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REGIONAL WATER BOARD RESPONSE (SWRCB/OCC File A-1846(a) and A-1846(b)) 11- <br /> PETITIONS FOR REVIEW OF Vt�.-E DISCHARGE REQUIREMENTS <br /> ORDER NO. R5-2007-0036 (NPDES NO. CA0079154) AND <br /> TIME SCHEDULE ORDER NO R5-2007-0037 <br /> CITY OF TRACY, WASTEWATER TREATMENT PLANT <br /> Figure 1 : Modeled Salinity Impacts <br /> Old River at Tracy Blvd Bridge , <br /> ! Monthly Average <br /> 1,000 <br /> 900 <br /> 800 - - <br /> 700 - <br /> [-]Tracy <br /> Portion' <br /> _ _ <br /> E 600 <br /> 500 [a Other EC Inputs" <br /> U 400 <br /> 300 ■Ambient EC <br /> Upstream of Tracy <br /> 200 - Discharge <br /> I� 100 <br /> 0 0 0 0 <br /> 0 0 0 <br /> li N N N N N I <br /> Q (A UO Z <br /> II <br /> The Tracy Portion is DSM2 model predictions using a reasonable worst-case scenario as described in <br /> Attachment H. The Other EC Inputs were calculated based on the measured EC at Tracy Blvd Bridge <br /> —Tracy Portion—measured ambient EC upstream of Tracy discharge. <br /> In Order No. R5-2007-0036, the Regional Water Board found that imposing WQBELs for <br /> salinity that require the construction and operation of reverse osmosis facilities to treat <br /> discharges prior to implementation of other measures to reduce the salt loading in the <br /> southern Delta was not a reasonable approach. The City of Tracy discharge is one of many <br /> contributors to the salinity problems in the southern Delta. Even if the City of Tracy discharge <br /> was removed it would not solve the salinity problems in the area. The Order provides <br /> reasonable salinity controls, as described below, that put the Discharger on the path to <br /> reducing its salt loading to the Delta. <br /> The Order includes an interim annual mass loading effluent limitation for TDS and requires the <br /> Discharger to implement measures to reduce the salinity of its discharge to Old River. The <br />