A. A minimum of four grab samples must be used for pH, cyanide, total phenols, oil and grease, sulfide, and volatile organics. The director will determine on a case-by-case basis whether the user will be able to composite the individual grab samples. For all other pollutants, twenty-four-hour composite samples must be obtained through flow-proportional composite sampling techniques where feasible. The city 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 being discharged.

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 city 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 wastestream formula of 40 CFR 403.6(e) in order to evaluate compliance with the applicable categorical pretreatment standards. For other SIUs, for which the city 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 permit, 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. (Ord. 3070-08 § 5.1, 2008.)