National Emission Standards for Hazardous Air Pollutants:
                         Secondary Aluminum Production

Summary of Public Comments and Responses on Proposed Rule (77 FR 8576, February 14, 2012) and Supplemental Proposal (79 FR 72874, December 8, 2014)

                     U.S. Environmental Protection Agency
                 Office of Air Quality Planning and Standards
                     Sector Policies and Programs Division
                       Research Triangle Park, NC 27711

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                               Table of Contents

Section	Page
List of Acronyms and Abbreviations	4
Purpose and Background	5
Commenters	5
1. Risk Assessment	6
1.1 	Risk Assessment Inputs: Processing of ICR Data into Modeling File	6
1.2 	Risk Assessment Methods	8
1.2.1	Modeling of MACT Allowable Emissions	8
1.2.2	Modeling of Acute Exposure	9
1.2.3	Multipathway Screening	10
1.3 	Uncertainties in Risk Assessment	12
1.3.1	Individual Variability and Exposures	13
1.4	Risk Assessment Results	19
2. Rule Provision Changes	21
2.1 	Control Device Shutdown	21
2.2 	Change of Furnace Classification	22
2.3 	Hydrogen Fluoride Compliance	27
2.4	Hydrogen Chloride Compliance	27
2.5	Operating Requirements/Work Practices	29
2.6	Other Technical Corrections/Clarifications	32
3. Testing and Monitoring	38
3.1 	Testing Uncontrolled Group 1 Furnaces	43
3.2 	Worst Case Scenario Testing	44
3.3 	Reporting	48
3.5	Other	50
4. Compliance Dates	51
5. Startup, Shutdown, and Malfunction	52
5.1 	Removal of SSM Exemption	52
5.2 	Startup and Shutdown	64
5.3 	Malfunction and Affirmative Defense	74
6. Regulatory Impacts	89
6.1 	Cost and Economic Impacts	89
7. Miscellaneous Comments	92
7.1 	Commenter Endorsements	92
7.2	Other Comments	92

List of Acronyms and Abbreviations

ACGIH
American Conference of Governmental Industrial Hygienists
CAA
Clean Air Act
CBI
Confidential Business Information
CRWI
Coalition for Responsible Waste Incineration
D/F
Dioxins and Furans
EPA
U. S. Environmental Protection Agency
ERT
Electronic Reporting Tool
FAX
Fascimile
FR
Federal Register
HAP
HCl
Hazardous Air Pollutant
Hydrogen Chloride
HF
Hydrogen Fluoride
HON
Hazardous Organic NESHAP
MACT
Maximum Achievable Control Technology
MIR
Maximum Individual Risk
MOA
Mode of Action
NAAQS
National Ambient Air Quality Standards
NATA
National-Scale Air Toxics Assessment
NESHAP
National Emission Standards for Hazardous Air Pollutants
NFFS
Non-Ferrous Founders' Society
OM&M
Operation, Maintenance and Monitoring
PB-HAP
Persistent Bioaccumulative Hazardous Air Pollutant
PSD
Prevention of Significant Deterioration
RTR
Risk and Technology Review
SAPU
Secondary Aluminum Processing Unit
SIP
State Implementation Plan
SSM
Startup, Shutdown, and Malfunction
TTN
Technology Transfer Network
URE
Unit Risk Exposure

Purpose and Background

On February 14, 2012, the EPA proposed revisions to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Secondary Aluminum Production to address the results of a residual risk and technology review and to correct and clarify rule requirements and provisions. The EPA received 12 comment letters on the 2012 proposal. On December 8, 2014, the EPA issued a supplemental proposal that addressed a limited set of issues. The EPA received 16 comment letters on the supplemental proposal. The purpose of this document is to summarize and respond to the comments received on the 2012 proposed rule and 2014 supplemental proposal that are not addressed in the final rule preamble; however, the final rule preamble also contains discussions of several of these topics. In the summarized comments below, we have indicated those comments that were submitted on the 2014 supplemental proposal. Unless otherwise noted, the remaining comments were received on the 2012 proposed rule. All comments are contained in Docket EPA-HQ-OAR-2010-0544.
Commenters
The commenter, affiliation, and item number in Docket EPA-HQ-OAR-2010-0544 are listed below in Table 1.
 Table 1. Public Comments for Secondary Aluminum Production NESHAP, 2012 Proposed Rule and 2014 Supplemental Proposal, Docket EPA-HQ-OAR-2010-0544
                        Docket No. EPA-HQ-OAR-2010-0544
                                Commenter Name
                                  Affiliation
                              2012 Proposed Rule
                                     0183
J. W. Vinzant
Kaiser Aluminum
                                     0189
Eileen A. Sottile
LKQ Corporation
                                     0190
Melvin Keener
Coalition for Responsible Waste Incineration (CRWI)
                                     0191
James Mallory
Non-Ferrous Founders' Society (NFFS)
                                     0192
J. W. Vinzant
Kaiser Aluminum
                                     0193
Charles D. Johnson
The Aluminum Association
                                     0194
Mike Palazzolo
Alcoa
                                     0195
Russell Frye
SSM Coalition
                                     0196
Marcus Cooke
Cooke Companies International
                                     0197
Shannon Broome
Air Permitting Forum
                                     0198
J. W. Vinzant
Kaiser Aluminum (duplicate of 0192)
                                     0199
G. C. Barnett
Aleris International, Inc.
                          2014 Supplemental Proposal

                                     0286
Jerry Call
American Foundry Society
                                     0287
G. Vinson Hellwig, Robert H. Colby
National Association of Clear Air Agencies
                                     0288
G.C. Barnett
Aleris
                                     0289
Sean O. Alteri
Kentucky Department for Environmental Protection
                                     0290
J. Roger Crawford
Kaiser Aluminum
                                     0291
Garret Morris
Greater Baltimore Health Alliance
                                     0292
Matt Owens
Century Aluminum
                                     0293
J. Roger Crawford
Kaiser Aluminum(duplicate of 0290)
                                     0294
James D. Jones
Alcoa
                                     0295
Charles D. Johnson
The Aluminum Association
                                     0296
James L. Mallory
Non-Ferrous Founders' Society
                                     0297
Shannon Broome
Air Permitting Forum
                                     0298
Russell Frye
SSM Coalition
                                     0299
Ronald A. Amirikian
Delaware Division of Air Quality
                                     0300
Steven Klafka
Wingra Engineering
                                     0301
Emma Cheuse
Earthjustice

1. Risk Assessment
1.1 	Risk Assessment Inputs: Processing of ICR Data into Modeling File
Comment #1: In a comment on the supplemental proposal, commenter 0300 stated that when developing the original NESHAP for secondary aluminum, the EPA removed die casting operations from the NESHAP. The commenter stated that it would be appropriate for the EPA to revisit its decision to not develop NESHAP for die casting operations. The commenter stated that similar to the secondary aluminum production operations, furnaces at die casting facilities have emissions of dioxins/furans, chlorine, hydrogen chloride and particulate and the hazardous air pollutants released from the partial combustion of lubricants have not be identified, and likely contain products of incomplete combustion such as polycyclic aromatic hydrocarbons (PAHs).
Response: This comment was not made on the 2012 proposal and is outside the scope of the 2014 supplemental proposal, which solicited comment only on specific topics identified in the notice. See 79 FR at 72883-84. For informational purposes only, we have attempted to respond to the commenter's concerns.
The EPA disagrees with the commenter's statement that aluminum die casting operations were removed from the NESHAP and, therefore, are not subject to the NESHAP. Die casting operations that are substantially like operations at other secondary aluminum production facilities are subject to subpart RRR requirements. Specifically, a die casting facility that is a major source, is generally considered a secondary aluminum production facility and subject to subpart RRR if they operate a sweat furnace, a thermal chip dryer or a scrap dryer/delacquering kiln/decoating kiln. In addition, regardless of the types of operations conducted at a major source die casting facility, they are subject to the NESHAP if they process anything other than clean charge, internal scrap, or customer returns. See section 40 CFR 63.1503, definition of secondary aluminum production facility. Like a furnace at a major source die casting facility, a furnace at an area source die casting facility is subject to the subpart RRR emission standards for D/F with one exception. A furnace operated by an area source die casting facility that would be subject to subpart RRR only because the facility operates a thermal chip dryer, is not subject to the requirements of subpart RRR if the furnace melts only clean charge, internal scrap and customer returns, although the thermal chip dryer would be subject. See 40 CFR 63.1500(f). Although furnaces at die casters that are major sources of HAP would not be subject to subpart RRR if the furnaces handled only clean charge, internal scrap, or customer returns, and if the facility did not operate thermal chip dryers, delacquering/decoating kilns, or sweat furnaces, the EPA is not aware of any die casting facilities that are major sources of HAP that operate furnaces and are not subject to subpart RRR, and the commenter did not submit any contrary information.
Comment #2: In a comment on the supplemental proposal, commenter 0301 stated that the EPA's data collection found emissions of mercury and other pollutants for which the EPA has not proposed to set any emission standards; that is unlawful under section 7412(d) and (f), and National Lime Association. Commenter 0301 stated that as the D.C. Circuit has held, the EPA has a "clear statutory obligation to set emissions standards for each listed HAP." The commenter stated that the Act requires the EPA to set standards for all emitted hazardous air pollutants, and the EPA has no lawful basis for not doing so here; the EPA must set emission standards that assure the maximum achievable degree of emission reduction for mercury and other emitted HAPs that are currently unrestricted by the Secondary Aluminum standards.
Response: The subpart RRR MACT standards have regulated most HAP since promulgation in 2000. The standards include emissions limits for D/F, PM (as a surrogate metal HAP other than mercury), THC (as a surrogate for non-D/F organic HAP) and HCl (as a surrogate for acid gases including HF, chlorine and fluorine).
We currently do not have sufficient data to establish emissions standards for mercury for this source category. To explain further, during the data collection efforts to support the RTR (including for developing emissions estimates and other inputs for the secondary aluminum RTR risk assessment), we gathered a substantial amount of emissions test data for PM, THC, HCl and D/F from many facilities through an information collection request (ICR). We also requested nine secondary aluminum companies to generate and submit compound-specific metallic and organic HAP data so that we could develop emissions estimates for all the HAP for input to the risk assessment model. The metallic HAP data collected were the measured concentration of the individual HAP metals in the baghouse dust. We did not collect actual emissions test data for any of these metal HAPs. To develop emissions estimates for each of these HAP metals for input to the risk model, a ratio of total PM to each HAP metal was developed based on the baghouse dust analyses. The ratios were then applied to the source specific PM emissions estimates to calculate the emissions estimates for each metal HAP for each source. This calculation approach is based on the assumption that the concentration of these metals in baghouse dust is the same as the concentration in the PM emitted from the process stack outlets. (See Development of the RTR Supplemental Proposal Risk Modeling Dataset for the Secondary Aluminum Production Source Category, EPA-HQ-OAR-2010-0544-0239). We believe this method resulted in reliable estimates of the emissions of the particulate metal HAPs (such as Pb, Be, Cd, As, Mn, Ni and Cr) since these metals are mostly, or entirely, in particulate form. However, mercury is different. Mercury is emitted in three main forms (i.e., gaseous elemental mercury, gaseous oxidized mercury, and particulate bound mercury). We have no data regarding what percent of the mercury are in particulate versus gaseous forms for this source category. However, based on our knowledge and experience of mercury emissions from other industries, we believe a significant portion would be in the gaseous forms. Therefore, the mercury data collected for this source category, which is entirely based on baghouse dust samples, are not measurements of mercury emissions since the mercury in the baghouse dust consists of the particulate bound mercury portion only. The gaseous mercury emissions were not measured from any units. Therefore, there are significant uncertainties regarding the mercury emissions estimates for this source category.
We used these limited baghouse dust mercury data to generate rough estimates of mercury emissions for secondary aluminum sources for input to the risk modeling so that we could estimate the potential risks due to mercury emissions. Based on this approach, we estimated that the entire source category emits a total of less than one pound of mercury per year nationwide (as shown in table 3.1-1 of the risk assessment report). Nevertheless, these baghouse data and rough estimates of emissions are insufficient to establish emissions standards for mercury for this source category. Therefore, we are not promulgating emission standards for mercury as requested by the commenter at this time in this action.
With regard to the other metal HAP and organic HAP, as mentioned above, the subpart RRR MACT standards have regulated those HAP since promulgation in 2000. The standards use PM as a surrogate to regulate the metal HAP (other than mercury) and THC as a surrogate to regulate non-D/F organic HAP. In addition, the 2000 rulemaking set separate MACT limits for D/F expressed as toxic equivalents and HCl as a surrogate for acid gases including HF, chlorine and fluorine, and in this rulemaking we are promulgating specific compliance provisions for HF, as discussed in the preambles to the proposed rules. Thus, the rule currently regulates all HAP known to be emitted from these facilities in measurable quantities.
1.2 	Risk Assessment Methods
1.2.1	Modeling of MACT Allowable Emissions
Comment #1: Commenter 0287 recommended that the EPA consider potential or allowable emissions, rather than actual emissions, as much as possible in evaluating residual risk. The commenter stated that because facility emissions could increase over time for a variety of reasons, and with them the associated impacts, the use of potential or allowable emissions is more appropriate; an analysis based on actual emissions from a single point in time could underestimate the risk. The commenter stated that the major source HAP thresholds are based on maximum potential-to-emit, as opposed to actual emissions, and air agencies issue permits based on potential emissions. The commenter stated that limiting the scope of a risk evaluation to actual emissions would be inconsistent with the applicability section of part 63 rules. The commenter stated that they were pleased that the EPA used allowable emissions in parts of the rulemaking but were concerned that the EPA continues to use actual emissions in other parts of its assessment. The commenter encouraged the agency to use allowable emissions in the future, including in assessing acute health risks.
Response: Consistent with previous risk assessments, the EPA considers both allowable and actual emissions in assessing chronic exposure and risk under section 112(f)(2). See, e.g., National Emission Standards for Coke Oven Batteries (70 FR 19998-19999, April 15, 2005); proposed and final National Emission Standards for Organic Hazardous Air Pollutants from the Synthetic Organic Chemical Manufacturing Industry (71 FR 34428, June 14, 2006, and 71 FR 76603, December 21, 2006). This approach is both reasonable and consistent with the flexibility inherent in the Benzene NESHAP framework for assessing ample margin of safety. As a general matter, modeling allowable emissions levels is inherently reasonable since this reflects the maximum level sources could emit and still comply with national emission standards. But it is also reasonable to consider actual emissions, where such data are available, in both steps of the risk analysis. See National Emission Standards for Coke Oven Batteries, 70 FR 19992, 19998 (April 15, 2005). The chronic inhalation risk assessment for the secondary aluminum source category was conducted using actual and allowable emissions, and all of the results were considered in determining risk acceptability and ample margin of safety.
The commenter also urges the Agency to rely on allowable emissions for the purpose of our acute screening assessment. The use of allowable emissions was not considered in the acute assessment due to the conservative assumptions used to gauge worst-case potential acute health effects. The conservative assumptions built into the acute health risk screening analysis include: (1) use of peak 1-hour emissions that are on average ten times the annual average 1-hour emission rates; (2) that all emission points experience peak emissions concurrently; (3) worst-case meteorology (from 1 year of local meteorology); and (4) that a person is located downwind at the point of maximum impact during this same 1hour period. Thus, performing an acute screen based on allowable emissions would be overly conservative and at best, of questionable utility to decision makers.
1.2.2	Modeling of Acute Exposure
Comment #1: One commenter (0193) noted that the EPA concludes that the acute level health risk from the secondary aluminum source category is within acceptable bounds, even after using worst case values for dose response, dispersion modeling, hourly maximum exposure location, meteorology and stationary out-of-doors human activity, which the commenter stated exaggerates risk. The commenter emphasized that the acute risk estimates the EPA calculates are the result of combined worst case assumptions, are very conservative and have a low probability of occurring.

Response: The acute risk assessment is a screening-level assessment designed to identify facilities and pollutants that need further analysis and can provide information for our risk-based decisions. The screen provides us information such that for those facilities where the hazard quotients are less than 1, we do not expect acute effects, and for those situations where the hazard quotients are greater than 1, the potential for acute effects may exist. For those situations where the acute hazard quotients are greater than 1 based on our screening assessment, the fact that it is a screening-level assessment is taken into consideration. A finding of unacceptable risks is not based on any one risk metric (e.g., acute hazard quotients), but rather considering all of the health and other information available and the degree of uncertainty associated with that information.

Comment #2: In a comment on the supplemental proposal, commenter 0287 stated that they have expressed their concerns in the past with the EPA's use of Acute Exposure Guideline Levels (AEGLs) or Emergency Response Planning Guidelines (ERPGs) values to address acute exposures in the residual risk assessments and it appears the EPA is still using them for those purposes in this proposal. The commenter stated that in the December 2002 EPA document, "A Review of the Reference Dose and Reference Concentration Processes," the EPA stated that the primary purpose of the AEGL program is to develop guidelines for once-in-a-lifetime short-term exposures to airborne concentrations of acutely toxic chemicals; they are not meant to evaluate the acute impacts from routine emissions that occur over the life of a facility. The commenter stated that unlike the reference concentrations (RfCs) for chronic exposures, the AEGLs and ERPGs do not include adequate safety and uncertainty factors and cannot be relied upon to protect the public from the adverse effects of exposure to toxic air pollutants; the use of AEGLs or ERPGs in residual risk assessments is not appropriate and does not ensure that public health is adequately protected from the acute impacts of HAP exposure. The commenter stated that they were gratified to see that the EPA has increased its reliance on the California Reference Exposure Levels (RELs) to address acute exposures in the residual risk assessments and continue to urge the EPA to use the RELs for these assessments.

Response: The EPA does not rely exclusively upon AEGL or ERPG values for assessment of acute exposures. Rather, the EPA's approach is to consider various acute health effect reference values, including the California REL, in assessing the potential for risks from acute exposures. To better characterize the potential health risks associated with estimated acute exposures to HAP, and in response to a key recommendation from the SAB's peer review of the EPA's RTR risk assessment methodologies, we generally examine a wider range of available acute health metrics (e.g., RELs, AEGLs) than we do for our chronic risk assessments. This is in response to the SAB's acknowledgement that there are generally more data gaps and inconsistencies in acute reference values than there are in chronic reference values. In some cases, when Reference Value Arrays for HAP have been developed, we consider additional acute values (i.e., occupational and international values) to provide a more complete risk characterization. As discussed in the preamble to the proposed rule (79 FR 72874), the exposure guidelines the EPA considers depends on which exposure guidelines are available for the various hazardous air pollutants emitted. The EPA uses AEGL and ERPG values (when available) in conjunction with REL values (again, when available) to characterize potential acute health risks. However, it is often the case that HAP do not have all of these acute reference benchmark values. In these instances, the EPA describes the potential acute health risk in relation to the acute health values that are available. Importantly, when interpreting the results, we are careful to identify the benchmark being used and the health implications associated with any specific benchmark being exceeded.

1.2.3	Multipathway Screening
Comment #1: One commenter (0193) stated that the EPA's multi-pathway risk screening analysis combines multiple extreme assumptions and leads to an unrealistic estimate of risk. The commenter provided examples of the EPA's assumptions and data inputs which the commenter believes exaggerate potential risks:
 The site modeled is a farm adjacent to a secondary aluminum facility, including an aquatic pond. All foods are consumed daily for the entire duration by the farm occupants locally from on-site, including all fish from the pond.
 Downwind air dispersion of HAP's from the facility to the farm site and pond is assumed continuously using worst-case dispersion characteristics.
 Each person has an ingestion rate of food that exceeds expected body weight-normalized ingestion rates. In other words, all food stuffs are each consumed at a 90th percentile daily rate adding up to an enormous food intake rate per person. Fish consumption is all from the pond at the site, and the ingestion rate is assumed at the 99th percentile of daily population intake.
 The ingestion of fish also includes the assumption that upper-trophic level fish (due to an absence of large-bodied herbivore/detritivore fish to favor higher concentrations of bioaccumulative chemicals) results in higher concentrations in consumed fish. The linear food-chain assumption further maximizes concentration of bioaccumulative chemicals in higher-trophic level fish.
 The lifetime risk calculation includes continuous ingestion and dermal exposure at the site, including all food originating from the site, 365 days per year.
 Individuals were assumed to be exposed on a fraction of their bodies (i.e., their head, forearms, hands, lower legs, and feet) to contaminated soil from the TRIM.FaTE surface soil parcel with the highest concentration (N1) on a daily basis. For the water evaluation, individuals were assumed to be exposed to contaminated surface water with the same PBHAP concentration as the TRIM.FaTE screening scenario pond over their entire bodies on a daily basis.
 All livestock feed is from the local farm site (including grains and silage) and are all derived from most highly impacted locations.
 A nursing mother is assumed to be continuously exposed to contaminants by all ingestion pathways modeled and can pass the contaminants on to her infant through breast milk, including dioxins and mercury.
The commenter noted that it is remotely possible that a small number of these ultra-upper-bound assumptions might occur at some site at some point of time, it is unrealistic to model all of these extreme assumptions simultaneously and continuously for any realistic assessment of risk. Given the exaggerated levels estimated in the analysis, the commenter stated that the EPA has reached a reasonable conclusion with regard to the multi-pathway results. Beyond this conclusion, the commenter maintained, results of the multi-pathway analysis have no value and a more realistic and reasonable multi-pathway assessment would result in much lower risk estimates.
Response: The EPA originally developed the multipathway screening analysis to estimate worst-case non-inhalation exposures to PB-HAP. The approach uses numerous worst-case assumptions to ensure that exposure to PB-HAP is not underestimated. However since the time of proposal, the EPA has refined its emission screening thresholds for the multipathway analysis based on improved toxicity rating/scaling methods for POMs and dioxin congeners, as well as improved fate, transport, and uptake behavior through the aquatic food chain. We also expanded the multipathway analysis to include separate exposure scenarios, one for a subsistence fisher and one for a subsistence farmer. (See Appendix 4 of the risk assessment document for more details). Further, rather than using all worst-case meteorological and lake distance assumptions, we have incorporated more facility specific information into the multipathway screening scenarios. Given that it is highly unlikely that the most-exposed farmer is the same person as the most-exposed fisher, we consider these scenarios separately and do not consider it reasonable to add the risk results from these two exposure scenarios. While the screening analysis was not designed to produce a quantitative risk result, the factor by which the emissions exceed the threshold serves as a rough gauge of the "upper-limit" risks we would expect from a facility. Based on actual emissions from the secondary aluminum source category, facility-level emissions of POMs from all sources are below our revised multipathway screening threshold. With respect to dioxins, our revised multipathway screening threshold for cancer is exceeded by up to 70 times. None of the pollutants exceeded the chronic noncancer multipathway screening thresholds. Considering that these results are screening estimates that still incorporate a number of worst-case assumptions, it is likely that the actual multipathway cancer MIR and noncancer HQ values would be substantially less than 70-in-1-million and 1, respectively.
1.3 	Uncertainties in Risk Assessment
Comment #1: One commenter (0193) stated that the EPA's residual risk conclusions are reasonable; however the risk assessment calculations are likely to be substantial overestimations of the actual risk for secondary aluminum facilities. The commenter thought that each of these factors in and of themselves lead to an overestimation of risk, but when combined likely result in a synergistic impact leading to a much greater overestimation of risks. The commenter believes that the EPA's risk evaluation demonstrates more than an ample margin of safety for the existing Secondary Aluminum NESHAP.

Response: Uncertainty and the potential for bias are inherent in all risk assessments, including those performed for this rulemaking. Although uncertainty exists, our approach, which uses conservative tools and assumptions, ensures that our decisions are appropriately health protective and environmentally protective. A brief discussion of the uncertainties in the RTR emissions datasets, dispersion modeling, inhalation exposure estimates and dose-response relationships can be found in the supplemental proposal for this rulemaking (79 FR 72874). A more thorough discussion of these uncertainties is included in the Residual Risk Assessment for the Secondary Aluminum Source Category in Support of the 2015 Risk and Technology Review Final Rule, which is available in the docket for this action.

1.3.1	Individual Variability and Exposures
Comment #1: One commenter (0193) objected to the use of a safety factor of ten applied to the estimated hourly emissions maximum for short term acute health concerns such as for hydrogen chloride and hydrogen fluoride exposures. The commenter noted that the default value of ten is based on a study by the EPA of emissions in the Houston Texas area dominated by VOC emissions from petroleum and chemical operations that may not be representative of the emissions profile for hourly events in Secondary Aluminum. The commenter continued that a large uncertainty exists for evaluating acute risks, and the EPA has chosen a very conservative order-of-magnitude level safety margin in assessing acute exposure levels. The commenter stated that this level of conservatism will lead to a substantial overestimate of risk for acute exposures.
Response: This choice of a factor of ten for screening was originally based on engineering judgment. To develop a more robust peak-to-mean emissions factor, and in response to one of the key messages from the SAB consultation on our RTR Assessment Plan, we performed an analysis using a short-term emissions dataset from a number of sources located in Texas (originally reported by Allen et al. 2004). In that report, the Texas 	Environmental Research Consortium Project compared hourly and annual emissions data for volatile organic compounds for all facilities in a heavily-industrialized 4-county area (Harris, Galveston, Chambers, and Brazoria Counties, TX) over an eleven-month time period in 2001. We obtained the dataset and performed our own analysis, focusing on sources which reported emitting high quantities of HAP over short periods of time (see Appendix 3, "Analysis of data on short-term emission rates relative to long-term emission rates"). Most peak emission events were less than twice the annual average, the highest was a factor of 74 times the annual average, and the 99[th] percentile ratio of peak hourly emission rate to the annual hourly emission rate was 9. Based on these results, we chose the factor of ten for all initial screening; it is intended to cover all possible hourly 	peaks associated with routinely variable emissions. While there have been some documented emission excursions above this level, our analysis of the data from the Texas Environmental Research Consortium suggests that this factor should cover more than 99 percent of the short-term peak gaseous or volatile HAP emissions from typical industrial sources.
Thus, in the absence of source category-specific data or estimates, we use this default factor of 10 in the acute health screen. We further note that the commenter did not provide specific evidence that the acute factor of 10 is inappropriate for this source category, nor did the commenter suggest a different acute screening factor. However, even using this factor of 10, the potential for acute health risks from this source category was negligible.
Comment #2: One commenter (0193) asserted that the omission of a mobility/activity analysis is estimated by the EPA to overestimate risk by 25 percent for particulate HAPS (such as metals) based only on short-term mobility patterns, but the inclusion of long-term activity patterns, such as moving residences and job locations, would result in even lower risk estimates.
The commenter noted that another omission resulting in over estimation is consideration of indoor versus outdoor exposures in the assessment. The commenter argued that for particulate types of emissions the difference is significant, noting that the EPA estimates that indoor exposures for particulate types of emissions may be reduced by a value of 25 to 30 percent. The commenter concludes that the risks projected for metals and dioxin emissions are also additionally overestimated by a factor of 25 to 30 percent.
The commenter maintained that combined with the mobility pattern issue impacts on risk, chronic individual and population risks from these factors are likely overestimated by an additional factor of two.
The commenter also argued that the EPA's omission of population mobility will bias the risk estimate for cancer incidence, as there is continued scientific interest in using a non-linear dose-response modeling approach for dioxin compounds.
Response: In general, we strive to strike a balance in our assessments, meaning that while some factors likely lead to overestimates of risk (e.g., 70-year exposure duration), others likely lead to underestimates of risk (e.g., building downwash not modeled). We conclude that the risk assessment for this source category is sufficient to support decisions on the acceptability of the risk and ample margin of safety.
The commenter is correct that the EPA did not consider short-term or long-term mobility in the assessment. Mobility was not considered because we do not believe that assumption, in combination with other modeling assumptions, leads to a significant bias in the risk results in any one direction. For example, the EPA does not consider that homes and businesses may locate closer to facilities over time, which could lead to an underestimation of risk. Additionally, estimates of the maximum individual risk (MIR) contain uncertainty, because they are derived at census block centroid locations rather than actual residences. This uncertainty is known to create potential underestimates and overestimates of the actual MIR values for individual facilities, but overall, we believe it does not have a significant impact on the estimated MIR for a source category. Processes like deposition, plume depletion, and atmospheric degradation are not considered, which may introduce bias to the population exposure estimates. Finally, we did not factor in the possibility of a source closure occurring during the 70-year chronic exposure period, leading to a potential upward bias in both the MIR and population risk estimates; nor did we factor in the possibility of population growth during the 70-year chronic exposure period, leading to a potential downward bias in both the MIR and population risk estimates. These uncertainties are described in section 4.1 of the risk assessment document.
In assessing risk, we estimate the MIR or the maximum HI, which are defined as the risk (or hazard) associated with a lifetime of exposure at the highest concentration where we determine people may actually reside. For this assessment, we used the annual average ambient air concentration of each HAP at each census block centroid as a surrogate for the lifetime inhalation exposure concentration of all the people who reside in the census block. Basing exposure estimates at census block centroids may underestimate or overestimate actual exposure concentrations at some residences, as discussed in the response below. Further reducing exposure estimates for the most highly exposed residents by modeling their short-term behavior could add a systematic low bias to these results and is not expected to affect the MIR result. Thus, this risk analysis did not consider the short-term human activity patterns and their potential influence on exposure. Our experience with the National-Scale Air Toxics Assessments (NATA) (which modeled daily activity using the EPA's HAPEM model) suggests that, given our current understanding of microenvironment concentrations and daily activities, modeling short-term activity would, on average, reduce risk estimates about 25 percent for particulate HAP; it would also reduce risk estimates for gaseous HAP, but typically by much less.
We acknowledge that our assumption that people may be present at their homes for 24 hours per day over a 70-year lifetime represents a scenario that likely overestimates the actual exposures received by people living near the facilities. Most people have daily activities that take them to areas where exposure concentrations are different and people may move to new residences periodically. Both of these behaviors will likely tend to lower lifetime exposures and, therefore, risk if they are no longer in the vicinity of sources in the source category.
In our risk assessments, we estimate risk for the "maximum individual risk" (MIR) which is different than the "maximum exposed individual (MEI)." The MEI could be equal to or greater than the MIR as the MEI is the highest estimated risk to a hypothetical exposed individual, regardless of whether people are expected to occupy that area. The MIR, on the other hand, is the highest estimated risk to an exposed individual in areas people may actually occupy. We are using the MIR to be considered equivalent to the "individual most exposed" phrase from the CAA section 112(f)(2). This approach is consistent with the Commission on Risk Assessment and Risk Management report recommendation that exposure assessments should not be based on a hypothetical MEI.
Comment #3: In a comment on the supplemental proposal, commenter 0287 stated that in using long-term concentrations affecting the most highly exposed census block for each facility, the EPA's analysis dilutes the effect of sources' emissions by estimating the impact at the centroid of the census block instead of at the property line or wherever the maximum exposed individual is located. The commenter stated that census blocks can be large geographically, depending on the population density, so the maximum point of impact can be far from the centroid, including at or near the property line where people may live or work; the EPA itself alludes to this problem in the preamble. The commenter stated that even if the area near the property line is not developed, over time homes and businesses could locate closer to the facility. The commenter stated that while it is possible that population distribution is homogenous over a census block, this assumption is not necessarily accurate in considering the predicted impacts from the location of a source; using HEM-3, the EPA can identify the maximum individual risk at any point in a census block that is within a 50-kilometer radius from the center of the modeled facility. The commenter stated that based on HEM-3's power and ability, they suggest that the EPA abandon its use of the predicted chronic exposures at the census block centroid as surrogates for the exposure concentrations for all people living in that block; rather, they recommended that the EPA use the truly maximum individual risk, irrespective of its location in the census block.
Response: In a national-scale assessment of lifetime inhalation exposures and health risks from facilities in a source category, it is appropriate to identify exposure locations where it may be reasonably expected that an individual will spend a majority of his or her lifetime. In determining chronic risks, it is appropriate to use census block information on where people actually reside, rather than points at the property line, to locate the estimation of exposures and risks to individuals living near such facilities. Census blocks are the finest resolution available as part of the nationwide population data (as developed by the US Census Bureau); on average, a census block is comprised of approximately 40 people and about 10 households. In the EPA risk assessments, the geographic centroid of each census block containing at least one person is used to represent the location where all the people in that census block live. The census block centroid with the highest estimated exposure then becomes the location of maximum exposure, and the entire population of that census block is assumed to experience the maximum individual risk. In some cases, because actual residence locations may be closer to or farther from facility emission points, this may result in an overestimate or underestimate of the actual annual concentrations (although there is no systematic bias for average levels). Given the relatively small dimensions of census block in densely-populated areas, there is little uncertainty introduced by using the census block centroids in lieu of actual residence locations. There is the potential for more uncertainty when the census block are larger, although there is still no systematic bias. The EPA concludes that the most appropriate locations at which to estimate chronic exposures and risks are the census block centroids because: 1) census blocks are the finest resolution available in the national census data; 2) facility fence lines do not typically represent locations where chronic exposures are likely (i.e., people do not typically live at the fence line of facilities); and 3) there is no bias introduced into the estimate of the maximum individual risk (MIR) by using census block centroid locations. In its peer review of the methodologies used to estimate risks as part of the RTR rulemaking efforts, the EPA's Science Advisory Board (SAB) endorsed this approach.
In addition to the approach described above, the EPA recognizes that where a census block centroid is located on industrial property or is large and the centroid is less likely to be representative of the block's residential locations, the block centroid may not be the appropriate surrogate. For this source category, as described in the risk assessment document available in the docket, in cases where a census block centroid was within 300 meters of any emission source (and therefore possible on facility property), we viewed aerial images of the facility to determine whether the block centroid was likely located on facility property. Likewise, we examined aerial image of all large census blocks within one kilometer of any emission source. If the block centroid did not represent the residential locations within that block, we relocated it to better represent them and/or we added receptors for residences nearer to the facility than the centroid. For this source category, we added several receptors for census blocks where the centroid location was not representative of the residential locations. Appendix 7 of the risk assessment, entitled Residual Risk Assessment for the Secondary Aluminum Production Source Category in Support of the 2015 Risk and Technology Review Final Rule provide additional information on these changes.
In assessing risk, we estimate the MIR, which is defined as the risk associated with a lifetime of exposure at the highest concentration where we determine people may actually reside. For this assessment, we used the annual average ambient air concentration of each HAP at each census block centroid as a surrogate for the lifetime inhalation exposure concentration of all the people who reside in the census block. Basing exposure estimates at census block centroids may underestimate or overestimate actual exposure concentration at some residences. Further reducing exposure estimates for the most highly exposed residents by modeling their short-term behavior could add a systematic low bias to these results and is not expected to affect the MIR results. Thus, this risk analysis did not consider the short-term human activity patterns and their potential influence on exposure. Our experience with the EPA's National-Scale Air Toxics Assessment (NATA) (which model daily activity using the EPA's HAPEM model) suggests that, given our current understanding of microenvironment concentrations and daily activities, modeling short-term activity would, on average, reduce risk estimates about 25 percent for particulate HAPs; it would reduce risk estimates for gaseous HAPs, but typically by much less.
Comment #4: In a comment on the supplemental proposal, commenter 0287 stated that in considering environmental justice issues, improvements are needed in the EPA's methods of evaluating environmental justice and encouraged the EPA to continue to consider these factors in developing the final rule and subsequent regulations. The commenter recommended that the EPA conduct the demographic analysis on individuals projected to experience a risk greater than 1-in-1-million and also on individuals living within five kilometers of the facility, regardless of projected risk, consistent with the approach used for the Hard and Decorative Chromium Electroplating and Chromium Anodizing Tanks source category. The commenter stated that the socio-economic analysis for this rule did not evaluate potential disparities within five kilometers for cancer risk at maximum allowable emission levels; this type of analysis is especially important in instances where a facility is located in a minority and low-income community. The commenter stated that the EPA only evaluated the risk to the population within a 50-kilometer radius, which could dilute the results by including populations not in the demographic groups most at risk. The commenter stated that this is especially the case if the source is located in or next to a minority or low-income population. The commenter recommended that an analysis at the five-kilometer distance be conducted to assess facility impacts to nearby environmental justice communities and that the rule writers work with the EPA Office of Environmental Justice to develop criteria and specific guidance on how to interpret and apply the outcome of these types of analyses in the rulemaking process.
Response: The commenter is correct that we performed the demographic analyses for the Secondary Aluminum source category differently than we did for the October 2010 proposed RTR for the chrome electroplating and anodizing source categories (75 FR 65067, October 21, 2010). We performed the demographic analyses for the chrome source categories using two approaches as examples of how such analyses might be developed, and invited public comment on the approaches used and the interpretations made from the results. In the first approach, we focused the analysis on the total populations residing within 5 km of each facility, regardless of their estimated risks, and examined the distributions across various demographic groups within those 5 km circles. That analysis was a "proximity" analysis in that it considered only the distance from the emission sources to surrounding populations, and not the estimated risks to those populations
In the second approach, we focused the analysis on the populations within 5 km of any facility estimated to have exposures to HAP which result in cancer risks of 1-in-1 million or greater or non-cancer hazard indices of 1 or greater. We examined the distributions of those risks across various demographic groups. In each approach, we compared the percentages of particular demographic groups to the total number of people in those demographic groups nationwide. We stated in the proposed rule for the chrome source categories that in future rules we planned to extend the analyses to cover the entire modeled domain for a facility (50 km radius) to capture all individuals with risks above 1-in-1 million or greater or non-cancer hazard indices of 1 or greater. We also stated that generally we have found that using a 5 km radius in the analysis will capture more than 90 percent of the individuals with cancer risks above 1-in-1 million.
In the February 2012 supplemental proposal for the RTR for the chrome source categories, our demographic analyses included populations within 50 km of each source (including those very near the sources) with risks of 1-in-1 million or greater or non-cancer hazard indices of 1 or greater (77 FR 6628, Feb. 8, 2012). We did not include analyses using a 5 km radius in that supplemental proposal. We believe that, where a risk assessment has been performed, it is more informative to consider the demographics of all populations (including those beyond 5 km) with elevated risks than to limit the demographics analysis to populations located within 5 km of a facility. Where a risk assessment has been performed, these populations are identified, and the source parameters such as low release height are taken into account. As discussed above, we have found that most exposure locations with the highest estimated risks are within 5 km of a facility, so extending the radius to 50 km has little impact on an analysis based on risks, but makes more sense because 50 km corresponds to the risk modeling radius and includes all populations with elevated risk estimates. We also note that we are working with the Office of Environmental Justice to implement the latest guidance, issued May 29, 2015, as appropriate, to ensure that environmental justice issues are being considered in the rulemaking process.
Comment #5: One commenter (0193) argued against the EPA's use of the upper bound estimates for dioxin related risk, and stated that given the wide-spread and common occurrence of dioxin and furans in nature, it is not likely that there are no defense mechanisms in the human body to protect against dioxin impacts, and it is unlikely that low dose exposures are as potent, molecule-for-molecule, as high dose exposures. The commenter concluded that the EPA dose-response model is likely to be a conservative overestimate of risks, especially at low exposure levels, but the quantification of the overestimate is not possible at this time.

The commenter cited several statements from the SAB Dioxin Review Panel concerning the need for nonlinear and linear methods for characterizing cancer risk which the commenter asserted indicate that the EPA's assumption of no-threshold linearity in the dioxin dose-response curve is likely to be most conservative and may overestimate risk substantially, especially at low dose levels.

Response: We disagree that the EPA should consider that the human body has natural defense mechanisms against health effects associated with dioxin exposure and note that the commenter provided no evidence in support of such assertions. In general the development of UREs and RFCs consider results from animal toxicological studies and/or human studies where an effect has been observed notwithstanding whatever natural defenses (if any) from HAP may be present in the species tested. Furthermore, the commenter provided no evidence for its conclusion that it is unlikely that low dose exposures are as potent as high dose exposures.
With respect to model use, the EPA's long standing science policy approach has been to use linear low-dose extrapolation as a default option for carcinogens for which the mode of action (MOA) has not been identified. We expect future EPA dose-response assessments may identify nonlinear MOAs and we intend to use those analyses, as appropriate, in our risk assessments. At this time, however, there is no available carcinogen dose-response assessment for inhalation exposure to dioxin that is based on a nonlinear MOA.
Comment #6: One commenter (0193) disagreed with the EPA's assumption of a 70 year lifetime calculation for exposures to HAPs in the risk analysis, and the EPA's assumption that facilities will not experience partial or full curtailments of operations, asserting that this leads to additional overestimates of long term cumulative risk estimates. The commenter pointed out that over the last two decades, many Secondary Aluminum plants have been shut-down or experienced short and multi-year curtailments, leading to overestimation of cumulative risks.
Response: The commenter is correct that the EPA assumes no curtailment of operations over the 70 year chronic exposure period. In assessing risk, we estimate the maximum individual risk (MIR) or the maximum hazard index (HI), which are defined as the risk (or hazard) associated with a lifetime of exposure at the highest concentration. For this assessment, we used the annual average ambient air concentration of each HAP at each census block centroid as a surrogate for the lifetime inhalation exposure concentration of all the people who reside in the census block. Basing exposure estimates at census block centroids may underestimate or overestimate actual exposure concentrations at some residences. The risk assessment also contains other assumptions that could lead to an underestimation or overestimation of risk; for example the assessment does not take into account population growth or human activity patterns over the 70 year period.
1.4	Risk Assessment Results
Comment #1: One commenter (0189) expressed support for the proposed amendments, stating that the emission standards proposed in this amendment will adequately protect the environment and communities close to Secondary Aluminum Production facilities, although the commenter also offered suggestions for the proposed rule (addressed elsewhere in this document or the preamble to the final rule).
Response: The EPA acknowledges the commenter's support.

Comment #2: In a comment on the supplemental proposal, commenter 0290 stated that they support The Aluminum Association's (TAA) comments asserting that the EPA's risk estimates are generally overestimated for hazardous air pollutant (HAP) emissions from secondary aluminum facilities because the EPA bases it calculations on unreasonable and overly conservative worst-case risk assumptions.

In a comment on the supplemental proposal, commenter 0295 stated that they support the EPA's finding of acceptable risks but believes that the EPA risk estimates are generally overestimated. The commenter stated that each of the factors assessed by the EPA in their risk assessment, including emissions, population location and exposures, multi-pathway exposures, and the dose response and health risk values of the emitted pollutants of concern, includes uncertainties that the EPA addresses in the preamble. The commenter stated that generally, the EPA addresses uncertainties by biasing the analysis high using a worst-case upper bound risk preference; the EPA also assesses ample margin of safety to provide risk protection as mandated under the CAA. The commenter stated that several key high-bias risk assumptions combine to make the estimates of risk high and well above actual risks likely to occur. The commenter concluded that the current MACT emission limits provide more than an ample margin of safety, including emissions from co-located facility-wide operations. The commenter stated that the factors that lead to this conclusion include:
 The determination of hourly emissions estimates based on annual emission rates,
 The decision not to address individual or population mobility, including long and short term activity patterns and indoor exposure differentials,
 The assumption of 70 year lifetime risk assuming no facility shutdowns, partial curtailments or other reductions in emissions that may occur,
 The conservative nature of the dose-response especially for D/F speciation that rely on unit risk estimates derived from the multi-stage single-hit no threshold models for calculating carcinogenic risk,
 For acute health concerns, the combined assumptions of worst case dose-response, worst case dispersion modeling, worst case hourly maximum exposure location, worst case meteorology and worst case stationary human activity,
 For the multi-pathway analysis, a combination of implausible assumptions for exposure/ingestion rates coupled with unlikely food source scenarios.

Response: Uncertainty and the potential for bias are inherent in all risk assessments, including those performed for this rulemaking. Although uncertainty exists, our approach, which used conservative tools and assumptions, ensures that our decisions are appropriately health protective and environmentally protective. We disagree with the commenter that the EPA's risk estimates are based on "unreasonable and overly conservative worst-case risk assumptions." A brief discussion of the uncertainties in the RTR emissions datasets, dispersion modeling, inhalation exposure estimates and dose-response relationships can be found in the proposal for this rulemaking (79 FR 72874). A more thorough discussion of these uncertainties is included in the Residual Risk Assessment for the Secondary Aluminum Production Source Category in Support of the August 2015 Risk and Technology Review Final Rule, which is available in the docket for this action.

Comment #3: In a comment on the supplemental proposal, commenters 0294 and 0296 stated that they believe that the EPA's conclusions regarding residual risk for the Secondary Aluminum source category are appropriate and they supported the Agency's proposed findings.

Response: The EPA acknowledges the commenter's support.

2. Rule Provision Changes
2.1 	Control Device Shutdown
Comment #1: Commenters (0192, 0193, 199) disagreed with the EPA's proposal to require a period of 24 hours before controls can be turned off on idled furnaces.
Commenter 0192 stated that in batch-operated furnaces emissions stop once operations end, and that different furnaces have different emission characteristics so the shutdown sequence should be specified in the OM&M Plan.
Commenter 0193 argued that there is no reason to wait 24 hours to shut down APCD if a furnace is not operating. The commenter asserted that this is an unreasonable and unnecessary new restriction. The commenter proposed that the EPA allow controls to be turned off immediately after completion of the cycle, as there will be no emissions present and, further, that the EPA add the following new provision:
The owner or operator of a new or existing affected source that meets the following criteria may temporarily turn off associated fans, hoods, and APCD. During the idle period, the source will:
 Only burn clean fuel
 Not receive new charge, flux or alloying material
 Before charging resumes, all associated fans, hoods and APCD must be turned on and operated continuously.
Facilities should also be allowed to turn off controls, without idling for 24 hours. The following reasons are examples:
 If a bag leak detection system (BLDS) alarm sounds and inspection requires entry into the baghouse to conduct a bag leak check.
 Additionally, if a source is going to do a routine internal baghouse inspection, the proposed change would require the furnace be idled 24 hours prior to this so the baghouse can be shut down.
 Finally, if a source is going to a complete bag change, the proposed change would add 24 hours of idle time before the baghouse can be shut off.
Commenter 0199 suggested the following rule language:
      "The owner or operator of a new or existing affected source that will be idle for at least 24 hours and will burn clean fuel only, and will not receive new charge, flux or alloying material, may immediately upon idling the source, temporarily turn off associated fans, hoods and any APCD. Before charging resumes, all associated fans, hoods and APCD must be turned on and operated continuously. "

Response: The commenters misinterpreted the proposed rule. The proposed rule did not require a furnace to be shut down for 24 hours before a control device can be turned off. The provision as finalized applies to "natural gas-fired, propane-fired or electrically heated group 1 furnaces that will be idled for at least 24 hours..." and allows associated capture and collection system fans and APCD to be temporarily turned off so long as the furnace will not receive new feed/charge, flux or alloying material. See 40 CFR 63.1506(m)(7) and Table 2 to Subpart RRR. Nor does the final rule require owners or operators to wait 24 hours before turning off a baghouse to respond to a bag leak detection system alarm, conduct a routine baghouse inspection, or conduct a change out of bags in a baghouse. The EPA's goal, as stated in the preamble to the proposed rule, is to allow owner/operators to turn off control devices for furnaces that will be shut down for extended periods, such as a weekend. The final regulation in 40 CFR 63.1506(m)(7) and Table 2 makes clear that if a furnace will be idled for at least 24 hours after the end of a cycle, then the associated capture and collection systems and APCD may be temporarily turned off. The rule also makes clear that before charging resumes, all associated capture and collection systems and APCD must be turned on and operated continuously.
Comment #2: One commenter (0189) noted that there are a variety of reasons, such as ordinary maintenance or market material issues, when there could be periods shorter than twenty-four (24) hours when the furnace could shut down or remain idle and not be charged with aluminum and/or fluxing. The commenter suggested that instead of allowing facilities to discontinue use of control devices only after remaining idle after a twenty-four hour period, the commenter proposed a thirty (30) minute time frame after the charge area is emptied and melting has completed.
Response: As discussed in the preceding response, the regulation does not require a furnace to be shut down for 24 hours before a control device can be turned off. The purpose of this rule change is to allow facilities with furnaces that will be idle over a weekend, or other period exceeding 24 hours to discontinue use of control devices while the furnace is idle. The purpose of the rule change is not to allow control devices to be shut down if the furnace is idle for shorter periods of time. The EPA believes the added flexibility provided by the rule change will accommodate most situations identified by industry while balancing the need to practically and effectively enforce the emission control requirements of subpart RRR. In the EPA's experience, if control systems and devices for furnaces were allowed to be temporarily turned off for short time periods (i.e., less than 24 hours) based on the furnace being "idle" it would be difficult for a compliance inspector to retroactively confirm with certainty that capture and collection systems and APCD were being operated as required to achieve continuous compliance with emission standards and were being turned off only as permitted. The EPA has clarified in the final rule that use of control devices can be discontinued after the furnace cycle has been completed, if the furnace will remain idle for at least 24 hours.
2.2 	Change of Furnace Classification
Comment #1: Commenters (0192, 0193) disagreed with requirements of §63.1514(c) for furnaces changing to from group 1 to group 2. The commenter stated that the EPA has provided no basis for reducing the limits or for requiring performance tests for group 2 furnaces, which, according to the commenter, have no potential for significant HAP emissions.
Response: The original subpart RRR MACT rule subcategorized furnaces into group 1 and group 2 based on the difference in HAP emission potential from the materials melted (non-clean charge v. clean charge) and the type and amount of flux added (lack or presence of reactive flux). See 64 FR 6946, 6960 (February 11, 1999) (proposed rule). A group 2 furnace is defined as a furnace that melts, holds, or processes only clean charge and that performs no fluxing or performs fluxing using only nonreactive, non-HAP-containing/non-HAP-generating gases or agents. We defined and exempted group 2 furnaces from subpart RRR numerical MACT emission standards in part on the basis that they are clean and emit little or no HAP emissions; instead, we required work practice procedures under section 112(h). Id. at 6961. Although group 2 furnaces generally are not subject to numerical emission standards under subpart RRR, the EPA believes it is appropriate to require a furnace that seeks to change from group 1 to group 2, and therefore will no longer be subject to numerical group 1 emission standards, to demonstrate based on performance testing that it qualifies as a group 2 furnace. Unlike other group 2 furnaces, these furnaces were allowed to operate as group 1 furnaces without being restricted to clean charge and no reactive flux. The EPA is requiring these furnaces to demonstrate that they can operate within the emission profile of a group 2, rather than group 1, furnace. The EPA proposed specific emission levels for this purpose and received no comments that served to alter the proposed emission levels, and we are adopting them in the final rule as proposed. We note that the commenter did not submit any testing or other emissions information to document its assertion concerning the potential for HAP emissions. We also note that in the absence of a performance test requirement to confirm the low level of emissions of furnaces changing from group 1 to group 2, the EPA might consider whether allowing such changes is appropriate or whether its regulatory approach to group 2 furnaces should be reviewed.
Comment #2: Commenters (0192, 0199) objected to the requirements of §63.1514(d) for area sources to repeat testing every 5 years, as they are contrary to the requirements developed by the EPA that one-time testing was sufficient for area sources after a detailed evaluation for the 2000 NESHAP. The commenter asserted that since the original NESHAP included the ability to change operating modes there is nothing about changing modes that changes that situation. The commenter claimed that the EPA provides no basis in the proposed rule for imposing the burden of repeat testing on area sources.
Response: We did not intend for area sources to repeat testing every 5 years under the change of classification provisions, and we have made it clear in the final rule that area sources are not required to repeat testing every 5 years.
Comment #3: In a comment on the supplemental proposal, commenter 0294 stated that the proposed limit at Section 63.1514(e) allowing four furnace operating mode changes in any 6-month period, with the ability of sources to apply to the permitting authority for additional furnace operating mode changes, is appropriate.

In a comment on the supplemental proposal, commenter 0295 stated that while they objected in their comments on the 2012 proposal to the restrictions proposed for changing furnace classification, given the analysis provided in the supplemental proposal indicating that limited changes actually occur, and the EPA's proposal to allow furnace operating mode changes no more than 4 times in a 6-month period, or to obtain prior approval from the permitting authority if additional changes are needed, the requirements appear reasonable.

Response: The EPA acknowledges the commenters' support of the rule requirements on the frequency of switching furnace operating modes.
Comment #4: One commenter (0194) recommended that the EPA delete the parameter for "throughput" in §§63.1514(c)(1)(ii), (c)(3)(ii), (d)(1)(i) and (d)(2)(ii), and the requirement to establish a performance testing parameter. The commenter observed that this requirement is not necessary as emission limits under the rule are already normalized to process throughput (i.e., lb/ton).
Response: To ensure that any furnace that is changing its classification or operating mode is subject to the same testing requirements that apply to all furnaces at secondary aluminum production facilities, specific performance testing and compliance demonstration requirements, for example the requirement to establish process throughput or lime injection rates, have been removed from section 63.1514 in the final rule. Instead, section 63.1514 of the final rule requires that operating parameters be established in accordance with the performance testing and compliance demonstration requirements in sections 63.1511 and 63.1512.
Comment #5: One commenter (0194) stated that the requirements in Sections 63.1514(c)(1) and (d)(1) should be clarified to state that only uncontrolled group 1 furnaces must conduct performance testing for HF.
Response: The commenter is correct in that HF testing is only required for uncontrolled group 1 furnaces, and Section 63.1514 is revised accordingly in the final rule.
Comment #6: One commenter (0194) stated that §§63.1514(a)(1)(ii), (a)(2)(iii), (a)(3)(ii), (a)(4)(iii), (a)(6)(iii), (b)(1)(ii), (b)(2)(iii) (b)(3)(ii), (b)(4)(iii), (b)(6)(iii), (c)(1)(ii), (c)(3)(ii) and (d)(1)(i) require the establishment of a "flux" rate parameter during performance testing, but it does not consider the fact that some group 1 furnaces do not flux. The commenter recommended that references to establishing a "flux rate" parameter during performance testing should be qualified to state "where applicable."
Response: In the final rule, as discussed above, the change of furnace classification provisions do not list monitoring and operating parameters that must be established; instead, the provision requires that the parameters be established in accordance with §63.1511(g).
Comment #7: One commenter (0194) noted that §§ 63.1514(a)(1)(ii), (a)(3)(ii), (a)(5)(iii), (b)(1)(ii), (b)(3)(iii), (b)(5)(iii), (c)(1)(ii), (c)(3)(ii) and (d)(1)(i) require the establishment of a "lime injection" parameter during furnace testing. The commenter observed that some baghouses used to control emissions from Subpart RRR regulated group 1 furnaces are not lime-injected, and the reference to establishing a "lime injection" parameter should be qualified to state "where applicable."
Response: In the final rule as discussed above, the change of furnace classification provisions do not list parameters that must be established; instead, the provisions require that operating parameters be established in accordance with §63.1511(g).
Comment #8: One commenter (0194) recommended that the performance test language throughout §63.1514 should be revised to match §63.1511(b)(1) of the current Subpart RRR rule:
      "The owner or operator must conduct each test while the affected source or emission unit is operating at the highest production level with charge materials representative of the range of materials processed by the unit and, if applicable, at the highest reactive fluxing rate."
One commenter (0199) asserted that in paragraph §63.1514(a)(l)(i), the EPA should clarify that highest throughput expected means throughput for the scrap chosen for the test, and that the scrap should be the worst-case material likely to be processed in the affected source.

One commenter (0199) stated that in paragraphs §63.1514(b)(l)(i), §63.1514(c)(l)(i), §63.1514(c)(3)(i), §63.1514(d)(1)(i), and §63.1514(d)(2)(i), regarding the rule text, "The performance test must be conducted with the scrap containing the highest level of contamination expected to be processed, at the highest throughput expected and using the highest rate of reactive flux injection expected ..." the EPA should clarify that these worst-case charge materials, and blends of these, have differing process rates and, therefore, the charge rate from the stack tests is not representative of the production rate that will be achieved during normal operations.
The commenter (0199) disagreed with wording in paragraphs §63.1514(c)(1)(ii), §63.1514(c)(3)(ii) and §63.1514(d)(l)(i), "Parameters for throughput, capture, flux rate, and lime injection must be established during these tests," stating that throughput should not be included as a parameter. The commenter asserted that because the test requires "scrap containing the highest level of contamination expected to be processed ... " throughput should not be determined when running worst case materials.

Response: As discussed in the 2014 supplemental proposal (79 FR at 72902) and in section 3.2 of this document, we are clarifying the requirements for conditions under which performance tests for group 1 furnaces must be conducted. As provided in the final rule at 40 CFR 63.1511(b)(1), testing must be conducted "under representative conditions expected to produce the highest level of HAP emissions ... (considering the extent of scrap contamination, reactive flux addition rate and feed/charge rate)." If a single test condition is not expected to produce the highest level of emissions for all HAP, "testing under two or more sets of conditions (for example high contamination at low feed/charge rate, and low contamination at high feed/charge rate) may be required." Id. Regarding the establishment of operating parameter values used to monitor compliance, the final rule requires that those parameters be established as part of changing furnace classification in accordance with the section 63.1511(g) requirements for the establishment of monitoring and operating parameter values.

Comment #9: One commenter (0194) recommended that the EPA either delete the requirement to establish "parameters for capture" in paragraphs §§63.1514(a), (b) and (c) or provide detailed clarification on the specific parameters an owner or operator must establish for capture and then allow the aluminum industry an opportunity to comment on these specific requirements.
One commenter (0199) stated that in paragraphs §63.1514(a)(l)(ii), §63.1514 (a)(3 )(ii), §63.1514 (a)(4)(iii), §63.1514 (b)(1)(ii), §63.1514 (b)(2)(iii), §63.1514 (b)(3)(ii), §63.1514 (c)(1)(ii), §63.1514 (d)(l )(i), and §63.1514 (d)(2 )(iii), the EPA has not defined the term "capture" or what qualifies as a parameter suitable to meet this requirement. The commenter asked that the EPA define what is an acceptable capture parameter. The commenter stated that baghouse flow rate, baghouse pressure drop, or baghouse fan RPM are appropriate to be included as in such a definition of a capture parameter. The commenter also asked that the EPA make certain that it provide for alternative parameters to be used as appropriate.
Commenter (0197) recommended that the EPA should clarify the definition of a Capture and Collection System to read "systems including duct systems and fans and in some cases, hoods" to allow for a capture and collection system that does not have a hood.
Response: To ensure that any furnace that is changing its classification or operating mode is subject to the same testing and compliance requirements that apply to the relevant classification of furnaces, specific performance testing and compliance demonstration requirements, including parameters for capture, have been removed from section 63.1514 in the final rule. Instead, section 63.1514 of the final rule requires that operating parameters be established in accordance with the performance testing and compliance demonstration requirements in sections 63.1511 and 63.1512. Specifically, in the final rule, furnaces that change their operating mode, like all furnaces subject to subpart RRR requirements, are subject to the applicable requirements for capture and collection systems in section 63.1506(c), the monitoring requirements for capture and collection systems in section 63.1510(d) as well as the testing requirements in section 63.1512, including the requirements for testing uncontrolled furnaces. We agree with the commenter's suggestion to modify the definition of "capture and collection system" to account for those systems that do not have a hood and the definition in the final rule reflects that change.
Comment #10: One commenter (0199) suggested that §63.1514(a)(6)(i) and §63.1514(b)(6)(i) be changed to read, "Change label on the furnace to reflect uncontrolled operation."
Response: The commenter correctly points out an inadvertent error in these two provisions. The final rule makes the appropriate corrections.
Comment #11: One commenter (0199) recommended that in paragraph §63.1514(c)(5)(iii), the text, "change the label on the furnace to reflect group 2 operation;" the label can be designed to reflect all planned operating modes and include compliant parameters for each mode.
Response: Because the operating mode of the furnace is not always obvious, the purpose of the label is to make clear to facility staff responsible for compliance, regulatory compliance inspectors, and others the current operating mode of the furnace. Therefore, it is necessary that the label affixed to the furnace communicate clearly the furnace's current operating mode, rather than all potential or planned operating modes, so the recommended change is not appropriate.
2.3 	Hydrogen Fluoride Compliance
Comment #1: Commenters (0193, 0194) supported the EPA's rationale for adding an HF limit for uncontrolled group 1 furnaces that is the same as the current HCl emission limit. The commenter observed that both chloride- and fluoride-based salt fluxes are used to remove impurities or to dry dross; chlorine and fluorine are chemically similar; and the amount of flux required largely depends on the amount of impurities to be removed. The commenter further stated that establishing a flux usage limit for chloride- and fluoride-based fluxes will limit HCL and HF emissions from a furnace.
Response: The EPA acknowledges the commenters' support.

Comment #2: One commenter (0199) recommended that in §63.151l(c)(9), because the EPA has already approved Method 26 for HCl in an alternative request, it should list Method 26 along with Method 26A.
Response: The EPA has listed Method 26 along with Method 26A.
2.4	Hydrogen Chloride Compliance
Comment #1: Commenters (0192, 0193, 0194) supported the addition of the HCl estimation technique provided in §63.1510(t)((2)(ii), but noted that the definition of reactive flux does not specify which fluxes are considered to be reactive, except to state that argon and nitrogen are not reactive. The commenters suggested that the EPA include sodium chloride and potassium chloride in the list of non-reactive fluxes. Commenters 0192, 0193 included two attachments that demonstrate that sodium chloride and potassium chloride do not produce HCl when used as flux in aluminum refining processes. The commenters expressed concern that not recognizing the scientific evidence that sodium chloride and potassium chloride are non-reactive and do not produce HCl would lead to an unrealistic estimate of chloride emissions and unnecessary regulatory requirements with no environmental benefit. The commenters stated that this is particularly important for facilities that are area sources of HAPs and therefore do not have to test for HCl emissions. The commenters suggested that the rule language for §63.1510(t)((2)(ii) and §63.1512(e)(3) say, "chlorine contained in reactive flux" and "fluorine contained in reactive flux."
Response: In addition to the commenters' submissions, the EPA has obtained HCl emissions data from testing conducted at the Hydro Aluminum North America facility in Monett, Missouri. A test conducted on the Holding Furnace (EU0030) which receives molten metal from two melting furnaces and uses Metallpur(R)315 flux, which is primarily sodium chloride and potassium chloride, indicated low but detectable amounts of HCl (averaging 0.001 lb/ton for 3 runs; test results are in the docket for this rulemaking). Based on the limited information available to the EPA including the commenters' submissions and the Hydro Aluminum test results, the EPA concludes that use of flux containing sodium chloride and potassium chloride has the potential to produce HCl emissions. Therefore, we are not adding sodium chloride and potassium chloride to the list of non-reactive fluxes. We note that the Hydro Aluminum testing was conducted at a relatively low fluxing rate (25 pounds of flux per batch, 50 pounds of flux total per run of two batches) compared to furnaces such as rotary furnaces, which may use thousands of pounds of flux per furnace charge. For this reason, furnaces that use greater amounts of flux, if they use sodium chloride and potassium chloride fluxes, likely would have greater HCl emissions than the tested Hydro Aluminum furnace. However, we have revised the rule language for §63.1510(t)((2)(ii) and §63.1512(e)(3) to read, "chlorine contained in reactive flux" and "fluorine contained in reactive flux."
Comment #2: One commenter (0196) requested that the EPA correct the definition of cover flux. The commenter indicated that the definition is unclear and inaccurate. The commenter stated that cover flux is not reactive, even if the molten metal bed is agitated or moved. The commenter stated that the definition of cover flux proposed in the new Secondary Aluminum MACT is technically incorrect and is inconsistent with the definition that the EPA has used to define flux in the secondary aluminum industry for 38 years. The commenter continued by presenting the EPA standing definition of cover flux from the Air and Water Effluent Guideline for Aluminum Smelting (1974), given here:
      Fluxing. The addition of a covering flux to the molten aluminum melt forms a barrier for gas absorption and oxidation of the metal. The flux also reacts with nonmetallics, residues from burned coating, and dirt in the scrap, collects such impurities and allows physical separation from the molten aluminum. The exact composition flux cover used varies from smelter to smelter, but is generally some combination containing one or more of the following: sodium chloride, potassium chloride, calcium chloride, calcium fluoride, aluminum fluoride, and cryolite. A common flux mixture is 47.5 percent NaCl, 47.5 percent KCl, and 5 percent cryolite. At the melting point of aluminum, the fluxes usually range from a tacky semisolid to a liquid depending on the composition of the mixture and the technique used to remove it from the melt.
      The amount of flux used depends primarily on the material charged. Scrap containing a relatively large surface area, such as borings or turnings, creates large amounts of oxides and requires proportionally larger amounts of flux. The flux generally is added along with the aluminum scrap in amounts from less that 10 percent to 33 percent by weight of the material charged.
The commenter (0196) discussed why cover flux is used and described the processes in great detail. The commenter also stated that cover flux (NaCl, KCl, and cryolite) is inert and harmless. The commenter was concerned with the assertion that agitation of cover flux somehow causes reactions and increased emissions. The commenter indicated that calling cover flux reactive is inconsistent with the distinction between cover flux and reactive flux; and the physical constraints of processing secondary aluminum. The commenter recommended that the EPA should fix this inaccurate definition in the Final Rule, correcting terminology that defines cover flux as reactive flux if the metal bed is moved.
Response: The commenter did not provide any stack test data that indicate that HCl is not formed when NaCl, and KCl are used as fluxes, or that HF is not formed when aluminum fluoride or cryolite is used in a flux. HF is known to be evolved from cryolite above 930F (500C) in the presence of water vapor (Alcoa MSDS for Synthetic Cryolite, available in docket EPA-HQ-OAR-2010-0544). However, we agree with the commenter that there are no test data indicating that agitation of the molten metal bath underneath a cover flux causes a cover flux to emit HAPs, and we have revised the definition of cover flux in the final rule as follows: Cover flux means salt added to the surface of molten aluminum in a group 1 or group 2 furnace, without surface agitation of the molten aluminum, for the purpose of preventing oxidation. Any flux added to a rotary furnace is not a cover flux.
2.5	Operating Requirements/Work Practices
Comment #1: One commenter (0191) recommended that the agency not attempt to add specifications for cleaning processes such as those required for runaround scrap. The commenter did not believe that it is appropriate for the agency to delve into this topic and that the determination of the appropriateness of cleaning techniques be made in each affected facility. The commenter continued that if it was the agency's intention to continue to apply the requirements of the Subpart RRR rule to aluminum foundries that melt only clean charge and operate a thermal chip dryer, then the EPA should have stated that such facilities are covered only for the requirements covering the thermal chip dryer. The commenter also suggested that the definition of clean charge should be restated in its entirety, and not simply as a subtext in the discussion of appropriate scrap cleaning techniques. One commenter (0197) noted that the EPA solicited comment on whether it is necessary to include specifications for cleaning processes, principally thermal drying and centrifuging, to ensure that materials qualify as clean charge. The commenter asserted that any specifications for cleaning processes are not necessary for aluminum chips because there are sufficient financial, operational, and safety incentives to ensure chips are "clean." The commenter contended that such specifications are unnecessary for aluminum chips ("chips") in thermal chip dryers, given that facilities have sufficient operational incentives to ensure that chips are clean before processing them in their units. The commenter further explained the processes and incentives for cleaning chips. The commenter also noted that setting specifications is impractical as cleaning processes vary with the type and amount of contamination.
Response: In the proposal, we solicited comments on what methods could be used for cleaning scrap to ensure that scrap processed by certain methods qualified as clean charge. We did not propose scrap cleaning requirements but were interested in gathering information on appropriate specifications that could be applied to cleaning processes that would produce clean charge. However, we did not receive any information and are not making any rule changes to address specifications for cleaning processes.
Comment #2: Commenters (0192, 0193, 0194, 0199) opposed the proposed change to the §63.1510(b) rule language related to the revision of OM&M Plans. The commenters noted that the current language in §63.1510(b) related to submittal of revised OM&M Plans does not contain a 60-day waiting period and was part of an EPA and Aluminum Association settlement agreement under litigation of the 2000 Secondary Aluminum NESHAP ( 67 FR 16374, April 5, 2002). The commenters observed that the EPA provided no reason for changing this settlement agreement language, and thus did not provide the industry an opportunity to comment on the EPA's new reasoning. The commenters stated that the current approach for OM&M Plan revisions works well for State agencies and operating facilities, so the revised rule language would simply result in an unnecessary 60-day delay in operations' ability to respond to product or market needs. The commenters requested that the proposed changes to §63.1510(b) be deleted, otherwise, the EPA should describe why the change is needed and provide an opportunity for the aluminum industry to comment on the EPA's reasons.
Commenter 0199 objected to the change because the OM&M Plan for a given facility commonly needs to be revised for any of a variety of reasons, such as the addition of a malfunction type, repair or replacement of equipment resulting in compliant operating parameter changes, new stack tests, or addition of new equipment, among others. The commenter observed that when these changes occur, it is necessary that the facility move forward and begin operating with the new procedures or parameters, without the need to wait for agency approval of the revised plan, or for a 60-day waiting period. The commenter noted that most states do not respond in any way to the submittal of an OM&M Plan. The commenter stated that, under the existing procedure, if the permitting authority determines any revisions are necessary, the owner or operator assumed the risk by beginning to operate under the revised OM&M Plan upon submittal.
In a comment on the 2012 proposal and the 2014 supplemental proposal, commenter 0197 and 0297 stated that regardless of the deadline set, the EPA should make clear that the source has achieved compliance by submittal of required documentation to the permitting authority in order to ensure that sources are not penalized for failure of regulatory authorities to act on submittals in a timely manner or situations where a regulatory authority requests plan revision and the pre-existing OM&M plan remains in effect after the compliance period. The commenters stated that alternatively, the EPA could revert to the prior rule language, under which a facility would operate under a newly-submitted plan unless the Agency indicated that revision was needed, and then the facility would be given a reasonable time to accomplish revisions and operate in compliance with that revised plan after submission.
Response: In response to the comments, we have removed from the final rule the proposed provision that an owner or operator must not begin operating under a revised plan until approval is received or until after 60 days.
Comment #3: Commenters (0192, 0193, 0194) stated that anodized aluminum is clean charge material. Commenter 0193 argued that the EPA did not provide any data or information on what, if any, HAPs are emitted from melting anodized scrap, and that most dyes are inorganic and are used at very low application rates therefore this should not alter the scrap material. Commenter 0193 requested that the EPA maintain the current provisions.
Response: We proposed to clarify that anodized aluminum that contains dyes or sealants with organic compounds is not clean charge. Anodized aluminum containing organic dyes or sealants has the potential to result in formation of D/F when the aluminum is melted in secondary aluminum production processes, in the same way that D/F can be formed when aluminum coated with paints, other coatings, or lubricants is melted. The commenters submitted no test data or other documentation to support their assertion that anodized aluminum containing dyes or sealants with organic compounds is different from aluminum with paints, coatings, or lubricants that are already excluded from the definition of clean charge, such that melting such anodized aluminum in a group 1 furnace does not result in emissions of D/F or other organic HAPs. Therefore we are finalizing the provision as proposed.
Comment #4: The commenter (0197) indicated that the operation, maintenance, and monitoring provisions contained in section 63.1506(a)(5) of the proposed rule are redundant with the OM&M plan requirements and recommended that they should be deleted. The commenter stated that the OM&M plan requirements are sufficient to ensure compliance with the specific emission standards and work practices required under this Subpart. The commenter therefore proposed section 63.1506(a)(5) should not be included as a separate paragraph in this final rule.
Response: The OM&M plan requirements in section 63.1510(b) are consistent, and not redundant, with the provision in section 63.1506(a)(5) that an owner or operator must operate and maintain any affected source in a manner consistent with safety and good air pollution control practices for minimizing emissions. A determination of compliance with the provisions in section 63.1506(a)(5) include a review by the appropriate authority of information available including a review of operation and maintenance procedures, such as those contained in the OM&M plan. Section 63.1506(a)(5) is also consistent with the General Provisions in 40 CFR 63, Subpart A. We are adopting the revision to section 63.1506(a)(5) as proposed.
Comment #5: One commenter (0199) stated that the requirements of §63.1506(g)(5), (k)(3), and (m)(4) regarding continuous injection devices, may not be feasible in the case of repaired or replaced equipment, where a feeder setting may be lower on the repaired or replaced equipment than was established during the performance test while still providing the same lime flow rate (pounds/hour). According to the commenter, when this occurs, it should be sufficient to document the repair and show through a verification procedure that the lime flow rate is equal to or above the level established during the performance test at the new lime feeder setting.
The commenter suggested the following language be added:
      "For a continuous injection device, maintain free-flowing lime in the hopper to the feed device at all times and maintain the lime feeder setting at or above the level established during the performance test. In the event the equipment is repaired or replaced after the performance testing has been conducted, and the feeder setting required to maintain the lime flow rate is lower than that established during the performance testing, that lower the lime feeder setting should be documented in the OM&M Plan."
Response: In the final rule amendments, §63.1510(i)(4) has been revised as follows: "At least once per month, verify that the lime injection rate in pounds per hour (lb/hr) is no less than 90 percent of the lime injection rate used to demonstrate compliance during your most recent performance test. If the monthly check of the lime injection rate is below the 90 percent, the owner or operator must repair or adjust the lime injection system to restore normal operation within 45 days. The owner or operator may request from the permitting authority for major sources, or the Administrator for area sources, an extension of up to an additional 45 days to demonstrate that the lime injection rate is no less than 90 percent of the lime injection rate used to demonstrate compliance during the most recent performance test. In the event that a lime feeder is repaired or replaced, the feeder must be calibrated, and the feed rate must be restored to the lb/hr feed rate operating limit established during the most recent performance test within 45 days. The owner or operator may request from the permitting authority for major sources, or the Administrator for area sources, an extension of up to an additional 45 days to complete the repair or replacement and establishing a new setting. The repair or replacement, and the establishment of the new feeder setting(s) must be documented in accordance with the recordkeeping requirements of § 63.1517."

In addition, §63.1517(b)(4)(ii) has been revised as follows:
"(ii) If lime feeder setting is monitored, records of daily inspections of feeder setting, including records of any deviation of the feeder setting from the setting used in the performance test, with a brief explanation of the cause of the deviation and the corrective action taken. If a lime feeder has been repaired or replaced, this action must be documented along with records of the new feeder calibration and the feed mechanism set points necessary to maintain the lb/hr feed rate operating limit. These records must be maintained on site and available upon request."

Comment #6: One commenter (0199) noted that in regard to §63.1506(n)(l), "Maintain the total reactive chlorine flux injection rate and fluorine flux addition rate for each ...," until additional tests are conducted we do not have a fluorine injection rate to monitor or maintain.
The commenter recommended that terminology should be consistent. The commenter observed that the proposal is currently written as chlorine flux injection rate and fluorine flux addition rate. The commenter suggested that the terms should be either flux injection rate or flux addition rate for both chlorine and fluorine.
Response: The EPA agrees with the commenter and this paragraph has been revised in the final rule to say "...chlorine flux injection rate and fluorine injection rate...." However, the EPA thinks both terms are equivalent and are used interchangeably throughout the rule.
Comment #7: In a comment on the supplemental proposal, commenter 0299 supports the additions and changes as they apply to sweat furnaces and believes they provide greater clarity and will improve understanding of the requirements for these facilities.
Response: The EPA acknowledges the commenter's support of the rule requirements for sweat furnaces.
2.6	Other Technical Corrections/Clarifications
Comment #1: One commenter (0192) requested that the EPA allow facilities to terminate the required scrap sampling and analysis if the facility has strict purchasing specifications and has generated a long-term database that shows very low oil and coatings content in scrap purchased in accordance with the purchasing specifications.
Response: Owners or operators are responsible for inspecting scrap to confirm that the contaminant level is no greater than that of the scrap charged during the performance test. Monitoring of scrap contamination is essential to demonstrate continuous compliance with the standard. Therefore, we are not changing the rule as recommended by the commenter.
Comment #2: One commenter (0192) agreed with the proposed change to the group 2 furnace definition to clarify that pots are not furnaces, but the commenter recommended that the words "to customers" should be deleted.
Response: In response to the comment, the last sentence of the definition of group 2 furnaces has been revised to read, "Unheated pots, to which no flux is added and that are used to transport metal, are not furnaces."
Comment #3: Commenters (0193, 0194) asked that the EPA clarify the definition of an aluminum scrap shredder. The commenters expressed concern that the addition of the term "shearing" to this definition would redefine the affected source and expand the applicability of scrap shredder requirements well beyond the types of shredders that the EPA considered when developing the 2000 Secondary Aluminum NESHAP. The commenters noted that under the 2000 NESHAP rule, the EPA established emission standards for aluminum scrap shredders that are stand-alone devices used to size a variety of aluminum scrap for further processing in a scrap dryer/delacquering kiln or furnace and have emission control devices to capture particulate emissions generated from crushing and grinding, as well as paints, coatings and other contaminants present on the scrap. The commenters' concern is that the addition of the term "shearing" could expand applicability of the rule to continuous "shearing" operations used to cut aluminum plate, sheet or foil products to final width. The commenters explained that this type of shearing operation is not a stand-alone operation for processing scrap, does not generate significant particulate emissions and does not have separate capture or add-on air pollution control. The commenters concluded that NESHAP requirements for aluminum scrap shredders (e.g., 0.01 gr/dscf limit, bag leak detector, etc.) could therefore not be reasonably applied to this type of "shearing" operation.
The commenters recommended that the EPA either delete the proposed addition of the word "shearing" to the aluminum scrap shredder definition or clarify in the definition that "shearing and cutting operations performed at rolling mills and aluminum finishing operations (such as slitters) are not aluminum scrap shredders."
Response: The definition has been revised by adding the sentence, "Shearing and cutting operations performed at rolling mills and aluminum finishing operations (such as slitters) are not aluminum scrap shredders."
Comment #4: One commenter (0192) supported removing the outdated guidance document for bag leak detection systems. The commenter stated that the use of the manufacturers operating and maintenance instructions is the most reliable method for assuring proper operation of the systems.
Response: The EPA acknowledges the commenter's support.
Comment #5: One commenter (0194) supported using manufacturer's O&M instructions for bag leak detectors and deleting the reference to the EPA Triboflow leak detector guidance. The commenter stated that the leak detector guidance had caused confusion with respect to good practice for at least one of the commenter's locations.
Response: The EPA acknowledges the commenter's support.
Comment #6: One commenter (0194) recommended that the added reference to "HF" in §63.1516(b)(2)(iii) should be deleted, because this provision relates to furnaces with add-on control devices and these furnaces are not subject to the new HF limit.
Response: We agree with the commenter and the final rule does not include the reference to HF in §63.1516(b)(2)(iii).
Comment #7: The commenter (0197) recommended that the EPA should clarify the definition of Clean Charge. The commenter noted that all materials listed in the first sentence are separated by semicolons with the exception of the final material, "runaround scrap". The commenter stated that "runaround scrap" is a distinct and defined item and a semicolon should be inserted after the "or higher; and before the "and runaround scrap" to delineate it from the previous term.
In a comment on the supplemental proposal, Commenter 0286 stated that the EPA needs to clarify the definition of "clean charge" to be consistent with its guidance and policy found in the Agency's Applicability Determination Index (ADI) Database. The commenter stated that on July 26, 2007, the EPA published in the FR recent postings to the ADI Database including determination M060039 (dated 03/01/2005), which provided guidance as to whether aluminum sows, ingots, and T-bars that have painted markings are considered clean charge under subpart RRR. According to the commenter, determination M060039 noted that there was a typographical error in the definition of clean charge and that the EPA intended these charge materials, "notwithstanding ink, grease or paint markings, should be treated as clean charge." The commenter stated that the EPA then published an amendment in the FR on October 3, 2005 correcting a punctuation error found in the definition of clean charge and clarified that the phrase "known by the owner or operator to be entirely free of paints, coatings, and lubricants" should only apply to aluminum scrap. The commenter recommends that the EPA should take the opportunity to clarify that the phrase, "known by the owner or operator to be entirely free of paints, coatings, and lubricants" applies only to aluminum scrap and does not apply to charge materials such as T-bar, sow, ingot, billet, pig and alloying elements. The commenter recommend that, to ensure that the definition of "clean charge" is consistent with the EPA's current policy and guidance on this matter as described in ADI M060039, the EPA add a sentence to the definition of clean charge (as proposed February 14, 2012) to read as follows:
      "Clean charge means furnace charge materials, including molten aluminum; T-bar; sow; ingot; billet; pig; alloying elements; aluminum scrap known by the owner or operator to be entirely free of paints, coatings, and lubricants; uncoated/unpainted aluminum chips that have been thermally dried or treated by a centrifugal cleaner; aluminum scrap dried at 343 °C (650 °F) or higher; aluminum scrap delacquered/decoated at 482 °C (900 °F) or higher, and runaround scrap. Aluminum T-bars, sows, ingots, billets, pigs and alloying elements notwithstanding ink, grease or paint markings, are clean charge. Anodized aluminum that contains dyes or sealants with organic compounds is not clean charge."
Response: The comma following "or higher" has been replaced with a semi-colon in the final rule amendments to promote ease of reading; however, this is not a substantive change.
Regarding the comment received on the supplemental proposal concerning the definition of "clean charge" and certain aluminum sows, ingots, and T-bars, the scope of the 2014 supplemental proposal was limited to discrete topics that we expressly stated did not include "clean charge definition." 79 FR at 72884. Even in the 2012 proposal, our proposed revision to the definition of "clean charge" only addressed the topic of anodized aluminum. Accordingly, this comment is outside the scope of this rulemaking, and no action was taken in the final rule in response to the commenter's request.
Comment #8: One commenter (0199) suggested that in §63.1503 the definition of "tap" be revised to read: "Tap means the portion of an operating cycle when processed molten aluminum is poured from a furnace." The commenter expressed concern that as proposed, there may be a problem when conducting stack testing of multiple furnaces. The commenter noted that the commenter currently conducts stack testing of multiple furnaces with each one starting at a different point in the operating cycle and continuing through a complete operating cycle for each furnace, with each cycle containing a number of operating tasks including charging, melting, skimming, alloying, and tapping. The commenter stated that these stack tests have been accepted by both the EPA and the states. The commenter explained that for stack testing purposes, the beginning or end of the cycle can be at any point as long as all tasks are accomplished, meaning that tapping should not be defined as the end of the furnace cycle, rather tapping should only refer to the removal of molten aluminum from the furnace. The commenter noted that the commenter would not have the personnel required to simultaneously test multiple furnaces if the test runs all had to begin concurrently with charging and end with tapping.
Response: To address the commenter's concern, we have revised the definition of "tap" as follows, to address the commenter's concern: "Tap means the end of an operating cycle of any individual furnace when processed molten aluminum is poured from that furnace."
Comment #9: One commenter (0199) stated that the EPA has recognized through test plans and alternative requests that a facility can use both charge pounds and aluminum produced pounds within the same facility for different furnaces. The commenter provided as an example the commenter's Aleris Rolled Products, Inc. facility in Lewisport, Kentucky, which has melting furnaces that use pounds charged while the holders use calculated aluminum pounds produced. The commenter noted that this particular case is documented in the "Lewisport Uncontrolled Reverberatory Furnace Test Protocol", Appendix G in the commenter's Consent Decree (attached to comment letter). The commenter maintained that there is no justification for restricting individual furnaces from using pounds of aluminum produced or pounds charged when determining compliance.

Response: The proposed rules did not include changes to subpart RRR requirements regarding whether individual furnaces should be allowed to use pounds of aluminum produced or pounds charged when determining compliance and we do not believe a rule change is necessary based on the information available to the EPA.

Comment #10: One commenter (0193) supported the proposed addition of the new edition of the ACGIH guidelines manual for hooding requirements and allowing the older reference to remain. However, the commenter stated that due to the many different furnace types and configurations, the rule should be modified, with similar wording as is in the current Iron and Steel Foundry Area Source MACT, to state that each capture and collection system must be designed using acceptable engineering standards, such as those published by the American Conference of Governmental Industrial Hygienists. According to the commenter, this would allow hoods to be designed using the ACGIH guidelines as they were intended, as guidelines to assist in the design of capture and collection systems. The commenter recommended that the EPA clarify in the rule that the ACGIH-manual hooding specifications are intended to be used as guidelines, and that good engineering practices be included for site-specific instances where ACGIH hooding specifications are not practical and/or other engineering designs can be effective.
The commenter argued that the hooding guidelines promulgated by ACGIH were not intended to be regulation. The commenter stated that certain limitations exist within the guideline language that should be addressed by the EPA with engineering alternatives on a site specific basis. According to the commenter, where ACGIH hooding specifications are not practical due to furnace design, safety, and operating limitations/access, the EPA should consider work practice standards for furnace operations to minimize the potential for fugitive emission releases.
Commenter 0197 contended that the 23rd and 27th edition of Industrial Ventilation: A Manual of Recommended Practice, American Conference of Governmental Industrial Hygienists ("ACGIH Manuals"), do not contain specific requirements to guide facilities and should not be incorporated wholesale, by reference, into regulations. The commenter stated that EPA, in promulgating emission standards must explicitly state the requirements. The commenter recommended that the EPA should remove the reference to the ACGIH manuals, as well as the requirement in proposed section 63.1502 that capture and collection systems meet ACGIH Standards, the EPA should specify the elements that it believes are important and required so that the regulatory requirements are clear, and to the extent the manuals are referenced in the final rule, the EPA must specify which particular aspects of the manuals are being incorporated.
In a comment on the supplemental proposal, commenter 0297 stated that in the supplemental proposal, the EPA plans to provide an alternative to the ACGIH Manuals for design, installation, and operation of sweat furnaces only, and would not allow alternatives to the ACGIH Manuals for capture and collection systems installed on other sources subject to the rule. As they stated in their comments on the 2012 proposal, incorporating the ACGIH Manuals and requiring systems to be designed and installed to meet the ACGIH standards is inappropriate; the EPA must explicitly state the requirements as the ACGIH Manuals do not provide specific requirements for a facility to follow. The commenter stated that the 2012 proposal appears to actually exacerbate the problem in that it incorporates the entire manual rather than just sections 3 and 5. The commenter stated that due process and basic principles of rulemaking under the Administrative Procedure Act and Clean Air Act require the EPA to reasonably inform regulated entities of their obligations, but because the ACGIH Manuals are voluminous and it is unclear which specific aspects of the manual the EPA is intending to incorporate, finalizing the rule as proposed would contravene these fundamental legal requirements. The commenter stated that the manuals provide the general ventilation equations and simple diagrams for hoods and ductwork, also providing a framework to design simple conveyance systems; it does not and was not intended to address complex industrial exhaust systems with wide ranges of temperatures. The commenter stated that, thus, it is unclear what specific requirements from the manual the EPA intends to incorporate in proposed section 63.1506(c)(1) for the complex operations regulated here; under this proposal, sources will not have fair notice of the operating requirements for capture and collection systems.
Commenters (0192, 0193, 0199) requested that Secondary Aluminum Production facilities be allowed to use any ACGIH manual edition from the 23rd on rather than restricting the industry to the 23rd and 27th editions.
Commenter 0192 supported the EPA's decision to allow use of the updated 27th edition of the ACIGH manual, and recommended that the EPA allow the use of any future editions that may be published. The commenter noted that the 27th edition has been renamed: "Industrial Ventilation: A Manual of Recommended Practice for Design."
Response: We acknowledge commenter 0193's support for allowing the use of either the 23[rd] or 27[th] edition of the ACGIH Guidelines manual. In the preamble to the proposed rule, we solicited comment on whether there are alternatives to the ACGIH guidelines, such as ventilation rules or guidelines developed by other professional organizations, governmental agencies, or industry organizations that could be used in a more flexible rule provision. We also solicited comment on other ways to increase flexibility, such as using minimum face velocity, elimination of visible emissions, minimum pressure drop, or other suitable parameters to determine capture effectiveness. We did not receive any information from commenters or others on the potential parameters we listed but received the comments summarized above. We note that commenter 0193 requests that the rule provision be broadened to allow "acceptable engineering standards, such as those published by the [ACGIH]" and argues that the ACGIH manual be treated as guidelines as opposed to regulatory requirements, while commenter 0197 takes a different approach, asserting that the EPA should explicitly state the particular elements in the ACGIH manual that are required by the rule or preferably remove the regulatory reference to the ACGIH manual entirely. Based on our experience implementing the rule and in light of the lack of any comments containing recommended alternative ventilation rules or guidelines, as well as the lack of comments on potential capture efficiency parameter approaches listed by the EPA at proposal, we conclude there is no reason to adopt an approach different from the current one, i.e., incorporating by reference the ACGIH manual, with the revisions adopted in the final rule to allow use of the 27[th] edition in addition to the 23[rd] edition. We do not consider "acceptable engineering standards" to be sufficient or appropriate for capture and collection systems in this rulemaking, because this language does not provide sufficient guidance to the secondary aluminum industry and to permitting authorities as to what constitutes adequate capture and collection systems under the relevant provisions of subpart RRR. We also believe it is not necessary to revise the rule to specify particular elements of the ACGIH manual. We note that site-specific issues may continue to be addressed as facilities work with the EPA and delegated authorities during implementation of the rule. Accordingly, we are retaining the incorporation by reference of Chapters 3 and 5 of the 23[rd] edition and adding all of the 27[th] edition of the ACGIH Industrial Ventilation manual, as proposed.
The final rule incorporates by reference Chapters 3 and 5 of the 23[rd] edition, and the entire 27[th] edition, and the final rule accounts for the correct title of the 27[th] edition ("Industrial Ventilation: A Manual of Recommended Practice for Design"). However, it is not appropriate to incorporate by reference future editions of a document; in general, only editions already published may be incorporated by reference.
In further response to the comment on the 2014 supplemental proposal concerning a proposed alternative to ACGIH Guidelines being limited to "sweat furnaces only", the commenter does not appear to oppose the proposed alternative for sweat furnaces but instead reiterates and supplements its comments on the 2012 proposal that ACGIH Guidelines should not be incorporated into Subpart RRR requirements. We have responded to the commenter's 2012 comments above, and to the extent the commenter provided new or additional comments in response to the 2014 supplemental proposal, they are outside the scope of that notice, which was limited to discrete topics that we expressly stated did not include "ACGIH Guidelines." 79 FR at 72884.
3. Testing and Monitoring

Comment #1: One commenter (0192) objected to the proposed language that "Performance tests be conducted under such conditions as the Administrator specifies based on representative performance of the affected source for the period being tested" under §1511(a). The commenter noted that this language seems to be extracted from subpart A section 63.7(e) but is incomplete and in a different context. The commenter questioned whether it has a different meaning in proposed subpart RRR. The commenter stated that if it does have a different meaning, it has not been explained or justified in the proposal; if it does not have a different meaning, it is unnecessary, and because it is incomplete and out of context, could lead to confusion. The commenter recommended that it should be deleted in either case.
Response: As discussed in the proposed and final rule documents, subsequent to a court decision we are eliminating the SSM exemption in subpart RRR, requiring that standards apply at all times, and making revisions to the applicability of the General Provisions. As in the proposed rule, the final rule removes from subpart RRR, Appendix A the applicability of §63.7(e)(1), which contains superseded references to periods of SSM, and revises §63.1511(a) to reflect pertinent portions of §63.7(e)(1). The commenter did not explain why it says revised §63.1511(a) is incomplete, out of context, and confusing, but making §63.7(e)(1) not applicable eliminates any conflict between the two provisions.
Comment #2: Commenters (0193, 0194) stated that monthly verification of lime injection rate is unnecessary and overly burdensome given that lime feed measurement is not likely to change significantly over short periods of time. The commenter recommended that the EPA establish a lime rate verification frequency of "at least once every 6 months" which would be consistent with all other monitoring devices used under the Secondary Aluminum NESHAP.
Commenter 0192 suggested that the EPA should exempt facilities with automated systems based on load cells to assure adsorbent flow from this requirement, as these systems create alarms or error messages when adsorbent flow is interrupted, making periodic verifications not necessary.
One commenter (0199) objected to the requirements of §63.1510(i)(4): "At least once per month, verify that the lime injection rate in pounds/hour (lb/hr) is no less than 90 percent of the lime injection rate used to demonstrate compliance during your performance test." The commenter asserted that this proposed measure contravenes the standard negotiated in a 2009 Consent Decree resolving a federal enforcement action against the company. The commenter agreed that lime flow rate is the important parameter and that it is necessary to periodically verify lime flow rates, but asserted that it is not necessary to verify lime flow rates monthly.
The commenter explained that under their Consent Decree, two time periods are used for the two lime flow rate methods: measuring volumetrically or using a scale. The commenter stated that if a scale is used, the Consent Decree provides that the commenter checks scale calibration semi-annually, and if the lime flow rate is determined volumetrically, it is appropriate to perform a routine verification. The commenter explained that where this has been necessary, the Consent Decree provides for bi-monthly verification if flow is monitored visually as required by §63.1510(i)(1)(i), and verification once every four (4) months if flow is monitored electronically as in §63.1510(i)(1)(ii).
Response: The lime injection rate is a necessary parameter established during performance test to ensure continuous compliance with the emission standard, in the absence of monitoring emissions on a continuous basis and in light of performance testing that is required only every 5 years. Operation with potentially inadequate lime injection for a period of up to six months before the need for corrective action is determined could reduce the effectiveness of or damage the control device and thereby increase emissions above the emission standard. The commenters did not submit any supporting documentation for their assertions that monthly verification is "overly burdensome" or that lime feed measurement is "not likely to change significantly over short periods of time." Facilities with automated systems based on periodically calibrated scales or load cells should be able to verify lime injection rate easily by integrating the recorded hopper weight loss. Therefore, we are adopting the requirement as proposed.
Regarding the 2009 Consent Decree, the decree at paragraph 122 states clearly that each company is responsible for achieving and maintaining complete compliance with all applicable federal laws and regulations, and compliance with the Consent Decree does not necessarily mean compliance with the Clean Air Act or implementing regulations. Further, the Consent Decree does not limit the EPA's authority to revise subpart RRR.
Comment #3: Commenters (0192, 0193, 0194) stated that the new list provided in §1510(a) adds the phrase "including, but not limited to," which does not clarify which provisions of Subpart RRR actually apply to area sources. The commenters requested that the EPA delete the phrase from §1510(a). The commenter observed that if something is missing from §1510(a)(1) through (19), it should be added to provide clarity for area sources.
Response: Owners or operators of area sources are subject to monitoring requirements for those affected sources listed in §63.1500(c)(1)-(4). We are not changing the language in 63.1510(a) because the list is intended to be informational and a guide to applicable requirements to assist compliance by area sources, not to alter the applicability of promulgated Subpart RRR requirements. In addition to the requirements listed in § 63.1510(a), they must conduct whatever monitoring is necessary to ensure that these affected sources are operated in a manner consistent with safety and good air pollution control practices.
Comment #4: Commenters (0192, 0193) requested that the requirement, "for the purpose of annual certifications of compliance required by 40 CFR part 70 or 71, the owner or operator of a major or area source subject to this subpart must certify continuing compliance" be removed, as this would result in an additional requirement for area sources and it is a Title V reporting burden that was specifically exempted for the secondary aluminum production.
Response: After review of the comments received, we agree this requirement would impose additional burden on area sources subject to Subpart RRR and provide limited benefit. We note the existing rule generally exempted secondary aluminum area sources from Title V permitting, and we did not propose to remove the exemption. The proposed compliance certification requirement for area sources is not included in the final rule.
Comment #5: Commenters (0193, 0194) stated that the proposed §63.1511(g)(5) states that "[i]f the owner or operator wants to conduct a new performance test and establish different operating parameter values, they must meet the requirements in paragraphs (g)(1) through (4) of this section and submit a revised site specific test plan and receive approval in accordance with paragraph (a) of this section." The commenters observed that paragraphs (g)(1) through (4) of this section are only relevant if an owner or operator wants to "use existing data in addition to the results of performance tests to establish operating parameter values....", but are not relevant if the facility "wants to conduct a new performance test and establish different operating parameter values." The commenters suggested that the new §63.1511(g)(5) should be revised to delete the reference to paragraphs (g)(1) through (4) to say: "[i]f the owner or operator wants to conduct a new performance test and establish different operating parameter values, they must submit a revised site specific test plan and receive approval in accordance with paragraph (a) of this section."
Response: The requirements of §63.1511(g)(1) through (4) apply to cases where an owner or operator wants to conduct a new performance test and establish operating parameter values, and in doing so wants to use existing data in addition to the results of the new performance test to establish operating parameter values for compliance monitoring. In the final amendments, paragraph (g) (5) has been revised to read, "If the owner or operator wants to conduct a new performance test and establish different operating parameter values, they must submit a revised site specific test plan and receive approval in accordance with paragraph (a) of this section. In addition, if an owner or operator wants to use existing data in addition to the results of the new performance test to establish operating parameter values, they must meet the requirements in paragraphs (g)(1) through (4) of this section."