Selective Non-Catalytic Reduction...............................          $3,222          $3,637              13

Selective Catalytic Reduction...................................           5,176           7,874              52
----------------------------------------------------------------------------------------------------------------
                                             SO2 Control Technology
----------------------------------------------------------------------------------------------------------------
Dry Sorbent Injection...........................................           1,857           3,088              66
Dry Flue Gas Desulfurization....................................           5,090           9,359              84
Wet Flue Gas Desulfurization....................................           5,505           8,229              50
----------------------------------------------------------------------------------------------------------------

    Response: As noted in our proposed rule and TSD, we revised upwards
our contractor's original control cost estimates based on certain site-
specific factors noted by TEP in its letter dated May 10, 2013. We
incorporated many, but not all, of the factors raised in that letter.
In its comment letter on our proposed rule, TEP raised additional
factors and asserted that the cost estimates for each of the control
options is underestimated. In the case of SCR, dry FGD, and wet FGD, we
stated in our proposed rule that we consider these control options to
not be cost-effective, either in general or in relation to their
anticipated visibility benefits. In the case of SNCR and DSI, even if
we were to accept all of TEP's revisions included in the comment
letter, we would still consider these options to be cost-effective
generally and to be BART based on our consideration of costs and
visibility benefits.
    Comment: NPS commented that that although EPA has not stated the
reasonable level of cost-effectiveness, it assumes that the Agency
typically uses $5,000/ton and 0.5 deciviews (dv) as thresholds. Yet,
NPS has seen higher cost-effectiveness thresholds from EPA and other
states. While NPS commends EPA for its presentation of cumulative
visibility impacts and cumulative visibility benefits of reducing
emissions, NPS also requested that EPA work with NPS to develop a
consistent and transparent method to relate cost to visibility
improvement.
    Response: As noted in responses to other comments, we have not
established specific thresholds for the cost and visibility factors for
BART. NPS is therefore correct to note that BART determinations made by
EPA may not precisely align along a specific set of $/ton or deciview
improvement values. Further, even where the costs of compliance and
expected degree of visibility improvement are similar at two different
sources, consideration of other statutory factors may result in
different outcomes.\66\ With regard to determinations made by state
agencies, we note that the RHR provides states with significant
discretion in considering and weighing the five BART factors, so long
as the factors are appropriately evaluated and the state's
determination is supported by reasoned explanations for adopting the
technology-based limits selected as BART. As a result, while a direct
comparison of $/ton and deciview improvement values associated with
BART determinations from multiple state agencies and EPA is informative
and should carry weight in the ultimate decision, such comparisons are
not outcome determinative.
---------------------------------------------------------------------------

    \66\ We also note that it is unusual for controls at two
different sources to have similar visibility benefits across all
affected Class I areas.
---------------------------------------------------------------------------

    Comment: NPS indicated that it has collected and reviewed close to
100 BART determinations for EGUs and has found that the average cost
per deciview for NOX reductions at EGUs is $14 million and
the maximum cost per deciview is $34 million based on the Class I area
with highest visibility improvement. NPS asserted that the $14 million
figure is a good indication of the value states have placed upon
reducing NOX for visibility purposes.
    Response: We agree with NPS that cost per deciview improvement is
informative as a cost-effectiveness metric, including comparing the
effect of controls on sources located in different parts of the
country. We provided calculations of this metric in our proposal for
this action. However, consistent with the BART Guidelines,\67\ we have
relied more heavily on cost-effectiveness calculated as cost per
pollutant ton reduced and related visibility improvements in deciviews
(both at individual areas and as a cumulative sum over all affected
areas) as opposed to the cost per deciview metric.
---------------------------------------------------------------------------

    \67\ See e.g. 70 FR 39167 (``For purposes of air pollutant
analysis, `effectiveness' is measured in terms of tons of pollutant
emissions removed, and `cost' is measured in terms of annualized
control costs.'')
---------------------------------------------------------------------------

    Comment: NPS expressed support for EPA's inclusion of the
cumulative visibility impacts and improvements associated with the
control scenarios that were considered, noting that the EGUs evaluated
are unusual because they impact from ten to 15 Class I areas within 300
kilometers (km).
    Response: We agree with NPS that it is important to account for
visibility impacts at multiple Class I areas, given that the goal of
the visibility program is to remedy visibility impairment at all Class
I areas.\68\ The cumulative sum, while not the only means of analyzing
benefits across multiple Class I areas, is an easily understood and
objective method of weighing cumulative visibility improvement, and is
useful as part of the overall BART determination.
---------------------------------------------------------------------------

    \68\ CAA section 169A(a)(1).
---------------------------------------------------------------------------

    Comment: TEP stated that EPA should adopt version 6.42 of CALPUFF
as the approved regulatory version for modeling regional haze, since
this version corrects deficiencies in the chemistry and the dispersion
functions of CALPUFF version 5.8. TEP indicated that several studies
conducted over the last few years demonstrate that the deficiencies in
version 5.8 result in over-estimation of the visibility impacts of
NOX emissions in Class I areas. This causes erroneous over-
estimation of the visibility improvements from proposed BART controls
leading to biased cost-benefit values.
    Response: We disagree with TEP for two reasons. First, CALPUFF 5.8
is approved as a regulatory model for use by EPA in regional haze
determinations. CALPUFF version 5.8 has been thoroughly tested and
evaluated, and has been shown to perform consistently with the initial
2003 version in the analytical situations for which CALPUFF has been
approved. CALPUFF 6.42 is not an approved regulatory model because
CALPUFF 6.42 has not yet undergone adequate review. We relied on
version 5.8 of

CALPUFF because it is the EPA-approved version in accordance with the
Guideline on Air Quality Models (``GAQM'', 40 CFR part 51, Appendix W,
section 6.2.1.e). We updated the specific version to be used for
regulatory purposes on June 29, 2007, including minor revisions as of
that date. Second, EPA took into account limitations with Version 5.8
when it suggested use of the 98th percentile day versus the maximum
day.\69\
---------------------------------------------------------------------------

    \69\ Memorandum in docket, ``Full Technical Response to Modeling
Comments for June 2014 Final Arizona Regional Haze FIP (Phase
III),'' Colleen McKaughan and Scott Bohning, EPA, June 16, 2014.
---------------------------------------------------------------------------

    Comment: TEP commented that the background ammonia concentration
used in visibility modeling is critical because ammonia is a precursor
to particulate ammonium nitrate. EPA's use of 1.0 parts per billion
(ppb) for ammonia background concentration for all months of the year
will tend to overestimate the visibility benefits associated with
reductions of NOX, particularly in the winter months. TEP
noted that monthly ammonia measurement data from the IMPROVE monitoring
network site in southern Arizona (Chiricahua) indicate that ammonia
concentrations below 1.0 ppb (e.g., 0.5 ppb) are present at this site
during the winter months. TEP asserted that use of those values will
more accurately predict the visibility improvements expected from the
reductions in NOX emissions. Although TEP did not perform
any new modeling for comparison to EPA's results in the proposal, TEP
sent a letter to EPA in May 2013 that provided clarification regarding
certain modeling parameters and the results of modeling performed by
TEP's contractor (AECOM). According to TEP, the modeling performed by
AECOM included a BART control scenario involving SNCR and DSI, similar
to EPA's proposed BART determination for Sundt Unit 4. The results of
AECOM's modeling was a maximum visibility improvement of 0.16 dv at
Saguaro National Park East compared to the baseline case. The TEP noted
that EPA's modeling representing the same control configuration (SNCR
and DSI) reported a maximum visibility improvement of 0.49 dv. TEP
acknowledged that these differences in modeling results have little
practical effect, as EPA has proposed that its results support a BART
determination involving application of SNCR and DSI on Sundt Unit 4,
and TEP does not dispute that overall finding. However, should EPA find
a need to do additional modeling to support its final BART
determination for Sundt Unit 4, TEP recommended that EPA incorporate
the modeling improvements suggested in TEP's letter of May 10, 2013.
    Response: We disagree that the 1.0 ppb ammonia background we
assumed for CALPUFF modeling is too high. It is consistent with EPA
guidance given that some ammonia measurements are higher than 1.0 ppb,
and the available ammonia data is variable over the areas included in
the visibility modeling. The uncertainty over appropriate ammonia
values leaves us without a reasonable basis for choosing a different
constant value, or a more complex monthly varying scheme as recommended
by the commenter. Ambient ammonia measurements for use as input to
modeling are scarce, and measurements that include it in the form of
ammonium still scarcer. In the absence of compelling ammonia background
estimates, the EPA Interagency Work Group on Air Quality Modeling
(IWAQM) Phase 2 guidance recommends the use of a 1.0 ppb ammonia
background for arid lands, which includes Arizona.\70\ This is the only
guidance available on this issue. It is worth noting that there are
measurements of gaseous ammonia (NH3) that by themselves are
close to or greater than 1.0 ppb, even in winter.\71\ Therefore, we
consider the 1.0 ppb ammonia background that we used to be appropriate
for this action. Finally, we agree with the commenter that the
recommended modeling changes would have little practical effect on the
BART determination for Sundt Unit 4.
---------------------------------------------------------------------------

    \70\ Interagency Work Group on Air Quality Modeling (IWAQM)
Phase 2 Summary Report And Recommendations For Modeling Long Range
Transport Impacts (EPA-454/R-98-019), EPA OAQPS, December 1998,
http://www.epa.gov/scram001/7thconf/calpuff/phase2.pdf.
    \71\ Memorandum in docket, ``Full Technical Response to Modeling
Comments for June 2014 Final Arizona Regional Haze FIP (Phase
III),'' Colleen McKaughan and Scott Bohning, EPA, June 16, 2014.
---------------------------------------------------------------------------

B. Nelson Lime Plant Kilns 1 and 2

1. Subject to BART Determination
    Comment: ADEQ asserted that EPA improperly disapproved ADEQ's
finding that Nelson Lime Plant is not subject to BART. ADEQ argued that
ADEQ's use of a three-year average 98th percentile value
``appropriately recognizes the highly variable visibility conditions
that prevail in western states due to periodic wildfires that can
result in short-term spikes in visibility impairment'' and is
consistent with how EPA determines compliance with certain NAAQS.
    Response: These comments largely pertain to EPA's partial
disapproval of the Arizona RH SIP and are therefore untimely, as EPA
has already taken final action on the SIP.\72\ To the extent that the
comments dispute EPA's proposed determination that the Nelson Lime
Plant is subject to BART under the FIP, we disagree with the substance
of their argument. The BART Guidelines recommend use of the 98th
percentile modeled visibility impact across multiple years of modeling
in order to identify sources that cause or contribute to visibility
impairment in a Class I area.\73\ There are at least three different
ways to determine the 98th percentile impact across three years of
modeling: The maximum 8th high in any one year, the 22nd high impact
over all three years, or the three-year average of the 8th high impacts
from each year. Of these three methods, the three-year average is the
least conservative way of determining the 98th percentile impact.
Depending on the yearly distribution of the results, the most
conservative 98th percentile impact may come from the maximum 8th
highest value for each of the three years or the 22nd highest value for
all years merged. While the BART Guidelines do not specify which value
to use, given that the subject-to-BART determination is a screening
test, EPA's position is that a more conservative approach, i.e., the
22nd high of three merged years or the maximum 8th high of any one
year, is more appropriate for this screening test. The FLMs also
recommend a more conservative approach and have noted that other states
have used such an approach.\74\
---------------------------------------------------------------------------

    \72\ 78 FR 46142.
    \73\ 40 CFR part 51, appendix Y, section III.A.3.
    \74\ Federal Land Managers' Air Quality Related Values Work
Group (FLAG) Phase I Report--Revised (2010) (FLAG 2010) at 23;
National Park Service Comments on EPA Review of Arizona Department
of Environmental Quality (ADEQ) Determinations of Best Available
Retrofit Technology (BART) at 2-3, and Reasonable Progress (RP)
March 6, 2013.
---------------------------------------------------------------------------

    We also do not agree with ADEQ that a three-year average approach
``appropriately recognizes the highly variable visibility conditions
that prevail in western states due to periodic wildfires that can
result in short-term spikes in visibility impairment.'' The visibility
impacts of individual sources, including the Nelson Lime Plant, are
determined by calculating the change in deciviews caused by the source
compared to natural visibility conditions.\75\ While natural conditions
could include short-term spikes from wildfires, the effect of such a
spike in the background level of pollution is to decrease the relative
deciview impact of

a given source.\76\ Thus, the possibility of short-term spikes from
wildfires would, if anything, argue for a more conservative approach to
evaluate an individual source's contribution. Moreover, we do not agree
that the use of a three-year average is appropriate here simply because
certain NAAQS use a three-year averaging period. Thus, consistent with
the FLMs' recommendation and with the approach used by EPA and other
states for making subject-to-BART determinations, we find that use of
the 98th percentile impact of any one year is appropriate for making
subject-to-BART determinations for purposes of this action.
---------------------------------------------------------------------------

    \75\ 40 CFR part 51, appendix Y, section III.A.3.
    \76\ See 70 FR at 39124 (``as a Class I area becomes more
polluted, any individual source's contribution to changes in
impairment becomes geometrically less'').
---------------------------------------------------------------------------

    With regard to the modeling performed for the Nelson Lime Plant,
ADEQ's comments refer to three different modeling analyses: (1) The
initial modeling performed by LNA; (2) the refined modeling analysis
performed by LNA using the revised IMPROVE equation; and (3) an
additional analysis referred to by LNA in its comments on the Phase 2
proposal. ADEQ included the results of the first two analyses in the
Arizona RH SIP. Both sets of results showed that for a single year,
2003, the Nelson plant's 8th high visibility impact exceeded 0.5
dv.\77\ Under EPA's interpretation of the 0.5 dv threshold, this makes
the facility subject to BART. The complete results of the third
analysis performed by LNA were not submitted to EPA.\78\ However, more
recent modeling performed by LNA shows that the 98th percentile impact
of the facility exceeds 0.5 dv in each of the three years modeled.\79\
Thus, even under the three-year averaging approach preferred by the
State, the Nelson Lime Plant is subject to BART, according to the most
recent modeling performed by the facility's owner. As explained above,
under EPA's interpretation of the 0.5 dv threshold, the Nelson Lime
Plant is subject to BART based on prior modeling. Therefore, for the
reasons set out in our Phase 2 proposed and final rulemakings and in
this response, we are finalizing our determination that the Nelson Lime
Plant is subject to BART.
---------------------------------------------------------------------------

    \77\ Arizona Regional Haze SIP at 152-53, Table 10.9 and Table
10.10.
    \78\ See 78 FR at 46154.
    \79\ BART Five Factor Analysis, Lhoist North America Nelson Lime
Plant; Prepared by Trinity Consultants in conjunction with Lhoist
North America of Arizona, Inc. (Public version dated September 27,
2013), Table 4-7. As explained in our proposal, these results are
conservative (i.e., tending to overestimate rather than
underestimate the impacts), but appropriate for purposes of a
subject-to-BART determination.
---------------------------------------------------------------------------

2. BART Analysis and Determination for NOX
    Comment: NPS indicated that it agrees with EPA that visibility
improvements expected as a result of applying SNCR support this
technology as BART for NOX.
    Response: We agree with NPS, and acknowledge its support on this
issue.
    Comment: ADEQ asserted that the three-year compliance time provided
in the rule does not provide enough time to retrofit SNCR on Kilns 1
and 2 because of the difficulty of installing such controls. In
contrast, Earthjustice argued that EPA should set a one-year compliance
deadline for the installation of SNCR at the plant. According to
Earthjustice, EPA recognized in the proposal that SNCR can be installed
in one year, but speculated without any support that it might take
longer at the Nelson Lime Plant because of a ``lack of information
regarding SNCR installation schedules on lime kilns.'' The commenter
stated that allowing an extra two years without any supporting record
violates the CAA's requirement that BART be installed as expeditiously
as practicable.
    Response: We disagree with ADEQ's assertion that a three-year
compliance schedule is too short and with Earthjustice's assertion that
it is too long. ADEQ has not provided any support for its assertion
that three years is an insufficient period of time for installation,
nor has the facility's owner made such an assertion. Regarding
Earthjustice's contention that a shorter deadline is required, we note
that the examples cited are for SNCR installations on cement kilns.
There are multiple operational and design differences between cement
and lime production.\80\ Cement and lime production processes are
sufficiently different that it is not appropriate to assume that SNCR
installation times for cement kilns are directly transferable to the
application of SNCR on lime kilns. To our knowledge, SNCR has never
been installed on a lime kiln. Given that this control technology will
be retrofitted to a new source category for the first time, it is not
unreasonable to expect unforeseen challenges and delays. EPA's timeline
is conservative and takes into account this possibility. Therefore, we
find that a requirement to install SNCR within three years is
consistent with the provisions of the CAA and the RHR requiring
compliance with BART emission limits as expeditiously as practicable.
---------------------------------------------------------------------------

    \80\ ``Comments on Draft NOX Control Measure Summary
for Lime Kilns'', National Lime Association, March 30, 2006; AP-42,
Section 11.6, Portland Cement Manufacturing; AP-42, Section 11.17,
Lime Manufacturing.
---------------------------------------------------------------------------

    Comment: Earthjustice agreed that SNCR is a technically feasible
control technology at the Nelson Lime Plant, but disagreed that the
control efficiency for SNCR should be limited to 50 percent.
Earthjustice stated that EPA's analysis must include the most stringent
emissions reductions possible with SNCR (citing the BART Guidelines),
and asserted that SNCRs can achieve control efficiencies significantly
higher than 50 percent for the reasons discussed by Earthjustice in
relation to the Clarkdale and Rillito cement plants. Earthjustice added
that higher NOX reductions are especially appropriate at
Nelson Lime Plant given the facility's high baseline NOX
emissions. Earthjustice also noted that EPA provided no support in the
record for the CEMS emissions data used in the development of the
NOX emissions baseline.
    Response: We disagree with this comment. The information provided
by Earthjustice consists of examples of SNCR on cement kilns. There are
substantial differences between cement kilns and lime kilns that do not
allow for direct comparisons of technical feasibility or control
effectiveness. As noted previously, neither we nor the commenter were
able to identify an instance of a lime kiln operating with SNCR in the
United States. In addition, Earthjustice has not provided any
information supporting an SNCR control efficiency more stringent than
50 percent on a lime kiln.
    LNA has provided a summary of CEMS emission data, but considers it
CBI since it also includes lime production data. We have included a
summary of the lb/ton values from the testing period in our docket for
the final rule because the BART limit is established in terms of lb/
ton.\81\ We have not included the mass emission rates from the testing
period, since including both the lb/hour and lb/ton data in the docket
would allow for the back-calculation of the lime production data.
---------------------------------------------------------------------------

    \81\ Non CBI--Summary of LNA Nelson March, May and June 2013
CEMS Testing.xlsx.
---------------------------------------------------------------------------

3. BART Analysis and Determination for SO2
    Comment: Earthjustice disagreed with EPA's rejection of DSI
technology based on cost considerations, and with EPA's BART reduction
approach that relies on a change in fuels. Earthjustice disagreed with
what it considers EPA's uncritical agreement with the company (i.e.,
DSI at 40 percent reduction) and asserted that, given the almost 4,000
tpy of SO2

emitted from the two kilns, EPA's determination of the most stringent
control efficiencies achievable should have been more thorough and
technically grounded. Earthjustice asserted that a DSI can be optimized
and can achieve far greater than 40 percent reduction, as the company's
own tests show (i.e., short-term efficiencies ranging from 17 to 84
percent). Earthjustice also asserted that even with what it considers a
flawed analysis, the calculated cost-effectiveness value of about
$4,000/ton reduced is well within acceptable ranges. As a result,
Earthjustice disagreed with the weight that EPA gave to the incremental
cost-effectiveness values and urged EPA to reconsider its
SO2 BART determination for the Nelson Lime Plant in the
final rule.
    By contrast, NPS said that it supports EPA's conclusion, noting
that it is most important to reduce process emissions before adding
expensive emissions controls. NPS indicated support for EPA's decision
because it generally favors moving toward cleaner fuels. After changing
the fuel at the plant, however, NPS noted that it may be appropriate to
revisit requiring emissions controls at that time.
    Response: We acknowledge NPS's support on this issue. We disagree
with Earthjustice that a more stringent DSI control efficiency is
appropriate. Although the commenter notes that site-specific test data
suggest short-term control efficiencies as high as 84 percent, there is
no evidence that the upper range of short-term control efficiencies is
sustainable over longer periods. As a result, when calculating annual
emissions reductions in tpy, which is performed on an annual average
basis, we do not consider it appropriate to use a control efficiency
achieved over a short-term period because it might not achievable over
a long-term annual average. Although Earthjustice asserted that the
determination of a DSI control efficiency in our proposed rule should
be more thorough and technically grounded, it has not provided any
information regarding how, specifically, we should revise our analysis
or that supports a more stringent control efficiency.
    Furthermore, as explained in more detail in a response to a comment
from LNA below, the total cost figures in our proposed rule
inadvertently omitted annual indirect costs. Correcting this error
results in approximate average and incremental cost-effectiveness
values of $4,800/ton and $10,200/ton for Kiln 1 and $4,500/ton and
$9,500/ton for Kiln 2.\82\ The largest incremental visibility benefit
of DSI relative to the visibility benefit of the proposed fuel mixture
change at a single Class I area is 0.11 dv at Grand Canyon National
Park.\83\ We do not consider this level of incremental cost to be
warranted by the incremental visibility benefit of DSI relative to the
fuel mixture change. However, additional controls for the Nelson Lime
Plant, such as DSI, should be considered for purposes of ensuring
reasonable progress in future planning periods.
---------------------------------------------------------------------------

    \82\ ``LNA Nelson Control Costs (revised for Final Rule).xlsx.''
    \83\ See 79 FR 9341, Table 26.
---------------------------------------------------------------------------

    Comment: LNA determined that compliance with the SO2
emission limits within six months after the effective date of the final
rule in the Federal Register, likely in July 2014, is not feasible.
Therefore, the proposed six-month compliance window is unreasonable.
Compliance with the SO2 emission limits is based on a two-
step process: (1) Use of a CEMS to determine actual SO2
emissions from each kiln; and (2) use of daily production tonnage. LNA
estimated that an 18-month period is a more reasonable compliance
timeframe for a system that supports both NOX and
SO2 CEMS as well as new weigh scales on lime storage silo
transfer belts.
    Response: We agree that a six-month time period is an insufficient
amount of time for the design, installation, and optimization of an
SO2 CEMS in this case. In other cases in which compliance
with a BART limit does not involve construction of add-on controls, but
does involve installation of CEMS, we have provided a twelve-month
window for compliance.\84\ In this case, taking into account that
multiple CEMS (NOX and SO2) will need to be
installed, and the fact that the facility does not currently operate
with CEMS, may not have existing systems or infrastructure in place,
and is replacing lime weigh scales, we consider an 18-month compliance
time frame to be as expeditious as practicable. Therefore, we are
revising the compliance deadline for SO2 at Nelson Lime
Plant to eighteen months from the effective date for the final rule in
the Federal Register.
---------------------------------------------------------------------------

    \84\ 77 FR 72578. The Cholla Power Plant SO2 BART
limit required installation of inlet CEMS, with a twelve-month
compliance deadline.
---------------------------------------------------------------------------

    Comment: LNA stated that in its BART analysis submitted to EPA, the
fuel mixture control option was based upon a maximum of 6.5 percent ash
content in the proposed fuel mixture. LNA asserted that it did not
choose this value arbitrarily, but based the value on operational
knowledge and on information provided by the manufacturer of the kilns,
Kennedy Van Saun (KVS).
    Response: As noted in the proposed rule, we used a fuel mixture
consistent with a maximum 6.5 percent ash content in the SO2
BART analysis. We have not received any other comments regarding this
issue, and the final SO2 limits finalized in today's rule
reflect this maximum ash content.
    Comment: LNA asserted that EPA's estimate of the costs for DSI is
unrealistic because EPA did not use site-specific input values. In
addition, LNA said that there are errors in EPA's cost calculations.
LNA noted various issues with EPA's cost analysis for DSI and asserted
that the value of $4,200/ton of SO2 removed is too low.
    Response: We agree that our cost calculations contain an error in
the ``cost summary'' tab, which is also reflected in the TSD and in the
Federal Register preamble to our proposed rule. The total annual cost
for DSI should represent the sum of annual direct and annual indirect
costs, but did not include the annual indirect cost. We corrected this
error in a new version of the spreadsheet for today's final rule.\85\
As a result, the average cost-effectiveness values for DSI on kilns 1
and 2 increase to about $4,800/ton and $4,500/ton (from $4,174/ton and
$4,085/ton, respectively). The incremental cost-effectiveness values of
DSI, relative to the fuel mixture change, are about $10,200/ton and
$9,500/ton (from $8,803/ton and $8,576/ton, respectively). As noted in
the proposed rule, we did not consider DSI to be cost-effective on an
incremental basis relative to the fuel mixture change, given the
relatively small visibility benefits expected from DSI (0.10 dv at the
most improved class I area and 0.29 dv cumulative). Therefore, we do
not consider DSI to be cost-effective, relative to the fuel mixture
change, based on these revised and even higher dollar/ton values.
---------------------------------------------------------------------------

    \85\ ``LNA Nelson Control Costs (revised for Final Rule).xlsx''.
---------------------------------------------------------------------------

    LNA provided EPA with a detailed version of DSI cost calculations
that was designated as CBI along with a public version with most of the
calculations redacted. Because we are generally prohibited from
disclosing CBI, we relied on the publicly available information to
develop a separate set of calculations for the proposed rule. While
there are several elements of our cost estimates that differ from LNA's
CBI-protected cost calculations, these differences are immaterial in
light of our finding that DSI is not a cost-effective control option
relative to the fuel

mixture change. Therefore, we have not further revised our cost
analysis for DSI based on LNA's comments because the changes suggested
by LNA would not alter our determination that DSI is not cost-effective
for either kiln on an incremental basis.
4. BART Analysis and Determination for PM10
    Comment: ADEQ expressed support for EPA's determination that the
existing baghouse at the Nelson Lime Plant is BART for PM10.
    Response: We acknowledge ADEQ's support on this issue.
5. Other Comments
    Comment: LNA asserted that EPA's BART proposal does not provide for
differing emission rates during startup, shutdown, and malfunction
(SSM), and stated that EPA should reconsider this decision that is not
supported by the available information. The CEMS data for
NOX and SO2 that LNA submitted in its BART
analysis is based on periods of steady-state operation that does not
include periods of startup and shutdown. Since the CEMS data do not
include these emissions, LNA did not consider it appropriate for the
proposed limits to include emissions from startup and shutdown. LNA
proposed that the rolling 30-day limits in the proposed rule should
apply only during periods of normal operation, and proposed
establishing separate emission limits during periods of startup and
shutdown. LNA provided emissions data for each of the various types of
startup and shutdown events.
    Response: We agree that the emission limits in the proposed rule
did not account for emissions from periods of startup and shutdown and
we agree that the emission limits should include such periods. Because
Section 302(k) of the CAA requires emission limits such as BART to be
continuous,\86\ BART emission limits must apply at all times, including
during periods of startup, shutdown, and malfunction. We therefore
consider it appropriate to revise the proposed emission limits for
NOX and SO2 to account for emissions from periods
of startup and shutdown. In order to revise the emission limits to
appropriately account for startup and shutdown emissions, we sought
additional information from LNA following the close of the public
comment period.\87\ In response, LNA suggested retaining the rolling
30-day limits that would apply at all times, but revising them upward
to accommodate startup and shutdown emissions.\88\ Following further
discussions between EPA and LNA,\89\ LNA proposed revising the rolling
30-day limit to an annual average limit that would apply at all
times.\90\ LNA also proposed establishing short-term ton/day limits for
the Kilns, which would correspond to the short-term 24-hour average
emission rates used in the visibility modeling.\91\
---------------------------------------------------------------------------

    \86\ 42 U.S.C. 7602(k).
    \87\ Phone call between Colleen McKaughan, EPA, and Ed Barry,
LNA, on April 10, 2014.
    \88\ Letter from Ed Barry, LNA, to Colleen McKaughan, EPA (April
29, 2014).
    \89\ Conference calls between EPA and LNA, May 2 and 7, 2014.
    \90\ Letter from Ed Barry, LNA, to Colleen McKaughan, EPA (May
9, 2014).
    \91\ Id.
---------------------------------------------------------------------------

    Based on our evaluation of the additional information provided by
LNA, we are making the following revisions to the proposed emission
limits. First, we are revising the lb/ton limits from a rolling 30-day
basis to a rolling 12-month basis. As described in LNA's comments,
periods of startup can exhibit substantial emissions, but with little
to no lime production. While these startup emissions are not higher
than those observed during normal operation on a simple mass basis
(e.g., lb/hour, or ton/day), the fact that there is no production
associated with these emissions complicates their inclusion when
determining compliance with a lb/ton limit. As a result, the particular
day(s) during which a startup event occurs will appear as a short-term
spike in the kiln's emission rate (lb/ton). When combined with the
preceding 29 days of emission data, this emission spike has the effect
of driving the rolling 30-day emission rate (lb/ton) upwards. It may
then be necessary for the unit to operate at a much lower rate of
emissions over the next 29 days in order to ensure compliance with the
30-day limit, which may not be technically feasible. By establishing
the limit on a rolling 12-month basis, such short-term spikes are
averaged with data values from over an entire year, making its impact
on the rolling emission rate less pronounced.
    Second, in order to ensure that performance of the SNCR system
installed at the Nelson Lime Plant is optimized, we are including in
the final rule a series of control technology demonstration
requirements. In particular, LNA is required to prepare and submit to
EPA: (1) A design report describing the design of the ammonia injection
system to be installed as part of the SNCR system; (2) data collected
during a baseline period; (3) an optimization protocol; (4) data
collected during an optimization period; (5) an optimization report
establishing optimized operating parameters; and (6) a demonstration
report including data collected during a demonstration period. While
this type of control technology demonstration is not typically required
as part of a regional haze plan, we consider it to be appropriate here,
given the minimal data available about the performance of SNCR at lime
kilns. Based upon the data collected during this process, EPA may
revise the rolling 12-month average for the NOX emission
limit in a future notice-and-comment rulemaking action.
    Third, we are establishing short-term 24-hour average emission
limits (ton/day) consistent with the emission rate used in the
visibility modeling for each respective control option. As noted above,
revising the averaging period to an annual basis minimizes the effect
of short-term spikes in emissions over a greater data set. In effect,
this allows the Nelson Plant greater short-term emissions variability
while still demonstrating compliance with the BART limit. To ensure
that this variability does not interfere with the modeled visibility
benefit, which is based upon reductions from the highest 24-hour
average emission rate, we are establishing short-term ton/day emission
limits. These limits are combined limits that apply across both Kiln 1
and 2, on a rolling 30-kiln operating day basis. We are finalizing a
combined Kilns 1 and 2 NOX limit of 3.20 tons/day and
SO2 limit of 10.10 tons/day.

C. Comments on the Hayden Smelter

1. General Comments
    Comment: ASARCO agreed with the BART Guidelines ``that BART is not
`to redesign the source,' '' and stated this understanding is inherent
in Congress' denomination of the technology as ``best available
retrofit technology.''
    Response: We agree that BART does not require redesign of the
source.
    Comment: ASARCO noted that the BART Guidelines are not
``mandatory'' as applied to the Hayden Smelter, and that EPA must
depart from them if presented with sound technical justification.
    Response: We agree that the BART Guidelines are not binding with
respect to the Hayden Smelter, but note that the BART Guidelines serve
as persuasive guidance for all BART sources.
    Comment: ASARCO stated that, as further changes to air pollution
controls at the Hayden Smelter will be required to demonstrate
attainment of the 1-hour SO2 NAAQS, ASARCO supports EPA's
proposal to promulgate ``a performance standard as BART rather than

prescribing a particular method of control,'' if EPA determines
additional controls are needed. ASARCO stated that reconfiguration of
the smelter might be required to attain the 1-hour SO2 NAAQS
in the form of a ``converter retrofit project'' or CRP. ASARCO argued
that while detailed engineering of the CRP is substantially completed,
details must be worked out before the final project can be permitted.
Thus, ASARCO concluded that it is critical for EPA not to finalize a
BART FIP for SO2 that interferes with the Hayden area's
attainment of the SO2 NAAQS. Similarly, ADEQ urged EPA to
reevaluate its SO2 BART decision for the Hayden Smelter and
align it with controls that ASARCO has to implement in order to comply
with the 1-hour SO2 NAAQS.
    Response: Following the close of the public comment period, ASARCO
provided us with additional information concerning the CRP, including a
description of plans to replace the BART-eligible Peirce-Smith
converters with new converters. If the BART-eligible converters are
replaced prior to the BART compliance deadline, then the BART
requirements would no longer apply. Accordingly, there is no basis to
expect that the RH FIP will interfere with ASARCO's ability to ensure
attainment of the SO2 NAAQS. We also agree that a
performance standard rather than a particular method of control is
appropriate for BART. As explained further below and in a revised BART
determination included in the docket for this final rule, ASARCO has
demonstrated that separate levels of control are necessary for the
primary and secondary capture systems. Therefore, we are setting the
level of control to 99.8 percent (equivalent to the existing double
contact acid plant) for the primary capture system and 98.5 percent for
the secondary capture system. These limits only apply if ASARCO does
not replace the BART-eligible converters prior to the BART compliance
deadline.
2. BART Analysis and Determination for SO2 From Converters
    Comment: ADEQ said that EPA's disapproval of ADEQ's SO2
BART determination for the Miami and Hayden Smelters is unsupported.
Similarly, AMA requested that EPA reconsider its decision to disapprove
parts of the Arizona RH SIP because the State should make a BART
determination for the smelters according to the CAA.
    Response: These comments concern EPA's partial disapproval of the
Arizona RH SIP and are therefore untimely, as EPA has already taken
final action on the SIP.\92\ The commenters have provided no legal
basis for EPA to reconsider that action.
---------------------------------------------------------------------------

    \92\ 78 FR 46142.
---------------------------------------------------------------------------

    Comment: NPS expressed support for EPA's decisions based on the
expected substantial visibility improvements associated with installing
a new acid plant as BART for SO2 at the Hayden Smelter. In
particular, NPS agreed with EPA's decisions to protect many Class I
areas.
    Response: We appreciate NPS's support and note that the BART level
of control for the converters is a performance standard and not any
particular method of control.
    Comment: ASARCO, ADEQ, and AMA expressed doubt over the technical
feasibility of a double contact acid plant for controlling secondary
ventilation gases. ASARCO asserted that acid plants are not an
``applicable'' technology, and therefore, not an ``available''
technology for controlling secondary ventilation gases because of low
concentrations of SO2 and high variability in the exhaust
gas stream. ASARCO stated that EPA failed to evaluate the technical
feasibility of double contact acid plants when applied to these low-
strength gases, which is the second step of a BART analysis. ASARCO
argued that, had EPA conducted an adequate analysis, it would have
concluded that double contact acid plants are not an ``applicable''
technology because they do not have a ``practical potential for
application'' to the secondary ventilation gases and hence are not an
``available'' technology. ADEQ and AMA echoed ASARCO's comments, urging
EPA to look at the information submitted by ASARCO and reconsider its
proposal.
    Response: We do not agree that a double contact acid plant is
technically infeasible for the secondary gas stream at the Hayden
Smelter. As explained in the BART Guidelines, control technologies are
technically feasible if either (1) they have been installed and
operated successfully for the type of source under review under similar
conditions, or (2) the technology could be applied to the source under
review.\93\ The BART Guidelines further explain that the regulatory
authority must exercise technical judgment in determining whether a
control alternative is applicable to the source type under
consideration. In most cases, a commercially available control option
is presumed applicable if it has been used on the same or a similar
source type. Absent a showing of this type, one must evaluate technical
feasibility by examining the physical and chemical characteristics of
the pollutant-bearing gas stream, and comparing them to the gas stream
characteristics of the source types to which the technology had been
applied previously.\94\ In this instance, a double contact acid plant
is already in use at the Hayden Smelter. Therefore, it is presumed to
be an applicable technology, absent a demonstration that specific
circumstances preclude its application to a particular emission unit.
Generally, such a demonstration involves an evaluation of the
characteristics of the pollutant-bearing gas stream and the
capabilities of the technology.\95\ No such demonstration of technical
infeasibility has been made here. On the contrary, the record
establishes that a double contact acid plant is feasible for the
secondary gas stream at the Hayden Smelter.
---------------------------------------------------------------------------

    \93\ 40 CFR part 51, appendix Y, section IV.D.2.
    \94\ Id.
    \95\ See Id.
---------------------------------------------------------------------------

    In particular, while the secondary gas stream has a lower
SO2 concentration and higher volumetric flow rate than the
primary gas stream, these differences do not render a double contact
acid plant technically infeasible. Indeed, EPA concluded more than 30
years ago that ``[i]t is technically feasible . . . to design acid
plants that will operate auto-thermally on feed streams that exhibit
SO2 concentrations below the 3.5 to 4.0 percent range.''
\96\ The commenters have offered no evidence to refute this conclusion.
Contrary to the commenters' suggestions, ASARCO's contractors, Gas
Cleaning Technologies (GCT) and MECS,\97\ have not stated that use of a
double contact acid plant is technically infeasible.\98\ Rather, they
have indicated that use of this technology would present additional
technical challenges that would make it more costly and less effective
than estimated by EPA. In particular, GCT states that ``[a] more
realistic 60 ppmv [parts per million by volume] outlet concentration
would mean only 96 [percent] SO2 removal efficiency by such
an acid plant at ASARCO. . . . when a realistic capital cost and
removal efficiency is used for the acid plant, the $/ton SO2
removed estimate will be more than double the $872/ton

SO2 indicated by EPA.'' \99\ However, as explained in the
BART Guidelines, where the resolution of technical difficulties is
merely a matter of increased cost, you should consider the technology
to be technically feasible.\100\ Therefore, in this instance, EPA
considers a double contact acid plant to be a technically feasible
option for control of the secondary gas stream. ASARCO's assertions
regarding cost-effectiveness are addressed below.
---------------------------------------------------------------------------

    \96\ 1984 NSPS Review at 4-3.
    \97\ This is the name of the company.
    \98\ See Letter from Steven Puricelli, MECS, to Matt Russell,
GCT (March 5, 2014)(``MECS Letter'') (``A double acid plant could
operate with this low secondary gas concentration . . .''); Letter
from Matt Russell, GCT, to Jack Garrity, ASARCO (``GCT
Letter'')(February 12, 2014) at 2 (``it may be technically feasible
to operate an acid plant on the converter secondary gases . . .'').
    \99\ GCT Letter at 2 (``A more realistic 60 ppmv outlet
concentration would mean only 96% SO2 removal efficiency
by such an acid plant at ASARCO . . . when a realistic capital cost
and removal efficiency is used for the acid plant, the $/ton
SO2 removed estimate will be more than double the $872/
ton SO2 indicated by EPA.'').
    \100\ 40 CFR part 51, appendix Y, section IV.D.2.
---------------------------------------------------------------------------

    Comment: ASARCO stated that there are deficiencies in EPA's cost
analysis for an acid plant. First, ASARCO asserted that EPA cannot rely
upon the cost formula from the 1984 NSPS Review for an acid plant
without validating current costs and, as a result, has substantially
underestimated the cost of the proposed acid plant for the secondary
ventilation gases. ASARCO stated that the equation that EPA used was
derived from double-contact acid plants that were processing primary
ventilation gases with significantly higher SO2
concentration (4.5 percent to 8.0 percent) and flow rates up to 140,000
standard cubic feet per minute (scfm). This compared to rates for
secondary ventilation gases at 0 to1 percent SO2 and 275,000
scfm.\101\ ASARCO stated that EPA's extrapolation to lower
concentrations cannot be justified because none of the data points
included double-contact acid plants treating secondary ventilation
gases, for which MECS gave a significantly higher cost estimate.
---------------------------------------------------------------------------

    \101\ The original comment referred to a ``0-0.1'' percent
concentration for secondary ventilation gases. ASARCO Comment Letter
at 9. However, this appears to be an error, as the same letter also
states that ``[a]t the Hayden Smelter, the SO2 content of
secondary ventilation gas ranges from 0 to 1 [percent]
SO2 or approximately 0 to 10,000 ppm, and averages 1580
ppm.'' ASARCO Commenter Letter at 5.
---------------------------------------------------------------------------

    Second, ASARCO stated that supplemental heating of the acid plant
influent gas is required, but there is no supplemental heat available
to reduce heat load requirements as suggested by EPA. ASARCO noted that
GCT evaluated the potential for using existing sources for heat and
concluded that it ``does not expect any available heat source to be
able to provide more than a small percentage of the heat required.''
ASARCO added that EPA does not appear to have accounted for the
additional heat required after the interpass absorption process, nor
the additional electrical energy associated with handling this larger
volume of secondary ventilation gases.
    Third, ASARCO stated that EPA failed to account for other costs
including dehumidification, which is expensive due to equipment
installation and maintenance costs as well as the energy required to
run the refrigeration system. ASARCO also stated that the incoming gas
stream will require added compensatory preheating of the gas stream,
which is an additional energy requirement that EPA does not appear to
have addressed. Finally, ASARCO stated that EPA cannot reduce the cost
to control secondary ventilation gas by shifting additional gas to the
primary acid plant because the existing plant does not have the
capacity to take any secondary gases without converter retrofit.
    Based on the foregoing, ASARCO and ADEQ asserted that EPA had
underestimated the cost of a new acid plant by at least a factor of
two.
    Response: We do not agree that the cost estimates provided by MECS
and GCT are more accurate than EPA's cost estimates because both
contractors characterized their estimates as ``ballpark,''
``approximate,'' and ``order-of-magnitude.'' \102\ Nonetheless, we note
that, even if our original cost estimate for an acid plant of $872/ton
is increased by a factor of two, as suggested by the commenter, this
would result in control costs of about $1,800/ton of SO2. We
consider $1,800/ton of SO2 to be very cost-effective,
especially in light of the large visibility benefits that are expected
to result from these controls. However, based on additional information
provided by ASARCO, we have revised our BART analysis in several
respects, including the addition of an amine scrubber as a third
control option. As explained in a revised BART analysis included in the
docket for the final rule,\103\ we find that an amine scrubber would
result in greater emission reductions and would be even more cost-
effective than an acid plant. Therefore, we are revising our BART
determination to reflect use of an amine scrubber rather than an acid
plant for the secondary stream.
---------------------------------------------------------------------------

    \102\ MECS Letter at 1; GCT Letter at 2.
    \103\ Revised BART Analysis for SO2 at ASARCO
Hayden--Converters 1, 3, 4, and 5 (June 2014).
---------------------------------------------------------------------------

    Comment: ASARCO stated that EPA underestimated the costs of wet
scrubbing. For example, ASARCO asserted that the TSD does not address
the technical feasibility of applying caustic wet scrubbing to the
characteristics of the secondary ventilation gases at the Hayden
Smelter compared to other applications for caustic wet gas scrubbing.
ASARCO asserted that these differences affect the design basis and
capital and operating costs associated with caustic wet scrubbing.
ASARCO further noted that EPA omitted the cost of treating or
landfilling the sludge from the caustic wet scrubbers, installing and
operating a booster fan, and possible stack modifications. ASARCO
stated that its own estimates for treating and landfilling the sludge
are more than double EPA's total annual cost estimate.
    Response: In the proposed FIP, we estimated an annual cost of $972/
ton to control SO2 from the secondary gas stream using a
caustic wet scrubber. This estimate is based on cost information
provided by ASARCO. If we increase the sludge disposal costs to the
degree that ASARCO proposes while simultaneously increasing the control
efficiency from 85 to 90 percent as ASARCO suggested,\104\ our estimate
of annual costs range from $909/ton, if the sludge is treated as solid
waste, to $1,291/ton, if all sludge is treated as hazardous waste. We
consider any cost in this range to be highly cost-effective. However,
as explained in our revised BART analysis, use of a wet scrubber is
more expensive on a $/ton basis and would result in fewer emissions
reductions than an amine scrubber. Therefore, we consider a control
efficiency of 98.5 percent, achievable with an amine scrubber, to
constitute BART.
---------------------------------------------------------------------------

    \104\ GCT Letter at 4.
---------------------------------------------------------------------------

    Comment: ASARCO stated that EPA failed to properly consider the
energy and non-air quality environmental impacts of compliance, which
is the second BART factor. ASARCO asserted that the energy requirements
for the proposed acid plants for the secondary ventilation gases are
excessive and would require additional heat supplementation and
additional electrical energy associated with handling the larger volume
of secondary ventilation gases compared to primary ventilation gases.
ASARCO also stated that the collateral emissions from preheating would
be excessive. ASARCO provided a table using AP-42\105\ for large
boilers and assuming low NOX burners, which shows that the
acid plant will cause a net increase in pollutants. This increase,
according to ASARCO, would be greater than the actual NOX
emissions from the BART-eligible units.
---------------------------------------------------------------------------

    \105\ ``AP 42'' refers to EPA's Compilation of Air Pollutant
Emission Factors. See http://www.epa.gov/ttnchie1/ap42/.

---------------------------------------------------------------------------

    Response: We do not agree that we failed to properly consider the
energy and non-air quality environmental impacts of compliance. We have
weighed these impacts along with the other four BART factors in
reaching a BART determination. In particular, we do not agree that the
energy requirements for the proposed double contact acid plant for
secondary ventilation gases are excessive. On the contrary, we consider
these impacts to be reasonable given the significant emission
reductions and associated visibility benefits. Finally, we expect that
any new combustion equipment required to heat the secondary stream will
emit well below the AP-42 levels, which were published in 1998.
However, if they were to emit at the levels claimed by the commenter,
these emissions would have a far lower impact on visibility than the
thousands of tons of SO2 presently emitted annually through
the annular stack. In particular, the increases in the major
visibility-impairing pollutants cited by the commenter (68.5 tpy of
NOX, 0.29 tpy of SO2 and 3.7 tpy of PM) are quite
modest in comparison to the projected reductions in SO2 of
about 20,000 tpy resulting from these controls.
    Comment: ASARCO stated that the volume of wet scrubber sludge
creates collateral environmental impacts, such as increased truck
emissions, truck traffic, risks of accidents, and consumption of
landfill space.
    Response: Most of the impacts noted by ASARCO are either air
impacts (e.g., increased truck emissions) or non-environmental impacts
(e.g., risk of accidents), and therefore do not fall within the scope
of ``energy and non-air quality environmental impacts.'' With regard to
the consumption of landfill space, we consider this impact to be
reasonable in relation to the large visibility benefits and modest
costs of control. As noted above, even if we were to double the sludge
disposal costs, our estimate of annualized costs would not increase
significantly.
    Comment: ASARCO stated that EPA has not demonstrated that its
proposed SO2 removal rate (52.145(l)(4)(i)) is achievable in
practice by the existing primary acid plant. ASARCO asserted that EPA
cannot use a 365-day average performance estimate as a 30-day limit
because the 99.8 percent estimate is based on what the acid plant will
achieve on average over the course of a year. ASARCO stated that a 30-
day limit forces the existing acid plant to perform better than an
annual limit even though EPA did not undertake a BART analysis to
support the lower 30-day limit. Further, ASARCO stated that the
proposed removal rate applies to periods that contain SSM events, which
typically are not included in annual acid plant performance estimates
or vendor guarantees. Therefore, ASARCO concluded that no data exists
to support EPA's inclusion of SSM emissions in the proposed limit. ADEQ
also suggested that EPA may have misinterpreted information provided by
ASARCO concerning the performance of the primary acid plant, converting
the annual design value to a rolling 30-day limit.
    Response: We agree that the control efficiency was determined using
annual production and emissions data. Based on this information, we
have modified the final determination so that the limit on the double
contact acid plant is a rolling 365-day average rather than a rolling
30-day average. This revision also addresses ASARCO's concern regarding
SSM emissions because the 99.81 percent control efficiency estimate
provided by ASARCO includes all emissions going to the acid plant and
therefore accounts for startup and shutdown emissions.\106\
Furthermore, excess emissions from malfunctions are, by definition,
unforeseeable and therefore cannot be accounted for within an emission
limit.
---------------------------------------------------------------------------

    \106\ Letter from Jack Garrity, ASARCO to Thomas Webb, EPA, July
11, 2013 at 15.
---------------------------------------------------------------------------

    Comment: ASARCO stated that EPA's proposed method for the
determination of compliance with the proposed limit is subject to
significant error. Specifically, ASARCO stated that the measurement
error in its tailstack CEMS is ``sufficient to vary calculated results
a full 0.1 [percent]'' and ``[t]he measurement error on the strong gas
analyzer is nearly as great as the span of the tail gas CEMS.'' ASARCO
added that its measurements of sulfuric acid production also ``lack the
precision and accuracy needed for continuous demonstration of
compliance.'' AMA also asserted that it is not technically feasible to
continuously measure SO2 in order to demonstrate compliance
with the requirement contemplated by EPA.
    Response: We do not agree with these comments. Because compliance
with the emission limit is determined on a cumulative mass basis over a
rolling 365-day period, it is measurable as a practical matter. The
difference in scale between the inlet and outlet CEMS is not relevant
because control efficiencies are calculated based on the ratio of the
data from the two CEMS, not the difference.
    For example, consider a situation where 1,000 pounds of
SO2 enters the acid plant and is controlled by 99.8 percent,
resulting in emissions of 2 pounds of SO2. The inlet
measurement could vary by 10 percent (i.e., the CEMS could read
anything from 900 to 1,100 pounds, which is +/- 100 pounds) without
affecting the compliance measurement, which is rounded to the tenths
place. The following sample calculations with varying inlet CEMS
readings demonstrate this concept:
    The control efficiency is calculated using the following equation:

(1 - (SO2-out/SO2-in)) * 100 percent = Control
efficiency as a percent

    If the inlet CEMS provides a true measurement, the control
efficiency would be:

(1 - (2/1000)) * 100 percent = 99.8 percent

    If the inlet CEMS reads 100 pounds low, the control efficiency
would be:

(1 - (2/900)) * 100 percent = 99.778 percent, which rounds to 99.8
percent

    If the inlet CEMS reads 100 pounds high, the control efficiency
would be:

(1 - (2/1100)) * 100 percent = 99.818 percent, which rounds to 99.8
percent

    Therefore, even if the inlet measurement varied by 100 pounds (10
percent), it would not affect the control efficiency. Thus, the
difference in scale between the acid plant inlet CEMS and tailstack
CEMS is not relevant. Finally, we note that, while the FIP provides for
an alternative compliance demonstration using acid production rates, we
are not requiring the use of this method. Therefore, ASARCO may use the
CEMS rather than acid production rates to demonstrate compliance.
    Comment: ASARCO expressed concern that EPA incorrectly
characterized ASARCO as using ``limited cesium catalyst,'' and may not
recognize that ASARCO has already installed cesium-promoted catalyst to
the extent recommended by MECS.
    Response: Our characterization of ASARCO's use of cesium catalyst
as ``limited'' was not intended to suggest that additional cesium-
promoted catalyst is necessary or appropriate for the existing double
contact acid plant at the Hayden Smelter. Rather, we noted the
``limited'' use of cesium catalyst at the existing double contact acid
plant as evidence that the 99.8 percent control efficiency achieved by
the existing double contact acid plant is a reasonable estimate of the
efficiency achievable at a new double contact acid plant.
    Comment: ASARCO stated that the proposed limit should be adjusted
to

reflect the realities of metallurgical acid plant operation. ASARCO
added that a simpler measure, similar to the NSPS for Primary Copper
Smelters' use of a limit on SO2 in the tail gas, is likely a
better solution, which would accommodate the process variation and
measurement error that will be encountered. Until such a standard is
developed, ASARCO asserted that the work practice standard in paragraph
(l)(12) and the existing NSPS limit of 650 ppmv, six-hour average,
under which the smelter already achieves substantial emission
reductions, provides a workable limitation to ensure existing emission
reductions are maintained.
    Response: We recognize the variable nature of the process and the
difficulty involved in measuring a high control efficiency. For these
reasons, we are proposing a rolling 365-day average calculated on a
cumulative mass basis. Furthermore, because the amount of
SO2 emitted by the converters is constantly varying, a
simple concentration-based limit cannot be used to demonstrate that the
process is under control.
    Comment: ASARCO stated that caustic wet scrubbing of the acid plant
tail gas is not cost-effective for BART.
    Response: We agree that adding a wet scrubber to scrub the acid
plant tail gas is not cost-effective for BART.
    Comment: Earthjustice stated that its primary concern with EPA's
SO2 BART determination for the Hayden Smelter is the fate of
the ``uncaptured'' or fugitive emissions which, while a large amount
estimated at 1,209 tpy, are not addressed by EPA. Earthjustice
indicated that EPA should require an analysis of shop ventilation using
a computational fluid dynamic (CFD) model that, according to
Earthjustice, is a common technique used to enhance capture of fugitive
emissions in older shops. Earthjustice stated that requiring
implementation of the resulting recommendations would enhance the
capture system for the shop so that fugitive emissions are captured by
a modified primary or secondary system, which would allow for treatment
in the current/proposed emissions control systems (such as the PM
controls and the acid plant).
    Response: We recognize that there is uncertainty in the
determination of fugitive emissions from the Hayden Smelter. Therefore,
rather than specify a capture efficiency, we have established a work
practice standard that requires ASARCO to design and operate a
secondary capture system optimized to capture the maximum amount of
process off-gas vented from each converter at all times. In order to
demonstrate compliance with this requirement, ASARCO must submit a
written operation and maintenance plan to EPA for approval 180 days
prior to the applicable compliance date and must comply with this plan
thereafter, once it is approved by EPA. Since ASARCO has performed CFD
analyses on the Hayden Smelter, we would expect the company to submit
such analyses for review by EPA in determining whether the secondary
capture system is optimized to capture the maximum amount of process
off-gas.
    Comment: Earthjustice stated that EPA's decision to split emissions
between the baseline primary, secondary, and uncontrolled, uncaptured
streams might not be accurate, because EPA does not provide any support
for these emissions levels other than noting that they are based on
estimates by the company.
    Response: We disagree with this comment, which refers to emissions
calculations in the Arizona RH SIP and a comment letter from ASARCO
regarding the SIP.\107\ Our BART analysis did not rely on these
emissions calculations. Rather, we relied upon emissions data reported
by ASARCO to ADEQ, which we consider to be the best emissions
information available for the Hayden Smelter. The data for the primary
and secondary emissions is based on CEMS. While there is uncertainty
inherent in any calculation of uncaptured emissions, Earthjustice has
not provided any more credible emissions information or provided a
mechanism for decreasing uncertainty in the quantification of
uncaptured emissions. We do not have a copy of the 1994-1995 fugitive
emissions study and did not rely directly on this study to estimate
uncaptured emissions.
---------------------------------------------------------------------------

    \107\ See Earthjustice Comment Letter at 31, notes 53-56.
---------------------------------------------------------------------------

    Comment: Earthjustice stated that EPA proposed to require a 99.81
percent reduction of the Hayden Smelter's SO2 emissions from
the primary and secondary capture systems apparently based on the fact
that the existing plant is capable of achieving that level of control.
However, Earthjustice asserted that greater control efficiencies are
achievable, and that EPA must therefore revise its BART analysis to
incorporate the most stringent emission control level that the
technology is capable of achieving (citing the BART Guidelines).
Earthjustice, citing a paper regarding the Kennecott Smelter, stated
that 99.95 percent control efficiency is achievable. Based on another
report by the technology vendor Cansolv, Earthjustice suggested that a
99.93 percent reduction is achievable. Earthjustice noted that the
latter report also states that the CANSOLV[supreg] SO2
Scrubbing System can achieve an outlet SO2 concentration as
low as 0.15 lb SO2/ton acid, as opposed to EPA's proposed
BART level of 2.49 lb/ton acid. Earthjustice urged EPA to increase the
requirement for control at the acid plant(s) to 99.93 percent or
greater.
    Response: We do not agree that our proposal to require a 99.8
percent control efficiency is insufficiently stringent. The examples
cited by Earthjustice are not directly comparable to the Hayden
Smelter. The Kennecott Smelter uses a flash copper converting
technology that produces copper on a continuous basis, unlike the
Hayden Smelter's batch-process system. Replacing the batch-process
converters at the Hayden Smelter with continuous converters would
require a redesign of the system, which is not within the scope of
BART.\108\ Therefore, we do not consider the 99.95 percent control
efficiency achieved at the Kennecott Smelter to be appropriate for
determining BART at the Hayden Smelter.
---------------------------------------------------------------------------

    \108\ 70 FR 39164 (``We do not consider BART as a requirement to
redesign the source when considering available control
alternatives.'')
---------------------------------------------------------------------------

    The report on the Cansolv system provided by Earthjustice is a
presentation given by Cansolv representatives at a trade show for
fertilizer manufacturers. The figure of 0.15 lbs SO2 per ton
of acid produced (10 ppmv SO2) is a low-end estimate and is
lower than any of the outlet concentrations in the table of results
provided by Earthjustice. The report did not provide enough information
to allow us to determine whether any of the facilities listed in the
table operate a process similar enough to batch process copper smelting
to be directly comparable to the Hayden Smelter. However, as explained
above, ASARCO's contractors have stated that, ``for this application,
Cansolv has indicated that they can achieve close to 99 [percent]
removal efficiency with a 20 ppmv outlet gas stream.''\109\ Therefore,
we consider 98.5 percent to be a reasonable estimate of the control
efficiency achievable with Cansolv for treatment of the secondary
stream at the Hayden Smelter.
---------------------------------------------------------------------------

    \109\ GCT Letter at 3.
---------------------------------------------------------------------------

    Comment: Earthjustice stated that EPA should have considered DSI
for the control of the acid plant tailstack.
    Response: We disagree with this comment. DSI is commonly used to
control SO2 at combustion sources such as coal-fired power
plants and

incinerators. DSI requires particulate control (e.g., a baghouse or
electrostatic precipitator) in order to collect the used sorbent. Thus,
DSI may be a cost-effective technology when sorbent can be injected
upstream of a particulate control device that either is already in
service or otherwise required to meet a particulate matter limit.
However, we are not aware of any facilities in any industry that use
DSI downstream of an acid plant. Therefore, we do not consider it a
technically feasible technology in this case.
3. BART Analysis and Determination for SO2 From the Anode
Furnaces
    Comment: Earthjustice asserted that the 38 tpy of SO2
emissions from the anode furnaces are significant, and that EPA has
routinely controlled sources with this level of SO2
emissions in many other instances. Accordingly, Earthjustice urged EPA
to require DSI for SO2 controls for the anode furnaces,
which typically achieves emissions reductions in the range of 50 to 70
percent or greater depending on process conditions. Earthjustice
indicated that EPA should fully evaluate this option. According to
Earthjustice, EPA suggested a work practice standard requiring the use
of blister copper or higher purity copper. Earthjustice stated that it
is unclear how this work practice standard will help reduce emissions
(because presumably the anode furnaces are currently charged with the
98 to 99 percent pure blister copper), or how it will be enforced.
    Response: At the Hayden Smelter, the anode furnaces are charged
only with blister copper, which is nearly 98 percent pure copper. While
the estimated 38 tpy of SO2 emissions from the anode
furnaces may not be ``insignificant,'' they are undoubtedly small
compared to the more than 20,000 tpy of uncaptured emissions from the
converters. Moreover, while Earthjustice asserted that ``EPA has
routinely controlled sources with this level of SO2
emissions in many other instances,'' it has not provided any examples
of controls on emissions of this level under the RHR. Because the
potential SO2 emissions from the anode furnaces are quite
low relative to the airflow, DSI would not be cost-effective for
SO2 removal at roughly $25,000/ton.\110\ We have included
work practice standards and recordkeeping requirements in the FIP to
assure that only blister copper is used in the anode furnace.
---------------------------------------------------------------------------

    \110\ See ``Anode Furnace--DSI Cost Calculations.'' We note that
these capital costs in these calculations are based upon a much
lower flowrate than that of the anode furnaces, Therefore, we
consider these estimates to be very conservative (i.e., tending to
underestimate rather than overestimate in this instance).
---------------------------------------------------------------------------

    Comment: ASARCO stated that EPA should clarify that the requirement
for ``charging'' only high quality copper does not preclude fluxes and
reducing agents such as natural gas and steam. ASARCO is concerned that
the proposed language in 40 CFR 52.145(l)(4)(v) could be misinterpreted
to prevent the company from poling (i.e., reducing the metal in the
furnace to remove oxides) or adding any final fluxing agents to achieve
anode casting chemistry requirements. ASARCO explained that while the
bulk of converting occurs in the converters, some final refining occurs
in the anode furnaces prior to anode casting. Therefore, ASARCO must be
able to ``pole'' or reduce the furnace (using natural gas and/or steam)
and add flux agents to achieve final chemistries. ASARCO suggested the
following revision:

    Anode furnaces 1 and 2 shall only be charged
with blister copper or higher purity copper. This charging
limitation does not extend to the use or addition of poling or
fluxing agents necessary to achieve final casting chemistry.

    Response: We are including this language in the final regulatory
text because we base our cost calculations for controlling
SO2 emissions from the anode furnaces on the current use of
the anode furnaces, which do not process concentrates or matte with
significant sulfur content. We have modified the regulatory language
explicitly to allow the use of poling and fluxing agents. We expect any
SO2 emissions resulting from the use of such agents to be de
minimis because of the very low SO2 content of natural gas
and steam.
4. BART Analysis and Determination for NOX
    Comment: ADEQ asserted that EPA's disapproval of ADEQ's
determination that the Hayden and Miami Smelters are not subject to
BART for NOX has no statutory basis, and that EPA's
imposition of BART for NOX emissions on smelters is
arbitrary and capricious. ADEQ argued that it had correctly determined
that the smelters are not subject to BART for NOX because:
    (1) EPA's regulations provide that a facility whose potential to
emit (PTE) a particular pollutant is below a certain ``significance''
threshold--40 tpy for NOX --is automatically not subject to
BART; and
    (2) the units' NOX emissions do not cause or contribute
to regional haze, because the modeled impacts for each facility's
NOX emissions are less than 0.5 dv.
    ADEQ said that EPA argued that the PTE for the smelters should be
calculated assuming continuous operation at maximum capacity. In ADEQ's
opinion, this was inconsistent with EPA's acknowledgement of the
smelters' batch process which precludes continuous operation. ADEQ
further reasoned that even if the NOX emissions from the
smelters were above the 40 tpy threshold and considered significant,
the emissions still would not contribute to regional haze because their
impact is less than 0.5 dv from each of the facilities. The estimated
visibility impacts from NOX emissions are expected to be
0.11 dv for the Miami Smelter and 0.01 dv from the Hayden Smelter,
according to ADEQ.
    Response: To the extent that these comments concern EPA's partial
disapproval of the Arizona RH SIP, they are untimely. EPA has already
taken final action on the SIP.\111\ To the extent that that comments
dispute EPA's proposed determination that the copper smelters are
subject-to-BART for NOX, we disagree with their substance.
Under the RHR, a BART determination is required for each ``BART-
eligible source'' in the State that emits ``any air pollutant'' which
may cause or contribute to any impairment of visibility in any Class I
area. All such sources are subject to BART.\112\ Thus, EPA and states
``must look at SO2, NOX, and direct PM
emissions'' in determining whether sources cause or contribute to
visibility impairment.\113\ When all of these emissions are accounted
for, the Hayden Smelter has a total visibility impact greater than 0.5
dv at multiple Class I areas, and is therefore subject to BART.\114\
---------------------------------------------------------------------------

    \111\ 78 FR 46142.
    \112\ 40 CFR 51.308(e)(ii)(A).
    \113\ BART Guidelines, 40 CFR Part 51, appendix Y, section
III.A.2.
    \114\ See, e.g. TSD at 68, Table III.D-4 (showing base case
impact of greater than 0.5 dv at 11 Class I Areas).
---------------------------------------------------------------------------

    Once a source is determined to be subject to BART, the RHR allows
for the exemption of a specific pollutant from a BART analysis only if
the PTE for that pollutant is below a specified de minimis level, in
this instance, 40 tpy for NOX.\115\ PTE is defined as the
maximum capacity of a stationary source to emit a pollutant under its
physical and operational design.\116\ Physical or operational
limitations on emissions capacity (e.g., restrictions on hours of
operation) may be taken into account, but only if those limitations are
federally enforceable. 40 CFR 51.301. There are currently no federally

enforceable physical or operational limitations that would limit the
PTE of the BART-eligible units at either the Hayden or Miami Smelters
below the NOX de minimis threshold of 40 tpy. Therefore, we
are finalizing our determination that both smelters are subject to BART
for NOX.
---------------------------------------------------------------------------

    \115\ 40 CFR 51.308(e)(1)(ii)(C).
    \116\ 40 CFR 51.301.
---------------------------------------------------------------------------

    Comment: AMA disagreed with EPA's proposed NOX emissions
cap. AMA asserted that EPA does not have the authority to finalize the
proposed cap on NOX emissions. According to AMA, if the
source has been determined to be subject to BART for a particular
pollutant, EPA has, according to the CAA, the following two options:
(1) Impose BART controls based on the outcome of the five-factor
analysis or (2) determine that a source's emissions are de minimis and
exempt them from the BART analysis.\117\ AMA said that the
NOX emission caps are arbitrary and capricious and should
not be included in the final rule.
---------------------------------------------------------------------------

    \117\ See Freeport-McMoRan Copper & Gold, Comments on Proposed
Federal Implementation Plan for Arizona Regional Haze (EPA-R09-OAR-
2013-0588) and Request for Reconsideration of the Partial
Disapproval of Arizona State Implementation Plan at 14.
---------------------------------------------------------------------------

    Response: We do not agree with this comment. Regional haze SIPs and
FIPs must contain ``emission limitations representing BART'' for all
subject-to-BART sources.\118\ In particular, either the State or EPA
must establish an enforceable emission limit ``for each subject
emission unit at the source'' and ``for each pollutant subject to
review'' that is emitted from the source.\119\ This requirement applies
even where BART is determined to be an emission limit consistent with
existing controls. Otherwise, emissions could increase to a level where
additional controls would be warranted for BART, but no mechanism would
exist to require such controls.
---------------------------------------------------------------------------

    \118\ 40 CFR 51.308(e).
    \119\ BART Guidelines, 40 CFR part 51, appendix Y, section V.
---------------------------------------------------------------------------

    Comment: ASARCO commented that a traditional low-NOX
burner does not have practical application to the converters. ASARCO
noted that EPA cites ``AirControlNet, Version 4.1 documentation report
by E.H. Pechan and Associates, Inc.'' dated May 2006, section III, page
445, as support for its claimed 50 percent control efficiency for low-
NOX burners in the converters and/or anode furnaces. ASARCO
asserted that this claim is erroneous because the report is based on
NOX SIP Call data, which did not focus on the primary metals
industry and is of questionable relevance. Further, ASARCO stated that
EPA would need to demonstrate that low-NOX burner flame
design and size constraints are appropriate for use in the converter
and anode furnace architecture. ASARCO also stated that it is likely
that low-NOX burners cannot achieve 50 percent control at
the Hayden Smelter. Therefore, EPA has underestimated the cost of
control and must recalculate.
    Response: ASARCO did not provide any documentation to support its
claims regarding control efficiency and cost. Therefore, there is no
basis in the record for EPA to revise our own estimates. In any case,
any increases in the estimated cost-effectiveness of controls would not
alter the ultimate outcome in this case, since we are finalizing our
determination that BART for NOX is an emission limit
consistent with no additional controls.
    Comment: ASARCO stated that BART does not authorize
``precautionary'' limits or other limits to ``ensure the
enforceability'' of a determination that no controls are required.
ASARCO also stated that EPA must increase the limit to account for any
NOX generated by EPA-mandated controls. ASARCO asserted that
EPA does not cite, nor can it, any legal basis for imposing an
``unqualified limit'' where the BART analysis concludes ``no further
controls.''
    Response: We do not agree with this comment. RH SIPs and FIPs must
contain ``emission limitations representing BART'' for all subject-to-
BART sources. In particular, either the State or EPA ``must establish
an enforceable emission limit for each subject emission unit at the
source and for each pollutant subject to review that is emitted from
the source.'' This requirement applies even where BART is determined to
be an emission limit consistent with existing controls. As explained
elsewhere in this notice, we are finalizing our determination that the
Hayden Smelter is subject-to-BART for NOX. Therefore, an
emission limitation representing BART for NOX is required.
    We also do not agree that our proposed limit of 40 tpy effectively
imposes controls. As explained in our proposal, the baseline emission
rate of 50 tpy used for purposes of our BART analysis ``assumes that
all of the converters are all operating simultaneously, which is not
how they typically operate. Therefore, we expect actual emissions to be
well below 40 tpy, which is consistent with ASARCO's own estimate.''
\120\ ASARCO has not retracted or modified its prior statement that
actual NOX emissions from the Hayden Smelter are below 40
tpy. Accordingly, ASARCO should be able to meet a limit of 40 tpy
without installation of any new controls. Furthermore, setting an
emission limit of 40 tpy NOX satisfies the requirements of
40 CFR 51.308(e) for NOX and ensures that NOX
emissions from the BART-eligible units will not contribute
significantly to visibility impairment in the future.
---------------------------------------------------------------------------

    \120\ 79 FR 9347 (citing Letter from Krishna Parameswaran,
ASARCO, to Gregory Nudd, EPA dated March 6, 2013, page 15).
---------------------------------------------------------------------------

    Comment: ASARCO stated that the long-term strategy does not require
emission limits on the smelter, stating that NOX emissions
from the smelter contribute 0.01 dv or less to regional haze. As such,
ASARCO asserted that imposing limits on the smelter is not necessary to
achieve the RPGs established by Arizona and, therefore, EPA has no
legal basis for imposing a 40 tpy cap.
    Response: We do not agree with this comment. As noted above, the
promulgation of NOX limits for the BART-eligible units at
the Hayden Smelter is required under 40 CFR 51.308(e). With regard to
the requirements of the long-term strategy, in addition to the
requirement cited by ASARCO, 40 CFR 51.308(d)(3)(v)(F) requires
consideration of the ``enforceability of emission limitations and
control measures'' (including BART emission limitations) as part of the
long-term strategy.
    Comment: Earthjustice asserted that EPA's analysis and conclusions
regarding NOX emissions from the Hayden Smelter are flawed
because EPA estimated the Hayden Smelter's NOX emissions
based solely on the consumption of natural gas used as fuel in the
converters and anode furnaces. EPA did not account for process
emissions of NOX, such as thermal NOX. According
to ASARCO, EPA did not evaluate thermal or process NOX
emissions for any of the converters and anode furnaces at the Hayden
Smelter, and did not address why there would not be thermal
NOX generation at these sources. Earthjustice requested that
EPA redo its entire NOX analysis, and start by requiring
NOX test data from the smelters for their various sources.
Earthjustice stated that EPA should then properly assess the baseline
NOX emissions and proceed accordingly in terms of control
technology evaluation and modeling, as needed.
    Earthjustice added that even if EPA maintains the proposed 12-month
rolling cap of 40 tpy as BART in the final rule, it should require
testing to demonstrate compliance with the BART limit. Earthjustice
believes that such testing should not only ensure that the

Hayden Smelter's NOX emissions stay below 40 tpy, but would
inform the analysis in 2018 for the second implementation period.
Earthjustice stated that for the Hayden Smelter and all other sources,
it is important to use actual emissions data based on site-specific
testing, rather than rough emissions estimates based on AP-42 or other
unsupported emissions factors.
    Finally, Earthjustice stated that in order to more accurately
determine the Hayden Smelter's NOX emissions, EPA should
also analyze NOX emissions from the flash furnaces which,
although not BART-eligible, might also be significant sources of
NOX emissions. Even though the flash furnaces are not BART-
eligible, Earthjustice stated that EPA should require reasonable
progress controls at the flash furnaces to put Arizona's Class I areas
closer to the 2064 glide path.
    Response: We agree that some NOX emissions might be
formed in the converters, but we have no reliable means of estimating
the quantity of such thermal NOX. We note that, because of
the high activation energy of the reactions required to form
NOX from oxygen and nitrogen, the rate of reaction is known
to increase rapidly at temperatures above 1540 [deg]C. This is hotter
than the temperatures found in a Peirce-Smith converter.\121\
---------------------------------------------------------------------------

    \121\ Alternative Control Techniques Document--NOX
Emissions from Process Heaters (Revised), OAQPS (September 1993).
---------------------------------------------------------------------------

    Further, we do not consider an evaluation of NOX
emissions from the flash furnaces to be necessary or appropriate for
purposes of ensuring reasonable progress for this planning period. As
explained in our proposal, we conducted a screening of point sources of
NOX throughout Arizona to determine which sources would be
potential candidates for RP controls.\122\ We did not identify the
flash furnaces at the Hayden Smelter as a potentially affected source
because they did not have any reported NOX emissions. This
evaluation should be revisited in future planning periods.
---------------------------------------------------------------------------

    \122\ See 79 FR 9352.
---------------------------------------------------------------------------

5. Comments on Emission Limitations for PM10
    Comment: Earthjustice noted that EPA's BART analysis only focused
on SO2 pollution for the various subject-to-BART units at
the Hayden Smelter and suggested that EPA note the availability of
superior fabric filter products that can provide increased PM control
capabilities.
    Response: This comment is not timely. We previously approved ADEQ's
determination that BART for PM10 at the Hayden Smelter is
the existing controls. Therefore, we did not conduct a BART analysis
for PM10.
    Comment: ASARCO stated that BART does not authorize
``precautionary'' limits or other limits to ``ensure the
enforceability'' of a no-control determination. ASARCO asserted that
both ADEQ and EPA have determined that PM10 BART requires no
more than existing controls. Therefore, EPA must rely on some legal
basis for imposing a limit where BART establishes none. ASARCO stated
that, at most, EPA can specify only the existing limits in the Hayden
Smelter air permit.
    Response: We do not agree with this comment. Regional Haze SIPs and
FIPs must contain ``emission limitations representing BART'' for all
subject-to-BART sources.\123\ We previously approved Arizona's
determination that existing controls constitute BART for
PM10 at the Hayden Smelter. However, the SIP contained no
emission limitation representing BART. Therefore, we are required to
promulgate an emission limitation representing BART for
PM10, as well as compliance requirements to ensure the
enforceability of this emission limit as part of the FIP.\124\
---------------------------------------------------------------------------

    \123\ 40 CFR 51.308(e). Alternatively, plans may include an
emissions trading program or other alternative that achieves greater
reasonable progress toward natural visibility conditions than
source-specific limits. No such alternative is at issue here.
    \124\ Id. See also CAA section 302(y), 42 U.S.C. 7602 (defining
FIP as ``a plan (or portion thereof) promulgated by the
Administrator to fill all or a portion of a gap or otherwise correct
all or a portion of an inadequacy in a State implementation plan,
and which includes enforceable emission limitations or other control
measures.'').
---------------------------------------------------------------------------

    Comment: ASARCO stated that EPA's approval of the Arizona RH SIP's
``demonstration'' that no additional PM10 controls are
warranted is not based in any way on 40 CFR part 63, subpart QQQ
(NESHAP) requirements. ASARCO asserted that the PM10
demonstration and EPA's approval of it were based on the CALPUFF
modeling and cost alone, and not in any way on 40 CFR part 63, subpart
QQQ. Thus, ASARCO stated the final FIP should include a determination
that 40 CFR part 63, subpart QQQ requirements are not necessary to
enforce the PM10 BART determination and should exclude any
40 CFR part 63, subpart QQQ requirements accordingly.
    AMA expressed similar opinions and asserted that the Arizona RH SIP
was not based on 40 CFR part 63, subpart QQQ, but rather on the
determination that there was no significant visibility impact from PM
emissions. AMA asserted that for this reason, existing emission limits
are all that are appropriate for the Hayden Smelter.
    Response: We do not agree with these comments. As explained in the
previous response, enforceable emission limits are required to
implement Arizona's BART determinations for PM10.\125\ ADEQ
made the following BART determinations for PM10 at the
Hayden Smelter:
---------------------------------------------------------------------------

    \125\ See 40 CFR 51.308(e) and BART Guidelines section V, 70 FR
39172.

    Primary Off-gas System: The existing combination of cyclones,
wet scrubbers, and double contact double absorption acid plant
represents BART for the primary off-gas stream because it represents
the best current technology. BART is therefore selected as no
further control beyond the cyclones, wet scrubbers, double contact
double absorption acid plant system.
    Secondary Off-gas System: The existing secondary hood baghouse
is determined to be the best retrofit technology for the secondary
off-gas. BART is therefore selected as no further controls beyond
the secondary hood baghouse.
    Tertiary Ventilation System: Given the extremely small
visibility impact and the magnitude of the costs incurred, ADEQ has
determined that tertiary ventilation control as BART is not a
feasible option.\126\
---------------------------------------------------------------------------

    \126\ SIP Supplement, Appendix D Section IX. This language
appears to have been excerpted from ASARCO's own BART Demonstration.
Compare id. with letter from Eric Hiser, Counsel for ASARCO, to
Balaji Vaidyanathan, ADEQ dated March 20, 2013 (``ASARCO' BART
Demonstration'') at 5.

ADEQ determined that the existing controls on the primary and secondary
off-gas systems are the best available for PM10 and that
tertiary ventilation control is not feasible for purposes of BART. ADEQ
did not specify what emission limits would represent these existing
controls. Thus, EPA must determine what emission limits reflect the
``degree of reduction achievable'' \127\ by the selected control
technology, in this case existing controls, to satisfy the regulatory
requirements.
---------------------------------------------------------------------------

    \127\ 40 CFR 51.301.
---------------------------------------------------------------------------

    In making this determination, EPA considered ASARCO's own BART
demonstration, which explicitly relies on the emission limits and
compliance requirements in Subpart QQQ. In particular, for both the
primary and secondary off-gas streams, ASARCO stated that,
``[c]onsistent with the Guidelines, ASARCO has chosen to use the
`streamlined approach' by relying on the particulate limit set for an
acid plant in the National Emission Standard for Hazardous Air
Pollutants (NESHAP) Subpart QQQ, Primary Copper Smelting . . .'' \128\
For the primary off-gas stream, ASARCO explained that Subpart QQQ
``sets a limit of 6.2 milligrams per dry

standard cubic meter (mg/dscm) non-sulfuric acid particulate matter''
and that ``[c]ompliance with this limit would be determined by annual
testing in accordance with Section 63.1450(b) and continuous monitoring
of scrubbing liquid flow rate over the final two towers in the acid
plant established, reestablished and maintained in accordance with
Section 63.1444(h).''\129\ For the secondary off-gas stream, ASARCO
explained that Subpart QQQ ``sets limit of 23 mg/dscm PM'' with annual
compliance testing in accordance with Section 63.1450(a).\130\
---------------------------------------------------------------------------

    \128\ ASARCO BART Demonstration at 5 (citing BART Guidelines
section IV.C).
    \129\ Id.
    \130\ Id.
---------------------------------------------------------------------------

    Given that ASARCO relied on the Subpart QQQ requirements as the
basis for its own streamlined BART analysis for PM10, EPA
considers it appropriate to include these requirements in the FIP.
Incorporating these requirements into the FIP also fulfills the
requirements of 40 CFR 51.308(e) for promulgation of BART emission
limitations and is consistent with the BART Guidelines, which allow for
streamlined BART analyses, such as the one EPA approved for
PM10 at the Hayden Smelter, as long as the ``most stringent
controls available are made federally enforceable for the purpose of
implementing BART.'' \131\ Therefore, we are finalizing the
incorporation of the requirements of Subpart QQQ into the FIP.
---------------------------------------------------------------------------

    \131\ BART Guidelines section IV.D, 70 FR 39165.
---------------------------------------------------------------------------

    Comment: ASARCO stated that the CAA's general SIP/FIP provisions do
not support EPA's argument that sources for which there are no
additional control requirements must nonetheless have emission limits
established. ASARCO also stated that EPA's proposal is unacceptable
because it suggests that where a state elects not to include a source
in a SIP, it must include emission limits in the SIP that limit the
non-included source's emissions to its baseline, a requirement not
found in the CAA and unworkable as a practical matter.
    Response: We do not agree with this comment. First, we note that
the statutory and regulatory provisions cited in footnote 179 of our
proposed rule (CAA section 110(a)(2)(F) and 40 CFR 51.212(c),
51.308(d)(3)(v)(C) and (F)) are not the only basis for including
emission limitations and related compliance requirements for
PM10 in the FIP. Several provisions of the CAA and EPA's
regulations require the promulgation of enforceable emission
limitations in SIPs and FIPs generally, and in regional haze plans
specifically. In particular, CAA section 110(a)(2)(A) requires SIPs to
``include enforceable emission limitations and other control measures,
means, or techniques . . . as may be necessary or appropriate to meet
the applicable requirements of [the CAA].'' \132\ One of the
``applicable requirements'' of the CAA is that plans contain ``such
emission limits . . . as may be necessary to make reasonable progress''
toward natural visibility conditions, including provisions for BART and
a LTS.\133\ Under the RHR, plans must contain ``emission limitations
representing BART'' for all subject-to-BART sources, as well as (1) a
schedule for compliance with BART emission limitations for each source
subject to BART; (2) a requirement for each BART source to maintain the
relevant control equipment; and (3) procedures to ensure control
equipment is properly operated and maintained.\134\ Furthermore, the
LTS must include consideration of ``emission limitations and schedules
for compliance to achieve the reasonable progress goal'' and the
``enforceability of emission limitations and control measures.'' \135\
Among the measures needed to ensure the enforceability of emission
limits (including BART limits) are requirements for monitoring,
recordkeeping, and reporting, as authorized by CAA section 110(a)(2)(F)
and 40 CFR 51.212(c).
---------------------------------------------------------------------------

    \132\ 42 U.S.C. 7410(a)(2)(A). See also Montana Sulphur &
Chemical Co. v. EPA, 666 F.3d 1174, 1196 (9th Cir. 2012) (``EPA
correctly reads 42 U.S.C. [ ] 7410(a)(2) as requiring states to
include enforceable emission limits and other control measures in
the plan itself.'').
    \133\ CAA section 169A(b)(2), 42 U.S.C. 7491.
    \134\ 40 CFR 51.308(e)(1)(iv), (v).
    \135\ Sec.  51.308(d)(3)(v)(C) and (F).
---------------------------------------------------------------------------

    Second, contrary to ASARCO's suggestion, the Hayden Smelter is
included in the Arizona RH SIP. In particular, while the State
erroneously found that the Hayden Smelter was not ``subject-to-BART''
for PM10, the SIP nonetheless included a BART determination
for PM10 at the Hayden Smelter. EPA disapproved the State's
not-subject-to-BART finding, but approved its BART determination that
existing controls constitute BART for PM10. Thus, a BART
determination for PM10 for the Hayden Smelter is part of the
approved Arizona RH SIP. However, the SIP did not include any
enforceable emission limitations or related compliance requirements to
implement this determination. Therefore, we found that the SIP did not
meet the requirements of 40 CFR 51.212(c) and 51.308(e)(1)(iv) and
(v).\136\ We also disapproved the State's RPGs and portions of its LTS
because the SIP did not include enforceable emission limits to
implement the State's BART determinations.\137\ We are now required to
promulgate a FIP to fill the gaps resulting from disapproved portions
of the SIP. Thus, we are required to promulgate enforceable emission
limitations to implement the State's BART determination for
PM10 at the Hayden Smelter.
---------------------------------------------------------------------------

    \136\ 78 FR 46159.
    \137\ 78 FR 46171.
---------------------------------------------------------------------------

    Finally, we do not agree that the promulgation of enforceable
emission limits where no new controls are required is ``novel.'' As
explained above, inclusion of such limits is a requirement of the RHR,
and EPA has previously promulgated such limits, even where no
additional controls were required for BART.\138\ Even where existing
controls represent BART, there must be an emission limitation that
reflects ``the degree of reduction achievable'' \139\ by such controls.
---------------------------------------------------------------------------

    \138\ See, e.g. 77 FR 57884 (explaining that BART emission
limits must be established for all pollutants subject to review,
even where no new controls are required); id. at 57916 (establishing
an SO2 BART limit for Holcim Cement Plant based on no new
controls).
    \139\ 40 CFR 51.301.
---------------------------------------------------------------------------

    Comment: ASARCO stated that EPA has no legal basis for imposing
additional limits on PM beyond the existing limits at the Hayden
Smelter given that the PM emissions from the smelter contribute 0.04 dv
or less to regional haze. Thus, further limits are not necessary to
achieve the RPGs. ASARCO asserted that the LTS also does not require
emission limits.
    Response: We do not agree with this comment. As explained above,
the promulgation of PM10 limits for the BART-eligible units
at ASARCO Hayden is required under 40 CFR 51.308(e). With regard to the
requirements of the LTS, in addition to the requirement cited by the
commenter, 40 CFR 51.308(d)(3)(v)(F) requires consideration of the
``enforceability of emission limitations and control measures''
(including BART emission limitations) as part of the LTS.
6. Other Comments
    Comment: ASARCO stated that a CEMS on the bypass stack, as EPA has
proposed at CFR 51.145(l)(6)(i), is impractical and that the stack is
actually a shutdown ventilation duct used to redirect in-transit
SO2 and other gases out of the work environment in the event
that the primary ventilation system becomes unavailable. ASARCO stated
that events leading to the use of the shutdown ventilation duct are
always associated with the cessation of

smelting and converting and can be planned or unplanned.
    ASARCO explained that the estimated annual SO2 emissions
resulting from 60 events per year (based on average process parameters
measured during GCT's engineering study of the current system, assuming
30 unplanned events at full calculated mass SO2 and 30
planned events at reduced SO2 accounting for the clearing of
the gas before shutdown) are 2.81 tons for the BART-eligible units.
ASARCO considered this amount, less than 0.09 percent of the post-
improvement SO2 emissions, to be de minimis.
    ASARCO stated that it also considered deployment of a
SO2 CEMS to quantify emissions resulting from use of the
shutdown ventilation duct to be impractical because it would require
ranging of the concentration analyzer and flow measurement
instrumentation to enable quantification of the emissions during the
infrequent and very brief events, while recording zero/near zero levels
the majority of the time. The relative accuracy test audit (commonly
called ``RATA'') required could only be done by passing representative-
strength SO2 gas past the analyzer for test periods totaling
several hours, a situation that cannot occur (bypassing process gas
while operating).
    Response: We agree with this comment. Because of the difficulties
involved in operating a CEMS on a bypass stack, we have modified the
BART determination to allow the Hayden Smelter to use test data to
quantify emissions during normal startups and shutdowns, provided the
facility is operated according to a startup and shutdown plan.
    Comment: AMA asserted that EPA should extend the compliance
deadline in the rule, noting that if the rule continues as scheduled
(promulgation by late June), the compliance date would be in June 2017.
According to AMA, this is just months prior to the deadline of October
4, 2018, for Arizona to comply with the 1-hour SO2 NAAQS,
meaning that the smelters would have to have completed their projects
to reduce SO2 emissions to prevent causing or contributing
to violations of the NAAQS. AMA noted that the two smelters, as
indicated by their owners ASARCO and FMMI, are already planning to
substantially modify their plants resulting in large SO2
reductions in order to prevent violations of the SO2 NAAQS,
which will cost a significant amount of money, an amount higher than
what EPA would consider reasonable under BART. AMA asked that EPA
consider this significant undertaking by the two smelters and align the
BART compliance deadline with the SO2 attainment deadline.
    AMA added that if nothing else, considering the projects the two
smelters are undertaking, the EPA should consult with ASARCO and FMMI
to ensure that the final rule does not interfere with plans the
smelters have to reduce SO2 emissions in order meet the 1-
hour SO2 NAAQS. AMA stated that coordination of the BART
requirements with the facilities' effort to comply with the new
SO2 NAAQS is necessary to maintain the viability of these
smelters, thereby preserving high-paying jobs and adding new jobs as
the smelters install additional controls to comply with the CAA's
visibility requirements and other programs.
    Response: We partially agree with this comment. The BART level of
control in the FIP is a performance standard. We do not prescribe any
particular method of control. As a result, we do not anticipate any
incompatibility with any changes that may be needed to comply with any
attainment plan required by the 1-hour SO2 NAAQS. With
regard to the compliance deadline, we note that Arizona is required to
develop a SIP that provides for attainment of the 1-hour SO2
NAAQS as expeditiously as practicable, but no later than October 4,
2018.\140\ Furthermore, as explained in EPA's Guidance for 1-hour
SO2 Nonattainment Area SIP Submissions ``. . . EPA expects
attainment plans to require sources to comply with the requirements of
the attainment strategy at least 1 calendar year before the attainment
date.'' \141\ Therefore, the Hayden and Miami Smelters would be
required to comply with the attainment strategy by January 1,
2017.\142\ Accordingly, the expected source compliance date under the
1-hour SO2 NAAQS actually precedes the proposed compliance
date in the RH FIP of three years from promulgation of the final rule
(i.e., about July 2017).
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    \140\ 78 FR 47190, 47193.
    \141\ Memorandum from Stephen Page to Regional Air Division
Directors, Guidance for 1-Hour SO2 Nonattainment Area SIP
Submissions (April 23, 2014) at 10.
    \142\ Id.
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    Furthermore, based on additional information received during the
comment period, we have decided to extend the compliance deadline for
the secondary control system at the Hayden Smelter by an additional
year (i.e., to about July 2018). As explained elsewhere in response to
comments and in our revised BART analysis for the Hayden Smelter, our
BART determination for the secondary stream now reflects the use of an
amine scrubber rather than acid plant. We are not aware of any
instances of an amine scrubber being used at any similar facility in
the United States. Therefore, we no longer consider three years to be
sufficient time for design, construction, and a shakedown period.
Accordingly, we are finalizing a compliance deadline of four years from
publication of the final rule for the requirements applicable to the
secondary stream. We are retaining the proposed compliance deadline of
three years from publication of the final rule for the requirements
applicable to the primary stream.
    Finally, we also note that, during the development of our proposed
FIP, we requested and received information from ASARCO and FMMI
regarding control upgrades planned for purposes of attaining the 1-hour
SO2 NAAQS.\143\ During the comment period on the proposed
FIP, we received more detailed additional information from both
companies.\144\ We have also met with representatives from both
companies.\145\ As described elsewhere in this document, we have made
certain revisions to the regulatory text applicable to the smelters to
ensure that there is no incompatibility between the requirements of the
RH FIP and the smelters' plans to ensure attainment of the 1-hour
SO2 NAAQS.
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    \143\ See Letters from Colleen McKaughan, EPA, to Jack Garrity,
ASARCO, and Derek Cooke, FMMI (June 27, 2013); Letter from Jack
Garrity, ASARCO, to Thomas Webb, EPA (July 11, 2013); letter from
Derek Cooke, FMMI, to Thomas Webb, EPA (July 12, 2013).
    \144\ See comment letters from ASARCO and FMMI.
    \145\ See Memo Regarding Communications with ASARCO on RH FIP;
Memo Regarding Meeting with FMMI (April 28, 2014).
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D. Comments on the Miami Smelter

1. General Comments
    Comment: ADEQ stated that EPA's disapproval of ADEQ's
SO2 BART determinations for the Miami and Hayden Smelters is
unsupported. Similarly, AMA, NMA and FMMI requested that EPA reconsider
its decision to disapprove these BART determinations. In particular,
FMMI asserted that once EPA accounts for the technical deficiencies in
its own BART analysis, the Agency will conclude that additional
controls at the Miami Smelter are not justified as BART.
    Response: We do not agree with these comments. Our action on the
Arizona RH SIP is now final, and the commenters have cited no legal
basis for EPA to reconsider that action. Moreover, the commenters have
mischaracterized EPA's disapproval of Arizona's SO2 BART
determinations for the copper smelters, which was based on multiple

deficiencies including the lack of any five-factor analysis and any
enforceable emission limits. The commenters' assertions regarding
purported deficiencies in EPA's own BART analysis are addressed in
other responses.
    Comment: ADEQ asserted that EPA's disapproval of ADEQ's
determination that the Miami Smelter is not subject to BART for
NOX has no statutory basis, and that EPA's imposition of
BART for NOX emissions is arbitrary and capricious.
    Response: To the extent this comment concerns our action on the
Arizona RH SIP, it is untimely, as that action is now final. To the
extent it concerns our proposed FIP, we do not agree with its substance
for the reasons set forth in response to similar comments on the Hayden
Smelter above.
2. BART Analysis and Determination for SO2 From the
Converters
    Comment: FMMI noted that Converter 1 has been out of service since
the mid-1980s, and the company has no plans to reactivate it.
Therefore, all of the SO2 emissions from the converter aisle
should be attributed to Converters 2-5, which are the BART-eligible
units.
    Response: We appreciate the clarification regarding Converter 1.
Because emissions from the different converters cannot be separated for
technical reasons, we treated all converter emissions as BART-eligible.
Thus, the fact that Converter 1, which is not a BART-eligible unit, is
inoperable, does not affect our BART analysis. We have revised the
regulatory text to clarify that the requirements of the FIP do not
apply to Converter 1.
    Comment: FMMI asserted that the ``secondary hood'' required by 40
CFR 63.1444(d)(2) does not apply to Miami Smelter's Hoboken converters
because the Miami Smelter does not use Peirce-Smith converters. FMMI
also requested that EPA structure the FIP in a way that will ensure
consistency between any new BART requirements and the controls that
FMMI intends to install to ensure that the emissions from the Miami
Smelter do not interfere with attainment of the 1-hour SO2
NAAQS. ADEQ, AMA and NMA echoed these comments.
    Response: We agree that 40 CFR 63.1444(d)(2) does not apply to the
Miami Smelter converters. Our reference to that provision of the NESHAP
in the proposed FIP was not intended to suggest otherwise. Rather, it
was intended to ensure that FMMI install a secondary capture system to
collect emissions that currently escape the existing primary capture
system at the Miami Smelter's converters. This secondary system for the
Hoboken need not be identical to the secondary capture system used for
the Peirce-Smith converters. Rather the FIP provides FMMI with
substantial flexibility to design a capture system appropriate for the
unique configuration of its converters, provided that FMMI demonstrates
that this system is designed and operated to maximize collection of
process off-gases vented from the converters. In fact, the aisle
capture system that FMMI plans to install is itself a type of secondary
capture system that could meet the requirements of the FIP, provided
that it is optimized to capture the maximum amount of process off-gases
vented from the converters. We have revised the regulatory language to
clarify this requirement by removing the reference to 40 CFR
63.1444(d)(2) and defining ``capture system'' to reflect the broad
range of components that could be included in the system.
    Comment: FMMI stated that it is not technically feasible to route
additional captured SO2 from the converters to the acid
plant. FMMI explained that while, in an earlier letter, it had stated
that SO2 emissions collected by the roofline capture system
would be routed to the acid plant, this was an error since the routing
is not technically feasible. Specifically, FMMI asserted that ``the
SO2 concentrations in this gas stream are much too low and
the flow volume too high to allow the existing acid plant to handle
this stream'' and that ``gases from the aisle capture system would also
have significant heating requirements, and associated air emissions, if
they were to be routed to the existing acid plant.'' ADEQ, AMA, and NMA
echoed FMMI's concerns regarding the technical feasibility of the
proposed requirements for SO2.
    Response: We do not agree that the FIP requirements for the Miami
Smelter are technically infeasible. In particular, as explained in
response to comments from ASARCO above, while higher flow volumes and
lower SO2 concentrations may reduce the control efficiency
and cost-effectiveness of a double contact acid plant, they do not
render use of such an acid plant infeasible. Nonetheless, if FMMI
determines that the existing double contact acid plant is not adequate
to treat emissions captured by the secondary capture system, it may use
an alternative approach to comply with the requirements of the FIP. In
particular, because the FIP does not prescribe any particular method of
control, any combination of control devices may be employed to meet the
99.7 percent control requirement. For example, FMMI may continue to use
the existing double contact acid plant and tailstack scrubber on the
primary stream and construct a new scrubber to treat the secondary
stream, as it currently plans to do. Because the control efficiency is
calculated on a cumulative mass basis, it will be determined largely by
the degree of control achieved by the existing double contact acid
plant and tailstack scrubber, which treat the vast majority of
emissions from the converter aisle.\146\
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    \146\ FMMI previously estimated a capture efficiency of up to 98
percent for the primary capture system. Letter from Derek Cooke,
FMMI to Tom Webb, EPA (January 25, 2013) at 5. More recently, FMMI
has indicated that this capture efficiency will be improved by
installation of actuated mouth covers, Freeport-McMoRan Miami Inc.
BART Analysis (March 2014) (FMMI BART Report), at 2-4, and could be
as high as 99.57 percent. See Memorandum from J. Nikkari, Hatch to
C. West, FMMI (November 14, 2013) (Hatch Memo), section 3.1.2.
---------------------------------------------------------------------------

    For example, consider a situation where 100,000 pounds of
SO2 is emitted by the converters.\147\ Of this 100,000
pounds, 99 percent is captured by the primary capture system and ducted
to the acid plant system, which has a control efficiency of 99.8
percent.\148\ The remaining 1 percent is captured by the secondary
capture system and ducted to a caustic scrubber with a control
efficiency of 90 percent.\149\
---------------------------------------------------------------------------

    \147\ Present emissions from the converter aisle are estimated
to be 161,564. Id.
    \148\ The estimated control efficiency of the acid plant and
tailstack scrubber system is currently 99.69 percent. Id. section
3.4. This control efficiency could be increased through increased
use of the tailstack scrubber, as described further below, and
conversion of tail gas scrubber to utilize caustic (NaOH), to
enhance the SO2 control efficiency, which FMMI intends to
do. See ADEQ Significant Permit Revision Application, ADEQ Class I
Permit Number 53592, Smelter Expansion & Enhanced Controls; (July
2013) (FMMI Permit Application), section 4.1.1.
    \149\ Id. section 4.1.4 (``Captured SO2 emissions
were assumed to be controlled by the scrubber with an average
efficiency of roughly 90 [percent].''

Ducted to acid plant: 99 percent of 100,000 lbs = 99,000 lbs
Controlled by acid plant: 99.8 percent of 99,000 lbs = 98,802 lbs
Ducted to scrubber: 1 percent of 100,000 lbs = 1,000 lbs
Controlled by scrubber: 90 percent of 1,000 lbs = 900 lbs
Overall control efficiency: (98,802 + 900)/100,000 = 0.997 = 99.7
percent

    Thus, FMMI can meet this overall control efficiency by improving
the efficiency of the primary capture system, improving the efficiency
of the primary control system (e.g., increasing the use of cesium
promoted catalyst, increasing operation of the tailstack scrubber, or
converting the tailstack scrubber from a magnesium oxide scrubber to a
caustic or amine scrubber),

maximizing the efficiency of any new equipment installed to control
emissions from the secondary capture system, or any combination of
these options.
    Comment: FMMI asserted that by using a mass-balance approach to
estimate SO2 emissions from the converter aisle, EPA had
overestimated emissions and thereby overestimated the visibility
improvement and underestimated the cost per ton of additional
SO2 controls. FMMI described ``its own attempts to measure
fugitive SO2 emissions'' (i.e., the Roofline Study) and
asserted that EPA should have used emission estimates based on the
Roofline Study, instead of emission estimates based on a mass-balance
method, which FMMI characterized as ``highly imprecise'' and
``unclear.'' FMMI further noted that ``EPA's calculation does not
incorporate the effect of the new converter mouth covers, which reduce
process fugitive emissions from the converters.'' Finally, FMMI
concluded that EPA's use of a mass-balance approach is contrary to the
BART Guidelines, which state that the baseline emission rate ``should
represent a realistic depiction of anticipated annual emissions from
the source.'' Similarly, Earthjustice and NMA both questioned EPA's
estimate of uncollected SO2 emissions.
    Response: We disagree that we overestimated uncaptured baseline
SO2 emissions.\150\ We estimated uncaptured baseline
SO2 emissions from the converters using the following mass-
balance approach: (1) We calculated the amount of sulfur in the
concentrate processed by the smelter using throughput and composition
data provided by FMMI for the maximum production day and a baseline
year (2010); (2) we assumed full conversion of sulfur to
SO2; (3) we apportioned 65 percent of the SO2 to
the smelter aisle and 35 percent to the converter aisle based on
information provided by FMMI; \151\ and (4) We assumed 95 to 98 percent
capture of emissions by the Hoboken converters' side flues.\152\ We
consider this modified mass-balance approach to provide a more accurate
depiction of emissions than the mass-balance approach in the Arizona RH
SIP, which FMMI notes ``has proven to be unreliable.''
---------------------------------------------------------------------------

    \150\ FMMI describes uncaptured emissions from the converters as
``fugitive emissions.'' However, under the RHR, ``fugitive
emissions'' are defined as ``those emissions which could not
reasonably pass through a stack, chimney, vent, or other
functionally equivalent opening.'' 40 CFR 51.301\.\ Because FMMI is
planning to capture a significant portion of these emissions and
route them to a scrubber, they are, by definition, not fugitive.
    \151\ Letter from Derek Cooke, FMMI to Thomas Webb, EPA (July
12, 2013).
    \152\ See Letter from Derek Cooke, FMMI to Tom Webb, EPA
(January 25, 2013) at 5 (reporting a range of values of 87 percent
to 98 percent). We used the high end of this range to ensure that
our cost per ton estimates were conservative. That is, we assumed
the baseline level of uncaptured emissions was lower and that there
were therefore fewer emission reductions available, resulting in
higher cost per ton values.
---------------------------------------------------------------------------

    With regard to the Roofline Study, while we encourage ongoing
efforts by FMMI to increase understanding of emissions that bypass the
existing capture systems, we do not agree that the results of the
Roofline Study are more accurate than the values that we used in our
emission calculations. The Roofline Study measured emissions at four
points along the open roof.\153\ Given that the roof and sides of the
building are not fully enclosed, it is very unlikely that these four
points accurately reflect all of the emissions currently escaping from
the converter aisle.\154\ Indeed, the authors of the Roofline Study
acknowledge that the emission rates presented ``may not adequately
measure the true value of the parameter'' and are presented for
``illustration purposes.'' \155\ We also note that, following the close
of the comment period, we received from FMMI a report summarizing the
results of an ``extended roofline sampling campaign'' from
approximately March 2013 through December 2013.\156\ While this
extended sampling effort is intended to provide ``more representative,
long-term roofline SO2 emission estimates for current
operation,'' \157\ it still does not account for ``unmeasured fugitive
emissions.'' \158\ Therefore, we do not agree that this the Roofline
Study necessarily provides a more accurate estimate of SO2
emissions than the mass-balance method we used.
---------------------------------------------------------------------------

    \153\ Roofline Study, prepared by Trinity Consultants for
Freeport McMoRan, Inc. (November 2013).
    \154\ We note that the FMMI Permit Application indicates that
the roofline capture system will collect 84 percent of ``process
fugitives'' (i.e. currently uncaptured emissions) from the
converters, meaning that the remaining 16 percent will escape
elsewhere. Given that FMMI is not even attempting to capture any
emissions at the roofline now, we expect that more than 16 percent
of presently uncaptured emissions are bypassing the roofline
monitors and are therefore not reflected in the results of the
roofline study.
    \155\ Id. Section 5.1.
    \156\ Report: Extended Roofline SO2 Emissions Summary
(March 2014).
    \157\ Id. section 1, page 2.
    \158\ Id. section 3.1, page 2.
---------------------------------------------------------------------------

    Furthermore, even assuming for the sake of argument that FMMI's
revised emission estimates based on the Roofline Study are correct,
uncaptured baseline emissions from the converters would be 547
tpy.\159\ In order to reach the 109 tpy estimate of uncaptured
SO2 emissions from the converters employed in its BART
analysis, FMMI relies on an unverified and unenforceable 80 percent
capture efficiency from improvements to the converter mouth
covers.\160\ However, use of this ``expected'' capture efficiency does
not provide an adequate basis for reducing baseline uncaptured
emissions from the converters from the current emissions level, as
measured estimated by the Roofline Study. As explained in the BART
Guidelines, in the absence of enforceable limitations, you calculate
baseline emissions based upon continuation of past practice.\161\
Although we support measures to increase the amount of emissions
captured by the side flue and ducted to the acid plant, at present,
there is no enforceable emission limitation that ensures that the mouth
covers will achieve 80 percent capture of the existing uncaptured
converter emissions. Therefore, even if the extended roofline study did
provide an accurate estimate of uncaptured emissions and FMMI's
allocation of those emissions among various emission units was correct,
baseline uncaptured emissions from the converters would be at least 547
tpy, not 109 tpy, as indicated by FMMI.