2010 PM10 Maintenance Plan and 

Redesignation Request for the 

Coso Junction Planning Area 

May 17, 2010 

Prepared by: 

Great Basin Unified Air Pollution Control District 

2010 District Governing Board: 

Tom Sweeney, Alpine County, Chairman 

Linda Arcularius, Inyo County, Vice-Chairman 

Richard Cervantes, Inyo County 

Byng Hunt, Mono County 

D. “Hap” Hazard, Mono County 

Neil McCarroll, Town of Mammoth Lakes 

Henry “Skip” Veatch, Alpine County 

Authors: 

Duane Ono, Deputy Air Pollution Control Officer 

Ken Richmond, ENVIRON International Corp. 

Great Basin Unified Air Pollution Control District 

Theodore Schade, Air Pollution Control Officer 

157 Short Street 

Bishop, California 93514 

Tel: (760) 872-821, Fax: (760) 872-6109 

Website: www.gbuapcd.org

 
The authors gratefully acknowledge the excellent support from Mike Slates for providing 

maps, Phill Kiddoo and Chris Howard for analyzing the PM10 and meteorological data, 

Dan Johnson for data collection and photo documentation at Coso Junction, and Jonathan 

Becknell for updating the emissions inventory for permitted facilities. 
2010 Coso Junction PM10 Maintenance Plan 

i 

PM10 Maintenance Plan and Redesignation Request 

for the Coso Junction PM10 Planning Area 

EXECUTIVE SUMMARY 

This document is a revision to the 2004 PM10 State Implementation Plan (SIP) for the Coso 

Junction PM10 Planning Area. It includes 1) a request to redesignate the area from 

nonattainment for the National Ambient Air Quality Standard for PM10 (federal standard) to 

attainment based on monitoring data and a modeling analysis, and 2) a maintenance plan that 

contains requirements to ensure the federal PM10 standard will not be violated in the future. As 

required to redesignate the area to attainment, the enclosed monitoring data and modeling 

analysis show the Coso Junction Planning Area (CJPA) had less than or equal to 1.0 average 

annual exceedances of the federal PM10 standard (150 μg/m3 for a 24-hour average) during the 

3-year period from January 2007 through December 2009. 

The 2004 State Implementation Plan for the Coso Junction Planning Area examined the PM10 

problem during the period from 1985 to 2003. During that period, 15 violations of the federal 

24-hour PM10 standard were monitored at the Coso Junction rest area on Highway US 395. 

Thirteen of those violations were found to have been caused by windblown dust from the dry 

lake bed of Owens Lake that is 14 miles outside (to the north) of the Coso Junction Planning 

Area. In November 2004, the District adopted a SIP for the CJPA to explain how the area would 

be brought into attainment. Since PM10 violations at Coso Junction were primarily caused by 

windblown dust from Owens Lake, the Coso Junction attainment demonstration relied on 

implementing dust controls outside of the planning area. Under the 2003 Owens Valley PM10 

SIP, windblown dust from 29.8 square miles of the dry lake bed at Owens Lake were required to 

be controlled by December 2006. A dispersion modeling analysis showed these dust mitigation 

efforts would be adequate to bring the Coso Junction Planning Area into attainment. 

A review of daily ambient monitoring data from Coso Junction showed three monitored 

exceedances of the federal 24-hour PM10 standard (150 micrograms per cubic meter, μg/m3

) 

during the 3-year period from January 2007 through December 2009. The federal 24-hour PM10 

standard allows no more than an average of 1.0 expected exceedances per year over a 3-year 

period. Since daily PM10 monitor data showed the monitor site had an average of 1.0 

exceedances per year, PM10 levels near the monitor site can be considered to be in attainment 

with the federal standard. 

A closer examination of the three exceedances found that two exceedances in 2007 (6/5/2007, 

217 μg/m3

; 12/6/2007, 283 μg/m3) were caused by windblown dust from an unpaved truck 

parking area west of the PM10 monitor site. The owner of the unpaved parking area was notified 

and the area was graveled in 2008 and surfaced with asphalt in 2009 to control fugitive dust. 

The third monitored exceedance (12/22/2009, 168 μg/m3

) was caused by windblown dust from 

Owens Lake. During that event, dust source areas at Owens Lake that were not previously 

identified in the 2003 Owens Valley SIP contributed to the exceedance at Coso Junction. A 

revision to the Owens Valley SIP in 2008 included the majority of these dust source areas as part 

of an additional 9.8 square miles of the lake bed that was controlled using shallow flooding in 
2010 Coso Junction PM10 Maintenance Plan 

ii 

April 2010. Another 3.5 square miles of the lake bed are expected to be controlled by October 

2010. Therefore, dust control measures were implemented to mitigate the causes of dust for all 

three PM10 exceedances at Coso Junction that took place during the 3-year attainment 

demonstration period. 

Although daily PM10 monitor data collected at the Coso Junction rest area showed the area 

could be considered to be in attainment with the federal standard, higher PM10 levels are likely 

to have occurred at locations closer to Owens Lake, since this is the primary source of 

windblown dust that caused Coso Junction to be designated nonattainment. The monitor site at 

the Coso Junction rest area is about 18 miles south of Owens Lake, while the northern boundary 

of the CJPA is closer at 14 miles from Owens Lake. To determine if windblown dust from 

Owens Lake caused PM10 violations at the northern boundary or at other locations in the CJPA, 

a dispersion model was run to analyze windblown dust impacts for the 3-year period from July 

2006 through June 2009. 

To evaluate attainment through a modeling analysis, the fourth highest value over a 3-year 

period must be below 150 μg/m3 at all locations. The District used the CALPUFF dispersion 

model, which is a guideline model recommended by the United States Environmental Protection 

Agency (US EPA) for long-range transport and situations where complex winds influence 

dispersion. As expected, the CALPUFF model showed the highest PM10 concentrations were at 

the northern boundary of the CJPA. The highest site had two days with modeled impacts above 

150 μg/m3 and a third high concentration of 150 μg/m3. Since 150 μg/m3 is not an exceedance of 

the PM10 standard there were only two modeled exceedances at the highest receptor site in the 

CJPA. The fourth highest modeled value at the same site for the 3-year period was 137 μg/m3. 

Therefore, the CALPUFF model analysis demonstrated it is reasonable to believe that attainment 

of the standard was achieved at all locations in the planning area. 

As a result of our evaluation of monitoring data and a CALPUFF modeling analysis, the District 

recommends through the adoption of this SIP revision that the California Air Resources Board 

request the US EPA redesignate the Coso Junction Planning Area from nonattainment to 

attainment for the federal PM10 standard. 

To ensure compliance with the federal PM10 standard is maintained in future years, the District 

evaluated future activities that could affect PM10 levels in the planning area and the adequacy of 

existing rules, policies and emission control requirements to control emissions from those 

sources and activities. District staff found that existing rules for fugitive dust and new source 

review were adequate to control potential new sources within the Coso Junction Planning Area. 

For PM10 sources outside the planning area, the major concern is for windblown dust from 

Owens Lake. District staff believes the control strategy and contingency requirements in the 

2008 Owens Valley PM10 SIP are adequate to protect air quality in the Coso Junction area. 

Therefore, no additional contingency measures will be needed to ensure future compliance with 

the federal PM10 standard in the Coso Junction Planning Area. 
2010 Coso Junction PM10 Maintenance Plan 

iii 

PM10 Maintenance Plan and Redesignation Request 

for the Coso Junction PM10 Planning Area 

Table of Contents

Page

Executive Summary i 

Table of Contents iii 

Glossary v 

 

Sections

1 Planning Area 1 

2 Clean Air Act Regulatory History 1 

3 Air Quality 4 

4 Attainment Emissions Inventory 9 

 4.1 Stationary Source Emissions 9 

 4.2 Area Source Emissions 9 

 4.3 Mobile Source Emissions 10 

 4.4 Emissions Growth Forecast 10 

 4.5 Wind Erosion from Sources Other than Owens Lake 11 

5 Control Strategy 11 

 5.1 Contingency Measures 12 

 5.2 Miscellaneous Sources and Model Background 15 

6 Air Quality Modeling and Attainment Demonstration 16 

 6.1 Modeling Techniques 16 

 6.2 Model Results 18 

7 Transportation Conformity 22 

8 General Conformity 22 

9 Request to Redesignate Coso Junction to Attainment 22 

10 Request to Approve Coso Junction PM10 Maintenance Plan 23 

11 References 24 

 
2010 Coso Junction PM10 Maintenance Plan 

iv 

 

PM10 Maintenance Plan and Redesignation Request 

for the Coso Junction PM10 Planning Area

Table of Contents

 Appendices 

A PM10 Air Quality Data for Coso Junction, CA (1985 – 2009)

B PM10 Concentrations and Hourly Meteorological Data for Exceedance Days 

C Board Order #080128-01 Requiring the City of Los Angeles to Undertake 

Measures to Control PM10 Emissions from the Dried Bed of Owens Lake

D Dispersion Modeling Results for Coso Junction PM10 Planning Area 

 

 Figures Page 

1 Coso Junction PM10 Planning Area map 2 

2 Former Searles Valley PM10 Planning Area map 3 

3 PM10 monitors in and near the Coso Junction Planning Area 5 

4 Emissions trend for Owens Lake emission reductions 13 

5 Photo of truck parking area west of Coso Junction PM10 monitor site 15 

6 CALPUFF modeling domain 17 

7 4th highest PM10 model concentration from July 2006 through June 2009 20 

8 Map of 24-hour average PM10 predictions for the design day 21 

 

 Tables

1 Summary of PM10 exceedances in the Coso Junction Planning Area 6 

2 Exceedances associated with windblown dust from Owens Lake 7 

3 Annual PM10 Concentrations in the Coso Junction Planning Area 8 

4 PM10 emissions inventory for the Coso Junction Planning Area (2009-2025) 10 

5 Existing District Rules and Regulations for control sources of PM10 14 

6 Summary of maximum PM10 model predictions 19 

 

 
2010 Coso Junction PM10 Maintenance Plan 

v 

GLOSSARY 

CALPUFF A USEPA recommended air quality model for long-range transport 

and situations where complex winds influence dispersion. 

CARB California Air Resources Board 

CFR Code of Federal Regulations 

CH&SC California Health and Safety Code 

CJPA Coso Junction Planning Area 

CoGa Coso Gate model receptor site 

CoJu Coso Junction model receptor site 

District Great Basin Unified Air Pollution Control District 

Dust ID Program Owens Lake Dust Identification Program 

Federal Standard National Ambient Air Quality Standard 

(PM10 = 150 μg/m3

 for a 24-hour average) 

GBUAPCD Great Basin Unified Air Pollution Control District 

PM10 particulate matter less than 10 microns 

PSD Prevention of Significant Deterioration 

SIP State Implementation Plan 

US EPA United States Environmental Protection Agency 

 

km kilometers 

m/s meters per second 

mph miles per hour 

μg/m3

 micrograms per cubic meter 

 
2010 Coso Junction PM10 Maintenance Plan 

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BLANK PAGE
2010 Coso Junction PM10 Maintenance Plan 

1 

PM10 Maintenance Plan and Redesignation Request 

for the Coso Junction PM10 Planning Area 

1 Planning Area 

The Coso Junction PM10 Planning Area (CJPA) is located in Eastern California in the southern 

portion of Inyo County (Figure 1). It is an arid desert area that receives less than 5 inches of rain 

per year. The area is rural in nature and sparsely populated. The principle PM10 monitor site is 

located at the Coso Junction rest area in the Rose Valley. This valley is flanked by the Sierra 

Nevada and Coso mountain ranges. The China Lake Naval Air Weapons Station, which covers 

most of the CJPA, is generally restricted from public access. 

Air pollution in the Coso Junction Planning Area is dominated by windblown dust transported 

from Owens Lake, which is located outside the planning area. Air pollution from District 

permitted facilities within the CJPA boundaries has generally not had a significant impact on 

PM10 concentrations in the planning area. These sources include the Coso geothermal power 

operations, military operations at the China Lake Naval Air Weapons Station, and volcanic 

cinder and pumice mining operations. Although generally not a problem in the planning area, 

high PM10 readings were documented in 1990 due to windblown dust from abandoned 

agricultural land, in 2002 from a wildfire, and in 1990 from windblown dust from an unpaved 

truck parking area. None of these types of events are expected to recur at Coso Junction. The 

agricultural land just north of the monitor site was stabilized by natural vegetation cover in 1991 

after the land was fallowed. Since that time no agricultural activities have taken place in the 

CJPA. Dust from the unpaved truck parking area, located adjacent to the PM10 monitor site 

was mitigated by covering it with gravel in 2008 and then asphalt pavement in 2009. 

2 Clean Air Act Regulatory History 

 

The Coso Junction Planning Area was initially designated as a PM10 nonattainment area in 1987 

along with the Indian Wells Valley and Trona. Together they comprised the Searles Valley 

PM10 nonattainment area as shown in Figure 2. The Great Basin Unified Air Pollution Control 

District adopted a State Implementation Plan (SIP) for the Coso Junction portion of the Searles 

Valley PM10 nonattainment area in November 1991 (GBUAPCD, 1991). This was followed by 

air quality plans for the Indian Wells Valley and Trona, which were regulated by the Kern 

County Air Pollution Control District and the Mojave Desert Air Quality Management District 

(formerly San Bernardino County Air Pollution Control District). 

In August 2002, the United States Environmental Protection Agency (US EPA) redesignated the 

Searles Valley into three separate PM10 nonattainment areas. Under this regulatory action, Coso 

Junction and the Indian Wells Valley were classified as moderate PM10 nonattainment areas, 

and a finding of attainment was made for Trona. (Federal Register, 2002a, 2002b) In 2003, 

Indian Wells Valley was reclassified to attainment with US EPA’s approval of the Moderate 

Area SIP and Maintenance SIP. (Federal Register, 2003a and 2003b) In November 2004, the 

Great Basin Unified Air Pollution Control District adopted a SIP revision for the Coso Junction 

PM10 Planning Area that forecast compliance with the federal PM10 standard in 2010. 
2010 Coso Junction PM10 Maintenance Plan 

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Figure 1. The Coso Junction Planning Area is located in the southern portion of Inyo County, CA. 

Much of the planning area is covered by the China Lake Naval Air Weapons Station, which has 

restricted access for the general public. Most of the PM10 standard exceedances monitored at 

Coso Junction were caused by windblown dust from the exposed lake bed at Owens Lake. 

 
2010 Coso Junction PM10 Maintenance Plan 

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Figure 2. The Searles Valley PM10 Nonattainment Area was reclassified into three separate 

planning areas in 2002. Indian Wells Valley and Trona were classified attainment for the federal 

PM10 standard in 2002 and 2003. 

The Coso Junction attainment demonstration was based on controlling dust from Owens Lake, 

which was scheduled to implement dust control measures on 29.8 square miles of the lake bed by 

December 31, 2006. The 2004 Coso Junction SIP included a CALPUFF dispersion model 

analysis that indicated that after dust controls were implemented at Owens Lake at the end of 

2006, the Coso Junction Area would be in attainment. However, an additional 3 years of data 

collection and monitoring were needed to demonstrate the CJPA had attained the PM10 standard. 

This document is intended to provide the air quality monitoring data and modeling analysis to 

demonstrate the area has attained the PM10 standard. In addition, it includes regulatory 

requirements to ensure the CJPA will maintain compliance with the federal PM10 standard in the 

future. 

 
2010 Coso Junction PM10 Maintenance Plan 

4 

3 Air Quality 

Twenty-two exceedances of the federal 24-hour PM10 standard were monitored at Coso Junction 

in the 24 years from 1985 to 2009. Eighteen out of 22 of these exceedances were caused by dust 

from Owens Lake. High northerly winds and high PM10 concentrations near Owens Lake are 

good indicators for windblown dust to be transported from the exposed lake bed at Owens Lake 

to the CJPA. 

To document the Owens Lake dust impact at Coso Junction and other downwind sites, a specialpurpose monitoring network was operated from 1993 to 1996. The monitoring network shown 

in Figure 3 measured Owens Lake dust impacts at five downwind sites and found exceedances of 

the standard as far as 50 miles from Owens Lake. PM10 monitors at Coso Junction, Navy I, and 

Pearsonville are within the CJPA boundaries. Sites north of Coso Junction are in the Owens 

Valley PM10 planning area and the monitor sites in Ridgecrest and Inyokern are in the Indian 

Wells PM10 planning area. 

Table 1 shows a summary of the PM10 exceedances monitored in the CJPA and the levels 

measured at other sites in the network. Table 2 shows PM10 concentrations, wind speed and 

directions in the Owens Lake area for these exceedance days. As previously mentioned, 18 of 

the 22 exceedances in the CJPA were caused by dust from Owens Lake. The exceptions to this 

are four events measured at Coso Junction on 4/23/90, 7/25/02, 6/5/07, and 12/6/07. 

• The event on 4/23/90 was caused by windblown dust from abandoned agricultural land 

located upwind from the monitor site. In 1991, this agricultural field naturally revegetated after heavy March rains. Since that time, the field has remained covered with 

volunteer vegetation and has not been observed as a dust source area. (GBUAPCD, 1991) 

• The event on 7/25/02 was caused by smoke from the McNally wildfire in the Sierra about 

20 miles west of the planning area. About 150,000 acres of mixed conifer, heavy brush 

and grass burned from July 21 to August 29, 2002. (Wilderness Society, 2003) 

• Two events on 6/5/07 and 12/6/07 were caused by windblown dust from an unpaved 

truck parking area west of the PM10 monitor site. The truck stop owner was notified and 

the parking area was surfaced with gravel in 2008 and recycled asphalt in 2009. 

Table 3 shows the number of monitored exceedances per year, and the expected number of 

exceedances per year based on the monitoring frequency. Prior to 2006, samples were normally 

collected on a once every sixth-day, or once every third-day schedule. In 2006, daily PM10 

monitoring was initiated at Coso Junction. Table 3 also includes the 3-year annual average 

PM10 concentrations for Coso Junction, which in 2009 was 19 μg/m3

. However, it should be 

noted that the US EPA revoked the annual PM10 standard in 2006, which at the time was set at 

50 μg/m3. A complete list of PM10 monitor data for Coso Junction and other nearby sites is 

included in Appendix A, and hourly data for the 22 exceedances is summarized in Appendix B. 
2010 Coso Junction PM10 Maintenance Plan 

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Figure 3. PM10 monitor locations in and near the Coso Junction Planning Area. 
2010 Coso Junction PM10 Maintenance Plan 

6 

Table 1. Summary of PM10 exceedances monitored over 150 μg/m3 in the Coso Junction Planning 

Area and concentrations at other sites on the same day. See Table 2 for causes of exceedances 

in the CJPA for the dates shown below and Appendix B for hourly meteorological data for these 

events. 

 24-Hour Average PM-10 Concentrations (μg/m3

) 

 

Coso Junction Planning 

Area 

Indian Wells 

Valley Owens Valley Planning Area 

Exceedance 

Date 

Coso 

Junction Navy Pearsonville 

Ridgecrest Inyokern Keeler Olancha Lone 

Pine 

Dirty 

Socks 

Flat 

Rock 

Shell 

Cut 

4/25/1985 307 92 

4/2/1986 1175 95 

6/7/1986 157 44 

1/15/1987 196 100 25 

2/3/1989 227 101 1861 126 

4/23/1990 866 94 200 

10/26/1993 254 131 16 59 112 346 

12/23/1993 188 50 18 9 412 185 58 

1/5/1994 388 239 75 199 365 76 

4/8/1995 692 392 235 158 128 107 

4/9/1995 567 331 2252 52 

4/21/1995 337 268 51 119 16 

4/27/1996 50 18 176 92 81 65 657 28 

5/23/1996 309 132 31 79 259 42 34 

3/6/1998 91 246 305 33 42 

3/18/1998 409 49 46 228 

7/25/2002 175 36 87 71 64 75 100 90 

2/2/2003 484 162 484 1062 116 10933 395 9162 

12/28/2006 296 2101 428 126 104 735 94 

6/5/2007 217 35 159 55 71 68 508 182 

12/6/2007 283 13 38 15 29 10 16 

12/22/2009 168 236 76 42 17 217 34 

 
2010 Coso Junction PM10 Maintenance Plan 

7 

Table 2. Over the last 25 years, violations of the federal PM10 standard in the Coso Junction 

Planning Area were primarily caused by dust from the Owens Lake area. See Table 1 for PM10 

concentrations on the dates shown below and Appendix B for hourly meteorological data for 

these events. 

Exceedance 

Date 

Maximum Hourly Wind 

Max Speed Primary Cause of Exceedance 

MPH @ 10 m 

Direction of 

Max Wind 

Degrees 

4/25/1985 30.0 335 N wind all day, Owens Lake Dust, Coso Met 

4/2/1986 37.5 350 N wind all day, Owens Lake Dust 

6/7/1986 27.5 315 Variable winds during day, Owens Lake 

Dust 

1/15/1987 40.0 35 N wind all day, Owens Lake Dust 

2/3/1989 38.0 285 Variable winds during day, Owens Lake 

Dust 

4/23/1990 26.0 272 Abandoned Ag Land Dust 

10/26/1993 29.3 18 N wind all day, Owens Lake Dust 

12/23/1993 25.7 35 N wind all day, Owens Lake Dust 

1/5/1994 31.0 22 Variable winds during day, Owens Lake 

Dust 

4/8/1995 23.2 316 Coso Junction Met, Owens Lake Dust 

4/9/1995 35.9 358 Coso Junction Met, Owens Lake Dust 

4/21/1995 29.2 7 N wind all day, Owens Lake Dust 

4/27/1996 26.0 38 N wind all day, Owens Lake Dust 

5/23/1996 30.7 5 N wind all day, Owens Lake Dust 

3/6/1998 34.9 354 Variable winds during day, Owens Lake 

Dust 

3/18/1998 12.0 48 Variable winds during day, Owens Lake 

Dust 

7/25/2002 17.6 163 McNally Fire smoke 

2/2/2003 36.2 3 N wind all day, Owens Lake Dust 

12/28/2006 46.8 337 N wind all day, Owens Lake Dust 

6/5/2007 36.2 264 W wind, Coso Junction Parking Area Dust 

12/6/2007 42.6 252 W wind, Coso Junction Parking Area Dust 

12/22/2009 39.1 1 N wind, Regional and Owens Lake Dust 

 
2010 Coso Junction PM10 Maintenance Plan 

8 

Table 3. The expected number of exceedances per year has decreased since dust control 

measures were implemented on 29.8 square miles of the Owens Lake bed in December 2006. 

 PM10 Concentration (μg/m3) Number 

of 

Exceeds 

Expected 

Number of 

Exceedances 

Per Year 

Number 

Sample 

Days 

 Annual 

Average 

3-Year 

Average 

Peak 

24-Hour 

Year 

1985 Invalid 307 1 49 

1986 51.51 1175 2 12 58 

1987 33.62 196 1 6 59 

1988 22.12 35.75 92 0 0 59 

1989 27.50 27.74 227 1 6 61 

1990 29.37 26.33 866 1 6 60 

1991 18.80 25.22 93 0 0 60 

1992 Invalid 38 0 36 

1993 28.78 254 2 12 59 

1994 16.69 388 1 6 61 

1995 32.28 25.92 692 2 12 58 

1996 Invalid 309 1 51 

1997 Invalid 92 0 54 

1998 23.31 409 1 6 59 

1999 14.84 46 0 0 114 

2000 15.02 17.72 74 0 0 110 

2001 11.88 13.91 100 0 0 122 

2002 18.04 14.98 175 1 3 115 

2003 20.54 16.82 484 1 3 121 

2004 14.89 17.82 66 0 0 121 

2005 18.24 17.89 97 0 0 119 

2006 20.72 17.95 296 1 1 273 

2007 19.91 19.62 283 2 2 363 

2008 18.63 19.75 137 0 0 366 

2009 18.59 19.04 168 1 1 362 

 
2010 Coso Junction PM10 Maintenance Plan 

9 

More information on the Coso Junction PM10 monitor site is included in the District’s annual 

Ambient Air Monitoring Network Plan, which was approved by the US EPA. (GBUAPCD, 

2009a) As a commitment in the maintenance plan for the CJPA the District is authorized to 

continue daily PM10 monitoring at the Coso Junction rest area to ensure new and existing 

sources of PM10 are identified and controlled, if necessary. (CH&SC §40001) 

4 Attainment Emissions Inventory 

The attainment emissions inventory for the CJPA is based on estimated daily PM10 emissions 

for 2008. Emission estimates for 2008 are typical of emissions in the CJPA over the 3-year 

period (2007-09) when PM10 compliance was determined from monitoring and modeling 

evaluations. PM10 emissions generated in the CJPA are primarily from permitted facilities on 

the China Lake Naval Air Weapons Station property, which is generally restricted from public 

access. Table 4 shows the daily PM10 emissions inventory for permitted facilities in the CJPA 

and for area and mobile sources. Total PM10 emissions are estimated at 1,478 pounds per day. 

In comparison, total daily PM10 emissions generated in the CJPA are less than 0.1% of the 

emissions caused by windblown dust from Owens Lake, which is the primary cause of PM10 

violations at Coso Junction. PM10 emissions from Owens Lake were estimated at 1.55 million 

pounds for the CJPA design day (January 5, 2007). 

4.1 Stationary Source Emissions

The point source emission estimates shown in Table 4 were developed from information 

contained in current District and federal Title V permit files. Unpaved road and haul road 

emissions for permitted sources are included in the daily emissions for each facility. Emissions 

were based on 10-hour workdays for the pumice and rock plants. 

4.2 Area Source Emissions

Unpaved road dust emissions in the area source category are estimated for non-permitted facility 

related traffic. An estimate of PM10 emissions from reentrained road dust from unpaved roads is 

based on the method found in US EPA’s Compilation of Air Pollution Emission Factors, AP-42

(USEPA, 2006). 

 ܧ ൌ ௞ ൫௦ ଵଶ ൗ ൯

ೌ

൫ௌ

ଷ଴ ൗ ൯೏

൫ெ

଴.ହ ൗ ൯

೎ െ ܥ Eq. 1 

Where: E = PM10 emissions in pound per vehicle mile traveled 

s = silt content of road surface material (5%) 

S = mean vehicle speed (30 miles per hour) 

M = surface material moisture content (assume 0.3%) 

C = emission factor for 1980’s vehicle fleet exhaust, brake wear and tire wear 

(0.00047 for PM10). 

For PM10 from public unpaved roads: k = 1.8, a = 1, d = 0.5 and c = 0.2. 

 
2010 Coso Junction PM10 Maintenance Plan 

10 

Table 4. Daily PM10 emissions inventory for the Coso Junction Planning Area for 2008 through 

2025. For the purpose of the maintenance plan, no significant growth is expected in the 

emissions inventory through the year 2025. 

Equation 1 yields an emission rate of 0.83 pounds of PM10 per vehicle mile traveled. Assuming 

an average of 2 vehicle trips per day on 50 miles of unpaved roads in the public portion of the 

CJPA, yields 100 vehicle-miles per day and 83 pounds of PM10 per day. (CARB, 2010a) 

PM10 from paved road dust is based on CARB’s emission estimates for Inyo County in 2008 

(0.99 tons of PM10 per day) and pro-rated for the proportion of traffic in the CJPA (5.1%), 

which yields 101 pounds per day. (CARB, 2010b) 

Based on population growth in Inyo County, area source emissions are not expected to change 

significantly in future years. 

4.3 Mobile Source Emissions

PM10 from on-road motor vehicle emissions (excludes re-entrained road dust) is based on 

CARB’s emission estimates for Inyo County in 2008 (0.12 tons of PM10 per day) and pro-rated 

for the proportion of traffic in the CJPA (5.1%), which yields 12 pounds per day. (CARB, 2010) 

The mobile source emissions are not expected to change in future years. 

4.4 Emissions Growth Forecast

Due to the sparse population, lack of population growth, and the expectation that industrial 

operations in the planning area will not change significantly, the emissions inventory forecast 

will remain stable for all future years. The 2000 US census shows 102 people living in the Coso 

Junction Planning area in the communities of Pearsonville and Homewood Canyon. This is 

about 0.5% of the total population of Inyo County. According to the US Census Bureau, Inyo 

County’s population declined from 18,281 in 1990 to 17,945 in 2000. Population continued to 

Daily PM10 Emissions for 2008 through 2025

Stationary Sources Pounds/day

California Lightweight Pumice 167

China Lake Naval Air Weapons Station   84

Coso Operating Company 953

Halliburton Services 20

Twin Mountain Rock 58

Area Sources

Unpaved Roads 83

Paved Roads 101

Mobile Sources

On‐Road Motor Vehicles 12

Total PM10 (pounds per day) 1,478
2010 Coso Junction PM10 Maintenance Plan 

11 

decline to 17,136 in 2008. Over those 18 years, Inyo County’s population decreased by 4.5%. 

(US Census Bureau, 2010) 

For the purpose of the emissions forecast for the maintenance plan, the daily PM10 emissions 

inventory will be the same as shown in Table 4 for the next 17 years through the year 2025. 

4.5 Wind Erosion from Sources Other than Owens Lake

Undisturbed open areas in the CJPA are generally invulnerable to significant wind erosion. 

Ambient monitors show low PM10 concentrations (23 μg/m3

) on windy days when winds are not 

from the direction of Owens Lake or other known windblown dust source areas (see section 5.2). 

Two known windblown dust source areas in the CJPA, however were found to be significant. 

In 1990 and 2007, three exceedances of the federal PM10 standard were monitored at Coso 

Junction, which were caused by windblown dust from a fallow agricultural field and an unpaved 

truck parking area (see Table 2). As noted in the air quality discussion, these areas are no longer 

a dust problem since the agricultural field is protected by volunteer vegetation cover and the 

truck parking area is now paved. Since these areas are no longer a significant source of dust, 

they are not included in the daily PM10 emissions in Table 4 for the years 2008 through 2025. 

However, PM10 emissions from these source areas can be estimated for each of the event days in 

1990 and 2007. 

A wind tunnel-based emissions algorithm was developed for the 1998 Owens Valley PM10 SIP, 

which can be used to estimate PM10 emissions from the agricultural field , public unpaved 

roadways and the unpaved truck parking area. The Owens Lake emissions equation for the fall 

period (equation 2) provides a good estimate for wind erosion in the CJPA since the surfaces can 

be considered to be disturbed, but they lack the efflorescent salts that characterize the lake bed 

surface at Owens Lake in the spring. (E = 0 in equation 2 for u < 7.6 m/s) (GBUAPCD, 1998) 

ܧ ൌ 1.34 ൈ 10ିହ ݁ሺ଴.ଶହൈ௨ሻ Eq. 2 

Where: E = PM10 emissions in grams per square meter per second 

u = Hourly average wind speed at 10 m in meters per second (for u > 7.6 m/s) 

Appendix B includes meteorological data for these three wind events. The agricultural field 

covered 314.5 acres on 4/23/1990, and the PM10 emissions on that day are estimated at 12,566 

pounds. Wind erosion from the unpaved truck parking area (4.7 acres) is estimated at 551 

pounds on 6/5/2007 and 763 pounds on 12/6/2007. Wind erosion from unpaved roadways in the 

CJPA (46.8 acres) is estimated at 5,489 pounds on 6/5/2007 and 7,611 pounds on 12/6/2007. 

5 Control Strategy 

As discussed in the Air Quality section of this document, PM10 exceedances in the CJPA are 

primarily due to the transport of windblown dust from the Owens Lake area. Therefore, 

achieving emission reductions at Owens Lake is the primary control strategy for reaching 

attainment in the CJPA. The US EPA classified the southern Owens Valley as a serious PM10 
2010 Coso Junction PM10 Maintenance Plan 

12 

nonattainment area in 1993 and required a SIP be developed to achieve compliance with the 

federal standard. A SIP was adopted in 1998 and approved by the US EPA for the Owens Valley 

with an interim control strategy that required dust controls on 16.5 square miles of the lakebed. 

Under the Owens Valley SIP, the City of Los Angeles is responsible for mitigating the dust 

generated from Owens Lake in order to bring the area into attainment with the federal standard. 

(GBUAPCD, 1998) The Owens Valley SIP was revised in 2003 to expand dust controls to 29.8 

square miles of the lake bed by December 31, 2006. (GBUAPCD, 2003) The City of Los 

Angeles successfully implemented these control measures by the required deadline. Another 

revision to the Owens Valley SIP in 2008 expanded control requirements to a total of 43.1 square 

miles of the Owens Lake bed. The Board Order to implement control measures in the 2008 SIP 

is included as Appendix C of this document. The City of Los Angeles is expected to have dust 

control measures implemented on 39.6 square miles of the lakebed by April 1, 2010, and then to 

expand the control area to 43.1 square miles by October 1, 2010. (GBUAPCD, 2008; 

GBUAPCD, 2009b) 

Figure 4 shows the annual PM10 emissions trend for the Owens Valley planning area. The blue 

line represents total PM10 emissions from all sources in the planning area, and the red line 

represents the windblown dust emissions from the Owens Lake bed. The dashed lines represent 

emission forecasts for Owens Lake based on the implementation of additional control measures 

on the lake bed and in the Keeler Dunes. Actual PM10 emissions from the Owens Lake bed 

have been reduced by 90% since 2000 when the City of Los Angeles initiated efforts to control 

windblown dust at Owens Lake. Windblown dust emissions were estimated using hourly PM10 

emission measurements collected through the Owens Lake Dust Identification Program. Hourly 

data on windblown dust was collected from 2000 through 2008 using the methodology described 

in the Owens Valley PM10 SIP. (GBUAPCD, 2008) The decrease in windblown dust emissions 

from Owens Lake after 2006 is reflected in the reduction in Owens Lake-caused PM10 

exceedances monitored at Coso Junction in 2007, 2008 and 2009 (Table 3). The additional 2008 

Owens Valley SIP control measures, which will be implemented in 2010 should result in even 

lower PM10 levels at Coso Junction than those observed during this 3-year period. 

Other sources of PM10 that caused exceedances of the federal standard at Coso Junction 

included; a wildfire and windblown dust from agricultural operation and from an unpaved truck 

parking area. These events were discussed in the Air Quality section of this document. Current 

District rules are adequate to prevent agricultural operations, prescribed burning, and windblown 

dust from disturbed surface areas from causing exceedances of the standard in the future. Table 

5 shows the current District rules that limit PM10 emissions in the planning area. 

5.1 Contingency Measures

The Owens Valley SIP also includes contingency measures (referred to as Supplemental Control 

Requirements in the Owens Valley SIP) that require the City of Los Angeles to implement dust 

control measures on any new windblown dust areas on the lakebed and to improve dust control 

measures in areas where it is necessary to prevent exceedances of the PM10 standard at any 

location on the shoreline of Owens Lake (see Appendix C, Board Order #080128-01 Requiring 

the City of Los Angeles to Undertake Measures to Control PM10 Emissions from the Dried Bed 

of Owens Lake). The District will rely on all the PM10 control measures and the Supplemental 

Control Requirements in the Owens Valley SIP, and existing District rules to ensure compliance
2010 Coso Junction PM10 Maintenance Plan 

13 

Figure 4. Since 2000, actual PM10 emissions from the exposed lakebed at Owens Lake have 

decreased by 90% as a result of dust control measures implemented by the City of Los Angeles. 

PM10 emissions will decrease in 2011 after additional dust controls are implemented on 13.3 

square miles of the lake bed. This will bring the total to 43.1 square miles of dust control areas. 

is maintained in the CJPA. The Board Order in Appendix C includes all the Owens Lake control 

measures and the Supplemental Control Requirements, which the District will rely on to prevent 

Owens Lake dust from causing future violations in the CJPA. (GBUAPCD, 2008) 

The District is authorized to continue daily ambient PM10 monitoring at Coso Junction (CH&SC 

§ 40001). If an exceedance of the federal PM10 standard is monitored the District will 

investigate the cause of the exceedance within 60 days following the end of the calendar quarter 

during which the event occurred. Exceedances found to be caused by dust from Owens Lake 

will be investigated to determine if the required control measures were properly implemented in 

accordance with Board Order #080128-01. Exceedances found to be caused by dust from local 

sources that are subject to current District regulations will be addressed and corrected. 

Exceedances found to be caused by Exceptional Events, such as wildfires or earthquakes will be 

flagged in accordance with US EPA policy (Federal Register, 2007). 

To prevent new facilities from causing an air pollution problem, any new facilities in the CJPA 

that may emit air pollution will be subject to the District’s new source review rules (209-A, 216 

and 216-A). Facilities that qualify as a major source under the US EPA federal permitting 

guidelines will also be subject to federal PSD (Prevention of Significant Deterioration) 

permitting requirements (40 CFR 51.166 and 52.21). 
2010 Coso Junction PM10 Maintenance Plan 

14 

Table 5. Existing District rules and regulations to control sources of PM10. 

 

District 

Rule Description

209-A 

Requires new sources with PM10 emissions greater than 250 pounds per day of total 

suspended particulates, or facility modifications of greater than 15 tons per year of 

PM10 to apply Best Available Control Technology to control PM emissions. 

216 Requires the Air Pollution Control Officer to evaluate air pollution impacts before 

issuing an Authority to Construct or Permit to Operate for a new facility. 

216-A Requires permits for any new secondary source of air pollution including buildings, 

commercial parking and housing developments. 

400 Limits visible emissions from any source, except those exempted under Rule 405, to 

less than Ringelmann 1 or 20% opacity. 

401 Requires reasonable precautions be taken to prevent visible particulate emissions from 

crossing the property boundary. 

402 Prohibits sources of air pollution from causing a nuisance to the public or endangering 

public health and safety. 

408 Limits agricultural burning operations to designated burn days and requires a burn 

permit. 

409 Limits range improvement burning to designated burn days and requires a burn plan 

be approved by the Air Pollution Control Officer. 

410 Limits forest management burning to designated burn days and requires a burn plan be 

approved by the Air Pollution Control Officer. 

411 Limits wildland management burning to designated burn days and requires a burn plan 

be approved by the Air Pollution Control Officer. 

502 Requires conservation management plans to reduce fugitive dust emissions from 

agricultural operations greater than 10 acres in Inyo, Mono and Alpine Counties 

Reg. XII 

Requires that federal actions and federally funded transportation-related projects 

conform to SIP rules and that they do not interfere with efforts to attain federal air 

quality standards. 

Reg. XIII 

Requires that federal actions and federally funded projects conform to SIP rules and 

that they do not interfere with efforts to attain federal air quality standards. Federal 

actions that have the potential to emit more than 100 tons per year of PM10 in the 

CJPA will be required to complete a conformity determination. 

 
2010 Coso Junction PM10 Maintenance Plan 

15 

Figure 5. Windblown dust from this truck parking area located west of the PM10 monitor site at 

the Coso Junction rest area caused two exceedances of the PM10 standard in 2007. The parking 

area was graveled in 2008 to control dust. In 2009, most of it was paved and used as a staging 

area for a highway construction project. The PM10 monitor site is the structure with the railing on 

top in the center of the photo. Coso Junction wind measurements are taken at a 10 m height on 

the tower to the left (north) of the PM10 monitor. (View looking to the northeast, February 24, 2010) 

5.2 Miscellaneous Sources and Model Background

To determine the PM10 contribution from miscellaneous sources other than Owens Lake on days 

with Owens Lake dust events, the District reviewed the hourly PM10 data from the Coso 

Junction monitor site. By looking at hours with high winds (>7 m/s, 16 mph) and screening out 

wind directions from Owens Lake and the unpaved parking area located to the west of the 

monitor, the average PM10 concentration at Coso Junction was determined to be 23 μg/m3

 on 

windy days. This is close to the average background concentration of 20 μg/m3 that was 

determined for sites in the Owens Valley Planning Area. If the unpaved parking area had been 

included in the wind direction screening, the average PM10 concentration for high wind hours 

would have been 40 μg/m3

. However, since this source has already been adequately controlled 

by gravel and asphalt pavement it will not be treated in the model attainment demonstration. 

Figure 5 shows a photo taken on February 24, 2010 of the paved truck parking area located west 

of the Coso Junction PM10 monitor site. To account for sources other than windblown dust 

from Owens Lake in the attainment demonstration a background concentration of 20 μg/m3 was 

added to all 24-hour model predictions. 
2010 Coso Junction PM10 Maintenance Plan 

16 

6 Air Quality Modeling and Attainment Demonstration 

Since 18 of the 22 PM10 violations monitored at Coso Junction were found to have been caused 

by windblown dust from the Owens Lake bed, the Owens Valley PM10 model was used to 

model the attainment demonstration for the Coso Junction PM10 redesignation request and 

maintenance plan. It should be noted the four non-Owens Lake-caused exceedances, were 

caused by: windblown dust from a fallow agricultural field, which is now stabilized with 

volunteer vegetation; an unpaved truck parking area, which has since been paved and graveled; 

and a wildfire in 2002. The air quality modeling study was not intended to simulate these types 

of non-recurrent events. 

Dispersion modeling was performed to estimate PM10 concentrations during high wind events 

along the southern boundary of the Owens Valley PM10 Planning Area, which is the northern 

boundary of the CJPA. Dust source areas at Owens Lake were simulated using the methods 

described in the Owens Valley PM10 Planning Area 2003 and 2008 State Implementation Plan 

revisions (GBUAPCD, 2003; GBUAPCD, 2008). Based on the sand flux and meteorological 

data collected during July 2006 to June 2009, the simulations suggest PM10 concentrations from 

dust source areas on Owens Lake will not cause violations of the federal PM10 standard in the 

neighboring Coso Junction PM10 planning area. 

6.1 Modeling Techniques

Dispersion model simulations were performed with the regulatory version 5.8 of the CALPUFF 

modeling system following the techniques of the Owens Lake Dust ID Program summarized in 

the 2003 and 2008 Owen Valley SIPs. The data collected by the Owens Lake Dust ID Program 

include surface meteorological data (at 10 m height), upper air meteorological soundings, source 

area delineations, and horizontal sand flux observations. Sand flux measurements are used as the 

basis for PM10 emission rates from windblown sources on Owens dry lakebed. Full details on 

the modeling protocol for this study can be found in District Board Order #080128-01, 

Attachment C, Section 6.0 (included as Appendix C of this document). Some of the features of 

the Coso Junction CALPUFF model simulation were: 

• Model simulation period was from July 2006 to June 2009 using the last three years of 

data available from the Owens Lake Dust ID Program. 

• The Owens Valley study domain was extended to the south to include the common 

boundary of the southern Owens Valley and northern Coso Junction PM10 planning 

areas. The revised modeling domain is depicted in Figure 6. The revised study domain is 

36 km-by-67 km versus the Owens Valley domain of 34 km-by-48 km. 

• The same vertical and horizontal mesh sizes are used in both modeling analyses. 

• Data collected at two additional surface meteorological stations in the southern portions 

of the current domain were used to construct the wind fields for the simulations. Data 

from the Coso Junction (CoJu) and Coso Gate (CoGa) sites shown in Figure 6 were 

prepared using the same methods as described in the Owens Valley PM10 SIP. 

 
2010 Coso Junction PM10 Maintenance Plan 

17 

400 405 410 415 420 425 430

UTM East-West (km)

3990

3995

4000

4005

4010

4015

4020

4025

4030

4035

4040

4045

4050

4055

UTM North-South (km)

Keel

Lone

Sock

Olan

Atow

Delt

Flat

Scut

Cott

Mill

CoJu CoGa

Btow

Stan

Lizt

Figure 1. Dispersion Modeling Domain

Monitoring Stations Shown on 1-km Mesh Size Land Use and Terrain 

Terrain Contours in Meters, USGS Land Use

10

20

30

40

50

60

70

80

90

100

USGS

Land Use

NAA Boundary

Mixed urban

Agriculture

Range

Forest

Water

Wetland

Salt Flat/Sand/Barren

Snow

Tundra/Bare

Met. Site

TEOM

 

Figure 6. The dispersion modeling domain for the Owens Valley and Coso Junction Planning 

Areas was 36 km by 67 km. 
2010 Coso Junction PM10 Maintenance Plan 

18 

• To assess attainment, PM10 concentration predictions were obtained at 90 receptors 

placed along the southern Owens Valley PM10 Planning Area boundary. The receptor 

interval shown in Figure 6 is 300-600 m. A receptor was also placed at the Coso Junction 

site where current and historical PM10 observations are/have been collected. 

• Area source PM10 emission fluxes were calculated using hourly Sensit sand motion data 

and seasonal proportionality constants (K-factors) for July 2006 to June 2009. The 

procedures used to derive the seasonal 75th percentile K-factors are described in the 2003 

and 2008 Owens Valley PM10 SIPs. 

• Twelve different area source configurations were available from the Owens Lake Dust ID 

Program based on source delineations for the three-year period. 

• No additional controls were assumed for the Owens Lake sources. Sources were 

characterized as observed during the simulation period without the effects of controls 

planned for many of these areas. 

• As in the 2003 and 2008 Owens Valley SIP attainment demonstrations, the current 

simulations only include windblown emissions from sources on the lakebed and the 

Keeler Dunes. As discussed in the previous section, in order to account for background 

and miscellaneous sources, model predictions were added to a background concentration 

of 20 μg/m3

. This same background concentration is also included in the modeling 

protocol for the Owens Valley SIP (GBUAPCD, 2003; GBUAPCD, 2008). 

• Attainment for the 24-hour PM10 NAAQS was assessed using the fourth highest daily 

prediction at the same receptor during the three-year simulation. 

Appendix D of this document provides a summary of the model results. It also includes an 

evaluation of model performance comparing predictions and observations for 10 monitor sites in 

the Owens Valley and Coso Junction planning areas. The model performance results suggest 

model predictions as a whole are relatively unbiased, but scattered, and that the predicted 

frequency distributions are generally within a factor-of-two of the observed distribution. 

6.2 Model Results

Table 6 summarizes the results for the CALPUFF simulations of Owens Lake dust events during 

July 2006 through June 2009, conservatively assuming no future controls would reduce 

emissions. Figure 7 shows predicted 24-hour design concentrations at the common planning area 

boundary. The design concentration is the 4th highest 24-hour prediction in the three-year 

simulation. If the design concentration is under the federal standard of 150 μg/m3

, then that 

location is in attainment with the standard. The modeling results show the highest design 

concentration including background at the boundary of the CJPA is 137 μg/m3

. 
2010 Coso Junction PM10 Maintenance Plan 

19 

Table 6. Summary of maximum PM10 model predictions in the Coso Junction Planning Area for 

the period from July 2006 through June 2009. The design concentration is the 4th highest 24-hour 

prediction in the three-year simulation at the same location, in this case it is 137 μg/m3

. 

Summary of Maximum PM10 Predictions 

July 2006 to June 2009 

Statistic Period 

PM10 

(μg/m3) 

Max 24-hour 3q06-2q09 225.5 

2nd 24-hour 3q06-2q09 164.2 

3rd 24-hour 3q06-2q09 150.5 

4th 24-hour 3q06-2q09 136.6 

Average 3q06-2q07 20.6 

Average 3q07-2q08 21.1 

Average 3q08-2q09 21.7 

Average 2007 20.4 

Average 2008 21.2 

As would be expected, the highest 24-hour PM10 concentration occurred at the boundary of the 

Owens Valley and Coso Junction planning areas near the valley floor and along the west side of 

the valley. The model showed PM10 concentrations decreasing at distances further from Owens 

Lake. The added distance to the southern boundary of the Owens Valley Planning Area and 

associated greater dilution of dust source plumes, produces much lower predictions than for 

receptors placed along the Owens Lake shoreline. Figure 8 shows that 24-hour average PM10 

concentrations for the model design day for Coso Junction (January 5, 2007) decreased at 

locations further from Owens Lake. 

The dust sources on the Owens Lake bed were simulated as ground level area sources located 

inside the historical shoreline. The CALPUFF modeling system assumes passive, non-buoyant 

ground based sources remain ground based as they travel downwind and concentrations within 

individual dust plumes always decrease with downwind distance. Stagnation and re-circulation 

of dust source plumes that might result in pockets of higher concentrations at fixed downwind 

receptor locations generally do not occur concurrently with the regional high wind events that are 

necessary to produce emissions on the lakebed. When only emissions from lakebed sources are 

considered, attainment of the PM10 standard at the northern boundary of the CJPA is sufficient 

to demonstrate attainment within the entire planning area. 

 
2010 Coso Junction PM10 Maintenance Plan 

20 

400 405 410 415 420 425 430

UTM East-West (km)

3990

3995

4000

4005

4010

4015

4020

4025

4030

4035

4040

4045

4050

4055

UTM North-South (km)

Keel

Lone

Sock

Olan

Atow

Delt

Flat

Scut

Cott

Mill

CoJu CoGa

Btow

Stan

Lizt

39

46

61 11611580

116

7983 86

9387

8379 66

67

65

59

57

56

56 47

Figure 6. Predicted 4th Highest 24-hour PM10 (μg/m3)

Receptors at Southern Limit of Owens Valley PM10 Planning Area

July 2006 to June 2009, Every 4th Prediction Plotted

Hi-4th Highest = 136.6 μg/m3

CoJu 4th Hi = 57.8 μg/m3

 

Figure 7. The predicted 4th highest 24-hour PM10 concentration over 3 years for receptors on 

the northern boundary of the CJPA are shown on the map below. Every 4th receptor 

concentration is plotted on the map. The 3-year modeling period is from July 2006 through 

June 2009. 
2010 Coso Junction PM10 Maintenance Plan 

21 

Figure 8. This isopleth map shows model concentrations for the 4th highest day in the CJPA over 

the 3-year modeling period (January 5, 2007). Modeled 24-hour average PM10 concentrations are 

below the federal standard of 150 μg/m3 at all locations in the CJPA. 
2010 Coso Junction PM10 Maintenance Plan 

22 

It should be noted the current analysis used estimates of windblown emissions during July 2006 

through June 2009—future emissions will be substantially lower. The model simulations for the 

attainment demonstration did not account for controls currently planned on many of these source 

areas that will be implemented in the future. If planned controls, such as the 13.3 square miles 

that will be completed in October 2010 were considered in the modeling analysis, predicted 

concentrations would be much lower than suggested by the current simulations. 

7 Transportation Conformity 

Transportation conformity requirements contained in District Regulation XII require that federal 

actions and federally funded transportation projects conform to SIP rules and that they do not 

interfere with efforts to attain federal air quality stands. Transportation sources were not found 

to contribute to the nonattainment problem at Coso Junction and PM10 from paved roads. 

Estimated at 113 pounds per day, paved road emissions comprise less than 10% of the daily 

PM10 emissions in the CJPA (see Table 4), and less than 1/100th of a percent of the Owens Lake 

dust emissions on the design day (1.55 million pounds on January 5, 2007). Due to their benign 

role in the PM10 problem in the CJPA, transportation-related projects such as road construction 

will be exempt from Transportation Conformity determination requirements under District 

Regulation XII. 

8 General Conformity 

General conformity requirements contained in District Regulation XIII require that federal 

actions and federally funded projects conform to SIP rules and that they do not interfere with 

efforts to attain federal air quality standards. A conformity determination is currently required 

for any federally funded (non-transportation) project or action that takes place in a moderate 

PM10 nonattainment area, including the CJPA that has the potential to exceed a de minimis

PM10 emissions threshold of 100 tons per year. In order to maintain the stringency of control 

requirements in the CJPA under a maintenance plan, the District will retain the 100 tons of 

PM10 per year de minimis emissions threshold for triggering a conformity determination as 

currently required under District Regulation XIII. 

9 Request to Redesignate Coso Junction to Attainment 

Through this document the District demonstrated that, over the 3-year period from January 2007 

through December 2009, the Coso Junction area attained the federal 24-hour standard for PM10. 

Daily PM10 monitoring data collected at Coso Junction over the last 3 years has not shown more 

than 1.0 exceedances of the PM10 standard per year as required to demonstrate attainment of the 

federal standard. In addition, a dispersion modeling analysis was performed for a 3-year period 

to demonstrate no more than 1.0 exceedances of the PM10 standard could be expected at any 

location in the Coso Junction Planning Area. The District believes the Coso Junction PM10 

Planning Area has attained the federal PM10 standard and requests the California Air Resources 

Board recommend to the US Environmental Protection Agency that the area be redesignated 

from nonattainment to attainment with the federal PM10 standard. 
2010 Coso Junction PM10 Maintenance Plan 

23 

10 Request to Approve Coso Junction PM10 Maintenance Plan 

To ensure that compliance with the federal PM10 standard is maintained in future years, the 

District evaluated future activities that could affect PM10 levels in the planning area and the 

adequacy of existing rules, policies and emission control requirements to control emissions from 

those sources and activities. District staff found that existing rules for fugitive dust, new source 

review and General Conformity were adequate to control potential new sources within the Coso 

Junction Planning Area. 

Emissions from PM10 sources in the CJPA decreased over the last 18 years due to a drop in local 

population and the closing of one of the permitted facilities. Emission sources in the CJPA are 

not expected to increase in the future, but it is more likely that they will either remain steady or 

decline. However, if new facilities are constructed in the CJPA, District regulations for new 

source review (Rule 209-A, 216, and 216-A) and federal PSD regulations (40 CFR 51.166 and 

52.21) will prevent PM10 emissions from new facilities from causing or contributing to 

exceedances of the PM10 standard. 

The major concern for maintaining PM10 compliance in the CJPA is for windblown dust from 

Owens Lake. Since 13.5 square miles of additional control measures are expected to be 

implemented at Owens Lake by October 1, 2010, PM10 air quality is expected to continue to 

improve in the CJPA as emissions from Owens Lake decline. District staff believes the control 

strategy and contingency requirements in the 2008 Owens Valley PM10 SIP are adequate to 

protect air quality in the Coso Junction area. Therefore, no additional contingency measures will 

be needed to ensure future compliance with the federal PM10 standard in the CJPA. 

Furthermore, as a commitment in the Coso Junction PM10 Maintenance Plan, the District will 

continue daily monitoring of PM10 at the Coso Junction rest area to help ensure new sources of 

PM10 are identified and controlled if necessary. If an exceedance of the federal PM10 standard 

is monitored the District will investigate the cause of the exceedance within 60 days from the end 

of the calendar quarter in which the event occurred. Exceedances found to be caused by dust 

from Owens Lake will be investigated to determine if the required control measures were 

properly implemented in accordance with Board Order #080128-01. Exceedances found to be 

caused by dust from local sources that are subject to current District regulations will be 

addressed and corrected. Exceedances found to be caused by Exceptional Events, such as 

wildfires or earthquakes will be flagged in accordance with US EPA policy (Federal Register, 

2007). 

The District requests that this document be approved by the California Air Resources Board as 

the PM10 Maintenance Plan for the Coso Junction Planning Area and submitted to the US 

Environmental Protection Agency for their consideration and approval. 

 
2010 Coso Junction PM10 Maintenance Plan 

24 

11 References 

CARB, 2010a. Comments on CJPA PM10 Emissions Inventory, California Air Resources Board, 

May 4, 2010. 

CARB, 2010b. Emissions Inventory Data, California Air Resources Board, website accessed 

February 11, 2010, http://www.arb.ca.gov/ei/emissiondata.htm. 

Federal Register, 2002a. Clean Air Act Redesignation and Reclassification, Searles Valley 

Nonattainment Area; Designation of Coso Junction, Indian Wells Valley, and Trona 

Nonattainment Areas; California; Determination of Attainment of the PM-10 Standards for the 

Coso Junction Area Particulate Matter of 10 microns or less (PM-10), Federal Register, August 

6, 2002, Vol. 67, no. 151, pp 50805-50808. 

Federal Register, 2002b. Clean Air Act Redesignation and Reclassification, Searles Valley 

Nonattainment Area; Correction, Federal Register, September 19, 2002, Vol. 67, no. 182, pp 

59005-59006. 

Federal Register, 2003a. Approval and Promulgation of Implementation Plans and Designation 

of Areas; California – Indian Wells Valley PM-10 Nonattainment Area, Federal Register, May 7, 

2003, vol. 68, no. 88, pp. 24368-24370. 

Federal Register, 2003b. Correction of Areas for Air Quality Planning Purposes; California-- 

PM-10 Nonattainment Area, Federal Register, June 23, 2003, vol. 68, no. 120, pp. 37090-37091. 

Federal Register, 2007. Treatment of Data Influenced by Exceptional Events, Federal Register, 

March 22, 2007, vol. 72, no. 55, pp 13560-13581. 

GBUAPCD, 1991. Great Basin Unified Air Pollution Control District, PM10 State Implementation 

Plan for the Searles Valley Planning Area, GBUAPCD, Bishop, California, November 1991. 

GBUAPCD, 1998. Great Basin Unified Air Pollution Control District, Owens Valley PM10 Planning 

Area Demonstration of Attainment State Implementation Plan, GBUAPCD, Bishop, California, 

November 16, 1998. 

GBUAPCD, 2003. Great Basin Unified Air Pollution Control District, Owens Valley PM10 Planning 

Area Demonstration of Attainment State Implementation Plan 2003 Revision, GBUAPCD, Bishop, 

California, November 13, 2003. 

GBUAPCD, 2008. Great Basin Unified Air Pollution Control District, 2008 Owens Valley PM10 

Planning Area Demonstration of Attainment State Implementation Plan, GBUAPCD, Bishop, 

California, January 28, 2008. 

GBUAPCD, 2009a. Great Basin Unified Air Pollution Control District, Ambient Air Monitoring 

Network Plan, GBUAPCD, Bishop, CA, March 27, 2009. 
2010 Coso Junction PM10 Maintenance Plan 

25 

GBUAPCD, 2009b. Great Basin Unified Air Pollution Control District, Findings and Order 

Granting Regular Variance from Requirements Set Forth in Governing Board Order 080128-0,

Docket No. GB09-06, Bishop, California, September 25, 2009. 

US Census Bureau, 2010. U.S. Census Bureau, State and County QuickFacts, accessed February 11, 

2010, http://quickfacts.census.gov/qfd/states/06/06027.html. 

USEPA, 2006. United States Environmental Protection Agency, Compilation of Air Pollution 

Emission Factors AP-42 (Fifth Edition), USEPA, Research Triangle Park, North Carolina, updated at 

http://www.epa.gov/ttn/chief/ap42/index.html. 

Wilderness Society, 2003. Wilderness Society, Summary of the McNally Fire, California: July 21-

August 29, 2002, Science & Policy Brief, Wilderness Society, Ecology and Economics Research 

Department, Washington, DC, No. 10, March 2003. 

 
2010 Coso Junction PM10 Maintenance Plan 

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