UNITED STATES ENVIRONMENTAL PROTECTION 

AGENCY 

REGION 10 

1200 Sixth Avenue, Suite 900 

Seattle, WA 98101-3140 

MAY 17 2013 

Mr. Curt Fransen, Director 

Idaho. Department of Environmental Quality 

1410 N. Hilton 

Boise, Idaho 83706 

Dear Mr. Fransen: 

OFFICE OF 

AIR, WASTE AND TOXICS 

The purpose of this letter is to inform you of the US Environmental Protection Agency's (EPA) 

determination of the adequacy for transportation conformity purposes of the motor vehicle 

emissions budgets (MVEBs) in the Northern Ada County PMJ 0 State Implementation Plan, 

Maintenance Plan: Ten-Year Update (Maintenance Plan Update) for the PM10 national ainbient 

air quality standard (NAAQS). As a result of our adequacy finding, the Community Planning 

Association of Southwest Idaho, the Idaho Transportation Department and the U.S. Department 

of Transportation must use these budgets in future conformity analyses. 

The Maintenance Plan Update was submitted to the EPA on March 11 , 2013, and a clarification 

to the MVEB·was submitted on Aprill6, 2013. We announced receipt of the Maintenance Plan 

Update on the Internet and requested public comment by no later than May 15, 2013. We 

received no comments during the comment period. The EPA also reviewed the State's response 

to comments received during the state comment process. One commenter requested an 

explanation of the differences in the State's current and previous PM10 emission budgets, and a 

justification for the State's reliance on an emission factor that differed from the factor previously 

relied-upon in the State's emission budget. The EPA finds that the State addressed the 

discrepancy identified by the commenter and adequately explained the derivation of the State's 

current PM1o emission budget. 

The Maintenance Plan Update identifies MVEBs for PM10, nitrogen oxides (NOx), and volatile 

organic compounds (VOC) for 2008, 2015, and 2023. This letter transmits our decision that the 

MVEBs are adequate for transportation conformity decisions. The adequate budgets are listed in 

the following table. 

MVEB for Northern Ada County PM10 Maintenance Area 

(tons per day) 

Budget Year PM10 NOx voc 

2008 31.0 29.5 12.6 

2015 42.9 29.5 12.6 

2023 60.1 34.2 17.2 

In reaching this decision, we have reviewed the Maintenance Plan Update, including responses 

to public comments on the plan, and have determined that the related MVEBs, when considered 

with all other emissions sources in the Northern Ada County area, are consistent with applicable 
requirements for maintenance of the PM10 NAAQS through the year 2023. The budgets also 

meet the other adequacy criteria found in 40 CFR 93 .118( e)( 4) as detailed in the enclosure. A 

copy of this letter and its enclosure will be posted on the Internet at 

http://www .epa.gov I otaq/ stateresources/transconf/ adequacy .htm. 

The EPA intends to publish a notice of this adequacy determination in the Federal Register and 

the determination will become effective 15 days after the Federal Register publication. If you 

have any questions, please contact Claudia Vaupel of my staff at (206) 553-6121. 

Enclosure 

cc: MaryAnn Waldinger 

Community Planning Association 

of Southwest Idaho 

Matt Stoll 

Community Planning Association 

of Southwest Idaho 

Tiffany Floyd 

Idaho Department of 

Environmental Quality 

David Luft 

Idaho Department of 

Environmental Quality 

Rick Hardy 

Idaho Department of 

Environmental Quality 

Mike Edwards 

Idaho Department of 

Environmental Quality 

J!t 

Director 

~4 0 e of Air, Waste and Taxies 

Ned Conroy 

Federal Transit Administration 

Scott Frey 

Federal Highway Administration 

Nathan Hesterman 

Idaho Transportation Department 

2