust that is detectable on 

neighboring properties.

City of Durango’s Municipal Code 

Ord. No. 10-1-31 (l) (6) “Self-storage Facilities”

Self-storage facilities are prohibited for any use 

that produces dust or fumes

City of Durango’s Municipal Code 

Ord. No. 10-2-4 “Bicycle Parking Spaces”

The surfaces of all bicycle parking spaces do not 

have to be paved, but shall be finished to reduce 

mud and dust

City of Durango’s Municipal Code 

Ord. No. 10-5-14 (a)(6) “Campgrounds” 

All recreational campgrounds that have parking 

spaces and interior roads are required to be paved 

or treated to reduce dust

City of Durango’s Municipal Code 

Ord. No. 10-10-16 (c)(11) (e)

Construction sites are required to evaluate and 

control dust pollutants for runoff potential

City of Durango’s Municipal Code 

Ord. No. 10-10-16 (y)(1)(d)

Construction sites are required to have an erosion 

control plan for gravel, sand, dirt, or topsoil 

removal

City of Durango’s Municipal Code 

Ord. No. 2000-10, § 1, 5-2-00 

All work in the public right-of-way shall control 

dust and debris and promptly remove dirt and 

material deposited on roadways

City of Durango’s Municipal Code 

Ord. No. 6-2-1 (a)(4))

All planned residential districts must comply with 

dust ordinances and not be objectionable due to 
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Rule/Ordinance Description

dust emissions

La Plata County Land Use Code (LPLUC)2

Sec. 82-191-193 

Proposed developments must conduct a 

compatibility assessment, including a 

neighborhood meeting, if there is a potential to 

produce dust or significant dust influence. Possible 

solution for dust may include changing emitter 

specifications to mitigate problem. Dust emissions 

cannot have significant adverse impacts on 

neighbors. 

La Plata County Land Use Code (LPLUC)1

Sec. 82-167 (b)(3) 

Proposed multiple unit developments are required 

to contain and/or mitigate dust among other 

external nuisances.

La Plata County Land Use Code (LPLUC)1

Sec. 90-124 (c)(8) 

Roads and access driveways for all new facilities 

shall be constructed in a manner that suppresses 

dust through construction, drilling, and operational 

activities. Facilities that reduce or destroys existing 

vegetation may consult with the Soil Conservation 

Service (renamed the Natural Resources 

Conservation Service in 1994) and develop a revegetation plan, specifying particular species as 

well as appropriate planting schedules and methods

La Plata County Land Use Code (LPLUC)1

Sec. 74-174 (a)

Cattle guards are required to be kept clean of all 

sand, silt, dirt, and other solid debris.

The City of Durango, La Plata County, and the Southern Ute Indian Tribe have implemented dust control 

regulatory measures for numerous sources. Both the City and the County have a number of proactive 

programs that reduce dust from significant PM10 source categories in La Plata County. The following 

detail local dust control ordinances as of March 2012 for the Durango area: 

Street Sweeping and Sanding Controls 

The City of Durango performs street sweeping five days per week in the downtown area on a rotating 

basis and once every two months in residential areas. The City is responsible for street sweeping State 

Highways 550 and 160 that run through the City. In 2012, the City estimates sweeping an average of 

11,873 miles per year, running sweeper operations 2,130 hours, and removing 4,195 cubic yards of 

debris. The town of Bayfield in La Plata County performs street sweeping on town streets periodically. 

The City of Durango employs a Snow and Ice Division that uses street maintenance crews to remove 

snow and ice for 30% of their time. This Division de-ices major streets prior to snow with magnesium 

chloride (MgCl2). Streets are plowed and sanded according to priority (i.e. hazardous intersections, snow 

routes, downtown, and bus routes) after snowstorms. The City spends on average 2,968 hours per year 

plowing streets (as of 2012). The City estimates that it spends on average 979 hours sanding/salting 

streets (as of 2012). 

Dust Suppressant Program

La Plata County currently employs a dust suppressant program. The major focus of the program is to 

reduce dust from gravel roads. La Plata County has approximately 196 miles of paved roads and about 

490 miles of gravel roads. Approximately 220 centerline miles of gravel road are treated with about 

 

2 The LPLUC applies to all county lands, which includes the exterior boundaries of the Southern Ute Indian 

Reservation, except trust lands, in order to decrease nuisances from approved land uses.
109

950,000 million gallons of MgCl2 annually. The County typically begins application of MgCl2 in late 

April or early May, and continues as needed through September. In May and June (annually), roads not 

slated to receive new gravel are the first to be treated with MgCl2. During July through September 

(annually), other roads are treated, including roads being resurfaced, and those roads needing a second 

application. 

Landfills

La Plata County closed the Durango Landfill in 1990, and has been working with the Colorado 

Department of Public Health and Environment to ensure post-closure care and maintenance standards are 

met. These include, but are not limited to, minor grading to correct any erosion, maintenance of the 

surface drainage, and ground cover enhancement. 

The remaining landfill in La Plata County, Bondad Landfill, is located approximately 15 miles south of 

Durango within the exterior boundaries of the Southern Ute Indian Reservation, and has been in operation 

since 1997. The landfill is privately owned and operated by WCA Waste Corporation. 

The landfill has a fugitive dust emission control plan in its Part 71 permit currently enforced by the 

Environmental Protection Agency (EPA) (Region 8). 

On March 2, 2012, the Southern Ute Indian Tribe received full approval from EPA to administer its Part 

70 Operating Permit Program within the exterior boundaries of the Reservation. The Tribe is currently 

conducting the process of its Transition Plan to inform the Landfill (and other Title V sources) about the 

jurisdictional change. The Southern Ute Indian Tribe will transition Part 71 permits to the Tribe-issued 

Part 70 permits for all Reservation Title V sources. This transition process will take place over a threeyear period in accordance with the Tribe’s Transition Plan (found at: http://www.southernute-nsn.gov/airquality/part-70 ). The transition process is planned to be completed by March 2, 2015 (three years (36 

months) after the program was approved by EPA).

Durango Train Smoke Mitigation Task Force

The Durango and Silverton Narrow Gauge Railroad operates historic coal-fired steam locomotives from 

its yard located on the south-side of Durango. Because of the potential for thermal stress damage 

(cracking) to the antique boilers (greater than 100 years in age) from repeated cycling between cold and 

hot, they must idle throughout the night in order to be ready for use the next day, creating emissions from 

various pollutants. In 2001, the train operator installed scrubbers at the train yard roundhouse to control 

emissions from some of the locomotives while idling overnight. However, space limitations at the 

roundhouse prevented the operator from controlling all of the locomotives. 

In 2007, the train operator pledged to spend $1 million over 5 years to reduce emissions by 10% each 

year. The railroad employs several emission-reducing alternatives, including burning wood pellets instead 

of coal at night to keep engines warm, building a new ash pit in Silverton to reduce idle time in Durango 

in 2005, using diesel for all switching and track maintenance, and specialized training for engine firemen 

on how to place coal and wood pellets. Durango Service Clubs collaborated to completely offset the 

carbon footprint of the D&SNGRR through the purchase of Green Power through La Plata Electric 

Association. IN 2009, the Urban Reforestation Project to offset Greenhouse gas emissions associated with 

Railroad vehicle fleet planted 2,587 trees in Durango and Silverton. The planted trees also reduce wind 

erosion and blowing dust. 

There is a Train Smoke Mitigation Task Force that was created to proactively implement a responsible 

smoke mitigation program that maintains the railroad’s historic steam engine operations while reducing 

smoke and pollution. The Task Force began meeting in late 2005 to address public and neighborhood 

concerns. Currently as of 2013, the Train Smoke Mitigation Task Force is seeking funding to construct an 

expanded scrubber system, estimated at $1.2 million dollars. 
110

Vegetative Cover/Parks

The Durango Parks and Recreation Department removes sand, dirt, and organic debris from park roads, 

City parking lots, and hard surfaces twice a year and sweeps the hard surface trails monthly. There are 

14.49 miles of hard surface trails in Durango. The multi-use trails systems are either in completion or 

construction phases, which have multiple benefits, including reducing motor vehicle use and reducing 

fugitive dust from lengthy unpaved trails. The largest of these projects are the Animas River Trail (ART) 

and the Safe, Multi-Modal, Aesthetic, Regional Transportation trail aligning along Highway 160 

(SMART 160). The ART is an ongoing project to provide a 10 foot wide cement trail along the river 

corridor. Each year the City completes a new stage of the project as it is all cash funded. The SMART 160 

project is also ongoing. There is a large section of the walking trails that will be finished in the summer of 

2014. There are approximately 93.2 of natural surface unpaved trails in the open space surrounding 

Durango that are primarily dirt and native rock. 

The City of Durango built a new 15 acre soccer complex at 700 Talon Lane on the Fort Lewis College 

campus. It is called Smith Sports Complex and it is anticipated to open in the fall of 2013. The 15 acre 

site was previously open dirt (as shown in Figure 62) and now it is full covered with turf grass, parking, 

restroom facility and playground area. The complex including the 8-acre turf grass playing fields is 

irrigated. 

Figure 62: Site of the new Smith Sports Complex. (Google Earth 2011)

From 2010-2013, the Three Springs subdivision developer planted and irrigated the vegetation in the 

34.78 acre Three Springs Southern Open Space located at 700 Wilson Gulch Drive (shown in Figure 63). 

Additionally, the 15.28 acre Three Springs Confluence Park has been constructed in phases within the 

development at 100 Confluence Avenue (also shown in Figure 63).
111

Figure 63: Three Springs Southern Open Space and the Three Springs Confluence Park before Completion (Google 

Earth 2011)

Oil and Gas Exploration and Development Standards for Federal Lands

• La Plata County and the Southern Ute Indian Reservation contain oil and gas exploration and 

development sites. The Bureau of Land Management (BLM) and the Forest Service (FS) have 

surface operating standards and guidelines for oil and gas exploration and development (see: 

(http://www.blm.gov/pgdata/etc/medialib/blm/wo/MINERALS__REALTY__AND_RESOURCE

_PROTECTION_/energy/oil_and_gas.Par.18714.File.dat/OILgas.pdf ). These standards control 

dust from a number of contributing sources, including: 

• Road maintenance is required for all roads that will be constructed or used in conjunction with 

drilling. These maintenance plan activities include blading, surface replacement, dust abatement, 

spot repairs, slide removal, ditch cleaning, culvert cleaning, litter cleanup, noxious weed control, 

and snow removal. Key maintenance considerations include regular inspections; reduction of ruts 

and holes; maintenance of crowns and outslope to keep water off the road; replacement of 

surfacing materials; clearing of sediment blocking ditches and culverts; maintenance of interim 

reclamation; and noxious weed control (page 30). 

• Regarding BLM resource and FS local roads (page 25):

o The design speed limit on roads, specific to oil and gas roads, is 10 to 30 miles per hour. 

For the FS, this should generally be less than 15 miles per hour. 

o The road gradient should not exceed 8 percent except for pitch grades (300 feet or less in 

length) in order to minimize environmental effects. 

o Drainage control must be ensured over the entire road through the use of drainage dips, 

insloping, natural rolling topography, ditch turnouts, ditches, or culverts. 

• Regarding BLM local and FS collector roads (page 26):

o The design speed limit is generally 15 to 50 miles per hour. For the FS, it is 15 to 25 

miles per hour. 
112

o Maximum grades should not exceed 8 percent. Pitch grades for lengths not to exceed 300 

feet may be allowed to exceed 8 percent in some cases.

• Regarding BLM collector and FS arterial roads:

o Design speed is 30 miles per hour or greater unless otherwise directed.

o Maximum grades should not exceed 8 percent. Pitch grades for lengths not to exceed 300 

feet may be allowed to exceed 8 percent in some cases.

Windblown Dust from Disturbed Soils

Durango has a semi-arid climate with approximately 19 inches of precipitation annually. The town is 

located in southwest Colorado near the Four Corners area where New Mexico, Colorado, Utah, and 

Arizona connect at about 6,500 feet. In winter and spring, regional windstorms are common, especially in 

drier years. It is during these high velocity windstorms that Durango may experience PM10 issues. Figure 

3 illustrates potential areas of local soil disturbance that have been evaluated by the Division.

Figure 64: Relative positions of Durango PM10 Monitor and potential disturbed soil. (Image from Google Earth 2011)

Site A (approximately 2.5 acres) in Figure 64 is west of town at the north end of Tech Center Dr. This 

land is zoned by the City of Durango as “Industrial”. This site is a privately owned vacant lot. The land 

was once leveled and compacted but has since been allowed to return to its natural state. The site is 

naturally vegetated and the soil is very compacted. . Therefore, this lot is not considered to be 

anthropogenically disturbed soils and should be considered to be a natural source as of this writing. If 

future high wind or other exceptional events occur, the Division will re-assess this lot to determine if it 

should still be considered to be a natural source. 

Site B (approximately 11 acres) in Figure 64 is west of Roosa Ave, south of Ella Vita Court and east of 

the Greenmount Cemetery. This land is zoned by the City of Durango as “Planned Development”. The 

cemetery informed the Division that this land is open space that is naturally vegetated. Therefore, this lot 

A

B

C
113

is not considered to be anthropogenically disturbed soils and should be considered to be a natural source 

as of this writing. If future high wind or other exceptional events occur, the Division will re-assess this 

lot to determine if it should still be considered to be a natural source. 

Site C (approximately 35 acres) in Figure 64 is along the river to the south west of town. This land is 

zoned by the City of Durango as “Public”. Further investigation revealed that this site is the Durango 

Dog Park Off-Leash area. The park is comprised of scrublands with a natural surface trail and was 

converted from a city park into an off-leash area in 2003. A sign at the park's entrance and three signs 

around the park mark the border of the property. The park has no fencing but the Durango Director of 

Parks and Recreation notes the city has not experienced issues or air quality concerns within the park's 

natural boundaries of Smelter Mountain and the Animas River. 

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

Figure 64 were present during the 2010 exceedances. During the course of these assessments, the 

Division discovered that these sites were either reasonably controlled or considered to be natural sources 

during the April 5, 2010 high wind event. Therefore, these sites were not significant contributors to 

fugitive dust in the Durango area during the April 5, 2010 high wind event.
114

6.0 Summary and Conclusions

APCD is requesting concurrence on exclusion of the PM10 values from Alamosa-Adams State 

College (08-003-0001), Alamosa-Municipal Building (08-003-0003), and Pagosa Springs-Middle 

School (08-007-0001) on April 28, 2010. 

APCD is requesting concurrence on exclusion of the PM10 values taken at Pagosa Springs-Middle 

School (08-007-0001) and Durango-River City Hall (08-067-0004) on April 29, 2010.

Elevated 24-hour PM10 concentrations were recorded across Colorado on April 28 and 29, 2010. All of the 

noted April 28 and 29, 2010, twenty-four-hour PM10 concentrations were above the 90th percentile 

concentrations for their locations (see Table 24 and Table 25). The statistical data and meteorological 

analysis clearly shows that but for this high wind blowing dust event, Alamosa, Pagosa Springs, and 

Durango would not have exceeded the 24-hour NAAQS on April 28 and 29, 2010. Since at least 2005, 

there has not been an exceedance that was not associated with high winds carrying PM10 dust from distant 

sources in these areas. This is evidence that the event was associated with a measured concentration in 

excess of normal historical fluctuations including background. 

The PM10 exceedances in Alamosa, Pagosa Springs and Durango on April 28 and 29, 2010, would not 

have occurred if not for the following: (a) dry soil conditions over southeastern Utah, northeastern 

Arizona, portions of extreme northwestern New Mexico, and portions of southern Colorado with 30-day 

precipitation totals below the thresholds for blowing dust; (b) a strong surface and upper-level low 

pressure system that caused widespread strong gusty winds through a deep layer of the atmosphere over 

the area of concern; and (c) friction velocities over the desert regions of northwest New Mexico, Utah, 

Arizona and much of Colorado that were high enough to allow entrainment of dust from natural sources 

with subsequent transport of the dust into (or within) Colorado in strong, southwesterly winds.

Surface weather maps for the Four Corner States show evidence of widespread blowing dust and winds 

above the threshold speeds for blowing dust on April 28 and 29, 2010. These surface analyses show that 

wind speeds were as high as 53 mph and wind gusts were as high as 70 mph on April 28 and 29, 2010, 

occurred. These speeds are above the thresholds for blowing dust identified in EPA draft guidance and in 

detailed analyses completed by the State of Colorado. These PM10 exceedances were due to an 

exceptional event associated with regional windstorm-caused emissions from erodible soil sources over a 

large area of Arizona, northwest New Mexico, southeast Utah and southwest Colorado. These sources are 

not reasonably controllable during a significant windstorm under abnormally dry or moderate drought 

conditions.

The blowing dust climatology for the Four Corners area indicates that the area can be susceptible to 

blowing dust when winds are high. Landform imagery shows that northeastern Arizona and southeastern 

Utah in particular have experienced a long-term pattern of wind erosion and blowing dust when winds 

have been southwesterly and blowing into western and southern Colorado. Forecast products from the 

Navy Aerosol Analysis and Prediction System model provide evidence for a widespread blowing dust 

event in the Four Corners states, suggesting that significant source regions for dust transported into

Colorado were located in arid regions of Arizona, Utah, and New Mexico. NOAA HYSPLIT forward and 

backward trajectories provide clear supporting evidence that dust from desert regions of northwest New 

Mexico and Arizona caused the PM10 exceedances measured across portions of southwestern Colorado on 

April 28 and 29, 2010. Soils in the Four Corners area and in northeastern Arizona, southeastern Utah, and 

extreme northwestern New Mexico in particular were dry enough to produce blowing dust when winds 

were above the thresholds for blowing dust. 
115

Both wind speeds and soil moisture in the Four Corners area and northeastern Arizona were conducive to 

the generation of significant blowing dust. Soils in southeastern Utah, northwestern New Mexico, and 

northeastern Arizona in particular were dry enough to produce blowing dust when winds were above the 

thresholds for blowing dust. At these locations of concern wind speeds were as high as 53 mph and wind 

gusts were as high as 70 mph on April 28 and 29, 2010. But for the dust storm on April 28 and 29, 2010, 

this exceedance would not have occurred.

Friction velocities in wide area of northern Arizona, northwestern New Mexico, southeastern Utah, and 

southwestern Colorado had friction velocities above 1.0 meters per second during the second half of the 

day on April 28, 2010. Even undisturbed desert soils normally resistant to wind erosion will be 

susceptible to blowing dust when friction velocities are greater than about 1.0 to 2.0 meters per second.

Note that blowing dust will typically only occur where these values are high and the soils are dry and not 

protected by vegetation, forest cover, boulders, rocks, etc. This is why blowing dust occurred in the desert 

and more arid areas of Arizona, northwestern New Mexico, southeastern Utah, and southwestern 

Colorado on April 28 and 29, 2010. These elevated friction velocities (shown in Figure 34 and Figure 35) 

and the data on soil moisture conditions presented elsewhere in this report, and the prevalence of winds 

above blowing dust thresholds prove that this dust storm was a natural event that was not reasonably 

controllable or preventable.

MODIS and GOES satellite imagery shows that the Painted Desert and Four Corners area in general were 

source regions for the blowing dust that spanned April 28 and 29, 2010, 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 of this document. The observations of winds above 

blowing dust thresholds and restricted visibilities in the areas of concern demonstrate that this is a natural 

event that cannot be reasonably controlled or prevented. 

The Center for Snow and Avalanche Studies has been studying the effects of wind-blown desert dust from 

Arizona, New Mexico, and Utah on snowpack albedo and snowmelt in the San Juan Mountains of 

Colorado. The Center for Snow and Avalanche Studies lists April 28, 2010, as one of nine Dust-on-Snow 

events for the 2009/2010 water year, and this provides clear supporting evidence that a regional blowing 

dust event with long-range transport caused the PM10 exceedances measured across portions of Colorado 

on April 28, 2010. Snow cover data provide strong evidence that a widespread, regional, blowing dust 

event caused exceedances at these locations. In addition, scientists at the NOAA Satellite Services 

Division reported significant dust transport from northeastern Arizona and northwestern New Mexico into 

Colorado during this event. Friction velocities provide a measure of the near-surface meteorological 

conditions necessary to cause blowing dust. Friction velocities were high enough to sustain blowing dust 

over undisturbed soils in each of the Four Corners states during this event. But for the dust storm on April 

28 and 29, 2010, this exceedance would not have occurred.
116

7.0 References 

Colorado Department of Public Health and Environment, City of Lamar, Prowers County Commissioners, 

Natural Events Action Plan for High Wind Events – Lamar, Colorado, April 1998. 

Draxler, R.R. and Rolph, G.D., 2012. HYSPLIT (HYbrid Single-Particle Lagrangian Integrated 

Trajectory) Model access via NOAA ARL READY Website (http://ready.arl.noaa.gov/HYSPLIT.php). 

NOAA Air Resources Laboratory, Silver Spring, MD. 

Marticorena, B., G. Bergametti, D. Gillette, and J. Belnap, 1997, Factors controlling threshold friction 

velocity in semiarid and arid areas of the United States, Journal of Geophysical Research 102 D19, 

23,277-23, 287. 

Technical Services Program, Air Pollution Control Division, Colorado Department of Public Health and 

Environment, November 22, 2011,Technical Support Document for the January 19, 2009 Lamar 

Exceptional Event. 

United States Environmental Protection Agency, June 2012, draft 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. 
A-1 

Appendix A- Grand Junction, Colorado, Blowing Dust Climatology

January 24, 2012

There can be significant transport of regional blowing dust into Grand Junction from source regions in 

Utah and Arizona. While there are sources for wind-blown dust within the Grand Valley and Grand 

Junction itself, there is evidence from the analysis of soil features, wind and precipitation climatology, 

and statistical analyses of Grand Junction exceedances of the PM10 standard that regional sources often 

play a significant role during these blowing dust events. This document provides a weight of evidence 

analysis for dust transport into Colorado. 

Grand Junction, Colorado, is located in a part of the country that is largely arid to semi-arid. Figure A-1 

through A-3 show the annual average precipitation for Colorado, Arizona, and Utah, respectively. Grand 

Junction is in the Grand Valley of Western Colorado where the annual precipitation is typically less than 

10 inches. Northeastern Arizona, which is frequently upwind of Grand Junction during blowing dust 

events, receives between 5 and 15 inches of precipitation each year. The Colorado River Basin in eastern 

and southeastern Utah, which is also frequently upwind of Grand Junction during blowing dust events, 

also receives 5 to 10 inches per year.

Figure A-4 shows the 1971-2000 monthly normal precipitation amounts for Grand Junction, Colorado. 

The annual average for this time period is 8.99 inches. The wettest months are March through May and 

August through October. The driest months are January, February, June, July, November, and December. 

These months receive an average of 0.57 inches per month. The annual monthly average precipitation is 

0.75 inches. 

Arid to semi-arid soils make much of the region susceptible to blowing dust. The map in Figure A-5 

shows that portion of the Colorado Plateau (circled in red) where modern wind erosion features are 

common and clearly visible in Google Earth images. These features include longitudinal dunes and other 

sand or soil erosion structures with a predominant southwest to northeast orientation. This orientation is 

the result of the predominant southwesterly flow that occurs during high wind and blowing dust events in 

the region. Figures A-6 through A-12 present aerial views of ubiquitous erosion features in northeastern 

Arizona and southeastern Utah. The Painted Desert of northeastern Arizona is frequently the source for 

much of the blowing dust in the Four Corners region. Figure A-13 provides a particularly good satellite 

image of a blowing dust event originating in the Painted Desert and extending northeastward across the 

junction of the Four Corners (source: NASA Tera satellite, http://earthobservatory.nasa.gov/IOTD/view.php?id=37791). 

Strong southwesterly winds caused this blowing dust event. 

The text that accompanies this image on NASA’s Earth Observatory 10th Anniversary page follows 

below: 

“A dust storm struck northeastern Arizona on April 3, 2009. With winds over 145 kilometers (90 

miles) per hour reported near Meteor Crater, east of Flagstaff, the storm reduced visibility and 

forced the temporary closure of part of Interstate 40, according to The Arizona Republic.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite 

captured this image on April 3, 2009. Clear skies allow a view of multiple source points of this 

dust storm. The source points occur along an arc that runs from northwest to southeast. 

This dust storm occurred in the area known as Arizona’s Painted Desert, and the dust plumes 

show why. Whereas many dust plumes are uniform in color, these plumes resemble a band of 
A-2 

multicolored ribbons, ranging from pale beige to red-brown, reflecting the varied soils from 

which the plumes arise. The landscapes of the Painted Desert are comprised mostly of Chinle 

Formation rocks—remains of sediments laid down during the time of the first dinosaurs, over 200 

million years ago.” 
A-3 

Figure A-1. Average annual precipitation in Colorado based on 1961-1990 normals. 
A-4 

Figure A-2. Average annual precipitation in Arizona based on 1961-1990 normals. 
A-5 

Figure A-3. Average annual precipitation in Utah based on 1961-1990 normals. 
A-6 

Figure A-4. 1971-2000 monthly normal precipitation in Grand Junction Colorado. 

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1 2 3 4 5 6 7 8 9 10 11 12

Precipitation - Inches

Month

Grand Junction 1971-2000
A-7 

Figure A-5. The portion of the Colorado Plateau in Utah, Arizona, and New Mexico that exhibits 

widespread surface soil and sand erosion features in Google Earth imagery. Much of the highlighted area 

within Arizona is within the Painted Desert.

Figure A-6. Southwest to northeast soil and sand erosion structures in southeastern Utah. 

Figure A-7. Southwest to northeast soil and sand erosion structures in northeastern Arizona (Painted 

Desert).
A-8 

Figure A-8. Southwest to northeast soil and sand erosion structures in southeastern Utah. 

Figure A-9. Southwest to northeast soil and sand erosion structures in northeastern Arizona (Painted 

Desert). The slip faces of dunes (lighter bands) face in the direction of wind flow – toward the northeast.
A-9 

Figure A-10. Southwest to northeast soil and sand erosion structures in southeastern Utah. 

Figure A-11. Southwest to northeast soil and sand erosion structures in northeastern Arizona (Painted 

Desert). 
A-10

Figure A-12. Southwest to northeast soil and sand erosion structures in northeastern Arizona (Painted 

Desert).
A-11

Figure A-13. NASA Tera satellite image of a dust storm on April 3, 2009, in southwesterly flow over the 

Painted Desert of northeastern Arizona (http://earthobservatory.nasa.gov/IOTD/view.php?id=37791). 
A-12

Figure A-14 displays the surface weather map for this event (00Z April 4, 2009, or 5 PM MST April 3, 

2009). A strong low pressure system in southern Colorado, strong southwesterly winds in the Four 

Corners area, and the blowing dust symbol (infinity sign) at Farmington (New Mexico) and Cortez 

(Colorado) are evident in this map. Blowing dust in this region is frequently associated with 

southwesterly flow. 

Figure A-14. Surface weather map for 00Z April 4, 2009, (5 PM MST April 3, 2009), showing a strong 

low pressure system in southern Colorado, strong southwesterly winds in the Four Corners area and the 

blowing dust symbol (infinity sign) at Farmington (New Mexico) and Cortez (Colorado). 

A USGS map of the Colorado Plateau in Figure A-15 shows the prevalence of eolian or wind-blown sand 

deposits in southeastern Utah and northeastern Arizona. An analysis of the annual frequency of dust 

storms (Orgill and Sehmel, 1976) in the western half of the U.S. suggests that portions of eastern and 

western Utah and northeastern Arizona are source regions for blowing dust (see Figure A-16). Soil and 

sand structures point to the prevalence of southwesterly flow during blowing dust events, and 

precipitation climatology highlights the potential for blowing dust across much of the region. In 

addition, an analysis of back trajectories associated with high PM10 concentration events in Grand 

Junction discussed in the next section of this document supports the conclusion that soils in Arizona and 
A-13

Utah are likely significant contributors to PM10 measured during many dust storms affecting Grand 

Junction. 
A-14

Figure A-15. USGS map of eolian sand features on the Colorado Plateau 

(http://geochange.er.usgs.gov/sw/impacts/geology/sand/ ).

Figure A-16. Number of dust storms per year from: Orgill, M.M., Sehmel, G.A., 1976. Frequency and 

diurnal variation of dust storms in the contiguous USA. Atmospheric Environment 10, 813–825. 

NOAA HYSPLIT 36-hour back trajectories were calculated for Grand Junction for the eight 24-hour 

periods from 2004 through early 2009 with the Powell monitor PM10 concentrations in excess of 75 

μg/m3

, strong regional winds, and dry soils. Trajectories were modeled every 4 hours for each day. Data 

presented later in this document provides evidence that the moderate to high PM10 levels on these days 

were from blowing dust. The 6 back trajectories for each day were calculated for an arrival height of 500 

meters using EDAS40 data and model vertical velocities (see: http://www.arl.noaa.gov/HYSPLIT.php ). 

The eight days used in the analysis and the Powell monitor concentrations measured on these days are 

presented in Table A-1. 
A-15

The back trajectories for these high-concentration days are shown in Figure A-17. Transport was 

generally from the west through southwest. A high density of trajectory points is found in northeast 

Arizona and southeast Utah. Most of these trajectories in Figure A-17 are also consistent with transport 

from or across suspected or known blowing dust source regions highlighted in Figures A-5, A-13, A-15, 

and A-16. 

Table A-1. Grand Junction Powell monitor days with concentrations in excess of 75 μg/m3

 and blowing 

dust conditions (from 2004 through early 2009). 

Year Month Day

Powell 24-hour PM10 concentration 

in μg/m3

2005 4 19 197.8 

2008 4 15 116.1 

2008 4 21 103.6

2004 9 3 102

2006 3 3 98.3

2008 5 21 86.7 

2008 4 30 83.5

2006 6 7 77.9

Figure A-17. NOAA HYSPLIT 36-hour back trajectories for Grand Junction for those eight 24-hour periods from 

2004 through early 2009 with the Powell monitor PM10 concentrations in excess of 75 μg/m3

, strong regional 
A-16

winds, and dry soils. Trajectory points are sized and color-coded to reflect 24-hour PM10 concentrations in μg/m3. 

Trajectories were calculated every 4 hours for each day. 

The trajectories in Figure A-17 point to the possibility that, at times, dust from Utah and Arizona can have a 

major impact on Grand Junction and less of an impact elsewhere in western Colorado. This non-homogeneity is 

possible given the fact that dust storms are frequently organized into discreet plumes from discreet areas that 

maintain their integrity for long distances. An example of this can be seen in Figure A-18 that shows plumes of 

dust in New Mexico during a windstorm on May 20, 2008. 

Figure A-19 shows the NOAA HYSPLIT back trajectories for the highest concentration day during the 2004 

through early 2009 period: April 19, 2005. Twenty-four hour back trajectories for each hour during the period 

with high winds (using EDAS40 data and 500-meter arrival heights) show that the back trajectories for Grand 

Junction were more likely to have crossed the Painted Desert and southeastern Utah than those for Telluride and 

Durango, which measured lower PM10 concentrations on this day. 

Figure A-18. Discreet plumes of blowing dust in New Mexico, Mexico, and Arizona visible in GOES satellite 

imagery for May 20, 2008 (http://www.osei.noaa.gov/Events/Dust/US_Southwest/2008/DSTusmx142_G12.jpg ).

K-means cluster analysis has been applied to Grand Junction Powell PM10 concentrations, Grand Junction and 

Painted Desert 30-day total precipitation for each PM10 monitoring day, and Grand Junction and Painted Desert 

daily maximum wind gust speeds for each monitoring day. K-means cluster analysis is a statistical method for 
A-17

identifying clusters or groupings of values for many variables. For environmental variables, these clusters often 

represent distinct processes, conditions, or events. In this case, cluster analysis differentiates PM10 concentrations 

associated with strong winds, low soil moistures, and blowing dust by providing mean values for these 5 variables 

for 5 distinct categories of PM10 events. The period of record considered was from January 2004 through March 

2009. The Hopi weather station located in the central portion of the Painted Desert was used to represent Painted 

Desert conditions in northeastern Arizona, and the Grand Junction National Weather Service station was used to 

represent Grand Junction conditions. The 30-day total precipitation values appear to be a better metric for 

blowing dust conditions than shorter-term totals. 

Figure A-19. 24-hour NOAA HYSPLIT back trajectories for every hour from 1500 MST to 2200 MST for Grand 

Junction (red), Telluride (green), and Durango (blue) for the dust storm of April 19, 2005. 

The results of the cluster analysis are presented in Table A-2 below. Cluster 1 represents high soil moisture 

conditions, moderate gust speeds, and low PM10 concentrations. Cluster 2 represents very low soil moisture, 

moderate PM10, and low gust speeds. Cluster 3 represents low soil moisture, moderate gusts, and low PM10. 

Cluster 4 represents moderate soil moisture, low gusts, and low PM10. Finally, Cluster 5 represents high PM10, 

high gusts, and low soil moisture. Cluster numbers, Grand Junction Powell PM10 concentrations, and Grand 

Junction daily maximum gust speeds are plotted in Figure A-20. 

The data in Figure A-20 clearly show that the highest PM10 concentrations tend to occur in Cluster 5 with gusts 

above 40 mph. The only exceedance in this period occurred on a day with a peak gust of 43 mph. Cluster 2 is 
A-18

likely to be indicative of wintertime inversion conditions with lighter winds and moderately elevated PM10. Figure 

A-21 shows the concentrations and cluster values associated with Hopi station daily maximum gust speeds. The 

overall pattern is similar. The highest concentration day is associated with a peak gust of 47 mph at Hopi. All of 

the days/events presented in Figure A-17, A-19, and Table A-1 were classified as Cluster 5.

Table A-2. K-means cluster analysis means for Grand Junction PM10 and meteorological variables.

Cluster Variables

Cluster 1 

Means

Cluster 2 

Means

Cluster 3

Means

Cluster 4

Means

Cluster 5

Means

Powell 24-hour PM10 in μg/m3 24.5 37.3 24.3 21.8 74.9

Hopi Wind Gust in mph 20.8 18.0 32.5 20.7 40.5

Grand Junction Wind Gust in mph 20.4 16.5 31.8 19.6 43.1

Grand Junction 30-day 

Precipitation 1.7 0.4 0.5 0.8 0.6

Hopi 30-day Precipitation 1.8 0.2 0.5 0.7 0.3

Count 85 120 170 147 24

Figure A-20. Grand Junction Powell 24-hour PM10 concentrations versus Grand Junction gust speed by 

cluster.

Figures A-22 and A-23 show Powell PM10 concentrations versus Grand Junction and Hopi 30-day 

precipitation totals, respectively, by cluster. The blowing dust group, Cluster 5, is generally associated 

with 30-day precipitation totals of less than 1.00 inches at Grand Junction and less than 0.50 inches at 

Hopi. While this is not proof that the measured dust in Grand Junction is from Arizona, it adds to the 

weight of evidence that the Painted Desert makes a significant contribution to PM10 concentrations in 

0

50

100

150

200

250

051015202530354045505560

Grand Junction Gust Speed in mph

Grand Junction Powell 24-hr PM10 - ug/m3

Clusters

1

4

2

3

5
A-19

Grand Junction during many blowing dust events. Of interest in this regard are the two high 

concentrations (greater than 100 μg/m3

) that occurred when Grand Junction 30-day precipitation totals 

were greater than an inch (see Figure A-22). One of these occurred when transport was from the 

southwest. On this day (April 21, 2008) the NOAA Satellite Smoke Text Archive reported the following 

(see http://www.ssd.noaa.gov/PS/FIRE/smoke.html ):

“Blowing dust is seen over most of Utah (and part of western Nevada) and the dust is moving toward the 

northeast, reaching into northwestern Colorado and southern Wyoming.” 

Figure A-21. Grand Junction Powell 24-hour PM10 concentrations versus Hopi gust speed by cluster.

0

50

100

150

200

250

051015202530354045505560

Hopi Gust Speed in mph

Grand Junction Powell 24-hr PM10 - ug/m3

Clusters

3

4

5

1

2
A-20

Figure A-22. Grand Junction Powell 24-hour PM10 concentrations versus Grand Junction 30-day total 

precipitation by cluster. 

Figure A-23. Grand Junction Powell 24-hour PM10 concentrations versus Hopi 30-day total precipitation 

by cluster.

0

50

100

150

200

250

0.0000.2500.5000.7501.0001.2501.5001.7502.0002.2502.5002.7503.000

Grand Junction 30-day Precipitation in Inches Grand Junction Powell 24-hr PM10 - ug/m3

Clusters

4

2

3

1

5

0

50

100

150

200

250

0.0000.2500.5000.7501.0001.2501.5001.7502.0002.2502.5002.7503.000

Hopi 30-day Precipitation in Inches

Grand Junction Powell 24-hr PM10 - ug/m3

Clusters

3

4

5

1

2
A-21

The other occurred on April 15, 2008, when the flow was from Arizona and southeast Utah. The transport 

conditions, the discrepancy between high recent precipitation in Grand Junction and low recent precipitation at 

Hopi for these two days, and, in one case, analyst discussion of what was visible in satellite images suggest that 

much of the dust might have originated from outside of the Grand Junction environment. 

Figure A-24 shows Grand Junction Powell 24-hour PM10 concentrations versus peak gust wind directions at the 

Little Delores RAWS weather station about 25 miles west-southwest of Grand Junction. Grand Junction is 

situated on the floor of the Grand Valley, a major northwest to southeast trending basin than can force or channel 

synoptic scale flows. As a result, surface wind directions in Grand Junction may not be useful indicators of the 

direction of longer-range transport. Little Delores is on the Umcompahgre Plateau, and winds here are more 

likely to reflect the larger-scale transport directions for the region. This graph indicates that high PM10 at Grand 

Junction (Cluster 5) is associated with winds from the south-southeast to west-southwest at Little Delores. These 

directions point to dust sources in southeast Utah and northeastern Arizona. This is further evidence that dust 

from these areas may make a significant contribution to PM10 measured in Grand Junction during blowing dust 

events.

Figure A-24. Grand Junction Powell 24-hour PM10 concentrations versus peak gust wind directions at the Little 

Delores RAWS weather station, by cluster.

Figure A-25 presents monthly percentiles for Grand Junction gust speeds. Wind gusts generally considered to be 

high enough for significant blowing dusts (40 mph or higher) are within the upper 5 to 15 percent during each 

month of the year. Consequently, these events can be viewed as exceptional rather than normal. Gusts in this 

category can occur any month of the year, but are most likely in March, April, May and October. Figure A-4 

shows that in Grand Junction these are typically among the wettest months of the year. It is in drier years, 

therefore, that blowing dust may be most prevalent during the spring and fall months. January, February, and 

June are typically very dry, and might be expected to have a significant proportion of blowing dust events. 

0

50

100

150

200

250

0306090120150180210240270300330360

Little Delores Gust Direction

Grand Junction Powell 24-hr PM10 - ug/m3

Clusters

1

4

2

3

5
A-22

Figures A-26 and A-27 show histograms for Grand Junction and Hopi wind gusts, respectively. The 95th

percentile gust speed for Grand Junction is 43 mph. For Hopi it is 41 mph. For both sites, it is clear that gusts in 

the range that is associated with blowing dust are the exception rather than the rule. Cluster analysis also shows 

that the blowing dust events represent only 4% of the PM10 sample days (from Table A-2, Cluster 5 had 24 cases 

out of a total of 546). The weight of evidence presented in this document clearly suggests that source regions in 

Arizona and Utah can have a significant impact on PM10 concentrations in Grand Junction during blowing dust 

events and that these events occur when dry soils are affected by winds of exceptional strength. Control of these 

sources, which are outside of Colorado, may not be reasonably achievable or possible.

The precipitation climatology for the Four Corners area indicates that the area can be susceptible to blowing 

dust when winds are high. Landform imagery shows that northeastern Arizona and southeastern Utah in 

particular have experienced a long-term pattern of wind erosion and blowing dust when winds have been 

southwesterly and blowing into western and southern Colorado. Back trajectories, case studies, satellite 

imagery, and statistical analyses have also shown that northeastern Arizona and southeastern Utah are a 

significant source for blowing dust transported into Colorado. Elevated PM10 in Grand Junction during 

windstorms is generally associated with wind gusts of 40 mph or higher at Grand Junction and Hopi in 

northeastern Arizona and southwesterly flow in Grand Junction. Elevated PM10 in Grand Junction is generally 

associated with 30-day precipitation totals of less than 1.00 inches at Grand Junction and less than 0.50 inches at Hopi.

Reference:

Orgill, M.M., Sehmel, G.A., 1976. Frequency and diurnal variation of dust storms in the contiguous USA. 

Atmospheric Environment 10, 813–825 

Figure A-25. Percentile plot of Grand Junction daily maximum 5-second gust speed in miles per hour 

showing that gusts of 40 mph or greater always occur within the top 15 percentile speeds for each month 

of the year.

0

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10 11 12

Percentile Plot

Grand Junction Daily Max 5-second Gust in mph

Month

Gust Speed in mph

Top 15% in Red, Lower 15% in Blue, Median Orange

January 2004-February 2009
A-23

Figure A-26. Histogram of daily maximum 5-second wind gusts at Grand Junction based on January 2004 – 

February 2009. 

Figure A-27. Histogram of daily maximum 5-second wind gusts at Hopi based on January 2004 – February 2009.

0

71

143

214

286

357

429

500

0 10 20 30 40 50 60 70

Daily Max 5-second Gust in mph

Count

0

43

86

129

171

214

257

300

0 10 20 30 40 50 60 70

Daily Max Gust in mph

Count
B-1 

Appendix B- Weather Warnings and Blowing Dust Advisories for April 

28 and 29, 2010

 

WWUS75 KABQ 281034

NPWABQ

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE ALBUQUERQUE NM

434 AM MDT WED APR 28 2010

...DANGEROUSLY WINDY CONDITIONS DEVELOPING ACROSS NEW MEXICO

WEDNESDAY AND THURSDAY...

.A VIGOROUS PACIFIC STORM SYSTEM MOVING OVER CENTRAL CALIFORNIA

WEDNESDAY MORNING WILL DIVE RAPIDLY TO CENTRAL ARIZONA BY

THURSDAY...AS SURFACE LOW PRESSURE DEEPENS STEADILY OVER EASTERN

COLORADO. STRONG SOUTHWEST WINDS WILL DEVELOP BY LATE WEDNESDAY

ACROSS NEW MEXICO...WITH DANGEROUS GUSTS DEVELOPING BY WEDNESDAY

AFTERNOON. WIND SPEEDS WILL DECREASE ONLY GRADUALLY

OVERNIGHT BEFORE REDEVELOPING ONCE AGAIN ON THURSDAY OVER MUCH OF

THE STATE. WIND SPEEDS WILL DECREASE THURSDAY EVENING TO EASE

THESE DANGEROUS WIND CONDITIONS.

NMZ532-533-281800- 

/O.UPG.KABQ.WI.Y.0022.100428T1800Z-100429T0200Z/

/O.EXA.KABQ.HW.W.0006.100428T1800Z-100429T0200Z/

/O.CON.KABQ.HW.A.0007.100429T1500Z-100430T0300Z/

EASTERN SAN MIGUEL COUNTY-GUADALUPE COUNTY434 AM MDT WED APR 28 2010

...HIGH WIND WARNING IN EFFECT FROM NOON TODAY TO 8 PM MDT THIS

EVENING...

...HIGH WIND WATCH REMAINS IN EFFECT FROM THURSDAY MORNING

THROUGH THURSDAY EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WARNING...WHICH IS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING. THE WIND ADVISORY IS NO LONGER IN EFFECT. A HIGH

WIND WATCH REMAINS IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING. 

* LOCATION...EXPECT STRONG WINDS ACROSS INTERSTATE 40 FROM MILAGRO

 TO MONTOYA...OR FROM MILE POST 24O TO MILE POST 310...AND ACROSS

 STATE ROAD 104 NEAR CONCHAS LAKE STATE PARK. EXPECT STRONGEST

 WINDS ACROSS HILLTOPS AND THROUGH GAPS.

* WINDS...SOUTHWEST WIND SPEEDS WILL INCREASE TO 40 MPH...WITH

 GUSTS TO 60 MPH. SPEEDS WILL DECREASE TO 35 MPH WITH GUSTS TO 50

 MPH OVERNIGHT. ON THURSDAY...WIND SPEEDS WILL REDEVELOP TO 45

 MPH...WITH GUSTS TO 65 MPH.

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL
B-2 

 DECREASE OVERNIGHT...WITH HAZARDOUS WIND SPEEDS REDEVELOPING

 THURSDAY MORNING. WIND SPEEDS WILL DECREASE THURSDAY

 EVENING TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO A MILE

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

REMEMBER...A HIGH WIND WATCH MEANS CONDITIONS ARE FAVORABLE FOR

A POTENTIALLY DAMAGING HIGH WIND EVENT IN AND CLOSE TO THE WATCH

AREA. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR GUSTS OF 58 MPH

OR MORE CAN LEAD TO PROPERTY DAMAGE. MONITOR THE LATEST FORECASTS

AT WEATHER.GOV/ABQ...LISTEN TO NOAA WEATHER RADIO OR YOUR

FAVORITE MEDIA OUTLET.

&&

$$

NMZ510-516-281800- 

/O.UPG.KABQ.WI.Y.0022.100428T1800Z-100429T0200Z/

/O.EXA.KABQ.HW.W.0006.100428T1800Z-100429T0200Z/

/O.EXA.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

SAN JUAN MOUNTAINS-UPPER RIO GRANDE VALLEY434 AM MDT WED APR 28 2010

...HIGH WIND WARNING IN EFFECT FROM NOON TODAY TO 8 PM MDT THIS

EVENING...

...HIGH WIND WATCH IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WARNING...WHICH IS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING. A HIGH WIND WATCH HAS ALSO BEEN ISSUED. THIS HIGH

WIND WATCH IS IN EFFECT FROM THURSDAY MORNING THROUGH THURSDAY

EVENING. THE WIND ADVISORY IS NO LONGER IN EFFECT. 

* LOCATION...EXPECT STRONG WINDS ACROSS RIO ARRIBA AND TAOS

 COUNTIES...ESPECIALLY ALONG HIGHWAYS 64 AND 84...AND HIGHWAY

 285. EXPECT STRONGEST WINDS OVER SUMMITS AND THROUGH GAPS.

* WINDS...SOUTHWEST WIND SPEEDS WILL INCREASE TO 40 TO 45 MPH WITH

 DANGEROUS GUSTS TO 65 MPH ON WEDNESDAY. WIND SPEEDS WILL

 DECREASE TO 35 MPH OVERNIGHT BEFORE REDEVELOPING TO 40 MPH WITH

 GUSTS TO 60 MPH ON THURSDAY.
B-3 

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT...WITH HAZARDOUS WIND SPEEDS REDEVELOPING

 THURSDAY MORNING. WIND SPEEDS WILL DECREASE THURSDAY

 EVENING TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO A MILE

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

REMEMBER...A HIGH WIND WATCH MEANS CONDITIONS ARE FAVORABLE FOR

A POTENTIALLY DAMAGING HIGH WIND EVENT IN AND CLOSE TO THE WATCH

AREA. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR GUSTS OF 58 MPH

OR MORE CAN LEAD TO PROPERTY DAMAGE. MONITOR THE LATEST FORECASTS

AT WEATHER.GOV/ABQ...LISTEN TO NOAA WEATHER RADIO OR YOUR

FAVORITE MEDIA OUTLET.

&&

$$

NMZ523-524-526-281800- 

/O.UPG.KABQ.WI.Y.0022.100428T1800Z-100429T0200Z/

/O.EXA.KABQ.HW.W.0006.100428T1800Z-100429T0200Z/

/O.CON.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

CENTRAL HIGHLANDS-SOUTH CENTRAL HIGHLANDS-SOUTH CENTRAL MOUNTAINS434 AM MDT WED APR 28 2010

...HIGH WIND WARNING IN EFFECT FROM NOON TODAY TO 8 PM MDT THIS

EVENING...

...HIGH WIND WATCH REMAINS IN EFFECT FROM THURSDAY MORNING

THROUGH THURSDAY EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WARNING...WHICH IS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING. THE WIND ADVISORY IS NO LONGER IN EFFECT. A HIGH

WIND WATCH REMAINS IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING. 

* LOCATION...EXPECT HAZARDOUS WINDS ACROSS INTERSTATE 40 FROM NEAR

 MORIARTY TO MILAGRO...OR FROM MILE POST 200 TO MILE POST

 240...ACROSS HIGHWAY 60 NEAR ENCINO AND DURAN...HIGHWAY 54 NEAR

 CORONA AND ANCHO...AND HIGHWAYS 70 AND 380 ACROSS SOUTHERN

 LINCOLN COUNTY. EXPECT STRONGEST WINDS ACROSS SUMMITS AND
B-4 

 HILLTOPS...AND THROUGH GAPS.

* WINDS...SOUTHWEST WIND SPEEDS WILL INCREASE TO 40 TO 45

 MPH...WITH GUSTS TO 60 TO 65 MPH DEVELOPING ON WEDNESDAY. WIND

 SPEEDS WILL DECREASE TO 35 MPH WITH GUSTS TO 50 MPH OVERNIGHT

 BEFORE REDEVELOPING THURSDAY TO 45 MPH WITH GUSTS TO 65 TO 70

 MPH. 

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT...WITH HAZARDOUS WIND SPEEDS REDEVELOPING

 THURSDAY MORNING. WIND SPEEDS WILL DECREASE THURSDAY

 EVENING TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO A MILE

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

REMEMBER...A HIGH WIND WATCH MEANS CONDITIONS ARE FAVORABLE FOR

A POTENTIALLY DAMAGING HIGH WIND EVENT IN AND CLOSE TO THE WATCH

AREA. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR GUSTS OF 58 MPH

OR MORE CAN LEAD TO PROPERTY DAMAGE. MONITOR THE LATEST FORECASTS

AT WEATHER.GOV/ABQ...LISTEN TO NOAA WEATHER RADIO OR YOUR

FAVORITE MEDIA OUTLET.

&&

$$

NMZ501-281800- 

/O.UPG.KABQ.WI.Y.0022.100428T1800Z-100429T0200Z/

/O.EXA.KABQ.HW.W.0006.100428T1800Z-100429T0200Z/

NORTHWEST PLATEAU434 AM MDT WED APR 28 2010

...HIGH WIND WARNING IN EFFECT FROM NOON TODAY TO 8 PM MDT THIS

EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WARNING...WHICH IS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING. THE WIND ADVISORY IS NO LONGER IN EFFECT. 

* LOCATION...EXPECT HAZARDOUS WINDS ACROSS MUCH OF SAN JUAN

 COUNTY...INCLUDING HIGHWAY 64 NEAR SHIPROCK...FARMINGTON...AND

 BLOOMFIELD...AND HIGHWAYS 491 AND 550...AND STATE ROAD 371.
B-5 

 EXPECT STRONGEST WINDS OVER HILLTOPS AND THROUGH GAPS.

* WINDS...SOUTHWEST WIND SPEEDS WILL INCREASE STEADILY TO 40 MPH

 WITH FREQUENT GUSTS TO 60 MPH.

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO TWO MILES 

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

&&

$$

NMZ506-281800- 

/O.EXA.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

/O.CON.KABQ.HW.W.0006.100428T1800Z-100429T0200Z/

WEST CENTRAL MOUNTAINS434 AM MDT WED APR 28 2010

...HIGH WIND WARNING REMAINS IN EFFECT FROM NOON TODAY TO 8 PM

MDT THIS EVENING...

...HIGH WIND WATCH IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WATCH...WHICH IS IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING. A HIGH WIND WARNING REMAINS IN EFFECT FROM NOON

TODAY TO 8 PM MDT THIS EVENING. 

* LOCATION...EXPECT DANGEROUSLY GUSTY WINDS ACROSS INTERSTATE 40

 FROM CHURCH ROCK TO BLUEWATER...OR FROM MILE POST 30 TO MILE

 POST 70...AND ACROSS STATE ROAD 53 NEAR EL MORRO...AND STATE

 ROAD 117 NEAR ACOMA PUEBLO AND EL MALPAIS NATIONAL MONUMENT.

 EXPECT STRONGEST WINDS ACROSS SUMMITS AND HILLTOPS...AND THROUGH

 GAPS.

* WINDS...EXPECT SOUTHWEST WINDS INCREASING TO 45 MPH...WITH GUSTS

 TO 65 MPH TODAY. WIND SPEEDS WILL DECREASE TO 35 MPH OVERNIGHT.

 ON THURSDAY...WIND SPEEDS WILL INCREASE TO 45 MPH WITH GUSTS TO

 65 MPH.
B-6 

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT...WITH HAZARDOUS WIND SPEEDS REDEVELOPING

 THURSDAY MORNING. WIND SPEEDS WILL DECREASE THURSDAY

 EVENING TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO TWO MILES 

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

REMEMBER...THE HIGH WIND WATCH THURSDAY MEANS CONDITIONS ARE

FAVORABLE FOR A POTENTIALLY DAMAGING HIGH WIND EVENT IN AND CLOSE

TO THE WATCH AREA. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE. MONITOR THE

LATEST FORECASTS AT WEATHER.GOV/ABQ...LISTEN TO NOAA WEATHER

RADIO OR YOUR FAVORITE MEDIA OUTLET.

&&

$$

NMZ527-528-530-531-281800- 

/O.EXA.KABQ.HW.A.0007.100429T1500Z-100430T0300Z/

/O.CON.KABQ.HW.W.0006.100428T1800Z-100429T0200Z/

RATON RIDGE/JOHNSON MESA-FAR NORTHEAST HIGHLANDS-UNION COUNTYHARDING COUNTY434 AM MDT WED APR 28 2010

...HIGH WIND WARNING REMAINS IN EFFECT FROM NOON TODAY TO 8 PM

MDT THIS EVENING...

...HIGH WIND WATCH IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WATCH...WHICH IS IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING. A HIGH WIND WARNING REMAINS IN EFFECT FROM NOON

TODAY TO 8 PM MDT THIS EVENING. 

* LOCATION...EXPECT DANGEROUS WINDS TODAY AND THURSDAY ACROSS

 INTERSTATE 25 FROM VALMORA AND WATROUS TO THE COLORADO LINE AT

 RATON PASS...OR FROM MILE POST 360 TO MILE POST 470...AND ACROSS

 HIGHWAYS 64 AND 87...HIGHWAYS 56 AND 412...AND STATE ROAD 39.

* WINDS...SOUTHWEST WINDS WILL INCREASE TO 45 MPH BOTH WEDNESDAY

 AND THURSDAY...WITH GUSTS REACHING 60 TO 65 MPH EACH AFTERNOON.
B-7 

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT...WITH HAZARDOUS WIND SPEEDS REDEVELOPING

 THURSDAY MORNING. WIND SPEEDS WILL DECREASE THURSDAY

 EVENING TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO TWO MILES 

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

REMEMBER...THE HIGH WIND WATCH THURSDAY MEANS CONDITIONS ARE

FAVORABLE FOR A POTENTIALLY DAMAGING HIGH WIND EVENT IN AND CLOSE

TO THE WATCH AREA. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE. MONITOR THE

LATEST FORECASTS AT WEATHER.GOV/ABQ...LISTEN TO NOAA WEATHER

RADIO OR YOUR FAVORITE MEDIA OUTLET.

&&

$$

NMZ512>515-281800- 

/O.EXA.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

/O.CON.KABQ.HW.W.0006.100428T1800Z-100429T0200Z/

WEST SLOPES SANGRE DE CRISTO MOUNTAINSNORTHERN SANGRE DE CRISTO MOUNTAINS ABOVE 9500 FEET/RED RIVERSOUTHERN SANGRE DE CRISTO MOUNTAINS ABOVE 9500 FEETEAST SLOPES SANGRE DE CRISTO MOUNTAINS434 AM MDT WED APR 28 2010

...HIGH WIND WARNING REMAINS IN EFFECT FROM NOON TODAY TO 8 PM

MDT THIS EVENING...

...HIGH WIND WATCH IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WATCH...WHICH IS IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING. A HIGH WIND WARNING REMAINS IN EFFECT FROM NOON

TODAY TO 8 PM MDT THIS EVENING. 

* LOCATION...EXPECT DANGEROUS WINDS ACROSS THE SANGRE DE CRISTO

 MOUNTAINS...WITH STRONGEST WINDS OVER SUMMITS AND THROUGH GAPS

 AND PASSES. EXPECT DANGEROUS WINDS ACROSS HIGHWAY 64 NEAR ANGEL

 FIRE AND EAGLE NEST...STATE ROAD 38...AND STATE ROAD 434.
B-8 

* WINDS...SOUTHWEST WINDS WILL INCREASE TO 40 TO 45 MPH...WITH

 GUSTS TO 60 TO 65 MPH DEVELOPING TODAY. WIND SPEEDS WILL

 DECREASE TO 35 MPH OVERNIGHT BEFORE WIND SPEEDS RETURN TO 40 TO

 45 MPH WITH GUSTS TO 60 TO 65 MPH ON THURSDAY.

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT...WITH HAZARDOUS WIND SPEEDS REDEVELOPING

 THURSDAY MORNING. WIND SPEEDS WILL DECREASE THURSDAY

 EVENING TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO TWO MILES 

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

REMEMBER...THE HIGH WIND WATCH THURSDAY MEANS CONDITIONS ARE

FAVORABLE FOR A POTENTIALLY DAMAGING HIGH WIND EVENT IN AND CLOSE

TO THE WATCH AREA. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE. MONITOR THE

LATEST FORECASTS AT WEATHER.GOV/ABQ...LISTEN TO NOAA WEATHER

RADIO OR YOUR FAVORITE MEDIA OUTLET.

&&

$$

NMZ529-281800- 

/O.CON.KABQ.HW.W.0006.100428T1800Z-100429T0200Z/

/O.CON.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

NORTHEAST HIGHLANDS434 AM MDT WED APR 28 2010

...HIGH WIND WARNING REMAINS IN EFFECT FROM NOON TODAY TO 8 PM

MDT THIS EVENING...

...HIGH WIND WATCH REMAINS IN EFFECT FROM THURSDAY MORNING

THROUGH THURSDAY EVENING...

A HIGH WIND WARNING REMAINS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING. A HIGH WIND WATCH REMAINS IN EFFECT FROM THURSDAY

MORNING THROUGH THURSDAY EVENING. 

* LOCATION...EXPECT DANGEROUS WINDS ACROSS INTERSTATE 40 FROM

 RIBERA TO WATROUS...OR FROM MILE POST 320 TO MILE POST 365...AND

 ACROSS STATE ROAD 104. EXPECT STRONGEST WINDS OVER HILLTOPS AND
B-9 

 THROUGH GAPS.

* WINDS...SOUTHWEST WINDS WILL INCREASE TO 45 MPH WITH GUSTS TO 65

 MPH BOTH TODAY AND THURSDAY.

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT...WITH HAZARDOUS WIND SPEEDS REDEVELOPING

 THURSDAY MORNING. WIND SPEEDS WILL DECREASE THURSDAY

 EVENING TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO A MILE OR 

 LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

REMEMBER...A HIGH WIND WATCH MEANS CONDITIONS ARE FAVORABLE FOR A

POTENTIALLY DAMAGING HIGH WIND EVENT IN AND CLOSE TO THE WATCH

AREA. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR GUSTS OF 58 MPH

OR MORE CAN LEAD TO PROPERTY DAMAGE. MONITOR THE LATEST FORECASTS

AT WEATHER.GOV/ABQ...LISTEN TO NOAA WEATHER RADIO OR YOUR FAVORITE

MEDIA OUTLET.

&&

$$

NMZ502-505-281800- 

/O.CON.KABQ.HW.W.0006.100428T1800Z-100429T0200Z/

CHUSKA MOUNTAINS-WEST CENTRAL PLATEAU434 AM MDT WED APR 28 2010

...HIGH WIND WARNING REMAINS IN EFFECT FROM NOON TODAY TO 8 PM

MDT THIS EVENING...

A HIGH WIND WARNING REMAINS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING. 

* LOCATION...EXPECT DANGEROUS WINDS TODAY ACROSS THE CHUSKA

 MOUNTAINS AND NEAR THE ARIZONA BORDER. THIS INCLUDES INTERSTATE

 40 FROM THE ARIZONA LINE TO GALLUP...OR FROM MILE POST ZERO TO

 MILE POST 30...AND ACROSS STATE ROAD 134...STATE ROAD 

 264...STATE ROAD 53...AND STATE ROADS 32 AND 604. EXPECT

 STRONGEST WINDS ACROSS SUMMITS AND THROUGH GAPS AND PASSES.

* WINDS...SOUTHWEST WINDS WILL INCREASE TO 45 MPH...WITH FREQUENT
B-10

 GUSTS TO 65 MPH.

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO A MILE OR 

 LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

&&

$$

NMZ507-511-517>519-281800- 

/O.EXA.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

/O.CON.KABQ.WI.Y.0022.100428T1800Z-100429T0200Z/

WEST CENTRAL HIGHLANDS-JEMEZ MOUNTAINS-LOWER CHAMA RIVER VALLEYSANTA FE METRO AREA-ALBUQUERQUE METRO AREA434 AM MDT WED APR 28 2010

...WIND ADVISORY REMAINS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING...

...HIGH WIND WATCH IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WATCH...WHICH IS IN EFFECT FROM THURSDAY MORNING THROUGH

THURSDAY EVENING. A WIND ADVISORY REMAINS IN EFFECT FROM NOON

TODAY TO 8 PM MDT THIS EVENING. 

* LOCATION...EXPECT HAZARDOUS WINDS ACROSS INTERSTATE 40 FROM

 GRANTS TO TIJERAS...OR FROM MILE POST 80 TO MILE POST 175...AND

 ACROSS INTERSTATE 25 FROM BELEN TO GLORIETA PASS...OR FROM MILE

 POST 190 TO MILE POST 300..AND ACROSS HIGHWAY 550...STATE ROAD

 4...AND HIGHWAYS 84 AND 285. EXPECT STRONGEST WINDS ACROSS

 SUMMITS AND HILLTOPS AND THROUGH GAPS.

* WINDS...SOUTHWEST WIND SPEEDS WILL INCREASE TO 35 MPH...WITH 

 GUSTS TO 55 MPH. DAMAGING WIND GUSTS OF 65 TO 70 MPH MAY BE 

 POSSIBLE THURSDAY. 

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT...WITH HAZARDOUS WIND SPEEDS REDEVELOPING
B-11

 THURSDAY MORNING. WIND SPEEDS WILL DECREASE THURSDAY

 EVENING TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO TWO MILES 

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

MOTORISTS SHOULD EXERCISE CAUTION WHILE TRAVELING. SUDDEN GUSTS

OF WIND MAY CAUSE YOU TO LOSE CONTROL OF YOUR VEHICLE. EXTRA

ATTENTION SHOULD BE GIVEN TO CROSS WINDS.

REMEMBER...THE HIGH WIND WATCH THURSDAY MEANS CONDITIONS ARE

FAVORABLE FOR A POTENTIALLY DAMAGING HIGH WIND EVENT IN AND CLOSE

TO THE WATCH AREA. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE. MONITOR THE

LATEST FORECASTS AT WEATHER.GOV/ABQ...LISTEN TO NOAA WEATHER

RADIO OR YOUR FAVORITE MEDIA OUTLET.

&&

$$

NMZ534>538-281800- 

/O.CON.KABQ.WI.Y.0022.100428T1800Z-100429T0200Z/

/O.CON.KABQ.HW.A.0007.100429T1500Z-100430T0300Z/

QUAY COUNTY-CURRY COUNTY-ROOSEVELT COUNTY-DE BACA COUNTYCHAVES COUNTY PLAINS434 AM MDT WED APR 28 2010

...WIND ADVISORY REMAINS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING...

...HIGH WIND WATCH REMAINS IN EFFECT FROM THURSDAY MORNING

THROUGH THURSDAY EVENING...

A WIND ADVISORY REMAINS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING. A HIGH WIND WATCH REMAINS IN EFFECT FROM THURSDAY

MORNING THROUGH THURSDAY EVENING. 

* LOCATION...EXPECT HAZARDOUS WINDS ACROSS HIGHWAYS 60 AND

 84...HIGHWAYS 70 AND 380...AND HIGHWAY 285. EXPECT STRONGEST

 WINDS OVER HILLTOPS AND THROUGH GAPS.

* WINDS...SOUTHWEST WIND SPEEDS WILL INCREASE TO 35 MPH...WITH

 GUSTS TO 55 MPH. ON THURSDAY...WIND SPEEDS WILL INCREASE TO 45

 MPH WITH GUSTS TO 60 TO 65 MPH.

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT...WITH HAZARDOUS WIND SPEEDS REDEVELOPING
B-12

 THURSDAY MORNING. WIND SPEEDS WILL DECREASE THURSDAY

 EVENING TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO TWO MILES 

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

MOTORISTS SHOULD EXERCISE CAUTION WHILE TRAVELING. SUDDEN GUSTS

OF WIND MAY CAUSE YOU TO LOSE CONTROL OF YOUR VEHICLE. EXTRA

ATTENTION SHOULD BE GIVEN TO CROSS WINDS.

REMEMBER...THE HIGH WIND WATCH THURSDAY MEANS CONDITIONS ARE

FAVORABLE FOR A POTENTIALLY DAMAGING HIGH WIND EVENT IN AND CLOSE

TO THE WATCH AREA. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE. MONITOR THE

LATEST FORECASTS AT WEATHER.GOV/ABQ...LISTEN TO NOAA WEATHER

RADIO OR YOUR FAVORITE MEDIA OUTLET.

&&

$$

NMZ508-509-520>522-525-539-540-281800- 

/O.CON.KABQ.WI.Y.0022.100428T1800Z-100429T0200Z/

/O.CON.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

SOUTHWEST MOUNTAINS-SAN FRANCISCO RIVER VALLEYLOWER RIO GRANDE VALLEY-SANDIA/MANZANO MOUNTAINS-ESTANCIA VALLEYUPPER TULAROSA VALLEY-EASTERN LINCOLN COUNTYSOUTHWEST CHAVES COUNTY434 AM MDT WED APR 28 2010

...WIND ADVISORY REMAINS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING...

...HIGH WIND WATCH REMAINS IN EFFECT FROM THURSDAY MORNING

THROUGH THURSDAY EVENING...

A WIND ADVISORY REMAINS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING. A HIGH WIND WATCH REMAINS IN EFFECT FROM THURSDAY

MORNING THROUGH THURSDAY EVENING. 

* LOCATION...EXPECT HAZARDOUS WINDS ACROSS INTERSTATE 40 FROM

 TIJERAS TO MORIARTY...OR FROM MILE POST 170 TO MILE POST

 210...AND ACROSS INTERSTATE 25 FROM ELEPHANT BUTTE LAKE STATE

 PARK TO BELEN...OR FROM MILE POST 100 TO MILE POST 190...AND

 ACROSS HIGHWAYS 60 AND 180...STATE ROAD 12...STATE ROADS 14 AND

 337...HIGHWAYS 70 AND 380...AND HIGHWAY 285. EXPECT STRONGEST

 WINDS OVER SUMMITS AND HILLTOPS AND THROUGH GAPS.

* WINDS...SOUTHWEST WIND SPEEDS WILL INCREASE TO 35 MPH...WITH 
B-13

 GUSTS TO 55 MPH. DAMAGING WIND GUSTS OF 65 TO 70 MPH MAY BE 

 POSSIBLE THURSDAY. 

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL

 DECREASE OVERNIGHT...WITH HAZARDOUS WIND SPEEDS REDEVELOPING

 THURSDAY MORNING. WIND SPEEDS WILL DECREASE THURSDAY

 EVENING TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO TWO MILES 

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

MOTORISTS SHOULD EXERCISE CAUTION WHILE TRAVELING. SUDDEN GUSTS

OF WIND MAY CAUSE YOU TO LOSE CONTROL OF YOUR VEHICLE. EXTRA

ATTENTION SHOULD BE GIVEN TO CROSS WINDS.

REMEMBER...THE HIGH WIND WATCH THURSDAY MEANS CONDITIONS ARE

FAVORABLE FOR A POTENTIALLY DAMAGING HIGH WIND EVENT IN AND CLOSE

TO THE WATCH AREA. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE. MONITOR THE

LATEST FORECASTS AT WEATHER.GOV/ABQ...LISTEN TO NOAA WEATHER

RADIO OR YOUR FAVORITE MEDIA OUTLET.

&&

$$

NMZ503-504-281800- 

/O.CON.KABQ.WI.Y.0022.100428T1800Z-100429T0200Z/

FAR NORTHWEST HIGHLANDS-NORTHWEST HIGHLANDS434 AM MDT WED APR 28 2010

...WIND ADVISORY REMAINS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING...

A WIND ADVISORY REMAINS IN EFFECT FROM NOON TODAY TO 8 PM MDT

THIS EVENING. 

* LOCATION...EXPECT HAZARDOUS WINDS ACROSS HIGHWAYS 64 AND 84 IN

 EASTERN SAN JUAN AND WESTERN RIO ARRIBA COUNTIES INCLUDING

 NAVAJO STATE PARK AND DULCE...HIGHWAY 550 NEAR CUBA...JEMEZ

 PUEBLO...AND ZIA PUEBLO...AND STATE ROAD 197 NEAR TORREON.

* WINDS...SOUTHWEST WIND SPEEDS WILL INCREASE TO 35 MPH...WITH 

 GUSTS TO 55 MPH. 

* TIMING...WIND SPEEDS WILL INCREASE STEADILY THIS MORNING TO

 REACH HAZARDOUS SPEEDS BY EARLY AFTERNOON. WIND SPEEDS WILL
B-14

 DECREASE OVERNIGHT TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE REDUCED LOCALLY TO TWO MILES 

 OR LESS IN BLOWING DUST. 

* LOCAL IMPACTS...GUSTY SOUTHWEST WINDS WILL IMPACT LARGE OR 

 TALL VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN STRONG AND 

 GUSTY WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

MOTORISTS SHOULD EXERCISE CAUTION WHILE TRAVELING. SUDDEN GUSTS

OF WIND MAY CAUSE YOU TO LOSE CONTROL OF YOUR VEHICLE. EXTRA

ATTENTION SHOULD BE GIVEN TO CROSS WINDS.

&&

$$

WWUS75 KFGZ 281107

NPWFGZ

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE FLAGSTAFF AZ

407 AM MST WED APR 28 2010

AZZ011>014-017-040-282100- 

/O.EXB.KFGZ.WI.Y.0008.100429T0500Z-100430T0200Z/

/O.CON.KFGZ.HW.W.0004.100428T1600Z-100429T0500Z/

CHUSKA MOUNTAINS AND DEFIANCE PLATEAULITTLE COLORADO RIVER VALLEY IN COCONINO COUNTYLITTLE COLORADO RIVER VALLEY IN NAVAJO COUNTYLITTLE COLORADO RIVER VALLEY IN APACHE COUNTY-WHITE MOUNTAINSNORTHEAST PLATEAUS AND MESAS SOUTH OF HWY 264- 

INCLUDING THE CITIES OF...WINDOW ROCK...GANADO...WINSLOW...

HOLBROOK...SNOWFLAKE...ST. JOHNS...SPRINGERVILLE...SHOW LOW...

DILKON

407 AM MST WED APR 28 2010

...HIGH WIND WARNING REMAINS IN EFFECT FROM 9 AM THIS MORNING TO

10 PM MST THIS EVENING...

...WIND ADVISORY IN EFFECT FROM 10 PM THIS EVENING TO 7 PM MST

THURSDAY...

THE NATIONAL WEATHER SERVICE IN FLAGSTAFF HAS ISSUED A WIND

ADVISORY...WHICH IS IN EFFECT FROM 10 PM THIS EVENING TO 7 PM MST

THURSDAY. A HIGH WIND WARNING REMAINS IN EFFECT FROM 9 AM THIS

MORNING TO 10 PM MST THIS EVENING. 

* TIMING: STRONG SOUTHWEST WINDS WILL DEVELOP THIS MORNING AND

 CONTINUE THROUGH LATE EVENING AS A STORM SYSTEM APPROACHES THE

 REGION. GUSTY WINDS WILL PERSIST THURSDAY...THOUGH NOT AS STRONG

 AS TODAY.
B-15

* WINDS: SUSTAINED SOUTHWEST WINDS OF 35 TO 45 MPH WITH GUSTS OF

 55 TO 70 MPH ARE LIKELY.

* IMPACTS: FOR HIGH PROFILE VEHICLES...TRAVEL WILL BE DIFFICULT

 ACROSS NORTHERN ARIZONA. IN ADDITION TO THE STRONG WINDS...

 EXPECT AREAS OF BLOWING DUST WHICH COULD REDUCE THE VISIBILITY

 TO 1/4 MILE OR LESS AT TIMES. SPECIFICALLY...AN AREA THAT MAY

 EXPERIENCE NEAR-ZERO VISIBILITIES IN BLOWING DUST WILL BE

 INTERSTATE 40 FROM TWIN ARROWS TO WINSLOW. MOTORISTS ARE URGED

 TO USE CAUTION IN THESE AREAS. MINOR PROPERTY OR TREE DAMAGE IS 

 ALSO POSSIBLE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A HIGH WIND WARNING MEANS A HAZARDOUS HIGH WIND EVENT IS EXPECTED

OR OCCURRING...WITH SUSTAINED WIND SPEEDS GREATER THAN 40 MPH OR

GUSTS GREATER THAN 58 MPH. WINDS THIS STRONG CAN CAUSE PROPERTY

DAMAGE. CONTINUE TO MONITOR THE LATEST FORECASTS. ADDITIONAL

WEATHER INFORMATION IS ON THE WEB AT WWW.WEATHER.GOV/FLAGSTAFF.

&&

PUBLIC INFORMATION STATEMENT

NATIONAL WEATHER SERVICE FLAGSTAFF AZ

930 PM MST WED APR 28 2010

...STRONG WINDS ACROSS NORTHERN ARIZONA ON WEDNESDAY...

A LOW PRESSURE SYSTEM MOVING INTO THE WESTERN U.S. PRODUCED STRONG 

AND GUSTY SOUTHWEST WINDS TO MUCH OF NORTHERN ARIZONA TODAY. THESE 

STRONG WINDS PRODUCED SIGNIFICANT BLOWING DUST ACROSS AREA ROADWAYS 

FROM THE LITTLE COLORADO RIVER VALLEY TO THE FOUR CORNER REGION WITH 

VISIBILITIES BELOW 10 FEET REPORTED IN SOME LOCATIONS. INTERSTATE 40 

WAS CLOSED NEAR WINSLOW DUE TO THE STRONG WINDS AND BLOWING DUST IN 

THE AREA. POWER OUTAGES WERE ALSO REPORTED NEAR WINSLOW DUE TO THE 

STRONG WINDS BLOWING DOWN POWER LINES.

SOME PEAK WIND GUSTS REPORTED AS OF 8 PM MST TODAY INCLUDE:

TWO GUNS ..................... 73 MPH.

WINSLOW ...................... 69 MPH.

HOUSE ROCK ................... 64 MPH.

LIMESTONE CANYON ............. 63 MPH.

DONEY PARK ................... 61 MPH. 

TUBA CITY .................... 60 MPH.

LUPTON ....................... 60 MPH.

WUPATKI ...................... 59 MPH. 

MOGOLLON AIR PARK ............ 57 MPH.

FOUR SPRINGS ................. 55 MPH. 

FLAGSTAFF AIRPORT ............ 55 MPH. 

GRAND CANYON ................. 55 MPH. 

SHOW LOW AIRPORT ............. 53 MPH.

FRAZIER WELLS ................ 51 MPH. 
B-16

SAINT JOHNS .................. 51 MPH.

SEDONA AIRPORT ............... 49 MPH.

HOPI RAWS .................... 48 MPH.

SUNSET POINT ................. 45 MPH.

PRESCOTT ..................... 43 MPH.

PLEASANT VALLEY .............. 40 MPH.

COLDER AND UNSETTLED AIR WILL MOVE INTO THE REGION ON THURSDAY WITH 

DAYTIME TEMPERATURES CLOSE TO 20 DEGREES BELOW NORMAL...ALONG WITH 

SNOW AND RAIN SHOWERS. WINDS WILL REMAIN STRONG IN THE LITTLE 

COLORADO RIVER VALLEY ON THURSDAY...HOWEVER THE WIND SPEEDS WILL BE 

MUCH LIGHTER THAN TODAY.

$$

WWUS75 KGJT 280842

NPWGJT

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE GRAND JUNCTION CO

242 AM MDT WED APR 28 2010

...VERY STRONG WINDS WILL BLOW ACROSS EASTERN UTAH AND WESTERN

COLORADO TODAY...

.WINDS WILL CONTINUE TO STRENGTHEN TODAY WITH HIGH WIND GUSTS TO

OVER 60 MPH EXPECTED BY THIS AFTERNOON AND EVENING. THESE HIGH

WINDS WILL DEVELOP IN ADVANCE OF A VIGOROUS COLD FRONT MOVING

ACROSS UTAH. THE STRONGEST WINDS WILL OCCUR LATE IN THE AFTERNOON

AS THE FRONT MOVES INTO SOUTHEAST UTAH AND APPROACHES WESTERN

COLORADO. FOR THE LATEST UPDATES...VISIT THE NATIONAL WEATHER

SERVICE GRAND JUNCTION WEB PAGE AT WEATHER.GOV/GJT.

COZ002-003-006-007-009-011-017>021-UTZ022-025-027>029-282130- 

/O.EXT.KGJT.HW.W.0001.100428T0842Z-100429T0300Z/

CENTRAL YAMPA RIVER BASIN-ROAN AND TAVAPUTS PLATEAUS-GRAND VALLEYDEBEQUE TO SILT CORRIDOR-GRAND AND BATTLEMENT MESASCENTRAL GUNNISON AND UNCOMPAHGRE RIVER BASINUNCOMPAHGRE PLATEAU AND DALLAS DIVIDENORTHWEST SAN JUAN MOUNTAINS-SOUTHWEST SAN JUAN MOUNTAINSPARADOX VALLEY/LOWER DOLORES RIVERFOUR CORNERS/UPPER DOLORES RIVER-SOUTHEAST UTAH-TAVAPUTS PLATEAUARCHES/GRAND FLAT-LA SAL AND ABAJO MOUNTAINSCANYONLANDS/NATURAL BRIDGESINCLUDING THE CITIES OF...CRAIG...HAYDEN...MEEKER...RIO BLANCO...

GRAND JUNCTION...FRUITA...PALISADE...RIFLE...SILT...PARACHUTE...

MESA...SKYWAY...CEDAREDGE...DELTA...HOTCHKISS...MONTROSE...

RIDGWAY...GLADE PARK...OURAY...TELLURIDE...LAKE CITY...

SILVERTON...RICO...HESPERUS...GATEWAY...NUCLA...CORTEZ...

DOVE CREEK...MANCOS...BLANDING...BLUFF...MEXICAN HAT...MOAB...

CASTLE VALLEY...THOMPSON SPRINGS...MONTICELLO AND VICINITY

242 AM MDT WED APR 28 2010

...HIGH WIND WARNING NOW IN EFFECT UNTIL 9 PM MDT THIS EVENING...
B-17

THE HIGH WIND WARNING IS NOW IN EFFECT UNTIL 9 PM MDT THIS

EVENING. 

* TIMING...HIGH WINDS EXPECTED THROUGH 9 PM MDT THIS EVENING.

* WINDS...SUSTAINED STRONG WINDS FROM THE SOUTHWEST OF 20 TO 40 

 MPH WILL BE COMMON. HIGH WIND GUSTS TO 60 MPH FOR THE VALLEYS 

 AND 75 MPH IN THE MOUNTAINS WILL BE POSSIBLE. 

* VISIBILITY...VISIBILITY WILL BE SIGNIFICANTLY REDUCED FROM 

 BLOWING DUST...ESPECIALLY ALONG INTERSTATE 70 FROM GREEN RIVER 

 TO FRUITA. 

* IMPACTS...BUFFETING WINDS WILL CREATE HAZARDOUS DRIVING 

 CONDITIONS FOR HIGH PROFILE VEHICLES. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A HIGH WIND WARNING MEANS A HAZARDOUS HIGH WIND EVENT IS EXPECTED

OR OCCURRING. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR GUSTS

OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

PEOPLE...ESPECIALLY THOSE WITH RESPIRATORY ILLNESSES...HEART

DISEASE...THE ELDERLY...AND CHILDREN ARE RECOMMENDED TO STAY

INDOORS AND AVOID PROLONGED OUTDOOR EXERCISE OR HEAVY EXERTION

DUE TO WIND-BLOWN DUST.

&&
B-18

WWUS75 KABQ 291040

NPWABQ

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE ALBUQUERQUE NM

440 AM MDT THU APR 29 2010

...VERY WINDY CONDITIONS CONTINUING ACROSS NORTH AND CENTRAL NEW

MEXICO TODAY...

.A POWERFUL WEATHER SYSTEM OVER NORTHERN ARIZONA WILL MOVE TO

WESTERN NEW MEXICO BY LATE THIS AFTERNOON. A COLD FRONT

APPROACHING THE FOUR CORNERS THIS MORNING WILL SWEEP SOUTH AND

EAST ACROSS THE STATE BY THIS EVENING TO PRODUCE DANGEROUSLY GUSTY

WINDS STATEWIDE AS THE FRONT MOVES THROUGH. AS THE WEATHER SYSTEM

MOVES OVER NEW MEXICO THIS EVENING...WIND SPEEDS WILL DECREASE

AFTER SUNSET TO EASE THESE DANGEROUSLY WINDY CONDITIONS.

NMZ502-291800- 

/O.CAN.KABQ.HW.W.0006.000000T0000Z-100429T1200Z/

/O.EXB.KABQ.WI.Y.0022.000000T0000Z-100430T0300Z/

CHUSKA MOUNTAINS440 AM MDT THU APR 29 2010

...HIGH WIND WARNING REPLACED BY WIND ADVISORY...IN EFFECT UNTIL 9

PM MDT THIS EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A WIND

ADVISORY...WHICH IS IN EFFECT UNTIL 9 PM MDT THIS EVENING. THE

HIGH WIND WARNING HAS BEEN CANCELLED. 

* LOCATION...EXPECT HAZARDOUS WINDS ACROSS THE CHUSKA

 MOUNTAINS...WITH STRONGEST WINDS ACROSS SUMMITS AND THROUGH

 GAPS. EXPECT HAZARDOUS WINDS ACROSS STATE ROAD 134.

* WINDS...SOUTHWEST WINDS TO 40 MPH WITH GUSTS UP TO 55 MPH.

* TIMING...HAZARDOUS SOUTHWEST WIND SPEEDS WILL REDEVELOP THIS MORNING

 AND CONTINUE THROUGH THE AFTERNOON. WIND SPEEDS WILL DECREASE

 AFTER SUNSET TO EASE THESE HAZARDOUS WIND CONDITIONS.

* VISIBILITY...VISIBILITIES WILL BE LOCALLY REDUCED IN BLOWING DUST.

* LOCAL IMPACTS...HAZARDOUS CROSS WINDS WILL IMPACT LARGE OR TALL

 VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE IN GUSTS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

MOTORISTS SHOULD EXERCISE CAUTION WHILE TRAVELLING. SUDDEN GUSTS

OF WIND MAY CAUSE YOU TO LOSE CONTROL OF YOUR VEHICLE. EXTRA

ATTENTION SHOULD BE GIVEN TO CROSS WINDS.

&&
B-19

$$

NMZ506-512>515-523-526-529-539-540-291800- 

/O.CAN.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

/O.EXT.KABQ.HW.W.0006.000000T0000Z-100430T0300Z/ 

WEST CENTRAL MOUNTAINS-WEST SLOPES SANGRE DE CRISTO MOUNTAINSNORTHERN SANGRE DE CRISTO MOUNTAINS ABOVE 9500 FEET/RED RIVERSOUTHERN SANGRE DE CRISTO MOUNTAINS ABOVE 9500 FEETEAST SLOPES SANGRE DE CRISTO MOUNTAINS-CENTRAL HIGHLANDSSOUTH CENTRAL MOUNTAINS-NORTHEAST HIGHLANDSEASTERN LINCOLN COUNTY-SOUTHWEST CHAVES COUNTY440 AM MDT THU APR 29 2010

...HIGH WIND WATCH UPGRADED TO HIGH WIND WARNING...IN EFFECT

UNTIL 9 PM MDT THIS EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS CANCELLED THE

HIGH WIND WATCH. THE HIGH WIND WARNING IS NOW IN EFFECT UNTIL

9 PM MDT THIS EVENING. 

* LOCATION...EXPECT DANGEROUS WIND SPEEDS ACROSS INTERSTATE 40

 FROM THE ARIZONA LINE TO MILAGRO...OR FROM MILE POST ZERO TO

 MILE POST 240...AND ACROSS INTERSTATE 25 FROM ELEPHANT BUTTE

 LAKE STATE PARK TO WATROUS AND VALMORA...OR FROM MILE POST 100

 TO MILE POST 365. EXPECT STRONGEST WINDS ACROSS SUMMITS AND

 THROUGH GAPS.

* WINDS...SOUTHWEST WINDS 45 TO 50 MPH WITH GUSTS OF 65 TO 75 MPH. 

* TIMING...STRONG WINDS WILL CONTINUE THROUGH THIS EVENING BEFORE

 DECREASING SPEED AFTER SUNSET.

* VISIBILITY...EXPECT LOCALLY POOR VISIBILITIES IN BLOWING DUST.

* LOCAL IMPACTS...DANGEROUS CROSS WINDS WILL IMPACT LARGE OR TALL

 VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE. TREE LIMBS MAY

 BREAK OFF WITH DAMAGE POSSIBLE TO BUILDINGS...POWER LINES...AND

 LARGE SIGNS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

&&

$$

NMZ527-528-291800- 

/O.CAN.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

/O.EXT.KABQ.HW.W.0006.000000T0000Z-100430T0300Z/

RATON RIDGE/JOHNSON MESA-FAR NORTHEAST HIGHLANDS440 AM MDT THU APR 29 2010
B-20

...HIGH WIND WATCH UPGRADED TO HIGH WIND WARNING...IN EFFECT

UNTIL 9 PM MDT THIS EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS CANCELLED THE

HIGH WIND WATCH. THE HIGH WIND WARNING IS NOW IN EFFECT UNTIL

9 PM MDT THIS EVENING. 

* LOCATION...THIS INCLUDES INTERSTATE 25 FROM WATROUS AND VALMORA

 TO THE COLORADO LINE AT RATON PASS...OR FROM MILE POST 365 TO

 MILE POST 460.

* WINDS...EXPECT SOUTHWEST WINDS TO 45 MPH WITH GUSTS TO 65 MPH. 

* TIMING...HAZARDOUS WIND SPEEDS EARLY THIS MORNING WILL INCREASE

 TO DANGEROUS SPEEDS BY LATE MORNING. WIND SPEEDS WILL DECREASE

 AFTER SUNSET TO EASE THESE DANGEROUS WIND CONDITIONS.

* VISIBILITY...EXPECT LOCALLY POOR VISIBILITIES IN BLOWING DUST.

* LOCAL IMPACTS...DANGEROUS CROSS WINDS WILL IMPACT LARGE OR TALL

 VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE. TREE LIMBS MAY

 BREAK OFF WITH DAMAGE POSSIBLE TO BUILDINGS...POWER LINES...AND

 LARGE SIGNS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

&&

$$

NMZ507>511-521-522-524-291800- 

/O.UPG.KABQ.WI.Y.0022.000000T0000Z-100429T1200Z/

/O.UPG.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

/O.EXB.KABQ.HW.W.0006.000000T0000Z-100430T0300Z/

WEST CENTRAL HIGHLANDS-SOUTHWEST MOUNTAINSSAN FRANCISCO RIVER VALLEY-SAN JUAN MOUNTAINS-JEMEZ MOUNTAINSSANDIA/MANZANO MOUNTAINS-ESTANCIA VALLEY-SOUTH CENTRAL HIGHLANDS440 AM MDT THU APR 29 2010

...HIGH WIND WARNING IN EFFECT UNTIL 9 PM MDT THIS EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WARNING...WHICH IS IN EFFECT UNTIL 9 PM MDT THIS EVENING.

THE WIND ADVISORY IS NO LONGER IN EFFECT. THE HIGH WIND WATCH IS

NO LONGER IN EFFECT. 

* LOCATION...THIS INCLUDES INTERSTATE 40 FROM MILAN TO ACOMA

 PUEBLO...OR FROM MILE POST 80 TO MILE POST 130...AND FROM

 TIJERAS TO MORIARTY...OR FROM MILE POST 170 TO MILE POST
B-21

 200...AND HIGHWAY 60 NEAR QUEMADO AND MAGDALENA...SOCORRO...

 MOUNTAINAIR...AND WILLARD...AND HIGHWAY 180 NEAR LUNA AND

 GLENWOOD.

* WINDS...EXPECT SOUTHWEST WINDS INCREASING TO 40 TO 50 MPH...WITH

 GUSTS OF 60 TO 75 MPH. 

* TIMING...STRONG WINDS EARLY THIS MORNING WILL CONTINUE THROUGH

 EARLY EVENING. WIND SPEEDS WILL DECREASE AFTER SUNSET TO EASE

 THESE DANGEROUS WIND CONDITIONS. 

* VISIBILITY...EXPECT LOCALLY POOR VISIBILITIES IN BLOWING DUST.

* LOCAL IMPACTS...DANGEROUS CROSS WINDS WILL IMPACT LARGE OR TALL

 VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE. TREE LIMBS MAY

 BREAK OFF WITH DAMAGE POSSIBLE TO BUILDINGS...POWER LINES...AND

 LARGE SIGNS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

&&

$$

NMZ516>520-525-291800- 

/O.UPG.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

/O.EXB.KABQ.HW.W.0006.000000T0000Z-100430T0300Z/

UPPER RIO GRANDE VALLEY-LOWER CHAMA RIVER VALLEYSANTA FE METRO AREA-ALBUQUERQUE METRO AREALOWER RIO GRANDE VALLEY-UPPER TULAROSA VALLEY440 AM MDT THU APR 29 2010

...HIGH WIND WARNING IN EFFECT UNTIL 9 PM MDT THIS EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WARNING...WHICH IS IN EFFECT UNTIL 9 PM MDT THIS EVENING.

THE HIGH WIND WATCH IS NO LONGER IN EFFECT. 

* LOCATION...EXPECT DANGEROUS WINDS ACROSS INTERSTATE 40 IN THE

 ALBUQUERQUE METRO AREA...AND ACROSS INTERSTATE 25 FROM ELEPHANT

 BUTTE LAKE STATE PARK TO GLORIETA PASS...OR FROM MILE POST 100

 TO MILE POST 300...AND ACROSS HIGHWAY 60...HIGHWAY 550...AND

 HIGHWAYS 84 AND 285.

* WINDS...SOUTHWEST WINDS WILL INCREASE SPEED TO 40 TO 45

 MPH...WITH GUSTS OF 60 TO 65 MPH. 

* TIMING...DANGEROUS WINDS REDEVELOPING EARLY THIS MORNING WILL

 CONTINUE THROUGH THIS EVENING. WIND SPEEDS WILL DECREASE AFTER

 SUNSET TO EASE THESE DANGEROUS WIND CONDITIONS.
B-22

* VISIBILITY...EXPECT LOCALLY POOR VISIBILITIES IN BLOWING DUST. 

* LOCAL IMPACTS...DANGEROUS CROSS WINDS WILL IMPACT LARGE OR TALL

 VEHICLES. LOOSE OBJECTS MAY BECOME AIRBORNE. TREE LIMBS MAY

 BREAK OFF WITH DAMAGE POSSIBLE TO BUILDINGS...POWER LINES...AND

 LARGE SIGNS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A HIGH WIND WARNING MEANS DAMAGING WINDS ARE IMMINENT

OR HIGHLY LIKELY. SUSTAINED WIND SPEEDS OF AT LEAST 40 MPH OR

GUSTS OF 58 MPH OR MORE CAN LEAD TO PROPERTY DAMAGE.

&&

$$

NMZ530>538-291800- 

/O.UPG.KABQ.HW.A.0007.100429T1200Z-100430T0300Z/

/O.EXB.KABQ.HW.W.0006.000000T0000Z-100430T0300Z/

UNION COUNTY-HARDING COUNTY-EASTERN SAN MIGUEL COUNTYGUADALUPE COUNTY-QUAY COUNTY-CURRY COUNTY-ROOSEVELT COUNTYDE BACA COUNTY-CHAVES COUNTY PLAINS440 AM MDT THU APR 29 2010

...HIGH WIND WARNING IN EFFECT UNTIL 9 PM MDT THIS EVENING...

THE NATIONAL WEATHER SERVICE IN ALBUQUERQUE HAS ISSUED A HIGH

WIND WARNING...WHICH IS IN EFFECT UNTIL 9 PM MDT THIS EVENING.

THE HIGH WIND WATCH IS NO LONGER IN EFFECT. 

* LOCATION...EXPECT DANGEROUS WINDS ACROSS HIGHWAYS 64 AND

 87...HIGHWAYS 56 AND 412...STATE ROADS 120...104...AND

 39...HIGHWAY 60...HIGHWAYS 70 AND 380...AND HIGHWAY 285. THIS

 INCLUDES INTERSTATE 40 FROM MILAGRO TO THE TEXAS LINE...OR FROM

 MILE POST 240 TO MILE POST 370.

WWUS75 KFGZ 291659

NPWFGZ

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE FLAGSTAFF AZ

959 AM MST THU APR 29 2010

AZZ014-017-300100- 

/O.UPG.KFGZ.WI.Y.0008.000000T0000Z-100430T0200Z/

/O.NEW.KFGZ.HW.W.0006.100429T1659Z-100430T0200Z/

LITTLE COLORADO RIVER VALLEY IN APACHE COUNTY-WHITE MOUNTAINSINCLUDING THE CITIES OF...ST. JOHNS...SPRINGERVILLE...SHOW LOW

959 AM MST THU APR 29 2010

...HIGH WIND WARNING IN EFFECT UNTIL 7 PM MST THIS EVENING...
B-23

THE NATIONAL WEATHER SERVICE IN FLAGSTAFF HAS ISSUED A HIGH WIND

WARNING...WHICH IS IN EFFECT UNTIL 7 PM MST THIS EVENING. THE

WIND ADVISORY IS NO LONGER IN EFFECT. 

* TIMING: STRONG SOUTHWEST WINDS WILL CONTINUE TODAY BEFORE 

 DECREASING THIS EVENING. 

* WINDS: SUSTAINED SOUTHWEST WINDS OF 35 TO 45 MPH WITH GUSTS UP

 TO 65 MPH WILL CONTINUE.

* IMPACTS: FOR HIGH PROFILE VEHICLES...TRAVEL WILL BE DIFFICULT

 ACROSS NORTHERN ARIZONA. IN ADDITION TO THE STRONG WINDS...AREAS

 OF BLOWING DUST WILL CONTINUE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A HIGH WIND WARNING MEANS A HAZARDOUS HIGH WIND EVENT IS EXPECTED

OR OCCURRING...WITH SUSTAINED WIND SPEEDS GREATER THAN 40 MPH OR

GUSTS GREATER THAN 58 MPH. WINDS THIS STRONG CAN CAUSE PROPERTY

DAMAGE. CONTINUE TO MONITOR THE LATEST FORECASTS. ADDITIONAL

WEATHER INFORMATION IS ON THE WEB AT WWW.WEATHER.GOV/FLAGSTAFF.

&&

$$

AZZ016-300100- 

/O.EXA.KFGZ.WI.Y.0008.000000T0000Z-100430T0200Z/

EASTERN MOGOLLON RIM959 AM MST THU APR 29 2010

...WIND ADVISORY IN EFFECT UNTIL 7 PM MST THIS EVENING...

THE NATIONAL WEATHER SERVICE IN FLAGSTAFF HAS ISSUED A WIND

ADVISORY...WHICH IS IN EFFECT UNTIL 7 PM MST THIS EVENING. 

* TIMING: STRONG SOUTHWEST WINDS WILL CONTINUE TODAY BEFORE 

 DECREASING THIS EVENING. 

* WINDS: SUSTAINED SOUTHWEST WINDS OF 30 TO 40 MPH WITH GUSTS UP

 TO 55 MPH WILL CONTINUE.

* IMPACTS: FOR HIGH PROFILE VEHICLES...TRAVEL WILL BE DIFFICULT

 ACROSS NORTHERN ARIZONA.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND ADVISORY MEANS THAT SUSTAINED WINDS OF 30 TO 39 MPH...OR

GUSTS FROM 40 TO 57 MPH...ARE EXPECTED. WINDS THIS STRONG CAN

MAKE DRIVING DIFFICULT...ESPECIALLY FOR HIGH PROFILE VEHICLES.

CONSIDER SECURING LOOSE BELONGINGS ON YOUR PROPERTY. ADDITIONAL

WEATHER INFORMATION IS ON THE WEB AT WWW.WEATHER.GOV/FLAGSTAFF.

&&
B-24

$$

AZZ011>013-040-300100- 

/O.CON.KFGZ.WI.Y.0008.000000T0000Z-100430T0200Z/

CHUSKA MOUNTAINS AND DEFIANCE PLATEAULITTLE COLORADO RIVER VALLEY IN COCONINO COUNTYLITTLE COLORADO RIVER VALLEY IN NAVAJO COUNTYNORTHEAST PLATEAUS AND MESAS SOUTH OF HWY 264- 

INCLUDING THE CITIES OF...WINDOW ROCK...GANADO...WINSLOW...

HOLBROOK...SNOWFLAKE...DILKON

959 AM MST THU APR 29 2010

...WIND ADVISORY REMAINS IN EFFECT UNTIL 7 PM MST THIS EVENING...

A WIND ADVISORY REMAINS IN EFFECT UNTIL 7 PM MST THIS EVENING. 

* TIMING: STRONG SOUTHWEST WINDS WILL CONTINUE TODAY BEFORE 

 DECREASING THIS EVENING. 

* WINDS: SUSTAINED SOUTHWEST WINDS OF 30 TO 40 MPH WITH GUSTS UP

 TO 55 MPH WILL CONTINUE.

* IMPACTS: FOR HIGH PROFILE VEHICLES...TRAVEL WILL BE DIFFICULT

 ACROSS NORTHERN ARIZONA. IN ADDITION TO THE STRONG WINDS...AREAS

 OF BLOWING DUST WILL CONTINUE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND ADVISORY MEANS THAT SUSTAINED WINDS OF 30 TO 39 MPH...OR

GUSTS FROM 40 TO 57 MPH...ARE EXPECTED. WINDS THIS STRONG CAN

MAKE DRIVING DIFFICULT...ESPECIALLY FOR HIGH PROFILE VEHICLES.

CONSIDER SECURING LOOSE BELONGINGS ON YOUR PROPERTY. ADDITIONAL

WEATHER INFORMATION IS ON THE WEB AT WWW.WEATHER.GOV/FLAGSTAFF.

&&

WWUS75 KGJT 291038

NPWGJT

URGENT - WEATHER MESSAGE

NATIONAL WEATHER SERVICE GRAND JUNCTION CO

438 AM MDT THU APR 29 2010

...STRONG SOUTHWEST WINDS WILL CONTINUE OVER THE FOUR CORNERS AND

SAN JUAN MOUNTAINS THROUGH MIDDAY... 

...UNSEASONABLY COLD TEMPERATURES EXPECTED TONIGHT...

.STRONG SOUTHWEST WINDS AHEAD OF AN APPROACHING COLD FRONT WILL

CONTINUE TO BUFFET THE FOUR CORNERS REGION THROUGH NOON TODAY.

ONCE THE FRONT PASSES THROUGH LATER THIS MORNING WINDS WILL

DECREASE IN INTENSITY.

UNSEASONABLY COLD TEMPERATURES ARE BEHIND THE FRONT AND WILL
B-25

SPREAD ACROSS THE AREA TODAY. AS A RSULT...WIDESPREAD FREEZING

TEMPERATURES ARE EXPECTED TONIGHT.

FOR THE LATEST WEATHER UPDATES...VISIT THE NATIONAL WEATHER

SERVICE GRAND JUNCTION WEB PAGE AT WEATHER.GOV/GJT.

COZ021>023-291800- 

/O.CON.KGJT.WI.Y.0007.000000T0000Z-100429T1800Z/

FOUR CORNERS/UPPER DOLORES RIVER-ANIMAS RIVER BASINSAN JUAN RIVER BASININCLUDING THE CITIES OF...CORTEZ...DOVE CREEK...MANCOS...

DURANGO...BAYFIELD...IGNACIO...PAGOSA SPRINGS AND VICINITY

438 AM MDT THU APR 29 2010

...WIND ADVISORY REMAINS IN EFFECT UNTIL NOON MDT TODAY...

A WIND ADVISORY REMAINS IN EFFECT UNTIL NOON MDT TODAY. 

* TIMING...STRONG WINDS WILL CONTINUE ACROSS THE REGION THROUGH 

 MIDDAY. 

* WINDS...SOUTHWEST 20 TO 30 MPH WITH GUSTS TO 50 MPH.

* VISIBILITY...BLOWING DUST MAY SIGNIFICANTLY REDUCE VISIBILITY.

* IMPACTS...STRONG CROSS WINDS WILL CREATE HAZARDOUS DRIVING 

 CONDITIONS FOR HIGH PROFILE VEHICLES. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND ADVISORY MEANS THAT A SIGNIFICANT WIND EVENT IS EXPECTED

OR OCCURRING. WINDS THIS STRONG CAN MAKE DRIVING DIFFICULT. USE

EXTRA CAUTION.

PEOPLE...ESPECIALLY THOSE WITH RESPIRATORY ILLNESSES... HEART

DISEASE...THE ELDERLY...AND CHILDREN ARE RECOMMENDED TO STAY

INDOORS AND AVOID PROLONGED OUTDOOR EXERCISE OR HEAVY EXERTION

DUE TO WIND-BLOWN DUST.

&&

$$

COZ018-019-291800- 

/O.CON.KGJT.WI.Y.0007.000000T0000Z-100429T1800Z/

NORTHWEST SAN JUAN MOUNTAINS-SOUTHWEST SAN JUAN MOUNTAINSINCLUDING THE CITIES OF...OURAY...TELLURIDE...LAKE CITY...

SILVERTON...RICO...HESPERUS

438 AM MDT THU APR 29 2010

...WIND ADVISORY REMAINS IN EFFECT UNTIL NOON MDT TODAY...

A WIND ADVISORY REMAINS IN EFFECT UNTIL NOON MDT TODAY. 
B-26

* TIMING...STRONG WINDS WILL CONTINUE ACROSS THE REGION THROUGH 

 MIDDAY. 

* WINDS...SOUTHWEST 30 TO 40 MPH WITH GUSTS TO 60 MPH OR MORE.

* VISIBILITY...VISIBILITY WILL BE SIGNIFICANTLY REDUCED FROM 

 BLOWING DUST. 

* IMPACTS...STRONG CROSS WINDS WILL CREATE HAZARDOUS DRIVING 

 CONDITIONS FOR HIGH PROFILE VEHICLES. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND ADVISORY MEANS THAT A SIGNIFICANT WIND EVENT IS EXPECTED

OR OCCURRING. WINDS THIS STRONG CAN MAKE DRIVING DIFFICULT. USE

EXTRA CAUTION.

PEOPLE...ESPECIALLY THOSE WITH RESPIRATORY ILLNESSES... HEART

DISEASE...THE ELDERLY...AND CHILDREN ARE RECOMMENDED TO STAY

INDOORS AND AVOID PROLONGED OUTDOOR EXERCISE OR HEAVY EXERTION

DUE TO WIND-BLOWN DUST.
C

Appendix C- Final Natural Events Action Plan For High Wind 

Events, Alamosa, Colorado

FINAL NATURAL EVENTS ACTION PLAN

FOR

HIGH WIND EVENTS

ALAMOSA, COLORADO

CITY OF ALAMOSA,

ALAMOSA COUNTY,

and

COLORADO AIR POLLUTION CONTROL DIVISION

4300 Cherry Creek Drive South

Denver, Colorado 80222-1530

(303) 692-3100

May 2003
ALAMOSA NATURAL EVENTS ACTION PLAN

C-i 

I. EXECUTIVE SUMMARY

On March 31 and April 9, 1999 and again on April 18 and December 17, 2000, the monitor 

located in Alamosa, Colorado recorded exceedances of the 24-hour National Ambient Air 

Quality Standard (NAAQS) for PM10 (particulate matter having a nominal aerodynamic diameter 

equal to or less than 10 microns). Each of these exceedances was associated with high winds and 

blowing dust in the Alamosa area. 

Recognizing that certain uncontrollable natural events, such as high winds, wildfires, and 

volcanic/seismic activity can have on the NAAQS, the Environmental Protection Agency (EPA) 

issued a Natural Events Policy (NEP) on May 30, 1996. The NEP sets forth procedures through 

the development of a Natural Events Action Plan (NEAP) for protecting public health in areas 

where the PM10 standard may be violated due to these uncontrollable natural events. The guiding 

principles of the policy are: 

1. Federal, State, and local air quality agencies must protect public health; 

2. The public must be informed whenever air quality is unhealthy; 

3. All valid ambient air quality data should be submitted to the EPA Aerometric 

Information Retrieval System (AIRS) and made available for public access;

4. Reasonable measures safeguarding public health must be taken regardless of the source 

of PM10 emissions; and, 

5. Emission controls should be applied to sources that contribute to exceedances of the PM10

NAAQS when those controls will result in fewer violations of the standards. 

In response to Alamosa’s four exceedances of the PM10 NAAQS in 1999 and 2000, the Colorado 

Department of Public Health and Environment’s Air Pollution Control Division (Division), in 

conjunction with the City of Alamosa, Alamosa County, and other agencies developed a NEAP 

for the Alamosa area. The referenced NEAP was developed based on Natural Events Policy that 

calls for states to “develop a NEAP for any area where natural events cause or have caused a 

PM10 NAAQS to be violated within eighteen (18) months of the date of the violation.” April 18, 

2000 was the triggering event for the development of the NEAP. The referenced NEAP was 

developed and submitted to EPA in October 2001. A revised version of the NEAP (including 

U.S. EPA recommendations) was submitted February 2002. A copy of the letter of concurrence 

for these submittals is available in the Appendix. 

The Natural Events Policy also indicates that in attainment areas (such as Alamosa), best 

available control measures (BACM) must be implemented within three (3) years after the 

triggering event. With that, this Final Natural Events Action Plan for Alamosa, Colorado
ALAMOSA NATURAL EVENTS ACTION PLAN

C-ii

includes BACM not identified in the February 2002 submittal and includes additional efforts in 

the community to limit blowing dust and its impacts on public health. 

The Final Natural Events Action Plan also addresses PM10 exceedances experienced in the area 

that have occurred since the December 17, 2000 event. 

The plan provides analysis and documentation of the exceedances as attributable to 

uncontrollable natural events due to unusually high winds. In addition, the NEAP is designed to 

protect public health, educate the public about high wind events; mitigate health impacts on the 

community during future events; and, identify and implement Best Available Control Measures 

(BACM) for anthropogenic sources of windblown dust. 
ALAMOSA NATURAL EVENTS ACTION PLAN

C 

TABLE OF CONTENTS

Executive Summary ........................................................................................................................ i

Introduction ..................................................................................................................................... 1 

 Background ........................................................................................................................ 2 

Natural Events Policy ..................................................................................................................... 3 

Background ......................................................................................................................... 3 

Content ............................................................................................................................... 3 

Natural Events Action Plan ......................................................................................................... 5 

Element 1: Documentation & Analysis ............................................................................... 5

Element 2: Public Education Programs .............................................................................. 7 

Element 3: Public Notification Program and Health Advisory Program .............................. 9 

Element 4: Determination and Implementation of BACM .................................................10 

 

Stakeholder Agreements..................................................................................................14

Public Review and Periodic Evaluation............................................................................19 
ALAMOSA NATURAL EVENTS ACTION PLAN

C-1 

II. INTRODUCTION

The City of Alamosa is located in Alamosa County in south central Colorado. Situated in the 

San Luis Valley, Alamosa serves as one of the largest cities and the agricultural center for south 

central Colorado. The area surrounding Alamosa consists of gently rolling to nearly level 

uplands where the dominant slopes are less than 3 percent. The climate is generally mild and 

semiarid. Annual precipitation is about 7.5 inches. Summers are considered short and cool, with 

winters long and cold. In winter and spring, windstorms are common, especially in drier years. It 

is due to these high velocity windstorms that Alamosa experiences most of the PM10 problems for 

the area.

Area Map

On March 31 and April 9, 1999 and again on April 18 and December 17, 2000 the PM10 monitor 

located on the roof of Alamosa’s Adams State College recorded exceedances of the primary 24-

hour NAAQS for PM10. The PM10 concentrations of 263 μg/m3, 190 μg/m3, 238 μg/m3, and 217 

μg/m3 respectively, were recorded on these days - as were unusually high wind speeds and little 

or no precipitation. The circumstances surrounding the Alamosa exceedances has provided 

Alamosa
ALAMOSA NATURAL EVENTS ACTION PLAN

C-2 

adequate reason for the Division to believe the high wind events and blowing dust have caused 

exceedances of the NAAQS that otherwise would not have occurred. 

As required by the NEP, each of the exceedances was flagged by the Division’s Technical 

Services Program in the AIRS system. The flags appear after the recorded values in AIRS with 

the descriptor code “A” for high winds. According to EPA guidance the type and amount of 

documentation provided for each event should be sufficient to demonstrate that the natural event 

occurred, and that it impacted a particular monitoring site in such a way as to cause the PM10

concentrations measured. This documentation has been previously submitted to EPA. 

Recognizing the need to protect public health in areas where PM10 exceeds the NAAQS due to 

natural events such as the unusually high winds, a Natural Events Action Plan has been 

developed for the Alamosa area based on the NEP guidance. This plan outlines specific 

procedures to be taken in response to future high wind events. In short, the purpose of the plan is 

to: 

1. Educate the public about the problem; 

2. Mitigate health impacts on exposed populations during future events; and 

3. Identify and implement Best Available Control Measures (BACM) for anthropogenic 

sources of windblown dust. 

A. Background 

High winds are common to the southern region of Colorado. Under some conditions, these 

winds are strong enough to lift particulate matter into the air and cause elevated levels of PM10

above the Federal and State standards. Due to observed problems in Alamosa, particulate 

monitoring of total suspended particulate pollution was instituted at the Adams State College 

monitoring site in 1970. In 1989, monitoring for PM10 began. 

More recently, an additional monitoring site has been established in the Alamosa area. 

Specifically, a second PM10 monitor was established at the Alamosa Municipal Building to ensure 

adequate coverage of local air quality monitoring and to ensure protection of public health. This 

monitor, like the first PM10 monitor at Adams State College, operates on an everyday sampling 

protocol. 

Alamosa’s monitoring history shows that the annual PM10 standard of 50 μg/m3

 (averaged over an 

annual period) has never been exceeded. The 24-hour PM10 standard of 150 μg/m3 has been 

exceeded on a number of occasions. However, all exceedances have been due to natural events. 

The associated weather conditions on each of the exceedance days conform to a repeated pattern 

of regional high winds and blowing dust. In each case an intense, fast-moving, surface lowpressure system tracked through Colorado. Typically these systems had surface lows that were 
ALAMOSA NATURAL EVENTS ACTION PLAN

C-3 

not collocated with a closed upper low or nearly-closed upper level trough. This distinction is 

important because the collocated or vertically “coupled” systems usually bring significant up 

slope snow or rain to the region. The intensity of the lows associated with the PM10 exceedances 

is evident in the average central pressure of 990 mb (corrected to sea level). This value is typical 

of a deep, well-organized system. Such well-organized systems usually generate high winds in 

the vicinity of the low center.

The NEP applies only to emissions caused by natural events that have occurred since January 1, 

1994. Only those high wind events experienced since that time are addressed by this NEAP. 

This submittal includes those exceedances occurring since the previous NEAP submittal as well. 

See table on page 6 for more details of all area exceedances. 

B. The Natural Events Policy

1. Background

On May 30, 1996, EPA issued the Natural Events Policy in a memorandum from Mary D. 

Nichols, Assistant Administrator for Air and Radiation. In this memorandum EPA announced its 

new policy for protecting public health when the PM10 NAAQS are violated due to natural events. 

Under this policy three categories of natural events are identified as affecting the PM10 NAAQS: 

(1) volcanic and seismic activity; (2) wildland fires; and, (3) high wind events. Only high wind 

events will be addressed in this NEAP. 

Based on EPA’s natural events policy high winds are defined as uncontrollable natural events 

under the following conditions: (1) the dust originated from non-anthropogenic sources; or, (2) 

the dust originated from anthropogenic sources controlled with best available control measures 

(BACM). Furthermore, the conditions that create high wind events vary from area to area with 

soil type, precipitation, and the speed of wind gusts. 

2. Content

In order for exceedances of the NAAQS to be considered as due to a natural event, a Natural 

Events Action Plan must be developed to address future events. The following is a summary of 

the specific EPA guidance regarding development of a NEAP. 

1. Analysis and documentation of the event should show a clear causal relationship between 

the measured exceedance and the natural event. The type and amount of documentation 

provided should be sufficient to demonstrate that the natural event occurred, and that it 

impacted a particular monitoring site in such a way as to cause the PM10 concentrations 

measured.
ALAMOSA NATURAL EVENTS ACTION PLAN

C-4 

2. Establish education programs. Such programs may be designed to educate the public 

about the short-term and long-term harmful effects that high concentrations of PM10 could 

have on their health and inform them that: (a) certain types of natural events affect the air 

quality of the area periodically, (b) a natural event is imminent, and (c) specific actions 

are being taken to minimize the health impacts of events.

3. Minimize public exposure to high concentrations of PM10 through a public notification 

and health advisory program. Programs to minimize public exposure should (a) identify 

the people most at risk, (b) notify the at-risk population that a natural event is imminent 

or currently taking place, (c) suggest actions to be taken by the public to minimize their 

exposure to high concentrations of PM10, and (d) suggest precautions to take if exposure 

cannot be avoided. 

4. Abate or minimize appropriate contributing controllable sources of PM10. Programs to 

minimize PM10 emissions for high winds may include: the application of BACM to any 

sources of soil that have been disturbed by anthropogenic activities. The BACM 

application criteria require analysis of the technological and economic feasibility of 

individual control measures on a case-by-case basis. The NEAP should include analyses 

of BACM for contributing sources. If BACM are not defined for the anthropogenic 

sources in question, step 5 listed below is required. 

5. Identify, study, and implement practical mitigating measures as necessary. The NEAP 

may include commitments to conduct pilot tests of new emission reduction techniques. 

For example, it may be desirable to test the feasibility and effectiveness of new strategies 

for minimizing sources of windblown dust through pilot programs. The plan must 

include a timely schedule for conducting such studies and implementing measures that 

are technologically and economically feasible.

6. Periodically reevaluate: (a) the conditions causing violations of a PM10 NAAQS in the 

area, (b) the status of implementation of the NEAP, and (c) the adequacy of the actions 

being implemented. The State should reevaluate the NEAP for an area every 5 years at a 

minimum and make appropriate changes to the plan. 

7. The NEAP should be developed by the State in conjunction with the stakeholders 

affected by the plan. 

8. The NEAP should be made available for public review and comment and may, but is not 

required, to be adopted as a revision to the State Implementation Plan (SIP) if current SIP 

rules are not revised.
ALAMOSA NATURAL EVENTS ACTION PLAN

C-5 

9. The NEAP should be submitted to the EPA for review and comment. 

The following text describes the Alamosa NEAP and its conformance with the above-described 

EPA guidance on natural events. 

III. NATURAL EVENTS ACTION PLAN

A. Element 1: Documentation & Analysis

On March 31 and April 9, 1999 and again on April 18 and December 17, 2000, the air quality 

monitor located in Alamosa, Colorado recorded exceedances of the 24-hour National Ambient 

Air Quality Standard (NAAQS) for PM10 (Figure 1). Each of these exceedances was associated 

with unusually high winds in the Alamosa area (Table 1). 

Figure 1. Recent Alamosa PM10 Concentrations

n.e.- Natural Event

On October 29, 1999 and again on March 30, 2000 the Division submitted documentation to 

EPA Region VIII in support of Alamosa’s most recent exceedances of the PM10 NAAQS due to 

natural events. The documentation contained monitoring data, meteorological data, PM10 filter 

analysis and receptor model results, maps of the area, news accounts of the events and other 

miscellaneous supporting material. On July 3, 2001, EPA concurred that the aforementioned 

0 

50

100

150

200

250

300

350

400

450

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000

PM10 concentration (ug/m3)

Alamosa PM10 Concentrations 1991 through 2001

Max. w/n.e. Ann. Avg. w/n.e.

Max. w/o n.e. Ann. Avg. w/o n.e.

Yearly Maximum and Annual Averages with and without natural event concentrations

National Ambient Air Quality Standards:

24-hour Average: 150 ug/m3

Annual Arithmetic Mean: 50 ug/m3
ALAMOSA NATURAL EVENTS ACTION PLAN

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natural events were, in fact, high wind events (Table 1). The EPA letter of concurrence can be 

found in the Appendix of this NEAP. 

More recently (since the February 2002 submittal), several additional exceedances of the PM10

NAAQS have been experienced in the community. These exceedances were recorded at the 

Adams State site only; none have been seen at the recently sited PM10 monitor at the Municipal 

Complex. Details are included in the table below and documentation for these events is on file 

with EPA.

Table 1. Recent 24 Hour PM-10 Values in Alamosa Colorado 

EVENT 

Date

PM-10 

Concentration

Details

3/31/99 263 μg/m3 Natural Event- EPA concurrence on July 3, 2001

4/9/99 190 μg/m3 Natural Event- EPA concurrence on July 3, 2001

4/18/00 238 μg/m3 Natural Event- EPA concurrence on July 3, 2001

12/17/00 217 μg/m3 Natural Event- EPA concurrence on July 3, 2001

2/8/02 215 μg/m3 Natural Event Under EPA consideration

2/25/02 182 μg/m3 Natural Event Under EPA consideration

3/23/02 164 μg/m3 Natural Event Under EPA consideration

5/21/02 160 μg/m3

Natural Event Under EPA consideration

Taken together, the supporting documentation establishes a clear, casual relationship between the 

measured exceedances and the natural events as required by the NEP. On the days of Alamosa’s 

PM10 exceedances, unusually high winds and/or wind gusts were experienced over a prolonged 

period of time. For example, meteorological data in and around the area (Trinidad, Colorado) 

demonstrate that on April 18, 2000, maximum wind speeds were over 41 miles per hour and gust 

speeds were as high as nearly 59 miles per hour. Meterological data for the December 18, 2000 

event indicate that gusts were as high as 49 miles per hour in the Alamosa area. Both events were 

coupled with dry periods of weather. 

According to the Natural Events Policy, “the conditions that create high wind events vary from 

area to area with soil type, precipitation and the speed of wind gusts.” Thus, states are to 

determine the conditions that define high winds in an area. Making a precise determination, 

however, is a complex task that requires detailed information on soil moisture, daily wind 

speeds, temperature, and a number of other variables that are not readily available at this time. 

Until such research and/or guidance is available, the Division will use the definition of high 

winds included in the Guideline on the Identification and Use of Air Quality Data Affected by 

Exceptional Events for the Alamosa area. According to this guidance, high winds are defined as: 
ALAMOSA NATURAL EVENTS ACTION PLAN

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“An hourly wind speed of greater than or equal to 30 mph or gusts equal to or greater than 40 

mph, with no precipitation or only a trace of precipitation.” In all these high wind events, hourly 

wind speeds and/or wind gust data coupled with low precipitation levels meet this high wind 

definition. 

The analysis and documentation of the natural high wind events fulfill Element 1 as described on 

page 3 of this NEAP. 

B. Element 2: Public Education Programs

The purpose of this program is to inform and educate the public about the problem. The 

Division has worked with the City of Alamosa, Alamosa County Commissioners, and interested 

stakeholders to educate the public about the problems associated with elevated levels of PM10 in 

the Alamosa area. Several meetings have taken place with the City and County governments to 

discuss these issues and to develop a plan to address future high wind events in Alamosa. 

Elements of the public education program include: informing the public when air quality in the 

area is unhealthy; explaining what the public can expect when high wind events occur; what 

steps will be taken to control dust emissions during future high wind events; and, how to 

minimize the public’s exposure to high concentrations of PM10 during high wind conditions. The 

public notification and education programs will include but are not limited to: 

• An informational and health-related brochure has been and will continue to be distributed 

by the local governments, the Alamosa County Health Nurses, and Alamosa County 

conservation and agricultural extension agencies to sensitive populations (elderly and 

local school districts) as well as the general public. Distribution of the Blowing Dust 

Health Advisory Brochure began in March 2000. A copy of this brochure is available in 

the Appendix. More recent (since the February 2002 submittal of the NEAP) activities 

include: 1) the revision of the area brochure to highlight additional activities in the 

community and make the document more reader friendly; 2) a review of the effectiveness 

of the brochure distribution in the community. The brochure is now available at 

additional sites in the community (e.g., County Land Use office), and; 3) the 

development of a Spanish version of the brochure. 

• Beginning in February 2002, blowing dust watches and health advisories are being issued 

by the Alamosa County Public Health Nursing office during the high wind season (see 

Appendix for details). More recent (since the February 2002 submittal of the NEAP) 

activities include: 1) expanding the public education effort to include staff from the 

County Land Use office; 2) meetings with city, county, and local public health nurse to 

devise improved ways to educate/reach the community regarding blowing dust and its 

impacts. 
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• Media press releases for both the print and local radio will be issued in the community as 

needed. More recent (since the February 2002 submittal of the NEAP) activities include: 

1) newspaper articles highlighting the significant impacts of the drought on blowing dust 

in the Alamosa area (e.g., “Biblical Level Help Needed for Drought,” The Denver Post, 

April 22, 2002. This referenced article also highlighted some of the mitigation strategies 

underway to limit impacts), and; 2) identifying possible Public Service Announcement 

outlets for additional outreach into the community and the ongoing development of an 

area press release on the NEAP development and control strategies. 

• Meetings have been held to review the requirements of and local involvement in the 

NEAP. Other meetings will be convened as deemed necessary by State and/or local 

agencies. 

• Advertising at local meetings (e.g. Sunshine Festival - Summer 2003) of ongoing efforts 

to reduce blowing dust and its impacts. This is new effort not part of the February 2002 

submittal.

• Development of a logo/brand to better familiarize area residents to the NEAP and 

components of that plan including the blowing dust advisory. An example of that logo 

can be found on the revised Blowing Dust Health Advisory Brochure, located in the 

Appendix. This is new effort not part of the February 2002 submittal. 

• Ongoing development of educational materials to be made available through the 

County’s tax announcement (2004). These educational materials will be distributed in the 

mail alongside tax announcements and are expected to go to all area residents 

(approximately 13,000 notices). Materials are likely to be in both English and Spanish. 

This is new effort not part of the February 2002 submittal. 

• The Division in conjunction with the area County Public Health Nurse is revising the 

blowing dust education/notification procedure to highlight public health issues associated 

with blowing dust. 

• Finally, County building inspectors will also educate citizens (home owners and 

contractors) about blowing dust issues and strategies to minimize such. This will be done 

in all construction zones in the county and documented as an item on the inspector’s 

checklist of building issues covered during the permitting process. This is new effort not 

part of the February 2002 submittal. 

This section fulfills the requirement of Element 2 as described on page 4. 
ALAMOSA NATURAL EVENTS ACTION PLAN

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C. Element 3: Public Notification Program and Health Advisory Program

The Blowing Dust Health Advisory program will notify the public that a high wind/blowing dust 

event is imminent or currently taking place, and will include an advisory suggesting what actions 

can be taken to minimize PM10 emissions and exposure to high concentrations of particulate 

matter. 

Advisories are issued by the Alamosa area Public Health Nursing office, with forecasting 

assistance provided by the National Weather Service (Pueblo) and the Colorado Air Pollution 

Control Division. Since 2002, five (5) advisories have been issued locally. The forecasting 

methodology, the public education brochure, and a copy of the text of blowing dust forecasts and 

health advisories are provided in the Appendix. 

Alamosa County will be investigating, during 2003, the possibility of modifying the 911 data 

base for reverse notification of sensitive populations during high wind events. This is new 

activity not included in the February 2002 submittal. 

Finally, high winds are currently being documented to determine if the Division and the local 

agencies can better address these issues. For example, the Alamosa County Public Health 

Nursing office maintains records of all blowing wind events and the associated notifications. 

Included in this analysis is a rudimentary review of the high wind data to identify patterns of 

events and possible solutions to minimize public exposure. Given the drought conditions 

affecting the Alamosa area over the past several years, no consistent pattern (outside of 

extremely dry conditions and lack of rainfall) has been noted. Nonetheless, the Division is 

committed to continually investigating this issue and improving the advisory as possible. 

Ongoing review of those records will continue to investigate patterns of the exceedances and the 

notifications. This is a new activity that was not part of the February 2002 submittal and 

demonstrates additional efforts by the Division and the local agencies to minimize blowing dust 

and protect public health. 

This section fulfills the requirement of Element 3 as described on page 4.
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D. Element 4: Determination and Implementation of BACM

1. BACM Determination

According to the NEP, Best Available Control Measures (BACM) must be implemented for 

anthropogenic sources contributing to NAAQS exceedances in attainment and unclassifiable 

areas, like Alamosa. BACM must be in place for those contributing sources within three years

after the first NAAQS violation attributed to high wind event(s) for sources in the Alamosa area. 

BACM must be in place no later than April 18, 2003. BACM for PM10 are defined (in 59 F.R. 

42010, August 16, 1994) as techniques that achieve the maximum degree of emissions reduction 

from a source as determined on a case-by-case basis considering technological and economic 

feasibility. 

On September 2, 1999 the Division attended several meetings in Alamosa with officials 

representing the City of Alamosa and Alamosa County Commissioners. Discussed were the 

monitoring data, meteorological data, potential contributing sources to the high wind events, the 

development of a NEAP, and possible control measures. In addition, meetings in December 2001 

and February 2002 and numerous correspondences at other times have covered the same. The 

meetings, coupled with the analyses of the supporting documentation, identified two distinct sets 

of circumstances that lead to Alamosa’s high wind/blowing dust exceedances of the PM10

NAAQS: 

10. High concentrations of PM10 caused by a mixture of anthropogenic and non-anthropogenic 

sources coming largely from outside the area under high wind conditions; and, 

2. Prolonged climatic conditions of low precipitation over an extended period of time that 

act to dry area soils, making them more susceptible to airborne activity under high wind 

conditions. 

Discussions with the community stakeholders also covered local agricultural practices. Alamosa 

County is a predominately agricultural area where a lack of water, coupled with the frequent high 

winds experienced during late fall and early spring, can destroy crops, encourage pests, and 

damage soil surfaces lending them susceptible to wind erosion. 

Other potential contributing sources may include construction sites, wind erosion of open areas, 

paved and unpaved roads, residential wood burning, and/or open burning. See below for more 

details on each of these potentially contributing sources and their consideration for BACM. 
ALAMOSA NATURAL EVENTS ACTION PLAN

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2. BACM Options Considered

Based on the contributing source analysis and/or in review with community stakeholders, the 

following BACM options were considered as possible PM10 control measures for the community: 

a) Street Sweeping Activities- community street sweeping programs have demonstrated 

effectiveness in other communities. Such activities were considered as a local control measure. 

Expanding the current street sweeping program was also reviewed. 

b) Construction/Demolition Activity – local ordinances to control emissions from construction 

and demolition sites have been implemented in other parts of the state with good success. 

c) Wind Erosion of Open Areas – several practices were reviewed regarding the wind erosion of 

open areas, including both local and regional efforts.

d) Control of Stationary Source Emissions- as identified elsewhere in this NEAP, a review of 

stationary sources and their relative contribution to overall PM concentrations was completed. 

It was determined that six PM-10 sources exist in the area, appearing to contribute a small 

amount of particulate matter to the overall inventory. 

e) Road Stabilization- In a effort to better understand the effects of road stabilization, several 

options were reviewed including the use of chemical stabilizers and water as a stabilizing 

measure. 

Also, periodic assessments to determine if traffic levels on unpaved roads surpass Colorado 

Regulation No. 1 limits were considered. If daily traffic counts exceed 200 trips per day on 

unpaved roads, state regulations apply that reduce PM-10 emissions from those roads. 

Specifically, periodic assessments of traffic levels on unpaved roads within the city limits and 

within one mile of the city limits were considered. State regulation calls for a road traffic count 

and dust control plan for roads that exceed the 200 trips threshold. 

In addition, Alamosa currently suggests that drivers maintain their vehicles at a slow speed on 

unpaved roads and other dirt surfaces to reduce dust emissions. 

f) Woodburning Curtailment Programs- the possibility of instituting a citywide curtailment 

program was reviewed and considered. This consideration includes discouraging wood burning 

on high wind days. 

g) Open Burning- The usefulness of imposing and maintaining an open burning curtailment 

program during high wind events was reviewed. Current state air pollution control laws and 

regulations provide some guidance on the effort. 
ALAMOSA NATURAL EVENTS ACTION PLAN

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h) Avoidance of Dust Producing Equipment- The effectiveness of avoiding the use of dust 

producing equipment has also been considered. Currently Alamosa discourages the use of dustproducing equipment (e.g., leaf blowers) in an effort to reduce PM10 emissions and does so 

through public education and outreach efforts. 

(i) Reducing or Postponing Tilling and Plowing or Other Agricultural Practices that Contribute 

to PM10 Emissions- It is well recognized that dust-producing activities such as tilling, plowing, 

and other agricultural practices increase the amount of PM10 released. As such, these control 

measures were discussed as part of the effort to reduce PM10 impacts on Alamosa. Review of 

existing and potentially future control practices were considered at the local, regional, state, and 

federal (e.g., Natural Resources Conservation Service) level. 

j) Wind Break- Various trees are found throughout Alamosa. However, the placement of one row 

of barrier trees (e.g., Russian Olives) would block potential contributing sources. The Russian 

Olive is a quick growing large shrub/small tree will do well given the windy climate of Alamosa. 

According to section 3.5.2.1 of EPA guidance entitled Fugitive Dust Background Document and 

Technical Information Document for Best Available Control Measures, dated September 1992, 

one-row of trees is considered an effective windbreak. 

k) Vegetative Cover/Sod- Efforts elsewhere in the State have demonstrated the usefulness of 

using a vegetative cover at sites where dust is known to blow. Efforts to use this control measure 

were reviewed for applicability and effectiveness.

Alamosa PM10 Stationary Source Emissions 

To ensure that PM10 emissions from local stationary sources are not a significant contributing 

factor to area exceedances, an emission inventory was prepared and reviewed. Identified 

stationary sources are as follows: Public Service Company (natural gas/fuel oil plant), Rakhra 

Mushroom Farm Corporation (coal-fired boilers and one natural gas fired boiler), Rocky 

Mountain Soils (fugitive dust emissions), Rogers Family Mortuary (crematorium), San Luis 

Valley Regional Medical Center (biomedical waste incinerator), and Southwest Ready Mix 

(concrete batch plant). While no emission inventory of natural sources was prepared as part of 

this NEAP, appreciation for the significant sand dunes at Great Sand Dunes National Monument 

highlights that these few and limited stationary sources have very little effect on the total PM10

emission inventory for the Alamosa area. The following table demonstrates their limited impacts 

on the total emission estimation. 
ALAMOSA NATURAL EVENTS ACTION PLAN

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Alamosa PM10 Emission Inventory (circa 2003) 

Source Emissions in lbs/day

Public Service Company of Colorado 44.4

Southwest Ready Mix 4.4

San Luis Valley Regional Medical Center 0.1

Rakhra Mushroom Farm Corp. 11.1

Rocky Mountain Soils, Inc. 11.5

Rogers Family Mortuary 0.5

TOTAL EMISSIONS

72.1

Limited Stationary Source Impacts

The largest of these stationary sources, Public Service Company of Alamosa (PSC), is 44.4 

pounds per day of particulate matter (as reported to the Colorado APCD). At PSC, the site 

consists of two turbines that can run on natural gas, #1 fuel oil, #2 fuel oil, or a combination 

thereof. PSC must stay in compliance with Colorado Air Quality Regulation No. 1 particulate 

standard. PSC must also meet the state 20% opacity standard. 

Other Alamosa area stationary sources have considerably smaller particulate matter emissions 

than PSC and their own existing control measures in place. For example:

Southwest Ready-Mix has a concrete batch plant in the City of Alamosa. Southwest Ready-Mix 

has several outside storage piles for their raw materials (sand & aggregate). There exists a 

sprinkler system at the facility to keep these piles watered. Cement and fly ash are stored in silos, 

each controlled with a baghouse to capture particulate when the silos are being loaded. When all 

of the raw materials are loaded into the concrete trucks, 25% of the total water is loaded first, 

followed by rock, sand, cement, and then the remaining water. This helps to minimize the 

particulate emissions from the truck during loading. The baghouses are part of the Southwest 

Ready-Mix permit, and as such are required. This source is also subject to the 20% opacity 

standard. Finally, Southwest Ready-Mix may be upgrading their baghouses. 

San Luis Valley Regional Medical Center has a permit for a biomedical waste incinerator, which 

is natural gas fired. The incinerator is subject to New Source Performance Standards which limit 

opacity to 10% and also has a particulate standard. Ash removal from the incinerator must be 

done in an enclosed area to limit particulate emissions. Ash must be completely enclosed during 

transport as well.
ALAMOSA NATURAL EVENTS ACTION PLAN

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3. BACM Options Discounted

Several BACM options were discounted from further consideration based on meteorological 

analysis, on-site inspections, and discussions with local government officials and sources. 

Woodburning curtailment was discounted because high wind events are actually beneficial to 

good atmospheric clearing of particulate matter. In addition, woodburning curtailment was not 

recognized as an effective control measure on high wind days. Lastly, many of the community 

citizens rely on woodburning as their sole source of home heating- reducing or eliminating wood 

burning is thus not an option. 

BACM of stationary sources at great distances from the City were discounted as their impacts 

would be negligible, if seen at all. 

Finally, for this revised NEAP (since the February 2002 submittal), the community remains 

committed to meet BACM in all instances, as feasible. For example, meetings with local officials 

indicate that the ongoing regional drought may significantly impact the amount of water 

available as a control measure (e.g., watering of roads to reduce PM10). With that, water 

restrictions (and related economic impacts of the drought) will likely dictate the utility of this 

control measure. 

4. BACM Implemented

Refer to the stakeholder agreements for details of selected BACM.

IV. STAKEHOLDER AGREEMENTS

The City of Alamosa, Alamosa County, the Division, and participating federal agencies have 

been working diligently to identify contributing sources and to develop appropriate BACM as 

required by the Natural Events Policy. A copy of relevant agreements and supplemental 

information are included in the Appendix. This section fulfills the requirements of Element 4 as 

described on page 4. 

City of Alamosa

The City of Alamosa has been active in addressing potential PM10 sources within the Alamosa 

area through various efforts. Some of these efforts, plus other potential future measures, include 

the adoption of local ordinances to reduce PM10. Copies of current ordinances and any related 

commitments are included in the Appendix. 
ALAMOSA NATURAL EVENTS ACTION PLAN

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Street Sweeping 

Currently, the City of Alamosa sweeps on an every 6-week schedule or as needed, as determined 

by local officials on a case by case situation (e.g., following each snowstorm and/or where sand 

was applied). Sweeping occurs on every single City street with an emphasis on the downtown 

corridor where public exposure is expected to be greatest. In fact, street sweeping in the 

downtown corridor currently takes place three times per week. 

In addition, the City recently agreed to lease/own a new TYMCO 600 (brush-assisted head) 

sweeper. Efforts are underway to get this effective piece of equipment into place immediately. 

This new sweeper will complement a mobile mechanical sweeper already in use. 

Unpaved Roads within the City

While very few unpaved roads exist in the City of Alamosa, the city did recently annex new 

land. This annexation includes roadways not currently paved. The City of Alamosa is discussing 

the paving of these annexed roads. At a minimum, the City of Alamosa commits to continually 

provide in-kind engineering services for the development of the annexed lands. 

Sod/Vegetative Cover Projects in the City of Alamosa 

The development and construction of a local park, Eastside Park, is underway in Alamosa. It is 

anticipated that sodding at the park will take place this year. This commitment is anticipated to 

reduce blowing dust from this previously undeveloped site. 

Alamosa County

Alamosa County has also been active in addressing blowing dust and is preparing county 

ordinance as such. Examples can be found below and available supporting documents in the 

Appendix.

Unpaved Roads 

Alamosa County is presently addressing unpaved roads and lanes that are anticipated to 

contribute to PM10 emissions in the community. As of 2002, Alamosa County was nearing the end 

of its five-year road paving plan and was developing their next plan with the intention of paving 

on a yearly basis, based on traffic and community needs/priorities. 

In 2002, Alamosa County addressed approximately ten (10) miles of unpaved roads. This 

includes the stabilization of approximately five section roads, the seal coating of two roads, and 

the overlay (repaving) of four (4) additional roads. 

For 2003, approximately 14 miles of roads are scheduled for paving. This includes the Seven 

Mile Road (three miles long), Road 109 (one mile long), and 10th Street (also one mile long). 

These roads are in close proximity to the City of Alamosa, are upwind (prevailing) from the city, 
ALAMOSA NATURAL EVENTS ACTION PLAN

C-16

and have heavy traffic. Paving is anticipated to greatly reduce blowing dust and impacts in the 

vicinity. 

In addition, once it gets cold enough in the area, the County will wet down some of the more 

sandy roads. Once the water soaks in and freezes, it is anticipated that good dust suppression will 

be seen. These commitments are anticipated to reduce PM10 emissions in and near Alamosa. This 

control measure will be balanced with the availability of water in the area. 

Finally, Alamosa County assesses the need to use MgC12 treatment on roads in front of 

residences that request such service. Assessments include the sensitivity to dust of residents, the 

materials of the road base for safety reasons, and possible environmental concerns of the 

neighborhood. Most requests for treatment are granted. Road construction areas are being 

dampened with water for dust control. Other areas for treatment, such as commercial 

construction zones or gravel pits, are investigated on a case by case basis. 

Dust Control Plans 

Alamosa County is considering changes in local ordinances governing dust control plans at 

construction sites. This will be addressed through the revision of Alamosa County’s 

Comprehensive Plan and supporting zoning codes. Alamosa County is currently reviewing 

language from other successful dust control programs for inclusion in their local ordinances. The 

process is due for completion in December 2003 or early 2004 and will specifically include dust 

control language. This effort is anticipated to reduce PM10 emissions in Alamosa, especially as it 

relates to impacts on the community and high recorded PM10 values. The Division commits to 

providing copies of this language to EPA upon finalization and availability. 

Wind Erosion of Open Areas

To reduce PM10 emissions from open areas outside of the City limits, low tilling and other soil 

conservation practices will continue to be utilized in the community. In addition, the community 

is using in strategic areas the State of Colorado Agricultural Office’s program to purchase and 

plant shelter trees to reduce wind erosion in open areas. These trees have a demonstrated 

advantage for the community and for air quality. Once the trees reach maturity, it is anticipated 

that the equivalent of 112 miles of double-rowed trees will be in place. 

In addition, there is ongoing planting of trees (approximately 50) on newly developed Alamosa 

County property south/southwest of Alamosa (prevailing winds from southwest) and the Airport 

south of Alamosa for added air quality improvement. 

These commitments are anticipated to further reduce the PM-10 emissions in Alamosa. 
ALAMOSA NATURAL EVENTS ACTION PLAN

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Sod and Vegetative Projects in the County

Numerous projects to reduce blowing dust and its impacts have happened or are happening at the 

County Airport. For example:

• Through additional grounds maintenance of the 40-acre Alamosa County airport south of 

the city, grass is being grown for aesthetics and dust control. 

• Sodding and the placement of decorative rock and ground cover will be implemented in 

the landscaping of the Alamosa County property, as well. These measures will directly 

abate blowing dust at the Airport. 

• Also, the widening of the airport’s safety areas (250 feet on either side of the runway) is 

now complete and seeding of natural grasses was incorporated in the project. Trees and 

grass were incorporated in the approaches to the airport and have provided additional 

wind-break advantages to South Alamosa. 

In other areas where watering is a problem, xeriscape (the use of native drought resistant

vegetation and/or rock cover) is being encouraged for County owned property and for all other 

property owners.

These efforts are anticipated to further reduce PM10 emissions in Alamosa.

Open Burning Issues at the County

The Colorado air pollution control laws and regulations prohibit open burning throughout the 

state unless a permit has been obtained from the appropriate air pollution control authority. In 

granting or denying any such permit, the authority will base its action on the potential 

contribution to air pollution in the area, climatic conditions on the day or days of such burning, 

and the authority’s satisfaction that there is no practical alternate method for the disposal of the 

material to be burned. No open burning is allowed when local wind speeds exceed 5 miles per 

hour. 

Colorado State University Co-Op Extension Office

In response to extremely dry conditions, the need to maintain area topsoil, and reduce impacts, 

the Colorado State University Co-Op Extension Office of Alamosa County provides the 

following outreach efforts and recommendations: 

• Modification of grazing practices to improve protective crop cover 

• Increasing crop residues left in the fields to reduce blowing dust 

• Planting of Fall crops to maintain fields

• Application of manure to protect top soils from blowing away 

• Staggering of the harvest to minimize blowing dust 
ALAMOSA NATURAL EVENTS ACTION PLAN

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• Outreach programs on soil conservation efforts 

• Development of outreach/education materials (e.g., news articles, newsletters, fact sheets, 

etc.), and

• Attendance at Statewide workshop to educate other Co-Op offices to various practices to 

reduce blowing top soil and minimize impacts

These control strategies are not meant to be enforceable. They are meant only to demonstrate the 

regional nature of cooperation in addressing blowing dust and its impacts on the community. 

Natural Resources Conservation Service

As stated elsewhere in this NEAP, Alamosa County is a predominately agricultural area where 

limited water, coupled with the frequent high winds experienced during late fall and early spring, 

can destroy crops, encourage pests, and damage soil surfaces lending them susceptible to wind 

erosion. Thus, activities that improve the topsoil and prevent its lifting during high wind events 

are encouraged. Some notable NRCS and agricultural examples include:

• Cover crops and perennial crops (e.g., alfalfa) are recommended to protect soils; 

• NRCS works with area farmers in the development of conservation compliance plans to 

also protect topsoil; 

• NRCS encourages the use of perennial crops or the leaving in place of weeds on the 

corners of area acreage (instead of tilling that might lead to open, barren lands) to reduce 

the lifting of topsoil;

• NRCS “cost shares” on conservation practices with local farmers to prevent soil erosion, 

and; 

• The NRCS works with Colorado State University to identify other strategies that 

minimize blowing dust.

Other successful agricultural practices encouraged in the area include: timing of tillage, crop 

rotation, amount of crop residue left on the land, and proper water usage. 

These control strategies are not meant to be enforceable. They are meant only to demonstrate the 

regional nature of cooperation in addressing blowing dust and its impacts on the community.

Natural Events Policy guidance indicates that control options must be implemented within three 

years of the exceedance in question. For Alamosa, BACM must be in place no later than April 

18, 2003. This submittal is meant to meet that three year commitment. 

This section fulfills the requirement of Element 4. 
ALAMOSA NATURAL EVENTS ACTION PLAN

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V. PUBLIC REVIEW AND PERIODIC EVALUATION

This section describes the public process used to develop this NEAP and the commitment made 

to periodically evaluate the plan. 

Stakeholder Involvement

The EPA’s NEAP development guidance states that the NEAP should be developed by the State 

in conjunction with the stakeholders affected by the Plan. The Colorado APCD worked with 

stakeholders mentioned throughout this document. Numerous meetings and telephone 

conversations occurred with stakeholders, and the final agreement here reflects control measures 

offered as part of the NEAP.

Public Review

The Division made this documentation available for and presented the NEAP and its strategies to 

the public to ensure public review and comment. Examples of these efforts in Alamosa, 

beginning with the earliest community involvement, include: 

• Briefing of the San Luis Valley County Commissioners, “Air Quality Briefing,” San Luis 

Valley County Commissioners’ Association Meeting, September 1999. 

• “Control Alamosa’s Dust? Lots of Luck.” Newspaper article appearing in Pueblo 

Chieftan indicating the area is developing a plan (NEAP) to address blowing dust – 

November 1, 2001. 

• Briefing of the Alamosa City Council, “Alamosa Air Quality and the Development of a 

Local Natural Events Action Plan,” a meeting to reintroduce the NEAP to City Council 

staff, February 6, 2002. 

• Placement of Natural Events Action Plan for Alamosa, Colorado at the area library 

(Southern Peaks Public Library) for public review, February 2002. 

• “Odd Issues Keep Alamosa Busy.” Newspaper article appearing in Valley Courier

indicating NEAP being developed and available for public review at the Southern Peaks 

Public Library, February 2002.

• Briefing of the Alamosa City Council, “Alamosa Natural Events Action Plan,” a meeting 

to incorporate comments from the City Council, local stakeholders, and the public, 

February 20, 2002. 

• Briefing of the Colorado Air Quality Control Commission, “Natural Events Action Plan 

for Alamosa, Colorado,” May 2002. 

• Briefing of the Colorado Air Quality Control Commission, “Alamosa Natural Events 

Action Plan – Final Activities,” January 2003. 

• Public Notice, “Natural Events Action Plan for Alamosa, Colorado” Available for Public 

Review and Comment at the Public Library, April 2003. 

• “Media Advisory” notifying public of upcoming Alamosa City Council meeting to 
ALAMOSA NATURAL EVENTS ACTION PLAN

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discuss the NEAP, monthly city council meeting agenda published in the area newspaper, 

May 2003. 

• “Media Advisory” notifying public of City Council meeting to discuss the NEAP, 

Channel Ten Cable Access Channel Public Service Announcement, May 2003. 

• Briefing of the Alamosa City Council, “Final Alamosa Natural Events Action Plan,” May 

2003. 

Periodic Evaluation 

EPA’s Natural Events Policy guidance requires the state to periodically reevaluate: 1) the 

conditions causing violations of the PM10 NAAQS in the area, 2) the status of implementation of 

the NEAP, and 3) the adequacy of the actions being implemented. The State will reevaluate the 

NEAP for Alamosa at a minimum of every 5 years and make appropriate changes to the plan 

accordingly. 

Evaluation of the effectiveness of the NEAP included several key strategies to ensure protection 

of public health and a robust plan. Strategies included: review of Natural Events Policy in 

specific relation to the Alamosa community, review of the effectiveness/appropriateness of 

ongoing control strategies, consideration of new/additional control options, review of 

meteorological and climatological conditions leading to blowing dust, review of local and 

regional PM10 monitoring data, discussions with other States (e.g., South Dakota, Washington) 

and Federal (US EPA) personnel regarding NEAP updates and protocols, review of the 

established emission inventory and identification of any new emission sources, review of the 

blowing dust advisory protocol and notification records, public/stakeholder meetings and 

community outreach/education efforts, etc. 

The Division commits to continually review the effectiveness of the Alamosa Natural Events 

Action Plan and improve the effort, where feasible. 

The Division commits to evaluate the NEAP at a minimum of every five years.

Submittal to EPA

The NEAP was submitted in its initial form to EPA in October 2001. Following EPA comment 

and input from stakeholders, appropriate changes were made to the NEAP. The Alamosa City 

Council heard and approved the NEAP in February 2002. Since that period, meetings with local 

agencies and stakeholders have led to finalization of stakeholder agreements (found elsewhere in 

the NEAP). The Final Natural Events Action Plan for Alamosa, Colorado and its Best Available 

Control Measures, where feasible, are presented here as required under the Natural Events 

Policy. 

This section fulfills the requirements of Elements 6, 7, 8, and 9 as described on page 4 and 5. 
D-1 

Appendix D – Copy of Affidavit of Public Notice