ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 52 EPA-R08-0AR-2007-1035; FRL- Approval and Promulgation ofState Implementation Plans; State ofColorado; Interstate Transport ofPollution Revisions for the 1997 8-hour Ozone NAAQS: "Interferencewith Maintenance" Requirement AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed Rule. SUMMARY: EPA is proposingto approve the "State ofColorado Implementation Plan to Meet the Requirements ofClean Air Aet Section 110(a)(2)(D)(i)(I)

- Interstate Transport Regarding the 1997 8-Hour Ozone Standard" addressing the "interference with maintenance" requirement 01'section 11 0(a)(2)(D)(i)(I). OnJune 18,2009 the State ofColorado submitted an interstate transport State Implementation Plan (SIP) addressing the interstatetransport requirements under section 11 0(a)(2)(D)(i) ofthe Clean Air Act (CAA). In this action, EPA is proposingto approve the Colorado Interstate Transport 

### SIP provisions that address the section 11O(a)(2)(D)(i)(I) requirementprohibiting a state's emissions from interfering with maintenance ofthe 1997 8-hoUi'

ozone National Ambient Air Quality Standards (NAAQS) by any other state. This action is being taken under section 110 ofthe CAA.

Federal Reoisterj,

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_ ...-. ADDRESSES: Submityour comments, identified by Docket ID No. EPA-R08-0AR-2007­ 1035, by one ofthe following methods: ht1n)/wwW
..regulations.go.\::. Followthe on-line instructions for submitting comments,Page 2 orJO E-mail:**mastmp~J~LQ9.menico{(I)epa.** \LOV Fax: (303) 312-6064 (please alcl1 the individual listed in the FOR FURTHER**I~FORVIATION** CONTACT iryou arc faxing comments). Mail: Callie Videtich. Director. Air Program. Environmental Protection Agency (EPA). Region 8, Mailcode 8P-AR, 1595 Wynkoop Street, Denver, Colorado 80202-1129. Hand Delivery: Callie Videtich, Director. Air Program, Environmental Protection Agency (EPA), Region 8. Mailcode 8P-AR, 1595 Wynkoop, Denver, Colorado 80202-1129. Such deliveries are only accept(2d Monday through Friday, 8:00

a.m. to 4:30 p.m., excludingfederal holidays. Special arrangements should be made !()r deliveries ofboxed information. 

### Instructions: Direct your commentsto Docket 

### ID No. EPA-R08-0AR-2007-1035. EPA'spolicy is that all comments received will be included in the public docket without change and may be made available online at httnJlwww.regulatiQmggy, including any personal inl()rmation provided. unless the comment includes inl()rmation claimed to be Confidential Business Information (CHI) or other information whose disclosure is restricted by statute. Do not submit information that you considerto be 

## em or otherwise protected through http://www.regulati_QDs.gov ore-mail. The http://www.regu[ations.gov Web site is an "anonymous access" system, which means EPA will not know your identity or contact information unless you provide it in the body ofyour comment. Ifyou send an e-mail comment directly to EPA, without going through**h.llilj/\y'y.rw.r~g),l9tions.u.ov,**your e-mail address will be automatically captured and included as part orthe comment that is placed in the public docketPage 3 01'30 and made available on the Internet. Ifyou submit an electroniccomment, EPA recommends that you include your name and other contact information in the body ofyour comment and with any disk.or 

### CD-ROM you suhmit. IfEPA cannotread your commentdue to technical difficulties and cannotcontact you for clarification, EPA may notbe ahle to consider your comment. Electronic files should avoid the use ofspecial characters, any form ofencryption, and be free of any defects or viruses. For additional instructions on submittingcomments, go to Section 

### 1. General Information ol'the

### SUPPLEMENTARY INFORMIATION section ofthis document. 

### f)ocket· All documents in the docket are listed in the b!!.p:l/www.rygulations.!.!.ov index. Although listed in the index, some information is not publicly available, e.g., CBI orother information whose disclosure is restricted by statute. Celiain othermaterial, such as copyrighted material, will he publicly available only in hard copy. Publicly-available docket materials are availahle eitherelectronically in http://v.::ww.regulations.!.!.ov orin hard copy at the AirProgram, Lnvironmental Protection Agency (EPA), Region 8, Mailcode 8P-AR, 1595 Wynkoop, Denver, Colorado 80202-1129. EPA requests that ifat all possihle, you contact the individual listed in the 

### FOR FURTHER INFORMATION CONTACT section to view the hard copy ofthe docket. You may view the hard copy ofthe docket Monday through Friday, 

### 8:00 a.m. to 

### 4:00 p.m., excluding Federal holidays. 

### FOR FURTHER INFORMATION CONTACT: Domenico Mastrangelo, Air Program, U.S. Environmental Protection Agency, Region 8, Mailcode 8P-AR, 1595 Wynkoop, Denver, Colorado 80202-1129, (303) 312-6436,**Olastr~ngelo.~iol11enj~Q(fiJ,epa.goV',** 

### SUPPLEMENTARY**I~FORMATION:** DefinitionsPage 4 of30 For the purpose ofthis document, we arc giving meaning to certain words or initials as follows: (i) The words or initials Act or**~J\f1** mean orreferto the Clean Air Act, unless the context indicates otherwise. (ii) The words**I~EA_,\:Y~(?,** us or 91!.I: mean orreferto the United States Environmcntal Protection Agency. (iii) Thc initials SIP mean orrefcrto State Implementation Plan. (iv) The words**Co19L~<J..Q.** and State mean the State ofColorado. TableofContents I. General Information What Should IConsider as I Prepare My Comments for EPA'? II. Background III. What Action Is EPA Proposing? IV. What Is the State Process to Submit TheseMaterials to EPA? V. EPA's Review and Technical Information A. EPA's**l~valuation** ofInterfcrence with Maintenance B. Colorado Transport SIP VI. Proposed Action VII. Statutory and Executive Order Reviews I. General Information What should I consider as I prepare my comments for EPA'? 1. ,\'uhll7i/ling ('8/ Do not suhmit CBI to EPA through**J)JJ11.H~~:yv,rel!qI<I.1i_t)ns:lli.l_Y**or email. Clearly mark the part or all ofthe information that you claim to be CHI. For CHIPage 5 of30 information in a disk or CD ROM that you mail to EPA, mark the outside ofthe disk orCD ROM as CHI and then identify electronically within the disk or CD ROM the specific information that is claimed as

## em. In addition to one complete version orthe commentthat includes information claimed as 

## em, a copy ofthe comment that docs not contain the inror111ation claimed as CBI must be submitted for inclusion in the public docket. Information so marked will not be disclosed except in accordance with procedures set forth in 40 CFR part 2. 

### 2. Tipsj(Jr PreparinR Your ('omrnents. When submitting comments, remember to:

a. Identiry the rulemakingby docket numberand other identifying information (subject heading, Federal Register date and page number). b. Follow directions

- The agency may ask you to respond to specific questions or organize comments by referencing a Code ofFederal Regulations (CFR) part or section number.

c. Explain why you agree or disagree; suggest altematives and substitute language for yourrequested changes. d. Describe any assumptions and provide any technical information and/or data that you used.

e. If you estimate potential costs or burdens. explain how you arrived at your estimate in sufJicient detail to allow for it to be reproduced. 

# r. Provide specific examples to illustrate your concerns, and suggest alternatives. g. Explain your views as clearly as possible, avoiding the usc ofprofanity or personal threats. h. Make sure to submit your comments by the commentperiod deadline identified.Page 6 or30 II. Background On July 18, Ic)C)7, EPA promulgated new NAAQS for ozone and for tine particulate matter (PM25). This action is beingtaken in response to the promulgation ofthe 1997 8-hour

ozone NAAQS. This action does not address the requirements for the 1997 or 2006 PM2 5, orthe 2008 8-hour ozone NAAQS; those standards will be addressed in later actions. Section 11 O(a)( I) ofthe CAA requires states to submit SIPs to address a new orrevised NAAQS within 3 years afterpromulgation ofsuch standards, or within such shorter period as EPA may prescribe. Section 110(a)(2) lists the clementsthat such new SIPs must addrcss, as applicable, induding scction I I0(a)(2)(D)(i), which pertainsto interstate transport ofcertain emissions. On August 15,2006, EPA issued its "Guidance for State Implementation Plan (SIP) Submissions to Meet Current Outstanding Obligations Under Section 11 O(a)(2)(D)(i) for the 8­ I-IOLlr Ozone and PM25 National Ambient Air Quality Standards" (2006 Guidance). EPA developed the 2006 Guidance to makerecommendations to states for making submissionsto meet the requirements ofsection II0(a)(2)(D)(i) for the 1997 8-hour ozone standards and the 19')7 PM25 standards. As identified in the 2006 Guidance, the "good neighbor" provisions in section 11 O(a)(2)(D)(i) require each state to submit a SIP that prohibits emissionsthat adverscly affect another state in the ways contemplated in the statute. Section 110(a)(2)(D)(i) contains four distinct requirements related to the impacts ofinterstate transport. The SIP mLlst prevent sources in the state from emitting pollutants in amounts which will: (1) contribute significantly to nonattainment ofthe i\iAAQS in olhcr slates; (2) interfere with maintenance ofthe NAAQS in other states; (3) interfere with provisions to prevent significant deterioration ofairquality inPage 7 of30 otherstates; or (4) interfCre with efhnts to protect visibility in other states. On June IiL 2009. EPA received a SIP revision from the State ofCoJarado intended to address the requirements ofsection 11O(a)(2)(D)(i)(I) for the 1097 8-hour ozone standards. ln this rulemaking, EPA is addressing only the requirements that pertainto preventing sources in Colorado from emitting pollutants that will interfere with maintenance ofthe 1997 8-hour ozone NAAQS by otherstates. 1n its submission, the State ofCo[orado indicatedthat its current SIP is adequate to prevent such interference. With this submission, the state intended to meetthe recornmendations ofthe 2006 Guidance for SIP submissions to meet the second clement of section J 1O(a)(2)(D)(i) for the 1997 8-hourozone standard. 

### Ill. WhatAction 

### Is 

### EllA Proposing? EPA is proposing approval ofa portion ofthe Colorado Interstate Transport ofAir Pollution SIP addressing the requirements ofCAA section 11O(a)(2)(D)(i)(l) for the 1997 8-hour

ozone NAAQS. On December 30, 2008, the Colorado Air Quality Control Commission (AQCC) adopted the "State ofColorado Implementation Plan to Meet the Requirements ofthe Clean Air Act Section 110(a)(2)(d)(i)(l)

- Interstate Transport Regarding the 1997 8-1 lour Ozone Standard" (Colorado Interstate Transport SIP). Colorado submitted this SIP revision to EPA on June 18,2009. In this Federal Register action EPAis proposingto approve onlythe language and demonstration that, in this SIP revision, address the requirements ofclement (2), i.e., the prohibition ofinterference with maintenance ofthe 1997 8-hourozoneNAAQS by any other state. 

### IV. What 

### Is the State Process to SubmitThese Materials to EPA? Section 110(k) ofthe CAA addresses EPA's rulcmaking action on SIP submissions byPage 8 of30 states. The CAA requires states to observe certain procedural requirements in developing SIP revisions t(lr submittal to EPi\. Section 110(a)(2) ofthe CAA requires that each SIP revision be adopted alter reasonable notice and public hearing. This must occurpriorto the revision being submitted by a state to EPA. The Colorado AC)CC held in early December 2008 a public hearing f()r the Colorado Interstate Transport SIP revision, adopted it on December ]0, 2008, and the State submitted it to EPA on June 18,2009. On November 18, 2009, the AQCC provided EPA with an exact colorduplicate ofthe SIP adopted by the AQeC on December30, 2008 and included in the June 18, 2009 submittal to EPA. In the original submittaL AQee provided a black and white copy. The SIP's color duplicate. available for review as part ofthe Docket makes it easier to understand modeling results reported in several graphs that are part ofthe SIP technical demonstration. EPA has reviewed the submittal from the State ofColorado and has determined that the State met the requirements for reasonable notice and public hearing under section I IO(a)(2) of the ('Ai\. V. EPA's Review and Technical Information A. EPA's Evaluation oflnterferencewith :vIaintenance The second element ofsection II O(a)(2)(D)(i) requires that a state's SIP must prohibit any source or othertype ofemissions activity in the state from emittingpollutants that would '"interfere with maintenance" ofthe applicable NAAQS by any other state. This term is not defined in the statute. Therefore, EPA has interpreted this term in past regulatory actions, such

as the 1998 \()x SIP CalL in which EPA took action to eliminate emissions ofNOx thatPage 9 01'30 signdicantly contributed to nonattainment, or interfered with maintenance of, the then applicable

ozone NAAQS through interstate transport ofNOx and the resulting ozone. I The NOx SIP Call

was the mechanismthrough which EPA evaluated whether ornotthe NOx emissions from

sources in certain states had such prohibited interstate impacts, and ifthey had such impacts, required the states to adopt substantive SIP revisions to eliminatethe NOx emissions, whether through participation in a regional cap and trade program or by othermeans. Afterpromulgation ofthe 1997 8-hourozone NAAQS and the 1997 PM25 NAAQS, EPA again recognizedthat regional transport was a serious concern throughout the eastern C).S. and therefore developed the 2005 Clean Air Interstate Rule (CAJR) to address emissions ofS02 and NOx that exacerbate ambient ozone and PM25 levels in many downwind areas through interstate transport. 2 Within CAIR, EPA likewise interpreted the term "interfere with maintenance" as part ofthe evaluation 

### ot'whether ornot the emissions ofsources in certain states had such impacts on
areas that EPA determined would eitherbe in violation oftheNAAQS, or would be injeopardy ofviolating the NAAQS, in a modeled future year unless action were taken by upwind states to reduce S02 and NOx emissions. Through CAIR, EPA again required states that had such interstate impacts to adopt substantive SIP revisions to eliminate the S02 and NOx emissions, whetherthrough participation in a regional cap and trade program orby othermeans. EPA's 2006 Guidance addressed section 11O(a)(2)(D) requirements for the 1997 8-hour

ozone NAAQS and 1997 PM25NAAQS. Forthose states subjectto CAIR, EPA indicated that



### --_..

# _. __..-..--.._.--_.._._.--'--- Sec, 63 FR 57356 (October 27, 1998). EPA's general approach to section 110(a)(2)(D) was upheld in Michigan v. EPA, 213 F.3d M3 (D.C. Cir. 20(0), cert denied, 532 U.S. 904 (2001) However, EPA's approach to interference with maintellance in the NOx SIP Call was not explicitly reviewed by the coul1. Sec, North Carolina v. EPA, 531 F.3d 896, 907·-09 (DC. Cir. 20(8). ) Sec, 70 FR 25162 (May 12,2005) IPage 10 of30 compliance with ('AIR would meet the two requirements ofsection llO(a)(2)(D)(i)(I) for these**~AAQS.** For states not within the CAIR region, EPA recommended that states evaluate whether or not emissions from their sources would "interfere with maintenance" in other states. following the conceptual approach adopted by EPA in CAIR. A11er recommending various types ofinformation that could be relevant for the technical analy5is to support the SIP submission, such as the amount ofemissions and meteorological conditions in the state, EPA further indicated that it would be appropriate for the state to assess impacts ofits emissions on other states using considerations comparable to those used by EPA "in evaluating significant contribution to nonattainment in the CAIR."" EPA did notr1ake specific recommendations for how states should assess "interfere with maintenance" separately, and discussed the first two elements ofsection] 1O(a)(2)(D) together without explicitly differentiating between them. In 2008, however, the U.S. Court ofAppeals for the D.C. Circuit found that CAIR and the related CArR federal implementationplans were unlawful.·1 Among other issues. the court held that EPA had not correctly addressed the second clement ofseetion 110(a)(2)(D)(i)(I) in CAIR. The court noted that "EPA gave no independent significance to the'interfere with maintenance' prong orsection 110(a)(2)(D)(i)(I) to separately identify upwind sources interfering with downwind maintenanee."s EPA's approach, the court reasoned, would leave

areas that arc "barely meeting attainment" with "no recourse" to address upwind emissions

3 Memorandum hom William T. Ilarllett entitled, "Guidance for State Implementation Plan (SIP) Submissions to Meet Current Outstanding Obligations Under- Section 110(a)(2)(D)(i) 1'0:' the 8-hour O/.one and PM25 N8tional Ambient Air (,)u,lIity Standards." Aug. 15,2006, p. 5. ("2006 Guidance"). Available for review in**[~PA** 's September 15.2010 doc"et document entitled: "Relevant Guidance and Supporting Documentation for the Proposed Rulcmaking**b:del'~II_RcgistCl"** Action Docket rD /f EPA-R08-0AR-2007--1 035" : Scc, :\onh Carolilia v. !':I'/\, 531 1,3d 896 (DC. Cir. :2(08) ; Id,at()09,Page] ] of30

sources.l) The court therefore concluded that a plain language reading ofthe statute requires EPA to give independent meaning to the interfere with maintenance requirement ofsection ] 1O(a)(2)(])) and that the approach used by EPA in CAIR failed to do so. In addition to affecting CAIR directly, the court's decision in the North Carolinacase indirectly affects EPA's recommendations to states in the 2006 Guidance with respect to the interfere with maintenance clement ofsection 110(a)(2)(D)(i)(I) because the agency's guidance suggested that states use an approach comparable to that Llscd hy EPA in CAIR. States such as Colorado developed and adopted their Interstate Transport SIPs not long alter the Court's July 2008 decision, but well before EPA, in the Transport Rule Proposal (see below), was able to propose a new approach for the interference with maintenance clement. Without recommendations from EPA, Colorado's SIP may not have sufficiently differentiated between the signilicant contribution to nonattainment and interference with maintenance clements ofthe statute, and relied in a general way on the difference between monitored concentrations and the 1097 is-hour ozone .\/\AQS to evaluate the impacts orState emissions on maintenance ofthe NAAQS in neighboring states. EPA believes that it is necessary to evaluate these state submissions for section 11 O(a)(2)(D)(i)(1) in such a way as to assure thatthe interfere with maintenance element ofthe statute is given independent meaning and is appropriately evaluated using the types ofinformation that EPA recommended in the 2006 Guidance. To accomplish this, U>A believes it is necessary to usc an updated approach to this issue and to supplement the technical analysis provided by the state in orderto evaluate the submissions with respect to the

(, Id.Page 12 of30 inter1Cre with maintenance element ofsection 110(a)(2)(D)(I). EPA has recently proposed a new rule to address interstate transport pursuant to section IIO(a)(2)(D)(i), the "'Federal Implementation Plans to Reduce Interstate Transpol1 ofFine Particulate Matter and Ozone" Crransport Rule Proposal), in orderto address thejudicial remand orCAIR. 7 As part ofthe Transport Rule ProposaL EPA specifically reexamined the section 110(a)(2)(D)(i) requirernent that emissions from sources in

# ,I state must not "interfere with maintenance" ofthe 1997 8-hour ozone NAAQS and 1997 PM25 NAAQS hy other states In the proposal, EPA developed an approach to identify areas that it predicts to he closeto the level of the 1997 8-hour ozone NAAQS and 1997 PM25 NAAQS in the future, and therefore at risk to hecome or continue to he nonattainment for these NAAQS c:nlcss emissions from sources in other states are appropriately controlled. This approach**star~~s** hy identifyi:1g those specific geographic areas jClr which further evaluation is appropriate. and difTerentiates hetween areas where the concern is with interference withmaintenance, rather than with significant contrihution to nonattainment. As described in more detail below, EPA's analysis evaluates data from existing monitors

overthree overlappingthree year periods (i.e., 2003-2005, 2004-2006, and 2005-2(07). as well

as airquality modeling data. in orderto determine which areas arc**prcdict(~d** to be violating the 1997 8-hourozone and PM2 .'i NAAQS in 2012. and which areas arc predicted potentially to have difficulty with maintaining attainment as arthat date. In essence, if' an area's projected data f'or 2012 indicates that it would be violating the NAAQS based**~)J1** the average ofthese three

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### _----­ 7 See "Federal Implementation Plans to Reduce Interstate Transport ofFine Particulate Matter and Ozone," 75 FR 45210 (August 2, 20 I0).Page 13 ono overlapping periods, then this monitor location is appropriate for comparison for purposes ofthe significant contribution to nonattainment element ofsection 1IO(a)(2)(D)(i).**If~** however, an area's projected data indicate that it would be violating the NAAQS based on the highest single period, hut not overthe average ofthe three periods, then this monitor location is appropriate for comparison for purposes ofthe interfere with maintenance element ofthe statute. By this method, EPA has identified those areas with monitors that are appropriate "maintenance sites" ormaintenance "receptors" for evaluating whetherthe emissions from

sources in another state could interfere with maintenance in that particular area..EPA then uses other analytical tools to examine the potential impacts ofemissions from upwind states on these maintenance receptors in downwind states. EPA helieves that this new approach for identifying those areas that arc predicted to have maintenance problems is appropriate to evaluate the section 110(a)(2)(D)(i) SIP submission ofa state for the interfere with maintenance element.x EPA's 2006 Guidance did not providethis specific recommendation to states, but in light ofthe court's decision on CAIR, EPA will itselffollow this approach in acting upon the Colorado submission. As explained in the 2006 Guidance, EPA does not believe that section 110(a)(2)(D)(i) SIP suhmissions from all states necessarily need to follow preciselythe same analytical approach

as CAIR. In the 2006 Guidance, EPA stated that: "EPAbelieves thatthe contents ofthe SIr submission required by section II0(a)(2)(D)(i) may vary depending upon the facts and circumstances related to the specific NAAQS. In particular, the data and analytical tools

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## _--_.... ­ "To begin tllis Cln<1lysis, U'A !irst identifies alllllonitors projected to be in nonattainment or, based on historic variability in air quality, projected to have maintenance problems in 2012, These maintenance receptors arc close to the level ofthe )l)97 ozone and PM.>, l\iAAQS such that minor variations in weather or emissions could result in violations ofthe NAAQS in 2012.Page 1401'30 available at the time the State develops and submits a SIP for a new orrevised NAAQS necessarily alTccts the contents ofthe required submission.,,') EPA also indicated in the 2006 Cluidance that it did not anticipate that sources in states outside the geographic area covered by CAIR were significantly contributing to nonattainment, or interfering with maintenance, in other states. IO As noted in the Transport Rule ProposaL EPA continues to believe that the more widespread and serious transport problems in the eastern United States are analytically distinct. For the 1997 8-hourozone NAAQS and the 1997 PM: 5 NAAQS, EPA believes that nonattainment and maintenance problems in the western United States are relatively local in nature with only limited impacts from interstate transport. I I In the Transport Rule Proposal, EPA did notcalculate interstate ozone or PM2 , contributions to or from western states. Accordingly, EPA believes that section 110(a)(2)(D)(i) SIP submissions for states not evaluated in the Transport Rule Proposal may be evaluated using a "weight ofthe evidence" approach that takes into account available relevant information, such as that recommended by EPA in the 2006 Guidance lor states outside the area affected by CAIR. Such information may include, but is not limited to, the amount ofemissions in the state relevant to the NAAQS in question, the meteorological conditions in the area, the distance hom the state to the nearest monitors in other states that are appropriate receptors, or such other information as may be probative to consider whether sources in the state may interfere with maintenance ofthe 1997 8­ hour ozone NAAQS in other states. These submissions can rely on modeling when acceptable modeling technical analyses are available, but EPA does not believe that modeling is necessarily

'J 200() (iuidancc at 4. I() Id. at 5.Page 15 of30 required ifotheravailable information is sufficientto evaluatethepresenceordegree of interstate transport in a given situation. B. Colorado Transport SIP To meet the requirements ofsection 11O(a)(2)(D)(i)( [) for the 1997 8-hourozone standard, the State ofColorado developed and submitted to EPA on June 18, 2009 an Interstate Transport

### SIP that focused primarily on the "significantcontribution to nonattainment" requirement ofsection 11O(a)(2)(D)(i) and, as noted earlier, addressed only in a limited way the interference with maintenance requirement ofsection 110(a)(2)(D)(i)(l). On June 3, 2010, EPA approved the Colorado Interstate Transport SIP provision that require that emissions from a state's sourccs do not significantly contribute to nonattainmcnt ofthe 1997 8-hourozone NAAQS in any otherstate. To demonstrate that emissions from Colorado do not inter1ere with maintenance ofthe 1997 8-hourozoneNAAQS in neighboring states, the Colorado Interstate Transport SIP uses results from Colorado's 2009 "8-Hour Ozone Attainment Plan" for the D!'v1A/NFR. nonattainmcnt area, and a report from the Western States Air Resource (WESTAR) Council to underscore that: (a) local anthropogenic ozone contribution to high ozone concentrations in Denveris only about 

### 25%; and (b) on**day~;** ofhighest ozone concentrations (reflecting a design value of84.9 ppb) in the DMA/NFR area. the projected design values decrease to 63 ppb or less for all downwind Colorado counties cast ofan imaginary north-south line approximately 70 miles cast from Denver. 12 EPA does not agreethe State ofColorado

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### -

# _._..-.- --------,..

### _--- Ii See, Trans[Jol"t Rule Proposal, 75 FR 45210, 45277. I! COlora(lo Interstutc Transpol1 SII), December 12,2009, Figure 5 at 15. Note that the modeling analysis domain ,"or the DMA/NFR attainment plan was limitcd to the Statc's tCITitory, and that the 70 mile distance ['cpresents the approximate distancc t1'O!1l Denverto the westem border ofMorgan County, Colorado.Page 1601'30 Interstate Transport SIP's assessment that these results demonstrate that "'the magnitudc 0 I'o/.one transport rrom Colorado to other states is too low to .., interlere with maintenance by any other state with respect to the O.Og ppm NAAQS" as thc sole basis for evaluatingthe state's interference. 13 The limited contribution oflocal emissionsto nonattainmcnt in the DMA/NFR and the quick drop in ozone levels in the easternmost Colorado counties, in and by themselves do not exclude a potential for interference with maintenance ofthe 8-hour ozone NAAQS from Colorado emissions to downwind maintenance areas. Rather, as a reflection ofemission levels, the relatively (to the 1997 8-hour ozone NAAQS) moderate ozone concentrations in eastern Colorado and in neighboring states somewhat reduce the probabilitythat State emissions interfere with maintenance ofthe NAAQS bythese states. 14**I~PI\** is evaluating the Colorado Interstate Transport SIP taking into account thc mcthodologies and analysis results developed in the Transport Rule Proposal in response to the judicial remand ofCAIR. As noted previously. the Transport Rule Proposal includes a new approach to determine whether emissions from a state interfere with maintenance ofthe 1997 ghour ozone NAAQS and the 1997 PM

### n NAAQS by other states. In this action, EPA is using a comparable approach to that ofthe Transport Rule Proposal in orderto determine ifemissions from Colorado sources interfere with maintenance ofthe 1997 8-hour ozone NAAQS by other states. To evaluate ambient impacts from upwind statesto maintenance receptors, the Transport Rule Proposal evaluates. through air quality modeling ofeach state's emissions, the contribution

,; lei at 17.Page 170f30 from individual states to downwind maintenance receptors. States that contribute pollutant concentrations below the significancethreshold for interference with maintenance, proposed at

one percent ofthe NAAQS. are excluded from further analysis. 15 Forthe 1997 8-hourozone standard state contributions of(J.8 ppb and higher are considered above the threshold. while ()/onc contribution less than 0.8 ppb are below the threshold. [n the Transp0l1 Rule Proposal, EPA projected future concentrations ofozone at monitors to identify areas that are expected to be out ofattainment with NAAQS or to have diflicu[ty maintaining compliance with the NAAQS in 20]2. To determine the states that may cause interlcrcnce at the maintenance receptors, the Transport Rule Proposal models the states' ozone contribution to these maintenance receptors. Because the Transport Rule Proposal does not model the contribution ofemissions from Colorado (and other western states not fully inside the Transport Rule Proposal's modeling domain) to 8-hourozone maintenance receptors in other states, ourassessment relics on a weightofevidence approach that considers relevant information (such as identification ofmaintenance receptors and estimates ofozone contriolltions) 

### lJ"Oln th(;' Transport Rule Proposal pertaining to states within its modeling domain, and additional material such as geographical and meteorological factors. modeling analysis results from other studies, back trajectory analyses, and AQS monitoring data. While conclusions reached for each ofthe factors considered in the following analysis are not in and by themselves determinative, consideration ofthese factors together provides a reliable qualitative conclusion that emissions from Colorado arc not likely to interfere with maintenance ofthe 1997

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__.._-------- ------'­ II Similar cvidt:nl.:l: is provided by the substantial gap between the 1997 R-hour ozone standard and the dt:sign values at monitors in adjal.:l.:nt downwind states sUl.:h ilS Kansas, 1\ew Mexico, l;tah, and WY0Inmg Id. at 7-8.Page 18 ofJO 8-hour ozone l\;\AQS at monitors in other states. Our analysis begins by assessing Colorado's contribution to the closest maintenance receptors Itl!'the 1997 8-hourozone standard. The Transport Rule Proposal identifies within its modeling domain (consisting ofJ7 states cast ofthe Rocky Mountains, and the District or Columbia) 16 maintenance receptors, among which the eight closestto Colorado are eight receptors in the Dallas Fort Worth (DFW) and llouston-Galveston-Brazoria (HUB) 8-hour ozone

.**I~** nonatta1l1ment areas. Two ofthe three D1"W area maintenancc receptors arc in Dallas County (I-linton Street and Dallas Executive Airport sites), and the third is in Tarrant County (Keller site).17 These monitors arc at least 500 miles from Colorado. I g Distance by itscIfis not an obstacle to long range transport ofozone and/or its precursors. NOx, the primary ozone precursorthat is the object ofthe Transport Rule ProposaL may be transported for long distances, and contribute significantly to high ozone concentrations in other states. However, with increasing distance there are greater opportunities for ozone or NOx dispersion and/orremoval from the atmosphere due to the ciTect ofwinds or chemical sink processes. As a result, one may concludethat the approximately 500 miles from Colorado sources ofNOx emissions to the DFW area maintenance receptors reduces, but does not exclude, the possibility that the Colorado emissions

I) Transport Rule Proposal, 75 FR 45210.45254. 1(, Thl: rl:maining eight maintenance-only sites are in a handfu! ofEast Coast states: Connecticut, (jeorgia. New York and Pennsylvania See Table IV C-11. Transpol't Rule Proposal, at 452S2-253 [7 The 500 mile estimate represents the approximate distance between Lamar, in the southeastern corner or Colorado, and Dallas, Texas. The monitors' Site [[) Numbers are: Hinton, 48-113-0069; Executive Airport, 48-11]­ 0087; and Keller, 48-439-2003. See id. For**monitor~'** site names,**~ee** online TCQC web page at**11ll~2:f/!\,_\y~,-t&~,state.** tx.**~ls/cgi.:.QinLs;,9m121** iance.LmoIJSWii!.'?ite infoJ2l IX**Thi~** distance underestimates the average distance covered by**emis~ions** from Colorado sources for at least two reasons: a) most Colorado sources are further north and/or west from the DFW area than Lamar; b) 500 miles

### Page 19 of30 interlere with mainknance ofthe 0JAAQS at these receptors. Because pollutant transport is linked to wind direction, we examine how frequently air

masses from Colorado pass through orend in the 

### DFW area lhat includes the maintenance receptors identified above. The State of'I'

### exas' 2007 attainment demonstration for the 

### DFW area points out, without quantifying contributions, how heavily the area's ozone concentrations are aftected by substantial transport from other areas. Average ozone background levels for 

### DfW (re!lecting concentrations contributedto the area by emissions from sources within Texas but olltside the nonattainment area, and from sources outside Texas) arc estimated to range between 44 and ()I ppb, with peak averages between 64 and 68 ppb on days when 8-hourozone concentrations exceed the 1997 standard. IY 

### To evaluate the impactofwind direction on ozone transport from Colorado to the 

### DFW maintenance receptors, we rely onthe results oftwo back tra;jectory studies, including a set of trajectories witl1 end points at the maintenance receptors in the D

### FW area.20 

### EPA generated these trajectories using the IIYSPLIT 4.9 online computerapplication, selectingthe archived Eta Data Assimilation System (EDAS) meteorological data sets with the highest degree ofresolution (40 km).21 Back trajectories were run for the days ofthe 2005-2006 years in which ozone concentrations at these receptors exceeded the 1997 8-hour NAAQS-i.e., monitored ozone

-----------------_._-- ---------_._-------­ rerresents the distance along a straight pathway from Lamar to Dallas, Texas, as compared to the rathways full of twists and turns that often characterize the long range transpon ofair parcels. I') "Dallas-!'"ort Wonh Eight-Hour Ozone Nonattainll1ent Area: Attainme:lt Demonstration," TCEQ, May 23, 2007, p. I 'II**USL~I'A** Region 8 marped o,teK traJectories using software and data files maintained by the National Oceanic and i\tll1osrheric Administration (:'';OA;\) Air Resource Laboratory (ARL). 21 [)raxieI', R R. and Rolph, (j D
.. IIYS 1)1,11' (I IYbrid Single-PartieIe Lagrangian Integrated Trajectory) Model (20 10), available via NOAA ARL READY Website, http://rcady.arlnoaa.gov/IIYSPLlT.php. NOAA Air R.esources l,aboratory, Silver Spring, MD. See also Rolph, G.D., R.eal-time Environmental Applications and Display sYstemPage 20 of30 concentrations were 85 ppb or above. Exceedance days were identified using the Air Quality System (AQS), EPA's repository ofmonitored ambient air quality data. At each monitor, trajectories were started at 22:00 Coordinated Universal Time (UTC), equivalent to 4:00 pm CST, and were run backwards in time for 72 hours (three days.) Thetrajectory height at the starting point is 1500 meters above ground level. From the individual bal:k trajectories, "spider web" maps were generated for all three monitors combined and for each monitor (Figure 1.1 and Figures 1.1.21 through 1.1.c in Appendix A ofEPA's TSD).22 These maps indicate that air parcel pathways from Colorado and ending at maintenance receptors in Dallas and Tarrant Counties are
rare during the three days preceding ozone exceedances atthese receptors. Ononly one day, of the 35 exeeedance-days at maintenance receptors in 2005-2006, did the air mass pathway go through Colorado, and even in this one instance air parl:cls crossed the State along a short pathway through its northeast corner, before continuing on their southeastward l:ourse. 23 Backtrajectory analysis results included in the May 23, 2007 DFW areaAttainment Demonstration corroborate'these conclusions. The analysis, also based on the IIYSPLITmodel, includes all Jays during the years 2001-2003, with trajectories 01'48 hours (2 days) duration, heights of 100, 500 and 1300 meters, and start times of20, 21 and 22 UTe (2:00, 3:00, and 4:00 pm CST.) The resulting density plots in Figure 3-1 ofthe DFW attainment demonstration clearly show that during most ofthe ozone season, on high and lowozone days, air parcels from



### ---_. ---.-..

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### _ 

## _-_.



# __. (READY) Website (20I0). hltp:l/n:ady.arl.noaa.gov.**~()AA** Air Resources Laboratory. Silver Spring. MD.**~'See** back trajectory maps in Appendix AoCthe EPA's TSD supporting documentation in Docket ID No. r'YA­ R08-0AR-2007-!035 "EPA's TSD is available for review as part oCthe supporting documentation for Docket ID N. EPA-ROR-OAR­ 2007-1035.Page 21 

### 01'30 Colorado infrequently end in orpass through the DFW area.24 Because back trajectory analysis results map pathways ofair parc<:\s that mayor may not transport pollutants, they cannot be considered**deterrninativ(~** as to the transport ofozone and its precursors, or ofthe absence ofsuch transport, from Colorado emissions. However, the rarity of air parcel trajectories from Colorado to the DFW area and to its maintenance receptors strongly support the conclusion thatemissions ofozone and its precursors from Colorado arc not likely to interfere with maintenance ofthe 1997 ozone NAAQS at these receptors. A final piece ofevidence ofa different type is found in a modeling analysis developed by EPA to assistthe State ofNew Mexico in its assessment ofozone and PM25 transport from New Mexico to other states. This modeling analysis, part ofthe New Mexico Interstate Transport SIP submission ofJuly 30, 

### 2007, relies on data developed by the Central Regional Air PlanningAssociation (CI:NRAP) that includes a 2002 third quarter CENRAP modeling dataset. 25 It is based on a 36 km national grid that includes Colorado, and uses the ozone source apportionment tool (OSAT) to determine potential linkages between state emissions and downwind states.2() Modeling results indicate that at the height ofthe 

### 2002 ozone season, the highest ozone contribution from Colorado emissions to the DFW monitors (including its maintenance receptors) averaged 0.4 ppb or less. That is well belowthe contribution threshold of0.8 ppb, used in the proposed Transport Rule. The other five Texas monitors identifiedby the Transport Rule Proposal as maintenancconly receptors in Texas arc located in lIarris County, which lies within the HGB nonattainment

.!I Dallas-r:ort Worth Attainment Demonstration, May 23, 2007, at 3-1 to 3-2. 2) "\.;ew Mexico State Interstate Tl'ansport SIP," submitted to [PA July 30, 2007: Appendix D, Exhibit 9 ModelingPage 22 of30

area. This area is at least 700 miles from Colorado?? General considerations on the effect of distance on ozone transport from Colorado to the DFW area, discussed above, also apply to the potential ror transport rrom Colorado to the maintenance receptors in the HGB area. The greater distance (hy ahuut onc third) hetwecn Colorado and the 11GB area increases the chance !()r dispersion ofany Colorado ozone during its transport to IIGf3 maintenance receptors. and increases the odds for air masses from Colorado to pick up greaterquantities ofozone and/or precursors during their longertravel through emissions rich Texas. Again, these considerations reduce, but do not exclude, the possibility ofemissions from Colorado interfering with maintenance ofthe 8-hourozone NAAQS at the 11GB maintenance receptors. A similarconclusion is suggested by the EPA hack trajectories mapped for the 11GB maintenance receptors. Using the same online 

### HYSPUT4.9 onlinecomputer application as for the ])FW trajectories,28 EPA ranback trajectories from the HGB areamaintenance receptors for all 2005-2006 ozone excecdances days. The pathways ofairparcels ending at, orpassing through, these monitors when ozone concentrations reached levels of85 ppb orhigherare shown in Figure 2.1 ofAppendix A in FPA's supporting documentation. At each monitor, trajectories started at 22:00 Coordinated Universal Time (UTC), equivalent to 4:00 pIll CST. and ran

Data and Rep0l1 for New Mexico," at 2. 26 For details on the model and on the analysis see: id
.

. 27 The 700 mile estimate represents the approximate .distance between Lamar. in the southeastern corner of' Colorado. and Houston, Texas. The jive monitoring sites' names (ID No.) are: Aldine (48-201-0024), NOl1hwest l!aITis (48-201-0029), Lynchburg Ferry (48-201-101S), Clinton (48-201-1tnS), and Seabrook [;riendship Park (48-20 I-I(50). The approximate 850 mile distance between Denver and Houston is intended to represent the distance to be covered by the emi.'isions from Colorado to the five maintenance monitors. It is to be noted that the measured distance represents that ofthe straight (and shOltest) path, which docs not reflect the more circuitous paths I"ollowed by air parcels. 'x Sec note 24 'Ibovl'.Page 23 

# or30 backwards in time for 72 hours (three days), at 1500 mcters above ground level. 2'i Results show that air parcel pathways passing 1500 meters above the HGB maintenance receptors at 4:00 pm
on exceedance days rarely camefrom Colorado. Figure 3 ofthe back trajectories report shows that only in one out of53 exceedance days at the maintenance receptors did the air parcel's pathway go through Colorado. Even in this one instance, the pathway crossed Colorado for a very short distance through the State's northeast corner, before continuing on its southeastward
\Ii course. Back trajectory analysis results from a 2009 report, "Effects ofMeteorology on Pollutant Trends" report, corroborate these conclusions. The analysis uses 1IYSPUT with EDAS meteorological datasets to plot72 hourbacktrajectories centered in 

### fIouston, at 300 meters height and for various times ofthe day. Trajectories are plotted for all days with available data between May 1and October 31, 2000-2007. A clustering algorithm built into I[YSPUT is used to group individual back trajectories into several classes based on shape ancl direction. 3l Due to the greater number ofdays plotted, the six clusters oftrajectories shown in Figures 6-17 to 6-22 include a much larger number ofair parcel pathways than EPA's back trajectory analysis referenced above, but still showsimilarresults concerningtrajectories from Colorado. Air parcels from Colorado to the I[ouston area are rare, as shown by the few trajectories from

"J Sec Tabk I, !:IlA's**"B,IC~** Trajectories Analysis f)ocumeillatiun," Table [. 't, The trajectory's path that ended at the :\onhwest HaiTi, !'eceptor on August 31, :2006, is almost the same as the one that on June IS, 2005 ended at the Keller receptor in Tarrant. This IS likely to be a coincidence, or an Indication about the pathways ofair masses that go through eastern Colorado before ending in eastern Texas (DFW and 11GB areas). 31 f),lve Sullivan, "Effects oPv1eteoroiogy on Pollutant Trends," March 16,2009, at 27-34. This repon is available as one ofthe documents in EPA'sTSD documentation, and may also be reviewed 0111ine at**http://www.t~.lUiJ~.tx.us!~sscts!pll.QllcjjmnJ~nJ.mill1iS)ll!air!.i!.IJJ! G_()Il\ract"Lrepol"\~LQ.<tl5&2Q**  5QP245FY080 I 200903**16-LJt.:-IJ1£L£JJ~ts** ...Q!l....J2QlliLtlJ!lUlfI19S.pdf.Page 24 of30 Colorado in cluster 3 (Figure 6-19) as compared with the total sample of 1416 trajectories included in the six clusters. Figure 6-15 summarizes effectively the overall scarcity ofwind pathways from Colorado, and from the west/lower northwest sector in generaL to the HGB area. It shows the mean centerlines for the six identitied clusters, and at their closest point to Colorado's borders the mean centerline (number 3) is still at an estimated distance of approximately 200 miles. Again, back trajectories map pathways orair parcels that mayormay not transport pollutants, and they cannot be considered determinative as to the transport ofozone and its precursors. llowever, the infrequency ofair parcels trajectories from Coloradoto the HGB area in generaL and to its maintenance receptors in particular, strongly support the conclusion that

ozone precursors' emissions and ozone from Colorado are not likely to interfere with maintenance ofthe 1997 ozone NAAQS at these receptors. The EPA modeling analysis referenced earlier (concerning contribution from Colorado

sourcesto the DFW area) includes information on the contribution ofthe Stateemissions to the 11GB area as well. The 2002 modeled contribution from Colorado ozone emissions to the HGB

area is estimated at 0.3 ppb or less. This fraction ofthe significantcontribution threshold of0.8 ppb, set in EPA's Transport Rule Proposal ofAugust 2,2010, strengthens ourassessment that Colorado emissions are unlikely to interfere with maintenance ofthe 1997 ozoneNAAQS at the 11GB maintenance receptors.}2 As noted previously, eight ofthe 16 maintenance receptors identified within the modeling

" l'\ew Vlexieo Stille Interstate Trallsport SIP, 2007. Appendix D, at 52.Page 25 of30 by the Transport Rule Proposal analysis are in a handful ofEast Coast states: Connecticut, Cicorgia, New York and Pennsylvania.]] The westernmost states "linked" by the Transport Rule Proposal to the eight maintenance receptors in these states include Indiana, Kentucky, Tennessee, and Alabama. None ofthe 13 states west ofthese contributing states and east of Colorado (such as North and South Dakotaand Nebraska) was found to contribute significantly to the maintenance receptors in the east.]l In addition, among the 13 non-contributing states closerthan Colorado to the maintenance receptors in the easL there arc states such as Illinois, Wisconsin, Iowa, Missouri, Arkansas, and I,ouisianathat in 2005 had NOx emissions up to twice

as high as Colorado's. Because the analysis for the Transport Rule Proposal found that these states with substantially largerNOx emissions than Colorado, and closerthan Colorado to the maintenance receptors in the cast, do not to contribute significantly to maintenance receptors in Connecticut, Georgia, New York and Pennsylvania, it is logical to concludethat it is quite unlikely for Colorado emissions to interfere with maintenance ofthe 1997 8-hourozoneNAAQS at these same receptors. To assist in the evaluation ofwhether states' emissions interfere with maintenance ofthe NAAQS in western states, t;;PA has developed, independent ofthe Transport Rule Proposal, a modeling analysis identifying monitors at risk for maintenance ofthe NAAQS within a modeling domain that includes the western states.';'; The analysis presented in the memo, "Documentation

;) Table IV C-12, Transport Rule, at 196-197. ;·1 [n addition to North Dakota, South Dakota and Nebraska, the 13**state~;** include: Kansas, Oklahoma, Minnesota, Iowa, Missouri, Arizona. Wisconsin, Michigan. Illinois, and [,ouisiana. Table IV-C-21, Transport Rule Proposal, at 45269-70. l'; !\ memorandum in the docket for tillS action provides the inlonnation EPA used in order to identify monitors that 'In: !'ccep(ors for l'vahldtion ofinterference with maintenance for cCl1ain staks in the western Unitcd States. See.Page 26 of30 ofFuture Year Ozone and Annual PM2 :i Design Values for Western States" (Western States Design Values), uses model results from the Transport Rule modeling Continental U.S. 36 km grid, which is coarserthan the 12 km grid used in the TransportRule, but docs not necessarily yield less reliable results. 3!> EPA's modeling analysis ofwestern states to determine the monitors that are at risk for maintenance ofthe 1997 8-hourozone NAAQS identifies only four such maintenance receptors, and all four are in California, in Mercer, Placer, Riverside, and Sacramento Counties. Distance and topography are not favorable to ozone transport from Denver, which is approximately 750 miles east ofthe monitors in Placerand Sacramento Counties. and 850 miles northeastto a Riverside County monitor. In the absence o(significant norlhwesterly regional transport winds. mountain ranges between Denver and the Californiamaintenance receptors, such as the Rocky Mountains, theWasatch and the SierraNevada, present large obstaclesto ozone transport from Colorado to California. Thus, geography and topography reduce the likelihood oftransport from Colorado to California's maintenance receptors. Prevailing wind orientation in**t~lct** strongly supports the conclusion that Colorado's emissions are unlikely to interfere with maintenance ofthe 1997 8-hourozone standard in California. West ofthe Continental Divide the prevailing winds generally move from southwesterly, westerly, ornorth-westerly directions, as indicated by the typical movement ofweather systems. To further evaluate the direction ofregional transport winds affecting the Calif()rnia maintenance receptors, we have plotted backtrajectories sterting at each maintenance receptor
\!kll1orandull1 rrOIl1 Bnan Tirnin orleI'A's Ortice orJ\ir Quality Plannil;g and**Standal'd~.** Ait' Qualit)' Modeling Ciroup entitled "Docull1entation ofFuture Year Ozone and Annual PM::! 5 Design Value, ror Western Stales"Page 27 of30

on high ozone days. Iligh ozone days include the top one trlird ofthe exceedance days (forthe 1997 8-hourol:one :,\AAQS) registered at each monitorin 2005 and 2006. As shown by the trajectories mapped for all four maintenance receptors in Figure 3.1, Appendix A ofEPA's supporting documentation, on high ozone days air parcels converge on the Mercer, Placer, Sacramento and Riverside monitors from the northwest, south and southeast, but there arc no pathways from the cast/northeast directions reaching even as far as the eastern Nevada border, let alone Colorado For a large number ofreceptors in western states, EPA's modeling analysis could not calculate 2012 projected design values becausethese receptors did not have at least 5 days with base year concentrations equal to or greaterthan 70 ppb, as required by**~PA's** modeling guidance. However, the observed maximum design values at these sites in the 2003-2007 period

were generally well below the 1997 ozone N/\AQS. The highest (non-Calit()rnial?) site had a maximum design value 01'77 ppb. Additionally, the 2012 modeling results at western monitors (where a future year design value could be estimated, shows a downward trend in ol:one. There

are no areas in the West where ozone is predictedto be higher in 2012 (without CArR) compared to 2005. Onthese bascs it is plausibleto concludethat it is highly unlikely,butnot impossible, !()r these monitors to be at risk for maintenance ofthe 1997 8-hour ozone NAAQS. In conclusion. the variety

# ordata and the weight ofevidence analysis prcsenkd in this

-----------------**-------~--------------** .. ---._-- - .-- ._-- ----­ "Memorandum to Docket**EPA-RO~-OAR-2()07-1035,,.** EPA, August 23, 2010. ii, Id. at 5. 37 We are excluding the California monitors from this portion afoul' analysis because above we have already demonstrated that Colorado's emissions are unlikely to interfere with maintenance at the mOdeled California maintenance monitors in the northern, centra] and southern sections ofthe state. The factors we considered-·­ distance, topography, and wind orientation·apply equally to the un-modeled monitors and make it plausible to cOJl(.:lude th,1t the same demol1stratiol1 is true for Colorado emissions' impact on California non-modeled monitors.Page 28 of30 scction support the position orthe Colorado Interstatc Transport SIP (adopted into the State SIP

on Dccembcr 3D, 2008 and submittedto EPA June 18,2009)that emissions from Colorado do not intertCre with maintenancc ofthc 1997 8-hour ozone NAAQS by any othcr state, consistent with the rcquiremcnts ofelcment (2) ofCAA section IIO(a)(2)(D)(i). VI. Proposed Action EPA is proposingpartial approval ofthe Colorado SIP to meet the requirements of Section IIO(a)(2)(D)(i)(I) regarding the 1997 8-hourozone standard. Specifically, in this action EPA is proposingto approve only the language and demonstration that address the requirements ofclement (2): prohibition ofinterference with maintenance ofthe 1997 8-hour ozone NAAQS by any otherstate. EPA approved in a 

### JLIne 3, 2010 final actionthe language and demonstration addressing clement (1): prohibition ofsignificantcontribution to nonattainment ofthe 1997 8­ hourozone NAAQS in any other state. VII. Statutory and Executive Order Review Under the Clean Air Act. the Administrator is required to approve a SIP submission that complics with the provisions ofthe Act and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve state choices, provided that they meet the criteriaofthe Clean Air Act. Accordingly, this action merely approves state lawas meeting Federal requirements and does not impose additional rcquirements beyond those imposed by state law. Forthat reason, this action:

• Is not a "significant regulatory action" subject to reviewby thc Office ofManagemcnt and Budget under**l~xecLltive** Order 128G6 (58 FR 51735. October4, 1993);Page 

### 29 of:;O

• J)oes not impose an information collection burden under the provisions ofthe Paperwork Reduction Act (44 Us.c. 3501 el seq.);

• Is certified as not having a significant economic impact on a substantial numberofsmall entities underthe Regulatory Flexibility Act 

### (5 U.S.c. 601 et seq.);

• Does not contain any unfunded mandate or significantly oruniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Public Law 104-4):

• Does not have Federalism implications as speci1ied in Execlltive Order 13132 

### (64 FR 

### 43255, August J0, 1(99);

• Is not an economically significantregulatory action based on health or safety risks subjectto Executive Order 

### 13045 (62 FR 19885, April 23, 19(7);

• Is not 

### a significantregulatory action subject to Executivc Order 

### 132J

### 1(66 FR 28355, May 22, 

### 2001);

• Is not subjectto requircments ofSection 12(d)**ofthi~** National Technology Transfer and Advancement Act of 1995 (15 U.S.c. 272 note) because application ofthose requirements would be inconsistent withthe Clean AirAct; and

• Docs not provide EPA with the discretionary authority to address, as appropriate, disproportionate human health orenvironmental efkcts, using practicable and legally permissible methods, under Executive Order 

### 12i{98 (59 FR 

### 7629, February 1(), 

### 19(4). In addition, this rule c10es not have tribal implications as specified by Executive Order J3J75 (65 FE 

### 67249, November 9,2000), because the SIP is not approved to apply in Indian country

### Page 30 of30 

### IDENTIFICATION OF DOCUMENT: Approval and Promulgation ofState Implementation Plans; State ofColorado; Interstate TransportofPollution Revisions for the 1997 8-hour Ozone NAAQS: "Interference with Maintenance" Requirement. Proposed Rule. (EPA-R08-0AR-2007-1035) Page 30 of30 located in the state, and EPA notes that it will not impose substantial direct costs on tribal governments orpreempt tribal law. 

### List ofSubjects in 40 CFRPart 52 Environmental protection, Airpollution control, Incorporation by reference, Intergovernmental relations, Nitrogen dioxide, Ozone, Particulate matter, Reporting and rccordkeeping requirements, Volatile Organic Compounds. 

### Authority: 

### 42 U.S.c. 7401 et seq.



# __**rL9~**

# ~~~ Dated: Carol Rushin Acting Regional Administrator Region 8