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SPX CORPORATION ORDER R5-2019-0018 <br /> SPX MARLEY COOLING TECHNOLOGIES GROUNDWATER CLEANUP NPDES NO. CA0081787 <br /> analysis considering varying ambient hardness and flow conditions. To do this, the <br /> Central Valley Water Board has ensured that the receiving water hardness and <br /> criteria selected for effluent limitations are protective under "reasonable-worst case <br /> ambient conditions." These conditions represent the receiving water conditions <br /> under which derived effluent limitations would ensure protection of beneficial uses <br /> under all ambient flow and hardness conditions. <br /> Reasonable worst-case ambient conditions: <br /> • "Low receiving water flow." CTR design discharge conditions (1Q10 and 7Q10) <br /> have been selected to represent reasonable worst case receiving water flow <br /> conditions. <br /> • "High receiving water flow (maximum receiving water flow)." This additional flow <br /> condition has been selected consistent with the Davis Order, which required <br /> that the hardness selected be protective of water quality criteria under all flow <br /> conditions. <br /> • "Low receiving water hardness." The minimum receiving water hardness <br /> condition of 124 mg/L was selected to represent the reasonable worst case <br /> receiving water hardness. <br /> • "Background ambient metal concentration at criteria." This condition assumes <br /> that the metal concentration in the background receiving water is equal to CTR <br /> criteria (upstream of the facility's discharge). Based on data in the record, this <br /> is a design condition that has not occurred in the receiving water and is used in <br /> this analysis to ensure that limits are protective of beneficial uses even in the <br /> situation where there is no assimilative capacity. <br /> Iterative approach. An iterative analysis has been used to select the ambient <br /> hardness to calculate the criteria that will result in effluent limitations that protect <br /> beneficial uses under all flow conditions. <br /> The iterative approach is summarized in the following algorithm and described <br /> below in more detail. <br /> ATTACHMENT F- FACT SHEET F-18 <br />