saint paul, mn 55155-4194(ncore) monitoring stations by january 1, 2011. pending the final...

Minnesota Pollution Control Agency 520 Lafayette Road North Saint Paul, MN 55155-4194

http://www.pca.state.mn.us 651-296-6300 or 800-657-3864 toll free

TTY 651-282-5332 or 800-657-3864 toll free Available in alternative formats

Authors and Contributors Cassie McMahon

Melissa Sheffer

Kellie Gavin

Rick Strassman

Editing and Graphics

Peggy Hicks

Mark Schifsky

Jennifer Holstad

aq10-04

The MPCA is reducing printing and mailing costs by using the Internet to distribute reports and information to a

wider audience. For additional information, see the Web site: http://www.pca.state.mn.us/air/monitoringnetwork.htm

2011 Source-oriented Lead Monitoring Plan Minnesota Pollution Control Agency

for Minnesota • May 2010 i

Table of Contents

Document History ......................................................................................................................................... i

List of Tables ................................................................................................................................................. ii

List of Figures ................................................................................................................................................ ii

Acronyms, Abbreviations, and Definitions.................................................................................................... iii

Background .................................................................................................................................................... 1

Non-source Oriented Lead Monitoring .......................................................................................................... 2

Identifying Facilities Requiring Source-oriented Monitoring ........................................................................ 2

Air Dispersion Modeling Methodology ......................................................................................................... 4

Air Dispersion Modeling Results ................................................................................................................... 4

Facility Specific Modeling Results and Monitor Siting ................................................................................ 4

Gopher Resource Corporation ................................................................................................................ 5

Grede Foundries, St. Cloud Inc. .............................................................................................................. 8

Federal Cartridge Company-Anoka ........................................................................................................ 11

Dotson Company Inc. ............................................................................................................................. 14

US Steel Corporation, Minntac ............................................................................................................... 17

Summary of Public Comments ............................................................................................................... 20

Document History

The 2010 Source-oriented Lead Monitoring Plan for Minnesota, as required by the 2009 National Ambient Air

Quality Standard revision for lead, was first released for public review and comment in October 2009.

Following the release of the 2010 plan, the Environmental Protection Agency (EPA) proposed revisions to the

ambient monitoring requirements for airborne lead. Published in the Federal Register on December 30, 2009,

EPA’s proposed revisions affect both the source-oriented lead monitoring network, which began operations on

January 1, 2010, and the population based monitoring network, which is required to begin operations on

January 1, 2011. The text of the proposed changes to the lead ambient monitoring requirements can be found

on the EPA’s website at: http://www.epa.gov/air/lead/fr/20091230.pdf

This document, which will serve as the 2011 Lead Monitoring Plan for Minnesota, updates the information

included in the 2010 Lead Monitoring Plan to reflect the proposed changes to the ambient monitoring

requirements. In addition, this document provides status updates on the source-oriented monitors that began

operations on January 1, 2010.

http://www.epa.gov/air/lead/fr/20091230.pdf

List of Tables

1. EPA identified facilities potentially requiring source-oriented monitoring. .............................................. 3

2. Adjusted lead emissions estimates for facilities potentially requiring source-oriented monitoring........... 3

3. Modeled source impacts ............................................................................................................................ 4

List of Figures

1. Gopher Resource Corporation aerial view ................................................................................................. 5

2. Modeled maximum monthly average lead concentration contours for Gopher Resources........................ 6

3. Directional photos of land use around MPCA 465 at Gopher Resources .................................................. 7

4. Grede, St. Cloud Inc. aerial view ............................................................................................................... 8

5. Modeled maximum monthly average lead concentration contours for Grede, St. Cloud Inc. ................... 9

6. Directional photos of land use surrounding the monitoring site at Grede, St. Cloud Inc. ......................... 10

7. Federal Cartridge Company-Anoka aerial view ........................................................................................ 11

8. Modeled maximum monthly average lead concentration contours for Federal Cartridge ......................... 12

9. Close up of modeled maximum monthly average lead concentration contours at Federal Cartridge ........ 13

10. Bird-eye view of monitoring site at Federal Cartridge ............................................................................ 13

11. Dotson Company, Inc. aerial view ........................................................................................................... 14

12. Modeled maximum monthly average lead concentration contours for Dotson Company, Inc. based on

AP-42 emission factors .................................................................................................................................. 15

13. Modeled maximum monthly average lead concentration contours for Dotson Company, Inc. based on

October 2009 stack test results ...................................................................................................................... 16

14. US Steel Corp., Minntac processing facility aerial view ......................................................................... 17

15. US Steel Corp., Minntac ambient air boundary ....................................................................................... 18

16. Modeled maximum monthly average lead concentration contours for US Steel Corp., Minntac ............ 19


for Minnesota • May 2010 iii

Acronyms, Abbreviations, and Definitions

AERMOD – Air dispersion modeling tool

AMS/EPA – Advanced Monitoring Systems for the Environmental Protection Agency

AP-42 - a compilation of air pollution emission factors

AQS – Air Quality System: EPA's repository of ambient air quality data

ATEI – Air Toxics Emissions Inventory

CAA – Clean Air Act

CBSA – Core Based Statistical Area

CFR – Code of Federal Regulations

Criteria Pollutants – the six pollutants regulated by the 1970 Clean Air Act (particulate matter, ozone, nitrogen

dioxide, sulfur dioxide, carbon monoxide, and lead)

EPA – Environmental Protection Agency

FEM – Federal Equivalent Method

FRM – Federal Reference Method

HAPs – hazardous air pollutants

MPCA – Minnesota Pollution Control Agency

MSA – Metropolitan Statistical Area

NAAQS – National Ambient Air Quality Standard

NEI – National Emissions Inventory

NESHAPS – National Emissions Standards for Hazardous Air Pollutants

NSR – new source review

NOX – nitrogen oxides

Pb – lead

PM – particulate matter

PTE – potential to emit

SLAMS – State and Local Air Monitoring Stations

tpy – tons per year

TRI- Toxic Release Inventory

TSP – total suspended particulate matter

VOC – volatile organic compound


for Minnesota • May 2010 1

Background

Lead is a metal found naturally in the environment as well as in manufactured products. Since lead was phased

out of gasoline, air emissions and ambient air concentrations have decreased dramatically. Currently, metals

processing facilities (lead and other metals smelters) and leaded aviation fuel are the primary sources of lead

emissions.

Lead emitted into the air can be inhaled directly or ingested after it settles onto surfaces or soils. Exposure to

lead can cause damage to organs such as the kidneys and liver; it also may lead to high blood pressure and

increased heart disease. In addition, lead exposure may contribute to osteoporosis and reproductive disorders.

Even at low concentrations exposure to lead can cause brain and nerve damage to fetuses and young children.

Elevated lead levels are also detrimental to animals and to the environment. Wild and domestic animals

experience the same adverse effects as people exposed to lead. Elevated levels of lead in the water can cause

reproductive damage in some aquatic life and cause blood and neurological changes in fish.

In 1978, to ensure public health protection from the adverse effects of lead in the ambient air, the

Environmental Protection Agency (EPA) established the first lead National Ambient Air Quality Standard

(NAAQS) at 1.5µg/m3. From 1980 to 2007, reductions in lead emissions, primarily from the elimination of

lead in gasoline, resulted in more than a 90% reduction in ambient lead concentrations nationally. However,

recent scientific studies indicate that even exposure to low levels of lead can cause adverse health and

environmental effects. As a result, in October 2008, EPA announced a ten-fold tightening of the lead standard

to 0.15 µg/m3.

Nationally, as the average concentration of lead in the ambient air fell well below the 1978 standard of 1.5

µg/m3, monitoring agencies were encouraged to reduce the number of lead monitors in their networks. In light

of the 2008 revision, the current national lead monitoring network is not sufficient to determine whether many

areas of the country meet the newly tightened standard. To ensure public health protection, the EPA expanded

the existing lead monitoring network by requiring monitoring near sources with lead emissions equal to or

greater than one ton per year (tpy) by January 1, 2010, and in urban areas with more than 500,000 people by

January 1, 2011.

On December 23, 2009, the EPA announced proposed revisions to the ambient monitoring

requirements for lead. If finalized, these proposed revisions will lower the emissions threshold for required source-oriented lead monitoring from 1.0 tpy to 0.50 tpy. Additionally, the population based

monitoring requirement will be replaced with a requirement that lead monitors be placed at all National Core (NCore) monitoring sites. The EPA took comment on these proposed revisions in early

2010 and a final rule is expected this fall.



Non-source Oriented Lead Monitoring

The final lead rule requires a minimum of one non-source oriented (population based) lead monitor in any

Core Based Statistical Area (CBSA) with a population greater than or equal to 500,000. These population

based monitors must be located to measure neighborhood scale lead concentrations in urban areas impacted by

re-entrained dust from roadways, closed industrial sources - which previously were significant sources of lead

(Pb), hazardous waste sites, construction and demolition projects, or other fugitive dust sources of lead. Non-

source oriented lead monitors must be operational by January 1, 2011.

Minneapolis-St. Paul, with a 2007 U.S. Census population estimate of 3,538,781, is the only CBSA in

Minnesota with a population greater than 500,000. The Minnesota Pollution Control Agency (MPCA)

currently monitors for lead at eleven sites throughout the Twin Cities metropolitan area, six of which measure

at neighborhood scale. For this reason, the MPCA does not anticipate siting an additional non-source oriented

lead monitor as a result of this rule. For a description of these existing lead monitoring sites, see the 2010 Air

Monitoring Network Plan for Minnesota at: http://www.pca.state.mn.us/air/monitoringnetwork.html.

Identifying Facilities Requiring Source-oriented Monitoring

At a minimum, the final lead rule requires source-oriented monitoring at facilities which emit more than 1.0

tpy of lead, based on either the most recent National Emissions Inventory (NEI) or other scientifically

justifiable methods and data (such as improved emissions factors or site-specific data). However, modeling and

monitoring data indicates that facilities which emit less than 1.0 tpy of lead may still exceed the revised lead

NAAQS of 0.15 µg/m3. Therefore, the MPCA proposes locating source-oriented lead monitors at facilities

with lead emissions equal to or greater than 0.70 tpy, unless modeling results indicate ambient lead

concentrations at the facility’s fence line are less than one-half the NAAQS, or 0.075 µg/m3. Table 1

summarizes the facilities identified by the EPA for Source-oriented monitoring in Minnesota based on

emissions estimates from the NEI and the national Toxics Release Inventory (TRI).

The proposed revisions to the lead monitoring requirements eliminate the population-based lead

monitoring network, and replace it with a requirement that lead monitors be placed at all National Core

(NCore) monitoring stations by January 1, 2011. Pending the final monitoring rule, which is expected to be released in fall 2010, the MPCA intends to include lead monitoring at its existing NCore monitoring

station in Blaine. Additional information on the MPCA’s NCore station is available in Appendix B of the 2010 Air Monitoring Plan for Minnesota at: http://www.pca.state.mn.us/air/monitoringnetwork.html

If finalized, the proposed revisions to the source-oriented lead monitoring network will lower the emissions threshold for source-oriented ambient lead monitoring from 1.0 tpy to 0.5 tpy. During the initial review of

facilities requiring source-oriented lead monitoring, the MPCA considered and modeled all facilities which emitted more than 0.7 tpy based on the 2006, 2007 and 2008 State Emissions Inventories. While the proposed

rule requires monitoring at facilities which emit more than 0.5 tpy, the State Emissions Inventory does not

indicate that any additional facilities would be included in this analysis based on the revised threshold. Therefore, the MPCA does not anticipate any additional facilities will require source-oriented lead monitoring

as a result of this proposed revision.



Table 1: EPA identified facilities potentially requiring source-oriented monitoring

Facility City County

Emissions Estimates (tpy)

NEI TRI

02 05 04 05 06

Federal Cartridge Anoka Anoka 0.1 0.9 - 0.0 0.0

Dotson Company Inc Mankato Blue Earth 0.4 0.6 0.0 0.0 0.0

NSP dba Xcel Energy Mankato Blue Earth 4.3 4.3 - - -

Gopher Resource Corporation Eagan Dakota 3.7 3.2 1.3 2.0 0.7

Fergus Falls Resource Recovery Fergus Falls Otter Tail 3.7 3.7 - - -

US Steel Corporation, MinnTac Mountain Iron

St. Louis 2.4 2.5 - - -

Grede Foundries – St. Cloud Inc.

St. Cloud Stearns 0.4 0.8 - 0.0 0.0

Due to inconsistencies with TRI and NEI emissions estimates, the MPCA Emission Inventory staff reviewed

both the annual criteria emission inventory and the triennial Air Toxic Emission Inventory (ATEI) and

compiled a revised list of facilities potentially requiring monitoring. The list consists of facilities that emitted

near or more than 0.5 tpy of lead within a 3-year period: 2005, 2006 and 2007. Many of the facilities used

default AP-42 emission factors to calculate their lead emissions on the annual criteria emission inventories, but

provided different information to the 2005 ATEI. To ensure accurate emissions reporting, the MPCA

Emissions Inventory staff sent a letter to the listed facilities to request their review of lead emissions for the

2005, 2006 and 2007 inventory years. The Emissions Inventory staff worked closely with responding facilities

and guided them to report site-specific information. As a result, the state list of facilities with more than 0.5 tpy

lead was updated and submitted to the EPA for approval. Table 2 summarizes changes to emissions estimates

for the EPA identified facilities potentially requiring source-oriented monitoring.

Table 2: Adjusted lead emissions estimates for facilities potentially requiring source-oriented monitoring

Facility State Emissions Inventory (tpy) Comments

2005 2006 2007 Federal Cartridge 0.9 0.9 0.9 Reported 0.94 tpy to ATEI

Dotson Company Inc 0.6 0.7 0.7 No change1

NSP dba Xcel Energy 0.0 0.0 0.0 Unit error in NEI emissions (lbs to tons)

Gopher Resource Corporation 1.9 0.6 0.6 Stack test completed in 2006

Fergus Falls Resource Recovery 0.0 - - Facility closed in 2006

US Steel Corporation, Minntac 0.9 0.9 0.8 Stack test completed in 2007

Grede Foundries – St. Cloud Inc. 1.5 1.5 0.8 Changed to partial mass balance in 2007

1 In October 2009, Dotson Company completed stack testing to refine their annual lead emissions. Based on the

results of these tests, the estimated lead emissions at this facility are now 0.03 tpy. This change will be reflected in

the 2009 State Emissions Inventory.



Air Dispersion Modeling Methodology

Air dispersion modeling was performed to estimate the ambient lead concentrations for the five sources

identified in Table 2: Federal Cartridge, Grede Foundries - St. Cloud Incorporated, Gopher Resource

Corporation, Dotson Company Incorporated, and US Steel Corporation, Minntac. The MPCA used EPA’s

AMS/EPA Regulatory Model (AERMOD) version 07026 for this modeling analysis. Sources were modeled

with five years of meteorology and all sources, except Gopher Resources, were based on maximum hourly

potential emissions (lb/hr). Potential emissions (PTE’s) were chosen to provide the most conservative results

in determining whether a source oriented monitor would be required. Modeling for Gopher Resources was

based on actual and estimated actual emissions. These were provided by Gopher Resources and their

consultants at ENVIRON, and were approved by MPCA staff.

An ambient background concentration was derived from EPA’s AirData – Monitoring Values web site and

added to the modeled impacts to determine if the total impacts would be greater than or less than 50 percent of

the new NAAQS for lead. EPA’s LEADPOST version 09041 was used to take the monthly averages from

AERMOD and calculate the rolling three month averages for each source.

Elevated terrain was used for all the sources modeled and receptors were placed around each sources’ ambient

air boundary. A 5 km radius polar receptor grid was used for Federal Cartridge, Grede Foundries-St. Cloud

Incorporated, and Dotson Company Incorporated while a 15 km radius polar receptor grid was used for US

Steel Corporation, Minntac. This much larger grid used for Minntac was due to the expansive size of the

source’s property and ambient air boundary. Gopher Resources used a 6 km by 6 km Cartesian receptor grid.

Air Dispersion Modeling Results

Results from the air dispersion modeling for the five sources requiring modeling are summarized in Table 3.

Each source’s impact has been compared to 50 percent or greater (0.075 μg/m3 or greater) of the new lead

NAAQS to determine if ambient lead monitoring is required at the facility. If the total impacts are 50 percent

or lower than the new lead NAAQS ambient lead monitoring is not required.

Table 3: Modeled source impacts

Source Name Max. 3-Month

Rolling Average (μg/m

3)

Background Concentration

(μg/m3)

Total NAAQS Impact (μg/m

3)

Is Total Impact > 50% of NAAQS?

Gopher Resources 0.778 0.01 0.788 Yes

Federal Cartridge 100.573 0.01 100.583 Yes

Grede – St. Cloud 0.646 0.01 0.656 Yes

Dotson (AP-42) 3.418 0.01 3.428 Yes

Dotson (stack test) 0.099 0.01 0.109 Yes2

US Steel - Minntac 0.000 0.01 0.010 No

As shown by Table 3, four of the five modeled sources show a potential maximum ambient impact greater than

50% of the NAAQS. The expected ambient concentrations near US Steel-Minntac are less than 50% of the

NAAQS. Because Minntac’s annual lead emissions are less than the 1.0 tpy monitoring threshold established

in the 2008 lead rule, a waiver for monitoring is not required.

Facility Specific Modeling Results and Monitor Siting

The following pages include a detailed description of modeling results for each facility and monitor siting

information for Gopher Resources, Federal Cartridge, and Grede Foundries – St. Cloud Incorporated.

2 While the modeled maximum ambient impact at Dotson Company is more than one-half the NAAQS, the MPCA

intends to file a monitoring waiver for this location. Additional information is available on page 11 of this

document.



Eagan - Gopher Resource Corporation

Site Information: AQS Site ID: 27-037-0465

MPCA Site ID: 465

Address: Yankee Doodle Rd & Hwy 149

City: Eagan

County: Dakota

Location Setting: Suburban

Latitude: 44.834306

Longitude: -94.225833

Year Established: 2006

Annual Lead Emissions Estimates (tpy):

2005 2006 2007

1.9 0.6 0.6

Facility Description: Gopher Resource Corporation is a lead recycling, smelting and refining facility located in Dakota County near

the northwest corner of State Highway 149 and Yankee Doodle Road. Lead monitoring has occurred near this

facility since 1989, and the area was previously designated nonattainment for the 1978 lead standard in January

1992. The nonattainment area, which encompassed a 4.5 square mile area around the facility, was redesignated

as a maintenance area in December 2004. Based on 2006-2008 data from the existing monitor (MPCA 465)

which is approximately 100 meters east of the facility, it is expected that the area surrounding Gopher

Resources Corporation will be designated nonattainment for the 2008 lead NAAQS.

Figure 1: Gopher Resource Corporation aerial view

MPCA 465



Modeling results and monitor siting:

Gopher Resources is located on the corner of Dodd Road and Yankee Doodle Road in Eagan, MN. Fourteen

point sources were modeled at Gopher Resources, which includes their main stack, a torit stack, a scrubber

stack, nine refinery stacks and two exhaust fans. Also modeled were 111 volume sources, which capture

traffic-related dust emissions, furnace fugitives and afterburner gaps, and slag bin emissions. Based on

modeling results, Source-oriented monitoring is required at the facility.

Lead has been monitored near Gopher Resources since 1989. The current monitoring location (MPCA 465) is

located approximately 100 meters east of the facility (44.834603°N, 93.116049°W). Lead concentrations at

this monitor from 2006-2008 indicate that ambient lead concentrations near the facility exceed the revised lead

NAAQS, with a design value of 0.697 µg/m3. Due to the pending nonattainment designation for the existing

monitor, the MPCA intends to maintain the existing monitoring location.

Figure 2 describes the modeled monthly average lead concentration contours near Gopher Resources. The

point of maximum ambient concentration is located directly south of the facility near the shoulder of the west

bound lane of Yankee Doodle Road. Due to the proximity of Yankee Doodle Road (a 4-lane highway) and

other nearby obstructions, monitoring near the point of modeled maximum concentration is not logistically

feasible. At this time the MPCA does not anticipate siting a second lead monitor near the facility. However,

should the EPA require the addition of a second monitor, or a relocation of the existing monitor, the MPCA

will further explore monitoring options in this area.

Figure 2: Modeled maximum monthly average lead concentration contours for Gopher Resources

Maximum Impact: 0.778 μg/m3



Figure 3: Directional photos of land use around MPCA 465 at Gopher Resources

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St. Cloud – Grede Foundries, St. Cloud Inc.


MPCA Site ID: 3053

Address: 5200 Foundry Circle

City: St. Cloud

County: Stearns


Latitude: 45.5646

Longitude: -94.2263



2005 2006 2007

1.5 1.5 0.8

Facility Description: Grede Foundries, St. Cloud Incorporated is a ductile iron foundry located northwest of County Roads 15 and

23 in Stearns County. Prior to 1995 the facility operated as a steel foundry, but has since been converted to

produce ductile iron castings for automotive, farm equipment, construction, light construction and other

industries. In general the major emissions from foundries are Particulate Matter (PM) and Volatile Organic

Chemicals (VOC). PM is generated from virtually all of the operations at the foundry. Every particulate

emitting source at the facility is controlled by a baghouse. Most emission units are totally enclosed and it has

been assumed that 100 percent of the particulate emissions go through a baghouse. The exceptions are the

scrap and charge handling area, the induction furnaces and the original BMD pouring area.

Figure 4: Grede, St. Cloud Inc. aerial view




Grede Foundries, St. Cloud Incorporated has two emission units, coreless induction furnaces, which emit lead to a

shared stack with a height of 53 feet. For modeling, this stack was represented by a point source located on the

southwest side of Grede’s main building. Stack vent parameters in the modeling were taken from information on file

with the MPCA and the stack location was provided by Grede. Modeling results indicate that ambient lead

concentrations may exceed the revised lead NAAQS, with a potential maximum impact of 0.646 µg/m3. As a result,

Source-oriented lead monitoring is required at the facility.

The modeled point of maximum ambient concentration is located on a non-fenced area of Grede’s property directly

west of the primary employee parking lot. The MPCA has sited a new lead monitor just west of this area along the

facility’s property boundary at coordinates 45.564637°N, 94.226345°W. Due to siting requirements (distance from

obstructions) and logistics (access to power), the monitoring site is approximately 35 meters west of the modeled point

of maximum impact. Modeled lead concentrations in the monitoring location also indicate the potential to exceed the

revised lead NAAQS, therefore the MPCA believes this location will accurately reflect the impact of lead emissions

from the facility.

Figure 5: Modeled maximum monthly average lead concentration contours for Grede, St. Cloud Inc.




Figure 6: Directional photos of land use surrounding the monitoring site at Grede, St. Cloud Inc.

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* Note: These images were taken from the point of maximum impact. The monitoring site is located south west of this

vantage point.



Anoka – Federal Cartridge Company - Anoka


MPCA Site ID: 6020

Address: 900 Ehlen Dr

City: Anoka

County: Anoka


Latitude: 45.198083




2005 2006 2007

0.9 0.9 0.9

Facility Description: Federal Cartridge Company-Anoka is a manufacturer of small arms, shotgun, rimfire and centerfire

ammunitions. The 175 acre facility is located southeast of Highway 10 and 169 in Anoka County. The

facility’s air quality permit limits the NOx and Hazardous Air Pollutants (HAPs) emissions such that the

facility is classified as a non-major source under federal New Source Review (NSR, 40 CFR § 52.21), under

federal Operating Program (40 CFR pt. 70) and an area source under the National Emissions Standards for

Hazardous Air Pollutants (NESHAPs, 40 CFR pt. 63).

Figure 7: Federal Cartridge Company-Anoka aerial view




According to the most recent emissions inventory (2007), Federal Cartridge emits lead from only one source,

the rimfire ballistics alley. However, on December 28, 2007, Federal Cartridge received a state permit which

authorized the emitting of lead from 23 additional emission units. At the time of this modeling analysis, there

were no actual emissions data on these new sources and there were some discrepancies with the actual

emissions given for the rimfire ballistics alley. Therefore, maximum hourly potential emissions (from air

permit #00300156-003) were used for all sources modeled at this facility.

In the modeling analysis there were 23 point sources and one area source, with about half of the stacks being

capped stacks. The area source is a scrap propellant burn pad that has a roof, but is open to the air on all sides.

The point sources consisted of rimfire alleys, ballistics alleys, pistol function tanks, melt pot exhaust, rimfire

hoods, shotshell ballistics alleys, centerfire ballistics alleys, a deactivator baghouse, and a scrap ammunition

deactivator. Stack vent locations were provided by Federal Cartridge. Ten of the stack vents were capped,

which were accounted for in the model by setting the exit velocity to 0.001 m/s. This was done in accordance

with the AERMOD Implementation Guide revised on March 19, 2009, from the EPA, section 6.1 – Capped

and Horizontal Stacks.

Figures 8 and 9 summarize the modeled maximum monthly averaged lead concentration contours for Federal

Cartridge. The area of maximum impact is located southwest of the facility, on the fence line between Federal

Cartridge and neighboring Hoffman Enclosures’ parking lot. The MPCA has sited a lead monitor on the

Hoffman Enclosures’ side of the shared fence-line at coordinates 45.198083°N, 93.370916°W. Figure 10

provides a birds-eye view of the monitoring location.

Figure 8: Modeled maximum monthly average lead concentration contours for Federal Cartridge




Figure 9: Close up of modeled maximum monthly average lead concentration contours at Federal Cartridge

Figure 10: Birds-eye view of monitoring site at Federal Cartridge

Monitoring Site



Mankato – Dotson Company, Inc.

Facility Information: Address: 200 W Rock St

City: Mankato

County: Blue Earth

Latitude: 44.175032



2005 2006 2007 Stack Test

(2009)

0.6 0.7 0.7 0.0

Facility Description: Dotson Company operates a gray and ductile iron foundry located in the city of Mankato in Blue Earth

County. The facility is a secondary metal production plant subject to the 100 tpy New Source Review (NSR)

major source threshold. Steel scrap, foundry returns, and pig iron are used as input to two electric induction

furnaces. Molten iron is poured into green sand molds at one of three turntables, and cooled on the associated

conveyor. Following shakeout, the castings are finished at one or more of several grinders, cut off saws, and

shot blast operations. Some of these operations are exhausted inside the building.

Figure 11: Dotson Company, Inc. aerial view




Dotson has two emissions units, electric induction furnaces, which emit to separate stacks. These stacks are 28

feet in height and are located on the southern side of Dotson’s building. Two model runs were completed for

Dotson Company. The first utilized annual emissions estimates based on generic AP-42 emission factors,

which found the expected concentration at the area of maximum impact to be 3.418 µg/m3.

Upon learning of the modeling results, the facility underwent stack testing to further refine their emissions

estimates. Based on the stack test results, annual lead emissions at the facility are 0.03 tpy. This emissions

level is below the threshold for required source-oriented lead monitoring. However, modeling was conducted

to assess the level of maximum impact near the facility. Modeling results indicate two areas of maximum

ambient impact, both located within unfenced areas of the facility’s property boundaries, with modeled

concentrations near 0.1 µg/m3. These results indicate that ambient concentrations around Dotson are expected

to meet the NAAQS, but may be greater than one-half the standard, which is the recommended modeled

concentration for consideration of a monitoring waiver.

Figures 12 and 13 summarize the modeled maximum monthly average lead concentration contours for the

facility based on AP-42 emissions factors and stack test results.

Figure 12: Modeled maximum monthly average lead concentration contours for Dotson Company, Inc. based on AP-42 emission factors




Figure 13: Modeled maximum monthly average lead concentration contours for Dotson Company, Inc. based on October 2009 stack test results

As shown in Figure 13, the modeled ambient concentrations are below one-half the NAAQS at the facility’s

property boundary line. Due to siting requirements and logistics (i.e. distance from obstructions, minimal

impact on the facility operations) the MPCA cannot locate a lead monitor in either area of maximum impact.

The nearest possible monitoring site is located just west of the facility along a former rail line. However,

ambient concentrations in this area are expected to be below one-half the NAAQS. For this reason, in addition

to the fact that facility’s annual lead emissions are now below the source-oriented lead monitoring

requirement, the MPCA does not intend to site a lead monitor near Dotson Company.


Local Impact: 0.098 μg/m3



Mountain Iron – US Steel Corporation, Minntac


2005 2006 2007

0.9 0.9 0.8

Facility Description: US Steel Corporation, Minntac is a taconite mining and processing facility on the Mesabi Range north of the

city of Mountain Iron in St. Louis County. Taconite is a rock bearing 15 to 30 percent magnetic iron. The ore

is mined in an open pit, and reduced in size by crushers until it reaches a powdery consistency. Iron oxide

concentrate is separated magnetically, while the remaining portion of the ore (tailings) is sent to a disposal

basin. Limestone and/or dolomite (fluxstone) is added with bentonite (binder) to the concentrate. The mixture

is formed into round “green balls” (unfired pellets) in a balling drum. Green balls are fed into an agglomerator

line consisting of a traveling grate and a rotary kiln. Pellets are hardened (induration), with the fluxstone

constituent calcined (calcination), in the kiln at high temperature. Leaving the kiln, pellets are cooled and

stored for transport to blast iron furnaces out of state. When operating at full capacity, Minntac produces 16.5

million tons of taconite annually.

Figure 14: US Steel Corp., Minntac processing facility aerial view



Figure 15: US Steel Corporation, Minntac ambient air boundary



Modeling results:

Modeling parameters and the maximum hourly potential emission rates used in this analysis were obtained from

Minntac’s most recent air permit (#13700005-005) from the MPCA. Stack parameter locations were unavailable for

this analysis. However, based on previous modeling reports and modeling at nearby facilities, a representative location

for the stacks was chosen. MPCA records identified 14 emission units, consisting of boilers and gas stacks, which emit

lead to 12 stacks. Based on guidance for merged parameters for multiple stacks from EPA’s “Screening Procedures for

Estimating the Air Quality Impact of Stationary Sources, Revised” (October 1992), Minntac’s 12 stacks were merged

into four representative stacks. Stacks with similar stack heights, volumetric flow rates and stack gas exit temperatures

were merged into a single representative stack.

Figure 16 displays the modeled maximum monthly average lead concentration contours for US Steel Corporation,

Minntac. Based on these modeling results, the point of maximum impact is well below 0.075 ug/m3 monitoring

threshold. For this reason, the MPCA does not anticipate siting a Source-oriented lead monitor at Minntac.

Figure 16: Modeled maximum monthly average lead concentration contours for US Steel Corp., Minntac



Summary of Public Comments A previous version of this report was available for public comment in October, 2009. The MPCA did not receive any

public comments during the 30-day public comment period.

saint paul, mn 55155-4194(ncore) monitoring stations by january 1, 2011. pending the final...

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