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September 15 1.0 inches <br />October 2 0.95 inches <br />Of the seven rainstorm events, four exceeded the 10-year,24-hour design storm event of <br />2.1 inches, and one storm exceeded the 100-year, 24-hour storm of 3.25 inches. <br />Recorded flows over the nine year period ranged from a low of 0 cfs at station S-1 to a high of <br />195 cfs at station S-1 in March 1985. Maximum recorded flow was approximately 300 cfs <br />during April 1986, which was estimated at the mine haul road culvert crossing. In terms of <br />average flow, 1985 was the highest and 1989 was the lowest. Flows measured in September <br />1993 were higher than those measured over the past several years due to the storms received <br />during that period. Spreadsheets and graphs of flow recorded at each station are presented in <br />Appendix I. <br />Surface water chemistry was observed to be stable over the nine year monitoring period (Table 1 <br />and Appendix n. The water may be classified as amixed calcium magnesium-sulfate/bicarbon- <br />ate type water. The degree of ionization varied with season, being highest during low flow and <br />lowest during high flow. The ratio of calcium to magnesium was generally consistent over the <br />seasons; however, there is a shift in the ratio of sulfate to bicarbonate, with bicarbonate being <br />more prevalent during high flow conditions. These ionic conditions also influenced the <br />conductivity and TDS as exhibited in the graphs in Appendix I. <br />' Analysis of trace metals indicates low concentrations. Aluminum and iron were detected in all <br />samplings, higher values being reported during high flow events (Appendix n. Manganese and <br />zinc were also sampled and found in only trace amounts. <br />1 Mining and reclamation operations at the Chimney Rock Mine appear to have little or no effect <br />on the quantity or quality of area surface waters. This may be due to the mines inactive status <br />' during 1985 through 1989. Backfill and grading activities occurred in the Revision 1 Pit and <br />Surface facilities during 1990 and 1991; however, sediment control ponds established on the <br />disturbed areas eliminated runoff of surface waters from the mine site. All NPDES fontts were <br />' filed with the Department of Health during quarterly reporting periods. CDMG also received <br />copies of these reports. During 1993, discharges were reported from the ponds during the storm <br />event which exceeded the 100-year, 24-hour design criteria. Results of the annual pond survey <br />conducted in October are contained in Appendix III. <br />' Groundwater <br />The three alluvial wells A-1, W-1 and W-5 were replaced and added to the monitoring program. <br />' Water levels were measured during the third and fourth quarters with water chemistry being <br />analyzed during the fourth quarter. Al] data is contained in Appendix II. <br />' Water levels in well A-1 dropped significantly from the third to fourth quarter measuremenu. <br />Well W-5 remained static over the two periods while well W-1 was dry during the third quarter <br />' and had a very small quantity of water during the fourth quarter. <br />5 <br />1 <br />