December 13, 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 management and MACT rule writers

From: 	Peter Westlin, SPPD, MPG
	Raymond Merrill, AQAD, MTG

This is a note regarding the handling of below detection level (BDL) data and in developing representative detection level (RDL) data in evaluating the floor and setting emissions limits for your NSPS, MACT, and RTR rule making projects.  At the end of this note is a table which includes several updates.  The updates include corrected values for metals RDL, an easier to use table (e.g., sample  volume versus sampling time) 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 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), we believe that the result is representative of the best performing testing companies and laboratories using the most sensitive analytical procedures. We believe 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 minimum value for reporting was other than the detection level).  We then call the resulting mean of the method detection levels as the representative detection level (RDL) as 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. This step is similar 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 that also indicates that such relative imprecision, from 10 to 20 percent, remains constant over the range of the methods. 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 floor or emissions limit which results in a concentration where the method would produce measurement 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 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. 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 for the proposal that may have been based on data sets smaller than seven tests and as few as one test.  We also 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 compliance at the levels of the adjusted emissions limits when applied in the manner representative of this protocol.

We recommend that rule writers considering emissions limits for these pollutants review the existing data sets and compare the RDL values 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 representative 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 rule reconsideration and the proposed utility MACT in light of the comments to review the effect of available larger 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 several hundred emissions tests used in the floor calculations (i.e., best performers) for the boilers and utility rules.  We presume that data for the best performing units also reflect the capabilities of high quality testing companies and laboratories.  Further, the method 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 below 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 calculated representative detection levels 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 reporting limits rather than method detection limits) and that the utility D/F data set includes fewer of these misreported data.  As a result, we believe that the RDLs determined from the utility D/F data set are more representative of current expected measurement data quality.  The application procedures described in the table reflect this conclusion.

Also attached to this note is a spreadsheet example 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 representative method detection capabilities.  We will prepare new procedures for you and 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 available 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

Raymond Merrill
Measurement Technology Group
Air Quality Assessment Division

Addressees:
SPPD management
SPPD technical staff

cc:
Conniesue Oldham, MTG, AQAD
Jason Dewees, MTG, AQAD
Kim Garnett, MTG, AQAD
Kristen Benedict, MTG, AQAD
Robin Segall, MTG, AQAD


Summary of pollutant emissions representative method detection level analyses 
              and a regulatory emissions limit setting procedure
				

                                     RDL 
                                      (ng)
                                 3 x RDL (ng)
                       3 x RDL Concentrations (ng/dscm)

                                       
                                       
                                  1 dscm test
                                  2 dscm test
                                  3 dscm test
                                  4 dscm test
                                  6 dscm test
                                  8 dscm test
Ind. Boilers D/F total mass
(Method 23)
                                    5.6E-01
                                    1.7E+00
                                    1.7E+00
                                    8.5E-01
                                    5.7E-01
                                    4.3E-01
                                    2.8E-01
                                    2.1E-01
Ind. Boilers TEQ
(Method 23)
                                    8.2E-02
                                    2.5E-01
                                    2.5E-01
                                    1.3E-01
                                    8.3E-02
                                    6.3E-02
                                    4.2E-02
                                    3.1E-02
Utilities D/F total mass
(Method 23)
                                    3.1E-01
                                    9.2E-01
                                    9.2E-01
                                    4.6E-01
                                    3.1E-01
                                    2.3E-01
                                    1.5E-01
                                    1.2E-01
Utilities TEQ
(Method 23)
                                    3.6E-02
                                    1.1E-01
                                    1.1E-01
                                    5.5E-02
                                    3.7E-02
                                    2.8E-02
                                    1.8E-02
                                    1.4E-02

								

                                   RDL (ug)
                                       
                                 3 x RDL (ug)
                       3 x RDL Concentrations (ug/dscm)

                                       
                                       
                                  1 dscm test
                                  2 dscm test
                                  3 dscm test
                                  4 dscm test
HCl/Cl2  (Method 26A)
                                    6.0E+1
                                    1.8E+2
                                    1.8E+02
                                    9.0E+01
                                    6.0E+01
                                    4.5E+01
PM filterable (Method 5)
                                    1.0E+3
                                    3.0E+3
                                    3.0E+03
                                    1.5E+03
                                    1.0E+03
                                    7.5E+02
Ind. Boiler Hg (Method 29)
                                    8.3E-01
                                    2.5E+00
                                    2.1E+00
                                    1.0E+00
                                    7.1E-01
                                    6.2E-01

                                       
                                       
                                       
                                       
                                       
                                       

                                       
                                       
                                   120L test
                                   240L test
                                   360L test
                                       
HCl/CL2 (Method 26)
                                    1.0E+01
                                    3.0E+01
                                    2.5E+02
                                    1.3E+02
                                    8.3E+01
                                       


Summary of pollutant emissions representative method detection level analyses and regulatory emissions limit setting procedure for Method 29 Metals using Inductively Coupled Atomic Emission Spectroscopy or Atomic Absorption Analysis
                                       
                                Method 29 Metal
                                      RDL
                                 ICP/AES or AA
                                     (ug)
                             3 X RDL ICP/AES or AA
                                     (ug)
                                       
                        3 x RDL Concentrations (g/dscm)
                                       
                                       
                                       
                                  1 dscm test
                                  2 dscm test
                                  3 dscm test
                                  4 dscm test
Antimony
                                                                        1.2E+01
                                                                        3.5E+01
                                                                        3.5E+01
                                                                        1.7E+01
                                                                        1.2E+01
                                                                        8.6E+00
Arsenic
                                                                        1.9E+01
                                                                        5.7E+01
                                                                        5.7E+01
                                                                        2.9E+01
                                                                        1.9E+01
                                                                        1.4E+01
Barium
                                                                        8.0E-01
                                                                        2.4E+00
                                                                        2.4E+00
                                                                        1.2E+00
                                                                        8.0E-01
                                                                        6.0E-01
Beryllium
                                                                        1.1E-01
                                                                        3.3E-01
                                                                        3.3E-01
                                                                        1.7E-01
                                                                        1.1E-01
                                                                        8.3E-02
Cadmium
                                                                        1.5E+00
                                                                        4.5E+00
                                                                        4.5E+00
                                                                        2.3E+00
                                                                        1.5E+00
                                                                        1.1E+00
Chromium
                                                                        2.5E+00
                                                                        7.5E+00
                                                                        7.5E+00
                                                                        3.8E+00
                                                                        2.5E+00
                                                                        1.9E+00
Cobalt
                                                                        2.5E+00
                                                                        7.5E+00
                                                                        7.5E+00
                                                                        3.8E+00
                                                                        2.5E+00
                                                                        1.9E+00
Copper
                                                                        2.1E+00
                                                                        6.3E+00
                                                                        6.3E+00
                                                                        3.2E+00
                                                                        2.1E+00
                                                                        1.6E+00
Lead
                                                                        1.5E+01
                                                                        4.5E+01
                                                                        4.5E+01
                                                                        2.3E+01
                                                                        1.5E+01
                                                                        1.1E+01
Manganese
                                                                        7.0E-01
                                                                        2.1E+00
                                                                        2.1E+00
                                                                        1.1E+00
                                                                        7.0E-01
                                                                        5.3E-01
Mercury*
                                                                        5.6E-01
                                                                        1.7E+00
                                                                        1.7E+00
                                                                        8.4E-01
                                                                        5.6E-01
                                                                        4.2E-01
Nickel
                                                                        5.4E+00
                                                                        1.6E+01
                                                                        1.6E+01
                                                                        8.1E+00
                                                                        5.4E+00
                                                                        4.1E+00
Phosphorus
                                                                        2.7E+01
                                                                        8.1E+01
                                                                        8.1E+01
                                                                        4.1E+01
                                                                        2.7E+01
                                                                        2.0E+01
Selenium
                                                                        2.7E+01
                                                                        8.1E+01
                                                                        8.1E+01
                                                                        4.1E+01
                                                                        2.7E+01
                                                                        2.0E+01
Silver
                                                                        2.6E+00
                                                                        7.8E+00
                                                                        7.8E+00
                                                                        3.9E+00
                                                                        2.6E+00
                                                                        2.0E+00
Thallium
                                                                        1.4E+01
                                                                        4.3E+01
                                                                        4.3E+01
                                                                        2.2E+01
                                                                        1.4E+01
                                                                        1.1E+01
Zinc
                                                                        8.0E-01
                                                                        2.4E+00
                                                                        2.4E+00
                                                                        1.2E+00
                                                                        8.0E-01
                                                                        6.0E-01
*Mercury analyzed by Cold Vapor AA
RDL = Method derived regulatory detection limit based.
ICP/AES = Inductively Coupled Argon Plasma/Atomic Emission Spectroscopy
AA = Atomic Absorption Spectroscopy
GFAA = Graphite Furnace Atomic Absorption spectroscopy
Summary of pollutant emissions representative method detection level analyses and regulatory emissions limit setting procedure  for Method 29 Metals using Inductively Coupled Plasma/Mass Spectrometry or Graphite Furnace Atomic Absorption Analysis
                                       
Method 29 Metal 
                                      RDL
                                 ICP/MS or GFAA
                                   (g/dscm)
                            3 X RDL ICP/MS or GFAA
                                   (g/dscm)
                                       
                            Concentrations (g/dscm)
                                       

                                       
                                       
                                  1 dscm test
                                  2 dscm test
                                  3 dscm test
                                  4 dscm test
                                  5 dscm test
Antimony
                                                                        1.1E+00
                                                                        3.3E+00
                                                                        3.3E+00
                                                                        1.7E+00
                                                                        1.1E+00
                                                                        8.3E-01
                                                                        6.6E-01
Arsenic
                                                                        4.0E-01
                                                                        1.2E+00
                                                                        1.2E+00
                                                                        6.0E-01
                                                                        4.0E-01
                                                                        3.0E-01
                                                                        2.4E-01
Barium**
                                                                        8.0E-01
                                                                        2.4E+00
                                                                        2.4E+00
                                                                        1.2E+00
                                                                        8.0E-01
                                                                        6.0E-01
                                                                        4.8E-01
Beryllium
                                                                        8.0E-02
                                                                        2.4E-01
                                                                        2.4E-01
                                                                        1.2E-01
                                                                        8.0E-02
                                                                        6.0E-02
                                                                        4.8E-02
Cadmium
                                                                        3.0E-02
                                                                        9.0E-02
                                                                        9.0E-02
                                                                        4.5E-02
                                                                        3.0E-02
                                                                        2.3E-02
                                                                        1.8E-02
Chromium
                                                                        3.0E-01
                                                                        9.0E-01
                                                                        9.0E-01
                                                                        4.5E-01
                                                                        3.0E-01
                                                                        2.3E-01
                                                                        1.8E-01
Cobalt
                                                                        3.0E-01
                                                                        9.0E-01
                                                                        9.0E-01
                                                                        4.5E-01
                                                                        3.0E-01
                                                                        2.3E-01
                                                                        1.8E-01
Copper**
                                                                        2.1E+00
                                                                        6.3E+00
                                                                        6.3E+00
                                                                        3.2E+00
                                                                        2.1E+00
                                                                        1.6E+00
                                                                        1.3E+00
Lead
                                                                        3.0E-01
                                                                        9.0E-01
                                                                        9.0E-01
                                                                        4.5E-01
                                                                        3.0E-01
                                                                        2.3E-01
                                                                        1.8E-01
Manganese
                                                                        3.0E-01
                                                                        9.0E-01
                                                                        9.0E-01
                                                                        4.5E-01
                                                                        3.0E-01
                                                                        2.3E-01
                                                                        1.8E-01
Mercury*
                                                                        5.6E-01
                                                                        1.7E+00
                                                                        1.7E+00
                                                                        8.4E-01
                                                                        5.6E-01
                                                                        4.2E-01
                                                                        3.4E-01
Nickel**
                                                                        5.4E+00
                                                                        1.6E+01
                                                                        1.6E+01
                                                                        8.1E+00
                                                                        5.4E+00
                                                                        4.1E+00
                                                                        3.2E+00
Phosphorus**
                                                                        2.7E+01
                                                                        8.1E+01
                                                                        8.1E+01
                                                                        4.1E+01
                                                                        2.7E+01
                                                                        2.0E+01
                                                                        1.6E+01
Selenium
                                                                        8.0E-01
                                                                        2.4E+00
                                                                        2.4E+00
                                                                        1.2E+00
                                                                        8.0E-01
                                                                        6.0E-01
                                                                        4.8E-01
Silver**
                                                                        2.6E+00
                                                                        7.8E+00
                                                                        7.8E+00
                                                                        3.9E+00
                                                                        2.6E+00
                                                                        2.0E+00
                                                                        1.6E+00
Thallium
                                                                        3.0E-01
                                                                        9.0E-01
                                                                        9.0E-01
                                                                        4.5E-01
                                                                        3.0E-01
                                                                        2.3E-01
                                                                        1.8E-01
Zinc
                                                                        8.0E-01
                                                                        2.4E+00
                                                                        2.4E+00
                                                                        1.2E+00
                                                                        8.0E-01
                                                                        6.0E-01
                                                                        4.8E-01
*Mercury analyzed by Cold Vapor AA
** Common metals analyzed by Inductively Coupled Plasma/AES or Flame Atomic Absorption Spectroscopy
RDL = Method derived regulatory detection limit based on 1.25 dscm collected in 1 hour.
ICP/MS = Inductively Coupled Argon Plasma/Mass Spectrometry
GFAA = Graphite Furnace Atomic Absorption spectroscopy

Except for assessing boiler and CISWI data, we recommend that you select D/F data calculated from the utilities' data set rather than for 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 in bold) to the calculated UPL.  If 3xRDL mass < UPL mass, use the UPL value for rulemaking.  If 3xRDL > UPL, use the 3xRDL value for rulemaking.  For source categories other than boilers, use the 3xRDL D/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 for Hg).  If so, repeat steps 1 and 2 selecting the concentration associated with the sample volume appropriate for your ICR or regulatory decision.  You may also determine to convert the values in the table to other emissions formats (e.g., lb/MMBtu or lb/MWh) for these comparisons.

Example spreadsheet:
                                                                               
                                                                               
(ng/dscm @ 7 percent O2)
ng
ng


mass (average of all congener data in set)
TEQ (average of all TEQ per congener in set)

lab mass
TEQ
Total OCDD
                                                                       2.19E-02
                                                                       6.24E-06

                                                                       8.77E-02
                                                                       2.50E-05
Total OCDF

                                                                       6.72E-03
                                                                       1.89E-06

                                                                       2.69E-02
                                                                       7.55E-06
1,2,3,4,6,7,8 HpCDD
                                                                       2.95E-03
                                                                       2.70E-05

                                                                       1.18E-02
                                                                       1.08E-04
1,2,3,4,6,7,8 HpCDF
                                                                       6.10E-03
                                                                       6.02E-05

                                                                       2.44E-02
                                                                       2.41E-04
1,2,3,4,7,8 HxCDD
                                                                       1.16E-03
                                                                       1.06E-04

                                                                       4.63E-03
                                                                       4.25E-04
1,2,3,4,7,8 HxCDF
                                                                       8.24E-03
                                                                       8.10E-04

                                                                       3.30E-02
                                                                       3.24E-03
1,2,3,4,7,8,9 HpCDF
                                                                       3.08E-03
                                                                       3.00E-05

                                                                       1.23E-02
                                                                       1.20E-04
1,2,3,6,7,8 HxCDD
                                                                       1.33E-03
                                                                       1.23E-04

                                                                       5.32E-03
                                                                       4.93E-04
1,2,3,6,7,8 HxCDF
                                                                       9.64E-04
                                                                       8.83E-05

                                                                       3.86E-03
                                                                       3.53E-04
1,2,3,7,8 PeCDD
                                                                       4.40E-03
                                                                       4.33E-03

                                                                       1.76E-02
                                                                       1.73E-02
1,2,3,7,8 PeCDF
                                                                       1.82E-03
                                                                       5.26E-05

                                                                       7.29E-03
                                                                       2.10E-04
1,2,3,7,8,9 HxCDD
                                                                       3.37E-03
                                                                       3.26E-04

                                                                       1.35E-02
                                                                       1.30E-03
1,2,3,7,8,9 HxCDF
                                                                       7.81E-04
                                                                       6.93E-05

                                                                       3.12E-03
                                                                       2.77E-04
2,3,4,6,7,8 HxCDF
                                                                       2.35E-03
                                                                       2.27E-04

                                                                       9.40E-03
                                                                       9.09E-04
2,3,4,7,8 PeCDF
                                                                       1.61E-03
                                                                       4.61E-04

                                                                       6.43E-03
                                                                       1.85E-03
2,3,7,8-TCDD
                                                                       3.38E-03
                                                                       3.34E-03

                                                                       1.35E-02
                                                                       1.34E-02
2,3,7,8-TCDF
                                                                       2.24E-03
                                                                       2.18E-04

                                                                       8.98E-03
                                                                       8.73E-04








max DL
                                                                       2.19E-02
                                                                       4.33E-03

                                                                       8.77E-02
                                                                       1.73E-02

min DL
                                                                       7.81E-04
                                                                       1.89E-06

                                                                       3.12E-03
                                                                       7.55E-06

mean DL
                                                                       4.26E-03
                                                                       6.05E-04

                                                                       1.70E-02
                                                                       2.42E-03








sum
                                                                       7.24E-02
                                                                       1.03E-02

                                                                       2.90E-01
                                                                       4.11E-02
RDL = EDL x 2
                                                                       1.45E-01
                                                                       2.06E-02

                                                                       5.80E-01
                                                                       8.22E-02
RDL x 3 > floor?
                                                                       4.35E-01
                                                                       6.17E-02

                                                                       1.74E+00
                                                                       2.47E-01

