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results of the gauging stations along Trout Creek indicate that the monitoring program is being placed on-line early <br />enough in the year to record flow prior to the peak runoff period for each year. The individual data points show the monthly <br />average flows and give some indication of the variability between mild winters (winters of less snow accumulation) and <br />harsh winters. The graph showing 2002-2004 data indicates a decrease in total streamflow in 2004 from 2003 and an <br />increase from 2002 levels. The 1995-2004 graph suggests that 2004 was a mild winter for the pas[ decade. <br />The flow record for 2004 shows a low peak flow to have occurred in May as it did during 1996, 2000 and 2001. <br />The runoff from the mine site was lower in 2004 than in previous years due to less snowpack on the mine site and the on-set <br />of warmer temperatures occurring earlier in the spring. The flow data presented in Figure 1 consists only of information <br />derived from continuous flow records. Instantaneous flow measurements obtained between 1989 and June 1994 for this <br />location are provided in Appendix A. Prior to that time, instability of the stream channel caused by a 1984 flood precluded <br />the installation of any type of monitoring station in the vicinity. The old Stevens chart recorders were replaced with <br />electronic streamflow recorders in April 2003. <br />The bridge located immediately downstream of TR-a was replaced in the fall of 2001 potentially altering the current <br />stage rating curve. Therefore, the decision was made to update the stage/discharge curves for TR-a and TR-b. Over the 2001 <br />season, a total of nine cross-sections and associated velocities were measured at each cross section location. This data was <br />used to compute a stage rating curve at each location. <br />The stage rating curve for TR-a was developed from flows ranging from I I cfs to 145 cfs. The curve equation and <br />rZ for the curve are asfollows: y = 44.469x3.zsoe where y =flow in cfs and x =depth of flow; rZ = 0.98. Flows for much of <br />2004 were below the 1 I cfs used to develop the rating curve; therefore, the calculated flows may to be tow. A channel cross- <br />section was developed using survey results that verifies streambed stability (Drawing 1). <br />The stage rating curve for TR-b was developed from flows ranging from 13 cfs to 144 cfs. The curve equation and <br />rZ for the curve are as follows: y = 65.049x2.431, where y =flow in cfs and x =depth of flow; rZ = 0.99. Flows for much of <br />2004 were below the 13 cfs used to develop the rating curve; therefore, the calculated flows may to be low. This appears to <br />indicate a good correlation between the upstream and downstream flows. A channel cross-section was developed using <br />survey results that verifies streambed stability (Drawing 1). <br />Irrigation ditch flow observations were made in April, June, and July of 2004. The TR-A site was observed with no <br />flow except for June 1, 2004, when the flow was 2.49 cfs. Flow observations are provided in tabular forma[ in Appendix A. <br />NPDES MONITORING <br />Monitoring of point discharges from sedimentation impoundments is accomplished under Colorado Department of <br />Public Health and Environment Colorado Permit Discharge System Permit CO-0032638. Copies of required Discharge <br />Monitoring Reports are provided to the Division of Minerals and Geology under separate cover, and are included in this <br />report by reference. <br />2a Revised 11/14/05 <br />