Okla. Admin. Code § 252:606-6-3
An effluent's C95 concentration is used to characterize the effluent to determine if there is reasonable potential for a substance. Permit applicants must retain all analytical laboratory reports used for effluent characterization in a permit application and provide copies to DEQ upon request. Where DMRs or facility records are used to characterize effluent DEQ will use, at a minimum, the most recent two-year period of record. When characterizing whole effluent toxicity, DEQ may use the most recent five-year period of record. Effluent monitoring data must be defensible analytical data, must be representative of the discharge, and must account for any seasonality or other variability in effluent quality. For reasonable potential determination, see OAC 252:606-6-3 through 6-9.
Okla. Admin. Code § 252:606-6-3