PART B OF THE SUPPORTING STATEMENT

INFORMATION COLLECTION EFFORT FOR FACILITIES WITH COMBUSTION UNITS

1\. [Respondent Universe ]{.underline}

The vacated Boiler NESHAP and the remanded CISWI standard were developed
using a1997 a database of combustion units. The database was built using
data from the Industrial Combustion Coordinated Rulemaking "inventory"
and additional data received from non-fossil facilities "survey". These
inventory and survey databases contained 3,894 solid fuel fired units,
or units that fired a combination of solid fuels and other
fuels/materials. Since the vacature of the boiler and process heater
NESHAP and the CISWI definition rule, the Agency has been working with
state agencies to re-establish the population of facilities with boilers
or process heaters that were subject to the NESHAP. This data has been
collected mostly on the facility level, and at this time the Agency has
minimal unit level data to generate a revised estimate of the population
of boilers and process heaters that have emission test data gaps.
However, the new initial notification and permit data indicates that the
total number of facilities having boilers and process heaters
potentially subject to the vacated NESHAP is approximately 2,360, which
is much less then the 15,900 facilities with affected units listed in
the 1997 inventory and survey databases. Given that the new population
of facilities is much less, the Agency assumes that the number of
solid-fuel units within this population will also be much less than the
3,894 solid-fuel units contained in the 1997 data. Therefore, a sample
size of 350 units, which was based on the much larger 1997 dataset, is
unlikely to be needed, and the number of actual stack tests is expected
to be much less, assuming that the number of potential CISWI units is
also less than expected. The agency expects that the number of CISWI
units responding will be those covered by the 2000 standard as well as
those specifically exempted from that standard. Thus, the Agency expects
that there will be no more than 1,036 facilities with projected CISWI
units. Once the Agency reviews and analyzes the data received from the
electronic questionnaire, it will be able to revise the number of stack
tests needed in order to obtain a statistically valid sample based on
the new respondent universe. The sample design described below is an
example approach of how the Agency would select test site candidates.
Although the example is based on solid-fuel units from the 1997
database, the Agency may identify data gaps in other combinations of
fuel and combustor type. For example, the survey may not provide
sufficient emission data for CO or organic HAP from gas-fired units, and
the Agency may request that a sample of gas-fired units test for CO
only.

2\. [Respondent Universe Stratification ]{.underline}

Two variables that appear to have an effect on HAP emissions are
fuel/material type and combustor design (for combustion-based HAP such
as CO). The emission control device also has an impact on HAP emissions,
however the process for establishing a MACT floor will take into account
the top 12 percent of the best performing units, regardless of control
device, and so we have not included this variable in our sample design.
For the purposes of grouping the combustion units into categories, these
two variables will be used so to select a representative sample of
combustion units for testing. Commenters requested that the Agency add a
third variable, combustion unit size (i.e., design capacity), to the
sample design. The Agency notes that combustion HAP emissions are a
function of combustor design, not the size of the boiler. In the vacated
boiler and process heater NESHAP, the Agency defined the small
subcategory of boilers to be units that are less than 10 million Btu per
hour or units that have a fire tube type combustor design. The Agency
will collect data on the design capacity during the survey component of
this ICR, but it will not use combustor size as a variable in its sample
design.

In the example below, solid fuel types are categorized as they were in
the model units for the vacated boiler NESHAP: coal (fired-alone), a
blend of coal/wood/non-fossil liquid/non-fossil solids, a blend of
gas/wood/other biomass/liquid fossil fuel, blend of non-fossil
liquid/non-fossil solid, blend of gas/non-fossil liquid/non-fossil
solid, wood (fired alone), and a blend of wood/other biomass/non-fossil
liquid/non-fossil solid. Combustor design was also categorized as it was
used in the model units for the boiler NESHAP: all (incorporating
multiple combustor types), wall-fired/PC/Other, and Fluidized
Bed/Stoker/Dutch Oven/Other.

In the 1997 population dataset, some of the fuel categories did not
contain the full array of combustor designs. Based on the 1997 data, and
the six categories of solid fuel types, there were 8 defined categories
that each combustion unit could be assigned to. The number of units in
each category is shown on the following table.

  ----------------------------------------- ---------------------------------------------- -------------------- -----------
  **1997 Boiler Population **                                                                                   
                                                                                                                
                                            **Combustor Type**                                                  
                                                                                                                
  **Material**                              **Fluidized Bed/ Stoker/ Dutch Oven/ Other**   **Wall-fired/ PC**   **All**
  Coal                                      1,778                                          634                  **2,412**
  Coal/Wood/NFF Liquid/NFF Solid                                                                                **173**
  Gas/Wood/Other Biomass/Liquid FF                                                                              **302**
  NFF Liquid/NFF Solid/Gas                                                                                      **122**
  Wood                                      638                                            54                   **692**
  Wood/Other Biomass/NFF Liquid/NFF Solid                                                                       **193**
                                                                                                                
  **Total**                                 **2,416**                                      **688**              **3,894**
                                                                                                                
  ----------------------------------------- ---------------------------------------------- -------------------- -----------

Please note that the variation in combustor design and total number of
units assigned to each fuel/material category, and even the types of
fuel/material categories amongst the new data to be collected under the
first component of this ICR, could be strikingly different than the 1997
boiler and process heater population. Therefore, the Agency may use
different variables of fuel/material and combustor design when designing
the revised sample size. Several commenters requested that a facility
should be given the opportunity to opt out of a test if it stops burning
a fuel/material selected as part of the sample design. The goal of this
testing program is to fill data gaps. If a facility elects to
permanently stop burning a fuel/material identified as having a data
gap, the Agency would not require a test at this facility.

3\. [Sample Size ]{.underline}

One of the most important factors in sample design is that of
determining how large a sample is needed for the estimates obtained in
those selected samples (or units) to be statistically reliable enough to
meet the objectives of the study. In the determination of sample sizes
for studies where virtual certainty (i.e., a high level of reliability)
is needed, a level of 95 percent confidence, and 5% margin of error is
established to assure the objectives of the study will be met. A simple
stratified sample design determines the sample size (n) by the following
Microsoft Excel Function:

*n =
0.25\*NORMSINV(0.95+(1-0.95)/2)\^2/((0.05\^2)+(0.25\*NORMSINV(0.95+(1-0.95)/2)\^2)/N)*

Setting N = 3,894, since there are 3,894 solid fuel units in the 1997
boiler and process heater population databases, a 95 percent confidence
in the sample size obtained, and a 5 percent margin of error, the sample
size n = 350.

Given the eight categories from which units to be sampled can be
selected, the units to be sampled can be selected in a couple different
ways: i) equally (or relatively so) among the eight categories, or ii)
proportional allocation of units to be sampled to stratified population
(units within each category). In proportional allocation, the sampling
fraction (n~h~/N~h~) is specified to be the same for each category. The
number of units (n~h~) taken from each category is given by:

*`n`~`h`~` `*`= `(N*~[`h`]{.underline}~*)*~[` `]{.underline}~*(n)*~[` `]{.underline}~*

*`N`*

where N~h~ is the number of units in each category, n is the total
number of units to be sampled (i.e., 350), and N is the total number of
units (i.e., 3,894). Since the results of the electronic questionnaire
will replace the 1997 boiler and process heater population, and these
new data may have a different distribution of units within each
category, or perhaps even more specific fuel/material type or combustor
design categories, the actual number to be obtained from each category
cannot be determined at this time. Further, stack tests will only be
obtained for those combinations of fuel/material type and combustor
design where there are gaps in available emission data.

Some commenters suggested that the number of facilities required to test
should be a function of the number of unit subcategories the Agency
anticipates. The number of facilities required to test will be based
upon the identified emission data gaps for certain fuel and combustor
design combinations. The subcategories for the rulemaking cannot be
identified prior to the survey collection and testing program.

4\. [Respondent Sample Collection ]{.underline}

A random selection process will be used to determine a statistically
significant number of candidates within each category to participate in
this testing program. The Agency will then submit this list of
candidates to stakeholders for review and comment on the technical
feasibility and least cost impact of testing units within each candidate
pool. Several members of industry commented that not all facilities have
accessible testing ports, some facilities may be small entities, some
units may vent to common stacks, and other facilities may be shutdown
due to seasonal operations during the testing timeframe. Given these
practical constraints, it is not possible to conduct a truly "random"
sample, however the Agency will ensure that the test sites ultimately
selected will represent a statistically significant pool of candidate
test sites, and will not allow for industry self-selection of individual
test sites. If possible, once a unit from a particular site has been
selected, no other units at that site will be chosen for that particular
category. In addition, the Agency will work to ensure that if a company
has multiple plants, no more than two plants owned by the same entity
will be selected for testing. This approach will provide us with more
information from a larger number of facilities given that all operations
are not the same due to differing environmental conditions (e.g.,
weather), equipment, and load (e.g., fuel feed rates). Each site will
also have a different mix of fuel (even within the same fuel category),
since most facilities will obtain solid fuels from multiple sources.
Testing at multiple plants (sites) will provide additional information
on the variability of emissions across the mix of fuels/materials.

Commenters also requested that the Agency exclude from any testing
requirements units that were already tested to support compliance with
the vacated NESHAP standard. The Agency recognizes that the results of
any test conducted under the vacated NESHAP standard will be submitted
as part of the survey component of this ICR. The Agency is only seeking
new test data where there are data gaps. If a facility has already
submitted test data for a defined set of pollutants under the
questionnaire component, they would not be required to re-test for those
pollutants under the stack test component of this ICR. However, this
facility may be required to test for other HAP or HAP surrogates if the
unit at the facility belongs to one of the fuel/material and combustor
type groupings with an identified data gap or for section 129 pollutants
if a data gap is identified.

5\. [Response Rates ]{.underline}

Since the information will be requested pursuant to the authority of
section 114 of the Act, EPA anticipates that all respondents requested
to submit information will do so.