Air Quality Technical Analysis Report 

Review of Submittals Supporting the 

Holcim (US) Inc. Tires Combustion Proposal 

Prepared for: 

Montana Department of Environmental Quality 

P.O. Box 200901 

Helena, Montana 59620 

Prepared by: 

Lorenzen Engineering, Inc. 

P.O. Box 65 

Jefferson City, MT 59638 

December 2004
Table of Contents 

1. Introduction ..........................................................................................................................................1 

1.1 Objective......................................................................................................................................1 

1.2 Materials Reviewed .....................................................................................................................1 

1.3 Organization of Report................................................................................................................2 

2. Data Adequacy Review........................................................................................................................3 

2.1 Emissions Inventory Data Adequacy Review .............................................................................3 

2.1.1 Criteria Pollutant Emissions Inventory...............................................................................3 

2.1.2 HAP and Air Toxic Emissions Inventory ...........................................................................3 

2.2 Additional Information Provided by Holcim...............................................................................5 

2.3 Dispersion Modeling Adequacy Review.....................................................................................5 

3. Review of Emissions Inventory Methods ............................................................................................6 

3.1 Emissions Estimation Methodology............................................................................................6 

3.2 Tire-burning Emissions Inventory Database ...............................................................................7 

3.3 Estimating Emissions from Kiln Upsets......................................................................................8 

4. Criteria Pollutant Emissions Inventory ..............................................................................................11 

4.1 Carbon Monoxide......................................................................................................................11 

4.2 Sulfur Dioxide ...........................................................................................................................12 

4.3 Nitrogen Oxides.........................................................................................................................12 

4.4 Particulate Matter and ESP Efficiency ......................................................................................13 

5. Hazardous and Toxic Air Pollutant Emissions Inventory ..................................................................15 

5.1 Incremental HAPs Increase from Burning Tires.......................................................................15 

5.2 Expanded Emissions Inventory .................................................................................................16 

5.3 Recommended Adjustments in Emissions Inventory ................................................................16 

5.4 Summary of HAPs Emission Estimates ....................................................................................18 

6.0 Air Dispersion Modeling Review ..................................................................................................21 

6.1 AERMOD Modeling System.....................................................................................................21 

6.2 AERMET Meteorological Data Processing...............................................................................21 

6.3 Sources and Modeling Parameters ............................................................................................22 

6.4 Modeling Receptors...................................................................................................................24 

6.5 Summary of Modeling Results..................................................................................................25 

7. Conclusions and Recommendations...................................................................................................39 

8. References..........................................................................................................................................40 

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List of Tables 

TABLE 1: Potential Annual Kiln Criteria Pollutant Emissions ..............................................11 

TABLE 2: Estimated Kiln HAP Emissions.............................................................................19 

TABLE 3: Gallatin County Industrial Emissions Sources ......................................................24 

TABLE 4: Peak Model Results................................................................................................31 

List of Figures 

FIGURE 1: Wind Rose for Holcim’s Trident Meteorological Monitoring Station ..................23 

FIGURE 2: Fine Receptor Grid and Boundary Receptors........................................................26 

FIGURE 3: Expanded Modeling Terrain and Receptor Grid....................................................27 

FIGURE 4: Annual Average Dispersion Coefficients ..............................................................29 

FIGURE 5: Peak 1-hour Average Dispersion Coefficients.......................................................30 

Appendices 

APPENDIX A: Baseline Emissions Inventory 

APPENDIX B: Cumulative Emissions Inventory 

APPENDIX C: Emissions Factor Comparison 

APPENDIX D: Final Dispersion Modeling Protocol and Report 

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1. Introduction 

Holcim Cement Company (Holcim) is proposing to use tires as fuel in their Trident cement kiln.

Montana Department of Environmental Quality (DEQ) is in the process of preparing an 

Environmental Impact Statement (EIS) to identify potential impacts from the proposed project. 

Holcim is currently authorized to burn natural gas, coal, petroleum coke, or any combination of 

these as a fuel for the kiln. The permit application requests the mid-kiln combustion of whole 

waste tires for up to 15 percent of the total fuel heat input to the kiln (on a Btu basis). Burning 

tires for fuel will change the amount and composition of air contaminant emissions from the 

cement kiln stack and may affect the concentration of contaminants in the cement kiln dust 

(CKD). 

1.1 Objective 

The objective of this Air Quality Technical Analysis Report is to report on the third-party review 

of Holcim’s tire-burning emissions estimates and air quality impact analyses. Lorenzen 

Engineering, Inc. has worked with DEQ and DEQ’s risk assessment contractor throughout the

EIS process. The results and conclusions presented in this report have been discussed with other 

members of the EIS team. 

This report is intended to supplement material that is already part of the public record and does 

not repeat information available in the original documents. Holcim has estimated the total 

emissions from the kiln using the current fuel mix, the total potential emissions using tires as a 

supplemental fuel, and the change in emissions due to tire combustion. Holcim has also 

prepared and submitted computerized air dispersion modeling results to show ambient air 

contaminant concentrations resulting from the cement plant. 

1.2 Materials Reviewed 

Holcim has been working with DEQ since 2001 to obtain a Montana air quality permit alteration 

allowing them to proceed with their tire-burning proposal. In January 2004, Holcim compiled all 

of the relevant application submittals into a single document titled “Application for Alteration to 

Air Quality Permit #0982-10” (ref. 1). The compilation provides a clear record of information 

submitted by Holcim and decisions made regarding the proposed project. This report will refer 

to the permitting compilation (ref. 1) rather than referring to earlier submittals. 

Holcim submitted additional information regarding emissions inventory and air dispersion 

modeling during the EIS review process. The additional submittals are included as appendices to

this report. Expanded emissions inventories are included in Appendices A and B. A comparison 

of Holcim’s estimated emissions and source test data is contained in Appendix C. Appendix D is 

Holcim’s final modeling report. Holcim provided the modeling files electronically and they

were verified as part of the review process. Holcim’s final modeling results have been used to 

generate illustrative figures for this report. 

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1.3 Organization of Report 

This technical analysis report includes a critical review of the contaminant emissions information 

provided by Holcim both in the original permit application materials and in subsequent 

submittals. It examines the source of emissions information and the methodology used to

estimate emissions from the Trident kiln. Emissions estimates from the current fuel mix and the 

proposed fuel mix are included in this report. 

Dispersion modeling review in this report includes evaluation of the choice of model,

applicability of the meteorological data and treatment of terrain features. The report also 

includes graphical representations of the modeling results. 

The Air Quality Technical Analysis Report is organized in the following main sections: 

1. Introduction 

2. Data Adequacy Review

3. Review of Emissions Inventory Methods 

4. Criteria Pollutant Emissions Inventory 

5. Hazardous and Toxic Air Pollutant Emissions Inventory 

6. Air Dispersion Modeling Review 

7. Conclusions and Recommendations 

8. References 

2 
2. Data Adequacy Review 

The first step in the EIS air quality analysis was review of the project file and all information 

submitted in support of the permit application. The purpose of this data adequacy review was to

determine whether sufficient information existed in the project file for a complete evaluation of

impacts from the tire-burning proposal. 

Following the data adequacy review, DEQ requested additional information from Holcim to be 

used to complete the EIS. Scoping comments relating to air quality were also reviewed and

information has been included in this report to address these comments. 

2.1 Emissions Inventory Data Adequacy Review 

Holcim submitted emissions inventory information for criteria pollutants, hazardous air 

pollutants (HAPs) and other toxic air pollutants that are commonly related to tire burning in 

kilns. 

2.1.1 Criteria Pollutant Emissions Inventory 

Holcim submitted emissions estimates for total kiln criteria pollutant emissions as well as 

emission changes resulting from the tire-burning proposal. Gaseous criteria air pollutants are 

carbon monoxide (CO), sulfur dioxide (SO2), ozone and nitrogen dioxide (NO2). Lead (Pb) and 

particulate matter smaller than 10 microns (PM10) are solid or particulate phase criteria 

pollutants. Volatile organic compounds (VOC) are regulated because they lead to the formation 

of ozone in the atmosphere. 

The criteria pollutant emissions inventory was found to be adequate for EIS review and no 

additional information was requested. Criteria pollutant emissions are regulated through 

Montana’s air quality permitting process. Holcim has conducted emissions tests on the cement

kiln stack, as required by DEQ, to determine the emissions of criteria air pollutants. Emissions 

from the Trident facility have been estimated by DEQ and Holcim and are included in Holcim’s

proposed pre-construction permit #0982-11 (ref. 2). 

2.1.2 HAP and Air Toxic Emissions Inventory

Holcim estimated HAPs emissions from tire burning for use in their health risk assessment (ref. 

1). The HAPs and air toxics information was also used in DEQ’s subsequent risk study titled, 

“Human Health and Ecological Risk assessment of Kiln-Related Emissions at the Holcim

Trident Cement Plant (ref. 3).” 

The risk assessment considers all HAPs as chemicals of potential concern (COPCs) (ref. 3). 

Holcim added zinc to the risk assessment calculations, even though it is not a HAP and is exempt

from consideration under Montana regulations. Holcim chose to include zinc because it is a

known constituent in tires and was noted as a potential concern by the interested public (ref. 1). 

Holcim initially estimated only the incremental increase in HAP emissions resulting from the 

addition of tires to the kiln fuel stream. Although the original emissions inventory produced 

conservative estimates of the emissions increase, it did not provide information about the total 

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HAP emissions from the kiln. Through the data adequacy review, it became clear that additional 

inventory information would be needed for a complete review of the change in plant emissions 

resulting from the proposed project. Scoping comments indicated that the public was interested 

in the emissions resulting from all kiln raw material feeds as well as coal, coke and tire 

combustion. In addition to mined limestone, silica and shale, Holcim uses recycled glass as a 

silica source and recycled smelter slag as an iron source. 

Based on public comment and review of reference materials, DEQ determined that a risk 

assessment based only on the incremental change in emissions is not adequate. In a health 

consultation prepared for a similar project in Colorado, the U.S. Department of Health and

Human Services Agency for Toxic Substances and Disease Registry (ATSDR) reached the same

conclusion (ref. 4). ATSDR reviewed the risks from that project and found that the regulatory 

agency “had analyzed stack test data with and without the burning of tires at other cement kilns

and calculated the percent change in emissions.” In their report, ATSDR stated, “It is not the 

percent of change that is significant – it is the dose of a particular chemical that is important. ... 

We do not agree with the comparative risk methodology used in the report to determine if the 

stack emissions would adversely affect public health (ref. 4).” 

DEQ requested that Holcim provide an emissions inventory to include total kiln emissions, 

including emissions from tire burning. In response, Holcim developed an emission inventory for 

the kiln emissions using all currently permitted fuels and kiln feeds. The existing inventory 

(without tires) is referred to as the “baseline” inventory and is included in Appendix A of this 

report. Appendix A also includes a memo provided by Holcim explaining the emissions 

inventory procedures. 

The baseline inventory represents potential emissions from currently allowed kiln fuels and 

feeds. It contains estimated emissions from use of coal and coke as fuel, with recycled glass used

as a source of silicate in the kiln feed. Holcim provided two versions of the baseline inventory, 

one with a typical production rate of 315,000 tons of clinker per year and one with the maximum 

allowable production rate of 425,000 tons of clinker per year. The baseline emissions inventory 

is based on the 425,000-ton allowable production rate. 

Holcim also provided a “cumulative” emissions inventory using allowed kiln raw material feeds

and using tires as 15% of the total fuel stream. The cumulative emissions inventory and 

accompanying memo are included in Appendix B of this report. The cumulative emission 

inventory includes estimated emissions from the use of coal, coke and tires as fuel, and all 

approved kiln feed materials. The cumulative inventory represents the maximum potential 

emissions of HAPs from the kiln with the use of tires as fuel. The cumulative emissions

inventory is based on a maximum annual production rate of 425,000 tons of clinker. 

Following submittal of the baseline and cumulative emissions inventories, the EIS team 

concluded that the HAPs emissions inventory information was adequate for the EIS review. 

4 
2.2 Additional Information Provided by Holcim 

In addition to the revised emissions inventories, DEQ requested that Holcim provide the 

following information to allow the EIS team to fully evaluate the emissions inventory. All the 

data was provided and was used in the air quality technical analysis. 

• Design and operation information for the particulate control equipment for the Trident 

kiln, 

• HAP stack test results for the Holcim kiln. 

• Coal analyses for the Holcim coal fuel. 

• Petroleum coke analyses for the Holcim coke fuel. 

• Analyses of the emissions from adding recycled glass to the kiln. 

• Chemical analyses of the smelter slag used for iron-substitute in the kiln. 

The EIS team concluded that the additional submittals provide adequate information for a full 

EIS review. 

2.3 Dispersion Modeling Adequacy Review 

Computerized air dispersion modeling was used to estimate the impacts of the plant emissions on 

ambient concentrations of air contaminants. The adequacy review includes evaluation of the 

dispersion model selection, based on the criteria established in EPA’s Guideline on Air Quality 

Models. The choice and quality of meteorological data was reviewed to determine its

applicability to the air quality impact area. 

In their October 2001 submittal, Holcim used EPA’s Industrial Source Complex (ISC3) model to 

model the changes in kiln emissions resulting from tire burning. During the next few years, EPA 

worked on establishing the AERMOD model as a preferred model for air quality permit 

application modeling. In May 2002, Holcim submitted revised kiln modeling using the thencurrent version of AERMOD. In February 2003, Holcim submitted additional modeling 

including the cement kiln dust (CKD) handling sources as well as the kiln in the AERMOD 

model. When EIS review began in January 2004, EPA had updated the AERMOD model and the

version used by Holcim was no longer available (see www.epa.gov/ttn/scram). As a result, DEQ 

requested that Holcim perform the additional modeling using the most current AERMOD 

version. 

DEQ requested that Holcim model the total baseline emissions and the total cumulative 

emissions from the facility. Previous HAPs modeling had only included the incremental change 

in emissions from tire burning. DEQ also requested that Holcim extend the modeling impact 

grid beyond the original 10 km radius around the plant. The additional modeling request made it 

necessary for Holcim to update the modeling files to the latest version of EPA’s recommended 

model. Holcim provided the modeling files in electronic format so they could be duplicated and 

used as needed during the EIS review. Following submission of the additional modeling, the EIS

team concluded that the modeling data is adequate for a complete EIS review. 

5 
3. Review of Emissions Inventory Methods 

Holcim estimated criteria pollutant and HAPs emissions from the Trident kiln using a variety of

methodologies. Kiln criteria pollutant emissions were obtained from source tests and existing

permit limits. Estimates of HAP emissions are much harder to develop because the emissions

are small, difficult to test, and less data is available. Holcim gathered a database of source tests 

from other cement kilns using tires as fuel and used the data to estimate HAPs from the Trident 

kiln. 

The emissions inventory review will include a review of the methodology used by Holcim to 

arrive at their emissions estimates. The HAPs emissions estimation methodology will be

reviewed in detail because of the uncertainty associated with HAPs emissions estimates. The

assumptions and calculations used to account for the effects of kiln upsets on emissions are 

described in detail in Section 3.3. 

3.1 Emissions Estimation Methodology 

Common methods of determining emissions from an existing or proposed facility or process are 

listed below. Discussion of the appropriateness of using each approach for criteria pollutant and

HAPs follows. 

• Use of EPA emission factors. 

• Calculation of material balance for a specific compound. 

• Use of source test data from similar sources. 

• Source testing of an existing source or permitted process. 

• Continuous emissions monitoring system (CEMS). 

EPA has developed emission factors for numerous industries and processes that produce air 

pollution. The emission factors are contained in EPA’s Compilation of Air Pollutant Emission 

Factors, commonly referred to as AP-42. The Introduction to AP-42 discusses the relative 

reliability of the emissions estimate methodologies listed above (ref. 5). 

AP-42 Section 11.6 contains criteria pollutant emission factors for portland cement kilns as well 

as total particulate matter (PM) emission factors for various material handling operations

throughout the process. AP-42 also contains HAPs and air toxics emission factors for 26 

particulate compounds (including metals) and 44 gaseous compounds. The factors in AP-42 are 

appropriate for estimating emission from traditional fuels such as coal and natural gas but may 

not be appropriate for kilns using tire-derived fuel (TDF). The EPA AP-42 emission factors 

have been used for reference in establishing the emissions inventory for the proposed project. 

A material balance (or mass balance) approach may provide reliable average emission estimates 

for specific sources. In general, material balances are appropriate for use in situations where a 

high percentage of material is lost to the atmosphere. Calculation of emissions through mass

balance is frequently used for estimation of SO2 emission, based on a number of simplifying 

assumptions (ref. 5). Sulfur content of fuel is readily measured, and SO2 emissions are estimated

based on an assumption that all of the sulfur in the fuel is oxidized. Mass balance calculations for 

6 
trace contaminants such as gaseous and particulate phase HAPs are not feasible due to the small 

amounts of these contaminants in the fuel stream and the gas stream. 

Holcim has used source test data from similar sources to develop an extensive database for

emissions from cement kilns burning tires or TDF. The datasets are shown in the emissions 

inventories in Appendix A and Appendix B. Holcim used the source test database primarily for

development of HAP emissions factors, but also used it as a reference source for criteria 

pollutant estimates. 

Holcim has performed source tests on the Trident cement kiln for criteria pollutants including 

CO, NO2, SO2 and PM10. They are also operating continuous emissions monitoring systems 

(CEMS) for NO2 and SO2. The source tests and CEMS provide the most reliable emissions 

information, but are limited to the baseline case. Changes in criteria pollutant emissions due to 

tire burning have been estimated from other sources. 

3.2 Tire-burning Emissions Inventory Database 

Typically, emission inventory development relies heavily on AP-42 as the primary source of 

emission factors. As Holcim stated in the permit application, AP-42 does not specifically address 

emissions from Portland cement kilns using TDF in the fuel mix. Therefore, Holcim needed to

obtain emission factors for HAPs from TDF combustion from other sources. The approach

Holcim took to developing the TDF emission factors was similar to the approach used by EPA in 

developing the AP-42 emission factors. 

Holcim relied largely on source test data from other sources to estimate HAPs emissions from 

the proposed project. In developing the emissions inventory for the cement kiln while burning 

tires, Holcim compiled source test data from a number of cement kilns. The sources had been 

tested while burning tires or TDF as part of the fuel stream. Many of the sources in the database 

also performed baseline testing without tires during the same testing period. 

The source test database used for this analysis included 13 source tests from 11 kilns using tires

or TDF for a portion of the fuel. The database includes both baseline tests (without TDF) and 

cumulative tests (with TDF). TDF use ranged from 7% to 33% of the fuel, on a heat basis. The 

baseline fuels used were coal, coal and coke, coal and oil, coal and waste oil, and coal and 

hazardous waste. The data set included tests from seven dry process kilns and four wet process 

kilns. TDF was reported to be in the form of chipped tires for six of the tests, whole tires for 

four of the tests, and not specified in the other test reports. According to the permit application, 

the emissions inventory did not include any facility that exactly matched the Trident kiln’s

operating parameters [long, wet kiln; coal/coke baseline fuel; mid-kiln introduction of whole 

tires; tires as 15 heat-percent of fuel mix; electrostatic precipitator (ESP) emission control] (ref. 

1). Nonetheless, the emissions testing data set contains a large number of samples and provides 

enough information to ensure that a conservative emissions estimate has been developed. 

Holcim has developed the emissions inventory for their tire-burning proposal in a manner similar

to that used by EPA to develop the AP-42 emission factors. When developing emission factors

for use in AP-42, EPA compiled source test data from numerous source tests at Portland cement

plants (ref. 7). EPA converted all the source test results to units of pound per ton of clinker. EPA

7 
used 71 stack tests, dated from 1971 to 1992 to develop the emissions factors in the current

version of AP-42 Section 11.6. EPA rated the source tests based on available knowledge about

the tests and the sources. After discarding tests with low quality ratings, EPA averaged the 

remaining results to develop the AP-42 emission factors. 

Holcim took a more detailed approach to analyze the tire-burning stack test data set, including all 

the tests with available data for each compound. Data sets with more than two data points 

allowed calculation of an upper 95% confidence limit (UCL) for the data set, which was used to

project emissions at Trident. For data sets with less than two data points, the maximum data 

point was used to project emissions at Trident. For data sets where the 95% UCL exceeded the

maximum data point, the maximum point was used to project emissions at Trident. More

detailed information about the method used to process the source test data can be found in 

Holcim’s permit application (ref. 1) and the memos in Appendices A and B. 

Holcim used a methodology similar to EPA’s for standardizing the source test results. Instead of 

standardizing the test results based on clinker production Holcim standardized the source test 

results based on fuel usage. This is an appropriate basis for comparison because the primary 

source of HAPs from the kiln is from fuel combustion, and Holcim was attempting to isolate the 

impacts from changing the fuel mix. 

Source testing has been performed on the Holcim Trident kiln for most of the criteria pollutants

and some of the HAP compounds. The testing was performed with the kiln operating under

currently permitted conditions without using tires as fuel. Montana’s air quality regulations do

not allow Holcim to conduct a test burn with tires until they obtain an air quality permit allowing 

them to burn tires. Therefore, it is not possible to obtain source-specific emission test data for 

the Trident kiln while burning tires.

Holcim has performed source tests on the Trident stack to measure emissions of 13 HAPs, 

copper (a non-HAP) and dioxins/furans. Data from Holcim’s site-specific stack tests has been 

used to verify the emissions estimates obtained through the database. Holcim has submitted a

table comparing stack test results, database projected emission rates and AP-42 emission rates. 

The table and a memo explaining the data are contained in Appendix C. 

Holcim’s database projected cumulative emissions are all higher than the Trident source test

data. The database values are close enough to the test results to provide confidence in the

analysis, but are high enough to provide conservative estimates of emissions. The database 

projected cumulative emissions are comparable to values calculated using AP-42 emission 

factors. This comparison provides confidence that the database-projected emission rates for 

other HAPs are within an acceptable range. 

3.3 Estimating Emissions from Kiln Upsets 

Holcim developed a methodology for estimating potential HAP emissions from tire combustion 

during Trident kiln upsets. An upset is assumed to cause the ESP to be off-line and particulate

phase HAP emissions are assumed to be uncontrolled until the ESP is back online. The duration 

of an average upset was estimated based on the duration of upset events that occurred during

2000 and 2001. The average duration of an upset was 13.2 minutes, but DEQ has recommended 

8 
that the duration of an upset be set to 30 minutes in an hour for the analysis of short term impacts 

from upsets (ref. 1) 

The total annual duration of upset conditions was estimated based on the average of the hours of

upsets that occurred during 2000 and 2001. The kiln experienced 110 hours of upsets during 

2000 and 53 hours of upsets during 2001, resulting in an average of 81.6 hours of upsets over the 

two-year period. The number and duration of upsets has been reduced since 2001, partially due 

to the use of a continuous opacity monitoring system (COMS) on the kiln stack. 

Assumed upset conditions were used to develop an ‘upset multiplier’ for each HAP. The upset

multiplier for a 1-hour averaging period is different from the upset multiplier for the annual 

averaging period. The upset multiplier is applied to the modeled impact to produce a 

conservative ambient concentration value for use in the risk assessment. The upset multipliers

have not been applied to the emissions estimates discussed later in this report. 

DEQ and Holcim have assumed an ESP collection efficiency of 99.4%. When the ESP is not 

running, the particulate matter control efficiency is assumed to drop from 99.4% to 0%. ESP 

efficiency for particulate matter control is reviewed in Section 4.4 of this report. Control 

efficiency for gaseous emissions (other than SO2) is always 0% because the ESP does not control 

gaseous emissions. 

Emission rates provided in the emissions inventory are controlled emission rates. The following 

equation is used to determine the uncontrolled kiln emission rate for particulate matter. 

controlled rate = uncontrolled rate * (100% - 99.4%) 

uncontrolled rate = controlled rate / (100% - 99.4%) 

uncontrolled rate = controlled rate * 166.67 

The particulate matter hourly upset multiplier (UM1) to account for a 1⁄2 hour upset during the 

hour is calculated as follows: 

UM1 = [controlled rate * 1⁄2 hr + uncontrolled rate * 1⁄2 hr] / (1 hr) 

 = controlled rate * .5 + (controlled rate * 166.67 * .5) 

 = controlled rate * 83.8 

The particulate matter annual upset multiplier (UMA) to account for 81.6 hours of upset during a 

year is calculated as follows: 

UMA = [controlled rate * (8760 hr – 81.6 hr) + uncontrolled rate * 81.6 hr] / (8760 hr) 

 = [controlled rate * 8678.4 hr + controlled rate * 166.67 * 81.6 hours] / (8760 hr) 

 = controlled rate * 2.54 

The particulate HAP emissions that are controlled by the ESP include volatile metals, semivolatile metals, non-particulate metals, inorganic compounds and organic compounds (ref. 1). 

Volatile metals: Mercury 

An ESP upset only affects the particulate portion of the volatile metal emissions while the

gaseous portion of the volatile metal emissions remains the same. Mercury is assumed to be 5%

9 
particulate phase and 95% gaseous phase when it reaches the ESP. The upset multipliers for

mercury are calculated as follows: 

UM1 = gaseous emissions + particulate emissions * 83.8 

 = (95% * controlled emission rate) + (5% * controlled rate * 83.8) 

 = 5.14 * controlled rate 

UMA = gaseous emissions + particulate emissions * 2.54 

 = (95% * controlled rate) + (5% * controlled rate * 2.54) 

 = 1.08 * controlled rate 

Semi-volatile metals: antimony, lead, cadmium, selenium and zinc (non-HAP) 

Non-volatile metals: chromium, arsenic, nickel, manganese 

Holcim assumed the semi-volatile and non-volatile metals are 100% particulate matter and are 

controlled by the ESP. An ESP upset will affect the total emissions of these metals, and the 

appropriate upset multipliers are as follows: 

UM1 = 100% * controlled rate * 83.8 

UMA =100% * controlled rate * 2.54 

Inorganic HAPs: hydrogen chloride, hydrogen fluoride 

Holcim assumed 95% of the hydrogen chloride and hydrogen fluoride emissions are gaseous and 

5% are particulate matter. Therefore the upset multipliers for these compounds will be the same

as for mercury. 

Organic HAPs: dioxin/furan (TCDD eq.) 

Holcim assumed 80% of the dioxin/furan emissions are gaseous phase and 20% are particulate 

phase. Therefore, 20% of the dioxin/furan emissions are particulate phase and would be affected 

by an ESP upset. The upset multipliers for dioxin/furan are calculated as follows: 

UM1 = gaseous emissions + particulate emissions * 83.8 

 = (80% * controlled rate) + (20% * controlled rate * 83.8) 

 = 17.6 * controlled rate 

UMA = gaseous emissions + particulate emissions * 2.54 

 = (80% * controlled rate) + (20% * controlled rate * 2.54) 

 = 1.31 * controlled rate 

The ESP does not control emissions of gaseous HAPs. Emissions of these HAPs are not affected 

by ESP upsets. The upset multipliers for gaseous pollutants are equal to one (1.0). 

10 
4. Criteria Pollutant Emissions Inventory 

This section will evaluate the estimated criteria pollutant emissions changes resulting from use of 

tires as fuel. Criteria pollutant emissions are regulated through Montana’s air quality permitting

process. Maximum potential emissions from the Trident facility while using tire-derived fuel 

(ref. 1) are listed in Table 1. 

TABLE 1 

Potential Annual Kiln Criteria Pollutant Emissions 

Pollutant Baseline Emission Rate 

tons/year 

Cumulative Emission Rate 

tons/year 

SO2 543 543

NOx 6,868 6,868

CO 121 310

PM10 164 164

VOC 6 6

Lead 0.15 0.15

Source: Holcim, 2004 

Fuel combustion is the primary source of criteria pollutants. CO is emitted as a result of

incomplete combustion of carbon in fuel. Combustion of tires as fuel in the kiln is expected to 

cause an increase in CO emissions. VOCs can be emitted as a result of unburned fuel or can be 

formed in the combustion process. 

Combustion causes the formation of NOx emissions due to oxidation of nitrogen in the 

combustion air and in the fuel. VOC and NOx emissions are not expected to increase as a result 

of tire burning. In fact, NOx has been show to decrease significantly as a result of replacing a 

portion of the coal or coke fuel with tires. 

SO2 is formed as a result of the oxidation of sulfur in the fuel during the combustion process. 

Because tires have lower sulfur content than coal, SO2 emissions are expected to decrease when

a portion of the fuel is replaced with tires. 

4.1 Carbon Monoxide 

Holcim has estimated that kiln CO emissions will increase significantly as a result of tire

burning. Holcim estimates that addition of tires to the fuel mix would increase potential kiln CO 

emissions from 121 to 310 tons per year. During the permit review process, Holcim increased 

the estimated CO emissions beyond the value presented in the original permit application. The

Holcim permit application states: “Analysis of available CO test data from other facilities shows 

that when combusting tires, some facilities realize an increase in CO emissions while some

facilities realize a decrease in CO emissions. However, more recent data from facilities with wet

kilns indicates that tire combustion may result in a significant increase in CO emissions (ref. 1).” 

Review of the literature and available source test data shows a mix of results and interpretations 

on the CO emissions issue. The data shows that combustion of TDF does not consistently lead to 

an increase in CO emissions, but combustion of whole tires can cause an increase in CO

11 
emissions. Because Holcim is proposing combustion of whole tires, an estimated increase in CO 

emissions is appropriate. Holcim’s baseline CO emission rate for the Trident kiln is 0.769 

pounds per ton of clinker (lb/ton). The proposed allowable CO emission rate for the kiln is 1.461 

lb/ton, which is equivalent to a concentration of 200 parts per million (ppm) in the stack gas.

The AP-42 CO emission factor for wet process cement kilns is 0.12 lb/ton, based on a single

source test result (ref. 6). The AP-42 emission factor has a rating of D, indicating that it is not a 

well-supported emission factor. 

The estimated increase of 189 tons per year exceeds the Prevention of Significant Deterioration 

(PSD) significant increase level of 100 tpy. Therefore, the proposed tire-burning project is 

subject to PSD requirement for Best Available Control Technology (BACT) review. Holcim has 

submitted a top-down CO BACT analysis to meet the PSD requirements. DEQ has reviewed and

approved the BACT analysis. 

4.2 Sulfur Dioxide 

No increase in sulfur dioxide emissions is projected from the tire-burning project. Studies have 

shown that sulfur oxide emissions are reduced as a result of burning tires in kilns (ref. 8). SO2

emissions from cement kilns are generated from oxidation of sulfur compounds in the raw

materials and from sulfur in the fuel. The alkaline nature of the cement provides for direct 

absorption of SO2 into the product, thereby mitigating the quantity of SO2 emissions in the 

exhaust stream. Depending on the process and the source of the sulfur, SO2 absorption ranges 

from about 70 % to more than 95 % (ref. 6). Estimated SO2 control efficiency for Holcim’s

Trident kiln is 87% (ref. 2). 

The amount of SO2 generated in the kiln is proportional to the SO2 content of the fuel burned. 

Holcim has provided DEQ with sulfur content information for their coal and petroleum coke fuel 

sources (ref. 11). According to the analysis attached to Holcim’s air quality pre-construction 

permit #0982-10, petroleum coke has a sulfur content of 5.3% by weight (ref. 2). Sulfur content 

of the coal delivered to the Holcim plant is generally less than 1% by weight (ref. 11). Sulfur 

content of tires ranges from 1 to 3 percent by weight (ref. 8). Holcim’s SO2 permit limit is 124 

pounds per hour (lb/hr) and will not change as a result of the proposed action. 

In the permit application (ref. 1), Holcim provided a review of the potential SO2 emissions from 

a range of cement kilns. Emissions were broken down into categories, including dry kilns, wet 

kilns, kilns burning whole tires, kilns burning TDF with coal and coke as baseline fuels, and 

kilns burning TDF with coal as the baseline fuels. Overall, the kiln emissions showed an 18%

reduction in SO2 emissions due to substitution of 10-20% of the fuel with tires. SO2 emissions 

from dry kilns showed an increase of 20%, while SO2 emissions from wet kilns showed a 

decrease of 32%. Use of whole tires inserted at mid-kiln showed a 2% increase in SO2

emissions, based on a very small number of test results (ref. 1). 

4.3 Nitrogen Oxides 

Substitution of tires and TDF for baseline fuels consistently causes a reduction in NOx emissions

(ref. 8). Total NOx emissions for all the tests in the database showed lower NOx emissions on a 

production basis than the NOx allowed at Holcim. The data summarized in the air quality permit 

application shows that the NOx emissions were reduced by 23% for all kilns, and were reduced 

12 
in every category. The proposed permit would limit the allowable NOx emissions to 1350 lb/hr, 

on a 1-hour average basis. Holcim operates a NOx continuous emissions monitor and reports the 

hourly readings to DEQ. 

4.4 Particulate Matter and ESP Efficiency 

Particulate matter emissions from the Holcim kiln are controlled by an ESP and will not be

affected by the tire-burning proposal. The air quality permit limits kiln particulate matter 

emissions to 0.77 lb/ton clinker (ref. 2). The source test data set showed that the PM10 emissions 

were reduced or unchanged by the use of tires for fuel (ref. 1). 

An evaluation of Holcim’s ESP efficiency is included in the EIS review for two reasons. The 

review must establish whether the particulate control equipment at Holcim is generally 

comparable to the control equipment for sources in the emissions inventory database. This is 

important because it helps determine whether the database is applicable to the Trident kiln.

Second, the collection efficiency of the Trident kiln was evaluated to determine the validity of

calculations included in the permit application materials. DEQ and Holcim have assumed an 

ESP collection efficiency of 99.4% (ref. 1). This value was used to estimate the amount of 

particulate HAPs, primarily metals, present in the CKD. 

Holcim provided the following description of the ESP used on the Trident kiln: 

Trident’s Electrostatic Precipitator is a Wheelabrator-Frye unit and was installed in 

1972. The precipitator is one chamber wide and two fields deep in the direction of gas

flow, creating two individual collecting cells. Each individual collecting cell contains 79 

collecting plates spaced 10” apart, creating 78 gas passages. Collecting plates that 

measure 30’ tall and 14.5’ wide, are formed by nine strip plates that are suspended from 

a common beam at the upper end and are stabilized by a shock bar at the lower end.

These shock bars are individually struck by tumbling hammers during each cleaning 

cycle. Rigid discharge electrode grids are suspended in each gas passage and are

cleaned by a lift-and-drop hammer system. The electrical energization for this unit is 

supplied through two Westinghouse Transformer /rectifier sets. Both units are rated at: 1 

phase, 60 hertz, 480 primary volts, 267 primary amps, 45 kV, 2000 mA (communication 

from Holcim).

The electrostatic precipitation process consists of three fundamental steps: (1) particle charging, 

(2) particle collection, and (3) removal of the collected dust from the collection plates. Once a

particle is charged, it migrates toward the collection surface. An indicator of particle movement 

toward the collection electrode is called the particle migration velocity. 

Specific collecting area (SCA) is a parameter used to compare ESPs and roughly estimate their 

collection efficiency. SCA is the total collector plate area divided by gas volume flow rate (ref. 

9). The Holcim ESP has two fields in series. Gas from the kiln passes through the first field 

where it is cleaned. The gas from the first field is further cleaned in the second field before

exiting the stack. 

13 
The total collection area for each field in the Holcim ESP is 67,860 square feet (ft2

), and the gas 

flow rate through the ESP is 170,265 actual cubic feet per minute (acfm). SCA for each field is 

equal to 398 ft2

/1000 acfm. According to EPA’s ESP reference, an SCA of 400 ft2/1000 acfm is 

a medium SCA value. Therefore, one field of the Holcim ESP provides a medium SCA. Use of 

two fields in series increases the SCA to 800 ft2

/1000 acfm, compared to a ‘large’ SCA value of

900 ft2

/1000 acfm. This SCA comparison indicates that the Holcim 2-field ESP is a medium to 

high efficiency ESP. 

The Handbook of Air Pollution Control Engineering and Technology (ref. 10) provides typical 

migration velocities for various ESP applications. The listed migration velocity for a wet process 

cement kiln is 0.33 to 0.37 feet per second (fps). Efficiency of a precipitator under ideal 

conditions can be estimated using the Deutsch-Anderson Equation (ref. 10): 

E = 1 – e(-wA/Q) 

Where: E = collection efficiency of the precipitator 

A = the effective collecting plate area of the precipitator (ft

2

) 

Q = gas flow rate through the precipitator (acfs) 

e = base of natural logarithm = 2.718 

w = migration velocity (ft/s) 

Based on the above equation, the efficiency of a single field of the Holcim ESP would be greater 

than 99.9%. This calculation does not account for the variables including re-entrainment and 

rapping. The use of two fields in series provides additional particulate removal. 

Based on this rough analysis, it is clear that the Holcim ESP efficiency is comparable to other 

ESPs used in the cement industry. Particulate emission control, including particulate metals, is 

expected to be equivalent to the particulate control at the facilities from which the emission

estimates were made. Holcim’s assumption of 99.4% control efficiency for the ESP is found to 

be valid and appropriately conservative. 

14 
5. Hazardous and Toxic Air Pollutant Emissions Inventory 

Combustion sources can emit trace amounts of HAPs including organic compounds and 

hazardous metals compounds. The HAPs can either be a portion of the unburned fuel or raw 

material, or can be generated during combustion. Holcim’s baseline and cumulative emissions 

inventory identified and quantified HAPs that have a potential to increase as a result of the tireburning project. Methodology used to develop the emission inventory was reviewed in Section 3 

of this report. This section addresses emissions estimates for specific HAPs. 

The EIS team has recommended that DEQ adjust the allowable emissions increases in the 

Holcim permit based on review of the additional information submitted in support of the EIS. 

The original proposed permit limits were based on the estimates of the incremental increase in 

emissions from tire burning and did not reflect a comparison of the baseline and cumulative 

emissions estimates. 

The original emission estimates, and the baseline and cumulative emissions are shown in Table 

2, Section 5.4. The baseline emissions inventory refers to the emissions from the cement kiln 

without tires as a fuel supplement. Baseline kiln fuels are coal and petroleum coke. The Trident 

kiln is permitted to burn natural gas, but Holcim has no plans to use natural gas fuel. Emissions 

of criteria and HAPs from natural gas would be lower than emissions from other fuels. 

Baseline kiln emissions also include the emissions from kiln feed. The primary kiln feed is

limestone from the Holcim quarry. There are no alternative sources of calcium for the kiln. Silica

is needed for the cement process and is mined on-site. Holcim has the option to use postconsumer recycled glass for the silica source in the kiln. Baseline and cumulative kiln emissions 

include recycled glass emissions. During the EIS review, it came to light that Holcim uses

smelter slag as a source of iron in the cement raw materials mix. No additional emissions or

changed emissions have been identified as a result of slag use. 

5.1 Incremental HAPs Increase from Burning Tires 

The initial emissions inventory is reviewed here because it was used by DEQ to establish the 

allowable HAP emission rates in the draft air quality permit (ref. 2). The purpose of Holcim’s 

original emission inventory was to determine worst-case potential impacts from the addition of

tires to the kiln fuel stream. Holcim gathered emissions test data from cement kilns that used

whole tires and TDF as part of the fuel stream. Emissions data were contained in at least one of

the tests for 165 different compounds or groups of compounds. Of the compounds in the testing

database, 65 were HAPs as defined in the list of HAPs identified in Section 112(b) of the federal 

Clean Air Act. 

Each pollutant-specific potential increase was determined by identifying the emissions test with

the greatest increase between the with-tire and without-tire cases. If the test results showed that

the with-tire case was higher than the without-tire case, the difference was listed as positive. If

the test results showed that the with-tire case was lower than the without-tire case, the difference 

was listed as negative. 

15 
Holcim initially reported only the emission rate change for each HAP but not the entire kiln 

emission. Holcim tabulated the emissions differences for the source tests that had data for both 

the baseline case and the cumulative case. They selected the highest increase and reported it as 

the maximum predicted increase of that pollutant. This approach is highly conservative and 

meets the needs of the air permitting requirements. 

5.2 Expanded Emissions Inventory 

Holcim produced both a baseline emission inventory and a cumulative emission inventory using 

the entire database. In this case, the data was not limited to source test reports containing both 

baseline and cumulative emissions for a particular pollutant. The baseline data for each HAP was 

evaluated to establish an appropriate baseline emission factor. Likewise, the cumulative (with

tires) data for each HAP was evaluated to establish an appropriate cumulative emission factor. 

This approach resulted in a larger number of data points available for many of the HAPs. 

Holcim is permitted to use recycled glass as a kiln feed and the glass emissions are included in 

the baseline and cumulative inventories. None of the database source tests are known to include 

recycled glass. The glass was accounted for by adding the estimated potentia1 emissions from 

glass to both inventories. When Holcim applied for the permit to allow the use of recycled glass,

they completed a screening level risk assessment. Estimated HAPs emissions resulting from the 

glass were as follows: 

Chromium (total), uncontrolled: 9.6 lb/yr 

Chromium (total), controlled by ESP, 99.4% control: 0.0576 lb/yr 

Di-n-Butylphthalate: 0.272 lb/yr 

Butylbenzylphthalate: 0.053 lb/yr 

5.3 Recommended Adjustments in Emissions Inventory 

Emissions estimates for some of the pollutants were adjusted based on the emissions inventory 

review. Each emissions inventory change is discussed below.

Formaldehyde

Holcim used the database to estimate emissions of formaldehyde from the kiln with and without 

tire fuels. Four stack test results were available for the baseline inventory and five stack tests 

were available for the cumulative inventory. The original increase estimate showed a 

formaldehyde increase of 2.18 lb/hr or 9.55 tons per year (tpy). Comparison of the baseline and 

cumulative inventories, however, indicated a decrease in formaldehyde emissions of 4.74 lb/hr. 

This wide discrepancy in the formaldehyde emissions values triggered further review. 

Examination of the database showed that the formaldehyde stack test results varied widely. 

Emissions from the four stack tests used to estimate the baseline emissions were 7.36, 0.026, 

1.23, and 0.21 lb/hr. The value of 7.36 lb/hr appears to be an outlier and is not consistent with 

other data. Statistical evaluation of the baseline formaldehyde emissions data with the outlier 

removed showed that the 95% UCL value would be 1.24 lb/hr. 

16 
The data set for the cumulative emissions case ranged from 0.0054 lb/hr to 2.4 lb/hr, with a 95% 

UCL value of 1.56 lb/hr. The estimated increase due to burning tires is the difference between 

the cumulative and baseline emissions estimates, or 0.32 lb/hr. 

Dioxin/Furan

Dioxin/furan limits are expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent (TCDD eq.). 

Table 2 includes dioxins/furans under the TCDD group heading. The TCDD eq. baseline value 

is based on Holcim's 2000 stack test, corrected from actual to maximum potential production 

using a ratio of the potential and actual production rates. The TCDD cumulative value assumes a

60% increase for tires, based on review of data. Dioxin/furan emissions estimates are included in 

the emissions inventory but are not carried forward into the risk assessment. 

DEQ has determined that both the baseline and cumulative risk assessment analyses should be 

based on the PC-MACT regulatory dioxin/furan limit. Dioxin and furan emissions are regulated 

under the PC-MACT rules. PC-MACT sets the dioxin/furan emissions limit for all fuels at 0.2 

ng/dscm toxicity equivalent quotient (TEQ) for temperatures above 400 degrees F (ref. 12). 

Using the maximum kiln production and projected kiln flow rate, the allowed dioxin/furan

emissions are 7.66 E-09 g/sec TEQ at Trident (ref. 1). 

Mercury

Data used by Holcim to develop the highest possible increase in emissions due to tire burning 

yielded a high mercury emissions increase estimate. The estimated maximum potential increase 

in mercury as a result of burning tires was estimated to be 1.02E-2 lb/hr or 89 lb/yr. Comparison 

of the baseline and cumulative emission inventories shows a lower potential increase. The 

comparison is shown in Table 2. 

Using the database analysis, Holcim estimated that baseline mercury emissions would be 4.21E2 lb/hr (369 lb/yr). The cumulative mercury emissions from the database were 1.42E-2 lb/hr (124 

lb/year), a reduction of 245 lb/yr. This discrepancy in the emissions data indicated that further

review of the mercury data was warranted. 

The emissions database includes ten stack tests for both baseline and cumulative mercury 

emissions. The data set includes one test where the baseline mercury emissions were 1.31E-01 

lb/hr, while the cumulative emissions were 6.99E-06 lb/hr. Both these values are outside the 

range of all other test data, and have been eliminated from the analysis. The statistical analysis

has been repeated using only nine stack test results. The adjusted baseline 95% UCL emission

rate is 1.16E-02 lb/hr (102 lb/yr) and the adjusted cumulative 95% UCL emission rate is 1.57E02 lb/hr (137 lb/yr). The mercury increase from burning tires is estimated to be 35 lb/yr, which is

a 34% increase over the adjusted baseline emission rate of 102 lb/yr. 

The adjusted mercury increase of 34% is comparable to results found at other facilities. For 

example, the ATSDR study in Colorado (ref. 4) showed an increase of 29% mercury while 

burning 19.2% tires. The EIS review has resulted in a recommendation that DEQ change the 

allowable mercury increase in the permit from the current 89 lb/yr to 35 lb/yr. 

 

17 
Manganese

Holcim’s original emissions increase estimate for manganese was 7.9E-02 lb/hr. The manganese 

emissions in the baseline and cumulative emissions inventories were 1.02E-02 lb/hr and 4.18E02 lb/hr respectively. The difference between the baseline and cumulative emissions rates was 

3.16E-02 lb/hr, which is equivalent to 277 lb/yr. The EIS review has resulted in a 

recommendation that DEQ change the allowable manganese increase in the permit from the 

current 691 lb/yr to 277 lb/yr. 

Other Compounds

The EIS review resulted in the following recommended emission inventory changes for

compounds that were present in one case but not the other. 

• Acrolien, dimethyl phthalate: recommend using the baseline value for the cumulative

value 

• 4-nitrophenol: recommend using the cumulative value for the baseline value 

5.4 Summary of HAPs Emission Estimates 

The scoping comments included questions about the differences in emissions between cement 

kilns burning whole tires and TDF. The database used to estimate HAPs emissions included

both TDF and whole tires as fuel. No differences in the emissions were noted between the two 

fuel types. Questions were also raised about the emissions differences between wet process 

cement kilns and dry process cement kilns. Holcim has addressed the differences in the permit 

application materials as they relate to criteria pollutants (ref. 1). No apparent differences were

noted in the HAPs emissions database between the two kiln types. 

Scoping comments indicated concerns about the age and condition of tires being burned in the 

kiln. In particular, there was a concern about tires containing pesticides, presumably from the

tire piles being sprayed to control mosquitoes. It is not possible to isolate every variable while 

burning tires for fuel in cement kilns, but the breadth of the database provides some assurance 

that most variables are present. The database of kiln emissions tests spans more than a decade

and includes tests from kilns in several states. It is expected that a wide range of tire ages and

conditions were used in the source tests and any differences in emissions are reflected in the test 

results. 

All of the HAPs emissions estimates have been compiled in Table 2 for comparison purposes. 

HAPs for which the source test results were below the detection limit are excluded from the 

table. Changes in the emissions inventory for formaldehyde, mercury etc., as discussed above, 

are included in Table 2. 

The column titled “original” is Holcim’s initial estimate of the emissions increase due to tire 

burning. The “baseline” and “cumulative” columns are the total kiln emissions. The values in 

the “difference” column are calculated by subtracting the baseline value from the cumulative

value. A negative difference indicates that a decrease in emissions of that pollutant is predicted. 

18 
TABLE 2 

 Estimated Kiln HAP Emissions 

Compound Original Baseline Cumulative Difference

lb/hr lb/hr lb/hr lb/hr

Acetaldehyde -4.09E-01 4.77E-01 6.79E-02 -4.09E-01

Acrolien 1.12E-02 1.12E-02

Trichloroethene 2.78E-03 3.72E-04 3.15E-03 2.78E-03

Antimony 5.13E-06 3.43E-04 3.48E-04 5.13E-06

Arsenic 7.15E-05 5.79E-04 3.87E-04 -1.92E-04

Benzene 2.10E-01 1.05E-00 8.62E-01 -1.92E-01

Beryllium 8.17E-06 1.70E-04 1.28E-04 -4.23E-05 

Bis (2-ethylhexyl)phthalate 1.17E-02 4.90E-02 6.07E-02 1.17E-02

Bromomethane (Methyl Bromide) -1.66E-03 4.93E-03 3.27E-03 -1.66E-03

1,3 Butadiene/Butadiene -2.29E-03 3.54E-03 9.11E-03 5.57E-03

2-Butanone (MEK) -7.08E-05 1.02E-03 9.49E-04 -7.16E-05

Butylbenzylphthalate* 6.05E-05 6.05E-05

Cadmium 5.01E-04 1.04E-03 4.02E-04 -6.36E-04

Carbon Disulfide -1.12E-01 1.30E-01 1.83E-02 -1.12E-01

Carbon Tetrachloride ND 3.82E-04 3.82E-04 

Chlorine 1.24E-01 6.02E-01 7.25E-01 1.24E-01

Chlorobenzene 6.56E-04 7.75E-03 7.85E-03 1.02E-04

Chloromethane (Methyl chloride) 5.31E-03 4.97E-02 2.06E-02 -2.91E-02

Chromium (total)* 1.09E-05 1.51E-03 1.14E-03 -3.67E-04

Chromium 6 5.11E-05 2.76E-04 1.48E-04 -1.29E-04

Cobalt -3.94E-04 8.47E-04 4.52E-04 -3.95E-04

Di-n-Butyphthalate* 1.53E-03 1.53E-03

1,4 Dichlorobenzene 8.57E-03 1.53E-03 1.01E-02 8.55E-03

Dichloromethane -2.71E-02 4.49E-02 3.10E-01 2.65E-01

Dimethyl Phthalate 2.13E-03 2.13E-03

2,4-Dinitrophenol 1.15E-02 1.70E-03 -9.84E-03

Ethylbenzene 1.43E-01 2.22E-01 3.41E-01 1.19E-01

Chloroethane (ethyl chloride) 3.26E-03 ND 

Formaldehyde 2.18E-00 1.24E-00 1.56E-00 3.19E-01

Hydrogen chloride 5.98E-01 7.28E-01 7.66E-01 3.82E-02

Hydrogen fluoride 1.22E-02 2.24E-02 3.47E-02 1.22E-02

Lead 1.48E-02 1.45E-02 1.47E-02 2.41E-04

Manganese 7.89E-02 1.02E-02 4.18E-02 3.16E-02

Mercury 1.02E-02 1.16E-02 1.56E-02 4.05E-03

4-Methyl phenol -1.41E-03 6.46E-03 5.04E-03 -1.42E-03

Methylene chloride 2.26E-01 4.18E-02 2.02E-01 1.60E-01

Naphthalene 1.85E-02 6.53E-02 5.26E-02 -1.27E-02

Nickel 1.84E-03 1.79E-03 2.27E-03 4.74E-04

Nitrobenzene 1.13E-04 1.54E-03 1.66E-03 1.12E-04

4-Nitrophenol ND 3.28E-02

Phenol -3.85E-02 1.06E-01 6.76E-02 -3.86E-02

Phosphorus 9.05E-04 3.35E-03 4.26E-03 9.08E-04

Selenium -3.97E-07 8.63E-03 5.37E-03 -3.26E-03

Styrene 2.68E-01 2.71E-01 5.39E-01 2.68E-01

1,1,1 Trichloroethane 7.22E-04 1.84E-04 1.46E-03 1.27E-03

Toluene 1.10E-00 1.32E-00 2.00E-00 6.78E-01

Vinyl chloride 8.41E-03 1.07E-02 1.91E-02 8.40E-03

19 
Compound Original Baseline Cumulative Difference

lb/hr lb/hr lb/hr lb/hr

Xylenes, total 7.50E-01 9.78E-01 1.59E-00 6.13E-01

Zinc 1.43E-02 5.45E-01 2.16E-01 -3.29E-01

TCDD Eq. 2.41E-07 8.46E-10 1.35E-09 5.08E-10 

Total PCBs 1.84E-04 4.43E-04 4.17E-04 -2.58E-05

PAH- Total 1.89E-02 8.63E-02 6.41E-02 -2.23E-02

PAH-Non-carcinogenic totals 2.79E-04 2.09E-02 1.13E-02 -9.64E-03

PAH-Carcinogenic totals 1.87E-02 6.54E-02 5.28E-02 -1.26E-02

Note: ND indicates that the compound concentration was found to be lower than the detection limit of the test. 

20 
6.0 Air Dispersion Modeling Review 

Holcim has submitted air dispersion modeling to predict the impacts of the proposed tire-burning

project on ambient concentrations of criteria pollutants and HAPs. Holcim submitted the final 

modeling for tire combustion on May 10, 2004. The modeling memo for the revised modeling is 

included in Appendix D. Holcim provided DEQ with electronic modeling input and output files 

for use in the EIS review. 

6.1 AERMOD Modeling System 

Holcim’s final modeling of the Trident plant was performed using EPA’s AERMOD model. The

following is a brief description of the AERMOD modeling system provided on EPA’s website: 

“The AERMOD is actually a modeling system with three separate components: AERMOD 

(AERMIC Dispersion Model), AERMAP (AERMOD Terrain Preprocessor), and AERMET 

(AERMOD Meteorological Preprocessor). AERMOD includes a treatment of dispersion in the 

presence of intermediate and complex terrain that improves on that currently in use in ISCST and 

other models, yet without the complexity of the Complex Terrain Dispersion Model-Plus 

(CTDMPLUS). To the extent practicable, the structure of the input or the control file for 

AERMOD is the same as that for the ISCST3. At this time, the AERMOD contains the same

algorithms for building downwash as those found in the ISCST3 model. The AERMET is the 

meteorological preprocessor for the AERMOD. Input data can come from hourly cloud cover

observations, surface meteorological observations and twice-a-day upper air soundings. Output 

includes surface meteorological observations and parameters and vertical profiles of several 

atmospheric parameters. The AERMAP is a terrain preprocessor designed to simplify and 

standardize the input of terrain data for the AERMOD. Input data include receptor terrain 

elevation data. The terrain data may be in the form of digital terrain data that is available from 

the U.S. Geological Survey. Output includes, for each receptor, location and height scale, which 

are elevations used for the computation of air flow around hills (see www.epa.gov/ttn/scram).” 

Holcim performed the final modeling using AERMOD version 03273, AERMET Version 03273 

and AERMAP version 03107. EPA sets the version number for each model version based on the

year and Julian day of issue. Montana DEQ has reviewed and approved Holcim’s choice of 

models. DEQ and Holcim have agreed that additional revisions of the AERMOD modeling will 

not be required if EPA updates the AERMOD model during the EIS review process. 

6.2 AERMET Meteorological Data Processing 

The AERMET program creates the meteorological input file for AERMOD using cloud cover

data, surface meteorological data and upper air data. National Weather Service (NWS) surface 

meteorological data can be substituted for on-site data in the event there are no on-site data to

use. If the on-site profiles of wind or temperature are missing, AERMET uses NWS data to 

create the profile of wind and/or temperature. No surface temperature, wind direction or wind

speed data were missing from the Holcim data set. AERMET used the Great Falls, Montana 

NWS surface data only for cloud cover values. 

Upper air observations are made by the NWS using radiosonde technology. The closest upper 

air station to the Trident site is at the Great Falls airport. The radiosonde is a small, expendable 

instrument package that is suspended below a 6-foot (2-meter) wide balloon filled with hydrogen 

21 
or helium. As the radiosonde rises at about 1,000 feet/minute (300 meters/minute), sensors on the 

radiosonde measure profiles of pressure temperature and relative humidity. These sensors are 

linked to a battery powered radio transmitter that sends the sensor measurements to a ground

receiver. 

The AERMOD model requires hourly surface meteorological data parameters. Holcim’s 

meteorological monitoring station was located on the Holcim property 1228 feet (374 meters) 

southwest of Holcim’s cement kiln stack (ref. 1). DEQ has reviewed Holcim’s meteorological 

station siting and data collection methods and has approved the meteorological data set for use in 

compliance modeling. 

The meteorological sensors were located at the same elevation as the kiln exhaust. Elevation at 

the Holcim meteorological station was 4,132 feet above mean sea level (ft msl) and the height of

the meteorological tower was 33 ft (10 meters). Elevation of the wind speed and wind direction 

sensors was therefore 4,165 ft msl. Elevation at the kiln stack base is 4,035 ft msl, and the kiln 

stack height is 130 ft, resulting in a kiln stack exhaust elevation of 4,165 ft msl (ref. 1).

Bluffs along the west bank of the Missouri River across from the Holcim facility rise to 

elevations of nearly 4,500 ft msl. The hills east and southeast of the facility are also 4,500 ft or

higher. Wind patterns recorded at Holcim’s meteorological station show that this confining 

terrain causes the wind to follow the Missouri River in a southwest-northeast orientation. Figure 

1 is a wind rose showing the monitored wind patterns at the Holcim location. The wind rose 

shows the frequency of winds from each of 16 cardinal directions (north, north-northeast,

northeast, etc.). The length of each “petal” indicates the frequency of winds blowing from that

direction. As described in the legend, the bands in the petals indicate the frequency of the listed 

wind speeds. 

The wind rose for the Holcim site shows a strong southwest-northeast orientation of the wind 

pattern, as would be expected due to the topography of the monitoring site. As shown in Figure 

1, 25% of the hourly average wind directions were from the southwest and 13% of the hourly 

average wind directions were from the north-northeast. The strongest (highest velocity) winds 

were from the north-northeast, as shown by the relatively large dark section at the end of the 

north-northeast petal of the wind rose. The dark section indicates wind speeds greater than 10.8 

meters per second (m/s) or 24 miles per hour (mph). 

6.3 Sources and Modeling Parameters 

The air dispersion modeling protocol for the final modeling is described in detail in Holcim’s 

modeling memo in Appendix D. Holcim modeled the kiln criteria pollutant and HAP emissions. 

They also modeled CKD fugitive dust sources including silo loading, silo unloading and the 

CKD monofill. The kiln is a point source with a vertical stack and a buoyant high-temperature 

plume. The CKD sources are fugitive dust sources released near ground level and at ambient 

temperature. Emissions from the CKD sources have little momentum and do not impact 

receptors far beyond the plant boundary. CKD emissions are particulate matter and may contain 

trace amounts of HAPs. Partitioning of HAPs into the CKD was described in detail in the permit 

application materials (ref. 1). The partitioning can be viewed in Section 6.4 of this report. 

22 
FIGURE 1 

Wind Rose for Holcim’s Trident Meteorological Monitoring Station

 Source: Lorenzen Engineering, Inc.

Wind Rose for Holcim's Trident Meteorological Monitoring Station

April 1, 2000 through March 31, 2001

N

S

W E

No observations were missing.

Wind flow is FROM the directions shown.

Rings drawn at 5% intervals.

Calms excluded.

 2.84 12.63

 5.24

 3.14

 2.00

 2.04

 4.11

 5.83

 8.70

 10.86

 24.66

 10.45

 2.51

 1.29

 1.99

 1.72

Wind Speed ( Meters Per Second)

0.1 1.54 3.09 5.14 8.23 10.8

23 
Downwash caused by influences of buildings on the kiln plume were modeled using EPA 

procedures and software. Downwash results from wake effects as the plume encounters 

buildings and can result in higher pollutant concentrations in the building wake. AERMOD was 

run with EPA’s regulatory default options. 

Compliance with the ambient air quality standards requires that sources evaluate the impacts of 

other sources that could potentially affect the same area. Holcim’s criteria pollutant compliance 

demonstration did not include modeling of other sources. As part of the EIS review, industrial 

sources located within 30 miles (50 km) of the Holcim plant have been identified and are listed 

in Table 3. EPA’s facility emissions web site (see www.epa.gov/air) was used to identify 

emissions sources in Gallatin County. Neighboring Madison and Broadwater Counties each 

have one industrial emission source, both of which are located more than 50 km from the Holcim

site. 

TABLE 3 

Gallatin County Industrial Emissions Sources 

Facility Name Location Type of Source Actual Emissions(1)

Luzenac 

America 

Sappington Talc Processing Plant CO – 0.94 tpy NOx – 3.23 tpy 

VOC – 0.19 tpy SO2 – 0.15 tpy 

PM10 – 9.67 tpy 

Luzenac 

America 

Three Forks Talc Processing Plant CO – 4.3 tpy NOx – 10.5 tpy 

VOC – 0.52 tpy SO2 – 0.24 tpy 

PM10 – 32.2 tpy 

Montana State 

University

Bozeman Central Heating Plant CO – 0.51 tpy NOx – 20.0 tpy 

VOC – 0.88 tpy SO2 – 0.09 tpy 

PM10 – 1.92 tpy 

JTL Group Belgrade Portable Aggregate 

Crushing and

Screening Plant 

CO – 42.5 tpy NOx – 3.12 tpy 

VOC – 19.8 tpy SO2 – 24.4 tpy 

PM10 – 40.0 tpy 

(1) Reported emissions obtained from EPA’s air data web site for the most recent available year, 1999. 

Table 3 lists actual emissions reported to DEQ and ultimately to EPA. EPA maintains emissions 

data for reference years to allow comparison of source data. The most recent year of data 

available from EPA is 1999. 

The EIS review concluded that there is no need to model the off-site sources because their

emissions are not expected to measurably impact the Holcim peak impact receptors. Emissions 

from industrial emissions sources in Gallatin County are quite low and are not expected to 

impact the same terrain as the Holcim emissions. The primary source of emissions from talc 

processing and aggregate crushing is fugitive particulate matter. NOx and CO are generated 

from burning natural gas and/or diesel for heating. 

6.4 Modeling Receptors 

AERMOD uses receptors with location and elevation programmed into the modeling files.

Location is denoted with Universal Transverse Mercator (UTM) coordinates. UTM coordinates 

are oriented north/south and east/west with coordinates in units of meters. Modeling receptors

are typically placed in a grid pattern. Smaller grid spacing provides more refined modeling 

results, but requires a large amount of computer resources. Upon completion of initial modeling, 

it is customary to add a refined receptor grid at very close spacing around highest impact

24 
receptors. Figures 2 and 3 are surface maps showing the modeling receptor grids. Holcim used 

the following modeling grids in their final modeling analysis: 

• Property Boundary Receptors. Receptors located along the Holcim property 

boundary at a spacing of approximately 50 meters, shown in Figure 2. 

• Fine Receptor Grid. Receptors extend at least 2.5 km in all directions from the

cement plant at a spacing of 100 meters, shown in Figure 2. 

• 5-km Grid. Receptors extend from the fine receptor grid out to a distance of 5 km 

from the plant at a spacing of 250 meters. The inner edge of the 5-km grid is visible

on Figure 2. 

• 10-km Grid. Receptors extend from the 5-km grid out to a distance of 10 km from 

the plant at a spacing of 500 meters. 

• Refined Grid. Receptors surrounding the points of highest impact from the fine grid

and boundary modeling. Spacing of the refined grids is 50 meters. The largest 

refined grid is located northwest of the kiln location along the Missouri River bank. 

A smaller refined grid is located on the northeast plant boundary. Refined receptors 

can be seen in Figure 2. 

• Expanded Grid. Holcim has provided an expanded modeling grid extending 33 km 

west, 39 km east, 50 km south and 32 km north of the plant. The expanded grid has a 

spacing of 2,500 meters and is shown on Figure 3. 

Figure 2 shows the terrain and receptors within approximately 3 km of the cement kiln stack. 

Location of the kiln stack is indicated on the figure. The surface map in Figure 2 was created

using the receptor elevation data from the AERMOD input files. Figure 2 shows that there are 

no receptors located within the Holcim property boundary. 

Figure 3 is a surface map of the entire expanded modeling domain. Approximate locations of

towns and the Holcim site are shown for reference. Elevations for the surface map are the

elevations used in the AERMOD modeling. The modeling receptor grid has been overlain onto

the surface map to show the extent of the modeling. 

During the EIS review, receptors were added along the Madison, Jefferson and Gallatin Rivers 

upstream of Trident and along the Missouri River downstream of Trident. DEQ’s risk

assessment contractor used the concentrations at the river receptors to calculate aquatic impacts 

for the risk assessment. Results at various river receptors are shown on Figure 2-2 of the risk 

assessment report (ref. 3). 

6.5 Summary of Modeling Results 

Modeling results for criteria pollutant impacts were not changed by any of the findings of the 

EIS review. Holcim demonstrated compliance with all ambient standards. Results of their 

modeling are summarized in Appendix D. The EIS review did not result in changes to any 

criteria pollutant emission rates or modeling parameters. Therefore the criteria pollutant

modeling results are unchanged. Peak modeled impacts of criteria pollutants occur at or near the 

Holcim property boundary. Modeled impacts drop off with distance from the source, so 

compliance only needs to be demonstrated at the point of peak impact. 

25