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S. Wanstedt <br />May 20, 2016 <br />Page 2 <br />Based on the elevated conductivity values for all samples in the table above and the high chloride <br />concentrations measured in a limited number of samples, chloride was investigated as a primary <br />source of toxicity to D. magna and P. promelas. We attempted to determine a relationship between <br />conductivity and chloride so that we could estimate chloride concentrations for samples in which <br />conductivity was measured, but chloride wasn't. This approach was based on your assessment that <br />the chemical composition of the water was stable. Unfortunately, there was not a reliable relationship <br />between conductivity and chloride for this dataset, which was limited (n = 4). <br />TRE has extensive historical chloride toxicity databases for D. magna and P. promelas. Our next <br />approach was to compare the responses in the WET tests (based on chloride) to our in-house <br />chloride LC5o databases. Using the studies in Table 1 that have LC50 values as well as chloride <br />concentrations, the LC50 values were converted to mg/L chloride instead of percent effluent. This <br />resulted in three studies with LC50 values expressed as mg/L chloride, one for D. magna and two for <br />P. promelas. Those results were overlaid onto our reference toxicant charts which plot LC50 as <br />chloride over time. The resultant chart for D. magna is presented below (Figure 1): <br />4100 , -- -- - - -- - - - <br />3900 <br />d <br />.°3700 <br />`2 <br />v <br />3500 <br />R <br />O <br />O <br />3300 <br />Z <br />Co <br />3100 <br />2900 <br />Test Dates <br />♦ Ref Tox 48h LC50 LCL UCL • Deserado Mine 48h LC50 <br />Figure 1. 48h LC50 as mg/L chloride for D. magna, TRE in-house reference toxicant database <br />and Deserado Mine data <br />TRE Environmental Strategies, LLC <br />L <br />Q 1 <br />v �r <br />U <br />1 <br />�r ck _ O <br />CoCL0 <br />Cn <br />-i_0---- -2 <br />--- <br />N <br />LL� N <br />O <br />r <br />O <br />-- <br />Q-- j <br />O <br />i <br />Test Dates <br />♦ Ref Tox 48h LC50 LCL UCL • Deserado Mine 48h LC50 <br />Figure 1. 48h LC50 as mg/L chloride for D. magna, TRE in-house reference toxicant database <br />and Deserado Mine data <br />TRE Environmental Strategies, LLC <br />