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• COLORADO DEPARTMENT OF FIEALTH, Watts Quality Control Division Rationale, Amendment No. 1 -Page 2 Perntit No. CO-0032115 IV. PURPOSE OF AMENDMENT: This amendmem is to modify the acute WET testing requirements jor this permit. This includes one change. applicable for autfalls 002 and 006.• the monitoring frequency jor acute WET testing has been changed from quarterly to annually jor both species. V. DISCUSSION OF AMENDMENT: /n a letter dated December 28, 1992, the permittee requested a waiver from the biomonitoring requirements of this permit for discharge points 002 and 006, based upon the successful completion of jour consecutive quarters of WET testing jor each discharge point that was done. The Division has reviewed this request with respect to the present existing regulations, and the Division has determined that, although no statistically sign cant mortaliry lira occurred in any of these txiv outfall wastewater concentrations, WET testing is still required, since some degree of toxicity has occurred in WET testing for this facility. Thus, for this facility, a waiver of the biomonitoring requirements it not appropriate. However, the Division has made some nuxlificntions to the permit requirements far WET testing jor this facility. The basis jor the permittee's request was in previous existing Section 6.9.7(2J(nJ(iJ(GJ of the Reerdationc (nr Starr Di.cchnree Permit System, which stated that "The biomonimring requirements contained in Section 6.9. 7 shall be presumed not ro apply to ": "industrial facilities having simple effluents of consistent quality which can lie completely characterized chemically may request a waiver from biomanitoring jar the remainder ojrhe life ojrhe perrrut, ijthe first jour quarters of testing show no exceedance ojrhe acute toxicity limit. Quarterly biomo»itoring .vill be required for the first year following each pernut renewrtl. " Since the time of the amendment request, the Reuaations for State Dirchar~ee Permit System were amended on February 2, 1993. The changes in this regulation were applicable jar WET testing requirementsc. There changes included the speck deletion of a[f types of exemptions from WET testing from the regulations', ns' well ru many other changes. The revised requirentenec for WET testing are now included in Sections 6.9.2(5J(aJ(iiJ tJvmrgh 6.9.2(SJ(aJ(vJ ojthese regulations. These sections require the Division: /J to consider for each perrrut the .cene~iti oily of the species to toxicity resting (~rherr evaluating whale effluent toxicity); 2J to inebule effluent (imitc far whale efjlueru to.ticin• if a di.achnrge emu'es or has reasonable pnrential m cnuce or measurably contributes m an instream ercursion above the numeric criterion far whole effluent tosicit}~; and 3J to evaluate the necessity of N'ET limits in perrruts, which are not necessary where the Division denwnsrrates in the rationale ojrhe permit that chemical-specific linuts jar the e,~Iuent are sufficient to attain and maintain applicable numeric antl narrative water qualirv standards. !n reviewing this permit nmendmem request, the Divrion has determined that p~pically, mine water discharges are Trot considered simple effluents of consistent quality which can be completely characterized chemically. TJnrs, the previous exemption (which is no longer included in die state regulations) jor this type of industrial discharge is not applicable, and n waiver from biantonitoring jar the remainder of the life of the pernut i.r also not applicable jar this situation at this time. !n nl! of the WET testing smrytles jor this facility, no statistically sign cunt mortality occurred; and in nw.ct ojrhe previous WET testing srunp[es for outfnllc 002 and 006, sporadic low levels of mortality occurred Sonee degree of mxiciq~ has been shown in the previous WET testing results for both discharges at various dilution caucentrnrions far dye samples ca/lected during the fourth quarter aj /992, which may indicate a change in effluent quality. Al/ dye «cute toxicity data is inckrded with t/rr permit applieatiae submittal, and a .cunanan• ojtJrlc data nrrrde by thr• Division, are both included in the pernut file.