2007 EMISSIONS INVENTORY UPDATE 

FOR THE 

GILA RIVER INDIAN COMMUNITY 

Assistance ID No. A-98920909-0 

U.S. Environmental Protection Agency, Region IX 

For Submittal To: 

Ms. Deborah Jordan 

U.S. EPA, Region IX 

75 Hawthorne Street, Air 1 

San Francisco, California 941 05 

Submitted By: 

Gila River Indian Cornm~.~nity 

Department of Environmental Quality 

P.O. Box 97 

Sacaton, Arizona 85247 

(520) 562-2234 

(520) 562-2245 Fax 

Prepared By: 

Daniel C. Blair 

Compliance and Enforcement Manager 

January 2009 
TABLE OF CONTENTS 

1 EXECUTIVE SUMMARY ........................................................................................... 1 

2 INTRODUCTION ....................................................................................................... 2 

2.1. Background ............................................................................................. 2 

2.2. StudyArea ................................................................................................. 3 

3 METHODOLOGIES ................................................................................................... 4 

3.1. Point Sources ............................................................................................ 4 

3.2. Area Sources ............................................................................................. 4 

3.3. Mobile Sources .......................................................................................... 5 

4 SUMMARY OF RESULTS ......................................................................................... 6 

5 POINT SOURCES ..................................................................................................... 7 

5.1. Ongoing Sources ....................................................................................... 7 

5.2. New Sources .......................................................................................... 9 

5.3. Discontinued So~~rces ............................................................................. 10 

5.4. Facilities Below Permitting And Reporting Thresholds ............................ 10 

6 AREA SOURCES .................................................................................................... 12 

7 MOBILE SOURCES ................................................................................................ 13 

7.1. Nonroad ................................................................................................... 13 

7.2. Onroad .................................................................................................... 13 

7.2.1. Data Collection ........................................................................ 14 

7.2.2. Calculation Methods ................................................................. 15 

8 REFERENCES ........................................................................................................ 17 

FIGURES 

1 Map of the Gila River Indian Community. Arizona 

2 Map of Gila River Indian Community. Maricopa and Pinal Counties. and PMIO NonAttainment Area 

3 Map of Agricultural Areas on the Gila River Indian Community 
1 EXECUTIVE SUMMARY 

This report contains the 2007 Emissions Inventory (El) Update (2007 El) conducted within the 

exterior boundaries of the Gila River Indian Community (GRIC). An El is an itemized list of 

emission estimates for sources of air pollution in a given area for a specified time period. 

This 2007 El is an update to the original El that was developed and submitted for 1997. 

Therefore, it should be recognized that emission sources may fluctuate drastically within the 10- 

year time frame only to return to their original levels when the next 10-year El update is 

conducted. Similarly, due to fluctuating market conditions and changes tolimplementation of the 

GRIC Master Plan, emission sources in years preceding and following the El update may be 

dramatically different (or absent) from the year the El update was completed.. Some sources 

(e.g., construction) did not significantly contribute to the overall err~issions during ,the years in 

which the Els were conducted and were, therefore, not included in the 1997 and 2007 Els. 

The 2007 El includes emissions from point sources, area sources, onroad mobile, nonroad 

mobile and non-anthropogenic sources of air pollution. The inventory provides emissions 

estimates for carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOX), volatile 

organic compounds (VOCs), and particulate matter less than 10 microns in diameter (PM10). 

Emissions of lead were not calculated since there are no significant sources emitting ambient 

lead emissions within the Community and leaded gasoline is no longer available in Arizona. 

Emissions were calculated using several methods including mass balance, best engineering 

estimates, AP-42 emissions factors, CARB emissions factors, performance test results, permit 

applications, Mobile 6 model outputs from the Maricopa Association of Governments (MAG), 

vehicle traffic counts, Maricopa County emissions factors and the State of Arizona emissions 

factors. Emissions inventories from several individual facilities were developed by private 

consultants or in-house environmental personnel, using the above calculation methods, 

information gathered from site visits, and these were reviewed by GRIC's Compliance and 

Enforcement Manager (CEM). 

Since the Community experiences relatively slow growth when compared with the growth of 

corrlmunities like Metropolitan Phoenix, some of the emission data from the 1997 El was carried 

over to this 2007 El Update. For example, the levels of open burning and residential burning 

have remained relatively constant and many small stationary sources have also experienced 

little or no growth since 1997. Also, many of the small stationary sources do not keep accurate 

production data records because the facilities are below the permitting and reporting thresholds. 

The Gila River Tribal Council has recently approved an Air Quality Management Plan (AQMP), 

which allows for the irr~plementation of an air quality regulatory program, permitting program, 

and a compliance inspection program. The Community's Air Quality Department is in the 

process of developing their first set of Non-Title V air quality permits for several industries 

located on the Community. 
2.1. Background 

The Gila River lndian Community (GRIC), a federally-recognized tribe, is a rural corr~munity 

located on approximately 374,000 acres in south- central Arizona, adjacent to the southern 

border of Phoenix, Chandler and Gilbert, with an on-reservation population of 

approximately 15,500 people (Figures 1 & 2). The reservation was established in 1859 by 

Executive Order with Congressional approval. Members of the Gila River Indian 

Community are Akimel O'odham (Pima) and Pee Posh (Maricopa) and form the fourth 

most populous lndian Reservation in the United States. On the northern boundary, the 

Community is adjacent to the rapidly growing Phoenix metropolitan area. A portion of the 

Community (92,000 acres) lies within Maricopa County. This portion of the GRlC is located 

within the Federal Non-Attainment Area for particulate matter less than 10 microns (PMI O), 

which has been classified as "serious" by EPA (Figure 2). It is currently undetermined to 

what extent air pollution from the Phoenix metropolitan area affects air quality within GRlC 

boundaries. 

The Community has three (3) industrial parks containing approximately 50 industrial plants 

along with several industrial facilities located in out-lying areas. The Lone Butte Industrial 

Park, the largest of the three industrial parks, lies within the Maricopa County nonattainment area and includes one Federally-regulated major source (Pimalco). The 

remaining two industrial parks are much smaller and contain only minor sources of air 

pollution. 

Agricultural production throughout the Community has not changed significantly since 

1997. There are currently approximately 35,000 acres in agricultural production throughout 

the Community. Approximately 6,700 agricultural acres are located within the Maricopa 

County non-attainment area. 

The largest source of air pollution within the Community is vehicle emissions. Interstate 1 0 

is the single largest source of pollution with approximately 1,400,000 vehicle miles traveled 

(VMT) daily. GRlC has approximately 160 niiles of unpaved roads that are very rarely 

traveled and consist mainly of farm roads and roads accessing very remote areas. 

The Maricopa County PM10 non-attainment area was designated in 1974 to include the 

urbanized portions of Maricopa County but also included the northern portion of GRlC 

(Figure 2). The boundary was arbitrarily developed based on the Maricopa Association of 

Governments (MAG) operational area and did not include any scientific information from 

GRlC to support the non-attainment designation. GRlC was not allowed to comment 

during the designation process nor was scientific evidence from GRlC used to determine 

the boundaries of the nonattainment areas. No evidence has ever indicated that any 

portion of GRlC is in non-attainment or even contributes to the non-attainment status within 

Maricopa County. GRlC plans to conduct additional monitoring in the future to support this 

position. 
The Community is facing several issues arising from the non-attainment status of the 

northern portion of the Community, including NSR and Title 5 permittirlg requirements for 

new industrial facilities plannirlg to locate within the Community. The Gila River Tribal 

Council has recently approved an Air Quality Management Plan (AQMP), which allows for 

the implementation of an air quality regulatory program, permitting program, and a 

compliance inspection program. The Community's Air Quality Department is in the process 

of developing their first set of Non-Title V air quality permits for several industries located 

on the Community. 

2.2. Study Area 

The Gila River Indian Community extends from the towns of Phoenix and Chandler on the 

north, south to almost Casa Grande, to the Estrella Mountains on the west to Coolidge on 

the east (Figure 2). The Gila River Indian Community lies in Sonoran Desert terrain that is 

primarily light scrub and cactus with an elevation of approximately 1,200 to 1,400 feet 

above sea level. The temperature varies from approximately 20°F in the winter to >I 15°F 

in the summer. Annual precipitation is light with approximately 36 days per yearwith >0.01 

inches. Wind speed and direction can vary, but generally the wind blows from the 

southwest to the northeast in the morning and reverses direction in the afternoon. Wind 

speed can vary from a slight breeze to 70 mile per hour winds during the monsoon season. 
To update the 1997 El, the Gila River Department of Environmental Quality (DEQ) 

assessed both stationary and mobile source emissions. 

3.1. Point Sources 

For the purposes of this El, point sources are defined as stationary facilities (with point 

and/or area sources) within the boundaries of the Community. The point sources listed in 

1997 El were divided into the following five categories for this update: 

1. Ongoing (since 1997); 

2. Ongoing with changed names (since 1997); and 

3. New (operating in 2006 but not in 1997); 

4. Discontinued (not operating in 2006); 

5. Below the permitting and reporting thresholds. 

Emissions for the new point sources were developed using information supplied by the 

source or obtained during site visits pertaining to the type of processes employed, the 

types of materials/chemicals used, quantities of materials input to processes and type of 

pollution control equipment operated. After collecting this data, emissions were estimated 

using AP-42 emissions factors, mass balance equations, source test information, and best 

engineering estimates. 

Several of the new sources were in operation for only a short period of time in 2007 or did 

not have readily available production data. Therefore, these sources were included under 

a category with facility emissions below the permitting and reporting threshold. Emissions 

from these sources will be included in the next GRlC El, provided the emissions from these 

facilities exceed the permitting and reporting threshold. The Community's Air Quality 

Department is in the process of developing their first set of Non-Title V air quality permits 

for several industries located on the Community. This process will continue until all 

sources required to have a permit within the community are permitted. All permitted 

sources will be required to submit an annual El to the GRlC DEQ as a condition of their 

operating permit. 

3.2. Area Sources 

Area source emissions include open burning emissions, agricultural emissions from tillage 

and harvesting, and construction emissions. There has been little or no net change in the 

quantities of open burning and construction emissions since 1997; therefore, the 2007 area 

source emissions were assumed to be identical to 1997 area source emissions for these 
sources. Agric~.~ltural-related emissions were adjusted for a slight increase in the amount of 

land under agricultural production between 1997 and 2006. 

3.3. Mobile Sources 

EPA's Mobile 6 model was used to estimate emissions from onroad mobile sources 

(vehicle traffic). Emissions of PMI 0 from dirt roads and from paved roads were estimated 

using formulas provided in AP-42. Vehicle counts and road n-~ileages were obtained for the 

most recent year available from the Arizona Department of Transportation (2006), GRlC 

Department of Transportation (2003, 2004), Maricopa County Department of 

Transportation (2005), and MAG (2005). 
4 SUMMARY OF RESULTS 

Annual emissions estimates were developed for the five criteria pollutants - PMI 0, CO, 

NOx, SOX and VOCs. A summary of the 2007 criteria pollutant emissions from each of the 

three sources categories is shown in Table 4.1. 

TABLE 4.1 Summary of Source Emissions (tonslyr) 

Point 

Mobile 

Area 

TOTAL 

1,048 

386 

759 

2,193 

161 

10,588 

63 

10,812 

175 

2,055 

52 

2,282 

142 

929 

56 

1,127 

31 

37 

0 

68 
5 POINT SOURCES 

For the purpose of this inventory, point sources are defined as stationary facilities within 

the boundaries of the Community. The point sources from the 1997 El were divided into 

the following five categories for this update: 

1. Ongoing (since 1997); 

2. Ongoing with changed names (since 1997); and 

3. New (operating in 2006 but not in 1997); 

4. Discontinued (operating in 1997 but not in 2006); 

5. Below the permitting and reporting thresholds. 

A summary of the emissions from the new and ongoing point sources is presented in Table 

5.1 below. 

TABLE 5.1 Point Source Emissions (tonslyr) 

"-" = zero value or not applicable 

5.1. Ongoing Sources 

Ongoing point sources on the Community are those sources that were operating in 1997 

and 2006. Several orrgoing facilities also underwent a name change since 1997. 

Available emissions data is limited for these ongoing sources because most of the sources 

do not currently have an air quality permit. Also, most of these sources have not changed 

significantly since 1997. Therefore, with the exception of two facilities (Rinker's Maricopa 

and Santan plants), the 1997 El emissions data was used for the 2007 El Update. 

A surrlmary of the ongoing sources (without a name change) and their associated 

emissions is presented in Table 5.2. 
TABLE 5.2 ongoing' Point Source Emissions (tonslyr) 

I Bondurant 19 1 4 1 2.57 1 

I Casa Blanca MKT I - I - I - I 3.1 1 - I 

I Classy Closets 0.3 1 - - 

voe 

2 

0.17 

- 

Saum t, plm,,,, 

I DBCl I - I - I - I - I - I 

GO. 

0.05 

- 

- 

EiOx 

Alexco 

Arizona Box 

BMC West 

. -. 

0.24 

- 0.02 

0.2 

I Pima Valve 0.28 1 1 

Fertizona San Tan 

Firebird Raceway 

Gila River Farms Gin 

Gila River Gas Station 

Komate gas station (53 Ave & Pecos Rd) 

KT Fabrication 

Pacific Scientific 

I Rock Solid 9.5 1 - 

I Romic I - I - I - I 3.3 1 - I 

0.67 

6.7 

1 Therm-0-Rock West 48.7 1 1.8 1 7.4 1 0.2 1 0.03 1 I Triangle Truss 0.4 1 0.1 I 

- 

- 

1.7 

A summary of the ongoing sources with a name change, their former name, and their 

associated emissions is presented in Table 5.3. 

13 

Wilbur Ellis 

TOTAL 

I Honeywell I Allied Signal 2.8 1 11.3 1 3.6 1 8 1 3.2 ] 

0.22 

- 

0.75 

10 

5.1 

- 

0.03 

"-" = zero value or not applicable ' = Operating in 1997 and 2006 

- 

73.35 

TABLE 5.3 Ongoing Changed ~ame' Point Source Emissions (tonslyr) 

I Kaiser Aluminum I Plvmouth Tube I 0.11 1 0.19 1 0.93 1 9.9 1 - I 

- 

- 

- 

- 

setme 

Animal Nutrition 

I MTD I Rvobi 1 0.024 1 8.4 1 0.006 1 3 1 0.003 1 

53.5 

I Rinker (Maricopa plant) I United Metro #41 1 22.45 1 35.83 1 28.27 1 8.73 1 14.75 1 

1997 ~lwne I pm, 1 GO I ~aix 1 voc SOX 

I Rinker (San Tan plant) I United Metro #48 1 22.73 1 51.68 1 98.27 1 16.64 1 11.18 ( 

42.36 

Dairv Nutrition 

I Monsanto I Stoneville Seed 1 34 1 0.1 1 0.4 1 - I - I I Triumph Thermal Processing I AMTl 0.05 1 0.26 1 1.2 1 0.03 1 

94.11 

2 1 

0.12 

"-" = zero value or not applicable ' = Sources with a name change between 1997 and 2006 

- 

Waste Management Inc. I Sanifil 

- 

TOTAL 1 85.71 1 107.55 1 131.74 1 47.47 1 29.16 

1.6 1 - - 
Rinker submitted Non-Title V permit applications for their two facilities (Maricopa and San 

Tan plants) to satisfy the requirements of GRIC's Non-Title V permitting process. The 

information and emission data supplied in their permit applications was used for this 2007 

El update. 

5.2. New Sources 

New point sources on the Community are those sources that were not operating in 1997 

but were operating in 2006. A summary of the new sources and their associated emissions 

is presented in Table 5.4. 

TABLE 5.4 ~ew' Point Source Emissions (tonslyr) 

Cemex I 12.4 1 - I - I - I 

Charnoion Homes Redman Homes I - I - 1 - I - I 

Hanson I 3.5 1 0.09 1 0.37 1 0.02 1 1.33 

Gila River Sand & Gravel - Maricopa 

Gila River Sand & Gravel - Santan 

429.89 

441.8 

I I I I I 

Love's Travel Center 

Maricooa Readv Mix 

0.04 

0.04 

- 

1.04 1 

Superlite Block 

Triumph Engines 

Five of the new sources listed in Table 5.4 submitted production data andlor emission data 

to satisfy the requirements of GRIC's permitting process. Additional information was 

collected by the CEM while conducting on-site visits and various methodologies were 

applied to derive the estimated emissions. The remaining five sources were only operating 

for a short period of time toward the end of 2007 or have limited production or emission 

factor data available. Emissions from these five sources were not included in this update 

because GRlC is using data generated between 1997 and 2006 for the 2007 updated 

Emission Inventory. 

- 

- 

Triumph Precision Castings 

TOTAL 

Emissions from the point sources were calculated using mass balance, material usage 

estimates and AP-42 emission factors. Several of the above-listed sources hired 

consultants or used in-house environmental personnel to develop their individual permit 

application with emission estimates. The permit applications were reviewed by the GRlC 

CEM for reasonableness, completeness and correct emission factors before including the 

emissions data in the permit applications into the 2007 El. Emission estimates for other 

sources were prepared by GRlC consultants using the information supplied in the permit 

applications. 

0.21 

0.21 

"-" = zero value or not applicable ' = Operating in 2006, but not in 1997 

888.63 

0.02 

0.02 

0.01 

0.01 

- 

0.1 7 

- 

0.79 

- 

0.06 1.35 
5.3. Discontinued Sources 

A list of the discontinued sources and their associated emissions is presented in Table 5.5. 

TABLE 5.5 ~iscontinued' Point Source Emissions (tonslyr) 

5.4. Facilities Below Permitting And Reporting Thresholds 

Source 

Arizona Processing 

Fertizona Coolidge 

Image of Wicker 

Phillips Services 

Solkatronic 1 Air Products 

TOTAL 

Several facilities are below the permitting thresholds or have equipment that is exempt 

from permitting. The permitting thresholds are identified in the AQMP and include, but are 

not limited to, facilities that emit one ton per year or less of any single regulated air 

pollutant; 1,000 pounds per year or less of any singe HAP or one ton of any combination of 

HAPs; or 300 pounds per year or less of any single ultra-HAP or combination of ultraHAPs. These facilities are listed in Table 5.6. 

TABLE 5.6 Facilities Below Permitting And Reporting ~hresholdsl 

"-" = zero value or not applicable ' = Operat~ng In 1997 but not in 2006 

PW~O 

35 

0.76 

5.5 

- 

41.26 

CO 

0.16 

- 

0.16 

souffie 

A & A Precast 

I Acker Stone I Lumber Products 

Source 

Gila River Utility Authority 

Allison LLC (sublease to Lumber Products) 

Access Recovery 

NOx 

0.94 

0.94 

Iron City Rentals 

Lone Butte Trade Center 

ADESA 

Beaudry RV 

Environmental Stoneworks 

I Freightliner Sterlina Western Star of Arizona I Verizon Wireless I 

VOC 

0.01 

0.15 

- 

0.32 

0.48 

McNeil Brothers 

Monty Brother's Landscaping 

Peterson Transportation 

Factory Expo Home Center 

Ferrell Gas 

Fillmore Partnership 

I Gila River Telecomm - 

1 = One ton per year or less of any single regulated air pollutant; 1,000 pounds per year or less of any singe HAP or one ton of 

any combination of HAPs; or 300 pounds per year or less of any single ultra-HAP or combination of ultra-HAPS. 

SOX 

- 

Robert Ewing General Contractor 

Rock N Roll Trucking 

San Carlos Irrigation Proiect 

6 AREA SOURCES 

For the purpose of this El update, area emission sources include open burning, agricultural 

tillage and harvesting, residential fuel combustion, agricultural wind blown dust (nonanthropogenic) and agricultural nitrogen fertilizer usage (non-anthropogenic). Emissions 

from wildfires have not been calculated since wildfires rarely occur in the GRlC Sonoran 

Desert environment. 

Except for agricultural-related sources (e.g., tilling, harvesting, windblown dust, and 

fertilizer usage), the area sources have not changed significantly since 1997. Therefore, 

for non-agricultural sources, the 1997 El emissions data was used for this 2007 El Update. 

For agricultural sources, the 1997 El indicates that 32,196 acres were in agl-icultural 

production. In 2006, the most recent year with available data, there were 35,065 acres in 

production (see Figure 3, attached). For both El timeframes (1997 and 2006), the major 

crops produced on the Gila River Indian Community included alfalfa, cotton, wheatlbarley, 

citrus, and vegetables. These crop types were used to estimate the emissions for the 

agricult~~ral sources in both the 1997 and 2007 Els. Therefore, the 8.9% increase in 

agricultural production from 1997 to 2006 was applied to the 1997 emissions for tilling & 

harvesting (448.1 I tpy PMlo), windblown dust (241 tpy PMI0), and fertilizer usage (45 tpy 

NOx) to estimate the emissions for this El. A summary of the area source emissions for 

the 2007 El is presented in Table 6.1 below. 

TABLE 6.1 Area Source Emissions (tonslyr) 

"-" = zero value or not applicable 

Sottrctb 

Open Burning 

Agricultural Tilling & Harvesting 

Residential Fuel (gas) Combustion 

Residential Wood Combustion 

Agricultural Windblown Dust 

Nitrogen Fert~lizer Usage 

TOTAL 

0.12 

487.99 

0.027 

8.4 

262.45 

758.99 

CO 

1.2 

0.33 

61.4 

- 

62.93 

VOC 

0.026 

55.9 

- 

55.93 

1 

: WQx 

1.97 

0.6 

- 

49 

51.57 

SOX 

0.002 

0.1 

- 

0.10 
7 MOBILE SOURCES 

Mobile emission sources include nonroad vehicles and onroad vehicles. 

7.1. Nonroad 

Emissions from nonroad mobile sources result from combustion of fuels from mobile 

equipment other than onroad motor vehicles. These sources include recreational vehicles, 

construction equipment, lawn and garden equipment, farm equipment, marine vessels and 

locomotives. The majority of sources listed in this category will not be addressed in this 

section due to the lack of these activities within the boundaries of the Community. 

Emissions from marine vessels, recreational vehicles, lawn and garden equipment and 

construction activities are not addressed in this inventory due to the lack of these activities 

during the 2006 calendar year. Emissions from locomotives are considered insignificant 

since only small rail sidings are present within the Community and rail trafic is almost 

nonexistent. 

Emissions from farm equipment are the only significant source of nonroad emissions within 

the Community. The ratio of 2006 to 1997 agricultural acreage was used to adjust the 

1997 El data for the 2007 El Update (i.e. an increase of 8.9%). The nonroad emissions for 

the 2007 El Update is presented in Table 7.1 below. 

TABLE 7.1 Nonroad Mobile Source Emissions (tonslyr) 

"-" = zero value or not applicable 

Saume, 

Agricultural Tractor Operation 

7.2. Onroad 

This section explains the development of onroad niotor vehicle emissions estimates from 

vehicle traffic within the boundaries of GRIC. Vehicle traffic through the Community by far 

represents the most predominant source of air pollution within the Community. The 

majority of the vehicle traffic can be attributed to Interstate 10 running between Phoenix 

and Tucson bisecting the GRIC. 

PNIId 

22 

h#rx 

28 

WC 

5 

SOX 
A summary of the onroad emissions for the 2007 El Update is presented in Table 7.2. 

TABLE 7.2 Onroad Mobile Source Emissions (tonslyr) 

"-" = zero value or not applicable 

7.2.1. Data Collection 

Vehicle counts for roads maintained by the State of Arizona were supplied by the Arizona 

Department of Transportation (ADOT). MAG supplied a map listing vehicle counts over 

stretches of road maintained by the Maricopa County Department of Transportation 

(MCDOT). The GRlC Department of Transportation supplied information documenting the 

total mileage of paved and dirtlgravel roads within the Community. A portion of these 

roads are maintained by the Bureau of Indian Affairs and vehicle counts are not available. 

The total mileage of roads maintained by the State and County was subtracted from the 

total roads within the Community to reveal those roads without vehicle counts. Estimates 

of daily vehicle traffic were made for the portion of roads without vehicle counts. Daily 

Vehicle Miles Traveled (VMT) were calculated by multiplying the numbers of vehicles per 

day (vpd) by mileage information supplied by the State, County and GRIC. A summary of 

the daily VMT for the five major road types is presented in Table 7.3 below. 

TABLE 7.3 Onroad Mobile Source VMT 

VMT = Vehicle Miles Traveled per day 

Emission factors were obtained from EPA's Mobile 6 model. MAG SI-~pplied GRlC with the 

2005 Mobile 6.2.03 input and output files used to calculate emissions factors for their 2006 

El. One set of output emissions factors included credit for implementation of the Area A 

(roughly Maricopa County) IM-240 vehicle emissions testing program. These factors were 

applied to the daily VMT within Maricopa County. Another set of emissions factors was 
generated for vehicles not required to pass the Maricopa County emissions testing 

program (IM-240) and these factors were applied to the daily VMT within Pinal County. 

7.2.2. Calculation Methods 

Criteria pollutant emissions for each vehicle classification traveling within each road type 

were calculated according to the following equation: 

Ex = EFx x VMT, x VCP x 

365 days ( yr )x(45~6g)x(2~~lb) 

Where: Ex = Criteria pollutant X emissions (i.e., PM10, CO, etc.) for a specific 

vehicle class 

EFx = Emission factor for criteria pollutant X from Mobile 6 

VMT = Daily vel-~icle rr~iles traveled for road type Y (i.e., urban interstate, 

etc.) 

VCP = Vehicle class percentage of total vehicles 

The resulting emissions for each vehicle classification were totaled to generate the total 

PMI0, CO, NOx, VOC and SOX emissions for each road type. 

PMIO err~issions from road dust generated by vehicle traffic on paved roads were 

calculated using the equation for paved roads listed in AP-42 Section 13.2.1 (Equation 1) 

and silt loading values from Maricopa County's 2005 El. Daily VMT were broken down to 

three categories with three different silt loading (sL) values: 

Interstates (sL = 0.02 glm2); 

Roads with <5,000 VMTlday (sL = 0.067 glm2); and 

Roads with >5,000 VMTlday (sL = 0.23 glm2). 

The AP-42 equation for vehicles traveling on paved public roads is: 

Where: EF = Particulate emissions factor (IbsNMT) 

k = Particle size multiplier for particulate size range of interest (0.016 

lbNMT for PM10, AP-42 Table 13.2.1-1) 

sL = Road surface silt loading (glm2, Maricopa County 2005 El) 

W = Weight of vehicle (3 tons, Maricopa County 2005 El) 

C = Emission factor for 1980's vehicle exhaust, break & tire wear 

(0.00047 IbNMT, AP-42 Table 13.2.1-2) 
PMlO emissions from road dust generated by vehicle traffic on unpaved roads were 

calculated using the equation for unpaved roads listed in AP-42 Section 13.2.2 (Equations 

I b and 2), a silt loading value from Maricopa County's 2005 El, and daily VMT generated 

using best available engineering estimates. Since vehicle traffic on unpaved roads is very 

limited within the Community, it was assumed that two vehicles per day traveled on each 

unpaved segment. The rural portion of the Community has remained relatively unchanged 

since 1997; therefore, the length of unpaved roads from the 1997 El was used for the 2007 

El Update (162.8 miles). 

The AP-42 equation for vehicles traveling on unpaved public roads is: 

Where: EF = Emission factor (IbsNMT) 

k = Particle size multiplier (1.8 for PM10, AP-42 Table 13.2.2-2) 

s = Silt content of road surface (1 1.9%, Maricopa County 2005 El) 

S = Mean vehicle speed (25 mph, Maricopa County 2005 El) 

M = Surface material moisture content (0.5%' Maricopa County 2005 El) 

C = Emission factor for 1980's vehicle exhaust, break & tire wear (0.00047 

IbNMT, AP-42 Table 13.2.2-4) 

p = #of dayslyr with rainfall of at least 0.01 in. (31 days, Western Regional 

Climate Center, Sacaton, AZ) 

a = for PMlO (1, AP-42 Table 13.2.2-4) 

c = for PMlO (0.2, AP-42 Table 13.2.2-4) 

d = for PMlO (0.5, AP-42 Table 13.2.2-4) 
8 REFERENCES 

Arizona Department of Transportation Website. Vehicle Counts for Arizona Roads 2003 - 

2006. 

Compilation of Air Pollution Emissions Factors AP-42, Fifth Edition, Volume I 

Gila River lndian Community. 1997 Emissions lnventory for the Gila River lndian 

Community, dated October 1998. 

Gila River lndian Community Department of Transportation. List of Unpaved / Paved 

Roads by District - for Air Quality Program (memorandum dated March 4, 2005). 

Gila River lndian Community Department of Transportation. Traffic Count Data 

(memorandum dated April 7, 2004). 

Maricopa Association of Governments. Mobile 6 input and output files for 2005. 

Maricopa County Air Quality Department. 2005 Periodic Err~issions lnventory for PM10 for 

the Maricopa County, Arizona, Nonattainment Area, dated May 2007. 

Maricopa County Department of Transportation Website. Traffic Counts for 1999 - 2005. 
FIGURES 

([I 

: 

- 

([I 

. 

c - 

L