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 ofEnvironmental Quality 1410 N. Hilton Boise, Idaho 83706 Dear Mr. Fransen: OFFICE OF AIR, WASTE AND TOXICS

The purpose ofthis letter is to inform you ofthe US Environmental Protection Agency ' s (EPA) determination ofthe adequacy for transportation conformity purposes ofthe motor vehicle emissions budgets (MVEBs) in the Northern Ada County PMJ0 State Implementation Plan, Maintenance Plan: Ten-Year Update (Maintenance Plan Update) for the PM 10 national ainbient air quality standard (NAAQS). As a result ofour adequacy finding, the Community Planning Association of Southwest Idaho, the Idaho Transportation Department and the U.S. Department ofTransportation 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 ofthe 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 ofthe differences in the State's current and previous PM 10 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 ofthe State's current PM1o emission budget. The Maintenance Plan Update identifies MVEBs for PM 10, 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 PM 10 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 havereviewed 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 applicablerequirements for maintenance ofthe PM 10 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 ofthis letter and its enclosure will be posted on the Internet at http: //www.epa.govIotaq/stateresources/transconf/adequacy
.htm. The EPA intends to publish a notice ofthis 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 ofmy staff at (206) 553-6121.

Enclosure

cc: MaryAnn Waldinger Community Planning Association

ofSouthwest Idaho
Matt Stoll Community Planning Association

ofSouthwest 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**~4** Director 0 e ofAir, Waste and Taxies

Ned Conroy Federal Transit Administration

Scott Frey Federal Highway Administration

Nathan Hesterman Idaho Transportation Department

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