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WASTE DISCHARGE REQU&MENTS ORDER NO. R5-2004-002te. -17- CITY OF MANTECA, CITY 07 LATHROP AND DUTRA FARMS WASTEWATER QUALITY CONTROL FACILITY SAN JOAQUIN COUNTY 41. Studies by the National Marine Fisheries Service, the U.S. Fish and Wildlife Service, the California Department of Fish and Game, the University of California at Davis, et. al., have identified the Central Valley Chinook Salmon and the Central Valley Steelhead as sensitive species that are affected by elevated temperatures in the San Joaquin River. There are four runs of salmon in the Central Valley that results in there being adults and juveniles in portions of the Delta every month of the year. Generally, adults would be moving upstream in the fall, and fry and smolt moving downstream in the winter and spring. River temperatures above 68 °F are unsuitable for supporting salmonids. Migration of adults is usually delayed when river temperatures reach this level. hi a Department of Water Resources Study, adult salmon will cease migration if water temperatures are above 70 °F. At 77 °F, adult mortality may occur. The Thermal Plan does not protect aquatic life from high temperature wastewater being discharged to an elevated temperature river. However, the Thermal Plan limits incremental increases in temperature. Discharge from the wastewater treatment plant of treated effluent with an elevated temperature may affect salmon and other migrating fish in the San Joaquin River. In so far as elevated temperature is deleterious to Chinook salmon, effluent temperature must be limited so as not to cause the receiving water to be harmful to the salmon. When the assimilative capacity of the river is diminished, effluent temperature must be held to the water quality criteria. The CALFED Bay-Delta Program target is to maintain water temperatures below 68 °F in migratory routes of anadromous fish in the spring and fall. This Order requires the Discharger to study the potential impacts to the fishery associated with a discharge of effluent with elevated temperature. 42. pH: The Discharger requested in a 17 October 2002 letter that the effluent pH range for discharges to the San Joaquin River be restricted to pH 6.5 to 8.0. The reason for restricting the pH of the discharge is to facilitate less restrictive ammonia effluent limitations for the discharge to the San Joaquin River. These pH limits are included in this Order. 43. Ammonia-Nitrogen: Treated and untreated domestic wastewater, including the discharge from the WQCF, contains ammonia. Nitrification is a biological process that converts ammonia to nitrite and nitrite to nitrate. Denitrification is a process that converts nitrate to nitrite or nitric oxide and then to nitrous oxide or nitrogen gas, which is then released to the atmosphere. Wastewater treatment plants commonly use nitrification to remove ammonia from the waste stream. Inadequate or incomplete nitrification may result in the discharge of ammonia to the receiving stream. Ammonia is known to cause toxicity to aquatic organisms in surface waters. The USEPA has developed Ambient Water Quality Criteria for the Protection of Freshwater Aquatic Life,recommending acute criteria for ammonia that are pH-dependent and chronic criteria that are pH- and temperature-dependent. The WQCF effluent has a reasonable potential to cause or contribute to an in-stream excursion above USEPA acute and chronic water quality criteria for ammonia. Consistent with 40 CFR section 122.44(d)(vi)(A) and the Basin Plan "Policy for Application of Water Quality Objectives", this Order implements the Basin Plan narrative toxicity objective by applying USEPA's Ambient Water Quality Criteria for the Protection of Freshwater Aquatic Life for ammonia. This Order includes effluent limitations for ammonia,based on the narrative toxicity objective and the USEPA's Ambient Water Quality Criteria for the Protection of Freshwater Aquatic Life.