The effect of the vacatur is that the cross-reference to 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1) in Table 2 to subpart LLL no longer operates to incorporate an SSM exemption.
      In light of the Sierra Club decision, EPA proposed to require that sources be in continuous compliance with emissions limits at all times, even during startup, shutdown, and malfunction74 FR at 21161-62. We proposed that these sources meet the same standards during these operating modes as during normal operation.  Id.  We also specifically asked for information on emissions during startup, shutdown, and malfunction, and how these periods might be defined.
      In these final amendments we have eliminated the cross-reference to the vacated General Provisions' exemptions contained in Table 1 of current subpart LLL.  In establishing the standards in this rule, EPA has taken into account cement kilns' operating properties during startup and shutdown periods and, for the reasons explained below, has established different standards for those periods.  EPA is not setting separate standards for malfunctions so that, for the reasons explained below, the standard that applies during normal operations applies during periods of malfunctions.  We have also revised Table 2 (the General Provisions table) in several respects.  For example, we have not incorporated the General Provisions' requirement that the source develop an SSM plan.  We also are not incorporating certain recordkeeping and reporting requirements related to the SSM exemption.  EPA has attempted to ensure that we have not incorporated into the regulatory text any provisions that are inappropriate, unnecessary, or redundant in the absence of the SSM exemption.
      Startup is the period of time between when fuel is first introduced into a cement kiln that is not firing fuel, and when the kiln temperatures are within normal operating limits, the kiln is using its normal operating fuel, and the kiln is producing clinker. During kiln startup, fuel is first introduced into the kiln to raise the kiln to the appropriate operating temperatures.  In the case of a cold start the fuel is typically a natural gas or distillate fuel.  Once the kiln reaches certain temperatures, the normal operation fuel is introduced.  After the kiln reaches stable operating temperatures, kiln feed is introduced in low amounts which are gradually increased.  Because the kiln feed is a significant source of most kiln emissions (HAP and otherwise), we would consequently expect that kiln emissions, on a concentration basis, would not be any higher during startup than during normal operations, though it is possible that there could be some short-term emission spikes due to transient conditions or release of emissions from materials left in the kiln after shutdown. Indeed, on a pure concentration basis, kiln emissions over time would likely be lower than during normal operation given the lesser volume of inputs being processed, and (at startup) the cleaner fuel being used to heat the kiln to normal operating conditions.
      As noted, we proposed the same standards at startup (and shutdown and malfunction, which are discussed separately below) as apply during normal operation.  Notwithstanding that stack concentrations over time would likely be the same or less than during normal operation, in some cases, the manner in which the standard is expressed is not appropriate during startup.  Most particularly, the mercury and PM standards are normalized to kiln production (amount of pollutant allowed being linked to a ton of clinker produced).  During startup, production is by definition either non-existent or very low.  Even where there is a modest amount of production during startup, relationships between HAP concentration and amount of product are so skewed as to make this means of measurement inappropriate.  In addition, normalized standards require accurate measurements of kiln volumetric flow rate (used to convert concentration into mass) and kiln flow rate changes in important ways from normal values during startup.  When considered along with such phenomena as varying kiln stack moisture contents and flow rate, flow rate measurements are significantly less accurate during startup than during normal operation.
      For these reasons, we are establishing standards for mercury and PM to be the same stack concentration as would apply during normal operation, but are expressed as that concentration, i.e., are no longer normalized to a unit of production.  Mercury and PM would be measured during startup with a CEMS (as during normal operation) and the concentration standard would be met on the basis of 7-day averages.  We do not believe a 30-day average is appropriate for these periods because they are of short duration, and it might take a period of 1 year or more to accumulate 30 days of startup operation.  We considered an averaging period equal to the time period of each startup, but that would have meant different averaging period for each event.  Therefore, we choose 7 days as a period short enough that you could accumulate the data necessary to calculate the average over a reasonable period (certainly less than a year) but long enough to allow averaging out any transients that may occur.  In this way, unavoidable short-term spikes which occur during startup would be averaged against the lower concentrations which otherwise typically maintained, and the standard is expected to be readily achievable.  A consequence of this compliance regime (as for the standards which apply during normal operation), is that a source (at least initially) cannot determine compliance based on any single startup (or shutdown) event.  Seven days of data will need to be averaged.
      All of the discussion above applies to THC emissions during startup: feed (the main source of THC emissions) is introduced gradually so THC emissions should ordinarily be lower, cleaner fuels are initially used to heat the kiln to normal temperatures, there can be transient emission excursions since the unit is not yet in steady state conditions.  The difference is that the THC standard is already expressed as a concentration, so the measurement difficulties with a normalized standard do not exist.  Consequently, EPA is adopting the same standard for THC during startup as applies during normal operation.  The standard is measured with a CEMS and is based on a 7-day average so that again the lower concentrations which ordinarily maintain at startup should balance out any transient events occurring because the kiln is not yet in steady state mode.
      HCl is also expressed as an un-normalized stack concentration.  Where measured with a CEM, EPA knows of no reason the same standard as applies during normal operation should not be met during startup (2 ppmvd measured and averaged with aCEMSover a 30-day averaging period).  However, for those units equipped with wet scrubbers, sources may choose to demonstrate compliance by means of stack testing and parametric monitoring. See section IV.A.3.  In such a circumstance, there are no parameters to measure because HCl will not be emitted.  This is because HCl is emitted only as kilns begin burning normal fuel, not the natural gas or distillate used as a fuel during startup.  Consequently, EPA is providing that emissions of HCl shall be zero at all such times as distillate or natural gas is used to fire the kiln (and that is the parameter which would be measured).
      The current standard for dioxins and furans is expressed either as a concentration, or a combination of concentration and temperature control at the inlet to the PM control device.  Continuous compliance is determined based on demonstrating the measured temperature at the inlet to the PM control device does not exceed the limit established during dioxin compliance testing. This is because higher PM control inlet temperature can increase dioxin emissions. See 63 FR 14196, March 24, 1998.  Based on a comment indicating that there can be an increase in short-term temperature fluctuations during startup (and shutdown), EPA is indicating in the startup standard that temperature measurements can increase by 10% during these periods.
      A number of the standards during normal operation are adjusted so that oxygen does not function as a diluent (the so-called oxygen correction factor).  These oxygen correction factors are out-of-place for a standard applicable during startup because the oxygen content of the exhaust gas is highly variable and not representative of the levels during normal operation.  For this reason we are not requiring the calculation of an oxygen correction factor during startup.
      Shutdown is the period of time between when kiln raw material feed is shutoff and gas flow through the kiln ceases.  Shutdown operations are in many ways a mirror image of startup.  During shutdown, the same transient conditions and low product production rates occur as during startup.  Cement kilns cannot be immediately shut off.  Even after the feed is stopped, gas flow must be continued through the kiln and the kiln continues to rotate to prevent a kiln over temperature conditions and/or kiln warping.  Moreover, the concerns about inability to have normalized standards or standards with oxygen correction factors, air pollution control inlet temperature variability, and lack of measureable HCl emissions when the kiln is fired with distillate or natural gas and is not HCl CEM-equipped, all apply at shutdown for the same reasons as at startup.  For this reason, we are setting the same limits for kilns during shutdown operations as during startup.
      Periods of startup, normal operations, and shutdown are all predictable and routine aspects of a source's operations.  However, by contrast, malfunction is defined as a "sudden, infrequent, and not reasonably preventable failure of air pollution control and monitoring equipment, process equipment or a process to operate in a normal or usual manner * * * ''(40 CFR 63.2).  EPA has determined that malfunctions should not be viewed as a distinct operating mode or condition and, therefore, any emissions that occur at such times do not need to be factored into development of CAA section 112(d) standards, which, once promulgated, apply at all times.  See, Mossville Environmental Action Now v. EPA, 370 F.3d 1232, 1242 (D.C. Cir. 2004)(discussing reasonableness of standards that have factored in variability of emissions under all operating conditions.)  It is reasonable to interpret section 112(d) as not requiring EPA to account for malfunctions in setting emissions standards.   For example, we note that Section 112 uses the concept of "best performing" sources in defining MACT, the level of stringency that major source standards must meet.  Applying the concept of "best performing" to a source that is malfunctioning presents significant difficulties.  The goal of best performing sources is to operate in such a way as to avoid malfunctions of their units.
      Moreover, even if malfunctions were considered a distinct operating mode, we believe it would be impracticable to take malfunctions into account in setting CAA section 112(d) standards for this (or any other) source category.  As noted above, by definition, malfunctions are sudden and unexpected events and it would be difficult to set a standard that takes into account the myriad different types of malfunctions that can occur across all sources in the category.  Moreover, malfunctions can vary in frequency, degree, and duration, further complicating standard setting.
      In the event that a source fails to comply with the applicable CAA section 112(d) standards as a result of a malfunction event, EPA would determine an appropriate response based on, among other things, the good faith efforts of the source to minimize emissions during malfunction periods, including preventative and corrective actions, as well as root cause analyses to ascertain and rectify excess emissions.  EPA would also consider whether the source's failure to comply with the CAA section 112(d) standard was, in fact, "sudden, infrequent, not reasonably preventable" and was not instead "caused in part by poor maintenance or careless operation."  40 C.F.R. § 63.2 (definition of malfunction).
5.  What are EPA's final actions on compliance dates?
      For existing sources we proposed a compliance date of 3 years after the promulgation of the new emission limits for mercury, THC, PM, and HCl to take effect.  This is the maximum period allowed by law.  See section 112(i)(3)(A).  We continue to believe a 3 year compliance period is justified because most facilities will have to install emissions control devices (and in some cases multiple devices) to comply with the proposed emissions limits.  Therefore, we have retained a 3 year compliance data in the final rule.
	For new sources, the compliance date will be the effective date of the final rule or startup, whichever is later.  Because this is a major rule as defined by the Congressional Review Act, the effective date of the rule is 60 days after publication of the Federal Register.
      In determining the proposal date that determines if a source is existing or new, we have decided to select the proposal date of these final amendments, which is May 6, 2009, for all the standards.
	At proposal, we considered three possible dates, including March 24, 1998; December 5, 2005; and the proposal date of these final amendments, which was May 6, 2009.  As we noted at proposal, Section 112 (a)(4) of the Act states that a new source is a stationary source if "the construction or reconstruction of which is commenced after the Administrator first proposes regulations under this section establishing an emissions standard applicable to such source."  "First proposes" could refer to the date EPA first proposes standards for the source category as a whole, or could refer to the date the agency first proposes standards under a particular rulemaking record.  The definition is also ambiguous with regard to whether it refers to a standard for the source as a whole, or to a HAP-specific standard (so that there could be different new source standards for different HAP which are regulated at different times).  At proposal we choose the date of December 5, 2005, as the proposal date that determines if a source is new or existing for the mercury, HCl, and THC, and the May 6, 2009, date for PM.
      After consideration of comments on the selection of the date for mercury, THC, and HCl, we believe that the May 6, 2009, date for all pollutants is more in keeping with the evident intent Section 112 (a)(4) that source should have sufficient notice that new source controls requirements can be considered in the initial design.  We accept commenters' argument that sources coming into existence between the proposed date of the 2006 standards and the May 6, 2009, proposal date of these amendments would have no reasonable means of ascertaining the standards' final content and so lacked notice of what controls and strategies to adopt.  Since this is antithetical to the policy underlying new source standards, EPA is adopting May 6, 2009, as the date which determines if a source is existing or new.
      We note that there are currently sources subject to new source limits for mercury and THC contained in the December 20, 2006, rule.  However, the mercury the new source standards in this final rule are significantly different than the limits in the December 20, 2006, rule, and we do not see how the affected sources could have anticipated this change prior to proposal of these amendments.
   B. What are EPA's Final Actions on to 40 CFR part 60, subpart F?
1.  What are the final kiln and clinker cooler emissions limits under 40 CFR part 60, subpart F?
For "new" affected facilities constructed, modified, or reconstructed after June 16, 2008, the final emission limits amend the existing rules as follows:
   * Change the format of the PM emission limits from lb/ton of dry feed to lb/ton of clinker product;
   * Reduce the PM emission limit for kilns from 0.3 lb/ton of dry feed to 0.01 lb/ton of clinker;
   * Set a limit on NOX emissions from kilns of 1.50 lb/ton of clinker; and
   * Set a limit on SO2 emissions from kilns of 0.4 lb/ton of clinker, or, as an alternative, demonstrate a reduction in SO2 emissions from the kiln of at least 90 percent; and
   * Reduce the PM emissions limit for clinker coolers from 0.1 lb/ton dry feed to 0.01 lb/ton of clinker.
The emission limits for affected facilities constructed, modified, or reconstructed before June 16, 2008, remain unchanged in this subpart.  The rationale for these actions is discussed below
      a.  NOx Limits for Kilns
EPA proposed a NOx limit of 1.5 lb/ton of clinker based on application of Selective Non-Catalytic Reduction (SNCR) to a new precalciner kiln.  At proposal we also considered a level of 1.95 lb/ton clinker based on the use of SNCR control technology, and a limit of 0.5 lb/ton clinker based on the use of selective catalytic reduction (SCR) technology.
	After evaluation of the comments, we have decided to adopt the level of 1.5 lb/ton clinker in this final rule, as proposed.  In general, commenters agreed with the selection of SNCR as the basis of the standard (i.e., it represents the performance of BDT).  However, there was disagreement over the appropriate emission limit that represents BDT.
      Industry commenters requested a higher limit, claiming that site specific properties of raw materials could create a situation where application of SNCR technology to a well designed preheater/precalciner kiln could not achieve the level of 1.5 lb/ton clinker without high ammonia injection rates that would result in significant ammonia emissions.  To support their arguments they noted that EPA based the 1.5 lb/ton clinker level on the assumption that a well designed new preheater/precalciner kiln could meet a level of 3.0 lb/ton clinker without SNCR, so that this 3.0 lb/ton clinker should be the baseline from which performance of SNCR is evaluated.  73 FR at 34079.  They pointed to several newer kilns that had difficulty meeting a level of 3.0 lb/ton clinker without SNCR, and attributed this difficulty to "hard to burn" raw materials at certain sites.
      We have rejected the industry argument that 1.5 lb/ton clinker is not achievable for all new kilns using SNCR technology for the following reasons.  First, the commenters note some kilns without SNCR cannot meet a NOx level of 3.0 lb/ton clinker.  However, they did not provide the actual levels of NOx emissions the sources were designed to meet.  The NOx emissions for a new preheater/precalciner kiln are primarily a function of precalciner design.  Though two kilns may have the same basic precalciner design, certain site specific design parameters will also affect NOx emissions.  A precalciner designed to meet a level above 3.0 lb/ton clinker, will not necessarily be designed exactly the same way as one designed to meet 3.0 lb/ton clinker.  We are also aware that there are kiln precalciner designs that were installed that do not represent best design.  We thus do not believe that these kilns' performance alters the baseline from which performance of SNCR is evaluated.  In addition, we have enough examples of new preheater/precalciner kilns in various locations in the country to indicate to us that a NOx limit of 3.0 lb/ton clinker is generally achievable, regardless of location, if the precalciner is properly designed.  For example, several kilns in Florida and a kiln in California have NOx emissions below 2.0 lb/ton clinker with no add-on controls.  According to our information, raw materials in Florida can be considered "hard to burn" because of the significantly different hardness of Florida limestone and silica (limestone being soft which create a fine grind, the silica being harder which creates a more coarse grind) creates problems with size distribution for the raw material necessitating more fuel use and higher kiln temperatures with a consequent increase in NOx emissions.  Additional test data for two plants with reported "hard to burn" mix were 1.89 and 2.4 lb/ton.  Given these facts, we believe the assumption that a new kiln without add-on controls can meet a level of 3.0 lb/ton clinker over the long term is very reasonable and so should represent a baseline for application of SNCR performance.  See also 73 FR at 34079 noting many other examples of kilns without end-of-stack controls burning hard-to-burn inputs meeting a level of 2.5 lb/ton of clinker.
      Second, although we based our 1.5 lb/ton clinker level on a SNCR emission reduction of 50 percent, there are numerous examples of SNCR systems achieving emission reductions greater than 50 percent and as high as 80 percent or more.  Id.  These reductions were achieved without appreciable ammonia slip.  So even if a new kiln were to emit at levels above 3.0 lb/ton clinker without end-of-stack controls, application of SNCR would allow such a kiln to meet the 1.5 lb/ton clinker level.  For example, a new kiln emitting at 4.0 lb/ton clinker would only need an emission reduction of 63 percent to meet the 1.5 lb/ton clinker level for NOx.
      Finally, the NOx limit is based on a 30-day averaging period to be consistent with the averaging periods for other regulated kiln pollutants, and to allow for averaging of raw mill on and off emissions.  See 74 FR at 21144.  Compared to other averaging options (hourly or daily), this longer averaging time allows additional operating flexibility to meet the limit.
      Based on comments received, we also considered setting a NOx limit lower than 1.5 lb/ton clinker based on performance of SNCR.  However, we also rejected that option.  We do have data that indicates that some cement kilns are below 1.5 lb/ton clinker, but we do not believe the current data support that any new kiln, regardless of location (and consequent raw material inputs), could meet a level that low.
      At proposal we also considered a NOx emissions level of 0.5 lb/ton clinker based on performance of SCR.  We rejected that option because at that time we did not believe that SCR was sufficiently demonstrated technology for this industry.  We are aware that there have been three cement kilns in Europe that have successfully used SCR, and that SCR technology is a demonstrated control technology for NOx control for other source categories, such as utility boilers.  We also are aware that that one domestic cement company has agreed to install SCR technology on one kiln as part of a settlement agreement.  However, we continue to question if SCR technology would be effective at all locations where new kilns might be installed.  The main concern is the potential for dust buildup on the catalyst, which can be influenced by site specific raw material characteristics present in the facility's proprietary quarry, such as trace contaminants that may produce a stickier particulate than is experienced at sites where the technology has been installed.  This buildup could reduce the effectiveness of the SCR technology, and make cleaning of the catalyst difficult resulting in kiln downtime and significant costs.  We were unable to estimate these costs and did not include these costs in our overall cost estimates for SCR.  For these reasons, we have not selected SCR technology as the basis of BDT.  We will continue to follow this technology as it is applied in the U.S., and will reconsider this decision in the next review of this standard.
      Kilns equipped with alkali bypasses cannot be expected to meet the NOx limit for the portion of the exhaust that goes to bypass.  Bypass gases are quickly cooled and do not remain at a temperature long enough to treated using an SNCR systems.  For that reason, we have revised the rule to clarify that for kilns with an alkali bypass, only the main kiln exhaust gases are subject to the NOx limit. Because all kilns do not require an alkali bypass and the bypass gas stream is a small fraction of the total kiln exhaust gas flow, the any additional NOx emission resulting from this exclusion will be minimal.
      b.  SO2 Limits for kilns
      EPA proposed an emissions limit of 1.33 lb/ton clinker or 90 percent emissions reduction SO2 based on the performance of a limestone wet scrubber applied to a kiln with high sulfur raw materials.  73 FR at 34080.  Commenters noted that this level was considerably above the level of many of the recent best available control technology (BACT) determinations, and was also above the level actually achieved by the facility EPA used as the basis of this proposed standard.
      At the time EPA proposed the 1.33 lb/ton clinker limit, we also considered a limit of 0.4 lb/ton clinker based on the average of recent BACT determinations for cement kilns.  We chose the higher limit at proposal because the 0.4 lb/ton limit would have resulted in new kilns with moderate sulfur content raw materials experiencing a cost per ton of SO2 removed of $6,000.  However, we have changed our proposed decision for two reasons.  First, as a result of the NESHAP requirement to meet a HCl emissions level of 2 ppmvd, we estimate that all new kilns will have to install wet scrubbers for HCl control.  See section VI below.  Hence, the cost of meeting the 0.4 lb/ton clinker limit in the NSPS is minimal, only the cost of the SO2 CEM.  Second, since proposal we have revised our costs for dry lime injection, which is the most cost-effective control technology for controlling a moderate sulfur raw material kiln to the 0.4 lb/ton clinker level.  Based on our revised information, the cost of meeting a 0.4 lb/ton clinker emission limit now ranges from $470 to $1430/ton SO2 for a kiln with high or moderate sulfur raw materials, even if these costs are attributed to the NSPS rather than to the NESHAP.  Kilns with low sulfur raw materials can meet the 0.4 lb/ton clinker level with no add-on controls.  We consider these to be reasonable costs, comparable with other costs for SO2 control EPA has deemed reasonable such as those in the Clean Air Transport Rule.  See 70 FR at 25583 (May 12, 2005).  So, even if a new facility is able to meet the NESHAP HCl limit without any acid gas controls, the cost per ton to meet a 0.4 lb/ton SO2 NSPS limit is still reasonable.
      In the proposal, we considered a SO2 emissions level of 0.2 lb/ton clinker.  However, this level adds little environmental benefit beyond the 0.4 lb.ton limit, and for many facilities would not be achievable based on the use of wet scrubber technology, which means these facilities would opt for the 90 percent emission reduction alternative (discussed below).  For these reasons, we did not choose this level as BDT.
We also proposed a 90 percent reduction as an alternative limit to the 1.33 lb/ton emissions limit.  We are retaining this alternative in the final rule.  The alternative 90 percent reduction is to account for situations where the sulfur content of the raw materials is so high that, even with the most efficient SO2 control, a kiln cannot meet the 0.4 lb/ton of clinker emissions limit.  Design and performance data indicate the 90 percent control is continuously achievable for a well designed and operated wet scrubber.  Compliance with the 90 percent reduction would be determined by continuously monitoring SO2 at the control device inlet and outlet.  Continuous monitoring of SO2 at the inlet and outlet is a positive demonstration that the standard is being continuously met.
      c.  PM Emissions Limits for Kilns and Clinker Coolers
      We proposed a PM emissions limit of 0.86 lb/ton clinker based on fabric filters using membrane bags.  This specific level was chosen because it is representative of the performance of this technology and was equivalent to the new source limit contained in the Hazardous Waste Combustor (HWC) NESHAP for cement kilns burning hazardous waste.  This rationale is no longer applicable, since EPA is reassessing the PM limit in the HWC NESHAP.  See USEPA Motion for Voluntary Remand in # 05-1441 (D.C. Circuit, August 29, 2008).
      As previously discussed in section IV.A., in this action we are setting PM limits under the Portland Cement NESHAP of 0.04 lb/ton clinker for existing sources and 0.01 lb/ton clinker for new sources based on a 30 day rolling average. We project that new cement kilns meeting the 0.01 lb/ton clinker limit will be using the same technology which formed the basis of the proposed NSPS PM limit, namely fabric filters and membrane bags.  It should also be noted that we estimate that many new facilities will need to install fabric filters in series as part of mercury controls.  This means that a new kiln will install PM controls required to meet the 0.01 lb/ton limit in any case, so establishing the same limit for PM in the NSPS not only is technically justified, but has no cost.  We also assessed the costs of installing and operating fabric filters with membrane bags at proposal, and found this to be a cost-effective control technology in any case.  73 FR at 34077.  The technology would now be evaluated as more cost-effective than at proposal, since greater PM reductions will result from its use.  Therefore, we are establishing an NSPS PM limit of 0.01 lb/ton clinker in this final NSPS, averaged over 30 days (rolling average) and measured with a CEM.  For reasons previously discussed, we are setting the same limit for clinker coolers.  See section IV.A.g of this preamble above.  See section V for a discussion on measuring  compliance with a PM CEM.
	d.  Change in Format of the Standard from lb/ton Feed to lb/ton Clinker
The change in format of the standard from feed to lb/ton clinker was actually proposed in the NSPS.  However, this issue was also raised in response to the proposed PM and mercury limits in the NESHAP, and was previously discussed in section IV.A.1.i.
      e.  Applicability of NSPS Limits to Modified kilns
      At proposal we had one set of emission limits for PM, SO2 and NOx that were applicable to all new, reconstructed, and modified kilns.  Commenters expressed concerns of the ability of a modified kiln to meet the same limits as a newly constructed kiln.
      The PM and SO2 limits are based on control technologies that can be applied to any kiln type and achieve the same control levels that would be expected with a new kiln at similar costs.  We see no issue here as to technical feasibility.  However, this is not necessarily the case with NOx.  New preheater/precalciner kilns with staged combustion achieve NOx levels in the 2.0 to 3.0 lb/ton clinker range. As discussed above, in developing the NOx limit, we assumed this level as baseline in assessing the level achievable with SNCR, which is the technology basis of BDT.  However, older kiln designs can have much higher NOx levels, ranging from 2.0 to 8.0 lb/ton clinker.  Kilns in the higher end of the range might need to achieve an 80 percent emissions reduction to meet the 1.5 lb/ton clinker NOx limit.  Industry commenters requested that EPA either exempt modification from the NSPS, or set separate limits.
      In this final rule we are still including modified kilns as an affected source.  The suggestion that modified kilns be outright exempted from these NSPS revisions appears legally strained, given that modified sources are a type of new source for which EPA is obligated to develop, and review and revise as appropriate.  Moreover, if we were to exempt modified kilns, then such sources would be free to increase emissions without application of BDT, a particular concern with respect to pollutants like NOx which are not presently regulated by the NSPS.  This would undermine the basis of section 111 standards, where Congress wanted to assure that BDT was applied to modified sources qualifying as "new."  The purpose of the Act is to enhance the Nation's air quality (CAA section 101 (b)(1)), and new source performance standards under section 111 serve that goal.  Asarco v. EPA, 578 F. 2d 319, 327 (D.C. Cir. 1978). Commenters had also claimed that other regulatory programs, most notably new source review, would result in a site specific BACT determination if emissions increased.  Though we are always mindful of the interrelationship of different EPA regulatory programs and their effects, we do not see this as sufficient reason not to establish a NOx emissions limits for modified kilns.
      We further investigated whether we should set a different NOx emissions limit for modified kilns.  However, we believe the BDT is the same, and are therefore establishing the 1.5 lb/ton clinker as the limit for modified kilns.  We have two reasons for doing so.  First, we note that there are kilns of older design that meet levels below 1.5 lb/ton clinker, and in some cases below 1.0 lb/ton clinker, with SNCR control.  Therefore, modified kilns would not necessarily be unable to meet the 1.5 lb/ton clinker limit.  However, sources always have the option of adding sufficient NOx control to avoid an hourly emissions increase and avoid thus triggering the modification provision (and also avoid PSD for NOx).  CF. Asarco, 578 F. 2d at 328 ("the operator of an existing facility can make any alternations he wishes in the facility without becoming subject to the NSPS as long as the level of emissions from the altered facility does not increase. Thus, the level of emissions before alterations take place, rather than the strict NSPS, effectively defines the standard that an altered facility must meet" (emphasis original); the Court did rule on the validity of these unchallenged provisions (id. at n. 32)).  The NOx control available to cement kilns which could be utilized to prevent an increase in NOx emissions, in addition to SNCR, are conversion to indirect firing, mid-kiln fuel injection, mid-kiln air injection, and substitution of steel slag for some limestone.  Given these available controls, we believe it would be extremely unlikely that a source that determines the 1.5 lb/ton limit is not achievable would be unable to apply some type of NOx control that would avoid triggering the modification or PSD provisions.
      f.  Regulation of VOC/CO
	We are not establishing limits for CO or volatile organic compound (VOC) emissions from cement kilns.  VOC emissions from new cement kilns will mainly result from organics in the raw materials.  Organic constituents in the raw materials can be driven off in the kiln preheater prior to reaching temperature zone that would result in combustion.  All new cement kilns will be subject to a continuous 24 ppmvd THC emissions limit by the Portland Cement NESHAP previously discussed.  Because most of the THC are also VOC, the THC limit also directly limits VOC, and serves as the baseline for the NSPS analysis.  This limit is also the new source limit based on the best performing source.  Therefore we determined that no additional regulation of VOC emissions is necessary or feasible.
Emissions of CO can come from two sources, unburned fuel from the precalciner and CO evolved from the raw materials by the same mechanism as the THC emissions.  Unburned fuel represents an economic loss to the facility.  Therefore, new precalciners are designed to combust fuel as efficiently as possible, and CO emissions from fuel combustion are minimized, regardless of any potential emission limit.
Emissions of CO evolved from raw materials can be significant if there are substantial levels of organics in the raw material.  As noted at proposal, the only control technology identified to reduce CO emissions is a RTO (which also would concurrently reduce any VOC emissions).  However, we believe application of an RTO as BDT for CO would result in significant cost and adverse energy impacts.  Therefore we determined that no additional regulation of CO emissions is feasible.
  We also noted that in no cases had add-on controls for CO (or VOC) been required as BACT under new source review.
      g.  Regulation of Greenhouse Gases (GHGs)
      In the proposal we did not propose standards of performance covering GHGs due to concerns about "issues related to the regulation of GHGs under the CAA" and noted that we were in the process of evaluating avenues for addressing such concerns.  See 73 FR at 34,084.  These concerns were specifically related to the Prevention of Significant Deterioration and title V permitting programs and the unmanageable permitting burden that we anticipated would arise should GHGs become subject to these programs as a result of regulation under the Act.
      Since that time, we have issued regulations for GHG emissions under the CAA through the light duty vehicle rule (75 FR 25324, (May 7, 2010)) and have finalized the greenhouse gas "tailoring" rule (75 FR 31514 (June 3, 2010)) and the Johnson memo (75 FR 17004 (April 2, 2010)).  As a result of these actions, as of January 2, 2011, GHGs will become "subject to regulation" under the Act.  Accordingly, the Agency has now finalized a framework addressing the concerns that were the basis of our decision not to propose standards of performance for GHG emissions from this industry at the time we proposed this 8-year review action.
      Today's final rule does not include a standard of performance for GHG.  There are two reasons for this.  First, we did not propose such a standard.  Promulgating such a standard without providing opportunity to comment on it would not be a logical outgrowth of the proposal and would, accordingly, violate the norms of notice and comment rulemaking.  Second, we do not yet have adequate information about GHG emissions and control strategies for the Portland cement industry.  This information forms the basis of standards of performance, which must take into account achievability and cost of such controls.
      This is not the end of the matter.  To the contrary, based on our current knowledge we believe that it may be appropriate for the Agency to set a standard of performance for GHGs.  We have historically declined to propose standards for a pollutant where it is emitting in low amounts or where we determined that a BDT analysis would result in no control.  National Lime Assoc'n v. EPA, 627 F.2d 416, 426( D.C. Cir. 1980).  Based on current information we do not believe such circumstances are present here.  Without prejudging the outcome of a future regulatory process, we note the following considerations.
      First, Portland cement is one of the largest stationary source categories of GHG emissions, ranking as the third highest U.S. source of CO2 emissions. Second, based on our initial evaluation it appears that there are cost-effective control strategies for this source category that would provide an appropriate basis for establishing a standard of performance for GHG emissions.   See 73 FR 44491, July 30, 2008.  These control strategies include, for example, energy efficiency measures, reductions in cement clinker content, and raw materials substitution. There may be other cost-effective controls as well.
      Based upon this preliminary evaluation, the Agency is working towards a proposal for GHG standards from Portland cement facilities.  We are not, however, proposing such standards at this time because in order to develop proposed standards we need additional information on site specific factors that affect performance of these controls, where they are currently applied, and control costs.  We would also solicit information on overall facility energy management practices.  To this end, the Agency will be sending out information requests to fill these information gaps so that we are able to propose a standard addressing GHGs in a timeframe that would allow the regulated community to make sound investment decisions in response to these MACT and NSPS requirements.
2.  What is our final action on the other emission limits in the NSPS?
	We did not propose changes to the other emissions limits in the NSPS, such as materials handling operations.  We received one comment recommending that we promulgate NSPS limits for clinker storage piles, raw materials handling, and baghouse fall-out.  Open clinker piles are being regulated as part of the NESHAP as previously discussed.  Materials handling operations are currently regulated under NESHAP.  We believe baghouse fall out would be regulated as part of materials handling standards.
 3.  What other changes are being promulgated?
	As previously noted, cement kilns are potentially subject to both the NSPS and the Portland Cement NESHAP (40 CFR part 63, subpart LLL).  In §63.1356 of subpart LLL, we exempt any source subject to that subpart from applicable standards under the NSPS and the Metallic Minerals Processing NSPS (subpart OOO).  That language was appropriate because the NSPS only regulated PM, and the PM limits in the NSPS and NESHAP were identical.  At proposal, where the proposed new source PM limits in the NSPS and NESHAP were different, we proposed to add language in both the NSPS and the NESHAP to state that when there are emissions standards for a specific pollutant that apply to an affected source in both the NESHAP and the NSPS, the source should comply with the most stringent limit, and is not subject to the less stringent limit.
	This proposed language is still applicable even though in this final rule we are setting identical new source PM standards in the NSPS and NESHAP rule.  For example, a cement kiln that is an existing source under NESHAP subject to the 0.04 lb/ton clinker emissions limit could potentially become modified under NSPS and also be subject to the 0.01 lb/ton clinker emissions limit.  In addition, there is always a possibility that other situation may occur where a source is subject to differing emission limits under NSPS and NESHAP as a result of rule changes.
4.  What are the final testing requirements under subpart F?
There are no PM, NOX or SO2 compliance testing requirements; compliance is based on the use of a continuous emissions monitor (see below).
5.  What are the final monitoring requirements under subpart F?
To demonstrate compliance with the PM emission limits, we are amending the monitoring requirements to require the installation and operation of a PM CEMS.  The reason for this decision was previously discussed.  Because this requirement is also part of the Portland Cement NESHAP, it will also apply to existing kilns currently subject to the NSPS.  Consequently, affected facilities under this rule are not subject to an opacity standard to monitor compliance with the final PM standard.  The PM CEMS must be installed and operated in accordance with the requirements of §60.63(g).
      We are also adding monitoring requirements for all emission sources that are subject to the 10 percent opacity standard  -  that is, emission sources other than the kiln and clinker cooler.  We are requiring that they meet the monitoring requirements for these same emission points contained in the Portland Cement NESHAP, 40 CFR part 63, subpart LLL in order to make the two rules consistent.
Under the final amendments, compliance with the emission limits for NOX and SO2 are also determined using continuous emissions monitoring systems (CEMS).  The requirements for the installation, operation, and calibration of each CEM, including minimum data requirements, are specified in the requirements in §60.63(k) and (l).  Under the final amendments, the owner or operator of kilns that elect to comply with the alternative SO2 emission limit of 90 percent reduction are required to continuously monitor SO2 emissions at the scrubber inlet as well as the outlet. These are the same requirements proposed.  We received no comments on the NOx monitoring provisions.  Commenters objected to the SO2 monitoring requirement for facilities that do not require SO2 controls, suggesting stack tests every five years instead.  However, in these cases, it is possible that a source might change a raw material and significantly increase SO2 emissions beyond the standard.  If monitoring is not in place, these excess emissions could be unchecked for five years before they were discovered.  We believe the cost of the SO2 monitor ($56,000) is reasonable to prevent these excess emissions.  These monitors are well established technology that are already installed on over 30 cement kilns, including those without SO2 controls.
C.  What is EPA's Sector-Based Approach?
	Sector-based approaches are based on integrated assessments that consider multiple pollutants in a comprehensive and coordinated manner to manage emissions and CAA requirements.  One of the many ways we can address sector-based approaches is by reviewing multiple regulatory programs together whenever possible. This approach essentially expands the technical analyses on costs and benefits of particular technologies, to consider the interactions of rules that regulate sources.  The benefit of multi-pollutant and sector-based analyses and approaches include the ability to identify optimum strategies, considering feasibility, costs, and benefits across the different pollutant types while streamlining administrative and compliance complexities and reducing conflicting and redundant requirements, resulting in added certainty and easier implementation of control strategies for the sector under consideration.
	In order to benefit from a sector-based approach for the cement industry, EPA analyzed how the NESHAP under reconsideration relates to other regulatory requirements currently under review for Portland cement facilities. The requirements analyzed affect HAP and/or criteria pollutant emissions from cement kilns and cover the NESHAP reconsideration, area source NESHAP, NESHAP technology review and residual risk, and the NSPS revision and their collateral impacts on other programs such as New Source Review (NSR), Regional Haze and the National Ambient Air Quality Standards (NAAQS).
      As a result of the sector-based analyses, this rulemaking will reduce conflicting and redundant requirements by setting the same PM emission limit requirement for both the Cement NESHAP and the Cement NSPS.  Also the sector-based approach facilitated the streamlining of monitoring, record keeping and reporting requirements on both rules reducing administrative and compliance complexities associated with complying with both regulations. In addition, the sector-based approach promotes a comprehensive control strategy that maximizes the co-control of multiple regulated pollutants (i.e.,mercuryand HCl) while obtaining SO2 and PM2.5 emission reductions as co-benefits. These collateral SO2 and PM2.5 emission reductions may be considered for "netting" and "offsets" purposes under the major NSR program or as credits that could help areas around the country with attainment of the SO2 or PM2.5 NAAQS
      For more information on our sector's analyses, its benefits and interaction with NSR, NAAQS and Regional Haze please refer to the preamble of the proposal of this rule (74 FR 21159-61)
V.  Responses to Major Comments

	This section presents a summary of responses to major comments. A summary of the comments received and our responses to those comments may be found in Docket ID No. EPA-HQ-OAR-2007-0877 for subpart F and Docket ID No. EPA-HQ-OAR-2002-0051 for subpart LLL.
A.  What are the significant comments and responses on 40 CFR part 63, subpart LLL?
Adequacy of data
Comment: One commenter (2829) disagreed with EPA's calculation of the MACT standard emission limits. The commenter stated that to account for variability, EPA should first establish standards that are the actual average emission rates of the 12 percent of existing sources, and then use longer averaging times (perhaps 60 or 90 day averages) to allow for short term variability and spikes in emissions.
Response:  EPA's legal obligation in establishing MACT floors is to reasonably estimate the average performance achieved by the best performing 12 percent of best performing sources, or for new sources, the performance of the best controlled similar source.  The statute does not speak to the issue of permissible averaging times in constructing standards, so it may be that in factually appropriate cases, a choice of averaging time to account for best performing sources' variability could be legitimate.  However, automatic (i.e., a priori) determinations to adopt long-term averages for any type of data set regardless of circumstances of sources' performance and robustness of the data set, would go too far.  In addition, if the commenter is suggesting that EPA simply average short-term test results and then hope to account for variability by assigning a longer averaging period, EPA rejects such a methodology as both qualitative and arbitrary  -  it could easily result in estimates of performance that are either overly stringent or lax due to the rough estimate of variability underlying the methodology.  It is better to more accurately assess sources' initial performance (for example, as with the mercury standard in this rule where EPA changed its baseline for best performing plants based on information about materials these sources process even though they did not do so in the 30-day sampling regime), and to use statistical methodologies to account for the variability reflected in the resulting data set.
Comment: Many commenters (2830, 2832, 2836, 2841, 2844, 2845, 2858, 2859, 2863, 2864, 2874, 2890, 2908, 2910, 2914, 2915, 2916, and 2917) stated that setting MACT floors on a pollutant-by-pollutant basis violates the law and results in MACT floors that bear no relation to emission limits that are being achieved at the best performing existing sources.  According to commenters, this method violates the plain language and intent of §112(d) of the Clean Air Act (CAA) and its effect is a MACT floor that reflects a standard that no one plant in existence currently achieves.  Commenters 2832, 2841, 2844, 2845, 2846, 2910, 2914, 2915, and 2916 stated that §112(d)'s use of the terms best-performing and existing clearly means that sources in a category or subcategory that are used to set the MACT floor are to be real, not theoretical or hypothetical, sources (42 U.S.C. §7412(d), 2006 and Northeast Maryland Waste Disposal Authority, 358 F.3d at 954). The phrase achieved in practice can only mean that Congress intended actual sources, performing under real-life conditions, to be the benchmark for determining the MACT floors. Furthermore, the language of the statute does not speak in terms of the best-performing source or sources for each listed pollutant or group of pollutants (42 U.S.C. §7412(d)). Rather, the focus is on the best existing source or sources for all pollutants, and what these sources truly can achieve on an overall basis. EPA's pollutant-by-pollutant methodology is also at odds with the legislative history underlying §112(d) (S. Rep. No. 228, 101st Cong., 1st Sess. 169, 1989).
According to the commenters, the focus on overall performance is not surprising because in the 1990 CAA Amendments Congress abandoned §112's previous focus on individual pollutant standards, and adopted the technology-based multi-pollutant approach to regulating toxics in use under the Clean Water Act (CWA). See S. Rep. No. 228, 101st Cong., 1st Sess. 133-34 (1989). Thus, if one source can achieve a firm degree of control for one pollutant but not for another, there may be no justification for including it in the set of sources from which the floor is calculated (Tanners' Council of America v. Train, 540 F.2d 1188, 1193 (4th Cir. 1976) deeming CWA effluent limitations guidelines not achievable where plants in EPA's database were capable of meeting the limitations for some, but not all, of the pollutant parameters).
      Several commenters (2845, 2910) stated that EPA's previous use of a pollutant-by-pollutant analysis was based on authorities not applicable to the CAA.  EPA attempted to defend its practice of establishing pollutant-by-pollutant MACT standards by citing Chemical Mfr. Ass'n. v EPA, 870 F.2d 177, 239 (1989), clarified 885 F.2d 253, 264 (5th Cir. 1989), cert. denied, 495 U.S. 910, (1990), a case where the Court held that, under the CWA, best available technology (BAT) referred to the single best-performing plant on a pollutant-by-pollutant basis.
      According to commenters 2845 and 2910, EPA's reliance on Chemical Mfr. Ass'n is misplaced as the CAA's procedure regarding the selection of MACT technologies differs on a textual basis from the CWA's procedure for identifying best available technology. Under the CWA, BAT standards are to be set based on the best practicable control technology currently available. 33 U.S.C. §1311(b)(1)(A)(i)(2006). This has led to pollutant-by-pollutant determinations. The CAA more narrowly limits the basis for MACT designation to what has been achieved at existing sources, not what could be hypothetically achievable on a per-pollutant basis.
	One commenter (2890) stated that EPA appears to be forgetting that the floor is only the first step in the process. Once EPA has established a floor based on physical sources, it is directed to go back and look at options beyond the floor. Those beyond the floor options would include the best control for each pollutant on every source. By correcting the floor approach, the EPA would also correct the issue identified by Judge Williams in his concurring opinion to the Brick vacatur, where a floor that is designed to represent what has been achieved is more stringent than what would be deemed achievable under a MACT.
Response:  EPA does not accept the argument that the Agency is compelled to establish MACT floors under section 112 (d) (3) based on single plants' performance for all emitted HAP.  A reasonable interpretation is that MACT floors may be established on a HAP-by-HAP basis, so that there can be different pools of best performers for each HAP.  Indeed, as illustrated below, a total facility approach can lead to results so arbitrary that the approach may simply not be legally permissible.
	Congress has not spoken directly to this issue.  Congress specified in section 112(d)(3) the minimum level of emission reduction that could satisfy the requirement to adopt MACT.  For new sources, this floor level is to be "the emission control that is achieved in practice by the best controlled similar source."  For existing sources, the floor level is to be "the average emission limitation achieved by the best performing 12 percent of the existing sources" for categories and subcategories with 30 or more sources, or "the average emission limitation achieved by the best performing 5 sources" for categories and subcategories with fewer than 30 sources.  This language does not address whether floor levels can be established HAP-by-HAP or by any other means. The existing source MACT floor achieved by the average of the best performing 12 percent can reasonably be read as referring to the source as a whole or to performance as to a particular HAP. The statutory definition of "emission limitation" (assuming it applies) likewise is ambiguous, since "requirements limiting quantity, rate, or concentration of pollutants" could apply to particular HAPs or to all HAPs. The reference in the new source MACT floor provision to "emission control achieved by the best controlled similar source" can mean emission control as to a particular HAP or emission control achieved by a source as a whole.
	The reason EPA has long adopted the interpretation that the existing and new source MACT floors are to be applied on a HAP-by-HAP basis are that a whole plant approach likely yields least common denominator floors  -  that is floors reflecting mediocre or no control, rather than performance which is the average of what best performers have achieved.  See 61 FR at 173687 (April 19, 1996); 62 FR at 48363-64 (September 15, 1997) (same approach adopted under the very similar language of section 129 (a)(2)).  For example, if the best performing 12 percent of facilities for HAP metals did not control organics as well as a different 12 percent of facilities, the floor for organics and metals would end up not reflecting best performance. For new sources, not only would the floor reflect unoptimized control, but EPA would have to make some type of value judgment between control of organics and metals just to decide which source was best controlled.  For example, one of the highest mercury emitting sources is also a best performer for HCl emissions.  Inclusion of this source as a best performer for HCl would have added the single highest mercury emitting source to the MACT floor pool.
    These types of results are at odds with Congress' purpose in adopting MACT floors.  The central purpose of the amended air toxics provisions was to apply strict technology-based emission controls on HAPs. See, e.g., H. Rep. No. 952, 101st Cong. 2d sess. 338.  The floor's specific purpose was to assure that consideration of economic and other impacts not be used to "gut the standards. While costs are by no means irrelevant, they should by no means be the determining factors. There needs to be a minimum degree of control in relation to the control technologies that have already been attained by the best existing sources." A Legislative History of the Clean Air Act Vol. II at 2897 (statement of Rep. Collins).  An interpretation that the floor level of control must be limited by the performance of devices that only control some of these pollutants effectively "guts the standards" by including worse performers in the averaging process, whereas  EPA's interpretation promotes the evident Congressional objective of having the floor reflect the average performance of best performing sources.  Since Congress has not spoken to the precise question at issue, and the Agency's interpretation effectuates statutory goals and policies in a reasonable manner, its interpretation must be upheld. See Chevron v. NRDC, 467 U.S. 837 (1984).
	In asserting that section 112 (d)(3) mandates a total facility approach, commenters stressed that section 112 (d) requires that floors be based on actual performance from real facilities, pointing to such language as "existing source," "best performing," and "achieved in practice."  EPA agrees that this language refers to sources' actual operation, but we repeat that the language says nothing about whether it is referring to performance as to individual HAP or to a single facility's performance for all HAP.  Commenters also said that Congress could have mandated a HAP-by-HAP result by using the phrase "for each HAP" at appropriate points in section 112 (d).  Doing so would have removed ambiguity from section 112 (d), but does not compel any inference that Congress was sub-silentio mandating a different result when it left the provision ambiguous on this issue.  The argument that MACT floors set HAP-by-HAP are based on the performance of a hypothetical facility, so that the limitations are not based on those achieved in practice, just re-begs the question of whether section 112 (d)(3) refers to whole facilities or individual HAP.  All of the limitations in the floors in this rule of course reflect sources' actual performance and were achieved in practice.  We also address below the issue of whether optimized performance for one HAP precludes optimized performance for another.
	A few commenters indicated that a HAP-by-HAP approach is inconsistent with legislative history to section 112 (d), citing to page 169 of the Senate Report.  Since this Report was to a version of the bill which did not include a floor provision at all (much less the language at issue here), it is of no relevance. National Lime II,  233 F. 3d at 638.
	The section 112(d) air toxic provisions were modeled on the technology-based control scheme for water toxics in the Clean Water Act (as some industry commenters correctly recognized).  S. Rep. No. 228, 101[st] Cong. 2d sess. 133-34.  Section 301 (b) (2) (A) of the Clean Water Act requires plants to control discharges of toxic pollutants to a degree reflecting performance of "best available technology economically achievable."  In Chemical Manufacturers Ass'n v. EPA, 870 F. 2d 177, 238 (5[th] Cir. 1989) the Court held that this requirement could permissibly be applied on a pollutant-by-pollutant basis:
The legislative history of the CWA indicates that the "best available technology" refers to the single best performing plant in an industrial field. The EPA urges that because the Act and the legislative history do not provide more particular guidance, it was free to determine the "best" plant on a pollutant-by-pollutant basis. The Supreme Court has stated that "it is by now commonplace that 'when faced with a problem of statutory construction, this Court shows great deference to the interpretation given the statute by the officers or agency charged with its administration.'" This Court defers to the EPA's interpretation of the Act. The EPA's interpretation of the Act is rational and is not precluded by the legislative history" (internal citations omitted).

The Court reaffirmed its holding on this issue at 885 F. 253, 264 (5[th] Cir. 1989). See also American Iron and Steel Inst. v. EPA, 526 F. 2d 1027 (3d Cir. 1978) (same).
      Commenters stated that the Clean Water Act requirement of Best Available Technology Economically Achievable and Best practicable Technology is not the same as the Clean Air Act's requirement of maximum achievable control technology.  These distinctions do not seem pertinent to the issue at hand.  Both statutes require technology-based performance to control all toxics discharged or emitted, and both require standards to be achievable.  The Legislative history to section 112 (d) makes clear that the CAA provisions are modeled after those in the Water Act (as commenters correctly noted).  EPA does not see any more certainty in the CWA than in the Air Act on this point and believes its interpretation that a pollutant-by-pollutant approach is justified is as reasonable under section 112 (d) (3) of the CAA as it is under section 301 (b) (2) of the Clean Water Act.
      Commenters also noted that EPA retains the duty to investigate and, if justifiable, to adopt beyond the floor standards, so that potential least common denominator floors resulting from the whole facility approach would not have to "gut the standards."  That EPA may adopt more stringent standards based on what is "achievable" after considering costs and other factors is irrelevant to how EPA is required to set MACT floors.  MACT floors are intended to assure that the standards, at a minimum, reflect a level of performance which is the average of what a given percentage of best performers have achieved, and is to make this determination without consideration of cost.  At best, standards reflecting a beyond-the-floor level of performance will have to be cost-justified; at worst, standards will remain at levels reflecting mediocre performance.  Under either scenario, Congress' purpose in requiring floors is compromised.
        EPA notes, however, that if optimized performance for different HAPs is not technologically possible due to mutually inconsistent control technologies (for example, metals performance decreases if organics reduction is optimized), then this would have to be taken into account by EPA in establishing a floor (or floors). (Optimized controls for both types of HAPS would not be MACT in any case, since the standards would not be mutually achievable.) The Senate Report indicates that in such a circumstance, EPA is to optimize the part of the standard providing the most environmental protection. S. Rep. No. 228, 101st Cong. 1st sess. 168 (although, as noted, the bill accompanying this Report contained no floor provisions). It should be emphasized, however, that "the fact that no plant has been shown to be able to meet all of the limitations does not demonstrate that all the limitations are not achievable." Chemical Manufacturers Association v. EPA, 885 F. 2d at 264 (upholding technology-based standards based on best performance for each pollutant by different plants, where at least one plant met each of the limitations but no single plant met all of them).
     All available data for cement kilns indicate that there is no technical problem achieving the floor levels for each HAP simultaneously, using the MACT floor technology.  For most kilns, compliance with the mercury limits will be accomplished using activated carbon injection followed by a second PM control consisting of a fabric filter.  There is no technical impediment to using this same system for control of THC (or organic HAP).  Note that the ACI system would have to be installed downstream of the existing PM control, therefore there would be no effect on the cement kiln dust collected in the existing PM control.  One commenter claimed that carbon is not effective on mercury and THC at the same time.  However, we see no basis for that statement as long as the correct type of carbon is used.  Another commenter claimed ACI increases dioxin emissions.  Considering the fact that ACI can actually be used to remove dioxins from kiln exhaust gas, we see no basis for that statement either.
	After the ACI system, a wet scrubber can be used for HCl control.  We would expect the wet scrubber to be the downstream control because it creates a moisture laden exhaust that would require reheating to then apply ACI.  Again, there is no technical impediment to adding a wet scrubber after the ACI system, and the two control devices should not interfere with each other's performance.  If the facility required an RTO to meet the THC limit, the RTO would be installed downstream of the wet scrubber in order to protect the RTO from any acid gases in the kiln exhaust.  The wet scrubber/RTO combination has been demonstrated in cement kiln applications.
	In order to meet the PM standard a facility could choose to modify their existing PM control to meet the new limit, or design the baghouse downstream of the ACI injection point to meet the PM limit.
	Though we have described some fairly complicated control scenarios, there are applications of control technology that would likely be pertinent here.  One example would be simultaneous injection of alkaline materials (lime or sodium compounds) and activated carbon downstream of the existing PM control device followed by collection with a fabric filter.  This type of injection scheme would potentially control acid gases (HCl and SO2), THC (or organic HAP) mercury, and PM.
	Commenters made much of the fact that no single facility is presently achieving all of the HAP limits proposed.  But this only shows that plants will need to reduce their emissions of certain HAP to meet standards reflecting average of best industry performers for that HAP.
Impacts of pollutant-by-pollutant approach
Comment:  Commenters 2831, 2844, 2845, and 2874 stated that in evaluating the economic cost of achieving emission reductions, looking at one plant's emission control of only one pollutant to the exclusion of all other emission controls produces a disjointed view of cost implications and compliance feasibility. While an individual MACT floor for one pollutant might not appear cost-prohibitive, when combined with all of the other MACT floors for other pollutants, the total cost implications could become especially onerous. While the CAA was authored with the intent of reducing air pollution, Congress did not intend to disrupt the productive capacity of the United States through the promulgation of economically unachievable standards. 42 U.S.C. §7401(b)(1)(2006). By setting MACT floors individually and ignoring the collective cost implications of the entire NESHAP, EPA would effectively disregard the CAA's requirement that air pollution control be advanced while promoting the nation's productive capacity. Id.
Response: EPA is forbidden by law from considering costs in determining MACT floors.  NRDC v. EPA, 489 F. 3d 1364, 1376 (D.C. Cir. 2007); National Lime, 233 F. 3d at 640.  Although one of the overall goals of the Act is to protect and enhance the quality of the Nation's  air and resources so as to promote the public health and welfare and the productive capacity of the population," CAA section 101 (b) (1), this overall goal does not somehow authorize EPA to adopt floors that either consider costs (overall or otherwise) or to base floors on other than what best performers achieve.
Subcategory for each HAP
Comment: One commenter (2890) asked EPA to clarify the statement on page 21145 of the proposal preamble that EPA may create a subcategory applicable to a single HAP, rather than a source category, if the facts warrant (so that, for example, a subcategory for kilns emitting mercury, but a single category for kilns emitting HCl, is legally permissible with a proper factual basis).  The commenter took this to mean that EPA is creating a subcategory for a single HAP.
Response: See fuller discussion where EPA discusses whether to subcategorize on the basis of quarry limestone mercury levels.  If EPA had chosen to do so, the subcategory would have contained two sources and would apply to emissions of mercury only.
2.3.3	Lowest Emitters Versus Best Performers
Comment: One commenter (2834) stated that the Brick MACT ruling of the D.C. Circuit Court reinforces earlier holdings in National Lime Association vs. EPA.  The Court again held that floors are to be based on the emission level actually achieved by the best performers (those with lowest emission levels), not the emission level achievable by all sources.
Response:  In this rule, EPA is choosing as best performers those sources with lowest emissions of each HAP, on a normalized basis, with sources' variability taken into account in assessing which had the lowest emissions.
Comment:  Many commenters (2841, 2844, 2845, 2846, 2858, and 2914) stated that EPA established its proposed floors equating best performing sources with those that have the lowest emissions for particular HAPs even though there are other ways to measure performance and, in some cases, other methodologies may comply with the statute where the "lowest emitter" approach does not.  Commenter 2845 noted that equating best performer with lowest emitter contravenes a Congressional directive that, in developing MACT standards, EPA cannot require substitution of raw materials in mineral processing industries, such as cement manufacturing, quoting the Joint Explanatory Statement of the Committee of Conference for the 1990 CAA Amendments stated: For categories and subcategories of sources of [HAPs] engaged in mining, extraction, beneficiation, and processing of nonferrous ores, concentrates, minerals, metals, and related in-process materials, the Administrator shall not consider the substitution of, or other changes in, metal- or mineral-bearing raw materials that are used as feedstocks or material inputs . . . in setting emission standards, work practice standards, operating standards or other prohibitions or requirements or limitations under this section for such categories and subcategories. H.R. Rep. No. 101-952, at 339 (1990). According to the commenters, enormous amounts of limestone are fed into a kiln to manufacture clinker, and it is cost-prohibitive to import limestone from further away. If the plant's quarry contains limestone with high concentrations of mercury or high concentrations of organics, the kilns will emit more mercury or THC and potentially more organic HAPs. Because limestone with high mercury or organic emissions will result in higher HAP emissions, and it is not cost-effective to import limestone from far away, equating the lowest emitters with the best performing sources makes no sense in the context of cement facilities. It also would be squarely in opposition to the Joint Explanatory Statement.
Response: The commenter is citing to the "Joint Explanatory Statement" that accompanied the Conference Committee Report to the 1990 Clean Air Act Amendments. This legislative history is of limited utility here.  As explained at 353 F. 3d 388: "The Joint Explanatory Statement describes how the differences between the Senate and House were resolved in the Conference Committee.... The Joint Explanatory Statement may be helpful in determining Congress's intent, but does not carry the same weight as the Conference Committee Report itself." See id. at 236-37.  If there were some ambiguity in the statute, the Joint Conference Committee Report could shed some light on Congress' intent, but there is no exception to section 112 (d)(2) (A)'s requirement that EPA consider "substitution of materials" for each source category. Thus, the statement cannot be read to negate the express statutory command that MACT is to be based on, among other things, measures, processes, or systems which reduce the volume of pollutant emissions through substitution of materials or other process modifications.  Indeed, EPA's attempts to identify best performers by ignoring the contribution of raw material inputs have been soundly rejected.  Brick MACT, 489 F. 3d at 882-883.  In fact, brick and ceramic production, like Portland cement production, involves extraction of mined material from a quarry located proximate to the production facility because transport of raw material over long distances is "infeasible".  489 F. 3d at 879.  The language from the Joint Explanatory Statement no more allows EPA to ignore raw material contribution to Portland cement plants' HAP emissions than it did raw material HAP contributions to brick and ceramic plants' HAP emissions.
Comment:  Commenter 2844 stated that EPA could interpret §112(d)(3) as Brick MACT appears to do, as one unitary concept meaning sources with the lowest emission levels, or EPA can interpret it as a more complex concept that the EPA may determine the emission control (using any of the various definitions in the CAA) that sources have achieved in practice (as estimated by reasonably predictive variability factors) and rank them according to their relative emissions levels (i.e., a quantitative measure of achievement). Having done so, the Agency can then evaluate each of the lowest emitters in terms of whether they meet the Agency's criteria for best controlled similar source. With regard to best controlled, EPA may evaluate this from a purely quantitative angle (lowest emissions) or from more qualitative aspects (reduction efficiency, environmental and health (or cross-media) impacts, cost-effectiveness of reductions achieved, impacts on other HAP or pollutant emissions, and so on.
Commenter 2845 provided several examples of Court MACT decisions endorsing a technology approach to setting the standards, in which EPA selected the best performing sources based on the relative performance of air pollution control technology.
Commenter 2844 stated that EPA also has the discretion to define best performers as sources other than those with the lowest achieved emission levels. In the current proposal, the many difficulties associated with evaluating the impact of HAP content in the raw material inputs to mercury emission control and other factors could support a decision by the agency to establish a standard based on efficiency (i.e., a percent reduction standard) if not for the source category as a whole, then such a standard might be established for a particular subcategory as relevant, or as an alternative compliance strategy. EPA's discretion is sufficiently broad to encompass many reasonable decisions identifying and estimating the emission control of best performing sources on bases other than lowest emissions data, assuming the floor for the standard is based on a reasonable methodology estimating the percent reduction achieved in practice by the best performing sources under the reasonably foreseeable worst operating conditions.
 Commenter 2844 stated that before EPA can determine a floor, EPA must define the following terms in regard to the selection of a best performer for new sources: Emission control; Achieved in practice; Best controlled; and Similar source.
To set the floor for existing sources, the commenter stated that EPA should define the following terms:  Average emission limitation; Achieved; and Best performing.
Response:  EPA must make determinations in each standard as to each of these terms and has done so here.  In this rule, EPA is determining that the best controlled similar source is the source with the lowest emissions of the HAP in question on a normalized basis (for mercury and PM), and on a concentration basis (for THC and HCl) considering variability in determining both which source is best controlled and its achieved performance.  EPA is adopting the same approach for existing sources in determining which are the 12 percent of best performing sources and the performance they achieve.  This approach accounts for all HAP inputs and outputs (i.e., accounts for HAP in all raw material and feed inputs as well as all emission controls), and is consistent with the case law.
Comment: Commenters 2832, 2846, and 2890 stated that rather than selecting sources with the lowest emissions for particular HAP as best performing sources, EPA could use the relative performance of air pollution control technology to select the best performing sources, applying the best reasonable method for determining best-performers, which does not necessarily have to equate to lowest emissions.
Response:  EPA discussed this issue at some length at proposal.  See 74 FR at 21149.  The problem with equating best performance with performance of pollution control alone is that it ignores the contribution of raw materials and fuels to HAP emissions.  Basing standards exclusively on performance of control technology is legally permissible when the control technology is the sole factor influencing performance, which is not the case here.  National Lime, 233 F. 3d at 633-34.  EPA thus is not adopting these commenters' approach.
Comment: Commenter 2859 stated that EPA is making an unrealistic conclusion that best performing is equivalent to lowest emitting when applied to the Portland cement NESHAP. In cement manufacturing, lowest emitting may be strictly related to a cement plant located adjacent to a source of limestone that has the lowest level of contaminants. The goal of the NESHAP is to reduce emissions of HAPs to the lowest possible level using the best technology. There are several examples in this rulemaking where the lowest emitting sources are not the most modern cement manufacturing technologies or utilizing the most modern pollution control measures. Conversely, some of the highest emitters are the most modern cement manufacturing technologies that employ the most modern pollution control measures.
Response:  The statement (without supporting citation) that "the goal of NESHAP is to reduce emissions of HAPs to the lowest possible level using the best technology" again ignores the contribution of raw material and fuel inputs.
Comment: Several commenters (2845, 2846, 2874, and 2915) stated that EPA is proposing to calculate MACT floors by averaging the top 12 percent of sources for which CEMS data are available (even if that amounts to less than 30 sources), rather than by considering the top 12 percent of sources for which EPA has emissions information. As a result, EPA is proposing to establish the MACT floor based on data from only 2 sources. The commenters stated that CAA §112(d) obligates EPA to set the MACT floor looking at no fewer than 5 sources, recognizing the value of relying on the maximum amount of data available.
Commenter 2841 stated that the use of a minimum of five facilities should be adopted in the establishment of THC standards as well as the other standards in this proposed regulation. The establishment of requirements based on a small amount of data would run counter to the intent of the CAA in utilizing data that is truly representative of the best-performing facilities throughout an entire industry.
	Commenter 2841 stated that in previous MACT rulemakings, EPA used the five best performing facilities if the number of facilities was less than 30. Consistent with these prior rulemakings, the commenter stated that this approach should be used for this proposed Portland Cement NESHAP rule and that EPA needs additional data points in order to appropriately set limits for the industry as a whole.
Response:  EPA believes that it has discretion to use the data which most accurately measure sources' performance, which in this case are data obtained from CEM-equipped sources.  EPA also believes that it has a reasoned technical basis for not combining CEMS data with non-CEM data, since this would be a classic apples-to-oranges comparison due to the difference in   measuring  times and methods.  EPA does not agree that section 112 (d)(3) mandates a minimum of 5 sources in all instances, notwithstanding the incongruity of having less data to establish floors for larger source categories than is mandated for smaller ones.  The literal language of the provision appears to compel this result.
Comment: One commenter (2898) supported EPA's decision to not rank best performers based on their relative mercury removal efficiency. Relying on mercury removal efficiency in setting the MACT floor for the Portland cement manufacturing industry would downplay the role of HAP inputs on emissions. EPA characterizes Brick MACT's statement that best performers are those emitting the least HAP as appearing arguably in dicta. However, the Brick MACT Court itself characterizes the statement as the holding of the Cement Kiln case. Brick MACT, 479 F.3d at 880 (relying on Cement Kiln's holding that §7412(d)(3) requires floors based on the emission level actually achieved by the best performers or those with the lowest emission levels). The proposed alternative of setting the MACT floor on the basis of percentage of emission reduction achieved by sources would minimize, if not eliminate, the consideration of cleaner inputs in setting MACT floors, as EPA acknowledges, and is therefore contrary to statutory dictates and case law.
Response:  EPA agrees that the chief legal issue with a percent reduction approach is that it undervalues the role of HAP inputs.  EPA is not adopting that approach in this rulemaking.
Comment:  Several commenters (2831 and 2901) stated that EPA retains considerable discretion on how to set MACT floors. The commenters supported the Agency's authority to set floor standards based on control efficiency, or any method as long as their method reasonably estimates the performance of the relevant best performing plants. There is nothing in the Court's decisions that requires EPA to use the straight-emissions approach favored in this rule. The commenter stated that the Court has expressly decided that a straight emissions or arithmetical methodology is not required.   EPA's technology based approach that estimated performance rather than deriving the standards through an arithmetic-straight emissions approach is supported by the Courts, as long as it results in a reasonable estimate of the performance of the best controlled units.  According to the commenter (2901), Brick MACT does not endorse a straight emissions approach; nor could it. To do so would mean that the Brick MACT Court was overturning the Chevron step one holding in Sierra Club and National Lime II, something that it cannot do.
Response:  EPA is adopting the straight emissions (so-called) approach in this rulemaking and believes that the approach is permissible under the statue and case law.  Commenters also did not convincingly address the issue of how the alternative approaches they mention account for HAP inputs.  Moreover, Sierra Club and National Lime II make clear that a straight emissions approach may not be mandated under the language of the statute, but also make clear that there must be a reasoned basis for estimating which performers are best.  National Lime II, and later Brick MACT further make clear that contribution of HAP inputs in raw materials and fuels must be accounted for in making best performer determinations. See 233 F. 3d at 634, 639; 479 F. 3d at 882-83.  Each panel viewed these holdings as consistent with the Chevron analysis in Sierra Club.  233 F. 3d at 631-32, 633-34; 479 F. 3d at 878.
Comment: One commenter (2844) stated that the CAA requires that lawfully promulgated NESHAP standards must be achievable. Section 112(d)(2) of the Act requires EPA to establish emission standards for HAPs that require the maximum degree of reduction in emissions taking into consideration the cost of the emission reduction and non-air quality health and environmental impacts and energy requirements, that the EPA Administrator determines is achievable for new or existing sources. Further, House Rep. 101-490, Part 1 (328) stated that "The Committee expects MACT to be meaningful, so that MACT will require substantial reductions in emissions from uncontrolled levels. However, MACT is not intended to require unsafe control measures, or to drive sources to the brink of shutdown."  The commenter noted that the proposed Portland cement proposed NESHAP standards do not comply with §112's achievability requirements.
Response:  The commenter refers to legislative history to versions of the 1990 amendments which did not include floor requirements, so it is not directly applicable in interpreting the enacted provisions.  Moreover, as held repeatedly by the D.C. Circuit, the "achievability" requirement in section 112 (d)(2) does not alter the minimum level of stringency requirements mandated by section 112 (d)(3)'s requirements.   See, e.g., Cement Kiln Recycling Coalition, 255F. 3d at 861-62.
Comment:  Commenter 2844 stated that EPA's conclusion that §112(d)(3) and/or Brick MACT requires or even permits the Agency to ignore the achievability requirements of §112(d)(2) is an unreasonable reading of the statute and of Brick MACT. The Agency retains more than sufficient discretion to devise NESHAP standards that successfully bridge the tension between achieved and achievable in §112's standard-setting provisions by appropriately using both subcategorization and variability methodologies.
Response:  EPA believes that variability needs to be assessed in order to accurately measure both which performers are best and what their performance is.  However, authority to subcategorize is discretionary and need not be exercised where there are rational grounds not to do so, such as not authorizing emissions of large amounts of a dangerous neurotoxin.  See also previous response.
Comment:  Commenter 2844 stated that EPA's floor setting methodology does not comply with three of Brick MACT's requirements:  Floors must be based on emissions achieved in practice by best-performing sources; EPA's use of variability factors and methodologies to adjust reported emissions data must be based on demonstrated relationships, so that the floor setting methodology serves to reasonably estimate or predict the performance of the best performing sources; and EPA must consider the impact of nontechnology factors, such as raw material and fuel inputs, on a source's emission control levels.
Commenter 2844 stated that in the Portland cement proposal, EPA set MACT floor levels that reflect the specific conditions at the time the data were generated and do not include any of the operational variability. The commenter suggests that EPA must look beyond its snap shots of performance to make a reasoned evaluation and estimation of all operating conditions and factors that might impact the level of actual emissions from those kilns in practice, and adjust their reported short term test data appropriately. EPA can and should adjust raw emissions results to estimate sources' achieved emissions levels when setting MACT floors and standards. Since Brick MACT, EPA's methodology now must be able to reasonably estimate the impacts of variability associated with both technological and nontechnological factors over the full range of circumstances.
Response:  EPA disagrees that it has based the floors for any of the HAP on snapshot levels of performance and has not accounted for potential variability in sources' performance.  Each of the floors reflects a reasonable estimate of what the best performing sources (or source) will achieve over time.  Also, each of the floors considers the impact of non-technology factors, notably HAP inputs in raw materials and fuels, on the source's emissions.  Specifically, for mercury the standard reflects 30-days of data for all mercury inputs, reasonable estimates of control device performance (for the few controlled sources), plus a reasonable statistical methodology to account for variability (including variability of mercury content of kiln inputs).  See IV.A.1.c of this preamble and 74 FR at 21142-44.  The standard for THC reflects hundreds of observations gathered continuously over time using a CEMS from which variability can be calculated directly.  See IV.A.1.d of this preamble.  The floors for HCl are set at the minimum quantification level, which is a factor of five above the actual measured levels.  Floors for PM are based on multiple stack measurements which have been adjusted by reasonable statistical methodologies to account for variability.  See IV.A.1.f of this preamble.  Moreover, the PM standard reflects performance of fabric filters with membrane bags, which are known to perform independent of inputs and to have relatively small operating variabilities.  Consequently, for each HAP, EPA is assessing sources' performance over time and not ignoring their operating variability.
Comment:  Commenter 2844 also stated that EPA adopted a floor setting methodology that is based on using lowest reported emission results with minimal variability adjustments to estimate emission control achieved in practice by best performing sources. EPA considered test-to-test variability, but did not consider the inherent variability due to raw materials, product mix, fuels, operating conditions and plant types. The commenter stated that EPA has not evaluated or validated whether its methodology accurately estimates emissions control achieved in real world circumstances at sources.
Response:  This comment is inaccurate on a number of counts.  First, the statistical methodology used to estimate variability depends on the distribution of data to the formula.  Any variation in that data  -  be it due to differences in raw material concentration, fuel composition, or device operation  -  is evaluated by the formula.  The data base for each pollutant reflects all of these factors (and indeed, the data base for mercury consists almost entirely of measured inputs).   Consequently, EPA's methodology does evaluate variability of inputs, not just control device operating variability.   Second, for mercury and THC, EPA gathered data over time, as explained in the preamble and in the previous response.  Third, for mercury, EPA compared its calculated relative standard deviation of a longer term data set of a particular source's mercury inputs and found it to be within the same range as that estimated by EPA for other sources based on the distribution of 30-day values in the data set for the MACT pool of best performers, suggesting strongly that the calculated variability was reasonable.  74 FR at 21143.  Fourth, in the case of mercury, industry had ample opportunity to provide longer term sampling data and (with a few exceptions, which EPA evaluated and accepted) did not do so.
Comment:  Commenter 2844 stated that EPA cannot evaluate floors using methodologies that focus exclusively on technology if the resulting standards do not reflect actual average limitation[s] achieved (Brick MACT, 479 F.3d at 882). The commenter concludes that Brick MACT requires EPA to address the role of nontechnological factors that impact emissions in setting floors and EPA must develop a methodology that accurately estimates the actual emissions achieved in practice by the best performing sources under a variety of operating conditions, taking into consideration testing and technological and nontechnological variability.  As proof that EPA failed to properly account for sources' variability in setting the standards, the commenter (and commenter 2845) included a chart purporting to demonstrate that the kilns comprising the pool of best performers for each HAP could not themselves meet the proposed standard.
Response: EPA believes that its methodology reasonably estimates the variability of the best performing sources, taking into account both technological (emission control device) and non-technological (varying inputs) variability.  EPA disagrees that the record shows that the kilns comprising the MACT pool for each floor cannot themselves meet the promulgated standards (see previous response).  In fact, for each pollutant, the record indicates that every kiln in the MACT pool (not just the kilns below the average of the best performers) would be in compliance.
Comment:  Commenter 2844 stated that the proposed standards cannot be viewed as assessing the emissions control achieved by best performing sources, given that there is no single existing source that meets the standards simultaneously and for two of the pollutants, no existing units meet the standards without operational changes. The EPA has an obligation to devise appropriate variability methodologies and to collect the information necessary to do so.
Response:  EPA has responded above to the argument that the statute unambiguously compels that floors be established on a complete facility basis.
Comment: One commenter (2845) stated that case law and policy dictate that the EPA must consider variability in establishing MACT standards, and the approach used by EPA in Prevention of Significant Deterioration (PSD) permitting should also apply in establishing MACT standards. To evaluate the emission limits achieved by existing sources, EPA is required to develop methodologies for estimating the variability associated with all factors that impact a source's emissions, including process, operational and non-technological variables (see Nat'l Lime Ass'n v. EPA, 627 F.2d 416, 443, D.C. Cir. 1980). While Courts have affirmed EPA's authority to choose a methodology designed to estimate emissions in setting the MACT floor, the Courts have also made clear that EPA's method must allow a reasonable inference as to the performance of the top 12 percent of units (Cement Kiln Recycling Coalition v. EPA, 255 F.3d 855, 862 (D.C. Cir. 2001) (citing Sierra Club v. EPA, 167 F.3d 658, 663, D.C. Cir. 1999). Accordingly, the Court of Appeals for the D.C. Circuit has stated that EPA must show not only that it believes its methodology provides an accurate picture of the relevant sources' actual performance, but also why its methodology yields the required estimate (Cement Kiln Recycling Coalition, 255 F.3d at 862).
Response:  EPA agrees that sources' variability should be accounted for both in determining which sources are best performers and what their achieved performance is.  EPA also believes that it has reasonably accounted for sources' variability here, including both variability in inputs and operating variability.
Comment:  Commenter 2845 further stated that EPA has a clear policy of considering long-term variability when establishing enforceable emission rates. In considering appropriate enforceable emissions rates in PSD permits under the CAA, the Environmental Appeals Board has held that a permitting authority is not required to set the BACT emissions limit at the most stringent emissions rate that has been demonstrated in practice by a facility using similar emission controls (In re Newmont Nevada Energy Investment, 12 E.A.D. 429, 441-42, EAB 2005 (citing Kendall New Century Dev., 11 E.A.D. 40, 53, EAB 2003). The Board has recognized the use of safety factor[s] in the calculation of permit limits to take into account both the variability and fluctuation in the expected performance of pollution controls and the fact that setting emissions limitations for one facility at the highest control efficiency demonstrated at another facility would make violations of the permit unavoidable (Id. at 442, citing In re Masonite Corp., 5 E.A.D. 551, 560, EAB 1994).
Response:  Although BACT determinations under PSD are by no means analogous to determining MACT floors (cost is considered in determining BACT, for example), EPA agrees that consideration only of single data points may not adequately represent sources' performance over time, and EPA consequently is not utilizing that methodology in this rule.
Comment:  Commenters 2844, 2845, and 2916 objected to EPA's interpretation of CAA Sections 112(d)(2) and 112(d)(3) and the Brick MACT opinion (Commenter 2845 provided a white paper as an appendix to their comments for the HWIMI MACT proposal, dated December 01, 2008.).  The paper, titled "Implications of the Brick MACT Decision on EPA's Discretion in Setting MACT Floors," discusses variability at some length. The paper's main points were:
The Agency has chosen to focus on setting MACT floors based on lowest emitting sources derived from limited test results that are not appropriately adjusted to account for stack test variability.
The Brick MACT decision holds that EPA must base MACT floors on achieved emissions control rather than control technology, but it does not require EPA to ignore operational variability in determining those floors.  Variability methodologies must reasonably estimate or predict emissions or variability through a demonstrated relationship between the data used and the performance intended to be estimated.  Non-technological factors (i.e., raw materials and fuel) must be considered in determining emission control achieved by best performers.  It is within the EPA's discretion to define the best performing sources.
EPA should estimate variability in determining achieved emissions.  The Agency can and must seek appropriate data from regulated entities and other stakeholders, and to develop appropriate fact-based estimating methodologies on the data available.
Response:  EPA largely agrees with these general points and believes that it has adhered to these concepts in the final rule.  EPA has also implored, and in many instances, compelled (through section 114 letters) industry to provide additional data to better gauge sources' performance.
Comment: Several commenters (2834, 2844, 2845, and 2859) stated that the Brick MACT decision makes the expectations of what is expected by EPA in regards to setting the floor very clear:
Floors must be based on emission control achieved in practice by the best performers; Variability methodologies must reasonably be calculated to estimate such actual performance levels; Nontechnological factors that impact emissions must be considered in determining the achieved emissions levels; and
In devising new methodologies to set lawful floors, EPA must ensure that compliance with §112(d)(2) general standard setting criteria is also met.  EPA can use discretion to define the factors necessary to establish a floor under §112(d)(3) that meet the CAA's statutory intention to be technology-forcing and require compliance with the best that has been demonstrated to be achieved in practice while considering costs, other non-air health and environmental impacts, and energy impacts when defining achievable MACT standards.
Response:  The case law makes overwhelmingly clear that the requirement in section 112 (d)(2) that MACT standards be achievable after considering various factors does not supersede the requirement of section 112 (d)(3) that they be of minimal stringency as determined by the criteria for establishing MACT floors. See Cement Kiln Recycling Coalition, 255 F. 3d at 861-62.
Based on these points, the Brick MACT decision requires that EPA's floor analyses include a review of the best performers and consideration of variable factors that can affect emissions achieved in practice by the best performing sources. EPA's analyses and methodological choices must be based on facts and records that support its final determination. It is appropriate that a full review of the existing records and the development of new data be considered in making a final decision.
Comment: Several commenters (2832 and 2859) opposed the approach taken by EPA in its beyond-the-floor MACT analysis. Among other things, EPA failed to consider the creation of incremental greenhouse gas emissions associated with the construction, installation and operation of new emissions control equipment, and the minimal incremental environmental benefit associated with those controls. Also, EPA failed to consider the cost of carbon credit purchases by the industry.
Response: In all cases we rejected the beyond-the-floor analyses based on costs or technological factors.  Evaluating other disbenefits for an option already rejected would have no purpose.
Comment: Many commenters (2830, 2845, 2846, 2855, 2858, 2859, 2879, 2887, and 2890) stated that CEMS are not a proven technology and should not be required to determine compliance.
Commenters 2588, 2844, 2845, 2846, 2858, and 2890 stated that EPA has no data showing that mercury CEMS are feasible on cement kilns and that emissions from cement kilns will likely be outside of the range of the current CEMS technology. The commenters stated that EPA must evaluate mercury CEMS through long-term field trials at cement plants in accordance with the proposed performance specifications and quality assurance procedures before imposing this regulatory requirement. The commenters proposed a mass-balance approach for monitoring, which is accurate and was used by EPA in setting the mercury standard.
Commenter 2855 stated that mercury sorbent trap monitoring systems have not been evaluated through long term field trials at cement plants in the United States (U.S.) in accordance with the proposed performance specifications and quality assurance procedures, so the reliability and performance of these measurement systems and the adequacy of the technical specifications cannot be determined.
Commenters 2855 and 2900 disagreed with EPA's interpretation of the operating experience with mercury CEMS in Germany. The commenters stated that mercury CEMS are inaccurate and difficult to maintain. Further, mercury CEMS operating in Germany are subject to monitoring regulations that are different than the U.S. regulations and are used in a different regulatory context than that proposed by EPA. The monitors used in Germany, or those available from other European or Asian manufacturers were not able to demonstrate acceptable performance in the Electric Power Research Institute (EPRI) Trimble County Mercury CEMS study.
Commenter 2855 stated that there is no legitimate technical basis on which to establish detailed performance specifications or quality assurance (QA) requirements for these CEMS. There is no legitimate technical basis to conclude that these CEMS could meet such requirements over any extended period when installed and operated at a cement plant. The commenter recommended that EPA evaluate the performance of mercury CEMS at cement kiln systems and acquire the information necessary to serve as the basis for technical specifications and requirements. After such information is available and analyzed, EPA should re-propose appropriate and demonstrated performance specifications and quality assurance procedures for mercury CEMS to monitor kiln and kiln/in-line raw mill mercury emissions.
Commenter 2855 disagreed with EPA's interpretation that mercury CEMS can be applied to the cement industry based on successful use on utility boilers. The commenter evaluated the following issues:
Number of Installations in the Utility Industry  -  there are 35  -  40 continuous mercury monitors (CMMs) installed and certified to date (not yet with a NIST traceable calibration source).
NIST Certification  -  In mercury CEMS certification requirements outlined in Performance Specification (PS)-12A, it states that all calibration and span gases must be NIST certified. The draft protocols were just released by NIST in July 2009. The major vendors of mercury CEMS are just now advertising NIST-certified calibration sources. Therefore, none of the mercury CEMS that have been previously installed are certified. NIST does not currently directly certify oxidized mercury calibrations. The Interim EPA Traceability Protocols now in place provide for certification of evaporative generators by certification of the individual components of the calibrator. Therefore, the language used in Section 7.0 that refers to a NIST trace oxidized mercury calibrator needs to be clarified or changed.
Difficulties Encountered in the Utility Industry  -  The commenter gave examples of power plants' difficulties with mercury CEMS.
Installation on Wet Stacks  -  Installing a mercury CEMS on a wet stack can result in problems: plugging, corrosion, and buildup of solids. Although wet scrubbers are not currently common in the cement industry, under the proposed rule, they may be required to a greater extent, and many of these same problems with mercury CEMS potentially could occur for the cement industry as well.
Data Output Requirements  -  There is no need for dry basis measurements under the proposed rule and the language in either Subpart LLL should be included to provide an exemption from this requirement for cement plants or PS-12A should be revised. This language needs to be clarified by EPA.
Cost  -  The commenter provided information about CEMS costs, estimating that if mercury CEMS were installed on all non-waste-burning U.S. cement facilities, the total capital costs would be approximately $45 million, with annual operating costs being about $25 million.
Commenter 2901 stated that CEMS should not be used as a compliance method for cement plants for the following reasons:
EPA reported in 1997 on an experiment where CEMS were installed on a cement kiln burning hazardous waste. The Agency found substantial problems regarding mercury CEMS measurement accuracy and precision, deciding not to require Mercury CEMS at cement plants. The commenter stated that the primary issue is whether there is a NIST traceable standard that can be used to calibrate the unit. Because compliance is based on the production rate and using a 30-day average, it is difficult to know what range to calibrate these units.
The reliability of CEMS on cement kiln stacks has not been demonstrated in the U.S., where standards and requirements are different. Demonstrations in the U.S. at coal-fired power plants have different conditions than those at cement kilns.
There is no legal imperative for EPA to require CEMS. Under the CAA, EPA's monitoring requirements must provide a reasonable assurance of compliance with emission standards Sierra Club v. EPA, 353 F.3d 976, 990-991 (DC Cir 2004) (Copper Smelters) citing Natural Res. Def. Council, Inc. v. EPA, 194 F.3d 130, 136 (D.C. Cir 1999).
Response:  Commenters raised several issues about the extent to which mercury CEMS are a demonstrated technology for cement kilns.  We believe that they are in fact demonstrated for cement kilns based on the experience of the utility industry and that there is no technical reason why they will not work for the cement kiln industry.  Many of the issues cited by the commenters represent earlier generations of CEMS, and these have been resolved.  Also, since proposal, mercury CEMS have been installed on two cement kilns.
      Commenters also raised specific concerns, such as the reported lack of NSIT standards (which are available now) and issues associated with using CEMS on wet stacks (EPA is aware of difficulties, but the technology has improved).  Regarding data output requirements in PS-12A, the specification has been revised to state that dry measurements are not required.  Commenters also questioned the costs of using CEMS, but we believe the cost model used by EPA has been verified.
Comment: Several commenters (2841, 2844, 2846, and 2916) stated that MACT standards may only address HAP pollutants, but EPA is trying to control sulfur dioxide and other non-HAP pollutants through application of control technology used to reduce HCl.
      Commenter 2846 stated that basing MACT limits on such considerations is not permissible and limiting compliance flexibility by excluding other options is not good policy. Section 112(d)(2) provides an express list of factors that EPA may consider in setting MACT standards  -  including the cost of achieving such emission reduction, and any non-air quality health and environmental impacts and energy requirements. This list does not allow consideration of non-HAP air quality benefits, such as the co-benefits of reducing PM2.5 emissions.
      One commenter (2898) stated that Congress intended EPA to consider benefits such as a reduction in emissions of SO2 and other acid gases, along with condensable PM, ammonia, and semivolatile compounds when setting a MACT floor, and EPA has appropriately considered these co benefits in deciding not to set health-based standards for HCl.
Response:  EPA is regulating SO2 emissions for new sources and modified sources under the NSPS rulemaking.  EPA recognizes that any other SO2 emission reduction obtained from existing sources is a co-benefit resulting from the control technology selected to comply with either themercuryand/or HCl NESHAP limits.  EPA recognizes the multi pollutant interactions and co-benefits of this rulemaking and how a well planned integrated control strategy can maximize the environmental results while optimizing the cost invested by a facility to comply with such regulation.
Comment:  Commenter 2845 stated that EPA should require that compliance with HCl limits should be measured by periodic stack tests. Because the HCl floors were developed from HCl stack test data, the standard for HCl should be based on periodic stack testing. EPA must evaluate valid data from Method 321/ASTM D6348 stack tests instead of the data contained in Table 5 of the proposal. Using CEMS to measure compliance effectively makes the standard more stringent than what has been achieved by the best-performing sources. If CEMS compliance demonstration is retained, then the limit for CEMS compliance must be raised to reflect the added variability that will be measured by the CEMS. While continuous measurement will capture variability of emissions 24 hours per day, 7 days per week over the full range of process and control system operating conditions over the life of the plant and its associated quarry, the stack test is merely a snapshot in time. By definition, a stack test contains no parameter related to variability other than that obtained during the three hours of testing. In addition to the inherent variability of HCl emissions, a CEMS standard must also consider the inaccuracy of the CEMS as determined (and allowed) relative to the required stack test methods, the uncertainty of calibration standards/materials, and other factors affecting the sampling, transport, and analysis of HCl which is a highly reactive compound.
Response:  HCl CEMS will be measuring HCl with the same technology that was used in the period stack tests (M321) used to set the standard.  An allowance for variability has been built in through the process of setting the standard, including setting the standard based on the 99[th] precentile  UPL.  The 30-day averaging period also evens out variability in operations.  As described elsewhere, EPA has obtained additional HCl data, resulting in a new floor determination of 0.4 ppmvd.
Comment: Two commenters (2845 and 2859) said that
EPA has not promulgated any regulations requiring PM CEMS at any source category due to its inability to address fundamental technical and policy issues and must resolve these issues through formal rulemaking before requiring PM CEMS at any cement plants.  Furthermore EPA has not performed a legitimate technical analysis of emissions variability and compliance determination uncertainty to allow the use of PM CEMS for determining continuous compliance with a PM limit at cement plants.
      The use of PM CEMS in Europe and other countries does not constitute a valid basis for application of PM CEMS at cement plants in the United States. Light scattering, light transmission, and extractive beta attenuation instruments are all inferential measurement devices and a correlation must be established to relate the device output to the actual PM concentration, then the accuracy and bias of the reference test and the uncertainty of the statistical correlation, as well as the stability of the correlation must be considered. Under the German TUV and the European monitoring standard (EN 14181) these uncertainties are considered; emissions are not considered to exceed the allowable limit until the lower bound of the confidence interval and/or tolerance interval exceeds the emission limit; emission standards may contain different averaging periods requiring different levels of conformance; and when a problem is encountered, the emphasis is on resolving the emission problem rather than direct enforcement and collection of financial penalties. All of these considerations place the European monitoring program in an entirely different regulatory context than the proposed PM monitoring requirements.
Response:  The 1999 Portland cement rule implementation was deferred until a PM performance specification was developed.  Use of PM CEMS has been proposed for other large source categories such as the ICI boiler rule and coal preparation rule.  In addition, dozens of consent decrees have used them with successful installations and correlations.  We are not relying on the European application of PM CEMS as primary support for the Portland Cement rule.
Comment:  Two commenters (2845 and 2859) had the following comments concerning technical issues associated with application of PM CEMS.  EPA has not addressed nor resolved the primary technical issues limiting the effective application of PM CEMS at cement plants including:
   * inability to generate a sufficiently wide range of PM concentrations to establish an acceptable correlation (i.e., calibration),
   * accuracy and precision limitations of reference method at PM levels necessary to generate valid correlation, and
   * subsequent changes in effluent matrix and/or PM (i.e., particle size distribution, refractive index, particle density, etc.) that influence the stability of the correlation and hence, the relationship between the output of the inferential measurement device relative to actual PM concentration.
Valid PM CEMS correlations cannot be established for PM CEMS at cement plants due to limitations of process operation and control equipment in conjunction with the proposed emission limitation.  The requirements in Appendix A, PS-11 for the PM CEMS correlation and in Appendix F, Procedure 2 do not provide a sufficiently reliable means to determine compliance with emission limitations.
Response:  We have not identified problems cited by the commenters at existing installations.  In fact, PS-11 and Procedure 2 are working well.  We note that PS-11 has several features to address correlation issues.  For example, PS-11 provides for the addition of a zero point, which enhances the ability to provide a calibration.  It also strongly suggests the use of paired trains to insure that accuracy and precision is obtained.  Changes in the effluent matrix could be a problem with light scattering technologies but this has not been shown to be a problem with existing installations.  This would not be a problem with beta attenuation monitors.
Comment:  Two commenters (2845 and 2859) had the following comments concerning PS-11 and Procedure 2.  The requirements at §63.1349 for PM CEMS are incomplete and ambiguous and EPA has failed to specify important QA frequencies and other information relevant to the implementation of PM CEMS in accordance with PS-11 and Procedure 2. The proposed Subpart LLL revisions fail to address critical elements including the following sections of PS-11 and Procedure 2:
   * PS-11 3.20, species reference method as method defined in applicable regulations (Method 5 with 250ºF filtration temperature) but this is inadequate for low concentrations where Method 5I should be used, and is inapplicable to sources with PM that condenses between the stack temperature (mill on and mill off, if applicable) and 250ºF where Method 17 should be used or ASTM D 6831.
   * PS-11, 6.2 You must ensure that the averaging time, the number of measurements in an average, the minimum data availability, and the averaging period for your CEMS conform to those specified in the applicable regulation - but none are specified.
   * When using PS-11, 6.5 Your CEMS must sample the stack effluent such that the averaging time, the number of measurements in an average, the minimum sampling time, and the averaging procedure for reporting and determining compliance conform to those specified in the applicable regulation - but none are specified.
   * Procedure 2, 10.3 You must conduct an response correlation audit (RCA) and an relative response audit (RRA) at the frequency specified in the applicable regulation...  but none are specified.
   * Procedure 2, 10.3, You must perform an RRA at the frequency specified in the applicable regulation...  but none is specified.
   * When using Procedure 2, 10.3(7) You must perform an RCA at the frequency specified in the applicable regulation...  but none is specified.
   * When using Procedure 2, 10.9 You must report the accuracy results for your PM CEMS at the frequency specified in the applicable regulation...  but none is specified.
Response:  We left the frequency of some QA audits up to specific industries, but have specified in several consent decrees that RRA's be done every year and that RCA's be done every 2 years. ACA's are required quarterly.
      Regarding the appropriate reference method, the source should use the PM method defined in the applicable regulations to correlate the PM CEMS.  The reference method should be adequate for the industry compliance for the PM limit and for correlation of the PM CEMS if required in the regulation.  The PM method used for compliance must be reported to the agency and is sufficient for this purpose.
      We added paragraph 63.1350(p)(4) to state how to calculate the 30-day rolling average in response to comments that more information is needed on how to calculate the averaging period.
Comment:  One commenter (2786) stated that EPA should not eliminate opacity standards in the proposed rule. The commenter stated that there are benefits to having an opacity standard in conjunction with a particulate matter standard. Opacity measurements can be made by anyone who is trained to measure opacity, which can include members of the public and not just inspectors, and opacity measurements are a cheaper method of getting more frequent measurements.
Response:  We disagree.  Given the sensitivity of the BLD and PM CEMs, we find the opacity requirements to be redundant.
Comment: One commenter (2898) stated that EPA should require PM CEMS and retain the opacity monitoring requirements. EPA is proposing installation and operation of a BLD system, along with stack testing using EPA Method 5 conducted at a frequency of five years for demonstrating compliance with the proposed PM emissions limit. As an alternative, a PM CEMS that meets the requirements of PS - 11 may be used, and EPA is proposing to eliminate the current requirement of using an opacity monitor. The proposed rule solicits comment on making the use of a PM CEMS a requirement. The commenter stated that EPA should both require CEMS and retain the use of opacity monitors.
EPA should abandon the BLD system requirement outlined in the proposed rule and mandate the use of PM CEMS instead. The agency previously concluded that PM CEMS is a superior monitoring technology that can be implemented at a reasonable price. EPA has found that BLD systems, standing alone, are inadequate to verify compliance and has also found that continuous opacity monitors (COMS) operate as a useful check on PM emissions and proper operation of PM CEMS.
Providing a superior level of compliance assurance is not the only benefit of PM CEMS. EPA has acknowledged that the assumptions to assure compliance are fewer and less conservative (direct measure of the standard is the top of the monitoring hierarchy), CEMS mean facilities need to monitor only one emissions parameter to assure compliance rather than multiple operating limits, often relevant to more than one standard, and that the cost of installing PM CEMS technology is reasonable.
Response: We would support the use of multi-metal CEMS, should they become available.  We have not yet seen evidence that COMS are well-suited continuous compliance as are BLD or PM CEMS.
Comment: Many commenters (2832, 2845, 2859, 2863, 2864, 2874, 2890, 2914, and 3193) stated that EPA should follow the intent of the CAA sections 111 and 112 which established the requirement that new and existing sources recognized in the proposed rule use the published date of May 06, 2009, as the new source trigger date for mercury, HCl, and THC emission standards instead of the proposed retroactive date of December 2005 when the amendments for mercury, THC, and HCl were first proposed. The commenters stated that despite the direct acknowledgements in the proposed rule, EPA arbitrarily decided to apply a proposal date for mercury, THC and HCl that reaches back and applies new source standards to any plant constructed since December of 2005 and admitted that the 2005 proposal did state EPA's desire to establish floors for THC, HCl and mercury. According to the commenters, this is irrelevant because sources constructed in the past four years cannot have reasonably anticipated their need to comply with the 2009 proposed floors based on the 2005 proposed rulemaking. The 2005 rulemaking resulted in a final rule with floors for THC and mercury, and no HCl floor (due to its classification as a threshold pollutant), which are significantly different than the 2009 proposal and the 2005 proposal did not reference a desire to establish a floor for PM, nor one as stringent as that set forth in the current proposal.
Response: As explained above, EPA agrees with these comments and has adopted a May 6, 2009, compliance date for determining when sources come into existence for purposes of determining which sources are subject to new source MACT.
Comment: Several commenters (2832 and 2859) opposed the proposed requirement to install CEMS in order to satisfy compliance assurance monitoring (CAM) for selected pollutants. Instead, the commenter proposed that CAM requirements be satisfied using periodic stack testing to the extent that stack testing is requested or require by state air permits. According to EPA's proposal, the MACT floor for new and existing sources in this industry will be determined by stack testing results of sources within the MACT pool. If EPA were to finalize a numeric emissions limitation based on this approach to setting the new and existing MACT floors, that limitation will be based on the same stack testing data. CEMs will have played no role in this process. It stands to reason that compliance assurance should be based on stack testing results, and not a CEMS data that has played no part in this process.
      One commenter (2916) stated that EPA can achieve a reasonable assurance of compliance without the use of CEMS. The requirement to use CEMS is unreasonably costly and unnecessary, given that other reliable means of showing compliance are available for all relevant pollutants. Raw material sampling and kiln parametric monitoring, in conjunction with periodic testing, would work well for THC and HCI. The sorbent trap method for mercury is a good alternative to mercury CEMS and should be retained in the final rule. EPA should refrain from requiring PM CEMS in the final rule. Bag leak detection systems and parametric monitoring of ESPs are proven methods for assuring ongoing compliance with PM limits.
Response:  We disagree.  In the case of THC, emissions may change significantly due to a process change without any advance indication.  In addition, the THC emission limits were established using data from CEMS, and the standard itself is a 30-day average, requiring 30 monthly measurements (only practically obtainable with a CEM).   Therefore, CEMS are the obvious compliance assurance choice.  In the case of mercury emissions, short term test data do not necessarily reflect the long term emissions.  In addition, the performance of the available mercury controls may be significantly affected by operational factors.  To devise a test plan to clearly establish the performance of mercury control under all conditions would be difficult, and for that reason it would be difficult to establish the proper control device operating parameters and operating limits.  Therefore, mercury CEMS are essential in demonstrating continuous compliance with the mercury emissions limits.  If the facility does not have a wet scrubber, changes in raw materials, or fuels could significantly increase emissions without any indications unless a CEMS is used.
Comment: One commenter (2858) stated that while THC CEMS have been used by cement plants for years, CEMS monitors for mercury, HCl and PM have not been demonstrated to be reliable and sufficiently accurate to satisfy EPA's performance specifications when operating on cement kilns.
Response: We disagree.  Mercury CEMS have been widely applied in the utility industry and there are no technical reasons that would imply that do not work equally well on a cement kiln.  PM CEMS have also been demonstrated in utility boilers.  Hydrochloric Acid CEMS have been used on source categories such as municipal waste combustors and utility boilers.
B. What are the significant comments and responses on 40 CFR part 60, subpart F?

Comment: Several commenters (62, 65, and 69) objected to EPA not proposing standards for greenhouse gas (GHG) emissions under the proposed NSPS. One commenter (62) criticizes EPA's decision to not propose any NSPS for GHG emissions from Portland cement plants. The commenter states that even though the Courts have confirmed that GHGs are air pollutants subject to regulation under the CAA, EPA has not issued any such standards, instead issuing an Advance Notice of Proposed Rulemaking (ANPR) that seeks public comment on whether to regulate GHG emissions under the CAA at all. Commenter 62 protests this course of action, and requests that EPA revise the proposed rule to include NSPS for GHG emissions.