(A)   Except as indicated in subsection (B) below, the user shall collect wastewater samples using flow proportional composite collection techniques. In the event flow proportional sampling is infeasible, the city manager may authorize the use of time proportional sampling. Where time-proportional composite sampling or grab sampling is authorized by the city manager, the samples must be representative of the discharge. Using protocols (including appropriate preservation) specified in 40 CFR Part 136 and appropriate EPA guidance, multiple grab samples collected during a 24-hour period may be composited prior to the analysis as follows: for cyanide, total phenols, and sulfides the samples may be composited in the laboratory or in the field; for volatile organics and oil and grease, the samples may be composited in the laboratory. Composite samples for other parameters unaffected by the compositing procedures as documented in approved EPA methodologies may be authorized by the city manager, as appropriate. In addition, grab samples may be required to show compliance with instantaneous discharge limits.
   (B)   Samples for oil and grease, temperature, pH, cyanide, phenols, sulfides, and volatile organic compounds shall be obtained using grab collection techniques.
   (C)   For sampling required in support of baseline monitoring and 90-day compliance reports required in section 19-71 and 19-73 (40 CFR 403.12(b) and (d)), a minimum of four grab samples must be used for pH, cyanide, total phenols, oil and grease, sulfide and volatile organic compounds for facilities for which historical sampling data do not exist; for facilities for which historical sampling data are available, the city manager may authorize a lower minimum. For the reports required by section 19-74 (40 CFR 403.12(e) and 403.12(h)), the industrial user is required to collect the number of grab samples necessary to assess and assure compliance by with applicable pretreatment standards and requirements.
   (D)   Samples should be taken immediately downstream from pretreatment facilities if such exist or immediately downstream from the regulated process if no pretreatment exists. If other wastewaters are mixed with the regulated wastewater prior to pretreatment the user should 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 pretreatment standards. Where an alternate concentration or mass limit has been calculated in accordance with 40 CFR 403.6(e) this adjusted limit along with supporting data shall be submitted to the city.
(`64 Code, Sec. 25-58) (Ord. No. 2494, 2761, 2875)