CLIFFS 

TILDEN MINING COMPANY L.C. 

Managed by The Cleveland-Cliffs Iron Company 

PO Box 2000, Ishpeming, Ml 49849-0901 

P 906 475.3600 F 906.475 3777 cliffsnaturalresources.com 

May 25, 2012 

I{D) IE © IE 0 W IEfi)) 

!Ill MAY 2 9 2012 ~I A& 

8NJ Attn: Compliance Tracker, AE-171 

Air Enforcement and Compliance Assurance Branch 

U.S. Environmental Protection Agency 

Region 5 

77 W. Jackson Boulevard 

Chicago, Illinois 60604 

AIR ENFORCEMENT BRANCH 

U.S. EPA REGION 5 

Re: Tilden Mining Company, L.C. Response to Clean Air Act Section 114 Request to 

Provide Information Regarding Best Available Retrofit Technology (BART) 

Compliance 

This letter and the enclosed data disks are the response of Tilden Mining Company L.C. (referred 

to herein as "Tilden" or "we") to the "Request to Provide Information Requested Pursuant to the 

Clean Air Act" (the "Request"), regarding the iron ore processing facility located at 1 Tilden 

Mine Road, which we received on April 26, 2012. The Request required a response within 15 

days of receipt. Upon receipt of the Request, Tilden requested separate response dates for 

Questions 1-16 and Questions 17-25 to enable the facility to most effectively respond to the 

Request. Separate response dates were approved by Molly DeSalle and the response date for 

Questions 1-16 was set for May 25, 2012. Tilden hereby provides this timely response to the 

Request, with the understandings and clarifications noted herein. 

Tilden has given careful consideration to this Request and each of its questions to ensure that its 

response is accurate and properly tailored to the information EPA has requested. Most of the 

information requested is public information that has been submitted previously to a regulatory 

agency, so Tilden is not requesting that any portion of this response be considered Confidential 

Business Information. 

This response restates each of the questions in the Request and provides a narrative explanation 

of the responsive information. Responsive documents are referenced in the narrative and 

included on the data disks enclosed with this letter. The disks are organized by numbered folders 

that correspond to the questions below. Each disk is labeled with the company name, folders 

contained on that disk, and the date of response. Documents responsive to multiple questions are 

identified in the narrative response to each question, and are included on the disks under the 

question to which the documents are most responsive. The documents provided have been 

scanned for viruses using McAfee software. If you have any questions or concerns about the 
information provided, please direct your questions to Tilden's counsel, Douglas McWilliams, at 

Douglas.McWilliams@squiresanders.com. 

1. Provide process flow diagrams for both the taconite iron ore mining and the taconite 

pellet manufacturing processes. Include in the description, at a minimum, information on 

the following: mining operations, ore transfer and storage, coarse ore crushing, fine ore 

crushing, ore classification screens, ore storage bins, grinding rod/ball mills, separation, 

thickeners, balling drums/pellet formation, indurating furnace, pellet cooling and storage, 

and the process boilers. Include a detailed narrative process description and photographs 

to explain the indurating furnace process (separately for each furnace). For each 

photograph, provide a coded diagram/map to clearly identifY the location of the image in 

the photograph. Photographs must correspond to each of the process stages described. 

Responsive documents are included in Folder 1: 

• Document 1-1 contains process flow diagrams depicting the processing of magnetite 

and hematite and the pellet production process. 

Iron ore mining operations include the removal of overburden material, removal of 

waste rock material, and mining of ore. The ore is loaded onto trucks, hauled to the 

primary crusher, crushed and conveyed to the Crude Ore Bam. A tripper conveyor 

system in the peak of the bam distributes the ore among 11 Primary Grinding Mills. 

A twelfth mill is used to grind the limestone required for producing flux pellets. Ore 

from the ore bam is ground by 11 autogenous primary mills and then proceeds 

through pebble mills. 

Magnetic separators are used during magnetite production to remove magnetite ore 

from the tailings. The hematite process uses a series of thickening and flotation steps 

to separate the iron particles from the tailings. Processes performed in the 

concentrator are wet operations, and several small wet scrubbers are used to control 

dust generated at concentrate conveyor transfer points. Tailings are pumped in a 

slurry form to the tailings basin. Concentrate is dewatered using steam filtration, 

steam is required to reduce the viscosity of the intergranular water and attain proper 

moisture content. Tilden operates three natural gas-fired process boilers to provide 

steam for production processes such as filtering and chemical processing, in addition 

to comfort heating and domestic hot water. After filtration the concentrate is 

conveyed to the dryers and the concentrate bins on the balling floor. 

Green pellets are produced in balling drums and conveyed to one of two AllisChalmers grate-kiln systems, described in greater detail below. Emissions from each 

grate-kiln are controlled by 3 dry electrostatic precipitators. Fired pellets are 

conveyed to the pellet stock pile or railroad loadout bin for direct loading into rail 

cars. Once loaded into rail cars pellets are transported from the facility. 

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• Document 1-2 contains a schematic drawing of the indurating furnace. This 

schematic is being provided in lieu of photographs because Tilden does not possess 

current photographs of the indurating furnaces that would be useful in this context. 

Both furnaces are of the same design and therefore the diagram and description below 

are equally applicable to both Line 1 and Line 2. Only Line 1 is subject to BART, 

and therefore the process description below includes the dimensions for the Line 1 

furnace. The schematic includes labeling identifying the processes described below. 

As stated above, the Tilden Mine owns and operates two Allis-Chalmers grate-kiln 

systems. Each unit consists of a three pass traveling grate, rotary kiln, and annular 

cooler. The traveling grate is a metal casting conveyor which is subdivided into 3.5 

bays of updraft drying, 7.5 bays of downdraft drying and 8 bays of downdraft 

preheating for drying and preheating the green balls. The grate is 18'7" wide and 

210'8" long, and has three natural gas-fired preheat burners. A heat recuperation 

system is utilized. 

The grate empties into a refractory lined rotary kiln with a 25' inside shell diameter 

that is 160' long. Each kiln is equipped with two main burners, one for natural gas 

and one for coal. The kilns are supplied with diesel powered emergency drives. 

The pellets travel through the kiln into a refractory lined annular cooler (66' mean 

diameter x 10'2" W), which incorporates both primary and secondary heat 

recuperation. As the annulus cooler rotates, air is directed to heat recuperation ducts 

and is delivered to the drying zone of the grate. 

Incorporated in each unit are three dry electrostatic precipitators. Exhaust gases from 

downdraft drying are cleaned by two electrostatic precipitators. The exhaust gases 

from updraft are cleaned by a third electrostatic precipitator. 

Thomas O'Brien (Environmental Engineer) and Scott Rasmussen (Area Manager 

Metallurgical Processing) of Tilden Mining provided information for this response. 

2. For the time period January 1, 2010, to December 31, 2011, provide manufacturing 

specifications and operating data to demonstrate operating parameters for each of the 

facility's indurating furnaces and dryers. Operating parameters and data must include, at 

a minimum: flue gas composition, entrance air temperature, exit air temperature, preheat 

zone temperature, burner temperature, pellet residence time, and air flow rate. 

Responsive information is included in Folder 2, Document 2-1. Tilden does not have 

operating data for flue gas composition, entrance air temperature, burner temperature, air 

flow rate or residence time for the indurating furnaces for the requested time period. 

Residence time is estimated to be between 37-87 minutes from the time the pellets enter the 

grate to the time they exit the cooler. This estimate was derived by dividing the total length 

of the grate, kiln, and cooler by the expected low and high speeds for each device. Kiln 

speed was assumed to be the same as the grate speed in this estimate. The remaining 

requested data has been provided for the indurating furnaces. Burner temperature and outlet 

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temperature are included for the dryer. To the extent estimated normal operational 

parameters are available, these have also been included in Document 2-1. 

Thomas O'Brien (Environmental Engineer) and Jeremy Pletka (Senior Mineral Processing 

Engineer) of Tilden Mining provided information for this response. 

3. For the time period January 1, 2007, to December 31, 2011, provide records of the natural 

gas used by each specific indurating furnace and dryer at the facility. 

Monthly natural gas usage is included in Folder 3 as Document 3-1. 

Thomas O'Brien (Environmental Engineer) and Jeremy Pletka (Senior Mineral Processing 

Engineer) of Tilden Mining provided information for this response. 

4. For the time period January 1, 2007, to December 31, 2011, if coal was used as a fuel 

source at the facility, provide documentation of the average sulfur content for coal used 

by each specific indurating furnace and dryer at the facility. 

Sulfur data for coal used by the indurating furnaces is included in Folder 4 as Document 4-1. 

Tilden has composite monthly samples tested aud records the results in Excel format for 

reporting purposes. Coal is not tested separately for each indurating furnace. Coal is not 

combusted in the thermal dryer. 

Thomas O'Brien (Environmental Engineer) of Tilden Mining provided information for this 

response. 

5. For the time period January 1, 2005, to December 31, 2011, provide copies of all stack 

tests conducted on any emissions unit for any reason, and include all test runs, even if a 

full test series was not completed. IdentifY the emissions unit; specifY the date of the test, 

test method used, and the filter temperature during the time of the test, if applicable. 

Provide all calculations relative to the stack test, and provide copies of the full test report, 

including the section describing the process parameters and production or processing 

rates at the time of the test, as well as copies of any reports of visible emission 

observations conducted during each test. For each test during which the source was not 

operating at maximum design capacity, provide an explanation why production was 

limited. 

US EPA's request letter states that US EPA is "requesting information on the facility's 

furnaces, dryers, and other nitrogen oxide (NOx) and sulfur dioxide (S02) emitting units." 

Consistent with the scope of the request, Tilden is providing stack test information related to 

NOx and SOz emissions at the facility during this time. Tilden did not operate continuous 

opacity monitors at the time of testing and therefore does not have any independent opacity 

data for the test provided. 

A stack test report measuring S02 from the indurating furnaces in 2005 is included in Folder 

5 as Document 5-1. This test was run under normal operating conditions. 

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Thomas O'Brien (Enviromnental Engineer) of Tilden Mining provided information for this 

response. 

6. Provide an electronic Excel workbook with the complete nitrogen oxide (NO,J and sulfur 

dioxide (SOl) facility-wide potential to emit calculations. Include in the response a written 

description of how each column in the Excel workbook is generated. 

Tilden's potential to emit calculations for NOx and S02 are in Folder 6, Document 6-1. 

References are within the spreadsheet and give an explanation of how each calculation was 

conducted. The potential to emit calculations may change when BART limits for NOx and 

S02 become effective. PTE calculations do not include emissions from insignificant 

sources. 

Thomas O'Brien (Environmental Engineer) of Tilden Mining and Teresa Kinder (Barr 

Engineering) provided information for this response. 

7-9. Questions 7 through 9 request specific information related to the BART report submitted by 

Tilden in 2006 (hereinafter "Tilden BART Report"). The following information is provided 

as common background for Questions 7, 8, and 9 of the Request. Additional information 

specific to each Question is further included in each section as appropriate. 

As indicated in EPA's Section 114 Request, the Tilden BART Report was developed in 

2006 using control technology that was considered available and technically feasible at that 

time. In preparing the report, two guidance documents were relied on to establish the 

process and methodology. These were: 

• MPCA's "Guidance for Facilities Conducting a BART Analysis"; and 

• EPA's "Regional Haze Regulations and Guidelines for Best Available Retrofit 

Technology (BART) Determinations," 70 Fed. Reg. 39164, 39164-70 (July 6, 2005). 

EPA's "Regional Haze Regulations and Guidelines" document provided the five step BART 

review process, as supported by MPCA's "Guidance for Facilities Conducting a BART 

Analysis." In addition, Tilden's BART report followed the MPCA guidance document in 

considering the Taconite MACT to be equivalent to BART for particulate sources subject to 

both rules. These documents are included in Folder 7-9 _Background Documents. 

The Michigan Department of Environmental Quality did not provide state-specific BART 

guidance, but instead relied upon that published by the state of Minnesota. Although MPCA 

guidance and data on the taconite industry in Minnesota was considered for purposes of 

Tilden's BART report, Tilden's BART is a facility-specific evaluation and the BART 

determination is based on facility-specific considerations. 

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7. The facility's Best Available Retrofit Technology report ("BART report") discusses the 

low efficiency of the facility's wet scrubbers on the Line 1 dryer for S02• Provide all 

documentation, including reports and studies, to determine the current S02 efficiency of 

all water scrubbers at the facility. Additionally, provide all documents, including reports 

and studies, completed for the technical feasibility of efficiency upgrades for each 

scrubber. 

Documents regarding wet scrubber S02 removal efficiency are included in Folder 7. This 

folder includes documents specific to Tilden as well as documents on the taconite industry 

generally that informed the BART report. 

• Document 7-1 contains internal correspondence from Barr Engineering discussing 

potential costs and control potential of installing a second scrubber at Tilden. As 

explained in the Tilden BART Report, installation of a second scrubber at this unit is 

not cost effective and was not evaluated further. 

• Document 7-2 estimates potential S02 control efficiencies if a second scrubber was 

installed at Tilden. As explained in the Tilden BART Report, installation of a 

second scrubber at this unit is not cost effective and was not evaluated further. 

• Document 7-3 is an "Evaluation of Minnesota Taconite Wet Scrubbers at Minntac, 

Keetac, HibTac, and UTac" by John Engesser (Minnesota Department of Natural 

Resources). This report does not discuss Tilden's scrubbers specifically, but 

information on the S02 removal efficiency of scrubbers in the taconite industry 

generally was considered in preparing Tilden's BART Report. 

• Document 7-4 is a report prepared by Barr Engineering in 2003 for the Minnesota 

Pollution Control Agency entitled "Potential Impacts of the Federal Regional Haze 

and Best Available Retrofit Technology Rules on the Taconite Industry in 

Minnesota." This report discusses the potential removal efficiencies of wet 

scrubbers for the taconite industry beginning at pages 46 and 66. This report does 

not discuss Tilden's scrubbers specifically, but information on the S02 removal 

efficiency of scrubbers in the taconite industry generally was considered in preparing 

Tilden's BART Report. 

• Document 7-5 contains the BACT analysis performed for the Northshore facility's 

restart of Line 5. Information on the expected control efficiency of wet scrubbers is 

included on page A-5-17. This document does not discuss Tilden's scrubbers 

specifically, but information on S02 removal efficiency at other taconite facilities 

was considered in preparing Tilden's BART Report. 

George Pruchnofski, Beth Havlik, Jack Kennedy, Erik Boleman, and Teresa Kinder of Barr 

Engineering provided information for this response under the direction of Thomas O'Brien. 

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8. The BART report discusses the technical feasibly of low NOx burners, a variety of 

selective catalytic reduction (SCRs) systems and selective non-catalytic reduction (SNCRs) 

systems. Provide all documentation, including reports and studies, to determine the 

technical feasibility of low NOx burners, SCRs and SNCRs at the facility's Line 1 

indurating furnace and Line 1 dryer. 

Responsive documents are included in Folder 8: 

• Document 8-1 contains emails discussing the low-NOx burner retrofit recently 

completed by Dauieli-Corus at a straight-grate taconite induration furnace in the 

Netherlands. At the time of this email (2006), this technology was determined to be 

"not available" for taconite indurating furnaces because only one facility used the 

technology audit had not been sold outside of the compauy. 

• Document 8-2 contains emails between personnel from Barr Engineering, Tilden, 

and an equipment vendor discussing the option of low-NOx burners in the preheat 

section of the furnace at Tilden. Low NOx burners cannot be used in the indurating 

zone of the furnace because the reduced flame temperatures associated with low NOx 

burners would adversely affect product quality. 

• Document 8-3 contains an email from Teresa Kinder at Barr Engineering to Brent 

Ketzenberger and Tom O'Brien at Tilden explaining why SNCR technology is not 

technically feasible and how high temperatures reduce control efficiency for ultra 

low-NOx burner technology at taconite facilities. 

• Document 8-4 contains a Barr Engineering memorandum evaluating the technical 

feasibility of SNCR technology for an indurating furnace and concluding that the 

technology is not feasible due to high process temperatures aud chemical reactions 

with the taconite greenball. 

• Document 8-5 discusses the different control technologies that could be considered 

for a taconite facility aud potential difficulties unique to Tilden's equipment. 

• Document 8-6 is Tilden's response to MDEQ's request for additional information 

related to Tilden's BART Report from 2006. 

• Document 8-7 contains a 2010 Barr Engineering memoraudum to MDEQ 

recommending BART for the Tilden facility. 

• Documents 8-8a and 8-8b contain internal Barr Engineering emails discussing a 

recent SCR pilot study and potential problems for taconite facilities and an Excel 

spreadsheet summarizing data from the pilot study. This document does not discuss 

Tilden specifically, but information on this technology as it applies to taconite 

facilities was considered in preparing Tilden's BART Report. 

• Document 8-9 contains internal Barr Engineering emails discussing potential 

difficulties with applying RSCR technology to taconite facilities. This document 

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does not discuss Tilden specifically, but information on this technology as it applies 

to taconite facilities was considered in preparing Tilden's BART Report. 

Responsive information is also included in Folder 7, Document 7-4 and Document 7-5. 

These reports do not discuss Tilden's operations specifically, but information on the 

applicability of these technologies to the taconite industry generally was considered in 

preparing the BART report for Tilden. In Document 7-5, the information most relevant to 

low NO, burners, SCR and SNCR is located at pages 45-47 and 62-65. In Document 7-6, 

information most relevant to these technologies is located at pages A-5-26 to A-5-27 and A5-31 to A-5-33. 

George Pruchnofski, Beth Havlik, Jack Kennedy, Erik Boleman, and Teresa Kinder of Barr 

Engineering provided information for this response under the direction of Tom O'Brien. 

9. The BART report discusses the technical feasibly of induced flue gas technology. Provide 

all documentation, including reports and studies, to determine the technical feasibility of 

induced flue gas technology at the facility's Line 1 dryer. 

As provided on page 64 of Tilden's BART Report, process knowledge was used to 

determine that the configuration of the dryer and the operating parameters of the drying 

process were compatible with IFGR technology. This assessment was based on engineering 

judgment and did not rely on existing reports or studies. 

George Pruchnofski, Beth Havlik, Jack Kennedy, Erik Boleman, and Teresa Kinder of Barr 

Engineering provided information for this response under the direction of Tom O'Brien. 

10. IdentifY the manufacturer, including contact information, for all low NOx burners, SCR, 

SNCR, scrubber, and induced flue gas technologies considered technically feasible for use 

at the facility. 

The manufacturer company names, contacts, email addresses, and phone numbers are 

provided below for low NOx burners (LNB), SCR, induced flue gas recirculation/ultra-low 

NOx burner technology (IFGR-ULNB), wet scrubbers, and wet electrostatic precipitators 

(Wet ESP). Tilden's BART Report also discussed dry sorbent injection (DSI) and spray 

dryer absorption (SDA) technologies, but specific manufacturers were not identified for 

these technologies. 

Control Company Contact Email Phone 

LNB Metso Kenneth kenneth.gardner@metso.com 570.271.7637 IFGR-ULNB Gardner 

LNB Outokumpu Jan Weekes Jan.Weckes@outokumpu.com 

LNB Danieli Peter Peter.Zonneveld@danieli-corus.com +39 (0432) 

Zonneveld 597821 

LNB Danieli KoenMeijer Koen.Meijer@danieli-corus.com +31(6513) 

93458 

LNB Joho Zink Jason Jason.McAdams@johnzink.com 918.234.2728 IFGR-ULNB McAdams 

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Control Company Contact Email Phone 

LNB Fives Jack Jack.Cochenour@fivesgroup.com 216.271.6000 Cochenour 

Schreiber, Bob SCR Yonley, and Schreiber Assoc. 

SCR Babcock Bob Harold BHarold@babcockpower.com 508.854.3941 Power 

SCR Cormetech Elizabeth GoveyEM@Carmetech.com 919.620.3000 Govey 

Wet Scrubber STS Hal Taylor taylor@stsconsultants.com 847.279.2541 Consultants 

Wet ESP Durr Rodney Rodeny.Pennington@durrusa.com 407.822.9203 Pennington 

George Pruchnofski, Beth Havlik, Jack Kennedy, Erik Boleman, and Teresa Kinder of Barr 

Engineering provided information for this response under the direction ofT om O'Brien. 

11. For the time period January 1, 2002, to the date of this information request, provide all 

documentation, including engineering studies or mass balance studies, conducted to 

determine emissions of NOx from each waste-gas stack at all indurating furnaces and 

dryers at the facility. 

Tilden has not performed any mass balance studies to determine NOx emissions from each 

waste gas stack at the facility. Available NOx testing data is included in Folder 11: 

• Document 11-1 contains 2004 NOx test results for the North and South stacks at the 

Line 1 furnace. The test was conducted using Method 7E. 

• Document 11-2 contains NOx testing data from 2012 for the North and South stacks 

at the Line 1 furnace. The test was conducted using Method 7E. 

Thomas O'Brien (Environmental Engineer) and Marty Hanninen (retired employee) of 

Tilden Mining provided information for this response. 

12. Provide an electronic Excel workbook listing the following information from the NOx 

and/or S02 continuous emissions monitoring system (CEMS) from the date the CEMS 

were installed to the date of this information request. Provide the information on an 

hourly basis, where applicable. The Excel workbook must include the following: 

a. CEMS identijjling name or marker; 

b. CEMS location; 

c. Pollutant monitored; 

d. Date and time; 

e. NO,/ S02 emissions rate in pounds per million British thermal units (1 b/mmBtu); 

f. Raw NO,/ S02 in ppm; 

g. NO,/ S02 emissions rate in pounds per hour; 

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h. Flow rate in actual cubic feet per minute (acfm); and 

i. Furnace temperature in °F. 

Tilden does not own or operate continuous emissions monitors (CEMS) and therefore has no 

information responsive to this request. 

Thomas O'Brien (Environmental Engineer) of Tilden Mining provided information for this 

response. 

13. Describe how the NOx CEMs located at your facility are used, or could be used, to 

optimize your taconite pellet manufacturing process. Provide supporting documentation. 

Tilden has not evaluated how a NOx CEMS could be used for process optimization at 

Tilden, and any response to this request as it relates to Tilden's operations would be 

speculative. CEMS are intended for use as monitoring devices, not as process control tools. 

Temperature and other parameters that may be adjusted on boilers and other combustion 

devices to control NOx emissions are critical to pellet quality, and cannot necessarily be 

adjusted for NOx optimization at a taconite facility in the same way they can be adjusted at 

other facilities. Process optimization using NO, CEMS at taconite facilities is not a proven 

technology, nor is it commercially available as a method ofNOx control. NOx CEMS have 

not been documented as a NOx control technology at any taconite facilities and therefore are 

not "available" or "applicable" for BART purposes. 

Thomas O'Brien (Environmental Engineer) of Tilden Mining provided information for this 

response. 

14. For the period from January 1, 2002, to the date of this information request, provide NOx 

emissions data on a daily basis and on a 30-day rolling basis for Line 1 and its 

corresponding dryer. 

Tilden does not own or operate continuous emissions monitors (CEMS) and therefore has no 

information responsive to this request. 

Thomas O'Brien (Environmental Engineer) of Tilden Mining provided information for this 

response. 

15. IdentifY all NOx emlsswn sources and factors contributing to NOx emlsswns at the 

facility's indurating furnaces and dryers, including but not limited to, the burners. 

Understanding of NOx generation in indurating taconite furnaces is relatively young as 

compared to more traditional burners in the power industry, but continues to evolve. The 

three mechanisms by which NOx production is believed to occur in an indurating furnace are 

thermal, fuel, and prompt NOx. Thermal NOx occurs when nitrogen contained in air 

oxidizes at high temperatures, and would primarily occur in the flame zone of the burners. 

Fuel NOx occurs when nitrogen contained in the fuel oxidizes during combustion. Prompt 

NOx occurs at the burners as turbulent diffusion mixes fuel and air and creates eddies ideal 

for NO formation. 

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The amount ofNOx generated by each of these mechanisms is not well understood. NOx in 

a grate-kiln system is primarily influenced by flame temperature, turbulence in the flame, 

length of time in the flame, and oxygen content. Burning zone temperature, quantity of 

secondary air, and oxygen content are process driven and are difficult to adjust without 

affecting pellet quality. Anything that would significantly change the burner or burner 

performance cannot be completed without understanding the effects on pellet quality and 

production rates. 

Thomas O'Brien (Environmental Engineer) and Marty Hauninen (retired employee) of 

Tilden Mining provided information for this response. 

16. Identify all persons, including employees, consultants, representatives of the taconite 

industry, or representatives of air pollution control manufacturers, who assisted in the 

preparation, or were consulted for the purpose of preparing, the BART report. 

The following personnel at Barr Engineering contributed to the BART report: 

• George Pruchnofski (Principle in Charge) 

• Beth Havlik (Project Manager) 

• Jack Kennedy (Technical) 

• Erik Boleman (Technical) 

• Kim Alfonsi 

• Teresa Kinder (Technical) 

The following employees of Tilden and Cliffs Natural Resources were consulted for 

purposes of preparing the BART report: 

• Thomas O'Brien (Environmental Engineer- Tilden) 

• Keri Schiferl (former employee - Tilden) 

• Brent Ketzenberger (Area Manager, Environmental - Tilden) 

• Leonard Parker (Director, Environmental Permitting, Michigan and Canada Iron Ore 

- Cliffs Natural Resources) 

Manufacturers consulted for purposes of preparing the BART report are listed in response to 

Question 10. 

Thomas O'Brien (Environmental Engineer) of Tilden Mining and Teresa Kinder of Barr 

Engineering provided information for this response. 

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Since~~ 

~:a var Vice President- General Manager 

Empire Iron Mining Partnership 

by The Cleveland-Cliffs Iron Company as Managing Agent 

& Tilden Mining Company L.C. 

by The Cleveland-Cliffs Iron Company as Managing Agent 

Enclosure 

cc: Scott Gischia 

Brent Ketzenberger 

Thomas O'Brien 

Douglas Me Williams 

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