good proxy for the better controlled units and that there were
shortfalls in reaching the necessary 12 percent, EPA has never
explained why it made sense to use the highest of its test run data to
make up the gap.'' Id.
    Subsequent court decisions also addressed the type of information
EPA may use to estimate emissions performance and establish MACT floors
for existing units. In NLA II, the Court rejected the Sierra Club's
claim that it was unreasonable for EPA to select ``the median
[performing] plant out of the best twelve percent of the plants for
which it had information and set the * * * floor at the level of the
worst performing plant in its databases using th[e same] technology [as
the median plant].'' 233 F.3d at 630. As long as EPA's estimate of the
performance of the top 12 percent was reasonable, the Court held, EPA
was not required to use actual emissions data. Id. While in CKRC the
Court held that EPA had not justified in the HWC rulemaking basing the
floor on emissions levels of the worst performing plant utilizing MACT
control technology, when record evidence indicated other factors beyond
MACT technology affected emissions performance, the Court reiterated
that EPA could use estimates, as long as they reflected a
``reasonable[] estimate [of] the performance of the * * * best-
performing plants.'' 255 F.3d at 862.
    Specifically regarding the use of State permits to determine MACT
floors, the Court in Northeast Maryland Waste Disposal Authority v.
EPA, 358 F.3d 936 (D.C. Cir. 2004) (``NMWDA''), rejected EPA's approach
for small municipal waste combustion units because ``as in Sierra Club,
EPA stated only that it `believes' state permit limits reasonably
reflect the actual performance of the best performing units without
explaining why this is so.'' 358 F.3d at 954. There, EPA had asserted
that the inherent variability of emission levels made other data
inaccurate, but the Court concluded that EPA gave ``no evidence that
the [State] permit levels reflect the emission levels of the best-
performing'' units, and that EPA's stated ``belief'' did not rise to
the level of a ``reasonable estimate.'' Id. However, in Mossville
Envt'l Action Now v. EPA (370 F.3d 1232 (D.C. Cir. 2004)), the Court
concluded that ``instead of simply claiming that it believes its
[relied upon] standards estimate what the best five plants actually
achieve, EPA points to some evidence. In its response to comments, EPA
cited its analysis of three years of data, and * * * met its burden of
establishing that its standards reasonably estimate the performance of
the best five performing sources. Having cited the great variability of
emission levels, even within the same plants, and the inherent
difficulty in other standards it considered, the EPA's selection of the
[relevant] standards as the MACT floor is reasonable because it has
supported its decision with record data that shows the connection
between its MACT floor and the top performing plants.'' 370 F.3d at
1242.
    a. The Possibility that HMIWI Sources are Substantially
Overachieving their Regulatory Limits. With regard to the Sierra Club
Court's first concern, the Court itself noted early in its opinion that
``the necessary relationship [of regulatory data serving as a
reasonable proxy to indicate HMIWI performance] seems quite reasonable
here. Indeed, it seems likely that any jurisdiction bothering to impose
limits would not knowingly set them below what it found firms to be
achieving in practice. And there seems no reason to think that
underachieving firms would be overrepresented in jurisdictions making
this effort.'' 167 F.3d at 662. The Court also expressed support for
the notion that, when faced with limited actual emissions information,
a substitute `` `reasonable sample' may be used `to find out what the
best 12 percent are doing[,]' '' (id., citing Oral Arg. Tr. at 11), and
that ``EPA typically has wide latitude in determining the extent of
data-gathering necessary to solve a problem.'' Id. Specifically, the
Court noted ``that since EPA had data on only one percent of about 3000
[HMIWI]s, [* * *] the data-gathering costs of any non-sampling method
may well have been daunting.'' Id., at 663.
    There are three reasons why EPA chose to use the regulatory limits
at their face value in calculating the existing source MACT floor for
the 1997 rule. First, regulatory data were used because there was very
little actual emissions data available and very little data available
indicating the type of air pollution control used by the best
performing units. (See 61 FR at 31738.) None of the available
information indicated that the regulated entities were substantially
overachieving or underachieving their regulatory limits. Second, there
was no information before the Agency suggesting that the State
regulatory agencies erred in establishing the regulatory limits or that
the States' regulatory limits were outdated. It was thus reasonable for
EPA to expect that the State regulatory limits provided a reasonable
estimate of the actual performance of HMIWI units. Third, it was
reasonable for EPA to expect that regulated entities take their
regulatory limits into account when designing their control equipment.
To some extent, control equipment can be designed to meet various
levels of emissions, and regulated entities do not normally spend more
money than necessary to meet a regulatory limit. As noted above, the
Court observed that ``there seems no reason to think that
underachieving firms would be overrepresented'' by regulatory limits
(167 F.3d at 662). Conversely, there is no reason to generally assume
that substantially overachieving firms would be overrepresented in
jurisdictions imposing regulatory limits. Rather, what is most likely
is that sources in regulated jurisdictions will have assessed whether
steps to control emissions are needed to comply with the regulatory
limits, and that, in order to account for emissions variability when
applying control technologies, they will be targeting their emissions
levels at some safe point below the regulatory limits. Hence, with no
information in the 1997 rulemaking record to indicate otherwise, EPA
generally expected that regulatory limits were being achieved, through
application of emissions control methods, at emissions levels that
sources deem necessary in order to minimize the risk of violating the
relevant limit, and were neither substantially overachieving the limits
nor underachieving them.
    The Court noted that the administrative record indicated that, in
some cases, sources were overachieving their regulatory limits, where
the floors based on the weighted average of the regulatory limits and
the ``uncontrolled'' (i.e., combustion-controlled) data were
significantly higher than the values used for combustion-controlled
data. (See 167 F.3d at 663, citing A-91-61, IV-B-024 at 2-3). Here, the
Court was referring to some regulatory limits that, in fact, reflected
higher emissions levels than did EPA's uncontrolled (i.e., combustion-
controlled) emission estimates, and suggested that in these cases it
would be unreasonable for EPA to view the best performing 12 percent

of sources as actually polluting at levels so much higher than the test
units for which EPA assumed no emissions controls were in place. Id.,
at 663-664.
    EPA agrees that a regulatory limit does not reflect ``actual
performance'' when that limit is higher than the level attributed to
the worst reasonably foreseeable performance of an uncontrolled (i.e.,
combustion-controlled) source. Since the data forming the basis for the
existing source MACT floor must provide a reasonable estimation of the
``actual performance'' of the best performing 12 percent of HMIWI, such
high regulatory limits should not have been included in the best-
performing 12 percent. Therefore, in our re-visiting the MACT floor for
existing HMIWI based on the 1997 record, in situations for which there
is no information in the 1997 record indicating the presence of an add-
on pollution control device (``APCD'') or other use of air pollution
control methods but there are regulatory limits, we propose the
substitution of combustion-controlled data for regulatory limits where
those data reflect lower emissions levels than do regulatory limits
that appear to be unrelated to actual controls. We propose to continue
to use combustion-controlled data in situations for which there is no
information indicating air pollution controls are in use and there are
no regulatory limits.
    b. Emission Control on HMIWI Not Subject to Regulatory Limits. The
Court's second concern was that EPA had not made a finding that HMIWI
that were not subject to regulatory requirements did not use emissions
controls of any kind. The Court viewed such a finding as a necessary
prerequisite to using uncontrolled (i.e., combustion-controlled) data
for units not subject to regulatory requirements. This issue can be
partly resolved by correcting a misunderstanding that may have resulted
from our 1997 administrative record. The Court focused on information
submitted in 1995 by the AHA suggesting that ``over 55% of [HMIWI]s in
each category were controlled by wet scrubbers.'' (See 167 F.3d at 664,
citing AHA Comments, Exhibit 3.) Based on its review of the AHA
comments, the Court assumed that under EPA's estimation of the HMIWI
population, more than 12 percent in each category ``would as a matter
of mathematical necessity have to be controlled.'' Id., at 664, n. 8.
The Court then observed that ``it is difficult to see how it was
rational to include any uncontrolled [i.e., combustion-controlled]
units in the top 12 percent, at least with respect to pollutants that
wet scrubbing controls.'' Id., at 664.
    With regard to the AHA ``data'' identified by the Court as
indicating 55 percent of HMIWI use wet scrubbers, EPA believes that the
Court was led by this information into assuming that unregulated HMIWI
were in fact applying add-on emissions controls, when the record does
not actually substantiate such an assumption, especially for small
HMIWI. The AHA asserts ``almost all properly designed, operated, and
controlled [HMIWI] can readily meet a particulate emission limit of
0.10 gr/dscf without an [add-on air pollution control] system'' (IV-D-
637, Exhibit 2, emphasis added). The AHA then concludes ``[t]herefore,
it is reasonable that as many as 50 percent of those [HMIWI] having
such an emission limit would be uncontrolled.'' Id. The AHA goes on to
assume that 50 percent of all HMIWI with particulate emission limits of
0.10 gr/dscf or higher are controlled with wet scrubbers, while an even
higher percentage of units with more stringent particulate emission
limits are assumed to be controlled. Id. This is akin to saying that,
because homeowners are generally not required to install wet scrubbers
on fireplaces, it is reasonable to assume that as many as 50 percent of
homes with fireplaces do not have wet scrubbers, while the other 50
percent of home fireplaces are equipped with wet scrubbers. The AHA
makes a basic assumption that at least 50 percent of all HMIWI have wet
scrubbers, no matter what requirements they are subject to. With no
other information to support its assumption, AHA's ``data'' indicating
55 percent of HMIWI are equipped with wet scrubbers is altogether
unreliable. In addition, EPA's documented difficulty in identifying
sources with add-on controls during the development of the HMIWI
emission testing program is in direct conflict with the large number of
controlled sources suggested by the AHA ``data.''
    Based on information from various sources in the docket from the
1997 rulemaking, including an AHA HMIWI inventory, we now estimate that
about 32 percent of large, 4 percent of medium, and 1 percent of small
HMIWI at the time of the 1997 rulemaking were equipped with add-on
control systems. Other sources in the 1997 record that provided an
indication of whether or not HMIWI were equipped with add-on air
pollution control and upon which these estimates are based include a
survey of HMIWI in California and New York, air permits from State
regulatory agencies, responses to information collection requests,
telephone contact summaries, HMIWI emissions test reports, and various
inventories. (See Legacy Docket ID No. A-91-61, items IV-J-82, IV-B-07,
II-B-94, II-D-175 through 178, II-I-151, IV-J-89, IV-E-65, IV-E-74, IV-
E-86, and II-B-61; Docket EPA-HQ-OAR-2006-0534, document titled ``List
of Test Reports Used to Identify HMIWI Control Devices''). Our
assessment that few HMIWI were equipped with add-on controls is also
supported by economics in that it would not have made sense for an
HMIWI to be voluntarily equipped with an air pollution control device
that costs one to three or more times as much as the entire HMIWI.
Further supporting our assessment is the fact that the expected outcome
of the regulation (which was not refuted by any commenters), that 50 to
80 percent of existing incinerators (including 100 percent of the small
units) would shut down rather than meet the regulations because those
that chose to meet the regulations would have to install air pollution
control to comply, was, in fact, more than realized. (See 60 FR 10665,
61 FR 31768, and 62 FR 48372.) In fact, all but 8 small units, 6 of
which meet the rural criteria and did not have to install air pollution
control to comply, 20 medium units, and 44 large units have shut down,
rather than meet the standards that would have been achieved by use of
the very controls AHA appeared to assume were in place. Consequently,
EPA concludes that the 1997 record, as confirmed by recent data showing
the vast reduction in sources (as opposed to sources installing
controls), shows that most HMIWI were not equipped with add-on air
pollution control and that the use of uncontrolled (i.e., combustion-
controlled) emission estimates where there was no indication of air
pollution control (and where any applicable regulatory limits allowed
higher levels of emissions than our combustion-controlled emissions
values reflected) was warranted. Based on the number of HMIWI
shutdowns, it appears very likely that there were even fewer HMIWI with
air pollution controls than we estimated based on the information
discussed above (i.e., that about 32 percent of large, 4 percent of
medium, and 1 percent of small HMIWI were equipped with add-on control
systems).
    c. EPA's Use of the Highest Emissions Data to Reflect Uncontrolled
(i.e., Combustion-Controlled) Emissions. The Court's third concern
regarded our use of the highest of the test run data to reflect
uncontrolled (i.e., combustion-controlled) emissions in cases where
regulatory data did not comprise the

necessary 12 percent of best performing sources. Our reason for this
approach is the same as the reason described earlier regarding new
units for using the highest data point from MACT-particular technology
to reflect the performance of that technology and identify the ``best
controlled similar unit.'' As the Court stated in NLA I, ``where test
results are relied upon, it should involve the selection or use of test
results in a manner which provides some assurance of the achievability
of the standard for the industry as a whole, given the range of
variable factors found relevant to the standard's achievability.'' (See
627 F.2d at 433). EPA reads the Court's opinion in Sierra Club as at
least endorsing the principles of NLA I with respect to existing units,
as the Court described as ``counterintuitive'' the Sierra Club's
``proposition that an `achieved' level may not be `achievable[.]' ''
(See 167 F.3d at 662). In addition, we also read CKRC as allowing this
approach, where no evidence in the record contradicts the assumption
that ``factors other than the control have a negligible effect [on
emissions performance],'' 255 F.3d at 866, and, therefore, the presence
or absence of known effective MACT controls is the prime determinant of
emissions performance.
    Where regulatory data indicating use of emissions control was
absent in the 1997 rulemaking record, EPA needed to find a surrogate
emission limitation that reflected uncontrolled (i.e., combustion-
controlled) emissions, expecting, when not faced with data indicating
otherwise, that facilities with no regulatory limits would not be
controlling their emissions with add-on controls or other control
methods (beyond combustion control). In this situation, EPA used the
highest test data point from a well-operated HMIWI as a surrogate for
the worst reasonably foreseeable circumstances. The highest test data
points reflect the normal, and unavoidable, variation in emissions that
would be expected to recur over time. Table 7 of this preamble
summarizes the performance values used for units for which there is no
information indicating an APCD is present and there are no regulatory
limits, or where regulatory limits do exist but reflect emissions
levels that are higher than the values for uncontrolled (i.e.,
combustion-controlled) units.

 Table 7.--Uncontrolled (i.e., Combustion-Controlled) Performance Values
------------------------------------------------------------------------
                                                            Performance
                    Pollutant  (units)                       value \1\
------------------------------------------------------------------------
HCl (ppmv)...............................................      2,770
CO (ppmv) -..............................................    \1\ 584.9
Pb (micrograms per dry standard cubic meter [mu]g/dscm)..      8,629
Cd ([mu]g/dscm)..........................................      3,520
Hg ([mu]g/dscm)..........................................      6,543.4
PM (gr/dscf).............................................      \2\ 0.278
CDD/CDF, total (ng/dscm).................................  \2\ 8,102
CDD/CDF, TEQ (ng/dscm)...................................    \2\ 236
NOX (ppmv)...............................................        224.5
SO2 (ppmv)...............................................         46.39
------------------------------------------------------------------------
\1\ All performance values are measured at 7 percent oxygen.
\2\ Based on 1-second combustion level

    d. Determining the MACT Floor and MACT for Existing Units. As
discussed above, the Sierra Club Court identified some potential errors
in EPA's methodology for determining the existing source MACT floors
for HMIWI. After reviewing the 1997 HMIWI record in the context of the
Court's opinion, EPA agrees that, in determining the MACT floor, the
Agency should not have used regulatory limits that reflected higher
emissions levels (and that did not appear to be related to any air
pollution controls) than those corresponding to EPA's combustion-
controlled emission estimates. Furthermore, as we examined the 1997
record and our estimates of the performance of HMIWI where we had some
indication that add-on controls may have been used, we determined that
we should not have used combustion-controlled emission estimates in the
floor calculations to represent the performance of those sources.
Additionally, for this rulemaking we propose that where actual
emissions test data reflecting emissions performance was available in
the 1997 record for use in determining the MACT floor, that data should
take precedence over other types of data (i.e., regulatory limits or
performance values).
    EPA's reassessment of the 1997 MACT floors and MACT decisions,
based on an adjusted methodology that addresses the Court's issues
discussed above, results in proposed emission limits that in many cases
are more stringent than the limits promulgated in 1997. EPA's first
step in redoing the MACT analysis based on the 1997 record for existing
HMIWI was to determine the pollutant-specific values that make up the
best performing 12 percent of existing units within each size category.
Actual test data, where available in the 1997 record, were the initial
type of pollutant-specific values considered. Next, where the 1997
record has information indicating that a source employed some type of
add-on control but there are no test data or regulatory limits for that
source, an average of the maximum dry and wet control system
performance was determined for each pollutant, and those values were
added to the data set towards comprising the best performing 12
percent. We believe that use of these averages is an appropriate method
of estimating the performance of HMIWI (1) where the 1997 record has
limited information indicating the presence of some type of add-on
control but no test data for the unit, and (2) where we are unsure if
the control is similar to, or is as efficient as, those for which we
have data, or if the unit even employed a true control device. As
previously stated, we believe it very likely that there were fewer
HMIWI with air pollution controls than we estimated in 1997, and to
which we have assigned pollutant-specific average control device
values. If, in fact, those sources were employing true control devices,
common sense dictates that there wouldn't have been the large number of
unit shut downs that occurred in response to the promulgated standards.
However, because we had some indication that an add-on control device
was in place on those sources, we recognize that the use of
uncontrolled (i.e., combustion-controlled) emission estimates (at
promulgation) did not provide a reasonable estimate of their
performance. Similarly, use of performance values associated with a
specific type of add-on control device seems inappropriate when no
details are available on the control device and there is, in fact, some
doubt as to the presence of a true control device at all. Despite the
doubts of the presence of a true control device, the approach we have
selected assumes that the 1997 record is correct and assigns
``default'' performance values to the units that are based on the
expected performance of the types of control devices used in the
industry in 1997. These default performance values, based on the
average of the maximum dry and wet control system performance, also are
used where regulatory limits exist but are higher than the default
performance values.
    Table 8 of this preamble summarizes the performance values for HCl,
Pb, Cd, Hg, CDD/CDF, and PM for units for which the 1997 record has
information indicating that they employed some

type of add-on control but has no test data or regulatory limits
corresponding to specific controls, or where regulatory limits exist
but are higher than the values based on an average of the maximum dry
and wet control system performance.

  Table 8.--Performance Values Based on Average of Maximum Dry and Wet
                       Control System Performance
------------------------------------------------------------------------
                                                            Performance
                    Pollutant  (units)                       value \1\
------------------------------------------------------------------------
HCl (ppmv)...............................................        53.165
Pb ([mu]g/dscm)..........................................       568.5
Cd ([mu]g/dscm)..........................................        83.65
Hg ([mu]g/dscm)..........................................       459.5
PM (gr/dscf).............................................         0.0195
CDD/CDF, total (ng/dscm).................................        65.35
CDD/CDF, TEQ (ng/dscm)...................................         1.296
------------------------------------------------------------------------
\1\ All performance values are measured at 7 percent oxygen.

    The values for CO, NOX and SO2 are based on
the performance of combustion-controlled HMIWI because, as stated at
proposal and promulgation of the 1997 HMIWI standards, as well as
earlier in this preamble, CO emission levels are affected by combustion
practices rather than the control systems used by HMIWI; NOX
control had not been demonstrated on HMIWI; and the acid gas controls
used by HMIWI were not effective in reducing SO2 emissions
from HMIWI due to the low inlet levels of SO2 associated
with hospital/medical/infectious waste. Therefore, for units (1) where
the 1997 record contains information indicating that they employed some
type of add-on control but for which there was no test data or
regulatory limits, or (2) where regulatory limits existed but were
higher than the values for CO, NOX, or SO2 based
on combustion-controlled HMIWI, the performance values for CO (584.9
ppmv), NOX (224.5 ppmv), and SO2 (46.39 ppmv) are
the same as those presented in Table 7 of this preamble.
    The next step in the MACT analysis for existing HMIWI was to
determine the average emission limitation achieved by the best-
performing 12 percent of existing sources where there are 30 or more
sources in the category or subcategory. Our general approach to
identifying the average emission limitation has been to use a measure
of central tendency, such as the arithmetic mean or the median. If the
median is used when there are at least 30 sources, then the emission
level that is at the bottom of the best performing 6 percent of sources
(i.e., the 94th percentile) represents the MACT floor control level. We
based our MACT floors for each pollutant within each size category on
this approach. We then determined the technology associated with each
``average of the best-performing 12 percent'' value by comparing the
average values to average performance data for wet scrubbers, dry
injection fabric filters (also known as dry scrubbers), and combustion
controls (no add-on air pollution controls). Those pollutants with
average values that were higher than the relevant combustion-controlled
emission estimate were identified as having a ``combustion control''
floor, even if the pollutant is not reduced by combustion control. The
technology needed to meet the remaining average values reflects the
technology used by the average unit in the top 12 percent and serves as
the basis for the MACT floor. EPA then considered, on a pollutant-
specific basis, technologies that were more stringent than the MACT
floor technologies.
    Add-on control technology-based MACT floors were identified for
large HMIWI for HCl, Pb, Cd, Hg, PM, and CDD/CDF. The MACT floor
technology for all size units for NOX and SO2 is
``combustion control'' although, as previously explained in this
preamble, combustion control results in no emission reductions for
those pollutants. ``Good combustion'' (i.e., 2-second combustion) was
identified as the MACT floor technology for all size units for CO.
``Combustion control'' floors were identified for medium HMIWI for Pb,
Cd, Hg, and CDD/CDF and for small HMIWI for HCl, Pb, Cd, Hg, and CDD/
CDF. However, for these pollutants for all medium and most small HMIWI,
we have decided to propose limits that are more stringent than the
``combustion control'' floors and are consistent with the control
technology-based MACT floors that were identified for large HMIWI for
these pollutants (i.e., Pb, Cd, Hg, and CDD/CDF for medium HMIWI and
HCl, Pb, Cd, Hg, and CDD/CDF for small HMIWI). The control technologies
identified as the MACT floors for HCl and PM for medium HMIWI, and for
PM for small HMIWI, provide an indication of the level of control of
the other pollutants--a level of technology that is consistent with
those technologies identified for large HMIWI. The rationale for not
basing the proposed emission limits on other technologies that would
result in even more stringent limits can be found at 62 FR 48371-72. As
at the 1997 promulgation, MACT for small HMIWI that meet certain
``rural criteria'' was determined to be at the MACT floor level for
each pollutant (i.e., no ``beyond-the-floor''-based emission limits).
    Table 9 of this preamble shows the average emission value, based on
the ranking of emissions data, regulatory data, and performance data,
of each pollutant for the top 12 percent of HMIWI in each subcategory.
The values in Table 9 allow EPA to identify the technology associated
with the average unit in the top 12 percent of HMIWI.

   Table 9.-- Average Emission Values for Top 12 Percent of Hmiwi \1\
------------------------------------------------------------------------
                                                  HMIWI size
          Pollutant (units)          -----------------------------------
                                         Small      Medium       Large
------------------------------------------------------------------------
HCl (ppmv)..........................   2,770          53          50
CO (ppmv)...........................     100         100         100
Pb (mg/dscm)........................       8.63        8.63        0.569
Cd (mg/dscm)........................       3.52        3.52        0.084
Hg (mg/dscm)........................       6.54        4.27        0.460
PM (gr/dscf)........................       0.080       0.030       0.020
CDD/CDF, total (ng/dscm)............   8,102       8,102          65.4
CDD/CDF, TEQ (ng/dscm)..............     236         236           1.30
NOX (ppmv)..........................     225         225         225
SO2 (ppmv)..........................      46.4        46.4        46.4
------------------------------------------------------------------------
\1\ All emission values are measured at 7 percent oxygen.

    Table 10 of this preamble shows the technology associated with each
average emission value.

                                        Table 10.--MACT Floor Technology
----------------------------------------------------------------------------------------------------------------
                                                                       HMIWI Size
          Pollutant (units)           --------------------------------------------------------------------------
                                                Small                    Medium                   Large
----------------------------------------------------------------------------------------------------------------
HCl (ppmv)...........................  combustion control.....  dry scrubber...........  dry scrubber.
CO (ppmv)............................  good combustion........  good combustion........  good combustion.
Pb (mg/dscm).........................  combustion control.....  combustion control.....  wet scrubber.
Cd (mg/dscm).........................  combustion control.....  combustion control.....  wet scrubber.
Hg (mg/dscm).........................  combustion control.....  combustion control.....  dry scrubber.
PM (gr/dscf).........................  low-efficiency wet       moderate-efficiency wet  moderate-efficiency wet
                                        scrubbber.               scrubber.                scrubber.
CDD/CDF, total (ng/dscm).............  combustion control.....  combustion control.....  wet scrubber.
CDD/CDF, TEQ (ng/dscm)...............  combustion control.....  combustion control.....  wet scrubber.
NOX (ppmv)...........................  combustion control.....  combustion control.....  combustion control.
SO2 (ppmv)...........................  combustion control.....  combustion control.....  combustion control.
----------------------------------------------------------------------------------------------------------------

    For small units, the CO and PM values indicate that good combustion
control (i.e., 2-second combustion) and a low-efficiency wet scrubber
reflect the CO and PM MACT floors. For medium units, as well as large
units, the CO, HCl, and PM values indicate that good combustion control
used in conjunction with either a dry scrubber or moderate-efficiency
wet scrubber reflects the CO, HCl, and PM MACT floors. As previously
stated, EPA concluded that emission limits for small units that meet
the rural criteria should reflect the MACT floor level of control for
all pollutants. The average emission value and MACT floor level of
control for PM vary by unit size, and we are proposing emission limits
based on those levels of control. The average emission values, and
associated MACT floor levels of control, for CO, NOX, and
SO2 are the same for all size units. For most small units
and all medium units, however, we concluded that emission limits for
HCl, Pb, Cd, Hg, and CDD/CDF should reflect the MACT floor level of
control for large units for those pollutants.
    The resulting numerical emission limits were determined by
combining the appropriate average emission value for each pollutant for
each size HMIWI with a variability factor. We believe it is necessary
to account for variability given the limited amount of actual data
available in the 1997 record and the resulting need for use of various,
and often presumptive, types of information to formulate the best
performing 12 percent of HMIWI. At promulgation, we recognized the need
to account for variability and did so as described earlier in this
preamble. Although we maintain that the methodology we used was not
unreasonable given the available information at promulgation, we now
have additional information (the 2002 compliance test data for all of
the currently operating units) for use in calculating pollutant-
specific variability factors. While these data were not available at
promulgation, they are the only data available for providing a
quantitative assessment of variability of emissions from well-
controlled HMIWI. To determine the pollutant-specific variability
factors, a statistical analysis was conducted. Specifically, the
emission limit achievable for each pollutant was determined based on
the combination of actual emissions test data, regulatory data, and
estimated performance levels (as described earlier) and a statistics-
based variability factor calculated for each pollutant. To calculate
the variability factors, we used the general equation: variability
factor = t * standard deviation. This general equation has been used by
EPA in similar analyses. (See, e.g., 68 FR 27650; 69 FR 55235-7; 70 FR
28615.) We selected the 90th percentile confidence level for this one-
sided t-statistics test. The 90th percentile provides a variability
factor appropriate for well-controlled sources that is based on data
from well-controlled sources (i.e., the only sources that are still in
operation).
    Table 11 of this preamble presents the values determined by adding
the variability factors to the average emission values for each
pollutant for existing large and medium HMIWI. The table also presents
the proposed revised emission limits for existing large and medium
HMIWI necessary to respond to the Court's remand and the percent
reduction limits for HCl, Pb, Cd, and Hg. The percent reduction limits
are based on average combustion-controlled emissions estimates and
maximum performance values for the MACT identified for each pollutant
for each subcategory. This is the same approach used at the time of
promulgation of the 1997 rule, except that the proposed percent
reduction limits do not include the addition of 10 percent to the
maximum performance values or the rounding up of those figures.

 Table 11.--Average Emission Values, Considering Variability, and Emission Limits \1\--Existing Large and Medium
                                                      HMIWI
----------------------------------------------------------------------------------------------------------------
                                                      Large                                Medium
                                     ---------------------------------------------------------------------------
         Pollutant  (units)             Average +                             Average +
                                       variability      Emission  limit      variability      Emission  limit
----------------------------------------------------------------------------------------------------------------
HCl (ppmv)..........................        78      78 or 93% reduction           57.9    78 \3\ or 93%
                                                     \2\.                                  reduction \2\.
CO (ppmv)...........................       110      40 \2\................       113      40 \2\
Pb (mg/dscm)........................         0.78   0.78 or 71% reduction.         9.02   0.78 \3\ or 71%
                                                                                reduction \3\.
Cd (mg/dscm)........................         0.11   0.11 or 66% reduction.         3.56   0.11 \3\ or 66%
                                                                                reduction \2\.
Hg (mg/dscm)........................         0.64   0.55 \2\ or 87%                4.34   0.55 \2\ or 87%
                                                     reduction.                            reduction \3\.
PM (gr/dscf)........................         0.025  0.015 \2\.............         0.043  0.030 \2\

CDD/CDF, total (ng/dscm)............       115      115...................     8,150      115 \3\
CDD/CDF, TEQ (ng/dscm)..............         2.16   2.2...................       237      2.2 \3\
NOX (ppmv)..........................       284      250 \2\...............       273      250 \2\
SO2 (ppmv)..........................        61      55 \2\................        51.8    55 \2\
----------------------------------------------------------------------------------------------------------------
\1\ All emission values are measured at 7 percent oxygen.
\2\ No change from current emission limit.
\3\ Emission limit is the same as that for large HMIWI.

    Table 12 of this preamble presents the same information for
existing small non-rural HMIWI and for existing small HMIWI meeting the
rural criteria.

 Table 12.-- Average Emission Values, Considering Variability, and Emission Limits \1\--Existing Small And Small
                                                   Rural HMIWI
----------------------------------------------------------------------------------------------------------------
                                                             Large                              Medium
                                          ----------------------------------------------------------------------
            Pollutant  (units)               Average +                                  Average +     Emission
                                            variability         Emission limit         variability      limit
----------------------------------------------------------------------------------------------------------------
HCl (ppmv)...............................     2,772      78 \3\ or 93% reduction         3,125      \2\ 3,100
                                                          \2\..
CO (ppmv)................................       103      40 \2\.....................       109        \2\ 40
Pb (mg/dscm).............................         8.85   0.78 \3\ or 71% reduction           8.88          8.9
                                                          \3\.
Cd (mg/dscm).............................         3.54   0.11 \3\ or 66% reduction           3.54          4
                                                          \2\.
Hg (mg/dscm).............................         6.55   0.55 \2\ or 87% reduction           6.56          6.6
                                                          \3\.
PM (gr/dscf).............................         0.095  0.050 \2\..................         0.089     \2\ 0.086
CDD/CDF, total (ng/dscm).................     8,335      115 \3\....................     8,518       \2\ 800
CDD/CDF, TEQ (ng/dscm)...................       239      2.2 \3\....................       244        \2\ 15
NOX (ppmv)...............................       225      250 \2\....................       273       \2\ 250
SO2 (ppmv)...............................        46.4    55 \2\.....................        51.8     \2\ 55
----------------------------------------------------------------------------------------------------------------
\1\ All emission values are measured at 7 percent oxygen.
\2\ No change from current emission limit.
\3\ Emission limit is the same as that for large HMIWI.

    For pollutants where this remand analysis (based on the average of
the best performing 12 percent of HMIWI plus the variability factor)
resulted in emission limits less stringent (i.e., higher) than the
current emission limits, we retained the current emission limits. This
is because we see no reason to upwardly revise standards that the
regulated industry has already demonstrated are achievable based on
compliance data. In fact, now that we have received the 2002 compliance
data for HMIWI units, it is apparent that EPA's estimate of the
achievable emissions performance levels from use of the identified MACT
technology was reasonably accurate. While we are not in this proposal
attempting to justify our prior existing unit MACT floor decisions post
hoc based on new data that we could not have relied upon in the 1997
rulemaking itself, we note that, similar to the Mossville case, we
currently find ourselves in a situation where actual emissions data
fairly confirms our prior estimates of what the best controlled HMIWI
units could achieve when using MACT controls.
    The resulting emission limits being proposed for medium HMIWI for
HCl and SO2; for small HMIWI for NOX and
SO2; and for small rural HMIWI for SO2 are the
same as those being proposed for large HMIWI because, in these
instances, the medium, small, and small rural HMIWI are expected to
achieve reductions similar to large HMIWI.

B. Rationale for the Proposed Amendments (CAA Section 129(a)(5) 5-Year
Review)

    In recent rulemakings (see, e.g., 71 FR 34422, 34436-38 (June 14,
2006) (proposed amendments to the NESHAP for Hazardous Air Pollutants
for Organic Hazardous Air Pollutants from the Synthetic Organic
Chemical manufacturing Industry)) EPA has addressed the similar
technology review requirement under CAA section 112(d)(6). EPA stated
that the statute provides the Agency with broad discretion to revise
MACT standards as we determine necessary, and to account for a wide
range of relevant factors, including risk. EPA does not interpret such
technology review requirements to require another analysis of MACT
floors for existing and new units, but rather requires us to consider
developments in pollution control in the industry and assess the costs
of potentially stricter standards reflecting those developments. (See,
id., at 34436-47.) Moreover, as a general matter, EPA has stated that
where we determine that existing standards are adequate to protect
public health with an ample margin of safety and prevent adverse
environmental effects, it is unlikely that EPA would revise MACT
standards merely to reflect advances in air pollution control
technology. Id., at 34437-38.
    Under CAA section 112(d)(6), the first round of technology review
for MACT standards is subject to the same statutory timeframe as EPA's
residual risk review under CAA section 112(f)(2), with both reviews
occurring 8 years following initial promulgation of MACT. We interpret
CAA section 129(a)(5)'s technology review

requirement as providing us the same degree of discretion in terms of
whether to revise MACT standards, for the reasons discussed in those
prior rulemakings. (See, id., at 34436-38.) However, the deadline for
the first round of technology review under section 129(a)(5) (5 years
following MACT promulgation) does not coincide with the deadline for
residual risk review under section 112(f)(2) (9 years, in the case of
HMIWI standards). Therefore, this first section 129(a)(5) technology
review for HMIWI does not account for or reflect our residual risk
analysis. In future rounds of review under section 129(a)(5) for the
HMIWI standards, we intend to follow our general policy, and for our
technology reviews and conclusions to be informed by our residual risk
analysis, which we will have performed by that point.
    In exercising its discretion under CAA section 129(a)(5), EPA is
proposing in this technology review to adopt emission limits based on
the 2002 data because it believes that these limits represent the cost-
effective operation of the MACT control technology. EPA is aware of the
possibility that regulated units are likely to operate at a level
somewhat below emission standards in order to account for operational
variability. It is not our intent to preclude this practice through
successive rounds of the section 129(a)(5) technology review. EPA
requests comment on its proposal (as outlined below) to adopt more
stringent emission limits in this instance through its section
129(a)(5) technology review.
1. How were the proposed emission limits developed?
    The proposed revised emission limits resulting from our 5-year
review of the HMIWI standards under section 129(a)(5) of the CAA are
based on the performance of units within the industry that currently
are subject to the MACT standards. One set of emission limits is
proposed for existing HMIWI regulated under CAA section 111(d)/129(b)
emission guidelines, and another set of emission limits is proposed for
new HMIWI (units commencing construction after February 6, 2007)
regulated under CAA section 111(b)/129(a) NSPS. Units that were subject
to the 1997 NSPS as new units (referred to as ``1997 NSPS units'' for
the remainder of this preamble) will remain subject to the 1997 NSPS
(including revisions resulting from EPA's response to the Court
remand), but will also be subject to any requirements of the revised
emission guidelines that are more stringent than the 1997 NSPS
requirements. The proposed emission limits for existing units, 1997
NSPS units, and new units were developed following the procedures
discussed below.
    As background, with one exception resulting from the analyses
associated with our response to the Court remand, the proposed emission
limits for new and existing units are based on the application of the
same control technologies upon which the 1997 MACT standards were
based. For new large and medium units, both the current and proposed
emission limits are based upon good combustion and the application of
combined control systems that include both dry scrubbers (i.e., dry
injection fabric filters or spray dryer fabric filters) with carbon
injection and wet scrubbers. The current and proposed emission limits
for new small units are based on good combustion and the application of
a moderate-efficiency wet scrubber. For large, medium, and most small
existing units, the current and proposed emission limits are based on
good combustion control for CO; combustion controls (i.e., no add-on
controls) for NOX and SO2; and the application of
either dry scrubbers or wet scrubbers (with various ``efficiencies''
depending on the size of the unit) for the remaining pollutants. The
current emission limits for one additional subcategory, existing small
rural units, are based solely on good combustion (i.e., the MACT floor
identified in the 1997 analysis was not based on add-on control
technology). With the exception of PM, the proposed emission limits for
existing small rural units also are based solely on good combustion. In
our remand analysis, we identified a low-efficiency wet scrubber as
being the MACT floor for PM for these units. Although all small rural
units currently use only good combustion, to address this difference in
the MACT floors (i.e., 1997 analysis versus remand analysis), we are
proposing a PM emission limit for existing small rural units based on
the application of low-efficiency wet scrubbers to existing small non-
rural units (i.e., MACT floor for small non-rural units in the 1997
analysis as well as the remand analysis). While this performance level
is associated with the expected performance of a low-efficiency wet
scrubber, the combustion controls in place on these six existing small
rural units achieve this performance level, based on the initial
compliance tests for these units.
    In performing this 5-year review, we have not recalculated new MACT
floors, but have proposed to revise the emission limits to reflect the
actual performance of the MACT technologies. We believe this approach
reflects the most reasonable interpretation of the review requirement
of CAA section 129(a)(5), and is consistent with how we have
interpreted the similar review requirement of CAA section 112(d)(6)
regarding MACT standards promulgated under section 112. (See 71 FR
27327-28; 69 FR 48350-51; and 70 FR 20008.) The language of section
129(a)(5) directs EPA to ``review'' our promulgated standards under CAA
section 111/129, and to ``revise such standards and requirements'' ``in
accordance with this section and section 111.'' It does not, however,
direct EPA to conduct, at 5-year-intervals, new MACT floor and beyond-
floor analyses based on each 5-years' changing information as to what
might comprise the top 12 percent of sources or constitute the best
controlled similar unit. There is no indication that Congress intended
for section 129(a)(5) to inexorably force existing source standards
progressively lower and lower in each successive review cycle, the
likely result of requiring successive floor determinations.
    Following MACT compliance in September 2002, EPA obtained
compliance test reports from all operating HMIWI (76 units at 70
facilities) and used those data to evaluate MACT performance. When the
HMIWI regulations were first proposed in 1995, re-proposed in 1996, and
promulgated in 1997, only limited information was available about HMIWI
emission controls, and significant engineering judgment was necessary
in selecting the emission limits. The year 2002 compliance data show
that the control technologies that were installed and the practices
that were implemented to meet the 1997 NSPS and emission guidelines
achieved reductions somewhat superior to what we expected under the
1997 limits for many of the pollutants. EPA used the compliance test
data to develop the emission limits contained in the amendments we are
proposing under the 5-year review. EPA believes that the proposed
emission limits more accurately reflect actual real-world HMIWI MACT
performance than what we had estimated in 1997 and what we re-estimated
based on the 1997 record in response to the Court's remand (discussed
previously in this preamble). We believe that it is necessary, as well
as appropriate, to update the 1997 promulgated standards based on the
actual performance of MACT technologies in situations where compliance
test data indicate that the technologies achieve better performance
levels than those we previously

estimated based on the information available at the time of
promulgation.
    a. Existing Units. The first step in the analysis was to assess the
performance of the HMIWI currently subject to the emission guidelines
with respect to each regulated pollutant. We first examined the data
separately for each unit size, and the data showed, for all pollutants
except PM, that the performance of units with add-on controls,
regardless of size, (excluding small rural units, which do not employ
add-on controls), is similar. Therefore, we combined the data,
regardless of unit size, for all of the pollutants except PM, and
conducted analyses on the combined data sets. In addition, for the
pollutants with emission limits based on good combustion and combustion
control (i.e., no add-on controls), namely CO, NOX, and
SO2, the data for small rural units also were combined with
the data for all of the other subcategories of units. Analyses were
performed on each data set, and we calculated the 99 percent upper
tolerance limit (UTL), which is the emission level that 99 percent of
the HMIWI would be expected to achieve. A similar methodology was used
for stack test-based emission limits in the 5-year review recently
conducted for large municipal waste combustors (MWC). In the preamble
to that final action, EPA indicated that analysis of data to estimate
emission limits to be enforced by stack test methods must be done using
a different approach (i.e., lower percent UTL) than where enforcement
is to be based on CEMS and that the percentile must also reflect a
reasonable consideration of emissions variability and compliance
limitations of stack testing (See 71 FR 27329). EPA further indicated
that for this type of technology review, the 99 percent UTL was
appropriate to use as a tool for estimating achievable emission levels
for emission limits enforced by stack testing. Id. In this proposed
rulemaking, the 99 percent UTL was used as the starting point for
selecting the revised emission limits. We compared the 99 percent UTL
values to several other values, including the 1997 promulgated emission
limits and the revised limits that we are proposing in response to the
Court's remand (``remand limits''). For several pollutants, the value
associated with the 99 percent UTL was higher than the remand limit. In
these cases, we selected the remand limit, rather than the 99 percent
UTL value, as the proposed emission limit. We also graphically compared
the 99 percent values and remand limits, where applicable, to all of
the data that were used to calculate the percentile values. In many
cases, this visual comparison revealed that the 99 percent UTL value or
remand limit fell within a break in the data that indicated a level of
performance that the technologies, considering variability, could
readily achieve but that the ``worst performing'' units were not
achieving during their compliance tests. Thus, our analyses indicate
that the emission limits that we selected reflect the actual
performance of the MACT control technologies while also serving to
require modest improvements in performance from units that are not
achieving the performance levels demonstrated in practice by the
control technologies currently being used in the industry.
    For small non-rural HMIWI, we used a different methodology for
assessing PM performance because there are only two units and,
therefore, statistics are not a useful tool. Both of the small non-
rural units are equipped with wet scrubbers. Because existing medium
units are predominantly equipped with wet scrubbers, the PM emission
limit developed using the 99 percent UTL value of the data set for
existing medium units also is being proposed for small non-rural units.
    A different methodology also was used for assessing performance of
the six small rural HMIWI. To determine the actual performance of these
small combustion-controlled units while considering the inherent
variability in emissions, we obtained test data for all six units
(although, as allowed in the emission guidelines, not all of the
pollutants were tested at every unit) and selected as the emission
limit the highest individual test run from the compliance testing for
HCl, Pb, Cd, Hg, and CDD/CDF. This methodology uses actual test data to
provide a reasonable estimate of the performance of the small rural
units for these pollutants, where statistics are not a useful tool,
while accounting for variability. There are exceptions to this
methodology for CO, NOX, and SO2. As previously
mentioned in this preamble, the CO, NOX, and SO2
data for small rural units were combined with the CO, NOX,
and SO2 data for the other subcategories of units. The 99
percent UTL methodology was then used as the starting point, as
previously described in this preamble, to determine proposed emission
limits that would apply to all of the subcategories of existing HMIWI.
Another exception to this methodology is the proposed emission limit
for PM. As previously explained in this preamble, we are proposing a PM
emission limit for existing small rural units based on the application
of low-efficiency wet scrubbers to existing small non-rural units
(i.e., we are proposing the same PM emission limit for small rural and
non-rural units). While many of the resulting proposed emission limits
for small rural units are significantly more stringent than the 1997
promulgated limits, the proposed limits more accurately reflect the
actual performance of these units.
    Finally, we examined the available data for calculating percent
reduction requirements for HCl, Pb, Cd, and Hg. Percent reduction
standards were included in the 1997 promulgated standards for these
pollutants, and we are proposing to update these requirements to
reflect the now-known actual performance of HMIWI utilizing MACT
controls. For HCl, we obtained percent reduction data from five large
HMIWI using dry scrubbers (i.e., the control technology upon which the
emission limits for existing large, medium, and small non-rural units
are based), and these data showed percent reductions from 94.2 percent
to greater than 99 percent. To account for variability, we based the
proposed percent reduction requirement of 94 percent on the lowest
percent reduction recorded during the individual test runs (i.e., 94.2
percent). The three-run test that included the 94.2 percent value
showed significant variability and demonstrates the need to account for
variability. The percent reduction values for the three runs ranged
from 94.2 percent to 97.8 percent while there was no identifiable
change in the operation of the unit or the dry scrubber. For Pb and Cd
from existing large, medium, and small non-rural HMIWI, we used the
same methodology as for HCl, and the data sets showed even greater
variability. For Hg, we used the only available estimate of percent
reduction. The proposed percent reduction standards are 71 percent for
Pb, 74 percent for Cd, and 96 percent for Hg. The 5-year review
methodology used to assess performance of existing HMIWI resulted in no
change to the PM standards for existing large and medium units, and
CDD/CDF standards for existing small rural units. All of the other
standards for existing HMIWI were adjusted based on either the 5-year
review or the remand analyses.
    Table 13 of this preamble summarizes the emission limits
promulgated in 1997, the emission limits resulting from the proposed
response to the Court remand, and the emission limits being proposed as
a result of the 5-year review for existing HMIWI. Note that these
proposed limits for existing HMIWI only apply to units for which
construction was commenced on or before June 20,

1996, or for which modification was commenced before March 16, 1998.

 Table 13.--Summary of 1997 Promulgated Emission Limits, Proposed Remand Response Emission Limits, and Proposed 5-Year Review Limits for Existing HMIWI
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Proposed remand
         Pollutant  (units)                 Unit  size\1\        Promulgated  limit\2\     response limit\2\         Proposed 5-year review limit\2\
--------------------------------------------------------------------------------------------------------------------------------------------------------
HCl (ppmv)..........................  L, M, S.................  100 or 93% reduction..  78 or 93% reduction...  51 or 94% reduction.
                                      SR......................  3,100.................  3,100.................  398
CO (ppmv)...........................  All.....................  40....................  40....................  25
Pb (mg/dscm)........................  L, M, S.................  1.2 or 70% reduction..  0.78 or 71% reduction.  0.64 or 71% reduction.
                                      SR......................  10....................  8.9...................  0.60
Cd (mg/dscm)........................  L, M, S.................  0.16 or 65% reduction.  0.11 or 66% reduction.  0.060 or 74% reduction.
                                      SR......................  4.....................  4.....................  0.050
Hg (mg/dscm)........................  L, M, S.................  0.55 or 85% reduction.  0.55 or 87% reduction.  0.33 or 96% reduction.
                                      SR......................  7.5...................  6.6...................  0.25
PM (gr/dscf)........................  L.......................  0.015.................  0.015.................  0.015
                                      M.......................  0.03..................  0.030.................  0.030
                                      S.......................  0.05..................  0.050.................  0.030
                                      SR......................  0.086.................  0.086.................  0.030
CDD/CDF, total (ng/dscm)............  L, M, S.................  125...................  115...................  115
                                      SR......................  800...................  800...................  800
CDD/CDF, TEQ (ng/dscm)..............  L, M, S.................  2.3...................  2.2...................  2.0
                                      SR......................  15....................  15....................  15
NOX (ppmv)..........................  All.....................  250...................  250...................  212
SO2 (ppmv)..........................  All.....................  55....................  55....................  28
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ L = Large; M = Medium; S = Small; SR = Small Rural
\2\ All emission limits are measured at 7 percent oxygen.

    Table 14 of this preamble summarizes the emission limits
promulgated in 1997 and the emission limits being proposed as a result
of EPA's response to the Court remand for the 1997 NSPS HMIWI. Note
that these proposed limits for 1997 NSPS HMIWI only apply to units for
which construction was commenced after June 20, 1996, and on or before
the date of this proposal, or for which modification is commenced
before the date 6 months after promulgation of the proposed limits.
Also note that where the proposed 5-year review limits for existing
HMIWI are more stringent than those resulting from the remand response
for 1997 NSPS HMIWI, the more stringent limits for existing HMIWI are
included in the table as the limits being proposed. HMIWI subject to
the 1997 NSPS, however, will not find these proposed limits, as
presented in Table 14 of this preamble, in subparts Ec or Ce of 40 CFR
part 60. Instead, they must consider the proposed revisions to subpart
Ec of 40 CFR part 60 regarding existing HMIWI, as well as in the
proposed revisions to subpart Ce of 40 CFR part 60 regarding 1997 NSPS
HMIWI, and comply with the more stringent emission limit.

  Table 14.--Summary of 1997 Promulgated Emission Limits and Proposed Limits in Response to the Remand for 1997
                                                   NSPS HMIWI
----------------------------------------------------------------------------------------------------------------
                                                             Promulgated
       Pollutant (units)               Unit size\1\            limit\2\       Proposed remand response limit\2\
----------------------------------------------------------------------------------------------------------------
HCl (ppmv).....................  L, M, S................  15 or 99%          15 or 99% reduction.
                                                           reduction.
CO (ppmv)......................  L, M, S................  40...............  25 \3\.
Pb (mg/dscm)...................  L, M...................  0.07 or 98%        0.060 or 98% reduction.
                                                           reduction.
                                 S......................  1.2 or 70%         0.64 \3\ or 71% reduction.
                                                           reduction.
Cd (mg/dscm)...................  L, M...................  0.04 or 90%        0.030 or 93% reduction.
                                                           reduction.
                                 S......................  0.16 or 65%        0.060\3\ or 74% reduction \3\.
                                                           reduction.
Hg (mg/dscm)...................  L, M, S................  0.55 or 85%        0.33\3\ or 96% reduction \3\.
                                                           reduction.
PM (gr/dscf)...................  L, M...................  0.015............  0.0090
                                 S......................  0.03.............  0.018
CDD/CDF, total (ng/dscm).......  L, M...................  25...............  20
                                 S......................  125..............  111
CDD/CDF, TEQ (ng/dscm).........  L, M...................  0.6..............  0.53
                                 S......................  2.3..............  2.0 \3\.
NOX (ppmv).....................  L, M, S................  250..............  212 \3\.
SO2 (ppmv).....................  L, M, S................  55...............  28 \3\.
----------------------------------------------------------------------------------------------------------------
\1\ L = Large; M = Medium; S = Small
\2\ All emission limits are measured at 7 percent oxygen.
\3\ Because the proposed 5-year review limit for existing HMIWI is more stringent than the one resulting from
  the remand response for 1997 NSPS HMIWI, the more stringent limit for existing HMIWI is being proposed.

    b. New Units. The first step in the analysis for new large and
medium HMIWI was to assess the performance of the units currently
operating a combined dry/wet control system, which is the control
technology upon

which the 1997 NSPS for large and medium HMIWI was based. Four units
currently are operating such controls, and we obtained compliance test
data for each unit for use in assessing performance. We selected as the
proposed emission limit the highest individual test run from the
compliance testing for each pollutant. This methodology uses actual
test data from the best-controlled sources in the industry to provide a
reasonable estimate of the performance of these units, while accounting
for variability. In several instances, the emission limit suggested by
the highest run from the four combined-control sources was higher than
either the emission limit for new sources that we are proposing in
response to the Court remand or the 5-year review emission limit that
we are proposing for existing sources. This was likely a result of the
small amount of data that we used to establish the limits, and, in
these instances, we are proposing the most stringent among these three
limits for new sources.
    Although there are no small HMIWI subject to the current NSPS, we
are proposing emission limits based on the performance of moderate-
efficiency wet scrubbers, which is the control technology upon which
the 1997 limits for new small units was based. As an initial step in
selection of these emission limits, we used the performance values
representative of control with a moderate-efficiency wet scrubber as
determined for the existing medium HMIWI. We then compared these values
to the values for new small units developed in response to the remand
and, in each case, we selected the more stringent value as the proposed
emission limit.
    To determine proposed percent reduction requirements for new units
for HCl, Pb, Cd, and Hg, we followed a methodology similar to that used
for existing units. For HCl, we obtained percent reduction data from
two units controlled with the MACT control technology for HCl for new
large and medium units (wet scrubbers), and these data showed percent
reductions greater than 99 percent. To account for variability, we
based the percent reduction requirement of 99 percent on the lowest
percent reduction recorded during the individual test runs (i.e., 99.1
percent). We used the same methodology for each of the three metals for
new large and medium units, and the corresponding percent reduction
standards based on the MACT control technology (dry scrubbers) are 99
percent for Pb, 99 percent for Cd, and 96 percent for Hg. For HCl from
new small HMIWI, we used the same methodology as for new large and
medium units because the MACT control technology upon which the
reductions are based is the same (wet scrubbers). For Pb and Cd from
new small HMIWI, we used the same methodology as for new large and
medium units, except that the MACT control technology upon which the
reductions are based is a wet scrubber. For Hg, we used the only
available estimate of percent reduction. The proposed percent reduction
standards for new small units are 99 percent for HCl, 71 percent for
Pb, 74 percent for Cd, and 96 percent for Hg. The 5-year review
methodology used to assess performance of new units resulted in no
change to the HCl standards for all new units. All of the other
standards for new units were adjusted based on either the 5-year review
or the remand analyses.
    Table 15 of this preamble summarizes the emission limits
promulgated in 1997 and the emission limits being proposed as a result
of the 5-year review for new HMIWI. Note that these proposed limits for
new HMIWI only apply to units for which construction is commenced after
the date of this proposal, or for which modification is commenced on or
after the date 6 months after promulgation of the proposed limits.

     Table 15.--Summary of 1997 Promulgated Emission Limits and Proposed 5-Year Review Limits for New HMIWI
----------------------------------------------------------------------------------------------------------------
                                                          Promulgated limit
       Pollutant  (units)             Unit size \1\              \2\           Proposed 5-year review limit \2\
----------------------------------------------------------------------------------------------------------------
HCl (ppmv).....................  L, M, S................  15 or 99%          15 or 99% reduction.
                                                           reduction.
CO (ppmv)......................  L, M, S................  40...............  25
Pb (mg/dscm)...................  L, M...................  0.07 or 98%        0.060 or 99% reduction.
                                                           reduction.
                                 S......................  1.2 or 70%         0.64 or 71% reduction.
                                                           reduction.
Cd (mg/dscm)...................  L, M...................  0.04 or 90%        0.0050 or 99% reduction.
                                                           reduction.
                                 S......................  0.16 or 65%        0.060 or 74% reduction.
                                                           reduction.
Hg (mg/dscm)...................  L, M...................  0.55 or 85%        0.19 or 96% reduction.
                                                           reduction.
                                 S......................  0.55 or 85%        0.33 or 96% reduction.
                                                           reduction.
PM (gr/dscf)...................  L, M...................  0.015............  0.0090
                                 S......................  0.03.............  0.018
CDD/CDF, total (ng/dscm).......  L, M...................  25...............  16
                                 S......................  125..............  111
CDD/CDF, TEQ (ng/dscm).........  L, M...................  0.6..............  0.21
                                 S......................  2.3..............  2.0
NOX (ppmv).....................  L, M, S................  250..............  212
SO2 (ppmv).....................  L, M...................  55...............  21
                                 S......................  55...............  28
----------------------------------------------------------------------------------------------------------------
\1\ L = Large; M = Medium; S = Small.
\2\ All emission limits are measured at 7 percent oxygen.

2. How did EPA determine the proposed performance testing and
monitoring requirements?
    We are proposing minor adjustments to the performance testing and
monitoring requirements that were promulgated in 1997. For existing
HMIWI and 1997 NSPS HMIWI, we are proposing retaining the current
requirements of the rule and adding the following requirements: Annual
inspections of scrubbers and fabric filters; and one-time testing of
the ash handling operations at the time of the next compliance test
using EPA Method 22 of appendix A of 40 CFR part 60. These proposed
requirements were selected to provide additional assurance that sources
continue to operate at the levels established during their initial
performance test. The proposed amendments would allow sources to use
the results of previous emissions tests to demonstrate compliance with
the

revised emission limits as long as the sources certify that the
previous test results are representative of current operations. Only
those sources whose previous emissions tests do not demonstrate
compliance with one or more revised emission limits would be required
to conduct another emissions test for those pollutants (note that
sources are already required to test for HCl, CO, and PM on an annual
basis).
    Additional requirements also are proposed for new HMIWI. For new
sources, we are proposing retaining the current requirements and adding
the following requirements: Use of CO CEMS; annual inspections of
scrubbers and fabric filters; use of bag leak detection systems on
fabric filter-based control systems; and annual testing of the ash
handling operations using EPA Method 22 of appendix A of 40 CFR part
60. For existing sources, in addition to the proposed changes in
monitoring requirements, we also are proposing to allow for the
optional use of bag leak detection systems. We also are clarifying that
the rule allows for the following optional CEMS use: CO CEMS for
existing sources and 1997 NSPS sources; and PM CEMS, HCl CEMS, multi-
metals CEMS, Hg CEMS, and semi-continuous dioxin monitoring for
existing, 1997 NSPS, and new sources. The optional use of HCl CEMS,
multi-metals CEMS, and semi-continuous dioxin monitoring will be
available on the date a final performance specification for these
monitoring systems is published in the Federal Register or the date of
approval of a site-specific monitoring plan. The proposed testing and
monitoring provisions are discussed below.
    a. Bag Leak Detection Systems. The proposed amendments would
provide, as an alternative PM monitoring technique for existing sources
and 1997 NSPS sources and a requirement for new sources, the use of bag
leak detection systems on HMIWI controlled with fabric filters. Bag
leak detection systems have been applied successfully at many
industrial sources. EPA is proposing to drop the opacity testing
requirements for HMIWI that use bag leak detection systems.
    b. CO CEMS. The proposed amendments would require the use of CO
CEMS for new sources, and allow the use of CO CEMS on existing sources
and 1997 NSPS sources. Owners and operators that use CO CEMS would be
able to discontinue their annual CO compliance test as well as their
monitoring of the secondary chamber temperature. The continuous
monitoring of CO emissions is an effective way of ensuring that the
combustion unit is operating properly. The proposed amendments
incorporate the use of performance specification (PS)-4B
(Specifications and Test Procedures for Carbon Monoxide and Oxygen
Continuous Monitoring Systems in Stationary Sources) of appendix B of
40 CFR part 60.
    The proposed CO emission limits are based on data from infrequent
(normally annual) stack tests and compliance would be demonstrated by
stack tests. The change to use of CO CEMS for measurement and
enforcement of the same emission limits must be carefully considered in
relation to an appropriate averaging period for data reduction. EPA
considered this issue and concluded the use of a 24-hour block average
was appropriate to address CO emissions variability, and EPA has
included the use of a 24-hour block average in the proposed rule. The
24-hour block average would be calculated following procedures in EPA
Method 19 of appendix A of 40 CFR part 60. Facilities electing to use
CO CEMS as an optional method would be required to notify EPA 1 month
before starting use of CO CEMS and 1 month before stopping use of the
CO CEMS. In addition, EPA specifically requests comment on whether
continuous monitoring of CO emissions should be required for all
existing HMIWI and all 1997 NSPS HMIWI.
    c. PM CEMS. The proposed amendments would allow the use of PM CEMS
as an alternative testing and monitoring method. Owners or operators
who choose to rely on PM CEMS would be able to discontinue their annual
PM compliance test. In addition, because units that demonstrate
compliance with the PM emission limits with a PM CEMS would clearly be
meeting the opacity standard, compliance demonstration with PM CEMS
would be considered a substitute for opacity testing. Owners and
operators that use PM CEMS also would be able to discontinue their
monitoring of minimum wet scrubber pressure drop, horsepower, or
amperage. The proposed amendments incorporate the use of PS-11
(Specifications and Test Procedures for Particulate Matter Continuous
Emission Monitoring Systems at Stationary Sources) of appendix B of 40
CFR part 60 for PM CEMS, and PS-11 QA Procedure 2 to ensure that PM
CEMS are installed and operated properly and produce good quality
monitoring data.
    The proposed PM emission limits are based on data from infrequent
(normally annual) stack tests and compliance would be demonstrated by
stack tests. The use of PM CEMS for measurement and enforcement of the
same emission limits must be carefully considered in relation to an
appropriate averaging period for data reduction. EPA considered this
issue and concluded the use of a 24-hour block average was appropriate
to address PM emissions variability, and EPA has included the use of a
24-hour block average in the proposed rule. The 24-hour block average
would be calculated following procedures in EPA Method 19 of appendix A
of 40 CFR part 60. An owner or operator of an HMIWI unit who wishes to
use PM CEMS would be required to notify EPA 1 month before starting use
of PM CEMS and 1 month before stopping use of the PM CEMS.
    d. Other CEMS and Monitoring Systems. EPA also is proposing the
optional use of HCl CEMS, multi-metals CEMS, Hg CEMS, and semi-
continuous dioxin monitoring as alternatives to the existing methods
for demonstrating compliance with the HCl, metals (Pb, Cd, and Hg), and
CDD/CDF emissions limits. For the reasons explained above for CO CEMS
and PM CEMS, EPA has concluded that the use of 24-hour block averages
would be appropriate to address emissions variability, and EPA has
included the use of 24-hour block averages in the proposed rule. The
24-hour block averages would be calculated following procedures in EPA
Method 19 of appendix A of 40 CFR part 60. Although final performance
specifications are not yet available for HCl CEMS and multi-metals
CEMS, EPA is considering development of performance specifications. The
proposed rule specifies that these options will be available to a
facility on the date a final performance specification is published in
the Federal Register or the date of approval of a site-specific
monitoring plan.
    The use of HCl CEMS would allow the discontinuation of HCl sorbent
flow rate monitoring, scrubber liquor pH monitoring, and the annual
testing requirements for HCl. EPA has proposed PS-13 (Specifications
and Test Procedures for Hydrochloric Acid Continuous Monitoring Systems
in Stationary Sources) of appendix B of 40 CFR part 60 and believes
that performance specification can serve as the basis for a performance
specification for HCl CEMS use at HMIWI. In addition to the procedures
used in proposed PS-13 for initial accuracy determination using the
relative accuracy test, a comparison against a reference method, EPA is
taking comment on an alternate initial accuracy determination
procedure, similar to the one in section 11 of PS-15 (Performance
Specification for

Extractive FTIR Continuous Emissions Monitor Systems in Stationary
Sources) of appendix B of 40 CFR part 60 using the dynamic or analyte
spiking procedure.
    EPA believes multi-metals CEMS can be used in many applications,
including HMIWI. EPA has monitored side-by-side evaluations of multi-
metals CEMS with EPA Method 29 of appendix A of 40 CFR part 60 at
industrial waste incinerators and found good correlation. EPA also
approved the use of multi-metals CEMS as an alternative monitoring
method at a hazardous waste combustor. EPA believes it is possible to
adapt proposed PS-10 (Specifications and Test Procedures for Multi-
metals Continuous Monitoring Systems in Stationary Sources) of appendix
B of 40 CFR part 60 or other EPA performance specifications to allow
the use of multi-metals CEMS at HMIWI. In addition to the procedures
used in proposed PS-10 for initial accuracy determination using the
relative accuracy test, a comparison against a reference method, EPA is
taking comment on an alternate initial accuracy determination
procedure, similar to the one in section 11 of PS-15 using the dynamic
or analyte spiking procedure.
    Relative to the use of Hg CEMS, EPA believes that PS-12A
(Specifications and Test Procedures for Total Vapor Phase Mercury
Continuous Emission Monitoring Systems in Stationary Sources) of
appendix B of 40 CFR part 60 can provide the basis for using Hg CEMS at
HMIWI. An owner or operator of an HMIWI unit who wishes to use Hg CEMS
would be required to notify EPA 1 month before starting use of Hg CEMS
and 1 month before stopping use of the Hg CEMS. The use of multi-metals
CEMS or Hg CEMS would allow the discontinuation of wet scrubber outlet
flue gas temperature monitoring. Mercury sorbent flow rate monitoring
could not be eliminated in favor of a multi-metals CEMS or Hg CEMS
because it also is an indicator of CDD/CDF control. Additionally, there
is no annual metals test that could be eliminated.
    The semi-continuous monitoring of dioxin would entail use of a
continuous automated sampling system and analysis of the sample using
EPA Reference Method 23 of appendix A of 40 CFR part 60. The option to
use a continuous automated sampling system would take effect on the
date a final performance specification is published in the Federal
Register or the date of approval of a site-specific monitoring plan.
Semi-continuous monitoring of dioxin would allow the discontinuation of
fabric filter inlet temperature monitoring. Dioxin/furan sorbent flow
rate monitoring could not be eliminated in favor of semi-continuous
monitoring of dioxin because it also is an indicator of Hg control.
Additionally, there is no annual CDD/CDF test that could be eliminated.
If semi-continuous monitoring of dioxin as well as multi-metals CEMS or
Hg CEMS are used, Hg sorbent flow rate monitoring and CDD/CDF sorbent
flow rate monitoring (in both cases activated carbon is the sorbent)
could be eliminated. EPA requests comment on other parameter monitoring
requirements that could be eliminated upon use of any or all of the
optional CEMS discussed above. Table 16 of this preamble presents a
summary of the HMIWI operating parameters, the pollutants influenced by
each parameter, and alternative monitoring options for each parameter.

   Table 16.--Summary of HMIWI Operating Parameters, Pollutants Influenced by Each Parameter, and Alternative
                                      Monitoring Options for Each Parameter
----------------------------------------------------------------------------------------------------------------
                                Pollutants Influenced by Operating Parameter (by Control Device
     Operating parameter/                                    Type)                                 Alternative
    monitoring requirement    ------------------------------------------------------------------    monitoring
                                   Dry scrubber          Wet scrubber         Combined system        options
----------------------------------------------------------------------------------------------------------------
Maximum charge rate..........  All \1\.............  All \1\.............  All \1\.............  None.
Minimum secondary chamber      PM, CO, CDD/CDF.....  PM, CO, CDD/CDF.....  PM, CO, CDD/CDF.....  CO CEMS \2\.
 temperature.
Maximum fabric filter inlet    CDD/CDF.............  ....................  CDD/CDF.............  Semi-continuous
 temperature.                                                                                dioxin
                                                                                monitoring
                                                                                system
                                                                                (SCDMS).
Minimum CDD/CDF sorbent flow   CDD/CDF.............  ....................  CDD/CDF.............  SCDMS and multi-
 rate.                                                                                metals CEMS or
                                                                                Hg CEMS.
Minimum Hg sorbent flow rate.  Hg..................  ....................  Hg..................
Minimum HCl sorbent flow rate  HCl.................  ....................  HCl.................  HCl CEMS.
Minimum scrubber pressure      ....................  PM..................  PM..................  PM CEMS.
 drop/ horsepower amperage.
Minimum scrubber liquor flow   ....................  HCl, PM, Cd, Pb, Hg,  HCl, PM, Cd, Pb, Hg,  HCl CEMS, PM
 rate.                                                CDD/CDF.              CDD/CDF.              CEMS, multi-
                                                                                metals CEMS,
                                                                                and SCDMS.
Minimum scrubber liquor pH...  ....................  HCl.................  HCl.................  HCl CEMS.
Maximum flue gas temperature   ....................  Hg..................  ....................  Hg CEMS or
 (wet scrubber outlet).                                                                           multi-metals
                                                                                CEMS.
Do not use bypass stack        All \1\.............  All \1\.............  All \1\.............  None.
 (except during startup,
 shutdown, and malfunction).
Air pollution control device   All \1\.............  All \1\.............  All \1\.............  None.
 inspections.
----------------------------------------------------------------------------------------------------------------
\1\ ``All'' pollutants designation does not include SO2 and NOX, which are regulated at combustion-controlled
  levels (no add-on controls) and have no associated parameter monitoring.
\2\ Optional method for existing and 1997 NSPS sources; required for new sources.

    Table 17 of this preamble presents a summary of the HMIWI test
methods and approved alternative compliance methods.

                    Table 17.--Summary of HMIWI Test Methods and Approved Alternative Methods
----------------------------------------------------------------------------------------------------------------
                                                                  Approved alternative
         Pollutant/parameter              Test method(s) \1\           method(s)                 Comments
----------------------------------------------------------------------------------------------------------------
PM...................................  Method 5, Method 29....  PM CEMS................  PM CEMS are optional
                                                                                for all sources in
                                                                                lieu of annual PM
                                                                                test.
CO...................................  Method 10..............  CO CEMS................  CO CEMS are optional
                                                                                for existing and 1997
                                                                                NSPS sources in lieu
                                                                                of annual CO test; CO
                                                                                CEMS are required for
                                                                                new sources.
HCl..................................  Method 26 or Method 26A  HCl CEMS...............  HCl CEMS are optional
                                                                                for all sources in
                                                                                lieu of annual HCl
                                                                                test.
Cd...................................  Method 29..............  Multi-metals CEMS......
Pb...................................  Method 29..............  Multi-metals CEMS......
Hg...................................  Method 29..............  ASTM D6784-02, multi-
                                                                 metals CEMS or Hg CEMS.
CDD/CDF..............................  Method 23..............  Semi-continuous dioxin
                                                                 monitoring system.
Opacity..............................  Method 22..............  Bag leak detection       Bag leak detection
                                                                 system or PM CEMS.       systems are optional
                                                                                for existing and 1997
                                                                                NSPS sources; and are
                                                                                required for new
                                                                                sources.
Flue and exhaust gas analysis........  Method 3, 3A, or 3B....  ASME PTC 19-10-1981
                                                                 Part 10.
Opacity from ash handling............  Method 22..............  None...................
----------------------------------------------------------------------------------------------------------------
\1\ EPA Reference Methods in appendix A of 40 CFR part 60.

V. Impacts of the Proposed Action for Existing Units

    The emission limits for existing HMIWI that we are proposing as
part of this action are based on the actual performance of the MACT
control technologies. This proposed action is expected to result in
modest improvements in performance being required by HMIWI that are not
achieving the performance levels demonstrated in practice by the
control technologies currently being used in the industry. Based on
compliance test reports from all existing operating HMIWI (72 units at
67 facilities) following MACT compliance in September 2002, 18 existing
large HMIWI and 4 existing medium HMIWI are likely to find it necessary
to improve performance of their units in order to achieve the proposed
emission limits which their compliance test data indicates they would
not meet. The modest improvements anticipated include adding lime (for
SO2), increasing lime use (for HCl and SO2),
increasing natural gas use (for CO and CDD/CDF), and increasing
scrubber horsepower (for Pb, Cd, and Hg). Facilities may resubmit
previous compliance test data that indicates that their HMIWI meets the
proposed emission limits if the facility certifies that the test
results are representative of current operations. Those facilities
would then not be required to test for those pollutants to prove
compliance with the emission limits.

A. What are the primary air impacts?

    As a result of the modest improvements estimated to be required at
22 HMIWI such that they would achieve the proposed emission limits, EPA
estimates that a total of approximately 24,700 pounds per year (lb/yr)
of the regulated pollutants would be reduced. Approximate reductions by
pollutant follow:
     HCl--20,600 lb/yr
     CO--400 lb/yr
     Pb--35 lb/yr
     Cd--3 lb/yr
     Hg--30 lb/yr
     PM--2,700 lb/yr
     CDD/CDF--0.0007 lb/yr
     NOX--200 lb/yr
     SO2--700 lb/yr

B. What are the water and solid waste impacts?

    EPA estimates that approximately 80 tpy of additional solid waste
and 267,000 gallons per year of additional wastewater would be
generated as a result of the increase of lime use by some facilities.

C. What are the energy impacts?

    EPA estimates that approximately 3,600 megawatt-hours per year of
additional electricity would be required to support the increase in
scrubber horsepower that we estimate would be required to enable some
facilities to achieve the proposed emission limits.

D. What are the secondary air impacts?

    Secondary air impacts associated with this proposed action are
direct impacts that result from the increase in natural gas use and/or
wet scrubber horsepower that we estimate may be required to enable some
facilities to achieve the proposed emission limits. We estimate that
the adjustments could result in emissions of 211 lb/yr of PM; 1,880 lb/
yr of CO; 1,230 lb/yr of NOX; and 1,450 lb/yr of
SO2 from the increased electricity and natural gas usage.

E. What are the cost and economic impacts?

    EPA estimates that the national total costs for the 72 existing
HMIWI and 4 1997 NSPS HMIWI to comply with this proposed action would
be approximately $488,000 in the first year of compliance. This
estimate includes the costs that would be incurred by the 22 HMIWI that
we anticipate needing to improve performance (i.e., costs of
improvements in emissions control and emissions tests for pollutants
for which the improvements are made), and the additional monitoring
(i.e., annual control device inspections), testing (i.e. initial Method
22 test), and recordkeeping and reporting costs that would be incurred
by all 76 HMIWI as a result of this proposed action. Approximately 50
percent of the estimated total cost in the first year is for emissions
control, 11 percent is for monitoring, 32 percent is for testing, and 7
percent is for recordkeeping and reporting. National total costs for
subsequent years are estimated to be approximately $308,000 per year,
with approximately 78 percent of the total cost for emissions control,
18 percent for monitoring, and 3 percent for testing.
    Economic impact analyses focus on changes in market prices and
output

levels. If changes in market prices and output levels in the primary
markets are significant enough, impacts on other markets are also
examined. EPA's economic impact analysis for this proposed action
assessed the magnitude of the cost of market changes resulting from the
proposed amendments by comparing annualized costs to annual sales. We
were able to assess the cost of market changes for 70 HMIWI (sales
information was unavailable for the other 6 units). For purposes of
assessing economic impacts of the proposed action, the total annualized
cost of this proposed action is estimated to be $328,000 and was
determined by first annualizing at 7 percent over 15 years the
difference between the first year costs and subsequent year costs for
each of the 76 HMIWI, and adding to that value the subsequent year
costs for each HMIWI; followed by then combining the annualized costs
for the 76 HMIWI. The $328,000 was distributed among the 76 HMIWI,
resulting in cost-to-sales ratios ranging from 0.0006 percent to 0.06
percent, with an average cost-to-sales ratio of 0.003 percent. Because
of the small size of these regulatory costs and estimated impacts, no
additional market analysis is needed. Neither the modest national costs
nor the facility level costs are anticipated to significantly impact
any market.

VI. Impacts of the Proposed Action for New Units

    The current NSPS apply to HMIWI for which construction began after
June 20, 1996, or for which modification began after March 16, 1998.
There are three new HMIWI and one modified HMIWI that are subject to
the current NSPS. No additional units have become subject to the NSPS
since 2002. Considering this information, EPA does not anticipate any
new HMIWI, and, therefore, no impacts of the proposed standards for new
units. However, in the unlikely event that a new HMIWI is constructed,
we are proposing new emission limits for those units based on
performance of the control technology upon which current NSPS limits
are based, as well as additional monitoring requirements, including use
of CO CEMS and use of bag leak detection systems for fabric filters.
Because EPA does not anticipate any new HMIWI, we, therefore, do not
expect there to be any air impacts, water or solid waste impacts,
energy impacts, or cost or economic impacts associated with the
proposed standards for new sources.

VII. Relationship of the Proposed Action to Section 112(c)(6) of the
CAA

    Section 112(c)(6) of the CAA requires EPA to identify categories of
sources of seven specified pollutants to assure that sources accounting
for not less than 90 percent of the aggregate emissions of each such
pollutant are subject to standards under CAA section 112(d)(2) or
112(d)(4). EPA has identified medical waste incinerators as a source
category that emits five of the seven CAA section 112(c)(6) pollutants:
Polycyclic organic matter (POM), dioxins, furans, Hg, and
polychlorinated biphenyls (PCBs). (The POM emitted by HMIWI is composed
of 16 polyaromatic hydrocarbons (PAH) and extractable organic matter
(EOM).) In the Federal Register notice Source Category Listing for
Section 112(d)(2) Rulemaking Pursuant to Section 112(c)(6)
Requirements, 63 FR 17838, 17849, Table 2 (1998), EPA identified
medical waste incinerators (now referred to as HMIWI) as a source
category ``subject to regulation'' for purposes of CAA section
112(c)(6) with respect to the CAA section 112(c)(6) pollutants that
HMIWI emit. HMIWI are solid waste incineration units currently
regulated under CAA section 129. For purposes of CAA section 112(c)(6),
EPA has determined that standards promulgated under CAA section 129 are
substantively equivalent to those promulgated under CAA section 112(d).
(See Id. at 17845; see also 62 FR 33625, 33632 (1997).) As discussed in
more detail below, the CAA section 129 standards effectively control
emissions of the five identified CAA section 112(c)(6) pollutants.
Further, since CAA section 129(h)(2) precludes EPA from regulating
these substantial sources of the five identified CAA section 112(c)(6)
pollutants under CAA section 112(d), EPA cannot further regulate these
emissions under that CAA section. As a result, EPA considers emissions
of these five pollutants from HMIWI units ``subject to standards'' for
purposes of CAA section 112(c)(6).
    As required by the statute, the CAA section 129 HMIWI standards
include numeric emission limitations for the nine pollutants specified
in that section. The combination of good combustion practices and add-
on air pollution control equipment (dry sorbent injection fabric
filters, wet scrubbers, or combined fabric filter and wet scrubber
systems) effectively reduces emissions of the pollutants for which
emission limits are required under CAA section 129: Hg, CDD/CDF, Cd,
Pb, PM, SO2, HCl, CO, and NOX. Thus, the NSPS and
emissions guidelines specifically require reduction in emissions of
three of the CAA section 112(c)(6) pollutants: Dioxins, furans, and Hg.
As explained below, the air pollution controls necessary to comply with
the requirements of the HMIWI NSPS and emission guidelines also
effectively reduce emissions of the following CAA section 112(c)(6)
pollutants that are emitted from HMIWI units: POM and PCBs. Although
the CAA section 129 HMIWI standards do not have separate, specific
emissions standards for PCBs and POM, emissions of these two CAA
section 112(c)(6) pollutants are effectively controlled by the same
control measures used to comply with the numerical emissions limits for
the enumerated CAA section 129 pollutants. Specifically, as byproducts
of combustion, the formation of PCBs and POM is effectively reduced by
the combustion and post-combustion practices required to comply with
the CAA section 129 standards. Any PCBs and POM that do form during
combustion are further controlled by the various post-combustion HMIWI
controls. The add-on PM control systems (either fabric filter or wet
scrubber) and activated carbon injection in the fabric filter-based
systems further reduce emissions of these organic pollutants, as well
as reducing Hg emissions. The post-MACT compliance tests at currently
operating HMIWI show that the HMIWI MACT regulations reduced Hg
emissions by greater than 80 percent and CDD/CDF emissions by about 90
percent from pre-MACT levels. In light of the fact that similar
controls have been demonstrated to effectively reduce emissions of POM
and PCBs from another incineration source category (municipal solid
waste combustors), it is, therefore, reasonable to conclude that POM
and PCB emissions are substantially reduced at all 76 HMIWI. Thus,
while the proposed rule does not identify specific limits for POM and
PCB, they are, for the reasons noted above, nonetheless ``subject to
regulation'' for purposes of section 112(c)(6) of the CAA.

VIII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order 12866 (58 FR 51735; October 4, 1993), this
proposed action is a ``significant regulatory action'' because it is
likely to raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order. Accordingly, EPA submitted this proposed action to
the Office of Management and Budget (OMB) for

review under Executive Order 12866, and any changes made in response to
OMB recommendations have been documented in the docket for this action.

B. Paperwork Reduction Act

    The information collection requirements associated with this
proposed action are included in the information collection requirements
addressing the HMIWI standards in their entirety, which have been
submitted for approval to the OMB under the Paperwork Reduction Act, 44
U.S.C. 3501 et seq. The Information Collection Request (ICR) documents
prepared by EPA have been assigned EPA ICR number 1899.04 for subpart
Ce and 1730.05 for subpart Ec.
    The requirements in this proposed action result in industry
recordkeeping and reporting burden associated with review of the
amendments for all HMIWI, initial EPA Method 22 testing for all HMIWI,
annual inspections of scrubbers and fabric filters for all HMIWI, and
stack testing and development of new parameter limits for HMIWI that
need to make performance improvements. The total nationwide
recordkeeping and reporting burden of this proposed action is estimated
at 722 hours at a cost of approximately $32,800. This burden and cost
would only be applicable once. After that, the total nationwide
recordkeeping and reporting burden and costs would be $0 (above and
beyond current burden and costs).
    The annual average burden associated with the emission guidelines
over the first 3 years following promulgation of this proposed action
is estimated to be 49,878 hours at a total annual labor cost of
$2,433,045. The total annualized capital/startup costs and operation
and maintenance (O&M) costs associated with the monitoring
requirements, EPA Method 22 testing, storage of data and reports, and
photocopying and postage over the 3-year period of the ICR are
estimated at $407,953 and $333,258 per year, respectively. (The annual
inspection costs are included under the recordkeeping and reporting
labor costs.) The annual average burden associated with the NSPS over
the first 3 years following promulgation of this proposed action is
estimated to be 2,004 hours at a total annual labor cost of $91,011.
The total annualized capital/startup costs are estimated at $13,046,
with total operation and maintenance costs of $36,310 per year.
    Burden means the total time, effort, or financial resources
expended by persons to generate, maintain, retain, or disclose or
provide information to or for a Federal agency. This includes the time
needed to review instructions; develop, acquire, install, and utilize
technology and systems for the purposes of collecting, validating, and
verifying information, processing and maintaining information, and
disclosing and providing information; adjust the existing ways to
comply with any previously applicable instructions and requirements;
train personnel to be able to respond to a collection of information;
search data sources; complete and review the collection of information;
and transmit or otherwise disclose the information.
    An Agency may not conduct or sponsor, and a person is not required
to respond to a collection of information unless it displays a
currently valid OMB control number. The OMB control numbers for EPA's
regulations are listed in 40 CFR part 9.
    To comment on the Agency's need for this information, the accuracy
of the provided burden estimates, and any suggested methods for
minimizing respondent burden, including the use of automated collection
techniques, EPA has established a public docket for this action, which
includes these ICR documents, under Docket ID No. EPA-HQ-OAR-2006-0534.
Submit any comments related to the ICR documents for this proposed
action to EPA and OMB. See ADDRESSES section at the beginning of this
notice for where to submit comments to EPA. Send comments to OMB at the
Office of Information and Regulatory Affairs, Office of Management and
Budget, 725 17th Street, NW., Washington, DC 20503, Attention: Desk
Office for EPA. Since OMB is required to make a decision concerning the
ICR between 30 and 60 days after February 6, 2007, a comment to OMB is
best assured of having its full effect if OMB receives it by March 8,
2007. The final action will respond to any OMB or public comments on
the information collection requirements contained in this proposal.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency
to prepare a regulatory flexibility analysis of any rule subject to
notice and comment rulemaking requirements under the Administrative
Procedures Act or any other statute unless the agency certifies that
the proposed action will not have a significant economic impact on a
substantial number of small entities. Small entities include small
businesses, small government organizations, and small government
jurisdictions.
    For purposes of assessing the impacts of this proposed action on
small entities, small entity is defined as follows: (1) A small
business as defined by the Small Business Administration's (SBA)
regulations at 13 CFR 121.201; (2) a small governmental jurisdiction
that is a government of a city, county, town, school district or
special district with a population of less than 50,000; or (3) a small
organization that is any not-for-profit enterprise that is
independently owned and operated and is not dominant in its field.
    After considering the economic impacts of this proposed action on
small entities, I certify that this action will not have a significant
economic impact on a substantial number of small entities. Because none
of the HMIWI facilities are expected to be significantly impacted by
this proposed action, that also means that none of the four small
entity-owned facilities would be expected to be significantly impacted.
None of the 22 HMIWI that we estimate would need to make improvements
in order to meet the proposed emission limits are owned by small
entities. The only estimated economic impacts on small entities would
result from the additional monitoring requirements (annual control
device inspections), testing requirements (one-time EPA Method 22
testing), and associated recordkeeping and reporting requirements of
this proposed action.
    We continue to be interested in the potential impacts of this
proposed action on small entities and welcome comments on issues
related to such impacts.

D. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act (UMRA) of 1995, Public
Law 104-4, establishes requirements for Federal agencies to assess the
effects of their regulatory actions on State, local, and Tribal
governments and the private sector. Under section 202 of the UMRA, EPA
generally must prepare a written statement, including a cost-benefit
analysis, for proposed and final rules with ``Federal mandates'' that
may result in expenditures by State, local, and Tribal governments, in
the aggregate, or by the private sector, of $100 million or more in any
1 year. Before promulgating an EPA rule for which a written statement
is needed, section 205 of the UMRA generally requires EPA to identify
and consider a reasonable number of regulatory alternatives and adopt
the least costly, most cost-effective, or least burdensome alternative
that achieves the objectives of the proposed rule. The provisions of
section 205 do not apply when they are inconsistent with applicable
law. Moreover, section 205 allows EPA to

adopt an alternative other than the least costly, most cost-effective,
or least burdensome alternative if EPA publishes with the final rule an
explanation why that alternative was not adopted.
    Before EPA establishes any regulatory requirements that may
significantly or uniquely affect small governments, including Tribal
governments, EPA must develop a small government agency plan under
section 203 of the UMRA. The plan must provide for notifying
potentially affected small governments, enabling officials of affected
small governments to have meaningful and timely input in the
development of EPA's regulatory proposals with significant Federal
intergovernmental mandates, and informing, educating, and advising
small governments on compliance with the regulatory requirements.
    EPA has determined that this proposed action does not contain a
Federal mandate that may result in expenditures of $100 million or more
for State, local, and Tribal governments, in the aggregate, or the
private sector in any 1 year. Thus, this proposed action is not subject
to the requirements of section 202 and 205 of the UMRA. In addition,
EPA has determined that this proposed action contains no regulatory
requirements that might significantly or uniquely affect small
governments. Therefore, this proposed action is not subject to the
requirements of section 203 of the UMRA.

E. Executive Order 13132: Federalism

    Executive Order 13132 (64 FR 43255; August 10, 1999), requires EPA
to develop an accountable process to ensure ``meaningful and timely
input by State and local officials in the development of regulatory
policies that have federalism implications.'' ``Policies that have
federalism implications'' are defined in the Executive Order to include
regulations that have ``substantial direct effects on the States, on
the relationship between the national government and the States, or on
the distribution of power and responsibilities among the various levels
of government.'' This proposed action does not have federalism
implications. It will not have substantial direct effects on the
States, on the relationship between the national government and the
States, or on the distribution of power and responsibilities among the
various levels of government, as specified in Executive Order 13132.
This proposed action will not impose substantial direct compliance
costs on State or local governments, and will not preempt State law.
Thus, Executive Order 13132 does not apply to this proposed action.
    In the spirit of Executive Order 13132, and consistent with EPA
policy to promote communications between EPA and State and local
governments, EPA specifically solicits comment on this proposed action
from State and local officials.

F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments

    Executive Order 13175, (65 FR 67249; November 9, 2000), requires
EPA to develop an accountable process to ensure ``meaningful and timely
input by Tribal officials in the development of regulatory policies
that have Tribal implications.''
    This proposed action does not have Tribal implications, as
specified in Executive Order 13175. It will not have substantial direct
effects on Tribal governments, on the relationship between the Federal
government and Indian tribes, or on the distribution of power and
responsibilities between the Federal government and Indian tribes, as
specified in Executive Order 13175. EPA is not aware of any HMIWI owned
or operated by Indian Tribal governments. Thus, Executive Order 13175
does not apply to this proposed action.

G. Executive Order 13045: Protection of Children From Environmental
Health and Safety Risks

    Executive Order 13045 (62 FR 19885; April 23, 1997), applies to any
rule that: (1) Is determined to be ``economically significant'' as
defined under Executive Order 12866, and (2) concerns an environmental
health or safety risk that EPA has reason to believe may have a
disproportionate effect on children. If the regulatory action meets
both criteria, EPA must evaluate the environmental health or safety
effects of the planned rule on children, and explain why the planned
regulation is preferable to other potentially effective and reasonably
feasible alternatives EPA considered.
    EPA interprets Executive Order 13045 as applying only to those
regulatory actions that are based on health or safety risks, such that
the analysis required under section 5-501 of the Executive Order has
the potential to influence the regulation. This proposed action is not
subject to Executive Order 13045 because it is based on technology
performance and not on health and safety risks.

H. Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution or Use

    This proposed action is not a ``significant energy action'' as
defined in Executive Order 13211, ``Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use'' (66 FR
28355; May 22, 2001) because it is not likely to have a significant
adverse effect on the supply, distribution, or use of energy. EPA
estimates that the requirements in this proposed action would cause
some HMIWI to increase the horsepower of their wet scrubbers, resulting
in approximately 3,600 megawatt-hours per year of additional
electricity being used.
    Given the negligible change in energy consumption resulting from
this proposed action, EPA does not expect any price increase for any
energy type. The cost of energy distribution should not be affected by
this proposed action at all since the action would not affect energy
distribution facilities. We also expect that there would be no impact
on the import of foreign energy supplies, and no other adverse outcomes
are expected to occur with regard to energy supplies.

I. National Technology Transfer Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement
Act (NTTAA) of 1995 (Pub. L. 104-113, Section 12(d), 15 U.S.C. 272
note) directs EPA to use voluntary consensus standards (VCS) in its
regulatory activities, unless to do so would be inconsistent with
applicable law or otherwise impractical. The VCS are technical
standards (e.g., materials specifications, test methods, sampling
procedures, and business practices) that are developed or adopted by
VCS bodies. The NTTAA directs EPA to provide Congress, through OMB,
explanations when the Agency does not use available and applicable VCS.
    This proposed action involves technical standards. EPA cites the
following standards: EPA Methods 1, 3, 3A, 3B, 5, 9, 10, 10B, 22, 23,
26, 26A, and 29 in 40 CFR part 60, appendix A. Consistent with the
NTTAA, EPA conducted searches to identify voluntary consensus standards
in addition to these EPA methods. No applicable voluntary consensus
standards were identified for EPA Methods 9 and 22. The search and
review results are in the docket for this proposed action.
    Two voluntary consensus standards were identified as acceptable

alternatives to EPA test methods for the purposes of this proposed
action. The voluntary consensus standard ASME PTC 19-10-1981-Part 10,
``Flue and Exhaust Gas Analyses,'' is cited in the proposed action for
its manual method for measuring the oxygen content of exhaust gas. This
part of ASME PTC 19-10-1981-Part 10 is an acceptable alternative to EPA
Method 3B.
    The voluntary consensus standard ASTM D6784-02, ``Standard Test
Method for Elemental, Oxidized, Particle-Bound and Total Mercury Gas
Generated from Coal-Fired Stationary Sources (Ontario Hydro Method),''
is an acceptable alternative to EPA Method 29 (portion for mercury
only) as a method for measuring Hg.
    The search for emissions measurement procedures identified 16 other
voluntary consensus standards. EPA determined that these 16 standards
identified for measuring emissions of the pollutants subject to
emission standards in this proposed action were impractical
alternatives to EPA test methods for the purposes of this action.
Therefore, EPA does not intend to adopt these standards for this
purpose. A document that discusses the determinations for these 16
methods is located in the docket to this proposed action.
    Section 60.56c of subpart Ec of 40 CFR part 60 and Sec.  60.37e of
subpart Ce of 40 CFR part 60 list the testing methods included in the
proposed action. Under 40 CFR 60.8(b) and 60.13(i) of subpart A
(General Provisions), a source may apply to EPA for permission to use
alternative test methods or alternative monitoring requirements in
place of any required testing methods, performance specifications, or
procedures.

List of Subjects in 40 CFR Part 60

    Environmental protection, Administrative practice and procedure,
Air pollution control, Intergovernmental relations, Reporting and
recordkeeping requirements.

    Dated: January 26, 2007.
Stephen L. Johnson,
Administrator.
    For the reasons stated in the preamble, title 40, chapter I, part
60 of the Code of Federal Regulations is proposed to be amended as
follows:

PART 60--[AMENDED]

    1. The authority citation for part 60 continues to read as follows:

    Authority: 42 U.S.C. 7401, et seq.

Subpart Ce--[Amended]

    2. Section 60.32e is amended by revising paragraphs (a) and (i) to
read as follows:

Sec.  60.32e  Designated facilities.

    (a) Except as provided in paragraphs (b) through (h) of this
section, the designated facility to which the guidelines apply is each
individual HMIWI for which construction was commenced on or before June
20, 1996 and each individual HMIWI currently subject to subpart Ec as
promulgated in 1997 (for which construction was commenced after June
20, 1996 but no later than February 6, 2007 or for which modification
commenced after March 16, 1998 but no later than 6 months after the
date of promulgation of this subpart).
* * * * *
    (i) Beginning 3 years after the date of promulgation of this
subpart, or on the effective date of an EPA approved operating permit
program under Clean Air Act title V and the implementing regulations
under 40 CFR part 70 in the State in which the unit is located,
whichever date is later, designated facilities subject to this subpart
shall operate pursuant to a permit issued under the EPA-approved
operating permit program.
    3. Section 60.33e is amended by revising paragraph (b) to read as
follows:

Sec.  60.33e  Emission guidelines.

* * * * *
    (b) For approval, a State plan shall include the requirements for
emission limits at least as protective as those requirements listed in
Table 2 of this subpart for any small HMIWI constructed on or before
June 20, 1996 which is located more than 50 miles from the boundary of
the nearest Standard Metropolitan Statistical Area (defined in Sec.
60.31e) and which burns less than 2,000 pounds per week of hospital
waste and medical/infectious waste. The 2,000 lb/week limitation does
not apply during performance tests.
* * * * *
    4. Section 60.36e is amended by adding paragraphs (c) and (d) to
read as follows:

Sec.  60.36e  Inspection guidelines.

* * * * *
    (c) For approval, a State plan shall require that each HMIWI
subject to the emission limits under Sec.  60.33e(a) undergo an initial
air pollution control device inspection that is at least as protective
as the following within 1 year following approval of the State plan:
    (1) At a minimum, an inspection shall include the following:
    (i) Inspect air pollution control device(s) for proper operation,
if applicable;
    (ii) Ensure proper calibration of thermocouples, sorbent feed
systems, and any other monitoring equipment; and
    (iii) Generally observe that the equipment is maintained in good
operating condition.
    (2) Within 10 operating days following an air pollution control
device inspection, all necessary repairs shall be completed unless the
owner or operator obtains written approval from the State agency
establishing a date whereby all necessary repairs of the designated
facility shall be completed.
    (d) For approval, a State plan shall require that each HMIWI
subject to the emission limits under Sec.  60.33e(a) undergo an air
pollution control device inspection annually (no more than 12 months
following the previous annual air pollution control device inspection),
as outlined in paragraphs (c)(1) and (2) of this section.
    5. Section 60.37e is amended by revising paragraphs (a) and (b)(1)
and adding paragraph (e) to read as follows:

Sec.  60.37e  Compliance, performance testing, and monitoring
guidelines.

    (a) Except as provided in paragraph (b) of this section, for
approval, a State plan shall include the requirements for compliance
and performance testing listed in Sec.  60.56c of subpart Ec of this
part, excluding the fugitive emissions annual testing requirement under
Sec.  60.56c(c)(3), the CO CEMS requirements under Sec.  60.56c(c)(5),
and the bag leak detection system requirements under Sec.  60.57c(g).
Sources may, however, elect to use CO CEMS as specified under Sec.
60.56c(c)(5) or bag leak detection systems as specified under Sec.
60.57c(g).
    (b) * * *
    (1) Conduct the performance testing requirements in Sec.
60.56c(a), (b)(1) through (b)(9), (b)(11) (Hg only), (b)(12), and
(c)(1) of subpart Ec of this part. The 2,000 lb/week limitation under
Sec.  60.33e(b) does not apply during performance tests.
* * * * *
    (e) The owner or operator of a designated facility may use the
results of previous emissions tests to demonstrate compliance with the
emission limits, provided that the conditions in paragraphs (e)(1)
through (e)(3) of this section are met:
    (1) The previous emissions tests must have been conducted using the
applicable procedures and test methods

listed in Sec.  60.56c(b)(1) through (b)(9), (b)(11) (Hg only), and
(b)(12). Previous emissions test results obtained using EPA-accepted
voluntary consensus standards are also acceptable.
    (2) The HMIWI at the affected facility shall be operated in a
manner (e.g., with charge rate, secondary chamber temperature, etc.)
that would be expected to result in the same or lower emissions than
observed during the previous emissions test(s), and the HMIWI may not
have been modified such that emissions would be expected to exceed
(notwithstanding normal test-to-test variability) the results from
previous emissions test(s).
    (3) The previous emissions test(s) must have been conducted in 1997
or later.
    6. Section 60.38e is amended by revising paragraph (a) and adding
paragraph (c) to read as follows:

Sec.  60.38e  Reporting and recordkeeping guidelines.

    (a) For approval, a State plan shall include the reporting and
recordkeeping requirements listed in Sec.  60.58c(b), (c), (d), (e),
and (f) of subpart Ec of this part, excluding Sec.  60.58c(b)(7)
(siting).
* * * * *
    (c) For approval, a State plan shall require the owner or operator
of each HMIWI subject to the emission limits under Sec.  60.33e(a) to:
    (1) Maintain records of the annual air pollution control device
inspections, any required maintenance, and any repairs not completed
within 10 days of an inspection or the timeframe established by the
State regulatory agency; and
    (2) Submit an annual report containing information recorded under
paragraph (c)(1) of this section no later than 60 days following the
year in which data were collected. Subsequent reports shall be sent no
later than 12 calendar months following the previous report (once the
unit is subject to permitting requirements under title V of the Act,
the owner or operator shall submit these reports semiannually). The
report shall be signed by the facilities manager.
    7. Section 60.39e is amended as follows:
    a. By revising paragraph (a);
    b. By revising paragraph (c) introductory text;
    c. By revising paragraph (d)(3); and
    d. By revising paragraph (f).

Sec.  60.39e  Compliance times.

    (a) Not later than 1 year after the date of promulgation of this
subpart, each State in which a designated facility is operating shall