Okla. Admin. Code § 252:623-19-2
A user shall have an affirmative defense to an enforcement action brought against it for noncompliance with the general prohibitions in OAC 252:623-1-7(a) or specific prohibitions in OAC 252:623-3-1, if it can prove that it did not know, or have reason to know, that its discharge, alone or in conjunction with discharges from other sources, would cause pass through or interference and that either:
Added at 18 Ok Reg 1601, eff 6-1-01