A. The director will determine on a case-by-case basis the required sampling intervals, the number of samples required and whether the user will be able to composite the individual grab samples. The frequency of monitoring shall be as prescribed within the permit. At a minimum, except for zero discharge users, users with approved waivers, and NSCIUs, users shall sample their discharge at least twice per year. Samples with a short holding time (pH, volatile organics, etc.) or samples that cannot be sampled with a composite sampler (fats, oil and grease) will need to be collected via grab sampling at specified intervals. For pollutants with a holding time that allows it, 24-hour composite samples must be obtained through flow-proportional composite sampling techniques where feasible. The director may waive flow-proportional composite sampling for any user that demonstrates that flow proportional is not feasible. In such cases, samples may be obtained through time-proportional composite sampling techniques or through a minimum of four grab samples where the user demonstrates that this will provide a representative sample of the effluent from the regulated discharge.

B. Samples should be taken immediately downstream from pretreatment facilities if such exist or immediately downstream from the regulated or manufacturing process if no pretreatment exists or as determined by the director and/or contained in the user’s wastewater discharge permit. For categorical users, if other wastewaters are mixed with the regulated wastewater prior to pretreatment the user shall measure the flows and concentrations necessary to allow use of the combined waste stream formula of 40 CFR 403.6(e) in order to evaluate compliance with the applicable categorical pretreatment standards. For other SIUs, for which the director has adjusted its local limits to factor out dilution flows, the user shall measure the flows and concentrations necessary to evaluate compliance with the adjusted pretreatment standard(s).

C. All sample results shall indicate the time, date and place of sampling, and methods of analysis, and shall certify that such sampling and analysis is representative of normal work cycles and expected pollutant discharges from the user. If a user sampled and analyzed more frequently than what was required in its wastewater discharge approval, using methodologies in 40 CFR Part 136, it must submit all results of sampling and analysis of the discharge as part of its self-monitoring report.

D. Where a treated regulated process waste stream is combined prior to treatment with wastewaters other than those generated by the regulated process, the industrial user may monitor either the segregated process waste stream or the combined waste stream for the purpose of determining compliance with applicable pretreatment standards. If the industrial user chooses to monitor the segregated process waste stream, it shall apply the applicable categorical pretreatment standard. If the user chooses to monitor the combined waste stream, it shall apply an alternative discharge limit calculated using the combined waste stream formula as provided in 40 CFR 403.6(e). The industrial user may change monitoring points only after receiving approval from the director. The director shall ensure that any change in an industrial user’s monitoring point(s) will not allow the user to substitute dilution for adequate treatment to achieve compliance with applicable standards. [Ord. 2020-07-016 § 1; Ord. 2019-11-032 § 1].