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.luly 1993 -16- 923-2515 • 5.0 RESULTS AND ]DISCUSSION OF THE ECOLOGICAL INVESTIGATION S.1 Gras~Creek 5.1.1 Streamflow. Ground Water. and Water Oualitv There are three stream flow monitoring stations along Grassy Creek (Figure 2). Station YSGFS is located in section 16, of TSN, R87W just west of Twenty Mile (Windy Point) Road. Station SW-S2-1 is located in section 34, of T6N, R87, upstream of the confluence of Grassy and Little Grassy creeks. Station SW-S2-2 is located in section 27, of T6N, R87 below the junction of Little Grassy Creek, but upstream of the junction with Scotchmans Gulch. The twelve year (June 1, 1980-March 3, 1992) mean flow in Grassy, Creek at station SW-S2-1 • just above the confluence with Little Grassy Creek is 1.18 cubic feet per second (cfs) (Peabody 1992a). About 2000 feet further down Grassy Creek below the confluence with Little Grassy Creek at station SW-S2-2 the flow is slightly higher at 1.95 cfs (Peabody 1992a). Table 5.1 provides mean flow data by month for the period of March through the first six days of August, 1992 for station YSGFS. The mean flow in 1992 was highest in April (0.845 cfs) and dropped to a low of 0.109 cfs in August. The greatest volume of water (36.807 acre feet) flowed in April. Tables 5.2, 5.3 and 5.4 provide stream flow data for the three Grassy Creek monitoring stations and also includes data on water quality. The mean flow in 1991-1992 beginning at the upstream station was 0.384 cfs, .472 cfs, and 1.031 cfs, respectively. Surface water quality data in Grassy Creek are from three permanent monitoring sites, YSGFS, SW-S2-1, SW-S2-2, and two same-day, down-drainage collection sites, SP-1 and SP-2 (Figure 2). The data for 42 water quality parameters analyzed in the laboratory are presented in Tables 5.2 through Table 5.6, and include conductivity, sodium adsorption ratio (SAR), pH, boron, • chloride, aluminum, arsenic, cadmium, copper, lead, manganese, molybdenum, nickel, Golder Associates