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Mr. Alan Cox <br />November 30, 2007 Page 5 <br />2004 dropped below 2 mg/l. The initial sample in 2005 was about 3 mg/1 with subsequent samples <br />during that year at about 1 mg/I. In 2006, there was minimal flow in Windy Gulch and the only <br />sample taken was just below 2 mg/l. In 2007, the highest concentration during the initial spring <br />runoff period was just over 2 mg/1 with subsequent samples during the active flow period around 1 <br />mg/1. During 2007, a sample taken during the tail of the runoff period showed slightly increased zinc. <br />This sample was taken during a period of relatively low flow in Windy Gulch when the proportion of <br />water derived from flow in the streambed sediments was higher. Longer contact time with the <br />streambed sediments is expected to result in higher constituent concentrations. Cadmium <br />concentrations shown in Figure 4 have a similar pattern of variation to the zinc concentrations. Both <br />zinc and cadmium concentrations exhibit a downward trend over time. <br />Figures 5 and 6 show TDS and sulfate concentration trends. Both figures show some correlation <br />between concentrations at the upper and lower weirs, although the concentrations measured at the <br />lower weir are always higher. The higher concentrations at both weirs generally occur during the <br />initial spring runoff period and then decrease as runoff continues. This characteristic variation in <br />concentration during the runoff period is typical of streams where the relative contribution of direct <br />surface runoff and water derived from stream bed sediments or, in the case of the upper weir, shallow <br />groundwater varies during the runoff period. <br />The 2007 data, supported by results from 2006, 2005 and 2004, indicate that the final reclamation <br />activities have significantly improved the water quality in lower Windy Gulch. The water quality has <br />clearly improved over the pre-reclamation levels and now meets the agricultural standards established <br />in the August 23, 2002, monitoring plan for most sampling periods. There are still some slight <br />exceedances of the agricultural standard for zinc during the rising limb of the discharge hydrograph <br />(i.e., maximum total concentration of 2.17 mg/1 compared to the standard of 2.O.mg/1) that are likely <br />the result of flushing of accumulated weathering products from the Windy Gulch channel sediments <br />as the stream starts to flow in the spring. Although the overall trend in zinc concentration is <br />decreasing, it is not clear how long this spring flushing will result in slight exceedances. For now, we <br />recommend continued monitoring of water quality in Windy Gulch. <br />Sincerely, <br />Water Management Consultants, Inc. <br />~ ~~~- ~ <br />Jerry Rowe, P.E. <br />