Date: December 16, 2011 

Subject: National Emission Standards for Hazardous Air Pollutants (NESHAP) Maximum 

Achievable Control Technology (MACT) Floor Analysis for Coal- and Oil-fired 

Electric Utility Steam Generating Units for Final Rule 

From: Jeffrey Cole (RTI International) 

To: Bill Maxwell 

 OAQPS/SPPD/ESG (D243-01) 

 U.S. Environmental Protection Agency 

 Research Triangle Park, NC 27711 

Introduction 

Section 112 of the Clean Air Act (CAA) requires that the U.S. Environmental Protection 

Agency (EPA) establish National Emission Standards for Hazardous Air Pollutants (NESHAP) 

for the control of the hazardous air pollutants (HAP) emitted from both new and existing sources 

in a source category. These standards must reflect the maximum degree of reduction in the HAP 

emissions that is achievable. The minimum level of control is referred to as the “Maximum 

Achievable Control Technology (MACT) floor.” The method for determining the MACT floor 

as the minimum control level allowed for establishing standards for a NESHAP is defined for 

both new and existing sources by CAA section 112(d)(3). For new sources, the MACT floor 

cannot be less stringent than the emission control that is achieved in practice by the 

best-controlled similar source. For existing sources, the MACT floor cannot be less stringent 

than the average emission limitation achieved by the best-performing 12 percent of existing 

sources for source categories with 30 or more sources, or the best-performing 5 sources for 

source categories with fewer than 30 sources. 

The purpose of this memorandum is to present the methodology and the results of the 

MACT floor analysis for the NESHAP source category “Coal- and Oil-fired Electric Utility 

Steam Generating Units” (referred to in this memorandum as “EGUs”). This MACT floor 

analysis uses data collected in a nationwide survey of EGU owners and operators conducted by 

the EPA in 2010 under the Information Collection Request For National Emission Standards For 

Hazardous Air Pollutants (NESHAP) for Coal- And Oil-Fired Electric Utility Steam Generating 

Units (OMB Control No. 2060‐0631). Individual EGU operating and air emissions data reported 

by respondents to the Information Collection Request (ICR) were compiled into a Microsoft 

Access® data base that serves as the data set used for this MACT floor analysis (referred to in 

this memorandum as the “ICR data set”). 

MACT Floor Analysis Hazardous Air Pollutants 

The specific chemicals, compounds, or groups of compounds designated to be HAP are 

listed in CAA section 112(b). Included on the list are metals, organic compounds, and inorganic 

chemicals. From this HAP list, the following HAP, among others, were identified to be emitted 

from EGUs and were included in the MACT floor analysis: the metals antimony (Sb), arsenic 
2 

(As), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), lead (Pb), manganese (Mn), 

mercury (Hg), nickel (Ni), and selenium (Se); organic HAP, and the acid gases hydrogen 

chloride (HCl) and hydrogen fluoride (HF). In addition to these individual pollutants, MACT 

floor levels were analyzed using filterable particulate matter (fPM) emissions as a surrogate for 

HAP metals other than Hg (non-Hg metallic HAP) for coal-fired units and as a surrogate for total 

HAP metals for oil-fired units. In addition, MACT floor levels were analyzed using HCl as a 

surrogate for all acid gas HAP, and sulfur dioxide (SO2) emissions as an alternative equivalent 

surrogate pollutant for acid gas HAP for units equipped with flue gas desulfurization systems for 

coal-fired units and solid oil-fired units. 

MACT Floor Analysis Subcategories 

Under CAA section 112(d)(1), the EPA has the discretion to “...distinguish among 

classes, types, and sizes of sources within a category or subcategory in establishing...” standards. 

When separate subcategories are established, a MACT floor is determined separately for each 

subcategory. To determine whether the EGU source category warrants subcategorization for the 

MACT floor analysis, the EPA reviewed EGU design, operating information, and air emissions 

data compiled in the ICR data set and other information collected by the Agency for 

development of the NESHAP for this source category. Based on this review, the EPA concluded 

that there are significant design and operational differences in EGUs that affect the levels of 

emissions of certain HAP to justify subcategorizing EGUs for the purpose of establishing MACT 

floors. 

The data available to the EPA show that the levels of HAP emissions for EGUs burning 

solid coal are the same for all of the HAP constituents except Hg. To account for the differences 

in Hg emissions from these units, the EPA identified two subcategories for EGUs burning solid 

coal. The HAP emissions from integrated gasification combined cycle (IGCC) EGUs are distinct 

from EGUs burning solid coal because IGCC burn a synthetic gas derived from coal or from a 

blend of coal and solid oil-derived solid fuel (i.e., petroleum coke). Consequently, a separate 

subcategory is defined for IGCC units. The data also show differences in all HAP emissions 

from oil-fired EGUs compared to coal-fired EGUs. Within the grouping of oil-fired EGUs, we 

have established four (4) subcategories based on distinct differences in the HAP emissions levels 

from the subcategories. For liquid oil-fired EGUs, we are establishing a subcategory for units 

located inside the continental United States, a subcategory for units located outside the 

continental United States, and a subcategory for oil-fired EGUs located inside the continental 

United States that have an annual oil-fired capacity factor of less than 8 percent. Furthermore, we 

are also establishing a subcategory for solid oil-fired EGUs because there are distinct differences 

in the HAP emissions levels from oil-fired EGUs units depending on whether liquid fuel oil is 

burned or a petroleum-derived solid fuel is burned. 
3 

For the MACT floor analysis, the following seven EU subcategories were defined: 

Subcategory 1. New and existing EGUs designed to burn a coal having a calorific value 

(moist, mineral matter-free basis) of greater than or equal to 19,305 kJ/kg (8,300 Btu/lb) 

that are not coal-fired EGUs in the “unit designed for low rank, virgin coal” subcategory.1

Subcategory 2. New and existing EGUs designed to burn and burning nonagglomerating 

virgin coal having a calorific value (moist, mineral matter-free basis) of less than 19,305 

kJ/kg (8,300 Btu/lb) that are constructed and operated at or near the mine that produces 

such coal. 

Subcategory 3. New and existing IGCC EGUs. 

Subcategory 4. New and existing EGUs located inside the continental United States that 

burn liquid oil and have an annual oil-fired capacity factor of greater than or equal to 

8 percent. 

Subcategory 5. New and existing EGUs located inside the continental United States that 

burn liquid oil and are classified as limited use by having an annual oil-fired capacity 

factor of less than 8 percent. 

Subcategory 6. New and existing EGUs located outside the continental United States that 

burn liquid oil. 

Subcategory 7. New and existing EGUs that burn solid oil-derived fuel. 

Calculating Emission Values used in the MACT Floor Analysis 

The EPA received emissions data from industry respondents under the Electric Utility 

(EU) MACT ICR in a number of different units of measure and converted these units of measure 

to a common pound per million British thermal units (lb/MMBtu) and pounds per megawatt-hour 

(lb/MWh) basis shown in the statistical analysis spreadsheets. The emissions data could have 

been submitted under Part II of the ICR (historical stack testing conducted from 1/1/2005 to 

12/31/2009) or from Part III of the ICR (testing done in 2010 or 2011 specifically for the 2010 

EGU MACT ICR). Although the Part III data was submitted in the units of measure specified by 

EPA, the Part II data came in a variety of units of measure. The procedures used for making 

these unit conversions and the EPA’s procedure for converting a unit’s stack emission data from 

a lb/MMBtu basis to a lb/MWh basis are presented in Attachment A. To ensure data quality, the 

EPA performed three levels of outlier analyses on the submitted data averages before they were 

considered for the floors. The first level was a visual plotting of the data via a scatter plot to 

identify obvious outliers that warranted removal from the data set pending further investigation. 

Using the scatter plot method of outlier identification, 14 data averages were removed from floor 

consideration. These averages, their pollutant, and unit name are also listed in a table in the 

attachments. Once these data were removed, the remaining data were then sorted by emission 

average (low to high) and the MACT floor sets of averages were chosen following the 

methodology discussed in the following sections. Subsequent outlier analyses were conducted as 

part of the statistical analysis as discussed on page 12. 

 

1

 Subcategories 1 and 2 were differentiated for mercury emissions only. The remaining standards finalized in this 

action are the same for the two subcategories. 
4 

MACT Floor Analysis Methodology 

The first step in the MACT floor analysis for each subcategory and HAP (or surrogate) 

was to rank all of the EGUs in the subcategory (for which there were emissions data in the ICR 

data set) for the pollutant type by emission level (lowest to highest). From this ranking, a MACT 

floor pool of sources was identified for determining the minimum control level allowed for the 

MACT floor, consistent with the criteria defined for new and existing sources by CAA section 

112(d)(3). For the new-source MACT floors, the best-controlled similar source was identified for 

which there were individual source test run data in the ICR data set. For the existing-source 

MACT floors, selection of the MACT floor pool size (i.e., number of EGUs to be included in the 

determination of the average emission limitation value) was determined on an individual 

subcategory basis as described below. 

Subcategory 1. The existing-source MACT floors for fPM, HCl, SO2, total non-Hg HAP 

metals, and individual non-Hg HAP metals emissions were based on the top 12 percent of 

the total number of EGUs in the nationwide subcategory coal- and oil-fired EU 

population (12% of 1,082 sources or 130 EGUs). The existing-source MACT floor for 

Hg emissions was based on the top 12 percent of the total number of the subcategory

EGUs with Hg emissions in the ICR data set (12% of 388 sources or 47 EGUs). In the 

ICR, EPA required the units selected for non-mercury metal HAP testing to also test for 

mercury because the test methods are similar for mercury and non-mercury HAP. 

Subcategory 2. This subcategory includes greater than 30 (i.e., 36) sources. The EPA 

differentiated coal-fired units solely for Hg emissions and the existing-source MACT 

floors for fPM, HCl, SO2, total non-Hg HAP metals, and individual non-Hg HAP metals 

emissions were based on the same MACT floor data pool used for Subcategory 1. The 

existing-source MACT floor for Hg emissions for this subcategory was based on the top 

2 EGUs of the subcategory for which the EPA had emissions data (12% of 11 sources or 

2 EGUs). 

Subcategory 3. This subcategory includes 2 sources. The existing-source MACT floors 

for all HAP and surrogate pollutant emissions were based on the data for both IGCC 

EGUs in the subcategory. 

Subcategory 4. This subcategory includes 40 sources. The existing-source MACT floors 

for all HAP and HAP surrogates emissions were based on the top 12 percent of the total 

number of the subcategory EGUs in each specific pollutant’s ICR data set. 

Subcategory 5. This subcategory includes 78 sources. The existing- and new-source 

MACT floors will be achieved through work practice standards with no numerical 

emission limits established. 

Subcategory 6. This subcategory includes 31 sources. The existing-source MACT floors 

for all HAP and HAP surrogates emissions were based on the top 12 percent of the total 

number of the subcategory EGUs in each specific pollutant’s ICR data set. 

Subcategory 7. This subcategory includes 11 sources and the ICR data set includes data 

from 9 of those sources. The existing-source MACT floors for all HAP and HAP 

surrogates were based on the top five EGUs of the subcategory EGUs in the ICR data set. 

The next step in the MACT floor analysis was to incorporate data variability into the 

calculations of the applicable MACT floor limits for the subcategories using a 99 percent upper 
5 

prediction limit (UPL) approach. Specifically, the MACT floor limit is an UPL calculated with 

the Student’s t-test using the “TINV” function in Microsoft Excel® software. The Student’s t-test 

has also been used in other EPA rulemakings (e.g., NESHAP for Portland Cement, NSPS for 

Hospital/Medical/Infectious Waste Incinerators [HMIWI], NESHAP for Industrial, Commercial, 

and Institutional Boilers and Process Heaters) in accounting for variability and reflects the level 

of confidence. The level of confidence represents the level of protection afforded to facilities 

whose emissions are in line with the best performers, and consequently, the level of confidence 

is not arbitrary. For example, a 99 percent level of confidence means that a facility whose 

emissions are in line with the best performers has one chance in 100 of exceeding the floor limit. 

A prediction interval for a single future observation (or an average of several test observations) is 

an interval that will, with a specified degree of confidence, contain the next (or the average of 

some other pre-specified number) of randomly selected observation(s) from a population. In 

other words, the UPL estimates what the upper bound of future values will be, based upon 

present or past background samples taken. The UPL consequently represents the value at which 

we can expect the mean of future observations for the HAP or HAP surrogate emissions to fall 

within a specified level of confidence, based upon the measurements from an independent 

sample from the same population. The UPL approach encompasses all the data point-to-data 

point variability. The predictions derive from the data set to which it is applied, and, thus, can be 

applied to any type of data. 

The form of the UPL equation differs somewhat depending upon the nature of the data 

set to which it is applied. To this end, the data sets were evaluated for each HAP and HAP 

surrogate to ascertain whether the data were normally distributed, or distributed in some other 

manner (i.e., log normally). For data sets where the number of available EGUs was 15 or more, 

use of the UPL was based on assuming a normal distribution based on the Central Limit Theorem

(Durrett, 1996). The Central Limit Theorem states that regardless of the shape of the original 

distribution, if the distribution has a finite mean (μ) and variance (σ2), the sampling distribution 

of the mean approaches a normal distribution with a mean of (μ) and a variance of σ2/N as N, the 

sample size, increases (Durrett, 1996). 

When the sample size is smaller than 15 and the distribution of the data is unknown, the 

Central Limit Theorem cannot be used to support the normality assumption. Statistical test of the 

kurtosis, skewness, and goodness of fit test are then used to evaluate the normality assumption. 

The skewness statistic (S) characterizes the degree of asymmetry of a given data distribution. 

Normally distributed data have an S value of 0. An S value that is greater (less) than 0 indicates 

that the data are asymmetrically distributed with a right (left) tail extending towards positive 

(negative) values. Further, the standard error of the skewness statistic (SES) can be 

approximated by SES = SQRT(6/N), where N is the sample size. According to the small sample 

skewness hypothesis test, if the S value is greater than two times the SES, the data distribution 

can be considered non-normal. The kurtosis statistic (K) characterizes the degree of peakedness 

or flatness of a given data distribution in comparison to a normal distribution. Normally 

distributed data have a K value of 3. A K value that is greater (less) than 3 indicates a relatively 

peaked (flat) distribution. Further, the standard error of the kurtosis statistic (SEK) can be 

approximated by SEK = SQRT(24/N), where N is the sample size. According to the small 

sample kurtosis hypothesis test, if the K value is greater than two times the SEK value, the data 

distribution is typically considered to be non-normal. 
6 

For each data set to which the UPL was applied (i.e., the separate data sets for each HAP 

and HAP surrogate type applicable to the subcategory), the S and K statistics were calculated 

using both the reported test values and the log-transformed reported test values. If the S and K 

values statistics of the reported data set were both less than twice the SES and SEK, respectively, 

the dataset was classified as normally distributed. If neither of the S and K values, or only one of 

these statistical values were less than twice the SES or SEK, respectively, then the skewness and 

kurtosis hypothesis tests were conducted for the natural log-transformed data. If the S and K 

values of the log-transformed reported data set were both less than twice the SES and SEK, 

respectively, the log-transformed dataset was classified as normally distributed. In this case, the 

MACT floor was calculated using an UPL equation developed for log-normal data (Bhaumik and 

Gibbons, 2004). If both the reported values and the natural-log transformed reported values had 

S and K values that were greater than twice the SES or SEK, respectively, the normally 

distributed dataset was selected as the basis of the floor to be conservative. If the results of the 

skewness and kurtosis hypothesis tests were mixed for the reported values and the natural logtransformed reported values, the normal distribution was chosen to be conservative. This 

approach is more accurate and obtained more representative results than a more simplistic 

normal distribution assumption. 

Specifically, in the case of normal distributed data, the MACT floor limit is an UPL 

calculated as: 

UPL = 2

,.99

1 1

df xt s

n m

       

Where: 

 = mean of the top performing sources calculated as 

1 1

1 i N n

ij

i j

x x

n  

 

n = Number of test runs = 

m = Number of future test runs in the compliance average 

N = Number of sources 

s

2

 = pooled variance calculated as 

t df, 99 = 99th – quantile of t-distribution with df degrees of freedom 

df = degrees of freedom calculated as 

 

1

N

i

i

n





 2 2

1

1

1

n

i

i

s x X

n 

   

1

1

N

i

i

df n 

        
7 

This calculation was performed using the following Excel® functions: 

Normal distribution: 99th Confidence UPL = AVERAGE(Test Runs in Top 12%) + 

[STDEV(Test Runs in Top 12%) x TINV(2 x probability, n-1 degrees of 

freedom)*SQRT((1/n)+(1/m))], for a one-tailed t-value, probability of 0.01, and sample 

size of n. 

The 99th confidence UPL was selected as a reasonable upper limit because only 1 percent 

of future tests of the MACT pool of lowest emitting EGUs will exceed the limit if they are 

performing as well as the emission test data indicate (i.e., these EGUs will be below or achieve 

the limit 99 percent of the time in the future). If variability was not accounted for in this manner 

and a limit was set based solely on the average performance, then these EGUs could exceed the 

limit half the time or more. 

For some data sets, a single floor average per source or unit was available; analysis based 

solely in these single per unit observations will not reflect any possible within-source variability. 

In cases where additional available emissions data from past years were available, it was decided 

to incorporate these data in the estimation of the variance term, s2

, allowing for consideration of 

within- and between-source variability. The most recent data (e.g., single floor average) were 

used to calculate the average in the UPL equation. The UPL equation for this case is calculated 

as: 

UPL = 2

,.99

1 1

df xt s

N m

       

Where: 

m = Number of future test runs in the compliance average 

N = Number of units involved in calculating the average (a single measurement (e.g., floor 

average) per unit) 

ni = Number of data points (e.g., stack averages) collected in the past for the i-th source 

1

N

i

i

nN n  

i x = Current information (e.g., single floor average) for the i-th source 

i y = Past information (e.g., stack average) for the i-th source 

x = mean of the top performing sources calculated as 1

1 N

i

i

x x

N 

 

x

 = grand mean (mean of the current and past information from the top performing sources 
8 

1 11

1 i N N n

i i

i ij

x x y

n  

 

       

s

2

 = variance calculated as     2 2 2

1 11

1

1

i N N n

i ij

i ij

s xx y x

n  

 

         

t df, 99 = 99th quantile t-distribution with df degrees of freedom 

df = Degrees of freedom = n -1 

The calculation of this UPL was performed using the following Excel® function: 

Normal distribution: 99% UPL = AVERAGE (Test Runs in Top 12%) + [STDEV(Test 

Runs in Top 12%, stack averages) x TINV(2 x probability, (n-1) degrees of 

freedom)*SQRT((1/N)+(1/3))], for a one-tailed t-value (with 2 x probability), probability 

of 0.01, and sample size of n. 

The UPL, to test compliance based on a 3-run average and assuming log-normal data, is 

calculated by the following equation (Bhaumik and Gibbons, 2004): 

2ˆ 22 2 2

2 4 ˆ .99 2 22 ˆˆ ˆ ˆˆ ˆ ˆ ( 1) 2( 1)

z UPL e me e m e

m nn

          

        

Where: 

  1

log ˆ

n

i i y

n

    the average of the log transformed data from the top performing sources 

    2

2 1 log ˆ ˆ 1

n

i i y

n



    

 the variance estimate of the log transformed data from the top 

performing sources 

z.99 is the 99th-percentile of the log-normal distribution estimated using the trapezoidal rule 

approach from the following equation: 

  .99    2 4

1 3 2

0

336

1 3 ( ) .99 6 24

z z z z z

zz z

  

        

  
9 

The calculation of this log-normal based UPL was performed using the following Excel®

function: 

Normal distribution: 99% UPL = 

EXP(AVERAGE(LN(Test Runs in Top 12%)) + VAR(LN(Test Runs in Top 12%))/2) + 

(99TH-PERCENTILE LOGNORMAL DISTRIBUTION/m)* 

SQRT(m*EXP(2* AVERAGE(LN(Test Runs in Top 12%))+ VAR(LN(Test Runs in Top 

12%)))*(EXP(VAR(LN(Test Runs in Top 12%)))-1)+ 

m^2* EXP(2* AVERAGE(LN(Test Runs in Top 12%))+ VAR(LN(Test Runs in Top 

12%)))*( VAR(LN(Test Runs in Top 12%))/n+ VAR(LN(Test Runs in Top 12%))^2/(2*(n1))) 

The 99th percentile of the log-normal distribution was calculated following Bhaumik and 

Gibbons (2004). 

Adjustment for Below Detection Level Emissions Data 

To account for the effect of measurement imprecision associated with the data in the ICR 

databases (that include method detection level data), a protocol specified by the EPA was used. 

The procedure for determining a representative detection level (RDL) begins with identifying all 

of the available reported pollutant-specific method detection levels for the best performing units 

regardless of any subcategory (e.g., existing or new, fuel type, etc.). From that combined pool of 

data, we calculate the arithmetic mean value. By limiting the data set to those tests used to 

establish the floor or emissions limit (i.e., best performers), the EPA believes that the result is 

representative also of the best performing testing companies and laboratories. The EPA also 

believes that the outcome should minimize the effect of a test(s) with an inordinately high 

method detection level (e.g., the sample volume was too small, the laboratory technique was 

insufficiently sensitive, or the procedure for determining the detection level was other than that 

specified). The EPA then calls the resulting mean of the method detection levels the RDL, and 

the Agency considers it characteristic of accepted source emissions measurement performance. 

The second step in the process is to calculate three times the RDL to compare with the 

calculated floor or emissions limit. We use the multiplication factor of 3 to approximate a 99 

percent upper confidence interval for a data set of 7 or more values. For comparing to the floor, 

if three times the RDL were less than the calculated floor or emissions limit (e.g., calculated 

from the UPL), we would conclude that measurement variability was adequately addressed. The 

calculated floor or emissions limit would need no adjustment. If, on the other hand, the value 

equal to three times the RDL were greater than the UPL, we would conclude that the calculated 

floor or emissions limit does not account entirely for measurement variability. If indicated, we 

substituted the value equal to three times the RDL for the calculated MACT floor (UPL) 

emissions level. 

The equation used to determine emission rates for these RDLs is located in the summary 

tab of each of the statistical analysis spreadsheets with the exception of the Hg statistical analysis 

spreadsheet. Method 30B mercury stack testing is a performance-based test method and as such 

is not compatible with the “3 x RDL” procedure described above. And, because the vast majority 

of emissions data from Hg testing collected under the ICR is derived from Method 30B testing, 

the procedure was not utilized at all in the Hg statistical analysis spreadsheet. The RDL equation 

that was utilized, in the appropriate spreadsheet, is either Equation 19-1 (if the F factor utilized is 
10 

based on oxygen content, dry basis) or Equation 19-6 (if the F factor utilized is based on carbon 

dioxide content, dry basis) from the EPA’s Method 19. Based on representative concentrations in 

the ICR data set, the EPA chose to use an oxygen concentration of 6 percent or a carbon dioxide 

concentration of 9 percent depending on the subcategory. Depending on the fuel type being 

analyzed (i.e., coal, liquid oil, solid oil, or syngas), a different F factor was utilized as shown in 

Table 1. 

To convert the calculated RDL values from units of lb/MMBtu to units of lb/MWh, the 

EPA derived a conversion factor of 10 million Btu/MW from the 2010 ICR data. This is an 

average factor derived from data and was needed so the minimum RDL’s calculated in 

accordance with Method 19 could be compared to the output based UPLs in units of lb/MWh. 

We determined the RDL for each pollutant using data from tests of all the best 

performers for all of the final regulatory subcategories (i.e., pooled test data). We applied the 

same pollutant-specific RDL and emissions limit adjustment procedure to all subcategories for 

which we established emissions limits. The review cited above resulted in the existing and new 

MACT floors using three times the RDL value rather than the calculated UPL value for the 

pollutants listed in Table 2. 

MACT Floor Analysis Data Set 

In determining the MACT floor levels of performance for each subcategory, two types of 

statistical analyses were utilized depending on the amount of data available from the EGU ICR: 

 The basic component of the variability analysis was used for all existing floor 

calculations to reflect variability between the emissions levels achieved by the 

top performers in the respective subcategory. For smaller data sets (e.g., 

Subcategories 3 and 7) run-by-run data were utilized. For larger data sets (e.g., 

Subcategories 1, 2, 4 and 6), the minimum test average was used. 

 The extended component was added to the variability analysis for pollutants with 

sufficient data to quantify normal variations in unit performance due to various 

operating factors. These analyses always utilized test averages (i.e., no 

run-by-run emissions data sets were used). 

Table 3 indicates by subcategory and pollutant the form of the variability analysis utilized. The 

additional data utilized in the extended analyses were filtered so that only those data from 

emissions tests with the same pollutant control configurations were included. For example, if a 

company supplied Hg emissions data (i.e., annual tests conducted on a unit from 2005 through 

2009) and the air pollution control within the ICR survey, for example, indicated the installation 

of an activated carbon injection (ACI) system and a fabric filter on the unit in 12/2007, only data 

following installation of the most recent APCD upgrade was used. 

After excluding each emissions test conducted on a unit prior to installation of the most 

recent air pollution control upgrade, all available data from the ICR was sorted to determine the 

lowest level of emissions control that was achieved for each unit within each subcategory. 

Available data for each unit reflecting emissions higher than the minimum value were utilized to 

determine the variability of emissions. 
11 

Table 1. F-Factor and Oxygen Content used in Each Representative Detection Level Equation by 

Fuel Type and Subcategory 

Fuel Type Dry F factor (Fd)/O2 

Content (%) 

Carbon F factor (Fc)/CO2 

Content 

Coal (Subcategories 1 and 2) 9,780 / 6 

IGCC (Syngas, Subcategory 3) 2,313 / 9 

Liquid Oil (both Subcategories 4 and 6) 9,180 / 6 

Solid Oil (Subcategory 7) 9,830 / 6 

Table 2. Pollutants where EPA Substituted the 3 x RDL value for the Calculated RDLs by 

Subcategory 

Existing MACT Floors 

(lb/MMBtu) 

Existing MACT 

Floors (lb/MWh) New MACT Floors (lb/MWh) 

Subcategory 1 Sb, Ni Sb, Ni fPM, Metal Total (non-Hg), HCl, 

Sb, As, Be, Co, Pb, Ni, Se 

Subcategory 2 Sb, Ni Sb, Ni fPM, Metal Total (non-Hg), HCl, 

Sb, As, Be, Co, Pb, Ni, Se 

Subcategory 3 Sb, Be, Ni Sb, Be, Ni Be, Co, Ni 

Subcategory 4 None None HCl, HF, As, Be, Cd 

Subcategory 6 None None None 

Subcategory 7 Sb, Be Sb, Be HCl, Sb, As, Be, Co, Ni, Se 

Table 3. Variability Analyses Used in Each MACT Floor Subcategory 

Basic Component of 

Variability Analysis 

(variability across units 

run-by-run) 

Basic Component of 

Variability Analysis 

(variability across 

units test averages) 

Extended Component of 

Variability Analysis 

(variability across best performers 

and unit level variability test 

averages) 

Subcategories 

1 and 2 (Coal) 

N/A 

Total and Individual 

Metals (non-Hg) and 

SO2

fPM, HCl, Hg 

Subcategory 3 

(IGCC, Syngas) All Pollutants N/A N/A 

Subcategory 

4 and 6 (Liquid 

Oil) 

N/A 

Total and Individual 

Metals including Hg 

HCl, HF 

fPM 

Subcategory 7 

(Solid Oil) All Pollutants N/A N/A 

 
12 

In addition to the initial scatter plot analysis conducted on submitted emissions data, 

another outlier analysis was performed once the data were entered into the UPL spreadsheet. 

This outlier analysis (to identify gross outliers) determined if the maximum test average in a 

unit’s set of test averages was two orders of magnitude greater than the minimum value for the 

given unit. Such gross outliers were removed from floor consideration. The third and final level 

of outlier analyses was the use of Tukey's Exploratory Data Analysis Model. 

Only four test averages were excluded from the data sets based on the second outlier 

analysis and no test averages were excluded based on the third outlier analyses. The four 

removed test averages were all associated with Hg emissions tests and were not used to calculate 

the Hg floors for Subcategory 1. All of these data were from Part II stack tests; two of the four 

excluded data points were submitted with no run-level data. Without run-level data, it was not 

possible to further evaluate the validity of these outliers. The two remaining averages reflect 

non-detect values from a Method 29 test on two units sharing a common stack. These units also 

submitted Method 30B run-level data under Part III with emission rates above the detection 

limit. Because the outlier was due to limitation of the sampling method, these test averages were 

removed from further analysis. The emission data averages excluded from each respective 

spreadsheet using the “two orders of magnitude” check and Tukey's Model are shown in 

Row 42 of their respective UPL spreadsheet’s columns (where applicable). 

Other Data Excluded from MACT Floor Data Sets 

There were five companies operating six of the oil-fired EGUs required to perform 

emissions testing by the 2010 ICR that requested permission from EPA to continue their normal 

operating practice of co-firing No. 6 residual fuel oil with natural gas (i.e., greater than 10 

percent natural gas on a heat basis) while conducting their testing in order to meet the ICR 

reporting deadline. The EPA informed the companies in question that they should complete their 

testing and that EPA might use their emissions data in the final MACT floor calculations. The 

EPA ultimately chose to exclude emissions data reported for these EGUs from the data sets used 

for Subcategory 4 and 5 MACT floor calculations because their emissions are not representative 

of other oil-fired EGUs under the ICR. 

One Method 29 test on an oil-fired unit was excluded because the testing contractor 

expressed concerns that the testing had not been completed in accordance with the reference 

method. This excluded data was submitted for Florida Power and Light’s Port Everglades 

Station, Unit 4. 

The MACT floors for new sources are, according to the CAA, based on the emission 

control that is achieved in practice by the best-controlled similar source, as determined by the 

Administrator. In one case, the EPA determined that the unit with the lowest level of emissions 

for a particular HAP was not the best-controlled similar source. For the Subcategory 

7 fPM lb/MMBtu floor limit, the EPA determined that a source with only a fabric filter and an 

SCR was not the best controlled source because a similar unit with a fabric filter, SCR, and a dry 

scrubber had a very similar level of emissions. Therefore, the EPA determined that the best 

controlled source was the unit with the most comprehensive set of air pollution controls. In other 

cases as in the new-source MACT floors for Subcategories 1 and 2, there were situations for 

some pollutants where only a single test average and no individual run-level data were available 

for the EGU identified as the best-controlled source. In these cases, no emission variability could 

be determined based on a single data point. Therefore, the next best-controlled similar source 
13 

with sufficient data to account for variability was used to determine the new-source MACT 

standard as presented in Table 4. 

Additionally, similar to the approach used in the HMIWI rulemaking, if the emission 

limit for new sources was less stringent than the emission limit for existing sources in the same 

subcategory, the EPA decided to use existing-source limits for new sources. Although the 

minimum average test run for the best performing source resulted in the lowest three‐run average 

test, the 99 percent UPL‐based limit incorporated variability between test runs. As the sample 

size—in this case the number of test runs—gets smaller, the t‐statistic increases. When the 

sample size of test runs is small, and there is a large variability between test runs, the calculated 

limit using the UPL approach can be larger than the variability among a larger set of test runs 

from units in the best performing 12 percent, especially if the performance of the best performing 

units is comparable. 

Finally, EPA determined that the best controlled Subcategory 1 unit for Hg emissions 

was Logan, Unit 1 (ORIS 10043) because the only units with lower emissions [Spruance Genco, 

LLC (ORIS 54081), Generators 2a and 2b or Spruance Genco, LLC, Generators 3a and 3b] are 

of an atypical design (stoker units) for the subcategory that does not represent the most recently 

permitted and constructed units reflected in the RACT/BACT/LAER clearinghouse. 

MACT Floor Analysis Results 

Tables 5, 6, 7, and 8 present the new-source and existing-source MACT floor values 

determined for the EGU source category. Attachment B presents the summary tables with mean, 

UPL, and floor values for new and existing sources. The data points removed due to being 

outliers are shown in Attachment C to this memorandum. Attachment D shows the outlier data 

removed via the scatter plot analysis method. It should be noted that all tables presented exclude 

reference to subcategory 5 because no numerical limits were calculated under the MACT floor 

analysis for this subcategory. 

References 

Bhaumik, D.K. and Gibbons, R.D. 2004. An Upper Prediction Limit for the Arithmetic Mean of 

a Lognormal Random Variable. Technometrics, 46(2):239-248. 

Durrett, Richard (1996). Probability: Theory and Examples (Second edition). 
14 

Table 4. EU New-source MACT Floor Data Set Substitutions 

Pollutant Data Set Substitution 

Hg 

(Subcategory 1) 

Did not use the data for either Spruance Genco, LLC (ORIS 54081), Gen 

2a and 2b or Spruance Genco, LLC, Gen 3a and 3b, are of an atypical 

design (stoker units) that does not represent the most recently permitted and 

constructed units reflected in the RACT/BACT/LAER clearinghouse. 

Therefore, the run-level data for Logan, Unit 001 (ORIS 10043) were used 

in the new MACT floor. 

Chromium 

(Subcategory 1 and 2) 

Did not use the data for Dallman, Unit 34 (ORIS 963) as no run-level data 

were available; used the run-level data for Cholla, Unit 3 (ORIS 113) in the 

new MACT floor. 

SO2

(Subcategory 1 and 2) 

Could not use the data for Stanton, Unit 10 (ORIS 2824) or R. Gallagher, 

Unit 2 (1008) as no run-level data were available; used the run-level data 

for Port of Stockton District Energy Facility, Unit 1 (ORIS 54238) in the 

new MACT floor. 

fPM 

(Subcategory 7) 

Could not use the data for Manitowoc, Unit 9 (ORIS 4125) because its 

control configuration does not represent the most recently permitted and 

constructed units reflected in the RACT/BACT/LAER clearinghouse. 

Therefore, the run-level data for Northside, Unit 1A (ORIS 667) were used 

in the new MACT floor. 
15 

Table 5. Summary of Existing-source MACT Floor Results for Hg and Non-Hg Metal HAP 

Subcategory Parameter Antimony (Sb) Arsenic (As) Beryllium (Be) Cadmium (Cd) Chrom

1 

No. in MACT floor 130 130 130 130 

99% UPL of top 12% (i.e., MACT 

floor; except where noted) 

0.80 lb/TBtua

0.0080 lb/GWha

1.1 lb/TBtu 

0.020 lb/GWh 

0.20 lb/TBtu 

0.0020 lb/GWh 

0.30 lb/TBtu 

0.0030 lb/GWh 

2.8 l

0.030 

2 

No. in MACT floor 130 130 130 130 

99% UPL of top 12% (i.e., MACT 

floor; except where noted) 

0.80 lb/TBtua

0.0080 lb/GWha

1.1 lb/TBtu 

0.020 lb/GWh 

0.20 lb/TBtu 

0.0020 lb/GWh 

0.30 lb/TBtu 

0.0030 lb/GWh 

2.8 l

0.030 

3 

No. in MACT floor 2 2 2 2 

99% UPL (i.e., MACT floor) 1.40 lb/TBtua 0.020 lb/GWha 1.5 lb/TBtu 0.020 lb/GWh 0.10 lb/TBtua 0.0010 lb/GWha 0.15 lb/TBtu 0.0020 lb/GWh 2.90 

0.030 

4 

No. in MACT floor 3 3 3 3 

99% UPL of top 12% (i.e., MACT 

floor) 

13 lb/TBtu 

0.20 lb/GWh 

2.8 lb/TBtu 

0.030 lb/GWh 

0.20 lb/TBtu 

0.0020 lb/GWh 

0.30 lb/TBtu 

0.0020 lb/GWh 

5.5 l

0.060 

6 

No. in MACT floor 2 2 2 2 

99% UPL of top 12% (i.e., MACT 

floor) 

2.2 lb/TBtu 

0.020 lb/GWh 

4.3 lb/TBtu 

0.080 lb/GWh 

0.60 lb/TBtu 

0.0030 lb/GWh 

0.30 lb/TBtu 

0.0030 lb/GWh 

31 lb

0.30 

7 

No. in MACT floor 5 5 5 5 

99% UPL of top 5 (i.e., MACT floor) 0.80 lb/TBtua 0.0070 lb/GWha 0.30 lb/TBtu 0.0050 lb/GWh 0.060 lb/TBtua 0.00050 lb/GWha 0.3 lb/TBtu 0.0040 lb/GWh 0.80 

0.020 

Subcategory Parameter Lead (Pb) Manganese (Mn) Nickel (Ni) Selenium (Se) Total Non Hg HAP Metals F

1 

No. in MACT floor 130 130 130 130 130 

99% UPL of top 12% (i.e., MACT floor; except where noted) 

1.2 lb/TBtu 

0.020 lb/GWh 

4.0 lb/TBtu 

0.050 lb/GWh 

3.5 lb/TBtua

0.040 lb/GWha

5.0 lb/TBtu 

0.060 lb/GWh 

0.000050 lb/MMBtu 

0.50 lb/GWh 

0.0

0

2 

No. in MACT floor 130 130 130 130 130 

99% UPL of top 12% (i.e., MACT floor; except where noted) 

1.2 lb/TBtu 

0.020 lb/GWh 

4.0 lb/TBtu 

0.050 lb/GWh 

3.5 lb/TBtua

0.040 lb/GWha

5.0 lb/TBtu 

0.060 lb/GWh 

0.000050 lb/MMBtu 

0.50 lb/GWh 

0.0

0

3 

No. in MACT floor 2 2 2 2 2 

99% UPL (i.e., MACT floor) 189 lb/TBtub 1.80 lb/GWhb 2.5 lb/TBtu 0.030 lb/GWh 6.5 lb/TBtua 0.070 lb/GWha 22 lb/TBtu 0.30 lb/GWh 0.000060 lb/MMBtu 0.50 lb/GWh 0.0

0

4 

No. in MACT floor 3 3 3 3 2f 

99% UPL of top 12% (i.e., MACT floor) 

8.1 lb/TBtu 

0.080 lb/GWh 

22 lb/TBtu 

0.30 lb/GWh 

109 lb/TBtu 

1.1 lb/GWh 

3.3 lb/TBtu 

0.040 lb/GWh 

0.00080 lb/MMBtu 

0.0080 lb/MWh 

0.0

0

6 

No. in MACT floor 2 2 2 2 1f 

99% UPL of top 12% (i.e., MACT floor) 

4.9 lb/TBtu 

0.080 lb/GWh 

20 lb/TBtu 

0.30 lb/GWh 

465 lb/TBtu 

4.1 lb/GWh 

9.8 lb/TBtu 

0.20 lb/GWh 

0.00060 lb/MMBtu 

0.0070 lb/MWh 

0.0

0

7 

No. in MACT floor 5 5 5 5 5 

99% UPL of top 5 (i.e., MACT floor) 

0.80 lb/TBtu 

0.020 lb/GWh 

2.3 lb/TBtu 

0.040 lb/GWh 

9.0 lb/TBtu 

0.20 lb/GWh 

1.2 lb/TBtu 

0.020 lb/GWh 

0.000040 lb/MMBtu 

0.60 lb/GWh 

0.0

0

a Based on 3x the specific test method’s recommended detection limit. b Based on a log normal UPL calculation method. c Subcategory 1 used the top 47 data averages to calculate the MACT floor for mercury. d Subcategory 2 used the top 2 data averages to calculate the MACT floor for mercury. e Beyond the floor. f Subcategory 4 and 6’s Total Non Hg HAP Metals value includes Hg emissions in the floor value. 
16 

Table 6. Summary of Existing-source MACT Floor Results for Acid Gases HAP Sources 

Subcategory Parameter HCl HF 

1 

Number in MACT floor 130 N/A 

99% UPL of top 12% (i.e., MACT floor; 

except where noted) 

0.0020 lb/MMBtu 

0.020 lb/MWh 

N/A 

0.20 

1.5 

2 

Number in MACT floor 130 N/A 

99% UPL of top 12% (i.e., MACT floor; 

except where noted) 

0.0020 lb/MMBtu 

0.020 lb/MWh 

N/A 

0.20 

1.5 

3 

Number in MACT floor 2 N/A 

99% UPL (i.e., MACT floor) 

0.00050 lb/MMBtu 

0.0050 lb/MWh 

N/A 

4 

Number in MACT floor 3 3 

99% UPL of top 12% (i.e., MACT floor) 

0.0020 lb/MMBtu 

0.010 lb/MWh 

0.00040 lb/MMBtu 

0.0040 lb/MWh 

6 

Number in MACT floor 2 2 

99% UPL of top 12% (i.e., MACT floor) 

0.00020 lb/MMBtu 

0.0020 lb/MWh 

0.000060 lb/MMBtu 

0.00050 lb/MWh 

7 

Number in MACT floor 5 N/A 

99% UPL of top 5 (i.e., MACT floor) 

0.0050 lb/MMBtu 

0.080 lb/MWh 

N/A 

0.30 

2.0 

a Based on 3x the specific test method’s recommended detection limit. 
17 

Table 7. Summary of New-source MACT Floor Results for Hg and Non-Hg Metal HAP 

Subcategory Parameter Antimony (Sb) Arsenic (As) Beryllium (Be) Cadmium (Cd) Chromium (Cr) 

1 99% UPL of top performer (test runs) 0.0080 lb/GWha 0.0030 lb/GWha 0.00060 lb/GWha 0.00040 lb/GWh 0.0070 lb/GWhb 2 99% UPL of top performer (test runs) 0.0080 lb/GWha 0.0030 lb/GWha 0.00060 lb/GWha 0.00040 lb/GWh 0.0070 lb/GWhb 3 99% UPL of top performer (test runs) 0.020 lb/GWh 0.020 lb/GWh 0.0010 lb/GWha 0.0020 lb/GWh 0.040 lb/GWh 4 99% UPL of top performer (test runs) 0.010 lb/GWh 0.0030 lb/GWha 0.00050 lb/GWha 0.00020 lb/GWha 0.020 lb/GWh 6 99% UPL of top performer (test runs) 0.0080 lb/GWh 0.060 lb/GWh 0.0020 lb/GWh 0.0020 lb/GWh 0.020 lb/GWh 7 99% UPL of top performer (test runs) 0.0080 lb/GWha 0.0030 lb/GWha 0.00060 lb/GWha 0.00070 lb/GWh 0.0060 lb/GWh 

Subcategory Parameter Lead (Pb) Manganese (Mn) Nickel (Ni) Selenium (Se) Total non-Hg HAP Metals Filter

1 99% UPL of top performer (test runs) 0.0020a lb/GWha 0.0040 lb/GWh 0.040 lb/GWha 0.0060 lb/GWha 0.060 lb/GWha 0.

lb/M

2 99% UPL of top performer (test runs) 0.0020a lb/GWha 0.0040 lb/GWh 0.040 lb/GWha 0.0060 lb/GWha 0.060 lb/GWha 0.

lb/M

3 99% UPL of top performer (test runs) 0.0090 lb/GWh 0.020 lb/GWh 0.070 lb/GWha 0.30 lb/GWh 0.40 lb/GWh 0.080 4 99% UPL of top performer (test runs) 0.0080 lb/GWh 0.020 lb/GWh 0.090 lb/GWh 0.020 lb/GWh 0.00020 lb/MWhc 0.070 6 99% UPL of top performer (test runs) 0.030 lb/GWh 0.10 lb/GWh 4.1 lb/GWhd 0.020 lb/GWh 0.0070 lb/MWhc 0.20 7 99% UPL of top performer (test runs) 0.020 lb/GWhd 0.0070 lb/GWh 0.040 lb/GWha 0.0060 lb/GWha 0.60 lb/GWhd 0.020 

a Based on 3x the specific test method’s recommended detection limit. b EPA chose to use an alternative unit for new MACT floor because it was the lowest emitting tested unit with run-by-run data. c Subcategory 4 and 6’s Total Non Hg HAP Metals value includes Hg emissions in the floor value. d Used existing MACT Floor’s limit as the new MACT floor calculated would have been less restrictive than the existing MACT floor. e EPA chose to use an alternative unit for new MACT floor because of boiler size and design. f EPA chose to use an alternative unit for new MACT floor because it was characteristic of the control technology that a newly built unit will employ. 
18 

Table 8. Summary of New-source MACT Floor Results for Acid Gases HAP Sources 

Subcategory Parameter HCl HF 

1 99% UPL of top performer (test runs) 0.00040 lb/MWha N/A 0.42 99% UPL of top performer (test runs) 0.00040 lb/MWha N/A 0.43 99% UPL of top performer (test runs) 0.0020 lb/MWh N/A 4 99% UPL of top performer (test runs) 0.00040 lb/MWha 0.00040 lb/MWha 6 99% UPL of top performer (test runs) 0.0020 lb/MWh 0.00050 lb/MWhb 7 99% UPL of top performer (test runs) 0.00040 lb/MWha N/A 0.

a Based on 3x the specific test method’s recommended detection limit. b Used existing MACT Floor’s limit as the new MACT floor calculated would have been less restrictive than the existing MACT floor. c EPA chose to use an alternative unit for new MACT floor because it was the lowest emitting tested unit with run-by-run data. 
A-1 

ATTACHMENTS 

 
2 

Attachment A: Explanation of EPA’s Calculation of the Final MACT Floor Values For 

New and Existing Sources 

The EPA received emissions data from industry respondents under the 2010 EGU MACT 

ICR in a number of different units of measure and had to convert them to a common lb/MMBtu 

and lb/MWh basis shown in the statistical analysis spreadsheets. The emissions data could have 

been submitted under Part II of the ICR (historical stack testing conducted from 1/1/2005 to 

12/31/2009) or from Part III of the ICR (testing done in 2010 or 2011 specifically for the EU 

MACT ICR). While the Part III data was submitted in the units of measure specified by the EPA, 

the Part II data came in a variety of units of measure. The procedures used for making these unit 

conversions on Part II ICR emissions data are explained in this Attachment. In addition, the 

EPA’s procedure for converting a unit’s stack emission data from a lb/MMBtu basis to a 

lb/MWh basis is also explained below. 

Part II Emission Calculations 

 The pollutant test results could be entered into the database as an emission factor (e.g., 

lb/MMBtu), an emission rate (e.g., lb/hr) and/or a concentration (e.g., μg/dscm) as a run 

or a test average. Because the MACT floor was calculated using an emission factor 

(lb/MMBtu), a hierarchy was selected to be able to use as much company-provided data 

as possible. The hierarchy was the following order: 

1. Company-provided emission factor 

2. Company-provided emission rate 

3. Company-provided concentration 

 Calculations were used to calculate the emissions factor (lb/MMBtu) from the provided 

emission rate or concentration: 

o Using the emission rate required that one of the following two sets of data were 

provided per run: 

 The unit load (MW), or 

 The fuel flow rate (dry lb/hr) and the fuel heating value (Btu/lb) 

o The calculations were: 

݈ܾ ݐܽ݊ݐݑ݈݈݋݌

ݎ݄

ሺ rate heat unit כ ܹܯ ܽ݀݋݈ ݐ݊݅ݑ

1

MMBtu /MWhሻ ൌ emission factor lb/MMBtu

 ,ݎ݋

݈ܾ ݐܽ݊ݐݑ݈݈݋݌

ݎ݄

݈ܾ ݁ݐܽݎ ݓ݋݂݈ ݈݁ݑ݂ݑݐܤ ݁ݑ݈ܽݒ ݅݊݃ݐ݄݁ܽ ݈݁ݑ݂ כ ݎ݄ݑݐܤܯܯ 1 כ ݈ܾ

ݑݐܤ 1,000,000

ݎ݋ݐ݂ܽܿ ݊݋݅ݏݏ݁݉݅ ൌ

݈ܾ

ݑݐܤܯܯ
3 

o If the units are originally kg/hr, then the following equation is used to convert 

kg/hr to lb/hr 

݇݃ ݐܽ݊ݐݑ݈݈݋݌

݈ܾ כ ݎ݄

 ݐܽ݊ݐݑ݈݈݋݌ ൌ ݇݃ 0.453593

݈ܾ

ݎ݄

o Using the concentration required that one of the following two sets of data were 

provided per run: 

 Fuel type and flue gas oxygen content 

 Fuel type and flue gas carbon dioxide content, and 

 Flue gas moisture content, if concentration was provided on a wet basis. 

o The F-factor method used in EPA Test Method 19 was used to calculate an 

emission factor for each run that provided the necessary data. The following 

equations were used: 

 Equation 19-1: when measurements are on a dry basis for both oxygen and 

pollutant concentrations 

 Equation 19-4: when the pollutant concentration is on a wet basis and 

oxygen concentration is on a dry basis 

 Equation 19-6: when measurements are on a dry basis for both carbon 

dioxide and pollutant concentrations 

 Equation 19-8: when pollutant concentration is measured on a wet basis 

and carbon dioxide is measured on a dry basis 

o Concentration units were converted to lb/scf based on the following conversions 

Concentration Conversions 

Concentration units Conversion to ng/scm Conversion to lb/scf 

gr/scf 2.2883E+09 1.428571E-04 

mg/scm 1000000 6.242797E-08 

ng/scm * 1 6.242797E-14 

μg/scm 1000 6.242797E-11 

*Not used for particulate or mercury conversions. 

o Calculated a Wet_Dry_O2_CO2_Factor 

 If dry O2, factor = ଶ଴.ଽ

ଶ଴.ଽି%ைଶ ௖௢௡௧௘௡௧

 If wet O2, factor = ଶ଴.ଽ

ሺଵି೑೒ ೘೚೔ೞ೟ೠೝ೐ ೎೚೙೟೐೙೟

భబబ ሻכሺଶ଴.ଽିௗ௥௬ %ைଶ ௖௢௡௧௘௡௧ሻ

 If dry CO2, factor = ଵ଴଴

%஼ைଶ ௗ௥௬ ௖௢௡௧௘௡௧
4 

 If wet CO2, factor = ଵ଴଴

ሺଵି೑೒ ೘೚೔ೞ೟ೠೝ೐ ೎೚೙೟೐೙೟

భబబ ሻכሺ%஼ைଶ ௗ௥௬ ௖௢௡௧௘௡௧ሻ

o F-factors**: 

 Fd = 9,780 dscf/MMBtu (bituminous and subbituminous coal) 

 Fc = 1,800 scf/MMBtu (bituminous and subbituminous coal) 

 Fd= 9,860 dscf/MMBtu (low rank virgin coal) 

 Fc = 1,910 scf/MMBtu (low rank virgin coal) 

 Fd = 9,190 dscf/MMBtu (fuel oil) 

 Fc = 1,410 scf/MMBtu (fuel oil) 

**If a Part II test report showed a tested unit firing coal refuse only, and provided the unit’s 

emissions in units of concentration only, an emission factor was not calculated. This was 

because Method 19 does not provide F factors for coal refuse-firing. 

o Completed the calculation as follows: 

ݎ݋ݐ݂ܽܿ ݊݋݅ݏݏ݁݉݅

݈ܾ

ݑݐܤܯܯ

݊݋݅ݐܽݎݐ݊ܿ݁݊݋ܿ ൌ

݈ܾ݂ܿݏ ݎ݋ݐ݂ܽܿ െ ܨ כ ݂ܿݏ

ݎ݋ݐܽܿܨ_ܱ2ܥ_ܱ2_ݕݎܦ_ݐܹ݁ כ ݑݐܤܯܯ

With the exception of the calculations for the output-based Hg MACT floor standard, the EPA 

converted a unit’s reported emission rates from a lb/MMBtu basis to a lb/MWh basis using unitspecific heat rates to convert between the input- (lb/MMBtu) and output- (lb/MWh) based 

emission factors. Each unit’s heat rate was calculated by dividing their maximum heat input by 

the gross summer generating capacity. 

In response to public comments the EPA completed output-based Hg MACT floor calculations 

using a different methodology. The EPA received comments on the proposed rule that the output 

based Hg standard should reflect the heat rates of the most efficient units. One commenter stated 

that the “EPA should not assume a heat rate any higher than 9,854 Btu/kWh in developing a Hg 

MACT limit in terms of lb/GWh to comply with the goal of rewarding energy efficiency.” 

Commenters had also stated that “... the EPA should simply convert the average Hg emission 

rate in lb/MMBtu to lb/MWh (or lb/GWh) based on a reasonable heat rate.” 

The EPA agrees with the commenters that Hg calculations should be completed using a different 

methodology because of the antagonistic relationship between low Hg emissions and high 

thermal efficiency in coal combustion that is evident at the lowest emitters in Subcategory 1.

This antagonistic relationship is attributable to the high carbon content (i.e., high loss on ignition 

(LOI)) typical of inefficient combustion units and the affinity of this high-carbon flue gas stream 
5 

for Hg. For example the units achieving the lowest level of Hg emissions in Subcategory 1 were 

largely stoker-fired units and fluidized bed combustors (FBCs). Many of the stoker-fired units 

and some of the FBCs had approximately 25 to 30 percent lower efficiencies than the most 

efficient pulverized coal-fired units in the floor pool. The best performing unit on a lb/MMBtu 

basis was a stoker unit with an emission factor half the value of the lowest emitting pulverized 

coal source. This disparity between thermal efficiency and Hg removal efficiency increases the 

intra-unit variability predicted by the UPL calculation. 

For the conversion of the Hg emission rates for the best performing (lowest emitting) sources in 

Subcategory 1, EPA utilized the average heat rate for the sources in the input based floor pool 

(i.e., the 47 sources used to set the lbs Hg/MMBtu standard) and maintained the same units and 

their rankings between the input and output based standards. The numerical value of this average 

heat rate is 11.18 MMBtu/MWh. 

In order to eliminate the mercury-specific statistical artifact resulting from the disparity between 

thermal efficiency and mercury removal efficiency exhibited in the lowest emitters in 

Subcategory 1, prior to completing the UPL calculation to set the lb/MWh alternative emission 

standard, EPA converted the lb/MMBtu emission rates for the lowest emitters to lb/MWh by 

multiplying by the average heat rate (11.18 MMBtu/MWh) for the sources in the input based 

floor pool (i.e., the 47 sources used to set the lbs Hg/MMBtu standard) and maintained the same 

units and their rankings between the input and output based standards. 
B-1 

Attachment B: Summary Tables with Mean, Upper Prediction Limit, and Final MACT 

Floor Values for New and Existing Sources 

Table B-1. Subcategory 1 Existing Sources 

Summary of UPLs using emission averages ................................................................................B-2 

Table B-2. Subcategory 2 Existing Sources 

 Summary of UPLs using emission averages ...............................................................................B-3 

Table B-3. Subcategory 3 Existing Sources 

 Summary of UPLs using emission averages ...............................................................................B-4 

Table B-4. Subcategory 4 Existing Sources 

 Summary of UPLs using emission averages ...............................................................................B-5 

Table B-5. Subcategory 6 Existing Sources 

 Summary of UPLs using emission averages ...............................................................................B-6 

Table B-6. Subcategory 7 Existing Sources 

 Summary of UPLs using emission averages ...............................................................................B-7 

Table B-7. Subcategory 1 New Sources 

 Summary of UPLs using emission averages ...............................................................................B-8 

Table B-8. Subcategory 2 New Sources 

Summary of UPLs using emission averages ................................................................................B-9 

Table B-9. Subcategory 3 New Sources 

 Summary of UPLs using emission averages .............................................................................B-10 

Table B-10. Subcategory 4 New Sources 

Summary of UPLs using emission averages ..............................................................................B-11 

Table B-11. Subcategory 6 New Sources 

 Summary of UPLs using emission averages .............................................................................B-12 

Table B-12. Subcategory 7 New Sources 

 Summary of UPLs using emission averages .............................................................................B-13 

 
B-2 

Table B-1. Subcategory 1 Existing Sources - Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MMBtu) 

UPL 

(lb/MMBtu) 

Number of 

units in 

the floor UPL (lb/TBtu) Floor value Units 

Filterable PM 0.00216 0.0278 130 0.030 lb/MMBtu 

Metal total 0.0000179 0.0000453 130 0.000050 lb/MMBtu 

Antimony (Sb) 2.1004E-07 5.5482E-07 130 0.554824085 0.80a lb/TBtu 

Arsenic (As) 3.9963E-07 1.0021E-06 130 1.002124046 1.1 lb/TBtu 

Beryllium (Be) 4.2310E-08 1.1305E-07 130 0.113047058 0.20 lb/TBtu 

Cadmium (Cd) 9.7248E-08 2.0328E-07 130 0.203278401 0.30 lb/TBtu 

Chromium (Cr) 1.1594E-06 2.7159E-06 130 2.715890762 2.8 lb/TBtu 

Cobalt 2.8382E-07 7.2317E-07 130 0.723171199 0.80 lb/TBtu 

Lead (Pb) 5.0430E-07 1.1530E-06 130 1.15298026 1.2 lb/TBtu 

Manganese (Mn) 1.6328E-06 3.9917E-06 130 3.991746516 4.0 lb/TBtu 

Nickel (Ni) 1.3248E-06 3.0971E-06 130 3.097081415 3.5a lb/TBtu 

Selenium (Se) 1.4124E-06 4.6602E-06 130 4.660200683 5.0 lb/TBtu 

Mercury (Hg) 1.9429E-08 1.1324E-06 47 1.132429224 1.2 lb/TBtu 

HCl 0.000190 0.001586 130 0.0020 lb/MMBtu 

SO2 0.063421 0.144796 130 0.20 lb/MMBtu a Based on 3x the specific test method’s recommended detection limit.

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in 

the floor 

UPL 

(lb/GWh) 

Floor 

value Units 

Filterable PM 0.021 0.285 130 0.30 lb/MWh 

Metal total 0.000187 0.000472 130 0.50 lb/GWh 

Antimony (Sb) 2.1488E-06 5.6182E-06 130 0.00561823 0.0080a lb/GWh 

Arsenic (As) 4.1470E-06 1.0434E-05 130 0.01043371 0.020 lb/GWh 

Beryllium (Be) 4.3912E-07 1.1778E-06 130 0.00117776 0.0020 lb/GWh 

Cadmium (Cd) 1.0015E-06 2.1479E-06 130 0.00214787 0.0030 lb/GWh 

Chromium (Cr) 1.2091E-05 2.9125E-05 130 0.02912466 0.030 lb/GWh 

Cobalt 2.9352E-06 7.6633E-06 130 0.00766334 0.0080 lb/GWh 

Lead (Pb) 5.0486E-06 1.1398E-05 130 0.01139832 0.020 lb/GWh 

Manganese (Mn) 1.7012E-05 4.1872E-05 130 0.04187177 0.050 lb/GWh 

Nickel (Ni) 1.4058E-05 3.3263E-05 130 0.03326290 0.040a lb/GWh 

Selenium (Se) 1.5062E-05 4.9694E-05 130 0.04969358 0.060 lb/GWh 

Mercury (Hg) 2.1717E-07 1.2658E-05 47 0.01265789 0.013 lb/GWh 

HCl 0.001918 0.016199 130 0.020 lb/MWh 

SO2 0.642155 1.444099 130 1.5 lb/MWh a Based on 3x the specific test method’s recommended detection limit.
B-3 

Table B-2. Subcategory 2 Existing Sources - Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MMBtu) 

UPL 

(lb/MMBtu) 

Number of 

units in the 

floor 

UPL 

(lb/TBtu) 

Floor 

value Units 

Filterable PM 0.00216 0.0278 130 0.030 lb/MMBtu 

Metal total 0.0000179 0.0000453 130 0.000050 lb/MMBtu 

Antimony (Sb) 2.1004E-07 5.5482E-07 130 0.554824085 0.80a lb/TBtu 

Arsenic (As) 3.9963E-07 1.0021E-06 130 1.002124046 1.1 lb/TBtu 

Beryllium (Be) 4.2310E-08 1.1305E-07 130 0.113047058 0.20 lb/TBtu 

Cadmium (Cd) 9.7248E-08 2.0328E-07 130 0.203278401 0.30 lb/TBtu 

Chromium (Cr) 1.1594E-06 2.7159E-06 130 2.715890762 2.8 lb/TBtu 

Cobalt 2.8382E-07 7.2317E-07 130 0.723171199 0.80 lb/TBtu 

Lead (Pb) 5.0430E-07 1.1530E-06 130 1.15298026 1.2 lb/TBtu 

Manganese (Mn) 1.6328E-06 3.9917E-06 130 3.991746516 4.0 lb/TBtu 

Nickel (Ni) 1.3248E-06 3.0971E-06 130 3.097081415 3.5a lb/TBtu 

Selenium (Se) 1.4124E-06 4.6602E-06 130 4.660200683 5.0 lb/TBtu 

Mercury (Hg) 1.0672E-06 1.0574E-05 2 10.5740272 4.0b lb/TBtu 

HCl 0.000190 0.001586 130 0.0020 lb/MMBtu 

SO2 0.063421 0.144796 130 0.20 lb/MMBtu 

a

 Based on 3x the specific test method’s recommended detection limit. 

b

 Beyond the floor.

 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in the 

floor 

UPL 

(lb/GWh) 

Floor 

value Units 

Filterable PM 0.021 0.285 130 0.30 lb/MWh 

Metal total 0.000187 0.000472 130 0.50 lb/GWh 

Antimony (Sb) 2.1488E-06 5.6182E-06 130 0.00561823 0.0080a lb/GWh 

Arsenic (As) 4.1470E-06 1.0434E-05 130 0.01043371 0.020 lb/GWh 

Beryllium (Be) 4.3912E-07 1.1778E-06 130 0.00117776 0.0020 lb/GWh 

Cadmium (Cd) 1.0015E-06 2.1479E-06 130 0.00214787 0.0030 lb/GWh 

Chromium (Cr) 1.2091E-05 2.9125E-05 130 0.02912466 0.030 lb/GWh 

Cobalt 2.9352E-06 7.6633E-06 130 0.00766334 0.0080 lb/GWh 

Lead (Pb) 5.0486E-06 1.1398E-05 130 0.01139832 0.020 lb/GWh 

Manganese (Mn) 1.7012E-05 4.1872E-05 130 0.04187177 0.050 lb/GWh 

Nickel (Ni) 1.4058E-05 3.3263E-05 130 0.03326290 0.040a lb/GWh 

Selenium (Se) 1.5062E-05 4.9694E-05 130 0.04969358 0.060 lb/GWh 

Mercury (Hg) 1.1464E-05 1.1213E-04 2 0.11213482 0.040b lb/GWh 

HCl 0.001918 0.016199 130 0.020 lb/MWh 

SO2 0.642155 1.444099 130 1.5 lb/MWh a

 Based on 3x the specific test method’s recommended detection limit. 

b

 Beyond the floor. 

 
B-4 

Table B-3. Subcategory 3 Existing Sources - Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MMBtu) 

UPL 

(lb/MMBtu) 

Number of 

units in the 

floor 

Floor 

value Units 

Filterable PM 1.0772E-02 3.5195E-02 2 0.040 lb/MMBtu 

Metal total 2.3539E-05 5.0551E-05 2 0.000060 lb/MMBtu 

Antimony (Sb) 1.1454E-07 4.2298E-07 2 1.4a lb/TBtu 

Arsenic (As) 6.3633E-07 1.4137E-06 2 1.5 lb/TBtu 

Beryllium (Be) 1.1236E-08 2.5025E-08 2 0.10a lb/TBtu 

Cadmium (Cd) 5.9005E-08 1.4769E-07 2 0.15 lb/TBtu 

Chromium (Cr) 1.2311E-06 2.8173E-06 2 2.9 lb/TBtu 

Cobalt (Co) 1.3523E-07 1.1354E-06 2 1.2b lb/TBtu 

Lead (Pb) 5.9758E-06 1.8860E-04 2 189b lb/TBtu 

Manganese (Mn) 1.0094E-06 2.4143E-06 2 2.5 lb/TBtu 

Nickel (Ni) 2.0434E-06 4.9097E-06 2 6.5a lb/TBtu 

Selenium (Se) 1.2342E-05 2.1355E-05 2 22 lb/TBtu 

Mercury 9.1481E-07 2.4877E-06 2 2.5 lb/TBtu 

HCl 1.8795E-04 4.4175E-04 2 0.00050 lb/MMBtu 

a

 Based on 3x the specific test method’s recommended detection limit. 

b

 Based on a log normal UPL calculation method. 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in the 

floor 

Floor 

value Units 

Filterable PM 1.0886E-01 3.5661E-01 2 0.40 lb/MWh 

Metal total 2.3485E-04 4.9940E-04 2 0.50 lb/GWh 

Antimony (Sb) 1.1355E-06 4.1735E-06 2 0.020a lb/GWh 

Arsenic (As) 6.3263E-06 1.3906E-05 2 0.020 lb/GWh 

Beryllium (Be) 1.1164E-07 2.4580E-07 2 0.0010a lb/GWh 

Cadmium (Cd) 5.8654E-07 1.4564E-06 2 0.0020 lb/GWh 

Chromium (Cr) 1.2376E-05 2.8575E-05 2 0.030 lb/GWh 

Cobalt (Co) 1.3574E-06 1.1257E-05 2 0.020b lb/GWh 

Lead (Pb) 5.8991E-05 1.7941E-03 2 1.8b lb/GWh 

Manganese (Mn) 1.0156E-05 2.4517E-05 2 0.030 lb/GWh 

Nickel (Ni) 2.0345E-05 4.8367E-05 2 0.070a lb/GWh 

Selenium (Se) 1.2365E-04 2.1639E-04 2 0.30 lb/GWh 

Mercury 9.0777E-06 2.4576E-05 2 0.030 lb/GWh 

HCl 1.8909E-03 4.4910E-03 2 0.0050 lb/MWh 

a

 Based on 3x the specific test method’s recommended detection limit. 

b

 Based on a log normal UPL calculation method. 
B-5 

Table B-4. Subcategory 4 Existing Sources - Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MMBtu) 

UPL 

(lb/MMBtu) 

Number of 

units in the 

floor 

Floor 

value Units 

Filterable PM 1.3314E-03 2.4893E-02 4 0.030 lb/MMBtu 

Metal total (including Mercury) 2.4825E-05 7.8679E-04 2 0.00080 lb/MMBtu 

Antimony (Sb) 1.4555E-06 1.2398E-05 3 13 lb/TBtu 

Arsenic (As) 4.2018E-07 2.7038E-06 3 2.8 lb/TBtu 

Beryllium (Be) 4.0680E-08 1.3306E-07 3 0.20 lb/TBtu 

Cadmium (Cd) 3.8431E-08 2.0859E-07 3 0.30 lb/TBtu 

Chromium (Cr) 1.1867E-06 5.4468E-06 3 5.5 lb/TBtu 

Cobalt 7.0384E-07 2.0771E-05 2 21 lb/TBtu 

Lead (Pb) 1.1334E-06 8.0993E-06 3 8.1 lb/TBtu 

Manganese (Mn) 3.3671E-06 2.1030E-05 3 22 lb/TBtu 

Mercury (Hg) 1.9933E-08 1.8671E-07 3 0.20 lb/TBtu 

Nickel (Ni) 1.6894E-05 1.0802E-04 3 109 lb/TBtu 

Selenium (Se) 7.4541E-07 3.2101E-06 3 3.3 lb/TBtu 

HCl 1.3813E-04 1.0360E-03 3 0.0020 lb/MMBtu 

HF 5.9000E-05 3.9720E-04 3 0.00040 lb/MMBtu 

 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in the 

floor 

Floor 

value Units 

Filterable PM 1.3315E-02 2.5344E-01 4 0.30 lb/MWh 

Metal total (including Mercury) 2.4851E-04 7.8059E-03 2 0.0080 lb/MWh 

Antimony (Sb) 1.3953E-05 1.1513E-04 3 0.20 lb/GWh 

Arsenic (As) 4.1225E-06 2.6934E-05 3 0.030 lb/GWh 

Beryllium (Be) 4.0527E-07 1.2688E-06 3 0.0020 lb/GWh 

Cadmium (Cd) 3.7605E-07 1.9946E-06 3 0.0020 lb/GWh 

Chromium (Cr) 1.2081E-05 5.8542E-05 3 0.060 lb/GWh 

Cobalt 7.0479E-06 2.0588E-04 2 0.30 lb/GWh 

Lead (Pb) 1.1062E-05 7.8478E-05 3 0.080 lb/GWh 

Manganese (Mn) 3.5511E-05 2.2775E-04 3 0.30 lb/GWh 

Mercury (Hg) 1.8441E-07 1.6744E-06 3 0.0020 lb/GWh 

Nickel (Ni) 1.6341E-04 1.0106E-03 3 1.1 lb/GWh 

Selenium (Se) 7.3915E-06 3.1453E-05 3 0.040 lb/GWh 

HCl 1.3620E-03 9.8579E-03 3 0.010 lb/MWh 

HF 5.8726E-04 3.5975E-03 3 0.0040 lb/MWh 
B-6 

Table B-5. Subcategory 6 Existing Sources - Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MMBtu) 

UPL 

(lb/MMBtu) 

Number of 

units in the 

floor 

Floor 

value Units 

Filterable PM 1.2700E-02 2.1977E-02 2 0.030 lb/MMBtu 

Metal total (including Mercury) 4.5871E-04 5.6896E-04 1 0.00060 lb/MMBtu 

Antimony (Sb) 4.4789E-07 2.1463E-06 2 2.2 lb/TBtu 

Arsenic (As) 2.6443E-06 4.2902E-06 2 4.3 lb/TBtu 

Beryllium (Be) 7.6624E-08 5.0492E-07 2 0.60 lb/TBtu 

Cadmium (Cd) 6.6022E-08 2.5659E-07 2 0.30 lb/TBtu 

Chromium (Cr) 1.3835E-06 3.0666E-05 2 31 lb/TBtu 

Cobalt 1.9783E-05 1.1270E-04 2 113 lb/TBtu 

Lead (Pb) 8.5809E-07 4.8932E-06 2 4.9 lb/TBtu 

Manganese (Mn) 6.6888E-06 1.9361E-05 2 20 lb/TBtu 

Mercury (Hg) 2.1831E-08 3.5917E-08 2 0.040 lb/TBtu 

Nickel (Ni) 4.0120E-04 4.6425E-04 2 465 lb/TBtu 

Selenium (Se) 9.4374E-07 9.7515E-06 2 9.8 lb/TBtu 

HCl 1.2095E-04 1.8416E-04 2 0.00020 lb/MMBtu 

HF 2.1756E-05 5.2130E-05 2 0.000060 lb/MMBtu 

 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in the 

floor 

Floor 

value Units 

Filterable PM 1.3185E-01 2.1372E-01 2 0.30 lb/MWh 

Metal total (including Mercury) 5.0411E-03 6.2527E-03 1 0.0070 lb/MWh 

Antimony (Sb) 4.8254E-06 1.6104E-05 2 0.020 lb/GWh 

Arsenic (As) 2.6572E-05 7.7602E-05 2 0.080 lb/GWh 

Beryllium (Be) 7.9423E-07 2.1190E-06 2 0.0030 lb/GWh 

Cadmium (Cd) 6.3449E-07 2.3752E-06 2 0.0030 lb/GWh 

Chromium (Cr) 1.4080E-05 2.7391E-04 2 0.30 lb/GWh 

Cobalt 2.1952E-04 1.3569E-03 2 1.4 lb/GWh 

Lead (Pb) 9.0902E-06 7.6756E-05 2 0.080 lb/GWh 

Manganese (Mn) 6.9665E-05 2.1207E-04 2 0.30 lb/GWh 

Mercury (Hg) 2.1573E-07 3.6387E-07 2 0.00040 lb/GWh 

Nickel (Ni) 3.5305E-03 4.0854E-03 2 4.1 lb/GWh 

Selenium (Se) 9.9111E-06 1.3208E-04 2 0.20 lb/GWh 

HCl 1.2018E-03 1.8604E-03 2 0.0020 lb/MWh 

HF 2.0860E-04 4.9981E-04 2 0.00050 lb/MWh 
B-7 

Table B-6. Subcategory 7 Existing Sources - Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MMBtu) 

UPL 

(lb/MMBtu) 

Number of 

units in the 

floor Floor value Units 

Filterable PM 2.4854E-03 7.7373E-03 5 0.0080 lb/MMBtu 

Metal total 1.6248E-05 3.3086E-05 5 0.000040 lb/MMBtu 

Antimony (Sb) 3.8154E-08 8.7808E-08 5 0.80a lb/TBtu 

Arsenic (As) 1.4149E-07 2.8119E-07 5 0.30 lb/TBtu 

Beryllium (Be) 1.8805E-08 4.9371E-08 5 0.060a lb/TBtu 

Cadmium (Cd) 9.9768E-08 2.1618E-07 5 0.30 lb/TBtu 

Chromium (Cr) 3.4205E-07 7.2031E-07 5 0.80 lb/TBtu 

Cobalt (Co) 3.4111E-07 1.0863E-06 5 1.1 lb/TBtu 

Lead (Pb) 4.0216E-07 7.4535E-07 5 0.80 lb/TBtu 

Manganese (Mn) 9.7323E-07 2.2392E-06 5 2.3 lb/TBtu 

Nickel (Ni) 3.5824E-06 8.9021E-06 5 9.0 lb/TBtu 

Selenium (Se) 5.0506E-07 1.1126E-06 5 1.2 lb/TBtu 

Mercury 8.2310E-08 1.5996E-07 5 0.20 lb/TBtu 

HCl 1.0296E-03 4.0628E-03 5 0.0050 lb/MMBtu 

SO2 8.0859E-02 2.1346E-01 5 0.30 lb/MMBtu 

a Based on 3x the specific test method’s recommended detection limit. 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in the 

floor Floor value Units 

Filterable PM 2.6840E-02 8.3421E-02 5 0.090 lb/MWh 

Metal total 1.9811E-04 3.6323E-04 5 0.60 lb/GWh 

Antimony (Sb) 4.1331E-07 7.6573E-07 5 0.0080a lb/GWh 

Arsenic (As) 1.6539E-06 4.0507E-06 5 0.0050 lb/GWh 

Beryllium (Be) 2.1359E-07 4.8671E-07 5 0.00060a lb/GWh 

Cadmium (Cd) 1.4616E-06 3.2344E-06 5 0.0040 lb/GWh 

Chromium (Cr) 5.6987E-06 1.4692E-05 5 0.020 lb/GWh 

Cobalt (Co) 4.3110E-06 1.0409E-05 5 0.020 lb/GWh 

Lead (Pb) 5.5763E-06 1.1608E-05 5 0.020 lb/GWh 

Manganese (Mn) 1.4346E-05 3.4025E-05 5 0.040 lb/GWh 

Nickel (Ni) 4.7150E-05 1.2121E-04 5 0.20 lb/GWh 

Selenium (Se) 6.3226E-06 1.3132E-05 5 0.020 lb/GWh 

Mercury 8.4520E-07 1.6051E-06 5 0.0020 lb/GWh 

HCl 1.8168E-02 7.8803E-02 5 0.080 lb/MWh 

SO2 8.3935E-01 1.9019E+00 5 2.0 lb/MWh 

a Based on 3x the specific test method’s recommended detection limit. 

 
B-8 

Table B-7. Subcategory 1 New Sources - Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number 

of units 

in the 

floor 

UPL 

(lb/GWh) Floor value Units 

Filterable PM 0.00224 0.00414 1 0.0070a lb/MWh 

Metal total 0.0000135 0.0000191 1 0.060a lb/GWh 

Antimony (Sb) 2.9040E-08 1.5157E-07 1 0.00015157 0.0080a lb/GWh 

Arsenic (As) 2.4741E-07 7.9714E-07 1 0.00079714 0.0030a lb/GWh 

Beryllium (Be) 1.8323E-08 2.2213E-08 1 0.00002221 0.00060a lb/GWh 

Cadmium (Cd) 7.3840E-08 3.6937E-07 1 0.00036937 0.00040 lb/GWh 

Chromium (Cr) 1.3085E-06 6.3194E-06 1 0.00631940 0.0070b lb/GWh 

Cobalt 1.3748E-07 7.1620E-07 1 0.00071620 0.0020a lb/GWh 

Lead (Pb) 8.9650E-07 1.4190E-06 1 0.00141905 0.0020a lb/GWh 

Manganese (Mn) 1.3326E-06 3.0511E-06 1 0.00305110 0.0040 lb/GWh 

Nickel (Ni) 1.0770E-06 3.1608E-06 1 0.00316076 0.040a lb/GWh 

Selenium (Se) 1.1974E-07 2.7349E-07 1 0.00027349 0.0060a lb/GWh 

Mercury (Hg) 4.6691E-08 1.9899E-07 1 0.00019899 0.000020c lb/GWh 

HCl 0.000113 0.000239 1 0.00040a lb/MWh 

SO2 0.0912 0.3883 1 0.40d lb/MWh 

a

 Based on 3x the specific test method’s recommended detection limit. b

 EPA chose to use an alternative unit for new MACT floor because of the best unit having a single average value (i.e., no run-byrun data). 

c

 EPA chose to use an alternative unit for new MACT floor because of boiler size and design. d

 EPA chose to use an alternative unit for new MACT floor because it was the lowest emitting tested unit with run-by-run data.

 
B-9 

Table B-8. Subcategory 2 New Sources- Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in the 

floor 

UPL 

(lb/GWh) Floor value Units 

Filterable PM 0.00224 0.00414 1 0.0070a lb/MWh 

Metal total 0.0000135 0.0000191 1 0.060a lb/GWh 

Antimony (Sb) 2.9040E-08 1.5157E-07 1 0.00015157 0.0080a lb/GWh 

Arsenic (As) 2.4741E-07 7.9714E-07 1 0.00079714 0.0030a lb/GWh 

Beryllium (Be) 1.8323E-08 2.2213E-08 1 0.00002221 0.00060a lb/GWh 

Cadmium (Cd) 7.3840E-08 3.6937E-07 1 0.00036937 0.00040 lb/GWh 

Chromium (Cr) 1.3085E-06 6.3194E-06 1 0.00631940 0.0070b lb/GWh 

Cobalt 1.3748E-07 7.1620E-07 1 0.00071620 0.0020a lb/GWh 

Lead (Pb) 8.9650E-07 1.4190E-06 1 0.00141905 0.0020a lb/GWh 

Manganese (Mn) 1.3326E-06 3.0511E-06 1 0.00305110 0.0040 lb/GWh 

Nickel (Ni) 1.0770E-06 3.1608E-06 1 0.00316076 0.040a lb/GWh 

Selenium (Se) 1.1974E-07 2.7349E-07 1 0.00027349 0.0060a lb/GWh 

Mercury (Hg) 1.0726E-05 3.4543E-05 1 0.03454321 0.040 lb/GWh 

HCl 0.000113 0.000239 1 0.00040a lb/MWh 

SO2 0.0912 0.3883 1 0.40c lb/MWh a

 Based on 3x the specific test method’s recommended detection limit. b

 EPA chose to use an alternative unit for new MACT floor because of the best unit having a single average value (i.e., no runby-run data). c

 EPA chose to use an alternative unit for new MACT floor because it was the lowest emitting tested unit with run-by-run data.

 
B-10 

Table B-9. Subcategory 3 New Sources- Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in the 

floor 

UPL 

(lb/GWh) 

Floor 

value Units 

Filterable PM 1.5233E-02 7.3966E-02 1 0.080 lb/MWh 

Metal total 2.0439E-04 3.5845E-04 1 0.35844614 0.40 lb/GWh 

Antimony (Sb) 5.3304E-07 1.6941E-05 1 0.01694051 0.020 lb/GWh 

Arsenic (As) 3.7662E-06 1.3169E-05 1 0.01316932 0.020 lb/GWh 

Beryllium (Be) 6.1049E-08 1.5247E-07 1 0.00096255 0.0010a lb/GWh 

Cadmium (Cd) 3.4277E-07 1.6018E-06 1 0.00160182 0.0020 lb/GWh 

Chromium (Cr) 6.7312E-06 3.1134E-05 1 0.03113404 0.040 lb/GWh 

Cobalt 8.9184E-07 3.1390E-06 1 0.00360955 0.0040a lb/GWh 

Lead (Pb) 2.3758E-06 8.6936E-06 1 0.00869363 0.0090 lb/GWh 

Manganese (Mn) 4.8551E-06 1.7680E-05 1 0.01768028 0.020 lb/GWh 

Nickel (Ni) 1.4376E-05 2.7198E-05 1 0.06497191 0.070a lb/GWh 

Selenium (Se) 9.9489E-05 2.9550E-04 1 0.29549610 0.30 lb/GWh 

Mercury (Hg) 4.0666E-06 3.2809E-05 1 0.03280946 0.040 lb/GWh 

HCl 9.0994E-04 1.0743E-03 1 0.0020 lb/MWh 

a

Based on 3x the specific test method’s recommended detection limit.

 
B-11 

Table B-10. Subcategory 4 New Sources-Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in the 

floor Floor value Units 

Filterable PM 9.9560E-03 6.5380E-02 1 0.070 lb/MWh 

Total Metals (including 

Mercury) 1.1139E-04 1.4413E-04 1 0.00020 lb/MWh 

Antimony (Sb) 3.3944E-06 9.1970E-06 1 0.010 lb/GWh 

Arsenic (As) 1.6590E-06 1.7190E-06 1 0.0030a lb/GWh 

Beryllium (Be) 2.8769E-07 2.9925E-07 1 0.00050a lb/GWh 

Cadmium (Cd) 1.4385E-07 1.4963E-07 1 0.00020a lb/GWh 

Chromium (Cr) 8.6940E-06 1.7775E-05 1 0.020 lb/GWh 

Cobalt 3.4404E-06 2.0932E-05 1 0.030 lb/GWh 

Lead (Pb) 2.3853E-06 7.8272E-06 1 0.0080 lb/GWh 

Manganese (Mn) 8.4398E-06 1.3215E-05 1 0.020 lb/GWh 

Mercury (Hg) 6.4837E-08 9.3613E-08 1 0.00010 lb/GWh 

Nickel (Ni) 4.9223E-05 8.6803E-05 1 0.090 lb/GWh 

Selenium (Se) 4.0341E-06 1.4859E-05 1 0.020 lb/GWh 

HCl 1.5213E-04 1.6682E-04 1 0.00040a lb/MWh 

HF 1.5661E-04 1.7130E-04 1 0.00040a lb/MWh a Based on 3x the specific test method’s recommended detection limit.

 
B-12 

Table B-11. Subcategory 6 New Sources-Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in 

the floor Floor value Units 

Filterable PM 9.7155E-02 1.3453E-01 1 0.20 lb/MWh 

Total Metals (including 

Mercury) 5.0411E-03 6.2527E-03 1 0.0070 lb/MWh 

Antimony (Sb) 4.6207E-06 7.7015E-06 1 0.0080 lb/GWh 

Arsenic (As) 2.5646E-05 5.2717E-05 1 0.060 lb/GWh 

Beryllium (Be) 7.7019E-07 1.0080E-06 1 0.0020 lb/GWh 

Cadmium (Cd) 6.0290E-07 1.0847E-06 1 0.0020 lb/GWh 

Chromium (Cr) 9.3654E-06 1.2084E-05 1 0.020 lb/GWh 

Cobalt 1.9888E-04 2.5213E-04 1 0.30 lb/GWh 

Lead (Pb) 7.8624E-06 2.3734E-05 1 0.030 lb/GWh 

Manganese (Mn) 6.7081E-05 9.3682E-05 1 0.10 lb/GWh 

Mercury (Hg) 1.6618E-07 1.8700E-06 1 0.00040a lb/GWh 

Nickel (Ni) 3.5205E-03 7.4115E-03 1 4.1a lb/GWh 

Selenium (Se) 7.6945E-06 1.7693E-05 1 0.020 lb/GWh 

HCl 9.5001E-04 1.1240E-03 1 0.0020 lb/MWh 

HF 2.0082E-04 7.1472E-04 1 0.00050a lb/MWh a Used existing MACT Floor’s limit as the new MACT floor calculated would have been less restrictive than the 

existing MACT floor.

 
B-13 

Table B-12. Subcategory 7 New Sources - Summary of UPLs using emission averages 

Pollutant 

Mean 

(lb/MWh) 

UPL 

(lb/MWh) 

Number of 

units in the 

floor Floor value Units 

Filterable PM 4.4581E-03 1.7873E-02 1 0.020a lb/MWh 

Total Metals 1.3441E-04 5.5697E-04 1 0.60b lb/GWh 

Antimony (Sb) 2.1008E-07 8.4167E-07 1 0.0080c lb/GWh 

Arsenic (As) 4.8046E-07 1.2775E-06 1 0.0030c lb/GWh 

Beryllium (Be) 6.7508E-08 7.0105E-08 1 0.00060c lb/GWh 

Cadmium (Cd) 2.3972E-07 6.2101E-07 1 0.00070 lb/GWh 

Chromium (Cr) 1.2450E-06 5.9693E-06 1 0.0060 lb/GWh 

Cobalt (Co) 6.3762E-07 1.5659E-06 1 0.0020c lb/GWh 

Lead (Pb) 3.9369E-06 1.3036E-05 1 0.020b lb/GWh 

Manganese (Mn) 1.6067E-06 6.1877E-06 1 0.0070 lb/GWh 

Nickel (Ni) 1.9944E-06 6.3292E-06 1 0.040c lb/GWh 

Selenium (Se) 7.0615E-07 8.2187E-07 1 0.0060c lb/GWh 

Mercury 7.1153E-07 1.0105E-06 1 0.0020 lb/GWh 

HCl 2.1559E-04 2.7169E-04 1 0.00040c lb/GWh 

SO2 2.4601E-01 3.6175E-01 1 0.40 lb/MWh 

a

 EPA chose to use an alternative unit for new MACT floor because it more characteristic on the control technology 

that a newly built unit will employ. 

b

 Used existing MACT Floor’s limit as the new MACT floor calculated would have been less restrictive than the 

existing MACT floor. 

c

 Based on 3x the specific test method’s recommended detection limit. 
C-1 

Attachment C: Data Excluded from the Analysis for Existing Sources using the Gross 

Outlier Method or Tukey Exploratory Data Analysis Model 

The following data were excluded from the MACT floor calculations via the Gross Outlier 

Method or the Tukey Exploratory Data Analysis Model (see memorandum text for details of 

these data exclusions): 

HAP Plant name and unit ID Emission value test average 

excluded 

Hg Spruance Genco, LLC (ORIS Code 54081) / Spruance Genco Unit 4A 1.62 x 10-6 lb/MMBtu 

Hg Spruance Genco, LLC (ORIS Code 54081) / Spruance Genco Unit 4A 2.10 x 10-5 lb/MWh 

Hg Spruance Genco, LLC (ORIS Code 54081) / Spruance Genco Unit 4B 1.62 x 10-6 lb/MMBtu 

Hg Spruance Genco, LLC (ORIS Code 54081) / Spruance Genco Unit 4B 2.10 x 10-5 lb/MWh 

Hg TIFD VIII-W, Inc. (ORIS Code 10143) / Colver Power Project Unit 

AAB01 4.07 x 10-6 lb/MMBtu 

Hg TIFD VIII-W, Inc. (ORIS Code 10143) / Colver Power Project Unit 

AAB01 3.74 x 10-5 lb/MWh 

Hg Cedar Bay Generating Company L.P. (ORIS Code 10672) / Cedar Bay 

Station Unit CBA1 2.48 x 10-6 lb/MMBtu 

Hg Cedar Bay Generating Company L.P. (ORIS Code 10672) / Cedar Bay 

Station Unit CBA1 2.87 x 10-5 lb/MWh 
D-1 

Attachment D: Outlier Data Removed From MACT Floor Consideration after The Scatter plot 

Method of Outlier Identification 

Using the scatter plot method of outlier identification (described above), ten data averages were 

removed from MACT floor consideration. These averages are listed below. 

HAP Plant name and unit ID and Report ID Emission value test average 

excluded 

Hg Interstate Power and Light / Burlington, Unit 1 (ORIS Code 1104), 

Report ID: BGS-Hg-20071010 3.62 x 10-3 lb/MMBtu 

Hg Basin Electric Power Cooperative/ Leland Olds, Unit 1 (ORIS Code 

2817), Report ID: LOS Mercury Alstom Demo 5.26 x 10-3 lb/MMBtu 

Hg Basin Electric Power Cooperative/ Antelope Valley Station, Unit 1 

(ORIS Code 6469), AVS Mercury Demo 5.09 x 10-3 lb/MMBtu 

Hg Wisconsin Power and Light / Columbia, Unit 1 (ORIS Code 8023), 

Report ID: COL1-Hg-20071023 6.99 x 10-3 lb/MMBtu 

HCl Allegheny Energy Supply Company LLC / Harrison Power Station, 

Unit 1 (ORIS Code 3944), Report ID: 9 9.00 x 10-1 lb/MMBtu 

HCl Public Service Enterprise Group (PSEG) / Hudson Generating Station, 

Unit 2 (ORIS Code 2403), Report ID: EG08009 3.94 x 10-4 lb/MMBtu 

HCl Public Service Enterprise Group (PSEG) / Hudson Generating Station, 

Unit 2 (ORIS Code 2403), Report ID: EG07044 4.59 x 10-4 lb/MMBtu 

fPM Arizona Public Service Company / Cholla, Unit 3 (ORIS Code 113), 

Report ID: 21 9.21 x 100 lb/MMBtu 

fPM Allegheny Energy Supply Company LLC / Harrison Power Station, 

Unit 1(ORIS Code 3944), Report ID: Report ID: 9 9.76 x 101 lb/MMBtu 

fPM Wisconsin Electric Power Company / South Oak Creek, Unit 7 (ORIS 

Code 4041), Report ID: OCPP-PM-B7B8-6.2005 1.52 x 101 lb/MMBtu 

fPM Wisconsin Electric Power Company / South Oak Creek, Unit 8 (ORIS 

Code 4041), Report ID: OCPP-PM-B7B8-6.2005 8.63 x 100 lb/MMBtu 

fPM Indiantown Cogeneration L.P./ Indiantown Cogeneration L.P., 

Unit AAB01 (ORIS Code 50976), Report ID: 10669-3 2.44 x 101 lb/MMBtu 

fPM Indiantown Cogeneration L.P./ Indiantown Cogeneration L.P., 

Unit AAB01 (ORIS Code 50976), Report ID: from Part III testing 3.22 x 10-6 lb/MMBtu 

SO2

Public Service Enterprise Group (PSEG) / Hudson Generating Station, 

Unit 2 (ORIS Code 2403), Report ID: HUDU2E2PT2OS1-Coal 1.83 x 10-1 lb/MMBtu