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z1 <br />l~ <br />• <br />5 WILLOW CREEK WATER QUALITY <br />5.1 Historic solute concentrations in Willow Creek <br />From 1966 to 1993, water samples along various reaches of Willow Creek have been collected <br />and analyzed for chemical species including cadmium and zinc. Many of the sample analyses <br />have been archived in a database by the Homestake Mining Company. As part of the Windy <br />Gulch evaluation, sampling records for which the location can be reasonably verified have been <br />divided into several reaches as shown in Plan 5.1 and analyzed to better understand potential <br />source areas of chemical solutes such as cadmium and zinc. West Willow Creek was divided as <br />follows: water above the Equity Mine, water between the Equity Mine and the Commodore <br />Mine/Nelson Tunnel, water below the Commodore MinelNelson Tunnel and above the confluence <br />with East Willow Creek, water between the confluence of West Willow and East Willow and just <br />above Windy Gulch, water below Windy Gulch and above Creede, and water below Creede down <br />to the Rio Grande River. The overall historic average for the total concentration of each chemical <br />species was calculated for each reach. The average values are presented in Table 5.1 and shown <br />graphically in Figure 5.1. <br />Table 5.1 Willow Creek historic average cadmium and zinc concentrations <br />Reach name Number of <br />samples Mean Cd <br />concentrations <br />(mg/L) Mean Zn <br />concentrations <br />(mglL) <br />A) West Willow Creek -Above Equity Mine 15 0.00070 0.0082 <br />B) West Willow Creek -Below Equity Mine <br /> and above Commodore Mine/Nelson 46 0.0025 0.20 <br /> Tunnel <br />C) West Willow Creek -Below Nelson <br /> 8 0.027 1.8 <br /> Tunnel and above E. Willow confluence <br />D) Willow Creek -Between E. Willow/ <br /> W. Willow confluence and above 16 0.0089 1.1 <br /> Windy Gulch <br />E) Willow Creek -Below Windy Gulch and <br />22 <br />0.0073 <br />0.88 <br /> above town of Creede <br />• F) Willow Creek -Below Creede and above 53 0.012 3.0 <br />Rio Grande confluence <br />