Opinion ID: 519994
Heading Depth: 3
Heading Rank: 4

Heading: CMA's Challenge to the EPA's Choice of the Minimum

Text: 286 Analytical Value to Assign to Non-Detect Readings 287 To calculate the long-term averages for plants in the data base the EPA included non-detect values. As previously discussed, the value assigned to a non-detect reading was the minimum analytical value. To derive the limitations for the polynuclear aromatics, the EPA assigned to these pollutants the published minimum analytical value of 10 ppb that appears in Part 136. 216 288 The BAT 2 limitations for the polynuclear aromatics were based on data from plant 1293T. 217 CMA notes that the EPA lab reported an average minimum analytical value of 13.3 ppb for this plant. CMA asserts that the published Part 136 minimum analytical values were determined based on pollutant samples in pure reagent water free of other interfering chemicals and do not account for real-world interference from other compounds that raise the minimum analytical value, such as the reported minimum analytical value at plant 1293T. CMA argues that the EPA therefore erred by using the published minimum analytical value, rather than the lab-reported average minimum analytical value for plant 1293T, and this error of 3.3 ppb made the limitations more stringent. 289 The EPA's methodology for deriving the effluent limitations included several conservative assumptions that created a margin for error and ensured that the limitations are achievable. 218 The first of these conservative assumptions is that when a data base plant reported a non-detect reading, the EPA assigned the minimum analytical value to such a reading. 219 By assigning the minimum analytical value, rather than zero, to plants that reported non-detect readings, the EPA raised each plant's long-term average above the true treatment level achieved by the plant. This resulted in higher, less stringent, limitations than would have been imposed if the EPA had assigned a zero to non-detect readings. 220 Second, in calculating the variability factors for each pollutant, the EPA did not use data from plants that consistently reported non-detect readings. 221 Consequently, data from the best performing plants were not used to derive the BAT variability factors, thus avoiding higher BAT limitations. The EPA's error, if any, in using the published Part 136 minimum analytical value, rather than the wastestream-specific value reported for plant 1293T, was, therefore, offset by the EPA's conservative methodology used to develop the BAT limitations. 290 The record shows that the BAT 2 limitations based on data from plant 1293T are achievable. 222 The lowest of the effluent limitations based on the performance of this plant is well above the minimum analytical level whether 10 ppb or 13.3 ppb is used. For instance, the BAT 2 maximum daily limitation for benzo(k)fluoranthene is 47 ppb, while the maximum monthly average is 19 ppb. 223 The data show that plant 1293T performed within these limits whether the minimum analytical value is 10 ppb or 13.3 ppb. 224 291 CMA also asserts that at least one plant reported minimum analytical values of 100 ppb for toluene and chloroethane and 60 ppb for chlorobenzene. CMA contends that the EPA erred by assigning the Part 136 minimum analytical value of 10 ppb to toluene and chlorobenzene and 50 ppb to chloroethane in promulgating the limitations. 292 The EPA asserts that the reported minimum analytical values of 100 ppb for toluene and chloroethane and 60 ppb for chlorobenzene were not representative of the data as a whole and that these data should have been excluded from its calculation of the limitations. The EPA attributed these extremely high minimum analytical values at one plant to dilution due to interference from other chemicals. The EPA's data-editing criterion was to exclude data from plants whose samples could not be measured down to the minimum levels listed in Part 136. Thus the data associated with the extremely high analytical minimums identified by CMA should have been excluded. If these data had been excluded the limitations would have been the same, based on the remaining data, because in calculating the limitations the EPA relied on the median performance of the best plants and the vast majority of the readings for toluene, chlorobenzene, and chloroethane were non-detect readings with minimum analytical values equal to those assigned in Part 136. 225 Because the limitations based on the other data would have been the same even if the EPA had excluded the objectionable data, the EPA's error in including these data in the data base was harmless.