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• <br />• <br />• <br />These ambient based standards were based of the 50 percentiles of TR iron values <br />collected on streams prior to mining. The following is from section 61.8(2)(b)(iv) of Reg. <br />61, Discharge Permits... <br />"Where subsection (b) is applicable, the permit shall be written with effluent limitations <br />that respect the methods by which water quality standards were derived, and the degree <br />of variation of water quality that exists in the relevant stream segment or ground water <br />on a seasonal basis or otherwise." <br />The Cripple Creek and Victor CPDS Permit CO- 0043648 Rationale provides an example <br />as how to apply this method into a discharge permit. On page 10, it states: "The Division <br />has analyzed the latest five years of data for zinc at Outfall OOIA and the 85 percentile <br />of that data is 590 ug /l which is 98.3% of the 600,u g/l water quality standard. Therefore, <br />there is a reasonable potential that the discharge from the Sedimentation Pond will cause <br />or contribute to an exceedance of this water quality standard and a limit of 600 ,ug/l will <br />be set in the permit. The limit, with respect to the method by which the water quality <br />standard was derived for adoption by the Commission, will be set based on a "moving <br />8 5 th percentile" of five years of data including the month for which reporting is <br />required." <br />The ambient based Sage Creek standard was based on nineteen years worth of premining <br />data. The Dry Creek standard was based on seven to twenty -one worth of premining data <br />from three sites. As these time frames are exceptionally long, Seneca suggests that their <br />ambient based standards for TR iron in this CPDS permit be based on a moving 50 <br />percentile of five years of data, similar to the Cripple Creek and Victor permit. If the <br />Division decides to put an `administrative extension' on this permit, then we would ask <br />that the TR iron standards for outfalls on Grassy, Sage and Dry Creeks be updated as a <br />`permit amendment'. <br />One another matter, Seneca wishes to inform the Division that by the end of May 2011, <br />Seneca will have enough data points (10) to perform reasonable potential (RP) analyses <br />on the remaining outfalls that were not done in the March 2010 permit amendment. Those <br />outfalls are 005, 011 and 013 (which have a MN prefix in the permit and DMRs). Seneca <br />will provide those data to the Division in electronic (Excel) format upon request. As with <br />the iron standards, if the Division decides to put an `administrative extension' on this <br />permit, then we would ask that the RP analyses be updated as a `permit amendment'. <br />Now, back to the application form: <br />1 to 3: See application form. <br />4: See Figure 1. <br />