2014-07-11_REPORT - C1980007 - Laserfiche WebLink

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West Elk Mine 2013 Annual Hydrology Report 49 conductivity was 978 µmhos /cm (980 µmhos /cm, duplicate) compared to the baseline maximum conductivity of 597 µmhos /cm; dissolved iron levels were 0.07 mg /L (0.08 mg /L duplicate) compared to the baseline maximum of 0.05 mg /L; total iron concentrations were 2.43 mg /L (2.69 mg/L duplicate) compared to the maximum baseline value of 0.17 mg /L; and total dissolved solids (TDS) were 560 mg/L (550 mg /L duplicate) compared to the baseline maximum of 430 mg /L. The elevated concentrations of these parameters are not believed to be mine related, as there was no MWPF discharge (MCC, 2014). One laboratory sample (May 2013) was collected at Middle Dry Fork in WY 2013. Electrical conductivity was 139 µmhos /cm compared to the baseline maximum conductivity of 76 µmhos /cm. In August 2013, field electrical conductivity was 626 µmhos /cm compared to the baseline maximum of 480 µmhos /cm. On sample (May 2013) was collected at Upper Dry Fork in WY 2013. Total iron was 4.19 mg /L compared to the baseline maximum of 3.64 mg /L. Total suspended solids (TSS) were 155 mg /L compared to the baseline 88 mg /L. One sample and one duplicate (May 2013) were collected at Upper Deep Creek in WY 2013. Dissolved iron was elevated at 0.39 mg /L compared to the baseline maximum of 0.04 mg /L (However, this result is considered suspect, because the laboratory duplicate value was 0.03 mg /L). Total iron was also elevated at 46.50 mg /L (46.30 mg /L duplicate) compared to the baseline maximum of 9.43 mg/L. One sample (May 2013) was collected at Lower Deep Creek in WY 2013. Total iron was 12.1 mg /L compared to the baseline maximum of 5.83 mg /L. There were no mining related activities in the Deep Creek area that could have contributed to the baseline level water quality exceedance. Stream water quality measurements at least 10 percent above baseline values were observed at the Poison Gulch monitoring station in WY 2013. In May 2013, total iron was 3.19 mg /L compared to the maximum baseline value of 0.43 mg /L, and TSS concentrations were 122 mg /L compared to the baseline maximum of 28 mg /L. These increased concentrations are not mining related, since mining discharges have not and are not occurring in these areas. The elevated measurements are likely due to below average flow conditions during the peak flow period in WY 2013. 5.1.2 Impacts to Area Stream Water Quantity As mentioned previously, stream flows for the Upper North Fork of the Gunnison River (USGS), Middle Sylvester Gulch, Lower Minnesota Creek (USGS), Upper Minnesota Creek Flume (USGS), Upper, Lower and Middle Dry Fork Flume, Lick Creek Flume, Deep Creek Ditch, and the Minnesota Reservoir Flume stations are measured with data loggers that collect data continuously. Stream flows of the other monitored streams (Upper and Lower Sylvester Gulch, Lower Gribble Gulch, Horse Gulch; East Gulch east of Horse Gulch, Upper and Lower Deep Creek. Box Canyon, Upper and Lower Raven Gulch, Deer Creek, and Poison Gulch) are measured as instantaneous flow three times per year, corresponding with rising limb, peak flow, and low flow periods. No specific flow data are available for the Lower North Fork of the Gunnison River, although no June 2014 HydroGeo, Inc.