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NPDES Monitoring Requirement -2- 10 September 2001 <br /> pollutants (such a heavy metals)where the toxicity of the constituents varies with pH and/or <br /> hardness. Section 3 of the SIP prescribes mandatory monitoring of dioxin congeners. <br /> 2. In addition to the specific requirements of the SIP, the Board is requiring the following monitoring <br /> needed for permit development: <br /> a. Organophosphorous pesticides,principally diazinon and chlorpyrifos, are commonly-used <br /> insecticides found in many domestic wastewater discharges at concentrations which can cause <br /> toxicity both in effluent and in receiving water. These pesticides are not"priority pollutants"and <br /> so are not part of the analytical methods routinely performed for NPDES discharges. This <br /> monitoring is required of domestic wastewater dischargers only. <br /> b. Drinldng water constituents. Constituents for which dnnldng water Maximum Contaminant <br /> Levels(MCLs)have been prescribed in the California Code of Regulation are included in the <br /> Water Quality Control Plan, Fourth Edition,for the Sacramento and San Joaquin River Basins <br /> (Basin Plan). The Basin Plan defines virtually all surface waters within the Central Valley <br /> Region as having existing or potential beneficial uses for municipal and domestic supply. The <br /> Basin Plan further requires that, at a minimum,water designated for use asdomestic or <br /> municipal supply shall not contain concentrations of chemical constituents in excess of the <br /> MCLS contained in the California Code of Regulations. <br /> c. Effluent and receiving water temperature. This is both a concern for application of certain <br /> temperature sensitive constituents,such as fluoride,.and for compliance with the Basin Plan's <br /> thermal discharge requirements. <br /> d. Effluent and receiving water hardness and pH. These are necessary because several of the CTR <br /> constituents are hardness or pH dependent. <br /> e. Receiving water flow is needed to determine possible dilution available in the receiving water. <br /> The receiving water flows, in combination with the receiving water pollutant concentrations,will <br /> be used to determine if there is assimilative capacity in the receiving water for each pollutant, <br /> and whether dilution credits can be granted. Dilution credits can increase the concentrations of <br /> pollutants allowed in your effluent discharge if assimilative capacity is available in the receiving <br /> water. <br /> Pursuant to Section 13267 of the California Water Cade,you are required to submit monitoring data <br /> for your effluent and receiving water as described in Attachments I through IV. <br /> Attachment I—Sampling frequency and number of samples. <br /> Attachment lI—Constituents to be monitored. This list identifies the constituents to be monitored. <br /> It is organized into groupings (Volatile Organics, Semi-Volatile Organics, Inorganics, <br /> Pesticides/Polychlorinated Biphenyls (PCBs),Other Constituents, and Discharge&Receiving Water <br /> Flows),which correspond to groupings in Attachment I. Also-listed are the Controlling Water <br /> Quality Criteria and their concentrations. The criteria concentrations are compiled in the Central <br /> Valley Regional Water Board's staff report,A Compilation of Water Quality Goals.' Minimum <br /> quantitation levels for the analysis of the listed constituents will be equal to or less than the <br />