An upset shall be an affirmative defense to an enforcement action brought against a user or violating a pretreatment standard and requirement if the following conditions are met:
(1) 
The user can identify the cause of the upset;
(2) 
The facility was operating in a prudent and workmanlike manner at the time of the upset and was in compliance with applicable O&M procedures;
(3) 
The user submits, within 24 hours of becoming aware of the upset, a description of the discharge and its causes, the period of noncompliance (if not corrected, then time noncompliance is anticipated to end), and the steps being taken to reduce, eliminate and prevent recurrence of the noncompliance;
(4) 
If this report is given orally, the user must also submit a written report containing such information within five days unless waived by the director;
(5) 
Upset shall mean an exceptional incident in which there is unintentional and temporary noncompliance with categorical pretreatment standards and requirements because of factors beyond the reasonable control of the industrial user. Noncompliance caused by operational error, improperly designed pretreatment facilities, inadequate treatment facilities, lack of preventive maintenance, or careless or improper operation does not constitute an upset.
(Code 1985 § 22-82A)
An industrial user shall have an affirmative defense to an enforcement action brought against it for noncompliance with the general and specific prohibitions in SCC § 13.55.050 if it can prove that it did not know or have reason to know that its discharge would cause pass through or interference and that either: (1) a local limit exists for each pollutant discharged and the user was in compliance with each limit directly prior to and during the pass through or interference, or (2) no local limit exists, but the discharge did not change substantially in nature or constituents from the user's prior discharge when the city was regularly in compliance with its NPDES permit, and in the case of interference, in compliance with applicable sludge use or disposal requirements.
(Code 1985 § 22-82B)
The intentional diversion of wastestreams from any portion of an individual user's treatment facility shall be an affirmative defense to an enforcement action brought against the industrial user if the user can demonstrate that such a bypass was unavoidable to prevent loss of life, personal injury, or severe property damage. In order to be eligible for the affirmative defense, the industrial user must demonstrate that there was no feasible alternative to the bypass and submit notice of the bypass as required by 40 CFR 403.17.
(Code 1985 § 22-82C)