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1 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br />1 <br /> <br />~ , <br />operation is considered, there is a very small decrease in flows in the streams in the sF~ring during <br />the period the streams aze recharging the alluvium. This is due to an overall slight increase in total <br />aquifer storage, after accounting for the alluvium removed and the unlined pits z.dded. The <br />maximum decrease in flows occurs in May and averaged I0.6 ac-ft, or about 0.18 cfs. Likewise, a <br />very small increase in streamflow occurs in the fall and winter months, due to the increase in <br />discharge from the alluvium back to the stream. The largest decrease in streamflow is in September <br />and averages 6.5 ac-ft, or about 0.11 cfs. The cumulative impact of the total mining operation is also <br />shown in Figure 4. <br />Most of the impacts shown in Table 7 and Figure 4 are expected to manifest in the South Branch of <br />the St. Vrain River. Small decreases in streamflow may occur in the spring and equally small <br />increases in streamflow may occur in the fall. Very small impacts such as these a~•e within the <br />margin of error of the estimation methods used and are therefore not statisticall}' significant. <br />Furthermore, the cumulative changes resulting from this mining operation (less t}ian 0.18 cfs) <br />represent less than 0.04 percent of the average flow in the St. Vrain River on an annual basis. These <br />changes in streamflow are so small that they will not be noticed in the stream. Therefore, there are <br />no expected impacts to streamflows and the historic alluvial aquifer-stream system interaction caused <br />by the mining operation at the Lyons - Rockin' WP Pit. <br />-33- <br />Ri.~Gn/i-lb nUlru .I ~;m r~iin, l u~. <br />