# E C 

# / R Incorporated Providing Environmental Technical Support Since 198 9

501 Eastowne Drive, Suite 250  Chapel Hill, North Carolina 27514 Telephone: (919)484-0222  Fax: (919) 484-0122 

### MEMORANDUM

Date: September 3, 2010

To: Anita Lee, U.S. EPA/Region 9

From: Nancy Jones, EC/R Incorporated

Subject: Ammonia Mobile Source Risk Estimates for Four Corn ers Power Plant

1. Introduction

This memo describes the air dispersion modeling an alysis conducted in response to
comments EPA received on the Advanced Notice of Pro posed Rulemaking (ANPR) of the Best Available Retrofit Technology (BART) for the Four C orners Power Plant (FCPP) located on the Navajo Nation, near Farmington New Mexico. The com menters noted that the increased pollutants released in the transportation of ammoni a to the facility to be used for selective catalytic reduction (SCR) of NO

x 

### emissions would generate emissions of NO

x 

### , CO, VOC, PM 10 

### , and other pollutants. The modeling study was condu cted using the Human Exposure Model Version 3 (HEM3) that contains as its air dispersio n model the American Meteorological Society (AMS) and EPA Regulatory Model (AERMOD).

As shown in Figure 1, the roadway emissions were m odeled as five area sources approximately overlying the roads. Air concentrat ions at census blocks near the roadway were estimated based on the pollutants emissions rates a nd the site-specific meteorology and terrain input into the model. The census block locations a re shown in Figure 2. Detailed model inputs are presented in Attachment 2. Potential risks fro m toxic air pollutants were estimated by comparing the modeled air concentrations to OAQPS’ dose response values contained within HEM3. Criteria pollutant air concentration estimat es were compared to their National Ambient Air Quality Standards (NAAQS) and Class I increment s.

2. Emissions Estimates

Emissions were estimated from the estimated 15 add itional trucks per week needed to transport the ammonia in the form of urea crystals from the railway station in Gallup, New Mexico to FCPP (approximately 100 miles each way). The number of trucks needed to transport
urea to the FCPP was calculated based on the size o f the plant using data presented in a technical and economic comparison of SCR ammonia options ( http://www.mcilvainecompany.com/NOx_Decision_Tree/s ubscriber/Tree/DescriptionTextLinks /CostAnalyWashGrp.pdf ). The report provided data on the number of truck s or railcars that would be needed to transport various forms of ammon ia and estimated it would take 19 truck
deliveries to deliver 370 tons of urea or 19.5 tons per truckload.Ammonia Mobile Source Risk Estimates
Four Corners Power Plant September 3, 2010



### 2 Figure 1. Approximate Locations of Line Sources f rom Gallup, New Mexico
to the Four Corners Power Plant

The FCPP BART analysis provided updated annual rea gent costs for each of the five units. The reagent costs for each of the units wer e converted to annual tons using the estimated cost for urea presented in the BART analysis, as $4 50 per ton of urea. The number of truck deliveries was then estimated using the annual tons of urea needed per unit and the amount of urea per truck provided in the ammonia optimization report. A summary of the results is presented in Table 1.

Emissions estimates for criteria pollutants were d eveloped from the most conservative EMFAC2007 (version 2.3) Emission Factors for On-Roa d Heavy-Heavy-Duty Diesel Trucks for 2010 from South Coast Air Quality Management Distri ct (SCAQMD) ( http://www.aqmd.gov/ceqa/handbook/onroad/onroad.htm l ). Toxic air pollutant emission factors were developed from the reactive organic ga s (ROG) and PM 2.5 

### emission factors using EPA/OAQPS’ Speciate Database ( http://cfpub.epa.gov/si/speciate/ ). Table 2 presents the SCAQMD emissions factors and the criteria pollutant emissions estimates used in the analysis. Table 3 presents the toxic air pollutant emissions estimates developed using the speciate factors.Ammonia Mobile Source Risk Estimates
Four Corners Power Plant September 3, 2010



### 3 Figure 2. Approximate Locations of Line Sources i n Red and Census Block Receptor Locations in Green

Table 1. Development of Estimates of Urea Truck Tr affic for SCR at FCPP

Four Corners Unit
Number Annual Reagent Cost ($/yr) 1 Annual Tons of Urea (Tons/yr) 2 Number of Truck
Deliveries (Deliveries/yr) 3

Unit 1 $871,000 1,936 99.4

Unit 2 $713,000 1,584 81.3

Unit 3 $842,000 1,871 96.1

Unit 4 $2,231,000 4,958 254.6

Unit 5 $2,231,000 4,958 254.6

Total $6,888,000 15,307 786

1 Annual reagent costs obtained from APS FCPP BART A nalysis submitted 8/19/2008.

2 The annual tons of urea were calculated by dividin g the annual reagent cost by the cost of urea from the FCPP BART Analysis, $450/Ton.

3 Number of truck deliveries calculated using the an nual tons of urea and the tons of urea per truckloa d.Ammonia Mobile Source Risk Estimates
Four Corners Power Plant September 3, 2010



### 4 Table 2. Criteria Pollutant Emission Rates Used to Estimate Risk from Transporting Urea
to FCPP for SCR

Pollutant SCAQMD EF (lb/mi) Emissions 786 trucks/yr, 200 miles roundtrip (TPY)

Reactive Organic Gases (ROG) 3.04E-03 2.36E-01

CO 1.20E-02 9.32E-01

NO X 3.82E-02 2.98E+00

SO X 4.13E-05 3.22E-03

PM 10 1.83E-03 1.43E-01

PM 2. 5 including tires & brakes 1.60E-03 1.25E-01

PM 2.5 engine exhaust 1.55E-03 1.21E-01



### Table 3. Toxic Air Pollutant Emission Rates Used t o Estimate Risk from Transporting
Urea to FCPP for SCR

Pollutant SCAQMD

EF (lb/mi) Weight Percent of

VOC from Speciate Calculated HAP

Emission Factor (lb/mile) Emissions 786

trucks/yr, 200 miles roundtrip (TPY)

Gas Phase Speciate Database Record # 4674: Diesel E xhaust - Medium Duty Trucks

ROG* 3.04E-03

1,3-Butadiene 1.18E-01 3.60E-04 2.80E-02

2,2,4-Trimethylpentane 4.73E-01 1.44E-03 1.12E-01

Acetaldehyde 1.59E+01 4.85E-02 3.78E+00

Acrolein 1.30E+00 3.94E-03 3.08E-01

Benzene 1.05E+00 3.18E-03 2.48E-01

Ethyl benzene 1.79E-01 5.45E-04 4.25E-02

Formaldehyde 8.51E+00 2.59E-02 2.02E+00

M & p-xylene 8.89E-01 2.70E-03 2.11E-1

Naphthalene 2.35E-01 7.16E-04 5.58E-02

O-xylene 3.17E-01 9.63E-04 7.51E-2

Propionaldehyde 5.34E+00 1.62E-02 1.27E+00

Toluene 1.52E+00 4.62E-03 3.60E-01

Dibenzofuran 1.09E-02 3.33E-05 2.60E-03

Acetophenone 1.95E+00 5.92E-03 4.61E-01

Particulate Phase Speciate Database Record # 322082 .5: Heavy Duty Diesel Trucks

Diesel engine emissions 1.55E-03 1.21E-01

Arsenic compounds 1.50E-02 2.33E-05 1.82E-03

Manganese compounds 9.00E-03 1.40E-05 1.09E-03

Nickel compounds 2.70E-02 4.20E-05 3.27E-03 * Assumed that reactive organic gases (ROG) are equ ivalent to volatile organic compounds (VOC).Ammonia Mobile Source Risk Estimates
Four Corners Power Plant September 3, 2010



### 5 3. Impacts of Criteria Air Pollutant Emissions

In order to place into perspective peoples’ exposu re to criteria air pollutants, the modeled air concentration from the census blocks was compar ed to the NAAQS and Class I increments (when applicable) for the pollutant. The NAAQS and Class I increments for the criteria pollutants include both short-term and long-term av erage air concentrations (see Attachment 1). Table 4 presents the NAAQS levels used in this anal ysis, with the concentrations converted as necessary from expression as parts per million or b illion to milligrams per cubic meter (mg/m 3 

### ). As shown in Table 5, the annual average air concent rations modeled at the most impacted census block (the populated census block with the highest modeled air concentration) are well below the NAAQS and Class I increments. The population at th is census block in San Juan County, New Mexico is seven individuals. As shown in Table 6, the short-term average air concentrations are also well below the NAAQS and Class I increments wi th the one-hour highest average concentrations occurring at a census block with a p opulation of seven in McKinley County, the highest eight-hour and 24-hour average concentratio ns occurring at a census block with a population of nine in San Juan County.

Table 4. NAAQS and Class I Increments Used in Crit eria Pollutant Comparison

Pollutant NAAQS Level

as Codified NAAQS Level for

Comparison (mg/m 3 ) Class I Increments (mg/m 3 ) Averaging

time

CO 10 mg/m 3 10 8-hour

40 mg/m 3 40 1-hour

NO 2 53 ppb 0.1 0.0025 Annual

100 ppb 0.19 1-hour

PM 10 0.004 Annual

0.15 mg/m 3 0.15 0.008 24-hour

PM 2.5 0.015 mg/m 3 0.015 0.001 (proposed) Annual

0.035 mg/m 3 0.035 0.002 (proposed) 24-hour

SO 2 0.03 ppm 0.08 0.002 Annual

0.005 24-hour

0.025 3-hour
75 ppb 0.2 1-hour



### Table 5. Comparison of Modeled Annual Averages to NAAQS and Class I Increments

Pollutant Annual Average

NAAQS Level (mg/m 3 ) Class I Annual Average

Increments (mg/m 3 ) Annual Average Modeled

Air Concentration (mg/m 3 )

CO NA NA 0.000020

NO 2 0.1 0.0025 0.000065

PM 10 NA 0.004 0.0000031

PM 2.5 0.015 0.001 (proposed) 0.0000027

SO 2 0.08 0.002 0.00000007Ammonia Mobile Source Risk Estimates
Four Corners Power Plant September 3, 2010



### 6 Table 6. Comparison of Modeled Short Term Concentr ations to NAAQS and Class I

Increments

Pollutant Short-Term Average

NAAQS Level (mg/m 3 ) Class I Short-Term

Average Increments (mg/m 3 ) Short-term Average

Modeled Air Concentration

(mg/m 3 ) 1-hour Average Air Concentrations

CO 

### 40. NA 

### 0.0054

NO 2 

### 0.19 NA 

### 0.017

SO 2 

### 0.2 NA 

### 0.000019
8-hour Average Air Concentrations

CO 

### 10. NA 

### 0.00041
24-hour Average Air Concentrations

PM 10 

### 0.15 0.008 

### 0.00063

PM 2.5 

### 0.035 0.002 (proposed) 

### 0.000054

SO 2 

### NA 0.005 

### 0.0000014

4. Impacts of Toxic Air Pollutants

NAAQS have not been established for the hundreds o f toxic air pollutants that have the potential to cause cancer and other non-cancer adve rse health effects. Toxicological dose response values have been established for use in es timating many toxic air pollutants’ adverse health effects. OAQPS has established a table of p ollutant-specific values that are used with
modeled or measured air concentrations in order to quantify the impact of exposure to these pollutants. The long-term or chronic dose response values used in the analysis can be found at http://www.epa.gov/ttn/atw/toxsource/summary.html in Table 1. As shown in Table 7 below, the
estimated cancer risk summed over all modeled toxic air pollutants is less than one in one million and the hazard quotient is well below one. This v alue is for the highest impacted census block located in San Juan County, New Mexico with a popul ation of 36 individuals. For the other impacted census blocks, the risks are estimated to be as low as 1 x 10 -10 

### and the hazard quotients
are estimated to be as low as 0.00001.

Table 7. Modeled Risk Estimates for Toxic Air Pollutants

Cancer Risk 5 x 10 -7 Five excess cancer case over a lifetime exposure per 10 million people exposed

Non-Cancer Hazard Quotient 0.2 A value of the HQ at or below one indicates that the exposure is not likely to result in adverse hea lth
effects.



### 5. Comparison of Modeled Results to Background Concent rations and the 2002 NATA

In addition to estimating impacts by comparing mod eled air concentrations to levels such as the NAAQS or toxicological dose response values, another way to characterize risk is to compare estimates to other values such as monitored concentrations or other estimated values. For the criteria pollutants, a large monitoring net work has been established for the purpose ofAmmonia Mobile Source Risk Estimates
Four Corners Power Plant September 3, 2010



### 7 determining whether or not an area has attained the NAAQS. While the number of monitors for air toxics has increased in recent years, few areas of the nation are covered, and no air toxics
monitors are sited in the area of interest in New M exico. Thus, for this analysis, we used the most recent NATA analysis for comparisons. The NAT A analysis is a county-level air toxics study that provides modeled air concentration and r isk estimates for the entire United States and that is completed every three years. The results o f the 2002 NATA are presented for comparison here, since the 2005 NATA has not been finalized at this time.

As shown in Table 8, the expected impact of the in creased truck traffic necessary to deliver urea to the FCPP to operate the SCR for NO

x 

### control is very low when compared to nationally monitored concentrations ( http://www.epa.gov/airtrends/ ). Additionally, the total NO

x 

### estimated to be emitted from this mobile source is 3 tons per year, while at 80 percent emissions reduction, the emissions reduction anticipated from SCR is over 33,000 tons at the FCPP (Four Corners BART Analysis – Cost Analysis, 8/19/2008). Tables 9 and 10 show that for air toxics, the impact from the transportation of urea to the F CPP is well below the impact estimated in NATA and in fact, for pollutants where background v alues are available, the modeled estimates are well below background levels.

Table 8. Comparison of Annual Average Modeled Crit eria Pollutant Concentrations to
National Monitored Values

FCPP 2008 Range of Monitored Values (μg/m 3 )

Poll. Avg.
Period Modeled

Air Conc. (μg/m 3 ) Poll. Avg. Period
10th
%ile Arithmetic

Avg. 90th

%ile # of
sites CO Highest
8-hour 

### 0.41 CO 2 nd Highest
8-hour 1,200 2,100 3,100 206

NO2 Annual 0.065 NO 2 Annual 8.7 25. 40. 151

PM 10 Annual 0.0031 PM 10 Seasonal wt.
annual 33. 56. 88. 325

PM 2.5 Highest
24-hour 0.055 PM 2.5 2 nd Highest
24-hour 7.4 11. 14. 728

SO 2 Annual 0.00007 SO 2 Annual 3.7 9.1 15.5 141



### Table 9. Comparison of Modeled Total Air Toxic Ris ks to NATA Estimates for San Juan County, NM Total Risks

Toxic Air Pollutant FCPP 2002 NATA Analysis

Modeled Risk Total Background

Cancer Risk 5 x 10 -7 2 x 10 -6 1.5 x 10 -6

Non-Cancer Hazard Quotient 0.2 2 naAmmonia Mobile Source Risk Estimates
Four Corners Power Plant September 3, 2010



### 8 Table 10. Comparison of Modeled Air Concentrations of Risk Driver Air Toxics to NATA Estimates for These Pollutants for San Juan County, NM

Toxic Air Pollutant FCPP 2002 NATA Analysis

Modeled Annual Average Air Conc. (μg/m 3 ) Total Annual

Average Air Conc. (μg/m 3 ) Background

Annual Average Air Conc. (μg/m 3 )

Acetaldehyde 0.031 28.00 0.574

Acrolein 0.0025 6.20 NA

Arsenic Compounds 0.000015 0.0053 NA

Diesel Engine Emissions 0.00098 0.1094 NA

Formaldehyde 0.016 110.75 0.689Attachment 1

National Ambient Air Quality StandardsNational Ambient Air Quality Standards (NAAQS) (Source: http://epa.gov/air/criteria.html )
Primary Standards Secondary Standards
Pollutant Level Averaging Time Level Averaging Time

Carbon
Monoxide 9 ppm

(10 mg/m 3 ) 8-hour (1) None

35 ppm (40 mg/m 3 ) 1-hour (1)

Lead 0.15 μg/m 3 (2) Rolling 3-Month Average Same as Primary

1.5 μg/m 3 Quarterly Average Same as Primary
Nitrogen
Dioxide 53 ppb (3) Annual (Arithmetic Average) Same as Primary

100 ppb 1-hour (4) None

Particulate

Matter (PM 10 ) 150 μg/m 3 24-hour (5) Same as Primary

Particulate

Matter (PM 2.5 ) 15.0 μg/m 3 Annual (6)
(Arithmetic Average) Same as Primary

35 μg/m 3 24-hour (7) Same as Primary

Ozone 0.075 ppm

(2008 std) 8-hour (8) Same as Primary

0.08 ppm (1997 std) 8-hour (9) Same as Primary

0.12 ppm 1-hour (10) Same as Primary

Sulfur
Dioxide 0.03 ppm Annual (Arithmetic Average) 0.5 ppm 3-hour (1) 0.14 ppm 24-hour (1)

75 ppb (11) 1-hour None

(1) Not to be exceeded more than once per year.

(2) Final rule signed October 15, 2008.
(3) The official level of the annual NO 2 standard is 0.053 ppm, equal to 53 ppb, which is s hown here for the purpose of clearer comparison to the 1-hour standard

(4) To attain this standard, the 3-year average of the 98th percentile of the daily maximum 1-hour averag e at each monitor within an area must not exceed 100 ppb (eff ective January 22, 2010).

(5) Not to be exceeded more than once per year on aver age over 3 years.

(6) To attain this standard, the 3-year average of the weighted annual mean PM2.5 concentrations from sin gle or multiple community-oriented monitors must not excee d 15.0 μg/m3.

(7) To attain this standard, the 3-year average of the 98th percentile of 24-hour concentrations at each populationoriented monitor within an area must not exceed 35 μg/m3 (effective December 17, 2006).

(8) To attain this standard, the 3-year average of the fourth-highest daily maximum 8-hour average ozone
concentrations measured at each monitor within an a rea over each year must not exceed 0.075 ppm. (eff ective May 27, 2008)
(9) (a) To attain this standard, the 3-year average of the fourth-highest daily maximum 8-hour average oz one concentrations measured at each monitor within an a rea over each year must not exceed 0.08 ppm. (b) The 1997 standard—and the implementation ru les for that standard—will remain in place for impl ementation purposes as EPA undertakes rulemaking to address th e transition from the 1997 ozone standard to the 20 08 ozone
standard. (c) EPA is in the process of reconsidering thes e standards (set in March 2008).

(10) (a) EPA revoked the 1-hour ozone standard in all areas, although some areas have continuing obligations under that standard ("anti-backsliding"). (b) The standard is attained when the expecte d number of days per calendar year with maximum hou rly average concentrations above 0.12 ppm is < 1.

(11) (a) Final rule signed June 2, 2010. To attain this standard, the 3-year average of the 99th percentil e of the daily maximum 1-hour average at each monitor within an ar ea must not exceed 75 ppb.Attachment 2

Air Modeling InputsTable 1.1 Modeling Options for the HEM3 Air Disper sion Modeling

Options Value Terrain used, rural land use, no deposition or depletion Site specific terrain values for locations and hill heights
from HEM3. Receptors Census blocks within 25 km of center of e ach line (see memorandum Figure 2). 13 rings of radial receptors, every 30 degrees from 25 to
50 km of center. Meteorological Data Albuquerque, NM 1991 AERMET fil e contained within
HEM3. Acute Emissions Multiplier Annual emissions multipl ied by 10 to account for
variations in short-term emissions.

Table 1.2 Source Input Data for the HEM3 Air Dispe rsion Modeling

Source

ID UTM East (m) SW
corner for

area source UTM

North (m),
SW corner
for area

source UTM

zone Length in
x direction (m) Length in

y direction (m) Rotation

Angle (degrees) 1 Release

height (m)

line1 3,933,935 703,077 12 10 36,441 0 3

line2 3,970,375 702,889 12 10 10,095 50 3

line3 3,975,446 711,618 12 10 98,194 0 3

line4 706,555 4,073,510 12 25,012 10 5 3

line5 727,081 4,063,284 12 8,500 10 60 3

1 HEM3 requires that the rotation angle be 90 degree s or less. As a result, area sources 4 and 5 had t o be
rotated and the X and Y coordinates for a new south west corner developed for these sources.