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WASTE DISCHARGE R*T REMENTS ORDER NO. 5-01-119PVISED) <br /> STOCKTON COGEN COMPANY -4- <br /> SAN JOAQUIN COUNTY <br /> 15. Effluent limitations, and toxic effluent standards established pursuant to Sections 3 0 E 302, 303, <br /> 304, and 307 of the Clean Water Act(CWA) and amendments thereto are applicable ' the <br /> discharge. <br /> 16. The discharge is presently governed by Waste Discharge Requirements Order No. 95-148, dated <br /> 23 June 1995. <br /> 17. The technology-based monitoring requirements and effluent limits for the steam electric power <br /> generating point source category at 40 CFR Part 423.15 are applicable to this discharge. <br /> a) The requirements of Part 423.15 0) are applicable to pollutants discharged in the coolin tower <br /> blowdown. g <br /> b) The requirements of Part 423.15 (c) are applicable to pollutants discharged from internal low <br /> volume waste sources. There are two significant low volume waste sources at this facility: <br /> The first is the boiler blowdown, steam condensate, and miscellaneous machinery drains which <br /> collect in the internal sump system and is discharged back to the cooling tower system. The <br /> second is that portion of the RO concentrate that is mixed with cooling tower blowdown prior <br /> to discharge North Littlejohn Creek. <br /> The cooling tower blowdown, internal low volume waste sump discharge, and RO concentrate <br /> (portion mixed with cooling tower blowdown only) internal waste streams will each need to be <br /> monitored separately per the Monitoring and Reporting Program No. 5-01-119 to determine <br /> compliance with the applicable technology-based limits listed in Internal Waste Stream <br /> Limitations D.1. These monitoring requirements and effluent limits were not part of the previous <br /> WDR Order No. 95-148. <br /> 18. The previous permit provided for a mixing zone for compliance with the Basin Plan water quality <br /> objectives for temperature and chlorine residual. The mixing zone extended throughout the entire <br /> length of North Littlejohns Creek, to the confluence with French Camp Slough. <br /> With regard to mixing zones, the Basin Plan states, "...the Regional Water Board may designate <br /> mixing zones within which water quality objectives will not apply provided the discharger has <br /> demonstrated to the satisfaction of the Regional Water Board that the mixing zone will not <br /> adversely impact beneficial uses... In determining the size of such mixing zones, the Regional <br /> Water Board will consider the applicable procedures and guidelines in EPA's Water Quality <br /> Standards Handbook and the Technical Support Document for Water Quality-based Toxics <br /> Control..." The Board finds that,based on water quality evidence and the applicable procedures <br /> guidelines currently available, provisions for a mixing zone by allowing compliance with water <br /> quality objectives to be determined at French Camp Slough should not be continued. <br /> Because available dilution is negligible, the Board will not designate any mixing zone within <br /> which Basin Plan water quality objectives will not apply. The elimination of the mixing zone <br /> within North Littlejohns Creek requires that this permit apply Basin Plan water quality objectives, <br /> which have never been applied to this specific area of the water body for this Discharger. <br /> Receiving water limitations for temperature and effluent limitations for chlorine residual have been <br />