Question # 559

559. A covered petroleum refinery manufactures naphtha from crude oil. A paraffin, olefin, naphthalene and aromatics (PONA) analysis revealed that the naphtha contains 2.5 percent by weight of C9 alkylbenzenes. Only two out of a possible eight C9 alkylbenzenes are reportable under Section 313. How would this manufacturer calculate the Section 313 reporting threshold for the generic chemical name category of C9 alkylbenzenes in this instance?
The facility should not report for the generic mixture name, such as C9 alkylbenzenes, but for the specific chemical. Since the facility does not know the concentration of each chemical in the naphtha, and assuming 2.5 percent as the upper bound for each is unrealistic, the facility should assume that each listed C9 alkylbenzene is present and divide the concentration evenly between the eight.