1 

### MEMORANDUM

Date: August 2012
To: Jim Eddinger, US EPA

From: Eastern Research Group, Inc.

Subject: CO CEMS MACT Floor Analysis (A ugust 2012) for the Industrial, Commercial, and Institutional Boilers and Process Heaters National Emission Standards for Hazardous Air Pollutants – Major Source

This memorandum describes the rationale , available data, and methodology for the alternative compliance option of a CO continuous emissions monitor (CEMS) MACT floor
emission limit for the Boiler MACT amended final rule. This alternative is provided to increase compliance flexibility for boilers which already employ CEMS or may need to install CEMS for other regulations and it also provide s flexibility for load-swinging units.

The memorandum is organized as follows:

1.0 Introduction
2.0 CEMS MACT Floor Calculati on Methodology – Existing Source 2.1 Determining Best Performers 2.2 Upper Prediction Limit Calculation 2.3 Maximum Rolling Average of Top 6%
2.4 Selection of CO CEMS MACT Floor
3.0 CEMS MACT Floor Calcul ation Methodology - New Source
4.0 Available CEMS Data
5.0 CO CEMS MACT Floor Results 5.1 Existing Source MACT Floors
5.2 New Source MACT Floors
6.0 References Appendix A: CO CEMS Subcat egory Rankings and Raw Data Appendix B: CO CEMS Existing Source UPL Calculations Appendix C: CO CEMS New Source UPL Calculations2 

### 1.0 INTRODUCTION

For the Boiler MACT rule reconsideration proposal, a MACT floor analysis using the available CO CEMS data was performed in response to requests from petitioners. 1 

### Commenters
on the alternative CO CEMS limits in the re consideration proposal provided additional CO CEMS data for certain subcategories for use in the current analysis. There were a few subcategories which still did no t have data, but there was enough data available to analyze the options for most of the subcategories outlined in the amended final rule. Given the dataset available and definition changes regarding 10-day and 30-day rolling averages in the amended final rule, the CO CEMS MACT floors were computed using multiple methods.

As will be discussed in the subsequent sections, the items mentioned below were changed
for the amended final Boiler MACT rule from the December 2011 reconsideration proposal:

1. In addition to 10-day rolling averages, 30- day rolling averages were calculated when sufficient data was provided to compute thes e longer averaging times; see section 4.0.
2. Rolling averages were calculated using daily data and hourly data to provide four rolling average options; see sections 2.1 and 4.0.

a. 10-day rolling averages
b. 240-hour rolling averages (modified 10-day rolling average)

c. 30-day rolling averages
d. 720-hour rolling averages (modified 30-day rolling average)
3. When multiple rolling averages were able to be calculated for a given subcategory, a hierarchy for use in UPL calculations wa s used: 720-hour rolling averages > 30-day rolling averages > 240-hour ro lling averages > 10-day rol ling averages; see sections
2.1 and 4.0.
4. The raw hourly or daily CO CEMS data were not used as inputs to the UPL equations for the MACT floor analysis, instead this data was reduced to the appropriate hourly or daily rolling averages, and the rolling average values themselves were used as inputs in the UPL calcula tions; see section 2.2.
5. The UPL formula was modified such that the m parameter of the UPL equation—the test condition—now equals 1 instead of 1 /the rolling average period; see section 2.2.3 

### 6. The highest value between the UPL and the maximum rolling average of the top 6 percent was selected as the MACT floor for each subcategory; see section 2.3. This is consistent with the method presente d in the alternative proposed CO CEMS emission limit for the December 2011 proposal.
7. Alternative CO CEMS limit were not fina lized for units desi gned to burn heavy liquids, light liquids, and non-continental li quids because facilities which did have CEMS data have permanently shut down since the December 2011 proposal; see
section 4.0.
8. Flagged periods of malfunc tion were included in the UP L calculation for the biomass suspension/grate subcat egory; see section 4.0.

2.0 CEMS MACT FLOOR CALCULATION METHODOLOGY – EXISTING SOURCE

2.1 DETERMINING BEST PERFORMERS

For existing sources, MACT cannot be less stringent than the average emission limitation achieved by the best performing 12 percent of ex isting sources (for which emission information is available) for categories and subcategories with 30 or more sources or the best performing five sources for subcategories with less than 30 sour ces. The size of the subcategory was determined according to the number of units in the boiler a nd process heater invent ory, not the number of units within each subcategory that had emission data available.

To identify the universe of best performing units in each subcategory, we calculated 10- day or 30-day rolling averages based on the av ailable CO CEMS data. For the reconsideration proposal, 10-day rolling averages were calcula ted (with two exceptions where a 1-day block average and a 3-hr rolling average were calculated), but due to the availability of additional data and with the support of commente rs, longer averaging periods we re analyzed for the amended final rule. Furthermore, with the submittal of a dditional hourly CO CEMS data, rolling averages were calculated using hourly CE MS data in addition to daily da ta. When using hourly data, the 30-day rolling average is more appropriately considered a 720-hour rolling average and the 10- day rolling average equated to a 240-hour rolling av erage for the purposes of performing the MACT floor calculation and ranking. By using hourly data the vari ability which naturally occurs4 

### due to fluctuations in boiler load were more ad equately captured and oper ating days with only a few hours of operation do not skew the rolling averag es over the course of a time period equivalent to 30 days and 24 hour s of operation per day. If a s ubcategory has hourly CO CEMS available, then the ranking base d on the 720-hour or 240-hour ro lling averages superseded the rolling averages ranking based on daily averages. If however, a subcategory did not have hourly CEMS data available then daily rolling averages were used in the rankin g and UPL analysis. In addition, if a subcategory had enough data to calcu late a 30-day (720-hour) rolling average then 10-day (240-hour) rolling averages were not considered when determining best performers. Instead, the longer rolling averag e available for each subcategor y was used for the analysis. Selecting a longer averaging period when data are available to do so is more representative of unit operations over the long term. Since these CO CEMS emission limits apply at all times (excluding periods of startup an d shutdown) it is appropriate to select the longer, more representative averagin g times. See section 4.0 for details on calculating hourly and daily rolling

averages.
Within each subcategory, the minimum 10- day (240-hour) or 30-day (720-hour) rolling averages were ranked from lowest to highest to determine the best performing 12 percent. If the number of units in the subcategory was grea ter than 30, the best performing 12 percent was determined by multiplying the number of units in each subcategory with CEMS data by 12 percent and rounding up to the nearest whole integer. Given th e dataset, the top 12 percent represented a single combustion unit for all of the subcategories with greater than 30 units, except for wet biomass stoker, where the top 12 pe rcent represented two un its. If the number of units in the subcategory was less than 30, the units with the five lowest minimum 10-day (240- hour) or 30-day (720-hour) rolling averages were iden tified as best performers; however, in these instances most subcategories only had a single unit with CO CEMS data, with the exception of the biomass fluidized bed subcategory which had four units with CO CEMS data. When determining the top 12 percent, the number of un its which had either daily or hourly CEMS data
available was used. This is seen in the wet biomass stoker rankings, wh ere although only five units have enough data to calculate 720-hour rolling aver ages (which would e qual one unit in the top 12 percent), the top 12 percent is based on all 13 units that reported CO CEMS data and thus
two units were considered in the top 12 percent. Th e top two units in the wet biomass stoker5 

### subcategory when ranking by hourly data were th e same top performers as when ranking by daily CO CEMS data; therefore, the units in the floor calculation did not change when calculating the floor with hourly data instead of daily data and the use of hourly data led to a more robust and longer term dataset serving as the basis of the MACT floor emission limit. After ranking by minimum rolling averages, a compar ison of the units used in the CO stack testbased floors were performed. Wher e we have CEMS data for units that were part of the stack test-based MACT floors, we also included the CEMS data from those units in the CEMS-based
floors because those units were demonstrated best performers for CO when conducting stack tests. The rankings for all subcate gories are provided in Appendix A-4.

2.2 UPL CALCULATION

With the best performing 12 percent for each subcategory determined, a 99 percent upper predictive limit (UPL) was calculate d for each subcategory. This is the same level of confidence
selected for the stack test-based emission limits . First, it was determined if each CO CEMS dataset was best characterized by a normal or lo gnormal distribution. To ev aluate the distribution of the best performing dataset, we computed the skewness and kurtosis statistics and then conducted the appropriate small-sample hypothes is tests. When perf orming the statistical analyses for the CO CEMS UPL ca lculations, the rolling averages of the reported dataset were used. This differs from the reconsideration prop osal analysis, where the raw reported data was used for the UPL analyses (for the reconsideration proposal the rolling averages were only used to determine the rankings). It was determined that use of rolling averages would provide more appropriate limits since the test condition requires that each rolling averages must be below the
MACT floor. This revised UPL analysis provides a limit based on the conditions required by the
amended final rule.

The distribution of the rolling average datasets were determ ined using the same skewness and kurtosis techniques discussed in the December 2011 proposal analysis. 1



### For datasets that were determined to be normally distributed, the UPL is computed using
a student’s t-test statistic. The t-statistic is calculated using the following Excel equation:

t-statistic = TINV(2*(1-0.99),n-1)6 

### Where: n = the number of rolling averages in the best performing 12 percent

Next, the mean and standard deviation of th e CO CEMS data were calculated and the UPL calculated via the following equation:

Where: the mean of rolling averages for the best performing 12 percent

s 2 

### = the standard deviation of the rolling averages in th e best performing 12 percent n = the number of rolling averages in the best performing 12 percent

For datasets that were determined to be l ognormally distributed, the same t-statistic was applied, but a slightly diffe rent UPL equation was used.

Where: the mean of the natural log-transformed rolling averages for the best performing 12 percent

s 2 

### = the standard deviation of the natural log-transformed rolling averages in the best performing 12 percent n = the number of rolling averages in the best performing 12 percent

For each subcategory the analysis showed that the datasets were lognormally distributed. Note also that in each UPL formula, the term (1/m) was not included as was at the reconsideration proposal. 1 

### At reconsideration, the ‘m’ represented the number of daily averages in the compliance average, but the equation has since been corrected such that it is set equal to 1. If the rule required a facility to demonstrate compliance by showing that the "average of 10" 10-7 

### day rolling averages is below the threshold, then m can be set equal to 10. However, the amended final rule requires an affected source to demonstrate complian ce by showing that each of its rolling averages (regardless of them bei ng 10-day or 30-day rolling averages) are below the
threshold.

Similar to the data validation rules used for the stack-test MACT floors and the December 2011 proposed CO CEMS-based MACT fl oors, for subcategories with one boiler in the top 12 percent, the top performing unit must be firing a fuel which is representative of and reasonable to obtain for the entire subcategory a nd not process specific nor based on co-fired configurations; this exception is the same as for new sources. The exis ting source calculations
for the coal fluidized bed subcat egory, however, were based on a bo iler co-firing natural gas; see
section 3.0 for additional details and disc ussion for inclusion of this boiler.

2.3 MAXIMUM ROLLING AVERAG E OF TOP 6 PERCENT

In addition to calculating a UPL for each subcategory, the maximum rolling average of the top 6 percent for each subcategory was also determined. After the rankings were determined, the emissions of the top ha lf of the best performing units (top 6 percent, or often the top single unit) were further analyzed. For each of these units the rolling averages were calculated, as shown in section 4.0, and reviewed to identify th e maximum rolling average. After the maximum rolling average was determined for each unit, the highest maximum rolling average from the top half of the best performers for each subcateg ory was identified. In the CEMS-based compliance alternative, it is necessary for MACT floors to be achieved by the best pe rformers at all times, even during large CO swings; the maximum rolling average value from the top half of the best performers is chosen as an alte rnative value to represent the pe rformance of the average emission limitation achieved by the best performing 12 pe rcent of existing sources (for which emission information is available).

Since only one unit’s maximum rolling averag e is used for this option, the unit’s operation must be representative of the entire su bcategory. Therefore, the unit selected must be firing a fuel which is reasonable to obtain for th e entire subcategory and not process specific nor based on co-fired configurations; this exception is the same as for new sources. For the light8 

### liquid subcategory, the top two ra nked facilities are co-firing natural gas and are thus not representative of light liquid fu el boilers; the third ranked fac ility is used for the maximum rolling average. The new source calculations for th e coal fluidized bed and biomass fluidized bed subcategories, however, were based on boilers co-f iring natural gas; see section 3.0 for additional
details and discussion for inclusion of this data. The maximum rolling average for the top 6 percent of units in each subcategory is s hown alongside the rankings in Appendix A-4.

2.4 SELECTION OF CO CEMS MACT FLOOR

As a final step, the 99% UPL value from th e top twelve percent of units was compared with the maximum rolling average from the top 6 percent of units to determine the MACT floor for each subcategory. This final step was incl uded to ensure that best performers could demonstrate compliance with the CO CEMS limits at all times. Due to the variable nature of boilers and process heaters and the limited data set for many subcategories it is known that significant CO swings do o ccur and CO values greater than the UPL may occur even for the best performers. To ensure this is not the case, the maximum value between the UPL and maximum rolling average of the top half of the best performers is chos en. Sections 5.1 and 5.2 show the
data and final determinations of the MACT fl oor for each subcategory based on this comparison.

3.0 CEMS MACT FLOOR CALCULATIO N METHODOLOGY - NEW SOURCE

A similar methodology used to calculate th e existing source UPL and maximum rolling average of the top 6 percent was used to calculate the new source UPL and maximum rolling average of the best performer. For the new sour ce calculations, however, only data from the top performing unit in each subcategory were used in the analyses. Since most of the subcategories only have one unit in the top 12 percent this makes little difference in the computed MACT floors. However, the top performing unit must be firing a fuel which is representative of and reasonable to obtain for the entire subcategory a nd not process specific nor based on co-fired configurations. If a boiler were not firing a si milar fuel available to others in the same subcategory, then the new source floor could be biased. This same exception is also used in the
new source floors for the CO stack test MACT fl oors. For the light liqu id subcategory, the top9 

### two ranked facilities are co-firing natural gas and are thus not representative of light liquid fuel boilers; the third ranked facility is used for the UPL.

Data from boilers in two subcat egories were from co-firing of natural gas, but were used for floor calculations. In light of the available data it was determined these were the best available option for performing the CO CEMS analyses.

 Biomass fluidized bed, GATempleInlandRome, WF: Boiler was co-firing natural gas in small quantities but the other boiler with enough CEMS data to calculate 720-hour rolling averages (ALIPCourtland, No. 3 Co mbination Boier / 11CU301) was co-firing natural gas and process-specific fuel.

 Coal fluidized bed, MITBSimonPowerPlant, Unit 4: Boiler was co-firing natural gas, but this was the only boiler for th is subcategory with hourly data.

There was also one additional step for new sources to ensure that the emission limit for new sources is not less stringe nt than the emission limit for existing sources in the same subcategory. If the value selected to represen t the MACT floor value for new sources is less stringent than the emission limit selected to repr esent the MACT floor for existing sources, then the floor corresponding to the same subcategory for existing sources was used as the basis for the floor for new sources. Although the minimum averag e test run for the best performing source resulted in the lowest 10-day (240-hour) or 30 -day (720-hour) CEMS rolling average, the 99 percent UPL limit incorporat es variability. As the sample size - in this case the number of hourly or daily CEMS values - gets smaller, the t-statis tic increases. When the sample size is small, and there is large variability in the CEMS values, the calculated limit using the UPL approach can be larger than the variability among a larger set of data in the best performing 12 percent.

4.0 AVAILABLE CEMS DATA

The CEMS data was obtained from two Information Collection Requests (ICRs) approved under OMB Control No. 2060-0616: ICR numbers 2286.01 and 2286.03, as well as additional voluntary data submittals. 3,4,5,6,710 

### The ICR Phase I survey requested that owners submit CO CEMS data for the most recent 30 days of operation (i.e., thirty 24-hour averages). Owners were asked to exclude data if they were from periods of start-up, shutdown, or malfunctions (SSM) and submittal was not required if the CEMs monitor was not installed for regul atory purposes. Owners we re also requested to submit a “typical” operating rate, which often repres ented the average rate for the 30-day period, but it did not request daily load averages to correspond to the daily average CO CEMS emission concentrations. Phase II of the ICR requested 30 days of CEMS data, including hourly data and the corresponding hourly heat input and steam output of the boiler. The additional voluntary data submittals were provided as minute, hourly or daily averages.

Consistent with the data eligibility criteria in the stack-test MACT floor analysis, when determining the applicable data for the CEMS an alysis, the fuel fired during the CEMS analysis must meet a 90% heat input threshold to be considered for a subcategory. 8 

### While the fuel was indicated for the majority of the data, assumpti ons for two boilers were necessary as described
here:

1. GATempleInlandRome, WF: Used oil along with wood bark are listed for certain data, but the percentage of us ed oil contributing to the heat input is not provided in all instances. For those instances when the percentage of used oil was provided it was always substantially less than 10 percent of total heat input, which would still allow
the data to be considered in the bioma ss fluidized bed CEMS analysis. Also, only 6 percent of the data points were from firing of used-oil with bar k. It was assumed all CEMS data points for this unit meet the 90% threshold for biomass since used oil is typically burned in su ch small quantities.
2. MITBSimonPowerPlant, Unit 4: Bituminous coal and natural gas are fired and the percentage each contributed to the heat input are not provi ded for the dates associated with the CO CEMS monitoring data. However, other fuel data for this boiler in other portions of the Phase I ICR survey showed that natural gas is burned in miniscule amounts. Therefore, it was assumed all CEMS data meets the 90% threshold for
bituminous coal.11 

### Three subcategories were impacted by the shutdown of boilers which were used to perform the CO CEMS analysis for the reconsid eration proposal; heavy liquid, light liquid, and non-continental liquid. While th ese units were used to pe rform the analysis for the reconsideration proposal, if a boile r is permanently shutdown its da ta are no longer applicable to a subcategory. The resulting outcome for each subcategory is described:

1. Heavy liquid: NJVinelandMuniElectric-H owardDown, Unit 9 has shut down. The heavy liquid subcategory now ha s one unit with CO CEMS data, TXOXEABayCity M-460, however this unit was co-firing natural gas and thus not representative of the heavy liquid subcategory.
2. Light liquid: Four units at NYConEdH udsonAve have shut down; boiler 71, boiler 72, boiler 81, and boiler 82. The light liquid subcategory now has two units with CO CEMS data at the facility NJMerckRahway, E750011 - Boiler #11 and E750012 - Boiler #12, but they are co-firing natural gas and thus not representative of the lig ht liquid subcategory.
3. Non-continental liquid: USVIHovensa, H-4101A has shut down. No other CO
CEMS data was available.

Without additional data an alternative CO CEMS MACT floor will not be calculated for the heavy liquid, light liquid, or non- continental liquid subcategories.

CO CEMS data from periods of malfunction we re included in the analysis. This change was due to the fact that when facilities comp ly with the amended final Boiler MACT frequent periods of malfunction cannot qua lify for the Affirmative Defense provisions in the amended final rule and these data will need to be included in the rolling averages. It would thus not be appropriate to exclude them from the calc ulations. Only one subcategory, biomass suspension/grate, provided data which specif ically noted certain values were during a malfunction. Other subcategories flagged data as startup or shutdown periods, which were appropriately excluded from these analyses. Th e rolling averages for this subcategory include
data from malfunctions.12 

### With the submittal of additional data after th e reconsideration proposal coupled with what was already available, most subcategories had a sufficient amount of CO CE MS data available to calculate an alternative CO CEMS MACT floor. Furthermore, there was additional data submitted as hourly averages which provided flexib ility in determining floor limits. Given the data, we considered multiple rolling average periods for each dataset, with a focus on using hourly data to incorporate variability in the UPL limits. Using hourly rolling averages was also consistent with the requests from commenters, many of which had requested that EPA consider hourly data from the previous 240 or 720 opera ting hours when developing a CO CEMS-based
MACT floor emission limit. The modified defin itions in the amended final rule state that
facilities were to use 240-hour or 720-hour rolling averages to co mply with the finalized limits.

When units reported hourly CO CEMS da ta, the following methodology was used to calculate 240 (or 720) hour rolling averages for each boiler. The hourly data points were sorted sequentially by hour and date. Then 240 (or 720) c onsecutive hours were av eraged together to provide hourly rolling averages ov er the time period available.

Daily averages were also calculated. For thos e subcategories without hourly data this was necessary because it was the source for the UPL calculations, while for those subcategories with hourly data the daily averages were used for comparison and to determine the number of units with CEMS data for each subcategory. To de termine daily rolling av erages where sources reported CEMS data on both an hourly and daily av erage basis we first reduced the hourly data into daily averages. The hourly data points fo r each boiler were sorted sequentially, grouped together by day, and then averaged to comput e daily averages. Next, we combined the two datasets, sorted the data in sequ ential calendar date order and co mputed a series of 10-day (or 30- day) rolling averages from each unit.

The rolling averages represent sequential, but not necessarily continuou s, calendar dates. In some cases the data reported by the facility sk ipped certain days due to unit downtime or data associated with startup or s hutdown conditions. Also note that only data m eeting the 90 percent
fuel data validation criteria were incl uded in the hourly and daily averages.13 

### With a variety of data available, a hierarc hy was selected to determine which data would
be used in the UPL calculations. This order is as follows: (1) 30- day rolling average using hourly data to compute 720-hour rolling averages, (2) 30 -day rolling averages using daily averages, (3) 10-day rolling average using hourly data to co mpute 240-hour rolling averages, and (4) 10-day rolling averages using daily averages. Table 1 shows the s ubcategories which have hourly CO
CEMS data available to calcula te 240-hour or 720-hour rolling averages. The far right column denotes which, if either, of the hourly rolling averages was used for the UPL calculation. Table 2 shows the subcategories which have daily CO CE MS data available to calculate 10-day or 30- day rolling averages. Again, the far right column denotes which, if either, of the daily rolling averages was used for the UPL calculation.

Table 1. Available hourly CO CEMS data for each subcategory, to determine a 10

‐ day (240

‐ hour) or 30

‐ day (720–hour) rolling average.

Fuel Category Combustor Design Number of Units in Subcategory Number of Units with Hourly Avg CO CEMS Data to Compute 240

‐ Hr

Rolling Avgs Number of Units with Hourly Avg CO CEMS Data to Compute 720

‐ Hr

Rolling Avgs Number of Units In Top

12% Basis for UPL

Calc

Coal FB 35 1 1 1 720

‐ Hr FB w/Heat Exchanger a a a a PC 190 2 1 1 720

‐ Hr Stoker/SlopedGrate/Other 391 2 1 1 720

‐ Hr

Biomass Dutch Oven/Pile Burner 24 a a a a FB 24 3 2 2 720

‐ Hr Fuel Cell 14 a a a a Suspension Burner 47 1 0 1 240

‐ Hr Suspension/Grate 18 1 1 1 720

‐ Hr Wet Biomass Stoker/SlopedGrate/Other 305 6 5 3 (b) 720

‐ Hr Dry Biomass Stoker/SlopedGrate/Other 74 a a a a Heavy Liquid N/A 320 a a a a Light Liquid N/A 581 a a a a Non

‐ Continental Liquid N/A 44 a a a a
Process Gas N/A 129 a a a a Note: a. Data was not available to calculate a rolling average on an hourly basis. b. Includes 1 unit which was a stack test best performer. The 12% of units with data is based on the 13 units with hourly or daily data instead of just the 5 units with data available for 720-hr rolling averages.14 Table 2. Available daily average CO CEMS data for each subcategory, to determine a 10

‐ day or 30

‐ day rolling average.

Fuel Category Combustor Design Number of Units in Subcategory Number of Units with Daily Avg CO

CEMS Data to Compute 10

‐ Day

Rolling Avgs Number of Units with Daily Avg CO CEMS Data to Compute 30

‐ Day

Rolling Avgs Number of Units In Top

12% Basis for UPL

Calc

Coal FB 35 6 5 1 b FB w/Heat Exchanger 1 1 1 30

‐ Day PC 190 3 1 1 b Stoker/SlopedGrate/Other 391 6 0 1 b

Biomass Dutch Oven/Pile Burner 24 1 a 1 10

‐ Day FB 24 4 2 4 b Fuel Cell 14 a a a a Suspension Burner 47 2 0 1 b Suspension/Grate 18 1 1 1 b Wet Biomass Stoker/SlopedGrate/Other 305 13 5 3 (c) b Dry Biomass Stoker/SlopedGrate/Other 74 a a a a Heavy Liquid N/A 320 a a a a Light Liquid N/A 581 a a a a Non

‐ Continental Liquid N/A 44 a a a a
Process Gas N/A 129 a a a a Notes: a. Data was not available to calculate a rolling average on a daily basis. b. UPL computed using hourly data. c. Includes 1 unit which was a stack test best performer.



### 5.0 CO CEMS MACT FLOOR RESULTS

5.1 EXISTING SOURCE MACT FLOORS

After the CO CEMS MACT floor calculations were performed for each subcategory the same rounding technique used in the stack-test based MACT floors emission limits was applied. Each MACT floor was determined by rounding the limit up to two significant figures. Rounding up is appropriate for establishing emission standard s that must be complied with at all times. The CO CEMS MACT floors for existing sources are summarized in Table 3. Both the UPL value and the maximum rolling average from the top 6% are shown for each subcategory; the value used for determining the MACT floor is hi ghlighted. The rolling average basis for each15 

### subcategory is also noted; 10-day, 240-hr, 30-da y, or 720-hr. The rankings and maximum rolling average of the top 6% for each subcategory are shown in Appendix A and the UPL floor calculations for each subcategory are shown in Appendix B.

In reviewing Tables 1 and 2 above, note ther e are six subcategories which do not have CO CEMS data available. While substituting a MA CT floor from a different subcategory for the subcategories with no data was considered, ultimately it was determined that an alternative CO
CEMS floor would not be provided for subcategorie s with no data. If othe r subcategories’ data were used to fill in incomplete subcategories, this data would not be representative of the applicable boilers operations and it would not be appropriate to subj ect boilers to a limit which is not based off representative data.

Table 3. Summary of CO CEMS MACT floor limits for existing boilers and process heaters, 10

‐ day (240

‐ hr) or 30

‐ day (720

‐ hr) rolling averages.

Fuel Category Combustor Design Category Rolling Average

Basis 99% UPL Maximum Rolling Avg of Top 6% Rounded CO CEMS MACT Floor (ppm @ 3% O2)

Coal FB 720

‐ Hr 224.0 164.7 230 FB

‐ Heat Exchanger 30

‐ Day 138.6 146.0 150 PC 720

‐ Hr 89.6 315.7 320 Stoker/SlopedGrate/Other 720

‐ Hr 309.9 336.9 340

Biomass Dutch Oven/Pile Burner 10

‐ Day 516.5 220.1 520 FB 720

‐ Hr 268.3 305.5 310 Fuel Cell a a a a Suspension Burner 240

‐ Hr 1929.2 1334.7 2000 Suspension/Grate 720

‐ Hr 848.3 893.9 900 Wet Biomass Stoker/SlopedGrate/Other 720

‐ Hr 718.9 297.4 720 Dry Biomass Stoker/SlopedGrate/Other a a a a Heavy Liquid N/A a a a a Light Liquid N/A a a a a Non

‐ Continental Liquid N/A a a a a Process Gas N/A a a a a Notes:

a. No applicable CO CEMS data available for this subcategory

 Cells highlighted blue designate the value chosen for the MACT Floor.



### 5.2 NEW SOURCE MACT FLOORS16 

### The new source CO CEMS MACT floors ar e summarized in Table 4 and the UPL calculations are provided in Appendix C. Both the UPL value and the maximum rolling average from the top performer are shown for each sub category; the value used for determining the MACT floor is highlighted. The rolling average ba sis for each subcategory is also noted; 10-day, 240-hr, 30-day, or 720-hr. Only one subcategory, we t biomass stoker/slope d grate/other, has a new source limit which is different than the existing source limit.

Table 4. Summary of CO CEMS MACT floor limits for new boilers and process heaters, 10

‐ day (240

‐ hr)

or 30

‐ day (720

‐ hr) rolling averages.

Fuel Category Combustor Design Category Rolling Average

Basis 99% UPL Maximum Rolling Avg of Top 6% Rounded CO CEMS MACT Floor (ppm @ 3% O2)

Coal FB 720

‐ Hr 224.0 164.7 230 FB

‐ Heat Exchanger 30

‐ Day 138.6 146.0 150 PC 720

‐ Hr 89.6 315.7 320 Stoker/SlopedGrate/Other 720

‐ Hr 309.9 336.9 340

Biomass Dutch Oven/Pile Burner 10

‐ Day 516.5 220.1 520 FB 720

‐ Hr 271.6 305.5 310 Fuel Cell a a a a Suspension Burner 240

‐ Hr 1929.2 1334.7 2000 Suspension/Grate 720

‐ Hr 848.3 893.9 900 Wet Biomass Stoker/SlopedGrate/Other 720

‐ Hr 380.01 297.4 390 Dry Biomass Stoker/SlopedGrate/Other a a a a Heavy Liquid N/A a a a a Light Liquid N/A a a a a Non

‐ Continental Liquid N/A a a a a Process Gas N/A a a a a Notes:

a. No applicable CO CEMS data available for this subcategory

 Cells highlighted blue designate the value chosen for the MACT Floor.17 

### 6.0 REFERENCES

1. Eastern Research Group, Inc. CO CEMS MA CT Floor Analysis (November 2011) for the Industrial, Commercial, and Institutional Boilers and Pro cess Heaters National Emission Standards for Hazardous Air Pollutants – Major Source. November 2011.

2. EPA. Data Quality Assessment: Statistical Methods for Practitioners. EPA QA/G-9S. February 2006. Available on-line at: http://www.epa.gov/quality/q s-docs/g9s-final.pdf

3. Phase I ICR 2008 Combustion Survey. [ICR No. 2286.01]. OMB Control No. 2060-0616 -
Information Collection Effort for Facilities with Combustion Units. Approved by OMB on August 1, 2008.
4. Phase II ICR Test Plan Requesting Emission Testing from Boilers, Process Heaters, and CISWI. [ICR No. 2286.03]. OMB Control No. 2060-0616 - Information Collection Effort for Facilities with Combustion Units. Approved by OMB on May 21, 2009.

5. Eastern Research Group, Inc. Handling and Pro cessing of Corrections and New Data in the EPA ICR Databases. January 2011.

6. Eastern Research Group, Inc. Handling and Pro cessing of Corrections and New Data in the
EPA ICR Databases – Revised November 2011.

7. Eastern Research Group, Inc. Handling and Pro cessing of Corrections and New Data in the EPA ICR Databases – Revised August 2012.

8. Eastern Research Group, Inc. Revised MACT Floor Analysis (November 2011) for the Industrial, Commercial, and In stitutional Boilers and Proce ss Heaters National Emission Standards for Hazardous Air Pollutants – Major Source. November 2011.