Opinion ID: 519994
Heading Depth: 2
Heading Rank: 5

Heading: The EPA's Sampling Techniques

Text: 300 CMA asserts that in developing the BAT data base the EPA used sampling points that contained non-OCPSF process water, and thus the resulting limitations are based on lower concentrations due to dilution. In its petition for review CMA identifies five plants where it claims samples were taken at points including non-OCPSF flow. CMA contends that the limitations should be adjusted to account for this dilution. 301 To accurately measure BAT-treatment performance wastestream samples must be taken before (influent sampling) and after (effluent sampling) BAT treatment. If dilution occurs after influent sampling, but before effluent sampling, then the effluent sample represents dilution as well as treatment performance and the long-term average is inflated by dilution. If, however, dilution occurs before influent sampling, the dilution has no effect on the measure of treatment performance, provided the influent to the treatment system contains a sufficient threshold concentration of a pollutant. 230 302 The EPA states that to sample influent it established sampling points only at locations where OCPSF process wastewater flows were not later significantly diluted by non-process flows. 231 The EPA determined that the dilution at the five plants identified by CMA occurred before the BAT treatment stage and before the points at which influent samples were taken. The record also shows that the influents at these five plants contained sufficient toxics to meet the threshold for meaningful measurement of each plant's treatment performance. 232 Thus the samplings at the five plants identified by CMA served as an accurate measure of BAT treatment performance.