IDEM INDIANA DEPARTMENT OF ENVIRONMENTAL MANAGEMENT

We Protect Hoosiers and Our Environlllellt.

Mitchell E. Daniels Jr. 100 North Senate Avenue

Governor Indianapolis, Indiana 46204

(317) 232-8603

Thomas W. Easterly Toll Free (800) 451-6027

Commissioner www.idem.lN.gov

April 8, 2011

Ms. Susan Hedman

Regional Administrator

U.S. Environmental Protection Agency

Region 5

77 West Jackson Boulevard

Chicago, IL 60604-3950

Re: Request to Parallel Process the Draft

Request for Redesignation Petition

and Maintenance Plan for the Indiana

Portion (Lake and Porter counties) of

the Chicago-Gary-Lake IL-IN

Nonattainment Area for Fine Particles

Dear Ms. Hedman:

The Indiana Department of Environmental Management (IDEM) submits a draft

Redesignation Petition and Maintenance Plan for the Indiana Portion (Lake and Porter

counties) of the Chicago-Gary-Lake IL-IN Nonattainment Area, which was designated as

nonattainment of the annual standard for fine particles on April 5, 2005. IDEM will

conduct a public hearing concerning the Redesignation Petition and Maintenance Plan on

May 18, 2011, and the public comment period will conclude on May 20, 2011. IDEM

requests the United States Environmental Protection Agency (U.S. EPA) to proceed with

its proposed approval of IDEM's April 3, 2008 submittal and to parallel process this draft

submission concurrently.

The attached document consists of the following:

Redesignation Petition and Maintenance Plan

• A formal request that the Indiana Portion (Lake and Porter counties) of the

Chicago-Gary-Lake IL IN Nonattainment Area for Fine Particles be redesignated to

attainment and reclassified as maintenance. It contains and meets the

requirements set forth in Section 107 of the Clean Air Act and in U.S. EPA

Redesignation Guidance.

• A maintenance year of 2025 is established and 2015 and 2020 are analyzed as

interim years.

• The appendices of the document contain historical air quality trend data, projected

emission inventory dataand thorough documentation of the mobile emissions

analysis.

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Ms. Hedman, Page 2

Motor Vehicle Emissions Budgets

• Contained in the Redesignation Petition is a new Motor Vehicle Emissions Budget

for 2016 and 2025. The Northwestern Indiana Regional Planning Commission's

(NIRPC's) travel demand forecasting model and the U.S. EPA's software program

referred to as MOBILE6.2 were used to determine emissions for the annual fine

particle nonattainment area.

• A conservative margin of safety was applied to the 2016 and 2025 projected

emissions.

• The travel demand model was updated with the best available assumptions.

• Vehicle registration data gathered from the Indiana Bureau of Motor Vehicles were

used to replace the MOBILE6.2 default vehicle age distribution.

Upon completion of the public participation process and documentation, IDEM will

forward the official transcript and a summary and response to substantive oral and written

comments under separate cover.

IDEM requests that the U.S. EPA proceed with review and approval of this

submittal. If you have any questions or need additional information, please contact Scott

Deloney, Chief, Air Programs Branch, at (317) 233-5694.

Sincerely,

Keith Baugues

Assistant Commissioner

Office of Air Quality

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Enclosures:

Draft Request for Redesignation Petition and Maintenance Plan Under the Annual

National Ambient Air Quality Standard for Fine Particles for the Indiana Portion of

the Chicago-Gary-Lake County, IL-IN Nonattainment Area

Cc: John Summerhays, U.S. EPA Region 5 (wi enclosures)

Matt Rau, U.S. EPA Region 5 (wi enclosures)

John Mooney, U.S. EPA Region 5 (no enclosures)

Cheryl Newlon, U.S. EPA Region 5 (no enclosures)

Pat Morris, U.S. EPA Region 5 (no enclosures)

Bill Brown, NIRPC (wi enclosures)

Rob Kaleel, Illinois EPA (wi enclosures)

Scott Deloney, IDEM (no enclosures)

Christine Pedersen, IDEM (no enclosures)

Gale Ferris, IDEM (wi enclosures)