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• r • <br />Water quality issues <br />A number of issues were raised by the DOW regarding overall water quality and impacts to the <br />surface water system and resident aquatic life. <br />Flathead chub <br />The DOW has expressed concerns that mining activity could impact the flathead chub <br />population identified in portions of Lorencito Canyon and the Purgatoire River. The <br />applicant responded that the control and treatment of dischazges from the mining azea, <br />water quality monitoring and NPDES dschage monitoring (including Whole Effluent <br />Toxicity testing) should be adequate to protect resident chub populations. Discussions <br />with the DOW indicate that they believe actual, periodic population sampling is necessary <br />to determine the on-going status of chub populations. The DOW has verbally committed <br />to discuss this issue and respond with a recommendation toward the end of June. This <br />issue remains inadequate at this time. <br />Brown Trout <br />The DOW has concerns based on past experience that 'von concentrations of 2.4 mg/1 <br />indicate other metals (specifically cadmium, copper, and zinc) aze present at toxic levels <br />to aquatic life. While no specifics were provided, the Division assumes that acid <br />conditions likely prevail under this scenazio, causing the metals problem. The applicant <br />has presented baseline data indicating the concentrations of cadmium, copper, and zinc. <br />The Water Quality Control Commission determines effluent limitations as part of the <br />Colorado Discharge Permit System, based on stream classification and standazds. <br />Furthermore, the Division's experience indicates iron and manganese concentrations are <br />relatively high in coal basins, while pH levels aze neutral to alkaline and other meta] <br />concentrations aze below the detection limit. Not withstanding, the Division believes the <br />DOW concern is valid and will make every effort to analyze water sampling data to <br />determine whether metal concentrations aze increasing due to mining activities through <br />review of the annual hydrology report required to be submitted. Currently, there is no <br />evidence which indicates that mining will cause concentrations of cadmium, copper, and <br />zinc to increase beyond applicable standazds. Tlils issue is therefore adequately addressed. <br />Detection limits <br />The DOW expressed the concem that the method used to analyze vazious constituents be <br />changed to allow detection of small concentrations of the constituent. This is appazently <br />necessary due to very low levels of some metals being toxic to fish and aquatic life. <br />However, as hardness and alkalinity go up, the toxicity is reduced. For example, for <br />copper, fresh water organisms should not be affected at 4-day average concentrations of <br />6.5, 12, and 21 ug/1 at a hazdness of 50, 100 and 200 mg/1 respectively (F.PA, 1986). The <br />baseline surface water hazdness in Lorencito Canyon is neazly 200 mg/1. This <br />phenomenon is also recognized for cadmium. However, the Division concurs that <br />detection limits should be at the lowest possible levels given equipment and analysis <br />