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Table 1. Comparison of water quality parameters from the Sanborn Creek Mine and the North <br />Fork of the Gunnison River. Ranges are shown where data were available. <br />Parameter Mine Effluent North Fork Units <br />Alkalinity as CaC03 1455-1938 42-126 mg/1 <br />Bicarbonate as CaC03 1090 42-118 mg/1 <br />Conductivity 4150 80-222 µmos/cm <br />pH 8.1-9.2 7.2-8.6 standard <br />TDS 2940 32-152 mg/1 <br />SOa 134 n/a mg/1 <br />COQ 800 8 mg/1 <br />Cl- 216 n/a mg/I <br />Na 1005 n/a mg/1 <br />Fe (total) 1.22 0.03-1.25 mg/1 <br />Ca 13.2 n/a mg/1 <br />Mg 7.88 n/a mg/1 <br />K 5.99 n/a mg/1 <br />Sr 2.32 n/a mg/I <br />Cu <0.005 0.01 max mg/1 <br />Pb < 0.05 0.06 max mg/1 <br />Mn 0.04 0.08 max mg/1 <br />Zn 0.21 0.02 max mg/1 <br />n/a denotes not available <br />METHODS <br />The aquatic impairment study was conducted in accordance with guidelines obtained from the <br />Colorado Water Quality Control Division (WQCD). Methods were developed following <br />discussion with WQCD of a draft work plan in November, 1993, and field reconnaissance of <br />the site. <br />Biological Inventory: <br />Biological sampling was conducted at five stations upstream and five stations downstream of <br />the discharge point. Actual lengths of the upstream and downstream reaches to be sampled <br />were limited by the proximity of other potential pollutant sources, including other mines, as <br />well as municipal sources near the town of Somerset. The downstream reach from where the <br />5 <br />