September 22 , 2011

**Note** Subject: Updated data and procedure for handling below detection level data in analyzing various pollutant emissions databases for MACT and RTR emissions limits To: SPPD MACT management and rule writers This is an update to the note we sent on September 13 regarding the handling of BDL and 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 similar to the one we sent you last week but which includes several updates . The updates include an easier to use table (e.g., sampling time versus sample volume) and some pollutants not covered in the initial table (e.g., HCl and filterable PM) . **We again**  **recommend that rule writers considering emissions limits**  **for these pollutants review the**  **exis ting data sets and compare the R**  **DL 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**  **cu rrent rule development projects**  **and in setting representative emissions limits.** 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 the July 6, 2010 procedures but with revisions reflecting 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. We will post the attached table on the G:user/share/MPG/method detection level directory and we will continue to update the table as we can collect appropriate data. Please contact Peter Westlin or Stef Johnson if you have any questions about how to apply these data or the scope of the proposed procedure. 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, AQAD**Summary of pollutant**  **emissions representative**  **method detection level analyses and a regulatory**  **emissions limit setting procedure**  RDL mass (ng) 3xRDL (ng) Concentrations (ng/dscm) 1 hour test 2 hour test 3 hour test 4 hour test 6 hour test 8 hour 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 Concentrations (ug/dscm) (ug) (ug) 1 hour test 2 hour test 3 hour test 4 hour test Ind. Boiler Hg (Method 29) 8.3E - 01 **2.5E+00** 2.5E+00 1.2E+00 8.3E - 01 6.2E - 01 HCl/Cl2 (Method 26) 1.0E+1 **3.0E+1** 2.5E+2 1.3E+2 HCl/Cl2 (Method 26A) 6.0E+1 **1.8E+2** 1.8E+2 9.0E+1 6.0E+1 4.5E+1 PM filterable (Method 5) 1.0E+3 **3.0E+3** 3.0E+3 1.5E+3 1.0E+3 7.5E+2 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.