Prepared for: Prepared by: CalPortland Company AECOM Glendora, CA Camarillo, CA 60282724 March 2014 

### Environment



# Evaluation of EPA’s Reasonable Progress Analysis for Kiln 4 at CalPortland Company’s Rillito Cement PlantPrepared for: Prepared by: CalPortland Company AECOM Glendora, CA Camarillo, CA 60282724 March 2014 

### Environment



# Evaluation of EPA’s Reasonable Progress Analysis for Kiln 4 at CalPortland Company’s Rillito Cement Plant

_________________________________ Prepared By Steven L. Heisler

_________________________________ Reviewed By Sara J. HeadAECOM Environment

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## Contents

1.0 Introduction ............................................................................................................... 1-1

2.0 Nitrogen Oxides Control Efficiency for Applying Selective Non-Catalytic Reduction to Kiln 4.................................................................................................... 2-1

3.0 Costs and Cost Effectiveness for Applying Selective Non-Catalytic Reduction to Kiln 4.................................................................................................... 3-1

4.0 Visibility Modeling to Evaluate Visibility Improvements.......................................... 4-1 4.1 Differences between EPA and AECOM Visibility Modeling ............................................4-1 4.1.1 Errors in Emissions from Kilns 1 through 3 at the Rillito Cement Plant .............4-1 4.1.2 Errors in Rillito Kiln 4 Stack Parameters .........................................................4-2 4.1.3 Coarse Particle Geometric Mean Diameter and Minimum Turbulence Velocities ......................................................................................................4-3 4.1.4 Monthly Background Ammonia Concentrations ..............................................4-3 4.2 Visibility Modeling Results ...........................................................................................4-5


### 5.0 Conclusions .............................................................................................................. 5-1AECOM Environment

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## List of Tables Table 4-1 Corrected Hourly Emission Rates for Kilns 1 through 3 for Visibility Modeling.....................4-2 Table 4-2 Corrected Stack Parameters for Kiln 4 for Visibility Modeling .............................................4-2 Table 4-3 Background Monthly Ammonia Concentrations (ppb) Used in the Modeling .......................4-5 Table 4-4 EPA and AECOM Visibility Modeling Results with Monthly Ammonia Background for

AECOM Modeling ......................................................................................................4-7 Table 4-5 EPA and AECOM Visibility Modeling Results with Constant 1 ppb

Ammonia Background for AECOM Modeling ..............................................................4-8



## List of Figures Figure 2-1 Depiction of Rillito Cement Plant Kiln 4 Modified Loop Calciner and Mojave Cement

Plant Kiln Calciner .....................................................................................................2-4 Figure 4-1 IMPROVE NHx Concentrations from April 2011 to January 2012 .................................4-4 Figure 4-2 2009 IMPROVE Composition Data for Saguaro East National Park .............................4-5AECOM Environment

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## List of Abbreviations

o C degrees Celsius

o F degrees Fahrenheit
AZ Arizona
BART Best Available Retrofit Technology CA California CDPHE Colorado Department of Public Health and Environment CO carbon monoxide CO 2 carbon dioxide CPC CalPortland Company
dv deciview
EPA United States Environmental Protection Agency
FIP Federal Implementation Plan
FR Federal Register
H hydrogen
H 2 O water IMPROVE Interagency Monitoring of Protected Visual Environments IWAQM Interagency Workgroup on Air Quality Modeling
N 2 molecular nitrogen
NH 2 amine radical
NH 3 ammonia
NHx ammonia plus ammonium ion
NM National Monument NO nitric oxide NO 2 nitrogen dioxideAECOM Environment

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NOx nitrogen oxides
NP National Park O 2 molecular oxygen OH hydroxyl radical
PM 10 particles smaller than 10 microns diameter ppb part per billion
RP Reasonable Progress SIP State Implementation Plan SNCR selective non-catalytic reduction SO 2 sulfur dioxide tpy tons per year TSD Technical Support Document
WA Wilderness AreaAECOM Environment

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## Executive Summary

On February 18, 2014, the United States Environmental Protection Agency (EPA) published in the Federal Register (79 FR 9318) a proposed Federal Implementation Plan (FIP) to address the requirements of the Regional Haze Rule and interstate visibility transport for the disapproved portions of Arizona’s Regional Haze State Implementation Plan (SIP) as described in EPA’s final rule published on July 30, 2013. As part of the proposed FIP, EPA is proposing to require nitrogen oxides (NOx) emissions reductions consistent with the application of Selective Non-Catalytic Reduction (SNCR) on Kiln 4 at the CalPortland Company (CPC) Rillito Cement Plant. The proposed requirement is based on a Reasonable Progress (RP) analysis conducted by EPA for the CPC Rillito Cement Plant. Various aspects of EPA’s RP analysis for Kiln 4 at the Rillito Cement Plant have been evaluated by AECOM for this report. These aspects include:

x The NOx control efficiency that is assumed for applying SNCR to Kiln 4;

x The costs for applying SNCR to Kiln 4; and

x Modeling conducted to estimate the degree of improvement in visibility that could result from applying SNCR to reduce NOx emissions from Kiln 4. EPA’s assumption of a 50 percent NOx control efficiency for applying SNCR to Kiln 4 is too high. This control efficiency was based in part on an SNCR optimization report for CPC’s Mojave Plant in California submitted to EPA on August 30, 2013. Emission data provided in this report indicates a range of SNCR control efficiency of 30 percent to 60 percent at the Mojave Plant, depending upon operating parameters. Although SNCR control efficiencies as high as 60 percent were observed at the Mojave Plant, there are differences between Kiln 4 at the Rillito Cement Plant and the cement kiln at the Mojave Plant which would lead to a lower NOx control efficiency from applying SNCR to Kiln 4. Although site-specific tests would be required to quantify the control efficiencies that might be achieved with SNCR for Kiln 4, CPC has considered these differences between Kiln 4 at Rillito and the cement kiln at the Mojave Plant and, based on its engineering judgment, concluded that 35 percent NOx control efficiency would be an appropriate estimate for Kiln 4. EPA’s estimate of the annualized cost for applying SNCR to Kiln 4 of $1,089,566 is too low. Based on more accurate estimates of the annual cost for ammonia reagent, a more reasonable annualized cost estimate is $1,348,084. The resulting cost effectiveness, based on a 35 percent NOx control efficiency, is $1,850 per ton of NOx removed, which is approximately 78 percent higher than EPA’s estimate of $1,047 per ton of NOx removed. AECOM conducted additional visibility modeling to estimate the potential improvements in visibility that would result from applying SNCR with a NOx control efficiency of 35 percent to Kiln 4. In addition to the difference in the assumed SNCR NOx control efficiency, AECOM’s visibility modeling included the following differences from EPA’s modeling:

x Errors in emissions from Kilns 1 through 3 at the Rillito Cement Plant were corrected;

x Errors in the stack parameters for Kiln 4 were corrected;

x Values used for the coarse particle geometric mean diameter and for minimum turbulence velocities differed from those used by EPA; andAECOM Environment

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x Visibility was calculated using both constant and seasonal NH 3 background concentrations. The highest modeled visibility benefits at a Class I area from applying SNCR to Kiln 4 with an assumed NOx control efficiency of 35 percent is 0.15 deciview (dv) with a seasonally varying NH 3 background concentration and 0.18 dv with a constant 1 part per billion (ppb) NH 3 background concentration. These visibility improvements are substantially less than the maximum improvement of 0.24 dv indicated by EPA’s modeling and too low to be detected by the available technology for particulate monitors (much less than 0.3 dv) and less than 18 percent of the perceptible levels that can be visually detected (1 dv). Furthermore, in its RP analysis for Springerville Units 1 and 2 for the proposed FIP, EPA concluded that “While the cost per ton for SNCR may be reasonable, the projected visibility benefits are relatively small (0.18 dv at the most affected area)” and did not propose additional controls on these units. Consistent with this conclusion, it would not be reasonable to propose the application of SNCR to Kiln 4 at the Rillito Cement Plant based on the similar small benefit.AECOM Environment

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## 1.0 Introduction

On February 18, 2014, the United States Environmental Protection Agency (EPA) published in the Federal Register (79 FR 9318) a proposed Federal Implementation Plan (FIP) to address the requirements of the Regional Haze Rule and interstate visibility transport for the disapproved portions of Arizona’s Regional Haze State Implementation Plan (SIP) as described in EPA’s final rule published on July 30, 2013. As part of the proposed FIP, EPA is proposing to require nitrogen oxides (NOx) emissions reductions consistent with the application of Selective Non-Catalytic Reduction (SNCR) on Kiln 4 at the CalPortland Company (CPC) Rillito Cement Plant. The proposed requirement is based on a Reasonable Progress (RP) analysis conducted by EPA for the CPC Rillito Cement Plant. This document presents AECOM’s evaluation of various aspects of EPA’s RP analysis for Kiln 4 at the Rillito Cement Plant. These aspects include:

x The NOx control efficiency that is assumed for applying SNCR to Kiln 4;

x The costs for applying SNCR to Kiln 4; and

x Modeling conducted to estimate the degree of improvement in visibility that could result from applying SNCR to reduce NOx emissions from Kiln 4.AECOM Environment

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## 2.0 Nitrogen Oxides Control Efficiency for Applying Selective Non-Catalytic Reduction to Kiln 4

The SNCR process is basically the injection of aqueous or anhydrous ammonia (NH 3 ) or urea into the cement kiln flue gas at a suitable temperature. SNCR removes NOx (90 to 95 percent of NOx in flue gas is nitric oxide, NO) by a two-step process, as follows:

x Ammonia reacts with available hydroxyl radicals (OH) to form amine radicals (NH 2 ) and water (H 2 O):
NH 3 + OH ĺ NH 2 + H 2 O (1)

x Amine radicals combine with NO to form nitrogen (N 2 ) and water:
NH 2 + NO ĺ N 2 + H 2 O (2) These 2 steps are typically expressed as follows:

4 NO + 4 NH 3

+ O 2 ĺ 4 N 2 + 6 H 2 O (3)
and
4 NH 3

+ 2 NO 2 + O 2 ĺ 3 N 2 + 6 H 2 O (4) Equation 3 is the predominant reaction because 90 to 95 percent of NOx in flue gas is NO. These equations suggest that SNCR will function best in an oxidizing atmosphere, whereas the following equation shows that in a reducing atmosphere carbon monoxide (CO) competes with ammonia for available OH radicals, thus inhibiting reaction 1.

CO + OH ĺ CO 2 + H (5) The temperature window for the SNCR reactions is critical. At higher temperatures, ammonia will react with oxygen, thereby increasing NOx concentrations. At lower temperatures, the rates of NOx reduction reactions become too slow, resulting in excessive ammonia slip (high concentrations of unreacted ammonia in exhaust) or the excessive build-up of ammonia in raw materials. The optimum range is 870 o C to 1,100 °C (1,600 o F to 2,000 °F). In a preheater/precalciner kiln, reagent injection occurs after the exit of the kiln in the calciner or the lower part of the preheater tower. This injection location is generally readily accessible using conventional injection technology. EPA assumed a 50 percent NOx control efficiency for applying SNCR to Kiln 4 in its RP analysis. This control efficiency was based in part on an SNCR optimization report for CPC’s Mojave Plant in California submitted by CPC to EPA on August 30, 2013. The report provided emission data from the first seven months of 2013 in which adjustments were made to multiple control technology operatingAECOM Environment

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parameters. Emission data provided in this report indicates a range of SNCR control efficiency of 30 percent to 60 percent at the Mojave Plant, depending upon operating parameters. However, the emission data from the Mojave optimization period are highly variable (due to the operational variability that is part of the optimization), and CPC has not determined what control efficiency or emission rate is appropriate to use as the basis for an emission limit for the Mojave Plant. Although SNCR control efficiencies as high as 60 percent were observed at the Mojave Plant, there are differences between Kiln 4 at the Rillito Cement Plant and the cement kiln at the Mojave Plant. The designs of the two kilns are not the same; Kiln 4 at Rillito is older than the kiln at the Mojave Plant, and it has a modified loop calciner, which is different from the precalciner on the kiln at the Mojave Plant. The precalciner on the cement kiln at the Mojave Plant and the modified loop calciner on Kiln 4 are illustrated in Figure 2-1. The following differences between Kiln 4 at Rillito and the cement kiln at the Mojave Plant would lead to a lower NOx control efficiency for SNCR for Kiln 4:

x Temperatures in the reasonably accessible potential NH 3 injection locations for Kiln 4 are only 1,100 o F to 1,500 o F, which are below the lower limit of the optimum temperature range of 1,600 oF to 1,900 oF, while temperatures at the NH 3 injection locations for the kiln at the Mojave Plant are in the range of 1,650 o F to 1,750 o F, which are within the optimum temperature range. Therefore, the rates of NOx reduction reactions would be much slower for Kiln 4, leading to less reduction of NOx emissions.

x Because of the differences in the type of calciner, O 2 concentrations in the Kiln 4 exhaust are substantially lower than O 2 concentrations in the exhaust from the cement kiln at the Mojave Plant, which would lead to a lower rate for Reaction 3 above and, as a result, a lower control efficiency.

x As depicted in Figure 2-1, the precalciner on the cement kiln at the Mojave Plant is a cyclonic vessel where fuel and tertiary air are injected in such a way as to promote efficient combustion within the small vessel. The cyclonic flow created in the vessel provides good mixing between the injected NH 3 and the kiln exhaust gas, which promotes contact between the NH 3 and the other reactants in the gases. In contrast, the modified loop calciner on Kiln 4 at the Rillito Cement Plant depicted in Figure 2-1 is essentially a duct without a vessel. Because of the duct design there is poor mixing of the fuel and air providing little opportunity for the NH 3

and exhaust gases to interact. The inferior mixing of the Kiln 4 modified loop calciner impedes the ability of the SNCR reactions to reduce the NOx concentrations.

x CO emissions from Kiln 4 are approximately 10 times higher than CO emissions from the cement kiln at the Mojave Plant. As shown in Equation 5 above, the much higher CO concentrations in the Kiln 4 exhaust would compete with NH 3 for hydroxyl radicals, which would reduce the NOx control effectiveness.

x Although the retention time in the modified loop calciner on Kiln 4 is slightly longer than the retention time in the precalciner on the kiln at the Mojave Cement Plant (approximated 1.5 seconds for Kiln 4 and 0.5 to 0.75 seconds for the Mojave kiln), the longer retention time does not offset the substantially lower reaction rates caused by the lower calciner temperatures, lower O 2 concentrations, poorer mixing and higher CO concentrations. Because of these differences, the SNCR NOx control efficiencies obtained for the cement kiln at the Mojave Plant cannot be applied to Kiln 4 at Rillito. Although site-specific tests would be required to quantify the control efficiencies that might be achieved with SNCR for Kiln 4, CPC has consideredAECOM Environment

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these differences between Kiln 4 at Rillito and the cement kiln at the Mojave Plant and, based on its engineering judgment, concluded that 35 percent NOx control efficiency would be an appropriate estimate for Kiln 4. EPA also cited NOx control efficiencies between 45 percent and 50 percent for four additional preheater/precalciner cement kilns in the TSD to support the assumption of 50 percent NOx control efficiency for applying SNCR to Kiln 4. EPA did not provide any design or operating details for these four kilns to allow a comparison with Kiln 4. However, it is unlikely that these kilns have modified loop calciners so differences between these kilns and Kiln 4 may be similar to the differences between the Mojave calciner and the Kiln 4 calciner in Rillito. Therefore, it is not appropriate to apply the SNCR NOx control efficiencies for these cement kilns to Kiln 4.AECOM Environment

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Figure 2-1 Depiction of Rillito Cement Plant Kiln 4 Modified Loop Calciner and Mojave Cement Plant Kiln CalcinerAECOM Environment

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## 3.0 Costs and Cost Effectiveness for Applying Selective Non-Catalytic Reduction to Kiln 4

For its RP analysis, EPA estimated that the annualized cost for applying SNCR to Kiln 4 would be $1,089,566. Based on annual average uncontrolled NOx emissions from Kiln 4 of 2,082 tons per year (tpy) and an SNCR control efficiency of 50 percent, EPA estimated that annual average NOx emissions would be reduced by 1,041 tpy, resulting in a cost effectiveness of $1,047 per ton of NOx reduced. EPA’s analysis of the costs for applying SNCR to Kiln 4 is essentially the same as an analysis in “Reasonable Progress Analysis for CalPortland Company Rillito Cement Plant Kilns” submitted by CPC to EPA on May 9, 2013, except for the estimated annual cost for NH 3 reagent for the SNCR system. EPA used an NH 3 cost of $1,000 per ton, estimated at approximately double historical urea price highs (excluding 2008 high), while CPC used an estimated NH 3 cost of $1,640 per ton. CPC has refined its estimate of NH 3 costs based on information provided by CPC’s aqueous NH 3 vendor, Airgas Specialty Products, and projections to 2018, which is the earliest that SNCR would begin operating on Kiln 4. The estimated price is $0.1204 per pound for 19 percent aqueous NH 3 , plus $1.31 per mile fuel surcharge from Buckeye, AZ to Rillito per 15-ton tanker truck load, plus a $25.00 hazardous material manifest fee per truck load. The travel distance from Buckeye to Rillito from Google Maps is approximately 131 miles, leading to an estimated cost for a 15-ton tanker truck load of: 15 tons x 2,000 pounds/ton x $0.1204/pound + 131 miles x $1.31/mile + $25.00 = $3,809 per 15 tons The estimated cost per ton of ammonia would be: $3,809 / 15 tons solutions / 0.19 tons NH 3 /ton solution = $1,336 per ton NH 3 EPA calculated the annual NH 3 usage by assuming the use of one mole of ammonia for each mole of uncontrolled NOx. The resulting annual ammonia usage, based on 2,082 tpy uncontrolled NOx, is: 2,082 tpy NOx / 46 pounds NOx per pound-mole x 17 pounds NH 3 per pound-mole = 769.4 tons NH 3

per year EPA’s estimate of annual costs for NH 3 is 769.4 tpy x $1,000 per ton NH 3 = $769,400
Annual NH 3 costs using CPC’s revised NH 3 price is 769.4 tpy x $1,336 per ton NH 3 = $1,027,918 Thus, the estimated annual NH 3 cost based on CPC’s estimated NH 3 price is $258,518 more than EPA’s estimate, and the estimated total annualized cost for SNCR is $1,089,566 + $258,518 = $1,348,084. As discussed in Section 2.0, CPC estimates that 35 percent is an appropriate NOx control efficiency for applying SNCR to Kiln 4. The resulting annual reduction in NOx emissions would be 0.35 x 2,082 tpy uncontrolled NOx = 728.7 tpy, resulting in a cost effectiveness of $1,850 per ton of NOx reduced, which is approximately 78 percent higher than EPA’s estimate.AECOM Environment

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## 4.0 Visibility Modeling to Evaluate Visibility Improvements

EPA and its contractor, the University of North Carolina, conducted visibility modeling to estimate the potential improvement in visibility at Class I areas that could result from applying SNCR with a NOx control efficiency of 50 percent to Kiln 4 at Rillito. EPA concluded that applying SNCR to Kiln 4 with a NOx control efficiency of 50 percent could improve visibility by 0.24 deciviews (dv) at the eastern unit of Saguaro National Park (NP), by 0.19 dv at Galiuro Wilderness Area (WA), and by less for other areas. As discussed in Section 2, CPC has concluded that assuming a NOx control efficiency of 35 percent for Kiln 4 is more appropriate than assuming a control efficiency of 50 percent. Therefore, AECOM has conducted additional visibility modeling to estimate the potential improvements in visibility that would result from applying SNCR with a NOx control efficiency of 35 percent to Kiln 4. In addition to the difference in the assumed SNCR NOx control efficiency, AECOM’s visibility modeling included the following differences from EPA’s modeling:

x Errors in emissions from Kilns 1 through 3 at the Rillito Cement Plant were corrected;

x Errors in the stack parameters for Kiln 4 were corrected;

x Values used for the coarse particle geometric mean diameter and for minimum turbulence velocities differed from those used by EPA; and

x Visibility was calculated using both constant and monthly NH 3 background concentrations. These differences are described in Section 4.1. The rest of the modeling procedures were the same as used by EPA and its contractor, including the base case NOx emission rate for Kiln 4. Visibility modeling results are presented in Section 4.2. 

### 4.1 Differences between EPA and AECOM Visibility Modeling 4.1.1 Errors in Emissions from Kilns 1 through 3 at the Rillito Cement Plant Emissions from Kilns 1 through 3 at the Rillito Plant used by EPA and its contractor for the modeling are calculated in the Excel file: E-13_2014-01_Cement_Plant_Emission_Calculations_(final_for_NPRM_docket).xlsx This Excel file can be found in the docket for the proposed FIP. The following errors were identified in this file:

x The hourly maximum feed rates for Kilns 1 through 3 were not converted to clinker production rates in the cell labeled as tons/hr under clinker production rate. Additionally, the value entered was 17 tons/hour, but the actual capacity is 19 tons/hour.

x Total clinker production for Kilns 1 through 3 for 2006 should be 368,314 tpy instead of 368,315 tpy.AECOM Environment

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x Total clinker production for Kilns 1 through 3 for 2005 should be 342,999 tpy instead of 343,000 tpy.

x The hourly NOx and sulfur dioxide (SO 2 ) emission rates for Kilns 1 through 3 in the worksheet labeled “CalPortland Cement – Model” are not the values in the worksheet labeled “CalPortland – Base Case.”

x The hourly PM 10 emission rate for Kilns 1 through 3 in in the worksheet labeled “CalPortland Cement – Model” is three times the value calculated for all three kilns combined in the worksheet labeled “CalPortland – Base Case.” Hourly NOx, SO 2 and PM 10 emission rates listed for the modeling in the Excel file and the corrected values are shown in Table 4-1. Table 4-1 Corrected Hourly Emission Rates for Kilns 1 through 3 for Visibility

Modeling
Pollutant EPA Emission Rate (pounds/hour) Corrected Emission Rate (pounds/hour) NOx 450 403 SO 2 10.64 8.47 PM 10 30.02 10.01



### 4.1.2 Errors in Rillito Kiln 4 Stack Parameters Stack parameters for the cement kilns at the Rillito Plant used by EPA and its contractor for the modeling are calculated in the Excel file: E-13_2014-01_Cement_Plant_Emission_Calculations_(final_for_NPRM_docket).xlsx This Excel file can also be found in the docket for the proposed FIP. The stack parameters in the worksheet labeled “Stack Parameters” are the parameters for a cement kiln that was proposed for construction at the Rillito Cement Plant to replace Kilns 1 through 4 (Kiln 6). However, this kiln has not been constructed. The stack parameters in the Excel file and the correct stack parameters for Kiln 4 are listed in Table 4-2. It should also be noted that the visibility modeling for “Reasonable Progress Analysis for CalPortland Company Rillito Cement Plant Kilns” submitted by CPC to EPA on May 9, 2013 also used the incorrect stack parameters for Kiln 4. Table 4-2 Corrected Stack Parameters for Kiln 4 for Visibility Modeling

Parameter EPA Value Correct Kiln 4 Value Height (meters) 40 22.86 Diameter (meters) 4.88 3.048 Exit Velocity (meters/second) 14.58 16.22 Exit Temperature (degrees Kelvin) 478 519AECOM Environment

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### 4.1.3 Coarse Particle Geometric Mean Diameter and Minimum Turbulence Velocities EPA’s contractor assumed a geometric mean diameter for coarse particulate matter of 0.48 microns in its CALPUFF modeling. Because coarse particles are particles larger than 2.5 microns diameter, AECOM assumed a geometric mean diameter of 6 microns. EPA’s subcontractor used non-default minimum turbulence velocities sigma-v (SVMIN) and sigma-w (SWMIN) for each stability class over land and over water of 0.5 m/s. According to comments in their CALPUFF modeling files, using the default values gave them an error message and the only way to bypass it and run the model to completion was to set SVMIN and SWMIN to 0.5. AECOM used the default values without encountering errors from CALPUFF. 

### 4.1.4 Monthly Background Ammonia Concentrations EPA’s subcontractor used a constant 1 part per billion (ppb) ammonia background concentration in the POSTUTIL post-processor to calculate the partitioning of nitrate between gaseous nitric acid and particulate ammonium nitrate. The Technical Support Document (TSD) for the proposed rule states that “Ambient ammonia measurements for use as input to modeling are scarce, and measurements that include it in the form of ammonium even scarcer. In the absence of compelling ammonia background estimates, the EPA IWAQM Phase 2 guidance recommends the use of a 1 ppb ammonia background for arid lands, which includes Arizona.” At the time the IWAQM Phase 2 guidance was developed, CALPUFF did not have the capability of accommodating monthly varying background ammonia. However, the current version does have this capability. Additionally, the IMPROVE monitoring network recently began to incorporate routine measurements of gaseous ammonia at specific sites. A recently issued technical paper 1 on this subject showed monthly NHx (NHx = ammonia plus ammonium ion) measurements at these sites, including one in southern Arizona (Chiricahua), less than 200 kilometers (124 miles) from the Rillito Cement Plant. A review of the measurements taken to date at these sites (see Figure 4-1) indicates that ammonia concentrations less than 1 ppb (e.g., 0.5 ppb) are present at this site in winter. In an independent analysis, the Colorado Department of Public Health and Environment (CDPHE) performed a sensitivity modeling analysis to explore the effect of the ammonia concentration input to CALPUFF on the predicted visibility impacts for a source with high NO X emissions relative to SO 2 emissions. 2 It is noteworthy that the largest sensitivity occurs for ammonia input values between 1 and 0.1 ppb. In that range, the difference in the peak visibility impacts predicted by CALPUFF is slightly more than a factor of 3 between ammonia concentration input values of 1 and 0.1 ppb. This sensitivity analysis shows that the choice of background ammonia is very important in terms of the magnitude of visibility impacts predicted by CALPUFF. Furthermore, since the results are highly

1 Chen, X., D. Day, B. Schichtel, W. Malm, J. Mojica, C. McDade, E. Hardison, S. Kreidenweis, and J. Collett, 2012. A Pilot Monitoring Study of Atmospheric NHx at Selected IMPROVE Sites. Extended Abstract # 19. Presented at the 2012 Aerosol and Atmospheric Optics: Visibility & Air Pollution Specialty Conference, held September 25-28 th , 2012 in Whitefish, MT. Air & Waste Management Association, Pittsburgh, PA. 2 Supplemental BART Analysis: CALPUFF Protocol for Class I Federal Area Visibility Improvement ModelingAnalysis (DRAFT), revised June 25, 2010, available at http://www.colorado.gov/airquality/documents/DraftColoradoSupplementalBARTAnalysisCALPUFFProtocol-25June2010.pdf.AECOM Environment

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sensitive to the NH 3 value, the assumption of 1 ppb for winter likely introduces over-predictive conservatism in the modeling results for NOx effects upon haze. The visibility composition plots depicted in Figure 4-2 from an IMPROVE monitor located in Saguaro East National Park show that the majority of nitrate (shown by the red portions of the composition columns) forms during cold temperature (in the modeled predictions and in the real world) and, therefore, the model is not sensitive to the selected ammonia values in summer, but would be highly sensitive to values in winter months. Based upon this available ammonia measurement information (which conservatively includes bothgaseous and particulate form concentration contributions), AECOM has developed a set of monthlyvarying ammonia background concentrations (see Table 4-3) that correspond to the actual measured values noted above. Consistent with the EPA values, an ammonia background of 1 ppb is used for many of the non-winter months. Figure 4-1 IMPROVE NHx Concentrations from April 2011 to January 2012AECOM Environment

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Figure 4-2 2009 IMPROVE Composition Data for Saguaro East National Park

Table 4-3 Background Monthly Ammonia Concentrations (ppb) Used in the Modeling Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0.5 0.5 0.6 0.7 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.8

The use of monthly background NH 3 concentrations is consistent with visibility modeling conducted by EPA for Best Available Retrofit (BART) sources in western Wyoming (79 FR 5111-5113). For that modeling, EPA used monitored NHx from a site in western Wyoming that was within the modeling domain for the sources in western Wyoming to estimate monthly background NH 3 concentrations for the visibility modeling. As stated by EPA, “ the IWAQM Phase 2 report recommends use of the background values it provides for different land use categories, unless specific data is available in the modeling domain as a more accurate substitute for its recommended default values, and allows for the consideration of background ammonia concentrations that vary seasonally or spatially.” Thus, the use of monitored NHx concentrations from Chiricahua to estimate monthly background NH 3 concentrations for visibility modeling for the Rillito Cement Plant is similar to EPA’s use of monitored NHx concentrations to estimate monthly background NH 3 concentrations for visibility modeling for the western Wyoming sources. 

### 4.2 Visibility Modeling Results Results from the visibility modeling for Class I areas within 300 kilometers (km) of the CPC Rillito Cement Plant are presented in Tables 4-4 and 4-5. These tables list the visibility impacts for the base case and the visibility impacts and benefits relative to the base case for the application of SNCR to Kiln 4. Results from both EPA’s and AECOM’s modeling are listed. The CALPOST post-processor method 8b (new IMPROVE extinction calculation equation and impacts relative to 20 percent best natural condition days) was used to obtain both the EPA and AECOM results. Table 4-4 shows results using seasonally varying NH 3 background concentrations for the AECOM modeling and Table 4-5 shows results using a constant 1 ppb NH 3 background concentration for the AECOM modeling.AECOM Environment

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As shown in Table 4-4, AECOM’s modeling with a seasonally varying NH 3 background concentration indicates that applying SNCR to Kiln 4 with a NOx control efficiency of 35 percent could improve visibility by 0.15 dv at Galiuro WA, by 0.14 dv at the eastern unit of Saguaro NP, and by less for other areas. Also, as shown in Table 4-5, AECOM’s modeling with a constant 1 ppb NH 3 background concentration indicates that applying SNCR to Kiln 4 with a NOx control efficiency of 35 percent could improve visibility by 0.18 dv at the eastern unit of Saguaro NP and by 0.16 dv at Galiuro WA. These visibility improvements are substantially less than the maximum improvement of 0.24 dv at the eastern unit of Saguaro NP indicated by EPA’s modeling.AECOM Environment

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Table 4-4 EPA and AECOM Visibility Modeling Results with Monthly Ammonia

Background for AECOM Modeling
Class I Area a Visibility Impacts (dv) Visibility Benefits (dv) Base Case SNCR on Kiln 4 SNCR on Kiln 4 EPA AECOM EPA AECOM EPA AECOM Chiricahua NM 0.25 0.21 0.19 0.17 0.06 0.04 Chiricahua WA 0.23 0.19 0.18 0.15 0.05 0.03 Galiuro WA 1.02 0.88 0.83 0.72 0.19 0.15 Gila WA 0.12 0.10 0.09 0.08 0.03 0.02 Mazatzal WA 0.13 0.10 0.10 0.08 0.03 0.02 Mount Baldy WA 0.11 0.09 0.08 0.07 0.03 0.02 Petrified Forest NP 0.11 0.09 0.08 0.07 0.03 0.02 Pine Mountain WA 0.11 0.08 0.09 0.07 0.02 0.02 Saguaro NP 1.26 0.97 1.02 0.83 0.24 0.14 Sierra Ancha WA 0.13 0.10 0.10 0.08 0.03 0.02 Superstition WA 0.30 0.23 0.24 0.19 0.06 0.04 Sycamore Canyon WA 0.09 0.07 0.07 0.06 0.02 0.01 Maximum 1.26 0.97 1.02 0.83 0.24 0.15 Cumulative (sum) 3.85 3.10 3.07 2.58 0.78 0.52 Number of areas >= 0.5 dv 2 2 2 2 0 0

a NM = National Monument, NP = National Park, WA = Wilderness AreaAECOM Environment

Evaluation of EPA’s Reasonable Progress Analysis for CalPortland Rillito Kiln 4 March 2014 4

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Table 4-5 EPA and AECOM Visibility Modeling Results with Constant 1 ppb Ammonia

Background for AECOM Modeling
Class I Area a Visibility Impacts (dv) Visibility Benefits (dv) Base Case SNCR on Kiln 4 SNCR on Kiln 4 EPA AECOM EPA AECOM EPA AECOM Chiricahua NM 0.25 0.23 0.19 0.19 0.06 0.04 Chiricahua WA 0.23 0.20 0.18 0.17 0.05 0.04 Galiuro WA 1.02 0.93 0.83 0.77 0.19 0.16 Gila WA 0.12 0.10 0.09 0.08 0.03 0.02 Mazatzal WA 0.13 0.11 0.10 0.09 0.03 0.02 Mount Baldy WA 0.11 0.09 0.08 0.08 0.03 0.02 Petrified Forest NP 0.11 0.10 0.08 0.08 0.03 0.02 Pine Mountain WA 0.11 0.09 0.09 0.07 0.02 0.02 Saguaro NP 1.26 1.08 1.02 0.90 0.24 0.18 Sierra Ancha WA 0.13 0.11 0.10 0.09 0.03 0.02 Superstition WA 0.30 0.27 0.24 0.23 0.06 0.05 Sycamore Canyon WA 0.09 0.08 0.07 0.06 0.02 0.02 Maximum 1.26 1.08 1.02 0.90 0.24 0.18 Cumulative (sum) 3.85 3.39 3.07 2.80 0.78 0.59 Number of areas >= 0.5 dv 2 2 2 2 0 0

a NM = National Monument, NP = National Park, WA = Wilderness AreaAECOM Environment

Evaluation of EPA’s Reasonable Progress Analysis for CalPortland Rillito Kiln 4 March 2014 5

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## 5.0 Conclusions

The evaluations and analyses presented in this document lead to the following conclusions regarding EPA’s RP analysis for Kiln 4 at CPC’s Rillito Cement Plant:

x EPA’s assumption of a 50 percent NOx control efficiency for applying SNCR to Kiln 4 is too high. Based on differences between Kiln 4 at the Rillito Cement Plant and the cement kiln at CPC’s Mojave Plant in California, a control efficiency of 35 percent for applying SNCR to Kiln 4 is considered to be more appropriate.

x EPA’s estimate of the annualized cost for applying SNCR to Kiln 4 of $1,089,566 is too low. Based on more accurate estimates of the annual cost for ammonia reagent, a more reasonable annualized cost estimate is $1,348,084. The resulting cost effectiveness, based on a 35 percent NOx control efficiency, is $1,850 per ton of NOx removed, which is approximately 78 percent higher than EPA’s estimate of $1,041 per ton of NOx removed.

x The highest modeled visibility benefits at a Class I area from applying SNCR to Kiln 4 with an assumed NOx control efficiency of 35 percent (along with other corrections to the model inputs) is 0.15 dv with a monthly varying NH 3 background concentration and 0.18 dv with a constant 1 ppb NH 3

background concentration. These visibility improvements are substantially less than the maximum improvement of 0.24 dv indicated by EPA’s modeling and too low to be detected by the available technology for particulate monitors (much less than 0.3 dv) and less than 18 percent of the perceptible levels that can be visually detected (1 dv). Furthermore, in its RP analysis for Springerville Units 1 and 2 in the proposed FIP, EPA concluded that “While the cost per ton for SNCR may be reasonable, the projected visibility benefits are relatively small (0.18 dv at the most affected area)” and did not propose additional controls on these units. Consistent with this conclusion, it would not be reasonable to propose the application of SNCR to Kiln 4 at the Rillito Cement Plant based on the similar small benefit.