2016-04-13_REPORT - C1981014 - Laserfiche WebLink

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Rob Zuber Page 2 April 14, 2016 Review of Surface Water Data The flows measured in all three creeks in the second quarter of 2015 were unusually high in comparison with historical data. Figure 1 gives a visual summary of streamflow data for the Southfield Mine from 1992 to 2015, (note that: MC -1 was monitored from 1985 and SA -1 was monitored from 1990, with no flow measured at either location until 1992; NC -1, NC -2 and MC - 2 were first monitored in 1997). The precipitation data shown in figure 1 was collected at NOAA station USC00051294, which is approximately 12 miles north of the mine site, in Canon City. It shows total monthly precipitation, aggregated from continuous daily measurements. In contrast, the streamflow measurements from the Southfield Mine are instantaneous data points, collected relatively infrequently. Despite the differences in the two datasets, it is possible to see a positive correlation between periods of high precipitation and measureable streamflow. (As noted by EFCI, streamflow at the Southfield Mine can also be the result of snow melt runoff) Considering just the streamflow data, apparent anomalies (for example, Magpie Creek appears to discharge a greater volume of water than Newlyn Creek in 1999, but the pattern is reversed in 2015) can be accounted for by the "flashy" nature of the watershed, coupled with periods of up to several days between measurements at different monitoring locations; although less than ideal, this is not out of compliance with the approved monitoring plan. The water quality sample taken at the downstream monitoring point on Newlin Creek (NC -1) raises no red flags in terms of dissolved constituents; no Manganese was present in the sample, and only a minimal amount of Iron (0.17 mg/L); Total Dissolved Solids (126 mg/L) were average for samples taken between 1997 and 2015. It should be noted that Total Suspended Solids (TSS) were at a new maximum (216 mg/L), however given that the measured streamflow was also a new maximum, this is not surprising. Figure 2 shows TSS plotted against streamflow, for the occasions during the monitoring period when a significant flow was measured. The limitations of the data are such that the relationship cannot be quantified, particularly as no account is made for the timing of the sample with respect to the precipitation event that caused the stream to flow, however it is possible to see a weak correlation between the two quantities, and to see the extent to which the May '15 event was an outlier. Finally, it should be noted that the upstream monitoring point, NC -2, also saw a new maximum for TSS with this event (22 mg/L). The water quality data from Magpie and Second Alkali Creeks raise no concerns, and are in line with historical records.