# E C 

# /

R Incorporated Providing Environmental Technical Support Since 1989

501 Eastowne Drive, Suite 250  Chapel Hill, North Carolina 27514 Telephone: (919)484

- 0222  Fax: (919) 484

- 0122 MEMORANDUM

Date: July 3 0 , 2012

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

From: Steve Fudge and Stephen Edgerton , EC/R Incorporated

Subject: Mobile Source Risk Estimates for Nava j o Generating Station due to Transportation of Anhydrous Ammonia or Urea

1. Introduction

This memorandum describes two air dispers ion modeling analyse s conducted in response

to comme nts that the EPA received on the Advance d Notice of Proposed Rulemaking (ANPR) of the Best Available Retrofit Technology (BART) for the Navajo Generating Station (NGS) in Arizona. The commenters noted that the transportation of anhydrous ammonia to the facility for

a selective catalytic reduction (SCR) system to reduce NO X emissions would generate emissions

of NO

x , CO, VOC, PM 10 , and other pollutants. In addition to SCR, selective non

- catalytic reduction (SNCR) is being considered for NO

x control at the NGS facility. For this system , urea would be used in place of anhydrous ammonia as a reagent to reduce NO

x . The air dispersion modeling analys e s w ere performed to es t imate the emissions and risk that would result from the transportation of anhydrous ammonia to NGS in support of SCR, and urea crystal s in support of

SNCR.

Both modeling studies were conducted using the Human Exposure Model Version 3 (HEM3) that contains as its air dispersion model the American Meteorological Society (AMS) and EPA Regulatory Model (AERMOD). Potential risks from toxic air pollutants were estimated by comparing the modeled air concentrations to EPA’s O ffice of A ir Q uality P lanning and

S tandards ’ (OAQPS’) dose response values contained within HEM3. Criteria pollutant air concentration estimates were compared to their Nati onal Ambient Air Quality Standards (NAAQS) and Class I increments.

The commenters also expressed concern about the risks involved in the transport and storage of anhydrous ammonia. The final section of this memorandum , Section 6, presents background on anhydrous ammonia, discusses the EPA’s various programs for hazardous materials and the quantities that meet the threshold for regulation, and presents a qualitative assessment of the risks of the use of anhydrous ammonia at NGS.

2. Transportation Modeling

For both the SCR and SNCR modeling analyses, the roadway emissions were modeled as 20 area sources appr oximately overlying the roads between Flagstaff, Arizona and NGS

. These area sources are shown in Figure 1.2

Figure 1. Approximate Locations of Line Sources from Flagstaff, Arizona to the Navajo Generating Station

Air concentrations at census blocks near the roadway were e stimated based on the pollutant emissions rates and the site

- specific meteorology and terrain input into the model. As

show n in Figure 2, which show s the modeling of a representative segment of road ( State Road 98

which connect s the facility access road with U.S. Highway 89 ) , two types of receptors were used in the modeling. The first set of receptors, represented as squares i n Figure 2, are the locations of the census block (year 2000) centroids within 25 kilometers of the center of the road segment. The second receptor set, represented as circles, are the polar grid receptors that are located along3

13 rings of radial receptor s, every 30 degrees beginning at half of the line length from the center of the line and extending to 50 km of center. A summary of the modeling options is presented in Table 1. Detailed model inputs are presented in Attachment 2.

Figure 2. Example o f Receptor Locations: Line Source f rom the Navajo Generating

Station Access R oad to U.S. Highway 89

Table 1. Options for the HEM3 Air Dispersion Modeling of Transporting Reagent to

NGS for SCR and S N CR

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 (year 2000) within 25 km of center of

each line

.

13 rings of radial receptors, every 30 degrees out to
50 km of center of each line

. Meteorological Data 1991 AERMET file contained within HEM3

– Prescott, AZ surface file, Tucson, AZ upper air file. Acute Emissions Multiplier Annual emissions multiplied by 10 to account for

variations in short

- term emissions.4

For the SCR modeling analysis, emissions were estimated from the two additional trucks daily cited by the commenter as being needed to transport the anhydrous ammonia from the railway station in Flagstaff, AZ to NGS (approximately 135 miles each way) based on the size of the plant. This corresponds to 728 trucks per year to transport anhydrous ammonia for SCR. Similarly, f or the SNCR modeling analysis, e missions were estimated from the approximately 1,583 truck trip s per year (about 4 trucks per day) needed to transport the urea crystals along the

same route . The number of truck trip s needed to transport urea to the NGS plant was calculated from estimates provided by the plant and from data presented in a technical and economic comparison of SCR ammonia opti ons. 1 The report provided data on the number of trucks or railcars that would be needed to transport various forms of ammonia and estimated it would take

19 truck deliveries to deliver 370 tons of urea

, or 19.5 tons per truckload. The NGS plant

estimated t hat 30,873 tons/yr of urea would be needed to support SNCR

. 2 Using the figure of

19.5 tons of ur ea per truckload , 1,583 truckloads of urea per year was computed

.

Criteria pollutant emissions released by the trucks were developed from South Coast Air Quality Management District’s (SCAQMD ’s ) “Highest (Most C onservative) EMFAC2007 (version 2.3) Emission Factors for On

- Road Heavy

- Heavy

- Duty Diesel Trucks for 2010.” 3

Table 2 presents the SCAQMD emission factors and the criteria pollutant emissions estimate s used in both analyse s. Toxic air pollutant emission factors were developed from the reactive organic gas (ROG) and PM 2.5 emission factors using OAQPS’ Speciate Database

. 4 Table 3 presents the toxic air pollutant emissions estimates developed using the Sp eciate factors.

Table 2

. Criteria Pollutant Emission Rates Used to Estimate Risk from Transporting Reagent to NGS for SCR and SNCR

Pollutant SCAQMD EF (lb/mi) Emissions 728 trucks/yr, 270 miles roundtrip (TPY) for

SCR Emissions 1

, 583 trucks/yr, 270 miles roundtrip (TPY) for

SNCR Reactive Organic Gases (ROG) 3.04E

- 03 2.99E

- 01 6.50E

- 01

CO 1.20E

- 02 1.17E+00 2.56E+00

NO X 3.82E

- 02 3.76E+00 8.16E+00

SO X 4.13E

- 05 4.06E

- 03 8.83E

- 03

PM 10 1.83E

- 03 1.80E

- 01 3.91E

- 01

PM 2.5 including tires & brakes 1.60E

- 03 1.57E

- 01 3.42E

- 01

PM 2.5 engine exhaust 1.55E

- 03 1.53E

- 01 3.31E

- 01

1 http://www.fwc.com/publications/tech_papers/files/TP_SCR_03_03.pdf

2 Grant Smedley, < grant.smedley@srpnet.com >, “Urea Cost Estimate,” email message to Anita Lee, March 23,

2012.

3 http://www.aqmd.gov/ceqa/handbook/onroad/onroad.html

4 http://cfpub.epa.gov/si/speciate/5

Table 3

. Toxic Air Pollutant Emission Rates Used to Estimate Risk from Transporting Reagent to NGS for SCR and SNCR

Pollutant SCAQMD

EF (lb/mi) Weight

Percent of

VOC from

Speciate Calculated

HAP

Emission

Factor (lb/mile) Emissions 728 trucks/yr, 270 miles roundtrip (TPY) for SCR Emissions 1

, 583 trucks/yr, 270 miles roundtrip (TPY) for

SNCR
Gas Phase Speciate Database Record # 4674: Diesel Exhaust

- Medium Duty Trucks

ROG* 3.04E

- 03

1,3

- Butadiene 1.18E

- 01 3.60E

- 04 3.53E

- 02 7.69E

- 02
2,2,4

- Trimethylpentane 4.73E

- 01 1.44E

- 03 1.41E

- 01 3.08E

- 01

Acetaldehyde 1.59E+01 4.85E

- 02 4.77E+00 1.04E+01

Acrolein 1.30E+00 3.94E

- 03 3.88E

- 01 8.42E

- 01

Benzene 1.05E+00 3.18E

- 03 3.12E

- 01 6.80E

- 01

Ethyl benzene 1.79E

- 01 5.45E

- 04 5.36E

- 02 1.16E

- 01

Formaldehyde 8.51E+00 2.59E

- 02 2.54E+00 5.53E+00

M & p

- xylene 8.89E

- 01 2.70E

- 03 2.66E

- 01 5.77E

- 01

Naphthalene 2.35E

- 01 7.16E

- 04 7.03E

- 02 1.53E

- 01

O

- xylene 3.17E

- 01 9.63E

- 04 9.46E

- 02 2.06E

- 01

Propionaldehyde 5.34E+00 1.62E

- 02 1.60E+00 3.46E+00

Toluene 1.52E+00 4.62E

- 03 4.54E

- 01 9.87E

- 01

Dibenzofuran 1.09E

- 02 3.33E

- 05 3.27E

- 03 7.12E

- 03

Acetophenone 1.95E+00 5.92E

- 03 5.81E

- 01 1.27E+00
Particulate Phase Speciate Database Record # 322082.5: Heavy Duty Diesel Trucks
Diesel engine

emissions 1.55E

- 03 1.53E

- 01 3.31E

- 01
Arsenic compounds 1.50E

- 02 2.33E

- 05 2.29E

- 03 4.98E

- 03 Manganese compounds 9.00E

- 03 1.40E

- 05 1.37E

- 03 2.99E

- 03
Nickel compounds 2.70E

- 02 4.20E

- 05 4.12E

- 03 8.98E

- 03
* Assumed that reactive organic gases (ROG) are equivalent to volatile organic compounds (VOC)

.

3. Impacts of Criteria Air Pollutant Emission s

In order to place into perspective peoples’ exposure to criteria air pollutants

, the modeled

air concentration was compared to the NAAQS for the pollutant. The NAAQS for the criteria pollutants include both short

- term and long

- term average air concentrations (see Attachment 1).

Table 4 pre sents the NAAQS levels used in this analysis, with the concentrations converted as necessary from expression as parts per million or billion to milligram s per cubic meter (mg/m 3 )

. As shown in Table s 5 and 6 , the SCR and SNCR annual average and short

- term a ir

concentrations modeled at the most impacted census block s (the populated census block s with6

the highest modeled air concentration of a pollutant ) are well below the NAAQS and Class I

increments

.

Table 4

. NAAQS and Class I Increments Used in Criteria 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 Annual 0.035 mg/m 3 0.035 0.002 24

- hour

SO 2 0.03 ppm 0.08 0.002 Annual 0.14 ppm 0.37 0.005 24

- hour

75 ppb 0.2 1

- hour

Table 5

. Comparison of Modeled Annual Average Air Concentrations from Emi ssions
from Transporting Reagent to NGS for SCR and S N CR to NAAQS and

Class I I ncrements

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

Increments

(mg/m 3 ) SCR Annual Average Modeled

Air Concentration (mg/m 3 ) SNCR Annual Average Modeled

Air Concentration (mg/m 3 )

CO NA NA 0.000013 0.000031

NO 2 0.1 0.0025 0.00004 0.000098

PM 10 NA 0.004 0.0000019 0.0000047

PM 2.5 0.015 0.001 0.0000017 0.0000041

SO 2 0.08 0.002 0.000000043 0.000000117

Table 6

. Comparison of Modeled Short

- Term C oncentrations from Emi ssions from Transporting Reagent to NGS for SCR and S N CR to NAAQS and Class I

Increments

Pollutant Short

- Term Average NAAQS

Level (mg/m 3 ) Class I Short

- Term Average Increments (mg/m 3 ) SCR Short

- term Average Mod eled

Air Concentration (mg/m 3 ) SNCR Short

- term Average Modeled

Air Concentration (mg/m 3 )

1

- hour Average Air Concentrations

CO 40. NA 0.0043 0.0094

NO

x 0.19 NA 0.014 0.030

SO

x 0.2 NA 0.000015 0.000033

8

- hour Average Air Concentrations

CO 10. NA 0.00094 0.0020

24

- hour Average Air Concentrations

PM 10 0.15 0.008 0.000064 0.00015

PM 2.5 0.035 0.002 0.000056 0.00013

SO

x 0.37 0.005 0.0000014 0.0000034

4. Impacts of Toxic Air Pollutants

N ational A mbient A ir Q uality S tandards have not been established for the hundreds of toxic air pollutants that have the potential to cause cancer and other non

- cancer adverse health

effects. For these pollutants, t oxicological dose response values have been established for use in estimating ma ny toxic air pollutants ’ adverse health effects. The OAQPS has established a table of pollutant

- 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 chro nic dose response values used in the analysis can be found at http://www.epa.gov/ttn/atw/toxsource/summary.html

in Table 1.

Cancer risk for exposure to a pollutant at a particular concentration is expressed in terms of the number of cancers that would be expected to be caused in a population exposed for a lifetime, for example one cancer per 1 million persons exposed (abbreviated as 1 x 10 - 6 ). For purposes of this measure, a lifetim e of exposure is defined as 70 years

. As a general rule in the EPA’s evaluation of risks, a risk of 1 x 10 - 6 or less would be considered acceptable.

Non

- cancer health effects are quantified using hazard quotients and hazard indices for various target organs

. The hazard quotient (HQ) for a given chemical and target organ is the ratio

of the ambient concentration of the chemical to the “ reference concentration ” (RfC) at which no adverse effects are expected from continuous inhalation for a lifetime ( t his is defined as

70 years )

. T herefore

, no adverse effects are expected as a result of exposure if the HQ is less than

1 .0

. The chronic hazard index (HI) for a given target organ is the sum of hazard quotients for substances that affect that organ (e.g., resp iratory). As with the HQ, aggregate exposures equal to or below an HI of 1.0 likely will not result in adverse non

- cancer health effects over a lifetime of exposure and would ordinarily be considered acceptable.8

As shown in Table 7 below , the maximum es timated cancer risk summed over all modeled toxic air pollutants for the SCR modeling analyses is less than 1 x 10 - 6 , and it is 1 x 10 - 6
for the SNCR modeling analysis

. For non

- cancer health effects, the respiratory system is the target organ most affected by the modeled pollutants that would be emitted by trucks transporting reagent to NGS. As shown in Table 7, the respiratory HIs for both SCR and SNCR

are well below 1.0

. In both the SCR and SNCR modeling analyse s, the maximum cancer risk

occurs at a census block located immediately adjacent to the road in Coconino County, Arizona with a populat ion of 45 individuals

. For the other impacted census blocks, the risks in the SCR analysis are estimated to be as low as 5 x 10 - 1 2 and the H I s are estimated to be as low as

0.0000 02 ; for the SN CR analysis, as low as 1 x 10 - 11 and 0.000 0 0 3

.

Table 7

. Modeled Risk Estimates for Toxic Air Pollutants from Emi ssions from Transporting Reagent to NGS for SCR and S N CR

Risks Due to Transportation of Anhydrous Ammonia for SCR

Cancer Risk 7 x 10 - 7 Seven excess cancer cases over a lifetime exposure per 10 million people exposed.

Non

- Cancer Respiratory

Hazard Index 0.2 2 A value of the H I at or below 1 .0 indicates that the exposure is not likely to result in adverse

health effects.

Risks Due to Transportation of Urea for SNCR

Cancer Risk 1 x 10 - 6 One excess cancer case over a lifetime exposure per 1 million people exposed.

Non

- Cancer Respiratory

Hazard Index 0.47 A value of the H I at or below 1 .0 indicates that the exposure is not likely to result in adverse

health effects.

5. Comparison of Modeled Results to Existing Concentrations and the 2005 NATA

In addition to estimating impacts by comparing modeled 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 network has been established for the purpose of determining whether an area has attained the NAAQS. While the number of monitors for air toxics has increased in recent years, few areas of th e nation are covered, and no air toxics

monitors are sited in the area of interest in Arizona . Thus, for this analysis, we used the most

recent National Air Toxics Assessment ( NATA ) analysis for comparisons. T he NATA analysis is a county

- level and census t ract

- level air toxics study that provides modeled air concentration and risk estimates for the entire United States and is completed every 3 years. The results of the

2005 tract

- level NATA are presented for comparison here.9

As shown in Table 8 , the expected impact of the increased truck traffic to NGS necessary to deliver either anhydrous ammonia for SCR or urea for SNCR is very low when compared to nationally monitored concentrations ( http://www.epa.gov /airtrends/ ). Tables 9 and 10 show that for air toxics, in most cases the transportation of either anhydrous ammonia or urea to NGS

would have minimal impact on the existing levels of risk or existing ambient concentrations

estimated in NATA

. The values in T ables 9 and 10 for NATA represent the census tract that contains the census block with the highest concentrations resulting from reagent transportation as reported in the previous tables. Although the results shown in Table 9 indicate that the existing

2005 total modeled respiratory HI in the most impacted census tract in Coconino County is already close to 1.0 , levels well in excess of 1.0 are not uncommon nationally

. For comparison, the 2005 NATA report ed a n average total respiratory HI of 3. 2 for Maricopa County, AZ ( the county containing Phoenix)

, with a total respiratory HI of 9.5 in the highest census tract with in that county. F or Pima County, AZ (the county containing Tucson)

, the 2005 NATA reported an average total respiratory HI of 1.5, with a value of 3.3 reported for the highest census tract with in the county.

Table 8

. Comparison of Annual Average Modeled Cr iteria Pollutant Concentrations from Emissions from Transporting Reagent to NGS for SCR and S N CR to
National Monitored Values

Poll

. Avg.

Period SCR at

NGS

Modeled

Air

Conc. (μg/m 3 ) SNCR at

NGS

Modeled

Air

Conc. (μg/m 3 ) 2008 Range of Monitored Values (μg/m 3 )

Poll Avg.

Period 10th

%ile Arithmetic Avg. 90th

%ile # of

sites

CO Highest

8

- hour 0.94 2.0 CO 2 nd Highest

8

- hour 1,200 2,100 3,100 206

NO

x Annual 0.040 0.098 NO 2 Annual 8.7 25. 40. 151

PM 10 Annual 0.0019 0.0047 PM 10 Seasonal

wt. annual 33. 56. 88. 325

PM 2.5 Highest

24

- hour 0.056 0.13 PM 2.5 2 nd Highest

24

- hour 7.4 11. 14. 728

SO

x Annual 0.000043 0.00011 SO 2 Annual 3.7 9.1 15.5 141

Table 9

. Comparison of Modeled Total Air Toxic Risks to NATA Risk Estimates for

Census Tract 04005000500 in Coconino C ounty, AZ

Toxic Air Pollutant s SCR at NGS SN CR at NGS 2005 NATA Analysis

Modeled Risk Modeled Risk Modeled Total Risk

Cancer Risk 7 x 10 - 7 1 x 10 - 6 2.6 x 10 - 5

Non

- Cancer Respiratory

Hazard Index 0. 22 0.47 0.9 810

Table 10

. Comparison of Modeled Air Concentrations of Risk Driver Air Toxics to

NATA Es timates for These Pollutants in Census Tract 04005000500 in

Coconino County, AZ

Toxic Air

Pollutant SCR at NGS SNCR at NGS 2005 NATA Analysis

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

Acetaldehyde 0.051 0.12 1.18

Acrolein 0.0041 0.010 0.021

Arsenic Compounds 0.000024 0.000060 0.00015 Diesel Engine

Emissions 0.0016 0.0040 0.2 6

Formaldehyde 0.027 0.067 1.1

6. Transport and Storage of Anhydrous Ammonia

Anhydrous ammonia is a colorless gas with a pungent odor. It is stored and transported as a liquid under pressure. Ammonia vapor is lighter than air and tends to rise when released to atmosphere.

Ammonia is used widely and in large quantities for a var iety of purposes. Estimated use

of ammonia in the United States in 2010 totaled 14.7 million metric tons. 5 Approximately

87 percent of this total was for fertilizer use, including direct application to the soil from tanks containing the liquefied gas as we ll as in the production of urea, ammonium nitrates, ammonium phosphates, and other nitrogen compounds. 6 Other agricultural uses of ammonia include use as a source of protein in livestock feeds, as a pre

- harvest cotton defoliant, as an anti

- fungal agent on certain fruits, and as a preservative for the storage of high

- moisture corn.

Non

- agricultural uses of anhydrous ammonia include refrigeration systems, water treatment, and heat treatment. It is used to produce nitric acid and other chemicals, dyes, sulf a drugs, vitamins, and cosmetics; to neutralize acid constituents of crude oil and to protect equipment from corrosion; to extract certain metals from their ores; for stabilizing natural and synthetic latex during transportation; for pulping wood; in the m anufacture of synthetic fibers such as nylon and rayon; in the manufacture of phenolics and polyurethanes; as a curing agent and a slime and mold preventative in tanning liquors and as a protective agent for leathers and furs in storage; and in weak ammoni a solutions as commercial and household cleaners and detergents. 7

5 http://minerals.usgs.gov/minerals/pubs/commodity/nitrogen/mcs

- 2011

- nitro.p df

6 Ibid.

7 R.M. Technologies, Mount Laurel, NJ. http://www.rmtech.net/Chemical%20Plants.htm11

Anhydrous ammonia is toxic and can present a health hazard unless proper handling, operation, and maintenance procedures are followed . Effects of inhalation of anhydrous ammonia range from lung irritation to severe respiratory injuries, with possible fatality at higher concentrations. Anhydrous ammonia also is corrosive and can burn the skin and eyes. Anhydrous ammonia is stored as a liquid and has a boiling point of minus 28 degrees Fa hrenheit. At this temperature it can cause freezing burns. 8

Federal Risk Management Programs

There are a number of federal regulations that require reporting of the use and release of hazardous materials. The EPA programs are:

• Emergency Planning and Co mmunity Right

- to

- Know Act (EPCRA), also known as

Title III of the Superfund Amendments and Reauthorization Act of 1986 (SARA),

• Comprehensive Environmental Response, Compensation and Liability Act (CERCLA),

• Section 112(r) of the Clean Air Act (CAA). 9

E PCRA section 302 covers the presence of extremely hazardous substances (EHSs) in quantities at or above the Threshold Planning Quantity (TPQ). The TPQ for anhydrous ammonia is 50 pounds. Section 302 requires Local Emergency Planning Committees (LEPCs) to d evelop emergency response plans and facility owners or operators to notify the State Emergency Response Commission and LEPC if a chemical is present at the facility in quantities at or above the EHS’s TPQ. Releases of reportable quantities (RQ) of EHSs are subject to state and local reporting under section 304 of EPCRA. The RQ for anhydrous ammonia is 100 pounds under this program. EPCRA section 313 also pertains to toxic chemicals. Emissions, transfers, and waste management data for chemicals listed under section 313 must be reported annually as part of the community right

- to

- know provisions. Releases of CERCLA hazardous substances, in quantities equal to or greater than their RQ, are subject to reporting to the National Response Center under CERCLA. The RQ for anhydrous ammonia under CERCLA is also 100 pounds.

Under the accident prevention provisions of section 112(r) of the CAA, EPA developed a list of 77 toxic substances and 63 flammable substances. Threshold quantities (TQs) were

established for these substances. The list and TQs identify processes subject to accident prevention regulations known as Risk Management Programs (RMP). Anhydrous ammonia is listed as a toxic substance under section 112(r) with a TQ of 10,000 pounds. Additional

information is available at http://www.epa.gov/oem/content/rmp/caa_faqs.htm

.

Transportation activities are exempted from compliance with the RMP regulations because these regulations apply only to stationary sources. Transportation

- related chemical safety is the responsibility of the U.S. Department of Transportation (DOT). Specifi cally, the chemicals in the tank car are exempt only if the tank car is in transportation. The EPA considers a container to be in transportation as long as it is attached to the motive power (e.g., truck or

8 Ibid.

9 LIST OF LISTS: Consolidated List of Chemicals Subject to the Emergency Planning and Community Right

To

- Know Act (EPCRA), Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) and Section 112(r) of the Clean Air Act. May 2010. Avai lable at: http://www.epa.gov/emergencies/tools.htm#lol12

locomotive) that delivered it to the site. If the tank car is detached from the motive power, and therefore no longer in transportation, the contents of the tank car must be considered in the TQ determination under the risk management program rule.

Specific to transportation, anhydrous ammonia is regul ated domestically by the DOT as a

non

- flammable gas, but meets the definition of a Federal Motor Carrier Safety Administration (FMCSA) hazardous material because it is toxic by inhalation. It is covered under the FMCSA regulations that require a Hazardous Material (HM) Safety Permit when transported in a packaging having a capacity greater than 13,248 L (3,500 gallons).

Qualitative Assessment of Risks from the Transport and Storage of Anhydrous Ammonia

A FMCSA

- supported risk assessment estimated that app roximately 15,000 HM accidents and incidents occur each year. (Accidents and incidents involving anhydrous ammonia represent an unknown fraction of this total.) Of the HM incidents and accidents, about 75 percent represent
l oading and unloading incidents. En route HM accidents total about 2,500 annually with about 700 (28 percent) of these being spill accidents. The estimated number of annual incidents and accidents were converted into rates using annual vehicle miles of HM operation based on the

1997 Commo dity Flow Survey. The average HM accident rate is 0.32 accidents per million

vehicle

- miles and the average HM incident rate is 0.51 incidents per million vehicle

- miles. 10

With a round

- trip distance of 270 miles per delivery of anhydrous ammonia to NGS and two deliveries per day, the total miles traveled by delivery tankers would be 197,100 miles per year. Only half of this total, or 98,550 miles per year, would be traveled by tanker trucks loaded with anhydrous ammonia. At the overall HM accident rate from the FMCSA risk assessment, one would expect one accident involving an NGS tanker truck approximately every 15 years. For the laden tanker trucks, the estimated frequency would be one accident in approximately

30 years. According to the figures from the FM CSA risk assessment, only 28 percent of such accidents would be expected to involve a spill. Given that the vast majority of the route passes through a very sparsely populated area, the likelihood of injury to the populace from an accident is extremely sma ll.

The infrequency of releases from transport and storage of anhydrous ammonia is confirmed by reported information on such releases. The U.S. Agency for Toxic Substances and Disease Registry (ATSDR) operates the National Toxic Substance Incidents Progr am (NTSIP)

. The program collects and combines information from many resources, including the EPA and DOT, to protect people from harm caused by spills and leaks of toxic substances. A download

from the National Database 11 on anhydrous ammonia incidents betw een 2005 and 2010 contained 45 entries. All of the entries were associated with the agricultural use of anhydrous ammonia. Of these incidents, the vast majority were associated with loading operations or soil applications rather than transport on highways or other areas where the public may be exposed. There were no incidents involving anhydrous ammonia use at a power plant or its transport to a

10 Comparative Risks o f Hazardous Materials a nd Non

- Hazardous Materials Truck Shipment Accidents/Incidents

. Prepared for Federal Motor Carrier Safety Administration by Battelle Institu te. Columbus, OH. March 2001. http://www.phmsa.dot.gov/staticfiles/PHMSA/DownloadableFiles/Files/ hazmatriskfinalreport.pdf

11 http://www.atsdr.cdc.gov/ntsip/national_database.html13

power plant during that 5

- year period. Given the very widespread use of anhydrous ammonia, the

small number of in cidents between 2005 and 2010 and the types of settings where they occurred show that the likelihood of a release associated with the transport and storage of anhydrous ammonia for use in SCR at NGS would be very small.

While the Federal Government’s saf ety net of programs were put in place to keep the public and workers safe while dealing with flammable, hazardous, or toxic materials, they do add an expense to the owners and operators of facilities dealing with these materials. Based on its use of anhydr ous ammonia, Navajo Generating Station would fall under the CAA section 112(r)’s RMP requirements as well as notification requirements under other programs. However, the costs of complying with these programs would be a very small fraction of the total cos ts related to the use of SCR at the facility.14

(This page intentionally left blank.)Attachment 1

National Ambient Air Quality Standards(This page intentionally left blank.)National 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 shown 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 average at each

monitor within an a rea must not exceed 100 ppb (effective January 22, 2010).

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

(6) To attain this standard, the 3

- year average of the weighted annual mean PM2.5 concentrations from single or multiple commu nity

- oriented monitors must not exceed 15.0 μg/m3.

(7) To attain this standard, the 3

- year average of the 98th percentile of 24

- hour concentrations at each population

oriented 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 area over each year must not ex ceed 0.075 ppm. (effective May 27, 2008)

(9) (a ) 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 area over each year must not exceed 0.08 ppm. (b) The 1997 standard

— and the implementation rules f or that standard

— will remain in place for implementation purposes as EPA undertakes rulemaking to address the transition from the 1997 ozone standard to the 2008 ozone

standard. (c) EPA is in the process of reconsidering these standards (set in March 2 008).

(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 expected number of days per calendar year with maximum hourly 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 percentile of the daily

maximum 1

- hour a verage at each monitor within an area must not exceed 75 ppb.(This page intentionally left blank.)Attachment 2

Detailed Air Modeling Inputs(This page intentionally left blank.)Detailed Air Modeling Inputs Used to Estimate Risk from Transporting Anhydrous Ammonia and Urea to Navajo Generating Station for

SCR and S N CR

Original Road Segment Location Identification Road Segment Location for Use in HEM3 Modeling Emissions Distribution

ID End 1 of Road Segment (m)

- Zone 12 End 2 of Road Segment (m)

- Zone 12 Length of

Road Segment 1 Rotated SW Corner (m)

- Zone 12 Length in x

direction Length in y

direction Rotation Angle 2 Area of Road Segment

UTM E UTM N UTM E UTM N (m) UTM E UTM N (m) (m) degrees (m2) %

A 456,327 4,083,346 464,762 4,083,385 8,435 456,327 4,083,346 8,435 10 0 84,348 4.00%

B 452,785 4,071,198 456,327 4,083,346 12,654 452,785 4,071,198 10 12,654 15 126,536 6.00%

C 451,295 4,071,211 452,785 4,071,198 1,490 451,295 4,071,211 1,491 10 0 14,905 0.71%

D 444,449 4,058,241 451,295 4,071,211 14,666 444,449 4,058,241 10 14,666 30 146,658 6.95%

E 443,631 4,058,247 444,449 4,058,241 818 443,631 4,058,247 818 10 0 8,179 0.39%

F 443,502 4,054,555 443,631 4,058,247 3,694 443,502 4,054,555 10 3,694 0 36,935 1.75%

FG 441,746 4,054,457 443,502 4,054,555 1,758 441,746 4,054,457 1,758 10 0 17,585 0.83%

G 441,205 4,050,393 441,746 4,054,457 4,100 441,205 4,050,393 10 4,100 10 40,999 1.94%

H 441,205 4,050,393 447,498 4,040,662 11,588 441,205 4,050,393 11,588 10 60 115,878 5.49%

I 447,498 4,040,662 464,083 4,003,616 40,589 447,498 4,040,662 40,589 10 65 405,895 19.23%

K 463,983 3,987,320 464,083 4,003,616 16,296 463,983 3,987,320 10 16,296 0 162,958 7.72%

L 463,983 3,987,320 464,574 3,983,514 3,852 463,983 3,987,320 3,852 10 85 38,517 1.83%

M 462,822 3,970,288 464,601 3,983,406 13,238 462,822 3,970,288 10 13,238 8 132,384 6.27%

N 460,686 3,966,609 463,009 3,970,296 4,357 460,686 3,966,609 10 4,357 30 43,572 2.06%

O 454,515 3,950,178 460,686 3,966,609 17,552 454,515 3,950,178 10 17,552 20 175,522 8.32%

P 447,270 3,915,624 454,515 3,950,178 35,305 447,270 3,915,624 10 35,305 12 353,051 16.73%

Q 447,270 3,915,624 450,695 3,909,008 7,451 447,270 3,915,624 7,451 10 65 74,505 3.53%

R 450,497 3,902,939 450,695 3,909,008 6,071 450,497 3,902,939 10 6,071 0 60,715 2.88%

S 447,930 3,899,615 450,559 3,903,568 4,747 447,930 3,899,615 10 4,747 40 47,468 2.25%

T 446,510 3,897,703 447,930 3,899,615 2,381 446,510 3,897,703 10 2,381 35 23,812 1.13%

1 Width = 10 m 2 HEM3 requires angle be between 0 and 90 degrees. 2,110,421 = total area