# November 17, 2011

Note

Subject: Data and procedure for handling below detection level data in analyzing various

pollutant emissions databases for MACT and RTR emissions limits

To: SPPD MACT manageme nt and rule writers

This is a note regarding the handling of belo w detection level (BDL) data and in developing

representative detection level (RDL) data in ev aluating the floor and setting emissions limits for

your NSPS, MACT, and RTR rule maki ng projects. At the end of th is note is a table similar to

the one we sent you last week but which includes several updates. The upda tes include an easier

to use table (e.g., sampling time versus sample vol ume) and some pollutants not covered in the

initial table (e.g., HCl and filterable PM).

The RDL determination procedure

The revised procedure for determining an RDL starts with identifying all of the available

reported pollutant specific method detection leve ls 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), we believe that the result is representative of the

best performing testing companies and laborat ories using the most sensitive analytical

procedures. We believe that the outcome shoul d minimize the effect of a test(s) with an

inordinately high met hod detection level (e.g. , the sample volume was too small, the laboratory

technique was insufficiently sensitive, or the procedure for determining the minimum value for

reporting was other than the det ection level). We then call th e resulting mean of the method

detection levels as the represen tative detection level (RDL) as characteristic of accepted source

emissions measurement performance.

The second step in the process is to calculate th ree times the RDL to comp are with the calculated

floor or emissions limit. This step is simila r to what we have used before in rulemaking

applications. We use the multiplication factor of three to approximate reduce the imprecision of

the analytical method until the imprecision in the field sampling reflects the relative method

precision as estimated by the ASME study 1 

# that also indicates that such relative imprecision,

from 10 to 20 percent, remains constant over th e range of the method.es. 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 w ould conclude that measurement variability was adequately

addressed. The calculated floor or emissions lim it 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 meas urement variability. If

indicated, we substituted the value equal to th ree times the RDL for the calculated floor or

emissions limit which results in a concentra tion where the method would produce measurement

1 

# (ReMAP): PHASE 1, Precision of Manual Stack Emission Measurements; American Society of Mechanical Engineers, Research Committee on

Industrial and Municipal Waste, February 2001.

# accuracy on the order of 10 to 20 percent similar to other EPA test methods and the results found

in the ASME study.

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

of the final regulatory subcateg ories (i.e., pooled test data). We applied the same pollutantspecific RDL and emissions limit adjustment pr ocedure to all subcategories for which we

established emissions limits. We believe that emissions limits adjusted in this manner better

ensure measurement variability is adequately addressed relative to compliance determinations

than did the procedure applied fo r the proposal that may have been based on data sets smaller

than seven tests and as few as one test. We al so believe that the emissions testing procedures

and technologies available now and in the future will be adequate to provide the measurement

certainty sufficient for sources to demonstrate comp liance at the levels of the adjusted emissions

limits when applied in the manner re presentative of this protocol.

We recommend that rule writers considering emissions limits for these pollutants review

the existing data sets and compare the RDL value s used in earlier analyses with the revised

RDLs shown in the attached table. We believe that these revised values and the procedures

described in the table better reflect representat ive method capabilities and should be used

in data review for current rule development projects and in setting representative

emissions limits.

Results of MDL/RDL data analyses

We have collected data used for the boilers ru le reconsideration and the proposed utility MACT

in light of the comments to revi ew the effect of available larg er pools of dioxin/furan emissions

as measured with Method 23 and the Hg emissions as measured with Method 29 of data for these

sources. The expanded data set represents seve ral hundred emissions test s used in the floor

calculations (i.e., best performers) for the boilers a nd utility rules. We presume that data for the

best performing units also reflect the capabi lities of high quality testing companies and

laboratories. Further, the me thod detection levels calculated from larger data are more

representative of the inherent measurement variability both within and between testing

companies. We have also included data on the RDL values for the individual metals as

measured with Method 29 based on a similar assessment of data collected during method

development. The tables attached belo w express the results in two formats:

1) The mass of pollutant sample the method can detect quantitatively and is representative of the

method detection level (RDL) for the set of data collected for the specific rule development; and

2) The lowest concentrations that could be measured quantitatively for a range of sample

volumes for use in comparing to calculated UPL values and in setting applicable emissions

limits.

The first table represents a thorough review of D/ F emissions data for both the boilers and utility

data sets. Not too surprisingly, the resulting values are similar but not identical. Our first

observation is that these calcula ted representative detection le vels are generally greater in

# magnitude than those calculated for the initial reviews and particularly for establishing new

source limits (i.e., for the single best performing unit). The second observation is that the RDLs

determined for the utility ICR data set are lower in magnitude than for the boiler data collected

during an earlier ICR project. We believe that the boiler data set includes some data reported

incorrectly (e.g., laboratory repor ting limits rather than method detection limits) and that the

utility D/F data set includes fewer of these misr eported data. As a resu lt, we believe that the

RDLs determined from the utili ty D/F data set are more repr esentative of current expected

measurement data quality. The application proc edures described in th e table reflect this

conclusion.

Also attached to this note is a spreadsheet ex ample of the calculations used to develop these

values.

As rule writers collect additional data in the future and test methods and techniques improve,

there will be a need to assess new data for repres entative method detection capabilities. We will

prepare new procedures for you a nd your contractors to use as needed in future rule making

activities based on these findings. We will build on these procedures to reflect greater reliance

on the broadest set of measurement data availabl e and provide default values to use when there

are only a few (e.g., fewer than seven) performance test results available for a source category.

Peter Westlin

Measurement Policy Group

Sectors Policies and Programs Division

Addressees:

SPPD management

SPPD technical staff

cc:

Conniesue Oldham, MTG, AQAD

Jason Dewees, MTG, AQAD

Kim Garnett, MTG, AQAD

Kristen Benedict, MTG, AQAD

Ray Merrill, MTG, AQAD

Robin Segall, MTG, AQADSummary of pollutant emissions representative method detection level analysesand a regulatory emissions limit setting procedureRDL mass(ng)3xRDL(ng)Concentrations(ng/dscm)21 hour test 2 hour test 3 hour test 4 hour test 6 hour test 8 hour testInd. Boilers D/F totalmass(Method 23)5.6E-011.7E+001.7E+00 8.5E-01 5.7E-01 4.3E-01 2.8E-01 2.1E-01Ind. Boilers TEQ(Method 23)8.2E-022.5E-012.5E-01 1.3E-01 8.3E-02 6.3E-02 4.2E-02 3.1E-02Utilities D/F total mass(Method 23)3.1E-019.2E-019.2E-01 4.6E-01 3.1E-01 2.3E-01 1.5E-01 1.2E-01Utilities TEQ(Method 23)3.6E-021.1E-011.1E-01 5.5E-02 3.7E-02 2.8E-02 1.8E-02 1.4E-02Concentrations (ug/dscm)(ug)(ug)1 hour test2 hour test 3 hour test 4 hour testHCl/Cl2 (Method 26) 1.0E+13.0E+12.5E+2 1.3E+2HCl/Cl2 (Method 26A) 6.0E+11.8E+21.8E+2 9.0E+1 6.0E+1 4.5E+1PM filterable (Method 5) 1.0E+33.0E+33.0E+3 1.5E+3 1.0E+3 7.5E+2Ind. Boiler Hg (Method 29) 8.3E-012.5E+002.1E+00 1.0E+00 7.1E-01 6.2E-012For the purposes of these calculations, a 1 hour sample collected with Methods 5, 23, and 26A, represents 1 dscm; a 1 hour sample with Method 29 represents1.2 dscm; and a 1 hour sample collected with Method 26 represents 120 L.Summary of pollutant emissions representative method detection level analyses and regulatoryemissions limit settingprocedure for Method 29 Metals using Atomic Emission or Atomic Absorption AnalysisMethod 29 MetalRDLICP/AESor AA(ug)3 X RDLICP/AESor AA(ug)Concentrations( 

# g/dscm)1 hour test 2 hour test 3 hour test 4 hour testAntimony 11.5 34.5 34.5 17.3 11.5 8.6Arsenic 19.1 57.3 57.3 28.7 19.1 14.3Barium 0.8 2.4 2.4 1.2 0.8 0.6Beryllium 0.11 0.33 0.33 0.2 0.1 0.1Cadmium 1.5 4.5 4.5 2.3 1.5 1.1Chromium 2.5 7.5 7.5 3.8 2.5 1.9Cobalt 2.5 7.5 7.5 3.8 2.5 1.9Copper 2.1 6.3 6.3 3.2 2.1 1.6Lead 15.1 45.3 45.3 22.7 15.1 11.3Manganese 0.7 2.1 2.1 1.1 0.7 0.5Mercury 0.56 1.68 1.68 0.8 0.6 0.4Nickel 5.4 16.2 16.2 8.1 5.4 4.1Phosphorus 27 81 81 40.5 27.0 20.3Selenium 27 81 81 40.5 27.0 20.3Silver 2.6 7.8 7.8 3.9 2.6 2.0Thallium 14.4 43.2 43.2 21.6 14.4 10.8Zinc 0.8 2.4 2.4 1.2 0.8 0.6RDL = Method derived regulatorydetection limit based on 1.25 dscm collected in 1 hour.ICP/AES = Inductively Coupled ArgonPlasma/Atomic Emission SpectroscopyAA = Atomic Absorption SpectroscopyGFAA = Graphite Furnace Atomic Absorption spectroscopySummary of pollutant emissions representative method detection level analysesand regulatory emissions limit settingprocedure for Method 29 Metals using AtomicEmission or Atomic Absorption AnalysisMethod 29 MetalRDLICP/MSor GFAA( 

# g)3 X RDLICP/MS orGFAA( 

# g)Concentrations( 

# g/dscm)1 hour test 2 hour test 3 hour test 4 hour testAntimony 1.1 3.3 1.65 1.1 0.825 1.65Arsenic 0.4 1.2 0.6 0.4 0.3 0.6Barium 0.8 2.4 1.2 0.8 0.6 1.2Beryllium 0.08 0.24 0.12 0.08 0.06 0.12Cadmium 0.03 0.09 0.045 0.03 0.0225 0.045Chromium 0.3 0.9 0.45 0.3 0.225 0.45Cobalt 0.3 0.9 0.45 0.3 0.225 0.45Copper 2.1 6.3 3.15 2.1 1.575 3.15Lead 0.3 0.9 0.45 0.3 0.225 0.45Manganese 0.3 0.9 0.45 0.3 0.225 0.45Mercury* 0.56 1.68 0.84 0.56 0.42 0.84Nickel 5.4 16.2 8.1 5.4 4.05 8.1Phosphorus 27 81 40.5 27 20.25 40.5Selenium 0.8 2.4 1.2 0.8 0.6 1.2Silver 2.6 7.8 3.9 2.6 1.95 3.9Thallium 0.3 0.9 0.45 0.3 0.225 0.45Zinc 0.8 2.4 1.2 0.8 0.6 1.2*Mercury analyzed by Cold Vapor AARDL = Method derived regulatorydetection limit based on 1.25 dscm collected in 1 hour.ICP/MS = Inductively CoupledArgon Plasma/Mass SpectrometryGFAA = Graphite Furnace Atomic Absorption spectroscopyExcept for assessing boiler and CISWI data, werecommend that you selectD/F data calculated from theutilities’ data set rather thanfor the industrial boilers in conducting the following analyses.1.Calculate the UPL for your respective data set in units of pollutant mass as sampled by the test method (e.g., total ng of D/F,total TEQ of D/F, ug of Hg).2.Compare the 3xRDL mass value (shown inbold) to the calculated UPL. If 3xRDLmass < UPL mass, use the UPL value forrulemaking. If 3xRDL > UPL, use the 3xRDL value for rulemaking. For source categories other than boilers, use the 3xRDLD/F values shown above for Utilities.3.Alternatively, you may calculate the UPL for your data set in units of pollutant concentration (ng/dscm for D/F, ug/dscm forHg). If so, repeat steps 1 and 2 selecting the concentrationassociated with the sample volume appropriate for your ICR orregulatory decision. You may also determineto convert the values in the table to other emissions formats (e.g., lb/MMBtu orlb/MWh) for these comparisons.Example spreadsheet:(ng/dscm@7percentO2)ngngmass(averageofallcongenerdatainset)TEQ(averageofallTEQpercongenerinset)labmassTEQTotalOCDD2.19E‐026.24E‐068.77E‐022.50E‐05TotalOCDF6.72E‐031.89E‐062.69E‐027.55E‐061,2,3,4,6,7,8HpCDD2.95E‐032.70E‐051.18E‐021.08E‐041,2,3,4,6,7,8HpCDF6.10E‐036.02E‐052.44E‐022.41E‐041,2,3,4,7,8HxCDD1.16E‐031.06E‐044.63E‐034.25E‐041,2,3,4,7,8HxCDF8.24E‐038.10E‐043.30E‐023.24E‐031,2,3,4,7,8,9HpCDF3.08E‐033.00E‐051.23E‐021.20E‐041,2,3,6,7,8HxCDD1.33E‐031.23E‐045.32E‐034.93E‐041,2,3,6,7,8HxCDF9.64E‐048.83E‐053.86E‐033.53E‐041,2,3,7,8PeCDD4.40E‐034.33E‐031.76E‐021.73E‐021,2,3,7,8PeCDF1.82E‐035.26E‐057.29E‐032.10E‐041,2,3,7,8,9HxCDD3.37E‐033.26E‐041.35E‐021.30E‐031,2,3,7,8,9HxCDF7.81E‐046.93E‐053.12E‐032.77E‐042,3,4,6,7,8HxCDF2.35E‐032.27E‐049.40E‐039.09E‐042,3,4,7,8PeCDF1.61E‐034.61E‐046.43E‐031.85E‐032,3,7,8‐TCDD3.38E‐033.34E‐031.35E‐021.34E‐022,3,7,8‐TCDF2.24E‐032.18E‐048.98E‐038.73E‐04maxDL2.19E‐024.33E‐038.77E‐021.73E‐02minDL7.81E‐041.89E‐063.12E‐037.55E‐06meanDL4.26E‐036.05E‐041.70E‐022.42E‐03sum7.24E‐021.03E‐022.90E‐014.11E‐02RDL=EDLx21.45E‐012.06E‐025.80E‐018.22E‐02RDLx3>floor?4.35E‐016.17E‐021.74E+002.47E‐01