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(SW-S2-l) a mean discharge of 0.47 cubic feet per second (cfs) is chazacteristic of stream flow during the period June through September, the historic irrigation period in this portion of Routt County. A minimum flow of zero and maximum flow of 7.89 cfs has occurred during the period of record up through 2006. June through September TDS concentrations have increased, from a 1987 average of 718 milligrams per liter (mg/l), to a 2006 average of 880 mg/1. Outflow from the Wadge Impoundment (NPDES 002) which, along with the Northwest Impoundment (NPDES 003), is located downstream of site SW-S2-1, is governed by three sources; snowmelt runoff, rainfall runoff and spoils aquifer inflow. During the period June through September for the period of record through 2006, a peak flow of 5.64 cfs has been recorded at NPDES 002, minimum flow was zero, and mean flow was 0.25 cfs. These flows are taken from weekly measurements. An increase in TDS concentration has been observed during the period of record, from an average of 2,332 mg/1 in 1987 to an average of 4,155 mg/1 for the June through September period in 2006. A second pond which discharges to Grassy Creek is the Northwest Impoundment (NPDES 003). The June through September mean flow is approximately 0.14 cfs, with a peak flow of 0.88 cfs and minimum flow of zero. June through September TDS concentrations of 1,504 mg/1 were characteristic before September 1984, prior to discharges from atruck-wash facility (which contributes flow to the Northwest Impoundment) using Wadge Impoundment water as a source. Subsequently, as the Northwest Impoundment discharges have increased, June through September TDS has increased to an average of 3,115 mg/1 in the effluent in 2006. At the surface water monitoring station on Grassy Creek below Seneca II Mine (SW-S2-2), the quantity and quality ofwater exiting the mine is monitored. The June through September mean flow for the period of record is 0.83 cfs, with minimum of 0 cfs and maximum of 10.06 cfs. A June through September mean concentration of TDS (2,695 mg/1) has been observed at this site in 1987. A mean June through September concentration of TDS (3,360 mg/I) was observed at this site in 2006. Fish Creek Drainage Basin Cow Camp Creek Since 1982, surface water flow and quality on Cow Camp Creek have been monitored at site SW-S2-6, 1/4 mile downstream of Pond 004, and at the outfall of Pond 004. Flow rates measured at the 004 outfall and at SW-S2-6 aze directly related. In 1983 the yearly average flow was 0.154 cfs at site SW-S2-6. This site is no longer part of the monitoring network and was discontinued in June, 1997. At Pond 004 in 2006 the yearly average flow was 0.14 cfs. Prior to mining disturbance in the Cow Camp Creek drainage, the creek was ephemeral. 22