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Minrec, Incorporated Water Quality Assessment CO- 0048233 <br />The permittee will have the option of choosing either the NIL's or ADBAC's. For the purposes of this <br />review, where there was no previous permit limitation, a new or increased impact was assumed. <br />For the parameters that show a new or increased impact, the final two significance determination tests <br />(bioaccumulative and concentration) need to be applied, to determine if AD limits are applicable. For the <br />bioaccumulative test, the determination of the baseline water quality (BWQ), the baseline water quality <br />loading (BWQload), the threshold load (TL) and the threshold load concentration (TL conc) needs to <br />occur. For the concentration test, the BWQ, significant concentration thresholds (SCT) and <br />antidegradation based average concentrations (ADBACs) need to be calculated. These calculations are <br />explained in the following sections, and each significance determination test will be performed as the <br />necessary calculations are complete. <br />Determination of Baseline Water Quality (BWQ) <br />The BWQ defines the baseline low flow pollutant concentration, and for bioaccumulative toxic pollutants, <br />the baseline load. The BWQ is to take into account the influence of the discharger if the discharge was in <br />place prior to September 30, 2000. In such a case, data from a downstream location should be used to <br />determine the BWQ. If only upstream data is available, then a mass balance equation may be applied, <br />using the facilities effluent data to determine the BWQ. If the discharge was not present prior to <br />September 30, 2000, then the influence of that discharge would not be taken into account in determining <br />the BWQ. <br />This discharger was in place as of September 30, 2000, and therefore the BWQ will include the influence <br />of the discharger. Consistent with current Division procedures, the BWQ concentrations for all pollutants <br />of concern should be established so that it can be used as part of an antidegradation review. <br />The BWQ concentrations were correctly determined for dissolved cadmium, dissolved copper, total <br />recoverable iron, dissolved lead, total mercury, dissolved nickel, dissolved selenium, and dissolved silver as <br />part of a previous WQA (2001). These are summarized in Table A -10. <br />Table A -10 <br />BWQ Concentrations Based on Previous Determinations Using U stream and Effluent Data <br />Pollutant <br />Meff <br />Qeff (cfs) <br />MM/S <br />Q -/S (cfs) <br />BWQ <br />WQS <br />Cd, Dis (µg /t) <br />4 <br />0.39 <br />0.0 <br />0.20 <br />2.6 <br />2.8 <br />Cu, Dis (µg /t) <br />0 <br />0.39 <br />2.2 <br />0.20 <br />0.75 <br />11 <br />Fe, TR (µg /1) <br />780 <br />0.39 <br />830.0 <br />0.20 <br />797 <br />1000 <br />Pb, Dis (µg /1) <br />0 <br />0.39 <br />0.0 <br />0.20 <br />0 <br />3.4 <br />Hg, Tot (µg /1) <br />0 <br />0.39 <br />0.0 <br />0.20 <br />0 <br />0.01 <br />Ni, Dis (µg /1) <br />0 <br />0.39 <br />0.0 <br />0.20 <br />0 <br />66 <br />Se, Dis (µg /1) <br />0 <br />0.39 <br />0.25 <br />0.20 <br />0.085 <br />4.6 <br />Ag, Dis (µg /1) <br />0 <br />0.39 <br />0.0 <br />0.20 <br />0 <br />0.12 <br />The BWQ concentrations were not determined for dissolved and total arsenic, dissolved manganese, <br />dissolved zinc, sulfide, and boron in the previous WQA (2001). Therefore, the BWQ for these <br />constituents is determined as part of this WQA analysis. <br />Appendix A (WQA v 7.0) Page 19 of 25 Last Revised Sept 14, 2009 /ES <br />