§ 56.20 NATIONAL CATEGORICAL PRETREATMENT STANDARDS.
   (A)   Users must comply with the categorical pretreatment standards found at 40 CFR Chapter I, Subchapter N, Parts 405-471.
      (1)   Where a categorical pretreatment standard is expressed only in terms of either the mass or the concentration of a pollutant in wastewater, the city may impose equivalent concentration or mass limits in accordance with divisions (5) and (6) below.
      (2)   When the limits in a categorical pretreatment standard are expressed only in terms of mass of pollutant per unit of production, the city may convert the limits to equivalent limitations expressed either as mass of pollutant discharged per day or effluent concentration for purposes of calculating effluent limitations applicable to individual industrial users.
      (3)   Combined wastestream formula. When wastewater subject to a categorical pretreatment standard is mixed with wastewater not regulated by the same standard, the city shall impose an alternate limit in accordance with SC R.61-9.403.6(f).
      (4)   Net/gross adjustments. The city, at its discretion, may allow a categorical industrial user to obtain a net/gross adjustment to a categorical pretreatment standard in accordance with SC R.61-9.403.15 with the restriction that the calculated limit shall not exceed the local limit established by the city for any parameter.
      (5)   Equivalent mass limits. When a categorical pretreatment standard is expressed only in terms of pollutant concentrations, an industrial user may request that the city convert the limits to equivalent mass limits. The determination to convert concentration limits to mass limits is within the discretion of the city. The city may establish equivalent mass limits only if the industrial user meets all the conditions set forth in SC R 61-9.403.6(d)(5).
      (6)   Equivalent concentration limits. The city may convert the mass limits of the categorical pretreatment standards of 40 CFR Parts 414, 419, and 455 to concentration limits for purposes of calculating limitations applicable to individual industrial users. The conversion is at the discretion of the city.
      (7)   Once included in its permit, the industrial user must comply with the equivalent limitations developed in this section in lieu of the promulgated categorical standards from which the equivalent limitations were derived.
      (8)   Many categorical pretreatment standards specify one limit for calculating maximum daily discharge limitations and a second limit for calculating maximum monthly average, or four-day average, limitations. Where such standards are being applied, the same production or flow figure shall be used in calculating both the average and the maximum equivalent limitation.
      (9)   Any industrial user operating under a permit incorporating equivalent mass or concentration limits calculated from a production-based standard shall notify the city within two business days after the user has a reasonable basis to know that the production level will significantly change within the next calendar month. Any user not notifying the city of such anticipated change will be required to meet the mass or concentration limits in its permit that were based on the original estimate of the long term average production rate.
(Ord. 16-04-001, passed 4-19-16)