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<br />COLORADO DEPARTMENT OF PUBL/C HEALTH AND ENV/RONMENT, Water Quality Control Division <br />Amendment No. 3-Ra[ionale. Page 4, Perini[ No. CO-0000132 <br />Where: <br />Q, = Upstream lnx~ flow (41 cjsl <br />Q1 = Mtttimurn discharge flniv (0.45 cjs nr 0.288 MGD) <br />Q3 =Combined downstream Jlnw (Qr + Q;} <br />tY1, = Upstream background poflutant conretttrarion -represents t/te mean of quarterly samples collected in 1998 <br />by [he permittee as required by the Colorado Division gf.Minerals artd Geology <br />rti1, _ (lttknown; Mnxi[nuttt allowable e~luettt pollutant concentration calculated using mass balance equation <br />M, = Maxintttm dmvnstrearn allox~able pollu[artt concentration (WQS for segment 3) <br />Tl:e teen M3QJ represents the mass of a polhaan[ that can be carried by the receiving stream without violating stream <br />stmtdards. The terns M1Q, represents the pollutant load that already exists instream above the discharge point in <br />question. Tl:e difference between the nvo loads, which it MjQJ - MrQr, represents the loading shot can he allocated to <br />the discharge. <br />The Division will authorize this discharge. Al! terms and conditions, including effluent limitations and monitoring <br />requirements, that currently apply to outfall 011 will apply to this temporary discharge point. Additionally, to verify <br />that the discharge metals concentra[ions are insigniftcan[, the Division will require, by separate letter, a second nte[als <br />analysis using the !owes! method detection level. These results will be reviewed. If there is reason for concern that <br />the discharge may exceed potential limitations, the Division will work with the permittee to assure that adequate <br />treatment is occurring, and may reopen the permit to take appropriate ac[ion. <br />Additionally, since whole effluent toxicity (WET) testing is required for oulfa[l 011 on a quarterly basis and no <br />discharge has occurred from the permanent discharge location during the second calendar quarter of 1999, the <br />Division requests that the permittee collect a satttple for this purpose from this temporary outfa[I during [he first week <br />of discharge. This will provide an additional measure of the quality of this discharge. This sample will count as [/re <br />routine sampee for the second quarter that is required under Pan !. B.I. (b) of the permit. <br />This authorization is for aone-time short-term activity only. The permittee projects that when the mine reopens, <br />pumping will resume and discharge will occur at the authorized mine water discharge point, autfall 011. !f the <br />perntittee determines that this inflow to the mine will be chronic and this water will need to be discharged on a long- <br />term basis, they will need to submit a request for a permanent amendment to authorize it. <br />Figure 4 is being added to the permit to show the location of temporary outfall 011. This figure is added as page 21a <br />of the permit. <br />Because this action does not change any permit conditions, it is not subject to public notice provisions <br />Jon C. Kubic <br />April 30, 1999 <br />