2014 martin marietta materials final technical report … · 2014. 8. 28. · 2014 martin marietta...

2014 MARTIN MARIETTA MATERIALS

FINAL TECHNICAL REPORT

REVIEW OF DRAFT

AIR QUALITY PERMIT 13LR2446

Prepared for:

LARIMER COUNTY

AND

CITY OF FORT COLLINS

Prepared by:

D. HOWARD GEBHART

Air Resource Specialists, Inc.

1901 Sharp Point Drive, Suite E

Fort Collins, Colorado 80525

Telephone: 970-484-7941

Fax: 970-484-3423

August 2014

Martin Marietta Materials Air Permit Review – Technical Report

Prepared by D. Howard Gebhart


TABLE OF CONTENTS

Section Page

1.0 Introduction 1-1

1.1 Background 1-1

1.2 Overview of Martin Marietta Asphalt Plant Site 1-1

1.3 Site Characteristics 1-3

2.0 Review of Emission Estimates 2-1

2.1 Criteria Air Pollutants 2-1

2.2 Hazardous Air Pollutants 2-2

3.0 Review of Dispersion Modeling 3-1

3.1 APCD Modeling Studies 3-1

3.2 Additional HAP Modeling Analysis 3-4

4.0 Reasonably Available Control Technology 4-1

4.1 RACT for VOC Emissions 4-1

4.2 RACT for CO Emissions 4-2

5.0 Technical Comments on Draft Permit 5-1

6.0 Summary & Conclusion 6-1

LIST OF FIGURES

Figure Page

1-1 Martin Marietta Materials Google Earth Image 1-2

1-2 MMM Asphalt Batch Plant 1-3

4-1 Image of Recycle Air Collection Point at MMM Asphalt Plant 4-2

LIST OF TABLES

Table Page

2-1 MMM Emissions (ton/year) 2-1

2-2 MMM Emissions (lbs/year) 2-2

3-1 1-Hour Averages CO Impact 3-2

3-2 8-Hour Average CO Impacts 3-2

3-3 Location of Public Receptors near MMM 3-5

3-4 MMM HAP Modeling Results – Acute Impacts 3-6

3-5 MMM HAP Modeling Results – Chronic Impacts 3-7

3-6 Background HAP Levels – Fort Collins, Colorado 3-8

4-1 RBLC Query Results: Asphalt Concrete Manufacturing 4-3




1.0 INTRODUCTION

1.1 Background

Martin Marietta Materials (MMM) operates a hot mix asphalt plant at 1800 North Taft

Hill Road, located within Larimer County, Colorado (County) and just outside the limits for the

City of Fort Collins (City). The County and City have requested the services of a qualified

environmental consultant to review the draft MMM air quality permit issued for public notice by

the Colorado Air Pollution Control Division (APCD) and provide input to the County’s

Environmental and Science Advisory Board (ESAB) and the City’s Air Quality Advisory Board

(AQAB). The ESAB and AQAB will be responsible for considering the draft permit and

providing any recommendations for submitting official comments on the draft permit by either

the County or City.

Air Resource Specialists, Inc. (ARS) has been selected by the County and City to assist in

the MMM draft permit review. ARS has been assigned the following work, which is documented

in this technical report.

Review Draft Air Permit and Permit Conditions

Review Air Emissions Inventory that supports the MMM Draft Permit

Review Air Dispersion Modeling that supports the MMM Draft Permit

Assess Potential Public Health Impacts of Hazardous Air Pollutant (HAP)

Emissions

Summarize Findings in a Technical Report

Present Findings to a Meeting(s) of the EASB and AQAB

In essence, this study is a “review of the review” conducted by APCD. The study

objectives are to confirm that APCD’s technical analysis supporting the permit decision is based

on sound science and standard regulatory practice. Also, ARS’ review is designed to ensure that

the issued permit is protective of public health and the environment.

The technical review work by Air Resource Specialists, Inc. (ARS) is described in this

report and has been jointly funded by the County and City. A single report has been prepared that

documents the results of the ARS studies.

1.2 Overview of MMM Asphalt Plant Site

According to MMM, mining and processing for aggregate materials has been conducted

at the North Taft Hill Road site since the 1950s. MMM acquired the asphalt plant site in 2011.

The current asphalt plant was relocated to the site under the authority of a “portable source”

permit. Under Colorado Air Pollution Control Commission Regulation #3, an emissions unit can

remain at a single site for only 18 months under a “portable source” permit. MMM wishes to

permanently locate the asphalt plant at the present site and as such, has requested a “stationary

source” permit pursuant to Regulation #3 from the APCD.




The MMM asphalt plant site is located at 1800 North Taft Hill Road, Fort Collins, CO.

On the west side of Taft Hill Road, MMM operates additional aggregate mining and processing

operations. An image of the asphalt plant site from Google Earth is shown as Figure 1-1.

Figure 1-1. Martin Marietta Materials Google Earth Image.

*Indicates the MMM Asphalt Location

According to materials provided by MMM, the plant produces “warm mix” asphalt,

which is a combination of liquid asphalt cement, aggregate, sand, asphalt binder, and recycled

asphalt pavement (RAP). Based on claims by MMM, a “warm mix” plant operates at

temperatures of less than 300 degrees F, which is 30-70 degrees F cooler than a more

conventional “hot mix” plant. The “warm mix” plant consumes about 20% less fuel.




Figure 1-2 shows a typical asphalt batch plant.

Figure 1-2. Asphalt Batch Plant (provided by MMM).

At the Taft Hill Road asphalt plant, the air emissions are routed through a fabric filter

emissions control system, also known as a baghouse, before existing through a stack located at

the edge of the baghouse. The fabric filter dust collector is primarily a control device for removal

of particulate matter (PM) emissions and is required to meet the emissions limitations in the

applicable New Source Performance Standards (NSPS) at 40 CFR 60 Subpart I. During a visit to

the facility, ARS confirmed that the baghouse is present to control emissions and appears to be

working effectively based on the lack of visible emissions in the stack exhaust. ARS staff also

observed additional pollution abatement measures not listed in the draft MMM permit. First,

there is a collection point along the product conveyor leading to the asphalt storage silos that

routes volatile organic compound (VOC) emissions lost through the conveyor back to the asphalt

plant burner for destruction. Also, MMM has installed condensers to collect VOC emissions lost

at the liquid asphalt storage tanks. Some of the collected VOC may also be regulated as

hazardous air pollutants (HAPs).

1.3 Site Characteristics

The immediate MMM plant site is rural in character, with some residential housing to the

south. The City of Fort Collins Poudre River Trail also abuts the MMM property on the south

side, with a parking lot for trail access along Taft Hill Road to the immediate south of the MMM

property. The Lincoln Middle School (operated by the Poudre School District) lies about

1 kilometer (km) southeast of the MMM plant site.




2.0 REVIEW OF EMISSION ESTIMATES

2.1 Criteria Air Pollutants

Table 2-1 summarizes the emissions data for the main stack at the MMM asphalt plant, as

determined by the APCD and summarized in the draft permit.

Table 2-1

MMM Emissions (ton/year)

PM PM10 PM2.5 NOX SO2 VOC CO

Stack 5.4 1.8 1.3 6.5 0.8 7.6 72.2

Fugitive 3.7 0.9 0.1

Total 9.1 2.7 1.4

ARS confirmed that MMM emissions listed above were determined using the maximum

production rate in the permit of 475,000 tons/yr.

For NOX, VOCs, and SO2, the emissions were calculated using the AP-42 emission

factors for drum mix hot mix asphalt plants fired on natural gas. These emission factors and the

AP-42 citation are listed below:

NOX: 0.026 lb/ton, AP-42, Table 11.1-7

SO2: 0.0034 lb/ton, AP-42, Table 11.1-7

VOC: 0.032 lb/ton, AP-42, Table 11.1-8

For CO emissions, the AP-42 factor is 0.13 lb/ton, but MMM has requested

CO emissions equal to 0.291 lb/ton when combusting natural gas and 0.40 lb/ton when

combusting liquefied petroleum gas (LPG or propane). The reason for the higher CO emissions

at the MMM asphalt plant were not documented in the materials released to the public which

accompanied the draft permit. In response to ARS questions, APCD’s explanation for this

discrepancy is a claim that historical experience shows that the AP-42 CO factor is too low based

on emissions testing at other asphalt plants. For additional discussion of the CO emissions,

please refer to Section 4, Reasonably Available Control Technology.

The PM emissions were calculated by APCD and differ somewhat from the AP-42

values. AP-42 lists uncontrolled emission factors for PM and PM10 of 28 lb/ton and 6.5 lb/ton

respectively (See AP-42, Table 11.1-3). The Division’s PM factor is close to AP-42

(27.916 vs. 28 lb/ton) and the Division’s PM10 factor exceeds the AP-42 value by a small amount

(8.3748 lb/ton vs. 6.5 lb/ton).

PM2.5 is not directly tabulated in AP-42, but AP-42 Table 11.1-4 lists the particle size

distributions from asphalt plant drum mix dryers, and gives a PM2.5 fraction of 5.5% for the

uncontrolled emissions. When these data are applied to the AP-42 uncontrolled PM factor

(28 lb/ton), the derived PM2.5 factor is 1.54 lb/ton. APCD calculated 2.3476 lb/ton for the draft

permit.




The technical basis for the Division’s emission calculations for PM, PM10, and PM2.5

were not provided in the materials released to the public which accompanied the draft permit.

However, subsequent correspondence with APCD staff indicates that the Division’s PM

estimates were based on the grain loading from the applicable New Source Performance

Standard (NSPS) which is 0.04 gr/dscf. This is a reasonable approach as the PM emissions are

then consistent with the proposed permit limit.

2.2 Hazardous Air Pollutants (HAPs)

Table 2-2 summarizes the HAP emissions calculated by APCD for the MMM facility.

Please note that HAP emissions are reported in pounds whereas the other pollutant emissions are

listed in tons. All HAPs documented in the APCD materials are released at the asphalt plant

baghouse stack.

Table 2-2

MMM Emissions (lbs/year)

Acetaldehyde Formaldehyde Toluene Benzene Ethylbenzene Quinone HCl

618 1,473 1,378 185 114 76 95

ARS confirmed that the MMM HAP emissions listed above were determined using the

maximum production rate in the permit of 475,000 tons/yr.

HAP emissions listed for benzene, ethylbenzene, and formaldehyde match the AP-42

data for emissions from a natural gas-fired drum mix asphalt plant (AP-42, Table 11.1-10).

These factors are as follows: benzene (0.0039 lb/ton), ethylbenzene (0.00024 lb/ton), and

formaldehyde (0.0031 lb/ton). The APCD toluene factor (derived from the APCD’s emissions

estimate) is 0.0029 lb/ton, compared to the AP-42 factor of 0.00015 lb/ton. The toluene factor

used by APCD is the AP-42 factor for an asphalt plant fired on #2 fuel oil, so it appears that

APCD may have used this factor by mistake instead of the natural gas factor. After correcting for

this error, the toluene emissions would be reduced from 1,378 lb/yr to 71 lb/yr.

In the draft permit, APCD also listed HAP emissions for acetaldehyde, quinone, and

hydrochloric acid (HCl); however, these emissions are not included within the published AP-42

emissions data. In later correspondence with ARS, APCD acknowledged that the data were listed

in error and the expectation is that the estimates for these particular HAP pollutants will be

dropped when the final permit is released.

There are also other HAPs listed in the AP-42 data (AP-42, Table 11.1-10) that have

emissions comparable to the HAPs where emissions were calculated by APCD. These HAPs are

hexane (0.00092 lb/ton), xylene (0.00020 lb/ton), and polycyclic aromatic hydrocarbons or

PAHs (0.00019 lb/ton). The most prevalent PAHs based on AP-42 data are naphthalene and

2-methylnaphthalene. It is unknown why these HAPs were not considered given that the

emissions are comparable to other HAPs where emissions were tabulated by APCD. At the

maximum permitted production rate of 475,000 tons per year, the resulting emissions would be:

hexane 437 lb/yr, xylene 95 lb/yr, and PAHs 90 lb/yr.




3.0 REVIEW OF DISPERSION MODELING

3.1 APCD Modeling Studies

APCD conducted air quality dispersion modeling for CO emissions using the

US Environmental Protection Agency (US EPA) AERSCREEN model (Version 11126).

AERSCREEN is a simple “screening” model tool that predicts the worst-case concentration

expected from a single emission source over a wide range of possible meteorological dispersion

conditions.

Based on ARS’ review of the modeling documents provided by APCD, it has been

determined that the modeling was done correctly and followed the applicable regulatory

guidelines governing air quality dispersion modeling (40 CFR 51 Appendix W). If anything, for

reasons explained below, the modeling results are likely to be a significant overestimate of the

actual CO impacts which might be realistically expected for the MMM asphalt plant. These

conservatisms are especially pronounced for the 8-hour CO concentration modeling.

For the APCD modeling, the CO emission rate was set to 160 lb/hr, which equals the

expected CO emission rate at the maximum capacity of the asphalt plant (400 ton per hour) when

operating on LPG (emissions of 0.4 lb/ton). AERSCREEN returns the worst-case expected

concentration for an averaging time of 1-hour by calculating the expected concentrations from

the emission source under a wide array of different meteorological dispersion conditions. The

1-hour concentration predicted by AERSCREEN is then adjusted to other averaging times using

an EPA-recommended scaling factor. The 1-hour average AERSCREEN result was converted to

an 8-hour average by APCD for comparison with the 8-hour National Ambient Air Quality

Standard (NAAQS) using a scaling factor of 0.9.

The AERSCREEN modeling result is also added to a “background” concentration, which

accounts for ambient concentrations attributable any regional pollutant sources not explicitly

included in the modeling. APCD reports that it used ambient monitoring data collected over the

period 2004-2006 at the Fort Collins monitor located near the Colorado State University (CSU)

campus to determine the “background”. This is the only ambient CO monitor in the Fort Collins

region. APCD’s analysis states that using background data from the Fort Collins monitor likely

overstates the real background values at the MMM site and ARS concurs with that assessment.

The assumed background level accounts for about 1/3rd

of the total ambient CO impact in

APCD’s modeling analysis.

AERSCREEN also parameterizes “building downwash”, which describes how the airflow

around nearby buildings and structures within the plant affect atmospheric dispersion and the

resulting pollutant concentrations. There are three (3) structures at MMM that were considered

by APCD for these effects: 1) the lime silo adjacent to the baghouse stack, 2) the product silos

south of the baghouse stack, and 3) the baghouse structure itself. Since AERSCREEN is limited

to addressing only a single building in any given model run, APCD executed the model

separately for each of the three building configurations and then selected the worst-case result

from these model runs. The AERSCREEN output showed that the building configuration with




the lime silo caused the highest ambient concentrations and was therefore used by APCD for the

CO modeling results.

AERSCREEN was set such that the minimum source-to-receptor distance modeled was

87 meters, which is the distance from the asphalt plant baghouse stack to the closest property

boundary along Taft Hill Road which borders the facility of the west side. ARS confirmed that

the 87 meter distance matches the distance from the MMM baghouse stack to the closest

property boundary.

AERSCREEN was modeled by APCD using a unit emission rate (1.0 grams per second).

The modeling results were then adjusted to the actual emission rate (160 lb/hr or 20.18 g/sec) by

multiplying the AERSCREEN model output by the emission rate in grams per second. This

methodology accounts for the known relationship in the model that concentrations are linearly

proportional to the emissions rate. The model results are compared to the National Ambient Air

Quality Standards (NAAQS). The CO NAAQS are:

1 – Hour: 35 ppm (40,000 ug/m3)

8 – Hour: 9 ppm (10,000 ug/m3)

AERSCREEN modeling results for the three building configurations are listed below in

Tables 3-1 and 3-2 for the 1-hour average and 8-hour average CO concentrations.

Table 3-1

1-Hour Average CO Impacts – Martin Marietta Materials

Micrograms per cubic meter

Building

Configuration

AERSCREEN

Concentration

Background

Concentration

Total

Concentration NAAQS

Lime Silo 7,203 5,750 12,953 40,000

Product Silo 4,639 5,750 10,389 40,000

Baghouse Building 3,078 5,750 8.828 40,000

Table 3-2

8-Hour Average CO Impacts – Martin Marietta Materials

Micrograms per cubic meter

Building

Configuration

AERSCREEN

Concentration

Background

Concentration

Total

Concentration NAAQS

Lime Silo 6,483 3,450 9,933 10,000

Product Silo 4,175 3,450 7,625 10,000

Baghouse Building 2,770 3,450 6,220 10,000




One can see from the APCD modeling results that the predicted concentration using

AERSCREEN complies with the NAAQS for all building scenarios, although the margin of

compliance is small for the worst-case 8-hour average impacts. However, there is ample

conservatism in the modeling analysis such that there is high confidence that the NAAQS would

not be exceeded. The model conservatisms are detailed below.

First, one can see that the modeling results are strongly dependent on which building

affects the airflow. Predicted AERSCREEN concentrations for the building configurations other

than the lime silo produce much lower concentrations compared to the worst-case result.

Based on ARS’ review of the actual AERSCREEN modeling output files provided by

APCD, the lime silo only affects ambient concentrations when winds are generally in a

north-south direction and there is no building effect on concentrations when winds are in an

east-west orientation. However, the minimum distance to the property line of 87 meters occurs

directly to the west of the baghouse stack, which is a direction where the building effects from

the lime silo would be non-existent. So, the worst-case modeling result reported by APCD

actually occurs for an unrealistic scenario. The AERSCREEN output file indicates that the worst-

case flow vector is 300 degrees, and the distance to the property boundary was calculated to be

about 97 meters for that direction. The AERSCREEN modeling results also show that

concentrations decrease rapidly as the downwind distance increases. For the AERSCREEN

results for 300 degrees at 100 meters, the predicted concentration decreases by about 10 percent,

which drops the 8-hour CO level to less than 9,300 micrograms per cubic meter and provides

additional compliance margin, assuming that all other model inputs are unchanged.

Another important conservatism is that APCD’s modeling is based on the higher

short-term emission rate (160 lb/hr) which occurs only when the asphalt plant is fired on LPG.

Under normal operations when the unit is fired on natural gas, the maximum allowable emissions

would be 0.291 lb/ton or 116.4 lb/hr. LPG is a back-up fuel and limited to no more than40,000

tons per year production under the draft permit (which would equal 100 hours per year of

operation at the maximum 400 tph asphalt production rate). If the natural gas CO emissions rate

were applied instead, the modeling result would be more than 25% lower, and the resulting

8-hour CO concentration would be somewhere near 8,160 micrograms per cubic meter, assuming

that all other model inputs are unchanged.

Additional conservatism is introduced by the 0.9 factor used to estimate the 8-hour

concentration. First, the meteorological conditions must be relatively persistent at the worst-case

dispersion condition for the entire 8-hour period for this factor to provide a realistic modeling

result. Second, the asphalt plant must also operate at or near its maximum operating capacity

(400 tons per hour) and use LPG fuel for the entire 8-hour period. Neither condition is likely to

persist for any consecutive 8-hour period, making the APCD modeling results conservative from

that perspective too.

Lastly, as indicated previously, the assumed background concentration (which accounts

for about 1/3rd

of the total CO impact for the worst-case condition) is also a conservative

overestimate of the true CO background for the MMM plant site given that the background data




comes from monitoring data at an urban site (downtown Fort Collins) with considerably more

vehicular traffic emissions.

In summary, the CO modeling results presented by APCD demonstrate compliance with

the NAAQS, although compliance is by a small margin for the 8-hour average NAAQS.

However, the APCD modeling analysis contains a number of conservative assumptions, all

which must occur simultaneously with the worst-case dispersion condition for the predicted

impacts to be a realistic depiction of the actual CO impacts. Given that it is unlikely that all of

the conservative model assumptions would occur simultaneously, there is high confidence based

on the APCD modeling that the NAAQS standards will be achieved in the area surrounding the

MMM asphalt batch plant.

3.2 Additional HAP Modeling Analysis

At the request of Larimer County and the City of Fort Collins, ARS conducted an

assessment of the public health impacts associated with the reported hazardous air pollutant

(HAP) emissions from the MMM asphalt plant. This analysis goes beyond the regulatory

analysis conducted by APCD given that HAP concentrations in the ambient air are not

specifically regulated by the State of Colorado.

The HAP modeling analysis was conducted using the modeling results reported for the

APCD modeling analysis of CO emissions. The results for each HAP of interest were determined

using the APCD unit emissions rate modeling by simply multiplying the APCD AERSCREEN

modeling results by the appropriate emissions data for the HAP pollutant of interest. APCD’s

analysis reports emissions for the following HAPs: acetaldehyde, formaldehyde, toluene,

benzene, ethyl benzene, quinone, and hydrochloric acid. Please note that ARS included

acetaldehyde, quinone, and hydrochloric acid in our analysis despite the understanding that

APCD has since determined these emissions were listed in error. Also, the ARS HAP modeling

is based on the corrected toluene emissions data.

The additional HAP modeling was conducted for specific receptors near MMM where

people were known to live and/or congregate. The locations are as follows:

1) Residence located near the Poudre River Trail parking lot, 2) Residence on Stonecrest Drive

(3rd

house west from Taft Hill Road, which was determined to be the closest residence along that

street to the MMM asphalt plant emissions stack), and 3) Lincoln Middle School. The UTM

coordinates for each of these locations were determined along with the baghouse stack using

Google Earth and the distance and azimuth of each receptor point relative to the baghouse stack

was calculated using simple geometric relationships. These data are listed below along with the

worst-case AERSCREEN result for that receptor based on the unit emission rate APCD

modeling (1.0 gram per second).




Table 3-3

Location of Public receptors near MMM

Distance

(meters)

Azimuth

(degrees from North)

Worst-Case

AERSCREEN

Model Result

(ug/cubic meter)

Residence near Trailhead 239 160.2 232.9

Stonecrest Drive (3rd

House) 632 194.3 146.7

Lincoln Middle School (NW Corner of

school building) 1,130 155.6 13.57

As documented previously, the modeling results considered ambient air quality impacts

under three (3) separate scenarios where the influence of nearby buildings and structures were

considered. However, not every building scenario influences pollutant transport in all directions.

For the purpose of this HAP impact analysis, the model results for a given building scenario

were considered only when transport in the direction of the receptor was impacted by that

particular building. Then, the worst-case AERSCREEN model result at the distance of the

receptor of interest was tabulated and using the remaining AERSCREEN data that result was

scaled by the appropriate emissions rate for the HAP pollutant of interest.

The HAP modeling analysis prepared by ARS considered both acute (short-term) and

chronic (long-term) health effects of the pollutant of interest. For the acute effects analysis, ARS

estimated the maximum 1-hour concentration of each HAP and for the chronic effects analysis,

ARS estimated the maximum annual average concentrations for each HAP. The annual

concentration was scaled from the 1-hour AERSCREEN model prediction using the

EPA-recommended factor of 0.1.

The modeling results were compared to “safe” concentration levels determined for each

HAP pollutant and averaging time. The “safe” concentration level was determined from data

reported by USEPA in the document A Preliminary Risk-Based Screening Approach for Air

Toxics Monitoring Data Sets (October 2010), including any subsequent updates to the data tables

from that report. Where multiple concentration thresholds were listed by USEPA’s Risk-Based

Screening Approach, the most conservative threshold, i.e., lowest concentration, was selected

provided that the concentration threshold was for the appropriate averaging time.

For the acute exposures, the lowest concentration threshold in the USEPA Risk-Based

Screening Approach was generally the California “Reference Exposure Level” (REL), which is

defined as the expected concentration level for the pollutant of interest below which no adverse

health effects are anticipated. Most California RELs are derived for an exposure of one hour and

are available online at http://ww.oehha.ca.gov/air/acute_rels/index.html. For ethylbenzene, the

most stringent threshold listed is from the Acute Exposure Guideline Levels (AEGL) developed

by USEPA’s Office of Prevention, Pesticides, and Toxic Substances. The AEGL-1 is the

published threshold for mild health effects. For quinone, the only listed threshold is based on the

Immediately Dangerous to Life & Health (IDLH) concentrations divided by a safety factor of 10.

http://ww.oehha.ca.gov/air/acute_rels/index.html




The IDLH concentrations were developed by the National Institute for Occupational Safety &

Health (NIOSH).

The acute HAP modeling results are shown below in Table 3-4 for each receptor of

interest.

Table 3-4

MMM HAP Modeling Results – Acute Impacts

Pollutant

Max

Hourly

Emissions

(g/sec)

Calculated

1-Hour Average HAP Exposure

(micrograms/cubic meter) “Safe”

Concentration

Threshold

(micrograms/cubic

meter)

Receptor:

Residence near

Trailhead:

AERSCREEN

= 232.9 ug/

cubic meter

Receptor:

Stonecrest

Drive (3rd

House):

AERSCREEN

= 146.7 ug/

cubic meter

Receptor:

Lincoln Middle

School:

AERSCREEN

= 13.57 ug/

cubic meter

Acetaldehyde 0.0656 15.3 9.6 0.9 470

Formaldehyde 0.1564 36.4 22.9 2.1 55

Toluene 0.0076 1.8 1.1 0.1 37,000

Benzene 0.0197 4.6 2.9 0.3 1,300

Ethylbenzene 0.0121 2.8 1.8 0.2 140,000

Quinone 0.0081 1.9 1.2 0.1 10,000

Hydrogen

Chloride 0.0101 2.3 1.5 0.1 2,100

For the chronic exposure threshold, a “safe” concentration for HAPs rated as a

carcinogen was determined based on the unit risk factors published by USEPA in the May 21,

2012 update to Table 1 in the Risk-Based Screening Threshold document and assuming an

acceptable excess cancer risk of 1-in-1 million. The potential carcinogens are acetaldehyde,

formaldehyde, benzene, and ethylbenzene. For non-carcinogens, the chronic inhalation threshold

concentration from the USEPA Risk-Based Screening Threshold document was selected. In the

USEPA report, no data are reported for chronic exposures to quinone.




The chronic HAP modeling results are reported in Table 3-5 below.

Table 3-5

MMM HAP Modeling Results – Chronic Impacts

Pollutant

Max

Hourly

Emissions

(g/sec)

Calculated

Annual Average HAP Exposure

(micrograms/cubic meter) “Safe”

Concentration

Threshold

(micrograms/cubic

meter)

Receptor:

Residence

near

Trailhead:

AERSCREEN

= 232.9 ug/

cubic meter

Receptor:

Stonecrest

Drive (3rd

House):

AERSCREEN

= 146.7 ug/

cubic meter

Receptor:

Lincoln

Middle

School:

AERSCREEN

= 13.57 ug/

cubic meter

Acetaldehyde* 0.0089 0.207 0.130 0.012 2.2

Formaldehyde* 0.0212 0.494 0.311 0.029 13

Toluene 0.0010 0.024 0.015 0.001 5,000

Benzene* 0.0027 0.062 0.039 0.004 7.80

Ethylbenzene* 0.0016 0.038 0.024 0.002 2.50

Quinone 0.0011 0.025 0.016 0.001 n/a

Hydrogen

Chloride 0.0014 0.032 0.020 0.002 20

*Denotes HAP pollutants that are carcinogens. For these pollutants, the “safe” concentration represents

the threshold for a 1-in-1 million excess cancer risk.

Background concentrations for HAPs were not considered in the above modeling

analysis. Generally, background concentrations for HAPs are low compared to the “safe”

concentration levels; as such, the inclusion of a background level does not significantly alter the

modeling results. Background HAP measurements in Fort Collins were derived from a limited

set of samples collected by APCD in July 2006 at a site near the Colorado State University

Foothills Campus (3414 West Laporte Avenue). Table 3-6 summarizes the limited HAP

measurement data from Fort Collins.




Table 3-6

Background HAP Levels – Fort Collins, Colorado

Monitoring Data from Three Samples Collected in July 2006

Samples Collected Near Foothills Campus (3414 West Laporte Ave)

Pollutant Sample Concentrations (ppb)

Average MW

(ppb) (ug/m3)

Acetaldehyde 2.73 2.41 3.02 2.72 4.89 44

Formaldehyde 3.55 2.94 4.09 3.53 4.32 30

Toluene 0.788 0.685 1.01 0.83 3.11 92

Benzene 0.433 0.395 0.696 0.51 1.62 78

Hexane

As n-hexane 0.276 0.324 0.958 0.52

1.83 86

Xylene

As m-xylene/

p-xylene

0.7 0.634 0.725 0.69 2.97

106

Ethylbenzene 0.226 0.149 0.245 0.21 0.90 106

Based on the analysis presented above, the HAP emissions from the MMM Fort Collins

asphalt plant have been determined to present no significant risk to public health at nearby

receptors frequented by members of the general public.




4.0 REASONABLY AVAILABLE CONTROL TECHNOLOGY

Because of the MMM location in Fort Collins, emissions control for selected pollutants

must meet the regulatory definition of “reasonably available control technology” or RACT. The

RACT controls are required for nitrogen oxides (NOX) and volatile organic compounds (VOCs),

which are precursors to ozone formation. Fort Collins lies within the Colorado Front Range

ozone “non-attainment area”, meaning that existing concentrations for ozone do not comply with

the National Ambient Air Quality Standards (NAAQS). RACT is also triggered for CO

emissions at MMM. Fort Collins is a CO “maintenance area”, meaning that Fort Collins was

formerly designated as non-attainment for CO, but is currently in attainment with the NAAQS.

The definition of Reasonably Available Control Technology (RACT) is found in the

Colorado Air Quality Control Commission Common Provisions Regulation:

Technology that will achieve the maximum degree of emission control that a

particular source is capable of meeting and that is reasonably available

considering technological and economic feasibility. It may require technology

that has been applied to similar, but not necessarily identical, source categories.

It is not intended that extensive research and development be conducted before a

given control technology can be applied to the source. This does not preclude

requiring a short-term evaluation program to permit the application of a given

technology to a particular type of source.

This report section contains additional information about the proposed MMM controls

and considers whether the proposed emission controls listed in the permit constitute RACT. The

ARS report covers only VOC and CO emissions. NOX emissions were not reviewed because

these emissions are already low (NOX emitted at the MMM asphalt plant only totals 6.5 tons per

year) and as such there would be little perceived environmental benefit associated with improved

NOX emission controls.

4.1 RACT for VOC Emissions

As mentioned previously, MMM has implemented certain voluntary measures aimed at

curbing VOC and HAP emissions which have not been explicitly required in the draft air quality

permit. These measures are:

Collecting exhaust air from the asphalt product conveyer and recycling this air to

the asphalt plant burner for destruction of any associated VOCs and/or HAPs.

Installation of vapor condensers on the liquid asphalt tanks.

Figure 4-1 shows a picture of the recycle air collection point on the MMM asphalt

product conveyor.




Figure 4-1. Image of Recycle Air Collection Point at MMM Asphalt Plant

Because the above controls have been voluntarily implemented by MMM, it is reasonable

to conclude that these measures are reasonably available considering technological and

economic feasibility, which is the legal definition of RACT under Colorado’s air quality

regulations. The MMM draft air quality permit should be revised to legally require the

installation and operation of MMM’s voluntary VOC/HAP pollution control measures as RACT.

4.2 RACT for CO Emissions

The draft MMM air permit has established CO emission limits equal to 0.291 lb/ton when

the asphalt plant is fired on natural gas and 0.40 lb/ton when the asphalt plant is fired on back-up

LPG fuel. As noted above, the AP-42 CO factor for natural gas-fired drum mix asphalt plants is




0.13 lb/ton. APCD staff stated to ARS that they believe that the CO AP-42 emissions are not

technically achievable and as such, the proposed CO emissions (0.291 lb/ton and 0.40 lb/ton) are

RACT because additional emission controls are not cost-effective. However, the MMM permit

and APCD’s supporting technical information provided to the public do not provide any

substantive support for this RACT claim. Based on the permit record, there is no evidence that

APCD in fact evaluated the technical feasibility and cost of any alternative emission controls for

the CO RACT analysis.

The fact that AP-42 data present significantly lower CO emissions (0.13 lb/ton) suggests

that better CO control is indeed technically achievable and likely has been achieved in practice at

other asphalt plants. Given this finding, a technical and economic review of improved CO

controls should have been performed for the MMM draft permit. Without such an analysis, the

CO RACT analysis is deficient.

At the request of the AQAB and ESAB, ARS conducted a review of other asphalt plant

permits to determine if lower CO emissions are in fact technically achievable. ARS conducted a

query using the USEPA RACT/BACT/LAER Clearinghouse (RBLC) that turned up emissions

data for two asphalt plants located in Clark County, Nevada (Las Vegas). These data are

summarized in Table 4-1. It should be noted that both asphalt plants listed in the RBLC were

subject to “best available control technology” (BACT) as the applicable emissions standard and

not RACT. However, the selection of lower CO emissions to meet BACT requirements

documents the technical feasibility of improved CO emissions control and as such, mandates that

such controls be considered as RACT.

Table 4-1

RBLC Query Results: Asphalt Concrete Manufacturing

Source ID RBLC ID CO Permit Limit (BACT)

Nellis Air Force Base NV-0047 0.13 lb/ton, 16.25 lb/hr

Aggregate Industries – Sloan Quarry NV-0045 0.10 lb/ton, 45.0 lb/hr

ARS also located four recent USEPA permits for asphalt plants located on tribal lands in

the western United States. These permits are:

Pioneer Asphalt, Inc. – Permit R10NT502400 (Draft)

Granite Construction Company – Permit R10NT502300 (9/19/2012)

Knife River, Inc. – Permit R10NT502200 (9/19/2012)

Mickelsen Construction, Inc. – Permit R10NT502501 (Draft)

For all of the USEPA permits listed above, the CO emissions control was not subject to

RACT, BACT, or any other emissions standard. Nevertheless, all permits were issued based on

CO emissions at 0.13 lb/ton, which equals the AP-42 emissions value for a natural gas-fired

drum mix asphalt plant. However, none of the USEPA permits appear to have required emissions

testing for CO, so it is unknown if the 0.13 lb/ton emissions level was actually achieved in

practice at any of these facilities.




In summary, for those cases where asphalt plant emissions control data are posted in the

RBLC and in other asphalt plant permits issued by USEPA Region X, the CO emissions are

significantly lower than the RACT limit established by APCD in the MMM draft permit. The

APCD RACT analysis is deficient without a detailed evaluation of CO emission control options

that might lead to better emissions control and lower allowable CO emissions under the permit.

A review of asphalt plant permits issued elsewhere would suggest that improved CO controls are

technically achievable, so control options to achieve improved CO controls should have been

evaluated by APCD for application as RACT. There is no evidence in the MMM permit record

that such an analysis was conducted.




5.0 TECHNICAL COMMENTS ON DRAFT PERMIT

This section summarizes possible comments that might be offered by Larimer County

and/or the City of Fort Collins with respect to the proposed Martin Marietta Materials asphalt

plant permit.

HAP Emissions: It appears that the draft permit used the AP-42 toluene factor for drum mix

asphalt plants fired on #2 fuel oil. The AP-42 factors for natural gas drum mix asphalt plants

were used to calculate HAP emissions for other pollutants. This appears to be an oversight and

should be corrected. There are also other HAPs listed in the AP-42 data (AP-42, Table 11.1-10)

that have emissions comparable to the HAPs where emissions were calculated. These HAPs are

hexane (0.00092 lb/ton), xylene (0.00020 lb/ton), and PAHs (0.00019 lb/ton). It is unknown why

these HAPs were not considered by APCD given that the emissions are comparable to other

HAPs where emissions were tabulated.

General Comment: In assessing the asphalt plant, the APCD appears to have considered only the

emissions directly related to the asphalt plant in its analysis. However, MMM owns and operates

other air emission sources in the immediate vicinity of the asphalt plant, including an aggregate

materials mining and processing operation on the west side of Taft Hill Road immediately to the

west of the asphalt plant. Under the Clean Air Act, a “source” is defined as “Any building,

structure, facility, equipment, or installation, or any combination thereof belonging to the same

industrial grouping that emit or may emit any air pollutant subject to regulation under the

Federal Act that is located on one or more contiguous or adjacent properties and that is owned

or operated by the same person or by persons under common control.” MMM’s other aggregate

processing activities located across Taft Hill Road are located on “contiguous or adjacent

properties” and should therefore be considered in the assessment of the overall facility emissions.

ARS’ understanding is that all of the aggregate used in the asphalt plant comes directly from

MMM operations on the west side of Taft Hill Road, so the adjoining operations are “support

facilities” and as such, it cannot be claimed that the asphalt plant is part of a separate source

based on the differences in Standard Industrial Classification (SIC) code. It is probably unlikely

that the added emissions from adjoining MMM operations will alter the minor/major source

classification of the asphalt plant, but a complete and accurate analysis requires that these

emissions also be considered when determining the total emissions of the “source”.

Condition 3, Operating & Maintenance Plan: This permit condition requires that MMM submit

an Operating & Maintenance (O&M) Plan for APCD approval. The plan describes the ongoing

monitoring and recordkeeping activities that MMM will undertake to document compliance with

the terms and conditions of its permit. In essence, any commitments for compliance monitoring

and recordkeeping made by MMM in the O&M Plan will become enforceable requirements of

the permit. While the O&M Plan is not normally subject to review and comment by the public,

due to the sensitivity of emissions to the nearby public in this case, an opportunity for public

input on the O&M Plan could be requested to ensure that the approved O&M Plan provides the

necessary compliance monitoring and recordkeeping to assure permit compliance.

Condition 7, Emissions Control Equipment: This condition lists the pollution control equipment

that MMM must employ to abate pollutant emissions to the atmosphere. However, MMM has




voluntarily installed additional equipment to mitigate volatile organic compound (VOC) and

associated hazardous air pollutant (HAP) emissions, including recycling exhaust air from the

asphalt plant outlet conveyor back to the asphalt plant burner along with installing condensers on

the liquid asphalt storage tanks. These voluntary measures adopted by MMM to abate emissions

should be made enforceable legal requirements through the APCD’s air permit. This will assure

that such emissions abatement practices continue going forward. Please also refer to comments

on Condition #10 (Odors) and Condition #13 (RACT).

Condition 10, Odor Control: This is a general requirement referencing Regulation #2 concerning

control and abatement of odors. Given that the MMM asphalt plant has in the past been the

subject of odor complaints, additional requirements for abatement of odors should be considered

for the air quality permit. The voluntary controls that MMM has applied at the asphalt plant

(See Condition 7 above) could be made enforceable requirement on the basis that such controls

are needed to assure compliance with Condition 10 and the associated odor requirements under

Regulation #2.

Condition 13, Reasonably Available Control Technology (RACT) – VOC Emissions: The

Fort Collins region lies within the designated non-attainment area for ozone, and new/modified

emissions of ozone precursors (including VOCs) within the non-attainment area are required

under Regulation #3, Part B, III.E to install reasonably available control technology (RACT) for

emissions control. The APCD has determined that “no additional control” meets RACT.

However, MMM has voluntarily installed additional control for VOC emissions, including

recirculating exhaust air from the asphalt plant product conveyor to the asphalt plant burner and

installing condenser equipment on the liquid asphalt tanks. The mere presence of such equipment

at the MMM Taft Hill Road facility demonstrates the technical feasibility and economic viability

of such emissions controls and therefore mandate that such controls be deemed RACT. As

described under Condition #7, the voluntary VOC emission controls implemented by MMM

should be classified as RACT and required under Permit Condition 13.

Condition 13, Reasonably Available Control Technology (RACT) – CO Emissions: The

Fort Collins region lies within the designated attainment-maintenance area for carbon monoxide

(CO), and new/modified CO emission sources within this area are required under Regulation #3,

Part B, III.E to install reasonably available control technology (RACT) to control emissions. The

APCD has determined that “no additional control” meets RACT. However, it is noted that AP-42

listed emissions for CO at natural gas-fired of 0.13 lb/ton, which is less than 50% of the

0.291 lb/ton limit established at Condition 16 of the draft permit. Permits issued in other

jurisdictions have also set CO permit limits at the AP-42 emissions value (0.13 lb/ton) or lower.

There is no discussion in the permit record as to why lower CO emissions cannot be achieved by

MMM, although APCD has claimed in separate communications with ARS staff that the AP-42

CO emission levels are not achievable. Absent any evidence to the contrary, it would be prudent

for APCD to find that CO emissions at the listed AP-42 value for natural gas-fired drum mix hot

asphalt plants (0.13 lb/ton) represents RACT. Such a limit should be considered for this permit

or APCD should provide the technical basis for its decision and these data should be made

available for review by the public and other interested parties. This comment also affects the

allowable emissions limit for CO contained in Permit Condition 16.




Condition 14 – O&M Plan: Condition 14 duplicates Condition 3. There is no need to repeat the

O&M Plan requirements in the permit.

Condition 15 – Opacity Testing: This permit condition requires opacity testing to show

compliance with the underlying permit requirements. Since the asphalt plant is approved to

operate on both natural gas and LPG as fuel, the opacity testing should be completed for the

plant on both approved fuels.

Condition 16 – Emissions Testing: This permit condition requires emissions testing to show

compliance with the specified limits for emissions of particulate matter (PM), carbon monoxide

(CO), and oxides of nitrogen (NOx). Since the asphalt plant is approved to operate on both

natural gas and LPG as fuel, the emissions testing should be completed for the plant on both

approved fuels. Also, for clarity, the permit should specify whether or not the particulate testing

is required to include condensable particulate matter (CPM). The hot exhaust from the baghouse

emissions stack suggest that CPM emissions may be present, so the CPM fraction of the PM

emissions needs to be regulated even if not otherwise included in the proposed permit limits.

Condition 16 – Emissions Testing – HAPs: The draft permit as written does not require any

testing for emissions of regulated hazardous air pollutants (HAPs). Generally, without any

authority for regulating HAPs at sources within Colorado, emissions are not tested as there is no

enforceable emissions limit and/or standard for comparison of the testing results. However, HAP

testing could be requested, especially for those HAPs which are known to be carcinogenic

(acetaldehyde, formaldehyde, benzene, etc.). This would provide more reliable data from which

to make a reliable assessment of the possible impact of these emissions on public health.

Condition 21 – Change in Location: It is presumed that the intent of this condition restricts

relocating the asphalt plant within the MMM property. If so, the condition should be clarified

given that a typical hot asphalt plant is known to change locations on a regular basis.




6.0 SUMMARY & CONCLUSIONS

The major findings of the ARS technical review are summarized below.

The emissions data used for the MMM permit are generally supported by AP-42 and other

appropriate data. However, the CO emissions used by APCD are higher than the

corresponding AP-42 data. APCD claims that historical emissions data do not support the

lower emissions reported by AP-42; however, this claim has not been substantiated by

APCD. Because Fort Collins is a designated maintenance area, CO emissions are required to

meet RACT. AP-42 data along with permits issued to asphalt plants in other jurisdictions

suggest that lower CO emissions are in fact achievable and would represent RACT. APCD

should require lower CO emissions or better document why the selected CO emissions level

is in fact RACT.

MMM has voluntarily adopted emission controls for reduction of VOC and HAP emissions;

specifically, recycling exhaust air from the product conveyor to the asphalt plant burner and

capturing emissions at the liquid asphalt tanks using condensers. The adoption of these

control measures by MMM in fact means that such controls are both technically achievable

and economically viable. Any voluntary controls adopted by MMM would meet the criteria

for RACT and should be legally required under the air quality permit.

The MMM draft permit used the AP-42 toluene emissions factor for drum mix asphalt plants

fired on #2 fuel oil. The AP-42 factors for natural gas drum mix asphalt plants were used to

calculate HAP emissions for other pollutants. This appears to be an oversight by APCD and

should be corrected. Also, other HAPs listed in the AP-42 data (AP-42, Table 11.1-10) where

emissions are comparable to the HAPs calculated by APCD. These HAPs are hexane, xylene,

and PAHs. It is unknown why these HAPs were not considered by APCD given that the

emissions are comparable to other HAPs where emissions were tabulated. APCD’s permit

analysis should be amended to address hexane, xylene, and PAH emissions in addition to the

other HAPs.

In assessing the asphalt plant, the APCD appears to have considered only those emissions

directly related to the asphalt plant. However, MMM owns and operates other air emission

sources in the immediate vicinity of the asphalt plant, including an aggregate materials

mining and processing operation on the west side of Taft Hill Road. MMM’s other aggregate

processing activities are located on “contiguous or adjacent properties” and should therefore

be considered in the assessment of the overall facility emissions. It is unlikely that the added

emissions from adjoining MMM operations will alter the minor/major source classification

of the asphalt plant, but a complete and accurate analysis by APCD requires that these

emissions also be considered when determining the total emissions of the “source”.




The AERSCREEN modeling for MMM’s CO emissions has been conducted following

standard regulatory practices and principles. This modeling also employed several significant

conservative assumptions. Although the modeling showed that MMM’s emissions comply

with the NAAQS by a small margin, the conservatisms inherent in the modeling study means

that MMM’s operations will comply with the NAAQS, very likely with a substantial safety

margin.

ARS used APCD’s AERMOD modeling results to make an assessment of potential HAP

impacts on public health and the environment. The HAP modeling results from MMM were

compared to “safe” concentration levels determined using USEPA’s Risk-Based Screening

Approach. ARS’ modeling assessment determined that HAP emissions from MMM’s asphalt

plant operations would not cause ambient concentrations above the “safe” concentration

levels determined from USEPA data.

Recommendations have been provided for consideration by the ESAB and AQAB on formal

comments on the draft MMM air quality permit. This includes making any voluntary

pollution control practices adopted by MMM enforceable requirements under the permit.

These recommendations are intended to make the final permit more protective of public

health and the environment.

2014 martin marietta materials final technical report … · 2014. 8. 28. · 2014 martin marietta...

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