2008-04-15_REVISION - M1980244 (325)

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~ 4 Main project area hydrologic conditions Surface Water Surface water conditions in the Wilson Creek drainage are monitored at six locations (Figure 3.1). There are four surface stations in the North Fork of Wilson Creek (Theresa Creek) and Wilson Creek above the confluence with Bateman Creek; T-1, T-2, T-3, and WCSW. There is one surface water station in Bateman Creek (BCSW), and there is one station in Wilson Creek below the confluence of Bateman Creek (WCSW-01). The City of Victor POTW discharges to Wilson Creek about half the distance between stations T- 3 and WCSW. Water quality statistics, streamflow data and field parameter data summaries have been compiled for the sample stations T-1, T-2, T-3, WCSW, BCSW, and WCSW-01 for the period of record, and are provided in Tables A10 through A15 (Attachment A), respectively. Surface water flows in the North Fork of Wilson Creek drainage (T1, T2, T3, WCSW) are seasonal and variable (0 to 1,275 gpm). Flows, if observed, occur in the spring due to snowmelt runoff and/or in the summer due to seasonal rains and runoff. Flow rates, when multiple stations report flow on or about the same day, generally increase downstream, especially between T3 and WCSW. Surface water flows in Bateman Creek (BCSW) are seasonal and variable (0 to 229 gpm). Surface water flows .in Wilson Creek below the confluence of Bateman Creek and the North Fork of Wilson Creek (WCSW-1) (which is seasonal) are year-round, due to the City of Victor POTW's continual release of treated water, and variable (6 to 850 gpm). The surface water in the North Fork of the Wilson Creek (T-1, T-2, and T-3 iri Theresa Creek) is characterized as calcium-sulfate-bicarbonate type. Figure 3.4 is a piper plot showing the major ion water chemistry for the Wilson Creek drainage surface water stations. Data show average pH values are near neutral and are stable downstream from 7.3 su at T-1 to 7.1 su at T-2, and to 7.6 su at T-3. Average nitrate values increase from T-1 (0.05 mg/L) to T-2 (4.9 mg/L) and then decrease to T-3 (1.9 mg/L). Average sulfate values increase in the downstream direction from 35 mg/L at T-1, to 323 mg/L at T-2, and to 477 mg/L at T-3. The average pH and nitrate values in Wilson Creek between T-3 and WCSW increase from 7.6 su to 8.0 su and 1.9 mg/L to 2.6 mg/L, respectively. Average sulfate values in Wilson Creek between T-3 and WCSW decrease from 477 mg/L to 156 mg/L, respectively. Surface water in Bateman Creek (station BCSW) is characterized as calcium- bicarbonate water. Data indicate the average pH value in this area is slightly alkaline (7.6 su). Average nitrate and sulfate values are 0.23 mg/L and 51 mg/L, respectively. Surface water in Wilson Creek below the North Fork and Bateman Creek confluence is characterized as calcium-sulfate water. Data indicate the average pH value in this area is near-neutral (7.8 su). Average nitrate and sulfate values are 4.2 mg/L and 136 mg/L, respectively. Groundwater Groundwater conditions in Wilson Creek are monitored via a network of three monitoring wells which are completed in granite (Figure 3.1): WCMW-2, WCMW-3, and WCMW-6. Nine monitoring wells have been plugged and abandoned in the Wilson Creek drainage; WCMW-1, WCMW-5-20, WCMW-5-125, WCMW-6-19, WCMW-6-53, WCMW-6-81, WCMW-7-16, WCMW-8-20, and WCMW-9-390. The period of record, water quality 2736 - Cripple Creek & Victor Gold Mining Company Water Management Consultants