(1) Except as indicated in subsections (2) and (3) of this section, the user must collect wastewater samples using 24-hour-flow proportional composite sampling techniques, unless time-proportional composite sampling or grab sampling is authorized by the Director. Where time-proportional composite sampling or grab sampling is authorized by the City, the samples must be representative of the discharge. Using protocols (including appropriate preservation) specified in 40 C.F.R. 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, as appropriate. In addition, grab samples may be required to show compliance with instantaneous limits.

(2) Samples for oil and grease, temperature, pH, cyanide, total phenols, sulfides and volatile organic compounds must be obtained using grab collection techniques.

(3) For sampling required in support of baseline monitoring and 90-day compliance reports required in MMC 10.20.170 and MMC 10.20.240(1), 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 Director may authorize a lower minimum. For the reports required by MMC 10.20.240(2), the industrial user is required to collect the number of grab samples necessary to assess and assure compliance with applicable pretreatment standards and requirements. (Ord. 106 § 7(3), passed 10-9-2012; Code 2014 § 52.07(C))