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WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2004-0028 -11- WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2004-0028 -12-
<br /> CITY OF MANTECA,CITY OF LATHROP AND DUTRA FARMS CITY OF MANTECA,CITY OF LATHROP AND DUTRA FARMS
<br /> WASTEWATER QUALITY CONTROL FACILITY WASTEWATER QUALITY CONTROL FACILITY
<br /> SAN JOAQUIN COUNTY SAN JOAQUIN COUNTY
<br /> Application of Water Quality Objectives").Based on information submitted as part of the Based Toxics Control((EPA/505/2-90-001)TSD)recommends a coefficient of variation of 0.6
<br /> application,in studies,and in monitoring reports,the Regional Board finds that the discharge be utilized as representative of wastewater effluent sampling. The TSD recognizes that a
<br /> does have a reasonable potential to cause or contribute to an in-stream excursion above a water minimum often data points is necessary to conduct a valid statistical analysis. The multipliers
<br /> quality standard for aluminum,ammonia,arsenic,chlorine,copper,cyanide,bis(2- contained in Table 5-2 of the TSD are used to determine a maximum daily limitation based on a
<br /> ethylhexyl)phthalate,bromodichloromethane,dibromochloromethane,electrical conductivity, long-term average objective. In this case,the long-term average objective is to maintain,at a
<br /> iron,manganese,MBAS,mercury,nitrate,nitrite,pH,temperature,total dissolved solids and minimum,the current plant performance level. Therefore,when there are less than ten sampling
<br /> 2,4,6-trichlorophenol. Final effluent limitations and/or interim performance-based effluent points for a constituent,interim limitations are based on 3.11 times the maximum observed
<br /> limitations and interim requirements with compliance schedules for the pollutants listed above sampling result to obtain the daily maximum interim limitation(TSD,Table 5-2). The Regional
<br /> are included in this Order. In addition,this Order contains provisions that: Board finds that the Discharger can undertake source control and treatment plant measures to
<br /> maintain compliance with the interim limitations included in this Order. Interim limitations are
<br /> a. Require the Discharger to conduct a study to provide information as to whether the levels established when compliance with NTR-and CTR-based effluent limitations cannot be achieved
<br /> of dioxins in the discharge cause or contribute to an in-stream excursion above a water by the existing discharge. Discharge of constituents in concentrations in excess of the final
<br /> quality standard,including Basin Plan numeric or narrative objectives; effluent limitations,but in compliance with the interim effluent limitations,can significantly
<br /> degrade water quality and adversely affect the beneficial uses of the receiving stream on a long-
<br /> b. If the discharge has a reasonable potential to cause or contribute to an in-stream excursion term basis. The interim limitations,however,establish an enforceable ceiling concentration until
<br /> above a water quality standard,requires the Discharger to submit information to calculate compliance with the effluent limitation can be achieved.
<br /> effluent limitations for those constituents;and
<br /> 31. Dilution:As discussed in the information sheet,the Discharger developed a model to assess
<br /> C. Allows the Regional Board to reopen this Order and include effluent limitations for those dilution and mixing zones. The accuracy of the model results are questionable due to a lack of
<br /> constituents. site data to calibrate and validate the model,the lack of accounting for tidal cycles and
<br /> recirculation,and the lack of accounting for the Brown Sand,Inc.discharge adjacent to the
<br /> On 10 September 2001,the Executive Officer issued a letter,in conformance with California outfall. However,because there is no in-stream flow meter in the vicinity of the discharge to
<br /> Water Code Section 13267,requiring the Discharger to prepare a technical report assessing provide real-time data,this Order relies on flow information from the Vernalis monitoring
<br /> water quality. This Order is intended to be consistent with these requirements in requiring station,as well as some of the model information as it is available. This Order also requires the
<br /> sampling for dioxins to determine the full water quality impacts of the discharge. The technical Discharger to install a flow monitoring station in the vicinity of the outfall to provide real-time
<br /> report requirements are intended to be more detailed,listing specific constituents,detection data to better assess available dilution.
<br /> levels,and acceptable time frames and shall take precedence in resolving any conflicts.
<br /> In the immediate vicinity of the outfall,little dilution is available for the side-bank discharge. In
<br /> 30. As stated in the above Finding,the USEPA adopted the NTR and the CTR,which contains water addition,the dilution is reduced due to the added discharge from the Brown Sand impoundment
<br /> quality standards applicable to this discharge. The SIP contains policies and procedures for immediately downstream. No dilution is available for the acute aquatic criteria due to the
<br /> implementation of the NTR and CTR. The SIP,Section 2.2.1,requires that if a compliance limited mixing of the side-bank discharge near the outfall,the commingling with an adjacent
<br /> schedule is granted for a CTR or NTR constituent,the Regional Board shall establish interim NPDES discharge,the 1-hour exposure interval that the acute criteria are intended to protect,and
<br /> requirements and dates for their achievement in the NPDES permit. The interim limitations the periods of slack tide that can occur at low river flows.
<br /> must be based on current treatment plant performance or existing permit limitations,whichever
<br /> is more stringent;include interim compliance dates separated by no more than one year,and;be The SIP requires that a mixing zone not dominate or compromise the integrity of the entire water
<br /> included in the Provisions.The interim limitations in this Order are based on the current body and shall be as small as practicable. The thermal modeling,while not proven to be
<br /> treatment plant performance. In developing the interim limitation,where there are ten sampling accurate,as discussed in the information sheet,presented a spatial definition to the changes in
<br /> data points or more,sampling and laboratory variability is accounted for by establishing interim temperature that occur in the receiving water. This was used to define a mixing zone for
<br /> limits that are based on normally distributed data where 99.9%of the data points will lie within constituents subject to chronic aquatic criteria and dilution to be determined at the edge of this
<br /> 3.3 standard deviations of the mean(Basic Statistical Methods for Engineers and Scientists, mixing zone. As discussed further in the information sheet,the mixing zone will be restricted to
<br /> Kennedy and Neville,Harper and Row). Therefore,the interim limitations in this Order are the surface layer of the water column in a plume hugging the eastern shore of the river and
<br /> established as the mean plus 3.3 standard deviations of the available data. Where actual extending to 450 feet downstream of the outfall. Temperature differences at the edge of this
<br /> sampling shows an exceedance of the proposed 3.3-standard deviation interim limit,the mixing zone indicate that a 4:1 dilution exists at the edge of this mixing zone. Therefore,for
<br /> maximum detected concentration has been established as the interim limitation. When there are constituents subject to chronic aquatic criteria,a 4:1 dilution will be applied. This mixing zone
<br /> less than ten sampling data points available,the Technical Support Document for Water Quality
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