May 9, 2012

Attn: Compliance Tracker, AE-17J Air Enforcement and Compliance Assurance Branch U.S. Environmental Protection Agency Region 5 77 West Jackson Boulevard Chicago, IL 60604

Re: Request to Provide Information Pursuant to the Clean Air Act

On April 18, 2012, Barr Engineering Company received y our Request to Provide Information Pursuant to the Clean Air Act; the requested information is rega rding the the Minnesota taconite iron ore mining and pellet manufacturing industry.

Barr Engineering Company completed Best Availa ble Retrofit Technology (BART) analyses for the following Minnesota facilities:

 U.S. Steel Corporation’s Keewatin Taconite Operations (Keetac)

 U.S. Steel Corporation’s Minnesota Ore Operations (Minntac)

 Northshore Mining Company (NMC)

 Hibbing Taconite Company (Hibbtac)

 United Taconite (Utac)

 Mittal Steel USA – Minorca Mine (Mittal Steel)

The enclosed compact disk, labeled “Barr Engineerin g Company, Disk 1 of 1 for Information Request Response, May 10, 2012” includes the following files:

TABLE OF CONTENTS Description Filename Cover/TOC/Certification Letter (electronic co py of this letter) Cover Letter and TOC.pdf Screen Print of Anti-Virus Scan Results Antivirus Scan.pdf Question 1 through 5 Response Response 1 through 5.pdf Attachments to Question 1 through 5 Response Attachment A – Summary of Relevant Economic Feasibility Control Costs Att A Cost Threshold Response 1.pdf

Attachment B – Annualized Pollution Control Cost Basis - Keetac Att B Keetac Cost Response 2.pdf

Attachment C – Annualized Pollution Control Cost Basis – Minntac Att C Minntac Cost Response 2.pdfCompliance Tracker, AE-17J, USEPA May 9, 2012 Page 2

Description Filename Attachment D – Annualized Pollution Control Cost Basis – North Shore Mining Att D NMC Cost Response 2.pdf

Attachment E – Annualized Pollution Control Cost Basis – Hibbtac Att E Hibbtac Cost Response 2.pdf

Attachment F – Annualized Pollution Control Cost Basis - Utac Att F Utac Cost Response 2.pdf Attachment G – Annualized Pollution Control Cost Basis – Mittal Steel Att G Mittal Cost Response 2.pdf

Enclosures Referenced in Question 5 Response Application for a Permit to Construct and Operate an Integrated Steel Plant, Volume II, Appendix C Best Available Control Technology Review, Prepared for Minnesota Steel Industries, LLC, May 2007 MSI BACT Report Response 5.pdf

Best Available Control Technology Analysis, Prepared for Essar Steel Minnesota LLC, October 2011 Essar BACT Response 5.pdf

Air Emissions Permit Application for the Furnace 5 Reactivation Project, Volume I, BACT Analysis, Prepared for Northshore Mining Company, May 2, 2005 NMC Furnace 5 Restart Vol I BACT Response 5.pdf

NOx Reduction Technology Ev aluation and Mitigation, Proposal for Keetac Expansion, February 10, 2010 Keetac NOx Technology Evaluation Response 5.pdf

I certify under penalty of law that I have examined a nd am familiar with the information in the enclosed documents, including all attachments. Based on my inquiry of those individuals with primary responsibility for obtaining the information, I certify that the statements and information are, to the best of my knowledge and belief, true and complete. I am aware that there are significant penalties for knowingly submitting false statements and information, including the possibility of fines or imprisonment pursuant to Section 113(c)(2) of the Act, and 18 U.S.C §§1001 and 1341.

We are not asserting a claim of business confidentia lity for any portion of the submitted information.

I further certify that the compact disks have been scanned using Microsoft Forefront Anti Virus software. A screen print of the scan results is included on the compact disc.

If you have questions regarding this response, pl ease contact Chandler Taylor at 952-832-2621 or ctaylor@barr.com.

Sincerely,

Tim Russel Vice President Barr Engineering Company