MEMORANDUM

TO: Brian Shrager/SPPD

FROM: Eastern Research Group, Inc.

DATE: November 2011

SUBJECT: Analysis of Dioxin/Furan Data and Minimum Detection Levels from Industrial,

Commercial, and Institutional Boilers and Process Heaters National Emission

Standards for Hazardous Air Pollutants – Major Source

1.0 INTRODUCTION

The purpose of this memorandum is to discuss the methodology used to compute a

value equal to three times the representative method detection limit (3x RDL) and how these

3x RDL values were used to establish emission standards for boilers and process heaters at

major sources of hazardous air pollutants.  3x RDL values were computed for dioxin/furan on a

toxic‐equivalent basis (TEQ D/F), mercury (Hg), filterable particulate matter (PM), and hydrogen

chloride (HCl) emissions data.  For each pollutant, a 3x RDL value was estimated by the EPA

Emissions Measurement Center (EMC) using data reported to support this rulemaking effort.1,2  

These 3x RDL values were estimated for various sample volumes and test methods in  each

subcategory for each of the aforementioned pollutants.  The calculated 3x RDL values were

then compared to the corresponding upper prediction limits (UPL) for the same subcategory in

order to determine whether the calculated UPL were below levels that could be reasonably

measured.  A discussion of the methodology used to assess the statistical variability in pollutant

emissions is presented in another memorandum.3

This memorandum is separated into the following sections:

1.0 Introduction
2.0 Background

3.0 Standardizing the 3x RDL to the Boiler/Process Heater Dataset

4.0 Calculating Pollutant‐Specific 3x RDL

5.0 Comparison of 3x RDL to Upper Prediction Limits (UPL)

6.0 References

Appendix A: Calculation of 3x RDL for TEQ Dioxins/Furans

Appendix B: Calculation of 3x RDL for Mercury (Hg)

Appendix C: Calculation of 3x RDL for Filterable Particulate Matter (PM)

Appendix D: Calculation of 3x RDL for Hydrogen Chloride (HCl)

Appendix E: Calculation of 3x RDL for Sum of Eight Selected Metallic HAP (TSM8)

   
2.0 BACKGROUND

Representative method detection levels (RDL) were calculated using different

methodology than that used for the promulgated March, 2011 rule.  Previously, the largest top

performer test run value flagged as below detection level (BDL) or detection level limited (DLL)

that was no greater than the mean of the best performer test run dataset was used to

represent the RDL for the subcategory.  This value was then multiplied by three in order to get a

3x RDL value.  A detailed description of the methods used to calculated 3x RDL values for the

promulgated rule can be found in another memorandum.4

In response to public comments and petitions on the approach used to estimate the 3x

RDL values, the EPA Emissions Measurement Center (EMC) reviewed test reports for Hg, non‐

Hg metals, and dioxin/furan from boilers and process heaters that were identified as best

performers under the March 2011 final rule.  As a result of this review, 3x RDL values were

developed for TEQ D/F and Hg for a variety of sampling times.  In addition to reviewing the test

reports from best performing boilers for Hg and dioxin/furan, EPA also reviewed test method

guidance for HCl and PM in order to establish a 3x RDL value based on published method

guidance for Methods 26 and 26A for HCl and for Method 5I—Determination of Low Level

Particulate Matter Emissions From Stationary Sources.  A discussion of the development of

these 3x RDL levels is detailed in another memorandum.1 A summary of the 3x RDL values is

shown in Table 2‐1 below.
Table 2-1: 3xRDL Mass and Concentrations for Industrial, Commercial, Institutional Boilers and Process Heaters 

According to Sample Time 

Pollutant/

Test Method

3x RDL

Mass (ng)

3x RDL Concentrations1

(ng/dscm, at stack oxygen levels)

1 hour test 2 hour test 3 hour test 4 hour test 5 hour test

TEQ D/F

(Method 23)

0.25 0.250 0.130 0.083 0.063 0.050

Pollutant/

Test Method

3x RDL

Mass (μg)

3x RDL Concentrations1

(μg/dscm, at stack oxygen levels)

1 hour test 2 hour test 3 hour test 4 hour test 5 hour test

Hg

(Method 29)

2.5 2.50 1.20 0.83 0.62 0.50

HCl

(Method 26)

30 250 125 83.3 62.5 50.0

HCl

(Method 26A)

180 180 90 60 45 36

PM

(Method 5I)

3,000 3,000 1,500 1,000 750 600

3.0 STANDARDIZING THE 3x RDL TO THE BOILER/PROCESS HEATER DATASET

The test reports reviewed by EPA focused on top performers as identified in the

promulgated March, 2011 rule with detailed laboratory appendices and test reports available

to review by the July 15th deadline specified in the notice delaying the effective dates of the

March, 2011 rule.4,5  Since the promulgation of that rule, additional test data and test data

corrections were received, which resulted in some changes to the list of top performers used in

this proposal.  A discussion of the additional test data received and corrections to existing test

data is provided in another memorandum.6

  As a result of these changes, the test report review

did not contain the necessary sample times or volumes and stack oxygen concentrations for all

of the current top performers.  The review also included sample times and oxygen

concentrations from units previously identified as best performers in the March Promulgation

that are no longer identified as best performers in this proposed rule.  Due to time constraints,

the sample times, volumes, and oxygen concentrations for these new top performers were

excluded from this 3x RDL analysis in most cases.  However, in limited circumstances, some of

the new test reports were reviewed if none of the current top performers had undergone a test
report review since information on at least one top performing unit’s sample times, volumes,

and oxygen concentrations for each subcategory was necessary in order to complete the

analysis described below.

As noted in Table 2‐1, the 3x RDL concentrations depend on the sampling time and

volume and represent stack conditions and are not adjusted to a specific oxygen concentration.  

However, the emissions data used to rank and identify best performing units for the

development of the Major Source Boiler and Process Heater NESHAP consist of a mixture of

sampling times and were standardized to a pollutant‐specific unit of measure and oxygen

correction.  For TEQ D/F, the standard units of measure were nanograms per cubic meter at dry

standard conditions, corrected to 7 percent oxygen (ng/dscm @ 7% O2).  For Hg, HCl, and PM,

the standard units of measure were pounds per million British thermal units of heat input,

corrected to zero percent oxygen (lb/MMBtu).  The methods and assumptions used to

standardize emissions data are presented in another memorandum.7

In order to compute the 3x RDL values for each subcategory, we developed average

sampling time and oxygen concentration parameters that were representative of the values

observed during stack tests at best performing units.

An analysis of test reports for top performing boilers and process heaters from the

March, 2011 final rule showed that stack sampling times from best performers range anywhere

from one to over four hours.  Sampling times from best performers were grouped according to

each pollutant and subcategory combination.  Then the sampling times in each group were

averaged and the average sample time for each subcategory was rounded to the nearest whole

number.  Because the data reviewed and extracted from the best performing test reports did

not always include a sample time, some assumptions were made to correlate sampling times

with sampling volumes in order to apply the 3x RDL values in Table 2‐1 to each data set.  EMC

staff provided the following guidelines to correlate reported sampling volumes with sample

times:

 For EPA stack testing methods 5I, 23, 29, and 26A, one hour of sampling time

provides a minimum of one cubic meter of stack gas at dry standard conditions.   

   
 For EPA stack testing method 26, one hour of sampling time provides a minimum

of 120 liters of stack gas.   

If sampling volumes were provided in lieu of sampling times, the volumes were

converted to times using the above guidelines and average sample time was computed using a

combination of reported sampling times and estimated sampling times based on reported

sampling volumes.  Next, the 3x RDL value in Table 2‐1 corresponding to the average sample

time was selected as the 3x RDL representing each pollutant/subcategory combination.   

After the appropriate 3x RDL value was identified using the values in Table 2‐1 and the

average sample time for each subcategory, the 3x RDL values needed to be standardized in

order to match the units of measure of the MACT Floor analysis.3  Similar to the grouping and

averaging of sampling times, we reviewed the reported oxygen levels during the stack tests

associated with the best performers for each subcategory and pollutant combination.  Then we

grouped the oxygen levels according to subcategory and pollutant and averaged the reported

stack oxygen levels from all of the top performers in each group.  Next we applied this average

oxygen concentration to adjust the 3x RDL concentrations in Table 2‐1 to standardized oxygen

adjusted values with the appropriate units of measure using Equations 1 and 2, below.

Equation 1 was used to correct the 3x RDL concentrations for TEQ D/F to 7 percent

oxygen:

3ݔ ܴܮܦ்ாொ ஽/ி ൌ ൫3ݔ ܴܮܦ௚௡/ௗ௦௖௠൯כቀ ଶ଴.ଽସ଺ି଻

ଶ଴.ଽସ଺ିைమ

ቁ Equation 1

Where:

3x RDLTEQ D/F = 3x RDL concentration for TEQ D/F, standardized to ng/dscm @ 7% O2.

3x RDLng/dscm = 3x RDL from Table 2‐1, ng/dscm.

20.946 = Constant, percentage of oxygen in ambient air.

7 = Constant, standardized oxygen correction for TEQ D/F.

O2 = Average stack oxygen concentration, percentage.

Equation 2 was used to standardize the 3x RDL concentrations for Hg, HCl, and PM to

lb/MMBtu.  This equation utilizes a fuel‐specific dry F factor (Fd) to convert from a stack gas

concentration basis to a heat input basis.  The Fd factors selected were from EPA Method 19.8

  
EPA Method 19 specifies Fd factors for coal, wood, bark, oil, gas, and municipal solid waste

(MSW).  The bituminous coal Fd factor was used for all coal subcategories since the majority of

the existing coal‐burning boilers and process heaters utilize bituminous coal.  This factor was

also used for the solid fuel subcategory since it is a larger factor than the wood or bark Fd

factors.  The average of the wood and bark Fd factors was used for all biomass subcategories

except stokers designed to burn kiln‐dried biomass; it was assumed that these units do not

burn bark since bark is not classified as a dry biomass in the emissions database for boilers and

process heaters.  Stokers designed to burn kiln‐dried biomass were assigned the wood Fd factor

from EPA Method 19.  EPA Method 19 states that the oil Fd factor applies to crude, residual,

and distillate oils, thus it was used as the basis for all liquid fuel subcategories.  The gas Fd factor

in EPA Method 19 applies to natural gas, propane, and butane; there is no process gas Fd factor.  

However, it was assumed that the process gas Fd factor would most closely equal the gas Fd

factor from EPA Method 19.  These assumptions are consistent with other data standardization

procedures incorporated in the regulatory analysis.7

3ݔ ܴܮܦ௕௟/ெெ஻௧௨ ൌ ൫3ݔ ܴܮܦఓ௚/ௗ௦௖௠൯ כ ሺ1ݔ10ି଺ሻ כ ቀ ଵ

ସହଷ.ହଽቁכቀ ଵଷହ.ଷଵହቁܨכௗ כ ቀ ଶ଴.ଽସ଺ି଴ଶ଴.ଽସ଺ିைమ

ቁ

Equation 2

Where:

3x RDLlb/MMBtu = 3x RDL concentration for Hg, HCl, or PM, standardized to lb/MMBtu.

3x RDLng/dscm = 3x RDL from Table 2‐1, μg/dscm.

1x10‐6 = Conversion factor, nanograms to grams.

453.59 = Conversion factor, grams to pounds.

35.315 = Conversion factor, dscm to dscf.

Fd = Dry F factor from EPA Method 19, dscf/MMBtu.

20.946 = Constant, percentage of oxygen in ambient air.

0 = Constant, standardized oxygen correction for Hg, HCl, and PM.

O2 = Average stack oxygen concentration, percentage.

4.0 CALCULATING POLLUTANT‐SPECIFIC 3x RDL

This section details how the 3x RDL were calculated and summarized for TEQ D/F, Hg,

PM, and HCl.  It also describes the separate methodology used to calculate 3x RDL for the sum
of eight metallic HAP (TSM8), which is composed of arsenic (As), beryllium (Be), cadmium (Cd),

chromium (Cr), lead (Pb), manganese (Mn), nickel (Ni), and selenium (Se).

4.1 Dioxin/Furans

In order to assess the percentage of the reported TEQ D/F data which were reported at

levels that could be reasonably measured, a 3x RDL was calculated for each proposed

combustor‐based subcategory.

Since there are no numeric emission limitations for TEQ D/F, a list of the top performers

from the promulgated March, 2011 rule was used to compute average oxygen and sample

volumes.  In addition to the tests previously reviewed, sample volumes and oxygen

concentrations were retrieved from three additional test reports, one each in the heavy liquid,

light liquid, and coal‐burning fluidized bed subcategories.  The sample times and oxygen

concentrations used in the development of the TEQ D/F 3x RDL values, as well as the

standardized 3x RDL values for TEQ D/F are presented in Appendix A.

4.2 Mercury

A list of all the Hg test data from top performers identified for this proposal for the solid,

liquid, and process gas subcategories was generated.  For each top performer Hg test, sample

times and stack oxygen concentrations were taken from test reports reviewed by EPA.  In

addition, sample times and stack oxygen concentrations were extracted from the a test report

for a unit in the liquid subcategory because the previously reviewed test reports  did not

provide the necessary data for adjusting the 3x RDL values for the liquid subcategory.  The

sample times and oxygen concentrations used in the development of the Hg 3x RDL values are

presented in Appendix B.

4.3 Filterable Particulate Matter

The methods used to calculate 3x RDL values for PM were identical to those used to

calculate 3x RDL values for Hg.  However, since the proposed PM emission limits are unique to

combustor designs, there are more subcategories for which a 3x RDL value was calculated.  
Average oxygen concentrations and sample times were calculated on a combustor‐design basis.  

Given this more detailed subcategorization, five additional test reports were reviewed in order

to extract the relevant sample time or oxygen concentration data needed to compute the 3x

RDL values.  The subcategories needing additional information to compute the 3x RDL were:  

Suspension burners, stokers designed to burn kiln‐dried biomass, units burning heavy/residual

liquids, units burning liquid fuels in non‐continental U.S. States or Territories, and units burning

process gas.  The sample times and oxygen concentrations used in the development of the PM

3x RDL values are presented in Appendix C.

A separate 3x RDL analysis was done for PM for the alternative regulatory option.  The

alternative regulatory option subcategorizes PM emission limits according to fuel type (solid,

liquid, gas) instead of according to combustor design.  More information on the alternative

option can be found in another memorandum.9

  3x RDL values were estimated for these three

subcategories under the alternative regulatory option since the units comprise the best

performers and as a result the computed average sampling times and oxygen concentrations

associated with this option were different.  Aside from the subcategory change, the same

methods used to estimate 3x RDL values for PM under the primary regulatory option were also

used for the alternative option analysis.  The sample times and oxygen corrections used in the

development of the PM 3x RDL values under the alternative option are presented in Appendix

C.

4.4 Hydrogen Chloride

The methods used to estimate 3x RDL values for HCl vary slightly from the methods used

for Hg and PM because there are separate 3x RDL values depending on the method used to

measure the pollutant (EPA Method 26 or 26A).  Instead of computing average sampling times

and oxygen concentrations first, the 3x RDL values were assigned to each unique test run based

on test method used for the measurement and the sampling time associated with each test

run.  Next, these assigned 3x RDL values were standardized to lb/MMBtu using the reported

oxygen concentration for that test run and Equation 2 above.  Finally, all of these 3x RDL values

were averaged for each subcategory.  The sample times, oxygen corrections, and stack testing
methods used in the development of the HCl 3x RDL values are presented in Appendix D.

4.5 Total Selected Metallic HAP (TSM8)

Although the EMC group developed 3xRDL values for individual non‐Hg metallic HAP, a

method for applying the computed 3xRDL values for a TSM8 number was not developed in time

for this proposal and it will be revisited in the final rule.

A separate calculation methodology was used to develop 3x RDL values for TSM8.  Since

TSM8 emissions are calculated from the sum of 8 metallic HAP an approach similar to that

taken for dioxin/furans 3xRDL values in the March final rule was used.  A summary of that

methodology is provided in another memorandum.4 The differences applicable to total selected

metals are described below.  The data used to compute the 3x RDL values for TSM8 is provided

in detail in Appendix E.

 Dioxin/furan emissions are characterized by 17 individual congeners.  A list of

these congeners is provided in another memorandum.10 The eight metals that

comprise TSM8 were treated as the congeners in the development of TSM8 3x

RDL values.  

 Total mass emissions of dioxins/furans were multiplied by a toxic‐equivalency

factor (TEF).  Emissions of TSM8 were developed and analyzed on a total mass‐

basis, and the emissions of the individual metals are not multiplied by a toxicity

factor.

4.6 New Source 3x RDL

New source 3x RDL values were also calculated for Hg, HCl, PM, and TSM8.  No new

source 3x RDL analysis was conducted for TEQ D/F because there are no new source numeric

emission limitations for this pollutant, and because the existing source 3x RDL analysis was

done for the sole purpose of estimating the percentage of test run emissions per subcategory

that were reported below the 3x RDL level.  For each of the other pollutants, the methods used

to calculate the 3x RDL values for existing sources were also used to calculate the new source

3x RDL values.  The only difference was that the subset of top performers was narrowed to

include only the unit that was the basis of the new source UPL calculation for each pollutant

and subcategory group.  The data used to calculate 3x RDL values for new sources for Hg, PM,
HCl, and TSM8 are presented in Appendices B, C, D, and E, respectively.

5.0 COMPARISON OF 3x RDL TO UPPER PREDICTION LIMITS (UPL)

This section discusses how the 3x RDL values for each pollutant compared to the

calculated UPL for the same subcategory.

5.1 Dioxin/Furans

After the conclusion of the 3x RDL analysis, it was noticed that several units reported

nearly all of their congeners as above the detection limit.  The majority of all congener

emissions across all subcategories were reported as either below the method detection limit

(BDL) or detection level limited (DLL).  This prompted a cursory review of the corresponding test

reports for those tests with the majority of the congeners reported above the detection limit.  

Upon review of the reports, these facilities had failed to properly denote the congener

emissions as BDL or DLL, and those flags were updated in the EPA ICR database.  A summary of

these changes is provided in another memorandum.6

The reported TEQ D/F data were then compared with the computed 3x RDL analysis for

each subcategory in order to determine the percentage of the TEQ D/F data reported at levels

that could be reasonably measured.  No data were available for four of the 14 regulated

subcategories.  For each of the remaining 10 subcategories for which TEQ D/F emissions were

available, the vast majority—between 80 and 100 percent for all subcategories—of reported

TEQ D/F data were reported below the computed 3xRDL values.  For six of the 10 subcategories

with D/F data, all of the reported TEQ D/F data were lower than the corresponding 3x RDL

value.  Based on the results of this analysis, it was determined that the application of

measurement technology to these sources is not practicable due to technological and economic

limitations, and the EPA, therefore, is establishing work practice standards in lieu of numeric

emission limitations for the emissions of TEQ D/F.

   
5.2 Mercury (Hg), Hydrogen Chloride (HCl), and Filterable Particulate Matter (PM)

For Hg, HCl, and PM, the calculated 3x RDL for all existing source subcategories were

less than the calculated UPL.  This applies to both the recommended and alternative regulatory

options for PM.  None of the calculated 3x RDL values for existing sources for these pollutants

were selected as the MACT floor.

For new sources, the calculated 3x RDL value was larger than the calculated UPL for two

subcategories:  Hg from solid fuel units, and Hg from liquid units.  The 3x RDL value was

selected as the MACT floor for Hg from solid fuel units.  For Hg from liquid units, a fuel

variability factor (FVF) was applied to the 3xRDL value and that value was selected as the MACT

floor for Hg at new liquid units. The methods used to develop FVF are presented in another

memorandum.3 For each of the remaining Hg, HCl, and PM subcategories for new sources, the

calculated UPL was larger than the calculated 3x RDL value.

5.3 Total Selected Metallic HAP (TSM8)

For the following subcategories for existing units, the calculated TSM8 3x RDL value was

larger than the calculated UPL for the same subcategory:  Hybrid suspension/grate units

designed to combust biomass, fluidized bed units designed to combust coal, and units designed

to combust light liquid.  The 3x RDL value was selected as the MACT floor for the hybrid

suspension/grate and light liquid subcategories.  For the coal‐fired fluidized bed subcategory, a

FVF was applied to the 3xRDL and that value was selected as the MACT floor.  

For the following subcategories for new sources, the calculated TSM8 3x RDL value was

larger than the calculated UPL for the same subcategory:  Fluidized bed units designed to

combust biomass, fuel cells designed to combust biomass, units that combust pulverized coal,

and stokers designed to combust coal.  For each of these subcategories, the calculated 3x RDL

value was selected as the MACT floor.  For each of the remaining subcategories, the calculated

UPL was larger than the calculated TSM8 3x RDL value.

   
6.0 REFERENCES

1. U.S. EPA.  Updated Data and Procedure for Handling Below Detection Level Data in

Analyzing Various Pollutant Emissions Databases for MACT and RTR Emission Limits.  

November 17, 2011.

2. Emissions Database for Boilers and Process Heaters Containing Stack Test, CEM, & Fuel

Analysis Data Reported under ICR No. 2286.01 & ICR No. 2286.03 (version 7).  November

2011.

3. Eastern Research Group, Inc.  Revised MACT Floor Analysis (November 2011) for the

Industrial, Commercial, and Institutional Boilers and Process Heaters National Emission

Standards for Hazardous Air Pollutants – Major Source.  November 2011.

4. Singleton, A., ERG.  Revised MACT Floor Analysis (2011) for the Industrial, Commercial,

and Institutional Boilers and Process Heaters National Emission Standards for Hazardous

Air Pollutants – Major Source.  January 2011.

5. U.S. EPA.  National Emission Standards for Hazardous Air Pollutants for new and existing

sources for Major Source Industrial, Commercial, and Institutional Boilers and Process

Heaters:  Proposed Notice of Selected Reconsiderations.  Federal Register.  Vol. 76, No.

54, pp. 15249.  March 21, 2011.

6. Eastern Research Group, Inc.  Handling and Processing of Corrections and New Data in

the EPA ICR Databses – Revised November 2011.  November 2011.

7. Eastern Research Group, Inc.  Revised (November 2011) Standardization of Reported

Data from the Public Comment Period and Questionnaire for Boilers, Process Heaters,

Incinerators, and Other Combustion Units.  November 2011.

8. U.S. EPA.  Method 19 – Determination of Sulfur Dioxide Removal Efficiency and

Particulate Matter, Sulfur Dioxide, and Nitrogen Oxide Emission Rates.

9. Eastern Research Group, Inc.  Revised (November 2011) Methodology for Estimating

Cost and Emissions Impacts for Industrial, Commercial, and Institutional Boilers and

Process Heaters National Emission Standards for Hazardous Air Pollutants – Major

Source.  November 2011.

10. Eastern Research Group, Inc.  Revised November 2011 Development of Baseline

Emission Factors for Boilers and Process Heaters at Commercial, Industrial, and

Institutional Facilities.  November 2011.

   
APPENDIX A

Calculation of 3x RDL for TEQ Dioxins/Furans  

   
APPENDIX B

Calculation of 3x RDL for Mercury (Hg)

   
APPENDIX C

Calculation of 3x RDL for Filterable Particulate Matter (PM)

   
APPENDIX D

Calculation of 3x RDL for Hydrogen Chloride (HCl)

   
APPENDIX E

Calculation of 3x RDL for Sum of Eight Selected Metallic HAP (TSM8)