An upset can be used as an affirmative defense to an action brought for noncompliance with categorical pretreatment standards, provided the industrial user meets certain conditions. An industrial user who wishes to establish the affirmative defense of upset must demonstrate through properly signed contemporaneous operating logs or other relevant evidence that:an upset occurred and the industrial user can identify the cause or causes; the facility was at the time being operated in a prudent and workmanlike manner and in compliance with applicable operational and maintenance procedures; the industrial user submitted the following information to the City within 24 hours of becoming aware of the upset:a description of the indirect discharge and cause of noncompliance; the period of noncompliance, including exact dates and times, or if not corrected, the anticipated time the noncompliance is expected to continue; and steps being taken or planned to reduce, eliminate, and prevent recurrence of the noncompliance; if this information is provided orally, a written submission must follow within 5 days; and the industrial user shall control production or all discharges to the extent necessary to maintain compliance with pretreatment standards upon loss, reduction, or failure of its treatment facility until the facility is restored or an alternative method of treatment is provided. City Code, 1976/83, art. 25, §7(e)(3) Ord. 91-775