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INFORMATION SHEET ORA NO. R5-2004-0028 • 10 <br /> CITY OF MANTECA, CITY OF LATHROP AND DUTRA FARMS <br /> WASTEWATER QUALITY CONTROL FACILITY <br /> SAN JOAQUIN COUNTY <br /> With regard to groundwater, domestic wastewater contains constituents such as total dissolved solids <br /> (TDS), specific conductivity, pathogens,nitrates, organics, and metals. The Discharger's use of <br /> unlined ponds and the application of wastewater and sludge to land may result in an increase in the <br /> concentration of these constituents in groundwater. Some degradation of groundwater by the <br /> Discharger is consistent with Resolution 68-16 provided that: <br /> a. The degradation is limited in extent; <br /> b. The degradation after effective source control,treatment, and control is limited to waste <br /> constituents typically encountered in municipal wastewater as specified in the <br /> groundwater limitations in this Order; <br /> c. The Discharger minimizes the degradation by fully implementing, regularly <br /> maintaining, and optimally operating best practicable control technology(BPCT) <br /> measures; and <br /> d. The degradation does not result in water quality less than that prescribed in the Basin <br /> Plan, e.g., does not exceed water quality objectives. <br /> The discharge to land authorized by this Order must comply with groundwater limitations, ground <br /> water monitoring requirements and a schedule to evaluate whether the Discharger is implementing best <br /> practicable treatment or control of the discharge. Compliance with this Order will result in use of best <br /> practicable treatment or control and will not further degrade the groundwater. <br /> 8 Acute Toxicity <br /> Order No. 97-115 prescribed stricter acute toxicity test procedures than the Discharger's previous <br /> permit. Specifically, the acute toxicity bioassay parameters were revised to require compliance with <br /> the latest testing procedures contained in EPA/600/4-90/027F. The new USEPA procedure requires <br /> the use of larval stage(0 to 14 days old) fathead minnows or golden shiners instead of the previous <br /> method of using juveniles (15 to 30 days old). Larvae are much more sensitive to ammonia levels than <br /> the juvenile species. The new USEPA procedure for the acute bioassay test constitutes a more <br /> stringent acute toxicity limitation. This Order allows the Discharger to remove ammonia prior to <br /> conducting acute toxicity tests until 1 April 2004,when facilities are required to be operational to fully <br /> nitrify the wastewater. <br /> 9 Non-priority pollutants <br /> 9.1 Residual Chlorine <br /> The Discharger currently uses chlorine for disinfection and has reported that it uses sodium <br /> hypochlorite for maintenance. Chlorine is extremely toxic to aquatic organisms. The Discharger uses <br /> a sulfur dioxide process to dechlorinate the effluent,but will discontinue this with the installation of <br /> the UV disinfection system. Because of the existing chlorine use and the future use of hypochlorite <br /> solutions without effluent dechlorination, there is reasonable potential for chlorine to be discharged at <br /> toxic concentrations. The Basin Plan contains a narrative toxicity objective. Consistent with 40 CFR <br /> 122.44(d), it is appropriate to use the USEPA ambient water quality criteria for chlorine for protection <br /> of freshwater aquatic life of 11 ug/l as a 4-day average (chronic) concentration, and 19 ug/I as a 1-hour <br />