UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 8 1595Wynkoop Street DENVER, CO 80202-1129 Phone 800-227-8917 http://www.epa.gov/region08 

## FEB 2 82007 Ref: 8P-AR

Ned Pettit Ho1cim (US), Inc. 4070 Trident Road Three Forks, MT 59752

Re: Results of"Subjectto" Visibility Modeling for Best Available Retrofit Technology (BART) and Request to Conduct a BART Analysis for BART-Eligible Units at Ho1cim (US), Inc.

Dear Mr. Pettit:

On June 19,2006, EPA received a letter from the Montana Department ofEnvironmental Quality that stated it was withdrawing its efforts to meetthe requirements ofthe Regional Haze Rule (RHR) specified at 40 CFR 51.308. On September 27,2006, EPA Region 8 sent a letter notifying you that we would be conducting modeling to determine which sources in Montana are "subjectto" the BestAvailable Retrofit Technology (BART) requirements in the RHRas part of

our effortto address the requirements ofthat rule. Since it was determined that Holcim (US), Inc. (Holcim) was BART eligible, we informed you that Ho1cim would be included in the modeling and asked you to certifythe datathat wouldbe used for this modeling.

EPA Region 8, withthe assistance ofthe Western Regional AirPartnership (WRAP), has

now completedthe visibility modeling for determining those Montana sources subject to BART. Based on the modeling, EPA Region 8 has determined that your facility is subject to BART. Accordingly, we are requesting that you submit a BART Analysis for Ho1cim within 90 days of this letter, as explained below.

In modeling Ho1cim's visibility impacts, EPA Region 8 followed the approach for determining ifa source is subjectto BART, including the specifics onhowthe modeling should be performed, set out in the final RHR and EPA's "Guidelines for Best Available Retrofit Technology Determinations" (BART Guidelines). See 70 FR 39104, July 6, 2005. The BART Guidelines canbe found at Appendix Yto 40 CFRPart 51. EPA Region 8's visibility modeling also generally followed the protocol outlined in the document "Draft CaipuffBARTModeling Protocol for Federal Mandatory Class 1Areas" (MontanaDepartment ofEnvironmental Quality, September 2006). An electronic copy ofthis protocol is located on EPA Region 8's website at http://www.epa.gov/region8/air/mtregionalhaze.html. Where necessary, we made slight variations to the protocol, such as instances where meteorological data was not available for a certain site.2

States (orEPA) have several options for detennining whether a source is subjectto BART, including the use ofdispersion modeling to detennine whether an individual source may be reasonably anticipated to cause or contribute to any visibility impainnent in any Class I area. When dispersion modeling is used, part ofthe process ofdetennining whether a source is subject to BART is the selection ofa deciview threshold against which to measure the visibility impact ofa source. For its analysis ofMontana sources, EPA Region 8has established a threshold of 0.5 deciviews as the appropriate threshold based onthe number and distribution ofsources impacting Class I areas in and around Montana. Ifdispersion modeling predicts that a source will have visibility impacts of0.5 deciviews ormore at a Class I area onthe 98th percentile of values, EPA Region 8 considers that source to be subjectto BART. Further infonnation regarding this approach to detennining whether a source is subject to BART can be found in sectionlILA ofthe BART Guidelines.

For Holcim, the modeling results show a maximum 98th percentile impact within a Class I area of 1.05 deciviews, which exceeds the threshold of0.5 deciviews. Since Holcim exceeds the 0.5 deciview threshold, and thus may reasonably be anticipated to cause orcontribute to visibility impainnentin one ormore Class I areas, EPA Region 8has concluded that Hokimis subject to BART.

A summary ofthe BART modeling results is enclosed. The enclosure provides a summary ofthe 98th percentile predictions for the three years modeled for Holcim at all federal Class I areas in the vicinity ofthe plant. More detailed modeling results, including the electronic CALPUFF/CALMET files, are available onthe WRAP website at http://pah.cert.ucr.edulagm/308/bart.shtml.

Because Holcim is subjectto BART, EPA Region 8is requesting that Holcim conduct a BART engineering analysis on the emissionunits specified onthe enclosed spreadsheet and submitthe analysis to our office. One ofthe requirements ofthe RHR is that each regional haze implementationplan contain enforceable emission limits for eligible stationary sources based on BART. The BART analysis will be used to identify the best system ofcontinuous emissions reduction and corresponding emission limits for each visibility impairing pollutantthat is emitted by the Holcim facility. The Clean Air Act and the RHRrequire that BARTbe established on a case-by-case basis taking into accountthe available retrofit control options, the costs of compliance, the energy and non-air quality impacts ofcompliance, any pollutioncontrol equipment inuse at the source, the remaining useful life ofthe source, and the degree of improvement in visibility which mayreasonably be anticipated to result from the use ofthe technology.

Forpurposes ofthe Regional Haze FIP for Montana, EPA Region 8 is intending to follow its BART Guidelines from 40 CFRPart 51, Appendix Y. The BART Guidelines are a statement ofEPA'sthinking on howbestto meet the requirements ofBART inthe CAA and RHR. Thus, in conducting the Holcim BART engineering analysis, you will need to follow the five-step4
accompanies the information when it is received by EPA, EPA may make the information available to the public without further notice to Holcim. Information subject to abusiness confidentiality claim will be disclosed by EPA only to the extent, and by means ofthe procedures, set forth at 40 CFRPart 2, Subpart B.

Once again, we look forward to working with you. Ifyou have any questions regarding the modeling results, please contact Kevin Golden ofmy staffat (303) 312-6442. For questions related to development ofthe BART analysis, please contact Laurel Dygowski at (303) 312­ 6144. Sincerely, 

## CarolL. Campoell
Stephen S. Tuber Assistant Regional Administrator Office ofPartnerships and Regulatory Assistance

Enclosure

@printedon RecycledPaperSummary ofCalpuffModeling Results for Holcim (US) Inc. Trident Plant

Class I Area Minimum Distance 98th Percentile for each Year 98th 3 Year Average Max Delta-dv (dv) 99th (dv) 98th (dv) Days
> 0.5 dv (km) 2001 2002 2003 yell Yellowstone NP 100 0.33 0.55 0.55 0.48 1.91 0.67 0.52 22 gamo Gates ofthe Mountains WA 101 1.05 0.55 0.70 0.77 2.77 1.01 0.61 33
anac Anaconda

- Pintler 132 0.25 0.21 0.20 0.22 0.76 0.36 0.24 8 redr Red Rock Lakes 141 0.16 0.26 0.16 0.19 1.15 0.36 0.18 6 scap ScapeQoat 154 0.28 0.28 0.21 0.26 1.51 0.57 0.28 11 noab North Absaroka Wilderness 157 0.22 0.29 0.45 0.32 1.76 0.45 0.30 9 boma Bob Marshall 189 0.28 0.25 0.12 0.22 1.38 0.41 0.24 9 wash Washakie Wilderness 202 0.07 0.09 0.11 0.09 0.36 0.16 0.10 0 teto Teton Wilderness 214 0.04 0.07 0.08 0.06 0.25 0.10 0.07 0 selw Selwav-BitterrootWilderness 217 0.10 0.18 0.15 0.14 1.72 0.24 0.15 2 mimo Mission Mountains WA 230 0.12 0.12 0.08 0.11 1.54 0.20 0.12 7 glac Glacier NP 298 0.12 0.09 0.05 0.09 0.57 0.16 0.11 1