UNrTED STATES ENVIRONMENTAL PROTECTION AGENCY RESEARCH TRIANGLE PARK, NC 27711



### Mr. David Isaacs Vice President, Government Policy Semiconductor Industry Association 1101 K Street, NW, Suite 450 Washington, D.C. 20005

Dear Mr. Isaacs: 

# AUG 2 f) 

### ?

## iJ 

# 1:

OFFICE OF AIR OUAli'TYPLANNING

AND STANDARDS



### The U.S. Environmental Protection Agency has received your letler dated July 29, 2011, in which you have articulated concerns about permitting for the semiconductor industry after the implementation of the Prevention ofSignificant Deterioration (PSD) and Title VGreenhouse Gas (GHG) Tailoring Rule (the "Tailoring Rule"). In particular, your letterrequested infonnation on the folJowing areas related to the application ofPSD to semiconductormanufacturing facilities:

l. 

### Treatment ofa semiconductor fabrication building (fab) as an "emissions unit" for purposes of dctennining PSD applicability. 2. Addressing the day-to-day changes for PSD applicability determinations. 3. Treatment ofcontrol measures when determining projected actual emissions (PAE). 4. Use ofGHG Plontwide Applicability Limits (PALs).

We understand from your letter that the regulation ofGHGs will trigger PSD permittingrequirements tor some semiconductormanufacturing facilities for the first time. Your letter explainedthat fabs may make changes on a daily basis and that the ability to make those changes quickly is critical. Our responses to yourquestions are designed to help the semiconductor industry understand and comply with their PSD requirements. Background

- The Semiconductor Industry

On January 2, 2011, GHG emissions from stationary sources bccwne covered by the PSD permitting program for the first Lime. Additionally, GHO emissions first became subject to the title Voperating permits program as ofJuly I, 20II. Semiconductor sources may now trigger permitting requirements under these two programs because oftheir GHG emissions. In the past, semiconductor sources have been able to avoid major source permitting requirements (i.e., PSD and title V) by implementing a series ofcontrol measures and accepting minor source emissions caps that kept them below major source thresholds. This approach has provided the semiconductor industry with needed operational flexibility.

Over the past 15 years members ofthe semiconductor industry have achieved reductions in fluorinated GHG emissions, including pertluorocarbons (PFCs), bydronuorocarbons (HFCs), and sulfur hexafluoride (SF,), 

### through process optimization, use ofalternative chemistry, and emissions abatement (i.e., installation ofair pollution control equipment). In large part.**th~** 

### reductions are attributable to a

lntemet Address (URL) • http://www.epa.gov Recycled/Rocllcloble •Prtnledwllh Vegetablll Oil Based Inial on Aecydad Paper (Minlmum:ZS% Postconsumar)voluntary partnership 1between the· Semiconductor Industry Association (SIA) and the EPA that pursuant to a memoranda ofunderstanding. As part ofthe partnership, member companies committed to reduce emissions offluorinated GHGs and to track and annuallyreport those emissions. In most cases, voluntarily installed GltG emission controls were not incorporated into facility air permits because there

were then no underlying applicable Clean AirAct requirements. SIA reports that GHG emission control devices were applied to etch and chamberclean processes primarily at newer fabrication plants. The most commontechnologies used are hightemperatureoxidizers followed by wet scrubbers to remove by-products.
Spccitic SIA Questions



### I. 

### Treatment ofa Semiconductor Fab as an "Emissions Unit" for Purposes ofDeterminingPSD Applicability

In your letteryou indicate that in minor source permitting ofsemiconductor manufacturing facilities, by local and state air pcnnitting agencies, each fab at a facility is normally treated as an individual emissions unit.2 You are now seeking confirmation that it is appropriate to treat each semiconductor fab at a manufacturing facility 

### as a single emissionsunit for the purposes ofdetermining PSD applicability. This approach seems appropriate becauseofthe interconnected nature ofthe "tools" in the fab. Similarly, the systems that deliver materials to those 

### tools and manage their discharges have also generally beentreated 

### as part ofthe emissions unit.


### Often, an "emissions unit" is assumed to

### be a single piece ofprocess equipment or activity. However, many pieces ofrelated process equipment grouped together may also fit within the definition of "emissions unit" under the federal PSDregulations. ln orderto determine how the "emissions unit" should be defined in this case we first look to the definition of"emissions unit" found at 

### 40 CFR §52.21 (b)(7).

Emissions unit means any part ofa stationary source that emits or would have the potential to emit any regulated NSR pollutant and includes an electric utility steam generating unit

### as defined in paragraph (b)(31) ofthis section. For purposes ofthis section, there are two types ofemissions units as described in paragraphs (b)(7)(i) and (ii) ofthis section:
(i) A new emissions unit is any emissions unit that is (or will be) newly constructed and that has existed for Jess than 2 years from the date such emissions unit first operated. {ii) Anexisting emissions unit is anyemissions unit that does not meet the requirements in paragraph (b)(7)(i) ofthis section. A replacement unit, as defined in paragraph (b)(33) of this section, is an existing emissions unit.
Additionally, although not determinative, New Source Performance Standards (NSPS) and National Emission Standards for Hazardous Air Pollutants (NESJlAP) can be sources ofinformation that may be

1PFC Reduction/Climate Partnership for the Semiconductor Industry; see http://www.epa.gov/semiconductor-pfc. 2 Some examples where this approach has been used arc: IBM Ea:st Fishkill Facility in Hopewell Junction, NY title V pennit; Vitesse Corp in Colorado Springs, CO state operating permit; Renesas Electronics in Roseville, CA operating penn it; and Micron Technology in Boise ID construction and operating pcnnit. 2

### helpful 

### in defining an emission unit. Inthis caseNESHAP SubpartBBBBB- National Emission Standards for Hazardous Air Pollutants for Semiconductor Manufacturing provides relevant information
on what a semiconductor manufacturing process unitmightbe. NESHAP Subpart BBBBB states that:

Asemiconductor manufacturing process unit includes the equipment assembled and connected by ductwork orhard-piping including furnaces and associated unit operations; associated wetand dry work benches; associated recovery devices; feed, intermediate, and product storage tanks; product transferracks and connected ducts and piping; pumps, compressors, agitators, pressurereliefdevices, sampling connecting systems, open-ended valves orlines, valves, connectors, and instrumentation systems; and control devices.

Ourpast guidance on the treatment of"emissions units" in other industries is consistent with this approach. In a letter issued by the EPA Region III on November 30, 2000, the EPA provided guidance regarding aproposed PSD modification at aDuPont faciJity. 3 

### The guidance indicated that DuPont's proposed projectcould be

### considered amodification to a single emissions unit. The emissions unit was defined as the entire solvent-spun synthetic fiber process that included the spinning, wash/draw, and solvent recovery operations. Similarly, in guidance issued by the EPA Region VIII datedFebruary 6) 

### 1990, regarding a determination ofLowest Achievable Emission Rate (LAER) for Coors Container,4 

### the EPA determined that an emissions unit consistedofthe entire coating operation (topcoat, basecoat, etc). In both determinations the NSPS definition ofemissions unit was relied upon; the rule provided a rationale for grouping the processes togetherto create a single emission limitation covering all ofthe equipment. This was the most technically-achievable and cost-effective way to evaluate control for these operations.

Given the flexibility provided for in the PSD definition ofemission unit, considering the treatment of semiconductorfacilities under the NESHAP, and considering ourprevious guidance on this matter we believe that the treatment ofafab as an emissions unit for PSD applicability purposes is appropriate. We believe it

### would usually 

### be consistent with the federal definition of"emissions unit" to include in the fab "emissions unit" the integrated contiguous cleanroom space, including all the tools, and systemsthat supportthe activities in the clean room. The fab emissions unit could be located in a single building or adjoining buildings as long as it is physically connected, integrated, and operated as a continuous clean
room space. However, ifa building or facility were to contain more than one physically separated and independent clean room, we believe it would generally be appropriate to treat those fabs as separate emissions units. Airpollutant control equipment that serves more than one fab may need to be treated as a separate emissions unit under

## the relevant regulatory definition of"emissions unit," for example a regenerative thermal oxidizer (RTO) that serves multiple fabs to control volatile organic compounds (VOC) emissions will emit GHGs and should be 

### treated as a separate emissionsunit. Not all contro] equipment will have additional emissions beyond that which they control. this needs to be considered when determining how fabs and their control equipment are treated as emissions units. We believe that it would generally be consistentwith the federal definitions of"emissions unit" to treat equipment serving

3 U.S. EPA, Region UI, to John Daniel, Director, AirProgram Coordination, Commonwealth ofVirginia, Department of Environmental Quality, 30 November 2000. 4 U.S. EPA, Region VHI, to Brad Beckham, Director, Air Pollution Control Division, Colorado Department ofHealth, 6 February 1990. 3multiple fabs (such as boilers, emergency generators, and similarauxiliary equipment), that are operated separately and are often located in a separate building, 

### as separateemissionsunits.

When conducting a PSD applicability determination, all emissions increases from emission units associated with, or affected by a project must 

### be included in the calculations. Applied to the fab, this
means that the PSD applicability determination would look at the overall increase across the entire fab emissions unit from a project, not the specific changes at each particulartool or other system within the fab. Implementing state and local agencies may adopt different and potentially more stringent orless flexible requirements under their STP-approved minor or major New Source Review (NSR) programs. We encourage you to work with your reviewing agencies to confirm the specific requirements applicable to individual semiconductor manufacturing facilities.



### II. 

### Addressingthe**"day~to~day** 

### changes" for PSD applicability determination

In your letter you indicated that a number ofsemiconductor fabs undergo dozens ofsmall changes each year as the production methods and operations are maintained, updated, adjusted and refined. You proposed three approaches or methods forpractical and efficient PSD applicability detennination for such changes described in your letter as "day-to-day changes" and requested whether each ofthe proposed methods would provide an adequate record ofPSD non-applicability.
rirst, we would like to clarify that our response to this request on "day-to-day changes" assumes that the subject facilities are potentially major PSD sources only due to GHG emissions (i.e., potential emissions ofall non-GHG regulated NSR pollutants are assun1ed to be below major source thresholds both before and afterthe project at issue). Accordingly, we are limiting ourresponse to PSD applicability procedures and requirements applicable to GHGs, more specifically to the established "subject to regulation" thresholds for GHGs, based on carbon dioxide (C02) equivalent (C02e) emissions.5This is consistent with the context ofthe SIA's proposed applicability determination methods and ourunderstanding that many semiconductor manufacturing facilities are potentially major sources under PSD only due to GHGs.

We summarized the three S[A proposed PSD applicability determination methods below with our corresponding responses.


### SJA's Proposed Method 1-This method would applywhen theProjected Actual Emissions ofthe fab are well below 75,000 tpy 

### C02

### e. In such a case, 

### ifit is determined thatthe change does not increase the Projected Actual Emissions, this determination will serve as a record that the change cannol trigger PSD. Underthis method, thefab ownerwould create and record an assessment of the Projected Actual Emissions and the review ofeach changewould be a simple determination that the projectwill 

### not increase the Projected Actual Emissions.

Under 40 CFR 52.2l(b)(49)(v)(b) GHGs arc subject to regulation for anexisting stationary source that emits orhas the potential to emit 100,000 tpy C02e, when the source undertakes a physical change or**~** 40 CFR 52.2I(bX49). As a result ofthe Tailoring Rule, GHGs are treated differently ftom non-01-10 regulated NSR pollutants under the PSO program. EPA has published detailed guidance on PSD applicability determinations and other permitting requirements for GHGs. See hnp://www.cpa.gov/nsr/ghgpcrmilting.html. 4change inthe method ofoperation that 

### will result in an emissions increase of75,000 tpy 

### C02c ormore. The temt "emissions increase" inthis context means both a significant emissions increase as calculated under 52.21(a)(2)(iv) and a significant net emissions increase as defined in 52.21(b)(3) and (b)(23).6 Under 52.21(a)(2)(iv) whether an emissions increase occurs for a project involving only existing emissions units (e.g., an existing fab) is detennined using the actual-to-projected-actual emissions test. In summary, thattest involves calculating baseline actual emissions and projected actual emissions for each emissions unit affected by a projectand calculating the project emissions increase as the sum ofthe differences betweenprojected actual emissions and baseline actual emissions for each unit.7The definition ofprojected actual emissions provides that the owner oroperatormay exclude, in calculating the increase from a particular emissions unit, thatportion ofthe unit's emissions following the project that the unit could have accommodated in the selectedbaseline actual emissions period and that are also unrelated to the project.8

SIA's proposed Method I relies on a simplified versionofthe actual-to-projected-actual emissions test
as an initial screen for purposes ofdetermining whetherthere is a significant emissions increase in evaluating whether GHGs are subjectto regulation for a project that, under certain circumstances, may provide a streamlined approach to these calculations. Because the proposed approach ignores baseline actual emissions, thereby assuming baseline actual emissions equal zero, and because it does not exclude any ofthe fab emissions following theproject in determining the increase, itrepresents a conservative estimate ofthe increasein emissions occurring from the fab as a result ofthe project. Moreover, 

### ifthe projected actualemissions alone from a fab do not exceed 75,000 tpy C02e, the calculation of significant emissions increase under the actual-to-projected-actual test for that fab would also not exceed 75,000 tpy C02e, suchthat GHGs would not be subjectto regulation for that project, assuming the fab
was the only affected emissions unit.

In general, we fmd Method 1 acceptable as an initial screen for purposes ofdetermining that there is not
a significant emissions increase in GHGs from a project in orderto determine whether GHGs are subject to regulation for that project. IfGHGs are not subjectto regulation for a project, PSD would not be triggered due to GHG emissions increases resulting from the project at a fab. However, we would liketo clarify certain additional requirements. First, our aggregationpolicy, discussed in further detail in our response to SIAproposed Method 3, requires that nominally separate changes that are sufficiently related based on established criteriabe aggregated into a single common project for the purpose of determining PSD applicability.9 Accordingly, owners oroperators should evaluate "day to day changes" to determine the properaggregation ofsuch changes priorto evaluating PSD applicability. Second, our interpretation ofthe Clean Air Act and long standing policyrequires that calculations ofprojeet emissions increases include not only those increases occurring from new ormodified emissions units but also affected non-modified units. 10 For example, a modification to an existing semiconductorfacility fab

6 40 CFR 52.2l(b)(49Xiii). 7 40 CFR 52.21(a)(2Xiv)(c). 840 CFR 52.21(b)(41Xii)(c). 9 For a collection ofpriorEPA memoranda relevant in detenniningwhether projects should be aggregated, please see 75 FR 19570-71 (April 15, 2010). While the policy discussion in this reconsideration notice does not represent a final agency position without further action by the agency, the numerous memoranda cited in this notice stand for themselves as examples ofour historic approach to aggregation. 10 The regulations define a "majormodification'' as one in which a physical change or a change in the method ofoperation ofa major stationary source results in a significantemissions increase ofa regulated NSR pollutant and a significant net 5may result in increased steam demand from facility boiler(s). 

### In that case, the boiler(s) could realize increased utilization on an annual basis (and a corresponding increase in GHG emissions) as a result of the changes in the fab and emissions from the boiler(s) must be evaluated using the actual-to-projectedactual emissions test to resolve the total emissions increase from the source that is related to the project.
17inally, your letter noted that the fab owner would create and record an**as..~essment** ofprojected actual emissions and requested whal record is adequate to demonstrate 

### PSD non-applicability.

# We believe that

a record that is consistent with the recordkeeping, monitoring, and reporting provisions of40 CFR 52.21 (r)(6) would be adequate to document a detennination ofPSD non-applicability in this situation.



### SIA

### 's Proposed Method 

### 2 - A simple variation on Method 1 can be used to deal with day-to-day changes at fahs that have Projected Actual Emissions over75,000 

### tpy C02 e. In this instance, the fab ownerwill also determine the Baseline Actual Emissions for a 24 

### month period in 

### the priorten years. Ifthe difference between theProjected Actual Emissions and the Baseline Actual Emissions is well below 75,000 

### tpy C02e, one applies the same approach as Method 1.
Proposed Method 

### 2 is a variation ofMethod 

### 1that incorporates baseline actual emissions into the calculation ofwhether a physical change or change in the method ofoperation ut 

### a stationary source that emits or has the potential to emit 

### I00,000 tpy 

### C02c 

### will result 

### in an significant emissions increase of 75,000 tpy C02e or more for purposes ofdetermining whetherGHGs are subject to regulation forthe project. As long as the calculation ofbaseline actual emissions and projected actual emissions comports with the regulatory definitions ofthose terms, we believe this approach is acceptable for determining that no significant increase ofemissions for GHGs occurred for the project and that GHGs are accordingly not subject to regulation for a project. 11 Ourresponse to proposed Method I related to project aggregation, the consideration ofall affected emissions units in the analysis, and appropriate recordkccping also applies to proposed Method 2.



### SIA's Proposed Method 

### 3- Underthis method, the fab ownerstarts each calendaryear with an assessment ofthe range ofchanges that may occur in the upcomingyear and then determines the nature oftheir C01

### e impacts. At the start ofthe year, the fab ownercompletes the actual-to· projected-actualemissions calculation to determine the maximum emissions increase thatcould result from the full 

### range ofchanges. That assessment can thenberelied upon to address applicability for all the day-to-day changes for that yearso long as the changes are consistentwith and within the scope ofchanges laid out at the start oftheyear. A reassessment is triggered annually orwith any mid-year departure from the plan ofaction thatwas assessed at the startof the year. Proposed Method 3 involves a project aggregation approach designed to reduce the burden of

### PSD applicability analyses for frequent, relatively minor physical and operational changes wilhin a fab. EPA has addressed project aggregation in several letters, memoranda, and rulemaking preambles that

emissions increase ofthatpollutant at the source. See40 CFR 52.21 (b)(2). Based on this, the total increase in emissions includes: ( 1) Increases occurring at all new or modified units, and (2) 11ny other increases at existing emissions units not being modified that experience emissions increases as a result

## orthe change. Increases occurring from units as a result of "debottlenecking" or"increased utilization'' caused by a project must be included in determining NSR applicability for the project. 11 Baseline actual emissions and projected actual emissions are defined in 40 CFR 52.21 (b)(48) and (b)(41 ), respectively. 6establish ourinterpretation oftheClean Air Actprovisions related to "modification" and policy on project aggregation.9 In brief, we look for indicia ofrelatedness among the individual actions at a source in order to determine whetherthe activities, in the aggregate, are one physical oroperational change as those terms are used in the statute and regulations. We have made clearinpast policy documentsthatthe EPA may enforce the major source permittingrequirements in cases when a source "circumvents" major NSR by dividing one change and its emissions increase into nominally-separate physical or operational changes. Ourpolicy on aggregation outlines an approach relying upon case-specific factors (e.g., timing, funding, and the company's own records) and the relationship between nominally-separate changes.

Ourpolicy does not preclude the aggregation ofmultiplephysical or operational changes when such changes taken together can be reasonably viewed as sufficiently related to be a single projecteven if individuallyorsmaller groupings also could be viewed as physical oroperational changes. So long as the grouping ofchanges aggregated togetheris consistent with our aggregation policies, does notresult in circumvention ofmajor modificationpermitting requirements, and does not create projectnetting opportunities that are inconsistent withthe regulatory provisions and ourpolicy, the group ofchanges may be assessed as one. The aggregation ofmultiple small changes that serve a common general purpose overthe course ofa reasonableplanning or funding time period (such as one year) as described inyour letter could qualify as a single project ifthe company's own records and representations support that conclusion, againconsistentwith our policy-based project aggregation criteria. In such circumstances we find it acceptable and appropriate to considerthe aggregate changes a singleproject within the fab.
Beyond the above relatively straight-forward contexthowever, application ofproposed Method 3 must take into consideration several additional factors to ensure compliancewith applicable regulatory provisions andpolicy. First, where individual changes are aggregated for the purpose ofapplicability analysis and streamlining, and individualchanges or smaller groupings ofchanges within the proposed aggregate 'project' appropriately could also be viewed as physical oroperational changes, the owner or operator should consider only those changes thatresult 

### in emissionsincreases 

### in the projection in the first step ofan applicability analysis and not any changes that result in emissions decreases when applyingthis method. 12 This is to ensure thatproject aggregation is notused as a mechanismto provide for "project netting", which

### as indicated above is not allowed by the regulations.
Second, we would like to make clear that there is no presumption that a one year aggregation period is appropriate orjustified for the purposes ofdetermining major modification applicability. Owners or operators mustcarefully review all proposed physical or operational changes occurring at a sourceto
ensure that they are appropriately aggregated in accordance with ourpolicy-based criteria. Separating components ofa project using proposed Method 3, for example- by accounting for some in one annual aggregation periodand others inthe next, could be considered circumvention ofPSD permitting requirements ifthe increase calculated usingproperproject aggregation is significant.

12 We have made clearthat only increases in emissions are accounted for under 'Step I' ofthe major modification applicability procedures (the determination oftheproject emissions increase). In orderto credit decreases in the applicability analysis, the owner or operatormust perform a contemporaneous netting analysis (i.e., 'Step2' ofthe applicability procedures). See, e.g., letter from Barbara A. Finazzo, U.S. EPA Region 2 to Kathleen Antoine, HOVENSA, L.L.C., "Re: HOVENSA Gas Turbine Nitrogen Oxides (GT NOx) Prevention ofSignificant Deterioration (PSD) Pennit ApplicationEmission Calculation Clarification;" March 30, 2010. 7Third, as described in ourresponses to proposed Methods 1and 2 the applicability analysis is notlimited to modified emissions units (e.g., anexisting fab in this scenario) but rather must include all units atthe

source that could be affected by the project. This includes non-modified emissions units that are debottlenecked or could realize increased utilization as a resultofthe changes inthe fab. Lastly, with respect to what would constitute an adequate record to documenta PSD non-applicability determination,
we believe that a record that is consistent withprovisions of40 CFR 52.21(r)(6) would be sufficient to document a determination ofPSD non-applicability in this situation.



### Ill. Treatmentofunenforceable controls when determining projected actual emissions

To determine PSD applicability (both for determining

### ifGHGs are subject to regulation and when evaluating whetherthere is a major modification at anexisting major stationary source), an owner or operator. may use one oftwotests to determine the emissions increase from an existing emissions unit: the "actual-to-projected-actual" emissionstest orthe "actual-to-potential" emissions test. 13 Ifthe emissions unit at an existing source is newthe owneroroperatormust use the "actual-to-potential" emissions test to calculateemissions increases at that unit. "Baseline actual emissions" are used to establish pre-project emissionsfor applicability purposes underbothtests.

For an existing emissions unit that is not an electric utility steam generating unit, "baseline actual emissions" are generallythe average rate in tons-per-yearat whichthe unit actuaHy emitted a regulated pollutant during any consecutive 24 month period (selectedbythe applicant) in the prior 10 years. 14 "Projected actual emissions" are the maximum annual rate, in tons-per-year that an existing unit is projected to emit a regulated pollutant in any one ofthe 5 or 10 years following the date the unit resumes regular operation after the project depending on whethercertain regulatory criteria are met.15 In calculating an increase usingthe "actual-to-projected-actual"emissions test the owneror operatormay exclude the portion ofthe unit's emissions following the project thatan existing unit couldhave accommodated during the baseline actual emissions period and that are also unrelated to the particular project including any increased utilization dueto product demand growth. 16 "Potential to emit" is the maximwn capacity ofa unit to emit a pollutant under its physical and operational design. Any physical
or operational limitation onthe capacity to emit, including airpollutioncontrol equipment and restrictions onhours ofoperationoronthe type or amountofmaterial combusted, stored, orprocessed, shall be treated as partofthe unit's design ifthe limitation orthe effect 

### it would have on emissions is enforceable as a practical matter. 11

Forthe purpose oflimiting potentialto emit, air pollution control equipment orthe effect it has on emissions must be enforceable as a practical matter. In general, this means that applicable permit

13 40CFR 52.2I(b)(2)(iv) and (b)(41). 14 40 CFR 52.2I(b)(48)(ii).
IS 40 CFR52.2I(b)(41). 16 40 CFR 52.2I(b)(4I)(ii)(c). 17 52.2l(b)(4). While the definition of"potential to emit" in the PSD regulations contains the tenn "federally enforceable," this aspect ofthatdecision was vacated in ChemicalManufacturersAssociation v. EPA, 70 F.3d 637 (D.C. Cir. 1995). See also National MiningAssociation v. EPA, 59 F.3d 1351, 1362-63 (D.C. Cir. 1995). We thus interpretthis tennto mean "federally enforceable or legally and practicably enforceable bya state orlocal airpollution control agency." See, e.g., Interim Policy ofFederal Enforceability Requirements for Limitations on Potential to Emitat 3-4 (Jan. 22, 1996). For simplification, we here use the term "enforceableas a practical matter" to encompass "federallyenforceable orlegally and practicably enforceable by a state or local airpollution control agency." 

### 8

### conditions establish a legal obligation to install and operatethe equipment and that compliance with the relevant permit limits canbe verified. However, for calculating projected actual emissions, it is not required that air pollution control equipment orthe effect such equipment has on emissions be enforceable to be considered, noris it required that the projected emissions themselves be made enforceable. As such, when calculatingprojected actual emissions, 

### in additionto considering legally enforceable restrictions, owners or operators may consider the effect on emissions ofdesign or operational parameters, including airpollution control equipment, that are notenforceable.
Projected actual emissions should be calculated consistent with the criteria contained in the definition of that term. 18 

### Generally, projected actual emissions are based onthe design and operational parameters that determine the emission rate perunit ofproduction or time and projected annual production or utilization rate. For the purposes ofprojected actual emissions, the design and operational parameters
can include airpollution control equipmentinstalled and operated on a unit 

### regardless ofwhether such equipment is legally enforceable. This approach provides consistency between the way voluntary controls are considered incalculating projected actual emissions and baseline actual emissions, thereby
more accurately resolving increases in emissions resulting from physical or operational changes.
Notwithstandingthe above conclusion, the burden is on the source owner or operator to ensure that projected actual emissions, including the effectofair pollution control equipment, arebased on sound scientific information, are reasonable, and that air pollutioncontrols are designed and operated consistentwith representations made inthe applicability calculations or else an emissions increase that could trigger PSD may occur. Capture and control efficiencies, outlet concentrations, or other metrics used to estimate controlled emissions should be supported by sourcetest data, vendor design specifications, guarantees, or engineering calculations as appropriate. In circumstances where air pollution control equipment has been considered in detcnniningprojected actual emissions for one or morepollutants from an existing emissions unit, it is incumbent onthe owner or operator to maintain and operate the equipment in accordance with good air pollution control practices, regardless ofwhether
or not such equipment is legally enforceable. At a minimum this means that any manufacturer recommended operating and maintenance procedures are followed andthat a record ofany parameter monitoring performed, maintenance activities, and periods ofcontrol equipment downtime be maintained. 

### It is important to stress that the EPA is authorized to take enforcement actionfor a violation ofPSD

### ifthe projection is notconsistent with the regulatory requirements.



### IV. Use ofGHGPlantwide Appiieability

### Limits

We acknowledge yourrequest for information as it relates to the use ofPALs for the semiconductor industry. We are in the process ofanalyzing your request and the applicable regulations and will be responding to this aspect ofyour request in a subsequent letter to be issued in the coming weeks.

18The definition ofprojected actual emissions specifiesthat owners or operators shall consider all relevant information, including but not limited to, historical operating data and the company's representations and highest projections ofbusiness activity. The definition also specifies that fugitive emissions, to the extentquantifiable, and emissions associated with startups, shutdowns, and malfunctions shall be included. See 40 CFR 52.21 (b)(41)(ii). 9Conclusion

The responses to your questions provided in this Jetter and associated interpretations pertain to the Federal PSD regulations. Implementing state and local agencies may adopt different and potentially

more stringent or less flexible requirements under their SIP-approved minor or major New Source Review (NSR) programs. We encourage youto work with yourreviewing agencies to confirm the specific requirements applicable to individual semiconductormanufacturing facilities.

I appreciate this opportunity to respond to your questions, and I hope this response answers your questions. Ifyou have additional questions, please contact Juan Santiago at (919) 541-1084.
Again, thank you for yourletter. 

### T appreciate the opportunity to be ofservice and trust the information provided is helpful.

cc: Janet McCabe, OAR AnnaMarie Wood, OAQPS Phil Brooks, OECA Elliott Zenick, OGC Juan Santiago, OAQPS Raj Rao, OAQPS Sincerely,

# ?~!l.W~ /A Stephen D. Page 

# f""' Director Office ofAir Quality Planning and Standards

10