criteria pollutant air dispersion modeling analysisaermod is a preferred air dispersion model in the...

Criteria Pollutant Air Dispersion Modeling

Analysis for

Metro Transit’s Existing Hiawatha Light Rail Vehicle Operation &

Maintenance Facility, Proposed Paint Booth,

and Proposed Light Rail Support Facility

Prepared for

Metropolitan Transit

Original Submittal:May 28, 2010

Resubmitted:November 10, 2010

January 21, 2011

aq5-28

Wenck File #0141-89Phases 13

Prepared for:

METROPOLITAN TRANSIT560 6th Avenue North

Minneapolis, MN 55411

Criteria Pollutant Air Dispersion Modeling

Analysis for

Metro Transit’s Existing Hiawatha Light Rail Vehicle Operation &

Maintenance Facility, Proposed Paint Booth,

and Proposed Light Rail Support Facility

Prepared by:

WENCK ASSOCIATES, INC.1802 Wooddale Drive

Suite 100Woodbury, MN 55125

(651) 294-4580

Original Submittal:May 28, 2010

NoResubmitted:

vember 10, 2010January 21, 2011

Table of Contents

1.0 INTRODUCTION ........................................................................................................... 1-1

2.0 MODEL INPUT............................................................................................................... 2-1

2.1 Model Selection ................................................................................................... 2-1 2.2 Model Options ..................................................................................................... 2-1 2.3 Building Downwash............................................................................................. 2-2 2.4 Receptor Grid....................................................................................................... 2-2 2.5 Meteorological Data............................................................................................. 2-3

3.0 AIR EMISSION SOURCES........................................................................................... 3-1

4.0 ANALYSIS OF RESULTS ............................................................................................. 4-1

TABLES (included throughout the text)

3-1 Modeling Source Parameters 4-1 Estimated Criteria Pollutant Ambient Air Concentrations FIGURES (included throughout the text) 2.1 Air Dispersion Modeling Receptor Grid 2.2 Near-Field Air Dispersion Modeling Receptors 4.1 NO2 1-Hour Average High Modeled Concentrations 4.2 PM2.5 24-Hour Average High Modeled Concentrations APPENDICES A Criteria Pollutant Air Dispersion Modeling

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1-1

1.0 Introduction

Air dispersion modeling was completed for Metro Transit’s existing Hiawatha Light Rail Vehicle

Operations & Maintenance (HLRV O&M) Facility and the proposed Light Rail Support (LRS) Facility.

The two facilities are considered a single stationary source for air permitting by the MPCA. The HLRV

O&M site includes a proposed paint booth and expansion of the building footprint. This air dispersion

modeling supports the air permit application for the facilities. In addition, air dispersion modeling was

completed to support the Screening-Level Air Emissions Risk Analysis (AERA) conducted for the

facilities; please refer to the AERA for details.

Modeling was submitted in April, May, and November 2010. Following those submittals, plans for the

HLRV O&M expansion had matured to the extent that they were able to be included in this modeling

report. This report updates earlier modeling to incorporate MPCA comments as well as the proposed

expansion.


2-1

2.0 Model Input

2.1 MODEL SELECTION

The Metro Transit modeling used the AMS/EPA Regulatory Model with Plume Rise Model

Enhancements (AERMOD), version 09292, to estimate criteria pollutant concentrations at and around the

HLRV O&M and LRS facilities. AERMOD is a preferred air dispersion model in the United States

Environmental Protection Agency’s (EPA) Guideline on Air Quality Models, 40 CFR 51 Appendix W.

Pollutant specific concentrations were entered for PM2.5, PM10, CO, NOx, lead, and SO2.

2.2 MODEL OPTIONS

All options within AERMOD recommended by the EPA as regulatory defaults were used. These options

include: 1) using elevated terrain algorithms that require the input of terrain height data; 2) using stack-tip

downwash as applicable; 3) using routines to process averages during calm winds; and 4) using

algorithms to handle missing meteorological data.

Averaging periods with an applicable National Ambient Air Quality Standard (NAAQS), Minnesota

Ambient Air Quality Standard (MAAQS), or Significant Impact Level (SIL) were modeled.

In accordance with EPA’s March 19, 2009, “AERMOD Implementation Guidance”, the Urban Mode was

selected. The Urban Mode estimates the effects of urban heat islands. Current EPA guidance is to use

the Urban Mode for all sites within urban statistical areas regardless of whether nearby land uses would

be considered urban or not, and regardless of the location of the meteorological data site. A population of

1,000,000 will be entered for the Minneapolis/St. Paul area, obtained from MPCA on other recent air

dispersion modeling. Selection of the Urban Mode is a change from earlier modeling submitted for the

facility, in response to MPCA’s comments dated August 19, 2010.


2-2

2.3 BUILDING DOWNWASH

The Building Profile Input Program with Plume Rise Model Enhancements (BPIP-PRIME), version

04274, was used to calculate building downwash parameters for the modeling analysis. Elevations of

stacks and buildings were input into BPIP-PRIME.

2.4 RECEPTOR GRID

A Cartesian receptor grid was used in the modeling analysis to determine concentrations for the modeling

analysis. The grid extended 1.5 kilometers from the property line in each direction, in accordance with

MPCA’s RASS guidance for stacks less than 50 meters tall. The receptors were placed at 100 meter

spacings. In addition, receptors were located at every 25 meters along the facility property line as well as

along the bike path running through the northeast side of the facility. Receptor locations are shown in

Figures 1 and 2.

In response to MPCA comments, elevated (or “flagpole”) receptors were placed at the nearest point to the

HLRV site for the three apartment buildings located between Franklin Avenue and 22nd St., just west of

Hiawatha Avenue. The buildings appear to be 12 stories tall from aerial photographs of the site, not

including the penthouses. The penthouses do not appear to include residences. A height of 120 feet was

assumed for each building. Flagpole heights were included at ground level, 30 ft, 60 ft, 90, ft, and 120 ft

for each building.

Flagpole receptors will also be included for the senior housing located on Cedar Avenue and Sixth Street,

north/northwest of the facility. The senior housing appears to be 26 stories tall from aerial photographs.

Flagpole heights were included at heights of ground level, 65 ft, 130 ft, 195 ft, and 260 ft at the corner of

the building closest to the Metro Transit property line. The modeling results predict that concentrations

are lower at the elevated flagpole heights than at ground level.

High concentration occurs along the facility property lines and, therefore, the 1.5 kilometer grid captures

high facility concentrations. Receptor elevations were determined using the AERMOD Terrain

preprocessor (AERMAP), version 09040, and USGS National Elevation Dataset (NED) files. The option


2-3

of “NADA=4” was used to reference the North American Datum (NAD) of 1983 anchor coordinates

based on the AERMAP User’s Guide.

2.5 METEOROLOGICAL DATA

Minneapolis/St. Paul, Minnesota surface meteorological data was selected for the years 2000 through

2004. Processed meteorological data was provided by MPCA. The Minneapolis/St. Paul site is the

closest meteorological data site to the area of interest for this project, and is the most urban of the

available upper Midwestern meteorological data. Therefore, the Minneapolis/St. Paul data is believed to

be the most representative.

Upper air data for the corresponding years were obtained from the Minneapolis National Weather Service

station.

Metro Transit Wenck Associates, Inc.

1800 Pioneer Creek Center Maple Plain, MN 55359-0429

November 2010

Air Dispersion Modeling Receptor Grid Figure 2-1 T:\0141\89\tech\Phase 3 - Modeling\Expansion Modeling\Criteria Pollutant Report Figures and Tables.doc

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January 2011

Property line receptors are shown as a purple +. Discrete receptors are shown as a yellow +. Property lines are shown in red. Building footprints are shown in blue.

Metro Transit Wenck Associates, Inc. 1800 Pioneer Creek Center Maple Plain, MN 55359-0429

Nov. 2010 Near-Field Air Dispersion Modeling Receptors Figure 2-2

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3-1

3.0 Air Emission Sources

The modeled source parameters are attached in Table 3-1. Supporting calculations for criteria pollutants

are included with the AERA report and are not repeated here. The facilities Make-up Air Units (MAUs)

nos. 1-4 exhaust indoors. The exhaust fans that are interlocked with these MAUs were modeled as the

exhaust points for the MAUs. Material use emissions that occur throughout the facility were included in

the AERA. The only criteria pollutant emissions from material use are VOCs and, therefore, are not

included in the criteria pollutant modeling analysis.

Correspondence with MPCA indicated that it is reasonable to exclude insignificant sources from the air

dispersion modeling and health risk assessment. These excluded emission units include the combustion

units with a capacity of less than 1% of the total facility heat input for the AERA. Emission units

excluded from the AERA were also excluded from the criteria pollutant analysis. Criteria pollutant

sources with emissions less than 0.1 lb/hr such as the facility’s sand silo were also excluded. The facility

sand silo has no toxic emissions and has particulate emissions less than 0.1 lb/hr.

A “Tier 2” NO2 ambient concentration of 75% of total NOx emissions is proposed for 1-hour NO2

modeling. The Tier 2 value is the national default value for the average annual ambient concentration of

NO2 versus total NOx, obtained from 40 CFR 51 Appendix W. A significant fraction of NOx from

combustion sources is emitted as NO. NO is converted to NO2 in the atmosphere. The conversion time

and fraction is dependent upon a number of variables such as temperature and ozone concentrations, and

is not instantaneous.

For comparison to the annual (as opposed to 1-hour) NO2 National Ambient Air Quality Standard, the

Tier 2 value was not used. Instead, the conservative Tier 1 assumption of 100% conversion of NOx to

NO2 was used. For the 1-hour NO2 National Ambient Air Quality Standard, EPA’s Tier 2 NO2/NOx

ratio of 75% was applied to the NOx emission rates so that 1-hour NO2 concentrations were estimated by

AERMOD. Since emissions are directly proportional to concentrations in AERMOD, the same results

would be obtained by entering total NOx emission rates and multiplying the predicted NOx concentration


3-2

by 75% to obtain 1-hour NO2 concentrations. The 75% value applies to estimated ambient concentrations

rather than the emission rates that would be expected “in-stack”.

EPA indicated in the June 28, 2010 memorandum on “The Applicability of Appendix W Modeling

Guidance for the 1-Hour NO2 National Ambient Air Quality Standard” that for low-level sources with

limited plume rise that the 75% Tier 2 value will likely be conservative. High 1-hour concentrations in

the previously submitted Metro Transit modeling occurred at the property line. The highest proposed

stack height at the facility is 60 feet above ground and all exit velocities are below 10 m/s. Therefore, the

facility sources can be characterized as “low-level with limited plume rise”.

The NO2 modeling, for all five meteorological years, each of the 1st high and 8th high 1-hour NO2

concentrations occurred either during the night or in winter morning hours (such as 6:00 am in January

and February). EPA also noted in the June 28, 2010 memorandum that stable nighttime conditions would

limit the entrainment of ozone and, therefore, the 75% concentration is expected to be conservative for

these meteorological conditions. Wenck does not expect additional modeling will change which

meteorological conditions predict the highest ambient concentrations. Therefore, the 75% NO2/NOx

value appears to be conservative for estimation of 1-hour NO2 ambient concentrations.

The ratio of ambient NO2 to NOx concentrations is effected more by atmospheric conversion of NO to

NO2, compared to the in-stack concentrations of NO2, since the majority of NOx is emitted as NO rather

than NO2 from uncontrolled combustion sources. For the Ozone Limiting Method (OLM) in Tier 3 NO2

modeling, a 0.10 NO2/NOx in-stack ratio is often used as a default in the absence of stack test data,

therefore, EPA’s discussion of ambient and stack discharge conditions where the Tier 2 value is

conservative is applicable to the Metro Transit modeling.

Criteria pollutant emission rates for the modeling are presented in the facility’s air permit application.

The calculations are also included electronically in Appendix A. The modeled emission rates include a

daily paint booth coatings limit, an annual paint booth coatings limit, and a proposed annual natural gas

limit.

Table 3-1 Point Source Exhaust Parameters

Location

Base Elevation

(m)

Exhaust Height Height Exit Exhaust Exit

Velocity (m/s) Source Source Description

UTM East (m)

UTM North (m)

from Ground Above Temperature Flowrate Diameter

(ft) (m) Roof (ft)

(K) (oF) (acfm) (ft) (m)

SV001 HLRV Paint Booth Vent 1

(EF-11) 480,399.1 4,979,052.0 257.1 36.0 11.0 8.0 298.0 77 7,700 7.97 2.5 0.76


(EF-26) 480,400.0 4,979,050.0 257.1 36.0 11.0 8.0 298.0 77 8,500 8.80 2.5 0.76


(EF-27) 480,388.0 4,979,074.4 257.1 36.0 11.0 8.0 298.0 600 8,500 8.80 2.5 0.76

SV005 HLRV Welding 480,346.7 4,979,047.0 257.1 42.0 12.8 1.0 298.0 77 600 3.04 1.13 0.34

SV006 HLRV Water Heater 480,329.9 4,979,054.4 257.1 49.0 14.9 8.0 394.3 250 143 1.34 0.83 0.25

SV007 HLRV Bryan B-1 Boiler 480,331.9 4,979,055.6 257.1 49.0 14.9 8.0 394.3 250 477 4.48 0.83 0.25

SV008 HLRV RTU-5 480,305.6 4,979,110.6 257.1 32.0 9.8 8.0 394.3 250 426 25.6 0.33 0.10

SV009 HLRV Pressure Washer 480,379.6 4,979,081.4 257.1 36.0 11.0 8.0 394.3 250 157 1.47 0.83 0.25

SV010 HLRV South Air Curtain

Furnace 480,407.8 4,979,047.6 257.1 31.8 9.7 8.0 298.0 77 123 0.82 1.0 0.30

SV011 HLRV North Air Curtain

Furnace 480,373.1 4,979,119.4 257.1 31.8 9.7 8.0 298.0 77 123 0.82 1.0 0.30

SV012 HLRV Gun Cleaning 480,403.2 4,979,042.8 257.1 12.0 3.7 Side of Bldg

298.0 77 185 0.53 1.5 0.46

SV013 HLRV MAU1 Vent 1 (EF-1) 480,371.3 4,979,054.8 257.1 32.0 9.8 4.0 298.0 77 4,000 6.96 1.93 0.59



SV016 HLRV MAU1 Vent 4 (EF-4) 480,363.4 4,979,091.7 257.1 32.0 9.8 4.0 298.0 77 650 3.04 1.18 0.36



SV019 HLRV MAU2 (EF-9) 480,380.2 4,979,076.1 257.1 32.0 9.8 4.0 298.0 77 5,300 5.52 2.5 0.76

SV020 HLRV MAU3 (EF-11) 480,399.1 4,979,052.0 257.1 36.0 11.0 8.0 298.0 77 7,700 7.97 2.5 0.76



SV023 HLRV MAU4 Vent 3 (EF-15) 480,393.2 4,979,063.4 257.1 31.0 9.5 3.0 298.0 77 985 3.43 1.4 0.42

SV024 HLRV MAU5 480,356.4 4,978,963.7 257.1 32.0 9.8 8.0 394.3 250 321 19.29 0.3 0.10

SV025 HLRV MAU6 480,276.0 4,979,133.2 257.1 32.0 9.8 8.0 394.3 250 321 19.29 0.3 0.10

SV026 HLRV MAU7 480,337.8 4,978,954.9 257.1 32.0 9.8 8.0 394.3 250 321 19.29 0.3 0.10

3-3

Table 3-1 Point Source Exhaust Parameters

Location

Base Elevation

(m)

Exhaust Height Height Exit Exhaust Exit

Velocity (m/s) Source Source Description

UTM East (m)

UTM North (m)

from Ground Above Temperature Flowrate Diameter

(ft) (m) Roof (ft)

(K) (oF) (acfm) (ft) (m)

SV027 HLRV MAU8 480,256.7 4,979,124.6 257.1 32.0 9.8 8.0 394.3 250 321 19.29 0.3 0.10

SV028 HLRV VP-1 480,321.5 4,978,982.0 257.1 32.0 9.8 8.0 394.3 250 116 3.1 0.5 0.15

SV029 HLRV VP-2 480,267.9 4,979,094.6 257.1 32.0 9.8 8.0 394.3 250 116 3.1 0.5 0.15

SV030 LRS HVAC RTU-1 480,856.8 4,978,216.4 256.6 34.0 10.4 7.7 394.3 250 115 6.91 0.3 0.10

SV031 LRS MAU1 480,860.5 4,978,209.3 256.6 34.0 10.4 7.7 394.3 250 198 11.88 0.3 0.10

SV032 LRS Boiler B-1 480,840.3 4,978,216.2 256.6 24.0 7.3 7.7 394.3 250 106 6.24 0.3 0.10

SV033 LRS Boiler B-2 480,838.7 4,978,215.4 256.6 24.0 7.3 7.7 394.3 250 106 6.24 0.3 0.10

Table 3-2

Area Source Exhaust Parameters

Source

Source Description

Location

Base Elevation

(m)

Release Height

Easting Side

Length (m)

NorthingSide

Length (m)

Angle of

Rotation(deg)

Initial Vertical

Dimension(m)

UTM East (m)

UTM North (m)

(ft) (m)

HLRVMSC1 HLRV Misc. Maint. Act. 1 480,330.2 4,978,948.6 257.1 24.0 7.3 43.4 192.0 -25.7 0





LRSMSC1 LRS Misc. Maint. Act. 1 480,837.7 4,978,211.1 256.6 16.3 5.0 31.9 31.1 -26.7 0



3-4


4-1

4.0 Analysis of Results

Estimated ambient air concentrations from the modeling analysis are shown in Table 4-1.

Following MPCA’s guidance for Minn. Stat. § 116.07 Subd. 4a, the Prevention of Significant

Deterioration (PSD) Significant Impact Levels (SILs) were used as an acceptable ambient

concentration for the HLRV O&M and LRS impacts without background. In addition,

background concentrations were added to the high modeled concentrations to obtain total

ambient impacts for comparison to the National and Minnesota Ambient Air Quality Standards.

Background concentrations were obtained from MPCA’s SAM spreadsheet, unless otherwise

noted. Option 1 values were selected. Option 1 values are for sites that do not include nearby

sources in the air dispersion modeling. Concentrations were selected for Minneapolis if

available, or for the Twin Cities where separate Minneapolis values were not listed by the

MPCA.

Lead and 1-hour NO2 background concentrations were not included in the SAM spreadsheet.

MPCA recommended an NO2 urban background 1-hour average concentration of 83 ug/m3 for 1-

hour NO2 based on the Blaine monitoring station on another recent project. The Blaine NO2

concentration is higher than other NO2 monitoring sites in Minnesota.

The lead background concentration was obtained from MPCA’s 2011 Annual Air Monitoring

Network Plan, page 26, indicating the majority of sites in Minnesota have monitored lead

concentrations below 0.01 ug/m3. Figure 16 from this monitoring network plan shows that the

nearby 2727 10th Ave S., Chase Anderson School monitoring site (No. 963) has concentrations at

this level.


4-2

To minimize run times for the project, a multi-CPU processor computer was used for this

analysis. Lakes Environmental has developed a version of AERMOD that is designed to

minimize run times on multi-CPU processor computers that are now commonly available. The

version is called AERMOD MPI. The modeling completed in this analysis utilized Lakes

Environmental’s AERMOD MPI executable. AERMOD MPI reduced the run-times for this

analysis by approximately eight-fold.

In past projects approved by MPCA, Wenck completed a comparison of the design

concentrations using the US EPA SCRAM AERMOD version 09292 and Lakes Environmental’s

AERMOD MPI. The demonstration showed that the results were identical using both versions.

Therefore, Wenck believes it is valid to rely upon Lakes Environmental’s AERMOD MPI

executable for this modeling demonstration.

The modeling shows that the HLRV O&M and LRS facilities meet all ambient air quality

standards both at and beyond the facilities property lines. The site meets most SILs with the

exception of the interim NO2 1-hour SIL and the final PM2.5 24-hour SIL. Isopleth contour

figures are included, showing the areas with predicted concentrations above the SILs. The larger

of the two areas, the NO2 impact area, is being addressed in the cumulative impacts analysis.

EPA sets the NAAQS to be protective of human health. EPA reviewed the NO2 and PM2.5

NAAQS in 2010 and 2006, respectively. Therefore, the scientific background data used by EPA

for the NAAQS health risk assessments is expected to be up-to-date. The SILs are not based on

health risk criteria but are typically used to demonstrate a source does not have culpability

towards a high concentration, or that a full air quality analysis is not required. The SILs are

applied to the Metro Transit facility to identify the area that will be discussed in the cumulative

impacts analysis.

Table 4-1.

Estimated Criteria Pollutant Ambient Air Concentrations

Pollutant Averaging Period and High Selected

HLRV and LRS

Modeled Concentration

(g/m3)

PSD Significant

Impact Level

(g/m3)

Background Concentration

(g/m3)

Estimated Ambient Air

Concentration (g/m3)

National Ambient Air

Quality Standard (g/m3)

Minnesota Ambient Air

Quality Standard (g/m3)

24-Hour, 1st High 3.8 1.2 26 30 35 --- PM2.5

Annual, High 0.2 0.3 10 10 15 ---

24-Hour, 1st High 3.8 5 60 64 150 150 PM10 Annual, High 0.2 1 23 23 --- 50

CO 1-Hour, 1st High 65.5 2000 3,565 3,631 40,000 35,000 8-Hour, 1st High 39.1 500 2,760 2,799 10,000 10,000

1-Hour, 1st High 0.5 7.8 110 111 --- 1,300 3-Hour, 1st High 0.4 25 86 86 1,300 915 24-Hour, 1st High 0.2 5 34 34 365 365

SO2

Annual, High 1 0.03 1 5 5 80 60 Lead 3-Month Average

(rolling), High Month Identified

0.00003 --- 0.01 0.01 0.15 1.5

NO2/NOx 2 1-Hour, 1st High 58.5 7.5 83 141.5 189 ---

Annual, High 0.8 1 17 18 100 100 1 Separate model runs including proposed annual throughput limits were not completed for SO2 since the estimated annual concentrations for this pollutant is below the applicable significant impact level or ambient air quality standard. Including annual limits would reduce predicted annual average concentrations. 2 For the 1-hour NO2 analysis, the 40 CFR 51 Appendix W NO2/NOx fraction of 0.75 was used to estimate the fraction of NOx in the form of NO2 in the ambient air. For the annual NO2 analysis, all NOx emissions were assumed to form NO2 in the ambient air.

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Contours are in units of g/m3. The NO2 1-Hour Interim Significant Impact Level (SIL) of 7.5 g/m3 is shown in bold. Metro Transit Wenck Associates, Inc.


November 2010

NO2 1-Hour Average High Modeled Concentrations Figure 4-1 T:\0141\89\tech\Phase 3 - Modeling\Expansion Modeling\Criteria Pollutant Report Figures and Tables.doc

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January 2011

Contours are in units of g/m3. The PM2.5 24-Hour Average Significant Impact Level (SIL) of 1.2 g/m3 is shown in bold. Metro Transit Wenck Associates, Inc.


Nov. 2010

PM2.5 24-Hour Average High Modeled Concentrations Figure 4-2 T:\0141\89\tech\Phase 3 - Modeling\Expansion Modeling\Criteria Pollutant Report Figures and Tables.doc

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January 2011

Appendix A

Electronic Dispersion Modeling Files

(CD-ROM)

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