technical problem achieving the floor levels for each pollutant
simultaneously, using the MACT floor technology. For most kilns,
compliance with the Hg limits will be accomplished using ACI followed
by a second PM control consisting of a FF. There is no technical
impediment to using this same system for control of PCDD/PCDF. We note
that the ACI system would have to be installed downstream of the
existing PM control, therefore, there would be no effect on the cement
kiln dust collected in the existing PM control. One industry commenter
claimed ACI increases dioxin emissions. Considering the fact that ACI
can actually be used to remove dioxins from kiln exhaust gas, we see no
basis for that statement. Regarding the commenter's claim that ACI
increases D/F in MWC, our experience with the MWC source category has
shown that this technology has been demonstrated to be effective at
reducing D/F emissions from these sources and is being used extensively
by MWC units. Furthermore, we have not been provided information from
either the commenter or the MWC industry that substantiates the
commenter's claim that ACI increases D/F emissions from these sources.
    After the ACI system, a wet scrubber can be used for HCl and
SO2 control. We would expect the wet scrubber to be the
downstream control because it creates a moisture laden exhaust that
would require reheating to then apply ACI. Again, there is no technical
impediment to adding a wet scrubber after the ACI system, and the two
control devices should not interfere with each other's performance. If
the facility required an RTO to meet the CO limit, the RTO would be
installed downstream of the wet scrubber in order to protect the RTO
from any acid gases in the kiln exhaust. The wet scrubber/RTO
combination has been demonstrated in cement kiln applications.
    In order to meet the PM and metals standards a facility could
choose to modify their existing PM control to meet the revised limits,
or design a new baghouse downstream of the ACI injection point to meet
the PM and metals limits.
    Though we have described some fairly complicated control scenarios,
there are simpler applications of control technology that would likely
be used successfully. One example would be simultaneous injection of
alkaline materials (lime or sodium compounds) and activated carbon
downstream of the existing PM control device followed by collection
with a FF. This type of injection scheme would potentially control acid
gases (HCl and SO2), PCDD/PCDF, Hg, and PM.
    Regarding the comment that EPA should consider work practice
standards in lieu of emission limits for certain types of ERUs, we
again point out that CAA section 129(a)(4) says that the standards
promulgated under CAA section 129 shall specify numerical emissions
limitations for each pollutant enumerated in that provision. Section
129(a)(4) requires MACT standards for, at a minimum, PM,
SO2, HCl, NOX, CO, Pb, Cd, Hg, and PCDD/PCDF.
Section 129 does not contain a work practice standard provision similar
to that contained in CAA section 112(h) and applicable to NESHAP.
    Finally, several commenters suggested that EPA must consider costs
when establishing MACT standards. EPA is prohibited from considering
costs when determining the minimum standards for each pollutant--the
``MACT floor;'' however, EPA is required to consider costs, among other
things, when evaluating whether the MACT standards should be more
stringent than the MACT floor, so called ``beyond-the-floor''
standards. See section 129(a)(2). EPA did consider costs in its beyond-
the-floor analysis consistent with the statute.
2. MACT-on-MACT
    Comment: Several commenters argued that EPA's recalculation of the
2000 MACT floors using post-MACT compliance data results in so-called
``MACT-on-MACT'' standards. They suggest that the limits are being set
using a very small amount of data from a very small number of sources.
The commenters argue that for the incinerator subcategory, the presumed
reason a small number of units are being used to set the limits is that
the existing standard caused many units to shut down. The commenters
suggest that the remaining units likely installed or improved controls
in order to comply with the original CISWI standards, effectively
resulting in the new limits being set based on the top performers among
the already top performers. One commenter asserted that these floors
cannot be achieved and are contrary to the CAA and the intent of
Congress. The commenter urged EPA to use the population of pre-2000
CISWI incinerators and their emissions data to establish the revised
MACT floors. The commenter declares that the CAA never intended to
impose technology every 5 years with no consideration of costs and
risk, and that it is not reasonable to assume that Congress intended
for existing sources subject to CAA section 129 to have their standards
tightened up to levels comparable to those for new sources over time
where their circumstances have not changed.
    Response: We disagree with the commenters' assertions that we are
employing a MACT-on-MACT approach to set limits that are not achievable
by CISWI. The purpose of this action is not to force units who have
complied with a lawfully adopted MACT standard to have to subsequently
comply with another round of updated MACT standards, but to respond to
the voluntary remand granted by the Court. As stated at proposal, we
requested a voluntary remand of the 2000 CISWI standards after Sierra
Club filed a petition for review of the final CISWI standards, and the
Court issued its Cement Kilns decision which called into question EPA's
procedures for establishing MACT floors for CISWI units. Cement Kiln
Recycling Coalition v. EPA, 255 F.3d 855 (DC Cir. 2001). Specifically,
EPA established the 2000 CISWI MACT floors by identifying the MACT
floor control technology and calculating the MACT floor using emissions
information from all units, not only best-performing units, that used
the MACT floor technology. EPA

recognized that the Court rejected this methodology in the Cement Kilns
case in which the Court rejected EPA's MACT floor approach under CAA
section 112 and concluded that EPA may account for variability by
setting the floor at a level that reasonably estimates the performance
of the best controlled sources under the worst foreseeable conditions
but not the worst foreseeable conditions faced by any unit in the
source category. Id. at 865. The MACT processes under CAA sections 112
and 129 are essentially the same, thus the decision identified a flaw
in EPA's 2000 CISWI standards.
    CAA section 129 requires EPA to set the MACT floor based on
emissions limitations actually achieved by the best-performing solid
waste incineration units. In addition, the Court has made it abundantly
clear that in issuing revised MACT standards pursuant to remand, EPA
may not ignore this Court's intervening holdings:

    If the Environmental Protection Agency disagrees with the Clean
Air Act's requirements for setting emissions standards, it should
take its concerns to Congress. If EPA disagrees with this court's
interpretation of the Clean Air Act, it should seek rehearing en
banc or file a petition for a writ of certiorari. In the meantime,
it must obey the Clean Air Act as written by Congress and
interpreted by this court.

Sierra Club v. EPA (Brick), 479 F.3d 875, 884 (DC Cir. 2007).

    The best way to ascertain the actual emissions limitations achieved
by the best-performing units, and thus comply with the Court's
dictates, is to use data reflecting the actual emissions of operating
units. For that reason, EPA collected data from solid waste
incineration units, including the existing units in the incinerator
subcategory, pursuant to a CAA section 114 ICR. In establishing the
revised CISWI standards, we used the emissions information from the
existing sources in each subcategory to set the MACT limits. For the
incinerator subcategory, we determined that the information available
from the 2000 rulemaking was insufficient and limited, and that it did
not represent the current emissions limitations achieved by the sources
in that subcategory since many of the units in that data set have since
shut down.
    Notwithstanding that clear statutory mandate to establish the MACT
floors based on the emission limitations actually achieved by the best-
performing sources, commenters assert that EPA's promulgation of the
CISWI standards for the incinerators subcategory conflicts with the
intent of the statute. Commenters use the term ``MACT-on-MACT'' to give
the false impression that EPA's resetting of the MACT floors pursuant
to CAA section 129(a)(2) somehow requires sources to constantly upgrade
their control technologies. Commenters' MACT-on-MACT label is based on
the faulty premise that the original MACT floors accurately reflected
what the statute required. Although the units in the incinerators'
subcategory had to comply with the 2000 MACT floors, the standards were
not established based on the performance of the best-performing units
as the statute requires and, therefore, the limitations are likely
considerably higher than the limits being achieved by the then existing
best controlled incinerator units. Accordingly, a more accurate label
for the MACT standards as EPA re-proposed them in 2009 might be:
``MACT-on-Unsupportable-Standards-Erroneously-Labeled-as-MACT.''
    We also disagree with commenters' assertion that we should not use
the new emissions information from units in the incinerator
subcategory, and instead base the MACT standards for the incinerator
subcategory on the population of pre-2000 CISWI incinerators and their
emissions data to establish the revised MACT floors. The first problem
with this approach is that, as commenters note, many of the then
existing incinerator units are no longer in operation. Section
129(a)(2) of the CAA requires EPA to establish standards for new units
based on the ``best controlled similar unit'' and, for existing units,
based on ``the average emissions limitation achieved by the best-
performing 12 percent of units in the category.'' We fail to see how
the statute would allow us to consider emissions limitations from
sources no longer in existence or ignore the emissions information on
which we based the revised standards, and instead rely on information
that does not reflect what sources are actually achieving today.
Furthermore, even if we believed we had the authority to ignore the new
data and establish the standards based on the inventory of units in
existence before the 2000 CISWI standards, we do not have sufficient
data from those units on which to base MACT standards based on that
pre-2000 universe of sources. Specifically, EPA has data on only 17
units out of an estimated 112 units then in existence, and we have a
complete data set for only 12 units. Because we do not have a complete
data set, EPA cannot determine whether the then existing units for
which we have data from that time period were best-performing units at
that time, such that we could develop MACT standards consistent with
the statute, and there is no mechanism by which EPA could reconstruct
the category at this time.
    Finally, we disagree with commenters' assertion that the units in
the incinerator subcategory are unable to meet the revised CISWI
standards. As stated above, the emissions data upon which the revised
standards rely comes directly from CISWI units that have achieved the
resulting levels, and we accounted for variability in establishing the
standards to account for the performance of sources over a period time
and different operating conditions. We believe that together this
demonstrates that the incinerator units can achieve the individual
standards, though admittedly units may have to take additional steps to
comply with the validly established MACT standards.
3. Methodology (UL or UPL)
     Comment: At proposal, EPA requested comment on whether an
alternate statistical interval should be used, the 99 percent UPL. Some
commenters supported the use of the 99 percent UPL, citing cases where
this statistical interval had been used in other rulemakings for
boilers and cement kilns. Several commenters stated that the
statistical method used by EPA in setting the CISWI MACT floors is
flawed due to the use of data sets that are not statistically
significant. Commenters asserted that the 99 percent UL floor is
calculated from data which 99 percent of units in MACT floor data
population would fall below, which they argue sets up an automatic 1
percent failure rate for the top 12 percent sources. Commenters request
that this be addressed by using a statistical approach which increases
the allowance for variability of the data set.
    One commenter stated that since EPA is using a limited data set
that in some cases contains predominantly nondetect values to set
floors that units must meet at all times, consideration of variability,
and use of the appropriate statistical approach is crucial to ensuring
units can achieve the emission limits. The commenter argues that in
cases of severely limited or censored data sets, EPA should use either
the 99.9 percent UL or use the UTL, which is meant for use in
situations where the amount of data available does not represent the
entire population. The commenter maintains that EPA is inappropriately
using the 99 percent UL statistic to calculate the proposed CISWI
emission limits because this does not capture enough variability in
emissions to ensure the limits will be met by the top performers 100
percent of the time. They argue that the approach is flawed,

given that the number of units the limits are based on is very small,
and the limits are being developed on a pollutant-by-pollutant basis in
a way that does not account for variability of the fuels and wastes
being burned. The commenter asserts that EPA does not justify the
appropriateness of the use of the 99 percent UL over the use of other
statistical procedures typically used for censored or limited data.
Further, the commenter argues that although this calculation
methodology was used in the HMIWI standard, it is not consistent with
statistical procedures used to develop other emission standards. For
example, the commenters explain that EPA used a complicated statistical
approach in the development of the HWC NESHAP standard to account for
intra-unit variability as well as inter-unit variability among the
units in the MACT floor.
    Response: In assessing sources' performance, EPA may consider
variability both in identifying which performers are ``best'' and in
assessing their level of performance. Sierra Club v. EPA (Brick MACT),
479 F.3d 875, 881-82 (D.C. Cir. 2007); see also Mossville Environmental
Action Now v. EPA, 370 F.3d 1232, 1241-42 (DC Cir 2004) (EPA must
exercise its judgment, based on an evaluation of the relevant factors
and available data, to determine the level of emissions control that
has been achieved by the best-performing sources considering these
sources' operating variability). The Brick MACT decision reiterated
that EPA may account for variability in setting floors; however, the
Court found that EPA erred in assessing variability because it relied
on data from the worst performers to estimate best performers'
variability. The Court held that ``EPA may not use emission levels of
the worst performers to estimate variability of the best performers
without a demonstrated relationship between the two.'' 479 F.3d at 882.
    In determining the MACT limits, we first determine the floor,
which, for existing sources, is the emissions limitation achieved in
practice by the average of the top 12 percent of existing sources, or
the level achieved in practice by the best controlled similar source
for new sources. In this rule, EPA is using lowest emissions limitation
as the measure of best performance. We are then assessing variability
of the best performers by using a statistical formula designed to
estimate a MACT floor level that can be met by the average of the best-
performing sources based on the expected distribution of future
compliance tests (or calculated inputs in the case of Hg for waste-
burning kilns). Specifically, for ERUs and waste-burning kilns, the
MACT floor limit is an UPL, and for incinerators and small remote
incinerators, the UL calculated with the student's t-test using the
TINV function in Microsoft Excel[supreg]. The student's t-test has also
been used in other EPA rulemakings (e.g., NSPS for HMIWI, NESHAP for
Industrial, Commercial, and Institutional Boilers and Process Heaters)
in accounting for variability.
    As we discussed at proposal, the UL computation assumes that the
data available represents the entire population of data from the best-
performing CISWI units used to establish the standards. We have
concluded that this statement applies to the incinerator and small
remote incinerator subcategories, since we believe our inventory of
these units is more certain than is our inventory of ERUs and waste-
burning kilns for several reasons. In the 2000 CISWI rule, EPA only
regulated solid waste incineration units that operated for the sole
purpose of disposing of waste. Many incinerators subject to the 2000
CISWI rule ceased operation before the compliance date for those
standards. Once the revised CISWI standards are finalized, these types
of solid waste incineration units (i.e., incinerators and small remote
incinerators) will either comply with the revised CISWI standards or
cease operation, much as they did in response to the 2000 standards.
The same is not necessarily correct for units in the ERUs and waste-
burning kilns subcategories. For those sources, once the CISWI
standards are promulgated, they will likely either comply with the
CISWI standards or cease burning solid waste and comply with the
applicable NESHAP. We think units in those subcategories will generally
not cease operation. Furthermore, because incinerator and small remote
incinerator unit's sole purpose is waste disposal, the only practical
manner in which additional sources will be added to the inventory is
through new construction. Again, this is different than for ERUs and
waste-burning kilns because, for those subcategories, additional units
may be added if existing boilers (and process heaters) and cement kilns
begin combusting solid waste and thereby become ERUs and waste-burning
kilns, respectively. For these reasons, we believe we have a complete
inventory of units in the incinerators and small remote incinerators
subcategories.
    We sent Phase II testing requests to all incinerator and small
remote incinerator units that are in our inventory. We required testing
for all incinerator and small remote incinerator units, making
allowances for identical units from a facility to only test one unit,
and not each identical unit. Therefore, our data represent the entire
population of data for these two subcategories. For this reason, we
believe the UL is the appropriate statistical approach for the
incinerators and small remote incinerators subcategories. The 99
percent UL represents a value that 99 percent of the data in the MACT
floor population would fall below, and therefore accounts for the run-
to-run and test-to-test variability observed in the MACT floor data
set.
    For ERUs and waste-burning kilns, however, we recognize that our
data may not represent the entire population of units. As stated above,
there is greater uncertainty involved in determining the universe of
sources in these two source categories because we cannot be certain
that we have identified all the units that would be considered to be
burning solid waste, had the newly-adopted definition for solid waste
been promulgated and effective at the time of testing. We also do not
know whether the units we have identified will continue to burn waste
after the final CISWI standards are issued. Unlike incinerators and
small remote incinerators, the primary purpose of waste-burning kilns
and ERUs is the production of a product or generation of energy, not
the disposal of waste. Therefore, operators will decide whether it is
economically feasible to continue or start combusting solid waste to
support their industrial process and, if they decide that it is not,
they will use traditional fuels or non-waste inputs instead of solid
waste. For example, an ERU that is combusting solid waste that has
little or no cost may decide that compliance with CISWI is an
economically viable option compared to purchasing traditional fuels at
market rates; but, if the costs of compliance with CISWI exceed the
costs of traditional fuel, the source will likely cease burning solid
waste. Conversely, a boiler that currently combusts only traditional
fuels may be presented with a solid waste fuel option that makes it to
their economic advantage to begin combusting solid waste. For these
reasons, the population of units in the ERU and waste-burning kiln
subcategories is inherently uncertain. We have for these reasons
concluded that a prediction interval (e.g., UPL) is more appropriate
for these two subcategories, and this approach is also consistent with
the NESHAP statistical approach being used for the non-waste-burning
counterparts of these units (i.e.,

boilers/process heaters and cement kilns).
    A prediction interval for a future observation is an interval that
will, with a specified degree of confidence, contain the next (or some
other pre-specified) randomly selected observation from a population.
In other words, the prediction interval estimates what the upper bound
of future values will be, based upon present or past background samples
taken. The UPL consequently represents the value which we can expect
the mean of future observations (3-run average) to fall below within a
specified level of confidence, based upon the results of an independent
sample from the same population. In other words, if we were to select
at random a future test condition from any of the top 12 percent (MACT
floor pool) of sources (average of 3 runs), we can be 99 percent
confident that the reported level will fall at or below the UPL value.
Use of the UPL is appropriate in this rulemaking for these two
subcategories because it sets a limit any single or future source can
meet based on the performance of members of the MACT floor pool.
    The UPL is calculated as shown in Equation 1:
    [GRAPHIC] [TIFF OMITTED] TR21MR11.013

Where:

x = Mean of the sample data set
n = Number of test runs
m = Number of test runs in the compliance average
s\2\ = Observed variance
t = Student t distribution statistic

    This calculation was performed using the following spreadsheet
functions:
    Normal distribution: 99 percent UPL = AVERAGE (Test Runs in Top 12
percent) + [STDEV (Test Runs in Top 12 percent) x TINV (2 x
probability, n-1 degrees of freedom) * SQRT ((1/n) + (1/m))], for a
one-tailed t-value, probability of 0.01, and sample size of n. The
value of ``m'' denotes the number of future observations, and it is
used to calculate an estimate of the variance of the average of m-
future observations.
    This formula uses a pooled variance (in the s2 term)
that encompasses all the data-point to data-point variability of the
best-performing sources comprising the MACT floor pool for each
pollutant. Where variability was calculated using the UPL statistical
approach, we used the average (or sample mean) and sample standard
deviation, which are two statistical measures calculated from the data
distributions for each pollutant. The average is a central value of a
data set, and the standard deviation is the common measure of the
dispersion of the data set around the average. We note here that the
methodology accounts for both short-term and long-term variability and
encompasses run-to-run and test-to-test variability. The formula also
applies differently depending on how the underlying data set is
distributed. To this end, EPA carefully evaluated the data sets for
each HAP to ascertain whether the data were normally distributed, or
distributed in some other manner (i.e., lognormal). After applying
standard and rigorous statistical tests (involving the degree of
``skewness'' of the data), we determined the distributions for each
pollutant, which in turn determined the final form of the UPL equation.
See ``CISWI Emission Limit Calculations for Existing and New Sources''
in the docket.
    The results are floors that reasonably estimate the performance
over time of the best-performing sources, as do the standards based on
those floors. It is true that many sources will need to install
controls to meet these standards, and that these controls have
significant costs (although EPA estimates that the rule's costs are
substantially outweighed by its benefits). See section VI of this
preamble. This is part of the expected MACT process where, by
definition, the averaged performance of the very best performers sets
the minimum level of the standard. The EPA believes that it has
followed the statute and applicable case law in developing its MACT
floors. The summary of results of UL and UPL calculations and the MACT
floor emission limits for each subcategory for existing and new sources
are presented in Tables 4 through 9 of this preamble.

                  Table 4--Summary of MACT Floor Results for Existing Units--PM, Hg, Cd and Pb
----------------------------------------------------------------------------------------------------------------
                                                                PM (mg/      Hg (mg/      Cd (mg/      Pb (mg/
           Subcategory                     Parameter             dscm)        dscm)        dscm)        dscm)
----------------------------------------------------------------------------------------------------------------
Incinerators.....................  No. of sources in                   26           26           26           26
                                    subcategory =.
                                   No. in MACT floor =......            4            4            4            4
                                   Avg of top 12%...........        4.571       0.0006       0.0004       0.0013
                                   99% UL of top% (test           33.6004      0.00533      0.00256      0.00352
                                    runs) =.
                                   Limit =..................           34       0.0054       0.0026       0.0036
ERUs--Solids.....................  No. of sources in                   30           30           30           30
                                    subcategory =.
                                   No. in MACT floor =......            4            4            4            4
                                   Avg of top 12%...........      2.85061    0.0000520    0.0001713    0.0012704
                                   99% UPL of top% (test         246.9158       0.0003    0.0003(a)    0.0035(a)
                                    runs) =.
                                   Limit =..................          250      0.00033   0.00051(a)    0.0036(a)
ERUs--Liquid/Gas.................  No. of sources in                    6            6            6            6
                                    subcategory =.
                                   No. in MACT floor =......            1            1            1            1
                                   Avg of top 12%...........       18.588        0.001        0.001        0.005
                                   99% UPL of top% (test         101.7548        1.313        0.023        0.096
                                    runs) =.
                                   Limit =..................          110       0.0013        0.023        0.096
Waste-burning kilns..............  No. of sources in                   12           12           12           12
                                    subcategory =.
                                   No. in MACT floor =......            2            2            2            2
                                   Avg of top 12%...........       2.8378          N/A       0.0002       0.0012
                                   99% UPL of top% (test           6.1115    0.0079(b)       0.0005       0.0026
                                    runs) =.
                                   Limit =..................          6.2    0.0079(b)      0.00048       0.0026
Small, remote incinerators.......  No. of sources in                   14           14           14           14
                                    subcategory =.
                                   No. in MACT floor =......            2            2            2            2

                                   Avg of top 12%...........       84.052       0.0012        0.027        0.238
                                   99% UL of top% (test           220.826        0.006        0.603        2.657
                                    runs) =.
                                   Limit =..................          230       0.0057         0.61          2.7
----------------------------------------------------------------------------------------------------------------
\a\ A calculated limit equal to three times the MDL was used in place of the calculated MACT floor emission
  limit. For further explanation, see section V. of the preamble.
\b\ For details on this calculation, see the memorandum ``CISWI Emission Limit Calculations for Existing and New
  Sources'' in the Docket for this rulemaking.

                   Table 5--Summary of MACT Floor Results for Existing Units--CO, NOX and SO2
----------------------------------------------------------------------------------------------------------------
                                                                                NOX          SO2
               Subcategory                           Parameter              CO (ppmvd)    (ppmvd)      (ppmvd)
----------------------------------------------------------------------------------------------------------------
Incinerators............................  No. of sources in subcategory =           26           26           26
                                          No. in MACT floor =............            4            4            4
                                          Avg of top 12%.................       16.800         14.7        0.733
                                          99% UL of top% (test runs) =...       32.378       52.419       10.418
                                          Limit =........................           36           53           11
ERUs--Liquid/Gas........................  No. of sources in subcategory =            6            6            6
                                          No. in MACT floor =............            1            1            1
                                          Avg of top 12%.................        36.00       58.733      641.352
                                          99% UPL of top% (test runs) =..        36.00      75.6305     712.3156
                                          Limit =........................           36           76          720
ERUs--Biomass...........................  No. of sources in subcategory =           21           21           21
                                          No. in MACT floor =............            3            3            3
                                          Avg of top 12%.................     247.3333      86.7595       1.4039
                                          99% UPL of top% (test runs) =..     485.3681     287.9536       6.1751
                                          Limit =........................          490          290          6.2
ERUs--Coal..............................  No. of sources in subcategory =            9            9            9
                                          No. in MACT floor =............            2            2            2
                                          Avg of top 12%.................      40.3031     307.2352     624.0054
                                          99% UPL of top% (test runs) =..      58.0304     330.7464     641.9307
                                          Limit =........................           59          340          650
Waste-burning kilns.....................  No. of sources in subcategory =           12           12           12
                                          No. in MACT floor =............            2            2            2
                                          Avg of top 12%.................      70.4280     437.7682      15.6660
                                          99% UPL of top% (test runs) =..     105.0945     536.4268      37.9704
                                          Limit =........................          110          540           38
Small, remote incinerators..............  No. of sources in subcategory =           14           14           14
                                          No. in MACT floor =............            2            2            2
                                          Avg of top 12%.................       12.756       67.212        1.403
                                          99% UL of top% (test runs) =...       19.104      237.326      410.006
                                          Limit =........................           20          240          420
----------------------------------------------------------------------------------------------------------------
\a\ A calculated limit equal to three times the MDL was used in place of the calculated MACT floor emission
  limit.

                     Table 6--Summary of MACT Floor Results for Existing Units--HCl and D/F
----------------------------------------------------------------------------------------------------------------
                                                                                D/F (total TEQ
             Subcategory                         Parameter           HCl (ppmvd)   D/F (TMB)    basis) (ng/dscm)
                                                                                (ng/dscm)          \a\
----------------------------------------------------------------------------------------------------------------
Incinerators.........................  No. of sources in                      26           26                 26
                                        subcategory =.
                                       No. in MACT floor =.........            4            4                  4
                                       Avg of top 12%..............        0.181        0.238        0.004302537
                                       99% UL of top% (test runs) =       28.045        4.504             0.1286
                                       Limit =.....................           29          4.6               0.13
ERUs--Solids.........................  No. of sources in                      30           30                 30
                                        subcategory =.
                                       No. in MACT floor =.........            4            4                  4
                                       Avg of top 12%..............      0.16719     0.093487           .0088932
                                       99% UPL of top% (test runs)        0.4456       0.3443             0.0586
                                        =.
                                       Limit =.....................         0.45         0.35              0.059
ERUs--Liquid/Gas.....................  No. of sources in                       6            6                  6
                                        subcategory =.
                                       No. in MACT floor =.........            1            1                  1
                                       Avg of top 12%..............        4.440        1.110             0.0463
                                       99% UPL of top% (test runs)         4.927    13869.523            30.0133
                                        =.
                                       Limit =.....................      \(a)\14       14,000                 31
Waste-burning kilns..................  No. of sources in                      12           12                 12
                                        subcategory =.
                                       No. in MACT floor =.........            2            2                  2
                                       Avg of top 12%..............       3.5665       0.0752             0.0005
                                       99% UPL of top% (test runs)       24.8634       0.1909             0.0070
                                        =.

                                       Limit =.....................           25          0.2              0.007
Small, remote incinerators...........  No. of sources in                      14           14                 14
                                        subcategory =.
                                       No. in MACT floor =.........            2            2                  2
                                       Avg of top 12%..............       35.289      333.080              7.288
                                       99% UL of top% (test runs) =      214.233     1183.196             56.933
                                       Limit =.....................          220        1,200                 57
----------------------------------------------------------------------------------------------------------------
\a\ A calculated limit equal to three times the MDL was used in place of the calculated MACT floor emission
  limit.

                    Table 7--Summary of MACT Floor Results for PM and Metals for New Sources
----------------------------------------------------------------------------------------------------------------
                                                                PM (mg/      Hg (mg/      Cd (mg/      Pb (mg/
           Subcategory                     Parameter             dscm)        dscm)        dscm)        dscm)
----------------------------------------------------------------------------------------------------------------
Incinerators.....................  Avg of top performer.....       3.0608       0.0001       0.0002       0.0007
                                   99% UL of top (test runs)      17.7867     0.000151       0.0023  \(a)\0.0015
                                    =.
                                   Limit =..................           18      0.00016       0.0023  \(a)\0.0019
ERUs--Solids.....................  Avg of top performer.....     2.640916   0.00003192   0.00013696   0.00045367
                                   99% UPL of top (test         1094.5327       0.0028       2.8369       0.0030
                                    runs) =.
                                   Limit =..................     \(b)\250  \(b)\0.0003  \(b)\0.0005       0.0031
                                                                                3            1
ERUs--Liquid/Gas.................  Avg of top performer.....       18.588        0.001        0.001        0.005
                                   99% UPL of top (test          101.7548        1.313        0.023        0.096
                                    runs) =.
                                   Limit =..................          110  \(d)\0.0002        0.023        0.096
                                                                                5
Waste-burning kilns..............  Avg of top performer.....       1.2173          N/A       0.0001       0.0011
                                   99% UPL of top (test            2.3591  \(c)\0.0062       0.0006     0.045852
                                    runs) =.
                                   Limit =..................     \(a)\2.5  \(c)\0.0062  \(b)\0.0004  \(b)\0.0026
                                                                                8
Small, remote incinerators.......  Avg of top performer.....       83.534        0.001        0.011        0.086
                                   99% UL of top (test runs)     733.5002       0.0013       0.6692       0.2589
                                    =.
                                   Limit =..................     \(b)\230  \(a)\0.0035    \(b)\0.61         0.26
----------------------------------------------------------------------------------------------------------------
\a\ A calculated limit equal to three times the MDL was used in place of the calculated MACT floor emission
  limit.
\b\ The NSPS limit exceeds the EG limit. The EG limit was selected as the NSPS limit.
\c\ Hg limit was developed using material input data from CISWI kilns identified within the Portland Cement
  NESHAP database. See the memorandum ``CISWI Emission Limit Calculations for Existing and New Sources'' for
  details on this calculation.
\d\ Dioxin/furan TEQ and Hg limits for ERUs--liquid/gas were replaced with D/F TEQ limits for liquid fuel major
  source boilers. See ``CISWI Emission Limit Calculations for Existing and New Sources'' for details.

                       Table 8--Summary of MACT Floor Results for New Units--CO, NOX, SO2
----------------------------------------------------------------------------------------------------------------
               Subcategory                           Parameter              CO (ppmvd)  NOX (ppmvd)  SO2 (ppmvd)
----------------------------------------------------------------------------------------------------------------
Incinerators............................  Avg of top performer...........       12.000       9.0333       0.2233
                                          99% UL of top (test runs) =....       12.000      22.3685      39.5108
                                          Limit =........................           12           23      \(a)\11
ERUs--Liquid/Gas........................  Avg of top performer...........       36.000       58.733      641.352
                                          99% UPL of top (test runs) =...       36.000      75.6305     712.3156
                                          Limit =........................           36           76          720
ERUs--Biomass...........................  Avg of top performer...........     153.0000      62.3233       1.0492
                                          99% UPL of top (test runs) =...     153.0000     344.7699      20.8889
                                          Limit =........................          160     \(a)\290     \(a)\6.2
ERUs--Coal..............................  Avg of top performer...........      35.4778     307.2352     624.0054
                                          99% UPL of top (test runs) =...      45.0280     330.7464     641.9307
                                          Limit =........................           46          340          650
Waste-burning kilns.....................  Avg of top performer...........        58.57       1.4742       7.2187
                                          99% UPL of top (test runs) =...      89.7816     195.2522     124.3390
                                          Limit =........................           90          200      \(a)\38
Small, remote incinerators..............  Avg of top performer...........       12.000       60.769        0.131
                                          99% UL of top (test runs) =....       12.000       77.283        1.164
                                          Limit =........................           12           78          1.2
----------------------------------------------------------------------------------------------------------------
\a\ The NSPS limit exceeds the EG limit. The EG limit was selected as the NSPS limit.

                  Table 9--Summary of MACT Floor Results for New Units--HCl and Dioxins/Furans
----------------------------------------------------------------------------------------------------------------
                                                                                D/F (Total TEQ
            Subcategory                     Parameter            HCl (ppmvd)     D/F (TMB) (ng/    basis) (ng/
                                                                                dscm)          dscm) \a\
----------------------------------------------------------------------------------------------------------------
Incinerators......................  Avg of top performer.....           0.0413           0.0176      0.001266667
                                    99% UL of top (test runs)           0.0901           0.0228           2.1464
                                     =.

                                    Limit =..................            0.091       \(a)\0.052        \(b)\0.13
ERUs--Solids......................  Avg of top performer.....         0.068133           0.0161      0.000501333
                                    99% UPL of top (test                0.5435           0.0674           0.0103
                                     runs) =.
                                    Limit =..................        \(b)\0.45            0.068            0.011
ERUs--Liquid/Gas..................  Avg of top performer.....            4.440            1.110      0.046335368
                                    99% UPL of top (test          \(a)\13.2107       13869.5228          30.0133
                                     runs) =.
                                    Limit =..................          \(a)\14       (no limit)       \(c)\0.002
Waste-burning kilns...............  Avg of top performer.....           0.3994           0.0562         0.000105
                                    99% UPL of top (test                0.3994           0.0895           0.0029
                                     runs) =.
                                    Limit =..................           \(a)\3             0.09            0.003
Small, remote incinerators........  Avg of top performer.....           27.678          299.827      4.868700057
                                    99% UL of top (test runs)         196.6311        1700.6082          30.0810
                                     =.
                                    Limit =..................              200       \(d)\1,200               31
----------------------------------------------------------------------------------------------------------------
\a\ A calculated limit equal to three times the MDL was used in place of the calculated MACT floor emission
  limit.
\b\ The NSPS limit exceeds the EG limit. The EG limit was selected as the NSPS limit.
\c\ Dioxin/furan TEQ and Hg limits for ERUs--liquid/gas were replaced with D/F TEQ limits for liquid fuel major
  source boilers. See ``CISWI Emission Limit Calculations for Existing and New Sources'' for details.

    The measurements for HCl from waste-burning kilns are very close to
the detection limit for analytic Method 321 actually calculated in the
field for HCl. As discussed elsewhere, we have implemented a procedure
for adjusting limits to account for measurement variability using data
at the detection limit. This results in a floor of 3 ppmvd for the new
waste-burning kilns for HCl, adjusted to a dry basis at 7 percent
oxygen. This represents the lowest level that can be reliably measured
using this test method, and we therefore believe that it is the lowest
level we can set as the MACT limit taking the appropriate measurement
variability into account.
    The Hg standard for waste-burning kilns reflects 30 days of data
for all Hg inputs, reasonable estimates of control device performance
(for the few controlled sources), plus a reasonable statistical
methodology to account for variability (including variability of Hg
content of kiln inputs). EPA also used a pooled variability factor
(pooling variability for all kilns in the MACT floor pool), which
increased variability estimates. This analysis is based upon data
collected for development of the final Portland Cement NESHAP, but
screened such that the CISWI analysis used only the data from kilns
that would have been identified as CISWI units had the newly-adopted
solid waste definition been promulgated and effective at the time of
performance testing, and converted to a concentration basis for
consistency with the CISWI standards. See ``CISWI Emission Limits
Calculations for Existing and New Sources.''
4. Statistical Analysis (Lognormal vs. Normal Distribution)
    Comment: Several commenters suggested that EPA's data distribution
designations are flawed and that EPA must default to non-normal
distributions unless sufficient data are available to conduct robust
analyses which unambiguously show the distribution can only be
described by normal statistics. One commenter suggests that the non-
normal distribution is consistent with both conventional wisdom and
EPA's own guidance in ``Guidance for Data Quality Assessment: Practical
Methods for Data Analysis'', EPA/600/R-96/084, July 2000, which holds
that it is more likely that environmental data are distributed log-
normally. Commenters state that where there is any uncertainty
according to EPA's criteria using Excel skewness and kurtosis, EPA
biases its findings on distributions in favor of normality, the
opposite of EPA's own guidance. The commenter states that EPA's
Guidance for Data Assessment provides that the lognormal distribution
is ``a commonly met distribution in environmental work,'' also stating
``Environmental data commonly exhibit frequency distributions that are
non-negative and skewed with heavy or long right tails,'' and ``The
lognormal distribution is a commonly used distribution for modeling
environmental contaminant data.''
    Response: EPA has revised the methodology to use the lognormal
distribution when the normal distribution is not clearly indicated
based on the skewness and kurtosis tests to be more consistent with
EPA's guidance in ``Guidance for Data Quality Assessment: Practical
Methods for Data Analysis'' EPA/600/R-96/084, July 2000.
5. Treatment of Detection Levels
    Comment: Many commenters argued that EPA should not use data below
detection limits to set standards. They contend that EPA's use of data
below MDLs to set standards invalidates EPA`s analysis, creates
emissions limits that are biased low, and sets emission standards that
would not allow facilities to demonstrate compliance without taking
undue risk of facing non-compliance. They suggested that no numerical
emission standard for a pollutant should be set below the measurement
ability of the reference test method. Some commenters stated that EPA
does not appear to have systematically screened the emissions data for
cases where a detection limit should be applied, and has erroneously
recorded zero values for emissions where those are reported in the
original test reports. The commenters further assert that in addition
to failing to promulgate a method for measuring detection limits for
air emission test methods, EPA has ignored the issue of errors
associated with quantifying source emissions when they are low.
    At proposal, EPA requested comment on calculating a three times
method detection limit in cases where the floor emissions limit did not
adequately account for variability. While one commenter supports this
method, another argues that this approach is unlawful and inconsistent
with the CAA's directive to set the MACT floor at the emissions level
achieved by the best-performing sources because it allows for
facilities to emit at far higher levels than the best-performing
sources.

    Response: Although we disagree with commenters on the use of
nondetect values, we do agree that at very low emission levels where
emissions tests result in nondetect values, the inherent imprecision in
the pollutant measurement method has a large influence on the
reliability of the data underlying the MACT floor emission limit.
Because of sample and emission matrix effects, laboratory techniques,
sample size, and other factors, MDLs normally vary from test to test
for any specific test method and pollutant measurement. The confidence
level that a value measured at the detection level is greater than zero
is about 99 percent. The expected measurement imprecision for an
emissions value occurring at or near the MDL is about 40 to 50 percent.
Pollutant measurement imprecision decreases to a consistent level of 10
to 15 percent for values measured at a level about three times the MDL.
The approach EPA has used to account for measurement variability begins
by defining a MDL that is representative of the data used in the data
pool. The first step in the approach is to identify the highest test
specific MDL reported in a data set that is also equal to or less than
the average emission calculated for the data set. This approach has the
advantage of relying on the data collected to develop the MACT floor
emission limit, while to some degree, minimizing the effect of a
test(s) with an inordinately high MDL (e.g., the sample volume was too
small, the laboratory technique was insufficiently sensitive or the
procedure for determining the detection level was other than that
specified). The second step is to determine the value equal to three
times the representative MDL and compare it to the calculated MACT
floor emission limit. If three times the representative MDL were less
than the calculated MACT floor emission limit, we concluded that
measurement variability is adequately addressed, and we did not adjust
the calculated MACT floor emission limit. If, on the other hand, the
value equal to three times the representative MDL was greater than the
calculated MACT floor emission limit, we concluded that the calculated
MACT floor emission limit does not account entirely for measurement
variability. We therefore used the value equal to three times the MDL
in place of the calculated MACT floor emission limit to ensure that the
MACT floor emission limit accounts for measurement variability and
imprecision.
6. Use of CEMS Data
    Comment: Several commenters stated that EPA did not include CO,
SO2, or NOX data from CEMS that was provided by
companies and resides in EPA's databases. Commenters claimed that after
discussions with EPA rule writers in which affected sources were
encouraged to gather CEMS data as an alternative to stack test data,
facilities purposefully submitted such data and these data should be
used. Some commenters suggested that it is important that the MACT
floor data represent the real-world variability of emissions and that
CEMS data is clearly superior to stack test data in this regard.
Commenters suggested that EPA may believe it is not feasible to
incorporate CEMS data along with stack test data in its MACT floor
analyses due to the method it chose to rank and statistically analyze
the data. The commenters recommended using the UPL in the statistical
analysis to allow CEMS data to be used along with stack test to set
standards. Further, one commenter suggested that EPA obtain hourly
average CEMS data over a suitable period of time (several months or as
much data as can be readily obtained) from each source it can identify
that either has a permanent CEMS installed on the unit or provided data
in its response to the ICR survey or testing program.
    Response: In response to the ICR survey, most facilities that
reported CEMS data provided it as 24-hour block averages. We used these
data to determine baseline emissions and to calculate costs and impacts
of the final rule. EPA did not propose to use 24-hour block averages in
setting emissions standards for NOX, SO2, and CO.
We determined that to do so for these pollutants would be inconsistent
with the sampling time for the stack test data and the test methods
used to determine compliance with the final standards. For example,
typical instrument stack test method test runs would be around 1 hour
or less for NOX, CO, or SO2 stack tests
representing essentially 3-hour average of emissions. A 3-hour average
is not comparable to data obtained over a 24-hour sampling with a CEMS.
In response to comments, EPA has incorporated into the database hourly
CEMS data that were voluntarily submitted by some units that are best
performers within their subcategory, and where no stack test data are
available, and used these data in conjunction with stack test data from
other best performers to calculate the MACT floor emission limits.
    For a response to the comment on using the UPL in the statistical
analysis to calculate emissions, see section V.B of this preamble.

C. Control Technology Assumptions for the Floor and Beyond-the-Floor

1. Control Technologies and Cost Assumptions
    Comment: Many commenters argued that EPA underestimated the total
cost of controls and monitoring equipment required to comply with the
emissions standards. Several commenters stated that PM concentrations
will increase with the addition of SNCR and ACI systems and will
require facilities to invest in baghouse systems. Some commenters
asserted that there is no documentation to support that LBMS can
control CO emissions from boilers to achieve the emission levels.
Commenters also argued that biomass-to-energy facilities required to
install an oxidation catalyst to meet the CO emission limits may have
space limitations or other engineering constraints and may not be able
to achieve the emission limits. One commenter argued that packed bed
scrubbers to control HCl and SO2 from boilers is impractical
on units with high flow rates, high PM loading, and high inlet
pollutant concentration. Some commenters suggested that EPA does not
have an adequate understanding of how to reduce or control D/F
emissions from cement kilns. Some commenters asserted that the cost
memorandum assumes that for units requiring less than 10 percent
improvement in NOX, ``minor adjustments were considered
sufficient.'' They stated that EPA further assumes that these
adjustments (such as air handling and distribution adjustments in the
firebox) could be made at no additional cost. The commenters contended
however, that EPA provides no evidence in the record to support either
of these assumptions and that there are no boiler adjustments of this
type that are done at no cost.
    Response: EPA first notes that the rule does not specify particular
controls that sources must install and operate. Sources may evaluate
the emissions from their source and the emission limits that apply, and
then judge for themselves which controls may be best suited for their
particular unit to meet the emission limits. The control technology
assumptions and cost estimates are assumptions of controls which may be
required and an estimate of costs to retrofit and operate these
controls.
    EPA has, however, revised the costing assumptions and methodology
since proposal to address issues presented by commenters. For example,
in cases where ACI is being required, we have assumed that FF will need
to be installed to capture the spent carbon or,

if FF is already present, improvements will be required to the FF to
ensure capture of the sorbent. For larger ERUs that require acid gas
control, we have assumed that dry sorbent injection followed by DIFF
will be the preferred technology rather than wet scrubbers. For
NOX control, we acknowledge that small adjustments at no
cost may not be feasible for all affected units to meet the limits and
that sources may want to have some operational flexibility so that they
have suitable margin of compliance with the emission limits. Therefore,
we have used SNCR as the control technology if even small
NOX reductions are required to meet the limit. We have not
quantified PM increases due to SNCR addition. PM increases are a
function of flue gas characteristics of each unit, and we do not have
data for our units that would allow us to determine whether secondary
particulate formation would occur in certain units that an additional
PM control device would be required for the unit. We note, however,
that the units that require an SNCR to meet the limits are also
anticipated to need a PM control device to meet the limits for other
pollutants. Therefore, we expect that affected sources would account
for potential secondary PM formation in designing their overall air
pollution control system.
2. Technology-Based Beyond-the-Floor Comments
    Comment: Some commenters argued that EPA's decision to consider
beyond-the-floor limits equal to the new source floors was arbitrary
and unlawful. The commenters recommended that instead EPA should
examine multiple control technologies to determine what level of
emissions reductions are ``achievable'' based on cost and other
factors. The commenters asserted that beyond-the-floor technologies
should be evaluated for all pollutants in each subcategory of the CISWI
rule.
    Response: We have revised our beyond-the-floor analysis from that
set forth in the proposed rule to consider the performance of available
technology. For existing units, rather than considering as the only
beyond-the-floor option the potential of existing sources to meet the
new source limits, we have considered the technologies available to
control the various HAP and the reasonable control efficiencies of
those technologies. As discussed at proposal, EPA may adopt emissions
limitations and requirements that are more stringent than the MACT
floor (i.e., beyond-the-floor). Unlike the MACT floor methodology,
however, EPA must consider costs, nonair-quality health and
environmental impacts and energy requirements when considering beyond-
the-floor alternatives.
    In developing this final rule, EPA first analyzed the controls
available and being used for each subcategory and compared this to the
controls necessary for units to meet the MACT floor limits. We then
evaluated the different combinations of available emission control
technologies and practices, add-on controls different from those
required to meet the MACT floor limits, that existing units would have
to employ were we to require additional emissions reductions beyond-
the-floor levels set forth above. If we determined that any of these
additional control options were technically feasible for the units in a
subcategory, we then analyzed the costs, nonair quality environmental
impacts and benefits associated with adopting the identified control
option to determine whether the beyond-the-floor control was
reasonable. The following discussions detail this analysis for each
subcategory.
    Incinerators. Existing units in this subcategory are equipped with
afterburners, FFs, and wet scrubbers. We estimate that to comply with
the existing source MACT floor limits units in this subcategory may
require the addition of or improvement of an existing FF for the
control of PM, Cd and Pb; wet scrubbers for the control of HCl and
SO2 for many of the units that currently do not have wet
scrubbers; ACI system with a FF for the control of D/F and Hg; and in
several cases, afterburner retrofits for the control of CO; and SNCR
for NOX in certain instances. These controls are effective
and demonstrated on this subcategory of units for the pollutants they
are intended to control (see ``Revised CISWI Control Costs Memorandum''
in the docket). We estimate that some incinerator units in this
category will require retrofits of existing control or installation of
additional control technologies as set forth above to comply with the
MACT floor limits.
    Furthermore, as part of our costing and impacts analysis (discussed
in section VI of this preamble), we evaluated whether existing
facilities would choose to cease burning solid waste in incineration
units after promulgation of the final CISWI standards if alternative
disposal options, primarily diverting waste to a landfill, were less
costly. Based on the analysis, we expect that all but three facilities
with units in the incinerators subcategory will choose to cease
operations once the proposed MACT floor limits are promulgated. The
three units that we estimate to remain open will likely add ACI system/
FF and one will add SNCR for NOX control to meet the MACT
floor limits. There is no better control beyond the ACI system/FF for
D/F, Hg, PM, Cd, and Pb control. The reductions these units will
require for meeting the metals emissions will typically need to be
greater than 95 percent, therefore necessitating very efficient FF
systems. One unit that is not currently meeting the NOX MACT
floor limit must install SNCR to comply with the NOX floor
limit. To achieve further reductions for NOX, the unit would
require another control device, such as SCR, to comply with a beyond-
the-floor limit, and would require the other remaining units to also
install either SNCR or SCR. The cost of installing and operating the
SCR is typically four to five times higher than a comparable SNCR (see
``Revised CISWI Control Cost Memorandum''), and would force this unit
to close. In addition to cost considerations, SCR is typically used in
combustion units such as industrial boilers and process heaters, gas
turbines, and reciprocating internal combustion engines (Air Pollution
Control Technology Fact Sheet, SCR, EPA-452/F-03-032), and we are not
currently aware of any successful application of SCR technology to a
waste-combustion unit. We therefore question whether SCR could be
successfully applied to incineration units in any case. For acid gas
performance, all three units are well below the MACT floor with their
existing controls, and addition of wet scrubbers would only offer small
incremental improvements in emissions. From a cost perspective, the
likely result of requiring wet scrubbers on these units would be
closure of these units and diversion of waste to a landfill.
Considering these factors, we concluded that beyond-the-floor limits
are unreasonable for the incinerator subcategory.
    Small remote incinerators. Existing units in this subcategory are
typically equipped with an afterburner as the control device, with the
facility sometimes employing waste segregation practices to a certain
degree, usually to screen out recyclable materials and hazardous waste
materials. We received several comments stating that this subcategory
has unique climactic, geographic, and wildlife considerations that
influence the applicable controls that are available, and commenters
also stated that these small remote incinerators are the only viable
waste disposal option in certain regions of Alaska. See section V of
this preamble for more discussion from commenters

on these units. Of primary concern from a technical standpoint are
controls that require water to operate or those that have a large space
footprint. Water-based controls such as wet scrubbers, SNCR, and even
the evaporative cooling section of dry sorbent injection followed by
DIFF may pose ice fogging and equipment freezing concerns that could
prevent the use of the incinerator.
    To achieve the MACT floor limits, more than half of the units in
this subcategory will require afterburner upgrades, about two-thirds of
the units will require ACI system/FF or FF alone, and most will require
a more robust materials segregation plan that removes chlorinated and
non-ferrous metal components from the waste stream at these facilities.
These controls are the best demonstrated technologies that are
technologically feasible at these facilities, and they are sufficient
to meet the MACT floor limits. One technology that is beyond-the-floor
that is technically feasible would be higher efficiency FF or perhaps
the addition of a second FF. However, considering the small amount of
emissions that would remain after meeting the MACT floor, we expect the
incremental cost effectiveness for a second FF or higher efficiency FF
could be extraordinarily high, approaching $500,000/ton.
    We have also considered the costs of alternative disposal, and,
based on new information obtained during the comment period, we have
adjusted our estimates of those costs to be much higher than those we
estimated at proposal. Based on the adjusted cost estimates, we have
determined that the alternative disposal options exceed the costs of
controls necessary to meet the MACT floor limits. In addition, there is
still some uncertainty whether alternative disposal is an available
option during severe climate events. Our assessment indicates that a
beyond-the-floor limit would not be achievable to some facilities due
to aforementioned technical issues associated with available controls
and would significantly increase costs for others. In either case, we
conclude that establishing beyond-the-floor standards would likely
result in forced closure of some of the units in this subcategory, but
we also believe that some units that would otherwise close due to cost
related issues would be forced to operate at a loss because closure may
not be an option due to other nonair quality environmental regulations
aimed at protecting human health and wildlife. For both the
technological and cost related issue discussed above, and because of
nonair quality environmental issues, we conclude that there are no
reasonable beyond-the-floor alternatives for the small remote
incinerator subcategory.
    Waste-burning kilns. Existing kilns are currently equipped with
various combinations of ESPs, FF, SNCR and DIFF controls. We estimate
that kilns may need to add new controls or improve existing controls to
meet the MACT floor limits. These include improved FFs to meet the
reductions necessary to meet the Cd and Pb limits, activated carbon for
D/F and Hg control, and some kilns may need to add RTO to meet the CO
limits.
    As previously discussed, ACI system/FF are the best technologies
available for control of D/F, Hg, PM, Cd and Pb. To meet the floor, the
FF will need to be high efficiency, 99 percent in some cases, to meet
the MACT floor limit for Cd and Pb. The only further control available
would be a second FF, which would result in less than an additional 1
percent reduction of these pollutants. We estimate the cost
effectiveness for this to be in the $500,000 per ton range at a
minimum. Therefore, there are no further controls to consider as
beyond-the-floor options for these pollutants.
    For waste-burning kilns, a significant amount of CO emissions can
result from the presence of organic compounds in the raw materials (and
not only from incomplete combustion). Therefore, good combustion
controls and practices are not as effective for waste-burning kilns as
for other types of combustion units, and may not be enough for units to
meet the MACT floor CO limits. Oxidation catalysts have not been
installed on waste-burning kilns, and we believe they may not be as
effective on waste-burning kilns as they are on other sources due to
plugging problems. Specifically, the catalyst bed can become plugged or
blinded with dust, thereby covering up catalyst reactive sites
necessary to oxidize CO, which reduces the effectiveness of the unit.
To maintain the effectiveness of the catalyst, the unit may require
shutting down more frequently to replace the catalyst, which reduces
productivity of the unit and increases catalyst costs. To make an
oxidation catalyst feasible, it may be necessary to also use multiple
FF in series upstream of the catalyst which, as described above, is a
very costly measure. The only effective CO control for significant CO
reductions we could identify for waste-burning kilns is a RTO, and we
expect over half of the units will need to install a RTO to meet the
MACT floor limits. As a beyond-the-floor option, setting a CO limit at
a level that most of the remaining waste-burning kilns would also
require RTO could be considered, although we doubt that some of the
units requiring RTO to meet the MACT floor emission limit for CO would
be able to further reduce their emissions to that same extent.
Furthermore, the cost and energy consumption for these additional RTO
make this an impractical choice. Therefore, as there are no other
controls which could be applied to further reduce CO emissions from
these units and additional RTOs would be ineffective from a cost and
energy impacts perspective, we could not identify a beyond-the-floor
option for CO.
    We expect that waste-burning kilns will install scrubbers to meet
the MACT floor emission limits for HCl and SO2. The floor
limits for HCl are at the levels of quantification of the test method
used to determine compliance. Therefore, there are no additional
measures that could be employed to quantify any further reductions in
HCl emissions beyond that of the MACT floor limit. The only other
option for further HCl and SO2 control would be addition of
a dry sorbent injection system in series with the wet scrubber.
However, this would approximately double the costs for acid gas
control, with only about a 30 percent incremental reduction in
SO2 emissions and no measurable reduction in HCl emissions.
As a result, no beyond-the-floor options for acid gases from waste-
burning kilns exist because we cannot quantify further HCl reductions,
and the beyond-the-floor options for SO2 reductions are
unreasonable due to the cost of the additional controls in conjunction
with the limited benefits of such controls.
    The demonstrated control technology for NOX control on
waste-burning kilns is SNCR. In fact, several of the kilns are already
equipped with this technology and are able to comply with the
NOX MACT floor limit. We estimate that other kilns may
require the addition of SNCR to meet the MACT floor limits for
NOX. One kiln will require an SNCR that is optimized to the
capabilities of the technology to meet the MACT floor limits for
NOX. For this unit to be able to achieve an even lower
NOX limit would likely require another technology. As
discussed above, SCR is another technology that is used by some
combustion sources to reduce NOX emissions; however, SCR is
a catalyst technology that has not been demonstrated to work
effectively on cement kilns (or waste-burning kilns) in the United
States. We believe that SCR is not effective on waste-burning kilns due
to difficulties operating SCR in applications where there is
significant PM or sulfur loading in the gas stream. These two gas
stream constituents can

reduce catalyst activity, and lower the resulting effectiveness of the
SCR, through catalyst poisoning and blinding/plugging of active sites
by ammonia sulfur salts (formed from sulfur in the flue gas with the
ammonia reagent) and PM (Air Pollution Control Technology Fact Sheet,
SCR, EPA-452/F-03-032). We could not identify any other controls beyond
SCR and SNCR, alone or in tandem, to reduce NOX emissions
from waste-burning kilns. We believe that SCR is not technically
demonstrated on kilns currently and may not be technically feasible.
For these reasons, we are not selecting a limit for NOX that
is beyond-the-floor for the waste-burning kiln subcategory.
    Liquid waste ERUs. Existing units in this subcategory are equipped
with flue gas recirculation in a couple cases, and some settling
chambers for particulate control in a couple other units. We anticipate
units within this subcategory may need to install FF, CO catalyst, and
SNCR to meet the MACT floor limits. As discussed earlier, FFs are the
best control available for PM, Cd, and Pb control. The only further
control available would be a second FF or a very high efficiency FF.
The metals emissions from these units are very low to begin with, so
the only incremental reductions would be in PM. This would result in
perhaps an additional 10 percent reduction in emissions at almost
double the cost of current particulate controls. As mentioned before,
we anticipate cost effectiveness for this to be in the $500,000 per ton
range at a minimum. Likewise, SNCR is the best demonstrated technology
being applied to waste combustion units for NOX control. As
discussed earlier, SCR has been used in some boiler applications, but
SCR costs are approximately four to five times those of SNCR, for only
an additional 30 percent reduction from the baseline. Furthermore, we
observe that SCR has not been demonstrated to work effectively on waste
combustion units in the United States. Carbon monoxide control for
liquid waste ERUs could also be achieved by using a RTO, but at a far
greater energy requirement, notably in natural gas consumption, with
comparable control efficiency as the CO catalysts that we expect some
units will need to install to meet the MACT floor CO limits. Therefore,
we conclude that additional beyond-the-floor CO control would be
unreasonable for this subcategory.
    Additional D/F and Hg control could be achieved using ACI with
another FF. However, the baseline emissions for these pollutants are
already very small, with only marginal additional emissions reductions
available if additional controls were being used. Therefore, beyond-
the-floor limits for these pollutants will not be reasonable from a
cost effectiveness perspective.
    We also considered whether it is reasonable to go beyond-the-floor
with respect to SO2 for this subcategory. In this case, the
DIFF control technology could be applied to these units to reduce
SO2 emissions by about 70 percent with co-control of HCl (90
percent) as well as PM, Cd, and Pb. Most of these units will already
require the addition of a FF to meet the MACT floor limits, so the cost
of going beyond-the-floor for these units would entail the dry sorbent
injection components of the control device. For the units that do not
require FF to meet the floor, the additional costs would involve the
entire DIFF control device. The total cost for applying the relevant
controls to all the units is approximately $4.8 million per year in
annualized capital and operating costs for SO2 control
beyond-the-floor. The reduction in emissions of SO2 is
approximately 2,300 tpy, based on the baseline emissions estimate and a
70 percent reduction and accounting for SO2 emissions from
electricity generation needed to power the controls. It is worth noting
that the baseline estimates and MACT floor calculations for this
subcategory are based on data from the only unit for which we have
SO2 data in this subcategory. This unit has a baseline
SO2 concentration of 641 ppm, which has been applied to the
other five liquid ERUs as an estimated baseline concentration. The HCl
concentration for this unit is about 4 ppm, so co-benefit emission
reductions are significantly less than the SO2 emission
reductions. Because we are basing these analyses off of data from a
single unit within the subcategory, we realize that there is a large
margin of uncertainty on the control requirements within this source
category and the potential for SO2 emissions reductions at
the beyond-the-floor level.
    To get a better idea of the potential cost effectiveness for a
beyond-the-floor limit for SO2, we also looked at the costs
and emissions reductions solely for the unit which we have data for to
determine the cost effectiveness of control for this unit. In this
case, the additional cost of the dry injection system (the unit already
requires a FF to meet the MACT floor limits) is about $567,000 per
year, with an estimated emissions reduction of 103 tpy of
SO2 (and minor HCl reduction) adjusted for SO2
emissions from electricity generated to power the controls. This
results in an incremental cost effectiveness of $5,500 per ton of
SO2 control beyond-the-floor. While this number is generally
within the cost effective range we find reasonable, we are not adopting
a beyond-the-floor limit for SO2 given the uncertainty
associated with this number, the fact that we cannot adequately
estimate the costs for other units in the subcategory, and because the
controls required for HCl may actually reduce SO2 more than
is required based on the SO2 standard alone such that the
actual cost effectiveness of the beyond-the-floor option is not in line
with the estimate.
    Regarding co-control for PM, the fact that four of the six liquid
waste ERUs will likely require FF to meet MACT floor limits for Cd and
Pb means that going beyond-the-floor using DIFF controls would only net
additional PM control on the two remaining units. The FF portion of the
control costs for these two units is approximately $1.1 million per
year with an estimated PM reduction of fewer than five tpy, which
translates into an incremental cost-effectiveness of about $230,000 per
ton for additional PM control. Based on our analysis and realizing the
high degree of uncertainty regarding costs, emissions reductions and
resulting cost-effectiveness for this particular CISWI subcategory, we
have concluded that requiring beyond-the-floor controls on these units
is unreasonable.
    Solid waste ERUs. Existing units in this subcategory are equipped
with various combinations of ESPs, FF, scrubbers, SNCR spray towers,
and DIFF. We anticipate units within this subcategory may need to
install or improve different combinations of ACI system/FF, DIFF, FF,
LBMS, CO catalysts, and wet scrubber control technologies to meet the
MACT floor limits. As discussed earlier, a FF is the best control
available for PM, Cd, and Pb control. The Cd and Pb reductions
necessary are greater than 90 percent in many cases, indicating that
units will likely require highly efficient FF to meet the limits for
these pollutants and PM. Therefore, beyond-the-floor limits for PM, Cd,
and Pb would likely necessitate a second FF, essentially doubling the
cost for little additional reduction in emissions. Furthermore, the ACI
system is the BAT for reducing D/F and Hg emissions. The D/F reduction
necessary for some of these units approaches 99 percent, indicating
that beyond-the-floor limits that are more stringent than the MACT
floor limits may not be achievable by the control technology.
    In certain cases, units may require DIFF and wet scrubbers in
series to meet acid gas limits. There are no additional controls that
could be implemented in these cases to further reduce acid gas

emissions. Carbon monoxide control for solid waste ERUs could also be
achieved by using a RTO, but likely at a far greater energy requirement
(specifically natural gas) with comparable control efficiency as the CO
catalysts that we expect some units will need to install to meet the
MACT floor CO limits. Therefore, we conclude that additional beyond-
the-floor CO control would be unreasonable for this subcategory due to
additional cost and energy impacts.
    The demonstrated control technology for NOX control on
ERUs is SNCR. In fact, some of the ERUs are already equipped with this
technology. A couple of the units appear to comply with the
NOX MACT limit because they already have a SNCR in place. As
mentioned earlier, SCR is another technology that is used by some
combustion sources to reduce NOX emissions. However, SCR
costs can be about four to five times more costly than SNCR.
Furthermore, we observe that SCR has not been demonstrated to work
effectively on waste combustion units in the United States. We realize
that the industrial sectors that use units within this CISWI
subcategory are typically wood and forest product industries, sectors
that have suffered particular economic hardship. We are attempting to
make sure that the regulatory requirements are being satisfied, while
minimizing adverse economic impact wherever possible. Since there
remain some questions about a demonstrated control beyond the control
used to meet the MACT floor limits, and some units are already
utilizing SNCR to meet the MACT limit, coupled with the fact that the
potential beyond-the-floor technology is significantly more expensive,
we are not selecting a limit for NOX that is beyond-the-
floor for the solid waste ERU subcategory.
    New Units. As discussed elsewhere, we have concluded that only two
of the CISWI subcategories may see any new units within the immediate
future, primarily due to replacement of old units. These two
subcategories are the incinerator subcategory and the small remote
incinerator subcategory. While facilities may find alternative disposal
options are available, we are cognizant of the fact that, for these
subcategories, there may be instances where alternative disposal
options are unavailable, and a new incineration unit may be required.
For incinerators, we estimate units may require a combination of the
ACI system/FF, SNCR, and wet scrubbers to achieve the new source MACT
floor limits. As discussed above for existing incinerators, there are
no control technologies demonstrated or reasonably cost-effective that
we could consider at this time that would perform better or be more
cost-effective than those being used to meet the new source MACT floor
limits. Therefore, we have concluded that no beyond-the-floor emission
limits should be selected for new incinerators. For small remote
incinerators, we anticipate new sources will have an afterburner
installed to achieve the CO limit and that the afterburner will also be
equipped with low NOX burners, require waste segregation for
ferrous and non-ferrous metals and chlorinated plastics, and likely
require ACI system/FF to meet the new source MACT floor limits. As
discussed above for existing small remote incinerators, there are
technical issues with any control technologies that require water for
operation for this subcategory of unit. As a result, there are no
additional or better control technologies available other than those
being used to meet the new source MACT floor limits for the small
remote incinerator subcategory.

D. Rationale for Subcategories

1. Incinerators
    Comment: Some commenters argue that EPA wrongly concluded that all
incinerators are sufficiently similar to meet one emission limit. The
commenters suggest that the variability of combusted materials
necessarily means variability in emissions concentrations and that
variability cannot be masked exclusively by emissions control
performance or statistical analysis. One commenter claims that it will
be extremely difficult for incinerators combusting materials other than
what the best-performing incinerators are combusting to comply with the
limits in the proposed rule if EPA does not refine the overly-broad
incinerator subcategory.
    Response: EPA disagrees that incinerators should be further
subcategorized. As stated at proposal, ``incinerators, which are the
units currently regulated by the 2000 CISWI rule, are used to dispose
of solid waste materials, and emissions are a function of the types of
materials burned. Incinerators are designed without integral heat
recovery (but may include waste heat recovery). While there are
different designs, they all serve the same purpose: reduction in the
volume of solid waste materials. Incinerators can be operated on a
batch or continuous basis.'' We note that the MACT floor pool of
incinerators represents a wide variety of industrial sources, from
pharmaceuticals to heavy equipment manufacturers. From the data
available, these best-performing units also combust a wide variety of
materials, including liquid waste streams, expired pharmaceutical
products, and spent paint booth filters. Therefore, contrary to
commenters' arguments, there is a wide variety of materials being
combusted in the best-performing units. As we also explained at
proposal, the same types of add-on controls, including FF, wet
scrubbers, SNCR and ACI, can be applied to most incinerators. Our
estimates indicate that the reductions achieved by these controls will
allow incinerator units to comply with the emission limits.
    Furthermore, the commenters have provided no information that
indicates that the units in the incinerators subcategory are unable to
retrofit and/or take other actions (e.g., waste segregation) to satisfy
the standards in the final rule. Even if it were true that some sources
will be unable to meet the final standards, which we dispute, we still
believe it would not be reasonable to further subcategorize
incinerators based on the waste stream because such subcategorization,
taken to its logical conclusion, would lead to many subcategories with
one or only a few sources. We presume that Congress recognized when it
enacted CAA section 129 that solid waste incineration units would be
combusting a variety of waste and, in fact, CAA section 129 requires
different standards based on the potential waste streams: MSW; HMI
waste; and commercial and industrial waste. Congress provided
additional discretion to further subcategorize solid waste incineration
units, however, commenters have not provided compelling information
that indicates these units, which are already complying with the 2000
CISWI standards, should be further subcategorized. For these reasons,
we decline to further subcategorize the incinerators subcategory.
2. Energy Recovery Units
    Comment: Many commenters suggested that the ERU subcategory is
overly broad and should be subcategorized. The commenters stated that
EPA has broad authority to distinguish among groups of sources within a
source category or subcategory in setting a MACT standard. The
commenters maintained that the statute provides that EPA ``may
distinguish among classes, types, and sizes of sources within a
category or subcategory'' when establishing MACT standards. Several
commenters believed that Congress' use of the broad terms ``class,''
``type,'' and ``size'' show that EPA is intended to have broad
discretion in

the appropriate factors that warrant distinguishing among sources, and
EPA's proposed subcategories fall squarely within the meaning of
``types'' and ``sizes.'' The commenters argued that to the extent that
EPA may distinguish among sources within a category or subcategory on
the basis of ``any [reasonable] criterion of classification
whatsoever,'' and may create subcategories as appropriate, the CAA
clearly grants EPA authority to create additional subcategories for
ERUs.
    Many commenters suggested that the subcategorization of ERUs, where
differences among sources affect the applicability of control
technology, is consistent with MACT precedent. Commenters argued that
EPA's proposed inclusion of all types of ERUs (coal units, biomass
units, combination boilers, liquid boilers, and even gas fired units)
into one subcategory is inadequate. Several commenters suggested that
EPA create separate subcategories as it proposed in the Boiler and
Process Heater MACT. The commenters supported their suggestion by
offering the following rationale: (1) Since the CAA requires EPA to set
SO2 limits for CISWI units, and since coal contains
significant concentrations of sulfur, and biomass generally would
contain little or no sulfur, a subcategory for coal-fired boilers
should be established; expensive control devices such as a spray dryer
absorber could not reduce the outlet concentrations of SO2
to the single ppm levels equivalent to those of a biomass boiler; (2)
observation of the proposed Boiler MACT floor standards proposed for
biomass and coal units shows that there are significant differences in
outlet emissions of HCl, Hg, and CO; (3) likewise, the NOxx
emissions from the top performing biomass, coal, liquid, and gas-fired
units would all be significantly different due to inherent differences
in the design of these units.
    Response: The CAA allows EPA to divide source categories into
subcategories based on differences in class, type, or size. For
example, differences between given types of units can lead to
corresponding differences in the nature of emissions and the technical
feasibility of applying emission control techniques. The design,
operating, and emissions information that EPA has reviewed indicates
differences in unit design that distinguish different types of ERUs.
Data indicate that there are generally significant design and
operational differences between units that burn coal, biomass, liquid,
and gaseous fuels. Energy Recovery Units are therefore designed for
specific fuel types and will encounter problems if a fuel with
characteristics other than those originally specified is fired. Many
ERUs in the database are indicated to co-fire liquids or gases with
solid fuels, but, in actuality, most of these boilers commonly use fuel
oil or natural gas as a startup fuel only and then operate on solid
fuel during the remainder of their operation. In contrast, some co-
fired units are specifically designed to fire combinations of solids,
liquids, and gases. Changes to the fuel type would generally require
extensive changes to the fuel handling and feeding system (e.g., a
stoker using wood as fuel would need to be redesigned to handle fuel
oil or liquid wastes). Additionally, the burners and combustion chamber
would need to be redesigned and modified to handle different fuel types
and account for increases or decreases in the fuel volume. In some
cases, the changes may reduce the capacity and efficiency of the ERU.
An additional effect of these changes would be extensive retrofitting
needed to operate using a different fuel; therefore, the design of the
ERU impacts the degree of combustion.
    In our investigations resulting from commenters' statements, we
concluded that the data were sufficient for determining that a
distinguishable difference in performance exists based on unit design
type. Therefore, because different types of units have different
emission characteristics which may influence the feasibility or
effectiveness of emission control, they should be regulated separately
(i.e., subcategorized) for affected pollutants. Accordingly, we have
subcategorized ERUs based on unit design in order to account for these
differences in emissions and applicable controls. The two primary ERU
subcategories are units designed to burn solid wastes (solids) with
other solid fuels, and units designed to burn liquid wastes with liquid
or gaseous fuel (liquid/gas). The ERU solids subcategory is further
subcategorized into units designed to burn coal and units designed to
burn biomass for CO, NOX and SO2 to address
design differences and feasibility or effectiveness of emission control
between these types of units as commenters have suggested. The
subcategorization for these pollutants is also compelled by the data
available for the solid fuel sources. Specifically, coal fired ERUs
submitted exclusively CEMS data for CO, NOX, and
SO2, and biomass fired ERUs submitted almost exclusively
stack test data for these pollutants. We are unable to convert the vast
majority of CEMS data into equivalent stack test data and the converse
is true as well. Pursuant to CAA section 129(a)(2), EPA must establish
emission standards for existing sources based on the average emissions
limitation achieved by the best-performing 12 percent of sources.
Because the data for CO, NOX, and SO2 from the
biomass and coal fired ERUs are not in consistent formats, we would
have to ignore a subset of the available data in establishing the
floors for these pollutants if we did not further subcategorize solid
fuel ERUs. We therefore think it is reasonable to further subcategorize
these units for CO, NOX, and SO2 so the standards
are reflective of the data available to EPA, and we are properly
accounting for the different emissions characteristics associated with
the different types of fuels.
    These subcategories are based on the primary fuel that the ERU is
designed to burn. We are aware that some ERUs burn a combination of
fuel types or burn a different fuel type as a backup fuel if the
primary fuel supply is curtailed. However, ERUs are designed based on
the primary fuel type (and perhaps to burn a backup fuel) and can
encounter operational problems if another fuel type that was not
considered in its design is fired at more than 10 percent of the heat
input to the unit. Therefore, we subcategorized ERUs that burn at least
10 percent coal (on an annual heat input basis) as being in solid fuel/
coal subcategory, with the remaining solid ERUs being in the biomass
subcategory for ERUs.
3. Cement Kilns
    Comment: One commenter states that waste-burning cement kilns
differ among themselves significantly in terms of type, size,
configuration, and other relevant factors that can influence emissions,
and EPA should consider the further sub-categorization of kilns on this
basis. The commenters provide the example that in its evaluation of
organic emissions from kilns in support of the Portland Cement
rulemaking, they found significant differences due to configuration and
raw materials. The commenter did not develop specific recommendations
for sub-categorization of cement kilns under the proposed CISWI rule
citing the limited data and the limited time EPA has allowed for
comment in this rulemaking.
    Response: The authority to subcategorize is discretionary, even
where sources can otherwise be distinguished as a different class,
type, or size. In evaluating the population of kilns that may be
subject to CISWI and estimates of control technologies that may be
required to meet the limits, we realize that most of the kilns in the

CISWI population at proposal were subject to the standard solely due to
tire combustion. Further investigation indicated that all of these
kilns obtained the tires from established tire recycling programs.
Based on the new definition in Section 241.3, these tires would not be
considered to be solid wastes. Therefore, kilns that we considered as
CISWI units at proposal solely due to tire combustion are not part of
the CISWI category, and we removed them from the CISWI inventory. In
addition, we obtained information on used oil, biomass, and wood waste
being combusted by cement kilns. Based on the definition in 241.3, we
determined which of these materials would be considered to be solid
waste and removed any kilns from the CISWI inventory where we
determined none of the fuels were solid waste. This resulted in the
inventory of CISWI kilns being reduced to 12 kilns total. Of the 12
kilns in the current CISWI inventory, one is a wet kiln, four are
preheater kilns, and the remainder are preheater/precalciner kilns. We
recognize that differences in kiln design and configuration can effect
emissions. These effects are most evident on emissions of
NOX, CO, and SO2. However; all of these
pollutants are also affected by the site specific raw materials fed to
the kiln. We have insufficient data to differentiate between the raw
material affects and the kiln design affects. Therefore, we decided not
to develop separate subcategories for cement kilns. However, all of our
information indicates that NOX, SO2 and CO are
controllable to the level of the standard whether a kiln is wet or dry.
The control devices that may be necessary to comply with the CISWI
limits (including the standards for NOX, SO2 and
CO) may be applied to both types of kiln, and there do not appear to be
any feasibility or effectiveness issues that would necessitate
subcategorization in order for units to achieve the limits. For
example, the controls we estimate the wet kiln units may require in
order to meet the CISWI limits, such as SNCR, wet scrubbers, and RTO,
may be applied to all types of kilns. We are unaware of any design
considerations that prevent FF or RTO use for either the wet type or
preheater type of kiln. Therefore, EPA disagrees with this comment and
is not subcategorizing among waste-burning kilns.
4. Small Remote Incinerators
    Comment: Several commenters requested that EPA revise the
definition of small remote incinerator. Some commenters suggested that
the proposed definition would inadvertently exclude those incinerators
that are within the spirit of the definition, but are located within 50
miles of a MSW landfill or units that burn more than 1 ton of waste per
day. Other commenters specifically requested an exemption for small
remote incinerators that are not accessible by the Federal Highway
System. Several commenters explained that not all units are accessible
by vehicle, the affected units may or may not be within 50 miles of a
MSW landfill, and road access can be seasonal in Alaska.
    Commenters expressed particular concerns about small remote units
operating in remote locations of Alaska. Commenters explained that
waste accumulation due to unavoidable transportation delays could
attract animals, in potential violation of state law and policy and the
Federal Endangered Species Act. Several commenters explained that due
to the location of facilities, increased fog conditions and harsh
winters, it is unlikely that food waste can be transported off-site on
a daily basis. In these circumstances, stored waste may attract
wildlife to facility operations, which could in turn result in
potentially dangerous interactions with personnel. Commenters argued
that longer term on-site storage is not a safe option for either the
wildlife or humans. Further commenters explained that operational
areas, and areas where they can accumulate solid waste, are very small,
such that the ability to store multiple days of solid waste could be
problematic. The commenters asserted that the use of incinerators to
manage food waste has proven to be a valuable tool for preventing
human/wildlife interactions.
    Response: EPA has revised the definition of small, remote
incinerator to apply to a unit combusting less than 3 tons of waste per
day and located more than 25 miles from the nearest landfill. The
change to 25 miles and 3 tons of waste combusted per day, instead of
the parameters that were proposed, will help address the commenters'
concerns about applicability for intended units within this
subcategory.
5. Burn-Off Ovens
    Comment: Many commenters are opposed to regulating burn-off ovens
under CISWI. They assert that EPA severely underestimated the universe
of burn-off ovens and did not consider the potential subcategories of
burn-off ovens (e.g., metal parts recovery, drum reclamation, and
electric motor rewinding ovens). Several commenters argue that the
units do not use incineration or combustion processes and instead play
a vital role in the reclaiming and recycling process. Many commenters
claim that regulation of these units will result in job loss and
closure of businesses.
    Response: At proposal, we combined part, rack, and drum reclamation
units into one burn-off oven subcategory. We estimated that there were
approximately 36 units in the burn-off oven subcategory. We received
comments during the comment period that indicated that there may be
more than 15,000 units in the burn-off oven subcategory as we have
defined it. Furthermore, we have no data on drum reclamation units. We
also do not have data on all CAA section 129 pollutants for the burn-
off ovens we identified at proposal. For all these reasons, and because
we are not required to finalize standards for burn-off ovens to comply
with our CAA section 112(c)(6) obligation, we have determined that this
final action will not subject burn-off ovens to this standard.
6. Soil Treatment Units
    Comment: EPA received a comment that soil treatment units are
unique units and do not belong in the floor determination for kilns.
The commenter stated that soil treatment units are ``treating'' and not
``combusting'' soil and therefore should be considered in an
alternative floor analysis.
    Response: Based on the information received during the comment
period, EPA agrees that soil treatment units and kilns should be
separate subcategories. In addition, information we have obtained since
proposal indicates that there may be many more soil treatment units
than the two we have identified; and, therefore, we do not have
sufficient data to set emissions standards for soil treatment units.
For these reasons, we have determined that this final action will not
subject soil treatment units to this standard. We do not need to
regulate soil treatment units at this time in order to comply with our
CAA section 112(c)(6) obligation.

E. Emission Limits

1. Consistency Between Other Applicable NESHAP Limits
    Comment: Many commenters stated that EPA should adopt MACT
limitations of similar stringency for similar units, irrespective of
whether the source is regulated as a kiln or ERU under CAA section 112
or a CISWI unit under CAA section 129. Commenters stated that for some
emissions, the two rules apply to similar equipment burning similar
fuels for similar

purposes, but the emission limits are clearly different. They suggested
that efforts be made by the EPA either to explain the differences or to
develop more adequate and consistent limits in the regulations. One
commenter stated that EPA should express standards for waste-burning
cement kilns in a production-based form for a direct comparison of
standards with the Portland Cement NESHAP.
    Response: As commenters note, we have subcategorized units to the
extent we determined appropriate within the CISWI population, to
reflect similar design considerations as subcategories for non-CISWI
units, however, the fact that units are similar does not authorize EPA
to set similar standards under CAA section 112 and section 129. As we
have discussed elsewhere in our descriptions of the MACT floor
analysis, we are calculating emission limits based on data from units
that we believe are CISWI units based on the definition of solid waste
and the currently available information. Solid waste incineration units
may not be regulated under CAA section 112 once we have established CAA
section 129 performance standards for the category or subcategory, and
solid waste incineration units should not be included in the floor
calculations for CAA section 112 standards once the units are
identified as solid waste incineration units. The converse is also
true. The requirements for setting CAA section 129 standards are
different for new and existing units. For new units, EPA must base the
standards on the best-performing similar unit for each subcategory,
and, for existing units, we must base the standards on the average
emissions limitation achieved in practice for the best-performing 12
percent of units in the subcategory. See CAA section 129(a)(2). The
statute, therefore, provides some discretion for EPA to establish new
source standards based on the best controlled similar source, instead
of the best controlled source in the subcategory. For this reason, EPA
may consider CAA section 112 sources to the extent they are similar to
the CAA section 129 units when establishing the MACT floor for new
sources. For existing units, however, EPA is required to use
information from sources in the subcategory when establishing the MACT
standards. Section 112 of the CAA contains similar requirements for
establishing the MACT floors. See CAA section 112(d)(3). Because the
existing sources subject to CAA section 112 will have different
emissions information than the sources subject to CAA section 129, we
may not harmonize the existing source standards for similar units
regulated under both CAA section 112 and section 129.
    As to the comment that EPA should establish production based
standards for waste-burning kilns to coincide with the Portland Cement
NESHAP, we note that CAA section 129 solid waste incineration rules,
including the 2000 CISWI standards, have consistently presented numeric
limits in stack gas concentration bases. We are maintaining in the
final CISWI standards emission limits as stack gas concentrations;
however, in response to the comments on this issue, we note that the
kiln limits in Tables 1 and 2 of the preamble can be converted to lb/
ton clinker or lb/ton raw feed bases assuming 100,000 dscf/ton clinker
and 1.65 ton raw feed/ton clinker.
2. Opacity Limits
    Comment: Several commenters opposed the setting of opacity limits
for CISWI units. Commenters argued that opacity has long been
considered a surrogate monitoring methodology for demonstrating
continuous compliance with PM standards and that the proposed controls
and monitoring techniques eliminate the need for opacity monitoring.
Many commenters also suggested that a certified reader is only able to
distinguish opacity in increments of 5 percent and that the proposed
single digit limits are beyond the capabilities of Method 9. Commenters
also asserted that the correlation between PM and opacity is not
demonstrated based on a review of the data available at proposal.
Several commenters stated that it is not appropriate to apply a ratio
of PM to opacity based only on data from one facility in the
incinerator category and apply it to all types of units regulated under
this rule.
    Response: At proposal, we had opacity data for only one unit in the
incinerator subcategory. We developed opacity standards for the CISWI
subcategories by establishing a ratio of PM to opacity for the one
incinerator and multiplying that ratio by the PM MACT standards for
each of the subcategories to establish the opacity standards for the
different subcategories. 75 FR 31956. We requested comment on this
approach. We also requested comment on whether it was appropriate to
establish opacity standards for CISWI units at all. EPA is not required
to establish opacity standards for incineration units pursuant to CAA
section 129(a)(4), which requires EPA to set numeric emission
limitations for nine pollutants plus ``opacity (as appropriate).''
    EPA is not promulgating opacity limits for CISWI units at this
time. As commenters note, opacity is often required in CAA rules as a
surrogate for PM to assure compliance with PM standards when continuous
PM monitoring is not required under the applicable standard. In this
case, we are requiring PM stack testing in conjunction with continuous
parametric monitoring; therefore, the need for an opacity limit is
diminished with regards to CISWI units. In addition, we have determined
it is not appropriate to set opacity standards given the lack of
opacity data from all but one of the CISWI units. However, we continue
to maintain that opacity serves as an indicator of PM, and we may in
the future determine that it is appropriate to establish opacity limits
for CISWI units; therefore, EPA is requiring opacity testing for units
as part of their annual testing requirements. Opacity also serves as an
indicator of good air pollution control practices, and as such, is a
valuable tool for EPA in determining compliance with the general
provision at 40 CFR 60.11(d) that sources maintain and operate their
affected facility including associated air pollution control equipment
in a manner consistent with good air pollution control practices for
minimizing emissions.
3. Limits for TMB and TEQ for D/F
    Comment: Some commenters suggest that EPA arbitrarily set floors
for TEQ based on a 0.078 ratio between total mass and TEQ D/F data.
Commenters believe that the data EPA used to calculate the multiplier
was not limited to the best-performing 12 percent of sources and thus,
the approach does not conform to the statute, which requires MACT
floors to be set on the basis of the average of the emissions levels
actually achieved by the best-performing 12 percent of sources.
    One commenter asserts that nondetected target compounds (i.e., the
17 2,3,7,8-substituted PCDD/PCDF TEF congeners) were treated with a
zero concentration in all of the stack test reports and that target
compounds reported by the laboratory as an EMPC were treated with a
zero concentration for TEQ calculations. The commenter further states
that EPA used TEQs which treated both nondetected target compounds, as
well as those reported as an EMPC, with a zero concentration (i.e.,
ND=0; EMPC=0).
    Response: EPA is no longer using a ratio of TMB to TEQ to calculate
limits for D/F TEQ. EPA further reviewed the data, including data
corrections submitted after proposal, and used

individual and total mass congener data to establish TEQ limits for all
subcategories. The commenter's assertion that EMPC and ND values were
treated as zero concentration is incorrect. Estimated maximum possible
concentration and ND values were not incorporated into the analysis
unless a facility reported an actual value, including a reported value
of zero. The TEQ limits were calculated using the same statistical
approach used for the other regulated pollutants. See section V.B of
this preamble for discussions on establishing MACT floors,
incorporating nondetect values, and changes in the statistical approach
used to set limits.

F. New Data/Corrections to Existing Data

1. Discussion of EPA Data Validation and Inclusion of New Data Received
Since Proposal
    Comment: EPA received several comments on suggested data
corrections or new data to incorporate into the analysis.
    Response: See ``Data Amendments and Corrections Following
Proposal'' memorandum in the docket for a discussion on how data were
incorporated to address comments.

G. Testing and Monitoring

1. Monitoring Alternatives (CEMS in Lieu of Testing or Parametric
Monitoring, Decisions on PM CEMS and CO CEMS)
    Comment: While some commenters supported the use of CO and PM CEMS
to monitor emissions, others argued that CEMS should not be required
for all units due to unreasonable costs and impracticality. Several
commenters suggested that EPA evaluate the feasibility and measurement
capabilities of CEMS before requiring their use. Commenters stated that
multi-metals and PM CEMS can be inadequate in indicating the complex
nature of emissions and urged EPA not to remove any of the parametric
monitoring requirements in lieu of CEMS. Further, some commenters
suggested that compliance testing is not needed if CEMS is used to
monitor emissions.
    Response: For the operations and facilities subject to the rule, we
believe that the combination of periodic compliance emissions testing
and continuous monitoring of operational and parametric control measure
conditions is appropriate for assuring ongoing compliance. The rule
allows a source owner or operator to install and operate CEMS in lieu
of some testing and parametric monitoring requirements. This process
requires source owners to propose site-specific monitoring plans for
approval. These plans would include CEMS PS and periodic QA/QC steps to
assure the quality of the alternative monitoring data. Currently, EPA
has the requisite CEMS PS for Hg monitoring systems and not for
multiple metals CEMS.
    The final rule will not require CO CEMS for existing ERUs, as
proposed. The rule will require operational parametric monitoring, as
the commenter suggests, for most units affected by the rule, with CO
CEMS allowed as an option at the source owner's discretion.
    We agree that a PM CEMS installed and operated in accordance with
PS 11 and the associated QA procedures can provide assurance of ongoing
compliance without the need for additional periodic compliance testing.
The final rule authorized the optional use of PM CEMS. We have retained
the requirement for PM CEMS on existing ERUs greater than 250 mmBtu/hr
to measure continuous compliance for these larger units.
2. CEMS Data To Set Standards
    Comment: Several commenters suggested that any limit where CEMS are
required, CEMS data must be used to develop the emission limits. The
commenters discussed their experience with CEMS that shows variability
is much higher than what a periodic stack test will show. The
commenters suggested that 30 days of continuous emission monitoring is
insufficient. They stated that biomass boilers have seasonal
variability that would only be seen over the course of a year or more.
Commenters also requested that EPA be aware that there may be sources
that have installed for criteria pollutants under other permit
requirements, particularly for NOX, CO, and SO2,
and that sources would prefer to use the CEMS to demonstrate compliance
but for the fact that the standards are established using stack test
data. The commenters suggested that even if the standard only requires
a stack test, there are sources that will be using continuous emission
monitors for compliance purposes.
    Response: As noted earlier, we are not requiring CEMS for
compliance for existing units, other than PM CEMS for ERUs greater than
250 mmBtu/hr. No ERUs submitted PM CEMS data for us to evaluate in our
development of emission limits. Therefore, we were unable to establish
limits based on CEMS data as the commenter suggests; however, we have
included a longer averaging period to account for the variability in PM
emissions for these sources. In any case, given the controls available
for PM, we do not believe that the PM emissions should vary as much as
they may for other pollutants.
    Also, as stated above, the rule allows sources to install and
operate CEMS in lieu of some testing and parametric monitoring
requirements at their discretion. This process requires source owners
to propose site-specific monitoring plans for approval. These plans
would include CEMS PS and periodic QA/QC steps to assure the quality of
the alternative monitoring data. In allowing optional CEMS usage, we
are providing facilities with compliance flexibility in case they wish
to use existing CEMS to demonstrate compliance with the standards.
Facilities that are concerned that they will not be able to
continuously comply with the emissions limitations if they use CEMS for
those limitations established based on stack test data should not avail
themselves of the CEMS alternative.
3. Reduced Testing Provisions
    Comment: Commenters contended that the proposed performance testing
requirements are excessive and should be reduced to a reasonable and
appropriate level. EPA proposed at 40 CFR 63.2710(b) that all units
conduct performance tests for PM, HCl, fugitive emissions, and opacity
on an annual basis. EPA further proposed for ERUs that annual
performance tests be conducted for PM, HCl, Cd, lead, Hg, dioxins/
furans, opacity, fugitive emissions, NOX, and SO2
(unless a CEMS is used for either PM, HCl, Hg, NOX, and/or
SO2). Thereafter, EPA proposed to reduce the frequency to 3
years if there had been three tests in a row that had results of less
than 75 percent of the emission standard. Commenters recognized EPA has
included a provision to skip to a 3-year frequency provided a source
passes three tests in a row with at least a 25 percent margin. However,
commenters contended that with the very stringent limits EPA had
proposed, very few units would likely to qualify for this provision
and, therefore, they were not sure of its value.
    Response: We disagree with the commenters' assertions that the
performance testing requirements are excessive. As discussed earlier,
the combination of periodic compliance emissions testing and continuous
monitoring of operational and parametric control measure conditions is
appropriate for assuring continuous compliance with the emissions
limitations. Without recurring testing, we would have no way to know if

parameter ranges established during initial performance testing
remained viable in the future. The commenter correctly notes that CEMS
may be used as an option and, if so, annual performance testing is not
required for the pollutant being measured by a CEMS.
    Regarding the assertion that the margin for reduced testing is too
high to be effective, we disagree and note that the intent of this
provision is to provide an incentive for better performers. By
specifying the less than 75 percent of the emission standard margin, we
are providing such an incentive for good performance, and not rewarding
units that just barely meet the standard for a pollutant. Performance
testing is required for all pollutants rather than PM and HCl only.
    In addition, EPA is maintaining the reduced testing option for
units that demonstrate emissions a specified percentage below the
limits for 3 years. We have clarified and modified this option to state
that performance testing for a given pollutant may be performed every 3
years, instead of annually, if measured emissions during 2 consecutive
annual performance tests are less than 75 percent of the applicable
emission limit.
    Also note that sources that switch fuels during the year following
a performance test will not qualify for reduced testing.

H. Start-Up, Shutdown, and Malfunction Requirements

    Comment: Several commenters argued that emissions limits should not
apply during SSM events while other commenters stated that SSM
emissions should be included in calculations of emissions and
standards. Several commenters suggested that in order to assure that
SSM are appropriately accommodated, EPA must either assure that the
data on which the standard is based include representative data from
such periods or, alternatively, set a separate work practice standard
to properly accommodate SSM. Several commenters contended that EPA did
not consider enough data to adequately characterize emissions
variability, as the standards were set based only on 3-run stack test
data obtained under the best of operating conditions (and typically
only one operating condition), no long-term CEMS data were used, no
adjustment was made for fuel or feed pollutant content variability, and
no data collected during periods of startup or shutdown were analyzed.
Some commenters suggested that certain control devices take several
hours to warm-up and that emissions during these startup periods will
exceed the emissions standards and would never be able to recover to
meet the average limitations. Further, several commenters stated that
compliance with emissions standards during malfunction events will be
difficult to gauge since emissions testing during such events is near
impossible given the sporadic and unpredictable nature of malfunctions.
The commenters contended that the rule could have the effect of forcing
units to choose between safety and compliance with emissions
requirements. The commenters stated that for some affected units,
malfunctions by their very nature create unsafe conditions which can
lead to excessive combustible mixtures that can result in explosions,
equipment damage and personnel hazards.
    Response: The Court vacated portions of two provisions in EPA's CAA
section 112 regulations governing the emissions of HAP during periods
of SSM. Sierra Club v. EPA, 551 F.3d 1019 (DC Cir. 2008), cert. denied,
130 S. Ct. 1735 (U.S. 2010). Specifically, the Court vacated the SSM
exemption contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1), that
are part of a regulation, commonly referred to as the ``General
Provisions Rule,'' that EPA promulgated under section 112 of the CAA.
When incorporated into CAA section 112(d) regulations for specific
source categories, these two provisions exempt sources from the
requirement to comply with the otherwise applicable CAA section 112(d)
emission standard during periods of SSM.
    While the Court's ruling in Sierra Club v. EPA, 551 F.3d 1019 (DC
Cir. 2008), directly affects only the subset of CAA section 112(d)
rules that incorporate 40 CFR 63.6(f)(1) and (h)(1) by reference and
that contain no other regulatory text exempting or excusing compliance
during SSM events, the legality of source category-specific SSM
provisions such as those adopted in the 2000 CISWI rule is
questionable.
    Periods of startup, normal operations, and shutdown are all
predictable and routine aspects of a source's operations. However, by
contrast, malfunction is defined as a ``sudden, infrequent, and not
reasonably preventable failure of air pollution control equipment,
process equipment, or a process to operate in a normal or usual manner
* * *'' (40 CFR 60.2). EPA has determined that malfunctions should not
be viewed as a distinct operating mode and therefore, any emissions
that occur at such times do not need to be factored into development of
CAA section 129 standards, which, once promulgated, apply at all times.
In Mossville Environmental Action Now v. EPA, 370 F.3d 1232, 1242 (DC
Cir. 2004), the court upheld as reasonable standards that had factored
in variability of emissions under all operating conditions. However,
nothing in section 129 or in case law requires that EPA anticipate and
account for the innumerable types of potential malfunction events in
setting emission standards. See Weyerhaeuser v. Costle, 590 F.2d 1011,
1058 (DC Cir. 1978) (``In the nature of things, no general limit,
individual permit, or even any upset provision can anticipate all upset
situations. After a certain point, the transgression of regulatory
limits caused by `uncontrollable acts of third parties,' such as
strikes, sabotage, operator intoxication or insanity, and a variety of
other eventualities, must be a matter for the administrative exercise
of case-by-case enforcement discretion, not for specification in
advance by regulation.'').
    It is reasonable to interpret section 129 as not requiring EPA to
account for malfunctions in setting performance standards. For example,
we note that section 129 uses the concept of ``best controlled'' and
``best-performing'' unit in defining MACT, the level of stringency that
section 129 performance standards must meet. Applying the concept of
``best controlled'' and ``best-performing'' to a unit that is
malfunctioning presents significant difficulties. The goal of a best
controlled or best-performing unit is to operate in such a way as to
avoid malfunctions of the unit.
    Moreover, even if malfunctions were considered a distinct operating
mode, we believe it would be impracticable to take malfunctions into
account in setting CAA section 129 standards for CISWI units. As noted
above, by definition, malfunctions are sudden and unexpected events,
and it would be difficult to set a standard that takes into account the
myriad different types of malfunctions that can occur across all
sources in the category. Moreover, malfunctions can vary in frequency,
degree, and duration, further complicating standard setting.
    In light of the Sierra Club decision, EPA proposed to require that