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,.. , <br />.~. <br />Edna Mine Annual Hydrology ~ Wildlife Report <br />I. Hydrologic Monitoring System <br />During the year, several of the changes to the monitoring system <br />agreed to during permit review were made. Alluvial well TR-4 was <br />moved upstream on Trout Creek to a point adjacent to the Moffat area <br />and a new alluvial well TR-1.5 was established closer to the West <br />Ridge Area. Well TR-1.5 is shallower than intended because the drill <br />hole collapsed before the casing could be installed but it is still <br />suitable for collecting water Samples. Anew surface water flow <br />recorder system was installed in the drainage between Center Ridge <br />and West Ridge using a 3 foot H flume. This gauge was lost because <br />of runoff resulting from heavy thunderstorms, and no records are <br />available for 1982. This station will be re-established this year <br />using a heavier and larger flume. All of the other surface and <br />ground water stations performed normally except as noted elsewhere. <br />II. Flow Records <br />The stream flow and irrigation ditch flow records are included in the <br />attachments for 1981 and 1982. Both the peak flow and total volume <br />of flow were greater in 1982 than in 1981 on both Trout Creek and Oak <br />Creek. This corresponds to the heavier snowpac:c in 1982 after below <br />normal precipitation in 1981. The gauges performed fairly well <br />except for occasional recorder failures and the. unlikely high flow <br />shown at TR-b from July through October. It is planned that the <br />gauge rating curves will be recalibrated during 1983 to check whether <br />the 1982 high flows may have changed the channe'. geometry enough to <br />cause such inconsistencies. <br />III. Annual Salt Loading Estimate <br />A comparison of the 1982 hydrographs and the hydrographs in the <br />permit application in exhibit 2.5-3 shows a very similar pattern, but <br />with a shift in time for the peak flow from early to late June <br />between the baseline period and 1982. Also, the water quality values <br />(submitted separately in quarterly reports) show very similar <br />dissolved solids concentrations in time to those shown in exhibit <br />2.5-12b of the permit application. Since the flow and quality <br />patterns are so similar to the baseline results, the best estimate of <br />the salt loading is that it is the same as that found during the <br />baseline studies indicating that the mine's impact on the hydrology <br />of Trout Creek is following the predictions in section 2.5.3.5 of the <br />application. A further confirmation of the application's conclusions <br />is the quality of the runoff from the Center Ridge - West Ridge area <br />which was predicted to have a dissolved solids concentration of about <br />2100 mg/1 early in the permit term and 2800 mg/1 after mining is <br />complete (pg. 2.5-101 of the application). The average dissolved <br />solids concentration of the discharge from the sediment pond that <br />Page 1 <br />