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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 CaCO3 <br />1455 -1938 <br />42 -126 <br />mg /l <br />Bicarbonate as CaCO3 <br />1090 <br />42 -118 <br />mg /1 <br />Conductivity <br />4150 <br />80 -222 <br />Amos /cm <br />pH <br />TDS <br />8.1 -9.2 <br />7.2 -8.6 <br />standard <br />SO4- <br />2940 <br />32 -152 <br />mg /l <br />CO3- <br />134 <br />800 <br />n/a <br />8 <br />mg /1 <br />Cl- <br />216 <br />n/a <br />mg /1 <br />mg /l <br />Na <br />Fe (total) <br />1005 <br />n/a <br />mg /l <br />Ca <br />1.22 <br />0.03 -1.25 <br />mg /l <br />Mg <br />13.2 <br />n/a <br />mg 11 <br />K <br />7.88 <br />n/a <br />mg 11 <br />Sr <br />5.99 <br />n/a <br />mg /1 <br />Cu <br />2.32 <br />n/a <br />mg /l <br /><0-005 <br />0.01 max <br />mg /l <br />Pb <br /><0-05 <br />0.06 max <br />mg /l <br />Mn <br />0.04 <br />0.08 max <br />mg /1 <br />Zn <br />0.21 <br />0.02 max <br />mg /l <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 />