40 CFR § 420.04 - Calculation of pretreatment standards.
(a) Pretreatment standards shall be calculated for each operation using the applicable average rate of production reported by the owner or operator of the facility to the Control Authority in accordance with 40 CFR 403.12(b)(3).
(b) The average rate of production reported by the owner or operator in accordance with 40 CFR 403.12(b)(3) shall be based not upon the design production capacity but rather upon a reasonable measure of actual production of the facility, such as the production during the high month of the previous year, or the monthly average for the highest of the previous 5 years. For new sources or new dischargers, actual production shall be estimated using projected production.
(c) If, due to a change of circumstances, the average rate of production for an operation reported by the owner or operator of the facility to the Control Authority in accordance with 40 CFR 403.12(b)(3) does not represent a reasonable measure of actual production of that operation, the owner or operator must submit to the Control Authority a modified average rate of production.