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' 02/03/:995 16:08 303-782-0390 CDH WOCD W~CC PAGE 02 <br />COLORADO DEPARTMENT OF HEALTH. Water Quality Control Division {~U ' <br />Rationale -Page 7, Permit No. CO-0043648 1 <br />Since the mean hardness at both ojrhe stationrjot wttirch data xns sunvnarized (AG 1 and AG 1. S) u <br />greater than 400 rt{gR, which is the highest valet allowed Jot use in metals standards calculatrons, the <br />s+obte of 400 trtig/1 will 6e used to do the calculations. ]he reulting starulards will then apply at all <br />locations along Arcqua Gulch Tltcfollowing table summarize the metals standards jar all user. <br />Table Il!-1 Melds Standards Summary - Anqua Gulch, Segment ll ojthe Upper Arkansaf Sub-basin of <br />the Arkansas R/vrr Basle. All Canuntratianr Acs ug/1 <br />Mctlwd!) <br />(Total <br />AcrCC C7tryttie Qrrottbe. <br />Arsuuc 50 SO - <br />Cadmium 19 3.4 !0 <br />Qvortuum 11I SO SO - <br />Chromlum V/ 16 11 /00 <br />Copper 65 39 200 <br />Iron - 1000• - <br />Lead 899 28 /00 <br />Monganee - 1000• - <br />Mcrcury - 0.01 • - <br />Nicke/ 2645 274 2AD <br />Selenium !33 17 20 <br />Silver 22 - - <br />Zinc 379 343 2000 <br />Aquatic Life Use standan3r are bass upon the dissolved method of analysis, ercepr for iron and manganese <br />standards, which arc based upon the total recovnabfe method, and the mercury standard, which is based upon <br />the total method. <br />Due w the fact that there will be no sign cant source of ammonia associated with the active mining <br />operation, it will not be a po/futont of concern urttil reclamation of the lcach heap !t begun, of it is <br />ducrmintd that ryande rrmova! is requtred for any unanticipated discharge. Ar that rims, however, <br />ammonia will be created as a by-product of the chemical reacrianr that will be used in the destruction of <br />ryanide. Since the leach heap linens will be breached as part of the fine! reclamat(on ojthe site, it will <br />then be possible for any ammonia that remains within the heap to be leached into the underdrain rysttm, <br />and then enter Arequa Gulch. And, even brfore the Ilner u breached, Ir is possible that ammonia may <br />reach Arequa Gulch through leaks or spills. <br />Since ammonia limits will not be required prior to the nut permit renewal, it is nor necessary to discass <br />ammonia stream statulards ir. great detail rn this ranonaic. However it should be cared the the D/vision <br />standaMly use the Cobrado Ammonia Madcl in order ro evaluate ammonra effluent lirndtruians. Th1s <br />model requires 3 to 4 years worth of weekly instream pH and temperature measuremtn(s. <br />WhUe !t tr possible then the eta permit will be written early rnavRh to include provGlons for the rnllection <br />or this amours: of data prior to the need for ammonia limn, the perourtee . ~::~uld Independently track the <br />progress of the mining project anti prepare for the collection of pH and rnnperarure data apprarimately 4 <br />ro S years before the data wW be needed. Ar that time, the Division should be consulted with regard ro <br />the sped monitoring praeedurrs chat should be followed. <br />