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, COIsORADO DEPARTMENT OF HEALTH, Water Qunliry Control Division Rurmnrrle - PgKe 7, Permit No. CO-0043567 Discharge Point Chronic Low Flow, Facility Design Flow, IR'C, (%) 30E3, (cjs) (cjs) 001 -003 0 4 100 Because the low flow is zero, the IWC for this permit is 100% regardless ojrhe eQluent Jlo+v. 71ris represents a wastewater concentration of 100% e,~luent to 0% receiving stream. Therefore, chronic conditions are applicable to this permit. 3J Chronic WET Limitations: Previous monitoring darn has shown that mine water from cool mining facilities contains heavy metals and/or other toxic pollutants and, therefore rs likely to be toxic. Orr this basis, the Division believes there is reasonable potential jar the discharges from outfalls 001, 002 and 003 to interfere with attainrnen[ of applicable water quality classifications or standards. As required under section 6.9.2 (5J of the Reeulntions (ar the State Discharee Permit System, the chronic limitation has been incorporated into the permit and becomes effective immediately. The pennirtee is required to conduct routine monitoring. The results of the resting are to be reported on Division approved forms. The calculations will look at the full range of toxicity (lethality', growth and reproduction), i. e., whether there is a statistically significant difference in the lethnlirv (at the 95% confidence IevelJ between the control and any effluent concentration less than or equal ro dre ln.ctream Rraste Concentration QR'CJ. Exceedance ojrhe limitation specked in Part LA. 1. (hJ will trigger dre requirement for conducnng the automatic compliance schedule ident~ed in Pnrr 1. B. ojrhe permit. /f the toxicirv is due to differences in the growth ojrhe fathead minnows or the reproduction ojtlre Ceriodnphuin, no immediate action on the part of the permittee will be required. However, this inciden[, along with other Li'ET data, will be evaluated by the Division and ma}' john rlie basis for reopening the pernrit and including additional WET firrtits or other requirements. 4J Cenernl !n(ormnrian: The pennirtee should rend the WET testing sections ojPnrt LA. and 1. B. of the permit cnrefidh•. The permit outlines the rest requirements and the required follow-up actions the permittee roust take to resolve a toxicity incident. The permittee should read, along with the documents listed in Pnrr 1. B of the permit, the Colorado Water Oun(irv Control Division Biomonirorin~ Guidance Document. doted July 1, 1993.. 77ris document outlines the criteria used by the Divisrmr in such nrem~ as granting reliejfrom R'ET resting, modh•ing test rnedmds and chnngurg test species. The pennirtee should be aware that some of the conditions ourlmed above may be subject ro change f the fircilin' experiences n change in discharge, ns outlined in Pnrr ll.A.l of dre permit. Such chnn,pe~ shall be reported m the Drvision invnediatel}'. .. Srnnnwnrer: Active and inactive coal mining operations +vhere stonnwater comes into contact +with overburden, row nuuerml, imermedinte products, byproducts, finished products or ~rnste products locnrerl nr the mining sire ore mcluded in category (iii) ojrhe federal stonnwarer regulations. Such jncilirier ore rc'grdred ru bore applied for n pennir to discharge srornnrnrer rusocinred with mining nctivu}' on or brfore Ocmber 1, 1992. Kerr Caal has been covered under the general permit for surface coo( mines, +~/rich includes proei.ciar.c far stonnx•nrer discharges. 77ris facility's cerr fcntinn under the genera! pernur become e/jecnve nn July 1, /99?. The Kerr M11ine cerufcruion number is COG-85002/. %la rlisne~srd en r!i er m the rrruamfe, cu range%ar rhr.c fircrlity is changing from n penernl pernvr to un indmidurrl pennir. 77re npplicrrble smrnuvnter provisions will be included m rIris new CDPS pernur, rr, dc~cribed below. R9ien this inrliridunl pernur becomes effective, cerrficntion COG-S.i002I u•il! 6e urrrcn voted. Under the terncs ojrhe combined individual pennir (CO-0043567), Kerr Con! will 6e authuri~erl ru discharge sturur+wnrer n.c.cocinrerl st~irlr industrial ncrivin' into +:'arerc u(the Smre of Calorarlu.