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CEASE AND DESIST ORDER#. R5-2004-0029 �' -4- CITY OF MANTECA WASTEWATER QUALITY CONTROL FACILITY SAN JOAQUIN COUNTY 6. WDRs, Order No. R5-2004-0028, contains Effluent Limitation B.11 which reads as follows: "The maximum temperature of the discharge shall not exceed the natural receiving water temperature by more than 20 degree F." 7. WDRs, Order No. R5-2004-0028, contains Receiving Water Limitations which read, in part, as follows: "The discharge shall not cause the following in the receiving water:" "F.8. The creation of a zone, defined by water temperatures of more than 1°F above natural receiving water temperature,which exceeds 25 percent of the cross-sectional area of the river channel at any point." and "F.9. A surface temperature rise greater than 4°F above the natural temperature of the receiving water at any time or place". 8. Temperature modeling studies published in the "Draft Environmental Impact Report for the Manteca WQCF Phase III/IV Expansion Project, October 2000" indicate that the current and expanded continuous discharge is in violation of Effluent Limitation B.11 and causes violations of Receiving Water Limitations F.8 and F.9. To mitigate the receiving water violations, the discharger proposes to implement a timed discharge,where the discharge will occur only on the outgoing tide. Modeling indicates that Receiving Water Limitation F.9 will continue to be exceeded with the timed discharge,but the magnitude of the violation will be less significant. To mitigate the violation of Effluent Limitation B.11, the Discharger has requested a 30-day averaging period for compliance. The Discharge has requested an exception to the Thermal Plan, which would allow alternative effluent and receiving water limitations to be adopted that can be achieved. An exception cannot be authorized at this time due to a number of factors. First, the accuracy of the temperature model results which are the basis for the receiving water limitation violations are questionable due to a lack of site data to calibrate and validate the model, the lack of accounting for atmospheric heat gains and loss from the proposed holding pond and the river,the lack of accounting for tidal cycles and recirculation from the limited model run time, and the lack of accounting for the Brown Sand,Inc. discharge adjacent to the City's discharge. Second, the Discharger has not conducted regular monitoring of temperature at the outfall as required in its previous permit, and the available information is based on a limited data set which correlates the temperature at the plant site and at the outfall. Third, the Discharger has not provided adequate evidence that a 30-day averaging period for Effluent Limitation B.11 will not cause adverse impacts to aquatic life. Finally,the Discharger does not currently have the capability to implement a timed discharge on out-going tides. This Order includes a time schedule to (1) evaluate and implement alternatives'to comply with the Thermal Plan or to clearly demonstrate that an exception to the Thermal Plan will not cause