Commenter 0093-Steel Co. stated if a 0 percent opacity standard for melt shop emissions at all times was implemented, the EPA must exclude periods of malfunctions and upset conditions. The commenter explained that malfunctions occurred during the melting and casting operations that required extraordinary measures for corrective action, such as a "breakout." In an extremely dangerous situation, breakouts occurred when molten steel escaped from one or more mold strands at the caster or during casting. The commenter stated after a breakout and subsequent corrective action, emissions were generated and may exit the melt shop, and those emissions should not be considered in determining compliance with the 0 percent opacity melt shop requirement. The commenter said the EPA's proposed approach lacked an understanding of the significant dangers, risks, and related emissions associated with "breakouts" and other malfunction events that occur during the steelmaking processes, and the EPA should reconsider the 0 percent melt shop opacity standard.
Response 2-13: For the EPA's response to issues raised in this comment in regard to the proposed melt shop opacity standard, standard, see the EAF NSPS preamble to the final rule, section IV.B.2.

Comment 2-14: Canopy hood control costs.

Commenter 0097-Industry Trades stated the EPA did not examine advances in control technologies, process operations, design or efficiency improvements, or other systems of emission reduction, that are "adequately demonstrated". Rather, the EPA looked to a decades-old background information document (BID), concluded that "[c]anopy hoods are a common method of controlling fugitive EAF emissions," and assessed costs for: adding a partial roof canopy (segmented canopy hood, closed roof over furnace, open roof monitor elsewhere) to collect PM emissions that might otherwise escape through the shops to achieve complete control of melt shop fugitives.

Commenter 0097-Industry Trades and 0095-Steel Co. stated the EPA did not analyze whether canopy hoods were used by the 19 facilities that recorded 0 percent opacity during performance testing or were absent from the nine facilities that recorded the highest opacity during performance tests. This information was available to the EPA in the docket for the 40 CFR part 63, subpart YYYYY NESHAP for EAFs  -  the same docket that supplied the majority of the performance test data the EPA used in this rule. The EPA's own review of the survey responses in the 40 CFR part 60, subpart YYYYY docket in June 2005 shows that EPA knows that canopy hoods were used to capture fugitive emissions from 32 of the 38 EAFs described in the CAA section 114 survey responses, and that the presence or absence of a partial roof canopy did not determine whether the facilities responding to the survey could achieve 0 percent opacity. Therefore, the EPA has no basis to now conclude for purposes of demonstrating achievability and cost effectiveness that the singular act of installing a partial roof canopy will "achieve complete control of melt shop fugitives."

Commenter 0097-Industry Trades and 0095-Steel Co. stated the EPA's conclusion is also contradicted within the Agency's cost analysis. In order to estimate how much PM is emitted from a facility that emits 6 percent opacity, the EPA used the 1982 BID's estimate that EAFs emit an average of 29 lb/ton of uncontrolled PM emissions. The EPA then relied on the 1982 BID again to estimate that facilities emitting 6 percent opacity captured 90 percent of those emissions using a "segmented canopy hood, closed roof over furnace, open roof monitor elsewhere." This is the exact fugitive emission capture technology that the EPA's Cost Analysis presumes facilities with greater than 0 percent opacity can install to achieve 0 percent opacity. In other words, the EPA's Cost Analysis assumes that facilities with a "segmented canopy hood, closed roof over furnace, open roof monitor elsewhere" are emitting 6 percent opacity and if those facilities install a "segmented canopy hood, closed roof over furnace, open roof monitor elsewhere" they will achieve 0 percent opacity. Commenter 0097-Industry Trades and 0095-Steel Co. stated because it is arbitrary and unreasonable to assume that facilities will be able to achieve 0 percent opacity by doing nothing more than install the same systems that facilities already have installed without reaching 0 percent opacity, the EPA has failed to provide a cost estimate rationally related to reduction of opacity from 6 percent to 0 percent.

Response 2-14: For the EPA's response to issues raised in this comment in regard to the proposed melt shop opacity standard, standard, see the EAF NSPS preamble to the final rule, section IV.B.2.

Comment 2-15: Melt shop equipment needed to achieve 0 percent opacity.

Commenter 0097-Industry Trades stated melt shop partitions of the size necessary to meaningfully contain EAF emissions within the melt shop are not feasible in many mills given other equipment and shop design, including cranes. In particular, sizable partition walls are not feasible at many EAF steel mills because they will interfere with overhead cranes that transport scrap metal to the furnace. Similarly, transfer ladles that are carried by crane to and from the furnace for tapping molten metal would be blocked by partition walls.

Commenter 0097-Industry Trades said for existing facilities that may trigger an NSPS modification in the future, achieving 0 percent shop opacity would require extensive re-engineering that would be costly and introduce practical and worker safety concerns as well. For example, one [trade] association member stated that 0 percent shop opacity could only be achieved, if at all, with near total enclosure of the EAF and doubling the flow rate of the emission control system.

Commenter 0097-Industry Trades stated that only very short (and therefore marginally effective) partition walls could be installed above the crane because of the lack of space between the crane and the roof. They also noted that such short partitions deteriorated quickly due to the heat and other elements. Thus, to increase the size and collection efficiency to meet a 0 percent opacity requirement, the facility would have to raise the roof of the structure at an undetermined cost (a cost that likely would trigger a "major modification"), and potentially enclose the entire monovent, which would likely create worker safety and heat stress issues.

Commenter 0097-Industry Trades added, facilities would have to increase the number and volume of fans to the baghouse, as well as require new or additional fans in the shop and additional baghouses because the facility's current baghouses are operating at close to maximum capacity. Moreover, for servicing, cranes have to be moved to a different part of the melt shop due to the partitions being so close to the top of the cranes. To achieve compliance, existing facilities such as these also would have to enclose the large openings in the casting area to prevent winds from blowing through the shop or wall off the EAF operations. Neither option is feasible; melt shops are typically long buildings with EAF, LMS, and casting in the same structure.

Response 2-15: For the EPA's response to issues raised in this comment in regard to the proposed melt shop opacity standard, standard, see the EAF NSPS preamble to the final rule, section IV.B.2.

Comment 2-16: The Ferroalloys NESHAP cost considerations.

Commenter 0097-Industry Trades stated the docket for the Ferroalloys major source NESHAP should have apprised the EPA of the "irrationally [sic] of its control cost conclusions." In its economic analysis of the Ferroalloys NESHAP, the EPA conceded that discussion with vendors and ventilation experts and EPA research led to a conclusion that implementation of fugitive capture and control systems is complex and that system parameters are highly dependent on specific localized parameters (e.g., building volume, process locations, and airflow). And that any plans to implement a system for ventilation to control fugitive emissions should begin with a rigorous, systematic examination of the ventilation requirements throughout the building leading to design and implementation of an enhanced fugitive capture and control system (Harris Memo: Cost Impacts of Control Options Considered for the Ferroalloys Production NESHAP to Address Fugitive HAP Emissions, at 2).

Commenter 0097-Industry Trades said the Ferroalloys analysis is predicated on "[EPA's] expectations of the controls likely to be installed as a result of facility-specific ventilation analyses, the controls likely to be needed to address risk, and existing capture and control systems at the facilities." Thus, the EPA's Ferroalloys analysis is rooted in an understanding of context-specific control mechanisms that are unique to the facilities in which they must be installed. Said differently, the EPA did not intend for this cost-analysis of BSER [sic][MACT] proposed in the [NESHAP for the] ferroalloy industry to be universally applicable to all ferroalloy facilities, let alone those outside of the ferroalloy industry.

Commenter 0097-Industry Trades stated the Ferroalloys analysis relies on a mere two ferroalloy facilities to conduct the bulk of its cost analyses, with the only supplemental information coming from the Agency itself. To rely on such limited input, with no support for the representativeness of the two facilities selected, is problematic as it can hardly be presumed to be representative of the larger industry.

Commenter 0097-Industry Trades added having only two ferroalloy facilities present their cost analyses means the baseline understanding of costs adopts pre-existing measures these facilities employ. In other words, adopting only these two facilities cost analyses presupposes all the conditions present in these two facilities. The EPA itself recognizes the difficulty of retrofitting a one-size-fits-all solution onto a diverse milieu of facilities.

Commenter 0097-Industry Trades stated not only is the assumption of similar conditions problematic but relying on only two ferroalloy facilities similarly means extensive gaps about specific sites exist in the data. The EPA acknowledges this and remedies it by filling in those gaps with both "general considerations" and "facility-specific considerations." While some of these considerations are reasonable, others are too tenuous and, therefore, of little use.

Response 2-16: In the proposed 40 CFR part 60, subpart AAb, we used the mathematical approach presented in the ferroalloys production major source NESHAP (40 CFR part 63, subpart XXX), hereafter referred to as the "Ferroalloys NESHAP," to estimate canopy costs but tailored the model to steel-producing EAF by replacing the variables of air flow and labor rates to steel EAF and by scaling (upwards) all capital costs for steel-making EAF based on the ratio of air flow at steel-making EAF to air flow at EAF at ferroalloys production facilities. [See the Cost Memorandum prepared for the proposed[2] rule for details of this analysis] Note that there are only three Ferroalloy major sources in the U.S., therefore, using two facilities in the Ferroalloy cost analysis was a clear majority for the source category.

The commenter fails to identify the assumptions that are "too tenuous and, therefore, of little use" as opposed to the assumptions that are "reasonable"; therefore, we cannot address the commenters concerns with specificity. We also cannot do an individual cost analysis for individual EAF facilities to fill the alleged "extensive gaps about specific sites [that] exist in the data," as the commenter suggests, because the finalized NSPS standards apply to future facilities of unknown individual characteristics.. The approach and assumptions that were used to modify the cost estimating procedures taken from the Ferroalloys NESHAP for the proposal for the EAF NSPS are all reasonable and the best available to the EPA.

The EPA acknowledged the cost-effectiveness of local capture, such as canopy hoods, as compared to total enclosure in its response to comments on the proposed rule for the Ferroalloys NESHAP in 2015 ("Summary of Public Comments and Responses on Proposed Rule, (76 FR 72508, November 23, 2011) and Supplemental Proposal (79 FR 60238, October 6, 2014)" May 28, 2015. (Docket Item No. EPA-HQ-OAR-2010-0895-0302), on page (p.) 120, under section 4.6, "Fugitive Emissions Capture":

      ...full-building enclosure option with negative pressure may not be feasible and would have significant economic impacts on the facilities... [H]owever, we conclude[d] that the enhanced local capture option is a feasible and cost-effective approach to achieve significant reductions in fugitive HAP emissions and will achieve almost as much reductions as the full building enclosure option....

Further, in the same 2015 Ferroalloys NESHAP comment and response document, EPA explains how opacity would be used to tailor the capture system parameters to meet a rule's requirement for shop opacity:

      ...the opacity standard is a main piece of the compliance strategy for the process fugitive emissions standards. A key aspect of the opacity limit is that it can be used by the source to establish a correlation between successful operation of capture system parameter values (capture system fan motor amperes and all capture system damper positions or volumetric flow rate through each separately ducted hood that comprises the capture system) and opacity levels, and then the source can continuously monitor the parameters to help ensure the opacity limits are achieved continuously and that the capture and control system is effectively capturing fugitives on a continuous basis. This combination yields an enforceable parameter limit that is designed to ensure continuing operation of the capture system at a level consistent with operation during the performance test.

Id. at 129, under section 4.8, "Opacity Standards."

Comment 2-17: The EPA's estimates of the PM associated with shop opacity are unsupported and improper.

Commenter 0097-Industry Trades stated the EPA's quantification of PM emissions attributable to shop opacity and all resulting cost-effectiveness calculations rest on many assumptions for which the EPA provides no support. The EPA believes that the inverse relationship it presumes to exist between stack emissions (and therefore presumed capture efficiency) and shop opacity is borne out by the CAA section 114 performance test data for the 0 percent opacity and nonzero opacity facilities, but the opposite is true. A simple inspection of the data shows that 0 percent opacity is not correlated with higher stack emissions.

Commenter 0097-Industry Trades stated when the PM stack emissions values for the 13, 0 percent opacity facilities in the EPA's database and the PM stack emissions values for those nine facilities that recorded opacity values above 3 percent are plotted in a bar graph, the highest stack emission values are the same for both 0 percent opacity and 3 percent opacity facilities, and the values for the 3 percent opacity facilities are completely subsumed within the values for the 0 percent opacity facilities, with just the two lowest values in the 3 percent opacity dataset outside of the range of the 0 percent opacity dataset. In view of this, the EPA's presumption that there are statistically significant differences in the medians of the two data sets is not supportable. It is more likely that the calculated differences reflect variability wholly unrelated to the correlation theory espoused by the EPA. The EPA uses their stack emission/opacity correlation as the basis for ascribing a PM emission reduction value to its proposed 0 percent opacity standard.

Commenter 0097-Industry Trades and 0095-Steel Co. stated it is not possible to credibly correlate the measured opacity with the mass of filterable PM. The commenters noted melt shops contain numerous other equipment and activities (i.e., other than the EAF) which also can generate fugitive emissions that can be read as opacity. While it is correct that opacity is due to the presence of particles, quantifying the mass of particles that correspond to a given level of opacity is impossible because the observed opacity is a function of many variables include particle size and distribution, particle composition, ambient conditions, capabilities of the human (or non-human) observer, and others. The EPA falsely assumes a linear correlation between PM emissions and opacity, when in fact, at the low levels (i.e., under 6 percent) relevant here, opacity is often more a function of meteorology than emission level. Thus, even theoretically, there is no reason to presume a one-to-one correspondence between opacity and mass of PM. Much of the EPA's analysis supporting its proposed rule attempts to quantify the benefits (i.e., mass of PM reduced) as opacity is reduced from one level to a lower level  -  for example from 6 percent to 0 percent.

Commenter 0097-Industry Trades stated the EPA estimated the mass of fugitive emissions from the melt shop relying on: the measured baghouse exhaust PM level, the assumed baghouse efficiency, and the assumed melt shop capture efficiency. The commenter notes that while the value of the assumed baghouse efficiency may have some basis (i.e., may be available from some tests where both inlet and outlet PM were measured), there is no basis to presume the value of the assumed melt shop capture efficiency. Even complex computational fluid dynamic (CFD) models cannot properly estimate melt shop capture efficiency. The mass of PM emitted from the EAF as fugitive PM from the melt shop cannot be correlated to any level of opacity. In total, the EPA's analysis of the emissions reductions that will result from reducing melt shop opacity from one level down to a lower level, or the cost-effectiveness that may accompany such reductions, are speculation made with unsupported assumptions.

Response 2-17: The EPA disagrees that it did not provide support in the proposal for the estimates of PM associated with shop opacity. The commenter is conflating the statements in the proposal about emissions with 0 percent shop opacity. The emission calculations used in the proposal for canopy hood cost estimates compare estimated uncontrolled shop emissions (which are not available in the EPA EAF data or elsewhere as actual measurements) for a theoretical facility and emission estimates for controlled emissions from the melt shop at 6 percent opacity for the same theoretical facility. In addition, the assumption that facilities with 0 percent opacity have higher baghouse emissions than if the same facility achieved 6 percent opacity, does not equate to comparing baghouse PM emissions at one facility with 0 percent shop opacity to baghouse PM emissions at another facility achieving a 6 percent opacity. As shown in Figure 1-5, the 13 facilities in the EPA EAF data that achieved 0.000 percent shop opacity have only slightly higher total facility baghouse PM emissions compared to all 30 EAF facilities in the EPA EAF data, with identical highest and lowest total facility baghouse PM values.

We mostly agree with the commenter that "while it is correct that opacity is due to the presence of particles, quantifying the exact mass of particles that correspond to a given level of opacity is impossible because the observed opacity is a function of many variables include particle size and distribution, particle composition, ambient conditions, capabilities of the human (or non-human) observer, and others." However, we do not agree with the commenter that the only effort needed to demonstrate 0 percent opacity at a facility that consistently demonstrates 6 percent opacity is to wait for the conditions of particle size and distribution, particle composition, ambient conditions, and capability of the observer to align in a fortuitous manner.

For purposes of assessing cost estimates, simplifying assumptions and estimates for PM emissions need to be made in order to estimate the cost of control options. The need to make estimates also was evident in the Ferroalloys NESHAP cost estimates for fugitive EAF emissions, where controlled PM emission estimates were made based on assumptions, emissions factors, mass balance, and observations:
      ...emissions reductions were estimated for each facility based on emissions data received in an information collection request sent to the industry along with application of emissions factors, and other data analyses and calculations.
With more detail provided:
      We have not identified any emissions factors based on the direct measurement of fugitive emissions from ferroalloys production furnaces [in order] to estimate these emissions. Therefore, we used a mass balance approach to estimate these emissions.

      The furnace smelting fugitive emissions were estimated by calculating the uncontrolled PM emissions from the furnace and estimating the range of the uncontrolled PM emissions that are captured from the furnace. The difference between the uncontrolled pollutant emissions and the estimated captured pollutant emissions were assumed to be the furnace fugitive emissions.
      The uncontrolled PM pollutant emissions were calculated using the furnace annual emissions for PM and the estimated control efficiency. The assumed fabric filter and scrubber control efficiencies ...are based on expected control efficiencies found on the EPA Clean Air Technology Center website .... [T]he assumed process fugitive capture efficiencies are based on visual observations of the fugitive capture during process operations.
      It was assumed that 92 percent of the furnace control device emissions are generated from the furnace and 8 percent of the furnace control device emissions are generated during tapping of the furnace. These assumptions are based on engineering judgment of the furnace operations and the tapping fugitive capture systems.

Comment 2-18: The EPA's cost estimates are not cost effective because they will result in only marginal reductions in PM emissions.

Commenter 0097-Industry Trades stated the EPA's proposal does not reasonably account for the costs associated with the emissions limits that the Agency suggests are "achievable through the application of the BSER." The EPA's own data and analyses demonstrate that the proposed 40 CFR part 60, subpart AAb requirements will result in marginal reductions in PM emissions that will be incredibly cost ineffective. The costs EPA ascribes to this proposal are conspicuously underestimated. The commenter further stated the EPA uses assumptions to weigh the costs and benefits of PM reductions associated with a change from 6 percent shop opacity to 0 percent shop opacity. But the EPA's data show that melt shops at facilities are not emitting 6 percent opacity; they are emitting an average of 0.14 percent opacity. This 0.14 percent average opacity is broadly consistent with the Associations' members experience and at the heart of our concerns with the proposed 0 percent shop opacity standard and its lack of necessity. Most facilities meet 0 percent opacity most of the time, but we have serious concerns about the technological feasibility (and cost) of a standard that requires all new, modified, and reconstructed facilities to achieve 0 percent opacity at all times. The difference between 0.14 percent [shop]opacity and 0 percent opacity is, therefore, exceptionally expansive (and expensive to achieve) from the standpoint of compliance and cost, but negligible from the perspective of environmental benefit in the form of reduced PM emissions.

Commenter 0097-Industry Trades said the EPA estimates the changes from 6 percent [shop] opacity to 0 percent opacity will allow small facilities to reduce PM emissions by 56 tons per year (tpy) at a cost of $1,100 per ton, medium facilities reduce PM emissions by 730 tpy at a cost of $1,100 per ton, and large facilities reduce PM emissions by 4,000 tpy at a cost of $1,000 per ton. By evaluating the PM reduction potential from 0.14 percent instead of 6 percent, small facilities reduce PM emissions by 1.2 tpy at a cost of $50,000, medium facilities reduce PM emissions by 3.4 tpy at a cost of $235,294 per ton, and large facilities reduce PM emissions by 7.8 tpy at a cost of $512,821 per ton.

Commenter 0095-Steel Co. added because the EPA has not appropriately calculated either the benefit or the cost, the Proposed Rule's 0 percent opacity limit violates the CAA section 111 requirement that a standard of performance "tak[e] into account the cost of achieving such reduction." (42 U.S.C. section 7411(a)(1))

Response 2-18: Analysis of BSER for the EAF NSPS required EPA to compare the NSPS rule being reviewed, i.e., 40 CFR part 60, subpart AAa, where 6 percent shop opacity is required, and the revised proposed BSER of a canopy hood in the melt shop that achieves 0 percent shop opacity. Therefore, 0.14 percent opacity was not used to represent EAF facilities in the calculations for the opacity limit that reflects BSER for melt shops and we disagree with the commenter that we should have used 0.14 percent. While the difference in emissions between 0.14 percent shop opacity may not be significant, the difference between 6 percent and 0 percent shop opacity is significant and, hence, the reason for revising the 40 CFR part 60, subpart AAa standard in the new NSPS subpart AAb. Because many EAF facilities are very close to the 0 percent shop limit during melting and refining (i.e., operation outside of periods of charging and tapping) even when the current rule requires 6 percent shop opacity, we expect that only small changes in hood and exhaust operation will be needed to reduce opacity from opacity levels such as 0.14 percent to 0 percent shop opacity and will not require an entirely new canopy hood, as in the proposal's cost estimates for the limit under BSER, which reflects a change in melt shop opacity from 6 percent to 0 percent.

The EPA agrees with the commenter that "most facilities can meet 0 percent [shop] opacity most of the time." This underscores the likelihood that canopy hoods will not be needed in most cases to comply with the revised opacity limits in NSPS subpart AAb.

Comment 2-19: Monitoring opacity during the "period established to have the greatest potential for uncaptured emissions to escape the melt shop" is inappropriate and has not been demonstrated as achievable.

Commenter 0095-Steel Co. said the requirement to measure opacity at "the period established to have the greatest potential for uncaptured emissions to escape the melt shop" as opposed to measuring at a specific time (i.e., melting and refining, charging, or tapping) is vague and would create a "floating standard" that cannot be consistently met due to uncertainty of when the period of highest emissions may occur. The EPA did not explain what process should be used to establish the period of greatest potential emissions. The commenter said facilities may not be able to predict the highest period of potential opacity. The periods of time with potential for high in-shop opacity, such as charging, may not correspond to either the highest potential for uncaptured emissions from the melt shop or the highest visible emissions exiting from the melt shop. Emissions are influenced by ambient conditions like wind (airflow), pressure, temperature, and humidity. These ambient conditions often have greater impact on emissions than the EAF heat cycle. The commenter said it may be impossible to predict on a daily basis when the highest potential emissions or opacity from the melt shop will occur.

For plants with multiple EAFs within the same building, the commenters said it could be impossible to predict the time period during which the highest opacity will occur because the EAFs operate independently from each other and may be at different stages of the production cycle at any given time. The commenters said this provision was especially problematic if the highest opacity occurs during charging because the duration of charging is short relative to other periods of the cycle and not predictable enough to be able to measure that period every day for the several consecutive minutes required by Method 9. The commenter said it was not feasible to identify any particular time period that consistently and predictably has the "greatest potential for uncaptured emissions to escape the melt shop" where multiple EAFs are operated.

Commenter 0095-Steel Co. said the EPA had not demonstrated that monitoring opacity during the "period established to have the greatest potential for uncaptured emissions to escape the melt shop" was "achievable" and "adequately demonstrated" as required for standards published under section 111(a)(1) of the CAA. To be achievable, the commenter asserted that "a uniform standard must be capable of being met under most adverse conditions which can reasonably be expected to recur and which are not or cannot be taken into account in determining the `costs' of compliance." (National Lime Ass'n v. EPA, 627 F.2d 416, 431, n. 46 (D.C. Cir. 1980). The EPA must also account for routine operating variability associated with performance of the system on which the performance the standard is based. (National Lime Ass'n v. EPA, 627 F.2d at 431-433; and 79 FR at 39245) The EPA must show how a standard is achievable under the range of relevant conditions that may affect the emissions anywhere in the country and cannot simply show that the standard was achieved at a model plant for a short period of time. (National Lime Ass'n v. EPA, 627 F.2d at 433; Electric Arc Furnaces and Argon-Oxygen Decarburization Vessels in Steel Industry -Background Information for Proposed Revisions to Standards, Preliminary , at 2-6, 2-7, June 1982).

In addition, commenter 0095-Steel Co. said the proposed provision increased the likelihood of missed opacity observations since facilities would have to schedule their opacity observations to coincide with anticipated production schedules. Operational issues occur that could result in a shutdown of an EAF for the rest of the compliance period. If the visible emissions observation had not already been taken, it would be impossible for the observation to be performed during the "greatest potential for uncaptured emission to escape the melt shop" because the highest opacity event would have already occurred. The commenter recommended the EPA define a specific period of the heat cycle for shop opacity measurements to be taken rather than requiring facilities to measure opacity at the "greatest potential" time period. The commenter urged the EPA to address how any opacity requirement will be met at melt shops with multiple EAFs within a single melt shop building.

Response 2-19: As shown in the opacity data in the EPA/EAF data set, which included data from 31 facilities and numerous test reports from more than a 5-year span, the 0 percent melt shop opacity standard during melting and refining is achievable in a range of conditions anywhere in the country and is capable of being met under most adverse conditions. For the full EPA response to the issues raised in this comment in regard to melt shop opacity, see the EAF NSPS preamble to the final rule, section IV.E.2, IV.B.2 and B.3, for the EPA responses to comments on this subject.

3.0	REVISIONS TO 40 CFR PART 60, SUBPARTS AA AND AAa

Comment 3-1: The current compliance demonstration requirements using the fan amperage and damper position monitoring in 40 CFR part 60, subparts AA and AAa are the best methods for assuring compliance with the melt shop NSPS standards.

Commenters 0096 and 0093-Steel Co. asserted that the existing fan amperage and damper position monitoring in combination with opacity observations are the best methods of assuring compliance with the NSPS standards for the melt shop. The commenters opposed the proposed new monitoring requirements, including:
 Installation of bag leak detection monitoring systems on all baghouses, including multi-stack baghouses;
 Monitoring and operational restriction for furnace static pressure monitoring based on 15-minute averages on all EAFs;
 Monitoring and operational restriction for volumetric flow rate or static pressure at each separately-ducted hood, based on 15-minute averages on all EAFs;
 Removal of the option for monitoring and operational restriction for fan amps;
 Adding inspections and maintenance requirements for holes or other openings in the melt shop building; and
 Mandate for shop opacity observations to be made during charging and tapping or during the period of the heat cycle that generates the greatest uncaptured emissions.

The commenters considered these new monitoring requirements to be unnecessary, expensive, and, some cases, impractical. The commenters said the existing monitoring requirements in 40 CFR part 60, subparts AA and AAa are adequate for demonstrating compliance with the standards. The commenters stated that the existing fan amperage and damper position monitoring have worked efficiently and effectively for many years and the proposed new monitoring would be less effective and would impose "extreme technical and engineering complications" on EAF plants.

Similarly, commenter 0097-Industry Trades urged the EPA to keep the current requirement in 40 CFR part 60, subparts AA, AAa for monitoring fan amperage in place, because they said this parameter directly correlates to the air flow to the control device, via the fan curve, unique to each site.

Response 3-1: For the EPA's response to issues raised in this comment in regard to the proposed BLDS requirement, see the EAF NSPS preamble to the final rule, section IV.E.2, BLDS Response. For the EPA's response to issues raised in this comment in regard to damper position monitoring, see the EAF NSPS preamble to the final rule, section IV.E.2, Damper Position Response. For the EPA's response to issues raised in this comment in regard to fan amperage monitoring: See the EAF NSPS preamble to the final rule, section IV.E.2, Fan Amperage Response. For the EPA's response to issues raised in this comment in regard to furnace static pressure monitoring based on 15-minute averages: See the EAF NSPS preamble to the final rule, section IV.E.2, Furnace Static Pressure Response. For the EPA's response to issues raised in this comment in regard to melt shop inspections: See the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Inspection Response. For the EPA's response to issues raised in this comment in regard to melt shop opacity, see the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Opacity Response/ For the EPA's response to issues raised in this comment in regard to volumetric flow and static pressure monitoring, see the EAF NSPS preamble to the final rule, section IV.E.2, Volumetric Flow and Static Pressure Response.

Comment 3-2: The CAA limits the EPA's NSPS revision authority to only new sources.

Commenter 0096-Steel Co stated there is no denying that the proposed monitoring and associated revisions to 40 CFR part 60, subparts AA and AAa are materially substantive and are not error corrections, clarifications, or clerical adjustments. These changes far exceed the EPA's legal authority to revise a NSPS applicable to existing sources. The commenter continued, the EPA's legal authority under the CAA is very limited as it relates to revisions to existing NSPSs. The 40 CFR part 60, subparts AA and AAa [proposed] revisions (BLDS, furnace static pressure monitoring, volumetric flow monitoring, etc.) all constitute an "emission limitation" as defined by the CAA and, therefore, constitute a "standard of performance." The EPA has no authority under the CAA to make any such revisions to a "standard of performance" unless those revisions are expressly applicable to "new sources." Commenter 0097-Industry Trades said the proposed changes to the melt shop monitoring requirements were arbitrary and violate the basic premise of NSPS that revisions apply only to facilities that qualify as new, modified, or reconstructed after proposal of the NSPS requirements.

Commenter 0095-Steel Co. also said the EPA does not have the authority to add new monitoring requirements for charging and tapping operations. The existing shop opacity monitoring in 40 CFR part 60, subpart AAa verifies efficiency of the DEC during normal operations. By expanding monitoring requirements to cover tapping and charging (a time period the furnace roof is rolled back, and the DEC control is not engaged), the EPA was creating new monitoring requirements designed to monitor a standard that was not included in the original rule. The proposed monitoring during charging and tapping cannot evaluate DEC capture efficiency, as the shop opacity observations were originally designed to do. Hence, the addition of the new monitoring, the commenter said, represents an unlawful revision to the existing NSPS standard.

Commenter 0097-Industry Trades was concerned the EPA was adding entirely new installation, monitoring, and maintenance requirement for charging and tapping furnace modes, including requirements for operators to install, calibrate, and maintain monitoring devices that continuously record the capture system damper position(s) and either the volumetric flow rate through each separately ducted hood or the rolling 15-minute average static pressure at each separately ducted hood. The commenter said these requirements are unnecessary and that they ignore the 1999 rulemaking that provided alternative monitoring methods. The commenter also argued the EPA failed to provide a reasonable explanation for these changes, had not explained why the additional monitoring is needed, had not explained the EPA's change in position from prior EAF steel NSPS rulemakings, and had neglected to account for any costs associated with the monitoring requirements.

Response 3-2: For the EPA's response to issues raised in this comment in regard to melt shop opacity, see the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Opacity Response and General Monitoring Response. For the EPA's response to issues raised in this comment in regard to melt shop opacity, see the EAF NSPS preamble to the final rule, section IV.E.2, General Monitoring Response.

Comment 3-3: Proposed changes to 40 CFR part 60, subparts AA and AAa are substantial and not "corrections and clarifications."

Commenter 0096-Steel Co. stated the EPA proposes substantial revisions to 40 CFR part 60, subparts AA and AAa for existing EAF. In the preamble, the EPA identifies these substantial revisions as being proposed to "clarify and refine the rule requirements by adding, removing, or revising ambiguous or outdated definitions, compliance, measurement, monitoring, and reporting requirements to "clarify the rule and enhance compliance and enforcement." The proposed revisions to 40 CFR part 60, subparts AA and AAa are anything but clarifications, refinements, or minor changes. The commenter further stated the EPA has inherent authority to correct mistakes or make other clerical revisions or clarifications to existing regulations. (e.g., Citizens Against Pellissippi Parkway Extension, Inc. v. Mineta, 375 F.3d 412, 416 (6th Cir. 2004) (citations omitted); Dun & Bradstreet Corp. Found. v. U.S. Postal Serv., 946 F.2d 189, 193 (2nd Cir. 1991) (citations omitted)). However, that the proposed monitoring and associated revisions to 40 CFR part 60, subparts AA and AAa are materially substantive and are not error corrections, clarifications, or clerical adjustments.

Commenters 0096 and 0095-Steel Co. stated that CAA section 111 states that "standards of performance or revisions thereof shall become effective upon promulgation." (42 U.S.C. section 7411(b)(1)(B)) Therefore, quite plainly, if 40 CFR part 60, subparts AA and AAa are finalized as proposed, the vast array of [proposed] new monitoring and operational restrictions will become effective on the date of final promulgation. However, it will obviously be impossible to comply on the date of final promulgation. As proposed, BLDS, pressure monitors and flow monitors would all need to be procured, installed, calibrated, and tested. This of course cannot happen immediately but would take a considerable amount of time (likely years). As the EPA has no statutory authority under CAA section 111 to extend that compliance date, the only conclusion is that the EPA has no legal authority to impose such substantive revisions in an existing NSPS.

Commenter 0097-Industry Trades said that steel companies would need time to comply with the shop opacity limits for charging and tapping, parametric monitoring requirements, and BLDS requirements. There must be sufficient time to allow the required equipment to be designed and/or engineered, procured, installed, tested, and connected to data systems. There must be sufficient time after installation for the new monitoring equipment to collect data in preparation for the compliance stack test. Several years will be needed to complete these tasks. The commenter recommended the EPA provide existing facilities complying with 40 CFR part 60, subparts AA or AAa at least three years to comply with the new NSPS requirements. The commenter also suggested the EPA include a provision allowing facilities to request additional time if needed.

Commenters 0097-Industry Trades and 0095-Steel Co. stated unless the EPA's CAA section 111 authority to impose new regulatory requirements is limited to "new sources" that commence construction, modification, or reconstruction after the date the proposed standards are published, the CAA section 111(b)(1)(b) requirement that "[s]tandards of performance or revisions thereof...become effective upon promulgation" (42 U.S.C. section 7411(b)(1)(B)) would be altogether unworkable. Substantial new regulatory requirements can perhaps feasibly take effect upon promulgation when the affected facilities are in the midst of construction, modification, or reconstruction. Such requirements are decidedly infeasible when the affected facility is not undergoing these types of changes or any changes at all. For instance, the commenter questioned how might an existing source that currently does not operate a BLDS timely comply with a requirement to install, calibrate, and operate a BLDS that is "effective upon promulgation."

Commenters 0097-Industry Trades stated in the case of the EPA's proposed new requirement to conduct VE monitoring during "charging and tapping, or during the period established to have the greatest potential for uncaptured emissions to escape the melt shop," (Proposed revised 40 CFR 60.273(d) and 60.273a(d) would be altered to require shop opacity observations to be taken "during charging or tapping, or during the period established to have the greatest potential for uncaptured emissions to escape the melt shop," rather than "when the furnace is operating in the meltdown and refining period.") as opposed to the period of "melting and refining," EPA's proposed change effectively represents an entirely new emissions standard. Courts recognized that changes in monitoring requirements can effectively change the stringency of a standard. (Clean Air Implementation Project v. EPA, 150 F.3d 1200, 2014 (D.C. Cir. 2000))

Commenters 0097-Industry Trades stated while some aspects of the EPA's proposal could be considered as clarifying existing requirements, none of the proposed changes to the existing monitoring requirements in 40 CFR part 60, subparts AA and AAa can be plausibly construed as clarifications. These are completely new obligations that impose entirely new requirements and conditions on sources' ability to operate. As the D.C. Circuit has acknowledged, "[c]onverting a periodic standard into a continuous one makes the standard more rigorous because ... continuous monitoring will capture all the fluctuations and variability inherent in emissions and thus increase each source's number of `violations.'" (Clean Air Implementation Project v. EPA, 150 F.3d 1200, 2014 (D.C. Cir. 2000))

Commenters 0097-Industry Trades and 0095-Steel Co. stated in its 1983 revisions to the NSPS, the EPA used its authority to establish a new 40 CFR part 60, subpart to ensure that new regulatory requirements and obligations were appropriately constrained to those new and modified facilities, the construction, modification, or reconstruction of which commenced after publication of the proposed revision. (49 FR 43838 (Oct. 31, 1984); the 1999 Direct Final Rule revising the NSPS made changes to both 40 CFR part 60, subparts AA and AAa to add alternative requirements for the monitoring of EAF capture systems in response to recommendations made by the Common Sense Initiative (CSI) subcommittee on iron and steel. The CSI was established by the Administrator to bring together affected stakeholders to find cleaner, cheaper, and smarter environmental management solutions. These editorial changes did not affect the applicability or requirements of the rule. 64 FR 10105 (Mar. 2, 1999). Similarly, the 2005 revisions to the NSPS were adopted in response to a petition from the Steel Associations and did not add or increase the stringency of requirements applicable to facilities subject to 40 CFR part 60, subparts AA or AAa. 70 FR 8523 (Feb. 22, 2005).)

Commenters 0097-Industry Trades stated this [proposed] standard requires agencies to "examine the relevant data and articulate a satisfactory explanation for its action including a `rational connection between the facts found and the choice made.'" That said, if a "new policy rests upon factual findings that contradict those which underlay [an agency's] prior policy," the agency "must" provide "a more detailed justification" for its action. (F.C.C. v. Fox Television Stations, Inc., 556 U.S. at 515) The same is true if the agency's "prior policy has engendered serious reliance interests that must be taken into account." (F.C.C. v. Fox Television Stations, Inc., 556 U.S. at 515) In such cases, in order to offer "a satisfactory explanation" for its action, as part of providing "a rational connection between the facts found and the choice made," ( Motor Vehicle Mfrs. Ass'n of U.S., Inc. v. State Farm Mut. Auto. Ins. Co., 463 U.S. at 43 (1983) (internal quotations omitted)) the agency must give "a reasoned explanation ... for disregarding facts and circumstances that underlay or were engendered by the prior policy." (F.C.C. v. Fox Television Stations, Inc., 556 U.S. at 515) Here, for the proposed NSPS revisions, the EPA provides no explanation at all for its decision to impose new regulatory requirements and obligations on existing facilities through proposed amendments to the existing 40 CFR part 60, subparts (AA and AAa).

Commenters 0097-Industry Trades stated the EPA fails to articulate the problem(s) that its proposed changes purport to solve. Nor does the EPA's record reflect that the Agency meaningfully accounted for or even considered how the 40 CFR part 60, subparts AA and AAa monitoring requirements engendered serious reliance interests among sources that already installed, calibrated, and currently operate emissions monitoring technology required by the existing NSPS standards; incorporated those monitoring requirements into their Title V permit; engineered and operate their affected facility and emissions control technology to ensure compliance as measured by those monitoring requirements; and reasonably expected that these compliance monitoring provisions would not change unless the sources modify or reconstruct their EAF or AOD.

Commenter 0096-Steel Co. stated, the EPA presumably has authority to add optional monitoring requirements to a NSPS, as it has done previously with 40 CFR part 60, subpart AAa. (64 FR 10105 (March 2, 1999); 70 FR 8523 (February 22, 2005)). Doing so arguably does not change the performance standard, since an existing source subject to the standard can continue complying with existing terms by simply "opting out" of new, optional terms. There would be no need to "retrofit" an existing source to meet such optional standards, thus avoiding a conflict with Congress' stated intent for the NSPS program. The changes that the EPA proposes to 40 CFR part 60, subparts AA and AAa, however, are not optional changes. Rather, they are all mandatory revisions that significantly alter a source's compliance obligations. Because the EPA's proposed revisions to AA and AAa would apply to existing sources, those revisions are unlawful and arbitrary. Thus, the EPA must remove all such changes prior to finalizing the proposed rule.

Commenter 0097-Industry Trades and 0095-Steel Co. stated the proposed rule misleadingly characterizes these fundamental revisions to the existing NSPS standards (40 CFR part 60, subparts AA and AAa) as "minor" and "editorial and clarifying changes." This is not an accurate description of the proposed revisions, which are, in fact, dramatic deviations from the current standards and would require substantial additional modifications to the melt shop facility and furnace operations. Given this mischaracterization of the proposed changes, we question the validity of the Paperwork Reduction Act (PRA) analysis for the proposed rule and urge the Office of Management and Budget (OMB) to review our forthcoming comments in detail to ensure an accurate understanding of the proposed rule requirements and their cost impacts.

Response 3-3: The changes that are being included after consideration of comments are in the nature of possible additional recordkeeping requirements that don't impose significant additional burden because they are timed with already existing recordkeeping requirements in these subparts. For the EPA's full response to the issues raised in this comment, see the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Opacity Response, and General Monitoring Response.

Comment 3-4: The EPA's revisions to 40 CFR part 60, subparts AA and AAa constitute prohibited retroactive rulemaking.

Commenters 0097-Industry Trades and Commenters 0096 and 0095-Steel Co. stated the monitoring and operational revisions (i.e., revisions to 40 CFR part 60, subpart AAa that delete the portion of 40 CFR section 60.273a(d) that exempts facilities from the 40 CFR section 60.274a(f) requirement; remove the option to monitor control system amperes in lieu of flow rate and remove the option to measure flowrate at the baghouse rather than through each separately ducted hood; proposed requirement for static pressure monitoring devices to be installed in the duct immediately downstream from the hood exit; changing the frequency of monitoring from once-per-shift to continuous; and add ASTM D7520-16 to 40 CFR, part 60, subparts AA and AAa) that the EPA proposes to 40 CFR part 60, subparts AA and AAa constitute retroactive rulemaking that is inconsistent with the CAA, multiple court decisions interpreting the Act, and the EPA's long-standing implementation of CAA section 111, generally and with respect to the EAF NSPS, specifically. The Administrative Procedures Act (APA) prohibits retroactive rulemaking, which occurs when a new rule "attaches new legal consequences to events completed before [the new rule's] enactment." (National Min. Ass'n v. Department of Labor, 292 F.3d 849, 860 (D.C. Cir 2002)) Courts have held that the CAA gives no indication that Congress provided the EPA with the authority to implement rules retroactively. (Sierra Club v. Whitman, 285 F.3d 63, 68 (D.C. Cir. 2002)) The EPA should rescind those proposed NSPS Revisions that would retroactively impose new requirements on sources that have not been constructed, modified, or reconstructed on or after May 16, 2022.

Commenters 0097-Industry Trades stated a provision operates retroactively when it "impair[s] rights a party possessed when he acted, increase[s] a party's liability for past conduct or impose[s] new duties with respect to transactions already completed." (Landgraf v. USI Film Prods., 511 U.S. 244, 280 (1994))

Commenters 0097-Industry Trades and 0095-Steel Co. stated agencies are permitted to change policy positions and adopt new regulatory interpretations, but they cannot do so in the manner the EPA is proposing. (F.C.C. v. Fox Television Stations, Inc., 556 U.S. 502 (2009)) New and changed policy positions are subject to the same judicial review standards (F.C.C. v. Fox Television Stations, Inc., 556 U.S. 502 (2009) at 515 ("The [APA] makes no distinction ... between initial agency action and subsequent agency action undoing or revising that action.")) under which "a reviewing court shall ... hold unlawful and set aside agency action, findings, and conclusions found to be ... arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law." (5 U.S.C. section 706(2)(A))

Commenters 0095-Steel Co. and 0097-Industry Trades stated the EPA cannot rely on other rulemakings or court decisions (such as Title V or 40 CFR section 112 (e.g., MACT standards)) for determining whether increased monitoring constitute new substantive control requirements.

Response 3-4: We are not finalizing any changes to 40 CFR part 60, subparts AA and AAa that require the purchase of equipment and other significant costs. The changes that are being included after consideration of comments are in the nature of possible additional recordkeeping requirements that don't impose significant additional burden because they are timed with already existing recordkeeping requirements in these subparts. Further, as indicated in the preamble, facilities already complying with 40 CFR part 60, subparts AA and AAa will not be held responsible for past conduct that may contravene the finalized updates to 40 CFR part 60, subparts AA and AAa, and thus, these revisions will not have a retroactive effect. Rather, the compliance date for all of the updates to 40 CFR part 60, subparts AA and AAa is 180 days from the effective date of the final rule amendments for facilities complying with 40 CFR part 60, subparts AA and AAa. For the EPA's full response to the issues raised in this comment, see the EAF NSPS preamble to the final rule, section IV.E.2, General Monitoring Response.

Comment 3-5: The EPA cannot change monitoring requirements for 40 CFR part 60, subparts AA and AAa for charging and tapping operations and the decision is inconsistent with prior rulemakings.

Commenters 0095-Steel Co. and 0097-Industry Trades opposed the proposed changes to the monitoring requirements for the melt shop because they would increase the stringency of the existing opacity standard and associated monitoring requirements.

Commenter 0095-Steel Co. said that charging and tapping typically have higher opacity than the melting and refining phase. For 40 CFR part 60, subpart AA, the EPA initially set different opacity limits depending on the operations, with 0 percent opacity standard during most operations, 20 percent opacity during charging, and 40 percent opacity during tapping. (40 FR 43850 and 43853, September 23, 1975.) In 1999, the shop opacity was decreased to a uniform 6 percent opacity standard in 40 CFR part 60, subparts AA and AAa to ensure that compliance could be demonstrated by opacity measurements taken only during the melting and refining period. (64 FR 10105 and 10107, March 2, 1999) Since the shop opacity is based on an arithmetic average of 24 Method 9 observations and Method 9 monitoring is also based on an average of measurements, limiting observations to only the highest periods of potential opacity skews the average measurement higher than if it were to account for the average opacity throughout all heat cycles. Commenter 0097-Industry Trades said the EPA was shifting the point of compliance from the time period when the primary emission control is operational (during melting and refining when the DEC is in place) for a long duration during the heat cycle to a much shorter time period where fugitive emissions may be greater.

Commenter 0097-Industry Trades said that some facilities may not be able to comply with the proposed 40 CFR part 60, subpart AAa melt shop opacity standard and may have to re-engineer how they control emissions within the melt shop. At most EAF steel mills, the primary emission control system (e.g., DEC) is operational only during the melting and refining phase. The DEC is disconnected during charging and tapping when the furnace roof is swung open to allow the introduction of scrap metal and other feedstocks during charging or to allow pouring of molten metal from the EAF during tapping. By measuring shop opacity during melting and refining, the EPA adopted a shop opacity standard for 40 CFR part 60, subpart AAa facilities for the period when the primary emissions control system was operational. Fugitive emissions that escape from the EAF during melting and refining (as well as charging and tapping) are controlled by secondary pollution equipment, such as canopy hoods and scavenger ducts.

Commenter 0095-Steel Co. said the EPA cannot justify monitoring solely during periods with higher potential for opacity based on the EPA's prior assertion in the 1983 40 CFR part 60, subpart AAa rulemaking that the 6 percent opacity standard can be met during charging and tapping based on "full heat cycle" data, because there is no evidence in the record that the test data relied on over 40 years ago actually included complete charging and tapping events and even if they did, an average across solely higher opacity periods would be higher than an average across the "full heat cycle" If measurements account only for the highest periods, the commenter asserted the standard effectively becomes more stringent.

Similarly, commenter 0097-Industry Trades noted that in the 1982 40 CFR part 60, subpart AAa rulemaking the EPA said emissions during charging are more difficult to control than during melting and refining. The EPA has also acknowledged in previous rulemakings that the level of potential fugitive emissions may be greater during charging and tapping because the DEC is not in use and for most mills the DEC cannot be used during charging and tapping events. Requiring fugitive emission observations when the DEC is not engaged or when emissions otherwise "have the greatest potential" to be uncaptured is at odds with the original purpose of viewing the shop opacity observation requirement as a means to ensure proper operation of the primary control system. The commenter said the EPA appeared be using melt shop opacity monitoring as a means of enforce a fugitive emissions limit and as a surrogate for making the melt shop a total enclosure. The proposed new monitoring requirements are not an indicator of the proper operation of the primary control system but are instead a fundamental change to the purpose, substance, and stringency of the existing shop opacity standard.
Response 3-5: For the EPA's response to the issues raised in this comment in regard to melt shop opacity, see the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Opacity Response.

Comment 3-6: Monitoring opacity during charging and tapping is inappropriate.

Commenter 0095-Steel Co. disagreed with measuring opacity during the charging and tapping of the EAF. The commenter noted that for many EAFs, charging may be the time period with the greatest visible emissions inside the melt shop due to the rapid thermal shift involved in charging and because the DEC may not be operating with furnaces designed for open top charging. The commenter said that charging period does not necessarily correspond to the highest visible emissions exiting from the shop. Averages taken during charging may be skewed higher than an average taken across all heat cycles. The charging period only occurs one time per cycle, varies in duration, and can often be as short as 30 seconds. The short duration of any opacity associated with charging is not representative of average EAF opacity emissions or environmental performance.

Similarly, commenter 0091-State was concerned monitoring opacity during charging and tapping would not demonstrate proper operation of the EAF or result in emissions reductions because charging and tapping events occur for only a few minutes at a time.

Response 3-6: For the EPA's response to some of the issues raised in this comment in regard to melt shop opacity, see the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Opacity Response. In addition, the EPA acknowledges that the data obtained through the CAA section 114 requests only consisted of data collected during melting and refining, which is the time period required to test opacity in the current EAF NSPS rules. Therefore, we are allowing in the final rule for 40 FCR part 60, subpart AAb the current rule limit of 6 percent opacity to apply during charging and tapping, and retaining the proposed 0 percent melt shop opacity during melting and refining. We estimate that this change will decrease the emision reductions in the proposed rule by approximately 15 percent. Details of the changes to emissions and reductions for the final rule are discussed in the memorandum titled "Particulate Matter Emissions from Electric Arc Furnace Facilities," hereafter called the "Emissions Memorandum," and memorandum "Cost and Other Analyses to Determine BSER for PM Emissions and Opacity from EAF Facilities," hereafter referred to as the "Cost Memorandum." Both memoranda have been updated for the final rule and are located in the docket for this rule (Docket No. EPA-HQ-OAR-2002-0049). Note that we also are revising the method used to measure opacity during charging due to its short time period. See Comment #2-7 above for more details.

Comment 3-7: The proposed volumetric flow and static pressure monitoring requirements are unworkable.

Commenters 0096 and 0093-Steel Co. and 0097-Industry Trades opposed the proposed requirement to measure volumetric flow or static pressure at each ducted hood to obtain 15-minute averages. Commenter 0096-Steel Co. said that this monitoring would be unworkable due to the complex structure of many melt shops. As an example, the commenter noted that the Mansfield Works melt shop contains two EAFs, an Argon-Oxygen Decarburization (AOD), and a LMF, and is controlled by two baghouses. The two EAFs and AOD are all subject to 40 CFR part 60, subpart AAa requirements, while the ladle metallurgy furnace is not. The commenter said it would be impracticable to establish a minimum volumetric flow rate or static pressure at a facility with these complex set of overlapping operations. The commenter added that the melt shop operations are variable, and a 15-minute average would not adequately capture the variability. The commenter added that technical complications with flow monitors used in areas of extreme heat or in dusty conditions would increase the need for re-calibrations and likely lead to periodic failures of the monitors. Some shops (e.g., Butler Works) have long runs of ductwork on the roof of the melt shop that pose access and safety difficulties for installing and maintaining flow monitors. Depending on the technical specifications for where flow or pressure monitors must be installed, redesigns and retrofits of hoods and ductwork could be necessary.

Commenters 0096, 0093, and 0098-Steel Co. said they are not aware of any melt shops that currently effectively measure furnace static pressure based on 15-minute averages, as the harsh environment in the furnace makes pressure monitoring difficult. Commenter 0096-Steel Co. noted that their experience monitoring pressure in furnaces showed it was difficult to generate useful data on furnace operation and capture efficiency. This commenter suggested measurement of volumetric flow or static pressure at each separately ducted hood or furnace pressure would not generate useful data that will enable an understanding of how well the capture system is operating.

Commenters 0093 and 0098-Steel Co. said that maintaining flow meters in the highly abrasive and corrosive EAF ducts is difficult and that equipment fouling and damage is a problem. Commenter 0098-Steel Co. said that in their experience the monitoring equipment was "virtually impossible to operate and maintain" because the monitoring equipment does not survive. Commenter 0093-Steel Co. said that few EAFs are equipped with volumetric flow rate equipment due to the high particulate loadings and corresponding fouling. Where the volumetric flowrate monitors are present, the flowrate monitors are typically post-baghouse to take advantage of the cleaner air stream or a single volumetric flowrate monitoring system is installed in a common duct. Requiring a volumetric flowrate monitoring device in each separately ducted hood would be difficult to maintain due to the highly abrasive exhaust prior to the control device.

Commenter 0097-Industry Trades stated that the 1999 rulemaking allowed daily visible emissions monitoring as an alternative to installation of a furnace static pressure monitoring device. In that rulemaking, the EPA recognized that furnace static pressure monitors presented practical problems with maintenance and installation. The commenter said the EPA recognized that daily visible emissions observations were as good or better an indicator of control device capture efficiency. The free space above an EAF is subject to severe conditions of high temperature and dust. Several owners and operators have had problems with frequent plugging of the pressure monitoring sensor. Due to the location of the sensor, maintenance and repair can be both difficult and dangerous. The EPA does not address the difficulties with installing, operating, and maintaining monitors on a continuous basis in the harsh furnace environment. Commenter 0097-Industry Trades said that any requirement for furnace pressure monitoring would have to provide for the regular downtime that would be needed to maintain the monitors. In addition, the electronics that would be used to transmit the pressure data on a continuous basis to a data recorder must be able to survive the same harsh environment. These issues are the primary reason most EAFs do not use furnace static pressure monitors to comply with the existing requirements.

Commenter 0097-Industry Trades stated that the significant costs of installing and maintaining furnace static pressure monitors were not considered in the proposal.

All commenters supported the existing approach that uses a combination of damper positions and fan motor amperes because they said it provides an adequate assurance of compliance.

Response 3-7: For the EPA's response to this comment, see the EAF NSPS preamble to the final rule, section IV.E.2, Furnace Static Pressure Response and General Monitoring Response.

Comment 3-8: The EPA should not remove options to monitor either control system fan motor amperes or volumetric flow rate at the control device inlet (baghouse) or to replace with requirement to monitor volumetric flow rate or static pressure at each separately ducted hood.

Commenter 0095-Steel Co. added that using amperage monitoring to monitor flow rate is more efficient because the amperage measurements are proportionally related and monitoring the fans and motors is required anyway to evaluate evacuation system performance, operational reliability, power management, and preventative maintenance and replacement projections. The commenter said that 40 CFR part 60, subpart AAa has always allowed monitoring of amperage and the alternative options to monitor flowrate through each duct or flowrate at the control device inlet were added as alternative methods in 1999 to increase compliance flexibility.

Response 3-8: For the EPA's response to this comment, see the EAF NSPS preamble to the final rule, section IV.E.2, General Monitoring Response.

Comment 3-9: Recommended changes to the proposed volumetric flow monitoring provisions.

Commenter 0097-Industry Trades opposed the proposed requirements for direct flow measurements, but recommended changes be made if the proposed provisions are incorporated into the final rulemaking. First, the EPA should allow placement of flow meters either in the clean side of the baghouse (for those baghouses that have stacks) or in the inlet side of the baghouse (for baghouses without stacks). Second, an 8-hour (or once-per-shift) averaging of the flow should be allowed to compare against set points to determine deviations. Flow rates to the baghouse can vary considerably based on heat-to-heat variations due to the dynamic nature of EAF operations. The EPA's proposal to assess flow on a 15-minute basis, the commenter said, will not capture the full extent of variability of the flows to the baghouse.

Response 3-9: For the EPA's response to this comment, see the EAF NSPS preamble to the final rule, section IV.E.2, General Monitoring Response.

Comment 3-10: The EPA conducted no cost analysis for its proposed changes to 40 CFR part 60, subparts AA and AAa.

Commenters 0097-Industry Trades and 0095-Steel Co. stated the EPA's Economic Impact Analysis considered "costs and emissions impacts" only associated with the proposed 40 CFR part 60, subpart AAb. The EPA assumes its changes to 40 CFR part 60, subparts AA and AAa will have no impact on emissions and will result in no new costs.

Commenters 0097-Industry Trades continued as such, while "the requirement that an agency provide a reasoned explanation for its action would ordinarily demand that it display awareness that it is changing position," (F.C.C. v. Fox Television Stations, Inc., 556 U.S. 502, 515) the Agency's proposed NSPS Revisions reflect no acknowledgement that the EPA is proposing a fundamental change that is both substantive and costly.

Commenter 0097-Industry Trades stated what the EPA labels as "editorial and clarifying changes," (87 FR at 29721 and 29726) are, in reality, substantive new requirements with real costs and burdens that are centrally relevant to a reasoned consideration of whether to impose regulatory burdens on facilities under 40 CFR part 60, subparts AA and AAa. (Michigan v. EPA, 135 S.Ct. 2699) The EPA failed to engage in reasoned decision-making by wholly ignoring the costs of these proposed new requirements.

Commenter 0097-Industry Trades stated the following are some of the proposed new 40 CFR part 60, subparts AA and AAa requirements that the EPA impermissibly excluded from its cost and economic impact analyses:

 Conduct daily observations of "Shop Opacity" "during charging or tapping, or during the period established to have the greatest potential for uncaptured emissions to escape the melt shop;" (Revised proposed 40 CFR 60.273(d), 60.273a(d), and 60.273b(d))
 Monitor and record on a continuous basis the rolling 15-minute average furnace static pressure; (Proposed 40 CFR 60.274(b)(1)(i), 60.274a(b)(1)(i), and 60.274b(b)(1)(i)).
 Install, calibrate, and maintain a monitoring device that continuously records damper position(s); and, (Proposed 40 CFR 60.274(b)(1)(ii), 60.274a(b)(1)(ii), and 60.274b(b)(1)(ii)).
 Install, calibrate, and maintain a monitoring device that continuously records on a rolling 15-minute average basis either the volumetric flow rate through each separately ducted hood or the static pressure at each separately ducted hood, (Proposed 40 CFR 60.274(b)(1)(iii), 60.274a(b)(1)(iii), and 60.274b(b)(1)(iii).)
 Install and utilize BLDS on all baghouses, rather than only for single stack fabric filters. (Proposed 40 CFR 60.273(c ) and (e), and 60.273a (c) and (e)).

Commenter 0095-Steel Co. stated promulgating such revisions without assessment of cost would also be unlawful for the independent reason that CAA section 111 requires the EPA to "tak[e] into account the cost of achieving such reduction and any non-air quality health and environmental impact and energy requirements" when issuing any standard under CAA section 111. (42 U.S.C. section 7411(a)(1)) And although the EPA does have some discretion when considering costs, "the law does require the EPA to `cogently explain why it has exercised its discretion in a given manner'." (Nat'l Parks Conserv'tion Ass'n v. EPA, 788 F.3d 1134, 1142-43 (9th Cir. 2015) (internal citations omitted) (in regional haze context, striking down a BART determination where the EPA provided no supporting rationale for why one cost level was acceptable, but another was not).) Furthermore, although the EPA is entitled to make assumptions in its cost analyses, it has a "duty to examine [and justify] key assumptions as part of its affirmative `burden of promulgating and explaining a nonarbitrary, non-capricious rule... '" (Appalachian Power Co. v. EPA, 135 F.3d 791, 818 (D.C. Cir. 1998).) and the EPA may not "promulgate rules on the basis of inadequate data, or on data that, to a critical degree, is known only to the agency." (Portland Cement Ass'n v. Ruckelshaus, 486 F.2d 375, 391-93 (D.C. Cir. 1973)) The EPA's failure to consider any costs associated with its proposed revisions to 40 CFR part 60, subparts AA and AAa runs afoul of these principles.

Commenter 0095-Steel Co. added that the EPA failed to evaluate costs associated with enclosing melt shops and that it was unlawful for the EPA to incorporate the building inspection and maintenance requirements into 40 CFR part 60, subparts AA, AAa, or proposed AAb without completing a full analysis of the costs.

Response 3-10: For the EPA's response to this comment, see the EAF NSPS preamble to the final rule, section IV.E.2, General Monitoring Response.

Comment 3-11: The EPA did not provide a rational explanation for changing the monitoring frequency for fan amperage and damper positions for 40 CFR part 60, subparts AA and AAa from once-per-shift to continuous.

Commenters 0095-Steel Co. and 0097-Industry Trades opposed changing the frequency of monitoring from once-per-shift to continuous. Commenter 0097-Industry Trades said that the EPA has failed to provide a rational explanation for changing the monitoring frequency for fan amperage and damper positions. The commenter added the EPA had failed to explain how continuously recording damper positions provides assurance for meeting an ambient air limit. They said the proposed provision imposes more data reporting requirements on the industry for no additional emissions reduction or monitoring benefit.

Response 3-11: For the EPA's response to issues raised in this comment in regard to damper position monitoring, see the EAF NSPS preamble to the final rule, section IV.E.2, Damper Position Response. In addition, the purpose of the CAA section 111 standards is not to meet ambient air limits but to establish emission limitations that will apply to new sources or sources that are modified or reconstructed.

Comment 3-12: The EPA should define the term "material impact" (40 CFR 60.274(e), 60.274a(d)) in terms of opacity limits and only require repairs when holes result in noncompliance with the opacity standards.

Commenter 0095-Steel Co. recommended the EPA better define a "material impact" on the capture system because they said the phrase was too vague. Any airflow changes, they said, may theoretically impact capture efficiency to some extent, but fluctuations that do not affect the compliance of the facility with the substantive emission and opacity standards should not be prohibited. The EPA should define material impacts in terms of opacity limits by revising 40 CFR part 60, subparts AA, AAa, and AAb to only require repairs to openings that lead to noncompliance with the opacity standards.

Response 3-12: See the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Inspection Response. For the EPA's response to issues raised in this comment in regard to melt shop opacity, see the EAF NSPS preamble to the final rule, section IV.B.2.

Comment 3-13: The proposed BLDS requirements are unworkable for multiple-outlet baghouses that allow alternative monitoring.

Commenter 0096-Steel Co. disagreed with the proposed new requirements for BLDS. The commenter said the EPA failed to provide adequate explanation for the proposed changes, which the commenter said made it difficult to provide comments. The Mansfield Works and Steelton plant currently comply with 40 CFR part 60 subpart AAa using the shop opacity observations and monitoring fan amperages and damper positions. The Butler Works demonstrates compliance using an alternate monitoring plan under which the plant performs additional shop opacity observations and monitors fan amperage but not damper positions. None of these mills employ BLDS. The commenter noted the Butler Works, Mansfield Works and Steelton plant all have multiple-outlet baghouses. The number of bag leak detection devices needed to monitor the baghouse outlets under the proposed rule would be 20, 28 and 34 devices, respectively, for the three plants. Due to false alarms from BLDS, industry commonly use backup bag leak detection devices. Hence, the number of BLDS would be 40, 56 and 68 devices, respectively, for each of the three plants. The commenter added that operating so many BLDS would be burdensome and add operational complications that the EPA did not recognize in the proposal.

Response 3-13: For the EPA's response to this comment, see the EAF NSPS preamble to the final rule, section IV.E.2, BLDS Response. In addition, if facilities have an alternative monitoring plan, revisions to the corresponding monitoring section(s) of 40 CFR part 60 subparts AA, AAa, and AAb will not affect these plans.

Comment 3-14: Requirement to use BLDS on all baghouses reverses prior Agency decisions.

Commenter 0097-Industry Trades opposed the proposed new requirement to install BLDS on all baghouses. When adopted in 1975, 40 CFR part 60 subpart AA originally required baghouse opacity to be monitored using a COMS. However, the 40 CFR part 60 subpart AAa amendments eliminated the requirement to use a COMS for emissions from modular, multiple-stack, negative-pressure or positive-pressure fabric filters provided the facility conducts daily Method 9 observations. The EPA determined that the use of visible emission standards was "technically sound and provides the most practical and inexpensive means to ensure that affected facilities are properly maintained and operated." (49 FR 43838 and 43840, October 31, 1984). The commenter also noted that the EPA acknowledged in the 1984 rulemaking that the capital and operating costs to install multiple COMS was unreasonable for modular, multi-stack baghouses. Amendments to the EAF steel NSPS in 2005 allowed mills to use a BLDS on single stack baghouses as an alternative to using COMS. (70 FR 8523, February 22, 2005). Facilities using BLDS were required to have site-specific monitoring plans, adopt corrective action plans, and conduct daily Method 9 observations when the EAF was in operation.

The commenter added that the EPA's proposal requiring facilities to install and operate BLDS ignores the reasons why the BLDS requirement was limited to single-stack fabric filter baghouses. BLDS have never previously been required for modular, multi-stack baghouses. BLDS are feasible for a baghouse that has one stack and requires only one BLDS. However, some EAF baghouses do not have a stack at all but have exhaust monitors from each compartment in the roof of the baghouse. It is not uncommon for baghouses to have dozens of compartments; therefore, facilities may need dozens of BLDS to monitor each individual compartment. This would substantially increase installation and operating costs. In 2005, the EPA determined that BLDS in conjunction with visible emission observations were appropriate for single-stack baghouses as an alternative to COMS. (70 FR 8523, February 22, 2005). The EPA did not propose BLDS on modular, multi-stack baghouses in 2005 because these facilities were exempt from the COMS requirement under the 1984 rulemaking due to the impracticality and unreasonableness of requiring a COMS on such are large number of stacks. Requiring multiple BLDS for all baghouses. The commenter said it was inconsistent with prior determinations to require multiple BLDS for all baghouses. The proposed change is particularly unreasonable because the EPA provides no explanation for it.

Response 3-14: For the EPA's response to the BLDS issue in this comment, see the EAF NSPS preamble to the final rule, section IV.E.2, BLDS Response.

4.0	MONITORING AND COMPLIANCE

4.1 Monitoring Requirements in Proposed 40 CFR Part 60, Subpart AAb

Comment 4-1: The current compliance demonstration requirements using the fan amperage and damper position monitoring [in 40 CFR part 60, subparts AA and AAa] are the best methods for assuring compliance with the melt shop NSPS standards, and therefore oppose the proposed new monitoring requirements for [40 CFR part 60, subpart] AAb.

Commenters 0093 and 0096-Steel Co. asserted that the existing fan amperage and damper position monitoring in combination with opacity observations are the best methods of assuring compliance with the NSPS standards for the melt shop.

The commenters opposed the proposed new monitoring requirements for [40 CFR part 60, subpart] AAb:
 Installation of bag leak detection monitoring systems on all baghouses, including multi-stack baghouses;
 Monitoring and operational restriction for furnace static pressure monitoring based on 15-minute averages on all EAFs;
 Monitoring and operational restriction for volumetric flow rate or static pressure at each separately-ducted hood, based on 15-minute averages on all EAFs;
 Removal of the option for monitoring and operational restriction for fan amps;
 Adding inspections and maintenance requirements for holes or other openings in the melt shop building; and
 Mandate for shop opacity observations to be made during charging and tapping or during the period of the heat cycle that generates the greatest uncaptured emissions.

The commenters considered these new monitoring requirements to be unnecessary, expensive, and, some cases, impractical. The commenters said the existing monitoring requirements (in 40 CFR part 60, subparts AA and AAa) are adequate for demonstrating compliance with the standards. The commenters stated that the existing fan amperage and damper position monitoring have worked efficiently and effectively for many years and the proposed new monitoring would be less effective and would impose "extreme technical and engineering complications" on EAF plants.

Similarly, commenter 0097-Industry Trades urged the EPA to keep the current requirement for monitoring fan amperage in place, because they said this parameter directly correlates to the air flow to the control device, via the fan curve, unique to each site.

Response 4-1: For the EPA's response to the issues raised in this comment in regard to on BLDS, see the EAF NSPS preamble to the final rule, section IV.E.2, BLDS Response. For the EPA's response to issues raised in this comment in regard to damper position monitoring, see the EAF NSPS preamble to the final rule, section IV.E.2, Damper Position Response. For the EPA's response to issues raised in this comment in regard to fan amperage monitoring: See the EAF NSPS preamble to the final rule, section IV.E.2, Fan Amperage Response. For the EPA's response to issues raised in this comment in regard to furnace static pressure monitoring based on 15-minute averages: See the EAF NSPS preamble to the final rule, section IV.E.2, Furnace Static Pressure Response. For the EPA's response to issues raised in this comment in regard to melt shop inspections for 40 CFR part 60, subpart AAb: See the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Inspection Response, as well as EPA's response in section IV.E.2 to the proposed requirements in 40 CFR 60.274b(d) for subpart AAb in regard to allowing operators discretion in an inspection as to what issues "materially impact" the capture system performance. For the EPA's response to issues raised in this comment in regard to melt shop opacity: See the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Opacity Response. For the EPA's response to the comment concerning whether the opacity standards in 40 CFR part 60, subpart AAb should apply at all times: See the EAF NSPS preamble to the final rule, section IV.D.2, in regard to EPA's response for 40 CFR part 60, subpart AAb. For the EPA's response to issues raised in this comment in regard to volumetric flow and static pressure monitoring, see the EAF NSPS preamble to the final rule, section IV.E.2, Volumetric Flow and Static Pressure Response. See also EPA's response to issues raised in this comment in the EAF NSPS preamble to the final rule, section IV.E.2, General Monitoring Response.

Comment 4-2: Requiring both static pressure monitoring and shop opacity observations for the melt shop is unnecessary. Facilities should be given the flexibility to monitor either static pressure or opacity.

Comment 0095-Steel Co. opposed the [portion of the new EAF NSPS rule, 40 CFR part 60, subpart AAb] that removed the previous exemption for facilities to install a furnace static pressure monitor [as described in 40 CFR 60.273a(d)] provided the facility conducts regular shop opacity monitoring. The commenter argued that removing the flexibility to select a compliance method is inconsistent with the EPA's prior statements made in the 1999 revision of 40 CFR part 60, subpart AAa in which the EPA acknowledged that furnace static monitors created operational and safety issues in some EAFs and that static pressure monitors are less reliable than shop opacity observations. (64 FR 10105 and 10106, March 2, 1999). The commenter said they agreed with the EPA's 1999 statements and added that in their experience most facilities use opacity monitoring because they have not overcome the technical problems associated with furnace static pressure monitors. The commenter said they considered opacity monitoring to be a more direct means of monitoring capture effectiveness of the DEC and that the EPA has not provided any rationale or support to justify reversing the Agency's prior decision by requiring facilities to install and operate a furnace static monitor.

Similarly, commenter 0093-Steel Co. noted that proposed 40 CFR 60.274b(f) and (g) begin with the phrase "Except as provided in 60.273b(d)". The commenter said that proposed 40 CFR 60.273b(d) requires shop opacity monitoring for all shops and does not say that a furnace static pressure device is not required if shop opacity is conducted. The commenter also said that their experience with furnace static pressure monitoring has shown them to be highly unreliable and subject to frequent fouling. The commenter recommended that proposed 40 CFR 60.274b(f) and (g) be deleted or made optional.

Response 4-2: For the EPA's response to issues raised in this comment in regard to furnace static pressure monitoring based on 15-minute averages: See the EAF NSPS preamble to the final rule, section IV.E.2, Furnace Static Pressure Response, as well as revised 40 CFR 60.273b(d) in the final rule for 40 CFR subpart AAb.

In addition, we note that in 1999 40 CFR part 60, subpart AA was amended to be consistent with 40 CFR part 60, subpart AAa to allow the pressure monitoring sensor to be moved to a location that would potentially result in fewer maintenance issues due to plugging, as follows:

      64 FR 10106: Concerns were raised to EPA (and the Common Sense Initiative) regarding the use of a pressure monitoring system in the free space above an EAF when it is equipped with a direct shell evacuation system. The free space above an EAF is subject to severe conditions of high temperature and dust. Several owners and operators have had problems with frequent plugging of the pressure monitoring sensor. Due to the location of the sensor, maintenance and repair can be both difficult and dangerous. Industry representatives sought a more practical means of monitoring.

      64 FR 10107: The EPA amended 40 CFR part 60, subpart AA in 1999 to allow owners or operators to locate the furnace static pressure monitor in the DEC duct prior to the introduction of ambient air. This change is consistent with the requirements in 40 CFR part 60, subpart AAa, and provided greater flexibility in locating the pressure sensors where plugging may not be as serious of a problem.

Therefore, we believe the amendments in1999 that allowed relocation of the furnace static pressure monitor provided a solution to the plugging issue that made furnace static pressure monitoring less reliable, as the commenter asserts.

The EPA proposed requiring continuous monitoring of furnace static pressure because it would provide information about capture at the EAF on a more frequent basis and because many facilities already use this equipment. However, because using this monitoring method/compliance option would involve the purchase of equipment not currently available or installed at all subject facilities, we agree with the commenters who stated that these changes should not be made as corrections nor included in 40 CFR part 60, subparts AA, AAa, and AAb. Therefore, the requirement for continuous furnace static pressure monitoring is not required in the final rules for 40 CFR part 60, subparts AA, AAa, and AAb because of potential significant cost implications.

In addition, it is stated in the final rule at 40 CFR 60.273b(d) that furnace static pressure monitoring is not required if opacity is performed. Lastly, it is stated in the final rule at 40 CFR 60.274b(f) that facilities using a DEC system can measure opacity instead of using a furnace static pressure monitor.

Comment 4-3: The EPA should clarify how the proposed new monitoring requirements improve compliance demonstration.

Commenter 0091-State said it was unclear how the additional monitoring requirements in the proposed [40 CFR part 60, subpart AAb] rule will improve data or accuracy in demonstrating compliance with applicable requirements. The proposed NSPS 40 CFR part 60, subpart AAb requires monitoring of parameters that are not required to be monitored under the existing NSPS 40 CFR part 60, subparts AA and AAa standards. The commenter recommended the EPA explain the benefits of new monitoring techniques and additional monitoring parameters. The monitoring requirements should provide enough data to accurately demonstrate compliance with applicable requirements. The commenter added that the EPA must consider the cost to air agencies and facilities and associated benefits to compliance before requiring additional monitoring. Additional monitoring with no clear benefit, is burdensome for both regulated facilities and permitting authorities due to additional equipment, maintenance, and operator costs.

Response 4-3: See the responses to Comment #4-1 above for same responses to this comment. In addition, we have removed the proposed requirements that would significantly impact EAF facility operating costs in the situations where existing sources are making modifications or being reconstructed in a manner such that compliance with 40 CFR part 60, subpart AAb is required. See EPA's response to issues raised in this comment in the EAF NSPS preamble to the final rule, section IV.E.2, General Monitoring Response.

Comment 4-4: The EPA should allow more flexibility by letting facilities decide where static pressure monitoring devices are installed. Installation "in the duct immediately downstream of the hood exit" may not be the best location.

Commenter 0095-Steel Co. said they opposed the requirement directing facilities to install the static pressure monitoring device immediately downstream of the hood exit. The commenter stated the EPA had not demonstrated the feasibility of installing the static pressure monitoring devices in the duct immediately downstream of the hood exit and had also not demonstrated this as the best location. The commenters recommended that the rule allow facilities more flexibility in selecting the best location for the static pressure monitoring devices and added that the EPA had not provided any reason why performance, maintenance and health and safety considerations should not be considered when selecting the location.

The commenter added that the EPA provides flexibility for the furnace static pressure monitor, which may be installed "in any appropriate location in the EAF or DEC duct prior to the introduction of ambient air such that reproducible results will be obtained." The EPA has not explained why the same flexibility cannot be provided to installation in other ducts [such as at hood exit] and that it would be arbitrary to not provide similar flexibility in [this] installation location. The commenter said when a facility installs monitoring equipment it is important that its installation location be sited for consistent performance, efficient maintenance, or subjecting workers responsible for maintenance to more significant health and safety risks. The EPA should accommodate such considerations of maintenance convenience and feasibility so long as they do not compromise the accuracy of the monitor. The EPA has not identified a basis in the record for ignoring such performance, maintenance or health and safety considerations. The commenter recommended proposed 40 CFR part 60, subpart AAb be changed to allow facilities to consider feasibility and maintenance when deciding where to install the monitoring devices. The commenter recommended the EPA revise the proposed text to read "downstream as close to the hood exit as feasible, taking into account performance, maintenance and health and safety considerations."

Response 4-4: We agree with the commenter that the proposed rule as written would allow a facility to monitor furnace static pressure in the duct after it combines with other ducts, which would be inappropriate. Therefore, we modified the language for the 40 CFR part 60, subparts AA, AAa, and AAb final rules (40 CFR 60.274(f), 60.274a(f), 60.274b(f)) to allow monitoring, as follows:

      ...in any appropriate location in the EAF or DEC duct prior to combining with other ducts and prior to the introduction of ambient air at a location that has no flow disturbance due to the junctions.

Comment 4-5: Monitoring opacity during charging and tapping is inappropriate.

Commenter 0095-Steel Co. disagreed with measuring opacity during the charging and tapping of the EAF. The commenter noted that for many EAFs charging may be the time period with the greatest visible emissions inside the melt shop due to the rapid thermal shift involved in charging and because the DEC may not be operating with furnaces designed for open top charging. The commenter said that charging period does not necessarily correspond to the highest visible emissions exiting from the shop. Averages taken during charging may be skewed higher than an average taken across all heat cycles. The charging period only occurs one time per cycle, varies in duration, and can often be as short as 30 seconds. The short duration of any opacity associated with charging is not representative of average EAF opacity emissions or environmental performance.

Similarly, commenter 0091-State was concerned monitoring opacity during charging and tapping would not demonstrate proper operation of the EAF or result in emissions reductions because charging and tapping events occur for only a few minutes at a time.

Response 4-5: For the EPA's response to some of the issues raised in this comment in regard to melt shop opacity, see the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Opacity Response as well as other responses in section IV.E.2. For the response to the comment concerning whether the opacity standards, as they are written in 40 CFR part 60, subparts AA, AAa, and AAb should apply at all times: See the EAF NSPS preamble section IV.D.2.

Comment 4-6: Monitoring opacity during the "period established to have the greatest potential for uncaptured emissions to escape the melt shop" is inappropriate and has not been demonstrated as achievable.

Commenter 0095-Steel Co. said the requirement to measure opacity at "the period established to have the greatest potential for uncaptured emissions to escape the melt shop" as opposed to measuring at a specific time (i.e., melting and refining, charging, or tapping) is vague and would create a "floating standard" that cannot be consistently met due to uncertainty of when the period of highest emissions may occur. The EPA did not explain what process should be used to establish the period of greatest potential emissions. The commenter said facilities may not be able to predict the highest period of potential opacity. The periods of time with potential for high in-shop opacity, such as charging, may not correspond to either the highest potential for uncaptured emissions from the melt shop or the highest visible emissions exiting from the melt shop. Emissions are influenced by ambient conditions like wind (airflow), pressure, temperature, and humidity. These ambient conditions often have greater impact on emissions than the EAF heat cycle. The commenter said it may be impossible to predict on a daily basis when the highest potential emissions or opacity from the melt shop will occur.

For plants with multiple EAFs within the same building, the commenters said it could be impossible to predict the time period during which the highest opacity will occur because the EAFs operate independently from each other and may be at different stages of the production cycle at any given time. The commenters said this provision was especially problematic if the highest opacity occurs during charging because the duration of charging is short relative to other periods of the cycle and not predictable enough to be able to measure that period every day for the several consecutive minutes required by Method 9. The commenter said it was not feasible to identify any particular time period that consistently and predictably has the "greatest potential for uncaptured emissions to escape the melt shop" where multiple EAFs are operated.

Commenter 0095-Steel Co. said the EPA had not demonstrated that monitoring opacity during the "period established to have the greatest potential for uncaptured emissions to escape the melt shop" was "achievable" and "adequately demonstrated" as required for standards published under section 111(a)(1) of the CAA. To be achievable, the commenter asserted that "a uniform standard must be capable of being met under most adverse conditions which can reasonably be expected to recur and which are not or cannot be taken into account in determining the `costs' of compliance." (National Lime Ass'n v. EPA, 627 F.2d 416, 431, n. 46 (D.C. Cir. 1980). The EPA must also account for routine operating variability associated with performance of the system on which the performance the standard is based. (National Lime Ass'n v. EPA, 627 F.2d at 431-433; and 79 FR at 39245) The EPA must show how a standard is achievable under the range of relevant conditions that may affect the emissions anywhere in the country and cannot simply show that the standard was achieved at a model plant for a short period of time. (National Lime Ass'n v. EPA, 627 F.2d at 433; Electric Arc Furnaces and Argon-Oxygen Decarburization Vessels in Steel Industry -Background Information for Proposed Revisions to Standards, Preliminary , at 2-6, 2-7, June 1982). The commenter said that all compliance testing and opacity emission reporting relied on by the EPA for setting the new opacity limits in 40 CFR part 60, subpart AAb are based on observations taken during the melting and refining phase as required under NSPS 40 CFR part 60, subpart AAa, and therefore, cannot be used as the basis for determining that a 0 percent opacity limit is consistently and predictably achievable during "the period established to have the greatest potential for uncaptured emissions to escape the melt shop."

In addition, commenter 0095-Steel Co. said the proposed provision increased the likelihood of missed opacity observations since facilities would have to schedule their opacity observations to coincide with anticipated production schedules. Operational issues occur that could result in a shutdown of an EAF for the rest of the compliance period. If the visible emissions observation had not already been taken, it would be impossible for the observation to be performed during the "greatest potential for uncaptured emission to escape the melt shop" because the highest opacity event would have already occurred. The commenter recommended the EPA define a specific period of the heat cycle for shop opacity measurements to be taken rather than requiring facilities to measure opacity at the "greatest potential" time period. The commenter urged the EPA to address how any opacity requirement will be met at melt shops with multiple EAFs within a single melt shop building.

Response 4-6: For the EPA's response to issues raised in this comment in regard to melt shop opacity, see the EAF NSPS preamble to the final rule, section IV.E.2, Melt Shop Opacity Response.

Comment 4-7: The proposed volumetric flow and static pressure monitoring requirements are unworkable.

Commenters 0096 and 0093-Steel Co. and 0097-Industry Trades opposed the proposed requirement to measure volumetric flow or static pressure at each ducted hood to obtain 15-minute averages.

Commenter 0096-Steel Co. said that this monitoring would be unworkable due to the complex structure of many melt shops. As an example, the commenter noted that the Mansfield Works melt shop contains two EAFs, an argon-oxygen decarburization (AOD), and a ladle metallurgy furnace (LMF), and is controlled by two baghouses. The two EAFs and AOD are all subject to 40 CFR part 60, subpart AAa requirements, while the LMF is not. The commenter said it would be impracticable to establish a minimum volumetric flow rate or static pressure at a facility with these complex set of overlapping operations. The commenter added that the melt shop operations are variable, and a 15-minute average would not adequately capture the variability. The commenter added that technical complications with flow monitors used in areas of extreme heat or in dusty conditions would increase the need for re-calibrations and likely lead to periodic failures of the monitors. Some shops (e.g., Butler Works) have long runs of ductwork on the roof of the melt shop that pose access and safety difficulties for installing and maintaining flow monitors. Depending on the technical specifications for where flow or pressure monitors must be installed, redesigns and retrofits of hoods and ductwork could be necessary.

Commenters 0093, 0096, and 0098-Steel Co. said they are not aware of any melt shops that currently effectively measure furnace static pressure based on 15-minute averages, as the harsh environment in the furnace makes pressure monitoring difficult. Commenter 0096-Steel Co. noted that their experience monitoring pressure in furnaces showed it was difficult to generate useful data on furnace operation and capture efficiency. This commenter suggested measurement of volumetric flow or static pressure at each separately ducted hood or furnace pressure would not generate useful data that will enable an understanding of how well the capture system is operating.
Commenters 0093 and 0098-Steel Co. said that maintaining flow meters in the highly abrasive and corrosive EAF ducts is difficult and that equipment fouling and damage is a problem. Commenter 0098-Steel Co. said that in their experience the monitoring equipment was "virtually impossible to operate and maintain" because the monitoring equipment does not survive. Commenter 0093-Steel Co. said that few EAFs are equipped with volumetric flow rate equipment due to the high particulate loadings and corresponding fouling. Where the volumetric flowrate monitors are present, the flowrate monitors are typically post-baghouse to take advantage of the cleaner air stream or a single volumetric flowrate monitoring system is installed in a common duct. Requiring a volumetric flowrate monitoring device in each separately ducted hood would be difficult to maintain due to the highly abrasive exhaust prior to the control device.

Commenter 0097-Industry Trades stated that the 1999 rulemaking allowed daily visible emissions monitoring as an alternative to installation of a furnace static pressure monitoring device. In that rulemaking, the EPA recognized that furnace static pressure monitors presented practical problems with maintenance and installation. The commenter said the EPA recognized that daily visible emissions observations were as good or better an indicator of control device capture efficiency. The free space above an EAF is subject to severe conditions of high temperature and dust. Several owners and operators have had problems with frequent plugging of the pressure monitoring sensor. Due to the location of the sensor, maintenance and repair can be both difficult and dangerous. The EPA does not address the difficulties with installing, operating, and maintaining monitors on a continuous basis in the harsh furnace environment. Commenter 0097-Industry Trades said that any requirement for furnace pressure monitoring would have to provide for the regular downtime that would be needed to maintain the monitors. In addition, the electronics that would be used to transmit the pressure data on a continuous basis to a data recorder must be able to survive the same harsh environment. These issues are the primary reason most EAFs do not use furnace static pressure monitors to comply with the existing requirements.

Commenter 0097-Industry Trades stated that the significant costs of installing and maintaining furnace static pressure monitors were not considered in the proposal.

All commenters supported the existing approach that uses a combination of damper positions and fan motor amperes because they said it provides an adequate assurance of compliance.

Response 4-7: For the EPA's response to issues raised in this comment in regard to furnace static pressure monitoring based on 15-minute averages: See the EAF NSPS preamble to the final rule, section IV.E.2, Furnace Static Pressure Response.

Comment 4-8: The EPA should not remove options to monitor either control system fan motor amperes or volumetric flow rate at the control device inlet (baghouse) or to replace with requirement to monitor volumetric flow rate or static pressure at each separately ducted hood.

Commenter 0095-Steel Co. added that using amperage monitoring to monitor flow rate is more efficient because the amperage measurements are proportionally related and monitoring the fans and motors is required anyway to evaluate evacuation system performance, operational reliability, power management, and preventative maintenance and replacement projections. The commenter said that 40 CFR part 60, subpart AAa allowed monitoring of amperage; the alternative options to monitor flowrate through each duct or flowrate at the control device inlet were added as alternative methods in 1999 to increase compliance flexibility.

Commenter 0093-Steel Co. recommended the phrase "As required, ..." be added to the beginning of 40 CFR 60.274b(h)(7) because the volumetric airflow through each separately ducted hood should be an optional requirement.

Response 4-8: For the EPA's response to issues raised in this comment in regard to furnace static pressure monitoring based on 15-minute averages: See the EAF NSPS preamble to the final rule, section IV.E.2, Furnace Static Pressure Response. For the EPA's response to issues raised in this comment in regard to volumetric flow and static pressure monitoring, see the EAF NSPS preamble to the final rule, section IV.E.2, Volumetric Flow and Static Pressure Response.

Comment 4-9: Recommended changes to the proposed volumetric flow monitoring provisions.

Commenter 0097-Industry Trades opposed the proposed requirements for direct flow measurements, but recommended changes be made if the proposed provisions are incorporated into the final rulemaking. First, the EPA should allow placement of flow meters either in the clean side of the baghouse (for those baghouses that have stacks) or in the inlet side of the baghouse (for baghouses without stacks). Second, an 8-hour (or once-per-shift) averaging of the flow should be allowed to compare against set points to determine deviations. Flow rates to the baghouse can vary considerably based on heat-to-heat variations due to the dynamic nature of EAF operations. The EPA's proposal to assess flow on a 15-minute basis, the commenter said, will not capture the full extent of variability of the flows to the baghouse.

Response 4-9: Placement of flow meters on the inlet or outlet of baghouse only provides a total flow from the system and doesn't provide specific information on the capture at each emission point. Duct positions change throughout the melt cycle; an 8-hour average would not provide useful information to understand whether capture during normal operations was consistent with capture during initial compliance demonstration. Therefore, the EPA disagrees with the commenter and is not including in the final rules the changes suggested by the commenter.

Comment 4-10: Melt shop opacity observations in 40 CFR 60.274b(b) are unnecessary and duplicative of 40 CFR 60.273b(d).

Commenter 0093-Steel Co. said that daily shop opacity readings are already required at 40 CFR 60.273b(d) [Emission Monitoring].

      60.273b(d) Shop opacity observations shall be conducted at least once per day during charging or tapping, or during the period established to have the greatest potential for uncaptured emissions to escape the melt shop. Shop opacity shall be determined as the arithmetic average of 24 consecutive 15-second opacity observations of emissions from the shop taken in accordance with EPA Method 9, or, as an alternative, according to ASTM D7520-16 (incorporated by reference, see 40 CFR 60.17), with the caveats described under Shop opacity in 40 CFR 60.271, or as the total duration of visible emissions measured according to EPA Method 22 over a 6 minute period, modified to require the recording of the aggregate duration of visible emissions at 15 second intervals. Shop opacity shall be recorded for any point(s) where visible emissions are observed. Where it is possible to determine that a number of visible emission points relate to only one incident of visible emissions, only one observation of shop opacity will be required. In this case, the shop opacity observations must be made for the point of highest opacity that directly relates to the cause (or location) of visible emissions observed during a single incident.

They said it was unclear why the EPA was requiring a second set of daily shop opacity readings under proposed 40 CFR 60.274b(b) [Monitoring of Operations].

      60.274b(b) Except as provided under paragraph (e) of this section, the owner or operator subject to the provisions of this subpart shall conduct observations of shop opacity at least once per day when the furnace is operating in the period of the heat cycle that generates the greatest uncaptured emissions....

The provisions in proposed 40 CFR 60.273b(d) [Emission Monitoring] are clearer. The commenter recommended the shop opacity language in 40 CFR 60.274b(b) should be deleted.

Response 4-10: The EPA agrees with the commenter that the daily opacity reading requirement from the proposed rule could be confused with adding additional requirements. While the two sections of the rule identified by the commenter have a different focus, both address issues with opacity. The EPA also agrees with the commenter that emission monitoring explains the details of opacity measurements. Therefore, we have deleted reference to opacity in 40 CFR 60.274b(b) in an effort to make the final rule clear.

Comment 4-11: Recommended changes to 40 CFR 60.274b(h).

Commenter 0093-Steel Co. recommended the following changes to 40 CFR 60.274b(h):

 40 CFR 60.274b(h)(5) should be deleted because it was redundant to 40 CFR 60.274b(h)(2):
      60.274b(h) During any performance test required under 40 CFR 60.8 or 40 CFR 60.272b(d), and for any report thereof required by 40 CFR 60.276b(f) of this subpart, or to determine compliance with 40 CFR 60.272b(a)(3) of this subpart, the owner or operator shall monitor the following information for all heats covered by the test:
         ........
         (h)(2) Heat times, including start and stop times, and a log of process operation, including periods of no operation during testing and, if a furnace static pressure monitoring device is operated pursuant to 40 CFR 60.274b(f), the pressure inside an EAF when DEC systems are used;
         ........
         (h)(5) Furnace static pressure;

 "As necessary," should be added to the beginning of 40 CFR 60.274b(h)(4) because the EAF test run is 4 hours, but the opacity demonstration under 40 CFR 60.11 is only three hours. This section implies that 12 hours (3 runs x 4 hours) of Method 9 or ASTM D7520-16 data are required.

      (h)(4) Continuous opacity monitor or EPA Method 9 data, or, as an alternative to EPA Method 9, according to ASTM D7520-16 (incorporated by reference, see 40 CFR 60.17), with the caveats described under Shop opacity in 40 CFR 60.271.

Response 4-11: We agree, in part, with the commenter and have removed the reference in 40 CFR 60.274b(h)(5) to furnace static pressure, but have retained the reference in 40 CFR 60.274b(b)(h)(2) but with the qualifying language: "if furnace static pressure monitoring device is operating pursuant to 40 CFR 60.274b(f)....".

We disagree with the commenter's interpretation that in the phrase "continuous opacity monitor or EPA Method 9 data" the word "continuous" modifies both opacity monitoring and Method 9 performance. In this case, the phrase "continuous opacity monitor" refers to an actual instrument, called a continuous opacity monitor (COM). To clarify, we have amended the regulatory text at 40 CFR 60.274b(h)(4) to indicate that this is referring to the instrument and not a description of the data collection. The readings done according to EPA Method 9 should be done to coincide with PM testing, but according to the time frames described in EPA Method 9 and in 40 CFR 60.271b under Shop Opacity.

4.2 Bag Leak Detection System (BLDS)

Comment 4-12: Facilities should be allowed 24 hours to respond to BLDS alarms and to complete the response as soon as practical in 40 CFR part 60, subparts AA, AAa, and AAb.

Commenter 0093-Steel Co. and 0097-Industry Trades disagreed with the proposed 40 CFR part 60, subpart AAb provisions that would require facilities to determine the cause of all BLDS alarms within one hour and alleviate the cause of the alarm within three hours by taking the necessary response action. The commenters recommended the EPA adopt a 24-hour timeframe to initiate corrective action and to require that response actions be completed as soon as practicable. This approach would recognize the practical realities in identifying and responding to BLDS alarms. The commenters added that this approach is the same as that used in the Integrated Iron and Steel NESHAP, and is consistent with 40 CFR part 63, subparts X (NESHAP From Secondary Lead Smelting), DDD (NESHAP for Mineral Wool Production), EEE (NESHAP from Hazardous Waste Combustors), MMM (NESHAP for Pesticide Active Ingredient Production), RRR (NESHAP for Secondary Aluminum Production), and TTT (NESHAP for Primary Lead Smelting). The commenters said there was no justification for the proposal to be different from other existing rules. They added that the proposed three-hours was arbitrary and ignored the numerous scenarios in which it can take longer than three hours to identify and fix the cause of an alarm. Allowing facilities 24 hours to identify the cause and requiring facilities to alleviate the cause of the alarm "as soon as practicable" is more practical, particularly where many baghouse compartments must be inspected to determine the cause of an alarm.

Commenter 0097-Industry Trades noted that there are situations in which more than three hours is needed to respond to a BLDS alarm and address its cause. Because many mills calibrate their BLDS to be very sensitive, the likelihood that a BLDS alarm will be falsely triggered is increased. The commenter included the following examples of situations in which false alarms can occur:

 Weather  -  BLDS alarms will occasionally trigger during a heavy downpour or when there are significant changes in temperature or humidity.
 Bag Cleaning Cycle  -  BLDS alarm may trigger at the end of the baghouse cleaning cycle due to the temporary absence of dust in the bags.
 New Bag Start  - BLDS alarms can be triggered following a replacement of some or all of the bags in the baghouse.
 Systems Checks/Testing  -  Some facilities may run systems checks on their BLDS that cause the system to alarm. For example, a facility may check the sensitivity of a BLDS by introducing a handful of flour into a port upstream from the probe. Facilities also evaluate and optimize their BLDS performance through drift checks, response tests, calibration exercises, and other quality assurance procedures. Some of these procedures require the alarm to be triggered in order to test performance, but in other instances the BLDS alarm may be inadvertently triggered during testing.
 Electrical Malfunctions  -  As BLDS detection is based on contact electrification, alarms can be triggered due to electrical surges impacting the sensors, processing electronics, or the connections between the sensor and processing electronics. These surges can either be environmental (lightning) or from variations/malfunctions in the BLDS system, its software, or its power source. Additionally, the abrasive environment in the baghouse duct can deteriorate the BLDS probe, probe housing, and housing insulation, which can cause an increase in malfunctions. BLDS alarms may be triggered during temporary power lapses or brief connectivity issues between the sensor and the processing electrics, or between the processing electronics and the system output/alarm. The BLDS can experience brief mechanical or software glitches/errors, including with respect to the sensor's signal amplification or with the configuration of the processing electronics.
 Repair/Maintenance  -  Some baghouse repair and maintenance activities may be conducted while the baghouse is in operation. In some of these cases, proper inspection and repair requires the baghouse to be operating in order to observe and repair malfunctions/maintenance issues. Often these activities are coordinated with a baghouse operator observing the BLDS readout in real time in order to identify the cause of an earlier alarm or to proactively identify maintenance or performance issues. Baghouse repair and maintenance activities sometimes must be conducted when the baghouse is operating because the repair/maintenance is urgently needed, and it is infeasible to quickly shut down the baghouse. These activities will cause BLDS alarms to trigger. Work on baghouse compartments and conveyances can introduce particulates into the system or dislodge caked or accumulated dust which triggers alarms. Sounding of BLDS alarms also can be caused by maintenance and repair activities conducted when the baghouse is not operating. These activities can introduce foreign material or dislodge accumulations of material from ducts, conveyances, access panels, joints, and other components of the system upstream from the probe. Then when the baghouse is restarted, the newly introduced or dislodged material can cause the BLDS alarm to be triggered.

Commenter 0097-Industry Trades pointed out that it is possible for a baghouse to operate within its emission and opacity limits even if the cause of a BLDS alarm is not identified and corrective measures taken. For example, if a broken bag in a compartment causes an alarm, the compartment can be isolated and shut down without affecting the rest of the baghouse.

Commenter 0097-Industry Trades noted that determining the cause of the alarm often requires operators to undertake a multi-step troubleshooting process of elimination requiring multiple rounds of physical inspections and diagnostic efforts. This process of elimination often requires more than three hours to complete. The process can be very time-consuming, particularly when the BLDS alarm lasts only a short time. Identifying the cause of a brief BLDS alarm, the commenter said, can be very difficult and sometimes proves impossible. Some baghouses in the EAF industry have 25 or more compartments housing 5,000 or more individual bags. Some mills do not have BLDS with detection capability in each separate compartment because the baghouse design does not allow for such monitoring (e.g., multiple compartments sharing common exit plenum). In these instances, mills must continue running and sequentially isolate compartments to determine which compartment may have caused the BLDS alarm. Facilities must then physically examine the compartment(s), which may contain 150 or more individual bags. If a bag has a significant rupture or has been dislodged, the cause of the alarm will likely be readily apparent. However, some alarms can be triggered by extremely small holes in bags and in these cases, finding the leak by physical inspection can take a long time.

Commenter 0097-Industry Trades said that EAF mills can have difficulty responding to multiple, intermittent alarms of short duration. The commenter noted that EAF facilities record the alarm as resolved where investigation shows no evidence of a bag leak. While the facility may be able to respond to each separate alarm in under three hours, the commenter said they are aware of one instance in which an enforcement authority determined the company was in violation of the three-hour response requirement because the total time the facility spent responding to each of the separate intermittent alarms exceeded three hours. The commenter said the enforcement authority misinterpreted the three-hour response requirement. This and provided this example was provided to show how a three-hour response requirement presents a compliance risk even when individual responses are completed within the three-hour window.

Commenters 0093-Steel Co. and 0097-Industry Trades recommended the following additions (shown in bold and underline) be made to 40 CFR 60.273b(f)(6) and (7) in all three rules in regard to the leak monitors to clarify false alarm situations.

      (6) Establishing to the extent acceptable by the delegated authority that the alarm was a false alarm and not caused by a bag leak or other malfunction that could reasonably result in excess particulate emissions, in which case alarms due to the [leak] monitor malfunctioning are not subject to the 3-hour response action requirement so long as the [leak] monitor malfunction is timely corrected;

      (7) Shutting down the process producing the particulate emissions; provided, however, that process unit shut down is not required if an operator reasonably believes repetitive alarms are the result of a [leak] monitor malfunction so long as the [leak] monitor malfunction is timely repaired.

Commenter 0093-Steel Co. also recommended 40 CFR 60.276b(h)(3) be revised to specify that malfunction of the [leak] monitor connected to the alarm can be a basis for not resolving an issue within three hours [if change to 24 hours response is not made].

Response 4-12: For the EPA's response to this comment, see the EAF NSPS preamble to the final rule, section IV.E.2.

Comment 4-13: The proposed BLDS requirements in proposed 40 CFR part 60, subpart AAb are unworkable for multiple-outlet baghouses that allow alternative monitoring.

Commenter 0096-Steel Co. disagreed with the proposed new requirements for BLDS. The commenter said the EPA failed to provide adequate explanation for the proposed changes, which the commenter said made it difficult to provide comments. The Mansfield Works and Steelton plant currently comply with 40 CFR part 60, subpart AAa using the shop opacity observations and monitoring fan amperages and damper positions. The Butler Works demonstrates compliance using an alternate monitoring plan under which the plant performs additional shop opacity observations and monitors fan amperage but not damper positions. None of these mills employ BLDS. The commenter noted the Butler Works, Mansfield Works and Steelton plant all have multiple-outlet baghouses. The number of bag leak detection devices needed to monitor the baghouse outlets under the proposed rule would be 20, 28 and 34 devices, respectively, for the three plants. Due to false alarms from BLDS, industry commonly use backup bag leak detection devices. Hence, the number of BLDS would be 40, 56 and 68 devices, respectively, for each of the three plants. The commenter added that operating so many BLDS would be burdensome and add operational complications that the EPA did not recognize in the proposal.

Response 4-13: For the EPA's response to this comment, see the EAF NSPS preamble to the final rule, section IV.E.2. BLDS Response. In addition, if facilities have an alternative monitoring plan, revisions to the corresponding monitoring section(s) of 40 CFR part 60, subparts AA, AAa, and AAb will not affect these plans.

Comment 4-14: Requirement in proposed 40 CFR part 60, subpart AAb to use BLDS on all baghouses reverses prior Agency decisions.

Commenter 0097-Industry Trades opposed the proposed new requirement to install BLDS on all baghouses. When adopted in 1975, 40 CFR part 60, subpart AA originally required baghouse opacity to be monitored using a COMS. However, the 40 CFR part 60, subpart AAa amendments eliminated the requirement to use a COMS for emissions from modular, multiple-stack, negative-pressure or positive-pressure fabric filters provided the facility conducts daily Method 9 observations. The EPA determined that the use of visible emission standards was "technically sound and provides the most practical and inexpensive means to ensure that affected facilities are properly maintained and operated." (49 FR 43838 and 43840, October 31, 1984). The commenter also noted that the EPA acknowledged in the 1984 rulemaking that the capital and operating costs to install multiple COMS was unreasonable for modular, multi-stack baghouses. Amendments to the EAF steel NSPS in 2005 allowed mills to use a BLDS on single stack baghouses as an alternative to using COMS. (70 FR 8523, February 22, 2005). Facilities using BLDS were required to have site-specific monitoring plans, adopt corrective action plans, and conduct daily Method 9 observations when the EAF was in operation.