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-27_ Upstream Downstream SW3 SW2 SW4 SW1 9090* 584 5 160 *Al1 data in mg/1 SW4 is located at the last downstream point directly draining the mining operation. The low levels of TSS at SW4 is due to the settling of solids in the beaver dams and in the lush grasses of the flood plain of Grassy Creek. From SW4 to SW1 the stream character changes, becoming more erosive in nature with less vegetative cover and fewer beaver dams. Dissolved solids are not affected by seepage through the dams as can be seen from the following data collected in April, 1980. Upstream Downstream SW3 SW2 SW4 SW1 190* 240 367 184 *All data in mg/1 Later samplings show levels exceeding 700 mg/1 at SW3. These levels fall within a category which could have detrimental effects on sensitive crops. As there is no irrigation or agricultural activity in the upper reaches of Grassy Creek, elevated levels of dissolved solids are not expected to have an impact on surface water usage. Dilution with downstream undisturbed waters will mitigate the impact of increases in total dissolved solids on usability of the water for irrigation on the Grassy Creek alluvial valley floor. Fe and Mn both show elevated levels in the upstream portions of Grassy Creek during high flows. Mn exceeded the Colorado Water Quality Criteria for agricultural water (0.2 mg/1) during one sampling event and had acceptable levels for all other analyses. Grassy Creek water samples from April, 1980 showed high levels of Fe directly downstream of disturbed mine sites. The levels of Fe are shown below. Upstream Downstream SW3 SW2 SW4 SW1 2.1* 9.8 1.0 1.8 *All data in total iron-mg/1 SW4, located downstream of all mining activity and at the permit boundary, shows greatly lowered levels of Fe. Later submitted data shows no high iron levels.