Opinion ID: 519994
Heading Depth: 3
Heading Rank: 2

Heading: Averaging of Variability Factors

Text: 263 The same plant using the same treatment method to remove the same toxic does not always achieve the same result. Tests conducted one day may show a different concentration of the same toxic than are shown by the same test the next day. This variability may be due to the inherent inaccuracy of analytical testing, i.e., analytical variability, or to routine fluctuations in a plant's treatment performance. 264 The EPA attempted to take this variability into account. To do so, it calculated the BAT limitations by multiplying the long-term average concentration of each pollutant by a variability factor that reflected observed variations in treatment performance experienced by plants that had attempted to remove that pollutant. The EPA computed the variability factor for each plant in the BAT data base for that pollutant or, if there were two or more plants with a significant number of data points in the detectable range, it averaged the variability factors for all the plants. 265 CMA asserts that averaging variability factors from different plants assumes that the plants are similar, an assumption that is not supported by the record, and that the EPA has failed to show that the different plants can reduce the amount of variability to the factor computed by the EPA. CMA further contends that the EPA should have created separate subcategories to account for the different variability experienced by the various types of plants using BAT. 266 As the EPA notes, averaging variability factors inures to the benefit of the industrial petitioners because it yields a greater variability factor than the factor that would have resulted from using data from the single plant that experienced the least variability. The EPA decided not to subcategorize BAT plants on the basis of variability because the EPA determined that OCPSF plants utilizing BAT could achieve uniformly high levels of removal of toxics. 202 267 The reasonableness of the variability factors used by the EPA is supported by the record. 203 Moreover, CMA has failed to demonstrate that the greater variability measured at some plants is due to uncontrollable factors rather than plant inefficiencies or that the fact of such greater variability shows that the limitations are not achievable.