13.05.020 National Categorical Pretreatment Standards.
Categorical Industrial Users (CIU) must comply with the Categorical Pretreatment Standards found at 40 CFR Chapter I, Subchapter N, Parts 405-471.
A. Where a Categorical Pretreatment Standard is expressed only in terms of either the mass or the concentration of a pollutant in wastewater, the Director may impose equivalent concentration or mass limits in accordance with subsection E and F of this section.
B. When the limits in a Categorical Pretreatment Standard are expressed only in terms of mass of pollutant per unit of production, the Director 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.
C. When wastewater subject to a Categorical Pretreatment Standard is mixed with wastewater not regulated by the same Standard, the Director shall impose an alternate limit in accordance with 40 CFR 403.6(e).
D. 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 Director. The city may establish equivalent mass limits only if the Industrial User meets all the conditions set forth in subsections (D)(1)(a) through (D)(1)(e) of this section.
1. To be eligible for equivalent mass limits, the Industrial User must:
a. Employ, or demonstrate that it will employ, water conservation methods and technologies that substantially reduce water use during the term of its industrial wastewater discharge permit;
b. Currently use control and treatment technologies adequate to achieve compliance with the applicable Categorical Pretreatment Standard, and not have used dilution as a substitute for treatment;
c. Provide sufficient information to establish the facility’s actual average daily flow rate for all wastestreams, based on data from a continuous effluent flow monitoring device, as well as the facility’s long-term average production rate. Both the actual average daily flow rate and the long-term average production rate must be representative of current operating conditions;
d. Not have daily flow rates, production levels, or pollutant levels that vary so significantly that equivalent mass limits are not appropriate to control the discharge; and
e. Have consistently complied with all applicable Categorical Pretreatment Standards during the period prior to the Industrial User’s request for equivalent mass limits.
2. An Industrial User subject to equivalent mass limits must:
a. Maintain and effectively operate control and treatment technologies adequate to achieve compliance with the equivalent mass limits;
b. Continue to record the facility’s flow rates through the use of a continuous effluent flow monitoring device;
c. Continue to record the facility’s production rates and notify the Director whenever production rates are expected to vary by more than 20 percent from its baseline production rates determined in subsection (D)(1)(c) of this section. Upon notification of a revised production rate, the Director will reassess the equivalent mass limit and revise the limit as necessary to reflect changed conditions at the facility; and
d. Continue to employ the same or comparable water conservation methods and technologies as those implemented pursuant to subsection (D)(1)(a) of this section so long as it discharges under an equivalent mass limit.
3. When developing equivalent mass limits, the Director:
a. Will calculate the equivalent mass limit by multiplying the actual average daily flow rate of the regulated process(es) of the Industrial User by the concentration-based daily maximum and monthly average standard for the applicable Categorical Pretreatment Standard and the appropriate unit conversion factor;
b. Upon notification of a revised production rate, will reassess the equivalent mass limit and recalculate the limit as necessary to reflect changed conditions at the facility; and
c. May retain the same equivalent mass limit in subsequent industrial wastewater discharger permit terms if the Industrial User’s actual average daily flow rate was reduced solely as a result of the implementation of water conservation methods and technologies, and the actual average daily flow rates used in the original calculation of the equivalent mass limit were not based on the use of dilution as a substitute for treatment pursuant to MMC 13.05.060. The Industrial User must also be in compliance with MMC 13.05.2020 regarding the prohibition of bypass.
E. The Director 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 Director.
F. 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.
G. Many Categorical Pretreatment Standards specify one limit for calculating maximum daily discharge limitations and a second limit for calculating maximum monthly average, or 4-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.
H. Any Industrial User operating under a permit incorporating equivalent mass or concentration limits calculated from a production-based Standard shall notify the Director within two business days after the Industrial User has a reasonable basis to know that the production level will significantly change within the next calendar month. Any Industrial User not notifying the Director 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. 4987, 2015).